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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]

In this paper, a stochastic hybrid predator-prey model with Beddington-DeAngelis functional response and Lévy jumps is studied. Firstly, it is proved that the model has a unique global solution. Secondly, sufficient conditions for weak persistence in the mean and extinction of prey and predator populations are established. Finally, sufficient conditions for the existence and uniqueness of ergodic stationary distribution are established. Moreover, several numerical simulations are presented to illustrate the main results. [ABSTRACT FROM AUTHOR]

This paper presents an optimal control of intervention strategies for the menace of Banditry taking into account media campaign against Banditry u2(t) rehabilitation of Bandits detainees u5(t) and use of military force against Banditry u6(t) as control strategies. The Banditry free equilibrium, Banditry present equilibrium and the basic reproduction number of Banditry R0B were obtained. The stability analysis results suggest that the Banditry free equilibrium is locally asymptotically stable when R0B>1 and otherwise when R0B>1. The Boko Haram presence equilibrium is globally asymptotically stable when R0B>1 and unstable if R0B>1. We used the three control strategies and updated the Banditry menace model. The optimal control issue was resolved using Pontryagin's Maximum Principle (PMP). It was discovered that there is a significant decrease in the population of Bandits and increase in the number of rehabilitated Bandits and detained Bandits when the control measures are implemented compared to the case without control. We solved the optimality control using a forward-backward sweep strategy implemented in MATLAB for numerical simulation. Additionally, we saw that the number of people detained fluctuates as the number of people receiving rehabilitation rises. We argue that in order to lessen or completely erase the menace caused by Bandits in society, the government should fund media campaigns and rehabilitation initiatives. [ABSTRACT FROM AUTHOR]

Purpose – Recently, acoustic characteristics of the indoor space are more important due to society economic development needs. Meanwhile, container houses are gradually widely used in quite a lot of space applications for sustainable and easy use features. Those are still need to remain the pleasant and quiet sound environment. The paper aims to discuss these issues. Design/methodology/approach – In this paper, commercial software Ecotect Analysis is used to calculate the sound characteristics of container house. And the decorated material of this small indoor space is redesigned for obtaining the acoustic comfort under the optimal reverberation time. First, three-dimensional model of the container house is constructed by default tools of software. The indoor acoustic characteristics for various design conditions can be obtained by the simulation process. Findings – By comparing the experiment and simulation results, excellent agreement is represented to verify the feasibility of the software. Second, the original container house is caused by reverberation time distribution in 140-315 ms. After selecting the interior material, its reverberation time distribution in 160-680 ms. Originality/value – Following the design process, the spatial designers can assess the indoor acoustic characteristics in concept design stage and good acoustic comfort environment of building is derived. Meanwhile, improve the quality of living and construction costs reducing can be implemented. [ABSTRACT FROM AUTHOR]

This paper aims to study the dynamical behaviours of an SIQR epidemiological model. Positivity and boundedness of the system are discussed. Stability analysis of the equilibrium points is presented. Numerical simulations are carried out to validate our analytical findings. Implications of our analytical and numerical ûndings are discussed critically. [ABSTRACT FROM AUTHOR]

This paper presents a performance analysis of the maximum likelihood (ML) estimator for finding the directions of arrival (DOAs) with a sensor array. The asymptotic properties of this estimator are well known. In this paper, the performance under conditions of low signal-to-noise ratio (SNR) and a small number of array snapshots is investigated. It is well known that the ML estimator exhibits a threshold effect, i.e., a rapid deterioration of estimation accuracy below a certain SNR or number of snapshots. This effect is caused by outliers and is not captured by standard techniques such as the Cramér-Rao bound and asymptotic analysis. In this paper, approximations to the mean square estimation error and probability of outlier are derived that can be used to predict the threshold region performance of the ML estimator with high accuracy. Both the deterministic ML and stochastic ML estimators are treated for the single-source and multisource estimation problems. These approximations alleviate the need for time-consuming computer simulations when evaluating the threshold region performance. For the special case of a single stochastic source signal and a single snapshot, it is shown that the ML estimator is not statistically efficient as SNR → ∞ due to the effect of outliers. [ABSTRACT FROM AUTHOR]

Many real-time systems are developed and maintained through the use of commercial software products, such as Matlab and MatrixX, that automatically (generate source code based on graphical control systems models. Testing these real-time models and the real-time software generated from them presents special problems during maintenance not faced with other forms of software. Very importantly, many of the models and software systems have to be tested through the use of simulations. Huge input and output data sets, the need for testing over a long duration of time (weeks or months), and computationally intensive requirements are Just a few of the difficulties. For testing during maintenance in such situations, this paper draws upon field experience to present a set of test types and a strategy for selecting test types used to create series of input values to serve as test cases. Also this paper presents strategies for applying these test types, using the assistance of a free, widely available testing tool that automates test case generation, executes the simulations, and supports the analysis of the test results. [ABSTRACT FROM AUTHOR]

Utilization of hydraulic-fracturing technology is dramatically increasing in exploitation of natural gas extraction. However the prediction of the configuration of propagated hydraulic fracture is extremely challenging. This paper presents a numerical method of obtaining the configuration of the propagated hydraulic fracture into discrete natural fracture network system. The method is developed on the basis of weighted fracture which is derived in combination of Dijkstra's algorithm energy theory and vector method. Numerical results along with experimental data demonstrated that proposed method is capable of predicting the propagated hydraulic fracture configuration reasonably with high computation efficiency. Sensitivity analysis reveals a number of interesting observation results: the shortest path weight value decreases with increasing of fracture density and length, and increases with increasing of the angle between fractures to the maximum principal stress direction. Our method is helpful for evaluating the complexity of the discrete fracture network, to obtain the extension direction of the fracture. [ABSTRACT FROM AUTHOR]

The paper focuses on a nonlinear model to represent the mechanical behaviour of a mix coil spring - rubber used in the secondary suspension of passenger rail vehicles. The principle of the model relies on overlapping of the forces corresponding to three components - the elastic component, the viscous component and the dry friction component. The model has two sources on non-linearity, in the elastic force and the friction force, respectively. The main attributes of the model are made visible by its response to an imposed displacement-type harmonic excitation. The results thus obtained from the applications of numerical simulation show a series of basic properties of the model, namely the dependence on amplitude and the excitation frequency of the model response, as well as of its stiffness and damping. [ABSTRACT FROM AUTHOR]

Numerical simulation of shielding effectiveness (SE) of a perforated shielding enclosure is carried out, using the finite element method (FEM). Possibilities of model definitions and differences between 2D and 3D models are discussed. An important part of any simulation is verification of the model results-here the simulation result are verified in terms of convergence of the model in dependence on the degrees of freedom (DOF) and by measurements. The experimental method is based on measurement of electric field inside the enclosure using an electric field probe with small dimensions is described in the paper. Solution of an illustrative example of SE by FEM is shown and simulation results are verified by experiments. [ABSTRACT FROM AUTHOR]

Integrated, process-based numerical models in hydrology are rapidly evolving, spurred by novel theories in mathematical physics, advances in computational methods, insights from laboratory and field experiments, and the need to better understand and predict the potential impacts of population, land use, and climate change on our water resources. At the catchment scale, these simulation models are commonly based on conservation principles for surface and subsurface water flow and solute transport (e.g., the Richards, shallow water, and advection-dispersion equations), and they require robust numerical techniques for their resolution. Traditional (and still open) challenges in developing reliable and efficient models are associated with heterogeneity and variability in parameters and state variables; nonlinearities and scale effects in process dynamics; and complex or poorly known boundary conditions and initial system states. As catchment modeling enters a highly interdisciplinary era, new challenges arise from the need to maintain physical and numerical consistency in the description of multiple processes that interact over a range of scales and across different compartments of an overall system. This paper first gives an historical overview (past 50 years) of some of the key developments in physically based hydrological modeling, emphasizing how the interplay between theory, experiments, and modeling has contributed to advancing the state of the art. The second part of the paper examines some outstanding problems in integrated catchment modeling from the perspective of recent developments in mathematical and computational science. [ABSTRACT FROM AUTHOR]

How to develop efficient numerical schemes while preserving energy stability at the discrete level is challenging for the three-component Cahn-Hilliard phase-field model. In this paper, we develop a set of first- and second-order temporal approximation schemes based on a novel 'Invariant Energy Quadratization' approach, where all nonlinear terms are treated semi-explicitly. Consequently, the resulting numerical schemes lead to well-posed linear systems with a linear symmetric, positive definite at each time step. We prove that the developed schemes are unconditionally energy stable and present various 2D and 3D numerical simulations to demonstrate the stability and the accuracy of the schemes. [ABSTRACT FROM AUTHOR]

The Linear Switched Reluctance motor, with his simple structure, robustness and high power density, can replace gear trains, belts, and pulleys. In these circumstances this paper presents a new LSRM for shunting the railways channels. Moreover, the actual motorization, using asynchronous motor associated to gear trains, is considered very cumbersome. The proposed LSRM have been analyzed with Finite Elements Methods (FEM). The variations of flux density and produced force, calculated via computer simulation, are presented and discussed. Finally, a LSRM model, using Matlab-simulink, was built following the proposed design and was verified by simulations results. [ABSTRACT FROM AUTHOR]

The paper deals with an electromechanical model of liquid flow in a tube in order to model blood flow in vessels. The present paper deals with detailed mathematical development of a model based on the theory of electrical long line with distributed elements. The detailed derivation of primary parameters of the analogical electric circuit is described. There are presented some results of application of the model like wave impedance and wave vector of the blood pulse wave, which are important for the model application to the blood vessels system diagnosis. The significant parameter of the pulse wave - the pulse wave velocity (PWV) has been evaluated and the calculated values of phase and group velocities in selected vessels have been confronted with physiological data. [ABSTRACT FROM AUTHOR]

This paper proposes a rule-based motion planning system for agent-based crowd simulation, consisting of sets of rules for both collision avoidance and collision response. In order to avoid an oncoming collision, a set of rules for velocity sampling and evaluation is proposed, which aims to choose a velocity with an expected time to collision larger than a predefined threshold. In order to improve the efficiency over existing methods, the sampling procedure terminates upon finding an appropriate velocity. Moreover, the proposed motion planning system does not guarantee a collision-free movement. In case of collision, another set of rules is also defined to direct the agent to make a corresponding response. The experiment results show that the proposed approach can be applied in different scenarios, while making the simulation execution efficient. [ABSTRACT FROM AUTHOR]

The vision of grid computing is to make computational power, storage capacity, data and applications available to users as readily as electricity and other utilities. Grid infrastructures and applications have traditionally been geared towards dedicated, centralized, high-performance clusters running on UNIX ‘flavour’ operating systems (commonly referred to as cluster-based grid computing). This can be contrasted with desktop-based grid computing that refers to the aggregation of non-dedicated, de-centralized, commodity PCs connected through a network and running (mostly) the Microsoft Windows operating system. Large-scale adoption of such Windows-based grid infrastructure may be facilitated via grid enabling existing Windows applications. This paper presents the WinGrid approach to grid-enabling existing Windows-based commercial-off-the-shelf simulation packages (CSPs). Through the use of two case studies developed in conjunction with a major automotive company and a leading investment bank, respectively, the contribution of this paper is the demonstration of how experimentation with the CSP Witness (Lanner Group) and the CSP Analytics (SunGard Corporation) can achieve speedup when using WinGrid middleware on both dedicated and non-dedicated grid nodes. It is hoped that this research would facilitate wider acceptance of desktop grid computing among enterprises interested in a low-intervention technological solution to speeding up their existing simulations. Copyright © 2009 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper presents a novel initial value compensation (IVC) using an additional input for semi-closed control systems. The authors have already proposed the IVC approach using the additional input for residual vibration suppression in the fast and precise positioning control. In the approach, however, an essential subject has remained, i.e., the positioning control in the load side could not satisfy the required performance because the systems have been constructed under the assumption of a semi-closed control system. An improvement of the control performance in load position, therefore, is discussed in this paper, where the appropriate assignments of poles and zeros in IVC are ensured, considering the transfer functions of position in both sensor and load for the control initial values. The effectiveness of the proposed approach has been verified by numerical simulations and experiments using a prototype. [ABSTRACT FROM AUTHOR]

In video transmission, the compressed signal is extremely vulnerable to bit errors. Error concealment is widely used in video decoder to recover corrupted frames. Due to the use of variable length codes (VLCs), a single bit error in block-based bitstream may propagate to following of this slice. Especially, the effectiveness of error concealment technique relies heavily on correctly locating errors. In this paper an error detector based on syntax and continuity which consists of two stages is proposed. The first stage is to find erroneous slice according to checking constraints imposed on video bitstream syntax or detecting special error patterns. In the second stage, the precise position of the first erroneous macroblock (MB) is found based on the continuity of spatial or temporal data of neighbor MBs. Simulation results demonstrate that the proposed method improves performance of error detection significantly compared with the traditional syntax-based method'. [ABSTRACT FROM AUTHOR]

In this paper, we report a method for nonuniform data-dependent noise prediction (DDNP), in which the noise predictive filters do not have an identical order (number of taps). To accommodate this new architecture, we implemented a partial decision feedback strategy for branch metric computations of the higher order predictive filters. Theoretical analysis and computer simulations show that our proposed DDNP can achieve a better tradeoff between detection performance and computational complexity compared with the previously reported DDNP. [ABSTRACT FROM AUTHOR]

The incorporation of the orthogonal frequency(multiplexing (OFDM) with the space-time or space-frequency coding is a robust and effective method to achieve a transmit-diversity gain and to suppress an intersymbol interference for the broadband wireless transmissions. This paper is concerned with the downlink-performance improvement using multiple transmit antennas for the OFDM systems with a large delay spread. A delay-spread reduction method using space-frequency block coding and statistical prefiltering (SPF) was proposed, which combines signal prealignment and multiple transmit beamformers designed with the statistical knowledge of the downlink channel state information. The proposed method, which is called the SPF-OFDM, transforms a large delay-spread channel into multiple channels, each with small delay spread. Thus, it does not only shorten the effective excess delay but also preserves the path diversity through the use of the space-frequency coding. Computer simulations have evaluated the effectiveness of the proposed scheme, and comparisons have been made with the conventional solutions. [ABSTRACT FROM AUTHOR]

The BaBar experiment requires simulated events beyond the ability of a single computing site to provide. This paper describes the evolution of simulation and job management methods to meet the physics community requirements and how production became distributed to use resources beyond any one computing center. The evolution of BaBar simulation along with the development of the distribution of the computing effort is described. As the computing effort is distributed to more sites there is a need to simplify production so the effort does not multiply with number of production centers. Tools are created to be flexible in handling errors and failures that happen in the system and respond accordingly, this reduces failure rates and production effort. This paper will focus on one cycle of simulation production within BaBar as a description of a large scale computing effort which was fully performed, and provided new simulation data to the users on time. [ABSTRACT FROM AUTHOR]

This paper deals with the hybrid shunt active filter for harmonic compensation of a three-phase diode rectifier in a 480-V adjustable-speed motor drive system. The hybrid filter is formed by a three-phase LC filter tuned around the seventh harmonic frequency and a small-rated three-phase voltage-source PWM inverter. The LC filter and PWM inverter are directly connected in series. As a result, the DC capacitor voltage of the PWM inverter in the hybrid filter is much lower than that of a conventional pure shunt active filter. This results in higher efficiency, less switching ripple, and less EMI emission. Computer simulation is carried out to compare the hybrid filter with the pure filter in terms of circuit configuration and filtering performance. Simulation results indicate that the hybrid filter is superior in effectiveness and viability to the pure filter. In addition, theoretical analysis based on vector loci confirms the validity of the simulation results. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 153(2): 61–70, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20145 [ABSTRACT FROM AUTHOR]

In this paper, we investigate the performance of a generic filterbank transceiver in the presence of a carrier frequency offset. We propose a theoretical model to compute the error probability in the case of a generic frequency-selective channel. Moreover, the proposed method is also extended to deal with nonuniform, i.e., wavelet, transceivers. The accuracy of the model is evaluated by means of computer simulations, using several types of filterbank transceivers. Systems based on cyclic prefix (CP) and zero padding (ZP) are considered to avoid interblock interference (IBI) in frequency-selective channels. The analytical results obtained with the proposed method allow us to quickly compare different systems, characterized by a different filterbank selectivity, as well as by different methods to combat IBI (ZP or CP). [ABSTRACT FROM AUTHOR]

To develop a usable Virtual Reality system, the prospective context of use of such a system may need to be considered in order to make sure it meets the requirements and restrictions of that context. In this paper, a contextual analysis is described for a virtual reality system to aid medical diagnosis and treatment planning of vascular disorders. Semi-structured interviews were coupled with observations in an ethnographic approach to requirements gathering in the daily work environment of (interventional) radiologists and vascular surgeons. The identified potential usability problems of a fully immersive prototype, coupled with the needs, requirements and real-life environment of the end-users lead to guidelines for the development of a VR application on a semi-immersive desktop environment. The findings lead us to believe that contextual analysis can be a powerful way to inform the design of a VR application by offering an understanding of the context of use and to inform developers of the most appropriate degree of immersiveness of the VR environment. [ABSTRACT FROM AUTHOR]

The condition of rolls has significant influence on the process conditions such as longitudinal tension and lateral error in web transport systems such as in metal and film processes. In particular, a roll-shape defect such as an eccentricity is a major cause for the periodic tension disturbance in the web. In this paper, the authors aim to reject these disturbances caused by unknown shapes of rolls. In order to reject the tension disturbance due to the roll shape, an adaptive eccentricity estimator and eccentricity compensation methods are proposed. The validity of the compensation method including the adaptive eccentricity estimator was tested through computer simulation and experimental study. [ABSTRACT FROM AUTHOR]

The Ait-Sahalia-Rho model is an important tool to study a number of financial problems, including the term structure of interest rate. However, since the functions of this model do not satisfy the linear growth condition, we cannot study the properties for the solution of this model by using the traditional techniques. In this paper we overcome the mathematical difficulties due to the nonlinear growth condition by using numerical simulation. Thus we first discuss analytical properties of the model and the convergence property of numerical solutions in probability for the Ait-Sahalia-Rho model. Finally, an example for option pricing is given to illustrate that the numerical solution is an effective method to estimate the expected payoffs. [ABSTRACT FROM AUTHOR]

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Spatial simulations are a valuable tool in understanding dynamic spatial processes. In developing these simulations, it is often required to make decisions about how to represent features in the environment and how events unfold in time. These spatial and temporal choices have been shown to significantly alter model outcomes, yet their interaction is less well understood. In this paper, we make use of a simple group foraging model and systematically vary how features are represented (cell size of the landscape) as well as how events unfold in time (order in which foragers take action) to better understand their interaction. Our results show similar nonlinear responses to changes in spatial representation found in the literature, and an effect of the order in which agents were processed. There was also a clear interaction between how features are represented and how events unfold in time, where, under certain environmental representations results were found to be more sensitive to the order in which individuals were processed. Furthermore, the effects of feature representation, scheduling of agents, and their interaction were all found to be influenced by the heterogeneity of the spatial surface (food), suggesting that the statistical properties of the underlying spatial variable will additionally play a role. We suggest that navigating these interactions can be facilitated through a better understanding of how these choices affect the decision landscape(s) on which agents operate. Specifically, how changes to representation affect aggregation and resolution of the decision surface, and thereby the degree to which agents interact directly or indirectly. We suggest that the challenges of dealing with spatial representation, scheduling, and their interaction, while building models could also present an opportunity. As explicitly including alternate representations and scheduling choices during model selection can aid in identifying optimal agent–environment representations. Potentially leading to improved insights into the relationships between spatial processes and the environments in which they occur. [ABSTRACT FROM AUTHOR]

Simulation of the nonlinear mechanical response of materials with explicit representation of microstructural features is extremely challenging. These models typically involve a very large number of degrees of freedom, and are prone to convergence difficulties when searching for roots to nonlinear equilibrium equations. We focus on an idealized material model that is motivated by the microstructure of synthetic nacre: individual ‘bricks’ (representing ceramic platelets) interact through nonlinear cohesive springs (representing a small volume fraction of polymer that bonds the platelets). The model simulates composite fracture through rupture of the cohesive springs. The problem is cast in terms of energy minimization and is essentially described by ‘nearest neighbor’ interactions. The principal focus of this paper is to illustrate the computational gains achievable by the strategic marriage of robust, global Monte Carlo minimization algorithms to the graphics processing unit architecture, and to describe how they were realized on the Nvidia GPU. Results comparing the computation times for graphics processing unit and central processing unit implementations demonstrate that a new adaptive version of the simulated annealing algorithm yields a speedup of approximately 5 times, whereas the graphics processing unit implementation yields a speed-up of about 16 times over conventional four-core central processing unit implementations. The resulting speed enhancement for adaptive graphics processing unit minimization of a factor of 80 enables a far broader range of simulations than has previously been possible. Simulations involving as many as 300,000 bricks can be performed in hours, as compared to weeks required by central processing unit implementation. Many aspects of this approach are translatable to other physical problems involving energy minimization in systems with large numbers of degrees of freedom. [ABSTRACT FROM AUTHOR]

A single-species population model exhibiting a symmetric slow variation for the carrying capacity and intrinsic growth rate is evaluated explicitly. However, it is unrealistic to eliminate the possibility of a clear separation in the evolution of the biotic environmental elements; thus, this paper considers the situation where these elements have a hierarchical variation on the time scales. Accordingly, two particular situations are recognized, which are the carrying capacity varies faster than the growth rate and vice versa. Applying the multi-time scaling technique in such a system provides a small parameter, which leads us to construct analytical approximate expressions for the population behavior, using the perturbation approach. Such approximations display very good agreement with the numerical simulations. [ABSTRACT FROM AUTHOR]

Ferrogels, i.e., magnetic nanoparticles immersed into a swollen polymer gel, are materials which combine the magnetic properties of a ferrofluid with the elastic properties of a hydrogel. This makes it possible to control their shape and elasticity by means of external magnetic fields. Magnetic gels are therefore considered for medical and technical applications such as actuation and drug delivery systems. In this paper, we focus on a special class of magnetic gels in which the magnetic nanoparticles act as the cross-linkers of the polymer network. Experimentally this is achieved by functionalizing the nanoparticles' surface such that the polymers can covalently bind to it. In this way, a coupling between the orientation of the nanoparticles and the polymer matrix is created. When an external magnetic field is applied to such a system, the magnetic particles align to the field, and due to the coupling between the nanoparticles' orientation and the gel matrix, a strain is exerted on the polymers. This leads to a shrinking of the gel as a whole. In this paper, we explain how to extend a two-dimensional simulation model for such a system (Soft Matter 8 (2012) 9923 [18] ) to three dimensions. We will show that, while an isotropic deformation was observed in the two-dimensional case, in three dimensions the gel shrinks anisotropically. This is due to the fact that orientational fluctuations of the nanoparticles are hindered in the direction perpendicular to an external magnetic field. [ABSTRACT FROM AUTHOR]

A new design and analysis of a wide-band double-negative metamaterial, considering a frequency range of 0.5 to 7 GHz, is presented in this paper. Four different unit cells with varying design parameters are analyzed to evaluate the effects of the unit-cell size on the resonance frequencies of the metamaterial. Moreover, open and interconnected 2 × 2 array structures of unit cells are analyzed. The finite-difference time-domain (FDTD) method, based on the Computer Simulation Technology (CST) Microwave Studio, is utilized in the majority of this investigation. The experimental portion of the study was performed in a semi-anechoic chamber. Good agreement is observed between the simulated and measured S parameters of the developed unit cell and array. The designed unit cell exhibits negative permittivity and permeability simultaneously at S-band (2.95 GHz to 4.00 GHz) microwave frequencies. In addition, the designed unit cell can also operate as a double-negative medium throughout the C band (4.00 GHz to 4.95 GHz and 5.00 GHz to 5.57 GHz). At a number of other frequencies, it exhibits a single negative value. The two array configurations cause a slight shift in the resonance frequencies of the metamaterial and hence lead to a slight shift of the single- and double-negative frequency ranges of the metamaterial. [ABSTRACT FROM AUTHOR]

This paper analyzes the effect of permanent magnets (PMs) on the formation of chaos in doubly salient PM (DSPM) machines. Based on the newly derived nonlinear system dynamical equation, the corresponding Poincaré map and bifurcation diagram show that the sizing of PMs significantly affects the stability of DSPM machines. Chaos may be resulted if the PMs are not properly designed. Both computer simulations and experimental results are provided, to support the theoretical derivation. [ABSTRACT FROM AUTHOR]

Transmission error is an important reason for instability in helical gears. A six-degree-of-freedom dynamic model coupled flexional, torsional and axial motion of a helical gear transmission system, which includes time varying mesh stiffness, bearing supporting stiffness, mesh damping and backlash, is developed, after taking into account the dynamic characteristics and vibration responses of helical gear in three dimensions. Influences of involute contact ratio, bearing supporting stiffness, mesh damping and backlash on the dynamic transmission errors and vibration stability of the helical gear system are investigated using numerical simulation technique. The effects on dynamic transmission errors and stabilities by contact ratio, supporting stiffness and mesh damping as well as gear backlash are analyzed. The intrinsic relationship between above parameters and dynamic transmission errors and stabilities for helical gear system are presented. The stable and unstable regions under different parameters are given. The results in this paper can be helpful to the dynamic and stable design of a helical gear transmission system. [ABSTRACT FROM AUTHOR]

'The problem with simulations is that they are doomed to succeed.' So runs a common criticism of simulations-that they can be used to 'prove' anything and are thus of little or no scientific value. While this particular objection represents a minority view, especially among those who work with simulations in a scientific context, it raises a difficult question: what standards should we use to differentiate a simulation that fails from one that succeeds? In this paper we build on a structural analysis of simulation developed in previous work to provide an evaluative account of the variety of ways in which simulations do fail. We expand the structural analysis in terms of the relationship between a simulation and its real-world target emphasizing the important role of aspects intended to correspond and also those specifically intended not to correspond to reality. The result is an outline both of the ways in which simulations can fail and the scientific importance of those various forms of failure. [ABSTRACT FROM AUTHOR]

This paper presents a novel general-purpose simulation analysis application that combines concurrent operations simulation with the advanced data interrogation and user interaction capabilities of immersive virtual reality systems. The application allows for interactive modification of the simulation parameters, while providing the users with the available simulation information by effectively placing the operator in the midst of the environment being simulated. The major contribution of this research is the total integration of the immersive virtual reality environment with the simulation, allowing users in the environment to interactively change the inputs to the simulation as it is running. Implementation and functionality details of the developed application are presented. The experience of using the application to analyze a manufacturing operation in a collaborative scenario is also discussed. [ABSTRACT FROM AUTHOR]

This paper describes a real-time welding simulation method for use in a desktop virtual reality simulated Metal Inert Gas welding training system. The simulation defines the shape of the weld bead, the depth of penetration, and the temperature distribution in the workpiece, based on inputs from the motion-tracking system that tracks the position of the welding gun as a function of time. A finite difference method is used to calculate the temperature distribution, including the width of the weld bead and the depth of penetration. The shape of the weld bead is then calculated at each time step by assuming a semi-spherical volume, based on the width of the weld bead, the welding speed, and the wire feed rate. The real-time performance of the system is examined, and results from the real-time simulation are compared to physical tests and are found to have very good correlation for welding speeds up to 1,000 mm/min. [ABSTRACT FROM AUTHOR]

This paper presents a hybrid approach for solving thermal unit commitment problems. The solution methodology comprises of two stages processes of unit selection and economic dispatch of the committed units. The Modified Priority List (MPL) is used for unit selection, which is developed by sorting the units in descending order in respect of their Contribution Factor (CF). Sequential Approach with Matrix Framework (SAMF) is applied to determine the optimal real power dispatches of the committed units. The proposed methodologies are validated by solving standard ten unit system and suitably scaled 20, 40, 60, 80 and 100 unit systems with one day schedule horizon. Further, the potential of the proposed approach is verified for solving a unit commitment problem with ramp rate constraints. Numerical simulation results indicate an improvement in total cost saving and hence the superiority of the proposed method has also been revealed. [ABSTRACT FROM AUTHOR]

Abstract  Presentation of content is an important aspect of today’s virtual reality applications, especially in domains such as virtual museums. The large amount and variety of exhibits in such applications raise a need for adaptation and personalization of the environment. This paper presents a content personalization platform for Virtual Museums, which is based on a semantic description of content and on information implicitly collected about the users through their interactions with the museum. The proposed platform uses stereotypes to initialize user models, adapts user profiles dynamically and clusters users into similar interest groups. A science fiction museum has been set up as a case study for this platform and an evaluation has been carried out. [ABSTRACT FROM AUTHOR]

In this paper, we propose a new robust congestion- control strategy for a differentiated-services (DiffServ) network. A sliding-mode-based variable structure control technique is utilized to design a congestion controller on the basis of a fluid flow model. The performance of our proposed scheme is then demonstrated on a DiffServ network. Our proposed algorithm is developed for an interconnected network as a hop-by-hop distributed-control approach. A formal analysis of the controlled network is conducted, where it is shown that the error dynamics of the overall time-delay-dependent system is ℒ∞ stable. Numerical simulations are provided to demonstrate the capabilities of our proposed methodology. [ABSTRACT FROM AUTHOR]

Allan Franklin has identified a number of strategies that scientists use to build confidence in experimental results. This paper shows that Franklin's strategies have direct analogues in the context of computer simulation and then suggests that one of his strategies—the so-called 'Sherlock Holmes' strategy—deserves a privileged place within the epistemologies of experiment and simulation. In particular, it is argued that while the successful application of even several of Franklin's other strategies (or their analogues in simulation) may not be sufficient for justified belief in results, the successful application of a slightly elaborated version of the Sherlock Holmes strategy is sufficient. [ABSTRACT FROM AUTHOR]

The article features a prototype for hardware-in-the-loop simulation (HILS) of a distributed control architecture. The study presents work with regard to specification of requirement, design, and development of a HILS-based advance tool for the configuration, validation, and management of a control network. It examines the basic infrastructure require to realize the HILS tool for its most of the state-of-the-art attributes of control software including modularity, flexibility, GUI-conformant user-friendliness, and multiuser capability.

Abstract: This paper proposes two new distance-constrained capacitated vehicle routing problems (DCVRPs) to investigate for the first time, and study potential benefits in flexibly assigning start and end depots. The first problem, DCVRP_Fix is an extension of the traditional symmetric DCVRP, with additional service and travel time constraints, minimization of the number of vehicles and flexible application to both symmetric and asymmetric problems. The second problem, DCVRP_Flex is a relaxation of DCVRP_Fix to enable the flexible assignment of start and end depots. This allows vehicles the freedom to start and end their tour at different depots, while allowing for intermediate visits to any depot (for reloading) during the tour. Network models, integer programming formulations and solution algorithms for both problems are developed and presented in this paper. An analytical comparison of both problems is carried out with Singapore as a case study, considering the impact of depot locations and problem symmetry using four cases. Results show a generation of cost savings up to 49.1% by DCVRP_Flex across all the four cases. A significant portion of this stems from the flexibility to reload at any depot while the rest of it is derived from the flexibility to return to any depot. DCVRP_Flex’s adaptability and superior performance over DCVRP_Fix provides strong motivation for further research on improved exact algorithms and heuristics for this problem. [Copyright &y& Elsevier]

Abstract: In this paper, we investigate bidirectional associative memory Cohen–Grossberg neural networks with time delays. By applying the Young inequality technique, Dini derivative, and introducing many real parameters, a series of new and useful criteria on the existence and uniqueness of an equilibrium point and its global asymptotical stability are established. It is shown that in some special cases of the results, the stability criteria can be easily checked. Finally, an example is given to illustrate the result obtained in this paper. [Copyright &y& Elsevier]