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This paper presents a coherent approach to evaluate the roll damping derivatives for the standard Basic Finner Model. The study compares and analyses the results obtained through a range of techniques, including experimental testing, numerical simulations and semi-empirical models. The study aims to evaluate the reliability and accuracy of these methods and to identify the factors that contribute to their sensitivity. The paper concludes by summarizing the findings of the study and discussing the implications of the results for the design and operation of rockets. The experimental and numerical analysis used in this study provides a robust and comprehensive evaluation of the roll damping coefficient. [ABSTRACT FROM AUTHOR]

This paper proposes a new method to improve re performance of intra-field interpolation which is the mos~ important element of deinterlacing method. Traditional edge- based methods were poor at determining accurate edge iirection which decides interpolation performance. The 7roposed method decides the direction and slope of edge based on locally adaptive-thresholded binary image to mprove efficiency and accuracy, and it also increased the ~orizontal size of search window to 15 for better direction ietermination at gentle slope. Compared to traditional edge- based methods, interpolation based on binary image, which is ,`enerated using the proposed method, leads to great erformance improvement. With computer simulations for a ~`ariety of images, this paper shows the new approach is much ~etter than traditional methods.. [ABSTRACT FROM AUTHOR]

This paper presents an implementation of an ~daptive beamformer in a hands-free unit. The proposec~ ~daptive beamformer suppresses stationary noise an~ nterference sound. The adaptive beamformer and acoustic `cho canceller were implemented in a compact hands-free mit with a low-cost DSP. Experimental results demonstrate he noise reduction performance of the hands-free unit'. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the behavior of a spherical absorber composed of two parts, an inner sphere and a supporting convex spherical dish in which the ball is placed. Considering only the planar behavior of the system, a set of governing nonlinear differential equations was derived and solved numerically. Firstly, the system is exposed to the harmonic excitation of the supporting bowl and its time response is analyzed for all time dependent variables. By gradually changing the angular frequency of the excitation, a resonance curve is obtained, which is examined in detail with respect to the changing amplitudes of the excitation force and the nonlinear behavior. The effect of internal damping and different settings of the absorber characteristics are also investigated. The effect of initial conditions without the presence of an external excitation force is also numerically analyzed by means of phase portraits for selected pairs of initial conditions. [ABSTRACT FROM AUTHOR]

In this paper, our aim is mathematical analysis and numerical simulation of a prey-predator model to describe the effect of predation between prey and predator with nonlinear functional response. First, we develop results concerning the boundedness, the existence and uniqueness of the solution. Furthermore, the Lyapunov principle and the Routh–Hurwitz criterion are applied to study respectively the local and global stability results. We also establish the Hopf-bifurcation to show the existence of a branch of nontrivial periodic solutions. Finally, numerical simulations have been accomplished to validate our analytical findings. [ABSTRACT FROM AUTHOR]

In this paper, our aim is mathematical analysis and numerical simulation of a prey-predator model to describe the effect of predation between prey and predator with nonlinear functional response. First, we develop results concerning the boundedness, the existence and uniqueness of the solution. Furthermore, the Lyapunov principle and the Routh–Hurwitz criterion are applied to study respectively the local and global stability results. We also establish the Hopf-bifurcation to show the existence of a branch of nontrivial periodic solutions. Finally, numerical simulations have been accomplished to validate our analytical findings. [ABSTRACT FROM AUTHOR]

Highlights • Constitutive equations for a vertical rod bundle are reviewed. • Dependence of distribution parameter on flow conditions is discussed. • 1D momentum equation by considering void fraction distribution is discussed. • Effect of channel size on interfacial area concentration is discussed. Abstract In view of the quality assurance of two-phase flow simulations, CSAU (Code Scalability, Applicability, and Uncertainty) methodology and code V & V (Verification and Validation) have been proposed. The estimation of simulation uncertainty is indispensable in using best-estimate computational codes. A key of successful two-phase flow simulations is to use the state-of-the-art constitutive equations to close the mathematical system used in two-phase flow analyses. The advanced constitutive equations should be developed based on “physics” behind phenomena and should consider scaling parameters which enable their application beyond test conditions used for a code validation. Two-phase flow simulations in a rod bundle is important in various industrial apparatuses such as heat exchangers and nuclear reactors. Constitutive equations for two-phase flows in a vertical rod bundles have been advanced in recent five years. In view of this, this paper provides a comprehensive review of most advanced constitutive equations for two-phase flow analyses in a vertical rod bundle. The constitutive equations of two-phase flow parameters reviewed in this paper are flow regime map, void fraction, void fraction covariance and relative velocity covariance, interfacial area concentration and wall friction. In addition, an exact formulation of one-dimensional momentum equation in two-fluid model considering void fraction distribution is discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Lattice beam model extended to self-healing in cementitious materials. • A new rate dependent discrete damage-healing model is presented. • Healing response derived from healing-agent chemo-physical properties. • Detailed information is provided on the size and disposition of cracking and healing zones throughout a transient analysis. • The model provides valuable information required for designing a self-healing system. • Model validated using experiments with healing under fixed and moving crack conditions. • Nature and extent of damage-healing zones determined numerically. This paper describes the development of a discrete lattice model for simulating structures formed from self-healing cementitious materials. In particular, a new approach is presented for simulating time dependent mechanical healing in lattice elements. The proposed formulation is designed to simulate the transient damage and healing behaviour of structures under a range of loading conditions. In addition, multiple and overlapping damage and healing events are considered. An illustrative example demonstrates the effects of varying the healing agent curing parameters on the computed mechanical response. The model is successfully validated using published experimental data from two series of tests on structural elements with an embedded autonomic self-healing system. The meso -scale model gives detailed information on the size and disposition of cracking and healing zones throughout an analysis time history. The model also provides an accurate means of determining the volume of healing agent required to achieve healing for all locations within a structural element. The importance of the information provided by the model for the design of self-healing cementitious material elements is highlighted. [ABSTRACT FROM AUTHOR]

The existing experimental methods and numerical models were difficult to get accurate aerodynamic characteristics of the anti-torque system of a NOTAR under rotor wake. To solve this problem, a new three-dimensional aerodynamic model with momentum source based on finite volume method was proposed in this paper. By means of time domain equalization and spatial interpolation, the complicated dynamic meshes on blade were replaced by the nonblade fixed rotor domain with momentum source. And the model was calculated by steady, compressible and three-dimensional Reynolds averaged N-S equation. In this paper, a typical NOTAR was took for research, the aerodynamic characteristics including flow field and variation regularity of lateral force with momentum coefficient of anti-torque system during hover condition was obtained by applying the above computational model, and the accuracy of which was verified by corresponding experimental data. In addition, the model was also used to analyze the key factors that influence working condition of the tail boom, including length of tail boom, area of nozzle and fan pressurization. And the curves of variation regularity were given. The model and work in this paper could provide reference for further research and design on anti-torque system for NOTAR. [ABSTRACT FROM AUTHOR]

This paper presents an optimal design of low noise amplifier (LNA) using an efficient swarm-based optimizer called firefly algorithm (FA). Many researchers have used firefly algorithm to solve various nonlinear engineering problems and reported outstanding results. In view of this, FA is implemented for the first time in this paper to optimize the parameters of LNA like gain and noise figure (NF). Two case studies have been performed which includes the minimization of NF and maximization of gain. Optimization of these two parameters has been carried out by considering each parameter as a single objective function. Penalty factor method is considered for handling the constraints. Other parameters of LNA like power consumption, linearity, and stability are also discussed for both the cases. The designed LNA has a cascode structure with inductive source degeneration topology and is implemented in UMC 0.18-μm CMOS technology using CADENCE software. LNA is designed for 5.5-GHz frequency. The performance of FA in optimizing the parameters of LNA is also compared with the performance of other similar contemporary algorithms like particle swarm optimization (PSO), human behavior PSO (HB-PSO), backtracking search algorithm, and cuckoo search algorithm (CSA). The optimized value of LNA parameter using FA and other algorithms when simulated in MATLAB environment is compared with the simulated result of CADENCE. Statistical analysis is also performed for each case study, and the results are compared with the above-mentioned optimization algorithms. Simulation results, comparative study, and statistical analysis confirm the superiority of FA over other methods in terms of its computational efficiency, consistency, and robustness. [ABSTRACT FROM AUTHOR]

In this paper we present an analytical and numerical modeling of a general polymerization process with possible lengthening by an agglomeration mechanism. The proposed model takes into account the 2D spatial diffusion of the monomers for the mass transfer between monomers and polymers. We investigate the well-posedness of this general polymerization model and propose an adequate numerical scheme based on a generalization of the anti-dissipative method developed in Goudon (Math. Models Methods Appl. Sci. 23:1177–1215, 2013). [ABSTRACT FROM AUTHOR]

In order to facilitate the replacement of damaged components and prevent the weak-story mechanism of frame structure after strong earthquakes, a novel assembled self-centering buckling-restrained brace (ASC-BRB) is proposed in this paper. The proposed bracing system is comprised of the buckling-restrained brace (BRB) system and the self-centering (SC) system. The SC system consists of two sets of steel strands and one group of disc springs stacked in series to achieve the goal of large deformability and post-hardening behavior. The detailed configuration, fundamental working mechanism, and restoring force model of the ASC-BRB are first presented. Different from SC systems with bilinear elastic behavior of existing SC-BRBs, the SC system of ASC-BRB exhibits trilinear elastic behavior due to its special configuration. Then, quasi-static tests are conducted to validate the effectiveness of the proposed ASC-BRB. The experimental results indicate that the ASC-BRB has a flag-shaped hysteretic response with excellent self-centering capability, stable energy dissipation capability, and appreciable deformation capacity with a maximum ductility coefficient of 25.58. More importantly, the specimen can exhibit the anticipated post-hardening behavior. The refined numerical model of ASC-BRB is established and verified by the experimental results, which can effectively analyze the mechanical behavior of the main components of ASC-BRB, making up for the deficiency of the tests. According to the problems discovered in the tests and numerical analyses, an improved configuration of the ASC-BRB is proposed and validated by the numerical simulation of the BRB system before and after improvement. The numerical results indicate that the improved BRB system exhibits more stable hysteretic behavior, and the stress levels of the inner and outer tubes become much lower after replacing 1-shaped cores with steel angle cores. • An innovative assembled self-centering buckling restrained brace (ASC-BRB) with high post-yield stiffness was proposed. • Experimental results indicated that the proposed ASC-BRB exhibited stable hysteretic behavior, appreciable self-centering capability, large deformability, and prominent post-hardening behavior. • The theoretical restoring force model of the ASC-BRB coincided well with the experimental hysteretic curve. • The refined numerical model could effectively analyze the mechanical behavior of the main components of the ASC-BRB. • An improved configuration of the ASC-BRB was proposed and validated by the numerical simulation. [ABSTRACT FROM AUTHOR]

To improve the interception performance in missile guidance applications, this paper proposes a novel control strategy for the integrated guidance and control design subject to input constraints. The system constraints are translated into a restriction in an invariant set, which is then enforced by manipulating the derivative of the applied reference. For the integrated system in the presence of disturbances and parametric uncertainties, disturbance observers are applied to estimate the lumped disturbances existing in each loop. The quadratic stability via dynamic surface control is guaranteed, and an ellipsoidal approximation of the invariant set is obtained, which can be enlarged to allow some degree of the input saturation. The effectiveness of the proposed scheme is illustrated using numerical simulations against a maneuvering target. [ABSTRACT FROM AUTHOR]

Numerical models for vibro-acoustic analyses of complex mechanical systems are becoming more and more popular, in particular in the field of virtual product development. Therefore, reliable, comprehensive, and validated modeling methodologies remain crucial. However, system characteristics such as elasticities of the drive train components and nonlinear characteristics can lead to complex, and costly numerical models with a huge number of degrees of freedom. This may raise not only the need for novel and reasonable modeling strategies, but also exacerbates validation process, due to the wide scope in terms of operating conditions. In practice, structure-borne noise signals, for example, from accelerometers, are often used for the validation of mechanical systems. By choice of a sufficient number of measurement points, the interpretation becomes more complex. A lot of vibration response curves then need to be compared and interpreted over a wide operating range. In general, the interpretation focuses on deviations in quality and quantity. In this paper, to overcome these mentioned challenges, a validation methodology is proposed allowing a fast and transparent check of a number of captured signals. Therefore, it is shown how the original information can be reduced in a meaningful manner, making it possible to run a fast and accurate validation. The method is demonstrated on a real application with high mechanical complexity and it is shown that the chosen parameters are reliable. [ABSTRACT FROM AUTHOR]

This paper presents a novel hybrid observer structure to estimate the lateral tire forces and road grip potential without using any tire-road friction model. The observer consists of an Extended Kalman Filter structure, which incorporates the available prior knowledge about the vehicle dynamics, a feedforward Neural Network structure, which is used to estimate the highly nonlinear tire behavior, and a Recursive Least Squares block, which predicts the road grip potential. The proposed observer was evaluated under a wide range of aggressive maneuvers and different road grip conditions using a validated vehicle model, validated tire model, and sensor models in the simulation environment IPG CarMaker®. The results confirm its good and robust performance. [ABSTRACT FROM AUTHOR]

The launch and recovery of equipment such as remotely operated vehicles (ROVs) is a critical task that defines the operability limits of many marine operations. This paper considers the analysis of control systems that are designed to maximize the operability limits for launch and recovery of a ROV from a small unmanned surface vessel (USV). We use numerical simulation for the analysis, where the method combines recent approaches for wave compensating dynamic positioning, active heave compensation, and positioning control of the ROV with multi-body dynamic simulation of the surface vessel and ROV, including hydrodynamic forces and dynamic interactions from wires that depend on the ROV depth and moonpool. The results show that the choice of control algorithms and their tuning parameters has a significant effect on the system's operability, and should be carefully designed and tuned to optimize the operability limits for any given sea state, weather and operational setup. The results show that numerical analysis with a system's simulation is an effective tool to verify operability and its sensitivity to various parameters for the given ROV recovery application. • The choice of ROV control system, unmanned surface vessel dynamic positioning and active heave compensation control algorithms and their tuning parameters has a significant effect on the system's operability. • Control systems should be carefully designed and tuned to optimize the operability limits for any given sea state, weather and operational setup. • A numerical simulation model for ROV recovery in the moonpool of a small USV is presented, validated and used in analyzing operability. • Numerical system simulation that integrates all physical elements and control systems is an effective method to verify operability from a systems perspective. [ABSTRACT FROM AUTHOR]

In this paper, a control allocation scheme is presented for a multirotor type of an Unmanned Aerial Vehicle (UAV). The control allocation scheme depends on the multirotor configuration and rotor system parameters, and it enables analysis of dynamics of different multirotor designs depending on the purpose and the task which the multirotor has to carry out. The analysis of force and moment distribution in space shows that the non-flat design with passively tilted rotors can overcome an inherent underactuated condition of flat multirotor configurations. By increasing the tilt angle, the multirotor is able to achieve full controllability over its six degrees of freedom (6 DOFs). A robust chattering-free sliding mode asymptotic tracking control design of a fully actuated multirotor is presented. The simulation results show satisfying tracking performance of the proposed controller. [ABSTRACT FROM AUTHOR]

Reliability demonstration test (RDT) is a critical and necessary step before the acceptance of an industrial system. Generally, a RDT focuses on designing a test plan through which one can judge whether the system reliability indices meet specific requirements. There are many established RDT plans, but few have incorporated the reliability growth aspects of the corresponding products. In this paper, we examine a comprehensive test plan that involves information concerning the reliability growth stage. An approach for RDT under the assumption of the power-law model is proposed. It combines data related to the growth stage with those pertaining to the test stage of the product to reduce the cost of the test. Through simulation studies and numerical examples, we illustrate the characteristics of the test plan and significant reduction in test costs through our approach. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

We present the latest enhancement of the nonlinear monotone finite volume method for the near-well regions. The original nonlinear method is applicable for diffusion, advection-diffusion, and multiphase flow model equations with full anisotropic discontinuous permeability tensors on conformal polyhedral meshes. The approximation of the diffusive flux uses the nonlinear two-point stencil which reduces to the conventional two-point flux approximation (TPFA) on cubic meshes but has much better accuracy for the general case of non-orthogonal grids and anisotropic media. The latest modification of the nonlinear method takes into account the nonlinear (e.g., logarithmic) singularity of the pressure in the near-well region and introduces a correction to improve accuracy of the pressure and the flux calculation. In this paper, we consider a linear version of the nonlinear method waiving its monotonicity for sake of better accuracy. The new method is generalized for anisotropic media, polyhedral grids and nontrivial cases such as slanted, partially perforated wells or wells shifted from the cell center. Numerical experiments show noticeable reduction of numerical errors compared to the original monotone nonlinear FV scheme with the conventional Peaceman well model or with the given analytical well rate. [ABSTRACT FROM AUTHOR]

Abrasive flow machining has become an efficient and economical ultra precision process for machining micro-bore parts. In this paper, aiming at viscosity temperature characteristics of abrasive flow finishing on micro-bore nozzle, under the guidance of the three governing equations of fluid mechanics theory, mixed phase model and discrete phase model were conducted, FLUENT software was resorted to simulate the discrete and fluid phase numerical characteristics of the solid-liquid two-phase flow field in the nozzle orifice with various field temperature and viscosity of slurry, the mechanism of erosion and wear of particles and effect of different processing parameters on particle erosion rate were uncovered, which provides a theoretical basis for the nozzle structure of abrasive flow machining. [ABSTRACT FROM AUTHOR]

In this paper, a protocol and a control law are designed for a single robot so that a team of such robots can interact and cooperate to reach the displacements from an eligible reference formation. Each robot is equipped with displacement sensors of limited sensing ranges. Communication channels are assumed to be unavailable to the team, and each robot works in stealth mode. The team is scalable such that new robots can be recruited, and existing robots can be dismissed. In order for the team size to be scalable, the extended formation based on relative displacement is established as the reference formation. Thus, using the extended formation as a reference, the control law and the protocol could be flexible. As potential conflicts deflect the robot team from the desired formation, the control law is designed to expose the conflicts to the involved neighboring robots such that the protocol can resolve them. A numerical example is given to illustrate how an extended formation is designed, and a simulation example is conducted to demonstrate the performance and merits of the proposed techniques. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: The paper presents a case study of progressive collapse analysis of a selected multistory building. The subject of the numerical study is an existing 8-story steel framed structure built for fire tests in the Cardington Large Building Test Facility, UK. The problem is investigated using nonlinear dynamic finite element simulations carried out following the GSA guidelines. The paper focuses on model development for global models subject to increasing vertical loading and notional column removal. Taking advantage of parallel processing on multiprocessor computers, a detailed 3D model with large number of finite elements has been developed for the entire structure. The objective of the presented feasibility study is to identify modeling parameters affecting the final result (potential of progressive collapse) and propose a hierarchical verification and validation program for reducing outcome uncertainties. [Copyright &y& Elsevier]

Identification of the probe height above the sample surface is a highly useful method to acquire atomic-resolution AFM images. Most AFM systems in non-contact mode use amplitude or phase measurement to identify the sample-probe distance and thereby the sample topography. However, this process is time consuming. For the purpose of sample height estimation in this paper we propose an adaptive nonlinear observer capable of high-precision probe height estimation within a small fraction of the probe transient motion. In addition, to maintain constant sample height at the set point level determined by the user during scanning and imaging in non-contact mode and achieve high rate data sampling, this paper develops a novel output state feedback controller. In this case, the surface topography image of the sample is created through the feedback signal which adjusts the vertical movements of the sample during scanning. The stability of the proposed observer and control method is proved by the Lyapunov stability analysis. Numerical simulations are employed to evaluate the feasibility and effectiveness of the proposed scheme. [ABSTRACT FROM AUTHOR]

In this paper we describe the numerical model of a semiconductor disk laser, developed and implemented in the Photonics Group, Institute of Physics, Lodz University of Technology, Poland. It consists of four strongly interrelated components for: carrier transport, heat flow, material gain and optical phenomena calculations. Combination of these components gives the steady-state self-consistent model which enables a simulation of various aspects of a semiconductor disk laser operation. A numerical analysis of carrier and power losses within the active region of 1.3-μm GaInNAs/GaAs semiconductor disk laser has been carried out using this model. [ABSTRACT FROM AUTHOR]

In this paper, based on the exponential dichotomy theory and contraction mapping fixed point theorem, we obtain some sufficient conditions ensuring the global exponential stability of almost periodic solutions for a new generalized cellular neural network model with time-varying delays in leakage (or forgetting) terms. Our results complement some recent ones. Moreover, an illustrative example and its numerical simulation are given to demonstrate the effectiveness of the obtained results. [ABSTRACT FROM AUTHOR]

SUMMARY This paper deals with a design problem of an adaptive output feedback control for discrete-time systems with a parallel feedforward compensator (PFC), which is designed for making the augmented controlled system 'Almost Strictly Positive Real' (ASPR). A PFC design scheme by a fictitious reference iterative tuning (FRIT) approach with only using an input/output experimental data set will be proposed for discrete-time systems in order to design an adaptive output feedback control system. Furthermore, the effectiveness of the proposed PFC design method will be confirmed through numerical simulations by designing an adaptive control system with adaptive NN (neural network) for an uncertain discrete-time system. © 2014 Wiley Periodicals, Inc. Electr Eng Jpn, 187(1): 24-32, 2014; Published online in Wiley Online Library (). DOI 10.1002/eej.22456 [ABSTRACT FROM AUTHOR]

A permanent magnet synchronous motor (PMSM) model with smooth air gap and an exogenous periodic input is introduced and analyzed in this paper. With a simple mathematical transformation, a new nonautonomous Lorenz-like system is derived from this PMSM model, and this new three-dimensional system can display the compliceated dynamics such as the chaotic attractor and the multiperiodic orbits by adjusting the frequency and amplitude of the exogenous periodic inputs. Moreover, this new system shows a double-deck chaotic attractor that is completely different from the four-wing chaotic attractors on topological structures, although the phase portrait shapes of the new attractor and the four-wing chaotic attractors are similar. The exotic phenomenon has been well demonstrated and investigated by numerical simulations, bifurcation analysis, and electronic circuit implementation. [ABSTRACT FROM AUTHOR]

The hydrodynamics of the waterjet propelled ships represents a challenging problem due to the complexity of the waterjet system itself and the waterjet/hull interaction. In this paper, the self-propulsion computations of a trimaran were performed by solving the unsteady RANS equations. The waterjet was simulated directly with multi-reference frame model to improve the precision of the numerical simulations. Mesh independence studies of the hull and waterjet were carried out individually. Numerical simulations with/without the waterjet were performed in a speed range of 0.196 < Fr < 0.707. Comparisons between numerical predictions and experimental data showed the numerical method could accurately predict the self-propulsion performance. A numerical tool was developed to obtain the capture area based on tracking the streamlines upstream, which was practical and greatly simplified the post-processing. According to the ITTC procedures and guidelines, the overall efficiency and its components were analyzed in detail. The results showed that the resistance increment was always positive while the waterjet thrust deduction fraction was negative. The overall efficiency of the waterjet was mainly affected by the ideal jet efficiency and the pump efficiency. The analysis of the waterjet powering characteristics can better understand the energy conversion and the interaction between the ship hull and waterjet. • In this paper, numerical simulations and analysis on the self-propulsion performance of a waterjet propelled trimaran were conducted based on a RANS solver. • The pump effect of the waterjet system was simulated directly by using the MRF model to improve the accuracy of prediction. • The validity of the numerical method was proven by comparing the numerical results with the experimental results. • A numerical tool was developed to obtain the capture area based on tracking the streamlines upstream. • The analysis of the waterjet powering characteristics can better understand the energy conversion and the interaction between the ship hull and waterjet. [ABSTRACT FROM AUTHOR]

Abstract: An online optimization method was proposed in this paper to improve the accuracy of numerical–experimental hybrid simulations of bridges subjected to earthquake forces. The online optimization method aims to solve the problem induced by the inconsistency of the multiple identical bridge piers where only one or a few of them are simulated experimentally by physical specimens, while the others are numerically simulated within a hybrid framework. This method adopts multi-variable nonlinear optimization in order to find the optimal material parameters of the numerical models, and updates the numerical models instantaneously during the hybrid simulation. A numerical verification of a bridge hybrid simulation was conducted using the proposed online optimization method. The numerical results showed that the online optimization method is capable of obtaining better material parameters during the first few seconds of a hybrid simulation, which results in more accurate nonlinear dynamic response under earthquake loading. [Copyright &y& Elsevier]

Abstract: This paper addresses the problem of simulating a Gaussian random vector with zero mean and given variance–covariance matrix, without conditioning constraints. Variants of the Gibbs sampler algorithm are presented, based on the proposal by Galli and Gao, which do not require inverting the variance–covariance matrix and therefore allow considerable time savings. Numerical experiments are performed to check the accuracy of the algorithm and to determine implementation parameters (in particular, the updating and blocking strategies) that increase the rates of convergence and mixing. [Copyright &y& Elsevier]

Abstract: In this paper we will investigate numerically gravity induced skeletal structure evolution during liquid phase sintering. Applying three-dimensional domain methodology, solid skeleton evolution will be introduced by the definition of skeleton units determined by the equilibrium dihedral angle and the formation of large solid skeletons arranged in a long chain of connected solid phase domains. The settling procedure will be simulated by using two general submodels: for free settling, in which solid phase domains fall under gravity over domains that have already settled, and for extended settling, in which settled domains continue their motion until they reach a position of local equilibrium. The same submodels will be applied for free settling and extended settling of solid skeletons. It will be assumed that under gravity conditions, Stokes’s law settling usually dominates microstructure formation, where the settling procedure will be simulated by computation of the settling time and average migration distance during a defined time interval. Thus gravity induced skeleton structure evolution will be simulated by simultaneous computation of the displacement of the center of mass. [Copyright &y& Elsevier]

Abstract: In this paper, the variation of the fiber orientation distribution along the flow of fresh UHPCC was studied. In order to describe the rotational motion of a single fiber, Jeffery’s equation was adopted, in which the interaction among fibers is neglected. Two cases of flow patterns were considered: shear flow and radial flow. Starting with a three-dimensional random distribution of fibers, the fiber orientation distribution along the flow distance was simulated. These results reveal that fibers gradually become more parallel (in the case of shear flow) and perpendicular (in the case of radial flow) to the flow direction as the flow distance increases. This approach will be useful to predict flow-dependent tensile behavior considering the change of fiber orientation distribution. [Copyright &y& Elsevier]

PROMETHEE methods based on the outranking relation theory are extensively used in multicriteria decision aid. A preference index representing the intensity of preference for one pattern over another pattern can be measured by various preference functions. The higher the intensity, the stronger the preference is indicated. In contrast to traditional single-layer perceptrons (SLPs) with the sigmoid function, this paper develops a novel PROMETHEE II-based SLP using concepts from the PROMETHEE II method involving pairwise comparisons between patterns. The assignment of a class label to a pattern is dependent on its net preference index, which the proposed perceptron obtains. Specially, this study designs a genetic-algorithm-based learning algorithm to determine the relative weights of respective criteria in order to derive the preference index for any pair of patterns. Computer simulations involving several real-world data sets reveal the classification performance of the proposed PROMETHEE II-based SLP. The proposed perceptron performs well compared to the other well-known fuzzy or non-fuzzy classification methods. [ABSTRACT FROM AUTHOR]

This paper presents a generalized predictive control (GPC) strategy for a spatially distributed transport-reaction process based on time–space decomposition. First, the Karhunen–Loève (K–L) decomposition is used for time–space decomposition to find the principal spatial structures and to reduce the dimension of the data. Then, an autoregressive exogenous (ARX) model is identified using the excitation input signals and the temporal coefficients obtained by the K–L decomposition. A GPC strategy is investigated based on the ARX model, with or without considering the system constraints. Numerical simulations on a catalytic rod illustrate the effectiveness of the proposed methods. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we propose an assignment model on urban networks to simulate parking choices; this model is able to simulate the impact of cruising for parking on traffic congestion. For simulating parking choice and estimating the impact of cruising on road congestion we propose a multi-layer network supply model, where each layer simulates a trip phase (on-car trip between the origin and destination zone, cruising for parking at destination zone and walking egress trip). In this model the cruising time is explicitly simulated on the network. The proposed model is tested on a trial network and on a real-scale network; numerical tests highlighted that the proposed model is able to simulate user parking choice behaviour and the impact of cruising for parking upon road congestion, particularly when the average parking saturation degrees exceed 0.7. [Copyright &y& Elsevier]

Abstract: It is essential to model the transient heat transfer phenomena during the controlled pulse key-holing plasma arc welding (PAW) for practical application of this novel process. In this paper, a three-dimensional transient model is developed to analyze the periodic changes of the temperature field, weld pool and keyhole shape and dimensions during the controlled pulse key-holing process. An adaptive, combined, and volumetric heat source is proposed for the numerical analysis of the temperature fields in PAW process. The force action at the weld pool surface is considered to calculate the keyhole shape inside the weld pool. The dynamic variation features of weld pool and keyhole shape in a pulse cycle are numerically simulated. The phenomena of “one keyhole in each pulse” and periodic partial-open keyhole transformation are quantitatively simulated. Experiments are conducted to validate the numerical simulation results. The calculated weld cross-section is consistent with the measured ones. The predicted information on the dynamic evolution of the temperature profiles, weld pool and keyhole geometry is useful for optimizing the multi process parameters in the controlled pulse key-holing PAW process. [Copyright &y& Elsevier]

Quantum Monte Carlo (QMC) methods are often used to calculate properties of many body quantum systems. The main cost of many QMC methods, for example, the variational Monte Carlo (VMC) method, is in constructing a sequence of Slater matrices and computing the ratios of determinants for successive Slater matrices. Recent work has improved the scaling of constructing Slater matrices for insulators so that the cost of constructing Slater matrices in these systems is now linear in the number of particles, whereas computing determinant ratios remains cubic in the number of particles. With the long term aim of simulating much larger systems, we improve the scaling of computing the determinant ratios in the VMC method for simulating insulators by using preconditioned iterative solvers. The main contribution of this paper is the development of a method to efficiently compute for the Slater matrices a sequence of preconditioners that make the iterative solver converge rapidly. This involves cheap preconditioner updates, an effective reordering strategy, and a cheap method to monitor instability of incomplete LU decomposition with threshold and pivoting (ILUTP) preconditioners. Using the resulting preconditioned iterative solvers to compute determinant ratios of consecutive Slater matrices reduces the scaling of QMC algorithms from O(n³) per sweep to roughly O(n²), where n is the number of particles, and a sweep is a sequence of n steps, each attempting to move a distinct particle. We demonstrate experimentally that we can achieve the improved scaling without increasing statistical errors. Our results show that preconditioned iterative solvers can dramatically reduce the cost of VMC for large(r) systems. [ABSTRACT FROM AUTHOR]

This paper presents the determination of virtual micro-forming limit diagrams from two types of numerical simulations based on the finite element method: one with modelling of the full tool for micro-deep drawing and a thin blank with geometric imperfections, based on a defined roughness; and a second called "reduced simulation" where different deformation paths were simulated with appropriate boundary conditions by introducing the same type of geometric imperfections on aluminium 1050A (99.5%). A new test for detecting the onset of necking, called the "change of slope" criterion has been defined. Several methods based on histograms to represent the distributions of major and minor strains, have been used to determine the strain at the onset of necking. The numerical micro-forming limit diagrams (MFLD) were then compared to one obtained experimentally. [ABSTRACT FROM AUTHOR]

The response of plate subjected to underwater explosion loading is of major concern in a variety of marine, ship and offshore platform applications. This paper first conducts the theoretical analysis of the shock loading acting on the plate exposed to underwater explosion. Thereafter, an effective numerical method is adopted to compute the central plastic deformation of the rectangular plates shocked by primary shock wave without regard to the modeling of surrounding water. Therefore numerical computation efficiency is highly improved. Due to the disregard of the gas bubble pulsation energy, numerical central deflections of the rectangular plates are less than the experimental results. Thus, an energy-modified method is advanced to modify the numerical results according to the energy distribution during underwater explosion. The comparison of two types of modified numerical predictions with experimental results piece-wise shows good agreement. [ABSTRACT FROM PUBLISHER]

The stability analysis of the adaptation process, performed by the filtered-x least mean square algorithm on weights of active noise controllers, has not been fully investigated. The main contribution of this paper is conducting a theoretical stability analysis for this process without utilizing commonly used simplifying assumptions regarding the secondary electro-acoustic channel. The core of this analysis is based on the root locus theory. The general rules for constructing the root locus plot of the adaptation process are derived by obtaining root locus parameters, including start points, end points, asymptote lines, and breakaway points. The conducted analysis leads to the derivation of a general upper-bound for the adaptation step-size beyond which the mean weight vector of the active noise controller becomes unstable. Also, this analysis yields the optimum step-size for which the adaptive active noise controller has its fastest dynamic performance. The proposed upper-bound and optimum values apply to general secondary electro-acoustic channels, unlike the commonly used ones which apply to only pure delay channels. The results are found to agree very well with those obtained from numerical analyses and computer simulation experiments. [ABSTRACT FROM AUTHOR]

Abstract: The role of turbulence in droplet growth in clouds is controversial, in part because of the difficulty of studying underlying processes in the cloud environment, and in part because of the difficulty of achieving real cloud conditions in controlled laboratory or computational studies. This paper is a synthesis of research on turbulence effects on cloud droplets that includes field and laboratory studies. Results from cloud measurements show that the turbulence exhibits similar internal intermittency to that observed in the laboratory, and in direct numerical simulations. We explore the consequences of this by relating measurements of droplet accelerations in the laboratory, to conditions observed in the clouds. We show that there is a strong likelihood of droplet accelerations in clouds exceeding the acceleration due to gravity. We discuss these observations in terms of the dynamics of droplets, including velocity statistics and clustering, and their influence on droplet growth. [ABSTRACT FROM AUTHOR]

The paper develops three new modified maximum likelihood predictors (MMLPs) to predict unobserved order statistics from Weibull samples with type II censoring. A Monte Carlo simulation study is conducted to evaluate the performance of the proposed prediction method. When the sample size is small, numerical results indicate that a significant improvement over the normal-based MMLP can be achieved by employing the proposed procedure to predict type II censored data. [ABSTRACT FROM AUTHOR]