Table of Content

10 September 2003, Volume 21 Issue 3

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Articles

The Application of Improved Genetic Algorithm Based on Real Coding in Flatness Error Evaluation

WEN Kiu-lan, SONG Ai-guo

2003, 21(3):  221-224. 

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According to the characteristics of flatness error evaluation, a novel improved genetic algorithms based on real coding is proposed. A generation-alternation modei based on the minimal generation gap (MGP) and blend crossover operators (BLX-α) are employed. Compared with conventional methods, it has the advantages of simple algorithms, strong robustness and high op timization efficiency. In the meantime, the objective function calculation approach in flatness error evaluation by genetic algorithms is presented. Finally, the experiment results evaluated by differ-ent methods show that the improved genetic algorithm converges to the global optimum more rapidly than conventional methods.

Capacity Analysis and Enhancement of Capacity in WPAN System

YE Zhi-hui, SHEN Lian-feng, XU Ping-ping, CHAN Kam-tai

2003, 21(3):  225-230. 

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An adaptive control method of packet length is presented in this paper in order to im-prove the capacity of WPAN. This technique is based on the analysis of system capacity in WPAN standard, which uses FHSS schemes such as Bluetooth. A comparison of system capacities be-tween adaptive packet length and fixed packet length has been made for the case of ACL link and SCO link of Bluetooth. Simulation results show that the adaptive packet length algorithm can im-prove the capacitv of WPAN effectively.

The Relationship Between the Wave-Packet Duration of Ultrasonic Guided Waves and the Inner-Radius-Thickness Ratio of Pipes

TA De-an, LIU Zhen-qing

2003, 21(3):  231-235. 

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The relationship between the wave-packet duration of ultrasonic longitudinal guided waves with lower order and the inner-radius-thickness ratio(IRTR) of free pipes was analyzed at various propagation distances, various frequency-thickness products and various cycle numbers of the input pulse signal. The results show that when IRTR is smaller, the change of IRTR has a greater influence on the wave-packet duration of guided waves; but with the increase of IRTR, the influence of IRTR on guided waves will be reduced. The influence of IRTR on guided waves will also be reduced with the increase of the order of guided waves. On the other hand, for pipes of different IRTR, one should select different modes, and choose different cycle numbers and different frequency-thickness products.

An Analysis of Dispersion Characteristics in 2-D Dielectric PBG Structure by Using FDTD Method

BAO Xiu-long, ZHANG Wen-xun, ZHENG Long-gen, LI Le-wei

2003, 21(3):  236-240. 

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In this paper, the dispersion characteristics in 2-D dielectric PBG structure are analyzed by using FDTD method. The computed κ-ω curves show that under the same ratio of dielectric occupancy in the period cell and in the case of a single dielectric cylinder only, the dispersion curves are not sensitive to the geometry of this cylinder. However, in the case of multiple separat-ed cylinders, the central frequency of TM band-gap rises with the increased number of cylinders, and its relative bandwidth is almost constant.

The Supermemory Gradient Method with Inexact Line Searches

SHI Zhen-Jun

2003, 21(3):  241-243. 

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The paper presents a new supermemory gradient algorithm for unconstrained minimiza-tion problems. The algorithm makes full use of the previous iterative information to generate the search direction at each iteration and uses Armijo's line search to find the stepsize. We can prove its global convergence under mild conditions.

The Physical Simulation of Inclusions-Induce Formation Nucleation of Intragranular Ferrite

YU Sheng-fu, YU Yang-chun, ZHANG Yuan-qin, XIE Ming-li, LI Zhi-yuan

2003, 21(3):  244-248. 

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The roles of inclusions MnS, Al₂O₃ and Al₂O₃·MnS in the formation nucleation of intragranular ferrite were studied by means of the plysical simulation method. The microstructures of the micro-zone adjacent to the inclusions were observed with metallurgical microscope and the chemical compositions of the micro-zone adjacent to the inclusions were analyzed with an electron probe mircoanalyzer. The results show that inclusions MnS, Al₂O₃ and Al₂O₃·MnS can not change the chemical composition of the metai micro-zone adjacent to the inclusions. The MnS and Al₂O₃·MnS have an ability to induce the nucleation of intragranular ferrite, but the Al₂O₃ has no potential for nucleating intragranular ferrite during the thermal cycle. The MnS in compound inclusions Al₂O₃·MnS plays an important role in the formation nucleation of intragranular ferrite.

The Analogical Method for the Design of Adiabatic Capillary Tubes

ZHANG Chun-lu, DING Guo-liang

2003, 21(3):  249-252. 

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The capillary tube expansion device is widely used in the refrigerating and air-condition-ing equipment. The analogical method is one of the most popular design methods for capillary tubes. However, it is an empirical method. Based on the differential governing equations of an adi-abatic capillary tube, the theoretical formulation of the analogical design method has been devel-oped here. It is simple but helpful to engineers in improving designing efficiency.

Heat Conduction in Fractal Porous Media

ZHANG Dong-hui, JIN Feng, SHI Ming-heng, YANG Hao

2003, 21(3):  253-257. 

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In this paper, heat conduction in fractal porous media is analysed and sirnulated by means of the finite volume method. Fractal porous media can be simplified as a kind of binary mix-ture with different thermal conductivities. The calculated results show that heat transfer in fractal porous media is very complicated. Thermal coupling effects between matrix and pore structure are studied. When heat transfer in pore structure is neglected, the effective thermal conductivity in random Sierpinski carpet is shown as the index of matrix, which is in agreetment with Archie's law. All these results are helpful to the understanding heat of transfer mechanism in porous media.

Research on the Curve-Fitting Method Based on Curvature Data

WU Jia-qi, YANG Dong-ying, SHEN Lin-yong, CHEN Jian-jun

2003, 21(3):  258-262. 

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This paper presents the curve-fitting methods based on the curvature data, to meet the requirement of the modei reconstruction of the endoscope. After the transformation from linear strain to curvature and the curvature linear interpolation, three methods based on curvature inte-gral are developed for curve fitting by means of the differential geometrv method. A test is carried out to validate the curve fitting methods and analyse the causes of errors. Finally some measures to reduce the fitting errors are suggested.

Synthetic Coordination Methods for Fuzzy Multi-objective Optimization of the Reliability of Mechanical Systems

WU Wei-dong, HUANG Hong-zhong, GU Ying-kui, LI Yong-hua

2003, 21(3):  263-267. 

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In view of the fact that the problem of the multi-objective optimization of the reliability of mechanical systems with conflicting attributes is incapble of being solved by means of conven-tional mathematical programming techniques, a synthetic coordination method based on fuzzy optimization decision-making is presented to solve this problem. Using the property of membership function in fuzzy sets theory, each sub-objective function is transformed into coordination satisfac-tory function with weighted exponent, the weighted exponent shows the relative importance of each sub-objective function, and the coordination satisfactory function are synthesized into a sin-gle-objective optimization modei by correcting weighted function with dynamic real-time change. The satisfactory solution of the multi-objective optimization modei can be worked out by conven-tional multi-objective mathematical programming techniques. Finally, an example is given to illus-trative the method.

An Experiment on Cetyltrimethyl Ammonium Chloride Drag Reducing Fluid by Using PDA

XU Peng, WANG De-zhong, HU Li-guang, ZHOU Hao-jun

2003, 21(3):  268-271. 

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Phase Doppler anemometry (PDA) was applied to the measuring of the turbulent char-acteristics of drag-reducing fluid, and the mean velocity profiles were gained. The relation be-tween the profile shape and the drag reduction ratio was discussed. The effects of the velocity fluctuations in normai direction on the drag reduction were investigated. The Reynolds stresses of drag-reducing fluid were contrasted with those of Newtonian fluid, which showed that the Reynolds shear stresses of drag-reducing fluid decreased drastically.

The Optimization of Heat Exchanger Network Systems

MENG Fan-zhen, XIE Fei, WANG Ning-hui, ZHANG Qing-cui

2003, 21(3):  272-275. 

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On the basis of genetic algorithmic techniques, the systematic structure and operating parameter are optimized simultaneously for the heat exchanger network systems. The problem of optimal combination of this network is thus solved.

The Relation between the Optimal Refrigeration Rate and the Performance Coefficient of a CIass of Irreversible Carnot Refrigerators

HU Hua

2003, 21(3):  276-278. 

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By applying the heat transfer law Q∝△Tⁿ, a class of irreversible Carnot refrigerators affected by heat resistance, heat leak and internai irreversibilities is investigated, and the relationship between the optimal refrigeration rate and the performance coefficient of the refrigerators is derived. Moreover, the significance of using this relationship to study the optimal performance and performance bounds of a real refrigerator is also expounded.

Sensitivity Analysis for CO Coupling Reaction by Use of Adjoint Operators

MENG Fan-dong, YAO Miao-xin, XU Gen-hui, GUO Rong-qun

2003, 21(3):  279-283. 

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By use of the nonlinear functional analysis approach-the method of adjoint operators, the sensitivity analysis for CO coupling is comprehensively carried out in order to reveal important parameters in the research of reaction mechanism and in the design and operation of a tubular reac tor for synthesis of diethyl oxalate on the basis of the simplified mathematical reactor modei. The influence of operating and kinetic parameter variations from their nominal values on conversion and reactor bed temperature profile is cliscussed. The results provide an effective approach to the opti mal control for existed industrial plants and the identification of reaction mechanism.

Quick Clustering of Large Log Data in Library

SONG Ai-bo, ZHUANG Xiao-qing, HE Jie-yue, YE Ning, DONG Yi-sheng

2003, 21(3):  284-288. 

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In this paper, a simple and efficient method is presented for quick clustering and trend analyzing of library large log data. First, log data is clustered into a number of subclasses based on the underlying regularity of reader's borrowing and returning books. Then a fuzzy clustering algorithm is given for clustering the subclasses. The time complexity is linear, so our method can scale to large dataset. Finally, regression analysis is performed on the each cluster in order to dis cover the trend of borrowing and returning books. The experiment shows that this approach is successful.

An Approach to Applying Genetic Algorithm to Predicate Refinement

CAO Xiao-xia, MIAO Huai-kou, GAO Xiao-lei

2003, 21(3):  289-295. 

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Selecting rules is the most difficult and creative work in predicate refinement. This paper gives a method of refinement from specification to program code by combining Manna's program synthesis method with Caroll Morgan's refinement calculus. The paper also presents a method for applying genetic algorithm to predicate refinement.

The PC-Based Package Development for the Multiple Variables Predictive Control System

ZOU Tao, YAN Zhi-heng, LI Shao-yuan

2003, 21(3):  296-301. 

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The PC-based package development of the multiple variables predictive control scheme with constraints is discussed in this paper. The system's modul鐂 for modei Identification and predictive control, arithmetic of multiple variables predictive control and constraints processing are realized in the package. The system's properties can be simulated and further analyzed by using this PC-based package. Moreover, the real-time control of the object of typical process control can also be realized by using this package.

Research on the Algorithm for Creating Progressive Meshes with Multi-attributes

NIE Jun-hong, ZHANG Li-yan, TANG Jie, ZHOU Lai-shui, ZHOU Ru-rong

2003, 21(3):  302-307. 

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Progressive meshes are used for LoD (Ievel of detail) modeling, progressive transmis-sion, etc. A new algorithm to create progressive meshes with multi-attributes is suggested in this paper. By extending the vertex vector from 3-dimension to n-dimension, the algorithm can create progressive meshes with additional attributes such as color, texture etc. The progressive mesh is represented by a simplified mesh and a splitting sequence. While creating the splitting sequence, the algorithm confines the simplified mesh vertices to the subset of the original mesh vertices, by means of which the information of splitting sequence is reduced and the algorithm efficiency im-proved. Several examples in the paper illustrate the effect of the algorithm.

Numerical Simulation of Airflows in Unfurnished Room

XU Yu-dang, ZHANG Li

2003, 21(3):  308-312. 

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The numerical modeling of room airflows is considered in this paper. It also illustrates the usefulness of computer fluid dynamics (CFD) as a tool for IAQ researches. The time-averaged equations for the conservation of mass, momentum, and energy are solved. A low Reynolds num-ber κ-ε modei is used to simulate the turbulent transport. The code was validated by comparing it with benchmark data for buoyancy-driven cavity flows. The airflows in unfurnished room were then simulated. The use of computational fluid dynamics enables the velocity and temperature fields to be investigated in significantly greater detail than is possible with either analytical or ex-perimental models.

A Further Discussion on the Fatal Problem of H-L Theory Used in the Non-Linearity Field

YU Tian-xiang, CHENG Gang-hu, ZHANG Zu-ming, ZHANG Xuan-sheng, XU Hong-wei

2003, 21(3):  313-316. 

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The theories of second-moment and H -L which have been used widely in the engineer-ing structure are analyzed contrastively. The fatal problem of the H-L theory in the non-linear field is found. The fatal fault is that the theory of H-L is unfit for the reliability design of high non-linear mechanical elements.

An Analysis of the Stepped Shaft's Heat Transfer

MIAO En-ming, FEI Ye-tai

2003, 21(3):  317-321. 

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This paper systematically analyses the temperature distribution of the transmission shaft in machine design and puts forward the theoretical computation modei of temperature distribution in bearings of different diameters and types. The paper also discusses the proper arrange-ment of the driving parts. The theoretical mathematic mode is established and solved for direct ap-plication in machine design.

Application of the Elastic Guide in Micro Displacement Worktable with Six Degrees of Freedom

HUANG Qi-sheng, YU Xiao-fen, WANG Yong-hong

2003, 21(3):  322-323. 

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This paper presents the structure, the principle and the designing and calculation method of the micro displacement worktable which has six degrees of freedom. The application of elastic guide and flexible hinge in the micro displacement worktable is described. This type of micro displacement worktable is not only simple in structure but also easy in manufacture. Syn-chronously, the jam caused by the different moving directions of the worktable is avoidable. Therefore, high displacement accuracy can be obtained.

A Study on the Comprehensive Evaluation Method for the Thermodynamic System

LIU Wei-hua, ANG Hai-song

2003, 21(3):  324-327. 

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A delaminating evaluation method is suggested in this paper. The demands of social de-velopment upon every aspect of thermodynamic system is considered. As the first layer, and the specific evaluation indexes as the second one. By combining these two with the comprehensive fuzzy evaluation method, the subjection degree of fuzzy calculation shows the evaluation results. This paper proves the feasibility and rationality of the method through practical examples in prac-tice as well.

A Research on the Optimization Problem of Street Lighting

GAO Shang

2003, 21(3):  328-330. 

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The optimization problem of street lighting is studied. The characteristic of lighting in-tensity is analyzed. The area of space determined by a nonlinear equation can be obtained by the Monte Carlo method, The optimization problem of lighting with a single lamp and two lamps is solved by the golden section method and coordinate alternation method. The methods can be ap-piied to the optimization problem of lighting with many lamps.