Using self-similar properties of turbulent premixed flames to downsize chemical tables in high-performance numerical simulations

Detailed chemical mechanisms have to be incorporated in turbulent combustion modelling to predict flame propagation, ignition, extinction or pollutant formation. Unfortunately, hundreds of species and thousands of elementary reactions are involved in hydrocarbon chemical schemes and cannot be handled in practical simulations, because of the related computational costs and the need to model the complexity of their interaction with turbulent motions. Detailed chemistry may be handled using look-up tables, where chemical parameters such as reaction rates and/or species mass fractions are determined from a reduced set of coordinates, progress variables or mixture fractions, as proposed in ILDM, FPI or FGM methods. Nevertheless, these tables may require large computer memory spaces and non-negligible access times. This issue becomes of crucial importance when running on massively parallel computers: to implement these databases in shared memories would induce a large number of data exchanges, reducing the overall code performance; on the other hand duplicating databases in every local processor memory may become impossible either for large databases or small local memories. This work proposes to take advantage of the self-similar behaviour of turbulent premixed flames to reduce the size of these chemical databases, specifically when running on massively parallel machines, under the FPI (Flame Prolongation of ILDM) framework. Several approaches to reduce the database are investigated and discussed both in terms of memory requirements and access times. A very good compromise is obtained for methane–air turbulent premixed flames, where the size of the database is decreased by a factor of 1000, while the access time is reduced by about 60%.     

基于Dempster-Shafer证据理论的信任评估模型

从网格的动态性、分布性、不确定性等特征出发,参考社会学的人际信任关系结构,提出了一种基于Dempster-Shafer证据理论（简称D-S理论）的信任评估模型．该模型根据网格节点间的历史交易记录,给出“直接信任”的形式化描述,建立网格节点信任推荐机制,并利用D-S理论对证据进行组合,从而得到“间接信任”．然后将直接信任和间接信任进一步组合为“综合信任”,从而有效实现信任信息的融合．将本文提出的信任度评估方法应用到调度算法中,结果证明了该信任模型的可行件和实用件．     

Quantum Fourier Transform-Based Arithmetic Logic Unit on a Quantum Processor

This study proposes and construct a primitive quantum arithmetic logic unit (qALU) based on the quantum Fourier transform (QFT). The qALU is capable of performing arithmetic ADD (addition) and logic NAND gate operations. It designs a scalable quantum circuit and presents the circuits for driving ADD and NAND operations on two-input and four-input quantum channels, respectively. By comparing the required number of quantum gates for serial and parallel architectures in executing arithmetic addition, it evaluates the performance. It also execute the proposed quantum Fourier transform-based qALU design on real quantum processor hardware provided by IBM. The results demonstrate that the proposed circuit can perform arithmetic and logic operations with a high success rate. Furthermore, it discusses in detail the potential implementations of the qALU circuit in the field of computer science, highlighting the possibility of constructing a soft-core processor on a quantum processing unit.     

激光雷达辅助驾驶道路参数计算方法研究

针对特定场景辅助驾驶的需求,构建道路场景车载激光雷达三维扫描系统,并设计基于三维激光点云的道路参数提取与计算方法,包括路面宽度、横杆或桥梁或隧道限高、拐弯半径等等,为辅助判断道路的可通过性提供决策依据。测试和对比实验表明,所设计算法效果稳定、精度良好,在效率和自动化程度上有一定优势,可为辅助驾驶提供非常有益的决策参数。     

The Application of Fractal Transform and Entropy for Improving Fault Tolerance and Load Balancing in Grid Computing Environments

This paper applies the entropy-based fractal indexing scheme that enables the grid environment for fast indexing and querying. It addresses the issue of fault tolerance and load balancing-based fractal management to make computational grids more effective and reliable. A fractal dimension of a cloud of points gives an estimate of the intrinsic dimensionality of the data in that space. The main drawback of this technique is the long computing time. The main contribution of the suggested work is to investigate the effect of fractal transform by adding R-tree index structure-based entropy to existing grid computing models to obtain a balanced infrastructure with minimal fault. In this regard, the presented work is going to extend the commonly scheduling algorithms that are built based on the physical grid structure to a reduced logical network. The objective of this logical network is to reduce the searching in the grid paths according to arrival time rate and path’s bandwidth with respect to load balance and fault tolerance, respectively. Furthermore, an optimization searching technique is utilized to enhance the grid performance by investigating the optimum number of nodes extracted from the logical grid. The experimental results indicated that the proposed model has better execution time, throughput, makespan, latency, load balancing, and success rate.     

BEPC中电子云导致的束团横向尺寸增长研究

多束团正电子储存环中可能发生电子云不稳定性. 由于电子云导致的束团横向尺寸增长已经成为提高对撞机对撞亮度的主要限制因素之一. 介绍了在BEPC储存环中, 利用条纹相机直接测量由于电子云导致的束团横向尺寸增长结果, 并与模拟计算进行了比较.     

彩色遥感图像薄云去除方法

针对彩色遥感图像中薄云带来的降质问题,提出了一种基于低秩矩阵分解的去云方法。将彩色遥感图像分成三个单通道图像,对每一个通道进行低秩矩阵分解,得到单通道薄云信息;根据薄云在三个通道中均匀分布的特点,选取合适的阈值对薄云信息进行自动判定,提取代表三个通道的薄云图像;用三个通道的图像分别减去对应通道的薄云图像,并融合三个通道的结果得到去云后的彩色遥感图像。实验结果表明,该方法不仅能够保留无云区域信息的完整性,而且对有云区域的处理在主观视觉效果和客观评价指标上都具有较好的效果。     

真值表查询式光学符号替换

本文提出了一种新的符号替换光学处理方法.采用互补编码和地点寻址的真值表查询,构造了一种可进行返回运算的全加数字处理器.利用由液晶光阀构成的行逻辑器件对这一符号替换系统进行了实验验证并给出了实验结果.     

一种复杂多边形最大内圆的快速查找算法

任意多边形的最大内圆的快速查找在多个领域有着重要的应用。首先给出了任意多边形的Voronoi图的生成方法,以及基于Voronoi图实现该多边形的最大内圆的寻找算法,在此基础上分别采用中线简化及并行化处理对算法进行了效率方面的改进,并重点研究了矢量数据并行化过程中的数据分配策略,给出了其最优数据划分策略——算法复杂度均衡法。最后对北美阿拉斯加地区的多个湖泊进行了最大内圆的查找实验,相应的实验结果表明,改进的方法能够很大程度地提高最大内圆的查找效率。     

基于JASMIN的地下水流大规模并行数值模拟

针对具有精细网格剖分、长时间跨度特征的地下水流模拟中计算时间长、存储开销大等瓶颈问题,基于MODFLOW三维非稳定流计算方法,提出基于网格片的核心算法以及基于影像区的通信机制,并在JASMIN框架上研制了大规模地下水流并行数值模拟程序JOGFLOW.通过河南郑州市中牟县雁鸣湖水源地地下水流的模拟,对程序正确性和性能进行了验证;通过建立一个具有精细网格剖分的假想地下水概念模型对可扩展性进行测试.相对于32核的并行程序,在512以及1 024个处理机上的并行效率分别可达77.2%和67.5%.数值模拟结果表明,JOGFLOW具有较好的计算性能与可扩展性,能够有效使用数百上千计算核心,支持千万量级以上网格剖分的地下水流模型的大规模并行计算.