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1.
Liang Wang XiaoShuang Chen Wei Lu Yan Huang XiaoFang Wang JiJun Zhao 《中国科学E辑(英文版)》2009,52(7):1928-1932
The structural and optical properties of amorphous semiconductor mercury cadmium telluride (a-MCT) are obtained by the first
principles calculations. The total pair distribution functions and the density of states show that the a-MCT has the semiconductor
characteristic. The calculated results of dielectric function show that E
2 peak of the imaginary of dielectric function for the crystal mercury cadmium telluride abruptly disappears in the amorphous
case due to the long-range disorders. And the imaginary of dielectric function of a-MCT shows a large broad peak, which is
in agreement with the available results of other amorphous semiconductors. From the linear extrapolation of the curve ħωɛ
2(ω)1/2 versus ħω, it can be obtained that the optical energy gap of amorphous semiconductor Hg0.5Cd0.5Te is 0.51±0.05 eV.
Supported by the National Basic Research Program of China (“973” Project) (Grant No. 2007CB613205), the National Natural Science
Foundation of China (Grant Nos.10725418, 10734090, 60576068), the Key Fund of Shanghai Science and Technology Foundation (Grant
No. 08JC1421100) and the Knowledge Innovation Program of the Chinese Academy of Sciences 相似文献
2.
On the numerical simulation of active scalar, a new explicit algebraic expression on active scalar flux was derived based
on Wikstr?m, Wallin and Johansson model (a
WWJ
model). Reynolds stress algebraic expressions were added by a term to account for the buoyancy effect. The new explicit Reynolds
stress and active scalar flux model was then established. Governing equations of this model were solved by finite volume method
with unstructured grids. The thermal shear stratified cylinder wake flow was computed by this new model. The computational
results are in good agreement with laboratorial measurements. This work is the development on modeling of explicit algebraic
Reynolds stress and scalar flux, and is also a further modification of the a
WWJ
model for complex situations such as a shear stratified flow.
Supported by the National Nature Science Foundation of China (Grant Nos. 50679019, 50009001), the National Basic Research
Program of China (“973” Project) (Grant No. 2008CB418202), the Project of “Six Talent Peak” of Jiangsu Province (08-C), Social
Technology Development Foundation of Jiangsu Province (Grant No. BS2006095) and the “908” Special Foundation of Jiangsu Province
(Grant No. JS-908-02-06) 相似文献
3.
Al electrodes are well known as ohmic contact electrodes for the PTC component, the influence of their thickness on final
component properties was investigated by comparing their ohmic characteristics with the ones of InGa electrodes. After observing
the Al paste physical and chemical behaviors during rising temperature by thermal analysis (DTA), the firing operation of
Al electrodes could be divided into three main subsections: the temperature rising time (tr), the peak firing temperature (Tp) and the hold time at peak firing temperature (th). The effects of these three parameters on final component properties were discussed in detail.
LIANG Fei: Born in 1975
Funded by the State “863” Project (No. 715-006-0080) 相似文献
4.
YuJie Yuan GuoFu Hou JianJun Zhang JunMing Xue LiRan Cao Ying Zhao XinHua Geng 《中国科学E辑(英文版)》2009,52(6):1756-1761
High pressure radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) process was adopted to investigate the
effect of constant hydrogen dilution technique and gradient hydrogen dilution technique on the structural evolution of intrinsic
films and the performance of n-i-p microcrystalline silicon solar cells. The experiment results demonstrated that the grain size and crystalline volume fraction
along the growth direction of intrinsic films can be controlled and the performance of solar cells can be greatly improved
by gradient hydrogen dilution technique. An initial active-area efficiency of 5.7% (V
oc=0.47 V, J
sc=20.2 mA/cm2, FF=60%) for the μc-Si:H single-junction n-i-p solar cells and an initial active-area efficiency of 10.12% (V
oc=1.2 V, J
sc=12.05 mA/cm2, FF=70%) for the a-Si:H/μc-Si:H tandem n-i-p solar cells has been achieved.
Supported by the National Basic Research Program of China (“973” Program) (Grant Nos. 2006CB202602, 2006CB202603) and the
Tianjin Assistant Foundation for the National Basic Research Program of China (Grant No. 07QTPTJC29500) 相似文献
5.
KIM Tongbeum 《中国科学E辑(英文版)》2009,52(6):1688-1697
The solidification behavior of two-phase heterogeneous materials such as close-celled aluminum foams was analytically studied.
The proposed analytical model can precisely predict the location of solidification front as well as the full solidification
time for a two-phase heterogeneous material composed of aluminum melt and non-conducting air pores. Experiments using distilled
water simulating the aluminum melt to be solidified (frozen) were subsequently conducted to validate the analytical model
for two selected porosities (ɛ), ɛ=0 and 0.5. Full numerical simulations with the method of finite difference were also performed to examine the influence of
pore shape on solidification. The remarkable agreement between theory and experiment suggests that the delay of solidification
in the two-phase heterogeneous material is mainly caused by the reduction of bulk thermal conductivity due to the presence
of pores, as this is the sole mechanism accounted for by the analytical model for solidification in a porous medium.
Supported by the National Basic Research Program of China (“973” Project) (Grant Nos. 2006CB601202, 2006CB601203), the National
Natural Science Foundation of China (Grant Nos. 10572111, 10632060), the National 111 Project of China (Grant No. B06024)
and the National High-Tech Research and Development Program of China (“863” Project) (Grant No. 2006AA03Z519). 相似文献
6.
WenYao Xu 《中国科学E辑(英文版)》2008,51(10):1659-1664
Magnetic activity indices are widely used in theoretical studies of solar-terrestrial coupling and space weather prediction.
However, the indices suffer from various uncertainties, which limit their application and even mislead to incorrect conclusion.
In this paper we analyze three most popular indices, Kp, AE and Dst. Three categories of uncertainties in magnetic indices are discussed: “data uncertainty” originating from inadequate data
processing, “station uncertainty” caused by incomplete station covering, and “physical uncertainty” stemming from unclear
physical mechanism. A comparison between magnetic disturbances and related indices indicate that the residual Sq will cause an uncertainty of 1–2 in K measurement, the uncertainty in saturated AE is as much as 50%, and the uncertainty in Dst index caused by the partial ring currents is about a half of the partial ring current.
Supported by the National Natural Science Foundation of China (Grant No. 40436016), the National Basic Research Program of
China (“973”) (Grant No. 2006CB806305), and the KIP Pilot Project of the Chinese Academy of Sciences (Grant No. kzcx3-sw-144) 相似文献
7.
A number of three-point bending and fracture tests of 200 MPa-level reactive powder concrete (RPC) with the various fiber
contents have been conducted to probe the nature and characteristics of toughness of RPC200. The contribution of the embedded
fibers to improving the crack-resistant capacity, energy absorption capacity and toughness with various deformation mechanisms
has been analyzed. Taking account of that the first-crack deformation, peak-load deformation and their improvement varied
with the fiber contents and that the deformation mechanism affected differently the performance at the first crack and the
peak load, we took the peak-load deformation of plain RPC200 as the reference deformation to measure the toughness of fibered
RPC200. Two toughness indices T
2(n−1)(n) and FT
2(n−1)(n) have been formulated based on P-δ responses and P-CMOD responses. The indices quantify the toughness of RPC200 with the various deformation mechanisms relative to perfectly
elastoplastic materials by setting the toughness level 2(n−1) as the initial reference. It is shown that the toughness index T
2(n−1)(n) reflects the function of fibers to improve the toughness of RPC with the deformation throughout specimens, but overestimates
the contribution to enhancing the toughness in post-peak periods. It underestimates, on other hands, the contribution to improving
the toughness in the period from the first crack to the peak load. In contrast, the toughness index FT
2(n−1)(n) properly presents the capability that fibers absorb energy and constrain crack propagation in the matrix when the deformation
is concentrated on the open crack. The proposed index unveils the contribution of fibers to toughening RPC200 both in the
period from the first-crack to the peak load and in the period of post peak. This characterization method not only reveals
the nature of toughness but also levels the toughness of RPC200. It could provide a way to establish an objective toughness
characterization for RPC200 and facilitate its applications.
Supported by the New Century Excellent Talents Program (Grant No. NCET-05-0215), the Natural Science and Engineering Research
Council of Canada (Grant No. PGS D2 2006), the Laboratory Innovation Plan of Beijing Science and Education Committee (Grant
No. JD102900671) and the National Basic Research Project of China (“973” Project) (Grant No. 2002CB412705) 相似文献
8.
With the high-voltage electrostatic theory and numerical analysis, the dynamics of conductive and nonconductive particles under high-voltage electrostatic coupling fields was studied. The oscillation behavior of the conductive particle between the corona electrode and ground electrode was analyzed and its oscillation amplitude was Sm=(ta+ts)·νm/2. It was found that there was the "lift-off voltage (Ulo)" for the conductive particle between the electrostatic electrode and ground electrode. The concepts of "cr... 相似文献
9.
Based on the empirical electron theory of solids and molecules (EET), the statistical values of valence electron structure
parameters Sn
A and SE
A which can characterize the properties of alloy phases are calculated, and influences of alloying elements (e.g., V, Nb, Mo,
Hf, Zr, Fe, Mn, Co, Cr, Si, and so on) on the phase transition temperature and eutectoid reaction of titanium alloy are discussed
with the statistical values of valence electron structure parameters. The research results agree well with real situations.
Supported by the National Natural Science Foundation of China (Grant No. 50471022, 50741004) and National Key Basic Research
Program of China (“973”) (Grant No. 2007CB613807) 相似文献
10.
The Morris-Lecar (ML) neuronal model with current-feedback control is considered as a typical fast-slow dynamical system to
study the combined influences of the reversal potential V
Ca of Ca2+ and the feedback current I on the generation and transition of different bursting oscillations. Two-parameter bifurcation analysis of the fast subsystem
is performed in the parameter (I, V
Ca)-plane at first. Three important codimension-2 bifurcation points and some codimension-1 bifurcation curves are obtained
which enable one to determine the parameter regions for different types of bursting. Next, we further divide the control parameter
(V
0, V
Ca)-plane into five different bursting regions, namely, the “fold/fold” bursting region R1, the “fold/Hopf” bursting region
R2, the “fold/homoclinic” bursting region R3, the “subHopf/homoclinic” bursting region R4 and the “subHopf/subHopf” bursting
region R5, as well as a silence region R6. Codimension-1 and -2 bifurcations are responsible for explanation of transition
mechanisms between different types of bursting. The results are instructive for further understanding the dynamical behavior
and mechanisms of complex firing activities and information processing in biological nervous systems.
Supported by the National Natural Science Foundation of China (Grant Nos. 10872014 and 10702002) 相似文献
11.
The humanoid robot SJTU-HR1’s concept is introduced and its characteristics tree is given. The basic states for SJTU-HR1 are
proposed, including lying, sitting, standing and handstanding, abstracted from the daily exercises of human beings. The G
F
(generalized function) set theory is exploited to achieve the kinematic characteristics of the interested EEs (end-effectors)
of SJTU-HR1 for the lying states. Finally, the results show that the large amounts of states can be described using the abbreviations
in a systematic manner. Although we have focused on the application of the G
F
set theory to humanoid robots, particularly the SJTU-HR1, this methodology can also be applied to quadruped robots and hexapedal
robots, especially when the desired tasks are complex.
Supported by the Natural Basic Research Program of China (“973”) (Grant No. 2006CB705400), the National Natural Science Foundation
of China (Grant Nos. 60534020, 30770538), Joint Research Fund for Young Scholars in China and Abroad (Grant No. 50728503),
and the Graduate Innovation Foundation of Shanghai Jiao Tong University 相似文献
12.
Multi-channel micro neural probe fabricated with SOI 总被引:1,自引:0,他引:1
WeiHua Pei Lin Zhu ShuJing Wang Kai Guo Jun Tang Xu Zhang Lin Lu ShangKai Gao HongDa Chen 《中国科学E辑(英文版)》2009,52(5):1187-1190
Silicon-on-insulator(SOI) substrate is widely used in micro-electro-mechanical systems(MEMS).With the buried oxide layer of SOI acting as an etching stop,silicon based micro neural probe can be fabri-cated with improved uniformity and manufacturability.A seven-record-site neural probe was formed by inductive-coupled plasma(ICP) dry etching of an SOI substrate.The thickness of the probe is 15 μm.The shaft of the probe has dimensions of 3 mm×100 μm×15 μm with typical area of the record site of 78.5 μm2.The im... 相似文献
13.
The effects of the composite-collector structure and the δ-doping density in InGaAs/InP DHBT on the Kirk current have been studied.The effective grade layer in the discretely graded layer goes into the InGaAs setback layer.The formulas of the maximum doping density,the maximum Kirk current,and the corresponding δ-doping density are derived under different Kirk-effect conditions.Both the maximum collector doping density and the maximum Kirk current are dependent on the δ-doping layer.By opti-mizing the delta... 相似文献
14.
A ferroelectric memory diode consisting of Au/PZT/BIT/p-Si multilayer configuration has been fabricated by pulsed laser deposition (PLD) technique. The ferroelectric properties and the memory characteristics are investigated. The P-E curve of the PZT/BIT/p-Si films system had an asymmetry saturated hysteresis loop with P, = 15 μC/cm2 and Ec = 48 kV/cm, and the decay in remanent polarization was only 10% after 109 switching cycles, meanwhile the increase in coercive field was 12% . The C-V hysteresis loop and the I-V curve showed a memory effect derived from the ferroelectric polarization of PZT/BIT films, and the current density was 6.7 × 10-8 A/cm2 at a voltage of + 4V. Our diode had nonvolatile and nondestructive memory readout operation. There was a read current disparity of 0.05 μA for logic "1" and logic "0" at a read voltage of + 2V, and the stored logical value ("1" or "0") could be read out in 30 min. 相似文献
15.
The high-dense nanocrystalline BaTiO3 (BT) ceramics with grain size smaller than 100 nm have been successfully prepared by the two step sintering and the spark
plasma sintering (SPS) process. The successive transitions in nanograin BT ceramics from rhombohedral to orthorhombic, tetragonal
and cubic transitions, similar to those in coarse BT ceramics, were revealed by in-situ temperature dependent Raman spectrum.
The multiphase coexistence and the diffused phase transition character were demonstrated in the 8 nm nanocrystalline BT ceramics.
Supported by the National Basic Research Program of China (“973” Project) (Grant No. 2002CB613301) and the National Natural
Science Foundation of China (Grant No. 50872093) 相似文献
16.
Superplastic behaviors of quasicrystal phase containing Mg-5.8Zn-1Y-0.48Zr alloy sheets fabricated by combination of extrusion and hot-rolling processes have been investigated at temperature ranging from 623 to 753 K and at the strain rates ranging from 10-4 to 10-2 s-1 by uniaxial tensile tests. An excellent superplasticity with the maximum elongation to failure of 1020% was obtained at 753 K and the strain rate of 1.04×10-3 s-1 and its strain rate sensitivity, m, is as high as up to 0.75. The microstructure was stable during superplastic deformation due to the uniformly distributed fine quasicrystal particles. In addition, micro-cavities and their coalescences were observed in the superplastic deformation of the ZW61 magnesium alloy. Grain boundary sliding (GBS) was considered to be the main deformation mechanism during the superplastic deformation. Dislocation creep controlled by atom diffusion through grain boundaries or interior grains is suggested mainly to accommodate the GBS in super-plastic deformation. 相似文献
17.
An in-situ polymerization method was employed to synthesize the nanosilica/acrylic/epoxy (SAE) hybrid coating on AISI 430 stainless
steel (430SS), as compared with a traditional blending method. Microstructures of the blending SAE hybrid coating (BC) and
in-situ SAE hybrid coating (ISC) were characterized by transmission electron microscopy (TEM). Corrosion resistance of BC
and ISC on 430SS was evaluated by the neutral salt spray test and potentiodynamic polarization technique. Failure mechanism
of the BC on 430SS was suggested by the microstructures and corrosion behaviors. Serious aggregation of nanosilica particles
in the BC impairs its structural uniformity and induces the flaws formation. These flaws in the BC initiates the failures
of pitting, filiform corrosion and peeling which are accelerated by the O2 concentration cell and H+ self-catalysis in chlorine-containing moist environments. The ISC-coated 430SS shows a more advantageous corrosion resistance
than that of the BC-coated. The ISC-coated 430SS can suffer the salt spray over 1000 h. Besides, it exhibits a high corrosion
potential beyond 0.925 V and good passivation characteristics during the potentiodynamic polarization.
Supported by the National Basic Research Program of China (“973” Program) (Grant No. 2004CB619305) and the National Natural
Science Foundation of China (Grant No. 50571044) 相似文献
18.
AMADOR António 《中国科学E辑(英文版)》2009,52(7):1958-1965
Numerical simulation of water flow over the stepped spillway is conducted using Mixture multiphase flow model. Different turbulence models are chosen to enclose the controlling equations. The turbulence models investigated are realizable k-ε model, SST k-ω model, v2-f model and LES model. The computational results by the four turbulence models are compared with experimental ones in the following aspects: mean velocity, the spanwise vorticity and the growth of the turbulent boundary layer thickness in the st... 相似文献
19.
HaiLing Zhu JunYing Zhang TianMin Wang LiuGang Wang Xiang Lan BaiBiao Huang 《中国科学E辑(英文版)》2009,52(8):2175-2179
Aiming at reducing the recombination of photo-induced carriers in semiconductor photocatalytic process, we prepared TiO2 thin film with its surface modified by a connected Cu micro-grid via a microsphere lithography strategy, which showed higher
photocatalytic activity than the pure TiO2 film. The improvement of photocatalytic activity of Cu micro-grid to the TiO2 film is due to the charge carrier separation and electron transfer by the conducting metal grid. The photocatalytic activity
was improved as metal loading increased, which obtained the best performance at a certain loading amount, and then decreased
at higher loading amount. This phenomenon was attributed to the metal’s bulk effect which could be explained by the relationship
between the energetic positions and the metal cluster size.
Supported by the National Natural Science Foundation of China (Grant Nos. 50672003, 50872005) and the National Basic Research
Program of China (“973” Project) (Grant No. 2007CB613302) and the Fok Ying Tong Education Foundation (Grant No. 111050) 相似文献
20.
Ultralight X-type lattice sandwich structure (I): Concept,fabrication and experimental characterization 总被引:1,自引:1,他引:0
ZHANG QianCheng HAN YunJie CHEN ChangQing & LU TianJian State Key Laboratory for Mechanical Behavior of Materials School of Material Science Engineering Xi’an Jiaotong University Xi’an China MOE Key Laboratory for Strength Vibration School of Aerospace Department of Engineering Mechanics AML Tsinghua University Beijing 《中国科学E辑(英文版)》2009,52(8):2147-2154
A new type of ultra-lightweight metallic lattice structure (named as the X-type structure) is reported. This periodic structure
was formed by two groups of staggered struts in the traditional pyramid structure, and fabricated by folding expanded metal
sheet along rows of offset nodes and then brazing the folded structure (as the core) with top and bottom facesheets to form
sandwich panels. The out-of-plane compressive and shear properties of the X-type lattice sandwich structure were investigated
experimentally and compared to those of the sandwich having a pyramidal truss core. It is found that the formation of the
2-dimensional staggered nodes can effectively make the X-type structure more resistant to inelastic and plastic buckling under
both compression and shear loading than the pyramidal lattice truss. Obtained results show that the compressive and shear
peak strengths of the X-type lattice structure are about 30% higher than those of the pyramidal lattice truss having the same
relative density.
Supported by the National Basic Research Program of China (“973” Project) (Grant No. 2006CB601202), the National Natural Science
Foundation of China (Grant Nos. 10632060,10825210), the National “111” Project of China (Grant No. B06024) and the National
High-Tech Research and Development Program of China (“863” Project) (Grant No. 2006AA03Z519) 相似文献