Beijing, China

The University of Science and Technology Beijing , formerly known as Beijing Steel and Iron Institute before 1988, is a national key university in Beijing, China. USTB's metallurgy and materials science programmes are highly regarded in China. Wikipedia.

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University of Science and Technology Beijing | Date: 2016-03-15

This present invention provides a method for preparing a stainless reinforcing steel bar resistant to corrosion of chloride ions, and belongs to the technical field of corrosion-resistant materials. This method particularly comprises the steps of: selecting a reinforcing steel bar blank, and performing oil removing, rust removing, water washing, and drying treatments on the surface of the reinforcing steel bar blank to be treated, or directly performing sand blasting or shot blasting on a reinforcing steel bar blank whose surface is only slightly rusted; placing the reinforcing steel bar blank in a chromium-containing environment, and keeping at a certain temperature for a certain time such that chromium in the environment is capable of diffusing into the surface of the reinforcing steel bar blank to form a chromium-containing diffusion layer, wherein an area in the diffusion layer where the weight content of Cr exceeds 12% meets the basic component requirements for a stainless steel, and this area is the effective diffusion layer described in this invention; and performing cooling treatment on the heat diffusion treated reinforcing steel bar. In this invention, a reinforcing steel bar blank is pre-formed, a heat diffusion technique is optimized, and the corrosion resistance to chloride ions of the stainless reinforcing steel bar of this invention is superior to that of the 316L stainless reinforcing steel bar.

Chen Z.,University of Science and Technology Beijing | Du F.,Beihang University
Measurement: Journal of the International Measurement Confederation | Year: 2017

In the large-size product assembly process, the inspection of the large-size components and quality assurance of the product requires advanced digital metrologies, which include high-precision and high-efficiency measuring devices, and corresponding measuring approaches. The single measuring device or measurement field usually cannot meet the demands of measuring in the large-size assembly site; instead, a measurement network based on the combination of multi devices, is a better choice for the manufacturers. In this paper, a measurement network constructed by iGPS and portable scanner is proposed. The measuring principles of the two kinds of measuring devices are studied firstly, as well as the characteristics of their layouts and measurement uncertainties, based on simulating and actual measuring experiments. Then, the measuring principle, structure and uncertainty characteristics of the measurement network are discussed in detail, with measurement data analysis of the measuring experiments. Finally, a few conclusions and the future work are illustrated. © 2017 Elsevier Ltd

Zhao C.,University of Science and Technology Beijing | Feng Z.,University of Science and Technology Beijing
Measurement: Journal of the International Measurement Confederation | Year: 2017

Planetary gearboxes vibration signals are highly complex due to the intricate kinematics and the amplitude modulation and frequency modulation nature, and their spectra have intricate sidebands, leading to difficulty in planetary gearbox fault identification. To address this issue, multi-domain features are extracted for fault identification from vibration signals to construct feature vectors in time-domain, frequency-domain and through instantaneous amplitude energy analysis. Variational mode decomposition (VMD) is utilized for the merits which are entirely non-recursive, free from pseudo mode and negative frequency and much robust to noise to decompose a signal into a set of mono-components, based on which the instantaneous amplitude energy is calculated. In order to inhibit and eliminate the undesirable features while concentrate the fault identification information to several outperforming features, sparse filtering which is essentially hyper-parameter-free is applied to extract sparse features without considering the selection of k-nearest neighborhood involved in manifold learning. Finally, the proposed method is validated via analyses of planetary gearbox dataset collected in both lab experiments and a wind farm. Based on clustering analysis of multi-domain sparse features extracted, the localized faults are successfully identified. © 2017 Elsevier Ltd

Guo Q.,University of Science and Technology Beijing | Wen Z.,University of Science and Technology Beijing | Dou R.,University of Science and Technology Beijing
International Journal of Heat and Mass Transfer | Year: 2017

Results from experimental and numerical studies of the transient heat-transfer characteristics of circular air-jet impingement are presented. The circular nozzle has an inner diameter of 6 mm. The Reynolds number is defined based on the nozzle diameter varied from 14,000 to 53,000. The nondimensional distance between the nozzle exit and the target plate is varied from 4 to 8. The local Nusselt number variation with the time obtained from the experimental and numerical studies are presented. The local Nusselt number rapidly increases when the air jet began its impingement. The increasing speed of Nuloc slows down as the jet impingement continues to cool down. At the 50–80 s region, the Nuloc at various radii R/Dn get the maximum point and remain almost constant from 80 s until the end of the experiment. © 2016 Elsevier Ltd

Li F.,University of Science and Technology Beijing | Wang X.,CAS National Center for Nanoscience and Technology | Xia Z.,University of Science and Technology Beijing | Pan C.,CAS National Center for Nanoscience and Technology | Liu Q.,University of Science and Technology Beijing
Advanced Functional Materials | Year: 2017

The development of new luminescent materials for anticounterfeiting is of great importance, owing to their unique physical, chemical, and optical properties. The authors report the use of color-tunable colloidal CdS/ZnS/ZnS:Mn2+/ZnS core/multishell quantum dots (QDs)-functionalized luminescent polydimethylsiloxane film (LPF) for anticounterfeiting applications. Both luminescent QDs and as-fabricated, stretchable, and transparent LPF show blue and orange emission simultaneously, which are ascribed to CdS band-edge emission and the 4T1 → 6A1 transition of Mn2+, respectively; their emission intensity ratios are dependent on the power-density of a single-wavelength excitation source. Additionally, photoluminescence tuning of CdS/ZnS/ZnS:Mn2+/ZnS QDs in hexane or embedded in LPF can also be realized under fixed excitation power due to a resonance energy transfer effect. Tunable photoluminescence of these flexible LPF grafted doped core/shell QDs can be finely controlled and easily realized, depending on outer excitation power and intrinsic QD concentration, which is intriguing and inspires the fabrication of many novel applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ren Y.,University of Science and Technology Beijing | Zhang L.,University of Science and Technology Beijing
Ironmaking and Steelmaking | Year: 2017

A reaction model was developed to better understand the evolution of inclusions in Al–Ti-killed steels during the ladle mixing process. The fluctuation of steel chemistry gave rise to the transient evolution of inclusions during the mixing process. The formed Al2O3 in the steel can be hardly influenced by the addition of FeTi, while adding Al can effectively modify the TiOx-containing oxides to solid Al2O3. The formation of Al2O3–TiOx inclusions can be suppressed by increasing Al and lowering Ti in the steel. The alloying sequence of adding Ti after the Al addition is beneficial to improve the recovery of Ti. The one-point strong air absorption may cause the formation of the unwanted Al2O3–TiOx inclusions in Al–Ti-killed steels. The critical oxygen contents in the molten steel with varying Al and Ti concentrations were predicted to avoid the formation of Al2O3–TiOx inclusions and Ti loss. © 2017 Institute of Materials, Minerals and Mining

Li Z.,University of Science and Technology Beijing
Journal of Computational and Theoretical Nanoscience | Year: 2016

Elasticity is one of the characteristics of cloud computing. In order to achieve this feature, cloud service provider needs to allocate resource dynamically according to the user's demand. In fact, the cloud resource allocation is non-optimal in most cases. To maximum the benefits and resource utilization while satisfying users requests, it is essential for cloud service provider to allocate resources adaptively for different conditions. In this article, the differential game theory is used to solve the problem of cloud resource allocation. A non-cooperative differential game model is proposed to solve the independent optimization. The experiments results support a theoretical foundation which can help cloud service provider make the optimal dynamic strategies when users dynamically change their strategies. Copyright © 2016 American Scientific Publishers All rights reserved.

Gautier R.,University of Nantes | Li X.,University of Nantes | Xia Z.,University of Science and Technology Beijing | Massuyeau F.,University of Nantes
Journal of the American Chemical Society | Year: 2017

A strategy to design step by step an inorganic single-doped white phosphor is demonstrated. The method consists in tuning different contributions of the emission by successively controlling the chemical compositions of the solid solution or nanosegregated host matrix and the oxidation states of the single dopant. We use this approach to design a white phosphor Na4CaMgSc4Si10O30:Eu with excellent color rendering (CRI > 90) that is similar to common mixed-phosphor light sources but for a single-phase. We show that this methodology can also be extended to other phosphors for use in diverse applications such as biomedicine or telecommunications. © 2017 American Chemical Society.

Guo Y.-F.,University of Science and Technology Beijing | Guo X.-M.,University of Science and Technology Beijing
ISIJ International | Year: 2017

Aiming to better understand the effect of MgO on sintering process of iron ores, the formation of [Mg1-x,Fex]O·Fe2O3 in solid-state reactions between MgO and Fe2O3 was studied. Experiment was carried out in air from 873 K to 1 573 K by MgO mixing with Fe2O3. X-ray diffraction, optical microscope, scanning electron microscopy and energy-dispersive spectroscopy were used to characterize the phase change of the sintered samples. The content of ferrous ion in the sintered samples was determined by potassium dichromate titration for distinguishing the MgO·Fe2O3 (x=0) and the Fe3O4 (x=1). Thermogravimetric and differential scanning calorimeter test was carried out in air by MgO mixing with Fe2O3 to investigate the thermal decomposition of Fe2O3. The results show that the reactions between the Fe2O3 and MgO in air formed first the magnesium ferrite at 1 073 K, subsequently magniferous magnetite appeared at 1 173 K, resulting that the thermal decomposition of Fe2O3 was carried out at a lower temperature than that of its own self. The following conversion of the magniferous magnetite to the magnesium ferrite was also observed with the temperature increasing to 1 482 K. It has been deduced that the [Mg1-x,Fex]O·Fe2O3 is formed by the reaction between the prior formed MgO·Fe2O3 and the Fe2O3 in the heating-up process. It was obtained that amount of ferrous ion formed in sintering process is mainly related by the amount of MgO in raw materials and it's diffusion rate. Therefore, adding MgO appropriately into raw material can be beneficial to improve the low temperature reduction degradation of iron ore sinter. © 2017 ISIJ.

Wang Y.,University of Science and Technology Beijing | Song R.,University of Science and Technology Beijing | Li Y.,University of Science and Technology Beijing
Materials Characterization | Year: 2017

The thixoforging of 9Cr18 steel was conducted in a designed set-up. A functionally graded material (FGM) with a hard surface and tough center was fabricated. The microstructural evolution inside and outside the solid/liquid boundary was investigated, respectively. The relationship between microstructure and mechanical properties was clarified. The results showed that phase transformation of solid particles was mainly determined by the alloying elements. Meta-austenite was retained after thixoforging. Martensite transformation might occur during certain kinds of subsequent heat treatment, which would be harmful to the inner strength due to the high hardness and carbide precipitation. The wear-resisting skin layer outside the solid/liquid boundary could be retained after heat treatment and the FGM structure improved the inner mechanical properties. The optimal heat treatment strategy for 9Cr18 thixoforging specimen was to temper at 550 °C for 2 h. The inner area exhibited a strong work hardening behavior and the ultra-compressive strength could reach 4680 MPa with the compressive strain of 53.2%. The high strength was attributed to the fact that the austenite structure was retained and the brittle eutectic structure was extruded outside the solid/liquid boundary. © 2017 Elsevier Inc.

Liu C.-S.,Hohai University | Liu C.-S.,National Taiwan Ocean University | Li B.,University of Science and Technology Beijing
Composite Structures | Year: 2017

For the free vibration of composite beams and non-uniform beams we propose a new upper bound theory to approximate the first few natural frequencies. The Rayleigh quotient is expressed in terms of boundary functions, instead of that in terms of eigenfunctions. The boundary function satisfies all boundary conditions of the given beam, and is at least the fourth-order polynomial with leading coefficient to be one. We prove that the maximality of the Rayleigh quotient in the space of the kth order boundary functions is equivalent to the orthogonality of the kth order boundary function to lower order optimal boundary functions. Hence, we can easily find the kth order natural frequency through an orthogonalization technique provided. When the first three natural frequencies are compared with the exact or numerically found ones, good results are obtained, which confirm the applicability of the present upper bound theory. We address the inverse problems of composite beam equations, where we use the orthogonal system of boundary functions as bases to expand the unknown functions and derive linear algebraic equations to determine the expansion coefficients. As a consequence, we can fast and accurately estimate the unknown rigidity function and planar inertial function with the help of the first three natural frequencies, and the supplemented measured data of recovered function on two boundaries. The robustness of the present inversion methods is demonstrated by numerical examples. © 2017 Elsevier Ltd

Shao X.,University of Science and Technology Beijing | Ma X.,Beijing Union University | Li X.,Tsinghua University | Liang C.,Tsinghua University
Energy and Buildings | Year: 2017

Fast prediction of indoor temperature distribution is valuable to recognize the status and assist in rapid decision making and heat source control. Prediction using a superposition theorem based on the assumption of fixed flow field is an alternative method of performing fast prediction. However, little research revealed the methods’ reliability based on fixed flow field, and previous prediction methods primarily focused on the temperature at a steady state. In this paper, an algebraic expression was established to predict the temperature distribution based on the definition of transient accessibility indices for temperature. The prediction accuracy was mainly verified using a numerical method with 14 cases. It was concluded: (1) the proposed expression can perform fast prediction once the transient accessibility indices are prepared in advance; (2) the fixed flow field adopted in the proposed method should be built by a thermal scenario considering the heat source at a certain intensity, rather than a scenario with no heat source. The accuracy is acceptable for positions outside the heat source area; (3) there is no significant effect of the choice of supply air temperature utilized in building the fixed flow field on prediction accuracy. The research on prediction accuracy is helpful for a reasonable application of the proposed method in real projects. © 2017 Elsevier B.V.

Liu Q.,Tsinghua University | Gan M.,University of Science and Technology Beijing | Jiang R.,Tsinghua University
BMC Systems Biology | Year: 2017

Background: Most disease-associated variants identified by genome-wide association studies (GWAS) exist in noncoding regions. In spite of the common agreement that such variants may disrupt biological functions of their hosting regulatory elements, it remains a great challenge to characterize the risk of a genetic variant within the implicated genome sequence. Therefore, it is essential to develop an effective computational model that is not only capable of predicting the potential risk of a genetic variant but also valid in interpreting how the function of the genome is affected with the occurrence of the variant. Results: We developed a method named kmerForest that used a random forest classifier with k-mer counts to predict accessible chromatin regions purely based on DNA sequences. We demonstrated that our method outperforms existing methods in distinguishing known accessible chromatin regions from random genomic sequences. Furthermore, the performance of our method can further be improved with the incorporation of sequence conservation features. Based on this model, we assessed importance of the k-mer features by a series of permutation experiments, and we characterized the risk of a single nucleotide polymorphism (SNP) on the function of the genome using the difference between the importance of the k-mer features affected by the occurrence of the SNP. We conducted a series of experiments and showed that our model can well discriminate between pathogenic and normal SNPs. Particularly, our model correctly prioritized SNPs that are proved to be enriched for the binding sites of FOXA1 in breast cancer cell lines from previous studies. Conclusions: We presented a novel method to interpret functional genetic variants purely base on DNA sequences. The proposed k-mer based score offers an effective means of measuring the impact of SNPs on the function of the genome, and thus shedding light on the identification of genetic risk factors underlying complex traits and diseases. © 2017 The Author(s).

Sun W.,University of Science and Technology Beijing | He W.,University of Science and Technology Beijing
Proceedings - 2016 31st Youth Academic Annual Conference of Chinese Association of Automation, YAC 2016 | Year: 2016

In this paper, we address the tracking control problems of a robotic system with uncertain dynamics. To cope with the problem of the unknown nonlinear function terms in the system and improve the robustness, adaptive fuzzy logic control is proposed for an approximation of uncertain parameters to achieve the control objectives. Furthermore, both non-constraint and output constraint are considered in the control design. Based on the Lyapunov theory, the stability of the closed-loop system is proved via choosing appropriate parameters. A tan-type barrier Lyapunov technique has been presented to ensure overall closed-loop system achieve uniformly ultimate bounded for output constraint. Tracking performance is guaranteed under the condition of output constraint and unknown parameters. Some numerical simulation results and discussions show the effectiveness of the proposed fuzzy logic strategy. © 2016 IEEE.

Yuan L.,University of Science and Technology Beijing | Li F.,University of Science and Technology Beijing
Proceedings - 2016 31st Youth Academic Annual Conference of Chinese Association of Automation, YAC 2016 | Year: 2016

In Sparse Representation based Classification (SRC), the construction of the dictionary is very important for the sparse model. The atoms in the dictionary are hoped to be representative and discriminant. In this paper, we propose the face recognition with occlusion via support vector discrimination dictionary and Gabor occlusion dictionary based Sparse Representation Classification (SVGSRC). We apply support vector machine (SVM) scheme to train the non-occlusion dictionary, guaranteeing that the resulting dictionary can not only express testing samples from the same class, but also can reduce the interferene of samples of different classes; Meanwhile, we use the Gabor features to learn a compact occlusion dictionary. It will reduce the dimension and increase the sparsity. We put the method on the AR face database which has natural occlusion and USTB multimodal database. Compared with other SRC methods, according to the experimental results, the proposed method gets better performance on recognition rate. © 2016 IEEE.

Li J.,University of Science and Technology Beijing | Zhang Q.,University of Science and Technology Beijing
Proceedings - 2016 31st Youth Academic Annual Conference of Chinese Association of Automation, YAC 2016 | Year: 2016

There are many industrial fields need to locate the specific texture or contour of the particular objects in the image with complex scenes. Edge detection algorithm based on gray transform is generally hard to handle these issues. This paper presented a model that can accurately locate the specific texture or contour in RGB images with complex scenes by modifying and improving the CNN-based edge detection model HED. It described and practiced the improving method in detail, using accurately locating the outer contour of the plate in images as an example. It achieves the target effectively and accurately and is proved to be a method for only locating the specific texture in images. © 2016 IEEE.

Gao H.,University of Science and Technology Beijing | He W.,University of Science and Technology Beijing
Proceedings - 2016 31st Youth Academic Annual Conference of Chinese Association of Automation, YAC 2016 | Year: 2016

In this paper, the dynamic model of a singlelink flexible robotic manipulator developed with the assumed mode method (AMM) is investigated. Subsequently, we obtain a discretized model for the flexible manipulator system. Base on the dynamic model, fuzzy control are studied to achieve the control objectives. Aiming at ensuring stability rigorously, the closed-loop system is uniform ultimate boundedness (UUB) via the Lyapunovs stability. By appropriately choosing design parameters, the state of the system is proven to converge to zero with a small neighborhood. Eventually, Simulations for the flexible manipulator system are given to verify the effectiveness of the proposed fuzzy control strategy, and the final performance is compared with that of proportional derivative (PD) control strategy. The feasibility of the proposed control is verified. © 2016 IEEE.

Feng X.,Peking University | Zhang Y.,University of Science and Technology Beijing | Wang L.,Peking University
Journal of Theoretical Biology | Year: 2017

In iterated continuous games, the cooperative investment in a given round is determined by the initial investment and the reciprocation rate, which describe the investment in the first round and the dependence of current investment on the partner's last move, respectively. These two traits usually intertwine during evolution. However, their coevolution is not fully explored. In this paper, we thereby study their coevolution in the iterated continuous public goods games. We find that the reciprocation rate plays a dominant role during the coevolution in both finite and infinite populations. If it exceeds a threshold, a stingy population where individuals invest no more than their partner's last investment evolves to full cooperation, and a generous population where individuals invest more than their partner's last investment decreases to a moderate cooperative state, investing a portion in the first round and then escalating investment in the following rounds. Otherwise, the stingy population evolves to full defection, and the generous one rises to another moderate cooperative state. © 2017 Elsevier Ltd

Feng X.,University of Electronic Science and Technology of China | Wu S.,University of Science and Technology Beijing | Zhou W.,University of Tennessee at Knoxville | Quan M.,University of Science and Technology Beijing
Knowledge-Based Systems | Year: 2017

Constructing a graph to represent the structure among data objects plays a fundamental role in various data mining tasks with graph-based learning. Since traditional pairwise distance-based graph construction is sensitive to noise and outliers, sparse representation based graphs (e.g., ℓ1-graphs) have been proposed in the literature. Although ℓ1-graphs prove powerful and robust for many graph-based learning tasks, it suffers from weak locality and high computation costs. In this paper, we propose a locality weighted sparse representation (LWSR), which aims for good preservation of the locality structure among data objects and a significant reduction of the computation time. LWSR approximates each object as a sparse linear combination of its nearest neighbors, and weights their corresponding coefficients by their distances to the target object. Experimental results show that LWSR-graph based learning methods outperform state-of-the-art methods in both effectiveness and efficiency for graph-based learning. © 2017.

Song L.,Northwestern Polytechnical University | Lin J.,University of Science and Technology Beijing | Li J.,Northwestern Polytechnical University
Materials and Design | Year: 2017

Ordered ω phases are equilibrium phases at intermediate temperatures in TiAl alloys. However, a systematical research on the effects of alloying elements on the ordered ω phase transformations is still lacking. The effects of alloying elements on the ordered ω phase formation should be considered in future design of TiAl alloys. In this study, the effects of Cr, Mn and Ni on the ordered ω phase formation are investigated. The results show that the precipitation of ordered ω phase is promoted by addition of Ni, i.e., the sizes of ordered ω phase were in micron-level. However, the addition of Mn greatly suppresses the growth of ordered ω phases. During thermal exposure at 850 °C, a Ti-Al-Ni ternary phase formed within the original βo phase areas in the Ni-containing alloy. Meanwhile, no ordered ω phase existed in an annealed Mn-containing alloy. In both as-cast and annealed conditions, the effects of Cr seemed to be similar to those reported in Mo and W-containing alloys. Differential scanning calorimetry (DSC) experiments suggested that the precipitation temperatures of ordered ω phase in these three alloys were affected by minor alloying elements, which fitted well with the observed phenomena in the electron microscopy study. © 2016 Elsevier Ltd

Kong L.,University of Science and Technology Beijing | Sun J.,University of Science and Technology Beijing | Bao Y.,University of Science and Technology Beijing
RSC Advances | Year: 2017

A nanofluid is a dispersion of nanoparticles in a base fluid and it has been a hot topic of great interest in recent years primarily due to its potential application in various fields. This review presents an overview of the remarkable progress on nanofluids during the past two decades. Nanoparticles have been investigated intensively as an additive for lubricants due to their special tribological properties. This article is focused on various synthetic methods and characterization techniques of nanofluids. Factors enhancing the stability and lubrication mechanism have been delineated in detail. Although nanofluids are potential candidates for tribological applications, there are still many challenges to overcome. These challenges involve the long term stability of nanofluids and validation of lubrication mechanisms. Especially, nanofluid stability and high costs of production are obstacles for the application of nanofluids. The current review also discusses the problems of nanofluids applied in lubrication. © The Royal Society of Chemistry.

Zhang G.H.,University of Science and Technology Beijing | Sun G.D.,University of Science and Technology Beijing | Chou K.C.,University of Science and Technology Beijing
Journal of Alloys and Compounds | Year: 2017

In this study, a thermodynamic analysis of the reaction between MoS2and Si was performed, which indicated that when the molar ratio of MoS2to Si is 1:4, the final products were composed of SiS and MoSi2, without other solid phases, in the temperatures range of 0 °C–1700 °C. The reaction between MoS2and Si powders with a MoS2/Si molar ratio of 1:4 was investigated in the range of 800 °C–1600 °C. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to study the phase composition and microstructure of the products, respectively. The content of sulfur in MoSi2product was measured using an infrared carbon-sulfur analyzer. It was found that pure MoSi2can be successfully synthesized in the temperature range of 1100 °C–1600 °C after reacting for 2 h with very little sulfur residual. Meanwhile, gaseous SiS was also generated and escaped from the MoSi2. It was also found that the reaction rate between MoS2and Si was very slow at 800 °C and 900 °C. The microstructural analyses indicated that grain size of the MoSi2product increased with increasing temperature. © 2016 Elsevier B.V.

Song K.,University of Science and Technology Beijing | Ni H.,University of Science and Technology Beijing | Fan L.-Z.,University of Science and Technology Beijing
Electrochimica Acta | Year: 2017

Flexible supercapacitors based on paper-like electrodes have attracted significant interest because of the increasing demands in the energy storage, and they are recently claimed to be minimized and portable for meeting practical applications. As promising binder-free electrode materials in the supercapacitors, graphene-based films have been developed for enhancing their performance in energy storage by insetting “spacers” in-between nanosheets to prevent inevitable aggregations. In this study, a facile and versatile strategy is presented for fabricating graphene-based composite films by introducing activated carbonized cotton fibers to regulate the chemical composition, surface area and pore size distribution. The obtained composite films permit to present substantially increased energy storage capability (capacitance of 310 F g−1 and 150 F g−1 at 0.1 A g−1 and 10 A g−1 in 6 mol L−1 KOH electrolyte, respectively). Furthermore, tunable areal capacitance is realized by altering the stacked film layers without loss of mass specific capacitance. The devices based on composite films with excellent power density (up to 156.5 mW cm−2) and energy density (240 μWh cm−2) highlight a controllable, mini-sized and high-efficiency stage for energy storage. Such unique strategy suggests great potential in the commercialization of portable electronic devices, which require greater capacitance in a limited area. © 2017 Elsevier Ltd

Liu Y.,University of Science and Technology Beijing | Li J.,University of Science and Technology Beijing | Gao X.,University of Science and Technology Beijing
Journal of Magnetism and Magnetic Materials | Year: 2017

Alloys of Fe82Ga18−xAlx (x=0, 4.5, 6, 9, 12, 13.5) were prepared by directional solidification technique and exhibited a <001> preferred orientation along the axis of alloy rods. The saturation magnetostriction value of the Fe82Ga13.5Al4.5 alloy was 247 ppm under no pre-stress. The tensile properties of alloys of Fe82Ga18−xAlx at room temperature were investigated. The results showed that tensile ductility of binary Fe-Ga alloy was significantly improved with Al addition. The fracture elongation of the Fe82Ga18 alloy was only 1.3%, while that of the Fe82Ga9Al9 alloy increased up to 16.5%. Addition of Al increased the strength of grain boundary and cleavage, resulting in the enhancement of tensile ductility of the Fe-Ga-Al alloys. Analysis of deformation microstructure showed that a great number of deformation twins formed in the Fe-Ga-Al alloys, which were thought to be the source of serrated yielding in the stress-strain curves. The effect of Al content in the Fe-Ga-Al alloys on tensile ductility was also studied by the analysis of deformation twins. It indicated that the joint effect of slip and twinning was beneficial to obtain the best ductility in the Fe82Ga9Al9 alloy. © 2016 Elsevier B.V.

Liao F.,University of Science and Technology Beijing | Li L.,University of Science and Technology Beijing
Optimal Control Applications and Methods | Year: 2017

For a class of uncertain discrete-time systems, a preview controller based on linear matrix inequality is proposed. A new method is derived to construct an augmented error system instead of taking the difference of the error signal and the system equation. The new approach avoids applying the difference operator to the time-varying matrix and can simplify the augmented error system. For the augmented error system of the uncertain system, state feedback is introduced. The sufficient condition of asymptotic stability of the closed-loop system is derived for the performance index by using the relevant theorems of robust control theory. The condition can be realised by solving a linear matrix inequality optimization problem. By incorporating the controller obtained into the original system, we obtain the preview controller. Moreover, introducing an integrator allows the closed-loop system to robustly track the desired tracking signal without steady-state error. © 2017 John Wiley & Sons, Ltd.

Yin S.-H.,University of Science and Technology Beijing | Xie F.-F.,University of Science and Technology Beijing
Zhongguo Youse Jinshu Xuebao/Chinese Journal of Nonferrous Metals | Year: 2016

During the in-situ leaching process of ion-absorbed rare earth, the rational determination of infiltration head is helpful for reducing infiltration time and enhancing leaching efficiency. With Green-Ampt soil infiltration model and infiltration experiment on variation of water head of ion-absorbed rare earth, the relationships between infiltration rate, infiltration head and depth of wetting front, and the relationships between infiltration time, cumulative infiltrated water volume and infiltration head were established. The results show that infiltration head of leaching solution is not the higher the better. With the increasing of infiltration head, the infiltrate rate presents a tendency of increasing and then decreasing. There is an optimized infiltration head. Conducting a column leaching experiment on the ion-adsorption type rare earth source from Gan Nan, its optimized infiltration head is 26.69 cm. The infiltrate rate of interface determines the infiltration effect of the solution in a certain range. © 2016, Science Press. All right reserved.

He Y.,CAS Academy of Mathematics and Systems Science | Guo J.,University of Science and Technology Beijing
Journal of Systems Science and Complexity | Year: 2017

This paper investigates the FIR systems identification with quantized output observations and a large class of quantized inputs. The limit inferior of the regressors’ frequencies of occurrences is employed to characterize the input’s persistent excitation, under which the strong convergence and the convergence rate of the two-step estimation algorithm are given. As for the asymptotical efficiency, with a suitable selection of the weighting matrix in the algorithm, even though the limit of the product of the Cramér-Rao (CR) lower bound and the data length does not exist as the data length goes to infinity, the estimates still can be asymptotically efficient in the sense of CR lower bound. A numerical example is given to demonstrate the effectiveness and the asymptotic efficiency of the algorithm. © 2017 Institute of Systems Science, Academy of Mathematics and Systems Science, CAS and Springer-Verlag Berlin Heidelberg

Liu X.,University of Science and Technology Beijing | Yang Y.,University of Science and Technology Beijing | Guan S.,CAS Technical Institute of Physics and Chemistry
Chemical Physics Letters | Year: 2017

We have developed the CoMoO4 nanorods (NRs) electrode with a specific one-dimensional nanostructure, which exhibited superior electrocatalytic performance for Oxygen Evolution Reaction (OER), such as lower potential (343 mV at a current density of 10 mA cm− 2), Tafel slope (67 mV decade−1) and excellent catalytic stability (for 10 h). Benefiting from enhancement of electrical conductivity and one-dimensional nanostructure, the CoMoO4 NRs show improved OER activity than Co3O4 cubes, demonstrating that one-dimensional nanostructures could be promising to achieve the OER catalysts with excellent property. © 2017

Dangui-Mbani U.O.,University of Science and Technology Beijing | Zheng L.,University of Science and Technology Beijing | Tathy C.,Marien Ngouabi University
International Journal of Heat and Mass Transfer | Year: 2017

In this paper, an innovative constitutive model of modified Fourier's heat conduction law (Fick's diffusion law), which takes the effects of relaxation time, Philip n-diffusion flux on heat transfer (diffusion) and thermal diffusivity parameters into account, the n-diffusion Cattaneo telegraph equation is firstly proposed. The approximate analytical solutions are obtained by employing the Adomian decomposition method which coincide with exact solution in good agreement. Moreover, the involved parameters have strong effects on the temperature distribution which are presented graphically and discussed. The mathematical method and techniques employed in this paper also have the significance for some other problems in science and engineering. The results showed that the temperature oscillates and decreases with increasing and decreasing of thermal diffusivity and relaxation time parameters, without and with reaction term respectively, but the oscillations of temperature decay rapidly until reaching zero with decreasing of Philip n-diffusion parameter for spatial evolution with and without reaction term. The temperature decreases with increasing parameter of relaxation time, Philip n-diffusion or thermal diffusivity for temporal evolution. © 2017 Elsevier Ltd

Yang T.,University of Science and Technology Beijing | Fu D.,University of Science and Technology Beijing
Journal of Systems Engineering and Electronics | Year: 2016

Consider the efficiency of p-norm multiple kernel learning (MKL), which is extended to a semi-supervised learning (SSL) scenario by applying the manifold regularization technique. A manifold regularized p-norm multiple kernels model is constructed and applied to a semi-supervised classification task. Solutions are proposed for the case of p = 1, p > 1 and p = ∞, with an analysis of theorems and their proofs. In addition, experiments are conducted on several datasets using state-of-the-art methods to verify the efficiency of the proposed manifold regularized p-norm multiple kernels model in semi-supervised classification. © 2016 Beijing Institute of Aerospace Information.

Yin Q.,University of Science and Technology Beijing | Chen L.,University of Science and Technology Beijing
Materials Research Express | Year: 2017

In this research, the effects of Sn alloying on structure transformation and electrical characteristics of Ge2Sb2Te5 (GST) thin films were studied. It was discovered that the SnTe phase formed in GST thin films when Sn content exceeded 26 at%, and the addition of Sn atoms expanded the lattice parameter, as a result of atomic radii difference between Ge and Sn atoms. Furthermore, temperature dependent sheet resistance measurements on the GST:Sn thin films were performed for the electrical characteristics to be studied. Sn substitution fraction of 16 at% was discovered to maximize the crystallization temperature of GST thin films. Compared to the GST thin films, crystallization temperature difference and lower amorphous resistance of the GST:Sn thin films were mainly due to lower bonding energy of Sn-Te. Moreover, the amorphous conductivity activation energies (Eσ) corresponding to different grain sizes were calculated with the Arrhenius equation. The Eσ value of GST:Sn thin films decreased significantly as the Sn content increased due to grain size effects, which appears to improve the temperature stability of conductivity of phase change memory.

Gao L.,University of Science and Technology Beijing | Wang J.,University of Science and Technology Beijing
Journal of Applied Polymer Science | Year: 2017

Liquid oxidized poly(1,2-butadiene) (LOPB) with multi epoxy groups is synthesized to modify diglycidyl end-caped poly(bisphenol A-co-epichlorohydrin) (DGEBA) cured by 4,4′-diaminodiphenyl sulfone (DDS). FTIR spectra shows that DGEBA and LOPB can be effectively cured by DDS, and the epoxide rubber particles are evenly distributed in the composites till their addition up to 20 wt % of DGEBA as seen from the scanning electron microscope (SEM). Their decomposition temperatures (Td) increase with the increase in LOPB addition at around 10 wt % of DGEBA while the Td for the composite containing 20 wt % LOPB of DGEBA is lower than that of the neat epoxy. The addition of LOPB improves their storage moduli and especially these values at temperatures higher above 150 °C; all the composites exhibit higher glass transition temperature (Tg) than that of the neat epoxy, and the maximum Tg reaches up to 255 °C for the composite containing 15 wt % LOPB of DGEBA. The incorporation of LOPB effectively decreases their dielectric constants and the composite with 10 wt % LOPB of DGEBA possesses the lowest one. The synergic improvements in their various properties are attributed to the networks formation via covalent linkage between the two phases in these reactive blends. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44689. © 2017 Wiley Periodicals, Inc.

Ding X.-W.,University of Science and Technology Beijing | Ding X.-W.,Beijing Foreign Studies University
International Journal of Emerging Technologies in Learning | Year: 2016

Literature suggests the potential of problembased learning (PBL) in critical thinking (CT) development, but empirical research on the effect of PBL on CT in foreign language pedagogy is limited. This study aims at a better understanding of the relationship between PBL and CT disposition of learners of English as a foreign language (EFL learners). A mixed research design was adopted in both an authentic in-class context and a WeChat-assisted after-class context, with an Adapted California Critical Thinking Disposition Inventory (CCTDI) as measurement tool of quantitative data, and with classroom observation notes and students' written comments on PBL experiences as qualitative data to supplement the quantitative analysis. The research findings confirmed that the PBL practice significantly improved EFL students' CT disposition in general, in Independent Inquiry step, and regarding all CT subscales. The study also revealed that the PBL practice eliminated significant gender difference in Group Negotiation, although there seemed a significant gender difference in Hypothesis Proposition after the PBL practice. Implications and limitations of this study, as well as suggestions for future research are also discussed accordingly.

Pi Q.,Chinese Academy of science | Pi Q.,Guilin University of Technology | Hu R.,Chinese Academy of science | Xiong B.,Guilin University of Technology | And 2 more authors.
Mineralium Deposita | Year: 2017

The contiguous region between Guangxi, Guizhou, and Yunnan, commonly referred to as the Golden Triangle region in SW China, hosts many Carlin-type gold deposits. Previously, the ages of the gold mineralization in this region have not been well constrained due to the lack of suitable minerals for radiometric dating. This paper reports the first SIMS U–Pb age of hydrothermal rutile crystals for the Zhesang Carlin-type gold deposit in the region. The hydrothermal U-bearing rutile associated with gold-bearing sulfides in the deposit yields an U-Pb age of 213.6 ± 5.4 Ma, which is within the range of the previously reported arsenopyrite Re–Os isochron ages (204 ± 19 to 235 ± 33 Ma) for three other Carlin-type gold deposits in the region. Our new and more precise rutile U-Pb age confirms that the gold mineralization was contemporaneous with the Triassic W–Sn mineralization and associated granitic magmatism in the surrounding regions. Based on the temporal correlation, we postulate that coeval granitic plutons may be present at greater depths in the Golden Triangle region and that the formation of the Carlin-type gold deposits is probably linked to the coeval granitic magmatism in the region. This study clearly demonstrates that in situ rutile U–Pb dating is a robust tool for the geochronogical study of hydrothermal deposits that contain hydrothermal rutile. © 2017 Springer-Verlag Berlin Heidelberg

He W.,University of Science and Technology Beijing | Huang H.,University of Science and Technology Beijing | Ma X.,University of Science and Technology Beijing
Materials Letters | Year: 2017

First-principles calculations were employed to investigate elastic and entropy properties of B2 ferromagnetic and antiferromagnetic FeRh phases. We calculated lattice parameters, elastic constants, isotropic moduli like bulk modulus B, shear modulus G, Young's modulus E, and Poisson's ratio of two phases and compared these with other calculations and experiments. At finite temperatures, the values of vibrational (from both Debye model and phonon dispersion) and thermal electronic contributions to the total entropy change between the two phases are calculated about -50 J/kg/K and 7.8 J/kg/K comparable to the experimental results (−33 ± 9 J/kg/K and 8 ± 1 J/kg/K). © 2017

Yan B.,University of Science and Technology Beijing | Wang X.,University of Science and Technology Beijing | Yang Z.,University of Science and Technology Beijing
Journal of Alloys and Compounds | Year: 2017

Phase equilibria in the MgO-SiO2-TiOx system at 1873 K were investigated under controlled atmosphere by employing the method of high-temperature equilibration followed by quenching, electron probe microanalysis (EPMA) and XRD analysis. Based on the experimental results, isothermal phase diagram of the MgO-SiO2-TiOx system under oxygen partial pressure of 4.85 × 10−11 atm was constructed. By comparing with the phase diagram of MgO-SiO2-TiO2, the effect of oxygen partial pressure on the phase relations was obtained. Firstly, anosovite (Ti3-xMgxO5) replaces TiO2 and MgTi2O5 to equilibrate with liquid phase. Secondly, the compound MgTiO3 no longer exists under the reducing condition. Thirdly, the single liquid region shrinks due to the lower oxygen partial pressure. Furthermore, the equilibria between liquid and anosovite were investigated under other two oxygen partial pressures of 1.94 × 10−9 and 2.75 × 10−13 atm, respectively. The saturated solubility of titanium oxide in the liquid phase decreases with the decreasing of the oxygen partial pressure and higher SiO2 content increases the activity coefficient of TiOx in liquid phase. © 2016 Elsevier B.V.

Wang L.,University of Science and Technology Beijing | Tang D.,University of Science and Technology Beijing | Song Y.,University of Science and Technology Beijing
Journal of Iron and Steel Research International | Year: 2017

A new approach describing the flow stress of ferrite-pearlite steel has been proposed, which divided the deformation process into three stages based on whether ferrite or pearlite yielded. Iso-work increment assumption was applied to describe the transfer of load between the components. The physically based model to describe ferrite was approximated with Swift's equation in order to obtain the analytic solution. The tensile strength of ferrite-pearlite had a linear relation with pearlite volume fraction, square root reciprocal of ferrite grain size and reciprocal of pearlite interlamellar spacing. Moreover, a model to calculate the tensile strength of ferrite-pearlite steel was proposed. The predicted values of tensile strength were in good agreement with experimental results when the pearlite volume fraction was less than 20%. Considering the plastic relaxation mechanisms, the internal stress was modified with pearlite volume fraction, total strain, yield stress of ferrite and pearlite when the pearlite volume fraction was more than 20%. © 2017 Central Iron and Steel Research Institute

Liu H.,University of Science and Technology Beijing | Chen L.,University of Science and Technology Beijing
Gongneng Cailiao/Journal of Functional Materials | Year: 2017

The surface morphology and microstructure of Cu/Co bilayer films with different thickness were investigated by atomic force microscope (AFM) and X-ray diffraction (XRD), and the hysteresis loops of Cu/Co bilayer films were measured by vibrating sample magnetometer (VSM). The results reveal that the surface of the films was composed of uniform islands. As Co films thickness increased, the height of islands increased while parts of them merged and grew up. Only fcc Co films obtained at the thickness of 5 and 15 nm, but fcc and hcp coexisted while Co films grew up to 30 nm. Further investigation shows that coercive force, saturation magnetization and squareness of hysteresis loops increased with the deposition of Co films. © 2017, Chongqing Functional Materials Periodical Press Co. Ltd. All right reserved.

Wang Y.,University of Science and Technology Beijing | Wang X.-G.,University of Science and Technology Beijing
Journal of Dispersion Science and Technology | Year: 2017

The instability of emulsion explosive matrices is mainly due to the crystallization of interphases as oversaturated aqueous solutions of nitrate salts. The principal features of crystallization for this type of emulsion have been previously studied; however, there is no consensus regarding the mechanism of crystallization for an emulsion explosive matrix. This study is devoted to the investigation of the crystallization behavior of interphase droplets. By monitoring the mass change of emulsions during their aging process, it was found that the mass of the emulsions remains almost constant and that water still completely existed in the emulsion system after crystallization of the interphase droplets. The ammonium nitrate (NH4NO3) crystals in the emulsion explosive matrices were then separated successfully using a simple method. The thermal behavior of pure NH4NO3 and crystals in the emulsion explosive matrices was studied by differential scanning calorimetry-thermogravimetric analysis (DSC-TG) at a heating rate of 10 K/min. The experimental results show that the thermal behavior of the crystals in the emulsions was exactly the same as for pure NH4NO3, meaning that only NH4NO3 crystallized from the emulsion explosive matrices with no water crystals. Thus, it could be concluded that after crystallization of the dispersed drops in the emulsion explosive matrices, pure NH4NO3 crystals and new smaller droplets were produced. © 2017 Taylor & Francis.

Jia X.,University of Science and Technology Beijing | Wei F.,Tsinghua University
Topics in Current Chemistry | Year: 2017

Recent decades have witnessed many breakthroughs in research on carbon nanotubes (CNTs), particularly regarding controllable synthesis, production scale-up, and application advances for this material. This sp2-bonded nanocarbon uniquely combines extreme mechanical strength, exceptionally high electrical conductivity, as well as many other superior properties, making it highly attractive for fundamental research and industrial applications. Synthesis and mass production form the solid basis for high-volume applications of CNTs. During recent decades, CNT production capacity has reached more than thousands of tons per year, greatly decreasing the price of CNTs. Although the unique physiochemical properties of an individual CNT are stated repeatedly, manifestation of such unique properties in a macroscopic material, e.g., realization of high-strength CNT fibers, remains a great challenge. If such challenges are solved, many critical applications will be enabled. Herein we review the critical progress in the development of synthesis and scaled-up production methods for CNTs, and discuss advances in their applications. Scientific problems and technological challenges are discussed together. © 2017, Springer International Publishing Switzerland.

Li F.,University of Science and Technology Beijing | Xia Z.,University of Science and Technology Beijing | Liu Q.,University of Science and Technology Beijing
ACS Applied Materials and Interfaces | Year: 2017

The ability to control dopants and defects, as well as the core/shell structures, of quantum dots (QDs) is an essential nanotechnology to modify and optimize their photoluminescence properties. Herein, the optimized ZnS:Mn2+/ZnS/ZnS:Cu2+/ZnS core/multishell QDs have been prepared, and their luminescence properties depending on the ratios of the starting materials and the injection temperature of an extra sulfur source were discussed; finally the white light can be possibly obtained by mixing the blue light (emission peak at 450 nm originating from Cu2+ dopants or emission peaks at 405 and 430 nm corresponding to a defect emission center) and orange light (emission peak at 585 nm from Mn2+ dopants). As a controlled synthesis comparison, the optimum core/shell structures and key synthesis parameters have been determined, and the quantum yield (QY) of the as-obtained ZnS:Mn2+/ZnS/ZnS:Cu2+/ZnS core/multishell white light emitting QDs without defect emission was determined to be 38%. The practical white light device prototype has been also fabricated and the CIE color coordinate of (0.32, 0.34) with a warm white light has been realized upon the excitation of the commercial 370 nm UV LED chip, which demonstrated potential application for micro/nano optical functional devices. © 2017 American Chemical Society.

She X.,University of Science and Technology Beijing | Zhang Z.,Pohang University of Science and Technology
Nanoscale Research Letters | Year: 2017

In this study, ZnFe2O4 (ZFO) nanotapers are fabricated on the ZnO nanorods (NRs) by recycling rare-earth oxide (REO) slag as the iron source, which thereby exhibits dramatically enhanced photoelectrochemical (PEC) efficiency. Our studies demonstrate that the electron-hole separation and charge migration can be facilitated by the cascade band alignment of ZFO and ZnO and the branched nanotaper structures. Not only the iron source, the slag particles can also act as the passivation layers, leading to improved electron lifetime and significant PEC enhancement. The current study presents a novel REO-slag-modified PEC anode for high-efficiency PEC devices and offers a possibility of recycling industrial waste for renewable energy generation. © 2017, The Author(s).

Zuo H.,University of Science and Technology Beijing | Liu Y.,University of Science and Technology Beijing
Ceramics International | Year: 2017

Al2O3-SiC-SiO2-C composite refractories are interesting potential blast furnace hearth lining materials that feature several advantageous properties. In this study, the corrosion resistance of a novel Al2O3-SiC-SiO2-C composite refractory to blast furnace slag was investigated by adopting a rotating immersion method (25 r/min) at 1450–1550 °C and comparing it against a conventional corundum-based refractory at 1550 °C as a benchmark. The results showed that the apparent activation energy of Al2O3-SiC-SiO2-C composite refractory over the dissolution process in the slag is 150.4 kJ/mol. Dissolution of the Al2O3 and 3Al2O3·2SiO2 phases appeared to be the main cause of Al2O3-SiC-SiO2-C composite refractory corrosion. High-melting-point compounds in the slag layer formed a protective layer which mitigated the corrosion. The novel Al2O3-SiC-SiO2-C composite refractory is better suited to blast furnace hearth lining than the conventional corundum-based refractory, because the carbon phase and SiC phase in the material are not readily wetted by the blast furnace slag and therefore are more resistant to slag penetration. Higher melting point phases also may crystallize on the hot face of the hearth lining due to the high thermal conductivity of the Al2O3-SiC-SiO2-C composite refractory, promoting a more stable protective layer. © 2017 Elsevier Ltd and Techna Group S.r.l.

Li P.,University of Science and Technology Beijing | Miao S.-J.,University of Science and Technology Beijing
Meitan Xuebao/Journal of the China Coal Society | Year: 2016

The study of in-situ stress field is an important task in rock mechanics and mining engineering. With the coal mining goes into deep mining, the effect of in-situ stress is more prominent. Some new understandings about the in-situ stress field distribution characteristics and the relationship between in-situ stress and fault activity in China's coal mining area are obtained with the analysis of the 219 sets of measured in-situ stress data. There are mainly two types of stress field in China coal mining area: σH>σh>σv and σH>σv>σh, but the type of σH>σv>σh accounts for a larger percentage. In the research area, the high ground stress is the majority, the medium stress and the super high stress mining area also occupy a certain proportion, and the low stress mining area is the least. The maximum horizontal principal stress, the minimum horizontal principal stress and the vertical principal stress almost linearly increase with the depth, and the horizontal tectonic stress is in the leading position. The three lateral pressure coefficients decrease with the increase of depth, KH gradually tends to 1.31, Kh gradually tends to 0.74 and Kav gradually tends to 1.03. The distribution of horizontal differential stress is discrete, its range is from 0.85 MPa to 19.51 MPa and the average is 8.80 MPa. Ratio of maximum horizontal principal stress and minimum horizontal principal stress is mainly concentrated from 1.5 to 2.0. The faults of the study area are less prone to sliding instability phenomenon when the friction coefficient are 0.6 and 1.0 under the current stress state, in the overall evaluation of the fault stability of the study area, the standard of the fault sliding instability criteria for the friction coefficient of 0.6 is more appropriate. © 2016, Editorial Office of Journal of China Coal Society. All right reserved.

Tu R.,University of Science and Technology Beijing | Hwang Y.,University of Maryland University College | Ma F.,University of Science and Technology Beijing
Applied Thermal Engineering | Year: 2017

A heat pump driven multi-stage fresh air handler using solid desiccant plates is proposed in this paper. This system can be operated under four modes depending on the outdoor air temperature and humidity ratio. This paper discusses the performances of the system under the solid desiccant dehumidification mode, which realizes a desired supply air humidity ratio with lower power consumption by adjusting the activated stage number according to the process air inlet temperature and humidity. First, influences of the total thickness of desiccant plates, the total stage number and the switching period on performances of this system were analyzed under Beijing summer condition. After the power consumption of both the compressor and the fans considered, a four-stage system with the total thickness of desiccant plates being 240 mm was suggested. Next, the optimal activated stage number under four typical working conditions of Beijing summer cooling period were discussed based on the suggested system. It was found that when the outdoor air humidity ratio were lower than 14 g·kg−1, the suggested active stage number was 2–3. © 2017 Elsevier Ltd

Shi Z.-Z.,University of Science and Technology Beijing | Liu X.-F.,University of Science and Technology Beijing
Journal of Alloys and Compounds | Year: 2017

With the help of trace analysis, cross-grain boundary (cross-GB) contraction twin (CTW) pairs and bands can be identified more easily in a deformed Mg alloy. Cross-GB CTW pairs can form in two neighboring grains with misorientations from 5° to 60°. Schmid factor (SF) analysis reveals that the majority of them are high SF twin variants, indicating that the applied macro stress plays the most important role in their nucleation. Twinning shear compatibility over GB has been explicitly evaluated by a geometrical compatibility parameter (m′). It is found that nearly half of the cross-GB contraction twin pairs have high m′ values greater than 0.7, indicating that their formation is mainly due to twinning shear transmission over GBs. However, dramatically different from cross-GB extension twin pairs and bands reported before, the rest of the cross-GB contraction twin pairs have low m′ values smaller than 0.4. Their formation is due to the dominance of the applied macro stress near GBs. © 2016 Elsevier B.V.

Zheng X.,University of Science and Technology Beijing | Shen B.,CAS Institute of Physics
Zhongguo Xitu Xuebao/Journal of the Chinese Rare Earth Society | Year: 2017

People pay much attention on magnetocaloric materials for the applications on magnetic refrigeration. In order to improve the performance of ErGa compound, Er atom is substituted by heavy rare earth Gd. The crystal structure, magnetic property and magnetocaloric effect of GdxEr1-xGa (x=0~1.0) were studied in detail. The Gd-substitution did not change the crystal structure of ErGa compound according to the results of X-ray powder diffraction and Neutron powder diffraction experiments. According to the magnetic measurements, the spin reorientation transition temperature and Curie temperature were changed with different degrees by Gd-substitution. On basis of the change of transition temperatures, the maximal magnetic entropy change, refrigerant temperature span and refrigerant capacity were also affected obviously by Gd-substitution. After comprehensive considerations, the performance was the better when the content of Gd was 0.2 and 0.3. © 2017, Editorial Office of Journal of the Chinese Society of Rare Earths. All right reserved.

Zhang L.,Peking University | Tian F.,University of Science and Technology Beijing | Xie Z.,Peking University | Qin G.,Peking University
Solar Energy | Year: 2017

Compared with the conventional organic cation lead halide perovskite, the mixed-cation lead mixed-halide perovskite CsxFA1− xPb(I1− yBry)3 (FA: NH2CH = NH2) possesses a much better stability thanks to the substitutions of Cs for FA, and Br for I. Moreover, its band gap, Eg, can be tuned in a wide range to meet the request of a high efficient tandem solar cell (TSC) with it as a subcell material. In this work, efficiencies for the four-terminal CsxFA1− xPb(I1− yBry)3/c-Si TSCs are theoretically investigated. Herein, Eg of CsxFA1− xPb(I1− yBry)3 is adjusted approaching 1.75 eV, which is the optimal Eg of top cell material for the TSC with c-Si as the bottom cell. By means of density functional calculations, three sets of x and y for CsxFA1− xPb(I1− yBry)3, which have Eg around 1.75 eV, are obtained. And their refractive indices and extinction coefficients, are also calculated. With the thickness of perovskite top cell, d1, changing from 100 nm to 10 μm, the highest efficiencies of the three sets of CsxFA1− xPb(I1− yBry)3/c-Si TSCs and the corresponding thicknesses of c-Si bottom cell, d2, are studied. For the top cell, radiative recombination is considered. For the bottom cell, Auger recombination is also taken into account. Besides, the radiation coupling effect between two subcells is included. It is found that the Cs0.11FA0.89Pb(I0.56Br0.44)3/c-Si TSCs achieve the highest efficiency among the three sets of TSCs with the same d1. With a 500-nm-thick Cs0.11FA0.89Pb(I0.56Br0.44)3 top cell, the highest efficiency of the Cs0.11FA0.89Pb(I0.56Br0.44)3/c-Si TSC reaches 35.5% when d2 is 160 μm. In an extreme situation, when the thickness of the Cs0.11FA0.89Pb(I0.56Br0.44)3 top cell is 10 μm, the highest efficiency of the TSC is 40.0% and d2 is 190 μm. © 2017

Xu Q.,University of Science and Technology Beijing | Feng J.,University of Science and Technology Beijing
Applied Thermal Engineering | Year: 2017

In this study, the nozzle characteristics of zoned and staged double P-type gas-fired radiant tube were improved to optimize combustion efficiency. A three-dimensional finite element model was established, and a grid-independence study was conducted to guarantee the accuracy of the calculation results. Corresponding experiments were designed to prove the reliability and accuracy of the simulation model. Then, the developed mode was used to determine the flow field characteristics of the zoned and staged gas-fired radiant tube. Moreover, the gas and wall temperatures were calculated by altering the gas speeds in the main and branch tube nozzles respectively. The effects of nozzle gas speed on the radiant tube were compared. Results showed that increasing the air speed of the main tube nozzle could decrease the maximum temperature and the wall temperature difference, improve temperature uniformity, and slightly increase thermal efficiency. Increasing the air speed of the branch tube nozzle could reduce the maximum wall temperature and enhance surface temperature uniformity; but these effects were relatively not significant. © 2017 Elsevier Ltd

Chen X.,University of Science and Technology Beijing | Wang X.,University of Science and Technology Beijing
Theoretical and Applied Fracture Mechanics | Year: 2017

Brittle coatings may suffer edge cracking due to thermal transients. The thermal stress intensity factor (TSIF) is used here to characterize the driving force for such damage modes. The purpose of this paper is to investigate the effect of substrate thickness and heat transfer scheme on the edge cracking behavior. The transient temperature and thermal stress field of the un-cracked system are first obtained in closed forms. The weight functions suitable for thermal loading are then developed for the edge-cracked coating. The TSIF at the crack tip is finally obtained based on the principle of superposition, with the equal thermal stresses utilized as the crack surface tractions. The dependence of the normalized TSIF is examined on different thermal boundary condition, normalized time, and relative crack depth as well as substrate/coating thickness ratio. It is found the thicker substrate leads to much higher driving force for the edge cracking. The heat transfer schemes on the lower surface of the substrate, however, have insignificant effect on it. The findings of this study may assist in the integrity analysis of coatings due to rapidly changing thermal environments. © 2017 Elsevier Ltd.

Wang T.,University of Science and Technology Beijing | Jiang J.,University of Science and Technology Beijing
Zhongguo Xitu Xuebao/Journal of the Chinese Rare Earth Society | Year: 2017

The rapid development of information technology promotes the requirements of high-speed computing. Therefore, organic transistors based on small molecular weight materials are attracting more and more interests recently. Depending on the special π conjugated systems and nice stability of phthalocyanine molecules, as well as the interesting energy levels and electronic structures of rare earth elements, sandwich-type phthalocyanine rare earth complexes can be very good candidates for constructing field-effect transistor. Actually, the organic field-effect transistors devices fabricated from sandwich-type phthalocyanine rare earth complexes show high and balanced ambipolar performance with high mobilities for both holes and electrons. And the properties of these devices can be modulated by changing the molecular structures or the self-assembled nanostructures of these systems. This manuscript will briefly summarize the progress achieved in this research field recently. © 2017, Editorial Office of Journal of the Chinese Society of Rare Earths. All right reserved.

Fu L.,University of Science and Technology Beijing | Wu S.,University of Science and Technology Beijing
Cybernetics and Information Technologies | Year: 2016

Internal clustering validation is recognized as one of the vital issues essential to clustering applications, especially when external information is not available. Existing measures have their limitations in different application circumstances. There are still some deficiencies for Internal Validation of Boolean clustering. This paper proposes a new Clustering Validation index based on Type of Attributes for Boolean data (CVTAB). It evaluates the clustering quality in the light of Dissimilarity of two clusters for Boolean Data (DBD). The attributes in the Boolean Data are categorized into three types: Type A, Type O and Type E representing respectively the attribute values 1,0 and not the same for all the objects in the set. When two clusters are composed into one, DBD applies the numbers of attributes with the types changed and the numbers of objects changed to measure dissimilarity of two clusters. CVTAB evaluates the clustering quality without respect to external information.

Zhang H.,University of Science and Technology Beijing | Zhang S.,University of Science and Technology Beijing | Yin Y.,University of Science and Technology Beijing
Neurocomputing | Year: 2017

Sequential learning algorithms are a good choice for learning data one-by-one or chunk-by-chunk. Liang et al. has proposed OS-ELM algorithm based on the ordinary ELM algorithm, which produces better generalization performance than other famous sequential learning algorithms. One of the deficiencies of OS-ELM is that all the observations are weighted equally regardless of the acquisition time. However, the training data often have timeliness in many real industrial applications. In this paper, we propose a modified online sequential learning algorithm with the forgetting factor (named WOS-ELM algorithm) that weights the new observations more. Then a convergence analysis is presented to make sure the estimation of output weights tend to converge at the exponential speed with the arriving of new observations. For the determination of the value of forgetting factor, it would change with the forecast error automatically and get rid of excessive human interference. We employ several applications in the simulation part including time-series predication, time-variant system identification and the weather forecast problem. The simulation results show that WOS-ELM is more accurate and robust than other sequential learning algorithms. © 2017 Elsevier B.V.

Wang M.,University of Science and Technology Beijing | Jiang Z.,University of Science and Technology Beijing
Hydraulic Engineering IV - Proceedings of the 4th International Technical Conference on Hydraulic Engineering, CHE 2016 | Year: 2016

To improve the dust removal efficiency of gas–water nozzle spray in coal mine workplaces of high-concentration dust, gas–water nozzle atomization characteristic parameters have been realized through experiments, and the changing rule between droplet average diameter and gas/water flow was concluded. This paper studied the dust removal process of gas–water spraying in comprehensive tunneling face, establishing the corresponding mathematical model, deducing the relation formula for gas–water nozzle spray efficiency, drawing the curve of dust removal efficiency by using MatLab. The research shows that, on the one hand, when the water flow remains constant, dust removal efficiency increased with the increase of gas flow, on the other hand, when the gas flow remains constant, dust removal efficiency first increased and then decreased as the water flow increased. There exists the best gas–water flow ratio to maximize the dust removal efficiency. The larger the dust size, the easier the dust could settle. Based on the dust size distribution and removal requirement of dust in working face, both a better dust removal effect and economic benefit can be achieved by choosing the best gas/water flow ratio, with reference to the relationship curve. © 2016 Taylor & Francis Group, London, UK.

Zhang B.M.,University of Science and Technology Beijing | Sun J.L.,University of Science and Technology Beijing
IOP Conference Series: Materials Science and Engineering | Year: 2017

Multilayer-MoS2 nanoparticles were dispersed in water-based lubricating fluid in a convenient and economical way. Oleic acid and triethanolamine were used as the main surfactants in this solution. Tribological performances of this fluid were tested under high pressure and high rotating speed. FEI Tecnai G20 TEM, Malvern Zetasizer Nano ZS were used to study the particle size and Zeta potential of the lubricants. Tribological performances of this water system with multilayer-MoS2 nanoparticles and the 3D-surfaces of wear scars after the experiments were analyzed by means of four-ball wear test machine and Olympus laser confocal microscope. According to Hertz theory and experimental data, it is practical significance to combine MoS2 nanoparticles with water-based lubricating fluid. Under high loading and high rotating speed the mixed suspension can provide good lubricating properties. On the basis of calculation the binding energy of layers in MoS2 nanoparticles is less than the energy of shearing in friction pairs. The layers in MoS2 nanoparticles slide in the process of friction. The best lubrication effects can be displayed when friction process lasts about 500 s. © Published under licence by IOP Publishing Ltd.

Yu Z.,University of Science and Technology Beijing | Zheng Y.,University of Science and Technology Beijing | Feng Q.,University of Science and Technology Beijing
Scripta Materialia | Year: 2017

We designed a [001] tilt grain boundary by self-diffusion bonding technique in a single crystal superalloy. The effects of the grain boundary plane as well as its misorientation on discontinuous precipitation (DP) were investigated quantitatively. The anisotropic formation of DP colonies was associated with the anisotropic mobility of grain boundary plane. The critical misorientation for DP transformation is in between 20 and 25° for SXG3 alloy. The method proposed in this work can be used to investigate the misorientation tolerance of grain boundaries that occurs during casting of single crystal turbine blade. © 2016 Acta Materialia Inc.

Tang B.,University of Science and Technology Beijing
Radioengineering | Year: 2016

The scattering center of extended streamlined targets can slide when the direction of radiation is changed. The sliding scattering center has influence on the micro-Doppler effect of micro-motion of the extended streamlined target. This paper focused on the micro-Doppler of the extended streamlined target for the bistatic radar. Based on the analysis, the analytical expressions of the micro-Doppler of coning motion with sliding scattering center model were given for bistatic radar. And the results were validated by the simulated results of the scattering field based on the full-wave method of the electromagnetic computation. The results showed that the sliding of the scattering center can make the micro-Doppler be less and distorted, and the influence of the sliding is different for two different types of the sliding scattering centers: sliding on the surface and sliding on the bottom circle. The analytical expressions of the micro-Doppler are helpful to analyze the time-frequency presentations (TFR) of the coning motion of the extended streamlined target and to estimate the parameters of the target.

Chen Y.,University of Science and Technology Beijing | Jiang Z.-A.,University of Science and Technology Beijing
Journal of Electrical and Computer Engineering | Year: 2017

This paper studies the problem of dynamically modeling the quality of web service. The philosophy of designing practical web service recommender systems is delivered in this paper. A general system architecture for such systems continuously collects the user-service invocation records and includes both an online training module and an offline training module for quality prediction. In addition, we introduce matrix factorization-based online and offline training algorithms based on the gradient descent algorithms and demonstrate the fitness of this online/offline algorithm framework to the proposed architecture. The superiority of the proposed model is confirmed by empirical studies on a real-life quality of web service data set and comparisons with existing web service recommendation algorithms. © 2017 Ya Chen and Zhong-an Jiang.

Song L.,Northwestern Polytechnical University | Lin J.,University of Science and Technology Beijing | Li J.,Northwestern Polytechnical University
Journal of Alloys and Compounds | Year: 2017

During the processing of high Nb-containing TiAl (Nb-TiAl) alloys, the cooling rate at certain parts of the components can be very high, especially at thin parts. Moreover, annealing treatment must be applied to TiAl alloys to improve their mechanical properties. In this study, the phase transformation mechanisms in a quenched Ti-45Al-8.5Nb-0.2W-0.2B-0.02Y alloy during subsequent annealing were characterized using a scanning electron microscope (SEM) and a transmission electron microscope (TEM). The results show that βo, α2, and massively transformed γ phases co-exist in the as-quenched microstructure. Some fine γ laths nucleated in the primary α2 phase in the quenched samples. After annealing at 800 °C for 1 h, numerous extremely fine γ laths precipitated in the bulk α2 phase and could only be recognized using TEM imaging. The ωo particles at sizes of 0.5–1 μm precipitated in the retained βo phase and nearly consumed all of the βo areas. More interestingly, some coarsened γ grains in true-twin relationship were observed at the boundaries of the lamellar colony and βo(ω) regions. The orientation relationship between βo(ω) and coarsened γ was confirmed to be the following: [110]β//[112¯ 0]ω//[111]γ, (111¯)β//(0001)ω//(11¯ 0)γ. After annealing at 800 °C for 100 h, the βo phase region transformed into small ωo particles and equiaxed γ grains and still followed the above-mentioned orientation relationship. The α2 phase only existed as thin laths in the lamellar structures in a small volume fraction. These results indicate that the ωo phase is stable at 800 °C. Possible mechanisms of these phase transformations are discussed. © 2016 Elsevier B.V.

Liu Y.,University of Science and Technology Beijing | Liu Y.,Nankai University | Fan L.-Z.,University of Science and Technology Beijing | Jiao L.,Nankai University
Journal of Materials Chemistry A | Year: 2017

Graphene monolayers or bilayers highly scattered in porous carbon nanofibers (denoted as G/C) are first prepared by a feasible electrospinning technique. Meanwhile, G/C with the character of a flexible membrane adherent on copper foil is directly used as binder-free anode for Na-ion batteries, exhibiting fascinating electrochemical performance in terms of high reversible capacity (432.3 mA h g-1 at 100 mA g-1), exceptional rate capability (261.1 mA h g-1 even at 10 000 mA g-1), and ultra-long cycling life (91% capacity retention after 1000 cycles). This is due to the synergistic effect between the highly exfoliated graphene layers and the porous carbon nanofibers, which can provide massive active Na-storage sites, ensure sufficient electrolyte infiltration, offer open ionic diffusion channels and oriented electronic transfer pathways, and prevent graphene agglomeration as well as carbon nanofiber fracture upon prolonged cycling. The findings shed new insights into the quest for high-performance carbon-based anode materials of sodium-ion batteries. © 2017 The Royal Society of Chemistry.

Ren Y.,University of Science and Technology Beijing | Ding D.-W.,University of Science and Technology Beijing
International Journal of Control, Automation and Systems | Year: 2017

This paper addresses the problem of integrated fault detection and control for two-dimensional (2-D) Roesser systems. A fault detection observer/controller is designed to detect faults in low-frequency domain and satisfy some control specifications simultaneously. By the generalized Kalman-Yakubovich-Popov (KYP) lemma and some useful lemmas, this design problem is formulated as a multiobjective optimization problem. A two-step algorithm is proposed to solve this non-convex problem. The effectiveness of the proposed algorithm is illustrated by a numerical example. © 2017 Institute of Control, Robotics and Systems and The Korean Institute of Electrical Engineers and Springer-Verlag Berlin Heidelberg

Guo J.,University of Science and Technology Beijing | Liu H.,University of Science and Technology Beijing
IET Control Theory and Applications | Year: 2017

This study focuses on a discrete-time Hammerstein system to investigate the identification with quantised inputs and quantised output observations. After the discussion of the system identifiability and by parameterising the static non-linear function, a three-step algorithm is proposed to estimate the unknown parameters for the identifiable system. The strong convergence and the mean-square convergence rate of the algorithm are established. It is shown that the asymptotic efficiency can be achieved in terms of the Cramér-Rao lower bound by selecting a suitable transformation matrix. A numerical simulation is given to demonstrate the effectiveness of the algorithm. © The Institution of Engineering and Technology 2016.

Chen Z.,University of Science and Technology Beijing
International Journal of Advanced Manufacturing Technology | Year: 2017

With the rapid development of digital and flexible manufacturing technologies in the area of aircraft manufacturing, the digital metrologies and measurement data are applied and used not only in the phrase of product inspection but also in the phrases of product design and assembly. A reasonable plan is always needed for making good use of the digital measurement devices due to their complexities. In order to support the measuring planning and measurement data mining activities, in this paper, the digital measurement process is analyzed to build a digital metrology process model (MPM), which illustrates the contents of a measurement process with a three-dimensional structure, and reveals the measurement datum flow chains (MDFC). Then, the paper discusses the approaches of information management and measuring planning based on the metrology process model. To make them applicable, the digital measurement process platform is developed. The complete digital measurement system can be implemented by the DMPP application together with the digital measurement devices. The proposed model and methods provide a theoretically feasible way to effectively employ the digital metrologies in aircraft assembly. © 2017 Springer-Verlag London

Mao L.-F.,University of Science and Technology Beijing
ETRI Journal | Year: 2017

Drain-induced barrier lowering (DIBL) is one of the main parameters employed to indicate the short-channel effect for nano metal-oxide semiconductor field-effect transistors (MOSFETs). We propose a new physical model of the DIBL effect under two-dimensional approximations based on the energy-conservation equation for channel electrons in FETs, which is different from the former field-penetration model. The DIBL is caused by lowering of the effective potential barrier height seen by the channel electrons because a lateral channel electric field results in an increase in the average kinetic energy of the channel electrons. The channel length, temperature, and doping concentration-dependent DIBL effects predicted by the proposed physical model agree well with the experimental data and simulation results reported in Nature and other journals. © 2017 ETRI.

Ma J.,University of Science and Technology Beijing | Qi L.,University of Science and Technology Beijing | Deng L.,University of Science and Technology Beijing
Expert Systems with Applications | Year: 2017

The simulation and analysis of structure within decision making unit (DMU) is the basis on which network data envelopment analysis (DEA) opens the “black box” and evaluates the efficiency of system with complex internal structure. The efficiency measurements of system with sub-DMU in series or with sub-DMUs in parallel are two common cases in the theory development and applications of two-stage DEA. However, the research on parallel-series hybrid system is not rich enough. The paper develops a set of DEA models to treat a two-stage system comprised of three sub-DMUs in hybrid form with additional inputs to the second stage. The proposed models simulate precisely the system's parallel-series internal structure, employ synthetically additive and multiplicative DEA approaches to estimate and decompose the efficiencies of system, and adopt a heuristic method to convert non linear program due to the additional inputs into a linear program. This approach gives more information about the sources of inefficiency by penetrating into the depth of system and modeling the efficiency formation mechanism. A model application is provided. © 2017 Elsevier Ltd

Wang W.-J.,University of Science and Technology Beijing | Liu X.-F.,University of Science and Technology Beijing
Key Engineering Materials | Year: 2017

Surface treated copper foil and its preparation is very important and widely used. The science research and enterprise competition always focus on the surface treated methods in the copper foil field. This paper summarized the typical surface treated processes of copper foil, and emphasized on research progress and problems of copper foil surface treated processes. The brush plating-dealloying treated process of copper foil was proposed based on the problems. The principle and research status of new process was introduced. At last, the future development of surface treated process and application prospect were forecast. © 2017 Trans Tech Publications.

Miao H.,University of Science and Technology Beijing | Li L.,University of Science and Technology Beijing
Proceedings - 2016 9th International Symposium on Computational Intelligence and Design, ISCID 2016 | Year: 2017

This paper describes a resource management and a scheduling policy, spot scheduling algorithm (SpotSA). Infrastructure-as-a-Service providers offers their unused resources in the form of variable-priced virtual machines (VMs), known as 'spot instances', at prices significantly lower than their standard fixed-priced resources. The SpotSA addresses the problem of running deadline-constrained computational jobs on a pool of resources that composed solely of spot instances. The SpotSA considers the differences of spot instances in price and performance so that users can run applications quickly and economically. And the SpotSA is a part of the system architecture. The purpose of this system is to help organizations to run computational jobs on dynamically provisioned resources when these organizations do not have a local cluster of resources. © 2016 IEEE.

Xu Z.,University of Science and Technology Beijing | Wang M.,University of Science and Technology Beijing
2016 IEEE International Conference on Systems, Man, and Cybernetics, SMC 2016 - Conference Proceedings | Year: 2016

For many industrial production processes obeying certain statistical laws, a new method of establishing a SISO control model is put forward based on pattern recognition technology. Firstly, k-means clustering algorithm is used to partition input and output data collected into several classes respectively. Secondly, the distance between two classes is described by the distance of the two class centers. Then the mapping relationship between input and output of the control model is established based on pattern classification technology. And input and output orders of the model are identified by conditional entropy. Lastly experimental results illustrate the feasibility of the modeling method using the data collected from an actual industrial process. © 2016 IEEE.

Wang D.,Beijing University of Posts and Telecommunications | Liao F.,University of Science and Technology Beijing
Proceedings - 2016 8th International Conference on Intelligent Human-Machine Systems and Cybernetics, IHMSC 2016 | Year: 2016

In this paper, the design of multi-model adaptive preview controller for multirate systems with unknown piecewise constant coefficients is investigated. Based on the discrete lifting technique, the multirate system with unknown coefficients is transformed into a single-rate system, and corresponding augmented error system for this single-rate system with unknown coefficients is constructed by preview control theory. According to the direct multi-model adaptive control, a finite set of fixed controllers with preview compensation are derived, and by designing a switching law, an adaptive preview controller for the original systems in a multirate setting is eventually obtained. © 2016 IEEE.

Liu S.,University of Science and Technology Beijing | Huang K.,University of Science and Technology Beijing | Zhu H.,University of Science and Technology Beijing
Separation and Purification Technology | Year: 2017

Source of boron and phosphorus as the impurities in the silicon wiresawing slurry was clearly confirmed by systematical study on their elements content variation in the related materials in the cutting process. Extensive studies were concerned about the recovery of silicon particles in the wiresawing slurry. But there is little attention paid to the metal and nonmetal impurities in the slurry, especially for boron and phosphorus, which would affect the efficiency and reliability of the solar silicon cell. It was experimentally tested that for a typical steel sawing wire the boron content is about 4500 ppmw and phosphorus content is about 1000 ppmw, while in the other materials the content of the both impurities is very low. These impurities would be mixed with the silicon and silicon carbide particles after wiresawing cutting, instead of incorporating in the silicon crystal lattices. So conventional acid leaching was considered for using to effectively remove boron and phosphorus, and it was found that under optimal leaching conditions, the removal percentages of iron, boron and phosphorus were 95.50%, 82.95%, and 86.92%, respectively. © 2016 Elsevier B.V.

Guo M.,University of Science and Technology Beijing | Bhasin A.,University of Texas at Austin | Tan Y.,Harbin Institute of Technology
Construction and Building Materials | Year: 2017

An asphalt mastic imparts most of its characteristics to the asphalt concrete mixture and also dictates several forms of distresses in asphalt mixtures and pavements. Several studies have demonstrated that the interaction between asphalt binder and mineral fillers has a significant impact on the properties and performance of asphalt mastics and mixtures. The objective of this study was to investigate the nature of binder adsorption on mineral filler surface while simultaneously quantifying the influence of such adsorption on the properties of the binder in the immediate vicinity of the interface and bulk. An adsorption test using mineral fillers and binders was conducted to achieve this goal along with measurements of asphaltene content and rheology on the original binder and the residual binder from the adsorption tests. Results show that polar fractions preferentially adhered to the surface of the mineral filler. Such preferential adsorption resulted in a significant increase in the complex modulus of the adsorbed or fixed asphalt with a concomitant decrease in the complex modulus of the free or bulk asphalt binder. These changes in complex modulus varied only slightly as a function of the frequency. The magnitude of adsorption was dictated by the mineral nature of the surface and more importantly by the specific surface area of the particles. The findings from this study are useful to better understand and model the failure mechanisms in the micro structure of asphalt composites. © 2017 Elsevier Ltd

Song R.,University of Science and Technology Beijing | Wei Q.,CAS Institute of Automation | Song B.,University of Science and Technology Beijing
Neurocomputing | Year: 2017

In this paper, a synchronous solution method for multi-player zero-sum games without system dynamics is established based on neural network. The policy iteration (PI) algorithm is presented to solve the Hamilton-Jacobi-Bellman (HJB) equation. It is proven that the obtained iterative cost function is convergent to the optimal game value. For avoiding system dynamics, off-policy learning method is given to obtain the iterative cost function, controls and disturbances based on PI. Critic neural network (CNN), action neural networks (ANNs) and disturbance neural networks (DNNs) are used to approximate the cost function, controls and disturbances. The weights of neural networks compose the synchronous weight matrix, and the uniformly ultimately bounded (UUB) of the synchronous weight matrix is proven. Two examples are given to show that the effectiveness of the proposed synchronous solution method for multi-player ZS games. © 2017 Elsevier B.V.

Xuedong G.,University of Science and Technology Beijing | Kan G.,University of Science and Technology Beijing
Cybernetics and Information Technologies | Year: 2016

The traditional time series studies consider the time series as a whole while carrying on the trend detection; therefore not enough attention is paid to the stage characteristic. On the other hand, the piecewise linear fitting type methods for trend detection are lacking consideration of the possibility that the same node belongs to multiple trends. The above two methods are affected by the start position of the sequence. In this paper, the concept of overlapping trend is proposed, and the definition of milestone nodes is given on its base; these way not only the recognition of overlapping trend is realized, but also the negative influence of the starting point of sequence is effectively reduced. The experimental results show that the computational accuracy is not affected by the improved algorithm and the time cost is greatly reduced when dealing with the processing tasks on dynamic growing data sequence.

Mu Y.,University of Science and Technology Beijing | Bao H.,University of Science and Technology Beijing
Journal of Physics: Conference Series | Year: 2017

In order to obtain a visualization of the complex internal structure of ternary phase diagram, the paper realized a three-dimensional topology model of ternary phase diagram with the designed data structure and improved algorithm, under the guidance of relevant theories of computer graphics. The purpose of the model is mainly to analyze the relationship between each phase region of a ternary phase diagram. The model not only obtain isothermal section graph at any temperature, but also extract a particular phase region in which users are interested. © Published under licence by IOP Publishing Ltd.

Huo W.T.,Northwest Institute for Nonferrous Metal Research | Shi J.T.,University of Science and Technology Beijing | Hou L.G.,University of Science and Technology Beijing | Zhang J.S.,University of Science and Technology Beijing
Journal of Materials Processing Technology | Year: 2017

A simple thermo-mechanical treatment (W-TMT) based on the idea of deformation-enhanced precipitation (DEP) and particle-stimulated nucleation (PSN) of recrystallization was proposed for Al–Zn–Mg–Cu alloy. The AA 7075 alloys were subjected to the proposed W-TMT, conventional hot rolling or a traditional thermo-mechanical treatment (RI-ITMT). During W-TMT, the coarse MgZn2 particles induced by DEP create preferential nucleation sites for recrystallization, and tailoring the sizes of these particles can effectively regulate or control the final grain sizes. Under the same total reduction of 85%, the grain size of W-TMT processed sheet can be decreased to ≤ 10 μm, similar to that of RI-ITMT processed sheet while relatively coarse grains (grain size > 25 μm) were obtained by hot rolling. After peak-aging (T6) treatment, the strength of all processed sheets were identical to each other, yet the fracture elongation of W-TMT processed fine-grained sheet was notably increased to 18.5%, compared to 13.1% for hot rolled sheet with coarse grains. Resultantly, this proposed short-cycled W-TMT processing possesses the synergetic capacity of grain refinement, ductility modification, as well as strength retention for Al–Zn–Mg–Cu alloy. © 2016 Elsevier B.V.

Wang J.,University of Science and Technology Beijing | Song Y.,University of Science and Technology Beijing
Small | Year: 2017

Nanohybrids composed of two or more components exhibit many distinct physicochemical properties and hold great promise for applications in optics, electronics, magnetics, new energy, environment protection, and biomedical engineering. Microfluidic systems exhibit many advantages due to their unique characteristics of narrow channels, variable length, controllable number of channels and multiple integrations. Particularly their spatial-temporarily splitting of the formation stages during nanomaterials formation along the microfluidic channels favors the online control of the reaction kinetic parameters and in situ tuning of the product properties. This Review is focused on the features of the current types of microfluidic devices in the synthesis of different types of nanohybrids based on the classification of the four main kinds of materials: metal, nonmetal inorganic, polymer and composites. Their morphologies, compositions and properties can be adjusted conveniently in these synthesis systems. Synthesis advantages of varieties of microfluidic devices for specific nanohybrids of defined surfaces and interfaces are presented according to their process and microstructure features of devices as compared with conventional methods. A summary is presented, and challenges are put forward for the future development of the microfluidic synthesis of nanohybrids for advanced applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Wang Y.,University of Science and Technology Beijing | Li C.H.,University of Science and Technology Beijing
Rock Mechanics and Rock Engineering | Year: 2017

Researchers have recently realized that the natural fractures in shale reservoirs are often cemented or sealed with various minerals. However, the influence of cement characteristics of natural fracture on fracturing network propagation is still not well understood. In this work, laboratory-scaled experiments are proposed to prepare model blocks with discrete orthogonal fractures network with different strength of natural fracture, in order to reveal the influence of cemented natural fractures on the interactions between hydraulic fractures and natural fractures. A series of true triaxial hydraulic fracturing experiments were conducted to investigate the mechanism of hydraulic fracture initiation and propagation in model blocks with natural fractures of different cement strength. The results present different responses of interactions between hydraulic and natural fractures, which can be reflected on the pump pressure profiles and block failure morphology. For model blocks with fluctuated pump pressure curves, the communication degree of hydraulic and natural fractures is good, which is confirmed by a proposed new index of “P-SRV.” The most significant finding is that too high and too low strength properties of cemented natural fracture are adverse to generate complex fracturing network. This work can help us better understand how cemented natural fractures affect the fracturing network propagation subsurface and give us reference to develop more accurate hydraulic fracturing models. © 2017 Springer-Verlag Wien

Qiao S.,University of Science and Technology Beijing | Shang X.,University of Science and Technology Beijing
Archive of Applied Mechanics | Year: 2017

Three-dimensional scattering and dynamic stress concentration of Lamb-like waves around a spherical inclusion (inhomogeneity and a cavity) in a thick spherical shell are investigated theoretically and numerically. Two spherical coordinates, located at the spherical shell center and the inclusion center, are established to express the incident and scattered wave potential functions. By a kind of addition formulas, all the potential functions can be transformed into the same coordinate, then the analytical solution of the displacements and stresses are derived, and all the undetermined coefficients are solved by satisfying the boundary condition and the interface condition. In order to describe the 3-D stresses concentration, multiple DSCFs are employed and the 3-D distributions are depicted. The results reveal the influences of inclusion material and the cavity on the distributions of DSCFs, and the influence of incident wave frequency and inclusion position are also calculated. This research is expected to provide theoretical understanding on dynamic analysis and mechanical properties evaluation of the spherical shells. © 2017 Springer-Verlag Berlin Heidelberg

Xiong X.,University of Science and Technology Beijing | Tao J.,University of Science and Technology Beijing
Applied Mathematics and Mechanics (English Edition) | Year: 2017

The relationship between stabilities of the buoyancy boundary layers along an inclined plate and a vertical plate immersed in a stratified medium is studied theoretically and numerically. The eigenvalue problem of energy stability is solved with the method of descending exponentials. The disturbance energy is found to be able to grow to 11.62 times as large as the initial disturbance energy for Pr = 0.72 when the Grashof number is between the critical Grashof numbers of the energy stability and the linear stability. We prove that, with a weighted energy method, the basic flow of the vertical buoyancy boundary layer is stable to finite-amplitude streamwise-independent disturbances. © 2017 Shanghai University and Springer-Verlag Berlin Heidelberg

Li L.,University of Science and Technology Beijing | Liao F.,University of Science and Technology Beijing | Deng J.,Leeds Beckett University
Asian Journal of Control | Year: 2017

This paper investigates the problem of H∞ preview tracking control with robust performance for uncertain discrete-time systems. In order to avoid applying the difference operator to the time-varying matrix, by taking advantage of the difference between the system state variables, input variables, and the corresponding auxiliary variables, instead of the usual difference between system states, an augmented error system including previewed information is constructed, which converts the tracking problem into a regulator problem. A sufficient condition based on the free-weighting matrices technique and the Lyapunov stability theory is derived for the robust asymptotic stability of uncertain systems. Moreover, a state feedback control law with preview action design method is obtained via the linear matrix inequality approach. Based on these, a state observer for preview control systems is formulated. Previewable reference signals are fully utilized through reformulation of the output equation while designing the state observer. The proposed construction method of augmented error system is applicable to uncertain discrete-time systems in which the uncertainties are general. Also an integrator is introduced to ensure the closed-loop system tracking performance with no static error. The numerical results also show the effectiveness of the preview control law for uncertain systems in the paper. © 2017 Chinese Automatic Control Society and John Wiley & Sons Australia, Ltd.

Wang H.-B.,University of Science and Technology Beijing | Ren X.-N.,University of Science and Technology Beijing | Tu X.-Y.,University of Science and Technology Beijing
Applied Soft Computing Journal | Year: 2017

In order to obtain better generalization abilities and mitigate the impacts of the best and worst individuals during the process of optimization, this paper suggests Bee and Frog Co-Evolution Algorithm (abbreviation for BFCEA), which combines Mnemonic Shuffled Frog Leaping algorithm With Cooperation and Mutation (abbreviation for MSFLACM) with improved Artificial Bee Colony (abbreviation for ABC). The contrast experimental study about different iteratively updating strategies was acted in BFCEA, including strategy of integrating with ABC, regeneration of the worst frog and its leaping step. The key techniques focus on the first 10 and the last 10 frogs evolving ABC in BFCEA, namely, the synchronous renewal strategy for those winner and loser should be applied, after certain G times’ MSFLACM-running, so as to avoid trapping local optimum in later stage. The ABC evolution process will be called between all memes’ completing inner iteration and all frogs’ outer shuffling, the crossover operation is removed from MSFLACM for its little effect on time-consuming and convergence in this novel algorithm. Besides, in ABC, the scout bee is generated by Cauchy mutating instead at random. The performance of proposed approach is examined by well-known 16 numerical benchmark functions, and obtained results are compared with basic Shuffled Frog Leaping algorithm (abbreviation for SFLA), ABC and four other variants. The experimental results and related application in cloud resource scheduling show that the proposed algorithm is effective and outperforms other variants, in terms of solution quality and convergence, and the improved variants can obtain a lower degree of unbalanced load and relatively stable scheduling strategy of resources in complicated cloud computing environment. © 2017 Elsevier B.V.

We discuss the possibility of breather-to-soliton conversions for a higher-order nonlinear Schrödinger–Maxwell–Bloch system with quintic terms describing the propagation of ultrashort optical pulses, up to the attosecond duration, in an erbium-doped fiber. The analytic forms for the vector breather solutions of that system with complex (not pure imaginary) eigenvalues are obtained with the Darboux transformation. With the special values of the eigenvalues, we find that vector breather solutions can be converted into the vector soliton solutions on the constant (not zero) backgrounds. The condition for such conversion is explicitly derived. We show the interactions between vector breathers and vector solitons. © 2017 Springer Science+Business Media Dordrecht

Ma C.,University of Science and Technology Beijing | Qiao H.,CAS Institute of Automation
Neurocomputing | Year: 2017

This paper investigates the distributed asynchronous event-triggered consensus problem for a class of nonlinear multi-agent systems. The extended dissipative performance index is introduced for solving the consensus problem with disturbances, which can provide H∞, L2−L∞, passivity and dissipative consensus performances by tuning weighting matrices, respectively. Based on model transformation, sufficient consensus conditions are developed and the desired consensus controllers are designed such that the extended dissipative performance can be achieved. Two illustrative examples are utilized to show the effectiveness of the established theoretical method. © 2017 Elsevier B.V.

Peng K.,University of Science and Technology Beijing | Wang M.,University of Science and Technology Beijing | Dong J.,University of Science and Technology Beijing
Neurocomputing | Year: 2017

In this paper, the subspace identification method (SIM) based event-triggered fault detection (FD) is put forward to deal with the process monitoring of networked control systems (NCSs). The core concept is to construct a SIM based event-triggered residual generator. For this purpose, a parity space based residual generator is firstly established directly from test data, instead of the process model. Moreover, the event-triggered strategy is introduced to obtain an event-triggered residual generator, which is of great efficiency to reduce data transmission and guarantee the fault detection accuracy simultaneously. Finally, the application of the proposed method is illustrated by the computer control system of hot strip mill process (HSMP). © 2017 Elsevier B.V.

Wang W.,University of Science and Technology Beijing | Ma W.,University of Science and Technology Beijing | Lai X.,Renmin University of China
Nonlinear Analysis: Real World Applications | Year: 2017

A mathematical model for virus infection dynamics with absorption effect and chemotaxis is proposed to study the repulsion effect on superinfecting virions by infected cells. The basic reproduction number R0 is established. Furthermore, we show that the threshold dynamics can be expressed by the basic reproduction number R0 in a bounded domain. It is shown that the infection-free steady state E0 is asymptotically stable if R0<1, and the virus is uniformly persistent if R0>1 in the case of spatially heterogeneous infections. The stability properties and Turing instability of the proposed model have been extensively discussed for the case of spatially homogeneous infections. In addition, the existence of the travelling wave solutions is discussed in unbounded domain. At last, numerical simulations are carried out to illustrate the main results. © 2016 Elsevier Ltd

Gan M.,University of Science and Technology Beijing | Jiang R.,Tsinghua University
Future Generation Computer Systems | Year: 2017

In big data era people are dependent on a variety of social media to manage their social circles. Many online social networks employ social recommendation as an increasingly important component. Although global and local recommendation methods have achieved remarkable success, current studies seldom consider to play advantages of both in social networks. To demonstrate the effectiveness of incorporating local methods to global ones, we first investigated associations between triangular motifs and existing social relations and found that potential links are related with common relations. Further, we analyzed correlations of all methods and clustered them and found obvious strong correlations among methods with same type, which demonstrated the necessity of taking advantages of both. Consequently, we proposed a novel method FLOWER which resorts to Fisher's combined probability test to systematically calibrate statistical significance of global and local associations. FLOWER utilizes information of social relations in both local and global scopes, which are less correlated with each other, and therefore imply possibilities of different aspects for a candidate link. We demonstrated the effectiveness of FLOWER by considering each possible pairwise combination of six global approaches with two local methods and performing 10-fold cross-validation experiments on five real social network datasets (Facebook,, Epinions, HEP-PH and Delicious). Results show that FLOWER-based methods significantly outperform either their global or local components in accuracy and retrieval performance. © 2017 Elsevier B.V.

Zhang G.-H.,University of Science and Technology Beijing | Zheng W.-W.,University of Science and Technology Beijing | Chou K.-C.,University of Science and Technology Beijing
Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science | Year: 2017

The present study investigated the influences of Na2O and K2O additions on electrical conductivity of blast furnace type CaO-MgO-Al2O3-SiO2 melts by the four-electrode method. Both the single addition of Na2O or K2O and the double additions of Na2O and K2O were studied. It was found that electrical conductivity monotonously increased as the amount of Na2O addition was gradually increased, whereas, when K2O was added, there was a continuous decrease of electrical conductivity. With melts containing both Na2O and K2O, electrical conductivity first decreased but then increased when Na2O was gradually substituted for K2O while keeping the molar fractions of other components constant. In other words, the mixed-alkali effect took place in CaO-Mg-Al2O3-SiO2-ΣR2O melts. © 2017 The Minerals, Metals & Materials Society and ASM International

Li K.,Ghent University | Zhu D.,University of Science and Technology Beijing | Van Deun R.,Ghent University
Dyes and Pigments | Year: 2017

Novel red-emitting phosphors K2BaGe8O18:Mn4+ (KBGO:Mn4+) were synthesized via the high-temperature solid-state reaction method. X-ray diffraction and Rietveld refinements illustrated that pure phase K2BaGe8O18 was obtained from the as-prepared samples. The excitation spectrum of KBGO:0.002Mn4+ monitored at 666 nm showed a wide band with two obvious peaks at 319 and 468 nm. It can be deconvoluted into four bands with maxima at 313, 350, 391 and 462 nm which corresponded to Mn4+-O2- charge transfer, Mn4+ 4A2-4T1, 4A2-2A2 and 4A2-4T2 transitions, respectively. Upon 468 nm excitation, the emission spectrum presented a narrow band from 600 to 700 nm (red region) with the maximum emission around 666 nm, which originated from Mn4+ 2Eg-4A2 transition in GeO6 octahedral environment. Therefore, K2BaGe8O18:Mn4+ phosphor can be considered as a red-emitting component candidate in UV and blue light excited white light-emitting diodes (w-LEDs). © 2017 Elsevier Ltd

Wang J.,University of Science and Technology Beijing | Han D.,Jiangsu University
Physica A: Statistical Mechanics and its Applications | Year: 2017

In recent years, wireless communication plays an important role in our lives. Cooperative communication, is used by a mobile station with single antenna to share with each other forming a virtual MIMO antenna system, will become a development with a diversity gain for wireless communication in tendency future. In this paper, a fitness model of evolution network based on complex networks with mixed attachment mechanisms is devised in order to study an actual network—CCFN (cooperative communication fitness network). Firstly, the evolution of CCFN is given by four cases with different probabilities, and the rate equations of nodes degree are presented to analyze the evolution of CCFN. Secondly, the degree distribution is analyzed by calculating the rate equation and numerical simulation with the examples of four fitness distributions such as power law, uniform fitness distribution, exponential fitness distribution and Rayleigh fitness distribution. Finally, the robustness of CCFN is studied by numerical simulation with four fitness distributions under random attack and intentional attack to analyze the effects of degree distribution, average path length and average degree. The results of this paper offers insights for building CCFN systems in order to program communication resources. © 2016 Elsevier B.V.

Xu J.,University of Science and Technology Beijing | Gu Q.,University of Science and Technology Beijing
EPL | Year: 2017

We study the transverse spin dynamics of trapped polarized Fermi gases in the high-temperature limit. In the non-interacting collisionless regime, a magnetic-field gradient induces collective spin wave oscillations. In the strongly interacting collisional regime, the dynamics are governed by spin diffusion. These two limits have been extensively studied both experimentally and theoretically, but the crossover between them has received less attention. In this paper, we use a quantum Boltzmann equation to study transverse spin dynamics and show how the excitations evolve from dispersive to diffusive in the high-temperature limit. We provide analytical solutions in the two limiting regimes, which agree well with our numerical results. © CopyrightEPLA, 2017.

Li R.,University of Science and Technology Beijing | Mi J.-X.,University of Science and Technology Beijing
Wuli Xuebao/Acta Physica Sinica | Year: 2017

Understanding how the groups at interface influence the friction of carbon nanotubes can provide reference for their applications. In this paper, we investigate the influences of hydroxyls on motion and friction of carbon nanotube on graphite substrate by molecular dynamics simulation. The simulation cases include the ideal vertical carbon nanotube on the ideal graphite substrate, the ideal vertical carbon nanotube on the graphite with hydroxyls on the top layer, the carbon nanotube and the graphite both with hydroxyls on the surface. The results show that the lateral force of carbon nanotube changes when hydroxyls are introduced into the interfaces. If hydroxyls are only on the graphite, the fluctuation of lateral force increases obviously. The reason can be attributed to the increase of atomic surface roughness. Moreover, due to the small contact area between vertical aligned carbon nanotube and substrate, the mean friction becomes raised with hydroxyl content increasing, which is different from the conclusion obtained from silicon tip sliding on graphene with hydrogen on the surface. In that case, owing to the large contact area, the mean friction of tip reaches a maximum value at hydrogen content in a range between 5 and 10% because of the competition between the increase in the number of hydrogen atoms and the weakening of the interlock due to the increase in separation of tip from substrate. Hydrogen bond and Coulomb force appear between interfaces when hydroxyls are both on carbon nanotube and on graphite, which significantly increases friction force on carbon nanotube. And slip interfaces translate rapidly from between carbon nanotube and graphite into between graphite layers. Like the case with hydroxyls only on the graphite, the sliding of carbon nanotube perpendicular to the initial velocity also occurs when carbon nanotube and graphite are both with hydroxyls. This phenomena can be explained as the fact that the introduction of hydroxyls breaks the equilibrium of the force on the carbon nanotube in the Y direction. Moreover, the random distribution of hydroxyls causes the random motion of the carbon nanotube. © 2017 Chinese Physical Society.

Song R.,University of Science and Technology Beijing | Wei Q.,CAS Institute of Automation
Chinese Physics B | Year: 2017

We develop an optimal tracking control method for chaotic system with unknown dynamics and disturbances. The method allows the optimal cost function and the corresponding tracking control to update synchronously. According to the tracking error and the reference dynamics, the augmented system is constructed. Then the optimal tracking control problem is defined. The policy iteration (PI) is introduced to solve the min-max optimization problem. The off-policy adaptive dynamic programming (ADP) algorithm is then proposed to find the solution of the tracking Hamilton-Jacobi-Isaacs (HJI) equation online only using measured data and without any knowledge about the system dynamics. Critic neural network (CNN), action neural network (ANN), and disturbance neural network (DNN) are used to approximate the cost function, control, and disturbance. The weights of these networks compose the augmented weight matrix, and the uniformlyultimately bounded (UUB) of which is proven. The convergence of the tracking error system is also proven. Two examples are given to show the effectiveness of the proposed synchronous solution method for the chaotic system tracking problem.

Hao Y.,University of Science and Technology Beijing
European Physical Journal D | Year: 2017

Abstract: We investigate the ground state properties of anti-ferromagnetic spin-1 Bose gases in one dimensional harmonic potential from the weak repulsion regime to the strong repulsion regime. The Hamiltonian is diagonalized in the Hilbert space composed of the single particle wavefunctions and spin components. With the numerical diagonalization method, the density distributions, magnetization distribution, one body density matrix, and momentum distribution for each component are obtained. It is shown that the spinor Bose gases of different magnetization exhibit the same total density profiles in the full interaction regime, which evolve from the single peak structure embodying the properties of Bose gases to the fermionized shell structure of spin-polarized fermions. But each component displays different density profiles, and magnetic domains emerge in the strong interaction limit for M = 0.25. In the strong interaction limit, one body density matrix and the momentum distributions exhibit the same behaviour as those of spin-polarized fermions. The fermionization of momentum distribution takes place, in contrast to the δ-function-like distribution of single component Bose gases in the full interaction regime. Graphical abstract: [Figure not available: see fulltext.] © 2017, EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg.

Jiang H.,University of Science and Technology Beijing | Zhu J.,University of Science and Technology Beijing
Chinese Physics B | Year: 2017

The magnetomechanical behavior of single-crystal Galfenol alloy was found to be strongly dependent on the loading paths. An energy-based anisotropic domain rotation model, assuming that the interaction between domains can be ignored and the probability of the magnetic moment pointing along a particular direction is related to the free energy along this direction, is used to simulate the magnetostriction versus magnetic field and stress curve and to track the magnetic domain motion trail. The main reason for loading path dependent effect is the rotation/flipping of the magnetic domains under different loading paths. The effect of loading and unloading paths on 90° magnetic domain motion was studied by choosing different loading and unloading state and paths. The results show that prior loading magnetic field can make the 90° magnetic domains flip to the directions of 45° domains because the magnetic field is the driving force to make the domains rotate, and the final loading state and the loading path both have great influence on the motion of 90° magnetic domains. © 2017 Chinese Physical Society and IOP Publishing Ltd.

Yu H.,University of Science and Technology Beijing | Hu C.,University of Science and Technology Beijing
Proceedings - 2016 IEEE 1st International Conference on Data Science in Cyberspace, DSC 2016 | Year: 2016

Police big data analytics is a hot issue. This paper designs a police big data analytics platform aiming to efficiently analyze and utilize police big data. This platform is based on the key technologies of big data analytics and has a four-layer structure: data acquisition, data storage, processing analytics and application service. Furthermore, this paper presents usage scenarios, application cases and platform construction strategies by considering the actualities of police work. Overall, this paper provides an insight into big data analytics for police. © 2016 IEEE.

Tian L.,University of Science and Technology Beijing | Mu Z.,University of Science and Technology Beijing
Proceedings - 2016 9th International Congress on Image and Signal Processing, BioMedical Engineering and Informatics, CISP-BMEI 2016 | Year: 2016

Ear recognition is gaining on popularity in recent years. The human ear are neither affected by expressions like faces are nor do need closer touching like finger-prints do. In this paper, a novel algorithm was proposed to do ear recognition using deep convolutional neural network and provide a visualization of the learned network. We design a convolutional neural network with three convolutional layers, a fully-connected layer and a soft-max classifier. The experimental results on USTB ear database indict that our proposed method is easier botain high accuracy and outperforms the traditional method in dealing with partial occlusion. © 2016 IEEE.

News Article | April 17, 2017

XI'AN, China--(BUSINESS WIRE)--Forbes announced its list of “Forbes 30 under 30 Asia” of 2017, the annual ranking of Asia’s brightest young entrepreneurs, innovators and game changers. Yeahmobi CEO Xiaowu Zou is named in the list, based on his outstanding performance on entrepreneurship. Forbes sifted through thousands of nominations and then convened a panel of judges – from Kaifu Lee and Jean Liu to Jimmy Choo and Sonny Bill Williams to bring out the list. The Asian list is a continuation of the global expansion of the Forbes 30 under 30 franchise – a franchise that includes alumni such as Palmer Luckey from Oculus, Evan Spiegel and Bobby Murphy from Snapchat, basketball superstar LeBron James and K-pop star G-Dragon. Forbes’s announcement remarked Zou’s outstanding performance managing Chinese marketing company Yeahmobi. The company reported a profit of $13 million on revenues of $93 million last year. Throughout the process of startup, Zou holds on to one opinion: to find the thing he truly loves. As the now 29-year-old entrepreneur said in an interview, startup is a long and arduous paths, with numerous setbacks and obstacles awaiting. The weapon used to conquer the route is to be clear that what you do is what you truly love to do. Zou claims he made through the difficult path bearing in mind that marketing and connecting good products with potential users is where his true passion lies on. Like many young Chinese students, after obtaining Bachelor’s degree from the University of Science and Technology Beijing, Zou chose to seek further education abroad. He went to the University of Arizona and obtained Master’s degree there. During his studies abroad, Zou started the business specialized in marketing, monetizing traffic of his blog. He soon accumulated his first bucket of gold, and went back China to found his overseas marketing company Yeahmobi with several friends. Now Yeahmobi grows to a world’s leading mobile advertising platform designated to help mobile technology companies, app developers and e-commerce platforms to acquire active users, monetize inventory and reach rapid growth in new markets. The company also won “best mobile ad service” and “mobile champion of China channel partner” titles from Google, and on mobile marketing analytics platform AppsFlyer’s performance index, ranked 12th among global counterparts.

Li H.-Y.,Huafan University | Weng W.-C.,Huafan University | Yan W.-M.,National University of Tainan | Wang X.-D.,University of Science and Technology Beijing
Journal of Power Sources | Year: 2011

This work establishes three-dimensional transient numerical models of proton exchange membrane fuel cells (PEMFCs) with different cathode flow field designs. Exactly how flow field design and voltage loading affect the transient characteristics of the PEMFCs are examined. When the operating voltage instantaneously drops from 0.7 V to 0.5 V, the electrochemical reactions increase. To ensure sufficient oxygen supply for the fuel cell, the oxygen mass fractions are high in the cathode gas diffusion and cathode catalyst layers, causing overshoot of the local current density distribution. When the operating voltage suddenly increases from 0.5 V to 0.7 V, the electrochemical reactions become mild, and furthermore the oxygen mass fraction distribution becomes low, leading to undershoot of the local current density distribution. The transient response time required to reach the steady state for the parallel flow field with baffle design is longest in the event of overshoot or undershoot among the different cathode flow field designs. The overshoot or undershoot phenomena become more obvious with larger voltage loading variations. Moreover, the transient response time for the Z-type flow field with baffle design is longer than for the Z-type flow field design. © 2010 Elsevier B.V. All rights reserved.

Pan G.,Beijing Normal University | Zhu J.,Beijing Normal University | Ma S.,Beijing Normal University | Sun G.,Beijing Normal University | And 2 more authors.
ACS Applied Materials and Interfaces | Year: 2013

Cobalt is a promising soft metallic magnetic material used for important applications in the field of absorbing stealth technology, especially for absorbing centimeter waves. However, it frequently presents a weak dielectric property because of its instability, aggregation, and crystallographic form. A method for enhancing the electromagnetic property of metal Co via phase-controlled synthesis of Co nanostructures grown on graphene (GN) networks has been developed. Hexagonal close-packed cobalt (α-Co) nanocrystals and face-centered cubic cobalt (β-Co) nanospheres with uniform size and high dispersion have been successfully assembled on GN nanosheets via a facile one-step solution-phase strategy under different reaction conditions in which the exfoliated graphite oxide (graphene oxide, GO) nanosheets were reduced along with the formation of Co nanocrystals. The as-synthesized Co/GN nanocomposites showed excellent microwave absorbability in comparison with the corresponding Co nanocrystals or GN, especially for the nanocomposites of GN and α-Co nanocrystals (the reflection loss is -47.5 dB at 11.9 GHz), which was probably because of the special electrical properties of the cross-linked GN nanosheets and the perfect electromagnetic match in their microstructure as well as the small particle size of Co nanocrystals. The approach is convenient and effective. Some magnetic metal or alloy materials can also be prepared via this route because of its versatility. © 2013 American Chemical Society.

Wang H.,University of Science and Technology Beijing | Qian K.,Peking University | Wang K.,University of Science and Technology Beijing | Bian Y.,University of Science and Technology Beijing | And 2 more authors.
Chemical Communications | Year: 2011

Homoleptic tetrakis[2,3,9,10,16,17,23,24-octa(butyloxy)phthalocyaninato] dysprosium-cadmium quadruple-decker complex 1 was isolated in relatively good yield of 43% from a simple one-pot reaction. This compound represents the first sandwich-type tetrakis(phthalocyaninato) rare earth-cadmium quadruple-decker SMM that has been structurally characterized. © The Royal Society of Chemistry 2011.

Chen Y.,University of Science and Technology Beijing | Yu H.,Peking University | Zhang L.,Peking University | Yang H.,University of Science and Technology Beijing | And 2 more authors.
Chemical Communications | Year: 2014

A series of photoresponsive halogen-bonded liquid crystals (LCs) were successfully constructed using molecular halogen and azopyridine compounds, which show interesting properties of photoinduced phase transition upon UV irradiation. In addition, bromine-bonded LCs were first obtained with high mesophase stability. This journal is © the Partner Organisations 2014.

Yin X.-C.,University of Science and Technology Beijing | Yin X.,University of Science and Technology Beijing | Huang K.,Xi'an Jiaotong - Liverpool University | Hao H.-W.,CAS Institute of Automation
IEEE Transactions on Pattern Analysis and Machine Intelligence | Year: 2014

Text detection in natural scene images is an important prerequisite for many content-based image analysis tasks. In this paper, we propose an accurate and robust method for detecting texts in natural scene images. A fast and effective pruning algorithm is designed to extract Maximally Stable Extremal Regions (MSERs) as character candidates using the strategy of minimizing regularized variations. Character candidates are grouped into text candidates by the single-link clustering algorithm, where distance weights and clustering threshold are learned automatically by a novel self-training distance metric learning algorithm. The posterior probabilities of text candidates corresponding to non-text are estimated with a character classifier; text candidates with high non-text probabilities are eliminated and texts are identified with a text classifier. The proposed system is evaluated on the ICDAR 2011 Robust Reading Competition database; the f -measure is over 76%, much better than the state-of-the-art performance of 71%. Experiments on multilingual, street view, multi-orientation and even born-digital databases also demonstrate the effectiveness of the proposed method. Finally, an online demo of our proposed scene text detection system has been set up at scene-text-detection/. © 2013 IEEE.

Chen W.,University of Science and Technology Beijing | Chen W.,Xidian University | Li X.,Baoji University of Arts And Sciences | Ren W.,University of California at Riverside | Wen C.,Nanyang Technological University
IEEE Transactions on Automatic Control | Year: 2014

This note addresses the adaptive consensus problem of first-order and second-order linearly parameterized multi-agent systems with unknown identical control directions. First, we propose a new Nussbaum-type function based on which a key lemma is established. The lemma plays an important role in analyzing the consensus of the closed-loop multi-agent systems. Second, the Nussbaum-type function is used to design adaptive control laws for first-order and second-order linearly parameterized multi-agent systems so that each agent seeks for the unknown control direction adaptively and cooperatively. Then, under the assumption that the interconnection topology is undirected and connected, it is proved that the first-order and second-order multi-agent systems can achieve consensus by choosing proper design parameters. Two simulation examples are given to illustrate the effectiveness of the proposed control laws. © 1963-2012 IEEE.

Yang H.,University of Science and Technology Beijing | Jing L.,University of Science and Technology Beijing | Zhang B.,Peking University
Journal of Hazardous Materials | Year: 2011

A technique with coal-based direct reduction followed by magnetic separation is presented in this study for recovering and reusing iron otherwise wasted in vanadium tailings. Process parameters such as usage of additives, tailings/reductant/additives ratio, reduction temperature and time, as well as particle size were experimentally determined. The optimum process parameters were proposed as follows: using lime as the additive, lignite as the reductant, weight ratios of vanadium tailings/lignite/lime at 100:30:10, reduction roasting at 1200. °C for 60. min, and particle size of 98% less than 30. μm in the final roasted product feeding to magnetic separation. Under these conditions, a magnetic concentrate containing 90.31% total iron and 89.76% metallization iron with a total iron recovery rate of 83.88% was obtained. In addition, mineralography of vanadium tailings, coal-based reduction product and magnetic concentrate were studied by X-ray powder diffraction technique (XRD). The microstructures of above products were analyzed by scanning electron microscope (SEM) to help understand the mechanism. © 2010 Elsevier B.V.

Yang W.,CAS Beijing National Laboratory for Molecular | Yang W.,Shanghai University | Li J.,CAS Beijing National Laboratory for Molecular | Wang Y.,Shanghai University | And 4 more authors.
Chemical Communications | Year: 2011

Anatase TiO2 nanosheets-based hierarchical spheres with over 90% {001} facets synthesized via a diethylene glycol-solvothermal route were used as photoanodes of dye-sensitized solar cells, which generated an energy conversion efficiency of 7.51%. © 2011 The Royal Society of Chemistry.

Zhou E.P.,University of Science and Technology Beijing | Lu J.G.,University of Science and Technology Beijing | Tong H.,Chinese Academy of Sciences | Xu R.X.,University of Science and Technology Beijing | Xu R.X.,Peking University
Monthly Notices of the Royal Astronomical Society | Year: 2014

Glitch (sudden spin-up) is a common phenomenon in pulsar observations. However, the physical mechanism of glitch is still a matter of debate because it depends on the puzzle of pulsar's inner structure, i.e. the equation of state of dense matter. Some pulsars (e.g. Vela like) show large glitches (Δν/ν ~ 10-6) but release negligible energy, whereas the large glitches of AXPs/SGRs (anomalous X-ray pulsars/soft gamma repeaters) are usually (but not always) accompanied with detectable energy releases manifesting as X-ray bursts or outbursts.We try to understand this aspect of glitches in a starquake model of solid quark stars. There are two kinds of glitches in this scenario: bulk-invariable (type I) and bulk-variable (type II) ones. The total stellar volume changes (and then energy releases) significantly for the latter but not for the former. Therefore, glitches accompanied with X-ray bursts (e.g. that of AXP/SGRs) could originate from type II starquakes induced probably by accretion, while the others without evident energy release (e.g. that of Vela pulsar) would be the result of type I starquakes due to, simply, a change of stellar ellipticity. © 2014 The Authors.Published by Oxford University Press on behalf of the Royal Astronomical Society.

Feng Y.,Peking University | Zhang M.,University of Science and Technology Beijing | Guo M.,University of Science and Technology Beijing | Wang X.,Peking University
Crystal Growth and Design | Year: 2010

With the introduction of poly ethylene glycol (PEG) (10000), relatively well dispersed and oriented ZnO microrod arrays and ZnO microsphere arrays were successfully synthesized on unmodified indium tin oxide (ITO) substrate by a hydrothermal method. The growth behaviors of the two different kinds of ZnO arrays were experimentally investigated with variations of PEG addition and the precursor solution's concentration. The PEG-assisted growth mechanism of ZnO microrod arrays and ZnO microsphere arrays has also been carefully discussed. Both the dissolved state of PEG and the interaction between PEG and ZnO crystalline grains were found to play important roles in the fabrication of the two different ZnO structure arrays. The research on PEG-assisted growth mechanism for these two kinds of ZnO structure arrays will provide more theoretical references for preparations of ZnO one-dimensional rod arrays and other kinds of assembled structures on the substrate. © 2010 American Chemical Society.

Xu T.,Control Iron and Steel Research Institute, China | Zheng L.,University of Science and Technology Beijing | Wang K.,Control Iron and Steel Research Institute, China | Misra R.D.K.,University of Louisiana at Lafayette
International Materials Reviews | Year: 2013

The review is aimed at presenting a unified approach in understanding the mechanism of nonequilibrium grain boundary segregation, which can satisfactorily describe the three types of intergranular embrittlement, namely, reverse temper embrittlement of steels, intergranular corrosion embrittlement of stainless steels and intermediate temperature embrittlement of metals and alloys. The review starts with a broad perspective of non-equilibrium grain boundary segregation, including thermally induced non-equilibrium grain boundary segregation and stress induced non-equilibrium grain-boundary segregation. Next, it focuses on the recent progress made in the non-equilibrium grain boundary segregation, including (1) critical time, (2) segregation peak temperature, (3) segregation peak temperature movement for thermally induced and stress induced non-equilibrium grain boundary segregation, and (4) the effect of temperature difference on thermally-induced non-equilibrium grain boundary segregation. Next, the attention is focused on the grain boundary coverage of elements and intergranular embrittlement phenomena. Three types of intergranular embrittlement is analysed in terms of (1) the ductility healing effect induced by the critical time, (2) embrittlement peak or ductility trough induced by the segregation peak temperature, (3) embrittlement peak or ductility trough movement induced by the segregation peak temperature movement and (4) widening and deepening of ductility trough induced by differences in temperature. These experimental phenomena concerning the three types of intergranular embrittlement are consistent with the models of thermally induced and stress induced non-equilibrium grain boundary segregations of impurities, instead of precipitation or equilibrium grain boundary segregation. Towards the end, we visit the subject of grain boundary segregation and associated embrittlement process from the viewpoint of fracture resistance and briefly discuss different perspectives that are of practical significance. © 2013 Institute of Materials, Minerals and Mining and ASM International.

Zhang Z.,University of Science and Technology Beijing | Long K.,University of Science and Technology Beijing | Wang J.,City University of Hong Kong | Dressler F.,University of Innsbruck
IEEE Communications Surveys and Tutorials | Year: 2014

Inspired by swarm intelligence observed in social species, the artificial self-organized networking (SON) systems are expected to exhibit some intelligent features (e.g., flexibility, robustness, decentralized control, and self-evolution, etc.) that may have made social species so successful in the biosphere. Self-organized networks with swarm intelligence as one possible solution have attracted a lot of attention from both academia and industry. In this paper, we survey different aspects of bio-inspired mechanisms and examine various algorithms that have been applied to artificial SON systems. The existing well-known bio-inspired algorithms such as pulse-coupled oscillators (PCO)-based synchronization, ant-and/or bee-inspired cooperation and division of labor, immune systems inspired network security and Ant Colony Optimization (ACO)-based multipath routing have been surveyed and compared. The main contributions of this survey include 1) providing principles and optimization approaches of variant bio-inspired algorithms, 2) surveying and comparing critical SON issues from the perspective of physical-layer, Media Access Control (MAC)-layer and network-layer operations, and 3) discussing advantages, drawbacks, and further design challenges of variant algorithms, and then identifying their new directions and applications. In consideration of the development trends of communications networks (e.g., large-scale, heterogeneity, spectrum scarcity, etc.), some open research issues, including SON designing tradeoffs, Self-X capabilities in the 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE)/LTE-Advanced systems, cognitive machine-to-machine (M2M) self-optimization, cross-layer design, resource scheduling, and power control, etc., are also discussed in this survey. © 2014 IEEE.

Xie H.,University of Science and Technology Beijing | Zhang C.,University of Science and Technology Beijing | Zou K.,University of Science and Technology Beijing
Renewable and Sustainable Energy Reviews | Year: 2012

Solar energy utilization can not only decrease conventional energy consumption but also reduce environmental pollution. China has abundant solar energy resources and has the biggest solar water heater market in the world, so it is necessary for Chinese government to enact incentive policies and measures to enlarge the utilization scale of solar water heaters. According to international experience, solar obligation is probably the most powerful instrument for promoting the use of solar thermal in buildings and expanding the solar water heater market. Currently, there are many provinces and cities in China having adopted the solar obligation, leading to the discussion of solar obligation at national level. This paper firstly analyzed basic conditions to implement the solar obligations in China. Then, 34 provinces and cities' local regulations were reviewed and main problems of them were analyzed. According to domestic and international practices, some recommendations for the design and implementation of solar obligations at national level were induced at the end. © 2011 Elsevier Ltd. All rights reserved.

Qiu J.,Peking University | Guo M.,University of Science and Technology Beijing | Feng Y.,Peking University | Wang X.,Peking University
Electrochimica Acta | Year: 2011

Branched hierarchical ZnO nanowire arrays are synthesized on fluorine-doped tin oxide (FTO) substrate via a two-step electrochemical deposition process, which involves the electrodeposition of ZnO nanowire arrays on conductive glass substrate, followed by the electrochemical growth of ZnO nanorod branches on the backbones of the primary ZnO nanowires. The formation mechanism of the branched hierarchical nanostructure is discussed. It is demonstrated that coating the primary nanowire arrays with ZnO nanoparticles seed layer plays a key role in synthesising the branched hierarchical ZnO nanostructure. By adjusting the concentration of Zn(CH3COO)2 colloid in coating process and the reaction time of the second-step deposition, the density and the length of the secondary nanorod branches in the hierarchical nanostructures can be both varied. Moreover, the photoelectrochemical properties of the dye-sensitized solar cell (DSSC) based on branched hierarchical ZnO nanowire arrays are investigated. Due to the enlargement of the internal surface area within the branched nanostructure photoelectrode, the DSSC consisting of branched hierarchical ZnO nanowire arrays yields a power conversion efficiency of 0.88%, which is almost twice higher than that of the DSSC fabricated using bare ZnO nanowire arrays. © 2011 Elsevier Ltd. All rights reserved.

Zhang L.X.,Beijing Normal University | Song B.,University of Science and Technology Beijing | Chen B.,Beijing Normal University
Journal of Cleaner Production | Year: 2012

The Chinese government has increasingly turned to agricultural industry policy as a means of promoting rural development, which have not necessarily led to an improvement in rural incomes nor to the achievement of other social and environmental goals. Emergy synthesis methods were applied to four agricultural production systems, i.e.; two local traditional production systems as maize plantation and pond fish farming, one scaled Shaoxing duck (Anas Platyrhyncha var. domestica) rearing system, and one newly introduced specialty production system of common mushroom (Agaricus Bisporus) cultivation, in Weishan county of Shandong province of China in the year 2007, to assess and compare their environmental performances. Additionally, aiming at understanding the benefits and driving forces of agricultural diversification, environmental performance results were contrasted with traditional economic indicators. As indicated by EYR, ELR and ESI, it can be clearly shown that the scaled duck rearing and newly introduced common mushroom cultivation alternatives are not in a sustainable pattern, although having better economic performance than maize cropping and pond fish farming. Nevertheless, the development of rural agricultural diversification is also affected by land accessibility, investment ability and even labor availability. Therefore, achieving a profitable and environmental sustainable diversified farming system is not an easy task in Weishan area as well as in whole China. It is unwise to encourage development of agricultural diversification in current manners without too much consideration on environmental degradation. © 2011 Elsevier Ltd. All rights reserved.

Fang Y.,Peking University | Wang C.,Peking University | Su S.,University of Science and Technology Beijing | Yu H.,University of Science and Technology Beijing | Huang Y.,Peking University
Organic and Biomolecular Chemistry | Year: 2014

We described two orthogonal heterocycle syntheses, where an arene bearing both an alkyne and a triazene functionality underwent two distinct cyclization pathways mediated by different transition metals. Starting from the same substrates, a synthesis of 2H-indazole was accomplished by a Cu(ii) salt promoted oxidative cyclization, while 2-substituted indoles could be accessed via a Ag(i) salt mediated N-N bond cleavage. This method represents the first synthesis of indoles from alkynyl triazenes. Computational analysis was performed for both reaction pathways, supporting a Lewis acid role for Cu and a π-acid catalysis for Ag. This journal is © The Royal Society of Chemistry.

Wang V.,Xi'an University of Technology | Kawazoe Y.,Tohoku University | Kawazoe Y.,RAS Kutateladze Institute of Thermophysics | Geng W.T.,University of Science and Technology Beijing | Geng W.T.,Psi Quantum Materials LLC
Physical Review B - Condensed Matter and Materials Physics | Year: 2015

Using hybrid density functional theory combined with a semiempirical van der Waals dispersion correction, we have investigated the structural and electronic properties of vacancies and self-interstitials in defective few-layer phosphorene. We find that both a vacancy and a self-interstitial defect are more stable in the outer layer than in the inner layer. The formation energy and transition energy of both a vacancy and a self-interstitial P defect decrease with increasing film thickness, mainly due to the upward shift of the host valence band maximum in reference to the vacuum level. Consequently, both vacancies and self-interstitials could act as shallow acceptors, and this well explains the experimentally observed p-type conductivity in few-layer phosphorene. On the other hand, since these native point defects have moderate formation energies and are stable in negatively charged states, they could also serve as electron compensating centers in n-type few-layer phosphorene. © 2015 American Physical Society

Chen L.,Peking University | Zhang X.-R.,Peking University | Zhang X.-R.,Doshisha University | Cao S.,University of Science and Technology Beijing | Bai H.,University of Science and Technology Beijing
International Journal of Heat and Mass Transfer | Year: 2012

Natural convective flow of supercritical fluid has become hot topic both in scientific research and engineering applications. Natural circulation thermosyphon using supercritical/trans-critical CO 2 can be a potential substitute for effective transportation of heat and mass without valves/pumping devices. This paper presents numerical investigations into the effect of unsteady heat input on the trans-critical CO 2 thermosyphon, including sudden/quick increase of heat input, gradual/slow increase of heat input and sudden decrease of heat input. Those unsteady input situations are often seen in real applications and have become the core problem of efficiency and safety improvement. In the present study, two-dimensional rectangular natural circulation loop model is set up and numerically investigated. New heat transport model aiming at trans-critical thermosyphon heat input and system stability laws is proposed with supercritical/trans-critical turbulence model incorporated. It is found that when compared with supercritical CO 2 condition, trans-critical CO 2 thermosyphon has quite different behaviors. Natural convective thermosyphon stability is found to be of routinely dependent for different heat input change mode. Stability factors of natural convective trans-critical CO 2 flow and its implications on real system control are also discussed in this paper. © 2012 Elsevier Ltd. All rights reserved.

Hsieh Y.-H.,National Chiao Tung University | Liou J.-M.,National Cheng Kung University | Huang B.-C.,National Sun Yat - sen University | Liang C.-W.,National Chiao Tung University | And 5 more authors.
Advanced Materials | Year: 2012

In strongly correlated oxides, heterointerfaces, manipulating the interaction, frustration, and discontinuity of lattice, charge, orbital, and spin degrees of freedom, generate new possibilities for next generation devices. In this study, existing oxide heterostructures are examined and local conduction at the BiFeO3-CoFe2O4 vertical interface is found. In such hetero-nanostructures the interface cannot only be the medium for the coupling between phases, but also a new state of the matter. This study demonstrates a novel concept on for oxide interface design and opens an alternative pathway for the exploration of diverse functionalities in complex oxide interfaces. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Zhang G.-H.,University of Science and Technology Beijing | Chou K.-C.,University of Science and Technology Beijing | Chou K.-C.,Shanghai University
Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science | Year: 2010

The electrical conductivity of oxide melts is an important physicochemical property for designing the electric smelting furnaces. Although the data of many slag systems have been measured, the quantitative relationships of electrical conductivity to slag composition and temperature are still limited. In this article, a model is proposed based on the optical basicity corrected for the cations required for the charge balance of AlO4 -5, in which Arrhenius Law is used to describe the relationship between electrical conductivity and temperature. In this model, the activation energy is expressed as a linear function of the corrected optical basicity. Successful applications to CaO-MgO-Al2O3-SiO2 and CaO-Al 2O3-SiO2 systems indicate that this model can work well in the electrical conductivity estimation. © The Minerals, Metals & Materials Society and ASM International 2009.

Zhang L.X.,Beijing Normal University | Wang C.B.,Beijing Normal University | Song B.,University of Science and Technology Beijing
Journal of Cleaner Production | Year: 2013

Given the rising expectations for the substitution of fossil energy with renewable energy as one of the solutions to cope with climate change, the carbon emission reduction potential of possible solutions should be evaluated in a holistic and systematic way. In this paper, a systematic account of carbon emission reduction potential was conducted for a typical household biogas system with a digester volume of 8 m3, using a hybrid life-cycle assessment method. Using a 20 year operation scenario, the total life cycle CO2 emission of this family-size biogas utilization system is 2.60 tons, i.e., 0.02 kg CO2/MJ, of which 98.46% is attributed to indirect emissions from building materials and labor inputs. Considering the carbon emission savings due to energy and fertilizer substitution, the annual CO2 emission reduction potential is 1.25 tons for the biogas system that is under consideration. Consequently, such rural household biogas systems should be operated for at least 1.78 years to achieve a positive reduction benefit, i.e., cumulative CO2 emission savings could offset the life-cycle-related CO2 emissions. The results also indicate that long-term, stable running and maintenance are key points to maximize the benefits of household biogas as an effective approach for carbon emission abatement in the rural areas of China. © 2012 Elsevier Ltd. All rights reserved.

Ren H.,University of Science and Technology Beijing | Yu R.,University of Science and Technology Beijing | Wang J.,CAS Institute of Process Engineering | Jin Q.,CAS Institute of Process Engineering | And 6 more authors.
Nano Letters | Year: 2014

Herein, uniform multishelled TiO2 hollow microspheres were synthesized, especially 3- and 4-shelled TiO2 hollow microspheres were synthesized for the first time by a simple sacrificial method capable of controlling the shell thickness, intershell spacing, and number of internal multishells, which are achieved by controlling the size, charge, and diffusion rate of the titanium coordination ions as well as the calcination process. Used as anodes for lithium ion batteries, the multishelled TiO2 hollow microspheres show excellent rate capacity, good cycling performance, and high specific capacity. A superior capacity, up to 237 mAh/g with minimal irreversible capacity after 100 cycles is achieved at a current rate of 1 C (167.5 mA/g), and a capacity of 119 mAh/g is achieved at a current rate of 10 C even after 1200 cycles. © 2014 American Chemical Society.

Dong J.,University of Science and Technology Beijing | Wang Y.,University of Science and Technology Beijing | Zhang J.,University of Science and Technology Beijing | Zhan X.,Peking University | And 3 more authors.
Soft Matter | Year: 2013

Multiple stimuli-responsive polymeric micelles that can respond to light, temperature and pH have been prepared by a novel polymer, pyrene-functionalized poly (dimethylaminoethyl methacrylate), where the pyrene-quaternized segments form a light-responsive shell and the unquaternized segments form a temperature/pH-responsive core. Under UV irradiation, the micelles could be dissociated; when the temperature increased above the lower critical solution temperature, the micelles shrunk. At pH 3, the micelles could be swelled/dissociated and at pH 10, the micelles could be collapsed to complex micelles. The controlled release of Nile Red from the micelle under stimuli was demonstrated. This novel multiple stimuli-responsive micelle shows potential as a new nanocarrier and delivery system. © The Royal Society of Chemistry 2013.

Xie X.,Henan Polytechnic University | Ma H.,Northeastern University China | Zhao Y.,Shenyang Institute of Engineering | Ding D.-W.,University of Science and Technology Beijing | Wang Y.,Northeastern University China
IEEE Transactions on Fuzzy Systems | Year: 2013

This paper proposes relaxed stabilization conditions of discrete-time nonlinear systems in the Takagi-Sugeno (T-S) fuzzy form. By using the algebraic property of fuzzy membership functions, a novel nonparallel distributed compensation (non-PDC) control scheme is proposed based on a new class of fuzzy Lyapunov functions. Thus, relaxed stabilization conditions for the underlying closed-loop fuzzy system are developed by applying a new slack variable technique. In particular, some existing fuzzy Lyapunov functions and non-PDC control schemes are special cases of the new Lyapunov function and fuzzy control scheme, respectively. Finally, two numerical examples are provided to illustrate the effectiveness of the proposed method. © 2012 IEEE.

Ma H.,Cisco Systems | Bastani F.,Massachusetts Institute of Technology | Yen I.-L.,University of Texas at Dallas | Mei H.,University of Science and Technology Beijing
IEEE Transactions on Services Computing | Year: 2013

Service-oriented architecture provides a framework for achieving rapid system composition and deployment. To satisfy different system QoS requirements, it is possible to select an appropriate set of concrete services and compose them to achieve the QoS goals. In addition, some of the services may be reconfigurable and provide various QoS tradeoffs. To make use of these reconfigurable services, the composition process should consider not only service selection, but also configuration parameter settings. However, existing QoS-driven service composition research does not consider reconfigurable services. Moreover, the decision space may be enormous when reconfigurable services are considered. In this paper, we deal with the issues of reconfigurable service modeling and efficient service composition decision making. We introduce a novel compositional decision making process, CDP, which explores optimal solutions of individual component services and uses the knowledge to derive optimal QoS-driven composition solutions. Experimental studies show that the CDP approach can significantly reduce the search space and achieve great performance gains. We also develop a case study system to validate the proposed approach and the results confirm the feasibility and effectiveness of reconfigurable services. © 2013 IEEE.

Sun C.-A.,University of Science and Technology Beijing | El Khoury E.,University of Groningen | Aiello M.,University of Groningen
IEEE Transactions on Services Computing | Year: 2011

Service-Oriented Computing (SOC) is becoming the mainstream development paradigm of applications over the Internet, taking advantage of remote independent functionalities. The cornerstone of SOC's success lies in the potential advantage of composing services on the fly. When the control over the communication and the elements of the information system is low, developing solid systems is challenging. In particular, developing reliable web service compositions usually requires the integration of both composition languages, such as the Business Process Execution Language (BPEL), and of coordination protocols, such as WS-AtomicTransaction and WS-BusinessActivity. Unfortunately, the composition and coordination of web services currently have separate languages and specifications. The goal of this paper is twofold. First, we identify the major requirements of transaction management in Service-oriented systems and survey the relevant standards. Second, we propose a semiautomatic approach to integrate BPEL specifications and web service coordination protocols, that is, implementing transaction management within service composition processes, and thus overcoming the limitations of current technologies. © 2011 IEEE.

Zhong A.,Peking University | Bian Y.,University of Science and Technology Beijing | Zhang Y.,University of Science and Technology Beijing
Journal of Physical Chemistry C | Year: 2010

Density functional theory (DFT) calculations were carried out to investigate the semiconductor performance for the organic field effect transistor (OFET) of PbPc, PbPc(α-OC2H5) 4, and PbPc(α-OC5H11)4 {Pc2- = dianion of phthalocyanine; [Pc(α-OC2H 5)4]2- = dianion of 1, 8, 15, 22-tetraethoxyphthalocyanine; [Pc(α-OC5H11) 4]2- = dianion of 1, 8, 15, 22-tetrakis(3-pentyloxy) phthalocyanine} in terms of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy, ionization energy (IE), electron affinity (EA), and their reorganization energy (λ) during the charge-transport process. On the basis of Marcus electron transfer theory, transfer integral (t) and field effect transistor (FET) properties for the three compounds with known crystal structure have been calculated. In line with the experimental result that PbPc can also work as an n-type semiconductor in addition to a p-type one, theoretical calculations reveal that PbPc has relatively large electron affinity to ensure effective electron injection from Au electrode. Introducing four ethoxy groups on the nonperipheral positions of PbPc decreases both the hole and electron injection barrier relative to Au electrode, and the hole and electron reorganization energy becomes very balanced, making PbPc(α-OC2H5)4 a better ambipolar semiconductor material than PbPc. However, nonperipheral pentyloxy substitution lifts the energy level of both HOMO and LUMO and thus decreases both the IP and EA value of PbPc, resulting in improved hole injection ability but worsened electron injection process. The transfer mobility for electron is revealed to be as large as 0.39 cm2 V-1 s-1 for PbPc and 0.16 cm2 V-1 s-1 for PbPc(α-OC5H11)4. The present work will be helpful to understand the electronic nature for PbPc to work as ambipolar semiconductor and to rationally design novel semiconductor materials for OFET usage. © 2010 American Chemical Society.

Xiang X.,University of Science and Technology Beijing | Lin C.,Tsinghua National Laboratory for Information Sciences and Technology | Chen X.,Beijing Information Science and Technology University
IEEE Wireless Communications Letters | Year: 2014

Mobile cloud computing (MCC) converges mobile computing and Cloud computing for augmenting resource-poor mobile devices to run ¿¿ heavier¿¿ applications. With the increasing ubiquity of mobile devices, MCC exhibits vast application potential in various areas. Energy-efficient data transmission is a key issue in MCC due to energy-poverty of mobile devices. In this letter, we address the issue of energy-efficient link selection and data transmission scheduling for delay-tolerant and data-intensive applications in MCC. We first formulate the problem as a discrete-time stochastic dynamic program (SDP) that aims to optimize both system throughput and energy consumption. To solve the formulated SDP, we then propose a scalable approximate dynamic programming (ADP) algorithm that does not require the statistics of exogenous stochastic information (e.g., data arrival). Simulation studies show that the proposed ADP algorithm can reduce the average energy consumed for delivering a packet by a maximum of over 40 percent compared to alternative minimum-delay and SALSA policies. © 2012 IEEE.

Guo S.F.,Huazhong University of Science and Technology | Guo S.F.,University of Science and Technology Beijing | Liu L.,Huazhong University of Science and Technology | Li N.,Huazhong University of Science and Technology | Li Y.,National University of Singapore
Scripta Materialia | Year: 2010

Using alloy design, an Fe77Mo5P9C7.5B1.5 bulk metallic glass matrix composite reinforced by in situ formed ductile α-Fe dendrites has been developed. In contrast to the monolithic Fe-based bulk metallic glasses that usually fail in brittle fracture, the resulting composite shows a significant plastic strain of more than 30% as well as a high fracture strength of over 3.0 GPa. The in situ formation of the ductile α-Fe dendrites accounts for the significant enhancement of the plasticity. © 2009 Acta Materialia Inc.

Wang L.J.,University of Science and Technology Beijing | Sheng L.Y.,Peking University | Sheng L.Y.,PKU HKUST ShenZhen Hong Kong Institution | Hong C.M.,China Banknote Printing and Minting Corporation
Materials and Design | Year: 2012

Precipitation behavior of grain boundary carbides and its influence on mechanical properties and fracture mechanism of the high nitrogen austenitic stainless steel produced by different processing methods were studied. The simulation software Thermo-calc was applied to analyze the effects of element content on precipitation of carbides. The results show that hot-rolled plate has higher strength, but solution-treated one followed by water quenching has excellent combination of strength and ductility (toughness). M23C6 is the main precipitate and deteriorates the toughness of the steel obviously when it precipitates along grain boundaries. In this case, intergranular fracture is the predominant failure mechanism and the fracture surface is characterized by the shape of rock candy. The toughness at -40°C is decreased by 53% when small amount of carbides precipitates during sand cooling process after solution treatment. The simulation results exhibit that with the decrease of C content, both the precipitation quantity and precipitation temperature of M23C6 decrease. Cr and N have no influence on precipitation quantity of M23C6, but the precipitation temperature will increase with the increase of Cr and the decrease of N. © 2012 Elsevier Ltd.

Hou X.-m.,University of Science and Technology Beijing | Chou K.-C.,University of Science and Technology Beijing | Chou K.-C.,Shanghai University
Corrosion Science | Year: 2010

The isothermal oxidation mechanism of the carbon-containing composites has been investigated based on the experimental data reported in the literature. The results showed that the oxidation kinetics was affected not only by temperature and time but also by carbon content and the sample shape. For the oxidation kinetics, a series of quantitative kinetic models have been developed based on the controlling step. In this model, the effects of carbon content, sample size and temperature on the reaction fraction have been especially discussed. Incorporation of the experimental data into the new model indicates that a good agreement has been reached. © 2009 Elsevier Ltd. All rights reserved.

Li X.,University of Science and Technology Beijing | Zhang T.-Y.,Shanghai University | Su Y.J.,University of Science and Technology Beijing
Nano Letters | Year: 2015

First-principles calculations were conducted on armchair graphene nanoribbons (AGNRs) to simulate the elastic behavior of AGNRs with hydrogen-terminated and bare edges. The results show width-dependent elastic properties with a periodicity of three, which depends on the nature of edge. The edge eigenstress and eigendisplacement models are able to predict the width-dependent nominal Youngs modulus and Poissons ratio, while the Clar structure explains the crucial role of edges in the periodically modulated size-dependent elastic properties. © 2015 American Chemical Society.

Guo S.,University of Science and Technology Beijing | Xu L.,University of Science and Technology Beijing | Zhang L.,University of Science and Technology Beijing | Chang W.,China National Offshore Oil Corporation | Lu M.,University of Science and Technology Beijing
Corrosion Science | Year: 2012

Scanning electron microscopy (SEM), X-ray Diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) were employed to analyze the corrosion scale formed on API X65, 1Cr, 2Cr and 3Cr steels in CO 2 containing environment. The evolution of scale on 2Cr steel was characterized with electrochemical impedance spectroscopy (EIS) and in situ pH monitoring. The results show that Cr content can alter the crystalline state of corrosion scale via changing pH value. Localized corrosion occurs on 2Cr steel when FeCO 3 crystal stripes form on the amorphous scale. The critical Cr content for general corrosion is 3wt.%. © 2012 Elsevier Ltd.

Gan M.,University of Science and Technology Beijing | Jiang R.,Tsinghua National Laboratory for Information Sciences and Technology
Expert Systems with Applications | Year: 2013

Nowadays, personalized recommender systems have become more and more indispensable in a wide variety of commercial applications due to the vast amount of overloaded information accompanying the explosive growth of the internet. Based on the assumption that users sharing similar preferences in history would also have similar interests in the future, user-based collaborative filtering algorithms have demonstrated remarkable successes and become one of the most dominant branches in the study of personalized recommendation. However, the presence of popular objects that meet the general interest of a broad spectrum of audience may introduce weak relationships between users and adversely influence the correct ranking of candidate objects. Besides, recent studies have also shown that gains of the accuracy in a recommendation may be frequently accompanied by losses of the diversity, making the selection of a reasonable tradeoff between the accuracy and the diversity not obvious. With these understandings, we propose in this paper a network-based collaborative filtering approach to overcome the adverse influence of popular objects while achieving a reasonable balance between the accuracy and the diversity. Our method starts with the construction of a user similarity network from historical data by using a nearest neighbor approach. Based on this network, we calculate discriminant scores for candidate objects and further sort the objects in non-ascending order to obtain the final ranking list. We validate the proposed approach by performing large-scale random sub-sampling experiments on two widely used data sets (MovieLens and Netflix), and we evaluate our method using two accuracy criteria and two diversity measures. Results show that our approach significantly outperforms the ordinary user-based collaborative filtering method by not only enhancing the recommendation accuracy but also improving the recommendation diversity. © 2012 Elsevier Ltd. All rights reserved.

Zhao D.,Beihang University | Zhou W.,Beihang University | Cui X.,University of Science and Technology Beijing | Tian Y.,Beihang University | And 2 more authors.
Advanced Materials | Year: 2011

Uniform homeotropic and homogeneous alignment of liquid crystals (LCs) is facilely achieved by dispersing Ni nanoparticles (Ni NPs) into the LCs. The alignment mode depends on the morphology of the Ni NPs. The mechanism of NP-induced LC alignment is elucidated clearly, indicating that the perfect orientation arises from the adsorption of Ni NPs on the substrate. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Faccenda A.,University of Windsor | Bonham C.A.,University of Windsor | Vacratsis P.O.,University of Windsor | Zhang X.,World Precision Instruments | And 2 more authors.
Journal of the American Chemical Society | Year: 2010

We present a simple method by which gold nanoparticles (AuNPs) are used to simultaneously isolate and enrich for free or modified thiol-containing peptides, thus facilitating the identification of protein S-modification sites. Here, protein disulfide isomerase (PDI) and dual specificity phosphatase 12 (DUSP12 or hYVH1) were S-nitrosylated or S-glutathionylated, their free thiols differentially alkylated, and subjected to proteolysis. AuNPs were added to the digests, and the AuNP-bound peptides were isolated by centrifugation and released by thiol exchange. These AuNP-bound peptides were analyzed by MALDI-TOF mass spectrometry revealing that AuNPs result in a significant enrichment of free thiol-containing as well as S-nitrosylated, S-glutathionylated, and S-alkylated peptides, leading to the unequivocal assignment of thiols susceptible to modification. © 2010 American Chemical Society.

Agency: GTR | Branch: NERC | Program: | Phase: Research Grant | Award Amount: 203.66K | Year: 2016

Our overall aim is to build earthquake resilience in China by improving (a) the assessment of seismic hazard and risk from earthquakes and consequent events and (b) the communication and use of probabilistic information in the development of more proportionate and risk-based strategies for disaster risk reduction. We will build on and extend a recently-developed historical catalogue for earthquakes, extend it for the first time to include consequent events (landslides, debris/mud-flows, outburst floods), unify this new database with modern instrumental data, use state-of the art statistical techniques to quantify the associated uncertainties, and incorporate social science-based understanding of risk communication and governance to improve policy development and implementation. The work programme will be carried out in Si-chuan (including the 2008 Wenchuan earthquake) and Yun-nan provinces. While they are both tectonically active, and mountainous, and thus vulnerable not only to earthquakes but also to consequent hazards of earthquake-triggered landslides and flooding, Si-chuan is one of the wealthiest provinces in China, while Yun-nan is one of poorest. These differences in wealth, combined with the recency of the devastating 2008 Wenchuan in Si-chuan compared to the more attenuated memory of the 1996 Lijiang earthquake in Yun-nan, make for a natural experiment in which to test the efficacy of improved probabilistic assessment of risk and associated uncertainty to people and property by earthquakes, and consequent event hazards, in supporting more risk-based approaches to disaster reduction. This project will promote long-term sustainable growth in earthquake prone regions of China by improving both the assessment of earthquake hazard and consequent event risk and the communication, understanding, and use of the resulting probabilistic forecasts for disaster risk reduction by policymakers and local publics. It addresses several specific capacity gaps identified in successive Chinese national disaster risk reduction strategies. As well as engaging with policymakers at both the national and local levels to improve the effectiveness of emergency planning and building code regulation, we will also engage directly with local publics to enhance public understanding of risk and capacity to deal with it. In so doing, the project will also fulfil the UKs Official Development Assistance (ODA) commitment to promoting the economic development and welfare of developing countries by drawing on UKs science base to address a key vulnerability differentially affecting the very poorest in China.

Qiao J.W.,University of Science and Technology Beijing | Qiao J.W.,Taiyuan University of Technology | Sun A.C.,Yuan Ze University | Huang E.W.,National Central University | And 3 more authors.
Acta Materialia | Year: 2011

A Ti-based bulk metallic glass matrix composite (BMGMC) with a homogeneous distribution of dendrites and the composition of Ti46Zr 20V12Cu5Be17 is characterized by a high tensile strength of ∼1640 MPa and a large tensile strain of ∼15.5% at room temperature. The present BMGMC exhibits the largest tensile ductility and highest fracture absorption energy under the stress-strain curve of all dendrite-reinforced BMGMCs developed to date. Tensile deformation micromechanisms are explored through experimental visualization and theoretical analyses. After tension, fragmentation of the dendrites, rather than crystallization within the glass matrix and/or atom debonding near the interface of dual-phase composites, is responsible for the high tensile ductility. The subdivisions within the interior of dendrites are separated by shear bands and dense dislocation walls, and local separation of dendrites under modes I and II prevails. The multiplication of dislocations, severe lattice distortions, and even local amorphization dominate within the dendrites. Good structural coherency of the interface is demonstrated, despite being subjected to significant plastic deformation. Theoretical analyses reveal that the constitutive relations elastic-elastic, elastic-plastic, and plastic-plastic of dual-phase BMGMC generally correspond to the (1) elastic, (2) work-hardening, and (3) softening deformation stages, respectively. The capacity for work-hardening is highly dependent on the large plastic deformation of the dendrites and the high yield strength of the glass matrix. The present study provides a fundamental basis for designing work-hardening dual-phase BMGMCs exhibiting remarkably homogeneous deformation. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Song L.,Peking University | Han Z.,University of Houston | Han Z.,Kyung Hee University | Zhang Z.,University of Science and Technology Beijing | Jiao B.,Peking University
IEEE Journal on Selected Areas in Communications | Year: 2012

It has been well recognized that channel state information (CSI) feedback is of great importance for dowlink transmissions of closed-loop wireless networks. However, the existing work typically researched the CSI feedback problem for each individual mobile station (MS), and thus, cannot efficiently model the interactions among self-interested mobile users in the network level. To this end, in this paper, we propose an alternative approach to investigate the CSI feedback-rate control problem in the analytical setting of a game theoretic framework, in which a multiple-antenna base station (BS) communicates with a number of co-channel MSs through linear precoder. Specifically, we first present a non-cooperative feedback-rate control game (NFC), in which each MS selects the feedback-rate to maximize its performance in a distributed way. To improve efficiency from a social optimum point of view, we then introduce pricing, called the non-cooperative feedback-rate control game with price (NFCP). The game utility is defined as the performance gain by CSI feedback minus the price as a linear function of the CSI feedback-rate. The existence of the Nash equilibrium of such games is investigated, and two types of feedback protocols (FDMA and CSMA) are studied. Simulation results show that by adjusting the pricing factor, the distributed NFCP game results in close optimal performance compared with that of the centralized scheme. © 2012 IEEE.

Qiu J.,Peking University | Guo M.,University of Science and Technology Beijing | Wang X.,Peking University
ACS Applied Materials and Interfaces | Year: 2011

We present a two-step electrochemical deposition process to synthesize hierarchical zinc oxide (ZnO) nanorod-nanosheet structures on indium tin oxide (ITO) substrate, which involves electrodeposition of ZnO nanosheet arrays on the conductive glass substrate, followed by electrochemical growth of secondary ZnO nanorods on the backbone of the primary ZnO nanosheets. The formation mechanism of the hierarchical nanostructure is discussed. It is demonstrated that annealing treatment of the primary nanosheets synthesized by the first-step deposition process plays a key role in synthesizing the hierarchical nanostructure. Photovoltaic properties of dye-sensitized solar cells (DSSCs) based on hierarchical ZnO nanostructures are investigated. The hierarchical ZnO nanorod-nanosheet DSSC exhibits improved device performance compared to the DSSC constructed using photoelectrode of bare ZnO nanosheet arrays. The improvement can be attributed to the enhanced dye loading, which is caused by the enlargement of internal surface area within the nanostructure photoelectrode. Furthermore, we perform a parametric study to determine the optimum geometric dimensions of the hierarchical ZnO nanorod-nanosheet photoelectrode through adjusting the preparation conditions of the first- and second-step deposition process. By utilizing a hierarchical nanostructure photoelectrode with film thickness of about 7 μm, the DSSC with an open-circuit voltage of 0.74 V and an overall power conversion efficiency of 3.12% is successfully obtained. © 2011 American Chemical Society.

Wei Y.,CAS Institute of Mechanics | Li Y.,CAS Institute of Mechanics | Zhu L.,CAS Institute of Mechanics | Liu Y.,CAS Institute of Mechanics | And 7 more authors.
Nature Communications | Year: 2014

The strength-ductility trade-off has been a long-standing dilemma in materials science. This has limited the potential of many structural materials, steels in particular. Here we report a way of enhancing the strength of twinning-induced plasticity steel at no ductility trade-off. After applying torsion to cylindrical twinning-induced plasticity steel samples to generate a gradient nanotwinned structure along the radial direction, we find that the yielding strength of the material can be doubled at no reduction in ductility. It is shown that this evasion of strength-ductility trade-off is due to the formation of a gradient hierarchical nanotwinned structure during pre-torsion and subsequent tensile deformation. A series of finite element simulations based on crystal plasticity are performed to understand why the gradient twin structure can cause strengthening and ductility retention, and how sequential torsion and tension lead to the observed hierarchical nanotwinned structure through activation of different twinning systems. © 2014 Macmillan Publishers Limited.

I’ve apparently been collected extra stories to share for a few weeks. Scroll on down if you want some more EV and clean transport reading. To kick things off, here’s one looking forward to the new year: 11–13 Electric Cars To Light Up The Market In 2016 Between the electric car models that are just arriving on the US market and the ones that will likely hit the market by the end of 2016, we have an exciting year ahead. Below are 11 electric cars that I think will light up 2016 (or 13 if you count cars in a particular way). The Tesla Model X SUV will begin hitting the company’s showrooms throughout the US towards the beginning of January, according to some recent reports. Mark Templeton Shares His Thoughts On The Model X (After Owning It For A Few Months) The CEO of Citrix Systems, Mark Templeton, was one of the lucky ones to have taken delivery of his Tesla Model X SUV at the Model X launch event at the end of September — more than 2 months ago, as of the time of writing this. Tesla Model S (and Model X, I suppose) owners throughout Europe, Australia, and Hong Kong, will be given access to Spotify Premium following a new firmware update, according to recent reports. Tesla HQ Running Out of Room for Employee Parking Success brings its own set of new problems to be solved. There are so many people working at Tesla headquarters these days that the company has set up a valet parking service, according to Business Insider. Tesla currently has 14,000 total employees with 1,600 open positions to fill, and over the next 4 years, Tesla plans to add another 4,500 new employees just in California alone. As indicated, it’s a wiki for FAQ regarding the Tesla Model X. This excellent resource deserves it’s own thread. Although it obviously suffers from the same selection bias as any other nonrandom voluntary data set, the numbers are substantial enough to provide real information. Anyone who has reserved a MX is encouraged to register, then update their information through the order and delivery process. Although the Tesla Model X all-electric SUV was first unveiled in prototype form way back in February 2012, and limited customer deliveries began in September of this year, the car is still shrouded in mystery. With somewhere between 20,000 and 30,000 pre-orders for the vehicle, the Model X is arguably the most highly anticipated SUV of the decade. And yet you still can’t go to the Tesla web site to find out pricing details or a comprehensive description of the various options and configurations that are available. I’m new to the forum (but long time lurker). Doing a random search on Google I find this document that I think was never mentioned:…onse_Guide.pdf It contains lot’s of new informations (to me at least ) In Light of Model X Options, Did the Shareholder “Vegan Uprising” Succeed? While browsing YouTube for elusive new Model X videos, I got this “recommended” video, hilariously titled: “Elon Musk faces the Vegan Uprising at Tesla shareholder meeting (6.9.15).” Is There Really a Difference? 2015 vs 2013 Took delivery of my 2015 P90D last week. Love the car, but also loved my 2013. Aside from the performance, is there really a difference worth the upgrade? It’s a decision I struggled with for 8 months before finally pulling the trigger. The auto pilot software was what finally put me over the edge. Beyond that and Next Gen seats, can’t say there’s really much of a difference. I got the same joy out of my 2013 as I do the 2015. The 2015 allows me to show off its muscle to friends. Is that worth another $33,000?? That’s for each individual to decide. The next gen seats are certainly nicer, but not quite as big of a difference as I expected. The Auto Pilot feature so far has done more of scaring the crap out of me than it has been a useful tool. Jury is still out on that one. Assuming it will get better with time. Overall, absolutely love my new car, but at the same time, I loved my 2013 too. We’ve had our S85 for about 2.5 years and have loved every minute of it. My wife is not a car person at all, but with the Tesla it’s a different story. We live in New England and the while the rear wheel drive isn’t bad in the snow, we shy away from taking it to the mountains and on occasion we find ourselves having to dig a path through the snow to get up our driveway. So, this weekend we decided to take a look at the 70D and take it for a spin. I had not driven any AWD version yet, nor had I experienced AP. AWD is a different experience… less of a push feel and more of a launch feel… if that makes sense. And, the AP and additional safety features were very cool and helped with selling the idea of trading to the wife. I’ve owned Porsches, plenty of BMWs and my new Tesla replaced my Merc SLK… I cannot get rid of the Tesla grin… I am incapable of putting words to describe my feeling, just incredible. SpaceX’s immaculate reception last night gives Tesla Motors (and Tesla Energy) a brand boost that Big Auto would love to have, but never will. They’ve tried for decades to associate their cars with rockets and aircraft, especially during the space-happy 1950s and 60s. Space-age design, space-age materials, jet-inspired fins, turbine taillights, cockpit ergonomics. Well, now we have a car company that actually does share engineering DNA with flying things, since the CEO is a real-life rocketeer who is taking us where no man has gone before. The 500k number comes from Tesla’s ability to produce cars given the restraints of the NUMMI factory and Gigafactory 1 at fully operational. But what if after the March reveal, preorders exceed expectations? What if preorders hit 500k in a few months? Or even higher? Once the Model 3 goes into production, it would take years to clear the backlog. Would Tesla really stand idly by? 30 Reasons Why Tesla Model S is Such a Great Car My friend asked me yesterday “Why have your ordered Tesla?”. Well, I didn’t have much time, so I said “Because it’s best car in the world.” And since he knew nothing on how true my statement was, I did this short list of major reasons why it is so and emailed it to him. Let me know if you think I’ve missed some that should be in top 30. On New Year’s Day, a Tesla Model S in Norway caught fire while charging and was totally destroyed. There is no known cause for the incident but Tesla is investigating and promises a full report soon. I Upgraded to Ludicrous and got Launch Mode!!! Is it worth it? Here is my review. This last thursday I picked up my newly retrofitted P85DL which also came with the new software upgrade offering “Launch Mode.” First off to help put some context to my opinion towards the “is it worth it” debate, I was looking at this decision from a mostly impractical view. A.) the performance it gets you is way cheaper than what you’d have to pay to make any ice to improve it that much, B.) it gets my P85D back up to the king of the hill status and C.) I have always wanted a sub 3 second 0-60 car and a sub 11 second quarter mile car and I am done with ICE so here we are. Cruising down the Florida Turnpike on cruise control is probably what the “beta” version of our software was programed for? I drove 3+ hours and the software made almost no mistakes with the exception of wanting to “exit out” a few times driving in the right lane. The car steered to follow the right lane indicator and wanted to exit out to the right. I have now learned to “guide the car” through exit areas and the autopilot is getting more adaptive. Nevertheless, the car basically drove itself for 220 miles, and in my book, this is very impressive. Why I Think Tesla is Unlikely to Fail Speculation and predictions of Tesla’s demise are rampant. Some people here as well as a number of “experts” in the auto media believe that the mainstream car makers are on the verge of killing Tesla with their own BEV. Tesla may still fail, their success is not guaranteed, but I don’t believe any failure will be for the reasons the experts believe. What Will The TSLA Share Price Be At Closing December 30th 2016? I think we have a very exciting year ahead of us, due to many reasons: And I think TSLA will do very well this year as a result. I would be surprised if we don’t see the share price go over 300 this year, so I’m betting on 318.27 USD per share at closing on Friday the 30th of December. Happy New Year everyone! A 2016 Chevrolet Volt driven by Wayne Gerdes in Southern California returned 111.9 miles on a single charge and he said under ideal circumstances 125 miles is possible. Saab, the former Swedish car maker, is now NEVS and has been awarded a $12 billion contract to build 225.000 electric cars. It plans to launch 5 new models. The city of Leipzig in Germany recently took delivery of a new 50-strong fleet of BMW i3s, to be used by city council and municipal waterworks employees, amongst others, according to a recent press release. On a recent trip to Vermont I stopped at Prestige BMW in New Jersey on both legs of the journey. They recently installed two 24 kW DC Fast Charge stations that are accessible 24/7 and free to use. A robust DC Fast charge infrastructure is crucial for mass EV adoption. The Mercedes-Benz S550e Plug-In Hybrid is packed with some of the best safety technology and creature comforts you can get in any new car today, regardless of price. It also moves smartly, with an advanced plug-in hybrid system that lets you plug in overnight—or even for a few hours—and then drive for a dozen or so miles before transitioning into an especially smooth gasoline-electric hybrid. Mercedes says its GLE 500 e plug-in hybrid SUV is 42% more energy efficient than its conventional cousin over its lifetime, even though it requires more energy to build. XALT Energy to Supply Li-ion Packs to Efficient Drivetrains for PHEVs XALT Energy and Efficient Drivetrains (EDI) announced a tentative agreement through which XALT will supply EDI with its NMC graphite Lithium-ion battery energy storage packs for use in EDI’s PHEV PowerDrive and electric power export solutions. Chevrolet has trademarked the names Corvette E-Ray and E-Ray. Does that mean an electric Corvette is planned? Maybe, if only to compete with Porsche. Researchers at Tsinghua University, with colleagues from the University of Science and Technology Beijing, have discovered that the multi-reversible magnetization of ferromagnetic material can be controlled via the lithiation/delithiation reaction in a Li-ion battery by varying the discharge–charge potential at room temperature. This phenomenon couples magnetism and electrochemistry, and enables precise quantitative magnetization manipulation using an electrochemical method. An open-access paper on their discovery is published in the ACS journal Nano Letters. Navigant Forecasts Global Light Duty Electrified Vehicle Sales to Exceed 6.0M in 2024; PEVs to Account for Roughly Half In a new report, Electric Vehicle Market Forecasts, Navigant research projects that under its base scenario, global sales of light duty electrified vehicles (i.e., vehicles that use electricity for traction, including hybrids, plug-in hybrids, and battery-electrics) will grow from 2.6 million vehicle sales in 2015 to more than 6.0 million in 2024. As discussed in this article by Ambrose Evans-Pritchard in the Telegraph, the “OPEC Oil Outlook” recently published assumes that neither global warming regulation nor electric vehicles will influence oil demand much until 2040. The California DMV announced that the maximum of 85,000 Green Clean Air Vehicle Decals had been issued to plug-in hybrid electric vehicles, denying new Volt and plug-in Prius owners the coveted sticker allowing them free access to HOV and HOT lanes. I don’t know which channel my daughter in law was streaming onto their projector, but just before they dropped the ball in Times Square, Bill Nye the Science Guy told the world that he hopes in 2031 that we can reach 80% electric cars on the road. He said once you drive an electric vehicle you will never go back… How true, how true. The fifth race of the second Formula E season will be held March 12 in Mexico City at the historic Autodromo Hermano Rodriguez before moving to Long Beach. Bain: Germany’s Goal of 1M Electric Cars by 2020 is Unattainable; Fewer than 50,000 Units on Road by End of This Year The German Federal Government plan to have one million electric cars on its roads by 2020 has failed, according to the analysis of international management consulting firm Bain & Company. By the end of 2015, there will be a total of about 50,000 electric cars and plug-in hybrids on the roads in Germany (about 75% below plan); nevertheless, structural transformation towards electromobility is continuing, according to the firm. Environmental groups have sent a letter to CARB urging the Volkswagen be punished to the full extent of the law for selling diesel powered cars it knew did not conform to state emissions regulations. If every other passenger car in Norway is plugged into the electric network by 2020, Europe will have to produce more electricity – mainly from coal-fired power plants – to meet the demand. But it will be a plus for the climate nonetheless. Aside from my own presentation, which I’ll share soon, there are a couple more EV Transportation & Technology Summit presentations that I recorded and wanted to share. I don’t have much to say about them, so I’ll just drop the videos below. COP21 was arguably one of the most epic meetings in the history of humanity. In a spirit of mutual cooperation, the international community agreed to finally begin to turn away from a fossil fuel-powered economy toward a clean, sustainable future. While it may be important to make general commitments to cut CO2 and methane emissions, and to keep under a certain temperature increase, what it comes down to in the end is making practical changes in how we live our lives and run our societies. Analysis of EV Charging in Ireland Suggests Public Fast-Charging Infrastructure May Become Commercially Viable in Short- to Medium Term A study of EV charging behavior by a team at Trinity College Dublin has found that, from the household data available, EV users prefer to carry out the majority of their charging at home in the evening—the period of highest demand on the electrical grid indicating that incentivization may be required to shift charging away from this peak grid demand period. The Dutch electric vehicle charging solutions company EV-Box will now be entering the markets of the nearby countries of Belgium and Luxembourg, according to a recent email sent to EV Obsession. A new solar powered EV charging station in the city of Vestby, Norway will produce 16,000 kWh of electricity annually, enough to go 47,000 miles in a Tesla. Aside from my own presentation, which I’ll share soon, there are a couple more EV Transportation & Technology Summit presentations that I recorded and wanted to share. I don’t have much to say about them, so I’ll just drop the videos below. Tesla faces headwinds from rivals. You’ve read it ad nauseum. But it you’re American, then Tesla could face headwinds from you. American motorists fall into two categories: current plaintiffs and future plaintiffs. We like to sue. In fact, we sue better than we drive. And we’re about to give ourselves more excuses to sue. Autonomous driving could start a litigation beat-down for any company that dares pioneer it. Autonomous technology will be the hot topic in the world of automobiles in 2016, as all carmakers rush to bring self-driving cars to market. Oil giant Exxon was studying climate change impacts in the 1970s and 80s, and their projections from 35 years ago accurately portray what is happening now. Knowing what they knew, they chose to continue business as usual. Now this astounding article in the LA Times. Car-Free Movement Gaining Steam in Europe and Elsewhere Athlyn Cathcart-Keays of The Guardian-Cities chronicles the advancement of the international urban car-free movement as well as auto regulations that focus on air pollution. The most recent city to join the growing list is Oslo, Norway. On December 18, Congress passed a bill to fund the government for fiscal year 2016. This particular bill includes $500 million in funding for the tremendously popular TIGER discretionary grant program, the same funding level as fiscal year 2015. The TIGER program helps communities build a broad range of innovative transportation projects, including improvements for people on bikes. Chicago, with funding from the four major wireless carriers, has achieved a major amenity for transit users: 4G internet service along 22 miles of subway tracks in the CTA system. The Los Angeles County Metropolitan Transportation Authority (Metro) is implementing a new vision for “transit-oriented communities.” As a result of the “defeat device” software it installed in diesel cars, Volkswagen faces multiple criminal investigations in Europe. And it will likely face criminal penalties in the U.S., along with hundreds of civil suits from angered owners. Now, it seems the company may also be in legal trouble in China over potential diesel-emissions cheating. COP21: Shows the End of Fossil Fuels is Near, We Must Speed Its Coming The wheel of climate action turns slowly, but in Paris it has turned. There’s much in this deal that frustrates and disappoints me, but it still puts the fossil fuel industry squarely on the wrong side of history.    Get CleanTechnica’s 1st (completely free) electric car report → “Electric Cars: What Early Adopters & First Followers Want.”   Come attend CleanTechnica’s 1st “Cleantech Revolution Tour” event → in Berlin, Germany, April 9–10.   Keep up to date with all the hottest cleantech news by subscribing to our (free) cleantech newsletter, or keep an eye on sector-specific news by getting our (also free) solar energy newsletter, electric vehicle newsletter, or wind energy newsletter.  

Cheng F.,Beijing Jiaotong University | Yu J.,University of Science and Technology Beijing | Xiong H.,Shanghai JiaoTong University
IEEE Transactions on Neural Networks | Year: 2010

The Gaussian process (GP) approaches to classification synthesize Bayesian methods and kernel techniques, which are developed for the purpose of small sample analysis. Here we propose a GP model and investigate it for the facial expression recognition in the Japanese female facial expression dataset. By the strategy of leave-one-out cross validation, the accuracy of the GP classifiers reaches 93.43% without any feature selection/extraction. Even when tested on all expressions of any particular expressor, the GP classifier trained by the other samples outperforms some frequently used classifiers significantly. In order to survey the robustness of this novel method, the random trial of 10-fold cross validations is repeated many times to provide an overview of recognition rates. The experimental results demonstrate a promising performance of this application. © 2010 IEEE.

Song L.,University of Science and Technology Beijing | Xu X.J.,Zhongyuan University of Technology | Sun J.,Shanghai JiaoTong University | Lin J.P.,University of Science and Technology Beijing
Materials Characterization | Year: 2014

The cooling rate effects on the βo → ωo phase transformation in Ti-45Al-8.5Nb-(W, B, Y) (at.%) alloy were investigated by annealing the alloy at 950 °C followed by different cooling methods. The morphology and the distribution of the ω-related phases were analyzed by TEM. The amount and morphology of the ω-related phases are very sensitive to the cooling rate. The ω-related phases could not be resolved in the water-quenched sample whereas it grew into nano-particles in the air-cooled sample. In the furnace-cooled sample, the ωo phase with B82 structure grew into micron-sized particles and occupied the whole βo area. The nucleation of the ordered ω embryos can be explained by the well accepted displacive mechanism because of the instability of the βo(B2) structure, accompanied by a short-range diffusion process between neighboring {111}βo planes. However, the growth of the ω-related phases is controlled by a long-range diffusion process. Due to ready nucleation and growth, the ordered ω formation is bound to occur in as-cast and heat-treated high Nb-TiAl alloys. © 2014 Elsevier Inc. All rights reserved.

Kelly F.J.,King's College London | Zhu T.,University of Science and Technology Beijing
Science | Year: 2016

In cities across the globe, road transport remains an important source of air pollutants that are linked with acute and chronic health effects. Decreasing vehicle emissions-while maintaining or increasing commuter journeys-remains a major challenge for city administrators. In London, congestion-charging and a citywide low-emission zone failed to bring nitrogen dioxide concentrations under control. n Beijing, controls on the purchase and use of cars have not decreased transport emissions to a sufficient extent. As cities continue to grow, not even zero-emission vehicles are the solution. Moving increasingly large numbers of people efficiently around a city can only be achieved by expanding mass transit systems.

Hao Y.,University of Science and Technology Beijing | Chen S.,CAS Institute of Physics
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2012

We investigate the dynamical properties of anyons confined in one-dimensional optical lattices combined with a weak harmonic trap using the exact numerical method based on a generalized Jordan-Wigner transformation. The evolving density profiles, momentum distributions, occupation distributions, and occupations of the lowest natural orbital after quench of the harmonic trap are obtained for different statistical parameters. The density profiles of anyons display the same behaviors irrespective of statistical parameter in the full evolving period, while the behaviors dependent on statistical property are shown in the momentum distributions and occupations of natural orbitals. © 2012 American Physical Society.

Zhang X.,University of Science and Technology Beijing | Zhang X.,Pacific Northwest National Laboratory | Zhang Y.,University of Science and Technology Beijing | Liao Q.,University of Science and Technology Beijing | And 2 more authors.
Small | Year: 2013

We designed and constructed reduced graphene oxide (rGO) functionalized high electron mobility transistor (HEMT) for rapid and ultra-sensitive detection of label-free DNA in real time. The micrometer sized rGO sheets with structural defects helped absorb DNA molecules providing a facile and robust approach to functionalization. DNA was immobilized onto the surface of HEMT gate through rGO functionalization, and changed the conductivity of HEMT. The real time monitor and detection of DNA hybridization by rGO functionalized HEMT presented interesting current responses: a "two steps" signal enhancement in the presence of target DNA; and a "one step" signaling with random DNA. These two different recognition patterns made the HEMT capable of specifically detecting target DNA sequence. The working principle of the rGO functionalized HEMT can be demonstrated as the variation of the ambience charge distribution. Furthermore, the as constructed DNA sensors showed excellent sensitivity of detect limit at 0.07 fM with linear detect range from 0.1 fM to 0.1 pM. The results indicated that the HEMT functionalized with rGO paves a new avenue to design novel electronic devices for high sensitive and specific genetic material assays in biomedical applications. A rapid and ultra-sensitive DNA sensor with a novel recognition pattern is constructed by a reduced graphene oxide (rGO)-functionalized high electron mobility transistor (HEMT). The rGO-HEMT DNA sensor presents interesting "two step" current responses toward target DNA, which paves a new avenue to design novel electronic devices for highly sensitive and specific genetic material assays in biomedical applications. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Zhang Y.,University of Science and Technology Beijing | Zuo T.T.,University of Science and Technology Beijing | Tang Z.,University of Tennessee at Knoxville | Gao M.C.,U.S. National Energy Technology Laboratory | And 4 more authors.
Progress in Materials Science | Year: 2014

This paper reviews the recent research and development of high-entropy alloys (HEAs). HEAs are loosely defined as solid solution alloys that contain more than five principal elements in equal or near equal atomic percent (at.%). The concept of high entropy introduces a new path of developing advanced materials with unique properties, which cannot be achieved by the conventional micro-alloying approach based on only one dominant element. Up to date, many HEAs with promising properties have been reported, e.g., high wear-resistant HEAs, Co1.5CrFeNi1.5Ti and Al0.2Co 1.5CrFeNi1.5Ti alloys; high-strength body-centered-cubic (BCC) AlCoCrFeNi HEAs at room temperature, and NbMoTaV HEA at elevated temperatures. Furthermore, the general corrosion resistance of the Cu 0.5NiAlCoCrFeSi HEA is much better than that of the conventional 304-stainless steel. This paper first reviews HEA formation in relation to thermodynamics, kinetics, and processing. Physical, magnetic, chemical, and mechanical properties are then discussed. Great details are provided on the plastic deformation, fracture, and magnetization from the perspectives of crackling noise and Barkhausen noise measurements, and the analysis of serrations on stress-strain curves at specific strain rates or testing temperatures, as well as the serrations of the magnetization hysteresis loops. The comparison between conventional and high-entropy bulk metallic glasses is analyzed from the viewpoints of eutectic composition, dense atomic packing, and entropy of mixing. Glass forming ability and plastic properties of high-entropy bulk metallic glasses are also discussed. Modeling techniques applicable to HEAs are introduced and discussed, such as ab initio molecular dynamics simulations and CALPHAD modeling. Finally, future developments and potential new research directions for HEAs are proposed.

Song L.,University of Science and Technology Beijing | Zhang L.Q.,University of Science and Technology Beijing | Xu X.J.,Zhongyuan University of Technology | Sun J.,Shanghai JiaoTong University | Lin J.P.,University of Science and Technology Beijing
Scripta Materialia | Year: 2013

The omega phase in as-cast high-Nb-containing TiAl alloy exhibits particles with sizes on the nano- or microscale within the B2 matrix. Omega particles are transformed from the B2 phase by heterogeneous nucleation on the B2/γ boundaries or homogeneous nucleation within the B2 phase. After annealing at 900 °C, the omega particles disappear and transform into B2 phase. The transformation is rapidly initiated, but is difficult to complete. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Peng R.,University of Science and Technology Beijing | Li Y.F.,École Centrale Paris | Zhang W.J.,University of Warwick | Hu Q.P.,CAS Academy of Mathematics and Systems Science
Reliability Engineering and System Safety | Year: 2014

This paper studies the fault detection process (FDP) and fault correction process (FCP) with the incorporation of testing effort function and imperfect debugging. In order to ensure high reliability, it is essential for software to undergo a testing phase, during which faults can be detected and corrected by debuggers. The testing resource allocation during this phase, which is usually depicted by the testing effort function, considerably influences not only the fault detection rate but also the time to correct a detected fault. In addition, testing is usually far from perfect such that new faults may be introduced. In this paper, we first show how to incorporate testing effort function and fault introduction into FDP and then develop FCP as delayed FDP with a correction effort. Various specific paired FDP and FCP models are obtained based on different assumptions of fault introduction and correction effort. An illustrative example is presented. The optimal release policy under different criteria is also discussed. © 2014 The Authors. Published by Elsevier Ltd. All rights reserved.

Zhu Z.,Beijing Materials University | Zhang D.,Taiyuan University of Technology | Yan H.,Beijing Materials University | Li W.,University of Science and Technology Beijing | Qilu,Beijing Materials University
Journal of Materials Chemistry A | Year: 2013

This work developed a novel ammonium oxalate-carbonate composite co-precipitation method to prepare spinel LiNi0.5Mn 1.5O4. By this method combined with a facile hydrothermal treatment and particular cooling process, an ideal spinel with precise stoichiometric Ni/Mn and classic Fd3m structure is obtained, and furthermore, the Mn3+ content can be strictly limited. Additionally, the prepared LiNi0.5Mn1.5O4 has a spherical hierarchical morphology, composed of nano or submicron primary particles. This LiNi 0.5Mn1.5O4 shows superlative electrochemical performance. It delivers a discharge capacity of 141.2 mA h g-1, and importantly 98.2% of which discharges at 4.7 V. After 200 cycles at 0.3 C, 1 C and 3 C, the capacity retentions are 96.3%, 94.4% and 91.1%, respectively. Chemical and electrochemical measurements indicate that the elimination of the majority of Mn3+ in the obtained LiNi0.5Mn 1.5O4 results in the high capacity proportion at 4.7 V. Additionally, the retained Fd3m structure and spherical hierarchical morphology also effectively favour the cycling and rate performances. This journal is © 2013 The Royal Society of Chemistry.

Li P.,University of Science and Technology Beijing | Liao Q.,University of Science and Technology Beijing | Yang S.,CAS Institute of Physics | Bai X.,CAS Institute of Physics | And 7 more authors.
Nano Letters | Year: 2014

The fatigue behavior of ZnO nanowires (NWs) and microwires was systematically investigated with in situ transmission electron microscopy electromechanical resonance method. The elastic modulus and mechanical quality factors of ZnO wires were obtained. No damage or failure was found in the intact ZnO wires after resonance for about 108-109 cycles, while the damaged ZnO NW under electron beam (e-beam) irradiation fractured after resonance for seconds. The research results will provide a useful guide for designing, fabricating, and optimizing electromechanical nanodevices based on ZnO nanomaterials, as well as future applications. © 2014 American Chemical Society.

Li J.,Beijing University of Posts and Telecommunications | Li X.,University of Science and Technology Beijing | Zhang X.,Beijing University of Posts and Telecommunications | Tian F.,Beijing University of Posts and Telecommunications | Xi L.,Beijing University of Posts and Telecommunications
Optics Express | Year: 2010

The stability of single-sideband (SSB) modulator based recirculating frequency shifter (RFS) is analyzed theoretically. The optimum radio frequency (RF) drive peak-to-peak voltage used to drive the modulator is studied with considering the amplified spontaneous emission (ASE) noise of optical amplifier and crosstalk so as to obtain a maximum overall effective optical signal to noise ratio (OSNR) which is defined to quantify the quality of generated tones. Small desired tones number and lower RF peak-to-peak voltage can reduce the crosstalk effectively. While the trade-off should be considered since the larger desired tones number it is, the higher optimum drive voltage should be used when the SSB-based RFS reached the maximum OSNR. The theoretical results show that the optimum operation condition is helpful to improve the performance of RFS which can be a good application for the T-bit/s optical transmission in practice. © 2010 Optical Society of America.

Xiao W.,University of Science and Technology Beijing | Xiao J.-L.,Inner Mongolian University for Nationalities
International Journal of Modern Physics B | Year: 2011

We study the vibrational frequency, the ground-state energy and the ground-state binding energy of the strong-coupling impurity bound magnetopolaron in an anisotropic quantum dot. The effects of the transverse and longitudinal effective confinement lengths, the electronphonon coupling strength, the cyclotron frequency of a magnetic field and the Coulomb bound potential are taken into consideration by using an linear combination operator and unitary transformation methods. It is found that the vibrational frequency, the ground-state energy and the ground-state binding energy will increase rapidly with decreasing confinement lengths. The vibrational frequency is an increasing function of the Coulomb bound potential, the electronphonon coupling strength and cyclotron frequency, whereas the ground-state energy is a decreasing function of the potential and coupling strength, and the ground-state binding energy is an increasing function of the potential and coupling strength. The ground-state energy and the ground-state binding energy increases with increasing cyclotron frequency. © 2011 World Scientific Publishing Company.

Wei D.,University of Wollongong | Jiang Z.,University of Wollongong | Han J.,University of Science and Technology Beijing
Computational Materials Science | Year: 2013

Metal owns the ability of self-healing to some extent, and the ability of the internal crack healing is most desirable for improving the reliability of metal. A molecular dynamics simulation has been further developed to investigate the evolution of a nanoscale crack in body centred cubic Fe crystal under the conditions of heating or compressive pressure. When system temperature drops, the evolution of the crack that was at elevated temperature has been studied for the first time. N-body potential according to the embedded atom method has been adopted. The original nanoscale crack is expressed by removing some atoms in the centre of the cell, and the minimum vertical distance between the atoms on the top and bottom crack surfaces has been defined as Dm for assessing the process of crack evolution. The results show that a crack healing process can be accelerated significantly with an increase of temperature. When the system temperature decreases, Dm of the crack that was in healing process does not change significantly but fluctuates in a narrow range. This means that the crack healing is the result of Fe atoms diffusing into the crack area but not the thermal stress incurred in the simulation cell at elevated temperature. The pre-compressive pressure under the condition of both biaxial and uniaxial loadings can help promote the crack healing significantly and results in more uniform distribution of defects after healing. © 2012 Elsevier B.V. All rights reserved.

Zhou X.,University of Science and Technology Beijing | Chen X.,Beijing University of Posts and Telecommunications | Long K.,University of Science and Technology Beijing
IEEE Photonics Technology Letters | Year: 2012

A wide-range frequency offset estimation algorithm is proposed for optical coherent systems, which removes the modulated phase information from the received signal accurately using training sequence instead of traditional Mth power operation. A large frequency offset approximating to ±0.5 times the symbol rate can be traced in arbitrary M-ary phase-shift-keying (MPSK) M-ary quadrature amplitude modulation (MQAM) systems by the proposed algorithm with the low computational complexity and the negligible training overhead. © 2011 IEEE.

Zhu Z.,Beijing Materials University | Yan H.,Beijing Materials University | Zhang D.,Taiyuan University of Technology | Li W.,University of Science and Technology Beijing | Lu Q.,Beijing Materials University
Journal of Power Sources | Year: 2013

LiNi0.5Mn1.5O4 as a 4.7 V cathode material is prepared through an oxalic acid-pretreated solid-state method. Oxalic acid is added to react with the mixture of LiOH•H2O, MnO2 and Ni(OH)2. This chemical pretreatment results in a sufficient mixing of Li, Ni and Mn ions in the precursor, and therefore promotes the generation of pure LiNi0.5Mn1.5O4 in the following calcination even at a temperature as low as 500 °C. The material prepared at 750 °C has a highest crystallinity and a regular crystal shape with smoothly surface. Compared to traditional method, the LiNi 0.5Mn1.5O4 synthesized by this novel method shows much better electrochemical performances with an initial discharging capacity of 136.9 mAh g-1 and capacity retention of 93.4% after 300 cycles under 0.3C. And most importantly 97.2% of the total capacity displays at 4.7 V, which significantly favors the cell energy density. The novel preparation technique is also available to get high rate performance for LiNi 0.5Mn1.5O4. The material synthesized at 900 °C has a capacity of 121.2 mAh g-1 and stable cycling performance under 3C due to its lower polarization resistance. © 2012 Elsevier B.V. All rights reserved.

Yu M.,University of Science and Technology Beijing | Qiu H.,University of Science and Technology Beijing | Chen X.,Beijing Technology and Business University
Thin Solid Films | Year: 2010

About 300 nm-thick Zn0.87Al0.06Ni0.07O, Zn0.83Al0.06Ni0.11O and Zn 0.81Al0.04Ni0.15O films were deposited on glass substrates at 300 K by co-sputtering ZnO:Al and Ni targets. The films were annealed in vacuum at 673 K for 2 h under a magnetic field of 4.8 × 104 A/m applied along the film plane and then were cooled down to room temperature without magnetic field. All the films have a wurtzite structure and consist of thin columnar grains perpendicular to the substrate. The annealing promotes the (002) orientation growth in the film growing direction for the Zn0.87Al0.06Ni0.07O and Zn 0.83Al0.06Ni0.11O films as well as the (100) orientation growth for the Zn0.81Al0.04Ni0.15O film. The annealing results in a slight increase in the grain size. A weak Ni diffraction peak was detected for the annealed films with high Ni content. The annealing enhances the room temperature ferromagnetism of the films. A temperature dependence of magnetization confirms that the Curie temperature is above 400 K for the annealed films. The films magnetically annealed exhibit an anisotropic magnetization behavior. The annealed Zn0.87Al 0.06Ni0.07O film has the lowest resistivity AR (8.73 × 10-3 Ω cm), the highest free electron concentration (1.73 × 1020 cm- 3) and Hall mobility AR (4.16 cm2V- 1 s- 1). A temperature dependence of the resistivity AR from 50 K to 300 K reveals that the carrier transport mechanism is Mott's variable range hopping in the low temperature range and thermally activated band conduction in the high temperature range. © 2010 Elsevier B.V.

Wu Z.,University of Western Australia | Liu Z.,University of Science and Technology Beijing | Yang H.,University of Western Australia | Liu Y.,University of Western Australia | Wu G.,CAS Institute of Physics
Applied Physics Letters | Year: 2011

This letter reports on an alloy design of Mn50 Ni37 In10 Co3 based on the principle of Mn-Mn ferromagnetic coupling via Co doping. The alloy is shown to exhibit a metamagnetic martensitic transformation and a high saturation magnetization of 118 emu/g in its austenitic state. The transformation generates a large magnetization difference of 89 emu/g, more than 200% of what is reported in the literature for similar alloys. A complete magnetic field induced martensitic transformation was achieved at 170 K. Such a high magnetization difference provides a strong driving force for magnetic-field-induced transformation, making this material a promising candidate for magnetic actuation applications. © 2011 American Institute of Physics.

Xia Z.,University of Science and Technology Beijing | Xia Z.,Northwestern University | Ma C.,Chongqing University of Posts and Telecommunications | Molokeev M.S.,RAS Kirensky Institute of Physics | And 3 more authors.
Journal of the American Chemical Society | Year: 2015

The union of structural and spectroscopic modeling can accelerate the discovery and improvement of phosphor materials if guided by an appropriate principle. Herein, we describe the concept of chemical unit cosubstitution as one such potential design scheme. We corroborate this strategy experimentally and computationally by applying it to the Ca2(Al1-xMgx)(Al1-xSi1+x)O7:Eu2+ solid solution phosphor. The cosubstitution is shown to be restricted to tetrahedral sites, which enables the tuning of luminescent properties. The emission peaks shift from 513 to 538 nm with a decreasing Stokes shift, which has been simulated by a crystal-field model. The correlation between the 5d crystal-field splitting of Eu2+ ions and the local geometry structure of the substituted sites is also revealed. Moreover, an energy decrease of the electron-phonon coupling effect is explained on the basis of the configurational coordinate model. © 2015 American Chemical Society.

Cheng S.,University of Science and Technology Beijing | Li Z.,University of Science and Technology Beijing | Mang H.-P.,University of Science and Technology Beijing | Neupane K.,Civil Engineer | And 2 more authors.
Applied Energy | Year: 2014

Biogas technology is becoming increasingly popular throughout the world, particularly in countries where governments promote domestic biogas systems. Despite its popularity, problems exist in biogas technology, such as low-quality construction, leakage of pipelines, low biogas production, and lack of maintenance. These problems should be identified and analyzed for effective implementation and efficient operation of small-sized biogas systems (SBS). This research applies the fault tree approach (FTA) to identify failures, and evaluate their effects on the operation of SBS from a technical point of view, based on a nationwide field study in Nepal. Ninety-four sets of SBS were selected and sampled in targeted areas. Five subsystems of SBS were defined, including structural components, biogas utilization equipment, piping system, biogas production, and effluent disposal system. Based on the statistical analysis of the 94 targeted cases, the fault probabilities of the five subsystems are 0.67, 0.48, 0.73, 0.26, and 0.64, respectively. The weights of five subsystems are determined by Delphi method and fault probability of SBS is calculated. The results show that faults on piping systems happen most frequently, and that proper disposal and reuse of bio-slurry are often neglected. Regardless of the social and economic benefits of SBS, implementation scenarios of SBS throughout Nepal are evaluated under a technical perspective, as follows: (1) the operational status of SBS is not optimal. (2) Based on criteria for failures, well-operation ratio is about 53% in practice. (3) Skilled masons are prerequisites for efficient functioning of SBS. (4) Maintenance plays a key role for efficient functioning. The study results prove that FTA is mostly suitable for SBS evaluation and is an effective analysis tool for technical evaluation in the field of biogas technology. © 2013 Elsevier Ltd.

Xiao X.,University of Science and Technology Beijing | Zhang Y.,University of Science and Technology Beijing | Wang J.,University of Science and Technology Beijing | Du H.,University of Wollongong
IEEE Transactions on Industrial Electronics | Year: 2016

The dc-link voltage fluctuation caused by the change of working state of the load motor has been one of the key issues in the pulse width modulation rectifier-inverter system. In this study, an improved model predictive control (MPC) scheme is proposed to address this problem. The MPC is applied to both the rectifier stage and the inverter stage in the system. Direct power control is used in the rectifier stage and the direct torque control is employed in the inverter stage, with the key novelty of the active power reference values being defined by both real-time and periodic compensation power based on the system-level power-balance model. Meanwhile, an MPC algorithm based on a two-step prediction is introduced to compensate for the delay of a digital controller. Comparison has been conducted between the proposed scheme and three other methods. Simulation and experimental results show that the proposed control scheme exhibits good performance in both the rectifier stage and the inverter stage with improved dynamic response and suppressed voltage fluctuation of the dc-link voltage. © 2016 IEEE.

Gao R.-Q.,North China University of Water Conservancy and Electric Power | Hou X.-M.,University of Science and Technology Beijing
International Journal of Minerals, Metallurgy and Materials | Year: 2013

Medical stone-based porous ceramics as a carrier were prepared by ultra-fine grinding and low-temperature sintering method. Nano-TiO2 thin films were loaded on the carrier by chemical liquid deposition method using titanium tetrachloride as a precursor. The micro-morphology and microstructure of the synthesized samples were characterized using X-ray diffraction, scanning electron microscopy with energy dispersive spectrometry, and mercury injection method. The photo-catalytic activity of the TiO2 thin films was investigated by degrading formaldehyde. The main crystalline phase in the TiO2 thin films calcined at 550 C is anatase with the average particle size about 10 nm. The specific surface area of the carrier-coated nano-TiO2 increases from 3.68 to 5.32 m2/g. The formaldehyde removal rate of the TiO2/medical stone-based porous ceramics irradiated under an ultraviolet lamp for 120 min reaches 85.6%. © 2013 University of Science and Technology Beijing and Springer-Verlag Berlin Heidelberg.

Wang H.,University of Science and Technology Beijing | Liu G.,University of Science and Technology Beijing | Ullah A.,University of Science and Technology Beijing | Ullah A.,Karakoram International University | Luan J.,University of Science and Technology Beijing
Applied Physics Letters | Year: 2012

Topological correlations of three-dimensional grains were investigated by Monte Carlo-Potts model simulation. The result shows that, unlike first nearest neighbors (the Aboav-Weaire law [D. Aboav, Metallography 3, 383 (1970) and D. Weaire, Metallography 7, 157 (1974)] holds), there appears to be very little correlation between grains and their second and third nearest neighbors (on average), i.e., the average number of faces of second nearest neighbors, m 2, and third nearest neighbors, m 3, are independent of faces f of the center grain (nearly m 2 14.984 and m 3 14.489). This result indicates that long range correlations beyond first nearest neighbors may have negligible effect on the growth of center grains and thus provides support to a topologically averaged growth law that only considered the non-random first nearest-neighbor interactions. © 2012 American Institute of Physics.

Li B.,Tsinghua University | Cao H.,Tsinghua University | Zhang J.,CAS Chengdu Institute of Organic Chemistry | Qu M.,CAS Chengdu Institute of Organic Chemistry | And 2 more authors.
Journal of Materials Chemistry | Year: 2012

Anchoring SnO 2 NPs encapsulated in carbon shells onto RGO exhibits superior anode performances in lithium ion batteries with specific capacities of 622 mA h g -1 after 100 cycles. © 2012 The Royal Society of Chemistry.

Yan R.,University of Science and Technology Beijing | Lapata M.,University of Edinburgh | Li X.,University of Edinburgh | Li X.,Beihang University
50th Annual Meeting of the Association for Computational Linguistics, ACL 2012 - Proceedings of the Conference | Year: 2012

As one of the most popular micro-blogging services, Twitter attracts millions of users, producing millions of tweets daily. Shared information through this service spreads faster than would have been possible with traditional sources, however the proliferation of user-generation content poses challenges to browsing and finding valuable information. In this paper we propose a graph-theoretic model for tweet recommendation that presents users with items they may have an interest in. Our model ranks tweets and their authors simultaneously using several networks: The social network connecting the users, the network connecting the tweets, and a third network that ties the two together. Tweet and author entities are ranked following a co-ranking algorithm based on the intuition that that there is a mutually reinforcing relationship between tweets and their authors that could be reflected in the rankings. We show that this framework can be parametrized to take into account user preferences, the popularity of tweets and their authors, and diversity. Experimental evaluation on a large dataset shows that our model outperforms competitive approaches by a large margin. © 2012 Association for computational Linguistics.

Wu H.-N.,Beihang University | Wang J.-W.,University of Science and Technology Beijing | Wang J.-W.,Beihang University | Li H.-X.,City University of Hong Kong | Li H.-X.,Central South University
IEEE Transactions on Fuzzy Systems | Year: 2014

This paper deals with the problem of fuzzy boundary control design for a class of nonlinear distributed parameter systems which are described by semilinear parabolic partial differential equations (PDEs). Both distributed measurement form and collocated boundary measurement form are considered. A Takagi-Sugeno (T-S) fuzzy PDE model is first applied to accurately represent the semilinear parabolic PDE system. Based on the T-S fuzzy PDE model, two types of fuzzy boundary controllers, which are easily implemented since only boundary actuators are used, are proposed to ensure the exponential stability of the resulting closed-loop system. Sufficient conditions of exponential stabilization are established by employing the Lyapunov direct method and the vector-valued Wirtinger's inequality and presented in terms of standard linear matrix inequalities. Finally, the advantages and effectiveness of the proposed control methodology are demonstrated by the simulation results of two examples. © 2014 IEEE.

Xing Y.,University of Science and Technology Beijing | Chen W.-H.,Beijing Institute of Technology | Jia W.,China Agricultural University | Zhang J.,Chinese University of Hong Kong
Journal of Experimental Botany | Year: 2015

Superoxide dismutases (SODs) are involved in plant adaptive responses to biotic and abiotic stresses but the upstream signalling process that modulates their expression is not clear. Expression of two iron SODs, FSD2 and FSD3, was significantly increased in Arabidopsis in response to NaCl treatment but blocked in transgenic MKK5-RNAi plant, mkk5. Using an assay system for transient expression in protoplasts, it was found that mitogen-activated protein kinase kinase 5 (MKK5) was also activated in response to salt stress. Overexpression of MKK5 in wild-type plants enhanced their tolerance to salt treatments, while mkk5 mutant exhibited hypersensitivity to salt stress in germination on salt-containing media. Moreover, another kinase, MPK6, was also involved in the MKK5-mediated iron superoxide dismutase (FSD) signalling pathway in salt stress. The kinase activity of MPK6 was totally turned off in mkk5, whereas the activity of MPK3 was only partially blocked. MKK5 interacted with the MEKK1 protein that was also involved in the salt-induced FSD signalling pathway. These data suggest that salt-induced FSD2 and FSD3 expressions are influenced by MEKK1 via MKK5-MPK6-coupled signalling. This MAP kinase cascade (MEKK1, MKK5, and MPK6) mediates the salt-induced expression of iron superoxide dismutases. © 2015 The Author.

Peng R.,University of Science and Technology Beijing | Zhai Q.,Beihang University | Xing L.,University of Massachusetts Dartmouth | Yang J.,Beihang University
Reliability Engineering and System Safety | Year: 2014

In many real-world applications, a mission may consist of several different tasks or phases that have to be accomplished in sequence. Such systems are referred to as phased-mission systems (PMS). In this paper we consider the demand-based PMS with parallel structure, where the system components function in parallel with different capacities in each phase of the mission and the mission is successful if and only if the total system capacity meets the predetermined mission demand in each phase. The reliability of the demand-based PMS (DB-PMS) with parallel structure subject to fault-level coverage (FLC) is first studied using a multi-valued decision diagram (MDD) based technique. The traditional MDD is modified to accommodate the FLC mechanism and new MDD construction and evaluation procedures are proposed for DB-PMS. To reduce the size of the MDD, an alternative construction procedure applying the branching truncation method and new reduction rules are further proposed. An upwards algorithm is put forward to evaluate the reliability of DB-PMS subject to FLC. The proposed approaches are illustrated through examples. © 2013 Elsevier Ltd.

Gao H.,Beihang University | Zhang J.,Beihang University | Wang R.,University of Science and Technology Beijing | Wang M.,Beihang University
Applied Catalysis B: Environmental | Year: 2015

Herein, Cu2O microcrystals are found to perform efficiently in hydrogen generation and formaldehyde degradation at room temperature, with MgO as a sacrificial agent, while other photocatalytic semiconductors such as TiO2, ZnO, Bi2O3, Fe2O3 and CuO exhibit poor capability under the same condition. This peculiarity of Cu2O microcrystals is comprehensively analyzed, focusing on exploring the formation of [Cu+]· paramagnetic during the reaction, which is first proposed as a principal factor for the hydrogen generation and formaldehyde degradation. Even more exciting, abundant hydroxyl radicals produced during this reaction process are detected via electron paramagnetic resonance spectrometry, which are particularly efficient in oxidizing formaldehyde and producing hydrogen. © 2015 Elsevier B.V.

Aleksandrov A.Y.,Saint Petersburg State University | Hu G.-D.,University of Science and Technology Beijing | Zhabko A.P.,Saint Petersburg State University
IEEE Transactions on Automatic Control | Year: 2014

Some classes of nonlinear time-delay systems are studied. It is assumed that the zero solution of a system is asymptotically stable when delay is equal to zero. By the Lyapunov direct method, and the Razumikhin approach, it is shown that in the case when the system is essentially nonlinear, i.e., the right-hand side of the system does not contain linear terms, the asymptotic stability of the trivial solution is preserved for an arbitrary positive value of the delay. Based on homogeneous approximation of a time-delay system some stability conditions are found. We treat large-scale systems with nonlinear subsystems. New stability conditions in certain cases, critical in the Lyapunov sense, are obtained. Three examples are given to demonstrate effectiveness of the presented results. © 2014 IEEE.

Pei Y.-L.,Beihang University | Liu Y.,University of Science and Technology Beijing
Journal of Alloys and Compounds | Year: 2012

Electrical and thermal transport properties of lead-based chalcogenides (PbTe, PbSe, and PbS) were studied with special emphasis on the lattice and the bipolar thermal conductivity. Both electrical resistivity and Seebeck coefficient show the transport behaviors related to the intrinsic excitation that determined by the band gap, power factors at room temperature reach 12 μW cm -1 K -2, 14 μW cm -1 K -2, and 16 μW cm -1 K -2 for PbS, PbSe and PbTe, respectively. PbTe shows the lowest total thermal conductivity, and PbS shows the highest total thermal conductivity, in which the bipolar thermal conductivity is proportional to the width of band gap, these contributions at 723 K were estimated to be 2.2%, 3.1%, and 1.1% for the PbTe, PbSe and PbS, respectively. This study demonstrates the possibility to enhance ZT value by the suppression of bipolar thermal conductivity by tuning the width of band gap, also indicates that inexpensive and earth-abundant PbSe and PbS would be promising alternative for PbTe in the thermoelectric applications. © 2011 Elsevier B.V. All rights reserved.

Xu Y.,University of Science and Technology Beijing | Wen X.,University of Science and Technology Beijing | Wen L.-S.,Liaoning University | Wu L.-Y.,CAS Academy of Mathematics and Systems Science | And 3 more authors.
PLoS ONE | Year: 2014

Nitrotyrosine is one of the post-translational modifications (PTMs) in proteins that occurs when their tyrosine residue is nitrated. Compared with healthy people, a remarkably increased level of nitrotyrosine is detected in those suffering from rheumatoid arthritis, septic shock, and coeliac disease. Given an uncharacterized protein sequence that contains many tyrosine residues, which one of them can be nitrated and which one cannot? This is a challenging problem, not only directly related to in-depth understanding the PTM's mechanism but also to the nitrotyrosine-based drug development. Particularly, with the avalanche of protein sequences generated in the postgenomic age, it is highly desired to develop a high throughput tool in this regard. Here, a new predictor called "iNitro-Tyr" was developed by incorporating the position-specific dipeptide propensity into the general pseudo amino acid composition for discriminating the nitrotyrosine sites from non-nitrotyrosine sites in proteins. It was demonstrated via the rigorous jackknife tests that the new predictor not only can yield higher success rate but also is much more stable and less noisy. A web-server for iNitro-Tyr is accessible to the public at For the convenience of most experimental scientists, we have further provided a protocol of step-by-step guide, by which users can easily get their desired results without the need to follow the complicated mathematics that were presented in this paper just for the integrity of its development process. It has not escaped our notice that the approach presented here can be also used to deal with the other PTM sites in proteins. © 2014 Xu et al.

Bao C.,University of Science and Technology Beijing | Bao C.,German Aerospace Center | Bessler W.G.,German Aerospace Center
Journal of Power Sources | Year: 2012

Computational efficiency is highly important for upscaling detailed electrode-level and cell-level models to the system level required for the design and control of fuel cells. We present a computationally efficient 1D + 1D fuel cell model based on a combination of analytical and numerical approaches. On the electrode level, we develop approximate analytical solutions for the 1D current/potential distribution via a hybrid algorithm of power-law approach and perturbation method. Compared to the conventional perturbation method, this work keeps the intrinsic nonlinearity of electrochemical kinetics, while providing clearer physical meaning than some purely mathematical methods like the Adomian decomposition method. By integrating the resulting overpotential profile into mass transfer models, concentration overpotentials are obtained and the thermodynamic framework is then used for analyzing the H 2/CO electrochemical co-oxidation kinetics. A novel expression is also presented to interconvert volume- and area-specific exchange current densities. On the cell level, a linear relationship between local current density and solid temperature is further developed for efficient 1D + 1D thermal along-the-channel numerical simulations without requiring computational iterations. Both the electrode-level and cell-level macroscopic fuel cell models are validated against full numerical solutions available in the open literatures over a wide range of operating conditions. With the hybrid analytical/numerical approximation in two dimensions, the computational framework is predicted to be sufficiently efficient for real-time simulations. © 2012 Elsevier B.V. All rights reserved.

Du Y.,Beihang University | Fang J.,Beihang University | Miao C.,University of Science and Technology Beijing
IEEE Transactions on Industrial Electronics | Year: 2014

This paper presents a frequency-domain identification method for an unmanned helicopter (UH) based on an adaptive genetic algorithm (AGA). By using a homemade microguidance, navigation, and control system (MGNCS), data regarding the inputs (control signals of servos) and outputs (states of the UH) are recorded. After data preprocessing, the attitude model of the UH is identified by employing the AGA. The identified model is then analyzed in the time domain and the frequency domain in comparison with the least squares (LS) method. Control compensators are designed based on the identified model. Automatic hovering is successfully achieved based on the compensators. Simulation and experimental results demonstrate the effectiveness and superiority of this identification method. © 1982-2012 IEEE.

Cao H.,Tsinghua University | Li B.,Tsinghua University | Zhang J.,CAS Chengdu Institute of Organic Chemistry | Lian F.,University of Science and Technology Beijing | And 2 more authors.
Journal of Materials Chemistry | Year: 2012

Herein, we report the synthesis of TiO 2-reduced graphene oxide composite (termed as TGC) nanostructures using tetrabutyl titanate as the titanium source via a solvothermal route. The TGC nanostructures were characterized by transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and adsorption-desorption isotherms for nitrogen measurements. The TGC was used as the anode of lithium ion batteries for investigation. The hybrid nanocomposite exhibited remarkable improvement in lithium ion insertion/extraction behaviour compared with TiO 2, which showed an initial irreversible capacity and a reversible capacity of 386.4 and 152.6 mAh g -1 for TGC after 100 cycles at a high charge rate of 5 C (1000 mA g -1), compared to 69.5 and 9.7 mAh g -1 for TiO 2, respectively. The enhanced electrochemical performance of TGC is attributed to the increased conductivity in the presence of reduced graphene oxide in TGC, the small size of the TiO 2 particles in TGC, which can shorten the transport paths for both Li + ions and electrons, and the enlarged electrode-electrolyte contact area, leading to more electroactive sites in TGC. © 2012 The Royal Society of Chemistry.

Duan S.,Beihang University | Wang R.,Beihang University | Wang R.,University of Science and Technology Beijing
NPG Asia Materials | Year: 2014

A synthetic route to achieve core/shell nanostructures consisting of noble metal cores and single crystal semiconductor shells with different crystal systems is proposed, which involves a simple phosphorization process from corresponding bimetallic heterostructures. The triphenylphosphine is designed to serve as both a capping agent and a phosphorous source during the formation of Au/Ni12P5 core/shell nanoparticles (NPs) from Au-Ni bimetallic heterodimers. The semiconductor shells of the obtained Au/Ni12P5 nanostructures are controlled to form single crystals with a thickness of B5 nm. The structure-dependent supercapacitor properties of Au-modified Ni12P5 nanostructures were further investigated. The synergistic effect of the metal/semiconductor nanostructure is observed to be superior to its oligomer-like counterpart when serving as a supercapacitor electrode. The specific capacitance of an electrode fabricated from core/shell NPs is 806.1 F g-1 with a retention of 91.1% after 500 charge-discharge cycles. © 2014 Nature Publishing Group All rights reserved.

Sun L.,Sichuan University | Yang T.,Sichuan University | Jia C.,University of Science and Technology Beijing | Xiong J.,Sichuan University
International Journal of Refractory Metals and Hard Materials | Year: 2011

The influence of the addition of 0.3, 0.5 and 0.7 wt.% VC on the density, microstructure and mechanical properties of WC-Cr3C2-11 wt.% Co with 0, 0.2, 0.4 and 0.6 wt.% Cr3C2 hard metals prepared by spark plasma sintering (SPS) at a temperature of 1200 °C (5 min, 40 MPa) was investigated. Microstructure analysis revealed that the WC grain size in the sintered hard metals was strongly influenced by the VC and Cr 3C2 content. With the addition of inhibitors and the increased amount of Cr3C2, the density is reduced, and on the contrary, the addition of VC as an inhibitor contributes to promoting the densification. The combined addition of Cr3C2 and VC could strongly reduce the WC grain growth to about 350 nm. Observation suggests that the fracture of WC-Co cemented carbide is brittle and intergranular. The amount of added VC/Cr3C2 should be controlled in a certain range. Samples with an appropriate proportion of VC/Cr3C2 added exhibit higher hardness which can be up to 1938 HV30. Toughness, too, can reach 16.34 MPa m1/2. © 2010 Elsevier Ltd. All rights reserved.

Wang J.-A.,University of Science and Technology Beijing | Wei X.-H.,Beijing Municipal Engineering Design Institute | Chen S.-J.,Shandong University of Science and Technology
Zhongguo Kuangye Daxue Xuebao/Journal of China University of Mining and Technology | Year: 2012

A quantitative relationship for the fractured rock permeability coefficient was obtained by conducting stress-strain permeability tests on intact and fractured rock samples. The stress seepage coupling mechanism is elucidated from these results. Mining a lower coal seam located above a confined aquifer in Shanxi province motivated this research. A discrete element numerical model was used to simulate fluid-solid coupling and determine stress and seepage in the floor strata. Four typical zones appear in the floor strata that are closely related to the horizontal stress. The damage state and the permeability are used to define these zones. If the direct floor stratum is seriously affected by mining induced pressure the horizontal stress is disordered and the damaged zone is about 13 m thick. The confining pressure in the strata above the Ordovician aquifer is low and hydraulic splitting fractures it easily. The thickness of the zone where water rises is about 17 m. The middle of the floor strata are less affected by mining and the confined aquifer. The horizontal stresses increase with increasing depth and the thickness of the water resisting layer is about 38 m. This is the zone that provides the key water resistant layer in the floor.

Tao H.-C.,University of Science and Technology Beijing | Huang M.,Tsinghua University | Fan L.-Z.,University of Science and Technology Beijing | Qu X.,University of Science and Technology Beijing
Solid State Ionics | Year: 2012

Si@SiO x/C nanoporous spheres as anode materials for high-performance lithium ion batteries were fabricated through a facile magnesiothermic reduction of well-ordered mesoporous silica and subsequent impregnating of carbon precursor into the Si@SiO x nanoporous spheres followed by carbonization at 800 °C. The obtained nanoporous spheres present an interweaved porous structure composed of high-capacity Si, inactive SiO x and conductive carbon, which can effectively enhance the electrochemical performance of the composite materials. The resulting Si@SiO x/C nanoporous spheres display a reversible specific capacity of 913 mA h g - 1 at the first cycle and the capacity retention ratio is 97% after 60 cycles at a current density of 100 mA g - 1. The nanoporous structure of Si, SiO x and C can effectively accommodate the volume change for Si-based materials' expansion, release the mechanical stress and improve the electronic conductivity. The Si@SiO x/C nanoporous spheres exhibit a great potential as anode materials for lithium ion batteries. © 2012 Elsevier B.V.

Zhu C.,University of Tennessee at Knoxville | Lu Z.P.,University of Science and Technology Beijing | Nieh T.G.,University of Tennessee at Knoxville
Acta Materialia | Year: 2013

Instrumented nanoindentation was conducted on a FeCoCrMnNi high-entropy alloy with a single face-centered cubic structure to characterize the nature of incipient plasticity. Experiments were carried out over loading rates of 25-2500 μN s-1 and at temperatures ranging from 22 to 150 °C. The maximum shear stress required to initiate plasticity was found to be within 1/15 to 1/10 of the shear modulus and relatively insensitive to grain orientation. However, it was strongly dependent upon the temperature, indicating a thermally activated process. Using a statistical model developed previously, both the activation volume and activation energy were evaluated and further compared with existing dislocation nucleation models. A mechanism consisting of a heterogeneous dislocation nucleation process with vacancy-like defects (∼3 atoms) as the rate-limiting nuclei appeared to be dominant. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

He J.Y.,University of Science and Technology Beijing | Liu W.H.,University of Science and Technology Beijing | Wang H.,University of Science and Technology Beijing | Wu Y.,University of Science and Technology Beijing | And 3 more authors.
Acta Materialia | Year: 2014

A series of six-component (FeCoNiCrMn)100-xAlx (x = 0-20 at.%) high-entropy alloys (HEAs) was synthesized to investigate the alloying effect of Al on the structure and tensile properties. The microstructures of these alloys were examined using transmission electron microscopy, and crystalline phase evolution was characterized and compared with existing models. It was found that the crystalline structure changed from the initial single face-centered cubic (fcc) structure to a duplex fcc plus body-centered cubic (bcc) structure and then a single bcc structure as the Al concentration was increased. Resulting from the structural changes there were also corresponding variations in tensile properties. In the single fcc region, alloys behaved like a solid solution with relatively low strength but extended ductility. In the mixed structure region, alloys behaved like a composite with a sharp increase in strength but reduced ductility. In the single bcc region, alloys became extremely brittle. In this study, close correlation between the microstructure and mechanical properties was also discussed and presented. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Feng Z.,University of Science and Technology Beijing | Feng Z.,University of Alberta | Zuo M.J.,University of Alberta | Chu F.,Tsinghua University
Mechanical Systems and Signal Processing | Year: 2010

Fractal dimension provides a measure of the complexity of a dynamic system, and contains the health information of a machine. The basics of regularization dimension and the effects of Gaussian kernel parameters on the regularization of a signal are introduced. Regularization dimension has advantages over other fractal dimensions because the scale-independent range can be selected according to the signal frequency components of interest. Experimental gearbox vibration signals are analyzed by means of spectral analysis firstly, and then according to the spectral structure, the scale-independent range is selected for computing the regularization dimension, which increases monotonically with increasing gear damage degree. Comparison with correlation dimension and kurtosis shows the advantages of regularization dimension in assessing the localized gear damage. © 2009 Elsevier Ltd. All rights reserved.

Wang J.J.,University of Science and Technology Beijing | Ma X.Q.,University of Science and Technology Beijing | Li Q.,Xi'an Jiaotong University | Britson J.,Pennsylvania State University | And 2 more authors.
Acta Materialia | Year: 2013

An efficient numerical algorithm based on a Fourier spectral iterative perturbation method is proposed to accurately compute the electrostatic fields in three-dimensional (3D) microstructures with arbitrary dielectric inhomogeneity and anisotropy. The method can be conveniently implemented in phase field modeling of microstructure evolution in systems with inhomogeneous dielectric constants as well as inhomogeneous polarization and charge distributions. It is employed to determine the temperature-shape (aspect ratio) phase diagram, domain structures, and domain switching of PbTiO3 nanoparticles using phase field simulations. It is shown that the Curie temperature is enhanced for nanowires and nanorods and reduced for nanodots. The critical sizes below which the ferroelectricity disappears for the nanowire and thin film are estimated to be around 1.4 nm. Vortex domain structures are found in nanorods, nanodots, and nanodisks. Results are in general agreement with existing experimental observations and first principle calculations. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Feng Z.,University of Science and Technology Beijing | Chu F.,Tsinghua University
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2013

A thorough understanding of the vibration signal spectral structure is helpful for fault diagnosis of planetary gearboxes via common yet effective spectral analysis. Considering both the amplitude modulation and the frequency modulation effects due to gear manufacturing errors or distributed faults, as well as the amplitude modulation caused by the passing effect of planets, signal models of normal and distributed fault cases and their Fourier transforms were given, and the spectral characteristics were summarized in closed form. Meanwhile, explicit equations for calculating the characteristic frequency of distributed gear fault were deduced. The theoretical derivations were validated using experimental datasets. According to the theoretical derivations, the naturally developed gear fault in a planetary gearbox was detected and located. © 2013 Chinese Society for Electrical Engineering.

Wang H.,University of Science and Technology Beijing | Wang K.,University of Science and Technology Beijing | Tao J.,Xiamen University | Jiang J.,University of Science and Technology Beijing
Chemical Communications | Year: 2012

Correlation between molecular structures and slow relaxation of magnetization of three mixed (phthalocyaninato)(porphyrinato) dysprosium(iii) double-deckers clearly reveals the effect of the sandwich-type molecular structure, in particular the twist angle, on the quantum tunneling (QT) at zero dc field of these complexes, providing the first direct evidence to the theoretical inference. © 2012 The Royal Society of Chemistry.

Zhang Y.,University of Science and Technology Beijing | Yang X.,University of Science and Technology Beijing | Liaw P.K.,University of Tennessee at Knoxville
JOM | Year: 2012

This article reviews the recent work on the high-entropy alloys (HEAs) in our group and others. HEAs usually contain five or more elements, and thus, the phase diagram of HEAs is often not available to be used to design the alloys. We have proposed that the parameters of δ and Ω can be used to predict the phase formation of HEAs, namely Ω ≥ 1.1 and δ ≤ 6.6%, which are required to form solid-solution phases. To test this criterion, alloys of TiZrNbMoV x and CoCr FeNiAlNb x were prepared. Their microstructures mainly consist of simple bodycentered cubic solid solutions at low Nb contents. TiZrNbMoV x alloys possess excellent mechanical properties. Bridgman solidification was also used to control the microstructure of the CoCrFeNiAl alloy, and its plasticity was improved tobe about 30%. Toour surprise, the CoCrFeNiAl HEAs exhibit no apparent ductile-to-brittle transition even when the temperatures are lowered from 298 K to 77 K. © 2012 TMS.

Feng Z.,University of Science and Technology Beijing | Chu F.,Tsinghua University
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2013

The frequency modulation part contains the gear fault information, and is free from the effect of time varying vibration transfer paths. This feature is helpful to avoid the complex sidebands in Fourier spectra and additional amplitude modulation caused by the planet passing effect or the time variant vibration propagation paths. According to the frequency modulation characteristics of planetary gearbox vibration signals, a frequency demodulation analysis method based on empirical mode decomposition was proposed to simplify the signal analysis in fault diagnosis. The criterion for selecting sensitive intrinsic mode function was proposed, the explicit equations for the Fourier spectra of instantaneous frequency were deduced, and the instantaneous frequency spectral characteristics of sun, planet and ring gear faults were summarized. The proposed method was validated using simulated signal and lab experimental datasets, and the localized damage of sun, planet and ring gears was diagnosed via frequency demodulation analysis. © 2013 Chin. Soc. for Elec. Eng.

Feng Z.,University of Science and Technology Beijing | Zhao L.,University of Science and Technology Beijing | Chu F.,Tsinghua University
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2013

Gear faults are usually originated from localized damage. The vibration spectral characteristics of sun, planet and ring gears with localized damage are different from those of distributed gear faults, thus it is important to investigate them for fault diagnosis of planetary gearboxes via vibration signal spectral analysis. Considering both the amplitude modulation and the frequency modulation effects due to localized gear damage, as well as the time variation of vibration transfer paths, signal models of sun, planet and ring gear localized damage cases and their Fourier spectra were given in closed form, and the spectral characteristics were summarized. Meanwhile, explicit equations for calculating the characteristic frequency of localized gear faults were deduced. The theoretical derivations were validated using experimental datasets. According to the theoretical derivations, the localized damage of sun, planet and ring gears in a planetary gearbox was detected and located via spectral analysis. © 2013 Chinese Society for Electrical Engineering.

Zhu L.-F.,University of Science and Technology Beijing | Zhang B.-P.,University of Science and Technology Beijing | Zhao L.,University of Science and Technology Beijing | Li J.-F.,Tsinghua University
Journal of Materials Chemistry C | Year: 2014

A series of solid solutions of BaTiO3-x(0.4CaTiO 3-0.6BaSnO3) (abbreviated as BT-x(CT-BS), x = 0.00-0.20 mol) were prepared to search for high performance lead-free piezoelectric ceramics. Through content tailoring, a complex phase transition was confirmed by X-ray diffraction and Raman spectra as well as temperature dependence of the dielectric constant, which occurs from tetragonal(T)-orthorhombic(O) coexistence at 0 ≤ x ≤ 0.12 to rhombohedral(R)-O-T and R-O/T-cubic(C) multiphase coexistence at x = 0.16 and 0.20, respectively. The lower EC = 1.31 kV cm-1 and higher Pr = 9.48 μm cm-2 as well as high piezoelectric response d33 = 570 pC N-1 were achieved in BT-x(CT-BS) ceramics at an optimal composition of x = 0.16. The ultrahigh converse piezoelectric coefficient d*33 = 1444 pm V-1 and strain = 0.070% which are the highest values reported so far in lead-free ceramics also were achieved at x = 0.16, suggesting that a BT-x(CT-BS) system is a promising lead-free alternative material for electromechanical actuator applications. This journal is © the Partner Organisations 2014.

Xu K.,Tsinghua University | Wang C.,Tsinghua University | Liu H.,University of Science and Technology Beijing | Qian Y.,Tsinghua University
Chemosphere | Year: 2011

This study investigated the simultaneous removal of P and K from synthetic urine through the precipitation of magnesium potassium phosphate hexahydrate (MPP, MgKPO4·6H2O) in bench-scale experiments. Results show that the removal efficiencies of P and K are mainly determined by the solution pH and the molar ratio of Mg:K:P. Co-precipitation of struvite-type compounds, i.e., magnesium ammonium phosphate hexahydrate (MAP, MgNH4PO4·6H2O), magnesium sodium phosphate heptahydrate (MSP, MgNaPO4·7H2O), and MPP, was confirmed by analysis of the solid precipitates using a Scanning Electron Microscope/Energy Dispersive X-ray Apparatus and an X-ray Diffractometer. The co-precipitation significantly influenced the removal of K. As much ammonium as possible should be removed prior to MPP precipitation because MAP had higher tendency to form than MPP. The inevitable co-precipitation of MPP and MSP resulted in the addition of more MgCl2·6H2O and Na2HPO4·12H2O to obtain the high removal of K. In total, the removal efficiencies of P and K were 77% and 98%, respectively, in the absence of ammonium when pH was 10 and the molar ratio of Mg:K:P was 2:1:2. The results indicate that the MPP precipitation is an efficient method for the simultaneous removal of P and K to yield multi-nutrient products. © 2011.

Ahmad M.,Tsinghua University | Rafi-Ud-din,University of Science and Technology Beijing | Pan C.,Tsinghua University | Zhu J.,Tsinghua University
Journal of Physical Chemistry C | Year: 2010

Hydrogen storage capabilities of controlled synthesized ZnO-based nanostructures have been investigated. The microscopic results reveal that the products consist of hollow ZnO microspheres composed of nanowires, hollow Sb-doped nanospheres, and Al-doped nanobelts. Energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) give evidence that Sb and Al dopants are successfully substituted into nanospheres and nanobelts, respectively. The photoluminescence (PL) spectra exhibit a strong green emission band due to defects in nanostructures which lead to a significant role in the hydrogen storage applications. The hydrogen storage characteristics prove that the defects in nanostructures are responsible for higher hydrogen absorption. Among the nanostructures the maximum hydrogen storage capacity of about 2.94 wt % is achieved under the pressure of 5 MPa for Al-doped ZnO nanobelts, and about 81.6% of the stored hydrogen can be released under ambient pressure at 373 K. The highly reversible absorption/desorption reactions exhibit that Al-doped nanobelts are promising material for hydrogen storage. © 2010 American Chemical Society.

Gao X.,University of Science and Technology Beijing | Xu L.-P.,University of Science and Technology Beijing | Xue Z.,CAS Beijing National Laboratory for Molecular | Feng L.,Tsinghua University | And 4 more authors.
Advanced Materials | Year: 2014

Large-area dual-scaled porous nitrocellulose (p-NC) membranes are fabricated by a facile, inexpensive and scalable perforating approach. These p-NC membranes show stable superhydrophilicity in air and underwater superoleophobicity. The p-NC membranes with intrinsic nanopores and array of microscale perforated pores could selectively and efficiently separate water from various oil/water mixtures with high efficiency (> 99%) rapidly. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

He J.Y.,University of Science and Technology Beijing | Zhu C.,University of Tennessee at Knoxville | Zhou D.Q.,University of Science and Technology Beijing | Liu W.H.,University of Science and Technology Beijing | And 2 more authors.
Intermetallics | Year: 2014

Steady state flow behavior of the FeCoNiCrMn high-entropy alloy at temperatures ranging from 1023 to 1123 K was systematically characterized. It was found that the stress exponent (i.e., the reciprocal of strain-rate sensitivity) was dependent on the applied strain rate, and specifically the stress exponent is high (∼5) in the high strain rate regime, but decreases with decreasing strain rate. Microstructural examinations of the samples before and after deformation were performed to understand the interplay of the microstructures with the corresponding properties. Based on the observations, it was proposed that, at high strain rates, the deformation of the current high-entropy alloy was controlled by dislocation climb and the rate limiting process was the diffusion of Ni. At low strain rates, however, the deformation appeared to be controlled by the viscous glide of dislocations. Moreover, at the slowest strain rate (i.e., the longest thermal exposure time), new phases evolved, which caused elemental redistribution and weakening of the material. © 2014 Elsevier Ltd. All rights reserved.

Wang H.,University of Science and Technology Beijing | Wang K.,University of Science and Technology Beijing | Bian Y.,University of Science and Technology Beijing | Jiang J.,University of Science and Technology Beijing | Kobayashi N.,Tohoku University
Chemical Communications | Year: 2011

Two novel mixed (phthalocyaninato)(porphyrinato) rare-earth and cadmium heterometal complexes have been fabricated in one-pot reaction and their sandwich quadruple-decker nature is unambiguously revealed by X-ray single crystal analysis. © 2011 The Royal Society of Chemistry.

Wang L.,University of Science and Technology Beijing | Wang L.,University of Tennessee at Knoxville | Lu Z.P.,University of Science and Technology Beijing | Nieh T.G.,University of Tennessee at Knoxville
Scripta Materialia | Year: 2011

Nanoindentation tests were performed on an Au49Ag 5.5Pd2.3Cu26.9Si16.3 metallic glass. The critical shear stress for the first pop-in, i.e. the onset of yielding, was measured at different temperatures. The volume and the activation free energy for the shear transformation zones were determined from the stress-temperature relationship. The strain-rate dependence of serrated flow in nanoindentation was also characterized. The sizes of shear band nucleus at different temperatures were found to be practically constant. The implication of a constant nucleus size is discussed. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Xiao L.-L.,University of Science and Technology Beijing | Xiao L.-L.,Chinese Academy of Geological Sciences | Liu F.-L.,Chinese Academy of Geological Sciences | Chen Y.,CAS Institute of Geology and Geophysics
Precambrian Research | Year: 2014

Garnet-bearing metapelites are cropped out in the Zanhuang metamorphic complex located in the central section of the N-S trending Trans-North China Orogen. Petrological studies indicate that these garnet-bearing metapelites preserve three distinct metamorphic assemblages (M1-M3). The cores of garnet porphyroblasts and fine-grained inclusions of plagioclase+quartz±biotite±apatite±magnetite±rutile±ilmenite define the prograde metamorphic stage (M1). The assemblage of the peak metamorphic stage (M2) consists of biotite+plagioclase+quartz±kyanite±hornblende±magnetite±ilmenite in equilibrium with the lowest-XMn garnet rims. The peak metamorphism was followed by a near-isothermal decompressional stage (M3) and the development of symplectitic coronas of biotite+plagioclase+quartz±hornblende±magnetite surrounding garnet porphyroblasts. Quantitative phase equilibria modeling and traditional thermobarometric estimations were applied to yield P-T conditions of 4.5-5.9kbar and 551-596°C for stage M1, 9.6-12.3kbar and 770-830°C for stage M2, and ~4.7kbar and ~635°C for stage M3. The combination of the mineral inclusions, mineral compositions, and metamorphic reactions in the Zanhuang metapelites defines a clockwise P-T path with nearly isothermal decompression, which is considered to have been related to the amalgamation of the Eastern and Western Blocks to form the North China Craton. Abundant U-Pb spot analyses of metamorphic zircons from the gneiss and amphibolite reveal two discrete, meaningful ages of metamorphism within the Zanhuang complex: the first age dates to ~2507Ma, and the second age dates to ~1839Ma. The first age group (~2507Ma) was most likely associated with a regional Neoarchean granulite-facies metamorphic event within the North China Craton, whereas the second age group (~1839Ma) is interpreted as the result of a Paleoproterozoic orogenic event that occurred in the Trans-North China Orogen (TNCO). © 2014 Elsevier B.V.

Zhang D.,Shandong University of Technology | Zhang D.,University of Science and Technology Beijing | Wang P.,Shandong University of Technology
Inorganic Chemistry Communications | Year: 2012

With a new pentacyanidecobalt(III) precursor K 2[Co(CN) 5(CH 3CN)] and a bicompartimental Schiff base manganese(III) compound, a new two-dimensional cyanide-bridged Co(III)-Mn(III) coordination polymer constructed by hydrogen-bond interactions has been successfully synthesized and characterized by elemental analysis, IR spectroscopy and X-ray structure determination. Single X-ray diffraction analysis reveals this cationic cyanide-bridged tetranuclear complex is self-complementary through coordinated aqua ligands from one complex and the free O 4 compartments from the neighboring complex, giving interesting 2D supramolecular structure. Investigation over magnetic susceptibility reveals the overall weak antiferromagnetic coupling between the adjacent Mn(III) ions. © 2012 Elsevier B.V.

Liu L.,Tsinghua University | Fu L.,Tsinghua University | Jiang Y.,Tsinghua University | Guo S.,University of Science and Technology Beijing
Renewable and Sustainable Energy Reviews | Year: 2011

Charging heating fees based on floor space in China leaves building developers no economic returns on the investment to weatherize the buildings and install regulation devices with terminal equipment. Therefore, they lack incentives to improve the thermal insulation properties of the buildings. Tenants also lack incentives to efficiently use heat, opening windows to cool down rooms when they are overheated, without concern for the amount of heat wasted. In response, over the past decade, the Chinese government has invested large amounts of resources in an effort to promote energy conservation with heating systems by trying to change the fee method based on floor space to amount of heat used, but with little effect. The major issues related to reform with the heat-metering system are elaborated in this paper by comparing the pros and cons of several metering methods. Firstly, room temperatures are unable to be effectively adjusted using the current methods, meaning that the original intention to save energy cannot be achieved. Secondly, current heat-metering methods are not acceptable to users, which creates its own problems. Heat metering based on households in apartment buildings, the primary living space for Chinese people, causes two problems: the energy consumed by households located at the top or at the corner of buildings is two to three times higher than households located elsewhere within the building; heating fees may increase by 20-30% if surrounding households are not heated. Current metering methods are unable to effectively resolve these two problems, therefore, they are not accepted. To overcome these difficulties, a proper metering and charging method must be developed which is both acceptable to users and able to guarantee good room temperature control at the same time. To achieve this goal, this paper presents a new method: the total heating fee of a building is allocated according to the accumulated on-time as well as the floor space of each household. Not only can this new method control the user behavior of opening windows or setting the starting point too high, but also resolve problems caused by location and heat transfer between households. It is also effective in promoting energy saving by users and appears to be acceptable to users. Survey results show that it is acceptable to a large number of users. It seems that this is the most practical way to reform the current methods for heat metering based on household use. © 2010 Elsevier Ltd.

Ge Z.-H.,University of Science and Technology Beijing | Zhang B.-P.,University of Science and Technology Beijing | Liu Y.,University of Science and Technology Beijing | Li J.-F.,Tsinghua University
Physical Chemistry Chemical Physics | Year: 2012

Nanostructured Bi 2-xCu xS 3 (x = 0, 0.002, 0.005, 0.007, 0.01, 0.03) thermoelectric polycrystals were fabricated by combining mechanical alloying (MA) and spark plasma sintering (SPS) methods. The effect of Cu content on the microstructure and thermoelectric property of Bi 2-xCu xS 3 bulk samples was investigated. It was found that the subtle tailoring of Cu content could reduce both the electrical resistivity and the thermal conductivity at the same time, and consequently enhancing the thermoelectric property. A low electrical resistivity of 1.34 × 10 -4 Ω m -1 and a low thermal conductivity of 0.52 W m -1 K -1 were obtained for the Bi 1.995Cu 0.005S 3 sample at 573 K. The low thermal conductivity is supposed to be due to the nanoscopic Cu-rich regions embedded in the host matrix. A peak ZT value of 0.34 at 573 K was achieved for the Bi 1.995Cu 0.005S 3 composition, which is the highest value in the Bi 2S 3 system reported so far. © 2012 the Owner Societies.

Du Y.,University of Science and Technology Beijing | Xiong P.,Georgia Institute of Technology | Fan Y.,Tsinghua University | Li X.,Massachusetts Institute of Technology
IEEE Transactions on Systems, Man, and Cybernetics Part A:Systems and Humans | Year: 2011

Current methods that deal with concurrent workflow temporal violations only focus on checking whether there are any temporal violations. They are not able to point out the path where the temporal violation happens and thus cannot provide specific solutions. This paper presents an approach based on a sprouting graph to find out the temporal violation paths in concurrent workflow processes as well as possible solutions to resolve the temporal violations. First, we model concurrent workflow processes with time workflow net and a sprouting graph. Second, we update the sprouting graph at the checking point. Finally, we find out the temporal violation paths and provide solutions. We apply the approach in a real business scenario to illustrate its advantages: 1) It can dynamically check temporal constraints of multiple concurrent workflow processes with resource constraints; 2) it can give the path information in the workflow processes where the temporal violation happens; and 3) it can provide solution to the temporal violation based on the analysis. © 2011 IEEE.

Ge Z.-H.,University of Science and Technology Beijing | Zhang B.-P.,University of Science and Technology Beijing | Li J.-F.,Tsinghua University
Journal of Materials Chemistry | Year: 2012

We have designed a composite-like microstructure to improve the thermoelectric (TE) properties of Bi 2S 3 polycrystals. The nanosized Bi 2S 3 powders derived from mechanical alloying (MA) were mixed with [001] oriented single crystalline Bi 2S 3 nanorods prepared by hydrothermal synthesis (HS), which were densified by spark plasma sintering (SPS) to form a composite-like microstructure bulk with road-like structures consisting of nanorods. Because the nanorods provide good electron transport paths, the carrier mobility of the composite-like Bi 2S 3 bulk materials was improved by more than two orders of magnitude by mixing 10 wt% nanorods into the MA-derived powders. The electrical resistivity was also reduced from 2.5 × 10 -2 to 8.5 × 10 -4 Ωm at 323 K, but the thermal conductivity was just slightly increased, resulting in a significantly enhanced ZT value, which was almost two times higher than that of the nanorod-free sample. This study demonstrated the possibility to significantly enhance the ZT value of TE bulks by combining the advantages of single crystals and polycrystals via controlling the microstructure without any chemical doping. © 2012 The Royal Society of Chemistry.

Wang L.,University of Science and Technology Beijing | Chen Y.,University of Jinan | Bian Y.,University of Science and Technology Beijing | Jiang J.,University of Science and Technology Beijing
Journal of Physical Chemistry C | Year: 2013

Crystalline nanostructures with octahedral morphology have been prepared by self-assembling of cationic porphyrin (H6TPyP)4+· 4Cl- produced through chemical reaction route in aqueous solution depending on the synergistic interactions among hydrogen-bonding, π-π stacking, and ion pairing. Unexpectedly, the gradual decrease in pH by the slow evaporation of solvent in the nano-octahedron aqueous suspension obtained in situ led to the selective etching of the original nanocrystal and the isolation of (H6TPyP)4+·4Cl- bulk single crystals in the last stage. More interestingly, the increase in pH by adding water again into this bulk single-crystal-containing system led to the regeneration of nano-octahedrons, indicating the reversible transformation between porphyrin nano-octahedrons and bulk single crystals triggered by pH. Mechanistic investigations through powder and single-crystal X-ray diffraction analyses together with the electron microscopic, in particular, HRTEM, clearly reveal that the unique surface effect and anisotropic character of the nanomaterials differing from the bulk organic materials are responsible for such pH-sensitive reversible transformation of the two crystalline materials by controlling the dissolution or aggregation of (H6TPyP)4+·4Cl -, which actually induces the reversible formation and breaking of the (pyridine)N+-H···Cl -···H-O(H2O) ···H-N+(pyridine) hydrogen bonds among cationic porphyrin building blocks at different pH. This result, to control the crystallinity and the unprecedented reversible transformation between nanocrystal and bulk single crystals just by tuning the pH of the synthesis process, as well as the use of the peculiar nanoeffect such as surface effect to adjust the self-assembling process, provides useful a tool for the controllable synthesis of crystalline materials and is expected to be helpful for further research and application of organic nanomaterials. © 2013 American Chemical Society.

Li Z.,Tsinghua University | Feng Z.,University of Science and Technology Beijing | Chu F.,Tsinghua University
Journal of Sound and Vibration | Year: 2014

Load identification, as a kind of indirect identification method, uses system characteristic and responses to calculate loads. A method based on wavelet multi-resolution analysis is proposed in this paper. By wavelet decomposition and transform at certain resolutions, the proposed method transforms the convolution relation between responses and loads in time domain into the linear multiplicative relation between system responses and wavelet responses in the wavelet domain. Loads can be identified as long as the linear multiplicative relation is solved. Qualitative and quantitative rules are proposed for selecting parameters that affect the accuracy of the proposed method, and are illustrated via numerical investigations. The method is illustrated by a multi-input-multi-output numerical simulation. A multi-input-multi-output laboratory experiment is performed to compare the proposed method with the frequency method on the identification ability. © 2013 Elsevier Ltd.

Si X.-S.,HIGH-TECH | Si X.-S.,Tsinghua University | Wang W.,University of Science and Technology Beijing | Hu C.-H.,HIGH-TECH | Zhou D.-H.,Tsinghua University
IEEE Transactions on Reliability | Year: 2014

The use of the observed degradation data of a system can help to estimate its remaining useful life (RUL). However, the degradation progression of the system is typically stochastic, and thus the RUL is also a random variable, resulting in the difficulty to estimate the RUL with certainty. In general, there are three sources of variability contributing to the uncertainty of the estimated RUL: 1) temporal variability, 2) unit-to-unit variability, and 3) measurement variability. In this paper, we present a relatively general degradation model based on a Wiener process. In the presented model, the above three-source variability is simultaneously characterized to incorporate the effect of three-source variability into RUL estimation. By constructing a state-space model, the posterior distributions of the underlying degradation state and random effect parameter, which are correlated, are estimated by employing the Kalman filtering technique. Further, the analytical forms of not only the probability distribution but also the mean and variance of the estimated RUL are derived, and can be real-time updated in line with the arrivals of new degradation observations. We also investigate the issues regarding the identifiability problem in parameter estimation of the presented model, and establish the according results. For verifying the presented approach, a case study for gyros in an inertial platform is provided, and the results indicate that considering three-source variability can improve the modeling fitting and the accuracy of the estimated RUL. © 2014 IEEE.

Li J.,University of Science and Technology Beijing | Wang Y.,University of Science and Technology Beijing | Dong E.,University of Science and Technology Beijing | Chen H.,University of Science and Technology Beijing | Chen H.,Tsinghua University
Lab on a Chip - Miniaturisation for Chemistry and Biology | Year: 2014

A technology is presented to fabricate a microfluidic chip in which the microchannels and the microelectrodes of sensors are integrated directly into the copper sheet on a printed circuit board. Then, we demonstrate an application of the generation of oil-in-water and water-in-oil emulsion droplets on this microfluidic chip driven by a USB interface, and the droplet size is detected by the microelectrodes on the downstream microchannel. The integration of the microfluidic chip is improved by the direct connection of the channels to the microelectrodes of the driving unit and of the sensors on the same substrate, and it is a promising way to integrate microfluidics into a more complex micro electrical-mechanical system (MEMS). This journal is © The Royal Society of Chemistry 2014.

Fukuma Y.,RIKEN | Wang L.,RIKEN | Wang L.,University of Science and Technology Beijing | Idzuchi H.,University of Tokyo | And 7 more authors.
Nature Materials | Year: 2011

The non-local spin injection in lateral spin valves is strongly expected to be an effective method to generate a pure spin current for potential spintronic application. However, the spin-valve voltage, which determines the magnitude of the spin current flowing into an additional ferromagnetic wire, is typically of the order of 1μV. Here we show that lateral spin valves with low-resistivity NiFe/MgO/Ag junctions enable efficient spin injection with high applied current density, which leads to the spin-valve voltage increasing 100-fold. Hanle effect measurements demonstrate a long-distance collective 2π spin precession along a 6-μm-long Ag wire. These results suggest a route to faster and manipulable spin transport for the development of pure spin-current-based memory, logic and sensing devices. © 2011 Macmillan Publishers Limited. All rights reserved.

Wang D.,University of Science and Technology Beijing | Zhou T.,Beijing University of Chemical Technology | Zha J.-W.,University of Science and Technology Beijing | Zhao J.,University of Science and Technology Beijing | And 3 more authors.
Journal of Materials Chemistry A | Year: 2013

The fabrication and dielectric properties of a novel multi-component high-k composite system consisting of poly(vinylidene fluoride), surface- functionalized graphene nanosheets and BT nanoparticles (fRGO-BT/PVDF) were investigated. The fRGO nanosheets were prepared through the π-π stacking of polyaniline and GO following in situ hydrazine reduction. The fRGO-BT/PVDF nanocomposites were fabricated by a solution casting and hot-pressing approach. SEM results confirm that fRGO and BT are well dispersed within the PVDF matrix. The dielectric properties of the binary fRGO/PVDF nanocomposites exhibit a typical percolation transition with the percolation threshold of 1.49 vol%. This type of nanocomposite, co-filled with conductive graphene nanosheets and high-k ceramics, shows a high kr (65) and a relatively low dielectric loss (tan δ = 0.35) at a high frequency of 1 MHz. Meanwhile, the dielectric properties of the fRGO-BT/PVDF nanocomposites show temperature independent behavior over a wide temperature range. These flexible, high-k fRGO-BT/PVDF nanocomposites are potential flexible dielectric materials for use in high-frequency capacitors and electronic devices. © 2013 The Royal Society of Chemistry.

Tao H.-C.,University of Science and Technology Beijing | Huang M.,Tsinghua University | Fan L.-Z.,University of Science and Technology Beijing | Qu X.,University of Science and Technology Beijing
Electrochimica Acta | Year: 2013

Core-shell structured Si/C nanocomposites with different nitrogen contents are prepared by in situ polymerization of aniline in the suspension of silicon nanoparticles followed by carbonization of Si/polyaniline (PANI) nanocomposites at different temperatures. The nitrogen contents of Si/C nanocomposites decrease gradually with increasing carbonization temperatures. The effect of nitrogen contents on the electrochemical performance of Si/C nanocomposites as anode materials for lithium ion batteries is investigated. It is found that the Si/C nanocomposites with 4.75 wt.% nitrogen exhibit the high specific capacity of 795 mAh g-1 after 50 cycles at a current density of 100 mA g -1 and excellent cycling stability. The appropriate nitrogen in Si/C nanocomposites plays a beneficial role in the improvement of electrochemical performance. The nitrogen in Si/C nanocomposites increases the reversible capacity, which may be due to the formation of vacancies and dangling bonds around the nitrogen sites. © 2012 Elsevier Ltd. All Rights Reserved.

Chen Y.,University of Science and Technology Beijing | Xu G.,University of Science and Technology Beijing | Li J.,University of Science and Technology Beijing | Zhang Y.,University of Science and Technology Beijing | And 2 more authors.
Electrochimica Acta | Year: 2013

Solid solution material of 0.5Li2MnO3·0. 5LiNi0.33Co0.33Mn0.33O2 (alternatively Li[Li0.2Mn0.54Ni0.13Co 0.13]O2) was synthesized by a fast co-precipitation method which takes sulfates with high solubility as the transition metal sources of mixed hydroxide precursor. The optimal synthetic conditions were determined through the design of orthogonal experiments. The properties of samples synthesized under the best conditions were investigated in detail. The XRD pattern of 0.5Li2MnO3·0.5LiNi0.33Co 0.33Mn0.33O2 revealed a well ordered hexagonal layered structure with the evident feature of super lattice caused by Li 2MnO3. FESEM images showed that the powders possess small and unagglomerated particles with size range of 100-300 nm. XPS analysis results demonstrated that the valence states of Ni, Co, Mn are +2, +3, and +3.52 respectively. The electrochemical measurements showed that the optimal material delivers initial discharge capacity of 315.3 mAh g-1 at 1/20 C between 2.0 and 4.8 V with good cycle stability after firstly several cycles. CV test proved that the high capacity performance is ascribed to the redox of oxygen or its species at the electrode surface. Rate test showed that 179.5 mAh g-1 was obtained at 2 C which is considerably high, as far as we concerned. © 2012 Elsevier Ltd.

Hou J.,University of Science and Technology Beijing | Cheng H.,University of Science and Technology Beijing | Takeda O.,Tohoku University | Zhu H.,University of Science and Technology Beijing
Angewandte Chemie - International Edition | Year: 2015

The photochemical conversion of carbon dioxide provides a straightforward and effective strategy for the highly efficient production of solar fuels with high solar-light utilization efficiency. However, the high recombination rate of photoexcited electron-hole (e-h) pairs and the poor photostability have greatly limited their practical applications. Herein, a practical strategy is proposed to facilitate the separation of e-h pairs and enhance the photostability in a semiconductor by the use of a Schottky junction in a bimetal-graphene-semiconductor stack array. Importantly, Au-Cu nanoalloys (ca. 3nm) supported on a 3D ultrathin graphene shell encapsulating a p-type Cu2O coaxial nanowire array promotes the stable photochemical reduction of CO2 to methanol by the synergetic catalytic effect of interfacial modulation and charge-transfer channel design. This work provides a promising lead for the development of practical catalysts for sustainable fuel synthesis. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

He F.,University of Science and Technology Beijing | Zhang Q.,Tsinghua University | Zhang Q.,University of Science and Technology Beijing | Lei J.,Tsinghua University | And 2 more authors.
Energy Policy | Year: 2013

This paper used data from 50 enterprises in China's iron and steel industry to evaluate their energy efficiency and productivity change. The study first used a conventional data envelopment analysis model and the Malmquist Productivity Index (MPI) to measure the energy efficiency and productivity change over the period 2001-2008. The results indicated inefficiency in many of the plants: The average energy efficiency was only 61.1%. The annual growth rate of productivity was 7.96$ over this period and technical change was the main contributor to this growth. The research then took undesirable outputs into consideration by using the Malmquist-Luenberger Productivity Index (MLPI) to explore the productivity change from 2006 to 2008. Omitting undesirable outputs would result in biased efficiency change and technical change. This paper also claimed that environmental regulation has a potentially positive impact on technical change. © 2012 Elsevier Ltd.

Ren H.,Tsinghua University | Wu Y.,Tsinghua University | Ma N.,University of Science and Technology Beijing | Xu H.,Tsinghua University | Zhang X.,Tsinghua University
Soft Matter | Year: 2012

In this paper we report the synthesis and study of a series of side-chain selenium-containing amphiphilic poly(ethylene oxide-b-acrylic acid) block copolymers PEO-b-PAA-Se. These block copolymers can self-assemble in aqueous solution and form spherical micellar aggregates. The selenide group of PEO-b-PAA-Se can change into hydrophilic selenoxide under mild oxidation of 0.1% hydrogen peroxide, leading to the disassembly of the spherical micellar aggregates. Small compounds like Nile Red can be encapsulated into the micellar aggregates and show fast release upon the addition of 0.1% hydrogen peroxide. More interestingly, the oxidation state of selenoxide can be reversed to selenide under reduction of Vitamin C, thus recovering the spherical aggregates. The reversible oxidation and reduction process shows good reversibility and can be repeated at least 7 times. It is hoped that this reversible redox controlled system may function as nanocontainers for potential application in the areas such as responsive drug delivery and anti-oxidation studies. © 2012 The Royal Society of Chemistry.

Xie S.,Tsinghua University | Liang P.,Tsinghua University | Chen Y.,University of Science and Technology Beijing | Xia X.,Tsinghua University | Huang X.,Tsinghua University
Bioresource Technology | Year: 2011

A coupled microbial fuel cell (MFC) system comprising of an oxic-biocathode MFC (O-MFC) and an anoxic-biocathode MFC (A-MFC) was implemented for simultaneous removal of carbon and nitrogen from a synthetic wastewater. The chemical oxygen demand (COD) of the influent was mainly reduced at the anodes of the two MFCs; ammonium was oxidized to nitrate in the O-MFC's cathode, and nitrate was electrochemically denitrified in the A-MFC's cathode. The coupled MFC system reached power densities of 14W/m3 net cathodic compartment (NCC) and 7.2W/m3 NCC for the O-MFC and the A-MFC, respectively. In addition, the MFC system obtained a maximum COD, NH4 +-N and TN removal rate of 98.8%, 97.4% and 97.3%, respectively, at an A-MFC external resistance of 5 Ω, a recirculation ratio (recirculated flow to total influent flow) of 2:1, and an influent flow ratio (O-MFC anode flow to A-MFC anode flow) of 1:1. © 2010 Elsevier Ltd.

Jia X.,Tsinghua University | Chen Z.,University of California at Los Angeles | Cui X.,University of California at Los Angeles | Peng Y.,University of California at Los Angeles | And 4 more authors.
ACS Nano | Year: 2012

Design and fabrication of effective electrode structure is essential but is still a challenge for current lithium-ion battery technology. Herein we report the design and fabrication of a class of high-performance robust nanocomposites based on iron oxide spheres and carbon nanotubes (CNTs). An efficient aerosol spray process combined with vacuum filtration was used to synthesize such composite architecture, where oxide nanocrystals were assembled into a continuous carbon skeleton and entangled in porous CNT networks. This material architecture offers many critical features that are required for high-performance anodes, including efficient ion transport, high conductivity, and structure durability, therefore enabling an electrode with outstanding lithium storage performance. For example, such an electrode with a thickness of ∼35 μm could deliver a specific capacity of 994 mA h g-1 (based on total electrode weight) and high recharging rates. This effective strategy can be extended to construct many other composite electrodes for high-performance lithium-ion batteries. © 2012 American Chemical Society.

Wang L.,University of Science and Technology Beijing | Chen Y.,University of Jinan | Jiang J.,University of Science and Technology Beijing
Nanoscale | Year: 2014

A series of porphyrin nanospindles with controlled long axis length distributions of 330, 550, 800 nm, and 4 μm have been successfully fabricated via hierarchical self-assembly of cationic porphyrin (H6TPyP) 4+ with the help of anionic surfactant sodium dodecyl sulfonate (SDS) due to the effective electrostatic interaction. These newly fabricated nanostructures are characterized by TEM and SEM techniques, powder X-ray diffraction analysis, electronic absorption spectroscopy, and confocal laser scanning microscopy (CLSM). The Z-scan technique with a laser duration of 5 ns at the wavelength of 532 nm reveals unreported size-dependent third-order NLO switching properties: the nonlinear absorption changes from saturation absorption to reversed saturation absorption and the nonlinear refraction from self-defocus to self-focus due to the change of the dominant scattering effect, from Rayleigh scattering for nanostructures with a smaller size than the wavelength of laser light, to Mie scattering for nanostructures with a larger size than the laser wavelength. This result is useful for the development of organic nanostructures with desired NLO properties, in particular the optical limiting properties. © 2013 The Royal Society of Chemistry.

Li S.,Tsinghua University | Li S.,University of Science and Technology Beijing | Lin Y.-H.,Tsinghua University | Zhang B.-P.,University of Science and Technology Beijing | And 2 more authors.
Journal of Physical Chemistry C | Year: 2010

Bismuth ferrite (BiFeO3) uniform microcrystals with various morphologies (microspheres and micro/submirocubes) were successfully synthesized by a controlled hydrothermal method. The resulting microstructures were characterized using X-ray diffraction, scanning/transmission electron microscopies and Raman spectroscopy. Possible formation mechanism for BiFeO 3 microcrystals was proposed. UV-vis spectra showed that the optical properties of the microsized BiFeO3 crystals were strongly related to their shape and size. We further demonstrated the useful photocatalytic activity of these regular-shaped structures as determined by degradation of Congo red under visible-light irradiation (λ > 400 nm). Additionally, magnetic responses were observed to be influenced by the morphology of as-synthesized BiFeO3 products, and the ferroelectric performance of BiFeO3 submicrocube was also studied by piezoelectric force microscopy (PFM). Being a multiferroic semiconductor with suitable narrow band gap (∼2.2 eV) and uniform morphologies, these BiFeO3 microcrystals might be useful for the design of devices combining magnetic, electronic, and optical functionalities. © 2010 American Chemical Society.

Yang X.,University of Science and Technology Beijing | Zhang Y.,University of Science and Technology Beijing | Zhang Y.,University of Tennessee at Knoxville | Liaw P.K.,University of Tennessee at Knoxville
Procedia Engineering | Year: 2012

The novel refractory high entropy alloys with the compositions of NbTiVTaAlx were prepared under a high-purity argon atmosphere and their microstructure and compressive properties at room temperature were investigated. Despite containing many constituents, all alloys had a single solid solution phase with body-centered cubic (BCC) structure, and possessed high compressive yield strength and ductility, which should be attributed to solid solution strengthening. © 2012 Published by Elsevier Ltd.

Kong X.,University of Jinan | Zhang X.,University of Jinan | Gao D.,University of Jinan | Qi D.,University of Science and Technology Beijing | And 2 more authors.
Chemical Science | Year: 2015

Simple solvent vapor annealing over QLS film-based OFET devices fabricated from (Pc)Eu[Pc(ONh)8]Eu[Pc(ONh)8] led to a high and balanced ambipolar performance that has never been observed for small molecule single-component-based solution processed devices, with mobilities of 1.71 and 1.25 cm2 V-1 s-1 for holes and electrons, respectively, under ambient conditions. © The Royal Society of Chemistry 2015.

Wang X.-D.,North China Electrical Power University | An B.,North China Electrical Power University | Lin L.,University of Science and Technology Beijing | Lee D.-J.,National Taiwan University of Science and Technology | Lee D.-J.,National Taiwan University
Applied Thermal Engineering | Year: 2013

An inverse geometric optimization for nanofluid-cooled microchannel heat sink (MCHS) considering effects of temperature-dependent thermophyiscal properties for the water-based Al2O3 nanofluid with 1% particle volume fraction was performed under a constant pumping power constraint. A three-dimensional fluid-solid conjugated MCHS model combining the simplified-conjugate-gradient-method was used as the optimization tool. The channel number, N, the channel aspect ratio, α, and the width ratio of channel to pitch, β, affect the cooling performance of MCHS, and were all incorporated in the present, three-parameter optimization study. Increase in viscosity of the nanofluid did not always lead to enhanced MCHS performance under fixed pumping power constraint, contradicting to the results for pure water. The optimal MCHS design is closely related to the assigned pumping power: increase in the pumping power enhances cooling performance; however, in high pumping power regime the performance enhancement is not as effective as in low pumping power regime. At pumping power of 0.05 W and a uniform heat flux of qw = 100 W cm-2, the optimal design for the nanofluid-cooled MCHS presented N = 51, α = 5.69 and β = 0.62, yielding the optimal thermal resistance of RT = 0.1059 K W -1. © 2013 Elsevier Ltd. All rights reserved.

Peng K.,University of Science and Technology Beijing | Zhang K.,University of Science and Technology Beijing | Li G.,Tsinghua University | Zhou D.,Tsinghua University
Control Engineering Practice | Year: 2013

In this paper, a nonlinear fault diagnosis scheme is established for the hot strip mill process (HSMP). In HSMP, the faults affecting quality index are denoted as quality-related faults, which should be taken care as soon as possible. Projection to latent structures (PLS) is a basic model for quality-related fault detection in linear processes. In the presented work, a total kernel PLS (T-KPLS) model is utilized for modeling and monitoring HSMP, which is a typical nonlinear process. However, diagnosis tools have not been developed aiming at the nonlinear case based on T-KPLS model. Motivated by the successful use of contribution plot for the linear case, a contribution rate plot is proposed to extend contribution plots to the nonlinear case. In the end of this paper, the proposed method is applied to the hot strip mill process effectively. © 2012 Elsevier Ltd.

Li Q.,University of Science and Technology Beijing | Zhang Z.,University of Tennessee at Knoxville
Journal of Physical Chemistry C | Year: 2016

In order to explore the fundamental features of plasmon evolutions in the plasmonic nanostructures along variable geometrical parameters, TiO2-Ag core-shell nanospheroids, which have the distinguishable antibonding and bonding modes, are first used to illustrate the phenomena of plasmon evolutions by simulations. The usual peak-shift behaviors and appearance of the new modes are observed in the far-field extinction spectra. Beneath those phenomena, the unusual mode transformations occur in some modes. In the variable core configuration, when the inner surface of the silver shell is in a close proximity to the outer surface, the dipole antibonding mode evolves to be mixed with the quadrupole mode on the outer surface, while the new emerging mode evolves to the octupole antibonding modes. In the variable shell configuration, when the outer surface approaches the inner surface, the dipole bonding mode tends to evolve to the octupole bonding mode and the new modes emerge and tend to be the triakontadipole-like and octupole-like mode on the outer and inner surfaces. When the polar radius is so large that the outer surface is far away from the inner surface, the dipole antibonding mode evolves to the octupole antibonding mode and the new mode emerges which belongs to the octupole bonding mode. In mode transformation phenomena, one feature is that the evolution is associated with the odd l number (l = 1 for dipole, l = 3 for octupole, and l = 5 for triakontadipole) except for the mixed modes. Another feature is that the antibonding modes can evolve from the octupole to dipole and then octupole modes, in which process the charge distributions for the octupole modes are totally inverse. The retardation effects and the dielectric core effects are also discussed based on the phenomena of the higher order modes. The peak-shift behaviors, the appearance of the new modes, and the mode transformation along variable geometrical parameters have great importance in plasmonic applications due to the tunable resonance wavelength and the local field control. © 2016 American Chemical Society.

Wang D.,Tsinghua University | Wang D.,University of Science and Technology Beijing | Wang X.,Tsinghua University
Progress in Polymer Science | Year: 2013

Amphiphilic polymers are well known for their characteristics to form various self-assembling structures under proper conditions. Amphiphilic azo polymers, which are amphiphilic polymers functionalized with aromatic azo moieties, can combine wealthy photoresponsive properties with the self-assembling feature. In recent years, a wide variety of amphiphilic azo polymers have been developed through different molecular design strategies and synthetic routes. This article reviews the background, recent development, current approaches, and outlook of this rapidly developing research area. The emphasis is placed on the synthesis, self-assembly, and photoresponsive properties of amphiphilic azo polymers. According to the molecular architecture, the amphiphilic azo polymers are classified as homopolymers, random copolymers, block copolymers, star-like and dendritic polymers. The polymers show strong tendency to form well-organized structures at surfaces or interfaces, in solutions or dispersion mediums, and through phase-separation in solid thin-films. Colloidal arrays and porous thin films of amphiphilic azo polymers can be obtained through the vertical deposition method and solvent-induced structure inversion. The amphiphilic azo polymers and their self-assembled structures exhibit a variety of photoresponsive properties triggered by the trans-cis photoisomerization of azo chromophores. Some interesting variations caused by the light irradiation, such as the surface wettability change, surface-relief-grating formation, domain orientation, colloid deformation, micelle dissociation, vesicle bursting and fusion, are described in this review in detail. Such properties are promising for applications in areas such as optical devices, sensors, and drug delivery. © 2012 Elsevier Ltd.

Gan M.,University of Science and Technology Beijing | Dou X.,University of Science and Technology Beijing | Jiang R.,Tsinghua University
The Scientific World Journal | Year: 2013

Advances in high-throughput experimental techniques in the past decade have enabled the explosive increase of omics data, while effective organization, interpretation, and exchange of these data require standard and controlled vocabularies in the domain of biological and biomedical studies. Ontologies, as abstract description systems for domain-specific knowledge composition, hence receive more and more attention in computational biology and bioinformatics. Particularly, many applications relying on domain ontologies require quantitative measures of relationships between terms in the ontologies, making it indispensable to develop computational methods for the derivation of ontology-based semantic similarity between terms. Nevertheless, with a variety of methods available, how to choose a suitable method for a specific application becomes a problem. With this understanding, we review a majority of existing methods that rely on ontologies to calculate semantic similarity between terms. We classify existing methods into five categories: methods based on semantic distance, methods based on information content, methods based on properties of terms, methods based on ontology hierarchy, and hybrid methods. We summarize characteristics of each category, with emphasis on basic notions, advantages and disadvantages of these methods. Further, we extend our review to software tools implementing these methods and applications using these methods. © 2013 Mingxin Gan et al.

Feng Z.,University of Science and Technology Beijing | Chu F.,Tsinghua University | Zuo M.J.,University of Alberta
Journal of Sound and Vibration | Year: 2011

Energy separation algorithm is good at tracking instantaneous changes in frequency and amplitude of modulated signals, but it is subject to the constraints of mono-component and narrow band. In most cases, time-varying modulated vibration signals of machinery consist of multiple components, and have so complicated instantaneous frequency trajectories on time-frequency plane that they overlap in frequency domain. For such signals, conventional filters fail to obtain mono-components of narrow band, and their rectangular decomposition of time-frequency plane may split instantaneous frequency trajectories thus resulting in information loss. Regarding the advantage of generalized demodulation method in decomposing multi-component signals into mono-components, an iterative generalized demodulation method is used as a preprocessing tool to separate signals into mono-components, so as to satisfy the requirements by energy separation algorithm. By this improvement, energy separation algorithm can be generalized to a broad range of signals, as long as the instantaneous frequency trajectories of signal components do not intersect on time-frequency plane. Due to the good adaptability of energy separation algorithm to instantaneous changes in signals and the mono-component decomposition nature of generalized demodulation, the derived time-frequency energy distribution has fine resolution and is free from cross term interferences. The good performance of the proposed time-frequency analysis is illustrated by analyses of a simulated signal and the on-site recorded nonstationary vibration signal of a hydroturbine rotor during a shut-down transient process, showing that it has potential to analyze time-varying modulated signals of multi-components. © 2010 Elsevier Ltd. All rights reserved.

Wang L.,University of Science and Technology Beijing | Wang L.,University of Tennessee at Knoxville | Bei H.,Oak Ridge National Laboratory | Gao Y.F.,University of Tennessee at Knoxville | And 3 more authors.
Acta Materialia | Year: 2011

Nanoindentation experiments were conducted on Zr-based metallic glass samples, which were elastically and plastically bent in order to investigate the effect of residual stresses on hardness. It was found that tensile residual stress reduced the hardness significantly, while compressive residual stress produced only a small effect on the hardness. These observations are consistent with three-dimensional continuum-plasticity-based finite-element simulations. The hardness was also found to vary more significantly with residual stresses, in particular in tension, than that caused by shear-banding-induced softening, suggesting hardness measurement is a practical method for the evaluation of tensile residual stresses in a metallic glass. Hardness variation in the bent sample was correlated with the residual-stress-induced volume dilatation through a free-volume-based model. In this paper, we also present a detailed stress analysis based on yield asymmetry under tension and compression to describe the distribution of residual stresses in bent metallic glass specimens. The calculations agree well with the hardness variations measured experimentally. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Liu H.,University of Queensland | Du X.,Tianjin University | Xing X.,University of Science and Technology Beijing | Wang G.,University of Technology, Sydney | Qiao S.Z.,University of Queensland
Chemical Communications | Year: 2012

Highly ordered mesoporous Cr 2O 3 materials with high specific surface area and narrow pore size distribution were successfully prepared by a vacuum assisted impregnation method. Both 2-dimensional hexagonal and 3-dimensional cubic Cr 2O 3 mesoporous replicas from SBA-15 and KIT-6 templates exhibit enhanced performance for gas sensors and lithium ion batteries, compared to the bulk Cr 2O 3 counterpart.

Feng Z.,University of Science and Technology Beijing | Liang M.,University of Ottawa | Chu F.,Tsinghua University
Mechanical Systems and Signal Processing | Year: 2013

Nonstationary signal analysis is one of the main topics in the field of machinery fault diagnosis. Time-frequency analysis can identify the signal frequency components, reveals their time variant features, and is an effective tool to extract machinery health information contained in nonstationary signals. Various time-frequency analysis methods have been proposed and applied to machinery fault diagnosis. These include linear and bilinear time-frequency representations (e.g., wavelet transform, Cohen and affine class distributions), adaptive parametric time-frequency analysis (based on atomic decomposition and time-frequency auto-regressive moving average models), adaptive non-parametric time-frequency analysis (e.g., Hilbert-Huang transform, local mean decomposition, and energy separation), and time varying higher order spectra. This paper presents a systematic review of over 20 major such methods reported in more than 100 representative articles published since 1990. Their fundamental principles, advantages and disadvantages, and applications to fault diagnosis of machinery have been examined. Some examples have also been provided to illustrate their performance. © 2013 Elsevier Ltd.

Kan J.,University of Science and Technology Beijing | Chen Y.,University of Jinan | Qi D.,University of Science and Technology Beijing | Liu Y.,CAS Institute of Chemistry | Jiang J.,University of Science and Technology Beijing
Advanced Materials | Year: 2012

A novel sandwich-type tris(phthalocyaninato) europium triple-decker complex bearing peripheral electron-withdrawing groups (see center of figure) is used to fabricate a field-effect transistor by the quasi-Langmuir-Schaefer method. The air-stable, single-component ambipolar OFET device displays the best carrier properties of a device fabricated by solution processing of a single phthalocyanine derivative so far, which makes the complex very promising for applications in nanoelectronics. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Li M.,University of Science and Technology Beijing | Li D.,Chongqing Three Gorges University | Wang J.,University of Science and Technology Beijing | Zhao C.,Tsinghua University | Zhao C.,Chongqing Three Gorges University
ISA Transactions | Year: 2013

Fractional-order proportional-integral (PI) and proportional-integral- derivative (PID) controllers are the most commonly used controllers in fractional-order systems. However, this paper proposes a simple integer-order control scheme for fractional-order system based on active disturbance rejection method. By treating the fractional-order dynamics as a common disturbance and actively rejecting it, active disturbance rejection control (ADRC) can achieve the desired response. External disturbance, sensor noise, and parameter disturbance are also estimated using extended state observer. The ADRC stability of rational-order model is analyzed. Simulation results on three typical fractional-order systems are provided to demonstrate the effectiveness of the proposed method. © 2013 ISA.

Tu R.,University of Science and Technology Beijing | Liu X.-H.,Tsinghua University | Jiang Y.,Tsinghua University
Energy Conversion and Management | Year: 2014

Rotary wheel dehumidification is an effective air drying method. This paper analyzes the factors influencing the regeneration temperature from the perspective of exergy. When the dehumidification capacity is fixed, there are two main ways to reduce the regeneration temperature. One is to decrease the exergy destruction during heat and mass transfer in the desiccant wheel, and the other is to decrease the thermal exergy obtained by the processed air after dehumidification. For the first way, the exergy destruction is influenced by the uniformity of the heat and mass transfer driving forces in the desiccant wheel, which can be described by the unmatched coefficient ς. The wheel should be evenly divided, and the two streams of air should have the same flow rate to reduce the exergy destruction. The regeneration temperature can be reduced from above 130 °C to below 70 °C when the air is dehumidified from 20 g/kg to 11 g/kg. For the second way, the thermal exergy obtained by the processed air is influenced by the temperature variation range during dehumidification. Multi-stage dehumidification and pre-cooling are effective mode, with required regeneration temperature lower than 40 °C. © 2014 Elsevier Ltd. All rights reserved. 2014 Elsevier Ltd. All rights reserved.

Kan J.,University of Science and Technology Beijing | Wang H.,University of Science and Technology Beijing | Sun W.,University of Science and Technology Beijing | Cao W.,University of Science and Technology Beijing | And 2 more authors.
Inorganic Chemistry | Year: 2013

Employment of the raise-by-one step method starting from M(TClPP)(acac) (acac = monoanion of acetylacetone) and [Pc(OPh)8]M′[Pc(OPh) 8] led to the isolation and free modulation of the two rare-earth ions in the series of four mixed tetrapyrrole dysprosium sandwich complexes {(TClPP)M[Pc(OPh)8]M′[Pc(OPh)8]} [1-4; TClPP = dianion of meso-tetrakis(4-chlorophenyl)porphyrin; Pc(OPh)8 = dianion of 2,3,9,10,16,17,23,24-octa(phenoxyl)phthalocyanine; M-M′ = Dy-Dy, Y-Dy, Dy-Y, and Y-Y]. Single-crystal X-ray diffraction analysis reveals different octacoordination geometries for the two metal ions in terms of the twist angle (defined as the rotation angle of one coordination square away from the eclipsed conformation with the other) between the two neighboring tetrapyrrole rings for the three dysprosium-containing isostructural triple-decker compounds, with the metal ion locating between an inner phthalocyanine ligand and an outer porphyrin ligand with a twist angle of 9.64-9.90 and the one between two phthalocyanine ligands of 25.12-25.30. Systematic and comparative studies over the magnetic properties reveal magnetic-field-induced single-molecule magnet (SMM), SMM, and non-SMM nature for 1-3, respectively, indicating the dominant effect of the coordination geometry of the spin carrier, instead of the f-f interaction, on the magnetic properties. The present result will be helpful for the future design and synthesis of tetrapyrrole lanthanide SMMs with sandwich molecular structures. © 2013 American Chemical Society.

Zhu L.-F.,University of Science and Technology Beijing | Zhang B.-P.,University of Science and Technology Beijing | Zhao X.-K.,University of Science and Technology Beijing | Zhao L.,University of Science and Technology Beijing | And 2 more authors.
Journal of the American Ceramic Society | Year: 2013

(Ba1-xCax)(Ti0.92Sn0.08)O 3 (x = 0.00-0.06 mol) ceramics with a high relative density over 96% were prepared by a conventional sintering method at 1480°C. At room temperature, a polymorphic phase transition from orthorhombic phase to tetragonal phase was confirmed by the XRD patterns in the composition range of 0.04 ≤ x ≤ 0.06. A high piezoelectric coefficient d33 up to 568 pC/N was obtained at x = 0.05 mol, which is higher than the other component of (Ba,Ca)(Ti,Sn)O3 system. At the same time, the corresponding planar electromechanical coupling factor kp, converse piezoelectric coefficient dS/dE, and dielectric constant εr reach 47.7%, 1013 pm/V, and 23000, respectively. These results indicate that the (Ba,Ca)(Ti,Sn)O3 ceramics are a promising candidate to replace for the lead-based piezoelectric materials. © 2012 The American Ceramic Society.

Lan J.-L.,Tsinghua University | Liu Y.-C.,Tsinghua University | Zhan B.,Tsinghua University | Lin Y.-H.,Tsinghua University | And 5 more authors.
Advanced Materials | Year: 2013

A high-performance thermoelectric oxyselenide BiCuSeO ceramic with ZT > 1.1 at 823 K and higher average ZT value (ZTave ≈0.8) is obtained. The heavy doping element and nanostructures can effectively tune its electronic structure, hole concentration, and thermal conductivity, resulting in substantially enhanced mobility, power factor, and thus ZT value. This work provides a path to high-performance thermoelectric ceramics. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ge Z.-H.,University of Science and Technology Beijing | Zhang B.-P.,University of Science and Technology Beijing | Chen Y.-X.,University of Science and Technology Beijing | Yu Z.-X.,University of Science and Technology Beijing | And 2 more authors.
Chemical Communications | Year: 2011

Polycrystalline Cu1.8S compounds were fabricated by using a combined process of mechanical alloying and spark plasma sintering. The Cu 1.8S sample with a second Cu1.96S phase and a lot of micro pores shows its maximum ZT value 0.5 at 673 K which is the highest value for p-type sulfide thermoelectric materials so far. © The Royal Society of Chemistry 2011.

Zhang Y.,University of Science and Technology Beijing | Li J.,University of Science and Technology Beijing | Kang F.,Tsinghua University | Gao F.,University of Science and Technology Beijing | Wang X.,University of Science and Technology Beijing
International Journal of Hydrogen Energy | Year: 2012

A nanoporous manganese oxide (MnO 2) film was fabricated via a polystyrene templated electrodeposition in the solution containing MnSO 4. The nanoporous MnO 2 film obtained has been characterized by field emission scanning electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge/discharge methods. The specific capacitance of 1018 F g -1 was observed at a low current density of 500 mA g -1. When the current density increased to 30.0 A g -1, the specific capacitance of 277 F g -1 remained. The high capacitance retention at high rates makes the prepared MnO 2 a promising candidate for supercapacitor applications. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Ge Z.-H.,University of Science and Technology Beijing | Zhang B.-P.,University of Science and Technology Beijing | Shang P.-P.,University of Science and Technology Beijing | Li J.-F.,Tsinghua University
Journal of Materials Chemistry | Year: 2011

After fabricating Bi2S3 nanorods with preferential (001) orientation by hydrothermal synthesis (HS) using Bi(NO3) 3 and Na2S2O3 as raw materials and ethylenediamine (EDA) as a pH modifier, Bi2S3 bulk materials were consolidated by spark plasma sintering (SPS). A single-phase, rod-like Bi2S3 crystal with a length in range of 2-10 μm and a diameter in range of 100-400 nm was formed by optimizing the hydrothermal process parameters. The rod-like structures were maintained in the Bi2S3 bulk, and as a result the orientation degree of the bulk sample prepared from Bi2S3 nanorods powders reached 0.69, being higher than 0.18 found for mechanical alloying (MA)-derived powder. The measurement of electric transport properties also confirmed that the Bi 2S3 bulk has obvious anisotropy. The electric resistivity normal to the pressing direction is one order higher than that in parallel to the pressing direction due to their anisotropic orientation. The power factor of the bulk sample along the direction perpendicular to the pressing direction is twice higher than that in parallel to the pressing direction, and also higher than the sample using the MA-processed powders. © 2011 The Royal Society of Chemistry.

Liu X.,University of Science and Technology Beijing | Zhang N.,Tsinghua University
Waste Management and Research | Year: 2011

Red mud is a solid waste residue of the digestion of bauxite ores with caustic soda for alumina production. Its disposal remains a worldwide issue in terms of environmental concerns. During the past decades, extensive work has been done by a lot of researchers to develop various economic ways for the utilization of red mud. One of the economic ways is using red mud in cement production, which is also an efficient method for large-scale recycling of red mud. This paper provides a review on the utilization of red mud in cement production, and it clearly points out three directions for the use of red mud in cement production, namely the preparation of cement clinkers, production of composite cements as well as alkali-activated cements. In the present paper, the chemical and mineralogical characteristics of red mud are summarized, and the current progresses on these three directions are reviewed in detail. © The Author(s) 2011.

Li F.,Tsinghua University | Li J.-F.,Tsinghua University | Zhao L.-D.,Northwestern University | Xiang K.,Tsinghua University | And 6 more authors.
Energy and Environmental Science | Year: 2012

This work revealed that BiCuSeO oxyselenide is a potential oxide-based thermoelectric material, whose dimensionless figure of merit (ZT) reaches ∼0.70 at 773 K. High phase-purity BiCuSeO polycrystalline materials with fine grains were synthesized by a facile method combining a solid-state reaction and spark plasma sintering. Purifying the constitutive phase and reducing the grain sizes by introducing a high-energy ball milling process before spark plasma sintering were found to be effective in property enhancement. The resultant single-phased BiCuSeO sample derived from ball-milled powders shows good electrical conductivity above 4.0 × 103 S m-1 and a large Seebeck coefficient above 200 μV K-1. This compound has a low thermal conductivity (∼0.5 W m-1 K-1), which is associated with its low phonon transport speed and Young's modulus. Results indicated that BiCuSeO-based materials are promising for energy conversion applications in the moderate temperature range. © 2012 The Royal Society of Chemistry.

Wang M.-S.,University of Science and Technology Beijing | Fan L.-Z.,University of Science and Technology Beijing | Huang M.,Tsinghua University | Li J.,University of Science and Technology of China | Qu X.,University of Science and Technology Beijing
Journal of Power Sources | Year: 2012

Diatomite, a natural clay mineral, is mainly composed of silica and contains a large number of fine microscopic pores. In the present work, a series of porous Si/C composites are successfully synthesized by employing diatomite as a raw material, followed by low temperature magnesiothermic reduction, impregnation and carbonization of phenolic resin. The obtained Si/C composites are consisted of porous Si coated with a 15 nm thick amorphous layer of carbon. Porous Si/C composites with different ratios of Si and C are investigated as anode materials for Li-ion batteries. The porous Si/C composite containing 33% carbon exhibits the highest reversible capacity of about 1628 mAh g -1 at the first cycle with excellent capacity retention in the following cycles. Moreover, the porous Si/C composites display the excellent rate performance at high current densities such as 1 and 2 A g -1. The optimum electrochemical performance could also be tuned by varying the proportions of porous Si and carbon precursors during the preparation process. The results indicate that the natural pore structures of Si and C are conducive to the electrochemical performance and clay mineral diatomite could be considered as a promising raw material for Si/C composites for lithium-ion batteries. © 2012 Elsevier B.V. All rights reserved.

Liu L.,University of Science and Technology Beijing | Fu L.,Tsinghua University | Jiang Y.,Tsinghua University
Applied Thermal Engineering | Year: 2012

Field test results show that 20%-30% of thermal energy is wasted because of poor heating system regulation in China. In order to solve these problems, a new "wireless on-off control" system for adjusting and metering household heat is proposed. The technology works in the following way: 1) a calorimeter is installed in each building to measure the total heat consumption of the building; 2) on-off valves are installed in each household with an individual indoor temperature control provided. The room temperature can be maintained by controlling the valves according to the on-time ratio which is predicted by the thermal strategies; and 3) the heating cost of each household can be allocated according to the heating area and the accumulative open time of the valve. The proposed technique has been applied in twenty-five residential communities with a total area of 2,500,000 m 2. The test results show that: 1) indoor temperatures were accurately controlled within ±0.5 °C of the set point; 2) the temperature difference in different rooms is less than 1 °C; 3) energy consumption in the households using a controlled system was approximately 30% lower than a similar within a similar building type with an uncontrolled system. © 2011 Published by Elsevier Ltd. All rights reserved.

Xia L.C.,University of Southern California | Ai D.,University of Southern California | Ai D.,University of Science and Technology Beijing | Cram J.,University of Southern California | And 3 more authors.
Bioinformatics | Year: 2013

Motivation: Local similarity analysis of biological time series data helps elucidate the varying dynamics of biological systems. However, its applications to large scale high-throughput data are limited by slow permutation procedures for statistical significance evaluation.Results: We developed a theoretical approach to approximate the statistical significance of local similarity analysis based on the approximate tail distribution of the maximum partial sum of independent identically distributed (i.i.d.) random variables. Simulations show that the derived formula approximates the tail distribution reasonably well (starting at time points > 10 with no delay and > 20 with delay) and provides P-values comparable with those from permutations. The new approach enables efficient calculation of statistical significance for pairwise local similarity analysis, making possible all-to-all local association studies otherwise prohibitive. As a demonstration, local similarity analysis of human microbiome time series shows that core operational taxonomic units (OTUs) are highly synergetic and some of the associations are body-site specific across samples. © 2012 The Author. Published by Oxford University Press. All rights reserved.

Xiao X.,University of Science and Technology Beijing | Sun J.,University of Science and Technology Beijing | Sun J.,Guizhou University | Jiang J.,University of Science and Technology Beijing
Chemistry - A European Journal | Year: 2013

A host-guest supramolecular polymer was constructed from cucurbit[6]uril host molecules (orange) and porphyrin guest molecules (red and blue) and its formation depends on host-enhanced hydrogen-bonding interactions in combination with ion-dipole interactions. The polymer is the first structurally characterized cucurbit[n]uril-porphyrin supramolecular polymer. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Si X.-S.,HIGH-TECH | Si X.-S.,Tsinghua University | Wang W.,University of Science and Technology Beijing | Hu C.-H.,HIGH-TECH | And 3 more authors.
IEEE Transactions on Reliability | Year: 2012

Remaining useful life estimation is central to the prognostics and health management of systems, particularly for safety-critical systems, and systems that are very expensive. We present a non-linear model to estimate the remaining useful life of a system based on monitored degradation signals. A diffusion process with a nonlinear drift coefficient with a constant threshold was transformed to a linear model with a variable threshold to characterize the dynamics and nonlinearity of the degradation process. This new diffusion process contrasts sharply with existing models that use a linear drift, and also with models that use a linear drift based on transformed data that were originally nonlinear. Both existing models are based on a constant threshold. To estimate the remaining useful life, an analytical approximation to the distribution of the first hitting time of the diffusion process crossing a threshold level is obtained in a closed form by a time-space transformation under a mild assumption. The unknown parameters in the established model are estimated using the maximum likelihood estimation approach, and goodness of fit measures are applied. The usefulness of the proposed model is demonstrated by several real-world examples. The results reveal that considering nonlinearity in the degradation process can significantly improve the accuracy of remaining useful life estimation. © 2006 IEEE.

Chen J.,University of Science and Technology Beijing | Yin Y.,University of Science and Technology Beijing | Sun F.,Tsinghua University
Asian Journal of Control | Year: 2012

This paper presents the novel results for stabilizing uncertain standard discrete-time fuzzy singularly perturbed systems (SPSs) via a state feedback control law. Two standard discrete-time fuzzy SPSs are constructed firstly by using the Takagi-Sugeno (T-S) fuzzy model. Based on a matrix spectral norm approach, two new ε-dependent stability conditions are derived, which guarantee the resulting closed-loop systems are asymptotically stable. The gains of controllers are obtained by solving a set of ε-dependent linear matrix inequalities (LMIs). In contrast to the existing results, the proposed methods have two advantages: (i) the designed controllers can overcome the external disturbances and parameter uncertainty; and (ii) the upper bound of ε is improved, especially it is not required to be smaller than one. Examples are provided to illustrate the reduced conservatism of our results. Copyright © 2011 John Wiley and Sons Asia Pte Ltd.

Jiang R.,Tsinghua University | Gan M.,University of Science and Technology Beijing | He P.,Tsinghua University
BMC Systems Biology | Year: 2011

Motivation: The inference of genes that are truly associated with inherited human diseases from a set of candidates resulting from genetic linkage studies has been one of the most challenging tasks in human genetics. Although several computational approaches have been proposed to prioritize candidate genes relying on protein-protein interaction (PPI) networks, these methods can usually cover less than half of known human genes.Results: We propose to rely on the biological process domain of the gene ontology to construct a gene semantic similarity network and then use the network to infer disease genes. We show that the constructed network covers about 50% more genes than a typical PPI network. By analyzing the gene semantic similarity network with the PPI network, we show that gene pairs tend to have higher semantic similarity scores if the corresponding proteins are closer to each other in the PPI network. By analyzing the gene semantic similarity network with a phenotype similarity network, we show that semantic similarity scores of genes associated with similar diseases are significantly different from those of genes selected at random, and that genes with higher semantic similarity scores tend to be associated with diseases with higher phenotype similarity scores. We further use the gene semantic similarity network with a random walk with restart model to infer disease genes. Through a series of large-scale leave-one-out cross-validation experiments, we show that the gene semantic similarity network can achieve not only higher coverage but also higher accuracy than the PPI network in the inference of disease genes.Contact: . © 2011 Jiang et al; licensee BioMed Central Ltd.

Gan M.,University of Science and Technology Beijing | Jiang R.,Tsinghua University
Decision Support Systems | Year: 2013

Recommender systems have become more and more indispensable in both commercial and research communities, due to the increasingly serious problem of information overload accompanying the rapid development of the internet technology in the recent years. As one of the dominant branches, collaborative filtering approaches base on similarities of user preferences in historical data have achieved remarkable successes in producing personalized recommendations. Nevertheless, the existence of popular objects may adversely influence the correct scoring of candidate objects and further yield unreasonable recommendation results. Meanwhile, it has been increasingly recognized that the gains of the recommendation accuracy are often accompanied by the losses of the diversity, yielding the accuracy-diversity dilemma for a personalized recommender system. In order to overcome these limitations while keeping a reasonable tradeoff between the accuracy and the diversity, we propose in this paper a method called PLUS (Power Law adjustments of User Similarities) to achieve personalized recommendations via the introduction of a power function to adjust user similarity scores, for the purpose of reducing adverse effects of popular objects in the user-based collaborative filtering framework. We perform a series of large scale validation experiments on two real data sets (MovieLens and Netflix) and compare the performance of our approach against that of an ordinary collaborative filtering method. Results show that our method outperforms the existing method not only in recommendation accuracy measured by the mean rank ratio and the recall enhancement, but also in recommendation diversity quantified by the mean personality and the mean novelty. © 2013 Elsevier B.V.

Jiang Y.,University of Science and Technology Beijing | Guan L.,Aerospace Research Institute of Materials And Processing Technology | Tang G.,Tsinghua University
Journal of Alloys and Compounds | Year: 2016

The recrystallized microstructure and texture of AZ31 Mg alloy after rapid thermal annealing (RTA) was investigated. A mathematical model of RTA temperature of AZ31 Mg alloy was established based on the thermal equilibrium theory. The two double-peak textures with basal poles tilted 5-10° away from the normal direction towards the rolling direction or towards the transverse direction were formed in the AZ31 alloy during RTA. The tilted basal texture was originated from recrystallized grains formed along grain boundaries for the low rolling reduction or recrystallized grains formed within the shear bands and twins for the high rolling reduction. During RTA, the recrystallization mechanism was sensitive to the previous rolling reduction and the annealing temperature, and the mechanisms of the microstructure and texture evolution of the AZ31 alloy during RTA were discussed. © 2015 Elsevier B.V.

Si X.-S.,HIGH-TECH | Si X.-S.,Tsinghua University | Wang W.,University of Science and Technology Beijing | Hu C.-H.,HIGH-TECH | And 2 more authors.
Mechanical Systems and Signal Processing | Year: 2013

Remaining useful life estimation (RUL) is an essential part in prognostics and health management. This paper addresses the problem of estimating the RUL from the observed degradation data. A Wiener-process-based degradation model with a recursive filter algorithm is developed to achieve the aim. A novel contribution made in this paper is the use of both a recursive filter to update the drift coefficient in the Wiener process and the expectation maximization (EM) algorithm to update all other parameters. Both updating are done at the time that a new piece of degradation data becomes available. This makes the model depend on the observed degradation data history, which the conventional Wiener-process-based models did not consider. Another contribution is to take into account the distribution in the drift coefficient when updating, rather than using a point estimate as an approximation. An exact RUL distribution considering the distribution of the drift coefficient is obtained based on the concept of the first hitting time. A practical case study for gyros in an inertial navigation system is provided to substantiate the superiority of the proposed model compared with competing models reported in the literature. The results show that our developed model can provide better RUL estimation accuracy. © 2012 Elsevier Ltd. All rights reserved.

Wang H.,University of Science and Technology Beijing | Kobayashi N.,Tohoku University | Jiang J.,University of Science and Technology Beijing
Chemistry - A European Journal | Year: 2012

Quintuple-decker sandwich: Homoleptic pentakis(2,3,9,10,16,17,23,24- octa(butyloxy)phthalocyaninato) lanthanide-cadmium quintuple-decker complexes were isolated and structurally characterized. They represent the first example of sandwich-type stacked tetrapyrrole-metal complexes with five decks (see figure; the tetrapyrrole molecules are represented by the blue/pink discs, TCB=1,2,4-trichlorobenzene). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Li J.-F.,Tsinghua University | Liu W.-S.,Tsinghua University | Liu W.-S.,University of Science and Technology Beijing | Zhao L.-D.,Tsinghua University | And 3 more authors.
NPG Asia Materials | Year: 2010

Thermoelectric effects enable direct conversion between thermal and electrical energy and provide an alternative route for power generation and refrigeration. Over the past ten years, the exploration of high-performance thermoelectric materials has attracted great attention from both an academic research perspective and with a view to industrial applications. This review summarizes the progress that has been made in recent years in developing thermoelectric materials with a high dimensionless figure of merits (ZT) and the related fabrication processes for producing nanostuctured materials. The challenge to develop thermoelectric materials with superior performance is to tailor the interconnected thermoelectric physical parameters - electrical conductivity, Seebeck coefficient and thermal conductivity - for a crystalline system. Nanostructures provide a chance to disconnect the linkage between thermal and electrical transport by introducing some new scattering mechanisms. Recent improvements in thermoelectric efficiency appear to be dominated by efforts to reduce the lattice thermal conductivity through nanostructural design. The materials focused in this review include Bi-Te alloys, skutterudite compounds, Ag-Pb-Sb-Te quaternary systems, half-Heusler compounds and some high-ZT oxides. Possible future strategies for developing thermoelectric materials are also discussed. © 2011 Tokyo Institute of Technology.

Qiao J.W.,University of Science and Technology Beijing | Liaw P.K.,University of Tennessee at Knoxville | Zhang Y.,University of Science and Technology Beijing
Scripta Materialia | Year: 2011

The maximum strength of monolithic bulk metallic glasses (BMGs) at 77 K is predicted according to the proposed equation, σmax.77= 55ρ0MΔTg+Δσ. For the dendrite-reinforced BMG-matrix composites, a distinctly increased maximum strength is seen; however, a ductile-to-brittle transition seems to be present when lowering the temperature to 77 K, which is caused by the ductile-to-brittle transition of the dendrites. The crack, initiated within the dendrites, may extend to the glass matrix at low temperatures. As a result, early failure of the composites occurs. © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Princeton University, Tsinghua University, University of Science and Technology Beijing | Date: 2015-08-18

Emulsion breaking and phase separation is achieved by droplet adhesion. An emulsion breaking device includes a channel having distinct adjacent zones with distinctly different surface wettability characteristics, namely, solvophilic and solvophobic surfaces. The device is positioned such that the upstream portion of the device is configured to be wetted by the continuous phase of the emulsion, and the downstream portion of the device is configured to be wetted by the dispersed phase of the emulsion. As the emulsion flows from the upstream zone to the downstream zone, the change in surface wettability characteristics promotes adhesion of the dispersed phase as the dispersed phase wets the surface of the downstream portion of the channel, which results in breaking of the emulsion. Subsequent collection of the broken emulsion in a collection vessel results in separation of the disparate phases to facilitate their recapture and recycling.

Fan L.-Z.,University of Science and Technology Beijing | Liu J.-L.,University of Science and Technology Beijing | Ud-Din R.,University of Science and Technology Beijing | Ud-Din R.,Pakistan Institute of Nuclear Science and Technology | And 2 more authors.
Carbon | Year: 2012

Graphene nanosheets were prepared by reducing graphite oxide with hydrazine hydrate. The effects of reduction time on the structure and morphology of graphene nanosheets have been investigated. Their electrochemical performance in aqueous and organic electrolytes was also analyzed. With an increase of reduction time, the C and N contents of graphene nanosheets increased, while the specific surface areas and the specific capacitances decreased. Changes in reduction time produced a significant effect on the numbers as well as the types of oxygen and nitrogen functionalities. The graphene nanosheets, prepared by using a reduction time of 30 min have the highest specific capacitance of 192 F g -1 in a 6 mol L -1 KOH electrolyte. All prepared graphene nanosheets have a good rate performance and cycle stability. © 2012 Elsevier Ltd. All rights reserved.

News Article | January 2, 2016

« Visteon showcasing advanced gesture recognition and HUD technologies at CES | Main | Fulcrum BioEnergy files LCFS application for municipal solid waste to FT diesel pathway with low CI of 37.47 g/MJ » Researchers at Tsinghua University, with colleagues from the University of Science and Technology Beijing, have discovered that the multi-reversible magnetization of ferromagnetic material can be controlled via the lithiation/delithiation reaction in a Li-ion battery by varying the discharge–charge potential at room temperature. This phenomenon couples magnetism and electrochemistry, and enables precise quantitative magnetization manipulation using an electrochemical method. An open-access paper on their discovery is published in the ACS journal Nano Letters. In their paper, they reported achieving reversible manipulation of magnetism over 3 orders of magnitude by controlling the lithiation/delithiation of a nanoscale α-Fe O -based electrode. The process was completed rapidly under room-temperature conditions. Our work reveals that magnetic properties are linked to the voltage control of LIBs. The concept of tuning physical properties using battery cycling clearly has strong potential because hundreds of active materials have already been developed as LIB electrodes. Our results indicate that in addition to energy storage LIBs, which have been under continuous development for several decades, provide exciting opportunities for the multireversible magnetization of magnetic fields.

Yan P.,CAS Institute of Automation | Liu D.,University of Science and Technology Beijing | Wang D.,CAS Institute of Automation | Ma H.,CAS Institute of Automation
Neurocomputing | Year: 2016

In this paper, we develop a novel data-driven multivariate nonlinear controller design method for multi-input-multi-output (MIMO) nonlinear systems via virtual reference feedback tuning (VRFT) and neural networks. To the best of authors' knowledge, it is the first time to introduce VRFT to MIMO nonlinear systems in theory. Unlike the standard VRFT for linear systems, we restate the model reference control problem with time-domain model in the absence of transfer functions and simplify the objective function of VRFT without a linear filter. Then, we prove that the objective function of VRFT reaches the minimum at the same point as the optimization problem of model reference control and give the relationship between the bounds of the two optimization problems of model reference control and VRFT. A three-layer neural network is used to implement the developed method. Finally, two simulations are conducted to verify the validity of our method. © 2015 Elsevier B.V.

Song R.,University of Science and Technology Beijing | Wei Q.,CAS Institute of Automation | Sun Q.,Northeastern University China
Neurocomputing | Year: 2015

In this paper, a novel adaptive dynamic programming (ADP) algorithm is developed to solve the nearly optimal finite-horizon control problem for a class of deterministic nonaffine nonlinear time-delay systems. The idea is to use ADP technique to obtain the nearly optimal control which makes the optimal performance index function close to the greatest lower bound of all performance index functions within finite time. The proposed algorithm contains two cases with respective different initial iterations. In the first case, there exists control policy which makes arbitrary state of the system reach to zero in one time step. In the second case, there exists a control sequence which makes the system reach to zero in multiple time steps. The state updating is used to determine the optimal state. Convergence analysis of the performance index function is given. Furthermore, the relationship between the iteration steps and the length of the control sequence is presented. Two neural networks are used to approximate the performance index function and compute the optimal control policy for facilitating the implementation of ADP iteration algorithm. At last, two examples are used to demonstrate the effectiveness of the proposed ADP iteration algorithm. © 2014 Elsevier B.V.

Tutuncu G.,University of Florida | Damjanovic D.,Ecole Polytechnique Federale de Lausanne | Chen J.,University of Science and Technology Beijing | Jones J.L.,University of Florida
Physical Review Letters | Year: 2012

In ferroic materials, the dielectric, piezoelectric, magnetic, and elastic coefficients are significantly affected by the motion of domain walls. This motion can be described as the propagation of a wall across various types and strengths of pinning centers that collectively constitute a force profile or energetic landscape. Biased domain structures and asymmetric energy landscapes can be created through application of high fields (such as during electrical poling), and the material behavior in such states is often highly asymmetric. In some cases, this behavior can be considered as the electric analogue to the Bauschinger effect. The present Letter uses time-resolved, high-energy x-ray Bragg scattering to probe this asymmetry and the associated deaging effect in the ferroelectric morphotropic phase boundary composition 0.36BiScO 3-0.64PbTiO 3. © 2012 American Physical Society.

Ding X.F.,University of Science and Technology Beijing | Lin J.P.,University of Science and Technology Beijing | Zhang L.Q.,University of Science and Technology Beijing | Su Y.Q.,Harbin Institute of Technology | Chen G.L.,University of Science and Technology Beijing
Acta Materialia | Year: 2012

The lamellar microstructure of TiAl-Nb alloys with and without low boron additions is controlled using double directional solidification (DS). In alloys without the addition of boron, the β phase is seeded during double DS. Complete peritectic transformation occurs in both the dendritic and interdendritic regions, which can lead to the successful alignment of both the high-temperature α phase and the lamellar microstructures. Well-aligned lamellar microstructures can be easily achieved if the alloy composition is close to the peritectic point on the hypo-peritectic side. In alloys with low boron additions, however, the competitive growth of the α phase breaks the continuity of the lamellar microstructure in the region ahead of stable growth, which finally results in columnar grain coarsening and unsuccessful alignment of the lamellar microstructures. © 2011 Published by Elsevier Ltd. on behalf of Acta Materialia Inc. All rights reserved.

Wang X.,University of Science and Technology Beijing | Wang Q.,University of Science and Technology Beijing | Wang S.,Chinese Research Academy of Environmental Sciences | Li F.,Chinese Research Academy of Environmental Sciences | Guo G.,Chinese Research Academy of Environmental Sciences
Bioresource Technology | Year: 2012

Four biopiles were constructed for the bioremediation of total petroleum hydrocarbons (TPHs) in aged oily sludge by indigenous microorganisms. Three biopiles were treated with bulking agent, nutrients or their combination with the fourth pile serving as the control. Responses of microbial community level physiological profiles (CLPPs) to these biostimulation strategies were estimated, and variances among three layers within each biopile were evaluated. Microbial metabolic activity and diversity and the numbers of two species of bacteria were significantly enhanced by the addition of bulking agent, which also made the layers more homogeneous. In contrast, the application of large amounts of nutrients had a suppressing effect on the microbes. After 220. days, 49.62% of TPHs were removed from the middle layer of the bulking agent pile, whereas only 20.44% were removed from the inner layer of the control. This study aims to provide experience to improve the remediation efficiency of future investigations. © 2012.

Ding S.X.,University of Duisburg - Essen | Yin S.,Harbin Institute of Technology | Peng K.,University of Science and Technology Beijing | Hao H.,University of Duisburg - Essen | Shen B.,University of Duisburg - Essen
IEEE Transactions on Industrial Informatics | Year: 2013

In this paper, a data-driven scheme of key performance indicator (KPI) prediction and diagnosis is developed for complex industrial processes. For static processes, a KPI prediction and diagnosis approach is proposed in order to improve the prediction performance. In comparison with the standard partial least squares (PLS) method, the alternative approach significantly simplifies the computation procedure. By means of a data-driven realization of the so-called left coprime factorization (LCF) of a process, efficient KPI prediction, and diagnosis algorithms are developed for dynamic processes, respectively, with and without measurable KPIs. The proposed KPI prediction and diagnosis scheme is finally applied to an industrial hot strip mill, and the results demonstrate the effectiveness of the proposed scheme. © 2013 IEEE.

Chen J.,University of Science and Technology Beijing | Nittala K.,University of Florida | Forrester J.S.,University of Florida | Jones J.L.,University of Science and Technology Beijing | And 3 more authors.
Journal of the American Chemical Society | Year: 2011

PbTiO3-based compounds are well-known ferroelectrics that exhibit a negative thermal expansion more or less in the tetragonal phase. The mechanism of negative thermal expansion has been studied by high-temperature neutron powder diffraction performed on two representative compounds, 0.7PbTiO3 - 0.3BiFeO3 and 0.7PbTiO3 - 0.3Bi(Zn1/2Ti1/2)O3, whose negative thermal expansion is contrarily enhanced and weakened, respectively. With increasing temperature up to the Curie temperature, the spontaneous polarization displacement of Pb/Bi (|zPb/Bi) is weakened in 0.7PbTiO3 - 0.3BiFeO3 but well-maintained in 0.7PbTiO3 - 0.3Bi(Zn1/2Ti1/2)O3. There is an apparent correlation between tetragonality (c/a) and spontaneous polarization. Direct experimental evidence indicates that the spontaneous polarization originating from Pb/Bi - O hybridization is strongly associated with the negative thermal expansion. This mechanism can be used as a guide for the future design of negative thermal expansion of phase-transforming oxides. © 2011 American Chemical Society.

Wang Y.,University of Science and Technology Beijing | Wang X.,University of Science and Technology Beijing | Jiang X.,Harbin Institute of Technology
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2015

A theory for nonlinear excitations in quantum plasmas is presented for narrow-gap semiconductors by considering the combined effects of quantum and pseudorelativity. The system is governed by a coupled Klein-Gordon equation for the collective wave functions of the conduction electrons and Poisson's equation for the electrostatic potential. This gives a closed system, including the effects of charge separation, quantum tunneling, and pseudorelativity. By choosing the typical parameters of semiconductor InSb, the quasistationary soliton solution, which is a multipeaked dark soliton, is obtained numerically and shows depleted electron densities correlated with a localized potential. The dynamical simulation result shows that the dark soliton is stable and has a multipeaked profile, which is consistent with the quasistationary solution. The present model and results may be useful in understanding the nonlinear properties of semiconductor plasma on an ultrafast time scale. © 2015 American Physical Society.

Zhang Z.-H.,Beijing Institute of Technology | Zhang Z.-H.,Impact Lab | Liu Z.-F.,Beijing Institute of Technology | Lu J.-F.,Beijing Institute of Technology | And 4 more authors.
Scripta Materialia | Year: 2014

Typical sintering experiments were conducted to understand the spark plasma sintering (SPS) mechanisms. Based on the results of the direct visual observations and characteristic microstructure analysis, we believe that spark discharge does indeed occur during the SPS process. The high-temperature spark plasma could be generated in the microgaps due to the discharge effect. Fast and efficient sintering can be achieved under the combined action of spark discharge, Joule heating, electrical diffusion and plastic deformation effect in the SPS process. © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Li H.,Harbin Institute of Technology | Lan C.M.,University of Science and Technology Beijing | Ju Y.,China University of Mining and Technology | Li D.S.,Dalian University of Technology
Journal of Bridge Engineering | Year: 2012

Corroded cables from a cable-stayed bridge in China that had been in service for 18years were employed to investigate the basic mechanical properties and residual fatigue life of wires and cables. First, the wires were randomly selected from the cables near the bottom anchorages and cut into segments as test specimens. The extent of corrosion of the wires was experimentally investigated. A tensile loading test was conducted on the wires to obtain the mechanical properties of the corroded single wires. The fatigue life of the corroded single wires was experimentally studied, and a dramatic degradation in fatigue life was observed. This phenomenon was interpreted using SEM images. Fatigue tests on two corroded cables were also conducted, and the test results indicated that the fatigue life of the cables had also decreased dramatically. A MonteCarlo simulation was conducted to obtain the fatigue life of cables. The simulation results indicated that the fatigue life of a cable was controlled by the small fraction of wires in the cable with the shortest fatigue lives. The fatigue life of a cable at a certain failure probability was dependent on the number of wires in the cable, but the mean fatigue life of a cable was not affected by the number of wires in the cable. © 2012 American Society of Civil Engineers.

Yin X.,University of Science and Technology Beijing | Yin X.-C.,University of Science and Technology Beijing | Hao H.-W.,CAS Institute of Automation | Iqbal K.,University of Science and Technology Beijing
Proceedings - International Conference on Pattern Recognition | Year: 2012

Text localization in natural scene images is an important prerequisite for many content-based image analysis tasks. In this paper, we proposed a novel and effective approach to accurately localize scene texts. Firstly, Maximally stable extremal regions(MSER) are extracted as letter candidates. Secondly, after elimination of non-letter candidates by using geometric information, candidate regions are constructed by grouping similar letter candidates using disjoint set. Candidate region features based on horizontal and vertical variances, stroke width, color and geometry are extracted. An AdaBoost classifier is built from these features and text regions are identified. The overall system is evaluated on the ICDAR 2011 competition dataset and the experimental results show that the proposed algorithm yields high precision and recall compared with the latest published algorithms. © 2012 ICPR Org Committee.

Ding H.,University of Science and Technology Beijing | Long Y.,Qingdao University | Shen J.,Suzhou University of Science and Technology | Wan M.,CAS Institute of Chemistry
Journal of Physical Chemistry B | Year: 2010

This article exposes a facial approach to self-assemble polyaniline (PANI) nanowires with thin diameter (∼10 nm) and high room-temperature conductivity (∼10° S/cm) by using Fe2(SO4)3 as a binary oxidant and dopant. The new method not only saves hard templates and postprocess of template removal but also simplifies the reagent. Formation yield, diameter, and room-temperature conductivity of the nanowires are affected by the molar ratios of Fe2(SO4)3 to aniline. The low redox potential of Fe2(SO4)3 not only results in a thinner diameter and higher room-temperature conductivity (10° S/cm) of the nanowires but also shows a much weaker temperature dependence of resistivity and smaller characteristic Mott temperature (T0 = 2.5 x 103 K). © 2010 American Chemical Society.

Chen S.,University of Science and Technology Beijing | Chen S.,Harbin Institute of Technology | Li L.,Harbin Institute of Technology | Chen Y.,Harbin Institute of Technology | Huang J.,University of Science and Technology Beijing
Journal of Alloys and Compounds | Year: 2011

Joining mechanism of Ti/Al dissimilar alloys was investigated during laser welding-brazing process with automated wire feed. The microstructures of fusion welding and brazing zones were analysed in details by transmission electron microscope (TEM). It was found that microstructures of fusion welding zone consist of α-Al grains and ternary near-eutectic structure with α-Al, Si and Mg2Si. Interfacial reaction layers of brazing joint were composed of α-Ti, nanosize granular Ti7Al 5Si12 and serration-shaped TiAl3. For the first time, apparent stacking fault structure in intermetallic phase TiAl3 was found when the thickness of the reaction layer was very thin (approximately less than 1 μm). Furthermore, crystallization behavior of fusion zone and mechanism of interfacial reaction were discussed in details. © 2010 Elsevier B.V. All rights reserved.

Li W.,École Centrale Paris | He D.,École Centrale Paris | Dang Z.,University of Science and Technology Beijing | Bai J.,École Centrale Paris
Composites Science and Technology | Year: 2014

Damage sensing of the fiber-reinforced structural composites have attracted a lot of attention. In this work, a small amount of carbon nanotubes (CNT)-Al2O3 hybrids are introduced into the woven glass fabric reinforced epoxy composites and serve as in situ sensor to monitor the damage initiation and propagation under mechanical loading. The hybrids with CNTs grown on the Al2O3 micro-spheres are synthesized by chemical vapor deposition. The addition of 0.5wt.% CNT-Al2O3 increased ac electrical conductivity of the glass fabric/epoxy composites at 103Hz 4-5 orders of magnitude in both in-plane and through-thickness directions. The electrical resistance of the composites was in situ measured under quasi-static tensile testing. With the increase of strain, the resistance response could be classified into three distinguished stages, corresponding to various damage modes (microcracks, fiber/matrix interfacial debonding, transverse cracks, delamination, fiber breakage, etc.). © 2014.

Liu Z.Y.,University of Science and Technology Beijing | Liu Z.Y.,Nanchang Hangkong University | Li X.G.,University of Science and Technology Beijing | Cheng Y.F.,University of Calgary
Corrosion Science | Year: 2012

This paper investigates mechanistically stress corrosion cracking (SCC) of an X70 pipeline steel that is under cathodic protection (CP) in a near-neutral pH solution. It was found that there is a critical potential range, i.e., -730 and -920mV SCE, where the steel is in a non-equilibrium electrochemical state, and anodic dissolution (AD) reaction may occur when the steel is polarized cathodically. When the applied potential is more positive than this range, SCC is AD-based; while the applied potential is more negative, SCC of pipelines is under hydrogen embrittlement (HE) mechanism. When the polarization potential is within the range, SCC of the steel is under the combined effect of AD and HE. Therefore, AD may still occur on pipeline steel that is under CP with the potential within this critical range, contributing to the cracking process. © 2011 Elsevier Ltd.

Yuan J.-K.,École Centrale Paris | Yao S.-H.,Joseph Fourier University | Dang Z.-M.,University of Science and Technology Beijing | Sylvestre A.,Joseph Fourier University | And 2 more authors.
Journal of Physical Chemistry C | Year: 2011

Carbon nanotubes have unprecedented electronic properties and large specific areas as nanoscale fillers, but their potential has not been fully realized in polymer composites due to the poor dispersion and weak interfacial interaction. Here, we present a robust and simple procedure to prepare polymer-based composites with a remarkable molecular level interaction at interfaces through melt-mixing pristine multiwalled carbon nanotubes (MWNTs) within poly(vinylidene fluoride) (PVDF) matrix. The interfacial interaction is confirmed by Raman spectroscopy as well as the formation of much thin PVDF layer on individual MWNT. The resultant nanocomposite with a huge interfacial area possesses a giant dielectric permittivity (3800) of 3 orders of magnitude higher than the PVDF matrix, while retaining a low conductivity level (6.3 A - 10 a-5 and an excellent thermal stability. These results could be explained by a reinforced Maxwell-Wagner-Sillars (MWS) effect based on the remarkable molecular level interaction. © 2011 American Chemical Society.

Wang W.,University of Science and Technology Beijing | Hussin B.,University of Technology Malaysia | Jefferis T.,UK Defence Science and Technology Laboratory
International Journal of Production Economics | Year: 2012

This paper presents a case study of condition based maintenance modelling based on measured metal concentrations observed in oil samples of a fleet of marine diesel engines. The decision model for optimising the replacement time of the diesel engines conditional on observed measurements is derived and applied to the case discussed. We described the datasets, which were cleaned and re-organised according to the need of the research. The residual time distribution required in the decision model was formulated using a technique called stochastic filtering. Procedures for model parameter estimation are constructed and discussed in detail. The residual life model presented has been fitted to the case data, and the modelling outputs are discussed. © 2011 Elsevier B.V.

Sun J.,Nanjing University of Aeronautics and Astronautics | Sun J.,University of Maryland University College | Zuo H.,Nanjing University of Aeronautics and Astronautics | Wang W.,University of Science and Technology Beijing | And 2 more authors.
Mechanical Systems and Signal Processing | Year: 2012

This paper presents the application of a state space model (SSM) for prognostics of an engineering system subject to degradation. A health index (HI) is inferred from a set of sensor signals to characterize the hidden health state of the system. Bayesian state estimation and prediction formulas, on the basis of the health indices modeled by the linear regression of observed signals, are carried out to sequentially update the current health state and then predict the future health state of the system. A Sequential Monte Carlo (SMC) method is used for computation. If a failure is defined in terms of a specified level of degradation, a time-to-failure distribution can be obtained based on the predicted degradation. The method is applied to a gas turbine that is simulated via a gas turbine software package and is subject to both gradual performance deterioration and abrupt faults in service. The analysis of the case study shows that the method can provide an estimate of Remaining Useful Life (RUL) with uncertainty as well as other reliability indices of interest for operators to plan effective condition-based maintenance. © 2011 Elsevier Ltd. All rights reserved.