基于MAS的协作学习机制研究

基于多Agent技术构建了一个网上协作学习系统模型MACL,给出了系统的结构框架,就其中的学生模型的构建、协作学习小组的创建以及协作学习和评价机制进行了探讨,结合KQML通信机制设计了Agent的交互模型,并进一步研究了协作小组的创建策略和算法.     

一个基于免疫的网络入侵检测模型

文章通过研究现有的入侵检测系统和学习计算免疫系统,提出了一种基于免疫的入侵检测模型。它运用免疫系统的多层性、分布性、自组织性等特性,通过具有免疫特性的多Agent实时检测网络,提高网络系统的安全性,具有分布性、适应性等特点。     

Partial Separation and Characterization of Papaya Endo- and Exo-Polygalacturonase

Exo- and endo-polygalacturonases (EC 3.2.1.40 and EC 3.2.1.15) in papayas were extracted, purified 20- and 90-fold, respectively, and characterized. Both enzymes functioned optimally at pH 4.6 and 45°C. Heat inactivation of the papaya PGases was biphasic and both phases followed first order kinetics. Decreasing the pH from 4.6 to 3.6 decreased the time required for their heat inactivation. The activation energies for the thermal inactivation at pH 3.6 and 4.6 were 85 and 92 kcal/mol, respectively, for endo-PGase (PG I) and 140 and 102 kcal/mol, respectively, for exo-PGase (PG II). The apparent molecular weight was determined by gel filtration to be 164,000 daltons for PG I and 34,000 daltons for PG II.     

Cr-Si粉末冶金工艺及其物理-力学性能

粉末冶金制作法主要有热压(HP)、热等静压(HIP)及常压烧结(Sinter)三种.采用热压及热等静压法可以很容易地得到高致密化的高温金属硅化物,但若要进行大尺寸的产品烧结,必须提升生产设备的规格和能力,例如加大热压机力吨位、扩大热压炉腔体等,致使设备投资及生产成本相对昂贵.所以大部分厂商宁可采用常压烧结法,虽然该法的高致密化工艺条件不易控制,却因可以制作大尺寸金属硅化物,加上设备投资及生产成本相对降低,使许多大厂已投入相当大的人力和物力在开发此工艺.该文作者试用不同真空烧结温度,造成Cr-Si合金粉末烧结性质的差异,探讨稳定而可大量生产的可行性;并通过对温度的控制,来改善Cr-Si的物理性质与力学性质.结果表明,提高烧结温度会使Cr-Si合金产生部分液相烧结的现象,从而使孔隙率显著下降;但显微结构也随之有偏析与晶粒粗化的现象.     

ECM-abrasive polishing of metals

The combined action of abrasives and electrochemical machining (ECM) results in a better surface finish than that could be achieved by using abrasives alone. From an initial roughness of R_tm 30 to 50 nm, flat carbon steel and stainless steel specimens could be finished to a roughness of R_tm 0-4 μm. The procedures in conducting the experiments and analysing the data are discussed in this paper.     

A New Calculation Method for Distinguishing Endo- from Exo-Polygalacturonases

A method which uses a comparison ratio (CR) of fluidity (1/n)sp)/μmoles reducing groups is proposed for comparing and distinguishing endo- and exo-polygalacturonases (PGases). This method is faster, easier and as accurate a method as the percent hydrolysis method. The CR method can also be used as a measure of the purity of endo- PGase with respect to exo-PGase.     

Learning Bayesian Networks with the Combination of Evolutionary Algorithm and EMI Method

Most Bayesian network （BN） learning algorithms use EMI algorithm to deal with incomplete data. But EMI algorithm is of low efficiency due to its iterative parameter refinement, and the problem will become even worse when multiple runs of EMI algorithm are needed. Besides, EMI algorithm usually converges to local maxima, which also degrades the accuracy of EMI based BN learning algorithms. In this paper, we replace EMI algorithm used in BN learning tasks with EMI method to deal with incomplete data. EMI is a very efficient method, which estimates probability distributions directly from incomplete data rather than performs iterative refinement of parameters. Base on EMI method, we propose an effec- tive algorithm, namely EMI-EA. EMI-EA algorithm uses EMI method to estimate probability distribution over local structures in BNs, and evaluates BN structures with a variant of MDL scoring function. To avoid getting into local maxima of the search process, EMI-EA evolves BN struc- tures with an Evolutionary algorithm （EA）. The experi- mental results on Alarm, Asia and an examplar network show that EMI-EA algorithm outperforms EMI-EA for all samples and E-TPDA algorithms for small and middle size of samples in terms of accuracy. In terms of efficiency, EMI-EA is comparable with E-TPDA algorithm and much more efficient than EMI-EA algorithm. EMI-EA also out- performs EMI-EA and M-V algorithm when learning BNs with hidden variables.     

Behaviors of recycled aggregate concrete-filled steel tubular columns under eccentric loadings

The paper investigates the behaviors of recycled aggregate concrete-filled steel tubular (RACFST) columns under eccentric loadings with the incorporation of expansive agents. A total of 16 RACFST columns were tested in this study. The main parameters varied in this study are recycled coarse aggregate replacement percentages (0%, 30%, 50%, 70%, and 100%), expansive agent dosages (0%, 8%, and 15%) and an eccentric distance of compressive load from the center of the column (0 and 40 mm). Experimental results showed that the ultimate stresses of RACFST columns decreased with increasing recycled coarse aggregate replacement percentages but appropriate expansive agent dosages can reduce the decrement; the incorporation of expansive agent decreased the ultimate stresses of RACFST columns but an appropriate dosage can increase the deformation ability. The recycled coarse aggregate replacement percentages have limited influence on the ultimate stresses of the RACFST columns and has more effect than that of the normal aggregate concrete-filled steel tubular columns.     

The application of Supercapacitor energy storage technology in the alongside replenishment equipment

本工作分析了航行横向补给系统的电动机再生发电问题,通过对蓄电池储能、超导线圈储能、飞轮储能和超级电容储能技术特点的对比,选用超级电容储能系统回收和利用再生电能,提出了超级电容储能系统的设计和应用方案,并对基本设计参数进行了计算。航行横向补给过程中,受到补给船和接收船距离不断变化的影响,补给装置绞车电机在电动和发电两种状态间频繁交互运行。电动机在发电状态下向变频器直流母线反馈大量再生电能,影响电网质量和设备的正常工作。由于超级电容具有功率密度高、充放电功率大、使用寿命长和工作温度范围广的优点,非常适用于电能的快速回收和释放,能够降低系统功率、减小对电网的影响、节约能源,在需要反复进行电能回收和释放的设备中具有较好的应用前景。     

入侵检测系统中检测技术的研究

该文从基于专家系统的技术、基于统计分析的技术和基于生物模拟的技术3个方面对入侵检测技术的研究进行了介绍,并对它们各自的特点、优势和不足进行了分析,最后,给出了当前的研究热点。