气固两相流电容相关流量测量仿真研究

以气/固两相流互相关测量系统为研究对象,采用计算机仿真的方法,对由电容传感器构成的基于离散相浓度的电容互相关流速测量机理进行研究。利用ANASYS软件分析电容传感器与离散相浓度的关系;采用Monte-Carlo方法,建立气/固两相流动模型;研究"凝固流动图型"、"非凝固流动图型",离散相浓度、粒度及速度分布对互相关测量系统的影响。     

浓相高密度气固流化床动力学特性模拟研究

气固流化床内部运动状态和流体力学特性是研究者普遍关心的问题。浓相高密气固流化床就有不同于一般化学工业流化床的特点：固相介质密度高（4．0—5．0g／cm^3），空隙率小（0．3～0．42），气相速度小（0．15—0．30m／s）。使用基于物质、质量守恒定律建立了双流体模型对气固流化床动力学特性进行了模拟研究。在二维直角坐标系中用控制容积差分法离散方程。并在气相表观速度为0．157m／s条件下，基于0．1cmm＊0．1cm的交错网格，求解了时间长度为1．2秒的固体介质流动状态。计算结果表明：固相的流动形态为中心上升边界下降的趋势。该结果与试验结果符合的很好。     

基于模拟退火算法的多孔介质三维重建

为了研究固相转换器内部流体的流动状态,将动态退火系数的模拟退火算法与基于改进的状态更新的随机重建方法相结合,提出一种对固相转换器这类多孔介质进行软件重建的三维随机重建策略.首先对显微CT采集得到的多孔介质图像进行处理,得到基于孔隙相与固体相的二值化图像,并将其作为参考模型;然后在保持多孔介质孔隙率不变的前提下对多孔介质进行重建,实现了对其采样、图像处理与重建的过程.实验结果表明,该策略可以提升重建速度与渗透率的精度,重建模型与参考模型的两点相关函数与孔隙分形维数有很好的一致性.     

一种简化的NS2链路模型

基于离散事件模拟技术的NS2网络模拟器被广泛运用于计算机网络的研究中。传统的NS2链路模型复杂度高,导致了大规模网络模拟由于需要大量的计算时间而难以实现。为降低网络模拟所需要的计算开销,以提高网络模拟的规模以及性能,提出一种简化的NS2链路模型。与传统的NS2链路模型相比,该模型在不影响网络模拟真实性的前提下,不再在链路模型中维护分组缓存队列,并将部分离散事件采用直接计算来处理,以减少离散事件个数,降低模拟运行时间。实验表明,该模型在保证真实性的前提下,使模拟运行时间减少35%以上。     

多孔介质3维孔隙空间的隐式曲面造型方法

多孔介质中孔隙空间的结构描述和问题求解是许多复杂形态实体微观分析和科学计算的基础,而实际的多孔介质孔隙空间结构由于异常复杂,采用简单的造型方法往往不能满足绘制和进一步计算的要求。为此,针对自然岩石核磁共振的3维体数据,提出了一种适用于多孔介质孔隙空间的造型方法。该方法首先通过最大球方法识别体数据中的孔隙空间,然后根据孔隙的层次关系和连通关系,通过建立孔隙空间的孔洞-网络模型来描述孔隙空间的拓扑结构,并结合隐式曲面造型方法来构造多孔介质孔隙空间的模型。将该方法运用到自然岩石的3维图像分析中的实验结果表明,该方法不仅使得多孔介质孔隙空间的复杂拓扑结构得以保留,而且保证了重建曲面的光滑性。     

多孔介质孔隙模型及其应用——毛细管束模型

在多孔介质中许多物理化学行为均与其自身的孔隙结构构型密切相关 ,建立一种切实可行的孔隙模型将会对研究材料和化工过程多孔介质提供很大的帮助。毛细管模型是一种较为简单的实用孔隙模型 ,它可以通过使用毛细管压对多孔介质的浸渗和排空情况进行计算 ,也可以用于对多孔介质中的浸渗和排空过程进行定性的解释。针对在研项目 ,对毛细管束模型情况做一评述     

多孔介质孔隙模型及其应用——毛细管束模型

在多孔介质中许多物理化学行为均与其自身的孔隙结构构型密切相关,建立一种切实可行的孔隙模型将会对研究材料和化工过程多孔介质提代很大的帮助。毛细管模型是一种较为简单的实用孔隙模型,它可以通过使用毛细管压对多孔介质的浸渗和排空情况进行计算,也可用于对多孔介质中的浸渗和排空过程进行定性的解释。针对在研项目,对毛细管束模型情况做一评述。     

离散系统快速递推仿真算法及其在柔性制造系统中的应用

本文对具有中央服务台形式,队列均为FCFS服务规则,不同顾客类不同路径和不同服务速率的闭网络进行了研究。文中引入多变量排队网络理论建立了一类离散事件系统仿真模型,提出一快速递推算法,该算法计算量小并应用于实际问题。     

一些气固催化反应的幂函数动力学模型的建立

本文针对化工领域中最常见的气固催化简单反应以及连串、平行复杂反应,将幂函数反应速度方程与催化动力学实验的本征动力学数据形式相结合,推出了相应的动力学处理的计算式,从而实现了对这两类反应建立其幂函数动力学模型的自动处理。     

N连接糖基化过程的动态图建模

单克隆抗体药物是当前国际市场上最具价值的药品种类之一,而N连接糖基化反应是单克隆抗体制备过程中非常重要的一个环节.本文采用有向图来描述糖蛋白结构,图模型描述反应网络,因此可以方便地采用分支限界法来生成整个反应网络.而且在这种图模型表示的反应网络中,糖基化反应的分析计算会变得更为容易.综合考虑实际细胞动态变化中高尔基体内转运反应的影响,提出了N连接糖基化反应的动态平衡方程,相比较现有的稳态模型可以提供更多的反应过程信息,并且为反应质量的实时控制做出了理论依据.另外,本文以理论计算与实测值偏差为目标,采用遗传算法对反应过程的大量生化参数进行优化,从而提高计算模型的精度.为了提升仿真模型的计算能力和对实验设计的指导作用,本文基于C++开发了一款专用的糖基化仿真计算平台,提供网络结构的可视化、反应过程的动态曲线、反应参数优化等功能.通过对比本文模型的数据分析与实际机理分析一致验证了模型的有效性.     

Heterogeneous Computing in Economics: A Simplified Approach

This paper shows the potential of heterogeneous computing in solving dynamic equilibrium models in economics. We illustrate the power and simplicity of C++ Accelerated Massive Parallelism (C++ AMP) recently introduced by Microsoft. Starting from the same exercise as Aldrich et al. (J Econ Dyn Control 35:386–393, 2011) we document a speed gain together with a simplified programming style that naturally enables parallelization.     

在Visual C++中调用MATLAB以实现数学算法

很多专业软件涉及到复杂的数学计算,同时也需要友好的用户界面。MATLAB具有很强的数值计算能力,而Visual C 则具有很强的普通软件尤其是图形用户界面的开发能力,两者的互补结合对快速、高效地开发专业计算软件具有很大的意义。讨论了在Visual C 中调用MATLAB文件的方法,它借助MATLAB的MCC命令和接口函数实现。通过该方法开发的软件可以独立于MATLAB而运行,并可以把MATLAB算法封装在动态链接库中,再在Visual C 中调用,提高了开发专业应用软件的速度及软件运行的效率和可靠性。     

形态滤波和空间滤波在两相流速度测量中的应用

为了快速、准确地对气固两相流速度进行测量,介绍一种利用形态滤波和空间滤波处理气固两相流信号的基本方法,首先研究电容传感器的空间滤波效应,并找出固体速度和电容传感器带宽之间的关系.然后通过对一维形态滤波算法理论进行分析,推导出可用于实时运算的形态滤波方法,此方法具有处理速度快,滤波效果好,适用性广的特点,可应用于多种信号的实时处理中.然后利用形态滤波确定传感器的带宽,进而求出固体速度.最后给出仿真实验结果,仿真实验结果表明:该方法可以满足气固两相流速度的测量要求.     

Microscale and mesoscale discrete models for dynamic fracture of structures built of brittle material

In this work we present the discrete models for dynamic fracture of structures built of brittle materials. The models construction is based on Voronoi cell representation of the heterogeneous structure, with the beam lattice network used to model the cohesive and compressive forces between the neighboring cells. Each lattice component is a geometrically exact shear deformable beam which can describe large rigid body motion and the most salient fracture mechanisms. The latter can be represented through the corresponding form of the beam constitutive equations, which are derived either at microscale with random distribution of material properties or at a mesoscale with average deterministic values. The proposed models are also placed within the framework of dynamics, where special attention is paid to constructing the lattice network mass matrix as well as the corresponding time-stepping schemes. Numerical simulations of compression and bending tests is given to illustrate the models performance.     

Developing applications in large scale,dynamic fog computing: A case study

In recent years, fog computing has emerged as a new distributed system model for a large class of applications that are data-intensive or delay-sensitive. By exploiting widely distributed computing infrastructure that is located closer to the network edge, communication cost and service response time can be significantly reduced. However, developing this class of applications is not straightforward and requires addressing three key challenges, ie, supporting the dynamic nature of the edge network, managing the context-dependent characteristics of application logic, and dealing with the large scale of the system. In this paper, we present a case study in building fog computing applications using our open source platform Distributed Node-RED (DNR). In particular, we show how applications can be decomposed and deployed to a geographically distributed infrastructure using DNR, and how existing software components can be adapted and reused to participate in fog applications. We present a lab-based implementation of a fog application built using DNR that addresses the first two of the issues highlighted earlier. To validate that our approach also deals with large scale, we augment our live trial with a large scale simulation of the application model, conducted in Omnet++, which shows the scalability of the model and how it supports the dynamic nature of fog applications.     

Delaunay 三角网生长算法改进与实现

对一般三角网生长法做了简要介绍和分析,针对限制算法效率提高的关键 步骤——“搜索符合条件的第三点”,提出了一种“第三点分区搜索法”的改进算法。通过 一系列的圆弧将离散点区域划分成多个分区,构网时规定只可在当前分区和相邻的下一分区 搜索第三点,当该分区的离散点搜索完毕后进入下一分区。在Microsoft Visual Studio 2008 的环境下使用C++进行编程测试,结果表明,该算法能够加快构网速度,生成的三角形形状 良好,具有一定的实际效用。     

The cascading neural network: building the Internet of Smart Things

Most of the research on deep neural networks so far has been focused on obtaining higher accuracy levels by building increasingly large and deep architectures. Training and evaluating these models is only feasible when large amounts of resources such as processing power and memory are available. Typical applications that could benefit from these models are, however, executed on resource-constrained devices. Mobile devices such as smartphones already use deep learning techniques, but they often have to perform all processing on a remote cloud. We propose a new architecture called a cascading network that is capable of distributing a deep neural network between a local device and the cloud while keeping the required communication network traffic to a minimum. The network begins processing on the constrained device, and only relies on the remote part when the local part does not provide an accurate enough result. The cascading network allows for an early-stopping mechanism during the recall phase of the network. We evaluated our approach in an Internet of Things context where a deep neural network adds intelligence to a large amount of heterogeneous connected devices. This technique enables a whole variety of autonomous systems where sensors, actuators and computing nodes can work together. We show that the cascading architecture allows for a substantial improvement in evaluation speed on constrained devices while the loss in accuracy is kept to a minimum.     

Tice: A real-time language compilable using C++ compilers

Model-based development (MBD) holds the promise to capture potential timing problems in embedded software during the early phases of the development, securing the production of bug-free embedded software. For most MBD approaches, the source code is just an intermediate artifact that can be generated automatically from the models. This assumption clashes with an undeniable fact: a large share of the commercial embedded software exploits existing libraries or is developed using C/C++ natively. A way to reconcile the ambitions of MBD with the use of a programming language is by offering new language constructs and an innovative compilation tool-chain that prevents model error and timing problems “by construction.” However, the persistent popularity of C/C++ among embedded programmers and the limited availability of tools have severely limited the uptake of alternative programming languages for embedded software. Therefore, we propose an original route. Our language proposal, named Tice, has been shaped as a C++ active library. Tice retains full compatibility with existing C++ code, which can be integrated easily into new Tice-based projects. The enforcement of Tice syntax and semantics can be made by a standard C++ compiler, forgoing the need for new tools. In this article, we describe Tice's syntax, semantics, and model of computation and communication. We demonstrate Tice's practical applicability on an industrial scale use-case and give ample evidence for Tice's efficient compilation using off-the-shelf C++ compilers. Finally, we show Tice's code generation process.     

基于分布式遗传算法的水质传感器布置优化研究

水质传感器优化布置是指在城镇配水管网中最优位置布置水质传感器对污染物进行检测,从而达到监测预警的目的,其本质是一类大规模离散组合优化问题。首先从数学上对该问题进行分析,论证了其具有NP-Complete特性;然后针对该问题计算开销大等特点,提出了基于Spark云计算模型的分布式遗传算法;最后以一个典型的复杂配水管网为对象进行实验,仿真结果表明,所提出的算法不仅具有搜索速度快、精度高等优点,而且还具有较好的线性加速比。     

Gauss: A Framework for Verifying Scientific Computing Software

High performance scientific computing software is of critical international importance as it supports scientific explorations and engineering. Software development in this area is highly challenging owing to the use of parallel/distributed programming methods and complex communication and synchronization libraries. There is very little use of formal methods to debug software in this area, given that the scientific computing community and the formal methods community have not traditionally worked together. The Utah Gauss project combines expertise from scientific computing and formal methods in addressing this problem. We currently focus on MPI programs which are the kind that run on over 60% of world's supercomputers. These are programs written in C / C++ / FORTRAN employing message passing concurrency supported by the Message Passing Interface (MPI) library. Large-scale MPI programs also employ shared memory threads to manage concurrency within smaller task sub-groups, capitalizing on the recent availability of small-scale (e.g. single-chip) shared memory multiprocessors; such mixed programming styles can result in additional bugs. MPI libraries themselves can be buggy as they strive to implement complex requirements employing aggressive techniques such as multi-threading. We have built a model extractor that extracts from MPI C programs a formal model consisting of communicating processes represented in Microsoft's Zing modeling language. MPI library functions are also being modeled in Zing. This allows us to run formal analysis on the models to detect bugs in the MPI programs being analyzed. Our preliminary results and future plans are described; in addition, our contribution is to expose the special needs of this area and suggest specific avenues for problem- driven advances in software model-checking applied to scientific computing software development and verification.