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Many information technologies for numerical analysis of electrical circuit parameters have been developed. The peculiarity of these methods is their applicability not only to DC but also AC circuits, not only to linear but also nonlinear circuits. This paper introduces the special mathematical model for rectifier circuits using semiconductor diodes. In previous studies, the rectifier circuit has been modelled by differential inclusions. However, the inclusions cannot be solved by the applied programs of information technology. In this paper, the new model writing by differential equation with a special right hand side is studied to replace the classical model. The main result of this is presented in a theorem that gives the correctness of the new model. The usefulness of this study is illustrated via a concrete example. [ABSTRACT FROM AUTHOR]

The paper presents the analysis of the behavior of a welded metal assembly using a specialized finite element analysis software. The aspect pursued is the determination of the nodal displacements that occur at a certain load, highlighting the areas of maximum stress. The paper also includes elements regarding the mathematical model of the studied phenomenon obtained with the help of variational methods and/or the method of weighted residuals. By modelling and simulating the dynamic behavior of the welded metal assembly, it is possible to determine the critical areas of welding deformations. The study carried out in this paper reveals the necessity of using numerical methods in the pre-design process of an engineering structure. [ABSTRACT FROM AUTHOR]

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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]

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]

In the recent years, different mathematical models have been suggested for maneuvering of displacement vessels, which are capable to estimate maneuvering of the vessel with acceptable precision. But, simulation of planing craft maneuverability through a mathematical model has not been developed yet. In this paper, a mathematical model is developed for maneuvering of the planing craft by including the rudder forces and moments. Different maneuvers, such as straight-line stability, course keeping, and turning circle, are executed through the mathematical model. Simulation results are validated with the published experimental results and it is shown that they are in good agreement. Finally, the in uence of rudder angle on maneuverability of planing craft is studied and, also, the effect of aspect ratio has been investigated. The mathematical model and hydrodynamic coefficients presented in this paper can be applied for the optimization of planing craft maneuvering and the course control purposes. [ABSTRACT FROM AUTHOR]

Finite element model updating is very effective procedure to determine the uncertainty parameters in structural model and minimize the differences between experimentally and numerically identified dynamic characteristics. This procedure can be practiced with manual and automatic model updating procedures. The manual model updating involves manual changes of geometry and analyses parameters by trial and error, guided by engineering judgement. Besides, the automated updating is performed by constructing a series of loops based on optimization procedures. This paper addresses the ambient vibration based finite element model updating of long span reinforced concrete highway bridges using manual model updating procedure. Birecik Highway Bridge located on the 81stkm of Şanlıurfa-Gaziantep state highway over Fırat River in Turkey is selected as a case study. The structural carrier system of the bridge consists of two main parts: Arch and Beam Compartments. In this part of the paper, the arch compartment is investigated. Three dimensional finite element model of the arch compartment of the bridge is constructed using SAP2000 software to determine the dynamic characteristics, numerically. Operational Modal Analysis method is used to extract dynamic characteristics using Enhanced Frequency Domain Decomposition method. Numerically and experimentally identified dynamic characteristics are compared with each other and finite element model of the arch compartment of the bridge is updated manually by changing some uncertain parameters such as section properties, damages, boundary conditions and material properties to reduce the difference between the results. It is demonstrated that the ambient vibration measurements are enough to identify the most significant modes of long span highway bridges. Maximum differences between the natural frequencies are reduced averagely from %49.1 to %0.6 by model updating. Also, a good harmony is found between mode shapes after finite element model updating. [ABSTRACT FROM AUTHOR]

A fully dynamic model of a microchannel evaporator is presented. The aim of the model is to study the highly dynamic parallel channel instabilities that occur in these evaporators in more detail. The numerical solver for the model is custom-built and the majority of the paper is focused on detailing the various aspects of this solver. The one-dimensional homogeneous two-phase flow conservation equations are solved to simulate the flow. The full three-dimensional (3D) conduction domain of the evaporator is also dynamically resolved. This allows for the correct simulation of the complex hydraulic and thermal interactions between the microchannels that give rise to the parallel channel instabilities. The model uses state-of-the-art correlations to calculate the frictional pressure losses and heat transfer in the microchannels. In addition, a model for inlet restrictions is also included to simulate the stabilizing effect of these components. In the final part of the paper, validation results of the model are presented, in which the stability results of the model are compared with the existing experimental data from the literature. Next, a parametric study is performed focusing on the stabilizing effects of the solid substrate properties. It is found that increasing the thermal conductivity and thickness of the solid substrate has a strong stabilizing effect, while increasing the number of microchannels has a small destabilizing effect. Finally, representative dynamic results are also given to demonstrate some of the unique capabilities of the model. [ABSTRACT FROM AUTHOR]

Knowledge about a correct topology model is required for monitoring, control and analyses of a power system. There are many papers which deal with the examination of correctness of the mentioned model. Among approaches to solving a problem of examination of that correctness there is one assuming utilization of raw analogue measurement data. That approach does not require complex numerical computations. It is utilized in the paper. In the paper, a next stage of investigation on topology verification based on utilization of so-called unbalance indices is presented. In that stage, the original idea of reduced unbalance indices, being a modification of the earlier-mentioned unbalance indices, is introduced. Utilization of the new unbalance indices increases possibility of taking verification decision when there are multiple topology errors and decreases sensitivity of topology verification to a lack of a full set of measurement data. The topology verification can be performed locally (e.g. in a substation what is often now considered) as it is in the case of earlier-defined unbalance indices. Utilization of the proposed method is shown on an example of topology verification of the IEEE 14-bus test system. [ABSTRACT FROM AUTHOR]

This paper considers the problem of designing a robust H∞ fuzzy state-feedback controller for a class of nonlinear Markovian jump systems with time-varying delay. A novel design methodology has been proposed for designing a controller that guarantees the L2-gain of the mapping from the exogenous input noise to the regulated output to be less than some prescribed value. Solutions to the problem are provided in terms of linear matrix inequalities. To illustrate the effectiveness of the design developed in this paper, a numerical example is also provided. [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]

Previous literature shows that financial networks are sometimes described by fuzzy data. This paper aims to extend classical models of financial contagion to the framework of fuzzy financial networks. The degree of default of each bank in the network is defined. It consists in a (real valued) measure of the fuzzy default and it is computed as a fixed point for the dynamics of a modified “ fictitious default algorithm ”. Two specific models of degree of default are also introduced and investigated; namely, an optimistic model and a pessimistic one. Finally, the algorithm is implemented in Matlab and tested numerically on a real data set. [ABSTRACT FROM AUTHOR]

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]

This paper presents the verification of the boundary layer modeling approach, which relies on a y-Reg, model proposed by Menter et al. (2006, "A Correlation-Based Transi-tion Model using Local Variables--Part I: Model Formation," J. Turbomach., 128(3), pp. 413-422). This model was extended by laminar-turbulent transition correlations pro-posed by Piotrowski et al. (2008, "Transition Prediction on Turbine Blade Profile with Intermittency Transport Equation," Proceedings of the ASME Turbo Expo, Paper No. GT2008-50796) as well as Stripfet al.'s (2009, "Extended Models for Transitional Rough Wall Boundary Layers with Heat Transfer--Part I: Model Formulation," J. Turbomach., 131(3), 031016) correlations, which take into account the effects of surface roughness. To blend between the laminar and fully turbulent boundary layer over rough wall, the modified intermittency equation is used. To verify the model, a flat plate with zero and nonzero pressure gradient test cases as well as the high pressure turbine blade case were chosen. Furthermore, the model was applied for unsteady calculations of the turbine blade profile as well as the Lou and Hourmouziadis (2000, "Separation Bubbles Under Steady and Periodic-Unsteady Main Flow Conditions," J. Turbomach., 122(4), pp. 634-643) flat plate test case, with an induced pressure profile typical for a suction side of highly-loaded turbine airfoil. The combined effect of roughness and wake passing were studied. The studies proved that the proposed modeling approach (ITMR hereinafter) appeared to be sufficiently precise and enabled for a qualitatively correct prediction of the boundary layer development for the tested simple flow configurations. The results of unsteady calculations indicated that the combined impact of wakes and the surface roughness could be beneficial for the efficiency of the blade rows, but mainly in the case of strong separation occurring on highly-loaded blade profiles. It was also demonstrated that the roughness hardly influences the location of wake induced transition, but has an impact on the flow in between the wakes. [ABSTRACT FROM AUTHOR]

This paper looks at the influence of lateral walls on peristaltic transport of a particle fluid suspension model applied in a non-uniform rectangular duct with slip boundaries. The peristaltic waves propagate on the horizontal sidewalls of a rectangular duct. The flow analysis has been developed for low Reynolds number and long wavelength approximation. Exact solutions have been established for the axial velocity and stream function. The effects of aspect the ratio β (ratio of height to width) and the volume fraction density of the particles C on the pumping characteristics are discussed in detail. The expressions for the pressure rise and friction forces on the wall of a rectangular duct were computed numerically and were plotted with variation of the flow rate for different values of the parameters. It is observed that in the peristaltic pumping ( Δ p > 0 , Q > 0 ) and retrograde pumping ( Δ p > 0 , Q < 0 ) regions the pumping rate increases with an increase in M , while in the copumping region ( Δ p < 0 , Q > 0 ) the behavior is quite opposite. Furthermore it is also observed that the pressure rise increases in the upper half of the channel and decreases in the lower half of the channel with the increase in l slip parameter. [ABSTRACT FROM AUTHOR]

Allocation of channel resources in a cognitive radio system for achieving minimized transmission energy at an increased transmission rate is a challenging research. This paper proposes a resource allocation algorithm based on the meta-heuristic search principle. The proposed algorithm is an improved version of the Group Search Optimizer (GSO), which is a currently developed optimization algorithm that works through imitating the searching behaviour of the animals. The improvement is accomplished through introducing dynamics in the maximum pursuit angle of the GSO members. A cognitive radio system, relying on Orthogonal Frequency Division Multiplexing (OFDM) for its operation, is simulated and the experimentations are carried out for sub-channel allocation. The proposed algorithm is experimentally compared with five renowned optimization algorithms, namely, conventional GSO, Particle Swarm Optimization, Genetic Algorithm, Firefly Algorithm and Artificial Bee Colony algorithm. The obtained results assert the competing performance of the proposed algorithm over the other algorithms. [ABSTRACT FROM AUTHOR]

In this paper, we present a new wavelet multigrid method for the numerical solution of elliptic type differential equations based on Daubechies (db4) high pass and low pass filter coefficients with modified intergrid operators. The proposed method is the robust technique for faster convergence with less computational cost which is justified through the error analysis and condition number of a system in comparison with integrated-RBF technique based on Galerkin formulation (Mai-Duy and Tran-Cong, 2009) and finite difference method. Some of the illustrative problems are presented to demonstrate the attractiveness of the proposed technique. [ABSTRACT FROM AUTHOR]

This paper describes a polynomial decay rate of solution for a transmission problem with 1 - D mixed type I and type II thermoelastic system with infinite memory acting in the first part. The main contributions here are to show that the infinite memory lets our problem still dissipative, and that the system is not exponentially stable, in spite of the kernel in the memory term is sub-exponential. Also we establish that the t-1 is the sharp decay rate. We extend the results in [27]. [ABSTRACT FROM AUTHOR]

Recently researchers have proposed innovative solutions aiming to improve the energy performance of building envelope components such as Trombe walls, ventilated storage walls. The principle of all the innovative systems can be simplified as heat/cold sources in walls. However, the thermal performance and energy savings potential of the innovative heating walls comparing to the traditional heating pattern with heat sources in room air are still lack of clarification. In this paper, the thermal response of an ideal building model under two ideal heating patterns, are analyzed by using a simple thermal and airflow macroscopic model. The analytical formulas for indoor air temperature and thermal mass temperature are also derived to identify the critical parameters that affect the levels and fluctuations of them. By numerical calculation, it can be observed that the indoor air temperature under HP1 quickly falls down as the heat source removed and has big variation, while the results of HP2 look favourable with less variation, and the mean air temperature during the non-heating period is higher than that of HP1. This implies that the heating pattern HP2 has the potentials to create a stable indoor thermal environment. [ABSTRACT FROM AUTHOR]

When designing ground source heat pump systems in northern regions, we usually face the problem of soil freezing/melting around ground heat exchanger. The impact of freezing on heat transfer should be evaluated. An improved thermal resistance and capacity model based on the effective heat capacity method is developed in the paper to evaluate the effect. Further comparisons have been carried out against measured data from an experimental set-up, and agreement of the results validates the proposed model when the parameters of the model are set properly. The heat transfer capacity could rise by 30% because of phase change. The quantity of heat transfer could stay at 75 W/m to 80 W/m during three-month operation, which is feasible for a GSHP system to operate normally in such extreme condition. [ABSTRACT FROM AUTHOR]

In this paper, we propose a pulsed flow control of the radiant system with a fixed on-time to replace the storage water in pipes and a variable off-time to regulate the capacity. We developed a three-dimension numerical model to simulate the performance of the radiant heating and cooling system in the pulsed flow control method. Through numerical simulation on radiant systems with various thermal masses, the average supply and return water temperature difference and surface temperature non-uniformity were compared between the pulsed flow control and the variable flow rate control. The results demonstrate that the pulsed flow control achieves a comparable supply and return water temperature difference and pump energy consumption to the variable flow rate control. However, the pulsed flow control method saves the initial cost by substituting proportional valves by two-way position valves and has a higher controllability in part load. Furthermore, the pulsed flow control yields a smaller surface temperature non-uniformity than variable flow rate control, which is beneficial to reduce the condensation risk in cooling condition. [ABSTRACT FROM AUTHOR]

A mathematical model of the processes taking place in laser melting with injection of metal powders is suggested. The model involves the self-consistent equations for the dynamics of the free surface, the temperature, the concentration of components and the melt flow velocities. The paper presents the algorithm of its numerical realization, as well as the results of test calculation of the temperature fields, the structure of the melt convective flows, the solute distribution and the geometric characteristics of the object to be formed. [ABSTRACT FROM AUTHOR]

Utilization of coal reserves in the protection area of the coal mine gives the possibility of unusual mining methods. Just use methods room pillar in lignite coal mining is quite unusual opportunity. Application of the room pillar method can become very beneficial to the place where it can be somehow limited extraction using longwall face. This method is respectful of the overburden and excavated areas stay stable. The paper deals with the issue of stability and stabilization of coal pillars by using rockbolt support. The problem with this method is currently designing pillars so as to sufficiently handle pass the load. [ABSTRACT FROM AUTHOR]

Abstract: The paper focuses on the assessment of greenhouse gas emissions produced by the walls of buildings according to their lifespan. These assessments take account of the construction, maintenance and end of life. The contribution of the utilization phase must be equivalent for all technical solutions for a given usage function. In the first part of the paper, the methodology is described by (1) considering a unit area of wall (i.e. 1 square metre), (2) determining a long service life, (3) choosing technical solutions in agreement with the specifications, (4) establishing the lifespan of each technical solution according to experts, (5) finding the corresponding greenhouse gas index from an appropriate database, and finally (6) modelling the evolution of these indicators with time. Several technical solutions (concrete, brick, stone, wood, aerated concrete) are considered and lifespans range from a few years to centuries. The results of this analysis suggest and quantify the important impact of lifespan on greenhouse gas emission indicators. For example, the best technical solution for a short lifetime can be the worst on a longer duration and vice versa. In the second part, since the lifespan of a product is very difficult to determine objectively, it is considered as a variable. The numerical results presented point out the need to revisit the current life cycle tools. [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]

Minimization of Boolean functions is one of basic Boolean algebra functions. This paper presents a method for minimizing Boolean functions. To do this, first a graph data structure that is needed for storing Boolean function and basic operations will be investigated.In fact, it is used for storing Karnaugh map adjacencies. Then, the adjacencies and conditions for selection of appropriate adjacencies for factoring are nominated. As a essential part of paper, a brief review of genetic algorithms is presented and finally usage of GA for selection of appropriate adjacencies is described. [ABSTRACT FROM AUTHOR]

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: Computational fluid dynamics (CFD) has been introduced to indoor environment study for decades. Analysis of CFD results will first require the reach of a grid-independent CFD solution to eliminate the false information induced by numerical causes, e.g., grid and numerical scheme. Judging a grid-independent solution has been mostly experience-based, leading the necessity of developing an objective and easy-to-use criterion for grid independency evaluation. This paper presents a new approach to assessing the grid independency of CFD modeling for indoor environment applications. A normalized root mean square error (RMSE) index is developed from the grid convergence index (GCI) concept in literature to evaluate the overall differences of predicted results with varying grid resolutions. The paper further introduces the use of numerical viscosity analysis method to verify the grid-independent solution of a CFD analysis, which also provides fundamental insight into the grid-induced error in numerical solutions. Although initially developed for indoor environment applications, the proposed RMSE index along with the numerical viscosity analysis method can be applied to most general CFD studies and has great potential of being incorporated into commercial CFD software to provide user a more accurate and objective alternative of checking grid independency of CFD simulation. [Copyright &y& Elsevier]

Abstract: This paper uses Diffuser Augmented Wind Turbine for reference. According to the characteristics of ocean current movement, this paper gives several dome model programs for the straight blade vertical-axis tidal turbine. Make use of it to increase its output power. This paper gives several dome model programs for the straight blade vertical-axis tidal turbine. And optimum scheme is chosen by numerical simulation. [Copyright &y& Elsevier]

Abstract: The paper adopts standard k−ɛ turbulence model and other mathematical models, and completing the blending lignite combustion numerical simulation of 600 MW boiler of one power plant. Three conditions were simulated in this paper, and these three conditions were compared and analyzed, the basic conclusion is consistent with the test. The result shows that the combustion character of blending lignite is lower than burning soft coal. Burning lignite shows a decline furnace temperature, and the simulation results are consistent with the experimental results. Pay attention to adjust the reasonable operating manner, and the operation is safety and economic. At the same time this paper also provides a useful reference for researching tangentially fired boiler furnace process. [Copyright &y& Elsevier]

Abstract: The mathematical model for dissolved oxygen interaction with biochemical oxygen demand in an open channel flow is presented in this paper. We consider unsteady flow in one dimension. The model is in the form of partial differential equations which require to solve the dissolved oxygen coupled with the biochemical oxygen demand at the same corresponding position and time. For some specific flow cases, unsteady flows approach to certain stationary solutions which are possible to derive some corresponding exact solutions. However, for complicated flow problems, analytical solution cannot be derived. Efficient and accurate numerical method is required to solve numerically such the model. In this paper, we present the finite element method with linear basis function for solving the system. The accuracy of numerical solutions have been observed and compared with some existing exact solutions for some steady flow cases. To show the ability of our presented numerical scheme, the interaction between the dissolved oxygen and the biochemical oxygen demand is simulated for unsteady flow cases. Furthermore, the impacts of flow parameters such as flow velocity, kinetic reaction order, and diffusion coefficient have been simulated to observe the dissolved oxygen and biochemical oxygen demand dynamics. [Copyright &y& Elsevier]

Abstract: The stress-strain behavior of frozen-thawed soil is a main issue of the frozen soil mechanics. In this paper, the change rules of soft soil shear strength, friction angle, cohesive force and other mechanical parameters were studied. After frozen-thawed cycles, the friction angle of soft soil increases with lower cohesive force, the constitutive property gradually weakened with the nature of transformation from cohesive soil to cohesionless soil. Mathematical characteristics for shear stress-strain curve of frozen-thawed soil are analyzed. Structure mechanism index is presented to indicate the relation between stress-strain curve and soil structure mechanism. The result of this paper is helpful to the numerical analysis and practical engineering design of frozen-thawed soil foundations. [Copyright &y& Elsevier]

Abstract: The traditional risk management model can’t process historical data efficiently, this paper proposed a high-risk customer management model based on rough set theory to solve this problem. In this paper we briefly analyze the characteristics and application of rough set, and then give a method to reduce the irrelevant indicators before generating rules. This method is based on the advantages of rough set in processing large scale data. The model combines risk management theory in engineering and rough set theory in a very good way to process the historical data. Finally this paper gives an experiment to illustrate how to establish and apply the proposed model. [Copyright &y& Elsevier]

A time-varying generalization of the classical deadbeat controller is derived directly from input-output data in the present paper. The natural extension of the time invariant deadbeat condition to the time-varying case is presented by using the key developments of the observer/Kalman filter time-varying system identification theory reported recently by the authors. In stark contrast to the time invariant deadbeat controller design, it is shown that the time- varying deadbeat controller parameters do not follow the recursive relationship that was developed in the past. In the special case of periodic systems, where repeated experimental data are available naturally, it seems that such a controller can be designed to set the output of the closed-loop system to rest after a few time steps. Numerical simulation example demonstrates the efficacy of the deadbeat controller design method proposed in this paper. A deadbeat controller, realized from the departure motion dynamics of a spacecraft, is then shown to enhance the performance of an attitude control system by minimizing the deviations from a reference trajectory. [ABSTRACT FROM AUTHOR]

This paper presents the development and application of a method for autonomous optimal deorbit guidance. The problem is for the guidance system to autonomously determine all the necessary guidance data and execute the finite- time deorbit maneuver in a minimum-propellant fashion that achieves desired entry interface conditions. While the traditional treatment of the maneuver as an impulsive velocity change serves the preliminary study of the problem well, it does not provide much of the needed information for guidance, such as burn timing (which in finite-time burn can be hundreds of seconds apart from that of the impulsive solution), duration of the burn, and thrust direction during the burn. In this paper the deorbit guidance problem is formulated as an optimal control problem with finite- time burn structure. Several sets of general targeting conditions are derived to be met at the entry interface. Numerical solutions are obtained by employing a fast multiburn shooting algorithm. The solution contains the coast times before and after a burn, duration of the burn, and thrust-direction profile during the burn. This study investigates both single- and two-burn deorbit maneuvers, and demonstrates how each works in different mission scenarios. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we investigate throughput optimization in multi-input multi-output (MIMO) systems using channel quality indicator (CQI) based scheduling. Existing MIMO CQI algorithms are mostly designed for sub-optimal linear symbol detectors such as minimum mean square error (MMSE). We consider in this paper how to select CQIs for both streams in order to maximize the total throughput when the non-linear optimal symbol detection technique, maximum likelihood (ML) detector, is employed. Specifically, we formulate a simple yet accurate mathematical model for throughput maximization in a MIMO channel using an ML detector. We make use of constellation constrained capacity to characterize the feasible rate region of such MIMO systems. Based on the information-theoretic analysis, a novel CQI algorithm for MIMO transmission is proposed. Numerical results indicate that the proposed CQI algorithm yields up to 4% throughput improvement over the CQI algorithm optimized for MMSE detectors in High Speed Downlink Packet Access (HSDPA). [Copyright &y& Elsevier]

The purpose of this paper is to present an analysis of the impact of solid particles on the development of cavitation flow conditions around a hydrofoil. Experimental studies were conducted in a cavitation tunnel with different mixtures of particles and water. The effect of the particles on the development of cavitation flows was modeled by using an additional phase particle dispersion model (Euler-Euler). Numerical modeling was performed using the CFD software. The impact on the cavity model with the parametric analysis of the entry conditions of particles in the calculation domain was investigated, with a focus on the solid shear viscosity. Another purpose of this research was to present the possibility of modeling the development of the vapor phase in the commercial CFD software package, while taking into account the impact of particles. This paper presents the results of the experimental measurements and their comparison with numerical simulations. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents an updated study and numerical modelling of the Tabas, eastern Iran earthquake (), which occurred on September 16, 1978, using new techniques recently proposed by various researchers. Firstly, the near-fault ground motions recorded at a station very close to the fault were examined based on the characteristics of the velocity pulses and the frequency content of the motions. Evidence of directivity effects in recorded, near-fault ground motion, has been investigated using various methods. In the second part of this paper, stochastic simulations of near-fault, strong ground motion, using finite-fault modelling, based on a dynamic corner frequency recently proposed by Motazedian and Atkinson [Motazedian, D. and Atkinson, G. “Stochastic finite-fault modelling based on a dynamic corner frequency”, Bull. Seismol. Soc. Amer., 95(2), pp. 995–1010 (2005)], have been presented. In order to model the impulsive behaviour of near-fault ground motion, the finite-fault model was combined with the mathematical expression of Mavroeidis and Papageorgiou [Mavroeidis, G.P. and Papageorgiou, A.S. “A mathematical representation of near-fault ground motions”, Bull. Seismol. Soc. Amer., 3, pp. 1099–1131 (2003)] for modelling pulse characteristics. A new set of modelling parameters has been recommended and good agreement has been found between the recorded and simulated response spectra. The velocity pulses observed in near-fault ground motion records could also be mimicked. [Copyright &y& Elsevier]

It has been reported that Internet Protocol (IP) packet traffic exhibits self-similarity or long range dependence (LRD) and causes the degradation of switch performance. Therefore, it is crucial for an appropriate buffer design of a switch. In this paper, we investigate the packet loss and delay behavior of the asynchronous switch under self-similar variable length packet traffic by modeling it as MMPP / M / 1 / K queueing system wherein MMPP (Markov-Modulated Poisson Process) is fitted by equating the variance of MMPP and that of self-similar traffic. MMPP model is already validated one to emulate the self-similar characteristics. We investigate the packet loss probability, mean waiting time against system parameters, traffic parameters and fitting parameters. Numerical results show that analysis presented in this paper is useful in dimensioning the switch. [ABSTRACT FROM AUTHOR]

A numerical model that can simulate the nonlinear behavior of ultra high strength fiber-reinforced concrete (UHSFRC) structures subject to monotonic loadings is introduced. Since engineering material properties of UHSFRC are remarkably different from those of normal strength concrete and engineered cementitious composite, classification of the mechanical characteristics related to the biaxial behavior of UHSFRC, from the designation of the basic material properties such as the uniaxial stress- strain relationship of UHSFRC to consideration of the bond stress-slip between the reinforcement and surrounding concrete with fiber, is conducted in this paper in order to make possible accurate simulation of the cracking behavior in UHSFRC structures. Based on the concept of the equivalent uniaxial strain, constitutive relationships of UHSFRC are presented in the axes of orthotropy which coincide with the principal axes of the total strain and rotate according to the loading history. This paper introduces a criterion to simulate the tension-stiffening effect on the basis of the force equilibriums, compatibility conditions, and bond stress-slip relationship in an idealized axial member and its efficiency is validated by comparison with available experimental data. Finally, the applicability of the proposed numerical model is established through correlation studies between analytical and experimental results for idealized UHSFRC beams. [ABSTRACT FROM AUTHOR]

Abstract: This paper explores a reasonable coupon rate for basket credit linked notes (BCLN) with issuer default risk. Based on the one factor Gaussian copula model, this paper proposes three methods of incorporating issuer default into BCLN pricing. Numerical results indicate that issuer default risk impacts BCLN coupon rate. Furthermore, coupon rate differs with changes in correlation structure among the three methods. One of the three methods is ultimately identified as the most suitable. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes a methodology for the direct calculation of noise from realistic nozzle geometries. The focus of the paper is on the numerical approach to this problem to provide noise predictions to engineering accuracy in an efficient manner. In addition, issues related to grid generation are discussed. The methodology uses structured multiblock grids. The block surrounding the jet centerline has a Cartesian form and the surrounding grid blocks have a cylindrical polar form – at least for nearly axisymmetric jet nozzle geometries. Appropriate block interface conditions are used. In the case of military style jet nozzles the nozzles are not smooth in the azimuthal direction but have facets representative of the movable flaps in such variable area nozzles. These features must be included in the grid. To enable efficient calculations, in addition to parallel computation, a dual time-stepping approach is used. The sub-iterations in the fictitious time are accelerated using a two-level multigrid approach. A Detached Eddy Simulation (DES) approach based on the Spalart-Allmaras (S-A) one-equation turbulence model is used. Comparisons are made between flow predictions using the DES with the S-A model everywhere and with the turbulence model turned off in the jet external flow. Noise predictions are made with the permeable surface Ffowcs Williams – Hawkings (FW-H) solution. Noise predictions are presented for both a smooth convergent-divergent nozzle as well as a nozzle representative of a military aircraft engine. Comparisons are made with available experimental data. [Copyright &y& Elsevier]

Abstract: This paper provides a review of several physics-based methods developed for predicting sound propagation in flows. The basic principle of physics-based methods is to incorporate some known properties of the underlying physics into the numerical model. For instance, instead of using standard polynomials or Chebyshev polynomials to interpolate the solution, physics-based methods generally use canonical solutions such as Green''s functions or plane waves to construct a local description of the solution. The methods described in this paper include the Green''s function discretisation, the partition of unity finite element method and the wave-based discontinuous Galerkin method. The principles of these methods are described and their performance and shortcomings are discussed. A key issue that emerges in several of these methods is that the canonical solutions are only valid for uniform coefficients, while the methods are intended to be used with strongly inhomogeneous propagation media. [Copyright &y& Elsevier]

Abstract: This paper reports the results of numerical studies carried out for a periodic sandwich propellant geometry with two-dimensional unsteady gas and condensed phase. A non-planar regressing surface along with a kinetic model of two reaction steps in the gas phase was used. This paper discusses the importance of lateral momentum equation to the combustion of sandwich propellants. It demonstrates that the instabilities in sandwich combustion reported in literature are due to neglect of lateral momentum equation and incorrect boundary conditions at the regressing surface. It demonstrates that neglect of momentum equations will lead to a different result from the one obtained considering the momentum equations for sandwich propellants. [Copyright &y& Elsevier]

This is Part I of a two-part series of papers describing the effects of high-pressure injection pockets on the operating conditions of tilting-pad thrust bearings. In Part 1 a numerical model based on the Reynolds equation is developed extending the three-dimensional thermoelastbhydrodynamic (TEHD) analysis of tilting-pad thrust bearings to include the effects of high-pressure injection and recesses in the bearing pads. The model is applied to the analysis of an existing bearing of large dimensions and the influence of the pocket is analyzed. In the analysis, the high-pressure oil injection used for hydrostatic jacking is turned off (i.e., only the effect of the pocket is studied). It is shown that a shallow pocket positively influences the performance of the bearing because it has characteristics similar to those of a Rayleigh-step bearing. In Part H of the paper (Heinrichson, N., Fuerst, A., and Satttos, I. F., 2007, ASME J. Tribol., 129(4), pp. 904-912) measurements of pressure profiles and oil film thickness for a test-pad are compared to theoretical results. The analysis of Part II deals both with flow situations, wh'ere the high-pressure injection is turned off, as well as with situations where it is turned on for hydrostatic jacking. [ABSTRACT FROM AUTHOR]

This is Part H of a two-part series of papers describing the effects of high-pressure injection pockets on the operating conditions of tilting-pad thrust bearings. The paper has two main objectives. One is an experimental investigation of the influence of an oil injection pocket on the pressure distribution and oil film thickness. Two situations are analyzed: (i) when the high-pressure oil injection is turned off and (ii) when the high-pressure injection is turned on. The other objective is to validate a numerical model with respect to its ability to predict the influence of such a pocket (with and without oil injection) on the pressure distribution and oil film thickness. Measurements of the distribution of pressure and oil film thickness are presented for tilting-pad thrust bearing pads of ~ 100 cm² surface area. Two pads are measured in a laboratory test rig at loads of ~1.5 MPa and ~4.0 MPa and velocities of up to 33 m/s. One pad has a plain surface. The other pad has a conical injection pocket at the pivot point and a leading-edge taper. The measurements are compared to theoretical values obtained using a three-dimensional thermoelastohydrodynamic (TEHD) numerical model. At the low load, the theoretical pressure distribution corresponds well with the measured values for both pads, although the influence of the pocket is slightly underestimated. At the high load, large discrepancies exist for the pad with an injection pocket. It is argued that the discrepancies are due mainly to geometric inaccuracies of the collar surface, although they may to some extent be due to the simplifications employed in a Reynolds equation description of the pocket flow. The measured and theoretical values of oil film thickness compare well at low loads and velocities. At high loads and velocities, discrepancies grow to up to 25%. This is due to the accuracy of the measurements. When using hydrostatic jacking the model predicts the start-up behavior well. [ABSTRACT FROM AUTHOR]

The paper deals with a magnetic system on the basis of permanent magnets with a running circular channel. The permanent axially-symmetric transverse magnetic field operates on the aqueous medium. The physico-mathematical model is created for the motion of the charged particle under the action of the magnetic field of the system with allowance for the forces of interaction: magnetic field with a charged particle, charged particles between themselves and action of the stream on the particles. This paper determinates the criteria of parameters choice for the magnetic system. [ABSTRACT FROM AUTHOR]

Internal dose assessment depends on the use of mathematical formulas for dose calculation and models of the human body and its organs. A simple, unified method for internal dose calculations is described, which brings together and simplifies concepts used in nuclear medicine and occupational internal dose systems previously described. Using the best current decay data and phantoms for internal dose calculations, dose factors for internal dose assessment are provided. Decay data for over 800 radionuclides from the data service at Brookhaven National Laboratory were combined with absorbed fraction data from a number of currently available mathematical whole body and organ models to provide the dose factors. This represents the first published update on nuclear medicine dose factors since MIRD Pamphlet No. 11 in 1975; in this paper, dose factors for many more nuclides are given (816 vs. 117 in MIRD 11), including some alp ha emitters. New models are also employed, and dose factors for bone and marrow have been updated with recently suggested corrections. The good agreement of the new dose factors with previously published values for several of the models gives good confidence in their accuracy. This article gives an overview of the technical basis for these dose factors and some example tables of data, but the bulk of the data files will be distributed electronically. The use of an "electronic publishing" approach permits the publication of this kind of voluminous information in mainstream journals while facilitating rapid access and use without the need to purchase often expensive and bulky paper documents. [ABSTRACT FROM AUTHOR]