An efficient parallelization technique for high throughput FFT-ASIPs

Fast Fourier Transformation (FFT) and it's inverse (IFFT) are used in Orthogonal Frequency Division Multiplexing (OFDM) systems for data (de)modulation. The transformations are the kernel tasks in an OFDM implementation, and are the most processing-intensive ones. Recent trends in the electronic consumer market require OFDM implementations to be flexible, making a trade-off between area, energy-efficiency, flexibility and timing a necessity. This has spurred the development of Application-Specific Instruction-Set Processors (ASIPs) for FFT processing. Parallelization is an architectural parameter that significantly influence design goals. This paper presents an analysis of the efficiency of parallelization techniques for an FFT-ASIP. It is shown that existing techniques are inefficient for high throughput applications such as Ultra Wideband (UWB), because of memory bottlenecks. Therefore, an interleaved execution technique which exploits temporal parallelism is proposed. With this technique, it is possible to meet the throughput requirement of UWB (409.6 Msamples/s) with only 4 non-trivial butterfly units for an ASIP that runs at 400MHz. © 2006 IEEE

Применение метода контрольных возмущений для определения характерных узлов присоединения комплексной нагрузки при расчетах динамической устойчивости

Рассматривается влияние способа замещения комплексной нагрузки на характер электромеханических переходных процессов в электрических системах (ЭС) от действия больших возмущений. Показано, что установить общие рекомендации относительно способа замещения нагрузки в сложных ЭС затруднительно. Предлагается для опреде­ления характерных узлов нагрузки, оказывающих существенное влияние на характер динамического перехода, применять известный метод контрольных возмущений. Приводятся результаты сравнительных расчетов с использованием предлагаемой методики

Magnetic field generation in first order phase transition bubble collisions

We consider the formation of a ring-like magnetic field in collisions of bubbles of broken phase in an abelian Higgs model. Particular attention is paid on multiple collisions. The small collision velocity limit, appropriate to the electroweak phase transition, is discussed. We argue that after the completion of the electroweak phase transition, when averaged over nucleation center distances, there exists a mean magnetic field $B\simeq 2.0\times 10^{20}$ G with a coherence length $9.1 \times 10^3 GeV^{-1}$ (for m_H=68 GeV). Because of the ring-like nature of B, the volume average behaves as $B \sim 1/L$. Taking into account the turbulent enhancement of the field by inverse cascade, we estimate that colliding electroweak bubbles would give rise to a mean field $B_{rms}\simeq 10^{-21}$ G at 10 Mpc comoving scale today.Comment: Latex, 18 pages, 8 figure

The impact of supply chain agility on business performance in a high level customization environment

To improve business performance in rapidly changing environments, supply chain agility can be a crucial requisite to address responsiveness issues, especially in environments with high levels of customization. This paper examines the effect of supply chain agility on customer service, differentiation, and business performance. A survey research methodology was employed using a sample of 156 manufacturing firms that provide high levels of customization. In particular, structural equation modeling (SEM) was employed to evaluate the proposed model. The results suggest that supply chain agility influences customer service and differentiation positively. However, it does not affect business performance directly; instead, better business performance can be achieved and mediated through improved customer service and differentiation. In particular, differentiation through customer service is the most effective way to improve business performance, and supply chain agility can help to achieve high-level customer service. The paper advises managers on details of how to fulfil their business performance ambitions better through suggested key agile supply chain management activities

Mean exit times and the multilevel Monte Carlo method

Numerical methods for stochastic differential equations are relatively inefficient when used to approximate mean exit times. In particular, although the basic Euler–Maruyama method has weak order equal to one for approximating the expected value of the solution, the order reduces to one half when it is used in a straightforward manner to approximate the mean value of a (stopped) exit time. Consequently, the widely used standard approach of combining an Euler–Maruyama discretization with a Monte Carlo simulation leads to a computationally expensive procedure. In this work, we show that the multilevel approach developed by Giles [Oper. Res., 56 (2008), pp. 607–617] can be adapted to the mean exit time context. In order to justify the algorithm, we analyze the strong error of the discretization method in terms of its ability to approximate the exit time. We then show that the resulting multilevel algorithm improves the expected computational complexity by an order of magnitude, in terms of the required accuracy. Numerical results are provided to illustrate the analysis