Table of Content

28 September 2012, Volume 46 Issue 09 Previous Issue    Next Issue

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Empirical Study on Underpricing Cause of Venture-backed IPOs Based on Information Asymmetry Hypothesis：Explanation from Reputation Effects LIU Xiao-Ming-1, HU Wen-Wei-2, LI Zhan-3 2012, 46 (09):  1059-1015.  Abstract ( 3482 )   Save Information asymmetry is one of main hypotheses that can be used to explain IPO underpricing. As the principal financial intermediaries in capital markets, underwriters and venture capital can exert the reputation effect and reduce the degree of information asymmetry, and therefore impose effects on the underpricing of venture-backed firms. The article innovatively puts forward the new measurements of venture capital and underwriter reputations, and finds that the reputations have significant effects on underpricing of venture-backed firms. Moreover, it proves that the higher reputation venture capital can attract higher reputation underwriters, which verifies the certificating role of venture capital and supports the information asymmetry hypothesis on IPO underpricing. The research plays an important role in showing the cause of IPO underpricing, verifying the reputation effects of underwriter and venture capital, probing the operation mechanism and exit strategies of venture capital, forming effective reputation mechanism in capital market and directing investors to invest rationally.   References | Related Articles | Metrics

Automation Technique, Computer Technology

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Geometrical Distortion Simulation Analysis of Data Matrix Code on Tool Cylinder LI Xia-Shuang, HE Wei-Ping, LEI Lei, WANG Wei, LIN Qing-Song 2012, 46 (09):  1349-1354.  Abstract ( 2806 )   Save The theory and process of geometrical distortion of Data Matrix (DM) code on tool cylinder were analysed. And the distortion modeling and simulation of DM code image were induced based on the perspective projection. The result shows that the model can better simulate the distortion of DM code on the tool cylinder. Through simulation analysis, appropriate size of DM code marked on certain curvature tool cylinder and appropriate geometric parameters of camera in acquisition process were obtained. References | Related Articles | Metrics

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Traffic Lights Recognition Based on Concatenated Filtering Method JIN Tao-a, WANG Chun-Xiang-a, WANG Bing-b, YANG Ming-b 2012, 46 (09):  1355-1360.  Abstract ( 3210 )   Save A method for detection and recognition of traffic lights based on intelligent vehiclemounted camera was proposed. Applying the threshold acquired by image training, the candidate regions of traffic lights are extracted using the color segmentation method. Next the concatenated filters are proposed as a way to classify the extracted candidate regions. And then template matching using normalized cross correlation techniques is adopted to validate the classified traffic lights candidates. The experimental results show that the proposed algorithm works effectively and robustly for traffic lights recognition for intelligent vehicles in complex urban environments.   References | Related Articles | Metrics

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An Efficient and Secure Spatial Encryption Scheme QI Cheng-Jie, DONG Xiao-Lei 2012, 46 (09):  1361-1365.  Abstract ( 2752 )   Save Spatial encryption was first introduced as an instance of generalized identity-based encryption by Boneh and Hamburg in 2008. Their scheme is only secure in selective model. This paper constructed a full secure and more efficient spatial encryption scheme which differs from Boneh and Hamburg’s scheme. The paper introduces a technique to map a vectors to elements of groups. Then it applies the dual system technique. With this technique and the three composite order bilinear groups decision problem, it can prove full security of the scheme in adaptive model. Because of only computing in composite groups without matrix, the efficiency of the scheme is much improved. Key words： References | Related Articles | Metrics

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Ship Ergonomics Evaluation Based on Virtual Human Real-Time Driven Modeling Technology QIU Shi-Guang-1, WU Dian-Liang-1, 2 , FAN Xiu-Min-1, 2 , HU Yong-3 2012, 46 (09):  1366-1370.  Abstract ( 2763 )   Save Aiming at the complex ergonomics problem during the design of ship a new method was proposed. In this method,  the virtual human realtime kinematics model was built based on dynamic constraints and rotation information, it can drive standard human with different percent in virtual reality environment. Then the realtime motion data captured by tracking system was mapped to the kinematics model for driving virtual human. Based on abovementioned method the virtual human realtime driven module was designed and realized. It was integrated to ship product navigation system (SPNavis), which is a virtual design platform for ship design evaluation.  The module was verified by a case of evaluating valve and channel layout in ship engine room. The result shows that body action is simulated fidelity and the evaluation process is simple and useful. References | Related Articles | Metrics

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Unmanned Surface Vehicle Local Path Planning Based on Marine Radar ZHUANG Jia-Yuan, SU Yu-Min, LIAO Yu-Lei, SUN Han-Bing 2012, 46 (09):  1371-1375.  Abstract ( 3111 )   Save  To solve the local path planning problem of unmanned surface vehicle (USV), this paper designed a path planning method based on marine radar image processing. An image’s edge preserving smoothing algorithm and an adaptive threshold election algorithm were used for marine radar image processing, then a mathematic model for the environment was founded, and the path was searched by a search of shortcut Dijkstra algorithm. Good results were received from experimental data in the sea and lake，with an optimal path identified in a short time that could satisfy the experimental need． References | Related Articles | Metrics

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Design of the Underwater Selfreconfigurable Sampler Module WU Xiao-Hui, GE Tong, LIU Jian-Min, ZHUANG Guang-Jiao, WU Chao 2012, 46 (09):  1376-1381.  Abstract ( 2155 )   Save This paper introduced a sampler module used on the underwater selfreconfigurable engineering prototype and designed a new grabtype sampler module used on the underwater selfreconfigurable engineering prototype based on the underwater selfreconfigurable system (USS). Detailed introduction of the working principle, carry way and controlling principle for the sampler module were given, at the same time, work force situation were analyzed. Finally, reliability of the sampler module was proved through the test and analysis. Key words： References | Related Articles | Metrics

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A Channel Reliability Based Multi-channel MAC Protocol in Wireless Sensor Networks XIAO Rong, JIANG Ling-Ge, HE Chen 2012, 46 (09):  1382-1386.  Abstract ( 2707 )   Save  In order to meet the demand of high bandwidth in resource-constrained sensor networks, a channel-reliability based multi-channel MAC protocol namely RB-MAC was proposed. This protocol introduces a new kind of control packet format and handshaking process. Moreover, a ready-to-send channel list concept and a ready-to-receive channel list concept were proposed. In order to find the most reliable channel for data transmission, the data channel selection problem is transformed into the multiarmed bandit problem which is solved by the upper confidence bound algorithm. The simulation results show that, compared with dynamic channel allocation MAC (DCA-MAC), RBMAC decreases the delay and packet loss ratio, thereby increase the throughput. Besides, RB-MAC is more immune to interferences.   References | Related Articles | Metrics

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BLP Based Access Control Mechanism in Multi-level Network Systems LIU Su-Na-1, 2 , PAN Li-1, 2 , 3 , YAO Li-Hong-2 2012, 46 (09):  1387-1391.  Abstract ( 2475 )   Save  N-BLP model for network access control was proposed based on the traditional BLP model. The new model can control the communication behavior between subjects by defining network elements and constructing new states transition rules. Also, the security validation of the model was given using the finite state machine theory. Further, an N-BLP access control prototype system based on LSM architecture and TCP/IP protocol was implemented. The results show that this system can finegrainedly control the connection establishment and data flow transmission, and guarantee the security of information exchanging between multi-level network systems.   References | Related Articles | Metrics

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Point-Based Medical Image Registration and Error Prediction Considering Noise Perturbation WANG Jun-Chen, WANG Tian-Miao, WANG Yun, HU Lei 2012, 46 (09):  1392-1397.  Abstract ( 3107 )   Save A novel point-based registration method for medical use considering noise perturbation was presented. The method is based on maximum likelihood esitimation (MLE), which is achieved by iteratively minimizing the absolute orientation problem (AOP) defined in the Mahalanobis space. The method can estimate not only the rigid transformation but also its variance based on the error propagation theory. The variance of the rigid transform is further propagated into the target registration error (TRE) and the expectation of the TRE is calculated for registration evaluation and fiducial marker (FM) configuration optimization. The numerical simulation shows the proposed method outperforms the classic AOP solution in both correctness and precision with the relative predictive error of the TRE less than 2%, of the standard deviation of the estimated transformation less than 4%.   References | Related Articles | Metrics

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Virtual Reference Feedback Tuning Control for Constrained Closed-Loop System WANG Jian-Hong, ZHU Yong-Hong, XIAO Xuan 2012, 46 (09):  1398-1405.  Abstract ( 2928 )   Save The virtual reference feedback tuning is a direct method that aims at minimizing a cost function of the 2-norm type by using a set of dates. To a nonlinear optimization problem with ellipsoid constrained conditions, the objective criterion function and two constrained conditions were converted to its corresponding linear matrix inequity. Then the ellipsoid optimization iterative algorithm was adopted to generate a sequence of ellipsoids with decreasing volume. An upper bound on the maximum number of possible iterates steps was derived. When considering the initialization of the ellipsoid optimization iterative algorithm, an initial ellipsoid strategy based on the level set of convex optimization theory was proposed. Finally, the simulation example results confirm the theoretical results. Then the results show when the virtual reference feedback tuning is used to design the two controllers in the closedloop system, the controller parameter estimation values are more accurate and the convergence speed of the ellipsoid optimization algorithm is fast.   References | Related Articles | Metrics

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Image Categorization Algorithm Based on Improved Sparse Coding Model TANG Feng-1, SUN Tan-Feng-1, 2 , JIANG Xing-Hao-1, 2 , LU Huan-1 2012, 46 (09):  1406-1410.  Abstract ( 4046 )   Save A novel image categorization algorithm based on improved sparse coding model for image representation and Random Forests for image classification was proposed. Firstly SIFT (ScaleInvariant Feature Transform) descriptors were extracted from images. Then sparse coding was adopted to train a visual dictionary and convert SIFT descriptors into sparse vectors. An efficient pooling method was employed to merge the sparse vectors in each grid of image and a pooled sparse vector was formed to represent the grid. According to the position of grids, the pooled sparse vectors were combined to form a single sparse vector for representing an image. Secondly Random Forests, a multiclass classifier was employed to classify sparse vectors which represent images. The experimental results show that the algorithm outperforms several stateofthearts in image categorization.   References | Related Articles | Metrics

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Wireless Endoscopic Robot System Applied in Gastrointestinal Tract GAO Peng, YAN Guo-Zheng 2012, 46 (09):  1411-1415.  Abstract ( 2811 )   Save To realize the minimally invasive diagnosis in the whole gastrointestinal tract, an endoscopic robot was developed with active locomotion ability and encapsulated with wireless technologies. Considering the locomotion environment and miniaturization of the endoscopic robot, three modules were designed and fabricated, which are inchworm-like flexible locomotion system, wireless power system and wireless communication system. The robotic prototype was also presented. The experimental results show that the endoscopic robot realizes the active locomotion for different environments; the wireless power system provides the minimum power of 360 mW with the input power of 14.7 W; the realtime telecontrol and video transmission with 30 f/s can be implemented within the distance of 8 m.     References | Related Articles | Metrics

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Modeling and Simulation of Flexible Cable Pendulum System Excited by Lifted Object Motion WANG Li-Quan-1, XU Yuan-Ge-1, HE Ning-2, LI Zhen-1 2012, 46 (09):  1416-1420.  Abstract ( 2754 )   Save According to the motion characteristics of flexible cable pendulum, the sling movement of crane vessel was decomposed into rope swing component and rope fluctuations component which are independent mutually. Using string vibration theory, this paper constructed a wire fluctuations mathematics model, which can ensure existence uniqueness under mixed initial boundary conditions. In addition, using unconditional stable hidden type difference method, it resolved the fluctuations equation numerical solutions stability. The life-like wire movement was  obtained by applying a hanging property swing mathematics model in which ball coordinates represent swing angle and the principle of superposition. The simulation results show that the mathematical model and the algorithm proposed in this paper can effectively solve the realistic sling real-time motion. References | Related Articles | Metrics

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Real-time Detection of Sea Surface Targets WAN Lei, ZENG Wen-Jing, QIN Zai-Bai, HUANG Shu-Ling 2012, 46 (09):  1421-1427.  Abstract ( 2700 )   Save A feasible method combining with the character of marine visible images was proposed to detect targets automatically in the sequential images from surface vehicle. It is not only suitable for small targets under seasky background but also for large targets under offshore background. First, the complexity of subimages and the average gray difference of their up and down neighborhood are measured to predict the sea line region, canny edge detection with surround suppression is applied to extract the contour of the region and Hough transforming is used to pick the longest line as sea line. There is no more processing if the image does not possess sea line region. Second, the region is defined as simple seasky background or complex offshore background according to the variance above the sea line. Clustering is implemented to extract the targets within the local region tailored by the sea line based on its smooth change of gray level. Third, gray characteristic of the rest sea is analyzed and sea gray range is obtained. Thus sea blocks and target blocks can be distinguished quickly. Finally, the segmented image is done with proper postprocessing in order to discard pseudo targets and mark the real targets. The experimental results prove that this method can locate the targets exactly. The time cost per frame is within 100 ms. It is robust and fast.   References | Related Articles | Metrics

Radiao Electronics, Telecommunication Technology

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Design and Fabrication of Drug-Loaded Metal Microneedle   CAO Yu-Tian, ZHU Jun, CAO Ying, LI Yi-Gui, CHEN Xiang, CHEN Di 2012, 46 (09):  1428-1430.  Abstract ( 2826 )   Save A novel structure design of coating out-of-plane microneedle was presented. With the combined adoption of anisotropic etching of silicon and photolithography of SU-8 photoresist, the mould of coating microneedle was prepared. The PDMS positive and negative structure was made by PDMS casting. Ni microneedle was prepared on the base of PDMS negative structure with low electric current electroforming. The fracture strength of the Ni microneedle is 366 MPa which is far higher than 3.183 MPa，the required insertion pressure of human skin. The design improves the drug-loaded ability of the microneedle.   References | Related Articles | Metrics

Automation Technique, Computer Technology

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Optimization Strategy for Bulk Ship Unloader Scheduling with Rail Routing Constraints HU Da-Yong, YAO Zhen-Qiang 2012, 46 (09):  1431-1435.  Abstract ( 2261 )   Save Based on the description of scheduling characteristics of ship unloaders, a scheduling optimization model was formulated to minimize the time for unloading operation. The components of a hybrid genetic algorithm were designed to obtain its near optimal solutions. By relaxing the complex constraints of the original problem, a lower bound for the relaxed problem was introduced to be a lower bound for the original problem. Moreover, computational experiments were conducted on instances of different sizes. The computational results show that the developed hybrid genetic algorithm can obtain reasonable solutions within an acceptable computational time.   References | Related Articles | Metrics

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Development of an MRI-Guided Puncture Location Robot with 6 Degree of Freedom MENG Ji-Chao-a, XIE Le-a, b , SHEN Xiang-Long-a 2012, 46 (09):  1436-1439.  Abstract ( 3052 )   Save The puncture surgery under MRI is always operated by the doctors’ hand, in which the patients are scanned multiple times, and the process is of low efficiency, high cost, which is difficult for doctors to finish the surgery. A novel puncture location robot under MRI with 6 degree of freedom was provided, which uses series and parallel mechanism design and driven by pneumatic. The magnetic resonance compatibility of the surgery robot was studied, including structure compatibility and material compatibility, and the location problem in puncture surgery was solved.   References | Related Articles | Metrics

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Fault Diagnosis of Rotating Mechanism Based on Ant Colony SVDD Algorithm and Cluster Method DU Wen-Liao-1, 2 , LI An-Sheng-2, SUN Wang-1, LI Yan-Ming-1, LIU Cheng-Liang-1 2012, 46 (09):  1440-1444.  Abstract ( 2690 )   Save For the absence of typical fault samples, the general machine learning methods can not be used directly. A hybrid fault diagnosis scheme for rotating mechanism was proposed combining the SVDD algorithm with the Davies Bouldin index (DBI) K-cluster method. Firstly, the SVDD model is constructed for the samples in the normal condition, and the ant colony algorithm is utilized to optimize the SVDD parameters. Then, when the number of rejected samples reaches a given threshold, the K-cluster method is employed to classify these samples and the labels are obtained; furthermore, the number of the classification is determined in accordance with the DBI. Finally, the one class samples are trained with SVDD individually, and the SVDD classifiers are joined to a complete diagnosis model based on a binary tree structure. For the multifault mode samples of rolling element bearing, the speed of training is nearly 10 times greater than that of the grid search approach, while the DBI is verified to determine the number of clusters, and the recognition rate for the bearing samples reaches 100%. References | Related Articles | Metrics

Radiao Electronics, Telecommunication Technology

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An Adaptive Speech Signal De-noising Algorithm Based on Estimation of Scaled Noise Energy XIE Wei-Sheng, YANG Gen-Ke 2012, 46 (09):  1445-1449.  Abstract ( 2440 )   Save A novel scheme of wavelet thresholding for speech signal de-noising was proposed. The scheme introduces a new thresholding function to overcome the drawbacks of traditional soft and hard thresholding functions. This newly introduced function is continuous at the threshold, so that it can curb the pseudogibbs phenomena effectively. Besides, it can reduce constant bias between the original wavelet coefficient and the estimated one, which helps to preserve the feature of the signal. With this threshold function, an adaptively selective algorithm of wavelet threshold was then proposed. This algorithm has both the virtues of spatial selective noise filtration method and the traditional threshold denoising method. It takes advantage of the inter-scale correlations of the wavelet coefficients to estimate the energy of scaled noise signal. In this algorithm, the threshold in each scale is selected based on the scaled noise energy. The simulations demonstrate that the proposed method is superior to some other existing adaptive wavelet de-noising methods.   References | Related Articles | Metrics

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Application of an Improved Image Distance Transform in Lane Detection JIANG Ru-Yi, LIU Hong-Tao, HU Wen, WANG Shi-Gang 2012, 46 (09):  1450-1454.  Abstract ( 2877 )   Save Based on the binary image from edge detection, an image processing method was suggested which applies a new “row” direction distance transform, taking the obtained distance value as the feature for the further lane detection. Moreover, experiments were conducted to validate that the resulting distance map is superior to and more effective than edge map in dealing with discontinuous lane marks. The results show that the new distance transform can not only provide distance information, but also make discontinuous lane boundaries continuous, and so as to improve the efficiency and robustness of lane detection.  References | Related Articles | Metrics

Metallography and Metallurgical Technology

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Analysis of Plasticity Deformation by In-Situ Means of High Strength Pipeline QI Li-Hua-1, ZHANG Wei-Wei-1, LIU Xiao-Feng-2, JI Ling-Kang-1, CHI Qiang-1, XIONG Qing-Ren-1 2012, 46 (09):  1455-1460.  Abstract ( 2913 )   Save X100 and X80 high grade pipeline steel dynamic plastic deformation behavior was investigated, by means of insitu SEM and insitu EEBSD analysis. The results show that, the microstructure of the two pipelines is mainly composed of acicular ferrite, granular bainite and M/A island. During the tensile process, acicular ferrite deforms firstly of the X100 microstructure. With the strain increase, the variable accumulation of the acicular ferrite leads to granular bainite deformation. Subsequently, inclusion nucleates micro crack nucleation core and extends with the externally applied stress increase. Micro-cracks connection leads to crack through the matrix until failure. Correspondingly, during insitu tensile process, the slide bands of the microstructure of the X80 pipeline run through the grains and deform cooperatively till fracture. By in-situ EBSD orientation of the X100 pipe, crystals after deformation rotate along the rolling surface for the {111} plane direction along the direction of tensile deformation.   References | Related Articles | Metrics

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Fatigue Fracture Behavior of K4169 Alloy Casting at Room Temperature KANG Mao-Dong, GAO Hai-Yan, WANG Jun, LING Li-Shi-Bao, SUN Bao-De 2012, 46 (09):  1461-1465.  Abstract ( 2366 )   Save The fatigue properties of the specimens cutting from the characteristic structure of the K4169 heavy investment casting were tested at room temperature. The mechanism of fatigue fracture was studied by combinational fracture analysis and temperature field simulation of solidification process. The results reveal that the structure of the casting has significant influence on the fatigue life. The fatigue failure of specimens is related to the content and distribution of the microporosity. A less microporosity leads to a well fatigue performance, and vice versa. The fatigue crack propagates along the interdentric Laves phase and carbide with low content of microporosity. However, the crack mainly accelerates through microporosity capturing with high content of microporosity, which leads to earlier failure of the specimen.   References | Related Articles | Metrics

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Experimental Study of Instability Mechanism on 1 200 MPa AdvancedHigh Strength Steel Sheets in the Process of Stamping HE Chang-Wei, GUO Bi-Meng, WANG Wu-Rong, WEI Xi-Cheng 2012, 46 (09):  1466-1470.  Abstract ( 2828 )   Save  The limit drawing formability of two advanced high strength steel sheets (AHSS) of tensile strength 1 200 MPa with the cup drawing test was studied. Their instability and failure mechanisms were also discussed from the standpoint of the microstructure. The results show that the limiting drawing ratio (LDR) of the DP1200 and the M1200 are 2.03 and 1.99, respectively. Their uniaxial tensile properties are difficult to accurately reflect the forming performance of material under the complex stress state. A large number of dimples on the fracture surfaces can be seen, which testifies the ductile fracture mode, but the crack propagation mechanism is not the same. For DP1200 steel, the failure mode is the crack propagation along the ferrite/martensite interfaces as well as through the martensitic grains. In M1200 steel, the crack propagates along the martensite interfaces. References | Related Articles | Metrics

General Industrial Technology

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A Failure Prediction Method of Fiber-Reinforced Composite Wing Stringer Subjected to Compressive Loading HU Yi-Le-1, YU Yin-1, WANG Hai-1, ZHAO Yi-2 2012, 46 (09):  1471-1475.  Abstract ( 3050 )   Save A method for predicting and analyzing the ultimate load and the location of failure of fiber-reinforced composite wing stringer subjected to compressive loading was proposed. A three dimensional FE model was established for displacement and damage analysis. The onset of damage was predicted by 2DHashin’s initiation criterion. A new stiffness degradation method of damaged material was suggested. The progression of damage was controlled by a damage evolution law, which combines stress failure and fracture energy dissipation of fracture mechanics. The model characterized damages in the form of damage variables. It was implemented with a user subroutine UMAT of ABAQUS/Standard by using a viscous regularization method which improves the convergence. The numerical prediction was compared with the experimental results of the compression test of composite wing stringers, and the ultimate load and failure location correlate well with the prediction results. Key words：  References | Related Articles | Metrics

Metallography and Metallurgical Technology

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High-Speed Jump Motion Control System for Electro-Discharge Machining Based on Programmable Multi-axis Controller LIANG Su, ZHAO Wan-Sheng, KANG Xiao-Ming 2012, 46 (09):  1476-1481.  Abstract ( 2769 )   Save  The requirements from designing high-speed jump motion control system for EDM (electro-discharge machining) were suggested in three terms: system capable of achieving high-speed motion control, system with good performance in responding and following the reference signal for axis and a jump motion course with high acceleration. A high-speed jump motion control system for EDM based on programmable multi-axis controller (PMAC) was studied and designed to meet the requirements suggested. The control system proposed was applied to type DK7140 commercial EDM machine and achieved stable main axis jump motion with maximum speed of 200 mm/s and maximum acceleration approximate to 9.68 m/s2.  Through the experiments of processing narrow slots, the control system obtains good results in terms of maximum machined depth and processing efficiency, and validates the good performance in control and machining. Key words：  References | Related Articles | Metrics

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Deep Drawability of 7075-T6 High Strength Aluminum Alloy at Warm Condition ZHOU Guo-Wei-a, LI Da-Yong-a, b , PENG Ying-Hong-a, b 2012, 46 (09):  1482-1486.  Abstract ( 3151 )   Save The forming properties of 7075-T6 high strength aluminum alloy were studied in the temperature range of 50~250  °C by warm deep drawing test. The experimental results show that: the limit drawing ratio(LDR) first shows an increasing trend and then decreases at the same tools temperature condition; while at different tools temperatures condition the LDR increases with temperature gradually, the drawability at different tools temperatures condition exceeds that of same tools temperature condition when the temperature is over 150  °C, the maximum load force declines with temperature increasing. The LDRs at various temperatures are different while the thickness of cross-section does not change apparently. The influences of holder force and punch velocity were investigated: the material could have better forming properties when the holder force is 5 kN, punch speed 10 mm/min. References | Related Articles | Metrics

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A Domain Decomposition Approach for Vibration Analysis of Joined Structures QU Ye-Gao, HUA Hong-Xing, MENG Guang, CHEN Yong, LONG Xin-Hua 2012, 46 (09):  1487-1492.  Abstract ( 2693 )   Save A domain decomposition approach was proposed for vibration analysis of joined structures with general boundary conditions. The joined structure is preliminarily divided into several substructures along the locations of the junctions and the prescribeddisplacement boundaries; then these substructures are further decomposed into regular subdomains to accommodate the computing requirement of highorder vibration modes. The constraint equations derived from interface continuity conditions between two adjacent subdomains are incorporated into the system energy functional by means of a subdomain generalized variational principle and leastsquares weighted residual method, which involves the reduction of conditional extremum problems to extremum problems without any constraints. To test the convergence, efficiency and accuracy of the present method, a typical joined conicalcylindricalconical shell with ring stiffeners was examined. Numerical solutions for natural frequency and dynamical response of the joined shell were compared with those obtained using the finite element program ANSYS. The present solution is found to be very efficient, robust and accurate. Key words： References | Related Articles | Metrics

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Numerical Simulation of Sink-Stability for Unmanned Underwater Lurk Vehicle PAN Guang, SHI Yao, DU Xiao-Xu, HUANG Qiao-Gao 2012, 46 (09):  1493-1497.  Abstract ( 10350 )   Save   The sink-stability of unmanned underwater lurk vehicle (UULV) was studied by using the computational fluid dynamics. First, the hexahedral mesh of the UULV in different sinking model was generated by ICEM CFD. Then the variation tendency of lateral force，lift force and rolling moment under different submarine speeds was gotten by using CFX. Based on the force analysis a mathematical model for the analysis of sink-UULV was established. Last, the effect of submarine speed and sinking model on UULV’s sink-stability was gotten through combining the numerical simulation’s result with that of math model. The result shows that the UULV can remain stable under 0.514 m/s submarine speed, it will be rollingover when the speed is equal to or greater than 1.028 m/s.   References | Related Articles | Metrics

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MOPOL Development and Uncertainties Analysis in IVR Assessment YANG Xiao, YANG Yan-Hua 2012, 46 (09):  1498-1502.  Abstract ( 2987 )   Save A program named MOPOL based on lumped parameter model was developed to assess IVR (invessel core debris retention) effectiveness according to the IVR assessment method——ROAAM (risk oriented accident analysis methodology), then the program was validated. Regarding the key parameters in IVR assessment such as break size, average effective time of irradiation and structure mass in the vessel, uncertainty analysis was made to evaluate the effects of these parameters to IVR effectiveness. The analysis results indicate that in the case of larger break accident and longer irradiation time, safety margins of the pressure vessel wall to thermal failure are smaller; in addition, properly increase structures mass in the pressure vessel can enhance IVR effectiveness. References | Related Articles | Metrics

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Dynamic Modeling and Analysis of Jeffcott Rotor-Annular Flow Coupled System SHI Ming-Lin, WANG De-Zhong, ZHANG Ji-Ge 2012, 46 (09):  1503-1508.  Abstract ( 2956 )   Save Based on the turbulent bulk flow theory and perturbation analysis, a dynamic model of Jeffcott rotor-annular flow coupled system was developed. Taking a large-scale canned motor pump rotor system as an example, the effects of rotating speed, rotor eccentricity, and stator and rotor wall frictions on dynamics of the rotor-annular coupled system were investigated using the complex mode analytical method. The analytical results show the annular flow causes the decrease of natural frequency greatly and generates divergence and leap of mode, the rotor eccentricity induces instability of rotor and the decrease of instability speed, and the stator and rotor wall friction effects increase rotor instability speed significantly. References | Related Articles | Metrics

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An Empirical Study on the Relationship between Stock Options Compensation and Risk of Chinese A-share Listed Companies LIU Yu-1, CHENG Dong-Quan-2, GU Feng-2 2012, 46 (09):  1516-1521.  Abstract ( 2783 )   Save Using the sample of Chinese A-share listed companies from 2006 to 2009, we make an empirical study on the relationship between managerial stock options compensation, investment risk and operating risk. We find that managerial stock options compensation, investment risk and operating risk have notably positive effects on each other. By introducing the concept of Vega, we indicate that the stock price volatility will increase the value of executives’ stock options, and reduce their risk aversion; thereby they will increase the company’s investment risk and operating risk. By controlling other factors and endogenous, we empirically prove the conclusion. References | Related Articles | Metrics

Mathematics

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BSDEs and Viscosity Solutions of the Associated System with Partial Integro-Differential Equations RAN Qi-Kang-a, b 2012, 46 (09):  1522-1528.  Abstract ( 2108 )   Save  An existence result and A uniqueness result of a  backward stochastic  differential equation driven by Teugels martingales associated with a Lévy process were obtained.  It is also shown that under some- conditions the solution of the BSDE provides a unique viscosity solution of the associated system with partial integro-differential equations.   References | Related Articles | Metrics

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Oscillation Criteria for a Class of Second Order Dynamic Equations with Damping on Time Scales YANG Jia-Shan 2012, 46 (09):  1529-1533.  Abstract ( 2470 )   Save The oscillation for certain second-order nonlinear variable delay dynamic equations with damping term and nonlinear neutral term on time scales was discussed. By using the time scales theory and the generalized Riccati transformation and the inequality technique, some new oscillation criteria for the equations were established. The results extend and improve some known results, but also unify the oscillation of second-order nonlinear delay differential equations and second-order nonlinear delay difference equations with damping term. Some examples were given to illustrate the main results of this article.   References | Related Articles | Metrics

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Theoretical Analysis of a Nonlinear Parabolic Equation with TimeDelay WU Hui-Ling 2012, 46 (09):  1534-1538.  Abstract ( 1970 )   Save Based on the denoising problem in image processing，the well-posedness of the initial-boundary value problem for a nonlinear parabolic equation with time-delay and a nonlocal term was studied.By using energy estimates and the fixed point theorem，the existence，uniqueness and stability of the weak solution to this initial-boundary problem were investigated．This study is helpful for the numerical simulation in image processing．   References | Related Articles | Metrics