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1.
The methods of homogenization and finite elements are employed to predict the effective elastic constants and stress-strain
responses of a new type of lattice structure, the X-structure proposed by the authors in a companion paper. It is shown that
in most cases the predictions by the equivalent homogenization theory agree well with the experimental and 3-dimensional finite
element calculated results. The theoretical and numerical study supports the argument that the X-structure is superior to
the pyramid lattice structure in terms of mechanical strength.
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
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.
The development of Hydro-Informatic Modelling System (HIMS) provides an integrated platform for hydrological simulation. To
extend the application of HIMS, an ecohydrological modeling system named ecohydrological assessment tool (EcoHAT) has been
developed. Integrating parameter-management tools, RS (remote sensing) inversion tools, module-design tools and GIS analysis
tools, the EcoHAT provides an integrated tool to simulate ecohydrological processes on regional scale, which develops a new
method on sustainable use of water. EcoHAT has been applied to several case studies, such as, the Yellow River Basin, the
acid deposition area in Guizhou province and the riparian catchment of Guanting reservoir in Beijing. Results prove that EcoHAT
can efficiently simulate and analysis the ecohydrological processes on regional scale and provide technical support to integrated
water resources management on basin scale.
Supported by the National Key Technology R&D Program in the 11th Five-year Plan of China (Grant No. 2006BAB06B07), the National
Natural Science Foundation of China (Grant No. 40671123), the National Basic Research Program of China (“973” Project) (Grant
Nos. 2005CB422207, G19990436), and the National Hi-Tech Research and Development Program of China (“863” Project) (Grant No.
2006AA12Z145) 相似文献
4.
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
5.
The coalbed methane transport model and its application in the presence of matrix shrinkage 总被引:1,自引:0,他引:1
Based on the theories of surface physical chemistry, theoretical formulations for permeability and porosity are presented
which include both stress effect and matrix shrinkage in a single equation. Then, a three-dimensional, dual porosity, nonequilibrium
adsorption, pseudosteady state mathematical model for gas and water is established and solved by the fully implicit method
and the block preconditioning orthomin algorithm. A history matching for the Qinshui Well TL003 is done. From the results,
it is shown that the obvious enhancement of permeability occurs along with the passing time but the reservoir pressure of
15# coal seam cannot fulfill the critical adsorption pressure as a result of the water recharge of the aquifer. Hence, it
is suggested to plug the 15# coal seam.
Supported by the National High Tech Research and Development Program of China (“863” Project) (Grant No. 2006AA06Z236) and
the National Basic Research Program (“973” Project) (Grant No. 2002CB11708) 相似文献
6.
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
7.
Application of time reversal mirror technique in microwave-induced thermo-acoustic tomography system
Microwave-induced thermo-acoustic tomography (MITAT) is a promising technique with great potential in biomedical imaging.
It has both the high contrast of the microwave imaging and the high resolution of the ultrasound imaging. In this paper, the
proportional relationship between the absorbed microwave energy distribution and the induced ultrasound source distribution
is derived. Further, the time reversal mirror (TRM) technique based on the pseudo-spectral time domain (PSTD) method is applied
to MITAT system. The simulation results show that high contrast and resolution can be achieved by the TRM technique based
on PSTD method even for the received signals with very low signal-to-noise ratio (SNR) and the model parameter with random
fluctuation.
Supported by the National Natural Science Foundation of China (Grant No. 60771042), the National Hi-Tech Research and Development
Program (“863” Project) (Grant No. 2007AA12Z159), 111 Project (Grant No. B07046), SiChuan Excellent Youth Foundation (Grant
No. 08ZQ026-039), Program for New Century Excellent Talents in University of China and Program for Changjiang Scholars 相似文献
8.
An Si/O patterned shell array was fabricated by a technique utilizing nanosphere self assembly and reactive pressure pulsed
laser deposition. The nanostructure produced by this technique enhanced the luminescence intensity by a factor of three compared
with that of a flat film. The amount of enhancement observed coincided well with the expected enhancement by simulation. The
technique in this paper provided a flexible, designable and compatible approach to luminescence enhancement.
Supported by the National Basic Research Program of China (“973” Project) (Grant No. 2002CB613505) and the National Nature
Science Foundation of China (Grant No. 90206046) 相似文献
9.
Monte Carlo (MC) method, which tracks small numbers of the dispersed simulation particles and then describes the dynamic evolution
of large numbers of real particles, constitutes an important class of methods for the numerical solution of population balance
modeling. Particle coagulation dynamics is a complex task for MC. Event-driven MC exhibits higher accuracy and efficiency
than time-driven MC on the whole. However, these available event-driven MCs track the “equally weighted simulation particle
population” and maintain the number of simulated particles within bounds at the cost of “regulating” computational domain,
which results in some constraints and drawbacks. This study designed the procedure of “differently weighted fictitious particle
population” and the corresponding coagulation rule for differently weighted fictitious particles. And then, a new event-driven
MC method was promoted to describe the coagulation dynamics between differently weighted fictitious particles, where “constant
number scheme” and “stepwise constant number scheme” were developed to maintain the number of fictitious particles within
bounds as well as the constant computational domain. The MC is named event-driven constant volume (EDCV) method. The quantitative
comparison among several popular MCs shows that the EDCV method has the advantages of computational precision and computational
efficiency over other available MCs.
Supported by the National Basic Research Program of China (“973” Project) (Grant No. 2006CB705800), the National Natural Science
Foundation of China (Grant No. 20606015) and the Fok Ying Tong Education Foundation (Grant No. 114017) 相似文献
10.
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
11.
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
12.
Centrifuge model test on earthquake-induced differential settlement of foundation on cohesive ground
Dynamic centrifuge model test was conducted to study the earthquake-induced differential settlement of foundation on cohesive
ground, and the influence of asymmetry of building was investigated. During the experiment, the overconsolidated kaolin clay
ground with a three-dimensional asymmetrical structure model was shaken by a basically balanced input motion, and bender elements
were used to measure shear wave velocities of model ground to reveal the soil fabric evolution during and after shaking. The
test results show that, the total seismic settlement of foundation is composed of instantaneous and long-term post-earthquake
settlements, and most of the differential settlement occurs immediately after the earthquake while the post-earthquake settlement
is relatively uniform despite its large amplitude. The asymmetry of building affects the settlement behavior considerably.
Compared with 1-or 2-dimensional structures, more evident differential settlement occurs under three-dimensional asymmetrical
building during shaking, which accounts for one-half of the total seismic settlements and results in complex spatial tilting
effects of foundation.
Supported by the National Basic Research Program of China (“973” Project) (Grant No. 2007CB714203), the China Postdoctoral
Science Foundation (Grant Nos. 20080430219, 20081476) and the Foundation for Seismological Researches, China Earthquake Administration
(Grant No. 200808022) 相似文献
13.
This paper firstly evaluated the impedance method and traveling waves method for fault location, and studied the robustness
of fault location method based on impedance. Then it proposed an assembled fault location method for a transmission line based
on single-terminal electrical quantities, in which the fault zone was firstly determined by impedance method with robustness
then the accurate fault position was pinpointed by traveling waves method. EMTP (Electromagnetic Transient Program) simulations
showed that the proposed method can overcome the drawbacks of impedance method and traveling waves method when either one
is used alone, and improve both the accuracy and the reliability of fault location.
Supported by the National Natural Science Foundation of China (Grant Nos. 50077011 and 50377019) and the National Basic Research
Program of China (“973” Project) (Grant No. 2004CB217906) 相似文献
14.
HU Sau-Lon James 《中国科学E辑(英文版)》2009,52(7):1999-2008
The IASC-ASCE Structural Health Monitoring Task Group developed a series of benchmark problems, and participants of the benchmark
study were charged with using a 12-degree-of-freedom (DOF) shear building as their identification model. The present article
addresses improperness, including the parameter and modeling errors, of using this particular model for the intended purpose
of damage detection, while the measurements of damaged structures are synthesized from a full-order finite-element model.
In addressing parameter errors, a model calibration procedure is utilized to tune the mass and stiffness matrices of the baseline
identification model, and a 12-DOF shear building model that preserves the first three modes of the full-order model is obtained.
Sequentially, this calibrated model is employed as the baseline model while performing the damage detection under various
damage scenarios. Numerical results indicate that the 12-DOF shear building model is an over-simplified identification model,
through which only idealized damage situations for the benchmark structure can be detected. It is suggested that a more sophisticated
3-dimensional frame structure model should be adopted as the identification model, if one intends to detect local member damages
correctly.
Supported by the National Hi-Tech Research and Development Program of China (“863” Project) (Grant No. 2006AA09Z331) and the
National Science Fund for Distinguished Young Scholars (Grant No. 50325927) 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.
JinBin Cao JunYing Yang ShiGan Yuan XuHui Shen YuanMo Liu ChunXiao Yan WenZhen Li Tao Chen 《中国科学E辑(英文版)》2009,52(7):2112-2118
Using the data from STAFF/TC-1, this paper for the first time analyzes the electromagnetic interferences of Chinese scientific
satellite. The electromagnetic interference of satellite exists mainly below 30 Hz, but can extend to 190 Hz with an obviously
decreasing power spectral density. The electromagnetic interferences at frequencies below 190 Hz have good correlation with
the solar aspect angle. The electromagnetic interferences at frequencies between 190 and 830 Hz have also correlation with
solar aspect angle. However, the electromagnetic interferences at frequencies above 830 Hz have no correlation with the solar
aspect angle. The correlation coefficient between solar aspect angel and electromagnetic interferences is around 0.90. The
larger the solar aspect angle, the stronger the satellite electromagnetic interference. When the solar aspect angle increases
from 90.6° to 93.6°, the electromagnetic interferences at frequencies <10 Hz increase by 8 times and those at frequencies
190–830 Hz increase by 60%. This close association of electromagnetic interferences with the solar aspect angle indicates
that the solar aspect angle is the main factor to determine the electromagnetic interferences. The electromagnetic interferences
of satellite in sunlight are larger than those in eclipse. The electromagnetic interference produced by solar panel occupies
about 87% in the low frequency band (<100 Hz) and 94% in the high frequency band (>100 Hz) of the total electromagnetic interference
produced by satellite. These in flight observations of electromagnetic radiation of satellites will be very helpful to the
designs of future satellites of space sciences or earthquake sciences.
Supported by the National Hi-Tech Research and Development Program of China (“863” Project) (Grant No. 2008AA12A216), the
National Science & Technology Supporting Program during the Eleventh Five-Year Plan, the National Natural Science Foundation
of China (Grant No. 40523006), the National Basic Research Program of China (“973” Project) (Grant No. 2006CB806305), and
the Specialized Research Fund for State Key Laboratories 相似文献
17.
Abstrac X-ray pulsar navigation (XPNAV) is a new approach for spacecraft autonomous navigation. The system gets position information
utilizing accurate timing methods. Among the timing models, the high-order relativistic effects on the propagated signal must
be incorporated to attain precise timing. The time transfer model is provided in detail here in two parts: the time frame
transformation and the relativistic effects.
Supported by the National Hi-Tech Research and Development Program of China (“863” Project) (Grant No. 2008AA12Z304) 相似文献
18.
The environmental problem caused by refrigerant has become the focus all over the world. As the most typical natural refrigerant,
CO2, of course, becomes the research focus. This paper introduces the development and application status of CO2 refrigeration and heat pump technology. The researches on CO2 refrigeration and heat pump, carried out by Thermal Energy Research Institute, Tianjin University, also are presented in
this paper.
Supported by the National Natural Science Foundation of China (Grant Nos. 50676064, 50506019) and the National Hi-Tech Research
and Development Program of China (“863” Project) (Grant No. 2007AA05Z262) 相似文献
19.
QingZhao Zhang ChangQing Xie Ming Liu Bing Li BaoQin Chen XiaoLi Zhu 《中国科学E辑(英文版)》2008,51(11):1990-1994
The punching thru mechanism of gate oxide (thickness about 15A) was investigated. Because of the thin thickness of gate oxide,
gate oxide punching thru may easily happen during the plasma process. It was found that what caused the punching thru was
not only the selectivity of poly-silicon/oxide but also the pattern topography. We used the basic SRAM pattern to check this
topography effect, and found that gate oxide located at the narrow spacing of two parallel serpentine lines was the most easily
punched thru. What caused the topography effect was the starvation of oxygen in these places which were induced by the residue
of poly-silicon and enhanced by electron shading effect. So, to solve the issue of gate oxide punching thru, firstly the selectivity
should be enough, secondly we should pay attention to the etching pattern topography.
Supported by the National High-Tech Research and Development Program of China (“863” Project) (Grant No. 2006AA843134) and
the National Basic Research Program of China ("973" Project) (Grant No. 2007CB935302) 相似文献
20.
Global optimization of tool path for five-axis flank milling with a cylindrical cutter 总被引:1,自引:0,他引:1
In this paper, optimum positioning of cylindrical cutter for five-axis flank milling of non-developable ruled surface is addressed
from the perspective of surface approximation. Based on the developed. interchangeability principle, global optimization of the five-axis tool path is modeled as approximation of the tool envelope surface to the data points
on the design surface following the minimum zone criterion recommended by ANSI and ISO standards for tolerance evaluation.
By using the signed point-to-surface distance function, tool path plannings for semi-finish and finish millings are formulated
as two constrained optimization problems in a unified framework. Based on the second order Taylor approximation of the distance
function, a sequential approximation algorithm along with a hierarchical algorithmic structure is developed for the optimization.
Numerical examples are presented to confirm the validity of the proposed approach.
Supported by the National Natural Science Foundation of China (Grant Nos. 50775147 and 50835004), the National Basic Research
Program of China (“973” Project) (Grant No. 2005CB724103), and the Science & Technology Commission of Shanghai Municipality
(Grant No. 07JC14028) 相似文献