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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.
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
3.
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
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.
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
6.
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
7.
In remote sensing applications, accurate extraction of land type area after classification is very important. But for images
of land use/cover change (LUCC) obtained from the special spatial resolution remote sensing data, it will be of great significance
to obtain the land type area information with higher resolution by making use of spatial distribution characteristcs information
of the land type itself first and further scaling-down in a given scale threshold on the basis of the existing spatial resolution
data. An explicit expression of the relationship between the measurement scale, global fractal dimension and the land type
area corresponding to different measurement scales is obtained on the research basis of the authors’ histo-variogram using
the standardized area index (SAI). A good attempt has been made to obtain the land type area information with higher resolution
by merely using the spatial distribution characteristcs information of the land type in the image itself and further scaling-down
in a given scale threshold on the basis of the existing spatial resolution data.
Supported by the National Natural Science Foundation of China (Grant No. 40601068), the National Basic Research Program of
China (“973” Project) (Grant No. 2007CB714402) and the Key Science and Technology R&D Program of Qinghai Province (Grant No.
2006-6-160-01) 相似文献
8.
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
9.
The understanding of hydrological cycle is the core of hydrology and the scientific base of water resources management. Meanwhile,
simulation of hydrological cycle has long been regarded as an important tool for the assessment, utilization and protection
of water resources. In this paper, a new tool named Hydro-Informatic Modelling System (HIMS) has been developed and introduced
with case studies in the Yellow River Basin in China and 331 catchments in Australia. The case studies showed that HIMS can
be employed as an integrated platform for hydrological simulation in different regions. HIMS is a modular based framework
of hydrological model designed for different utilization such as flood forecasting, water resources planning and evaluating
hydrological impacts of climate change and human activities. The unique of HIMS is its flexibility in providing alternative
modules in the simulation of hydrological cycle, which successfully overcome the difficulties in the availability of input
data, the uncertainty of parameters, and the difference of rainfall-runoff processes. The modular based structure of HIMS
makes it possible for developing new hydrological models by the users.
Supported by the National Natural Science Foundation of China (Grant No. 40671031), National Key Basic Research Development
Program of China (Grant Nos. G1999043601 and 2006CB403407) and National Key Technology R&D Program (Grant No. 2006BAB06N07) 相似文献
10.
To track and control the changes of process quality attributes in multistage machining processes (MMPs), an e-quality control
(e-QC) model is proposed. The e-QC model is defined as a quality information service node with e-formalizing technology, whose
input/output and intermediate process (that is IPO) are known to other nodes, and its implemention in MMPs is provided. In
order to establish the e-QC model, a measuring network is constructed to acquire the original quality data, and the changes
of process quality attributes are monitored and diagnosed by the integrated quality analysis tools attached to the e-QC, which
can be tracked by information template network in real time. Furthermore, a hierarchical control method is adopted to coordinate
e-QCs, in which the quality loss and adjusting cost are used to quantify the opportunities for e-QCs to improve process quality.
At last, a prototype is developed to verify the proposed methods.
Supported by the National Basic Research Program of China (“973”) (Grant No. 2005CB724106) and the National High-Tech Research
and Development Program of China (“863”) (Grant No. 2007AA00Z108) 相似文献
11.
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
12.
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
13.
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
14.
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
15.
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
16.
A low mass flux steam jet in subcooled water was experimentally investigated. The transition of flow pattern from stable jet
to condensation oscillation was observed at relatively high water temperature. The axial total pressures, the axial and radial
temperature distributions were measured in the jet region. The results indicated that the pressure and temperature distributions
were mainly influenced by the water temperature. The correlations corrected with water temperature were given to predict the
dimensionless axial pressure peak distance and axial temperature distributions in the jet region, the results showed a good
agreement between the predictions and experiments. Moreover, the self-similarity property of the radial temperature was obtained,
which agreed well with Gauss distribution. In present work, all the dimensionless properties were mainly dependent on the
water temperature but weakly on the nozzle size under a certain steam mass flux.
Supported by the National Natural Science Foundation of China (Grant Nos. 50676078, 50821064) and the National High-Tech Research
and Development Program of China (“863” Project) (Grant No. 2006AA05Z230) 相似文献
17.
Field measurement on wind characteristic and buffeting response of existing bridge is of great value to the development of
bridge wind engineering, and the structural health monitoring system (SHMS) employed in many long-span bridges provide a research
basis for the field measurement. In order to provide reliable basis for wind resistant evaluation of Runyang Suspension Bridge
(RSB), two anemometers and 85 accelerometers were installed in the SHMS of RSB. In August 2005, Typhoon Matsa crossed over
Jiangsu, the SHMS timely recorded the typhoon and structural vibration responses. In this paper by using the time-frequency
technique and statistical theory, the recorded data were analyzed to obtain the strong wind characteristics, the buffeting
response characteristics of the cable and deck, and the variation of buffeting response RMS versus wind speed. Results obtained
in this study can be employed to validate the credibility of current buffeting response analysis theory techniques, and provide
reference values for wind resistant evaluation of other long-span bridges.
Supported by the National Hi-Tech Research and Development Program of China (“863” Project) (Grant No. 2006AA04Z416), the
Key Project of the National Natural Science Foundation of China (Grant No. 50538020) and the Outstanding Youth Fund of the
National Natural Science Foundation of China (Grant No. 50725828) 相似文献
18.
To solve the engineering and scientific problems in construction diversion and its simulation analysis, a complete scheme
is presented. Firstly, the complex constraint relationship was analyzed among main buildings, diversion buildings and flow
control. Secondly, the time-space relationship model of construction diversion system and the general block diagram-oriented
simulation model of diversion process were set up. Then, the corresponding numerical simulation method and 3D dynamic visual
simulation method were put forward. Further, the simulation and optimization platform of construction diversion control process
was developed, integrated with simulation modeling, computation and visualization. Finally, these methods were applied to
a practical project successfully, showing that the modeling process is convenient, the computation and the visual analysis
can be coupled effectively, and the results conform to practical state. They provide new theoretical principles and technical
measures for analyzing the control problems encountered in construction diversion of hydraulic and hydroelectric engineering
under complex conditions.
Supported by the National Basic Research Program of China (“973” Program) (Grant No. 2007CB714101), the National Key Technology
R&D Program in the 11th Five year Plan of China (Grant No. 2006BAB04A13) and the National Science Fund for Distinguished Young
Scholars of China (Grant No. 50525927) 相似文献
19.
With the applications of high technology,a catastrophic failure of CNC equipment rarely occurs at normal operation conditions.So it is difficult for traditional reliability assessment methods based on time-to-failure distributions to deduce the reliability level.This paper presents a novel reliability assessment methodology to estimate the reliability level of equipment with machining performance degradation data when only a few samples are available.The least squares support vector machines(LS-SVM) are int... 相似文献
20.
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