共查询到20条相似文献,搜索用时 15 毫秒
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.
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
3.
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
4.
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
5.
In this paper, the problem of interferences between motors and non-motors in urban road mixed traffic network is considered
and the corresponding link impedance function is presented based on travel demand. On the base of this, the main factors that
influence travelers’ traffic choices are all considered and a combined model including flow-split and assignment problem is
proposed. Then a bi-level model with its algorithm for system optimization of urban road mixed traffic network is proposed.
Finally the application of the model and its algorithm is illustrated with a numerical example.
Supported by the National Natural Science Foundation of China (Grant No. 70631001) and the National Basic Research Program
of China (“973”) (Grant No. 2006CB705500) 相似文献
6.
This paper proposes vibration-based damage identification method, termed as substructure potential energy (SPE) method, which
is capable of accurately estimating the damage magnitudes of multiple members. While other existing damage severity estimation
methods require the information of several unabridged modes of the structure, the new method utilizes only a few lower mode
shapes of substructures measured from the damaged solid. The performance of the proposed method is compared with one existing
damage detection method, using a set of numerical simulations on a lattice material beam based on synthetic data generated
from finite element models.
Supported by the National Basic Research Program of China (“973”) (Grant No. 2006CB601206) 相似文献
7.
This paper presents a novel step kinematic calibration method for a 3 degree-of-freedom (DOF) planar parallel kinematic machine
tool, based on the minimal linear combinations (MLCs) of error parameters. The method using mapping of linear combinations
of parameters in error transfer multi-parameters coupling system changes the modeling, identification and error compensation
of geometric parameters in the general kinematic calibration into those of linear combinations of parameters. By using the
four theorems of the MLCs, the sets of the MLCs that are respectively related to the relative precision and absolute precision
are determined. All simple and feasible measurement methods in practice are given, and identification analysis of the set
of the MLCs for each measurement is carried out. According to the identification analysis results, a step calibration including
step measurement, step identification and step error compensation is determined by taking into account both measurement costs
and observability. The experiment shows that the proposed method has the following merits: (1) the parameter errors that cannot
influence precision are completely avoided; (2) it reflects the mapping of linear combinations of parameters more accurately
and enhances the precision of identification; and (3) the method is robust, efficient and effective, so that the errors in
position and orientation are kept at the same order of the measurement noise. Due to these merits, the present method is attractive
for the 3-DOF planar parallel kinematic machine tool and can be also applied to other parallel kinematic machine tools with
weakly nonlinear kinematics.
Supported by the “863” High-Tech Program of China (Grant Nos. 2006AA04Z204 and 2006AA04Z227), National Natural Science Foundation
of China (Grant Nos. 50775118 and 50605041), the “973” Basic Research Project of China (Grant Nos. 2006CB705406 and 2007CB714000),
and Tsinghua Basic Research Foundation (Grant No. JC200701) 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.
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
10.
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
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.
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
13.
Numerical modeling of concrete hydraulic fracturing with extended finite element method 总被引:2,自引:0,他引:2
The extended finite element method (XFEM) is a new numerical method for modeling discontinuity. Research about numerical modeling for concrete hydraulic fracturing by XFEM is explored. By building the virtual work principle of the fracture problem considering water pressure on the crack surface, the governing equations of XFEM for hydraulic fracture modeling are derived. Implementation of the XFEM for hydraulic fracturing is presented. Finally, the method is verified by two examples and the advan- tages of ... 相似文献
14.
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
15.
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
16.
Fluid flow in porous and fractured fractal reservoirs is studied in the paper. The basic formulae of seepage velocity, permeability
and porosity in both porous and fractured fractal media are developed. The pressure diffusion equation of slightly compressible
fluid in fractal reservoirs is derived. The analytical solutions of the transient pressure are given for the line-source well
and the well with well-bore storage and skin factor. The typical curves of pressure and the derivative of pressure are established,
along with the interpretation of the well-testing method via type-curve matching. In addition, 3-D pressure diffusion equations
for anisotropic fractal media are given in both Cartesian coordinates and Cylindrical coordinates.
Supported by the National Natural Science Foundation of China (Grant No. 10672159, 10702069) and National Basic Research Program
of China (“973”) (Grant No. 2006CB705805) 相似文献
17.
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
18.
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
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.
We present the solar-terrestrial transit process of three successive coronal mass ejections (CMEs) of November 4–5, 1998 originating
from active region 8375 by using a time-dependent three-dimensional magnetohydrodynamics (MHD) simulation. These CMEs interacted
with each other while they were propagating in interplanetary space and finally formed a “complex ejecta”. A newly developed
SIP-CESE MHD model was applied to solve MHD equations numerically. The quiet solar wind was started from Parker-like 1D solar
wind solution and the magnetic field map was calculated from the solar photospheric magnetic field data. In our simulation,
the ejections were initiated using pulse in the real active region 8375. The interplanetary disturbance parameters, such as
speed, direction and angular size of the expanding CME, were determined from the SOHO/LASCO data with the cone-model. We discussed
the three-dimensional aspects of the propagation, interaction and merging of the three ejections. The simulated interplanetary
shocks were compared with the nearby-Earth measurement. The results showed that our simulation could reproduce and explain
some of the general features observed by satellite for the “complex ejecta”.
Supported by the National Natural Science Foundation of China (Grant Nos. 40536029, 40621003, 40504020 and 40523006), the
National Basic Research Program of China (“973”) (Grant No. 2006CB806304), and the CAS International Partnership Program for
Creative Research Teams 相似文献