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15 July 2008, Volume 29 Issue 7 Previous Issue    Next Issue
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Minimax control based on statically structured uncertainty and its application in networks Qian, Xiao-Long (1); Jiang, Nan (1); Ren, Tao (1); Jing, Yuan-Wei (1) 2008, 29 (7):  913-916.  DOI: - Abstract ( 268 )   HTML   PDF (1519KB) ( 505 )   The problem of the minimax robust control of the statically structured uncertain time-delay systems is tackled. The sufficient conditions for the existence of minimax robust controller are derived aiming at the time-multiplying quadratic performance index by using Lyapunov function, with the convex optimization algorithm introduced in to solve the minimal upper bounds of performance index and the optimal parameter of minimax controller. The proposed algorithm is applied to the congestion control in TCP networks with time-delay factors so as to enable the queue length of router to converge at expected value faster with smaller oscillation in steady state. The simulation results reveal comparatively that the validity and superiority of the algorithm outperform other ones in application. References | Related Articles | Metrics

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Robust H∞ control of singular networked control systems with time-delay Liu, Li-Li (1); Zhang, Qing-Ling (1); Du, Zhao-Ping (1) 2008, 29 (7):  917-919.  DOI: - Abstract ( 229 )   HTML   PDF (920KB) ( 455 )   In this study what is to be controlled is the NCS (networked control system) of a singular control system. A discrete singular control system model with uncertainty and time-delay input is thus developed, where the sensor/actuator is time-driven with controller event-driven and the network-induced time-delay is shorter than a sampling cycle. The conditions of system stability are given by means of Lyapunov function and LMI, and a controller is designed satisfying both system stability and H∞ control state feedback to study the robust H∞ control. A simulation as example is given to verify the validity of the approach proposed. References | Related Articles | Metrics

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License plate character segmentation based on differencing projection and preferably segmented character Wu, Cheng-Dong (1); Fan, Yu-Quan (1); Zhang, Yun-Zhou (1); Liu, Meng (1) 2008, 29 (7):  920-923.  DOI: - Abstract ( 320 )   HTML   PDF (567KB) ( 1673 )   A new algorithm for license plate character segmentation based on differencing projection and preferably segmented characters is proposed. The level differencing projection is needed to correct skew character with level segmentation to implement simultaneously, thus reducing the complexity of the algorithm with improved positioning accuracy. Then the preferably segmented characters of a license plate can be found by combining vertical projection with connected domain algorithm to generate the sliding template for vertical segmentation of characters. In this way the problem of recognizing adherent and/or broken characters can be solved efficiently. Experimental results proved that the algorithm proposed has advantages of fast segmentation and preferably segmented characters, and self-learning ability and strong anti-jamming performance to recognize ambiguous characters on license plates. References | Related Articles | Metrics

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SVM-based multi-classifying algorithm for soft fault diagnosis of analog circuits Wang, An-Na (1); Qiu, Zeng (1); Wu, Jie (1); Qu, Fu-Ming (1) 2008, 29 (7):  924-927.  DOI: - Abstract ( 290 )   HTML   PDF (314KB) ( 1135 )   Based on the support vector machine (SVM) 1-v-1 and DDAG (decision directed acyclic graph) multi-classified algorithm, a new approach to the soft fault diagnosis of analog circuits is presented. The DDAG is a newly developed learning system on 1-v-1 basis in which the idea of directed acyclic graph of the graph theory is introduced to combine SVM subclassifiers together. Then, the SVM classification results by using different kernel functions are compared experimentally with each other. The simulation results show that the diagnosis accuracy is up to 99% if using the DDAG support vector machine algorithm. In this way the higher diagnostic accuracy is available. References | Related Articles | Metrics

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Optimal control based on real-coding genetic algorithm for fermentation process Guan, Shou-Ping (1); Zhang, Yan-Rui (1) 2008, 29 (7):  928-931.  DOI: - Abstract ( 259 )   HTML   PDF (1117KB) ( 539 )   Considering the complexity of the fermentation process of glutamic acid, a dynamic neural network model is developed for the fermentation process. To optimize simultaneously the operating variables based on the optimal object of the conversion rate to glutamic acid from carbohydrate, the real-coding genetic algorithm (RCGA) is applied to the multivariable optimal control for the whole fermentation process, thus finding out the optimal control trajectories of different operating variables. Considering the importance of fed-batch operation in the fermentation process, the starting/ending time of fed-batch operation are taken as variables and then optimized. Comparing the simulation results of the optimization of output rate of glutamic acid with the optimization proposed for the control of the fermentation process, the latter can improve greatly the conversion rate mentioned above with the output rate approximate to that the simulation results revealed. References | Related Articles | Metrics

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Improved CASVFMM algorithm and its application in scenery image analysis Gao, Li-Qun (1); Chang, Xing-Zhi (1) 2008, 29 (7):  932-935.  DOI: - Abstract ( 265 )   HTML   PDF (1588KB) ( 435 )   Introduces a newly improved method into scenery image segmentation, based on the CASVFMM (class-adaptive spatially variant finite mixture model) algorithm. By modifying the original potential function to strengthen the dependence of potential function on image pixel features, the segmentation continuity can be kept on with enhanced convergence stability. Thus, the segmented results obviously further conform to the corresponding image regions when the new algorithm is applied to the segmentation of images of different classes. Moreover, the structure expression of potential function is modified to a certain degree so as to accelerate the convergence rate of the algorithm and enhance the reasonableness of the segmented results when the algorithm comes into convergence. The simulation tests for scenery image analysis of the MIT standard image sets reveal comparatively that the newly improved algorithm is more efficient than the original CASVFMM and it is also available to other image analyses. References | Related Articles | Metrics

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Immune genetic algorithm the flexible job-shop scheduling problem Ma, Jia (1); Gao, Li-Qun (1); Shi, Gang (1); Li, Dan (1) 2008, 29 (7):  936-939.  DOI: - Abstract ( 520 )   HTML   PDF (196KB) ( 927 )   Analyzing the model of the flexible job-shop scheduling problem (FJSP), an immune genetic algorithm (IGA) is proposed to solve the problem. This algorithm preserves the random global search ability of simple genetic algorithm (SGA), and introduces the immune mechanism by which the necessary vaccine may be extracted with the scheduling vacinated so as to improve efficiently SGA's low ability for global search because of immature convergency and low local search ability. Thus, the IGA proposed can provide such ability and convergence rate that will implement the global optimum solution. Experimental results showed that the IGA can solve the FJSP effectively. References | Related Articles | Metrics

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Architecture of a solution to SPIT detection/prevention based on domain verification Wen, Ying-You (1); He, Guang-Yu (1); Luo, Ming (1); Zhao, Hong (1) 2008, 29 (7):  940-943.  DOI: - Abstract ( 256 )   HTML   PDF (496KB) ( 503 )   VoIP is an important application in next generation convergence network, and SIP is a key application protocol of VoIP. However, the SIP-based applications are facing to lots of challenges to information security, such as spam over Internet telephony (SPIT), since VoIP is sensitive to time delays and very difficult to understand the Internet messages correctly and rapidly and SPIT is hard to detect. To solve this problem, the architecture of the solution to SPIT detection/prevention based on domain verification is designed with the SIP amelioration in PULL mode and pre-classification cooperation both described for SPIT filtration/detection. The implementation and verification results reveal that the solution can provide an effective means for SPIT rejection. References | Related Articles | Metrics

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Division based on multidimensional eigenvector for web communities Ge, Xin (1); Zhao, Hai (1); Zhang, Xin (1); Li, Chao (1) 2008, 29 (7):  944-947.  DOI: - Abstract ( 237 )   HTML   PDF (920KB) ( 718 )   A spectral bisection algorithm based on multidimensional eigenvector is proposed for the division of web communities in large-scale complex networks, according to different community structures. It identifies those communities by way of the multidimensional eigenvectors of network's connection matrices, and then the effects of key parameters on the division results are analyzed through simulation so as to determine the parametrical values which make sure that the results of division are optimum. And the number of communities being identified can thus be confirmed by the factors integrating the threshold values of multidimensional eigenvector with the total number of communities in a network. The results of simulation done in a locally typical WWW evolution model demonstrated that the algorithm proposed enables the efficient division of many communities in relevant network where the clustering characteristics aren't so obvious. In addition, the algorithm is adaptable to the networks with various clustering characteristics, thus showing actually its high applicability to networks. References | Related Articles | Metrics

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Static grid dependent tasks scheduling based on reduced task-resource assignment graph Hao, Xian-Wen (1); Dai, Yu (1); Zhang, Bin (1); Chen, Ting-Wei (2) 2008, 29 (7):  948-951.  DOI: - Abstract ( 292 )   HTML   PDF (1041KB) ( 607 )   The dynamic and heterogeneous nature of grid resources is a great challenge to static scheduling strategies of dependent tasks. A new static scheduling model based on RT-RAG (reduced task-resource assignment graph) and algorithm are proposed which are more suitable for the grid heterogeneity and support unified scheduling/rescheduling process. The (re) scheduling problem based on the model is thus regarded as an optimization selection problem of RT-RAGs. The experimentation shows that the static scheduling algorithm has better adaptability to grid dynamic and heterogeneity and keeps greatly its superiority up in comparison to the dynamic one and it is also better than the AHEFT algorithm based on the DAG task graph model, especially in case of great resources heterogeneity. References | Related Articles | Metrics

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Weighted naive Bayes classification algorithm based on correlation coefficients Zhang, Ming-Wei (1); Wang, Bo (1); Zhang, Bin (1); Zhu, Zhi-Liang (2) 2008, 29 (7):  952-955.  DOI: - Abstract ( 490 )   HTML   PDF (157KB) ( 1924 )   Naive Bayes is based on an assumption of conditional independence and the assumption can scarcely be satisfied. A weighted naive Bayes classification algorithm based on correlation coefficients is proposed. By computing correlation coefficients between condition attributes and decision attribute, different condition attributes are weighted differently. Thereby, the classification performance can be improved effectively and simply. With a new method offered first to solve the weights of attributes on the basis of correlation coefficients discusses the operation principle of the algorithm, as well as its implementation. Simulation results of traditional China medicine paediatric pneumonia case data set and a variety of UCI data sets verify the effectiveness of this algorithm. References | Related Articles | Metrics

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Study on web service packaging to support dynamic service composition Wei, Wei-Jie (1); Zhang, Bin (1); Zhang, Xiao-Hong (1); Zhang, Ming-Wei (1) 2008, 29 (7):  956-959.  DOI: - Abstract ( 220 )   HTML   PDF (255KB) ( 730 )   How to package various web services that involve lots of complex operations so as to turn them into web service communities or web service clusters is discussed. Based on the web service log where various web services are indefinitely involved, a web service packaging method is proposed using the sequential-pattern mining technique. The method is implemented the way the technique is applied to mining the log to find out the serving function sequence which is then used to package various web service operations and form different functional services, thus providing web service communities/clusters. The web service communities/clusters thus packaged are available to support the dynamic service composition. References | Related Articles | Metrics

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Automated ranking of database fuzzy query results Meng, Xiang-Fu (1); Ma, Zong-Min (1); Yan, Li (1) 2008, 29 (7):  960-964.  DOI: - Abstract ( 429 )   HTML   PDF (1640KB) ( 565 )   There may be too many tuples in an answer after fuzzy query based on relational database. So, it is necessary to rank query results in accordance to user's needs. The ranking process is as follows. According to the degree of membership between tuple and fuzzy query, the tuples with different degree of membership in query results are differentiated from each other to form several membership classes. Then, the improved PIR (probability information retrieval) model and database workload are used to analyze the degree of correlation between the attribute values specified and unspecified in queries, thus ranking the tuples with the same degree of membership due to users' preferences. As a result, the DPR (degree of membership and probability ranking) process is proposed as an automated ranking approach for fuzzy query results, which has been proved to improve greatly the ranking quality of fuzzy query results through experiments and analysis. References | Related Articles | Metrics

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Automatic lung parenchyma segmentation on CT image Jia, Tong (1); Meng, Lu (1); Zhao, Da-Zhe (1); Wang, Xu (1) 2008, 29 (7):  965-967+975.  DOI: - Abstract ( 370 )   HTML   PDF (935KB) ( 1752 )   The automatic segmentation of lung parenchyma is one of the key techniques to the computer-aided diagnosis (CAD) system for lung cancer, emphysema and other lung diseases. A new automatic lung segmentation based on the 3-D CT image series is proposed integrating the adaptive gray-level threshold, region growing and math morphological algorithms together. And the graph search algorithm is used at specified layers to position accurately the narrow zone formed by the anterior and posterior lines connecting the left and right lung, thus overcoming efficiently the difficulties that the nodules at lung edge are easy to be missed and how to separate the left lung from right one. The experimental results of many sets of CT images verified that the technique proposed is highly exact and efficient for lung parenchyma segmentation. References | Related Articles | Metrics

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Channel estimation algorithm based on IEEE802.11a standard for MIMO-OFDM systems Wang, Han (1); Wang, Jin-Kuan (1) 2008, 29 (7):  968-971.  DOI: - Abstract ( 280 )   HTML   PDF (230KB) ( 453 )   For the channel estimation of MIMO-OFDM (multiple-input multiple-output-orthogonal frequency division multiplexing) systems based on IEEE 802.11a standard, a least square (LS) channel estimation scheme is proposed in time domain. The idea of this scheme is mainly to estimate the time-domain channel responses between transmitting and receiving antennas in accordance to the time-domain signals between transmitting and receiving ends. To make sure that the mean square error (MSE) is minimum in the LS channel estimation, an optimal scheme of pilot sequence is put forward, which requires less training symbols than conventional schemes and the number of those symbols will not increase with the increasing number of antennas. Moreover, the number of transmitting antennas is unlimited. In the scheme proposed all the pilot tones are required to be equipowered and the phase shift should be mutually orthogonal among the pilot sequences of different transmitting antennas. Simulation results show the effectiveness of the scheme proposed. References | Related Articles | Metrics

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An improved SLM technique to reduce PAPR of OFDM systems Zhang, Zhen-Chuan (1); Liu, Jiang-Ning (1); Yang, Ming-Hua (1); Song, Jun-Bao (1) 2008, 29 (7):  972-975.  DOI: - Abstract ( 271 )   HTML   PDF (1020KB) ( 500 )   SLM (selected mapping) is an effective algorithm to reduce peak-to-average power ratio (PAPR) of OFDM (orthogonal frequency division multiplexing) signal without distortion. But the conventional SLM technique has the disadvantage of the loss of data transmission rate due to the bandside information on phase sequence. An improved SLM technique is therefore put forward to reduce PAPR of OFDM system by way of embedding the information on phase sequence in the check symbols of OFDM data block, so as to avoid the loss of data transmission rate due to intentional bandside information transmission. Matlab simulation results showed that the improved SLM technique is better than the conventional one in reducing PAPR since no undue system complexity will happen. References | Related Articles | Metrics

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Research on CR process of Q390 HSLA heavy plate Du, Hai-Jun (1); Zhao, De-Wen (1); Du, Lin-Xiu (1); Liu, Xiang-Hua (1) 2008, 29 (7):  976-979+1003.  DOI: - Abstract ( 263 )   HTML   PDF (688KB) ( 860 )   The effect of controlled rolling (CR) process on the microstructure and mechanical properties of Q390 HSLA heavy plate was investigated by way of lab simulation test with process parameters optimized. The results showed that the 50 mm-thick heavy structural plates rolled with these parameters have high strength with better low-temperature toughness, i.e., Rm > 517 MPa, ReL> 382 MPa and the ductile-brittle transition temperature is in the range from -60°C to -70°C. Such properties are up to the standard GB/T1591-94. Holding the temperature below the complete solution temperature of Nb (C, N) makes for the improvement of the low-temperature toughness of steel. The number of rolling passes and finish rolling temperature from 830°C to 780°C have no remarkable effect on microstructure and properties of the plates when the total reduction of finishing pass and air cooling schedule remain unchanged. References | Related Articles | Metrics

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High precision short-term self-learning of rolling force in plate rolling process Zhu, Fu-Wen (1); Hu, Xian-Lei (1); Zhao, Zhong (1); Liu, Xiang-Hua (1) 2008, 29 (7):  980-983.  DOI: - Abstract ( 257 )   HTML   PDF (291KB) ( 501 )   At the present condition that most of China's plate mills have no gauge-meter, a high-precision self-learning model is therefore developed for the rolling force in plate rolling process without gauge-meter. With the natural logarithm applied to the division of layers of thickness, the division of deformation resistance parameters is carried out according to different layers of thickness to solve the self-learning of rolling force. Then, the method of exponential smoothing is introduced into the model to deal with the deformation resistance parameters of each and every layer of thickness. Based on the high precision spring model, a new approach is proposed that the workpiece thickness after last rolling pass or at exit is set as the target thickness so as to regress the deformation resistance parameters which have been rolled via all scheduled passes. The model has been applied to the process control system of a 3000 mm plate mill in China with favorable result obtained. References | Related Articles | Metrics

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Effects of different modes of nucleation on recrystallization process by cellular automata simulation Guo, Juan (1); Chen, Li-Yong (2); Zhao, Xian-Ming (1); Wu, Di (1) 2008, 29 (7):  984-987.  DOI: - Abstract ( 297 )   HTML   PDF (613KB) ( 1088 )   The improved site-saturated (ISS) mode and improved constant-rate (ICR) mode of nucleation were put forward on the basis of site-saturated (SS) mode and constant-rate (CR) mode of nucleation. A 2-D recrystallization model was developed to make crystal nuclei more uniform during recrystallization by coupling cellular automaton (CA) with Matlab. The effects of different modes of nucleation, neighborhood and boundary conditions on the kinetics of recrystallization, grain shapes and grain sizes were investigated. The results showed that the mode of nucleation affects greatly the kinetics but the neighborhood affects it unobviously. The final microstructures resulting from ISS and ICR modes present equiaxed grains and the grain size resulting from ISS mode is distributed most uniformly. References | Related Articles | Metrics

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Integral method to calculate magnetostatic field caused by irregular coil with rectangular section Lei, Hong (1); Wang, Xiu-Hua (1); He, Ji-Cheng (1) 2008, 29 (7):  988-991.  DOI: - Abstract ( 234 )   HTML   PDF (278KB) ( 505 )   Based on the Biot-Savart law and principle of vector superposition, an integral method was developed to calculate the magnetostatic field due to irregular coil of rectangular-section conductor. According to conductor shape, the DC coil is divided into two parts: Straight-line current elements and curved current elements, and the latter are fitted by several straight-line current elements. Then, the triple integral for all the straight-line current elements is simplified into simple integral equation to which the numerical solutions are given. To solve the integral equations quickly, some integral equations are derived for the magnetostatic field, including such shapes of current elements as trapezoidal prism, triangle prism and trapezoidal sheet. Numerical results show that the calculated values conform well with the theoretical values. References | Related Articles | Metrics

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Effects of Mn and Si on microstructure and mechanical properties of Al-Mg-Si-Cu alloy He, Li-Zi (1); Chen, Yan-Bo (2); Zhang, Hai-Tao (1); Cui, Jian-Zhong (1) 2008, 29 (7):  992-995.  DOI: - Abstract ( 224 )   HTML   PDF (631KB) ( 650 )   Effects of Mn and Si contents on microstructure and mechanical properties of the new-type Al-Mg-Si-Cu alloy were investigated by scanning electron microscopy (SEM), energy dispersive spectrum (EDS) and transmission electron microscopy (TEM). The results showed that the age-hardenability of the alloy decreases with increasing Mn content. When adding 0.35% Mn to the alloy, the ultimate tensile strength (Rm) changes little while the yield strength (ReL) and elongation (Ae) increase significantly. When adding 0.7% Mn to the alloy, both the strength and elongation decrease because the volume fractions of both coarse insolube constituents and fine dispersoids increase simultaneously. With the Si content increases, the age-hardenability of the alloy is improved with increasing Rm and decreasing ReL and Ae especially, the density of the age-hardening phase β″ precipitates increase. References | Related Articles | Metrics

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Oxidation behavior and wear resistance of biomedical Ti6Al7Nb alloy Guo, Ai-Hong (1); Cui, Wen-Fang (1); Liu, Xiang-Hong (2); Zhou, Lian (2) 2008, 29 (7):  996-999.  DOI: - Abstract ( 325 )   HTML   PDF (1490KB) ( 813 )   In order to improve the surface wear resistance of the biomedical titanium alloy Ti6Al7Nb, the oxidation behavior was studied in air at 500-800°C for 2-12 h and then its improved wear resistance was tested at room temperature. The testing results indicated that the oxidation rate is low at 500-600°C, and the oxidized surface hardness changes little in comparison with the hardness of the alloy matrix. When the temperature exceeds 750°C, the oxidation rate increases and the oxidation kinetics follows the parabolic rule. The oxides mainly consists of compact TiO2 with small amount of Al2O3. At 800°C the oxide particles grow rapidly, thus resulting in a loosened oxidized layer where the spalling effect frequently happens. Taking account of both the depth of hardened layer and oxidizing time, the optimum oxidization parameters are determined to be 750°C/8 h. By such an oxidization schedule, the surface hardness comes up to 1047 HV, especially the wear resistance is greater than 280 times that of original material. The mechanism of wear resistance improvement after oxidation is analyzed in detail. References | Related Articles | Metrics

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Viscosities of slags in CaO-Al2O3-CaF2-SiO2 system Dou, Zhi-He (1); Yao, Jian-Ming (1); Zhang, Ting-An (1); Niu, Li-Ping (1) 2008, 29 (7):  1000-1003.  DOI: - Abstract ( 253 )   HTML   PDF (395KB) ( 1091 )   The viscosities of different slags in CaO-Al2O3-CaF2-SiO2 system were measured by internal rotating cylinder method involving a spindle, and the high-temperature slag phases were analyzed by XRD. Then the viscous flow activation energies of the different slag samples were calculated. The results indicated that when the ratio of w (CaO)/w (Al2O3) is constant and the mass fraction of SiO2 in the slag system is lower than 8%, there is no obvious effect on the high-temperature viscosities of the slag samples. The viscosities of all the slags are lower than 0.5 Pa·s while the temperature is above 1490°C. When the mass fraction of SiO2 in slag comes up to 10%, the high-temperature viscosities of slags begin to decrease apparently. The viscosities of all the slags are lower than 0.2 Pa·s while the temperature is above 1440°C. The viscosities of slags decrease greatly with increasing SiO2 content because the original large meshed structure of slags is destroyed so as to reduce obviously the slag basicity. The viscous flow activation energies of the slag system CaO-Al2O3-CaF2-SiO2 tend to such a change that is compatible with the change in measured viscosities of slag samples. References | Related Articles | Metrics

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Intelligent optimization design for up-to-date machine products and its application Luo, Zhong (1); Liu, Hong-Yi (1); Tian, Hong-Hai (1); Wen, Bang-Chun (1) 2008, 29 (7):  1004-1007+1011.  DOI: - Abstract ( 264 )   HTML   PDF (307KB) ( 1227 )   Based on the achievements as shown in earlier works and the theory and methodology of intelligent control, an intelligent optimization design (IOD) is put forward for up-to-date machine products. With the intelligent machines taken as the object to investigate, what is to be implemented in IOD process include the working parameters, working process and conditions and fault diagnoses, etc. Analyzing the characteristics in designing up-to-date machine products, an IOD system is framed theoretically, involving its definition, implifications, objectives and basic theories. Taking a polishing robot which works in unstructured environment as example, the IOD process was studied experimentally, and the experimental results revealed that it can raise the level of intellectualization and improve the design quality of products in an all-round way. References | Related Articles | Metrics

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Simultaneously kinematical and dynamical optimizations of redundant robots Guo, Da-Zhong (1); Liu, Hong-Yi (1); Zhang, Wei (1); Li, Li-Na (1) 2008, 29 (7):  1008-1011.  DOI: - Abstract ( 251 )   HTML   PDF (308KB) ( 670 )   Kinematical optimization of redundant robots is proposed to be simultaneous with dynamical optimization according to the characteristics of their redundancies. The joint torques of a redundant robot are rationally distributed dynamically by the weighted least norm algorithm of acceleration, while the avoidability of singular positions of a redundant robot is optimized kinematically by gradient projection algorithm, and an algorithm of simultaneous solution is proposed to both kinematical and dynamical optimization. Simulation results showed that the algorithm is able to not only distribute rationally the joint torques but also optimize kinematically the motion of robots, thus implementing the simultaneous optimization of the redundant robots kinematically and dynamically. References | Related Articles | Metrics

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Reliability-based sensitivity design of mechanical components depending on incomplete information on probability Yang, Zhou (1); Zhang, Yi-Min (1) 2008, 29 (7):  1012-1015.  DOI: - Abstract ( 266 )   HTML   PDF (1922KB) ( 933 )   Based on the stochastic perturbation and fourth moment techniques, the theory of reliability design is combined with sensitivity analysis to develop a mathematical model for reliability-based sensitivity of mechanical components. Such a reliability-based sensitivity depending on the incomplete information on probability is extensively discussed, and a numerical method for the reliability-based sensitivity design is correspondingly presented, with a mathematical evaluation method given in which the reliability of mechanical components changes with design parameters. Furthermore, how the reliability-based sensitivity changes and the effect of design parameters on the reliability of mechanical components are studied with ideal numerical design results obtained. The method proposed thus provides the reliability design of mechanical components with a theoretical reference. References | Related Articles | Metrics

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Semi-analytical analysis about stability of dual-disc rub-impact rotor Li, Dong (1); Yuan, Hui-Qun (2); Zhu, Xiang-Zhe (1); Zhao, Xiao-Yu (2) 2008, 29 (7):  1016-1019.  DOI: - Abstract ( 268 )   HTML   PDF (392KB) ( 478 )   A dynamic model was developed with kinematic differential equation derived for a dual-disc over-hung rotor system with rub-impact fault. The stability of the system and stability regions were studied by setting up nonsingular linear transform matrix and by use of Jacobi matrix in combination with the theory of Routh Hurwitz. Then, the effects on the stability regions of the system were discussed with relevant parameters. The results showed that such a semi-analytical method is available to get the stability regions and their corresponding rotational speed and damping ratio. Simultaneously, it was found that the contact clearance and friction coefficient both affect the stability regions clearly, and the steady-state periodic solution can reflect the system response. The results as above will provide a theoretical reference for safe running in actual operation. References | Related Articles | Metrics

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Simulation and evaluation of vehicle's impact Zhao, Guang-Yao (1); Fan, Xin-Hua (2); Di, Jian-Wei (1); Fu, Dong-Yu (3) 2008, 29 (7):  1020-1024.  DOI: - Abstract ( 260 )   HTML   PDF (722KB) ( 1152 )   The frontal and side impact of a car were simulated and the whole body response and injury of passanger thus caused were evaluated on computer. FEA models were developed for the whole car in which the space occupied by the 50th percentile Hybrid III dummy and safety-belt restraint system. According to the basic principle of dynamic non-linear FEM, an equation describing the impact process and FEA discretization equation are given. The frontal and side impact of the integrated system of the whole car is numerically simulated and analyzed by the software LS-DYNA, then the time curves of displacement, speed and acceleration for car during impact are solved, as well as the effect of the main energy-absorbing parts, the energy/force transmitting path and the injury level of dummy due to impact. Simulation results revealed that such a simulation will predict not only the crashworthiness of the car but also the passengers' response and injury level comparatively accurately during its collision. It will be of significance to reducing the number of impact tests and expediting the R and D of new type/model of cars. References | Related Articles | Metrics

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Dynamic simulation of temperature field during friction stir welding Wang, Lei (1); Xie, Li-Yang (1); Zhang, Dan (2); Li, Bing (1) 2008, 29 (7):  1025-1028.  DOI: - Abstract ( 478 )   HTML   PDF (515KB) ( 1083 )   A simple and visual calorigenic model was developed via FEM for FSW (friction stir welding) process, which was applied to the dynamic simulation of temperature field in the process. Then, the thermal cycling curves at different time and different positions are given to make sure of how the temperature field is space-time distributed with different welding parameters. The results indicated that the maximum welding temperature is 496.5°C, i.e., lower than the melting point of Al-alloy. The temperature at different positions along the welded seam increases rapidly from its initial value to about 500°C then reverts slowly to the initial one. The nearer the position to the welded seam, the quicker the temperature rise and the higher the maximum temperature available. The temperature field is affected greatly by welding parameters in FSW process. References | Related Articles | Metrics

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Analysis of multitask reliability for manufacturing systems based on ESPN Zhang, Jun-Yi (1); Xie, Li-Yang (1); Wang, Zheng (1) 2008, 29 (7):  1029-1032.  DOI: - Abstract ( 202 )   HTML   PDF (1266KB) ( 525 )   Taking a manufacturing unit having three machines for simultaneous and multitask machining jobs as example, extended stochastic Petri nets (ESPN) is introduced to develop a multitask reliability model adaptable to such manufacturing systems that process time are arbitrary distributions. In addition, the model rises above the difficulty that the time-dependent dynamic behavior in manufacturing process cannot be involved by way of conventional reliability modeling. For the reliability model of complex manufacturing systems, the concept of moment generating function is introduced in the behavior expression so as to obtain the multitask reliability of the whole system by computing the transfer functions of the model without generating a reachability graph. In this way the performance in service of the whole manufacturing system for multitask machining jobs can be perceived clearer. References | Related Articles | Metrics

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An image denoising algorithm based on neighborhood noise evaluation Liu, Wei-Wei (1); Yan, Yun-Hui (1); Sun, Hong-Wei (1); Wang, Yong-Hui (1) 2008, 29 (7):  1033-1036.  DOI: - Abstract ( 256 )   HTML   PDF (365KB) ( 789 )   The loss of information on image details was often found in image denoising process if using the conventionally typical method of impulse noise filtering, which resulted in blurred images. Based on local similarity analysis and neighborhood noise evaluation, a new image denoising algorithm is proposed to analyze the local similarities between all pixels in an image so as to determine the outline and noise of an image. Then, the noises are detected through neighborhood impulse noise evaluation so as to enable the algorithm to just process noise pixels with the pixels of image outlines kept unchanged. In this way, the accuracy of noise detection can be improved more efficiently with image details well preserved. Experimental results showed that the new algorithm outperforms other prior-art methods in suppressing impulse noise and detail preservation, thus offering a new filter applicable to image processing. References | Related Articles | Metrics

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Supply chain operation modeling based on object-oriented Petri net Tang, Liang (1); Yu, Tian-Biao (1); Ding, Jun-Mei (1); Wang, Wan-Shan (1) 2008, 29 (7):  1037-1040.  DOI: - Abstract ( 275 )   HTML   PDF (963KB) ( 643 )   The object-oriented Petri net (OPN) was used to analyze the operation of supply chain in the circumstance of networked manufacturing. In this way the rules of the computer integrated manufacturing open system (CIMOS) were employed to model the operation of manufacturing supply chain. Describing what operations are needed in such a supply chain, the operation mode of supply chain supported by the networked manufacturing center was presented. Then, the OPN model for each and every object was developed to get the P-invariant by which such system defects as deadlock, overflow and conflict can be analyzed. With a manufacturer taken as example, the analysis of OCN-related matrix and P-invariant proved that the model thus designed has favorable performance. References | Related Articles | Metrics

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Measurement of residual stress distribution in pre-stretched thick aluminum plate Zhang, Yan-Cheng (1); Gong, Ya-Dong (1); Sun, Wei-Tang (1); Zhu, Li-Da (1) 2008, 29 (7):  1041-1044.  DOI: - Abstract ( 273 )   HTML   PDF (317KB) ( 773 )   Based on the theory of elastic mechanics, the improved formulae of strain layering-peeling are deduced to adapt for the two strains, i.e., the tensile and compressive strains due to relevant stress distributions in pre-stretched thick aluminum plate. To verify the exactness of the method, the known initial internal stresses are applied to specimen by FEM, and the process of layering peeled material is simulated using the Live and Death technique to solve the deep layer stress by way of substituting the strains thus obtained into the VB data processing system based on the deduced formulae. Comparing the solved stresses with known initial stresses, it is found that both coincide well with each other. The result reveals that the method proposed can be used to measure the residual stresses in pre-stretched thick aluminum plate. References | Related Articles | Metrics

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Modal analysis and testing of a certain white bodywork Yang, Ying (1); Zhao, Guang-Yao (1); Meng, Fan-Liang (1) 2008, 29 (7):  1045-1048.  DOI: - Abstract ( 418 )   HTML   PDF (972KB) ( 1835 )   The modes of vibration of a certain saloon car's white bodywork was investigated. According to FEM and static/dynamic theory, a FEA model of the white bodywork was developed describing reasonably its welding points with the software HyperMesh. A modal simulation was done to analyze the white bodywork by the software MSC. Nastran, so as to get the relationship between its natural frequency and corresponding modes of vibration of different orders. In test a fixed resonator was used to conduct a single-point resonance for the white bodywork, with relevant response signals picked up at multiple points to process and analyze them, thus obtaining the relationship between the natural frequency of the white bodywork and corresponding modes of vibration. Comparing the results of the simulation with that of test, the validity of the FEA model is verified. A new method is therefore proposed to determine the position where the maximum elastic deformation takes place by the strain energy distribution of the vibration modes of different orders. It can be used to improve the local rigidity of the bodywork. The modal analysis of white bodywork by FEA model is also important to improving the dynamic properties of bodywork, optimizing its structure, shortening R and D period and saving costs. References | Related Articles | Metrics

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Ti-N-C films deposited by MF unbalanced magnetron sputtering process with twin targets Zhang, Yi-Chen (1); Ba, De-Chun (1); Yan, Yun-Hui (1); Ma, Sheng-Ge (2) 2008, 29 (7):  1049-1052.  DOI: - Abstract ( 235 )   HTML   PDF (379KB) ( 750 )   Introducing the Hall ion source assisted MF unbalanced magnetron sputtering process with twin targets, the Ti/TiN/Ti (C, N) anti-wear hard films were deposited on such substrates as stainless and high-speed steels through changing the working ambience, bias mode, sputtering current and ion beam assisted current. The color, crystal structure and film's bonding strength are all tested and analyzed. The results showed that the color of films is highly sensitive to testing ambience, and the slight change in working ambience enables the film surface color to change greatly. No obvious preferred orientation is found in the crystal structure of the films prepared within the normal intake range of reaction gas and low bias voltage of substrate. But, a trend of preferred orientation of crystal plane will take place if the intake of reaction gas is excessive. The effect of unbalanced magnetron process on the preferred orientation of film's crystal structure is not great. And the bonding strength of films can be increased efficiently if applying Hall current in the film deposition process. References | Related Articles | Metrics

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Directional coarsening trend of γ'-grains of nickel-base single crystal super-alloy under load in [111] orientation Xia, Yong-Fa (1); Jin, Yu-Long (1) 2008, 29 (7):  1053-1056.  DOI: - Abstract ( 237 )   HTML   PDF (1507KB) ( 513 )   According to the service conditions and structural characteristics of nickel-base single crystal super-alloy, the trend of directional coarsening of γ'-grains under the load in the [111] orientation was systematically studied experimentally. The results showed that no trend of any directional coarsening of γ'-grains occurs but they are just growing isotropically by capillarity. FEM calculation showed that the applied stress makes the stress distribution in various matrix channels strongly anisotropic. However, all the channels extended in coarsening process are those where the Von Mises stress is high, while all the channels narrowed gradually are those where the Von Mises stress is low. Such results illustrated that the plastic deformation and its non-uniform distribution play a significant role. References | Related Articles | Metrics

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Ground state properties of mixed spin σ = 3/2 and S = 2 ising system in comparison with that of σ = 3/2 and S = 5/2 ising system Miao, Hai-Ling (1); Wei, Guo-Zhu (1) 2008, 29 (7):  1057-1060.  DOI: - Abstract ( 231 )   HTML   PDF (1099KB) ( 508 )   The ground state properties of mixed spin σ = 3/2 and S = 2 Ising system was studied comparatively with that of mixed spin σ = 3/2 and S = 5/2 Ising system. According to the principle of the lowest energy, the ground state phase diagram and ground state energy were obtained by comparing the ground state energy of various possible forms of ground states with each other. In the mixed spin σ = 3/2 and S = 2 Ising system there is no disordered phase, while in the mixed spin σ = 3/2 and S = 5/2 system only the ordered phase is found. The ground state energy of both systems increases linearly with the increasing values DA/(zJ) and DB/(zJ), but the slopes are found not the same in different regions. The greater the values of DA/(zJ) and DB/(zJ), the slower the increase in ground state energy. Furthermore, there is a concurrent point (0.5, 0.5) of four forms of ground states in the mixed spin σ = 3/2 and S = 2 Ising system, but the point is not found in the mixed spin σ = 3/2 and S = 5/2 system. References | Related Articles | Metrics

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Thermal and mechanical properties of PHBV/CaCO3 blends Xu, Xiao-Xu (0); Zhang, Bao-Yan (0); Fu, Lu-Xiang (0) 2008, 29 (7):  1061-1064.  DOI: - Abstract ( 238 )   HTML   PDF (907KB) ( 533 )   PHBV/CaCO3 blends were prepared by way of banburying, and the thermal and mechanical properties of the blends thus prepared were investigated by means of differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), tensile tester and rotary rheometer. The results showed that the atmosphere does not affect the thermal stability of PHBV blends, and a certain amount of CaCO3 nanoparticles as additive hardly affect the glass transition temperature and thermal decomposition temperature. Moreover, the blends have better toughening effect when the content of CaCO3 is 5%. References | Related Articles | Metrics