激光冲击强化数值计算中的光滑粒子法

为研究激光冲击强化(LSP)过程中激光诱导冲击波的时空分布规律,在对比分析有限元仿真的基础上,探索采用光滑粒子流体动力学(SPH)对激光冲击强化的物理过程进行仿真,并设计了冲击波测试平台,对仿真结果进行了初步试验验证。结果表明,SPH模型演化物理过程明显,计算结果和试验结果相似度高,为激光冲击强化物理仿真提供了一种新的研究思路和方法。     

Combining GA with Splitting Methods for Rearrangeably Nonblocking Grooming of Dynamic Traffic in SONET Ring Networks

SONET/WDM rings are widely deployed in today’s networks. To reduce the total cost of such a network, an efficient way is using the traffic grooming technique to minimize the number of add/drop multiplexers (ADMs) on the ring. Since traffic often changes frequently, the problem of supporting dynamic traffic patterns with minimum number of ADMs and wavelengths becomes incresingly important, which is referred to as grooming of dynamic traffic. In this paper, we will deal with rearrangeably nonblocking grooming of arbitrary dynamic traffic in such ring networks. We will discuss in detail the benefit of splitting methods to such a grooming way and apply them to this kind of grooming. A novel genetic algorithm (GA) approach with a hierarchical chromosome structure for each individual is proposed in combination with splitting methods to address such grooming problems. Computer simulation results under different conditions show that our algorithm is efficient in reducing both the numbers of ADMs and wavelengths.     

目标/星空背景光学特性仿真方法研究

为新一代成像导弹武器系统的研制提供目标光学仿真环境,需要进行光学特性仿真方法研究.从目标仿真系统的组成,即计算机图像生成软件、硬件,视频/光学图像转换器以及光学投影系统几方面,分析了各部分对可见光成像光学特性仿真的影响,并对其光学特性标校方法做了说明.在系统硬件确定后,调节图像生成软件中的三维模型的材质和纹理、场景中光源亮度、环境光亮度等是使仿真目标的光学特性与真实的相一致的有效方法.该方法已在导弹半实物仿真试验中得到应用和验证.     

Application of iterative moment-method solutions to ocean surfaceradar scattering

Numerical methods such as the banded matrix iterative approach (BMIA) represent a major advance in the direct numerical simulation of rough surface-wave scattering. This paper considers the application of iterative methods such as the BMIA to ocean-radar scattering. It is shown that for typical microwave radar frequencies and sea-surface roughness, the BMIA is actually of limited use. A more general iterative solution based on a multigrid decomposition and the generalized conjugate residual (GCR) method, is thus developed. The multigrid approach is ideally suited to the broad-band ocean surface, as it solves the scattering problem on a sequence of grids, each corresponding to a different range of spatial frequencies or length scales. This approach is applied here to several sea scattering problems, including very low grazing angles and both horizontal and vertical polarization. Good agreement is obtained with perturbation theory in the appropriate limits and several qualitative characteristics of radar backscatter data are reproduced     

Coverage‐aware connectivity‐constrained unattended sensor deployment in underwater acoustic sensor networks

Careful deployment of nodes in underwater acoustic sensor networks in a distributed manner with the goal of maximized coverage and guaranteed connectivity is a challenging problem because it is very difficult and costly to access the 3D underwater environment. This paper presents a novel algorithm for self‐deployment of nodes in underwater acoustic sensor networks assuming that the nodes are randomly dropped to the water surface and form a densely populated connected network at the water surface. The idea of the algorithm is based on calculating an optimized depth for each node in the network in such a way that the possible sensing coverage overlaps are minimized and the connectivity of final topology is guaranteed. The algorithm has three main phases. In the first phase, nodes are organized in a tree structure that is rooted at the surface station. In the second phase, the depths for all nodes are computed iteratively at surface station. In the final phase, the calculated depths are distributed to nodes so that the nodes start sinking. The performance of the proposed approach is validated through simulation. We observed that the proposed approach performs at least 10% better in terms of network coverage than contemporary schemes in the literature. Copyright © 2016 John Wiley & Sons, Ltd.     

Combined optical/electrical simulation of CCD cell structures bymeans of the finite-difference time-domain method

A complete optoelectronic simulation of a CCD cell structure is presented. We combined the finite-difference time-domain method for simulation of the light propagation with electric device simulation methods based on drift/diffusion charge carrier transport models. In this way, the operation of the CCD can be modeled in a rigorous manner without simplifications of the geometry or use of approximate methods. As pixel sizes are continuously reduced, such rigorous models are of crucial importance for the analysis and optimization of the device performance     

A simulation approach for computing systems reliability

The basis of the concept of reliability is that a given component has a certain stress-resisting capacity; if the stress induced by the operating conditions exceeds this capacity, failure results. Most of the published results in this area are based upon analytical modelling of stress and strength, using various probability distributions, and then trying to find an exact expression for system reliability, which can be very difficult to obtain sometimes. The approach used in this paper is very simple and uses simulation techniques to repeatedly generate stress and strength of a system by the computer, using a random number generator and methods such as the inverse transformation technique. The advantage of this approach is that it can be used for any stress-strength distribution functions. Finally, numerical results obtained from using this approach are compared with results obtained using the analytical methods for various strength-stress distribution functions, such as exponential, normal, log normal, gamma and Weibull. Results show the viability of the simulation approach.     

A Real-Time Digital Simulation of Synchronous Machines: Stability Considerations and Implementation

The study of the transient behavior of a large power system has been difficult and time consuming even on mainframe computers. One way to obtain real-time studies is to configure digital simulation modules in a parallel processing network that corresponds to the physical system. The focus of this work is on the creation of a generator module that is compatible with such a digital simulation network. To approach operation in real time, a fast and accurate state equation integrator is required. Investigation has revealed that the load imposed on the simulated generator plays a major role in the stability of the integration routines. The linearized stability limits of forward difference, modified Euler, fourth-order Runge-Kutta and Adams-Bashforth-Moulton integration methods were calculated for an impedance terminated generator. These were found to agree closely with the corresponding experimentally determined nonlinear limits. The TMS32010 digital signal processor was chosen as the heart of the generator simulator module, and fixed-point arithmetic routines were developed to make it a high-speed state equation integrator. Operation in real time was achieved for an infinite bus-type termination, but an impedance load led to a somewhat slower simulation.     

Modeling and simulation of resistivity of nanometer scale copper

A highly versatile simulation program was developed and used to examine how the resistivity of thin metal films and lines is increased as their dimensions approach and become smaller than the mean free path of electrons in metals such as copper and aluminum. The simulation program is flexible in that it can include the effects of surface and grain-boundary scattering on resistivity either separately or together, and it can simulate the effect on resistivity where each surface of a film or line has a different value for the scattering parameter. The simulation program (1) provides a more accurate calculation of surface scattering effects than that obtained from the usual formulation of Fuchs’ theory, (2) calculates grain-boundary effects that are consistent with the theory of Mayadas and Shatzkes, (3) shows that surface and grain-boundary scattering effects are interdependent, and (4) shows that the change in resistivity with temperature begins to increase as dimensions approach the bulk mean free path of the electrons in the metal.     

Model-based reasoning for electron-beam debugging of VLSI circuits

This article deals with prototype validation of VLSI circuits. Circuits are observed using electron-beam probing used in voltage contrast mode, in such a way that grey level images are obtained and processed in order to determine potential values of connexions. These values are compared against reference values, issued from fault-free simulation of the device under test. The list of discrepancies resulting from comparison constitutes input for a fault localization process done using a knowledge-based system. In this article, the reasons for the choice of such an approach are explained, the approach itself is described, as well as its implementation and the obtained results.