Mathematical Problems in Engineering http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. Statistical Pattern-Based Assessment of Structural Health Monitoring Data Wed, 17 Sep 2014 08:27:09 +0000 http://www.hindawi.com/journals/mpe/2014/926079/ In structural health monitoring (SHM), various sensors are installed at critical locations of a structure. The signals from sensors are either continuously or periodically analyzed to determine the state and performance of the structure. An objective comparison of the sensor data at different time ranges is essential for assessing the structural condition or excessive load experienced by the structure which leads to potential damage in the structure. The objectives of the current study are to establish a relationship between the data from various sensors to estimate the reliability of the data and potential damage using the statistical pattern matching techniques. In order to achieve these goals, new methodologies based on statistical pattern recognition techniques have been developed. The proposed methodologies have been developed and validated using sensor data obtained from an instrumented bridge and road test data from heavy vehicles. The application of statistical pattern matching techniques are relatively new in SHM data interpretation and current research demonstrates that it has high potential in assessing structural conditions, especially when the data are noisy and susceptible to environmental disturbances. Mohammad S. Islam and Ashutosh Bagchi Copyright © 2014 Mohammad S. Islam and Ashutosh Bagchi. All rights reserved. A Probabilistic Approach to Control of Complex Systems and Its Application to Real-Time Pricing Wed, 17 Sep 2014 00:00:00 +0000 http://www.hindawi.com/journals/mpe/2014/906717/ Control of complex systems is one of the fundamental problems in control theory. In this paper, a control method for complex systems modeled by a probabilistic Boolean network (PBN) is studied. A PBN is widely used as a model of complex systems such as gene regulatory networks. For a PBN, the structural control problem is newly formulated. In this problem, a discrete probability distribution appeared in a PBN is controlled by the continuous-valued input. For this problem, an approximate solution method using a matrix-based representation for a PBN is proposed. Then, the problem is approximated by a linear programming problem. Furthermore, the proposed method is applied to design of real-time pricing systems of electricity. Electricity conservation is achieved by appropriately determining the electricity price over time. The effectiveness of the proposed method is presented by a numerical example on real-time pricing systems. Koichi Kobayashi and Kunihiko Hiraishi Copyright © 2014 Koichi Kobayashi and Kunihiko Hiraishi. All rights reserved. Visualizing Exact and Approximated 3D Empirical Attainment Functions Wed, 17 Sep 2014 00:00:00 +0000 http://www.hindawi.com/journals/mpe/2014/569346/ Most real-world engineering optimization problems are inherently multiobjective, for example, searching for trade-off solutions of high quality and low cost. As no single optimal solution exists for such problems, multiobjective optimizers provide sets of optimal (or near-optimal) trade-off solutions to choose from. The empirical attainment function (EAF) is a powerful tool that can be used to analyze and compare the performance of these optimizers. While the visualization of EAFs is rather straightforward in two objectives, the three-objective case presents a great challenge as we need to visualize a large number of 3D cuboids. This paper addresses the visualization of exact as well as approximated 3D EAF values and differences in these values provided by two competing multiobjective optimizers. We show that the exact EAFs can be visualized using slicing and maximum intensity projection (MIP), while the approximated EAFs can be visualized using slicing, MIP, and direct volume rendering. In addition, the paper demonstrates the use of the proposed visualization techniques on a steel casting optimization problem. Tea Tušar and Bogdan Filipič Copyright © 2014 Tea Tušar and Bogdan Filipič. All rights reserved. Multipurpose Water Reservoir Management: An Evolutionary Multiobjective Optimization Approach Mon, 15 Sep 2014 13:12:40 +0000 http://www.hindawi.com/journals/mpe/2014/638259/ The reservoirs that feed large hydropower plants should be managed in order to provide other uses for the water resources. Those uses include, for instance, flood control and avoidance, irrigation, navigability in the rivers, and other ones. This work presents an evolutionary multiobjective optimization approach for the study of multiple water usages in multiple interlinked reservoirs, including both power generation objectives and other objectives not related to energy generation. The classical evolutionary algorithm NSGA-II is employed as the basic multiobjective optimization machinery, being modified in order to cope with specific problem features. The case studies, which include the analysis of a problem which involves an objective of navigability on the river, are tailored in order to illustrate the usefulness of the data generated by the proposed methodology for decision-making on the problem of operation planning of multiple reservoirs with multiple usages. It is shown that it is even possible to use the generated data in order to determine the cost of any new usage of the water, in terms of the opportunity cost that can be measured on the revenues related to electric energy sales. Luís A. Scola, Ricardo H. C. Takahashi, and Sérgio A. A. G. Cerqueira Copyright © 2014 Luís A. Scola et al. All rights reserved. A Study on Overestimating a Given Fraction Defective by an Imperfect Inspector Mon, 15 Sep 2014 12:23:26 +0000 http://www.hindawi.com/journals/mpe/2014/619639/ It has been believed that even an imperfect inspector with nonzero inspection errors could either overestimate or underestimate a given FD (fraction defective) with a 50 : 50 chance. What happens to the existing inspection plans, if an imperfect inspector overestimates a known FD, when it is very low? We deal with this fundamental question, by constructing four mathematical models, under the assumptions that an infinite sequence of items with a known FD is given to an imperfect inspector with nonzero inspection errors, which can be constant and/or randomly distributed with a uniform distribution. We derive four analytical formulas for computing the probability of overestimation (POE) and prove that an imperfect inspector overestimates a given FD with more than 50%, if the FD is less than a value termed as a critical FD. Our mathematical proof indicates that the POE approaches one when FD approaches zero under our assumptions. Hence, if a given FD is very low, commercial inspection plans should be revised with the POE concept in the near future, for the fairness of commercial trades. Moon Hee Yang and Kyung Chang Copyright © 2014 Moon Hee Yang and Kyung Chang. All rights reserved. Generalized Guidance Scheme for Low-Thrust Orbit Transfer Mon, 15 Sep 2014 08:38:23 +0000 http://www.hindawi.com/journals/mpe/2014/407087/ The authors present an orbital guidance scheme for the satellite with an electrical propulsion system using a Lyapunov feedback control. The construction of a Lyapunov candidate is based on orbital elements, which consist of angular momentum and eccentricity vectors. This approach performs orbit transfers between any two arbitrary elliptic or circular orbits without any singularity issues. These orbital elements uniquely describe a non degenerate Keplerian orbit. The authors improve the reliability of the existing Lyapunov orbital guidance scheme by considering the energy term. Additional improvement is achieved by adding the penalty function. Furthermore, it is shown that the final suggested approach is suitable for the satellite passing the earth’s shadow area. Henzeh Leeghim, Dong-Hyun Cho, Su-Jang Jo, and Donghoon Kim Copyright © 2014 Henzeh Leeghim et al. All rights reserved. An Advanced Coupled Genetic Algorithm for Identifying Unknown Moving Loads on Bridge Decks Mon, 15 Sep 2014 05:28:05 +0000 http://www.hindawi.com/journals/mpe/2014/462341/ This study deals with an inverse method to identify moving loads on bridge decks using the finite element method (FEM) and a coupled genetic algorithm (c-GA). We developed the inverse technique using a coupled genetic algorithm that can make global solution searches possible as opposed to classical gradient-based optimization techniques. The technique described in this paper allows us to not only detect the weight of moving vehicles but also find their moving velocities. To demonstrate the feasibility of the method, the algorithm is applied to a bridge deck model with beam elements. In addition, 1D and 3D finite element models are simulated to study the influence of measurement errors and model uncertainty between numerical and real structures. The results demonstrate the excellence of the method from the standpoints of computation efficiency and avoidance of premature convergence. Sang-Youl Lee Copyright © 2014 Sang-Youl Lee. All rights reserved. Undesirable Outputs’ Presence in Centralized Resource Allocation Model Mon, 15 Sep 2014 00:00:00 +0000 http://www.hindawi.com/journals/mpe/2014/675895/ Data envelopment analysis (DEA) is a common nonparametric technique to measure the relative efficiency scores of the individual homogenous decision making units (DMUs). One aspect of the DEA literature has recently been introduced as a centralized resource allocation (CRA) which aims at optimizing the combined resource consumption by all DMUs in an organization rather than considering the consumption individually through DMUs. Conventional DEA models and CRA model have been basically formulated on desirable inputs and outputs. The objective of this paper is to present new CRA models to assess the overall efficiency of a system consisting of DMUs by using directional distance function when DMUs produce desirable and undesirable outputs. This paper initially reviewed a couple of DEA approaches for measuring the efficiency scores of DMUs when some outputs are undesirable. Then, based upon these theoretical foundations, we develop the CRA model when undesirable outputs are considered in the evaluation. Finally, we apply a short numerical illustration to show how our proposed model can be applied. Ghasem Tohidi, Hamed Taherzadeh, and Sara Hajiha Copyright © 2014 Ghasem Tohidi et al. All rights reserved. Discrete Globalised Dual Heuristic Dynamic Programming in Control of the Two-Wheeled Mobile Robot Sun, 14 Sep 2014 09:12:49 +0000 http://www.hindawi.com/journals/mpe/2014/628798/ Network-based control systems have been emerging technologies in the control of nonlinear systems over the past few years. This paper focuses on the implementation of the approximate dynamic programming algorithm in the network-based tracking control system of the two-wheeled mobile robot, Pioneer 2-DX. The proposed discrete tracking control system consists of the globalised dual heuristic dynamic programming algorithm, the PD controller, the supervisory term, and an additional control signal. The structure of the supervisory term derives from the stability analysis realised using the Lyapunov stability theorem. The globalised dual heuristic dynamic programming algorithm consists of two structures: the actor and the critic, realised in a form of neural networks. The actor generates the suboptimal control law, while the critic evaluates the realised control strategy by approximation of value function from the Bellman’s equation. The presented discrete tracking control system works online, the neural networks’ weights adaptation process is realised in every iteration step, and the neural networks preliminary learning procedure is not required. The performance of the proposed control system was verified by a series of computer simulations and experiments realised using the wheeled mobile robot Pioneer 2-DX. Marcin Szuster and Zenon Hendzel Copyright © 2014 Marcin Szuster and Zenon Hendzel. All rights reserved. An ISM Based Approach for Product Innovation Using a Synthesized Process Sun, 14 Sep 2014 08:08:12 +0000 http://www.hindawi.com/journals/mpe/2014/341614/ Internet shopping has become a global business activity; it also increases the workload of delivery services. The Transnet logistics can easily deliver and collect cargos from everywhere, with difficulty of having the greatest efficiency. This study is composed of four parts; the first step of identifies opportunities in which proposing an auxiliary vehicle for Transnet truck to support service in narrow or crowded road. A weight calculation system determined the relative value of different items and applied the interpretive structural model (ISM) to modularize SET for constructing innovation from integrated new product development (iNPD). From finding GAPs in opportunities of search results are explored an innovative light electric carrier as an auxiliary vehicle is determined. The second part consists of quantifying 21 items based upon 7 specific attributes for user orientation. The third part describes a new kind of light electric vehicle which is developed and mounted on the rear side of transport trucks; it can be used to deliver goods along narrow roads. Finally, more specific details of a collapsible electric motor carrier with a battery that is recharged using truck’s power system after using it are presented. The results of this study establish a research and product design to help Transnet drivers by improving carrying efficiency in narrow and crowded roads. Ming-Tang Wang, Chang-Tzuoh Wu, Rain Chen, Wen-Liang Chen, and Chien-Yu Liu Copyright © 2014 Ming-Tang Wang et al. All rights reserved. LQG Control of Along-Wind Response of a Tall Building with an ATMD Sun, 14 Sep 2014 00:00:00 +0000 http://www.hindawi.com/journals/mpe/2014/206786/ Modern tall buildings use lighter construction materials that have high strength and less stiffness and are more flexible. Although this results in the improvement of structural safety, excessive wind-induced excitations could lead to occupant discomfort. The optimal control law of a linear quadratic Gaussian (LQG) controller with an active tuned mass damper (ATMD) is used for reducing the along-wind response of a tall building. ATMD consists of a second mass with optimum parameters for tuning frequency and damping ratio of the tuned mass damper (TMD), under the stationary random load, was used. A fluctuating along-wind load, acting on a tall building, was treated as a stationary Gaussian white noise and was simulated numerically, in the time domain, using the along-wind load spectra proposed by G. Solari in 1993. Using this simulated wind load, it was possible to calculate the along-wind responses of a tall building (with and without the ATMD), using an LQG controller. Comparing the RMS (root mean square) response revealed that the numerically simulated along-wind responses, without ATMD, are a good approximation to the closed form response, and that the reduced responses with ATMD and LQG controller were estimated by varying the values of control design parameters. Ki-Pyo You, Jang-Youl You, and Young-Moon Kim Copyright © 2014 Ki-Pyo You et al. All rights reserved. Modelling Inflation Uncertainty with Structural Breaks Case of Turkey (1994–2013) Thu, 11 Sep 2014 15:51:36 +0000 http://www.hindawi.com/journals/mpe/2014/284161/ In recent years, the importance attached to the concept of volatility has increased and become a phenomenon frequently encountered in every field ranging from financial markets to macroeconomic indicators. In this study, inflation data obtained from CPI index for the period of 1994:01–2013:12 in Turkey was used to determine the best representative of the inflation uncertainty. To realize this, both symmetric and asymmetric GARCH-type models were employed. Since there are many factors that may lead to structural change within the economic course of Turkey, a structural break in the series has first been investigated. By administering Bai-Perron structural break test, two different break points both in mean and variance have been detected to be in February 2002 and in June 2001, respectively. The inclusion of those break points to the related equations, appropriate forecasting models were projected. Moreover it was found that, while in the periods prior to the break in both variance and mean the inflation itself was the reason for inflation uncertainty, following the dates of the break, the relationship changed bidirectionally. In the meantime, when the series was taken as a whole without considering the break, bidirectional causality relationship was also detected in the series. Pınar Göktaş and Cem Dişbudak Copyright © 2014 Pınar Göktaş and Cem Dişbudak. All rights reserved. A Tree-Based Model for Setting Optimal Train Fare Zones Thu, 11 Sep 2014 07:14:40 +0000 http://www.hindawi.com/journals/mpe/2014/384321/ Given a railway line with stops and the number of travelers between each pair of stops, we show how to split these stops into different fare zones in order to maximize the benefit obtained from the sale of tickets to the travelers. We present a method to obtain this solution that is based on finding the longest path in a weighted root tree. This method improves in terms of efficiency the combinatorial method, where all the possible distributions have to be considered for deciding which is the optimal one. J. Alberto Conejero, Cristina Jordán, and Esther Sanabria-Codesal Copyright © 2014 J. Alberto Conejero et al. All rights reserved. Prediction of Depth of Sedation from Biological Signals Using Continuous Restricted Boltzmann Machine Thu, 11 Sep 2014 06:53:45 +0000 http://www.hindawi.com/journals/mpe/2014/189040/ Proper anesthesia is very important for patients to get through surgery without pain and then avoid some other problems. By monitoring the depth of sedation for a patient, it could help a clinician to provide a suitable amount of anesthetic and other clinical treatment. In hospital, a patient is usually monitored by different types of biological systems. To predict the depth of sedation from biological signals is able to ease patient monitoring services. In this study, continuous restricted Boltzmann machines based neural network is proposed to predict the depth of sedation. The biological signals including heart rate, blood pressure, peripheral capillary oxygen saturation, and body weight are selected as analytic features. To improve the accuracy, the signals related to the state of anesthesia including fractional anesthetic concentration, end-tidal carbon dioxide, fraction inspiration carbon dioxide, and minimum alveolar concentration are also adopted in this study. Using minimizing contrastive divergence, a continuous restricted Boltzmann machine is trained and then used to predict the depth of sedation. The experimental results showed that the proposed approach outperforms feed-forward neural network and modular neural network. Besides, it would be able to ease patient monitoring services by using biological systems and promote healthcare quality. Yeou-Jiunn Chen, Shih-Chung Chen, and Pei-Jarn Chen Copyright © 2014 Yeou-Jiunn Chen et al. All rights reserved. Performance Analysis of DTC-SVM Sliding Mode Controllers-Based Parameters Estimator of Electric Motor Speed Drive Thu, 11 Sep 2014 06:15:56 +0000 http://www.hindawi.com/journals/mpe/2014/127128/ This paper is concerned with a framework which unifies direct torque control space vector modulation (DTC-SVM) and variable structure control (VSC). The result is a hybrid VSC-DTC-SVM controller design which eliminates several major limitations of the two individual controls and retains merits of both controllers. It has been shown that obtained control laws are very sensitive to variations of the stator resistance, the rotor resistance, and the mutual inductance. This paper discusses the performances of adaptive controllers of VSC-DTC-SVM monitored induction motor drive in a wide speed range and even in the presence of parameters uncertainties and mismatching disturbances. Better estimations of the stator resistance, the rotor resistance, and the mutual inductance yield improvements of induction motor performances using VSC-DTC-SVM, thereby facilitating torque ripple minimization. Simulation results verified the performances of the proposed approach. Fatma Ben Salem and Nabil Derbel Copyright © 2014 Fatma Ben Salem and Nabil Derbel. All rights reserved. Minimizing Design Costs of an FIR Filter Using a Novel Coefficient Optimization Algorithm Thu, 11 Sep 2014 05:48:06 +0000 http://www.hindawi.com/journals/mpe/2014/497471/ This work presents a novel coefficient optimization algorithm to reduce the area and improve the performance of finite impulse response (FIR) filter designs. Two basic architectures are commonly used in filters—direct and transposed. The coefficients of a filter can be encoded in the fewest possible nonzero bits using canonic signed digit (CSD) expressions. The proposed optimization algorithm can share common subexpressions (CS) and reduce the number of replicate operations that involve the CSD coefficients of filters with a transposed architecture. The effectiveness of the algorithm is confirmed by using filters with the collision detection multiple access (CDMA) standard, the 121-tap high-pass band, and 105- and 325-tap low-pass bands as benchmarks. For example, the proposed algorithm used in the optimization of 105-tap filter has a 30.44% smaller combinational logic area and a 16.69% better throughput/area than those of the best design that has been developed to date. Experimental results reveal that the proposed algorithm outperforms earlier designs. Ming-Chih Chen and Tsung-Ting Chen Copyright © 2014 Ming-Chih Chen and Tsung-Ting Chen. All rights reserved. Quasipolynomial Approach to Simultaneous Robust Control of Time-Delay Systems Thu, 11 Sep 2014 05:44:10 +0000 http://www.hindawi.com/journals/mpe/2014/930697/ A control law for retarded time-delay systems is considered, concerning infinite closed-loop spectrum assignment. An algebraic method for spectrum assignment is presented with a unique optimization algorithm for minimization of spectral abscissa and effective shaping of the chains of infinitely many closed-loop poles. Uncertainty of plant delays of a certain structure is considered in a sense of a robust simultaneous stabilization. Robust performance is achieved using mixed sensitivity design, which is incorporated into the addressed control law. Nikolaj Semenič, Andrej Sarjaš, Amor Chowdhury, and Rajko Svečko Copyright © 2014 Nikolaj Semenič et al. All rights reserved. The Integration of Group Technology and Simulation Optimization to Solve the Flow Shop with Highly Variable Cycle Time Process: A Surgery Scheduling Case Study Thu, 11 Sep 2014 05:19:37 +0000 http://www.hindawi.com/journals/mpe/2014/796035/ Surgery scheduling must balance capacity utilization and demand so that the arrival rate does not exceed the effective production rate. However, authorized overtime increases because of random patient arrivals and cycle times. This paper proposes an algorithm that allows the estimation of the mean effective process time and the coefficient of variation. The algorithm quantifies patient flow variability. When the parameters are identified, takt time approach gives a solution that minimizes the variability in production rates and workload, as mentioned in the literature. However, this approach has limitations for the problem of a flow shop with an unbalanced, highly variable cycle time process. The main contribution of the paper is to develop a method called takt time, which is based on group technology. A simulation model is combined with the case study, and the capacity buffers are optimized against the remaining variability for each group. The proposed methodology results in a decrease in the waiting time for each operating room from 46 minutes to 5 minutes and a decrease in overtime from 139 minutes to 75 minutes, which represents an improvement of 89% and 46%, respectively. T. K. Wang, F. T. S. Chan, and T. Yang Copyright © 2014 T. K. Wang et al. All rights reserved. A Multiobjective Fuzzy Aggregate Production Planning Model Considering Real Capacity and Quality of Products Thu, 11 Sep 2014 05:16:44 +0000 http://www.hindawi.com/journals/mpe/2014/313829/ In this study, an attempt has been made to develop a multiobjective fuzzy aggregate production planning (APP) model that best serves those companies whose aim is to have the best utilization of their resources in an uncertain environment while trying to keep an acceptable degree of quality and customer service level simultaneously. In addition, the study takes into account the performance and availability of production lines. To provide the optimal solution to the proposed model, first it was converted to an equivalent crisp multiobjective model and then goal programming was applied to the converted model. At the final step, the IBM ILOG CPLEX Optimization Studio software was used to obtain the final result based on the data collected from an automotive parts manufacturing company. The comparison of results obtained from solving the model with and without considering the performance and availability of production lines, revealed the significant importance of these two factors in developing a real and practical aggregate production plan. Najmeh Madadi and Kuan Yew Wong Copyright © 2014 Najmeh Madadi and Kuan Yew Wong. All rights reserved. Analytical Model for High Impedance Fault Analysis in Transmission Lines Thu, 11 Sep 2014 05:16:08 +0000 http://www.hindawi.com/journals/mpe/2014/837496/ A high impedance fault (HIF) normally occurs when an overhead power line physically breaks and falls to the ground. Such faults are difficult to detect because they often draw small currents which cannot be detected by conventional overcurrent protection. Furthermore, an electric arc accompanies HIFs, resulting in fire hazard, damage to electrical devices, and risk with human life. This paper presents an analytical model to analyze the interaction between the electric arc associated to HIFs and a transmission line. A joint analytical solution to the wave equation for a transmission line and a nonlinear equation for the arc model is presented. The analytical model is validated by means of comparisons between measured and calculated results. Several cases of study are presented which support the foundation and accuracy of the proposed model. S. Maximov, V. Torres, H. F. Ruiz, and J. L. Guardado Copyright © 2014 S. Maximov et al. All rights reserved. Framework of Resource Management for Intercloud Computing Thu, 11 Sep 2014 00:00:00 +0000 http://www.hindawi.com/journals/mpe/2014/108286/ There has been a very rapid increase in digital media content, due to which media cloud is gaining importance. Cloud computing paradigm provides management of resources and helps create extended portfolio of services. Through cloud computing, not only are services managed more efficiently, but also service discovery is made possible. To handle rapid increase in the content, media cloud plays a very vital role. But it is not possible for standalone clouds to handle everything with the increasing user demands. For scalability and better service provisioning, at times, clouds have to communicate with other clouds and share their resources. This scenario is called Intercloud computing or cloud federation. The study on Intercloud computing is still in its start. Resource management is one of the key concerns to be addressed in Intercloud computing. Already done studies discuss this issue only in a trivial and simplistic way. In this study, we present a resource management model, keeping in view different types of services, different customer types, customer characteristic, pricing, and refunding. The presented framework was implemented using Java and NetBeans 8.0 and evaluated using CloudSim 3.0.3 toolkit. Presented results and their discussion validate our model and its efficiency. Mohammad Aazam and Eui-Nam Huh Copyright © 2014 Mohammad Aazam and Eui-Nam Huh. All rights reserved. Satellite Attitude Control System Design Taking into Account the Fuel Slosh and Flexible Dynamics Wed, 10 Sep 2014 11:45:30 +0000 http://www.hindawi.com/journals/mpe/2014/820586/ The design of the spacecraft Attitude Control System (ACS) becomes more complex when the spacecraft has different type of components like, flexible solar panels, antennas, mechanical manipulators and tanks with fuel. The interaction between the fuel slosh motion, the panel’s flexible motion and the satellite rigid motion during translational and/or rotational manoeuvre can change the spacecraft center of mass position damaging the ACS pointing accuracy. This type of problem can be considered as a Fluid-Structure Interaction (FSI) where some movable or deformable structure interacts with an internal fluid. This paper develops a mathematical model for a rigid-flexible satellite with tank with fuel. The slosh dynamics is modelled using a common pendulum model and it is considered to be unactuated. The control inputs are defined by a transverse body fixed force and a moment about the centre of mass. A comparative investigation designing the satellite ACS by the Linear Quadratic Regulator (LQR) and Linear Quadratic Gaussian (LQG) methods is done. One has obtained a significant improvement in the satellite ACS performance and robustness of what has been done previously, since it controls the rigid-flexible satellite and the fuel slosh motion, simultaneously. Alain G. de Souza and Luiz C. G. de Souza Copyright © 2014 Alain G. de Souza and Luiz C. G. de Souza. All rights reserved. A Computational Model to Assess Poststenting Wall Stresses Dependence on Plaque Structure and Stenosis Severity in Coronary Artery Wed, 10 Sep 2014 07:55:40 +0000 http://www.hindawi.com/journals/mpe/2014/937039/ The current study presents computational models to investigate the poststenting hemodynamic stresses and internal stresses over/within the diseased walls of coronary arteries which are in different states of atherosclerotic plaque. The finite element method is applied to build the axisymmetric models which include the plaque, arterial wall, and stent struts. The study takes into account the mechanical effects of the opening pressure and its association with the plaque severity and the morphology. The wall shear stresses and the von Mises stresses within the stented coronary arteries show their strong dependence on the plaque structure, particularly the fibrous cap thickness. Higher stresses occur in severely stenosed coronaries with a thinner fibrous cap. Large stress concentrations around the stent struts cause injury or damage to the vessel wall which is linked to the mechanism of restenosis. The in-stent restenosis rate is also highly dependent on the opening pressure, to the extent that stenosed artery is expanded, and geometry of the stent struts. The present study demonstrates, for the first time, that the restenosis is to be viewed as a consequence of biomechanical design of a stent repeating unit, the opening pressure, and the severity and morphology of the plaque. Zuned Hajiali, Mahsa Dabagh, and Payman Jalali Copyright © 2014 Zuned Hajiali et al. All rights reserved. Output-Feedback Control of a Chaotic MEMS Resonator for Oscillation Amplitude Enhancement Tue, 09 Sep 2014 06:19:57 +0000 http://www.hindawi.com/journals/mpe/2014/745963/ The present work addresses the problem of chaos control in an electrostatic MEMS resonator by using an output-feedback control scheme. One of the unstable orbits immersed in the chaotic attractor is stabilized in order to produce a sustained oscillation of the movable plate composing the microstructure. The orbit is carefully chosen so as to produce a high amplitude oscillation. This approach allows the enhancement of oscillation amplitude of the resonator at a reduced control effort, since the unstable orbit already exists in the system and it is not necessary to spend energy to create it. Realistic operational conditions of the MEMS are considered including parametric uncertainties in the model and constraints due to the difficulty in measuring the speed of the plates of the microstructure. A control law is constructed recursively by using the technique of backstepping. Finally, numerical simulations are carried out to confirm the validity of the developed control scheme and to demonstrate the effect of controlling orbits immersed in the chaotic attractor. Alexander Jimenez-Triana, Guchuan Zhu, and Lahcen Saydy Copyright © 2014 Alexander Jimenez-Triana et al. All rights reserved. Transverse Vibration and Waves in a Membrane: Frequency Domain Spectral Element Modeling and Analysis Tue, 09 Sep 2014 00:00:00 +0000 http://www.hindawi.com/journals/mpe/2014/642782/ Although the spectral element method (SEM) has been well recognized as an exact continuum element method, its application has been limited mostly to one-dimensional (1D) structures, or plates that can be transformed into 1D-like problems by assuming the displacements in one direction of the plate in terms of known functions. We propose a spectral element model for the transverse vibration of a finite membrane subjected to arbitrary boundary conditions. The proposed model is developed by using the boundary splitting method and the waveguide FEM-based spectral super element method in combination. The performance of the proposed spectral element model is numerically validated by comparison with exact solutions and solutions using the standard finite element method (FEM). Jungho Park, Ilwook Park, and Usik Lee Copyright © 2014 Jungho Park et al. All rights reserved. Effective Parameter Dimension via Bayesian Model Selection in the Inverse Acoustic Scattering Problem Sun, 07 Sep 2014 11:29:36 +0000 http://www.hindawi.com/journals/mpe/2014/427203/ We address a prototype inverse scattering problem in the interface of applied mathematics, statistics, and scientific computing. We pose the acoustic inverse scattering problem in a Bayesian inference perspective and simulate from the posterior distribution using MCMC. The PDE forward map is implemented using high performance computing methods. We implement a standard Bayesian model selection method to estimate an effective number of Fourier coefficients that may be retrieved from noisy data within a standard formulation. Abel Palafox, Marcos A. Capistrán, and J. Andrés Christen Copyright © 2014 Abel Palafox et al. All rights reserved. Methodology for Supply Chain Integration: A Case Study in the Artisan Industry of Footwear Sun, 07 Sep 2014 07:51:24 +0000 http://www.hindawi.com/journals/mpe/2014/508314/ The supply chain is a major issue in a global market. The efficient relationship between supplier-producer-retailer conforms the perfect combination to achieve a high level of competitiveness according to the needs of increasingly demanding and changing markets. The difficulty of synchronizing the members within the SC is related to the inherent uncertain factors. This paper proposes a methodology for integrating the supply chain that can be applied in any type of business. To demonstrate its relevance, a case study is performed at a handmade shoe company. An improved demand forecasting, an optimal balanced production line, a proper inventory management of raw materials, and an efficient calculation of the delivery time to the customer represent some of the main results. Jorge Raúl Pérez-Gallardo, Beatriz Hernández-Vera, Constantino Gerardo Moras Sánchez, Alberto Alfonso Aguilar Lasserre, Rubén Posada-Gómez, Ulises Juárez-Martínez, and Giner Alor-Hernández Copyright © 2014 Jorge Raúl Pérez-Gallardo et al. All rights reserved. Optimized K-Means Algorithm Sun, 07 Sep 2014 07:37:24 +0000 http://www.hindawi.com/journals/mpe/2014/506480/ The localization of the region of interest (ROI), which contains the face, is the first step in any automatic recognition system, which is a special case of the face detection. However, face localization from input image is a challenging task due to possible variations in location, scale, pose, occlusion, illumination, facial expressions, and clutter background. In this paper we introduce a new optimized k-means algorithm that finds the optimal centers for each cluster which corresponds to the global minimum of the k-means cluster. This method was tested to locate the faces in the input image based on image segmentation. It separates the input image into two classes: faces and nonfaces. To evaluate the proposed algorithm, MIT-CBCL, BioID, and Caltech datasets are used. The results show significant localization accuracy. Samir Brahim Belhaouari, Shahnawaz Ahmed, and Samer Mansour Copyright © 2014 Samir Brahim Belhaouari et al. All rights reserved. Self-Similarity Based Corresponding-Point Extraction from Weakly Textured Stereo Pairs Wed, 03 Sep 2014 13:24:09 +0000 http://www.hindawi.com/journals/mpe/2014/568034/ For the areas of low textured in image pairs, there is nearly no point that can be detected by traditional methods. The information in these areas will not be extracted by classical interest-point detectors. In this paper, a novel weakly textured point detection method is presented. The points with weakly textured characteristic are detected by the symmetry concept. The proposed approach considers the gray variability of the weakly textured local regions. The detection mechanism can be separated into three steps: region-similarity computation, candidate point searching, and refinement of weakly textured point set. The mechanism of radius scale selection and texture strength conception are used in the second step and the third step, respectively. The matching algorithm based on sparse representation (SRM) is used for matching the detected points in different images. The results obtained on image sets with different objects show high robustness of the method to background and intraclass variations as well as to different photometric and geometric transformations; the points detected by this method are also the complement of points detected by classical detectors from the literature. And we also verify the efficacy of SRM by comparing with classical algorithms under the occlusion and corruption situations for matching the weakly textured points. Experiments demonstrate the effectiveness of the proposed weakly textured point detection algorithm. Min Mao, Kuang-Rong Hao, and Yong-Sheng Ding Copyright © 2014 Min Mao et al. All rights reserved. Stability and Passivity of Spatially and Temporally Complex Dynamical Networks with Time-Varying Delays Wed, 03 Sep 2014 08:44:00 +0000 http://www.hindawi.com/journals/mpe/2014/412169/ This paper proposes a new complex dynamical network model, in which the state, input, and output variables are varied with the time and space variables. By utilizing the Lyapunov functional method combined with the inequality techniques, several criteria for passivity and global exponential stability are established. Finally, numerical simulations are given to illustrate the effectiveness of the obtained results. Shun-Yan Ren and Yue-Hui Zhao Copyright © 2014 Shun-Yan Ren and Yue-Hui Zhao. All rights reserved.