Modeling and simulation for train control system using cellular automata

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)     

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)     

Numerical study on the restriction speed of train passing curved rail in cross wind

The results of numerical investigations of aerodynamic forces and moment coefficients of flow passing a simplified train geometry under different wind speeds are summarized. To compute numerically the different coefficients, the three-dimensional Reynolds-Averaged Navier-Stokes (RANS) equations, combined with the k-ε turbulence model, were solved using finite volume technique. The pres-sure-velocity fields were coupled using the SIMPLE algorithm. At each iteration the pressure correction was obtained by sol...     

Acoustic properties of sintered FeCrAlY foams with open cells (II): Sound attenuation

Open-celled metal foams fabricated through metal sintering offers novel mechanical, thermal and acoustic properties. Previously, polymer foams were used as a means of absorbing acoustic energy. However, the structural applications of these foams are inherently limited. The metal sintering approach provides a cost-effective means for the mass-production of open-cell foams from a range of materials, including high-temperature steel alloys. The low Reynolds number fluid properties of sintered steel alloy (FeCrAlY) foams were investigated in a previous study. The static flow resistance of the foams was modeled based on a cylinder and a sphere arranged in a periodic lattice at general incidence to the flow, with the resulting predictions correlating well to measurements. The application of the flow resistance in an acoustic model is the primary focus of the present study. The predictions for the static flow resistance of the sintered foams are first used in a theoretical model to determine the characteristic impedances, as well as the propagation constants of the foams. Subsequently, the predicted acoustic performance of the foams is compared to experimental results. Finally, the design space for a simple acoustic absorber incorporating sintered foams is examined, with the effects of absorber size, foam selection, and foam spacing explored. Supported by the National Basic Research Program of China (Grant Nos. 2006CB601202, 2006CB601204), the National 111 Project of China (Grant No. B06024), US Office of Naval Research (Grant No. N000140210117), the National Natural Science Foundation of China (Grant Nos. 10572111, 10632060), and the National H-Tech Research and Development Program of China (Grant No. 2006AA03Z519)     

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     

Measurement-based load modeling: Theory and application

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     

Acoustic properties of sintered FeCrAlY foams with open cells (I): Static flow resistance

Open celled metal foams fabricated through the route of metal sintering are a new class of material that offers novel mechanical and acoustic properties. The metal sintering approach offers a cost-effective means for the mass-production of open-cell foams from a range of materials, including high-temperature steel alloys. The mechanical properties of open-celled steel alloy (FeCrAlY) foams have been characterized in previous studies, with focus placed on the influence of processing defects on stiffness and strength. In this work, the low-Reynolds number fluid properties of FeCrAlY foams were investigated both theoretically and experimentally. Specifically, the static flow resistance of the sintered foams important for heat transfer, filtration and sound absorption was modeled based on a cylinder and a sphere arranged in a periodic lattice at general incidence to the flow. Experimental measurements were subsequently carried out to validate theoretical predictions, with good agreement achieved. Supported by the National Basic Research Program of China (Grant Nos. 2006CB601202, 2006CB601204), the National 111 Project of China (Grant No. B06024), US Office of Naval Research (Grant No. N000140210117), the National Natural Science Foundation of China (Grant Nos. 10572111, 10632060), and the National Hi-Tech Research Development Program (Grant No. 2006AA03Z519)     

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)     

The steady-state solution of dendritic growth from the undercooled binary alloy melt with the far field flow

The steady-state dendritic growth from the undercooled binary alloy melt with the far field flow is considered. By neglecting the interface energy, interface kinetics and buoyancy effects in the system, we obtaine the steady-state solution for the case of the large Schmidt number, in terms of the multiple variable expansion method. The changes of the temperature and concentration fields, the morphology of the interface, the normalization parameter and the Peclet number of the system induced by uniform external flow are derived. The results show that, compared with the system of dendritic growth from undercooled pure melt, the convective flow in the system of growth from undercooled binary alloy has stronger effects on the morphology of the interface. Nevertheless, the shape of the interface still remains nearly a paraboloid. Supported by the National Basic Research Program of China (Grant No. 2006CB605205) and the National Natural Science Foundation of China (Grant No. 10672019)     

Development of ecohydrological assessment tool and its application

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)     

A new transient stability margin based on dynamic security region and its applications

A new transient stability margin is proposed based on a new expression of dynamic security region (DSR) which is developed from the existing expression of DSR. Applications of the DSR based transient stability margin to contingency ranking and screening are discussed. Simulations in the 10-machine 39-bus New England system are performed to show the effectiveness of the proposed DSR based transient stability margin. Supported by Chinese National Basic Research Program (Grant No. 2004CB217900), the National Natural Science Foundation of China (Grant Nos. 50525721, 50595411, 50707035) and China Postdoctoral Science Foundation (Grant No. 20060400518)     

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)     

Thermoelastic properties of sandwich materials with pin-reinforced foam cores

Pin-reinforced foam is a novel type of sandwich core materials formed by inserting pins (trusses) into a foam matrix to create a truss-like network reinforced foam core. Upon loading, the pins deform predominantly by local stretching whilst the deformation of foam is governed by local bending. This paper presents a theoretical study on the thermoelasticity of pin-reinforced foam sandwich cores. To calculate the effective thermoelastic properties of pin-reinforced foam cores, the energy-based homogenization approach is employed to develop a micromechanicsbased model, calibrated by the existing experimental data. It is found that the stiffness of the sandwich core is mainly governed by pin reinforcements: the foam matrix contributes little to sandwich stiffness. Compared with traditional foam cores without pin reinforcements, the changes in in-plane thermal expansion coefficients are not vigorous as a result of pin reinforcements, while the throughthickness thermal expansion coefficient changes significantly. It is also demonstrated that it is possible to design materials with zero or negative thermal expansion coefficients under such a context. Supported by the National Basic Research Program of China (Grant No. 2006CB601202), the National Natural Science Foundation of China (Grant Nos. 10572111, 10632060), the National 111 Project of China (Grant No. B06024), the National High Technology Research Development Program (Grant No. 2006AA03Z519), the NPU Foundation for Fundamental Research, the Open Foundation of State Key Laboratory of Structural Analysis of Industrial Equipment (Grant No. GZ0701), and the NPU Foundation for Scientific Innovation     

Influences of friction drag on spontaneous condensation in water vapor supersonic flows

A mathematical model was developed to investigate the water vapor spontaneous condensation under supersonic flow conditions. A numerical simulation was performed for the water vapor condensable supersonic flows through Laval nozzles under different flow friction conditions. The comparison between numerical and experimental results shows that the model is accurate enough to investigate the supersonic spontaneous condensation flow of water vapor inside Laval nozzles. The influences of flow friction drag on supersonic spontaneous condensation flow of water vapor inside Laval nozzles were investigated. It was found that the flow friction has a direct effect on the spontaneous condensation process and therefore it is important for an accurate friction prediction in designing this kind of Laval nozzles. Supported by the National Natural Science Foundation of China (Grant No. 50676002), the Specialized Research Fund for the Doctoral Program of Higher Education (Grant No. 20040005008) and the Beijing Best Innovation Person Selecting Project (2006)     

Design and fabrication of erbium doped photosensitive fibers

A kind of erbium doped photosensitive fiber (EDPF) was proposed and fabricated, whose core was made of double layers named photosensitive layer and erbium doped layer. The double-layer core design can overcome difficulties in fabrication of EDPF with single core design, i.e. the conflict between the high consistency rare earth doping and high consistency germanium doping. A sample was fabricated through the modified chemical vapor deposition method combined with solution doping technique. The peak absorption coefficient was 48.80 dB/m at 1.53 μm, the background loss was lower than 0.1 dB/m, and the reflectivity of the fiber Brag gratings (FBG) written directly on the sample fiber was up to 97.3% by UV-writing technology. Moreover, a C band tunable fiber laser was fabricated using the sample fiber, in which a uniform FBG was written directly on EDPFs as a reflector. A single wavelength lasing with a maximum wavelength tuning range of 1555.2–1558.0 nm was achieved experimentally. Within this tuning range, the full-width at half maximum (FWHM) of the laser output was smaller than 0.015 nm and the side mode suppression ratio (SMSR) was better than 50 dB. Supported by the National High Technology Research and Development Program of China (863 Project) (Grant No. 2007AA01Z258), the National Natural Science Foundation of China (Grant No. 60771008), Program for 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)     

Dynamic simulation and optimization approach to construction diversion of hydraulic and hydroelectric projects

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)     

Transmitting electric power system dynamics in SCADA using polynomial fitting

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     

Research and application of CO<Subscript>2</Subscript> refrigeration and heat pump cycle

The environmental problem caused by refrigerant has become the focus all over the world. As the most typical natural refrigerant, CO₂, of course, becomes the research focus. This paper introduces the development and application status of CO₂ refrigeration and heat pump technology. The researches on CO₂ refrigeration and heat pump, carried out by Thermal Energy Research Institute, Tianjin University, also are presented in this paper. Supported by the National Natural Science Foundation of China (Grant Nos. 50676064, 50506019) and the National Hi-Tech Research and Development Program of China (“863” Project) (Grant No. 2007AA05Z262)     

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)     

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...