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31 October 2013, Volume 18 Issue 5 Previous Issue    Next Issue

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Multi-Channel Spectrum Sensing in Cognitive Ad-hoc Networks: An Energy-Efficient Manner LI He1 (李 鹤), GAN Xiao-ying1,2* (甘小莺), CHEN Shi-yang1 (陈时阳), FENG Xin-xin1 (冯心欣) 2013, 18 (5):  513-519.  doi: 10.1007/s12204-013-1434-x Abstract ( 640 )   Cognitive radio, which is capable of enabling dynamic spectrum access, is a promising technology in future wireless communication. The feasibility of cognitive radio network greatly depends on the energy efficiency and reliability of spectrum sensing technology. In this paper, spectrum sensing in cognitive ad-hoc network (CAN) with wide-band dynamic spectrum is considered. A cognitive cluster head (CCH) is set and responsible for dividing the wide-band spectrum into multiple sub-channels; it can either sense sub-channels in a centralized manner, or make use of sensing modules to sense sub-channels in a distributed manner. Then cognitive users (CUs) can get sensing results and access to the available sub-channel. We take the cost of control message into consideration and formulate the energy consumption of CAN in terms of sub-channel sampling rate and whole-band sensing time. We define energy efficiency intuitively and solve the energy efficiency optimization problem with sensing reliability constraints by constructing a parametric problem and obtain the optimal sampling rate and the wholeband sensing time. Power dissipation model of a practical A/D convertor (ADC) is introduced, and numerical results are given to show the energy efficiency performance of two different sensing manners. References | Related Articles | Metrics

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A Cryogenic 10-bit Successive Approximation Register Analog-to-Digital Converter Design with Modified Device Model ZHAO Yi-qiang1* (赵毅强), YANG Ming1 (杨 明), ZHAO Hong-liang2 (赵宏亮) 2013, 18 (5):  520-525.  doi: 10.1007/s12204-013-1436-8 Abstract ( 557 )   A 10-bit 500 kHz low-power successive approximation register (SAR) analog-to-digital converter (ADC) for cryogenic infrared readout circuit is proposed. To improve the simulation accuracy of metal-oxidesemiconductor field-effect transistors (MOSFETs), corresponding modification in device model is presented on the basis of BSIM3v3 with parameter extraction at 77K. Corresponding timing is adopted in comparator to eliminate the influence caused by abnormal performance of MOSFETs at 77 K. The SAR ADC is fabricated and verified by standard 0.35 μm complementary metal oxide semiconductor (CMOS) process. At 77 K, measurement results show that signal to noise and distortion ratio (SNDR) is 54.74 dB and effective number of bits (ENOB) is 8.8 at the sampling rate of 500 kHz. The total circuit consumes 0.6mW at 3.3V power supply. References | Related Articles | Metrics

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Infrared and Visible Image Fusion Based on Region of Interest Detection and Nonsubsampled Contourlet Transform LIU Huan-xi1,2* (刘欢喜), ZHU Tian-hong1 (朱天竑), ZHAO Jia-jia3 (赵佳佳) 2013, 18 (5):  526-534.  doi: 10.1007/s12204-013-1437-7 Abstract ( 985 )   In order to enhance the contrast of the fused image and reduce the loss of fine details in the process of image fusion, a novel fusion algorithm of infrared and visible images is proposed. First of all, regions of interest (RoIs) are detected in two original images by using saliency map. Then, nonsubsampled contourlet transform (NSCT) on both the infrared image and the visible image is performed to get a low-frequency sub-band and a certain amount of high-frequency sub-bands. Subsequently, the coefficients of all sub-bands are classified into four categories based on the result of RoI detection: the region of interest in the low-frequency sub-band (LSRoI), the region of interest in the high-frequency sub-band (HSRoI), the region of non-interest in the low-frequency sub-band (LSNRoI) and the region of non-interest in the high-frequency sub-band (HSNRoI). Fusion rules are customized for each kind of coefficients and fused image is achieved by performing the inverse NSCT to the fused coefficients. Experimental results show that the fusion scheme proposed in this paper achieves better effect than the other fusion algorithms both in visual effect and quantitative metrics. References | Related Articles | Metrics

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Robust Ergodic Rate Transmission for Time Division Duplex Beamforming Systems ZHOU Bao-long1,2* (周宝龙), JIANG Ling-ge1 (蒋铃鸽), HE Chen1 (何 晨) 2013, 18 (5):  535-541.  doi: 10.1007/s12204-013-1435-9 Abstract ( 641 )   In time division duplex (TDD) beamforming systems, the base station estimates the channel state information (CSI) at transmitter based on uplink pilots and then uses it to generate the beamforming vector in the downlink transmission. Because of the constraints of the TDD frame structure and the uplink pilot overhead, there inevitably exists CSI delay and channel estimation error between CSI estimation and downlink transmission channel, which would degrade system ergodic rate. In this paper, we propose a robust ergodic rate transmission scheme, in which the uplink pilot time interval (UPTI) of an active user is adaptively adjusted according to the changing channel conditions such as Doppler frequency shift, uplink pilot signal to noise ratio (SNR), to minimize the impact of CSI delay and channel estimation error on the ergodic rate of TDD beamforming systems. In order to get the optimal UPTI, we first derive the average post-processing SNR for TDD beamforming systems with channel estimation error and CSI delay. We then obtain the optimal UPTI, which maximizes the average post-processing SNR, given the normalized pilot overhead (the number of pilot symbols per data symbol). The numerical simulation results validate that the the proposed robust ergodic rate transmission scheme not only maximizes the average post-processing SNR but also maximizes the system ergodic rate. Moreover, the scheme can adapt well to the changing channel environments compared with the current fixed UPTI scheme. Especially our research is valuable for the uplink sounding reference signal design in long term evolution advanced (LTEAdvanced) system. References | Related Articles | Metrics

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Bi-criteria Optimal Fault-Tolerable Control for SY-II Remote Operated Vehicle JIANG Shu-qiang1* (姜述强), JIN Hong-zhang1 (金鸿章), WEI Feng-mei2,3 (魏凤梅) 2013, 18 (5):  542-548.  doi: 10.1007/s12204-013-1438-6 Abstract ( 530 )   This paper proposed a bi-criteria weighting approach for fault tolerant control (FTC) of SY-II remote operated vehicle (ROV). This approach integrates the minimum kinetic energy (2-norm optimal) approach with the infinity-norm approach through a weighting coefficient, on the basis of SY-II ROV force allocation model. For the realization of fault tolerable control, this approach converts a quadratic programming problem into primaldual neural network. From the motion control simulations and experiments, bi-criteria optimization approach outperforms minimum kinetic energy optimization in FTC, SY-II ROV can realize 2-degree of freedom (DOF) horizontal fault tolerant control with one main thruster and any of horizontal ones. Therefore, this scheme is proved to be of superiority and computational efficiency, both the reliability and safety for ROV have been improved. References | Related Articles | Metrics

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Adaptive Robust Sliding Mode Control for Ship Straight-Line Tracking in Random Waves LIU Cheng1* (刘 程), ZOU Zao-jian1,2 (邹早建), LI Tie-shan3 (李铁山) 2013, 18 (5):  549-553.  doi: 10.1007/s12204-013-1430-1 Abstract ( 713 )   Since complex controllers do not suit for application, we design a simple controller with robustness in changeable sea state. The characteristics of ship motion are large inertia, strong nonlinearity and large time delay. This paper employs adaptive sliding mode technique. We focus on a class of underactuated ship systems with parametric uncertainties and wave effects. Random wave effects are seldom considered in former studies. Various simulations validate the adaptive characteristics and robustness of the proposed controller. The closed-loop system is stable and tracking error can be arbitrarily small by Lyapunov approach. References | Related Articles | Metrics

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Ontology-Based Model of Network and Computer Attacks for Security Assessment GAO Jian-bo1 (高建波), ZHANG Bao-wen1* (张保稳), CHEN Xiao-hua2 (陈晓桦), LUO Zheng3 (罗 铮) 2013, 18 (5):  554-562.  doi: 10.1007/s12204-013-1439-5 Abstract ( 805 )   With increased cyber attacks over years, information system security assessment becomes more and more important. This paper provides an ontology-based attack model, and then utilizes it to assess the information system security from attack angle. We categorize attacks into a taxonomy suitable for security assessment. The proposed taxonomy consists of five dimensions, which include attack impact, attack vector, attack target, vulnerability and defense. Afterwards we build an ontology according to the taxonomy. In the ontology, attack related concepts included in the five dimensions and relationships between them are formalized and analyzed in detail. We also populate our attack ontology with information from national vulnerability database (NVD) about the vulnerabilities, such as common vulnerabilities and exposures (CVE), common weakness enumeration (CWE), common vulnerability scoring system (CVSS), and common platform enumeration (CPE). Finally we propose an ontology-based framework for security assessment of network and computer systems, and describe the utilization of ontology in the security assessment and the method for evaluating attack effect on the system when it is under attack. References | Related Articles | Metrics

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Advanced Unified Failure Model on Uniformly Reinforced Concrete Box Section Members LUO Hua-xun* (骆华勋), LIU Xi-la (刘西拉) 2013, 18 (5):  563-569.  doi: 10.1007/s12204-013-1440-z Abstract ( 560 )   Based on the traditional Nielsen model, a unified failure model on the uniformly reinforced concrete box section members under combined forces was introduced by Luo and Liu. One of their contributions is adjustment of the shear carrying capacity of concrete at the member failure surface. In the unified failure model, the comparison with the experimental results verified this adjustment. Nevertheless, it should be pointed out that the adjustment factor of shear carrying capacity at member failure surface for the reinforced concrete members in the unified failure model is a fixed adjustment constant for all experiment data, which is basically determined by curve fitting. However, the adjustment factor should vary with the normal stress at the member failure surface. In this paper, an advanced theoretical model is introduced, in which the adjustment factor of shear carrying capacity at failure surface is a variable related to the normal stress at failure surface. Furthermore, the advanced unified failure model on the uniformly reinforced concrete box section member can still be expressed in a simple form. Finally, the comparison with several groups of test data has verified that this advanced model is more accurate and feasible to be used in design. References | Related Articles | Metrics

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AMEsim Based Simulation on Hydraulic Experiment Rig for Assembly of Stator Components HAO Ming (郝 明), JIANG Wei* (蒋 玮) 2013, 18 (5):  570-576.  doi: 10.1007/s12204-013-1429-7 Abstract ( 693 )   A hydraulic experimental platform for the assembly of stator components was developed, and the simulation on this system was performed based on software AMEsim. Characteristics of the system, such as the pressure and the displacement, were analyzed. The results guide design of the hydraulic system of experiment platform for the assembly of the stator. References | Related Articles | Metrics

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Stochastic Optimal Control for First-Passage Failure of Nonlinear Oscillators with Multi-Degrees-of-Freedom GAO Yang-yan (高阳艳), WU Yong-jun* (吴勇军) 2013, 18 (5):  577-582.  doi: 10.1007/s12204-013-1428-8 Abstract ( 574 )   To enhance the reliability of the stochastically excited structure, it is significant to study the problem of stochastic optimal control for minimizing first-passage failure. Combining the stochastic averaging method with dynamical programming principle, we study the optimal control for minimizing first-passage failure of multidegrees- of-freedom (MDoF) nonlinear oscillators under Gaussian white noise excitations. The equations of motion of the controlled system are reduced to time homogenous diffusion processes by stochastic averaging. The optimal control law is determined by the dynamical programming equations and the control constraint. The backward Kolmogorov (BK) equation and the Pontryagin equation are established to obtain the conditional reliability function and mean first-passage time (MFPT) of the optimally controlled system, respectively. An example has shown that the proposed control strategy can increase the reliability and MFPT of the original system, and the mathematical treatment is also facilitated. References | Related Articles | Metrics

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Experimental Investigation on Characteristics of Blast Load in Partially Confined Cabin Structure KONG Xiang-shao* (孔祥韶), WU Wei-guo (吴卫国), LI Jun (李 俊),LI Xiao-bin (李晓彬), XU Shuang-xi (徐双喜) 2013, 18 (5):  583-589.  doi: 10.1007/s12204-013-1431-0 Abstract ( 642 )   Some characteristics of interior explosions within a cabin structure with a venting hole are investigated. It may simulate a warhead explosion inside a cabin following its penetration through the cabin wall. The study includes both experimental and theoretical analyses of the problem. The experimental investigation comprises of two types of explosives at the center of the cabin. The pressure distributions at different locations on the cabin wall are obtained. The effect of internal shock reflection is analyzed by using the method of images (MOI). It is found that the geometric symmetries can cause the multiple reflected shocks to converge with strength comparable to the initial free shock. References | Related Articles | Metrics

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Numerical Investigation on the Hydrodynamic Difference Between Internal and External Turret-Moored FLNG ZHAO Wen-hua (赵文华), YANG Jian-min* (杨建民), HU Zhi-qiang (胡志强), WEI Yue-feng (魏跃峰) 2013, 18 (5):  590-597.  doi: 10.1007/s12204-011-1202-8 Abstract ( 666 )   Motion responses of the floating liquefied natural gas (FLNG) hull and the mooring loads in a 100- year return environmental condition are predicted with the help of the well known coupled dynamic analysis code DeepC. A ship-shaped turret-moored FLNG moored by 4×3 chain-polyester-chain lines in 1.5 km depth of water is studied. Two types of turrets such as internal and external turrets, resulting from different locations of the turrets, are adopted respectively in the numerical simulations. Motion responses of the FLNG hull and forces of the mooring lines obtained from the internal turret case and external turret case are compared with each other. Significant differences are obtained. Statistic analysis is also used to analyze the comparison results, and effects of the turret location on the FLNG hydrodynamic characteristics are summed up. The conclusion regarding the hydrodynamic differences between internal and external turret-moored FLNG systems would provide help for design of the FLNG system. References | Related Articles | Metrics

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Motion of an Underwater Self-Reconfigurable Robot with Tree-Like Configurations WU Chao (吴 超), WANG Xu-yang (王旭阳), ZHUANG Guang-jiao (庄广胶)，ZHAO Min (赵 敏), GE Tong* (葛 彤) 2013, 18 (5):  598-605.  doi: 10.1007/s12204-013-1433-y Abstract ( 642 )   Underwater self-reconfigurable system (USS), an underwater self-reconfigurable robot consisting of two types of modules, can reform various configurations in real time. Compared with normal underwater robots, its diverse configurations bring forward good adaptability and more abundant gaits. For the tree-like configurations, we propose a technique for dynamic modeling and configuration description. The eel-like configuration and the octopus-like one are chosen as examples to verify the technique, and some gaits are designed. For the eel-like configuration with the serpentine gait, the technique gives the same simulation results as existing eel-like models. For other cases, simulation results are consistent well with what happens in nature. References | Related Articles | Metrics

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An Efficient Approach for Solving Yard Crane Scheduling in a Container Terminal HE Jun-liang1,2* (何军良), ZHANG Wei-min1 (张为民), HUANG You-fang2 (黄有方), YAN Wei2 (严 伟) 2013, 18 (5):  606-619.  doi: 10.1007/s12204-013-1441-y Abstract ( 502 )   An efficient approach for yard crane (YC) scheduling is proposed in this paper. The definition of task group for YC scheduling is proposed. A mixed integer programming (MIP) model is developed. In the model, objective functions are subject to the minimization of the total delay of complete time for all task groups and the minimization of block-to-block movements of YCs. Due to the computational scale of the non-deterministic polynomial (NP) complete problem regarding YC scheduling, a rolling-horizon decision-making strategy is employed to solve this problem, by converting the MIP model into another MIP model in the scheduling of each rolling period. Afterwards, a heuristic algorithm based on modified A* search is developed to solve the converted model and obtain near optimal solution. Finally, the computational experiments are used to examine the performance of the proposed approach for YC scheduling. References | Related Articles | Metrics

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Slat Noise Suppression Using Upstream Mass Injection HUANG Hua (黄 华), LI Wei-peng (李伟鹏), WANG Fu-xin* (王福新) 2013, 18 (5):  620-629.  doi: 10.1007/s12204-013-1432-z Abstract ( 593 )   A new approach, mass injection near the slat cusp, is proposed for the suppression of slat noise. The mechanism and efficiency of the slat noise suppression using upstream mass injection are numerically studied with hybrid Reynolds-averaged Navier-Stokes simulation/Large eddy simulation (RANS/LES) of a three-component high-lift model. Ffowcs-Williams and Hawking (FW-H) integration is employed to obtain far-field acoustic characteristics. Results show that with injection, aerodynamic capability of the high-lift devices is sustained. In addition, a considerable noise reduction is observed in the downward direction. With detailed analysis of the time-averaged and instantaneous flow fields, two mechanisms are identified as the reason accounting for the noise suppression: upstream mass injection significantly reduces the scale and strength of the vortices stemming from the cusp; the shear layer is lifted up, which relieves the shear layer impingement on the slat lower surface. References | Related Articles | Metrics

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Network Structure and Reliability Analysis of a New Integrated Circuit Card Payment System for Hospital ZHANG Jing1 (章 菁), ZHENG Xi-tao3 (郑西涛), YU Ye-hua2 (俞夜花),ZHANG Yong-wei2 (张永伟), YANG Kun3 (杨 堃), SHI Jun2* (石 军) 2013, 18 (5):  630-633.  doi: 10.1007/s12204-013-1411-4 Abstract ( 643 )   This paper proposes a redundant network communication structure for the patient integrated circuit (IC) card payment system in a hospital information system (HIS), compares it with the network structure of normal hospital IC card system, and calculates the reliabilities of the related communications like the RS485 communication and the Ethernet communication. The new structure can effectively promote the reliability of the hospital operation and ensure the payment collection when the Ethernet network is broken. The system is applied to a local hospital and the cost-performance rate is satisfactory during the application. References | Related Articles | Metrics

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Application of Particle Swarm Algorithm in the Optimal Allocation of Regional Water Resources Based on Immune Evolutionary Algorithm QU Guo-dong* (屈国栋), LOU Zhang-hua (楼章华) 2013, 18 (5):  634-640.  doi: 10.1007/s12204-013-1442-x Abstract ( 681 )   The optimal allocation model of regional water resources is built with the purpose of maximizing the comprehensive economic, social and environmental benefits of regional water consumption. In order to solve the problems that easily appear during the model solution of regional water resource optimal allocation with multiple water sources, multiple users and multiple objectives like “curse of dimensionality” or sinking into local optimum, this paper proposes a particle swarm optimization (PSO) algorithm based on immune evolutionary algorithm (IEA). This algorithm introduces immunology principle into particle swarm algorithm. Its immune memorizing and self-adjusting mechanism is utilized to keep the particles in the fitness level at a certain concentration and guarantee the diversity of population. Also, the global search characteristics of IEA and the local search capacity of particle swarm algorithm have been fully utilized to overcome the dependence of PSO on initial swarm and the deficiency of vulnerability to local optimum. After applying this model to the allocation of water resources in Zhoukou, we obtain the scheme for optimization allocation of water resources in the planning level years, i.e. 2015 and 2025 under the guarantee rate of 50%. The calculation results indicate that the application of this algorithm to solve the issue of optimal allocation of regional water resources is reliable and reasonable. Thus it offers a new idea for solving the issue of optimal allocation of water resources. References | Related Articles | Metrics