A transient energy function for power systems including the induction motor model

A construction method for power system transient energy function is studied in the paper, which is simple and universal, and can unify the forms of some current energy functions. A transient energy function including the induction motor model is derived using the method. The unintegrable term is dealt with to get an approximate energy function. Simulations in a 3-bus system and in the WSCC 4-generator system verify the validity of the proposed energy function. The function can be applied to direct transient stability analysis of multi-machine large power systems and provides a tool for analysis of the interaction between the generator angle stability and the load voltage stability. Recommended by Prof. LU Qiang, Member of Editorial Committee of Science in China, Series E: Technological Sciences Supported by the Special Fund of the National Priority Basic Research of China (Grant No. 2004CB217904) and the National Natural Science Foundation of China (Grant No. 50323002)     

Compensation for time-delayed feedback bang-bang control of quasi-integrable Hamiltonian systems

The stochastic averaging method for quasi-integrable Hamiltonian systems with time-delayed feedback bang-bang control is first introduced. Then, two time delay compensation methods, namely the method of changing control force amplitude (CFA) and the method of changing control delay time (CDT), are proposed. The conditions applicable to each compensation method are discussed. Finally, an example is worked out in detail to illustrate the application and effectiveness of the proposed methods and the two compensation methods in combination. Supported by the National Natural Science Foundation of China (Grant No. 10772159), the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20060335125), Zhejiang Natural Science Foundation (Grant No. Y7080070), and Fujian Provincial Science and Technology Project (Grant No. 2005YZ1021)     

Damage detection test of a substructure model of the National Swimming Center

In order to detect the damage locations of complex spatial structures, a sensor region-based damage detection approach was developed based on the damage locating vectors method. A normalized damage locating index was introduced to identify the damage regions. An experiment on damage detection of a substructure model of the National Swimming Center ‘Water Cube’ was carried out. Two damage patterns were involved in the experiment. The test model was excited by using hammer impacts. Acceleration responses of the undamaged and damaged structure model were measured. Modal parameters were identified from the acceleration responses by utilizing the eigensystem realization algorithm (ERA). By using the developed sensor region-based method, the damage regions of the substructure model were located. The results show that the proposed method is able to effectively locate the damage regions. Supported by Beijing Natural Science Foundation (Grant No. 8041002), the National Natural Science Foundation of China (Grant No. 8041002), the National Science and Technology Committee of China (Grant No. 2004BA904B02), and Beijing Science and Technology Committee (Grant No. Z0004028040221)     

Risk assessment method of major unsafe hydroelectric project

Based on the characteristics of major unsafe hydroelectric projects and the data from field detection, in situ monitoring, and regular safety inspection, the fundamental principles of operation risk assessment are proposed in this paper. Meanwhile, a three layer hierarchical system is constructed, and an improved analytical hierarchical process combining genetic algorithm and analytical hierarchical process is established, with corresponding program. The operation risk of some unsafe dam was assessed with the principles, method and program presented in this paper and the major factors which would affect the operation of the dam were pointed out. Supported by Key Project of NNSF and Yalongjiang Hydroelectric Development Joint Research Fund (Grant No. 50539110), Science and Technology Support Plan (Grant No. 20006BAC14B03), National Natural Science Foundation Major Project (Grant Nos. 50539010, 50539030) and National Natural Science Foundation of China (Grant No. 50579010)     

p-moment stability of stochastic impulsive differential equations and its application in impulsive control

The exponential p-moment stability of stochastic impulsive differential equations is addressed. A new theorem to ensure the p-moment stability is established for the trivial solution of the stochastic impulsive differential system. As an application of the theorem proposed, the problem of controlling chaos of Lorenz system which is excited by parameter white-noise excitation is considered using impulsive control method. Finally, numerical simulation results are given to verify the feasibility of our approach. Supported by the National Natural Science Foundation of China (Grant No. 10772046)     

Dynamic security risk assessment and optimization of power transmission system

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)     

Ultralight X-type lattice sandwich structure (II): Micromechanics modeling and finite element analysis

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)     

BRVAAF and performance analysis for target detection

A bistatic range-velocity-acceleration ambiguity function (BRVAAF) is proposed. The model of radar measurements of an accelerating target involving the time delay, Doppler frequency and Doppler rate is given. The relationships between these measurements and the parameters of the bistatic geometry, target position, velocity and acceleration are derived. Moreover, the effects of the bistatic geometry factors on these measurements are analyzed. Besides, the two relationships of the bistatic integration loss and the bistatic optimum integration time with these factors are built and their change trends are described respectively. This research is helpful to analyze the influences of the bistatic geometry factors on the target detection and signal processing. Supported by the National Natural Science Foundation of China (Grant No. 60232010), the National Natural Science Foundation of China for Distinguished Young Scholars (Grant No. 60625104) and the Advanced Research Project (Grant Nos. 51307060504, 9140A07040806BQ01)     

Dynamic substructure model for multiple impact responses of micro/nano piezoelectric precision drive system

A dynamic substructure technique which considers the electromechanical coupling effect of the PZT and the inertial effect of flexible components is presented to study the multiple impact dynamic be- havior of micro/nano piezoelectric impact drive systems. It can investigate the step-like motion of ob- ject body and the multiple impacts behaviors reasonably by the comparison of the experimental data and the numerical solution of the spring-mass model. It is expected to have higher accuracy in the numerical s...     

Multi-channel sampling theorems for band-limited signals with fractional Fourier transform

Multi-channel sampling for band-limited signals is fundamental in the theory of multi-channel parallel A/D environment and multiplexing wireless communication environment. As the fractional Fourier transform has been found wide applications in signal processing fields, it is necessary to consider the multi-channel sampling theorem based on the fractional Fourier transform. In this paper, the multi-channel sampling theorem for the fractional band-limited signal is firstly proposed, which is the generalization of the well-known sampling theorem for the fractional Fourier transform. Since the periodic nonuniformly sampled signal in the fractional Fourier domain has valuable applications, the reconstruction expression for the periodic nonuniformly sampled signal has been then obtained by using the derived multi-channel sampling theorem and the specific space-shifting and phase-shifting properties of the fractional Fourier transform. Moreover, by designing different fractional Fourier filters, we can obtain reconstruction methods for other sampling strategies. Supported partially by the National Natural Science Foundation of China (Grant Nos. 60232010 and 60572094) and the National Natural Science Foundation of China for Distinguished Young Scholars (Grant No. 60625104)     

Method of change management based on dynamic machining error propagation

In multistage machining processes(MMPs),the final quality of a part is influenced by a series of machining processes,which are complex correlations.So it is necessary to research the rule of machin-ing error propagation to ensure the machining quality.For this issue,a change management method of quality control nodes(i.e.,QC-nodes) for machining error propagation is proposed.A new framework of QC-nodes is proposed including association analysis of quality attributes,quality closed-loop control,error tracing...     

Study on pure silica core optical fibers

An optimal refractive index profile of pure silica core optical fiber (PSCF) was designed, in combination with the characters of the modified chemical vapor deposition (MCVD) process. Techniques of preform fabrication by a new furnace round heating MCVD process and fiber drawing process were reviewed. Difficulties in doping fluorine in silica, widening the depressed-index cladding and maintaining the index of fiber core were discussed. Methods used to overcome these difficulties were given at the same time. Additionally, the optimal refractive index profiles of PSCF were presented. Supported by the Hi-Tech Research and Development Program of China (Grant No. 2002AA312190), National Natural Science Foundation of China (Grant No. 60477017), Program for the New Century Excellent Talents in University (Grant No. NCET-06-0076), Beijing Natural Science Foundation (Grant No. 4052023) and the Beijing Jiaotong University Foundation (Grant No. 2006XM003)     

Optimization model and algorithm for mixed traffic of urban road network with flow interference

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)     

Filterbank implementation for multi-channel sampling in fractional Fourier domain

Reconstruction of a continuous time signal from its periodic nonuniform samples and multi-channel samples is fundamental for multi-channel parallel A/D and MIMO systems. In this paper, with a filterbank interpretation of sampling schemes, the efficient interpolation and reconstruction methods for periodic nonuniform sampling and multi-channel sampling in the fractional Fourier domain are presented. Firstly, the interpolation and sampling identities in the fractional Fourier domain are derived by the properties of the fractional Fourier transform. Then, the particularly efficient filterbank implementations for the periodic nonuniform sampling and the multi-channel sampling in the fractional Fourier domain are introduced. At last, the relationship between the multi-channel sampling and the filterbank in the fractional Fourier domain is investigated, which shows that any perfect reconstruction filterbank can lead to new sampling and reconstruction strategies. Supported by the National Natural Science Foundation of China for Distinguished Young Scholars (Grant No. 60625104), the National Natural Science Foundation of China (Grant Nos. 60890072, 60572094) and the National Key Basic Research Program Founded by MOST (Grant No. 2009CB724003)     

Constitutive model for overconsolidated clays

Based on the relationships between the Hvorslev envelope, the current yield surface and the reference yield surface, a new constitutive model for overconsolidated clays is proposed. It adopts the unified hardening parameter, to which the potential failure stress ratio and the characteristic state stress ratio are introduced. The model can describe many characteristics of overconsolidated clays, including stress-strain relationships, strain hardening and softening, stress dilatancy, and stress path dependency. Compared with the Cam-clay model, the model only requires one additional soil parameter which is the slope of the Hvorslev envelope. Comparisons with data from triaxial drained compression tests for Fujinomori clay show that the proposed model can rationally describe overconsolidated properties. In addition, the model is also used to predict the stress-strain relationship in the isotropic consolidation condition and the stress paths in the undrained triaxial compression tests. Supported by the National Natural Science Foundation of China (Grant Nos. 50479001 and 10672010), the National Science and Technology Supporting Item (Grant No. 2006BAK12B12), and the National Basic Research Program of China (Grant No. 2007CB714203)     

New explicit algebraic stress and flux model for active scalar and simulation of shear stratified cylinder wake flow

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)     

A novel random phase-shifting digital holographic microscopy method

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     

Preparation and properties of ZnO nano-whiskers

By a novel controlled combustion synthesis method, a large amount of ZnO nano-whiskers with different morphologies like nanotetrapods, long-leg nanotetrapod and multipods, were prepared without any catalysts and additives in open air at high temperature. Their morphologies, structures and optical properties were investigated by using SEM, XRD and PL spectrum. The possible growth mechanisms on the ZnO nano-whiskers were proposed in this paper. Supported by the National Natural Science Foundation of China (Grant Nos. 50572010, 50742007 and 10672020), National Defense Founds of China (Grant Nos. 51420205BQ0154 and A2220061080), “863” Project of China (Grant No. 2007AA03Z103), and the Scientific Research Foundation of Graduate School of BIT (Grant No. AA200802)     

Transient pressure analysis in porous and fractured fractal reservoirs

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)     

RobustH ∞ controller design for a class of uncertain systems

TheH ^∞ control problem for a class of systems with time-varying and nonlinear uncertainties is considcred. A new sufficient condition based on LMI is provided to judge their robust stability andL ₂-gain finiteness. Solvability conditions are presented for both state feedback and output feedback cases, which are all reduced to solutions of LMIs. The design procedure is also discussed via LMI approach. Project supported by the National Natural Science Foundation of China (Grant No. 59704004).