新型层状表面相锆基固体酸催化酯化反应研究

将所研制的层状表面相锆基固体酸催化剂用于一元、二元醇醋酸酯和其他羧酸酯类产品的合成 ,考察了其催化性能。研究发现 :层状表面相锆基固体酸催化剂对所考察的酯化反应具有很好的普遍适用性 ,但其酯化率与醇的性质和结构密切有关。催化反应动力学研究表明乙酸与丁醇、戊醇、己醇的酯化反应均为二级反应 ,且反应活化能均较低 ,分别为 47 4kJ/mol、2 3 3kJ/mol和 19 8kJ/mo     

A novel method for camera external parameters online calibration using dotted road line

On board camera is the most important information source for driver assistant application which is based on computer vision. One problem for on board camera is that the external parameters are easy to be changed when moving on the road. Traditional method either calibrates external parameters offline or calibrates external parameters semi-online, which both need human intervention. By observation, it is found that corner connection of dotted road lane can form two groups of parallel lines. Using this geometric characteristics and through theoretical derivation, a novel online camera external parameter calibration method is proposed which focus on the situation when vehicle is moving. The pro of this method is that it maintains relatively high calculation accuracy and more important, it does not require any human intervention in whole calibration process. Experimental and comparison results show that this method is simple and have accurate results which fully meet the requirements of practical application.     

Effective naive Bayes nearest neighbor based image classification on GPU

Non-parametric classifier, Naive Bayes nearest neighbor, is designed with no training phase, and its performance outperforms many well-trained learning-based image classifiers. Unfortunately, despite its high accuracy, it suffers from great computational pressure from distance computations in space of local feature. This paper explores accelerating strategies from perspectives of both algorithm design and software development. Our approach integrates space decomposition capability of Product quantization (PQ) and parallel accelerating capability of underlying computational platform, Graphics processing unit (GPU). PQ is exploited to compress the indexed local features and prune the search space. GPU is used to ease most of computational pressure by processing the tasks in parallel. To achieve good parallel efficiency, a new sequential classification process is first designed and decomposed into independent components with high parallelism. Effective parallelization techniques are then presented to make use of computational resources. Parallel heap array is built to accelerate the process of feature quantization. Distance table lookup is built to speed up the process of feature search. Comparative experiments on UIUC-Sport dataset demonstrate that our integrated solution outperforms other implementations significantly on Core-quad Intel Core i7 950 CPU and GPU of NVIDIA Geforce GTX460. Scalability experiment on 80 million tiny images database shows that our approach still performs well when large-scale image database is explored.     

软件定义网络中交换机处理时延的仿真

针对目前的网络仿真工具在对软件定义网络(SDN)的仿真过程中,未考虑交换机的处理时延的问题,提出一种处理时延的仿真方法,目的是为了使仿真结果更加真实和准确。该方法首先将交换机的转发处理过程分解为对流表的查询操作和执行不同的动作;然后,利用交换机的处理器频率和访存周期,将查询流表和执行动作转换为处理时间。实验中测量了真实环境中不同配置的交换机处理时延,并与利用该方法仿真出的处理时延进行对比。实验结果表明,利用该方法仿真出的处理时延和真实交换机的处理时延基本一致,该方法能够较准确地仿真交换机处理时延。     

不同频率激励信号下土壤水分传感器性能试验

激励信号频率是影响高频电容式土壤水分传感器性能的重要因素。利用去离子水和2—异丙氧基乙醇(2—isoproxyethanol)或二氧六环(dioxane)2种溶液混合,配制了一系列等效土壤体积含水率为0.9%~51.8%的待测介电溶液来替代土样。从与土壤含水率的函数关系、温度变异性2个方面,分别对激励信号频率为40,50,60,70,80,90,100 MHz的7种土壤水分传感器进行了性能测试与分析。结果表明:7种频率的传感器的输出电压均与土壤体积含水率呈线性负相关,其相关系数R2均大于0.94;激励信号频率不影响传感器输出电压的温度变异性,温差是影响温度变异性的主要因素,其最大变异率均小于4%。试验结果可为设计高频电容式土壤水分传感器时选择激励信号频率提供依据。     

基于无线传感器网络的小粒种咖啡园滴灌自动控制系统

为实现小粒种咖啡种植园的精量灌溉,达到节水增收的目的,基于无线传感器网络（WSNs）设计了一种滴灌自动控制系统,主要由传感器节点、簇头、控制节点和汇聚节点组成.测试了节点间的有效通信距离为50m,并在此基础上,采用静态簇和节点定位布置的方法进行了灌区划分和节点部署,每个灌区为边长50m的正方形,内设1个簇头、1个控制节点和4个传感器节点.采用定时通信与时间同步技术、休眠技术相结合的方法实现节点数据的无线传输,融合土壤含水率、光强和空气温湿度等信息,采用分区轮灌策略实现滴灌的自动控制.实验结果表明：系统实现了预期设计目标,能应用于小粒咖啡园的精量灌溉管理.     

基于B/S模式的数据库应用系统安全

随着数据库技术和管理信息系统的发展,两者的结合越来越紧密,其安全性正逐步引起人们的重视。数据库应用系统是在数据库管理系统支持下建立的以数据库为基础和核心的计算机应用系统,由数据库系统、应用程序系统和用户组成。文中主要探讨了基于B/S模式的SQL Server数据库应用系统的安全问题。结合B/S模式的三层结构,分别从应用程序、服务器和数据库层次进行安全性研究。其中,应用程序安全采用输入验证、输出编码和会话管理技术;服务器安全采用安全协议、操作系统安全、防火墙技术和防SQL注入攻击技术;数据库安全技术采用用户认证、访问控制、数据加密、审计追踪和视图机制技术。     

新一代水管式沉降仪控制模块的研制

新一代低功耗水管式沉降仪控制模块是基于16单片机MSP430F5436为处理器的低功耗装置.该文详细介绍了其硬件结构和工作原理,分别从电源系统、电磁阀控制电路、控制流程、数据采集等部分阐述了其特点,诠释了水管式沉降仪控制模块在人机交互、工作稳定性等多方面所具备的优势.新一代水管式沉降仪控制模块已在实际工程中得到了成功应用,其稳定性和精确性为大坝监控系统提供了准确的实时数据.     

Fabrication and amplification of Rhodamine B‐doped step‐index polymer optical fiber

A step‐index polymer optical fiber (SI POF) containing Rhodamine B in poly(methyl methacrylate) (PMMA) has been fabricated by a preform technique. Fluorescence of different fiber lengths were observed and discussed. A high gain (23 dB) for a SI POF with 60‐cm length, 400‐μm diameter was obtained. The Rhodamine B content of the doped SI POF is 5 ppm‐wt. The signal wavelength providing the highest gain for a 60 cm SI POF is around 630 nm, and the optimum fiber length is about 60 cm at 10 kW launched pump power. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 681–685, 2004     

THE CALCULATION OF CRITICAL PROPERTIES OF MIXTURES FROM EQUATIONS OF STATE

The rigorous critical state criteria based on Helmholtz free energy is used with equations of state fordirect calculation of critical properties(T_c,P_c and V_c)of 44 binary and 5 ternary systems.Special at-tention is paid to systems containing polar component(s)and the improvement in critical volume prediction.For extending this method to polar systems,the recently developed Cubic Chain-of-Rotators equation ofstate has been applied.As compared with SRK and PR equations of state,the improvement in V_c pre-diction is most impressive.