Template Synthesis and UV-Vis Absorption Spectra of the Nanowire Arrays of Cadmium Chalcogenides

以多孔氧化铝为模板 ,用交流电分别通过含有相应的CdCl2 、ZnCl2 、单质S、Se等的二甲亚砜 (DMSO)溶液 ,沉积CdS、CdSe以及CdxZn1-xS半导体纳米线阵列并研究其紫外可见吸收光谱 .实验结果表明 ,当半导体纳米线的直径小于 2 5nm时 ,其吸收边相对于体相的吸收边产生蓝移 ,而且蓝移的幅度随着半导体纳米线直径的减小而增加 ,显示了明显的量子限域效应 .XU Shi_min, XUE Kuan_hong , KONG Jing_lin, SUN Dong_mei, FENG Yu_ying, LU Hai_yan (Dept. of Chem., Nanjing Normal Univ., Nanjing 210097, China) WANG Guang_hou (National Laboratory of Solid State Microstructures, Nanjing Univ., Nanjing 210093, China)The porous alumina membrane formed in the anodic oxidation of highly pure aluminum foil has attracted a great deal of attention in recent years [1] . It can be served as a desired template to prepare nanometer scale materials [2] due to its unique structure of discrete and cylindrical nanopores, paralleled one another, with the homogeneous size and distribution [3] . Chalcogenide semiconductors have promising prospect in the applications of photovoltaic [4] and photoconducting devices [5] and have been extensively exploited for many years. Olbright and his co_workers studied experimentally and theoretically the optical nonlinearties of CdS xSe 1-x _doped glass [6] ; Britt and Ferekides reported that the conversion efficiency in a solar cell of thin_film CdS/CdTe could be as high as 15.8% [7] . Here we report the fabrication and UV_Vis absorption spectra of CdS、CdSe and Cd xZn 1-x S nanowire arrays deposited into the template matrix of porous alumina. The diameters of these nanowires were varied from 10 nm to 50 nm in our experiments.作者联系地址：南京师范大学化学系!江苏南京210097,南京师范大学化学系!江苏南京210097,南京师范大学化学系!江苏南京210097,南京师范大学化学系!江苏南京210097,南京师范大学化学系!江苏南京210097,南京师范大学化学系!江苏南京210097,南京大学固体微结构国家重点实验室!江苏南京21009

Distributed Transaction Guarantee Mechanism for In-Memory Data Grid

在线事务处理（online transaction processing，OLTP）应用面临并发量和数据量持续增长的问题，并且高并发读写操作使得后台数据库成为瓶颈。内存数据网格（in-memory data grid，IMDG）是基于内存的新型分布式数据访问平台，是解决系统数据库写操作瓶颈的有效技术途径之一。然而内存数据网格中数据访问操作涉及的数据分布是不可预知的，需要提供分布式事务保障。针对内存数据网格的系统特点，提出了一种分布式事务保障机制，设计实现了事务处理模型、请求处理和数据定位方法以及事务保障协议，并规范化地定义了客户端与服务器端以及服务器端之间的操作接口。在事务处理基准测试TPC-W上的实验结果表明，新机制可以提高在线事务应用的处理速度，并具备良好的扩展性。 Online transaction processing (OLTP) Web applications face the continuous growth of concurrent users and data size. The high concurrent read and write operations make databases become the bottleneck. In-memory data grid (IMDG) is a new distributed data access platform based on memory, and an effective technical approach to elimi-nate the bottleneck of write operation in the database. However data distribution involved in data access operation of IMDG is unpredictable. A distributed transaction guarantee mechanism is necessary. For the IMDG system character-istics, this paper gives a distributed transaction guarantee mechanism, designs and implements a distributed transac-tion processing model, the way to do request processing and data accessing and the transaction guarantee protocol, and normalizes the application programming interface (API) between clients and servers. The experimental results on TPC-W show that the mechanism can improve the OTLP speed and support good scalability.Online transaction processing (OLTP) Web applications face the continuous growth of concurrent users and data size. The high concurrent read and write operations make databases become the bottleneck. In-memory data grid (IMDG) is a new distributed data access platform based on memory, and an effective technical approach to elimi-nate the bottleneck of write operation in the database. However data distribution involved in data access operation of IMDG is unpredictable. A distributed transaction guarantee mechanism is necessary. For the IMDG system character-istics, this paper gives a distributed transaction guarantee mechanism, designs and implements a distributed transac-tion processing model, the way to do request processing and data accessing and the transaction guarantee protocol, and normalizes the application programming interface (API) between clients and servers. The experimental results on TPC-W show that the mechanism can improve the OTLP speed and support good scalability

支持透明集成的数据缓存机制

　　数据缓存是提升动态Web应用性能的重要手段,传统数据缓存方案主要进行数据查询缓存,通常需要开发人员对应用程序进行大量修改并负责缓存失效维护,导致缓存方案的部署成本和维护成本过高.本文提出一种新的数据缓存机制EasyCache,支持缓存数据的自动加载,兼容常用的标准数据访问接口及SQL语法,并提供数据一致性保障策略.开发人员无需修改应用程序即可完成EasyCache的集成.TPC-W基准测试结果表明系统性能得到显著提升,在单表数据规模增加以及并发用户规模增加等情况下,系统响应速度可提高10倍,吞吐率提高近1倍

望天湖底栖动物种群密度与季节变动的初步观察

<正> 国内有关淡水底栖动物生态研究的报道较少,尤以底栖动物种群密度的季节变动资料更是缺乏。作者于1965年曾对望天湖底栖动物进行过调查,取得了一些资料。望天湖位于长江中游(湖北省浠水县),为中型(万亩左右)浅水湖泊,其底栖动物资料有一定的代表性,特整理发表,供有关方面参考

A data-driven trust evaluation model based on the perception source

为解决物联网数据源头的可靠问题，构建一种基于感知源的数据驱动信任评测模型。模型以监测模块为评测单元，由中继节点完成其所在监测模块内感知节点的信任评测，通过感知节点自身数据之间的关系实现直接信任的计算，利用监测模块内各邻居节点之间关系实现推荐信任的计算，再结合历史信任，输出感知节点的综合信任。同时与模型预设的可疑阈值和异常阈值进行对比，更新历史信任和信任列表，实现感知节点的异常检测，利用预警检测误差和失信检测误差对模型的检测效果进行评价，统计结果表明模型能够保持较低的平均误差。将信任机制引入到数据融合过程，用综合信任作为加权因子，从而提高了数据融合的准确度。最后，通过实验仿真对信任评测模型进行评价，结果表明引入信任评测模型后延长了节点开始死亡的时间，随着节点的更新迭代，失信节点越来越少，在一定程度上提高了节点的存活率，延长了网络的生命周期。</p

Path-Tracking of Wheeled Mobile Robot Using Preview and Predictive Control

This paper describes a method to make a wheeled mobile robot follow a given path just like a driver would decelerate the speed of a car before a corner and accelerate it on the straight course of the road. Two kinds of velocity vectors are introduced to determine an optimal direction and speed of the robot in order to follow the path. The velocity defined as a function of curvature of the path is mainly utilized to change the speed of the robot along the path. The other velocity given as the tangent of a virtual potential function produces an attraction force toward the path. Path tracking control of the robot is formulated with current and future sets of these velocity vectors in a frame of the digital preview and predictive control. By this method, the robust tracking performance is achieved