Assessment of the phase synchronization effect in modal testing during operation

The impact-synchronous modal analysis (ISMA), which uses impact-synchronous time averaging (ISTA), allows modal testing to be performed during operation. ISTA is effective in filtering out the non-synchronous cyclic load component, its harmonics, and noises. However, it was found that at operating speeds that coincide with the natural modes, ISMA would require a high number of impacts to determine the dynamic characteristics of the system. This finding has subsequently reduced the effectiveness and practicality of ISMA. Preservation of signatures during ISTA depends on the consistency of their phase angles on every time block but not necessarily on their frequencies. Thus, the effect of phase angles with respect to impact is seen to be a very important parameter when performing ISMA on structures with dominant periodic responses due to cyclic load and ambient excitation. The responses from unaccounted forces that contain even the same frequency as that contained in the response due to impact are diminished with the least number of impacts when the phase of the periodic responses is not consistent with the impact signature for every impact applied. The assessment showed that a small number of averages are sufficient to eliminate the non-synchronous components with 98.48% improvement on simulation and 95.22% improvement on experimental modal testing when the phase angles with respect to impact are not consistent for every impact applied.     

Students’ perceptions of the learning environment in tertiary science classrooms in Myanmar

We investigated students’ perceptions of their science classroom environments with the use of the What Is Happening In this Class? (WIHIC) questionnaire at the university level in Myanmar. The translated questionnaire was administered to 251 students in first-year science classes at a university. Both exploratory factor analysis and confirmatory factor analysis supported the reliability and factorial validity of the Myanmar version of the WIHIC. The constructs of the WIHIC were significantly correlated, but gender differences were not detected in correlations between WIHIC scales. Future research is needed to see if our Myanmar version of the WIHIC fits other samples in schools and universities in this context. It is also suggested that future studies include measures of student attitudes and academic achievement to permit investigation of associations between the learning environment and student outcomes in this country.     

高职院校青年教师领导行为的调查分析

高职院校青年教师领导行为的两种表现：＂关心学生＂和＂关心工作＂。从学生和教师自身的角度调查了解教师领导行为的状态,探讨形成差异的原因,以利于高职院校青年教师采取相应措施完善自我领导行为。     

半直线上的时间随机环境中可逗留的随机游动渐进性质

在经典直线上的时间随机环境中随机游动的若干性质的基础上,给出了半直线上的时间随机环境中可逗留的随机游动的模型,并研究了独立时间随机环境中随机游动的常返暂留准则和依概率收敛的大数定律,得到了非常返情形下的中心极限定理．     

柠檬酸改性竹屑吸附亚甲基蓝的动力学和热力学分析

为拓宽竹材剩余物的开发应用新途径。以竹屑为原料,柠檬酸为改性剂,制备了柠檬酸改性竹屑吸附剂,以亚甲基蓝（MB）为吸附对象,考察了pH、时间、吸附剂投量及吸附温度等对吸附剂吸附MB效果的影响,并对其吸附动力学和热力学进行了分析。结果表明：溶液pH增大,吸附剂对MB的吸附量增大,pH在5-9间变动,吸附剂对MB吸附量变化不大;染料初始浓度和吸附温度增加,吸附剂对MB吸附能力增强;在吸附120min,吸附达到平衡,吸附动力学过程符合二级动力学模型,吸附热力学过程符合Langmuir模型;在25℃、35℃、45℃时,吸附剂对MB的最大吸附量分别为106.38 mg/g、121.95 mg/g和125mg/g;竹屑吸附剂对MB的吸附过程是一个吸热的自发过程。     

兼职班主任职能与作用的研究——以石家庄职业技术学院为例

在分析设置兼职班主任必要性的基础上,分析了兼职班主任三种配置方案的利弊．兼职班主任的职能是：对学生进行专业教育;加强学生就业教育;做好沟通、协调与学生管理工作．兼职班主任的作用是：教育学生学会做人,帮助学生学会学习,提高学生的综合素质．     

基于PNA3621网络分析仪的天线虚拟实验系统

为了提高天线实践教学质量,培养学生动手能力,以天线实验开发平台为基础,以PNA3621型矢量网络分析仪为主要测试工具,利用Visual Basic和Flash软件开发工具,设计并实现了天线虚拟实验教学系统。首先介绍了天线实验的硬件设备与天线主要性能的测量方法,分析了天线虚拟实验系统的框架和软件设计,以八木天线为例演示了该系统在天线仿真、设计和测量方面的实现过程。该软件交互性好,实用逼真,已被应用于该校课内实验教学和课外创新,改变了传统的实验教学方式,取得了良好效果。     

英语自主学习中心的构建——以合肥师范学院为例

构建语言自主学习中心是语言教学的发展趋势,而人本主义心理学和认知心理学则奠定了语言自主学习中心构建的理论基础。以合肥师范学院大学英语自主学习中心为例,从硬件设施、软件平台和教学管理三个方面探讨英语自主学习中心的构建模式,以及在构建过程中值得关注的问题和对策。     

高锰含量Mn50＋xNi41-xSn9合金的相变和磁热效应

采用电弧熔炼方法制备了Mn50＋xNi41-xSn9系列铁磁形状记忆合金,并对其磁性、相变和磁热效应进行了研究。结果表明,合金在室温下均表现为四方马氏体相和立方奥氏体相的混合相,随着Mn含量的增加,由于价电子浓度的减少,马氏体转变温度逐渐下降,当x=2—4时,马氏体相变伴随着较大磁化强度的突变,同时合金表现出较大的逆磁热效应,这表明该系列合金在磁制冷领域有着潜在的应用价值。