Advanced propagation analysis methodology with fast simulation

Solving the solid-state diffusion equation in a typical pseudo-two-dimensional (P2D) battery model using conventional finite difference methods (FDM) substantially increases the model complexity (in terms of number of equations) as well as the computational time. In our previous work, we approximated the solid-state diffusion in spherical particles using Galerkin weak form method based on symmetric polynomials, which significantly improved the robustness of modeling, achieving a tenfold reduction in computational time, even for non-linear diffusion problems. However, we found that the equations represented in non-dimensional form for mathematical compactness are relatively difficult to interpret and apply in P2D and other battery models. Therefore, as a follow-up to previous work, we present the weak form formulations of solid-state diffusion in dimensional form to provide better physical interpretation and easier adaptability to battery modelling and other applications. Further, considering diverse particle morphologies in modern battery materials, we extend these formulations for cylindrical and rectangular coordinates, in addition to the spherical coordinate. We further present simulations using various experimentally reported concentration-dependent diffusivities and find that the solution convergence is strongly influenced by the degree of non-linearity in diffusion. The study enables the proposed formulation to be widely applicable facilitating accurate and fast simulations.

The simulation code named VXI (“Virtual X‐ray Imaging”) has been considerably improved since the issue of its first version, two years ago. Emphasis was particularly laid on devising faster (dedicated and optimized) ray tracing algorithms. At present, the computation time needed to simulate a transmitted image (i.e. formed by uncollided photons), with a polychromatic beam, complex sample geometry and high detector resolution, is typically in the range 0.01–10 s, with a simple personal computer (1 GHz microprocessor). This feature enables real‐time simulation of radioscopy and tomography setups. We have recently tackled the simulation of Rayleigh and Compton scattering using the same deterministic ray tracing approach. The performance of our code in the case of transmission images as well as preliminary results of the simulation of first‐order scattering are presented in this paper.

A rapid GPU-based heat transfer and solidification model for dynamic computer simulations of continuous steel casting

Algorithms used in the optimization of wireless deployments have computational time as one of their main drawbacks. This computational time is very dependent on the test points established to characterize a deployment scenario. The approach commonly used to define sample points is based on a regular grid, which leads to a remarkable number of sample points if accuracy is required. In this paper, a novel scenario-dependent sampling scheme based on mathematical morphology is presented. Its performance is evaluated and compared to regular sampling, outperforming typical schemes reducing computational time while maintaining very accurate results.

Introduction O VER the past decade there has been considerable progress in the development of numerical simulation techniques for unsteady transonic flow calculations. This activity was motivated by the need to supplement the expensive and time-consuming wind-tunnel investigations and flight tests with inexpensive, fast, and efficient computer simulation programs to accurately predict flutter boundaries and many other important aeroelastic phenomena in the transonic regime. Although the basic fluid motion in unsteady aerodynamics is governed by the Navier-Stokes (NS) equations, numerical simulations of the complete NS equations for general threedimensional flow problems are not yet sufficiently developed for flutter applications. Computational methods in threedimensional unsteady transonic flows concentrate mainly on the transonic small disturbance (TSD) equation or full potential (FP) equation. The major advantage of the simpler model using TSD or FP approach over those based on Euler and NS formulation is the large reduction in computational time and memory requirements. In Ref. 1, the TSD code UST3D was described. This code utilizes the time-linearization approach for solving the transonic small disturbance equation. It was demonstrated that the technique could be used with confidence for computations of three-dimensional unsteady transonic flows over an isolated thin wing. An improved version of the UST3D program was given in Ref. 2 and results from a validation study were presented. This transonic aerodynamics code was incorporated into the Institute for Aerospace Research (IAR) Flutter Analysis Program. This Note presents some results from an aerodynamic and flutter analysis of the AGARD 445.6 wing which was recommended by AGARD as a standard configuration for code validation.

We present a method to generate three-dimensional (3D) inverse synthetic aperture radar (ISAR) images of a target at arbitrary aspect angles using the shooting and bouncing ray (SBR) method. We have derived a 3D-image-domain ray-tube integration formula based on the SBR technique. The imaging formula is in a form of convolution, then a nonuniform fast Fourier transform (NUFFT) is induced to achieve the convolution, which can be used to generate 3D ISAR images rapidly. Compared to the conventional algorithm where the ISAR images are obtained by inverse Fourier transforming the computed scattered fields over a range of frequencies and a range of aspect angles, the new formula needs only one-time ray tracing and physical optics (PO) integration over a small angle span. Hence the computational time is decreased tremendously. The ISAR images of a missile target and an armored car for several aspect angles are presented to demonstrate the efficiency and accuracy of the proposed method.

The analysis of wave propagation via the Boundary Element Method (BEM) requires the description of the medium in terms of nodes at material discontinuities. The accuracy of the BEM solution improves as the number of the boundary elements and nodes inside each element increases. However, the improved accuracy and efficiency associated with the use of higher order elements is accompanied by an increase in the computational time needed to solve the equations generated. The present work assesses the benefit of using higher order elements by calculating the displacement and stress fields around a circular cylindrical cavity inclusion buried inside a two dimensional acoustic medium, for which the solution is known in closed form. In addition, this work examines the importance to the solution of the position of the nodes inside each element. It does so by varying their relative positions. The problem is formulated in the frequency domain and the boundary of the inclusion is discretized using constant, linear and quadratic elements.

Atmospheric turbulence disturbance degrades the quality of long-range image transmission in applications such as marine monitoring and satellite imaging. Simulating an atmospheric turbulence image dataset facilitates the correction of turbulence-distorted images. However, the current simulation algorithms suffer from long computation times, undersampling of frequency, and unrealistic turbulence image simulation. Therefore, we propose an algorithm based on atmospheric coherence length r0 and associated with the phase structure function for fast, high-precision, and realistic simulation of atmospheric turbulence images. This solution demonstrates strong performance in pixel displacement correlation, phase structure function, and long-exposure and short-exposure point spread functions (PSFs). The results show that the fitting accuracies between the long-exposure and short-exposure PSFs, which reflect the imaging quality of the simulated turbulence image and the theoretical curve are 0.99 and 0.98, respectively, when the r0 is 0.1 m. The fitting efficiency is high and closely aligns with the theoretical trends of atmospheric turbulence.

A new approach of transistor modeling is developed for fast statistical circuit simulation in the presence of variations. For both I-V and C-V characteristics of a transistor, finite data points are identified by their physical meaning; the impact of process and design variations is embedded into these points as closed-form expressions. Then, the entire I-V and C-V are extrapolated using polynomial formulas. This novel approach significantly enhances the simulation speed with sufficient accuracy. The model is implemented in Verilog-A at 65nm node. Compared to simulations with the BSIM model, the computation time can be reduced by 7times in transient analysis and 9times in Monte-Carlo simulations

Numerical design inverse reconstruction and parameter estimation of optical systems usually involves the multiple solution of an e.g. geometrically parameterized system. Long computational times however can rule out many possible applications like inverse scatterometry. The reduced basis method allows to split up the solution process of an e.g. geometrically parameterized system into an expensive offline and a cheap online part. In the offline phase the reduced basis is computed selfadaptively by solving the underlying model several times. During the real-time application the reduced system is solved in the order of seconds even for 3D problems. Error estimators assure the reliability of the reduced basis solutions. In our contribution we explain general ideas of the reduced basis method and apply it to the simulation of light scattering from 2D and 3D parameterized photo masks. We compare computational times and accuracy of reduced basis and rigorous finite element simulations.

Efficient full-chip thermal simulation is among the most challenging problems facing the EDA industry today, due to the need for solution of very large systems of equations that require unreasonably long computational times. However, in most cases, temperature is not required to be computed at every point of the IC but only at certain hotspots, in order to assess the circuits compliance with thermal specifications. This makes the thermal analysis problem amenable to Model Order Reduction (MOR) techniques. System-theoretic techniques like Balanced Truncation (BT) offer very reliable bounds for the approximation error, which can be used to control the order and accuracy of the reduced models during creation, at the expense of greater computational complexity to create them. In this paper, we propose a computationally efficient low-rank BT algorithm that retains all the system-theoretic advantages in the reduction of model order for fast hotspot thermal simulation. Experimental results demonstrate a 39X order reduction and very tight accuracy bounds.

S-Wave Accelerates Optimization-based Photoacoustic Image Reconstruction in vivo

Prediction of urban sound propagation is an integral part for the assessment of noise levels in cities. Several propagation modeling methods exist to predict sound propagation in city environments including parabolic equation, diffusion equation, radiosity, ray tracing, image source, modal analysis, and transmission line matrix methods. For this study, adaptive beam tracing as a geometrical acoustic prediction method is applied in the context of predicting sound propagation in complex urban environments. Adaptive beam tracing is advantageous compared to the ray tracing and image source methods by eliminating aliasing errors and spurious image sources, respectively. A model of diffraction [Svensson et al., J. Acoust. Soc. Am. 106, 2331–2344 (1999)] is integrated with the adaptive beam tracing algorithm in order to enhance the prediction capability of the proposed method. The effects of facade roughness, street canyon shielding, and building spacing are investigated. Comparison of the proposed method is made with a ray tracing method. Computation times, as well as various geometric configurations, are compared between the proposed method and the ray tracing method.

A distributed algorithm is presented that can be used to solve the single-destination shortest path (SDSP) problem or the all-pairs shortest path (APSP) problem for a class of clustered data networks. The network graph is assumed to be characterized with a balanced hierarchically clustered (BHC) topology. The BHC topology is introduced in this paper and is shown to be a realistic characterization for a large class of interconnected data networks. For certain types of BHC topologies, the SDSP problem can be solved with computation and communication time complexities of O(log n), assuming one processor is available at each of the n number of nodes. Assuming p processors are available at each node, computation and communication time complexities of O((n/p) log n) and O(n log n) are achievable, respectively, for solving the APSP problem. It is also shown that the algorithm converges in an asynchronous environment. >

At the multiplexer of an ATM network, the admissible cell loss probability is less than 10−12 for some service categories. Ordinary Monte Carlo (MC) simulation requires considerable computation time to obtain such a small probability. The importance sampling (IS) technique is effective in accclerating the MC simulation. In an IS simulation, the underlying distribution is biased so as to generate more samples in the target event. In order to achieve a fast simulation, it is important to have a simulation distribution that yields an estimate with minimum variance. This is called the optimal simulation distribution. In this paper, we investigate the survivor function P(Q > q) of a stationary queue length Q in ATM queuing and obtain an IS estimate of P(Q > q) at about 10−2 by means of the optimal simulation distribution. Conventional methods [1, 2] for determining the optimal distribution require a lot of computation time. We apply the large deviation theory to this problem to obtain the optimal simulation distribution analytically and carry out an IS simulation. We present some numerical results for M/D/1 and 2-state MMPP/D/1 which demonstrate that our estimates are obtained in a very small computation time and are accurate when compared to MC simulation. © Scripta Technica, Inc. Electron Comm Jpn Pt 1, 80(12): 28–37, 1997