矩阵变换器研究综述

矩阵变换器作为一种新型变换器,越来越引起人们的重视。矩阵变换器的关键技术主要包括:主回路的拓扑结构、安全换流技术、调制策略和保护电路设计等。通过这几个关键技术的介绍,进一步分析目前矩阵变换器的研究热点和应用前景。     

“邓小平理论课”教学实践中的若干体会

邓小平理论要做到进课堂、进教材、进头脑 ,党委要高度重视 ,具体做到位 ;其次任课教师要方法得当 ,采取理论联系实际的灵活多样方式。     

低幼儿童听力测验

早期干预能帮助弱听儿童可以更好地学习语言和沟通 ,也直接影响儿童的学习和成长。早期诊断 ,便成为早期干预的一个预先程序 ,可是要把听觉的毛病诊断出来 ,我们首先要明白如何测试不同年龄的儿童。这篇文章主要介绍了对不同年龄的低幼儿童进行行为听力测验的方法和技术     

如何淘到二手好货

正不知不觉中,"二手货"的定义早已悄悄发生了变化,这也源于人们观念的转变——曾经的二手货陈旧、单调,是旧货的代名词;而如今的二手货则被赋予了全新的概念:闲置品、奢侈品、收藏品成为了二手货市场的主力军。由于购买二手货不光省钱,而且"绿色、环保",因此这种消费方式也逐渐成为了一种时尚,影响着人们生活的方方面面。如何才能淘到二手好货?购买二手货时应该注意什么?看看我们为你提供的建议吧!     

The constructivist classroom learning environment and its associations with critical thinking ability of secondary school students in Liberal Studies

In this study, we investigated-secondary school students’ perceptions of their constructivist learning environment in Liberal Studies, and whether their perceptions were related to their critical thinking ability. A convenience sample of Secondary Three students (N = 967) studying Liberal Studies in Hong Kong participated in this research by completing a self-administered questionnaire which included the Constructivist Learning Environment Survey (CLES), Cornell Critical Thinking Test Level X, and demographic information on age and gender. Students perceived their learning environment to be moderately constructivist in nature. Both age and school banding differences were identified in that younger students and students in band 1 schools tended to perceive a higher degree of constructivist characteristics in their learning environment. Multiple regression analyses indicated that three of the five scales of CLES were predictors of critical thinking ability. Shared Control was the strongest predictor and negatively associated with critical thinking ability, while Personal Relevance and Critical Voice were positively related to critical thinking ability. Findings of the study are discussed with reference to developing students’ critical thinking ability in Liberal Studies classrooms.     

Effects of motion control footwear on running: a systematic review

Excessive foot pronation is a risk factor of running injuries and motion control footwear is designed to control foot pronation. With the movement transfer between foot pronation and tibial rotation, motion control footwear may not only be confined to controlling foot pronation. In view of the controversies in the literature on effectiveness of motion control footwear, this paper reviewed the efficacy of motion control footwear functions as reported in the literature. Eligible studies were identified from seven electronic databases. Two independent authors extracted the data and assessed the methodological qualities using the Jadad Scale. A total of 14 quasi randomised controlled trials were included. Even though the included studies were rated as "low quality" according to the Jadad Scale, the data were pooled and analysed. Results revealed that motion control footwear was effective in reducing the amount of foot pronation and the peak vertical impact during landing. There is no evidence that suggests motion control footwear for controlling kinematics of the proximal segments.     

An investigation into high-achiever and low-achiever knowledge organisation and knowledge processing in concept mapping: A case study

This study used concept map content analysis and interviews to gain insights into the knowledge organisation and knowledge processing of pre-service teachers. Forty-eight preservice teachers of elementary science from a teachers’ training college in Sarawak, Malaysia, participated in this study. Correlations between achievement and five concept map characteristics showed that there were significant positive correlations (p<.01) between achievement and: the number of appropriate links; the average number of appropriate concepts per cluster; and, the hierarchy score of subjects’ concept maps, and significant negative correlations (p<.01) between achievement and: the number of inappropriate links; and, the average number of inappropriate concepts per cluster. Interviews with high-achievers and lowachievers revealed that there were differences in the way they processed knowledge during concept mapping. The high-achievers were more thorough than were the low-achievers in cognitive processing of knowledge, taking time to make sense of concepts, sort and group concepts, form relevant links between concepts, and organise concepts hierarchically. Active cognitive processing of knowledge seems to be related to more complex, well-integrated cognitive structures for the material learned.     

Leptotrichia hongkongensis sp. nov., a novel Leptotrichia species with the oral cavity as its natural reservoir

A straight, non-sporulating, Gram-variable bacillus (HKU24T) was recovered from the blood culture of a patient with metastatic breast carcinoma. After repeated subculturing in BACTEC Plus Anaerobic/F blood culture broth, HKU24T grew on brucella agar as non-hemolytic, pinpoint colonies after 96 h of incubation at 37 °C in an anaerobic environment and aerobic environment with 5% CO2. Growth was enhanced with a streak of Staphylococcus aureus. HKU24T was non-motile and catalase-negative, but positive for alkaline phosphatase, β-glucosidase, and α-glucosidase. It hydrolyzed phenylphosphonate and reduced resazurin. 16S rRNA, groEL, gyrB, recA, and rpoB sequencing showed that HKU24T occupies a distinct phylogenetic position among the Leptotrichia species, being most closely related to Leptotrichia trevisanii. Using HKU24T groEL, gyrB, recA, and rpoB gene-specific primers, fragments of these genes were amplified from one of 20 oral specimens. Based on phenotypic and genotypic characteristics, we propose a new species, Leptotrichia hongkongensis sp. nov., to describe this bacterium.