Please wait a minute...
[an error occurred while processing this directive]
[an error occurred while processing this directive]
   清华大学学报自然科学版(英文版)
  2006年, 第11卷, 第6期 刊出日期:2006-06-20 上一期    下一期
全选: 合并摘要 显示图片
论文
Efficient Procedure for Seismic Analysis of Soil-Structure Interaction System 收藏
Jingbo Liu, Yin Gu, Yan Wang, Bin Li
清华大学学报自然科学版(英文版). 2006, (6): 625-631.   DOI: 10.1016/S1007-0214(06)70244-9
摘要 ( 179 )  
A simplified and efficient procedure, based on the viscous-spring artificial boundary and the modal superposition method, is developed to analyze the dynamic soil-structure interaction system in the time domain. The viscous-spring artificial boundary introduced in this procedure transforms the infinite soil-structure interaction system to an approximately finite system. A seismic wave input method is used to transform the wave scattering problem into the wave source problem. The modal superposition method is then applied to this approximate finite system. The results show that this method with only a few modes can significantly reduce the computational time with almost the same precision as the traditional direct integration method. Comparison of results from different loading times demonstrates that the advantages of this method are evident in computing with long loading time.
参考文献 | 相关文章 | 计量指标
Applied Study of Price Discrimination Implemented on a Two-Path Route Expressway 收藏
Jing Shi
清华大学学报自然科学版(英文版). 2006, (6): 632-639.   DOI: 10.1016/S1007-0214(06)70245-0
摘要 ( 142 )  
This study aims at implementing price discrimination to get maximum revenue on a two-path route expressway, focusing on the problems which occur in traffic forecasting when applying a “profit-maximizing” toll designed to maximize revenue for a certain toll road in Japan. A break-even discussion is inevitable in the process of planning a certain toll road. According to the theory of transportation economics, market segmentation price discrimination is supposed to be efficient in the transportation market to increase the revenue of fixed facilities. In the model, a bypass and an adjacent expressway form a two-path route section. Two different toll levels are implemented for the bypass: one is for through traffic, and the other is for inside-inside and inside-outside traffics. This two-path route plus two-toll-level system thus causes difficulty in traffic assignment that is based on the minimum route searching method. In the study, a rational approach of adjusting the through traffic is implemented to predict the traffic flow as well as revenue on two parallel routes with different toll levels. The approximate calculation method that fixes the split rate of the passing through traffic flow is applied to solve the two-path route plus two-toll-level problem since passing through traffic is price elastic. Market segmentation pricing, which gives two toll levels in a toll road, is proved to be practical for increasing revenue. The results are also verified to be rational by using the survey data of Meishin Expressway.
参考文献 | 相关文章 | 计量指标
Passive Control Reinforced Concrete Frame Mechanism with High Strength Reinforcements and Its Potential Benefits Against Earthquakes 收藏
Asad Ullah Qazi, Lieping Ye, Xinzheng Lu
清华大学学报自然科学版(英文版). 2006, (6): 640-647.   DOI: 10.1016/S1007-0214(06)70246-2
摘要 ( 164 )  
Severe earthquakes continue to cause major catastrophes. Many devices in active, hybrid, and semi-active structural control systems which are used as controllable force devices are costly to build and maintain. The passive control reinforced concrete frame (PCRCF) reinforced with high strength steel only in the columns presented here provides structural systems more resistance to lateral earthquake loadings at comparatively lower cost. The effectiveness is demonstrated by a nonlinear static analysis using fiber model for a single story single bay frame. The study shows that the use of high performance steel in columns prevents formation of plastic hinges at the critical column base sections and failures are always initiated by reinforcement yielding at the beam ends. Furthermore, after experiencing severe lateral drift, the passive control design has small residual displacements compared to ordinary reinforced concrete frames. PCRCF rehabilitation and strengthening can be achieved more easily as compared with ordinary reinforced concrete frame.
参考文献 | 相关文章 | 计量指标
Inelastic Deformation Analysis of Aluminum Bending Members 收藏
Ming Cheng, Yongjiu Shi, Yuanqing Wang
清华大学学报自然科学版(英文版). 2006, (6): 648-656.   DOI: 10.1016/S1007-0214(06)70247-4
摘要 ( 184 )  
Aluminum alloys are typical nonlinear materials, and consequently bending members made of this material exhibit a nonlinear behavior. Most design codes do not pay much attention to such deformations and adopt a simple linear analysis for the calculation of deflections. This paper presents an investigation of the nonlinear deformation of aluminum bending members using the finite-element analysis (FEA). The plastic adaptation coefficient, which can be used to limit the residual deflection, is introduced, and the influence of residual deflection is investigated. A method for evaluating the plastic adoption coefficient is proposed. This paper also shows the load-deflection curve of aluminum bending members and the influence of several parameters. A semi-empirical formula is derived, and some numerical examples are given by FEA. The coefficients of the semi-empirical formula are modified by the FEA results using the nonlinear fitting method. Based on these results, two improved design methods for strength and deformation of aluminum bending members are proposed. Through the comparison with test data, these methods are proved to be suitable for structural design.
参考文献 | 相关文章 | 计量指标
Strength of Concrete Filled Steel Tubular Columns 收藏
Muhammad Naseem Baig, Jiansheng Fan, Jianguo Nie
清华大学学报自然科学版(英文版). 2006, (6): 657-666.   DOI: 10.1016/S1007-0214(06)70248-6
摘要 ( 238 )  
Composite columns of steel and concrete have been used and studied world wide, but filled tubular columns need more attention. This paper presents an experimental study on the behavior of short concrete filled steel tubular columns (CFT) axially loaded in compression to failure. A total of 28 specimens (16 were filled with concrete and 12 were kept hollow) with different cross-sections were tested to investigate the load capacity. The length-to-diameter ratios of these columns were between 4 and 9. Parameters for the tests were tube shape and diameter-to-thickness ratio. Some of the concrete filled columns had internal bracing of #3 deformed bars. The test results are compared with the theoretical results and previous studies. The results show that the confinement effect on concrete does play a role in increasing the compressive strengths to almost 60% in some cases. Based on the test results, an equation to estimate the ultimate axial compressive loading capacities is also proposed for square CFT columns.
参考文献 | 相关文章 | 计量指标
Customer Satisfaction Theory Applied in the Housing Industry: An Empirical Study of Low-Priced Housing in Beijing 收藏
Song Yang, Yan Zhu
清华大学学报自然科学版(英文版). 2006, (6): 667-674.   DOI: 10.1016/S1007-0214(06)70249-8
摘要 ( 270 )  
A household satisfaction index (HSI) model based on the American customer satisfaction index (ACSI) model was fit to the housing industry in China and used with the software LISREL to measure the HSI in Beijing. Specifically, the empirical study analyzes the HSI of low-priced housing in Beijing. The results show that the HSI model is valid and the customer satisfaction theory can effectively analyze the housing industry. The results can help illustrate the factors which most affect customer satisfaction, and can be used to not only enhance the quality of homes and promote the housing market, but also to improve the standard of living for lower income people and provide suggestions to policy makers.
参考文献 | 相关文章 | 计量指标
Buyer Search and the Role of Broker in an Emerging Housing Market: A Case Study of Guangzhou 收藏
Siqi Zheng, Hongyu Liu, Rebecca Lee
清华大学学报自然科学版(英文版). 2006, (6): 675-685.   DOI: 10.1016/S1007-0214(06)70250-4
摘要 ( 155 )  
This paper examines homebuyer's search process and the role of real estate broker in China's urban housing market, where inactive housing resale transactions and an immature brokerage industry are distinct characteristics. Guangzhou is used as a case study to model the intensity and duration of the search process. This study finds that buyers make trade-off between two search costs, activity cost and duration cost. The study also demonstrates that despite the industry's immature nature, buyers using brokers do increase search intensity and shorten search duration by reducing the activity cost. Empirical results show that there is no specific buyer group who can effectively lower their search cost by their own efforts, due to the poor information transparency in the current housing market. The broker-choice model shows that besides search cost, buyers' confidence in broker's service quality can also greatly influence their choice, so improvement in service quality and reputation has important implications for China's brokerage industry.
参考文献 | 相关文章 | 计量指标
Optimization of Multi-Criteria Experiments with Fuzzy Results 收藏
Fan Yang, Su Wu, Tilo Pfeifer, Klaus Hense
清华大学学报自然科学版(英文版). 2006, (6): 686-692.   DOI: 10.1016/S1007-0214(06)70251-6
摘要 ( 164 )  
The classical design of experiments (DoE) method can optimize systems with one technical response and multiple inputs. The objective of this study is to optimize multiple technical responses at the same time by integrating fuzzy logic transformation into a DoE system. The transformation from technical responses to the individual fuzzy responses and the overall fuzzy response are first defined, and the fuzzy response system is established. The method used to optimize the overall fuzzy response is introduced and discussed. The results show that the established fuzzy response system can optimize systems with multiple technical responses and multiple inputs.
参考文献 | 相关文章 | 计量指标
Improved Methods for Process Routing in Enterprise Production Processes in Terms of Sustainable Development II 收藏
Xianchun Tan, Fei Liu, Liu Dacheng, Zheng Li, Haiying Wang, Yihua Zhang
清华大学学报自然科学版(英文版). 2006, (6): 693-700.   DOI: 10.1016/S1007-0214(06)70252-8
摘要 ( 129 )  
The selection of process planning methods during production influences the enterprise's production process planning performance with determination of the process flow as the most important influencing factor. A new production process determining method that focuses on sustainable manufacturing was developed based on case-based reasoning, expert systems, and feature technology for designing the process flow of a new component. This study matches a new component with preview case process information, modifies the case process information if necessary, and selects the process flow for the new component based on a sustainable development assessment according to the similarities between the case and the sustainable development characteristics. The feasibility and practicability of the method is verified by a case study of a machining process flow design for a new component.
参考文献 | 相关文章 | 计量指标
A General Mechanistic Model of Solid Oxide Fuel Cells 收藏
Yixiang Shi, Ningsheng Cai
清华大学学报自然科学版(英文版). 2006, (6): 701-711.   DOI: 10.1016/S1007-0214(06)70253-X
摘要 ( 174 )  
A comprehensive model considering all forms of polarization was developed. The model considers the intricate interdependency among the electrode microstructure, the transport phenomena, and the electrochemical processes. The active three-phase boundary surface was expressed as a function of electrode microstructure parameters (porosity, coordination number, contact angle, etc.). The exchange current densities used in the simulation were obtained by fitting a general formulation to the polarization curves proposed as a function of cell temperature and oxygen partial pressure. A validation study shows good agreement with published experimental data. Distributions of overpotentials, gas component partial pressures, and electronic/ionic current densities have been calculated. The effects of a porous electrode structure and of various operation conditions on cell performance were also predicted. The mechanistic model proposed can be used to interpret experimental observations and optimize cell performance by incorporating reliable experimental data.
参考文献 | 相关文章 | 计量指标
Relationship Between Measured Friction Coefficients and Two Tread Groove Design Parameters for Footwear Pads 收藏
Kai Way Li, Chin Jung Chen, Ching-Hua Lin, Yao Wen Hsu
清华大学学报自然科学版(英文版). 2006, (6): 712-719.   DOI: 10.1016/S1007-0214(06)70254-1
摘要 ( 299 )  
The shoe sole geometrical design parameters are believed to be important factors affecting the coefficient of friction (COF) between the shoe/floor interface. This study is concerned with the relationship between the measured COF and the tread groove orientation and width on the footwear pad. Friction measurements using the Brungraber Mark II slipmeter were conducted. Six tread groove width/orientations designs on the footwear pads under 27 footwear material/floor/contamination conditions were tested. The results show that tread orientation and width affect the measured COF significantly. Wider grooved footwear pads result in higher COF values and footwear pads with tread grooves perpendicular to the friction measurement direction have higher COF values. A regression model using measured COF as the dependent variable and tread groove width, groove orientation, footwear material, floor, and contamination conditions as independent variables was established. The models are significant at p<0.0001 with R2 of 0.97, which may be used in predicting the COF at the shoe-floor interface.
参考文献 | 相关文章 | 计量指标
Automatic Defect Detection in X-Ray Images Using Image Data Fusion 收藏
Yuan Tian, Dong Du, Guorui Cai, Wang Li, Hua Zhang
清华大学学报自然科学版(英文版). 2006, (6): 720-724.   DOI: 10.1016/S1007-0214(06)70255-3
摘要 ( 278 )  
Automatic defect detection in X-ray images is currently a focus of much research at home and abroad. The technology requires computerized image processing, image analysis, and pattern recognition. This paper describes an image processing method for automatic defect detection using image data fusion which synthesizes several methods including edge extraction, wave profile analyses, segmentation with dynamic threshold, and weld district extraction. Test results show that defects that induce an abrupt change over a predefined extent of the image intensity can be segmented regardless of the number, location, shape, or size. Thus, the method is more robust and practical than the current methods using only one method.
参考文献 | 相关文章 | 计量指标
Car Side Structure Crashworthiness in Pole and Moving Deformable Barrier Side Impacts 收藏
Dazhi Wang, Guang Dong, Jinhuan Zhang, Shilin Huang
清华大学学报自然科学版(英文版). 2006, (6): 725-730.   DOI: 10.1016/S1007-0214(06)70256-5
摘要 ( 249 )  
To clearly understand passenger car structure's crashworthiness in typical side impacts of pole and moving deformable barrier (MDB) impact modes, which could assist the establishment of Chinese vehicle side impact safety regulations, a full midsized car finite element model, calibrated by pole side impact test, was built and the pole side impact according to European New Car Assessment Program (EuroNCAP) and the MDB side impact according to ECE R95 regulations were simulated with LS-DYNA. The accelerations and the structure deformations from simulations were compared. It can be concluded that the pole side impact focuses primarily on side structure crashworthiness as a result of large intrusions, while the MDB side impact focuses primarily on full side structure crashworthiness. Accordingly, occupant protection strategies focus on different aspects to improve side impact safety. In the pole side impact the objective is to maintain the passenger compartment and protect the passenger's head from impacting the pole, while in the MDB side impact the objective is to protect the full human body. In the design of the car side structures, at least these two tests should be considered for assessing their side impact crashworthiness. Conducting these two side impact tests as certified tests provides insights into car safety during side impacts.
参考文献 | 相关文章 | 计量指标
Thorium-Based Fuel Cycles in the Modular High Temperature Reactor 收藏
Hong Chang, Yongwei Yang, Xingqing Jing, Yunlin Xu
清华大学学报自然科学版(英文版). 2006, (6): 731-738.   DOI: 10.1016/S1007-0214(06)70257-7
摘要 ( 246 )  
Large stockpiles of civil-grade as well as weapons-grade plutonium have been accumulated in the world from nuclear power or other programs of different countries. One alternative for the management of the plutonium is to incinerate it in the high temperature reactor (HTR). The thorium-based fuel cycle was studied in the modular HTR to reduce weapons-grade plutonium stockpiles, while producing no additional plutonium or other transuranic elements. Three thorium-uranium fuel cycles were also investigated. The thorium absorption cross sections of the resolved and unresolved resonances were generated using the ZUT-DGL code based on existing resonance data. The equilibrium core of the modular HTR was calculated and analyzed by means of the code VSOP'94. The results show that the modular HTR can incinerate most of the initially loaded plutonium amounting to about 95.3% net 239Pu for weapons-grade plutonium and can effectively utilize the uranium and thorium in the thorium-uranium fuel cycles.
参考文献 | 相关文章 | 计量指标
Stability Analysis of Equilibrium Manifolds for a Two-Predators One-Prey Model 收藏
Xin Zhang, Yun Tang, Rudolf Scherer
清华大学学报自然科学版(英文版). 2006, (6): 739-744.   DOI: 10.1016/S1007-0214(06)70258-9
摘要 ( 146 )  
The objective of this paper is to analyze the stability of equilibrium manifolds for a ratio-dependent two-predators one-prey model. Some model results are presented first with the bifurcation without parameters method, and then the method was used to study bifurcation along the equilibrium manifold for the model. The model does not lose stability even when some equilibria are locally unstable because the equilibrium manifold is stable when treated as a whole. The ecological implications of the results are discussed.
参考文献 | 相关文章 | 计量指标
版权所有 © 《清华大学学报自然科学版(英文版)》编辑部


本系统由北京玛格泰克科技发展有限公司设计开发 技术支持:support@magtech.com.cn