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1.
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
2.
3.
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
4.
Train control system plays a key role in railway traffic. Its function is to manage and control the train movement on railway
networks. In our previous works, based on the cellular automata (CA) model, we proposed several models and algorithms for
simulating the train movement under different control system conditions. However, these models are only suitable for some
simple traffic conditions. Some basic factors, which are important for train movement, are not considered. In this paper,
we extend these models and algorithms and give a unified formula. Using the proposed method, we analyze and discuss the space-time
diagram of railway traffic flow and the trajectories of the train movement. The numerical simulation and analytical results
demonstrate that the unified CA model is an effective tool for simulating the train control system.
Supported by the Program for Changjiang Scholars and Innovative Research Team in University (Grant No. IRT0605), the National
Natural Science Foundation of China (Grant Nos. 60634010, 60776829), the Program for New Century Excellent Talents in University
(Grant No. NCET-06-0074) and the Key Project of Ministry of Education of China (Grant No. 107007) 相似文献
5.
Load model is one of the most important elements in power system operation and control. However, owing to its complexity,
load modeling is still an open and very difficult problem. Summarizing our work on measurement-based load modeling in China
for more than twenty years, this paper systematically introduces the mathematical theory and applications regarding the load
modeling. The flow chart and algorithms for measurement-based load modeling are presented. A composite load model structure
with 13 parameters is also proposed. Analysis results based on the trajectory sensitivity theory indicate the importance of
the load model parameters for the identification. Case studies show the accuracy of the presented measurement-based load model.
The load model thus built has been validated by field measurements all over China. Future working directions on measurement-based
load modeling are also discussed in the paper.
Recommended by Prof. LU Qiang, Member of Editorial Committee of Science in China, Series E: Technological Sciences
Supported in part by the Chinese National Key Basic Research Special Fund (Grant No. 2004CB217901), the National Science Foundation
of China (Grant No. 50595410) and by the Program for Changjiang Scholars and Innovative Research Team in University under
IRT0515 相似文献
6.
A model of curvature and tip deflection of multilayer thermal cantilever actuators is derived. The simplified expression received
from the model avoids inverting complex matrices enhances understanding and makes it easier to optimize the structure parameters.
Experiment is performed, the modeled and experimental results demonstrate the validity of the model, and it also indicates
that Young’s module makes great contribution to the deflection; therefore, thin layers cannot be ignored arbitrarily.
Supported by the National Natural Science Foundation of China (Grant No. 60576053) and Hi-Tech Research and Development Program
of China (Grant No. 2007AA03Z333) 相似文献
7.
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
8.
The paper proposes an approach to transmit electric power system dynamics in the SCADA. With the prevalent application of
digital substation automation system, it is feasible for the remote terminal units (RTUs) to collect phasors within a substation.
However, limited communication capacity remains the bottleneck that prevents SCADA from transmitting system dynamics. This
paper proposes to compress dynamics data with curve fitting in the RTUs and reconstruct the dynamics in the SCADA server for
reducing communication demand. Dispatchers in the control center can thus get system dynamics with a delay of several seconds.
Simulation result shows that for a power system under disturbance with short-circuit that once occurred and was cleared, the
SCADA can approximate the original dynamics with satisfying precision using limited degree polynomial fitting. The approach
is highly scalable and adaptable, and can be implemented on existing communication infrastructure with a few software modifications.
The approach has extensive application potential.
Supported by the State Key Development Program for Basic Research of China (Grant No. 2009CB219701), National Natural Science
Foundation of China (Grant No. 50595414) and Youth Scientific and Technological Innovation Project of CSEE 相似文献
9.
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
10.
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
11.
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
12.
The paper presents a practical dynamic security region (PDSR) based dynamic security risk assessment and optimization model
for power transmission system. The cost of comprehensive security control and the influence of uncertainties of power injections
are considered in the model of dynamic security risk assessment. The transient stability constraints and uncertainties of
power injections can be considered easily by PDSR in form of hyper-box. A method to define and classify contingency set is
presented, and a risk control optimization model is given which takes total dynamic insecurity risk as the objective function
for a dominant contingency set. An optimal solution of dynamic insecurity risk is obtained by optimizing preventive and emergency
control cost and contingency set decomposition. The effectiveness of this model has been proved by test results on the New
England 10-genarator 39-bus system.
Supported by the key research of the National Natural Science Foundation of China (Grant No. 50595413) and The National Basic
Research Program of China (973 Program) (Grant No. 2004CB217904) 相似文献
13.
Runyang Suspension Bridge (RSB) with the main span of 1490 m is the longest bridge in China and the third longest one in the
world. In this bridge the rigid central buckle is employed for the first time in the mid-span of the suspension bridge in
China. For such a super-long-span bridge, the traditional finite element (FE) modeling technique and stress analysis methods
obviously cannot satisfy the needs of conducting accurate stress analysis on the central buckle. In this paper, the submodel
method is introduced and for the first time used in analyzing the stresses of the central buckle. After an accurate FE submodel
of the central buckle was specially established according to the analysis results from the whole FE model, the connection
technique between the two-scale FE models was realized and the accurate stresses of the central buckle under various vehicle
load cases were then conducted based on the submodel method. The calculation results were testified to be accurate and reliable
by the field measurements, which show the efficiency and reliability of the submodel method on analyzing the mechanical condition
of the central buckle of long-span suspension bridges. Finally, the working behavior and mechanical characteristics of the
central buckle of the RSB under vehicle loads were analyzed based on the calculation and measurement results. The results
obtained in this paper can provide theoretic references for analyzing and designing the rigid central buckle in long-span
suspension bridges in future.
Supported by the National High Technology Research and Development Program (“863” Project) (Grant No. 2006AA04Z416), the Key
Project of the National Natural Science Foundation of China (Grant No. 50538020), the National Natural Science Foundation
of China for Young Scholars (Grant No. 50608017) and the Ph.D. Programs Foundation of Ministry of Education of China (Grant
No. 200802861012) 相似文献
14.
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
15.
In the study of finite element model updating or damage detection, most papers are devoted to undamped systems. Thus, their
objective has been exclusively restricted to the correction of the mass and stiffness matrices. In contrast, this paper performs
the model updating and damage detection for damped structures. A theoretical contribution of this paper is to extend the cross-model
cross-mode (CMCM) method to simultaneously update the mass, damping and stiffness matrices of a finite element model when
only few spatially incomplete, complex-valued modes are available. Numerical studies are conducted for a 30-DOF (degree-of-freedom)
cantilever beam with multiple damaged elements, as the measured modes are synthesized from finite element models. The numerical
results reveal that applying the CMCM method, together with an iterative Guyan reduction scheme, can yield good damage detection
in general. When the measured modes utilized in the CMCM method are corrupted with irregular errors, assessing damage at the
location that possesses larger modal strain energy is less sensitive to the corrupted modes.
Supported by the National High-Tech Research and Development Program of China (“863”) (Grant No. 2006AA09Z331), the China
National Science Fund for Distinguished Young Scholars (Grant No. 50325927), and the National Natural Science Foundation of
China (Grant No. 50739004) 相似文献
16.
Power system is a typical energy system. Because Hamiltonian approaches are closely related to the energy of the physical
system, they have been widely researched in recent years. The realization of the Hamiltonian structure of the nonlinear dynamic
system is the basis for the application of the Hamiltonian methods. However, there have been no systematically investigations
on the Hamiltonian realization for different power system dynamic models so far. This paper researches the Hamiltonian realization
in power systems dynamics. Starting from the widely used power system dynamic models, the paper reveals the intrinsic Hamiltonian
structure of the nonlinear power system dynamics and also proposes approaches to formulate the power system Hamiltonian structure.
Furthermore, this paper shows the application of the Hamiltonian structure of the power system dynamics to design non-smooth
controller considering the nonlinear ceiling effects from the real physical limits. The general procedure to design controllers
via the Hamiltonian structure is also summarized in the paper. The controller design based on the Hamiltonian structure is
a completely nonlinear method and there is no linearization during the controller design process. Thus, the nonlinear characteristics
of the dynamic system are completely kept and fully utilized.
Supported in part by the National Natural Science Foundation of China (Grant Nos. 50707009 and 50525721), in part by Program
for Changjiang Scholars and Innovative Research Team in University under IRT0515 and in part by Ministry of Education of China
(Grant No. 20070079014) 相似文献
17.
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
18.
YongPing Yang YingHong Cui HongJuan Hou XiYan Guo ZhiPing Yang NinLing Wang 《中国科学E辑(英文版)》2008,51(8):1211-1221
Integrating solar power utilization systems with coal-fired power units, the solar aided coal-fired power generation (SACPG)
shows a significant prospect for the large-scale utilization of solar energy and energy saving of thermal power units. The
methods and mechanism of system integration were studied. The parabolic trough solar collectors were used to collect solar
energy and the integration scheme of SACPG system was determined considering the matching of working fluid flows and energy
flows. The thermodynamic characteristics of solar thermal power generation and their effects on the performance of thermal
power units were studied, and based on this the integration and optimization model of system structure and parameters were
built up. The integration rules and coupling mechanism of SACPG systems were summarized in accordance with simulation results.
The economic analysis of this SACPG system showed that the solar LEC of a typical SACPG system, considering CO2 avoidance, is 0.098 $/kW·h, lower than that of SEGS, 0.14 $/kW·h.
Supported by the National Natural Science Foundation of China (Grant Nos. 50776028 and 50606010) and the Program for New Century
Excellent Talents in University (Grant No. NCET-05-0217) 相似文献
19.
With the rapid development of functional magnetic resonance imaging (fMRI) technology, the spatial resolution of fMRI data
is continuously growing. This provides us the possibility to detect the fine-scale patterns of brain activities. The established
univariate and multivariate methods to analyze fMRI data mostly focus on detecting the activation blobs without considering
the distributed fine-scale patterns within the blobs. To improve the sensitivity of the activation detection, in this paper,
multivariate statistical method and univariate statistical method are combined to discover the fine-grained activity patterns.
For one voxel in the brain, a local homogenous region is constructed. Then, time courses from the local homogenous region
are integrated with multivariate statistical method. Univariate statistical method is finally used to construct the interests
of statistic for that voxel. The approach has explicitly taken into account the structures of both activity patterns and existing
noise of local brain regions. Therefore, it could highlight the fine-scale activity patterns of the local regions. Experiments
with simulated and real fMRI data demonstrate that the proposed method dramatically increases the sensitivity of detection
of fine-scale brain activity patterns which contain the subtle information about experimental conditions.
Supported by Chair Professors of Changjiang Scholars Program and CAS Hundred Talents Program, National Program on Key Basic
Research Projects (Grant No. 2006CB705700), National High-Tech R&D Program of China (Grant No.2006AA04Z216), National Key
Technology R&D Program (Grant No. 2006BAH02A25), Joint Research Fund for Overseas Chinese Young Scholars (Grant No.30528027),
National Natural Science Foundation of China (Grant Nos.30600151, 30500131 and 60532050), and Natural Science Foundation of
Beijing (Grant Nos. 4051002 and 4071003) 相似文献
20.
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