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Gas Sensing Properties and In Situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy Study of Acetone Adsorption and Reactions on SnO2 Films

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SENSORS AND MATERIALS 2014年第9期26卷 649-663页

作者： Zhang, Zhenxin Huang, Kaijin Yuan, Fangli Xie, Changsheng Huazhong Univ Sci & Technol State Key Lab Mat Proc & Die & Mould Technol Wuhan 430074 Peoples R China Chinese Acad Sci Inst Proc Engn State Key Lab Multiphase Complex Syst Beijing 100190 Peoples R China Wuhan Univ Technol State Key Lab Adv Technol Mat Synth & Proc Wuhan 430070 Peoples R China

SnO2 flat-type coplanar gas sensor arrays were fabricated by a screen-printing technique based on SnO2 nanopowders prepared by a sol-gel method. The SnO2 flat-type coplanar gas sensor arrays had good acetone gas-sensing characteristics such as a fast response, short recovery time, and an almost linear response to acetone concentration of 1-100 ppm. The response could reach 2.11 for acetone concentration as low as 1 ppm, and the response and recovery times for 1 ppm acetone were 8.9 and 10 s, respectively. The surface reactions were investigated by in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) at different temperatures, and a possible sensing mechanism was proposed. Formate, acetate, carbonate ions, CH3O(ads), CO2, H2O, and adsorbed acetone were detected when the SnO, flims were exposed to 100 ppm acetone at different temperatures.

关键词： flat-type coplanar gas sensor arrays acetone SnO2 films in situ DRIFTS

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Interfacial Reaction Between Nb Foil and n-Type PbTe Thermoelectric Materials During Thermoelectric Contact Fabrication

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JOURNAL OF ELECTRONIC MATERIALS 2014年第11期43卷 4064-4069页

作者： Xia, Haiyang Chen, Cheng-Lung Drymiotis, Fivos Wu, Aiping Chen, Yang-Yuan Snyder, G. Jeffrey CALTECH Dept Mat Sci Pasadena CA 91125 USA Tsinghua Univ Dept Mech Engn Beijing 100084 Peoples R China Minist Educ Key Lab Adv Mat Proc Technol Beijing Peoples R China Acad Sinica Inst Phys Taipei 11529 Taiwan

PbTe is a high-conversion-efficiency thermoelectric (TE) material that is commonly used in space exploration applications. Integration of PbTe in TE devices has a significant impact on the conversion efficiency and reliability of TE devices. Hence, our effort focuses on developing novel approaches for bonding metallic contacts to PbTe to improve device performance and reliability. In this study, pure Nb foil was directly bonded to PbTe-based TE materials to fabricate the hot-side contacts of TE elements using a rapid hot-press. The materials were sintered at 700A degrees C under pressure of 40 MPa for various holding times. We found that a reaction layer of needle-like Nb3Te4 mixed with Pb forms at the interface of the Nb/PbTe joints and that Pb is distributed in the gaps of the Nb3Te4 grains. We analyze the resulting microstructure and finally calculate the time exponent of the growth kinetics of the Nb3Te4 layer. Fracture surface analysis showed that the Nb/PbTe joint fractures at the interface between Nb and Nb3Te4 and within the PbTe matrix, indicating that the bonding between Nb and Nb3Te4 is weak.

关键词： PbTe-based thermoelectric materials Nb foil Nb/PbTe joints hot-press sintering

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Using Laser Surface Treatment to Produce a Slideway on a Computer Numerical Control (CNC) Machine Tool with Biomimetic Characteristics

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LASERS IN engineering 2015年第5-6期31卷 321-332页

作者： Wang, Y-Q. Yuan, X-H. Pan, X-H. Gu, Y. Zhejiang Univ Ningbo Inst Technol Ningbo 315100 Zhejiang Peoples R China Zhejiang Univ State Key Lab Fluid Power Transmiss & Control Hangzhou 310027 Zhejiang Peoples R China Zhejiang Prov Key Lab Part Rolling Forming Techno Ningbo 315000 Zhejiang Peoples R China

The machining accuracy and service life of a computer numerical control (CNC) machine tool declines with the wear of components. In order to improve the performance of accuracy sustainability, this work introduced the biological coupling theory into the field of CNC machine tool. First, the slideway with biomimetic surface characteristics was manufactured by the laser processing. Second, the slideway with biomimetic surface characteristics was examined using an optical microscope, a scanning electron microscope (SEM) and X-ray diffraction (XRD). Then, the reciprocating wear tests were carried out under boundary lubrication. The wear resistance of the slideway with biomimetic surface characteristics was greatly improved in comparison with the as-received slideway. The non-smooth surface and soft-hard segment structure were achieved, which contributed to the improvement of the anti-wear performance of the slideway with biomimetic surface characteristics. The present approach provides a new method for prolonging the accuracy sustainability of CNC machine tool.

关键词： Nd:YAG laser surface treatment computer numerical control (CNC) machine tool slideway biomimetic wear accuracy sustainability

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Upconversion Luminescence Properties of Phase and Size Controlled NaLnF₄:Yb³⁺, Er³⁺(Ln = Y, Gd) Nanoparticles

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JOURNAL OF NANOSCIENCE AND NANOtechnology 2015年第1期15卷 368-372页

作者： Hu, Rongxuan Ye, Song Wang, Huiyun Zhang, Wenjun Zhang, Zhiyuan Lin, Jian Wang, Deping Tongji Univ Sch Mat Sci & Engn Shanghai 201806 Peoples R China Tongji Univ Sch Phys Sci & Engn Shanghai 201806 Peoples R China

The upconversion luminescent nanoparticles of NaLnF(4) (Ln = Y, Gd):Yb3+, Er3+ were prepared through a facile modified solvothermal method, in which the phase (cubic or hexagonal) and size of the NaLnF(4) nanoparticles can be well controlled by adjusting Gd3+ content. The Gd3+ content dependent phase transformation and size change were systematically studied by the XRD and TEM measurements. The spectral measurement revealed that both the emission intensity and the intensity ratio of red (F-4(9/2) -> I-4(15/2)) to green (H-2(11/2), S-4(3/2) -> I-4(15/2)) are tunable, and a significant increase of the visible upconversion emission intensity can be realized by optimizing Gd3+ content at x = 0.25 under 980 nm excitation. Furthermore, the excitation power dependent red and green emission intensities of Er3+ were measured for various NaLnF(4) (Ln = Y, Gd):Yb3+, Er3+ nanoparticles with different Gd3+ content to investigate the influence of the phase and particle size on the upconversion luminescence properties. This research provided a new method to synthesize the upconversion nanoparticles with tunable luminescence properties by adjusting Gd3+ content.

关键词： Tunable Upconversion Luminescence NaLnF(4) (Ln = Y, Gd) Rare Earth Ions

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Creep Behaviors of Sn0.7Cu0.1Co0.05Ni/Cu Soldering Joints

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IEEE TRANSACTIONS ON COMPONENTS PACKAGING AND MANUFACTURING technology 2014年第12期4卷 2058-2065页

作者： Cheng, Fangjie Ma, Zhaolong Wang, Ying Zou, Qingbin Tianjin Univ Sch Mat Sci & Engn Tianjin 300072 Peoples R China Tianjin Key Lab Adv Joining Technol Tianjin 300072 Peoples R China

The creep behaviors of as-soldered and aged Sn0.7Cu0.1Co0.05Ni/Cu joints were studied in this paper. The results indicate that the creep behaviors of as-soldered Sn0.7Cu0.1Co0.05Ni/Cu joints are inferior to those of as-soldered Sn0.7Cu/Cu joints under shear stress of 15-22.5 MPa at 293 and 333 K, respectively. However, the creep behaviors of Sn0.7Cu0.1Co0.05Ni/Cu joints are superior to those of Sn0.7Cu/Cu joints after aging at 423 K for 24 h. The underlying creep mechanisms of the Sn0.7Cu and Sn0.7Cu0.1Co0.05Ni/Cu solder joints at experimental condition are suggested. Meanwhile, the microstructure analysis indicates that the superior creep properties of aged Sn0.7Cu0.1Co0.05Ni/Cu joints may mainly attribute to the coarsening resistance of interfacial intermetallic compounds during aging.

关键词： Aging creep behavior solder joints

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Optimized Hyperspectral Band Selection Using Particle Swarm Optimization

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IEEE JOURNAL OF SELECTED TOPICS IN APPLIED EARTH OBSERVATIONS AND REMOTE SENSING 2014年第6期7卷 2659-2670页

作者： Su, Hongjun Du, Qian Chen, Genshe Du, Peijun Hohai Univ Sch Earth Sci & Engn Nanjing 210098 Jiangsu Peoples R China Mississippi State Univ Dept Elect & Comp Engn Starkville MS 39762 USA DCM Res Resources LLC Germantown MD 20874 USA Nanjing Univ Jiangsu Prov Key Lab Geog Informat Sci & Technol Nanjing 210023 Jiangsu Peoples R China

A particle swarm optimization (PSO)-based system is proposed to select bands and determine the optimal number of bands to be selected simultaneously, which is near-automatic with only a few data-independent parameters. The proposed system includes two particle swarms, i.e., the outer one for estimating the optimal number of bands and the inner one for the corresponding band selection. To avoid employing an actual classifier within PSO so as to greatly reduce computational cost, criterion functions that can gauge class separability are preferred;specifically, minimum estimated abundance covariance (MEAC) and Jeffreys-Matusita (JM) distance are adopted in this research. The experimental results show that the 2PSO-based algorithm outperforms the popular sequential forward selection (SFS) method and PSO with one particle swarm in band selection.

关键词： Band selection hyperspectral imagery particle swarm optimization (PSO)

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Remodeling the network for microgroup detection on microblog

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KNOWLEDGE AND INFORMATION SYSTEMS 2014年第3期39卷 643-665页

作者： Xiong, Xiaobing Zhou, Gang Niu, Xiang Huang, Yongzhong Xu, Ke State Key Lab Math Engn & Adv Comp Zhengzhou Peoples R China Beihang Univ State Key Lab Software Dev Environm Beijing Peoples R China

In this paper, we focus on the problem of community detection on Sina weibo, the most popular microblogging system in China. By characterizing the structure and content of microgroup (community) on Sina weibo in detail, we observe that different from ordinary social networks, the degree assortativity coefficients are negative on most microgroups. In addition, we find that users from the same microgroup tend to share some common attributes (e. g., followers, tags) and interests extracted from their published posts. Inspired by these new findings, we propose a united method to remodel the network for microgroup detection while maintaining the information of link structure and user content. Firstly, the link direction is concerned by assigning greater weight values to more surprising links, while the content similarity is measured by the Jaccard coefficient of common features and interest similarity based on Latent Dirichlet Allocation model. Then, both link direction and content similarity between two users are uniformly converted to the edge weight of a new remodeled network, which is undirected and weighted. Finally, multiple frequently used community detection algorithms that support weighted networks could be employed. Extensive experiments on real-world social networks show that both link structure and user content play almost equally important roles in microgroup detection on Sina weibo. Our method outperforms the traditional methods with average accuracy improvement up to 39%, and the number of unrecognized users decreased by about 75%.

关键词： Microblogging Community detection Link structure User content United method

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Dynamic classifier selection using spectral-spatial information for hyperspectral image classification

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JOURNAL OF APPLIED REMOTE SENSING 2014年第1期8卷

作者： Su, Hongjun Yong, Bin Du, Peijun Liu, Hao Chen, Chen Liu, Kui Hohai Univ State Key Lab Hydrol Water Resources & Hydraul En Nanjing 210098 Jiangsu Peoples R China Nanjing Univ Jiangsu Prov Key Lab Geog Informat Sci & Technol Nanjing 210046 Jiangsu Peoples R China Wuhan Univ State Key Lab Informat Engn Surveying Wuhan 430079 Peoples R China Univ Texas Dallas Dept Elect Engn Richardson TX 75080 USA

This paper presents a dynamic classifier selection approach for hyperspectral image classification, in which both spatial and spectral information are used to determine a pixel's label once the remaining classified pixels' neighborhood meets the threshold. For volumetric texture feature extraction, a volumetric gray level co-occurrence matrix is used;for spectral feature extraction, a minimum estimated abundance covariance-based band selection is used. Two hyperspectral remote sensing datasets, HYDICE Washington DC Mall and AVIRIS Indian Pines, are employed to evaluate the performance of the developed method. The classification accuracies of the two datasets are improved by 1.13% and 4.47%, respectively, compared with the traditional algorithms using spectral information. The experimental results demonstrate that the integration of spectral information with volumetric textural features can improve the classification performance for hyperspectral images. (C) 2014 Society of Photo-Optical Instrumentation Engineers (SPIE)

关键词： dynamic classifier selection volumetric textural feature spectral feature hyperspectral image classification

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Self-consistent fluid modeling and simulation on a pulsed microwave atmospheric-pressure argon plasma jet

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JOURNAL OF APPLIED PHYSICS 2014年第15期116卷

作者： Chen, Zhaoquan Yin, Zhixiang Chen, Minggong Hong, Lingli Xia, Guangqing Hu, Yelin Huang, Yourui Liu, Minghai Kudryavtsev, A. A. St Petersburg State Univ Fac Phys St Petersburg 198504 Russia Anhui Univ Sci & Technol Coll Elect & Informat Engn Huainan 232001 Anhui Peoples R China Huazhong Univ Sci & Technol State Key Lab Adv Electromagnet Engn & Technol Wuhan 430074 Hubei Peoples R China

In present study, a pulsed lower-power microwave-driven atmospheric-pressure argon plasma jet has been introduced with the type of coaxial transmission line resonator. The plasma jet plume is with room air temperature, even can be directly touched by human body without any hot harm. In order to study ionization process of the proposed plasma jet, a self-consistent hybrid fluid model is constructed in which Maxwell's equations are solved numerically by finite-difference time-domain method and a fluid model is used to study the characteristics of argon plasma evolution. With a Guass type input power function, the spatio-temporal distributions of the electron density, the electron temperature, the electric field, and the absorbed power density have been simulated, respectively. The simulation results suggest that the peak values of the electron temperature and the electric field are synchronous with the input pulsed microwave power but the maximum quantities of the electron density and the absorbed power density are lagged to the microwave power excitation. In addition, the pulsed plasma jet excited by the local enhanced electric field of surface plasmon polaritons should be the discharge mechanism of the proposed plasma jet. (C) 2014 AIP Publishing LLC.

关键词： Plasma jets

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Discovery of a reductase-producing strain recombinant E. coli CCZU-A13 using colorimetric screening and its whole cell-catalyzed biosynthesis of ethyl (R)-4-chloro-3-hydroxybutanoate

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BIORESOURCE technology 2014年 172卷 342-348页

作者： He, Yu-Cai Zhang, Dan-Ping Tao, Zhi-Cheng Zhang, Xian Yang, Zhen-Xing Changzhou Univ Jiangsu Key Lab Adv Catalyt Mat & Technol Changzhou Peoples R China Rice Univ Dept Bioengn Houston TX USA

An NADH-dependent reductase (SsCR) was discovered by genome data mining. After SsCR was overexpressed in E. coli BL21, recombinant E. coli CCZU-A13 with high reductase activity and excellent stereoselectivity for the reduction of ethyl 4-chloro-3-oxobutanoate (COBE) into ethyl (R)-4-chloro-3-hydroxybutanoate ((R)-CHBE) was screened using one high-throughput colorimetric screening strategy. After the reaction optimization, a highly stereoselective bioreduction of COBE into (R)-CHBE (>99% ee) with the resting cells of E. coli CCZU-A13 was successfully demonstrated in n-butyl acetate-water (10:90, v/v) biphasic system. Biotransformation of 600 mM COBE for 8 h in the biphasic system, (R)-CHBE (>99% ee) could be obtained in the high yield of 100%. Moreover, the broad substrate specificity in the reduction of aliphatic and aromatic carbonyl compounds was also found. Significantly, E. coli CCZU-A13 shows high potential in the industrial production of (R)-CHBE (>99% ee) and its derivatives. (C) 2014 Elsevier Ltd. All rights reserved.

关键词： Asymmetric bioreduction Recombinant E. coli CCZU-A13 Ethyl 4-chloro-3-oxobutanoate Ethyl (R)-4-chloro-3-hydroxybutanoate Biphasic system

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