Tianjin, China
Tianjin, China

Tianjin University is a national university under the direct administration of the Ministry of Education of China. It is the first modern higher education institution in China. It was established in 1895 as Tientsin University/Imperial Tientsin University and later Peiyang University . In 1951, after restructuring, it was renamed Tianjin University, and became one of the largest multidisciplinary engineering universities in China. The university was one of the first 16 universities accredited by the State in 1959. It is also among the first group of institutions of higher learning in the national “211-Project” to which priority is given in construction. In order to carry out the “21st Century Education Revitalizing Action Plan”, in late 2000 the Ministry of Education and Tianjin Municipality signed an agreement which aims to build Tianjin University into a world famous university in the 21st Century. Wikipedia.


Time filter

Source Type

Patent
Tianjin University and Hainan Lingkang Pharmaceutical Co. | Date: 2015-11-20

It discloses Omeprazole Sodium semihydrate and preparation method thereof, wherein every mole of Omeprazole Sodium semihydrate contains 0.5 mole of water, and it has an X-ray diffraction pattern comprising characteristic peaks at diffraction angles 2 of 6.260.1, 11.100.1, 12.200.1, 15.580.1, 16.020.1, 17.120.1, 19.080.1, 21.000.1, 22.680.1, 23.480.1, 24.080.1, 26.520.1 and 28.080.1. A raw material of Omeprazole Sodium hydrate is added into an organic solvent, stirring for 29 hours at constant temperature of 2560 C., thereafter Omeprazole Sodium semihydrate is provided after filtrating and drying.


Patent
Tianjin University and Hainan Lingkang Pharmaceutical Co. | Date: 2015-11-20

A novel crystalline form of Cefathiamidine compound and its preparation method, characterizing in its X-ray powder diffraction pattern and differential scanning calorimetry thermogram. Dissolving Cefathiamidine compound with a purity of 98% or higher in a solvent at a temperature of 3045 C. to form a solution, whose concentration is controlled within 0.050.2 g/mL, and then adding a solventing-out agent to the solution, wherein the amount of the solventing-out agent is 35 times (in volume) of that of the solvent; followed by cooling the solution down to 010 C. at a rate of 0.21 C./min; continuing to stir for 13 hours, and separating the obtained solid-liquid suspension to provide a novel crystalline form of Cefathiamidine compound after drying.


Patent
Tianjin University and Hainan Lingkang Pharmaceutical Co. | Date: 2015-11-20

A novel crystalline form is defined by diffraction angle 2 of X-ray powder diffraction pattern and characteristic peak of differential scanning calorimetry (DSC). The novel crystalline form of Cefamandole Nafate is prepared as follows: adding Cefamandole Nafate in solid state to an organic solvent to form a suspension with a concentration of 0.040.3 g/ml, stirring the suspension at 4050 C. for a period of time, and then cooling to 515 C. at certain cooling rate, continuing to stir for a period of time, then suction filtrating the obtained suspension, the resulting filer cake is Cefamandole Nafate as wet product, which is dried to constant weight to provide the novel crystalline form of Cefamandole Nafate as final product.


Patent
Shenzhen Salubris Pharmaceuticals Co. and Tianjin University | Date: 2014-12-31

This invention provides a new preparation method of Clopidogrel Hydrogen Sulfate spherical crystal form I, using single 2-butanol as solvent, controlling the concentration, addition way and addition speed of sulfuric acid used to salify to shorten the process time, thus separating out Clopidogrel Hydrogen Sulfate from solution system stably with spherality. And the Clopidogrel Hydrogen Sulfate obtained complies with the requirements of the follow-up process on residual solvent, bulk density and mobility.


A cylindrical single-piece lithium-ion battery of 400 Ah includes: a cylindrical battery enclosure (1), a battery mandrel (3), a plurality of tabs (4), a wiring terminal (6), a positive and negative electrode cover (11); a positive electrode sheet, said battery positive electrode is composed of LiFePO_(4), conductive carbon-black, graphite, adhesive such as PVDF, and solvent such as NMP; a negative electrode sheet, the battery negative electrode is composed of lithium titanate, conductive carbon-black, graphite, adhesive such as PVDF, and solvent such as NMP. The cylindrical lithium-ion battery made by the invention has a capacity of 400 Ah which is the one reportedly having the largest capacity in the world presently.


The present invention proposes a method for solving the decomposition-coordination calculation based on Block Bordered Diagonal Form(BBDF) model by using data center. During the solving process, partitioning the electric power system network by using the existing network partitioning method to achieve the grid partition, and setting the parameters of virtual memories firstly, thus to establish the bin-packing model with the priority of energy efficiency; and then, setting each calculating step of the decomposition-coordination calculation based on BBDF as a task. Through the manners that servers host VMs and VMs map tasks, the decomposition-coordination algorithm can be executed in data center, and the running time and energy consumption of data center can be calculated. The present invention can shorten the calculating time of decomposition-coordination algorithm and reduce the energy consumption in data center. Moreover, with the increase of scale and the complexity of the electric power system, the advantages of the method using data center presented by the present invention are becoming much more obvious.


Wang Z.,Tianjin University | Liang M.,Tianjin University of Technology | Wang L.,Tianjin University of Technology | Hao Y.,Tianjin University of Technology | And 3 more authors.
Chemical Communications | Year: 2013

Three dithieno[3,2-b:2′,3′-d]pyrrole (DTP) units with different hexyloxyphenyl (HOP) substituents have been developed for triphenylamine organic dyes (XS54-XS56). The introduction of the 4-HOP-DTP unit has resulted in a stronger light harvesting capacity, accounting for the observed photocurrent enhancement in the case of XS54, while the 2-HOP-DTP/2,4-HOP-DTP units induce a strikingly large photovoltage improvement in the cases of XS55 and XS56 due to their higher steric hindrance. © 2013 The Royal Society of Chemistry.


Wu H.,Tianjin University | Zhang F.,Tianjin University | Cao S.,China Institute of Metrology | Xing S.,Tianjin University | Qu X.,Tianjin University
Optics Express | Year: 2014

We propose an interferometric method that enables to measure a distance by the intensity measurement using the scanning of the interferometer reference arm and the recording of the interference fringes including the brightest fringe. With the consideration of the dispersion and absorption of the pulse laser in a dispersive and absorptive medium, we investigate the cross-correlation function between two femtosecond laser pulses in the time domain. We also introduce the measurement principle. We study the relationship between the position of the brightest fringe and the distance measured, which can contribute to the distance measurement. In the experiments, we measure distances using the method of the intensity detection while the reference arm of Michelson interferometer is scanned and the fringes including the brightest fringe is recorded. Firstly we measure a distance in a range of 10 μm. The experimental results show that the maximum deviation is 45 nm with the method of light intensity detection. Secondly, an interference system using three Michelson interferometers is developed, which combines the methods of light intensity detection and time-of-flight. This system can extend the non-ambiguity range of the method of light intensity detection. We can determine a distance uniquely with a larger non-ambiguity range. It is shown that this method and system can realize absolute distance measurement, and the measurement range is a few micrometers in the vicinity of Nlpp, where N is an integer, and lpp is the pulse-to-pulse length. © 2014 Optical Society of America.


Shao J.-J.,Tianjin University | Lv W.,Tsinghua University | Yang Q.-H.,Tianjin University
Advanced Materials | Year: 2014

Due to its amphiphilic property, graphene oxide (GO) can achieve a variety of nanostructures with different morphologies (for example membranes, hydrogel, crumpled particles, hollow spheres, sack-cargo particles, Pickering emulsions, and so on) by self-assembly. The self-assembly is mostly derived from the self-concentration of GO sheets at various interfaces, including liquid-air, liquid-liquid and liquid-solid interfaces. This paper gives a comprehensive review of these assembly phenomena of GO at the three types of interfaces, the derived interfacial self-assembly techniques, and the as-obtained assembled materials and their properties. The interfacial self-assembly of GO, enabled by its fantastic features including the amphiphilicity, the negatively charged nature, abundant oxygen-containing groups and two-dimensional flexibility, is highlighted as an easy and well-controlled strategy for the design and preparation of functionalized carbon materials, and the use of self-assembly for uniform hybridization is addressed for preparing hybrid carbon materials with various functions. A number of new exciting and potential applications are also presented for the assembled GO-based materials. This contribution concludes with some personal perspectives on future challenges before interfacial self-assembly may become a major strategy for the application-targeted design and preparation of functionalized carbon materials. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Xue J.,Tianjin University of Technology | Wang X.,Tianjin University of Technology | Qi G.,General Motors | Wang J.,Tianjin University of Technology | And 3 more authors.
Journal of Catalysis | Year: 2013

To investigate the active Cu sites in the selective catalytic reduction of NO by NH3 (NH3 SCR) over Cu/SAPO-34 catalysts, a series of samples containing different Cu loadings has been prepared by an ion-exchange process. A combination of H2 TPR and EPR techniques was applied to identify and quantify the isolated Cu2+ sites. The trend of the isolated Cu2+ ions in the samples estimated by EPR is similar to that from TPR results and was found to be proportional to the NH3 SCR reaction rates. The turnover frequency (TOF) calculated based on the number of isolated Cu2+ ions on samples with varying Cu loadings showed a constant value at the same temperature. Thus, we conclude that the isolated Cu2+ species associated with the six-ring window and displaced into the ellipsoidal cavity of SAPO-34 (Site (I)) are the active sites for the NH3 SCR reaction in the temperature range 100-200 °C. © 2012 Elsevier Inc. All rights reserved.


Hu F.,Tianjin University | Lim C.-C.,University of Adelaide | Lu Z.,University of Adelaide
International Journal of Production Economics | Year: 2013

This paper studies a flexible ordering policy among a manufacturer and a supplier with random yield and demand uncertainty, where the order quantity lies between the minimum and the maximum quantity. We first determine the optimal flexible ordering policy and the corresponding raw material production quantity that maximize expected profit of the centralized supply chain, and find that our flexible ordering policy can significantly enhance the supply chain's expected profit compared to an invariable ordering policy. Then we analyze the decentralized scenario and propose a revenue sharing policy with an order penalty and rebate (OPR) contract to fully coordinate the supply chain. Finally, numerical examples are given to illustrate the results. © 2013 Elsevier B.V.


Yao X.,Tianjin University | Tan T.T.Y.,Nanyang Technological University | Wang Y.,Tianjin University
Journal of Chromatography A | Year: 2014

This work is the first demonstration of a simple thiol-ene click chemistry to anchor vinyl imidazolium β-CD onto thiol silica to form a novel cationic native cyclodextrin (CD) chiral stationary phase (CSP). The CSP afforded high enantioseparation ability towards dansyl (Dns) amino acids, carboxylic aryl compounds and flavonoids in chiral HPLC. The current CSP demonstrates the highest resolving ability (selectivity >1.1, resolution >1.5) towards Dns amino acids in a mobile phase buffered at pH. = 6.5, with the resolution of Dns- dl-leucine as high as 6.97. 2,4-dichloride propionic acid (2,4-ClPOPA) was well resolved with the selectivity and resolution of 1.37 and 4.88, respectively. Compared to a previously reported native CD-CSP based on a triazole linkage, the current cationic CD-CSP shows a stronger retention and higher resolution towards acidic chiral compounds, ascribed to the propitious strong electrostatic attraction. Stability evaluation results indicated that thiol-ene reaction can provide a facile and robust approach for the preparation of positively charged CD CSPs. © 2013 Elsevier B.V.


Zhang S.,Tianjin University | Wang G.,Tianjin University | Yu X.,Tianjin University | Yu X.,Sinohydro Bureau 14 Co.
Engineering Structures | Year: 2013

The seismic crack propagation of concrete gravity dams with initial cracks at the upstream and downstream faces has rarely been studied during strong earthquakes. In this paper, a numerical scheme based on the extended finite element method (XFEM), which has been widely used for the analysis of crack growth, is presented to deal with the numerical prediction of crack propagation in concrete gravity dams. The validity of the algorithm is discussed by comparing results obtained from the proposed XFEM with those reported in the literature. For this purpose, the cracking process and final crack profile of Koyna dam during the 1967 Koyna earthquake are simulated numerically by employing the XFEM. The computed distribution of cracking damage is consistent with the actual condition and the results of model test and available methods in literature, which verifies the validity of the calculation model. Subsequently, the Koyna dam with single and multiple initial cracks is also analyzed using the proposed approach, which is investigated to evaluate the seismic crack propagation of the concrete gravity dam with initial cracks. The effects of initial cracks on the crack propagation and seismic response of the concrete gravity dam are discussed. © 2013 Elsevier Ltd.


Zhang Y.-J.,Tianjin University | Li Z.-Q.,Tianjin University | Lin J.-J.,National Chiao Tung University
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

We have measured the Hall coefficient RH and the electrical conductivity σ of a series of ultrathin indium-tin-oxide films between 2 and 300 K. A robust RHlnT law is observed in a considerably wide temperature range of 2 and ∼120K. This lnT dependence is explained as originating from the electron-electron interaction effect in the presence of granularity as theoretically predicted. Furthermore, we observed a σlnT law from 3 K up to several tens K, which also arose from the Coulomb interaction effect in inhomogeneous systems. These results provide strong experimental support for the current theoretical concepts for charge transport in granular metals with intergrain tunneling conductivity gT1. © 2011 American Physical Society.


Zhu Z.,Tianjin University | Zhu Z.,University of Aalborg | Rosendahl L.,University of Aalborg | Toor S.S.,University of Aalborg | And 2 more authors.
Applied Energy | Year: 2015

Hydrothermal liquefaction (HTL) of barley straw with K2CO3 at different temperatures (280-400°C) was conducted and compared to optimize its process conditions; the aqueous phase as a co-product from this process was recycled to explore the feasibility of implementing wastewater reuse for bio-crude oil production. Results showed that low temperature favored the formation of bio-crude oil, with a maximum yield of 34.9wt% at 300°C. Contrarily, at high temperature, the bio-crude oil had better qualities in terms of less oxygen content and higher heating values (HHVs). The compounds identified in bio-crude oil were mainly phenolics, carboxylic acids, aldehydes and alcohols, among which the relative contents of phenolics and carboxylic acids decreased with increasing temperature. In the recirculation studies, bio-crude yield was enhanced gradually with aqueous phase addition at 300°C, and reached 38.4wt% after three cycles. The HHVs of bio-crude oil from HTL with aqueous phase were 28.4-29.4MJ/kg, slightly higher than those from HTL with fresh water. While no obvious differences in elemental distribution can be found after aqueous phase recirculation. In conclusion, this study gives a detailed insight into the HTL behavior of barley straw, and offers potential opportunities and benefits for bio-crude oil production through the reuse of aqueous phase. © 2014 Elsevier Ltd.


Wang L.,Tianjin University | Li X.,Guangdong University of Technology | Tang Z.,Tianjin University | Zhang X.,McNair Technology Company
Electrochemistry Communications | Year: 2012

Li 3V 2(PO 4) 3/Li 4Ti 5O 12/C (LVP/LTO/C) composite has been synthesized via a sol-gel method and investigated by physical and electrochemical methods. In the range of 3.0-4.3 V, the LVP/LTO/C electrodes exhibit excellent cyclic performance. The discharge capacity reached 90.3 and 75.5 mAh g - 1 for discharge rate of 50 C when the charge rate was 5 and 25 C, respectively. The excellent rate capability and cyclic performance are attributed to the existence of the carbon with high electronic conductivity and LTO with high lithium ion diffusion coefficient. © 2012 Elsevier B.V.


Wang T.,Peking University | Wang T.,Tianjin University | Zhou W.,Peking University | Yin H.,Peking University | And 3 more authors.
Angewandte Chemie - International Edition | Year: 2012

Hot couple: Propargyl azides were coupled with carboxylic acids by an iron-catalyzed dehydrogenative C-O bond formation (see scheme). This method enables propargylic C sp 3-H functionalization under mild reaction conditions and also may involve the application of the azido moiety as an assisting group in C-H activation. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Huang Q.-H.,Tianjin University | Ling T.,Tianjin University | Qiao S.-Z.,Tianjin University | Qiao S.-Z.,University of Adelaide | Du X.-W.,Tianjin University
Journal of Materials Chemistry A | Year: 2013

Pyrite (FeS2) nanorod arrays were produced on a fluorine doped tin oxide substrate by sulfurizing FeO(OH) nanorods, and then tested as the counter electrode (CE) for dye-sensitized solar cells (DSSCs). FeS2 nanorods show better catalytic properties than the FeS2 film and the Pt film due to their active facets, which helps to achieve a high short-circuit photocurrent density (Jsc) of DSSCs. On the other hand, FeS 2 nanorods have lower interface resistance than FeS2 thin films, which contributes to a higher fill factor (FF) of DSSCs. As a result, the solar cell with a CE of FeS2 nanorods exhibits an excellent power conversion efficiency, which is comparable to that of traditional DSSCs with a Pt CE. © 2013 The Royal Society of Chemistry.


Wang Z.,Tianjin University | Wang Z.,Beijing Normal University | Li M.,Tianjin University | Li J.,Tsinghua University
Information Sciences | Year: 2015

Feature selection is an important task in data mining and pattern recognition, especially for high-dimensional data. It aims to select a compact feature subset with the maximal discriminative capability. The discriminability of a feature subset requires that selected features have a high relevance to class labels, whereas the compactness demands a low redundancy within the selected feature subset. This paper defines a new feature redundancy measurement capable of accurately estimating mutual information between features with respect to the target class (MIFS-CR). Based on a relevance measure and this new redundancy measure, a multi-objective evolutionary algorithm with class-dependent redundancy for feature selection (MECY-FS) is presented. The MECY-FS algorithm employs the Pareto optimality to evaluate candidate feature subsets and finds compact feature subsets with both the maximal relevance and the minimal redundancy. Experiments on benchmark datasets are conducted to validate the effectiveness of the new redundancy measure, and the MECY-FS algorithm is verified to be able to generate compact feature subsets with a high predictive capability. © 2015 Elsevier Inc. All rights reserved.


Li W.,Tianjin University | Sun J.,Tianjin University of Technology | Chen M.,Tianjin University of Technology
Nano Energy | Year: 2014

Harvest energy from our environment for driving small electronics is an effective and practically applicable technology. Here, we demonstrated a simple, cost-effective arch-shaped triboelectric nanogenerator (TENG), which is fabricated by utilizing the triboelectric effect and related electrostatic induction between a biodegradable metal foil and a polymer sheet, with bactericidal nano-Ag ink painted on its top as electrode. The power generation mechanism and the electric output of the TENG were studied and illustrated. The instantaneous output voltage and current density of such a flexible TENG can reach as high as ~160V and 6.6μA/cm2. Based on these characteristics of the TENG, it is anticipated that the TENG comprised of a biodegradable metal foil and a bactericidal Ag film has potential application in biomedical field to drive small biomedical devices possibly in-vivo. © 2013 Elsevier Ltd.


Wang C.,Tianjin University | Dong X.-Y.,Tianjin University | Jiang Z.,Tianjin University of Technology | Sun Y.,Tianjin University
Journal of Chromatography A | Year: 2013

Novel composite cryogel monoliths were fabricated by incorporating polymeric resin particles and grafting anion-exchange groups on the pore wall surfaces. The embedded resin particles in different size distributions were prepared by grinding poly(glycidyl methacrylate-ethylene glycol dimethacrylate) monoliths. Observations by scanning electron microscopy clearly indicated that the composite cryogel had interconnected large pores (10-100. μm in width), similar to normal (pure) cryogel. However, the composite material had very rough pore walls, which provided larger surface area for protein adsorption. As a result, the dynamic binding capacity of bovine serum albumin (BSA) on the composite cryogel bed reached 6. mg/mL bed (flow velocity, 5. cm/min), which was 2.8 times higher than a cryogel bed without embedding the ground resin particles. The capacity value was also much higher than the BSA capacities of cryogel beds reported in literature (1-4. mg/mL). Though the capacity decreased by about 1. mg/mL with the increase of flow rate from 0.5 to 5. cm/min, it then kept almost unchanged till a flow rate up to 15. cm/min. The height equivalent to a theoretical plate of the composite bed was in the range of 1.1-1.4. mm, and kept nearly constant in a flow rate range of 5-20. cm/min. The results indicated that the composite cryogel bed offered a large improvement in protein adsorption capacity and was suitable for high-speed protein chromatography. © 2012 Elsevier B.V..


Li C.,Tianjin University | Dian L.,Tianjin University | Zhang W.,Shanghai University | Lei X.,Tianjin University | Lei X.,China National Institute of Biological Sciences
Journal of the American Chemical Society | Year: 2012

We report the first biomimetic syntheses of (-)-gochnatiolides A-C and (-)-ainsliadimer B based on our proposed biogenetic pathway. Our synthesis features one-pot cascade transformations including Saegusa oxidation, intermolecular Diels-Alder cycloaddition, and radical-mediated allylic oxidation, which allow for the rapid generation of (-)-gochnatiolides A-C in a collective manner. We also disclose an unprecedented "copper effect" on the stereochemical outcome of the radical-mediated allylic oxidation. Our synthetic endeavors led to the structural reassignment of (-)-gochnatiolide B. Ultimately, a biomimetic transformation from gochnatiolide B to ainsliadimer B was achieved through a remarkable direct enone hydration. © 2012 American Chemical Society.


Zhang K.,Tianjin University | Zhang K.,University of Texas at Dallas
Journal of Visual Languages and Computing | Year: 2012

Recent great advances of information visualization and visual languages have not been utilized in the management field. This View point article advocates the use of appropriate visual languages in general and visualization in particular to maximize human's visual perceptual power for rapid and effective communication in management. © 2012 Elsevier Ltd.


Zhang Y.,Tianjin University | Li Y.,Tianjin University | Liu W.,Tianjin University
Advanced Functional Materials | Year: 2015

High strength hydrogels were previously constructed based on dipole-dipole and hydrogen bonding reinforcement. In spite of the high tensile and compressive strengths achieved, the fracture energy of the hydrogels strengthened with sole noncovalent bondings was rather low due to the lack in energy dissipating mechanism. In this study, combined dipole-dipole and hydrogen bonding interactions reinforced (DHIR) hydrogels are synthesized by onestep copolymerization of three feature monomers, namely acrylonitrile (AN, dipole monomer), acrylamide (AAm, H-bonding monomer), and 2-acrylamido- 2-methyl-1-propanesulfonic acid (AMPS, anionic monomer) in the presence of PEGDA575, a hydrophilic crosslinker. The electrostatic repulsion from PAMPS allows the gel network to absorb water readily, and meanwhile the synergistic effect of dipole-dipole and H-bonding interactions enable the DHIR hydrogel to withstand up to 8.3 MPa tensile stress, 4.8 MPa compressive stress and 140-716% elongation at break with the fracture energy reaching as high as 5500 J/m2. In addition, this DHIR hydrogel exhibits reversible mechanical properties after undergoing cyclic loading and unloading. Interestingly, the DHIR hydrogels with appropriate compositions demonstrate temperaturetunable mechanical properties as well as accompanied shape memory effect. The dual noncovalent bonding strengthening mechanism reported here offers a universal strategy for significantly enhancing the comprehensive mechanical properties of hydrogels. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Wang D.,University of Victoria | Parkinson S.,University of Victoria | Miao W.,Tianjin University | Jia H.,Tianjin University | And 2 more authors.
Applied Energy | Year: 2013

In this paper, a new market integration approach for responsive loads is proposed. Large, spatially-distributed populations of heat pumps, electric vehicles, and electrolyzers are integrated into the conventional security constrained economic dispatch formulation using a hierarchical load management policy. Regional pockets of responsive loads are aggregated into models that describe population dynamics as an equivalent virtual power plant. This demand-side virtual power plant is then integrated into the market as a new source of spinning reserves. The potential impact of reserve capacity supported by responsive loads on the operating characteristics of the power system is investigated using a bottom-up modeling framework. Results indicate that by supplying spinning reserve, responsive loads can increase the flexibility of existing resources within the active power portion of the market. The hierarchical market integration policy enhances both the technical and economic efficiency of the power system, reduces operating costs and emissions, and supports increasing levels of variable generation on the grid. © 2012 Elsevier Ltd.


Wang C.,Tianjin University | Sun Y.,Tianjin University
Journal of Chromatography A | Year: 2013

Composite cryogel monoliths based on poly(2-hydroxyethylmethacrylate) (pHEMA) were fabricated by incorporating polymeric resin particles. The monoliths were sequentially modified by polyethylenimine (PEI) and diethylaminoethyl (DEAE). The novel composite material had rough pore walls and extended anion-exchange tentacles, which provided more binding sites for protein molecules. The dynamic adsorption capacity of bovine serum albumin (BSA) on the novel cryogel bed reached 11.2. mg/mL bed volume at a flow velocity of 8. cm/min, which was about 1.5-4.6 times higher than the cryogel beds obtained by single modifications. The capacity value was also much higher than the BSA capacities of cryogel beds reported in literature (1-6. mg/mL). The capacity decreased only slightly with increasing flow rate from 0.6 to 12. cm/min. The height equivalent to a theoretical plate of the composite beds was in the range 2-2.5. mm, changed indistinctively in a flow rate range 0.6-18. cm/min. Hence, the work has proved that the double-modification strategy was promising for enhancing protein adsorption capacity of cryogel monolith for high-speed protein chromatography. © 2013 Elsevier B.V.


Armstrong S.,Australian National University | Wang M.,Peking University | Teh R.Y.,Swinburne University of Technology | Gong Q.,Peking University | And 7 more authors.
Nature Physics | Year: 2015

Einstein, Podolsky and Rosen (EPR) pointed out in their famous paradox that two quantum-entangled particles can have perfectly correlated positions and momenta. Such correlations give evidence for the nonlocality of quantum mechanics and form the basis for quantum cryptography and teleportation. EPR steering is the nonlocality associated with the EPR paradox and has traditionally been investigated between only two parties. Using optical networks and efficient detection, we present experimental observations of multiparty EPR steering and of the genuine entanglement of three intense optical beams. We entangle the quadrature phase amplitudes of distinct fields, in analogy to the position-momentum entanglement of the original paradox. Our experiments complement tests of quantum mechanics that have entangled small systems or have demonstrated tripartite inseparability. Our methods establish principles for the development of multiparty quantum communication protocols with asymmetric observers, and can be extended to qubits, whether photonic, atomic, superconducting, or otherwise. © 2015 Macmillan Publishers Limited.


Jiao Y.,University of Adelaide | Zheng Y.,University of Adelaide | Jaroniec M.,Kent State University | Qiao S.Z.,University of Adelaide | Qiao S.Z.,Tianjin University
Chemical Society Reviews | Year: 2015

A fundamental change has been achieved in understanding surface electrochemistry due to the profound knowledge of the nature of electrocatalytic processes accumulated over the past several decades and to the recent technological advances in spectroscopy and high resolution imaging. Nowadays one can preferably design electrocatalysts based on the deep theoretical knowledge of electronic structures, via computer-guided engineering of the surface and (electro)chemical properties of materials, followed by the synthesis of practical materials with high performance for specific reactions. This review provides insights into both theoretical and experimental electrochemistry toward a better understanding of a series of key clean energy conversion reactions including oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). The emphasis of this review is on the origin of the electrocatalytic activity of nanostructured catalysts toward the aforementioned reactions by correlating the apparent electrode performance with their intrinsic electrochemical properties. Also, a rational design of electrocatalysts is proposed starting from the most fundamental aspects of the electronic structure engineering to a more practical level of nanotechnological fabrication. © 2015 The Royal Society of Chemistry.


Liang J.,University of Adelaide | Du X.,University of Adelaide | Gibson C.,Flinders University | Du X.W.,Tianjin University | Qiao S.Z.,University of Adelaide
Advanced Materials | Year: 2013

A novel nitrogen doped hybrid material composed of in situ-formed graphene natively grown on hierarchical ordered porous carbon is prepared, which successfully combines the advantages of both materials, such as high surface area, high mass transfer, and high conductivity. The outstanding structural properties of the resultant material render it an excellent metal-free catalyst for electrochemical oxygen reduction. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Yu L.-L.,Tianjin University | Sun Y.,Tianjin University
Journal of Chromatography A | Year: 2013

In Part I of this work, we have studied the effect of ionic capacity (IC) on bovine serum albumin (BSA) adsorption equilibria and kinetics to poly(ethylenimine) (PEI)-grafted Sepharose FF, and found a critical IC (cIC, 600mmol/L), above which both protein capacity and uptake rate increased drastically. In this work, five PEI-Sepharose FF resins of typical ICs reported earlier were selected to explore the effect of ionic strength (IS) on the adsorption equilibria and kinetics of BSA. Commercially available DEAE (IC=160mmol/L) and Q Sepharose FF (IC=269mmol/L) resins were used for comparisons. It is found that at similar ionic capacities, protein adsorption capacities on both the PEI-Sepharose FF resins and the commercial resins decreased with increasing IS, but on the capacity sensitivity to salt concentration, the former was lower than the latter. In addition, the effective diffusivities (De) of the former were smaller than the latter in the entire IS range studied. The low IS sensitivity of adsorption capacity of the PEI-Sepharose FF resins could be interpreted by the increase of pore accessibility with increasing IS; the smaller De values in the PEI-Sepharose FF resins were considered due to the lack of surface diffusion in the PEI-Sepharose FF resins of low PEI densities. For the PEI-Sepharose FF resins of high ICs (520, 740 and 1220mmol/L), both protein capacity and De values increased first and then decreased with increasing IS. The increasing trend of protein capacity in the low IS range was considered due to the increase of accessible pores for BSA. The rise-fall trend of De was attributed to the dependencies of the "chain delivery" effect on protein capacity and binding strength, both of which are related to IS. Moreover, the IS sensitivity of the De for the resins of ICs>cIC (740 and 1220mmol/L) was much higher than those of ICscIC. Furthermore, the two PEI-Sepharose FF resins of ICs>cIC kept high adsorption capacities and De values up to 200-300mmol/L NaCl. Therefore, the operating IS ranges for these two PEI-Sepharose FF resins can be much broader than the traditional ion-exchange media. © 2013 Elsevier B.V.


Liu C.,Tianjin University of Technology | Yang D.,Tianjin University | Jiao Y.,Tianjin University of Technology | Tian Y.,Tianjin University | And 2 more authors.
ACS Applied Materials and Interfaces | Year: 2013

Ternary TiO2-SiO2-Ag nanocomposites with enhanced visible-light photocatalytic activity have been synthesized through a facile biomimetic approach by utilizing lysozyme as both inducing agent of TiO 2 and reducing agent of Ag+. TiO2 nanoparticles (∼280 nm) are at first fabricated by the inducing of lysozyme. Afterward, SiO2 layers are formed as "pancakes" stuck out of TiO 2 nanoparticles through a sol-gel process. Finally, Ag nanocrystals (∼24.5 nm) are deposited onto the surface of TiO2-SiO2 composites via the reduction of lysozyme, forming TiO2-SiO 2-Ag nanocomposites. The resultant nanocomposites display a high photocatalytic activity for the degradation of Rhodamine B under the visible-light irradiation, which can be attributed to the synergistic effect of enhanced photon absorption from the surface plasma resonance of Ag nanocrystals and the elevated adsorption capacity for Rhodamine B from the high specific surface area of SiO2. This study may provide some inspiration for the rational design and the facile synthesis of composite catalysts with a high and tunable catalytic property through a green, efficient pathway. © 2013 American Chemical Society.


Wu Y.-N.,Tianjin University | Li Z.-Q.,Tianjin University | Lin J.-J.,National Chiao Tung University
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

We have measured the resistivities and Hall coefficients, RH, of a series of nonmagnetic Mox(SnO2)1-x nanogranular films with the Mo volume fraction x ranging from ∼0.29 to 1. We found that the magnitude of RH (2 K) largely increased by a factor of ∼800 as x was reduced from ∼0.8 to ≃0.36. Then, it slightly decreased with a further decrease in x down to ≃0.32, which was determined to be the classical percolation threshold, xc, from the resistivity dependence on x. This nearly 3 orders of magnitude enhancement in RH at a metal volume fraction x> xc is explained in terms of the recent theoretical concept of the local quantum-interference effect induced giant Hall effect in granular systems. © 2010 The American Physical Society.


Zhang Z.H.,Hong Kong Polytechnic University | Zhang Z.H.,National University of Singapore | Cheung C.S.,Hong Kong Polytechnic University | Yao C.D.,Tianjin University
Fuel | Year: 2013

This study is aimed to investigate the effects of fumigation methanol on the combustion and particulate emissions of a diesel engine under different engine loads and fumigation level. Experiments were performed on a 4-cylinder direct injection diesel engine operating at the engine speed of 1920 rev/min with five engine loads. The combustion characteristic analysis indicates that with fumigation methanol, the maximum cylinder pressure decreases at low to medium engine loads but increases at high engine load. Fumigation methanol increases the peak heat release rate and ignition delay but does not significantly change the combustion duration. The fumigation method results in a significant decrease in particulate mass and number concentrations from medium to high engine loads, due to the increase of fuel burned in the premixed mode and a reduction of diesel fuel involved. Fumigation methanol also slightly decreases the fraction of accumulation mode particles and thus the particulate geometric mean diameter (GMD). © 2013 Elsevier Ltd. All rights reserved.


Song G.,Tianjin University | Xin F.,Tianjin University | Chen J.,Tianjin University | Yin X.,Tianjin University of Technology
Applied Catalysis A: General | Year: 2014

A nanosheet of CdS-TiO2 with heterojunction was prepared by a two-step hydrothermal synthesis method and used as a photocatalyst for reducing CO2 in cyclohexanol. This heterostructured composite has been characterized by X-ray diffractometer (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible (UV-vis) diffuse reflectance spectroscopy (DRS). The activity of the CdS-TiO2 composite was tested in a batch slurry bed reactor. The results showed that CO2 absorbed in cyclohexanol was reduced to cyclohexyl formate (CF) on conduction band and the absorbent cyclohexanol was oxidized to cyclohexanone (CH) on valance band of the photocatalyst. It was revealed that the highest formation rates of 20.2 μmol/(gcat h) and 20.0 μmol/(g cat h) for CF and CH could be obtained when TiO2/CdS with the molar ratio of 8 was used. Overall, this work provides a novel pathway for photocatalytically reducing CO2 and preventing the catalyst from photocorrosion. © 2014 Elsevier B.V.


Yu L.-L.,Tianjin University | Tao S.-P.,Tianjin University | Dong X.-Y.,Tianjin University | Sun Y.,Tianjin University
Journal of Chromatography A | Year: 2013

To explore the details of protein uptake to polymer-grafted ion exchangers, Sepharose FF was modified with poly(ethylenimine) (PEI) to prepare anion exchanger of 10 different ionic capacities (ICs, 100-1220mmol/L). Adsorption equilibria and kinetics of bovine serum albumin (BSA) were then studied. It is found that ionic capacity, i.e., the coupling density of PEI, had significant effect on both adsorption capacity (qm) and effective protein diffusivity (De). With increasing ionic capacity, the qm value increased rapidly at IC<260mmol/L and then increased slowly till reaching a plateau at IC=600mmol/L. In the IC range of 100-600mmol/L, however, the De values kept at a low level (De/D0<0.07); it first decreased from 0.05±0.01 at IC=100mmol/L to 0.01±0.01 at IC=260mmol/L and then increased to 0.06±0.01 at IC=600mmol/L. Thereafter, sharp increases of the qm and De values [36% (from 201 to 273mg/mL) and 670% (from 0.06±0.01 to 0.49±0.04), respectively] were observed in the narrow range of IC from 600 to 740mmol/L. Finally, at IC>740mmol/L, the qm value decreased significantly while the De value increased moderately with increasing the IC. The results indicate that PEI chains played an important role in protein adsorption and transport. In brief, there was a critical IC (cIC) or PEI chain density, above which protein adsorption and transport behaviors changed drastically. The cIC was identified to be about 600mmol/L. Estimation of PEI grafting-layer thickness suggests that PEI chains formed an extended three-dimensional grafting-layer at IC>cIC, which provided high flexibility as well as accessibility of the chains for protein binding. Therefore, at IC>cIC, the adjacent PEI chains became close and flexible enough, leading to facilitated transport of adsorbed protein molecules by the interactions of neighboring chains mediated by the bound molecules. It is regarded as "chain delivery" effect. At the same time, improved accessibility of binding sites led the significant increase of binding capacity. The decrease of qm value at IC>740mmol/L is considered due to the decrease of effective porosity. The research has thus provided new insight into protein adsorption and transport in polymer-grafted ion-exchange media. © 2013 Elsevier B.V.


Yang J.,Tianjin University | Ling T.,Tianjin University | Wu W.-T.,Tianjin University | Liu H.,Tianjin University | And 4 more authors.
Nature Communications | Year: 2013

Monodisperse colloidal quantum dots with size dispersions <10% are of great importance in realizing functionality manipulation, as well as building advanced devices, and have been normally synthesized via 'bottom-up' colloidal chemistry. Here we report a facile and environmentally friendly 'top-down' strategy towards highly crystalline monodisperse colloidal PbS quantum dots with controllable sizes and narrow dispersions 5.5%<σ<9.1%, based on laser irradiation of a suspension of polydisperse PbS nanocrystals with larger sizes. The colloidal quantum dots demonstrate size-tunable near-infrared photoluminescence, and self-assemble into well-ordered two-dimensional or three-dimensional superlattices due to the small degree of polydispersity and surface capping of 1-dodecanethiol, not only serving as a surfactant but also a sulphur source. The acquisition of monodisperse colloidal PbS quantum dots is ascribed to both the quantum-confinement effect of quantum dots and the size-selective-vaporization effect of the millisecond pulse laser with monochromaticity and low intensity. © 2013 Macmillan Publishers Limited. All rights reserved.


Liang J.,University of Adelaide | Zhou R.F.,University of Adelaide | Chen X.M.,Tianjin University | Tang Y.H.,Flinders University | Qiao S.Z.,University of Adelaide
Advanced Materials | Year: 2014

An Fe-N-decorated hybrid material of carbon nanotubes (CNTs) grown in situ from porous carbon microblocks is designed and constructed. This material successfully combines the desirable merits for oxygen reduction reaction (ORR), such as highly active Fe-N species, good conductivity, large pore size, and sufficient surface area. These structural advantages give this low-priced material an outstanding catalytic performance for ORR closely comparable with Pt/C of the same quantity. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Kong X.,Liaocheng University | Chen L.,Tianjin University
Applied Catalysis A: General | Year: 2014

With benzaldehyde as a model compound, the hydrogenation of aromatic aldehydes to corresponding benzyl alcohols was investigated in a fixed-bed reactor. Co/γ-Al2O3 doped with a amount of SiO 2 displayed excellent catalytic performance for this reaction, Co/γ-Al2O3 is modified by SiO2 in two ways, the strong interaction between metal oxide and support is obviously reduced, and also a large number of acid sites are diminished on the catalyst. The first aspect apparently facilitated the reduction of metal oxide, and improved the hydrogenation activity of the catalyst; while the second aspect greatly inhibited the hydrogenolysis of the CO bond, and thus increased the selectivity toward benzyl alcohol. © 2014 Elsevier B.V.


Zhong C.,Tianjin University of Technology | Deng Y.,Tianjin University | Hu W.,Tianjin University of Technology | Hu W.,Tianjin University | And 3 more authors.
Chemical Society Reviews | Year: 2015

Electrolytes have been identified as some of the most influential components in the performance of electrochemical supercapacitors (ESs), which include: electrical double-layer capacitors, pseudocapacitors and hybrid supercapacitors. This paper reviews recent progress in the research and development of ES electrolytes. The electrolytes are classified into several categories, including: aqueous, organic, ionic liquids, solid-state or quasi-solid-state, as well as redox-active electrolytes. Effects of electrolyte properties on ES performance are discussed in detail. The principles and methods of designing and optimizing electrolytes for ES performance and application are highlighted through a comprehensive analysis of the literature. Interaction among the electrolytes, electro-active materials and inactive components (current collectors, binders, and separators) is discussed. The challenges in producing high-performing electrolytes are analyzed. Several possible research directions to overcome these challenges are proposed for future efforts, with the main aim of improving ESs' energy density without sacrificing existing advantages (e.g., a high power density and a long cycle-life) (507 references). © The Royal Society of Chemistry.


Li Y.,Tianjin University | Wang A.,Peking University
Journal of Lightwave Technology | Year: 2010

The design of bandgap-engineered all-solid photonic bandgap fibers based on a broken-ring structure is investigated in detail. Both density of states maps and Bloch mode field distributions are used to show how the bandgap structure can be engineered and a higher-order gap be greatly expanded by replacing the high-index germanium-doped rod in a repeating cell with a ring of several individual high-index rods. The strategy is that both the azimuthal and radial orders of the cladding LP modes can be controlled by the broken-ring parameters. In particular, the rod number determines the highest azimuthal order of the LP mode that is less affected by the broken-ring, and the bandgap width is largely affected by the rod size. The result of bandgap engineering is that the higher-order bandgap can be utilized to design all-solid photonic bandgap fibers with very broad transmission windows of 488 nm and 944 nm centered at 800 nm and 1550 nm, respectively, and with typical normal-zero-anomalous dispersion profiles. © 2006 IEEE.


Zhao H.,Tianjin University | Kunnath S.K.,University of California at Davis | Yuan Y.,Tongji University
Engineering Structures | Year: 2010

A computationally efficient macromodeling scheme to simulate the nonlinear behavior of composite structural connections consisting of steel-concrete composite beams and concrete-filled steel tubular (CFST) columns is investigated. The model proposed for composite beams, validated using four full scale composite beam tests, incorporates partial interaction between the concrete slab and the steel beam. The model proposed for CFST columns adopts fiber-based stress-strain relations that enable the consideration of strength and ductility for confined concrete and local buckling of the steel tube. The flexibility of the composite-beam-to-CFST-column connection is modeled as a panel zone. The validity of the simplified approach is evaluated by comparison of both overall response and local actions with those obtained from test results. The proposed methodology is shown to be viable for nonlinear analysis of composite structures wherein the modeling strategies are amenable to available features in modern nonlinear structural analysis software. © 2010 Elsevier Ltd.


Qin J.,Tianjin University | He C.,Tianjin University | Zhao N.,Tianjin University | Wang Z.,Tianjin University | And 3 more authors.
ACS Nano | Year: 2014

A facile and scalable in situ chemical vapor deposition (CVD) technique using metal precursors as a catalyst and a three-dimensional (3D) self-assembly of NaCl particles as a template is developed for one-step fabrication of 3D porous graphene networks anchored with Sn nanoparticles (5-30 nm) encapsulated with graphene shells of about 1 nm (Sn@G-PGNWs) as a superior lithium ion battery anode. In the constructed architecture, the CVD-synthesized graphene shells with excellent elasticity can effectively not only avoid the direct exposure of encapsulated Sn to the electrolyte and preserve the structural and interfacial stabilization of Sn nanoparticles but also suppress the aggregation of Sn nanoparticles and buffer the volume expansion, while the interconnected 3D porous graphene networks with high electrical conductivity, large surface area, and high mechanical flexibility tightly pin the core-shell structure of Sn@G and thus lead to remarkably enhanced electrical conductivity and structural integrity of the overall electrode. As a consequence, this 3D hybrid anode exhibits very high rate performance (1022 mAh/g at 0.2 C, 865 mAh/g at 0.5 C, 780 mAh/g at 1 C, 652 mAh/g at 2 C, 459 mAh/g at 5 C, and 270 mAh/g at 10 C, 1 C = 1 A/g) and extremely long cycling stability even at high rates (a high capacity of 682 mAh/g is achieved at 2 A/g and is maintained approximately 96.3% after 1000 cycles). As far as we know, this is the best rate capacity and longest cycle life ever reported for a Sn-based lithium ion battery anode. © 2014 American Chemical Society.


Chen L.,Shanghai Maritime University | Lu J.,Yantai University | Zhang N.,Tianjin University | Huang T.,Mount Sinai School of Medicine | Cai Y.-D.,Shanghai University
Molecular BioSystems | Year: 2014

In the Anatomical Therapeutic Chemical (ATC) classification system, therapeutic drugs are divided into 14 main classes according to the organ or system on which they act and their chemical, pharmacological and therapeutic properties. This system, recommended by the World Health Organization (WHO), provides a global standard for classifying medical substances and serves as a tool for international drug utilization research to improve quality of drug use. In view of this, it is necessary to develop effective computational prediction methods to identify the ATC-class of a given drug, which thereby could facilitate further analysis of this system. In this study, we initiated an attempt to develop a prediction method and to gain insights from it by utilizing ontology information of drug compounds. Since only about one-fourth of drugs in the ATC classification system have ontology information, a hybrid prediction method combining the ontology information, chemical interaction information and chemical structure information of drug compounds was proposed for the prediction of drug ATC-classes. As a result, by using the Jackknife test, the 1st prediction accuracies for identifying the 14 main ATC-classes in the training dataset, the internal validation dataset and the external validation dataset were 75.90%, 75.70% and 66.36%, respectively. Analysis of some samples with false-positive predictions in the internal and external validation datasets indicated that some of them may even have a relationship with the false-positive predicted ATC-class, suggesting novel uses of these drugs. It was conceivable that the proposed method could be used as an efficient tool to identify ATC-classes of novel drugs or to discover novel uses of known drugs. © 2014 The Royal Society of Chemistry.


Fan X.,Tianjin University | Zhang G.,Tianjin University | Zhang F.,Tianjin University
Chemical Society Reviews | Year: 2015

Scientific interest in graphene as a catalyst and as a catalyst support in heterogeneous catalytic reactions has grown dramatically over the past several years. The present critical review summarizes the multiple roles of graphene in heterogeneous catalysis and highlights the influence of defects, heteroatom-containing functionalities, and graphene's two-dimensional structure on catalytic performance. We first discuss the role and advantages of graphene as a catalyst support, with emphasis on its interactions with the catalytic phases and the influence of mass transfer processes. We then clarify the origin of the intrinsic catalytic activity of graphene in heterogeneous catalytic reactions. Finally we suggest challenges and potential practical applications for graphene in industrial processes. This journal is © The Royal Society of Chemistry.


Liu L.,Tianjin University | Zhang-Negrerie D.,Tianjin University | Zhao K.,Tianjin University
Organic Letters | Year: 2014

PhICl2 in wet DMF was found to form an efficient system for realizing difunctionalization of various alkenes and olefinic derivatives possessing a wide range of functional groups. This novel methodology provides convenient access to either regioselective chloroformyloxylated products or a-chlorinated olefinic products, depending on the type of structure of the original unsaturated starting material. The mechanism of the reaction is proposed and discussed. © 2013 American Chemical Society.


Grant
Agency: Cordis | Branch: FP7 | Program: CSA-SA | Phase: ENV.2009.5.1.0.1 | Award Amount: 1.07M | Year: 2010

SPRING is a supporting action under EU FP7 Environment theme, with the main objective of creating and providing a solid basis for future EU-China collaboration in environmental research. SPRING will identify common needs and opportunities, analyse potential topics of research cooperation and initiatives, map competences and potentials of Chinese research organisations and major infrastructure, investigate strategic development plans and initiate roadmaps for future collaborations. SPRING will analyse the hurdles, barriers, and cornerstones that need to be addressed to enable better research engagement by EU researchers to China, and vice versa. It will improve the visibility of research initiatives and strengths of Chinese regions to a wider audience in Europe. The project will create and maintain a web portal that will serve as a bilateral contact point, showcasing past projects and present project, and also update strategic plans for EU-China cooperation.


Grant
Agency: Cordis | Branch: FP7 | Program: CSA | Phase: ICT-2011.3.4 | Award Amount: 447.15K | Year: 2012

In 2010, the TOP500 project, which ranks and details the 500 (most powerful known computer systems in the world since the year of 1993, announced that the worlds most powerful computer system is Tianhe 1A in China (http://en.wikipedia.org/wiki/TOP500). This project aims at establishing a strategic collaboration with the host and developer of this computer system in China to explore a range of research issues, which can be highlighted as: (i) further test and evaluation with complex computing tasks, especially those in the areas of modelling, simulation, visualization and imaging etc, and hence identify a range of research challenges for further development in the area of computing systems as well as their applications; (ii) discussion with series of targeted workshops and seminars to explore and generate ideas in further developing super computer architectures, algorithms, configurations, and any other important issues across the boundaries of software engineering, distributed computing, cloud computing, and grid computing etc. (iii) exchange visits and personnel in developing the discussed ideas into project proposals and research programmes. (iv) joint publications and other dissemination activities; (v) establishing long-term collaborations in addressing ambitious and challenging research issues. The SCC-Computing has drawn a strong consortium with complementary expertise and multi-disciplinary research know-how to ensure successful delivery of this project, leading to fruitful discussion and initiation of new ideas for further research on super-computing systems.


Peng C.,Tianjin University | Gao F.,Tianjin University
Scientific Reports | Year: 2014

Essential genes, those critical for the survival of an organism under certain conditions, play a significant role in pharmaceutics and synthetic biology. Knowledge of protein localization is invaluable for understanding their function as well as the interaction of different proteins. However, systematical examination of essential genes from the aspect of the localizations of proteins they encode has not been explored before. Here, a comprehensive protein localization analysis of essential genes in 27 prokaryotes including 24 bacteria, 2 mycoplasmas and 1 archaeon has been performed. Both statistical analysis of localization information in these genomes and GO (Gene Ontology) terms enriched in the essential genes show that proteins encoded by essential genes are enriched in internal location sites, while exist in cell envelope with a lower proportion compared with non-essential ones. Meanwhile, there are few essential proteins in the external subcellular location sites such as flagellum and fimbrium, and proteins encoded by non-essential genes tend to have diverse localizations. These results would provide further insights into the understanding of fundamental functions needed to support a cellular life and improve gene essentiality prediction by taking the protein localization and enriched GO terms into consideration.


Wang D.,University of Victoria | Parkinson S.,University of Victoria | Miao W.,Tianjin University | Jia H.,Tianjin University | And 2 more authors.
Applied Energy | Year: 2012

A resilient strategy for optimal demand response control based on the management of highly-distributed electric loads is presented to meet transmission-level control aimed at maintaining voltage stability. The proposed load control scheme balances device- and grid-level objectives simultaneously, and is demonstrated for a system comprising a distributed responsive population of 14,000 residential-sized buildings integrated in a transmission system network consisting of six buses. Air-source heat pumps are implemented as the primary heating source in the responsive building population, and are introduced as a dispatchable grid-side energy resource, where aggregated output can be objectively ramped up or down through the use of an optimal centralized control strategy. A two step multi-objective optimization procedure is implemented to simultaneously satisfy balancing of the power system and customer objectives across a multi-scalar system. At the power system-level, the optimal preventive control scheme is obtained based on steady-state voltage stability constraints. At the customer-level, an optimal demand response strategy is proposed, wherein the aggregate power demand from a population of heat pumps is controlled to follow load-shedding requirements. The customer comfort is continuously maintained by constrained regulation of the thermal set-point governing operation of the heat pump device.The proposed demand-side strategy achieves similar goals to conventional approaches to regulation and spinning reserve ancillary services, but with the significant benefit of higher efficiencies. Under the proposed scheme, ancillary services provided by the electric loads effectively become virtual generators that enhance the voltage stability in power systems operating under increased uncertainty, and replace severe or multiple contingency reserves typically supplied by conventional generators. The proposed demand response control scheme can be extended to other potentially responsive end-use appliances, and opens avenues for increased exploitation of intermittent renewable energy resources while reducing operating costs and emissions. © 2011 Elsevier Ltd.


News Article | August 31, 2016
Site: www.nature.com

In a world of mobile devices, incremental improvements in the size, sustainability and efficiency of battery technology can have considerable economic ramifications. The global battery market is forecast to be worth US$120 billion a year by 2019, and the competition to lead the science is fierce. Chemist Jun Chen knows this well. His group at Nankai University in Tianjin attracted attention after it successfully created a rechargeable sodium–carbon dioxide battery in late 2015 ( et al. Angew. Chem. 55, 6482–6486; 2016). In principle, Na–CO batteries are more energy efficient than lithium-based rechargeable power packs, as well as cheaper because of the abundance of sodium and CO . But the performance of previous Na–CO batteries had been disappointing: the electrochemical reaction caused solid deposits to form on the cathode, preventing recharge. Chen's team overcame this by creating a cathode from a 3D carbon nanotube structure. The result was a battery with an energy density more than five times that of the lithium (Li)-ion batteries, widely used in mobile devices and nickel–metal hydride batteries, and with the ability to be recharged 200 times without any reduction in storage capacity. Chen is the chief investigator for energy conversion and storage research at the Collaborative Innovation Center of Chemical Science and Engineering (CICCSE), a partnership between Nankai University and Tianjin University. The government-funded centre is designed to link science with industry for the benefit of the economy, and is one of 38 collaborative innovation centres (CICs) established across the country since 2012. CICCSE is now home to 385 researchers drawn from academia and industry, most of whom are affiliated with the 2 universities. In response to a weakening low-cost manufacturing market, in 2011 then-Chinese president Hu Jintao's pushed to embed science in the Chinese economy. He called for greater collaboration between the country's top research groups and between science and industry. The CICs grew out of what became known as the 2011 Plan, and focus on fields ranging from aerospace and quantum technology to medicine and advanced materials. The links formed can be domestic or international and are frequently both. By exploiting the multidisciplinary nature of universities, the centres are intended to overcome some of the challenges to innovation that remain in China, including scattered resources and inefficient research planning. Jiannian Yao, a director of CICCSE and vice-president of China's science funding body for competitive grants, the National Natural Science Foundation of China, says that the centres foster cooperation between researchers and strengthen national innovation capacity and competitiveness. Yao compares the centres to other government-led collaborations such as the Australian Research Council's Centres of Excellence, Millennium Science Initiative in South America and Japan's World Premier International Research Center Initiative. CICs with a focus on natural science and engineering also act as hubs for the promotion of industry partnerships. These centres receive generous funding from the government — the CICCSE receives around 50 million yuan (US$7.5 million) each year — as well as flexibility in the selection of research projects and the recruitment of scientists (unusual freedoms within government programmes in China, according to Chen). Cong Cao, a science-policy analyst at the University of Nottingham in Ningbo, says that the “new normal” of the Chinese economy, referring to slowed growth, means that the government has had to look to science and technology, with programmes such as the CICs, as the way to restore dynamism. In 2007, the Progress of Science and Technology Law was passed. The law, which is often referred to as the Chinese Bayh–Dole Act — a celebrated 1980s US patent-rights law credited with accelerating US industrial innovation — enables the intellectual property generated by government-funded research to be commercialized by the research group that does the investigation. The law has made it much easier for research institutions such as Chen's to benefit from the work their researchers are doing. In the seven years after the enactment of the law, the number of domestic patents awarded to Chinese researchers increased more than five-fold. The legislation has also made research partnerships between universities and industry more attractive for both sides. Over the past four years in particular, Cao says, the Chinese government has introduced a range of policies “to emphasize innovation and reform of China's science and technology system to make it better and quicker to respond to demand from the economy”. This includes the launch of the thirteenth Five Year Plan in 2015, which put innovation in science and technology at the centre of China's development. And following Premier Li Keqiang's annual address to the National People's Congress in March, there have been further efforts to encourage co-operation between science and industry. Speaking to the 2,943 delegates in the Great Hall of the People in Beijing, Li echoed what President Xi Jinping had outlined in the Five Year Plan, using the word 'innovation' more than 50 times. The speech also included promises of new national science and technology programmes and science centres. By 2020, said Li, science and technology will account for 60% of the nation's economic growth. “We will implement the strategy of innovation-driven development, see that science and technology become more deeply embedded in the economy, and improve the overall quality and competitiveness of the real economy,” Li said. The government promised tax deductions for companies undertaking research and development; and, since the speech, it has begun efforts to substantially reduce the notorious red tape associated with government funding for research and to increase the income that Chinese scientists can receive for working on government-funded projects. Back at the CICCSE, Chen and his colleagues have secured a Chinese patent on their battery technology, one of 339 patents awarded to the centre's projects up until the end of 2015. They are now working on adjustments to scale the technology up and overcome the need for a pure CO environment. Chen expects to have an improved version in production in about two years. Chen's group is also collaborating with Tianjin-based Li-ion battery developer Lishen and with electronics manufacturer Samsung, on improvements to Li-ion batteries for devices such as electric cars. The CICCSE, like other centres, works with industry in three ways: companies are founding members of the centres and are represented on the board, Chinese petroleum giant Sinopec and the Tianjin Bohai Chemical Industry Group both have representatives on the CICCSE board, for example; the centre's researchers do joint research with industry on major national issues; and the companies fund research projects. Sinopec is currently funding research to improve hydrogen production for use in fuel processing and the chemical industry. The project is using nanofabrication techniques to increase the stability of nickel-based catalysts, which are used in the methane-steam reforming process to create hydrogen. The greater stability increases the efficiency so that alternative fuels such as ethanol can be used. The hydrogen can then be used to refine petroleum, particularly heavier crude oils. When complete, Sinopec will implement the new technology in a number of its fuel-processing plants. Yao says that another project has already seen crystallization technology developed by CICCSE researchers adopted by the pharmaceutical industry and increase revenue by nearly 4 billion yuan. Despite such success stories, there is concern that science is not yet playing a part in the Chinese economy in the way that Hu Jintao had hoped. There have been lots of the incremental improvements, but not yet an innovation that changes the market. Initiatives aimed at encouraging more innovation are beginning to show signs of success. The government says that there are now at least 81 million people in China who work in science and technology. But researchers and analysts say there is no guarantee that even successful programmes will continue without substantial change. Cong says that the nature of Chinese science policy means that change is never far away. Based on Li's statements at the 2016 National People's Congress, the 38 CICs are unlikely to be immune. The Ministry of Education may already be trying to put the premier's words into practice, says Cong. This means that “there could soon be different programmes put into place”, he says. For now the CICCSE is still receiving strong support from the ministry, which is responsible for the CIC programme. But Yao agrees that there is a risk that new policies, such as those put forward at this year's National People's Congress, and President Xi Jinping's efforts to create his own policy legacy, could mean the programme is superseded or significantly altered in coming years. This may not signal an end to the support for existing centres, but it could mean the central government introduces an updated version, perhaps rebranding the CICs as national laboratories. “The assessment of CICs should focus on how well the expected objectives are achieved; in other words, how well the centres address the major issues in science, technology and economic development,” says Yao. Yao is confident about CICCSE's future. By the end of 2015, he points out, the centres' researchers boasted not only hundreds of patents but also 295 contributions to high-quality journals. The move towards better collaboration between academics and industry in the hope of creating stronger links between science and economic and social needs has been occurring around the world over the past decade. After less than five years, it is still early days for China's experiment. But signs indicate that the country is on a promising path.


Home > Press > Saving sunshine for a rainy day: New catalyst offers efficient storage of green energy: Team led by U of T Engineering designs world's most efficient catalyst for storing energy as hydrogen by splitting water molecules Abstract: We can't control when the wind blows and when the sun shines, so finding efficient ways to store energy from alternative sources remains an urgent research problem. Now, a group of researchers led by Professor Ted Sargent at the University of Toronto's Faculty of Applied Science & Engineering may have a solution inspired by nature. The team has designed the most efficient catalyst for storing energy in chemical form, by splitting water into hydrogen and oxygen, just like plants do during photosynthesis. Oxygen is released harmlessly into the atmosphere, and hydrogen, as H2, can be converted back into energy using hydrogen fuel cells. "Today on a solar farm or a wind farm, storage is typically provided with batteries. But batteries are expensive, and can typically only store a fixed amount of energy," says Sargent. "That's why discovering a more efficient and highly scalable means of storing energy generated by renewables is one of the grand challenges in this field." You may have seen the popular high-school science demonstration where the teacher splits water into its component elements, hydrogen and oxygen, by running electricity through it. Today this requires so much electrical input that it's impractical to store energy this way -- too great proportion of the energy generated is lost in the process of storing it. This new catalyst facilitates the oxygen-evolution portion of the chemical reaction, making the conversion from H2O into O2 and H2 more energy-efficient than ever before. The intrinsic efficiency of the new catalyst material is over three times more efficient than the best state-of-the-art catalyst. The new catalyst is made of abundant and low-cost metals tungsten, iron and cobalt, which are much less expensive than state-of-the-art catalysts based on precious metals. It showed no signs of degradation over more than 500 hours of continuous activity, unlike other efficient but short-lived catalysts. Their work was published today in the leading journal Science. "With the aid of theoretical predictions, we became convinced that including tungsten could lead to a better oxygen-evolving catalyst. Unfortunately, prior work did not show how to mix tungsten homogeneously with the active metals such as iron and cobalt," says Dr. Bo Zhang, one of the study's lead authors. "We invented a new way to distribute the catalyst homogenously in a gel, and as a result built a device that works incredibly efficiently and robustly." This research united engineers, chemists, materials scientists, mathematicians, physicists, and computer scientists across three countries. A chief partner in this joint theoretical-experimental study was a leading team of theorists at Stanford University and SLAC National Accelerator Laboratory under the leadership of Dr. Aleksandra Vojvodic. The international collaboration included researchers at East China University of Science & Technology, Tianjin University, Brookhaven National Laboratory, Canadian Light Source and the Beijing Synchrotron Radiation Facility. "The team developed a new materials synthesis strategy to mix multiple metals homogeneously -- thereby overcoming the propensity of multi-metal mixtures to separate into distinct phases," said Jeffrey C. Grossman, the Morton and Claire Goulder and Family Professor in Environmental Systems at Massachusetts Institute of Technology. "This work impressively highlights the power of tightly coupled computational materials science with advanced experimental techniques, and sets a high bar for such a combined approach. It opens new avenues to speed progress in efficient materials for energy conversion and storage." "This work demonstrates the utility of using theory to guide the development of improved water-oxidation catalysts for further advances in the field of solar fuels," said Gary Brudvig, a professor in the Department of Chemistry at Yale University and director of the Yale Energy Sciences Institute. "The intensive research by the Sargent group in the University of Toronto led to the discovery of oxy-hydroxide materials that exhibit electrochemically induced oxygen evolution at the lowest overpotential and show no degradation," said University Professor Gabor A. Somorjai of the University of California, Berkeley, a leader in this field. "The authors should be complimented on the combined experimental and theoretical studies that led to this very important finding." ### Professor Sargent is the Canada Research Chair in Nanotechnology. The group's work was supported in large part by the Ontario Research Fund--Research Excellence Program, NSERC, the CIFAR Bio-Inspired Solar Energy Program and the U.S. Department of Energy. For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.


News Article | March 29, 2016
Site: www.cemag.us

We can’t control when the wind blows and when the sun shines, so finding efficient ways to store energy from alternative sources remains an urgent research problem. Now, a group of researchers led by Professor Ted Sargent at the University of Toronto’s Faculty of Applied Science & Engineering may have a solution inspired by nature. The team has designed the most efficient catalyst for storing energy in chemical form, by splitting water into hydrogen and oxygen, just like plants do during photosynthesis. Oxygen is released harmlessly into the atmosphere, and hydrogen, as H , can be converted back into energy using hydrogen fuel cells. “Today on a solar farm or a wind farm, storage is typically provided with batteries. But batteries are expensive, and can typically only store a fixed amount of energy,” says Sargent. “That’s why discovering a more efficient and highly scalable means of storing energy generated by renewables is one of the grand challenges in this field.” You may have seen the popular high-school science demonstration where the teacher splits water into its component elements, hydrogen and oxygen, by running electricity through it. Today this requires so much electrical input that it’s impractical to store energy this way — too great proportion of the energy generated is lost in the process of storing it. This new catalyst facilitates the oxygen-evolution portion of the chemical reaction, making the conversion from H O into O and H more energy-efficient than ever before. The intrinsic efficiency of the new catalyst material is over three times more efficient than the best state-of-the-art catalyst. The new catalyst is made of abundant and low-cost metals tungsten, iron and cobalt, which are much less expensive than state-of-the-art catalysts based on precious metals. It showed no signs of degradation over more than 500 hours of continuous activity, unlike other efficient but short-lived catalysts. Their work was published this week in the leading journal Science. “With the aid of theoretical predictions, we became convinced that including tungsten could lead to a better oxygen-evolving catalyst. Unfortunately, prior work did not show how to mix tungsten homogeneously with the active metals such as iron and cobalt,” says Dr. Bo Zhang, one of the study’s lead authors. “We invented a new way to distribute the catalyst homogenously in a gel, and as a result built a device that works incredibly efficiently and robustly.” This research united engineers, chemists, materials scientists, mathematicians, physicists, and computer scientists across three countries. A chief partner in this joint theoretical-experimental studies was a leading team of theorists at Stanford University and SLAC National Accelerator Laboratory under the leadership of Dr. Aleksandra Vojvodic. The international collaboration included researchers at East China University of Science & Technology, Tianjin University, Brookhaven National Laboratory, Canadian Light Source, and the Beijing Synchrotron Radiation Facility. “The team developed a new materials synthesis strategy to mix multiple metals homogeneously — thereby overcoming the propensity of multi-metal mixtures to separate into distinct phases,” says Jeffrey C. Grossman, the Morton and Claire Goulder and Family Professor in Environmental Systems at Massachusetts Institute of Technology. “This work impressively highlights the power of tightly coupled computational materials science with advanced experimental techniques, and sets a high bar for such a combined approach. It opens new avenues to speed progress in efficient materials for energy conversion and storage.” “This work demonstrates the utility of using theory to guide the development of improved water-oxidation catalysts for further advances in the field of solar fuels,” says Gary Brudvig, a professor in the Department of Chemistry at Yale University and director of the Yale Energy Sciences Institute. “The intensive research by the Sargent group in the University of Toronto led to the discovery of oxy-hydroxide materials that exhibit electrochemically induced oxygen evolution at the lowest overpotential and show no degradation,” says University Professor Gabor A. Somorjai of the University of California, Berkeley, a leader in this field. “The authors should be complimented on the combined experimental and theoretical studies that led to this very important finding.” Sargent is the Canada Research Chair in Nanotechnology. The group’s work was supported in large part by the Ontario Research Fund-Research Excellence Program, NSERC, the CIFAR Bio-Inspired Solar Energy Program, and the U.S. Department of Energy. Source: University of Toronto


Wei G.,King's College London | Dai J.S.,King's College London | Dai J.S.,Tianjin University
Journal of Mechanical Design, Transactions of the ASME | Year: 2014

This paper presents two integrated planar-spherical overconstrained mechanisms that are inspired and evolved from origami cartons with a crash-lock base. Investigating the crash-lock base of the origami cartons, the first overconstrained mechanism is evolved by integrating a planar four-bar linkage with two spherical linkages in the diagonal corners. The mechanism has mobility one and the overconstraint was exerted by the two spherical linkages. This mechanism is then evolved into another integrated planar-spherical overconstrained mechanism with two double-spherical linkages at the diagonal corners. The evolved mechanism has mobility one. It is interesting to find that the double-spherical linkage at the corner of this new mechanism is an overconstrained 6R linkage. The geometry evolution is presented and the constraint matrices of the mechanisms are formulated using screw-loop equations verifying mobility of the mechanisms. The paper further reveals the assembly conditions and geometric constraint of the two overconstrained mechanisms. Further, with mechanism decomposition, geometry and kinematics of the mechanisms are investigated with closed-form equations, leading to comparison of these two mechanisms with numerical simulation. The paper further proposes that the evolved overconstrained mechanism can in reverse lead to new origami folds and crease patterns. The paper hence not only lays the groundwork for kinematic investigation of origami-inspired mechanisms but also sheds light on the investigation of integrated overconstrained mechanisms. Copyright © 2014 by ASME.


Deng S.,Shanghai JiaoTong University | Deng S.,Tianjin University | Wang R.Z.,Shanghai JiaoTong University | Dai Y.J.,Shanghai JiaoTong University
Energy | Year: 2014

NZEB (Net zero energy building) is regarded as an integrated solution to address problems of energy-saving, environmental protection, and CO2 emission reduction in the building section. NZEB could be even possible with electricity production if enough renewable energy could be used. Moreover, various building-service systems with renewable energy sources have been widely considered for potential applications in NZEB. All of these new features extend the technical boundary of the conventional energy-efficient buildings, attach a more profound implication to the sustainable development of building technology, and therefore pose a challenge to evaluation works on NZEB performance.This paper presents a guided tour on NZEB evaluation through literature-research. An overview about definitions and energy-efficient measures of NZEB is presented so that the research object and technology boundary can be clarified for NZEB evaluation. Then, a summary of widely-used research method, tool and performance indicator in evaluation is provided for the methodology part. This part also includes a discussion on the application of LCA (life cycle assessment) in NZEB evaluation and LCA's role in promoting a well-defined NZEB. Finally, potential progress in NZEB evaluation with possible development trends is highlighted in terms of energy storage, load match and smart grid. © 2014 Elsevier Ltd.


Yao M.,Tianjin University | Liu H.,Tianjin University | Feng X.,University of Illinois at Urbana - Champaign
Energy Policy | Year: 2011

Reducing CO2 emissions from vehicles in China is crucial and will significantly alleviate the environmental burden of the Earth. Some promising technologies that make possible low-carbon vehicles are reviewed in this work, including electric vehicles, fuel cell vehicles, hybrid vehicles, biofuels vehicles, other alternative fuel vehicles, and conventional internal combustion engine vehicles with improvement. In the short term, expanding the use of mature technologies in conventional gasoline or diesel vehicles is the most realistic, effective, and timely solution for China to meeting the urgent challenges of energy saving and greenhouse gas reduction; while in the long run biofuel is a promising candidate due to their renewability and carbon neutrality. The blueprint of low-carbon vehicles for China depends on three aspects: breakthroughs in technology, awareness of public, and government guidance. © 2011 Elsevier Ltd.


Jin C.,Tianjin University | Yao M.,Tianjin University | Liu H.,Tianjin University | Lee C.-F.F.,University of Illinois at Urbana - Champaign | And 2 more authors.
Renewable and Sustainable Energy Reviews | Year: 2011

Butanol is a very competitive renewable biofuel for use in internal combustion engines given its many advantages. In this review, the properties of butanol are compared with the conventional gasoline, diesel fuel, and some widely used biofuels, i.e. methanol, ethanol, biodiesel. The comparison of fuel properties indicates that n-butanol has the potential to overcome the drawbacks brought by low-carbon alcohols or biodiesel. Then, the development of butanol production is reviewed and various methods for increasing fermentative butanol production are introduced in detailed, i.e. metabolic engineering of the Clostridia, advanced fermentation technique. The most costive part of the fermentation is the substrate, so methods involved in renewed substrates are also mentioned. Next, the applications of butanol as a biofuel are summarized from three aspects: (1) fundamental combustion experiments in some well-defined burning reactors; (2) a substitute for gasoline in spark ignition engine; (3) a substitute for diesel fuel in compression ignition engine. These studies demonstrate that butanol, as a potential second generation biofuel, is a better alternative for the gasoline or diesel fuel, from the viewpoints of combustion characteristics, engine performance, and exhaust emissions. However, butanol has not been intensively studied when compared to ethanol or biodiesel, for which considerable numbers of reports are available. Finally, some challenges and future research directions are outlined in the last section of this review. © 2011 Elsevier Ltd. All rights reserved.


Li S.,Northeastern University China | Dai J.S.,Tianjin University | Dai J.S.,King's College London
Journal of Mechanisms and Robotics | Year: 2012

This paper presents a new way of structure composition of single-driven metamorphic mechanisms to develop a systematic and modularized structure synthesis methodology of metamorphic mechanisms based on augmented Assur groups (AAGs). Planar metamorphic mechanisms can hence be constructed based on the developed AAGs by applying the structure composition rule of general planar mechanisms formed by Assur groups (AGs). First, the one-mobility AAGs are introduced based on class II and class III AGs; the structure formulation and composition methodology of planar metamorphic mechanisms are then proposed based on the AAGs, and the basic problems including mobility and synthesis of constrained metamorphic working mobility-configuration are investigated. This leads to the investigation of the degenerated equivalent AGs of AAGs in the metamorphic process and the corresponding kinematic characteristics, providing references for kinematic synthesis of metamorphic mechanisms. Further, a typical spatial metamorphic group is introduced based on the concept of AAGs, and the structure formation and composition of spatial metamorphic mechanisms are presented. Examples show that both planar and spatial metamorphic mechanisms can be constructed by utilizing the one-mobility blocks extended from the AGs. © 2012 American Society of Mechanical Engineers.


Dai J.S.,Tianjin University | Dai J.S.,King's College London
Journal of Mechanisms and Robotics | Year: 2012

Rigid body displacement can be presented with Chasles' motion by rotating about an axis and translating along the axis. This motion can be implemented by a finite displacement screw operator in the form of either a 3 × 3 dual-number matrix or a 6 × 6 matrix that is executed with rotation and translation as an adjoint action of the Lie group. This paper investigates characteristics of this finite displacement screw matrix and decomposes the secondary part that is the off diagonal part of the matrix into the part of an equivalent translation due to the effect of off-setting the rotation axis and the part of an axial translation. The paper hence presents for the first time the axial translation matrix and reveals its property, leading to discovery of new results and new formulae. The analysis further reveals two new traces of the matrix and presents the relationship between the finite displacement screw matrix and the instantaneous screw, leading to the understanding of Chasles' motion embedded in a rigid body displacement. An algebraic and geometrical interpretation of the finite displacementscrew matrix is thus given, presenting an intrinsic property of the matrix in relation to the finite displacement screw. The paper ends with a case study to verify the theory and illustrate the principle. © 2012 American Society of Mechanical Engineers.


Tian W.,Tianjin University | Gao W.,Tianjin University | Zhang D.,Tianjin University | Huang T.,Tianjin University | Huang T.,University of Warwick
International Journal of Machine Tools and Manufacture | Year: 2014

This paper presents a general and systematic approach for geometric error modeling of machine tools due to the geometric errors arising from manufacturing and assembly. The approach can be implemented in three steps: (1) development of a linear map between the pose error twist and source errors within machine tool kinematic chains using homogeneous transformation matrix method; (2) formulation of a linear map between the pose error twist and the error intensities of a machine tool; (3) combination of these two models for error separation. The merit of this approach lies in that it enables the source errors affecting the compensatable and uncompensatable pose accuracy of the machine tool to be explicitly separated, thereby providing designers and/or field engineers with an informative guideline for the accuracy improvement by suitable measures, i.e. component tolerancing in design, manufacturing and assembly processes, and error compensation. Two typical multi-axis machine tools are taken as examples to illustrate the generality and effectiveness of this approach. © 2014 Elsevier Ltd. All rights reserved.


Fang D.,Tianjin University | Yao P.,Tianjin University | Li H.,University of Wollongong
Ceramics International | Year: 2014

Mg-Al co-doped ZnO (AMZO) thin films were deposited on quartz glass via sol-gel spin coating method. The structural and optical properties of Mg-Al co-doped ZnO thin films annealed at different temperatures were characterized via X-ray diffraction, Raman spectroscopy, scanning electron microscopy (SEM) with energy dispersive X-ray spectra (EDS), ultraviolet-visible-near-infrared spectroscopy, and photoluminescence spectroscopy. XRD results revealed that the films had a hexagonal wurtzite structure, and the calculated average grain size increased from 23.02 nm to 49.85 nm when the annealing temperature was increased from 500 C to 800 C. The change in lattice parameters was demonstrated by grain size, strain, and residual stress. The SEM images showed that the AMZO thin film surface appeared flat, and the grain size was uniformly distributed at 500 C. When the annealing temperature was increased from 600 C to 800 C, the surface of the films showed larger grain sizes, numerous micropores, and some cracks. The EDS results confirmed the presence of Mg and Al elements in the AMZO thin films. Raman spectroscopy results showed that all films had E2 (high) mode, which indicates that all films had a ZnO wurtzite structure. Moreover, the optical transmittance of the AMZO thin films was over 85% in the visible region. The optical band gap of the AMZO thin films decreased from 3.348 eV to 3.304 eV when the annealing temperature was increased from 500 C to 800 C. The room temperature photoluminescence spectra showed an ultraviolet (UV) emission peak and a strong defect emission peak. The UV peaks of the AMZO thin films were red-shifted from 372 nm to 379 nm. In addition, the defect peaks of the AMZO thin films were blue-shifted from 598 nm to 527 nm when the annealing temperature was increased from 500 C to 800 C. The possible mechanisms of the defect peaks were studied. © 2013 Elsevier Ltd and Techna Group S.r.l.


Li X.,Pacific Northwest National Laboratory | Qi W.,Tianjin University | Mei D.,Pacific Northwest National Laboratory | Sushko M.L.,Pacific Northwest National Laboratory | And 2 more authors.
Advanced Materials | Year: 2012

By using a combination of theoretical and experimental techniques, it is demonstrated that functionalized graphene sheets (FGS) can function as a new class of molecular templates to direct the nucleation, crystalline phase transition, and self-assembly process of surfactant micelles and metal oxides. Novel, three-dimensional FGS-metal oxide nanocomposite materials with an ordered mesoporous structure can be synthesized. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Feng J.-M.,Tianjin University | Feng J.-M.,Institute of Seawater Desalination And Multipurpose Utilization | Dai Y.-J.,Tianjin University
Nanoscale | Year: 2013

Combining carbon nanotubes (CNTs) with graphene has been proved to be a feasible method for improving the performance of graphene for some practical applications. This paper reports a water-assisted route to grow graphene on CNTs from ferrocene and thiophene dissolved in ethanol by the chemical vapor deposition method in an argon flow. A double injection technique was used to separately inject ethanol solution and water for the preparation of graphene/CNTs. First, CNTs were prepared from ethanol solution and water. The injection of ethanol solution was suspended and water alone was injected into the reactor to etch the CNTs. Thereafter, ethanol solution was injected along with water, which is the key factor in obtaining graphene/CNTs. Transmission electron microscopy, scanning electron microscopy, X-ray diffraction, and Raman scattering analyses confirmed that the products were the hybrid materials of graphene/CNTs. X-ray photo-electron spectroscopy analysis showed the presence of oxygen rich functional groups on the surface of the graphene/CNTs. Given the activity of the graphene/CNT surface, CdS quantum dots adhered onto it uniformly through simple mechanical mixing. This journal is © 2013 The Royal Society of Chemistry.


Harik R.F.,Lebanese American University | Gong H.,Tianjin University | Bernard A.,CNRS Research Institute of Communication and Cybernetics of Nantes
CAD Computer Aided Design | Year: 2013

Flank milling is of importance to machining aircraft structural parts, turbines, blades and several other mechanical parts. It decreases manufacturing time, enhances quality and reduces cost. Since flank milling developable ruled surfaces do not contain geometrical errors, research on flank milling focuses on the generation of optimal tool trajectory for non-developable ruled surfaces, even generic free-form surfaces. This includes: envelope surfaces, geometrical errors (overcut, undercut), energy optimization in tool movement, surface deviations, tool geometry adaptation, tool wear and temperature, and surface roughness. In this article we present a survey on flank milling as well as suggesting guidelines for future considerations in solving flank milling tool trajectory optimization. © 2012 Elsevier Ltd. All rights reserved.


Li J.,Hebei United University | Zheng Z.,Tianjin University
Advances in Information Sciences and Service Sciences | Year: 2012

The problem of evaluating the technical innovation capacity of high-tech industry with uncertain linguistic information is the multiple attribute decision making (MADM) problems. In this paper, we investigate the multiple attribute decision making (MADM) problems for evaluating the technical innovation capacity of high-tech industry with uncertain linguistic information. We utilize the uncertain extended weighted geometric averaging (UEWGA) operator to aggregate the uncertain linguistic information corresponding to each alternative and get the overall value of the alternatives, then rank the alternatives and select the most desirable one(s) by using the formula of the degree of possibility for the comparison between two uncertain linguistic variables. Finally, an illustrative example for technical innovation capacity of high-tech industry with uncertain linguistic information is given.


Wang C.,Tianjin University | Liu M.,Tianjin University | Lu N.,Pacific Northwest National Laboratory
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2012

The intermission and uncertainty of renewable energy lead to many operation problems existing in power systems. Traditional method witnesses operational challenges to smooth renewable fluctuations due to the high operating cost limits of conventional storage devices. This paper presented a novel micro-grid (MG) tie-line power flow smoothing algorithm using residential thermostatically-controlled loads. The thermal dynamic of the heat pump was modeled by a simplified first-order equivalent thermal parameter model. The smoothing algorithm controlled the heat pumps based on a state-queueing control strategy through a reliable 2-way communication system. In a grid-connected community-based microgrid, 1000 residential electric heat pumps were simulated to provide this demand-side power smoothing service. The simulation results demonstrate that the algorithm is effective and robust. Sensitivity analysis was conducted for renewable penetrations, ambient temperatures, and the lower and upper limits of operating indoor temperatures and various impacts can be investigated. The results pave the path for a generalized energy storage system for future smart grid implementations. © 2012 Chinese Society for Electrical Engineering.


Wang X.,Carleton University | Chen X.,Tianjin University
Engineering Fracture Mechanics | Year: 2014

External circular crack in an infinite body is a well-known problem for three-dimensional elasticity theory. Although previously studied extensively, main focus has been on the determination of stress intensity factors, and thus only the stress components normal to the crack plane have been derived analytically. In this paper, the external circular crack problem is further studied for the purpose of determination of all components of T-stress, under both the axisymmetric (tension) and asymmetric loading (bending) loading conditions. Complete analytical expressions of stress components on the crack plane are derived first; and based on which the asymptotic analyses are carried out to obtain the components of T-stress. Comparisons of the full field solutions in the near crack front regions with asymptotic stress fields based on both stress intensity factors K and T-stresses (. K-. T field), and with the ones based on stress K alone (. K field) are carried out. It is demonstrated the K-. T field provides approximations with better accuracy comparing to the K field. The present derived T-stress solutions can be used for advanced three-dimensional fracture mechanics analyses of external cracks in engineering components. They can also be used as benchmark problems for the verifications of computational/numerical methods for the analyses of 3D crack problems. © 2014 Elsevier Ltd.


Cui L.,King's College London | Dai J.S.,King's College London | Dai J.S.,Tianjin University
Journal of Mechanisms and Robotics | Year: 2011

This paper investigates the 6R overconstrained mechanisms by looking at an arrangement that axes intersect at two centers with arbitrary intersection-angles. From the close-loop matrix equation of the mechanism, the paper develops a set of geometric constraint equations of the 6R double-centered overconstrained mechanisms. This leads to the axis constraint equation after applying the Sylvester's dialytic elimination method. The equation reveals the geometric constraint of link and axis parameters and identifies three categories of the 6R double-centered overconstrained mechanisms with arbitrary axis intersection-angles. The first two categories present two 6R double-centered overconstrained mechanisms and a 6R spherical mechanism. The last category evolves into the 6R double-spherical overconstrained mechanism with arbitrary axis intersection-angles at each spherical center. This further evolves into Baker's double-Hooke mechanism and his derivative double-spherical mechanism with orthogonal axis intersection. The paper further develops the joint-space solution of the 6R double-centered overconstrained mechanisms based on the geometric constraint equation and verifies the result with a numerical example. © 2011 American Society of Mechanical Engineers.


Dai J.S.,Tianjin University | Dai J.S.,King's College London
Mechanism and Machine Theory | Year: 2015

This paper reviews the Euler-Rodrigues formula in the axis-angle representation of rotations, studies its variations and derivations in different mathematical forms as vectors, quaternions and Lie groups and investigates their intrinsic connections. The Euler-Rodrigues formula in the Taylor series expansion is presented and its use as an exponential map of Lie algebras is discussed particularly with a non-normalized vector. The connection between Euler-Rodrigues parameters and the Euler-Rodrigues formula is then demonstrated through quaternion conjugation and the equivalence between quaternion conjugation and an adjoint action of the Lie group is subsequently presented. The paper provides a rich reference for the Euler-Rodrigues formula, the variations and their connections and for their use in rigid body kinematics, dynamics and computer graphics. © 2015 The Author. Published by Elsevier Ltd. This is an open access article under the CC BY license.


Cui L.,King's College London | Dai J.S.,Tianjin University | Dai J.S.,King's College London
Journal of Mechanisms and Robotics | Year: 2011

This paper presents a novel multifingered hand with an articulated palm that makes the hand adaptable and reconfigurable. The posture of the new multifingered hand is enhanced by the additional motion of the palm and the workspace of fingers is augmented by the palm workspace. To analyze this integrated workspace, this paper introduces finger-operation planes to relate the finger motion to the palm motion and its configuration. Normals of these operation planes are used to construct a Gauss map. Adding an additional dimension, a four-dimensional ruled surface can be generated from this map to illustrate variation of posture. With the change of palm configurations, a posture manifold can be developed from the posture ruled surfaces. The workspace analysis is developed by introducing a palm workspace-triangle. This workspace-triangle evolves into a helical workspace-triangle tube when palm inputs vary and further develops into a four-dimensional presentation. This progresses into a set of workspaces of the multifingered hand by varying the palm configuration, leading to a larger workspace of the new multifingered hand as the union of the workspaces corresponding to individual palm configuration. This paper further investigates manipulability of the multifingered hand by modeling the contact point as a hypothetical spherical joint. Based on reciprocity relationship of screw systems, the finger Jacobian matrices and the hand Jacobian matrix are established. With singular value decomposition, manipulability of each finger is explored and the hand manipulability is revealed by the diagonal nature of the Jacobian matrix of the hand. © 2011 American Society of Mechanical Engineers.


Boffety M.,University Paris - Sud | Hu H.,Tianjin University | Goudail F.,University Paris - Sud
Optics Letters | Year: 2014

Polarimetric imaging is often performed using light with a narrow spectrum for the sake of polarization measurement accuracy. However, due to the use of narrowband filters, this reduces the amount of light entering the system and thus the signal-to-noise ratio. This may not be the best choice for target detection applications, where a high target contrast is required rather than polarimetric accuracy. We address contrast optimization for broadband passive polarimetric imaging. We show through simulation and experiments that polarimetric contrast can be significantly increased by broadening the spectrum of analyzed light. In addition, we show that the contrast can be optimized by taking into account the spectral dependence of the scene and of the polarization analysis devices. © 2014 Optical Society of America.


« ABI Research: 6 transformative paradigms driving toward smart, sustainable automotive transportation | Main | First minimal synthetic bacterial cell designed and constructed by scientists at Venter Institute and Synthetic Genomics; 473 genes » Scientists from the Department of Energy’s SLAC National Accelerator Laboratory and the University of Toronto have developed a new type of ternary catalyst for the oxygen evolution reaction (OER) in water-splitting that exhibits a turnover frequency (TOF) that’s more than three-times above the TOF and mass activities of optimized control catalysts and the state-of-art NiFeOOH catalyst. The research, published in the journal Science, outlines a potential way to make a future generation of water-splitting catalysts from three abundant metals—iron (Fe), cobalt (Co) and tungsten (W)—rather than the rare, costly metals on which many of today’s catalysts rely. The gelled FeCoW oxy-hydroxide material exhibits the lowest overpotential (191 mV) reported at 10 mA per square centimeter in alkaline electrolyte. Further, the ternary catalyst showed no evidence of degradation following more than 500 hours of operation. The good things about this catalyst are that it’s easy to make, its production can be very easily scaled up without any super-advanced tools, it’s consistent, and it’s very robust. —Aleksandra Vojvodic, a SLAC staff scientist with the SUNCAT Center for Interface Science and Catalysis who led the theoretical side of the work In previous work, Vojvodic and her SUNCAT colleagues had used theory and computation to look at water-splitting oxide catalysts that contain one or two metals and predict ways to make them more active. For this study, Edward H. Sargent, a professor of electrical and computer engineering at the University of Toronto, asked them to look at the effect of adding tungsten to an iron-cobalt catalyst that worked, but not very efficiently. With the aid of powerful computers at SLAC and elsewhere and state-of-the-art computational tools, the SUNCAT team determined that adding tungsten should significantly increase the catalyst’s activity—especially if the three metals could be mixed so thoroughly that their atoms were uniformly distributed near the active site of the catalyst, where the reaction takes place, rather than separating into individual clusters as they normally tend to do. Based on that information, Sargent’s team developed a novel way to distribute the three metals uniformly within the catalyst: They dissolved the metals and other ingredients in a solution and then slowly turned the solution into a gel at room temperature, tweaking the process so the metal atoms did not clump together. The gel was then dried into a white powder whose particles were riddled with tiny pores, increasing the surface area where chemicals can attach and react with each other. In tests, the catalyst was able to generate oxygen gas three times faster, per unit weight, than the previous record-holder, Sargent said, and it also proved to be stable through hundreds of reaction cycles. Sargent said the researchers hope to use the same method to develop other three-metal catalysts for splitting water and also for splitting carbon dioxide, a greenhouse gas released by burning fossil fuels, to make renewable fuels and chemical feed stocks. He and five other members of the University of Toronto team have filed for a provisional patent on the technique for preparing the catalyst. There are a lot of things we further need to understand. Are there other abundant metals we can test as mixtures in oxides? What are the optimal mixtures of the components? How stable is the catalyst, and how can we scale up its production? It needs to be tested at the device level, really. Jeffrey C. Grossman, a professor of materials science and engineering at MIT who was not involved in the study, said: SLAC research associate Michal Bajdich and Stanford postdoctoral researcher Max García-Melchor also contributed to this work, along with researchers from the DOE’s Brookhaven National Laboratory; East China University of Science & Technology, Tianjin University and the Beijing Synchrotron Radiation Facility in China; and the Canadian Light Source. The research was funded by a number of sources, including the Ontario Research Fund – Research Excellence Program, Natural Sciences and Engineering Research Council of Canada and the CIFAR Bio-Inspired Solar Energy Program, as well as the DOE Office of Science, which funds SUNCAT, and the SLAC Laboratory Directed Research and Development program.


News Article | March 29, 2016
Site: www.rdmag.com

With a combination of theory and clever, meticulous gel-making, scientists from the Department of Energy’s SLAC National Accelerator Laboratory and the University of Toronto have developed a new type of catalyst that’s three times better than the previous record-holder at splitting water into hydrogen and oxygen—the vital first step in making fuels from renewable solar and wind power. The research, published in the journal Science, outlines a potential way to make a future generation of water-splitting catalysts from three abundant metals—iron, cobalt and tungsten—rather than the rare, costly metals that many of today’s catalysts rely on. “The good things about this catalyst are that it’s easy to make, its production can be very easily scaled up without any super-advanced tools, it’s consistent and it’s very robust,” said Aleksandra Vojvodic, a SLAC staff scientist with the SUNCAT Center for Interface Science and Catalysis who led the theoretical side of the work. Scientists have been searching for an efficient way to store electricity generated by solar and wind power so it can be used any time—not just when the sun shines and breezes blow. One way to do that is to use the electrical current to split water molecules into hydrogen and oxygen, and store the hydrogen to use later as fuel. This reaction takes place in several steps, each requiring a catalyst—a substance that promotes chemical reactions without being consumed itself—to move it briskly along. In this case, the scientists focused on a step where oxygen atoms pair up to form a gas that bubbles away, which has been a bottleneck in the process. In previous work, Vojvodic and her SUNCAT colleagues had used theory and computation to look at water-splitting oxide catalysts that contain one or two metals and predict ways to make them more active. For this study, Edward H. Sargent, a professor of electrical and computer engineering at the University of Toronto, asked them to look at the effect of adding tungsten—a heavy, dense metal used in light bulb filaments and radiation shielding—to an iron-cobalt catalyst that worked, but not very efficiently. With the aid of powerful computers at SLAC and elsewhere and state-of-the-art computational tools, the SUNCAT team determined that adding tungsten should dramatically increase the catalyst’s activity—especially if the three metals could be mixed so thoroughly that their atoms were uniformly distributed near the active site of the catalyst, where the reaction takes place, rather than separating into individual clusters as they normally tend to do. “Tungsten is quite a large atom compared to the other two, and when you add a little bit of it, it expands the atomic lattice, and this affects the reaction not only geometrically but also electronically,” Vojvodic said. “We were able to understand, on the atomic scale, why it works, and then that was verified experimentally.” Based on that information, Sargent’s team developed a novel way to distribute the three metals uniformly within the catalyst: They dissolved the metals and other ingredients in a solution and then slowly turned the solution into a gel at room temperature, tweaking the process so the metal atoms did not clump together. The gel was then dried into a white powder whose particles were riddled with tiny pores, increasing the surface area where chemicals can attach and react with each other. In tests, the catalyst was able to generate oxygen gas three times faster, per unit weight, than the previous record-holder, Sargent said, and it also proved to be stable through hundreds of reaction cycles. “It’s a big advance, although there’s still more room to improve,” he said. “And we will need to make catalysts and electrolysis systems even more efficient, cost effective and high intensity in their operation in order to drive down the cost of producing renewable hydrogen fuels to an even more competitive level.” Sargent said the researchers hope to use the same method to develop other three-metal catalysts for splitting water and also for splitting carbon dioxide, a greenhouse gas released by burning fossil fuels, to make renewable fuels and chemical feed stocks. He and five other members of the University of Toronto team have filed for a provisional patent on the technique for preparing the catalyst. “There are a lot of things we further need to understand,” Vojvodic said. “Are there other abundant metals we can test as mixtures in oxides? What are the optimal mixtures of the components? How stable is the catalyst, and how can we scale up its production? It needs to be tested at the device level, really.” Jeffrey C. Grossman, a professor of materials science and engineering at MIT who was not involved in the study, said, “The work impressively highlights the power of tightly coupled computational materials science with advanced experimental techniques, and sets a high bar for such a combined approach. It opens new avenues to speed progress in efficient materials for energy conversion and storage." SLAC research associate Michal Bajdich and Stanford postdoctoral researcher Max García-Melchor also contributed to this work, along with researchers from the DOE’s Brookhaven National Laboratory; East China University of Science & Technology, Tianjin University and the Beijing Synchrotron Radiation Facility in China; and the Canadian Light Source. The research was funded by a number of sources, including the Ontario Research Fund–Research Excellence Program, Natural Sciences and Engineering Research Council of Canada and the CIFAR Bio-Inspired Solar Energy Program, as well as the DOE Office of Science, which funds SUNCAT, and the SLAC Laboratory Directed Research and Development program.


News Article | February 15, 2017
Site: www.eurekalert.org

A chunk of conductive graphene foam reinforced by carbon nanotubes can support more than 3,000 times its own weight and easily bounce back to its original height, according to Rice University scientists. Better yet, it can be made in just about any shape and size, they reported, demonstrating a screw-shaped piece of the highly conductive foam. The Rice lab of chemist James Tour tested its new "rebar graphene" as a highly porous, conductive electrode in lithium ion capacitors and found it to be mechanically and chemically stable. The research appears in the American Chemical Society journal ACS Applied Materials and Interfaces. Carbon in the form of atom-thin graphene is among the strongest materials known and is highly conductive; multiwalled carbon nanotubes are widely used as conductive reinforcements in metals, polymers and carbon matrix composites. The Tour lab had already used nanotubes to reinforce two-dimensional sheets of graphene. Extending the concept to macroscale materials made sense, Tour said. "We developed graphene foam, but it wasn't tough enough for the kind of applications we had in mind, so using carbon nanotubes to reinforce it was a natural next step," Tour said. The three-dimensional structures were created from a powdered nickel catalyst, surfactant-wrapped multiwall nanotubes and sugar as a carbon source. The materials were mixed and the water evaporated; the resulting pellets were pressed into a steel die and then heated in a chemical vapor deposition furnace, which turned the available carbon into graphene. After further processing to remove remnants of nickel, the result was an all-carbon foam in the shape of the die, in this case a screw. Tour said the method will be easy to scale up. Electron microscope images of the foam showed partially unzipped outer layers of the nanotubes had bonded to the graphene, which accounted for its strength and resilience. Graphene foam produced without the rebar could support only about 150 times its own weight while retaining the ability to rapidly return to its full height. But rebar graphene irreversibly deformed by about 25 percent when loaded with more than 8,500 times its weight. Junwei Sha, a visiting graduate student at Rice and a graduate student at Tianjin University, China, is lead author of the paper. Co-authors from Rice are postdoctoral researchers Rodrigo Salvatierra, Pei Dong and Yongsung Ji; graduate students Yilun Li, Tuo Wang, Chenhao Zhang and Jibo Zhang; former postdoctoral researcher Seoung-Ki Lee; Pulickel Ajayan, chair of the Department of Materials Science and NanoEngineering, the Benjamin M. and Mary Greenwood Anderson Professor in Engineering and a professor of chemistry; and Jun Lou, a professor of materials science and nanoengineering. Naiqin Zhao, a professor at Tianjin University and a researcher at the Collaborative Innovation Center of Chemical Science and Engineering, Tianjin, is also a co-author. Tour is the T.T. and W.F. Chao Chair in Chemistry as well as a professor of computer science and of materials science and nanoengineering at Rice. The Air Force Office of Scientific Research and its Multidisciplinary University Research Initiative supported the research. This news release can be found online at http://news. A piece of rebar graphene stands up to a good soaking in a test at Rice University. (Credit: Tour Group/Rice University) Located on a 300-acre forested campus in Houston, Rice University is consistently ranked among the nation's top 20 universities by U.S. News & World Report. Rice has highly respected schools of Architecture, Business, Continuing Studies, Engineering, Humanities, Music, Natural Sciences and Social Sciences and is home to the Baker Institute for Public Policy. With 3,910 undergraduates and 2,809 graduate students, Rice's undergraduate student-to-faculty ratio is 6-to-1. Its residential college system builds close-knit communities and lifelong friendships, just one reason why Rice is ranked No. 1 for happiest students and for lots of race/class interaction by the Princeton Review. Rice is also rated as a best value among private universities by Kiplinger's Personal Finance. To read "What they're saying about Rice," go to http://tinyurl. .


The team has designed the most efficient catalyst for storing energy in chemical form, by splitting water into hydrogen and oxygen, just like plants do during photosynthesis. Oxygen is released harmlessly into the atmosphere, and hydrogen, as H2, can be converted back into energy using hydrogen fuel cells. "Today on a solar farm or a wind farm, storage is typically provided with batteries. But batteries are expensive, and can typically only store a fixed amount of energy," says Sargent. "That's why discovering a more efficient and highly scalable means of storing energy generated by renewables is one of the grand challenges in this field." You may have seen the popular high-school science demonstration where the teacher splits water into its component elements, hydrogen and oxygen, by running electricity through it. Today this requires so much electrical input that it's impractical to store energy this way—too great proportion of the energy generated is lost in the process of storing it. This new catalyst facilitates the oxygen-evolution portion of the chemical reaction, making the conversion from H2O into O2 and H2 more energy-efficient than ever before. The intrinsic efficiency of the new catalyst material is over three times more efficient than the best state-of-the-art catalyst. The new catalyst is made of abundant and low-cost metals tungsten, iron and cobalt, which are much less expensive than state-of-the-art catalysts based on precious metals. It showed no signs of degradation over more than 500 hours of continuous activity, unlike other efficient but short-lived catalysts. Their work was published today in the leading journal Science. "With the aid of theoretical predictions, we became convinced that including tungsten could lead to a better oxygen-evolving catalyst. Unfortunately, prior work did not show how to mix tungsten homogeneously with the active metals such as iron and cobalt," says Dr. Bo Zhang, one of the study's lead authors. "We invented a new way to distribute the catalyst homogenously in a gel, and as a result built a device that works incredibly efficiently and robustly." This research united engineers, chemists, materials scientists, mathematicians, physicists, and computer scientists across three countries. A chief partner in this joint theoretical-experimental study was a leading team of theorists at Stanford University and SLAC National Accelerator Laboratory under the leadership of Dr. Aleksandra Vojvodic. The international collaboration included researchers at East China University of Science & Technology, Tianjin University, Brookhaven National Laboratory, Canadian Light Source and the Beijing Synchrotron Radiation Facility. "The team developed a new materials synthesis strategy to mix multiple metals homogeneously—thereby overcoming the propensity of multi-metal mixtures to separate into distinct phases," said Jeffrey C. Grossman, the Morton and Claire Goulder and Family Professor in Environmental Systems at Massachusetts Institute of Technology. "This work impressively highlights the power of tightly coupled computational materials science with advanced experimental techniques, and sets a high bar for such a combined approach. It opens new avenues to speed progress in efficient materials for energy conversion and storage." "This work demonstrates the utility of using theory to guide the development of improved water-oxidation catalysts for further advances in the field of solar fuels," said Gary Brudvig, a professor in the Department of Chemistry at Yale University and director of the Yale Energy Sciences Institute. "The intensive research by the Sargent group in the University of Toronto led to the discovery of oxy-hydroxide materials that exhibit electrochemically induced oxygen evolution at the lowest overpotential and show no degradation," said University Professor Gabor A. Somorjai of the University of California, Berkeley, a leader in this field. "The authors should be complimented on the combined experimental and theoretical studies that led to this very important finding."


Nie J.,Tianjin University | Guo H.-C.,China Agricultural University | Cahard D.,INSA Rouen | Ma J.-A.,Tianjin University | Ma J.-A.,CAS Shanghai Institute of Organic Chemistry
Chemical Reviews | Year: 2011

Trifluoromethyl aldimines have emerged as powerful building blocks to construct important molecules in many fields of application. The protecting group on the oxygen was installed to prevent the ring closure into the corresponding oxazolidine during preparation of the substrate. This approach toward Cathepsin K inhibitors gives high diastereoselectivity, is suitable for multigram-scale synthesis, is complementary to the in situ generation of imines from oxazolidines. Trifluoroacetaldehyde imines featuring a chiral enantiopure auxiliary present the disadvantage of being self-immolative for the auxiliary because the nitrogen atom is incorporated in the final product and the stereogenic center is lost during the removal step. Trifluoropyruvates are nonenolizable ketones and more electrophilic than ethyl pyruvate due to the electronwithdrawing trifluoromethyl group.


Liu C.-J.,Tianjin University | Burghaus U.,North Dakota State University | Besenbacher F.,University of Aarhus | Wang Z.L.,Georgia Institute of Technology
ACS Nano | Year: 2010

The use of nanotechnology to develop a suite of sustainable energy production schemes is one of the most important scientific challenges of the 21st century. The challenge is to design, to synthesize, and to characterize new functional nanomaterials with controllable sizes, shapes, and/or structures. To summarize the progress of the research and development made in this important field, the Fuel Chemistry Division of the American Chemical Society (ACS) organized a symposium on "Nanotechnology for Sustainable Energy and Fuels" during the 240th ACS National Meeting in Boston, MA on August 22-26, 2010, with the ACS Catalysis Division as the cosponsor. This symposium was a global gathering of leading scientists at the intersection of energy and nanotechnology. The topics discussed at the symposium included nanotechnology, not only for traditional fossil fuel production but also for novel processes for renewable energy applications. This article aims to highlight some of the most exciting advances presented at the symposium, including the preparation and characterization of nanomaterials for clean fuel production, CO2 capture, solar cells and solar fuels, energy conversion and storage materials, hydrogen storage materials, and fuel cells. Finally, possible future developments in this important and timely area are discussed. © 2010 American Chemical Society.


Cao W.,Oklahoma State University | Singh R.,Los Alamos National Laboratory | Al-Naib I.A.I.,INRS EMT | He M.,Tianjin University | And 3 more authors.
Optics Letters | Year: 2012

We experimentally demonstrate a planar terahertz Fano metamaterial with an ultrahigh quality (Q) factor of 227. This is achieved by the excitation of the nonradiative dark modes by introducing a tiny asymmetry in the metamaterial structure. The extremely sharp quadrupole and Fano resonances are excited at normal incidence for orthogonal polarizations of the electric field. In order to capture the narrow linewidth of the dark resonance modes, we perform high resolution terahertz time-domain measurements with a scan length of 200 picoseconds and frequency resolution of 5 GHz. These high-Q metamaterials can be used in ultrasensitive label-free terahertz sensing, dense photonic integration, and narrowband filtering. © 2012 Optical Society of America.


Wang W.,Key Laboratory for Thermal Science and Power Engineering | Zhu C.,Tianjin University | Cao Y.,Tianjin Normal University
International Journal of Hydrogen Energy | Year: 2010

Density functional theory has been used to study the thermodynamics associated with steam reforming of ethanol under cold plasma conditions. The calculation results showed that the only thermodynamic obstacle of the production of hydrogen, carbon monoxide, methane and acetaldehyde was the dissociation of ethanol and steam molecules, which was easy to be overcome under cold plasma conditions. The formation of hydrogen and carbon monoxide was through a multi-step pathway via the methoxy radical conversion and dissociation of formaldehyde, while the recombination of H{radical dot} generated extra hydrogen. The syntheses of ethane and butane are from the recombination of CH3{radical dot} and CH3CH2{radical dot}, which could be primarily generated through ethanol dissociation. The structure of ethanol anion were also studied in this work. Theoretical calculation showed that the ethanol anion was less stable than the neutral molecule. The route for the formation of CH3{radical dot} and CH2OH{radical dot} from ethanol anion is thermodynamically favorable. © 2009 Professor T. Nejat Veziroglu.


Zhu X.,Tianjin University | Chen Z.,Hong Kong University of Science and Technology | Tang C.,Tianjin University
Optics Letters | Year: 2013

In optical metrology, state of the art algorithms for background and noise removal of fringe patterns are based on space-frequency analysis. In this Letter, an approach based on variational image decomposition is proposed to remove background and noise from a fringe pattern simultaneously. In the proposed method, a fringe image is directly decomposed into three components: a first one containing background, a second one fringes, and a third one noise, which are described in different function spaces and are solved by minimization of the functional. A simple technical process involved in the minimization algorithm improves the convergence performance. The proposed approach is verified with the simulated and experimental fringe patterns. © 2013 Optical Society of America.


Zhang X.,Tianjin University | Tian Z.,Tianjin University | Yue W.,King Abdullah University of Science and Technology | Gu J.,Tianjin University | And 4 more authors.
Advanced Materials | Year: 2013

A broadband terahertz wave deflector based on metasurface induced phase discontinuities is reported. Various frequency components ranging from 0.43 to 1.0 THz with polarization orthogonal to the incidence are deflected into a broad range of angles from 25° to 84°. A Fresnel zone plate consequently developed from the beam deflector is capable of focusing a broadband terahertz radiation. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Zhang B.,University of Pennsylvania | Zhang B.,Tianjin University | Jung Y.,University of Pennsylvania | Chung H.-S.,University of Pennsylvania | And 2 more authors.
Nano Letters | Year: 2010

The unique properties of nanostructured materials enable their transformation into complex, kinetically controlled morphologies that cannot be obtained during their growth. Solution-phase cation-exchange reactions can transform sub-10 nm nanocrystals/nanorods into varying compositions and superlattice structures; however, because of their small size, cation-exchange reaction rates are extremely fast, which limits control over the transformed products and possibilities for obtaining new morphologies. Nanowires are routinely synthesized via gas-phase reactions with 5-200 nm diameters, and their large aspect ratios allow them to be electrically addressed individually. To realize their full potential, it is desirable to develop techniques that can transform nanowires into tunable but precisely controlled morphologies, especially in the gas-phase, to be compatible with nanowire growth schemes. We report transformation of single-crystalline cadmium sulfide nanowires into composition-controlled ZnxCd(1-X)S nanowires, core-shell heterostructures, metal-semiconductor superlattices (Zn-ZnrCd (1-x)S), single-crystalline ZnS nanotubes, and eventually metallic Zn nanowires by utilizing size-dependent cation-exchange reaction along with temperature and gas-phase reactant delivery control. This versatile synthetic ability to transform nanowires offers new opportunities to study size-dependent phenomena at the nanoscale and tune their chemical/physical properties to design reconfigurable circuits. © 2010 American Chemical Society.


Kong X.,Tianjin University | Lu S.,Tianjin University | Wu Y.,Ministry of Housing and Urban Rural Development
Energy Policy | Year: 2012

With the increasing building energy consumption, the improvement of building energy efficiency (BEE) becomes a key part of the reduction of energy intensity in the "Eleventh Five-Year Plan" period (during 2006 and 2010) in China. For this reason, the China central government has enforced and implemented a series of policies to promote BEE. Based on the analysis of main characteristics of BEE development in China and developmental routes of BEE, this paper systematically explored six fiscal incentive policies. Meanwhile, four specific programs involving new building, existing residential building, government office building and large-scale public building, and applications of renewable energy in building were investigated. Besides, the key factors of BEE development and BEE developmental stages were analyzed. The research revealed the present progress of implementation on BEE policies, and identified the drawbacks of the present BEE mechanism. Moreover, four proposals were recommended to enhance the development of BEE in the next "Five-Year Plan" period. © 2011 Elsevier Ltd.


Qin Y.,Nanjing Southeast University | Chen Z.,Tianjin University
Steel and Composite Structures | Year: 2016

Cold-formed steel structures are increasingly attractive due to their benefits of good mechanical performance and constructional advantages. However, this type of construction is still not fully exploited as a result of the acknowledged difficulties involved in forming construction-efficient and cost-effective connections. Furthermore, there is a lack of information on the structural behavior of the cold-formed steel connections. In this study, the research on various cold-formed steel connections was comprehensively reviewed from both fundamental and structural points of view, based on the available experimental and analytical data. It reveals that the current design codes and guidelines for cold-formed steel connections tend to focus more on the individual bearing capacity of the fasteners rather than the overall structural behavior of the connections. Significant future work remains to be conducted on the structural performance of cold-formed steel connection. In addition, extensive previous research has been carried out to propose and evaluate an economical and efficient connection system that is obtained from the conventional connecting techniques used in the hot-rolled industry. These connecting techniques may not be suitable, however, as they have been adopted from hot-rolled steel portal frames due to the thinness of the sheet in cold-formed steels. The review demonstrates that with the increasing demand for cold-formed steel constructions throughout the world, it is crucial to develop an efficient connection system that can be prefabricated and easily assembled on site. Copyright © 2016 Techno-Press, Ltd.


Yuan H.-N.,Tianjin University | Wang S.,Tianjin University | Nie J.,Tianjin University | Meng W.,Tianjin University | And 2 more authors.
Angewandte Chemie - International Edition | Year: 2013

Key to success: The title reaction provides facile access to enantioenriched 3,4-dihydroquinazolin-2(1H)-ones containing a quaternary stereogenic center in high yields with excellent enantioselectivities. Subsequent transformations lead to the convenient preparation of the anti-HIV drug DPC 083 and N-fused polycyclic compounds without loss of enantiomeric excess. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Sun Y.,Tianjin University | Chen Q.,Nanjing Southeast University | Pugno N.,University of Trento | Pugno N.,Fondazione Bruno Kessler
Composite Structures | Year: 2014

In this paper, we analytically studied the in-plane elastic and transport properties of a peculiar hexagonal honeycomb, i.e., the multifunctional hierarchical honeycomb (MHH). The MHH structure was developed by replacing the solid cell walls of the original regular hexagonal honeycomb (ORHH) with three kinds of equal-mass isotropic honeycomb sub-structures possessing hexagonal, triangular and Kagome lattices. Formulas to calculate the effective in-plane elastic properties and conductivities of the MHH structure at all densities were developed. Results show that the elastic properties of the MHH structure with the hexagonal sub-structure were weakly improved in contrast to those of the ORHH. However, the triangular and Kagome sub-structures result in substantial improvements by one or even three orders of magnitude on Young's and shear moduli of the MHH structure, depending on the cell-wall thickness-to-length ratio of the ORHH. The present theory could be used in designing new tailorable hierarchical honeycomb structures for multifunctional applications. © 2013 Elsevier Ltd.


Qin Y.,Tianjin University | Tian Y.,Tianjin University | Zhang D.,Tianjin University | Shirinzadeh B.,Monash University | Fatikow S.,University of Oldenburg
IEEE/ASME Transactions on Mechatronics | Year: 2013

The Prandtl-Ishlinskii (PI) model is widely utilized in hysteresis modeling and compensation of piezoelectric actuators. For systems with rate-independent hysteresis, the inverse PI model is analytically feasible and it can be adopted as a feedforward compensator for the hysteretic nonlinearity of piezoelectric actuators. However, for the rate-dependent PI model, the applicable valid inversion methodology is not yet available. Although simply replacing all the rate-independent terms in the conventional inversion law with the rate-dependent terms can achieve acceptable results at very slow trajectories. However, a large theoretical modeling error is inevitable at fast trajectories, which is investigated through simulations. This paper proposes a new direct approach to derive the inverse PI model directly from experimental data. As no inversion calculation is involved, the proposed direct approach is efficient and the theoretical modeling error can be avoided. In order to validate the accuracy of the direct approach, a number of experiments have been implemented on a piezo-driven compliant mechanism by utilizing the inverse PI model as a feedforward controller. The tracking performance of the mechanism is significantly improved by the direct approach. © 1996-2012 IEEE.


Sun L.,China National Institute of Biological Sciences | Sun L.,University of Texas Southwestern Medical Center | Wang H.,China National Institute of Biological Sciences | Wang H.,University of Texas Southwestern Medical Center | And 13 more authors.
Cell | Year: 2012

The receptor-interacting serine-threonine kinase 3 (RIP3) is a key signaling molecule in the programmed necrosis (necroptosis) pathway. This pathway plays important roles in a variety of physiological and pathological conditions, including development, tissue damage response, and antiviral immunity. Here, we report the identification of a small molecule called (E)-N-(4-(N-(3-methoxypyrazin-2-yl)sulfamoyl)phenyl)-3-(5-nitrothiophene-2-yl) acrylamide - hereafter referred to as necrosulfonamide - that specifically blocks necrosis downstream of RIP3 activation. An affinity probe derived from necrosulfonamide and coimmunoprecipitation using anti-RIP3 antibodies both identified the mixed lineage kinase domain-like protein (MLKL) as the interacting target. MLKL was phosphorylated by RIP3 at the threonine 357 and serine 358 residues, and these phosphorylation events were critical for necrosis. Treating cells with necrosulfonamide or knocking down MLKL expression arrested necrosis at a specific step at which RIP3 formed discrete punctae in cells. These findings implicate MLKL as a key mediator of necrosis signaling downstream of the kinase RIP3. © 2012 Elsevier Inc.


Zhang H.,Tianjin University | Jia X.,Beihang University | Han F.,Tianjin University | Zhao J.,Tianjin University | And 3 more authors.
Biomaterials | Year: 2013

Tissue engineering of small-diameter blood vessels is still challenging because of restenosis and burst. To prevent thrombosis, rapid endothelialization along the lumen of grafts is intended, followed by proliferation of vascular smooth muscle cells (VSMCs) around the exterior for compliance. To this goal, two modified coaxial electrospinning techniques were developed to encapsulate vascular endothelial growth factor (VEGF) and platelet-derived growth factor-bb (PDGF), respectively, to regulate proliferation of vascular endothelial cells (VECs) and VSMCs. Release profiles, in vitro cell proliferation and in vivo implantation of double-layered electrospun membranes were investigated, and what made it special was the electrospun membranes were composed of chitosan hydrogel/poly(ethylene glycol)-b-poly(l-lactide-co-caprolactone) (PELCL) electrospun membrane loaded with VEGF as the inner layer and emulsion/PELCL electrospun membrane-loaded PDGF as the outer. It was found that dual-release of VEGF and PDGF could accelerate VEC proliferation in the first 6 days, and modulate slow VSMC proliferation in the initial 3 days whereas generate rapid proliferation after day 6, which is of great benefit to blood vessel regeneration. Four weeks of in vivo replacement of rabbit carotid artery demonstrated that VECs and VSMCs developed on the lumen and exterior of vascular grafts, respectively, and no thrombus or burst appeared. It was concluded that dual-delivery of VEGF and PDGF by the modified electrospun membranes could facilitate revascularization. © 2013 Elsevier Ltd.


Li Q.,Peking Union Medical College | Li Q.,China National Institute of Biological Sciences | Dong T.,Peking Union Medical College | Dong T.,China National Institute of Biological Sciences | And 3 more authors.
Journal of the American Chemical Society | Year: 2013

There is an increasing interest in the use of bioorthogonal ligation to advance biomedical research through selective labeling of biomolecules in living systems. Accordingly, discovering new reactions to expand the toolbox of bioorthogonal chemistry is of particular interest to chemical biologists. Herein we report a new bioorthogonal ligation enabled by click hetero-Diels-Alder (HDA) cycloaddition of in situ-generated o-quinolinone quinone methides and vinyl thioethers. This reaction is highly selective and proceeds smoothly under aqueous conditions. The functionalized vinyl thioethers are small and chemically stable in vivo, making them suitable for use as bioorthogonal chemical reporters that can be effectively coupled to various biomolecules. We utilized this bioorthogonal ligation for site-specific labeling of proteins as well as imaging of bioactive small molecules inside live cells. © 2013 American Chemical Society.


Tian Y.,Tianjin University | Tian Y.,Monash University | Zhang D.,Tianjin University | Shirinzadeh B.,Monash University
Precision Engineering | Year: 2011

This paper presents the dynamic modelling and performance evaluation methodologies of a flexure-base mechanism for ultra-precision grinding operation. The mechanical design of the mechanism is briefly described. A piezoelectric actuator is utilized to drive the moving platform. A flexure-based structure is utilized to guide the moving platform and to provide preload for the piezoelectric actuator. By simplifying the Hertzian contact as a linear spring and damping component, a bilinear dynamic model is developed to investigate the dynamic characteristics of the flexure-based mechanism. Based on the established model, the separation phenomenon between the moving platform and the piezoelectric actuator is analyzed. The influences of the control voltage and the preload stiffness on the maximum overshoot are extensively investigated. The slope and cycloidal command signals are utilized to reduce and/or avoid the overshoot of such flexure-based mechanism for rapid positioning. The effects of the rising time of the command signals on the maximum overshoot and the settling time are also explored. Experiments are performed to verify the established dynamic model and the performance of the developed flexure-based mechanism. © 2011 Elsevier Inc.


Dai J.,Nanjing Southeast University | Dai J.,Jiangsu University of Science and Technology | Xu C.X.,Nanjing Southeast University | Sun X.W.,Nanyang Technological University | Sun X.W.,Tianjin University
Advanced Materials | Year: 2011

The whispering gallery mode (WGM) lasing and microphotoluminescence from a hexagonal ZnO microrod are investigated. The hexagonal ZnO microrod is integrated on a p-GaN substrate to fabricate a heterostructured microlaser diode and the electrically pumped WGM lasing from the diode is realized. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Tian Y.,Tianjin University | Tian Y.,Monash University | Shirinzadeh B.,Monash University | Zhang D.,Tianjin University
Precision Engineering | Year: 2010

This paper presents the closed-form compliance equations for the filleted V-shaped flexure hinges. The in-plane and out-of-plane compliances of the flexure hinges are developed based on the Castigliano's second theorem. The accuracy of motion, denoted by the midpoint compliance of the flexure hinges, is also derived for optimized geometric design. The influences of the geometric parameters on the characteristics of the flexure hinges are investigated. It is noted that the filleted V-shaped flexure hinges have diverse ranges of compliance corresponding to different filleted radius R and angle θ. These types of hinges can provide both higher and lower stiffnesses than circular flexure hinges. This makes filleted V-shaped flexure hinges very useful for wide potential applications with different requirements. The finite element analysis is used to verify the established closed-form compliance equations for these filleted V-shaped flexure hinges. © 2009 Elsevier Inc. All rights reserved.


Home > Press > Graphene foam gets big and tough: Rice University's nanotube-reinforced material can be shaped, is highly conductive Abstract: A chunk of conductive graphene foam reinforced by carbon nanotubes can support more than 3,000 times its own weight and easily bounce back to its original height, according to Rice University scientists. Better yet, it can be made in just about any shape and size, they reported, demonstrating a screw-shaped piece of the highly conductive foam. The Rice lab of chemist James Tour tested its new "rebar graphene" as a highly porous, conductive electrode in lithium ion capacitors and found it to be mechanically and chemically stable. The research appears in the American Chemical Society journal ACS Applied Materials and Interfaces. Carbon in the form of atom-thin graphene is among the strongest materials known and is highly conductive; multiwalled carbon nanotubes are widely used as conductive reinforcements in metals, polymers and carbon matrix composites. The Tour lab had already used nanotubes to reinforce two-dimensional sheets of graphene. Extending the concept to macroscale materials made sense, Tour said. "We developed graphene foam, but it wasn't tough enough for the kind of applications we had in mind, so using carbon nanotubes to reinforce it was a natural next step," Tour said. The three-dimensional structures were created from a powdered nickel catalyst, surfactant-wrapped multiwall nanotubes and sugar as a carbon source. The materials were mixed and the water evaporated; the resulting pellets were pressed into a steel die and then heated in a chemical vapor deposition furnace, which turned the available carbon into graphene. After further processing to remove remnants of nickel, the result was an all-carbon foam in the shape of the die, in this case a screw. Tour said the method will be easy to scale up. Electron microscope images of the foam showed partially unzipped outer layers of the nanotubes had bonded to the graphene, which accounted for its strength and resilience. Graphene foam produced without the rebar could support only about 150 times its own weight while retaining the ability to rapidly return to its full height. But rebar graphene irreversibly deformed by about 25 percent when loaded with more than 8,500 times its weight. Junwei Sha, a visiting graduate student at Rice and a graduate student at Tianjin University, China, is lead author of the paper. Co-authors from Rice are postdoctoral researchers Rodrigo Salvatierra, Pei Dong and Yongsung Ji; graduate students Yilun Li, Tuo Wang, Chenhao Zhang and Jibo Zhang; former postdoctoral researcher Seoung-Ki Lee; Pulickel Ajayan, chair of the Department of Materials Science and NanoEngineering, the Benjamin M. and Mary Greenwood Anderson Professor in Engineering and a professor of chemistry; and Jun Lou, a professor of materials science and nanoengineering. Naiqin Zhao, a professor at Tianjin University and a researcher at the Collaborative Innovation Center of Chemical Science and Engineering, Tianjin, is also a co-author. Tour is the T.T. and W.F. Chao Chair in Chemistry as well as a professor of computer science and of materials science and nanoengineering at Rice. The Air Force Office of Scientific Research and its Multidisciplinary University Research Initiative supported the research. About Rice University Located on a 300-acre forested campus in Houston, Rice University is consistently ranked among the nation’s top 20 universities by U.S. News & World Report. Rice has highly respected schools of Architecture, Business, Continuing Studies, Engineering, Humanities, Music, Natural Sciences and Social Sciences and is home to the Baker Institute for Public Policy. With 3,910 undergraduates and 2,809 graduate students, Rice’s undergraduate student-to-faculty ratio is 6-to-1. Its residential college system builds close-knit communities and lifelong friendships, just one reason why Rice is ranked No. 1 for happiest students and for lots of race/class interaction by the Princeton Review. Rice is also rated as a best value among private universities by Kiplinger’s Personal Finance. To read “What they’re saying about Rice,” go to http://tinyurl.com/RiceUniversityoverview . Follow Rice News and Media Relations via Twitter @RiceUNews For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.


Better yet, it can be made in just about any shape and size, they reported, demonstrating a screw-shaped piece of the highly conductive foam. The Rice lab of chemist James Tour tested its new "rebar graphene" as a highly porous, conductive electrode in lithium ion capacitors and found it to be mechanically and chemically stable. The research appears in the American Chemical Society journal ACS Applied Materials and Interfaces. Carbon in the form of atom-thin graphene is among the strongest materials known and is highly conductive; multiwalled carbon nanotubes are widely used as conductive reinforcements in metals, polymers and carbon matrix composites. The Tour lab had already used nanotubes to reinforce two-dimensional sheets of graphene. Extending the concept to macroscale materials made sense, Tour said. "We developed graphene foam, but it wasn't tough enough for the kind of applications we had in mind, so using carbon nanotubes to reinforce it was a natural next step," Tour said. The three-dimensional structures were created from a powdered nickel catalyst, surfactant-wrapped multiwall nanotubes and sugar as a carbon source. The materials were mixed and the water evaporated; the resulting pellets were pressed into a steel die and then heated in a chemical vapor deposition furnace, which turned the available carbon into graphene. After further processing to remove remnants of nickel, the result was an all-carbon foam in the shape of the die, in this case a screw. Tour said the method will be easy to scale up. Electron microscope images of the foam showed partially unzipped outer layers of the nanotubes had bonded to the graphene, which accounted for its strength and resilience. Graphene foam produced without the rebar could support only about 150 times its own weight while retaining the ability to rapidly return to its full height. But rebar graphene irreversibly deformed by about 25 percent when loaded with more than 8,500 times its weight. Junwei Sha, a visiting graduate student at Rice and a graduate student at Tianjin University, China, is lead author of the paper. Co-authors from Rice are postdoctoral researchers Rodrigo Salvatierra, Pei Dong and Yongsung Ji; graduate students Yilun Li, Tuo Wang, Chenhao Zhang and Jibo Zhang; former postdoctoral researcher Seoung-Ki Lee; Pulickel Ajayan, chair of the Department of Materials Science and NanoEngineering, the Benjamin M. and Mary Greenwood Anderson Professor in Engineering and a professor of chemistry; and Jun Lou, a professor of materials science and nanoengineering. Naiqin Zhao, a professor at Tianjin University and a researcher at the Collaborative Innovation Center of Chemical Science and Engineering, Tianjin, is also a co-author. Tour is the T.T. and W.F. Chao Chair in Chemistry as well as a professor of computer science and of materials science and nanoengineering at Rice. Graphene foam invented at Rice University is reinforced with carbon nanotubes. It can hold thousands of times its own weight and still bounce back to its full height. Credit: Tour Group/Rice University Explore further: 'Rivet graphene' proves its mettle: Toughened material is easier to handle, useful for electronics


Wang X.,Institute for Infocomm Research | Nie W.,Tianjin University
Neurocomputing | Year: 2015

In recent years, we have witnessed a flourishing of 3D object modelling. Efficient and effective 3D model retrieval algorithms are high desired and attracted intensive research attentions. In this work, we propose a view-based 3D model retrieval algorithm based on weighted locality-constrained group sparse coding. Representative views are first selected by clustering and the corresponding weights are provided by considering the relationship among these views. By grouping the views from 3D models, a locality-constrained group sparse coding method is employed to find the reconstruction residual for each query view. The distance between query model and candidate model is taken as the weighted sum of residual. The query model is matched to the model which can best reconstruct the query model. Experimental comparisons have been conducted on the ETH 3D model dataset, and the results have demonstrated the effectiveness of the proposed method. © 2014 Elsevier B.V.


Lin J.,Rice University | Zhang C.,Rice University | Zhang C.,Tianjin University | Yan Z.,Rice University | And 5 more authors.
Nano Letters | Year: 2013

In this research, 3-dimensional (3D) graphene/carbon nanotube carpets (G/CNTCs)-based microsupercapacitors (G/CNTCs-MCs) were fabricated in situ on nickel electrodes. The G/CNTCs-MCs show impedance phase angle of -81.5 at a frequency of 120 Hz, comparable to commercial aluminum electrolytic capacitors (AECs) for alternating current (ac) line filtering applications. In addition, G/CNTCs-MCs deliver a high volumetric energy density of 2.42 mWh/cm3 in the ionic liquid, more than 2 orders of magnitude higher than that of AECs. The ultrahigh rate capability of 400 V/s enables the microdevices to demonstrate a maximum power density of 115 W/cm3 in aqueous electrolyte. The high-performance electrochemical properties of G/CNTCs-MCs can provide more compact ac filtering units and discrete power sources in future electronic devices. These elevated electrical features are likely enabled by the seamless nanotube/graphene junctions at the interface of the differing carbon allotropic forms. © 2012 American Chemical Society.


Zhang J.,University of Technology, Sydney | Huang M.L.,University of Technology, Sydney | Huang M.L.,Tianjin University
Concurrency Computation | Year: 2016

In this paper, we extended our density model to BigData analysis and visualization. BigData, which contains images, videos, texts, audio files and other forms of data collected from multiple datasets, is difficult to process and visualize using traditional database management and visualization tools. The challenges are in representing multiple datasets and illustrating and visualizing data patterns to meet business, government and organization needs. We have established the 5Ws density model which uses the 5Ws dimensions for BigData analysis and visualization. The 5Ws dimensions are what the data contain, why the data were transferred, where the data came from, when the data occurred, who received the data and how the data were transferred. According to the network log dataset, an example of BigData, each data incident can be classified into these 5Ws dimensions. The network log dataset ISCX2012 is tested throughout our model. This new model not only classifies network attributes and patterns but also establishes density patterns that provide more analytical features for BigData analysis and visualization. The experimental result shows that this new model with clustered visualization can be efficiently used for BigData analysis and network intrusion detection. Concurrency and Computation: Practice and Experience, 2014. Copyright © 2014 John Wiley & Sons, Ltd.


Li B.,Tsinghua University | Han C.,Tsinghua University | He Y.-B.,Tsinghua University | Yang C.,Tsinghua University | And 4 more authors.
Energy and Environmental Science | Year: 2012

The Li 4Ti 5O 12/C composite with lump morphology and excellent rate performance are synthesized using a facile hydrothermal method followed by a low temperature heat treatment. In the hydrothermal process, the introduction of cetyltrimethylammonium bromide (CTAB) as a surfactant significantly improves the rate performance of Li 4Ti 5O 12/C composite as anode material for lithium ion battery (LIB). The specific capacities of the obtained composite at charge and discharge rates of 0.1, 1, 5, 10 and 20 C are 176, 163, 156, 151 and 136 mA h g -1, respectively, which is apparently larger than those of the Li 4Ti 5O 12/C free from CTAB in the preparation. The Li 4Ti 5O 12/C prepared in presence of CTAB also shows excellent cycling performance at high rate, which is attributed to its larger diffusion coefficient of lithium ion (6.82 × 10 -12 cm 2 s -1) and smaller charge-transfer resistance (R ct) (19.2 Ω) than those of the composite (1.22 × 10 -13 cm 2 s -1 and 50.2 Ω) free from CTAB in the preparation. The Li 4Ti 5O 12 particles obtained in presence of CTAB are coated uniformly by a thin carbon layer with a thickness of ∼1 nm, whereas the Li 4Ti 5O 12 particles obtained in absence of CTAB are covered by relatively thick surface layers with a thickness of ∼2.5 nm, which is too thick, blocks the lithium ion diffusion and leads to low ionic conductivity. © 2012 The Royal Society of Chemistry.


Jia M.,Dalian University of Technology | Xie M.,Dalian University of Technology | Wang T.,Tianjin University | Peng Z.,University of Sussex
Applied Energy | Year: 2011

A full-cycle computational fluid dynamics (CFD) simulation coupled with detailed chemical kinetics mechanism has been used to investigate the effect of start of injection (SOI) timing and intake valve close (IVC) timing on performance and emissions of diesel premixed charge compression ignition (PCCI) engine. By sweeping SOI timing from -35 to -5. °CA ATDC and IVC timing from -140 to -80. °CA ATDC with fixed 50% exhaust gas recirculation (EGR) and 1.8. bar intake pressure, the contour plots for ignition timing, nitric oxides (NO. x), soot, hydrocarbon (HC), carbon monoxide (CO), indicated specific fuel consumption (ISFC), and ringing intensity have been developed. The results indicate that the operating range can be divided into kinetically controlled region and mixing-controlled region, in which the ignition timing is solely controlled by IVC timing and SOI timing respectively. To Minimize HC, CO, NO. x and soot emissions, SOI timing must be carefully adjusted within a limited range. With the retarded IVC timing, the operating range of SOI becomes wider for clean combustion. The IVC timing should be optimized with consideration of ignition timing and combustion efficiency at different SOI timing in order to improve fuel economy. For purpose of avoiding engine knock, the SOI timing around -20. °CA ATDC and early IVC timing are pursued. © 2011 Elsevier Ltd.


Sheng H.,Tianjin University | Chiang H.-D.,Cornell University
IEEE Transactions on Power Systems | Year: 2014

The widespread use of distributed generations (DGs) in utility distribution feeders is a trend, and it brings about several challenges to the operation, planning, and design of general distribution networks. In this paper, a comprehensive tool, Continuation Distribution Power Flow (CDFLOW), is presented and evaluated. CDFLOW can be used for tracing steady-state stationary behaviors of general unbalanced distribution systems due to various types of power injection variations, including high penetration of DGs. The major computation engine behind CDFLOW is the continuation method. Major components, either balanced or unbalanced, grounded or ungrounded, are well modeled in CDFLOW. A detailed description of CDFLOW and its implementation regarding the predictor, corrector, adaptive step-size control and parameterizations are presented. For illustrative purposes, CDFLOW was applied to the IEEE 8500-node test system and a practical 1103-node distribution networks with promising results. © 1969-2012 IEEE.


Li Z.,Tianjin University | Song G.-L.,Xiamen University | Song G.-L.,University of Queensland | Song S.,Tianjin University
Electrochimica Acta | Year: 2014

The effect of bicarbonate on biodegradation of pure magnesium in a simulated body fluid is investigated by means of X-ray diffraction, X-ray photoelectron spectroscopy, polarization curve and electrochemical impedance spectroscopy. The results show that magnesium biodegrades rapidly and non-uniformly during 27 h of immersion in four simulated body fluid solutions containing different concentrations of bicarbonate. The biodegradation rate first decreases and then increases with time. A small amount of bicarbonate in simulated body fluid has an inhibition effect on the Mg dissolution, while an overdose of bicarbonate addition activates the magnesium surface in the simulated body fluid. The interesting phenomena can be interpreted by a surface film model involving precipitation of calcium carbonate and further ionization of bicarbonate in the simulated body fluids, incorporation of calcium, carbonate and phosphate compounds in the surface film, and development of chloride-induced pitting corrosion damage on the magnesium with time. © 2013 Elsevier Ltd.


Li G.,Tianjin University | Chiang H.-D.,Cornell University
IEEE Transactions on Smart Grid | Year: 2016

Forecasting is considered to be one of the most cost-efficient solutions to integrating wind power into existing power systems. In some applications, unbiased forecasting is necessary, while in others, the forecasting value can be biased for optimal decision making. In this paper, we study optimal point forecasting problems under cost-oriented loss functions, which can lead to a forecasting process that is far more sensitive to the actual cost associated with forecasting errors. Theoretical points of optimal forecasting under different loss functions are illustrated, then a cost-oriented, boosted regression tree method is presented to formulate the optimal forecasting problem under study. Case studies using real wind farm data are conducted. A comparison between cost-oriented forecasting and traditional unbiased forecasting demonstrates the efficiency of the proposed method in maximizing benefits for the decision-making process. © 2016 IEEE.


Li H.,Tianjin University | Li H.,University of Jinan | Zhao Y.,Tianjin University | Yuan X.,Tianjin University
Soft Matter | Year: 2013

A superhydrophobic polymer coating is prepared by spraying a fluorinated acrylic random copolymer micelle solution. The surface morphology of the coating can be controlled by the solvent, and the possible formation mechanism of the superhydrophobic coating is proposed. The coating displays anti-icing properties and resistance to low temperature. This journal is © 2012 The Royal Society of Chemistry.


Hong X.,University of Bristol | Hong X.,Tianjin University | Van Dijk E.M.P.H.,University of Twente | Hall S.R.,University of Bristol | And 3 more authors.
Nano Letters | Year: 2011

Metal nanoparticles play a key role in sensing and imaging. Here we demonstrate the detection of metal particles down to 5 nm in size with a signal-to-noise ratio of ∼7 using interferometric cross-polarization microscopy at ultralow excitation powers (∼1 μW) compatible with single molecule detection. The method is background-free and induces no heating as it operates far from plasmonic resonance. The combination of unlimited observation time and protein-sized metal nanoparticles has great potential for biophysical applications. © 2011 American Chemical Society.


Wang W.,Tsinghua University | Wang W.,Tianjin University
Fuel Processing Technology | Year: 2010

Thermodynamics of glycerol partial oxidation for hydrogen production has been studied by Gibbs free energy minimization method. The optimum conditions for hydrogen production are identified: reaction temperatures between 1000 and 1100 K and oxygen-to-glycerol molar ratios of 0.4-0.6 at 1 atm. Under the optimal conditions, complete conversion of glycerol, 78.93%-87.31% yield of hydrogen and 75.12%-87.97% yield of carbon monoxide could be achieved in the absence of carbon formation. The glycerol partial oxidation with O2 is suitable for providing hydrogen-rich fuels for Molten Carbonate Fuel Cell and Solid Oxide Fuel Cell. The carbon-formed and carbon-free regions are found, which are useful in guiding the search for suitable catalysts for the reaction. Inert gases have a positive effect on the hydrogen and carbon monoxide yields. © 2010 Elsevier B.V.


Wang W.,Tsinghua University | Cao Y.,Tianjin University
International Journal of Hydrogen Energy | Year: 2010

Butanol partial oxidation for hydrogen-rich gas production has been studied by Gibbs free energy minimization method. The optimum conditions for hydrogen-rich gas production are identified: reaction temperatures between 1115 and 1200 K and oxygen-to-butanol molar ratios between 1.6 and 1.7 at 1 atm. Under the optimal conditions, complete conversion of butanol, 93.07%-96.56% yield of hydrogen and 94.02%-97.55% yield of carbon monoxide could be achieved in the absence of coke formation. The butanol partial oxidation with O 2 is suitable for providing hydrogen-rich fuels for Solid Oxide Fuel Cell (SOFC). Higher pressures have a negative effect, but inert gases have a positive effect, on the hydrogen yield. Coke tends to form at lower temperatures and lower oxygen-to-butanol molar ratios. © 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.


Fu H.,Tianjin University | Cao X.,Chinese Academy of Sciences | Tu Z.,University of California at Los Angeles
IEEE Transactions on Image Processing | Year: 2013

Co-saliency is used to discover the common saliency on the multiple images, which is a relatively underexplored area. In this paper, we introduce a new cluster-based algorithm for co-saliency detection. Global correspondence between the multiple images is implicitly learned during the clustering process. Three visual attention cues: contrast, spatial, and corresponding, are devised to effectively measure the cluster saliency. The final co-saliency maps are generated by fusing the single image saliency and multiimage saliency. The advantage of our method is mostly bottom-up without heavy learning, and has the property of being simple, general, efficient, and effective. Quantitative and qualitative experiments result in a variety of benchmark datasets demonstrating the advantages of the proposed method over the competing co-saliency methods. Our method on single image also outperforms most the state-of-the-art saliency detection methods. Furthermore, we apply the co-saliency method on four vision applications: co-segmentation, robust image distance, weakly supervised learning, and video foreground detection, which demonstrate the potential usages of the co-saliency map. © 1992-2012 IEEE.


Wu G.,Tsinghua University | He L.,Tianjin University | Chen D.,Tsinghua University
Chemosphere | Year: 2013

The molecular scale sorption, diffusion and distribution of asphaltene, resin, aromatic and saturate fractions of heavy crude oil on quartz surface were studied using molecular dynamic simulation. Sorption of saturates on quartz decreased by 31% when temperature increased from 298 to 398K while opposite trend was observed for resins, but insignificant changes were found in asphaltenes and aromatics. Despite of this variety, the main contribution of interactions was van der Waals energy (>90%) irrespective of molecular components and temperatures. The diffusion coefficient of saturates was predicted as 10.8×10-10m2s-1 while that of the remaining fractions was about 4×10-10m2s-1 at 298K. The most likely oil distribution on quartz surface was that aromatics and saturates transported randomly into and out of the complex consisting of asphaltenes surrounded by resins, which was influenced by temperature. Overall, the knowledge on quartz-oil and oil-oil interactions gained in this study is essential for future risk assessment and remediation activities as previous studies on soil remediation either limited to light oil fractions with <40 carbons or treated the heavy crude oil as a single pseudo entity ignoring the interactions between oil fractions. © 2013 Elsevier Ltd.


Luo H.,Tianjin University | Lin Y.,Tianjin University | Gao F.,Tianjin University | Zhang C.-T.,Tianjin University | Zhang R.,Wayne State University
Nucleic Acids Research | Year: 2014

The combination of high-density transposon-mediated mutagenesis and high-throughput sequencing has led to significant advancements in research on essential genes, resulting in a dramatic increase in the number of identified prokaryotic essential genes under diverse conditions and a revised essential-gene concept that includes all essential genomic elements, rather than focusing on protein-coding genes only. DEG 10, a new release of the Database of Essential Genes (available at http://www.essentialgene.org), has been developed to accommodate these quantitative and qualitative advancements. In addition to increasing the number of bacterial and archaeal essential genes determined by genome-wide gene essentiality screens, DEG 10 also harbors essential noncoding RNAs, promoters, regulatory sequences and replication origins. These essential genomic elements are determined not only in vitro, but also in vivo, under diverse conditions including those for survival, pathogenesis and antibiotic resistance. We have developed customizable BLAST tools that allow users to perform species- and experiment-specific BLAST searches for a single gene, a list of genes, annotated or unannotated genomes. Therefore, DEG 10 includes essential genomic elements under different conditions in three domains of life, with customizable BLAST tools. © 2013 The Author(s). Published by Oxford University Press.


Yang X.,Nanyang Technological University | Zhao D.,Nanyang Technological University | Leck K.S.,Nanyang Technological University | Tan S.T.,Nanyang Technological University | And 5 more authors.
Advanced Materials | Year: 2012

High-quality InP/ZnS core-shell nanocrystals with luminescence tunable over the entire visible spectrum have been achieved by a facile one-pot solvothermal method. These nanocrystals exhibit high quantum yields (above 60%), wide emission spectrum tunability and excellent photostability. The FWHM can be as narrow as 38 nm, which is close to that of CdSe nanocrystals. Also, making use of these nanocrystals, we further demonstrated a cadmium-free white QD-LED with a high color rendering index of 91. The high-performance of the resulting InP/ZnS NCs coupled with their low intrinsic toxicity may further promote industrial applications of these NC emitters. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Zhang R.,Wayne State University | Zhang C.-T.,Tianjin University
Current Genomics | Year: 2014

In theoretical physics, there exist two basic mathematical approaches, algebraic and geometrical methods, which, in most cases, are complementary. In the area of genome sequence analysis, however, algebraic approaches have been widely used, while geometrical approaches have been less explored for a long time. The Z-curve theory is a geometrical approach to genome analysis. The Z-curve is a three-dimensional curve that represents a given DNA sequence in the sense that each can be uniquely reconstructed given the other. The Z-curve, therefore, contains all the information that the corresponding DNA sequence carries. The analysis of a DNA sequence can then be performed through studying the corresponding Z-curve. The Z-curve method has found applications in a wide range of areas in the past two decades, including the identifications of protein-coding genes, replication origins, horizontally-transferred genomic islands, promoters, translational start sides and isochores, as well as studies on phylogenetics, genome visualization and comparative genomics. Here, we review the progress of Z-curve studies from aspects of both theory and applications in genome analysis. © 2014 Bentham Science Publishers.


Gao F.,Tianjin University | Zhang R.R.,Wayne State University
PLoS ONE | Year: 2011

Essential genes, those indispensable for the survival of an organism, play a key role in the emerging field, synthetic biology. Characterization of functions encoded by essential genes not only has important practical implications, such as in identifying antibiotic drug targets, but can also enhance our understanding of basic biology, such as functions needed to support cellular life. Enzymes are critical for almost all cellular activities. However, essential genes have not been systematically examined from the aspect of enzymes and the chemical reactions that they catalyze. Here, by comprehensively analyzing essential genes in 14 bacterial genomes in which large-scale gene essentiality screens have been performed, we found that enzymes are enriched in essential genes. Essential enzymes have overrepresented ligases (especially those forming carbon-oxygen bonds and carbon-nitrogen bonds), nucleotidyltransferases and phosphotransferases, while have underrepresented oxidoreductases. Furthermore, essential enzymes tend to associate with more gene ontology domains. These results, from the aspect of chemical reactions, provide further insights into the understanding of functions needed to support natural cellular life, as well as synthetic cells, and provide additional parameters that can be integrated into gene essentiality prediction algorithms. © 2011 Gao, Zhang. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.


Zhao B.,Zhejiang Electrical Power Test and Research Institute | Zhang X.,Zhejiang Electrical Power Test and Research Institute | Chen J.,Tianjin University | Wang C.,Wayne State University | Guo L.,Tianjin University
IEEE Transactions on Sustainable Energy | Year: 2013

Standalone microgrids with renewable sources and battery storage play an important role in solving power supply problems in remote areas such as islands. To achieve reliable and economic operations of a standalone microgrid, in addition to the consideration of utilization of renewable resources, the lifetime characteristics of a battery energy storage system also need to be fully investigated. In this paper, in order to realize the economic operation of a recently developed standalone microgrid on Dongfushan Island in China, an optimization model including battery life loss cost, operation and maintenance cost, fuel cost, and environmental cost is established to obtain a set of optimal parameters of operation strategy. Considering the lifetime characteristics of lead-acid batteries, a multiobjective optimization to minimize power generation cost and to maximize the useful life of lead-acid batteries has been achieved via the nondominated sorting genetic algorithm (NSGA-II). The results show that the proposed method can optimize the system operations under different scenarios and help users obtain the optimal operation schemes of the actual microgrid system. © 2013 IEEE.


Wang W.,Tsinghua University | Cao Y.,Tianjin University
International Journal of Hydrogen Energy | Year: 2011

Thermodynamic equilibrium for sorption enhanced steam reforming of butanol (SESRB) to hydrogen was investigated using Gibbs free energy minimization method. The optimal operation conditions for SESRB are at 800 K, the steam-to-butanol molar ratio of 10, the calcium oxide-to-butanol molar ratio of 8 and atmospheric pressure. Under the optimal conditions, complete conversion of butanol, 97.07% concentration of H2 and 0.05% concentration of CO2, and efficiency of 86.60% could be achieved and at which no coke tends to form. Under the same conditions in SRB, 58.18% concentration of H 2, 21.62% concentration of CO2, and energy efficiency of 81.51% could be achieved. Butanol steam reforming with CO2 adsorption has the higher H2 content and efficiency, and lower CO2 content than that without adsorption under the same reaction conditions. In addition, reaction conditions for coke-free and coke-formed regions are also discussed in butanol steam reforming with or without CO2 separation. © 2010 Professor T. Nejat Veziroglu. 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.


Shi G.,Tianjin University | Voyiadjis G.Z.,Louisiana State University
Journal of Applied Mechanics, Transactions ASME | Year: 2011

This paper presents the derivation of a new beam theory with the sixth-order differential equilibrium equations for the analysis of shear deformable beams. A sixth-order beam theory is desirable since the displacement constraints of some typical shear flexible beams clearly indicate that the boundary conditions corresponding to these constraints can be properly satisfied only by the boundary conditions associated with the sixth-order differential equilibrium equations as opposed to the fourth-order equilibrium equations in Timoshenko beam theory. The present beam theory is composed of three parts: the simple third-order kinematics of displacements reduced from the higher-order displacement field derived previously by the authors, a system of sixth-order differential equilibrium equations in terms of two generalized displacements w and φx of beam cross sections, and three boundary conditions at each end of shear deformable beams. A technique for the analytical solution of the new beam theory is also presented. To demonstrate the advantages and accuracy of the new sixth-order beam theory for the analysis of shear flexible beams, the proposed beam theory is applied to solve analytically three classical beam bending problems to which the fourth-order beam theory of Timoshenko has created some questions on the boundary conditions. The present solutions of these examples agree well with the elasticity solutions, and in particular they also show that the present sixth-order beam theory is capable of characterizing some boundary layer behavior near the beam ends or loading points. Copyright © 2011 by ASME.


Zhai H.,Tsinghua University | Shi L.,Tsinghua University | An Q.,Tianjin University
Energy | Year: 2014

The ORC (organic Rankine cycle) system is one of the most effective approaches for recovering energy from low grade heat sources like geothermal water. This paper describes the screen of fluids for geothermal ORC system. This study analyzed the influence of the working fluid properties of HC (hydro carbon) and HFC (hydro fluorine carbon) working fluids on the system performance and relates the properties to the molecular structures. HC and HFC working fluids were adopted. A theoretical ORC model was used to optimize the evaporating temperature to maximize the work output for each working fluid. The optimal working fluids are given for heat sources at 383.15K, 403.15K and 423.15K. The results show that for a specific source temperature, the optimized evaporating temperatures for all the working fluids are almost the same. Based on the influence of working fluid property on system performance, two indicators are given for screening working fluids. Fluids like R32, R134a and propylene with GWP (global warming potential)value less than1500 provide better performance than others, by extracting more energy from the heat source. © 2013 Elsevier Ltd.


Kou X.,Cornell University | Kou X.,Tianjin University | Watkins C.B.,Cornell University | Gan S.-S.,Cornell University
Journal of Experimental Botany | Year: 2012

Arabidopsis has been used as a model system to study many aspects of plant growth and development. However, fruit senescence in Arabidopsis has been less investigated and the underlying molecular and hormonal (especially ethylene) regulatory mechanisms are not well understood. It is reported here that the Arabidopsis silique has characteristics of a climacteric fruit, and that AtNAP, a NAC family transcription factor gene whose expression is increased with the progression of silique senescence, plays an important role in its senescence. Silique senescence was delayed for 4-5 d in the atnap knockout mutant plants. The ethylene climacteric was delayed for 2 d in the atnap silique and the associated respiratory climacteric was suppressed. Exogenous ethylene stimulated respiration in the wild type, but not in the atnap mutant. The decoupling of the ethylene and respiratory climacterics in the atnap mutant suggests that AtNAP is required for ethylene stimulation of respiration. qPCR analyses revealed that the expression patterns of genes involved in ethylene biosynthesis, perception, and signalling, ACS2, ETR1, CTR1, EIN2, EIN3, and ERF1, were also altered in the atnap mutant. The effects of exogenous ABA, SA, 6-BA, and NAA on ethylene production and respiration in siliques of the wild type and atnap mutant were also investigated. A model involving ABA-AtNAP-controlled stomatal opening in regulating ethylene-stimulated respiration in fruit senescence is presented. © 2012 The Author.


Long Z.,Tianjin University | Yao Q.,Tsinghua University
Powder Technology | Year: 2012

Numerical technology has been widely used for the study of the electrostatic precipitators (ESP) and the bag filters. This paper presents a numerical model for a scale hybrid particulate collector (HPC), which combines the ESP technology and the filtration technology together. The collection process of the HPC is unsteady as the pressure drop across the bag filter increases with the deposition of the particles. The physical processes of the model include the corona discharge, the fluid flow, the particle charging and the filtration. The corona discharge field is solved by using a finite volume method. For the fluid field, the unsteady and incompressible Navier-Stokes equations with the RNG κ- ε turbulence equations are solved. The effect of the electric field on the fluid field named electro-hydrodynamic is also considered. For the particle charging, the filed-diffusing combined model of Lawless (1996) [37] is adopted. For the filtration, an unsteady cake formation model is proposed. The pressure drop across the cake is calculated according to the mass density of the cake. The coefficient between the pressure drop and the mass density of the cake comes from the experimental data. Applying the numerical model to the HPC, the influence of the hole diameter of the perforated-plate on the collection efficiency of the electrostatic zone is analyzed. Numerical results show that the collection efficiency of the electrostatic zone of the HPC has no certain relation with the hole diameter of the perforated plate. The effect of the hole diameter of the perforated-plate on the collection efficiency of the electrostatic zone becomes weaker with increasing the applied voltage. © 2011 Elsevier B.V.


Wang T.,Tianjin University | Zhang Y.,Tianjin University | Peng Z.,University of Sussex | Shu G.,Tianjin University
Renewable and Sustainable Energy Reviews | Year: 2011

Internal combustion (IC) engines are the major source of motive power in the world, a fact that is expected to continue well into this century. To increase the total efficiency and reduce CO2 emissions, recently exhaust heat recovery (EHR) based on thermoelectric (TE) and thermal fluid systems have been explored widely and a number of new technologies have been developed in the past decade. In this paper, relevant researches are reviewed for providing an insight into possible system designs, thermodynamic principles to achieve high efficiency, and selection of working fluids to maintain necessary system performance. From a number of researches, it has been found the Rankine cycle (RC) has been the most favourite basic working cycle for thermodynamic EHR systems. Based on the cycle, various different system configurations have been investigated. Accepting a certain design and manufacture cost, a system based on heavy duty vehicle application can increase the total powertrain efficiency by up to 30% (based on NEDC driving condition). To achieve the highest possible system efficiency, design of systemic structure and selections for both the expander and the working fluid (medium) are critical. © 2011 Elsevier Ltd. All rights reserved.


Wang C.,Bohai University | He Q.,Hebei University | Chen D.,North China Electrical Power University | Hu Q.,Tianjin University
Information Sciences | Year: 2014

Attribute reduction has become an important step in pattern recognition and machine learning tasks. Covering rough sets, as a generalization of classical rough sets, have attracted wide attention in both theory and application. This paper provides a novel method for attribute reduction based on covering rough sets. We review the concepts of consistent and inconsistent covering decision systems and their reducts and we develop a judgment theorem and a discernibility matrix for each type of covering decision system. Furthermore, we present some basic structural properties of attribute reduction with covering rough sets. Based on a discernibility matrix, we develop a heuristic algorithm to find a subset of attributes that approximate a minimal reduct. Finally, the experimental results for UCI data sets show that the proposed reduction approach is an effective technique for addressing numerical and categorical data and is more efficient than the method presented in the paper [D.G. Chen, C.Z. Wang, Q.H. Hu, A new approach to attribute reduction of consistent and inconsistent covering decision systems with covering rough sets, Information Sciences 177(17) (2007) 3500-3518]. © 2013 Elsevier Inc. All rights reserved.


Huo M.-L.,Tsinghua University | Zhang D.-W.,Tianjin University
Energy Policy | Year: 2012

The paper first provides an overview of the current status of PV industry development in China, including the penetration speed, the market segments and the value chain. Further, it reviews the experience of governmental interventions composed of the legal framework, market incentives and manufacturing policies for lessons learning. After the Renewable Energy Law took effect in 2006, PV penetration was accelerated. Capital subsidies and feed-in tariffs, which were still in a trial stage, public bidding and the cooperation among relevant Ministries played important roles. A series of public R&D projects provided elemental technologies and meanwhile the preferential tax policies encouraged PV R&D nationwide. Then the paper looks into the future prospects, based on the technical potential, the national indicative targets in 2020, and the energy planning considering the governmental targets of energy transition and CO 2 mitigation. Consequently we analyze problems impeding the future development based on evidences. For instance, there was no predetermined degression of the capital subsidy to push cost reduction; the budget and the organization of public PV R&D were insufficient. Finally, we propose some recommendations on improving policy interventions. © 2012 Elsevier Ltd.


Wang W.,Tianjin University | Wang W.,Wayne State University | Li Y.,Tianjin University | Cheng L.,Tianjin University | And 2 more authors.
Journal of Materials Chemistry B | Year: 2014

Water-soluble phosphorus-containing carbon dots (PCDs) with strong green fluorescence were synthesized through a facile one-step microwave assisted approach using phosphorus-rich phytic acid as a carbon source. Owing to their strong green fluorescence and low cytotoxicity, the PCDs are promising as bio-imaging agents. © 2014 The Royal Society of Chemistry.


Chen Z.,Tianjin University | Augustyn V.,University of California at Los Angeles | Wen J.,University of California at Los Angeles | Zhang Y.,University of California at Los Angeles | And 3 more authors.
Advanced Materials | Year: 2011

High-performance asymmetric super-capacitors containing thick-film electrodes (over 100 Îm thick) made of CNT/V 2O 5 nanowire composite are designed. The excellent conductivity, high specific capacitance, and a large voltage window of the CNT/V 2O 5 nanocomposite enable the fabrication of devices with high energy and high power densities. Moreover, the resulting devices exhibit excellent cycling stability. This supercapacitor approach may be attractive for a wide range of device applications. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Patent
and Technology Inc., Tianjin University and University of Jinan | Date: 2015-06-03

A data monitoring system detects an anomaly condition of a device having attached sensors. The system builds one or more models to establish normal behaviors of the device by analyzing historical sensor data, and apply the models to target sensor data of the device to compute one or more anomaly scores of the device. The system reports the condition of the device based on an analysis of the anomaly scores. To build the one or more models, the system identifies at least one optimization problem for each of the models; constructs a dynamical system such that stable equilibrium points (SEPs) of the dynamical system have one-to-one correspondence with local optimal solutions of the at least one optimization problem; finds the local optimal solutions by computing the SEPs of the dynamical system; and identifies a global optimal solution to the at least one optimization problem among the local optimal solutions.


News Article | April 25, 2016
Site: cen.acs.org

They are also set to benefit from a new policy that liberalizes the transfer of technology from universities and institutes to companies and shifts from basic research to practical applications. The new technology transfer policy could have a greater impact on chemistry in China than the expected funding increase, observers say. The changes come after the conclusion in March of China’s annual parliament, the National People’s Congress (NPC), in Beijing. This is a transitional year for China as it moves from the 12th to the 13th five-year plan, which covers 2016–20. In these five-year plans, the Chinese government maps out how it will develop the country socially and economically, an approach China adopted from the Soviet Union in the 1950s. The newest plan includes a push for major breakthroughs in basic research, applied research, big data, and what the government calls “exploring frontiers,” which involves disciplines such as marine science. Speaking at NPC, Wang Yuanhong, senior economist from the State Information Center, explained how the government is increasing the ratio of deficit to gross domestic product to provide an additional $72 billion to spend on pro-growth measures. This includes setting up national-level efforts to boost research and innovation as China looks to science to fuel its slowing economy. The government estimates that scientific research will account for 60% of economic growth by 2020. During a news conference at NPC, Minister for Science & Technology Wan Gang confirmed that China will continue to increase research funding. Spending on R&D has increased by an annual average of 11.4% from 2012 to 2015 and will reach 2.5% of gross domestic product by 2020, up from 2.1% in 2015. Wan said overall R&D expenditure in China in 2015 amounted to $215 billion, 77% of which came from companies. Of that figure, $10.3 billion went to basic science, according to a summary from China’s National Bureau of Statistics that was released in advance of the full figures, which have not yet been made public. Yu Biao, vice director of Shanghai Institute of Organic Chemistry and director of State Key Laboratory of Bioorganic & Natural Products Chemistry, tells C&EN that work to address issues of health, energy, and climate change are important and reflect the Chinese government’s support of applied chemistry research. But he predicts that “it will be difficult to secure support for pure chemistry [research] and publishing papers.” Jay Siegel, dean of Tianjin University’s School of Pharmaceutical Science & Technology, agrees. “China is not a country that at this moment places a heavy importance on very basic research,” he says. “It wants to move toward basic science, but it’s a country that sees technology as a way to drive its economy in the next five years.” Yu foresees a strengthening of the relationship between basic and applied research in China. “The inherent mode of research is going to undergo a transformation,” he says. “Interdisciplinary and practical research will receive encouragement and vigorous support.” Chemists will need to consider focusing on problems in these areas of science. China’s government wants to make research outcomes more easily available to small businesses as well as big enterprises as part of its “Made in China 2025” policies aimed at boosting the economy. National research institutes and universities will be able to sell their intellectual property to businesses without needing national-level approval, which has previously involved lengthy waits. All profits earned on the sales will now be kept by the institutes where the research was conducted. New incentives aimed at researchers themselves may further speed up the commercialization of scientific research in China. At least 50% of the proceeds from the sale of findings will go to the researchers themselves. They will be able to work for the companies that buy their research for up to three years while maintaining their positions at the institute where they did the research. It is hoped that this will encourage greater productivity. Gao Xudong, deputy director of the Research Center for Technological Innovation at Tsinghua University, told People’s Daily, the official newspaper of the Chinese Communist Party, that this change should also resolve a fundamental issue: “Some enterprises who bought scientific research findings could not fully use them due to a lack of understanding of the findings.” In light of the increasing push to transfer technology to industry, Tianjin University in 2013 opened China’s first national center for patent and intellectual property. The Tianjin University Technology Transfer Center now has 18 full-time patent brokers who work on moving technology from the university to industry. “Passing greater autonomy to universities and cutting the red tape on the reporting for grants involving science and technology is a very big thing because, in general, funds have been very controlled. So if we see policies that allow for more entrepreneurial ventures within the university—your degree programs, new directions for research—that the university can control, then we get bottom-up control. This will have a big impact on research in general, and chemistry is poised to benefit enormously,” Siegel says.


Sun Z.,Tianjin University | Sun Z.,Tianjin University of Finance and Economy | Ma J.,Tianjin University
Nonlinear Dynamics | Year: 2012

This paper considers a Bertrand model based on nonlinear demand functions which are closer to reality and different from previous studies. We apply the model into Chinese cold rolled steel market and study game process of triopoly. By using the theory of bifurcations of dynamical systems, local stable region of Nash equilibrium point is obtained. Simulations show complex dynamical behaviors of the system. The results illustrate that altering the relevant parameters of system can affect the stability of Nash equilibrium point and cause chaos to occur, and the complex dynamical behaviors will disappear by parameters control method. The results have an important theoretical and practical significance to Chinese cold rolled steel market. © 2011 Springer Science+Business Media B.V.


Pang Y.,Tianjin University | Yuan Y.,Aston University
Neurocomputing | Year: 2010

Graph embedding is a general framework for subspace learning. However, because of the well-known outlier-sensitiveness disadvantage of the L2-norm, conventional graph embedding is not robust to outliers which occur in many practical applications. In this paper, an improved graph embedding algorithm (termed LPP-L1) is proposed by replacing L2-norm with L1-norm. In addition to its robustness property, LPP-L1 avoids small sample size problem. Experimental results on both synthetic and real-world data demonstrate these advantages. © 2009 Elsevier B.V. All rights reserved.


Hu Q.,Tianjin University | Zhang L.,Hong Kong Polytechnic University | An S.,Northeastern University China | Zhang D.,Hong Kong Polytechnic University | Yu D.,Harbin Institute of Technology
IEEE Transactions on Fuzzy Systems | Year: 2012

Rough sets, especially fuzzy rough sets, are supposedly a powerful mathematical tool to deal with uncertainty in data analysis. This theory has been applied to feature selection, dimensionality reduction, and rule learning. However, it is pointed out that the classical model of fuzzy rough sets is sensitive to noisy information, which is considered as a main source of uncertainty in applications. This disadvantage limits the applicability of fuzzy rough sets. In this paper, we reveal why the classical fuzzy rough set model is sensitive to noise and how noisy samples impose influence on fuzzy rough computation. Based on this discussion, we study the properties of some current fuzzy rough models in dealing with noisy data and introduce several new robust models. The properties of the proposed models are also discussed. Finally, a robust classification algorithm is designed based on fuzzy lower approximations. Some numerical experiments are given to illustrate the effectiveness of the models. The classifiers that are developed with the proposed models achieve good generalization performance. © 1993-2012 IEEE.


Zhang Y.,Tianjin University | Sun L.,Harbin Institute of Technology
IEEE Transactions on Industrial Electronics | Year: 2011

With regard to a five-level inverter comprising flying-capacitor asymmetric H-bridge, the impact on the capacitor voltage under conventional modulation approach is analyzed. Since it is sensitive to the fundamental period and the load current, it may introduce undesired low-order harmonics into the output voltage and may even break down the power switches due to the considerable fluctuation of the flying-capacitor voltage. Thus, this paper proposes a novel pulsewidth-modulation scheme with the positive and negative cross carriers, which controls the flying-capacitor voltage by utilizing the redundant switching states of the output voltages. Three modes of precharging the flying capacitor without extra equipments are presented. Moreover, the capacitance of the flying capacitor and the switching frequency of the power switches can be chosen according to the allowable fluctuation of the flying-capacitor voltage and the load current. In order to remove the overlapping of the level layers, the optimization of the line-to-line voltage waveform is proposed to synthesize the reference vector with the nearest three-vector approach. The theory is supported by the experimental results from the prototype. © 2010 IEEE.


Li X.,CAS Xi'an Institute of Optics and Precision Mechanic | Pang Y.,Tianjin University | Yuan Y.,Aston University
IEEE Transactions on Systems, Man, and Cybernetics, Part B: Cybernetics | Year: 2010

In this paper, we first present a simple but effective L1-norm-based two-dimensional principal component analysis (2DPCA). Traditional L2-norm-based least squares criterion is sensitive to outliers, while the newly proposed L1-norm 2DPCA is robust. Experimental results demonstrate its advantages. © 2006 IEEE.


Xi G.,Japan International Center for Materials Nanoarchitectonics | Xi G.,Chinese Academy of Inspection and Quarantine | Ye J.,Japan International Center for Materials Nanoarchitectonics | Ye J.,Tianjin University | And 4 more authors.
Journal of the American Chemical Society | Year: 2012

Metal/semiconductor hybrid materials of various sizes and morphologies have many applications in areas such as catalysis and sensing. Various organic agents are necessary to stabilize metal nanoparticles during synthesis, which leads to a layer of organic compounds present at the interfaces between the metal particles and the semiconductor supports. Generally, high-temperature oxidative treatment is used to remove the organics, which can extensively change the size and morphology of the particles, in turn altering their activity. Here we report a facile method for direct growth of noble-metal particles on WO 3 through an in situ redox reaction between weakly reductive WO 2.72 and oxidative metal salts in aqueous solution. This synthetic strategy has the advantages that it takes place in one step and requires no foreign reducing agents, stabilizing agents, or pretreatment of the precursors, making it a practical method for the controlled synthesis of metal/semiconductor hybrid nanomaterials. This synthetic method may open up a new way to develop metal-nanoparticle-loaded semiconductor composites. © 2012 American Chemical Society.


Martin D.J.,Group Solar | Umezawa N.,Japan International Center for Materials Nanoarchitectonics | Umezawa N.,Japan Science and Technology Agency | Umezawa N.,Tianjin University | And 3 more authors.
Energy and Environmental Science | Year: 2013

The photooxidation of water using faceted Ag3PO4 was investigated, guided by theoretical modelling. Firstly, theoretical calculations were performed to predict the optimum morphology for solar energy conversion by probing the surface energies of three primary low index facets of Ag 3PO4: {100}, {110} and {111}. It was elucidated that the {111} facet possessed considerably higher surface energy (1.65 J m-2) than either {110} or {100} (0.78 and 0.67 J m-2 respectively). We therefore attempted to fabricate Ag3PO4 crystals with {111} facets. Tetrahedral Ag3PO4 crystals, composed of {111} facets, were then successfully synthesised using a novel kinetic control method in the absence of surfactants. In comparison to rhombic dodecahedron {110} and cubic {100} structures, tetrahedral crystals show an extremely high activity for water photooxidation, with an initial oxygen evolution rate exceeding 6 mmol h-1 g-1, 10 times higher than either {110} or {100} facets. Furthermore, to the best of our knowledge it is the first time that the internal quantum yield for water photooxidation is almost unity at 400 nm, and greater than 80% from 365 to 500 nm, achieved by {111} terminated tetrahedrons. The excellent and reproducible performance is attributed to a synergistic effect between high surface energy and a small hole mass, leading to high charge carrier mobility and active surface reaction sites. © 2013 The Royal Society of Chemistry.


Liu L.,Japan International Center for Materials Nanoarchitectonics | Ouyang S.,Japan International Center for Materials Nanoarchitectonics | Ye J.,Japan International Center for Materials Nanoarchitectonics | Ye J.,Tianjin University
Angewandte Chemie - International Edition | Year: 2013

Broadband visible-light harvesting over TiO2 is achieved by introducing gold nanorods (Au NRs) as antennas based on localized surface plasmon resonance. Furthermore, surfactant removal is achieved by an HClO 4 oxidative method. Not only transversal but also longitudinal plasma of Au NRs can induce photooxidation of 2-propanol, which extends the light harvesting to the near-infrared region. Scale bar: 10 nm. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Pang Y.,Tianjin University | Li X.,CAS Xi'an Institute of Optics and Precision Mechanic | Yuan Y.,Aston University
IEEE Transactions on Circuits and Systems for Video Technology | Year: 2010

Tensor analysis plays an important role in modern image and vision computing problems. Most of the existing tensor analysis approaches are based on the Frobenius norm, which makes them sensitive to outliers. In this paper, we propose L1-norm-based tensor analysis (TPCA-L1), which is robust to outliers. Experimental results upon face and other datasets demonstrate the advantages of the proposed approach. © 2006 IEEE.


Tian L.,Tianjin University | Zhu C.,China Northwest Building Design Research Institute
Gongcheng Lixue/Engineering Mechanics | Year: 2013

Damage evaluation and protection technique of reinforced concrete RC column subjected to impulsive load are studied through numerical simulation of collision between a rigid ball and the RC column. On the basis of the bond-slip model for the RC column, a damage criterion is put forward to determine the damage degree of the RC column under impact based on the residual axial load-carrying capacity of the RC column. And correlativity between damage degree of the RC column and mass, initial velocity of rigid ball is studied qualitatively. Dynamic response and damage of RC columns before and after protection are analyzed, and the protective effects of strengthening with externally bonded steel plate and foamed aluminum are compared. The results indicate that: the damage degree increases faster than the mass and initial velocity of the rigid ball when the mass and initial velocity are in a low level, and the damage degree enhances fastest as the mass and initial velocity increase simultaneously; when the mass and initial velocity of rigid ball reach a certain value, the growth rate of damage degree will be lower than the mass and initial velocity's. Moreover, the two protective measures externally bonding steel plate and foamed aluminum can effectively reduce the mechanical response and damage degree of the RC columns; and the protection can also transfer the global failure mode of the RC column from bending-shear failure to bending failure.


Zhao B.,Zhejiang Electrical Power Test and Research Institute | Zhang X.,Zhejiang Electrical Power Test and Research Institute | Chen J.,Tianjin University
IEEE Transactions on Power Systems | Year: 2012

The paper presents an integrated microgrid laboratory system with a flexible and reliable multimicrogrid structure; it contains multiple distributed generation systems and energy storage systems and integrates with a diesel generator that serves as a back-up power source and flywheel energy storage for fast balancing to provide uninterruptible power-supply services in cooperation with the diesel generator. The microgrid system, by adopting the master-slave control strategy, can be transited flexibly between grid-connected and islanded modes and can be disconnected from the utility when a fault occurs or the power quality falls below specified standards. The developed bi-directional inverter which is applied in the system plays an important role. The small microgrids of this system are intended to operate separately or in the form of one large microgrid with a certain switch status. Furthermore, experiments on control, protection, and other technologies have been carried out. The results show that the operation conditions meet the related IEEE Standard 1547 and power quality requirements. The integrated microgrid laboratory system is able to operate stably and reliably under different conditions, including mode transition and fault events. © 1969-2012 IEEE.


Chang K.,Japan International Center for Materials Nanoarchitectonics | Mei Z.,Japan International Center for Materials Nanoarchitectonics | Wang T.,Japan International Center for Materials Nanoarchitectonics | Kang Q.,Japan International Center for Materials Nanoarchitectonics | And 3 more authors.
ACS Nano | Year: 2014

Exploiting noble-metal-free cocatalysts is of huge interest for photocatalytic water splitting using solar energy. Here we report a composite material consisting of CdS nanocrystals grown on the suface of a nanosized MoS2/graphene hybrid as a high-performance noble-metal-free photocatalyst for H2 evolution under visible light irradiation. Through the optimizing of each component proportion, the MoS2/G-CdS composite showed the highest photocatalytic H2 production activity when the content of the MoS2/graphene cocatalyst is 2.0 wt % and the molar ratio of MoS2 to graphene is 1:2. The photocatalytic H 2 evolution activity of the proposed MoS2/G-CdS composite was tested and compared in Na2S-Na2SO3 solution and lactic acid solution. A 1.8 mmol/h H2 evolution rate in lactic acid solution corresponding to an AQE of 28.1% at 420 nm is not only higher than the case in Na2S-Na2SO3 solution of 1.2 mmol/h but also much higher than that of Pt/CdS in lactic acid solution. The relative mechanism has been investigated. It is believed that this kind of MoS 2/G-CdS composite would have great potential as a promising photocatalyst with high efficiency and low cost for photocatalytic H2 evolution reaction. © 2014 American Chemical Society.


Li Y.,Tianjin University | Lu Z.,Zhejiang University | Zhu C.,Nanyang Technological University | Niu X.,Harbin Institute of Technology
IEEE Transactions on Image Processing | Year: 2012

In this paper, we propose a robust-hash function based on random Gabor filtering and dithered lattice vector quantization (LVQ). In order to enhance the robustness against rotation manipulations, the conventional Gabor filter is adapted to be rotation invariant, and the rotation-invariant filter is randomized to facilitate secure feature extraction. Particularly, a novel dithered-LVQ-based quantization scheme is proposed for robust hashing. The dithered-LVQ-based quantization scheme is well suited for robust hashing with several desirable features, including better tradeoff between robustness and discrimination, higher randomness, and secrecy, which are validated by analytical and experimental results. The performance of the proposed hashing algorithm is evaluated over a test image database under various content-preserving manipulations. The proposed hashing algorithm shows superior robustness and discrimination performance compared with other state-of-the-art algorithms, particularly in the robustness against rotations (of large degrees). © 2011 IEEE.


Yu D.,Tianjin University | Chen G.,Tianjin University | Yu W.,Nuclear Power Institute of China | Li D.,Guangdong University of Petrochemical Technology | Chen X.,Tianjin University
International Journal of Plasticity | Year: 2012

Experimental results of monotonic uniaxial tensile tests at different strain rates and the reversed strain cycling test showed the characteristics of rate-dependence and cyclic hardening of Z2CND18.12N austenitic stainless steel at room temperature, respectively. Based on the Ohno-Wang kinematic hardening rule, a visco-plastic constitutive model incorporated with isotropic hardening was developed to describe the uniaxial ratcheting behavior of Z2CND18.12N steel under various stress-controlled loading conditions. Predicted results of the developed model agreed better with experimental results when the ratcheting strain level became higher, but the developed model overestimated the ratcheting deformation in other cases. A modified model was proposed to improve the prediction accuracy. In the modified model, the parameter mi of the Ohno-Wang kinematic hardening rule was developed to evolve with the accumulated plastic strain. Simulation results of the modified model proved much better agreement with experiments. © 2011 Elsevier Ltd. All rights reserved.


Li H.,Leiden University | Li H.,Tianjin University | Li Y.,Tianjin University | Koper M.T.M.,Leiden University | Calle-Vallejo F.,French National Center for Scientific Research
Journal of the American Chemical Society | Year: 2014

Many catalytic reactions involving small molecules, which are key transformations in sustainable energy and chemistry, involve the making or breaking of a bond between carbon, nitrogen and oxygen. It has been observed that such heterogeneously (electro)catalyzed reactions often exhibit remarkable and unusual structure sensitivity, in the sense that they take place preferentially on catalyst surfaces with a long-ranged two-dimensional (100) atomic structure. Steps and defects in this two-dimensional structure lower the catalytic activity. Such structure sensitivity must be due to the existence of a special active site on these two-dimensional (100) terraces. Employing detailed density functional theory calculations, we report here the identification of this special active site for a variety of catalytic reactions. The calculations also illustrate how this specific site breaks the well-known rule that under-coordinated surface atoms bind adsorbates stronger, thereby providing the atomic-level explanation for the lack of reactivity of steps and defects for the reactions under consideration. The breakdown of such rule results in significant deviations from commonly observed energetic scaling relations between chemisorbates. Thus, this work provides new design rules for the development of thermodynamically efficient catalysts for an important class of bond-making and bond-breaking reactions. © 2014 American Chemical Society.


Li H.,China National Institute of Biological Sciences | Wang X.,Tianjin University | Lei X.,China National Institute of Biological Sciences | Lei X.,Tianjin University
Angewandte Chemie - International Edition | Year: 2012

A shared story: Three fawcettimine- and serratinine-type Lycopodium alkaloids are prepared from a common tetracyclic spirodiketone intermediate in concise total syntheses (see scheme). The intermediate was constructed by a remarkable biosynthesis-inspired transannular NC bond formation to the spiro-configured carbon center and a hydroxy-directed pinacol coupling promoted by SmI 2. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Liao D.,Tianjin University | Li H.,China National Institute of Biological Sciences | Lei X.,Tianjin University | Lei X.,China National Institute of Biological Sciences
Organic Letters | Year: 2012

An efficient method using silver oxide-mediated oxidation for the synthesis of ortho-quinone methides has been developed and applied to the biomimetic syntheses of novel trimeric natural products, (±)-schefflone and tocopherol trimers. Further studies of the critical trimerization as well as substrate scope and limitations are also reported. © 2011 American Chemical Society.


Liu A.-A.,Tianjin University | Li K.,Microsoft | Kanade T.,Carnegie Mellon University
IEEE Transactions on Medical Imaging | Year: 2012

We propose a semi-Markov model trained in a max-margin learning framework for mitosis event segmentation in large-scale time-lapse phase contrast microscopy image sequences of stem cell populations. Our method consists of three steps. First, we apply a constrained optimization based microscopy image segmentation method that exploits phase contrast optics to extract candidate subsequences in the input image sequence that contains mitosis events. Then, we apply a max-margin hidden conditional random field (MM-HCRF) classifier learned from human-annotated mitotic and nonmitotic sequences to classify each candidate subsequence as a mitosis or not. Finally, a max-margin semi-Markov model (MM-SMM) trained on manually-segmented mitotic sequences is utilized to reinforce the mitosis classification results, and to further segment each mitosis into four predefined temporal stages. The proposed method outperforms the event-detection CRF model recently reported by Huh as well as several other competing methods in very challenging image sequences of multipolar-shaped C3H10T1/2 mesenchymal stem cells. For mitosis detection, an overall precision of 95.8% and a recall of 88.1% were achieved. For mitosis segmentation, the mean and standard deviation for the localization errors of the start and end points of all mitosis stages were well below 1 and 2 frames, respectively. In particular, an overall temporal location error of 0.73 \pm 1.29 frames was achieved for locating daughter cell birth events. © 2011 IEEE.


Zhao J.,Tianjin University | Zhao J.,Tianjin Polytechnic University | Tang W.,Tianjin University | Wei J.,Academy of Military Transportation
International Journal of Production Economics | Year: 2012

This paper studies the pricing problem of substitutable products in a supply chain with one manufacturer and two competitive retailers. The consumer demands and manufacturing costs are of uncertainty, which are described by fuzziness. Based on different market structures, one centralized pricing model and three decentralized pricing models are developed, and the corresponding analytical equilibrium solutions are obtained using the game-theoretic approach. Finally, numerical examples are presented to illustrate the effectiveness of the theoretical results, and to gain additional managerial insights. © 2010 Elsevier B.V. All rights reserved.


Jiao K.,University of Waterloo | Li X.,University of Waterloo | Li X.,Tianjin University
Progress in Energy and Combustion Science | Year: 2011

Polymer electrolyte membrane fuel cell (PEMFC) has been recognized as a promising zero-emission power source for portable, mobile and stationary applications. To simultaneously ensure high membrane proton conductivity and sufficient reactant delivery to reaction sites, water management has become one of the most important issues for PEMFC commercialization, and proper water management requires good understanding of water transport in different components of PEMFC. In this paper, previous researches related to water transport in PEMFC are comprehensively reviewed. The state and transport mechanism of water in different components are elaborated in detail. Based on the literature review, it is found that experimental techniques have been developed to predict distributions of water, gas species, temperature and other parameters in PEMFC. However, difficulties still remain for simultaneous measurements of multiple parameters, and the cell and system design modifications required by measurements need to be minimized. Previous modeling work on water transport in PEMFC involves developing rule-based and first-principle-based models, and first-principle-based models involve multi-scale methods from atomistic to full cell levels. Different models have been adopted for different purposes and they all together can provide a comprehensive view of water transport in PEMFC. With the development of computational power, application of lower length scale methods to higher length scales for more accurate and comprehensive results is feasible in the future. Researches related to cold start (startup from subzero temperatures) and high temperature PEMFC (HT-PEMFC) (operating at the temperatures higher than 100 °C) are also reviewed. Ice formation that hinders reactant delivery and damages cell materials is the major issue for PEMFC cold start, and enhancing water absorption by membrane electrolyte and external heating have been identified as the most effective ways to reduce ice formation and accelerate temperature increment. HT-PEMFC that can operate without liquid water formation and membrane hydration greatly simplifies water management strategy, and promising performance of HT-PEMFC has been demonstrated. © 2010 Elsevier Ltd. All rights reserved.


Yu D.,Tianjin University | Chen X.,Tianjin University | Yu W.,Nuclear Power Institute of China | Chen G.,Tianjin University
International Journal of Plasticity | Year: 2012

Monotonic tension, isothermal/anisothermal fully reversed strain cycling and zero-to-tension cyclic tests were conducted within the temperature domain from room temperature to 823 Kto investigate the mechanical behavior of Z2CND18.12N austenitic stainless steel under various uniaxial loading conditions. Interesting results were observed from these tests, including obvious rate-dependence at room temperature but lack of rate-dependence at elevated temperatures with the occurrence of serrated flow stress in tensile tests, more cyclic hardening at higher temperature in strain cycling tests, and tendency to reach shakedown condition at elevated temperatures in zero-to-tension cyclic tests. Dynamic strain aging (DSA) effect was presumably believed to contribute to these characteristics of the material. A thermo-viscoplastic constitutive model was proposed to describe the mechanical behavior of the material under uniaxial loading conditions at small strains. Kinematic hardening rule with two components of back stress and isotropic hardening rule incorporating DSA effect are the novel features of the proposed model. The simulated and predicted results show reasonable agreement with the experimental data. © 2012 Elsevier Ltd. All rights reserved.


Tian B.,Tianjin University | Yin L.,Nanjing University of Technology | Wang H.,University of Manchester
IEEE Transactions on Industrial Electronics | Year: 2015

The finite-time tracking control for reusable launch vehicle with unmatched disturbance is investigated. An adaptive-multivariable-disturbance-compensation scheme is proposed to provide the estimation for external disturbances where the bounds of the perturbations are not known. Based on the estimation, a continuous multivariable homogeneity second order sliding mode controller is designed to ensure that the attitude tracking is achieved in finite time. A proof of the finite-time convergence of the closed-loop system under the integrated controller and disturbance observer is derived using the Lyapunov technique. The features of the proposed control scheme are that it does not require any information on the bounds of the disturbance and its gradient except for their existence. At the same time, the finite-time convergence, nominal performance recovery, and chattering alleviation are guaranteed. Finally, some simulation tests are provided to demonstrate the effectiveness of the proposed control scheme. © 2015 IEEE.


Li C.,Tianjin University | Yu X.,Tianjin University | Lei X.,Tianjin University | Lei X.,China National Institute of Biological Sciences
Organic Letters | Year: 2010

Figure Presented. A protecting group free and biomimetic total synthesis of (+)-ainsliadimer A has been accomplished in 14 steps from α-santonin. The synthesis relies on a hydrogen bonding promoted [4 + 2]-hetero-Diels-Alder dimerization to afford the key homodimer intermediate, which demonstrates the feasibility of using nonenzymatic conditions to achieve the proposed biosynthesis. © 2010 American Chemical Society.


Cui J.,Tianjin University | Zhang M.,Tianjin University | Zhang Y.,Tianjin Institute of Urban Construction
Inorganic Chemistry Communications | Year: 2010

A series of amino-salicylaldimine-palladium(II) complexes bearing 5-methyl-3-(R-1-ylmethyl)-salicylaldimine ligands (R = morpholine, piperidine, pyrrolidine, 4-methylpiperazin, diisopropylamine) have been prepared and characterized by IR, 1H NMR and elemental analysis. Crystal structure details of complex 2b have been confirmed by X-ray structure analysis. The obtained Pd(II) complexes were found to be effective catalysts for the Suzuki and Heck cross-coupling reactions which could be carried out in the undried solvent under air. © 2009 Elsevier B.V. All rights reserved.


Zamel N.,Fraunhofer Institute for Solar Energy Systems | Li X.,University of Waterloo | Li X.,Tianjin University
Progress in Energy and Combustion Science | Year: 2013

Multi-phase transport of reactant and product species, momentum, heat (energy), electron and proton in the components of polymer electrolyte membrane (PEM) fuel cells forms the three inter-related circuits for mass, heat (energy) and electricity. These intertwined transport phenomena govern the operation and design, hence the performance, of such cells. The transport processes in the cell are usually determined with their respective effective transport properties due to the porous nature of PEM fuel cell components. These properties include the effective diffusion coefficient for the mass transfer, effective thermal conductivity for heat transfer, effective electronic conductivity for electron transfer, effective protonic conductivity for proton transfer, intrinsic and relative permeability for fluid flow, capillary pressure for liquid water transfer, etc. Accurate determination of these effective transport properties is essential for the operation and design of PEM fuel cells, especially at high current density operation. Thus, it is the focus of intensive research in the recent years. In this article, a review is provided for the determination of these effective transport properties through the various PEM fuel cell components, including the gas diffusion layer, microporous layer, catalyst layer and the electrolyte membrane layer. Given the simplicity of the GDL in structure compared to the other components of the cell, much more work in literature is focused on its transport properties. Hence, its review in this paper is more extensive. Various methods used for the determination of the effective transport properties with and without the presence of liquid water are reviewed, including experimental measurements, numerical modeling and theoretical analyses. Correlations are summarized for these transport properties, where available and further work in this area is provided as a direction for future work. © 2012 Elsevier Ltd. All rights reserved.


Sato Y.,Osaka City University | Wang Z.-Q.,Tianjin University | Wang Z.-Q.,Utah State University
Advanced Nonlinear Studies | Year: 2015

In this paper we study the ground state solutions for a nonlinear elliptic system of three equations which comes from models in Bose-Einstein condensates. Comparing with existing works in the literature which have been on purely attractive or purely repulsive cases, our investigation focuses on the effect of mixed interaction of attractive and repulsive couplings. We establish the existence of least energy positive solutions and study asymptotic profile of the ground state solutions, giving indication of co-existence of synchronization and segregation. In particular we show symmetry breaking for the ground state solutions.


He J.,University of Maryland University College | Zhang P.,Tianjin University | Gong J.,Tianjin University | Nie Z.,University of Maryland University College
Chemical Communications | Year: 2012

This communication describes a one-step strategy for the facile synthesis of polymer-Au patchy particles (PPs) and Au nanocups using the interfacial reactions. © 2012 The Royal Society of Chemistry.


Fu H.,Nanyang Technological University | Xu D.,Nanyang Technological University | Zhang B.,Tianjin University | Lin S.,Microsoft
Proceedings of the IEEE Computer Society Conference on Computer Vision and Pattern Recognition | Year: 2014

We present a video co-segmentation method that uses category-independent object proposals as its basic element and can extract multiple foreground objects in a video set. The use of object elements overcomes limitations of low-level feature representations in separating complex foregrounds and backgrounds. We formulate object-based co-segmentation as a co-selection graph in which regions with foreground-like characteristics are favored while also accounting for intra-video and inter-video foreground coherence. To handle multiple foreground objects, we expand the co-selection graph model into a proposed multi-state selection graph model (MSG) that optimizes the segmentations of different objects jointly. This extension into the MSG can be applied not only to our co-selection graph, but also can be used to turn any standard graph model into a multi-state selection solution that can be optimized directly by the existing energy minimization techniques. Our experiments show that our object-based multiple foreground video co-segmentation method (ObMiC) compares well to related techniques on both single and multiple foreground cases. © 2014 IEEE.


Yue H.,Tianjin University | Sun X.,Microsoft | Yang J.,Tianjin University | Wu F.,Microsoft
IEEE Transactions on Multimedia | Year: 2013

Current image coding schemes make it hard to utilize external images for compression even if highly correlated images can be found in the cloud. To solve this problem, we propose a method of cloud-based image coding that is different from current image coding even on the ground. It no longer compresses images pixel by pixel and instead tries to describe images and reconstruct them from a large-scale image database via the descriptions. First, we describe an input image based on its down-sampled version and local feature descriptors. The descriptors are used to retrieve highly correlated images in the cloud and identify corresponding patches. The down-sampled image serves as a target to stitch retrieved image patches together. Second, the down-sampled image is compressed using current image coding. The feature vectors of local descriptors are predicted by the corresponding vectors extracted in the decoded down-sampled image. The predicted residual vectors are compressed by transform, quantization, and entropy coding. The experimental results show that the visual quality of reconstructed images is significantly better than that of intra-frame coding in HEVC and JPEG at thousands to one compression. © 1999-2012 IEEE.


News Article | March 25, 2016
Site: cen.acs.org

Manufacturers generally produce methanol, a key chemical building block and fuel, from petroleum-derived syngas, a mixture of carbon monoxide and hydrogen. Direct hydrogenation of the greenhouse gas carbon dioxide would be a more efficient and environmentally sustainable route to methanol. But practical catalysts capable of making this reaction happen on an industrial scale have been unavailable. Scientists had shown earlier that indium oxide catalyzes the direct hydrogenation of CO to CH OH on a lab scale. Javier Pérez-Ramírez of ETH Zurich and coworkers now demonstrate that zirconium oxide-supported In O catalyzes the process under conditions similar to those required for industrial production (Angew. Chem. Int. Ed. 2016, DOI: 10.1002/anie.201600943). The supported catalyst can convert CO and H to CH OH over at least 1,000 hours of continuous use and outperforms most other hydrogenation catalysts. The researchers proved experimentally that oxygen vacancies on the catalyst surface make the reaction possible—a mechanism predicted by theoretical calculations from a team led by Qingfeng Ge of Southern Illinois University and Tianjin University (ACS Catal. 2013, DOI: 10.1021/cs400132a). The ETH Zurich group optimized the reaction by adding CO to the starting materials and varying the temperature, both of which tuned the number of vacancies. The technique is “a long-sought breakthrough with the potential to realize continuous CO conversion to methanol on a commercial scale,” Ge says. Pérez-Ramírez and coworkers have filed patent applications on the technology in collaboration with French energy firm Total, which has started pilot studies of the process.


News Article | November 9, 2015
Site: cen.acs.org

Two massive blasts at a hazardous chemical storage warehouse in Tianjin’s harbor killed at least 50 people and injured hundreds of others on Aug. 12. Victims were primarily firefighters and employees of cargo handling firms operating in the Chinese harbor. Beijing Daily Group, a media group based in Beijing, reported that the first explosion had a force equivalent to 3 tons of TNT. The second blast, far larger, represented the equivalent of 21 tons of TNT. Chinese state media reported that windows were shattered on buildings miles away from the accident. Chinese TV news showed images of huge plumes of flames shooting into the sky. The accident occurred in Binhai New Area at the company Ruihai Logistics, a freight handler that according to state media reports is authorized to manage dangerous goods. Authorities took in several of the company’s employees for questioning. The firm’s website became inaccessible after the blasts. With a population of 15 million people, Tianjin is one of four cities directly managed by China’s national government. In a statement, Tianjin’s government said China’s President Xi Jinping had taken control of the situation. Xi issued several directives, notably ordering that the fire be rapidly put down and that those responsible be severely punished. In an account on the Chinese website Weibo, Tianjin’s fire department said it deployed 143 engines and 1,000 firefighters to control the fire, but that it didn’t know the nature of the chemicals involved in the disaster. According to Chinese media, several firefighters died and others are unaccounted for. Tianjin is home to some of China’s top universities, including Nankai University and Tianjin University (TJU). Jay Siegel, dean of the School of Pharmaceutical Science & Technology at TJU, tells C&EN that students and staff at his school are safe because the school is in the center of Tianjin, more than 40 miles away from the port. Binhai is, however, located about 8 miles from the Tianjin Economic-Technological Development Area, home to numerous pharmaceutical and chemical companies. Among international firms with operations in the area, according to TEDA, are Dow Chemical, Eastman Chemical, Cabot Corp., AkzoNobel, and GlaxoSmithKline. Vanessa Craigie, communications manager for Cabot, says the company’s plant is in an industrial park 20 km from the chemical warehouse and was not impacted by the explosion. “To our knowledge, none of our employees or their families were affected by the explosion,” she tells C&EN. “We are continuing to check in on each employee individually to confirm.”


Nor N.M.,Ritsumeikan University | Ma S.,Ritsumeikan University | Ma S.,Tianjin University
Bioinspiration and Biomimetics | Year: 2014

This paper presents a locomotion control based on central pattern generator (CPG) of a snake-like robot. The main point addressed in this paper is a method that produces a smooth transition of the body shape of a snake-like robot. Body shape transition is important for snake-like robot locomotion to adapt to different space widths and also for obstacle avoidance. By manipulating the phase difference of the CPG outputs instantly, it will results in a sharp point or discontinuity which lead to an unstable movement of the snake-like robot. To tackle the problem, we propose a way of controlling the body shape: by incorporating activation function in the phase oscillator CPG model. The simplicity of the method promises an easy implementation and simple control. Simulation results and torque analysis confirm the effectiveness of the proposed control method and thus, can be used as a locomotion control in various potential applications of a snake-like robot. © 2014 IOP Publishing Ltd.


Fu Y.B.,Keele University | Xie Y.X.,Tianjin University
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences | Year: 2012

The problem of localized bulging in inflated membrane tubes shares the same features with a variety of other localization problems such as formation of kink bands in fibrereinforced composites and layered structures. This type of localization is known to be very sensitive to imperfections, but the precise nature of such sensitivity has not so far been quantified. In this paper, we study effects of localized wall thinning/thickening on the onset of localized bulging in inflated membrane tubes as a prototypical example. It is shown that localized wall thinning may reduce the critical pressure or circumferential stretch by an amount of the order of the square root of maximum wall thickness reduction. As a typical example, a 10 per cent maximum wall thinning may reduce the critical circumferential stretch by 19 per cent. This square root law complements the wellknown Koiter's two-thirds power law for subcritical periodic bifurcations. The relevance of our results to mathematical modelling of aneurysm formation in human arteries is also discussed. This journal is © 2012 The Royal Society.


Liu W.-H.,Tianjin University | Xu X.-C.,Huazhong University of Science and Technology | Kouhpaenejad A.,University of Nevada, Las Vegas
Computers and Industrial Engineering | Year: 2013

In the design of the revenue-sharing contract, it is critical to determine a rational revenue-sharing coefficient which affects the coordination and stability of supply chain. In order to improve the existing system, one should take into account that the current revenue-sharing coefficient study only figures out its range rather than the specific value. This paper investigates the fairest revenue-sharing coefficient when the logistics service integrator and the functional logistics service provider implement revenue-sharing contract under stochastic demand condition; by focusing on a two-echelon logistics service supply chain composed of a logistics service integrator and a functional logistics service provider. Taken into consideration the non-storage property of logistics service supply chain, this paper establishes a Stackelberg game model by giving priority to the logistics service integrator. The interval of the revenue-sharing coefficient is obtained by revenue-sharing contract mechanism. Based on the principle of profit distribution equity, a fair entropy function is introduced and a non-linear programming model for solving the fairest revenue-sharing coefficient is established. Furthermore, this method is extended to a three-echelon logistics service supply chain composed of a logistics service integrator, a functional logistics service provider, and a logistics subcontractor. It is assumed that the logistics subcontractor fully commits to the logistics capacity of the functional logistics service provider and consequently a non-linear programming model is constructed to solve the fairest revenue-sharing coefficient of a three-echelon logistics service supply chain under stochastic demand condition. The results exemplifies that the proposed method can find out the fairest revenue-sharing coefficient in a two-echelon and a three-echelon logistics service supply chain, which provides an approach to revenue-sharing contract study. © 2013 Elsevier Ltd. All rights reserved.


Qin Y.,Tianjin University | Qin Y.,Johns Hopkins University | Chen Z.,Tianjin University | Wang X.,Tianjin University
Journal of Constructional Steel Research | Year: 2014

Two analytical models are presented to predict the flexural and shear strengths of through-diaphragm connections between concrete-filled rectangular steel tubular (CFRST) columns and steel beams, respectively. The first phase of this research program was to assess the moment transfer mechanism at the through-diaphragm connections using the analytical yield line method, which accounts for the influence of the axial load on the moment transfer in panel zone. The use of the proposed theoretical equations led to good agreement between predicted and experimentally measured strength. As the second phase of the research program, an analytical model for shear strength was presented according to the simplified trilinear shear-deformation relationship for connections. A theoretical method was proposed to evaluate the shear strength of the concrete compression strut at the yielding point of the steel tube. In addition, the contribution of steel frame mechanism in the panel zone was taken into account in the proposed model. Excellent agreement was found between theoretical and experimental results for both yield and ultimate shear strengths for connections. © 2014 Elsevier Ltd.


Qin Y.,Tianjin University | Qin Y.,Johns Hopkins University | Chen Z.,Tianjin University | Wang X.,Tianjin University
Journal of Constructional Steel Research | Year: 2014

The seismic performance of a new internal-diaphragm connection is investigated in this study. The new connection effectively alleviates the stress and strain concentration at the beam-ends and largely moves the plastic hinges away from the column face by utilizing horizontal stiffeners to form tapered beam flanges. This paper reports on an investigation into the cyclic behavior of internal-diaphragm connections to concrete filled tubular (CFT) columns using tapered plates. Two full-scale connections were tested under quasi-static cyclic loading. The strength, stiffness, deformation, ductility, energy dissipation capacity and strain distribution were evaluated at different load cycles. It is shown that the connection configuration provided stable hysteresis behavior with appropriate level of strength and stiffness. The results indicate that this connection can offer ductility and energy dissipation capacity appropriate for its potential application in composite intermediate moment frames in seismic region. © 2014 Elsevier Ltd.


Min F.,Zhangzhou Normal University | Hu Q.,Tianjin University | Zhu W.,Zhangzhou Normal University
International Journal of Approximate Reasoning | Year: 2014

Feature selection is an important preprocessing step in machine learning and data mining. In real-world applications, costs, including money, time and other resources, are required to acquire the features. In some cases, there is a test cost constraint due to limited resources. We shall deliberately select an informative and cheap feature subset for classification. This paper proposes the feature selection with test cost constraint problem for this issue. The new problem has a simple form while described as a constraint satisfaction problem (CSP). Backtracking is a general algorithm for CSP, and it is efficient in solving the new problem on medium-sized data. As the backtracking algorithm is not scalable to large datasets, a heuristic algorithm is also developed. Experimental results show that the heuristic algorithm can find the optimal solution in most cases. We also redefine some existing feature selection problems in rough sets, especially in decision-theoretic rough sets, from the viewpoint of CSP. These new definitions provide insight to some new research directions. © 2013 Elsevier Inc. All rights reserved.


Xia C.,Tianjin University | Xia C.,Tianjin Polytechnic University | Wang Y.,Tianjin University | Shi T.,Tianjin University
IEEE Transactions on Industrial Electronics | Year: 2013

A strategy based on finite-state model predictive control is proposed for permanent-magnet brushless dc motors (BLDCMs) to reduce commutation torque ripple. The main contribution is a detailed description of the algorithm design process applied to BLDCM for commutation torque ripple minimization, which points out that the optimal conduction status is directly selected and the exact duration of each conduction status is not required in control process. This method proposes a unified approach for suppressing commutation torque ripple over the entire speed range without distinguishing high speed and low speed and overcomes the difficulties of commutated-phase-current control, avoiding complex current controllers or modulation models. A discrete-time noncommutated-phase- current predictive model of BLDCM during commutation is established. According to the predefined cost function, the optimal switching state is directly selected and applied during the next sampling period so as to make the slope rates of incoming and outgoing phase currents match in the course of commutation, thus ensuring the minimization of commutation torque ripple. The simulation and experiment results show that the proposed method can effectively reduce commutation torque ripple within the whole speed range and achieve good performance in minimizing commutation torque ripple in both dynamic and steady states. © 2012 IEEE.


Wu Y.-T.,National Cheng Kung University | Siegel J.S.,University of Zürich | Siegel J.S.,Tianjin University
Topics in Current Chemistry | Year: 2014

This chapter summarizes the synthesis, physical properties, structure, and crystal packing of buckybowls. Buckybowls exemplify an intermediate class of polynuclear aromatic compounds between the closed-shell fullerenes and the flat extended arrays of graphene. These warped sheets can be seen as fragments of fullerenes or the end cap of single-walled carbon nanotubes; and, their curvature endows them with physical properties distinct from flat polynuclear hydrocarbons, which opens up unique possibilities for molecular bowls in various organic materials applications. © Springer-Verlag Berlin Heidelberg 2012.


Luo H.,Tianjin University | Zhang C.-T.,Tianjin University | Gao F.,Tianjin University | Gao F.,SynBio Research Platform
Frontiers in Microbiology | Year: 2014

DNA replication is one of the most basic processes in all three domains of cellular life. With the advent of the post-genomic era, the increasing number of complete archaeal genomes has created an opportunity for exploration of the molecular mechanisms for initiating cellular DNA replication by in vivo experiments as well as in silico analysis. However, the location of replication origins (oriCs) in many sequenced archaeal genomes remains unknown. We present a web-based tool Ori-Finder 2 to predict oriCs in the archaeal genomes automatically, based on the integrated method comprising the analysis of base composition asymmetry using the Z-curve method, the distribution of origin recognition boxes identified by FIMO tool, and the occurrence of genes frequently close to oriCs. The web server is also able to analyze the unannotated genome sequences by integrating with gene prediction pipelines and BLAST software for gene identification and function annotation. The result of the predicted oriCs is displayed as an HTML table, which offers an intuitive way to browse the result in graphical and tabular form. The software presented here is accurate for the genomes with single oriC, but it does not necessarily find all the origins of replication for the genomes with multiple oriCs. Ori-Finder 2 aims to become a useful platform for the identification and analysis of oriCs in the archaeal genomes, which would provide insight into the replication mechanisms in archaea. © 2014 Luo, Zhang and Gao.


Liu G.,CAS Qingdao Institute of Bioenergy and Bioprocess Technology | Liu G.,Tianjin University | Yan B.,Tianjin University | Chen G.,Tianjin University
Renewable and Sustainable Energy Reviews | Year: 2013

In present study, we investigated jet fuel production process, including the crude oil-based conventional process, unconventional oil sources-based process, Fischer-Tropsch synthesis (F-T) process and renewable jet fuel process and analyzed the details of each jet fuel production process. Among these jet fuel production technologies, the F-T synthesis and renewable jet fuel process supply alternative fuels with potential environmental benefit of reduced life cycle greenhouse gas (GHG) emissions and the economic benefits associated with increased fuel availability and lower fuel costs. The F-T synthesis has a major advantage with the possibility of accepting any carbon-based input, which makes it suitable for using a variety of sources such as coal, natural gas and 2nd generation biomass as feedstocks. The renewable jet fuel process such as Bio-Synfining™ (Syntroleum) and Ecofining™ (UOP) as well as C-L™ (Tianjin University) is a low capital cost process of producing high quality synthetic paraffinic kerosene (SPK) from bio-renewable feeds like vegetable oils/fats and waste cooking oils/fats, greases, energy plants of jatropha and algal. The SPK has superior fuel properties to other options available today, with higher cetane number, lower cloud point and lower emissions. © 2013 Published by Elsevier Ltd.


Xia C.,Tianjin University | Xia C.,Tianjin Polytechnic University | Xiao Y.,Tianjin University | Chen W.,Tianjin University | Shi T.,Tianjin University
IEEE Transactions on Industrial Electronics | Year: 2014

In this paper, a current optimization control method for reducing torque ripple in brushless dc drives using integral variable structure control (IVSC) is proposed. The conventional current control method will result in torque ripple if the back electromotive force (EMF) is a nonideal trapezoidal waveform. Based on back-EMF waveforms, the proposed method can optimize the reference currents in both two-phase conduction mode and commutation mode. A Luenberger full-order estimator is designed in order to estimate back-EMF waveforms. During commutation, commutation control with two-phase or three-phase switching mode is employed to reduce torque ripple by controlling the currents of noncommutated windings to trace the optimized reference current, and a three-phase inverter is switched between the two switching modes according to the current rate of change and the difference between the reference current and the actual current. Current controllers using IVSC, which exhibits broadband noise-suppressing capacity and strong robustness against external disturbances, are designed to obtain optimal phase currents, and the experimental results validate the effectiveness of the proposed method. © 1982-2012 IEEE.


Wang W.-M.,Tianjin Polytechnic University | Song J.,Tianjin University | Han X.,Tianjin Polytechnic University | Han X.,Tianjin University
Journal of Hazardous Materials | Year: 2013

In this study, schwertmannite was prepared through a hydrothermal method and used as a new Fenton-like catalyst in the oxidation of phenol by H2O2. The synthesized iron oxide had a formula of Fe8O8(OH)4.5(SO4)1.75 with a weak crystalline structure as well as a high specific surface area of 325.52m2g-1. However, schwertmannite has not been used as a Fenton-like catalyst so far, and its catalytic mechanism in the oxidation of phenol is still unknown. This study confirmed that schwertmannite had a good catalytic activity in the oxidation of phenol via a OH radical mechanism. The free radicals could be generated on the schwertmannite surface by Fe(III) species and in bulk solution by dissolved Fe(III) over a wide pH range. The synthesized schwertmannite also showed a high catalytic ability in the oxidation of phenol in the presence of 0.5M nitrate, chloride or sulfate anions at initial pH 5.0, indicating its potential application in the treatment of high salinity wastewater. In addition, phenol removal percentage could still reach 98% after schwertmannite was successively used for 12 cycles, indicating the good reusability of this catalyst, although a phase transformation of schwertmannite to goethite was observed. © 2013 Elsevier B.V.


Xia C.,Tianjin University | Xia C.,Tianjin Polytechnic University | Yan Y.,Tianjin University | Song P.,Tianjin University | Shi T.,Tianjin University
IEEE Transactions on Industrial Electronics | Year: 2012

A strategy based on internal model control (IMC) is proposed for a matrix converter-based permanent magnet synchronous machine (PMSM) drive system to reduce the adverse impact on drive performance caused by nonlinear output characteristics of matrix converter in the case of input voltage disturbance. Based on the duty-cycle space vectors and small-signal model, the relationship between output and input disturbances is obtained in the synchronous reference frame. Output characteristics of matrix converter are analyzed, and practical considerations are discussed for the purpose of controller design. A general design procedure of the robust IMC controller is described, and parameters of the controller are determined. Numerical simulations and experiments with a 10-kW prototype are carried out. The results show that good dynamic and steady-state performance on PMSM speed regulation is achieved under the unbalanced and distorted input voltage conditions, and the immunity of the drive system is verified to be improved. © 2011 IEEE.


Xu X.,Tianjin University | Zhao T.,Tianjin University | Liu N.,Southwest Jiaotong University | Kang J.,Tianjin University
Applied Energy | Year: 2014

In order to better understand sectoral greenhouse gas (GHG) emissions in China, this study utilized a logarithmic mean Divisia index (LMDI) decomposition analysis to study emission changes from a sectoral perspective. Based on the decomposition results, recently implemented policies and measures for emissions mitigation in China were evaluated. The results show that for the economic sectors, economic growth was the dominant factor in increasing emissions from 1996 to 2011, whereas the decline in energy intensity was primarily responsible for the emission decrease. As a result of the expansion of industrial development, economic structure change also contributed to growth in emissions. For the residential sector, increased emissions were primarily driven by an increase in per-capita energy use, which is partially confirmed by population migration. For all sectors, the shift in energy mix and variation in emission coefficient only contributed marginally to the emissions changes. The decomposition results imply that energy efficiency policy in China has been successful during the past decade, i.e., Top 1000 Priorities, Ten-Key Projects programs, the establishment of fuel consumption limits and vehicle emission standards, and encouragement of efficient appliances. Moreover, the results also indicate that readjusting economic structure and promoting clean and renewable energy is urgently required in order to further mitigate emissions in China. © 2014 Elsevier Ltd.


Wu S.,Hubei University | Liu X.,Hubei University | Yeung K.W.K.,University of Hong Kong | Liu C.,East China University of Science and Technology | And 2 more authors.
Materials Science and Engineering R: Reports | Year: 2014

Increased use of reconstruction procedures in orthopedics, due to trauma, tumor, deformity, degeneration and an aging population, has caused a blossom, not only in surgical advancement, but also in the development of bone implants. Traditional synthetic porous scaffolds are made of metals, polymers, ceramics or even composite biomaterials, in which the design does not consider the native structure and properties of cells and natural tissues. Thus, these synthetic scaffolds often poorly integrate with the cells and surrounding host tissue, thereby resulting in unsatisfactory surgical outcomes due to poor corrosion and wear, mechanical mismatch, unamiable surface environment, and other unfavorable properties. Musculoskeletal tissue reconstruction is the ultimate objective in orthopedic surgery. This objective can be achieved by (i) prosthesis or fixation device implantation, and (ii) tissue engineered bone scaffolds. These devices focus on the design of implants, regardless of the choice of new biomaterials. Indeed, metallic materials, e.g. 316L stainless steel, titanium alloys and cobalt chromium alloys, are predominantly used in bone surgeries, especially in the load-bearing zone of prostheses. The engineered scaffolds take biodegradability, cell biology, biomolecules and material mechanical properties into account, in which these features are ideally suited for bone tissue repair and regeneration. Therefore, the design of the scaffold is extremely important to the success of clinical outcomes in musculoskeletal surgeries. The ideal scaffolds should mimic the natural extracellular matrix (ECM) as much as possible, since the ECM found in natural tissues supports cell attachment, proliferation, and differentiation, indicating that scaffolds should consist of appropriate biochemistry and nano/micro-scale surface topographies, in order to formulate favorable binding sites to actively regulate and control cell and tissue behavior, while interacting with host cells. In addition, scaffolds should also possess a similar macro structure to what is found in natural bone. This feature may provide space for the growth of cells and new tissues, as well as for the carriers of growth factors. Another important concern is the mechanical properties of scaffolds. It has been reported that the mechanical features can significantly influence the osteointegration between implants and surrounding tissues, as well as cell behaviors. Since natural bone exhibits super-elastic biomechanical properties with a Young's modulus value in the range of 1-27 GPa, the ideal scaffolds should mimic strength, stiffness and mechanical behavior, so as to avoid possible post-operation stress shielding effects, which induce bone resorption and consequent implant failure. In addition, the rate of degradation and the by-products of biodegradable materials are also critical in the role of bone regeneration. Indeed, the mechanical integrity of a scaffold will be significantly reduced if the degradation rate is rapid, thereby resulting in a pre-matured collapse of the scaffold before the tissue is regenerated. Another concern is that the by-products upon degradation may alter the tissue microenvironment and then challenge the biocompatibility of the scaffold and the subsequent tissue repair. Therefore, these two factors should be carefully considered when designing new biomaterials for tissue regeneration. To address the aforementioned questions, an overview of the design of ideal biomimetic porous scaffolds is presented in this paper. Hence, a number of original engineering processes and techniques, including the production of a hierarchical structure on both the macro- and nano-scales, the adjustment of biomechanical properties through structural alignment and chemical components, the control of the biodegradability of the scaffold and its by-products, the change of biomimetic surface properties by altering interfacial chemistry, and micro- and nano-topographies will be discussed. In general, the concepts and techniques mentioned above provide insights into designing superior biomimetic scaffolds for bone tissue engineering. © 2014 Elsevier B.V.


Zhao Y.,Zhejiang University | Xiang X.,Zhejiang University | Li W.,Zhejiang University | He X.,Zhejiang University | And 2 more authors.
IEEE Transactions on Power Electronics | Year: 2013

An advanced symmetrical voltage quadrupler rectifier (SVQR) is derived in this paper to serve as the secondary rectification topology, which helps to extend the converter voltage gain and reduce the output diode voltage stresses. The output voltage is four times of the conventional full-bridge voltage rectifier with the same transformer ratio, which benefits to reduce the turns ratio of the transformer and decrease the parasitic parameters. Also, low voltage-rated diodes with high switching performance can be applied to improve the efficiency. Meanwhile, all the diodes in SVQR have the same voltage and current stresses, which simplifies the thermal design. Furthermore, two output electrolytic capacitors are connected in series to share the high output voltage, and the voltage balance can be realized naturally without any additional voltage-sharing scheme. A clear picture is made in this paper to give a general framework and universal applications for the derived SVQRs for high step-up and high output voltage conversion systems. A dual boost converter is used as an example to demonstrate the clear advantages of the derived SVQRs. © 2012 IEEE.


Qiao Z.,Tianjin University | Shi T.,Tianjin University | Wang Y.,Aviation Industry Corporation of China | Yan Y.,Tianjin University | And 3 more authors.
IEEE Transactions on Industrial Electronics | Year: 2013

This paper proposes a novel sliding-mode observer (SMO) to achieve the sensorless control of permanent-magnet synchronous motor (PMSM). An observer is built according to the back electromotive force (EMF) model after the back EMF equivalent signal is obtained. In this way, not only are low-pass filter and phase compensation module eliminated, but also estimation accuracy is improved. Numerical simulations and experiments with an 11-kW low-speed PMSM are carried out. The results demonstrate that the novel SMO can effectively estimate rotor position and speed and achieve good static and dynamic performance. © 2012 IEEE.


Xia C.,Tianjin University | Xia C.,Tianjin Polytechnic University | Song P.,Tianjin Design and Research Institute of Electrical Drive | Shi T.,Tianjin University | Yan Y.,Tianjin University
IEEE Transactions on Industrial Electronics | Year: 2013

The unstable oscillation of autonomous dynamic system of a matrix converter (MC) is studied based on nonlinear dynamic theory, and its chaotic characteristic is analyzed. Analysis based on the fundamental-harmonic nonlinear state equations shows that the system loses stability via a Hopf bifurcation. The behavior of the system near the critical power is examined through simulation. The trajectories obtained by the fundamental-harmonic nonlinear state equations show some typical chaotic characteristics such as extreme sensitivity to initial values and self-similarity. Power density spectrum and Lyapunov exponents of the MC are obtained from simulation results. Finally, the trajectories drawn based on experimental data show some behaviors very similar to those from simulation results, which implies a possible chaotic status in the electrical drive system fed by MC. © 2012 IEEE.


Song Z.,Tianjin University | Xia C.,Tianjin University | Xia C.,Tianjin Polytechnic University | Liu T.,Tianjin University
IEEE Transactions on Industrial Electronics | Year: 2013

A predictive current controller with an extended-state observer (ESO) is proposed for grid integration of wind energy systems. In each sampling period, the proposed strategy calculates the converter switching time that minimizes a cost function defined as a sum of squared current errors, leading to constant switching frequency. To achieve excellent dynamic performance, the impact of sampling delay is analyzed, and detailed compensation methods are proposed. In addition, an ESO is constructed to suppress parameter variations and modeling errors, which affect the performance of the controller. The parameter tuning and the stability of the observer are analyzed. The proposed strategy not only presents rapid dynamic response due to the use of the predictive current controller but also possesses robust control performance as a result of the observation algorithm. Simulation and experimental results are given to validate the effectiveness of the proposed solution. © 2012 IEEE.


Mu H.,CAS Changchun Institute of Applied Chemistry | Pan L.,Tianjin University | Song D.,University of Massachusetts Amherst | Li Y.,CAS Changchun Institute of Applied Chemistry | Li Y.,Tianjin University
Chemical Reviews | Year: 2015

A study is conducted to investigate relationships between catalyst structures and catalytic properties during the use of neutral nickel catalysts for olefin homo- and copolymerization. Extensive investigations on neutral nickel catalysts have been conducted. Research has mainly focused on salicylaldimine frameworks due to their amenability to structural modifications. These novel catalysts have been used in olefin polymerization and copolymerization under various conditions. Studies have also been carried out on the functions of the additional stabilizing ligands and the electronic or steric effects of substituents.


Xia C.,Tianjin University | Xia C.,Tianjin Polytechnic University | Shao H.,Tianjin University | Zhang Y.,Tianjin University | He X.,Zhejiang University
IEEE Transactions on Industrial Electronics | Year: 2013

Neutral-point (NP)-clamped three-level inverter, which is a widely used topology of multilevel converters, suffers from the NP voltage drift as its main technical drawback. The nearest-three-virtual-vector (NTV2) modulation method can control the NP voltage balance for any load over the full range of inverter output voltage. However, compared with the nearest-three-vector (NTV) modulation method, NTV2 increases the switching frequency. This paper combines NTV2 with NTV, and the two methods are used alternately in a fundamental cycle. The duty-cycle coefficients of the redundant small vectors are analyzed to explore the intervals where NTV can control the NP voltage balance in a fundamental cycle. The proportional parameter, which represents the combination of the two methods in hybrid space vector pulsewidth modulation, can be selected to achieve a high-performance NP balance control and low switching frequency. The steady-and transient-state behaviors of the proposed strategy are analyzed in this paper. The experimental results verify the validity of the proposed strategy. © 1982-2012 IEEE.


Xia C.,Tianjin University | Xia C.,Tianjin Polytechnic University | Zhao J.,Tianjin University | Yan Y.,Tianjin University | Shi T.,Tianjin University
IEEE Transactions on Industrial Electronics | Year: 2014

A novel direct torque control (DTC) strategy using duty cycle optimization is proposed for matrix converter (MC)-based permanent-magnet synchronous motor (PMSM) drive system, which is characterized by low torque ripples, no need for rotational coordinate transformation, and fixed switching frequency. Analytical expressions of change rates of torque and flux of PMSM as a function of MC voltage vectors are derived. An enhanced switching table is established by means of discretization and averaging, in which changes of torque and flux caused by voltage vectors are shown explicitly. Then, the proposed MC-fed DTC algorithm is implemented based on the table. Numerical simulation and experiments with a prototype are carried out. Both simulation and experimental results demonstrate that remarkable torque ripple reduction, more than 30%, has been achieved. As a result, the proposed strategy is proved to be effective in reducing torque ripples for MC-based PMSM drives. © 1982-2012 IEEE.


Ge S.,Tianjin University | Wang H.,Tianjin Electric Power Research Institute
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2013

Based on the system state transition sampling approach, this paper presents a sequential Monte Carlo simulation method for the reliability evaluation of the distribution system including distributed generations (DGs) with high penetration rate. The proposed method can be used to calculate both the generation and the distribution reliability indices. The state transition models of non-power components and DGs are established respectively. The chronological output of wind turbines, photovoltaic arrays and the time varying load as well as the utility grid capacity are all taken into account. The state of charge of battery is simulated by the Kinetic Battery Model (KiBaM) incorporating different battery dispatch strategies. The state space of the system is divided into two categories of the generation states and the distribution states. The system is treated as a distribution system when some non-power component is in its down state, and treated as generation system when all the non-power components are in up states. The validity of the proposed method was demonstrated by a study case. This method can be used for the optimal planning of distribution networks including DGs. © State Grid Electric Power Research Institute Press.


Ji J.,University of Texas at Austin | Ji J.,Tianjin University | Zhang L.L.,University of Texas at Austin | Ji H.,University of Texas at Austin | And 6 more authors.
ACS Nano | Year: 2013

Nanoporous nickel hydroxide (Ni(OH)2) thin film was grown on the surface of ultrathin-graphite foam (UGF) via a hydrothermal reaction. The resulting free-standing Ni(OH)2/UGF composite was used as the electrode in a supercapacitor without the need for addition of either binder or metal-based current collector. The highly conductive 3D UGF network facilitates electron transport and the porous Ni(OH)2 thin film structure shortens ion diffusion paths and facilitates the rapid migration of electrolyte ions. An asymmetric supercapacitor was also made and studied with Ni(OH) 2/UGF as the positive electrode and activated microwave exfoliated graphite oxide ('a-MEGO') as the negative electrode. The highest power density of the fully packaged asymmetric cell (44.0 kW/kg) was much higher (2-27 times higher), while the energy density was comparable to or higher, than high-end commercially available supercapacitors. This asymmetric supercapacitor had a capacitance retention of 63.2% after 10 000 cycles. © 2013 American Chemical Society.


Ji J.,University of Texas at Austin | Ji J.,Tianjin University | Ji H.,University of Texas at Austin | Zhang L.L.,University of Texas at Austin | And 5 more authors.
Advanced Materials | Year: 2013

A Si/graphene composite is drop-casted on an ultrathin-graphite foam (UGF) with three dimensional conductive network. The Si/graphene/UGF composite presents excellent stability and relatively high overall capacity when tested as an anode for rechargeable lithium ion batteries. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Wang Y.,Tianjin University | Shi X.,Tianjin University | Zuo Z.,Tianjin University | Chen M.Z.Q.,University of Hong Kong | Shao Y.,Tianjin University
Nonlinear Analysis: Real World Applications | Year: 2013

This paper is concerned with the finite-time stability problem for switched systems subject to both nonlinear perturbation and impulse effects. The average dwell time approach, combined with the algebraic matrix theory, is utilized to derive a criterion guaranteeing that the state trajectory does not exceed a certain threshold over a pre-specified finite-time interval. The requirement that at least one subsystem should be stable to ensure asymptotic stability is no longer necessary. Moreover, the finite-time stability degree could be positive, which is a relaxed condition for asymptotic stability. A numerical example is presented to illustrate the effectiveness of the proposed method. © 2012 Published by Elsevier Ltd.


Xie M.,Tianjin Research Institute for Water Transport Engineering | Xie M.,Tianjin University
Ocean Modelling | Year: 2011

A three-dimensional numerical model was established to simulate the wave-induced currents. The depth-varying residual momentum, surface roller, wave horizontal and vertical turbulent mixing effects were incorporated as major driving forces. A surface roller evolution model considering the energy transfer, roller density and bottom slope dissipation was developed. The expression of the wave-induced horizontal turbulent mixing coefficient proposed by Larson and Kraus (1991) was extended to three-dimensional form. Plenty of experimental cases were used to validate the established model covering the wave setup, undertow, longshore currents and rip currents. Validation results showed the model could reasonably describe the main characteristics of different wave-induced current phenomena. The incorporation of surface roller for breaking waves should not be neglected in the modeling of surfzone hydrodynamics. The wave-induced turbulent mixing affects the structures of wave-induced current either in horizontal or in vertical directions. Sensitivity analysis of the major calibration parameters in the established model was made and their ranges were evaluated. © 2011 Elsevier Ltd.


Pang Y.,Tianjin University | Yuan Y.,CAS Xi'an Institute of Optics and Precision Mechanic | Li X.,CAS Xi'an Institute of Optics and Precision Mechanic | Pan J.,Tianjin University of Technology and Education
Signal Processing | Year: 2011

While Histograms of Oriented Gradients (HOG) plus Support Vector Machine (SVM) (HOGSVM) is the most successful human detection algorithm, it is time-consuming. This paper proposes two ways to deal with this problem. One way is to reuse the features in blocks to construct the HOG features for intersecting detection windows. Another way is to utilize sub-cell based interpolation to efficiently compute the HOG features for each block. The combination of the two ways results in significant increase in detecting humansmore than five times better. To evaluate the proposed method, we have established a top-view human database. Experimental results on the top-view database and the well-known INRIA data set have demonstrated the effectiveness and efficiency of the proposed method. © 2010 Elsevier B.V. All rights reserved.


Zhu C.-L.,Tianjin University | Zhang F.-G.,Tianjin University | Meng W.,Tianjin University | Nie J.,Tianjin University | And 2 more authors.
Angewandte Chemie - International Edition | Year: 2011

A spiroing reactivity: A series of novel binol-derived P-spiro quaternary phosphonium salts were designed, prepared, and used for the first highly enantioselective amination of benzofuranones (see scheme; binol=1,1-2- binaphthol, Bn=benzyl). An unprecedented mechanism involving the π-π interactions between the substrate and the catalyst was proposed as the primary binding mode on the basis of molecular modelling and DFT calculations. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Zhang B.,Tianjin University | Zhao W.,Tianjin University | Wang D.,University of South Australia
Chemical Science | Year: 2012

In this paper, we have successfully directed self-assembly of colloidal nanoparticles (NPs) of Au and CdTe into perfect hexagonal microflakes or ultralong microwires, via stepwise reducing the electrostatic repulsion potential of neighboring NPs in their dispersions with the help of l-cysteine. The hexagonal microflakes were formed via slow self-assembly of short NP chains, while the ultralong microwires were formed via the fast self-assembly of long NP chains. The microwires were kinetically stable and gradually transformed to flakes during incubation in water. This underlines a pronounced correlation of the shape of the resulting supracrystals with the length of the starting NP chains and their self-assembly kinetics. This correlation should provide a fundamental basis not only for better interpretation and even prediction of shape-controlled crystallization but also for organization of nanoscale building blocks to mesoscopic and macroscopic artificial solids. This journal is © The Royal Society of Chemistry 2012.


Yan K.,Lakehead University | Lafleur T.,Lakehead University | Liao J.,Tianjin University
Journal of Nanoparticle Research | Year: 2013

Different loading of palladium (Pd) nanoparticles were successfully fabricated on multi-walled carbon nanotubes using Pd acetylacetonate as the precursor via a simple liquid impregnation method. The crystal phase, morphology, textural structure and the chemical state of the resulting Pd nanoparticles (Pd/CNT) catalysts were studied and the characterization results indicated that the uniform dispersion of small Pd nanoparticles with the size range of 1.0-4.5 nm was achieved. The synthesized Pd/CNT catalysts exhibited efficient performance for the catalytic hydrogenation of biomass-derived levulinic acid into biofuel γ-valerolactone. In comparison with the commercial 5 wt% Pd/C and the 5 wt% Pd/CNT catalyst prepared by Pd nitrate precursor, much higher activities were achieved, whereas the biofuel γ-valerolactone was highly produced with 56.3 % yield at 57.6 % conversion of levulinic acid on the 5 wt% Pd/CNT catalyst under mild conditions. The catalyst developed in this work may be a good candidate for the wide applications in the hydrogenation. © 2013 Springer Science+Business Media.


Li R.Y.,Tianjin University | Zhang T.,University of Hong Kong | Fang H.H.P.,University of Hong Kong
Bioresource Technology | Year: 2011

This paper reviews the application of molecular techniques in heterotrophic hydrogen production studies. Commonly used molecular techniques are introduced briefly first, including cloning-sequencing after polymerase chain reaction (PCR), denaturing gradient gel electrophoresis (DGGE), terminal-restriction fragment length polymorphism (T-RFLP), fluorescence in situ hybridization (FISH) and quantitative real-time PCR. Application of the molecular techniques in heterotrophic hydrogen production studies are discussed in details, focusing on identification of new isolates for hydrogen production, characterization of microbial compositions in bioreactors, monitoring microbial diversity variation, visualization of microbial distribution in hydrogen-producing granular sludge, and quantification of various microbial populations. Some significant findings in recent hydrogen production studies with the application of molecular techniques are discussed, followed by a research outlook of the heterotrophic biohydrogen field. © 2011 Elsevier Ltd.


Feng N.,Tianjin University | Wang H.J.,University of Delaware | Li M.,Tianjin University
Information Sciences | Year: 2014

With the increasing organizational dependence on information systems, information systems security has become a very critical issue in enterprise risk management. In information systems, security risks are caused by various interrelated internal and external factors. A security vulnerability could also propagate and escalate through the causal chains of risk factors via multiple paths, leading to different system security risks. In order to identify the causal relationships among risk factors and analyze the complexity and uncertainty of vulnerability propagation, a security risk analysis model (SRAM) is proposed in this paper. In SRAM, a Bayesian network (BN) is developed to simultaneously define the risk factors and their causal relationships based on the knowledge from observed cases and domain experts. Then, the security vulnerability propagation analysis is performed to determine the propagation paths with the highest probability and the largest estimated risk value. SRAM enables organizations to establish proactive security risk management plans for information systems, which is validated via a case study. © 2013 Elsevier Inc. All rights reserved.


Ma Z.,Tianjin University | Liu Y.,Tianjin University
Materials Chemistry and Physics | Year: 2011

The in situ X-ray diffraction technique is adopted to determine the degree of reaction between Mg and B at several isothermal temperatures below Mg melting. Based on these isothermal data, a kinetics analysis of MgB2 phase formation during the low-temperature sintering is carried out. It is found that the reaction between Mg and B is controlled by varied mechanisms. In the initial stage, the reaction rate is mainly controlled by a phase boundary reaction mechanism. As the reaction proceeds, the diffusion-limited mechanism gradually becomes dominant. The corresponding activation energy also firstly decreases, and then increases again during the whole reaction process. Combined with the classic solid-sintering theory, the determined kinetics model is valid and consistent with the actual sintering process. © 2010 Elsevier B.V. All rights reserved.


Chen C.,Tianjin University | Zhang Y.,Tianjin University | Ma L.,Tianjin University
Energy and Buildings | Year: 2012

This study puts forward to a comprehensive method to evaluate the environment impact and economic benefit of central heating systems. Three types of residential heating systems are compared about the energy use in one-year operation phase, including waste water heat pump system, coal boiler system and gas boiler system. The system, located in Tianjin City, China, is designed for residential buildings. The comparison is made with respect to cost, environment impact and integrated assessment. The results indicate that according to now power structure, if COP of the heat pump reaches 2.5 but lower than 3, heat pump system shows better environment performance but wastes more money than boiler heating systems. If the COP of the heat pump is above 3, heat pump heating system would have best integrated performance, i.e. it has lower cost and less environmental impact than the other systems. © 2011 Elsevier B.V. All rights reserved.


Chen J.,Tianjin University
Elektronika ir Elektrotechnika | Year: 2013

Many crowd counting methods were proposed in recently years. Most of these methods were implemented by extracting the human silhouette from the background image. But under some conditions it is difficult get a clear background image. In this paper a crowd counting method based on the images difference is proposed, instead of extract silhouette from background, the surveillance was divided into frames. Difference image of two frames is calculated by images subtraction. Then image features were extracted based on difference image and the crowed count is calculated based on these features. Experiment result show that this method is feasible.


Men C.,Tianjin University
Chaos (Woodbury, N.Y.) | Year: 2012

We investigate the propagation of spiking regularity in noisy feedforward networks (FFNs) based on FitzHugh-Nagumo neuron model systematically. It is found that noise could modulate the transmission of firing rate and spiking regularity. Noise-induced synchronization and synfire-enhanced coherence resonance are also observed when signals propagate in noisy multilayer networks. It is interesting that double coherence resonance (DCR) with the combination of synaptic input correlation and noise intensity is finally attained after the processing layer by layer in FFNs. Furthermore, inhibitory connections also play essential roles in shaping DCR phenomena. Several properties of the neuronal network such as noise intensity, correlation of synaptic inputs, and inhibitory connections can serve as control parameters in modulating both rate coding and the order of temporal coding.


Hou L.,Tianjin University
Applied Biochemistry and Biotechnology | Year: 2010

Fermentation properties under the control of multiple genes of industrial Saccharomyces cerevisiae strain are difficult to alter with traditional methods. Here, we describe efficient and reliable genome shuffling to increase ethanol production through the rapid improvement of stress resistance. The strategy is carried out using yeast sexual and asexual reproduction by itself instead of polyethylene glycol-mediated protoplast fusion. After three rounds of genome shuffling, the best performing strain S3-10 was obtained on the special plate containing a high ethanol concentration. It exhibits substantial improvement in multiple stress tolerance to ethanol, glucose, and heat. The cycle of fermentation of S3-10 was not only shortened, but also, ethanol yield was increased by up to 10.96% compared with the control in very-high-gravity (VHG) fermentations. In total, S3-10 possesses optimized fermentation characteristics, which will be propitious to the development of bioethanol fermentation industry. © 2009 Humana Press.


Du P.,Tianjin University | Xu C.,Tianjin University
Expert Review of Proteomics | Year: 2013

In the last two decades, predicting protein subcellular locations has become a hot topic in bioinformatics. A number of algorithms and online services have been developed to computationally assign a subcellular location to a given protein sequence. With the progress of many proteome projects, more and more proteins are annotated with more than one subcellular location. However, multisite prediction has only been considered in a handful of recent studies, in which there are several common challenges. In this special report, the authors discuss what these challenges are, why these challenges are important and how the existing studies gave their solutions. Finally, a vision of the future of predicting multisite protein subcellular locations is given. © 2013 2013 Expert Reviews Ltd.


Zhong S.,Tianjin University | Zhou L.,Tianjin University | Ma S.,Tianjin University | Jia N.,Tianjin University
Transportation Research Part A: Policy and Practice | Year: 2012

It is generally accepted that compliance behavior is affected by many factors. The purpose of this study is to investigate the effects of diverse factors on drivers' guidance compliance behaviors under road condition information shown on graphic variable message sign (VMS), and based on this to find out a better information release mode. The involved data were obtained from questionnaire survey, and ordinal regression was used to analyze the casual relation between guidance compliance behavior and its influencing factors. Based on an overall analysis of conditions in driver's route choice, an accurate method was proposed to calculate the compliance rate. The model testing information indicated that ordinal regression model with complementary log-log being the link function was appropriate to quantify the relation between the compliance rate and the factors. The estimation results showed that age, driving years, average annual mileage, monthly income, driving style, occupation, the degree of trust in VMS, the familiarity with road network and the route choice style were significant determinants of guidance compliance behavior. This paper also compared two different guidance modes which were ordinary guidance mode (M1) and predicted guidance mode (M2) through simulation. The average speed fluctuations and average travel time supported that M2 had better effect in improving traffic flow and balancing traffic load and resource. Some detailed suggestions of releasing guidance information were proposed with the explanation by flow-density curve and variation of traffic flows. These findings are the foundation to design and improve guidance systems by assessing guidance effect and modifying guidance algorithm. © 2012 Elsevier Ltd.


Zhu H.T.,Tianjin University
Nonlinear Dynamics | Year: 2012

This paper investigates the nonzero mean probability density function (PDF) of nonlinear oscillators under additive Poisson impulses. The PDF is governed by the generalized Fokker-Planck- Kolmogorov (FPK) equation which is also called the Kolmogorov-Feller (KF) equation. An exponentialpolynomial closure (EPC) method is adopted to solve the equation. Five examples are considered in numerical analysis to show the effectiveness of the EPC method. The nonzero mean response of nonlinear oscillators is formulated due to either nonlinearity type or nonzero mean amplitude of Poisson impulses. The analysis shows that the PDFs obtained with the EPC method agree with the simulated results when the polynomial order is 4 or 6. This agreement is also observed in the tail regions of the obtained PDFs. The comparison further shows that the nonzero mean PDF of displacement is nonsymmetrically distributed. Comparatively, the PDF of velocity still has a symmetrical distribution pattern when the nonlinearity only exists in displacement. © Springer Science+Business Media B.V. 2012.


Li H.-J.,Tianjin University | Xie J.,Tianjin University
Gongcheng Lixue/Engineering Mechanics | Year: 2011

With the attention on LNG storage tanks increasing and a large number of civil engineering constructions being carried out in cold areas, concrete structures will be widely used in low temperature and ultra-low temperature environments. For LNG cryogenic storage tanks, the concrete structure may be applied to an extreme environment with a temperature of -165°C. Thusly it is necessary to perform systematic researches on the material properties at cryogenic temperatures. The mechanical properties of structural materials under ultra-low temperatures are summarized based on review of a large number of domestic and foreign references. Especially, the mechanical performance of reinforced bars & prestressed reinforcements in ultra-low temperature environment, and the bonding behaviors between reinforcements and concrete at cryogenic temperatures are focused on.


Zhang J.,Tianjin University | Tang W.,Tianjin University
Nonlinear Dynamics | Year: 2012

This paper presents a novel bounded four-dimensional (4D) chaotic system which can display hyperchaos, chaos, quasiperiodic and periodic behaviors, and may have a unique equilibrium, three equilibria and five equilibria for the different system parameters. Numerical simulation shows that the chaotic attractors of the new system exhibit very strange shapes which are distinctly different from those of the existing chaotic attractors. In addition, we investigate the ultimate bound and positively invariant set for the new system based on the Lyapunov function method, and obtain a hyperelliptic estimate of it for the system with certain parameters. © 2011 Springer Science+Business Media B.V.


Tian R.,Tianjin Medical University | Chen J.,Tianjin University | Niu R.,Tianjin Medical University
Nanoscale | Year: 2014

To improve the anti-cancer efficacy and to counteract the side effects of chemotherapy, a variety of drug delivery systems have been invented in past decades, but few of these systems have succeeded in clinical trials due to their respective inherent shortcomings. Recently, low-molecular weight hydrogels of peptides that self-assemble via non-covalent interactions have attracted considerable attention due to their good biocompatibility, low toxicity, inherent biodegradability as well as their convenience of design. Low-molecular weight hydrogels have already shown promise in biomedical applications as diverse as 3D-cell culture, enzyme immobilization, controllable MSC differentiation, wound healing, drug delivery etc. Here we review the recent development in the use of low-molecular weight hydrogels for cancer therapy, which may be helpful in the design of soft materials for drug delivery. This journal is © the Partner Organisations 2014.


Gao Z.-K.,Tianjin University | Jin N.-D.,Tianjin University
Nonlinear Analysis: Real World Applications | Year: 2012

We propose a reliable method for constructing a directed weighted complex network (DWCN) from a time series. Through investigating the DWCN for various time series, we find that time series with different dynamics exhibit distinct topological properties. We indicate this topological distinction results from the hierarchy of unstable periodic orbits embedded in the chaotic attractor. Furthermore, we associate different aspects of dynamics with the topological indices of the DWCN, and illustrate how the DWCN can be exploited to detect unstable periodic orbits of different periods. Examples using time series from classical chaotic systems are provided to demonstrate the effectiveness of our approach. © 2011 Elsevier Ltd. All rights reserved.


Guo T.,Tianjin University | Wang H.,Tianjin University | Zhang S.,Tianjin University
International Journal of Energy Research | Year: 2011

Theoretical analyses of natural and conventional working fluids-based transcritical Rankine power cycles driven by low-temperature geothermal sources have been carried out with the methodology of pinch point analysis using computer models. The regenerator has been introduced and analyzed with a modified methodology considering the considerable variation of specific heat with temperature near the critical state. The evaluations of transcritical Rankine cycles have been performed based on equal thermodynamic mean heat rejection temperature and optimized gas heater pressures at various geothermal source temperature levels ranging from 80 to 120°C. The performances of CO2, a natural working fluid most commonly used in a transcritical power cycle, have been indicated as baselines. The results obtained show: optimum thermodynamic mean heat injection temperatures of transcritical Rankine cycles are distributed in the range of 60 to 70% of given geothermal source temperature level; optimum gas heater pressures of working fluids considered are lower than baselines; thermal efficiencies and expansion ratios (Expr) are higher than baselines while net power output, volume flow rate at turbine inlet (V1) and heat transfer capacity curves are distributed at both sides of baselines. From thermodynamic and techno-economic point of view, R125 presents the best performances. It shows 10% higher net power output, 3% lower V1, 1.0 time higher Expr, and 22% reduction of total heat transfer areas compared with baselines given geothermal source temperature of 90°C. With the geothermal source temperature above 100°C, R32 and R143a also show better performances. R170 shows nearly the same performances with baselines except for the higher V1 value. It also shows that better temperature gliding match between fluids in the gas heater can lead to more net power output. © 2010 John Wiley & Sons, Ltd.


Tian F.,China Institute of Medical Equipment | He C.N.,Tianjin University
Materials Chemistry and Physics | Year: 2010

The synthesis of carbon nanospheres (CNSs) by chemical vapor deposition (CVD) of methane on catalyst of Ni-Al composite powders was reported. The influence factors on the growth morphology of CNSs, such as reaction temperature, reaction time and different carrier gases concerning hydrogen, nitrogen as well as no carrier gas were investigated using transmission electron microscope. The results showed that the reaction temperature had great effect on the structure of CNSs, higher temperature led to high-crystallized CNSs with high purity. The reaction time brought no significant influence to the structure of CNSs, but the average diameter of the CNSs was obviously increased with prolonging the reaction time. Relatively pure CNSs could be obtained with hydrogen as the carrier gas but with poor product rate compared with the CNSs with no carrier gas. Proper amount of CNSs with pure characteristic could be obtained with nitrogen as the carrier gas. Finally, a growth mechanism of dissolution-precipitation-diffusion is proposed for elucidating the growth process of general CNSs. © 2010 Elsevier B.V. All rights reserved.


Guo B.,Tianjin University | Wang R.,Tianjin University | Li Y.,Tianjin University | Li Y.,National Engineering Research Center for Distillation Technology
Fuel | Year: 2011

Gasoline desulfurization is receiving attention worldwide due to the increasing stringent regulations on sulfur content for environmental protection purpose. As conventional hydrotreating technology leads to significant octane number loss and processing costs, the gasoline alkylation desulfurization process, which consists of weighing down the sulfuric compounds by catalytic alkylation with olefins present in the feed and distillation followed by, is a rather attractive way. In this paper, firstly alkylation of thiophenic compounds was researched over macroporous sulfonic resin Amberlyst 35 in methanol presence to increase the selectivity of catalyst, then kinetics of thiophenic sulfurs alkylation in FCC gasoline was researched without and with methanol. Results found that appropriate methanol (≤2 wt.% methanol in model gasoline and ≤1 wt.% methanol in FCC gasoline) could inhibit olefins oligomerization significantly without influence on the conversions of thiophenic compounds. The alkylation of thiophenic sulfurs could be described as pseudo first order reaction regardless of the existence of methanol. The introduction of methanol decreases the reaction rate constant and increases the activation energy of alkylation reactions. © 2010 Elsevier Ltd. All rights reserved.


Wang X.D.,Tianjin University | Zhao L.,Tianjin University | Wang J.L.,Tianjin University
Energy Conversion and Management | Year: 2011

An experimental study is conducted to investigate the performance of a low-temperature solar Rankine cycle system using working fluid R245fa. The experimental installation consists of a flat plate collector, a throttling valve, a working fluid pump and an air cooled condenser, etc. For the typical weather conditions of October in Tianjin, the experiment results show that the highest heat collecting efficiency of the flat plate collector is about 50%. The measured Rankine cycle efficiency of the system is lower than the theoretical value, due to superheating, subcooling of the working fluid and heat loss of the experimental prototype. Based on the experimental results, an internal heat exchanger is proposed in the solar Rankine cycle system using R245fa, which can obviously improve the Rankine cycle efficiency. © 2010 Elsevier Ltd. All rights reserved.


Guo Q.,Tianjin University | Qin X.,Tianjin University
ECS Solid State Letters | Year: 2013

We develop a novel approach to prepare tin oxide (SnO2)/graphene composite as an anode material for lithium ion batteries mainly through an oxidation-reduction reaction between graphene oxide (GO) and SnCl2 2H2O, as well as the promotion and neutralization effect of urea. The SnO2/graphene composite exhibits outstanding Li-battery performance with large reversible capacity and high rate capacity. The first discharge and charge capacities are 2751.4 mAh g?1 and 1254.6 mAh g?1 at the density of 100 mA g?1. After 30 cycles, the reversible discharge capacity still remains at 985.5 mAh g?1. The prepared products can be a promising alternative anode material used for high-storage lithium ion batteries. © 2013 The Electrochemical Society.


Su Y.,Tianjin University | Zhang C.,Tianjin University
Signal Processing | Year: 2011

Steganalysis is the art of detecting the information hidden in the media using steganography. In this paper, a steganalytic method is proposed to detect information hidden in the motion vectors of video bit-streams. Based on the statistical analysis of relative properties, the feature classification technique is adopted to determine the existence of hidden messages. The Support Vector Machine (SVM) is used as the discriminator. The experimental results show that the proposed method can detect the hidden data effectively in motion-vector-based steganography algorithms. © 2011 Elsevier B.V. All rights reserved.


Wang X.,Tianjin University | Lin J.,Tianjin University
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2010

Based on the simplification equivalent network, for the distribution system with distributed generations, a new reliability evaluation method by the Monte Carlo time sequential simulation is presented. After the zone element failure effect table is obtained on the simplification network, the impact of the DGs' stochastic power output, statuses of the devices, and the stochastic capacity of the loads on the distribution system are analyzed and calculated by the Monte Carlo time sequential simulation. By the equivalent network, the ransack processing during the reliability analysis and calculation is reduced significantly, and the repetitive failure analysis is avoided by the method of zone element failure effect table. As a result, the simulation calculation procedure is accelerated. Furthermore, during the stochastic simulation processing, the strategy of synchronous sampling for the statuses of DGs and the network devices is employed. Compared with the traditional methods, the proposed method increases the precision of the simulation and the speed of calculation. The results of the test examples demonstrate the validity and practicability of the new method. © 2010 State Grid Electric Power Research Institute Press.


Guo T.,Tianjin University | Wang H.X.,Tianjin University | Zhang S.J.,Tianjin University
Energy Conversion and Management | Year: 2011

A novel cogeneration system driven by low-temperature geothermal sources was investigated in this study. This system consists of a low-temperature geothermally-powered organic Rankine cycle (ORC) subsystem, an intermediate heat exchanger and a commercial R134a-based heat pump subsystem. The main purpose is to identify appropriate fluids which may yield high PPR (the ratio of power produced by the power generation subsystem to power consumed by the heat pump subsystem) value and QQR (the ratio of heat supplied to the user to heat produced by the geothermal source) value. Performances of the novel cogeneration system under disturbance conditions have also been studied. Results indicate that fluids group presenting higher normal boiling point values shows averagely 7.7% higher PPR values and R236ea and R245ca outstand among the group. ΔTP (pinch temperature difference in heat exchangers) and ηt (turbine efficiency) values play more important roles on the variation of PPR values. QQR values change slightly with various ΔT P, ηt and ηrp (refrigerant pump efficiency) values while the variation range is larger under various geothermal source and heating supply parameters. Smaller ΔTP value, higher ηt value, higher geothermal source parameters and lower heating supply parameters lead to higher PPR values but lower QQR values. © 2011 Elsevier Ltd. All rights reserved.


Fu Y.,Tianjin University | Li M.,Tianjin University | Chen F.,Tianjin University
International Journal of Project Management | Year: 2012

Requirement change is a major source of risk to software development projects. The prediction of requirement changes provides a challenge in software risk management, especially in early stages of software development projects. This paper predicts the risk of change propagation in terms of change propagation probability and change impact. First, the process of software requirement changes is discussed. Then, a probabilistic model based on design structure matrix (DSM) is established to evaluate the risk of change propagation from requirements to software architecture. Furthermore, the proposed model is utilized to estimate the schedule and cost of a software development project. The model supports the prediction of potential risk of change propagation for each component, which is able to accommodate module reorganization to avoid unnecessary redesigns. Thus it helps software project managers make a choice between different architecture candidates based on requirement changes. Finally, the proposed model is verified via computational experiments, in which sensitivity analysis is applied to validate the reliability of the model. © 2011 Elsevier Ltd and IPMA.


Yan L.,Jiangxi Science and Technology Normal University | Chang P.R.,Agriculture and Agri Food Canada | Zheng P.,Jiangxi Science and Technology Normal University | Ma X.,Tianjin University
Carbohydrate Polymers | Year: 2012

The hydrophobicity of carbon nanotubes (CNTs) limits their extensive application. The hydrophilicity and biocompatibility of CNTs can be improved by modifying them with biopolymers. As a natural biopolymer, guar gum (GG) was covalently grafted on the surfaces of multiwall carbon nanotube (MWCNT) to obtain GG-MWCNT composite. Then iron oxide nanoparticles were synthesized on the GG-MWCNT to prepare the magnetic GG-MWCNT-Fe 3O 4. The obtained nanocomposites were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, transmission electron microscopy, ultraviolet-visible (UV-vis) spectroscopy and X-ray diffraction. GG-MWCNT was composed of about 21.6 wt% GG components, which enhanced the dispersion of GG-MWCNT in aqueous solution and also acted as a template for growth of iron oxide nanoparticles. GG-MWCNT-Fe 3O 4 exhibited superparamagnetic with a saturation magnetization (13.3 emu g -1), and good adsorption on neutral red and methylene blue. GG-MWCNT-Fe 3O 4 could be easily separated from the aqueous solution in a magnetic field. © 2011 Elsevier Ltd. All rights reserved.


Dai C.,Tianjin University | Wang Y.,Tianjin University | Hou X.,Tianjin University
Carbohydrate Polymers | Year: 2012

In present work, porous dextran microspheres with good morphology were synthesized by reversed-phase suspension polymerization. Dextran was used as raw material, epichlorohydrin (ECH) as crosslinker, and dimethyl ether of polyethylene glycol (DMPE) as porogen. And porous dextran microspheres were prepared by freezing-drying method. The morphology of the porous dextran microspheres was characterized by the scanning electronic microscope (SEM). The dry and hydrated densities, average pore volume, porosity, hydroxyl content and equilibrium water content were measured. Micropore structure was found on the dextran microspheres. With the increase of porogen amount, the dry density decreased, the hydrated density, the average pore volume, porosity and equilibrium water content initially increased and then decreased, while the hydroxyl content increased. Bovine serum albumin (BSA) was used as an adsorbate model to examine the adsorption behavior of the porous microspheres. The saturated adsorption capacities of these microspheres ranged from 59.1 mg/g to 138.9 mg/g while the amount of porogen increased from 10% to 50%. © 2011 Published by Elsevier Ltd. All rights reserved.


Qin Y.,Tianjin University | Hu M.,Tianjin University | Zhang J.,Tianjin University
Sensors and Actuators, B: Chemical | Year: 2010

Nanowires and nanosheets of tungsten oxide were synthesized by solvothermal method with different tungsten hexachloride (WCl6) concentrations in 1-propanol solvent. The morphology and crystal structure of the tungsten oxide nanostructures were investigated by means of field emission scanning electron microscope, X-ray diffraction and transmission electron microscope. The specific surface area and pore size distribution were characterized by Brunauer-Emmett-Teller gas-sorption measurements. One-dimensional W 18O49 nanowire bundles were synthesized at the WCl 6 concentration of 0.01 M. With the concentration increasing to 0.02 M, the structure of the pure two-dimensional WO3 nanosheets was formed. The NO2 gas sensing properties of W18O 49 nanowires and WO3 nanosheets were investigated at 100 °C up to 250 °C over NO2 concentration ranging from 1 to 20 ppm. Both nanowires and nanosheets exhibit reversible response to NO2 gas at different concentrations. In comparison to WO3 nanosheets, W18O49 nanowire bundles showed a much higher response value and faster response-recovery characteristics to NO2 gas, especially a much quicker response characteristic with response time of 19 s at the concentration of 5 ppm. © 2010 Published by Elsevier B.V.


Zhang N.,Tianjin University | Liu F.-F.,Tianjin University | Dong X.-Y.,Tianjin University | Sun Y.,Tianjin University
Journal of Physical Chemistry B | Year: 2012

Considerable experimental evidence indicates that trehalose can counteract the denaturing effects of urea on proteins. However, its molecular mechanism remains unknown due to the limitations of current experimental techniques. Herein, molecular dynamics simulations were performed to investigate the counteracting effects of trehalose against urea-induced denaturation of chymotrypsin inhibitor 2. The simulations indicate that the protein unfolds in 8 mol/L urea, but at the same condition the protein retains its native structure in the ternary solution of 8 mol/L urea and 1 mol/L trehalose. It is confirmed that the preferential exclusion of trehalose from the protein surface is the origin of its counteracting effects. It is found that trehalose binds urea via hydrogen bonds, so urea molecules are also expelled from the protein surface along with the preferential exclusion of trehalose. The exclusion of urea from the protein surface leads to the alleviation of the Lennard-Jones interactions between urea and the hydrophobic side chains of the protein in the ternary solution. In contrast, the electrostatic interactions between urea and the protein change little in the presence of trehalose because the decrease in the electrostatic interactions between urea and the protein backbone is canceled by the increase in the electrostatic interactions between urea and the charged side chains of the protein. The results have provided molecular explanations for the counteraction of urea-induced protein denaturation by trehalose. © 2012 American Chemical Society.


Huang B.,Tianjin University | Liu F.-F.,Tianjin University | Dong X.-Y.,Tianjin University | Sun Y.,Tianjin University
Journal of Physical Chemistry B | Year: 2012

Protein A from the bacterium Staphylococcus aureus (SpA) has been widely used as an affinity ligand for purification of immunoglobulin G (IgG). The affinity between SpA and IgG is affected differently by salt and pH, but their molecular mechanisms still remain unclear. In this work, molecular dynamics simulations and molecular mechanics Poisson-Boltzmann surface area analysis were performed to investigate the salt (NaCl) and pH effects on the affinity between SpA and human IgG1 (hIgG1). It is found that salt and pH affect the interactions of the hot spots of SpA by different mechanisms. In the salt solution, the compensations between helices I and II of SpA as well as between the nonpolar and electrostatic energies make the binding free energy independent of salt concentration. At pH 3.0, the unfavorable electrostatic interactions increase greatly and become the driving force for dissociation of the SpA-hIgG1 complex. They mainly come from the strong electrostatic repulsions between positively charged residues (H137, R146, and K154) of SpA and the positively charged residues of hIgG1. It is considered to be the molecular basis for hIgG1 elution from SpA-based affinity adsorbents at pH 3.0. The dissociation mechanism is then used to refine the binding model of SpA to hIgG1. The model is expected to help design high-affinity peptide ligands of IgG. © 2011 American Chemical Society.


Wang S.-H.,Tianjin University | Dong X.-Y.,Tianjin University | Sun Y.,Tianjin University
Journal of Physical Chemistry B | Year: 2012

(-)-Epigallocatechin-3-gallate (EGCG) has been proven effective in preventing the aggregation of amyloid β-protein 42 (Aβ42), and the thermodynamic interactions between Aβ42 and EGCG have been studied in our previous work (J. Phys. Chem. B 2010, 114, 11576). Herein, to further probe the interactions between different regions of Aβ42 and EGCG, three Aβ42 fragments (i.e., Aβ1-16, Aβ1-30, and Aβ31-42) were synthesized, and the thermodynamic interactions between each of the fragments and EGCG at different EGCG and salt concentrations were investigated by isothermal titration calorimetry. The results indicate that, although hydrogen bonding and hydrophobic interaction are both involved in the interactions between Aβ42 and EGCG, hydrogen bonding mainly happens in Aβ1-16 while hydrophobic interaction mainly happens in Aβ17-42. It is found that when Aβ42 and its fragments are saturated by EGCG, their thermodynamic parameters have linear relationships. The saturated binding stoichiometry (Ns) for Aβ42 is the sum of the Ns values for Aβ1-30 and Aβ31-42, while ΔHs, ΔSs, and ΔGs for Aβ42 are half the sum of the values for Aβ1-30 and Aβ31-42. The result suggests that there are no specific interactions and binding sites in the Aβ42 and EGCG binding. The orders of ΔHs and TΔSs values for the Aβ fragments are determined as Aβ17-42 > Aβ31-42 > Aβ1-30 > Aβ1-16. Moreover, there is significant enthalpy-entropy compensation in the binding of EGCG to Aβ42 and its fragments, resulting in insignificant change of ΔG with the change of the solution environment. The research has shed new light on the molecular mechanisms of the interactions between EGCG and Aβ42. © 2012 American Chemical Society.


Wei Y.Y.,Tianjin University
Zhongguo zhen jiu = Chinese acupuncture & moxibustion | Year: 2010

OBJECTIVE: To investigate the specificity of the acupoints and related factors on acupuncture effects. METHODS: The rat model of cerebral median artery occlusion (MCAO) was established with thread ligation according to Zea-Longa method. The acupoint group and the non-acupoint group were stimulated by acupuncture with 9 different parameters (marked group No. I - VI) combined by frequency (60 Hz, 120 Hz, 180 Hz) and time (5 s, 60 s, 180 s). The acupoint of "shuigou" (GV 26) was selected for the acupoint group, the fixed point which was at a distance of 10 mm from the iliac crest below the ribs in the affected side. The acupuncture effect was evaluated with the percentage of brain infarct area after TTC dyeing. RESULTS: (1) Acupoint groups could obviously reduce the brain infarction area in MCAO rats. Under 9 intervention parameters, acupoint groups had much more effectiveness tendency than that of the non-acupoint groups. (2) Acupoint group VI was the most effective in reducing the brain infarction area among 9 acupuncture parameter groups. CONCLUSION: (1) Acupoint has specificity effect on reduction of brain infarct area in MCAO rats. (2) Acupoint group VI (180 Hz; 5 s) could significantly reduce the percentage of cerebral infarction area by TTC dyeing.


Wang L.,Tianjin University | He F.,Tianjin University | Wan Y.,Tianjin University
Journal of Alloys and Compounds | Year: 2011

Magnetic carbon fiber coated with Fe-Co alloy was prepared by electroplating at 25 °C for 5 min. The obtained magnetic coatings show sheet-like morphology and the crystal structure of the uniform coating is Co3Fe7 with a thickness of about 0.5 μm. The saturation magnetization of the magnetic carbon fiber reaches 31.5 emu/g with a coercivity of 87.1 Oe. The complex permittivity and permeability of magnetic carbon fiber/paraffin (30 wt%) composite were measured in the 2-18 GHz frequency range. The reflection loss below -10 dB covers the whole frequency range while below -20 dB the absorption frequency bandwidth is 6.8 GHz, and the minimum value is -48.2 dB at a coating thickness of 1.7 mm. Magnetic carbon fiber exhibits excellent electromagnetic wave absorption properties. © 2010 Elsevier B.V. All rights reserved.


Wang Y.,Tianjin University | Zhao T.,Tianjin University
Ecological Indicators | Year: 2015

A large accumulation of carbon dioxide and other greenhouse gases have caused great concern around the world. A great deal of general literature focus on the impact factors of CO2 emissions at the national, regional and city levels. However, there is little specific guidance on regional difference in CO2 emissions. In this paper, 30 provincial-level administrative units of China are divided into three different levels of economic development regions according to the GDP per capita from 1997 to 2012. A STIRPAT (Stochastic Impacts by Regression on Population, Affluence and Technology) model is used to examine the impact factors on energy-related CO2 emissions, including population, economic level, technology level, urbanization level, industrialization level and foreign trade degree. The results indicate that the effect of energy intensity is the greatest in highly developed region. Nevertheless, the impact of urbanization, industry structure and foreign trade degree in under developed region is higher than the other two regions. Population and GDP per capita have greater effect on carbon emissions in developing region than the others. Finally, differentiated measures for CO2 reductions should be adopted according to local conditions of different regions. © 2014 Elsevier Ltd.


Zhou Y.,Tianjin University | Wang Z.,Tianjin University | Liu C.,Tianjin University
Catalysis Science and Technology | Year: 2015

CO oxidation is one of the most extensively investigated reactions in the field of heterogeneous catalysis because of its importance in both environmental protection and fundamental studies. CO oxidation over Pd catalysts has attracted significant attention not only because of its high activity. It is an excellent model reaction for the study of the structure, metal-support interaction and other issues of various Pd-based catalysts with many important applications beyond CO oxidation. It is simple and can be easily operated with low cost. Density functional theoretical studies can be directly and easily combined with experimental investigations. Carbon monoxide itself is an excellent probe molecule for catalyst characterization. In this perspective, we summarize the progress in the study of CO oxidation over Pd-based catalysts. Various influencing factors will be discussed. Future challenges and opportunities will be addressed. © The Royal Society of Chemistry 2015.


Hua M.-Q.,Tianjin University | Cui H.-F.,Tianjin University | Wang L.,Tianjin University | Nie J.,Tianjin University | Ma J.-A.,CAS Shanghai Institute of Organic Chemistry
Angewandte Chemie - International Edition | Year: 2010

(Figure Presented) Towards perfect asymmetric catalysis: When binol-derived N-spiro quaternary ammonium salts were used as phase-transfer catalysts in the conjugate addi-tion of nitroalkanes to chalcones and its analogues, an intriguing reversal of enan-tioselectivity was observed. Novel chiral catalysts have been designed and synthe-sized (see structure). © 2010 Wiley-VCH Verlag GmbH & Co. KGaA.


Han Y.,Tianjin University | Bai T.,Tianjin University | Liu Y.,Tianjin University | Zhai X.,Tianjin University | Liu W.,Tianjin University
Macromolecular Rapid Communications | Year: 2012

In this study, we demonstrate that dipole-dipole interaction can be employed to not only tremendously enhance the mechanical properties of hydrogel, but also impart the gel to an amazing ability to memorize two temporary shapes. Cross-linked hydrogels synthesized by copolymerization of acrylonitrile, a dipole-dipole containing monomer and hydrophilic comonomer are shown to exhibit triple shape memory (SM) triggered by the dynamic association and dissociation of dipole-dipole pairing between cynao groups uniquely responding to zinc ion species and concentration. This approach contributes to design and fabrication of novel SM hydrogels in a distinct way from conventional SM materials. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Liu Y.,Tianjin University | Bai Y.,Tianjin University
Resources, Conservation and Recycling | Year: 2014

Despite the wealth of information concerning environmental awareness and the behavior of firms, there is little empirical research on the awareness and behavior of firms in developing the circular economy. The study employed a questionnaire survey and in-depth interviews with 157 firms from manufacturing clusters in China. Results indicated that the firms had a relatively good understanding about the circular economy and its values and had a strong willingness to operate a circular economy, but this was not indicative of enthusiastic behavior. A striking "gap" existed between a firm's awareness and its actual behavior in developing a circular economy. Reasons for the gap are explored mainly based on the results of interviews. Finally, recommendations for overcoming the gap between the awareness and behavior are suggested. © 2014 Elsevier B.V.


Shen Q.,Aberystwyth University | Zhao R.,Tianjin University
IEEE Transactions on Systems, Man, and Cybernetics Part A:Systems and Humans | Year: 2011

This paper presents an extension of the assumption-based truth maintenance system (ATMS), called credibilistic ATMS, which has the capability to cope with uncertain justifications and assumptions. Such justifications and assumptions are represented and dealt with in the framework of credibility theory. Important concepts in ATMS such as environments, labels, logical consequences, and consistency are redefined by the use of credibility measure. Based on these concepts, the label-updating procedure of the classical ATMS is extended, allowing effective computation of the membership function of any node within the network and that of its supporting environment. In addition, the contradictory environments can be captured with respect to their inconsistency degrees. This paper is compared to the most relevant existing research (i.e., ATMS using necessity as the truth value and ATMS using possibility as the truth value), demonstrating the significant improvements made. This paper also presents an illustrative application of credibilistic ATMS in supporting automated construction of domain models. © 2006 IEEE.


Wang J.,Tianjin University | Yuan Y.,Tianjin University | Xiong R.,Tianjin University | Zhang-Negrerie D.,Tianjin University | And 2 more authors.
Organic Letters | Year: 2012

The reaction of phenyliodine bis(trifluoroacetate) (PIFA) with a series of anilides 1 (E = CO 2Et) in CF 3CH 2OH was found to give 3-hydroxy-2-oxindole derivatives 2, while that with various anilides 1′ (E = CON(R 4)Ar) afforded the C 2-symmetric or unsymmetric spirooxindoles 3. These processes feature a metal-free oxidative C(sp 2)-C(sp 3) bond formation, followed by oxidative hydroxylation or spirocyclization. © 2012 American Chemical Society.


Yu L.-L.,Tianjin University | Dong X.-Y.,Tianjin University | Sun Y.,Tianjin University
Journal of Chromatography A | Year: 2012

We have previously found that addition of charged particles in a refolding solution can greatly increase the refolding yield of like-charged proteins. Herein, porous anion exchangers of different charged group densities, ligand chemistries, pore sizes and particle sizes were prepared with Sepharose FF gel for studying their effects on the oxidative refolding of like-charged lysozyme. We found that charge density had significant contribution to the enhancing effects on lysozyme refolding. At low resin concentration range (<0.04-0.1. g/mL), the refolding yield increased with increasing charged group density and resin concentration. The yield then reached a plateau at a critical resin concentration; the higher the charge density, the lower the critical resin concentration. This implies that gel particles of higher charge density were favorable to offer higher refolding yield at lower added concentrations. In the gel concentration range in which refolding yield has reached plateau, there existed an optimum charge density that gave the highest refolding yield. It was attributed to the electrostatic repulsion effect of the charged groups on the like-charged protein, which reduced the accessible pore volume for the protein. At the same charge density, the refolding yield was independent of ligand chemistry, but a polyelectrolyte group of higher molecular weight was more suitable for grafting the gel to prepare matrices of high charge density. The resins of smaller size exhibited better facilitating effect, and the microporous resin was better than that with superpores. The research is expected to help design more effective charged materials for facilitating protein refolding. © 2011 Elsevier B.V..


Bai N.,University of Central Florida | Bai N.,Infinera Corporation | Li G.,Infinera Corporation | Li G.,Tianjin University
Optics Express | Year: 2014

The equalizer tap length requirement is investigated analytically and numerically for differential modal group delay (DMGD) compensated fiber link with weakly random mode coupling. Each span of the DMGD compensated link comprises multiple pairs of fibers which have opposite signs of DMGD. The result reveals that under weak random mode coupling, the required tap length of the equalizer is proportional to modal group delay of a single DMGD compensated pair, instead of the total modal group delay (MGD) of the entire link. By using small DMGD compensation step sizes, the required tap length (RTL) can be potentially reduced by 2 orders of magnitude. © 2014 Optical Society of America.

Loading Tianjin University collaborators
Loading Tianjin University collaborators