Archive

15 December 2006, Volume 27 Issue 12 Previous Issue    Next Issue
---
OriginalPaper


For Selected:

Download Citations EndNote Ris BibTeX

Toggle Thumbnails

OriginalPaper

Select

Design algorithm of robust H∞ filter for a class of stochastic uncertain systems Sun, Ping (1); Jing, Yuan-Wei (1) 2006, 27 (12):  1299-1302.  DOI: - Abstract ( 206 )   HTML   PDF (158KB) ( 577 )   The robust H∞ filtering problem is studied using Lyapunov theory. A filter is therefore designed to ensure its robust stability which enables the filtering error to meet the requirements of prescribed H∞ performance for all admissible time-varying uncertainties. An auxiliary system is introduced to simplify the process of deduction, and the sufficient and necessary conditions for the existence of H∞ filter are given. An LMI method for designing filters is obtained through matrixing, thus giving conveniently the expression of filter with LMI as tool kit. A numerical example shows that the method is effective and feasible. References | Related Articles | Metrics

Select

Stability of network congestion control algorithm in discrete-time systems Yang, Hong-Yong (1); Wang, Fu-Sheng (2); Zhang, Si-Ying (1) 2006, 27 (12):  1303-1306.  DOI: - Abstract ( 211 )   HTML   PDF (171KB) ( 655 )   Studies the discrete-time Internet congestion control algorithm based on queue length, thus adjusting the congestion rate in accordance to the queue length connecting the nodes in Internet so as to determine the date transmission rate of source nodes. Taking the control algorithm with time delays as a complex and dynamic nonlinear feedback system and analyzing the congestion control algorithm for discrete-time systems, the criteria for locally asymptotic stability are given at the balance points in discrete-time network system under conditions that the time delays of communication loops are different. Simulation results show the validity and practicability of the criteria for asymptotic stability. References | Related Articles | Metrics

Select

Global asymptotical stability for cellular neural networks with both multiple and distributed delays Wang, Zhan-Shan (1); Zhang, Hua-Guang (1); Guan, Huan-Xin (1) 2006, 27 (12):  1307-1310.  DOI: - Abstract ( 246 )   HTML   PDF (1769KB) ( 808 )   Global asymptotical stability of a class of cellular neural networks with both multiple time-varying and distributed delays is studied on the basis of Young inequality approach and properly built Lyapunov function. Some new sufficient criteria are thus given to ensure the global asymptotical stability for the equilibrium points in relevant cellular neural networks. Compared with some results in earlier works, the obtained criteria are less conservative and wider in application. A simulation example verifies the effectiveness of what are concluded from the study. References | Related Articles | Metrics

Select

Influence of vibratory loads on the facet joints near injured intervertebral discs Guo, Li-Xin (1); Huang, Qiu-Ye (1); Song, Gui-Qiu (2); Xu, Zhi-Wei (2) 2006, 27 (12):  1311-1314.  DOI: - Abstract ( 216 )   HTML   PDF (167KB) ( 779 )   A nonlinear three-dimensional finite element model of human spine was used to investigate the biomechanical characteristics of injured spine in vibratory environment. The injury status of the spine includes the denucleation of intervertebral discs and facetectomy, and the influences of different frequencies and damping on the dynamic characteristics of human spine were also taken into account in simulation. The analytical results indicated that, under whole body vibration, the lumbar spine exhibits not only the vertical vibration but also the flexion-extension motion with small amplitude. The denucleation and degeneration of intervertebral discs might increase the facet contact force and it is quite disadvantage to the facet joints under vibration conditions. Moreover, the influence of vibration on the facet joints of lumbar spine is higher than other regions at the same motion segment. References | Related Articles | Metrics

Select

Finite element analysis of thermometric sensor for liquid steel Zhang, Hua (1); Liu, Wei (1); Xie, Zhi (1) 2006, 27 (12):  1315-1318.  DOI: - Abstract ( 222 )   HTML   PDF (177KB) ( 628 )   Analyzing the heat transfer of thermometric sensor for liquid steel, a relevant finite element model is developed for the sensor. Influencing factors on thermometry such as the structure of the sensor inner and outer layers, thermal properties and boundary conditions are discussed. Numerical simulation results revealed that the max error between modeling value and experimental value is less than 6K. The thermometric lag mainly depends on the properties of protective sheath, and the thermal parameter of the sensor can be regarded as a constant. If the convective heat transfer coefficient is great enough, its rechange has smaller effect on temperature response. These results can provide a theoretical basis for sensor optimum design and its application. References | Related Articles | Metrics

Select

Analysis of acoustic signal and BP neural network-based recognition of level of coal in ball mill Sha, Yi (1); Cao, Ying-Yu (1); Guo, Yu-Gang (1) 2006, 27 (12):  1319-1323.  DOI: - Abstract ( 196 )   HTML   PDF (243KB) ( 589 )   Analyzes the frequency and power spectra of acoustic signal due to the vibration of coal that is pulverizing in a ball mill. The results show that the low-frequency signal contains the information on coal level in ball mill, while the high-frequency signal is caused by the noises of working high-speed motor, exhaust fan and rotating drum of ball mill. Both are in a modulating relation. The acoustic signal is analyzed by Hilbert transform, from which the low-frequency signal is picked out to show the corresponding coal level in rotating drum by an envelope of analyzed signal. The relationship model between coal level in ball mill and relevant envelope of acoustic signal due to vibration is therefore developed to recognize automatically the coal level. The comparison of calculated values from the model with measured values indicates that the recognition accuracy is within ±1.5%. References | Related Articles | Metrics

Select

Research on the changing principle of the internet standard structure entropy Xu, Feng (1); Zhao, Hai (1); Ha, Tie-Jun (1); Zhang, Yong-Qing (1) 2006, 27 (12):  1324-1326.  DOI: - Abstract ( 236 )   HTML   PDF (644KB) ( 808 )   According to the theory of Shannon entropy, the Internet standard entropy was defined. By using the global Internet monitor data provided by CAIDA Skitter project, the change of the Internet standard entropy with time were computed and the results using the monitor data got by riesling showed that the Internet standard entropy was reduced from the maximum 0.379 in April 2000 to 0.318 in May 2004, i.e., the reduction per month was 0.12 percent. On the other hand the computing results using the monitor data got by apan-jp showed that the Internet standard entropy was reduced from the maximum 0.388 in April 2000 to 0.297 in May 2004, i.e., the reduction per month was 0.18 percent. The difference between them revealed that the Internet standard entropy tends to reduction. It implies that there is an information metabolism in the evolution process of Internet's macrotopological structure. References | Related Articles | Metrics

Select

Aspect-oriented XML Jiang, Yan (1); Wang, Guo-Ren (1) 2006, 27 (12):  1327-1330.  DOI: - Abstract ( 238 )   HTML   PDF (151KB) ( 599 )   Analyzes the newly developed aspect-oriented programming approach and the disadvantages of object-oriented theory in defining XML document. Defining the XML document by aspect-oriented programming to extend it is proposed to solve the problems found in original definition, such as too simple relationship of inclusion, code redundancy, scattered crosscut concerns and having to modify original elements if extending XML elements. Introducing the concept of crosscut concerns and weaving them statically/dynamically into the definition of XML document enables the XML document to serve the function of aspect-oriented programming. So, the identification elements covering aspect, pointcut and advice are added to the original definition of XML Schema as defined ones, and some representative symbols are given to them correspondingly with mathematic descriptions. The results indicate that such a form of definition can reduce the system code redundancy and coupling degree of modules with better modularity and transportability grained. References | Related Articles | Metrics

Select

Aggregate operations in vague relational data model Zhao, Fa-Xin (1); Ma, Zong-Min (1) 2006, 27 (12):  1331-1334.  DOI: - Abstract ( 238 )   HTML   PDF (2042KB) ( 583 )   Based on the theory of vague set, an extended vague relational data model is proposed. Then, the process of extended aggregate operation is discussed and a group of extended scalar aggregate operators for vague values are defined including count, sum, avg, max and min. According to the properties of max and min, the optimization algorithms for their preferences are developed to reduce their time complexity from O(nII) to O(n2). References | Related Articles | Metrics

Select

Cavitation erosion behavior of martensitic stainless steel for hydraulic turbine blades Zhang, Xiao-Bin (1); Liu, Chang-Sheng (1); Zhu, Jie (1); Zheng, Yu-Gui (2) 2006, 27 (12):  1335-1338.  DOI: - Abstract ( 266 )   HTML   PDF (1500KB) ( 644 )   Cavitation erosion behavior of two kinds of martensitic stainless steel used for hydraulic turbine blades was investigated in distilled water and simulated Yangtze River water through an ultrasonic vibration system. The microstructure and the eroded surface morphology were observed by SEM and EM, and the results were in contrast with those of 13-4 stainless steel. The results showed that the microstructures of all the three kinds of stainless steels consist of martensitic matrix, ferrite and residual austenite. After refining with C, S and Si decreased and Ni, Mo and Mn increased, the stainless steel has an obviously higher resistance to cavitation erosion than that of original stainless steel and 13-4 stainless steel. The weight loss of the new type alloy due to stable cavitation erosion is less than 7 mg/h, i.e., about 75% of the original stainless steel and 25% of 13-4 stainless steel. During the cavitation erosion, the soft ferrite phase drops out form martensitic matrix first and then the hard martensite, and the surface morphology of fatigue source was thus observed clearly. References | Related Articles | Metrics

Select

In-situ synthesis of TiB2/B4C composite ceramic powder through co-precipitation He, Feng-Ming (1); Xu, Hai-Fei (1); Guo, Kai (1); Ru, Hong-Qiang (1) 2006, 27 (12):  1339-1342.  DOI: - Abstract ( 212 )   HTML   PDF (730KB) ( 995 )   TiB2/B4C composite ceramic powder was synthesized in situ through co-precipitation mainly with TiCl4 solution and B4C powder as raw materials. TEM was used to investigate the effects of the pH value of the solution and titration rate of NH4 (OH) on Ti(OH)4-clad B4C, while XRD was used to the effect of synthesizing temperature on the phases of the powder. And the thermodynamics of synthesis of TiB2/B4C composite powder was analyzed. The results indicated that when the pH value of the solution is 5 with a titration rate of 2 ml/min the Ti(OH)4-clad B4C is best, and the TiB2/B4C composite powder is available to be synthesized if the synthesizing temperature is higher than 1350°C. References | Related Articles | Metrics

Select

Effect of annealing time on recrystallization texture of IF deep-drawing steel sheet Zhao, Xiang (1); He, Chang-Shu (1); Xu, Jun (1); Zuo, Liang (1) 2006, 27 (12):  1343-1346.  DOI: - Abstract ( 230 )   HTML   PDF (118KB) ( 930 )   The effect of annealing time on recrystallization texture of IF steel sheet annealed at 750°C and 800°C with different holding times was studied by means of three-dimensional orientation distribution functions (ODF) analysis. The results showed that the intensity of γ-fiber recrystallization texture component ({111}<uvw>) increases gradually with lengthened annealing time, while that of α-fiber component from {001}<110> to {112}<110> decreases and then increases. The intensity of γ-fiber component at 800°C is higher than at 750°C and, correspondingly, that of α-fiber component at 800°C is considerably lower than at 750°C. References | Related Articles | Metrics

Select

Effect of ferritic hot rolling schedule on texture and deep drawability of Ti-IF steel Wang, Zhao-Dong (1); Guo, Yan-Hui (1); Tian, Yong (1); Wang, Guo-Dong (1) 2006, 27 (12):  1347-1350.  DOI: - Abstract ( 249 )   HTML   PDF (199KB) ( 745 )   The properties after annealing and texture of a Ti-IF steel were investigated after different hot rolling reductions in ferrite region at different finished rolling temperatures. The results showed that the IF steel has better deep drawability, higher mechanical and texture strength and elongation if the hot rolling temperature was low with big reduction in ferrite region. The texture of cold rolled IF steel is the typical conventional cold texture, i.e., partial <110>//RD fibers and global <111>//ND fibers. After annealing for recrystallization, the strength of <110>//RD fibers decreases greatly and then transform into <111>//ND recrystallized fibers. Therefore, the texture strength of <111>//ND increases greatly. It was proved that among all the cold rolled specimens, the one hot rolled finally at 750°C. with total reduction of 80% has the highest strength of <111>//ND recrystallized fibers. References | Related Articles | Metrics

Select

Low-temperature superplasticity of a ultralight fine-grained Mg-8.4wt%Li alloy Cao, Fu-Rong (1); Li, Ying-Long (1); Ding, Hua (1); Cui, Jian-Zhong (1) 2006, 27 (12):  1351-1354.  DOI: - Abstract ( 251 )   HTML   PDF (553KB) ( 734 )   A 1.5 mm-thick Mg-8.4wt%Li alloy sheet was obtained through warm-rolling at 473 K with a total reduction of 92.5% after melting, casting, ingot homogenization annealing at 573 K for 24 h. A percentage elongation up to 500% was demonstrated for such sheet at 473 K and initial strain rate of 1.67 × 10-3/sec after said 1.5 mm sheet passed the recrystallized salt bath annealing. The strain rate sensitivity index was 0.47 through phenomenological calculation, indicating that grain boundary sliding is the dominant deformation mechanism. The microstructure of such sheet after 573 K × 1 h salt bath annealing and superplastic deformation was studied by TEM and optical microscope. It was found that the grain size after salt bath annealing was 2.4 μm and that within the gauge length of specimen after superplastic deformation was 5.8 μm, indicating the occurrence of certain grain growth which is relevant to the atomic diffusion mechanism. SEM was used to examine the fractograph of specimen after superplastic deformation. It was found that the dimples are fine, deep and roundly distributed, thus retaining the original feature of equiaxial grains. References | Related Articles | Metrics

Select

Effect of raw materials on the volume change of direct-bonded magnesia-chrome refractory bricks Li, Long (1); Yu, Jing-Kun (1); Zou, Zong-Shu (1) 2006, 27 (12):  1355-1357.  DOI: - Abstract ( 208 )   HTML   PDF (126KB) ( 574 )   Using the chrome ores from India and Tibet, middle/high-grade magnesia and fused magnesia as raw materials, the φ50 mm × 40 mm cylindrical specimens were compacted under 200 MPa and sintered at 1700-1750°C. The aspect ratio of specimens was measured before and after sintering to obtain their volume changes by which the effects of different raw materials used and their mixture proportions of grain sizes on the volume change of direct-bonded magnesia-chrome refractory bricks were discussed. Some measures were therefore proposed to control the volume change of those bricks, i.e., changing the amount of the chrome ore from India to be added in fine grain and adjusting the mixture proportion of middle-grade magnesia to high-grade one in fine powder. The experimental results showed that when the mass ratio of chrome ore from India to that from Tibet is high and the mass ratio of middle-grade magnesia to high-grade one is low, the volume change is relatively small and vice versa. References | Related Articles | Metrics

Select

Effect of MgO content on softening-melting property of sinter Jiang, Xin (1); Wu, Gang-Sheng (1); Jin, Ming-Fang (1); Shen, Feng-Man (1) 2006, 27 (12):  1358-1361.  DOI: - Abstract ( 347 )   HTML   PDF (1054KB) ( 768 )   The high-temperature metallurgical properties of sinter were investigated to improve its quality, of which the MgO contents are different, as well as the influencing mechanism of MgO on sinter. The experimental results showed that no obvious interzonal difference is found in softening temperature with increasing mass fraction of MgO, while the interzonal differences are obvious in melting and softening-melting temperature because of the increasing high melting-point MgO-containing substances in early slag. Such a result is more obvious for low-basicity sinter. Under the experimental conditions, when the mass fraction of MgO increases from 1.3% to 3.0%, the temperature of softening-melting zone of low-basicity sinter (R = 1.36) increases from 217.2°C to 325.5°C. But, for the high-basicity sinter (R = 1.76), it increases from 310.5°C to 389.3°C. A conclusion is thus drawn that decreasing MgO content is beneficial to improving the high-temperature metallurgical properties of sinter. References | Related Articles | Metrics

Select

Thermodynamic analysis of effective Na/K removal from metallic lithium by molten salt extraction Jin, Zhe-Nan (1); Zheng, Gui-Shan (1); Zhang, Fu-Shun (1); Li, Xi-Meng (1) 2006, 27 (12):  1362-1364.  DOI: - Abstract ( 305 )   HTML   PDF (2658KB) ( 415 )   It is conventionally difficult to obtain metallic lithium with ultra low Na/K content, to which the molten salt extraction is therefore suggested as a pioneer process to remove Na/K and relevant experiments. The thermodynamic analysis showed that K can react with both LiCl and Li2Cl, but Na can only react with Li2Cl, when using high-purity LiCl as extractant 923 K. So, removing Na/K from Li by molten salt extraction process is theoretically feasible. Furthermore, the experimental results also revealed that the molten salt extraction an effective way to remove Na and K, especially the K from metallic lithium, which is basically in conformity to the thermodynamic analysis. References | Related Articles | Metrics

Select

Hybrid position/force control based on intelligent prediction Liu, Hong-Yi (1); Wang, Lei (2); Wang, Fei (1) 2006, 27 (12):  1365-1368.  DOI: - Abstract ( 401 )   HTML   PDF (342KB) ( 1762 )   An intelligent prediction algorithm to be introduced in conventional hybrid position/force control model is developed to deal with the force-controlled execution of compliant robot tasks in an unknown environment. The algorithm makes use of the three factors to predict and readjust the expected trajectory given in hybrid position/force control model in future sampling, with the environmental change in curvature and stiffness taken into account. To verify the effectiveness of the proposed algorithm, an open architecture platform of robot force control is set up to investigate experimentally the force control on irregularly curved surfaces for different expected forces and different tracking velocities. The influences of unknown environmental parameters on the contact force are analyzed on the basis of experimental data. The experimental results verified that the way proposed for intelligent prediction has high adaptability to unknown environment in changing. The error of force controlling is within 3% in constrained motion. References | Related Articles | Metrics

Select

Influence of linear rolling guide joint on dynamic behavior of NC machine tools Liu, Yang (1); Li, Jing-Kui (1); Zhu, Chun-Xia (1); Cai, Guang-Qi (1) 2006, 27 (12):  1369-1372.  DOI: - Abstract ( 278 )   HTML   PDF (319KB) ( 1254 )   Such characteristic parameters as static/dynamic stiffness and damping force were studied for the linear rolling guide joint of NC machine tools on a CKS6116 horizontal NC lathe. A static/dynamic characteristic test was done to obtain all dynamic parameters of the lathe, then the software ANSYS for FEA was used to simulate and display various vibration modes and natural frequencies with the guide joint parameters taken into account. In addition, a vibration excitation test was done for the whole lathe to verify the exactness of the parameters obtained from simulation. As a result, it is proved that the static/dynamic stiffness and damping force of the linear rolling guide joint affect greatly the dynamic behavior of NC machine tools. References | Related Articles | Metrics

Select

Rolecontext-based delegation model Xu, Hong-Xue (1); Liu, Yong-Xian (1); Han, Ying (2) 2006, 27 (12):  1373-1376.  DOI: - Abstract ( 178 )   HTML   A rolecontext-based delegation model (RCBDM) is developed through studying the role-based delegation model (RDM) and extending the role-based access control model (RBAC). This model introduces rolecontext and delegation rules as the criterion for delegation. Rolecontext components including such attributes as delegation maximum and the domain, type and revocation type of delegation and relevant rules are defined to support the flexible and multi-step delegation, thus enabling system security management to control macroscopically the system at a higher level. Moreover, a delegation application example is given, by which the RCBDM is proved effective and useful. References | Related Articles | Metrics

Select

Influence of short fiber on carrying capability of FRP strengthened RC beams Li, Qing (1); Liu, Jun (1); Huang, Bao-Zong (1); Wei, Zhen-Yong (2) 2006, 27 (12):  1377-1380.  DOI: - Abstract ( 196 )   HTML   PDF (178KB) ( 551 )   Based on the continuous damage theory and considering the shear effect on adhesive, a high-order nonlinear FEM model was developed for the coupling of shear/flexure with in-plane deformation of the RC members strengthened with FRP. When strengthened, most failures were found because of the separation of the concrete surface layer near FRP from the protecting layer of reinforcements and few of them were found on the bonded interface between carbon-fiber cloth and concrete or tack coat. To enhance the strength of whole member especially the interlayer as above, short fibers were added to the RC beam especially the lower layer of concrete. It is revealed that the crack propagation is slow, and the mechanic properties of FRP strengthened RC beam with short fibers are thus improved in ductibility especially in carrying ability. References | Related Articles | Metrics

Select

Mechanical properties of concrete-filled steel tube columns strengthened with CFRP under axial load after high temperature Wang, Mao-Long (1); Liu, Ming (2); Zhu, Fu-Sheng (1) 2006, 27 (12):  1381-1384.  DOI: - Abstract ( 245 )   HTML   PDF (1120KB) ( 842 )   The mechanic properties and behavior of 12 concrete-filled short steel tube columns strengthened with carbon-fiber-reinforced polymer (CFRP) sheets wrapped externally as specimens after the effects of different constant high temperatures were investigated experimentally under axial loads with different restriction coefficients. The temperature, concrete compressive strength and number of CFRP layers are the main parameters to investigate. Comparisons were made for the standard section and equivalent sections with one and two layers of CFRP involving the improvements in stiffness and bearing capacity. The static test showed that the effect of constant high temperature results in decreased strength and weakend performance, and the mechanical properties of concrete-filled steel tube columns can be extended significantly by wrapping CFRP sheets externally. Analysis and experimental results including elastic modulus and compressive strength are given to demonstrate the validation of the proposed calculation method. References | Related Articles | Metrics

Select

Integrated assessment of job environment quality in workshop Guo, Fu (1); Liu, Chun-Hai (1); Wang, Su-Bing (1) 2006, 27 (12):  1385-1388.  DOI: - Abstract ( 234 )   HTML   PDF (183KB) ( 1656 )   An integrated assessment index system was built reasonably for job environment quality in workshop, including condition of illumination, color, microclimate, noise and atmosphere. The index was classified according to the hygienic standards for industrial plant design and ergonomics or how the environment affects humans in working, and the weight of index was determined by genetic algorithm and projection pursuit. A kind of integrated assessment is presented, i.e., MODMIIM (multiple objective decision-making ideal interval method), of which the date hierarchy and relevant formula are given, and it has been applied to the assessment of job environment quality in a workshop of a company in Shenyang. The result indicated that the assessment index system and its applications can evaluate comprehensively and scientifically the job environment quality and provide a guidance for many companies to improve that in their workshops. References | Related Articles | Metrics

Select

Combination bargaining method for multi-evaluation conclusions characterized by disagreement Yi, Ping-Tao (1); Guo, Ya-Jun (1); Zhang, Dan-Ning (2) 2006, 27 (12):  1389-1392.  DOI: - Abstract ( 232 )   HTML   PDF (162KB) ( 654 )   Disagreements between the conclusions drawn by different evaluation methods are often found in multi-attribute evaluation. A bargaining combination method is therefore proposed to deal with the multi-evaluation conclusions characterized by disagreement. With the information on bargaining obtained from both evaluation parties, a quadratic programming model based on the minimized total deviation at bargaining points is developed, then the different projects are ranked using the optimal bargaining point picked out. The method has advantages such as coordinating disagreements, integrating the knowledge of evaluators or decision-makers and optimizing evaluation conclusions. A numerical example is given to verify the effectiveness of the proposed method. References | Related Articles | Metrics

Select

Method based on data mining to forecast customers' value Zhao, Xiao-Yu (1); Huang, Xiao-Yuan (1) 2006, 27 (12):  1393-1396.  DOI: - Abstract ( 277 )   HTML   PDF (181KB) ( 1804 )   A new method to forecast customers' value is put forward using such data mining techniques as clustering and classification. The indicators reflecting old customers' value and business integrity are gained through analyzing the historical transaction data. Then, these old customers are clustered and further classified into different groups in accordance to their value indicators, i.e., each and every old customer is assigned with a mark equivalent to its value. The naive Bayesian classification method is used to forecast new or potential customers' value, and a relevant customer development strategy is thus available. A numerical example is given to verify the effectiveness and practicability of the method proposed. References | Related Articles | Metrics