Multi-frequency proportional-resonant （MFPR） current controller for PWM VSC under unbalanced supply conditions   总被引：1，自引：0，他引：1  

HU Jia-bing HE Yi-kang 《浙江大学学报(A卷英文版)》2007,8(10):1527-1531

This letter presents a multi-frequency proportional-resonant （MFPR） current controller developed for PWM voltage source converter （VSC） under the unbalanced supply voltage conditions. The delta operator is used in place of the shift operator for the implementation of MFPR by using a low-cost fixed-point DSE The experimental results with an alternative control strategy validated the feasibility of the proposed MFPR current controller for the PWM VSC during voltage unbalance.  相似文献   

Proteomic analysis of human umbilical vein endothelial cells exposed to PM<Subscript>2.5</Subscript>     

Ji Zhu  Lin-wen-si Zhu  Jin-huan Yang  Ying-ling Xu  Cui Wang  Zhuo-yu Li  Wei Mao  De-zhao Lu 《Journal of Zhejiang University. Science. B》2018,19(6):458-470

Exposure to fine ambient particulate matter (PM_2.5) is known to be associated with cardiovascular disease. To uncover the molecular mechanisms involved in cardiovascular toxicity of PM_2.5, we investigated alterations in the protein profile of human umbilical vein endothelial cells (HUVECs) treated with PM_2.5 using two-dimensional electrophoresis in conjunction with mass spectrometry (MS). A total of 31 protein spots were selected as differentially expressed proteins and identified by matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) MS. The results demonstrated that DNA damage and cell apoptosis are important factors contributing to PM_2.5-mediated toxicity in HUVECs. It is further proposed that PM_2.5 can inhibit superoxide dismutase (SOD) activity and increase reactive oxygen species (ROS) and malonaldehyde (MDA) production in a concentration-dependent manner. Induction of apoptosis and DNA damage through oxidative stress pathways may be one of the key toxicological events occurring in HUVECs under PM_2.5 stress. These results indicated that the toxic mechanisms of PM_2.5 on cardiovascular disease are related to endothelial dysfunction.  相似文献   

The relationship between parental bonding and peer victimization: examining child stress and hopelessness as mediators     

HaeJin Shin  Dong Hun Lee  Kumlan Yu  KyongAe Ham 《Asia Pacific Education Review》2016,17(4):637-650

The purpose of the current study was to investigate a two-stage model in which parent-related stress and hopelessness each served as mediators of the relationship between perceived parental bonding and South Korean adolescent peer victimization. This study also examined whether the mediating relationships differed by the gender of parents and adolescents. A casual chain with three links and four sets of variables were analyzed using structural equation modeling. Data were collected from 800 adolescents attending 10 middle schools in the Busan region of South Korea. Results indicated that both maternal and paternal parental bonding were negatively associated with stress, stress was positively associated with hopelessness, and hopelessness was positively associated with South Korean adolescent peer victimization. Most importantly, the significant negative associations between both maternal and paternal parental bonding and peer victimization were mediated by both stress and hopelessness. Furthermore, gender differences in these relationships existed for both parents and adolescents. Limitations and implications to practice were discussed.  相似文献   

课堂辅助式点播专家答疑系统的设计与实现     

陈丽婷  许益成 《远程教育杂志》2007,(2):65-69

本文针对高校教学中普遍存在着课堂教学辅导不足的情况,从实际教学需要出发,系统论述了课堂辅助式点播专家答疑系统所依据的理论基础,并从开发环境的选择、系统功能设计与解析以及系统的技术实现和运行状况测试等几个方面阐述了系统的开发过程。  相似文献   

The relation between metastrategic knowledge,strategy use and task performance: Findings and reflections from a numerosity judgement task     

Koen Luwel  Joke Torbeyns  Lieven Verschaffel 《European Journal of Psychology of Education - EJPE》2003,18(4):425-447

In the research literature several positions concerning the role played by metacognition in adaptive strategy choice can be distinguished. While many authors adhere so-called metacognitive models of strategy choice and strategy change, others have questioned the extent to which metacognitive factors are associated with strategy choice and task performance and have proposed alternative theoretical frameworks wherein strategy choices are described in terms of associative models. In the present article we report data coming from a larger research project on the development of children’s numerosity judgement strategies and skills. The experimental task involved judging numerosities of colored blocks presented in a rectangular grid. Participants were 59 second grade and 50 sixth grade children, whose strategic performance data — obtained by means of a systematic analysis of their response-time patterns — were compared with interview data collected at the end of the experiment. The major result of this comparison is that not only the children from the oldest age group, but also the children from the youngest age group showed clear evidence of metacognitive awareness and understanding of different aspects of their strategic performance.  相似文献   

大学生强迫症症状学的研究   总被引：2，自引：0，他引：2  

吴承红  蔡澄 《扬州大学学报(高教研究版)》2002,6(3):32-34

采用“SCL－90”症状评定量表和“16PF”测验，对部分在校大学生进行整群抽样，结果表明大学生强迫症状以轻度为主。强迫症状可以分为三类：“人格性强迫”、“疑虑性强迫”和“精神病性强迫”。强迫与抑郁呈较高相关（r＝0．621），其人格特质与正常者在“乐群”、“稳定”、“敢为”、“有恒”、“世故”、“忧虑”、“自律”、“紧张”等方面有显著性差异。  相似文献   

晶体结构与几何知识     

陈建荣 《化学教学》2005,(5):55-57

本文以如何应用数学中的几何知识解决化学中的晶体结构类试题为例,说明数学是解决化学中诸多问题的工具。提出晶体结构类试题因其题型的特殊性,在解决时经常要应用到几何中的正弦定律、余弦定律、空间向量、体积计算等数学知识。  相似文献   

Influences affecting the soil-water characteristic curve   总被引：2，自引：0，他引：2  

周建  俞建霖 《浙江大学学报(A卷英文版)》2005,6(8):797-804

INTRODUCTION The soil-water characteristic curve (SWCC) gives the relationship between the amount of water in the soil (i.e. gravimetric or volumetric water content) and soil suction (i.e. matric suction at low suction and total suction at high suction). Many properties of a partially saturated soil such as the coefficient of permeability, shear strength and volume strain, pore size distribution, the amount of water contained in the pores at any suction, can be obtained from the SWCC. …  相似文献   

Zum Verlauf des Zweitspracherwerbs im Migrationskontext     

Sonja Haug 《Zeitschrift für Erziehungswissenschaft》2005,8(2):263-284

Zusammenfassung Die Entwicklung der mündlichen und schriftlichen Kenntnisse in Deutsch und der Sprache des Herkunftslandes bei Angeh?rigen der ersten und zweiten Einwanderergeneration aus den Gastarbeiter-Anwerbel?ndern, bei Aussiedlern und neuen Zuwanderergruppen wird beschrieben und Erkl?rungsfaktoren für Unterschiede werden mit Hilfe bivariater und multivariater Verfahren untersucht. Die Deutschkenntnisse der ersten Generation steigen zwischen 1984 und 2001 kaum an, wohingegen Aussiedler und Zuwanderer in kurzer Zeit relativ gute Fortschritte aufweisen. Die meisten Befragten sind bilingual. Defizite bei Deutschkenntnissen variieren nach Herkunftsland. Der Zweitspracherwerb erfolgt im Generationenverlauf, d.h. in Deutschland geborene Personen mit Migrationshintergrund haben in der Regel bessere Deutschkenntnisse als die erste Generation. Die Aufenthaltsdauer hat per se keinen Einfluss auf den Spracherwerb, ebenso wie das Geschlecht, w?hrend das Einwanderungsalter und die Schulbildung entscheidende Faktoren sind. Personen mit niedrigem Einwanderungsalter, Personen, die eine weiterführende Schule im Herkunftsland oder eine h?here Schule in Deutschland abgeschlossen haben, haben eine h?here relative Chance, gute mündliche und schriftliche Deutschkenntnisse zu erwerben.   相似文献   

Educational Inequity from the Perspectives of Those Who Live It: Urban Middle School Students’ Perspectives on the Quality of their Education     

Mark G. Storz 《The Urban Review》2008,40(3):247-267

In interviews with over 250 urban young adolescents, many students make it clear that they are acutely aware of the educational inequities that exist in their schools and that these inequities are having a negative impact on their education. Student voice is used to highlight urban middle school students’ perspectives on the quality of their education particularly in terms of curricular issues, teacher quality, and lack of resources.

Mark G. StorzEmail:

  相似文献