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A steady-state sinusoidal and distortion-free excitation source is very important for the accuracy and consistency of the calibration parameters of micro-electro-mechanical systems (MEMS) inertial sensors. To solve the problem that the current MEMS inertial measurement unit (IMU) calibration device is unable to reproduce the spatial motion of linear and angular vibration coupling, research topics on the coupling vibration characteristics and parameter identification for an electromagnetic linear-angular vibration exciter are proposed. This research paper used Ampere's law and Lorentz force to establish the analytical expressions for the electromagnetic force and electromagnetic torque of the electromagnetic linear-angular vibration exciter. Then, the main purpose of this paper is to establish uniaxial and coupled vibration electromechanical analogy models containing mechanical parameters based on the admittance-type electromechanical analogy principle, and the parameter identification model is also obtained by combining the impedance formula with the additional mass method. Finally, the validity of the coupling vibration characteristics and the parameter identification model are verified by the frequency response simulation and the additional mass method, and the relative error of each parameter identification is within 5% in this paper. [ABSTRACT FROM AUTHOR]

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

Summary: This paper develops linear high‐order electromagnetic shunt damping techniques, which offer enhanced effectiveness without sacrificing the structural simplicity and the ease of practical implementation. Inspired by the state‐of‐the‐art vibration control techniques involving the inerter, this paper proposes three high‐order resonant electromagnetic shunt dampers, which are analogous to three distinct nontraditional inerter‐based dynamic vibration absorbers. A systematic optimization for all proposed shunt circuits is carried out and their optimal parameters are tuned and analytically formulated according to the H∞, H2 optimization criteria and the stability maximization criterion (SMC), respectively. Finally, the superior performance of proposed shunt circuits with respect to the conventional resistive‐inductive‐capacitive shunt is theoretically demonstrated via several metrics. Meanwhile, there is no need for electrically synthesizing any electrical components when realizing these high‐order shunts, facilitating their practical implementation. [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]

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

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 derives theoretical solutions for three radially layered piezoceramic/epoxy cylindrical composite transducers, which are composed of a solid epoxy disk, two axially polarized piezoceramic rings, and two epoxy rings. Two piezoceramic rings are the functional components, which can actuate and adjust the composite’s performance. According to different functions, three typical transducers are developed. The first one involves both of the two piezoceramic rings acting as actuating elements with parallel connections electrically. The other two involve only one piezoceramic ring as an actuating element, while the other ring that is connected to a resistor acts as a sensing element to adjust the electromechanical characteristics. Based on the plane stress assumption, theoretical solutions of these three transducers in radial vibration are derived, and performance differences of their electromechanical characteristics are analyzed and discussed. Furthermore, the solutions are validated by comparing with the ANSYS simulation results and the experimental data. The simulated and the measured first resonance and antiresonance frequencies are in a good agreement with the theoretical results, which validates the accuracy of the directed solution. This paper contributes to a comprehensive understanding of the proposed cylindrical composite’s electromechanical performance, which is helpful for further application in underwater sound and ultrasonic fields. [ABSTRACT FROM AUTHOR]

The increasing use of voltage-source converters (VSCs) in modern power systems has led to extensive studies on their frequency response and stability, which are characterized by power-frequency oscillations and overshoots following a disturbance. However, the existing small-signal analysis models do not adequately describe the impact of the types of disturbance on the torque-frequency dynamics of the multi-VSC parallel system. In this paper, based on the principle of electromechanical analogy, a unified equivalent admittance modeling method is proposed by analogizing the rotor dynamic model of a synchronous generator (SG) to the circuit network, which has the advantages of simple modeling, clear physical meaning and easy expansion. Firstly, the equivalent admittance model of a single SG/VSC is established, and then easily extended to the multi-VSC system. The proposed modelling method not only applicable to a variety of VSCs, but also can handle different types of disturbance. More importantly, the circuit theory can be applied to analyze the torque-frequency dynamic characteristics. Subsequently, the equivalence between the proposed model and the state-space model under different damping terms is compared. In addition, the response characteristics of two different damping terms are compared. Next, the dynamic response characteristics of single VSC and multi-VSC parallel systems under different disturbances are analyzed. Finally, related simulations and experiments are executed to verify the accuracy and effectiveness of the proposed method. [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]

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]

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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]

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]

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]

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]

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

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

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

The paper presents another phase of the study aimed at determining distributions of random pulses forcing vibration of an oscillator with damping. At this stage, the impact of the pulses amplitudes on distributions determined in a finite time interval is discussed. Application of a mathematical model in simulations allows to determine the differences between the distributions generated in MATLAB environment and those determined by a function. The experiment was designed so that the qualitative analysis of the issue was possible. [ABSTRACT FROM AUTHOR]

This paper deals with studying of two topics – measuring of velocity profile deformation behind a over-flooded construction and modelling of this velocity profile deformation by computational fluid dynamics (CFD). Numerical simulations with an unsteady RANS models - Standard k-ε, Realizable k-ε, Standard k-ω and Reynolds stress models (ANSYS Fluent v.18) and experimental measurements in a laboratory flume (using ADV) were performed. Results of both approaches showed and affirmed presence of velocity profile deformation behind the obstacle, but some discrepancies between the measured and simulated values were also observed. With increasing distance from the obstacle, the differences between the simulation and the measured data increase and the results of the numerical models are no longer usable. [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]

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]

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]

If an enterprise wishes to gain a competitive advantage through low cost, it needs to have a highly efficient and reliable logistics operation model, which is a vital instrument for the enterprise to win competitive tenders. This paper proposes a cooperation model between electronic commerce and third party logistics, to illustrate how to establish an evaluation index system and how to analyze it systematically using simulation. [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]

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]

This paper focuses on the evaluation of theoretical and numerical aspects related to an original DC microgrid power architecture for efficient charging of plug-in electric vehicles (PEVs). The proposed DC microgrid is based on photovoltaic array (PVA) generation, electrochemical storage, and grid connection; it is assumed that PEVs have a direct access to their DC charger input. As opposed to conventional power architecture designs, the PVA is coupled directly on the DC link without a static converter, which implies no DC voltage stabilization, increasing energy efficiency, and reducing control complexity. Based on a real-time rule-based algorithm, the proposed power management allows self-consumption according to PVA power production and storage constraints, and the public grid is seen only as back-up. The first phase of modeling aims to evaluate the main energy flows within the proposed DC microgrid architecture and to identify the control structure and the power management strategies. For this, an original model is obtained by applying the Energetic Macroscopic Representation formalism, which allows deducing the control design using Maximum Control Structure. The second phase of simulation is based on the numerical characterization of the DC microgrid components and the energy management strategies, which consider the power source requirements, charging times of different PEVs, electrochemical storage ageing, and grid power limitations for injection mode. The simulation results show the validity of the model and the feasibility of the proposed DC microgrid power architecture which presents good performance in terms of total efficiency and simplified control. [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]

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]

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]

2-D numerical simulations are used to demonstrate the Z2-FET as a competitive embedded capacitor-less dynamic random access memory cell for low-power applications. Experimental results in 28-nm fully depleted-silicon on insulator technology are used to validate the simulations prior to downscaling tests. Default scaling, without any structure optimization, and enhanced scaling scenarios are considered before comparing the bit cell area consumption and integration density with other eDRAM cells in the literature. [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]

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]

A pile is a fundamental part of fixed type platform which commonly used to support superstructure rig in the offshore area. A seamless pipe is usually used as the pile structure. However, this seamless pipe is a high-priced pipe and scarce to find in Indonesia. ERW (Electric Resistant Welded) pipe can be used for an alternative selection of the seamless pipe for piling structure. However, ERW pipe production may have a defect in the form of a cold weld and a hook crack. This paper studies the possibility of ERW pipe utilization as the piling structure. A case study was conducted for ERW pipe NPS 24 and length of 6 m. This research conducted by using eta-FEMB and LS-DYNA software to examine the effective stress of the pile structure during installation. Numerical simulations were carried out on the pile structure with crack modelling and withstand multiple impact loading. The result was compared with failure criterion based on API RP 2A WSD. Those criteria include Axial Allowable Tensile Stress (AATS), Axial Allowable Compressive Stress (AACS) and Critical Hoop Buckling Stress (CHBS). Based on this preliminary analysis, we hypothesize that the ERW pipe with defect length up to 5 mm can be used for the piling structure. However, this analysis need further investigation in order to be a recommendation for substituting seamless pipe for piling structure. [ABSTRACT FROM AUTHOR]

This paper presents the results from experiments and numerical simulations on the ballistic impact of 10 mm thick aramid fabric-epoxy composite laminates by a 7.62 mm armor piercing projectile at varying impact velocities. Post perforated residual velocity (RV), contact duration of projectile with the target and ballistic limit (BL) of composite were simulated using a finite element code HyperWorks-Radioss. Interaction of projectile with composite laminates was captured by high speed video. The predicted ballistic parameter from simulation compared well with the precision experimental results. The simulated energy and stress distribution during impact of projectile on composite laminate showed marked difference with variation in impact velocities (SV). The magnitude and duration of stress as well as the contact force was found to increase when projectile impacted at lower SV thus enhancing the extent of delaminating and the core damage area and the trend was reversed for higher SV. The findings corroborate the bullet inflicted damage of composite laminates experimentally determined by ultrasonic C-scan. [ABSTRACT FROM AUTHOR]

Bars alignment in a Split Hopkinson Pressure Bar influences the quality of signal recorded during experiments, and thus affects the data of material properties being measured. There are some parameters directly related to the bars alignment such as their straightness, the impact face parallelism, and the neutral axis offset. This paper presents the study on the effects of non-straightness of an SHPB bar systems, dome shaped specimen, and striker bar to incident bar offset using numerical simulations. The bar component is made of AISI 4340 material with 10 mm diameter and 1000 mm length. The non-straightness of the bars and dome shaped specimen which occured due to the limitation of manufacturing process and availability of material, were measured by using dial gauges with ring supports in every 100 mm. First the simulation of an SHPB using ideal bar geometries were carried out. The simulations were then repeated by incorporating bar straightness, specimen surface, and striker bar to incident bar offset in the numerical model. From the comparisons of the material properties obtained from all simulations, it can be concluded that dome shaped specimen is the most affecting factor to the results of the SHPB measurement.. [ABSTRACT FROM AUTHOR]

Reliability Block Diagrams (RBDs) allow us to model the failure relationships of complex systems and their sub-components and are extensively used for system reliability, availability and maintainability analyses. Traditionally, these RBD-based analyses are done using paper-and-pencil proofs or computer simulations, which cannot ascertain absolute correctness due to their inaccuracy limitations. As a complementary approach, we propose to use the higher-order logic theorem prover HOL to conduct RBD-based analysis. For this purpose, we present a higher-order logic formalization of commonly used RBD configurations, such as series, parallel, parallel-series and series-parallel, and the formal verification of their equivalent mathematical expressions. A distinguishing feature of the proposed RBD formalization is the ability to model nested RBD configurations, which are RBDs having blocks that also represent RBD configurations. This generality allows us to formally analyze the reliability of many real-world systems. For illustration purposes, we formally analyze the reliability of a generic Virtual Data Center (VDC) in a cloud computing infrastructure exhibiting the nested series-parallel RBD configuration. [ABSTRACT FROM AUTHOR]

Survivability or detecting and predicting failures for humans or animals is a matter of instinct. Unlike for robots, machines, or anything that bases its rationality in software, that assumption is not applicable, yet. In this paper we apply model checking techniques to avoid future complete malfunctioning. Scenarios where non existing states are evaluated in order to find solution to possible future problems. A model checker is used for online evaluation of all the states, including possible non-existing transitions and states. [ABSTRACT FROM AUTHOR]

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We have studied decompression processes when pressure changes that take place, in blood and tissues using a technical numerical based in electrical analogy of the parameters that involved in the problem. The particular problem analyzed is the behavior dynamics of the extravascular bubbles formed in the intercellular cavities of a hypothetical tissue undergoing decompression. Numerical solutions are given for a system of equations to simulate gas exchanges of bubbles after decompression, with particular attention paid to the effect of bubble size, nitrogen tension, nitrogen diffusivity in the intercellular fluid and in the tissue cell layer in a radial direction, nitrogen solubility, ambient pressure and specific blood flow through the tissue over the different molar diffusion fluxes of nitrogen per time unit (through the bubble surface, between the intercellular fluid layer and blood and between the intercellular fluid layer and the tissue cell layer). The system of nonlinear equations is solved using the Network Simulation Method, where the electric analogy is applied to convert these equations into a network-electrical model, and a computer code (electric circuit simulator, Pspice). In this paper, numerical results new (together to a network model improved with interdisciplinary electrical analogies) are provided. [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]

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]

Engineering education requires learning strategies to engage students and improve the development of disciplinary and transversal competencies. Additionally, as economic resources are generally limited, it is sought to avoid investing large sums of money in software and hardware, as well as in fitting out laboratories. This work presents a didactic proposal within the framework of active and collaborative learning that includes the flipped classroom technique to be applied in the curriculum of undergraduate engineering programs and inside a massive flexible digital master class. The activity is the mathematical modeling, simulation, and control system of a direct current motor where simulation work is carried out in open license computational packages. Students understand the physical phenomena involved in the motor's modeling and the input–output variables' relations. Moreover, an analogy between an electromechanical and a pure electrical model is carried out, where the relevant variables respond in an agile and reliable manner. To validate the modeling, the differential equations are solved by applying numerical methods, and tested for control purposes. The activity has been validated with a rule-based system applied to a Likert scale survey data. This type of human–computer interaction, in the context of active learning, could engage students and motivate them to develop competencies that are highly appreciated by industry practitioners. [ABSTRACT FROM AUTHOR]

For pursuing high performance, the development of semi-active suspension control tends to be complicated and ignores practicability. A new mixed control method effectively suppressing vibration of the vehicle body in the whole frequency band is proposed based on electromechanical analogy theory. Simulation results show that in comparison with passive suspension, on a long slope bumpy road, the mixed control reduces body acceleration by 21.49% and the maximum amplitude by 22.40%. On a C class road, the mixed control reduces body acceleration by 9.78%. Finally, an ECU hardware-in-the-loop test is conducted, which verifies the effectiveness and feasibility of the new mixed control method. [ABSTRACT FROM AUTHOR]

The article presents the results of measurements and analysis of the flow electrification process. The research is presented with a new type of measurement instrument, in which one of the electrodes moves in an oscillating manner. The arrangement comprises two parallel plates and the liquid is relocated in one dimension. One of the electrodes is in the form of a copper wire. As a result, the liquid distribution is assumed as very simple and similar to the classic Stokes boundary layer. The electrification current measurements for different oscillation frequencies were performed in such an arrangement. The basic characteristics of the measured current and the determined process models were tested. The nonlinear approach and the linear approach were used. In the case of the nonlinear mode, the displacement of electrode was employed as an input. Hammerstein's mode with a piecewise linear input nonlinearity estimator was used for identification. In the case of the linear mode, the calculated velocity magnitude was used as an input into the system. The discrete time Output Error model and the Transfer Function model were used as a linear model. In each case, very good compliance was obtained between the simulation responses and the actual current measurements. [ABSTRACT FROM PUBLISHER]

We consider LS-, LAD-, R-, M-, S-, LMS-, LTS-, MM-, and HBR-estimates for the parameters of a linear regression model with unknown noise distribution. With computer modeling for medium sized samples, we compare the accuracy of the considered estimates for the most popular probability distributions of noise in a regression model. For different noise distributions, we analytically compute asymptotic efficiencies of LS-, LAD-, R-, M-, S-, and LTS- estimates. We give recommendations for practical applications of these methods for different noise distributions in the model. We show examples on real datasets that support the advantages of robust estimates. [ABSTRACT FROM AUTHOR]

The wake characteristics of a wind turbine in a turbulent boundary layer under neutral stratification are investigated systematically by means of large-eddy simulations. A methodology to maintain the turbulence of the background flow for simulations with open horizontal boundaries, without the necessity of the permanent import of turbulence data from a precursor simulation, was implemented in the geophysical flow solver EULAG. These requirements are fulfilled by applying the spectral energy distribution of a neutral boundary layer in the wind-turbine simulations. A detailed analysis of the wake response towards different turbulence levels of the background flow results in a more rapid recovery of the wake for a higher level of turbulence. A modified version of the Rankine-Froude actuator disc model and the blade element momentum method are tested as wind-turbine parametrizations resulting in a strong dependence of the near-wake wind field on the parametrization, whereas the far-wake flow is fairly insensitive to it. The wake characteristics are influenced by the two considered airfoils in the blade element momentum method up to a streamwise distance of 14 D ( D = rotor diameter). In addition, the swirl induced by the rotation has an impact on the velocity field of the wind turbine even in the far wake. Further, a wake response study reveals a considerable effect of different subgrid-scale closure models on the streamwise turbulent intensity. [ABSTRACT FROM AUTHOR]