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August 15,2014
Volume 7,Issue 15
Pages -
Subject Area:Condensed Matter Physics,Explosion Mechanics,Fluid Mechanics,Experimental Solid Mechanics

Title: NH3 gas sensor based on Si nanowires synthesized on the sapphire substrate

Authors: ZHOU Chang, HU Lizhong, ZHANG Heqiu, QIU Yu, CHEN Jian, LI Lipeng
PP: 1567-1571
Abstract: In this study, Si nanowires were synthesized by chemical vapor transport（CVT） on the sapphire substrate, and their morphologies were analyzed by scanning electron microscope (SEM). The results showed that the morphology of Si nanowires was network-like. The length of the Si nanowires was in micrometers range. The diameter of the nanowires was in the range of 40 to 110 nm. A Si nanowires based NH3 gas sensor was prepared using a very simple on-chip fabrication method. And the sensing properties of the sensor were studied in different NH3 gas concentrations. Its advantage of quick recovery in less than 10 s was found. The simple fabrication and low cost of the sensor make it has potential value in practical production and application.
Keywords: semiconductor physics; Si nanowires; NH3 gas sensor; chemical vapor transport

Title: Growth and properties of ZnO: Eu NRs on B-doped diamond film

Authors: YU Qi, MA Yibo, PEI Xiaoqiang, LIU Junsong, SANG Dandan, YANG Yizhou, CHENG Shaoheng, WANG Qiliang, LI Hongdong
PP: 1562-1566
Abstract: In this paper, by hydrothermal method, the Eu doped zinc oxide nanorods (ZnO: Eu NRs) have been fabricated on p-type B-doped diamond films. The morphology, ultraviolet photoluminescence (UV-PL) and heterojunction electrical characteristic of the ZnO: Eu NRs are investigated. With increasing the doping level of Eu, a phenomenon of top aggregation emerges for the ZnO: Eu NRs, and the intensity of the UV-PL emission is enhanced. For the current-voltage measurements of the constructed ZnO: Eu NRs/p-diamond heterojunctions, a rectifying behavior is presented, and a possible negative differential resistance characteristic in the forward voltage is observed.
Keywords: semiconductor physics; ZnO; Eu doped; ZnO: Eu/p-diamond heterojunction; rectifying characteristic

Title: Molecular dynamics study of Si-terminated β-SiC(001) surface atomic structure changed with temperature

Authors: MA Li, ZHAO Yaolin, HE Chaohui, ZHANG Peng, ZANG Hang, GUO Daxi, XI Jianqi, LI Tao, CAO Xingqing
PP: 1556-1561
Abstract: Molecular dynamics (MD) simulations with Tersoff/ZBL potential have been performed to determine the surface atomic configurations for Si-terminated β-SiC(001) at different temperatures. Our results indicate that the Si-dimer is the major portion of the metastable configuration of Si-terminated β-SiC(001) at different temperatures and as the increases of temperature. Some Si-trimers are observed on the surface, which their number has a non-linear variation with temperature. In addition, there are many Si-C-tribonds on Si-terminated β-SiC(001) at T=2 200 K and a special kind of relationship at T>100 K is obtained, which is n3≈|n2-0.5|(where n2 denotes the atom number density of Si-dimers, n3 stands for the atom number density of Si-trimers). This study helps us to understand the metastable configuration of Si-terminated β-SiC(001) at different temperatures.
Keywords: condensed matter physics; surface; Si-dimer; Si-trimer; molecular dynamics

Title: A study on the dynamics of a biomacromolecule chain passing through biomembrane under bio-electricity action

Authors: WEN Xiaohui
PP: 1551-1555
Abstract: In this paper, molecular dynamics (MD) method is adopted to study the dynamics of a biomacromolecule chain passing through biomembrane under bio-electricity action. It is found that the length of biomacromolecule chain has well scale relation with the time of passing through biomembrane; due to the difference of physics mechanics between short and long biomacromolecule chain, their translocation process is also different. In addition, with the magnitude change of bio-electricity, the translocation time is different. This study helps us to understand the complex life process and acts as theoretical direction to potential applications.
Keywords: condensed matter physics; biomacromolecule chain; bio-electricity; translocation time

Title: First-principles study of the intrinsic defects in cubic BC2N

Authors: TIAN Fubo, LI Da, DUAN Defang, CHEN Changbo, SHA Xiaojing, LIU Bingbing, CUI Tian
PP: 1546-1550
Abstract: First principles pseudopotential method based on density functional theory was performed to investigate the stability and properties of intrinsic defects in cubic BC2N (c-BC2N). The calculated results show that antisite defect NB and all self-vacancies (VB, VCI, VCII, VN), have high formation energies and are hence unstable. The antisite defects BN, CB, BCI, and NCII have lower formation energies. The antisite defects BCII, CN, and NCI are the most stable defects with the lowest formation energies among the intrinsic defects in c-BC2N under B-rich, C-rich, and N-rich growth conditions, respectively. Further electronic structure studies indicate that BCII and CN show p-type conductivity and NCI exhibits n-type conductivity, and BN does not change the semiconducting character of c-BC2N according to the electronic structures.
Keywords: condensed matter physics; intrinsic defects; first-principle; formation energy; cubic BC2N

Title: Auto-identification for single cell back-scattering micro-spectrum using principal component analysis

Authors: WANG Cheng, WEN Miao, BAI Lihong, WENG Xiaofu2 WEI Xunbin
PP: 1541-1545
Abstract: In order to accomplish discrimination of the cell, based on confocal back scattering micro-spectroscopy system, a lot of normal stomach epithelial cells and cancerous cells micro spectra were collected. Statistic procedure of the micro-spectra of two kinds of the cells was made using principal component analysis (PCA) and the first two scores of the principal components were utilized to distinguish different kind of cells. The results showed that it can clearly distinguish the confocal back scattering micro-spectra of the normal gastric epithelial cells from cancer cells using PCA. This demonstrated that the confocal back scattering micro-spectroscopy system based on fiber is able to identify the different cell and realize automatically classifying cell using PCA. This will provide a new method for early diagnosis of gastric cancer with fast, accurate and cost-effective at single-cell level.
Keywords: optics; micro-spectrum; single cell; principal component analysis; automatic identification

Title: A design of a planar meta-lens for manipulation of terahertz wavefront

Authors: ZHENG Jingkui, MA Yungui
PP: 1535-1540
Abstract: Based on the transmission-line model and a meander metal line structure, we proposed a design of a set of phase-modulating units working at terahertz, and a further design of a terahertz wavefront-shaping len was proposed. This proposal is demonstrated for terahertz wave transmission with high efficiency over a subwavelength scale, which yields crucial benefits for terahertz technology improvements and applications.
Keywords: optics; terahertz; wavefront-shaping len; negative dielectric constant; phase modulation

Title: 2D surface soliton array at the interface of SBN and air due to longitudinal modulational instability

Authors: KANG Huizhen, LIU Ruixue, YANG Xi, SHAO Weiwei, ZHANG Tianhao
PP: 1531-1534
Abstract: In this paper, an electric field was applied on the grating formed by incident beam and reflected beam on the output face when total internal reflection of beam occurred on the crystal surface paralleled with the c-axis. For the first time, we observed two-dimensional surface soliton array due to longitudinal modulational instability (MI) at the interface of strontium barium niobate(SBN) and air. The applied electric field intensity and the stability time needed to form the 2D surface solitons array by ordinary and extraordinary beam were different. The patterns broke into filaments when the extraordinary beam was incident, while the patterns broke into the solitons arrays when the ordinary beam was incident.
Keywords: optics; longitudinal modulational instability; grain boundary; two-dimensional array

Title: Damage detection in thermal protection tiles based on modal analysis

Authors: XIA Wei, ZHAO Dongwei, ZHANG Zhengzhi
PP: 1525-1530
Abstract: Tiles are important outer structures in thermal protection system (TPS) of high-speed vehicles. They are usually damaged when subject to hypervelocity particle impacts. In this paper, a typical structural configuration of TPS is considered. The free vibration mode of ceramic tiles is analyzed based on finite element model, and the vibration based damage detection method is applied in ceramic tiles. With a thorough analysis for damage sensitivity of vibration natural frequency and mode shape, the conclusions are reached that the natural frequency is insensitive to tile damage, while modal assurance criteria (MAC) and coordinate modal assurance criteria (COMAC) values based on mode shapes are sensitive and can be used to detect tile damage level and location, respectively.
Keywords: vibration and wave; damage detection; ceramic tiles; vibration mode

Title: Meso-level numerical simulation of heterogeneous condensed explosive with binder

Authors: HUAN Shi, TAO Weijun
PP: 1519-1524
Abstract: Pore-collapse hot-spot mechanism is considered the main mechanism of shock initiation. Based on LS-DYNA program, the meso-level numerical simulation was carried out on the heterogeneous condensed explosives under impact. The numerical simulation showed that the effective plastic strain at the pore radii raised rapidly after two reflections, but the outer radii raised slowly. And the binder effectively extended the hot-spot formation time of the initial stage.
Keywords: explosion mechanics; explosive particle; meso-level; numerical simulation; pore

Title: Comparative analysis of alternating current electroosmosis, electrothermal effect and natural convection in microfluidic chips

Authors: ZHANG Feng, CHEN Han
PP: 1508-1518
Abstract: In this paper, the flow fields in microfluidic devices caused by alternating current electroosmosis (ACEO), electrothermal effect (ETE) and natural convection are investigated under various experimental parameters. The slip velocity on micro electrodes caused by ACEO and fluid volumetric force caused by ETE are firstly studied analytically. Then, numerical simulation is conducted to study the effects of ACEO, ETE and natural convection on the flow fields in microfluidic devices under various experimental parameters, and their relative importance is also analyzed. The conclusion is drawn that natural convection can be neglected under normal experimental conditions.
Keywords: fluid mechanics; alternating current electroosmosis; electrothermal effect; natural convection

Title: Experimental study of steel fiber reinforced concrete tri-axial split strength under quasi-static and impact loading

Authors: QU Jia, ZOU Guangping, XIA Peixiu
PP: 1501-1507
Abstract: Splitting tensile test methodology has been established for the concrete spheriform specimens with the principal stress ratio σ1∶σ2∶σ3=0.24∶0.24∶-1.00 in order to study the tensile-tensile-compressive tri-axial strength. With the application of universal material testing machine and split Hopkinson pressure bar (SHPB), the quasi-static and dynamic splitting tensile tests have been exerted for the concrete spheriform specimens with 1% steel fiber dosage. In the quasi-static test, the average strain rate of the steel fiber reinforced concrete specimens is 8.3×10-5 s-1 and the splitting tensile strength is 0.77 MPa, which is consistent with the existing papers. In high strain rate tests, the average strain rate is 170 s-1 and the splitting tensile strength is 1.01 MPa. Compared with the quasi-static testing results, it is shown that the splitting tensile strength of steel fiber reinforced concrete increases with the rise of strain rate.
Keywords: experimental solid mechanics; tri-axial split strength; split Hopkinson pressure bar; steel fiber reinforced concrete; principal stress ratio; strain rate

Title: Impacts of anisotropic lithiation induced deformation on the phase separation and stress in LiFePO4 electrode

Authors: SONG Yicheng, LI Zongzan
PP: 1494-1500
Abstract: This paper aims to explore the impacts of anisotropic lithiation induced deformation on the phase separation and stress of Li-poor and Li-rich phases in LiFePO4 film electrodes by phase field method. Multiphysics were coupled via energies, the governing equation of the diffusion of lithium ions was obtained with the variation theory, and finally the concentration of lithium ions and stress in phase separation structure were calculated with respect to different alignments of LiFePO4 lattice. It was found that aligning the direction of maximum lithiation deformation of LiFePO4 lattice along with the film plane and parallel to the phase boundary led to higher stress and strain energy, which significantly suppressed the phase separation structure, whereas the suppression was much less significant when the direction of maximum lithiation deformation was along the thickness of film and vertical to the phase boundary due to lower stress and strain energy. Therefore, the anisotropic lithiation induced deformation, which was important to the lithium ion concentration and distribution of stress, should be considered in the designing of an electrode to reduce the stress in charge and discharge and ensure the cycle life of electrodes.
Keywords: solid mechanics; lithium ion battery; lithiation; anisotropic; phase separation

Title: Morphology design of elastic plates containing inclusions with eigencurvature

Authors: TIAN Zhongliang, LIANG Haiyi
PP: 1485-1493
Abstract: Appearances of a deformed plate can be controlled by designing specific distribution of inclusions with eigencurvature within it. In this paper, some theory concerning the deformation of a plate containing inclusions with eigencurvature is introduced and corroborated by using ABAQUS. The out-of-place displacement of a plate containing one or more circular inclusions with eigencurvature is investigated and also the interactions between inclusions are studied through simulation. Ultimately, the idea of origami is carried out through dominating the deformation of a thin plate containing designated distribution of inclusions with eigencurvature.
Keywords: solid mechanics; plate; inclusion; eigencurvature; interaction

Title: Research progress of design and experiments for ultra-high temperature materials and its complex structure

Authors: YAO Xuefeng, MA Yinji, SU Yunquan
PP: 1469-1484
Abstract: When the hypersonic reentry vehicles enter into the orbit or return to the ground, the ultra-high temperature materials and its complex structure will be suffered from harsh aerodynamic loads and aerodynamic heating, which leads to the complicated relationships among the internal complex stress state of the materials and the structure, the failure mode and the thermal ablation coupled field. This paper analyzed and summarized the research progress about the design of ultra high temperature materials, the thermal barrier coatings, the thermo-mechanical coupling analysis and the high temperature experimental mechanics, which indicates the key scientific problems and the difficulties of the design and the experiments for the ultra-high temperature materials and its complex structure. The future research will be focused on: the microstructure oxide model of the ultra-high temperature materials, the buckling failure of the thermal barrier coating, the thermo-mechanical-ablation multi-field coupling analysis, optimal design of thermal protective structure, the ultra-high temperature plastic and oxide constitutive, the decoupling analysis for the thermo-mechanical coupling field and optimization of virtual field, the ultra-high temperature mechanical testing method at 1 873 K or more, ultra-high temperature non-contact testing standard and so on.
Keywords: solid mechanics; thermo-mechanical coupling; review; high temperature mechanics; thermal barrier coating; ultra high temperature experiment

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