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1.
Performance measurement of broadband, wide-angle polarizing beam splitter   总被引：2，自引：1，他引：2  
INTRODUCTION A polarizing beam splitter (PBS) cube is an op- tical element used in projection display systems where light must be spatially separated into or- thogonal linear polarizations. PBS is a key component in any liquid crystal projectors, whether they are transmitting or reflective. In reflective mode liquid crystal light valve projector, PBS is often used as both polarizer and analyzer. PBS transmits p-polarized light and reflects s-polarized light (You et al., 2005). The im…  相似文献   

2.
INTRODUCTION Oil-gas multiphase transport technology, in- cluding multiphase pressurization, multiphase flow- meter and multiphase flow control, has become very effective as an economic and reliable method for seabed oil exploitation. During the design of mixing transport system, prediction of pressure drop, heat transfer coefficients and void fraction is needed, so flow pattern identification is necessary. Among flow parameters, void fraction, defined as the cross section fraction occupie…  相似文献   

3.
ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｒａｔｅｏｆｄｉｆｆｕｓｉｏｎｏｆｓｕｒｆａｃｔａｎｔｓｉｎｇｅｌｓｉｓａｎｉｍｐｏｒｔａｎｔｐｒｏｐｅｒｔｙｂｏｔｈｆｏｒｔｈｅｃｈａｒａｃｔｅｒｉｚａ ｔｉｏｎｏｆｓｏｌｕｔｅ ｇｅｌｉｎｔｅｒａｃｔｉｏｎｓａｎｄｆｏｒｔｈｅｄｅｓｉｇｎｏｆｎｏｖｅｌａｐｐｌｉｃａｔｉｏｎｓｏｆｓｕｃｈｍａｔｅｒｉａｌｓ (Ｋｏｎｇｅｔａｌ.,1 997) .Ｃｏｎｖｅｎｔｉｏｎａｌｌｙ ,ｄｉｆｆｕｓｉｏｎｃｏｅｆｆｉ ｃｉｅｎｔｓｉｎｇｅｌｓａｒｅｍｅａｓｕｒｅｄｂｙｍｏｎｉｔｏｒｉｎｇｔ…  相似文献   

4.
This article explores the use of children’s photography as a method for conducting mathematics education research with young children. Collected as part of a study focusing on the experiences with measurement children have at the start of schooling, the photographs presented here were taken by children aged five and six years, from two Australian primary schools. The children took a digital camera home and were asked to photograph things that they considered to be related to measurement. While the intended use of the photographs was to provide insight into the types of experiences children have with measurement in the home context, an additional outcome to emerge from the research was a deeper understanding relating to the strengths and weaknesses of using children’s photography and photo elicitation as a research method with young children. This article presents some of the insights gleaned from this mathematics education research, and examines the use of children’s photography and photo elicitation as a research strategy for working in early years research contexts.  相似文献   

5.
An appraisal of techniques and equipment for cutting force measurement   总被引：2，自引：0，他引：2  
INTRODUCTION Metal machining processes are characterised mainly by quick changes in quantified elements. In- dividual changes do not occur in isolation and they influence each other. The analysis of these changes require study of the complicated complete systems in their real situations. The study of cutting processes such as turning and facing, from dynamic aspects, is very important. The trend towards the measurement of cutting forces in machining leads to many theo- retical and practic…  相似文献   

6.
In this paper, a low-cost measurement approach with bi-beam was presented, which can be used for real-time detection and online analysis of solution refractive index, based on systematical analysis and experiments of conventional detection methods on surface plasmon resonance sensor. This novel method was analyzed theoretically and based on it a sensor system set was established. The factors that affect the sensor's sensitivity and working range were discussed. The angular adjustment setup was simplified, errors produced by movable components were avoided and the maneuverability was enhanced with this new method. The noiseproof feature and stability of the sensor system were greatly improved as well.  相似文献   

7.
INTRODUCTION Multiphase flow is normal phenomena in indus- try. In past decades, investigations on multiphase flow measurement were mostly focused on the proc- ess tomography (PT) technology (Li, 2000), including electrical capacitance PT, electrical resistance PT, electromagnetism PT, X-ray PT, Ultrasonic PT and so on. Unfortunately, these PT technologies are not good enough to meet industrial requirements because of the image reconstruction quality, cost or safety. In recent year…  相似文献   

8.
Abstract

The meaning, measurement, and implications of ‘public opinion’ have long been a source of debate. In this paper, we examine the extent to which the educational priorities of elites in the US reflect the educational priorities of the American public. To do so, we focus on one particular segment of the education policy-making elite – education poll creators. Through a content analysis of questions asked between 1969 and 2013 in the Phi Delta Kappa/Gallup Poll of the Public’s Attitudes toward the Public Schools, we examine the salience of key educational issues over time. We compare these trends to the proportion of poll respondents who label those issues the ‘biggest problem’ facing schools, thereby approximating two different conceptions of public opinion regarding education. We find that the issues that receive the most coverage by pollsters do not typically match the issues that respondents claim to be the biggest problems in schools. In light of the important role that opinion polls may play in shaping discussion and debate over educational issues, we argue that further study of the construction of public opinion is warranted.  相似文献   

9.
Recent policy developments (such as the Children’s Plan) and the introduction of a new national strategy (the Social and Emotional Aspects of Learning programme) have re‐emphasised the importance of social and emotional skills in educational contexts. As such, educational psychologists are increasingly likely to be involved in the measurement of social and emotional skills, either as part of their case‐work or through research. They may also be asked to provide advice to schools looking to evaluate certain aspects of their practice in this area. The aim of this paper is to provide a discussion of key issues in the measurement of social and emotional skills in children and adolescents. These include: difficulties with the underlying theory and frameworks for social and emotional skills, inconsistent terminology, the scope and distinctiveness of available measures, psychometric properties, and more practical issues such as the type of respondent, location and purpose of measurement. The paper concludes with a call for more research and the further development of appropriate measures.  相似文献   

10.
《师资教育杂志》2012,38(4):435-451
This study sought to measure general teacher efficacy levels of in‐service primary teachers in Hong Kong. Participants included 725 Hong Kong in‐service teachers, who were invited to take part in the study. These in‐service teachers came from 28 different primary schools ranging from government, aided, private and direct subsidy schools. The Chinese version of the 12‐item Teachers' Sense of Efficacy (C‐TSE) Scale was applied to investigate the efficacy of the teachers. A factor analysis of these 12 items when male and female datasets were combined led to the extraction of only one factor. But separation of the two datasets led to the extraction of different factor analysis models. This could reflect the different perceptions that male and female teachers had about the formation of teacher efficacy. Overall, this study showed that female teachers were significantly more efficacious than male teachers. Moreover, years of teaching experience showed a weak but significant correlation to levels of general teacher efficacy. Interestingly, educational levels did not have a significant effect on the efficacy of this group of in‐service primary teachers. Overall, the C‐TSE was found to be a valid and reliable scale for measuring the efficacy levels of this particular group of in‐service primary teachers in Hong Kong.  相似文献   

11.
Currently, 18–21-year-olds account for 60% of university students; mature students represent 40%. Attrition (dropping out) can be related to discordance between a student's perception of the university created through branding and marketing of the institution and the university's actual environment and offerings delivery. This study adds to this research by indicating: (1) retention factors do vary for first-year students, depending on age and (2) academic environment is key to institutional commitment among non-traditional (22–55+ years of age) students whereas university and organizational support features contribute more to traditional (17–21 years of age) students' campus integration.  相似文献   

12.
Abstract

This study reports on the design of a video-based instrument to assess student teachers’ parent–teacher communication competences (PTCC) in a reliable and valid way. PTCC refer to the competences needed to communicate successfully with parents during conversations such as parent–teacher conferences. Taking into account both conceptual and methodological challenges regarding the measurement of competences, several methodological steps were followed to design a video-based instrument focusing on the assessment of student teachers’ perception, interpretation and decision-making skills (PID skills) regarding parent–teacher communication: designing video vignettes presenting realistic job situations regarding parent–teacher communication; developing instructions to elicit student teachers’ PID skills; designing a coding scheme to analyse student teachers’ responses; and implementing the instrument (n = 269) to test and refine it. This ultimately resulted in an instrument consisting of (1) three video vignettes, (2) a series of open-ended questions eliciting student teachers’ PID skills, and (3) three coding schemes to develop a perception score, an interpretation score and a decision-making score for PTCC. The (4) implementation of the instrument confirmed that this innovative video-based tool might be a promising approach to assess student teachers’ PTCC. To conclude, the quality and contribution of the measurement instrument and the implications for further research are discussed.  相似文献   

13.
INTRODUCTION Measurement technology for gas-solid two phase flow has important applications in fields such as process measurement, forecast and control in in- dustry (Teng et al., 2002). At present, most optical measurement methods, such as LDV (Laser Doppler Velocimetry), Laser Dust Particles Measurement Device, use an optical sensor probe that only yields information on a single point or a partial area in the flow field and cannot yield instantaneous multi-ori- entation flow states.…  相似文献   

14.
1 Introduction a Nowadays the E-business technology has endowed supply chain management (SCM) more abundant implications, especially by the introduction and diffusion of Internet technology through out SCM activities. Internet has changed the way in which…  相似文献   

15.
Students' perceptions of instructional quality have become an important information source for teachers' professional development. This requires knowledge of the structure of these perceptions, their validity, and generalizability. To this end, we conducted a study with 15,005 German 512 grade students from 690 classrooms in three different school types and three different grade levels. Assuming three basic dimensions of instructional quality with 7 facets, we investigated the factorial structure of students' perceptions with two-level confirmatory factor analyses as well as their generalizability with two-level measurement invariance analyses. Our results confirmed the postulated factorial structure and strict invariance across subject groups, school types, and grade levels. We confirmed the same structure in teachers' assessments of their instructional quality that were positively correlated with the students' assessments. As such, these findings shed light on the structure, validity, and generalizability of students’ perceptions of instructional quality.  相似文献   

16.

In this study, we measured students’ perceptions of mathematics classroom learning environment and investigated their associations with students’ achievement. The Mathematics-Related Constructivist-Oriented Classroom Learning Environment Survey (MCOLES) was developed with seven dimensions and 56 items, using theories surrounding classroom learning environment. For a sample of 423 grade 10 students from five schools in India, we validated the MCOLES by exploratory factor analysis and then by confirmatory factor analysis, which suggested the exclusion of 11 items and yielded an 11-factor solution. For achievement on a topic taught, mainly medium correlations emerged with the learning environment factors, suggesting practical implications for classroom teaching. This study is methodologically significant in proposing and validating the new MCOLES for measuring classroom learning environments in secondary-school mathematics.

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17.
INTRODUCTION Accurate measurement of multiphase fluids flow rates in the petroleum industry is of great importance. The most reliable measurement technique for multi-phase flow is separating the mixture and using con-ventional devices for measuring single-phase flow. However, in many cases the separation is not practical from both technical and economical points of view. An alternative solution is the multiphase flow me-tering system, usually consisting of a combination of devices for ph…  相似文献   

18.
As part of developing a comprehensive strategy for structural equation model building and assessment, a large‐scale Monte Carlo study of 7,200 covariance matrices sampled from 36 population models was conducted. This study compared maximum likelihood with the much simpler centroid method for the confirmatory factor analysis of multiple‐indicator measurement models. Surprisingly, the contribution of maximum likelihood to model analysis is limited to formal evaluation of the model. No statistically discernible differences were obtained for the bias, standard errors, or mean squared error (MSE) of the estimated factor correlations, and empirically obtained maximum likelihood standard errors for the pattern coefficients were only slightly smaller than their centroid counterparts. Further supporting the recommendations of Anderson and Gerbing (1982), the considerably faster centroid method may have a useful role in the analysis of these models, particularly for the analysis of large models with 50 or more input variables. These results encourage the further development of a comprehensive research paradigm that exploits the relative strengths of both centroid and maximum likelihood as complementary estimation procedures along an integrated exploratory‐confirmatory continuum of model specification, revision, and formal evaluation.  相似文献   

19.
The concept of energy is one key component of science education curricula worldwide. While it is still being taught in many science classrooms from a mainly conceptual knowledge perspective, the need to frame the concept of energy as a socioscientific issue and implement it in the context of citizenship education and education for sustainable development, is getting more and more explicit. As we will be faced with limited fossil fuels and the consequences of global climate change in the future, students have to be supported in becoming literate citizens who are able to reach informed energy-related decisions. In this article, we focus on students’ reasoning and decision-making processes about socioscientific energy-related issues. In more detail, we developed a paper-and-pencil measurement instrument to assess secondary school students’ competencies in this domain. The functioning of the measurement instrument was analysed with a sample of 850 students from grades 6, 8, 10 and 12 using item response theory. Findings show that the measurement instrument functions in terms of reliability and validity. Concerning student ability, elaborate reasoning and decision-making was characterised by the use of trade-offs and the ability to weigh arguments and to reflect on the structure of reasoning and decision-making processes. The developed measurement instrument provides a complement for existing test instruments on conceptual knowledge about the concept of energy. It aims to contribute to a change in teaching about energy, especially in physics education in the sense of education for sustainable development.  相似文献   

20.
Comparing self-perceived quality of teaching to students’ perception can be used in higher education to improve the quality of teaching of pre-service teachers in teacher education. However, comparing these measurements from different perspectives is only meaningful if the same constructs are being measured. To shed light on this comparison’s meaningfulness, we scrutinised whether aspects of quality of teaching are measured in the same way across pre-service teachers and their students by means of measurement invariance analyses. To do so, 272 pre-service teachers in teacher education rated aspects of their quality of teaching, and were rated by their 4851 students. Measurement invariance across these perspectives was tested in multilevel structural equation models. Strong measurement invariance held for two aspects of quality of teaching; for the third, one item lacked weak measurement invariance. Pre-service teachers perceived their quality of teaching lower than their students. In conclusion, aspects of quality of teaching can be compared across perspectives, and teacher education should encourage pre-service teachers to use students’ feedback as a valuable resource for improving their quality of teaching.  相似文献   

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