共查询到20条相似文献，搜索用时 421 毫秒
1.
ZHAI Guo-fu CHEN Yang-hua REN Wan-bin 《浙江大学学报(A卷英文版)》2007,8(3):422-425
The performance in vibration environment of switching apparatus containing mechanical contact is an important element when judging the apparatus’s reliability. A piecewise linear two-degrees-of-freedom mathematical model considering contact loss was built in this work, and the vibration performance of the model under random external Gaussian white noise excitation was investigated by using Monte Carlo simulation in Matlab/Simulink. Simulation showed that the spectral content and statistical characters of the contact force coincided strongly with reality. The random vibration character of the contact system was solved using time (numerical) domain simulation in this paper. Conclusions reached here are of great importance for reliability design of switching apparatus. 相似文献
2.
Xingyan Xiao 《Frontiers of Education in China》2008,3(3):448-459
Due to the social environment of China’s reform and opening up, as well as China’s education system with knowledge impartation
as its focus, some college students lack the humanistic care and education of value and significance of life. Universities
should plan effective activities to make students realize the importance of life. They should provide students with such education
as life conscience, failures in life, the ability to make a living and the values of life in order to have a clearer knowledge
of life education, so that the students can set up a positive, healthy and correct life view, realize the value and meaning
of life, and finally learn to respect life.
__________
Translated from Zhongguo Qingnian Zhengzhi Xueyuan Xuebao 中国青年政治学院学报 (Journal of China Youth College for Political Sciences), 2007, (5): 12–17 相似文献
3.
The primary purpose of this study is to investigate the mathematical characteristics of the test reliability coefficient ρ
XX′ as a function of item response theory (IRT) parameters and present the lower and upper bounds of the coefficient. Another
purpose is to examine relative performances of the IRT reliability statistics and two classical test theory (CTT) reliability
statistics (Cronbach’s alpha and Feldt–Gilmer congeneric coefficients) under various testing conditions that result from manipulating
large-scale real data. For the first purpose, two alternative ways of exactly quantifying ρ
XX′ are compared in terms of computational efficiency and statistical usefulness. In addition, the lower and upper bounds for
ρ
XX′ are presented in line with the assumptions of essential tau-equivalence and congeneric similarity, respectively. Empirical
studies conducted for the second purpose showed across all testing conditions that (1) the IRT reliability coefficient was
higher than the CTT reliability statistics; (2) the IRT reliability coefficient was closer to the Feldt–Gilmer coefficient
than to the Cronbach’s alpha coefficient; and (3) the alpha coefficient was close to the lower bound of IRT reliability. Some
advantages of the IRT approach to estimating test-score reliability over the CTT approaches are discussed in the end. 相似文献
4.
运用非平衡统计物理学的概念和方法 ,研究脆性电介质材料电 机械击穿的统计特性 .通过将根据实验资料总结出的传导微裂纹成核与长大的普遍规律与传导微裂纹演化方程相结合 ,统一推导出了电 机械击穿几率、可靠性、击穿几率密度分布函数和平均击穿寿命公式等 .所有结果被用于Al2 O3陶瓷材料 . 相似文献
5.
T. P. Radhakrishnan 《Resonance》1998,3(12):4-12
The concept of individual molecules functioning as active devices has been around for a few decades. The active device size
has continuously decreased during this century, starting with meter-sized vacuum valve tubes of the early 1930’s and 40’s,
through millimeter-sized transistors in the 1960’s to micrometer-sized integrated circuits in the 1970’s and 80’s. Thus the
molecular scale devices represent the logical evolution to nanoscale devices expected towards the end of this century and
the beginning of the next. This article presents some examples to provide a glimpse of the activity in this area.
An erratum to this article is available at . 相似文献
6.
7.
Angela M. Wiseman 《Early Childhood Education Journal》2009,36(4):333-338
The purpose of this study is to consider how mothers of kindergartners navigate their families’ experiences within a community
and how their children’s school experiences affect their interactions and investment in a place. The questions this research
asks is: How do mothers define and describe their neighborhood? What role does the school play as mothers navigate their children’s
experiences in the community? Findings indicate that the way that families conceptualize and manage their context indicates
that their values, needs, and life aspirations, which are clearly connected to their experiences and perceptions of the school. 相似文献
8.
Courtney A. Bell 《The Urban Review》2007,39(4):375-404
Prior research documents the almost universal preference for schools that are “convenient”. Drawing on longitudinal interview
data gathered from 36 urban parents, I argue parents’ preference for “convenient” schools is more complex than previously
understood. Conceptions of geography used by policy makers do not adequately capture the ways in which parents think about
geography. Instead of thinking about school as solely a location one must travel to, parents’ preferences for schools are
informed by space and place-based notions of geography. Parents’ geographic preferences connect to larger, more deeply held
ideas about parenting, family life, identity, child development, and one’s place in the larger stratified society. Further,
these preferences do not exist in a vacuum. Parents’ geographic preferences have implications for the resources parents’ must
activate in order to make certain schools possible. Geographic preferences also compete with other school preferences. This
paper shows how notions of space and place shape the schools parents choose as well as the schools they are willing to consider.
The study describes a fuller, more accurate portrayal of parents’ thinking. It also draws attention to the ways in which existing
historical and social contexts influence parents’ understandings of choice policy. 相似文献
9.
Julia Pond 《Children‘s Literature in Education》2011,42(1):44-55
From the early 1940s until the late 1960s, Lois Lenski embarked on an exploration of American regions through children’s books.
This body of work, which has become known as Lenski’s Regional Series, began by exploring the regions Lenski herself experienced
each year as she traveled from Connecticut to Florida for her health. As Lenski realized the importance and success of these
books, demonstrated by a Newberry Medal award for Strawberry Girl in 1946, she broadened her reach to include more geographical
areas of the United States including such states as California and South Dakota. Through her books, Lenski emphasizes the
importance of community and shared nationhood even across regional lines. This paper examines Lenski’s regional series first
from her own purpose in aiming for objectivity and fact that she could communicate to children of other regions, instructing
and exposing them to new ways of life. Second, this paper considers the paratextual elements of the Regional series, the forewords
and the maps that accompany each book, to reveal the ideology that Lenski unconsciously incorporates into her stories. A product
of her time, Lenski may have been influenced by the government’s American Guide Series, created by the Federal Writers’ Project,
which demonstrates the same successes and flaws. Lenski’s maps in particular demonstrate the influence of a particular time,
the layering of fact and fiction, and the reflection of Lenski’s personal values of certain regional characteristics. Recognition
of the ideology incorporated into Lenski’s series remains important as child readers receive not objective fact, but one perspective
of their nation. 相似文献
10.
Orla Doyle Louise McEntee Kelly A. McNamara 《European Journal of Psychology of Education - EJPE》2012,27(1):133-154
Socioeconomic inequalities in children’s skills and capabilities begin early in life and can have detrimental effects on future
success in school. The present study examined the relationships between school readiness and socioeconomic (SES) inequalities
using teacher reports of the Short Early Development Instrument (Janus et al. 2005) in a disadvantaged urban community of Ireland. It specifically examined differences in skills within a low SES community
in order to investigate the role of relative disadvantage on children’s development. SES differences across multiple domains
of school readiness were examined using Monte Carlo permutation tests and seemingly unrelated regression models. The false
discovery rate (Benjamini and Hochberg 1995) was used to control for multiple hypothesis testing. The results indicated that being from a relatively higher SES background
does not act as a protective factor for children residing in a disadvantaged community for the majority of school readiness
domains. This implies that the neighbourhood may play a role in children’s school readiness skills. These results suggest
that school readiness interventions should target all children living in disadvantaged communities as each child may be at
risk of poor school readiness. 相似文献
11.
Method of reliability tolerance design based on EDA technology and its application on DC hybrid contactor 总被引：1，自引：0，他引：1
WANG Shu-juan SHA You-tao ZHANG Hui ZHAI Guo-fu 《浙江大学学报(A卷英文版)》2007,8(3):426-433
Tolerance design, including tolerance analysis and distribution, is an important part of the electronic system’s reli- ability design. The traditional design needs to construct mathematic model of material circuit, which involves large amount of workload and lacks of practicability. This paper discusses the basic theory of electronic system’s reliability tolerance design and presents a new design method based on EDA (Electronic Design Automatic) software. This method has been validated through the application research on reliability tolerance design of the DC hybrid contactor’s control circuit. 相似文献
12.
This paper reports on an action research project undertaken with the primary aim of investigating the extent to which situations
that evoke a sense of wonder can promote scientific inquiry. Given the intense interest, curiosity, and wonder that some students
had begun to develop after seeing the film The Prestige, a science teacher used this film, which showed Tesla’s demonstrations on the wireless transmission of electrical power,
as a source of curiosity and wonder. The class that participated in this action research project was an 11th grade class in a rural area of southern Greece. Through an analysis of students’ journals, observation, informal discussions,
and paper-and-pencil tests, it was found that students (a) became involved with Tesla’s life and work, thus developing an
interest in current electricity; (b) learned about the skin effect, the biological effects of AC and DC currents; and (c)
better understood Ohm’s law in their attempt to find out the degree of damage or injury a certain measure of current can cause.
Moreover, some students began to develop scepticism and open-mindedness, in addition to their sense of wonder. The paper also
presents a planning framework for teaching the Tesla story. 相似文献
13.
Filippo Camerota 《Science & Education》2006,15(2-4):323-334
This article explores the transmission of practical knowledge in the XV and XVI centuries. According to cosmographer Egnatio
Danti, optics and other mathematical sciences had “been banished” from the main philosophical schools of his period, and “the
little which remains to us is limited to some practical aspects learned from the mechanical artificers”. The “mechanical artificers”
were architects, painters and surveyors whose mathematical training constitutes the subject dealt with in this article. The
context of Danti’s remark was the letter to the “Accademici del Disegno” of Perugia which introduce his Italian translation
of Euclid’s Optics. After the great Medieval season of optical studies, in effect, this science progressed mainly through its practical applications,
especially through “that part of perspective which pertains to painting” (Piero della Francesca), and through the spread of
methods and instruments for measuring by sight. 相似文献
14.
Princeton University Press recently published the American moral philosopher Harry Frankfurt’s book On Bullshit, which quickly made the New York Times best seller list. Originally published in the journal Raritan in 1986, Frankfurt’s book has been heralded as an important theoretical development in the study of what he (and society)
colloquially refer to as “bullshit.” Frankfurt formally defines BS as a situation where ones inclination and obligation to
speak about a topic or concept far exceeds one’s knowledge of the topic, which most certainly has been a rising problem for
a number of reasons over the past 20 years. However, Frankfurt’s book, which purports to be a moral victory of sorts, and
despite its popularity, is not only severely flawed and outdated from an educational, cognitive, and philosophical perspective,
but it is also highly oppressive in several different but very important ways. Because this book and its main arguments are
being cited favorably in a number of different academic circles (including the science education community), this paper highlights
the limitations and flaws of this book and develops a counter-argument and model of BS that has important implications for
science, mathematics, philosophy, and educational theory and research. 相似文献
15.
Recent research has shown that learned fear emerges in a response-specific sequence. For example, an odor conditioned stimulus (CS) previously paired with shock elicits behavioral expressions of fear like avoidance at a younger age than it elicits other behavioral expressions of fear like potentiation of the startle response (Richardson, Paxinos, & Lee, 2000). In the present study, the question of whether learned fear is expressed in a manner appropriate to the animal’s age at training or its age at testing was explored in three experiments, all using a within-subjects design. The results suggest that learned fear is expressed in a manner appropriate to the rat’s age at training, not its age at testing. The Discussion section focuses on the implications of these findings for (1) the developmental analysis of memory and (2) the idea that an aversive CS elicits a central state of fear. 相似文献
16.
William Yat Wai Lo 《Higher Education》2009,58(6):733-745
This paper aims to investigate the possible framework for encouraging the presence of local dimensions in an internationalised
and globally competitive system by using Taiwan’s higher education system as a case. It begins by discussing the notion of
internationalisation and its implications for higher education. It then turns to look at Taiwan’s responses to these global
developments. It also reviews different opinions on the position and importance of local dimensions in the world of globalised
higher education. Based on these perspectives, the paper advocates promoting the concept of state-building in Taiwan’s as
well as in other higher education systems for preserving or even strengthening the local dimensions of individual academic
systems operating in the international knowledge network. 相似文献
17.
真空断路器以其优良的机械寿命与电寿命、少维护等特点，在中压开关领域独领风骚．从机械寿命、分合闸特性、操作电源、智能化等方面对电磁机构、弹簧机构、永磁机构等操动机构进行比较分析，确定永磁机构应为真空断路器首选机构。 相似文献
18.
YANG Xiao-hua HUANG Jing-feng WANG Jian-wen WANG Xiu-zhen LIU Zhan-yu 《浙江大学学报(A卷英文版)》2007,8(6):883-895
Hyperspectral reflectance (350~2500 nm) data were recorded at two different sites of rice in two experiment fields including two cultivars, and three levels of nitrogen (N) application. Twenty-five Vegetation Indices (VIs) were used to predict the rice agronomic parameters including Leaf Area Index (LAI, m2 green leaf/m2 soil) and Green Leaf Chlorophyll Density (GLCD, mg chlorophyll/m2 soil) by the traditional regression models and Radial Basis Function Neural Network (RBF). RBF emerged as a variant of Artificial Neural Networks (ANNs) in the late 1980’s. A large variety of training algorithms has been tested for training RBF networks. In this study, Original RBF (ORBF), Gradient Descent RBF (GDRBF), and Generalized Regression Neural Network (GRNN) were employed. Results showed that green waveband Normalized Difference Vegetation Index (NDVIgreen) and TCARI/OSAVI have the best prediction power for LAI by exponent model and ORBF respectively, and that TCARI/OSAVI has the best prediction power for GLCD by exponent model and GDRBF. The best performances of RBF are compared with the traditional models, showing that the relationship between VIs and agronomic variables are further improved when RBF is used. Compared with the best traditional models, ORBF using TCARI/OSAVI improves the prediction power for LAI by lowering the Root Mean Square Error (RMSE) for 0.1119, and GDRBF using TCARI/OSAVI improves the prediction power for GLCD by lowering the RMSE for 26.7853. It is concluded that RBF provides a useful exploratory and predictive tool when applied to the sensitive VIs. 相似文献
19.
Rivka Feldhay 《Science & Education》2006,15(2-4):151-172
This paper attempts to draw attention to non-conventional but popular modes of transmitting scientific knowledge in Jesuit
institutions in the 17th century. The particular case study focuses on a fictive dialogue between Galileo, Mersenne and Paulus
Guldin on the power needed for moving the huge globe of the earth by mechanical means. The dialogue was written by a Jesuit
mathematician named Paolo Casati (1617–1707) and published in 1655. Apparently, Casati offers his readers an idealized representation
of a real event that took place at the Collegio Romano, where explanation of mathematical problems in a kind of public ritual
used to take place once or twice a month in presence of philosophers, theologians, visitors and students. My analysis of some
parts of Casati’s Terra Machinis Mota exemplifies the Jesuits’ success to accommodate the project of Renaissance practical mathematicians – the fusion of the pseudo-Aristotelian
interest in machines with the mathematical approach of Archimedes – to the framework of the traditional mixed mathematical
science that legitimized it and spread it among wide audiences. Casati’s text demonstrates how at least some Jesuit mathematicians
were ready to adopt Galileo’s early mechanical project. However, moving from an analysis of the contents of mechanical knowledge
popularized in this text to its analysis on the rhetorical level reveals the unbearable tensions by which Jesuit scientific
culture was actually torn. The rhetorical choice to construct a representation of a seemingly friendly dialogue between the
quasi-heretic Galileo, the Minim friar Mersenne and the suspected character of the Jesuit Guldin reveals the strategies by
which Galileo’s heretic image was tamed in order to fit the Jesuits’ needs to construct themselves an enlightened public image.
*Many thanks to Dr. Ido Yavetz, Professor Sabetai Unguru and Mr. Daniel Spitzer, who have read earlier versions of my paper
and helped me clarify both the text I was trying to interpret and my own thoughts about it. 相似文献
20.
Peer-to-Peer (P2P) networking in recent times has been touted as the ‘killer application’ that is poised to shape the Internet’s
future. The purpose of this article is to define P2P and explain its working. We also describe various models of P2P and diverse
applications of this innovative networking concept.
U Ananth Kini and Samarth M Shetty are computer science BE graduates from Sri Jayachamarajendra College of Engineering, University
of Mysore. They are currently doing a project on peer-to-peer networking at SERC, Indian Institute of Science, Bangalore.
Their interests include networking, operating systems and embedded systems. 相似文献