Mathematical Problems in Engineering http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. Vision-Based Bicycle Detection Using Multiscale Block Local Binary Pattern Wed, 01 Oct 2014 00:00:00 +0000 http://www.hindawi.com/journals/mpe/2014/370685/ Bicycle traffic has heavy proportion among all travel modes in some developing countries, which is crucial for urban traffic control and management as well as facility design. This paper proposes a real-time multiple bicycle detection algorithm based on video. At first, an effective feature called multiscale block local binary pattern (MBLBP) is extracted for representing the moving object, which is a well-classified feature to distinguish between bicycles and nonbicycles; then, a cascaded bicycle classifier trained by AdaBoost algorithm is proposed, which has a good computation efficiency. Finally, the method is tested with video sequence captured from the real-world traffic scenario. The bicycles in the test scenario are successfully detected. Hongyu Hu, Pengfei Tao, Zhenhai Gao, Qingnian Wang, Zhihui Li, and Zhaowei Qu Copyright © 2014 Hongyu Hu et al. All rights reserved. Fabrication of Compact Microstrip Line-Based Balun-Bandpass Filter with High Common-Mode Suppression Tue, 30 Sep 2014 12:46:09 +0000 http://www.hindawi.com/journals/mpe/2014/985064/ A new type of balun-bandpass filter was proposed based on the traditional coupled-line theory and folded open-loop ring resonators (OLRRs) configuration. For that, a new device with both filter-type and balun-type characteristics was investigated and fabricated. Both magnetic and electric coupling structures were implemented to provide high performance balun-bandpass responses. The fabricated balun-bandpass filters had a wide bandwidth more than 200 MHz and a low insertion loss less than 2.51 dB at a center frequency of 2.6 GHz. The differences between the two outputs were below 0.4 dB in magnitude and within 180 ± 7° in phase. Also, the balun-bandpass filter presented an excellent common-mode rejection ratio over 25 dB in the passband. An advanced design methodology had been adopted based on EM simulation for making these designed parameters of OLRRs, microstrip lines, and open stubs. The measured frequency responses agreed well with simulated ones. Chia-Mao Chen, Shoou-Jinn Chang, Yen-Liang Pan, Cheng-Yi Chen, and Cheng-Fu Yang Copyright © 2014 Chia-Mao Chen et al. All rights reserved. Optimization Model for Headway of a Suburban Bus Route Tue, 30 Sep 2014 12:03:53 +0000 http://www.hindawi.com/journals/mpe/2014/979062/ Due to relatively low passenger demand, headways of suburban bus route are usually longer than those of urban bus route. Actually it is also difficult to balance the benefits between passengers and operators, subject to the service standards from the government. Hence the headway of a suburban bus route is usually determined on the empirical experience of transport planners. To cope with this problem, this paper proposes an optimization model for designing the headways of suburban bus routes by minimizing the operating and user costs. The user costs take into account both the waiting time cost and the crowding cost. The feasibility and validity of the proposed model are shown by applying it to the Route 206 in Jiangning district, Nanjing city of China. Weightages of passengers’ cost and operating cost are further discussed, considering different passenger flows. It is found that the headway and objective function are affected by the weightages largely. Xiaohong Jiang, Xiucheng Guo, and Bin Ran Copyright © 2014 Xiaohong Jiang et al. All rights reserved. Stability and Bifurcation of a Computer Virus Propagation Model with Delay and Incomplete Antivirus Ability Tue, 30 Sep 2014 11:34:11 +0000 http://www.hindawi.com/journals/mpe/2014/475934/ A new computer virus propagation model with delay and incomplete antivirus ability is formulated and its global dynamics is analyzed. The existence and stability of the equilibria are investigated by resorting to the threshold value . By analysis, it is found that the model may undergo a Hopf bifurcation induced by the delay. Correspondingly, the critical value of the Hopf bifurcation is obtained. Using Lyapunov functional approach, it is proved that, under suitable conditions, the unique virus-free equilibrium is globally asymptotically stable if , whereas the virus equilibrium is globally asymptotically stable if . Numerical examples are presented to illustrate possible behavioral scenarios of the mode. Jianguo Ren and Yonghong Xu Copyright © 2014 Jianguo Ren and Yonghong Xu. All rights reserved. A Comparative Assessment of Spalart-Shur Rotation/Curvature Correction in RANS Simulations in a Centrifugal Pump Impeller Tue, 30 Sep 2014 11:33:30 +0000 http://www.hindawi.com/journals/mpe/2014/342905/ RANS simulation is widely used in the flow prediction of centrifugal pumps. Influenced by impeller rotation and streamline curvature, the eddy viscosity models with turbulence isotropy assumption are not accurate enough. In this study, Spalart-Shur rotation/curvature correction was applied on the SST - turbulence model. The comparative assessment of the correction was proceeded in the simulations of a centrifugal pump impeller. CFD results were compared with existing PIV and LDV data under the design and low flow rate off-design conditions. Results show the improvements of the simulation especially in the situation that turbulence strongly produced due to undesirable flow structures. Under the design condition, more reasonable turbulence kinetic energy contour was captured after correction. Under the low flow rate off-design condition, the prediction of turbulence kinetic energy and velocity distributions became much more accurate when using the corrected model. So, the rotation/curvature correction was proved effective in this study. And, it is also proved acceptable and recommended to use in the engineering simulations of centrifugal pump impellers. Ran Tao, Ruofu Xiao, Wei Yang, and Fujun Wang Copyright © 2014 Ran Tao et al. All rights reserved. Maximizing Lifetime of Wireless Sensor Networks with Mobile Sink Nodes Tue, 30 Sep 2014 11:25:35 +0000 http://www.hindawi.com/journals/mpe/2014/762979/ In order to maximize network lifetime and balance energy consumption when sink nodes can move, maximizing lifetime of wireless sensor networks with mobile sink nodes (MLMS) is researched. The movement path selection method of sink nodes is proposed. Modified subtractive clustering method, k-means method, and nearest neighbor interpolation method are used to obtain the movement paths. The lifetime optimization model is established under flow constraint, energy consumption constraint, link transmission constraint, and other constraints. The model is solved from the perspective of static and mobile data gathering of sink nodes. Subgradient method is used to solve the lifetime optimization model when one sink node stays at one anchor location. Geometric method is used to evaluate the amount of gathering data when sink nodes are moving. Finally, all sensor nodes transmit data according to the optimal data transmission scheme. Sink nodes gather the data along the shortest movement paths. Simulation results show that MLMS can prolong network lifetime, balance node energy consumption, and reduce data gathering latency under appropriate parameters. Under certain conditions, it outperforms Ratio_w, TPGF, RCC, and GRND. Yourong Chen, Zhangquan Wang, Tiaojuan Ren, Yaolin Liu, and Hexin Lv Copyright © 2014 Yourong Chen et al. All rights reserved. Swarm Intelligence-Based Hybrid Models for Short-Term Power Load Prediction Tue, 30 Sep 2014 11:09:20 +0000 http://www.hindawi.com/journals/mpe/2014/712417/ Swarm intelligence (SI) is widely and successfully applied in the engineering field to solve practical optimization problems because various hybrid models, which are based on the SI algorithm and statistical models, are developed to further improve the predictive abilities. In this paper, hybrid intelligent forecasting models based on the cuckoo search (CS) as well as the singular spectrum analysis (SSA), time series, and machine learning methods are proposed to conduct short-term power load prediction. The forecasting performance of the proposed models is augmented by a rolling multistep strategy over the prediction horizon. The test results are representative of the out-performance of the SSA and CS in tuning the seasonal autoregressive integrated moving average (SARIMA) and support vector regression (SVR) in improving load forecasting, which indicates that both the SSA-based data denoising and SI-based intelligent optimization strategy can effectively improve the model’s predictive performance. Additionally, the proposed CS-SSA-SARIMA and CS-SSA-SVR models provide very impressive forecasting results, demonstrating their strong robustness and universal forecasting capacities in terms of short-term power load prediction 24 hours in advance. Jianzhou Wang, Shiqiang Jin, Shanshan Qin, and Haiyan Jiang Copyright © 2014 Jianzhou Wang et al. All rights reserved. Competition with Online and Offline Demands considering Logistics Costs Based on the Hotelling Model Tue, 30 Sep 2014 10:43:48 +0000 http://www.hindawi.com/journals/mpe/2014/160782/ Through popular information technologies (e.g., call centers, web portal, ecommerce and social media, etc.), traditional shops change their functions for servicing online demands while still providing offline sales and services, which expand the market and the service capacity. In the Hotelling model that formulates the demand effect by considering just offline demand, the shops in a line city will locate at the center as a the result of competition by games. The online demands are met by the delivery logistics services provided by the shops with additional cost; the consumers’ waiting time after their orders also affects their choices for shops. The main purpose is to study the effects of the following aspects on the shops’ location competition: two logistics costs (consumers’ travelling cost for offline demands and the shops’ delivery logistics cost for online demands), the consumers’ waiting cost for online orders, and the ratios of online demands to the whole demands. Therefore, this study primarily contributes to the literature on the formulation of these aspects by extending the Hotelling model. These features and effects are demonstrated by experiments using the extended Hotelling models. Zhi-Hua Hu, Chen Wei, Qing Li, and Fan Xiao Copyright © 2014 Zhi-Hua Hu et al. All rights reserved. A Novel RFID Sensing System Using Enhanced Surface Wave Technology for Battery Exchange Stations Tue, 30 Sep 2014 08:54:49 +0000 http://www.hindawi.com/journals/mpe/2014/869489/ This paper presents a novel radio-frequency identification (RFID) sensing system using enhanced surface wave technology for battery exchange stations (BESs) of electric motorcycles. Ultrahigh-frequency (UHF) RFID technology is utilized to automatically track and manage battery and user information without manual operation. The system includes readers, enhanced surface wave leaky cable antennas (ESWLCAs), coupling cable lines (CCLs), and small radiation patches (SRPs). The RFID sensing system overcomes the electromagnetic interference in the metallic environment of a BES cabinet. The developed RFID sensing system can effectively increase the efficiency of BES operation and promote the development of electric vehicles which solve the problem of air pollution as well as protect the environment of the Earth. Yeong-Lin Lai, Li-Chih Chang, Tai-Hwa Liu, Yi-Chun Sung, and Cheng-Lun Yin Copyright © 2014 Yeong-Lin Lai et al. All rights reserved. Statistical Analysis of Nonlinear Processes Based on Penalty Factor Tue, 30 Sep 2014 08:25:22 +0000 http://www.hindawi.com/journals/mpe/2014/945948/ A new process monitoring approach is proposed for handling the nonlinear monitoring problem in the electrofused magnesia furnace (EFMF). Compared to conventional method, the contributions are as follows: (1) a new kernel principal component analysis is proposed based on loss function in the feature space; (2) the model of kernel principal component analysis based on forgetting factor is updated; (3) a new iterative kernel principal component analysis algorithm is proposed based on penalty factor. Yingwei Zhang, Chuanfang Zhang, and Wei Zhang Copyright © 2014 Yingwei Zhang et al. All rights reserved. Hybrid Particle and Kalman Filtering for Pupil Tracking in Active IR Illumination Gaze Tracking System Tue, 30 Sep 2014 08:04:03 +0000 http://www.hindawi.com/journals/mpe/2014/426234/ A novel pupil tracking method is proposed by combining particle filtering and Kalman filtering for the fast and accurate detection of pupil target in an active infrared source gaze tracking system. Firstly, we utilize particle filtering to track pupil in synthesis triple-channel color map (STCCM) for the fast detection and develop a comprehensive pupil motion model to conduct and analyze the randomness of pupil motion. Moreover, we built a pupil observational model based on the similarity measurement with generated histogram to improve the credibility of particle weights. Particle filtering can detect pupil region in adjacent frames rapidly. Secondly, we adopted Kalman filtering to estimate the pupil parameters more precisely. The state transitional equation of the Kalman filtering is determined by the particle filtering estimation, and the observation of the Kalman filtering is dependent on the detected pupil parameters in the corresponding region of difference images estimated by particle filtering. Tracking results of Kalman filtering are the final pupil target parameters. Experimental results demonstrated the effectiveness and feasibility of this method. Jian-nan Chi, Li-hua Xie, Peng-yun Zhang, Yi-fang Lu, and Guo-sheng Zhang Copyright © 2014 Jian-nan Chi et al. All rights reserved. A Day-to-Day Route Choice Model Based on Reinforcement Learning Tue, 30 Sep 2014 07:42:44 +0000 http://www.hindawi.com/journals/mpe/2014/646548/ Day-to-day traffic dynamics are generated by individual traveler’s route choice and route adjustment behaviors, which are appropriate to be researched by using agent-based model and learning theory. In this paper, we propose a day-to-day route choice model based on reinforcement learning and multiagent simulation. Travelers’ memory, learning rate, and experience cognition are taken into account. Then the model is verified and analyzed. Results show that the network flow can converge to user equilibrium (UE) if travelers can remember all the travel time they have experienced, but which is not necessarily the case under limited memory; learning rate can strengthen the flow fluctuation, but memory leads to the contrary side; moreover, high learning rate results in the cyclical oscillation during the process of flow evolution. Finally, both the scenarios of link capacity degradation and random link capacity are used to illustrate the model’s applications. Analyses and applications of our model demonstrate the model is reasonable and useful for studying the day-to-day traffic dynamics. Fangfang Wei, Shoufeng Ma, and Ning Jia Copyright © 2014 Fangfang Wei et al. All rights reserved. Water Breakthrough Shape Description of Horizontal Wells in Bottom-Water Reservoir Tue, 30 Sep 2014 07:41:29 +0000 http://www.hindawi.com/journals/mpe/2014/460896/ Horizontal wells have been applied in bottom-water reservoir since their advantages were found on distribution of linear dropdown near wellbore, higher critical production, and more OOIP (original oil in place) controlled. In the paper, one 3D visible physical model of horizontal physical model is designed and built to simulate the water cresting process during the horizontal well producing and find water breakthrough point in homogenous and heterogeneous reservoir with bottom water. Water cresting shape and water cut of horizontal well in between homogenous and heterogeneous reservoir are compared on the base of experiment’s result. The water cresting pattern of horizontal well in homogeneous reservoir can be summarized as “central breakthrough, lateral expansion, thorough flooding, and then flank uplifting.” Furthermore, a simple analysis model of horizontal well in bottom water reservoir is established and water breakthrough point is analyzed. It can be drawn from the analysis result that whether or not to consider the top and bottom border, breakthrough would be located in the middle of horizontal segment with equal flow velocity distribution. Shijun Huang, Baoquan Zeng, Fenglan Zhao, Linsong Cheng, and Baojian Du Copyright © 2014 Shijun Huang et al. All rights reserved. Performance Analysis for Distributed Fusion with Different Dimensional Data Tue, 30 Sep 2014 00:00:00 +0000 http://www.hindawi.com/journals/mpe/2014/571572/ Different sensors or estimators may have different capability to provide data. Some sensors can provide a relatively higher dimensional data, while other sensors can only provide part of them. Some estimators can estimate full dimensional quantity of interest, while others may only estimate part of it due to some constraints. How is such kind of data with different dimensions fused? How do the common part and the uncommon part affect each other during fusion? To answer these questions, a fusion algorithm based on linear minimum mean-square error (LMMSE) estimation is provided in this paper. Then the fusion performance is analyzed, which is the main contribution of this work. The conclusions are as follows. First, the fused common part is not affected by the uncommon part. Second, the fused uncommon part will benefit from the common part through the cross-correlation. Finally, under certain conditions, both the more accurate common part and the stronger correlation can result in more accurate fused uncommon part. The conclusions are all supported by some tracking application examples. Xianghui Yuan, Zhansheng Duan, and Chongzhao Han Copyright © 2014 Xianghui Yuan et al. All rights reserved. Redundant VoD Streaming Service in a Private Cloud: Availability Modeling and Sensitivity Analysis Tue, 30 Sep 2014 00:00:00 +0000 http://www.hindawi.com/journals/mpe/2014/764010/ For several years cloud computing has been generating considerable debate and interest within IT corporations. Since cloud computing environments provide storage and processing systems that are adaptable, efficient, and straightforward, thereby enabling rapid infrastructure modifications to be made according to constantly varying workloads, organizations of every size and type are migrating to web-based cloud supported solutions. Due to the advantages of the pay-per-use model and scalability factors, current video on demand (VoD) streaming services rely heavily on cloud infrastructures to offer a large variety of multimedia content. Recent well documented failure events in commercial VoD services have demonstrated the fundamental importance of maintaining high availability in cloud computing infrastructures, and hierarchical modeling has proved to be a useful tool for evaluating the availability of complex systems and services. This paper presents an availability model for a video streaming service deployed in a private cloud environment which includes redundancy mechanisms in the infrastructure. Differential sensitivity analysis was applied to identify and rank the critical components of the system with respect to service availability. The results demonstrate that such a modeling strategy combined with differential sensitivity analysis can be an attractive methodology for identifying which components should be supported with redundancy in order to consciously increase system dependability. Rosangela Maria De Melo, Maria Clara Bezerra, Jamilson Dantas, Rubens Matos, Ivanildo José De Melo Filho, and Paulo Maciel Copyright © 2014 Rosangela Maria De Melo et al. All rights reserved. Positive Solutions of a Third-Order Three-Point BVP with Sign-Changing Green’s Function Tue, 30 Sep 2014 00:00:00 +0000 http://www.hindawi.com/journals/mpe/2014/406815/ We are concerned with the following third-order three-point boundary value problem: and where and . Although the corresponding Green’s function is sign-changing, we still obtain the existence of at least two positive and decreasing solutions under some suitable conditions on by using the two-fixed-point theorem due to Avery and Henderson. Li-Juan Gao and Jian-Ping Sun Copyright © 2014 Li-Juan Gao and Jian-Ping Sun. All rights reserved. Impacts of Transportation Cost on Distribution-Free Newsboy Problems Tue, 30 Sep 2014 00:00:00 +0000 http://www.hindawi.com/journals/mpe/2014/307935/ A distribution-free newsboy problem (DFNP) has been launched for a vendor to decide a product’s stock quantity in a single-period inventory system to sustain its least maximum-expected profits when combating fierce and diverse market circumstances. Nowadays, impacts of transportation cost on determination of optimal inventory quantity have become attentive, where its influence on the DFNP has not been fully investigated. By borrowing an economic theory from transportation disciplines, in this paper the DFNP is tackled in consideration of the transportation cost formulated as a function of shipping quantity and modeled as a nonlinear regression form from UPS’s on-site shipping-rate data. An optimal solution of the order quantity is computed on the basis of Newton’s approach to ameliorating its complexity of computation. As a result of comparative studies, lower bounds of the maximal expected profit of our proposed methodologies surpass those of existing work. Finally, we extend the analysis to several practical inventory cases including fixed ordering cost, random yield, and a multiproduct condition. Ming-Hung Shu, Chun-Wu Yeh, and Yen-Chen Fu Copyright © 2014 Ming-Hung Shu et al. All rights reserved. Synchronization and Lag Synchronization of Hyperchaotic Memristor-Based Chua’s Circuits Tue, 30 Sep 2014 00:00:00 +0000 http://www.hindawi.com/journals/mpe/2014/203123/ A memristor-based five-dimensional (5D) hyperchaotic Chua’s circuit is proposed. Based on the Lyapunov stability theorem, the controllers are designed to realize the synchronization and lag synchronization between the hyperchaotic memristor-based Chua’s circuits under different initial values, respectively. Numerical simulations are also presented to show the effectiveness and feasibility of the theoretical results. Junjian Huang, Chuandong Li, Tingwen Huang, Hui Wang, and Xin Wang Copyright © 2014 Junjian Huang et al. All rights reserved. Attitude Estimation Based on the Spherical Simplex Transformation Modified Unscented Kalman Filter Tue, 30 Sep 2014 00:00:00 +0000 http://www.hindawi.com/journals/mpe/2014/925914/ An antenna attitude estimation algorithm is proposed to improve the antenna pointing accuracy for the satellite communication on-the-move. The extrapolated angular acceleration is adopted to improve the performance of the time response. The states of the system are modified according to the modification rules. The spherical simplex transformation unscented Kalman filter is used to improve the precision of the estimated attitude and decrease the calculation of the unscented Kalman filter. The experiment results show that the proposed algorithm can improve the instantaneity of the estimated attitude and the precision of the antenna pointing, which meets the requirement of the antenna pointing. Jianwei Zhao, Weimin Jia, Rong Wang, and Zhixiang Yan Copyright © 2014 Jianwei Zhao et al. All rights reserved. Accelerated Testing with Multiple Failure Modes under Several Temperature Conditions Tue, 30 Sep 2014 00:00:00 +0000 http://www.hindawi.com/journals/mpe/2014/839042/ A complicated device may have multiple failure modes, and some of the failure modes are sensitive to low temperatures. To assess the reliability of a product with multiple failure modes, this paper presents an accelerated testing in which both of the high temperatures and the low temperatures are applied. Firstly, an acceleration model based on the Arrhenius model but accounting for the influence of both the high temperatures and low temperatures is proposed. Accordingly, an accelerated testing plan including both the high temperatures and low temperatures is designed, and a statistical analysis method is developed. The reliability function of the product with multiple failure modes under variable working conditions is given by the proposed statistical analysis method. Finally, a numerical example is studied to illustrate the proposed accelerated testing. The results show that the proposed accelerated testing is rather efficient. Zongyue Yu, Zhiqian Ren, Junyong Tao, and Xun Chen Copyright © 2014 Zongyue Yu et al. All rights reserved. Time-Varying Integral Adaptive Sliding Mode Control for the Large Erecting System Mon, 29 Sep 2014 13:48:02 +0000 http://www.hindawi.com/journals/mpe/2014/950768/ Considering the nonlinearities, uncertainties of large erecting system, and the circumstance disturbances in erecting process, a novel sliding mode control strategy is proposed in this research. The proposed control strategy establishes the sliding mode without reaching phase using an integral sliding surface. Thus, robustness against uncertainties increases from the very beginning of the process. Furthermore, adaptive laws are used for the controller to estimate the unknown but bounded system uncertainties. Therefore, the upper bounds of the system uncertainties are not required to be known in advance. Then, the time-varying term is applied to ensure the global robustness. Moreover, the boundary layer method is used to attenuate the high frequency chattering. The experiment results demonstrated that the proposed strategy could effectively restrain parametric uncertainties and external disturbances and improve the tracking accuracy in the erecting process. In addition, the control performance of the proposed control strategy is better than that of the PID control and the conventional sliding mode control. Xie Zheng, Xie Jian, Du Wenzheng, Li Liang, and Guo Yang Copyright © 2014 Xie Zheng et al. All rights reserved. Delay-Dependent State Estimation of Static Neural Networks with Time-Varying and Distributed Delays Mon, 29 Sep 2014 13:47:27 +0000 http://www.hindawi.com/journals/mpe/2014/951973/ This paper focuses on studying the state estimation problem of static neural networks with time-varying and distributed delays. By constructing a suitable Lyapunov functional and employing two integral inequalities, a sufficient condition is obtained under which the estimation error system is globally asymptotically stable. It can be seen that this condition is dependent on the two kinds of time delays. To reduce the conservatism of the derived result, Wirtinger inequality is employed to handle a cross term in the time-derivative of Lyapunov functional. It is further shown that the design of the gain matrix of state estimator is transformed to finding a feasible solution of a linear matrix inequality, which is efficiently facilitated by available algorithms. A numerical example is explored to demonstrate the effectiveness of the developed result. Lei Shao, He Huang, Heming Zhao, and Tingwen Huang Copyright © 2014 Lei Shao et al. All rights reserved. An Affinity Propagation Clustering Algorithm for Mixed Numeric and Categorical Datasets Mon, 29 Sep 2014 13:45:21 +0000 http://www.hindawi.com/journals/mpe/2014/486075/ Clustering has been widely used in different fields of science, technology, social science, and so forth. In real world, numeric as well as categorical features are usually used to describe the data objects. Accordingly, many clustering methods can process datasets that are either numeric or categorical. Recently, algorithms that can handle the mixed data clustering problems have been developed. Affinity propagation (AP) algorithm is an exemplar-based clustering method which has demonstrated good performance on a wide variety of datasets. However, it has limitations on processing mixed datasets. In this paper, we propose a novel similarity measure for mixed type datasets and an adaptive AP clustering algorithm is proposed to cluster the mixed datasets. Several real world datasets are studied to evaluate the performance of the proposed algorithm. Comparisons with other clustering algorithms demonstrate that the proposed method works well not only on mixed datasets but also on pure numeric and categorical datasets. Kang Zhang and Xingsheng Gu Copyright © 2014 Kang Zhang and Xingsheng Gu. All rights reserved. Fitness Estimation Based Particle Swarm Optimization Algorithm for Layout Design of Truss Structures Mon, 29 Sep 2014 12:37:26 +0000 http://www.hindawi.com/journals/mpe/2014/671872/ Due to the fact that vastly different variables and constraints are simultaneously considered, truss layout optimization is a typical difficult constrained mixed-integer nonlinear program. Moreover, the computational cost of truss analysis is often quite expensive. In this paper, a novel fitness estimation based particle swarm optimization algorithm with an adaptive penalty function approach (FEPSO-AP) is proposed to handle this problem. FEPSO-AP adopts a special fitness estimate strategy to evaluate the similar particles in the current population, with the purpose to reduce the computational cost. Further more, a laconic adaptive penalty function is employed by FEPSO-AP, which can handle multiple constraints effectively by making good use of historical iteration information. Four benchmark examples with fixed topologies and up to 44 design dimensions were studied to verify the generality and efficiency of the proposed algorithm. Numerical results of the present work compared with results of other state-of-the-art hybrid algorithms shown in the literature demonstrate that the convergence rate and the solution quality of FEPSO-AP are essentially competitive. Ayang Xiao, Benli Wang, Chaoli Sun, Shijie Zhang, and Zhenguo Yang Copyright © 2014 Ayang Xiao et al. All rights reserved. Collaborative Opportunistic Scheduling in Heterogeneous Networks: A Distributed Approach Mon, 29 Sep 2014 11:39:17 +0000 http://www.hindawi.com/journals/mpe/2014/414689/ We consider a collaborative opportunistic scheduling problem in a decentralized network with heterogeneous users. While most related researches focus on solutions for optimizing decentralized systems’ total performance, we proceed in another direction. Two problems are specifically investigated. (1) With heterogenous users having personal demands, is it possible to have it met by designing distributed opportunistic policies? (2) With a decentralized mechanism, how can we prevent selfish behaviors and enforce collaboration? In our research, we first introduce a multiuser network model along with a scheduling problem constrained by individual throughput requirement at each user’s side. An iterative algorithm is then proposed to characterize a solution for the scheduling problem, based on which collaborative opportunistic scheduling scheme is enabled. Properties of the algorithm, including convergence, will be discussed. Furthermore in order to keep the users staying with the collaboration state, an additional punishment strategy is designed. Therefore selfish deviation can be detected and disciplined so that collaboration is enforced. We demonstrate our main findings with both analysis and simulations. Donglai Sun, Yang Liu, Jianhua Li, and Yue Wu Copyright © 2014 Donglai Sun et al. All rights reserved. Enhanced PID Controllers Design Based on Modified Smith Predictor Control for Unstable Process with Time Delay Mon, 29 Sep 2014 11:38:48 +0000 http://www.hindawi.com/journals/mpe/2014/521460/ A two-degree-of-freedom control structure is proposed for a class of unstable processes with time delay based on modified Smith predictor control; the superior performance of disturbance rejection and good robust stability are gained for the system. The set-point tracking controller is designed using the direct synthesis method; the IMC-PID controller for disturbance rejection is designed based on the internal mode control design principle. The controller for set-point response and the controller for disturbance rejection can be adjusted and optimized independently. Meanwhile, the two controllers are designed in the form of PID, which is convenient for engineering application. Finally, simulation examples demonstrate the validity of the proposed control scheme. Chengqiang Yin, Jie Gao, and Qun Sun Copyright © 2014 Chengqiang Yin et al. All rights reserved. Outage and Capacity Performance Evaluation of Distributed MIMO Systems over a Composite Fading Channel Mon, 29 Sep 2014 10:14:30 +0000 http://www.hindawi.com/journals/mpe/2014/510423/ The exact closed-form expressions regarding the outage probability and capacity of distributed MIMO (DMIMO) systems over a composite fading channel are derived. This is achieved firstly by using a lognormal approximation to a gamma-lognormal distribution when a mobile station (MS) in the cell is in a fixed position, and the so-called maximum ratio transmission/selected combining (MRT-SC) and selected transmission/maximum ratio combining (ST-MRC) schemes are adopted in uplink and downlink, respectively. Then, based on a newly proposed nonuniform MS cell distribution model, which is more consistent with the MS cell hotspot distribution in an actual communication environment, the average outage probability and capacity formulas are further derived. Finally, the accuracy of the approximation method and the rationality of the corresponding theoretical analysis regarding the system performance are proven and illustrated by computer simulations. Wenjie Peng, Yueheng Li, Meiyan Ju, Ping Huang, Guoping Tan, and Defu Jiang Copyright © 2014 Wenjie Peng et al. All rights reserved. Numerical Study on Different Series Modes of Jet Fan in a Longitudinal Tunnel Ventilation System Mon, 29 Sep 2014 09:27:49 +0000 http://www.hindawi.com/journals/mpe/2014/194125/ Efficient ventilation systems will contribute to maintaining air quality in the tunnel. In order to improve ventilation performance in normal traffic condition, the 3D tunnel models were established according to the original design for the tunnel located in central plains of China. Based on the commercial CFD software Fluent 6.3 and - turbulence model, numerical simulations were carried out to study the patterns of jet flow and the optimization of fan combinations. It is found that the axial velocity profile obtained from numerical simulation agrees quite well with turbulent free jet theory although there is a little difference on the magnitude. The comparison of four combination modes under the condition of operating four fans indicates that the ventilation effectiveness is affected mainly by both the interval of adjacent groups of fans and the combination modes of operational fans. According to the simulation results, a novel combination mode which consists of a group double paralleled fans and two groups single fan is designed. The novel combination mode is regarded as the optimum combination mode with respect to maximizing air velocity in the tunnel. Compared to the traditional combination modes, it will increase the air velocity by 5.7%. Guihong Pei and Jie Pan Copyright © 2014 Guihong Pei and Jie Pan. All rights reserved. A MOLP Method for Solving Fully Fuzzy Linear Programming with LR Fuzzy Parameters Mon, 29 Sep 2014 09:27:49 +0000 http://www.hindawi.com/journals/mpe/2014/782376/ Kaur and Kumar, 2013, use Mehar’s method to solve a kind of fully fuzzy linear programming (FFLP) problems with LR fuzzy parameters. In this paper, a new kind of FFLP problems is introduced with a solution method proposed. The FFLP is converted into a multiobjective linear programming (MOLP) according to the order relation for comparing the LR flat fuzzy numbers. Besides, the classical fuzzy programming method is modified and then used to solve the MOLP problem. Based on the compromised optimal solution to the MOLP problem, the compromised optimal solution to the FFLP problem is obtained. At last, a numerical example is given to illustrate the feasibility of the proposed method. Xiao-Peng Yang, Xue-Gang Zhou, Bing-Yuan Cao, and S. H. Nasseri Copyright © 2014 Xiao-Peng Yang et al. All rights reserved. Prevention and Trust Evaluation Scheme Based on Interpersonal Relationships for Large-Scale Peer-To-Peer Networks Mon, 29 Sep 2014 08:44:28 +0000 http://www.hindawi.com/journals/mpe/2014/189213/ In recent years, the complex network as the frontier of complex system has received more and more attention. Peer-to-peer (P2P) networks with openness, anonymity, and dynamic nature are vulnerable and are easily attacked by peers with malicious behaviors. Building trusted relationships among peers in a large-scale distributed P2P system is a fundamental and challenging research topic. Based on interpersonal relationships among peers of large-scale P2P networks, we present prevention and trust evaluation scheme, called IRTrust. The framework incorporates a strategy of identity authentication and a global trust of peers to improve the ability of resisting the malicious behaviors. It uses the quality of service (QoS), quality of recommendation (QoR), and comprehensive risk factor to evaluate the trustworthiness of a peer, which is applicable for large-scale unstructured P2P networks. The proposed IRTrust can defend against several kinds of malicious attacks, such as simple malicious attacks, collusive attacks, strategic attacks, and sybil attacks. Our simulation results show that the proposed scheme provides greater accuracy and stronger resistance compared with existing global trust schemes. The proposed scheme has potential application in secure P2P network coding. Lixiang Li, Jürgen Kurths, Yixian Yang, and Guole Liu Copyright © 2014 Lixiang Li et al. All rights reserved.