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1.
A new distribution pairs of the hydraulic transformer (HT) has been proposed to extend its output pressure range. A common
pressure rail (CPR) test-rig was built to test the performance of the HT. The simulation and the test were carried out to
explore the output pressure, the displacement and the speed stability of the HT. The research results have shown as follows.
Firstly, the designed HT can realize regulating the pressure, and its output pressure is determined by the control angle of
the port plate and affected by the load. The ratio of the load pressure (p
B) to the supply pressure (p
A) of the HT varies from 0 to 1.2. Secondly, the HT is a hydraulic component of variable displacement, and the displacement
of the every port of the HT depends on the control angle and is not affected by loads. Finally, the speed stability of the
HT becomes better with the control angle rising, and the movement zone exists while the control angle is lower than 15°. The
high pulsation of the driving torque of the HT results in the poor speed stability. The research will contribute to the improvement
of the HT performance in the future.
Supported by the National Excellent Young Scientists Fund (Grant No. 50425518) and the National Natural Science Foundation
of China (Grant No. 50305032). 相似文献
2.
In order to establish the quantitative relationship between equivalent strain and the performance index of the deformed material
within the range of certain passes for equal channel angular processing (ECAP), a new approach to characterize the equivalent
strain was proposed. The results show that there exists better accordance between mechanical property (such as hardness or
strength) and equivalent strain after rolling and ECAP in a certain range of deformation amount, and Gauss equation can be
satisfied among the equivalent strain and the mechanical properties for ECAP. Through regression analysis on the data of hardness
and strength after the deformation, a more generalized expression of equivalent strain for ECAP is proposed as: ɛ=k
0exp[−(k
1
M−k
2)2], where M is the strength or hardness of the material, k
1 is the modified coefficient (k
1∈(0, 1)), k
0 and k
2 are two parameters dependent on the critical strain and mechanical property that reaches saturation state for the material,
respectively. In this expression the equivalent strain for ECAP is characterized novelly through the mechanical parameter
relating to material property rather than the classical geometry equation.
Foundation item: Projects(50471102, 50671089) supported by the National Natural Science Foundation of China 相似文献
3.
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
4.
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
5.
The optimal decay rate problem is considered for boundary control system modeling by a flexible structure consisting of a Eular-Bernoulli beam. Controls are a bending moment in proportion to angular velocity and a shear force in proportion to velocity. A sensitivity asymptotic analysis of the system' s eigenvalues and eigenfunctions is set up. It is proved that, for every 00, y(0)=Y_0, Y_0=(Y_1,Y_2)~T ∈V×H form a Riesz basis of V×H, and the optimal exponential decay rate can be obtained from the spectrum of the system. 相似文献
6.
TheH
∞ control problem for a class of systems with time-varying and nonlinear uncertainties is considcred. A new sufficient condition
based on LMI is provided to judge their robust stability andL
2-gain finiteness. Solvability conditions are presented for both state feedback and output feedback cases, which are all reduced
to solutions of LMIs. The design procedure is also discussed via LMI approach.
Project supported by the National Natural Science Foundation of China (Grant No. 59704004). 相似文献
7.
The growth model of a spherical crystal in the undercooled melt including the surface energy, interfacial kinetics and convective
flow is established. The effect of the convective flow induced by a small far field flow on the evolution and morphological
stability of the interface of the spherical crystal is studied. The interface shape of the spherical crystal, which is affected
by the far field flow, and the dispersion relation of the growth rate of amplitude of the perturbed interface are derived.
It is shown that the convection induced by the far field flow makes the interface of the growing spherical crystal further
grow in the upstream direction of the far field flow and inhibit growth in the downstream direction; the interface of the
decaying spherical crystal further decays in the upstream direction and inhibits decay in the downstream direction. The theoretical
result suggests that both the growth of the sphere in the upstream direction and the decay of the sphere in the downstream
direction make the spherical crystal tend to evolve into an oval; the morphological stability of the interface depends on
a certain radius R
c
such that the spherical crystal is unstable when its radius is greater than R
c
and stable when its radius is less than R
c
. The surface energy and interfacial kinetics have strong stabilizing effects on the growth of the spherical crystal. In the
meantime interfacial kinetics is a table factor of the interface when the interface of the sphere is growing; it is an unstable
factor of the interface when the interface is decaying.
Supported by the National Basic Research Program of China (Grant No. 2006CB605205), the National Natural Science Foundation
of China (Grant Nos. 10672019 and 10572062), and the Science and Technology Foundation of Shanghai (Grant No. 055207081) 相似文献
8.
Hyperconcentrated viscous debris flows can move rapidly on low-gradient ravine under shear, because they have highly excessive pore pressure. The relationship between excessive pore-pressure (P_e) and volume concentration (C_(vt)) in viscous debris flows, i.e. P_e=2 494.76C_(vt)~(0.94), is quantitatively shown; the correlation coefficient γ=0.9671, 95% confidence interval is 0.9053<ρ<0.9937. About 92.29% of all grains (by weight) is supported by excessive pore pressure.##属性不符 相似文献
9.
Feng Gao ZuoRen Nie ZhiHong Wang HongMei Li XianZheng Gong TieYong Zuo 《中国科学E辑(英文版)》2009,52(8):2161-2166
A cradle-to-gate life cycle assessment was conducted in this paper to calculate the greenhouse gas (GHG) emissions, such as
CO2, CH4, CF4 and C2F6 emissions, based on statistic data of Chinese aluminum industry of the year 2003. The results showed that the GHG emissions
for 1 t primary aluminum production was 21.6 t CO2 equivalent which is 70% higher than that of worldwide average level of the year 2000. The main contributors of emission were
the alumina refining and aluminum smelting process accounting for 72% and 22% in accumulative emission, respectively. According
to the development and application of new process technologies for primary aluminum production and the ‘target of energy-saving
and emissions-reducing’ of Chinese government, the reduction potential of the GHG emissions for alumina and aluminum production
were estimated. The results indicated that China aluminum industry would achieve the target of reducing about 25% GHG emissions
by the end of 2010.
Supported by the National Natural Science Foundation of China (Grant No. 50525413), National Basic Research Program of China
(973 Program) (Grant No. 2007CB613706), and Beijing Natural Science Foundation (Grant No. 2081001) 相似文献
10.
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
11.
The self-consistent electronic structure calculations were carried out with the accurate frozen-core full-potential projector
augmented-wave method on 13 Ni-Pt intermetallic compounds of simple crystalline structures, i.e. A15, D019, D03 and L12 Ni3Pt and NiPt3, and α-NiAs, B1, B2, L2
a
, and L10 NiPt. The calculations reveal that the L12 Ni3Pt, L10 NiPt and L12 NiPt3 are energetically more stable than their respective competitive structures, indicating that the three structures may be formed
in some appropriate conditions. The obtained results match well with the experimental observation or other theory predictions.
It is found that there is hybridization between Ni 3d and Pt 5d states, which may significantly affect the structural stability and magnetism of metastable Ni-Pt intermetallic compounds.
Supported by the National Natural Science Foundation of China (Grant Nos. 50531040, 50871058), the Ministry of Science and
Technology of China (Grant No. 2006CB605201), and the Administration of Tsinghua University 相似文献
12.
A novel asymmetrical twin-core photonic crystal fiber was proposed, whose effective overlap core area A
eff can be designed to synchronize the variation of Raman gain coefficient with respect to frequency. This fiber possesses a
higher and flatter Raman gain efficiency coefficient curve r
R=g
R/A
eff over a specified band of wavelength than a conventional fiber. Therefore, it is a good candidate of gain medium for a flat,
broad gain band fiber Raman amplifier. It was numerically demonstrated that for the Raman gain efficiency r
R, relative fluctuations of less than 2.2% and 5.7% are achievable in the C (1530−1565 nm) band and L (1565−1625 nm) band, respectively.
Supported by the National Natural Science Foundation of China (Grant Nos. 60588502, 60607005, 60877033), the Science and Technology
Bureau of Sichuan Province (Grant No. 2006z02-010-3) and the Youth Science and Technology Foundation of UESTC (Grant No. JX0628) 相似文献
13.
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
14.
Ak-bitonic sort which generalizes the bitonic sort is proposed. The theorem of the bitonic sort, which merges two monotonic
sequences into one order sequence, is extended into the theorem ofk-bitonic sort. Thek-bitonic sort merges (K (=2k or 2k−1) monotonic sequences into one order sequence in steps, where is an integer andk≥1. Thek-bitonic sort is the Batcher's bitonic sort whenk=1.
Project supported by the National 863 Foundation of China (863-306-05-01-1) and the National Natural Science Foundation of
China (Grant No. 69673037). 相似文献
15.
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
16.
The phonon spectrum of ordered zincblende Si50Ge50 alloy is calculated by ab initio method. The energy band structure at zero pressure and the pressure dependence of phonon dispersion curves are shown up to
20 GPa. The calculation finds a pressure-induced softening of the transverse acoustic phonon mode and the mode frequency reaching
zero at about 14 GPa, which indicate breaking of the symmetry and formation of a new phase under high pressure.
Supported by the National Natural Science Foundation of China (Grant No. 50771090), the State Key Program for Basic Research
of China (Grant No. 2005CB724404) and the Program for Changjiang Scholars and Innovative Team (Grant No. IRT0650) 相似文献
17.
Asymptotic state behaviour and its modeling for saturated sand 总被引:3,自引:0,他引:3
A new double hardening elasto-plastic model is proposed in this paper based on the existing unified hardening model (UH model).
By assuming that there is part coupling effect between the plastic volumetric strain and plastic shear strain, hardening parameters
consisting of a coupled and an uncoupled components are adopted in this model. A unique feature of this model is that it can
describe not only the conventional drained and undrained behaviors of soil, but also the stress-strain relationships of soil
under partially drained conditions which can be volumetric compression or dilation. Adopting the asymptotic state concept,
simple equations for estimating the limiting stress ratio under undrained or earth pressure at rest (i.e. K
0) conditions are derived. The new model is relatively simple to be adopted in practice for two reasons. First, the same soil
parameters as in Cam-clay model are used except the addition of one extra parameter, the stress ratio at the characteristic
state. Second, all the parameters can be determined using conventional triaxial compression tests.
Supported by the National Natural Science Foundation of China (Grant Nos. 10672010 and 50479001) and the National Earthquake
Science Item (Grant No. 200808076) 相似文献
18.
A novel scale-free network model based on clique (complete subgraph of random size) growth and preferential attachment was
proposed. The simulations of this model were carried out. And the necessity of two evolving mechanisms of the model was verified.
According to the mean-field theory, the degree distribution of this model was analyzed and computed. The degree distribution
function of vertices of the generating network P(d) is 2m
2
m
1−3 (d − m
1 + 1)−3, where m and m
1 denote the number of the new adding edges and the vertex number of the cliques respectively, d is the degree of the vertex, while one of cliques P(k) is 2m
2
k
−3, where k is the degree of the clique. The simulated and analytical results show that both the degree distributions of vertices and
cliques follow the scale-free power-law distribution. The scale-free property of this model disappears in the absence of any
one of the evolving mechanisms. Moreover, the randomicity of this model increases with the increment of the vertex number
of the cliques.
Foundation item: Projects(60504027, 60573123) supported by the National Natural Science Foundation of China; Project(20060401037) supported
by the National Postdoctor Science Foundation of China; Project(X106866) supported by the Natural Science Foundation of Zhejiang
Province, China 相似文献
19.
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
20.
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