共查询到20条相似文献,搜索用时 31 毫秒
1.
LiXing Zhou 《中国科学E辑(英文版)》2008,51(8):1073-1086
The derivation and closure methods of the second-order moment (SOM) combustion model are proposed. The application of this
model to Reynolds averaged (RANS) and large-eddy simulation (LES) of turbulent swirling diffusion combustion, jet diffusion
combustion, and bluff-body stabilized premixed combustion is summarized. It is indicated that the SOM model is much better
than the eddy-beak-up (EBU) and presumed PDF models widely used in commercial software and engineering. The SOM modeling results
are close to those obtained using the most accurate but much more complex PDF equation model. Moreover, it can save much more
computation time than the PDF equation model. Finally, the SOM model is validated by the direct numerical simulation (DNS)
of turbulent reacting channel flows.
Supported by the National Natural Science Foundation of China (Grant Nos. 50606026 and 50736006), and the National Basic Research
Program of China (“973”) (Grant No. G-1999-0222-07) 相似文献
2.
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
3.
More and more piezoelectric materials and structures have been used for structure control in aviation and aerospace industry.
More efficient and convenient computation method for large complex structure with piezoelectric actuation devices is required.
A load simulation method of piezoelectric actuation is presented in this paper. By this method, the freedom degree of finite
element simulation is significantly reduced, the difficulty in defining in-plane voltage for multi-layers piezoelectric composite
is overcome and the transfer computation between material main direction and the element main direction is simplified. The
concept of simulation load is comprehensible and suitable for engineers of structure strength in shape and vibration control,
thereby is valuable for promoting the application of piezoelectric material and structures in practical aviation and aerospace
fields.
Supported by the National Natural Science Foundation of China (Grant Nos. 10772183 and 10532070) and Foundation Program of
Chinese Academy of Sciences (Grant No. KJCX2-YW-L07) 相似文献
4.
Molecular dynamics (MD) simulations were performed to do the test of sin-gle-walled carbon nanotubes (SWCNT) under tensile loading with the use of Bren-ner potential to describe the interactions of atoms in SWCNTs. The Young’s modulus and tensile strength for SWCNTs were calculated and the values found are 4.2 TPa and 1.40―1.77 TPa, respectively. During the simulation, it was found that if the SWCNTs are unloaded prior to the maximum stress, the stress-strain curve for unloading process overlaps with the loading one, showing that the SWCNT’s de-formation up to its fracture point is completely elastic. The MD simulation also demonstrates the fracture process for several types of SWCNT and the breaking mechanisms for SWCNTs were analyzed based on the energy and structure be-havior. 相似文献
5.
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
6.
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
7.
HuiMin Xie ZhenXing Hu FuLong Dai YanJie Li PengWan Chen QingMing Zhang FengLei Huang 《中国科学E辑(英文版)》2009,52(7):2048-2053
This paper proposes a new method that reconstructs the information of specimen by using random phase shift step in digital
holographic microscopy (DHM). The principles of the method are described and discussed in detail. In practical experiment,
because the phase shifter is neither perfectly linear nor calibrated, digital holograms with inaccurate phase shift step are
recorded by the charge-coupled device (CCD). The phase could be accurately reconstructed from the recorded digital holograms
by using the random phase-shifting algorithm, which makes up for reconstructed phase error caused by ordinary phase-shifting
algorithm. The phase aberration compensation is also discussed. In order to verify the flexibility of the proposed method,
numerical simulation of random phase-shifting DHM was carried out. The simulation results illustrated that the presented method
is effective when the phase shift step is unknown or random in DHM.
Supported by the National Basic Research Program of China (“973” Project) (Grant No. 2004CB619304), the National Natural Science
Foundation of China (Grant Nos. 10625209, 10472050, 10732080), the Project of Beijing Natural Sciences Foundation (Grant No.
3072007), the Program for New Century Excellent Talents (NCET) in Chinese University Ministry of Education (Grant No. NCET-05-0059),
and the Opening Funds from the State Key Laboratory of Explosion Science and Technology 相似文献
8.
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
9.
YanHui Wang 《中国科学E辑(英文版)》2009,52(9):2502-2509
The protective remolding and reusing of industrial historic buildings and sites is regarded as a great scientific matter in
today’s urban development. Based on discussing its significance and value, this paper, taking a specific example, makes a
systematic discussion on the design strategy and method from the aspects of overall planning, remolding the old buildings,
designing the new buildings, etc.
Supported by the Key Program of the National Natural Science Foundation of China (Grant No. 50878042) 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.
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
12.
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
13.
A macro-micro dual-drive positioning system showing good potential for high acceleration and high precision positioning required
in IC packaging applications is devised in this paper. The dual-drive positioning stage uses a VCM (voice coil motor) driven
macro positioning stage and a PZT piezo-electric driven micro positioning stage. The coupling characteristics of the system
are analyzed to produce a control structure with a micro positioning stage that can dynamically compensate for the positioning
error produced by the macro positioning stage. Models of the two positioning stages are described. The models cover both the
mechanism and the actuator. For the macro positioning stage, friction characteristics are taken into account, and a controller
with an LQG (linear-quadratic-Gaussian) control algorithm combining a feed-forward compensation algorithm is derived. A PID
controller is used to control the micro positioning stage. Detailed designs are derived for the proposed approach, and the
performance is validated by simulation.
Supported by the National Natural Science Foundation of China (Grant No. 50705027), the National High Technology Research
and Development Program of China (“863” Program) (Grant No. 2007AA04Z315) and Self-Planned Task of State Key Laboratory of
Robotics and System (HIT) (Grant No. SKLRS200804B) 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.
LIU Jie FAN GuangWei HAN PeiDe LIU JianSheng GE DongSheng & QIAO GuanJun School of Materials Science Engineering Xi’an Jiaotong University Xi’an China College of Materials Science Engineering Taiyuan University of Science Technology Taiyuan Taiyuan Iron Steel Company Ltd. Taiyuan College of Materials Science Engineering Taiyuan University of Technology 《中国科学E辑(英文版)》2009,52(8):2167-2171
Gleeble-1500D thermal simulation tester was employed in the hot-compression investigation of as-cast nuclear 304 austenitic stainless steel under conditions: deformation temperature 950―1200℃; deformations 30% and 50%; deformation rates 0.01 and 0.1 s?1. The results show that the flow stress decreases with temperature rise under the same strain rate and deformation, that the flow stress increases with deformation under the same temperature and strain rate, and that the flow stress increases with strain rate... 相似文献
16.
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
17.
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
18.
Internal state variable models for microstructure in high temperature deformation of titanium alloys
There exists an interaction between microstructural evolution and deformation behavior in high temperature deformation of
titanium alloys. And the microstructure of titanium alloys is very sensitive to the process parameters of plastic deformation
process. In this paper, on the basis of plastic deformation mechanism of metals and alloys, a microstructural model including
dislocation density rate equation and grain growth rate equation is established with the dislocation density rate being an
internal state variable. Applying the model to the high temperature deformation process of Ti60 titanium alloy, the average
relative errors of grain sizes between the experiments and the predictions are 9.47% for sampled data, and 13.01% for non-sampled
data.
Supported by the National Natural Science Foundation of China (Grant No. 50475144), the NPU Foundation for Research (Grant
No. NPU-FFR-006), and the National Basic Research Program of China (“973”) (Grant No. G20000672) 相似文献
19.
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
20.
Research on cohesive sediment erosion by flow: An overview 总被引:1,自引:0,他引:1
YongHui Zhu JinYou Lu HongZhi Liao JiaSheng Wang BeiLin Fan ShiMing Yao 《中国科学E辑(英文版)》2008,51(11):2001-2012
Erosion of cohesive sediment by flow is a very complicated phenomenon occurring worldwide. Understanding and modeling of the
erosion process are important for many issues such as the breaching of embankments, riverbank stability, siltation of harbors
and navigation channels, service life of reservoirs, distribution of (heavy metal) pollutants and water quality problems.
In the last few decades, numerous studies have been done on the erosion of cohesive sediment by flow. Nevertheless, the factors
affecting the erosion resistance of cohesive sediment are still not fully understood and the knowledge of the physics of cohesive
sediment erosion is inadequate, as a result the mathematical modeling of this erosion is far from satisfactory. In this paper
an overview of the studies on the erosion resistance, erosion threshold and the erosion rate of cohesive sediment by flow
is presented. The outcomes achieved so far from the studies and the existing problems have been analyzed and summarized, based
on which recommendations are proposed for future research.
Supported by the National Key Technology R&D Program of China (Grant Nos. 2006BAC14B02 and 2006BAB05B03) and the National
Basic Research Program (973 Program) of China (Grant No. 2007CB714106) 相似文献