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30 June 2014, Volume 19 Issue 3 Previous Issue    Next Issue

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Topology-Based Quantitative Assessment of Structural Robustness GAO Yang*(高扬), LIU Xi-la (刘西拉) 2014, 19 (3):  257-264.  doi: 10.1007/s12204-014-1497-3 Abstract ( 672 )   Local damages to a structure will cause disproportional collapse if the system is lack of robustness. This structural safety cannot be guaranteed by traditional ways, such as reliability analysis tools and construction management approaches. Therefore, it is very important to develop related theories for structural robustness. This paper presents a methodology to quantitatively assess the structural robustness from the topological point of view. In the proposed method, the structural failure is viewed as a feedback process. The transformations between the damage input and failure output form a closed-loop. The decisive factor of the operation of such a closed-loop is thought as the structural topology. Furthermore, the damage input and the failure output of the structure are measured by the uncertain disturbance and the change of the topology, respectively. After the sensitivity of the structural topology to the uncertain disturbance is studied, the transfer matrix is discovered to indicate the rationality of the topological relationship. The importance of each loading path, the structural robustness and the most vulnerable part of the system can be found concisely in accordance with this matrix. References | Related Articles | Metrics

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Development of the Large Increment Method in Analysis for Thin and Moderately Thick Plates JIA Hong-xue1* (贾红学), LONG Dan-bing2 (龙丹冰), LIU Xi-la3 (刘西拉) 2014, 19 (3):  265-273.  doi: 10.1007/s12204-014-1498-2 Abstract ( 547 )   Many displacement-based quadrilateral plate elements based on Mindlin-Reissner plate theory have been proposed to analyze the thin and moderately thick plate problems. However, numerical inaccuracies of some elements appear since the presence of shear locking and spurious zero energy modes for thin plate problems. To overcome these shortcomings, we employ the large increment method (LIM) for the analyses of the plate bending problems, and propose a force-based 8-node quadrilateral plate (8NQP) element which is based on Mindlin- Reissner plate theory and has no extra spurious zero energy mode. Several benchmark plate bending problems are presented to illustrate the accuracy and convergence of the plate element by comparing with the analytical solutions and displacement-based plate elements. The results show that the 8-node plate element produces fast convergence and accurate stress distributions in both the moderately thick and thin plate bending problems. The plate element is insensitive to mesh distortion and it can avoid the shear locking for thin plate analysis. References | Related Articles | Metrics

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Analysis of Epimetamorphic Rock Slopes Using Soft Computing KUMAR Manoj1, SAMUI Pijush2* 2014, 19 (3):  274-278.  doi: 0.1007/s12204-014-1499-1 Abstract ( 436 )   This article adopts three soft computing techniques including support vector machine (SVM), least square support vector machine (LSSVM) and relevance vector machine (RVM) for prediction of status of epimetemorphic rock slope. The input variables of SVM, LSSVM and RVM are bulk density, height, inclination, cohesion and internal friction angle. There are 53 datasets which have been used to develop the SVM, LSSVM and RVM models. The developed SVM, LSSVM and RVM give equations for prediction of status of epimetemorphic rock slope. The performance of SVM, LSSVM and RVM is 100%. A comparative study has been presented between the developed SVM, LSSVM and RVM. The results confirm that the developed SVM, LSSVM and RVM are effective tools for prediction of status of epimetemorphic rock slope. References | Related Articles | Metrics

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Distributed Cooperative Coverage of Mobile Robots with Consensus-Based Connectivity Estimation LI Xiao-li1,2* (李晓丽), ZHAO Shu-guang1 (赵曙光), LIU Hao1 (刘浩) 2014, 19 (3):  279-286.  doi: 10.1007/s12204-014-1500-z Abstract ( 583 )   This paper deals with the discrete-time connected coverage problem with the constraint that only local information can be utilized for each robot. In such distributed framework, global connectivity characterized by the second smallest eigenvalue of topology Laplacian is estimated through introducing distributed minimaltime consensus algorithm and power iteration algorithm. A self-deployment algorithm is developed to disperse the robots with the precondition that the estimated second smallest eigenvalue is positive at each time-step. Since thus connectivity constraint does not impose to preserve some certain edges, the self-deployment strategy developed in this paper reserves a sufficient degree of freedom for the motion of robots. Theoretical analysis demonstrates that each pair of neighbor robots can finally reach the largest objective distance from each other while the group keeps connected all the time, which is also shown by simulations. References | Related Articles | Metrics

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Stochastic Optimization in Cooperative Relay Networks for Revenue Maximization LU Hong-fang1,2*(吕红芳), ZHANG Hao1,3 (张浩) 2014, 19 (3):  287-293.  doi: 10.1007/s12204-014-1501-y Abstract ( 686 )   In cellular networks, cooperative relaying is an economic and promising way to enlarge the network capacity and coverage. In the case that multiple users and multiple relays are taken into account, efficient resource allocation is important in such networks. In this paper, we consider the joint relay power control with amplifyand- forward (AF) strategy and dynamic pricing for uplink cellular networks in order to maximize the network administrator’s system revenue. The system revenue is associated with pricing strategies and mobile users’ random data request, which is supported by the relay assisted transmission. To deal with the problem of the coupling in pricing and relay resource allocation, we utilize Lyapunov optimization techniques to design online pricing and relay power control without any statistic information of random events in networks. Theoretical analysis shows that the proposed algorithm can achieve a near-optimal performance and simulation results also validate its effectiveness and robustness. References | Related Articles | Metrics

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Simulation Platform for the Underwater Snake-Like Robot Swimming Based on Kane’s Dynamic Model and Central Pattern Generator YANG Ke (杨柯), WANG Xu-yang* (王旭阳), GE Tong (葛彤), WU Chao (吴超) 2014, 19 (3):  294-301.  doi: 10.1007/s12204-014-1502-x Abstract ( 818 )   A systematic method for swimming control of the underwater snake-like robot is still lacking. We construct a simulation platform of the underwater snake-like robot swimming based on Kane’s dynamic model and central pattern generator (CPG). The partial velocity is deduced. The forces which contribute to dynamics are determined by Kane’s approach. Hydrodynamic coefficients are determined by experiments. Then, we design a CPG-based control architecture implemented as the system of coupled nonlinear oscillators. The CPG, like its biological counterpart, can produce coordinated patterns of rhythmic activity while being modulated by simple control parameters. The relations between the CPG parameters and the speed of the underwater snake-like robot swimming are investigated. Swimming in a straight line, turning, and switching between swimming modes are implemented in our simulation platform to prove the feasibility of the proposed simulation platform. The results show that the simulation platform can imitate different swimming modes of the underwater snake-like robot. References | Related Articles | Metrics

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Calculation of 3D Sensitivity Matrix for Electromagnetic Tomography System Using Boundary Elements and the Perturbative Approach HE Min1 (何敏), ZHAO Qian2 (赵倩), YIN Wu-liang3*(尹武良) 2014, 19 (3):  302-307.  doi: 10.1007/s12204-014-1503-9 Abstract ( 639 )   Electromagnetic tomography (EMT) is a non-invasive imaging technique capable of mapping the conductivity and permeability of an object. In EMT, eddy currents are induced in the object by the activation coils, and the receiving coils can measure the EMT voltages. When the activation frequency is significantly large, we can treat the metallic targets as electrically perfect conductors (EPCs). In this situation, a thin skin approximation is reasonable and this type of scattering problem can be effectively treated by the boundary element method (BEM) formulated through integration equations. In this study, we compute three-dimensional (3D) sensitivity matrix between the sensors due to an EPC perturbation. Efficiency improvement is achieved through the utility of scalar magnetic potential. Two EPC objects, one sphere and one cube shaped, are simulated. The results agree well with the H dot H formula. Overall, we conclude that BEM can be used to calculate the 3D sensitivity matrix of an EMT system efficiently. This method is a general one for any shaped objects while the H dot H solution is only capable of producing the response for a small ball. References | Related Articles | Metrics

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Numerical Study on Die Design Parameters of Self-Pierce Riveting Process Based on Orthogonal Test HAN Shan-ling* (韩善灵), LI Zhi-yong (李志勇), GAO Yuan (高远), ZENG Qing-liang (曾庆良) 2014, 19 (3):  308-312.  doi: 10.1007/s12204-014-1504-8 Abstract ( 544 )   The concave die design of self-pierce riveting (SPR) is of critical importance for product quality. The optimization of concave die parameters based on orthogonal test is proposed to explore the relationship between self-pierce riveted joint quality and die parameters. There are nine independent die parameter factors in orthogonal test and each factor has 4 levels. In order to evaluate the interlock and neck thickness, we carry out numerical simulations by the software DEFORM-2D. Then, the primary and secondary factors that affect the joint quality have been found out by means of range analysis. Finally, an optimization scheme is brought forward to design concave die in SPR process, which indicates that the joint has higher quality than that of former orthogonal tests. This work can be extended by a detailed mechanical and fatigue analysis for the joint quality of SPR process. References | Related Articles | Metrics

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Receiver Autonomous Integrity Monitoring Availability and Fault Detection Capability Comparison Between BeiDou and GPS SU Xian-li1,2 (苏先礼), ZHAN Xing-qun1* (战兴群), NIU Man-cang1 (牛满仓), ZHANG Yan-hua1 (张炎华) 2014, 19 (3):  313-324.  doi: 10.1007/s12204-014-1505-7 Abstract ( 744 )   This paper used the statistical methods of quality control to assess receiver autonomous integrity monitoring (RAIM) availability and fault detection (FD) capability of BeiDou14 (Phase II with 14 satellites), BeiDou (Phase III with 35 satellites) and GPS (with 31 satellites) for the first time. The three constellations are simulated and their RAIM performances are quantified by the global, Asia-Pacific region and temporal variations respectively. RAIM availability must be determined before RAIM detection. It is proposed that RAIM availability performances from satellites and constellation geometry configuration are evaluated by the number of visible satellites (NVS, NVS > 5) and geometric dilution of precision (GDOP, GDOP < 6) together. The minimal detectable bias (MDB) and minimal detectable effect (MDE) are considered as a measure of the minimum FD capability of RAIM in the measurement level and navigation position level respectively. The analyses of simulation results testify that the average global RAIM performances for BeiDou are better than that for GPS except global RAIM holes proportion. Moreover, the Asia-Pacific RAIM performances for BeiDou are much better than that for GPS in all indexes. RAIM availability from constellation geometry configuration and RAIM minimum FD capability for BeiDou14 are better than that for GPS in Asia-Pacific region in all cases, but the BeiDou14 RAIM availability from satellites are worse than GPS’s. The methods and conclusions can be used for RAIM prediction and real-time assessment of all kinds of Global Navigation Satellite Systems (GNSS) constellation. References | Related Articles | Metrics

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Shafting Coupled Vibration Research Based on Wave Approach YANG Yong1,2 (杨勇), CHE Chi-dong1* (车驰东), TANG Wen-yong1 (唐文勇) 2014, 19 (3):  325-336.  doi: 10.1007/s12204-014-1506-6 Abstract ( 691 )   Because of propeller hydrodynamic influence, the shafting vibration is a coupled vibration which includes torsional, longitudinal and whirling vibrations. It is unsuitable to analyze different vibrations of propulsive shafting systems with development of shipbuilding technologies. To overcome the shortages of traditional marine standards, we establish a new numerical model of the shafting coupled vibration. And we put forward shafting coupled vibration calculation to ensure better reliability of main propulsion system. The shafting system is modeled into two sub-systems, a continuous one and a discrete one. Wave approach and transit matrix method are used to investigate displacement and stress fields in continuous and discrete sub-systems, respectively. And vibrations of different modes in both sub-systems are coupled by using dynamic equilibrium and continuity condition to deduce the global equations governing the motion of shafting. The coupling calculation is then used to research the reason of a very large crude carrier (VLCC) stern hull vibration. It is shown by the comparison of the results from both coupling and dependent vibration calculations that vibration in deferent directions will cause deformation in the same mode, which leads to extra stress and displacements on shafting, especially as the resonant frequencies of different vibration modes match each other. This is helpful to prevent ship stern vibration due to poor shafting vibration calculation. References | Related Articles | Metrics

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Operations Scheduling for Rail Mounted Gantry Cranes in a Container Terminal Yard BIAN Zhan1 (边展), LI Na1 (李娜), LI Xiang-jun2 (李向军), JIN Zhi-hong1* (靳志宏) 2014, 19 (3):  337-345.  doi: 10.1007/s12204-014-1507-5 Abstract ( 606 )   Arranging the retrieving sequence and making the operational plans for gantry cranes to enhance port efficiency have become vital issues for the container terminals. In this paper, the problem of retrieving containers from a yard in a given sequence is discussed as an important part of the ship-loading process. This problem is divided into three categories according to its optimization complexity, i.e., the retrieval problem of a crane with a single spreader (ACSS), the retrieval problem of a crane with multiple spreaders (ACMS), and the retrieval problem of multiple cranes with a single spreader (MCSS). Firstly, heuristic algorithms are proposed to develop a retrieving sequence for ACSS to reduce the operational time. Then, optimizing the assignment to multiple spreaders is conducted by exchanging the movements of the obtained retrieving sequence. Finally, the movements are further assigned to two cranes and integrated with the MCSS retrieval problem mentioned above. The numerical experiments show the effectiveness and practicability of the heuristic algorithms. References | Related Articles | Metrics

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Modified Numerical Model for Simulating Fluid-Filled Structure Response to Underwater Explosion with Cavitation XIAO Wei1 (肖巍), ZHANG A-man1* (张阿漫), WANG Yu2 (汪玉) 2014, 19 (3):  346-353.  doi: 10.1007/s12204-014-1508-4 Abstract ( 693 )   In this paper, a numerical method is established to analyze the response of fluid-filled structure to underwater explosion with cavitation and the validation of the method is illustrated. In the present implementation, the second-order doubly asymptotic approximation (DAA2) other than curved wave approximation (CWA) is used to simulate non-reflecting boundary. Based on the method, the difference between DAA2 non-reflecting boundary and CWA non-reflecting boundary is investigated; then, the influence of internal fluid volume and the influence of cavitation on dynamic response of spherical shell are analyzed. Compared with CWA non-reflecting boundary, DAA2 non-reflecting boundary treats added mass effects better. When the internal fluid is full, the displacement and velocity of spherical shell decrease, but, when the internal fluid is half, the displacement and velocity of spherical shell increase. The effect of cavitation is more obvious at the trailing point than at the leading point of spherical shell. References | Related Articles | Metrics

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Influence of the Inverse-Time Protection Relays on the Voltage Dip Index GAO Xin-ke1,2* (高新科), LIU Ya-peng3 (刘玡朋) 2014, 19 (3):  354-360.  doi: 10.1007/s12204-014-1509-3 Abstract ( 490 )   The probability-assessment analyses on the characteristic value of voltage dip by using Monte Carlo stochastic modeling method to stimulate the randomness of the short circuit fault are introduced. Using Matlab and Power Systems CAD (PSCAD), we design control interface which combines the electromagnetic transient simulation with the Monte Carlo method. Specifically, the designing of interface which is meant to employ the method of Matlab programming to control the electromagnetic transients including direct current (EMTDC) simulation is introduced. Furthermore, the influences of the protection devices on the voltage dip to ensure the authenticity and the referential reliability are simulated. A system with the inverse-time protection devices equipped on each line which can coordinate together is designed to cut off the short-circuit fault. The voltage dip of the designed system is assessed by the pre- and post-system average root mean square (RMS) variation frequency index, and the voltage dip index is compared with the Information Technology Industry Council (ITIC) curves. The simulation results demonstrate that the inverse-time relay protection equipments are well-coordinated, and the severity and the range of the voltage dip are influenced by the cooperation of the equipped inverse-time protection devices. References | Related Articles | Metrics

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Hydraulic Characteristics of Multi-Stage Orifice Plate AI Wan-zheng1* (艾万政), ZHOU Qi2 (周琦) 2014, 19 (3):  361-366.  doi: 10.1007/s12204-014-1510-x Abstract ( 517 )   Energy dissipater of multi-stage orifice plate, as a kind of effective energy dissipater with characteristics of high energy dissipation ratio and low cavitations risk, has become welcomed more and more by hydraulics researchers. The relationship between the contraction ratio of upper stage orifice plate and the lower one’s under the principle of equal-cavitation characteristics, and the reasonable distance between upper stage orifice plate and the lower one under the condition of complying with this principle, are two important factors to be considered for multi-stage energy dissipater design. In the present paper, these two factors were analyzed by theoretical consideration and numerical simulations, and solving methods were put forward. The conclusion in this paper was proved to be reasonable by model experiment. References | Related Articles | Metrics

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A New Algorithm to Automatically Extract the Drainage Networks and Catchments Based on Triangulation Irregular Network Digital Elevation Model QU Guo-dong1,2 (屈国栋), SU Dan-yang1* (苏丹阳), LOU Zhang-hua1 (楼章华) 2014, 19 (3):  367-377.  doi: 10.1007/s12204-014-1511-9 Abstract ( 778 )   A new algorithm to automatically extract drainage networks and catchments based on triangulation irregular networks (TINs) digital elevation model (DEM) was developed. The flow direction in this approach is determined by computing the spatial gradient of triangle and triangle edges. Outflow edge was defined by comparing the contribution area that is separated by the steepest descent of the triangle. Local channels were then tracked to build drainage networks. Both triangle edges and facets were considered to construct flow path. The algorithm has been tested in the site for Hawaiian Island of Kaho’olawe, and the results were compared with those calculated by ARCGIS as well as terrain map. The reported algorithm has been proved to be a reliable approach with high efficiency to generate well-connected and coherent drainage networks. References | Related Articles | Metrics

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Study of Graphene Doped Zinc Oxide Nanocomposite as Transparent Conducting Oxide Electrodes for Solar Cell Applications LI Pan-pan1 (李盼盼), MEN Chuan-ling1* (门传玲), LI Zhen-peng1 (李振鹏),CAO Min1 (曹敏), AN Zheng-hua2 (安正华) 2014, 19 (3):  378-384.  doi: 10.1007/s12204-014-1512-8 Abstract ( 865 )   The graphite oxide (GO) was prepared based on the modified Hummers method, then reacted with zinc acetate aqueous, sodium hydroxide aqueous and hydrazine hydrate, and was doped into ZnO eventually to form graphene doped ZnO, an alternative transparent conducting oxide (TCO) for solar cell applications. The samples were characterized by Raman spectrometer, X-ray diffractometer, Fourier transform infrared spectroscopy and scanning electron microscope, and compared with widely used aluminum doped ZnO (AZO) in resistivity and transmissivity. The results show that the transmissivity of graphene doped ZnO reaches the same level as that of AZO in visible light band. In ultraviolet light wave band, the transmissivity of graphene doped ZnO reaches as high as 50%, exceeding that of AZO which is only 20%. The resistivity of optimized graphene doped ZnO is 1.03 × 10?5 Ω · m, approaching AZO resistivity which is about 10 ?4—10?6 Ω · m. As a result, graphene doped ZnO may have potential applications in the area of TCO due to its low cost and high performance. References | Related Articles | Metrics