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15 March 2008, Volume 29 Issue 3 Previous Issue    Next Issue
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Stability analysis of non-linear real-time network control systems Liu, Li-Li (1); Zhang, Qing-Ling (1) 2008, 29 (3):  305-307.  DOI: - Abstract ( 228 )   HTML   PDF (2405KB) ( 529 )   Considering the general continuous non-linear network control systems and using the Razumikhin method to solve the value of network-induced time delay, a state feedback controller is designed to get the condition to keep the system state consistently stable, ie., the relationship between the state feedback matrix and the maximum permitted value of network-induced time delay. The condition is just the general condition to ensure the consistently stable closed-loop system. Then, the estimates of both the norm of the state feedback matrix for a class of continuous linear network control systems and the maximum value of network-induced time delay are given easily. Such a conclusion is drawn depending on time delay. Numerical simulation result shows the effectiveness of the proposed method. References | Related Articles | Metrics

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Observer-based robust passive control of uncertain descriptor systems Li, Qin (1); Zhang, Qing-Ling (1); Zhang, Yan (1) 2008, 29 (3):  308-311.  DOI: - Abstract ( 372 )   HTML   PDF (2430KB) ( 520 )   Aiming at a class of uncertain descriptor systems with norm bounded perturbations in state variables, the problem of observer-based robust passive control is discussed. Using the methods of Lyapunov function and the magnified inequalities, the conditions for the closed-loop system to be generalized quadratically stability and robust strictly passive are given in the form of matrix inequalities. Then, the sufficient conditions for the existence of designed observer are presented in terms of linear matrix inequality (LMI), and the parameters of the observer-based controller are provided with the algorithm to solve the problem given. A numerical example is given to illustrate the effectiveness of the proposed method. The conclusions can be extended to the cases that there are perturbations in both the state and input. References | Related Articles | Metrics

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Extraction of suspected nodular lung lesions based on multi-scale morphology filtering in thoracic CT images Wei, Ying (1); Xu, Xin-He (1); Jia, Tong (1); Zhao, Da-Zhe (1) 2008, 29 (3):  312-315.  DOI: - Abstract ( 250 )   HTML   PDF (436KB) ( 598 )   It is hard to segment and extract the suspected nodular lesions from CT images for lung CAD system. To solve the key problem, an extraction algorithm is proposed for the suspected nodular lung lesions area based on the multi-scale morphology filtering which focuses on the feature of tissue geometry. A series of circle-like structure elements with different dimensions are built to do the morphologic filtering. After multi-scale processing, all nodules of different sizes are enhanced and stood out from the suspected lung lesion area. On the other hand, such linear tissues as trachea, bronchi tubes and blood-vessels are weakened and suppressed. And a particular advantage of the proposed method is found that the geometric parameters of morphology operator and binary threshold parameters needn't chose manually. Experiment results indicated that the method can extract suspected nodular lesions automatically and effectively. References | Related Articles | Metrics

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Variable neighborhood search for solving vehicle routing problems with backhauls and time windows Liu, Shi-Xin (1); Liu, Ling (1); Zhang, Tao (2) 2008, 29 (3):  316-319.  DOI: - Abstract ( 401 )   HTML   PDF (2476KB) ( 675 )   Based on the background of goods distribution in e-business environment, a model for solving the problems VRPBTW, i.e., the vehicle routing problems with backhauls and time windows, is developed, and it is analyzed to improve the VNS (variable neighborhood search) algorithm so as to solve the problems. Applying the modified sequential cheapest insertion heuristic proposed originally by Braysy to generating an initial solution for improvement, the algorithm introduces four different local search operators in accordance to VNS mechanism. The results of computational tests including 15 examples were compared with that by conventional VNS and showed that the modified VNS algorithm is effective for solving the problems and greatly outperforms the conventional one. References | Related Articles | Metrics

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Routing metrics based on moments estimates for wireless sensor networks Zhao, Hai (1); Cheng, Da-Wei (1); Sun, Pei-Gang (1); Zhang, Xi-Yuan (1) 2008, 29 (3):  320-323.  DOI: - Abstract ( 211 )   HTML   PDF (329KB) ( 610 )   Computing the overhead traffic by an effective route metric is the basis for devising route protocols in wireless sensor networks. It was found through experimental study that there are some characteristics in bottom-layer communication link of wireless sensor networks, such as packet lass and asymmetry. However, mast of route metric are assuming that the bottom-layer communication link is ideal at present. So, the moment estimate is proposed as a new route metric by computing it between forward and backward packets receiving rates which were measured in the links of wireless sensor network. Then, the conventional AODV protocol is amended that the minimal hop metric in it is replaced by moment estimate. Results of simulation with NS-2 showed that the moment estimate is better than the original minimal hop for end-to-end throughput with packet loss rate greatly decreased. References | Related Articles | Metrics

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GA-based filtering algorithm to defend against DDoS attack due to bandwidth depletion Guo, Rui (1); Chang, Gui-Ran (1); Sun, Bao-Jing (2); Liu, An (2) 2008, 29 (3):  324-327.  DOI: - Abstract ( 242 )   HTML   PDF (2515KB) ( 506 )   With the DDoS (distributed denial of service) traffic which was implemented using depleted bandwidth is filtered by routers, the attached server owners should work together with ISP (Internet service provider) to defend against such DDoS attack the way the Netflow statistics is mainly used to allocate the weights for traffic routing by routers. A new algorithm is thus proposed to get efficiently maximum traffic by GA with the traffic filtered by routers, and its feasibility and validity have been verified in real network circumstances. The algorithm shows its advantages that it just occupies a small part of resources without any ISP router required to participate in, and the servers can be upgraded at low cast and allocated easily. Moreover, it can optimize the network traffic simultaneously with defending against DDoS attack, thus eliminating efficiently the global burst of traffic arising from normal traffic so as to improve greatly the efficiency of servers. References | Related Articles | Metrics

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A method generating data sets to test data mining algorithms Wei, Wei-Jie (1); Zhang, Bin (1); Wang, Bo (1); Zhang, Ming-Wei (1) 2008, 29 (3):  328-331.  DOI: - Abstract ( 328 )   HTML   PDF (2496KB) ( 688 )   Because of security, uncertain time, diversity of data etc, the problem of how to acquire the data set to test data mining algorithms has been confusing the study on data mining. A simulating method is therefore suggested to generate the data set on the basis of the genetic algorithm and entropy. The method extends a few data which were collected from reality by GA, then evaluates the similarity between extended data sets and real one with entropy, and generates the most similar data set of big size among the extended ones as the data set to test the data mining algorithms. A generation algorithm is also given. This method is available to generate the data set for testing, which has the same attributes, scales of attribute value and distributions of attribute value to the data set from reality, as well as the correlations among the attributes. This data set for testing will accelerate the study on data mining algorithms. References | Related Articles | Metrics

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On the radial distribution of cold deformation textures of pure copper wire Yao, Xu-Sheng (1); Liu, Yan-Dong (1); Zuo, Liang (1) 2008, 29 (3):  332-334.  DOI: - Abstract ( 221 )   HTML   PDF (384KB) ( 480 )   To explore the correlation between microstructure and deformation texture, the textures of copper wire were investigated in detail by XRD with a precision texture measurement suitable for wire samples provided. The radial distribution of deformation textures was analyzed by means of ODF. The results demonstrated that the surface textures of single-crystal copper wire consist of <100>, <112> and <110>, among which the <100> increases from surface to center of the wire and becomes the main texture in central layer, while <112> tends to increase then decrease from surface to center and <110> tends to decrease. However, the surface textures of poly-crystal copper wire consist of <100>, <112> and <111>, among which <100> tends to increase then decrease and <112> tends to decrease then increase from surface to center, while <111> tends to increase and both <100> and <111> become the main texture in central layer. References | Related Articles | Metrics

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Semisolid billet preparation and thixoforming of AlSi7MgBe alloy Zhao, Da-Zhi (1); Lu, Gui-Min (1); Wang, Ping (1); Cui, Jian-Zhong (1) 2008, 29 (3):  335-338.  DOI: - Abstract ( 261 )   HTML   PDF (850KB) ( 462 )   The effects of processing parameters of semi-solid billets preparation, reheating temperature and holding time on the semi-solid slurry microstructure of AlSi7MgBe alloy by liquidus semi-continuous casting were studied. And the thixoforming feasibility of semi-solid AlSi7MgBe alloy was investigated by analyzing the microstructure and properties of formed parts. The results showed that the microstructure is mainly the homogeneously fine rosette-shaped grains. The microstructure of the billets reheated at 595°C and held for 15 min are near-spherical grains suitable for semi-solid thixoforming. The semi-solid thixoformed parts of AlSi7MgBe alloy are clean-cut, compact and able to fulfill themselves through thixoforming which improves the microstructure and properties. Compared with the liquid forged castings, the hardness of SSM (semi-solid metal) forged castings is increased by 20%. References | Related Articles | Metrics

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Effect of heat treatment in γ + α region on microstructures and properties of strips with different initial structures Han, Hui-Quan (1); Liu, Yan-Chun (1); Zhang, Chi (1); Wang, Guo-Dong (1) 2008, 29 (3):  339-342.  DOI: - Abstract ( 284 )   HTML   PDF (442KB) ( 715 )   The 0.08C-1.2Mn-0.15Si steel was investigated for the effect of annealing and quenching processes in γ + α region on the microstructures and properties of such strips of which the initial structures are different. It was found that under the same heat-treatment regime the finer the grains are, the more the volume fraction of martensite is. If the initial structures are the same, the volume fraction of martensite increases slowly with the lengthening holding time for 2-30 min. The tensile strength of specimens comes up to 600 MPa after annealing and quenching processes, and the initial work hardening index n varies in the range 0.17-0.22, with the ratio Rel/Rm 0.5-0.6 and percentage elongation higher than 20%. References | Related Articles | Metrics

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On the TMCP process of Q345C high strength heavy plate steel Li, Jing (1); Zhao, De-Wen (1); Du, Lin-Xiu (1); Liu, Xiang-Hua (1) 2008, 29 (3):  343-346.  DOI: - Abstract ( 313 )   HTML   PDF (533KB) ( 656 )   TMCP process was applied to the rolling of 70 mm-thick Q345C heavy plate steel to control its strength, ductility and toughness. Describes the process and investigates the relationship between the controlled rolling process and the microstructure and properties of the steel as well as the structural morphologies. The results showed that the mechanical properties of the plate specimens thus rolled with heavy reduction in unrecrystallized zone and without heat-treatment can meat the requirements as listed in the Standard GB/T 1591-94, no matter what cooling type is taken (by air or accelerated). The mechanical properties are well homogenized in thickness direction. Accelerated cooling enables the ferritic grains to be clearly finer, but the size of ferritic grains in surface layer and in core are slightly different. The results of investigation will provide a reference for energy saving and cost reducing in the production of 70 mm-thick heavy plates. References | Related Articles | Metrics

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Numerical simulation and experiment on thermal stability of high-temperature superconductors Wu, Chun-Li (1); Xiao, Jing-Kui (2) 2008, 29 (3):  347-349+353.  DOI: - Abstract ( 237 )   HTML   PDF (2550KB) ( 549 )   Minimum quench energy (MQE) and minimum propagation current (Imin) are the two parameters crucial to not only the stability hut the self-protect ion of superconductor, A numerical simulation was done using FEM for the thermal stability of high-temperature Bi2223/Ag superconducting tape and the results were compared with experimental results. It was found that the temperature transition process from superconducting state to normal state can be conveniently simulated on computer through developing a suitable thermal analysis model, thus estimating MQE and Imin. The results from numerical simulation are basically in line with that from experiment, and such a fact is of theoretical significance to the practical application of high-temperature superconductors. References | Related Articles | Metrics

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Study on foaming performance of LF refining slag with high basicity Min, Yi (1); Wang, De-Yong (1); Liu, Cheng-Jun (1); Jiang, Mao-Fa (1) 2008, 29 (3):  350-353.  DOI: - Abstract ( 257 )   HTML   PDF (224KB) ( 709 )   The foaming performance of LF refining slag with high basicity was investigated systematically and analyzed theoretically under lab conditions, with the molybdenum wire used to measure the height of foamed slag and the height taken as performance index. The results showed that the relative height of foamed refining slag increases with increasing slag viscosity and decreasing slag surface tension and slag density. In addition, when keeping the slag composition constant the relative height of foamed slag tends to increase first then decrease with increasing temperature and gas blowing flowrate. It was found that the proper composition of refining slag is w (CaO)/w (SiO2) 5-8, w (Al2O3) 27%, w (CaF2) 3%-6%, w (MgO) 8% and w (FeO) within 0.5% respectively. References | Related Articles | Metrics

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Wave absorbability of porous metal coated with magnetic medium absorbent Liu, Xin (1); Xue, Xiang-Xin (1); Liu, Yu (1); Zhang, Yu (1) 2008, 29 (3):  354-357.  DOI: - Abstract ( 312 )   HTML   PDF (453KB) ( 534 )   Studies on the wave absorbability of magnetic medium absorbent/Al-alloy foams of which the surface were separately coated with Ni-Zn ferrite (CFe), nickel carbonyl (CNi) and the powdered compound of them. The coated Al-alloy foams were tested according to the Standard GJB 2038-94 'method to test the reflectivity of radar wave absorbing materials', i.e., the RCS (radar cross-section) method. The results indicated that in the 12-18 GHz band the wave absorbability of Al-alloy foams materials coated powder compound absorbent is founded between that of Al-alloy foams samples CFe and CNi which were coated with single absorbents samples. But in the 26.5-40.0 GHz band, the best wave absorbability belongs to Al-alloy foams coated powder compound absorbent in which the nickel carbonyl content is 40wt%, and the absorbability goes down gradually if the nickel carbonyl content is higher than 40wt%. So, the absorbability of Al-alloy foams coated powder compound of Ni-Zn ferrite in reasonable proportion to nickel carbonyl is available to be improved. References | Related Articles | Metrics

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Effect of Ni2+ ion content on electromagnetic properties of nanocrystalline NixZn1-xFe2O4 powder Ma, Rui-Ting (1); Tian, Yan-Wen (1); Zhang, Chun-Li (2); Li, Hong (2) 2008, 29 (3):  358-361.  DOI: - Abstract ( 258 )   HTML   PDF (2649KB) ( 576 )   The spinel-type nanocrystalline nickel-zinc ferrite powder (NixZn1-xFe2O4, where x = 0, 0.2, 0.5, 0.8 and 1) was synthesized by polyacrylamide gel method with acrylamide as monomer and N, N'-Methylenediacrylamide as lattice agent. FT-IR, XRD, TEM and waveguide were used to characterize the composition and morpholopy of the powder. The results showed that both the lattice constant and electromagnetic properties highly depends on Ni2+ content and a 60 cm-1 blue shift of the characteristic absorption peaks of M-O (metal and oxygen) ion bonds comes to pass with increasing Ni2+ content as shown in FT-IR spectra and, as shown in TEM images, the average particles size of the NixZn1-xFe2O4 changes little with x value, i.e., the size is 12, 17 and 15 nm when x is 0, 0.5 and 1, respectively. And the lattice constant decreases to 0.8327 nm from 0.8456 nm as calculated from XRD patterns. In addition, both the dielectric loss (tan Ε) and magnetic loss (tan μ) of the nanocrystalline NixZn1-xFe2O4 increase obviously with increasing Ni2+ content within the tasting frequency range. References | Related Articles | Metrics

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Research on multi-objective scheduling optimization for flexible job shop Liu, Xiao-Xia (1); Xie, Li-Yang (1); Tao, Ze (2); Hao, Chang-Zhong (2) 2008, 29 (3):  362-365+382.  DOI: - Abstract ( 316 )   HTML   PDF (386KB) ( 923 )   A hybrid genetic algorithm based on Pareto was proposed and applied to the multi-objective flexible job shop scheduling problem (FJSP), and a multi-objective FJSP optimization model was developed including make-span, total tardiness and machine utilization rate. The algorithm combines Pareto ranking strategy with Pareto competition method. The operation-based encoding and an active scheduling decoding method are employed. In order to promote solution diversity, the niche technology and many kinds of crossover operations are used here. Pareto filter saves the optimum individual occurring in the course of evolution, which avoids losing the optimum solutions. The set of Pareto optimum solutions is obtained. In the end, a simulation experiment was carried out to illustrate that the proposed method can solve multi-objective FJSP effectively. References | Related Articles | Metrics

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Modeling of parallel robots in coordination with flexible multibody system and dynamic simulation Zhu, Chun-Xia (1); Zhu, Li-Da (1); Liu, Yong-Xian (1); Cai, Guang-Qi (1) 2008, 29 (3):  366-370.  DOI: - Abstract ( 302 )   HTML   PDF (478KB) ( 975 )   An approach is proposed coordinately to model and simulate the dynamics of flexible multibody of a mechanism, and a spatial dynamic equation is given to the flexible mechanism on the basis of the dynamics of multibody system. Then, a simulation model is developed for the dynamics of flexible multibody of 3-TPT parallel robots by use of the software ADAMS for multibody dynamics and ANSYS for FEA, and the model is studied dynamically by simulation. To discuss the results more exactly, the simulation results of rigid and flexible bodies are compared with each other. Simulation results showed that the forces acting on any flexible members are highly nonlinear, and the judgment conforms to the actuality. Such simulation results will reflect dynamically and actually how the parallel robots operate more really and exactly, as well as the prediction of the performance of a mechanism. The approach proposed will provide a method to analyze the design and optimization of parallel robots. References | Related Articles | Metrics

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Theoretical analysis of magnetic field and eddy current loss within giant magnetostrictive material Sun, Hua-Gang (1); Yuan, Hui-Qun (1) 2008, 29 (3):  371-374.  DOI: - Abstract ( 331 )   HTML   PDF (2525KB) ( 740 )   Discussing the giant magnetostrictive material in the longitudinal exciting magnetic field and introducing the Maxwell's equation to obtain the magnetic field distribution function in terms of Bessel function within the giant magnetostrictive material, the Kelvin expression of magnetic field in giant magnetostrictive material is given by the analytical method from Bessel function. A qualitative analysis is made to the magnetic field distribution to reveal the classical hysteresis characteristic of internal magnetic field. Based on the theory of magnetic energy, the eddy current loss within material is preliminarily discussed to get the expression of eddy current loss within material in terms of Kelvin function. Then, the effect of the influencing factors on eddy current loss are also discussed, such as exciting frequency, electrical conductivity and radius of giant magnetostrictive material, thus laying down a foundation on which the selection of proper parameters for giant magnetostrictive material parameters is available. References | Related Articles | Metrics

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An algorithm of strip surface defect detection based on grayscale projection Wang, Hong (1); Zhu, De-Sheng (1); Tang, Wei (1) 2008, 29 (3):  375-377.  DOI: - Abstract ( 332 )   HTML   PDF (2513KB) ( 841 )   According to the defect image characteristics on steel strip surface, a defect detection algorithm was proposed on the basis of grayscale projection, where the steel strip image was projected downward and leftward to find out the defects and their positions. The algorithm is easy to implement and the load to be computed is less. The results showed that the average time is about 20 sec to detect a steel strip image by using the proposed algorithm that can eliminate the serious dependence of choosing reference image on the image difference recognition methods and improve further the reliability and stability. The algorithm has succeeded in defect detection on steel strip surface in many experiments. References | Related Articles | Metrics

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Study on contact force control based on detection by ultrasonic sensors Luo, Zhong (1); Liu, Hong-Yi (1); Sun, Yi-Lan (1); Li, Li-Na (1) 2008, 29 (3):  378-382.  DOI: - Abstract ( 285 )   HTML   PDF (411KB) ( 434 )   A method is presented for a robot using ultrasonic sensors to detect control force in unknown working environment. Developing a structure model for the exploring system, the operation principle of ultrasonic detection system is described. Then, an HSIC (human-simulated intelligent control) method is developed and applied to the control of contact force in unknown environment, since the uncertainty, variability and unstructured property feature the surface contacting job between robot and environment. In the method the environmental information obtained by ultrasonic sensors is taken as the basis of the upper-layer control strategy, then the appropriate programs prepared in advance are selected according to the size and sign of the control error and its change rate. The experimental results show that this method greatly improves the control precision in comparison with PID control method. References | Related Articles | Metrics

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Reliability calculation based on grey relation analysis and in situ data for vehicle components Wang, Tie (1); Zhou, Shu-Wen (1); Wang, Qing (1); Ba, De-Chun (1) 2008, 29 (3):  383-386.  DOI: - Abstract ( 220 )   HTML   PDF (2610KB) ( 705 )   In view of lightening and strength reliability, a method of reliability calculation is proposed on the basis of grey relation analysis and in situ force data and implemented by way of VB program. Analyzes the harsh conditions and inaccurate results of conventional calculation methods for stress tests and evaluation. Discusses how to calculate the standard difference in grey relation analysis and reliability of normal distribution and how to transform equivalently other distributions to normal distribution. In conclusion, the method proposed is available to get rid of the harsh conditions for calculation and make the results more accurate. Moreover, it can be used to transform the logarithmic normal distribution into equivalent one. References | Related Articles | Metrics

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An access control model for task-oriented workflow Wei, Yong-He (1); Wang, Cheng-En (2); Shu, Qi-Lin (2); Ma, Ming-Xu (2) 2008, 29 (3):  387-390+432.  DOI: - Abstract ( 256 )   HTML   PDF (2607KB) ( 571 )   Analyzing what are required for the access control of workflow, an access control model for task-oriented workflow is put forward, in which the idea of authorized task in order to separate the relation between roles and permissions. An authorization task is introduced to make the executive roles in no relation to authority, where the authority least approved to execute a task and the role assigned to execute the task are both the attributes of task authorization. The model also defines the conflict relationship between different tasks, then gives the dynamic constraint rules on the authorization to ensure and enforce the implementation of security strategies. In this model, the authorization flow is synchronized with workflow so as to meet the access control s requirements of dynamic authorization, authority least approved and separation of responsibility from duty. Differing from existing models, in the proposed model the separation of authority from executive role cancels the coupling of organizational model with workflow model. References | Related Articles | Metrics

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A method to locate driver's face under obscure conditions Yang, Ying (1); Zhao, Guang-Yao (1); Zhou, Wei (1) 2008, 29 (3):  391-394.  DOI: - Abstract ( 248 )   HTML   PDF (442KB) ( 482 )   To analyse the color image of driver's face taken by CCD camera under obscure conditions, the image noise jamming is eliminated first by erosion in combination with dilation operation, and the threshold processing is used for the grey level differences in the image to select preliminarily the threshold value of grey level. Then, a nonlinear quadratic equation is used to normalize the grey levels so as to intensify the difference among the grey levels and get again the threshold value which is taken as the segmentation threshold between human face and background. By projecting the grey image both horizontally and vertically, the face area can be determined to implement the face locating. Monitoring tests were carried out in different environments and on different roads in accordance to the method proposed, and the results showed that the mean accuracy comes up to 83% under obscure conditions with the advantages of real time and accurate. It benefits judging if a driver is tired in evening. References | Related Articles | Metrics

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On the GTP-based 3D interactive modeling method for geological faults Che, De-Fu (1); Wu, Li-Xin (1); Yin, Zuo-Ru (3); Guo, Jia-Teng (1) 2008, 29 (3):  395-398.  DOI: - Abstract ( 292 )   HTML   PDF (313KB) ( 1218 )   Based on the summarization and analysis to present methodologies of 3D modeling of the geological faults, a new method named rock pillar body partition (RPBP) modeling is put forward on GTP (generalized tri-prism) basis for 3D spatial modeling of faults. The RPBP method takes borehole data as its original data source, and the modeling process includes the steps as follows. Generate the constrained Delaunay TIN (CD-TIN) of terrain in accordance with the collar data of borehole and the outcrops of faults. Construct the limiting triangles in each rock pillar body (PRB) according to the types and modeling priority sequences of the fault system. Develop the 3D faults spatial model in accordance with the limiting triangles. The programming test showed that the RPBP method can accurately describe the complicated fault system involving obverse and reverse faults and its inter-clipping, and is smartly as well as reliably to construct interactively the 3D spatial modeling of complex fault system. References | Related Articles | Metrics

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Microseismic monitoring system establishment and its application study in Hongtoushan copper mine Zhao, Xing-Dong (1); Shi, Chang-Yan (1); Liu, Jian-Po (1); Li, Yuan-Hui (1) 2008, 29 (3):  399-402.  DOI: - Abstract ( 325 )   HTML   PDF (347KB) ( 1392 )   Aiming at the present situation that the ground pressure acts so intensively in Hongtoushan copper mine, a microseismic monitoring system was developed by optimizing the layout of sensors with a three-dimensional geological model developed relevantly to monitor realtime continuously how the ground pressure acts. The monitoring result is compared with the actual seismic source through blasting and it shows that the locating error is less than 5 m which is highly accurate in locating seismic source through a microseismic monitoring system. Capturing microseismic information from ground pressure activities and then locating the seismic source is proved of significance to forecasting dynamic disaster in deep mine. References | Related Articles | Metrics

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Effect of width correction of shallow foundation on bearing capacity of cohesive subsoil Liu, Zhong-Chang (1); Zhu, Fu-Sheng (1); Wang, Xin (3); Liu, Wen-Hua (1) 2008, 29 (3):  403-407.  DOI: - Abstract ( 308 )   HTML   PDF (2572KB) ( 670 )   A new method taking account of the effect of foundation dimensions on the bearing capacity of cohesive subsoil is proposed, based on the foundation loading tests which were done on two areas of cohesive subsoil in Shenyang City with loading plates of different dimensions used as foundations. The settling amount under the action of loading plates of different widths were measured and calculated, and the comparative analysis indicated that the control index of bearing capacity of cohesive subsoil should be taken from the deformation values of cohesive subsoil. The actual settling amount of highly/intermediately compressed subsoil is generally greater than that calculated by layered summation, and the bigger the width of foundation, the greater the discrepancy between the actual and calculated settling amount. An overall analysis was therefore made to the values taken for the bearing capacity of subsoil in design in view of the existing design problems. And a conceptual design is proposed for foundation engineering. Testing results showed. that bearing capacity of cohesive subsoil decreases exponentially with the increasing width of loading plates. References | Related Articles | Metrics

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Calculation of normal section bearing capacity of FRP-confined SRHC compression-bending columns Zhou, Le (1); Wang, Lian-Guang (1); Li, Sui (2) 2008, 29 (3):  408-411.  DOI: - Abstract ( 320 )   HTML   PDF (293KB) ( 935 )   Considering comprehensively the bearing capacity of SRC (steel-reinforced concrete) columns, a new column model, i.e., the composite FRP-confined SRHC column, is put forward without change in sectional area, which can increase the bearing capacity, shear strength and anti-earthquake ductility. The section steel is embedded in the RC column to become an SRHC column of which the surface is then wrapped spirally and stuck on vertically by FRP sheet during construction or at the moment the main structure has been built to a certain height, thus forming a composite FRP-confined SRHC column. And mast of such composite columns are eccentrically loaded. The confining effect of spirally wrapped FRP sheet on RC and the contribution the vertically stuck FRP sheet made to the normal section bearing capacity of SRHC column are therefore analyzed to determine the boundary hight of the compressive region of the composite column. A formula is given to calculate the normal section bearing capacity of the composite FRP-confined SRHC column under eccentric load. References | Related Articles | Metrics

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Numerical simulation of kerosene fire/smoke spread over subway station platform Zhang, Pei-Hong (1); Liu, Mu (2); Chen, Bao-Zhi (1); Fu, Jing-Yu (2) 2008, 29 (3):  412-415.  DOI: - Abstract ( 276 )   HTML   PDF (545KB) ( 506 )   Based on the Shenyang subway project, a numerical simulation of kerosene fire/smoke spread over the subway station platform was performed by the software CFD and SIMPLE algorithm for fluid mechanics, including 5 different types of smoke exhaust systems. The centers of two stairway openings on the plane 2 m above platform floor were taken as test points where the time-dependent relationship between temperature and CO2 mole fraction and the cloud charts of fire scene temperature and CO2 concentration fields were obtained to analyze how the different ways to exhaust smoke affect the spread of fire/smoke at subway station platform. The results showed that when the mechanical smoke exhauster is used solely, the position difference of exhauster outlets affects unobviously the fire/smoke control effectiveness. But, the exhauster in combination with forced draft system can inhibit more efficiently the spread of fire/smoke though periodical attenuation is found during the inhibition. The stairway farther from the fire center is proved the safer exit for human evacuation. References | Related Articles | Metrics

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On the dynamic assessment of system safety Zhou, Jia-Hong (1); Xu, Kai-Li (1); Chen, Zhi-Yong (2) 2008, 29 (3):  416-419.  DOI: - Abstract ( 293 )   HTML   PDF (2448KB) ( 645 )   Analyzing the uncertain factors and dynamic characteristics of a system, the system safety is dynamically assessed via SPA and Markov chain. A dynamic safety assessment method is proposed combining the state assessment with trend analysis, thus providing a new approach for safety assessment and verifying its feasibility by examplification. In the method the hazard grade is determined by the correlation coefficient of SPA, and a 3-variable model combining the safety state with set pair potential and pessimistic potential is developed to analyze further the development trend of the system and assess dynamically the current situation of system safety. According to the ergodicity of Markov chain, the final level of system safety can be predicted to provide a theoretic reference for decision-making in safety consideration. References | Related Articles | Metrics

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- - 2008, 29 (3):  420-423.  DOI: - Abstract ( 249 )   HTML   PDF (2475KB) ( 706 )   - References | Related Articles | Metrics

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- - 2008, 29 (3):  424-428.  DOI: - Abstract ( 270 )   HTML   PDF (395KB) ( 577 )   - References | Related Articles | Metrics

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- - 2008, 29 (3):  429-432.  DOI: - Abstract ( 410 )   HTML   PDF (240KB) ( 1417 )   - References | Related Articles | Metrics

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Existence of positive solution of three-point boundary value problems for second-order impulsive differential equation in banach space Sun, Tao (1); Yang, Jing-Yu (1); Duan, Xiao-Dong (2) 2008, 29 (3):  433-436.  DOI: - Abstract ( 232 )   HTML   PDF (243KB) ( 538 )   There were many methods were used in other papers to discuss the existence of solutions, positive solutions and multiple positive solutions of boundary value problem for nonlinear impulsive differential equation, such as the method of upper and lower solution, fixed point index theory. The fixed point theorem of cone is used to study the existence of multiple positive solutions to three-point boundary value problem as a case in particular to the nonlinear impulsive equation, i.e., η Ε (tm, 1] in Banach space. And an example is given to show the application of main result. References | Related Articles | Metrics

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Calculation of physical parameters in pencil beam dose calculation algorithm Zhang, Tie (1); Li, Jian-Dong (1); Wang, Zhong-Wen (3) 2008, 29 (3):  437-440.  DOI: - Abstract ( 420 )   HTML   PDF (293KB) ( 719 )   Electron beam is unsubstitutable to the therapy of tumors/cancers at body surface or superficial layer because of the limited irradiation range of high-energy electron beam that may avoid efficiently the irradiation into the deep tissue behind target area. The calculation of physical parameters included in the Hogstrom pencil-beam dose calculation algorithm is thus studied further to explore the basic principles of them and how to calculate them in accordance to practical clinical conditions. The results show that the Hogstrom algorithm is available to solve the problem of calculating electron beam dose. References | Related Articles | Metrics

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Electronic structure and magnetic order of perovskite material La1-xCaxMnO3 Li, Lin (1); Zhu, Lin (1); Cheng, Tai-Min (2); Shi, Hua-Jing (1) 2008, 29 (3):  441-444.  DOI: - Abstract ( 261 )   HTML   PDF (352KB) ( 821 )   DV-Xα molecular orbital method was employed to study the electronic structure of perovskite La1-xCaxMnO3 cubic system where the dopant concentrations are different. The dependence of magnetic and electrical properties on the dopant calcium concentration have been investigated. It was found that the spin-dependent Mn3d-O2p hybridization occurs in the whole perovskite La1-xCaxMnO3 system. The conductivity of the undoped system is metallic and the DOS (density of state) at Fermi level in major bands is higher than that in minor bands. With the increase in dopant concentration x, the conductivity of the manganite changes from metallic to half-metallic and the magnetic moment of Mn decreases monotonously in conformity with the changing regularity of the exchange splitting of Mn3d bands. The doped Ca increases the overlap of Mn3d and O2p orbits to intensify the Mn-O-Mn superexchange and cause the magnetic ordering of CaMnO3 to present G-type antiferromagnetism. Meanwhile, LaMnO3 presents orderly ferromagnetism due to the weak overlap of Mn3d and O2p. References | Related Articles | Metrics

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Medium-temperature internal friction of Fe-Nb alloys with martensitic surface layer carbonized Yu, Ning (1); Ji, Jing-Wen (1) 2008, 29 (3):  445-448.  DOI: - Abstract ( 373 )   HTML   PDF (256KB) ( 456 )   The tested wire specimens of Fe-Nb alloys were carbonized with 0.5wt%C in a hydrogen-benzene mixed gasflow at a temperature lower than A1 point. The metallograph observation on the quenched specimens showed that the structure of the carbonzied surface layer with a thickness about 40μm is martensite, whereas that inside the layer is α-Fe phase. The internal frictions of both the quenched specimens at room temperatures and the quenched-deformed specimens at the room-medium temperatures were measured by NHI-12 vacuum Keˆ-pentulum. It was found that there is an 1 × 10-2 high peak near 45°C in the quenched specimens, while in the quenched-deformed specimens, a higher peak (h = 1.7-2.0 × 10-2) by 45-60°C takes place with two small peaks, i.e., -300°C and -235°C peaks. It is considered that under the experimental conditions including the strongly macrostrutural stress, they are separately the diffusion peak of carbon atoms in body-centered tetragonal (bct) lattice, the SKK peak in the desolution process of metastable carbide in martensite and the SKK peak of the α-Fe deformed phase. References | Related Articles | Metrics

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Development of a gravity-driven mercury-dropping pump Xu, Zhang-Run (1); Tang, Xiao-Yan (1); Wang, Jian-Hua (1); Fang, Zhao-Lun (1) 2008, 29 (3):  449-452.  DOI: - Abstract ( 230 )   HTML   PDF (2464KB) ( 556 )   A miniaturized gravity-driven mercury-dropping pump was developed. The pump consists of a piece of 8 cm long capillary (200 μm i.d.) connected at both ends to two circular mercury reservoirs in the same construction for mercury dropping. The working: Principle of the pump was discussed with the influencing factors on its performance in conceptual design analyzed, such as the level variation of mercury, the inner diameter and length of the capillary, the loading flow resistance and the sectional area of the mercury reservoirs. Some of the figures of merit of the present mercury-dropping pump include its miniaturized dimensions, self-driven, free of mechanical parts, controllable flowrates by readily adjusting the differences between mercury levels via tilting the pump body and long-term repeated operation by overturning the pump body. A flow rate 1.09-1.34 μL/min was obtained within 4 hr successive operation, with an average flowrate 1.22 μL/min and precision 4.0% RSD (n = 24) provided. The pumping pressure was tested up to 4.5 kPa. References | Related Articles | Metrics

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Nonlinear vibration response of combination cantilever plates Guo, Xing-Hui (1); Wang, Yan-Qing (1); Li, Bing (1); Yan, Yun-Hui (2) 2008, 29 (3):  453-456.  DOI: - Abstract ( 259 )   HTML   PDF (2517KB) ( 542 )   Considering the shrouded blades of aeronautic engine and roll's lifting motor tray as combination cantilever plates, three coupled nonlinear differential equations of motion of cantilever plates are derived from the theory of thin elastic plate with the effects of damping and geometric large-amplitude vibration taken into account. Then, the Galerkin method is introduced to obtain nonlinear equations in the generalized coordinates. The nonlinear vibration response of combination cantilever plates is analyzed by the Runge-Kutta numerical method to obtain the frequency-response curves. The results show that the geometrical nonlinear effect on the system makes the nonlinear vibration response less than linear one, and the nonlinear resonant frequency is slightly higher than the nature frequencies of each of the combination cantilever plates. The nonlinear frequency-response curve shows the multi-value and jumping characteristic, and its shape relates to the amplitude of exciting force. References | Related Articles | Metrics