Mathematical Problems in Engineering http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. Mathematical Methods and Modeling in Machine Fault Diagnosis Thu, 18 Dec 2014 11:52:50 +0000 http://www.hindawi.com/journals/mpe/2014/516590/ Ruqiang Yan, Xuefeng Chen, Weihua Li, and Shuangwen Sheng Copyright © 2014 Ruqiang Yan et al. All rights reserved. Optimization in Industrial Systems Thu, 18 Dec 2014 11:41:08 +0000 http://www.hindawi.com/journals/mpe/2014/824539/ Kok Lay Teo, Hsiao-Fan Wang, and Changzhi Wu Copyright © 2014 Kok Lay Teo et al. All rights reserved. Trip Travel Time Forecasting Based on Selective Forgetting Extreme Learning Machine Thu, 18 Dec 2014 11:18:54 +0000 http://www.hindawi.com/journals/mpe/2014/829256/ Travel time estimation on road networks is a valuable traffic metric. In this paper, we propose a machine learning based method for trip travel time estimation in road networks. The method uses the historical trip information extracted from taxis trace data as the training data. An optimized online sequential extreme machine, selective forgetting extreme learning machine, is adopted to make the prediction. Its selective forgetting learning ability enables the prediction algorithm to adapt to trip conditions changes well. Experimental results using real-life taxis trace data show that the forecasting model provides an effective and practical way for the travel time forecasting. Zhiming Gui and Haipeng Yu Copyright © 2014 Zhiming Gui and Haipeng Yu. All rights reserved. Feature Based Stereo Matching Using Two-Step Expansion Thu, 18 Dec 2014 09:57:26 +0000 http://www.hindawi.com/journals/mpe/2014/452803/ This paper proposes a novel method for stereo matching which is based on image features to produce a dense disparity map through two different expansion phases. It can find denser point correspondences than those of the existing seed-growing algorithms, and it has a good performance in short and wide baseline situations. This method supposes that all pixel coordinates in each image segment corresponding to a 3D surface separately satisfy projective geometry of 1D in horizontal axis. Firstly, a state-of-the-art method of feature matching is used to obtain sparse support points and an image segmentation-based prior is employed to assist the first region outspread. Secondly, the first-step expansion is to find more feature correspondences in the uniform region via initial support points, which is based on the invariant cross ratio in 1D projective transformation. In order to find enough point correspondences, we use a regular seed-growing algorithm as the second-step expansion and produce a quasi-dense disparity map. Finally, two different methods are used to obtain dense disparity map from quasi-dense pixel correspondences. Experimental results show the effectiveness of our method. Liqiang Wang, Zhen Liu, and Zhonghua Zhang Copyright © 2014 Liqiang Wang et al. All rights reserved. Flying Robot Based Viewpoint Selection for the Electricity Transmission Equipment Inspection Thu, 18 Dec 2014 06:50:21 +0000 http://www.hindawi.com/journals/mpe/2014/783810/ In the process of inspection for the electricity transmission equipment using flying robots, an automatic way to find the best viewpoint to get the high quality of image would be beneficial to observe the state of the electricity transmission equipment. Finding the best viewpoint belongs to the viewpoint selection problem. A strategy is proposed in this paper to find the best viewpoint for the electricity transmission equipment inspection, according to which the candidate viewpoints can be generated based on the 3D model of the equipment. Then a scoring function is constructed which combines three factors including the amount of the information, the viewing quality, and the visibility of the information to evaluate the quality of the candidate viewpoint. Finally, the best viewpoint can be selected from all of candidate viewpoints according to the scoring function. The proposed algorithm is tested on the experiment to demonstrate its effectiveness. Chang-an Liu, Rui-fang Dong, and Hua Wu Copyright © 2014 Chang-an Liu et al. All rights reserved. The Improved Kriging Interpolation Algorithm for Local Underwater Terrain Based on Fractal Compensation Thu, 18 Dec 2014 00:11:17 +0000 http://www.hindawi.com/journals/mpe/2014/289521/ The interpolation-reconstruction of local underwater terrain using the underwater digital terrain map (UDTM) is an important step for building an underwater terrain matching unit and directly affects the accuracy of underwater terrain matching navigation. The Kriging method is often used in terrain interpolation, but, with this method, the local terrain features are often lost. Therefore, the accuracy cannot meet the requirements of practical application. Analysis of the geographical features is performed on the basis of the randomness and self-similarity of underwater terrain. We extract the fractal features of local underwater terrain with the fractal Brownian motion model, compensating for the possible errors of the Kriging method with fractal theory. We then put forward an improved Kriging interpolation method based on this fractal compensation. Interpolation-reconstruction tests show that the method can simulate the real underwater terrain features well and that it has good usability. Pengyun Chen, Ye Li, Yumin Su, and Xiaolong Chen Copyright © 2014 Pengyun Chen et al. All rights reserved. Real-Time Analysis and Forecasting of Multisite River Flow Using a Distributed Hydrological Model Thu, 18 Dec 2014 00:11:15 +0000 http://www.hindawi.com/journals/mpe/2014/659262/ A spatial distributed hydrological forecasting system was developed to promote the analysis of river flow dynamic state in a large basin. The research presented the real-time analysis and forecasting of multisite river flow in the Nakdong River Basin using a distributed hydrological model with radar rainfall forecast data. A real-time calibration algorithm of hydrological distributed model was proposed to investigate the particular relationship between the water storage and basin discharge. Demonstrate the approach of simulating multisite river flow using a distributed hydrological model couple with real-time calibration and forecasting of multisite river flow with radar rainfall forecasts data. The hydrographs and results exhibit that calibrated flow simulations are very approximate to the flow observation at all sites and the accuracy of forecasting flow is gradually decreased with lead times extending from 1 hr to 3 hrs. The flow forecasts are lower than the flow observation which is likely caused by the low estimation of radar rainfall forecasts. The research has well demonstrated that the distributed hydrological model is readily applicable for multisite real-time river flow analysis and forecasting in a large basin. Mingdong Sun and Gwangseob Kim Copyright © 2014 Mingdong Sun and Gwangseob Kim. All rights reserved. Stability Analysis of a Car-Following Model on Two Lanes Wed, 17 Dec 2014 06:38:24 +0000 http://www.hindawi.com/journals/mpe/2014/727560/ Considering lateral influence from adjacent lane, an improved car-following model is developed in this paper. Then linear and nonlinear stability analyses are carried out. The modified Korteweg-de Vries (MKdV) equation is derived with the kink-antikink soliton solution. Numerical simulations are implemented and the result shows good consistency with theoretical study. Yuhan Jia, Yiman Du, and Jianping Wu Copyright © 2014 Yuhan Jia et al. All rights reserved. Coordinate Descent Based Hierarchical Interactive Lasso Penalized Logistic Regression and Its Application to Classification Problems Tue, 16 Dec 2014 09:30:37 +0000 http://www.hindawi.com/journals/mpe/2014/430201/ We present the hierarchical interactive lasso penalized logistic regression using the coordinate descent algorithm based on the hierarchy theory and variables interactions. We define the interaction model based on the geometric algebra and hierarchical constraint conditions and then use the coordinate descent algorithm to solve for the coefficients of the hierarchical interactive lasso model. We provide the results of some experiments based on UCI datasets, Madelon datasets from NIPS2003, and daily activities of the elder. The experimental results show that the variable interactions and hierarchy contribute significantly to the classification. The hierarchical interactive lasso has the advantages of the lasso and interactive lasso. Jin-Jia Wang and Yang Lu Copyright © 2014 Jin-Jia Wang and Yang Lu. All rights reserved. Simulation Study on Train-Induced Vibration Control of a Long-Span Steel Truss Girder Bridge by Tuned Mass Dampers Tue, 16 Dec 2014 09:11:49 +0000 http://www.hindawi.com/journals/mpe/2014/506578/ Train-induced vibration of steel truss bridges is one of the key issues in bridge engineering. This paper talks about the application of tuned mass damper (TMD) on the vibration control of a steel truss bridge subjected to dynamic train loads. The Nanjing Yangtze River Bridge (NYRB) is taken as the research object and a recorded typical train load is included in this study. With dynamic finite element (FE) method, the real-time dynamic responses of NYRB are analyzed based on a simplified train-bridge time-varying system. Thereinto, two cases including single train moving at one side and two trains moving oppositely are specifically investigated. According to the dynamic characteristics and dynamic responses of NYRB, the fourth vertical bending mode is selected as the control target and the parameter sensitivity analysis on vibration control efficiency with TMD is conducted. Using the first-order optimization method, the optimal parameters of TMD are then acquired with the control efficiency of TMD, the static displacement of Midspan, expenditure of TMDs, and manufacture difficulty of the damper considered. Results obtained in this study can provide references for the vibration control of steel truss bridges. Hao Wang, Tianyou Tao, Huaiyu Cheng, and Xuhui He Copyright © 2014 Hao Wang et al. All rights reserved. Research on Overflow Monitoring Mechanism Based on Downhole Microflow Detection Tue, 16 Dec 2014 08:03:15 +0000 http://www.hindawi.com/journals/mpe/2014/676290/ The flow rate variation of the drilling fluid and micro-overflow loss is difficult to analyze. The purpose to prevent the occurrence of kick, lost circulation, and other complex conditions is not easy to be achieved. Therefore, the microflow-induced annulus multiphase flow rate and annulus pressure field model were studied, and a downhole microflow measurement system has been developed. A differential pressure type flow measurement was used in the system, and real-time downhole information was obtained to achieve deep, narrow windows and other safety-density complex formation security. This paper introduced a new bottom-hole flow meter which can measure the annular flux while drilling and monitor overflow and circulation loss. The accuracy and reliability of the MPD (managed pressure drilling) system can be improved obviously by applying the device; as a result, the safety of drilling is enhanced and the cost is reduced. Liang Ge, Ze Hu, Ping Chen, Lei Shi, Qing Yang, and Junbi Liao Copyright © 2014 Liang Ge et al. All rights reserved. EOQ Model for Deteriorating Items with Stock-Level-Dependent Demand Rate and Order-Quantity-Dependent Trade Credit Tue, 16 Dec 2014 06:46:34 +0000 http://www.hindawi.com/journals/mpe/2014/962128/ This paper develops a generalized inventory model for exponentially deteriorating items with current-stock-dependent demand rate and permissible delay in payments. In the model, the payment for the item must be made immediately if the order quantity is less than the predetermined quantity; otherwise, a fixed trade credit period is permitted. The maximization of the average profit per unit of time is taken as the inventory system’s objective. The necessary and sufficient conditions and some properties of the optimal solution to the model are developed. Simple solution procedures are proposed to efficiently determine the optimal ordering policies of the considered problem. Numerical example is also presented to illustrate the solution procedures obtained. Jie Min, Jian Ou, Yuan-Guang Zhong, and Xin-Bao Liu Copyright © 2014 Jie Min et al. All rights reserved. Consolidation by Prefabricated Vertical Drains with a Threshold Gradient Tue, 16 Dec 2014 00:10:41 +0000 http://www.hindawi.com/journals/mpe/2014/410390/ This paper shows the development of an approximate analytical solution of radial consolidation by prefabricated vertical drains with a threshold gradient. To understand the effect of the threshold gradient on consolidation, a parametric analysis was performed using the present solution. The applicability of the present solution was demonstrated in two cases, wherein the comparisons with Hansbo’s results and observed data were conducted. It was found that (1) the flow with the threshold gradient would not occur instantaneously throughout the whole unit cell. Rather, it gradually occurs from the vertical drain to the outside; (2) the moving boundary would never reach the outer radius of influence if , whereas it will reach the outer radius of influence at some time; (3) the excess pore pressure will not be dissipated completely, but it will maintain a long-term stable value at the end of consolidation; (4) the larger the threshold gradient is, the greater the long-term excess pore pressure will be; and (5) the present solution could predict the consolidation behavior in soft clay better than previous methods. Xiao Guo, Kang-He Xie, and Yue-Bao Deng Copyright © 2014 Xiao Guo et al. All rights reserved. ISP-Friendly Data Scheduling by Advanced Locality-Aware Network Coding for P2P Distribution Cloud Mon, 15 Dec 2014 12:53:12 +0000 http://www.hindawi.com/journals/mpe/2014/968328/ Peer-to-peer (P2P) file distribution imposes increasingly heavy traffic burden on the Internet service providers (ISPs). The vast volume of traffic pushes up ISPs’ costs in routing and investment and degrades their networks performance. Building ISP-friendly P2P is therefore of critical importance for ISPs and P2P services. So far most efforts in this area focused on improving the locality-awareness of P2P applications, for example, to construct overlay networks with better knowledge of the underlying network topology. There is, however, growing recognition that data scheduling algorithms also play an effective role in P2P traffic reduction. In this paper, we introduce the advanced locality-aware network coding (ALANC) for P2P file distribution. This data scheduling algorithm completely avoids the transmission of linearly dependent data blocks, which is a notable problem of previous network coding algorithms. Our simulation results show that, in comparison to other algorithms, ALANC not only significantly reduces interdomain P2P traffic, but also remarkably improves both the application-level performance (for P2P services) and the network-level performance (for ISP networks). For example, ALANC is 30% faster in distributing data blocks and it reduces the average traffic load on the underlying links by 40%. We show that ALANC holds the above gains when the tit-for-tat incentive mechanism is introduced or the overlay topology changes dynamically. Yanjun Li, Guoqing Zhang, and Guoqiang Zhang Copyright © 2014 Yanjun Li et al. All rights reserved. Nonlocal Problems Arising in Thermoelectrics Mon, 15 Dec 2014 07:08:29 +0000 http://www.hindawi.com/journals/mpe/2014/909078/ We revisit the derivation of a nonlocal problem modelling temperature distribution due to power generation using thermoelectric effect. The problem has nonlocal coefficients in reaction and convection terms rather than diffusion term, which makes the problem more interesting. In this paper, we prove that the nonlocal problem has a unique decreasing solution when electric current induced by the thermoelectric effect is small enough. Jaywan Chung and Byungki Ryu Copyright © 2014 Jaywan Chung and Byungki Ryu. All rights reserved. Model and Method for Multiobjective Time-Dependent Hazardous Material Transportation Sun, 14 Dec 2014 13:49:08 +0000 http://www.hindawi.com/journals/mpe/2014/832814/ In most of the hazardous material transportation problems, risk factors are assumed to be constant, which ignores the fact that they can vary with time throughout the day. In this paper, we deal with a novel time-dependent hazardous material transportation problem via lane reservation, in which the dynamic nature of transportation risk in the real-life traffic environment is taken into account. We first develop a multiobjective mixed integer programming (MIP) model with two conflicting objectives: minimizing the impact on the normal traffic resulting from lane reservation and minimizing the total transportation risk. We then present a cut-and-solve based -constraint method to solve this model. Computational results indicate that our method outperforms the -constraint method based on optimization software package CPLEX. Zhen Zhou, Ada Che, Feng Chu, and Chengbin Chu Copyright © 2014 Zhen Zhou et al. All rights reserved. Data Fusion and Fuzzy Clustering on Ratio Images for Change Detection in Synthetic Aperture Radar Images Sun, 14 Dec 2014 11:54:56 +0000 http://www.hindawi.com/journals/mpe/2014/403095/ The unsupervised approach to change detection via synthetic aperture radar (SAR) images becomes more and more popular. The three-step procedure is the most widely used procedure, but it does not work well with the Yellow River Estuary dataset obtained by two synthetic aperture radars. The difference of the two radars in imaging techniques causes severe noise, which seriously affects the difference images generated by a single change detector in step two, producing the difference image. To deal with problem, we propose a change detector to fuse the log-ratio (LR) and the mean-ratio (MR) images by a context independent variable behavior (CIVB) operator and can utilize the complement information in two ratio images. In order to validate the effectiveness of the proposed change detector, the change detector will be compared with three other change detectors, namely, the log-ratio (LR), mean-ratio (MR), and the wavelet-fusion (WR) operator, to deal with three datasets with different characteristics. The four operators are applied not only in a widely used three-step procedure but also in a new approach. The experiments show that the false alarms and overall errors of change detection are greatly reduced, and the kappa and KCC are improved a lot. And its superiority can also be observed visually. Wenping Ma, Xiaoting Li, Yue Wu, Licheng Jiao, and Dan Xing Copyright © 2014 Wenping Ma et al. All rights reserved. A Finite Points Method Approach for Strain Localization Using the Gradient Plasticity Formulation Thu, 11 Dec 2014 06:19:38 +0000 http://www.hindawi.com/journals/mpe/2014/782079/ The softening elastoplastic models present an unsuitable behavior after reaching the yield strength: unbounded strain localization. Because of the material instability, which is reflected in the loss of ellipticity of the governing partial differential equations, the solution depends on the discretization. The present work proposes to solve this dependency using the meshless Finite Points Method. This meshfree spatial discretization technique allows enriching the governing equations using gradient’s plasticity and introducing an internal length scale parameter at the material model in order to objectify the solution. Luis Pérez Pozo, Andy Campos, Sheila Lascano, Sergio Oller, and Antonio Rodríguez-Ferran Copyright © 2014 Luis Pérez Pozo et al. All rights reserved. Two-Stage Chaos Optimization Search Application in Maximum Power Point Tracking of PV Array Thu, 11 Dec 2014 00:10:48 +0000 http://www.hindawi.com/journals/mpe/2014/464835/ In order to deliver the maximum available power to the load under the condition of varying solar irradiation and environment temperature, maximum power point tracking (MPPT) technologies have been used widely in PV systems. Among all the MPPT schemes, the chaos method is one of the hot topics in recent years. In this paper, a novel two-stage chaos optimization method is presented which can make search faster and more effective. In the process of proposed chaos search, the improved logistic mapping with the better ergodic is used as the first carrier process. After finding the current optimal solution in a certain guarantee, the power function carrier as the secondary carrier process is used to reduce the search space of optimized variables and eventually find the maximum power point. Comparing with the traditional chaos search method, the proposed method can track the change quickly and accurately and also has better optimization results. The proposed method provides a new efficient way to track the maximum power point of PV array. Lihua Wang, Xueye Wei, Tianlong Zhu, and Junhong Zhang Copyright © 2014 Lihua Wang et al. All rights reserved. Image Inpainting Algorithm Based on Low-Rank Approximation and Texture Direction Wed, 10 Dec 2014 00:11:14 +0000 http://www.hindawi.com/journals/mpe/2014/621520/ Existing image inpainting algorithm based on low-rank matrix approximation cannot be suitable for complex, large-scale, damaged texture image. An inpainting algorithm based on low-rank approximation and texture direction is proposed in the paper. At first, we decompose the image using low-rank approximation method. Then the area to be repaired is interpolated by level set algorithm, and we can reconstruct a new image by the boundary values of level set. In order to obtain a better restoration effect, we make iteration for low-rank decomposition and level set interpolation. Taking into account the impact of texture direction, we segment the texture and make low-rank decomposition at texture direction. Experimental results show that the new algorithm is suitable for texture recovery and maintaining the overall consistency of the structure, which can be used to repair large-scale damaged image. Jinjiang Li, Mengjun Li, and Hui Fan Copyright © 2014 Jinjiang Li et al. All rights reserved. A Pulse Signal Characteristic Recognition Algorithm Based on Multifractal Dimension Tue, 09 Dec 2014 11:29:34 +0000 http://www.hindawi.com/journals/mpe/2014/376586/ In low SNR condition, it is difficult to identify the radio transient characteristics of the signals. To solve this problem, a new recognition algorithm based on multifractal dimension characteristics is proposed. In fractal theory, multifractal dimension is the most sophisticated characterize that can describe the similar characteristics of the signals. Therefore, multifractal dimension is used in this paper to extract the subtle features of different impulse noise signals, in order to achieve the purpose of the classification and identification of the radiation source. Yi-bing Li, Wei Nie, Fang Ye, and Jing-chao Li Copyright © 2014 Yi-bing Li et al. All rights reserved. Efficiency of High-Order Accurate Difference Schemes for the Korteweg-de Vries Equation Mon, 08 Dec 2014 11:53:36 +0000 http://www.hindawi.com/journals/mpe/2014/862403/ Two numerical models to obtain the solution of the KdV equation are proposed. Numerical tools, compact fourth-order and standard fourth-order finite difference techniques, are applied to the KdV equation. The fundamental conservative properties of the equation are preserved by the finite difference methods. Linear stability analysis of two methods is presented by the Von Neumann analysis. The new methods give second- and fourth-order accuracy in time and space, respectively. The numerical experiments show that the proposed methods improve the accuracy of the solution significantly. Kanyuta Poochinapan, Ben Wongsaijai, and Thongchai Disyadej Copyright © 2014 Kanyuta Poochinapan et al. All rights reserved. Research on Key Technologies of Unit-Based CNC Machine Tool Assembly Design Mon, 08 Dec 2014 11:36:29 +0000 http://www.hindawi.com/journals/mpe/2014/191069/ Assembly is the part that produces the maximum workload and consumed time during product design and manufacturing process. CNC machine tool is the key basic equipment in manufacturing industry and research on assembly design technologies of CNC machine tool has theoretical significance and practical value. This study established a simplified ASRG for CNC machine tool. The connection between parts, semantic information of transmission, and geometric constraint information were quantified to assembly connection strength to depict the assembling difficulty level. The transmissibility based on trust relationship was applied on the assembly connection strength. Assembly unit partition based on assembly connection strength was conducted, and interferential assembly units were identified and revised. The assembly sequence planning and optimization of parts in each assembly unit and between assembly units was conducted using genetic algorithm. With certain type of high speed CNC turning center, as an example, this paper explored into the assembly modeling, assembly unit partition, and assembly sequence planning and optimization and realized the optimized assembly sequence of headstock of CNC machine tool. Zhongqi Sheng, Lei Zhang, Hualong Xie, and Changchun Liu Copyright © 2014 Zhongqi Sheng et al. All rights reserved. A Regularization Process for Electrical Impedance Equation Employing Pseudoanalytic Function Theory Mon, 08 Dec 2014 00:10:34 +0000 http://www.hindawi.com/journals/mpe/2014/964081/ The electrical impedance equation is considered an ill-posed problem where the solution to the forward problem is more easy to achieve than the inverse problem. This work tries to improve convergence in the forward problem method, where the Pseudoanalytic Function Theory by means of the Taylor series in formal powers is used, incorporating a regularization method to make a solution more stable and to obtain better convergence. In addition, we include a comparison between the designed algorithms that perform proposed method with and without a regularization process and the autoadjustment parameter for this regularization process. Cesar Marco Antonio Robles Gonzalez, Ariana Guadalupe Bucio Ramirez, Volodymyr Ponomaryov, and Marco Pedro Ramirez Tachiquin Copyright © 2014 Cesar Marco Antonio Robles Gonzalez et al. All rights reserved. Analysis of Load-Carrying Capacity for Redundant Free-Floating Space Manipulators in Trajectory Tracking Task Mon, 08 Dec 2014 00:10:32 +0000 http://www.hindawi.com/journals/mpe/2014/125940/ The aim of this paper is to analyze load-carrying capacity of redundant free-floating space manipulators (FFSM) in trajectory tracking task. Combined with the analysis of influential factors in load-carrying process, evaluation of maximum load-carrying capacity (MLCC) is described as multiconstrained nonlinear programming problem. An efficient algorithm based on repeated line search within discontinuous feasible region is presented to determine MLCC for a given trajectory of the end-effector and corresponding joint path. Then, considering the influence of MLCC caused by different initial configurations for the starting point of given trajectory, a kind of maximum payload initial configuration planning method is proposed by using PSO algorithm. Simulations are performed for a particular trajectory tracking task of the 7-DOF space manipulator, of which MLCC is evaluated quantitatively. By in-depth research of the simulation results, significant gap between the values of MLCC when using different initial configurations is analyzed, and the discontinuity of allowable load-carrying capacity is illustrated. The proposed analytical method can be taken as theoretical foundation of feasibility analysis, trajectory optimization, and optimal control of trajectory tracking task in on-orbit load-carrying operations. Qingxuan Jia, Yong Liu, Gang Chen, Hanxu Sun, and Junjie Peng Copyright © 2014 Qingxuan Jia et al. All rights reserved. Geometric and Meshing Properties of Conjugate Curves for Gear Transmission Sun, 07 Dec 2014 14:16:17 +0000 http://www.hindawi.com/journals/mpe/2014/484802/ Conjugate curves have been put forward previously by authors for gear transmission. Compared with traditional conjugate surfaces, the conjugate curves have more flexibility and diversity in aspects of gear design and generation. To further extend its application in power transmission, the geometric and meshing properties of conjugate curves are discussed in this paper. Firstly, general principle descriptions of conjugate curves for arbitrary axial position are introduced. Secondly, geometric analysis of conjugate curves is carried out based on differential geometry including tangent and normal in arbitrary contact direction, characteristic point, and curvature relationships. Then, meshing properties of conjugate curves are further revealed. According to a given plane or spatial curve, the uniqueness of conjugated curve under different contact angle conditions is discussed. Meshing commonality of conjugate curves is also demonstrated in terms of a class of spiral curves contacting in the given direction for various gear axes. Finally, a conclusive summary of this study is given. Dong Liang, Bingkui Chen, Yane Gao, Shuai Peng, and Siling Qin Copyright © 2014 Dong Liang et al. All rights reserved. On the Relation between NARX Clusters and Even/Odd Nonlinearities through Frequency-Domain Analysis Sun, 07 Dec 2014 11:15:41 +0000 http://www.hindawi.com/journals/mpe/2014/650737/ Although polynomial NARX models have been intensively used in nonlinear system identification, few papers discussed how to relate the inner nonlinearities to specific types of clusters and regressors. The objective of this paper is to discuss this relationship for a class of systems that contain even or odd nonlinearities. This class covers block-structured models (Hammerstein, Wiener, and others) and systems with dynamic nonlinearities. To achieve the paper’s aim, a deep frequency-domain analysis is performed. For each type of nonlinearity, all the NARX clusters are investigated and the results show that each regressor type provides specific nonlinear contribution. The investigation is based on an output power spectra analysis when a specific multisinusoidal excitation is applied. According to the spectral contributions in some of the frequency lines, the nonlinearity classification is possible. By applying the same procedure to the clusters, one interprets how these clusters can (or not) contribute to explain the system nonlinearity. The paper findings have two major impacts: (i) one gains deep knowledge on how the nonlinearities are coded by the clusters, and (ii) this information can be used, for instance, to aid a structure selection procedure (ERR, term clustering, etc.) during the discarding of the clusters which are not able to explain the system nonlinear behavior. Some practical and experimental aspects are discussed, while numerical examples are presented to show the validity of the theoretical analysis. Alexandro G. Brito, Elder M. Hemerly, and Waldemar C. Leite Filho Copyright © 2014 Alexandro G. Brito et al. All rights reserved. Stability and Bifurcation Analysis of a Singular Delayed Predator-Prey Bioeconomic Model with Stochastic Fluctuations Sun, 07 Dec 2014 09:56:38 +0000 http://www.hindawi.com/journals/mpe/2014/535634/ This study investigates a singular delayed predator-prey bioeconomic model with stochastic fluctuations, which is described by differential-algebraic equations because of economic factors. The interior equilibrium of the singular delayed predator-prey bioeconomic model switches from being stable to unstable and then back to being stable, with the increase in time delay. The critical values for stability switches and Hopf bifurcations can be analytically determined. Subsequently, the effect of a fluctuating environment on the singular stochastic delayed predator-prey bioeconomic model obtained by introducing Gaussian white noise terms to the aforementioned deterministic model system is discussed. The fluctuation intensity of the population and harvest effort are calculated by Fourier transform method. Numerical simulation results are presented to verify the effectiveness of the conclusions. Yue Zhang and Qingling Zhang Copyright © 2014 Yue Zhang and Qingling Zhang. All rights reserved. Stochastic Consensus of Single-Integrator Multiagent Systems with Inherent Nonlinear Dynamics and Measurement Noises in Directed Fixed Topologies Sun, 07 Dec 2014 07:51:57 +0000 http://www.hindawi.com/journals/mpe/2014/487850/ Consensus of continuous-time single-integrator multiagent systems with inherent nonlinear dynamics and measurement noises is addressed in this paper. The consensus controller is developed for directed interaction topologies. Each agent’s control input is constructed based on its own state and its neighbors’ states corrupted by noises. The control input contains a time-varying consensus gain in order to attenuate the noises. Conditions for ensuring mean square convergence under noisy measurement and asymptotic convergence in the noise-free case are derived. Finally, some simulations were carried out to show the effectiveness of our control law and how it can solve the consensus problem. Sabir Djaidja and Qinghe Wu Copyright © 2014 Sabir Djaidja and Qinghe Wu. All rights reserved. Wastewater Treatment Optimization for Fish Migration Using Harmony Search Thu, 04 Dec 2014 13:25:00 +0000 http://www.hindawi.com/journals/mpe/2014/313157/ Certain types of fish migrate between the sea and fresh water to spawn. In order for them to swim without any breathing problem, river should contain enough oxygen. If fish is passing along the river in municipal area, it needs sufficient dissolved oxygen level which is influenced by dumped amount of wastewater into the river. If existing treatment methods such as settling and biological oxidation are not enough, we have to consider additional treatment methods such as microscreening filtration and nitrification. This study constructed a wastewater treatment optimization model for migratory fish, which considers three costs (filtration cost, nitrification cost, and irrigation cost) and two environmental constraints (minimal dissolved oxygen level and maximal nitrate-nitrogen concentration). Results show that the metaheuristic technique such as harmony search could find good solutions robustly while calculus-based technique such as generalized reduced gradient method was trapped in local optima or even divergent. Zong Woo Geem and Jin-Hong Kim Copyright © 2014 Zong Woo Geem and Jin-Hong Kim. All rights reserved.