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Abstract: A wide range of mathematical models for multiple effect evaporators in process industry including paper industry are well reported in the literature but not so extensive work on the dynamic behavior of MEE system is available in the literature. In the present study dynamic behavior of multi-effect evaporator system of a paper industry is obtained by disturbing the feed flow rate, feed concentration, live steam temperature and feed temperature. For this purpose an unsteady-state model for the multi-effect evaporator system is developed. Each effect in the process is represented by a number of variables which are related by the energy and material balance equations for the feed, product and vapor flow. A generalized mathematical model which could be applied to any number of effects and all kinds of feeding arrangements like forward feed, backward feed, mixed feed and spilt feed in the MEE system with simple modifications was finally obtained. Finally model for mixed feed sextuple effect falling film evaporators system was solved using MATLAB. For the steady state and dynamic simulation the ‘fsolve’ and ‘ode45’ solvers in MATLAB source code is used respectively. [Copyright &y& Elsevier]

Abstract: This paper concerns the modelling of an accumulator used in industrial elastic web processing plant such as paper mills, fabric, rolling mills etc. Accumulators are used to allow rewind or unwind core changes while the process continues at a constant web velocity. A new nonlinear model of a pneumatic actuated industrial accumulator including pneumatic jack model, static friction representation and web weight is first detailed which enables to deduce a linear model. These models are derived from physical laws that describe web tension and velocity dynamics in each web span. In a second part, the effects of time-varying mechanical parameters, such as web Young modulus, web length and rollers inertia on accumulator dynamics are presented. The performances of the modeled accumulator are illustrated by simulations in Matlab/Simulink software environment. [Copyright &y& Elsevier]

The numerical modelling of the internal heat generation in passenger vehicle tyres using finite element analysis is a well-known numerical approach. However, this application is rather uncommon for earthmover tyres. This paper describes the development of a finite element model of a 23.5R25 earthmover tyre for the numerical modelling of the temperature distribution in the tyre cross-section at steady-state heat transfer conditions using an uncoupled analysis procedure. Considering the non-linear behaviour of the rubber compounds used for the manufacturing of these tyres, as well as the complexity associated with the composite structural aspects of the tyre, the material properties used for the proposed numerical model were established experimentally. In the analyses completed, the tyre behaviour was studied by simulations at various inflation pressures, loads and rolling velocities. The numerical tyre defection was within an 8% deviation from the actual tyre behaviour. Thermal simulation results were used to derive an equation that can be used to predict the maximum temperature that would occur in the tyre’s cross-section as a function of its vertical deflection, its forward rolling velocity and the ambient temperature of the surroundings. The numerical models and simulations presented in this paper were completed using MSC.Marc/Mentat. [ABSTRACT FROM AUTHOR]

This paper addresses a multi-stage inventory model that allows different order quantities among the selected suppliers to obtain the optimal solutions. To achieve the objective of the study, the single-objective and multi-objective methods are adopted for suitable real-world applications. With respect to a single-objective method, this paper aims to minimize the total ordering costs, holding costs, and purchasing costs, subject to the price, quality, and capacity. With respect to a multi-objective method, it focuses on cost minimization, as well as quality and capacity maximization. The proposed model not only considers the allocation of different order quantities among the selected suppliers, but also incorporates the multi-stage inventory problem. Furthermore, a numerical example is provided to illustrate the usefulness of the proposed model and a comparative understanding of various methods. In addition, a simulation test is performed to effectively validate the proposed model which outperforms the previous works. Finally, a sensitivity analysis is carried out to investigate the impact of supply chain cost. [ABSTRACT FROM AUTHOR]

In this paper we present a multiphysics simulation model of Halcyon, an autonomous unmanned surface vehicle (USV). The simulation model presented in this paper has been developed to rapidly progress the design, development and validation of Halcyon’s autonomy management system, particularly in challenging sea conditions. Using simulation for this purpose enables extensive testing across the full environmental operating envelope of the vessel, hence greatly reducing the need for real-world sea-trials. The simulator is comprised of a novel and comprehensive sea-surface wave environment model, a six degree of freedom nonlinear unified seakeeping and manoeuvring boat dynamics model, an actuation dynamics model, an autopilot and an interface with an autonomy management system. Results are presented that show good agreement between real-world and simulated sea-trials data. [ABSTRACT FROM AUTHOR]

This paper proposes a new ranking algorithm based on comprehensive weighted clique degree (CWCDR) for ranking importance of nodes in complex network. Simulation results show that CWCDR algorithm can overcome the limitation of degree ranking algorithm and find important nodes in complex networks more precisely and effectively. To the shortage of small-world model and BA model, this paper proposes an evolutionary model of complex network based on CWCDR algorithms, named CWCDR model. Simulation results show that the CWCDR model accords with power-law distribution. Compared with BA model, this model has better average shortest path length and clustering coefficient. Therefore, the CWCDR model is more consistent with the real network. [ABSTRACT FROM AUTHOR]

This paper develops an analytical method to measure the performance of a multi-product unreliable production line with finite buffers between workstations. The performance measure used in this paper is Total Cycle Time. The proposed method is an approximation that generalizes the processing times to ease the variation of product types in a multi-product system. A decomposition method is then employed to approximate the production rate of a multi-product production line. The decomposition method considers generally distributed processing times as well as random failure and repair. A GI/G/1/N queuing model is also applied to obtain parameters such as blocking and starvation probabilities that are needed for the approximation procedure. Several numerical experiments under different scenarios are performed and results are validated by simulation models in order to assess the accuracy and strength of the proposed method. Consequent analysis and discussion of the results are also presented. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a generic high dimensional model representation (HDMR) method for approximating the system response in terms of functions of lower dimensions. The proposed approach, which has been previously applied for problems dealing only with random variables, is extended in this paper for problems in which physical properties exhibit spatial random variation and may be modelled as random fields. The formulation of the extended HDMR is similar to the spectral stochastic finite element method in the sense that both of them utilize Karhunen–Loève expansion to represent the input, and lower-order expansion to represent the output. The method involves lower dimensional HDMR approximation of the system response, response surface generation of HDMR component functions, and Monte Carlo simulation. Each of the low order terms in HDMR is sub-dimensional, but they are not necessarily translating to low degree polynomials. It is an efficient formulation of the system response, if higher-order variable correlations are weak, allowing the physical model to be captured by the first few lower-order terms. Once the approximate form of the system response is defined, the failure probability can be obtained by statistical simulation. The proposed approach decouples the finite element computations and stochastic computations, and consecutively the finite element code can be treated as a black box, as in the case of a commercial software. Numerical examples are used to illustrate the features of the extended HDMR and to compare its performance with full scale simulation. [Copyright &y& Elsevier]

Abstract: In this paper, four 3-D finite element models are developed to simulate the whole rod rolling process of GCr15 steel. The distribution and evolution of different field-variables, such as effective strain, effective strain rate and temperature, are obtained. Based on the simulated results and the microstructure evolution models of the steel, the paper designs a FORTRAN program to predict the evolution of recrystallization behavior and austenite grain size in rolled piece during the rolling. The surface temperatures of rolled piece calculated by FEM agree well with measured values. Comparison between calculated values and measured ones of grain size shows the validity of the program. [Copyright &y& Elsevier]

Abstract: This paper investigates the behaviour of subgroups in crowd dynamics by means of filming and observation. An existing crowd modelling program, CrowdDMX, based on a discrete element model (DEM) has been modified on the basis of observations made in this paper and literature. Each person is represented as three overlapping circles and motion is modelled in a Newtonian manner. It incorporates psychological forces as well as physical forces in a 2D time-stepping environment. The DEM model was modified to include realistic subgroup behaviour, representing people in the crowd desiring to stay together (families, friends, etc.). Subgroup psychological forces were incorporated. The previous model only simulated individuals moving independently, which was unrealistic in some situations as shown by the observation and filming part of the study. The revised program models subgroups realistically including the tendency to avoid subgroup division in cases of contra-flow. [Copyright &y& Elsevier]

Abstract: With the start up of West–East Natural Gas Transmission Project, the construction of natural gas-pipeline will enter on a new era in China. The development tendency will be towards large-diameter, high-pressure and long-distance for natural gas-pipelines. Correspondingly, the life cycle cost of natural gas-pipeline networks is increasing gradually. The mainline system is a vital part of natural gas network systems. The investment required for the mainline system is enormous, usually accounting for 80% of the total investment for this system. In general, the investment required for a gas-pipeline depends on its operating parameters. Therefore, based on the characteristics of gas networks, optimization for investment becomes indispensable to gas networks design. A comprehensive and optimal mathematic model of a gas networks system is established in this paper which considers all the factors influencing the total investment of a gas networks system (e.g. pipe diameter, thickness, pressure, length, compression ratio, etc). From the standpoint of the characteristics of a model comprising both continuous and discrete variables, a new methodology, rank-optimization, is presented. On the basis of this model, a simple and visual high-pressure networks optimization program has been compiled. Furthermore, the developed optimization program has been applied to a practical project and the effects of operating parameters on the total investment have been analyzed. The simulation model in this paper is shown to be an effective method to solve optimization on mainline system in high-pressure gas networks. [Copyright &y& Elsevier]

Abstract: This paper presents a condition-based order-replacement policy for a single-unit system, aiming to optimize the condition-based maintenance and the spare order management jointly. The concerned system deteriorates stochastically and gradually, and is inspected periodically. Under the proposed policy, both the preventive replacement and the spare order are decided based on the observed deterioration level of the system. Therefore, the decision variables for this order-replacement problem include the inspection interval, the ordering threshold, and the preventive replacement threshold. The analytical modeling of the condition-based order-replacement policy is presented in detail in this paper. The policy performance is evaluated in terms of the long-run average cost per unit time, the mean availability, and the rate of preventive replacement, for which the mathematical models are also derived. Numerical examples illustrate the performance of the condition-based order-replacement policy, especially the influences of the lead time of the spare order over the different performance criteria. [Copyright &y& Elsevier]

A new index for measuring the closeness to the singularities of parallel manipulators using geometric algebra is proposed in this paper. Constraint wrenches acting on the moving platform of a parallel manipulator are derived using the outer product and dual operations. Removing the redundant constraint wrenches, a singularity polynomial is obtained when the coefficient of the outer product of all the non-redundant constraint wrenches equals zero. A singularity surface can be drawn using the singularity polynomial. Similarly, an approximate singularity polynomial and approximate singularity surface can be obtained by imposing a threshold to the singular polynomial. Then the singularity volume is calculated as the space between singularity surface and approximate singularity surface. The new index is derived by calculating the ratio of the non-singularity workspace volume (the workspace volume minus the singularity volume) to the workspace volume. The proposed index is coordinate-free and has a clear geometrical and physical interpretation. This index can be a basis for selecting structural parameters, path planning and mechanism design. [ABSTRACT FROM AUTHOR]

In this paper, we introduce a flow shipment scheduling and hub location-routing problem in which the hub network is not fully interconnected, with the aim of maximizing the total amount of flow delivered by a predetermined latest arrival time and minimizing total fixed and routing costs. We present integer programming models to solve this problem in deterministic and stochastic environments when flow arrivals follow a piecewise linear form. A set of valid inequalities and preprocessing is suggested. An ε-constraint-based method and normalized weighted sum method are proposed to solve bi-objective problems. Furthermore, a case study on inter-province postal delivery system for the Islamic Republic of Iran Post Company and well-known test instances are used to evaluate the proposed models. Computational results show the viability of the models under different scenarios. [ABSTRACT FROM AUTHOR]

The paper considers a three-echelon supply chain which consists of one supplier, one manufacturer and one retailer for trading a single product. The market demand at the retailer is influenced by the retail price and the quality of the product. The quality of the finished product at the manufacturer depends on the supplier’s raw material quality. We analyze the model for both deterministic and stochastic demand patterns. We first study the centralized and decentralized systems, and then the decentralized system with a sub-supply chain coordination strategy (where the manufacturer chooses to merge with either the supplier or the retailer and then acts as a single entity) and the two-level retail fixed mark-up (RFM) strategy. In the case of the two-level RFM strategy, the manufacturer and the retailer use fixed mark ups over the supplier’s wholesale price. The proposed models are demonstrated through numerical examples. It is observed from the numerical study that the two-level RFM strategy is superior to the sub-supply chain coordination strategy. Further, the two-level RFM strategy in the stochastic demand scenario is not as effective as in the deterministic demand scenario. [ABSTRACT FROM AUTHOR]

In this paper, we propose a new mathematical model describing the effect of phosphocitrate (PC) on sodium sulphate crystallization inside bricks. This model describes salt and water transport, and crystal formation in a one dimensional symmetry. This is a preliminary study that takes into account mathematically the effects of inhibitors inside a porous stone. To this aim, we introduce two model parameters: the crystallization rate coefficient, which depends on the nucleation rate, and the specific volume of precipitated salt. These two parameters are determined by numerical fitting of our model for both the case of the brick treated with PC and non treated one. [ABSTRACT FROM AUTHOR]

Abstract: An active fault tolerant control (FTC) scheme is proposed in this paper to accommodate for an industrial steam turbine faults based on integration of a data-driven fault detection and diagnosis (FDD) module and an adaptive generalized predictive control (GPC) approach. The FDD module uses a fusion-based methodology to incorporate a multi-attribute feature via a support vector machine (SVM) and adaptive neuro-fuzzy inference system (ANFIS) classifiers. In the GPC formulation, an adaptive configuration of its internal model has been devised to capture the faulty model for the set of internal steam turbine faults. To handle the most challenging faults, however, the GPC control configuration is modified via its weighting factors to demand for satisfactory control recovery with less vigorous control actions. The proposed FTC scheme is hence able to systematically maintain early FDD with efficient fault accommodation against faults jeopardizing the steam turbine availability. Extensive simulation tests are conducted to explore the effectiveness of the proposed FTC performances in response to different categories of steam turbine fault scenarios. [Copyright &y& Elsevier]

Abstract: On the basis of analyzing the shortages of present studies on multi-echelon inventory control, and considering some restrictions, this paper applies the joint replenishment strategy into the inventory system and builds a multi-product multi-echelon inventory control model. Then, an algorithm designed by Genetic Algorithm (GA) is used for solving the model. Finally, we respectively simulate the model under three different ordering strategies. The simulation result shows that the established model and the algorithm designed by GA have obvious superiority on reducing the total cost of the multi-product multi-echelon inventory system. Moreover, it illustrates the feasibility and the effectiveness of the model and the GA method. [Copyright &y& Elsevier]

Abstract: Several researchers demonstrated that spectral parameters in induced polarization can be applied to discriminate different IP sources. In this paper it was applied an inversion procedure using the Gauss–Newton method to recover the spectral parameters of fractal model to complex resistivity. The finite element method was applied to carry out the forward modeling. The procedure was applied in synthetic data and simulations were carried out in five different frequencies. The inversion of the data were carried out in each frequency, further the inversion was applied also to each cell of the finite element mesh to recover the fractal parameter in order to analyze the possibility of using the fractal model parameters in the interpretation of the induced polarization response to this geological geometry. The results showed that the anomalies are well detected by the image of the fractal model parameters. [Copyright &y& Elsevier]

Abstract: In this paper, a simple and efficient contact algorithm is presented for the evaluation of density distribution in three-dimensional dynamic modeling of powder compaction processes. The contact node-to-surface algorithm is employed to impose the contact constraints in large deformation frictional contact, and the contact frictional slip is modified by the Coulomb friction law to simulate the frictional behavior between the rigid punch and the work-piece. The 3D nonlinear contact friction algorithm is employed together with a double-surface cap plasticity model within the framework of large finite element deformation in order to predict the non-uniform relative density distribution during the dynamic simulation of powder die-pressing. The accuracy and robustness of contact algorithm is verified by the impact analysis of two elastic rods, which is compared with the analytical solution. Finally, the performance of computational schemes is illustrated in dynamic modeling of a set of powder components. [Copyright &y& Elsevier]

Abstract: This paper presents results pertaining to the numerical modeling of the cryogenic system at the Canadian Light Source. The cryogenic system consists of a cryostat that houses a Radio Frequency (RF) cavity used for boosting the energy of an electron beam. For consistent operation of the RF cavity, it must be kept immersed in liquid helium at a constant level with the pressure in the gas space maintained to an accuracy of ±1mbar. An improvement to the cryostat model suggested in [3] using control volumes is described. The model and numerical method developed for the liquid helium supply and gaseous helium return lines are validated using two different cases, viz., the liquid helium flow rate from the liquid helium transfer line and the gaseous helium flow rate from the cryostat for various heater power input settings. The numerical method described here is significantly more accurate, efficient, and flexible than that used in [1] based on an iterative bisection method. [Copyright &y& Elsevier]

Abstract: In solid metal forming processes, such as forging, large distortions in the material present challenging problems for numerical simulation using grid based methods. Computations invariably fail after some level of mesh distortion is reached unless suitable re-meshing is implemented to cope with the mesh distortion arising from the material deformation. The issue of mesh distortion and the subsequent re-meshing are topics of much research for grid based methods. These problems can be overcome by using a mesh-less numerical framework. In this paper, the application of a mesh-less method called Smoothed Particle Hydrodynamics (SPH) for modelling three-dimensional complex forging processes is demonstrated. It is shown that SPH is a useful simulation method for obtaining insights into the material deformation and flow pattern during forging of realistic industrial components. The effect of process parameters and material properties on the quality of the forged component is evaluated via SPH simulations. This includes the determination of forging force required for adequate die filling which is an important criterion for die designs. Material hardening, controlled by the degree of heat treatment, is found to have a profound effect on the material deformation pattern and the final product. Forging defects such as incomplete die filling, asymmetry in forged components, flashing and lap formation are shown to be predicted by SPH. SPH can thus potentially be used both for assessment of the quality of forged products and evaluation of prototype forging system designs. [Copyright &y& Elsevier]

Abstract: This paper presents a VOF-based two-phase flow model for the simulation of wave interactions with seawall supported by a porous terrace. Firstly, the model was verified against laboratory data in a simple case for wave overtopping of a vertical wall. Comparison of computed and measured wave properties showed reasonably good agreement. The model was then applied to study the interactions of waves and a seawall protected by porous structures with a permeable terrace. The application results showed that the overtopping rate was strongly related to the energy dissipation through the drag force; the porous reef and terrace were very effective to produce a low crest type seawall. It is concluded that there exist two optimum values of porosity of the submerged reef, about of 0.25 and 0.7, that give minimum overtopping rates. Whereas, there is an effective range of porosity of the permeable terrace varying from 0.4 to 0.65 for significantly reducing the overtopping rate. The verification results confirm that the VOF-based two-phase flow model is sufficient robust to simulate the wave overtopping of coastal structures with reasonable accuracy. [Copyright &y& Elsevier]

Abstract: A novel impulsive control approach based on interval Type-2 T–S fuzzy model has been presented for nonlinear systems in this paper. This approach makes up for the drawback of Type-1 fuzzy impulsive control, which cannot fully handle the uncertainties in describing the complex nonlinear systems by Type-1 fuzzy membership functions and cannot give rigorous fuzzy rules. Further more, this approach uses the “broad band” effect of the Type-2 membership functions to solve the noise of training data and exterior disturbance of the Type-1 fuzzy impulsive control. By using Lyapunov theory and Lipschitz condition, which is combined with integrated approaches such as comparison methods and linear matrix inequalities, the Type-2 fuzzy impulsive controller is designed and the general asymptotical stability analysis of the systems is given. Finally, the simulation of the inverted pendulum model demonstrates the validity and superiority of the proposed method by easily determining the membership functions and choosing minimum number of fuzzy rules and the method can handle random disturbance and data uncertainties very well. [Copyright &y& Elsevier]

Abstract: In this paper, we propose VEISV (vulnerable – exposed – infectious – secured – vulnerable) network worm attack model, which is appropriate for measuring the effects of security countermeasures on worm propagation. Contrary to existing models, our model takes into consideration accurate positions for dysfunctional hosts and their replacements in state transition. Using the reproduction rate, we derive global stability of a worm-free state and local stability of a unique worm-epidemic state. Furthermore, simulation results show the positive impact of increasing security countermeasures in the vulnerable state on worm-exposed and infectious propagation waves. Finally, equilibrium points are confirmed by phase plots. [Copyright &y& Elsevier]

Abstract: Impinging jets over liquid surfaces are a common practice in the metallurgy and chemical industries. This paper presents a numerical study of the fluid dynamics involved in this kind of processes. URANS simulations are performed using the volume of fluid (VOF) method to deal with the multiphase physics. This unsteady approach with the appropriate computational domain allows resolution of the big eddies responsible for the low frequency phenomena. The solver we used is based on the finite volume method and turbulence is modelled with the realisable k-ϵ model. Two different configurations belonging to the dimpling and splashing modes are under consideration. The results are compared with PIV and LeDaR experimental data previously obtained by the authors. Attention is focused on the surroundings of the impingement, where the interaction between jet and liquid film is much stronger. Finally, frequency analysis is carried out to study the flapping motion of the jet and cavity oscillations. [Copyright &y& Elsevier]

Abstract: The behaviour of a fluid, which may contain particle suspensions, flowing in micro-dimensional channels is governed by both viscous and surface tension forces as well as high shear rates and geometric effects such as bifurcations, constriction, and high surface-to-volume ratio. This paper discusses some of the key design factors affecting fluid behaviour in micro-engineered products containing a main channel, constriction and side channel bifurcations. Differences in fluid behaviour at the macro and micro-scales are discussed. The dynamic bulk fluid behaviour is characterised in terms of: (i) fluid properties, (ii) governing physics and (iii) microchannel geometric features. At this stage of the analysis the fluids are assumed to be Newtonian and single phase, where any particle suspension is represented through a bulk density and viscosity. Based on these assumptions Computational Fluid Dynamics (CFD) is used to investigate the effect of both product inlet and outlet boundary conditions on the bulk flow behaviour. Discussions are provided on how these boundary conditions can affect particle separation efficiency. In particular, the so called pull-design whereby the fluid is pulled out of the device at the outlet, is shown to offer better performance compared to the mode of operation where the fluid is pushed into the device at the inlet. It is also observed that increasing the pressure at the outlet of the main channel can achieve a balanced flow rate ratio which leads to a uniform separation performance among all bifurcations. [Copyright &y& Elsevier]

Abstract: Comprehensive applications of modularization modeling method have proven its effectiveness and versatility in system simulation field. This paper establishes the modularization numerical model of a turbine test rig main test system by using a finite volume numerical system developed. The simulation study based on an experiment is conducted. The comparison with available experimental data indicates that the general trends of simulation curves are in agreement with test curves and that there is obvious thermal stratification phenomenon at different positions along combustion gas flow direction. Accordingly, it can be concluded that the analysis of experimental data is reasonable and the established numerical system is effective. It is also found that the modeling of valve spool throttling and the modeling of components-wall heat transfer are two key factors of affecting simulation accuracy. [Copyright &y& Elsevier]

Abstract: In this paper, an enriched finite element method is presented for numerical simulation of saturated porous media. The arbitrary discontinuities, such as material interfaces, are encountered via the extended finite element method (X-FEM) by enhancing the standard FEM displacements. The X-FEM technique is applied to the governing equations of porous media for the spatial discretization, followed by a generalized Newmark scheme used for the time domain discretization. In X-FEM, the material interfaces are represented independently of element boundaries and the process is accomplished by partitioning the domain with some triangular sub-elements whose Gauss points are used for integration of the domain of elements. Finally, several numerical examples are analyzed, including the dynamic analysis of the failure of lower San Fernando dam, to demonstrate the efficiency of the X-FEM technique in saturated porous soils. [Copyright &y& Elsevier]

Abstract: This paper is concerned with using the E-Bayesian method [M. Han, Applied Mathematical Modeling (2009) 1915–1922] for computing estimates for the parameter and reliability function of the Burr type XII distribution based on type-2 censored samples. The estimates are obtained based on squared error and LINEX loss functions. A comparison between the new method and the corresponding Bayes and maximum likelihood techniques is made using the Monte Carlo simulation. [Copyright &y& Elsevier]

Abstract: In this paper we present the application of regressive models to simulation of car-to-pole impacts. Three models were investigated: RARMAX, ARMAX and AR. Their suitability to estimate physical system parameters as well as to reproduce car kinematics was examined. It was found out that they not only estimate the one quantity which was used for their creation (car acceleration) but also describe the car’s acceleration, velocity and crush. A virtual experiment was performed to obtain another set of data for use in further research. An AR model to predict the behavior of a low-speed car impacting a rigid barrier was created and verified. [Copyright &y& Elsevier]

Abstract: This paper presents a new technique for model order reduction (MOR) that is based on an artificial neural network (ANN) prediction. The ANN-based MOR can be applied for different scale systems with substructure preservation. In the proposed technique, the ANN is implemented for predicting the unknown elements of the reduced order model. Prediction of the ANN architecture is based on minimizing the cost function obtained by the difference between the actual and desired system behaviour. The ANN prediction process is pursued while maintaining the full order substructure in the reduced model. The proposed ANN-based model order reduction method is compared to recently published work on MOR techniques. Simulation results verify the validity of the new MOR technique. [Copyright &y& Elsevier]

Abstract: The paper describes the use of the grid-free Smoothed Particle Hydrodynamics (SPH) method to investigate lava flow from volcanic eruptions using real three dimensional topography in the form of Digital Terrain Models (DTM). Heat transfer resulting from conduction and radiation and solidification of the lava modelled via a variable viscosity are coupled to the fluid flow solution. Simulations show that the run-out distance and the nature of the lava flow are affected significantly by the lava viscosity and that this is dependent on the scale of the volcanic eruption, with solidification effects strongest on the smallest scale. SPH appears to be a highly effective technique for predicting lava flow with very good representations of the fluid free surface, close interaction with the complex topography, easy inclusion of the thermal and solidification effects leading to very plausible flow predictions. The pile-up of the lava at the front as it solidifies and the subsequent deceleration of the flow are easily modelled by SPH. [Copyright &y& Elsevier]

Abstract: This paper presents the very fascinating simulation results of light pulse traveling within a ring resonator system that have shown the unexpected results with various applications. The design system consists of a nonlinear microring/nanoring resonator system incorporating an add/drop filter. The proposed fabricated material used is InGaAsP/InP, which can provide the required output behaviors. Three different forms of input light pulses are Gaussian pulse, dark and bright soliton, whereas the suitable simulation parameters are input power, pulse width, ring radii and the material refractive indices. Three different forms of the results have been interpreted, whereas the dominants behaviors are such as Gaussian soliton, multisoliton and tunable dark soliton are described, and the potential applications for new laser sources, new communication bands and dynamic optical tweezers have been discussed. [Copyright &y& Elsevier]

Abstract: In this paper a general three-dimensional simulation of turbulent fluid flow is presented to predict velocity and pressure fields for a centrifugal pump. A commercial CFD code was used to solve the governing equations of the flow field. In order to study the most suitable turbulence model, three known turbulence models of standard k–ε, RNG and RSM were applied. The complex flow configuration required us to use around 5,800,000 cells, and 12 computational nodes (processors) for parallel computing. Simulation results in the form of characteristic curves were compared with available experimental data, and an acceptable agreement was obtained. Additionally, effect of number of blades on the efficiency of pump was studied. The number of blades was changed from 5 to 7. The results show that the impeller with 7 blades has the highest head coefficient. Finally, it was observed also that the position of blades with respect to the tongue of volute has great effect on the start of the separation. Thus, to analyze the effect of blade number on the characteristics of the pump, the position of blade and tongue should be similar to each other. Investigations of this kind may help to reduce the required experimental work for the development and design of such devices. [ABSTRACT FROM AUTHOR]

Abstract: It is well known that the immune response plays an important role in eliminating or controlling the disease after human body is infected by virus. In this paper, we investigate the dynamical behavior of a viral infection model with retarded immune response. The effect of time delay on stability of the equilibria of the system has been studied and sufficient condition for local asymptotic stability of the infected equilibrium and global asymptotic stability of the infection-free equilibrium and the immune-exhausted equilibrium are given. By numerical simulating,we observe that the stationary solution becomes unstable at some critical immune response time, while the delay time and birth rate of susceptible host cells increase, and we also discover the occurrence of stable periodic solutions and chaotic dynamical behavior. The results can be used to explain the complexity of the immune state of patients. [Copyright &y& Elsevier]

Abstract: The main objective of this study is to utilize two dynamic models: a mathematical model and a simple model, to identify a pick-and-place mechanism (PPM) which is driven by a permanent magnet synchronous motor (PMSM). In this paper, Hamilton’s principle is employed to derive the mathematical model, which is a nonlinear differential equation, while Newton’s second law is utilized to derive the simple linear model. In system identification, we adopt the real-coded genetic algorithm (RGA) to find not only the parameters of the PPM, but also the PMSM simultaneously. From the identification simulations and experimental results, it is demonstrated that the identification results of the mathematical model present the better matching with the experimental results of the system. [Copyright &y& Elsevier]

Abstract: In this paper, we consider the classical mathematical model with saturation response of the infection rate and time delay. By stability analysis we obtain sufficient conditions for the global stability of the infection-free steady state and the permanence of the infected steady state. Numerical simulations are carried out to explain the mathematical conclusions. [Copyright &y& Elsevier]

Abstract: In the present paper the finite element method for the solution of the eigenvalue problems for piezoelectric bodies with voids is considered. The porosity change properties are taken into account according to Cowin–Nunziato model. The vector–matrix formulations of the modal piezoelectric problems for media with voids are given. The finite element approximations of the continual equations are carried out and the finite dimensional eigenvalue problems are obtained in the expanded and in the various reduced forms. Algorithmic features of the boundary conditions account for electrode surfaces and the surfaces contacting with rigid stamps are discussed. The finite element eigenvalue problems for practically important electric resonance and antiresonance frequencies are obtained. As a numerical example the focusing spherical ultrasonic piezoelectric emitter fulfilled from porous piezoceramics is considered. With the use of Cowin–Nunziato model the effective moduli of the porous piezoceramic material are defined precisely. The results, which we obtain, show a good optimal agreement with the experimental data. The resonant frequency behavior modelling for free and loaded on acoustic media piezoelectric transducer is realized. [Copyright &y& Elsevier]

Abstract: A diffused pneumatic silencer had been widely used in the pneumatic fields due to its small dimensions and high level of performance in noise reduction. A numerical simulation of its interior and exterior flow field was important for studying the gas flow in the silencer and the flow structure outside the silencer, as well as for understanding the mechanism of the silencer’s noise reduction. A porous media model and the Darcy–Forchheimer principle were used as the basic theoretical models in this paper. The unified governing equations were used here to describe the compressible flow in and out of the silencer. A robust numerical scheme was used to discritize the equations, and the TDBC (Time-dependent boundary conditions) was used to treat the non-reflecting boundaries. The detailed structures of the inner and outer flow fields of the diffused pneumatic silencer were obtained. The simulation results displayed the characteristics of the flow in the silencer. The nature of the flow outside the silencer, comparable with the experimental data, was also obtained. [Copyright &y& Elsevier]

Abstract: In grey prediction modeling, the more samples selected the more errors. This paper puts forward new explanations of “incomplete information and small sample” of grey systems and expands the suitable range of grey system theory. Based on the geometric sequence, it probes into the influence on the relative errors by selecting the different sample sizes. The research results indicate that to the non-negative increasing monotonous exponential sequence, the more samples selected, the more average relative errors. To the non-negative decreasing monotonous exponential sequence, a proper sample number exists that has the least average relative error. When the initial value of the sequence of raw data of new information GM(1,1) model changes, the development coefficient remains unchanged. The segmental correction new information GM(1,1) model (SNGM) can obviously improve the simulation accuracy. It puts forward the mathematic proofs that the small sample usually has more accuracy than the large sample when establishing GM(1,1) model in theory. [Copyright &y& Elsevier]

Abstract: In this paper, the problem of finding optimal paths in mobile ad hoc networks is addressed. More specifically, a novel bicriteria optimization model, which allows the energy consumption and the link stability of mobile nodes to be taken into account simultaneously, is presented. In order to evaluate the validity of the proposed model, a greedy approach is devised. Some preliminary computational experiments have been carried out, in a simulation environment. The numerical results are very encouraging, showing the correctness of the proposed model. Indeed, the selection of a shorter route leads to a more stable route, but to a greater energy consumption. On the other hand, if longer routes are selected the route fragility is increased, but the average energy consumption is reduced. [Copyright &y& Elsevier]

Abstract: In this paper, we study a discrete time Geom/Geom/1 queue with multiple working vacations. Using the quasi birth and death chain and matrix-geometric solution method, we give distributions for the number of customers in system and the waiting time of a customer and their stochastic decomposition structures, and obtain distributions of the additional number of customers and additional delay. Furthermore, we derive the formulae of expected regular busy period and expected busy cycle. Finally, by numerical examples, we analyze the effect of the parameters on the expected queue length and sojourn time. [Copyright &y& Elsevier]

Abstract: In this paper, we study the diffusive vector disease model with delay. This problem with strong biological background has attracted much research attention. We focus on the existence of traveling wave fronts, and find that there is a moving zone for the transition from the disease-free state to the infective state. To complete the theoretical analysis, we employ the mathematical tools including the monotone iteration technique as well as the upper and lower solution method. [Copyright &y& Elsevier]

Abstract: The pulp and paper industry plays an important role in European economies. The chemical reactions that transform wood chips in pulp occur mainly in a complex moving bed reactor, the digester. Nowadays the use of mathematical models to simulate the transient behaviour of the digester in terms of temperature and compound concentrations represents a real need for industry because it allows simulation of experiments that can not be afforded or that might be very risky. The digester – the most critical piece of the equipment of a pulp mill – is a heterogeneous reactor with an almost cylindrical shape, where wood chips react with an aqueous solution of sodium hydroxide and sodium sulfide, to remove the lignin from the cellulose fibers. From a mathematical point of view the dynamical behaviour of the reactor can be represented by a system of hyperbolic nonlinear partial differential equations. In this system, with 15 equations, we can identify three main types: the equations that describe the temperature and the concentration respectively of the solid, entrapped liquid and free liquid phase. Each of these type of equations present a certain complexity, its numerical simulation being a hard task. In this sense we point out the high nonlinearity of the functions that represent the chemical reactions; the discontinuities induced by the extraction and injection of the free liquor; the discontinuities in the convection velocity of the free liquor – positive where the liquid flown downwards and negative where the free liquid flows upwards. Numerical methods based on operator splitting, nonuniform refinement and some particular techniques to smooth discontinuities, are studied from a qualitative and quantitative viewpoint. Several simulations on temperature and concentrations of organic and inorganic compounds are presented. Special attention will be devoted to the effects induced in the process by discontinuities of wood chips composition. [Copyright &y& Elsevier]

Abstract: A simple analytical model for computing ground motion in a layered half-space due to a buried seismic source is presented in this paper. The buried earthquake source is represented as a distribution of double couples varying in time as a ramp function on the fault plane. The analysis is simplified by first decoupling the governing equations into P-SV and SH problem by a coordinate transformation in the frequency-wave number domain. These two problems are solved separately and the final solution is obtained by the sum of solutions of these individual problems. Explicit expressions for ground motion in a layered half-space due to an impulsive double couple are derived. In the sequel, Green’s function for the displacement field in an infinite medium is also presented. The developed source mechanism model is also demonstrated by simulating ground motion for the Kucth earthquake (M w =7.7) of 26th January 2001. [Copyright &y& Elsevier]

Abstract: Numerical simulation is a common approach to understand many phenomena, usually yielding a computationally intensive problem. To overcome insufficient computer capacity and computational speed, a grid computing environment is a suitable approach. In this paper we focus on the development of parallel algorithms to solve a 3D transport model in such a context. The solver is based on the multisplitting Newton method that provides a coarse-grained scheme. Algorithms are implemented using JACE, a grid-enabled Java Asynchronous Computing Environment. This programming environment allows users to design synchronous and asynchronous parallel iterative algorithms as well. Experiments are carried out on a heterogeneous grid environment in which the behaviour of both parallel iterative algorithms is analysed. The results allow us to draw some conclusions about the use of the programming library JACE and the design of parallel iterative algorithms in a grid computing environment. [Copyright &y& Elsevier]

Although several analytical models have been proposed in the literature for binary n-cubes with deterministic routing, most of them have not included the effects of virtual channel multiplexing on network performance. The only mathematical model for deterministic wormhole routing in hypercubes with virtual channels was proposed in [Y. Boura, Design and Analysis of Routing Schemes and Routers for Wormhole-routed Mesh Architectures, Ph.D. Thesis, Department of Computer Science and Engineering, Pennsylvania State University, 1995] which uses complex combinatorial analysis with a computation time of O(N=2n) for an n-dimensional hypercube. This paper proposes a new and simple analytical model to compute message latency in binary n-cubes with virtual channels. It is very simple and easy to understand which uses an average case analysis and requires a computation time of O(n) for an n-dimensional hypercube. Results from simulation experiments confirm that the proposed model exhibits a good degree of accuracy for various network sizes and under different operating conditions. [Copyright &y& Elsevier]

Abstract: This paper presents a discussion on a model for cover cracking due to corrosion expansion and uniform stress at infinity developed by Li et al. [Shu-cai Li, Ming-bin Wang, Shu-chen Li, Model for cover cracking due to corrosion expansion and uniform stresses at infinity, Appl. Math. Modell., doi:10.1016/j.apm.2007.06.003]. The model for cover cracking by the authors uses an equation of the penetration depth of corrosion with time developed from the Faraday’s Law. It is however shown in the discussion that the equation of the penetration depth due to corrosion developed by Li et al. is incorrect. Consequently other equations developed by Li et al. to model cover cracking that use the equation of penetration depth are also incorrect. [Copyright &y& Elsevier]