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Abstract: In this study, the determinability of time related colour changes in prints made using ink that dries on matte coated paper with the offset printing technique and infrared method, has been investigated with artifical neural networks after analysis of the experimental and numerical methods. In the experimental part a ECI 2002 CMYK test scale is printed on a 135g/m2 matte coated. The prints obtained were measured with a spectrophotometer at certain intervals and by converting the reflection data obtained into the CIELAB colour description spectrum, time related changes in printed colours have been determined. In the empirical study however, colour changes in prints made on matte coated paper using inks that dry with the infrared method are modelled numerically. The average deviation has been found to be 0.4%. As a result, artificial neural networks can be used with the aim to digitally calculate time related colour changes in the offset printing system. [Copyright &y& Elsevier]

In recent times, origami-inspired deployable structures have received significant interest from the research community as a major area of research in the fields of science and technology. This paper deals with the geometry and the deformation behavior of deployable cones based on the four-fold line origami concept. First, a novel geometric design algorithm is presented to develop axially foldable conical structures based on generalized Miura-ori pattern, which is then utilized to investigate the influence of four design parameters on folding geometry. The foldability of thus obtained origami patterns is verified with the help of physical models. The geometric incompatibilities during the deployment are highlighted using a simple experiment, showing the unfolding sequence of a paper model. The deformations due to incompatibilities are analyzed by adopting the concept of pin-jointed truss modeling of the origami structures. A mathematical model of the deployment problem is formulated to capture the deployment deformations of the structure, on the basis of which an algorithm for deformation analyses is developed. One example is considered to characterize the deformation behavior of the conical origami structures as the design parameters of the folding pattern are varied. The analytical findings demonstrate that the fold line strains of the origami cone are very sensitive to the changes in three design parameters, number of origami units (m), fold angle (α 0), and angle θ 2 ; except the length ratio (l r 0). The variation in design parameters may induce bi-stability in the deployment path of the conical structure. The findings of the analytical investigation are verified numerically, demonstrating that the strain responses obtained from the numerical analyses are completely consistent with the analytical results. [ABSTRACT FROM AUTHOR]

This paper presents a quasistatic problem of an elastic body in frictional contact with a moving foundation. The model takes into account wear of the contact surface of the body caused by the friction. We recall existence and uniqueness results obtained in Sofonea et al. (2017). The main aim of this paper is to present a fully discrete scheme for numerical approximation together with an error estimation of a solution to this problem. Finally, computational simulations are performed to illustrate the mathematical model. [ABSTRACT FROM AUTHOR]

Highlights • The mathematical model of corrugated shells with special shapes is presented. • Effect of corrugation parameters on critical load is investigated. • Linear and nonlinear buckling analyses are conducted. • Critical load of corrugated shells is compared to smooth ones. • Specific range of corrugation parameters significantly increase the value of relative critical load. Abstract The problem of elastic stability of the shells with special shapes with corrugated middle surfaces under external pressure is debated in the presented paper. Solution of the problem is based on FEM study. Corrugated barrelled, pseudo-barrelled, and cylindrical shells of constant mass are considered. Geometrical modification of the middle surface geometry is based on sine wave along principal directions. Middle surface of the corrugated shells are described referring to differential geometry of surfaces by parametric functions in three-dimensional Euclidean space. Linear and nonlinear buckling analyses are conducted. Examples of buckling modes are presented, which differ significantly from those typical for shells of revolution with positive or zero Gaussian curvature. It is proven that corrugation may lead to serious increase or decrease of critical load for all types of presented shells. [ABSTRACT FROM AUTHOR]

The nef cone volume appeared first in work of Peyre in a number-theoretic context on Fano varieties, and was then studied by Derenthal and co-authors in a series of papers on del Pezzo surfaces. The idea was subsequently extended to also measure the Zariski chambers of del Pezzo surfaces. We start in this paper to explore the possibility to use this attractive concept to effectively measure the size of the nef cone on algebraic surfaces in general. This provides an interesting way of measuring in how big a space an ample line bundle can be moved without destroying its positivity. We give here complete results for simple abelian surfaces that admit a principal polarization and for products of elliptic curves. [ABSTRACT FROM AUTHOR]

In order to make full use of the advantages of superheated steam (SHS), SHS injection in multi-point injection wells (MPIW) is proposed in this paper. Firstly, a mathematical model comprised of SHS flow model in inner tubing (IT) or long tubing (LT) and annulus, transient heat transfer model in oil layer is established. Secondly, type curves of SHS flow in MPIW is obtained by finite difference method on space and the iteration technique. Then, the effect of injection temperature on distributions of thermophysical properties of SHS in MPIW is discussed in detail. Results show that: (a) When the heat exchange between IT and annulus is taken into consideration. SHS temperature in IT has a decrease while SHS temperature in annulus has an increase. (b) With the help of MPIW, heating effect at both heel and toe points of the horizontal wellbores can be enhanced. (c) While the increase of SHS temperature certainly benefits the formation heating effect through the increase of both SHS temperature and superheat degree, the following decrease of SHS pressure in annulus will lead to the decrease of SHS absorption rate. This paper unravels some intrinsic flow characteristics of SHS in MPIW, which has a significant impact on the optimization of SHS injection parameters and analysis of heat transfer law in MPIW. [ABSTRACT FROM AUTHOR]

This paper describes Large Eddy Simulations of a turbulent premixed flame (the VOLVO rig) comparing Analytically Reduced Chemistry (ARC) with globally reduced chemistry for propane-air combustion, a dynamic Thickened Flame (TFLES) model with the usual non-dynamic TFLES model and a high-order Taylor Galerkin numerical scheme with a low-order Lax–Wendroff scheme. Comparisons with experimental data are presented for a stable case in terms of velocity and temperature fields. They show that going from two-step to ARC chemistry changes the flame stabilization zone. Compared to the usual non-dynamic TFLES model, the dynamic formulation allows to perform a parameter-free simulation. Finally, the order of accuracy of the numerical method is also found to play an important role. As a result, the high-order numerical method combined with the ARC chemistry and the dynamic TFLES model provides the best comparison with the experimental data. Since the VOLVO data base is used in various benchmarking exercises, this paper suggests that these three elements (precise chemistry description, dynamic parameter-free turbulent combustion model and high-order numerical methods) play important roles and must be considered carefully in any LES approach . [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 industrial applications, most of fluids have non-Newtonian fluid characteristics. It is of great significance to the economic development and energy consumption reduction to study the heat transfer of non-Newtonian power law fluid. In this paper, the heat transfer of non-Newtonian power law fluid in pipes with different cross sections are studied. The mathematical model and physical model of the non-Newtonian fluid are briefly introduced first, and the physical model is divided by the structured mesh. Then the numerical simulation of the laminar heat transfer of non-Newtonian fluid in different cross sections is carried out. On the basis of discussing the distribution of temperature field, many parameters which have influenced on the temperature field and the heat transfer is analyzed in this paper, such as tube shape, the power-law index ( n ) the Peclet number ( Pe ) and so on. The results show that the heat transfer characteristics of non-Newtonian fluid are related to the parameters we mentioned. [ABSTRACT FROM AUTHOR]

A biofilm is usually defined as a layer of bacterial cells anchored to a surface. These cells are embedded into a polymer matrix that keeps them attached to each other and to a solid surface. Among a large variety of biofilms, in this paper we consider batch cultures. The mathematical model is formulated in terms of a quasilinear system of diffusion- reaction equations for biomass and nutrients concentrations, which exhibits possible degeneracy and singularities in the nonlinear diffusion coefficient. In the present paper, we propose a set of efficient numerical methods that speeds up the solution of the model. Mainly, Crank-Nicolson finite differences techniques for discretisation are combined with a Newton algorithm for the nonlinearities. Moreover, some numerical examples show the expected behaviour of the biomass and nutrients concentrations and also clearly illustrate some theoretically proved qualitative properties related to exponential decays or convergence to a critical biomass concentration depending on the values of the model parameters. [ABSTRACT FROM AUTHOR]

In this paper, we consider the Kirchhoff type problem with radial potentials and locally L i p s c h i t z functional and there is no subcritical growth and no Ambrosetti–Rabinowitz type condition. This is in contrast with some recent papers concerning similar problems. [ABSTRACT FROM AUTHOR]

Crowd induced dynamic loading in large structures, such as gymnasiums or stadiums, is usually modelled as a series of harmonic loads which are defined in terms of their Fourier coefficients. Different values of these Fourier coefficients that were obtained from full scale measurements can be found in codes. Recently, an alternative has been proposed, based on random generation of load time histories that take into account phase lags among individuals inside the crowd. This paper presents the results of some studies carried out in order to compare the existing load models used to simulate periodic jumpings and develop a new load model. Generally the testing is performed on platforms or structures that can be considered rigid because their natural frequencies are higher than the excitation frequencies associated with crowd loading. But in this paper, to validate these load models test have been performed on a structure designed to be a gymnasium, which has natural frequencies within that range. Test results have been compared with predictions based on the load modelling alternatives with quite good agreement. A calibrated finite element model of the structure has been used for this purpose. The new model provides a clear improvement in the energy contained within higher frequencies. [ABSTRACT FROM AUTHOR]

Tumor growth models have proved as an important tool to produce an engineering background for cancer therapy either by designing therapeutic procedures combined with control engineering or by using the models for simulations and evaluation of treatment procedures. Mathematical modeling has been critical for the description of tumor growth, which is a highly complex process, as a finely chiseled tumor growth model always outlines the measurements and the physiological processes of the tumors. Therefore, a mathematical model involving partial differential equations for the growth of tumor have been studied, modified and developed in this paper. It is based on the deterministic model of an avascular tumor growth which is framed in a system of nonlinear coupled PDEs, describing the proliferating, quiescent, necrotic, and surrounding cells densities, accompanied by a supply of the nutrients. These equations are explained numerically by the Finite Difference Method. Furthermore, the simulations are carried out by introducing the Gompertz growth rate function for mitosis rate function g(c) of proliferating cells in the model. The discretization forms a system of coupled nonlinear difference equations which are solved at each iteration. The algorithm is implemented sequentially in MATLAB 2018a and numerical results suggest that the employed model is an authentic tool for analyzing the dynamics of tumor. [ABSTRACT FROM AUTHOR]

The paper presents two Direct Numerical Simulations of bubble swarms in a vertical turbulent channel flow and is intended as a complement to the companion paper, Santarelli and Fröhlich (2015). Both swarms addressed here are composed of spherical bubbles in contaminated fluid with a void fraction of 2.14%, as for the reference case in the companion paper. The first simulation reported is done for a monodisperse swarm of larger bubbles while in the second case a bidisperse swarm is considered. The influence of the bubble size and of the bidispersity is investigated by means of flow visualizations and quantitative statistical analysis. Due to the higher Reynolds number, the behavior of the larger bubbles differs from the one of the small bubbles and this impacts the turbulence of the carrier phase. The results show that for the parameter range considered both swarms induce elongated flow structures in the streamwise direction and that the liquid turbulence is enhanced by the bubbles, as quantified by the budget of the turbulence kinetic energy. In both cases the tendency of bubbles to align horizontally is confirmed while the analysis of mixed pairs in the bidisperse swarm allows elucidating the complex interaction of bubbles of different size. [ABSTRACT FROM AUTHOR]

The higher-order gradient plasticity theory is successful in explaining the size effects encountered at the micron and submicron length scale. Due to the incorporation of spatial gradients of one or more internal variables in these theories and the associated non-classical boundary conditions, special types of elements in the finite element method maybe necessary. This makes the numerical implementation of this higher-order theory not straightforward. In this paper, a robust but straightforward numerical implementation of higher-order gradient-dependent plasticity theories is presented. The novelty of this paper is in (1) the application of the meshless methods, particularly the moving weighted least square method, combined with the finite element method for the numerical computation of plastic strain gradients, and (2) the numerical implementation of different types of higher-order microscopic boundary conditions at internal/external surfaces, interfaces, and moving elastic–plastic boundaries. The proposed numerical implementation algorithms can be easily adapted in the implementation of any form of higher-order gradient-dependent constitutive models. Examples of applying the current numerical approach is demonstrated for capturing mesh-objective shear band formation and size effect and boundary layer formation in thin films on elastic substrates and metal matrix composites with embedded elastic inclusions through the consideration of stiff, intermediate, and soft interfaces. [ABSTRACT FROM AUTHOR]

Entrainment of bottom material has a substantial influence on the dynamics of slope flows such as snow avalanches and debris flows, and should therefore be taken into account by mathematical models. An approach based on the assumption that the entrainment takes place when the bed shear stress is equal to the shear strength of the bottom material was proposed by Issler and Pastor Pérez (2011). In this paper, this approach is applied to model laminar flows of Bingham and Herschel–Bulkley fluids as well as turbulent flows with entrainment. Full (not depth-averaged) equations are used to calculate the flow parameters including the shear stress at the bottom, the velocity profile and the flow depth variation with time due to entrainment. The paper focuses on studying of qualitative features of motion with basal entrainment. Modeling of real flows from start to stop is not considered here. It is shown that in entraining flows moving down long constant slopes the flow velocity increases. The velocity profiles in laminar flows described by Bingham and Herschel–Bulkley models at large time become almost linear except in a relatively narrow layer near the upper flow surface and the entrainment rate tends to a constant value. This value depends on the coefficients describing the flow material properties, the shear strength of the bottom material, and the slope angle. Asymptotic formulae for the entrainment rate and the shear rate in the linear part of the velocity profile are derived analytically and confirmed by numerical calculations. [ABSTRACT FROM AUTHOR]

Pressure cartridge type separation devices which are widely used in fairing, stage separations of space launch systems, and many other aerospace fields generate much lower pyroshock and produce no high-speed debris compared to frangible explosive separation devices. However, because the operation is completed in a few milliseconds and the releasing mechanism is complicated, their separation behavior is difficult to experimentally identify. This paper presents a mathematical model to simulate the separation behaviors for a split-type separation bolt, one of the pressure cartridge type separation devices. The mathematical model includes a combustion model, buckling resisting model, split behavior model related to static and dynamic friction, O-ring friction model, contact force model, and slip angle model. Each composing models are obtained by mathematical formulation or numerical analysis. An efficient contact model is constructed by using virtual penetration model appropriately for complex contact phenomenon. To validate the established model, separation experiments were performed; the results are then compared with the mathematical model. Present study show that complex mechanical behaviors coupled with combustion of solid propellant charge can be efficiently simulated by the mathematical model. • Established a mathematical model for a low-shock separation device using pressure cartridge. • Analyzed complicated separation behavior of the low-shock separation device. • Simulation results were well compared with separation experimental results. [ABSTRACT FROM AUTHOR]

This paper presents an analytical solution for the analysis of axially-loaded compressible floating piles embedded in a homogeneous elastic soil layer of finite thickness. The mathematical model is based on a Tajimi-type elastic continuum formulation, that allows deriving an accurate closed-form expression for the frictional stresses developing at the soil-pile interface. The pile and its underlying soil column are considered as one-dimensional axially deforming rods, and solution of their governing equations leads to closed-form expressions for pile and soil displacements and stresses. The proposed model provides results of similar accuracy to boundary integral solutions for the special case of floating piles in elastic half-space, and to numerical analyses for the general problem of floating piles embedded in a layer of finite thickness. As such, the model is used to prepare charts for the settlement analysis of floating piles in practice, based on a parametric analysis that unveils the sensitivity of the axial response of floating piles to the different problem parameters. [ABSTRACT FROM AUTHOR]

Numerical back analysis based on incomplete in situ stress measurements is widely used to estimate the three-dimensional (3D) in situ stress fields of large deep underground caverns. However, the variable collinearity caused by complex geological environments has rarely been considered. This paper proposes a numerical back analysis method for 3D in situ stress fields based on stepwise regression (BSSR). In BSSR, the collinearity between independent variables is associated with the surface topography, and insignificant variables caused by variable collinearity are eliminated through stepwise regression. BSSR was applied to the underground powerhouse of a hydropower station for validation, and the results showed that it can reliably estimate the 3D in situ stress field despite the complex geological environments. Multidimensional mathematical models of in situ stress fields were established with the improved predictive ability and clear physical meaning, which can quantify the contributions of six geological actions and three stress sources. The findings of this study can help with understanding the formation mechanism of in situ stress fields for large, deep underground caverns in complex geological environments and provide a useful reference for optimizing excavation schemes and support designs. [ABSTRACT FROM AUTHOR]

This paper introduces the principle of Ingested Debris Monitoring System in aero-engine and establishes a mathematical model of its core component, the ring-like probe; this paper simulates foreign object's movement based on the established model and performs numerical analysis of the induced charge pulse waveform. Pulse amplitude and pulse width are used as the two pulse features of pulse waveform. Numerical analysis gets the relationship between pulse features and foreign object's charge amount, velocity and radial position. A new method for estimating foreign object's radial position and charge amount has been proposed based on the conclusion of numerical analysis. Both the correctness of numerical analysis and the new estimating method has been verified in the oil calibration test rig. All the relative errors are within 10%. Further experiments with high velocity condition are carried out in an air-gun test rig. The occurrence time, radial position, charge amount, velocity and material category of foreign object can all be obtained, which has important significance to the safety of aero-engines. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we have considered a mathematical model of commensalism between two species (S 1 and S 2) with a limited resource of food, in addition the paper also highlights how the commensal and host species are harvested. The model is characterized by a couple of first order non-linear differential equations. Here, the stable equilibrium point is identified and its stability (both local and global) criteria are discussed (both analytical and numerical). An optimal harvesting strategy is being conversed using Pontriyagin’s maximum principle. We have explored the stochastic stability by finding the corresponding variances. Finally numerical simulations illustrate the effectiveness of our results. [Copyright &y& Elsevier]

Abstract: This paper proposes a methodology to help decision makers in deciding where to invest in order to improve systems usability. The methodology consists of a multicriteria analysis based on the use of the Choquet Integral. Alternatives and criteria to determine the usability of a product are approached in this paper relying on previous results by one of the authors and her collaborators. The alternatives are constructs related to each of the following metrics: Ease of learning; Ease of remembering; Error control; Efficiency; Effectiveness; and Satisfaction. The criteria are five and their valuations range from total disatisfaction to total satisfaction of users.The case study of the intranet of a Brazilian university illustrates the application of the proposed methodology. For this case study data on users’ preferences are surveyed. The resulting figures point out which are the most impacting metrics for the university's intranet system. Computations by using the Choquet Integral lead to the most relevant constructs (i.e., alternatives) that minimize the costs to improve the usability of the system. The paper closes with indications of the most important constructs for some major metrics. [Copyright &y& Elsevier]

Abstract: Fluid or mean-field methods are approximate analytical techniques which have proven effective in tackling the infamous state-space explosion problem which typically arises when modelling large-scale concurrent systems based on interleaving semantics. These methods are particularly suitable in situations which present large populations of simple interacting objects characterised by small local state spaces, since they require the analysis of a problem which is insensitive to the population sizes but is dependent only on the size of the local state spaces. This paper studies the case when the replicated objects are best described as composites which consist of smaller simple objects. A congenial formal modelling framework for situations of this kind may be given by stochastic process algebra. Using PEPA as a representative case, we find that fluid models with replicated copies of composite processes do not scale well with increasing population sizes, thus rendering intractable the analysis of the underlying system of ordinary differential equations (ODEs). We call this problem continuous state-space explosion, by analogy with its counterpart phenomenon in discrete state spaces. The main contribution of this paper is a result of equivalence that simplifies, in an exact way, the potentially massive ODE system arising in those circumstances to one whose size is independent from all the multiplicities in the model. As a byproduct, we find that these simplified ODEs turn out to characterise the fluid behaviour of a family of PEPA models whose elements cannot be related to each other through any known equivalence relation. A substantial numerical assessment investigates the relationship between the different underlying Markov chains and their unique fluid limit, demonstrating its generally good accuracy for all practical purposes. [Copyright &y& Elsevier]

Abstract: In several recent investigations dealing with the economic order quantity with permissible delay in payments, the following assumptions are made: (A) The supplier always offers the retailer fully permissible delay in payments independent of the order quantity. (B) The annual interest which is charged per dollar in stocks by the supplier is higher than the annual interest earned on investment per dollar. (C) The unit purchase cost c is the same as the selling price s per unit. Huang [1] generalizes the concept of fully permissible delay in payments by advocating that the supplier would offer the retailer partially permissible delay in payments where the order quantity is smaller than a predetermined quantity to relax the assumption (A). Motivated essentially by Huang’s work [1], the main purpose of this paper is twofold as stated below: (P1) This paper will extend Huang’s work [1] by establishing new inventory models without having the assumptions (B) and (C) to match the real world situation. (P2) This paper will present new solution procedures different from those of Huang [1]. Among other things, these new solution procedures will show that those of Huang [1] will cause misuses under some circumstances. Several numerical examples illustrate the fact that the percentages of the cost penalty (PCP) of misuses are terribly high in some cases. [Copyright &y& Elsevier]

Abstract: The aim of the paper is the description of fractional-order differential equations in terms of exact mechanical models. This result will be archived, in the paper, for the case of linear multiphase fractional hereditariness involving linear combinations of power-laws in relaxation/creep functions. The mechanical model corresponding to fractional-order differential equations is the extension of a recently introduced exact mechanical representation (Di Paola and Zingales (2012) [33] and Di Paola et al. (2012) [34]) of fractional-order integrals and derivatives. Some numerical applications have been reported in the paper to assess the capabilities of the model in terms of a peculiar arrangement of linear springs and dashpots. [Copyright &y& Elsevier]

Abstract: This paper presents an innovative hybrid analytic-numerical approach to modelling species transport in fuel cells suitable for application on the system level. The core principle of this modelling approach is taking 1D numerical model for gas-flow and superimposing onto it a 2D analytic solution for concentration distribution in the plane perpendicular to the gas-flow together giving a 3D information on species concentration in the fuel cell. A hybrid analytic numerical model of a simple geometry isothermal fuel cell is presented and comparatively evaluated by benchmarking it against a professional full 3D CFD simulation tool. This evaluation shows very close agreement with the benchmarking 3D CFD simulation and computational times comparable to 1D models. This computational efficiency originates in the model''s analytic nature in the other two dimensions making it suitable for system level application. The paper features an extensive appendix with a comprehensive detailed mathematical derivation of the hybrid analytic-numerical model. [Copyright &y& Elsevier]

Abstract: In air-conditioning field, a dehumidification has become increasingly important for human health and comfort especially in hot and humid climates. However, a conventional mechanical dehumidification with a vapor compression refrigerator has some problems. Therefore, much attention has been paid recently to a desiccant air-conditioning system as an alternative to the conventional system. In this paper, we focus on a rotary desiccant wheel which is the main component of the desiccant air-conditioning system and develop and validate the mathematical model by comparison with experimental results. The validation is conducted under various operating conditions. The mathematical model discussed in this paper includes, for example, the entrance region effect in air channel, detailed diffusion phenomenon in porous solid. In experiments, effects of the regeneration air temperature, air superficial velocity, wheel thickness and wheel rotational speed on the desiccant wheel performance are investigated. In addition, the temperature and humidity distribution at the outlet of the desiccant wheel are measured. As a result, an average relative error between the predicted and the measured humidity ratio difference distribution is 3.3% and temperature difference distribution 10.8%. Moreover, the effect of the regeneration air inlet temperature, the air superficial velocity, wheel thickness and wheel rotational speed on the desiccant wheel performance are clarified and the predicted results are totally in good agreement with the measured results. [Copyright &y& Elsevier]

Abstract: The purpose of this paper is to obtain the risk-neutral drift of the state variables directly from market data in a multifactor commodity futures model. Note that the risk-neutral drift is a key factor in the general asset pricing theory but it is not observable. In this paper, we derive some exact results which relate the risk-neutral drifts to the slope of the commodity futures price jointly with the factors. This fact allows us to estimate some of the coefficients of the pricing partial differential equation directly from the futures data available in the markets. Moreover, we do not have to estimate either the physical drift or the market price of risk. Therefore we considerably reduce the number of functions to estimate and, as a consequence, we reduce the computational cost as well as the misspecification error. In order to investigate the finite sample properties of this approach we carry out some numerical experiments. Finally, an application to crude oil and natural gas futures contracts traded at the New York Mercantile Exchange (NYMEX) is also illustrated. [Copyright &y& Elsevier]

Abstract: This paper is a consequence for a paper of Lin et al. [S.W. Lin, Y.W. Wou, P. Julian, Note on minimax distribution free procedure for integrated inventory model with defective goods and stochastic lead time demand, Appl. Math. Model. 35 (2011) 2087–2093]. We simplified their complicated solution procedure and then presented a revision to patch their negligence for the boundary minimums. Numerical examples are provided to demonstrate our findings. [Copyright &y& Elsevier]

Abstract: This paper addresses dynamic cell formation problem (DCFP) via a new bi-objective mathematical formulation. Although literature body of DCFP includes a vast number of research instances, human-related issues are mostly neglected as an important aspect of DCFP in the corresponding literature. In this paper, the first objective function seeks to minimize relevant costs of the problem including machine procurement and relocation costs, machine variable cost, inter-cell movement and intra-cell movement costs, overtime cost and labor shifting cost between cells, while labor utilization of the modeled DCFP is maximized through the second objective function. Due to NP-hardness of DCFP, an ant colony optimization (ACO) meta-heuristic is developed for the first time in the literature to tackle the problem. Also, authors enhance diversification of the developed algorithm is enhanced by hybridization of the proposed ACO algorithm with a genetic one. Finally, some numerical samples are generated randomly to validate the proposed model by which strengths of the developed algorithm is shown. [Copyright &y& Elsevier]

Abstract: The objective of this paper was to present a comprehensive analysis including analytical and numerical models which were developed to predict the performance of a solar chimney power plant in Kerman, Iran. The numerical model results including air temperature, velocity and electrical power output were validated by comparing with experimental data of the Manzanares prototype power plant. Also the mathematical model was verified with the practical power output of the Kerman pilot plant. Also in this paper, a novel approach to evaluate the influence of the site altitude on the potential of solar chimney power plants was presented and thereby a coefficient called altitude effectiveness was defined using Manzanares prototype geometrical parameters in different site altitudes. The developed model was applied to improve the performance of a solar chimney pilot power plant built in Kerman, Iran. Based on an approximate cost model, the thermo-economic optimal configurations of the pilot power plant were illustrated; and also it was found that the chimney diameter was the most important structural dimension to improve the performance of this pilot power plant. [Copyright &y& Elsevier]

Abstract: This paper focuses on two major issues in cellular manufacturing, namely manpower allocation and cell loading. Although significant work has been done in both of these fields, research to minimize the Total Tardiness (TT) within a multi-cell environment has been limited. The methodology adopted in this paper is a two-step one. First, manpower allocation for operations within a cell is determined using mathematical models. This step also includes variations of the mathematical model for sharing of operators between operations and sharing of operators with restrictions. The models with little or no restrictions have found to yield a higher production rate than the model with no operator sharing allowed. The next step involves a mathematical model for cell loading. The performance measure examined in this phase is the total tardiness subject to total Crew Size restriction. The total tardiness is reduced as the total crew size increases. However, it was also found that selection of alternative cell configurations affect the results as well total crew size. [Copyright &y& Elsevier]

Abstract: TOPSIS (technique for order preference by similarity to ideal solution) is a multiple criteria method to identify solutions from a finite set of alternatives based upon simultaneous minimization of distance from an ideal point and maximization of distance from a nadir point. This paper proposes a fuzzy TOPSIS algorithm to solve bi-level multi-objective decision-making (BL-MODM) problems, and in which the objective function at each level are non-linear functions which are to be maximized. The proposed model for getting the satisfactory solution of the BL-MODM problems includes the membership functions for the upper level decision variables vector with possible tolerances, the membership function of the distance function from the positive ideal solution (PIS) and the membership function of the distance function from the negative ideal solution (NIS). A numerical illustrative example is given to clarify the proposed TOPSIS approach of this paper. [Copyright &y& Elsevier]

Abstract: In this paper we present an extension of the Gurson model of cavity growth which includes the void size effect. To this end, we perform the limit analysis of a hollow sphere made up of a Fleck and Hutchinson’s strain gradient plasticity material. Based on the trial velocity field of Gurson, we derive an approximate closed form expression of the macroscopic criterion. The latter incorporates the void size dependency through a non dimensional parameter defined as the ratio of the cavity radius and the intrinsic length of the plastic solid. The accuracy of this approximate criterion is demonstrated by its comparison with numerical data. In the last part of the paper we present a complete plasticity model involving the damage rate and a power-law strain hardening of the matrix. It is shown that the cavity size effect has a strong dependency on damage growth as well as on the stress strain response. [Copyright &y& Elsevier]

Abstract: In this paper, it is proposed a new model of the behavior of elements of arbitrary aspect ratio. The model allows for the analysis of large and complex structures and it is based on concepts of classic fracture mechanics and continuum damage mechanics. The model considers independent variables that measure the degree of shear and flexural damage separately. This paper also presents an experimental analysis of the behavior of RC elements with the use of digital image correlation technique which allows for the classification and quantification of the different failure mechanisms in a much better way than the classic procedures. [Copyright &y& Elsevier]

Abstract: Recently, exploiting the centroids of stability regions (admissible regions) to be used in tuning two-parameter controllers has been considered as an approach to obtain non-fragile two-parameter controllers. Such an approach can be extended for three-dimensional stability spaces (admissible spaces) by considering the center of mass of these spaces in tuning three-parameter controllers. In this paper, the mentioned approach is used to tune PID controllers for controlling integrator plus dead-time (IPDT) and first order plus dead-time (FOPDT) processes. It is shown that the tuning method resulted from this approach is very similar to the Ziegler–Nichols step response tuning method. Consequently, this paper presents an analytic non-fragility justification for the mentioned tuning method. [Copyright &y& Elsevier]

Abstract: In this paper, we present a survivability evaluation model and analyze the performance of Wireless Sensor Networks (WSNs) under attack and key compromise. First, we present a survivability evaluation model of WSNs by representing the states of WSNs under attack. Here, the survivability of WSNs is expressed as a continuous time Markov Chain to describe the status of real WSNs. We propose a threshold condition to trigger the transition between the states of WSNs in the face of DoS attack. According to the threshold conditions, the survivability model is capable of taking action(s) and enables the formalization of the effect of action(s). We present an analytical model and numerical analysis to show the feasibility of our work in terms of availability, survivability, and cost. Second, we present a survivability model and evaluation of WSNs under key compromise. Sensor nodes in a network can be captured by an adversary. The compromised node can be identified by one of the intrusion detection mechanisms. After detecting the compromised node, the key in the node has to be revoked. In this paper, we present the effect of key compromise and key revocation in WSNs. We additionally present a survivability evaluation model using the SHARPE simulation tool in terms of availability. [Copyright &y& Elsevier]

Abstract: A theoretical model is developed for the exact contact analysis of magneto-electro-elastic half-plane materials indented by a moving rigid punch in this paper, which is Part I of a series of papers. A numerical analysis based on this theoretical model will be presented in Part II. The Galilean transformation and the Fourier sine and cosine transforms are applied to make the transient problem tractable. Detailed analyses of the eigenvalue distributions of the double-biquadrate order characteristic equation related to the magneto-electro-elastic governing equations are performed. Real fundamental solutions are derived for each eigenvalue distribution. The punch may have a flat or cylindrical profile and may be electrically and magnetically conducting, electrically conducting and magnetically insulating, electrically insulating and magnetically conducting, or electrically and magnetically insulating. For each type of punch, the singular integral equations are derived with the surface contact stress, surface electric charge, and/or surface magnetic induction inside the contact region as the unknown functions. Exact solutions to the system of integral equations are obtained. In particular, closed-form expressions for the stresses, electric displacements, and magnetic inductions in terms of fundamental functions are derived, which provide a scientific basis for the interpretation of the contact behaviors of multiferroic materials as will be shown in Part II of this series of papers. [Copyright &y& Elsevier]

Abstract: This paper presents experimental and numerical studies on periodic convection flow and heat transfer in a lid-driven arc-shape cavity with temperature differential. Three cases were considered: Gr=2×105, 5×105 and 1.2×106 at Re=100 (Gr = Grashof number; Re = Reynolds number). The mathematical model was proposed in our previous study. The current study performs an experiment to validate this model, to corroborate the existence of the periodic flow, and to more deeply probe the internal flow and temperature characteristics. The experimental setup primarily comprised an arc-shape cavity, a moving lid, a thermo-system, a smoke generator and an image acquisition system. The periodic convection flow in the cavity was visualized using kerosene smoke. The numerical and experimental results consistently reveal that the periodic flow pattern was observed in the case with Gr=5×105, whereas the steady-state flow pattern took place in the other two cases (Gr=2×105 and Gr=1.2×106). The numerical simulation produced reasonable and satisfactory agreement with the experiment for the periodic flow pattern and period. The difference between the predicted and measured periods is less than 5%. The transport properties, such as average kinetic energy, overall Nusselt number, stream function, phase space trajectory, local kinetic energy, velocity history and temperature distribution, were further analyzed and discussed in this paper. The proposed numerical simulation not only confirms the experimental observation, but also enhances the understanding of periodic convection in an arc-shape cavity subjected to a moving lid and temperature differential. [Copyright &y& Elsevier]

Abstract: In this paper, we introduce and consider a new class of equilibrium variational inequalities, called the mixed general equilibrium bifunction variational inequalities. We suggest and analyze some proximal methods for solving mixed general equilibrium bifunction variational inequalities using the auxiliary principle technique. Convergence of these methods is considered under some mild suitable conditions. Several cases are also discussed. Results in this paper include some new and known results as special cases. [Copyright &y& Elsevier]

Abstract: In this paper, we generalize the integer-order cable model of the neuron system into the fractional-order domain, where the long memory dependence of the fractional derivative can be a better fit for the neuron response. Furthermore, the chaotic synchronization with a gap junction of two or multi-coupled-neurons of fractional-order are discussed. The circuit model, fractional-order state equations and the numerical technique are introduced in this paper for individual and multiple coupled neuron systems with different fractional-orders. Various examples are introduced with different fractional orders using the non-standard finite difference scheme together with the Grünwald–Letnikov discretization process which is easily implemented and reliably accurate. [Copyright &y& Elsevier]

Abstract: This paper details the design of a new metallic cable-joining clip for slope stabilization nets. The main objective of this research paper is to numerically and experimentally analyze the resistance capacity of a new clip model for cables with diameters of 8 and 10mm. Firstly, laboratory tests are performed on the clip and the cable. Then, the clip performance during opening and displacement tests is simulated through a nonlinear finite element model. In the simulation, the different geometrical shapes are included, taking into account plasticity, large displacements and frictional contacts between cable and clip. Thirdly, an optimization is carried out based on a design-of-experiments (DOEs) statistical technique, with the aim of adjusting the mathematical model to the experimental results and examining the influence of the most important parameters. With this method, good results in terms of deformation and resistance have been obtained with the numerical and experimental models. This analogy helps to extrapolate the results to other non-tested clips that share a basic group of constant parameters. Finally, the most relevant conclusions as well as future lines of research are presented. [Copyright &y& Elsevier]

Abstract: Design, implementation and operation of solar thermal electricity plants are no more an academic task, rather they have become a necessity. In this paper, we work with power industries to formulate a multi-objective optimization model and attempt to solve the resulting problem using classical as well as evolutionary optimization techniques. On a set of four objectives having complex trade-offs, our proposed procedure first finds a set of trade-off solutions showing the entire range of optimal solutions. Thereafter, the evolutionary optimization procedure is combined with a multiple criterion decision making (MCDM) approach to focus on preferred regions of the trade-off frontier. Obtained solutions are compared with a classical generating method. Eventually, a decision-maker is involved in the process and a single preferred solution is obtained in a systematic manner. Starting with generating a wide spectrum of trade-off solutions to have a global understanding of feasible solutions, then concentrating on specific preferred regions for having a more detailed understanding of preferred solutions, and then zeroing on a single preferred solution with the help of a decision-maker demonstrates the use of multi-objective optimization and decision making methodologies in practice. As a by-product, useful properties among decision variables that are common to the obtained solutions are gathered as vital knowledge for the problem. The procedures used in this paper are ready to be used to other similar real-world problem solving tasks. [Copyright &y& Elsevier]

Abstract: This paper presents a novel approach to model the transient behavior of solid-oxide fuel cell (SOFC) stacks in two and three dimensions. A hierarchical model is developed by decoupling the temperature of the solid phase from the fluid phase. The solution of the temperature field is considered as an elliptic problem, while each channel within the stack is modeled as a marching problem. This paper presents the numerical model and cluster algorithm for coupling between the solid phase and fluid phase. For demonstration purposes, results are presented for a stack operated on pre-reformed hydrocarbon fuel. Transient response to load changes is studied by introducing step changes in cell potential and current. Furthermore, the effect of boundary conditions and stack materials on response time and internal temperature distribution is investigated. [Copyright &y& Elsevier]

Abstract: This paper concerns with meso-scale finite element (FE) modeling of asphalt mixtures. The proposed FE model is capable of simulating the complex geometry of several types of asphalt mixture in which different gradations of aggregates could be properly modeled. The meso-structure of the mixture is constructed by a novel technique identified in this paper. The main idea of such technique is that the aggregate particles could be randomly packed together into the simulation region, by defining a kind of artificial interaction forces among the particles. After that by the Voronoi tessellation method, the set of the generated discrete grains will alter to space-filling, adjoining polyhedrons with respect to the real geometry so that it were possible to investigate the behavior of mixture by finite element method. Such a model considers the main components of the asphalt mixture consisting of aggregate particles, mastic, interfacial zone and air voids. Moreover, different moving wheel loads with different passing velocities are considered and their effects on the mechanical responses of the asphalt mixture are examined. The FE model gives some better insights into the behavior of mixture''s components under moving loads. The responses include vertical displacement of the pavement surface as well as the development of stress in mixture components. The proposed models give results that are in agreement with theoretical predictions and previous studies. [Copyright &y& Elsevier]

Abstract: Offshore foundations are subject to combinations of vertical, horizontal and moment (VHM) loading. Different foundation solutions are appropriate, depending amongst others, on the expected load combinations. This paper investigates in detail the soil failure mechanisms and resulting foundation capacity under undrained VHM loading of a hybrid foundation concept. Comprising of a skirted mat combined with an internal caisson compartment, this foundation design is found to provide significantly increased horizontal capacity that is often critical in offshore applications, with key influences for increased moment capacity identified as well. The numerical study investigated both variations in the geometry of the internal caisson compartment and the soil shear strength profile. The paper concludes by proposing expressions that allow slightly conservative prediction of the combined capacity of a hybrid foundation. [Copyright &y& Elsevier]

Abstract: In this paper, we present within the finite element context the numerical algorithm for the integration of the thermodynamically consistent thermo-viscoelastic, thermo-viscoplastic, thermo-viscodamage, and thermo-healing constitutive equations derived in the first part of this paper. The nonlinear viscoelastic model is implemented using a recursive-iterative algorithm, whereas an extension of the classical rate-independent return mapping algorithm to the rate-dependent problems is used for numerical implementation of the viscoplasticity model. Moreover, the healing natural configuration along with the power transformation equivalence hypothesis, proposed in the first part of the paper, are used for the implementation of the viscodamage and micro-damage healing models. Hence, the thermo-viscoelastic and thermo-viscoplastic models are also implemented in the healing configuration. These numerical algorithms are implemented in the well-known finite element code Abaqus via the user material subroutine UMAT. A systematic procedure for identification of model parameters is presented. The model is then used to simulate the time-, temperature-, and rate-dependent response of asphalt concrete over an extensive set of experimental measurements including creep-recovery, creep, triaxial, constant strain rate, and repeated creep-recovery tests in both tension and compression. Comparisons of the model predictions and the experimental measurements show that the model is capable of predicting the nonlinear behavior of asphalt concrete subjected to different loading conditions. [Copyright &y& Elsevier]

Abstract: This paper concerns the mathematical and numerical modeling of solidification process of pure metals. Such process takes place without development of “mushy zone”, which very often occurs during solidification of alloys. The model is based on the finite element method (FEM) and takes into account the existence of a sharp solidification front which moves according to time. The paper discusses how to include the conditions of continuity on the moving interface as well as the technique of front tracking based on the level set method (LSM). The paper also presents the results of computer simulations of the solidification process of pure copper. Two in-home solvers for one- and two-dimensional problems were built. Both of them are based on FEM. The correctness of the front tracking technique was checked by comparing the results obtained from 2D simulation to 1D simulation. Furthermore, the final calculation process was done for the two-dimensional area at different temperatures on the boundaries to demonstrate the effectiveness of the solver for a complex shape of the solidification front. [Copyright &y& Elsevier]

Abstract: In this paper, least-cost minimum spanning tree (LC-MST) problem is defined as a method to construct a minimum cost spanning tree that has the least-cost edges in the network by using the distance (cost) matrix. The paper presents a new algorithm based on the distance matrix to solve the LC-MST problem. The studied cases show that the presented algorithm is efficient to solve the LC-MST problem in less time. Also, the presented algorithm can be modified to solve the DC-MST (Delay Constrained-Minimum Spanning Tree) problem presented by Lee and Atiquzzaman (2007) and the MRCT (Minimum Routing Cost Tree) problem presented by Cambos and Ricardo (2008), given as the applications of the presented algorithm. [Copyright &y& Elsevier]

Abstract: In this paper, we analyze a multirate time integration method for systems of ordinary differential equations that present significantly different scales within the components of the model. The main purpose of this paper is to present a hybrid a priori –a posteriori error analysis that accounts for the effects of projections between the coarse and fine scale discretizations, the use of only a finite number of iterations in the iterative solution of the discrete equations, the numerical error arising in the solution of each component, and the effects on stability arising from the multirate solution. The hybrid estimate has the form of a computable a posteriori leading order expression and a provably-higher order a priori expression. We support this estimate by an a priori convergence analysis. We present several examples illustrating the accuracy of multirate integration schemes and the accuracy of the a posteriori estimate. [Copyright &y& Elsevier]