Large-scale forcing with less communication in finite-difference simulations of stationary isotropic turbulence

This study proposes a new forcing scheme suitable for massively-parallel finite-difference simulations of stationary isotropic turbulence. The proposed forcing scheme, named reduced-communication forcing (RCF), is based on the same idea as the conventional large-scale forcing scheme, but requires much less data communication, leading to a high parallel efficiency. It has been confirmed that the RCF scheme works intrinsically in the same manner as the conventional large-scale forcing scheme. Comparisons have revealed that a fourth-order finite-difference model run in combination with the RCF scheme (FDM-RCF) is as good as a spectral model, while requiring less computational costs. For the range 80 < Re_λ < 540, where Re_λ is the Taylor microscale-based Reynolds number, large computations using the FDM-RCF scheme show that the Reynolds dependences of skewness and flatness factors have similar power-laws as found in previous studies.     

Plane-parallel biaxial plates as polarization interferometers

Plane-parallel biaxial plates as polarization interferometers. Knowing the refractive indices and the directions of the rays inside a birefringent crystal, it is possible to calculate the positions of the images formed, when a non-parallel light beam incides on it.We part from general expressions for images in plane-parallel plates of any type of medium and we use vectorial expressions for the incident and refractive rays and waves in both interfaces.From them, we obtained the interference patterns which are observed when the plate is placed between two crossed polarizers. This experimental device constitutes a polarization interferometer. In order to find the shape of the interference patterns, we superposed the wave's fronts emerging from the images determining, in this way, the phase difference curves of phase constant on a screen.     

光突发交换边缘路由器性能分析

本文详细分析了各种因素对光突发交换边缘路由器的性能的影响.结果显示,不同服务等级的时延要求可以通过控制组装的最大时延得以保证;不同等级数据包长的大范围变动会导致信道分配的不公平性;边缘节点越多,丢包率越高;在总输出容量一定的情况下,增加输出数据信道数可以在获得低的丢包率的同时达到较高的通道利用率,但随着边缘节点数的增加,增加输出信道数对丢包率的改善作用下降.     

Method of developing all-optical parallel to serial converter exploiting Kerr non-linearity of medium

Different all-optical logic operations, memory blocks etc. are developed using the inherent parallelism of optics. In any digital communication and computation system, the role of serial to parallel and parallel to serial data conversion are very much essential for making a data convenient for transition.Here in this paper, the authors propose a new scheme for developing an all-optical parallel to serial data conversion system by using optical J-K Flip-Flops and some logic gates based on optical non-linear switches. The uses of such switches are widely established in the area of optical parallel computation.This process can be extend for developing some all-optical digital devices like shift register, optical pulse counters etc. The proposed scheme deals with the best use of high parallelism of the optics, so the super-fast processing speed can be achieved.     

A fire field model implemented in a parallel computing environment

This paper describes the implementation of a fire field model in the parallel computing environment offered by multiple transputers. The fire model is built into the general purpose SIMPLE-based CFD code HARWELL-FLOW3D. The technique of domain decomposition has been applied tb convert the conventional serial version of FLOW3D into a code capable of efficiently utilizing an arbitrary number of transputers. Fire simulations consisting of up to 24 000 computational cells are performed on parallel systems with up to 15-processors. The run time for this simulation has been reduced from over 4 days on a single processor to just over 8 h on the 15-processor system. An interactive graphics system has also been developed which runs in parallel with the main computations.     

A dynamic production planning and scheduling algorithm for two products processed on one line

This paper presents a dynamic production planning and scheduling algorithm for two products processed on one line over a fixed time horizon. Production rates are assumed fixed, and restrictions are placed or inventory levels and production run lengths. The resulting problem is a nonlinear binary program, which is solved using an implicit enumeration strategy. The algorithm focuses on the run changeover period while developing tighter bounds on the length of the upcoming run to improve computational efficiency. About 99% pf 297 randomly generated problems with varying demand patterns are solved in less than 15 seconds of CPU time on a CDC Cyber 172 Computer. A mixed integer programming formulation of the generalized multi-product case under no-backlogging of demand is also given.     

Designing routes to minimize fleet operating costs

A route-planner must try to schedule the delivaries by a fleet of vehicles such that customer requirements are met and management objectives are satisfied. In most cases, the number of feasible arrangements is legion, and calculations relating to individual vehicle loads, mileages, delivery times, etc. are tedious, allowing only a small fraction of possible route plans to be established and compared. The problem presents an ideal opportunity for computer application, not least to ensure that solutions are timely and error free.Several algorithms have been developed to improve the quality of vehicle routes, but in practice only those that rely on simple selection rules have found widespread acceptance, due to the innate complexity of the calculations that follow from a more rigorous approach and to the great variety of customer, vehicle, and operational characteristics that distinguish transport systems and which must be accomodated.The method presented here is based upon the well-known ‘savings’ criterion, but avoids many of its deficiencies by employing a random selection mode and producing (efficiently) a large sample of schedules from which to choose the most suitable. In particular, this allows greater flexibility in defining management objectives, and has led to substantial reductions in both fleet sizes and distances travelled, compared to published results, for a set of nine test cases each involving more than 200 customer locations.     

Determination of relative molecular weights of fluorescent components in dissolved organic matter using asymmetrical flow field-flow fractionation and parallel factor analysis

Dissolved organic matter in aquatic systems is of variable structure and composition. Asymmetrical flow field-flow fractionation coupled to UV/vis diode array and fluorescence detectors (AF4–DAD–EEM) was used to assess the size and optical properties of dissolved organic matter. The results were analyzed using parallel factor analysis (PARAFAC) and statistical fractogram deconvolution to correlate fluorescing components with molecular weight fractions. This coupling, which is shown for the first time in this work, is a powerful method capable of revealing novel information about the size properties of PARAFAC components. Tyrosine/polyphenol-like fluorescence (peak B) was significantly correlated (p < 0.05) with the smallest size group (relative molecular weight = 310 ± 10 Da), microbial humic-like and terrestrial visible humic-like fluorescence (peaks M, C, A) with the intermediate size group (1600 ± 150 Da), and terrestrial fulvic-like and tryptophan/polyphenol-like fluorescence (peaks A and T) with the largest size group (4300 ± 660 Da).