Mitigating the integration error in numerical simulations of Newtonian systems

We introduce a method for mitigating the numerical integration errors of linear, second‐order initial value problems. We propose a methodology for constructing an optimal state‐space representation that gives minimum numerical truncation error, and in this sense, is the optimal state‐space representation for modelling given phase‐space dynamics. To that end, we utilize a simple transformation of the state‐space equations into their variational form. This process introduces an inherent freedom, similar to the gauge freedom in electromagnetism. We then utilize the gauge function to reduce the numerical integration error. We show that by choosing an appropriate gauge function the numerical integration error dramatically decreases and one can achieve much better accuracy compared to the standard state variables for a given time‐step. Moreover, we derive general expressions yielding the optimal gauge functions given a Newtonian one degree‐of‐freedom ODE. For the n degrees‐of‐freedom case we describe MATLAB^® code capable of finding the optimal gauge functions and integrating the given system using the gauge‐optimized integration algorithm. In all of our illustrating examples, the gauge‐optimized integration outperforms the integration using standard state variables by a few orders of magnitude. Copyright © 2006 John Wiley & Sons, Ltd.     

Efficient mapping of multiple VoIP vocoders in WiMAX systems

This paper addresses the problem of efficient mapping and allocation of voice over IP (VoIP) traffic with multiple VoIP vocoders in WiMAX systems. We show that by taking advantage of the periodicity of VoIP frames, generated by multiple vocoder types, and by applying semi‐fixed allocations in the existing resource allocation process, the mapping overhead can be reduced substantially. We present a system model that allows the evaluation of the proposed solutions for the problem at hand. Using this model, we show that the problem is NP hard and present a set of observations on the resource allocation process leading to good mapping decisions from the perspective of mapping overhead. We present a new mapping algorithm that implement the decisions and show by extensive simulations that the proposed mapping algorithm can reduce the overhead down to 25% of the overhead experienced in orthogonal frequency division multiple access (OFDMA)‐based systems such as WiMAX and IEEE802.16, while retaining a low computational complexity. Copyright © 2009 John Wiley & Sons, Ltd.     

Two-dimensional mapping for wireless OFDMA systems

The recent Orthogonal Frequency Division Multiple Access (OFDMA) transmission technique is gaining popularity as a preferred technology in the Broadband Wireless Access (BWA) emerging standards. In standards 802.16-2004 and 802.16e, the basic allocation units are comprised of sub-channels and OFDMA time symbols; each sub-channel is a group of sub-carriers, so that all the sub-channels are considered equally adequate to all users. We study the naturally arising new approach of two-dimensional mapping of incoming requests into the matrix that represents the system resources, where each allocation is of an arbitrary multi-rectangular shape (to the best of our knowledge, this approach has not been discussed elsewhere). We define a cost model and constraints related to practical OFDMA systems, which depend on the spatial shape of the two-dimensional allocation; the main objective function is the spatial efficiency. We show that the arising problem, even in its simplest form, is NP-hard . We present run-time efficient heuristic solutions for various mapping problems, taking into account the above QoS and OFDMA related constraints. In particular, a novel solution for two-dimensional mapping under priority constraints is suggested. Extensive simulations with parameters of real systems were used to investigate the performance of the proposed solutions in terms of throughput, delay and system load. The results show that high throughput can be achieved with relatively simple mapping algorithms. We believe that the proposed two-dimensional mapping approach is prospective, due to its fitness to modern standards.     

传统设计验证及其在倒装芯片应用中所面临的挑战

讨论了新一代器件推出在经济和技术方面所面临的挑战,介绍了便于设计人员迅速、有效地排除复杂而难以处理的器件故障的光探测故障查出技术。     

Effect of LaNiO3 electrodes and lead oxide excess on chemical solution deposition derived Pb(Zrx,Ti1 − x)O3 films

The effects of LaNiO₃ (LNO) and Pt electrodes on the properties of Pb(Zr_x,Ti_1 − x)O₃ (PZT) films were compared. Both LNO and PZT were prepared by chemical solution deposition (CSD) methods. Specifically, the microstructure of LNO and its influence on the PZT properties were studied as a function of PbO excess. Conditions to minimize the Pyrochlore phase and porosity were found. Remnant polarization, coercive field and fatigue limit were improved in the PZT/LNO films relative to the PZT/Pt films. Additionally, the PZT crystallization temperature over LNO was 500 °C, about ~ 50 °C lower than over Pt. The crystallization temperature reported here is amongst the lowest values for CSD-based PZT films.     

Preference‐based zone selection in 802.16 networks

We examine a new problem called the Zone Selection Problem (ZSP) in wireless Orthogonal Frequency‐Division Multiple Access (OFDMA)‐based systems. We consider the case where the mobile station (MS) informs the base station of its preferences regarding possible working modes supported by the system. In Worldwide Interoperability for Microwave Access (WiMAX) systems, which are used as a practical reference system for constraints and specific modes of operations, each working mode must be assigned at a different time interval called a Zone. Such zone may, in the downlink subframe, define a specific transmission scheme, which can be either single‐input single‐output or one of the multiple‐in multiple‐out (MIMO) modes supported by the system. We define ZSP as a problem where the base station assigns MSs to zones in a way that optimizes the system utilization (in terms of resource usage) while trying to satisfy the preferences of the users as much as possible. This makes ZSP a bi‐objective optimization problem. We derive assignment costs from physical channel models that integrate specific MIMO schemes and channel conditions. We provide an exact solution to ZSP by using a combinatorial optimization abstraction. We propose a simplified and practical mode ranking approach that enables the MS to define its preferences regarding operation in the optional MIMO modes in the system. We prove that ZSP is NP‐hard and describe two heuristic solutions: a greedy approach and a local search approach. Simulation results show the performance of the exact algorithms on a realistic WiMAX system assumptions and present the trade‐off between the user preferences and system preferences. Copyright © 2016 John Wiley & Sons, Ltd.     

Regularized discriminant analysis for face recognition

This paper studies regularized discriminant analysis (RDA) in the context of face recognition. We check RDA sensitivity to different photometric preprocessing methods and compare its performance to other classifiers. Our study shows that RDA is better able to extract the relevant discriminatory information from training data than the other classifiers tested, thus obtaining a lower error rate. Moreover, RDA is robust under various lighting conditions while the other classifiers perform badly when no photometric method is applied.     

深亚微米器件的诊断与特征分析变得越来越重要

深亚微米技术使制造满足更复杂应用所需的高度集成器件成为可能.采用深亚微米技术使半导体制造商继续利用传统基于设计仿真的方法获得芯片早期验证成功面临显著的更大的困难.这些困难使依赖相同的仿真方法进行芯片设计调试的传统方式很难在制造加工前发现设计问题.