Search

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 proposes improving the directivity of microstrip patch antennas (MPAs) by using metamaterials. Four different metamaterial types are used as a at lens in front of the MPA, respectively, which are tuned to 12 GHz (Ku-band) resonance frequency. Thus, it can be decided which metamaterial is more proper for antenna directivity enhancement at this band. One additional new metamaterial structure is proposed in this paper, which is called a Euro-shaped resonator, and other metamaterials used are the triangular split ring resonator, symmetrical ring structure, and split ring resonator. The permeability and permittivity of metamaterials are extracted from the S parameters by using a robust method. Microwave Studio by Computer Simulation Technology is used for modeling and simulation. The MPA and metamaterials are fabricated, and measurements are performed in the Yíldíz Technical University RF and Microwave Laboratory. It is observed that measured results are in close agreement with the computer simulations. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to investigate a method to derive component metal–metal electrostatic discharge (ESD) rating from its human body model (HBM) ESD rating. Symbolic computations and equivalent circuit simulations are used for this purpose. It can be seen from the components datasheets, that the machine model (MM) rating is often ten times less than the HBM rating. This paper proposes an explanation of this dependence derived from thermal failure physics. This paper presents a method of the ESD rating estimation based on injected power or charge analysis. This estimation method also could be applied for the CDM and charged board model (CBM) cases. We obtained a good correlation of HBM and MM ratings and a limited correlation of HBM and CBM/CDM ratings. The CBM case for power mosfet also was considered. [ABSTRACT FROM AUTHOR]

Designers of hydraulically driven machines and devices are obliged to ensure during design process their high service life with taking into account their operational conditions. Some of the machines may be started in low ambient temperature and even in thermal shock conditions (due to delivering hot working medium to cold components). In order to put such devices into operation appropriate investigations, including experimental ones - usually very expensive and time-consuming, are carried out. For this reason numerical calculations can be used to determine serviceability of a hydraulic component or system operating in thermal shock conditions. Application of numerical calculation methods is much less expensive in comparison to experimental ones. This paper presents a numerical calculation method which makes it possible to solve issues of heat exchange in elements of investigated hydraulic components by using finite elements method. For performing the simulations the following data are necessary: ambient temperature, oil temperature, heat transfer coefficient between oil and surfaces of elements, as well as areas of surfaces being in contact with oil. By means of computer simulation method values of clearance between cooperating elements as well as ranges of parameters of correct and incorrect operation of hydraulic components have been determined. In this paper results of computer simulation of some experimentally tested hydraulic components such as axial piston pump and proportional spool valve, are presented. The computer simulation results were compared with the experimental ones and high conformity was obtained. [ABSTRACT FROM AUTHOR]

This paper describes the improvements in the simulation of a heavy rainfall event due to the assimilation of surface wind observations from the Oceansat-2 scatterometer using ensemble Kalman filter (EnKF) technique. A heavy rainfall event over the southern peninsular region of India during the northeast Indian monsoon season is investigated in this paper using the Advanced Research Weather Research and Forecasting model. A control (CTRL) run where no surface wind observations are assimilated, as well as a 3-D variational (3DVar) run and an EnKF run wherein surface wind observations are assimilated using the 3DVar and EnKF techniques, is performed. Results indicate that the EnKF assimilation run simulates various meteorological fields, including precipitation fields during the rainfall event, better than the CTRL and the 3DVar runs. Qualitative and quantitative comparisons with Tropical Rainfall Measurement Mission precipitation observations indicate that the rainfall simulation shows improvement due to EnKF assimilation as compared with the other two model runs. Vertical profiles of area-averaged and time-averaged relative vorticities and temperature anomalies around the low-pressure system are also better reproduced in the EnKF experiment. Considering the importance of accurate real time simulations of heavy rainfall events associated with the Indian monsoon season, this paper provides encouraging results on the utility of EnKF technique as applied over the Indian region. [ABSTRACT FROM PUBLISHER]

In this paper, we study the location optimization problem of remote antenna units (RAUs) in generalized distributed antenna systems (GDASs). We propose a composite vector quantization (CVQ) algorithm that consists of unsupervised and supervised terms for RAU location optimization. We show that the CVQ can be used i) to minimize an upper bound to the cell-averaged SNR error for a desired/demanded location-specific SNR function, and ii) to maximize the cell-averaged effective SNR. The CVQ-DAS includes the standard VQ, and thus the well-known squared distance criterion (SDC) as a special case. Computer simulations confirm the findings and suggest that the proposed CVQ-DAS outperforms the SDC in terms of cell-averaged "effective SNR". [ABSTRACT FROM AUTHOR]

A superconducting transformer with the windings made of second-generation high-temperature superconducting (HTS) tape can limit short-circuit current effectively. Despite this, due to the small cross-section of normal metal layers and low thermal capacity of windings, fault current must be switched OFF by an additional device in relatively short time to prevent a catastrophic temperature rise. The paper presents the computer simulation of short-circuit fault suppressed by a single-phase 10 kVA superconducting transformer. Numerical results were comparedwith experimental data to validate the model. Authors attempted to extend the method to an industrial size HTS transformer and estimate the dimensions of copper cowindings. [ABSTRACT FROM AUTHOR]

The particle-in-cell (PIC) method has been widely used for plasma simulation, because of its noise-reduction capability and moderate computational cost. The immersed finite element (IFE) method is efficient for solving interface problems on Cartesian meshes, which is desirable for the PIC method. The combination of these two methods provides an effective tool for plasma simulation with complex interface/boundary. This paper introduces an improved IFE–PIC method that enhances the performance in both IFE and PIC aspects. For the electric field solver, we adopt the newly developed partially penalized IFE method with enhanced accuracy. For PIC implementation, we introduce a new interpolation technique to ensure the conservation of the charge. Numerical examples are provided to demonstrate the features of the improved IFE–PIC method. [ABSTRACT FROM AUTHOR]

In the present paper, experimental and numerical studies of a newly developed process of Hot-Blade Cutting used for free forming of double-curved surfaces and cost effective rapid prototyping of expanded polystyrene foam is carried out. The experimental part of the study falls in two parts. The first presents a number of large-scale cutting samples combining linear cuts with and without inclination measured from the horizontal direction of cutting, while in the second, the thermal phenomena in the process are studied based on infrared measurements of the hot-blade tool made by observation during the cutting process. A novel measurement method for determination of kerfwidth (i.e., the gap space after material removal) applying a commercially available large-scale optical 3D scanning technique was developed and used. A one-dimensional thermo-electro-mechanical numerical model for Hot-Blade Cutting similar to the one previously proposed by Petkov and Hattel (Int J Machine Tools Manuf 107:50-59 2016) for Hot-Wire Cutting of Polystyrene foam is used to simulate the process and describe the effects taking place within the hot-blade during different cutting procedures. The obtained results are graphically presented and discussed in relation to the aim for higher geometrical accuracy of the Hot-Blade Cutting process. [ABSTRACT FROM AUTHOR]

In modal testing, the measured frequency response functions (FRFs) are often affected by transducer mass effects. Especially when multiple sensors are employed, transducers mass effects are more significant. This paper deals with removing sensors mass effects from the measured FRFs in hammer impact testing. The proposed method offers some advantages over the available techniques in that extra FRFs measurements with different configurations are not required during the correction process. Firstly, correction method for single accelerometer case is discussed. Further, general correction formulation for multiple accelerometers case is derived. Then, validations of the proposed method are demonstrated using simulated and experimental data. It shows good effectiveness in experimental validation for single accelerometer case. Numerical simulation also demonstrates a good performance for multiple accelerometers case. However, further simulations with noisy-polluted data show that the accuracy of correction results will be affected to some extent by the noise. It is suggested that the measured FRFs be preprocessed using the curve-fitting procedure or noise reduction processing before applying the proposed method. [ABSTRACT FROM AUTHOR]

This paper presents the design consideration on a converged Rx surface acoustic wave (SAW) duplexer module for integrated RF front end. Two different matching-circuit and notch-circuit configurations were examined with importance placed on electrical characteristics (insertion loss and isolation of duplexer) and simplification of module, respectively. From circuit simulations and examinations, we verified that a simplified design was best in terms of both characteristics and space in the case of a finite inductor’s Q. We also fabricate a quad-band converged Rx module (Band I + II, V + VIII) using an SAW duplexer and verified that its electrical characteristics agree well with our simulation results. [ABSTRACT FROM PUBLISHER]

This paper analyzes the incline unbalanced magnetic pull (IUMP) generated in the permanent magnetic synchronous motor (PMSM) with the rotor misalignment. The motor magnetic field in such a motor is asymmetric, and both the magnitude and the action point of UMP vary in motor operation. This paper presents an analytical model for analyzing the 3-D effects of the UMP induced by the misalignment rotor. The numerical simulation results prove the effectiveness of the proposed analytic model. [ABSTRACT FROM PUBLISHER]

A team of specimens containing different dip angles of a single three- Dimensional (3D) crack were made by using a new type of unsaturated transparent and rock-like resin. The propagation and coalescence process of a single 3D crack under uniaxial compression were studied, and its production conditions and mechanism were further analyEed. It's shown by the test results that the failure process of specimens containing a single 3D crack can be generally divided into four stages. The fracture of a single 3D crack, which produces a variety of different forms of cracks, is much more complex than the fracture of a single 2D crack. In this paper, by employing the analysis software of FLAC3D and establishing a new elastic-brittle constitutive relation, as well as using superfine unit division, the propagation process of a single 3D crack were simulated and studied. The numerical results match well with the testing results in this paper and that obtained by former scholars, which suggests the effectiveness of the new numerical simulation method. [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]

To solve high heat flux cooling problems in case of modern electronic appliances, a novel heat pipe cold plate is designed and developed. The heat pipe cold plate is uniquely-different from normal thermosyphons, in which the acetone-aluminum heat pipe construction is composed of eight vertical heat pipe branches with their upper ends and lower ends connected with each other by two horizontal heat pipe branches, respectively, which make the working vapour and liquid flow smooth within the internal flow space of the heat pipe cold plate. In this paper, based on previous experimental and theoretical studies, a mathematical model for numerical simulations of the vapour-liquid two-phase flow and heat transfer phenomena in the heat pipe cold plate is presented. Two-fluid-model is employed to describe flow characteristics and phase interaction between vapour and liquid phases. Differential equations are solved by finite volume method and IPSA algorithm is employed to consider the vapour-liquid coupling effect. Effects of the total heating power and the cooling water flow rate on wall temperature distribution and two-phase flow heat transfer characteristics are numerically simulated. Computation results well agree with experimental results. The novel heat pipe cold plate possesses excellent heat transfer characteristics and temperature uniformity performance; it can provide a much better cooling solution for multi-heat-source and high heat-flux cooling problems than forced-convection cooling techniques. Also, numerical solution established and realized in this paper can be used as a reference. [ABSTRACT FROM AUTHOR]

This paper presents a simplified analysis of a generalized cycloconverter and suggests a new method for the estimation of the cycloconverter period as a function of the control mode. The paper presents generalized theoretical results supported by computer simulations and demonstrated by examples. [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]

Abstract: Real-time rendering of virtual weather conditions has been investigated in many papers. Inserting fog or snow in a scene is rather straightforward. Rain is one of the most encountered natural phenomena, but its rendering often lacks realism. In this paper, we propose a realistic real-time rain rendering method using programmable graphics hardware. In order to simulate the refraction of the scene inside a raindrop, the scene is captured to a texture which is distorted according to optical properties of raindrops. This texture is mapped onto each raindrop. Our method also takes into account retinal persistence, and interaction with light sources. [Copyright &y& Elsevier]

In this paper a new RC - active polyphase filter section is presented. The section uses three conventional current conveyor (CCII). With a cascade of these sections, any higher order polyphase filter function can be realized. Frequency transfer functions, gain and phase errors of the proposed section are derived for ideal and nonideal CCIIs. In the case of using nonideal CCIIs filter characteristics are investigated by performing computer simulations. Also the paper deals with the leakage caused by the effects of a limited gains of a current conveyors. [ABSTRACT FROM AUTHOR]

This paper describes an innovative scheme based on a pluralistic load frequency control (LFC) and aimed at performing cross-border power control, secondary frequency regulation, and internal congestion resolution. Such an LFC scheme applies to a pluralistic block of control areas, whose regulators can adjust the production of their generators with respect to the request of the coordinating area when the power flows through grid sections exceed their maximum admissible values. This paper introduces the theoretical aspects and functional design of such an advanced LFC scheme, capable of controlling at the same time the cross border exchanges of the pluralistic block and the power flows between network subareas defined as market zones. Simulations on the Italian power system show the performance, main advantages, and limits of the proposed control method. [ABSTRACT FROM AUTHOR]

This paper considers a profit-maximizing thermal producer that participates in a sequence of spot markets, namely, day-ahead, automatic generation control (AG C), and balancing markets. The producer behaves as a price-taker in both the day-ahead market and the AGC market but as a potential price-maker in the volatile balancing market. The paper provides a stochastic programming methodology to determine the optimal bidding strategies for the day-ahead market. Uncertainty sources include prices for the day-ahead and AGC markets and balancing market linear price variations with the production of the thermal producer. Results from a realistic case study are reported and analyzed. Conclusions are duly drawn. [ABSTRACT FROM AUTHOR]

This paper presents a systematic way of using linear analysis techniques to find and rank candidate locations for controlled shunt and series compensations for power system damping purposes. A two-stage approach based on frequency response computations is introduced using a 4780-bus system model of the Nordic power system for assessment of controlled shunt compensations. In the first stage, their controllability is determined by means of long-distance frequency responses. In the second stage, the frequency responses of the transfer functions from the bus shunt susceptance to the bus voltage magnitude are computed for buses that have shown high controllability. This paper shows that the interpretation of the frequency responses of these local transfer functions, for buses that have exhibited high controllability, is in most cases sufficient to predict the behavior of controlled shunt compensation at different locations in the system. The interpretation is based on the observation of amplitudes, phase angles, and the rate of change of the phase angles around the interarea resonance frequencies. An important finding was that controlled shunt compensation located in an area with high-power import over ac interconnections lowered the damping of at least one of the interarea oscillation modes if operating in normal voltage control. This finding was also verified with nonlinear simulations. The first stage of the proposed frequency response-based approach has also been introduced for assessment of controlled series compensations. The strength of the new methods is that they can be used with both linear and nonlinear system models. [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]

With the application of information technology, many parties involved in construction projects have turned to handle the management information using computer systems among themselves, while they still exchange information on papers between them. It has introduced such deficiencies as inefficiency of collaboration and re-entry of data in the management of construction projects. This study aims to develop a system for the parties in construction projects to collaborate on Web to improve the management of the exchanged information. In this paper, the characteristics of the exchanged information in construction projects in China are summarized based on the literature survey and field investigation, and a Web-based approach to developing a system for the management of exchanged information in construction projects is proposed. Then the prototype system that we have developed by using the latest information technologies including eXtensible Markup Language (XML) is examined and its applicability is discussed. [Copyright &y& Elsevier]

In most approaches to the problem of two-dimensional homomorphic deconvolution of ultrasound images, the estimation of a corresponding point-spread function (PSF) is necessarily the first stage in the process of image restoration. This estimation is usually performed in the Fourier domain by either successive or simultaneous estimation of the amplitude and phase of the Fourier transform (FT) of the PSF. This paper addresses the problem of recovering the FT-phase of the PSF, which is an important reconstruction problem by itself. The purpose of this paper is twofold. First, it provides a theoretical framework, establishing that the FT-phase of the PSF can be effectively estimated by a proper smoothing of the FT-phase of the appropriate radio-frequency (RF) image. Second, it presents a novel approach to the estimation of the FT-phase of the PSF, by solving a continuous Poisson equation over a predefined smooth subspace, in contrast to the discrete Poisson equation solver used for the classical least mean squares phase unwrapping algorithms, followed by a smoothing procedure. The proposed approach is possible due to the distinct properties of the FT-phases, among which the most important property is the availability of precise values of their partial derivatives. Since such an approximation is feasible subject to the restriction that the partial phase differences do not exceed π in absolute value, the discrete schemes perform satisfactory only for few practical situations. The proposed approach is shown to be independent of this restriction and, thus, it performs for a wider class of the phases with significantly lower errors. The main advantages of the novel method over the algorithms based on discrete schemes are demonstrated in a series of computer simulations and for in vivo measurements. [ABSTRACT FROM AUTHOR]

Several different seismic active control algorithms have been proposed in the last decades, most of these studies are based on the applications of the traditional linear quadratic regulator control (LQR). This paper develops a new control algorithm for SDOF structures based in Lyapunov method. This algorithm uses Lyapunov's direct approach for stability analysis in design of feedback controller. The approach requires the use of Lyapunov function candidate, which must be a positive definite function of the states of the system. The controller is designed so as to make the derivative of the Lyapunov function negative semidefinite. Numerical simulations using one story frame structure modeled as shear building structure subjected to earthquake excitations have been performed to evaluate the effectiveness of the proposed algorithm. [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]

A network is considered observable if its current state can be determined in finite time from knowledge of the observed states. The observability transitions in networks based on random or degree-correlated sensor placement have recently been studied. However, these placement strategies are predominantly based on local information regarding the network. In this paper, to understand the phase transition process of network observability, we analyze the network observability transition for a betweenness-based sensor placement strategy, in which sensors are placed on nodes according to their betweenness. Using numerical simulations, we compute the size of the network’s largest observable component (LOC) and compare the observability transitions for different sensor placements. We find that betweenness-based sensor placement can generate a larger LOC in the observability transition than the random or degree-based placement strategy in both model and real networks. This finding may help to understand the relationship between network observability and the topological properties of the network. [ABSTRACT FROM AUTHOR]

This paper describes the GridPACKTM framework, which is designed to help power grid engineers develop software capable of running on high-performance computers. The framework makes extensive use of software templates to provide high-level functionality while still providing flexibility to easily implement a broad range of models and algorithms. GridPACKTM contains modules for setting up distributed power grid networks, supporting application-specific bus and branch models, creating distributed matrices and vectors and using parallel linear and non-linear solvers. It also provides mappers to create matrices and vectors based on properties of the network and functionality to support Input/Output (IO) and to manage errors. The goal of GridPACKTM is to substantially reduce the complexity of writing software for parallel computers while still providing efficient and scalable software solutions. The use of GridPACKTM is illustrated for a simple powerflow example and performance results for the powerflow and dynamic simulations are discussed. [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]

The open shortest path first (OSPF) protocol has been widely applied to intra-domain routing in today’s Internet. Since a router running OSPF distributes traffic uniformly over equal-cost multi-path (ECMP), the OSPF-based optimal traffic engineering (TE) problem (i.e., deriving optimal link weights for a given traffic demand) is computationally intractable for large-scale networks. Therefore, many studies resort to multi-protocol label switching (MPLS) based approaches to solve the optimal TE problem. In this paper we present a generalized routing framework to realize the optimal TE, which can be potentially implemented via OSPF- or MPLS-based approaches. We start with viewing the conventional optimal TE problem in a fresh way, i.e., optimally allocating the residual capacity to every link. Then we make a generalization of network utility maximization (NUM) to close this problem, where the network operator is associated with a utility function of the residual capacity to be maximized. We demonstrate that under this framework, the optimal routes resulting from the optimal TE are also the shortest paths in terms of a set of non-negative link weights that are explicitly determined by the optimal residual capacity and the objective function. The network entropy maximization theory is employed to enable routers to exponentially, instead of uniformly, split traffic over ECMP. The shortest-path penalizing exponential flow-splitting (SPEF) is designed as a link-state protocol with hop-by-hop forwarding to implement our theoretical findings. An alternative MPLS-based implementation is also discussed here. Numerical simulation results have demonstrated the effectiveness of the proposed framework as well as SPEF. [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]

This paper deals with modeling and control strategies of the motion of wheeled mobile robots. The model of the vehicle has two driving wheels and the angular velocities of the two wheels are independently controlled. To illustrate how the kinematics model of the system can be used to design P controller and a PI controller is applied. The nonlinear and linearlised models are simulated in MATLAB® and simulink. The results are drawn here to evaluate the performance of the proposed controllers with concerned graphics. [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]

This paper presents a non-destructive, ultrasonic technique to evaluate the quality of bonds between substrates. Shear-horizontally polarized (SH) wave modes are investigated to infer the shear stiffness of bonds, which is necessarily linked to the shear resistance that is a critical parameter for bonded structures. Numerical simulations are run for selecting the most appropriate SH wave modes, i.e., with higher sensitivity to the bond than to other components, and experiments are made for generating-detecting pre-selected SH wave modes and for measuring their phase velocities. An inverse problem is finally solved, consisting of the evaluation of the shear stiffness modulus of a bond layer at different curing times between a metallic plate and a composite patch, such assembly being investigated in the context of repair of aeronautical structures. [ABSTRACT FROM AUTHOR]

Evans’ 1968 ANALOGY system was the first computer model of analogy. This paper demonstrates that the structure mapping model of analogy, when combined with high-level visual processing and qualitative representations, can solve the same kinds of geometric analogy problems as were solved by ANALOGY. Importantly, the bulk of the computations are not particular to the model of this task but are general purpose: We use our existing sketch understanding system, CogSketch, to compute visual structure that is used by our existing analogical matcher, Structure Mapping Engine (SME). We show how SME can be used to facilitate high-level visual matching, proposing a role for structural alignment in mental rotation. We show how second-order analogies over differences computed via analogies between pictures provide a more elegant model of the geometric analogy task. We compare our model against human data on a set of problems, showing that the model aligns well with both the answers chosen by people and the reaction times required to choose the answers. [ABSTRACT FROM AUTHOR]

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, two novel voltage-mode (VM) single- input-three-output (SITO) second-order multifunction analog filters for simultaneously realizing low-pass, bandpass, and high-pass responses from the same topology are proposed. They employ a single dual-output differential voltage current conveyor (DVCC), two grounded capacitors, and three resistors. Both of the proposed filters offer the following two important features: the simultaneous realization of low-pass, bandpass, and high-pass responses and the use of a minimum number of grounded capacitors and a single DVCC. The nonideal gain effects of the developed structures are examined. To show the performance of the proposed VM filters, computer simulation results using the SPICE program, together with ideal ones, are drawn. [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]

This paper presents set-membership (SM) adaptive algorithms based on time-varying error bounds for code-division multiple-access (CDMA) interference suppression. We introduce a modified family of SM adaptive algorithms for parameter estimation with time-varying error bounds. The considered algorithms include modified versions of the SM normalized least mean square (SM-NLMS), the affine projection (SM-AP), and the bounding ellipsoidal adaptive constrained (BEACON) recursive least-square technique. The important issue of error-bound specification is addressed in a new framework that takes into account parameter estimation dependency, multiaccess, and intersymbol interference (ISI) for direct-sequence CDMA (DS-CDMA) communications. An algorithm for tracking and estimating the interference power is proposed and analyzed. This algorithm is then incorporated into the proposed time-varying error bound mechanisms. Computer simulations show that the proposed algorithms are capable of outperforming previously reported techniques with a significantly lower number of parameter updates and a reduced risk of overbounding or underbounding. [ABSTRACT FROM AUTHOR]