Using group communication to monitor web-based group learning

Abstract  In a web group-learning environment, students must communicate with other group members on the Internet to accomplish group projects and share knowledge. Communication is likely to affect performance and so analysing the relationship between communicative relationships and group performance may help teachers to monitor groups effectively. Certain tasks are necessary to perform such an analysis — recording group communication, extracting communication relationships and determining the relationship between group communication and group performance. This study developed a method for determining relationships and rules for predicting performance to enable teachers to take act appropriately according to the predicted performance of the group. Four group performance indicators are considered — average grades within a group, project grade, frequency of resource-sharing and drop-out rate. Experimental results are presented, concerning the application of the methodology to a web class of 706 students, divided into 70 groups. The experimental results show that group communication patterns significantly affect group performance.     

Design and Implementation of Fuzzy Sliding-Mode Controller for a Wedge Balancing System

In this paper, we address the design and implementation of fuzzy sliding-mode controller for balancing a wedge system. At first, we examine the mathematical model of the wedge balancing system. The dynamic system is complex and ill defined; hence we propose the fuzzy sliding-mode control (FSMC) method to achieve the control objective. The proposed control method enhances the ability of fuzzy logic control so that the minimal number of fuzzy inference rules is systematically obtained even the plant parameters are unknown. Both computer simulations and real-time experiments are exploited to demonstrate the validity and feasibility of the developed control scheme.     

分布式防空C~3I智能辅助决策模型

文章针对战场环境的动态性、不确定性和不可预测性,依据分布式防空C3I系统结构,对决策需求进行了分析,以战区级为背景,提出了智能辅助决策模型。     

离网型低速高效永磁风力发电机的研制

本文针对风力发电机的技术条件,介绍了低速永磁式风力发电机的设计特点,详细分析和比较了径向、切向两种转子结构的优缺点,在此基础上,设计了一台样机,最后,根据低速永磁式发电机的特点,给出了发电机的试验方法和试验数据,结果令人满意.     

消雷器与黄岛油库雷击火灾事故

黄岛油库５号非金属半地式油罐，１９８９年８月１２日上和进９时５５分爆炸起火，损失惨重。经调查，起火原因纯属非金属油罐的固有缺陷，如油面暴露面积大，油气易泄漏钢筋混凝土罐体对雷电效应屏蔽能力差，存在多处引发雷电火花隐患等。     

电化学调控法抑硫浮选的研究

进行了电化学法抑硫浮选的研究，探索了化学试剂法和外控电位法对细粒煤浮选脱硫的影响，通过试验证实，在低的矿浆电位下，黄铁矿能被有效抑制，提高了脱硫效率，它是一种经济有效、简单而无污染的抑制黄铁矿的新方法．     

金属构件的损伤断裂与抗力衰减分析

现有的结构力学分析都假设结构为完好无损，然而结构在初始状态或使用过程中总存在各种损伤，而且损伤在使用过程中会不断积累和加剧。损伤不但缩短结构的使用寿命，而且引起结构力学性能下降。本文着重研究了具有宏观裂纹构件的强度和刚度随损伤发展的衰减规律；分析了平面应力、平面应变及弹塑性情况下带裂纹构件的强度衰减，提出了构件剩余抗力的计算方法；基于能量原理，推导了带裂纹构件的刚度；应用本文的方法分析了一个三杆结构，分析结果显示了裂纹引起的构件强度和刚度的变化对结构承载力和可靠度的显著影响。     

“两硬”综放采场支架受载浅析

在现场观测基础上，分析了两硬（坚硬顶板，坚硬煤层）综放采场来压情况；运用回归分析，得出支架初撑力和循环最大工作阻力间的关系，由此给出确定放顶煤支架合理工作阻力的方法。     

六相双Y移30°感应电机稳定性分析

以六相双Y移30°感应电机为对象,从建立电机数学模型入手,导出状态空间方程,应用特征值稳定判据分析多相感应电机的稳定性。该方法适合线性化的系统在稳定工作点附近微小振动的稳定性分析。针对电机定、转子参数和转动惯量的变化,对系统稳定性进行实例计算和分析。     

Tribological behavior of sialon ceramics sliding against steel lubricated by fluorine-containing oils

The friction and wear behavior of sialon ceramics sliding against steel and lubricated by perfluoropolyethers (PFPE), tetrakis (3-trifluoromethylphenoxy)-bis(4-fluoro-phenoxy)-cyclotriphosphazene (X-1P) and ionic liquid (1-methyl-3-octylimidazolium tetrafluoroborate, coded as L108) were investigated. It was found that the three fluorine-containing lubricants reduced friction coefficient and wear volume effectively. The effectiveness of the three lubricants in reducing wear volume could be ranked as L108>X-1P>PFPE. The antiwear films mainly consisting of organic oxyfluoride or carbonfluoride species and silicon fluoride are all observed for the three lubricants, while the degradation of PFPE during friction might account for the higher wear volume therewith. The lowest friction coefficient 0.065 was recorded for L108 under load of 0.5–400 N. This is dependent on the physically adsorbed ionic liquid on the rubbing surface and the formation of BN under the harsh conditions.