Mathematical Problems in Engineering http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2015 , Hindawi Publishing Corporation . All rights reserved. New Viewpoints about Pseudo Measurements Method in Equality-Constrained State Estimation Thu, 05 Mar 2015 14:00:42 +0000 http://www.hindawi.com/journals/mpe/2015/946952/ We discuss the pseudo measurement method which is one of the main approaches to equality-constrained state estimation for a dynamic system. We demonstrate by the fundamental theory of Kalman filtering that reviewing the equality constraint as a pseudo measurement seems questionable. The main reason is that the additional pseudo measurement is actually a constant here which cannot help to estimate the state. More specifically, when the states in an unconstrained dynamic system model have already satisfied the equality constraint, the extra constraint is obviously not necessary. When the true equality-constrained states do not satisfy the unconstrained dynamic process equation, the effect of pseudo measurement is projecting the estimate which is not optimal onto the constraint set. However, since the performance of a projected estimate is also certainly influenced by its original estimate, we show through a numerical example that the pseudo measurement method is not always a good choice, especially when the process equation mismatch is large. Bingjie Zhu, Yingting Luo, and Yunmin Zhu Copyright © 2015 Bingjie Zhu et al. All rights reserved. A Modified Hybrid Genetic Algorithm for Solving Nonlinear Optimal Control Problems Thu, 05 Mar 2015 13:59:28 +0000 http://www.hindawi.com/journals/mpe/2015/139036/ Here, a two-phase algorithm is proposed for solving bounded continuous-time nonlinear optimal control problems (NOCP). In each phase of the algorithm, a modified hybrid genetic algorithm (MHGA) is applied, which performs a local search on offsprings. In first phase, a random initial population of control input values in time nodes is constructed. Next, MHGA starts with this population. After phase 1, to achieve more accurate solutions, the number of time nodes is increased. The values of the associated new control inputs are estimated by Linear interpolation (LI) or Spline interpolation (SI), using the curves obtained from the phase 1. In addition, to maintain the diversity in the population, some additional individuals are added randomly. Next, in the second phase, MHGA restarts with the new population constructed by above procedure and tries to improve the obtained solutions at the end of phase 1. We implement our proposed algorithm on 20 well-known benchmark and real world problems; then the results are compared with some recently proposed algorithms. Moreover, two statistical approaches are considered for the comparison of the LI and SI methods and investigation of sensitivity analysis for the MHGA parameters. Saeed Nezhadhosein, Aghileh Heydari, and Reza Ghanbari Copyright © 2015 Saeed Nezhadhosein et al. All rights reserved. Control of Wind-Induced Vibration of Transmission Tower-Line System by Using a Spring Pendulum Thu, 05 Mar 2015 13:45:18 +0000 http://www.hindawi.com/journals/mpe/2015/671632/ The high-voltage power transmission tower-line system, which is a high flexible structure, is very susceptible to the wind-induced vibrations. This paper proposes the utilization of the internal resonance feature of the spring pendulum to reduce the wind-induced vibration of a transmission tower. The kinetic expression of the spring pendulum system is obtained through Lagrangian equation. The condition of the internal resonance is verified to be λ = 2, in which λ is the ratio of the spring mode frequency over the pendulum mode frequency. A 55 m tower in the Liaoning province is established in SAP2000 to numerically verify the effectiveness of the proposed device. The spring pendulum is modeled using Link element. The wind speed history is generated based on Kaimal spectrum using harmonic superposition method. Results show that, (1) compared with the suspended mass pendulum, the spring pendulum absorbs more energy and reduces the oscillation more effectively and (2) the vibration control performance of the proposed spring pendulum improves as the external wind load increases. Peng Zhang, Liang Ren, Hongnan Li, Ziguang Jia, and Tao Jiang Copyright © 2015 Peng Zhang et al. All rights reserved. Fusing Multiscale Charts into 3D ENC Systems Based on Underwater Topography and Remote Sensing Image Thu, 05 Mar 2015 11:38:52 +0000 http://www.hindawi.com/journals/mpe/2015/610750/ The purpose of this study is to propose an approach to fuse multiscale charts into three-dimensional (3D) electronic navigational chart (ENC) systems based on underwater topography and remote sensing image. This is the first time that the fusion of multiscale standard ENCs in the 3D ENC system has been studied. First, a view-dependent visualization technology is presented for the determination of the display condition of a chart. Second, a map sheet processing method is described for dealing with the map sheet splice problem. A process order called “3D order” is designed to adapt to the characteristics of the chart. A map sheet clipping process is described to deal with the overlap between the adjacent map sheets. And our strategy for map sheet splice is proposed. Third, the rendering method for ENC objects in the 3D ENC system is introduced. Fourth, our picking-up method for ENC objects is proposed. Finally, we implement the above methods in our system: automotive intelligent chart (AIC) 3D electronic chart display and information systems (ECDIS). And our method can handle the fusion problem well. Tao Liu, De-Peng Zhao, Ming-Yang Pan, and Kun Bai Copyright © 2015 Tao Liu et al. All rights reserved. Logistics Systems Optimization under Competition Thu, 05 Mar 2015 09:50:42 +0000 http://www.hindawi.com/journals/mpe/2015/106142/ Tsan-Ming Choi, Kannan Govindan, and Lijun Ma Copyright © 2015 Tsan-Ming Choi et al. All rights reserved. A Novel OBDD-Based Reliability Evaluation Algorithm for Wireless Sensor Networks on the Multicast Model Thu, 05 Mar 2015 08:56:09 +0000 http://www.hindawi.com/journals/mpe/2015/269781/ The two-terminal reliability calculation for wireless sensor networks (WSNs) is a #P-hard problem. The reliability calculation of WSNs on the multicast model provides an even worse combinatorial explosion of node states with respect to the calculation of WSNs on the unicast model; many real WSNs require the multicast model to deliver information. This research first provides a formal definition for the WSN on the multicast model. Next, a symbolic OBDD_Multicast algorithm is proposed to evaluate the reliability of WSNs on the multicast model. Furthermore, our research on OBDD_Multicast construction avoids the problem of invalid expansion, which reduces the number of subnetworks by identifying the redundant paths of two adjacent nodes and s-t unconnected paths. Experiments show that the OBDD_Multicast both reduces the complexity of the WSN reliability analysis and has a lower running time than Xing’s OBDD- (ordered binary decision diagram-) based algorithm. Zongshuai Yan, Chenhua Nie, Rongsheng Dong, Xi Gao, and Jianming Liu Copyright © 2015 Zongshuai Yan et al. All rights reserved. Parareal Algorithms Implemented with IMEX Runge-Kutta Methods Thu, 05 Mar 2015 08:37:08 +0000 http://www.hindawi.com/journals/mpe/2015/395340/ Parareal algorithm is a very powerful parallel computation method and has received much interest from many researchers over the past few years. The aim of this paper is to investigate the performance of parareal algorithm implemented with IMEX Runge-Kutta (RK) methods. A stability criterion of the parareal algorithm coupled with IMEX RK methods is established and the advantage (in the sense of stability) of implementing with this kind of RK methods is numerically investigated. Finally, numerical examples are given to illustrate the efficiency and performance of different parareal methods. Zhiyong Wang and Shulin Wu Copyright © 2015 Zhiyong Wang and Shulin Wu. All rights reserved. ANN Approach for State Estimation of Hybrid Systems and Its Experimental Validation Thu, 05 Mar 2015 08:04:29 +0000 http://www.hindawi.com/journals/mpe/2015/382324/ A novel artificial neural network based state estimator has been proposed to ensure the robustness in the state estimation of autonomous switching hybrid systems under various uncertainties. Taking the autonomous switching three-tank system as benchmark hybrid model working under various additive and multiplicative uncertainties such as process noise, measurement error, process–model parameter variation, initial state mismatch, and hand valve faults, real-time performance evaluation by the comparison of it with other state estimators such as extended Kalman filter and unscented Kalman Filter was carried out. The experimental results reported with the proposed approach show considerable improvement in the robustness in performance under the considered uncertainties. Shijoh Vellayikot and M. V. Vaidyan Copyright © 2015 Shijoh Vellayikot and M. V. Vaidyan. All rights reserved. The Framework Dedicated to Three Phase Flows Wellbore Modelling Thu, 05 Mar 2015 07:06:08 +0000 http://www.hindawi.com/journals/mpe/2015/183982/ To predict physical properties in a wellbore during oil and gas production, scientists use empirical correlations or mechanistic approach algorithms. The typical research in this field is concentrated on a single property analysis as heat transfer, pressure, temperature, and so forth. Here the most proper correlations, regarding the subject, are presented. And the authors studied how to join all correlations into the full framework which returns all production parameters at every depth in a wellbore. Additionally, the presented simulation results are studied here. Based on presented algorithms, the proper tool has been applied and the results shown in this paper are taken from this application. Bartlomiej Bielecki and Andrzej Krajka Copyright © 2015 Bartlomiej Bielecki and Andrzej Krajka. All rights reserved. Thinning of Concentric Circular Antenna Arrays Using Improved Binary Invasive Weed Optimization Algorithm Thu, 05 Mar 2015 06:56:25 +0000 http://www.hindawi.com/journals/mpe/2015/365280/ This study presents a novel optimization algorithm based on invasive weed optimization (IWO) for reduction of the maximum side lobe level (SLL) with specific half power beam width (HPBW) of thinned large multiple concentric circular arrays of uniformly excited isotropic elements. IWO is a powerful optimization technique for many continuous problems. But, for discrete problems, it does not work well. In this paper, the authors propose an improved binary IWO (IBIWO) for pattern synthesis of thinned circular array. The thinning percentage of the array is kept equal to or more than 50% and the HPBW is attempted to be equal to or less than that of a fully populated, uniformly excited, and half wavelength spaced concentric circular array of the same number of elements and rings. Simulation results are compared with previous published results of DE, MPSO, and BBO to verify the effectiveness of the proposed method for concentric circular arrays. Huaning Wu, Chao Liu, and Xu Xie Copyright © 2015 Huaning Wu et al. All rights reserved. Prediction of “Aggregation-Prone” Peptides with Hybrid Classification Approach Thu, 05 Mar 2015 06:45:25 +0000 http://www.hindawi.com/journals/mpe/2015/857325/ Protein aggregation is a biological phenomenon caused by misfolding proteins aggregation and is associated with a wide variety of diseases, such as Alzheimer’s, Parkinson’s, and prion diseases. Many studies indicate that protein aggregation is mediated by short “aggregation-prone” peptide segments. Thus, the prediction of aggregation-prone sites plays a crucial role in the research of drug targets. Compared with the labor-intensive and time-consuming experiment approaches, the computational prediction of aggregation-prone sites is much desirable due to their convenience and high efficiency. In this study, we introduce two computational approaches Aggre_Easy and Aggre_Balance for predicting aggregation residues from the sequence information; here, the protein samples are represented by the composition of k-spaced amino acid pairs (CKSAAP). And we use the hybrid classification approach to predict aggregation-prone residues, which integrates the naïve Bayes classification to reduce the number of features, and two undersampling approaches EasyEnsemble and BalanceCascade to deal with samples imbalance problem. The Aggre_Easy achieves a promising performance with a sensitivity of 79.47%, a specificity of 80.70% and a MCC of 0.42; the sensitivity, specificity, and MCC of Aggre_Balance reach 70.32%, 80.70% and 0.42. Experimental results show that the performance of Aggre_Easy and Aggre_Balance predictor is better than several other state-of-the-art predictors. A user-friendly web server is built for prediction of aggregation-prone which is freely accessible to public at the website. Bo Liu, Wenyi Zhang, Longjia Jia, Jianan Wang, Xiaowei Zhao, and Minghao Yin Copyright © 2015 Bo Liu et al. All rights reserved. Robust State Estimation for Delayed Neural Networks with Stochastic Parameter Uncertainties Wed, 04 Mar 2015 14:23:52 +0000 http://www.hindawi.com/journals/mpe/2015/948391/ This paper considers the problem of delay-dependent state estimation for neural networks with time-varying delays and stochastic parameter uncertainties. It is assumed that the parameter uncertainties are affected by the environment which is changed with randomly real situation, and its stochastic information such as mean and variance is utilized in the proposed method. By constructing a newly augmented Lyapunov-Krasovskii functional, a designing method of estimator for neural networks is introduced with the framework of linear matrix inequalities (LMIs) and a neural networks model with stochastic parameter uncertainties which have not been introduced yet. Two numerical examples are given to show the improvements over the existing ones and the effectiveness of the proposed idea. M. J. Park, O. M. Kwon, Ju H. Park, S. M. Lee, and E. J. Cha Copyright © 2015 M. J. Park et al. All rights reserved. An Improved Tabu Search Algorithm Based on Grid Search Used in the Antenna Parameters Optimization Wed, 04 Mar 2015 13:12:10 +0000 http://www.hindawi.com/journals/mpe/2015/947021/ In the mobile system covering big areas, many small cells are often used. And the base antenna’s azimuth angle, vertical down angle, and transmit power are the most important parameters to affect the coverage of an antenna. This paper makes mathematical model and analyzes different algorithm’s performance in model. Finally we propose an improved Tabu search algorithm based on grid search, to get the best parameters of antennas, which can maximize the coverage area and minimize the interference. Di He and Yunlv Hong Copyright © 2015 Di He and Yunlv Hong. All rights reserved. On the Uniform Exponential Stability of Time-Varying Systems Subject to Discrete Time-Varying Delays and Nonlinear Delayed Perturbations Wed, 04 Mar 2015 13:11:21 +0000 http://www.hindawi.com/journals/mpe/2015/641268/ This paper addresses the problem of stability analysis of systems with delayed time-varying perturbations. Some sufficient conditions for a class of linear time-varying systems with nonlinear delayed perturbations are derived by using an improved Lyapunov-Krasovskii functional. The uniform global asymptotic stability of the solutions is obtained in terms of convergence toward a neighborhood of the origin. Maher Hammami, Mohamed Ali Hammami, and Manuel De la Sen Copyright © 2015 Maher Hammami et al. All rights reserved. Design of a Multiorder OFDM Frequency Diversity Approach Wed, 04 Mar 2015 13:04:39 +0000 http://www.hindawi.com/journals/mpe/2015/291625/ Frequency diversity is used to reduce the effect of destructive fading, so as to improve the communication quality, by passing the information symbols through multiple independently faded paths, and ensure that reliable communication is possible as long as one of these paths is strong. In this paper a multiorder orthogonal frequency division multiplexing (OFDM) frequency diversity approach using properties of order theory and Hamming distance is proposed. The frequency diversity is obtained by specifying proper correlations among the transmitted symbols. As subchannels experience independent fading, at least one of the symbols may have robust signal, which can be used by the receiver to detect other symbols. Considering bit error rate (BER) performance, power consumption, bandwidth utilization, and practical implementation expense, simulation results show that the proposed approach outperforms other OFDM diversity techniques, such as Maximal Ratio Combination (MRC) and Space Frequency Block Coding (SFBC). Abdeldime Mohamed Salih Abdelgader and Lenan Wu Copyright © 2015 Abdeldime Mohamed Salih Abdelgader and Lenan Wu. All rights reserved. Optimized PID Position Control of a Nonlinear System Based on Correlating the Velocity with Position Error Wed, 04 Mar 2015 13:02:56 +0000 http://www.hindawi.com/journals/mpe/2015/796057/ We examined a design approach for a PID controller for a nonlinear ball and beam system. Main objective of our research was to establish a nonmodel based control system, which would also not be dependent on a specific ball and beam hardware setup. The proposed PID controller setup is based on a cascaded configuration of an inner PID ball velocity control loop and an outer proportional ball position control loop. The effectiveness of the proposed controller setup was first presented in simulation environment in comparison to a hardware dependent PD cascaded controller, along with a more comprehensive study on possible design approach for optimal PID controller parameters in relation to main functionality of the controller setup. Experimental real time control results were then obtained on a laboratory setup of the ball and beam system on which PD cascaded controller could not be applied without parallel system model processing. Nenad Muškinja and Matej Rižnar Copyright © 2015 Nenad Muškinja and Matej Rižnar. All rights reserved. A Wide Tuning-Range CMOS VCO with a Tunable Active Inductor Wed, 04 Mar 2015 11:32:08 +0000 http://www.hindawi.com/journals/mpe/2015/382483/ This study describes a wide tuning-range VCO using tunable active inductor (TAI) topology and cross-coupled pair configuration for radio frequency operation. The TAI used two feedback loops to form a cascode circuit to obtain more degrees of freedom for inductance value. The TAI-VCO was fabricated using a 0.18 μm CMOS technology. The coarse frequency tuning is achieved by TAIs while the fine tuning is controlled by varactors. The fabricated circuit provides an output frequency range from 0.6 to 7.2 GHz (169%). The measured phase noise is from −110.38 to −86.01 dBc/Hz at a 1 MHz offset and output power is from −11.11 to −3.89 dBm within the entire frequency range under a 1.8 V power supply. Hsuan-Ling Kao, Ping-Che Lee, and Hsien-Chin Chiu Copyright © 2015 Hsuan-Ling Kao et al. All rights reserved. Stock Market Trading Rules Discovery Based on Biclustering Method Wed, 04 Mar 2015 10:30:27 +0000 http://www.hindawi.com/journals/mpe/2015/849286/ The prediction of stock market’s trend has become a challenging task for a long time, which is affected by a variety of deterministic and stochastic factors. In this paper, a biclustering algorithm is introduced to find the local patterns in the quantized historical data. The local patterns obtained are regarded as the trading rules. Then the trading rules are applied in the short term prediction of the stock price, combined with the minimum-error-rate classification of the Bayes decision theory under the assumption of multivariate normal probability model. In addition, this paper also makes use of the idea of the stream mining to weaken the impact of historical data on the model and update the trading rules dynamically. The experiment is implemented on real datasets and the results prove the effectiveness of the proposed algorithm. Yun Xue, Zhiwen Liu, Jie Luo, Zhihao Ma, Meizhen Zhang, Xiaohui Hu, and Qiuhua Kuang Copyright © 2015 Yun Xue et al. All rights reserved. A Novel Neutral-Point Potential Balance Strategy for Three-Level NPC Back-to-Back Converter Based on the Neutral-Point Current Injection Model Wed, 04 Mar 2015 08:30:22 +0000 http://www.hindawi.com/journals/mpe/2015/736828/ The neutral-point (NP) potential balance control in three-level neutral-point-clamped (NPC) back-to-back converter is a research nodus. Its current strategies are the same as the strategies of a single three-level NPC converter. But the strategies do not give full play to its advantages that the neutral-point current can only flow through the connected midlines in both sides of the converter but does not flow through the DC-bus capacitors. In this paper, firstly the NP potential model based on the NP current injected is proposed. It overcomes numerous variable constraints and mutual coupling in the conventional model based on the zero-sequence voltage injected. And then on this basis, three NP-potential balance control algorithms, unilateral control, bilateral independent control, and bilateral coordinated control, are proposed according to difference requirements. All of these algorithms use the midlines rather than the DC-bus capacitors to flow the NP current as much as possible. Their control abilities are further quantitatively analyzed and compared. Finally, simulation results verify the validity and effectiveness of these algorithms. Yingjie Wang, Haiyuan Liu, Wenchao Wang, and Kangan Wang Copyright © 2015 Yingjie Wang et al. All rights reserved. Finite Frequency Filtering for Time-Delayed Singularly Perturbed Systems Wed, 04 Mar 2015 08:26:34 +0000 http://www.hindawi.com/journals/mpe/2015/456768/ This paper investigates the problem of finite frequency (FF) filtering for time-delayed singularly perturbed systems. Our attention is focused on designing filters guaranteeing asymptotic stability and FF disturbance attenuation level of the filtering error system. By the generalized Kalman-Yakubovich-Popov (KYP) lemma, the existence conditions of FF filters are obtained in terms of solving an optimization problem, which is delay-independent. The main contribution of this paper is that systematic methods are proposed for designing filters for delayed singularly perturbed systems. Ping Mei, Jingzhi Fu, and Yunping Liu Copyright © 2015 Ping Mei et al. All rights reserved. Mathematical Methods Applied to the Celestial Mechanics of Artificial Satellites 2014 Wed, 04 Mar 2015 07:55:20 +0000 http://www.hindawi.com/journals/mpe/2015/940427/ Antonio F. Bertachini A. Prado, Josep J. Masdemont, Maria Cecilia Zanardi, Silvia Maria Giuliatti Winter, Tadashi Yokoyama, and Vivian Martins Gomes Copyright © 2015 Antonio F. Bertachini A. Prado et al. All rights reserved. Outage Analysis of Cooperative Transmission with Energy Harvesting Relay: Time Switching versus Power Splitting Wed, 04 Mar 2015 07:53:10 +0000 http://www.hindawi.com/journals/mpe/2015/598290/ This paper investigates the multiuser transmission network with an energy harvesting (EH) cooperative relay, where a source transmits independent information to multiple destinations with the help of an energy constrained relay. The relay can harvest energy from the radio frequency (RF) signals transmitted from the source, and it helps the multiuser transmission only by consuming the harvested energy. By adopting the time switching and the power splitting relay receiver architectures, we firstly propose two protocols, the time switching cooperative multiuser transmission (TSCMT) protocol and the power splitting cooperative multiuser transmission (PSCMT) protocol, to enable the simultaneous information processing and EH at the relay for the system. To evaluate the system performance, we theoretically analyze the system outage probability for the two proposed protocols and then derive explicit expressions for each of them, respectively. Numerical results are provided to demonstrate the accuracy of our analytical results and reveal that compared with traditional noncooperative scheme our proposed protocols are green solutions to offer reliable communication and lower system outage probability without consuming additional energy. In particular, for the same transmit power at the source, the PSCMT protocol is superior to the TSCMT protocol to obtain lower system outage probability. Guanyao Du, Ke Xiong, and Zhengding Qiu Copyright © 2015 Guanyao Du et al. All rights reserved. Propagation Modeling of Point Source Excited Magnetoinductive Waves Based on a New Plane Wave Expansion Approach Wed, 04 Mar 2015 07:28:36 +0000 http://www.hindawi.com/journals/mpe/2015/951718/ The signal fading in wireless underground sensor networks (WUSNs), which is caused by lossy media such as soil and sand, can be reduced by applying technology of magnetoinductive (MI) propagation. This technology can effectively establish a communication at very low frequency (VLF). In contrast to the previous studies in the literature, which mostly focus on the propagation of plane waves, we propose a new approach based on the plane wave expansion (PWE) to model the near field MI waves. The proposed approach is based on excitation of a point source, which is a common case in a practical WUSN. The frequent usage of square lattice MI structure is investigated. To verify the mathematical derivation, the simulation of time domain based on the fourth-order Runge-Kutta (RK) method is carried out. Simulation results show that the new model can provide a precise prediction to the MI wave’s propagation, with the computation load being one-tenth of that of the time domain simulation. The characteristics of the propagation of the MI waves are presented and discussed. Finally, the reflection on the edge of the MI structure is reduced by analysing the terminal matching conditions and calculating a method for matching impedances. Feng Liu, Zhijun Zhang, Lianqing Zhu, and Yajun Liu Copyright © 2015 Feng Liu et al. All rights reserved. Delayed Bilateral Teleoperation of Wheeled Robots including a Command Metric Wed, 04 Mar 2015 06:15:57 +0000 http://www.hindawi.com/journals/mpe/2015/460476/ This paper proposes a control scheme applied to the delayed bilateral teleoperation of wheeled robots with force feedback, considering the performance of the operator’s command execution. In addition, the stability of the system is analyzed taking into account the dynamic model of the master as well as the remote mobile robot under asymmetric and time-varying delays of the communication channel. Besides, the performance of the teleoperation system, where a human operator drives a 3D simulator of a wheeled dynamic robot, is evaluated. In addition, we present an experiment where a robot Pioneer is teleoperated, based on the system architecture proposed. Franco Penizzotto, Sebastian García, Emanuel Slawiñski, and Vicente Mut Copyright © 2015 Franco Penizzotto et al. All rights reserved. Symbol Estimation Algorithm for MIMO Underwater Acoustic Communication System Based on Multiplicative Noise Model Tue, 03 Mar 2015 17:08:28 +0000 http://www.hindawi.com/journals/mpe/2015/719025/ The stochastic and time-varying underwater acoustic (UWA) channels are usually affected by serious multipath delays, energy loss and distortion factors, thus making the modeling and estimation of the UWA channel challenging problems in the research community. Based on the analysis of the UWA channel, the system with multiplicative noise (SMN) model is established to characterize the complicated factors such as random time-variation, nonlinearity, and energy attenuation. As to the multiple-input multiple-output (MIMO) UWA communication, the complicated SMN model is established for MIMO UWA channels; based on which, the transmitted symbols are estimated according to the optimal recursive filtering algorithm. The algorithm is derived based on the projection theorem, which is optimal in the sense of linear minimum variance, and can overcome the intersymbol interference and noise pollution efficiently. The optimal algorithm is computed recursively, which has the advantage of computation-efficiency and can track the random variation of the fast time-varying channel gain dynamically. Simulation results have validated the effectiveness of the algorithm. The model and the algorithm can be extended flexibly to certain practical problems, such as the joint channel and symbol estimation in underwater acoustic communication systems. Ling Zhang, Ming Li, Gangsheng Li, and Rui Wang Copyright © 2015 Ling Zhang et al. All rights reserved. Almost Automorphic Solutions for Fuzzy Cohen-Grossberg Neural Networks with Mixed Time Delays Tue, 03 Mar 2015 15:36:18 +0000 http://www.hindawi.com/journals/mpe/2015/812670/ This paper is concerned with the problem of almost automorphic solutions of a class of fuzzy Cohen-Grossberg neural networks with mixed time delays and variable coefficients. Based on inequality analysis techniques and combining the exponential dichotomy with fixed point theorem, some sufficient conditions for the existence and global exponential stability of almost automorphic solutions are obtained. Finally, a numerical example is given to show the feasibility of our results. Yongkun Li, Xiaofang Meng, and Xuemei Zhang Copyright © 2015 Yongkun Li et al. All rights reserved. Efficient Two-Dimensional Direction Finding via Auxiliary-Variable Manifold Separation Technique for Arbitrary Array Structure Tue, 03 Mar 2015 13:25:46 +0000 http://www.hindawi.com/journals/mpe/2015/740513/ A polynomial rooting direction of arrival (DOA) algorithm for multiple plane waves incident on an arbitrary array structure that combines the multipolynomial resultants and matrix computations is proposed in this paper. Firstly, a new auxiliary-variable manifold separation technique (AV-MST) is used to model the steering vector of arbitrary array structure as the product of a sampling matrix (dependent only on the array structure) and two Vandermonde-structured wavefield coefficient vectors (dependent on the wavefield). Then the propagator operator is calculated and used to form a system of bivariate polynomial equations. Finally, the automatically paired azimuth and elevation estimates are derived by polynomial rooting. The presented algorithm employs the concept of auxiliary-variable manifold separation technique which requires no sector by sector array interpolation and thus does not suffer from any mapping errors. In addition, the new algorithm does not need any eigenvalue decomposition of the covariance matrix and exhausted search over the two-dimensional parameter space. Moreover, the algorithm gives automatically paired estimates, thus avoiding the complex pairing procedure. Therefore, the proposed algorithm shows low computational complexity and high robustness performance. Simulation results are shown to validate the effectiveness of the proposed method. Guang Hua, Jiu-Dong Wu, Xi-Cheng Zhu, Hou-Xing Zhou, and Wei Hong Copyright © 2015 Guang Hua et al. All rights reserved. A Least-Squares FEM for the Direct and Inverse Rectangular Cavity Scattering Problem Tue, 03 Mar 2015 11:16:43 +0000 http://www.hindawi.com/journals/mpe/2015/524345/ This paper is concerned with the scattering problem of a rectangular cavity. We solve this problem by a least-squares nonpolynomial finite element method. In the method, we use Fourier-Bessel functions to capture the behaviors of the total field around corners. And the scattered field towards infinity is represented by a combination of half-space Green functions. Then we analyze the convergence and give an error estimate of the method. By coupling the least-squares nonpolynomial finite element method and the Newton method, we proposed an algorithm for the inverse scattering problem. Numerical experiments are presented to show the effectiveness of our method. Enxi Zheng, Fuming Ma, and Yujie Wang Copyright © 2015 Enxi Zheng et al. All rights reserved. Optimal Wind Turbines Micrositing in Onshore Wind Farms Using Fuzzy Genetic Algorithm Tue, 03 Mar 2015 10:59:03 +0000 http://www.hindawi.com/journals/mpe/2015/324203/ With the fast growth in the number and size of installed wind farms (WFs) around the world, optimal wind turbines (WTs) micrositing has become a challenge from both technological and mathematical points of view. An appropriate layout of wind turbines is crucial to obtain adequate performance with respect to the development and operation of the wind power plant during its life span. This work presents a fuzzy genetic algorithm (FGA) for maximizing the economic profitability of the project. The algorithm considers a new WF model including several important factors to the design of the layout. The model consists of wake loss, terrain effect, and economic benefits, which can be calculated by locations of wind turbines. The results demonstrate that the algorithm performs better than genetic algorithm, in terms of maximum values of net annual value of wind power plants and computational burden. Jun Yang, Rui Zhang, Qiuye Sun, and Huaguang Zhang Copyright © 2015 Jun Yang et al. All rights reserved. Research of the Classification Model Based on Dominance Rough Set Approach for China Emergency Communication Tue, 03 Mar 2015 10:34:59 +0000 http://www.hindawi.com/journals/mpe/2015/428218/ Ensuring smooth communication and recovering damaged communication system quickly and efficiently are the key to the entire emergency response, command, control, and rescue during the whole accident. The classification of emergency communication level is the premise of emergency communication guarantee. So, we use dominance rough set approach (DRSA) to construct the classification model for the judgment of emergency communication in this paper. In this model, we propose a classification index system of emergency communication using the method of expert interview firstly and then use DRSA to complete data sample, reduct attribute, and extract the preference decision rules of the emergency communication classification. Finally, the recognition accuracy of this model is verified; the testing result proves the model proposed in this paper is valid. Fan Zifu, Sun Hong, and Wang Lihua Copyright © 2015 Fan Zifu et al. All rights reserved.