CFD predictions of flow near impeller blades in baffled stirred vessels: Assessment of computational snapshot approach

The present article summarizes simulations of turbulent flow generated by a Rushton turbine (six blades with disc) and a downflow pitched blade turbine (four blades, 45° inclined) using a computational snapshot approach. The computational snapshot approach proposed by Ranade and Dommeti was extended and generalized to suit impellers of any shape. The approach was implemented using a commercial CFD code, FLUENT (Fluent Inc., USA). Mean flow and turbulence characteristics were computed by solving the Reynolds averaged Navier-Stokes equations combined with the standard k - l turbulence model. The QUICK discretization scheme (with SUPERBEE limiter function) was used to discretize all the governing equations. Preliminary numerical experiments were carried out to identify adequate grid resolution. The predicted results were compared with the comprehensive data set available in the literature. Simulated results show a pair of trailing vortex behind the blades of a turbine. The results were also compared quantitatively in the near-impeller region with the published experimental data and published simulated results using other approaches. The simulations have captured most of the key features of near-impeller flows with sufficient accuracy. The results and conclusions drawn from this study will have important implications for extending the applicability of CFD models to simulate complex stirred reactors.     

Evaluating the impact of mass housings' in-between spaces' spatial configuration on users' social interaction

This research examines the impact of in-between space configuration on users' social practices. The effects of different degrees of permeability of these spaces on the social interactions of the inhabitants are also analyzed. This research is based on a comparative approach using space syntax analysis and snapshot observations on four mass housing neighborhoods in Setif, Algeria. The neighborhoods are selected according to their degree of permeability, location in the city, realization period, and syntax measures from integrated to segregated. The activity patterns of two-week days for each study case are observed and recorded. Correlation results of observed social activities and syntactic measures demonstrate that spatial configuration affects people's use of in-between spaces. Moreover, connectivity and clustering coefficients are revealed to be important indicators of social activities. Previous urban studies argued that integrated spaces are mostly used by people. However, social interaction in the studied cases increases in the least connected areas, adjoining spaces to the buildings, and most closed spaces. This research finds that social activities are dependent on the degree of permeability, which when low, gives rise to increased social interaction and activities.     

面向存储区域网的磁盘数据备份

磁盘数据备份为数据的安全性和可用性提供了保障，本文分析和研究了目前存储区域网(SAN)中比较流行的一种磁盘数据备份方案：snapshot，给出了snapshot的结构设计，并阐述其关键技术和实现原理。     

Oracle数据库在宝钢远程数据通讯中的应用研究

结合Oracle数据库技术在宝钢远程数据通讯中的应用,介绍了Oracle数据通讯的多种实现方式,着重阐述了仿快照技术的应用程序实现方式,比较了它与TCP/IP Socket电文通讯的优缺点.     

文件系统SAN备份方案的研究与实现

SAN存储备份的高可用性要求在进行文件系统备份时不能停止文件系统访问服务，那么SAN存储下的文件系统备份软件就需要解决基本备份操作与文件系统数据访问之间的同步控制和联动。文章基于SAN的两种典型的备份技术：复制技术和快照技术，提出了UNIX文件系统的SAN备份的解决方案。     

光电子成像电子能谱仪新一代DLD(延迟线检测器)系统

介绍新型X射线激发光电子成像电子能谱仪配置新一代DLD光电子检测系统优点、结构和在能谱和成像应用方面特点。     

时态数据的可变Hash索引

索引技术是时态数据库查询优化的重要方法之一。本文提出的可变Hash（VH）索引是建立在时间属性上的一种新的动态索引技术，主要目的是提高时态数据库快照查询的效率。由于时间的不确定性，在时态数据的时间属性上建立Hash索引比较困难。VH索引克服了Hash索引这一难点，提出了索引参数可变的思想，并应用B^＋-树对Hash参数进行组织。查询时由时间值在B^＋-树上获得Hash参数，进而确定数据的存储地址。通过对其时间复杂度和空间复杂度的理论分析以及实验验证，表明该索引技术可以减少索引查找以及读取数据的I／O次数，并具有理想的空间利用率。     

实现屏幕抓拍的VB程序

使用Ｗｉｎｄｏｗｓ系统的ＡＰＩ函数以及ＶＢ编程环境,编制了实现屏幕抓拍的ＶＢ程序。     

低功耗异构计算架构的高光谱遥感图像分类研究

高光谱图像分类算法通常需要逐点对图像中的像素点进行迭代处理,计算复杂度及并行程度存在较大差异。随着高光谱遥感图像空间、光谱和辐射分辨率的不断提升,这些算法无法满足实时处理海量遥感图像数据的需求。通过分析NPU存储计算一体化模式与遥感图像分类算法的实现步骤,设计低功耗CPU+NPU异构资源计算架构的低秩稀疏子空间聚类（LRSSC）算法,将数据密集型计算转移至NPU,并利用NPU数据驱动并行计算和内置AI加速,对基于机器学习算法的海量遥感数据进行实时分类。受到big.LITTLE计算范式的启发,CPU+NPU异构资源计算架构由8 bit和低精度位宽NPU共同组成以提高整体吞吐量,同时减少图网络推理过程中的能量损耗。实验结果表明,与CPU计算架构和CPU+GPU异构计算架构的LRSSC算法相比,CPU+NPU异构计算架构的LRSSC算法在Pavia University遥感数据集下的计算速度提升了3~14倍。     

Continuous data aggregation and capacity in probabilistic wireless sensor networks

Due to the existence of many probabilistic lossy links in Wireless Sensor Networks (WSNs) (Liu et al., 2010)  [25], it is not practical to study the network capacity issue under the Deterministic Network Model (DNM). A more realistic one is actually the Probabilistic Network Model (PNM). Therefore, we study the Snapshot Data Aggregation (SDA) problem, the Continuous Data Aggregation (CDA) problem, and their achievable capacities for probabilistic WSNs under both the independent and identically distributed (i.i.d.) node distribution model and the Poisson point distribution model in this paper. First, we partition a network into cells and use two vectors to further partition these cells into equivalent color classes. Subsequently, based on the partitioned cells and equivalent color classes, we propose a Cell-based Aggregation Scheduling (CAS) algorithm for the SDA problem in probabilistic WSNs. Theoretical analysis of CAS and the upper bound capacity of the SDA problem show that the achievable capacities of CAS are all order optimal in the worst case, the average case, and the best case. For the CDA problem in probabilistic WSNs, we propose a Level-based Aggregation Scheduling (LAS) algorithm. LAS gathers the aggregation values of continuous snapshots by forming a data aggregation/transmission pipeline on the segments and scheduling all the cell-levels in a cell-level class concurrently. By theoretical analysis of LAS and the upper bound capacity of the CDA problem, we prove that LAS also successfully achieves order optimal capacities in all the cases. The extensive simulation results further validate the effectiveness of CAS and LAS.