Tsinghua Science and Technology

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Volume 10 No. 3
20 March 2005

Improvement and Parallelism of k-Means Clustering Algorithm

Jinlan Tian, Lin Zhu, Suqin Zhang, Lu Liu

2005, 10(3): 277-281. doi:10.1016/S1007-0214(05)70069-9

Abstract ( 191 ) ( 343 )

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Abstract The k-means clustering algorithm is one of the most commonly used algorithms for clustering analysis. The traditional k-means algorithm is, however, inefficient while working on large numbers of data sets and improving the algorithm efficiency remains a problem. This paper focuses on the efficiency issues of cluster algorithms. A refined initial cluster centers method is designed to reduce the number of iterative procedures in the algorithm. A parallel k-means algorithm is also studied ...

Web Services-Based Test Report Generation

Ling Luo, Xiaoying Bai

2005, 10(3): 282-287. doi:10.1016/S1007-0214(05)70070-5

Abstract ( 199 ) ( 328 )

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Tests involving a large number of test cases and test scenarios are always time- and effort-intensive, and use ad hoc approaches. Test management is needed to control the complexity and the quality of the testing of large software systems. The reporting mechanism is critical for monitoring the testing progress, analyzing test results, and evaluating the test effectiveness for a disciplined testing process throughout the testing lifecycle. This paper presents an XML-based report generation method...

Pessimistic Predicate/Transform Model for Long Running Business Processes

Jinling Wang, Beihong Jin, Jing Li

2005, 10(3): 288-297. doi:10.1016/S1007-0214(05)70071-7

Abstract ( 179 ) ( 347 )

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Many business processes in enterprise applications are both long running and transactional in nature. However, no current transaction model can provide full transaction support for such long running business processes. This paper proposes a new transaction model, the pessimistic predicate/transform (PP/T) model, which can provide full transaction support for long running business processes. A framework was proposed on the enterprise JavaBeans platform to implement the PP/T model. The framework e...

Finds in Testing Experiments for Model Evaluation

Ji Wu, Xiaoxia Jia, Chang Liu, Haiyan Yang, Chao Liu

2005, 10(3): 298-303. doi:10.1016/S1007-0214(05)70072-9

Abstract ( 145 ) ( 334 )

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To evaluate the fault location and the failure prediction models, simulation-based and code-based experiments were conducted to collect the required failure data. The PIE model was applied to simulate failures in the simulation-based experiment. Based on syntax and semantic level fault injections, a hybrid fault injection model is presented. To analyze the injected faults, the difficulty to inject (DTI) and difficulty to detect (DTD) are introduced and are measured from the programs used in the ...

Analysis of Factors Affecting Execution Performance of OpenMP Programs

Jianjiang Li, Jiwu Shu, Yongjian Chen, Dingxing Wang, Weiming Zheng

2005, 10(3): 304-308. doi:10.1016/S1007-0214(05)70073-0

Abstract ( 159 ) ( 320 )

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OpenMP is able to develop multithreaded programs with lower cost as a promising way to quickly parallelize a great number of serial programs. However, there are many difficulties when developing OpenMP multithreaded programs. Most importantly, the performance of OpenMP programs cannot be guaranteed, which has greatly affected the application of OpenMP. This paper examines several factors that affect the execution performance of OpenMP programs, including loop transformation, scheduling strategy,...

Resources Allocation Schemas for Web Information Monitoring

Kang Chen, Meiming Shen, Weimin Zheng

2005, 10(3): 309-315. doi:10.1016/S1007-0214(05)70074-2

Abstract ( 194 ) ( 320 )

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The web is an extremely dynamic world where information is updated even every second. A web information monitoring system fetches information from the web continuously and finds changes by comparing two versions of the same page. The updating of a specific web page is modeled as a Poisson process with parameter to indicate the change frequency. As the amount of computing resources is limited, it is necessary to find some policies for reducing the overall change-detection time. Different allocati...

Approximation of NURBS Curves and Surfaces Using Adaptive Equidistant Parameterizations

Wulamu Aziguli, Marc Goetting, Dirk Zeckzer

2005, 10(3): 316-322. doi:10.1016/S1007-0214(05)70075-4

Abstract ( 206 ) ( 336 )

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Non-uniform rational B-spline (NURBS) curves and surfaces are very important tools for modelling curves and surfaces. Several important details, such as the choice of the sample points, of the parameterization, and of the termination condition, are however not well described. These details have a great influence on the performance of the approximation algorithm, both in terms of quality as well as time and space usage. This paper described how to sample points, examining two standard parameteriz...

A Method to Identify Flight Obstacles on Digital Surface Model

Min Zhao, Xinggang Lin, Shouyu Sun, Youzhi Wang

2005, 10(3): 323-327. doi:10.1016/S1007-0214(05)70076-6

Abstract ( 188 ) ( 354 )

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In modern low-altitude terrain-following guidance, a constructing method of the digital surface model (DSM) is presented in the paper to reduce the threat to flying vehicles of tall surface features for safe flight. The relationship between an isolated obstacle size and the intervals of vertical- and cross-section in the DSM model is established. The definition and classification of isolated obstacles are proposed, and a method for determining such isolated obstacles in the DSM model is given. T...

Fair Micropayment System Based on Hash Chains

Zongkai Yang, Weimin Lang, Yunmeng Tan

2005, 10(3): 328-333. doi:10.1016/S1007-0214(05)70077-8

Abstract ( 223 ) ( 331 )

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Micropayment schemes usually do not provide fairness, which means that either the customer or the merchant, or both, can cheat each other and gain a financial advantage by misusing the protocols. This paper proposes an efficient hash chain-based micropayment scheme, which is an offline, prepaid scheme that supports simpler divisibility of digital coins. In the execution of payment protocol, the customer's disbursement and the merchant's submittal are performed step by step, whoever cannot gain a...

Housing Prices and General Economic Conditions: An Analysis of Chinese New Dwelling Market

Liu Hongyu, Shen Yue

2005, 10(3): 334-343. doi:10.1016/S1007-0214(05)70078-X

Abstract ( 224 ) ( 350 )

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This paper presents an investigation of the interaction between housing prices and general economic conditions in China for the period of 1986-2002. The empirical results indicate that housing prices in China are predictable by market fundamentals, which could explain most of the variations in housing prices. The results of Granger causality tests confirm that unemployment rate, total population, changes in construction costs, changes in the consumer price index (CPI) are all Granger causalities...

Influence of Spatial Features on Land and Housing Prices

Xiaolu Gao, Yasushi Asami

2005, 10(3): 344-353. doi:10.1016/S1007-0214(05)70079-1

Abstract ( 143 ) ( 319 )

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The analysis of hidden spatial features is crucial for the improvement of hedonic regression models for analyzing the structure of land and housing prices. If critical variables representing the influence of spatial features are omitted in the models, the residuals and the coefficients estimated usually exhibit some kind of spatial pattern. Hence, exploration of the relationship between the spatial patterns and the spatial features essentially leads to the discovery of omitted variables. The ana...

Software Practicalization for Analysis of Wind-Induced Vibrations of Large Span Roof Structures

Enuo Zhang, Weiguo Yang, Wei Zhen, Xiangqian Na

2005, 10(3): 354-358. doi:10.1016/S1007-0214(05)70080-8

Abstract ( 166 ) ( 349 )

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Wind loads are key considerations in the structural design of large-span structures since wind loads can be more important than earthquake loads, especially for large flexible structures. The analysis of wind loads on large span roof structures (LSRS) requires large amounts of calculations. Due to the combined effects of horizontal and vertical winds, the wind-induced vibrations of LSRS are analyzed in this paper with the frequency domain method as the first application of method for the analysi...

Construction Process Control of Large Extra Caissons

Shaowei Hu, Hongxia Wang, Jiansheng Fan

2005, 10(3): 359-363. doi:10.1016/S1007-0214(05)70081-X

Abstract ( 247 ) ( 369 )

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The complexity of geotechnical engineering and variability in construction circumstances of large extra caissons make the problem of maintaining appropriate sink attitude quite difficult, especially in keeping sink uniformity and achieving the expected final sink depth. A new construction control method is presented using H∞ theory, considering uncertainties in the mechanics model and external noise in the construction site parameters. The design method of an H∞ controller has consequently been ...

Implicit Parallel FEM Analysis of Shallow Water Equations

Chunbo Jiang, Kai Li, Ning Liu, Qinghai Zhang

2005, 10(3): 364-371. doi:10.1016/S1007-0214(05)70082-1

Abstract ( 227 ) ( 346 )

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The velocity field in the Wu River at Chongqing was simulated using the shallow water equation implemented on clustered workstations. The parallel computing technique was used to increase the computing power. The shallow water equation was discretized to a linear system of equations with a direct parallel generalized minimum residual algorithm (GMRES) used to solve the linear system. Unlike other parallel GMRES methods, the direct GMRES method does not alter the sequential algorithm, but bases t...

Integral Theorems Based on a New Gradient Operator Derived from Biomembranes (Part I): Fundamentals

Yajun Yin

2005, 10(3): 372-375. doi:10.1016/S1007-0214(05)70083-3

Abstract ( 186 ) ( 348 )

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A new gradient operator was derived in recent studies of topological structures and shape transitions in biomembranes. Because this operator has widespread potential uses in mechanics, physics, and biology, the operator's general mathematical characteristics should be investigated. This paper explores the integral characteristics of the operator. The second divergence and the differential properties of the operator are used to demonstrate new integral transformations for vector and scalar fields...

Integral Theorems Based on a New Gradient Operator Derived from Biomembranes (Part II): Applications

Yajun Yin

2005, 10(3): 376-380. doi:10.1016/S1007-0214(05)70084-5

Abstract ( 195 ) ( 326 )

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Based on the second gradient operator and corresponding integral theorems such as the second divergence theorem, the second gradient theorem, the second curl theorem, and the second circulation theorem on curved surfaces, a few new scalar differential operators are defined and a series of integral transformations are derived. Interesting transformations between the average curvature and the Gauss curvature are presented. Various conserved integrals related to the Gauss curvature and the second f...

Novel Micro Free-Piston Swing Engine and Its Feasibility Validation

Shimin Zhang, Jinsong Wang, Zhiping Guo

2005, 10(3): 381-386. doi:10.1016/S1007-0214(05)70085-7

Abstract ( 213 ) ( 339 )

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To develop high energy-density micro power generation systems, a novel two-stroke cycle micro free-piston swing engine (MFPSE), inspired by the concept of the micro internal combustion swing engine, is proposed to supply mechanical power for a micro power generation system. The working principle, gas exchange and ignition timing control cycles, and structure and operation advantages of the MFPSE are discussed in detail. A prototype where the timing control and geometric parameters are designed w...

Airbag Mapped Mesh Auto-Flattening Method

Jinhuan Zhang, Chunsheng Ma, Yuanli Bai, Shilin Huang

2005, 10(3): 387-390. doi:10.1016/S1007-0214(05)70086-9

Abstract ( 185 ) ( 330 )

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Current software cannot easily model an airbag to be flattened without wrinkles. This paper improves the modeling efficiency using the initial metric method to design a mapped mesh auto-flattening algorithm. The element geometric transformation matrix was obtained using the theory of computer graphics. The algorithm proved to be practical for modeling a passenger-side airbag model. The efficiency and precision of modeling airbags are greatly improved by this method.

Thermal Hydraulic Stability in a Coaxial Thermosyphon

Jianhui Yang, Wenqiang Lu, Qing Li, Qiang Li, Yuan Zhou

2005, 10(3): 391-397. doi:10.1016/S1007-0214(05)70087-0

Abstract ( 168 ) ( 334 )

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The heat transfer and thermal hydraulic stability in a two-phase thermosyphon with coaxial riser and down-comer has been experimentally investigated and theoretically analyzed to facilitate its application in cold neutron source. The flow in a coaxial thermosyphon was studied experimentally for a variety of heating rates, transfer tube lengths, charge capacities, and area ratios. A numerical analysis of the hydraulic balance between the driving pressure head and the resistance loss has also been...

Numerical Study of Void Fraction Distribution Propagation in Gas-Liquid Two-Phase Flow

Jianhui Yang, Qing Li, Wenqiang Lu

2005, 10(3): 398-403. doi:10.1016/S1007-0214(05)70088-2

Abstract ( 143 ) ( 323 )

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A dynamic propagation model was developed for waves in two-phase flows by assuming that continuity waves and dynamic waves interact nonlinearly for certain flow conditions. The drift-flux model is solved with the one-dimensional continuity equation for gas-liquid two-phase flows as an initial-boundary value problem solved using the characteristic-curve method. The numerical results give the void fraction distribution propagation in a gas-liquid two-phase flow which shows how the flow pattern tra...

Rotationally Symmetric Translating Solutions to Curvature Flows in Image Processing

Qinghua Liu, Xiuqing Chen

2005, 10(3): 404-407. doi:10.1016/S1007-0214(05)70089-4

Abstract ( 110 ) ( 328 )

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This paper proves the existence of rotationally symmetric solutions to a curvature flow in image processing. The flow includes the level sets flow and the mean curvature flow projected onto the normal. Sharp estimates are obtained for these solutions..