Simulations of lateral mixing in cross-channel flow

Cross flow phenomena between connected sub-channels are studied by means of numerical simulations based on lattice-Boltzmann discretization. The cross (that is lateral) transfer is largely due to macroscopic instabilities developing at two shear layers. The characteristic size and advection velocity of the instabilities favorably compare with experimental results from the literature on a geometrically similar system. The strength of the cross flow strongly depends on the Reynolds number, with cross flow developing only for Reynolds numbers (based on macroscopic flow quantities) larger than 1360. Mass transfer between the sub-channels has been assessed by adding a passive scalar to the flow and solving its transport equation. As a result of the intimate connection of cross flow and lateral mass transfer, also the mass transfer coefficient is a pronounced function of Re.     

T-MPLS网络互通问题分析及解决方案

随着数据流量的不断增长及其高突发性,基于SDH技术的传送网逐渐显示出不可解决的劣势.下一代传送网将被基于分组的传送技术所垄断,T-MPLS是一种新的基于分组传送的技术,目前T-MPLS主要定位在城域传送网络,并逐渐向核心网络部分进行扩张.本文基于ITU-T所定义的T-MPLS框架体系结构,结合已有的基于MPLS技术的组网方式,分析了T-MPLS未来的应用前景,并给出了未来传送网络可行的演进模型.     

High‐efficiency red‐phosphorescent organic light‐emitting diode with the organic structure of 2‐TNATA/Bebq2:SFC‐411/SFC‐137

Abstract— High‐efficiency and simple‐structured red‐emitting phosphorescent devices based on the hole‐injection layer of 4,4′,4″‐tris(2‐naphthylphenyl‐phenylamino)‐triphenylamine [2‐TNATA] and the emissive layer of bis(10‐hydroxybenzo[h] quinolinato)beryllium complex [Bebq²] doped with SFC‐411 (proprietary red phosphorescent dye) have been researched. The fabricated devices are divided into three types depending on whether or not the hole‐transport layer of N,N′‐bis(1 ‐naphthyl)‐N, N'‐diphenyl‐1,1′‐biphenyl‐4,4′‐diamine [NPB] or the electron‐transport layer of SFC‐137 (proprietary electron transporting material) is included. Among the experimental devices, the best electroluminescent characteristics were obtained for the device with an emission structure of 2‐TNATA/Bebq²:SFC‐411/SFC‐137. In this device, current density and luminance were found to be 200 mA/cm² and 15,000 cd/m² at an applied voltage of 7 V, respectively. Current efficiencies were 15 and 11.6 cd/A under a luminance of 500 and 5000 cd/m². The peak wavelength in the electroluminescent spectral distribution and color coordinates on the Commission Internationale de I'Eclairage (CIE) chart were 628 nm and (0.67, 0.33), respectively.     

网上交易中的电文固化系统设计

为应对网上交易等电子商务等存在安全问题,确保交易安全,并面对可靠的固化和保留交易所产生的电文作为交易证据进行保全和固化的需求,设计了一种电文固化系统,包含其网络拓扑架构,及所依赖的安全网络传输协议.整个系统采用电文固化中心和在交易平台方所设的电文固化本地代理的分布式结构.交易平台方在遇到电文固化需求时,通过本地代理与电...     

支持普适服务的新一代网络传输层构架

新一代网络没有准确定义,但普遍共识是提供全分组网络和普适服务.其中分组网络一般认为采用IP分组,但普适服务仍不清晰.3G、4G中称"泛在服务";NGI、NGN中强调无缝融合电信网和互联网服务;计算机界类似的概念是"普适计算";IEEE普适服务会议汇聚各种思想,首次提出了"普适服务"的模糊概念.虽然上述研究对普适服务的定义并不统一,但普遍共识是:多样化的服务种类、多样化的网络接入.文中分析传输层在新一代网络设计中的重要地位,以提供普适服务为目标,通过多连接抽象表示服务多样化、多路径抽象表示接入多样化,给出符合新一代网络要求的传输层构架.基于这一构架,可以提高网络的QoS支持、安全可靠性、移动性、可控可管性.文中通过理论分析和原型实现证明了新构架的正确性和可行性.     

A discontinuous Galerkin solver for Boltzmann–Poisson systems in nano devices

In this paper, we present results of a discontinuous Galerkin (DG) scheme applied to deterministic computations of the transients for the Boltzmann–Poisson system describing electron transport in semiconductor devices. The collisional term models optical-phonon interactions which become dominant under strong energetic conditions corresponding to nano-scale active regions under applied bias. The proposed numerical technique is a finite element method using discontinuous piecewise polynomials as basis functions on unstructured meshes. It is applied to simulate hot electron transport in bulk silicon, in a silicon n⁺–n–n⁺ diode and in a double gated 12 nm MOSFET. Additionally, the obtained results are compared to those of a high order WENO scheme simulation and DSMC (Discrete Simulation Monte Carlo) solvers.     

Replica Exchange Light Transport

We solve the light transport problem by introducing a novel unbiased Monte Carlo algorithm called replica exchange light transport, inspired by the replica exchange Monte Carlo method in the fields of computational physics and statistical information processing. The replica exchange Monte Carlo method is a sampling technique whose operation resembles simulated annealing in optimization algorithms using a set of sampling distributions. We apply it to the solution of light transport integration by extending the probability density function of an integrand of the integration to a set of distributions. That set of distributions is composed of combinations of the path densities of different path generation types: uniform distributions in the integral domain, explicit and implicit paths in light (particle/photon) tracing, indirect paths in bidirectional path tracing, explicit and implicit paths in path tracing, and implicit caustics paths seen through specular surfaces including the delta function in path tracing. The replica‐exchange light transport algorithm generates a sequence of path samples from each distribution and samples the simultaneous distribution of those distributions as a stationary distribution by using the Markov chain Monte Carlo method. Then the algorithm combines the obtained path samples from each distribution using multiple importance sampling. We compare the images generated with our algorithm to those generated with bidirectional path tracing and Metropolis light transport based on the primary sample space. Our proposing algorithm has better convergence property than bidirectional path tracing and the Metropolis light transport, and it is easy to implement by extending the Metropolis light transport.     

A self-organising mixture autoregressive network for FX time series modelling and prediction

Nowadays a great deal of effort has been made in order to gain advantages in foreign exchange (FX) rates predictions. However, most existing techniques seldom excel the simple random walk model in practical applications. This paper describes a self-organising network formed on the basis of a mixture of adaptive autoregressive models. The proposed network, termed self-organising mixture autoregressive (SOMAR) model, can be used to describe and model nonstationary, nonlinear time series by means of a number of underlying local regressive models. An autocorrelation coefficient-based measure is proposed as the similarity measure for assigning input samples to the underlying local models. Experiments on both benchmark time series and several FX rates have been conducted. The results show that the proposed method consistently outperforms other local time series modelling techniques on a range of performance measures including the mean-square-error, correct trend predication percentage, accumulated profit and model variance.     

Windows平台通用个人防火墙的分析与设计

定义个人防火墙系统应具备的主要功能,其核心技术是网络数据包的过滤。给出Windows系统网络协议分层体系结构,在对OSI参考模型和Windows网络体系结构对比分析的基础上给出实现包过滤的不同技术路线。对各技术路线进行评估,选择SPI作为实现方案,给出使用SPI进行包过滤的技术要点,个人防火墙系统的运行表明其具有较快的包过滤处理性能。