Modelling and Simulation in Engineering The latest articles from Hindawi © 2017 , Hindawi Limited . All rights reserved. Numerical Study on Turbulent Forced Convection and Heat Transfer Characteristic in a Circular Tube with V-Orifice Mon, 15 May 2017 00:00:00 +0000 Performance assessments on heat transfer, pressure loss, and thermal enhancement factor in the circular tube heat exchanger inserted with the V-orifices are investigated numerically. The influences of the blockage ratio, gap spacing ratio, and orifice arrangement are reported for turbulent regime, . The finite volume method and SIMPLE algorithm are selected to solve the present problem. The mechanisms on flow and heat transfer characteristics are described. The periodic concepts on flow and heat transfer are also studied. The numerical results show that the gap spacing ratio is main reason for the changes of the flow and heat transfer topologies. The gap distance helps to adjust the optimum point of the thermal performance, especially at high flow blockage ratio. In addition, the optimum thermal performance of the present system is around 2.25 at the lowest Reynolds number, . Withada Jedsadaratanachai and Amnart Boonloi Copyright © 2017 Withada Jedsadaratanachai and Amnart Boonloi. All rights reserved. Performance Evaluation and Optimal Management of Distance-Based Registration Using a Semi-Markov Process Wed, 10 May 2017 00:00:00 +0000 We consider the distance-based registration (DBR) which is a kind of dynamic location registration scheme in a mobile communication network. In the DBR, the location of a mobile station (MS) is updated when it enters a base station more than or equal to a specified distance away from the base station where the location registration for the MS was done last. In this study, we first investigate the existing performance-evaluation methods on the DBR with implicit registration (DBIR) presented to improve the performance of the DBR and point out some problems of the evaluation methods. We propose a new performance-evaluation method for the DBIR scheme using a semi-Markov process (SMP) which can resolve the controversial issues of the existing methods. The numerical results obtained with the proposed SMP model are compared with those from previous models. It is shown that the SMP model should be considered to get an accurate performance of the DBIR scheme. Jae Joon Suh, Kyeongtaek Kim, Hee-Seon Jang, and Jang Hyun Baek Copyright © 2017 Jae Joon Suh et al. All rights reserved. Pareto Optimization of a Half Car Passive Suspension Model Using a Novel Multiobjective Heat Transfer Search Algorithm Wed, 03 May 2017 00:00:00 +0000 Most of the modern multiobjective optimization algorithms are based on the search technique of genetic algorithms; however the search techniques of other recently developed metaheuristics are emerging topics among researchers. This paper proposes a novel multiobjective optimization algorithm named multiobjective heat transfer search (MOHTS) algorithm, which is based on the search technique of heat transfer search (HTS) algorithm. MOHTS employs the elitist nondominated sorting and crowding distance approach of an elitist based nondominated sorting genetic algorithm-II (NSGA-II) for obtaining different nondomination levels and to preserve the diversity among the optimal set of solutions, respectively. The capability in yielding a Pareto front as close as possible to the true Pareto front of MOHTS has been tested on the multiobjective optimization problem of the vehicle suspension design, which has a set of five second-order linear ordinary differential equations. Half car passive ride model with two different sets of five objectives is employed for optimizing the suspension parameters using MOHTS and NSGA-II. The optimization studies demonstrate that MOHTS achieves the better nondominated Pareto front with the widespread (diveresed) set of optimal solutions as compared to NSGA-II, and further the comparison of the extreme points of the obtained Pareto front reveals the dominance of MOHTS over NSGA-II, multiobjective uniform diversity genetic algorithm (MUGA), and combined PSO-GA based MOEA. Vimal Savsani, Vivek Patel, Bhargav Gadhvi, and Mohamed Tawhid Copyright © 2017 Vimal Savsani et al. All rights reserved. Numerical Modal Analysis of Vibrations in a Three-Phase Linear Switched Reluctance Actuator Tue, 18 Apr 2017 00:00:00 +0000 This paper addresses the problem of vibrations produced by switched reluctance actuators, focusing on the linear configuration of this type of machines, aiming at its characterization regarding the structural vibrations. The complexity of the mechanical system and the number of parts used put serious restrictions on the effectiveness of analytical approaches. We build the 3D model of the actuator and use finite element method (FEM) to find its natural frequencies. The focus is on frequencies within the range up to nearly 1.2 kHz which is considered relevant, based on preliminary simulations and experiments. Spectral analysis results of audio signals from experimental modal excitation are also shown and discussed. The obtained data support the characterization of the linear actuator regarding the excited modes, its vibration frequencies, and mode shapes, with high potential of excitation due to the regular operation regimes of the machine. The results reveal abundant modes and harmonics and the symmetry characteristics of the actuator, showing that the vibration modes can be excited for different configurations of the actuator. The identification of the most critical modes is of great significance for the actuator’s control strategies. This analysis also provides significant information to adopt solutions to reduce the vibrations at the design. José Salvado, Maria do Rosário Calado, António Espírito Santo, and Anna Guerman Copyright © 2017 José Salvado et al. All rights reserved. Enhancing the Performance of the Microwave Absorbing Materials by Using Dielectric Resonator Arrays Wed, 05 Apr 2017 06:14:20 +0000 We present a technique for enhancing the performance of microwave absorbing materials in terms of weight, thickness, and bandwidth. The introduced technique is based on fabricating the microwave absorbing (MA) material in a structure comprised of an array of circular cylinder dielectric resonators (CDR) backed by a perfect electric conductor (PEC) ground plane. Numerical electromagnetic methods are employed to study the properties of the proposed MA array structures, where 3D full wave simulation using finite-element method is implemented. The obtained results show that the performance of the MA-CDR arrays significantly outperforms that of a flat layer composed of the same material and having equivalent thickness. A flat layer of MA material with thickness of 5 mm backed by perfect electric conductor (PEC) shows as low as  dB reflection loss (RL) peak and ~3 GHz 10-dB bandwidth, whereas an MA-CDR array, composed of the same MA material, of height of 4 mm can achieve as low as ~−50 dB RL peak and ~12 GHz 10-dB RL bandwidth. Omar H. Al-Zoubi and Hameed Naseem Copyright © 2017 Omar H. Al-Zoubi and Hameed Naseem. All rights reserved. 3D Numerical and Experimental Study on Paraffin Wax Melting in Thermal Storage for the Nozzle-and-Shell, Tube-and-Shell, and Reducer-and-Shell Models Tue, 04 Apr 2017 07:36:29 +0000 Paraffin melting experienced in the nozzle-and-shell, tube-and-shell, and reducer-and-shell models in thermal storage with 3D numerical and experimental approach has been studied. The numerical study aims to evaluate the melting process and discover temperature distribution, liquid-solid interface, liquid fraction, and the average surface Nusselt number, while the aim of this experimental study is to determine the distribution of melting temperature. The comparison of temperature distribution between the numerical approach and experimental one indicates a good agreement. The comparison result between the three models shows that the melting process of the nozzle-and-shell model is the best, followed by tube-and-shell and reducer-and-shell models, successively. To finish the melting process, the time required is 6130 s for the nozzle-and-shell model, while tube-and-shell model requires 8210 s and reducer-and-shell model requires 12280 s. Agus Dwi Korawan, Sudjito Soeparman, Widya Wijayanti, and Denny Widhiyanuriyawan Copyright © 2017 Agus Dwi Korawan et al. All rights reserved. Modeling of Size Effects in Bending of Perforated Cosserat Plates Thu, 30 Mar 2017 00:00:00 +0000 This paper presents the numerical study of Cosserat elastic plate deformation based on the parametric theory of Cosserat plates, recently developed by the authors. The numerical results are obtained using the Finite Element Method used to solve the parametric system of 9 kinematic equations. We discuss the existence and uniqueness of the weak solution and the convergence of the proposed FEM. The Finite Element analysis of clamped Cosserat plates of different shapes under different loads is provided. We present the numerical validation of the proposed FEM by estimating the order of convergence, when comparing the main kinematic variables with an analytical solution. We also consider the numerical analysis of plates with circular holes. We show that the stress concentration factor around the hole is less than the classical value, and smaller holes exhibit less stress concentration as would be expected on the basis of the classical elasticity. Roman Kvasov and Lev Steinberg Copyright © 2017 Roman Kvasov and Lev Steinberg. All rights reserved. Service Oriented Integration of Distributed Heterogeneous IT Systems in Production Engineering Using Information Standards and Linked Data Sun, 19 Mar 2017 00:00:00 +0000 While design of production systems based on digital models brings benefits, the communication of models comes with challenges since models typically reside in a heterogeneous IT environment using different syntax and semantics. Coping with heterogeneity requires a smart integration strategy. One main paradigm to integrate data and IT systems is to deploy information standards. In particular, ISO 10303 STEP has been endorsed as a suitable standard to exchange a wide variety of product manufacturing data. One the other hand, service-oriented tool integration solutions are progressively adopted for the integration of data and IT-tools, especially with the emergence of Open Services for Lifecycle Collaboration whose focus is on the linking of data from heterogeneous software tools. In practice, there should be a combination of these approaches to facilitate the integration process. Hence, the aim of this paper is to investigate the applications of the approaches and the principles behind them and try to find criteria for where to use which approach. In addition, we explore the synergy between them and consequently suggest an approach based on combination of them. In addition, a systematic approach is suggested to identify required level of integrations and their corresponding approaches exemplified in a typical IT system architecture in Production Engineering. Navid Shariat Zadeh, Lars Lindberg, Jad El-Khoury, and Gunilla Sivard Copyright © 2017 Navid Shariat Zadeh et al. All rights reserved. Identification and Prioritization of “Black Spots” without Using Accident Information Wed, 15 Mar 2017 07:50:44 +0000 It is attempted to identify and prioritize the accident prone points (black spots) in “Iraanshahr-Sarbaaz-Chabahar” road located in Baluchistan, Iran, without no use of accident data but rather using Analytic Hierarchy Process (AHP), which is the enhanced procedure of road safety audit technique. First, by surveying the whole route, all factors that could influence accidents in this road were specified; then the route was divided into eight sections; this division was performed based on the uniformity and homogeny of each section in terms of geometric design and regional conditions. In each section, potentially hazardous locations were identified and some questionnaires were prepared, which were filled by 5 road traffic experts familiar with the route; then the collected data were analyzed by Analytical Hierarchy Process (AHP) using Expert Choice Software and the black spots were identified and prioritized. Finally, these black spots were compared with the black spots that had been obtained by traffic police based on accident data. Mahmoudreza Keymanesh, Hasan Ziari, Samira Roudini, and Ali Nasrollahtabar Ahangar Copyright © 2017 Mahmoudreza Keymanesh et al. All rights reserved. Systematic Theoretical Analysis of Dual-Parameters Readout by a Novel -Type Passive Sensor Mon, 13 Mar 2017 00:00:00 +0000 This paper systematically studied the simultaneous measurement of two parameters by a -type passive sensor from the theoretical perspective. Based on the lumped circuit model of the typical -type passive dual-parameter sensor system, the influencing factors of the signal strength of the sensor as well as the influencing factors of signal crosstalk were both analyzed. It is found that the influencing factors of the readout signal strength of the sensor are mainly quality factors ( factors) of the tanks, coupling coefficients, and the resonant frequency interval of the two tanks. And the influencing factors of the signal crosstalk are mainly coupling coefficient between the sensor inductance coils and the resonant frequency interval of the two tanks. The specific influence behavior of corresponding influencing factors on the signal strength and crosstalk is illustrated by a series of curves from numerical results simulated by using MATLAB software. Additionally, a decoupling scheme for solving the crosstalk problem algorithmically was proposed and a corresponding function was derived out. Overall, the theoretical analysis conducted in this work can provide design guidelines for making the dual-parameter -type passive sensor useful in practical applications. Qiulin Tan, Yanjie Guo, Guozhu Wu, Tao Luo, Tanyong Wei, Sanmin Shen, Wendong Zhang, and Jijun Xiong Copyright © 2017 Qiulin Tan et al. All rights reserved. Model-Based Dependability Analysis of Physical Systems with Modelica Wed, 08 Mar 2017 09:58:43 +0000 Modelica is an innovative, equation-based, and acausal language that allows modeling complex physical systems, which are made of mechanical, electrical, and electrotechnical components, and evaluates their design through simulation techniques. Unfortunately, the increasing complexity and accuracy of such physical systems require new, more powerful, and flexible tools and techniques for evaluating important system properties and, in particular, the dependability ones such as reliability, safety, and maintainability. In this context, the paper describes some extensions of the Modelica language to support the modeling of system requirements and their relationships. Such extensions enable the requirement verification analysis through native constructs in the Modelica language. Furthermore, they allow exporting a Modelica-based system design as a Bayesian Network in order to analyze its dependability by employing a probabilistic approach. The proposal is exemplified through a case study concerning the dependability analysis of a Tank System. Andrea Tundis, Lena Buffoni, Peter Fritzson, and Alfredo Garro Copyright © 2017 Andrea Tundis et al. All rights reserved. System Identification Based Proxy Model of a Reservoir under Water Injection Thu, 23 Feb 2017 00:00:00 +0000 Simulation of numerical reservoir models with thousands and millions of grid blocks may consume a significant amount of time and effort, even when high performance processors are used. In cases where the simulation runs are required for sensitivity analysis, dynamic control, and optimization, the act needs to be repeated several times by continuously changing parameters. This makes it even more time-consuming. Currently, proxy models that are based on response surface are being used to lessen the time required for running simulations during sensitivity analysis and optimization. Proxy models are lighter mathematical models that run faster and perform in place of heavier models that require large computations. Nevertheless, to acquire data for modeling and validation and develop the proxy model itself, hundreds of simulation runs are required. In this paper, a system identification based proxy model that requires only a single simulation run and a properly designed excitation signal was proposed and evaluated using a benchmark case study. The results show that, with proper design of excitation signal and proper selection of model structure, system identification based proxy models are found to be practical and efficient alternatives for mimicking the performance of numerical reservoir models. The resulting proxy models have potential applications for dynamic well control and optimization. Berihun M. Negash, Lemma D. Tufa, M. Ramasamy, and Mariyamni Bt. Awang Copyright © 2017 Berihun M. Negash et al. All rights reserved. Optimal Allocation of DG and DSTATCOM in Radial Distribution System Using Cuckoo Search Optimization Algorithm Sun, 19 Feb 2017 00:00:00 +0000 This paper proposes a new approach to determine the optimal location and sizing of Distributed Generation (DG) and Distribution STATic COMpensator (DSTATCOM) simultaneously in the distribution network. The objective function is formulated to minimize the total power losses of the system subjected to equality and inequality constraints. Loss sensitivity factor (LSF) and Voltage Stability Index (VSI) are used to predetermine the optimal location of DG and DSTATCOM, respectively. Recently developed nature-inspired cuckoo search algorithm (CSA) has been used to determine the optimal size of both DG and DSTATCOM. In the present work, five different cases have been considered during DG and DSTATCOM placement to access the performance of the proposed technique. To check the feasibility, the proposed method is tested on IEEE 12-bus, 34-bus, and 69-bus radial distribution system and the results were compared with other existing techniques. T. Yuvaraj, K. Ravi, and K. R. Devabalaji Copyright © 2017 T. Yuvaraj et al. All rights reserved. Modelling of Rough Contact between Linear Viscoelastic Materials Wed, 15 Feb 2017 13:19:30 +0000 The important gradients of stress arising in rough mechanical contacts due to interaction at the asperity level are responsible for damage mechanisms like rolling contact fatigue, wear, or crack propagation. The deterministic approach to this process requires computationally effective numerical solutions, capable of handling very fine meshes that capture the particular features of the investigated contacting surface. The spatial discretization needs to be supported by temporal sampling of the simulation window when time-dependent viscoelastic constitutive laws are considered in the description of the material response. Moreover, when real surface microtopography is considered, steep slopes inevitably lead to localized plastic deformation at the tip of the asperities that are first brought into contact. A computer model for the rough contact of linear viscoelastic materials, capable of handling deterministic contact geometry, complex viscoelastic models, and arbitrary loading histories, is advanced in this paper. Plasticity is considered in a simplified manner that preserves the information regarding the contact area and the pressure distribution without computing the residual strains and stresses. The model is expected to predict the contact behavior of deterministic rough surfaces as resulting from practical engineering applications, thus assisting the design of durable machine elements using elastomers or rubbers. Sergiu Spinu and Delia Cerlinca Copyright © 2017 Sergiu Spinu and Delia Cerlinca. All rights reserved. Analytical Modelling and Verification of Bus-Clamping Modulation Technique for Switched-Capacitor Converter Wed, 08 Feb 2017 06:08:21 +0000 Space vector modulation techniques have advantages of high output voltages and reduced harmonic content as they utilize the dc bus effectively. Bus-clamped pulse width modulation classified in space vector techniques has the ability to reduce the switching losses of the converter and has reduced harmonic distortion. This paper provides mathematical analysis for 60-degree bus-clamping strategy to obtain the complete closed-form solution for finding the harmonic coefficients using double Fourier integral expression. The effectiveness of the bus-clamped approach on switched capacitor based multilevel inverter has been shown with comparison to Sinusoidal PWM. The DSP controller TMS320F240 has been chosen for the real-time implementation of 60-degree bus-clamping modulation technique. Simulation and experimental results of the prototype are presented for RL load at different modulation indices showing the superiority of the configuration to cascaded multilevel inverter. Amarnath Yalavarthi and Akbar Ahmad Copyright © 2017 Amarnath Yalavarthi and Akbar Ahmad. All rights reserved. Application of a Microstructure-Based ISV Plasticity Damage Model to Study Penetration Mechanics of Metals and Validation through Penetration Study of Aluminum Sun, 29 Jan 2017 09:06:09 +0000 A developed microstructure-based internal state variable (ISV) plasticity damage model is for the first time used for simulating penetration mechanics of aluminum to find out its penetration properties. The ISV damage model tries to explain the interplay between physics at different length scales that governs the failure and damage mechanisms of materials by linking the macroscopic failure and damage behavior of the materials with their micromechanical performance, such as void nucleation, growth, and coalescence. Within the continuum modeling framework, microstructural features of materials are represented using a set of ISVs, and rate equations are employed to depict damage history and evolution of the materials. For experimental calibration of this damage model, compression, tension, and torsion straining conditions are considered to distinguish damage evolutions under different stress states. To demonstrate the reliability of the presented ISV model, that model is applied for studying penetration mechanics of aluminum and the numerical results are validated by comparing with simulation results yielded from the Johnson-Cook model as well as analytical results calculated from an existing theoretical model. Yangqing Dou, Yucheng Liu, Youssef Hammi, and Wilburn Whittington Copyright © 2017 Yangqing Dou et al. All rights reserved. Autotuning of Isotropic Hardening Constitutive Models on Real Steel Buckling Data with Finite Element Based Multistart Global Optimisation on Parallel Computers Mon, 16 Jan 2017 07:08:37 +0000 An automatic framework for tuning plastic constitutive models is proposed. It is based on multistart global optimisation method, where the objective function is provided by the results of multiple elastoplastic finite element analyses, executed concurrently. Wrapper scripts were developed for fully automatic preprocessing, including model and mesh generation, analysis, and postprocessing. The framework is applied to an isotropic power hardening plasticity using real load/displacement data from multiple steel buckling tests. M. J. D. Powell’s BOBYQA constrained optimisation package was used for local optimisation. It is shown that using the real data presents multiple problems to the optimisation process because the objective function can be discontinuous, yet relatively flat around multiple local minima, with similar values of the objective function for different local minima. As a consequence the estimate of the global minimum is sensitive to the amount of experimental data and experimental noise. The framework includes the verification step, where the estimate of the global minimum is verified on a different geometry and loading. A tensile test was used for verification in this work. The speed of the method critically depends on the ability to effectively parallelise the finite element solver. Three levels of parallelisation were exploited in this work. The ultimate limitation was the availability of the finite element commercial solver license tokens. Anton Shterenlikht, Mohammad M. Kashani, Nicholas A. Alexander, Gethin Williams, and Adam J. Crewe Copyright © 2017 Anton Shterenlikht et al. All rights reserved. Structural Modelling at the Micro-, Meso-, and Nanoscales Tue, 10 Jan 2017 06:49:50 +0000 Angelo Marcello Tarantino, Julius Kaplunov, Raimondo Luciano, Carmelo Majorana, Theodoros C. Rousakis, and Kasper Willam Copyright © 2017 Angelo Marcello Tarantino et al. All rights reserved. Fault Diagnosis and Detection in Industrial Motor Network Environment Using Knowledge-Level Modelling Technique Mon, 09 Jan 2017 11:43:15 +0000 In this paper, broken rotor bar (BRB) fault is investigated by utilizing the Motor Current Signature Analysis (MCSA) method. In industrial environment, induction motor is very symmetrical, and it may have obvious electrical signal components at different fault frequencies due to their manufacturing errors, inappropriate motor installation, and other influencing factors. The misalignment experiments revealed that improper motor installation could lead to an unexpected frequency peak, which will affect the motor fault diagnosis process. Furthermore, manufacturing and operating noisy environment could also disturb the motor fault diagnosis process. This paper presents efficient supervised Artificial Neural Network (ANN) learning technique that is able to identify fault type when situation of diagnosis is uncertain. Significant features are taken out from the electric current which are based on the different frequency points and associated amplitude values with fault type. The simulation results showed that the proposed technique was able to diagnose the target fault type. The ANN architecture worked well with selecting of significant number of feature data sets. It seemed that, to the results, accuracy in fault detection with features vector has been achieved through classification performance and confusion error percentage is acceptable between healthy and faulty condition of motor. Saud Altaf, Muhammad Waseem Soomro, and Mirza Sajid Mehmood Copyright © 2017 Saud Altaf et al. All rights reserved. A Fast Enhanced Secure Image Chaotic Cryptosystem Based on Hybrid Chaotic Magic Transform Wed, 04 Jan 2017 12:29:33 +0000 An enhanced secure image chaotic cryptosystem has been proposed based on hybrid CMT-Lanczos algorithm. We have achieved fast encryption and decryption along with privacy of images. The pseudorandom generator has been used along with Lanczos algorithm to generate root characteristics and eigenvectors. Using hybrid CMT image, pixels are shuffled to accomplish excellent randomness. Compared with existing methods, the proposed method had more robustness to various attacks: brute-force attack, known cipher plaintext, chosen-plaintext, security key space, key sensitivity, correlation analysis and information entropy, and differential attacks. Simulation results show that the proposed methods give better result in protecting images with low-time complexity. Srinivas Koppu and V. Madhu Viswanatham Copyright © 2017 Srinivas Koppu and V. Madhu Viswanatham. All rights reserved. Numerical Simulation of Magnetic Field Effect on Cryocooler Regenerators: Temperature Distribution Tue, 03 Jan 2017 00:00:00 +0000 Regenerative types of cryogenic refrigerators (or cryocoolers) employ magnetic intermetallic compounds of 3d and 4f elements to work well below 10 K. This paper presents the analysis of temperature distribution in regenerators of such cryocoolers under the influence of magnetic fields of 1 T, 3 T, and 4.3 T. Commercial code of finite element analysis (FEA) package, ANSYS (APDL) 14.5, is used to investigate the temperature distribution under above-mentioned fields. is selected as regenerator material and the criteria for its selection are discussed in detail. The cold end temperature is varied from 4.2 K to 10 K and hot end temperature is fixed at 20 K. The values obtained from FEA clearly show that the ineffectiveness of is at 8 K and 10 K at 3 T and 4.3 T. Rajendra Kumar and Sumit Shoor Copyright © 2017 Rajendra Kumar and Sumit Shoor. All rights reserved. On Torsion of Functionally Graded Elastic Beams Wed, 28 Dec 2016 10:16:09 +0000 The evaluation of tangential stress fields in linearly elastic orthotropic Saint-Venant beams under torsion is based on the solution of Neumann and Dirichlet boundary value problems for the cross-sectional warping and for Prandtl stress function, respectively. A skillful solution method has been recently proposed by Ecsedi for a class of inhomogeneous beams with shear moduli defined in terms of Prandtl stress function of corresponding homogeneous beams. An alternative reasoning is followed in the present paper for orthotropic functionally graded beams with shear moduli tensors defined in terms of the stress function and of the elasticity of reference inhomogeneous beams. An innovative result of invariance on twist centre is also contributed. Examples of functionally graded elliptic cross sections of orthotropic beams are developed, detecting thus new benchmarks for computational mechanics. Marina Diaco Copyright © 2016 Marina Diaco. All rights reserved. QFT Based Robust Positioning Control of the PMSM Using Automatic Loop Shaping with Teaching Learning Optimization Mon, 26 Dec 2016 13:00:03 +0000 Automation of the robust control system synthesis for uncertain systems is of great practical interest. In this paper, the loop shaping step for synthesizing quantitative feedback theory (QFT) based controller for a two-phase permanent magnet stepper motor (PMSM) has been automated using teaching learning-based optimization (TLBO) algorithm. The QFT controller design problem has been posed as an optimization problem and TLBO algorithm has been used to minimize the proposed cost function. This facilitates designing low-order fixed-structure controller, eliminates the need of manual loop shaping step on the Nichols charts, and prevents the overdesign of the controller. A performance comparison of the designed controller has been made with the classical PID tuning method of Ziegler-Nichols and QFT controller tuned using other optimization algorithms. The simulation results show that the designed QFT controller using TLBO offers robust stability, disturbance rejection, and proper reference tracking over a range of PMSM’s parametric uncertainties as compared to the classical design techniques. Nitish Katal and Shiv Narayan Copyright © 2016 Nitish Katal and Shiv Narayan. All rights reserved. Scenario Based Municipal Wastewater Estimation: Development and Application of a Dynamic Simulation Model Mon, 26 Dec 2016 11:57:17 +0000 This paper develops causal loop diagrams and a system dynamics model for estimation of wastewater quantity changes as a function of future socioeconomic development and the municipal water environment of the city under the influence of several key factors. Using Wuhan (a city with population more than 10 million in China) as a case study, the variability of Wuhan’s wastewater quantity and water environment is modeled under different development patterns by year 2030. Nine future scenarios are designed by assigning different values to those key factors, including GDP growth rate, water consumption of annual ten thousand GDP, and wastewater treatment fee. The results show that GDP growth leads to an increase in municipal wastewater quantity, but an increase in wastewater treatment fee can be in favor of reducing urban water pollution, and the impact of per ten thousand yuan GDP water consumption on the amount of municipal wastewater is larger in the near future, while the impact of GDP growth rate is much larger in the long term. The dynamic model has proven to be reliable for simulating the municipal wastewater changes, and it could help decision makers to make the scientific and reasonable decisions. Yong Zhang, Tingsheng Zhao, Aijiao Zhou, Zhengzhu Zhang, and Wen Liu Copyright © 2016 Yong Zhang et al. All rights reserved. A Note on Torsion of Nonlocal Composite Nanobeams Mon, 26 Dec 2016 08:36:49 +0000 The ERINGEN elastic constitutive relation is used in this paper in order to assess small-scale effects in nanobeams. Structural behavior is studied for functionally graded materials in the cross-sectional plane and torsional loading conditions. The governing boundary value problem has been formulated in a mixed framework. Torsional rotations and equilibrated moments are evaluated by solving a first-order differential equation of elastic equilibrium with boundary conditions of kinematic-type. Benchmarks examples are briefly discussed, enlightening thus effectiveness of the proposed methodology. Luciano Feo and Rosa Penna Copyright © 2016 Luciano Feo and Rosa Penna. All rights reserved. On Bending of Bernoulli-Euler Nanobeams for Nonlocal Composite Materials Sun, 25 Dec 2016 11:50:30 +0000 Evaluation of size effects in functionally graded elastic nanobeams is carried out by making recourse to the nonlocal continuum mechanics. The Bernoulli-Euler kinematic assumption and the Eringen nonlocal constitutive law are assumed in the formulation of the elastic equilibrium problem. An innovative methodology, characterized by a lowering in the order of governing differential equation, is adopted in the present manuscript in order to solve the boundary value problem of a nanobeam under flexure. Unlike standard treatments, a second-order differential equation of nonlocal equilibrium elastic is integrated in terms of transverse displacements and equilibrated bending moments. Benchmark examples are developed, thus providing the nonlocality effect in nanocantilever and clampled-simply supported nanobeams for selected values of the Eringen scale parameter. Luciano Feo and Rosa Penna Copyright © 2016 Luciano Feo and Rosa Penna. All rights reserved. Extended Macroscopic Study of Dilute Gas Flow within a Microcavity Wed, 14 Dec 2016 08:55:44 +0000 The behaviour of monatomic and dilute gas is studied in the slip and early transition regimes using the extended macroscopic theory. The gas is confined within a two-dimensional microcavity where the longitudinal sides are in the opposite motion with constant velocity . The microcavity walls are kept at the uniform and reference temperature . Thus, the gas flow is transported only by the shear stress induced by the motion of upper and lower walls. From the macroscopic point of view, the regularized 13-moment equations of Grad, R13, are solved numerically. The macroscopic gas proprieties are studied for different values of the so-called Knudsen number (Kn), which gives the gas-rarefaction degree. The results are compared with those obtained using the classical continuum theory of Navier-Stokes and Fourier (NSF). Mohamed Hssikou, Jamal Baliti, and Mohammed Alaoui Copyright © 2016 Mohamed Hssikou et al. All rights reserved. Finite Thin Cover on an Orthotropic Elastic Half Plane Mon, 12 Dec 2016 11:05:13 +0000 The present work deals with the mechanical behaviour of thin films bonded to a homogeneous elastic orthotropic half plane under plain strain condition and infinitesimal strain. Both the film and semi-infinite substrate display linear elastic orthotropic behaviour. By assuming perfect adhesion between film and half plane together with membrane behaviour of the film, the compatibility condition between the coating and substrate leads to a singular integral equation with Cauchy kernel. Such an equation is straightforwardly solved by expanding the unknown interfacial stress in series of Chebyshev polynomials displaying square-root singularity at the film edges. This approach allows handling the singular behaviour of the shear stress and, in turn, reducing the problem to a linear algebraic system of infinite terms. Results are found for two loading cases, with particular reference to concentrated axial forces acting at the edges of the film. The corresponding mode II stress intensity factor has been assessed, thus providing the stress concentrations at both ends of the covering. Possible applications of the results here obtained range from MEMS, NEMS, and solar Silicon cell for energy harvesting to welded joint and building foundation. Federico Oyedeji Falope and Enrico Radi Copyright © 2016 Federico Oyedeji Falope and Enrico Radi. All rights reserved. Axisymmetric Longitudinal-Bending Waves in a Cylindrical Shell Interacting with a Nonlinear Elastic Medium Sun, 27 Nov 2016 11:11:46 +0000 A nonlinear differential equation is derived which describes the propagation of axisymmetric stationary longitudinal-bending waves in infinite cylindrical shell of Timoshenko type, interacting with the external nonlinear elastic medium. A modified perturbation method based on the use of diagonal Pade approximants was applied to build exact solitary-wave solutions of the derived equation in the form of traveling front and the traveling pulse. Numerical solutions of the equation, obtained by means of finite difference method, are in good agreement with the corresponding exact analytical ones. Alexander I. Zemlyanukhin, Andrey V. Bochkarev, Lev I. Mogilevich, and Ekaterina G. Tindova Copyright © 2016 Alexander I. Zemlyanukhin et al. All rights reserved. Modelling of Creep and Stress Relaxation Test of a Polypropylene Microfibre by Using Fraction-Exponential Kernel Sun, 27 Nov 2016 09:43:42 +0000 A tensile test until breakage and a creep and relaxation test on a polypropylene fibre are carried out and the resulting creep and stress relaxation curves are fit by a model adopting a fraction-exponential kernel in the viscoelastic operator. The models using fraction-exponential functions are simpler than the complex ones obtained from combination of dashpots and springs and, furthermore, are suitable for fitting experimental data with good approximation allowing, at the same time, obtaining inverse Laplace transform in closed form. Therefore, the viscoelastic response of polypropylene fibres can be modelled straightforwardly through analytical methods. Addition of polypropylene fibres greatly improves the tensile strength of composite materials with concrete matrix. The proposed analytical model can be employed for simulating the mechanical behaviour of composite materials with embedded viscoelastic fibres. Andrea Sorzia Copyright © 2016 Andrea Sorzia. All rights reserved.