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.

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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.

Patent
Tianjin University | Date: 2016-09-28

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.

Patent
Tianjin University | Date: 2014-09-22

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.

Zheng Z.,Tianjin University of Technology | Wang X.,Tianjin University of Technology | Mi W.,Tianjin University
Carbon | Year: 2017

The electric field effects on the electronic structure of g-C2N/XSe2 (X = Mo, W) heterostructures are investigated by first-principles calculations. The g-C2N/MoSe2 heterostructure is an indirect semiconductor at an electric field from −0.1 to 0.3 V/Å. The band gap is 0.66, 0.54, 0.45, 0.39 and 0.34 eV, which almost changes linearly with the electric field. The maximum spin splitting at K point is 188 meV. The g-C2N/WSe2 heterostructure is still an indirect semiconductor at an electric field of −0.1 and 0 V/Å. At an electric field from 0.1 to 0.3 V/Å, the heterostructure with the valence band at Fermi level is a p-type semiconductor, where the band gap is 0.32, 0.26, 0.19, 0.12 and 0.06 eV and the maximum spin splitting at K point is 444 meV. Moreover, near Fermi level, the conduction band mainly comes from monolayer g-C2N, but the valence band comes from XSe2. Our results can bring much significant information on the potential applications in spintronic and field effect devices. © 2017 Elsevier Ltd

Zhang X.,Tianjin University | Zhang Y.,Tianjin University
Pacific Asia Conference on Information Systems, PACIS 2016 - Proceedings | Year: 2016

It is crucial to stimulate Individual Creativity(IC) for organizations to be innovative, as well as higher education. The booming of information and communication technology (e.g., Slack) supports the opportunity to figure out whether higher education in e-learning environment has potential for enhancing participants' individual creativity. Besides, as an essential antecedent of IC, we believe that, despite transformational leadership still plays an important role in IC, the mechanism of how it works is changing. Hence, adopting a perspective of Social Exchange Theory (SET), we test the moderate effect of Transformational Leadership (TL) on IC through knowledge sharing (KS). We design an 8-week course where WeChat and Slack are required to use as auxiliary tools for teams to complete a project online. 2 rounds of survey have been done to collect data (at 4th week and 8th week). Results show that KS has a positive effect on IC, and TL has a significant moderate effect on the relationship between extrinsic motivation and KS. Implications for theory and practice, and limitations are also given.

Zhang X.,Tianjin University | Yan X.,Tianjin University
Pacific Asia Conference on Information Systems, PACIS 2016 - Proceedings | Year: 2016

Nowadays, the booming of Mobile Healthcare Applications (MHAs) provides several new kinds of health services and methods of information transmission. However, it is a salient challenge for MHA vendors to attract users to adopt software continuously. Though users' perceived e-health literacy is recognized as a critical factor in some recent studies, its influence was still not clear. This paper has investigated how the users' perceived e-health literacy (PEHL) affects their continuance intention when adopting mobile healthcare applications based on elaboration likelihood model (ELM). We distributed questionnaires by Wechat (similar to Whatsapp) in China, where hundreds of MHAs can be downloaded, and 273 valid samples were collected. Result shows that ELM works well in this model with 6 of the 8 hypotheses are supported. The moderate effect of PEHL is largely significant on peripheral route but not significant on central route. The most interesting finding is that the relationship between PEHL and users' satisfaction in continuance adoption is positive. Possible reasons are discussed such as, there could exist a moderator on this relationship. Limitations, future researches and implications for theory and practice are also given. The paper should include an Abstract. The Abstract should be understandable by the general reader outside the context of the study. The Abstract should be formatted like this paragraph, and may be up to 200 words in length.

Gao Z.-K.,Tianjin University | Dang W.-D.,Tianjin University | Yang Y.-X.,Tianjin University | Cai Q.,Tianjin University
Chaos | Year: 2017

The exploration of the spatial dynamical flow behaviors of oil-water flows has attracted increasing interests on account of its challenging complexity and great significance. We first technically design a double-layer distributed-sector conductance sensor and systematically carry out oil-water flow experiments to capture the spatial flow information. Based on the well-established recurrence network theory, we develop a novel multiplex multivariate recurrence network (MMRN) to fully and comprehensively fuse our double-layer multi-channel signals. Then we derive the projection networks from the inferred MMRNs and exploit the average clustering coefficient and the spectral radius to quantitatively characterize the nonlinear recurrent behaviors related to the distinct flow patterns. We find that these two network measures are very sensitive to the change of flow states and the distributions of network measures enable to uncover the spatial dynamical flow behaviors underlying different oil-water flow patterns. Our method paves the way for efficiently analyzing multi-channel signals from multi-layer sensor measurement system.

Gao Z.-K.,Tianjin University | Dang W.-D.,Tianjin University | Xue L.,Tianjin University | Zhang S.-S.,Tianjin University
Chaos | Year: 2017

Characterizing the flow structure underlying the evolution of oil-in-water bubbly flow remains a contemporary challenge of great interests and complexity. In particular, the oil droplets dispersing in a water continuum with diverse size make the study of oil-in-water bubbly flow really difficult. To study this issue, we first design a novel complex impedance sensor and systematically conduct vertical oil-water flow experiments. Based on the multivariate complex impedance measurements, we define modalities associated with the spatial transient flow structures and construct modality transition-based network for each flow condition to study the evolution of flow structures. In order to reveal the unique flow structures underlying the oil-in-water bubbly flow, we filter the inferred modality transition-based network by removing the edges with small weight and resulting isolated nodes. Then, the weighted clustering coefficient entropy and weighted average path length are employed for quantitatively assessing the original network and filtered network. The differences in network measures enable to efficiently characterize the evolution of the oil-in-water bubbly flow structures.

Wang Y.,Tianjin University | Wang S.,Tianjin University
International Journal of Heat and Mass Transfer | Year: 2017

Bruggeman correlation with exponents of m = n = 1.5 (parameters relevant to tortuosity factor) has been extensively applied in the modeling of PEM fuel cells, however, many studies indicated that the usage of m = n = 1.5 will overestimate the gaseous effective diffusion coefficients in the porous mediums of a fuel cell, it is believed that m and n may fall in between 2.0 and 5.0, but with different values. This paper attempts to investigate the sensitivity of the gaseous diffusion to the various reported values of m and n by a three-dimensional two-phase fuel cell model to answer how much difference they will make in predicting cell performance. The numerical results demonstrate that the cell performance varies considerably with the variation of m and n, and the sensitivity of cell performance to m and n in cathode side and anode side, in GDL and CL can be of great distinction. © 2016 Elsevier Ltd

Zhang X.,Tianjin University | Meng Y.,Tianjin University
Pacific Asia Conference on Information Systems, PACIS 2016 - Proceedings | Year: 2016

Collaborative learning group in higher education is increasingly supported by communication tools, but there are still some problems regarding engagement. We examined students' engagement in collaborative learning groups with the help of communication tool-Slack. Students' motivation to engage in teamwork can be promoted through the openness of team members' effort on Slack. Moreover, free-rider and sucker effect can also be relieved. Teamwork engagement can prompt students' learning and work satisfaction. We proposed a research model and corresponding hypotheses. Surveys were issued online to graduate students at different time of our course. SmartPLS 3.0 was used to analyze data and test structure equations. We came to conclusions lastly as follows: mutual trust, social influence and reward valence are positively related to teamwork engagement, and teamwork engagement is positively related to personal success (i.e. learning and work satisfaction). However, the moderation role of task complexity between teamwork engagement and personal success is not supported. Theoretical and practical contributions are discussed. Research limitations and future research directions are also presented.

Zhao B.,Tianjin University | Jiang J.,Shenzhen University
Lecture Notes of the Institute for Computer Sciences, Social-Informatics and Telecommunications Engineering, LNICST | Year: 2017

While almost all down-sampling based video codecs gain additional compression at the expense of image degradation, we set a good example of achieving both large compression and even better reconstruction quality. Such progress is realized by: (i) minimizing the introduction of information loss with a proposed decomposition-based adaptive down-sampling method so that more reserved pixels can be allocated to image details where human visual perception is more sensitive. Specifically, a modified content complexity measurement is put forward and the optimum down-sampling rate is adaptively selected with a customized formula; (ii) maximizing the information compensation via a contentadaptive super-resolution algorithm, which is accelerated and optimized by two stages of pruning to select the closest correlated dictionary pairs. Extensive experiments support that, by using prevailing H.264 codec as benchmark, the proposed scheme achieves 5 times more of additional compression and the reconstruction quality outperforms other state-of-the-art approaches, and even better than decoded non-shrunken frames in human visual perception. © ICST Institute for Computer Sciences, Social Informatics and Telecommunications Engineering 2017.

Yi-Fei G.,Tianjin University
IOP Conference Series: Earth and Environmental Science | Year: 2017

with the continuous development and progress of productivity, product design spans with the age now and forms a diversified formation. But when there is a progress of science and technology, the speed of consumption of resources is also increasing, the relationship between mankind and the nature further worsens, resources will be exhausted, pollution is increasingly serious and shocking public nuisance events occur frequently. People pay more attention to the environment due to the harms to the nature caused by the development of industry, science and technology. Nowadays, people have clearly recognized the important role of design in environmental protection. The ecological research on constructing a new aesthetic relationship between human and nature has drawn wide attention from all circles of the society. Green innovation design has become the focus of global concern. © Published under licence by IOP Publishing Ltd.

Wang Z.,Tianjin University | Zhao J.,Tianjin University | Li M.,Tianjin University
Renewable and Sustainable Energy Reviews | Year: 2017

In order to keep sustainable development, the Chinese government has issued series of policies to reduce CO2 emissions. Renewable energy technologies applied in building field, mainly including solar energy and geothermal energy technologies, are recommended because of advances of energy efficiency, environmental protection and economic sustainability. Carbon trading has been widely accepted as an effective market approach, but it hasn't covered the renewable energy application in building projects in China as yet. Reasonable solutions should be proposed to encourage building projects to participate in the carbon trading market. This paper aims at establishing a feasible mechanism to help improve the carbon market for renewable energy application in buildings. To attend this goal, this paper introduces and analyzes the status of carbon trading market and the position for building projects in China. By comparing the present mechanisms, Programmatic CDM with building portfolio is considered appropriate for building projects with renewable energy application. Volume verifying method, the core of the mechanism, is modified to fit the building projects. Then five different specific cases are studied to prove the practicality and reasonableness of the methodology. Programmatic CDM with modified verifying method is concluded as the proper mechanism for renewable energy application in buildings in carbon trading market. © 2017 Elsevier Ltd

Zhang W.,University of Luxembourg | Yan J.-B.,Tianjin University
Structural Concrete | Year: 2017

The research presented herein describes the testing performed to examine the potential use of engineered cementitious composite (ECC) materials in lieu of traditional materials. Laboratory studies were used to examine the response of ECC materials under cyclic loading. The cyclic testing results indicated that ECC materials have a unique response to cyclic loading; the stiffness of ECC varies with the applied tensile strain and loading history. According to the cyclic response from the moment-curvature relation using cross-sectional analysis, a stress-strain model was proposed to simulate the cyclic response of ECC; the model showed good agreement with the experimental results. © 2017 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.

Wang Z.-Z.,Tianjin University | Tang Y.,Tianjin University
Tetrahedron | Year: 2016

A novel one-pot benign oxidative cyclization of alcohols with 2-aminobenzamides was successfully developed without catalyst to afford the quinazolinones under O2. This one-pot protocol involved oxidations and cyclizations to construct the skeleton of quinazolinones through possibly three kinds of distinct reaction mechanisms. © 2016 Elsevier Ltd. All rights reserved.

Zhang W.,National University of Singapore | Yan J.-B.,Tianjin University
ACI Materials Journal | Year: 2017

This paper presents experimental results that highlight the complex bond behavior in a CFRP plate-concrete externally bonded system with an additional anchor. The use of the anchor is aimed at achieving three goals, which are transverse strengthening, stiffness improvement, and load distribution. The experimental results from 30 direct shear tests, divided into three groups, are reported based on the failure mode, the load-displacement relationship, the strain distribution, and the local bond stress-slip relationship. Two new simple models are proposed based on the existing bond-slip model and experimental observations. A numerical analysis is performed based on the proposed models. These models not only agree well with the experimental results but also correctly predict the relationship between the bond length and anchorage strength. This research contributes information to the experimental database and for prediction methods to aid in the future development of design recommendations for externally bonded systems with an additional anchor. Copyright © 2017, American Concrete Institute. All rights reserved.

Peng X.-L.,Tianjin University | Huang G.-Y.,Tianjin University
International Journal of Engineering Science | Year: 2017

In the present work, by considering the thermoelastic effect, the JKR model is extended to study the non-slipping adhesive contact between two spheres of different initial temperature under the normal applied force. The analytical expressions for the tractions within the contact area and the applied force as a function of the contact radius are derived, based on which some numerical results are given. It is found that the thermoelastic effect can significantly influence the adhesive contact behaviors such as the pull-off force and the contact radius at zero applied force. The present work may cast light on optimizing the strength of the adhesive contact interfaces in engineering like various thermal bonding technologies. © 2017 Elsevier Ltd

Wang X.,Nanjing Forestry University | Wang N.,Illinois Institute of Technology | Liu X.,Tianjin University | Shi R.,Nanjing University
Renewable and Sustainable Energy Reviews | Year: 2017

This article evaluates the energy performance of the Modern Wing of the Art Institute of Chicago and provides suggestions for optimizing its energy performance and the Leadership in Energy and Environmental Design (LEED) certification. The goal is to find a feasible way of improving the energy-saving rate based on the ASHRAE standard model, enhancing its resource efficiency by making full use of on-site renewable natural resources for expanding glass-curtain wall buildings, and integrating LEED-accredited features. Finally, it evaluates the possibilities of using alternative design schemes and innovative building technologies for updating this building and explores green city strategies and sustainable urban planning ideas taking Beijing and Shanghai as typical instances in the future. © 2017 Elsevier Ltd

Shi L.,Tianjin University | Xing B.,Tianjin University | Fan S.,China Tobacco Hunan Industrial Co.
Tobacco Science and Technology | Year: 2017

To assess the capability of cigarette's physical index testing system accurately and systematically and make up the deficiency of traditional univariate measurement system, the physical index testing system was regarded as a multivariate one and assessed by a method which combined a two-phase method with a modified-region-based method. In the first phase of the two-phase method, the variation of measurement system was estimated with calibrated test rods; in the second phase, the total variation of measurement system was estimated through the historical measurement data of the same measurement equipment. The capability of the measurement system was assessed comprehensively by the modified-region-based method. Two important assessment indices, percentages of repeatability and reproducibility(%R&R)and ratio of precision to tolerance (%P/T), and their meaning were given. Also given were the formulas for calculating percentage of equipment variation(%EV)and percentage of appraiser variation(%AV)for equipment setting. The results showed that: 1)The created indexes %R&R and %P/T were 16.49% and 12.92% for the testing system, respectively; all in the range of 10%-30%, which indicated that the system had enough measurement capability and higher measurement precision. 2) Multivariate measurement system analysis method took the correlation between cigarette's physical indices into account, featured high accuracy and integrity, and was suitable for analyzing the capability of cigarette testing stations of different types. Keywords: Cigarette;Physical index;Test station;Multivariate analysis method;Percentage of repeatability and reproducibility(%R&R);Ratio of precision to tolerance(%P/T) measurement precision. 2) Multivariate measurement system analysis method took the correlation between cigarette's physical indices into account, featured high accuracy and integrity, and was suitable for analyzing the capability of cigarette testing stations of different types. © 2017, Editorial Office of Tobacco Science and Technology. All right reserved.

Chen Z.,Tianjin University | Zheng Y.,Tianjin University | Ma J.-A.,Tianjin University
Angewandte Chemie - International Edition | Year: 2017

We disclose an efficient one-pot transformation of trifluorodiazoethane and higher perfluorinated homologues with various nitroolefins. This method takes advantage of the nitro group as a traceless activating and directing group (TADG) that is released in the aromatization step to produce 4-substituted 3-perfluoroalkyl pyrazoles with complete regioselectivity. The potential of this method is further demonstrated by the synthesis of penthiopyrad. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Feng B.,Tianjin University | Yang Z.,Tianjin University | Zhai R.,Tianjin University
Energy | Year: 2017

Fluorine-containing refrigerants will still play an irreplaceable role in the process of research and development of new refrigerants. So it is critical to study the main toxic combustion product HF. This paper contributed to concentration characteristics of HF about R32 and R161 on particular concentrations when combustion reaction occurred. Firstly, a new enclosed test method of concentration of HF (CHF) was presented through comparative analysis different existent methods and results. Then based on the original experimental system independently designed and built, actual CHF of 16.9%/16.89% R32 and 4.17%–4.74% R161 were measured respectively under the conditions of normal temperature and humidity. Moreover, an equation was obtained to estimate the relationship between the actual CHF and concentration of R161 (CR161), when CR161 was in the range of lower flammability limit (LFL) and stoichiometric concentration (Cst). And the possible affected factors of the actual CHF were analyzed. Finally it should be given sufficient attention that the risk of high CHF still exists. Therefore, the results will be of universal guiding significance for the security application of fluorine-containing refrigerants in this paper. © 2017 Elsevier Ltd

Lu X.,Tianjin University | Kang Z.,University of Texas at Dallas
ACM International Conference Proceeding Series | Year: 2016

In this paper, we present a programmed experiment and the results on automatic generation of Joan Miro style of surrealism. Combining the artist's aesthetic theory with the authors' own understanding, the paper analyzes the characteristics of Miro's work and proposes a process modeling approach that consists of four steps: structured drawing, adaptive coloring, space filling and noise injection. The generation process is described in details and sample generated images styled on Miro's paintings are also demonstrated and discussed. By extracting and coding pictorial elements in paintings of Miro, different styled images could be generated under different sets of parameters. © 2016 ACM.

Zhou L.,Tianjin University | Wei H.,Tianjin University
Applied Thermal Engineering | Year: 2017

The object of this work is to enhance the ISAT performance for transient combustion simulations for both premixed and non-premixed combustion process. In this work, dynamic pruning (DP) strategy for not-frequently-accessed tabulated points has been employed. For DP approach, the action considered when the table is full is to delete the most recently used leaf (at the tail of most recently used leaf) and replace it by the new entry in ISAT. The performances of ISAT with DP are presented firstly both in a homogenous charged compression ignition (HCCI) engine and a diesel engine. In present study, we investigate the sensitivity of ignition and composition inhomogeneity to heat loss/chemistry model for HCCI combustion. Composition inhomogeneity is governed by heat loss, turbulence diffusion and chemical reaction. Meanwhile, the effect of composition and temperature inhomogeneity on chemistry acceleration with ISAT-DP is studied in detail. It is shown that, ISAT-DP method can effectively reduce computational cost and achieve a large speedup factor of around 2 compared with original ISAT method. Memory size in ISAT has a tight influence on computational efficiency. And an overall speed up factor of around 4 for diesel engine is also achieved. © 2016

Song Y.,Tianjin University | Wang X.,Tianjin University of Technology | Mi W.,Tianjin University
Physical Chemistry Chemical Physics | Year: 2017

The semimetallic WTe2 has sparked intense interest owing to the non-saturating magnetoresistance, pressure-driven superconductivity and possession of type-II Weyl fermions. The unexpected and fascinating quantum properties are thought to be closely related to its delicate Fermi surface and a special electron-hole-pocket structure. However, in the single-layer limit, the electron-hole-pocket structure is missing owing to the lack of interlayer interaction. Herewith, we demonstrate that 3d transition-metal adsorption is an effective method to modify the electronic properties of monolayer WTe2 by density functional theory. Spin-splitting and spin-degenerate bands are realized in Ti-, V-, Cr-, Mn-, Fe-, and Co- and Sc-, Ni-, Cu-, and Zn-adsorbed systems, respectively. Especially, the reemergence of the electron-hole pockets appears in the Ni-adsorbed system. The calculated results are robust against inclusion of spin-orbit coupling and Coulomb interaction. © the Owner Societies 2017.

He C.,University of British Columbia | He C.,Tianjin University | Li H.,University of British Columbia
Langmuir | Year: 2017

Single-molecule force spectroscopy (SMFS) and molecular dynamics (MD) simulations have revealed that shear topology is an important structural feature for mechanically stable proteins. Proteins containing a β-grasp fold display the typical shear topology and are generally of significant mechanical stability. In an effort to experimentally identify mechanically strong proteins using single-molecule atomic force microscopy, we found that staphylokinase (SAK), which has a typical β-grasp fold and was predicted to be mechanically stable in coarse-grained MD simulations, displays surprisingly low mechanical stability. At a pulling speed of 400 nm/s, SAK unfolds at ∼60 pN, making it the mechanically weakest protein among the β-grasp fold proteins that have been characterized experimentally. In contrast, its structural homologous protein streptokinase β domain displays significant mechanical stability under the same experimental condition. Our results showed that the large malleability of native-state SAK is largely responsible for its low mechanical stability. The molecular origin of this large malleability of SAK remains unknown. Our results reveal a hidden complexity in protein mechanics and call for a detailed investigation into the molecular determinants of the protein mechanical malleability. (Graph Presented). © 2016 American Chemical Society.

Shen Z.,Tianjin University | Shen Z.,University of Western Australia | Feng X.,University of Western Australia | Gourvenec S.,University of Western Australia
Geotechnique | Year: 2017

The effect of soil–foundation interface condition on the undrained capacity of rectangular mudmat foundations under loading in six degrees of freedom is investigated. Undrained failure envelopes for mudmats with zero-tension interface have been derived from finite-element analyses, and compared with the solutions from traditional methods and established for an unlimited-tension interface condition. The zero-tension interface has minimal effect on failure envelopes in the absence of moment, but significantly reduces the load-carrying capacity of mudmats under all other load paths that include moment. The traditional method for predicting the capacity of shallow foundations under multidirectional loading generally predicts lower capacity under any combined loading condition in comparison with the finite-element results for mudmats with zero-tension interface. Algebraic expressions are proposed to describe failure envelopes for mudmats with zero-tension interface. The proposed expressions can be implemented in an automated calculation tool to enable essentially instantaneous generation of failure envelopes and optimisation of a foundation design as a function of foundation dimension or material factor. © 2017, ICE Publishing. All rights reserved.

Liu L.,Tianjin University | Feng S.,Tianjin University
Organic and Biomolecular Chemistry | Year: 2017

A Cu(ii)-mediated synthesis of N,N′-diacylhydrazines and 1,3,4-oxadiazoles from aldehyde hydrazones has been developed. This is the first time that the synthesis of N,N′-diacylhydrazines and 1,3,4-oxadiazoles using N,N-dimethylamides as the acylation reagent and O2 in air as the oxidation reagent is reported. These reactions offered several advantages including simple workups, ligand-free inexpensive metal salts as mediators, high yields, and wide scope of substrates. © The Royal Society of Chemistry.

Zhang G.,Tianjin University | Gao F.,Tianjin University
PLoS ONE | Year: 2017

Due to different replication mechanisms between the leading and lagging strands, nucleotide composition asymmetries widely exist in bacterial genomes. A general consideration reveals that the leading strand is enriched in Guanine (G) and Thymine (T), and the lagging strand shows richness in Adenine (A) and Cytosine (C). However, some bacteria like Bacillus subtilis have been discovered composing more A than T in the leading strand. To investigate the difference, we analyze the nucleotide asymmetry from the aspect of AT and GC bias correlations. In this study, we propose a windowless method, the Z-curve Correlation Coefficient (ZCC) index, based on the Z-curve method, and analyzed more than 2000 bacterial genomes. We find that the majority of bacteria reveal negative correlations between AT and GC biases, while most genomes in Firmicutes and Tenericutes have positive ZCC indexes. The presence of PolC, purine asymmetry and stronger genes preference in the leading strand are not confined to Firmicutes, but also likely to happen in other phyla dominated by positive ZCC indexes. This method also provides a new insight into other relevant features like aerobism, and can be applied to analyze the correlation between RY (Purine and Pyrimidine) and MK (Amino and Keto) bias and so on. © 2017 Zhang, Gao. 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.

Yu Y.-M.,Tianjin University | Huang Y.-N.,Tianjin University | Deng J.,Tianjin University | Deng J.,Chongqing University
Organic Letters | Year: 2017

A facile synthetic approach to a series of chiral 4-chloromethyl-1,4-dihydro-2H-3,1-benzoxazin-2-one derivatives has been described. This transformation is achieved through the catalytic asymmetric chlorocyclization of 2-vinylphenylcarbamates using a newly developed organocatalyst. Furthermore, the resulting products can be easily converted into diverse bioactive agents. © 2017 American Chemical Society.

Du B.X.,Tianjin University | Li J.,Tianjin University
IEEE Transactions on Dielectrics and Electrical Insulation | Year: 2016

Cable accessories made of ethylene-propylene-diene terpolymer (EPDM) are considered to be the weakest part of HVDC cable system due to the existence of the interface between cable insulation and itself. The charges are likely to accumulate at the interface between insulation materials with different conductivity and permittivity, which may induce the occurrence of partial discharge and breakdown. Nanoparticles can be applied to adjust the interface charge behaviors. In this paper, carbon black (CB) nanoparticles were dispersed into EPDM with 0, 0.5, 1, 3 and 5 wt% respectively. The effects of nanoparticle doping on the interface charge distribution of LDPE and EPDM composite insulation were measured under -15 kV/mm. Furthermore, dielectric properties and DC conduction were introduced to discuss the suppression mechanism of carbon black nanoparticle doping. Obtained results show that the nanoparitcles are well dispersed in the EPDM. The permittivity increases with the nanoparticle fillgrade while the ac conductivity and tan(delta) at lower frequencies are lower than the base EPDM. The interface charge density can be suppressed to 0.5 C/m3 with 1 wt% carbon black nanoparticle doping, much less than the undoped and other doped groups. The mechanism of interface charge suppression is attributed to the decrease of conduction and permittivity mismatch by carbon black nanoparticle doping, which was proved by the dielectric spectroscopy and conduction current tests. The interface charge buildup and dissipation process depends on the time constant controlled by the doping proportion. As a consequence, the approximate 1 wt% carbon black nanoparticle doped EPDM can effectively suppress the accumulation of interface charge of cable accessories and will make a potential application for the dc cable accessories. © 2016 IEEE.

Zhen X.,Tianjin University of Technology and Education | Liu D.,Tianjin University of Technology and Education | Wang Y.,Tianjin University
Energy | Year: 2017

Methanol is an alternative fuel, and considered to be one of the most favorable fuels for engines. In this study, knocking combustion in a developed ORCEM (optical rapid compression and expansion machine) is studied based on the multi-dimensional simulation analysis. The LES (large-eddy simulation) models coupled with methanol chemical reaction kinetics (contains 21-species and 84-elementary reactions) is adopted to study knocking combustion. The results showed that the end-gas auto-ignition first occurred in the position near the chamber wall because of the higher temperature and pressure. The H2O2 species could be a good flame front indicator. OH radicals played the major role, and the HCO radicals almost could be ignored during knocking combustion. The HCO radicals generated little, so its concentration during knocking combustion almost may be ignored. The mean reaction intensity results of CH2O, OH, H2O2, and CO were higher than others during knocking combustion. Finally, this paper put forward some new suggestions on the weakness in the knocking combustion researches of methanol fuel. © 2017 Elsevier Ltd

Liu L.,Tianjin University | Han Y.,Tianjin University | Jin M.,University of Texas at Arlington
PLoS ONE | Year: 2017

The alternating projection algorithms are easy to implement and effective for large-scale complex optimization problems, such as constrained reconstruction of X-ray computed tomography (CT). A typical method is to use projection onto convex sets (POCS) for data fidelity, nonnegative constraints combined with total variation (TV) minimization (so called TV-POCS) for sparse-view CT reconstruction. However, this type of method relies on empirically selected parameters for satisfactory reconstruction and is generally slow and lack of convergence analysis. In this work, we use a convex feasibility set approach to address the problems associated with TV-POCS and propose a framework using full sequential alternating projections or POCS (FS-POCS) to find the solution in the intersection of convex constraints of bounded TV function, bounded data fidelity error and non-negativity. The rationale behind FS-POCS is that the mathematically optimal solution of the constrained objective function may not be the physically optimal solution. The breakdown of constrained reconstruction into an intersection of several feasible sets can lead to faster convergence and better quantification of reconstruction parameters in a physical meaningful way than that in an empirical way of trial-and-error. In addition, for large-scale optimization problems, first order methods are usually used. Not only is the condition for convergence of gradient-based methods derived, but also a primal-dual hybrid gradient (PDHG) method is used for fast convergence of bounded TV. The newly proposed FS-POCS is evaluated and compared with TV-POCS and another convex feasibility projection method (CPTV) using both digital phantom and pseudo-real CT data to show its superior performance on reconstruction speed, image quality and quantification. © 2017 Liu et al. 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.

Yan J.-B.,Tianjin University | Xie J.,Tianjin University
Construction and Building Materials | Year: 2017

Reinforced concrete (RC) structure applied in the Arctic engineering and low temperature environment keeps increasing. This paper, experimentally, analytically, and numerically investigated the ultimate strength behaviour of the RC beams under different low temperatures. This paper firstly reported the experimental studies on mechanical properties of the steel reinforcements and normal weight concrete under different low temperatures. Empirical formulae were developed to incorporate the influences of the low temperature on the mechanical properties of the steel reinforcements and concretes. The ultimate strength behaviour of the RC beams under low temperature were studied through twelve quasi-static tests. The influences of the low temperatures and flexural reinforcing ratio on the ultimate strength behaviours of RC beams have been analysed and discussed. Analytical models were developed to predict the resistances corresponding to first crack, steel yielding, and ultimate resistances of the RC beams under low temperatures. Finite element model (FEM) was also developed to simulate the ultimate strength behaviour of the RC beams under low temperature. The accuracies of the analytical models and FEM simulations were checked through validations of the predictions by different models against the test results. © 2017 Elsevier Ltd

Han Q.,Tianjin University | Wang L.,Tianjin University | Xu J.,Tianjin University
Construction and Building Materials | Year: 2017

Carbon Fiber Reinforced Polymer (CFRP) has many superior material properties and can be used as prestressing tendons for prestressing structures instead of steel. A large angle wedge type of anchorage using transverse enhanced CFRP tendons is designed and tested for beam string structure. The results of laboratory tests and numerical analysis under static loading conditions of the prototype of anchorage are discussed. For a wedge with an angle of 10°, the 5-mm-diameter CFRP tendon was anchored successfully, but 7-mm- and 9-mm-diameter were not due to high pressure. The results of test revealed that the sleeve should ensure adequate roughness of internal and external surface, enough wall thickness and cutting width, and appropriate length to avoid some failure mode caused by components themselves. Based on the failure mode analysis of laboratory tests and numerical results, some details were suggested to improve the large angle wedge type of anchorage for applying to large diameter CFRP tendon. © 2017 Elsevier Ltd

Du B.X.,Tianjin University | Li J.,Tianjin University
IEEE Transactions on Dielectrics and Electrical Insulation | Year: 2017

Polyimide (PI) films have excellent electrical, mechanical and thermal properties in aspect of resisting corona, aging and radiation. However, the pulse voltage combined with dc voltage often causes concentration of local electrical field, which makes the surface charge behaviors more complex and threatens the system. As a means of surface treatment, direct fluorination has been proved as an effective way to improve the polymer properties, without compositing the bulk characteristics. Therefore, this paper intends to reveal the effects of fluorination on surface charge coupling behaviors of the PI films under dc and pulse voltage combination. The PI samples fluorinated for 0, 15, 45 and 60 min were obtained. Surface corona discharging was stressed under the combination of dc and pulse voltage. The surface charge accumulation, decay and distribution were measured coupled with an analysis of trap distribution. The results show the surface charge dynamic behaviors are strongly correlated with the fluorination time, pulse voltage amplitude and polarities of the dc and pulse voltage combination. The trap distribution results imply that the effect of fluorination and charging condition attribute to the change of trap depth and amount. Besides, surface charge behaviors are greatly improved by appropriate fluorination. © 1994-2012 IEEE.

Zhao Y.,Tianjin University | Huang X.,Tianjin University
Micromachines | Year: 2017

Wearable technology has attracted significant public attention and has generated huge societal and economic impact, leading to changes of both personal lifestyles and formats of healthcare. An important type of devices in wearable technology is flexible and stretchable skin sensors used primarily for biophysiological signal sensing and biomolecule analysis on skin. These sensors offer mechanical compatibility to human skin and maximum compliance to skin morphology and motion, demonstrating great potential as promising alternatives to current wearable electronic devices based on rigid substrates and packages. The mechanisms behind the design and applications of these sensors are numerous, involving profound knowledge about the physical and chemical properties of the sensors and the skin. The corresponding materials are diverse, featuring thin elastic films and unique stretchable structures based on traditional hard or ductile materials. In addition, the fabrication techniques that range from complementary metal-oxide semiconductor (CMOS) fabrication to innovative additive manufacturing have led to various sensor formats. This paper reviews mechanisms, materials, fabrication techniques, and representative applications of flexible and stretchable skin sensors, and provides perspective of future trends of the sensors in improving biomedical sensing, human machine interfacing, and quality of life. © 2017 by the authors.

Xiong C.,Tianjin University | Guo Y.,Tianjin University
International Journal of Applied Electromagnetics and Mechanics | Year: 2017

Present paper aims to investigate a generalized electromagneto-thermoelastic diffusion problem for a half-space with variable properties in the context of the fractional order theory of thermoelastic diffusion. The variable properties are taken as linear functions of the temperature. The half-space is initially placed in an external magnetic field with constant intensity, and subjected to a time-dependent thermal load and a chemical load, respectively. The governing equations of the problem in the fractional order generalized electromagneto-thermoelastic diffusion are formulated. The bounding surface in contact with a permeating substance is prescribed to be traction-free. To solve the problem, normal mode analysis is adopted and the distributions of the non-dimensional temperature, displacement, stress, induced magnetic field, induced electric field, chemical potential and concentration are obtained and represented graphically. The effects of fractional order parameters are evaluated by comparing the results obtained in the presence and absence of fractional order parameters. © 2017 - IOS Press and the authors. All rights reserved.

Wang Y.,Tianjin University | Shi G.,Tianjin University
International Journal of Applied Mechanics | Year: 2017

Based on the quasi-conforming (QC) element technique, accurate and reliable eight-node and six-node solid-shell elements are presented in this paper. These QC solid-shell elements can alleviate shear and Poisson thickness locking by appropriately interpolating the strain fields over the element domain, and they are completely free from hourglass modes by ensuring the rank sufficiency of the element stiffness matrix a priori. Furthermore, the element stiffness matrices of the present elements are evaluated explicitly rather than resorting to the numerical integration, which leads to a high computational efficiency. The QC solid-shell elements with the properly interpolated element strain fields can rigorously pass both membrane and bending patch tests. The popular benchmark problems are used to evaluate the performance of the QC solid-shell elements. The numerical results show that the present QC solid-shell elements yield not only accurate displacements but also good stress results for all the stress components. Particularly, the present QC solid-shell elements are capable of giving quite accurate results even with very coarse mesh. © 2017 World Scientific Publishing Europe Ltd.

Ling J.,Tianjin University | Xie H.,Tianjin University
Neiranji Gongcheng/Chinese Internal Combustion Engine Engineering | Year: 2017

To precisely reveal the relation between fuel injection quantity and characteristic parameters defined from the fluctuation law of instantaneous rail pressure of high pressure common rail fuel injection system of diesel engines, a fuel injection quantity observation (IQO) method was proposed based on the characteristic parameters of instantaneous rail pressure waveforms. With this method, the instantaneous rail pressure waveforms were divided into a series of typical segments. Four characteristic points and four characteristic segments were defined to describe the instantaneous rail pressure fluctuation characteristics of each cylinder. And ten characteristic parameters were defined to evaluate the instantaneous rail pressure fluctuation characteristics in the fuel injection process of each cylinder. A database of the characteristics of rail pressure waveform groups was set up and the fluctuation law of the instantaneous rail pressure under different operating conditions was revealed by mean processing of the characteristic parameters of the instantaneous rail pressure fluctuation at every steady experimental operating point. An IQO model was established by the fuel continuity equations, and calibrated by the parameter identification and offline validation with the characteristics database of rail pressure waveform groups. The results show that the IQO model has simple structure and high observation accuracy and it lays a good foundation for further engineering application in electronic control unit (ECU). © 2017, Chinese Society for Internal Combustion Engines(CSICE). All right reserved.

Wang J.-S.,Tianjin University | Xu Y.-K.,Tianjin University
Jisuan Lixue Xuebao/Chinese Journal of Computational Mechanics | Year: 2017

The investigation of flow features on the three-dimensional square cylinder with a flexible plate is performed by the two way fluid-solid coupling method. The variation law of the drag coefficient, lift coefficient and Strouhal number of the square cylinder with a flexible plate are probed, which are compared with that of the single square cylinder. The numerical results show that the drag coefficient of the square cylinder reduces by 34.6% and its amplitude decreases greatly by adding a flexible plate in the region of the wake flow. Meantime, the RMS of the lift coefficient of square cylinder with a flexible plate reduces by 84.8% accompanying the drastic decrease of flow field pulsation. In addition, the Strouhal number reduces by 79.5%. The present results indicate that the vortex shedding can be effectively suppressed by adding a flexible plate at the back of the square cylinder, which results in the improvement of the wake flow characteristics of three-dimensional square cylinder. © 2017, Editorial Office of Chinese Journal of Computational Mechanics. All right reserved.

Lu Y.-M.,Tianjin University | Liu Z.-X.,Tianjin University
Tuijin Jishu/Journal of Propulsion Technology | Year: 2017

In order to quantitatively investigate the main influence factors on the tip leakage flow of centrifugal impellers, 11 unshroud impellers whose relative values of the tip clearance range from 0 to 10 percent are generated from the typical shrouded Eckardt impeller by equivalent cutting. Numerical simulation and quantitative analysis method are used to investigate the flow field around different tip clearances in the design condition, and then the factors related to the leakage flow, namely, the leakage intensity, scrapping pressure and tip load are quantified along the spanwise direction. After the calculation and discussion of "Scrapping Ratio" R, the quantified results are analyzed by the Partial least square (PLS) method. Finally, the quantitative formulas describing the relationship between the leakage flow and its main influence factors are established. The study shows that: (1)The value of R falls from 2.3 to about 0.25, which indicates that the effects of shroud scrapping on leakage flow increase along the spanwise direction. (2)The variable importance projection value of tip load (interval [1, 2])is a little bigger than the variable importance projection value of scrapping pressure (interval [0.7, 1]), and the regression coefficient value of tip load (interval [0.7, 1]) is a little bigger than the regression coefficient value of scrapping pressure (interval [0.6, 0.8]), which indicates that tip load plays a much more important role in promoting the leakage flow than scrapping pressure, but the influence of scrapping pressure on leakage flow can not be ignored. © 2017, Editorial Department of Journal of Propulsion Technology. All right reserved.

Han Q.,Tianjin University | Kang Y.,Tianjin University
Journal of Dispersion Science and Technology | Year: 2017

Water-in-oil emulsion separation through a fibrous media bed is a complex and challenging process in industries. In this article, we used a vertical column separator to investigate the effects of the height and porosity of the fiber bed, the structure arrangement (the mixed or the layered fibrous bed), the superficial velocity of the water-in-oil emulsion through the bed, and the influent water content of the emulsion on water removal. Four kinds of glass microfibers (GF1-GF4) with mean diameters of 0.6, 2.6, 4.6, and 8.0 µm, respectively, acted as the coalescence medium and composed the fibrous bed with different structure types. The separation efficiency could reach 97.1% with a relatively low pressure drop under the optimal bed structure and operational conditions. It also showed that the mixed bed had higher separation performance compared to the layered fibrous bed. © 2017 Taylor & Francis

Li X.,Tianjin University | Sun J.-Q.,University of California
Physica A: Statistical Mechanics and its Applications | Year: 2017

Drivers often change lanes on the road to maintain desired speed and to avoid slow vehicles, pedestrians, obstacles and lane closure. Understanding the effect of lane-changing on the traffic is an important topic in designing optimal traffic control systems. This paper presents a comprehensive study of this topic. We review the theory of microscopic dynamic car-following models and the lane-changing models, propose additional lane-changing rules to deal with moving bottleneck and lane reduction, and investigate the effects of lane-changing on the traffic efficiency, traffic safety and fuel consumption as a function of different variables including the distance of the emergency sign ahead of the lane closure, speed limit, traffic density, etc. Extensive simulations of the traffic system have been carried out in different scenarios. A number of important findings of the effect of various factors on the traffic are reported. These findings provide guidance on the traffic management and are important to the designers and engineers of modern highway or inner city roads to achieve high traffic efficiency and safety with minimum environmental impact. © 2016 Elsevier B.V.

Li T.,Tianjin University | Zhao H.,Tianjin Agricultural University
ISA Transactions | Year: 2017

The paper addresses the finite-time convergence problem of a uncalibrated camera-robot system with uncertainties. These uncertainties include camera extrinsic and intrinsic parameters, robot dynamics and feature depth parameters, which are all considered as time-varying uncertainties. In order to achieve a better dynamic stability performance of the camera-robot system, a novel FTS adaptive controller is presented to cope with rapid convergence problem. Meanwhile, FTS adaptive laws are proposed to handle these uncertainties which exist both in robot and in camera model. The finite-time stability analysis is discussed in accordance with homogeneous theory and Lyapunov function formalism. The control method we proposed extends the asymptotic stability results of visual servoing control to a finite-time stability. Simulation has been conducted to demonstrate the performance of the trajectory tracking errors convergence under control of the proposed method. © 2017 ISA.

Bai L.,University of Tennessee at Knoxville | Li F.,University of Tennessee at Knoxville | Jiang T.,Northeast Dianli University | Jia H.,Tianjin University
IEEE Transactions on Power Systems | Year: 2017

The security of natural gas network and the wind power uncertainty bring new challenges for power system operation. This letter develops a robust scheduling model for wind-integrated energy systems with the considerations of both gas pipeline and power transmission N-1 contingencies. The proposed method is robust against wind power uncertainty to ensure that the system can sustain possible N-1 contingency event of gas pipeline or power transmission line. Case studies demonstrate the effectiveness of the proposed model. © 1969-2012 IEEE.

Fang H.,Tianjin University | Wang D.,Tianjin University
IEEE Transactions on Energy Conversion | Year: 2017

This paper puts forward a novel design method of permanent magnet synchronous generator (PMSG). The most significant advantage of this method is that the output power of PMSG can be prominently improved without increasing any material costs. The main difference from the traditional design scheme is that the volume of permanent magnet (PM) remains unchanged during the entire design procedure. And the maximum output power scheme is found out just by optimizing the PM's shapes with the change of mechanical pole-arc coefficient. In other words, this method aims to obtain the maximum PM utilization design scheme that can produce more 'effective' magnet field so that it can generate the larger output power. The dimension parameters of PMs with different shapes are calculated by the equivalent analytic geometry method. To verify its availability, this novel method is performed on four common types of PMSGs with different rotor structures, and their satisfactory performance results are obtained. The comparison with the traditional machine design scheme is also presented to illustrate the innovation and priority. The finite-element analysis method based on Ansoft/Maxwell is applied for the electromagnetic models' building and simulation. © 2016 IEEE.

Fang S.,Tianjin University | Chiang H.-D.,Cornell University
IEEE Transactions on Power Systems | Year: 2017

In this letter, a forecasting model consisting of the Gaussian process with a novel composite covariance function for high-accuracy wind power forecasting is presented. The proposed composite covariance function is based on the exploration of joint effects between numerical weather prediction features. The performance of the proposed forecasting model is evaluated using the 2012 global energy forecasting competition wind power forecasting data, and the proposed model outperforms all of the competitors. © 1969-2012 IEEE.

Liu B.,Tianjin University | Luan W.,China Electric Power Research Institute | Yu Y.,Tianjin University
Applied Energy | Year: 2017

Non-intrusive load monitoring (NILM) is a novel and cost-effective technology for monitoring load electricity energy consumption details. In the event-based NILM, transient power waveform (TPW) time-series can be used as signatures to identify the transients of the electrical appliances in the aggregated load, and then to determine their operating states, estimate their power demand and cumulative energy consumption. In this paper, for load transient identification, the dynamic time warping (DTW) algorithm is adopted for the first time to measure the similarity between the variable-length raw TPW sample and template time-series. Accordingly, a nearest neighbor transient identification method is proposed to identify the appliance creating the TPW sample time-series, in which the DTW-based integrated distance is used to measure the similarity of TPW signatures. Three schemes to calculate the integrated distance are designed, combining multiple types of TPW signatures. Comparison tests with existing methods are conducted using public datasets. The comparison test results indicate that the proposed load transient identification method cannot only improve the accuracy of load transient identification, but also is easy to implement at a reasonable cost. Ultimately, the proposed method is implemented in an embedded system. The field test results show that it can identify the operating states of electrical appliances with high accuracy. © 2017 Elsevier Ltd

Yu Q.D.,Tianjin University
Applied Thermal Engineering | Year: 2017

It is a difficult problem to how to determine the reverse energy caused by units to water loop when a water-loop heat pump (WLHP) is in cooling and heating simultaneous mode, which not only has a great impact on energy-saving rate but also decides the use of auxiliary heat source in winter. This paper presents a theory of energy level to improve the research on WLHP system by using the relationship among building, circulating water and units. In this theory, the circulating water replaces building load as a new method to convert the reverse energy into energy change of circulating water and the equation of energy level also is built to determine the energy-saving range of WLHP system and report the capacity model of auxiliary heat source for all building types. An office building with different auxiliary powers is tested to analyze system operation characteristic and the effect of auxiliary heat source on unit and system and the results validate previous conclusions and suggest that an energy balance should be considered between units and auxiliary power to improve overall operation. © 2017 Elsevier Ltd

Han Z.,Tianjin University | Wang Y.,Tianjin University | Duan X.,Tianjin University
Analytica Chimica Acta | Year: 2017

This paper reports a surface functionalization strategy for protein detections based on biotin-derivatized poly(l-lysine)-grafted oligo-ethylene glycol (PLL-g-OEGx-Biotin) copolymers. Such strategy can be used to attach the biomolecule receptors in a reproducible way simply by incubation of the transducer element in a solution containing such copolymers which largely facilitated the sensor functionalization at an industrial scale. As the synthesized copolymers are cationic in physiology pH, surface biotinylation can be easily achieved via electrostatic adsorption on negatively charged sensor surface. Biotinylated receptors can be subsequently attached through well-defined biotin-streptavidin interaction. In this work, the bioactive sensor surfaces were applied for mouse IgG and prostate specific antigen (PSA) detections using quartz crystal microbalance (QCM), optical sensor (BioLayer Interferometry) and conventional ELISA test (colorimetry). A limit of detection (LOD) of 0.5 nM was achieved for PSA detections both in HEPES buffer and serum dilutions in ELISA tests. The synthesized PLL-g-OEGx-Biotin copolymers with different OEG chain length were also compared for their biosensing performance. Moreover, the surface regeneration was achieved by pH stimulation to remove the copolymers and the bonded analytes, while maintaining the sensor reusability as well. Thus, the developed PLL-g-OEGx-Biotin surface assembling strategy is believed to be a versatile surface coating method for protein detections with multi-sensor compatibility. © 2017 Elsevier B.V.

Yang Z.,Tianjin University | Wu X.,Tianjin University | Tian T.,Tianjin University
Refrigeration Science and Technology | Year: 2015

This paper describes the miscibility characteristics of the refrigerants HFCs (R227ea, R134a, R32, R161, R152a, R245fa), HCFCs (R22, R142b), CmHnOx (RE170), and their blends, with several types of lubricating oils, including mineral oils (MO) and polymer polyol ester oils (POE). A new experimental system was designed and built based on the ground of the related standards. Firstly, the typical statuses and microphenomenon of refrigerants and lubricants solutions were presented graphically; Secondly, the miscibility of MO and HCFCs (both pure and mixture refrigerants) was tested, compared and analyzed; In addition, after testing the miscibility of several HFCs with MO or POE oils, an exceptional case of successfully using the mineral oils for the HFC refrigerant was discussed.

Qin Z.C.,Tianjin University | Sun J.Q.,University of California at Merced
ASME 2016 Dynamic Systems and Control Conference, DSCC 2016 | Year: 2016

Themulti-objective optimal control design usually generates hundreds or thousands of Pareto optimal solutions. How to assist an user to select an appropriate controller to implement is a postprocessing issue. In this paper, we develop a method of cluster analysis of the Pareto optimal designs to discover the similarity of the optimal controllers. After we identify the clusters of optimal controllers, we then develop a switching strategy to select controls from different clusters to improve the performance. Numerical results show that the switching control algorithm is quite promising. Copyright © 2016 by ASME.

Deng Y.,Tianjin University | Pandey M.D.,University of Waterloo
Risk, Reliability and Safety: Innovating Theory and Practice - Proceedings of the 26th European Safety and Reliability Conference, ESREL 2016 | Year: 2017

Due to the physical limits, many degradation processes may have bounds in practical applications. For instance, the crack length should be nonnegative, and also below the structure thickness in a component. These physical limitations lead to bounded observations, and a decreasing trend to zero for the sample variance as the degradation approaches the physical bounds. When modeling these bounded records with unbounded processes, the unbounded process would underestimate the possibilities distributed to these records and cannot reproduce the decreasing observed variance in general. © 2017 Taylor & Francis Group, London.

Xu J.,Radboud University Nijmegen | Xu J.,Tianjin University
Optics InfoBase Conference Papers | Year: 2016

We pursue a supramolecular approach to the well-defined NLO micro-/nano- materials, in both the weak and strong coupling regimes. The clear "structure-property" relationship provides first principle design parameters for next generation multifunctional NLO materials. © OSA 2016.

Chen Y.,Tianjin University | Sun L.,Tianjin University
Kybernetes | Year: 2017

Purpose: The purpose of this paper is to investigate the dynamics and evolution of trust in organizational cross alliances. Design/methodology/approach: In alliances between corporations and nonprofit organizations, trust in decision-making is a dynamic process. Using the replicated dynamics model of evolutionary game theory, this paper provides a trust decision model and analyzes four scenarios under different parameters. A numerical simulation is developed to present an intuitive interpretation of the dynamic development of trust decisions and the effects of incentive and punishment mechanisms. Findings: Under different parameters, bounded rationality and utilities result in different but stable evolutionary strategies; the initial probability of adopting a trust strategy leads directly to whether participants adopt the strategy when the system reaches stability after continued games; and incentive and punishment mechanisms can significantly reduce the initial probability of adopting a trust strategy where the system evolves to meet stable state needs. Practical implications: The establishment of trust relationships is an important influence on the stable and coordinated development of an alliance. The proposed model can help the alliance build closer trust relationships and provide a theoretical basis for the design of the trust mechanism. Originality/value: Incentive and punishment bound by some degree of trust are introduced to address the problems of trust decisions and their dynamics; the model created reflects the bounded rationality and utility of each game stage. Useful evolutionary stable strategies using different variables are proposed to address the decision-making problems of trust in cross alliances. © 2017, © Emerald Publishing Limited.

Li Y.-L.,Tianjin University | Li J.,Tianjin University | Deng J.,Tianjin University of Technology
Advanced Synthesis and Catalysis | Year: 2017

A facile synthetic approach to a series of difluoromethyl ketones from β-ketoacids has been described. This transformation is achieved through the straightforward decarboxylative difluorination of β-ketoacids in the absence of any catalyst. Furthermore, the resulted difluoromethyl ketones can be easily converted into corresponding difluoromethylated building blocks for pharmaceuticals and materials. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Zhang D.,Tianjin University | Wang S.,Tianjin University
Mechanical Systems and Signal Processing | Year: 2017

This work examines the distinct resonance vibration of rotationally periodic structures. An analytical model of a sample stepped-plate structure subjected to standing wave excitation is developed by elasticity theory. Spatial-dependent resonance mode and resonance frequency are formulated by perturbation-superposition method. Different from the natural mode and natural frequency, a sinusoidal fluctuation of the resonance frequency is identified between the two split natural frequencies for single standing wave excitation. The resonance mode does not have preferred orientation because it is determined by excitation orientation. The resonance behaviors are different from those near the repeated natural frequencies. The response to a standing wave pair is also calculated and compared with that to the mathematically equivalent traveling wave, where significant difference is identified. The results indicate that purer traveling wave can be created by using a standing wave pair with pre-selected spatial phase and excitation frequency. Reverse traveling direction can be realized by altering excitation frequency. A test rig is designed and fabricated for verification purpose. The experiment validates that the response near the split natural frequencies is in phase with the external standing wave excitation. The resonance frequency varies with the excitation orientation for the split natural frequencies but it remains constant for the repeated natural frequencies. Potential applications of the spatial-dependent resonance mode and frequency are presented. © 2017 Elsevier Ltd

Han W.,University of Hong Kong | Chau K.T.,University of Hong Kong | Zhang Z.,Tianjin University
IEEE Transactions on Industrial Electronics | Year: 2017

This paper proposes and implements the concept of flexible induction heating based on the magnetic resonant coupling (MRC) mechanism. In conventional induction heating systems, the variation of the relative position between the heater and workpiece significantly deteriorates the heating performance. In particular, the heating effect dramatically reduces with the increase of vertical displacement or horizontal misalignment. This paper utilizes the MRC mechanism to effectuate flexible induction heating; thus, handling the requirements of varying vertical displacement and horizontal misalignment for various cooking styles. Differing from a conventional induction heating, the proposed induction heating adopts one resonant coil in the heater and one resonant coil in the workpiece, which can significantly strengthen the coupling effect, and, hence, the heating effect. Both the simulation and experimental results are given to validate the feasibility and flexibility of the proposed induction heating. © 2016 IEEE.

Wu O.,Tianjin University | Han M.,CAS Institute of Automation
Multimedia Tools and Applications | Year: 2017

Colors play particularly important roles in both designing and accessing Web pages. A well-designed color scheme improves the visual aesthetic of Web pages and facilitates user interactions. As far as we know, existing studies on color compatibility assessment and enhancement focus on images, and the assessment and enhancement for Web colors are rare. In order to aid Web designers evaluate and choose colors, this paper investigates color compatibility assessment for Web pages and applies this assessment to Web color editing based on Web screenshots rather than source codes. This study consists of four parts. First, the roles of color design in Web pages are discussed and a screenshot-based approach is proposed for the analysis of Web page regions. Second, a new method for extracting the color theme of a Web page is proposed. Then, we construct an assessment model that attributes scores to the color compatibility of Web pages through transfer learning. Third, we examine Web color transfer and combine it with the learned compatibility assessment model to create a new application that recommends colors for Web design. Lastly, the evaluation results suggest that the constructed compatibility assessment model and the proposed color transfer technique are effective and are superior over conventional methods. User studies suggest that our color recommendation application can generate new Web page screenshots that have higher color compatibility scores in comparison with those of the original pages. © 2017 Springer Science+Business Media New York

Ni Z.L.,Tianjin University | Ye F.X.,Tianjin University
Journal of Materials Processing Technology | Year: 2017

Higher temperature and more severe plastic deformations took place in the weld interface of Al/Cu joint with interlayer compared with that of Cu/Al joint with interlayer. For the both joints, the hardness perpendicular to the thickness direction of the aluminum sheet has a significant change compared with the original hardness. Peak lap shear tensile strength of Al/Cu joint with interlayer (78.3 MPa) is 27.3% higher than that of Cu/Al joint with interlayer (61.5 MPa). © 2017 Elsevier B.V.

Zhang Q.,Tianjin University | Yang Z.,Tianjin University | Gao Y.-D.,Tianjin University
Energy and Buildings | Year: 2017

Gas-engine driven heat pump could avoid energy loss in the process of generation, transmission and distribution, and effectively reduce the electric power load at the peak time in summer. In the present study, a novel stand-alone gas engine heat pump system with energy storage is put forward, which combined with the energy storage system and the autonomous power supply system. The annual performance optimization model of the gas engine heat pump system with energy storage system is proposed, which is calculated based on APSO algorithm. The simulation results were well agreed with experimental data, the average difference is 8.9%, 9.63% and 21.7% for the annual primary energy ratio of heating, cooling, transitional season, respectively. Based on the simulation results, the autonomous generating capacity E and the speed of engine n have high effect on the objective function, and the ratio of electricity to heat/cool/domestic hot water should be no greater than 0.1. The annual primary energy ratio of the gas engine heat pump system with energy storage system in heating, cooling and transitional season was increased by 6.11, 19.11% and 34.83% compared with the gas-engine driven heat pump system, respectively. The gas engine heat pump system with energy storage system can be used indifferent climate regions and buildings, which could provide a more stable work mode and higher annual primary energy ratio than the gas-engine driven heat pump system with a little energy loss. © 2017 Elsevier B.V.

Wang Y.,Tianjin University | Yue L.,Tianjin University | Wang S.,Tianjin University
Journal of Power Sources | Year: 2017

The cathode flow-field design of polymer electrolyte membrane (PEM) fuel cells determines the distribution of reactant gases and the removal of liquid water. A suitable design can result in perfect water management and thus high cell performance. In this paper, a new design for a cathode flow-field with a sub-channel was proposed and had been experimentally analyzed in a parallel flow-field PEM fuel cell. Three sub-channel inlets were placed along the cathode channel. The main-channel inlet was fed with moist air to humidify the membrane and maintain high proton conductivity, whereas, the sub-channel inlet was fed with dry air to enhance water removal in the flow channel. The experimental results indicated that the sub-channel design can decrease the pressure drop in the flow channel, and the sub-channels inlet positions (SIP, where the sub-channel inlets were placed along the cathode channel) and flow rates (SFR, percentage of air from the sub-channel inlet in the total cathode flow rate) had a considerable impact on water removal and cell performance. A proposed design that combines the SIP and SFR can effectively eliminate water from the fuel cell, increasing the maximum power density by more than 13.2% compared to the conventional design. © 2017 Elsevier B.V.

Liu H.W.,Tianjin University | Wang Y.,Tianjin University
CIE 2016: 46th International Conferences on Computers and Industrial Engineering | Year: 2016

With the development of industrialization, industrial equipments become more and more complex, and the user demand becomes more and more important. Traditional binary-state system cannot accurately describe the equipment status. A multi-state system (MSS) oriented to customers' demands can describe the operation status of equipments more accurately. The reliability of MSSs has been repeatedly researched and related reliability optimization is mainly designed based on redundancy strategy. However, no relevant review has been carried out in this field. To address those issues, a review of current research on MSSs was carried out in this paper. The review result shows that redundancy allocation problems of MSSs can be categorised in three classes according to different complexity: active redundancy allocation, standby redundancy allocation and redundancy allocation considering maintenance. Then active redundancy allocation on MSSs-from single objective optimization to multi-objective optimization-have been briefly reviewed.In this paper, the existing literature on redundancy allocation problems of MSSs can be summarized and the future research direction is proposed.

Liu H.W.,Tianjin University | Wang Y.,Tianjin University
CIE 2016: 46th International Conferences on Computers and Industrial Engineering | Year: 2016

With the development of industrialization, industrial equipments become more and more complex, and the user demand becomes more and more important. Traditional binary-state system cannot accurately describe the equipment status. A multi-state system (MSS) oriented to customers' demands can describe the operation status of equipments more accurately. Maintenance optimization policies of MSSs have become a practical and imperative research topic. However, no relevant review has been carried out in this field and the development of this field is not enough. To address those issues, a review of current research on MSSs was carried out in this paper. The review result shows that maintenance optimization policies of MSSs can be categorised in four classes according to the difference of maintenance actions: perfect maintenance, imperfect maintenance, selective maintenance and integrated maintenance. According to different maintenance scenarios, perfect maintenance can be distinguished by perfect continuous monitoring and inspection. Then imperfect maintenance models on MSSs-from binary-state elements to multistate elements-have been briefly reviewed. In addition, more complex maintenance optimization problems including selective maintenance and integrated maintenance are touched, which usually consider more maintenance actions or more complex maintenance scenarios. After induction and comparison for the existing related literature, several potential research directions are proposed.

Yuan Z.,Tianjin University | Bi X.,Tianjin University
CIE 2016: 46th International Conferences on Computers and Industrial Engineering | Year: 2016

The infrastructural construction of our country has long been mainly supported by the fiscal investment of the government and state-owned enterprises. But this model is gradually on the decline. Introducing and applying the PPP model to make the private capital involved in the infrastructural construction and urbanization has been the prevailing trend to implement a win-win result. Firstly, this paper combines with China's PPP practice for the PPP definition, analyses the type of China's PPP project and its three stages in the development. Then, according to its developmental maturity model and analyses the three dimensions of China's PPP model in maturity from the laws and regulations, management organizations and the public participation, concluding that China's PPP model is still in the primary level of maturity, but in the continuous development. Finally, the paper gives suggestions for the development of China's PPP model.

Tan J.,Nanjing Audit University | Jiang D.,Tianjin University
CIE 2016: 46th International Conferences on Computers and Industrial Engineering | Year: 2016

In recent years, humans have been creating more complicated systems than before due to the rapid development of technology. The tasks always require several steps to finish, which makes it more complex to assign them. The paper deals with an assignment problem to minimize total cost. In this problem, each task includes two steps, each of which will incurs cost for its assigned agent. The cost of each agent is dependent not only on the task assigned to it but also on the number of the tasks assigned to it. Firstly, a linear integer programming model for the problem was formulated. Then, a heuristic algorithm based on linear programs was developed to solve this problem and its worst-case ratio was also analyzed. Finally, experimental results demonstrated the developed heuristic can obtain better solution than the current best known algorithm.

Goh W.W.B.,National University of Singapore | Wang W.,Tianjin University | Wong L.,National University of Singapore
Trends in Biotechnology | Year: 2017

Effective integration and analysis of new high-throughput data, especially gene-expression and proteomic-profiling data, are expected to deliver novel clinical insights and therapeutic options. Unfortunately, technical heterogeneity or batch effects (different experiment times, handlers, reagent lots, etc.) have proven challenging. Although batch effect-correction algorithms (BECAs) exist, we know little about effective batch-effect mitigation: even now, new batch effect-associated problems are emerging. These include false effects due to misapplying BECAs and positive bias during model evaluations. Depending on the choice of algorithm and experimental set-up, biological heterogeneity can be mistaken for batch effects and wrongfully removed. Here, we examine these emerging batch effect-associated problems, propose a series of best practices, and discuss some of the challenges that lie ahead. Effectively dealing with batch effects will be the next frontier in large-scale biological data analysis, particularly involving the integration of different data sets.Given how batch-effect correction exaggerates cross-validation outcomes, cross-validation is becoming considered a less authoritative form of evaluation.Batch effect-resistant methods will become important in the future, alongside existing batch effect-correction methods. © 2017 Elsevier Ltd.

Mu C.,Tianjin University | Wang D.,CAS Institute of Automation
Neurocomputing | Year: 2017

In this paper, we investigate the neural-network-based adaptive guaranteed cost control for continuous-time affine nonlinear systems with dynamical uncertainties. Through theoretical analysis, the guaranteed cost control problem is transformed into designing an optimal controller of the associated nominal system with a newly defined cost function. The approach of adaptive dynamic programming (ADP) is involved to implement the guaranteed cost control strategy with the neural network approximation. The stability of the closed-loop system with the guaranteed cost control law, the convergence of the critic network weights and the approximate boundary of the guaranteed cost control law are all analyzed. Two simulation examples have been conducted and all simulation results have indicated the good performance of the developed guaranteed cost control strategy. © 2017 Elsevier B.V.

Gao P.-P.,Nankai University | Liu F.,Tianjin University
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2016

With the development of information technology and artificial intelligence, speech synthesis plays a significant role in the fields of Human-Computer Interaction Techniques. However, the main problem of current speech synthesis techniques is lacking of naturalness and expressiveness so that it is not yet close to the standard of natural language. Another problem is that the human-computer interaction based on the speech synthesis is too monotonous to realize mechanism of user subjective drive. This thesis introduces the historical development of speech synthesis and summarizes the general process of this technique. It is pointed out that prosody generation module is an important part in the process of speech synthesis. On the basis of further research, using eye activity rules when reading to control and drive prosody generation was introduced as a new human-computer interaction method to enrich the synthetic form. In this article, the present situation of speech synthesis technology is reviewed in detail. Based on the premise of eye gaze data extraction, using eye movement signal in real-time driving, a speech synthesis method which can express the real speech rhythm of the speaker is proposed. That is, when reader is watching corpora with its eyes in silent reading, capture the reading information such as the eye gaze duration per prosodic unit, and establish a hierarchical prosodic pattern of duration model to determine the duration parameters of synthesized speech. At last, after the analysis, the feasibility of the above method is verified. © 2016 SPIE.

Yang S.,Tianjin University | Jiang J.,Shenzhen University
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2017

In this paper, we introduce an idea of content-adaptive sparse reconstruction to achieve optimized magnification quality for those down sampled video frames, to which two stages of pruning are applied to select the closest correlated images for construction of an over-complete dictionary and drive the sparse representation of its enlarged frame. In this way, not only the sampling and dictionary training process is accelerated and optimized in accordance with the input frame content, but also an add-on video compression codec can be further developed by applying such scheme as a preprocessor to any standard video compression algorithm. Our extensive experiments illustrate that (i) the proposed content-adaptive sparse reconstruction outperforms the existing benchmark in terms of super-resolution quality; (ii) When applied to H.264, one of the international video compression standards, the proposed add-on video codec can achieve three times more compression while maintaining competitive decoding quality. © 2017 SPIE.

Tan Z.,Tianjin University | Chen D.,Tianjin University
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2016

In this work, an economical and high-efficiency method for detection of melamine in milk was developed. The enrichment effect of coffee-ring was combined with the micro-region analysis of confocal Raman spectroscopy, in addition, assisted with chemometric algorithmthe. Consequently, a desired result was obtained that the LOD of melamine in this method was 1 ppm, which was excellent because the sensitivity of conventional Raman detection was generally low. Furthermore, the whole process were processed in an easily available condition with almost no chemical reagents consumption, and the chosen substrates for the formation of coffee-ring were reusable. Thus, the method is environmental friendly and has a great potential application in food safety inspection. © 2016 SPIE.

Lu L.,Tianjin University | Zhang J.,Tianjin University | Tang W.,Tianjin University
RAIRO - Operations Research | Year: 2017

This paper investigates a distribution channel consisting of a manufacturer and a retailer under a cooperative program, where the manufacturer determines the national advertising and quality improving effort, while the retailer decides the local promotion effort and may undertake parts of the costs of national advertising and quality improving of the manufacturer. It is assumed that the manufacturer's national advertising and quality improving efforts positively affect the brand goodwill and reference price, whereas the retailer's local promotion effort damages them. Three scenarios of the non-cooperative and cooperative scenarios in the decentralized supply chain, and the centralized supply chain scenario, are analyzed. The corresponding equilibrium strategies and profits are obtained and compared, which shows that the cooperative program can achieve payoff-Pareto-improving, but cannot coordinate completely the supply chain. Furthermore, a revenue sharing contract combined with two-subsidy policy is designed to coordinate the decentralized supply chain. Numerical simulation and sensitivity analysis of the coordinating results on the key system parameters are provided to verify the effectiveness of the contract, and some managerial insights are provided. © 2017 EDP Sciences, ROADEF, SMAI.

Li C.,Tianjin University | Su L.,Chongqing University of Technology
Mechanical Systems and Signal Processing | Year: 2017

In this paper, the problems of blind detection and estimation of harmonic signal in strong chaotic background are analyzed, and new methods by using local linear (LL) model are put forward. The LL model has been exhaustively researched and successfully applied for fitting and forecasting chaotic signal in many chaotic fields. We enlarge the modeling capacity substantially. Firstly, we can predict the short-term chaotic signal and obtain the fitting error based on the LL model. Then we detect the frequencies from the fitting error by periodogram, a property on the fitting error is proposed which has not been addressed before, and this property ensures that the detected frequencies are similar to that of harmonic signal. Secondly, we establish a two-layer LL model to estimate the determinate harmonic signal in strong chaotic background. To estimate this simply and effectively, we develop an efficient backfitting algorithm to select and optimize the parameters that are hard to be exhaustively searched for. In the method, based on sensitivity to initial value of chaos motion, the minimum fitting error criterion is used as the objective function to get the estimation of the parameters of the two-layer LL model. Simulation shows that the two-layer LL model and its estimation technique have appreciable flexibility to model the determinate harmonic signal in different chaotic backgrounds (Lorenz, Henon and Mackey–Glass (M–G) equations). Specifically, the harmonic signal can be extracted well with low SNR and the developed background algorithm satisfies the condition of convergence in repeated 3–5 times. © 2016 Elsevier Ltd

Guo D.,Tianjin University | Guo D.,National University of Defense Technology
IEEE Transactions on Parallel and Distributed Systems | Year: 2017

Many data-intensive applications like MapReduce are network-bound in data centers, due to transfer massive amount of flows across successive processing stages. Data flows in such an incast or shuffle transfer are highly correlated and aggregated at the receiver side. Prior work aims to aggregate correlated flows of each transfer, during the transmission phase as early as possible, so as to directly lower down the network traffic. However, many applications do not constrain the flows' endpoints of each transfer as long as certain constraints are satisfied. Such uncertain transfers bring new opportunities and challenges to lower down the network traffic than prior deterministic transfers. In this paper, we focus on aggregating an uncertain incast transfer and minimizing the amount of caused network traffic. Prior approaches, relying on deterministic incast transfers, remain inapplicable. This paper makes the first step towards the study of aggregating uncertain incast transfer. We propose efficient approaches from two aspects, i.e., the initialization of uncertain senders and the incast tree building. We first design two initialization methods to pick the best deterministic senders for an uncertain incast transfer, so as to form the least number of disjoint sender groups. Thus, flows from each group would be aggregated as one flow on a common one-hop neighbor, irrespective of the location of a picked receiver. Accordingly, we propose the interstage-based and intrastage-based incast tree building methods to exploit the benefits of our initialization methods. We provide evidence to show that our approach can achieve the benefits of in-network aggregation for any uncertain incast transfer. Moreover, an uncertain incast transfer significantly outperforms any related deterministic one, in terms of the reduced network traffic and the saved network resources. © 2017 IEEE.

Lu S.-S.,Tianjin University | Lu S.-S.,Nankai University
Nonlinear Analysis: Real World Applications | Year: 2017

We consider the following autonomous Kirchhoff-type equation −(a+b∫RN|∇u|2)Δu=f(u),u∈H1(RN), where a≥0,b>0 are constants and N≥1. Under general Berestycki–Lions type assumptions on the nonlinearity f, we establish the existence results of a ground state and multiple radial solutions for N≥2, and obtain a nontrivial solution and its uniqueness, up to a translation and up to a sign, for N=1. The proofs are mainly based on a rescaling argument, which is specific for the autonomous case, and a new description of the critical values in association with the level sets argument. © 2016 Elsevier Ltd

Zheng S.,Tianjin University | Zhang D.,Tianjin University
Proceedings of IEEE Sensors | Year: 2017

We demonstrate a different strategy to characterize surface acoustic wave induced current in gas molecular doped graphene based on acoustoelectric effect. The measured acoustoelectric current is inversely proportional to conductivity rather than that direct current is proportional to. That behavior is consistent with a simple classical relaxation model. Experimentally the acoustoelectric current exhibits about 4-fold improved sensing sensitivity for chemical doping compared with direct current. Our finding takes new insight to the acoustically induced current and proposes a unique way towards SAW applications to benefit the nanomaterial gas sensors. © 2016 IEEE.

Wang J.,Dongbei University of Finance and Economics | Wang Y.,Tianjin University
International Journal of Green Energy | Year: 2017

Wind resources are becoming increasingly significant due to their clean and renewable characteristics, and the integration of wind power into existing electricity systems is imminent. To maintain a stable power supply system that takes into account the stochastic nature of wind speed, accurate wind speed forecasting is pivotal. However, no single model can be applied to all cases. Recent studies show that wind speed forecasting errors are approximately 25% to 40% in Chinese wind farms. Presently, hybrid wind speed forecasting models are widely used and have been verified to perform better than conventional single forecasting models, not only in short-term wind speed forecasting but also in long-term forecasting. In this paper, a hybrid forecasting model is developed, the Similar Coefficient Sum (SCS) and Hermite Interpolation are exploited to process the original wind speed data, and the SVM model whose parameters are tuned by an artificial intelligence model is built to make forecast. The results of case studies show that the MAPE value of the hybrid model varies from 22.96% to 28.87 %, and the MAE value varies from 0.47 m/s to 1.30 m/s. Generally, Sign test, Wilcoxon’s Signed-Rank test, and Morgan--Granger--Newbold test tell us that the proposed model is different from the compared models. © 2017 Taylor & Francis Group, LLC.

Zhang Z.,Tianjin University | Zhu K.,University of International Business and Economics | Hewings G.J.D.,University of Illinois at Urbana - Champaign
Energy Economics | Year: 2017

Pollution haven hypothesis is an important debate on the environmental effects of international trade, the pattern of which has been reshaped obviously by global production fragmentation recently. The production process is distributed globally, and the pollution haven effect of international trade is becoming more complicated. For instance, intermediate product trade corresponds to the largest share of embodied emissions, and the share of emissions induced by the global value chain related trade is increasing gradually. The aim of this paper is to make a comprehensive analysis on the pollution haven hypothesis in carbon emissions embodied in three different trade patterns from global, bilateral, and national perspectives. We propose a method to parcel the pollution haven hypothesis in a multi-regional input–output analysis and discuss the contribution of production fragmentation for global emissions. It is found that international production fragmentation generates global emissions savings. The intermediate product trade has a negative balance of avoided emissions. The final product trade becomes increasingly less environmentally effective during the period 1995–2009. There are significant differences in the environmental effects of different trade patterns for each country. © 2017

Sha Z.,Tianjin University | Feng H.,Tianjin University | Zeng Z.,Tianjin University
Optics Express | Year: 2017

A phase demodulation method specially developed for direct detection φ-OTDR is proposed and demonstrated. It is the only method to date that can be used for phase demodulation based on pure direct detection system. As a result, this method greatly simplifies the system configuration and lowers the cost. It works by firstly deriving a pair of orthogonal signals from the single-channel intensity and then realizing phase demodulation by means of IQ demodulation. Different forms of PZT induced vibration are applied to the fiber and the phase is correctly demodulated in each case. The experiment results show that this method can effectively perform phase demodulation with extremely simple system configuration. © 2017 Optical Society of America.

Chen B.,Tianjin University
Physical Review C | Year: 2017

I discuss the elliptic flows of ψ(2S) with different production mechanisms in sNN=2.76 TeV Pb-Pb collisions. If the final ψ(2S)s are mainly from the recombination of uncorrelated charm and anticharm quarks at T≈Tc, charm and anticharm quarks will carry large collective flows of the bulk medium, which will be inherited by the regenerated ψ(2S)s. This indicates a larger elliptic flow of ψ(2S) than that of J/ψ which can be regenerated at T≥Tc, v2ψ(2S)>v2J/ψ. However, if the final ψ(2S)s are mainly from the transitions of J/ψ→ψ(2S) caused by the color screening of quark-gluon plasma its elliptic flow should be close to the elliptic flow of J/ψ, v2ψ(2S)∼v2J/ψ. Therefore, ψ(2S) elliptic flow is a sensitive probe for its production mechanisms in relativistic heavy ion collisions. © 2017 American Physical Society.

Yang B.,Tianjin University | Wang Z.,Tianjin University

Mg0.35Cu0.2Zn0.45Fe2O4 nanosize particles have been synthesized by chemical co-precipitation method and characterized by X-ray diffraction (XRD) and vibrating sample magnetometry (VSM). The XRD patterns confirmed the single phase spinel structure of the synthesized powder. The average crystallite size of the powder varied from 14 to 55 nm by changing annealing temperature. The activation energy for crystal growth was estimated as about 18.61KJ/mol. With the annealing temperature increasing, saturation magnetization (MS) was successively increased while the coercivity (HC) was first increased, passed through a maximum and then declined. The sintering temperature has significant influence on bulk density, initial permeability and Curie temperature of Mg0.35Cu0.2Zn0.45Fe2O4 ferrite. © 2017 Author(s).

Chen X.-Y.,Tianjin University | Tian Z.,Tianjin University
Chinese Optics | Year: 2017

Graphene is a two-dimensional material and has unique electrical and optical properties, which has been widely used in the research of terahertz wave dynamic modulation in recent years. In this paper, we reviews the terahertz wave dynamic modulation device based on graphene, analyze the principle and advantages and disadvantages of three kind of modulation methods such as electrical modulation, optical modulation and photoelectric hybrid modulation. We introduce a series of research achievements on the application of graphene in THz wave dynamic modulation in recent years, compare and analyze the advantages and disadvantages of the modulation performance of different devices. Graphene tunable metamaterial provides a new way to achieve more rapid and efficient terahertz modulator. © 2017, China Science Publishing & Media LTD. All right reserved.

Shin D.W.,Hanyang University | Shin D.W.,Korea Institute of Energy Research | Guiver M.D.,Hanyang University | Guiver M.D.,Tianjin University | Lee Y.M.,Hanyang University
Chemical Reviews | Year: 2017

A fundamental understanding of polymer microstructure is important in order to design novel polymer electrolyte membranes (PEMs) with excellent electrochemical performance and stabilities. Hydrocarbon-based polymers have distinct microstructure according to their chemical structure. The ionic clusters and/or channels play a critical role in PEMs, affecting ion conductivity and water transport, especially at medium temperature and low relative humidity (RH). In addition, physical properties such as water uptake and dimensional swelling behavior depend strongly on polymer morphology. Over the past few decades, much research has focused on the synthetic development and microstructural characterization of hydrocarbon-based PEM materials. Furthermore, blends, composites, pressing, shear field, electrical field, surface modification, and cross-linking have also been shown to be effective approaches to obtain/maintain well-defined PEM microstructure. This review summarizes recent work on developments in advanced PEMs with various chemical structures and architecture and the resulting polymer microstructures and morphologies that arise for potential application in fuel cell, lithium ion battery, redox flow battery, actuators, and electrodialysis. © 2017 American Chemical Society.

News Article | April 17, 2017
Site: cen.acs.org

Unactivated alkanes are difficult to functionalize, and most catalysts that derivatize them by opening hydrocarbon C–H bonds are based on precious transition metals. Researchers have now developed a class of intermolecular C–H arylation reactions that use catalysts made from more-abundant materials: silicon and boron. The reaction adds aryl groups to C–H bonds of simple hydrocarbons, including to the notoriously inert bonds in methane, at mild temperatures (Science 2017, DOI: 10.1126/science.aam7975). “Alkanes are bulk components of gasoline and as such are supercheap commodities, which, if converted to functionalized compounds, would become much more valuable,” comments Jay Siegel of Tianjin University, who developed a related intramolecular reaction but was not involved in the new study. “This is an area rich in prospects, with a bright future for chemical synthetic methods development.” Hosea M. Nelson and coworkers at the University of California, Los Angeles, prepare the new organosilicon catalyst from an organosilane and a weakly coordinating carborane anion. The catalyst defluorinates an aryl fluoride starting material, likely generating an aryl cation intermediate that inserts electrophilically into a C–H bond of an alkane substrate to yield an arylated alkane. A key trimethylsilyl group on the aryl fluoride aids fluoride abstraction, helps the cation react quickly, and eases catalyst regeneration. At press time, Nelson was scheduled to discuss the findings this week in a Division of Organic Chemistry presentation at the ACS national meeting in San Francisco. “Electrophilic reactions with methane are exceptionally rare, and the C–H functionalization of methane reveals the extraordinary reactivity of this system,” says Douglas Klumpp of Northern Illinois University, an expert on highly reactive electrophilic intermediates. The clever use of a trimethylsilyl group, he says, enabled the researchers “to tame a lion,” the aryl cation intermediate, “and that lion is able to do some very nice tricks.” However, Klumpp notes that one limitation of the chemistry is that “the aryl fluoride starting materials are expensive or difficult to obtain.” “The chemistry isn’t ready for prime-time applications,” Nelson says. “It’s a new strategy that will hopefully fuel further study. We need to find ways to improve the reaction’s efficiency, selectivity, and substrate scope. We have filed a provisional patent and look forward to working with the chemical industry to develop practical applications.”

News Article | April 17, 2017
Site: phys.org

A "self-heating" boron catalyst that makes particularly efficient use of sunlight to reduce carbon dioxide (CO2) serves as a light harvester, photothermal converter, hydrogen generator, and catalyst in one. In the journal Angewandte Chemie, researchers introduce a photothermocatalytic reaction that requires no additives beyond water. This could form the basis of a new, more efficient process for converting the greenhouse gas CO2 into a useful carbon source for the production of fuels and chemical products. The ideal route for making CO2 useful is considered to be reduction aided by a photocatalyst to use sunlight as the only source of energy—a process that corresponds to the first step of photosynthesis. Despite decades of research, processes for converting CO2 are still too inefficient. "This is largely due to the insufficient utilization of solar light, the high energy barrier for CO2 activation, and the sluggish kinetics of the multiple electron and proton transfer processes," explains Jinhua Ye. Working with a team for the National Institute for Materials Science (NIMS) in Tsukuba, Ibaraki, and Hokkaido University in Sapporo (Japan), as well as Tianjin University and Nanjing University of Aeronautics and Astronautics (China), Ye is now pursuing a strategy that uses both the light and thermal energy provided by sunlight. When the sun shines on a surface, it is heated. The researchers want to use this ordinary photothermic effect to increase the efficiency of catalytic systems. Their material of choice is powdered elemental boron, which very strongly absorbs sunlight and efficiently converts it photothermically, heating itself up remarkably. This allowed the team to carry out the efficient reduction of CO2 to form carbon monoxide (CO) and methane (CH4) under irradiation in the presence of water, with no additional reagents or co-catalysts. Irradiation causes the boron particles to heat up to about 378 °C. At this temperature it reacts with water, forming hydrogen and boron oxides in situ. The boron oxides act as "traps" for CO2 molecules. The hydrogen is highly reactive and, in the presence of the light-activated boron catalyst, efficiently reduces the CO2 by providing the necessary protons (H+) and electrons. "The key to our success lies in the favorable properties of the boron powder, which make it an all-in-one catalyst: light harvester, photothermic converter, hydrogen source, and catalyst," says Ye. "Our study confirms the highly promising potential of a photothermocatalytic strategy for the conversion of CO2 and potentially opens new vistas for the development of other solar-energy-driven reaction systems." Explore further: Hydrogen from sunlight—but as a dark reaction More information: Guigao Liu et al. Elemental Boron for Efficient Carbon Dioxide Reduction under Light Irradiation, Angewandte Chemie International Edition (2017). DOI: 10.1002/anie.201701370

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

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.

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.

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 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.

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

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.

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.

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

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.

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: European Commission | 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: European Commission | 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.

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.

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.

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.

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.

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.

News Article | March 24, 2016
Site: phys.org

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."

News Article | February 15, 2017

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

News Article | March 29, 2016
Site: www.nanotech-now.com

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.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 | March 25, 2016
Site: www.greencarcongress.com

« 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.

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.

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.

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

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.

News Article | February 15, 2017
Site: phys.org

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

News Article | February 15, 2017
Site: www.nanotech-now.com

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.

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.

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.

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.

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.

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.

Patent
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.

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 Nï£¿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.

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.”

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.

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.

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.

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.