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Tsinghua Science and Technology

Issue 4 • Date Dec. 1999

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Displaying Results 1 - 25 of 26
  • [Front cover]

    Page(s): c1
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    Freely Available from IEEE
  • Contents

    Page(s): 1 - 2
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    Freely Available from IEEE
  • Universal adaptive observer for nonlinear time-varying deterministic systems

    Page(s): 1597 - 1601
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (993 KB)  

    Designing adaptive observers for MIMO nonlinear time varying deterministic systems is an open problem. In this paper a novel solution on to this problem is given by use of a “strong tracking fiIter (STF)”. First, the STF is outlined, then some technical points of view to use the STF as an adaptive observer are discussed. Finally, two typical examples are presented to illustrate the effectiveness of the proposed approach. View full abstract»

    Open Access
  • Point pattern matching using irreducible matrix and relative invariant

    Page(s): 1602 - 1605
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (726 KB)  

    Point pattern matching is an important problem in the fields of computer vision and pattern recognition. In this paper, new algorithms based on irredcible matrix and relative invariant for matching two sets of points with the same cardinality are proposed Thei r fundamental idea is transforming the two dimensional point sets with n points into the vectors in n-dimensional space. Considering these vectors as one dimensional point patterns, these new algorithms aim at reducing the point matching problem to that of sorting vectors in n-dimensional space as long as the sensor noise does not alter the order of the elements in the vectors. Theoretical analysis and simulation results show that the new algorithms are effective. View full abstract»

    Open Access
  • A new framework for Intranet-based group decision support system

    Page(s): 1606 - 1609
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    The burgeoning Intranet is becoming a standard platform for the new generation of IS (Information System) applications. This paper gives a brief survey of Group Decision Support Systems (GDSS). Then the influence of Intranet on GDSS and limitations of Intranet as a platform for GDSS are analyzed. A new framework for Intranet based GDSS is proposed, which extends the two tier browser/server architecture to multilevel distributed application architecture. A broker level and a middle application level are added, with a GDSS interface embedded in the web browser. The coterminous two levels in the new framework still comply wi th the tradi tional client/server architecture. This framework for Intranet based GDSS is called as extended GDSS (xGDSS, in short). Features of xGDSS include cost effective, short development cycle, open, flexible configuration, general-purpose, etc. View full abstract»

    Open Access
  • Fuzzy adaptive variable structure guidance with application to space interception

    Page(s): 1610 - 1614
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (968 KB)  

    The adaptive variable structure guidance (AVSG) is robust to target maneuvers, but apt to induce unwanted chattering. Fuzzy technique is used to implerrent the AVSG for eliminating chattering, and then a new guidance method called fuzzy AVSG is produced. The fuzzy AVSG is applied to the space interception problem Simulation results demonstrate the effectiveness of the new gui dance method. View full abstract»

    Open Access
  • Dynamic classifier combination method based on minimum cost criterion

    Page(s): 1615 - 1619
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (896 KB)  

    This paper presents a novel method for multi-classifier dynamic corrbinati on based on minimum cost criterion. Different from common combination methods, the proposed dynamic combination selects the most suitable group of classifiers according to the Performance Predication Feature (PPF) extracted from the input sample. PPFs are the features of sample that have great influence on the performance of class fiers being studied. The decision is made based on the criterion that the selected group of classifiers should minimize the cos caused by recognition error and recognition on time. Systematic methods for making this kind of combination is proposed and a practical example of application is given. Because the adjustment of cost function will result in di fferent trade-off between recognition rate and recognition speed, it is very convenient to satisfy di fferent needs. The application in on-line Chinese character recognition technology shows that this kind of combination method has the merits of high flexibility and practicality, and it is indeed able to improve the system performance. View full abstract»

    Open Access
  • Request dispatching algorithms for web server clusters based on load balancing

    Page(s): 1620 - 1623
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (725 KB)  

    Web server clusters has become a popular solution to achieve high performance due to their low price, high reliability, and good scalability. One of the key technologies is “request dispatching”, which is to centrally accept all the incoming HTTP requests and dispatch them to the servers in the cluster to achieve parallelism The research shows that the efficiency of request dispatching is determined by whether the server loads are balanced during the dispatching. spatching. This paper sudes the characteristics of the load generated by HTTP requests, gives an efficient method of load sampling, and preserts a novel request dispatching algorithm which can predict the load and balance it. The method can be used to build Web server clusters of heterogeneous machines. View full abstract»

    Open Access
  • Dispersion compensation of 50 km SMF optical transmission systems with a linearly chirped fiber grating

    Page(s): 1624 - 1627
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    A linearly chi rped fiber grating was written by tilting the fiber with a uniform phase mask. A bandwidth of 0. 25 nm was produced. Dispersion compensation over 50 km of standard single mode fiber (SMF) was demonstrated using this chirped fiber grating. A figure of merit of 0.88 was achieved with near perfect recompresson. View full abstract»

    Open Access
  • Progressive failure simulation for damaged composite laminates using nonlinear finite element method

    Page(s): 1628 - 1631
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (591 KB)  

    A nonlinear finite element program taking into account of the nonlinear shear stress-strain relation is used to simulate the progressive damage of composite laminates with a circular hole subjected to tensile loading. Stress, strain, and ultimate strength of the laminate are analyzed. Comparison between calculated result and test data shows that the nonlinear approach gives more accurate result, especially for orthotropic I am nate. Pararretric study shows that the variation of nonlinear factor has more effect on the result for orthotropic plate than for quasi-isotropic plate. View full abstract»

    Open Access
  • An integrated application of neural network, fuzzy and expert systems for machining operation sequencing

    Page(s): 1632 - 1637
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    A part is described using features. A reuro fuzzy system then determines the machining sequerce for each feature. Previous process plans were utilized to build, test, and validate the Neuro Fuzzy Network (NFN). Parts having simlar manufacturing sequences are grouped into families, also using an NFN. A standard manufacturing sequence is obtained for each family comprising all the operations applicable to the features of the parts in the family. An expert system then adapts this standard sequence for the particular part being planned. The optimal operation sequence is inherited by the new part. The procedure is demonstrated by an example industrial part. View full abstract»

    Open Access
  • 233U Breeding in accelerator sub-critical fast reactor

    Page(s): 1638 - 1641
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    Accelerator driven Sub-critical Fast Reactor (ADFR) is chosen as fissile material breeding reactor. (U Pu) Ox is chosen as fuel in the core and ThO2 as fertile material in the blanket zone to breed 233U. Molten lead is chosen as coolant because of its better neutronic and chemical characteristics over sodium. The program system used for neutronics study consists of: LAHET, for the simulation of the interaction between the proton with medium energy and the nuclei of the target; MONP4A, for the simulation of neutron transport with energy below 20 MeV in the sub critical reactor; CONNECT1, for the processing of some tallies provided by the output of MCNP4A in order to prepare micro-cross sections for elements used for burnup calculation; ORIGEN2, used for multi-region burnup calculation; CONNECT2, for the processing of atom dens ties of some elements provided in the output of ORIGEN2 in order to prepare input to LAHET calculation for next time step. The calculated results show that the proposed case is feasible for breeding fissile material considering the criticality safety, power density, burnup, etc. View full abstract»

    Open Access
  • Optimal treatment cost allocation methods in pollution control

    Page(s): 1642 - 1646
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (859 KB)  

    Total emission control is an effective pollution control strategy. However, Chinese application of total emission control lacks reasonable and fair methods for optimal treatment cost allocation, a critical issue in total emission control. This paper considers four approaches to allocate treatment costs. The first approach is to set up a multiple-objective planning model and to solve the model using the shortest distance ideal point method. The second approach is to define degree of satisfaction for cost allocation results for each polluter and to establish a method based on this concept. The third is to apply bargaining and arbitration theory to develop a model. The fourth is to establish a cooperative N-person game model which can be solved using the Shapley value method, the core method, the Cost Gap Allocation method or the Minimum Costs Remaining Savings method. These approaches are compared using a practicable case study. View full abstract»

    Open Access
  • Completeness of the higher order harmonics

    Page(s): 1647 - 1651
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    Applications using higher order harmonics (HOH) require knowledge of the corrpleteness of the HOH for the diffusion difference equation. This paper shows that the set of HOH for the fission source is complete, but that the set for the flux using the multi-group model is not complete. This paper uses the assumption that the set of flux vectors of HOH for every group is complete. This assumption can be proven only for those groups into which no scattering neutrons enter. However, it is also shown to be true for several practical reactor models. Analysis shows that the number of HOH with non-zero eigenvalues is equal to the number of difference meshes with fissile material, and that the eigenvalues have positive real values. This assumption is valuable for HOH applications, but requires further theoretical study to verify whether it is universally applicable. View full abstract»

    Open Access
  • R&D and reliability analysis of a digital protection system for nuclear heating reactors

    Page(s): 1652 - 1655
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    This paper discusses a scheme of digital Reactor Protection System (RPS). Advanced parallel processing channels, consisting of a microprocessor based unit and a General Array Logic (GAL)-based unit have been configured in each of the redundant trains to eliminate the risk of common mode failure of digital RPSs through the way of diversified equipment. Also several digital techniques are also applied to improve the system design. For example, the Voltage/Frequency (V/F) converter is applied to achieve the digitization of the measurement channel. GAL components greatly simplify the hardware ci rcuit design. Two types of communication buses are designed to improve the reliability of data transmission. By all these means, the reliability of RPS can be expected to achieve a great improvement. View full abstract»

    Open Access
  • A Multi-purpose electro-heat cogeneration plant

    Page(s): 1656 - 1660
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    In China a test heating reactor has been built and a commercial demonsration heat plant is under construction. In order to increase the thermal efficiency of the existing heating reactor, an electro-heat cogeneration plant concept is presented. The cogeneration plant keeps the advantages of the existing heating reactor: compact arrangement (smaller sizes than ordinary facility), simpler systems, good safety, and makes some improvements. For example, introduce boiling in the reactor, the cogeneration plant can be used for ship propulsion, movable desalination on plant, and process heating plant. Several variants have been analyzed from the view point of thermodynamics. Main features and parameters of the plant are given in the paper. View full abstract»

    Open Access
  • Dynamic model for the control system simulation and design of a 200 MW nuclear heating reactor

    Page(s): 1661 - 1665
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (954 KB)  

    The paper develops a nonlinear dynamc model used in a wide range control system simulation for a 200 MW Nuclear Heating Reactor (NHR 200). Besides a one point neutron kinetics equation and terrperature feedback based on the lumped fuel and coolant terrperature, which are the usual methods used in modeling of PWR, two other factors are also considered in order to suit the wide range operation. The first consideration is the natural circulation in the primary loop because it affects the heat transfer coefficients in the core and in the primary heat exchanger (PHE). The second consderation is the flow rate variation in the secondary loop which leads to some nonlinear properties. The simulation results show that the model is accurate enough for control system simulation. Some model reduction basis can be obtained through the dynamic analysis View full abstract»

    Open Access
  • Licensing of the construction permit of the NHR-200

    Page(s): 1666 - 1671
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    The nuclear heating reactor (NHR) was developed by the Institute of Nuclear Energy Technology (INET), Tsinghua University. The main design features and safety concepts of the NHR200, the criteria and principles that were followed in licensing the construction permit of the NHR 200 are discussed. Licensing activities and procedures are described. Some of the main safety licensing safety issues including accident analysis, secondary containment design, the requirements for the Diesel generators and the safety classification of systems and components are briefly addressed. View full abstract»

    Open Access
  • Numerical calculation of flows in turbomachinery with three dimensional viscous codes

    Page(s): 1672 - 1677
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1094 KB)  

    A fast and accurate three dimensional (3-D) viscous code for calculating flows in turbomachinery has been established. In this code, H meshes are adopted to build the discrete equations, and the conservation equations are solved on grid nodes at the corners of cuboid elements. In order to acceler ate convergence, local time stepping, residual smoothing and multigrid method are also applied, and the viscous effects are approximated by a very simple mixing length model. For verification of the accuracy and applicability of the method, transonic flows through compressor cascades of NASA rotor 37 and flows through a turbine stator of NASA have been calculated. The good agreement between experimental results and design data has demonstrated the reliability and applicability of the present method, which can be used for simulating the complex 3-D viscous flow phenomenon in turbomachinery. View full abstract»

    Open Access
  • Numerical investigation of a high-speed centrifugal compressor impeller

    Page(s): 1678 - 1682
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    High speed centrifuga compresrors are widely used in industry. It is important to understand its internal flow field in order to design higher efficiency and pressure ratio impellers. In this paper, a 3-D viscous code to solve the simplified Reynolds averaged Navier Stokes equations has been developed. The viscocs effect is simulated by viscous body force method. The governing equations are spatially discretized in the celt vortex finite volume scheme on a simple H mesh. The turbulence closure is made using the Baldwin Lomax model. This code is demonstrated for predicting the internal flow field of a high speed impeller. Some laser measured results are also illustrated for comparing with calculated data. View full abstract»

    Open Access
  • Future applications of power plant simulators — Total plant solution system

    Page(s): 1683 - 1687
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1003 KB)  

    Over the past three decades, power plant simulators have gone through several major phases of evolution and they have been widely used as a valuable tod for training plant operational personnel. Looking forward, the simulators will again prove their value far beyond the traditional training applications Simulators will serve as the engine of the envisioned “Total Plant Solution Sysem”, which will provide optimized solutions to every aspect of the plant operation including on line plant monitoring, control, diagroaics, automation, optimization, as well as simulation and analysis. Simulators will greatly enhance operational reliability, availability, efficiency, and safety. View full abstract»

    Open Access
  • Full-function numerical method for flow over a self-excited vibrating body

    Page(s): 1688 - 1691
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    This paper presents the concept of a fult-function numerical method for flow over a self excited vibrating body. It contains three dimensional (3-D) numerical analysis of unsteady aerodynamic force for a self excited vibrating body, calculation of the work done by unsteady aerodyramc force and damping, determination of the equili brium amplitude and dynamic stress as well as corresponding life evaluation. View full abstract»

    Open Access
  • Analysis of passivity and disturbance attenuationfor a class of power systems

    Page(s): 1692 - 1694
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    This paper investigates the dissipative performance of a class of power systems with disturbances, when viewed from a fixed set of inputs and outputs. A passivity result is obtained for a special regulation output, and the Hamilton-Jacobi inequality is solved by means of variable-gradient approach so that the power system has finite L2-gain less than or equal to a prescribed value. View full abstract»

    Open Access
  • Observation of the metallic vapor from a plasma focus

    Page(s): 1695 - 1697
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    Although many scientists suggested that the ionized metallic vapor produced in plasma focus plays a significant role in the X-ray emission, they did not give a visual image of the metallic vapor. In this paper the evolution of plasma sheath above the anode was recorded with a laser differential interferometer and the metallic vapor produced on the target surface by bombardment of an intense electron beam was observed for the first time. The results can help understanding of the physical process of the X-ray emission from plasma focus. View full abstract»

    Open Access
  • Calculation of three dimensional electrostatic field in potential transformers

    Page(s): 1698 - 1700
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (723 KB)  

    The electrostatic field in 500 kV potential transformers has been simulated with three dimensianal (3-D) models. The main purpose of calculating the electrostatic field is to investigate the effect of electrostatic shiel ding in transformers and to see if the shielding can be removed. The conclusions are that the shielding on the middle of the winding is not clearly profitable to the maximum electrostatic field strength and can be removed. To calculate the field a 3-D finite element software has been developed which is based on a powerful tetrahedral mesh generator. Meanwhile, axisymmetric models are also employed to simulate the effect of the shielding. View full abstract»

    Open Access

Aims & Scope

Tsinghua Science and Technology (Tsinghua Sci Technol) aims to highlight scientific achievements in computer science, electronic engineering, and other IT fields. Contributions all over the world are welcome.

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