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15 January 2008, Volume 29 Issue 1 Previous Issue    Next Issue
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On the discretization algorithm based on fuzzy rough set for continuous system variables Zhang, Hua-Guang (1); Xu, Yue (2); Sun, Qiu-Ye (2) 2008, 29 (1):  1-4.  DOI: - Abstract ( 273 )   HTML   PDF (342KB) ( 879 )   A new discretization algorithm based on fuzzy rough set with the number of breakpoints reduced is put forward and discussed, taking account of the supportability and confidence of its rules and the relation between them. Taking the discretization indices of attributes as criteria, the indices are proved the sufficient conditions for complete discretization. Discusses the effectiveness of the algorithm in view of the time and space complexity and compares the algorithm with similar ones. It is found that the algorithm can reduce the time and space complexity efficiently, thus avoiding the drawbacks often found in other conventional algorithms. Its effectiveness and practicality are verified through a numerical example applying it to fault diagnose for power network. References | Related Articles | Metrics

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Robust H∞ control of stochastic hyperbolic tangent model Wang, Yi-Zhong (1); Zhang, Hua-Guang (1) 2008, 29 (1):  5-8.  DOI: - Abstract ( 212 )   HTML   PDF (184KB) ( 492 )   Studies the problems of robust stabilization/H∞ control of a stochastic hyperbolic tangent model newly developed with time-varying delay. Based on linear matrix inequality (LMI) and Lyapunov-Krasovskii approaches, a delay-dependent stabilization criterion and robust nonlinear state feedback control law are given. And the controller thus designed is guaranteed asymptotically stable in terms of mean square for closed-loop systems. For the robust H∞ control problem, a design method of the robust H∞ controller is proposed to keep a closed-loop system asymptotically stable in terms of mean square with a pre-defined H∞ disturbance attenuation coefficient γ. An illustrative example and simulation results are given to verify the effectiveness of the approaches proposed. References | Related Articles | Metrics

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Output feedback based design of switching fuzzy control Liu, Yi (1); Zhao, Jun (1) 2008, 29 (1):  9-12.  DOI: - Abstract ( 278 )   HTML   PDF (280KB) ( 519 )   The output feedback control of a class of uncertain fuzzy switching systems is presented for a fuzzy switching system to which the states are unmeasurable. According to the switching technique and conventional design of PDC (parallel distributed compensation) controller, a fuzzy switching observer and controller are provided. The sufficient conditions to ensure the asymptotically stable output feedback control of closed-loop system are studied using the joint, single and multiple Lyapunov functions, with the switching law designed to implement the global asymptotic stability of fuzzy switching systems. The main condition is given in terms of LMI that is highly solvable. Simulation result shows the feasibility and effectiveness of the design method. References | Related Articles | Metrics

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Adaptive robust H∞ control of thyristor controlled series compensation Sun, Li-Ying (1); Zhao, Jun (1) 2008, 29 (1):  13-16.  DOI: - Abstract ( 267 )   HTML   PDF (1905KB) ( 424 )   The robust H∞ control problem is studied for the single machine-infinite bus TCSC (thyristor controlled series compensation) power system with parameter uncertainties and external disturbances. With the storage functions formed in control system by adaptive backstepping and Lyapunov methods, the robust H∞ controller and parameter updating law are obtained simultaneously. Both the effects of damping coefficients and direct unmeasurability of generator potential are considered in internal disturbance. The proposed controller will not only keep the nonlinearity of power system and the on-line real-time estimate of unknown parameters, but also suppress efficiently the influence of disturbance on system output. Simulation results reveal that the proposed controller can suppress oscillation rapidly to provide transient stability for the single machine-infinite bus TCSC power system. References | Related Articles | Metrics

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Reinforcement learning approach to ABR traffic control of ATM networks Li, Xin (1); Jing, Yuan-Wei (1); Ren, Tao (1); Zhang, Yang (2) 2008, 29 (1):  17-20.  DOI: - Abstract ( 280 )   HTML   PDF (1146KB) ( 810 )   The reinforcement learning approach is applied to the design of controller to solve the congestion problem in ATM (asynchronous transfer mode) networks. This approach does not rely on the mathematic model and priori-knowledge of network, but acquires the knowledge through trial-and-error method and interacts with environmental conditions to improve its behavior strategy. So, it has the self-learning ability and the queue length of buffer at bottleneck node thus approximates to the set value by readjusting the source traffic rate in the ABR (available bit rate) service. The stability of the system is therefore provided and able to avoid possible occurrence of congestion. Simulation results show the effectiveness of the approach proposed. References | Related Articles | Metrics

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Data reduction based on rough set theory and hierarchic analysis Zhang, Xue-Feng (1); Tian, Xiao-Dong (1); Zhang, Qing-Ling (1) 2008, 29 (1):  21-24.  DOI: - Abstract ( 299 )   HTML   PDF (231KB) ( 514 )   To find latent knowledge rules efficiently and quickly from a great deal of information, the studies on data mining (DM) and knowledge discovery of database (KDD) become more popular and profound. Combining the rough set theory with hierarchic analysis model in view of their characteristics and introducing the definition of importance into non-core attributes, a new data reduction algorithm is proposed using a simple discriminative matrix. The validity and completeness of the algorithm is proved, by which an ideographic problem is common in medical treatment decision-making system is successfully solved. The results reveal that the algorithm is able to mine the knowledge and rules effectively and improve the rationality of data reduction. References | Related Articles | Metrics

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Image enhancement based on fuzzy inference and soft morphological filtering Fu, Ping (1); Xue, Ding-Yu (1); Chi, Jian-Nan (2); Xu, Xin-He (1) 2008, 29 (1):  25-28.  DOI: - Abstract ( 227 )   HTML   PDF (519KB) ( 590 )   According to the correlative concept and properties of soft morphology, an image enhancement approach based on fuzzy inference and soft morphological filtering is proposed. With the idea of fingerprint image enhancement taken for reference, the directional structuring elements are defined, in which the fuzzy inference is introduced to judge the direction of image edges, and further, construct directional filter of soft morphology so as to filter off noise and enhance image edges. The coefficient of image enhancement is thus determined adaptively according to local mean value and entropy difference. Experimental results showed that the approach proposed can filter off the high-frequency noise and upgrade image edge effectively. References | Related Articles | Metrics

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On the embedded control system for autonomous mobile robot Zhang, Yun-Zhou (1); Wu, Cheng-Dong (1); Xue, Ding-Yu (1); Wang, Fei (1) 2008, 29 (1):  29-32.  DOI: - Abstract ( 249 )   HTML   PDF (384KB) ( 1152 )   To improve the control system performance of wheeled autonomous mobile robots, an embedded control system was designed and implemented with advanced microprocessor. Based on the hierarchic control method, two processors were applied to different control levels so as to attain complicated high-speed algorithm and real-time control. Multiple sensors were introduced to sense the environmental conditions with implemented via fuzzy logic for accurate control of moving route. Then, an actual status of target position could he judged visually. The system thus acquires many advantages such as modular structure, control flexibility and high reliability. The actual application results reveal that the system owns good real-time response and robustness. References | Related Articles | Metrics

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Hybrid modeling based on ELM for soft sensing of end temperature of molten steel in LF Tian, Hui-Xin (1); Mao, Zhi-Zhong (1); Wang, Jia-Zheng (2) 2008, 29 (1):  33-36.  DOI: - Abstract ( 321 )   HTML   PDF (272KB) ( 679 )   Combining the conventional mechanism model with the newly developed ELM (extreme learning machine), a hybrid model was developed for soft sensing of molten steel temperature with the aim to rise above the complexities of the physico-chemical reaction process and heat transfer process during LF (ladle furnace) refining. The intelligent ELM algorithm can correct the unacquainted parameters in mechanism model and then predict exactly them with the mechanism model. The hybrid model thus has the advantages not only overcoming the difficulty that the mechanism model is hard to implement exactly but also getting rid of the over reliance upon available data in the Black Box model. In addition, it can make up for the defect of conventional BP algorithm, thus improving the prediction accuracy. Simulation results showed its favorable predictability, i.e., the number of heats of which the predictive errors of end temperature of molten steel in LF are all not over ± 5°C is greater than 90%. References | Related Articles | Metrics

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Design and implementation of turbine governor model in hydropower simulation software system Zhao, Hai (1); Song, Chun-He (1); Xu, Jiu-Qiang (1); Zhang, Jun (1) 2008, 29 (1):  37-40.  DOI: - Abstract ( 578 )   HTML   PDF (395KB) ( 1068 )   The control parameters of PID governor in a simulation system of hydropower station can not be easily identified, hydropower governor model is therefore developed taking Matlab/Simulink as platform, introducing the self-tuning-fuzzy algorithm with control parameters optimized by genetic algorithm; the robustness of the model is improved. Then, the RTW (real-time workshop) as a function provided by Matlab itself is used to transform the Simulink software modularity diagram into VC code available to integrated R&D environment. Discusses the practicality of the algorithm and what should be noticed during the implementation of softwares. The whole R&D process of this approach is closely related to Matlab/Simulink platform, thus shortening R&D period and improving the reliability of VC code. References | Related Articles | Metrics

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Mathematic model analysis and improvement of guide vane opening in hydropower simulation Zhou, Yan (1); Zhao, Hai (1); Zhang, Jun (1); Li, Xiao-Feng (1) 2008, 29 (1):  41-44.  DOI: - Abstract ( 362 )   HTML   PDF (1174KB) ( 665 )   The hydroturbine governor model is crucial to a hydropower simulation system. To simulate a hydropower system, the key mathematic model of mixed-flow hydroturbine is improved so as to solve the problem of overspeed and unstability during starting and stopping the governor, i.e., a polynomial regression model is developed through regression analysis to derive a mathematic model for governor starting/stopping with relation to the guide vane opening of the hydroturbine by way of piecewise analysis/fitting. The approach proposed is simple in operation with high accuracy even if the input is in random fashion. And the results of reliability analysis/test showed that the approach will not only ensure the reliability and practicability but also solve the most complex problems with favorable effect available in the simplest and most direct way. The simulation practice in Fengman Hydropower Station exemplifies these advantages. References | Related Articles | Metrics

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On the behavior of weighted internet traveling time Li, Chao (1); Zhao, Hai (1); Zhang, Xin (1); Yuan, Shao-Qian (1) 2008, 29 (1):  45-48.  DOI: - Abstract ( 254 )   HTML   PDF (342KB) ( 541 )   Studies the Internet delay behavior. Defining the weighted Internet traveling time and traveling diameter, the statistics based on the giant data samples authorized by CAIDA reveals the distribution of the traveling time, and that the traveling diameter is regarded as an important influence on traveling time. Then, an algorithm is proposed to process the original data samples to obtain link delay. The statistical analysis of link delay shows that there exits dominant delay, which is the root cause of traveling time diversity. References | Related Articles | Metrics

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M/M/1/n-based study on overload performance of sink node in wireless sensor networks Zhang, Xi-Yuan (1); Zhao, Hai (1); Sun, Pei-Gang (1); Luo, Ding-Ding (1) 2008, 29 (1):  49-52.  DOI: - Abstract ( 216 )   HTML   PDF (252KB) ( 742 )   Overload congestion of sink nodes is an important influencing factor on the applications of wireless sensor network. Analyzing essentially the packet receiving process of sink nodes, the process can be divided into two parts: the wireless NIC interrupt processing and data processing. According to the theory of 2-level serial queueing network system, a model of packet receiving process is developed with the overload performance analyzed in detail for it. Then, an improved method-adaptive packet discarding scheme is proposed, and its performance has been tested through experiment on Micaz platform. The result indicated that it can solve well the congestion problem at sink node. References | Related Articles | Metrics

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User interests clustering based on PLSA Chen, Dong-Ling (1); Wang, Da-Ling (1); Yu, Ge (1); Yu, Fang (1) 2008, 29 (1):  53-56.  DOI: - Abstract ( 241 )   HTML   PDF (333KB) ( 919 )   To mine user's latent interests and make relevantly the clustering analysis during personalized search, it is proptxsed to combine the characteristics of Zipf distribution in latent semantic space with PLSA (the probability latent semantic analysis), so as to gain the semantemes of the whole text. Namely, the principle of Zipf distribution is introduced to find out the latent semantic space of files, where the user interest is clustered according to underlying factors and a user interest hierarchy tree is built in user profile. Experimental results show that the clustering result as proposed is clearly superior to that by the conventional VSM (vector space model) algorithm. In addition, the results of the recommended personalized experiment based on well-known CTI data set also indicates fully that the description of user profile on the basis of latent semantic space coincides actually with the user interest. References | Related Articles | Metrics

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Function dependencies in XML Zhao, Xiang-Guo (1); Wang, Guo-Ren (1); Han, Dong-Hong (1); Ding, Da-Bin (1) 2008, 29 (1):  57-60.  DOI: - Abstract ( 224 )   HTML   PDF (158KB) ( 693 )   Functional dependency is an integral part in the normalization research on XML data base. To express the XML functional dependency which give rise to data redundancy, various complicated constraints on functional dependency are analyzed with a path language proposed on DTD basis to give stronger expression to the navigation and location for an XML document. With a set of XML schemes and representation to formalize documents presented, a kind of definition of XML functional dependency (XFD) is given. Comparing with the XFD defined previously, this definition of XFD can express more functional dependencies existing in XML and is available to generalize about the constrainabilities on the functional dependencies defined before by the expression of path. References | Related Articles | Metrics

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Approach to framing the semantics-based super-peer networks Qiao, Bai-You (1); Wang, Guo-Ren (1); Xing, Yun-Long (1); Wang, Cai-Rong (1) 2008, 29 (1):  61-64.  DOI: - Abstract ( 214 )   HTML   PDF (449KB) ( 663 )   An approach to framing the semantics-based super-peer networks is proposed aiming at the data semantic space consisting of taxonomic hierarchies. The approach can dynamically group peers into many semantic clusters based on their individual semantics of data object. Then, the semantic clusters are organized into a semantic overlay network with appropriate routing relations established between them. Each and every semantic cluster consists of a super-peer and a set of peer nodes, and only responsible for answering queries in its semantic sub-space. A query is first routed to the appropriate semantic clusters by an efficient searching algorithm, then forwarded to the specific peers that hold the relevant data objects. Experimental results indicated that the approach achieves a competitive trade-off between search efficiency and cost, thus offering higher search performance and lower search cost to enhance the network scalability. References | Related Articles | Metrics

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MMSE V-BLAST algorithm based on iterative QR decomposition Wang, Yun (1); Wang, Jin-Kuan (1); Song, Xin (1); Xie, Zhi-Bin (1) 2008, 29 (1):  65-68.  DOI: - Abstract ( 374 )   HTML   PDF (962KB) ( 1233 )   An improved MMSE (minimum mean square error) V-BLAST algorithm based on iterative QR decomposition is proposed to solve the problem that the complexity of detection becomes higher because lots of pseudo-inverse operations have to be taken when detecting the receiving end of MIMO system with MMSE algorithm. As a result, the complexity is reduced efficiently with the detection performance clearly improved. In the environment where lots of wireless communications were scattered over, a simulation testing was done and the results showed that the computation complexity of the proposed algorithm is obviously reduced in comparison with conventional algorithms only if the BER doesn't change dramatically with the same SNR. The theoretical analysis proves that the more the number of effective antennae, the better the performance of the algorithm proposed. References | Related Articles | Metrics

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On the friction properties of 3D-meshy SiC ceramics-metal composites Ru, Hong-Qiang (1); Qu, Xiang-Yu (1); Ma, Li-Ping (1); Li, Jing-Yang (1) 2008, 29 (1):  69-72.  DOI: - Abstract ( 219 )   HTML   PDF (652KB) ( 916 )   The 3D-meshy SiC-Fe-Cu composites and SiC-40Cr composites are used as stationary and moving specimens, respectively, in tribologic test. The influences of normal load, rubbing time and pv value on the coefficient of friction were studied, as well as the effect of friction frequency on the wear lass of the stationary specimen. The microstructure and worn surface morphologies of the composites were observed by metolloscope to analyze the friction/wear properties and mechanism. The results showed that the steady coefficient of friction of the friction pair tested is 0.33-0.35, and the wear mechanism is mainly due to the friction of abrasive grains and viscous friction. The hardness of oxide layer formed by surface friction on composite surface is high and provides mainly the high wearability for those composites. References | Related Articles | Metrics

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Microstructural evolution of Al-1.3Si-0.7Mg-0.7Cu-0.3Mn aluminum alloy sheets during solution treatment Tian, Ni (1); Zhao, Gang (1); Liu, Chun-Ming (1); Zuo, Liang (1) 2008, 29 (1):  73-76.  DOI: - Abstract ( 251 )   HTML   PDF (1500KB) ( 550 )   The evolution of intermetallic phases, grains and textures of cold rolled Al-1.3Si-0.7Mg-0.7Cu-0.3Mn aluminum alloy sheets during solution treatment at 540°C was investigated by XRD, OM and TEM observation and texture measurement. The results showed that there are many insoluble intermetallic phases such as Al9Fe0.84Mn2.16Si, Al95Fe4Cr and Al6Mn in the as-cold rolled alloy sheets, as well as some soluble ones including Al1.9CuMg4.1Si3.3 and Mg2Si. The soluble intermetallic phases smaller than 1 μm can be dissolved completely into matrix when the cold rolled sheets are bathed in molten salt at 540°C for over 12 min, and the sheets can be recrystallized within 2 min through solution treatment at 540°C to form the recrystalline textures {001}<310> and {110}<113>, where the former is dominant and both are of low intensity. It was revealed that the size and shape of recrystallized grains and the component of recrystalline textures change un-obviously when lengthening the time for solution treatment at 540°C to 60 min. References | Related Articles | Metrics

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Structure and properties of 7050 alloy prepared through low frequency electromagnetic casting process Zuo, Yu-Bo (1); Cui, Jian-Zhong (1); Zhao, Zhi-Hao (1); Zhu, Qing-Feng (1) 2008, 29 (1):  77-80.  DOI: - Abstract ( 261 )   HTML   PDF (618KB) ( 1130 )   The φ120 mm ingots of 7050 alloy were prepared through a new process, i.e. LFEC (low frequency electromagnetic casting). Investigates how the low frequency electromagnetic field affects the structure and mechanical properties of the as-cast ingots. Then, the microstructure and mechanical properties of the ingots after extrusion and heat-treatment were studied in comparison with those prepared through DC casting. The results showed that LFEC can get grain refining and homogenize structural distribution to improve as-cast tensile strength and elongation. After solution and ageing treatments, the tensile strength/percentage elongation of extruded specimens through LFEC process and conventional DC process are 677.5 MPa/13.2% and 676.5 MPa/11.2% respectively. A conclusion is thus drawn that the LFEC process has no significant effect on final tensile strength of extruded 7050 alloy rods, but can improve their final percentage elongation. References | Related Articles | Metrics

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Prediction and optimization of microstructure and mean flow stress during hot rolling of steel plates Xu, Yun-Bo (1); Deng, Tian-Yong (1); Liu, Xiang-Hua (1); Wang, Guo-Dong (1) 2008, 29 (1):  81-84.  DOI: - Abstract ( 274 )   HTML   PDF (339KB) ( 721 )   A metallurgical model of Nb-V HSLA steels was developed considering the effects of dynamic, meladynamic and static recrystallization. The model was applied to the on-line prediction and control of austenite recrystallization, grain size and flow stress during plate hot rolling. The results showed that when the starting temperature of finish rolling is at 900-950°C with intermediate water cooling and the intermediate slab is 2-2.7 times as thick as the finished product, the final austenite grain size of 30 mm plate can be refined to about 30 μm with residual strain in a range from 0.08 to 0.4. The prediction accuracy of MFS (mean flow stress) in finish rolling will be greatly improved if introducing the effects of grain size and residual strain into MFS model. References | Related Articles | Metrics

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Effect of work roll shift on strip's edge drop Chang, An (1); Di, Hong-Shuang (1); Tong, Qiang (1); Yang, Dai-Jun (3) 2008, 29 (1):  85-88.  DOI: - Abstract ( 269 )   HTML   PDF (375KB) ( 1304 )   Edge drop is an important quality evaluating index for cross-section, which closely relates to side trimming and the rate of finished products. The control system of roll shift plays an important role in controlling the strip's edge drop on modern mills. Based-on the influence function, an analytic model is developed for the elastic deformation of rolls so as to simulate the strip rolling process on 6-high single cold mill with the intention to investigate the effect of work roll shift on strip's edge drop. To determine the optimum work roll shift for a strip product with certain specifications, an iterative computation was done, to which the convergence criterion of proportional crown is less than 1%. The results showed that a proper work roll shift can improve greatly edge drop. The shift value should be determined according to different steel grades, strip widths and relevant rolling parameters, meanwhile, the iterative computation is also available to the preset value of work roll shift. References | Related Articles | Metrics

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Effect of boron content on structure and properties of ZGMn13Cr2 He, Jiang-Ai (1); Gu, Lin-Hao (1); Li, Shu-Qin (1); Xue, Xiang-Xin (1) 2008, 29 (1):  89-92.  DOI: - Abstract ( 416 )   HTML   PDF (409KB) ( 1517 )   Adding different boron contents (0.0015%-0.01%) in ZGMn13Cr2, its hardness increases in a HBS range from 220 to 278 with the boron content added after water toughness treatment at 1110°C. Simultaneously, its impact toughness decreases in the range that the maximum αk=178.5 J/cm2 and minimum αk=135.6 J/cm2, and it is shown metallographically that the more the boron content, the more the undissolved carbides which are distributed dispersively in granular form. Moreover, its wearability is improved with increasing boron addition under the low-impact abrasive wear. SEM images show the morphology of its worn surface on which the furrow-like traces become mainly the milled traces and ditches with few furrow-like ones. It is revealed that the ZGMn13Cr2 in which 0.003%-0.006% of boron is added can offer best overall performance on the whole. References | Related Articles | Metrics

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Preparation and crystalline transition behavior of turbostratic boron nitride Yuan, Lei (1); Yu, Jing-Kun (1) 2008, 29 (1):  93-96.  DOI: - Abstract ( 458 )   HTML   PDF (1204KB) ( 784 )   Turbostratic boron nitride powder was prepared with boric acid and urea used as raw materials in nitrogen (N2) gas flow at 900°C by two-step method. The transition behavior of t-BN to h-BN at different temperature with different additives was investigated by XRD, and SEM was used to analyze the morphologies of t-BN/h-BN powder particles. Specific surface area of the powder was also measured under different conditions. The results showed that the transition of t-BN to h-BN gets better increasingly with temperature rising and more additive contents, but the specific surface area and activity decrease. The well crystallized h-BN was thus obtained at 1300°C. References | Related Articles | Metrics

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Study on emissivities and absorptivities of gas in reheating furnace Cui, Miao (1); Chen, Hai-Geng (1); Chen, Yu (1); Wu, Bin (1) 2008, 29 (1):  97-99+104.  DOI: - Abstract ( 371 )   HTML   PDF (1039KB) ( 618 )   The mean beam lengths of furnace gas to wall and to slab in reheating furnace are distinguished, then the simplified expressions to calculate them are given by the Gauss-Laguerre integration. It is supposed that there are two kinds of emissivities and six kinds of absorptivities of the furnace gas in a ternary model considering the non-gray radiation properties of the gas. The emissivities and absorptivities of furnace gas in upper hearth of a walking beam reheating furnace were simulated introducing the Leckner scries. The results showed that distinguishing the emissivities and absorptivities is necessary for correctly calculating the radiative heat exchange in reheating furnace. References | Related Articles | Metrics

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Study on nonisothermal crystallization behavior of MC nylon 6/ZnO nanocomposite Zhou, Li (1); Tian, Yan-Wen (1); Zang, Shu-Liang (2); Zhang, Jian-Zhong (3) 2008, 29 (1):  100-104.  DOI: - Abstract ( 266 )   HTML   PDF (493KB) ( 1181 )   The nonisothermal crystallization behavior of the MC nylon 6/ZnO nanocomposite prepared by in situ polymerization was studied by means of differential scanning calorimetry (DSC), where a kinetic analysis was made by Jeziomy, Mo and Kissinger methods based on modified Avrami equations. The results showed that the nucleus growth of MC nylon 6 is accelerated because the nano-sized ZnO particles are playing the role of nucleating agents to expedite the crystallizing rate and raise the temperature of MC nylon 6. At the same time, the movement of MC nylon 6 molecule chains is suppressed in crystallization process due to the interaction between nano-sized ZnO particles and MC nylon 6 molecule chains, thus increasing the activation energy of MC nylon 6 crystallization and decreasing the crystal growing rate and crystallinity. References | Related Articles | Metrics

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New evaluation model based on RCM II/CCF theory for hidden faults Ni, Ai-Wei (1); Xie, Li-Yang (1); Weng, Gang (2); Wu, Ke-Qin (1) 2008, 29 (1):  105-108.  DOI: - Abstract ( 262 )   HTML   PDF (1356KB) ( 525 )   It will possibly be a lethal mistake if using the defective mathematical model in terms of RCM II (reliability-centered maintenance II) to calculate the rate of hidden faults especially those hidden faults concerning safety and environmental adversity. So, based on the CCF (common cause failure) theory and analyzing lots of different failed CCF models in comparison with each other, a new evaluation model is developed first for hidden faults by way of modifying their defective assumption conditions, and the BP in neural network is used to solve efficiently the model in which 4 relatively accurate parameters are thus obtained. Compared with the original models and stochastic ones, the new model can express the process of hidden fault more exactly with higher accuracy of reliability evaluation and is therefore beneficial to actual design and maintenance in production. References | Related Articles | Metrics

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Study on reliability modeling of continuous systems like pipeline Hao, Guang-Bo (1); Xie, Li-Yang (1); He, Xiu-Yun (1); Li, Li (1) 2008, 29 (1):  109-112.  DOI: - Abstract ( 230 )   HTML   PDF (1288KB) ( 647 )   Describes briefly researches on the reliability modeling of continuous systems in recent years, where the pipelines and wire cables are taken typically as examples. Discretizing a continuous system into a number of elements that can be considered as a series system, a probability density function of system strength is derived introducing the minimal order statistics. Discusses the reliability modeling of dependent failure to such series systems and the two influencing factors on their material strength, i.e., the materials' inhomogeneity and quality instability. Then, a reliability model is developed for continuous systems such as pipelines, which can reflect the failure-dependence among those elements. The model provides a basis for the reliability design/computation of continuous system including pipeline and wire cables. References | Related Articles | Metrics

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Effects of steady temperature field on vibrational characteristics of a rotor system Zhu, Xiang-Zhe (1); He, Wei (1); Yuan, Hui-Qun (1) 2008, 29 (1):  113-116.  DOI: - Abstract ( 253 )   HTML   PDF (450KB) ( 1219 )   Thermal buckling is a common fault found in rotor system. The effect of steady-temperature field on the vibrational characteristics of rotor system of a certain turbine unit was studied by means of FEM and the coupling theory of thermal-structure dynamics. Comparing the unbalance response, thermal buckling response and the response coupling both together, the effects of steady temperature field, operational rotational speed on thermal vibration characteristics were discussed in detail with the sensitive parameters affecting thermal vibration found out. The results showed that the stiffness matrix of the rotor system is redistributed because of thermal buckling, thus resulting in the significant decrease in the first critical speed of the rotor system due to the thermal vibration. At the same time, the thermal buckling changes the balance position and causes the rotor system to vibrate periodically around a new balance position. The calculated results offer a theoretical foundation on which the design and fault diagnosis of rotor-bearing system are both available to avoid great thermal vibration. References | Related Articles | Metrics

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Kinematics and simulation of a new five-DOF parallel mechanism Yang, Qiang (1); Sun, Zhi-Li (1); Yan, Ming (1); Xu, Min (1) 2008, 29 (1):  117-120+129.  DOI: - Abstract ( 416 )   HTML   PDF (1659KB) ( 670 )   Based on the improved Delta/2-R mechanism, a new mechanism integrating independent translation with rotation is presented. An inverse solution is derived to all the poses of the mechanism by way of simple transformation of homogeneous coordinate and matrix operation without complicated mathematic derivation, thus enabling its programming to be easier. The 3-D analytical geometry and vector algebra are introduced into the normal kinematic solution so as to avoid the numerical solution to algebraic equation sets and option of multiple solutions for conventional parallel mechanism. With the virtual prototype software ADAMS, the movement of the mechanism was simulated to verify the correctness of both the normal and inverse kinematic solutions to the mechanism proposed. Owing to its big work space, high location accuracy, favorable micro-motion performance and low cost of manufacture/control, the new parallel mechanism is regarded as applicable to pick-place manipulator, inspection robot and laser cutting machine tool. So, it has good prospects in industrial applications. References | Related Articles | Metrics

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Contrast analysis of ecological footprint: Exemplification with of Shenzhen and Suzhou Li, Guang-Jun (1); Wang, Qing (1); Gu, Xiao-Wei (1); Liu, Jian-Xing (1) 2008, 29 (1):  121-124.  DOI: - Abstract ( 294 )   HTML   PDF (132KB) ( 1223 )   Recently, the comparative study on the development of China's Shenzhen and Suzhou cities was mainly based on their economy and people's living standard. However, the impact of economic development on their ecological environment was often overlooked. The principle and mathematical model of the ecological footprint were therefore introduced into the case studies of Shenzhen and Suzhou from 1997 to 2004, and the results showed that the development of the two cities has great impact on the ecological environment. Taking the year 2004 as example, the consumption of different resources in Shenzhen needed about 28 times its area to sustain the demand for the population in the city, and in Suzhou it was about 12 times its area. Energy consumption predominated in the cities, since the secondary industry is dominant in Suzhou and the secondary industry and tertiary industry are dominant in Shenzhen. References | Related Articles | Metrics

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Maintenance optimization of concrete bridge deck using the niched Pareto genetic algorithm Bian, Jing-Mei (1); Zhu, Fu-Sheng (1); Chen, Geng-Ye (1); Bai, Quan (1) 2008, 29 (1):  125-129.  DOI: - Abstract ( 240 )   HTML   PDF (218KB) ( 652 )   As the most damageable component of bridge, the concrete bridge deck is most required to maintain. The problem of obtaining the optimal maintenance strategy of concrete bridge deck under limited resources restriction is investigated. A multiobjective optimization model of concrete bridge deck is therefore developed for several objectives which conflict with each other, such as minimizing the total cost but maximizing the performance simultaneously, and the niched Pareto genetic algorithm (NPGA) is introduced to solve the model. The multiobjective optimization of bridge deck maintenance based on NPGA provides bridge managers with a set of feasible solutions for selection in accordance to their own preference, by which not only the disadvantage of single objective optimization without other influencing factors taken into account can be avoided but also some defects can be overcome in conventional solutions to the problem of multiobjective optimization. In this way the maintenance decision will be made more scientific and rational so as to make the maintenance for existing bridges proper. References | Related Articles | Metrics

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Study on several problems about point load test of rock Wang, Ru (1); Tang, Chun-An (2); Wang, Shu-Hong (1) 2008, 29 (1):  130-132+140.  DOI: - Abstract ( 377 )   HTML   PDF (121KB) ( 1768 )   Studies the field testing methods for ISRM (international society for rock mechanics) and the national standard for Engineering Classification of Rock Masses. The point load test is thus recommended, but two key problems retard its wide applications. It is suggested that the standard rock strength index under point load IS(50) is determined by the average value of Is. Then, by the point load test results with irregular rock specimens and regular gypsum modelled specimens, it is revealed that the relative standard deviation of the method suggested from conventional method is less than 2% if the number of specimens n2 whose D value > 50 mm is equal to the number of specimens n3 whose D < 50 mm on the whole. It is also suggested to formulate a national standard of point load tests for rock masses, with the application scope of the strength index under point load defined, which is of importance to the development and innovation of the point load test for rock masses. References | Related Articles | Metrics

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Simulation analysis of mechanical properties of deviating zone in externally prestressed bridge Xi, Guang-Heng (1); Chen, Xiao (1); Liu, Bin (1); Wang, Ji-Ying (2) 2008, 29 (1):  133-136.  DOI: - Abstract ( 224 )   HTML   PDF (506KB) ( 752 )   Baaed on the design of an externally prestressed trial bridge for a certain express highway, a spatial simulation was done using the special software MIDAS/Civil to analyze the mechanical properties in the deviating zones of the bridge, as well as the stress distribution, loading conditions and force transmission paths in the key zones. According to the constitutive relation and yielding criteria, the differential stress analysis is proposed as a manner for the yielding zones where there are potential hazards. A conclusion is thus drawn that the vertical compressive stress in a deviator is distributed mainly in the part above the rib of deviating pipe, while the vertical tensile stress is distributed mainly between the junction of deviator and base plate and the deviating pipes. It is suggested to widen the gaps between deviating pipes to reduce the stress concentration there. Some practical and feasible measures are suggested to take for engineering design and constructions. The results are expected to provide favorable reference for similar projects. References | Related Articles | Metrics

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Fractal statistics for copper price on shanghai futures market Yuan, Ying (1); Zhuang, Xin-Tian (1) 2008, 29 (1):  137-140.  DOI: - Abstract ( 245 )   HTML   PDF (390KB) ( 610 )   Parameters' estimation of fractal distribution, functional box dimension and multifractal analysis are used to study empirically the fractal characteristics of the time series of copper price on Shanghai futures market, it is found that the time series are not normally distributed and show long-term memory. The efficient market hypothesis is thus to be queried. The clustering structure and scale variation of the time series as revealed by the functional box dimension and multifractal analysis show that a single fractal model is not sufficient to describe the futures price in time series. However, the multifractal analysis as a powerful instrument can describe more exactly how the price of copper futures varies. References | Related Articles | Metrics

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On the incentive contract to keep trade credit with asymmetric information in supply chain Yu, Li-Ping (1); Huang, Xiao-Yuan (1); Li, Li-Jun (1) 2008, 29 (1):  141-144.  DOI: - Abstract ( 234 )   HTML   PDF (103KB) ( 755 )   In view of the principal-agent relation, the incentive effect of trade credit a manufacturer offers to his retailers in supply chain is studied. Comparing the design of incentive contracts with symmetric and with asymmetric information, the interest game between manufacturer and retailers is analyzed to determine the contract parameters so as to maximize the expected benefit of the principal by model optimization. The level of optimal effort made by a retailer with asymmetric information is proved lower than that with symmetric information. When information is asymmetric, the incentive value to trade credit decreases with retailers aversion to risk. A numerical example is given to illustrate the application of the proposed method. References | Related Articles | Metrics

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Group theory based analysis of crystal vibration modes of calcite and dft study on its infrared spectra Sun, Feng-Jiu (1); Lou, Dan-Hua (1); Li, Li-Juan (1) 2008, 29 (1):  145-148.  DOI: - Abstract ( 256 )   HTML   PDF (283KB) ( 2232 )   The factor group symmetry analysis and position symmetry analysis were both used for the crystal vibration modes of calcite (GaCO3), and those modes were found definitely and rapidly with their spectral characteristics described separately. The applicabilities of the two analyses are compared with each other. In addition to the real spectra, the infrared spectra were calculated ab initio for the model we developed for calcite crystal supercell by introducing the first principle of DFT (density functional theory), and the frequencies of 27 optical vibration modes were obtained in every particular. The results showed that the spectral characteristics of each and all of the frequencies conform to those calculated theoretically by group theory. Compared with the lattice dynamics, the calculation results as above conform better to experimental results. References | Related Articles | Metrics

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Synthesis, structures and properties of liquid-crystalline monomers/polymers containing biphenyl groups Hu, Jian-She (1); Li, Hao (1); Zhao, Zhan-Xiang (1); Zhang, Bao-Yan (1) 2008, 29 (1):  149-152.  DOI: - Abstract ( 343 )   HTML   PDF (367KB) ( 1185 )   Four LC (liquid-crystalline) monomers (M1-M4) and their corresponding polymers (P1-P4) were synthesized, and their LC structures and properties were characterized with FT-IR, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), polarizing optical microscopy (POM) and X-ray diffraction (XRD). The results showed that M1 and M2 present the enantiotropic nematic phase, M3 presents the nematic phase with SA, SC and SB smectic phases and M4 presents the nematic phase with SA, SC and SB monotropic phases. As to the polymers, P1 and P2 present the nematic phase, P3 and P4 present the SA phase with nematic phase. The melting temperature (tm), glass transition temperature (tg) and clearing point (ti) of monomers/polymers with terminal ethoxyl group are all proved higher than those with terminal ethyl group. Moreover, the monomers/polymers with the flexible spacer group tend to form smectic phase. TGA showed that the polymers P1-P4 all have wide LC temperature ranges and high thermal stability. References | Related Articles | Metrics