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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]

Discrete hard fault is always tested in existing node selection methods for analog circuit diagnosis. Actually, analog component parameter changes continuously and output node voltages distribute in a continuous voltage interval. In this paper, an novel test node selection method is proposed for continuous parameter shifting (CPS) fault. Firstly, CPS faults are sampled by parameter scan simulation in a single test frequency. Collected node voltages are seen as a data set in a statistical distribution. Secondly, ambiguous faults are identified according to the independent distributions of all CPS faults. The independence of CPS fault sample is deduced by Kruskal-Wallis non-parametric testing. Then, new fault dictionaries are generated for each test node according to ambiguous interval. The proposed fault dictionary represents the mutual independence of each pair of CPS faults. Finally, as fault dictionaries are considered as connected graphs, the optimal test nodes are selected based on an improved depth first search (DFS) algorithm. The effectiveness of method is verified by testing linear and nonlinear circuits. [ABSTRACT FROM AUTHOR]

Charge accumulation on a solid insulator surface is one of the critical factors for the development of dc gas-insulated equipment since it will lead to the overstress of polymeric insulation due to local field distortion and enhancement. Therefore, it is important to study the charge accumulation phenomenon on spacer surface under dc field. For decades, researchers have made tremendous progress on this subject by measurement and simulation. However, measurement results are quite different by different researchers due to various electrode configurations and experimental conditions. Further, most researchers use potential to represent charge density, which is not rigorous in that many charge density distribution details are hidden behind the potential. As for pure numerical simulation, reports are rather academic and sometimes cannot accord with the real fact. In this paper, attempts are made to characterize the charge accumulation patterns on spacer surface in HVDC gas-insulated system. Surface charge distributions on a model GIL spacer in 0.1 MPa air under DC voltage are obtained by an advanced measurement method, from which the dominant uniform charging pattern and random charge speckles are separated. Mechanism responsible for the dominant uniform charging pattern is discussed with the aid of a simulation model. Results indicate that, in a well-cleaned system, the electric current through the spacer bulk is the principal factor, but gas conduction is not negligible due to some inevitable ion sources. Highly localized pockets of charge are also observed, which are referred to as speckles. They may originate from micro discharges due to tiny metal particles on the spacer surface or microscopic protrusions on the electrodes. [ABSTRACT FROM PUBLISHER]

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]

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]

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]

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]

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]

In this paper, we present the first computer simulation of methanol exchange dynamics between the first and second solvation shells around different cations and anions. After water, methanol is the most frequently used solvent for ions. Methanol has different structural and dynamical properties than water, so its ion solvation process is different. To this end, we performed molecular dynamics simulations using polarizable potential models to describe methanol-methanol and ion-methanol interactions. In particular, we computed methanol exchange rates by employing the transition state theory, the Impey-Madden-McDonald method, the reactive flux approach, and the Grote-Hynes theory. We observed that methanol exchange occurs at a nanosecond time scale for Na+ and at a picosecond time scale for Cs+, Cl-, and I-. We also observed a trend in which, for like charges, the exchange rate is slower for smaller ions because they are more strongly bound to methanol. [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]

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]

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]

Abstract: Churn is a basic and inherent problem in P2P networks. A lot of relevant studies have been carried out, but all lack versatility. In this paper, a general solution is proposed which makes a peer-to-peer (P2P) network need not pay much attention to churn problem by introducing a logic layer named Dechurn, and most of churn could be eliminated in the Dechurn layer. For utilizing the complementary nature of node joining and leaving, a network scheme, named Constellation, for handling churn is designed on the Dechurn layer through which the resources cached in a node for its spouse node who has left network would be succeeded by a node in latent period. The simulation results indicate that the proposed solution is effective and efficient in handling churn and easy to put into practice. [Copyright &y& Elsevier]

Abstract: This paper addresses the attitude control problem for a twin rotor unmanned helicopter driven by DC motors. The control objective is to have the helicopter attitude, i.e., pitch and yaw angles, track specified angles. From the considered dynamics of the plant, it is observed that the main difficulty of the control problem is due to the existing nonlinear coupling effects between the two perpendicular rotors. Hence, a novel adaptive control approach based on the backstepping concept is developed to solve the problem. In the controller design, the system parameters are assumed to be unavailable and are estimated on-line. The stability of the overall closed-loop system is proven to be asymptotically stable based on the Lyapunov theorem. In order to demonstrate the applicability of the proposed control scheme, computer simulations and experiments are shown. [Copyright &y& Elsevier]

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]

Abstract: A number of models involving reaction–diffusion equations have been developed by different authors to describe the changes in frequency of alleles in a population. Each of these models describes the case in which there are only two possible alleles at the locus in question. In the present paper, we are interested in the more realistic possibility of three alternative alleles. A system of reaction–diffusion equations can be developed to describe this situation. After transforming to the traveling wave coordinates, we introduce a nonlinear transformation which allows us to find exact solutions under certain conditions imposed on two of the parameters. [Copyright &y& Elsevier]

Abstract: This paper deals with the qualitative analysis of a model describing the competition between tumor and immune cells. Such competition is characterized by proliferation–destruction phenomena and the interacting entities are characterized by a microscopic state which is modified by interactions. The model also includes the description of the natural trend of immune cells to reach a healthy or sentinel level, even when they have been involved in the competition with the tumor cells. The model is developed in the mathematical framework of the kinetic theory for active particles. [Copyright &y& Elsevier]

Abstract: In this paper, we consider the multipoint boundary value problem for one-dimensional -Laplacian subject to the boundary conditions: where . Applying the fixed point theorem due to Avery and Peterson, we study the existence of at least three symmetric positive solutions to the above boundary value problem. The interesting point is that the nonlinear term contains the first-order derivative explicitly and the boundary condition is of Sturm–Liouville type. [Copyright &y& Elsevier]

Abstract: In this paper, we give the solution of the inverse Sturm–Liouville problem on two partially coinciding spectra. In particular, in this case we obtain Hochstadt’s theorem concerning the structure of the difference for the singular Sturm Liouville problem defined on the finite interval having the singularity type at the points 0 and . [Copyright &y& Elsevier]

Abstract: This paper analyzes, on the basis of methods of the mathematical kinetic theory of active particles, some complexity problems related to the evolution of reciprocal feelings. Specifically, the analysis is focused on the complexity problems generated by triple interactions, with respect to simple binary encounters. Complexity refers not only to the structure of the equation, but also to the variable describing reciprocal feelings. [Copyright &y& Elsevier]

Abstract: Let be a sequence of i.i.d. random variables taking values in a real separable Hilbert space with mean zero and covariance and set . Let be the eigenvalues of arranged in non-increasing order and take into account the multiplicities. Let be the dimension of the corresponding eigenspace of largest eigenvalue . Let . This paper studies the precise rates for . We show that when and implies where is the Gamma function and . [Copyright &y& Elsevier]

Abstract: In this paper we have proven uniqueness theorems for estimation of the age-dependent parameter in the Gompertz survival model with a mortality deceleration rate, in the absence of age-specific mortality data. We obtained estimations dependent on and uniform in the population size . [Copyright &y& Elsevier]

Abstract: Upon demand realization in the newsvendor problem, it is often assumed that shortages result in lost sales penalties. However, in some practical situations, shortages are backlogged and the inventory manager is penalized based on the magnitude and duration of the shortage. In this paper, we investigate a variation of the newsvendor problem in which all shortages are backlogged and replenished through an emergency procurement process. Costs incurred during emergency procurement include a variable emergency ordering cost and a non-linear customer waiting cost. We derive closed form expressions for the optimal order quantity and emergency procurement rate for two special cases, and we propose a heuristic approximation for the general case. The effectiveness of the approximate solution is assessed through numerical experiments and sensitivity analysis. [Copyright &y& Elsevier]

Abstract: This paper presents the results of computer simulations of road safety barrier behaviour under vehicle crash conditions for high containment levels as mandated by the European standard EN 1317. Simulations were performed with the explicit finite element code LS-DYNA, running on a multiprocessor computational platform. A very good agreement of simulation and real crash tests results was observed, which in turn justifies the use of computer simulations in the process of development and certification of road safety barriers. [Copyright &y& Elsevier]

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]

Abstract: This paper considers the Liénard-type systems with continuously distributed delays. Some sufficient conditions for the existence and exponential stability of the almost periodic solutions are established, which are new and complement previously known results. [Copyright &y& Elsevier]

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]

Abstract: This paper presents a physically based simulation of atmospheric phenomena. It takes into account the physics of non-homogeneous media in which the index of refraction varies continuously, creating curved light paths. As opposed to previous research on this area, we solve the physically based differential equation that describes the trajectory of light. We develop an accurate expression of the index of refraction in the atmosphere as a function of wavelength, based on real measured data. We also describe our atmosphere profile manager, which lets us mimic the initial conditions of real-world scenes for our simulations. The method is validated both visually (by comparing the images with the real pictures) and numerically (with the extensive literature from other areas of research such as optics or meteorology). The phenomena simulated include the inferior and superior mirages, the Fata Morgana, the Novaya–Zemlya, the Viking''s end of the world, the distortions caused by heat waves and the green flash. [Copyright &y& Elsevier]

1. In recent years the use of species distribution models by ecologists and conservation managers has increased considerably, along with an awareness of the need to provide accuracy assessment for predictions of such models. The kappa statistic is the most widely used measure for the performance of models generating presence–absence predictions, but several studies have criticized it for being inherently dependent on prevalence, and argued that this dependency introduces statistical artefacts to estimates of predictive accuracy. This criticism has been supported recently by computer simulations showing that kappa responds to the prevalence of the modelled species in a unimodal fashion. 2. In this paper we provide a theoretical explanation for the observed dependence of kappa on prevalence, and introduce into ecology an alternative measure of accuracy, the true skill statistic (TSS), which corrects for this dependence while still keeping all the advantages of kappa. We also compare the responses of kappa and TSS to prevalence using empirical data, by modelling distribution patterns of 128 species of woody plant in Israel. 3. The theoretical analysis shows that kappa responds in a unimodal fashion to variation in prevalence and that the level of prevalence that maximizes kappa depends on the ratio between sensitivity (the proportion of correctly predicted presences) and specificity (the proportion of correctly predicted absences). In contrast, TSS is independent of prevalence. 4. When the two measures of accuracy were compared using empirical data, kappa showed a unimodal response to prevalence, in agreement with the theoretical analysis. TSS showed a decreasing linear response to prevalence, a result we interpret as reflecting true ecological phenomena rather than a statistical artefact. This interpretation is supported by the fact that a similar pattern was found for the area under the ROC curve, a measure known to be independent of prevalence. 5. Synthesis and applications. Our results provide theoretical and empirical evidence that kappa, one of the most widely used measures of model performance in ecology, has serious limitations that make it unsuitable for such applications. The alternative we suggest, TSS, compensates for the shortcomings of kappa while keeping all of its advantages. We therefore recommend the TSS as a simple and intuitive measure for the performance of species distribution models when predictions are expressed as presence–absence maps. [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]

A magnetically levitated motor (MLM) with two directions of movement is presented in this paper. The thrust and the levitation force of the proposed motor can be achieved simultaneously by using only a single power source. Analytical equations for the operation principle of the proposed MLM are derived. Computer simulations of the MLM characteristics by using the finite-element-analysis method are also presented. The same trend can be found between analytical equations and computer-simulation results. Then, some experimental results are provided to confirm the theoretical analysis. All of the results can provide very useful information of mechanical-structure design and control scheme development for the MLM. [ABSTRACT FROM AUTHOR]

In this paper we consider the problem of robust radar detection in the presence of Gaussian disturbance with unknown covariance matrix. We design and assess three new robust adaptive detectors, capable of operating in the presence of unknown discrepancies between the nominal and the actual steering vector. Remarkably the new decision rules exhibit a bounded constant false alarm rate (CFAR) behavior and allow, through the regulation of a design parameter, to trade off target sensitivity with sidelobes energy rejection. Finally computer simulations show that the proposed detectors achieve a visible performance improvement, in many situations of practical interest, over the traditional adaptive detection algorithms, especially in the presence of severe steering vector mismatches. [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]

Abstract: Real-time computer simulation is required in a number of applications, where the simulated dynamic systems are directly coupled with systems in the real world or with other systems also running in real-time. Typical problems of real-time simulations are that the dynamics of the modeled system are not represented in enough detail, either by not sampling the inputs or not producing output values frequently enough or both. Increasing the sampling frequencies may lead, as an additional problem, to real-time violations caused by insufficient computing power. The latter problem is amplified if the real-time is accelerated to achieve a kind of fast motion and reduce experiment times. In this paper, we show how the first problem can be solved by automatic frequency adjustment, minimizing the number of computations and how the remaining second problem can be reduced by trading a graceful degradation of accuracy against the computing power requirements automatically. Experiments show that simulation times could be reduced by a factor of 100 without unacceptable simulation errors. [Copyright &y& Elsevier]

This paper proposes a framework for versatile discrete objects simulation. The framework, named VEDO, is developed using object-oriented technology with design patterns. VEDO is capable of handling simultaneously discrete objects of various shapes and various mechanisms of interactions between discrete objects. It also has great flexibility in facilitating additions of new discrete object shapes and solution algorithms for discrete object interactions. Based on the proposed framework, a discrete objects simulation system, named Knight&Anne, has been implemented in C++ in this study. In addition, some application examples are given to demonstrate the capability and flexibility of the framework. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, a Markovian queue with two heterogeneous servers and multiple vacations has been studied. For this system, the stationary queue length distribution and mean system size have been obtained by using matrix geometric method. The busy period analysis of the system and mean waiting time distribution are discussed. Extensive numerical illustrations are provided. [Copyright &y& Elsevier]

In this paper, based on the application of the sum-product (SP) algorithm to factor graphs (FGs) representing the joint a posteriori probability (APP) of the transmitted symbols, we propose new iterative soft-input soft-output (SISO) detection schemes for intersymbol interference (ISI) channels. We have verified by computer simulations that the SP algorithm converges to a good approximation of the exact marginal APPs of the transmitted symbols if the FG has girth at least 6. For ISI channels whose corresponding FG has girth 4, the application of a stretching technique allows us to obtain an equivalent girth-6 graph. For sparse 151 channels, the proposed algorithms have advantages in terms of complexity over optimal detection schemes based on the Bahl-Cocke-Jelinek-Raviv (BCJR) algorithm. They also allow a parallel implementation of the receiver and the possibility of a more efficient complexity reduction. The application to joint detection and decoding of low-density parity-check (LDPC) codes is also considered and results are shown for some partial-response magnetic channels. Also in these cases, we show that the proposed algorithms have a limited performance loss with respect to that can be obtained when the optimal "serial" BCJR algorithm is used for detection. Therefore, for their parallel implementation, they represent a favorable alternative to the modified "parallel" BCJR algorithm proposed in the literature for the application to magnetic channels. [ABSTRACT FROM AUTHOR]

A new scheme for the compensation of traveling wave tube amplifier nonlinearities is proposed and analyzed in this paper. The approach is based on rational function models of the amplifier AM-AM and AM-PM conversions. Amplitude and phase predistortion are performed separately. The phase predistortion is a function of the output of the amplitude predistortion part of the predistorter, instead of the input signal amplitude of the predistorter. Computer simulations reveal an improved performance compared to published techniques and suggest that with the proposed technique the transmit power amplifier can operate far into its nonlinear region. The transfer characteristics of the cascade of the amplifier and the proposed predistorter match the optimum transfer characteristics of a saturating device. [ABSTRACT FROM AUTHOR]

This paper describes experiments on the formation and transport, in vacuum and plasma, of a low-energy (70-120 keV), high-intensity (10-30 A/cm²), long-pulse (0.5-1 μs) H+ ion beam. The beam was generated in a magnetically insulated diode with an applied radial B-field and active hydrogen-puff plasma source at the anode. The combination of a ballistic focusing large area anode (250 cm²) with a post-cathode toroidal magnetic tens and straight transport solenoid section provided beam transport to a distance of > 1 m with an overall efficiency of ≥50%. Two-dimensional single-particle computer simulations of the ion's trajectory in the lens/solenoid system supported optimization of the lens and solenoid parameters. [ABSTRACT FROM AUTHOR]

In this paper, we use a simplified model to simulate the amorphization phenomenon in metals under irradiation. The model has few parameters but can reflect the essential characteristics of the processes. Our simulation results show that the relaxation of collision cascades forms small crystal grains and the amorphization phenomenon is a result of total overlap of different grains, which depends on the irradiation temperature. [Copyright &y& Elsevier]

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]

Both simulation and analytic models of computer systems can be very useful for predicting the performance of proposed new systems or proposed changes to existing systems. Unfortunately, many potential users of models are reluctant to use them because of the complexity of many such models and the difficulty of relating the model to the real system. This tutorial paper leads the reader through the development and use of an easily understood analytic model. This is then placed in context with a class of similar analytic models. In spite of the simplicity of these models they have proved useful and quite accurate in predicting performance (utilization, throughput, and response) using only the most basic system data as input. These parameters can either be estimates or measurements from a running system. The model equations and assumptions are defined, and a detailed case study is presented as an example of their use. [ABSTRACT FROM AUTHOR]

The paper considers the implementation of distributed discrete event simulation (DDES) using what has been commonly called the Misra approach, after one of the inventors of the approach. A major problem with DDES is that deadlock can occur. Therefore, DDES algorithms must either avoid deadlock in the first place, or detect the existence of deadlock when it does occur and eliminate the deadlock. Misra proposes the use of NULL messages as one way to circumvent the deadlock problem. However, the number of NULL messages can become quite large. Methods are presented for reducing the number of NULL messages through the prediction of channel times. A framework is presented on which the distributed discrete event simulation can be built for applications which can be decomposed into feedforward and feedback networks. [ABSTRACT FROM AUTHOR]

In this paper, we present a general approach for constructing high-rate cycle codes having girth 12 which achieve the lower bound on the block length. An efficient encoding algorithm is also proposed for this class of codes. We estimate the word error rate of the cycle codes for additive white Gaussian noise (AWGN) channels under maximum likelihood decoding, using the minimum distance and its multiplicity. These estimates are compared to simulation results with iterative soft decoding. The performance of these codes for partial response channels is studied under iterative soft decoding using computer simulations. [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]