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15 August 2004, Volume 25 Issue 8 Previous Issue    Next Issue
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D-stable robust fault-tolerant control for delta operator systems Liu, Man (1); Jing, Yuan-Wei (1); Zhang, Si-Ying (1) 2004, 25 (8):  715-718.  DOI: - Abstract ( 285 )   HTML   PDF (237KB) ( 860 )   The problem of fault-tolerant control for delta operator systems based on circular regional pole assignment, which is defined as D-stable robust fault-tolerant control, is studied. By the use of linear matrix inequalities, the two sufficient conditions that the poles of the closed-loop system are assigned in a specific circular region and the nominal system possessing integrity against actuator failure are presented. Then, by means of algebraic Riccati equations, the robust fault-tolerant control problem for uncertain delta operator systems based on regional pole assignment is discussed, with the design methods for D-stable fault-tolerant controller and D-stable robust fault-tolerant controller both given. The proposed method can unify some previous related results of continuous and discrete time systems into the delta framework. References | Related Articles | Metrics

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Robust nonlinear fault diagnosis for sensors based on RBT neural network Jia, Ming-Xing (1); Wang, Fu-Li (1); He, Da-Kuo (1) 2004, 25 (8):  719-722.  DOI: - Abstract ( 244 )   HTML   PDF (312KB) ( 613 )   A new method of nonlinear fault diagnosis for sensors is proposed for a class nonlinear system. Transforming sensors faults into systematic ones via extended state variables with the fault derivative function estimated by RBF neural network, the method can adjust on-line the weights of network to implement real-time estimate of fault values. With the threshold processing technique applied to fault diagnosis for the uncertainties in the system, robustness is provided to the algorithm to a certain degree. The Lyapunov stability of the proposed method is proved and its correctness verified through a simulation as instance. References | Related Articles | Metrics

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Asymptotic stability of linear switched systems with polytopic perturbations Sun, Wen-An (1); Sun, Xi-Ming (1); Zhao, Jun (1) 2004, 25 (8):  723-726.  DOI: - Abstract ( 189 )   HTML   PDF (163KB) ( 629 )   The uncertainties of the linear switched systems with polytopic perturbations are formed by a convex combination of several known constant matrixes. For such systems, based on the convex combination of certainties and the norm concept of polytopic perturbations matrix, the single-Lyapunov function technique and multiple-Lyapunov function technique are used to give the sufficient conditions for the asymptotic stability and the design of switching laws, respectively. All the results are expressed by linear matrix inequalities which are easy checked in practice. The simulation results show the effectiveness of the method. References | Related Articles | Metrics

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Chaotic anticontrol of a class of multi-dimensional uninterrupted linear systems Huang, Wei (1); Zhang, Hua-Guang (1) 2004, 25 (8):  727-730.  DOI: - Abstract ( 186 )   HTML   PDF (169KB) ( 554 )   An anticontrol method for a class of multi-dimensional uninterrupted linear systems with state matrix featured with different negative eigenvalues is proposed by using samplified data. The method makes the given multi-dimensional uninterrupted linear systems in such chaos as what Li and Yorke meant by discretizing it then designing a state feedback controller in accordance to an anticontrol method for a discrete time systems. The system state variables are samplified at a given sampling rate and they are used to construct a discrete time state feedback controller to make the continuous-time linear system chaotic. During each sampling period, the feedback control input remains unchanged. The law of chaotic anticontrol is derived with a systematic procedure of design parameters provided to the feedback controller. Simulation results verify the effectiveness of the proposed method. References | Related Articles | Metrics

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Subsystem of fuzzed rough sets based on the equivalence classes Zhou, Jun (1); Zhang, Qing-Ling (1); Chen, Wen-Shi (2) 2004, 25 (8):  731-733.  DOI: - Abstract ( 262 )   HTML   PDF (265KB) ( 608 )   From the angle of the system, some properties about the class of fuzzy sets formed by rough sets being fuzzed by using the equivalence relation for given information system are discussed. It is proved that the class of fuzzy sets is the subsystem of the fuzzy system on the related universe of discourse. But this subsystem is a class special subsystem of fuzzy system. The transferable operation doesn't hold in this subsystem. The results supply some basic theories for how to research the relations between rough sets and fuzzy sets. References | Related Articles | Metrics

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Iterative learning of generalized predictive control for repeatable batch process Li, Shu-Chen (1); Xu, Xin-He (1); Li, Ping (2) 2004, 25 (8):  734-737.  DOI: - Abstract ( 242 )   HTML   PDF (123KB) ( 690 )   An algorithm of generalized predictive control with iterative learning (ILGPC) was proposed for a repeatable batch process. Adding an iterative learning feed-forward loop in GPC loop by utilizing the previous process I/O information, the algorithm improves the control performance of repeatable operation process and reduces the tracking error through predictive estimation and learning part of repeatable disturbance. The stability of the algorithm is also analyzed, and the stability and robustness of the proposed algorithm are verified by a simulation of an intermittent polymerization reaction process. References | Related Articles | Metrics

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Fuzzy classification based on moment invariant feature and neural networks for image pattern Fan, Li-Nan (1); Xu, Xin-He (1) 2004, 25 (8):  738-741.  DOI: - Abstract ( 276 )   HTML   PDF (174KB) ( 1055 )   A medical image recognition method based on moment invariant feature and neural networks is proposed, including the moment invariant feature extraction, moment invariant vector standardization, fuzzy preprocessing, BP net and competition selection. The feature vector of medical images, as extracted by the method of moment invariant, can effectively recognize the images characterized by translation, rotation and scaling invariants. Utilizing neural networks for classification, the extracted feature vector is classified. By use of fuzzy method, the feature data-input is preprocessed then recognized. Thus, the attribution of each and every image pattern is supposed to be expressed by a number from 0 to 1 to indicate how an image pattern is attributed to a class/sort. Experiment results demonstrated that the method is effective, and the net possesses high classing ability if trained up. References | Related Articles | Metrics

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Intelligent multi-constraint wavelength assignment algorithm in IP/DWDM optical internet Wang, Xing-Wei (1); Liu, Cong (1); Tian, Wei (1); Huang, Min (2) 2004, 25 (8):  742-745.  DOI: - Abstract ( 230 )   HTML   PDF (254KB) ( 680 )   Taking multi-constraint into account, such as cost, power and network performance, the wavelength may be assigned to fit further the actual network configurations. However, the problem of wavelength assignment will be more complex correspondingly with a hierarchical solution needed. As the sub-problem at each level is NP complete, the genetic and heuristic algorithms shall be used jointly. A simulation software was thus designed and implemented, by which the results show that the proposed algorithm can solve well the multi-constraint wavelength assignment in IP/DWDM optical Internet, i.e., not only obtaining the optimal configuration under the conditions as above, but also meeting the user connection requests as possible. References | Related Articles | Metrics

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Time-extended rotation model used for constructing data warehouse Xia, Xiu-Feng (1); Cong, Li-Hui (2); Yu, Ge (1) 2004, 25 (8):  746-749.  DOI: - Abstract ( 224 )   HTML   PDF (141KB) ( 589 )   A new time-extended rotation model is developed used to construct data warehouse, with some related concepts elucidated covering abstract attribute, generalized abstract attribute, time-labeling, time domain and widened abstract attribute. The principle, classification and correlated factors of time-extended rotation model are described, with the subject-oriented and time-oriented methods also introduced as the construction strategies. With some application examples, the advantages and disadvantages of traditional DW model and time rotation model are discussed in view of the storage efficiency, data extraction efficiency, convenience in construction and practicability. The data warehouse constructed using the time rotation model will support the OLAP and DM well. References | Related Articles | Metrics

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Performance analysis of overloaded EWS based on ERTOS Zhang, Wen-Bo (1); Zhao, Hai (1); Han, Guang-Jie (1); Wang, Xiao-Ying (1) 2004, 25 (8):  750-753.  DOI: - Abstract ( 226 )   HTML   PDF (158KB) ( 501 )   When an EWS overloads, CPU is almost completely used to process NIC interruption. Thus, the high-level application program can not be executed, with a receiving livelock occurring in EWS. For such a case, an analysis is made for the receiving process of an EWS, and the receive-packet process can be viewed as two parts, i.e., the NIC interrupting process and TCP/IP process. According to the theory of 2-level serial queuing network system, an improved method is proposed by means of establishing a model of receive-packet process and analyzing in detail. It means that the NIC interruption will be ended temporarily to reduce the packet arrival rate so as to resolve the problem of receiving livelock by way of predicting the oncoming livelock in the system. The method has been verified through testings. References | Related Articles | Metrics

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Approach to restraining growth of BGP routing table by filtration Wang, Hong-Jun (1); Wang, Rui-Jun (1); Wang, Da-Dong (2); Gao, Yuan (1) 2004, 25 (8):  754-757.  DOI: - Abstract ( 247 )   HTML   PDF (230KB) ( 680 )   The results of analyzing BGP routing tables show that there are a large number of routes of which the mask length of prefix exceeds the maximum mask length as specified by the address allocation policies. Based on the mask length of prefix, a method is presented to slow the growth of BGP routing table down so as to filter routes. For the prefixes of which the mask lengths are longer than those specified by the address allocation policies, they are only allowed to be announced in a certain range of distance. Once the route is traversing the range of given number of autonomous systems, it will be filtered out without announcement. In order to implement the filtering mechanism, the BGP is modified to add a new route attribute in it so as to record the maximum announced distance of the filtered route, thus implementing the route filtration. The method is proved feasible through simulation by using actual BGP routing tables and efficient for restraining the growth of BGP routing tables. References | Related Articles | Metrics

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Synthesis of Ag-cladding Al2O3 powder by chemical deposition Shi, Gui-Mei (1); Zhang, Zhi-Dong (2); Yang, Hong-Cai (1); Lee, Byong-Taek (3) 2004, 25 (8):  768-770.  DOI: - Abstract ( 209 )   HTML   PDF (178KB) ( 900 )   The raw Al2O3 particles are 200 nm in average diameter. Chemical deposition of Ag was carried out taking ammonia-based solution as bath in which the silver nitrate is primary component. In the reaction process such parameters as the concentration of reducing agent, reaction time and others were optimized in order to clad uniformly all of Al2O3 particles. The result show that all Ag-Al2O3 composite particles are of core-shell structure, of which the shell is composed of amorphous Ag and crystal Ag particles and their sizes are 5 nm and 10 nm respectively. The microstructure of Ag-cladding Al2O3 powder synthesized via silver chemical process was investigated by XRD, TEM and EDS techniques. References | Related Articles | Metrics

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PID control and optimization of infrared heating furnace Bian, Jun (1); Zhang, Fu-Bo (1); Liu, Xiang-Hua (1); Wang, Guo-Dong (1) 2004, 25 (8):  771-773.  DOI: - Abstract ( 286 )   HTML   PDF (873KB) ( 725 )   The new-style low heat-inertia fast-heating furnace for metal samples is controlled by PID algorithm to exert fast-heating and fast-cooling effects as well as circle control on rise-and-fall temperature on the samples. This system has been proved effective by experiment especially for sensitive adjustment to time and velocity, of which the temperature control theory and optimization design by PLC for system discrimination, PID (proportion-integral-differential) parameter setting etc. are presented. References | Related Articles | Metrics

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Mathematical model of solidification and heat transfer in mould of continuous caster for blooms Li, Dong-Hui (1); Liu, Xiang-Hua (1); Qiu, Yi-Qing (1); Wang, Guo-Dong (1) 2004, 25 (8):  774-777.  DOI: - Abstract ( 289 )   HTML   PDF (975KB) ( 729 )   A mathematical model of heat transfer and unstable solidification in the mould of continuous caster for blooms was developed and applied to predict the temperature distribution and solidified shell thickness profile in the mould of continuous caster for blooms. In view of the air gap in the mould and heat transfer is thus non-homogeneous, a heat exchange model related to the air gap is introduced. Meanwhile, the equivalent specific heat method is introduced to deal with the latent heat of fusion in the front of solidification phase. The model has been applied to calculate the temperature profile and solidified shell thickness in the mould of caster with the blooms supplied in situ as specimens. The effects of casting speed on temperature profile and solidified shell thickness were studied, which show that the data obtained by the model are in conformity with experimental measurements. References | Related Articles | Metrics

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Experimental study on continuous semi-solid expansion forming process of 6201 Al-alloy tubes Zhou, Tian-Guo (1); Wen, Jing-Lin (1); Chen, Yan-Bo (1); Li, Ying-Long (1) 2004, 25 (8):  778-781.  DOI: - Abstract ( 201 )   HTML   PDF (1144KB) ( 664 )   The 6201 Al-alloy tubes were produced successfully through semi-solid continuous expansion forming process with an extrusion ratio 3.52. The microstructure, mechanism and change of mechanical properties were studied under T6 and TA heat-treatment processes. The results indicate that the microstructure of tubes is fully recrystallized when the demoulding temperature exceeds 520°C, and the tube strength after semi-solid continuous expansion forming process and under T6 and TA heat-treatments increases obviously with the increase of aging time, but the elongation tends to decrease obviously. The key points to the expansion forming process are to make sure that the demoulding temperature should be over 520°C, and the tensile strength of tube up to 299 MPa in T6 state with the elongation 9.4%, as well as 258 MPa with 12.4% in TA state. An evolution mechanism analysis of mechanical properties shows that the conduit tubes made from 6201 Al-alloy for bus bars with an optimum combination of tensile strength and elongation can be obtained by choosing proper continuous expansion forming process and aging treatment. References | Related Articles | Metrics

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Viscosity effect of different lubricants on dynamic behavior of rubbed/impacted rotor-bearing system Chen, Hong (1); Song, Ming-Kai (2); Zhang, Xiao-Wei (1); Wen, Bang-Chun (1) 2004, 25 (8):  782-785.  DOI: - Abstract ( 238 )   HTML   PDF (375KB) ( 750 )   Considering the nonlinear oil-film force and oil lubricant viscosity, a dynamic model was set up for a rotor-bearing system with rub-impact faults. Its characteristics of rub-impact faults was analyzed by Runge-Kutta numeral simulation. Some ways to chaos was found, such as the motion of double periodic bifurcation and intermittent motion. Furthermore, the influence of changing the viscosity of oil in bearings on the dynamic behavior of a rotor-bearing system with rub-impact fault was investigated. The results show that when the angular speed of rotating rotor exceeds the double critical angular speed the rotor's responsivity is improved in the chaotic region with the decrease of oil viscosity. However, the reduction of oil viscosity affect its dynamic behavior much less if the rotor motion is in the region of sub-critical angular speed. The results provide a reference basis for the safe operation and the failure diagnosis of a rotor-bearing system with rub-impact faults. References | Related Articles | Metrics

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Taylor transform method for nonlinear dynamic characteristics of rotor system Zhang, Xiao-Wei (1); Yao, Hong-Liang (1); Chen, Hong (1); Wen, Bang-Chun (1) 2004, 25 (8):  786-789.  DOI: - Abstract ( 219 )   HTML   PDF (254KB) ( 528 )   Considering the nonlinear oil-film force, a nonlinear dynamic model of rotor system was established, with Taylor transform method introduced to transform the original analysis model of rotor vibration system into a set of algebraic equations in discrete domain and analyze nonlinearly the dynamic characteristics of the 1st-span rotor vibration system. The responses of the rotor system were thus obtained with the bifurcation rule found out. The nonlinear phenomena of rotor system were represented by bifurcation diagram, frequency spectrum, Poincare mapping and trajectory of the journal center of the system. The results indicate that the motion state of rotor system will change in such a sequence as periodic-double periodic-periodic-quasi-periodic or change directly from periodic to chaos with the increase of rotate speed as the film force taken into account. References | Related Articles | Metrics

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Fractal characteristics of short fatigue cracks on surface of weld metal for titanium alloy Hui, Li (1); Cao, Zhi-Tao (1); Xie, Li-Yang (1); He, Xue-Hong (1) 2004, 25 (8):  790-792.  DOI: - Abstract ( 227 )   HTML   PDF (154KB) ( 893 )   The grouping behaviour of short fatigue cracks on surface of the weld metal for TC2 titanium alloy was investigated according to the replicating experiment, and the replicas were analyzed on the basis of fractal theory. The results show that the feature of grouping behaviour of short fatigue crack satisfies fractal equation. The value of fractal dimension increases with the increase of the fatigue cycle frequency, and the value of fractal dimension can be regarded as a parameter to express better the fatigue damage and its evolution process. References | Related Articles | Metrics

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Case-based SVM method for maximal deformation forecasting of surrounding rocks of tunnels Jiang, An-Nan (1); Feng, Xia-Ting (1) 2004, 25 (8):  793-795.  DOI: - Abstract ( 286 )   HTML   PDF (139KB) ( 487 )   Based on the collection of samples of tunneling projects, the mapping relation of the project factors including dimension, submergence and surrounding rock quality to the maximal deformation of surrounding rock is regressed using the least squares support vector machines and a forecast model of maximal deformation of surrounding rocks is built. The kernel function parameters and penalty factors are optimized according to the learning samples. Compared with testing samples, the forecast has a maximal relative error of 14.4%, which indicates that the method is effective. References | Related Articles | Metrics

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Experimental study on frame joints of steel-encased high-strength reinforced concrete with dynamics simulation Zhang, Hai-Xia (1); Zhou, Xing-Guo (2); Zhu, Fu-Sheng (1); Wang, Lian-Guang (1) 2004, 25 (8):  796-799.  DOI: - Abstract ( 231 )   HTML   PDF (674KB) ( 620 )   The experiments of five joints of both steel-encased high-strength concrete column and high-strength reinforced concrete beam without steel-encased were carried out under cyclically reversed loading. Analyzing the horizontal shearing force distribution in joint core area, the calculation of such shearing force was discussed, as well as the shear stiffness conditions of the high-strength concrete, steel section web and hoopings in joint core area. The results indicate that the crack resistance of the section doesn't increase but the shear stiffness of joints increases greatly. The inflexion point on the loading-displacement curve is not found obviously because the steel section is encased in the high-strength concrete. The shear stiffness of joints is provided by that of concrete, section web and hoopings, among which the high-strength concrete is the predominant one. References | Related Articles | Metrics

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Hybrid algorithm for topology optimization of truss structures with discrete variables Zhu, Chao-Yan (1); Liu, Bin (1); Li, Yi (1); Zhang, Yan-Nian (1) 2004, 25 (8):  800-803.  DOI: - Abstract ( 242 )   HTML   PDF (191KB) ( 664 )   A hybrid algorithm (HA) integrating the quasi-full stress algorithm and the standard genetic algorithm (SGA) is proposed to expedite the evolving process of genetic algorithm so as to apply it to the topology optimization of truss structures with discrete variables. Based on a force analysis of truss structures, a necessary modification is done in a heuristic way to the topological structure types that form randomly, thus forming rapidly such types to meet the requirement of their adaptabilities. The genetic algorithm is used to optimize the topology of truss structures and the quasi-full stress algorithm used to optimize cross-sections, then the results of cross-section optimization are transferred to genetic algorithm as the basis of genetic operation in topology optimization. The solution space to be optimized simply by genetic algorithm can thus be reduced greatly so as to expedite search process. The exemplification results show that the method proposed is really simple, fast and efficient to the topology optimization of structures. References | Related Articles | Metrics

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Properties of polyvinyl dimethylsiloxane-polyvinylidene fluoride composite separation membranes Meng, Bo (1); Tan, Xiao-Yao (2); Yang, Nai-Tao (2); Zhang, Bao-Yan (1) 2004, 25 (8):  808-811.  DOI: - Abstract ( 158 )   HTML   PDF (1282KB) ( 655 )   A pore-distribution model was developed for predicting and evaluating gas separating property of polyvinyl dimethylsiloxane-polyvinylidene fluoride (PVDMS-PVDF) composite hollow fiber membranes. The experimental data of both permeability and selectivity are in good agreement with the theoretical results predicted by the pore-distribution model. The PVDMS-PVDF composite hollow fiber membranes were prepared through dry-wet phase inversion and dip-coating technique, of which the structural parameters of PVDF substrate membrane were estimated by gas permeation test, and the separating property was evaluated experimentally using N2/O2 as the medium. The experimental results indicate that the composite membrane has high selectivity/separating property and the thickness of PVDMS skin coat must be higher than 5 pm. so as to be compact without defects. References | Related Articles | Metrics

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Effect of damage on interlaminar crack singularity of composite laminate Liu, Jun (1); Huang, Bao-Zong (1); Li, Ying-Mei (1); Qiu, Jia-Hong (2) 2004, 25 (8):  812-815.  DOI: - Abstract ( 230 )   HTML   PDF (165KB) ( 594 )   Based on continuous damage theory, the crack-tip stress singularity of composite fiber-reinforced resin laminate with a Mode I crack was analyzed by finite element method and a nonlinear and multi-scalar damage model. Considering the geometrical non-linearity, a full coupling method iterating the damage and displacement simultaneously is applied to computation. The numerical results indicate that FEM is efficient to analyze stress singularity, and the stress singularity always exists in the hardening phase of material and decreases with the increment of damage in crack tip. The relationships between singularity and material properties are presented. References | Related Articles | Metrics