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15 March 2009, Volume 30 Issue 3 Previous Issue    Next Issue
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Backstepping-based sliding mode control algorithm for congestion control in DiffServ networks Zhang, Nan-Nan (1); Jing, Yuan-Wei (1); S.-Y., Zhang; M.-Y., Yang 2009, 30 (3):  305-308.  DOI: - Abstract ( 306 )   HTML   PDF (301KB) ( 583 )   Two typical services of DiffServ network are analyzed and controlled, i.e., the premium and assured traffic services. Based on the theory of nonlinear fluid flow, a DiffServ network model was developed to design a new adaptive sliding mode controller. The model was transformed into the form where all parameters are feedback strictly. Then, the backstepping procedure was employed to complete the design. The adaptive backstepping sliding mode controller designed in this way has an ideal regulation effect of buffer queue length on unknown system dynamics and uncertain disturbances and constricts them. In such an ideal sliding mode, the asymptotic stability is available. The effectiveness of the control scheme was verified by simulation results. References | Related Articles | Metrics

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Slip controller based on RBF neural network for automotive ABS Mao, Yan-E (1); Jing, Yuan-Wei (1); Cao, Yi-Peng (2); Zhang, Si-Ying (1) 2009, 30 (3):  309-312.  DOI: - Abstract ( 324 )   HTML   PDF (494KB) ( 1124 )   The slip controller based on RBF neural network was designed for automotive anti-lock braking system (ABS) to meet the requirements that the braking process should be fast and robust and the chattering due to conventional slip control should be alleviated as possible. Moreover, the robustness of adaptive control system simply based on neural network can be improved to some extent if using the slip controller we designed. The simulation using the software MATLAB/SIMULINK was done to investigate vehicles' braking effects on dry road pavement, thus verifying the effectiveness and feasibility of the control scheme proposed. References | Related Articles | Metrics

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Anti-synchronization between hyper-chaotic Chen system and hyper-chaotic Lorenz system Cai, Na (1); Jing, Yuan-Wei (1); Jiang, Nan (1); Zhang, Si-Ying (1) 2009, 30 (3):  313-317.  DOI: - Abstract ( 406 )   HTML   PDF (443KB) ( 856 )   The anti-synchronization problem between two different hyper-chaotic systems is studied. Two different control methods are used to design proper controllers for the response system to realize the anti-synchronization. A special antisymmetric structure is proposed, and based on it, the direct design method is given to design the anti-synchronization controller. To prevent the controller design by active control method from indiscrimination, a simplified judging method of negative definite matrix is introduced to give the anti-synchronization active design of controller. A numerical simulation was done for the anti-synchronization between hyper-chaotic Chen system and hyper-chaotic Lorenz system, and the results verified the effectiveness of both the direct design method and active control method. References | Related Articles | Metrics

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Stability of the singular networked control systems with time-delay and data packet dropout Liu, Li-Li (1); Zhang, Qing-Ling (1); Du, Zhao-Ping (1) 2009, 30 (3):  318-320+344.  DOI: - Abstract ( 221 )   HTML   PDF (182KB) ( 520 )   To solve the problems of data packet dropout and network-induced time delay, the networked control system for something as a singular system is modeled to become an asynchronously dynamical discrete system if the relevant sensors and controllers/actuators are time-driven and event-driven, respectively. Then, by Lyapunov function and linear matrix inequality (LMI), the sufficient conditions are given to make the singular networked control system exponentially stable. With the closed-loop networked control system exponentially stabilized, the state feedback control law which can make the system exponentially stable is also obtained by solving some LMIs. An example is given to illustrate the effectiveness of the proposed method. References | Related Articles | Metrics

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On-line leak-detection method for pressure time series of oil pipeline Liu, Jin-Hai (1); Zhang, Hua-Guang (1); Feng, Jian (1) 2009, 30 (3):  321-324.  DOI: - Abstract ( 299 )   HTML   PDF (403KB) ( 1055 )   An on-line leak-detection method based on pressure time series of oil pipeline is proposed for leakage. Reconstructing the phase-space of pressure time series of oil pipeline, the numbers of embedding dimensions and embedding computation delays are given as 5 and 4, respectively. Taking the 5-D reconstructing vectors as the input to the neural network model, the proposed method is used to train the network off-line so as to obtain the initial parameters and, then, train the model on-line to implement the on-line modification of the weighted values in the network model, thus realizing the real-time detection of leak. The datasets measured in simulation revealed that the method proposed is available to detect pressure faults efficiently. References | Related Articles | Metrics

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Distributed grid location estimation based on Euclidean distance Wu, Cheng-Dong (1); Jia, Zi-Xi (1); Zhang, Yun-Zhou (1); Huang, Yue (1) 2009, 30 (3):  325-328.  DOI: - Abstract ( 280 )   HTML   PDF (391KB) ( 1103 )   Based on the Euclidean distance, a distributed grid location estimation was proposed as follows to improve the original estimation. Comparing the information on hop count between the measured nodes and beacon nodes, the quick self-locating of measured nodes was implemented. How the Euclidean distance is used to substitute for the matched threshold so as to improve the accuracy of location and how to use the distributed computation to save the energy consumption of network were studied, then the Dijkstra algorithm was used to compute the minimum hop count between nodes. Simulation results showed that the improved estimation can locate the nodes quickly and accurately with energy saving at low cost especially with the high robustness provided. References | Related Articles | Metrics

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Clearance-based method of designing and solving structural parameters of steel wire rope Pang, Ha-Li (1); Du, Su-Zhong (2) 2009, 30 (3):  329-332+353.  DOI: - Abstract ( 318 )   HTML   PDF (566KB) ( 804 )   A clearance-based method of designing and solving structural parameters of steel wire rope was proposed. Considering twisting direction of strands and wires, producing technique and structure of rope in design process, an approach of stepwise nearness was adopted to optimize the lay of wires, clearances between wires and strands and other structural parameters. The proposed method avoids disadvantage of traditional design method that does not consider the producing technique constraints and, as a result, the design may not accord with practice. An actual design example of a complicated steel wire rope was presented to illustrate the effectiveness of proposed method, and design results accord with practice and can guide production effectively. References | Related Articles | Metrics

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Translation-invariant de-noising of body fluttering signal based on improved threshold function Jin, Jing-Jing (1); Wang, Xu (1); Wu, Xue (1); Yang, Dan (1) 2009, 30 (3):  333-336.  DOI: - Abstract ( 272 )   HTML   PDF (1358KB) ( 759 )   Body fluttering signal is weak and often involves a lot of noise arising from instrument and environment. The translation-invariant de-noising method based on improved threshold function was therefore studied to de-noise the body fluttering signal. A proper wavelet base suitable to body fluttering was selected, and the estimate method of noise variance on each and every scale after wavelet decomposition was analyzed. In addition, the capability and characteristics of improved threshold function were analyzed, based on which the translation-invariant de-noising method was applied to de-noising body fluttering signal with relevant algorithm given to implement the de-noising process. Compared the de-noised results by both hard and soft threshold functions, the body fluttering signal presents smooth wave shape with no attenuated amplitude at characteristic points. The comparison results of power spectral density between translation-invariant de-noised signal and original body fluttering signal revealed that the former can keep the characteristics of original body fluttering signal when de-noising. References | Related Articles | Metrics

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Query processing approach based on buffer management in wireless sensor networks Li, Fang-Fang (1); Li, Chuan-Wen (1); Yu, Ge (1) 2009, 30 (3):  337-340.  DOI: - Abstract ( 252 )   HTML   PDF (371KB) ( 909 )   A query processing approach based on buffer management is proposed for a mass of periodic queries and ad hoc queries, which are both expected to be supported simultaneously in soft real-time applications in the large-scale sensor networks. With a data storage structure designed in the network, a proper execution region is provided for query processing as a buffer where the nodes are able to map the data of remote nodes and the queries and relevant data both concur, so as to process queries in time. Based on queuing theory, a management model is developed for the queries in the buffer with its optimization scheme designed, thus giving the appropriate width and position of the buffer to design the algorithm of query processing. Test results showed that the approach proposed is efficient to the decrease in query missing rate and energy-saving. References | Related Articles | Metrics

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Medical image retrieval based on wavelet texture feature Zhang, Yi-Fei (1); Xiu, Fei (1); Bao, Yu-Bin (1); Yu, Ge (1) 2009, 30 (3):  341-344.  DOI: - Abstract ( 374 )   HTML   PDF (247KB) ( 1371 )   To eliminate the gap between the high-level semantics and the low-level features of images, a new method based on co-occurrence matrix is proposed to extract image texture feature. Combining the image's statistical features in the frequency domain with its spatial distribution attributes, the method extracts the local frequency information on image by wavelet transforming. Then the image's global structural characteristics are integrated with its wavelet properties to construct the wavelet-gray co-occurrence matrix so as to extract the image's texture features for the retrieval of medical images. The results of comparative test showed that the wavelet-gray co-occurrence matrix is superior in medical image retrieval in comparison to other ways where the co-occurrence matrix is separated from wavelet features in applications. References | Related Articles | Metrics

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Partition-based algorithm for 2D-skyline monitoring in wireless sensor networks Xin, Jun-Chang (1); Wang, Guo-Ren (1); Zhang, Xiao-Yi (1); Zhao, Yue (1) 2009, 30 (3):  345-348.  DOI: - Abstract ( 456 )   HTML   PDF (259KB) ( 546 )   The algorithms of skyline queries in conventional database as shown in earlier works are inapplicable to the wireless sensor network environment. A partition-based 2D-skyline (P2S) monitoring algorithm is therefore presented, which takes advantage of skyline query to partition off the 2D plane and allocate a rectangular area as the filter to each and every node so as to reduce data transmission in the network, thus decreasing the energy consumption. The experimental results showed that the P2S algorithm can effectively filter most of the unnecessary data updates and reduce the number of messages transmitted from nodes to base stations to make reasonable use of the limited power supply of nodes and prolong greatly the lifetime of wireless sensor network. References | Related Articles | Metrics

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Knowledge-based approach to fuzzy querying over relational database Meng, Xiang-Fu (1); Ma, Zong-Min (1); Yan, Li (1); Zhang, Xiao-Yan (1) 2009, 30 (3):  349-353.  DOI: - Abstract ( 294 )   HTML   PDF (274KB) ( 677 )   A new knowledge-based approach to fuzzy query translation for a database is proposed to overcome the shortcoming of conventional DBMS (database management system) that does not support the fuzzy queries over any of databases. Based on the theory of fuzzy sets, the formation conditions for fuzzy queries over database are described. Then an approach is presented to leverage the membership functions, domain knowledge and α-cut operation of fuzzy numbers for fuzzy query translation. The importance of query criteria and users' preferences are taken into consideration when a fuzzy query is expanded and translated. Neither SQL language nor the database engine requires modification to implement fuzzy queries by the approach proposed, thus enabling users to improve their interaction with the system. References | Related Articles | Metrics

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Grid job assignment scheme based on auction and immune optimization Wang, Xing-Wei (1); Cai, Ying (1); Tong, Cheng-Cheng (1); Huang, Min (1) 2009, 30 (3):  354-356+372.  DOI: - Abstract ( 252 )   HTML   PDF (1415KB) ( 510 )   A grid job assignment scheme is proposed on the basis of the microeconomic method and swarm intelligence algorithm. With the grid resource management model developed and the classical auction model improved, the grid resource is priced via the improved auction procedure. An affinity degree function is introduced in order to seek for the optimal job assignment solution through such steps as antibody generation, selection, clone extension, immunological memory, self-adaptive mutation and adjustment, all are based on the improved immune optimization algorithm with both time and cost balanced in consideration. A GridSim-based simulation was implemented for the proposed scheme, and the results are compared with other two existing schemes. It follows that the performance of the proposed scheme is superior to the other two. References | Related Articles | Metrics

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Flow-based cross-layer forwarding algorithm for concurrent multipath Han, Lai-Quan (1); Wang, Jin-Kuan (1); Wang, Cui-Rong (1) 2009, 30 (3):  357-360.  DOI: - Abstract ( 204 )   HTML   PDF (765KB) ( 752 )   With the rapid proliferation of computer virtualization, emerging programmable router and increasingly improved quality of service (QoS) requirement, the concurrent multipath (CMP) becomes a hotspot in research field and gets increasing interest recently. Based on the analysis of flow relationship and forwarding granularity, a flow-based CMP cross-layer forwarding (FCCF) algorithm is proposed, and compared with the technologies of single-path forwarding and random CMP forwarding. The algorithm is able to process TCP header in IP network layer and compute the Hash value of the flow to solve the disorder problem of CMP. NS2 simulation revealed that the algorithm comes up to a better forwarding performance with higher bandwidth utilization. References | Related Articles | Metrics

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Fast diversity-multiplexing tradeoff algorithm based on adaptive modulation and power allocation Xie, Zhi-Bin (1); Wang, Jin-Kuan (1); Gao, Jing (1); Wang, Yun (1) 2009, 30 (3):  361-364.  DOI: - Abstract ( 266 )   HTML   PDF (1458KB) ( 564 )   The characteristics of bit error rate (BER) of a multi-antenna system are analysed. Because the earlier works put stress on designing the schemes to extract either maximal diversity gain or maximal spatial multiplexing gain, but failed to take full advantage of the performance of the system, a multiple-input multiple-output (MIMO) diversity-multiplexing tradeoff algorithm is proposed on the basis of adaptive allocation of code bit and power and, further, an algorithm with less computational complexity is given. Based on the BER criterion, the proposed algorithm is chosen in an appropriate mode according to the instantaneous channel state information (CSI) and makes full use of the two gains as above to serve well the anti-interference function with less computational complexity provided to adapt to practical applications. Simulation results indicated that the performance of the proposed algorithm is superior to the conventional one with high effectiveness and feasibility. References | Related Articles | Metrics

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Transdomain authentication and key agreement mechanism for SIP communications Luo, Ming (1); Wen, Ying-You (1); Zhao, Hong (1) 2009, 30 (3):  365-368.  DOI: - Abstract ( 343 )   HTML   PDF (173KB) ( 705 )   Nowadays the problem how to authenticate mutually and then agree on a session key has not efficiently been solved in SIP communications. An identity-based cryptosystem key agreement protocol between different domains is therefore designed and based on it, an authentication and key agreement mechanism are proposed for SIP communications. The mechanism proposed rises above the difficulties of unilateral authentication and pre-sharing key under conditions of HTTP digest authentication, thus eliminating the deficiencies due to S/MIME protocol that is a certificate-based authentication without key agreement function provided. Moreover, it enables the SIP entities in different domains to use different system parameters. The security analysis and its implementation reveal that this mechanism can implement the transdomain bilateral authentication between SIP entities and provide the key agreement function for confidential transmission of subsequent media streaming and, simultaneously, meet the performance requirements of SIP communications. References | Related Articles | Metrics

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Temperature model of hot strip finishing mills in tandem and its self-learning strategy Li, Hai-Jun (1); Shi, Li-Jun (2); Xu, Jian-Zhong (1); Wang, Guo-Dong (1) 2009, 30 (3):  369-372.  DOI: - Abstract ( 315 )   HTML   PDF (342KB) ( 1196 )   The temperature model of hot strip finishing mills in tandem was discussed, as well as the conventional self-learning strategy relevant to it. To rise above the defects in the conventional self-learning strategy, a zonal compensation method is applied to temperature model self-learning, where the finish rolling temperature errors are assigned to each cooling zone according to certain temperature distribution coefficients, which can be readjusted according to the rolling force of each and every stand. In such a way the predicted precision of not only the rolling force but also the finish rolling temperature can be improved well. The new temperature model self-learning strategy has successfully been applied in Tianjin RockCheck 750 mm hot strip plant. References | Related Articles | Metrics

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Mathematical model of a continuous annealing simulator for cold rolled strips Li, Jian-Ping (1); Hua, Fu-An (1); Wang, Wen-Le (1); Wang, Guo-Dong (1) 2009, 30 (3):  373-376.  DOI: - Abstract ( 253 )   HTML   PDF (292KB) ( 1108 )   To improve the temperature control accuracy of a continuous annealing simulator, a mathematical model was developed for the process control of the simulator on the basis of the theories of heat transfer and adaptive control. According to the data acquired in experiments, the relevant annealing parameters were modified in real time, and such parameters as heating current and cooling gas flowrate were readjusted and compensated dynamically in either heating or cooling process, thus ensuring the accuracy of temperature control. In application the model showed that the temperature control accuracy is ±10°C, i.e., available to meet the requirements for process control of the annealing simulator. References | Related Articles | Metrics

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Direct growth behavior of spherical grains in vibration process of sloping corrugated plate Xie, Feng-Guang (1); Guan, Ren-Guo (2); Li, Jiang-Ping (2); Liu, Xiang-Hua (1) 2009, 30 (3):  377-380.  DOI: - Abstract ( 254 )   HTML   PDF (456KB) ( 733 )   Metalloscope and energy spectrometer were used to investigate the behavior of solidification and growth of Al-6Si-2Mg alloy. The results showed that in the vibration process of sloping corrugated plate, the alloy solidification process is accompanied with non-dendritic structure evolution and direct growth behavior of spherical grains when the molten alloy is flowing along the plate surface. The sloping plate can provide sufficiently the under-cooling for nucleation and lay a foundation for heterogeneous nucleation to form lots of nuclei of crystal internally and on the sloping plate surface, thus causing the melt to nucleates eruptively. Under the action of both metal flow and vibration, the nuclei formed on the sloping plate surface can move freely and disperse into the melt, and they are able to maintain the direct growth in spherical shape in the homogeneous composition and temperature fields. Both eruptive nucleation and direct growth of spherical grains are one of the important mechanisms of grain refining and spheroidization of the alloy under conditions of vibrating the sloping corrugated plate. References | Related Articles | Metrics

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Effects of w(MgO)/w(SiO2) on structure and flexural strength of glass ceramics made from converter slag Zhang, Da-Yong (1); Shi, Pei-Yang (1); Jiang, Mao-Fa (1) 2009, 30 (3):  381-383+404.  DOI: - Abstract ( 278 )   HTML   PDF (1017KB) ( 527 )   To reduce the environmental hazard resulting from converter slag, the glass ceramics in SiO2-CaO-MgO-Fe2O3 system were prepared using the slag through melting process. The effect of the ratio w(MgO)/w(SiO2) on structure and flexural strength of the glass ceramics was investigated by DTA, SEM and XRD. The results showed that glass transition temperature and crystallization peak temperature of the ceramics changed little with the increasing value of the ratio, but its phase composition changed greatly, i.e., from augite to diopside with grain size gradually decreased and crystals uniformly distributed. Meanwhile the flexural strength of glass ceramics increased. References | Related Articles | Metrics

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Resource depletion and environmental impact in evolution of alkali carbonate process for borax preparation Xue, Xiang-Xin (1); Qian, Hong-Wei (1); Jiang, Tao (1); An, Jing (1) 2009, 30 (3):  384-387.  DOI: - Abstract ( 254 )   HTML   PDF (746KB) ( 526 )   Through the IE (industrial ecology) matrix system evaluation method resources depletion and environmental impact in the evolution of alkali carbonate process for borax preparation were studied with the relevant calculation model improved and relationship between factor (stage) and environmental effect plotted. The results showed that a chemical plant is as a whole running in an environmentally friendly way to a certain extent if taking the alkali carbonate process as its technologic strategy to prepare borax. It follows that there will be a better technologic framework with a potential room for further development in the later-period industrial environment planning to actively build and perfect an eco-industrial park for borax industry, where all plants will be running in such a way. References | Related Articles | Metrics

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Mathematical model of decarburization in UHP electric arc furnace with hot metal charged Jiang, Zhou-Hua (1); Ruan, Xiao-Jiang (2); Li, Yang (1); Li, Jing-She (2) 2009, 30 (3):  388-391.  DOI: - Abstract ( 298 )   HTML   PDF (390KB) ( 757 )   A mathematical model was developed to describe the relationship between the decarburization rate in bath and the operation parameters in the UHP electric arc furnace with hot metal charged, based on the reaction kinetic and mass balance. The model can be used to accurately describe the variation of carbon content in the bath and dynamically control the carbon content at the melting end. The calculated results were in good agreement with the production data of an 100 t UHP electric arc furnace. The simulated results showed that the decarburization rate is proportional to the intensity of oxygen supply, the square root of carbon content and the carbon content in bath in the ranges of high, medium and low carbon content, respectively. An optimum melting effect can be obtained if operating in accordance to the most economical oxygen flowrate curve, i.e., in such a jetting way that the oxygen flowrate should be decreased with decreasing carbon content in molten steel. References | Related Articles | Metrics

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Preparation of CdS thin films by vacuum evaporation and their properties Shan, Yu-Qiao (1); Dang, Peng (1); Yu, Xiao-Zhong (1); Shan, Lian-Zhong (1) 2009, 30 (3):  392-395.  DOI: - Abstract ( 418 )   HTML   PDF (1297KB) ( 1013 )   CdS thin film was prepared by vacuum evaporation and its surface morphology, structure and photoelectric properties were tested and analyzed with scanning electron microscopy (SEM), X-ray diffraction (XRD), UV-visible spectroscopy and four-point probe method. The results showed that the CdS thin films deposited on the substrates at different temperatures are mainly of hexagonal phase with the crystal planes (002) in highly preferred orientation. The visible light transmittances of the films deposited on the substrates at different temperature are all over 70%, and the film resistance increases with increasing substrate temperature. The energy gap Eg of the thin film deposited on the substrate at 50°C is 2.41 eV. After annealed at 200°C, the thin film quality can be improved with crystallizability enhanced, resistance decreased and grain size increased, and the resistance of CdS films deposited on the substrate at 50°C is 255 Ω·cm. References | Related Articles | Metrics

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Microstructural study of layered colossal magnetoresistance material La1.2-xNdxSr1.8 Mn2O7 Wang, Ming-Guang (1); Qi, Yang (1) 2009, 30 (3):  396-399.  DOI: - Abstract ( 291 )   HTML   PDF (647KB) ( 913 )   The microstructure of layered colossal magnetoresistance material La1.2-xNdxSr1.8 Mn2O7 (x=0.2) was investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM) and high-resolution electron microscopy (HREM). The results showed that La1.2-xNdxSr1.8 Mn2O7 (x=0.2) is of tetragonal structure and Nd-doping has not evidently changed its structure. HREM results showed that many defects exist in the Nd-doped oxide La1.2 Sr1.8Mn2O7, such as intergrowth structures formed between matrix and other RP phase, (101) crystallographic shear structures and some more complicated defective structures. References | Related Articles | Metrics

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Characteristic analysis of looseness fault in rotor system Ma, Hui (1); Sun, Wei (1); Wang, Xue-Jun (2); Wen, Bang-Chun (1) 2009, 30 (3):  400-404.  DOI: - Abstract ( 478 )   HTML   PDF (876KB) ( 1369 )   A new loosening model is developed for the faults of bearing caps due to loosening, which were often found in actual operation in view of the advantages and disadvantages of various existing pedestal loosening models. With FEM used to simulate the rotor system on which the looseness fault is occurring, the fault characteristics are obtained as follows. When the vibration displacement of equivalent loosening mass is less than the loosening clearance, the system motion is from period-one through period-two to period-four, the amplitude of low-frequency components gradually increases and the elliptical path of axis center of rotor becomes spiral path along with the decreasing of pedestal loosening stiffness. When the vibration displacement of equivalent loosening mass is greater than the maximum loosening clearance, the multiple frequency components and continuous spectra appear in the system and the motion of axis center of rotor is restricted from both sides to form a trapezoid-like moving path with decreasing loosening clearance. These fault characteristics obtained under different conditions are helpful to the diagnosis and analysis of the faults as above. References | Related Articles | Metrics

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Selection of parameters of an anti-resonant vibrator with anti-resonant point just at the midpoint between two resonant points Liu, Jin-Tao (1); Liu, Jie (1); Li, Xiao-Hao (1); Liu, Hong-Yi (1) 2009, 30 (3):  405-408.  DOI: - Abstract ( 546 )   HTML   PDF (319KB) ( 1022 )   A method of selecting the parameters enabling the anti-resonant vibrator's amplitude to be stabilized was proposed to solve the problem that the amplitude of the mass on the anti-resonant vibrator is highly sensitive to both resonance frequency and fluctuation of the material quantity charged on the vibrator. The basic concept of the method is to locate the anti-resonant point just at the midpoint between two resonant points and, what's more, the distance between the two points should be long enough. Then, the amplitude-frequency response curve will be comparatively flat, thus enabling the amplitudes of both upper and lower mass to be basically stable so as to meet the requirements in practice. And only a readjustment in small range is needed if high accuracy of amplitude is required to implement. Computer simulation verifies the correctness and applicability of the method proposed. References | Related Articles | Metrics

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Virtual test for reliability of rolling bearing Li, Chang (1); Sun, Zhi-Li (1); Han, Xing (2) 2009, 30 (3):  409-413.  DOI: - Abstract ( 334 )   HTML   PDF (487KB) ( 998 )   Conventional tests and theoretic calculations are unable to analyze the effects of various random errors on relevant dynamic characteristics. A virtual test was therefore proposed for the reliability of rolling bearings. Based on dynamical contact mechanics and FEM of explicit dynamics, a 3-D parameterized FEM model was developed for ball bearing with deep filling slots. Then, a numerical simulation was done using the software LS-DYNA for the operating process of ball bearings to give the contact stress/strain variation between a bearing's inner race, outer race, balls and ball cage, as well as the pressure distribution in contact process. And the computation of pseudo-random numbers was programmed by multiplying the congruent number with the APDL language used. Taking account of the effects of original errors resulting from manufacture and the different working conditions such as rotating speed and load on the dynamic property of a bearing, the K-S inspection was done to determine the distribution of the data resulting from the virtual test and, consequently, the reliability was calculated with respect to the fatigue failure of bearings. Furthermore, the simulative computation was done 1000 times for the bearings with the Monte Carlo method to give the sensibilities of reliability of all parameters, thus providing theoretically the reference for both the calculation of bearing's fatigue strength and dynamically optimum design. References | Related Articles | Metrics

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Preparation of MoS2 nanopowder and its tribological properties Yan, Yu-Tao (1); Hu, Guang-Yang (2); Li, Ye (3); Sun, Zhi-Li (1) 2009, 30 (3):  414-417.  DOI: - Abstract ( 329 )   HTML   PDF (502KB) ( 1711 )   Molybdenum disulfide (MoS2) nanopowder particles as a solid lubricant were prepared by chemical precipitation with ammonium molybdate and ammonium sulfide as raw material and grain alcohol as surfactant. The morphology and phase structure of MoS2 nanoparticles were characterized by transmission electron microscope (TEM) and X-ray diffraction (XRD), and its tribological properties were investigated on a vertical universal friction/wear tester. The worn surfaces of specimens were observed by scanning electron microscope (SEM) and the surface element composition was determined by means of energy dispersion spectrometry (EDS). The results showed that the MoS2 nanoparticles are spherical-shaped with mean particle size about 40-50 nm, and lots of dangling bond and their high surface energy/activity can play the role as solid lubricant in reducing greatly the friction coefficient of a friction pair so as to improve the wearability. It was found that the lubricating mechanism is that the powdered MoS2 nanoparticles are easy to be firmly adsorbed on rubbing surface to form a MoS2 thin film that will reacts chemically with metallic surface to become a wearable protecting film under high load at high temperature. References | Related Articles | Metrics

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SPH-based numerical simulation for big deformation during metal cutting Su, Chong (1); Hou, Jun-Ming (1); Zhu, Li-Da (1); Wang, Wan-Shan (1) 2009, 30 (3):  418-421.  DOI: - Abstract ( 387 )   HTML   PDF (650KB) ( 1211 )   A numerical simulation was conducted using SPH for the constitutive behavior during metal cutting for complex materials, and the basic rules in metal cutting process were analyzed. The simulation results showed that the cutting process is actually a plastic deformation process in which the material layer being cut forms shearing slip because of the extrusion by cutting tool. The yield strength of the agglomerated material due to extrusion increases in the vicinity of cutting edge. It makes contact stress increase, and eventually results in microcrack on workpiece surface. The cutting force increases gradually, and then varies steadily in a certain range in the cutting process. After the formation of chip, the maximum contact stress on rake fluctuates at a certain distance to the cutting edge, where the cutting-tool is heavily worn. References | Related Articles | Metrics

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Residual stress and tribological characteristics of ground surface after abrasive jet restricted by grinding wheel Liu, Feng (1); Gong, Ya-Dong (1); Shan, Yu-Qiao (2); Cai, Guang-Qi (1) 2009, 30 (3):  422-425.  DOI: - Abstract ( 390 )   HTML   PDF (1143KB) ( 623 )   The residual stress and tribological characteristics of ground surface of a 45 steel workpiece as specimen after the AJF restricted by grinding wheel were investigated experimentally on M7120 surface grinder with the value of ground surface roughness Sa=0.6 μm. The residual stress of ground surface of specimen was measured with TW3040-60 X-ray diffractometer, and the effects of surface morphology on the friction coefficient and abrasiveness of the ground surface after AJF were investigated with the MG-2000 pin-on-disk wearing tester. The results showed that the tensile stress of ground surface changes into compressive stress gradually along with the increasing grinding time which affects greatly the residual stress, and the Sa value decreases from about 0.626 μm to about 0.2 μm with increasing grinding cycles. Compared with the ground surface before AJF, friction coefficient and abraded quantity of the surface after AJF are obviously reduced with surface hardness increases gradually-the fact is in conformity with the change in residual stress. References | Related Articles | Metrics

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Design model sharing and interactive technique in multidisciplinary collaborative process Zeng, Peng-Fei (1); Liu, Yong-Xian (1); Hao, Yong-Ping (2); Sun, Guo-Qiang (2) 2009, 30 (3):  426-429+433.  DOI: - Abstract ( 249 )   HTML   PDF (750KB) ( 1102 )   To meet the requirements of product design through multidisciplinary collaboration, an interactive control technique was put forward on the basis of the sharing model in 3D document format. Analyzing the multidisciplinary collaborative design in accordance to the view of sharing model, an environment is provided to share product design by building the Browser/Server (B/S) structure in the message-driven collaborative process. Thus, an interoperable process of model sharing with two tokens was implemented, based on the design priority and sorting time. And the XML packaging, exchange and sharing of design messages were all completed. In such a web networked environment, the development and verification of prototype system were realized. The process proposed provides a distributed work space for application model sharing in collaborative design. References | Related Articles | Metrics

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Image filtering algorithm for online detection system of steel strip surface defects Liu, Wei-Wei (1); Yan, Yun-Hui (1); Li, Zhan-Yu (2); Li, Jun (1) 2009, 30 (3):  430-433.  DOI: - Abstract ( 373 )   HTML   PDF (394KB) ( 939 )   Due to the complexity of surface texture, the images obtained from the existing online detection system cannot show the strip surface defects exactly, which becomes one of the important problems to be solved for the detection of surface defects of cold-rolled strip. A novel wavelet-based image filtering algorithm by virtue of anisotropic diffusion is therefore proposed. It decomposes the original image into the low and high-frequency components by wavelet transform, then the high-frequency components are regularized by wavelet diffusion coefficients and, finally, the filtered image is reconstructed by inverse wavelet transform. To achieve a satisfactory filtering result, the wavelet-based anisotropic diffusion is often performed iteratively. Experimental results indicated that this new algorithm could not only filter off the unnecessary texture background but also preserve the valuable information in detail effectively. With more favorable combinability in filtering, this algorithm will lay a solid foundation for the subsequent image processing, e.g. image edge detection, image auto-segment, etc. References | Related Articles | Metrics

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On the evaluation of soil environment quality in Hongtoushan copper mine area in Fushun Shi, Ping (1); Wang, En-De (1); Wei, Zhong-Yi (2); Zhang, Li-Hua (3) 2009, 30 (3):  434-437.  DOI: - Abstract ( 316 )   HTML   PDF (180KB) ( 722 )   The heavy metal pollution and nutritional conditions of the soil in the Hongtoushan Copper Mine Area were investigated and analyzed via developing a fuzzy comprehensive evaluation model and sampling the soil from waste dump and tailing deposit, with the aim of providing basic reference for the pollution control and land reclamation in future and, further, for the overall ecological restoration of the polluted area. The fuzzy evaluation results showed that the heavy metal pollution of the soil under waste dump and tailing deposit is terribly serious, and that of the soil around the two sites is less serious. In view of nutritive elements, what the soil under waste dump lacks most is total potassium and organic matters, and the potassium fertilizers will be necessary with extra soil incorporated during land reclamation. As to the soil of tailing deposit, what it lacks most is the readily available nitrogen fertilizer which will be indispensable during land reclamation with the nitrogen-fixation vegetation planted. References | Related Articles | Metrics

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Deformation analysis of composite concrete girders with cold-formed U-bar based on energy theory Wang, Lian-Guang (1); Ha, Na (1); Yu, Jian-Jun (2) 2009, 30 (3):  438-440+444.  DOI: - Abstract ( 260 )   HTML   PDF (1329KB) ( 636 )   To solve the problem that the relative slip occurring on the interface between U-bar and concrete slab in a composite girder causes the redistribution of stress under external loading and then the bearing capacity of the girder is reduced with deformation increased, a deformation analysis based on energy theory is made to the composite girder. Based on energy variation principle, the differential equations of deformation are derived considering the effect of relative slip, with the calculation formulas of deformation of the composite girder given to analyze the examples under different conditions, thus discussing the influences of connection stiffness and the steel plate thickness of cold-formed U-bar on the deformation of composite girder. Calculated results showed that the deformation of the composite girder is distributed nonlinearly along its length, and decreases with increasing connection stiffness and steel plate thickness. References | Related Articles | Metrics

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Analysis of influencing factor on fracture energy of concrete containers for nuclear waste Li, Yi (1); Liang, Lei (1); Zhao, Wen (1); Wang, Guo-Feng (1) 2009, 30 (3):  441-444.  DOI: - Abstract ( 260 )   HTML   PDF (692KB) ( 426 )   The antifracture property of concrete container for nuclear waste was investigated to ensure its long-time durability. According to RILEM Standard the three-point-bending test was carried out comparatively for the hybrid fiber reinforced concrete and the plain high-strength concrete (SP-13) at normal temperature and after 150°C heating. The results showed that the fracture energy of the former is 6.3-12.0 times higher than the latter before heating and 12.0-16.7 times higher than the latter after heating. The big-size steel fibers (types A and C) are superior to both the small-size steel fibers (type B) and polypropylene fibers in absorbing fracture energy, and the type C steel fibers (shear-indented type) is superior to type A (shear-threaded type)and type B (ultra-short/fine type)in improving the fracture energy. Based on the comprehensive flexure toughness index and the comparative analyses of range and variance, a conclusion is drawn that the types A and C are applicable to the materials to make concrete containers for nuclear waste. References | Related Articles | Metrics

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Modeling principal-agent multirelation in the perspective of control of high-tech corporation Liu, Ye (1); Li, Kai (1); Jin, Xiu (1); Gao, Fei (1) 2009, 30 (3):  445-448.  DOI: - Abstract ( 304 )   HTML   PDF (191KB) ( 559 )   To solve the problem of the ethical risk and adverse selection brought by the management of a corporation that is systematically in a principal-agent relationship, the owners should set up an optimal incentive payment mechanism to stimulate and restrict the behavior of the management so as to enable them to do best for the interest of the whole corporation on the basis of their own benefits. An objective function is built for the principal-agent multirelation between stockholders, the board of directors and management of a high-tech corporation, based on those of a conventional corporation. In addition, the model of the principal-agent multirelation between management and low-level employees of a high-tech corporation is developed on the basis of a conventional corporation. According to the results of comparison, it was found that there is a difference between high-tech and conventional corporations in their optimal incentive contracts because of the sole characteristics in the control of a high-tech corporation. References | Related Articles | Metrics

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Innovative selection/evaluation of entrepreneurs in accordance to factor analysis Mao, Hui-Yuan (1); Zhao, Xin-Liang (1) 2009, 30 (3):  449-452.  DOI: - Abstract ( 421 )   HTML   PDF (328KB) ( 564 )   It is crucial and very difficult to entrepreneur through appropriate evaluation in accordance to the competence or ability capital requirements of a clever entrepreneur. To achieve the goal, relevant literature was analyzed to form several constituent factors as a theoretical framework for the evaluation/selection of the entrepreneurs. A verifiable factor analysis was done via 268 efficient questionnaires to provide a 4-factor evaluation system for entrepreneur's competence/qualification, of which the goodness of fit of the theoretical model based on structural equation is high for the actually surveyed data. The results revealed that the competence/qualification of an entrepreneur in selection/evaluation comprises 4 basic factors including 32 items in detail, i.e., knowledge, intelligence, quality and health. References | Related Articles | Metrics

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On the supply chain coordination in the sales mode of bricks and clicks Qu, Dao-Gang (1); Guo, Ya-Jun (1); Yao, Yuan (2) 2009, 30 (3):  453-456.  DOI: - Abstract ( 346 )   HTML   PDF (1282KB) ( 554 )   Modeling the E-market-based two-stage supply chain comprising a manufacturer and distributor, how the distributor sells the products in the sales mode of Bricks and Clicks is discussed, and the supply chain coordination and the profit sharing among supply chain members after selling season are analyzed. It was found that the modified buy-back contract enable the E-market-based supply chain to be coordinated in the sales mode of Bricks and Clicks, thus making the ordered quantity of distributor optimum and causing both the manufacturer and distributor to achieve Pareto improvement, i.e., a win-win situation. A numerical example verified the conclusion mentioned above, which will provide a reference that is beneficial to the retailer who intends to sell the products in the sales mode of Bricks and Clicks. References | Related Articles | Metrics