Modelling and Simulation in Engineering The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. Fault Diagnosis of Batch Reactor Using Machine Learning Methods Tue, 22 Apr 2014 00:00:00 +0000 Fault diagnosis of a batch reactor gives the early detection of fault and minimizes the risk of thermal runaway. It provides superior performance and helps to improve safety and consistency. It has become more vital in this technical era. In this paper, support vector machine (SVM) is used to estimate the heat release () of the batch reactor both normal and faulty conditions. The signature of the residual, which is obtained from the difference between nominal and estimated faulty values, characterizes the different natures of faults occurring in the batch reactor. Appropriate statistical and geometric features are extracted from the residual signature and the total numbers of features are reduced using SVM attribute selection filter and principle component analysis (PCA) techniques. artificial neural network (ANN) classifiers like multilayer perceptron (MLP), radial basis function (RBF), and Bayes net are used to classify the different types of faults from the reduced features. It is observed from the result of the comparative study that the proposed method for fault diagnosis with limited number of features extracted from only one estimated parameter () shows that it is more efficient and fast for diagnosing the typical faults. Sujatha Subramanian, Fathima Ghouse, and Pappa Natarajan Copyright © 2014 Sujatha Subramanian et al. All rights reserved. Interaction of Submerged Breakwater by a Solitary Wave Using WC-SPH Method Sun, 13 Apr 2014 00:00:00 +0000 Interaction of a solitary wave and submerged breakwater is studied in a meshless, Lagrangian approach. For this purpose, a two-dimensional smoothed particle hydrodynamics (SPH) code is developed. Furthermore, an extensive set of simulations is conducted. In the first step, the generated solitary wave is validated. Subsequently, the interaction of solitary wave and submerged breakwater is investigated thoroughly. Results of the interaction of solitary wave and a submerged breakwater are also shown to be in good agreement with published experimental studies. Afterwards, the effects of the inclination and length of breakwater as well as distance between two breakwaters are evaluated on damping ratio of breakwater. Afshin Mansouri and Babak Aminnejad Copyright © 2014 Afshin Mansouri and Babak Aminnejad. All rights reserved. Developing a Chaotic-Simulation Based Model for Ranking High Selected Network Links in Hazardous Material Transportation Mon, 07 Apr 2014 12:10:05 +0000 Hazardous material transportation is one of the main concerns due to the nature of hazardous materials and their incident impacts. In general, transport risk is a main attribute to develop mathematical models for hazardous material routing problem as well as network designing or improving road safety. This paper presents a chaotic-simulation based model to determine the high selected links to improve road network quality for hazardous material transportation, in which risk is considered as a chaotic variable over the network whereas a simulation technique has been applied to cover a wide range of selecting paths. A real road network, consists of fifty-nine nodes and eighty two-way edges, is used for running the mathematical model and checking validation. Due to the large amounts of hazardous material transported by trucks, the proposed methodology is focused on fuel transportation, and high selected list of edges (links) has been obtained to improve road safety. Sensitivity analysis revealed that using different seeds for generating transport risk has no significant effects on finding the most frequent paths and high selected edges. Abbas Mahmoudabadi Copyright © 2014 Abbas Mahmoudabadi. All rights reserved. Modeling of Unsteady Flow through the Canals by Semiexact Method Thu, 20 Feb 2014 09:23:16 +0000 The study of free-surface and pressurized water flows in channels has many interesting application, one of the most important being the modeling of the phenomena in the area of natural water systems (rivers, estuaries) as well as in that of man-made systems (canals, pipes). For the development of major river engineering projects, such as flood prevention and flood control, there is an essential need to have an instrument that be able to model and predict the consequences of any possible phenomenon on the environment and in particular the new hydraulic characteristics of the system. The basic equations expressing hydraulic principles were formulated in the 19th century by Barre de Saint Venant and Valentin Joseph Boussinesq. The original hydraulic model of the Saint Venant equations is written in the form of a system of two partial differential equations and it is derived under the assumption that the flow is one-dimensional, the cross-sectional velocity is uniform, the streamline curvature is small and the pressure distribution is hydrostatic. The St. Venant equations must be solved with continuity equation at the same time. Until now no analytical solution for Saint Venant equations is presented. In this paper the Saint Venant equations and continuity equation are solved with homotopy perturbation method (HPM) and comparison by explicit forward finite difference method (FDM). For decreasing the present error between HPM and FDM, the st.venant equations and continuity equation are solved by HAM. The homotopy analysis method (HAM) contains the auxiliary parameter ħ that allows us to adjust and control the convergence region of solution series. The study has highlighted the efficiency and capability of HAM in solving Saint Venant equations and modeling of unsteady flow through the rectangular canal that is the goal of this paper and other kinds of canals. Farshad Ehsani, Seyed Ghorban Hosseini, and Hossein Soury Copyright © 2014 Farshad Ehsani et al. All rights reserved. Software Frameworks for Model Composition Tue, 18 Feb 2014 14:29:47 +0000 A software framework is an architecture or infrastructure intended to enable the integration and interoperation of software components. Specialized types of software frameworks are those specifically intended to support the composition of models or other components within a simulation system. Such frameworks are intended to simplify the process of assembling a complex model or simulation system from simpler component models as well as to promote the reuse of the component models. Several different types of software frameworks for model composition have been designed and implemented; those types include common library, product line architecture, interoperability protocol, object model, formal, and integrative environment. The various framework types have different components, processes for composing models, and intended applications. In this survey the fundamental terms and concepts of software frameworks for model composition are presented, the different types of such frameworks are explained and compared, and important examples of each type are described. Mikel D. Petty, Jungyoon Kim, Salvador E. Barbosa, and Jai-Jeong Pyun Copyright © 2014 Mikel D. Petty et al. All rights reserved. A New Approach to the Identification of Distillation Column Based on Hammerstein Model Tue, 18 Feb 2014 10:45:48 +0000 Developing a suitable nonlinear model is the most challenging problem in the application of nonlinear model based controllers to distillation column. Hammerstein model consists of a nonlinear static element described by wavenet based nonlinear function, followed by a linear dynamic element described by the Output Error(OE) model was used in this study to represent the nonlinear dynamics of the distillation column. The model parameters were identified using iterative prediction-error minimization method. The model validation results proved that the Hammerstein model was capable of capturing the nonlinear dynamics of distillation column. Ramesh Kanthasamy, Hisyam Anwaruddin, and Suriya Kumar Sinnadurai Copyright © 2014 Ramesh Kanthasamy et al. All rights reserved. Utilization Bound Scheduling Analysis for Nonpreemptive Uniprocessor Architecture Using UML-RT Thu, 13 Feb 2014 00:00:00 +0000 The key for adopting the utilization-based schedulability test is to derive the utilization bound. Given the computation times, this paper proposes two utilization bound algorithms to derive interrelease times for nonpreemptive periodic tasks, using a new priority scheme, “Rate Monotonic Algorithm-Shortest Job First.” The obtained task set possesses the advantage of Rate Monotonic Algorithm and Shortest Job First priority scheme. Further, the task set is tested for schedulability, by first deriving a general schedulability condition from “problem window” analysis and, a necessary and sufficient schedulability condition for a task to be scheduled, at any release time are also derived. As a technical contribution, success ratio and effective processor utilization are analyzed for our proposed utilization bound algorithms on a uniprocessor architecture modeled using UML-RT. S. Ewins Pon Pushpa and Manamalli Devasigamani Copyright © 2014 S. Ewins Pon Pushpa and Manamalli Devasigamani. All rights reserved. Optimal Tuning of Decentralized PI Controller of Nonlinear Multivariable Process Using Archival Based Multiobjective Particle Swarm Optimization Wed, 12 Feb 2014 13:51:02 +0000 A Multiobjective Particle Swarm Optimization (MOPSO) algorithm is proposed to fine-tune the baseline PI controller parameters of Alstom gasifier. The existing baseline PI controller is not able to meet the performance requirements of Alstom gasifier for sinusoidal pressure disturbance at 0% load. This is considered the major drawback of controller design. A best optimal solution for Alstom gasifier is obtained from a set of nondominated solutions using MOPSO algorithm. Performance of gasifier is investigated at all load conditions. The controller with optimized controller parameters meets all the performance requirements at 0%, 50%, and 100% load conditions. The investigations are also extended for variations in coal quality, which shows an improved stability of the gasifier over a wide range of coal quality variations. R. Kotteeswaran and L. Sivakumar Copyright © 2014 R. Kotteeswaran and L. Sivakumar. All rights reserved. Intelligent Selection of Machining Parameters in Multipass Turnings Using Firefly Algorithm Sun, 09 Feb 2014 11:17:45 +0000 Determination of optimal cutting parameters is one of the most important elements in any process planning of metal parts. In this paper, a new optimization technique, firefly algorithm, is used for determining the machining parameters in a multipass turning operation model. The objective considered is minimization of production cost under a set of machining constraints. The optimization is carried out using firefly algorithm. An application example is presented and solved to illustrate the effectiveness of the presented algorithm. Abderrahim Belloufi, Mekki Assas, and Imane Rezgui Copyright © 2014 Abderrahim Belloufi et al. All rights reserved. An Assessment of a Proposed Hybrid Neural Network for Daily Flow Prediction in Arid Climate Thu, 06 Feb 2014 11:42:11 +0000 Rainfall-runoff simulation in hydrology using artificial intelligence presents the nonlinear relationships using neural networks. In this study, a hybrid network presented as a feedforward modular neural network (FF-MNN) has been developed to predict the daily rainfall-runoff of the Roodan watershed at the southern part of Iran. This FF-MNN has three layers—input, hidden, and output. The hidden layer has two types of neural expert or module. Hydrometeorological data of the catchment were collected for 21 years. Heuristic method was used to develop the MNN for exploring daily flow generalization. Two training algorithms, namely, backpropagation with momentum and Levenberg-Marquardt, were used. Sigmoid and linear transfer functions were employed to explore the network’s optimum behavior. Cross-validation and predictive uncertainty assessments were carried out to protect overtiring and overparameterization, respectively. Results showed that the FF-MNN could satisfactorily predict stream flow during testing period. The Nash-Sutcliff coefficient, coefficient of determination, and root mean square error obtained using MNN during training and test periods were 0.85, 0.85, and 39.4 and 0.57, 0.58, and 32.2, respectively. The predictive uncertainties for both periods were 0.39 and 0.44, respectively. Generally, the study showed that the FF-MNN can give promising prediction for rainfall-runoff relations. Milad Jajarmizadeh, Sobri Harun, and Mohsen Salarpour Copyright © 2014 Milad Jajarmizadeh et al. All rights reserved. UML Profile for Mining Process: Supporting Modeling and Simulation Based on Metamodels of Activity Diagram Tue, 04 Feb 2014 13:14:54 +0000 An UML profile describes lightweight extension mechanism to the UML by defining custom stereotypes, tagged values, and constraints. They are used to adapt UML metamodel to different platforms and domains. In this paper we present an UML profile for models supporting event driving simulation. In particular, we use the Arena simulation tool and we focus on the mining process domain. Profiles provide an easy way to obtain well-defined specifications, regulated by the Object Management Group (OMG). They can be used as a presimulation technique to obtain solid models for the mining industry. In this work we present a new profile to extend the UML metamodel; in particular we focus on the activity diagram. This extended model is applied to an industry problem involving loading and transportation of minerals in the field of mining process. Andrea Giubergia, Daniel Riesco, Verónica Gil-Costa, and Marcela Printista Copyright © 2014 Andrea Giubergia et al. All rights reserved. Comparison of CFBP, FFBP, and RBF Networks in the Field of Crack Detection Tue, 04 Feb 2014 09:27:06 +0000 The issue of crack detection and its diagnosis has gained a wide spread of industrial interest. The crack/damage affects the industrial economic growth. So early crack detection is an important aspect in the point of view of any industrial growth. In this paper a design tool ANSYS is used to monitor various changes in vibrational characteristics of thin transverse cracks on a cantilever beam for detecting the crack position and depth and was compared using artificial intelligence techniques. The usage of neural networks is the key point of development in this paper. The three neural networks used are cascade forward back propagation (CFBP) network, feed forward back propagation (FFBP) network, and radial basis function (RBF) network. In the first phase of this paper theoretical analysis has been made and then the finite element analysis has been carried out using commercial software, ANSYS. In the second phase of this paper the neural networks are trained using the values obtained from a simulated model of the actual cantilever beam using ANSYS. At the last phase a comparative study has been made between the data obtained from neural network technique and finite element analysis. Dhirendranath Thatoi, Punyaslok Guru, Prabir Kumar Jena, Sasanka Choudhury, and Harish Chandra Das Copyright © 2014 Dhirendranath Thatoi et al. All rights reserved. Optimal ILP-Based Approach for Gate Location Assignment and Scheduling in Quantum Circuits Tue, 04 Feb 2014 09:06:08 +0000 Physical design and synthesis are two key processes of quantum circuit design methodology. The physical design process itself decomposes into scheduling, mapping, routing, and placement. In this paper, a mathematical model is proposed for mapping, routing, and scheduling in ion-trap technology in order to minimize latency of the circuit. The proposed model which is a mixed integer linear programming (MILP) model gives the optimal locations for gates and the best sequence of operations in terms of latency. Experimental results show that our scheme outperforms the other schemes for the attempted benchmarks. Naser Mohammadzadeh, Tayebeh Bahreini, and Hossein Badri Copyright © 2014 Naser Mohammadzadeh et al. All rights reserved. Effect of Flow Attack Angle of V-Ribs Vortex Generators in a Square Duct on Flow Structure, Heat Transfer, and Performance Improvement Sun, 02 Feb 2014 00:00:00 +0000 A numerical investigation has been carried out to examine the periodic laminar flow and heat transfer characteristics in a three-dimensional isothermal wall square duct with 20° inline V-ribs. The computations are based on the finite volume method, and the SIMPLE algorithm has been implemented. The fluid flow and heat transfer characteristics are presented for Reynolds numbers based on the hydraulic diameter of the square duct ranging from 100 to 2000. To generate main streamwise vortex flows through the tested section, V-ribs with an attack angle of 20° are mounted in tandem with inline arrangement, pointing downstream (V-Downstream) and pointing upstream (V-Upstream) placed on both the upper and lower walls. Effects of different blockage ratio (, BR) with a single pitch ratio (, PR) of 1 on heat transfer, pressure loss, and performance in the ribbed tube are studied. Apparently in each of the main vortex flows, streamwise twisted vortex flows can induce impinging flows on the walls of the interbaffle cavity leading to drastic increase in heat transfer rate over the square duct. In addition, the rise in the V-baffle height results in the increase in the Nusselt number and friction factor values. The computational results show that the optimum thermal enhancement factor is about 4.2 at and 0.15 for the V-Downstream and V-Upstream, respectively. Amnart Boonloi Copyright © 2014 Amnart Boonloi. All rights reserved. Modeling Large Deformation and Failure of Expanded Polystyrene Crushable Foam Using LS-DYNA Mon, 27 Jan 2014 06:01:25 +0000 In the initial phase of the research work, quasistatic compression tests were conducted on the expanded polystyrene (EPS) crushable foam for material characterisation at low strain rates ( s−1) to obtain the stress strain curves. The resulting stress strain curves are compared well with the ones found in the literature. Numerical analysis of compression tests was carried out to validate them against experimental results. Additionally gravity-driven drop tests were carried out using a long rod projectile with semispherical end that penetrated into the EPS foam block. Long rod projectile drop tests were simulated in LS-DYNA by using suggested parameter enhancements that were able to compute the material damage and failure response precisely. The material parameters adjustment for successful modelling has been reported. Qasim H. Shah and A. Topa Copyright © 2014 Qasim H. Shah and A. Topa. All rights reserved. A Comparison of Standard One-Step DDA Circular Interpolators with a New Cheap Two-Step Algorithm Mon, 20 Jan 2014 09:28:19 +0000 We present and study existing digital differential analyzer (DDA) algorithms for circle generation, including an improved two-step DDA algorithm which can be implemented solely in terms of elementary shifts, addition, and subtraction. Leonid Moroz, Jan L. Cieśliński, Marta Stakhiv, and Volodymyr Maksymovych Copyright © 2014 Leonid Moroz et al. All rights reserved. Study of Polarized Wave with a Hydrodynamic Model and Fourier Spectral Method Tue, 31 Dec 2013 17:51:45 +0000 The polarization effects in hydrodynamics are studied. Hydrodynamic equation for the nonlinear wave is used along with the polarized nonlinear waves and seismic waves act as initial waves. The model is then solved by Fourier spectral and Runge-Kutta 4 methods, and the surface plot is drawn. The output demonstrates the inundation behaviors. Consequently, the polarized seismic waves along with the polarized nonlinear waves tend to generate dissimilar inundation which is more disastrous. Dennis Ling Chuan Ching, Zainal Abdul Aziz, and Faisal Salah Copyright © 2013 Dennis Ling Chuan Ching et al. All rights reserved. Impact of the Air-Conditioning System on the Power Consumption of an Electric Vehicle Powered by Lithium-Ion Battery Thu, 26 Dec 2013 14:19:43 +0000 The car occupies the daily universe of our society; however, noise pollution, global warming gas emissions, and increased fuel consumption are constantly increasing. The electric vehicle is one of the recommended solutions by the raison of its zero emission. Heating and air-conditioning (HVAC) system is a part of the power system of the vehicle when the purpose is to provide complete thermal comfort for its occupants, however it requires far more energy than any other car accessory. Electric vehicles have a low-energy storage capacity, and HVAC may consume a substantial amount of the total energy stored, considerably reducing the vehicle range, which is one of the most important parameters for EV acceptability. The basic goal of this paper is to simulate the air-conditioning system impact on the power energy source of an electric vehicle powered by a lithium-ion battery. Brahim Mebarki, Belkacem Draoui, Boumediène Allaou, Lakhdar Rahmani, and Elhadj Benachour Copyright © 2013 Brahim Mebarki et al. All rights reserved. Simulating Growth Kinetics in a Data-Parallel 3D Lattice Photobioreactor Tue, 24 Dec 2013 18:25:27 +0000 Though there have been many attempts to address growth kinetics in algal photobioreactors, surprisingly little have attempted an agent-based modelling (ABM) approach. ABM has been heralded as a method of practical scientific inquiry into systems of a complex nature and has been applied liberally in a range of disciplines including ecology, physics, social science, and microbiology with special emphasis on pathogenic bacterial growth. We bring together agent-based simulation with the Photosynthetic Factory (PSF) model, as well as certain key bioreactor characteristics in a visual 3D, parallel computing fashion. Despite being at small scale, the simulation gives excellent visual cues on the dynamics of such a reactor, and we further investigate the model in a variety of ways. Our parallel implementation on graphical processing units of the simulation provides key advantages, which we also briefly discuss. We also provide some performance data, along with particular effort in visualisation, using volumetric and isosurface rendering. A. V. Husselmann and K. A. Hawick Copyright © 2013 A. V. Husselmann and K. A. Hawick. All rights reserved. An Implicit Algorithm Based on Continuous Moving Least Square to Simulate Material Mixing in Friction Stir Welding Process Tue, 24 Dec 2013 18:24:45 +0000 An implicit iterative algorithm, based on the continuous moving least square (CMLS), is developed to simulate material mixing in Friction Stir Welding (FSW) process. Strong formulation is chosen for the modeling of the mechanical problem in Lagrangian framework to avoid the drawback of numerical integration. This algorithm is well adapted to large deformations in the mixing zone in the neighborhood of the welding tool. We limit ourselves to bidimensional viscoplastic problem to show the performance of the proposed implicit algorithm. The results show that the proposed algorithm can be employed to simulate FSW. Abdelaziz Timesli, Bouazza Braikat, Hassane Lahmam, and Hamid Zahrouni Copyright © 2013 Abdelaziz Timesli et al. All rights reserved. A New Mathematical Model for Food Thermal Process Prediction Sun, 22 Dec 2013 18:26:08 +0000 A mathematical model was developed to correlate the four heat penetration parameters of 57 Stumbo’s tables (18,513 datasets) in canned food: (the difference between the retort and the coldest point temperatures in the canned food at the end of the heating process), (the ratio of the heating rate index to the sterilizing value), (the temperature change required for the thermal destruction curve to traverse one log cycle), and , (the cooling lag factor). The quantities , , and , are input variables for predicting , while , and are input variables for predicting the value of , which is necessary to calculate the heating process time , at constant retort temperature, using Ball’s formula. The process time calculated using the value obtained from the mathematical model closely followed the time calculated from the tabulated values (root mean square of absolute errors RMS = 0.567 min, average absolute error = 0.421 min with a standard deviation SD = 0.380 min). Because the mathematical model can be used to predict the intermediate values of any combination of inputs, avoiding the storage requirements and the interpolation of 57 Stumbo’s tables, it allows a quick and easy automation of thermal process calculations and to perform these calculations using a spreadsheet. Dario Friso Copyright © 2013 Dario Friso. All rights reserved. Quadratic Optimal Regulator Design of a Pneumatic Control Valve Sun, 22 Dec 2013 15:23:56 +0000 Pneumatic control valves are still the most used devices in the process industries, due to their low cost and simplicity. This paper presents a regulator for pneumatic control valves using pole-placement method, optimal control, full-order state observer, and minimum-order state observer and their responses will be compared with each other. Bondgraph method has been used to model the control valve. Simulation results have been made for four models of regulator. The results show that minimum overshoot and settling time are achieved using optimal regulator of pneumatic valve. Mohammad Heidari and Hadi Homaei Copyright © 2013 Mohammad Heidari and Hadi Homaei. All rights reserved. Image Quality Assessment for Different Wavelet Compression Techniques in a Visual Communication Framework Sun, 22 Dec 2013 10:10:54 +0000 Images with subband coding and threshold wavelet compression are transmitted over a Rayleigh communication channel with additive white Gaussian noise (AWGN), after quantization and 16-QAM modulation. A comparison is made between these two types of compression using both mean square error (MSE) and structural similarity (SSIM) image quality assessment (IQA) criteria applied to the reconstructed image at the receiver. The two methods yielded comparable SSIM but different MSE measures. In this work, we justify our results which support previous findings in the literature that the MSE between two images is not indicative of structural similarity or the visibility of errors. It is found that it is difficult to reduce the pointwise errors in subband-compressed images (higher MSE). However, the compressed images provide comparable SSIM or perceived quality for both types of compression provided that the retained energy after compression is the same. Nuha A. S. Alwan and Zahir M. Hussain Copyright © 2013 Nuha A. S. Alwan and Zahir M. Hussain. All rights reserved. Control Theory Concepts Applied to Retail Supply Chain: A System Dynamics Modeling Environment Study Wed, 20 Nov 2013 09:28:23 +0000 Control theory concepts have been long used to successfully manage and optimize complex systems. Using system dynamics (SD) modeling methodology, which is continuous deterministic simulation modeling methodology, we apply control theory concepts to develop a suitable performance functional (or objective function) that optimizes the performance of a retail supply chain. The focus is to develop insights for inventory management to prevent stock-outs and unfilled orders and to fill customer orders at the lowest possible cost to supply chain partners under different scenarios, in a two-player supplier-retailer supply chain. Moderate levels of inventory, defining appropriate performance functional, appear to be crucial in choosing the right policies for managing retail supply chain systems. The study also demonstrated how multiple objectives can be combined in a single performance functional (or objective function) by carefully assigning suitable weights to the components of objectives based on their priority and the existence of possible trade off opportunities. Balaji Janamanchi and James R. Burns Copyright © 2013 Balaji Janamanchi and James R. Burns. All rights reserved. Investigation into the Dynamics and Control of an Underwater Vehicle-Manipulator System Thu, 14 Nov 2013 08:54:09 +0000 This study addresses the detailed modeling and simulation of the dynamic coupling between an underwater vehicle and manipulator system. The dynamic coupling effects due to damping, restoring, and inertial effects of an underwater manipulator mounted on an autonomous underwater vehicle (AUV) are analyzed by considering the actuator and sensor characteristics. A model reference control (MRC) scheme is proposed for the underwater vehicle-manipulator system (UVMS). The effectiveness of the proposed control scheme is demonstrated using numerical simulations along with comparative study between conventional proportional-integral-derivative (PID) control. The robustness of the proposed control scheme is also illustrated in the presence of external disturbances and parameter uncertainties. Mohan Santhakumar Copyright © 2013 Mohan Santhakumar. All rights reserved. Modeling of Stenotic Coronary Artery and Implications of Plaque Morphology on Blood Flow Tue, 12 Nov 2013 10:10:45 +0000 A diseased coronary artery has been modeled to study the implications of plaque morphology on the fluid dynamics. In our previous study, we have successfully classified the coronary plaques of 42 patients who underwent intravascular ultrasound (IVUS) into four-types (Type I, Type II, Type III, and Type IV) based on the plaque morphology. In this study, we demonstrate that, for the same degree of stenosis (height of the plaques), hemodynamics parameters are strongly dependent on the plaque shape. This study is the first one to clearly demonstrate that in addition to wall shear stress, presence of turbulence and location of transition from laminar to turbulence state are additional hemodynamics parameters to identify plaques vulnerable to rupture. Carlos Moreno and Kiran Bhaganagar Copyright © 2013 Carlos Moreno and Kiran Bhaganagar. All rights reserved. Computational Modelling of Blood Flow Development and Its Characteristics in Magnetic Environment Mon, 11 Nov 2013 08:55:41 +0000 Of concern in this paper is an investigation of the entrance length behind singularities in cardiovascular hemodynamics under magnetic environment. In order to get better interpretation of scan MRI images, the characteristics of blood flow and electromagnetic field within the circulatory system have to be furthermore investigated. A 3D numerical model has been developed as an example of blood flowing through a straight circular tube. The governing coupled nonlinear differential equations of magnetohydrodynamic (MHD) fluid flow are reduced to a nondimensional form, which are then characterized by four dimensionless parameters. With an aim to validate our numerical approach, the computational results are compared with those of the analytical solution available in the developed region far from the singularity. The hydraulic impedance by unit length within the developed flow region increases with the magnetic field. The time average entrance length with a greater precision on the unsteady case decreases with increasing magnetic field strength. The overall voltage characteristics do not depend on the developed flow field within the entry region. Gopal Chandra Shit Copyright © 2013 Gopal Chandra Shit. All rights reserved. Parametric and Internal Resonances of an Axially Moving Beam with Time-Dependent Velocity Sun, 10 Nov 2013 14:08:05 +0000 The nonlinear vibration of a travelling beam subjected to principal parametric resonance in presence of internal resonance is investigated. The beam velocity is assumed to be comprised of a constant mean value along with a harmonically varying component. The stretching of neutral axis introduces geometric cubic nonlinearity in the equation of motion of the beam. The natural frequency of second mode is approximately three times that of first mode; a three-to-one internal resonance is possible. The method of multiple scales (MMS) is directly applied to the governing nonlinear equations and the associated boundary conditions. The nonlinear steady state response along with the stability and bifurcation of the beam is investigated. The system exhibits pitchfork, Hopf, and saddle node bifurcations under different control parameters. The dynamic solutions in the periodic, quasiperiodic, and chaotic forms are captured with the help of time history, phase portraits, and Poincare maps showing the influence of internal resonance. Bamadev Sahoo, L. N. Panda, and G. Pohit Copyright © 2013 Bamadev Sahoo et al. All rights reserved. Finite Element Simulation of Dynamic Stability of Plane Free-Surface of a Liquid under Vertical Excitation Sun, 10 Nov 2013 09:36:01 +0000 When partially filled liquid containers are excited vertically, the plane free-surface of the liquid can be stable or unstable depending on the amplitude and frequency of the external excitation. For some combinations of amplitude and frequency, the free-surface undergoes unbounded motion leading to instability called parametric instability or parametric resonance, and, for few other combinations, the free-surface undergoes bounded stable motion. In parametric resonance, a small initial perturbation on the free-surface can build up unboundedly even for small external excitation, if the excitation acts on the tank for sufficiently long time. In this paper, the stability of the plane free-surface is investigated by numerical simulation. Stability chart for the governing Mathieu equation is plotted analytically using linear equations. Applying fully nonlinear finite element method based on nonlinear potential theory, the response of the plane free-surface is simulated for various cases. Siva Srinivas Kolukula and P. Chellapandi Copyright © 2013 Siva Srinivas Kolukula and P. Chellapandi. All rights reserved. Multiple Dissipative Devices for Blast-Resisting Cable-Supported Glazing Façades Sun, 03 Nov 2013 14:22:27 +0000 The paper analyzes the structural response of a high-level air blast loaded cable-supported façade. Since the glass panels and the cables present a typical brittle behavior and are subjected to elevated tensile stresses when a high-level explosion occurs, multiple dissipative devices are simultaneously introduced in the conventional glazing system to mitigate the maximum effects of the design blast wave. Dynamic analyses are performed using a sophisticated FE-model to describe accurately the response of the façade equipped by dissipative devices. Based on numerical results of previous contributions, viscoelastic spider connectors (VESCs) are introduced in the points of connection between glass panels and pretensioned cables, to replace “rigid” spider connectors commonly used in practice. At the same time, rigid-plastic frictional devices (RPDs) are installed at the top of the bearing cables to mitigate furthermore the bracing system. As a result, due to the combined use of VESCs and RPDs opportunely calibrated, the maximum tensile stresses in the glass panels and in the cables appear strongly reduced. In addition, the proposed devices do not trouble the aesthetics of such transparent structural systems. At last, simple design rules are presented to predict the response of cable-supported façades subjected to high-level dynamic loads and to preliminary estimate the mechanical parameters of combined VESCs and RPDs. Claudio Amadio and Chiara Bedon Copyright © 2013 Claudio Amadio and Chiara Bedon. All rights reserved.