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1.
Vacuum interrupter, high reliability component of distribution switches, circuit breakers and contactors 总被引：1，自引：0，他引：1
SLADE Paul G LI Wang-pei MAYO Stephen SMITH R. Kirkland TAYLOR Erik D 《浙江大学学报(A卷英文版)》2007,8(3):335-342
The use of vacuum interrupters(VIs)as the current interruption component for switches,circuit breakers,reclosers and contactors operating at distribution voltages has escalated since their introduction in the mid-1950’s.This electrical product has developed a dominating position for switching and protecting distribution circuits.VIs are even being introduced into switching products operating at transmission voltages.Among the reasons for the VI’s popularity are its compactness,its range of application,its low cost,its superb electrical and mechanical life and its ease of application.Its major advantage is its well-established reliability.In this paper we show how this reliability has been achieved by design,by mechanical life testing and by electrical performance testing.We introduce the“sealed for life”concept for the VI’s integrity.We discuss this in terms of what is meant by a practical leak rate for VIs with a life of over 30 years.We show that a simple high voltage withstand test is an easy and effective method for monitoring the long-term vacuum integrity.Finally we evaluate the need for routine inspection of this electrical product when it is used in adverse ambient environments. 相似文献
2.
Learners studying mechanical or technical processes via dynamic visualizations often fail to build an accurate mental representation
of the system’s movements. Based on embodied theories of cognition assuming that action, perception, and cognition are closely
intertwined, this paper proposes that the learning effectiveness of dynamic visualizations could be enhanced by grounding
the movements of the presentation in people’s own bodily experiences during learning. We discuss recent research on embodied
cognition and provide specific strategies for how the body can be used to ground movements during the learning process: (1)
making or observing gestures, (2) manipulating and interacting with objects, (3) using body metaphors, and (4) using eye movements
as retrieval cues. Implications for the design of dynamic visualizations as well as directions for future research are presented. 相似文献
3.
困境与突破:论中国教育学范式 总被引：1，自引：0，他引：1
In this paper, the paradigm of China’s pedagogy means a way of thinking followed and adhered to by Chinese educationists from
the establishment of New China till now when they consider, study and conceive problems of pedagogy. This way of thinking
guides educationists to have particular study directions, unique modes of pedagogy establishment and special framework of
problem solving. And furthermore, it forms the study tradition of China’s pedagogy and stipulates the developing orientation
of China’s pedagogy. From the establishment of New China till now, we have been edified by the paradigms in the Soviet Union
and the Western countries and restricted by “Western paradigm” and “Soviet Paradigm”, without any paradigm of our own. The
paradigm crisis in the development of China’ pedagogy has obstructed the healthy development of China’s pedagogy. The establishment
of China’s pedagogy should start with establishing the subject-educationists and establishing the object-“paradigm system”.
The establishment of China’s pedagogy paradigm will contribute greatly to the origination of China’s pedagogy and its academic
schools.
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Translated from Dongbei Shifan Daxue Xuebao (Zhexue Shehui Kexue Ban) 东北师范大学学 报(哲学社会科学版) (Journal of Northeast Normal University (Philosophy and Social Sciences)), 2007, (3): 5–12 相似文献
4.
Matthew Militello Jason Schweid Stephen G. Sireci 《Educational Assessment, Evaluation and Accountability》2010,22(1):29-52
Recent legislative and local school accountability efforts have placed a premium on the collection, analysis, and use of student
assessment data for educational improvement. As a result, schools have sought assessments that will provide additional information
about student performance. In response, a burgeoning boon industry formed—formative educational assessment systems. In this
study we describe how districts search for and acquire formative assessment systems to meet their needs. We focus on three
school districts that adopted three different formative assessment systems. Our findings suggest the fit between a system’s
characteristics and a school district’s intended use is the most important consideration in instituting a successful formative
assessment system that will have a positive impact on teacher education and student learning. 相似文献
5.
Esther Ntuli Jared Keengwe Lydia Kyei-Blankson 《Early Childhood Education Journal》2009,37(2):121-126
The use of electronic portfolios is increasingly becoming popular in teacher education programs. The electronic portfolio
allows learners to express their work and take ownership over their own ability to plan and assess and reflect upon their
learning during a specific period of time. While many teacher education programs have adopted electronic portfolios in order
to meet accreditation requirements, others use electronic portfolios to develop and improve on students’ technology skills—train
students on how to better use technology in instruction and student assessment. Irrespective of the reasons for adoption,
there is the need to assess students’ perceptions of electronic portfolios, and especially to explore the benefits and challenges
students face in using electronic portfolios in their course work. Using a qualitative research design, the current study
explored teacher candidates’ attitudes toward electronic portfolios and the differences that electronic portfolios bring to
their profession. Such a study is necessary to help administrators identify students’ needs to ensure that they are gaining
the maximum benefits from the use of electronic portfolios in their programs of study. 相似文献
6.
ZOU Lian-ying ZOU Xue-cheng 《浙江大学学报(A卷英文版)》2006,7(4):591-596
INTRODUCTION With the development of Ethernet systems and the growing capacity of modern silicon technology, embedded communication networks are playing an increasingly important role in embedded and safety critical systems. Advances in VLSI technology have also pushed integration to the point where it is now possible to design and implement a microprocessor and network controller on a single chip, known as System-on-Chip (SoC). In a network of embedded systems, each system can communi… 相似文献
7.
Arbitrary topological curve network has no restriction in topology structure, so it has more powerful representing ability
in defining complex surfaces. A complex surface modeling system is presented based on arbitrary topological curve network
and the improved combined subdivision method, its functions including creating and editing curve network, and generating and
modifying curve network’s interpolated surface. This modeling system can be used to the process of products’ concept design,
and its applications is also significant to the development of subdivision method. 相似文献
8.
GAO Shu GUO Qing-ping 《浙江大学学报(A卷英文版)》2006,7(10):1669-1675
INTRODUCTION DSP-based parallel system is a kind of high- performance parallel computer which uses parallel accelerating boards based on SHARC DSP chip (Kuo and Gan, 2005) as plug-in boards and inserts them into the military reinforcing computer, military fault-tolerant computer, even the personal computer. The parallel accelerating board based on SHARC DSP is a high-performance parallel processing board-level product developed by the Wuhan Digital Engineering Institute and is su… 相似文献
9.
This article examines the implications for access and equity of the Syrian government’s efforts to reform higher education
in the country over the past decade. In the context of social and economic reforms that are moving the county from a state-controlled
to a social market economy, it focuses on adequacy in financing higher education, as well as efficiency and equity. Significant
progress has been made in access to higher education. The government has introduced a rich variety of options for accessing
higher education, resulting in a doubling of enrolled students over the past 10 years. In terms of equity, the gender gaps
in higher education enrollment and completion have all but disappeared nationally, although regional variations persist. The
study raises concerns about the system’s internal and external efficiency: despite some improvements, the quality of the curricula
and their relevance for the labour market remain serious issues. 相似文献
10.
ZHANG Ri-dong WANG Shu-qing 《浙江大学学报(A卷英文版)》2006,7(12):1984-1988
INTRODUCTION Bilinear systems are a kind of important nonlinear systems with relatively simple structure, and many industrial processes can be described as a bilinear system. Thus research on the control of this kind of systems is very important. On the other hand, model predictive control (MPC) (Clarke et al., 1987) has been widely used in industrial applications and many predictive control methods focusing on bilinear systems are emerging (Bloemen et al., 2001; Fontes et al., 2004; He… 相似文献
11.
Multisim软件用软件的方法虚拟电子与电工元器件和仪表,是一款用于原理电路设计、电路功能测试的虚拟仿真软件。病房呼叫系统的设计是数字电子技术课程中一个典型的综合应用电路。以病房呼叫系统设计为例,介绍Multisim10在综合应用电路仿真设计中的应用。给出了运用Multisim10软件绘制的电路原理图和仿真结果。 相似文献
12.
YE Xue-rong LIANG Hui-min ZHAI Guo-fu 《浙江大学学报(A卷英文版)》2007,8(3):439-443
Reliability tolerance design of electromagnetic relay during its design period plays an essential role in guaranteeing the consistencies of reliability and output characteristic. The reliability tolerance design can ensure that the products would work well under the influence of disturbing factors (including internal interference, external interference, and machining dispersion). Com- pared with static characteristic, dynamic characteristic of electromagnetic relay can describe its operating process better. This article researches influence of the three kinds of disturbing factors on the dynamic characteristic of electromagnetic relay based on calculating dynamic characteristic. Then, the dynamic reliability tolerance design method of electromagnetic relay is discussed considering three kinds of disturbing factors. Conclusions reached can help to assure the reliability of electromagnetic relay from the beginning of design. 相似文献
13.
The purpose of this study is to demonstrate that dynamic assessment based instruction increases children’s learning by using
a quasi-experimental research design in Korea. In this study, dynamic assessment is defined as a measurement method of the
zone of proximal development (ZPD) as well as the qualitative and quantitative diagnostic information for individual children.
In addition, dynamic assessment based instruction is defined as a teaching method using the diagnostic information types in
order to increase children’s learning. In this study, 59 children between the ages of 4 and 5 participated. Three types of
number concept achievement tests (pre-test, parallel test, and post-test) for each age group were developed and the content
validity, face validity, and split-half reliability were examined. After conducting the pre-test, the children of each age
group were divided into an experimental group and a control group. Dynamic assessment based instruction regarding number concepts
was undertaken only with the experimental group for 4 weeks. Both groups took a post-test after completing the 4 weeks of
classes. The ANCOVA technique wa ls used for data analysis. The result of this study shows that dynamic assessment based instruction
has a significant effect on children’s learning of number concepts (in the case of 4-year-old children, F = 12.34, p<0.01;
5-year-old children, F = 20.03, P<0.01). Therefore, dynamic assessment based instruction should be used widely for children’s
cognitive learning. 相似文献
14.
Min-Jeong Jeon Guemin Lee Jeong-Won Hwang Sang-Jin Kang 《Asia Pacific Education Review》2009,10(2):149-158
The purpose of this study was to investigate the methods of estimating the reliability of school-level scores using generalizability
theory and multilevel models. Two approaches, ‘student within schools’ and ‘students within schools and subject areas,’ were
conceptualized and implemented in this study. Four methods resulting from the combination of these two approaches with generalizability
theory and multilevel models were compared for both balanced and unbalanced data. The generalizability theory and multilevel
models for the ‘students within schools’ approach produced the same variance components and reliability estimates for the
balanced data, while failing to do so for the unbalanced data. The different results from the two models can be explained
by the fact that they administer different procedures in estimating the variance components used, in turn, to estimate reliability.
Among the estimation methods investigated in this study, the generalizability theory model with the ‘students nested within
schools crossed with subject areas’ design produced the lowest reliability estimates. Fully nested designs such as (students:schools)
or (subject areas:students:schools) would not have any significant impact on reliability estimates of school-level scores.
Both methods provide very similar reliability estimates of school-level scores. 相似文献
15.
In the structural design of tall buildings, peak factors have been widely used to predict mean extreme responses of tall buildings
under wind excitations. Vanmarcke’s peak factor is directly related to an explicit measure of structural reliability against
a Gaussian response process. We review the use of this factor for time-variant reliability design by comparing it to the conventional
Davenport’s peak factor. Based on the asymptotic theory of statistical extremes, a new closed-form peak factor, the so-called
Gamma peak factor, can be obtained for a non-Gaussian resultant response characterized by a Rayleigh distribution process.
Using the Gamma peak factor, a combined peak factor method was developed for predicting the expected maximum resultant responses
of a building undergoing lateral-torsional vibration. The effects of the standard deviation ratio of two sway components and
the inter-component correlation on the evaluation of peak resultant response were also investigated. Utilizing wind tunnel
data derived from synchronous multi-pressure measurements, we carried out a wind-induced time history response analysis of
the Commonwealth Advisory Aeronautical Research Council (CAARC) standard tall building to validate the applicability of the
Gamma peak factor to the prediction of the peak resultant acceleration. Results from the building example indicated that the
use of the Gamma peak factor enables accurate predictions to be made of the mean extreme resultant acceleration responses
for dynamic serviceability performance design of modern tall buildings. 相似文献
16.
Mark A. Seals 《Cultural Studies of Science Education》2010,5(1):251-255
In David Long’s article, Scientists at Play in a Field of the Lord, he studies the discourse between a network of regional scientists, atheists, activists and evolutionists at the opening
of The Creation Museum on Memorial Day, 2007. This review essay examines the teaching of evolution through the teacher’s ‘lens
of empathy’ and also considers a ‘pupil centeredness’ approach. As a practicing science educator, I have found it paramount
to take into consideration my students’ backgrounds and their families’ beliefs in order to understand their preconceived
notions about the origins of life. By teaching evolution as ‘a theory with both facts and fallacies’ only then does it become
an opportunity for critical thinking that fosters growth and risk taking in a safe environment. Most times students hear evolution
preached as a one-sided lecture by teachers who believe it’s “my way or the highway” and leave little or no room for dialogue.
I believe that a teacher’s job is to stay updated with current research on the theory of evolution and then present all the
information to students in a way that creates personal opportunities for them to adjust their existing schema without demeaning
them, their ideas, or their faith or belief system. This not only shows value, compassion and tolerance for them as thinking
humans, but also allows them opportunities to develop critical thinking, which helps to shape whom they become as adults. 相似文献
17.
电子电路实验是电子电路课程学习中的一个重要环节。介绍了应用电路仿真软件进行实现电子电路虚拟实验教学。在传统真实实验的基础上增加虚拟实验教学,有利于完善电工电子实验教学体系,也有利于培养学生的创新意识。 相似文献
18.
Coosje van der Pol 《Children‘s Literature in Education》2012,43(1):93-106
This article explores what it means to be a competent reader of picture storybooks by examining the abilities of some 4–6-year-olds,
who were read stories aloud in class. Jonathan Culler’s concept of “literary competence” was used to tease out the children’s
implicit knowledge of the structures and conventions that enable them to read a work of fiction as literature. From a more
practical point of view, Lawrence Sipe’s class-based work, discussing picture storybooks with first and second grade children,
provided some useful guidelines. This current study draws on an educational design experiment involving “literary conversation
guides,” which help probe children’s understanding of such story features as character and irony. 相似文献
19.
Babak Abedin Farhad Daneshgar John D’Ambra 《Education and Information Technologies》2011,16(3):227-244
By the proliferation of online courses, the social dimension of computer supported collaborative learning (CSCL) is becoming
more important than before. Research shows that communicative behavior adaptation to the computer medium is a critical issue
in CSCL social relationship development. Two dominant theories in the CSCL field, social information processing theory and
adaptive structuration theory, argue that individuals do not simply receive the technology passively but they adapt their
behavior to increase benefits from the technology. This paper develops an instrument in order to operationalize the notion
of individual’s communicative behavior adaptability in CSCL. Through an exploratory factor analysis performed on a small sample
of post graduate students of an online degree in an Australian university, three factors have been unveiled: (1) individual
perception of self-representation, (2) individual perception of compatibility, and (3) individual perception of the use of
computer technology. Identification of these factors is expected to facilitate understanding of individuals’ social behaviors
in CSCL environment, which in turn will guide the design of CSCL systems. In addition, the paper examines the relationships
between the extracted factors and four environmental factors: learner’s characteristics, course characteristics, instructor
characteristics, and technology characteristics. The results show that none of these characteristics strongly affect perception
of self-representation or perception of the use of computer technology. On the other hand, a strong relationship was found
between perception of compatibility and learner’s and course characteristics. The reliability as well as validity of the study
is examined and findings are discussed. These findings will provide further insights into the design process of CSCL systems. 相似文献
20.
Assessing college students’ perceptions of a case teacher’s pedagogical content knowledge using a newly developed instrument 总被引：1，自引：0，他引：1
Ongoing professional development for college teachers has been much emphasized. However, previous research on learning environments
has seldom addressed college students’ perceptions of teachers’ PCK. This study aimed to evaluate college students’ perceptions
of a physics teacher’s PCK development using a newly developed instrument and workshop intervention. A mixed method design
was employed incorporating both quantitative and qualitative techniques. The survey “Assessing Students’ Perceptions of College
Teachers’ PCK” was adopted as the instrument of research. This survey was conducted twice in this study; with the pre-test
carried out during the mid-term exam and the post-test given in the last week of the semester. The results indicate that only
SMK and IRS showed significant difference in the four categories of the survey, while IOC and KSU did not. Furthermore, the
organized workshops helped the case teacher to better understand students’ prior conceptions of the subject matter and learning
difficulties, and further facilitated her adjustment of instructional strategies. The limitations of this study are discussed
and suggestions for improvement are also provided. 相似文献