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  1. Interpreting the Third International Mathematics and Science Study (TIMSS) achievement scales using scale anchoring

    Science.gov (United States)

    Kelly, Dana L.

    1999-11-01

    The scale anchoring method was used to analyze and describe the TIMSS primary and middle school (Populations 1 and 2) mathematics and science achievement scales. Scale anchoring is a way of attaching meaning to a scale by describing what students know and can do at specific points on the scale. Student achievement was scrutinized at four points on the TIMSS primary and middle school achievement scales---the 25th, 50th, 75th, and 90th international percentiles for fourth and eighth grades. The scale anchoring method was adapted for the TIMSS data and items that students scoring at each of the four scale points were likely to answer correctly (with a 65 percent probability) were identified. The items were assembled in binders organized by anchor level and content area. Two ten-member panels of subject-matter specialists were convened to scrutinize the items, draft descriptions of student proficiency at the four scale points, and identify example TIMSS items to illustrate performance at each level. Following the panel meetings, the descriptions were refined through an iterative review process. The result is a content-referenced interpretation of the TIMSS scales through which TIMSS achievement results can be better communicated and understood.

  2. TIMSS 2015 Assessment Frameworks

    Science.gov (United States)

    Mullis, Ina V. S., Ed.; Martin, Michael O., Ed.

    2013-01-01

    Now entering into its 20th year of data collection, Trends in International Mathematics and Science Study, (TIMSS) is an international assessment of mathematics and science at the fourth and eighth grades. TIMSS 2015 is the most recent in the TIMSS series, which began with the first assessments in 1995 and has continued every four years--1999,…

  3. Examining mathematics attitude in a TIMSS 2003 pilot research

    Directory of Open Access Journals (Sweden)

    Kadijević Đorđe M.

    2003-01-01

    Full Text Available Apart from the data on test reliability, the psychometric features of the TIMSS variables are not officially available. It is therefore not clear whether the TIMSS findings capture real educational trends. Being concerned with mathematics attitude, the aim of this research was to determine the psychometric values of a mathematics attitude scale derived from a student questionnaire, and, if these are appropriate, to examine the relation of mathematics attitude to gender and mathematics achievement, and search for gender differences in the applied mathematics attitude indicators. By using a sample of 89 seventh-grade students involved in a TIMSS 2003 pilot research, it revealed the following findings: (a the representativity reliability, homogeneity and validity of the applied attitude scale were acceptable, (b attitude to mathematics was related to mathematics achievement, (c gender differences in mathematics attitude were not found and (d gender differences in the applied indicators were only present for the statement "I need to do well in mathematics to get into the faculty of my choice" where males expressed a higher agreement than females.

  4. TIMSS 2011 International Results in Mathematics

    Science.gov (United States)

    Mullis, Ina V. S.; Martin, Michael O.; Foy, Pierre; Arora, Alka

    2012-01-01

    The "TIMSS 2011 International Results in Mathematics" summarizes fourth and eighth grade student achievement in each of the 63 countries and 14 benchmarking entities which participated in TIMSS 2011. The report includes trends in mathematics achievement over time for participants in the previous TIMSS 1995, 1999, 2003, and 2007…

  5. TIMSS Advanced 2015 Assessment Frameworks

    Science.gov (United States)

    Mullis, Ina V. S., Ed.; Martin, Michael O., Ed.

    2014-01-01

    The "TIMSS Advanced 2015 Assessment Frameworks" provides the foundation for the two international assessments to take place as part of the International Association for the Evaluation of Educational Achievement's TIMSS (Trends in International Mathematics and Science Study) Advanced 2015--Advanced Mathematics and Physics. Chapter 1 (Liv…

  6. Linking National and International Educational Assessments: NAEP and TIMSS

    Science.gov (United States)

    Rahman, Taslima

    2013-03-01

    In an increasingly global economy, comparisons of student achievement in the United States to student achievement in other countries are of interest to the nation. The National Center for Education Statistics (NCES) reports on mathematics and science achievement of 4th- and 8th-grade students for the all U.S. states and 60 countries. However, the reports are based on two separate assessments. Results for the U.S. states are based on the National Assessment of Educational Progress (NAEP) and results for the other countries are based on the Trends in International Mathematics and Science Study (TIMSS). Further, unlike NAEP, TIMSS does not have an on-going state component. Thus, U.S. states cannot compare performance of their students with those of the students in other countries. To enable such comparisons, NCES launched a NAEP-TIMSS Linking study where the goal is to project TIMSS mathematics and science scores for the students in the 50 states that participated in NAEP. This linking study targeted eighth-grade students. NAEP assessments of mathematics and science were conducted in winter 2011 (January-March) and TIMSS assessments of mathematics and science were conducted in spring 2011 (April-June). Three approaches-- statistical moderation, calibration, and projection--are applied in linking the two scales. In this presentation, discussion will focus on the study design and approaches applied. In addition, results will be shared if released to the public by the NCES before March 2013. Otherwise results of earlier linking study conducted by the American Institutes for Research in 2007 using the statistical moderation technique will be shared.

  7. TIMSS 2011 User Guide for the International Database. Supplement 1: International Version of the TIMSS 2011 Background and Curriculum Questionnaires

    Science.gov (United States)

    Foy, Pierre, Ed.; Arora, Alka, Ed.; Stanco, Gabrielle M., Ed.

    2013-01-01

    The TIMSS 2011 International Database includes data for all questionnaires administered as part of the TIMSS 2011 assessment. This supplement contains the international version of the TIMSS 2011 background questionnaires and curriculum questionnaires in the following 10 sections: (1) Fourth Grade Student Questionnaire; (2) Fourth Grade Home…

  8. TIMSS and PISA Impact--The Case of Jordan

    Science.gov (United States)

    Ababneh, Emad; Al-Tweissi, Ahmad; Abulibdeh, Khattab

    2016-01-01

    Jordan has participated in international large-scale assessments (LSAs) since 1991 and in most of the Trends in International Mathematics and Science Studies (TIMSS) as well as the Programme for International Student Assessments (PISA). After a short description of education system and policy-making context in the country, this article provides an…

  9. TIMSS 2011 International Results in Science

    Science.gov (United States)

    Martin, Michael O.; Mullis, Ina V. S.; Foy, Pierre; Stanco, Gabrielle M.

    2012-01-01

    For more than 50 years, the International Association for the Evaluation of Educational Achievement (IEA) has been conducting comparative studies of educational achievement in a number of curriculum areas, including mathematics and science. TIMSS 2011 represents the fifth cycle of the Trends in International Mathematics and Science Study (TIMSS),…

  10. TIMSS 2011 Student and Teacher Predictors for Mathematics Achievement Explored and Identified via Elastic Net

    Directory of Open Access Journals (Sweden)

    Jin Eun Yoo

    2018-03-01

    Full Text Available A substantial body of research has been conducted on variables relating to students' mathematics achievement with TIMSS. However, most studies have employed conventional statistical methods, and have focused on selected few indicators instead of utilizing hundreds of variables TIMSS provides. This study aimed to find a prediction model for students' mathematics achievement using as many TIMSS student and teacher variables as possible. Elastic net, the selected machine learning technique in this study, takes advantage of both LASSO and ridge in terms of variable selection and multicollinearity, respectively. A logistic regression model was also employed to predict TIMSS 2011 Korean 4th graders' mathematics achievement. Ten-fold cross-validation with mean squared error was employed to determine the elastic net regularization parameter. Among 162 TIMSS variables explored, 12 student and 5 teacher variables were selected in the elastic net model, and the prediction accuracy, sensitivity, and specificity were 76.06, 70.23, and 80.34%, respectively. This study showed that the elastic net method can be successfully applied to educational large-scale data by selecting a subset of variables with reasonable prediction accuracy and finding new variables to predict students' mathematics achievement. Newly found variables via machine learning can shed light on the existing theories from a totally different perspective, which in turn propagates creation of a new theory or complement of existing ones. This study also examined the current scale development convention from a machine learning perspective.

  11. TIMSS 2011 Student and Teacher Predictors for Mathematics Achievement Explored and Identified via Elastic Net.

    Science.gov (United States)

    Yoo, Jin Eun

    2018-01-01

    A substantial body of research has been conducted on variables relating to students' mathematics achievement with TIMSS. However, most studies have employed conventional statistical methods, and have focused on selected few indicators instead of utilizing hundreds of variables TIMSS provides. This study aimed to find a prediction model for students' mathematics achievement using as many TIMSS student and teacher variables as possible. Elastic net, the selected machine learning technique in this study, takes advantage of both LASSO and ridge in terms of variable selection and multicollinearity, respectively. A logistic regression model was also employed to predict TIMSS 2011 Korean 4th graders' mathematics achievement. Ten-fold cross-validation with mean squared error was employed to determine the elastic net regularization parameter. Among 162 TIMSS variables explored, 12 student and 5 teacher variables were selected in the elastic net model, and the prediction accuracy, sensitivity, and specificity were 76.06, 70.23, and 80.34%, respectively. This study showed that the elastic net method can be successfully applied to educational large-scale data by selecting a subset of variables with reasonable prediction accuracy and finding new variables to predict students' mathematics achievement. Newly found variables via machine learning can shed light on the existing theories from a totally different perspective, which in turn propagates creation of a new theory or complement of existing ones. This study also examined the current scale development convention from a machine learning perspective.

  12. Why Students Answer TIMSS Science Test Items the Way They Do

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    Harlow, Ann; Jones, Alister

    2004-04-01

    The purpose of this study was to explore how Year 8 students answered Third International Mathematics and Science Study (TIMSS) questions and whether the test questions represented the scientific understanding of these students. One hundred and seventy-seven students were tested using written test questions taken from the science test used in the Third International Mathematics and Science Study. The degree to which a sample of 38 children represented their understanding of the topics in a written test compared to the level of understanding that could be elicited by an interview is presented in this paper. In exploring student responses in the interview situation this study hoped to gain some insight into the science knowledge that students held and whether or not the test items had been able to elicit this knowledge successfully. We question the usefulness and quality of data from large-scale summative assessments on their own to represent student scientific understanding and conclude that large scale written test items, such as TIMSS, on their own are not a valid way of exploring students'' understanding of scientific concepts. Considerable caution is therefore needed in exploiting the outcomes of international achievement testing when considering educational policy changes or using TIMSS data on their own to represent student understanding.

  13. Examination of the 8th grade students' TIMSS mathematics success in terms of different variables

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    Kaleli-Yılmaz, Gül; Hanci, Alper

    2016-07-01

    The aim of this study is to determine how the TIMSS mathematics success of the 8th grade students differentiates according to the school type, gender, mathematics report mark, parents' education level, cognitive domains and cognitive domains by gender. Relational survey method was used in the study. Six-hundred fifty two 8th grade students studying in the same city in Turkey participated in this study. In this study, a 45 question test that was made up by choosing TIMSS 2011 mathematics questionnaire was used as a data collection tool. Quantitative data analysis methods were used in the data analysis, frequency, percentage, average, standard deviation, independent sample test, one-way analysis of variance and post-hoc tests were applied to data by using SPSS packaged software. At the end of the study, it was determined that the school type, mathematics school mark, parents' education level and cognitive domains influenced the students' TIMSS mathematics success but their gender was a neutral element. Moreover, it was seen that schools which are really successful in national exams are more successful in TIMSS exam; students whose mathematics school marks are 5 and whose parents graduated from university are more successful in TIMSS exams than others. This study was produced from Alper HANCİ's master thesis that is made consulting Asst. Prof. Gül KALELİ YILMAZ.

  14. TIMSS 2011 User Guide for the International Database

    Science.gov (United States)

    Foy, Pierre, Ed.; Arora, Alka, Ed.; Stanco, Gabrielle M., Ed.

    2013-01-01

    TIMSS measures trends in mathematics and science achievement at the fourth and eighth grades in participating countries around the world, while also monitoring curricular implementation and identifying promising instructional practices. Conducted on a regular 4-year cycle, TIMSS has

  15. A Diagnostic Comparison of Turkish and Korean Students’ Mathematics Performances on the TIMSS 2011 Assessment

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    Sedat Şen

    2015-11-01

    Full Text Available The purpose of the present study was to analyze an international large-scale data set using a cognitive assessment approach. Although some researchers question the usefulness of international large-scale assessments (e.g., TIMSS, participating countries have continued to use the results from these large-scale assessments to improve their curricula and teaching methods. Despite the common reporting practice—single-score—in these large scale assessments gives useful insights about students’ overall performances, they still lack diagnostic information. Cognitive diagnosis models (CDMs were developed to provide more feedback on students’ cognitive strengths and weaknesses. This study retrofitted the TIMSS 2011 eighth grade mathematics assessment by applying a specific CDM called the DINA (the deterministic, inputs, noisy, “and” gate model to data from South Korea and Turkey. Results of the DINA model were used to make a detailed comparison between students of these two countries.

  16. Examining the Big-Fish-Little-Pond Effect on Students' Self-Concept of Learning Science in Taiwan Based on the TIMSS Databases

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    Liou, Pey-Yan

    2014-08-01

    The purpose of this study is to examine the relationship between student self-concept and achievement in science in Taiwan based on the big-fish-little-pond effect (BFLPE) model using the Trends in International Mathematics and Science Study (TIMSS) 2003 and 2007 databases. Hierarchical linear modeling was used to examine the effects of the student-level and school-level science achievement on student self-concept of learning science. The results indicated that student science achievement was positively associated with individual self-concept of learning science in both TIMSS 2003 and 2007. On the contrary, while school-average science achievement was negatively related to student self-concept in TIMSS 2003, it had no statistically significant relationship with student self-concept in TIMSS 2007. The findings of this study shed light on possible explanations for the existence of BFLPE and also lead to an international discussion on the generalization of BFLPE.

  17. Comparative study of middle school students' attitudes towards science: Rasch analysis of entire TIMSS 2011 attitudinal data for England, Singapore and the U.S.A. as well as psychometric properties of attitudes scale

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    Pey Tee, Oon; Subramaniam, R.

    2018-02-01

    We report here on a comparative study of middle school students' attitudes towards science involving three countries: England, Singapore and the U.S.A. Complete attitudinal data sets from TIMSS (Trends in International Mathematics and Science Study) 2011 were used, thus giving a very large sample size (N = 20,246), compared to other studies in the journal literature. The Rasch model was used to analyse the data, and the findings have shed some useful light on not only how the Western and Asian students responded on a comparative basis in the various scales related to attitudes but also on the validity, reliability, and unidimensionality of the attitudes instrument used in TIMSS 2011. There may be a need for TIMSS test developers to consider doing away with negatively phrased items in the attitudes instrument and phrasing these positively as the Rasch framework shows that response bias is associated with these statements.

  18. PENGEMBANGAN SOAL MATEMATIKA TIPE TIMSS MENGGUNAKAN KONTEKS RUMAH ADAT UNTUK SISWA SEKOLAH MENENGAH PERTAMA

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    Eva Susanti

    2016-06-01

    Full Text Available Penelitian ini bertujuan untuk: (1 menghasilkan soal-soal tipe TIMSS yang valid dan praktis menggunakan konteks Rumah Adat di SMP; (2melihat efek potensial soal-soal tipe TIMSS terhadap kemampuan penalaran matematika siswa di SMP. Penelitian ini merupakan penelitian pengembangan (development research. Subjek penelitian adalah siswa kelas VIII-7 SMP Negeri 9 Palembang sebanyak 32 orang. Pengumpulan data menggunakan analisis dokumen, dan tes soal tipe TIMSS. Semua data yang dikumpulkan dianalisis secara deskriptif kualitatif. Hasil analisis data menyimpulkan bahwa (1 penelitian ini telah menghasilkan suatu produk soal tipe TIMSS menggunakan konteks Rumah Adat untuk siswa kelas VIII SMP yang valid dan praktis. Valid tergambar dari hasil penilaian validator, dimana semua validator menyatakan sudah baik berdasarkan content, konstruk, dan bahasa.  Selain itu kevalidan soal tipe TIMSS ini tergambar setelah dilakukan analisis validasi butir soal pada siswa sebanyak 26 orang non subjek penelitian. Praktis tergambar dari hasil uji coba small group dimana sebagian besar siswa dapat menyelesaikan soal tipe TIMSS yang diberikan. (2 prototype soal tipe TIMSS  yang dikembangkan memilki efek potensial yang positif terhadap kemampuan penalaran matematika siswa. Hasil yang diperoleh rata-rata kemampuan penalaran matematika siswa dalam menjawab soal matematika tipe TIMSS sebesar 56 yang termasuk kategori baik. Kata Kunci: Penelitian Pengembangan, Soal tipe TIMSS, Konteks Rumah Adat DOI: http://dx.doi.org/10.22342/jpm.10.2.3631.53-74

  19. Africa's Participation in TIMSS-2003

    African Journals Online (AJOL)

    cce

    called the Trends in International Mathematics and Science Study (TIMSS). ... The International Study Centre (ISC) in Boston College's Lynch School of .... implies that majority of our students have poor knowledge of basic science and.

  20. TIMSS 2011 Assessment Frameworks

    Science.gov (United States)

    Mullis, Ina V. S.; Martin, Michael O.; Ruddock, Graham J.; O'Sullivan, Christine Y.; Preuschoff, Corinna

    2009-01-01

    Because of the educational importance of mathematics and science, IEA's (International Association for the Evaluation of Educational Achievement) Trends in International Mathematics and Science Study, widely known as TIMSS, is dedicated to providing countries with information to improve teaching and learning in these curriculum areas. Conducted…

  1. Grain Size and Parameter Recovery with TIMSS and the General Diagnostic Model

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    Skaggs, Gary; Wilkins, Jesse L. M.; Hein, Serge F.

    2016-01-01

    The purpose of this study was to explore the degree of grain size of the attributes and the sample sizes that can support accurate parameter recovery with the General Diagnostic Model (GDM) for a large-scale international assessment. In this resampling study, bootstrap samples were obtained from the 2003 Grade 8 TIMSS in Mathematics at varying…

  2. Eighth-grade science teachers use of instructional time: Examining questions from the Third International Mathematics and Science Study (TIMSS) and comparing TIMSS and National Science Foundation questionnaires

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    Davidson, Anne Burgess

    Did the Third International Mathematics and Science Study (TIMSS) ask science teachers the right questions about their use of instructional time? Part I of this 2-part study used the TIMSS database to answer the question: Do 8th grade science teachers in the U.S., Czech Republic, Hungary, Japan, and Korea differ significantly in their perceived use of instructional time? Using the instructional activities in the TIMSS teacher question "How did the lesson proceed?" the teacher-reported times were analyzed using a repeated measures multivariate analysis. Significant differences were found between teacher-reported times in the U.S. and the other 4 TIMSS countries, whose 8th grade students outperformed U.S. students on TIMSS achievement tests. Post-hoc analysis indicated that TIMSS U.S. 8th grade science teachers report spending more time on homework in class, on group activities, and on lab activities, but less time on topic development, than TIMSS teachers from some or all of the other countries. Part II of this study further examined the question "How did the lesson proceed?" by videotaping 6 classes of 8th grade science in Alabama and Virginia and comparing observer coding of the video to the teachers' recalled descriptions of the same class. The difference between observer and teacher responses using TIMSS categories was not significant; however, 43% of the total variance was explained by whether the teacher or the observer reported the times for the instructional activities. The teachers also responded to questions from the NSF Local Systemic Change Through Teacher Enhancement K--8 Teacher Questionnaire to describe the same class. The difference found between the teacher and the observer coding was not significant, but the amount of variance explained by the data source (observer or teacher) dropped to 33% when using NSF student activity categories and to 26% when using NSF teacher activity categories. The conclusion of this study was that questionnaires to

  3. Africa's Participation in TIMSS-2003

    African Journals Online (AJOL)

    cce

    In 2003, six African countries - Ghana Egypt, Tunisia, Morocco, Botswana and South. Africa - participated in an international assessment programme in science and mathematics, called the Trends in International Mathematics and Science Study (TIMSS). The study examined the performance of eighth graders in ...

  4. Linking TIMSS and NAEP Assessments to Evaluate International Trends in Achievement

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    Lim, Hwanggyu; Sireci, Stephen G.

    2017-01-01

    The Trends in International Mathematics and Science Study (TIMSS) makes it possible to compare the performance of students in the US in Mathematics and Science to the performance of students in other countries. TIMSS uses four international benchmarks for describing student achievement: Low, Intermediate, High, and Advanced. In this study, we…

  5. Equating TIMSS Mathematics Subtests with Nonlinear Equating Methods Using NEAT Design: Circle-Arc Equating Approaches

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    Ozdemir, Burhanettin

    2017-01-01

    The purpose of this study is to equate Trends in International Mathematics and Science Study (TIMSS) mathematics subtest scores obtained from TIMSS 2011 to scores obtained from TIMSS 2007 form with different nonlinear observed score equating methods under Non-Equivalent Anchor Test (NEAT) design where common items are used to link two or more test…

  6. Factors Predicting Mathematics Achievement of 8th Graders in TIMSS 2015

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    Mehmet Hayri SARI

    2017-09-01

    Full Text Available In the study, it is aimed to investigate the student, teacher and school factors predicting mathematics achievement of Turkish 8th grade students in TIMSS 2015. The group of the study consists of 6079 students and 220 teachers who attended TIMSS from Turkey. The data of the study was obtained from student and teacher questionnaires and mathematics cognitive test scores. In the data analysis, multilevel regression analysis was used in which dependent variables were plausible mathematics scores and independent variables were student, teacher and school scale scores. According to results, 34% percent of student-level variance was explained by student-level variables. It was found that self-confidence level of students was the most important predictor of mathematics achievement among student-level variables. Additionally, educational resources at home variable was also among the important predictors of mathematics achievement. Teacher and school factors explained 29% of between school variance. Among these variables, school emphasis on academic success and teaching limited by student needs were two significant variables that could predict mathematics achievement of students.

  7. Highlights from TIMSS and TIMSS Advanced 2015: Mathematics and Science Achievement of U.S. Students in Grades 4 and 8 and in Advanced Courses at the End of High School in an International Context. NCES 2017-002

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    Stephens, Maria; Landeros, Katherine; Perkins, Robert; Tang, Judy H.

    2016-01-01

    The Trends in International Mathematics and Science Study (TIMSS) 2015 is the sixth administration of this international comparative study since 1995 when first administered. TIMSS is used to compare over time the mathematics and science knowledge and skills of fourth- and eighth-graders. TIMSS is designed to align broadly with mathematics and…

  8. TIMSS 2011 Science Assessment Results: A Review of Ghana's Performance

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    Buabeng, Isaac; Owusu, Kofi Acheaw; Ntow, Forster Danso

    2014-01-01

    This paper reviews Ghana's performance in the TIMSS 2011 survey in comparison with other African and some high performing countries which participated in the TIMSS assessment. Students' achievement in the science content areas assessed were summarized and teacher preparation constructs of teachers of the students who took part in the assessment…

  9. The Link between Higher Order Thinking Skills, Representation and Concepts in Enhancing TIMSS Tasks

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    Nor’ain Mohd. Tajudin

    2016-08-01

    Full Text Available Students’ performances in TIMSS have featured strongly in recent discussions and debates about the quality of mathematical learning outcomes both from teachers and policy makers. Findings of TIMSS trends showed that most high school students in Malaysia continue to perform at less than satisfactory levels, particularly, in tasks that are cognitively demanding. In this article, we present a critical analysis of selected TIMSS Tasks and demonstrate how to support students better in the use of Higher Order Thinking Skills (HOTS in making progress with such tasks. In so doing we present analyses of TIMSS tasks and a model of these tasks that relate HOTS, representation and concepts which can be utilised by teachers to understand the role of HOTS better in empowering students shift to higher levels of cognitive funtioning in the context of tackling TIMSS and similarly demanding tasks. Our analyses and model provide an important starting point for the design of future professional development programs for Malaysian mathematics teachers in reconceptualising HOTS and implementing them in regular classrooms.

  10. TIMSS 2011 User Guide for the International Database. Supplement 4: TIMSS 2011 Sampling Stratification Information

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    Foy, Pierre, Ed.; Arora, Alka, Ed.; Stanco, Gabrielle M., Ed.

    2013-01-01

    This supplement contains documentation on the explicit and implicit stratification variables included in the TIMSS 2011 data files. The explicit strata are smaller sampling frames, created from the national sampling frames, from which national samples of schools were drawn. The implicit strata are nested within the explicit strata, and were used…

  11. Predicting Variations in Math Performancein Four Countries Using TIMSS

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    Daniel Koretz

    2001-09-01

    Full Text Available Although international comparisons of average student performance are a staple of U.S. educational debate, little attention has been paid to cross-national differences in the variability of performance. It is often assumed that the performance of U.S. students is unusually variable or that the distribution of U.S. scores is left-skewed – that is, that it has an unusually long ‘tail' of low-scoring students – but data from international studies are rarely brought to bear on these questions. This study used data from the Third International Mathematics and Science Study (TIMSS to compare the variability of performance in the U.S., Australia, France, Germany, Hong Kong, Korea, and Japan; investigate how this performance variation is distributed within and between classrooms; and explore how well background variables predict performance at both levels. TIMSS shows that the U.S. is not anomalous in terms of the amount, distribution, or prediction of performance variation. Nonetheless, some striking differences appear between countries that are potentially important for both research and policy. In the U.S., Germany, Hong Kong, and Australia, between 42 and 47 percent of score variance was between classrooms. At the other extreme, Japan and Korea both had less than 10 percent of score variance between classrooms. Two-level models (student and classroom were used to explore the prediction of performance by social background variables in four of these countries (the U.S., Hong Kong, France, and Korea. The final models included only a few variables; TIMSS lacked some important background variables, such as income, and other variables were dropped either because of problems revealed by exploratory data analysis or because of a lack of significance in the models. In all four countries, these sparse models predicted most of the between-classroom score variance (from 59 to 94 percent but very little of the within-classroom variance. Korea was the only

  12. Re-Examining Test Item Issues in the TIMSS Mathematics and Science Assessments

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    Wang, Jianjun

    2011-01-01

    As the largest international study ever taken in history, the Trend in Mathematics and Science Study (TIMSS) has been held as a benchmark to measure U.S. student performance in the global context. In-depth analyses of the TIMSS project are conducted in this study to examine key issues of the comparative investigation: (1) item flaws in mathematics…

  13. Alignment between South African mathematics assessment standards and the TIMSS assessment frameworks

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    Mdutshekelwa Ndlovu

    2012-12-01

    Full Text Available South Africa’s performance in international benchmark tests is a major cause for concern amongst educators and policymakers, raising questions about the effectiveness of the curriculum reform efforts of the democratic era. The purpose of the study reported in this article was to investigate the degree of alignment between the TIMSS 2003 Grade 8 Mathematics assessment frameworks and the Revised National Curriculum Statements (RNCS assessment standards for Grade 8 Mathematics, later revised to become the Curriculum and Assessment Policy Statements (CAPS. Such an investigation could help to partly shed light on why South African learners do not perform well and point out discrepancies that need to be attended to. The methodology of document analysis was adopted for the study, with the RNCS and the TIMSS 2003 Grade 8 Mathematics frameworks forming the principal documents. Porter’s moderately complex index of alignment was adopted for its simplicity. The computed index of 0.751 for the alignment between the RNCS assessment standards and the TIMSS assessment objectives was found to be significantly statistically low, at the alpha level of 0.05, according to Fulmer’s critical values for 20 cells and 90 or 120 standard points. The study suggests that inadequate attention has been paid to the alignment of the South African mathematics curriculum to the successive TIMSS assessment frameworks in terms of the cognitive level descriptions. The study recommends that participation in TIMSS should rigorously and critically inform ongoing curriculum reform efforts.

  14. A Cross-National Comparison of Reported Effort and Mathematics Performance in TIMSS Advanced

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    Eklöf, Hanna; Pavešic, Barbara Japelj; Grønmo, Liv Sissel

    2014-01-01

    The purpose of the study was to measure students' reported test-taking effort and the relationship between reported effort and performance on the Trends in International Mathematics and Science Study (TIMSS) Advanced mathematics test. This was done in three countries participating in TIMSS Advanced 2008 (Sweden, Norway, and Slovenia), and the…

  15. International Assessment: A Rasch Model and Teachers' Evaluation of TIMSS Science Achievement Items

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    Glynn, Shawn M.

    2012-01-01

    The Trends in International Mathematics and Science Study (TIMSS) is a comparative assessment of the achievement of students in many countries. In the present study, a rigorous independent evaluation was conducted of a representative sample of TIMSS science test items because item quality influences the validity of the scores used to inform…

  16. 2011 NAEP-TIMSS Linking Study: Linking Methodologies and Their Evaluations. NCES 2013-469

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    National Center for Education Statistics, 2013

    2013-01-01

    The 2011 NAEP-TIMSS linking study conducted by the National Center for Education Statistics (NCES) was designed to predict Trends in International Mathematics and Science Study (TIMSS) scores for the U.S. states that participated in 2011 National Assessment of Educational Progress (NAEP) mathematics and science assessment of eighth-grade students.…

  17. Using TIMSS 2007 Data to Examine STEM School Effectiveness in an International Context

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    Stanco, Gabrielle

    2012-01-01

    Because results from TIMSS 2007 showed a gap in mathematics and science achievement between students in the United States and those in the top-performing countries, TIMSS 2007 data were used to investigate how school effectiveness factors known to be strongly associated with higher STEM achievement operated in the United States compared to Chinese…

  18. Development of Reasoning Test Instruments Based on TIMSS Framework for Measuring Reasoning Ability of Senior High School Student on the Physics Concept

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    Muslim; Suhandi, A.; Nugraha, M. G.

    2017-02-01

    The purposes of this study are to determine the quality of reasoning test instruments that follow the framework of Trends in International Mathematics and Science Study (TIMSS) as a development results and to analyse the profile of reasoning skill of senior high school students on physics materials. This research used research and development method (R&D), furthermore the subject were 104 students at three senior high schools in Bandung selected by random sampling technique. Reasoning test instruments are constructed following the TIMSS framework in multiple choice forms in 30 questions that cover five subject matters i.e. parabolic motion and circular motion, Newton’s law of gravity, work and energy, harmonic oscillation, as well as the momentum and impulse. The quality of reasoning tests were analysed using the Content Validity Ratio (CVR) and classic test analysis include the validity of item, level of difficulty, discriminating power, reliability and Ferguson’s delta. As for the students’ reasoning skills profiles were analysed by the average score of achievements on eight aspects of the reasoning TIMSS framework. The results showed that reasoning test have a good quality as instruments to measure reasoning skills of senior high school students on five matters physics which developed and able to explore the reasoning of students on all aspects of reasoning based on TIMSS framework.

  19. Teachers' Perspective on whether the Mathematics Reform Will Change Turkey's Ranking in TIMSS

    Science.gov (United States)

    Sezer, Renan; Guner, Necdet; Ispir, Oylum Akkus

    2012-01-01

    Turkish elementary mathematics program was revised in 2005. In 2011, Turkey participated in TIMSS at the 4th-grade level for the first time. 4th graders were educated using the new curriculum and thus their success rate on TIMSS can be considered as an evaluation of the new program. This study investigated Turkish 4th grade teachers' expectation…

  20. The Link between Higher Order Thinking Skills, Representation and Concepts in Enhancing TIMSS Tasks

    Science.gov (United States)

    Tajudin, Nor'ain Mohd.; Chinnappan, Mohan

    2016-01-01

    Students' performances in TIMSS have featured strongly in recent discussions and debates about the quality of mathematical learning outcomes both from teachers and policy makers. Findings of TIMSS trends showed that most high school students in Malaysia continue to perform at less than satisfactory levels, particularly, in tasks that are…

  1. Pengembangan Soal Penalaran Model TIMSS Konteks Sumatera Selatan di Kelas IX SMP

    Directory of Open Access Journals (Sweden)

    Hazlita Hazlita

    2015-10-01

    Full Text Available AbstrakPenelitian ini bertujuan untuk menghasilkan soal-soal penalaran model TIMSS konteks Sumatera Selatan yang valid dan praktis dan untuk melihat efek potensial soal matematika tipe TIMSS konteks Sumatera Selatan terhadap kemampuan penalaran matematis siswa. Subjek penelitian adalah siswa kelas IX SMPN 9 Palembang yang berjumlah 29 orang. Metode penelitian adalah penelitian pengembangan. Hasil penelitian menunjukkan bahwa sebanyak 37,93% siswa menunjukkan tingkat kemampuan penalaran matematis yang baik. Sebanyak 55,17% siswa menunjukkan tingkat kemampuan penalaran matematis yang cukup dan sebanyak 6,90% siswa menunjukkan tingkat kemampuan penalaran matematis yang kurang. Berdasarkan hasil tes tersebut, jika nilai rata-rata siswa siswa sebesar 39,24 dijadikan sebagai batas acuan, maka bisa disimpulkan bahwa 31,03% siswa memiliki kemampuan penalaran matematis yang kurang, sementara 68,97% siswa sudah memiliki kemampuan pelanaran matematis yang cukup baik. Kata Kunci: Soal Penalaran; TIMSS; Konteks Sumatera Selatan  AbstractThe aim of this research was developing valid and practical TIMSS reasoning problem on mathematics context of South Sumatra. The subjects of this research were 29 students of class IX SMPN 9 Palembang. The method of research is the development of research. The results showed that 37.93% of students showed levels of good mathematical reasoning abilities, 55.17% of students showed levels sufficient mathematical reasoning ability and 6.90% of students showed levels of mathematical reasoning abilities are lacking. Based on the test results, if the 39.24 was determined as minimum limit of success, it means that 31.03% of students have less mathematical reasoning ability, while 68.97% of students already have sufficient mathematical reasoning ability. Keywords: Problem Reasoning; TIMSS; Context South Sumatra

  2. U.S. TIMSS and PIRLS 2011 Technical Report and User's Guide. NCES 2013-046

    Science.gov (United States)

    Kastberg, David; Roey, Stephen; Ferraro, David; Lemanski, Nita; Erberber, Ebru

    2013-01-01

    The "U.S. TIMSS and PIRLS 2011 Technical Report and User's Guide" provides an overview of the design and implementation of the Trends in International Mathematics and Science Study (TIMSS) 2011 and the Progress in International Reading Literacy Study (PIRLS) 2011 in the United States and the nine participating benchmarking states:…

  3. Examining the Evidence from TIMSS: Gender Differences in Year 8 Science Achievement in Australia

    Science.gov (United States)

    Thomson, Sue

    2008-01-01

    Australia's continuing participation in international science studies such as TIMSS provides a useful lens through which to monitor achievement in science over time. Gender differences in science were not evident in the early years of TIMSS but appear to be growing. This article examines gender differences in science achievement in early secondary…

  4. Factorial, Convergent, and Discriminant Validity of TIMSS Math and Science Motivation Measures: A Comparison of Arab and Anglo-Saxon Countries

    Science.gov (United States)

    Marsh, Herbert W.; Abduljabbar, Adel Salah; Abu-Hilal, Maher M.; Morin, Alexandre J. S.; Abdelfattah, Faisal; Leung, Kim Chau; Xu, Man K.; Nagengast, Benjamin; Parker, Philip

    2013-01-01

    For the international Trends in International Mathematics and Science Study (TIMSS2007) math and science motivation scales (self-concept, positive affect, and value), we evaluated the psychometric properties (factor structure, method effects, gender differences, and convergent and discriminant validity) in 4 Arab-speaking countries (Saudi Arabia,…

  5. The Attitudes and Opinions of the Students towards Mathematics Course: The Comparison of TIMSS 1999 and TIMSS 2007

    Science.gov (United States)

    Bilican, Safiye; Demirtasli, R. Nukhet; Kilmen, Sevilay

    2011-01-01

    The purpose of this study was to determine whether the attitudes of the students who participated in the application within the context of TIMSS 1999 and 2007 projects towards the "Maths course" and their opinions about "teaching activities in Maths course" had changed according to the mentioned years or not. The sample of…

  6. Klasseledelse, uro og mobning: Resultater fra TIMSS 2011

    DEFF Research Database (Denmark)

    Smith, Emil; Reimer, David

    2018-01-01

    This article studies classroom management and disciplinary climate drawing on the Trends in International Mathematics and Science Study (TIMSS) 2011. Relations between classroom management, disciplinary climate and academic achievement are analysed based on 2,800 Danish fourth grade students usin...

  7. TIMSS 2011 User Guide for the International Database. Supplement 2: National Adaptations of International Background Questionnaires

    Science.gov (United States)

    Foy, Pierre, Ed.; Arora, Alka, Ed.; Stanco, Gabrielle M., Ed.

    2013-01-01

    This supplement describes national adaptations made to the international version of the TIMSS 2011 background questionnaires. This information provides users with a guide to evaluate the availability of internationally comparable data for use in secondary analyses involving the TIMSS 2011 background variables. Background questionnaire adaptations…

  8. Ghana's achievement in mathematics in TIMSS 2007 | Mereku ...

    African Journals Online (AJOL)

    performance on the international benchmarks also improved significantly. The mathematics score, 309, placed Ghana at the 47th position on the overall mathematics achievement results table when the 48 participating countries, which met the TIMSS sampling requirements, were ranked by their mean performances.

  9. The Effects of Classroom Instructional Strategies on Science Achievement of Elementary-School Students in Japan: Findings from the Third International Mathematics and Science Study (TIMSS)

    Science.gov (United States)

    House, J. Daniel

    2006-01-01

    This article deals with the Third International Mathematics and Science Study (TIMSS). TIMSS has provided a comprehensive assessment of educational contexts and mathematics and science achievement (National Research Council, 1999). The initial TIMSS assessment was conducted in 1995 (TIMSS 1995) and several studies have examined factors related to…

  10. TIMSS 2011 User Guide for the International Database. Supplement 3: Variables Derived from the Student, Home, Teacher, and School Questionnaire Data

    Science.gov (United States)

    Foy, Pierre, Ed.; Arora, Alka, Ed.; Stanco, Gabrielle M., Ed.

    2013-01-01

    This supplement contains documentation on all the derived variables contained in the TIMSS 2011 data files that are based on background questionnaire variables. These variables were used to report background data in the TIMSS 2011 International Results in Mathematics and TIMSS 2011 International Results in Science reports, and are made available…

  11. Computational Typologies of Multidimensional End-of-Primary-School Performance Profiles from an Educational Perspective of Large-Scale TIMSS and PIRLS Surveys

    Science.gov (United States)

    Unlu, Ali; Schurig, Michael

    2015-01-01

    Recently, performance profiles in reading, mathematics and science were created using the data collectively available in the Trends in International Mathematics and Science Study (TIMSS) and the Progress in International Reading Literacy Study (PIRLS) 2011. In addition, a classification of children to the end of their primary school years was…

  12. Highlights from TIMSS 2011: Mathematics and Science Achievement of U.S. Fourth- and Eighth-Grade Students in an International Context. NCES 2013-009

    Science.gov (United States)

    Provasnik, Stephen; Kastberg, David; Ferraro, David; Lemanski, Nita; Roey, Stephen; Jenkins, Frank

    2012-01-01

    The Trends in International Mathematics and Science Study (TIMSS) is an international comparative study of student achievement. TIMSS 2011 represents the fifth such study since TIMSS was first conducted in 1995. Developed and implemented at the international level by the International Association for the Evaluation of Educational Achievement…

  13. Exploiting scale dependence in cosmological averaging

    International Nuclear Information System (INIS)

    Mattsson, Teppo; Ronkainen, Maria

    2008-01-01

    We study the role of scale dependence in the Buchert averaging method, using the flat Lemaitre–Tolman–Bondi model as a testing ground. Within this model, a single averaging scale gives predictions that are too coarse, but by replacing it with the distance of the objects R(z) for each redshift z, we find an O(1%) precision at z<2 in the averaged luminosity and angular diameter distances compared to their exact expressions. At low redshifts, we show the improvement for generic inhomogeneity profiles, and our numerical computations further verify it up to redshifts z∼2. At higher redshifts, the method breaks down due to its inability to capture the time evolution of the inhomogeneities. We also demonstrate that the running smoothing scale R(z) can mimic acceleration, suggesting that it could be at least as important as the backreaction in explaining dark energy as an inhomogeneity induced illusion

  14. A Comparison of TIMSS Items Using Cognitive Domains

    Science.gov (United States)

    Nixon, Ryan S.; Barth, Katie N.

    2014-01-01

    The results of international assessments such as the Trends in International Mathematics and Science Study (TIMSS) are often reported as rankings of nations. Focusing solely on national rank can result in invalid inferences about the relative quality of educational systems that can, in turn, lead to negative consequences for teachers and students.…

  15. Tutum, Değer Ve Özyeterlik Değişkenlerinin TIMSS-1999 ve TIMSS-2007 Sınavlarında Öğrencilerin Matematik Başarılarını Yordama Düzeyleri

    OpenAIRE

    DOĞAN, Nuri; BARIŞ, Fulya

    2010-01-01

    Bu araştırmada TIMSS–1999 ve TIMSS–2007 uygulamalarına giren Türk öğrencilerin bazı duyuşsalözelliklerinin matematik puanlarını yordama düzeyi incelenmiştir. TIMSS anketlerinde bulunan ve duyuşsalboyutları ölçen; tutum, değer ve öz-yeterlik puanları bağımsız değişken ve öğrencilerin matematik başarıpuanları bağımlı değişken olarak ele alınmıştır. Verilerin analizinde standart çoklu regresyon tekniğindenyararlanılmıştır. Analizler sonucunda, TIMSS-1999 ve TIMSS-2007 sınavlarında öğrencilerin m...

  16. PISA and TIMSS Science Score, Which Clock Is More Accurate to Indicate National Science and Technology Competitiveness?

    Science.gov (United States)

    Shi, Wei-Zhao; He, Xiqin; Wang, Yan; Fan, Zeng-Guang; Guo, Liangdong

    2016-01-01

    In 2015, PISA and TIMSS are coming up to us together. In this study, the data from PISA and TIMSS are used to investigate that which one is a better indicator of national science and technology (S&T) competitiveness? Number of S & T journal articles (per million people) is used as a measure to represent the national S&T…

  17. PENGEMBANGAN SOAL MATEMATIKA BERKARAKTERISTIK TIMSS TIPE PEMECAHAN MASALAH PADA TOPIK GEOMETRI PENGUKURAN VOLUME KUBUS DAN BALOK KELAS VIII

    Directory of Open Access Journals (Sweden)

    Ika Pratiwi

    2016-07-01

    Full Text Available This research aims to produce a TIMSS characterized math problems that are valid and reliable. The method of this research is Design Research. The sample of this study were 31 students of SMP Negeri 1 Inderalaya. The procedure of this study through the stages of Preliminary Evaluation and Formative Evaluation. Based on the results obtained 7 of TIMSS characterized with characteristics (1 using real-life contexts, (2 using characteristics of TIMSS, and (3 the type of problem-solving that problem logically and empirically valid  and reliable. Valid logically be fulfilled from the results of the assessment validator, where the validator comment on the terms of the content, construct, and  language. Valid empirically criteria for both internally for items validity and externally for the whole items validity. Items also expressed reliable with a high level of confidence as the test instrument through items with the analysis result reliability coefficient of 0,703.Keywords: TIMSS, Design Research, Problem Solving, Geometry, Volume Cube and Rectangular Prism

  18. Kritická místa v matematice u českých žáků na základě výsledků šetření TIMSS 2007 / Critical areas of mathematics for Czech pupils based on TIMSS 2007 data

    Directory of Open Access Journals (Sweden)

    Miroslav Rendl

    2014-02-01

    Full Text Available The goal of the empirical study is to describe critical areas of primary mathematics as can be found from the Czech Grade 8 pupils’ results in TIMSS 2007 and to identify possible causes of their difficulty for pupils. In the first part, a research background is briefly given – international comparative research in mathematics and possibilities of the secondary analyses of its data. The second part describes methodology in detail. We analysed data from so called TIMSS almanacs (results of Czech pupils at the level of concrete mathematical items from TIMSS and answers of the teacher questionnaire. To interpret possible causes we also used curricular documents and the analysis of the apparently most used primary mathematics textbooks. We set up a criterion for deciding whether the Czech pupils’ results for the given item is below their standard which we determined by comparing their average success rate with that of the international sample. Thus so called weak and very weak items were identified. They were divided into three areas which can be considered critical areas for Czech pupils: Algebra (with subareas of Functions, Substitution, Equations and inequalities, Expressions, Sequences, Shapes and solids. For each of the areas, weak and very weak items are presented together with their results and an outline of the nature of their difficulty for Czech pupils and possible causes of Czech pupils’ failure to solve them. It transpires that it is necessary to get a deeper insight into the nature of problems by clinical interviews with pupils. This will be a topic of further articles.

  19. Scale-invariant Green-Kubo relation for time-averaged diffusivity

    Science.gov (United States)

    Meyer, Philipp; Barkai, Eli; Kantz, Holger

    2017-12-01

    In recent years it was shown both theoretically and experimentally that in certain systems exhibiting anomalous diffusion the time- and ensemble-averaged mean-squared displacement are remarkably different. The ensemble-averaged diffusivity is obtained from a scaling Green-Kubo relation, which connects the scale-invariant nonstationary velocity correlation function with the transport coefficient. Here we obtain the relation between time-averaged diffusivity, usually recorded in single-particle tracking experiments, and the underlying scale-invariant velocity correlation function. The time-averaged mean-squared displacement is given by 〈δ2¯〉 ˜2 DνtβΔν -β , where t is the total measurement time and Δ is the lag time. Here ν is the anomalous diffusion exponent obtained from ensemble-averaged measurements 〈x2〉 ˜tν , while β ≥-1 marks the growth or decline of the kinetic energy 〈v2〉 ˜tβ . Thus, we establish a connection between exponents that can be read off the asymptotic properties of the velocity correlation function and similarly for the transport constant Dν. We demonstrate our results with nonstationary scale-invariant stochastic and deterministic models, thereby highlighting that systems with equivalent behavior in the ensemble average can differ strongly in their time average. If the averaged kinetic energy is finite, β =0 , the time scaling of 〈δ2¯〉 and 〈x2〉 are identical; however, the time-averaged transport coefficient Dν is not identical to the corresponding ensemble-averaged diffusion constant.

  20. The Inclusion of Geography in TIMSS: Can Consensus Be Reached?

    Science.gov (United States)

    Bourke, Terri; Lane, Rod

    2017-01-01

    An initial call by the editors of International Research in Geographical and Environmental Education prompted a study about the inclusion of geography in the Trends in International Mathematics and Science Study (TIMSS) tests. This study found that the geography education community were overwhelmingly in favour of such a move, believing that the…

  1. Highlights from TIMSS 2011: Mathematics and Science Achievement of U.S. Fourth- and Eighth-Grade Students in an International Context. Appendix E: Standard Error Tables. NCES 2013-009

    Science.gov (United States)

    National Center for Education Statistics, 2012

    2012-01-01

    The Trends in International Mathematics and Science Study (TIMSS) 2011 is the fifth administration of this international comparative study since 1995 when first administered. TIMSS is used to compare over time the mathematics and science knowledge and skills of fourth- and eighth-graders. TIMSS is designed to align broadly with mathematics and…

  2. Mathematical competencies and the role of mathematics in physics education: A trend analysis of TIMSS Advanced 1995 and 2008

    Directory of Open Access Journals (Sweden)

    Trude Nilsen

    2013-10-01

    Full Text Available As students advance in their learning of physics over the course of their education, the requirement of mathematical applications in physics-related tasks increases, especially so in upper secondary school and in higher education. Yet there is little empirical work (particularly large-scale or longitudinal on the application of mathematics in physics education compared with the research related to the conceptual knowledge of physics. In order to clarify the nature of mathematics in physics education, we developed a theoretical framework for mathematical competencies pertinent to various physics tasks based on theoretical frameworks from mathematics and physics education. We used this synthesis of frameworks as a basis to create a model for physics competence. The framework also served as a tool for analyzing and categorizing trend items from the international large-scale survey, TIMSS Advanced 1995 and 2008. TIMSS Advanced assessed students in upper secondary school with special preparation in advanced physics and mathematics. We then investigated the changes in achievements on these categorized items across time for nations who participated in both surveys. The results from our analysis indicate that students whose overall physics achievement declined struggled the most with items requiring mathematics, especially items requiring them to handle symbols, such as manipulating equations. This finding suggests the importance of collaboration between mathematics and physics education as well as the importance of traditional algebra for physics education.

  3. The Predictive Effects of Motivation toward Learning Science on TIMSS Grade 8 Students' Science Achievement: A Comparative Study between Malaysia and Singapore

    Science.gov (United States)

    Lay, Yoon Fah; Chandrasegaran, A. L.

    2016-01-01

    TIMSS routinely presents very powerful evidence showing that students with more positive motivation toward learning science have substantially higher achievement. The results from TIMSS 2011 are consistent with previous assessments. This study explored the predictive effects of motivation toward learning science on science achievement among…

  4. Pengembangan Soal Penalaran Model TIMSS Matematika SMP

    Directory of Open Access Journals (Sweden)

    A. Rizta

    2013-06-01

    Full Text Available Penelitian ini bertujuan mengembangkan soal penalaran model TIMSS pada mata pelajaran matematika SMP. Subjek penelitian adalah siswa kelas VIII.7 SMP Negeri 1 Palembang yang berjumlah 27 orang. Metode penelitian yang digunakan development research atau pengembangan. Hasil penelitian ini menunjukkan bahwa sebanyak 22,22% siswa mendapat skor  penalaran di atas 65%, dan 77,78% siswa memperoleh skor penalaran di bawah 65%. Lebih rinci pencapaian hasil tes penalaran pada domain penalaran generalize 11,11%,  domain penalaran justify 3,7%, domain penalaran integrate 29,63%, domain penalaran analyze 44,45%, dan domain penalaran non-routine problem 51,85%. Berdasarkan hasil tes tersebut, jika acuan batas pencapaian 65% maka  penalaran siswa masih berada di bawah batas pencapaian minimal dengan kata lain kemampuan penalaran siswa masih rendah.   The aim of this research was developing TIMSS reasoning problem on mathematics SMP. Subject of this research was 27 students on VIII.7 SMPN 1 Palembang. This research used development research. The result show that 22,22% students reach above 65% of reasoning problem, and vice versa. More detail result show that 11,11% reached generalize reasoning level, 3,7% reached justify level, 29,63% reached integrate level, 44,45% reached analyze level, and 51,85% reached non-routine problem. Based on the result, if 65% was determined as minimum limit of success, it means the student reasoning ability still low.  

  5. The difficulties of Indonesian fourth graders in learning fractions: An early exploration of TIMSS 2015 results

    Science.gov (United States)

    Wijaya, Ariyadi

    2017-08-01

    The present study investigates Indonesian fourth-graders low performance in dealing with fractions in TIMSS 2015. Furthermore, the present study also explores possible reasons for this low performance. The data for this study was drawn from TIMSS 2015 data which included test results and responses to Teacher Questionnaire. Descriptive statistics was used to analyze the data. Indonesian textbooks were also analyzed to portrait a broader scope of possible reasons for students' low performance. The analysis of TIMSS test result reveals that Indonesian students, in comparison to students from other countries, had low understanding of the basic concepts of fractions. From the Teacher Questionnaire it was found that a possible reason for this low understanding was the Indonesian curriculum for third grade which gave low emphasis on the basic concepts of fractions and introduced operations of fractions rather early. Furthermore, the result of textbook analysis shows that Indonesian textbooks restricted only to one definition of fractions, i.e. fractions as parts of wholes. This finding might also explain Indonesian fourth graders' low understanding of fractions.

  6. A Comparison of PISA and TIMSS 2003 Achievement Results in Mathematics

    Science.gov (United States)

    Wu, Margaret

    2009-01-01

    This study compares the Programme for International Student Assessment (PISA) 2003 Mathematics results with the Trends in International Mathematics and Science Study (TIMSS) 2003 Grade 8 mathematics results, using country mean scores for 22 participants of both studies. It is found that Western countries generally performed better in PISA than in…

  7. ANALYSIS OF STUDENTS’ DECISION MAKING TO SOLVE SCIENCE REASONING TEST OF TRENDS IN INTERNATIONAL MATHEMATICS AND SCIENCE STUDY (TIMSS

    Directory of Open Access Journals (Sweden)

    N. Novianawati

    2015-04-01

    Full Text Available This study aims to determine students’ decision making strategy to answer TIMSS science reasoning test in cognitive reasoning domain. This research is quantitative descriptive research. The result shows that students tend to use compensatory strategy for decision making in solving multiple-choice questions and use rational category to answer essay questions. The result shows that more than half of students have been able to answer the questions TIMSS science tests correctly.

  8. Linking Errors between Two Populations and Tests: A Case Study in International Surveys in Education

    Directory of Open Access Journals (Sweden)

    Dirk Hastedt

    2015-06-01

    Full Text Available This simulation study was prompted by the current increased interest in linking national studies to international large-scale assessments (ILSAs such as IEA's TIMSS, IEA's PIRLS, and OECD's PISA. Linkage in this scenario is achieved by including items from the international assessments in the national assessments on the premise that the average achievement scores from the latter can be linked to the international metric. In addition to raising issues associated with different testing conditions, administrative procedures, and the like, this approach also poses psychometric challenges. This paper endeavors to shed some light on the effects that can be expected, the linkage errors in particular, by countries using this practice. The ILSA selected for this simulation study was IEA TIMSS 2011, and the three countries used as the national assessment cases were Botswana, Honduras, and Tunisia, all of which participated in TIMSS 2011. The items selected as items common to the simulated national tests and the international test came from the Grade 4 TIMSS 2011 mathematics items that IEA released into the public domain after completion of this assessment. The findings of the current study show that linkage errors seemed to achieve acceptable levels if 30 or more items were used for the linkage, although the errors were still significantly higher compared to the TIMSS' cutoffs. Comparison of the estimated country averages based on the simulated national surveys and the averages based on the international TIMSS assessment revealed only one instance across the three countries of the estimates approaching parity. Also, the percentages of students in these countries who actually reached the defined benchmarks on the TIMSS achievement scale differed significantly from the results based on TIMSS and the results for the simulated national assessments. As a conclusion, we advise against using groups of released items from international assessments in national

  9. School Facilities and Student Achievement in Industrial Countries: Evidence from the TIMSS

    Science.gov (United States)

    Hopland, Arnt O.

    2013-01-01

    This paper studies the link between school facilities (buildings and grounds) and student achievement in eight countries using data from the TIMSS 2003 database. The results indicate a negative relationship, but the estimated coefficients are mainly insignificant. Interestingly, the coefficients differ heavily across countries. Whereas there seem…

  10. Eesti koolimatemaatika rahvusvahelise matemaatika ja loodusainete tasemeuuringu TIMSS 2003 tulemuste põhjal / Tiit Lepmann

    Index Scriptorium Estoniae

    Lepmann, Tiit

    2005-01-01

    Koolimatemaatika rahvusvahelise võrdlusuuringu TIMSS (Trends in International Mathematics and Science Style) ajaloost, 2003. a. testidest, valimist ja tulemustest (sh Eesti õpilaste omadest) riikide lõikes, samuti heade tulemuste saavutamisel kaasa aidanud teguritest

  11. TIMSS Advanced 2008: Fall i fysikk-kompetanse i Norge og Sverige

    Directory of Open Access Journals (Sweden)

    Carl Angell

    2011-02-01

    Full Text Available TIMSS Advanced 2008 is an international comparative study, and deals with examining student achievement in mathematics and physics in the final year at upper secondary school. The theme of this article is to look at how Norwegian and Swedish students performed in physics in 2008 compared to the study conducted in 1995. The results from the TIMSS Advanced study provide an unambiguous picture. There is a significant decline in the performance in physics since the previous study in 1995 for both Norwegian and Swedish students. One important reason is related to the generally low level of results in science and mathematics at all levels in schools as shown by the downward trend for students in lower grades. The decline in physics performance can thus be explained by the fact that students with significantly weaker skills than before in mathematics and science come into upper secondary school. Lack of knowledge of basic arithmetic and algebra seems to be a contributing factor for this downwards trend in physics at upper secondary school level.

  12. Benchmarking to the world's best in mathematics. Quality control in curriculum and instruction among the top performers in the TIMSS.

    Science.gov (United States)

    Phelps, R P

    2001-08-01

    This article describes the education quality control systems (for mathematics) used by those countries that performed best on the Third International Mathematics and Science Study (TIMSS). Enforced quality control measures are defined as "decision points"--where adherence to the curriculum and instruction system can be reinforced. Most decision points involve stakes for the student, teacher, or school. They involve potential consequences for failure to adhere to the system and to follow the program at a reasonable pace. Generally, countries with more decision points perform better on the TIMSS. When the number of decision points and TIMSS test scores are adjusted for country wealth, the relationship between the degree of (enforced) quality control and student achievement appears to be positive and exponential. The more (enforced) quality control measures employed in an education system, the greater is students' academic achievement.

  13. The Relationships between Indonesian Fourth Graders’ Difficulties in Fractions and the Opportunity to Learn Fractions: A Snapshot of TIMSS Results

    OpenAIRE

    Ariyadi Wijaya

    2017-01-01

    This paper reports an exploration into Indonesian fourth graders’ difficulties in fractions and their relation to the opportunity to learn fractions students got at schools. The concept of ‘opportunity to learn’ is often considered as a framework to investigate possible reasons for students’ difficulties. The data for this study was drawn from TIMSS 2015 that comprised test results and teachers’ responses to TIMSS Teacher Questionnaire. The test and questionnaire data were anal...

  14. PENGEMBANGAN SOAL MATEMATIKA MODEL TIMSS UNTUK MENDUKUNG PEMBELAJARAN MATEMATIKA SMP KELAS VII KURIKULUM 2013

    Directory of Open Access Journals (Sweden)

    M. Andy Rudhito

    2016-02-01

    DEVELOPING THE TIMSS MATH PROBLEM MODEL TO SUPPORT THE MATHEMATICS LEARNING IN GRADE VII USING THE 2013 CURRICULUM Abstract: This study was aimed to produce a valid and practical TIMMS math problem model for junior high school students using the 2013 curriculum. The study used the research and development design. The design process of the problems as assessment instruments was carried out through prototyping involving two stages. Prototype I was the design product and the problem development done by the researchers themselves, while Prototype II was the revision of Prototype I based on the feedback provided by experts, colleagues, and Mathematics teachers in the form of validators’ notes and the minutes taken from discussions. The findings showed that the book of math problems was written by grouping the chapters following the materials domains as those in TIMSS, that is, numbers, geometry, algebra, data, and probability. For the student book, it was not nsecessary to write the materials domain, the essential topics, and the cognitive domain. The feedback from the FGD was that the problems should be arranged from the easiest ones to the most difficult ones. The multiple choice items should not be written in the form of questions, but in the form of incomplete sentences with the blanks in the middle or the end of the sentences. The items should not ask about implication. Keywords: Development of problems, junior high school mathematics, TIMSS, Curriculum 2013

  15. Regional averaging and scaling in relativistic cosmology

    International Nuclear Information System (INIS)

    Buchert, Thomas; Carfora, Mauro

    2002-01-01

    Averaged inhomogeneous cosmologies lie at the forefront of interest, since cosmological parameters such as the rate of expansion or the mass density are to be considered as volume-averaged quantities and only these can be compared with observations. For this reason the relevant parameters are intrinsically scale-dependent and one wishes to control this dependence without restricting the cosmological model by unphysical assumptions. In the latter respect we contrast our way to approach the averaging problem in relativistic cosmology with shortcomings of averaged Newtonian models. Explicitly, we investigate the scale-dependence of Eulerian volume averages of scalar functions on Riemannian three-manifolds. We propose a complementary view of a Lagrangian smoothing of (tensorial) variables as opposed to their Eulerian averaging on spatial domains. This programme is realized with the help of a global Ricci deformation flow for the metric. We explain rigorously the origin of the Ricci flow which, on heuristic grounds, has already been suggested as a possible candidate for smoothing the initial dataset for cosmological spacetimes. The smoothing of geometry implies a renormalization of averaged spatial variables. We discuss the results in terms of effective cosmological parameters that would be assigned to the smoothed cosmological spacetime. In particular, we find that on the smoothed spatial domain B-bar evaluated cosmological parameters obey Ω-bar B-bar m + Ω-bar B-bar R + Ω-bar B-bar A + Ω-bar B-bar Q 1, where Ω-bar B-bar m , Ω-bar B-bar R and Ω-bar B-bar A correspond to the standard Friedmannian parameters, while Ω-bar B-bar Q is a remnant of cosmic variance of expansion and shear fluctuations on the averaging domain. All these parameters are 'dressed' after smoothing out the geometrical fluctuations, and we give the relations of the 'dressed' to the 'bare' parameters. While the former provide the framework of interpreting observations with a 'Friedmannian bias

  16. School effectiveness in science in Sweden and Norway viewed from a TIMSS perspective

    Directory of Open Access Journals (Sweden)

    Marie Wiberg

    2013-11-01

    Full Text Available Declining achievement in various core subjects has led to a debate on strategies to enhance student achievement. Identifying factors in the school environment that affect student performance in science, are therefore, of vital importance. The aim of this study is to identify school-level factors that are associated with eighth-grade students’ achievement in science based on results from TIMSS (Trends in International Mathematics and Science Study 2003 and 2007. Because the TIMSS data includes school-level factors at two different time points, we expected to find factors that influence science performance by Swedish and Norwegian students. Multilevel analysis was used, and this framework allowed us to account for the influence of the students’ home backgrounds. After controlling for student background, our results show that there are only a few school-level factors that are associated with student achievement in science, and the influence of these factors differ between Sweden and Norway.

  17. Error analysis of mathematical problems on TIMSS: A case of Indonesian secondary students

    Science.gov (United States)

    Priyani, H. A.; Ekawati, R.

    2018-01-01

    Indonesian students’ competence in solving mathematical problems is still considered as weak. It was pointed out by the results of international assessment such as TIMSS. This might be caused by various types of errors made. Hence, this study aimed at identifying students’ errors in solving mathematical problems in TIMSS in the topic of numbers that considered as the fundamental concept in Mathematics. This study applied descriptive qualitative analysis. The subject was three students with most errors in the test indicators who were taken from 34 students of 8th graders. Data was obtained through paper and pencil test and student’s’ interview. The error analysis indicated that in solving Applying level problem, the type of error that students made was operational errors. In addition, for reasoning level problem, there are three types of errors made such as conceptual errors, operational errors and principal errors. Meanwhile, analysis of the causes of students’ errors showed that students did not comprehend the mathematical problems given.

  18. Context factors and student achievement in the IEA studies: evidence from TIMSS

    Directory of Open Access Journals (Sweden)

    Elisa Caponera

    2016-08-01

    Full Text Available Abstract Background The present study investigates what factors related to the school context influence student achievement on TIMSS mathematics tests across countries. A systematic review of the literature on PIRLS, TIMSS, and ICCS was conducted upstream to identify those school, teacher, and classroom factors shown to be useful predictors of student performance in previous IEA studies. Data of student samples representative of grade 8 students from 28 countries who participated in TIMSS 2011 were analysed. The main aim of the present study is to verify what school and teacher characteristics are positively associated with students’ mathematics achievement, mainly focusing on disadvantaged schools. Furthermore, it aims at identifying how school context variables contribute to explaining the performance of students in disadvantaged schools in comparison with more advantaged schools. Methods A separate analysis was carried out for each considered country, and the same multilevel regression model was used on the sampled schools as a whole and treating schools with high (highest tertile and low (lowest tertile socio-economic backgrounds as distinct groups. Results The results confirmed that a high socio-economic status has a significant and positive effect on student achievement: compared with students from socio-economic disadvantaged schools, students from advantaged schools performed better in mathematics achievement. This difference is more evident in countries where the gap between rich and poor people as measured by the Gini coefficient, which measures how much an economy deviates from perfect equality, is wider. However, this difference is restricted in countries with a smaller gap between rich and poor people. Conclusions According to the literature in the field, the results show significant differences across countries in relation to the school and teacher characteristics that have an impact on mathematics achievement of students from

  19. Elementary Teacher Education in the Top Performing European TIMSS Countries: A Comparative Study

    Science.gov (United States)

    Sabrin, Mohammed

    2018-01-01

    This paper analyzed elementary teacher education (hereafter 'TED') programs in the top performing European (TIMSS) countries to help inform future elementary TED policy in the Kingdom of Saudi Arabia. Methodological emphasis revolved around how much emphasis should be placed on general content knowledge (GCK), as opposed to general pedagogical…

  20. Factors Predicting Turkish and Korean Students' Science and Mathematics Achievement in TIMSS 2011

    Science.gov (United States)

    Topçu, Mustafa Sami; Erbilgin, Evrim; Arikan, Serkan

    2016-01-01

    This study makes an important contribution to an expanding body of international comparative studies by exploring factors predicting differences in science and mathematics achievement by students in Turkey and the Republic of Korea on the 2011 TIMSS assessment. While these countries are similar with regards to population size, cultural beliefs…

  1. Why Singaporean 8th Grade Students Gain Highest Mathematics Ranking in TIMSS (1999-2011)

    Science.gov (United States)

    Lessani, Abdolreza; Yunus, Aida Suraya Md; Tarmiz, Rohani Ahmad; Mahmud, Rosnaini

    2014-01-01

    The international comparison of students' mathematics knowledge and competencies is an effective method of evaluating students' mathematics performance and developing policies to improve their achievements in mathematics. Trends in International Mathematics and Science Study (TIMSS) are among the most well-recognized international comparisons that…

  2. Mathematics beliefs and instructional strategies in achievement of elementary-school students in Japan: results from the TIMSS 2003 assessment.

    Science.gov (United States)

    House, J Daniel

    2007-04-01

    Recent findings concerning mathematics assessment indicate that students in Japan consistently score above international averages. Researchers have examined specific mathematics beliefs and instructional strategies associated with mathematics achievement for students in Japan. This study examined relationships among self-beliefs, classroom instructional strategies, and mathematics achievement for a large national sample of students (N=4,207) from the TIMSS 2003 international sample of fourth graders in Japan. Several significant relationships between mathematics beliefs and test scores were found; a number of classroom teaching strategies were also significantly associated with test scores. However, multiple regression using the complete set of five mathematics beliefs and five instructional strategies explained only 25.1% of the variance in mathematics achievement test scores.

  3. Examining the Effects of Turkish Education Reform on Students' TIMSS 2007 Science Achievements

    Science.gov (United States)

    Atar, Hakan Yavuz; Atar, Burcu

    2012-01-01

    The purpose of this study is to examine the effects of some of the changes such as student centered learning (i.e. inquiry science instruction), outfitting classrooms with latest technology and computers that the reform movement has brought about on students' TIMSS 2007 science achievements. Two-staged stratified sampling was used in the selection…

  4. Trends in Mathematics and Science Study (TIMSS): International Accountability and Implications for Science Instruction

    Science.gov (United States)

    Eckert, Jonathan M.

    2008-01-01

    International educational comparisons are relatively recent phenomena and have long been the source of international debate. Since the formation of the International Association for the Evaluation of Educational Achievement (IEA) in the 1950s, assessments have grown increasingly more valid and reliable. TIMSS is an exemplary attempt at…

  5. Forces for Change in Mathematics Education—: The Case of TIMSS

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    Donald S. Macnab

    2000-02-01

    Full Text Available The results of the Third International Study in Mathematics and Science Education (TIMSS were published in 1996/7. Since that time the participating countries have reacted in a variety of ways to the comparative performance of their students. This article investigates the diverse effects these reactions have had on mathematics curricula and teaching methodologies in a selection of these countries, within the context of a wider analysis of the motivations which determine change in education.

  6. The Relationships between Indonesian Fourth Graders’ Difficulties in Fractions and the Opportunity to Learn Fractions: A Snapshot of TIMSS Results

    Directory of Open Access Journals (Sweden)

    Ariyadi Wijaya

    2017-11-01

    Full Text Available This paper reports an exploration into Indonesian fourth graders’ difficulties in fractions and their relation to the opportunity to learn fractions students got at schools. The concept of ‘opportunity to learn’ is often considered as a framework to investigate possible reasons for students’ difficulties. The data for this study was drawn from TIMSS 2015 that comprised test results and teachers’ responses to TIMSS Teacher Questionnaire. The test and questionnaire data were analysed by using descriptive statistics. In addition to test and questionnaire, this study also included an analysis of Indonesian textbooks in order to get a broader scope of the opportunity to learn. Qualitative approach was used to analyse the textbooks. The analysis of the TIMSS results shows Indonesian students’ low conceptual understanding of fractions. Three possible reasons for students’ low conceptual understanding were revealed. First, the content of Indonesian curriculum that gave low emphasis on basic concepts of fractions and introduced operations of fractions too early. Second, the Indonesian mathematics textbooks only presented one definition of fractions, i.e. fractions as parts of wholes. Third, there is a limited use of models or representations of fractions in the classroom practices.

  7. A Dataset from TIMSS to Examine the Relationship between Computer Use and Mathematics Achievement

    Science.gov (United States)

    Kadijevich, Djordje M.

    2015-01-01

    Because the relationship between computer use and achievement is still puzzling, there is a need to prepare and analyze good quality datasets on computer use and achievement. Such a dataset can be derived from TIMSS data. This paper describes how this dataset can be prepared. It also gives an example of how the dataset may be analyzed. The…

  8. Determinants of Educational Achievement in Morocco: A Micro-Econometric Analysis Applied to the TIMSS Study

    Science.gov (United States)

    Ibourk, Aomar

    2013-01-01

    Based on data from international surveys measuring learning (TIMSS), this article focuses on the analysis of the academic performance Moroccan students. The results of the econometric model show that the students' characteristics, their family environment and school context are key determinants of these performances. The study also shows that the…

  9. The Contribution of TIMSS to the Link between School and Classroom Factors and Student Achievement

    Science.gov (United States)

    Drent, Marjolein; Meelissen, Martina R. M.; van der Kleij, Fabienne M.

    2013-01-01

    Worldwide, the interest of policy-makers in participating in studies from the International Association for the Evaluation of Educational Achievement (IEA), such as Trends in International Mathematics and Science Study (TIMSS) has been growing rapidly over the past two decades. These studies offer the opportunity to relate the teaching and…

  10. Turkish Mathematics and Science Teachers' Technology Use in Their Classroom Instruction: Findings from TIMSS 2011

    Science.gov (United States)

    Tas, Yasemin; Balgalmis, Esra

    2016-01-01

    The goal of this study was to describe Turkish mathematics and science teachers' use of computer in their classroom instruction by utilizing TIMSS 2011 data. Analyses results revealed that teachers most frequently used computers for preparation purpose and least frequently used computers for administration. There was no difference in teachers'…

  11. Similarity of TIMSS Math and Science Achievement of Nations

    Directory of Open Access Journals (Sweden)

    Algirdas Zabulionis

    2001-09-01

    Full Text Available In 1991-97, the International Association for the Evaluation of Educational Achievement (IEA undertook a Third International Mathematics and Science Study (TIMSS in which data about the mathematics and science achievement of the thirteen year-old students in more than 40 countries were collected. These data provided the opportunity to search for patterns of students' answers to the test items: which group of items was relatively more difficult (or more easy for the students from a particular country (or group of countries. Using this massive data set an attempt was made to measure the similarities among country profiles of how students responded to the test items.

  12. Using TIMSS and PISA Results to Inform Educational Policy: A Study of Russia and Its Neighbours

    Science.gov (United States)

    Carnoy, Martin; Khavenson, Tatiana; Ivanova, Alina

    2015-01-01

    In this paper, we develop a multi-level comparative approach to analyse Trends in International Mathematics and Science Survey (TIMSS) and Programme of International Student Achievement (PISA) mathematics results for a country, Russia, where the two tests provide contradictory information about students' relative performance. Russian students do…

  13. The Reasons for the Decline of the Results of Jordanian Students in "TIMSS 2015"

    Science.gov (United States)

    Abu Tayeh, Khaled; Al-Rsa'i, Mohammad S.; Al-Shugairat, Mohammad F.

    2018-01-01

    The study aimed at identifying the reasons behind the Jordanian students' drop of performance in the TIMSS 2015 from the point of view of their teachers. Survey method was used because teachers are the most able to decide upon the reasons of this fall and so a questionnaire was designed to recognize their point of view concerning the reasons of…

  14. Examination of the 8th Grade Students' TIMSS Mathematics Success in Terms of Different Variables

    Science.gov (United States)

    Kaleli-Yilmaz, Gül; Hanci, Alper

    2016-01-01

    The aim of this study is to determine how the TIMSS mathematics success of the 8th grade students differentiates according to the school type, gender, mathematics report mark, parents' education level, cognitive domains and cognitive domains by gender. Relational survey method was used in the study. Six-hundred fifty two 8th grade students…

  15. Determination of the Relationship between 8th Grade Students Learning Styles and TIMSS Mathematics Achievement

    Science.gov (United States)

    Yilmaz, Gül Kaleli; Koparan, Timur; Hanci, Alper

    2016-01-01

    In this study, it is aimed to determination of the relationship between learning styles and TIMSS mathematics achievements of eighth grade students. Correlational research design that is one of the quantitative research methods, was used in this study. The sample of the research consists of 652 8th grade students 347 are male and 305 are female…

  16. PENGEMBANGAN SOAL MATEMATIKA MODEL TIMSS UNTUK MENDUKUNG PEMBELAJARAN MATEMATIKA SMP KELAS VII KURIKULUM 2013

    OpenAIRE

    M. Andy Rudhito; D. Arif Budi Prasety

    2016-01-01

    Abstrak: Penelitian ini bertujuan untuk menghasilkan soal matematika model TIMSS yang valid dan praktis untuk siswa SMP berdasarkan Kurikulum 2013. Metode penelitian yang digunakan adalah penelitian pengembangan. Proses pendesainan soal sebagai instrumen penilaian dilakukan dengan prototyping. Prototyping meliputi dua tahap. Prototipe I merupakan hasil desain dan penyusunan soal-soal oleh peneliti sendiri, sedang prototipe II revisi dari prototipe I berdasarkan masukan dari pakar, teman sejaw...

  17. Comparing the Similarities and Differences of PISA 2003 and TIMSS. OECD Education Working Papers, No. 32

    Science.gov (United States)

    Wu, Margaret

    2010-01-01

    This paper makes an in-depth comparison of the PISA (OECD) and TIMSS (IEA) mathematics assessments conducted in 2003. First, a comparison of survey methodologies is presented, followed by an examination of the mathematics frameworks in the two studies. The methodologies and the frameworks in the two studies form the basis for providing…

  18. A Comparative Investigation of South Africa's High-Performing Learners on Selected TIMSS Items Comprising Multiplicative Concepts

    Science.gov (United States)

    Long, Caroline; Wendt, Heike

    2017-01-01

    South Africa participated in TIMSS from 1995 to 2015. Over these two decades, some positive changes have been reported on the aggregated mathematics performance patterns of South African learners. This paper focuses on the achievement patterns of South Africa's high-performing Grade 9 learners (n = 3378) in comparison with similar subsamples of…

  19. Exploring Cross-National Changes in Instructional Practices: Evidence from Four Cycles of TIMSS. Policy Brief No. 13

    Science.gov (United States)

    Rožman, Mojca; Klieme, Eckhard

    2017-01-01

    The International Association for the Evaluation of Educational Achievement's (IEA's) Trends in International Mathematics and Science Study (TIMSS) can reveal a great deal about national teaching cultures and policies. Changes in instructional practices over more than a decade may be studied from a cross-cultural perspective. Using teacher and…

  20. TIMSS Advanced 2015 and Advanced Placement Calculus & Physics. A Framework Analysis. Research in Review 2016-1

    Science.gov (United States)

    Lazzaro, Christopher; Jones, Lee; Webb, David C.; Grover, Ryan; Di Giacomo, F. Tony; Marino, Katherine Adele

    2016-01-01

    This report will determine to what degree the AP Physics 1 and 2 and AP Calculus AB and BC frameworks are aligned with the Trends in International Mathematics and Science Study (TIMSS) Advanced Physics and Mathematics frameworks. This will enable an exploration of any differences in content coverage and levels of complexity, and will set the stage…

  1. Confidence in Mathematics and Algebra Achievement of Eighth-Grade Students in Japan: Findings from the TIMSS 2011 Assessment

    Science.gov (United States)

    House, J. Daniel; Telese, James A.

    2014-01-01

    There is continuing interest in the identification of student and instructional factors associated with the mathematics achievement of students in Japan. The Trends in International Mathematics and Science Study (TIMSS) assessments have provided opportunities to examine factors associated with mathematics achievement. The purpose of this study was…

  2. Comparative Study of Middle School Students' Attitudes towards Science: Rasch Analysis of Entire TIMSS 2011 Attitudinal Data for England, Singapore and the U.S.A. as Well as Psychometric Properties of Attitudes Scale

    Science.gov (United States)

    Oon, Pey Tee; Subramaniam, R.

    2018-01-01

    We report here on a comparative study of middle school students' attitudes towards science involving three countries: England, Singapore and the U.S.A. Complete attitudinal data sets from TIMSS (Trends in International Mathematics and Science Study) 2011 were used, thus giving a very large sample size (N = 20,246), compared to other studies in the…

  3. Fast Decentralized Averaging via Multi-scale Gossip

    Science.gov (United States)

    Tsianos, Konstantinos I.; Rabbat, Michael G.

    We are interested in the problem of computing the average consensus in a distributed fashion on random geometric graphs. We describe a new algorithm called Multi-scale Gossip which employs a hierarchical decomposition of the graph to partition the computation into tractable sub-problems. Using only pairwise messages of fixed size that travel at most O(n^{1/3}) hops, our algorithm is robust and has communication cost of O(n loglogn logɛ - 1) transmissions, which is order-optimal up to the logarithmic factor in n. Simulated experiments verify the good expected performance on graphs of many thousands of nodes.

  4. Statistical Techniques Utilized in Analyzing PISA and TIMSS Data in Science Education from 1996 to 2013: A Methodological Review

    Science.gov (United States)

    Liou, Pey-Yan; Hung, Yi-Chen

    2015-01-01

    We conducted a methodological review of articles using the Programme for International Student Assessment (PISA) or Trends in International Mathematics and Science Study (TIMSS) data published by the SSCI-indexed science education journals, such as the "International Journal of Science and Mathematics Education," the "International…

  5. Optimizing Prediction Using Bayesian Model Averaging: Examples Using Large-Scale Educational Assessments.

    Science.gov (United States)

    Kaplan, David; Lee, Chansoon

    2018-01-01

    This article provides a review of Bayesian model averaging as a means of optimizing the predictive performance of common statistical models applied to large-scale educational assessments. The Bayesian framework recognizes that in addition to parameter uncertainty, there is uncertainty in the choice of models themselves. A Bayesian approach to addressing the problem of model uncertainty is the method of Bayesian model averaging. Bayesian model averaging searches the space of possible models for a set of submodels that satisfy certain scientific principles and then averages the coefficients across these submodels weighted by each model's posterior model probability (PMP). Using the weighted coefficients for prediction has been shown to yield optimal predictive performance according to certain scoring rules. We demonstrate the utility of Bayesian model averaging for prediction in education research with three examples: Bayesian regression analysis, Bayesian logistic regression, and a recently developed approach for Bayesian structural equation modeling. In each case, the model-averaged estimates are shown to yield better prediction of the outcome of interest than any submodel based on predictive coverage and the log-score rule. Implications for the design of large-scale assessments when the goal is optimal prediction in a policy context are discussed.

  6. Regression Levels of Selected Affective Factors on Science Achievement: A Structural Equation Model with TIMSS 2011 Data

    Science.gov (United States)

    Akilli, Mustafa

    2015-01-01

    The aim of this study is to demonstrate the science success regression levels of chosen emotional features of 8th grade students using Structural Equation Model. The study was conducted by the analysis of students' questionnaires and science success in TIMSS 2011 data using SEM. Initially, the factors that are thought to have an effect on science…

  7. Scale dependence of the average potential around the maximum in Φ4 theories

    International Nuclear Information System (INIS)

    Tetradis, N.; Wetterich, C.

    1992-04-01

    The average potential describes the physics at a length scale k - 1 by averaging out the degrees of freedom with characteristic moments larger than k. The dependence on k can be described by differential evolution equations. We solve these equations for the nonconvex part of the potential around the origin in φ 4 theories, in the phase with spontaneous symmetry breaking. The average potential is real and approaches the convex effective potential in the limit k → 0. Our calculation is relevant for processes for which the shape of the potential at a given scale is important, such as tunneling phenomena or inflation. (orig.)

  8. Working at the Nexus of Generic and Content-Specific Teaching Practices: An Exploratory Study Based on TIMSS Secondary Analyses

    Science.gov (United States)

    Charalambous, Charalambos Y.; Kyriakides, Ermis

    2017-01-01

    For years scholars have attended to either generic or content-specific teaching practices attempting to understand instructional quality and its effects on student learning. Drawing on the TIMSS 2007 and 2011 databases, this exploratory study empirically tests the hypothesis that attending to both types of practices can help better explain student…

  9. Israel’s Achievements in Mathematics in the Last International Examinations: Part I: The TIMSS 2011

    Directory of Open Access Journals (Sweden)

    Hanna DAVID

    2014-06-01

    Full Text Available After more than two decades of deterioration in the Israeli TIMSS results in mathematics, Israel scored number 7 among all countries participating in the world. As the probability of such a sudden, huge improvement seems negligible, this article sheds a new light on the Israel “achievements”. It shows that the students participating were not a sample according to statistical definitions and in additions – two sub-populations with the lowest Israeli achievements did not participate in this international examination.

  10. Engagement in Science Lessons and Achievement Test Scores of Eighth-Grade Students in Korea: Findings from the TIMSS 2011 Assessment

    Science.gov (United States)

    House, J. Daniel; Telese, James A.

    2015-01-01

    Scientific literacy and student engagement in science are important components of the school curriculum in Korea. In addition, several studies from the Trends in International Mathematics and Science Study (TIMSS) assessments have identified factors associated with the learning outcomes of students in Korea. The purpose of this study was to…

  11. The Effect of Teacher and Student Characteristics on TIMSS 2011 Mathematics Achievement of Fourth- and Eighth-Grade Students in Turkey

    Science.gov (United States)

    Yalcin, Seher; Demirtasli, Rahime Nükhet; Dibek, Munevver Ilgun; Yavuz, Hatice Cigdem

    2017-01-01

    This study investigated effect of student- and school-level variables on mathematics achievement of fourth- and eighth-grade students using the Trends in International Mathematics and Science Study (TIMSS) 2011 data of Turkey. The common variables addressed in student and school questionnaires were compared. Due to nested structure of the TIMSS…

  12. Identification of Large-Scale Structure Fluctuations in IC Engines using POD-Based Conditional Averaging

    Directory of Open Access Journals (Sweden)

    Buhl Stefan

    2016-01-01

    Full Text Available Cycle-to-Cycle Variations (CCV in IC engines is a well-known phenomenon and the definition and quantification is well-established for global quantities such as the mean pressure. On the other hand, the definition of CCV for local quantities, e.g. the velocity or the mixture distribution, is less straightforward. This paper proposes a new method to identify and calculate cyclic variations of the flow field in IC engines emphasizing the different contributions from large-scale energetic (coherent structures, identified by a combination of Proper Orthogonal Decomposition (POD and conditional averaging, and small-scale fluctuations. Suitable subsets required for the conditional averaging are derived from combinations of the the POD coefficients of the second and third mode. Within each subset, the velocity is averaged and these averages are compared to the ensemble-averaged velocity field, which is based on all cycles. The resulting difference of the subset-average and the global-average is identified as a cyclic fluctuation of the coherent structures. Then, within each subset, remaining fluctuations are obtained from the difference between the instantaneous fields and the corresponding subset average. The proposed methodology is tested for two data sets obtained from scale resolving engine simulations. For the first test case, the numerical database consists of 208 independent samples of a simplified engine geometry. For the second case, 120 cycles for the well-established Transparent Combustion Chamber (TCC benchmark engine are considered. For both applications, the suitability of the method to identify the two contributions to CCV is discussed and the results are directly linked to the observed flow field structures.

  13. Achievement of Eighth-Grade Students in Korea on the TIMSS 2011 Assessment: Effects of Confidence in Mathematics and Engagement in Mathematics Lessons

    Science.gov (United States)

    House, J. Daniel; Telese, James A.

    2016-01-01

    Research studies have identified several factors related to mathematics achievement of students in Korea. Further, results from the Trends in International Mathematics and Science Study (TIMSS) assessments have shown that instructional practices and beliefs about mathematics were significantly associated with mathematics achievement of students in…

  14. The effect of various grading scales on student grade point averages.

    Science.gov (United States)

    Barnes, Kelli D; Buring, Shauna M

    2012-04-10

    To investigate changes in and the impact of grading scales from 2005 to 2010 and explore pharmacy faculty and student perceptions of whole-letter and plus/minus grading scales on cumulative grade point averages (GPAs) in required courses. Grading scales used in 2010 at the University of Cincinnati College of Pharmacy were retrospectively identified and compared to those used in 2005. Mean GPA was calculated using a whole-letter grading scale and a plus/minus grading scale to determine the impact of scales on GPA. Faculty members and students were surveyed regarding their perceptions of plus/minus grading. Nine unique grading scales were used throughout the curriculum, including plus/minus (64%) and whole-letter (21%) grading scales. From 2005 to 2010 there was transition from use of predominantly whole-letter scales to plus/minus grading scales. The type of grading scale used did not affect the mean cumulative GPA. Students preferred use of a plus-only grading scale while faculty members preferred use of a plus/minus grading scale. The transition from whole-letter grading to plus/minus grading in courses from 2005 to 2010 reflects pharmacy faculty members' perception that plus/minus grading allows for better differentiation between students' performances.

  15. Influence of number of topics, topic duration, and curricular focus on biology achievement of Population 3 TIMSS countries

    Science.gov (United States)

    Hodges, Eddie Louis

    The purposes of this study were to determine if a relationship exists between biology achievement and (1) number of topics, (2) topic duration, (3) curricular focus, and (4) science achievement using TIMSS data from Population 3---the final year of secondary school. Students included in this study were subsets of the 55,675 students from 22 countries who participated in the science literacy portion of TIMSS at the Population 3 level (IEA, 1997). The sample included in this study for the four research questions were comprised of between (1) 17,769 and 37,794 students from 15 countries, (2) 17,769 and 37,794 students from 15 countries, (3) 21,715 and 46,458 students from 18 countries, and (4) 19,518 and 46,458 students from 18 countries, respectively. A Pearson's product moment correlation was used to determine whether a relationship exists between the number of biology topics addressed by intended national science curricula and mean student achievement on selected items by country. No statistically significant correlation was found by country between biology achievement and number of topics. To determine whether a relationship exists between the topic duration of biology topics addressed by released, biology-oriented, Population 3 Science Literacy items and student achievement on those items, a Pearson's product moment correlation was also used. A statistically significant correlation between biology achievement and topic duration for only one topic (Interdependence of Life) was found at the .05 level of significance. A possible relationship between the degree of curricular focus of Population 3 TIMSS countries and student achievement on selected items by country was evaluated using a Pearson's product moment correlation. No statistically significant correlation by country between biology achievement and degree of curricular focus was found. A Pearson's product moment correlation was used to determine whether a relationship exists between science literacy

  16. TIMSS 2011: Relationship between self-confidence and cognitive achievement for Serbia and Slovenia

    Directory of Open Access Journals (Sweden)

    Gordana Miscevic Kadijevic

    2015-08-01

    Full Text Available By using TIMSS Grade 4 2011 science data for Serbia and Slovenia, this study examined which of two dimensions towards science learning (self-confidence in learning science, or liking learning science, if any, was primarily related to students' cognitive achievement in science. This achievement was considered for three cognitive domains, namely: Knowing, Applying, and Reasoning. The analysis revealed that, in both countries, achievement was mainly linked to self-confidence in each of the three cognitive domains. Because of positive correlations, classroom work may be improved by including, whenever possible, activities aimed at strengthening students' beliefs in their own abilities to learn science.

  17. The effects of school policies and practices on eighth-grade science achievement: A multilevel analysis of TIMSS

    Science.gov (United States)

    Smyth, Carol Ann Mary

    Identifying the relative importance of both alterable school policies and fairly stable contextual factors as they relate to middle level science achievement, a domain of identified national concern, requires simultaneous investigation of multilevel predictors (i.e., student level and school level) specific to the grade level and academic subject area. The school level factors are predictors associated with both the school (e.g., average socioeconomic status, tracking, and instructional time) and the classroom (e.g., average academic press of peers, teacher collaboration, and instructional strategies). The current study assessed the effects of school policies, practices, and contextual factors on the science achievement of eighth grade students. These influences were considered to be both additive (i.e., influencing the mean achievement in a school after controlling for student characteristics) and interactive (i.e., affecting the relationships between student background characteristics and individual achievement). To account for the nested structure of predictors and cross level interactions among predictors, a multilevel model for middle level science achievement was estimated using hierarchical linear modeling (HLM) with data collected from eighth grade students, science teachers, and administrators in 1995 as part of the Third International Mathematics and Science Study (TIMSS). The major findings of this research suggest that although average eighth grade science achievement in a school was primarily associated with the contextual characteristics of the classroom and the school (e.g., average socioeconomic status and average academic press), both the academic differentiating influence of prior achievement and the social differentiating influence of parental education on the science achievement of eighth grade students were related not only to contextual characteristics of the classroom and the school, but also to the instructional policies of the classroom

  18. Examining the Big-Fish-Little-Pond Effect on Students' Self-Concept of Learning Science in Taiwan Based on the TIMSS Databases

    Science.gov (United States)

    Liou, Pey-Yan

    2014-01-01

    The purpose of this study is to examine the relationship between student self-concept and achievement in science in Taiwan based on the big-fish-little-pond effect (BFLPE) model using the Trends in International Mathematics and Science Study (TIMSS) 2003 and 2007 databases. Hierarchical linear modeling was used to examine the effects of the…

  19. Standard Errors for National Trends in International Large-Scale Assessments in the Case of Cross-National Differential Item Functioning

    Science.gov (United States)

    Sachse, Karoline A.; Haag, Nicole

    2017-01-01

    Standard errors computed according to the operational practices of international large-scale assessment studies such as the Programme for International Student Assessment's (PISA) or the Trends in International Mathematics and Science Study (TIMSS) may be biased when cross-national differential item functioning (DIF) and item parameter drift are…

  20. What Specific Science Abilities and Skills Are Romanian Students Developing during Primary Education? A Comparison with the Abilities Tested by the TIMSS 2011 Inquiry

    Science.gov (United States)

    Ciascai, Liliana; Dulama, Maria-Eliza

    2013-01-01

    The results of Romanian students at international comparative TIMSS and PISA tests have constantly proven to be unsatisfactory. The present paper aims at analyzing the school syllabi "Mathematics and Environment exploration", "Environmental Education" and "Natural Sciences" studied during primary education in Romania…

  1. Mathematics achievement of Serbian eighth grade students and characteristics of mathematics curriculum

    Directory of Open Access Journals (Sweden)

    Antonijević Radovan M.

    2006-01-01

    Full Text Available This paper considers the main results and some educational implications of the TIMSS 2003 assessment conducted in Serbia, in the fields of mathematics achievement of Serbian eighth grade students and the mathematics curriculum context of their achievement. It was confirmed that Serbian eighth graders have made average scale score of 477 points, and with this achievement they are placed in the zone of intermediate international benchmarking level. The average mathematics achievement of the Serbian eighth graders is somewhat above the average international mathematics achievement. The best result was achieved in the content domain of "algebra", and the lower result in the content domains of "measurement" and "data". In the defined cognitive domains the Serbian students have achieved the best results in "solving routine problems" and "knowing facts and procedures", and the weaker result in "reasoning". Statistically significant difference was found in the mathematics achievement between girls and boys in the Serbian TIMSS 2003 sample, so the girls’ average scale score was 480 points and the same value for the boys was 473 points. The achieved results raise many questions about the contents of mathematics curriculum in Serbia, its quality and basic characteristics of its implementation. These results can be eligibly used to improve the mathematics curriculum and teaching in Serbian primary school.

  2. Implementation of large-scale average geostrophic wind shear in WAsP12.1

    DEFF Research Database (Denmark)

    Floors, Rogier Ralph; Troen, Ib; Kelly, Mark C.

    The vertical extrapolation model described in the European Wind Atlas Troen and Petersen (1989) is modified to take into account large-scale average geostrophic wind shear to describe the effect of horizontal temperature gradients on the geostrophic wind. The method is implemented by extracting...... the average geostrophic wind shear from Climate Forecast System Reanalysis (CFSR) data and the values of nearest grid point are automatically used in the WAsP 12.1 user interface to provide better AEP predictions....

  3. Relationship between teacher preparedness and inquiry-based instructional practices to students' science achievement: Evidence from TIMSS 2007

    Science.gov (United States)

    Martin, Lynn A.

    The purpose of this study was to examine the relationship between teachers' self-reported preparedness for teaching science content and their instructional practices to the science achievement of eighth grade science students in the United States as demonstrated by TIMSS 2007. Six hundred eighty-seven eighth grade science teachers in the United States representing 7,377 students responded to the TIMSS 2007 questionnaire about their instructional preparedness and their instructional practices. Quantitative data were reported. Through correlation analysis, the researcher found statistically significant positive relationships emerge between eighth grade science teachers' main area of study and their self-reported beliefs about their preparedness to teach that same content area. Another correlation analysis found a statistically significant negative relationship existed between teachers' self-reported use of inquiry-based instruction and preparedness to teach chemistry, physics and earth science. Another correlation analysis discovered a statistically significant positive relationship existed between physics preparedness and student science achievement. Finally, a correlation analysis found a statistically significant positive relationship existed between science teachers' self-reported implementation of inquiry-based instructional practices and student achievement. The data findings support the conclusion that teachers who have feelings of preparedness to teach science content and implement more inquiry-based instruction and less didactic instruction produce high achieving science students. As science teachers obtain the appropriate knowledge in science content and pedagogy, science teachers will feel prepared and will implement inquiry-based instruction in science classrooms.

  4. Analyzing Turkey's data from TIMSS 2007 to investigate regional disparities in eighth grade science achievement

    Science.gov (United States)

    Erberber, Ebru

    Turkey is expected to be a full member of the European Union (EU) by 2013. In the course of its integration into the EU, Turkey has been simultaneously facing access, quality, and equity issues in education. Over the past decade, substantial progress has been made on increasing the access. However, improving the country's low level of education quality and achieving equity in quality education across the regions continue to be a monumental challenge in Turkey. Most recently, results from the Trends in International Mathematics and Science Study (TIMSS) 2007 indicated that Turkey's educational achievement at the eighth grade, the end of compulsory primary education in Turkey, was far below that of other countries in the EU. Considering Turkey's long standing socioeconomic disparities between the western and eastern parts of the country, the challenges of improving overall education quality are coupled with the challenges of achieving equity in learning outcomes for students across the regions. This dissertation used data from TIMSS 2007 to document the extent of Turkey's regional differences in science achievement at the eighth grade and to investigate factors associated with these differences. Findings from a series of analyses using hierarchical linear models suggested that attempts to increase Turkish students' achievement and close the achievement gaps between regions should target the students in the undeveloped regions, particularly in Southeastern Anatolia and Eastern Anatolia. Designing interventions to improve competency in Turkish and to compensate for the shortcomings of insufficient parental education, limited home educational resources, poor school climate for academic achievement, and inadequate instructional equipment and facilities might be expected to close the regional achievement gaps as well as raise the overall achievement level in Turkey.

  5. Instantaneous equations for multiphase flow in porous media without length-scale restrictions using a non-local averaging volume

    International Nuclear Information System (INIS)

    Espinosa-Paredes, Gilberto

    2010-01-01

    The aim of this paper is to propose a framework to obtain a new formulation for multiphase flow conservation equations without length-scale restrictions, based on the non-local form of the averaged volume conservation equations. The simplification of the local averaging volume of the conservation equations to obtain practical equations is subject to the following length-scale restrictions: d << l << L, where d is the characteristic length of the dispersed phases, l is the characteristic length of the averaging volume, and L is the characteristic length of the physical system. If the foregoing inequality does not hold, or if the scale of the problem of interest is of the order of l, the averaging technique and therefore, the macroscopic theories of multiphase flow should be modified in order to include appropriate considerations and terms in the corresponding equations. In these cases the local form of the averaged volume conservation equations are not appropriate to describe the multiphase system. As an example of the conservation equations without length-scale restrictions, the natural circulation boiling water reactor was consider to study the non-local effects on the thermal-hydraulic core performance during steady-state and transient behaviors, and the results were compared with the classic local averaging volume conservation equations.

  6. The Effects of Homework Activities and Teaching Strategies for New Mathematics Topics on Achievement of Adolescent Students in Japan: Results from the TIMSS 1999 Assessment

    Science.gov (United States)

    House, J. Daniel

    2004-01-01

    The importance of homework activities for student achievement has been extensively discussed. Research has indicated that, in general, students who spend more time on homework tend to show higher levels of academic achievement. For instance, results from the Third International Mathematics Study (TIMSS) indicated that adolescent students in Japan…

  7. Translation and Adaptation of Tests: Lessons Learned and Recommendations for Countries Participating in timss, pisa and other International Comparisons

    Directory of Open Access Journals (Sweden)

    Guillermo Solano-Flores

    2006-11-01

    Full Text Available In this paper we present a conceptual model and methodology for the review of translated tests in the context of such international comparisons as the Trends in International Mathematics and Science Study (TIMSS and the Programme for International Student Assessment (PISA. We also present the results of an investigation into the quality of the Mexican translation of the TIMSS-1995 into the Spanish language. We identified translation errors in a significant percentage of the items, as well as relatively high correlations between the severity of translation errors and the items’ p-values. These findings indicate that our error-coding system is highly sensitive to test-translation error. The results underscore the need for improved translation and translation-review procedures in international comparisons. In our opinion, to implement the guidelines properly for test translation in international comparisons, each participating country needs to have internal procedures that would ensure a rigorous review of its own translations. The article concludes with four recommendations for countries participating in international comparisons. These recommendations relate to: (a the characteristics of the individuals in charge of translating instruments; (b the use of review, not simply at the end of the process, but during the process of test translation; (c the minimum time needed for various translation review iterations to take place; and (d the need for proper documentation of the entire process of test translation.

  8. Defining the Relationship of Student Achievement Between STEM Subjects Through Canonical Correlation Analysis of 2011 Trends in International Mathematics and Science Study (TIMSS) Data

    Science.gov (United States)

    O'Neal, Melissa Jean

    Canonical correlation analysis was used to analyze data from Trends in International Mathematics and Science Study (TIMSS) 2011 achievement databases encompassing information from fourth/eighth grades. Student achievement in life science/biology was correlated with achievement in mathematics and other sciences across three analytical areas: mathematics and science student performance, achievement in cognitive domains, and achievement in content domains. Strong correlations between student achievement in life science/biology with achievement in mathematics and overall science occurred for both high- and low-performing education systems. Hence, partial emphases on the inter-subject connections did not always lead to a better student learning outcome in STEM education. In addition, student achievement in life science/biology was positively correlated with achievement in mathematics and science cognitive domains; these patterns held true for correlations of life science/biology with mathematics as well as other sciences. The importance of linking student learning experiences between and within STEM domains to support high performance on TIMSS assessments was indicated by correlations of moderate strength (57 TIMSS assessments was indicated by correlations of moderate strength (57 mathematics, and other sciences. At the eighth grade level, students who built increasing levels of cognitive complexity upon firm foundations were prepared for successful learning throughout their educational careers. The results from this investigation promote a holistic design of school learning opportunities to improve student achievement in life science/biology and other science, technology, engineering, and mathematics (STEM) subjects at the elementary and middle school levels. While the curriculum can vary from combined STEM subjects to separated mathematics or science courses, both professional learning communities (PLC) for teachers and problem-based learning (PBL) for learners can be

  9. Volume 42, Issue5 (May 2005)Articles in the Current Issue:Developmental growth in students' concept of energy: Analysis of selected items from the TIMSS database

    Science.gov (United States)

    Liu, Xiufeng; McKeough, Anne

    2005-05-01

    The aim of this study was to develop a model of students' energy concept development. Applying Case's (1985, 1992) structural theory of cognitive development, we hypothesized that students' concept of energy undergoes a series of transitions, corresponding to systematic increases in working memory capacity. The US national sample from the Third International Mathematics and Science Study (TIMSS) database was used to test our hypothesis. Items relevant to the energy concept in the TIMSS test booklets for three populations were identified. Item difficulty from Rasch modeling was used to test the hypothesized developmental sequence, and percentage of students' correct responses was used to test the correspondence between students' age/grade level and level of the energy concepts. The analysis supported our hypothesized sequence of energy concept development and suggested mixed effects of maturation and schooling on energy concept development. Further, the results suggest that curriculum and instruction design take into consideration the developmental progression of students' concept of energy.

  10. The average carbon-stock approach for small-scale CDM AR projects

    Energy Technology Data Exchange (ETDEWEB)

    Garcia Quijano, J.F.; Muys, B. [Katholieke Universiteit Leuven, Laboratory for Forest, Nature and Landscape Research, Leuven (Belgium); Schlamadinger, B. [Joanneum Research Forschungsgesellschaft mbH, Institute for Energy Research, Graz (Austria); Emmer, I. [Face Foundation, Arnhem (Netherlands); Somogyi, Z. [Forest Research Institute, Budapest (Hungary); Bird, D.N. [Woodrising Consulting Inc., Belfountain, Ontario (Canada)

    2004-06-15

    In many afforestation and reforestation (AR) projects harvesting with stand regeneration forms an integral part of the silvicultural system and satisfies local timber and/or fuelwood demand. Especially clear-cut harvesting will lead to an abrupt and significant reduction of carbon stocks. The smaller the project, the more significant the fluctuations of the carbon stocks may be. In the extreme case a small-scale project could consist of a single forest stand. In such case, all accounted carbon may be removed during a harvesting operation and the time-path of carbon stocks will typically look as in the hypothetical example presented in the report. For the aggregate of many such small-scale projects there will be a constant benefit to the atmosphere during the projects, due to averaging effects.

  11. Analisis Deskriptif Soal Geometri dalam Buku Matematika Bilingual untuk Sekolah Menengah Pertama Kelas VIII Berdasarkan Kriteria International Assessment TIMSS 2007

    Directory of Open Access Journals (Sweden)

    Etik Rahayu

    2012-06-01

    Full Text Available Tujuan penelitian ini adalah untuk mendeskripsikan  domain kognitif dan aspek kognitif (required behavior soal matematika dalam Buku Matematika Bilingual untuk Sekolah Menengah Pertama (SMP Kelas VIII berdasarkan kriteria International Assessment TIMSS 2007 dan proporsinya. Metode penelitian yang digunakan adalah deskriptif kualitatif, dengan subjek penelitian adalah soal geometri dalam Buku Matematika Bilingual SMP. yang berjudul “Mathematics for Junior High School Grade VIII 1st Semester” dan “Mathematics for Junior High School Grade VIII 2nd Semester” karangan karangan M. Cholik Adinawan dan Sugijono. Pengumpulan data menggunakan metode observasi dan wawancara tentang penggunaan buku matematika bilingual yang paling banyak digunakan di kota semarang. Pedoman analisis soal berdasarkan kriteria International Assessment TIMSS 2007, dengan validasi hasil oleh ahli. Hasil penelitian menunjukkan bahwa soal yang dianalisis memuat satu hingga tujuh aspek kognitif. Sebagian besar soal memuat 4 aspek kognitif yaitu 44.04 %, diikuti soal dengan 3 aspek kognitif  yaitu 36, 42%,  soal dengan 2 aspek kognitif yaitu 14, 90%, kemudian 1,99% untuk soal dengan 1 atau 5 aspek kognitif, dan 0,33% untuk soal dengan 6 atau 7 aspek kognitif. Proporsi tinggi pada recall (28.26% dan compute (26.57%, diikuti dengan SRP (10.85%, implement (10.65%, retrieve (8.36%, recognize (6.17%, analyze (1.99%, measure (1.59%, generalize (1.09%, SNRP (1.00%, classify (0.80%, represent (0.80%, justify (0.80%, select (0.60%, model (0.30%, synthesis (0.20%. Secara keseluruhan berdasarkan International Assessment TIMSS 2007 soal yang termasuk domain knowing memiliki persentase paling tinggi (52.28%, domain knowing-applying (24.83%, domain knowing- reasoning (12.91%, dan hanya sedikit yang termasuk domain knowing-apllying-reasoning (3.97%. Serta terdapat 4 soal (1.32% yang mempunyai ketidaksesuaian penggunaan mathematics terms serta 1 soal (0

  12. The Development of Statistical Literacy Skills in the Eighth Grade: Exploring the TIMSS Data to Evaluate Student Achievement and Teacher Characteristics in the United States

    Science.gov (United States)

    Mills, Jamie D.; Holloway, Charles E.

    2013-01-01

    This study investigated the relationship between student achievement in statistics and factors at the student and teacher/classroom levels using the US 8th-grade Data and Chance content domain from the Trends in International Mathematics and Science Study, 2007 (TIMSS, 2007). Using variables that have been linked to mathematics and statistics…

  13. Mathematics beliefs and achievement of adolescent students in Japan: results from the TIMSS 1999 assessment.

    Science.gov (United States)

    House, J Daniel

    2005-12-01

    A recent study (1) of undergraduate students in a precalculus course indicated that they expressed slightly positive attitudes toward mathematics. It is important, however, to examine relationships between students' initial attitudes and achievement outcomes. The present purpose was to assess the relationship between self-beliefs and mathematics achievement for a large national sample of students from the TIMSS 1999 international sample (eighth graders) from Japan. Several significant relationships between mathematics beliefs and test scores were noted. In addition, the overall multiple regression equation that assessed the joint significance of the complete set of self-belief variables was significant (F7.65 = 159.48, p < .001) and explained 20.6% of the variance in mathematics achievement test scores.

  14. Multi-Repeated Projection Lithography for High-Precision Linear Scale Based on Average Homogenization Effect

    Directory of Open Access Journals (Sweden)

    Dongxu Ren

    2016-04-01

    Full Text Available A multi-repeated photolithography method for manufacturing an incremental linear scale using projection lithography is presented. The method is based on the average homogenization effect that periodically superposes the light intensity of different locations of pitches in the mask to make a consistent energy distribution at a specific wavelength, from which the accuracy of a linear scale can be improved precisely using the average pitch with different step distances. The method’s theoretical error is within 0.01 µm for a periodic mask with a 2-µm sine-wave error. The intensity error models in the focal plane include the rectangular grating error on the mask, static positioning error, and lithography lens focal plane alignment error, which affect pitch uniformity less than in the common linear scale projection lithography splicing process. It was analyzed and confirmed that increasing the repeat exposure number of a single stripe could improve accuracy, as could adjusting the exposure spacing to achieve a set proportion of black and white stripes. According to the experimental results, the effectiveness of the multi-repeated photolithography method is confirmed to easily realize a pitch accuracy of 43 nm in any 10 locations of 1 m, and the whole length accuracy of the linear scale is less than 1 µm/m.

  15. Scaling Relations and Self-Similarity of 3-Dimensional Reynolds-Averaged Navier-Stokes Equations.

    Science.gov (United States)

    Ercan, Ali; Kavvas, M Levent

    2017-07-25

    Scaling conditions to achieve self-similar solutions of 3-Dimensional (3D) Reynolds-Averaged Navier-Stokes Equations, as an initial and boundary value problem, are obtained by utilizing Lie Group of Point Scaling Transformations. By means of an open-source Navier-Stokes solver and the derived self-similarity conditions, we demonstrated self-similarity within the time variation of flow dynamics for a rigid-lid cavity problem under both up-scaled and down-scaled domains. The strength of the proposed approach lies in its ability to consider the underlying flow dynamics through not only from the governing equations under consideration but also from the initial and boundary conditions, hence allowing to obtain perfect self-similarity in different time and space scales. The proposed methodology can be a valuable tool in obtaining self-similar flow dynamics under preferred level of detail, which can be represented by initial and boundary value problems under specific assumptions.

  16. Důraz školy na akademický úspěch: TIMSS 2011 jako sonda do reformy v České republice/ School emphasis on academic success in TIMSS 2011 as a window on curricular reform in the Czech Republic

    Directory of Open Access Journals (Sweden)

    Dominik Dvořák

    2015-04-01

    Full Text Available V šetření TIMSS 2011 se objevil index nazvaný „důraz školy na studijní úspěch“ (SEAS. Cílem článku je osvětlit skutečnost, že české školy vykazují poměrně nápadné hodnoty tohoto indexu. Dále pomocí SEAS analyzuje vztah mezi postoji českých škol k reformě a znalostmi a dovednostmi jejich žáků. Teoretický úvod popisuje konstrukt akademický optimismus a index SEAS zavedený v šetření TIMSS. Následně je provedena explorativní sekundární analýza dat o úrovni složek SEAS v případě českých škol se zaměřením na nápadné odchylky hodnot. Práce vychází z výsledků žáků čtvrtých ročníků v matematickém testu TIMSS 2011 a z odpovídajících učitelských a ředitelských dotazníků. Pro analýzu vztahů v datech jsou použity základní prostředky popisné a inferenční statistiky. Zjištění ukazují na disproporčně nízkou důvěru ředitelů ve snahu žáků ve škole dobře prospívat, která je společná regionálnímu klastru zemí. Dále analýza přinesla nečekaná zjištění o vztahu mezi postoji ředitelů a učitelů ke kurikulární reformě a výsledky jejich žáků v matematice. Z literatury známá i naše původní zjištění o komponentách indexu SEAS v podmínkách českých škol přinášejí zajímavé pohledy mj. na vnímání reformních procesů v českých školách a doplňují tak literaturu o implementaci, resp. recepci reformy.

  17. 透過PISA與TIMSS評比研究檢視西方與亞洲學生數學的相對強項 Using PISA and TIMSS Mathematics Assessments to Identify the Relative Strengths of Students in Western and Asian Countries

    Directory of Open Access Journals (Sweden)

    張立民 Margaret Wu

    2011-03-01

    Full Text Available Wu(2009)的研究曾將2003 年「國際學生能力評量計畫」(Programme for International Student Assessment, PISA)的數學表現,與「國際數學與科學教育成就趨勢調查」(Trends in International Mathematics and Science Study, TIMSS)八年級學生的數學表現做一比較,結果發現,西方國家在PISA 的表現大致上比在TIMSS的表現為佳。本研究則將TIMSS公開的題目分為兩組,一組與PISA 的架構相符,另一組則不相符。其中,TIMSS評比有很多幾何與代數的題目是屬於「純粹的數學」題(即未以真實生活情境作為背景的數學題),而這些題目並未出現在PISA 評比之中。本研究檢視六個國家在這兩組題目表現上的差異,藉此反映出西方與亞洲國家的相對強項與弱點,接著再將這些強項與弱點連結到PISA與TIMSS評比的內容上。有證據顯示,西方與亞洲國家在PISA 與TIMSS的差異表現可歸因於兩評比題目種類的不同。 A study was carried out that compared Programme for International Student Assessment (PISA 2003 Mathematics results with Trends in International Mathematics and Science Study (TIMSS 2003 Grade 8 Mathematics results (Wu, 2009. It was found that Western countries generally performed better in PISA than in TIMSS, and Eastern European and Asian countries generally performed better in TIMSS than in PISA. In this paper, TIMSS released items are divided into two sets: one that fits the PISA framework and one that does not. In particular, many geometry and algebra items in TIMSS are “inner mathematics” (mathematics without a real-life context, and such items do not appear in the PISA test. Differential performances of six countries on each set of items are examined. In this way, the relative strengths and weaknesses of Western and Asian countries are identified. These strengths and weaknesses are then linked back to the contents of the PISA and TIMSS

  18. TIMSS 2003: Relating dimensions of mathematics attitude to mathematics achievement

    Directory of Open Access Journals (Sweden)

    Kadijević Đorđe

    2008-01-01

    Full Text Available This study, which used a sample of 137,346 students from thirty three countries that participated in the TIMSS 2003 project in the eighth grade, examined the features of the individual and collective relations of three dimensions of mathematics attitude to mathematics achievement (MA, searching for the dimension mostly related to that achievement. The three dimensions of mathematics attitude were self-confidence in learning mathematics (SCLM, liking mathematics (LM and usefulness of mathematics (UM. By utilizing psychometrically valid and reliable measures of the three dimensions, it was found that: (1 each dimension of mathematics attitude alone was positively related to MA for almost all thirty three countries; (2 SCLM was primarily related to MA for thirty one countries; (3 when the two other dimensions were held constant, SCLM was positively related to MA for thirty three countries, LM was negatively related to MA for thirty countries, whereas UM was not related to MA for twenty one countries; (4 positive collective relationships of SCLM, LM and UM to MA considerably varied from country to country. Implications for research and practice are included.

  19. The Effects of Item Format and Cognitive Domain on Students' Science Performance in TIMSS 2011

    Science.gov (United States)

    Liou, Pey-Yan; Bulut, Okan

    2017-12-01

    The purpose of this study was to examine eighth-grade students' science performance in terms of two test design components, item format, and cognitive domain. The portion of Taiwanese data came from the 2011 administration of the Trends in International Mathematics and Science Study (TIMSS), one of the major international large-scale assessments in science. The item difficulty analysis was initially applied to show the proportion of correct items. A regression-based cumulative link mixed modeling (CLMM) approach was further utilized to estimate the impact of item format, cognitive domain, and their interaction on the students' science scores. The results of the proportion-correct statistics showed that constructed-response items were more difficult than multiple-choice items, and that the reasoning cognitive domain items were more difficult compared to the items in the applying and knowing domains. In terms of the CLMM results, students tended to obtain higher scores when answering constructed-response items as well as items in the applying cognitive domain. When the two predictors and the interaction term were included together, the directions and magnitudes of the predictors on student science performance changed substantially. Plausible explanations for the complex nature of the effects of the two test-design predictors on student science performance are discussed. The results provide practical, empirical-based evidence for test developers, teachers, and stakeholders to be aware of the differential function of item format, cognitive domain, and their interaction in students' science performance.

  20. Comparison among cognitive diagnostic models for the TIMSS 2007 fourth grade mathematics assessment.

    Science.gov (United States)

    Yamaguchi, Kazuhiro; Okada, Kensuke

    2018-01-01

    A variety of cognitive diagnostic models (CDMs) have been developed in recent years to help with the diagnostic assessment and evaluation of students. Each model makes different assumptions about the relationship between students' achievement and skills, which makes it important to empirically investigate which CDMs better fit the actual data. In this study, we examined this question by comparatively fitting representative CDMs to the Trends in International Mathematics and Science Study (TIMSS) 2007 assessment data across seven countries. The following two major findings emerged. First, in accordance with former studies, CDMs had a better fit than did the item response theory models. Second, main effects models generally had a better fit than other parsimonious or the saturated models. Related to the second finding, the fit of the traditional parsimonious models such as the DINA and DINO models were not optimal. The empirical educational implications of these findings are discussed.

  1. Length-scale dependent ensemble-averaged conductance of a 1D disordered conductor: Conductance minimum

    International Nuclear Information System (INIS)

    Tit, N.; Kumar, N.; Pradhan, P.

    1993-07-01

    Exact numerical calculation of ensemble averaged length-scale dependent conductance for the 1D Anderson model is shown to support an earlier conjecture for a conductance minimum. Numerical results can be understood in terms of the Thouless expression for the conductance and the Wigner level-spacing statistics. (author). 8 refs, 2 figs

  2. Comparison among cognitive diagnostic models for the TIMSS 2007 fourth grade mathematics assessment.

    Directory of Open Access Journals (Sweden)

    Kazuhiro Yamaguchi

    Full Text Available A variety of cognitive diagnostic models (CDMs have been developed in recent years to help with the diagnostic assessment and evaluation of students. Each model makes different assumptions about the relationship between students' achievement and skills, which makes it important to empirically investigate which CDMs better fit the actual data. In this study, we examined this question by comparatively fitting representative CDMs to the Trends in International Mathematics and Science Study (TIMSS 2007 assessment data across seven countries. The following two major findings emerged. First, in accordance with former studies, CDMs had a better fit than did the item response theory models. Second, main effects models generally had a better fit than other parsimonious or the saturated models. Related to the second finding, the fit of the traditional parsimonious models such as the DINA and DINO models were not optimal. The empirical educational implications of these findings are discussed.

  3. The TIMSS Videotape Classroom Study: Methods and Findings from an Exploratory Research Project on Eighth-Grade Mathematics Instruction in Germany, Japan, and the United States. A Research and Development Report.

    Science.gov (United States)

    Stigler, James W.; Gonzales, Patrick; Kwanaka, Takako; Knoll, Steffen; Serrano, Ana

    This report presents the methods and preliminary findings of the Videotape Classroom Study, a video study of eighth-grade mathematics lessons in Germany, Japan, and the United States. This exploratory research project is part of the Third International Mathematics and Science Study (TIMSS). The study included 231 eighth-grade mathematics…

  4. Premigration School Quality, Time Spent in the United States, and the Math Achievement of Immigrant High School Students.

    Science.gov (United States)

    Bozick, Robert; Malchiodi, Alessandro; Miller, Trey

    2016-10-01

    Using a nationally representative sample of 1,189 immigrant youth in American high schools, we examine whether the quality of education in their country of origin is related to post-migration math achievement in the 9th grade. To measure the quality of their education in the country of origin, we use country-specific average test scores from two international assessments: the Programme for International Student Assessment (PISA) and the Trends in International Mathematics and Science Study (TIMSS). We find that the average PISA or TIMSS scores for immigrant youth's country of origin are positively associated with their performance on the 9th grade post-migration math assessment. We also find that each year spent in the United States is positively associated with performance on the 9th grade post-migration math assessment, but this effect is strongest for immigrants from countries with low PISA/TIMSS scores.

  5. Effects of Public Preschool Expenditures on the Test Scores of 4 Graders: Evidence from TIMSS.

    Science.gov (United States)

    Waldfogel, Jane; Zhai, Fuhua

    2008-02-01

    This study examines the effects of public preschool expenditures on the math and science scores of 4(th) graders, holding constant child, family, and school characteristics, other relevant social expenditures, and country and year effects, in seven Organization for Economic Co-operation and Development (OECD) countries -- Australia, Japan, Netherlands, New Zealand, Norway, U.K., and U.S -- using data from the 1995 and 2003 Trends in International Mathematics and Science Study (TIMSS). Our results indicate that there are small but significant positive effects of public preschool expenditures on the math and science scores of 4(th) graders and preschool expenditures reduce the risk of children scoring at the low level of proficiency. We also find some evidence that children from low-resource homes and homes where the test language is not always spoken may tend to gain more from increased public preschool expenditures than other children,.

  6. A Comparative Study of Geometry in Elementary School Mathematics Textbooks from Five Countries

    Science.gov (United States)

    Wang, Tzu-Ling; Yang, Der-Ching

    2016-01-01

    The purposes of this study were to compare the differences in the use of geometry in elementary school mathematics textbooks among Finland, Mainland China, Singapore, Taiwan, and the USA and to investigate the relationships between the design of the textbooks and students' performance on large-scale tests such as TIMSS-4 geometry, TIMSS-8…

  7. Relationships Among Teacher Preparedness and Instructional Approaches to Secondary Student Achievement in STEM: A Secondary Analysis of TIMSS Data

    Science.gov (United States)

    Miller-Ricks, Karen A.

    Educational reform efforts in Science, Technology, Engineering, Math (STEM) place emphasis on teachers as conduits for student achievement. The purpose of this study was to use TIMSS 2011 data to examine relationships between Science-Technology-Society (STS) instructional practices (student-centered instruction established to promote learning through real-world applications) teacher preparedness, and student achievement and identify variations of achievement between and among eighth-grade science and math classes. The research was framed by both Harper's Anti-Deficit Achievement Theory and Bronfenbrenner's Ecological Systems Theory (BEST). 501 U.S. schools contributed to the TIMSS 2011 data from both the teacher questionnaires and student booklets. Chi-Square, Spearman Correlation, and 2-level hierarchical linear modeling (HLM) were used to analyze data about teachers' preparedness to teach science and math, frequency of using STS instructional practices, and student achievement. The chi-square null hypothesis for math teachers was rejected, providing the assumption that there was an association between the frequency of using STS instruction in math and teacher preparedness. However, the chi-square null hypothesis for science teachers failed to be rejected, providing the assumption that there was no significant association between the frequency of using STS instruction in science and science teacher preparedness. The Spearman Correlation revealed statistically positively significant differences between STS instruction and science achievement, as well as between teacher preparedness and science achievement. The HLM results suggested that 33% of the variance of mathematics achievement was at the individual level and 66% was at the group level. The results for science teachers suggested that 54% of the variance of science achievement was at the individual level and 46% of the variance was at the group level. The data findings support the conclusion that secondary STEM

  8. Science Understanding through Playground Physics: Organized Recess Teaching (SUPPORT)

    Science.gov (United States)

    Kincaid, Russell

    2010-03-01

    From 1995-2007, U.S. science students in grade four scored higher than the scaled TIMSS average, but their scores did not improve over this time. Moreover, in the area of physical science, the U.S. scored significantly lower than several Asian countries, as well as Russia, England, and Latvia (TIMSS). Methods to enhance student achievement in science are still being sought. An approach to utilizing playground equipment as a teaching tool for a variety of physics concepts was developed as a physical science teaching method. This program established an appropriate set of experiments, coordinated the effort with local school districts, and implemented a brief pilot study to test the teaching methodology. The program assigned undergraduate middle school science education majors to teach small groups of fourth grade students. The experimental group used the newly developed ``Playground Physics'' methodology while the control group used traditional approaches. Follow up activities will include an expansion of the duration and the scope of the program.

  9. Effects of Public Preschool Expenditures on the Test Scores of 4th Graders: Evidence from TIMSS

    Science.gov (United States)

    Waldfogel, Jane; Zhai, Fuhua

    2011-01-01

    This study examines the effects of public preschool expenditures on the math and science scores of 4th graders, holding constant child, family, and school characteristics, other relevant social expenditures, and country and year effects, in seven Organization for Economic Co-operation and Development (OECD) countries -- Australia, Japan, Netherlands, New Zealand, Norway, U.K., and U.S -- using data from the 1995 and 2003 Trends in International Mathematics and Science Study (TIMSS). Our results indicate that there are small but significant positive effects of public preschool expenditures on the math and science scores of 4th graders and preschool expenditures reduce the risk of children scoring at the low level of proficiency. We also find some evidence that children from low-resource homes and homes where the test language is not always spoken may tend to gain more from increased public preschool expenditures than other children,. PMID:21442008

  10. Statistical properties of the anomalous scaling exponent estimator based on time-averaged mean-square displacement

    Science.gov (United States)

    Sikora, Grzegorz; Teuerle, Marek; Wyłomańska, Agnieszka; Grebenkov, Denis

    2017-08-01

    The most common way of estimating the anomalous scaling exponent from single-particle trajectories consists of a linear fit of the dependence of the time-averaged mean-square displacement on the lag time at the log-log scale. We investigate the statistical properties of this estimator in the case of fractional Brownian motion (FBM). We determine the mean value, the variance, and the distribution of the estimator. Our theoretical results are confirmed by Monte Carlo simulations. In the limit of long trajectories, the estimator is shown to be asymptotically unbiased, consistent, and with vanishing variance. These properties ensure an accurate estimation of the scaling exponent even from a single (long enough) trajectory. As a consequence, we prove that the usual way to estimate the diffusion exponent of FBM is correct from the statistical point of view. Moreover, the knowledge of the estimator distribution is the first step toward new statistical tests of FBM and toward a more reliable interpretation of the experimental histograms of scaling exponents in microbiology.

  11. Reporting the incidence of school violence across grade levels in the U.S. using the Third International Mathematics and Science Study (TIMSS).

    Science.gov (United States)

    Yu, Lei

    2004-01-01

    School violence has increasingly captured public attention due to deadly school shootings. Controversy on school violence is demonstrated by a mixed picture of school safety and the lack of consensus on the definitions of violence, which makes comparison of findings across studies difficult. This study extended the application of the Rasch model to school violence research using TIMSS data. The results show that school violence occurred at a level much lower than the predictions of the measurement model. Across all grade levels the most frequently reported type of violence is intimidation or verbal abuse of students and the least frequently reported physical injury to teachers or staff. Copyright 2004

  12. Examining school effectiveness at the fourth grade: A hierarchical analysis of the Third International Mathematics and Science Study (TIMSS)

    Science.gov (United States)

    Stemler, Steven Edward

    This study explored school effectiveness in mathematics and science at the fourth grade using data from IEA's Third International Mathematics and Science Study (TIMSS). Fourteen of the 26 countries participating in TIMSS at the fourth grade possessed sufficient between-school variability in mathematics achievement to justify the creation of explanatory models of school effectiveness while 13 countries possessed sufficient between-school variability in science achievement. Exploratory models were developed using variables drawn from student, teacher, and school questionnaires. The variables were chosen to represent the domains of student involvement, instructional methods, classroom organization, school climate, and school structure. Six explanatory models for each subject were analyzed using two-level hierarchical linear modeling (HLM) and were compared to models using only school mean SES as an explanatory variable. The amount of variability in student achievement in mathematics attributable to differences between schools ranged from 16% in Cyprus to 56% in Latvia, while the amount of between-school variance in science achievement ranged from 12% in Korea to 59% in Latvia. In general, about one-quarter of the variability in mathematics and science achievement was found to lie between schools. The research findings revealed that after adjusting for differences in student backgrounds across schools, the most effective schools in mathematics and science had students who reported seeing a positive relationship between hard work, belief in their own abilities, and achievement. In addition, more effective schools had students who reported less frequent use of computers and calculators in the classroom. These relationships were found to be stable across explanatory models, cultural contexts, and subject areas. This study has contributed a unique element to the literature by examining school effectiveness at the fourth grade across two subject areas and across 14

  13. Do mathematics textbooks cultivate shallow teaching? Applying the TIMSS Video Study criteria to Australian eighth-grade mathematics textbooks

    Science.gov (United States)

    Vincent, Jill; Stacey, Kaye

    2008-04-01

    Australian eighth-grade mathematics lessons were shown by the 1999 TIMSS Video Study to use a high proportion of problems of low procedural complexity, with considerable repetition, and an absence of deductive reasoning. Using definitions from the Video Study, this study re-investigated this `shallow teaching syndrome' by examining the problems on three topics in nine eighth-grade textbooks from four Australian states for procedural complexity, type of solving processes, degree of repetition, proportion of `application' problems and proportion of problems requiring deductive reasoning. Overall, there was broad similarity between the characteristics of problems in the textbooks and in the Australian Video Study lessons. There were, however, considerable differences between textbooks and between topics within textbooks. In some books, including the best-selling textbooks in several states, the balance is too far towards repetitive problems of low procedural complexity.

  14. The flattening of the average potential in models with fermions

    International Nuclear Information System (INIS)

    Bornholdt, S.

    1993-01-01

    The average potential is a scale dependent scalar effective potential. In a phase with spontaneous symmetry breaking its inner region becomes flat as the averaging extends over infinite volume and the average potential approaches the convex effective potential. Fermion fluctuations affect the shape of the average potential in this region and its flattening with decreasing physical scale. They have to be taken into account to find the true minimum of the scalar potential which determines the scale of spontaneous symmetry breaking. (orig.)

  15. Different Multifractal Scaling of the 0 cm Average Ground Surface Temperature of Four Representative Weather Stations over China

    Directory of Open Access Journals (Sweden)

    Lei Jiang

    2013-01-01

    Full Text Available The temporal scaling properties of the daily 0 cm average ground surface temperature (AGST records obtained from four selected sites over China are investigated using multifractal detrended fluctuation analysis (MF-DFA method. Results show that the AGST records at all four locations exhibit strong persistence features and different scaling behaviors. The differences of the generalized Hurst exponents are very different for the AGST series of each site reflecting the different scaling behaviors of the fluctuation. Furthermore, the strengths of multifractal spectrum are different for different weather stations and indicate that the multifractal behaviors vary from station to station over China.

  16. Analyzing data from a fuzzy rating scale-based questionnaire. A case study.

    Science.gov (United States)

    Gil, María Ángeles; Lubiano, María Asunción; de la Rosa de Sáa, Sara; Sinova, Beatriz

    2015-01-01

    The fuzzy rating scale was introduced to cope with the imprecision of human thought and experience in measuring attitudes in many fields of Psychology. The flexibility and expressiveness of this scale allow us to properly describe the answers to many questions involving psychological measurement. Analyzing the responses to a fuzzy rating scale-based questionnaire is indeed a critical problem. Nevertheless, over the last years, a methodology is being developed to analyze statistically fuzzy data in such a way that the information they contain is fully exploited. In this paper, a summary review of the main procedures is given. The methods are illustrated by their application on the dataset obtained from a case study with nine-year-old children. In this study, children replied to some questions from the well-known TIMSS/PIRLS questionnaire by using a fuzzy rating scale. The form could be filled in either on the computer or by hand. The study indicates that the requirements of background and training underlying the fuzzy rating scale are not too demanding. Moreover, it is clearly shown that statistical conclusions substantially often differ depending on the responses being given in accordance with either a Likert scale or a fuzzy rating scale.

  17. TIMSS Y PISA. Dos proyectos internacionales de evaluación del aprendizaje escolar en ciencias

    Directory of Open Access Journals (Sweden)

    Acevedo Díaz, J.A.

    2005-09-01

    Full Text Available Durante la última década se han incrementado las aplicaciones de proyectos nacionales e internacionales de evaluación del aprendizaje escolar en ciencias y otras materias, posiblemente como consecuencia de las presiones políticas a las que se ven sometidos los sistemas educativos para evaluar su rendimiento. Los estudios e informes derivados de la puesta en práctica de las evaluaciones transnacionales han permitido la comparación entre países y, más allá de la comprobación de los niveles de conocimiento y comprensión del alumnado, se suelen usar como una medida global de la calidad de los sistemas educativos. En este artículo se muestran las principales características de los dos proyectos de este tipo más conocidos: TIMSS y PISA. Se pretende con ello animar al profesorado a que haga una lectura crítica más profesional y un análisis más reflexivo de los informes derivados de estas evaluaciones, para así llegar a sacar conclusiones por sí mismo.

  18. Averaging in spherically symmetric cosmology

    International Nuclear Information System (INIS)

    Coley, A. A.; Pelavas, N.

    2007-01-01

    The averaging problem in cosmology is of fundamental importance. When applied to study cosmological evolution, the theory of macroscopic gravity (MG) can be regarded as a long-distance modification of general relativity. In the MG approach to the averaging problem in cosmology, the Einstein field equations on cosmological scales are modified by appropriate gravitational correlation terms. We study the averaging problem within the class of spherically symmetric cosmological models. That is, we shall take the microscopic equations and effect the averaging procedure to determine the precise form of the correlation tensor in this case. In particular, by working in volume-preserving coordinates, we calculate the form of the correlation tensor under some reasonable assumptions on the form for the inhomogeneous gravitational field and matter distribution. We find that the correlation tensor in a Friedmann-Lemaitre-Robertson-Walker (FLRW) background must be of the form of a spatial curvature. Inhomogeneities and spatial averaging, through this spatial curvature correction term, can have a very significant dynamical effect on the dynamics of the Universe and cosmological observations; in particular, we discuss whether spatial averaging might lead to a more conservative explanation of the observed acceleration of the Universe (without the introduction of exotic dark matter fields). We also find that the correlation tensor for a non-FLRW background can be interpreted as the sum of a spatial curvature and an anisotropic fluid. This may lead to interesting effects of averaging on astrophysical scales. We also discuss the results of averaging an inhomogeneous Lemaitre-Tolman-Bondi solution as well as calculations of linear perturbations (that is, the backreaction) in an FLRW background, which support the main conclusions of the analysis

  19. Spacetime averaging of exotic singularity universes

    International Nuclear Information System (INIS)

    Dabrowski, Mariusz P.

    2011-01-01

    Taking a spacetime average as a measure of the strength of singularities we show that big-rips (type I) are stronger than big-bangs. The former have infinite spacetime averages while the latter have them equal to zero. The sudden future singularities (type II) and w-singularities (type V) have finite spacetime averages. The finite scale factor (type III) singularities for some values of the parameters may have an infinite average and in that sense they may be considered stronger than big-bangs.

  20. Self-similarity of higher-order moving averages

    Science.gov (United States)

    Arianos, Sergio; Carbone, Anna; Türk, Christian

    2011-10-01

    In this work, higher-order moving average polynomials are defined by straightforward generalization of the standard moving average. The self-similarity of the polynomials is analyzed for fractional Brownian series and quantified in terms of the Hurst exponent H by using the detrending moving average method. We prove that the exponent H of the fractional Brownian series and of the detrending moving average variance asymptotically agree for the first-order polynomial. Such asymptotic values are compared with the results obtained by the simulations. The higher-order polynomials correspond to trend estimates at shorter time scales as the degree of the polynomial increases. Importantly, the increase of polynomial degree does not require to change the moving average window. Thus trends at different time scales can be obtained on data sets with the same size. These polynomials could be interesting for those applications relying on trend estimates over different time horizons (financial markets) or on filtering at different frequencies (image analysis).

  1. The relationship between self-concept and achievement in TIMSS 2007: A comparison between American and Japanese students

    Science.gov (United States)

    Yoshino, Asako

    2012-04-01

    The purpose of this research was to investigate the relationship between eighth-grade students' maths-related self-concepts and their achievements in the Trends in International Mathematics and Science Study (TIMSS) 2007. The students' maths self-concept was compared with other variables, namely their mothers' education, their fathers' education and the amount of books held in the students' households. To investigate the potential role of culture, a comparison between American and Japanese students' scores was also included. The findings demonstrated that students' maths self-concept was positively associated with their achievement both in the United States and Japan, but Japanese students, while having higher achievement, had a lower maths self-concept than American students. Maternal education, paternal education and the number of books at home were also found to be positively related to achievement. Examining standardised coefficients, the study confirmed a strong interaction between maths self-concept and country, as well as a positive connection between maths self-concept as such (irrespective of the country) with maths achievement.

  2. Aperture averaging in strong oceanic turbulence

    Science.gov (United States)

    Gökçe, Muhsin Caner; Baykal, Yahya

    2018-04-01

    Receiver aperture averaging technique is employed in underwater wireless optical communication (UWOC) systems to mitigate the effects of oceanic turbulence, thus to improve the system performance. The irradiance flux variance is a measure of the intensity fluctuations on a lens of the receiver aperture. Using the modified Rytov theory which uses the small-scale and large-scale spatial filters, and our previously presented expression that shows the atmospheric structure constant in terms of oceanic turbulence parameters, we evaluate the irradiance flux variance and the aperture averaging factor of a spherical wave in strong oceanic turbulence. Irradiance flux variance variations are examined versus the oceanic turbulence parameters and the receiver aperture diameter are examined in strong oceanic turbulence. Also, the effect of the receiver aperture diameter on the aperture averaging factor is presented in strong oceanic turbulence.

  3. Communicating Quantitative Literacy: An Examination of Open-Ended Assessment Items in TIMSS, NALS, IALS, and PISA

    Directory of Open Access Journals (Sweden)

    Karl W. Kosko

    2011-07-01

    Full Text Available Quantitative Literacy (QL has been described as the skill set an individual uses when interacting with the world in a quantitative manner. A necessary component of this interaction is communication. To this end, assessments of QL have included open-ended items as a means of including communicative aspects of QL. The present study sought to examine whether such open-ended items typically measured aspects of quantitative communication, as compared to mathematical communication, or mathematical skills. We focused on public-released items and rubrics from four of the most widely referenced assessments: the Third International Mathematics and Science Study (TIMSS-95: the National Adult Literacy Survey (NALS; now the National Assessment of Adult Literacy, NAAL in 1985 and 1992, the International Adult Literacy Skills (IALS beginning in 1994; and the Program for International Student Assessment (PISA beginning in 2000. We found that open-ended item rubrics in these QL assessments showed a strong tendency to assess answer-only responses. Therefore, while some open-ended items may have required certain levels of quantitative reasoning to find a solution, it is the solution rather than the reasoning that was often assessed.

  4. Qualitative approaches to large scale studies and students' achievements in Science and Mathematics - An Australian and Nordic Perspective

    DEFF Research Database (Denmark)

    Davidsson, Eva; Sørensen, Helene

    Large scale studies play an increasing role in educational politics and results from surveys such as TIMSS and PISA are extensively used in medial debates about students' knowledge in science and mathematics. Although this debate does not usually shed light on the more extensive quantitative...... analyses, there is a lack of investigations which aim at exploring what is possible to conclude or not to conclude from these analyses. There is also a need for more detailed discussions about what trends could be discern concerning students' knowledge in science and mathematics. The aim of this symposium...... is therefore to highlight and discuss different approaches to how data from large scale studies could be used for additional analyses in order to increase our understanding of students' knowledge in science and mathematics, but also to explore possible longitudinal trends, hidden in the data material...

  5. Do large-scale assessments measure students' ability to integrate scientific knowledge?

    Science.gov (United States)

    Lee, Hee-Sun

    2010-03-01

    Large-scale assessments are used as means to diagnose the current status of student achievement in science and compare students across schools, states, and countries. For efficiency, multiple-choice items and dichotomously-scored open-ended items are pervasively used in large-scale assessments such as Trends in International Math and Science Study (TIMSS). This study investigated how well these items measure secondary school students' ability to integrate scientific knowledge. This study collected responses of 8400 students to 116 multiple-choice and 84 open-ended items and applied an Item Response Theory analysis based on the Rasch Partial Credit Model. Results indicate that most multiple-choice items and dichotomously-scored open-ended items can be used to determine whether students have normative ideas about science topics, but cannot measure whether students integrate multiple pieces of relevant science ideas. Only when the scoring rubric is redesigned to capture subtle nuances of student open-ended responses, open-ended items become a valid and reliable tool to assess students' knowledge integration ability.

  6. Evaluating the risk of nonresponse bias in educational large-scale assessments with school nonresponse questionnaires: a theoretical study

    Directory of Open Access Journals (Sweden)

    Sabine Meinck

    2017-01-01

    Full Text Available Abstract Survey participation rates can have a direct impact on the validity of the data collected since nonresponse always holds the risk of bias. Therefore, the International Association for the Evaluation of Educational Achievement (IEA has set very high standards for minimum survey participation rates. Nonresponse in IEA studies varies between studies and cycles. School participation is at a higher risk relative to within-school participation; school students are more likely to cooperate than adults (i.e., university students or school teachers. Across all studies conducted by the IEA during the last decade, between 7 and 33% of participating countries failed to meet the minimum participation rates at the school level. Quantifying the bias introduced by nonresponse is practically impossible with the currently implemented design. During the last decade social researchers have introduced and developed the concept of nonresponse questionnaires. These are shortened instruments applied to nonrespondents, and aim to capture information that correlates with both: survey’s main outcome variable(s, and respondent’s propensity of participation. We suggest in this paper a method to develop such questionnaires for nonresponding schools in IEA studies. By these means, we investigated school characteristics that are associated with students’ average achievement scores using correlational and multivariate regression analysis in three recent IEA studies. We developed regression models that explain with only 11 school questionnaire variables or less up to 77% of the variance of the school mean achievement score. On average across all countries, the R 2 of these models was 0.24 (PIRLS, 0.34 (TIMSS, grade 4 and 0.36 (TIMSS grade 8, using 6–11 variables. We suggest that data from such questionnaires can help to evaluate bias risks in an effective way. Further, we argue that for countries with low participation rates a change in the approach of computing

  7. An investigation of the effect of pore scale flow on average geochemical reaction rates using direct numerical simulation

    Energy Technology Data Exchange (ETDEWEB)

    Molins, Sergi [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Earth Sciences Division; Trebotich, David [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Computational Research Division; Steefel, Carl I. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Earth Sciences Division; Shen, Chaopeng [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Computational Research Division

    2012-03-30

    The scale-dependence of geochemical reaction rates hinders their use in continuum scale models intended for the interpretation and prediction of chemical fate and transport in subsurface environments such as those considered for geologic sequestration of CO2. Processes that take place at the pore scale, especially those involving mass transport limitations to reactive surfaces, may contribute to the discrepancy commonly observed between laboratory-determined and continuum-scale or field rates. In this study we investigate the dependence of mineral dissolution rates on the pore structure of the porous media by means of pore scale modeling of flow and multicomponent reactive transport. The pore scale model is composed of high-performance simulation tools and algorithms for incompressible flow and conservative transport combined with a general-purpose multicomponent geochemical reaction code. The model performs direct numerical simulation of reactive transport based on an operator-splitting approach to coupling transport and reactions. The approach is validated with a Poiseuille flow single-pore experiment and verified with an equivalent 1-D continuum-scale model of a capillary tube packed with calcite spheres. Using the case of calcite dissolution as an example, the high-resolution model is used to demonstrate that nonuniformity in the flow field at the pore scale has the effect of decreasing the overall reactivity of the system, even when systems with identical reactive surface area are considered. In conclusion, the effect becomes more pronounced as the heterogeneity of the reactive grain packing increases, particularly where the flow slows sufficiently such that the solution approaches equilibrium locally and the average rate becomes transport-limited.

  8. Averaging processes in granular flows driven by gravity

    Science.gov (United States)

    Rossi, Giulia; Armanini, Aronne

    2016-04-01

    One of the more promising theoretical frames to analyse the two-phase granular flows is offered by the similarity of their rheology with the kinetic theory of gases [1]. Granular flows can be considered a macroscopic equivalent of the molecular case: the collisions among molecules are compared to the collisions among grains at a macroscopic scale [2,3]. However there are important statistical differences in dealing with the two applications. In the two-phase fluid mechanics, there are two main types of average: the phasic average and the mass weighed average [4]. The kinetic theories assume that the size of atoms is so small, that the number of molecules in a control volume is infinite. With this assumption, the concentration (number of particles n) doesn't change during the averaging process and the two definitions of average coincide. This hypothesis is no more true in granular flows: contrary to gases, the dimension of a single particle becomes comparable to that of the control volume. For this reason, in a single realization the number of grain is constant and the two averages coincide; on the contrary, for more than one realization, n is no more constant and the two types of average lead to different results. Therefore, the ensamble average used in the standard kinetic theory (which usually is the phasic average) is suitable for the single realization, but not for several realization, as already pointed out in [5,6]. In the literature, three main length scales have been identified [7]: the smallest is the particles size, the intermediate consists in the local averaging (in order to describe some instability phenomena or secondary circulation) and the largest arises from phenomena such as large eddies in turbulence. Our aim is to solve the intermediate scale, by applying the mass weighted average, when dealing with more than one realizations. This statistical approach leads to additional diffusive terms in the continuity equation: starting from experimental

  9. Multi-Scale Visualization Analysis of Bus Flow Average Travel Speed in Qingdao

    Science.gov (United States)

    Yong, HAN; Man, GAO; Xiao-Lei, ZHANG; Jie, LI; Ge, CHEN

    2016-11-01

    Public transportation is a kind of complex spatiotemporal behaviour. The traffic congestion and environmental pollution caused by the increase in private cars is becoming more and more serious in our city. Spatiotemporal data visualization is an effective tool for studying traffic, transforming non-visual data into recognizable images, which can reveal where/when congestion is formed, developed and disappeared in space and time simultaneously. This paper develops a multi-scale visualization of average travel speed derived from floating bus data, to enable congestion on urban bus networks to be shown and analyzed. The techniques of R language, Echarts, WebGL are used to draw statistical pictures and 3D wall map, which show the congestion in Qingdao from the view of space and time. The results are as follows:(1) There is a more severely delay in Shibei and Shinan areas than Licun and Laoshan areas; (2) The high congestion usually occurs on Hong Kong Middle Road, Shandong Road, Nanjing Road, Liaoyang West Road and Taiping Road;(3) There is a similar law from Monday to Sunday that the congestion is severer in the morning and evening rush hours than other hours; (4) On Monday morning the severity of congestion is higher than on Friday morning, and on Friday evening the severity is higher than on Monday evening. The research results will help to improve the public transportation of Qingdao.

  10. To quantum averages through asymptotic expansion of classical averages on infinite-dimensional space

    International Nuclear Information System (INIS)

    Khrennikov, Andrei

    2007-01-01

    We study asymptotic expansions of Gaussian integrals of analytic functionals on infinite-dimensional spaces (Hilbert and nuclear Frechet). We obtain an asymptotic equality coupling the Gaussian integral and the trace of the composition of scaling of the covariation operator of a Gaussian measure and the second (Frechet) derivative of a functional. In this way we couple classical average (given by an infinite-dimensional Gaussian integral) and quantum average (given by the von Neumann trace formula). We can interpret this mathematical construction as a procedure of 'dequantization' of quantum mechanics. We represent quantum mechanics as an asymptotic projection of classical statistical mechanics with infinite-dimensional phase space. This space can be represented as the space of classical fields, so quantum mechanics is represented as a projection of 'prequantum classical statistical field theory'

  11. A practical guide to averaging functions

    CERN Document Server

    Beliakov, Gleb; Calvo Sánchez, Tomasa

    2016-01-01

    This book offers an easy-to-use and practice-oriented reference guide to mathematical averages. It presents different ways of aggregating input values given on a numerical scale, and of choosing and/or constructing aggregating functions for specific applications. Building on a previous monograph by Beliakov et al. published by Springer in 2007, it outlines new aggregation methods developed in the interim, with a special focus on the topic of averaging aggregation functions. It examines recent advances in the field, such as aggregation on lattices, penalty-based aggregation and weakly monotone averaging, and extends many of the already existing methods, such as: ordered weighted averaging (OWA), fuzzy integrals and mixture functions. A substantial mathematical background is not called for, as all the relevant mathematical notions are explained here and reported on together with a wealth of graphical illustrations of distinct families of aggregation functions. The authors mainly focus on practical applications ...

  12. Developing models to predict 8th grade students' achievement levels on timss science based on opportunity-to-learn variables

    Science.gov (United States)

    Whitford, Melinda M.

    Science educational reforms have placed major emphasis on improving science classroom instruction and it is therefore vital to study opportunity-to-learn (OTL) variables related to student science learning experiences and teacher teaching practices. This study will identify relationships between OTL and student science achievement and will identify OTL predictors of students' attainment at various distinct achievement levels (low/intermediate/high/advanced). Specifically, the study (a) address limitations of previous studies by examining a large number of independent and control variables that may impact students' science achievement and (b) it will test hypotheses of structural relations to how the identified predictors and mediating factors impact on student achievement levels. The study will follow a multi-stage and integrated bottom-up and top-down approach to identify predictors of students' achievement levels on standardized tests using TIMSS 2011 dataset. Data mining or pattern recognition, a bottom-up approach will identify the most prevalent association patterns between different student achievement levels and variables related to student science learning experiences, teacher teaching practices and home and school environments. The second stage is a top-down approach, testing structural equation models of relations between the significant predictors and students' achievement levels according.

  13. A statistical analysis of the characteristics of the intended curriculum for Japanese primary science and its relationship to the attained curriculum

    Directory of Open Access Journals (Sweden)

    Kenji Matsubara

    2016-08-01

    Full Text Available Abstract This study statistically investigates the characteristics of the intended curriculum for Japanese primary science, focusing on the learning content. The study used the TIMSS 2011 Grade 4 Curriculum Questionnaire data as a major source for the learning content prescribed at the national level. Confirmatory factor analysis was used to determine the extent to which a topic area was covered, as compared to the average among the 59 TIMSS 2011 participating countries. The study revealed that the topic areas of “Human Health” and “Changes in Environments,” both in the life science domain, showed statistically less coverage in the Japanese primary science curriculum when compared to the international average. Furthermore, in discussion, the study relates the characteristics found in the intended curriculum to those in the attained curriculum, examining the percent correct statistics for relevant items from the science assessment. Based on these findings, the study proposes two recommendations for revision of the Japanese primary science curriculum.

  14. 以TIMSS資料檢視2003至2011年臺灣八年級學生數學成就城鄉差異 Using TIMSS Data to Investigate Rural-Urban Differences of Taiwanese Eighth Graders’ Mathematics Achievement from 2003 to 2011

    Directory of Open Access Journals (Sweden)

    李哲迪 Che-Di Lee

    2016-12-01

    Full Text Available 本研究利用TIMSS 2003、2007與2011資料,分析臺灣八年級學生數學成就的城鎮都市間和鄉村都市間之差異。透過再中心化影響函數迴歸分析,發現城鎮都市間之成就差異從2007至2011年有顯著的擴大,此擴大是因都市學生成就提高所致。在2011年,都市低家庭教育資源後段學生成就進步,成就分布左側長尾縮短;都市高家庭教育資源中前段學生成就進步,成就分布向右拉長。在2011年,城鎮和鄉村學生平均落後都市學生0.45和0.57個標準差,約有一半是家庭教育資源城鄉差距所造成的。以TIMSS中級國際基準點作為基礎成就線,在2011年,落後人數比在都市、城鎮和鄉村分別是5%、13%和16%。家庭教育資源不足之學生,其落後人數比的城鄉差距較為嚴重。落後學生落後基礎成就線的幅度則無城鄉差異。 This study explored Taiwanese eighth graders’ mathematics achievement differences between town and urban areas and between rural and urban areas based on the data of TIMSS 2003 to 2011. Using recentered influence function regressions, the study has found that there were significant widening differences between the achievement of town students’ and that of urban students from 2007 to 2011 due to the improvement of urban students’ achievement. In 2011, the achievement of low ranking urban students with low home-education-resources have improved and the left tail of their distribution was shortened; the achievement of middle and high ranking urban students with high home-education-resources have improved and their distribution was stretched to the right. In 2011, comparing with urban students, town and rural students fall behind academically for 0.45 and 0.57 standard deviation on average, half of which was caused by the town-urban and rural-urban differences of homeeducation-resources. Using the intermediate international benchmark of TIMSS as the

  15. The Impacts of Student-, Teacher- and School-Level Factors on Mathematics Achievement: An Exploratory Comparative Investigation of Singaporean Students and the USA Students

    Science.gov (United States)

    Ker, H. W.

    2016-01-01

    Reports from the Trends in International Mathematics and Science Study (TIMSS) consistently show that there is a substantial gap in average mathematics achievement between Singapore and the USA. This study conducts an exploratory comparative investigation on the multilevel factors influencing the mathematics achievement of students from these two…

  16. Time average vibration fringe analysis using Hilbert transformation

    International Nuclear Information System (INIS)

    Kumar, Upputuri Paul; Mohan, Nandigana Krishna; Kothiyal, Mahendra Prasad

    2010-01-01

    Quantitative phase information from a single interferogram can be obtained using the Hilbert transform (HT). We have applied the HT method for quantitative evaluation of Bessel fringes obtained in time average TV holography. The method requires only one fringe pattern for the extraction of vibration amplitude and reduces the complexity in quantifying the data experienced in the time average reference bias modulation method, which uses multiple fringe frames. The technique is demonstrated for the measurement of out-of-plane vibration amplitude on a small scale specimen using a time average microscopic TV holography system.

  17. Mathematics beliefs and achievement of a national sample of Native American students: results from the Trends in International Mathematics and Science Study (TIMSS) 2003 United States assessment.

    Science.gov (United States)

    House, J Daniel

    2009-04-01

    Recent mathematics assessment findings indicate that Native American students tend to score below students of the ethnic majority. Findings suggest that students' beliefs about mathematics are significantly related to achievement outcomes. This study examined relations between self-beliefs and mathematics achievement for a national sample of 130 Grade 8 Native American students from the Trends in International Mathematics and Science Study (TIMSS) 2003 United States sample of (M age = 14.2 yr., SD = 0.5). Multiple regression indicated several significant relations of mathematics beliefs with achievement and accounted for 26.7% of the variance in test scores. Students who earned high test scores tended to hold more positive beliefs about their ability to learn mathematics quickly, while students who earned low scores expressed negative beliefs about their ability to learn new mathematics topics.

  18. When good = better than average

    Directory of Open Access Journals (Sweden)

    Don A. Moore

    2007-10-01

    Full Text Available People report themselves to be above average on simple tasks and below average on difficult tasks. This paper proposes an explanation for this effect that is simpler than prior explanations. The new explanation is that people conflate relative with absolute evaluation, especially on subjective measures. The paper then presents a series of four studies that test this conflation explanation. These tests distinguish conflation from other explanations, such as differential weighting and selecting the wrong referent. The results suggest that conflation occurs at the response stage during which people attempt to disambiguate subjective response scales in order to choose an answer. This is because conflation has little effect on objective measures, which would be equally affected if the conflation occurred at encoding.

  19. Image-processing of time-averaged interface distributions representing CCFL characteristics in a large scale model of a PWR hot-leg pipe geometry

    International Nuclear Information System (INIS)

    Al Issa, Suleiman; Macián-Juan, Rafael

    2017-01-01

    Highlights: • CCFL characteristics are investigated in PWR large-scale hot-leg pipe geometry. • Image processing of air-water interface produced time-averaged interface distributions. • Time-averages provide a comparative method of CCFL characteristics among different studies. • CCFL correlations depend upon the range of investigated water delivery for Dh ≫ 50 mm. • 1D codes are incapable of investigating CCFL because of lack of interface distribution. - Abstract: Countercurrent Flow Limitation (CCFL) was experimentally investigated in a 1/3.9 downscaled COLLIDER facility with a 190 mm pipe’s diameter using air/water at 1 atmospheric pressure. Previous investigations provided knowledge over the onset of CCFL mechanisms. In current article, CCFL characteristics at the COLLIDER facility are measured and discussed along with time-averaged distributions of the air/water interface for a selected matrix of liquid/gas velocities. The article demonstrates the time-averaged interface as a useful method to identify CCFL characteristics at quasi-stationary flow conditions eliminating variations that appears in single images, and showing essential comparative flow features such as: the degree of restriction at the bend, the extension and the intensity of the two-phase mixing zones, and the average water level within the horizontal part and the steam generator. Consequently, making it possible to compare interface distributions obtained at different investigations. The distributions are also beneficial for CFD validations of CCFL as the instant chaotic gas/liquid interface is impossible to reproduce in CFD simulations. The current study shows that final CCFL characteristics curve (and the corresponding CCFL correlation) depends upon the covered measuring range of water delivery. It also shows that a hydraulic diameter should be sufficiently larger than 50 mm in order to obtain CCFL characteristics comparable to the 1:1 scale data (namely the UPTF data). Finally

  20. Kan elevene mindre enn før? Naturfagkompetanse i Norden i perioden 1995 – 2003

    Directory of Open Access Journals (Sweden)

    Marit Kjærnsli

    2005-11-01

    Full Text Available This article presents and discusses changes in science competency in the period from 1995 to 2003 in the Nordic countries based on analyses of data from PISA and TIMSS. One central feature of the PISA and TIMSS surveys is to study changes in students’ competency over time in absolute terms. Some items are kept secure from cycle to cycle, and based on these items it is possible to create trend data, i.e. to place students who have taken tests at different times on the same cognitive scale. This is done by the use of modern psychometrical methods. The results show a decline in Norway and Sweden, while a positive development is found in Finland.

  1. How do american students measure up? Making sense of international comparisons.

    Science.gov (United States)

    Koretz, Daniel

    2009-01-01

    In response to frequent news media reports about how poorly American students fare compared with their peers abroad, Daniel Koretz takes a close look at what these comparisons say, and do not say, about the achievement of U.S. high school students. He stresses that the comparisons do not provide what many observers of education would like: unambiguous information about the effectiveness of American high schools compared with those in other nations. Koretz begins by describing the. two principal international student comparisons-the Trends in International Mathematics and Science Study (TIMSS) and the Program for International Student Assessment (PISA). Both assessments, he stresses, reflect the performance of students several years before they complete high school. PISA, which targets fifteen-year-old students, measures students' abilities to apply what they have learned in school to real-world problems. By contrast, TIMSS tests fourth and eighth graders. Unlike PISA, TIMSS follows the school curriculum closely. Because the findings of the two tests are sometimes inconsistent, Koretz stresses the importance of considering data from both sources. He cautions against comparing U.S. students with an "international average," which varies widely from survey to survey depending on which countries participate, and recommends instead comparing them with students in other nations that are similar to the United States or that are particularly high-achieving. Many observers, says Koretz, speculate that the lackluster average performance of American students in international comparisons arises because many, especially minority and low-income U.S. students, attend low-performing schools. But both TIMSS and PISA, he says, show that the performance of American students on the exams is not much more variable than that of students in countries that are socially more homogeneous or that have more equitable educational systems. Koretz emphasizes that the international comparisons

  2. Tipping the scales: Evolution of the allometric slope independent of average trait size.

    Science.gov (United States)

    Stillwell, R Craig; Shingleton, Alexander W; Dworkin, Ian; Frankino, W Anthony

    2016-02-01

    The scaling of body parts is central to the expression of morphology across body sizes and to the generation of morphological diversity within and among species. Although patterns of scaling-relationship evolution have been well documented for over one hundred years, little is known regarding how selection acts to generate these patterns. In part, this is because it is unclear the extent to which the elements of log-linear scaling relationships-the intercept or mean trait size and the slope-can evolve independently. Here, using the wing-body size scaling relationship in Drosophila melanogaster as an empirical model, we use artificial selection to demonstrate that the slope of a morphological scaling relationship between an organ (the wing) and body size can evolve independently of mean organ or body size. We discuss our findings in the context of how selection likely operates on morphological scaling relationships in nature, the developmental basis for evolved changes in scaling, and the general approach of using individual-based selection experiments to study the expression and evolution of morphological scaling. © 2016 The Author(s). Evolution © 2016 The Society for the Study of Evolution.

  3. 78 FR 38957 - Agency Information Collection Activities; Comment Request; Trends in International Mathematics...

    Science.gov (United States)

    2013-06-28

    ...; Comment Request; Trends in International Mathematics and Science Study (TIMSS): 2015 Recruitment and Field... of Collection: Trends in International Mathematics and Science Study (TIMSS): 2015 Recruitment and... Mathematics and Science Study (TIMSS) is an international assessment of fourth and eighth grade students...

  4. The academic effects of after-school paid and unpaid work among 14-year-old students in TIMSS countries.

    Science.gov (United States)

    Post, David; Pong, Suet-Ling

    2009-01-01

    What it means to be a 'student' varies within and between countries. Apart from the wide variety of school types and school quality that is experienced by young people, there also is, accompanying increased rates of school participation, a growing population of students who work part-time. The theoretical and actual consequences of student work have long been in dispute. This article reformulates the dispute as an empirical question that can be addressed using cross-national testing data and student background information from the Trends in International Math and Science Study (TIMSS). Drawing information from 20 countries with distinctive proportions of students who reported paid and unpaid work, this study first compares their academic achievement in each country. Next, regression analysis is used to control for students' home resources, and estimates are made of the effects of work and the differences in these effects cross-nationally. Finally, hierarchical linear models are estimated in each country so as to control for school effects, and to take into account the fact that working students may be clustered in lower-achieving schools. The results show that work after school, whether paid or unpaid, never positively affects academic achievement. However, after controlling for home resources and school effects, work negatively affects achievement only in certain countries. The article concludes with a discussion of the ways to interpret international differences in the effect of students' work.

  5. Brain scaling in mammalian evolution as a consequence of concerted and mosaic changes in numbers of neurons and average neuronal cell size

    Directory of Open Access Journals (Sweden)

    Suzana eHerculano-Houzel

    2014-08-01

    Full Text Available Enough species have now been subject to systematic quantitative analysis of the relationship between the morphology and cellular composition of their brain that patterns begin to emerge and shed light on the evolutionary path that led to mammalian brain diversity. Based on an analysis of the shared and clade-specific characteristics of 41 modern mammalian species in 6 clades, and in light of the phylogenetic relationships among them, here we propose that ancestral mammal brains were composed and scaled in their cellular composition like modern afrotherian and glire brains: with an addition of neurons that is accompanied by a decrease in neuronal density and very little modification in glial cell density, implying a significant increase in average neuronal cell size in larger brains, and the allocation of approximately 2 neurons in the cerebral cortex and 8 neurons in the cerebellum for every neuron allocated to the rest of brain. We also propose that in some clades the scaling of different brain structures has diverged away from the common ancestral layout through clade-specific (or clade-defining changes in how average neuronal cell mass relates to numbers of neurons in each structure, and how numbers of neurons are differentially allocated to each structure relative to the number of neurons in the rest of brain. Thus, the evolutionary expansion of mammalian brains has involved both concerted and mosaic patterns of scaling across structures. This is, to our knowledge, the first mechanistic model that explains the generation of brains large and small in mammalian evolution, and it opens up new horizons for seeking the cellular pathways and genes involved in brain evolution.

  6. Free Energy Self-Averaging in Protein-Sized Random Heteropolymers

    International Nuclear Information System (INIS)

    Chuang, Jeffrey; Grosberg, Alexander Yu.; Kardar, Mehran

    2001-01-01

    Current theories of heteropolymers are inherently macroscopic, but are applied to mesoscopic proteins. To compute the free energy over sequences, one assumes self-averaging -- a property established only in the macroscopic limit. By enumerating the states and energies of compact 18, 27, and 36mers on a lattice with an ensemble of random sequences, we test the self-averaging approximation. We find that fluctuations in the free energy between sequences are weak, and that self-averaging is valid at the scale of real proteins. The results validate sequence design methods which exponentially speed up computational design and simplify experimental realizations

  7. The average action for scalar fields near phase transitions

    International Nuclear Information System (INIS)

    Wetterich, C.

    1991-08-01

    We compute the average action for fields in two, three and four dimensions, including the effects of wave function renormalization. A study of the one loop evolution equations for the scale dependence of the average action gives a unified picture of the qualitatively different behaviour in various dimensions for discrete as well as abelian and nonabelian continuous symmetry. The different phases and the phase transitions can be infered from the evolution equation. (orig.)

  8. Average monthly and annual climate maps for Bolivia

    KAUST Repository

    Vicente-Serrano, Sergio M.

    2015-02-24

    This study presents monthly and annual climate maps for relevant hydroclimatic variables in Bolivia. We used the most complete network of precipitation and temperature stations available in Bolivia, which passed a careful quality control and temporal homogenization procedure. Monthly average maps at the spatial resolution of 1 km were modeled by means of a regression-based approach using topographic and geographic variables as predictors. The monthly average maximum and minimum temperatures, precipitation and potential exoatmospheric solar radiation under clear sky conditions are used to estimate the monthly average atmospheric evaporative demand by means of the Hargreaves model. Finally, the average water balance is estimated on a monthly and annual scale for each 1 km cell by means of the difference between precipitation and atmospheric evaporative demand. The digital layers used to create the maps are available in the digital repository of the Spanish National Research Council.

  9. Brief communication: Using averaged soil moisture estimates to improve the performances of a regional-scale landslide early warning system

    Science.gov (United States)

    Segoni, Samuele; Rosi, Ascanio; Lagomarsino, Daniela; Fanti, Riccardo; Casagli, Nicola

    2018-03-01

    We communicate the results of a preliminary investigation aimed at improving a state-of-the-art RSLEWS (regional-scale landslide early warning system) based on rainfall thresholds by integrating mean soil moisture values averaged over the territorial units of the system. We tested two approaches. The simplest can be easily applied to improve other RSLEWS: it is based on a soil moisture threshold value under which rainfall thresholds are not used because landslides are not expected to occur. Another approach deeply modifies the original RSLEWS: thresholds based on antecedent rainfall accumulated over long periods are substituted with soil moisture thresholds. A back analysis demonstrated that both approaches consistently reduced false alarms, while the second approach reduced missed alarms as well.

  10. Perceived Quality of Educational Technology Matters: A Secondary Analysis of Students' ICT Use, ICT-Related Attitudes, and PISA 2012 Test Scores

    Science.gov (United States)

    Petko, Dominik; Cantieni, Andrea; Prasse, Doreen

    2017-01-01

    In large-scale international assessments such as the Programme for International Student Assessment (PISA), the Trends in International Mathematics and Science Study (TIMSS), or the Progress in International Reading Study (PISA), research has struggled to find positive associations between the frequency of educational technology use in schools and…

  11. How to Construct an Organizational Field: Empirical Educational Research in Germany, 1995-2015

    Science.gov (United States)

    Zapp, Mike; Powell, Justin J. W.

    2016-01-01

    Over the past two decades, educational research in Germany has undergone unprecedented changes. Following large-scale assessments such as the Trends in International Mathematics and Science Study (TIMSS) and the Programme for International Student Assessment (PISA), and a political interest in evidence-based policy-making, quality assessment and…

  12. Focusing on Interactions between Content and Cognition: A New Perspective on Gender Differences in Mathematical Sub-Competencies

    Science.gov (United States)

    George, Ann Cathrice; Robitzsch, Alexander

    2018-01-01

    This article presents a new perspective on measuring gender differences in the large-scale assessment study Trends in International Science Study (TIMSS). The suggested empirical model is directly based on the theoretical competence model of the domain mathematics and thus includes the interaction between content and cognitive sub-competencies.…

  13. Application of Bayesian model averaging to measurements of the primordial power spectrum

    International Nuclear Information System (INIS)

    Parkinson, David; Liddle, Andrew R.

    2010-01-01

    Cosmological parameter uncertainties are often stated assuming a particular model, neglecting the model uncertainty, even when Bayesian model selection is unable to identify a conclusive best model. Bayesian model averaging is a method for assessing parameter uncertainties in situations where there is also uncertainty in the underlying model. We apply model averaging to the estimation of the parameters associated with the primordial power spectra of curvature and tensor perturbations. We use CosmoNest and MultiNest to compute the model evidences and posteriors, using cosmic microwave data from WMAP, ACBAR, BOOMERanG, and CBI, plus large-scale structure data from the SDSS DR7. We find that the model-averaged 95% credible interval for the spectral index using all of the data is 0.940 s s is specified at a pivot scale 0.015 Mpc -1 . For the tensors model averaging can tighten the credible upper limit, depending on prior assumptions.

  14. The efficiency of average linkage hierarchical clustering algorithm associated multi-scale bootstrap resampling in identifying homogeneous precipitation catchments

    Science.gov (United States)

    Chuan, Zun Liang; Ismail, Noriszura; Shinyie, Wendy Ling; Lit Ken, Tan; Fam, Soo-Fen; Senawi, Azlyna; Yusoff, Wan Nur Syahidah Wan

    2018-04-01

    Due to the limited of historical precipitation records, agglomerative hierarchical clustering algorithms widely used to extrapolate information from gauged to ungauged precipitation catchments in yielding a more reliable projection of extreme hydro-meteorological events such as extreme precipitation events. However, identifying the optimum number of homogeneous precipitation catchments accurately based on the dendrogram resulted using agglomerative hierarchical algorithms are very subjective. The main objective of this study is to propose an efficient regionalized algorithm to identify the homogeneous precipitation catchments for non-stationary precipitation time series. The homogeneous precipitation catchments are identified using average linkage hierarchical clustering algorithm associated multi-scale bootstrap resampling, while uncentered correlation coefficient as the similarity measure. The regionalized homogeneous precipitation is consolidated using K-sample Anderson Darling non-parametric test. The analysis result shows the proposed regionalized algorithm performed more better compared to the proposed agglomerative hierarchical clustering algorithm in previous studies.

  15. The consequences of time averaging for measuring temporal species turnover in the fossil record

    Science.gov (United States)

    Tomašových, Adam; Kidwell, Susan

    2010-05-01

    Modeling time averaging effects with simple simulations allows us to evaluate the magnitude of change in temporal species turnover that is expected to occur in long (paleoecological) time series with fossil assemblages. Distinguishing different modes of metacommunity dynamics (such as neutral, density-dependent, or trade-off dynamics) with time-averaged fossil assemblages requires scaling-up time-averaging effects because the decrease in temporal resolution and the decrease in temporal inter-sample separation (i.e., the two main effects of time averaging) substantially increase community stability relative to assemblages without or with weak time averaging. Large changes in temporal scale that cover centuries to millennia can lead to unprecedented effects on temporal rate of change in species composition. Temporal variation in species composition monotonically decreases with increasing duration of time-averaging in simulated fossil assemblages. Time averaging is also associated with the reduction of species dominance owing to the temporal switching in the identity of dominant species. High degrees of time averaging can cause that community parameters of local fossil assemblages converge to parameters of metacommunity rather that to parameters of individual local non-averaged communities. We find that the low variation in species composition observed among mollusk and ostracod subfossil assemblages can be explained by time averaging alone, and low temporal resolution and reduced temporal separation among assemblages in time series can thus explain a substantial part of the reduced variation in species composition relative to unscaled predictions of neutral model (i.e., species do not differ in birth, death, and immigration rates on per capita basis). The structure of time-averaged assemblages can thus provide important insights into processes that act over larger temporal scales, such as evolution of niches and dispersal, range-limit dynamics, taxon cycles, and

  16. Linking Errors between Two Populations and Tests: A Case Study in International Surveys in Education

    Science.gov (United States)

    Hastedt, Dirk; Desa, Deana

    2015-01-01

    This simulation study was prompted by the current increased interest in linking national studies to international large-scale assessments (ILSAs) such as IEA's TIMSS, IEA's PIRLS, and OECD's PISA. Linkage in this scenario is achieved by including items from the international assessments in the national assessments on the premise that the average…

  17. TIMSS, PISA, IGLU Y DEMÁS: RAZÓN Y SINRAZÓN DE LOS ESTUDIOS INTERNACIONALES DE RENDIMIENTO ESCOLAR

    Directory of Open Access Journals (Sweden)

    Wilfried Bos

    2009-01-01

    Full Text Available Treinta años después de que los Estados Unidos tuvieran que vérselas con la llamada "crisis del Sputnik", Alemania ha recibido su contrapartida bajo la forma de la llamada "crisis del TIMSS". A partir de la publicación, a mediados de los años 90, de los primeros resultados de este estudio internacional en las áreas de matemática y ciencias naturales, los alemanes se han visto obligados a reconocer que su nivel de educación es mucho más bajo de lo esperado. La sorpresa fue grande, debido a que hacía años que Alemania no participaba regulamente en estudios internacionales de evaluación a gran escala. Como resultado de la "crisis", se puso un énfasis mucho mayor en la investigación educativa de carácter empírico. Una consecuencia positiva de ello fue que pudo realizarse una investigación más amplia en este campo; otra consecuencia, esta vez negativa, fue que muchas personas comenzaron a hablar acerca de estos estudios sin tener una comprensión adecuada de los mismos. En el presente artículo se pasa brevemente revista a los estudios realizados en Alemania, se reseñan algunas falsas interpretaciones que han cobrado notoriedad y, por último, se señala las perspectivas que pueden esperarse de la investigación futura y la utilización de sus resultados tanto en la investigación como en la práctica.

  18. Session Overview

    Science.gov (United States)

    Spencer, Cherrill

    2010-02-01

    High-school teachers are amongst the most important contributors to the development of the science and technology workforce of the future. Many of the more than 23,000 US high-school physics teachers are not adequately prepared to teach the subject. Only one-third of them, for example, majored in physics or physics education. Can inadequate teacher preparation be a factor in the poor performance of US students on international assessments of their achievements in science and physics? Since 1995 the Trends in International Mathematics and Science Study (TIMSS) has been administered four times to many hundreds of thousands of students in over 60 countries. TIMSS is used to measure trends in the mathematics and science knowledge and skills of fourth- and eighth-graders. The Program for International Student Assessment (PISA) has been administered three times since 2000, it focuses on 15-year-olds' capabilities in reading literacy, mathematics literacy, and science literacy. TIMSS Advanced (1995) assessed school-leaving students who have had special preparation in advanced mathematics and physics. In all these studies the US students, including the Advanced Placement physics students, scored below the international average, sometimes in the bottom third of countries! Three speakers have been invited to talk about the physics K-12 education systems in other countries, one that consistently scores at the top of the PISA (Finland) or score much higher than the USA on TIMSS ( various Northern European countries) and significantly better on recent bi-lateral comparisons (China). What can we learn from the physics teaching systems in these high-scoring countries that might be applied in the USA? There will be a panel discussion following the 3 invited talks, audience participation will be encouraged. )

  19. Multiple-scale stochastic processes: Decimation, averaging and beyond

    Energy Technology Data Exchange (ETDEWEB)

    Bo, Stefano, E-mail: stefano.bo@nordita.org [Nordita, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, SE-106 91 Stockholm (Sweden); Celani, Antonio [Quantitative Life Sciences, The Abdus Salam International Centre for Theoretical Physics (ICTP), Strada Costiera 11, I-34151 - Trieste (Italy)

    2017-02-07

    The recent experimental progresses in handling microscopic systems have allowed to probe them at levels where fluctuations are prominent, calling for stochastic modeling in a large number of physical, chemical and biological phenomena. This has provided fruitful applications for established stochastic methods and motivated further developments. These systems often involve processes taking place on widely separated time scales. For an efficient modeling one usually focuses on the slower degrees of freedom and it is of great importance to accurately eliminate the fast variables in a controlled fashion, carefully accounting for their net effect on the slower dynamics. This procedure in general requires to perform two different operations: decimation and coarse-graining. We introduce the asymptotic methods that form the basis of this procedure and discuss their application to a series of physical, biological and chemical examples. We then turn our attention to functionals of the stochastic trajectories such as residence times, counting statistics, fluxes, entropy production, etc. which have been increasingly studied in recent years. For such functionals, the elimination of the fast degrees of freedom can present additional difficulties and naive procedures can lead to blatantly inconsistent results. Homogenization techniques for functionals are less covered in the literature and we will pedagogically present them here, as natural extensions of the ones employed for the trajectories. We will also discuss recent applications of these techniques to the thermodynamics of small systems and their interpretation in terms of information-theoretic concepts.

  20. AN OVERVIEW ON AVERAGE SPEED ENFORCEMENT SYSTEM AND ROAD SAFETY EFFECTS

    OpenAIRE

    ILGAZ, ARZU; SALTAN, MEHMET

    2017-01-01

    Averagespeed enforcement system is a new intelligent transportation system applicationthat has gained popularity all over the world following Europe and Australiawhich is recently being applied in Turkey as well. The main task of the systemis measuring the average speeds of motorized vehicles for the purpose oftraffic sanctions. A literature survey related with average speed enforcementsystem was carried out in this study at an international scale. In addition toproviding a comprehensive summ...

  1. Hybrid Reynolds-Averaged/Large Eddy Simulation of the Flow in a Model SCRamjet Cavity Flameholder

    Science.gov (United States)

    Baurle, R. A.

    2016-01-01

    Steady-state and scale-resolving simulations have been performed for flow in and around a model scramjet combustor flameholder. Experimental data available for this configuration include velocity statistics obtained from particle image velocimetry. Several turbulence models were used for the steady-state Reynolds-averaged simulations which included both linear and non-linear eddy viscosity models. The scale-resolving simulations used a hybrid Reynolds-averaged/large eddy simulation strategy that is designed to be a large eddy simulation everywhere except in the inner portion (log layer and below) of the boundary layer. Hence, this formulation can be regarded as a wall-modeled large eddy simulation. This e ort was undertaken to not only assess the performance of the hybrid Reynolds-averaged / large eddy simulation modeling approach in a flowfield of interest to the scramjet research community, but to also begin to understand how this capability can best be used to augment standard Reynolds-averaged simulations. The numerical errors were quantified for the steady-state simulations, and at least qualitatively assessed for the scale-resolving simulations prior to making any claims of predictive accuracy relative to the measurements. The steady-state Reynolds-averaged results displayed a high degree of variability when comparing the flameholder fuel distributions obtained from each turbulence model. This prompted the consideration of applying the higher-fidelity scale-resolving simulations as a surrogate "truth" model to calibrate the Reynolds-averaged closures in a non-reacting setting prior to their use for the combusting simulations. In general, the Reynolds-averaged velocity profile predictions at the lowest fueling level matched the particle imaging measurements almost as well as was observed for the non-reacting condition. However, the velocity field predictions proved to be more sensitive to the flameholder fueling rate than was indicated in the measurements.

  2. Testing averaged cosmology with type Ia supernovae and BAO data

    Energy Technology Data Exchange (ETDEWEB)

    Santos, B.; Alcaniz, J.S. [Departamento de Astronomia, Observatório Nacional, 20921-400, Rio de Janeiro – RJ (Brazil); Coley, A.A. [Department of Mathematics and Statistics, Dalhousie University, Halifax, B3H 3J5 Canada (Canada); Devi, N. Chandrachani, E-mail: thoven@on.br, E-mail: aac@mathstat.dal.ca, E-mail: chandrachaniningombam@astro.unam.mx, E-mail: alcaniz@on.br [Instituto de Astronomía, Universidad Nacional Autónoma de México, Box 70-264, México City, México (Mexico)

    2017-02-01

    An important problem in precision cosmology is the determination of the effects of averaging and backreaction on observational predictions, particularly in view of the wealth of new observational data and improved statistical techniques. In this paper, we discuss the observational viability of a class of averaged cosmologies which consist of a simple parametrized phenomenological two-scale backreaction model with decoupled spatial curvature parameters. We perform a Bayesian model selection analysis and find that this class of averaged phenomenological cosmological models is favored with respect to the standard ΛCDM cosmological scenario when a joint analysis of current SNe Ia and BAO data is performed. In particular, the analysis provides observational evidence for non-trivial spatial curvature.

  3. Testing averaged cosmology with type Ia supernovae and BAO data

    International Nuclear Information System (INIS)

    Santos, B.; Alcaniz, J.S.; Coley, A.A.; Devi, N. Chandrachani

    2017-01-01

    An important problem in precision cosmology is the determination of the effects of averaging and backreaction on observational predictions, particularly in view of the wealth of new observational data and improved statistical techniques. In this paper, we discuss the observational viability of a class of averaged cosmologies which consist of a simple parametrized phenomenological two-scale backreaction model with decoupled spatial curvature parameters. We perform a Bayesian model selection analysis and find that this class of averaged phenomenological cosmological models is favored with respect to the standard ΛCDM cosmological scenario when a joint analysis of current SNe Ia and BAO data is performed. In particular, the analysis provides observational evidence for non-trivial spatial curvature.

  4. Hybrid Reynolds-Averaged/Large Eddy Simulation of a Cavity Flameholder; Assessment of Modeling Sensitivities

    Science.gov (United States)

    Baurle, R. A.

    2015-01-01

    Steady-state and scale-resolving simulations have been performed for flow in and around a model scramjet combustor flameholder. The cases simulated corresponded to those used to examine this flowfield experimentally using particle image velocimetry. A variety of turbulence models were used for the steady-state Reynolds-averaged simulations which included both linear and non-linear eddy viscosity models. The scale-resolving simulations used a hybrid Reynolds-averaged / large eddy simulation strategy that is designed to be a large eddy simulation everywhere except in the inner portion (log layer and below) of the boundary layer. Hence, this formulation can be regarded as a wall-modeled large eddy simulation. This effort was undertaken to formally assess the performance of the hybrid Reynolds-averaged / large eddy simulation modeling approach in a flowfield of interest to the scramjet research community. The numerical errors were quantified for both the steady-state and scale-resolving simulations prior to making any claims of predictive accuracy relative to the measurements. The steady-state Reynolds-averaged results showed a high degree of variability when comparing the predictions obtained from each turbulence model, with the non-linear eddy viscosity model (an explicit algebraic stress model) providing the most accurate prediction of the measured values. The hybrid Reynolds-averaged/large eddy simulation results were carefully scrutinized to ensure that even the coarsest grid had an acceptable level of resolution for large eddy simulation, and that the time-averaged statistics were acceptably accurate. The autocorrelation and its Fourier transform were the primary tools used for this assessment. The statistics extracted from the hybrid simulation strategy proved to be more accurate than the Reynolds-averaged results obtained using the linear eddy viscosity models. However, there was no predictive improvement noted over the results obtained from the explicit

  5. A Cross-grade Comparison to Examine the Context Effect on the Relationships Among Family Resources, School Climate, Learning Participation, Science Attitude, and Science Achievement Based on TIMSS 2003 in Taiwan

    Science.gov (United States)

    Chen, Shin-Feng; Lin, Chien-Yu; Wang, Jing-Ru; Lin, Sheau-Wen; Kao, Huey-Lien

    2012-09-01

    This study aimed to examine whether the relationships among family resources, school climate, learning participation, science attitude, and science achievement are different between primary school students and junior high school students within one educational system. The subjects included 4,181 Grade 4 students and 5,074 Grade 8 students who participated in TIMSS 2003 in Taiwan. Using structural equation modeling, the results showed that family resources had significant positive effects for both groups of learners. Furthermore, a context effect for the structural relationship between school climate, learning participation, and science achievement was revealed. In the primary school context, Grade 4 students who perceived positive school climate participated in school activities more actively, and had better science performance. However, in the secondary school context, learning participation had a negative impact and led to lower science achievement. The implications about this result in relation to the characteristics of the two educational contexts in Taiwan were further discussed.

  6. Relationship between synoptic scale weather systems and column averaged atmospheric CO2

    Science.gov (United States)

    Naja, M.; Yaremchuk, A.; Onishi, R.; Maksyutov, S.; Inoue, G.

    2005-12-01

    Analysis of the atmospheric CO2 observations with transport models contributes to the understanding of the geographical distributions of CO2 sources and sinks. Space-borne sensors could be advantageous for CO2 measurements as they can provide wider spatial and temporal coverage. Inversion studies have suggested requirement of better than 1% precision for the space-borne observations. Since sources and sinks are inferred from spatial and temporal gradients in CO2, the space-borne observations must have no significant geographically varying biases. To study the dynamical biases in column CO2 due to possible correlation between clouds and atmospheric CO2 at synoptic scale, we have made simulations of CO2 (1988-2003) using NIES tracer transport model. Model resolution is 2.5o x 2.5o in horizontal and it has 15 vertical sigma-layers. Fluxes for (1) fossil fuels, (2) terrestrial biosphere (CASA NEP), (3) the oceans, and (4) inverse model derived monthly regional fluxes from 11 land and 11 ocean regions are used. SVD truncation is used to filter out noise in the inverse model flux time series. Model reproduces fairly well CO2 global trend and observed time series at monitoring sites around the globe. Lower column CO2 concentration is simulated inside cyclonic systems in summer over North hemispheric continental areas. Surface pressure is used as a proxy for dynamics and it is demonstrated that anomalies in column averaged CO2 has fairly good correlation with the anomalies in surface pressure. Positive correlation, as high as 0.7, has been estimated over parts of Siberia and N. America in summer time. Our explanation is based on that the low-pressure system is associated the upward motion, which leads to lower column CO2 values over these regions due to lifting of CO2-depleted summertime PBL air, and higher column CO2 over source areas. A sensitivity study without inverse model fluxes shows same correlation. The low-pressure systems' induced negative biases are 0

  7. The use of test scores from large-scale assessment surveys: psychometric and statistical considerations

    Directory of Open Access Journals (Sweden)

    Henry Braun

    2017-11-01

    Full Text Available Abstract Background Economists are making increasing use of measures of student achievement obtained through large-scale survey assessments such as NAEP, TIMSS, and PISA. The construction of these measures, employing plausible value (PV methodology, is quite different from that of the more familiar test scores associated with assessments such as the SAT or ACT. These differences have important implications both for utilization and interpretation. Although much has been written about PVs, it appears that there are still misconceptions about whether and how to employ them in secondary analyses. Methods We address a range of technical issues, including those raised in a recent article that was written to inform economists using these databases. First, an extensive review of the relevant literature was conducted, with particular attention to key publications that describe the derivation and psychometric characteristics of such achievement measures. Second, a simulation study was carried out to compare the statistical properties of estimates based on the use of PVs with those based on other, commonly used methods. Results It is shown, through both theoretical analysis and simulation, that under fairly general conditions appropriate use of PV yields approximately unbiased estimates of model parameters in regression analyses of large scale survey data. The superiority of the PV methodology is particularly evident when measures of student achievement are employed as explanatory variables. Conclusions The PV methodology used to report student test performance in large scale surveys remains the state-of-the-art for secondary analyses of these databases.

  8. State Averages

    Data.gov (United States)

    U.S. Department of Health & Human Services — A list of a variety of averages for each state or territory as well as the national average, including each quality measure, staffing, fine amount and number of...

  9. Performance on International Assessments and Learning Time: A Snapshot of How the U.S. Compares to Other Education Systems on an International Scale. Informing Policy & Improving Practice. Policy Brief

    Science.gov (United States)

    Saxena, Pooja; Sell, LeeAnn

    2016-01-01

    Drawing from two international measures, Trends in International Mathematics and Science Studies (TIMSS) and Program for International Student Assessment (PISA), this brief provides a snapshot comparison of the United States to other education systems. Specifically, this brief addresses how the U.S. compares to other countries in overall…

  10. Averaging hydraulic head, pressure head, and gravitational head in subsurface hydrology, and implications for averaged fluxes, and hydraulic conductivity

    Directory of Open Access Journals (Sweden)

    G. H. de Rooij

    2009-07-01

    Full Text Available Current theories for water flow in porous media are valid for scales much smaller than those at which problem of public interest manifest themselves. This provides a drive for upscaled flow equations with their associated upscaled parameters. Upscaling is often achieved through volume averaging, but the solution to the resulting closure problem imposes severe restrictions to the flow conditions that limit the practical applicability. Here, the derivation of a closed expression of the effective hydraulic conductivity is forfeited to circumvent the closure problem. Thus, more limited but practical results can be derived. At the Representative Elementary Volume scale and larger scales, the gravitational potential and fluid pressure are treated as additive potentials. The necessary requirement that the superposition be maintained across scales is combined with conservation of energy during volume integration to establish consistent upscaling equations for the various heads. The power of these upscaling equations is demonstrated by the derivation of upscaled water content-matric head relationships and the resolution of an apparent paradox reported in the literature that is shown to have arisen from a violation of the superposition principle. Applying the upscaling procedure to Darcy's Law leads to the general definition of an upscaled hydraulic conductivity. By examining this definition in detail for porous media with different degrees of heterogeneity, a series of criteria is derived that must be satisfied for Darcy's Law to remain valid at a larger scale.

  11. High Average Power, High Energy Short Pulse Fiber Laser System

    Energy Technology Data Exchange (ETDEWEB)

    Messerly, M J

    2007-11-13

    Recently continuous wave fiber laser systems with output powers in excess of 500W with good beam quality have been demonstrated [1]. High energy, ultrafast, chirped pulsed fiber laser systems have achieved record output energies of 1mJ [2]. However, these high-energy systems have not been scaled beyond a few watts of average output power. Fiber laser systems are attractive for many applications because they offer the promise of high efficiency, compact, robust systems that are turn key. Applications such as cutting, drilling and materials processing, front end systems for high energy pulsed lasers (such as petawatts) and laser based sources of high spatial coherence, high flux x-rays all require high energy short pulses and two of the three of these applications also require high average power. The challenge in creating a high energy chirped pulse fiber laser system is to find a way to scale the output energy while avoiding nonlinear effects and maintaining good beam quality in the amplifier fiber. To this end, our 3-year LDRD program sought to demonstrate a high energy, high average power fiber laser system. This work included exploring designs of large mode area optical fiber amplifiers for high energy systems as well as understanding the issues associated chirped pulse amplification in optical fiber amplifier systems.

  12. Parameterization of Time-Averaged Suspended Sediment Concentration in the Nearshore

    Directory of Open Access Journals (Sweden)

    Hyun-Doug Yoon

    2015-11-01

    Full Text Available To quantify the effect of wave breaking turbulence on sediment transport in the nearshore, the vertical distribution of time-averaged suspended sediment concentration (SSC in the surf zone was parameterized in terms of the turbulent kinetic energy (TKE at different cross-shore locations, including the bar crest, bar trough, and inner surf zone. Using data from a large-scale laboratory experiment, a simple relationship was developed between the time-averaged SSC and the time-averaged TKE. The vertical variation of the time-averaged SSC was fitted to an equation analogous to the turbulent dissipation rate term. At the bar crest, the proposed equation was slightly modified to incorporate the effect of near-bed sediment processes and yielded reasonable agreement. This parameterization yielded the best agreement at the bar trough, with a coefficient of determination R2 ≥ 0.72 above the bottom boundary layer. The time-averaged SSC in the inner surf zone showed good agreement near the bed but poor agreement near the water surface, suggesting that there is a different sedimentation mechanism that controls the SSC in the inner surf zone.

  13. Averaging models: parameters estimation with the R-Average procedure

    Directory of Open Access Journals (Sweden)

    S. Noventa

    2010-01-01

    Full Text Available The Functional Measurement approach, proposed within the theoretical framework of Information Integration Theory (Anderson, 1981, 1982, can be a useful multi-attribute analysis tool. Compared to the majority of statistical models, the averaging model can account for interaction effects without adding complexity. The R-Average method (Vidotto & Vicentini, 2007 can be used to estimate the parameters of these models. By the use of multiple information criteria in the model selection procedure, R-Average allows for the identification of the best subset of parameters that account for the data. After a review of the general method, we present an implementation of the procedure in the framework of R-project, followed by some experiments using a Monte Carlo method.

  14. 75 FR 6368 - Submission for OMB Review; Comment Request

    Science.gov (United States)

    2010-02-09

    ... Science Study (TIMSS: 11) and Progress in International Reading Literacy Study (PIRLS: 11). Frequency... and Science Study (TIMSS) 2011 and the Progress in International Reading Literacy Study (PIRLS) 2011, both coordinated by the International Association for the Evaluation of Educational Achievement (IEA...

  15. Partial Averaged Navier-Stokes approach for cavitating flow

    International Nuclear Information System (INIS)

    Zhang, L; Zhang, Y N

    2015-01-01

    Partial Averaged Navier Stokes (PANS) is a numerical approach developed for studying practical engineering problems (e.g. cavitating flow inside hydroturbines) with a resonance cost and accuracy. One of the advantages of PANS is that it is suitable for any filter width, leading a bridging method from traditional Reynolds Averaged Navier-Stokes (RANS) to direct numerical simulations by choosing appropriate parameters. Comparing with RANS, the PANS model will inherit many physical nature from parent RANS but further resolve more scales of motion in great details, leading to PANS superior to RANS. As an important step for PANS approach, one need to identify appropriate physical filter-width control parameters e.g. ratios of unresolved-to-total kinetic energy and dissipation. In present paper, recent studies of cavitating flow based on PANS approach are introduced with a focus on the influences of filter-width control parameters on the simulation results

  16. Effects of average degree of network on an order–disorder transition in opinion dynamics

    International Nuclear Information System (INIS)

    Cun-Fang, Feng; Jian-Yue, Guan; Ying-Hai, Wang; Zhi-Xi, Wu

    2010-01-01

    We have investigated the influence of the average degree (k) of network on the location of an order-disorder transition in opinion dynamics. For this purpose, a variant of majority rule (VMR) model is applied to Watts–Strogatz (WS) small-world networks and Barabási–Albert (BA) scale-free networks which may describe some non-trivial properties of social systems. Using Monte Carlo simulations, we find that the order–disorder transition point of the VMR model is greatly affected by the average degree (k) of the networks; a larger value of (k) results in a more ordered state of the system. Comparing WS networks with BA networks, we find WS networks have better orderliness than BA networks when the average degree (k) is small. With the increase of (k), BA networks have a more ordered state. By implementing finite-size scaling analysis, we also obtain critical exponents β/ν, γ/ν and 1/ν for several values of average degree (k). Our results may be helpful to understand structural effects on order–disorder phase transition in the context of the majority rule model. (general)

  17. History, Philosophy and Sociology of Science in Science Education: Results from the Third International Mathematics and Science Study

    Science.gov (United States)

    Wang, Hsingchi A.; Sshmidt, William H.

    Throughout the history of enhancing the public scientific literacy, researchers have postulated that since every citizen is expected to have informal opinions on the relationships among government, education, and issues of scientific research and development, it is imperative that appreciation of the past complexities of science and society and the nature of scientific knowledge be a part of the education of both scientists and non-scientists. HPSS inclusion has been found to be an effective way to reach the goal of enhancing science literacy for all citizens. Although reports stated that HPSS inclusion is not a new educational practice in other part of the world, nevertheless, no large scale study has ever been attempted to report the HPSS educational conditions around the world. This study utilizes the rich data collected by TIMSS to unveil the current conditions of HPSS in the science education of about forty TIMSS countries. Based on the analysis results, recommendations to science educators of the world are provided.

  18. 78 FR 54245 - Agency Information Collection Activities; Submission to the Office of Management and Budget for...

    Science.gov (United States)

    2013-09-03

    ... Science Study (TIMSS): 2015 Recruitment and Field Test. OMB Control Number: 1850-0695. Type of Review: A... policy interest in preparedness for college and for careers in science, technology, engineering, and... International Mathematics and Science Study (TIMSS): 2015 Recruitment and Field Test AGENCY: Institute of...

  19. FEL system with homogeneous average output

    Energy Technology Data Exchange (ETDEWEB)

    Douglas, David R.; Legg, Robert; Whitney, R. Roy; Neil, George; Powers, Thomas Joseph

    2018-01-16

    A method of varying the output of a free electron laser (FEL) on very short time scales to produce a slightly broader, but smooth, time-averaged wavelength spectrum. The method includes injecting into an accelerator a sequence of bunch trains at phase offsets from crest. Accelerating the particles to full energy to result in distinct and independently controlled, by the choice of phase offset, phase-energy correlations or chirps on each bunch train. The earlier trains will be more strongly chirped, the later trains less chirped. For an energy recovered linac (ERL), the beam may be recirculated using a transport system with linear and nonlinear momentum compactions M.sub.56, which are selected to compress all three bunch trains at the FEL with higher order terms managed.

  20. Neutron resonance averaging

    International Nuclear Information System (INIS)

    Chrien, R.E.

    1986-10-01

    The principles of resonance averaging as applied to neutron capture reactions are described. Several illustrations of resonance averaging to problems of nuclear structure and the distribution of radiative strength in nuclei are provided. 30 refs., 12 figs

  1. Possibilities for an International Assessment in Geography

    Science.gov (United States)

    Lane, Rod; Bourke, Terri

    2017-01-01

    A recent editorial in International Research in Geographical and Environmental Education (IRGEE) highlighted an opportunity for the inclusion of geography as a subject in the Trends in International Mathematics and Science Study (TIMSS) tests. At present, TIMSS tests only encompass mathematics and physical sciences. The IRGEE editors encouraged…

  2. Average gluon and quark jet multiplicities at higher orders

    Energy Technology Data Exchange (ETDEWEB)

    Bolzoni, Paolo; Kniehl, Bernd A. [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik; Kotikov, Anatoly V. [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik; Joint Institute of Nuclear Research, Moscow (Russian Federation). Bogoliubov Lab. of Theoretical Physics

    2013-05-15

    We develop a new formalism for computing and including both the perturbative and nonperturbative QCD contributions to the scale evolution of average gluon and quark jet multiplicities. The new method is motivated by recent progress in timelike small-x resummation obtained in the MS factorization scheme. We obtain next-to-next-to-leading-logarithmic (NNLL) resummed expressions, which represent generalizations of previous analytic results. Our expressions depend on two nonperturbative parameters with clear and simple physical interpretations. A global fit of these two quantities to all available experimental data sets that are compatible with regard to the jet algorithms demonstrates by its goodness how our results solve a longstanding problem of QCD. We show that the statistical and theoretical uncertainties both do not exceed 5% for scales above 10 GeV. We finally propose to use the jet multiplicity data as a new way to extract the strong-coupling constant. Including all the available theoretical input within our approach, we obtain {alpha}{sub s}{sup (5)}(M{sub Z})=0.1199{+-}0.0026 in the MS scheme in an approximation equivalent to next-to-next-to-leading order enhanced by the resummations of ln(x) terms through the NNLL level and of ln Q{sup 2} terms by the renormalization group, in excellent agreement with the present world average.

  3. Ensemble-average versus suspension-scale Cauchy continuum-mechanical definitions of stress in polarized suspensions: Global homogenization of a dilute suspension of dipolar spherical particles

    International Nuclear Information System (INIS)

    Almog, Y.; Brenner, H.

    1999-01-01

    The macroscale rheological properties of a dilute suspension exposed to a uniform external field and composed of identical, rigid, inhomogeneous, dipolar, spherical particles dispersed in an incompressible Newtonian fluid and possessing the same mean density as the latter fluid are derived from knowledge of its microscale properties by applying a global ensemble-averaging technique. Each dipole, which is permanently embedded in the particle, is assumed to be generated by the presence of an inhomogeneous external body-force field in the particle interior resulting from the action of the uniform external field on an inhomogeneous distribution of interior matter. It is shown that although the ensemble-average stress tensor is symmetric, the suspension nevertheless behaves macroscopically as if it possessed an asymmetric stress tensor. This seeming contradiction can be traced to the fact that the average body force acting on the contents of any arbitrarily drawn volume lying in the interior of the suspension does not vanish despite the fact that each particle is 'neutrally buoyant'. That this force is not zero stems from the fact that some particles necessarily straddle the closed surface bounding that volume, and that the distribution of external body forces over the interiors of these particles is nonuniform. As such, that portion of the spherical particle lying outside of the surface enclosing the domain exerts a force on the remaining portion of the sphere lying within that domain. We then demonstrate that the natural macroscopic model, which is derived by equating the divergence of the suspension-scale stress appearing in that model to the ensemble-average external body-force field, and which predicts a symmetric stress tensor, is macroscopically deficient with respect to the more intuitive asymmetric stress model usually proposed by continuum mechanicians for such a suspension. It is shown that the latter, continuum-mechanical model recovers all the physically

  4. Dygtige lærere er en forudsætning for folkeskolens resultater

    DEFF Research Database (Denmark)

    Andersen, Frans Ørsted; Egelund, Niels

    2014-01-01

    Artiklen refererer til en række internationale undersøgelser af lærere og elevers kompetencer, bl.a. PIACC, TEDS-M og TIMSS......Artiklen refererer til en række internationale undersøgelser af lærere og elevers kompetencer, bl.a. PIACC, TEDS-M og TIMSS...

  5. Thermal effects in high average power optical parametric amplifiers.

    Science.gov (United States)

    Rothhardt, Jan; Demmler, Stefan; Hädrich, Steffen; Peschel, Thomas; Limpert, Jens; Tünnermann, Andreas

    2013-03-01

    Optical parametric amplifiers (OPAs) have the reputation of being average power scalable due to the instantaneous nature of the parametric process (zero quantum defect). This Letter reveals serious challenges originating from thermal load in the nonlinear crystal caused by absorption. We investigate these thermal effects in high average power OPAs based on beta barium borate. Absorption of both pump and idler waves is identified to contribute significantly to heating of the nonlinear crystal. A temperature increase of up to 148 K with respect to the environment is observed and mechanical tensile stress up to 40 MPa is found, indicating a high risk of crystal fracture under such conditions. By restricting the idler to a wavelength range far from absorption bands and removing the crystal coating we reduce the peak temperature and the resulting temperature gradient significantly. Guidelines for further power scaling of OPAs and other nonlinear devices are given.

  6. Author Details

    African Journals Online (AJOL)

    Mereku, DK. Vol 3 (2005) - Articles On What Foundation is Africa Building its Science and Technology Base?: Africa\\'s Participation in TIMSS-2003. Abstract PDF · Vol 4 (2006) - Articles The Contexts for Learning and Instruction Influencing Ghanaian JSS2 Students\\' Dismal Performance in TIMSS-2003. Abstract PDF · Vol 10 ...

  7. Potential for efficient frequency conversion at high average power using solid state nonlinear optical materials

    International Nuclear Information System (INIS)

    Eimerl, D.

    1985-01-01

    High-average-power frequency conversion using solid state nonlinear materials is discussed. Recent laboratory experience and new developments in design concepts show that current technology, a few tens of watts, may be extended by several orders of magnitude. For example, using KD*P, efficient doubling (>70%) of Nd:YAG at average powers approaching 100 KW is possible; and for doubling to the blue or ultraviolet regions, the average power may approach 1 MW. Configurations using segmented apertures permit essentially unlimited scaling of average power. High average power is achieved by configuring the nonlinear material as a set of thin plates with a large ratio of surface area to volume and by cooling the exposed surfaces with a flowing gas. The design and material fabrication of such a harmonic generator are well within current technology

  8. Design, experimental analysis, and unsteady Reynolds-averaged Navier-Stokes simulation of laboratory-scale counter-rotating vertical-axis turbines in marine environment

    Science.gov (United States)

    Doan, Minh; Padricelli, Claudrio; Obi, Shinnosuke; Totsuka, Yoshitaka

    2017-11-01

    We present the torque and power measurement of laboratory-scale counter-rotating vertical-axis hydrokinetic turbines, built around a magnetic hysteresis brake as the speed controller and a Hall-effect sensor as the rotational speed transducer. A couple of straight-three-bladed turbines were linked through a transmission of spur gears and timing pulleys and coupled to the electronic instrumentation via flexible shaft couplers. A total of 8 experiments in 2 configurations were conducted in the water channel facility (4-m long, 0.3-m wide, and 0.15-m deep). Power generation of the turbines (0.06-m rotor diameter) was measured and compared with that of single turbines of the same size. The wakes generated by these experiments were also measured by particle image velocimetry (PIV) and numerically simulated by unsteady Reynolds-averaged Navier-Stokes (URANS) simulation using OpenFOAM. Preliminary results from wake measurement indicated the mechanism of enhanced power production behind the counter-rotating configuration of vertical-axis turbines. Current address: Politecnico di Milano.

  9. Zonally averaged model of dynamics, chemistry and radiation for the atmosphere

    Science.gov (United States)

    Tung, K. K.

    1985-01-01

    A nongeostrophic theory of zonally averaged circulation is formulated using the nonlinear primitive equations on a sphere, taking advantage of the more direct relationship between the mean meridional circulation and diabatic heating rate which is available in isentropic coordinates. Possible differences between results of nongeostrophic theory and the commonly used geostrophic formulation are discussed concerning: (1) the role of eddy forcing of the diabatic circulation, and (2) the nonlinear nearly inviscid limit vs the geostrophic limit. Problems associated with the traditional Rossby number scaling in quasi-geostrophic formulations are pointed out and an alternate, more general scaling based on the smallness of mean meridional to zonal velocities for a rotating planet is suggested. Such a scaling recovers the geostrophic balanced wind relationship for the mean zonal flow but reveals that the mean meridional velocity is in general ageostrophic.

  10. On Averaging Rotations

    DEFF Research Database (Denmark)

    Gramkow, Claus

    1999-01-01

    In this article two common approaches to averaging rotations are compared to a more advanced approach based on a Riemannian metric. Very offten the barycenter of the quaternions or matrices that represent the rotations are used as an estimate of the mean. These methods neglect that rotations belo...... approximations to the Riemannian metric, and that the subsequent corrections are inherient in the least squares estimation. Keywords: averaging rotations, Riemannian metric, matrix, quaternion......In this article two common approaches to averaging rotations are compared to a more advanced approach based on a Riemannian metric. Very offten the barycenter of the quaternions or matrices that represent the rotations are used as an estimate of the mean. These methods neglect that rotations belong...

  11. School Emphasis on Academic Success: Exploring Changes in Science Performance in Norway between 2007 and 2011 Employing Two-Level SEM

    Science.gov (United States)

    Nilsen, Trude; Gustafsson, Jan-Eric

    2014-01-01

    We study whether changes in school emphasis on academic success (SEAS) and safe schools (SAFE) may explain the increased science performance in Norway between TIMSS 2007 and 2011. Two-level structural equation modelling (SEM) of merged TIMSS data was used to investigate whether changes in levels of SEAS and SAFE mediate the changes in science…

  12. Third International Mathematics and Science Study 1999 Video Study Technical Report: Volume 2--Science. Technical Report. NCES 2011-049

    Science.gov (United States)

    Garnier, Helen E.; Lemmens, Meike; Druker, Stephen L.; Roth, Kathleen J.

    2011-01-01

    This second volume of the Third International Mathematics and Science Study (TIMSS) 1999 Video Study Technical Report focuses on every aspect of the planning, implementation, processing, analysis, and reporting of the science components of the TIMSS 1999 Video Study. The report is intended to serve as a record of the actions and documentation of…

  13. Average-energy games

    Directory of Open Access Journals (Sweden)

    Patricia Bouyer

    2015-09-01

    Full Text Available Two-player quantitative zero-sum games provide a natural framework to synthesize controllers with performance guarantees for reactive systems within an uncontrollable environment. Classical settings include mean-payoff games, where the objective is to optimize the long-run average gain per action, and energy games, where the system has to avoid running out of energy. We study average-energy games, where the goal is to optimize the long-run average of the accumulated energy. We show that this objective arises naturally in several applications, and that it yields interesting connections with previous concepts in the literature. We prove that deciding the winner in such games is in NP inter coNP and at least as hard as solving mean-payoff games, and we establish that memoryless strategies suffice to win. We also consider the case where the system has to minimize the average-energy while maintaining the accumulated energy within predefined bounds at all times: this corresponds to operating with a finite-capacity storage for energy. We give results for one-player and two-player games, and establish complexity bounds and memory requirements.

  14. Aggression in Primary Schools: The Predictive Power of the School and Home Environment

    Science.gov (United States)

    Kozina, Ana

    2015-01-01

    In this study, we analyse the predictive power of home and school environment-related factors for determining pupils' aggression. The multiple regression analyses are performed for fourth- and eighth-grade pupils based on the Trends in Mathematics and Science Study (TIMSS) 2007 (N = 8394) and TIMSS 2011 (N = 9415) databases for Slovenia. At the…

  15. Empirical scaling for present ohmic heated tokamaks

    International Nuclear Information System (INIS)

    Daughney, C.

    1975-06-01

    Empirical scaling laws are given for the average electron temperature and electron energy confinement time as functions of plasma current, average electron density, effective ion charge, toroidal magnetic field, and major and minor plasma radius. The ohmic heating is classical, and the electron energy transport is anomalous. The present scaling indicates that ohmic-heating becomes ineffective with larger experiments. (U.S.)

  16. Averaging of nonlinearity-managed pulses

    International Nuclear Information System (INIS)

    Zharnitsky, Vadim; Pelinovsky, Dmitry

    2005-01-01

    We consider the nonlinear Schroedinger equation with the nonlinearity management which describes Bose-Einstein condensates under Feshbach resonance. By using an averaging theory, we derive the Hamiltonian averaged equation and compare it with other averaging methods developed for this problem. The averaged equation is used for analytical approximations of nonlinearity-managed solitons

  17. Small-scale eruptive filaments on the quiet sun

    International Nuclear Information System (INIS)

    Hermans, L.M.; Martin, S.F.

    1986-01-01

    A study of a little known class of eruptive events on the quiet sun was conducted. All of 61 small-scale eruptive filamentary structures were identified in a systematic survey of 32 days of H alpha time-lapse films of the quiet sun acquired at Big Bear Solar Observatory. When fully developed, these structures have an average length of 15 arc seconds before eruption. They appear to be the small-scale analog of large-scale eruptive filaments observed against the disk. At the observed rate of 1.9 small-scale eruptive features per field of view per average 7.0 hour day, the rate of occurence of these events on the sun were estimated to be greater than 600 per 24 hour day.. The average duration of the eruptive phase was 26 minutes while the average lifetime from formation through eruption was 70 minutes. A majority of the small-scale filamentary sturctures were spatially related to cancelling magnetic features in line-of-sight photospheric magnetograms. Similar to large-scale filaments, the small-scale filamentary structures sometimes divided opposite polarity cancelling fragments but often had one or both ends terminating at a cancellation site. Their high numbers appear to reflect the much greater flux on the quiet sun. From their characteristics, evolution, and relationship to photospheric magnetic flux, it was concluded that the structures described are small-scale eruptive filaments and are a subset of all filaments

  18. Effect of wettability on scale-up of multiphase flow from core-scale to reservoir fine-grid-scale

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Y.C.; Mani, V.; Mohanty, K.K. [Univ. of Houston, TX (United States)

    1997-08-01

    Typical field simulation grid-blocks are internally heterogeneous. The objective of this work is to study how the wettability of the rock affects its scale-up of multiphase flow properties from core-scale to fine-grid reservoir simulation scale ({approximately} 10{prime} x 10{prime} x 5{prime}). Reservoir models need another level of upscaling to coarse-grid simulation scale, which is not addressed here. Heterogeneity is modeled here as a correlated random field parameterized in terms of its variance and two-point variogram. Variogram models of both finite (spherical) and infinite (fractal) correlation length are included as special cases. Local core-scale porosity, permeability, capillary pressure function, relative permeability functions, and initial water saturation are assumed to be correlated. Water injection is simulated and effective flow properties and flow equations are calculated. For strongly water-wet media, capillarity has a stabilizing/homogenizing effect on multiphase flow. For small variance in permeability, and for small correlation length, effective relative permeability can be described by capillary equilibrium models. At higher variance and moderate correlation length, the average flow can be described by a dynamic relative permeability. As the oil wettability increases, the capillary stabilizing effect decreases and the deviation from this average flow increases. For fractal fields with large variance in permeability, effective relative permeability is not adequate in describing the flow.

  19. Increasing average period lengths by switching of robust chaos maps in finite precision

    Science.gov (United States)

    Nagaraj, N.; Shastry, M. C.; Vaidya, P. G.

    2008-12-01

    Grebogi, Ott and Yorke (Phys. Rev. A 38, 1988) have investigated the effect of finite precision on average period length of chaotic maps. They showed that the average length of periodic orbits (T) of a dynamical system scales as a function of computer precision (ɛ) and the correlation dimension (d) of the chaotic attractor: T ˜ɛ-d/2. In this work, we are concerned with increasing the average period length which is desirable for chaotic cryptography applications. Our experiments reveal that random and chaotic switching of deterministic chaotic dynamical systems yield higher average length of periodic orbits as compared to simple sequential switching or absence of switching. To illustrate the application of switching, a novel generalization of the Logistic map that exhibits Robust Chaos (absence of attracting periodic orbits) is first introduced. We then propose a pseudo-random number generator based on chaotic switching between Robust Chaos maps which is found to successfully pass stringent statistical tests of randomness.

  20. A virtual pebble game to ensemble average graph rigidity.

    Science.gov (United States)

    González, Luis C; Wang, Hui; Livesay, Dennis R; Jacobs, Donald J

    2015-01-01

    The body-bar Pebble Game (PG) algorithm is commonly used to calculate network rigidity properties in proteins and polymeric materials. To account for fluctuating interactions such as hydrogen bonds, an ensemble of constraint topologies are sampled, and average network properties are obtained by averaging PG characterizations. At a simpler level of sophistication, Maxwell constraint counting (MCC) provides a rigorous lower bound for the number of internal degrees of freedom (DOF) within a body-bar network, and it is commonly employed to test if a molecular structure is globally under-constrained or over-constrained. MCC is a mean field approximation (MFA) that ignores spatial fluctuations of distance constraints by replacing the actual molecular structure by an effective medium that has distance constraints globally distributed with perfect uniform density. The Virtual Pebble Game (VPG) algorithm is a MFA that retains spatial inhomogeneity in the density of constraints on all length scales. Network fluctuations due to distance constraints that may be present or absent based on binary random dynamic variables are suppressed by replacing all possible constraint topology realizations with the probabilities that distance constraints are present. The VPG algorithm is isomorphic to the PG algorithm, where integers for counting "pebbles" placed on vertices or edges in the PG map to real numbers representing the probability to find a pebble. In the VPG, edges are assigned pebble capacities, and pebble movements become a continuous flow of probability within the network. Comparisons between the VPG and average PG results over a test set of proteins and disordered lattices demonstrate the VPG quantitatively estimates the ensemble average PG results well. The VPG performs about 20% faster than one PG, and it provides a pragmatic alternative to averaging PG rigidity characteristics over an ensemble of constraint topologies. The utility of the VPG falls in between the most

  1. The difference between alternative averages

    Directory of Open Access Journals (Sweden)

    James Vaupel

    2012-09-01

    Full Text Available BACKGROUND Demographers have long been interested in how compositional change, e.g., change in age structure, affects population averages. OBJECTIVE We want to deepen understanding of how compositional change affects population averages. RESULTS The difference between two averages of a variable, calculated using alternative weighting functions, equals the covariance between the variable and the ratio of the weighting functions, divided by the average of the ratio. We compare weighted and unweighted averages and also provide examples of use of the relationship in analyses of fertility and mortality. COMMENTS Other uses of covariances in formal demography are worth exploring.

  2. What does it mean to be average? : the miles per gallon versus gallons per mile paradox revisited

    NARCIS (Netherlands)

    Haans, A.

    2008-01-01

    In the efficiency paradox, which was introduced by Hand (1994; J R Stat Soc A, 157, 317-356), two groups of engineers are in disagreement about the average fuel efficiency of a set of cars. One group measured efficiency on a miles per gallon scale, the other on a gallons per mile scale. In the

  3. Quasi-analytical treatment of spatially averaged radiation transfer in complex terrain

    Science.gov (United States)

    LöWe, H.; Helbig, N.

    2012-10-01

    We provide a new quasi-analytical method to compute the subgrid topographic influences on the shortwave radiation fluxes and the effective albedo in complex terrain as required for large-scale meteorological, land surface, or climate models. We investigate radiative transfer in complex terrain via the radiosity equation on isotropic Gaussian random fields. Under controlled approximations we derive expressions for domain-averaged fluxes of direct, diffuse, and terrain radiation and the sky view factor. Domain-averaged quantities can be related to a type of level-crossing probability of the random field, which is approximated by long-standing results developed for acoustic scattering at ocean boundaries. This allows us to express all nonlocal horizon effects in terms of a local terrain parameter, namely, the mean-square slope. Emerging integrals are computed numerically, and fit formulas are given for practical purposes. As an implication of our approach, we provide an expression for the effective albedo of complex terrain in terms of the Sun elevation angle, mean-square slope, the area-averaged surface albedo, and the ratio of atmospheric direct beam to diffuse radiation. For demonstration we compute the decrease of the effective albedo relative to the area-averaged albedo in Switzerland for idealized snow-covered and clear-sky conditions at noon in winter. We find an average decrease of 5.8% and spatial patterns which originate from characteristics of the underlying relief. Limitations and possible generalizations of the method are discussed.

  4. Achievement of Serbian eighth grade students in science

    Directory of Open Access Journals (Sweden)

    Antonijević Radovan

    2006-01-01

    Full Text Available The paper considers the main results and some educational implications of the TIMSS 2003 assessment conducted in Serbia in the fields of the science achievement of Serbian eighth grade students and the science curriculum context of their achievement. There were 4264 students in the sample. It was confirmed that Serbian eighth graders had made average scale score of 468 points in the science, and with this achievement they are placed in the zone of the top of low international benchmarking level, very close to the point of intermediate benchmark. The average science achievement of the Serbian eighth graders is somewhat below the general international science achievement. The best results were achieved in the science content domain of "chemistry", and the lower results in the content domain of "environmental science". Across the defined science cognitive domains, it was confirmed that the Serbian students had achieved the best results in cognitive domain of "factual knowledge" and weaker results in "reasoning and analysis". The achieved results raise many questions about contents of the science curriculum in Serbia, its overall quality and basic characteristics of its implementation. These results can be eligibly used to improve the science curricula and teaching in Serbian primary school. .

  5. Coarse-mesh discretized low-order quasi-diffusion equations for subregion averaged scalar fluxes

    International Nuclear Information System (INIS)

    Anistratov, D. Y.

    2004-01-01

    In this paper we develop homogenization procedure and discretization for the low-order quasi-diffusion equations on coarse grids for core-level reactor calculations. The system of discretized equations of the proposed method is formulated in terms of the subregion averaged group scalar fluxes. The coarse-mesh solution is consistent with a given fine-mesh discretization of the transport equation in the sense that it preserves a set of average values of the fine-mesh transport scalar flux over subregions of coarse-mesh cells as well as the surface currents, and eigenvalue. The developed method generates numerical solution that mimics the large-scale behavior of the transport solution within assemblies. (authors)

  6. Bayesian model averaging and weighted average least squares : Equivariance, stability, and numerical issues

    NARCIS (Netherlands)

    De Luca, G.; Magnus, J.R.

    2011-01-01

    In this article, we describe the estimation of linear regression models with uncertainty about the choice of the explanatory variables. We introduce the Stata commands bma and wals, which implement, respectively, the exact Bayesian model-averaging estimator and the weighted-average least-squares

  7. Attention problems and hyperactivity as predictors of college grade point average.

    Science.gov (United States)

    Schwanz, Kerry A; Palm, Linda J; Brallier, Sara A

    2007-11-01

    This study examined the relative contributions of measures of attention problems and hyperactivity to the prediction of college grade point average (GPA). A sample of 316 students enrolled in introductory psychology and sociology classes at a southeastern university completed the BASC-2 Self-Report of Personality College Form. Scores on the attention problems scale and the hyperactivity scale of the BASC-2 were entered into a regression equation as predictors of cumulative GPA. Each of the independent variables made a significant contribution to the prediction of GPA. Attention problem scores alone explained 7% of the variability in GPAs. The addition of hyperactivity scores to the equation produced a 2% increase in explanatory power. The implications of these results for assessing symptoms of inattention and hyperactivity in college students are discussed.

  8. Factors significantly related to science achievement of Malaysian middle school students: An analysis of TIMSS 1999 data

    Science.gov (United States)

    Mokshein, Siti Eshah

    The importance of science and technology in the global economy has led to growing emphasis on math and science achievement all over the world. In this study, I seek to identify variables at the student-level and school-level that account for the variation in science achievement of the eighth graders in Malaysia. Using the Third International Math and Science Study (TIMSS) 1999 for Malaysia, a series of HLM analysis was performed. Results indicate that (1) variation in overall science achievement is greater between schools than within schools; (2) both the selected student-level and school-level factors are Important in explaining the variation in the eight graders' achievement In science; (3) the selected student-level variables explain about 13% of the variation in students' achievement within schools, but as an aggregate, they account for a much larger proportion of the between-school variance; (4) the selected school-level variables account for about 55% of the variation between schools; (5) within schools, the effects of self-concept In science, awareness of the social implications of science, gender, and home educational resources are significantly related to achievement; (6) the effects of self-concept in science and awareness of social implications of science are significant even after controlling for the effects of SES; (7) between schools, the effects of the mean of home educational resources, mean of parents' education, mean of awareness of the social implications of science, and emphasis on conducting experiments are significantly related to achievement; (8) the effects of SES variables explain about 50% of the variation in the school means achievement; and (9) the effects of emphasis on conducting experiments on achievement are significant even after controlling for the effects of SES. Since it is hard to change the society, it is recommended that efforts to Improve science achievement be focused more at the school-level, concentrating on variables that

  9. Digitale Medien in der Grundschule

    Directory of Open Access Journals (Sweden)

    Birgit Eickelmann

    2013-06-01

    Full Text Available Mit der internationalen Grundschulleistungsstudie Trends in International Mathematics and Science Study (TIMSS 2011; vgl. Bos/Wendt/Köller/Selter 2012; Suchań/Wallner-Paschon/Bergmüller/Schreiner 2012 liegen aktuelle Daten zur schulischen und außerschulischen Nutzung digitaler Medien durch GrundschülerInnen sowie Lehrerdaten über den Einsatz von digitalen Medien in der Schule sowie im Fachunterricht in den Fächern Mathematik und Naturwissenschaften vor. Mit diesem Beitrag sollen die für die beteiligten Länder repräsentativen Daten genutzt werden, um Einblicke in die schulische und außerschulische Nutzung digitaler Medien durch Grundschulkinder am Ende der vierten Klasse zu geben. Dabei werden die Länder Deutschland und Österreich fokussiert und verglichen. Die Befunde werden theoretisch im Gesamtkontext der Medienpädagogik und vor dem Hintergrund der Qualitätsentwicklung von Schulsystemen im internationalen Vergleich diskutiert.With the international large-scale assessment study TIMSS 2011 (Trends in International Mathematics and Science Study; cf. Bos/Wendt/Köller/Selter 2012; Suchań/Wallner-Paschon/Bergmüller/Schreiner 2012 rich data concerning primary students’ and teachers’ use of computers is available. This data gives insights into the use of digital media both at school and in subject specific courses such as mathematics and science. With this contribution representative TIMSS-data is used to examine the role of new technologies at the end of Grade 4. In this process, a description and a comparison of the educational systems in Germany and in Austria will be focused. Findings will be discussed in the light of media education and the quality of school systems in the context of international developments.

  10. How to average logarithmic retrievals?

    Directory of Open Access Journals (Sweden)

    B. Funke

    2012-04-01

    Full Text Available Calculation of mean trace gas contributions from profiles obtained by retrievals of the logarithm of the abundance rather than retrievals of the abundance itself are prone to biases. By means of a system simulator, biases of linear versus logarithmic averaging were evaluated for both maximum likelihood and maximum a priori retrievals, for various signal to noise ratios and atmospheric variabilities. These biases can easily reach ten percent or more. As a rule of thumb we found for maximum likelihood retrievals that linear averaging better represents the true mean value in cases of large local natural variability and high signal to noise ratios, while for small local natural variability logarithmic averaging often is superior. In the case of maximum a posteriori retrievals, the mean is dominated by the a priori information used in the retrievals and the method of averaging is of minor concern. For larger natural variabilities, the appropriateness of the one or the other method of averaging depends on the particular case because the various biasing mechanisms partly compensate in an unpredictable manner. This complication arises mainly because of the fact that in logarithmic retrievals the weight of the prior information depends on abundance of the gas itself. No simple rule was found on which kind of averaging is superior, and instead of suggesting simple recipes we cannot do much more than to create awareness of the traps related with averaging of mixing ratios obtained from logarithmic retrievals.

  11. Køn i standardiserede undersøgelser - og komplekse effekter

    DEFF Research Database (Denmark)

    Vittrup, Bonnie

    2013-01-01

    Artiklen undersøger hvordan køn konstrueres i to rapporter fra to store internationale undersøgelser, hhv. PISA og TIMSS og peger på (køns)pædagogiske konsekvenser.......Artiklen undersøger hvordan køn konstrueres i to rapporter fra to store internationale undersøgelser, hhv. PISA og TIMSS og peger på (køns)pædagogiske konsekvenser....

  12. Scaling laws and fluctuations in the statistics of word frequencies

    Science.gov (United States)

    Gerlach, Martin; Altmann, Eduardo G.

    2014-11-01

    In this paper, we combine statistical analysis of written texts and simple stochastic models to explain the appearance of scaling laws in the statistics of word frequencies. The average vocabulary of an ensemble of fixed-length texts is known to scale sublinearly with the total number of words (Heaps’ law). Analyzing the fluctuations around this average in three large databases (Google-ngram, English Wikipedia, and a collection of scientific articles), we find that the standard deviation scales linearly with the average (Taylor's law), in contrast to the prediction of decaying fluctuations obtained using simple sampling arguments. We explain both scaling laws (Heaps’ and Taylor) by modeling the usage of words using a Poisson process with a fat-tailed distribution of word frequencies (Zipf's law) and topic-dependent frequencies of individual words (as in topic models). Considering topical variations lead to quenched averages, turn the vocabulary size a non-self-averaging quantity, and explain the empirical observations. For the numerous practical applications relying on estimations of vocabulary size, our results show that uncertainties remain large even for long texts. We show how to account for these uncertainties in measurements of lexical richness of texts with different lengths.

  13. Position-Dependent Dynamics Explain Pore-Averaged Diffusion in Strongly Attractive Adsorptive Systems.

    Science.gov (United States)

    Krekelberg, William P; Siderius, Daniel W; Shen, Vincent K; Truskett, Thomas M; Errington, Jeffrey R

    2017-12-12

    Using molecular simulations, we investigate the relationship between the pore-averaged and position-dependent self-diffusivity of a fluid adsorbed in a strongly attractive pore as a function of loading. Previous work (Krekelberg, W. P.; Siderius, D. W.; Shen, V. K.; Truskett, T. M.; Errington, J. R. Connection between thermodynamics and dynamics of simple fluids in highly attractive pores. Langmuir 2013, 29, 14527-14535, doi: 10.1021/la4037327) established that pore-averaged self-diffusivity in the multilayer adsorption regime, where the fluid exhibits a dense film at the pore surface and a lower density interior pore region, is nearly constant as a function of loading. Here we show that this puzzling behavior can be understood in terms of how loading affects the fraction of particles that reside in the film and interior pore regions as well as their distinct dynamics. Specifically, the insensitivity of pore-averaged diffusivity to loading arises from the approximate cancellation of two factors: an increase in the fraction of particles in the higher diffusivity interior pore region with loading and a corresponding decrease in the particle diffusivity in that region. We also find that the position-dependent self-diffusivities scale with the position-dependent density. We present a model for predicting the pore-average self-diffusivity based on the position-dependent self-diffusivity, which captures the unusual characteristics of pore-averaged self-diffusivity in strongly attractive pores over several orders of magnitude.

  14. Collider Scaling and Cost Estimation

    International Nuclear Information System (INIS)

    Palmer, R.B.

    1986-01-01

    This paper deals with collider cost and scaling. The main points of the discussion are the following ones: 1) scaling laws and cost estimation: accelerating gradient requirements, total stored RF energy considerations, peak power consideration, average power consumption; 2) cost optimization; 3) Bremsstrahlung considerations; 4) Focusing optics: conventional, laser focusing or super disruption. 13 refs

  15. On Averaging Rotations

    DEFF Research Database (Denmark)

    Gramkow, Claus

    2001-01-01

    In this paper two common approaches to averaging rotations are compared to a more advanced approach based on a Riemannian metric. Very often the barycenter of the quaternions or matrices that represent the rotations are used as an estimate of the mean. These methods neglect that rotations belong ...... approximations to the Riemannian metric, and that the subsequent corrections are inherent in the least squares estimation.......In this paper two common approaches to averaging rotations are compared to a more advanced approach based on a Riemannian metric. Very often the barycenter of the quaternions or matrices that represent the rotations are used as an estimate of the mean. These methods neglect that rotations belong...

  16. Scale-by-scale contributions to Lagrangian particle acceleration

    Science.gov (United States)

    Lalescu, Cristian C.; Wilczek, Michael

    2017-11-01

    Fluctuations on a wide range of scales in both space and time are characteristic of turbulence. Lagrangian particles, advected by the flow, probe these fluctuations along their trajectories. In an effort to isolate the influence of the different scales on Lagrangian statistics, we employ direct numerical simulations (DNS) combined with a filtering approach. Specifically, we study the acceleration statistics of tracers advected in filtered fields to characterize the smallest temporal scales of the flow. Emphasis is put on the acceleration variance as a function of filter scale, along with the scaling properties of the relevant terms of the Navier-Stokes equations. We furthermore discuss scaling ranges for higher-order moments of the tracer acceleration, as well as the influence of the choice of filter on the results. Starting from the Lagrangian tracer acceleration as the short time limit of the Lagrangian velocity increment, we also quantify the influence of filtering on Lagrangian intermittency. Our work complements existing experimental results on intermittency and accelerations of finite-sized, neutrally-buoyant particles: for the passive tracers used in our DNS, feedback effects are neglected such that the spatial averaging effect is cleanly isolated.

  17. Lagrangian averaging with geodesic mean.

    Science.gov (United States)

    Oliver, Marcel

    2017-11-01

    This paper revisits the derivation of the Lagrangian averaged Euler (LAE), or Euler- α equations in the light of an intrinsic definition of the averaged flow map as the geodesic mean on the volume-preserving diffeomorphism group. Under the additional assumption that first-order fluctuations are statistically isotropic and transported by the mean flow as a vector field, averaging of the kinetic energy Lagrangian of an ideal fluid yields the LAE Lagrangian. The derivation presented here assumes a Euclidean spatial domain without boundaries.

  18. A Lagrangian dynamic subgrid-scale model turbulence

    Science.gov (United States)

    Meneveau, C.; Lund, T. S.; Cabot, W.

    1994-01-01

    A new formulation of the dynamic subgrid-scale model is tested in which the error associated with the Germano identity is minimized over flow pathlines rather than over directions of statistical homogeneity. This procedure allows the application of the dynamic model with averaging to flows in complex geometries that do not possess homogeneous directions. The characteristic Lagrangian time scale over which the averaging is performed is chosen such that the model is purely dissipative, guaranteeing numerical stability when coupled with the Smagorinsky model. The formulation is tested successfully in forced and decaying isotropic turbulence and in fully developed and transitional channel flow. In homogeneous flows, the results are similar to those of the volume-averaged dynamic model, while in channel flow, the predictions are superior to those of the plane-averaged dynamic model. The relationship between the averaged terms in the model and vortical structures (worms) that appear in the LES is investigated. Computational overhead is kept small (about 10 percent above the CPU requirements of the volume or plane-averaged dynamic model) by using an approximate scheme to advance the Lagrangian tracking through first-order Euler time integration and linear interpolation in space.

  19. How long the singular value decomposed entropy predicts the stock market? - Evidence from the Dow Jones Industrial Average Index

    Science.gov (United States)

    Gu, Rongbao; Shao, Yanmin

    2016-07-01

    In this paper, a new concept of multi-scales singular value decomposition entropy based on DCCA cross correlation analysis is proposed and its predictive power for the Dow Jones Industrial Average Index is studied. Using Granger causality analysis with different time scales, it is found that, the singular value decomposition entropy has predictive power for the Dow Jones Industrial Average Index for period less than one month, but not for more than one month. This shows how long the singular value decomposition entropy predicts the stock market that extends Caraiani's result obtained in Caraiani (2014). On the other hand, the result also shows an essential characteristic of stock market as a chaotic dynamic system.

  20. Scaling laws and fluctuations in the statistics of word frequencies

    International Nuclear Information System (INIS)

    Gerlach, Martin; Altmann, Eduardo G

    2014-01-01

    In this paper, we combine statistical analysis of written texts and simple stochastic models to explain the appearance of scaling laws in the statistics of word frequencies. The average vocabulary of an ensemble of fixed-length texts is known to scale sublinearly with the total number of words (Heaps’ law). Analyzing the fluctuations around this average in three large databases (Google-ngram, English Wikipedia, and a collection of scientific articles), we find that the standard deviation scales linearly with the average (Taylor's law), in contrast to the prediction of decaying fluctuations obtained using simple sampling arguments. We explain both scaling laws (Heaps’ and Taylor) by modeling the usage of words using a Poisson process with a fat-tailed distribution of word frequencies (Zipf's law) and topic-dependent frequencies of individual words (as in topic models). Considering topical variations lead to quenched averages, turn the vocabulary size a non-self-averaging quantity, and explain the empirical observations. For the numerous practical applications relying on estimations of vocabulary size, our results show that uncertainties remain large even for long texts. We show how to account for these uncertainties in measurements of lexical richness of texts with different lengths. (paper)

  1. Estimate of average glandular dose (AGD) in national clinics of mammography

    International Nuclear Information System (INIS)

    Mora, Patricia; Segura, Helena

    2004-01-01

    The breast cancer represents the second cause of death by cancer in the femme population of our country. The specialized equipment for the obtaining of the mammographic images is higher every day and its use increases daily. The quality of the radiographic study is linked to the dose that this tissue intrinsically sensible receives to the ionizing radiations. The present work makes the first national study to quantify the average glandular doses and to connect them with the diagnostic quality and the recommendations to international scale. (Author) [es

  2. ANALISIS KEMAMPUAN PEMECAHAN MASALAH MATEMATIKA SOAL SETIPE TIMSS BERDASARKAN GAYA KOGNITIF SISWA PADA PEMBELAJARAN MODEL PROBLEM BASED LEARNING

    Directory of Open Access Journals (Sweden)

    Lia Vendiagrys

    2015-08-01

    Full Text Available Gaya kognitif memiliki peran yang sangat penting dalam proses pemecahan masalah. Penelitian ini bertujuan untuk memperoleh deskripsi profil kemampuan pemecahan masalah  matematika soal setipe TIMSS pada siswa SMP kelas VIII dengan gaya kognitif FI dan FD. Penelitian ini merupakan penelitian deskriptif. Subjek penelitian ini adalah tiga siswa FI dan tiga siswa FD kelas VIII SMP 3 Kudus. Teknik pengumpulan data adalah dokumen, tes, dan wawancara. Analisis data meliputi reduksi, penyajian data,dan  penarikan kesimpulan. Hasil penelitian sebagai berikut (1 untuk subjek FI dalam  menyelesaikan masalah memiliki profil:  dapat memahami pernyataan verbal dari masalah dan mengubahnya ke dalam kalimat matematika, lebih analitis dalam menerima informasi,  dapat memperluas hasil pemecahan masalah dan pemikiran matematis, memberikan suatu pembenaran berdasarkan pada hasil,dan memecahkan masalah dalam konteks kehidupan nyata,  memperoleh jawaban yang benar, (2  Untuk subjek FD dalam menyelesaikan masalah memiliki profil: dapat memahami pernyataan verbal dari masalah,tetapi tidak dapat mengubahnya ke dalam kalimat matematika,  lebih global dalam menerima informasi, mudah terpengaruh manipulasi unsur pengecoh karena memandang secara global, tidak dapat memperluas hasil pemecahan masalah, memberikan suatu pembenaran berdasarkan pada hasil,dan memecahkan masalah dalam konteks kehidupan nyata, sering tidak dapat memperoleh jawaban yang benar.Cognitive style has a very important role in the process of problem solving. This study aimed to obtain a profile of mathematical problem solving ability student with FI and FD cognitive style. This research is a descriptive qualitative approach. Subjects in this study were students of class VIII SMP 3 Kudus, ie three students FI and FD. Data collection techniques is a document, test, interview. Data analysis included reduction, presentation, and conclusion. The results of the study show that subject FI in resolving

  3. An Experimental Observation of Axial Variation of Average Size of Methane Clusters in a Gas Jet

    International Nuclear Information System (INIS)

    Ji-Feng, Han; Chao-Wen, Yang; Jing-Wei, Miao; Jian-Feng, Lu; Meng, Liu; Xiao-Bing, Luo; Mian-Gong, Shi

    2010-01-01

    Axial variation of average size of methane clusters in a gas jet produced by supersonic expansion of methane through a cylindrical nozzle of 0.8 mm in diameter is observed using a Rayleigh scattering method. The scattered light intensity exhibits a power scaling on the backing pressure ranging from 16 to 50 bar, and the power is strongly Z dependent varying from 8.4 (Z = 3 mm) to 5.4 (Z = 11 mm), which is much larger than that of the argon cluster. The scattered light intensity versus axial position shows that the position of 5 mm has the maximum signal intensity. The estimation of the average cluster size on axial position Z indicates that the cluster growth process goes forward until the maximum average cluster size is reached at Z = 9 mm, and the average cluster size will decrease gradually for Z > 9 mm

  4. Averaging Principle for the Higher Order Nonlinear Schrödinger Equation with a Random Fast Oscillation

    Science.gov (United States)

    Gao, Peng

    2018-04-01

    This work concerns the problem associated with averaging principle for a higher order nonlinear Schrödinger equation perturbed by a oscillating term arising as the solution of a stochastic reaction-diffusion equation evolving with respect to the fast time. This model can be translated into a multiscale stochastic partial differential equations. Stochastic averaging principle is a powerful tool for studying qualitative analysis of stochastic dynamical systems with different time-scales. To be more precise, under suitable conditions, we prove that there is a limit process in which the fast varying process is averaged out and the limit process which takes the form of the higher order nonlinear Schrödinger equation is an average with respect to the stationary measure of the fast varying process. Finally, by using the Khasminskii technique we can obtain the rate of strong convergence for the slow component towards the solution of the averaged equation, and as a consequence, the system can be reduced to a single higher order nonlinear Schrödinger equation with a modified coefficient.

  5. Averaging Principle for the Higher Order Nonlinear Schrödinger Equation with a Random Fast Oscillation

    Science.gov (United States)

    Gao, Peng

    2018-06-01

    This work concerns the problem associated with averaging principle for a higher order nonlinear Schrödinger equation perturbed by a oscillating term arising as the solution of a stochastic reaction-diffusion equation evolving with respect to the fast time. This model can be translated into a multiscale stochastic partial differential equations. Stochastic averaging principle is a powerful tool for studying qualitative analysis of stochastic dynamical systems with different time-scales. To be more precise, under suitable conditions, we prove that there is a limit process in which the fast varying process is averaged out and the limit process which takes the form of the higher order nonlinear Schrödinger equation is an average with respect to the stationary measure of the fast varying process. Finally, by using the Khasminskii technique we can obtain the rate of strong convergence for the slow component towards the solution of the averaged equation, and as a consequence, the system can be reduced to a single higher order nonlinear Schrödinger equation with a modified coefficient.

  6. Output

    DEFF Research Database (Denmark)

    Mehlsen, Camilla

    2010-01-01

    Hvad får vi egentlig ud af internationale komparative undersøgelser som PISA, PIRLS og TIMSS? Hvordan påvirker de dansk uddannelsespolitik? Asterisk har talt med tre forskere med ekspertise på området.......Hvad får vi egentlig ud af internationale komparative undersøgelser som PISA, PIRLS og TIMSS? Hvordan påvirker de dansk uddannelsespolitik? Asterisk har talt med tre forskere med ekspertise på området....

  7. Educational outcomes: Pathways and performance in South African high schools

    OpenAIRE

    Reddy, Vijay; van der Berg, Servaas; Janse van Rensburg, Dean; Taylor, Stephen

    2012-01-01

    We analysed the pathways and performances in mathematics of high (secondary) school students in South Africa using a panel-like data set of Grade 8 students who participated in the 2002 Trends in International Mathematics and Science Study (TIMSS) and who were tracked to Grade 12 examination data sets. We examined the relationship between TIMSS mathematics performance and reaching Grade 12, the selection of and performance in Grade 12 mathematics, and success rates in the matriculation examin...

  8. Standardized Total Average Toxicity Score: A Scale- and Grade-Independent Measure of Late Radiotherapy Toxicity to Facilitate Pooling of Data From Different Studies

    Energy Technology Data Exchange (ETDEWEB)

    Barnett, Gillian C., E-mail: gillbarnett@doctors.org.uk [University of Cambridge Department of Oncology, Oncology Centre, Cambridge (United Kingdom); Cancer Research-UK Centre for Genetic Epidemiology and Department of Oncology, Strangeways Research Laboratories, Cambridge (United Kingdom); West, Catharine M.L. [School of Cancer and Enabling Sciences, Manchester Academic Health Science Centre, University of Manchester, Christie Hospital, Manchester (United Kingdom); Coles, Charlotte E. [University of Cambridge Department of Oncology, Oncology Centre, Cambridge (United Kingdom); Pharoah, Paul D.P. [Cancer Research-UK Centre for Genetic Epidemiology and Department of Oncology, Strangeways Research Laboratories, Cambridge (United Kingdom); Talbot, Christopher J. [Department of Genetics, University of Leicester, Leicester (United Kingdom); Elliott, Rebecca M. [School of Cancer and Enabling Sciences, Manchester Academic Health Science Centre, University of Manchester, Christie Hospital, Manchester (United Kingdom); Tanteles, George A. [Department of Clinical Genetics, University Hospitals of Leicester, Leicester (United Kingdom); Symonds, R. Paul [Department of Cancer Studies and Molecular Medicine, University Hospitals of Leicester, Leicester (United Kingdom); Wilkinson, Jennifer S. [University of Cambridge Department of Oncology, Oncology Centre, Cambridge (United Kingdom); Dunning, Alison M. [Cancer Research-UK Centre for Genetic Epidemiology and Department of Oncology, Strangeways Research Laboratories, Cambridge (United Kingdom); Burnet, Neil G. [University of Cambridge Department of Oncology, Oncology Centre, Cambridge (United Kingdom); Bentzen, Soren M. [University of Wisconsin, School of Medicine and Public Health, Department of Human Oncology, Madison, WI (United States)

    2012-03-01

    Purpose: The search for clinical and biologic biomarkers associated with late radiotherapy toxicity is hindered by the use of multiple and different endpoints from a variety of scoring systems, hampering comparisons across studies and pooling of data. We propose a novel metric, the Standardized Total Average Toxicity (STAT) score, to try to overcome these difficulties. Methods and Materials: STAT scores were derived for 1010 patients from the Cambridge breast intensity-modulated radiotherapy trial and 493 women from University Hospitals of Leicester. The sensitivity of the STAT score to detect differences between patient groups, stratified by factors known to influence late toxicity, was compared with that of individual endpoints. Analysis of residuals was used to quantify the effect of these covariates. Results: In the Cambridge cohort, STAT scores detected differences (p < 0.00005) between patients attributable to breast volume, surgical specimen weight, dosimetry, acute toxicity, radiation boost to tumor bed, postoperative infection, and smoking (p < 0.0002), with no loss of sensitivity over individual toxicity endpoints. Diabetes (p = 0.017), poor postoperative surgical cosmesis (p = 0.0036), use of chemotherapy (p = 0.0054), and increasing age (p = 0.041) were also associated with increased STAT score. When the Cambridge and Leicester datasets were combined, STAT was associated with smoking status (p < 0.00005), diabetes (p = 0.041), chemotherapy (p = 0.0008), and radiotherapy boost (p = 0.0001). STAT was independent of the toxicity scale used and was able to deal with missing data. There were correlations between residuals of the STAT score obtained using different toxicity scales (r > 0.86, p < 0.00005 for both datasets). Conclusions: The STAT score may be used to facilitate the analysis of overall late radiation toxicity, from multiple trials or centers, in studies of possible genetic and nongenetic determinants of radiotherapy toxicity.

  9. MMPI-2 validity, clinical and content scales, and the Fake Bad Scale for personal injury litigants claiming idiopathic environmental intolerance.

    Science.gov (United States)

    Staudenmayer, Herman; Phillips, Scott

    2007-01-01

    Idiopathic environmental intolerance (IEI) is a descriptor for nonspecific complaints that are attributed to environmental exposure. The Minnesota Multiphasic Personality Inventory 2 (MMPI-2) was administered to 50 female and 20 male personal injury litigants alleging IEI. The validity scales indicated no overreporting of psychopathology. Half of the cases had elevated scores on validity scales suggesting defensiveness, and a large number had elevations on Fake Bad Scale (FBS) suggesting overreporting of unauthenticated symptoms. The average T-score profile for females was defined by the two-point code type 3-1 (Hysteria-Hypochondriasis), and the average T-score profile for males was defined by the three-point code type 3-1-2 (Hysteria, Hypochondriasis-Depression). On the content scales, Health Concerns (HEA) scale was significantly elevated. Idiopathic environmental intolerance litigants (a) are more defensive about expressing psychopathology, (b) express distress through somatization, (c) use a self-serving misrepresentation of exaggerated health concerns, and (d) may exaggerate unauthenticated symptoms suggesting malingering.

  10. Average size of random polygons with fixed knot topology.

    Science.gov (United States)

    Matsuda, Hiroshi; Yao, Akihisa; Tsukahara, Hiroshi; Deguchi, Tetsuo; Furuta, Ko; Inami, Takeo

    2003-07-01

    We have evaluated by numerical simulation the average size R(K) of random polygons of fixed knot topology K=,3(1),3(1) musical sharp 4(1), and we have confirmed the scaling law R(2)(K) approximately N(2nu(K)) for the number N of polygonal nodes in a wide range; N=100-2200. The best fit gives 2nu(K) approximately 1.11-1.16 with good fitting curves in the whole range of N. The estimate of 2nu(K) is consistent with the exponent of self-avoiding polygons. In a limited range of N (N greater, similar 600), however, we have another fit with 2nu(K) approximately 1.01-1.07, which is close to the exponent of random polygons.

  11. Large interface simulation in an averaged two-fluid code

    International Nuclear Information System (INIS)

    Henriques, A.

    2006-01-01

    Different ranges of size of interfaces and eddies are involved in multiphase flow phenomena. Classical formalisms focus on a specific range of size. This study presents a Large Interface Simulation (LIS) two-fluid compressible formalism taking into account different sizes of interfaces. As in the single-phase Large Eddy Simulation, a filtering process is used to point out Large Interface (LI) simulation and Small interface (SI) modelization. The LI surface tension force is modelled adapting the well-known CSF method. The modelling of SI transfer terms is done calling for classical closure laws of the averaged approach. To simulate accurately LI transfer terms, we develop a LI recognition algorithm based on a dimensionless criterion. The LIS model is applied in a classical averaged two-fluid code. The LI transfer terms modelling and the LI recognition are validated on analytical and experimental tests. A square base basin excited by a horizontal periodic movement is studied with the LIS model. The capability of the model is also shown on the case of the break-up of a bubble in a turbulent liquid flow. The break-up of a large bubble at a grid impact performed regime transition between two different scales of interface from LI to SI and from PI to LI. (author) [fr

  12. An upscaled two-equation model of transport in porous media through unsteady-state closure of volume averaged formulations

    Science.gov (United States)

    Chaynikov, S.; Porta, G.; Riva, M.; Guadagnini, A.

    2012-04-01

    We focus on a theoretical analysis of nonreactive solute transport in porous media through the volume averaging technique. Darcy-scale transport models based on continuum formulations typically include large scale dispersive processes which are embedded in a pore-scale advection diffusion equation through a Fickian analogy. This formulation has been extensively questioned in the literature due to its inability to depict observed solute breakthrough curves in diverse settings, ranging from the laboratory to the field scales. The heterogeneity of the pore-scale velocity field is one of the key sources of uncertainties giving rise to anomalous (non-Fickian) dispersion in macro-scale porous systems. Some of the models which are employed to interpret observed non-Fickian solute behavior make use of a continuum formulation of the porous system which assumes a two-region description and includes a bimodal velocity distribution. A first class of these models comprises the so-called ''mobile-immobile'' conceptualization, where convective and dispersive transport mechanisms are considered to dominate within a high velocity region (mobile zone), while convective effects are neglected in a low velocity region (immobile zone). The mass exchange between these two regions is assumed to be controlled by a diffusive process and is macroscopically described by a first-order kinetic. An extension of these ideas is the two equation ''mobile-mobile'' model, where both transport mechanisms are taken into account in each region and a first-order mass exchange between regions is employed. Here, we provide an analytical derivation of two region "mobile-mobile" meso-scale models through a rigorous upscaling of the pore-scale advection diffusion equation. Among the available upscaling methodologies, we employ the Volume Averaging technique. In this approach, the heterogeneous porous medium is supposed to be pseudo-periodic, and can be represented through a (spatially) periodic unit cell

  13. Grade Point Average System of Assessment: the Implementation Peculiarities in Russia

    Directory of Open Access Journals (Sweden)

    B. A. Sazonov

    2012-01-01

    Full Text Available The paper analyzes the specificity, as well as flaws and faults of implementing the Grade Point Average (GPA system of students’ personal assessment in Russian higher schools. Nowadays, the above system is regarded as the basic functional element of educational process organization at the world’s leading universities. The author summarizes the foreign experience and demonstrates the advantages of the GPA system in comparison with the traditional domestic scale of assessment: full records of student’s assessment, objectivity, activation of responsibility for the results achieved, and self-control motivation. The standard GPA model is demonstrated, its application systemizing both the Russian and European requirements to the higher school graduates. The author suggests his own version of the assessment scale estimating and comparing the quality of education in Russian universities and worldwide. The research findings can be of interest to the specialists in the sphere of quality measurement and educational management. 

  14. The Role of Content in Inquiry-Based Elementary Science Lessons: An Analysis of Teacher Beliefs and Enactment

    Science.gov (United States)

    Furtak, Erin Marie; Alonzo, Alicia C.

    2010-05-01

    The Trends in International Mathematics and Science Study (TIMSS) Video Study explored instructional practices in the United States (US) in comparison with other countries that ranked higher on the 1999 TIMSS assessment, and revealed that 8th grade science teachers in the US emphasize activities over content during lessons (Roth et al. 2006). This study applies the content framework from the TIMSS Video Study to a sample of 28 3rd grade teachers enacting an inquiry-based unit on floating and sinking, and seeks a deeper understanding of teachers’ practices through analysis of interviews with those teachers. Transcripts of observed lessons were coded according to the TIMSS framework for types of content, and transcripts of teacher interviews were coded to capture the ways in which teachers described their role in and purposes for teaching science, particularly with respect to the floating and sinking unit. Results indicate that teachers focused more on canonical, procedural and experimental knowledge during lessons than on real-world connections and the nature of science; however, none of the types of content received major emphasis in a majority of the classrooms in the sample. During interviews, teachers described their practice in ways that prioritized helping students to like science over specific content outcomes. The study suggests that elementary school teachers’ emphasis on doing and feeling during inquiry-based lessons may interfere with teaching of content.

  15. Determining the scale in lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Bornyakov, V.G. [Institute for High Energy Physics, Protvino (Russian Federation); Institute of Theoretical and Experimental Physics, Moscow (Russian Federation); Far Eastern Federal Univ., Vladivostok (Russian Federation). School of Biomedicine; Horsley, R. [Edinburgh Univ. (United Kingdom). School of Physics and Astronomy; Hudspith, R. [York Univ., Toronto, ON (Canada). Dept. of Physics and Astronomy; and others

    2015-12-15

    We discuss scale setting in the context of 2+1 dynamical fermion simulations where we approach the physical point in the quark mass plane keeping the average quark mass constant. We have simulations at four beta values, and after determining the paths and lattice spacings, we give an estimation of the phenomenological values of various Wilson flow scales.

  16. Parents' Reactions to Finding Out That Their Children Have Average or above Average IQ Scores.

    Science.gov (United States)

    Dirks, Jean; And Others

    1983-01-01

    Parents of 41 children who had been given an individually-administered intelligence test were contacted 19 months after testing. Parents of average IQ children were less accurate in their memory of test results. Children with above average IQ experienced extremely low frequencies of sibling rivalry, conceit or pressure. (Author/HLM)

  17. Evaluations of average level spacings

    International Nuclear Information System (INIS)

    Liou, H.I.

    1980-01-01

    The average level spacing for highly excited nuclei is a key parameter in cross section formulas based on statistical nuclear models, and also plays an important role in determining many physics quantities. Various methods to evaluate average level spacings are reviewed. Because of the finite experimental resolution, to detect a complete sequence of levels without mixing other parities is extremely difficult, if not totally impossible. Most methods derive the average level spacings by applying a fit, with different degrees of generality, to the truncated Porter-Thomas distribution for reduced neutron widths. A method that tests both distributions of level widths and positions is discussed extensivey with an example of 168 Er data. 19 figures, 2 tables

  18. Skole i verdensklasse

    DEFF Research Database (Denmark)

    Andersen, Frans Ørsted

    2013-01-01

    Kronikken er en kommentar og ros til de gode danske PIRLS og TIMSS resultater offentliggjort i december 2012. Der argumenteres for at der tages hensyn til den registrerede fremgang i de igangværende reformprocesser vedr folkeskole og læreruddannelse.......Kronikken er en kommentar og ros til de gode danske PIRLS og TIMSS resultater offentliggjort i december 2012. Der argumenteres for at der tages hensyn til den registrerede fremgang i de igangværende reformprocesser vedr folkeskole og læreruddannelse....

  19. Averaged RMHD equations

    International Nuclear Information System (INIS)

    Ichiguchi, Katsuji

    1998-01-01

    A new reduced set of resistive MHD equations is derived by averaging the full MHD equations on specified flux coordinates, which is consistent with 3D equilibria. It is confirmed that the total energy is conserved and the linearized equations for ideal modes are self-adjoint. (author)

  20. Wavelength dependence of the effects of turbulence on average refraction angles in occultations by planetary atmospheres

    International Nuclear Information System (INIS)

    Haugstad, B.S.; Eshleman, V.R.

    1979-01-01

    Two recent adjacently published papers on the average effects of turbulence in radio and optical occultation studies of planetary atmospheres appear to disagree on the question of wavelength dependence. It is demonstrated here that in deriving a necessary condition for the applicability of their method. Hubbard and Jokipii neglect a factor which is proportional to the square of the ratio of the atmospheric or local Fresnel zone radius and the inner scale of turbulence. They also fail to establish sufficient conditions, thereby omitting as a further factor the square of the ratio of atmospheric scale height and the local Fresnel zone radius. The total descrepancy, which numerically is typically within several orders of magnitude of 10 11 for radio and 10 7 for optical occultations, means that their results correspond to geometrical optics and not to wave optics as claimed. Thus their results are inherently inapplicable in a discussion of the wavelength dependence of any parameter, such as the bias in the average refraction angle treated by Eshleman and Haugstad. We note that for power spectra characterized by the (--p) exponent of the turbulence wavenumber, the average turbulence-induced bias in refraction angles depends on the radiation wavelength as lambda/sup( p/--4)/2, or as lambda/sup en-dash1/6/ for Kolmogorov turbulence. Other features of the Hubbard-Jokipii analysis are also discussed

  1. NGA-West 2 GMPE average site coefficients for use in earthquake-resistant design

    Science.gov (United States)

    Borcherdt, Roger D.

    2015-01-01

    Site coefficients corresponding to those in tables 11.4–1 and 11.4–2 of Minimum Design Loads for Buildings and Other Structures published by the American Society of Civil Engineers (Standard ASCE/SEI 7-10) are derived from four of the Next Generation Attenuation West2 (NGA-W2) Ground-Motion Prediction Equations (GMPEs). The resulting coefficients are compared with those derived by other researchers and those derived from the NGA-West1 database. The derivation of the NGA-W2 average site coefficients provides a simple procedure to update site coefficients with each update in the Maximum Considered Earthquake Response MCER maps. The simple procedure yields average site coefficients consistent with those derived for site-specific design purposes. The NGA-W2 GMPEs provide simple scale factors to reduce conservatism in current simplified design procedures.

  2. Reproducing multi-model ensemble average with Ensemble-averaged Reconstructed Forcings (ERF) in regional climate modeling

    Science.gov (United States)

    Erfanian, A.; Fomenko, L.; Wang, G.

    2016-12-01

    Multi-model ensemble (MME) average is considered the most reliable for simulating both present-day and future climates. It has been a primary reference for making conclusions in major coordinated studies i.e. IPCC Assessment Reports and CORDEX. The biases of individual models cancel out each other in MME average, enabling the ensemble mean to outperform individual members in simulating the mean climate. This enhancement however comes with tremendous computational cost, which is especially inhibiting for regional climate modeling as model uncertainties can originate from both RCMs and the driving GCMs. Here we propose the Ensemble-based Reconstructed Forcings (ERF) approach to regional climate modeling that achieves a similar level of bias reduction at a fraction of cost compared with the conventional MME approach. The new method constructs a single set of initial and boundary conditions (IBCs) by averaging the IBCs of multiple GCMs, and drives the RCM with this ensemble average of IBCs to conduct a single run. Using a regional climate model (RegCM4.3.4-CLM4.5), we tested the method over West Africa for multiple combination of (up to six) GCMs. Our results indicate that the performance of the ERF method is comparable to that of the MME average in simulating the mean climate. The bias reduction seen in ERF simulations is achieved by using more realistic IBCs in solving the system of equations underlying the RCM physics and dynamics. This endows the new method with a theoretical advantage in addition to reducing computational cost. The ERF output is an unaltered solution of the RCM as opposed to a climate state that might not be physically plausible due to the averaging of multiple solutions with the conventional MME approach. The ERF approach should be considered for use in major international efforts such as CORDEX. Key words: Multi-model ensemble, ensemble analysis, ERF, regional climate modeling

  3. Averaging for solitons with nonlinearity management

    International Nuclear Information System (INIS)

    Pelinovsky, D.E.; Kevrekidis, P.G.; Frantzeskakis, D.J.

    2003-01-01

    We develop an averaging method for solitons of the nonlinear Schroedinger equation with a periodically varying nonlinearity coefficient, which is used to effectively describe solitons in Bose-Einstein condensates, in the context of the recently proposed technique of Feshbach resonance management. Using the derived local averaged equation, we study matter-wave bright and dark solitons and demonstrate a very good agreement between solutions of the averaged and full equations

  4. From micro-scale 3D simulations to macro-scale model of periodic porous media

    Science.gov (United States)

    Crevacore, Eleonora; Tosco, Tiziana; Marchisio, Daniele; Sethi, Rajandrea; Messina, Francesca

    2015-04-01

    In environmental engineering, the transport of colloidal suspensions in porous media is studied to understand the fate of potentially harmful nano-particles and to design new remediation technologies. In this perspective, averaging techniques applied to micro-scale numerical simulations are a powerful tool to extrapolate accurate macro-scale models. Choosing two simplified packing configurations of soil grains and starting from a single elementary cell (module), it is possible to take advantage of the periodicity of the structures to reduce the computation costs of full 3D simulations. Steady-state flow simulations for incompressible fluid in laminar regime are implemented. Transport simulations are based on the pore-scale advection-diffusion equation, that can be enriched introducing also the Stokes velocity (to consider the gravity effect) and the interception mechanism. Simulations are carried on a domain composed of several elementary modules, that serve as control volumes in a finite volume method for the macro-scale method. The periodicity of the medium involves the periodicity of the flow field and this will be of great importance during the up-scaling procedure, allowing relevant simplifications. Micro-scale numerical data are treated in order to compute the mean concentration (volume and area averages) and fluxes on each module. The simulation results are used to compare the micro-scale averaged equation to the integral form of the macroscopic one, making a distinction between those terms that could be computed exactly and those for which a closure in needed. Of particular interest it is the investigation of the origin of macro-scale terms such as the dispersion and tortuosity, trying to describe them with micro-scale known quantities. Traditionally, to study the colloidal transport many simplifications are introduced, such those concerning ultra-simplified geometry that usually account for a single collector. Gradual removal of such hypothesis leads to a

  5. Industrial Applications of High Average Power FELS

    CERN Document Server

    Shinn, Michelle D

    2005-01-01

    The use of lasers for material processing continues to expand, and the annual sales of such lasers exceeds $1 B (US). Large scale (many m2) processing of materials require the economical production of laser powers of the tens of kilowatts, and therefore are not yet commercial processes, although they have been demonstrated. The development of FELs based on superconducting RF (SRF) linac technology provides a scaleable path to laser outputs above 50 kW in the IR, rendering these applications economically viable, since the cost/photon drops as the output power increases. This approach also enables high average power ~ 1 kW output in the UV spectrum. Such FELs will provide quasi-cw (PRFs in the tens of MHz), of ultrafast (pulsewidth ~ 1 ps) output with very high beam quality. This talk will provide an overview of applications tests by our facility's users such as pulsed laser deposition, laser ablation, and laser surface modification, as well as present plans that will be tested with our upgraded FELs. These upg...

  6. Price Discrimination, Economies of Scale, and Profits.

    Science.gov (United States)

    Park, Donghyun

    2000-01-01

    Demonstrates that it is possible for economies of scale to induce a price-discriminating monopolist to sell in an unprofitable market where the average cost always exceeds the price. States that higher profits in the profitable market caused by economies of scale may exceed losses incurred in the unprofitable market. (CMK)

  7. Extracting gravitational waves induced by plasma turbulence in the early Universe through an averaging process

    International Nuclear Information System (INIS)

    Garrison, David; Ramirez, Christopher

    2017-01-01

    This work is a follow-up to the paper, ‘Numerical relativity as a tool for studying the early Universe’. In this article, we determine if cosmological gravitational waves can be accurately extracted from a dynamical spacetime using an averaging process as opposed to conventional methods of gravitational wave extraction using a complex Weyl scalar. We calculate the normalized energy density, strain and degree of polarization of gravitational waves produced by a simulated turbulent plasma similar to what was believed to have existed shortly after the electroweak scale. This calculation is completed using two numerical codes, one which utilizes full general relativity calculations based on modified BSSN equations while the other utilizes a linearized approximation of general relativity. Our results show that the spectrum of gravitational waves calculated from the nonlinear code using an averaging process is nearly indistinguishable from those calculated from the linear code. This result validates the use of the averaging process for gravitational wave extraction of cosmological systems. (paper)

  8. Evaluation of the utility of Liebowitz Social Anxiety Scale and Barratt Impulsiveness Scale in the diagnosis of social anxiety, impulsivity and depression.

    Science.gov (United States)

    Tyrała, Kinga; Seweryn, Mariusz; Bonk, Magdalena; Bulska, Weronika; Orszulak, Kamila; Bratek, Agnieszka; Krysta, Krzysztof

    2015-09-01

    Often mental disorders are serious problems concerning psychological well-being. They require comprehensive and specialized psychiatric and psychological help, but there are no public methods of controlling your mental state. The aim of study was the evaluation of the utility of Liebowitz Social Anxiety Scale and Barratt Impulsiveness Scale in the diagnosis of social anxiety, impulsivity and depression. The study included 85 persons. The study group had 34 patients treated in an open ward of the Department of Psychiatry and Psychotherapy of Medical University of Silesia in Katowice. The control group included 51 persons without mental disorders. Three self-rating questionnaires were used: Beck Depression Inventory, Barratt Impulsiveness Scale and Liebowitz Social Anxiety Scale. Statistica v10 Statsoft software was used for statistical analysis. The analyzed groups had significant differences in terms of Beck Scale (U Mann-Whitney test p=0.000001). Average score in study group: 22.94±12.50; in control group: 7.15±6.44. Groups had significant differences in terms of Liebowitz Scale (U test Mann-Whitney test, p=0.000164). Average score in the study group: 60.41±30.30; in control group: 35.01±23.94. Groups had significant differences in terms of Barratt Scale (t-student test p=0.000601). Average in study group: 66.35±9,49; in control group: 59.54±7.87. Significant positive correlation was observed between the results of Beck Scale and Liebowitz Scale (r=0.64465). Correlation was not observed between the results of the Liebowitz and Barrat (r=0.12091 and Beck and Barrat (r=0.21482). The intensity of the Liebowitz Social Anxiety Scale is directly proportional to the severity of depression according to the Beck Depression Inventory. The degree of impulsivity by Barrat Impulsiveness Scale does not correlate with the level of depression according to Beck Depression Inventory. The analyzed scales are relevant in the diagnosis of mental disorders.

  9. Numerical Analysis of a Small-Size Vertical-Axis Wind Turbine Performance and Averaged Flow Parameters Around the Rotor

    Directory of Open Access Journals (Sweden)

    Rogowski Krzysztof

    2017-06-01

    Full Text Available Small-scale vertical-axis wind turbines can be used as a source of electricity in rural and urban environments. According to the authors’ knowledge, there are no validated simplified aerodynamic models of these wind turbines, therefore the use of more advanced techniques, such as for example the computational methods for fluid dynamics is justified. The paper contains performance analysis of the small-scale vertical-axis wind turbine with a large solidity. The averaged velocity field and the averaged static pressure distribution around the rotor have been also analyzed. All numerical results presented in this paper are obtained using the SST k-ω turbulence model. Computed power coeffcients are in good agreement with the experimental results. A small change in the tip speed ratio significantly affects the velocity field. Obtained velocity fields can be further used as a base for simplified aerodynamic methods.

  10. 40 CFR 600.510-12 - Calculation of average fuel economy and average carbon-related exhaust emissions.

    Science.gov (United States)

    2010-07-01

    ... and average carbon-related exhaust emissions. 600.510-12 Section 600.510-12 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) ENERGY POLICY FUEL ECONOMY AND CARBON-RELATED EXHAUST EMISSIONS OF... Transportation. (iv) [Reserved] (2) Average carbon-related exhaust emissions will be calculated to the nearest...

  11. Experimental Quasi-Microwave Whole-Body Averaged SAR Estimation Method Using Cylindrical-External Field Scanning

    Science.gov (United States)

    Kawamura, Yoshifumi; Hikage, Takashi; Nojima, Toshio

    The aim of this study is to develop a new whole-body averaged specific absorption rate (SAR) estimation method based on the external-cylindrical field scanning technique. This technique is adopted with the goal of simplifying the dosimetry estimation of human phantoms that have different postures or sizes. An experimental scaled model system is constructed. In order to examine the validity of the proposed method for realistic human models, we discuss the pros and cons of measurements and numerical analyses based on the finite-difference time-domain (FDTD) method. We consider the anatomical European human phantoms and plane-wave in the 2GHz mobile phone frequency band. The measured whole-body averaged SAR results obtained by the proposed method are compared with the results of the FDTD analyses.

  12. Improved averaging for non-null interferometry

    Science.gov (United States)

    Fleig, Jon F.; Murphy, Paul E.

    2013-09-01

    Arithmetic averaging of interferometric phase measurements is a well-established method for reducing the effects of time varying disturbances, such as air turbulence and vibration. Calculating a map of the standard deviation for each pixel in the average map can provide a useful estimate of its variability. However, phase maps of complex and/or high density fringe fields frequently contain defects that severely impair the effectiveness of simple phase averaging and bias the variability estimate. These defects include large or small-area phase unwrapping artifacts, large alignment components, and voids that change in number, location, or size. Inclusion of a single phase map with a large area defect into the average is usually sufficient to spoil the entire result. Small-area phase unwrapping and void defects may not render the average map metrologically useless, but they pessimistically bias the variance estimate for the overwhelming majority of the data. We present an algorithm that obtains phase average and variance estimates that are robust against both large and small-area phase defects. It identifies and rejects phase maps containing large area voids or unwrapping artifacts. It also identifies and prunes the unreliable areas of otherwise useful phase maps, and removes the effect of alignment drift from the variance estimate. The algorithm has several run-time adjustable parameters to adjust the rejection criteria for bad data. However, a single nominal setting has been effective over a wide range of conditions. This enhanced averaging algorithm can be efficiently integrated with the phase map acquisition process to minimize the number of phase samples required to approach the practical noise floor of the metrology environment.

  13. Area-averaged surface fluxes and their time-space variability over the FIFE experimental domain

    Science.gov (United States)

    Smith, E. A.; Hsu, A. Y.; Crosson, W. L.; Field, R. T.; Fritschen, L. J.; Gurney, R. J.; Kanemasu, E. T.; Kustas, W. P.; Nie, D.; Shuttleworth, W. J.

    1992-01-01

    The underlying mean and variance properties of surface net radiation, sensible-latent heat fluxes and soil heat flux are studied over the densely instrumented grassland region encompassing FIFE. Flux variability is discussed together with the problem of scaling up to area-averaged fluxes. Results are compared and contrasted for cloudy and clear situations and examined for the influence of surface-induced biophysical controls (burn and grazing treatments) and topographic controls (aspect ratios and slope factors).

  14. Slope-scale dynamic states of rockfalls

    Science.gov (United States)

    Agliardi, F.; Crosta, G. B.

    2009-04-01

    Rockfalls are common earth surface phenomena characterised by complex dynamics at the slope scale, depending on local block kinematics and slope geometry. We investigated the nature of this slope-scale dynamics by parametric 3D numerical modelling of rockfalls over synthetic slopes with different inclination, roughness and spatial resolution. Simulations were performed through an original code specifically designed for rockfall modeling, incorporating kinematic and hybrid algorithms with different damping functions available to model local energy loss by impact and pure rolling. Modelling results in terms of average velocity profiles suggest that three dynamic regimes (i.e. decelerating, steady-state and accelerating), previously recognized in the literature through laboratory experiments on granular flows, can set up at the slope scale depending on slope average inclination and roughness. Sharp changes in rock fall kinematics, including motion type and lateral dispersion of trajectories, are associated to the transition among different regimes. Associated threshold conditions, portrayed in "phase diagrams" as slope-roughness critical lines, were analysed depending on block size, impact/rebound angles, velocity and energy, and model spatial resolution. Motion in regime B (i.e. steady state) is governed by a slope-scale "viscous friction" with average velocity linearly related to the sine of slope inclination. This suggest an analogy between rockfall motion in regime B and newtonian flow, whereas in regime C (i.e. accelerating) an analogy with a dilatant flow was observed. Thus, although local behavior of single falling blocks is well described by rigid body dynamics, the slope scale dynamics of rockfalls seem to statistically approach that of granular media. Possible outcomes of these findings include a discussion of the transition from rockfall to granular flow, the evaluation of the reliability of predictive models, and the implementation of criteria for a

  15. A time-averaged cosmic ray propagation theory

    International Nuclear Information System (INIS)

    Klimas, A.J.

    1975-01-01

    An argument is presented, which casts doubt on our ability to choose an appropriate magnetic field ensemble for computing the average behavior of cosmic ray particles. An alternate procedure, using time-averages rather than ensemble-averages, is presented. (orig.) [de

  16. Investigation of scale economies for African biogas installations

    International Nuclear Information System (INIS)

    Amigun, B.; Blottnitz, H. von

    2007-01-01

    Biogas technology can serve as a means to overcome energy poverty, which poses a constant barrier to economic development in Africa. This technology can be built on a wide range of scales, and conventional financial wisdom is that larger installations have advantages resulting from economies of scale. This study analyses the statistical evidence bearing on the existence of economies of scale in the small to medium scale production and use of biogas to support faster estimation (at the order of magnitude level) of investment costs for different plant sizes. Investment cost data were gathered for 21 biogas plants in the 4-100 m 3 range built since 1999 in eight African countries. Statistical regression indicates diseconomies of scale in the size range of the biogas industry investigated with a cost capacity factor (n) of 1.20 (R 2 = 0.90). The cost capacity factor obtained is notably greater than the conventionally used 0.6 factor rule. The result illustrates that the average cost size relationship is statistically significant with ±40% average estimating error

  17. Improving consensus structure by eliminating averaging artifacts

    Directory of Open Access Journals (Sweden)

    KC Dukka B

    2009-03-01

    Full Text Available Abstract Background Common structural biology methods (i.e., NMR and molecular dynamics often produce ensembles of molecular structures. Consequently, averaging of 3D coordinates of molecular structures (proteins and RNA is a frequent approach to obtain a consensus structure that is representative of the ensemble. However, when the structures are averaged, artifacts can result in unrealistic local geometries, including unphysical bond lengths and angles. Results Herein, we describe a method to derive representative structures while limiting the number of artifacts. Our approach is based on a Monte Carlo simulation technique that drives a starting structure (an extended or a 'close-by' structure towards the 'averaged structure' using a harmonic pseudo energy function. To assess the performance of the algorithm, we applied our approach to Cα models of 1364 proteins generated by the TASSER structure prediction algorithm. The average RMSD of the refined model from the native structure for the set becomes worse by a mere 0.08 Å compared to the average RMSD of the averaged structures from the native structure (3.28 Å for refined structures and 3.36 A for the averaged structures. However, the percentage of atoms involved in clashes is greatly reduced (from 63% to 1%; in fact, the majority of the refined proteins had zero clashes. Moreover, a small number (38 of refined structures resulted in lower RMSD to the native protein versus the averaged structure. Finally, compared to PULCHRA 1, our approach produces representative structure of similar RMSD quality, but with much fewer clashes. Conclusion The benchmarking results demonstrate that our approach for removing averaging artifacts can be very beneficial for the structural biology community. Furthermore, the same approach can be applied to almost any problem where averaging of 3D coordinates is performed. Namely, structure averaging is also commonly performed in RNA secondary prediction 2, which

  18. Experimental Quasi-Microwave Whole-Body Averaged SAR Estimation Method Using Cylindrical-External Field Scanning

    OpenAIRE

    Kawamura, Yoshifumi; Hikage, Takashi; Nojima, Toshio

    2010-01-01

    The aim of this study is to develop a new whole-body averaged specific absorption rate (SAR) estimation method based on the external-cylindrical field scanning technique. This technique is adopted with the goal of simplifying the dosimetry estimation of human phantoms that have different postures or sizes. An experimental scaled model system is constructed. In order to examine the validity of the proposed method for realistic human models, we discuss the pros and cons of measurements and nume...

  19. Gamma-Weighted Discrete Ordinate Two-Stream Approximation for Computation of Domain Averaged Solar Irradiance

    Science.gov (United States)

    Kato, S.; Smith, G. L.; Barker, H. W.

    2001-01-01

    An algorithm is developed for the gamma-weighted discrete ordinate two-stream approximation that computes profiles of domain-averaged shortwave irradiances for horizontally inhomogeneous cloudy atmospheres. The algorithm assumes that frequency distributions of cloud optical depth at unresolved scales can be represented by a gamma distribution though it neglects net horizontal transport of radiation. This algorithm is an alternative to the one used in earlier studies that adopted the adding method. At present, only overcast cloudy layers are permitted.

  20. 40 CFR 76.11 - Emissions averaging.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 16 2010-07-01 2010-07-01 false Emissions averaging. 76.11 Section 76.11 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) ACID RAIN NITROGEN OXIDES EMISSION REDUCTION PROGRAM § 76.11 Emissions averaging. (a) General...

  1. Average spectral efficiency analysis of FSO links over turbulence channel with adaptive transmissions and aperture averaging

    Science.gov (United States)

    Aarthi, G.; Ramachandra Reddy, G.

    2018-03-01

    In our paper, the impact of adaptive transmission schemes: (i) optimal rate adaptation (ORA) and (ii) channel inversion with fixed rate (CIFR) on the average spectral efficiency (ASE) are explored for free-space optical (FSO) communications with On-Off Keying (OOK), Polarization shift keying (POLSK), and Coherent optical wireless communication (Coherent OWC) systems under different turbulence regimes. Further to enhance the ASE we have incorporated aperture averaging effects along with the above adaptive schemes. The results indicate that ORA adaptation scheme has the advantage of improving the ASE performance compared with CIFR under moderate and strong turbulence regime. The coherent OWC system with ORA excels the other modulation schemes and could achieve ASE performance of 49.8 bits/s/Hz at the average transmitted optical power of 6 dBm under strong turbulence. By adding aperture averaging effect we could achieve an ASE of 50.5 bits/s/Hz under the same conditions. This makes ORA with Coherent OWC modulation as a favorable candidate for improving the ASE of the FSO communication system.

  2. An investigation of scale effects in family substance abuse treatment programs

    Directory of Open Access Journals (Sweden)

    Lee A James

    2010-07-01

    Full Text Available Abstract This short report investigates scale effects in family substance abuse treatment programs. In Massachusetts, the family substance abuse treatment programs were much more costly than other adult residential treatment models. State officials were concerned that the "scale" or size of these programs (averaging just eight families was too small to be economical. Although the sample size (just nine programs was too small to permit reliable inference, the data clearly signalled the importance of "scale effects" in these family substance abuse treatment programs. To further investigate scale effects in family substance abuse treatment programs, data from the Center for Substance Abuse Treatment's (CSAT's Residential Women and Children and Pregnant and Postpartum Women (RWC-PPW Demonstration were re-analyzed, focusing on the relationship between cost per family-day and the estimated average family census. This analysis indicates strong economies of scale up until an average family census of about 14, and less apparent scale effects beyond that point. In consideration of these and other study findings, a multidisciplinary interagency team redesigned the Massachusetts' family treatment program model. The new programs are larger than the former family treatment programs, with each new program having capacity to treat 11 to 15 families depending on family makeup.

  3. 7 CFR 51.2561 - Average moisture content.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Average moisture content. 51.2561 Section 51.2561... STANDARDS) United States Standards for Grades of Shelled Pistachio Nuts § 51.2561 Average moisture content. (a) Determining average moisture content of the lot is not a requirement of the grades, except when...

  4. New Empirical Earthquake Source‐Scaling Laws

    KAUST Repository

    Thingbaijam, Kiran Kumar S.

    2017-12-13

    We develop new empirical scaling laws for rupture width W, rupture length L, rupture area A, and average slip D, based on a large database of rupture models. The database incorporates recent earthquake source models in a wide magnitude range (M 5.4–9.2) and events of various faulting styles. We apply general orthogonal regression, instead of ordinary least-squares regression, to account for measurement errors of all variables and to obtain mutually self-consistent relationships. We observe that L grows more rapidly with M compared to W. The fault-aspect ratio (L/W) tends to increase with fault dip, which generally increases from reverse-faulting, to normal-faulting, to strike-slip events. At the same time, subduction-inter-face earthquakes have significantly higher W (hence a larger rupture area A) compared to other faulting regimes. For strike-slip events, the growth of W with M is strongly inhibited, whereas the scaling of L agrees with the L-model behavior (D correlated with L). However, at a regional scale for which seismogenic depth is essentially fixed, the scaling behavior corresponds to the W model (D not correlated with L). Self-similar scaling behavior with M − log A is observed to be consistent for all the cases, except for normal-faulting events. Interestingly, the ratio D/W (a proxy for average stress drop) tends to increase with M, except for shallow crustal reverse-faulting events, suggesting the possibility of scale-dependent stress drop. The observed variations in source-scaling properties for different faulting regimes can be interpreted in terms of geological and seismological factors. We find substantial differences between our new scaling relationships and those of previous studies. Therefore, our study provides critical updates on source-scaling relations needed in seismic–tsunami-hazard analysis and engineering applications.

  5. Event-Triggered Distributed Average Consensus Over Directed Digital Networks With Limited Communication Bandwidth.

    Science.gov (United States)

    Li, Huaqing; Chen, Guo; Huang, Tingwen; Dong, Zhaoyang; Zhu, Wei; Gao, Lan

    2016-12-01

    In this paper, we consider the event-triggered distributed average-consensus of discrete-time first-order multiagent systems with limited communication data rate and general directed network topology. In the framework of digital communication network, each agent has a real-valued state but can only exchange finite-bit binary symbolic data sequence with its neighborhood agents at each time step due to the digital communication channels with energy constraints. Novel event-triggered dynamic encoder and decoder for each agent are designed, based on which a distributed control algorithm is proposed. A scheme that selects the number of channel quantization level (number of bits) at each time step is developed, under which all the quantizers in the network are never saturated. The convergence rate of consensus is explicitly characterized, which is related to the scale of network, the maximum degree of nodes, the network structure, the scaling function, the quantization interval, the initial states of agents, the control gain and the event gain. It is also found that under the designed event-triggered protocol, by selecting suitable parameters, for any directed digital network containing a spanning tree, the distributed average consensus can be always achieved with an exponential convergence rate based on merely one bit information exchange between each pair of adjacent agents at each time step. Two simulation examples are provided to illustrate the feasibility of presented protocol and the correctness of the theoretical results.

  6. Determining average path length and average trapping time on generalized dual dendrimer

    Science.gov (United States)

    Li, Ling; Guan, Jihong

    2015-03-01

    Dendrimer has wide number of important applications in various fields. In some cases during transport or diffusion process, it transforms into its dual structure named Husimi cactus. In this paper, we study the structure properties and trapping problem on a family of generalized dual dendrimer with arbitrary coordination numbers. We first calculate exactly the average path length (APL) of the networks. The APL increases logarithmically with the network size, indicating that the networks exhibit a small-world effect. Then we determine the average trapping time (ATT) of the trapping process in two cases, i.e., the trap placed on a central node and the trap is uniformly distributed in all the nodes of the network. In both case, we obtain explicit solutions of ATT and show how they vary with the networks size. Besides, we also discuss the influence of the coordination number on trapping efficiency.

  7. Computation of the bounce-average code

    International Nuclear Information System (INIS)

    Cutler, T.A.; Pearlstein, L.D.; Rensink, M.E.

    1977-01-01

    The bounce-average computer code simulates the two-dimensional velocity transport of ions in a mirror machine. The code evaluates and bounce-averages the collision operator and sources along the field line. A self-consistent equilibrium magnetic field is also computed using the long-thin approximation. Optionally included are terms that maintain μ, J invariance as the magnetic field changes in time. The assumptions and analysis that form the foundation of the bounce-average code are described. When references can be cited, the required results are merely stated and explained briefly. A listing of the code is appended

  8. Average is Over

    Science.gov (United States)

    Eliazar, Iddo

    2018-02-01

    The popular perception of statistical distributions is depicted by the iconic bell curve which comprises of a massive bulk of 'middle-class' values, and two thin tails - one of small left-wing values, and one of large right-wing values. The shape of the bell curve is unimodal, and its peak represents both the mode and the mean. Thomas Friedman, the famous New York Times columnist, recently asserted that we have entered a human era in which "Average is Over" . In this paper we present mathematical models for the phenomenon that Friedman highlighted. While the models are derived via different modeling approaches, they share a common foundation. Inherent tipping points cause the models to phase-shift from a 'normal' bell-shape statistical behavior to an 'anomalous' statistical behavior: the unimodal shape changes to an unbounded monotone shape, the mode vanishes, and the mean diverges. Hence: (i) there is an explosion of small values; (ii) large values become super-large; (iii) 'middle-class' values are wiped out, leaving an infinite rift between the small and the super large values; and (iv) "Average is Over" indeed.

  9. Averaging and sampling for magnetic-observatory hourly data

    Directory of Open Access Journals (Sweden)

    J. J. Love

    2010-11-01

    Full Text Available A time and frequency-domain analysis is made of the effects of averaging and sampling methods used for constructing magnetic-observatory hourly data values. Using 1-min data as a proxy for continuous, geomagnetic variation, we construct synthetic hourly values of two standard types: instantaneous "spot" measurements and simple 1-h "boxcar" averages. We compare these average-sample types with others: 2-h average, Gaussian, and "brick-wall" low-frequency-pass. Hourly spot measurements provide a statistically unbiased representation of the amplitude range of geomagnetic-field variation, but as a representation of continuous field variation over time, they are significantly affected by aliasing, especially at high latitudes. The 1-h, 2-h, and Gaussian average-samples are affected by a combination of amplitude distortion and aliasing. Brick-wall values are not affected by either amplitude distortion or aliasing, but constructing them is, in an operational setting, relatively more difficult than it is for other average-sample types. It is noteworthy that 1-h average-samples, the present standard for observatory hourly data, have properties similar to Gaussian average-samples that have been optimized for a minimum residual sum of amplitude distortion and aliasing. For 1-h average-samples from medium and low-latitude observatories, the average of the combination of amplitude distortion and aliasing is less than the 5.0 nT accuracy standard established by Intermagnet for modern 1-min data. For medium and low-latitude observatories, average differences between monthly means constructed from 1-min data and monthly means constructed from any of the hourly average-sample types considered here are less than the 1.0 nT resolution of standard databases. We recommend that observatories and World Data Centers continue the standard practice of reporting simple 1-h-average hourly values.

  10. The average size of ordered binary subgraphs

    NARCIS (Netherlands)

    van Leeuwen, J.; Hartel, Pieter H.

    To analyse the demands made on the garbage collector in a graph reduction system, the change in size of an average graph is studied when an arbitrary edge is removed. In ordered binary trees the average number of deleted nodes as a result of cutting a single edge is equal to the average size of a

  11. The effects of sex and grade-point average on emotional intelligence.

    Science.gov (United States)

    Tapia, Martha; Marsh, George E

    2006-01-01

    This study was conducted to examine the effects of sex and grade-point average (GPA) on emotional intelligence on secondary students as measured by the Emotional Intelligence Inventory (EII). The EII is a 41-item Likert scale based on the original theoretical model of emotional intelligence developed by Salovey and Mayer. An exploratory factor analysis identified four factors, which were named Empathy, Utilization of Feelings, Handling Relationships, and Self-control. The sample consisted of 319 students, 162 males and 157 females, who attended school at a bilingual (English and Spanish) college preparatory school. General linear analysis revealed significant differences in empathy scores when grouped by gender. There were significant differences in self-control when grouped by GPA levels.

  12. The geometrically averaged density of states calculated from the local Green's function as a measure of localization

    International Nuclear Information System (INIS)

    Wortis, R.; Song Yun; Atkinson, W.A.

    2008-01-01

    With the goal of measuring localization in disordered interacting systems, we examine the finite-size scaling of the geometrically averaged density of states calculated from the local Green's function with finite energy resolution. Our results show that, unlike in a simple energy binning procedure, there is no limit in which the finite energy resolution is irrelevant

  13. Delineation of facial archetypes by 3d averaging.

    Science.gov (United States)

    Shaweesh, Ashraf I; Thomas, C David L; Bankier, Agnes; Clement, John G

    2004-10-01

    The objective of this study was to investigate the feasibility of creating archetypal 3D faces through computerized 3D facial averaging. A 3D surface scanner Fiore and its software were used to acquire the 3D scans of the faces while 3D Rugle3 and locally-developed software generated the holistic facial averages. 3D facial averages were created from two ethnic groups; European and Japanese and from children with three previous genetic disorders; Williams syndrome, achondroplasia and Sotos syndrome as well as the normal control group. The method included averaging the corresponding depth (z) coordinates of the 3D facial scans. Compared with other face averaging techniques there was not any warping or filling in the spaces by interpolation; however, this facial average lacked colour information. The results showed that as few as 14 faces were sufficient to create an archetypal facial average. In turn this would make it practical to use face averaging as an identification tool in cases where it would be difficult to recruit a larger number of participants. In generating the average, correcting for size differences among faces was shown to adjust the average outlines of the facial features. It is assumed that 3D facial averaging would help in the identification of the ethnic status of persons whose identity may not be known with certainty. In clinical medicine, it would have a great potential for the diagnosis of syndromes with distinctive facial features. The system would also assist in the education of clinicians in the recognition and identification of such syndromes.

  14. Averaging Robertson-Walker cosmologies

    International Nuclear Information System (INIS)

    Brown, Iain A.; Robbers, Georg; Behrend, Juliane

    2009-01-01

    The cosmological backreaction arises when one directly averages the Einstein equations to recover an effective Robertson-Walker cosmology, rather than assuming a background a priori. While usually discussed in the context of dark energy, strictly speaking any cosmological model should be recovered from such a procedure. We apply the scalar spatial averaging formalism for the first time to linear Robertson-Walker universes containing matter, radiation and dark energy. The formalism employed is general and incorporates systems of multiple fluids with ease, allowing us to consider quantitatively the universe from deep radiation domination up to the present day in a natural, unified manner. Employing modified Boltzmann codes we evaluate numerically the discrepancies between the assumed and the averaged behaviour arising from the quadratic terms, finding the largest deviations for an Einstein-de Sitter universe, increasing rapidly with Hubble rate to a 0.01% effect for h = 0.701. For the ΛCDM concordance model, the backreaction is of the order of Ω eff 0 ≈ 4 × 10 −6 , with those for dark energy models being within a factor of two or three. The impacts at recombination are of the order of 10 −8 and those in deep radiation domination asymptote to a constant value. While the effective equations of state of the backreactions in Einstein-de Sitter, concordance and quintessence models are generally dust-like, a backreaction with an equation of state w eff < −1/3 can be found for strongly phantom models

  15. High-Average-Power Diffraction Pulse-Compression Gratings Enabling Next-Generation Ultrafast Laser Systems

    Energy Technology Data Exchange (ETDEWEB)

    Alessi, D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2016-11-01

    Pulse compressors for ultrafast lasers have been identified as a technology gap in the push towards high peak power systems with high average powers for industrial and scientific applications. Gratings for ultrashort (sub-150fs) pulse compressors are metallic and can absorb a significant percentage of laser energy resulting in up to 40% loss as well as thermal issues which degrade on-target performance. We have developed a next generation gold grating technology which we have scaled to the petawatt-size. This resulted in improvements in efficiency, uniformity and processing as compared to previous substrate etched gratings for high average power. This new design has a deposited dielectric material for the grating ridge rather than etching directly into the glass substrate. It has been observed that average powers as low as 1W in a compressor can cause distortions in the on-target beam. We have developed and tested a method of actively cooling diffraction gratings which, in the case of gold gratings, can support a petawatt peak power laser with up to 600W average power. We demonstrated thermo-mechanical modeling of a grating in its use environment and benchmarked with experimental measurement. Multilayer dielectric (MLD) gratings are not yet used for these high peak power, ultrashort pulse durations due to their design challenges. We have designed and fabricated broad bandwidth, low dispersion MLD gratings suitable for delivering 30 fs pulses at high average power. This new grating design requires the use of a novel Out Of Plane (OOP) compressor, which we have modeled, designed, built and tested. This prototype compressor yielded a transmission of 90% for a pulse with 45 nm bandwidth, and free of spatial and angular chirp. In order to evaluate gratings and compressors built in this project we have commissioned a joule-class ultrafast Ti:Sapphire laser system. Combining the grating cooling and MLD technologies developed here could enable petawatt laser systems to

  16. Effect of average growing season temperature on seedling germination, survival and growth in jack pine (Pinus banksiana Lamb.)

    Science.gov (United States)

    A. David; E. Humenberger

    2017-01-01

    Because jack pine (Pinus banksiana Lamb.) is serotinous, it retains multiple years of cones until environmental conditions are favorable for releasing seed. These cones, which contain seed cohorts that developed under a variety of growing seasons, can be accurately aged using bud scale scars on twigs and branches. By calculating the average daily...

  17. Determinants of College Grade Point Averages

    Science.gov (United States)

    Bailey, Paul Dean

    2012-01-01

    Chapter 2: The Role of Class Difficulty in College Grade Point Averages. Grade Point Averages (GPAs) are widely used as a measure of college students' ability. Low GPAs can remove a students from eligibility for scholarships, and even continued enrollment at a university. However, GPAs are determined not only by student ability but also by the…

  18. Rotational averaging of multiphoton absorption cross sections

    Energy Technology Data Exchange (ETDEWEB)

    Friese, Daniel H., E-mail: daniel.h.friese@uit.no; Beerepoot, Maarten T. P.; Ruud, Kenneth [Centre for Theoretical and Computational Chemistry, University of Tromsø — The Arctic University of Norway, N-9037 Tromsø (Norway)

    2014-11-28

    Rotational averaging of tensors is a crucial step in the calculation of molecular properties in isotropic media. We present a scheme for the rotational averaging of multiphoton absorption cross sections. We extend existing literature on rotational averaging to even-rank tensors of arbitrary order and derive equations that require only the number of photons as input. In particular, we derive the first explicit expressions for the rotational average of five-, six-, and seven-photon absorption cross sections. This work is one of the required steps in making the calculation of these higher-order absorption properties possible. The results can be applied to any even-rank tensor provided linearly polarized light is used.

  19. Ergodic averages via dominating processes

    DEFF Research Database (Denmark)

    Møller, Jesper; Mengersen, Kerrie

    2006-01-01

    We show how the mean of a monotone function (defined on a state space equipped with a partial ordering) can be estimated, using ergodic averages calculated from upper and lower dominating processes of a stationary irreducible Markov chain. In particular, we do not need to simulate the stationary...... Markov chain and we eliminate the problem of whether an appropriate burn-in is determined or not. Moreover, when a central limit theorem applies, we show how confidence intervals for the mean can be estimated by bounding the asymptotic variance of the ergodic average based on the equilibrium chain....

  20. Deformed statistics Kullback–Leibler divergence minimization within a scaled Bregman framework

    International Nuclear Information System (INIS)

    Venkatesan, R.C.; Plastino, A.

    2011-01-01

    The generalized Kullback–Leibler divergence (K–Ld) in Tsallis statistics [constrained by the additive duality of generalized statistics (dual generalized K–Ld)] is here reconciled with the theory of Bregman divergences for expectations defined by normal averages, within a measure-theoretic framework. Specifically, it is demonstrated that the dual generalized K–Ld is a scaled Bregman divergence. The Pythagorean theorem is derived from the minimum discrimination information principle using the dual generalized K–Ld as the measure of uncertainty, with constraints defined by normal averages. The minimization of the dual generalized K–Ld, with normal averages constraints, is shown to exhibit distinctly unique features. -- Highlights: ► Dual generalized Kullback–Leibler divergence (K–Ld) proven to be scaled Bregman divergence in continuous measure-theoretic framework. ► Minimum dual generalized K–Ld condition established with normal averages constraints. ► Pythagorean theorem derived.

  1. Self-esteem in mastectomized women – application of Rosenberg’s scale

    OpenAIRE

    Marcela Marques Jucá Fernandes; Pricilla Cândido Alves; Míria Conceição Lavinas Santos; Elizabeth Moreira Mota; Ana Fátima Carvalho Fernandes

    2013-01-01

    The study aimed to identify the variables that influence the self-esteem of mastectomized women and assess their self-esteem level through the implementation of the Rosenberg Self-Esteem Scale. Exploratory, descriptive cross-sectional research carried out in July 2009 with 14 women of a support group in Fortaleza-CE, Brazil. Data were collected through semi-structured interview and application of this scale. The results showed an average age of 59 years, average time of 84.9 months after mast...

  2. Mean link versus average plaquette tadpoles in lattice NRQCD

    Science.gov (United States)

    Shakespeare, Norman H.; Trottier, Howard D.

    1999-03-01

    We compare mean-link and average plaquette tadpole renormalization schemes in the context of the quarkonium hyperfine splittings in lattice NRQCD. Simulations are done for the three quarkonium systems c overlinec, b overlinec, and b overlineb. The hyperfine splittings are computed both at leading and at next-to-leading order in the relativistic expansion. Results are obtained at a large number of lattice spacings. A number of features emerge, all of which favor tadpole renormalization using mean links. This includes much better scaling of the hyperfine splittings in the three quarkonium systems. We also find that relativistic corrections to the spin splittings are smaller with mean-link tadpoles, particularly for the c overlinec and b overlinec systems. We also see signs of a breakdown in the NRQCD expansion when the bare quark mass falls below about one in lattice units (with the bare quark masses turning out to be much larger with mean-link tadpoles).

  3. Mean link versus average plaquette tadpoles in lattice NRQCD

    International Nuclear Information System (INIS)

    Shakespeare, Norman H.; Trottier, Howard D.

    1999-01-01

    We compare mean-link and average plaquette tadpole renormalization schemes in the context of the quarkonium hyperfine splittings in lattice NRQCD. Simulations are done for the three quarkonium systems cc-bar, bc-bar, and bb-bar. The hyperfine splittings are computed both at leading and at next-to-leading order in the relativistic expansion. Results are obtained at a large number of lattice spacings. A number of features emerge, all of which favor tadpole renormalization using mean links. This includes much better scaling of the hyperfine splittings in the three quarkonium systems. We also find that relativistic corrections to the spin splittings are smaller with mean-link tadpoles, particularly for the cc-bar and bc-bar systems. We also see signs of a breakdown in the NRQCD expansion when the bare quark mass falls below about one in lattice units (with the bare quark masses turning out to be much larger with mean-link tadpoles)

  4. Mean link versus average plaquette tadpoles in lattice NRQCD

    Energy Technology Data Exchange (ETDEWEB)

    Shakespeare, Norman H.; Trottier, Howard D

    1999-03-01

    We compare mean-link and average plaquette tadpole renormalization schemes in the context of the quarkonium hyperfine splittings in lattice NRQCD. Simulations are done for the three quarkonium systems cc-bar, bc-bar, and bb-bar. The hyperfine splittings are computed both at leading and at next-to-leading order in the relativistic expansion. Results are obtained at a large number of lattice spacings. A number of features emerge, all of which favor tadpole renormalization using mean links. This includes much better scaling of the hyperfine splittings in the three quarkonium systems. We also find that relativistic corrections to the spin splittings are smaller with mean-link tadpoles, particularly for the cc-bar and bc-bar systems. We also see signs of a breakdown in the NRQCD expansion when the bare quark mass falls below about one in lattice units (with the bare quark masses turning out to be much larger with mean-link tadpoles)

  5. Application of method of volume averaging coupled with time resolved PIV to determine transport characteristics of turbulent flows in porous bed

    Science.gov (United States)

    Patil, Vishal; Liburdy, James

    2012-11-01

    Turbulent porous media flows are encountered in catalytic bed reactors and heat exchangers. Dispersion and mixing properties of these flows play an essential role in efficiency and performance. In an effort to understand these flows, pore scale time resolved PIV measurements in a refractive index matched porous bed were made. Pore Reynolds numbers, based on hydraulic diameter and pore average velocity, were varied from 400-4000. Jet-like flows and recirculation regions associated with large scale structures were found to exist. Coherent vortical structures which convect at approximately 0.8 times the pore average velocity were identified. These different flow regions exhibited different turbulent characteristics and hence contributed unequally to global transport properties of the bed. The heterogeneity present within a pore and also from pore to pore can be accounted for in estimating transport properties using the method of volume averaging. Eddy viscosity maps and mean velocity field maps, both obtained from PIV measurements, along with the method of volume averaging were used to predict the dispersion tensor versus Reynolds number. Asymptotic values of dispersion compare well to existing correlations. The role of molecular diffusion was explored by varying the Schmidt number and molecular diffusion was found to play an important role in tracer transport, especially in recirculation regions. Funding by NSF grant 0933857, Particulate and Multiphase Processing.

  6. Multiphase averaging of periodic soliton equations

    International Nuclear Information System (INIS)

    Forest, M.G.

    1979-01-01

    The multiphase averaging of periodic soliton equations is considered. Particular attention is given to the periodic sine-Gordon and Korteweg-deVries (KdV) equations. The periodic sine-Gordon equation and its associated inverse spectral theory are analyzed, including a discussion of the spectral representations of exact, N-phase sine-Gordon solutions. The emphasis is on physical characteristics of the periodic waves, with a motivation from the well-known whole-line solitons. A canonical Hamiltonian approach for the modulational theory of N-phase waves is prescribed. A concrete illustration of this averaging method is provided with the periodic sine-Gordon equation; explicit averaging results are given only for the N = 1 case, laying a foundation for a more thorough treatment of the general N-phase problem. For the KdV equation, very general results are given for multiphase averaging of the N-phase waves. The single-phase results of Whitham are extended to general N phases, and more importantly, an invariant representation in terms of Abelian differentials on a Riemann surface is provided. Several consequences of this invariant representation are deduced, including strong evidence for the Hamiltonian structure of N-phase modulational equations

  7. Analysis of Influence of the Thermal Dependence of Air Thermophysical Properties on the Accuracy of Simulation of Heat Transfer in a Turbulent Flow in Case of Applying Different Methods of Averaging Navier-Stokes Equations

    Directory of Open Access Journals (Sweden)

    A. D. Kliukvin

    2014-01-01

    Full Text Available There is theoretically investigated the influence of thermal dependence of air thermophysical properties on accuracy of heat transfer problems solution in a turbulent flow when using different methods of averaging the Navier-Stokes equations.There is analyzed the practicability of using particular method of averaging the NavierStokes equations when it’s necessary to clarify the solution of heat transfer problem taking into account the variability of air thermophysical properties.It’s shown that Reynolds and Favre averaging (the most common methods of averaging the Navier-Stokes equations are not effective in this case because these methods inaccurately describe behavior of large scale turbulent structures which strongly depends on geometry of particular flow. Thus it’s necessary to use more universal methods of turbulent flow simulation which are not based on averaging of all turbulent scales.In the article it’s shown that instead of Reynold and Favre averaging it’s possible to use large eddy simulation whereby turbulent structures are divided into small-scale and large-scale ones with subsequent modelling of small-scale ones only. But this approach leads to the necessarity of increasing the computational power by 2-3 orders.For different methods of averaging the form of additional terms of averaged Navier-Stokes equations in case of accounting pulsation of thermophysical properties of the air is obtained.On the example of a submerged heated air jet the errors (which occur when neglecting the thermal dependence of air thermophysical properties on averaged flow temperature in determination of convectional and conductive components of heat flux and viscous stresses are evaluated. It’s shown that the greatest increase of solution accuracy can be obtained in case of the flows with high temperature gradients.Finally using infinite Teylor series it’s found that underestimation of convective and conductive components of heat flux and

  8. Predicting dissolution patterns in variable aperture fractures: 1. Development and evaluation of an enhanced depth-averaged computational model

    Energy Technology Data Exchange (ETDEWEB)

    Detwiler, R L; Rajaram, H

    2006-04-21

    Water-rock interactions within variable-aperture fractures can lead to dissolution of fracture surfaces and local alteration of fracture apertures, potentially transforming the transport properties of the fracture over time. Because fractures often provide dominant pathways for subsurface flow and transport, developing models that effectively quantify the role of dissolution on changing transport properties over a range of scales is critical to understanding potential impacts of natural and anthropogenic processes. Dissolution of fracture surfaces is controlled by surface-reaction kinetics and transport of reactants and products to and from the fracture surfaces. We present development and evaluation of a depth-averaged model of fracture flow and reactive transport that explicitly calculates local dissolution-induced alterations in fracture apertures. The model incorporates an effective mass transfer relationship that implicitly represents the transition from reaction-limited dissolution to transport-limited dissolution. We evaluate the model through direct comparison to previously reported physical experiments in transparent analog fractures fabricated by mating an inert, transparent rough surface with a smooth single crystal of potassium dihydrogen phosphate (KDP), which allowed direct measurement of fracture aperture during dissolution experiments using well-established light transmission techniques [Detwiler, et al., 2003]. Comparison of experiments and simulations at different flow rates demonstrate the relative impact of the dimensionless Peclet and Damkohler numbers on fracture dissolution and the ability of the computational model to simulate dissolution. Despite some discrepancies in the small-scale details of dissolution patterns, the simulations predict the evolution of large-scale features quite well for the different experimental conditions. This suggests that our depth-averaged approach to simulating fracture dissolution provides a useful approach for

  9. Micro-Scale Properties of Different Bora Types

    Directory of Open Access Journals (Sweden)

    Vinko Šoljan

    2018-03-01

    Full Text Available In this paper we use 20 Hz wind measurements on three levels (2, 5, and 10 m to investigate the differences in micro-scale properties of different bora types, i.e., deep and shallow bora with further subdivision to cyclonic and anticyclonic bora cases. Using Fourier spectral analysis, we investigate a suitable turbulence averaging scale and bora gust pulsations. The obtained data set is further used to test the Monin–Obukhov similarity theory, the surface layer stratification, the behavior of the terms in the prognostic turbulence kinetic energy equation, and the wind profiles. One of our main goals is to identify possible micro-scale differences between shallow and deep bora types because of the possible different mountain wave dynamics in those flows. We found that a turbulence averaging scale of 30 min is suitable for this location and is in agreement with previous bora studies. The wind speed power spectral densities of all selected bora episodes showed pulsations with periods of 2–8 min. This suggests that mountain wave breaking was present in all cases, regardless of flow depth and synoptic type. The stability parameter analysis confirmed the near-neutral thermal stratification of bora; a consequence of intensive mechanical mixing. No significant differences related to bora type were observed in other micro-scale parameters.

  10. Tendon surveillance requirements - average tendon force

    International Nuclear Information System (INIS)

    Fulton, J.F.

    1982-01-01

    Proposed Rev. 3 to USNRC Reg. Guide 1.35 discusses the need for comparing, for individual tendons, the measured and predicted lift-off forces. Such a comparison is intended to detect any abnormal tendon force loss which might occur. Recognizing that there are uncertainties in the prediction of tendon losses, proposed Guide 1.35.1 has allowed specific tolerances on the fundamental losses. Thus, the lift-off force acceptance criteria for individual tendons appearing in Reg. Guide 1.35, Proposed Rev. 3, is stated relative to a lower bound predicted tendon force, which is obtained using the 'plus' tolerances on the fundamental losses. There is an additional acceptance criterion for the lift-off forces which is not specifically addressed in these two Reg. Guides; however, it is included in a proposed Subsection IWX to ASME Code Section XI. This criterion is based on the overriding requirement that the magnitude of prestress in the containment structure be sufficeint to meet the minimum prestress design requirements. This design requirement can be expressed as an average tendon force for each group of vertical hoop, or dome tendons. For the purpose of comparing the actual tendon forces with the required average tendon force, the lift-off forces measured for a sample of tendons within each group can be averaged to construct the average force for the entire group. However, the individual lift-off forces must be 'corrected' (normalized) prior to obtaining the sample average. This paper derives the correction factor to be used for this purpose. (orig./RW)

  11. Average Bandwidth Allocation Model of WFQ

    Directory of Open Access Journals (Sweden)

    Tomáš Balogh

    2012-01-01

    Full Text Available We present a new iterative method for the calculation of average bandwidth assignment to traffic flows using a WFQ scheduler in IP based NGN networks. The bandwidth assignment calculation is based on the link speed, assigned weights, arrival rate, and average packet length or input rate of the traffic flows. We prove the model outcome with examples and simulation results using NS2 simulator.

  12. Physics-preserving averaging scheme based on Grunwald-Letnikov formula for gas flow in fractured media

    KAUST Repository

    Amir, Sahar Z.

    2018-01-02

    The heterogeneous natures of rock fabrics, due to the existence of multi-scale fractures and geological formations, led to the deviations from unity in the flux-equations fractional-exponent magnitudes. In this paper, the resulting non-Newtonian non-Darcy fractional-derivatives flux equations are solved using physics-preserving averaging schemes that incorporates both, original and shifted, Grunwald-Letnikov (GL) approximation formulas preserving the physics, by reducing the shifting effects, while maintaining the stability of the system, by keeping one shifted expansion. The proposed way of using the GL expansions also generate symmetrical coefficient matrices that significantly reduces the discretization complexities appearing with all shifted cases from literature, and help considerably in 2D and 3D systems. Systems equations derivations and discretization details are discussed. Then, the physics-preserving averaging scheme is explained and illustrated. Finally, results are presented and reviewed. Edge-based original GL expansions are unstable as also illustrated in literatures. Shifted GL expansions are stable but add a lot of additional weights to both discretization sides affecting the physical accuracy. In comparison, the physics-preserving averaging scheme balances the physical accuracy and stability requirements leading to a more physically conservative scheme that is more stable than the original GL approximation but might be slightly less stable than the shifted GL approximations. It is a locally conservative Single-Continuum averaging scheme that applies a finite-volume viewpoint.

  13. Physics-preserving averaging scheme based on Grunwald-Letnikov formula for gas flow in fractured media

    KAUST Repository

    Amir, Sahar Z.; Sun, Shuyu

    2018-01-01

    The heterogeneous natures of rock fabrics, due to the existence of multi-scale fractures and geological formations, led to the deviations from unity in the flux-equations fractional-exponent magnitudes. In this paper, the resulting non-Newtonian non-Darcy fractional-derivatives flux equations are solved using physics-preserving averaging schemes that incorporates both, original and shifted, Grunwald-Letnikov (GL) approximation formulas preserving the physics, by reducing the shifting effects, while maintaining the stability of the system, by keeping one shifted expansion. The proposed way of using the GL expansions also generate symmetrical coefficient matrices that significantly reduces the discretization complexities appearing with all shifted cases from literature, and help considerably in 2D and 3D systems. Systems equations derivations and discretization details are discussed. Then, the physics-preserving averaging scheme is explained and illustrated. Finally, results are presented and reviewed. Edge-based original GL expansions are unstable as also illustrated in literatures. Shifted GL expansions are stable but add a lot of additional weights to both discretization sides affecting the physical accuracy. In comparison, the physics-preserving averaging scheme balances the physical accuracy and stability requirements leading to a more physically conservative scheme that is more stable than the original GL approximation but might be slightly less stable than the shifted GL approximations. It is a locally conservative Single-Continuum averaging scheme that applies a finite-volume viewpoint.

  14. Understanding the Gap between Cognitive Abilities and Daily Living Skills in Adolescents with Autism Spectrum Disorders with Average Intelligence

    Science.gov (United States)

    Duncan, Amie W.; Bishop, Somer L.

    2015-01-01

    Daily living skills standard scores on the Vineland Adaptive Behavior Scales-2nd edition were examined in 417 adolescents from the Simons Simplex Collection. All participants had at least average intelligence and a diagnosis of autism spectrum disorder. Descriptive statistics and binary logistic regressions were used to examine the prevalence and…

  15. Exact classical scaling formalism for nonreactive processes

    International Nuclear Information System (INIS)

    DePristo, A.E.

    1981-01-01

    A general nonreactive collision system is considered with internal molecular variables (p, r) and/or (I, theta) of arbitrary dimensions and relative translational variables (P, R) of three or less dimensions. We derive an exact classical scaling formalism which relates the collisional change in any function of molecular variables directly to the initial values of these variables. The collision dynamics is then described by an explicit function of the initial point in the internal molecular phase space, for a fixed point in the relative translational phase space. In other words, the systematic variation of the internal molecular properties (e.g., actions and average internal kinetic energies) is given as a function of the initial internal action-angle variables. A simple three term approximation to the exact formalism is derived, the natural variables of which are the internal action I and internal linear momenta p. For the final average internal kinetic energies T, the result is T-T/sup( 0 ) = α+βp/sup( 0 )+γI/sup( 0 ), where the superscripted ''0'' indicates the initial value. The parameters α, β, and γ in this scaling theory are directly related to the moments of the change in average internal kinetic energy. Utilizing a very limited number of input moments generated from classical trajectory calculations, the scaling can be used to predict the entire distribution of final internal variables as a function of initial internal actions and linear momenta. Initial examples for atom--collinear harmonic oscillator collision systems are presented in detail, with the scaling predictions (e.g., moments and quasiclassical histogram transition probabilities) being generally very good to excellent quantitatively

  16. Factors determining the average body size of geographically separated Arctodiaptomus salinus (Daday, 1885) populations.

    Science.gov (United States)

    Anufriieva, Elena V; Shadrin, Nickolai V

    2014-03-01

    Arctodiaptomus salinus inhabits water bodies across Eurasia and North Africa. Based on our own data and that from the literature, we analyzed the influences of several factors on the intra- and inter-population variability of this species. A strong negative linear correlation between temperature and average body size in the Crimean and African populations was found, in which the parameters might be influenced by salinity. Meanwhile, a significant negative correlation between female body size and the altitude of habitats was found by comparing body size in populations from different regions. Individuals from environments with highly varying abiotic parameters, e.g. temporary reservoirs, had a larger body size than individuals from permanent water bodies. The changes in average body mass in populations were at 11.4 times, whereas, those in individual metabolic activities were at 6.2 times. Moreover, two size groups of A. salinus in the Crimean and the Siberian lakes were observed. The ratio of female length to male length fluctuated between 1.02 and 1.30. The average size of A. salinus in populations and its variations were determined by both genetic and environmental factors. However, the parities of these factors were unequal in either spatial or temporal scales.

  17. Area-averaged evapotranspiration over a heterogeneous land surface: aggregation of multi-point EC flux measurements with a high-resolution land-cover map and footprint analysis

    Directory of Open Access Journals (Sweden)

    F. Xu

    2017-08-01

    Full Text Available The determination of area-averaged evapotranspiration (ET at the satellite pixel scale/model grid scale over a heterogeneous land surface plays a significant role in developing and improving the parameterization schemes of the remote sensing based ET estimation models and general hydro-meteorological models. The Heihe Watershed Allied Telemetry Experimental Research (HiWATER flux matrix provided a unique opportunity to build an aggregation scheme for area-averaged fluxes. On the basis of the HiWATER flux matrix dataset and high-resolution land-cover map, this study focused on estimating the area-averaged ET over a heterogeneous landscape with footprint analysis and multivariate regression. The procedure is as follows. Firstly, quality control and uncertainty estimation for the data of the flux matrix, including 17 eddy-covariance (EC sites and four groups of large-aperture scintillometers (LASs, were carefully done. Secondly, the representativeness of each EC site was quantitatively evaluated; footprint analysis was also performed for each LAS path. Thirdly, based on the high-resolution land-cover map derived from aircraft remote sensing, a flux aggregation method was established combining footprint analysis and multiple-linear regression. Then, the area-averaged sensible heat fluxes obtained from the EC flux matrix were validated by the LAS measurements. Finally, the area-averaged ET of the kernel experimental area of HiWATER was estimated. Compared with the formerly used and rather simple approaches, such as the arithmetic average and area-weighted methods, the present scheme is not only with a much better database, but also has a solid grounding in physics and mathematics in the integration of area-averaged fluxes over a heterogeneous surface. Results from this study, both instantaneous and daily ET at the satellite pixel scale, can be used for the validation of relevant remote sensing models and land surface process models. Furthermore, this

  18. Area-averaged evapotranspiration over a heterogeneous land surface: aggregation of multi-point EC flux measurements with a high-resolution land-cover map and footprint analysis

    Science.gov (United States)

    Xu, Feinan; Wang, Weizhen; Wang, Jiemin; Xu, Ziwei; Qi, Yuan; Wu, Yueru

    2017-08-01

    The determination of area-averaged evapotranspiration (ET) at the satellite pixel scale/model grid scale over a heterogeneous land surface plays a significant role in developing and improving the parameterization schemes of the remote sensing based ET estimation models and general hydro-meteorological models. The Heihe Watershed Allied Telemetry Experimental Research (HiWATER) flux matrix provided a unique opportunity to build an aggregation scheme for area-averaged fluxes. On the basis of the HiWATER flux matrix dataset and high-resolution land-cover map, this study focused on estimating the area-averaged ET over a heterogeneous landscape with footprint analysis and multivariate regression. The procedure is as follows. Firstly, quality control and uncertainty estimation for the data of the flux matrix, including 17 eddy-covariance (EC) sites and four groups of large-aperture scintillometers (LASs), were carefully done. Secondly, the representativeness of each EC site was quantitatively evaluated; footprint analysis was also performed for each LAS path. Thirdly, based on the high-resolution land-cover map derived from aircraft remote sensing, a flux aggregation method was established combining footprint analysis and multiple-linear regression. Then, the area-averaged sensible heat fluxes obtained from the EC flux matrix were validated by the LAS measurements. Finally, the area-averaged ET of the kernel experimental area of HiWATER was estimated. Compared with the formerly used and rather simple approaches, such as the arithmetic average and area-weighted methods, the present scheme is not only with a much better database, but also has a solid grounding in physics and mathematics in the integration of area-averaged fluxes over a heterogeneous surface. Results from this study, both instantaneous and daily ET at the satellite pixel scale, can be used for the validation of relevant remote sensing models and land surface process models. Furthermore, this work will be

  19. The relationship of the Reynolds Intellectual Assessment Scales and the Wechsler Adult Intelligence Scale-Third Edition.

    Science.gov (United States)

    Smith, Billy L; McChristian, Chrystal L; Smith, Teresa D; Meaux, Julie

    2009-08-01

    The purpose of this study was to compare scores on the Reynolds Intellectual Assessment Scales (RIAS) with scores on the Wechsler Adult Intelligence Scale-Third Edition (WAIS-III) in a group of college students diagnosed with a Learning Disability, Attention-Deficit Hyperactivity Disorder (ADHD), or a combination of the two. The RIAS Composite Index score was significantly higher than the WAIS-III Full Scale IQ, although scores on both tests were in the average range. Correlations between the two tests were significant on all measures. Male students were significantly higher than female students on both the RIAS Composite Index and on the WAIS-III Full Scale IQ. Although the ADHD group was higher on IQ than the Learning Disabled and combined disorder groups on all IQ measures, no significant differences were found.

  20. Average and local structure of α-CuI by configurational averaging

    International Nuclear Information System (INIS)

    Mohn, Chris E; Stoelen, Svein

    2007-01-01

    Configurational Boltzmann averaging together with density functional theory are used to study in detail the average and local structure of the superionic α-CuI. We find that the coppers are spread out with peaks in the atom-density at the tetrahedral sites of the fcc sublattice of iodines. We calculate Cu-Cu, Cu-I and I-I pair radial distribution functions, the distribution of coordination numbers and the distribution of Cu-I-Cu, I-Cu-I and Cu-Cu-Cu bond-angles. The partial pair distribution functions are in good agreement with experimental neutron diffraction-reverse Monte Carlo, extended x-ray absorption fine structure and ab initio molecular dynamics results. In particular, our results confirm the presence of a prominent peak at around 2.7 A in the Cu-Cu pair distribution function as well as a broader, less intense peak at roughly 4.3 A. We find highly flexible bonds and a range of coordination numbers for both iodines and coppers. This structural flexibility is of key importance in order to understand the exceptional conductivity of coppers in α-CuI; the iodines can easily respond to changes in the local environment as the coppers diffuse, and a myriad of different diffusion-pathways is expected due to the large variation in the local motifs

  1. Experimental demonstration of squeezed-state quantum averaging

    DEFF Research Database (Denmark)

    Lassen, Mikael Østergaard; Madsen, Lars Skovgaard; Sabuncu, Metin

    2010-01-01

    We propose and experimentally demonstrate a universal quantum averaging process implementing the harmonic mean of quadrature variances. The averaged variances are prepared probabilistically by means of linear optical interference and measurement-induced conditioning. We verify that the implemented...

  2. Stochastic Averaging and Stochastic Extremum Seeking

    CERN Document Server

    Liu, Shu-Jun

    2012-01-01

    Stochastic Averaging and Stochastic Extremum Seeking develops methods of mathematical analysis inspired by the interest in reverse engineering  and analysis of bacterial  convergence by chemotaxis and to apply similar stochastic optimization techniques in other environments. The first half of the text presents significant advances in stochastic averaging theory, necessitated by the fact that existing theorems are restricted to systems with linear growth, globally exponentially stable average models, vanishing stochastic perturbations, and prevent analysis over infinite time horizon. The second half of the text introduces stochastic extremum seeking algorithms for model-free optimization of systems in real time using stochastic perturbations for estimation of their gradients. Both gradient- and Newton-based algorithms are presented, offering the user the choice between the simplicity of implementation (gradient) and the ability to achieve a known, arbitrary convergence rate (Newton). The design of algorithms...

  3. Cognitive, academic, and attitudinal predictors of the grade point averages of college students with learning disabilities.

    Science.gov (United States)

    Murray, Christopher; Wren, Carol T

    2003-01-01

    This study examined cognitive, academic, and attitudinal predictors of college grade point average (GPA) among college students with learning disabilities (LD). The study population included 84 youth who attended a large private university in the midwestern United States. Measures of cognitive and academic functioning, along with a self-report measure of study habits and study attitudes, were used to predict college GPA. The results indicated that Full Scale IQ and one factor on the self-reported study habits scale accounted for a significant amount of variance in students' college GPA. These findings suggest that variables other than traditional cognitive and academic skills are important for determining the performance of youth with LD during college. The implications of these findings for future research efforts and practice are discussed.

  4. 20 CFR 404.220 - Average-monthly-wage method.

    Science.gov (United States)

    2010-04-01

    ... 20 Employees' Benefits 2 2010-04-01 2010-04-01 false Average-monthly-wage method. 404.220 Section... INSURANCE (1950- ) Computing Primary Insurance Amounts Average-Monthly-Wage Method of Computing Primary Insurance Amounts § 404.220 Average-monthly-wage method. (a) Who is eligible for this method. You must...

  5. Large-scale fluctuations in the diffusive decomposition of solid solutions

    International Nuclear Information System (INIS)

    Karpov, V.G.; Grimsditch, M.

    1995-01-01

    The concept of an instability in the classic Ostwald ripening theory with respect to compositional fluctuations is suggested. We show that small statistical fluctuations in the precipitate phase lead to gigantic Coulomb-like fluctuations in the solute concentration which in turn affect the ripening. As a result large-scale fluctuations in both the precipitate and solute concentrations appear. These fluctuations are characterized by amplitudes of the order of the average values of the corresponding quantities and by a space scale L∼(na) -1/2 which is considerably greater than both the average nuclear radius and internuclear distance. The Lifshitz-Slyozov theory of ripening is shown to remain locally applicable, over length scales much less than L. The implications of these findings for elastic light scattering in solid solutions that have undergone Ostwald ripening are considered

  6. Large-scale fluctuations in the diffusive decomposition of solid solutions

    Science.gov (United States)

    Karpov, V. G.; Grimsditch, M.

    1995-04-01

    The concept of an instability in the classic Ostwald ripening theory with respect to compositional fluctuations is suggested. We show that small statistical fluctuations in the precipitate phase lead to gigantic Coulomb-like fluctuations in the solute concentration which in turn affect the ripening. As a result large-scale fluctuations in both the precipitate and solute concentrations appear. These fluctuations are characterized by amplitudes of the order of the average values of the corresponding quantities and by a space scale L~(na)-1/2 which is considerably greater than both the average nuclear radius and internuclear distance. The Lifshitz-Slyozov theory of ripening is shown to remain locally applicable, over length scales much less than L. The implications of these findings for elastic light scattering in solid solutions that have undergone Ostwald ripening are considered.

  7. Leveraging Mechanism Simplicity and Strategic Averaging to Identify Signals from Highly Heterogeneous Spatial and Temporal Ozone Data

    Science.gov (United States)

    Brown-Steiner, B.; Selin, N. E.; Prinn, R. G.; Monier, E.; Garcia-Menendez, F.; Tilmes, S.; Emmons, L. K.; Lamarque, J. F.; Cameron-Smith, P. J.

    2017-12-01

    We summarize two methods to aid in the identification of ozone signals from underlying spatially and temporally heterogeneous data in order to help research communities avoid the sometimes burdensome computational costs of high-resolution high-complexity models. The first method utilizes simplified chemical mechanisms (a Reduced Hydrocarbon Mechanism and a Superfast Mechanism) alongside a more complex mechanism (MOZART-4) within CESM CAM-Chem to extend the number of simulated meteorological years (or add additional members to an ensemble) for a given modeling problem. The Reduced Hydrocarbon mechanism is twice as fast, and the Superfast mechanism is three times faster than the MOZART-4 mechanism. We show that simplified chemical mechanisms are largely capable of simulating surface ozone across the globe as well as the more complex chemical mechanisms, and where they are not capable, a simple standardized anomaly emulation approach can correct for their inadequacies. The second method uses strategic averaging over both temporal and spatial scales to filter out the highly heterogeneous noise that underlies ozone observations and simulations. This method allows for a selection of temporal and spatial averaging scales that match a particular signal strength (between 0.5 and 5 ppbv), and enables the identification of regions where an ozone signal can rise above the ozone noise over a given region and a given period of time. In conjunction, these two methods can be used to "scale down" chemical mechanism complexity and quantitatively determine spatial and temporal scales that could enable research communities to utilize simplified representations of atmospheric chemistry and thereby maximize their productivity and efficiency given computational constraints. While this framework is here applied to ozone data, it could also be applied to a broad range of geospatial data sets (observed or modeled) that have spatial and temporal coverage.

  8. Effects of reservoir heterogeneity on scaling of effective mass transfer coefficient for solute transport

    Science.gov (United States)

    Leung, Juliana Y.; Srinivasan, Sanjay

    2016-09-01

    Modeling transport process at large scale requires proper scale-up of subsurface heterogeneity and an understanding of its interaction with the underlying transport mechanisms. A technique based on volume averaging is applied to quantitatively assess the scaling characteristics of effective mass transfer coefficient in heterogeneous reservoir models. The effective mass transfer coefficient represents the combined contribution from diffusion and dispersion to the transport of non-reactive solute particles within a fluid phase. Although treatment of transport problems with the volume averaging technique has been published in the past, application to geological systems exhibiting realistic spatial variability remains a challenge. Previously, the authors developed a new procedure where results from a fine-scale numerical flow simulation reflecting the full physics of the transport process albeit over a sub-volume of the reservoir are integrated with the volume averaging technique to provide effective description of transport properties. The procedure is extended such that spatial averaging is performed at the local-heterogeneity scale. In this paper, the transport of a passive (non-reactive) solute is simulated on multiple reservoir models exhibiting different patterns of heterogeneities, and the scaling behavior of effective mass transfer coefficient (Keff) is examined and compared. One such set of models exhibit power-law (fractal) characteristics, and the variability of dispersion and Keff with scale is in good agreement with analytical expressions described in the literature. This work offers an insight into the impacts of heterogeneity on the scaling of effective transport parameters. A key finding is that spatial heterogeneity models with similar univariate and bivariate statistics may exhibit different scaling characteristics because of the influence of higher order statistics. More mixing is observed in the channelized models with higher-order continuity. It

  9. Light-cone averaging in cosmology: formalism and applications

    International Nuclear Information System (INIS)

    Gasperini, M.; Marozzi, G.; Veneziano, G.; Nugier, F.

    2011-01-01

    We present a general gauge invariant formalism for defining cosmological averages that are relevant for observations based on light-like signals. Such averages involve either null hypersurfaces corresponding to a family of past light-cones or compact surfaces given by their intersection with timelike hypersurfaces. Generalized Buchert-Ehlers commutation rules for derivatives of these light-cone averages are given. After introducing some adapted ''geodesic light-cone'' coordinates, we give explicit expressions for averaging the redshift to luminosity-distance relation and the so-called ''redshift drift'' in a generic inhomogeneous Universe

  10. Bounds on Average Time Complexity of Decision Trees

    KAUST Repository

    Chikalov, Igor

    2011-01-01

    In this chapter, bounds on the average depth and the average weighted depth of decision trees are considered. Similar problems are studied in search theory [1], coding theory [77], design and analysis of algorithms (e.g., sorting) [38]. For any diagnostic problem, the minimum average depth of decision tree is bounded from below by the entropy of probability distribution (with a multiplier 1/log2 k for a problem over a k-valued information system). Among diagnostic problems, the problems with a complete set of attributes have the lowest minimum average depth of decision trees (e.g, the problem of building optimal prefix code [1] and a blood test study in assumption that exactly one patient is ill [23]). For such problems, the minimum average depth of decision tree exceeds the lower bound by at most one. The minimum average depth reaches the maximum on the problems in which each attribute is "indispensable" [44] (e.g., a diagnostic problem with n attributes and kn pairwise different rows in the decision table and the problem of implementing the modulo 2 summation function). These problems have the minimum average depth of decision tree equal to the number of attributes in the problem description. © Springer-Verlag Berlin Heidelberg 2011.

  11. Lateral dispersion coefficients as functions of averaging time

    International Nuclear Information System (INIS)

    Sheih, C.M.

    1980-01-01

    Plume dispersion coefficients are discussed in terms of single-particle and relative diffusion, and are investigated as functions of averaging time. To demonstrate the effects of averaging time on the relative importance of various dispersion processes, and observed lateral wind velocity spectrum is used to compute the lateral dispersion coefficients of total, single-particle and relative diffusion for various averaging times and plume travel times. The results indicate that for a 1 h averaging time the dispersion coefficient of a plume can be approximated by single-particle diffusion alone for travel times <250 s and by relative diffusion for longer travel times. Furthermore, it is shown that the power-law formula suggested by Turner for relating pollutant concentrations for other averaging times to the corresponding 15 min average is applicable to the present example only when the averaging time is less than 200 s and the tral time smaller than about 300 s. Since the turbulence spectrum used in the analysis is an observed one, it is hoped that the results could represent many conditions encountered in the atmosphere. However, as the results depend on the form of turbulence spectrum, the calculations are not for deriving a set of specific criteria but for demonstrating the need in discriminating various processes in studies of plume dispersion

  12. Length scales for the Navier-Stokes equations on a rotating sphere

    International Nuclear Information System (INIS)

    Kyrychko, Yuliya N.; Bartuccelli, Michele V.

    2004-01-01

    In this Letter we obtain the dissipative length scale for the Navier-Stokes equations on a two-dimensional rotating sphere S 2 . This system is a fundamental model of the large scale atmospheric dynamics. Using the equations of motion in their vorticity form, we construct the ladder inequalities from which a set of time-averaged length scales is obtained

  13. Determination of the diagnostic x-ray tube practical peak voltage (PPV) from average or average peak voltage measurements

    Energy Technology Data Exchange (ETDEWEB)

    Hourdakis, C J, E-mail: khour@gaec.gr [Ionizing Radiation Calibration Laboratory-Greek Atomic Energy Commission, PO Box 60092, 15310 Agia Paraskevi, Athens, Attiki (Greece)

    2011-04-07

    The practical peak voltage (PPV) has been adopted as the reference measuring quantity for the x-ray tube voltage. However, the majority of commercial kV-meter models measure the average peak, U-bar{sub P}, the average, U-bar, the effective, U{sub eff} or the maximum peak, U{sub P} tube voltage. This work proposed a method for determination of the PPV from measurements with a kV-meter that measures the average U-bar or the average peak, U-bar{sub p} voltage. The kV-meter reading can be converted to the PPV by applying appropriate calibration coefficients and conversion factors. The average peak k{sub PPV,kVp} and the average k{sub PPV,Uav} conversion factors were calculated from virtual voltage waveforms for conventional diagnostic radiology (50-150 kV) and mammography (22-35 kV) tube voltages and for voltage ripples from 0% to 100%. Regression equation and coefficients provide the appropriate conversion factors at any given tube voltage and ripple. The influence of voltage waveform irregularities, like 'spikes' and pulse amplitude variations, on the conversion factors was investigated and discussed. The proposed method and the conversion factors were tested using six commercial kV-meters at several x-ray units. The deviations between the reference and the calculated - according to the proposed method - PPV values were less than 2%. Practical aspects on the voltage ripple measurement were addressed and discussed. The proposed method provides a rigorous base to determine the PPV with kV-meters from U-bar{sub p} and U-bar measurement. Users can benefit, since all kV-meters, irrespective of their measuring quantity, can be used to determine the PPV, complying with the IEC standard requirements.

  14. Averaging operations on matrices

    Indian Academy of Sciences (India)

    2014-07-03

    Jul 3, 2014 ... Role of Positive Definite Matrices. • Diffusion Tensor Imaging: 3 × 3 pd matrices model water flow at each voxel of brain scan. • Elasticity: 6 × 6 pd matrices model stress tensors. • Machine Learning: n × n pd matrices occur as kernel matrices. Tanvi Jain. Averaging operations on matrices ...

  15. Common scaling behavior in finance and macroeconomics

    Science.gov (United States)

    Podobnik, B.; Horvatic, D.; Petersen, A. M.; Njavro, M.; Stanley, H. E.

    2010-08-01

    In order to test whether scaling exists in finance at the world level, we test whether the average growth rates and volatility of market capitalization (MC) depend on the level of MC. We analyze the MC for 54 worldwide stock indices and 48 worldwide bond indices. We find that (i) the average growth rate of the MC and (ii) the standard deviation σ(r) of growth rates r decrease both with MC as power laws, with exponents αw = 0.28 ± 0.09 and βw = 0.12 ± 0.04. We define a stochastic process in order to model the scaling results we find for worldwide stock and bond indices. We establish a power-law relationship between the MC of a country's financial market and the gross domestic product (GDP) of the same country.

  16. 20 CFR 404.221 - Computing your average monthly wage.

    Science.gov (United States)

    2010-04-01

    ... 20 Employees' Benefits 2 2010-04-01 2010-04-01 false Computing your average monthly wage. 404.221... DISABILITY INSURANCE (1950- ) Computing Primary Insurance Amounts Average-Monthly-Wage Method of Computing Primary Insurance Amounts § 404.221 Computing your average monthly wage. (a) General. Under the average...

  17. The scale of biomass production in Japan

    Energy Technology Data Exchange (ETDEWEB)

    Matsumura, Yukihiko [School of Engineering, Hiroshima University, 1-4-1 Kagamiyama, Higashihiroshima-shi 739-8527 (Japan); Inoue, Takashi; Fukuda, Katsura [Global Warming Research Department, Mitsubishi Research Institute, Inc., 2-3-6 Ohtemachi, Chiyoda-ku, Tokyo 100-8141 (Japan); Komoto, Keiichi; Hada, Kenichiro [Renewable energy Team, Environment, Natural Resources and Energy Division, Mizuho Information and Research Institute, Inc., 2-3 Kanda-nishikicho, Chiyoda-ku, Tokyo 101-8443 (Japan); Hirata, Satoshi [Technical Institute, Kawasaki Heavy Industries, Ltd., 1-1 Kawasakicho, Akashi-shi, Hyogo 673-8666 (Japan); Minowa, Tomoaki [Biomass Recycle Research Laboratory, National Institute of Advanced and Industrial Science and Technology, 2-2-2 Hiro, Suehiro, Kure-shi, Hiroshima 737-0197 (Japan); Yamamoto, Hiromi [Socioeconomic Research Center, Central Research Institute of Electric Power Industry, 1-6-1 Ohtemachi, Chiyoda-ku, Tokyo 100-8126 (Japan)

    2005-11-01

    Policymakers working to introduce and promote the use of bioenergy in Japan require detailed information on the scales of the different types of biomass resources generated. In this research, the first of its type in Japan, the investigators reviewed various statistical resources to quantify the scale distribution of forest residues, waste wood from manufacturing, waste wood from construction, cattle manure, sewage sludge, night soil, household garbage, and waste food oil. As a result, the scale of biomass generation in Japan was found to be relatively small, on the average is no more than several tons in dry weight per day. (author)

  18. Averaging in SU(2) open quantum random walk

    International Nuclear Information System (INIS)

    Ampadu Clement

    2014-01-01

    We study the average position and the symmetry of the distribution in the SU(2) open quantum random walk (OQRW). We show that the average position in the central limit theorem (CLT) is non-uniform compared with the average position in the non-CLT. The symmetry of distribution is shown to be even in the CLT

  19. Averaging in SU(2) open quantum random walk

    Science.gov (United States)

    Clement, Ampadu

    2014-03-01

    We study the average position and the symmetry of the distribution in the SU(2) open quantum random walk (OQRW). We show that the average position in the central limit theorem (CLT) is non-uniform compared with the average position in the non-CLT. The symmetry of distribution is shown to be even in the CLT.

  20. Determining average yarding distance.

    Science.gov (United States)

    Roger H. Twito; Charles N. Mann

    1979-01-01

    Emphasis on environmental and esthetic quality in timber harvesting has brought about increased use of complex boundaries of cutting units and a consequent need for a rapid and accurate method of determining the average yarding distance and area of these units. These values, needed for evaluation of road and landing locations in planning timber harvests, are easily and...

  1. Average Revisited in Context

    Science.gov (United States)

    Watson, Jane; Chick, Helen

    2012-01-01

    This paper analyses the responses of 247 middle school students to items requiring the concept of average in three different contexts: a city's weather reported in maximum daily temperature, the number of children in a family, and the price of houses. The mixed but overall disappointing performance on the six items in the three contexts indicates…

  2. Biological scale for the estimation of sulfur dioxide pollution

    Energy Technology Data Exchange (ETDEWEB)

    Gilbert, O L

    1970-01-01

    By observing the distribution of lichens and bryophytes in an area where levels of SO/sub 2/ are well known it has been possible to produce a scale from which annual average levels of this pollutant can be estimated. Instructions on how to use the scale are given and its accuracy and possible usefulness are discussed.

  3. Notes on Well-Posed, Ensemble Averaged Conservation Equations for Multiphase, Multi-Component, and Multi-Material Flows

    International Nuclear Information System (INIS)

    Ray A. Berry

    2005-01-01

    At the INL researchers and engineers routinely encounter multiphase, multi-component, and/or multi-material flows. Some examples include: Reactor coolant flows Molten corium flows Dynamic compaction of metal powders Spray forming and thermal plasma spraying Plasma quench reactor Subsurface flows, particularly in the vadose zone Internal flows within fuel cells Black liquor atomization and combustion Wheat-chaff classification in combine harvesters Generation IV pebble bed, high temperature gas reactor The complexity of these flows dictates that they be examined in an averaged sense. Typically one would begin with known (or at least postulated) microscopic flow relations that hold on the ''small'' scale. These include continuum level conservation of mass, balance of species mass and momentum, conservation of energy, and a statement of the second law of thermodynamics often in the form of an entropy inequality (such as the Clausius-Duhem inequality). The averaged or macroscopic conservation equations and entropy inequalities are then obtained from the microscopic equations through suitable averaging procedures. At this stage a stronger form of the second law may also be postulated for the mixture of phases or materials. To render the evolutionary material flow balance system unique, constitutive equations and phase or material interaction relations are introduced from experimental observation, or by postulation, through strict enforcement of the constraints or restrictions resulting from the averaged entropy inequalities. These averaged equations form the governing equation system for the dynamic evolution of these mixture flows. Most commonly, the averaging technique utilized is either volume or time averaging or a combination of the two. The flow restrictions required for volume and time averaging to be valid can be severe, and violations of these restrictions are often found. A more general, less restrictive (and far less commonly used) type of averaging known as

  4. High-average-power 2 μm few-cycle optical parametric chirped pulse amplifier at 100 kHz repetition rate.

    Science.gov (United States)

    Shamir, Yariv; Rothhardt, Jan; Hädrich, Steffen; Demmler, Stefan; Tschernajew, Maxim; Limpert, Jens; Tünnermann, Andreas

    2015-12-01

    Sources of long wavelengths few-cycle high repetition rate pulses are becoming increasingly important for a plethora of applications, e.g., in high-field physics. Here, we report on the realization of a tunable optical parametric chirped pulse amplifier at 100 kHz repetition rate. At a central wavelength of 2 μm, the system delivered 33 fs pulses and a 6 W average power corresponding to 60 μJ pulse energy with gigawatt-level peak powers. Idler absorption and its crystal heating is experimentally investigated for a BBO. Strategies for further power scaling to several tens of watts of average power are discussed.

  5. Damping scaling factors for elastic response spectra for shallow crustal earthquakes in active tectonic regions: "average" horizontal component

    Science.gov (United States)

    Rezaeian, Sanaz; Bozorgnia, Yousef; Idriss, I.M.; Abrahamson, Norman; Campbell, Kenneth; Silva, Walter

    2014-01-01

    Ground motion prediction equations (GMPEs) for elastic response spectra are typically developed at a 5% viscous damping ratio. In reality, however, structural and nonstructural systems can have other damping ratios. This paper develops a new model for a damping scaling factor (DSF) that can be used to adjust the 5% damped spectral ordinates predicted by a GMPE for damping ratios between 0.5% to 30%. The model is developed based on empirical data from worldwide shallow crustal earthquakes in active tectonic regions. Dependencies of the DSF on potential predictor variables, such as the damping ratio, spectral period, ground motion duration, moment magnitude, source-to-site distance, and site conditions, are examined. The strong influence of duration is captured by the inclusion of both magnitude and distance in the DSF model. Site conditions show weak influence on the DSF. The proposed damping scaling model provides functional forms for the median and logarithmic standard deviation of DSF, and is developed for both RotD50 and GMRotI50 horizontal components. A follow-up paper develops a DSF model for vertical ground motion.

  6. Time scale algorithm: Definition of ensemble time and possible uses of the Kalman filter

    Science.gov (United States)

    Tavella, Patrizia; Thomas, Claudine

    1990-01-01

    The comparative study of two time scale algorithms, devised to satisfy different but related requirements, is presented. They are ALGOS(BIPM), producing the international reference TAI at the Bureau International des Poids et Mesures, and AT1(NIST), generating the real-time time scale AT1 at the National Institute of Standards and Technology. In each case, the time scale is a weighted average of clock readings, but the weight determination and the frequency prediction are different because they are adapted to different purposes. The possibility of using a mathematical tool, such as the Kalman filter, together with the definition of the time scale as a weighted average, is also analyzed. Results obtained by simulation are presented.

  7. 47 CFR 80.759 - Average terrain elevation.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Average terrain elevation. 80.759 Section 80.759 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES STATIONS IN THE MARITIME SERVICES Standards for Computing Public Coast Station VHF Coverage § 80.759 Average terrain elevation. (a)(1) Draw radials...

  8. HIGH AVERAGE POWER OPTICAL FEL AMPLIFIERS

    International Nuclear Information System (INIS)

    2005-01-01

    Historically, the first demonstration of the optical FEL was in an amplifier configuration at Stanford University [l]. There were other notable instances of amplifying a seed laser, such as the LLNL PALADIN amplifier [2] and the BNL ATF High-Gain Harmonic Generation FEL [3]. However, for the most part FELs are operated as oscillators or self amplified spontaneous emission devices. Yet, in wavelength regimes where a conventional laser seed can be used, the FEL can be used as an amplifier. One promising application is for very high average power generation, for instance FEL's with average power of 100 kW or more. The high electron beam power, high brightness and high efficiency that can be achieved with photoinjectors and superconducting Energy Recovery Linacs (ERL) combine well with the high-gain FEL amplifier to produce unprecedented average power FELs. This combination has a number of advantages. In particular, we show that for a given FEL power, an FEL amplifier can introduce lower energy spread in the beam as compared to a traditional oscillator. This properly gives the ERL based FEL amplifier a great wall-plug to optical power efficiency advantage. The optics for an amplifier is simple and compact. In addition to the general features of the high average power FEL amplifier, we will look at a 100 kW class FEL amplifier is being designed to operate on the 0.5 ampere Energy Recovery Linac which is under construction at Brookhaven National Laboratory's Collider-Accelerator Department

  9. Evaluation of scaling invariance embedded in short time series.

    Directory of Open Access Journals (Sweden)

    Xue Pan

    Full Text Available Scaling invariance of time series has been making great contributions in diverse research fields. But how to evaluate scaling exponent from a real-world series is still an open problem. Finite length of time series may induce unacceptable fluctuation and bias to statistical quantities and consequent invalidation of currently used standard methods. In this paper a new concept called correlation-dependent balanced estimation of diffusion entropy is developed to evaluate scale-invariance in very short time series with length ~10(2. Calculations with specified Hurst exponent values of 0.2,0.3,...,0.9 show that by using the standard central moving average de-trending procedure this method can evaluate the scaling exponents for short time series with ignorable bias (≤0.03 and sharp confidential interval (standard deviation ≤0.05. Considering the stride series from ten volunteers along an approximate oval path of a specified length, we observe that though the averages and deviations of scaling exponents are close, their evolutionary behaviors display rich patterns. It has potential use in analyzing physiological signals, detecting early warning signals, and so on. As an emphasis, the our core contribution is that by means of the proposed method one can estimate precisely shannon entropy from limited records.

  10. Evaluation of scaling invariance embedded in short time series.

    Science.gov (United States)

    Pan, Xue; Hou, Lei; Stephen, Mutua; Yang, Huijie; Zhu, Chenping

    2014-01-01

    Scaling invariance of time series has been making great contributions in diverse research fields. But how to evaluate scaling exponent from a real-world series is still an open problem. Finite length of time series may induce unacceptable fluctuation and bias to statistical quantities and consequent invalidation of currently used standard methods. In this paper a new concept called correlation-dependent balanced estimation of diffusion entropy is developed to evaluate scale-invariance in very short time series with length ~10(2). Calculations with specified Hurst exponent values of 0.2,0.3,...,0.9 show that by using the standard central moving average de-trending procedure this method can evaluate the scaling exponents for short time series with ignorable bias (≤0.03) and sharp confidential interval (standard deviation ≤0.05). Considering the stride series from ten volunteers along an approximate oval path of a specified length, we observe that though the averages and deviations of scaling exponents are close, their evolutionary behaviors display rich patterns. It has potential use in analyzing physiological signals, detecting early warning signals, and so on. As an emphasis, the our core contribution is that by means of the proposed method one can estimate precisely shannon entropy from limited records.

  11. Grassmann Averages for Scalable Robust PCA

    DEFF Research Database (Denmark)

    Hauberg, Søren; Feragen, Aasa; Black, Michael J.

    2014-01-01

    As the collection of large datasets becomes increasingly automated, the occurrence of outliers will increase—“big data” implies “big outliers”. While principal component analysis (PCA) is often used to reduce the size of data, and scalable solutions exist, it is well-known that outliers can...... to vectors (subspaces) or elements of vectors; we focus on the latter and use a trimmed average. The resulting Trimmed Grassmann Average (TGA) is particularly appropriate for computer vision because it is robust to pixel outliers. The algorithm has low computational complexity and minimal memory requirements...

  12. Empirical scaling for present Ohmically heated tokamaks

    International Nuclear Information System (INIS)

    Daughney, C.

    1975-01-01

    Experimental results from the Adiabatic Toroidal Compressor (ATC) tokamak are used to obtain empirical scaling laws for the average electron temperature and electron energy confinement time as functions of the average electron density, the effective ion charge, and the plasma current. These scaling laws are extended to include dependence upon minor and major plasma radius and toroidal field strength through a comparison of the various tokamaks described in the literature. Electron thermal conductivity is the dominant loss process for the ATC tokamak. The parametric dependences of the observed electron thermal conductivity are not explained by present theoretical considerations. The electron temperature obtained with Ohmic heating is shown to be a function of current density - which will not be increased in the next generation of large tokamaks. However, the temperature dependence of the electron energy confinement time suggests that significant improvement in confinement time will be obtained with supplementary electron heating. (author)

  13. Scale Dependence of Spatiotemporal Intermittence of Rain

    Science.gov (United States)

    Kundu, Prasun K.; Siddani, Ravi K.

    2011-01-01

    It is a common experience that rainfall is intermittent in space and time. This is reflected by the fact that the statistics of area- and/or time-averaged rain rate is described by a mixed distribution with a nonzero probability of having a sharp value zero. In this paper we have explored the dependence of the probability of zero rain on the averaging space and time scales in large multiyear data sets based on radar and rain gauge observations. A stretched exponential fannula fits the observed scale dependence of the zero-rain probability. The proposed formula makes it apparent that the space-time support of the rain field is not quite a set of measure zero as is sometimes supposed. We also give an ex.planation of the observed behavior in tenus of a simple probabilistic model based on the premise that rainfall process has an intrinsic memory.

  14. Individualized adjustments to reference phantom internal organ dosimetry—scaling factors given knowledge of patient external anatomy

    Science.gov (United States)

    Wayson, Michael B.; Bolch, Wesley E.

    2018-04-01

    Internal radiation dose estimates for diagnostic nuclear medicine procedures are typically calculated for a reference individual. Resultantly, there is uncertainty when determining the organ doses to patients who are not at 50th percentile on either height or weight. This study aims to better personalize internal radiation dose estimates for individual patients by modifying the dose estimates calculated for reference individuals based on easily obtainable morphometric characteristics of the patient. Phantoms of different sitting heights and waist circumferences were constructed based on computational reference phantoms for the newborn, 10 year-old, and adult. Monoenergetic photons and electrons were then simulated separately at 15 energies. Photon and electron specific absorbed fractions (SAFs) were computed for the newly constructed non-reference phantoms and compared to SAFs previously generated for the age-matched reference phantoms. Differences in SAFs were correlated to changes in sitting height and waist circumference to develop scaling factors that could be applied to reference SAFs as morphometry corrections. A further set of arbitrary non-reference phantoms were then constructed and used in validation studies for the SAF scaling factors. Both photon and electron dose scaling methods were found to increase average accuracy when sitting height was used as the scaling parameter (~11%). Photon waist circumference-based scaling factors showed modest increases in average accuracy (~7%) for underweight individuals, but not for overweight individuals. Electron waist circumference-based scaling factors did not show increases in average accuracy. When sitting height and waist circumference scaling factors were combined, modest average gains in accuracy were observed for photons (~6%), but not for electrons. Both photon and electron absorbed doses are more reliably scaled using scaling factors computed in this study. They can be effectively scaled using sitting

  15. Individualized adjustments to reference phantom internal organ dosimetry-scaling factors given knowledge of patient external anatomy.

    Science.gov (United States)

    Wayson, Michael B; Bolch, Wesley E

    2018-04-13

    Internal radiation dose estimates for diagnostic nuclear medicine procedures are typically calculated for a reference individual. Resultantly, there is uncertainty when determining the organ doses to patients who are not at 50th percentile on either height or weight. This study aims to better personalize internal radiation dose estimates for individual patients by modifying the dose estimates calculated for reference individuals based on easily obtainable morphometric characteristics of the patient. Phantoms of different sitting heights and waist circumferences were constructed based on computational reference phantoms for the newborn, 10 year-old, and adult. Monoenergetic photons and electrons were then simulated separately at 15 energies. Photon and electron specific absorbed fractions (SAFs) were computed for the newly constructed non-reference phantoms and compared to SAFs previously generated for the age-matched reference phantoms. Differences in SAFs were correlated to changes in sitting height and waist circumference to develop scaling factors that could be applied to reference SAFs as morphometry corrections. A further set of arbitrary non-reference phantoms were then constructed and used in validation studies for the SAF scaling factors. Both photon and electron dose scaling methods were found to increase average accuracy when sitting height was used as the scaling parameter (~11%). Photon waist circumference-based scaling factors showed modest increases in average accuracy (~7%) for underweight individuals, but not for overweight individuals. Electron waist circumference-based scaling factors did not show increases in average accuracy. When sitting height and waist circumference scaling factors were combined, modest average gains in accuracy were observed for photons (~6%), but not for electrons. Both photon and electron absorbed doses are more reliably scaled using scaling factors computed in this study. They can be effectively scaled using sitting

  16. An axially averaged-radial transport model of tokamak edge plasmas

    International Nuclear Information System (INIS)

    Prinja, A.K.; Conn, R.W.

    1984-01-01

    A two-zone axially averaged-radial transport model for edge plasmas is described that incorporates parallel electron and ion conduction, localized recycling, parallel electron pressure gradient effects and sheath losses. Results for high recycling show that the radial electron temperature profile is determined by parallel electron conduction over short radial distances (proportional 3 cm). At larger radius where Tsub(e) has fallen appreciably, convective transport becomes equally important. The downstream density and ion temperature profiles are very flat over the region where electron conduction dominates. This is seen to result from a sharply decaying velocity profile that follows the radial electron temperature. A one-dimensional analytical recycling model shows that at high neutral pumping rates, the plasma density at the plate, nsub(ia), scales linearly with the unperturbed background density, nsub(io). When ionization dominates nsub(ia)/nsub(io) proportional exp(nsub(io)) while in the intermediate regime nsub(ia)/nsub(io) proportional exp(proportional nsub(io)). Such behavior is qualitatively in accord with experimental observations. (orig.)

  17. 40 CFR 80.205 - How is the annual refinery or importer average and corporate pool average sulfur level determined?

    Science.gov (United States)

    2010-07-01

    ... volume of gasoline produced or imported in batch i. Si=The sulfur content of batch i determined under § 80.330. n=The number of batches of gasoline produced or imported during the averaging period. i=Individual batch of gasoline produced or imported during the averaging period. (b) All annual refinery or...

  18. JAERI femtosecond pulsed and tens-kilowatts average-powered free-electron lasers and their applications of large-scaled non-thermal manufacturing in nuclear energy industry

    International Nuclear Information System (INIS)

    Minehara, Eisuke J.

    2004-01-01

    We first reported the novel method that femto-second (fs) lasers of the low average power Ti: Sapphire one, the JAERI high average power free-electron laser, excimer laser, fiber laser and so on could peel off and remove both stress corrosion cracking (SCC) origins of the cold-worked (CW) and very crack-susceptible material, and residual tensile stress in the hardened surface of low-carbon stainless steel cubic samples for nuclear reactor internals as a proof of principle experiment except for the last and third origin of corrosive environment. Because it has been successfully demonstrated that the fs lasers could clearly remove the two SCC origins, we could resultantly prevent the cold-worked SCC in many field near future. The SCC is a well known phenomenon in modern material sciences, technologies, and industries, and defined as an insidious failure mechanism that is caused by the corrosive environment, and the crack-susceptible material and the surface residual tensile stress simultaneously. There are a large number of famous SCC examples for damaging stainless steels, aluminum alloys, brass and other alloy metals in many different cases. In many boiling light-water reactor (BWR) nuclear power plants and a few pressurized light water reactor (PWR) ones in Japan and the world up to now, a large number of the deep and wide cracks have been recently found in the reactor-grade low-carbon stainless steel components of core shroud, control-blade handle, re-circulating pipes, sheath and other internals in the reactor vessel under very low or no applied stresses. These cracks have been thought to be initiated from the crack-susceptible like very small-sized cracks, pinholes, concentrated dislocation defects and so on in the hardened surface, which were originated from cold-work machining processes in reactor manufacturing factories, and to be insidiously penetrated widely into the deep inside under the residual tensile stress and corrosive environment, and under no

  19. Sensitivity of point scale surface runoff predictions to rainfall resolution

    Directory of Open Access Journals (Sweden)

    A. J. Hearman

    2007-01-01

    Full Text Available This paper investigates the effects of using non-linear, high resolution rainfall, compared to time averaged rainfall on the triggering of hydrologic thresholds and therefore model predictions of infiltration excess and saturation excess runoff at the point scale. The bounded random cascade model, parameterized to three locations in Western Australia, was used to scale rainfall intensities at various time resolutions ranging from 1.875 min to 2 h. A one dimensional, conceptual rainfall partitioning model was used that instantaneously partitioned water into infiltration excess, infiltration, storage, deep drainage, saturation excess and surface runoff, where the fluxes into and out of the soil store were controlled by thresholds. The results of the numerical modelling were scaled by relating soil infiltration properties to soil draining properties, and in turn, relating these to average storm intensities. For all soil types, we related maximum infiltration capacities to average storm intensities (k* and were able to show where model predictions of infiltration excess were most sensitive to rainfall resolution (ln k*=0.4 and where using time averaged rainfall data can lead to an under prediction of infiltration excess and an over prediction of the amount of water entering the soil (ln k*>2 for all three rainfall locations tested. For soils susceptible to both infiltration excess and saturation excess, total runoff sensitivity was scaled by relating drainage coefficients to average storm intensities (g* and parameter ranges where predicted runoff was dominated by infiltration excess or saturation excess depending on the resolution of rainfall data were determined (ln g*<2. Infiltration excess predicted from high resolution rainfall was short and intense, whereas saturation excess produced from low resolution rainfall was more constant and less intense. This has important implications for the accuracy of current hydrological models that use time

  20. Average-case analysis of numerical problems

    CERN Document Server

    2000-01-01

    The average-case analysis of numerical problems is the counterpart of the more traditional worst-case approach. The analysis of average error and cost leads to new insight on numerical problems as well as to new algorithms. The book provides a survey of results that were mainly obtained during the last 10 years and also contains new results. The problems under consideration include approximation/optimal recovery and numerical integration of univariate and multivariate functions as well as zero-finding and global optimization. Background material, e.g. on reproducing kernel Hilbert spaces and random fields, is provided.

  1. Post-model selection inference and model averaging

    Directory of Open Access Journals (Sweden)

    Georges Nguefack-Tsague

    2011-07-01

    Full Text Available Although model selection is routinely used in practice nowadays, little is known about its precise effects on any subsequent inference that is carried out. The same goes for the effects induced by the closely related technique of model averaging. This paper is concerned with the use of the same data first to select a model and then to carry out inference, in particular point estimation and point prediction. The properties of the resulting estimator, called a post-model-selection estimator (PMSE, are hard to derive. Using selection criteria such as hypothesis testing, AIC, BIC, HQ and Cp, we illustrate that, in terms of risk function, no single PMSE dominates the others. The same conclusion holds more generally for any penalised likelihood information criterion. We also compare various model averaging schemes and show that no single one dominates the others in terms of risk function. Since PMSEs can be regarded as a special case of model averaging, with 0-1 random-weights, we propose a connection between the two theories, in the frequentist approach, by taking account of the selection procedure when performing model averaging. We illustrate the point by simulating a simple linear regression model.

  2. Large Deviations for Two-Time-Scale Diffusions, with Delays

    International Nuclear Information System (INIS)

    Kushner, Harold J.

    2010-01-01

    We consider the problem of large deviations for a two-time-scale reflected diffusion process, possibly with delays in the dynamical terms. The Dupuis-Ellis weak convergence approach is used. It is perhaps the most intuitive and simplest for the problems of concern. The results have applications to the problem of approximating optimal controls for two-time-scale systems via use of the averaged equation.

  3. Average L-shell fluorescence, Auger, and electron yields

    International Nuclear Information System (INIS)

    Krause, M.O.

    1980-01-01

    The dependence of the average L-shell fluorescence and Auger yields on the initial vacancy distribution is shown to be small. By contrast, the average electron yield pertaining to both Auger and Coster-Kronig transitions is shown to display a strong dependence. Numerical examples are given on the basis of Krause's evaluation of subshell radiative and radiationless yields. Average yields are calculated for widely differing vacancy distributions and are intercompared graphically for 40 3 subshell yields in most cases of inner-shell ionization

  4. Bayesian Averaging is Well-Temperated

    DEFF Research Database (Denmark)

    Hansen, Lars Kai

    2000-01-01

    Bayesian predictions are stochastic just like predictions of any other inference scheme that generalize from a finite sample. While a simple variational argument shows that Bayes averaging is generalization optimal given that the prior matches the teacher parameter distribution the situation is l...

  5. Emergence of scale-free characteristics in socio-ecological systems with bounded rationality.

    Science.gov (United States)

    Kasthurirathna, Dharshana; Piraveenan, Mahendra

    2015-06-11

    Socio-ecological systems are increasingly modelled by games played on complex networks. While the concept of Nash equilibrium assumes perfect rationality, in reality players display heterogeneous bounded rationality. Here we present a topological model of bounded rationality in socio-ecological systems, using the rationality parameter of the Quantal Response Equilibrium. We argue that system rationality could be measured by the average Kullback--Leibler divergence between Nash and Quantal Response Equilibria, and that the convergence towards Nash equilibria on average corresponds to increased system rationality. Using this model, we show that when a randomly connected socio-ecological system is topologically optimised to converge towards Nash equilibria, scale-free and small world features emerge. Therefore, optimising system rationality is an evolutionary reason for the emergence of scale-free and small-world features in socio-ecological systems. Further, we show that in games where multiple equilibria are possible, the correlation between the scale-freeness of the system and the fraction of links with multiple equilibria goes through a rapid transition when the average system rationality increases. Our results explain the influence of the topological structure of socio-ecological systems in shaping their collective cognitive behaviour, and provide an explanation for the prevalence of scale-free and small-world characteristics in such systems.

  6. Relationship between affect and achievement in science and mathematics in Malaysia and Singapore

    Science.gov (United States)

    Thoe Ng, Khar; Fah Lay, Yoon; Areepattamannil, Shaljan; Treagust, David F.; Chandrasegaran, A. L.

    2012-11-01

    Background : The Trends in International Mathematics and Science Study (TIMSS) assesses the quality of the teaching and learning of science and mathematics among Grades 4 and 8 students across participating countries. Purpose : This study explored the relationship between positive affect towards science and mathematics and achievement in science and mathematics among Malaysian and Singaporean Grade 8 students. Sample : In total, 4466 Malaysia students and 4599 Singaporean students from Grade 8 who participated in TIMSS 2007 were involved in this study. Design and method : Students' achievement scores on eight items in the survey instrument that were reported in TIMSS 2007 were used as the dependent variable in the analysis. Students' scores on four items in the TIMSS 2007 survey instrument pertaining to students' affect towards science and mathematics together with students' gender, language spoken at home and parental education were used as the independent variables. Results : Positive affect towards science and mathematics indicated statistically significant predictive effects on achievement in the two subjects for both Malaysian and Singaporean Grade 8 students. There were statistically significant predictive effects on mathematics achievement for the students' gender, language spoken at home and parental education for both Malaysian and Singaporean students, with R 2 = 0.18 and 0.21, respectively. However, only parental education showed statistically significant predictive effects on science achievement for both countries. For Singapore, language spoken at home also demonstrated statistically significant predictive effects on science achievement, whereas gender did not. For Malaysia, neither gender nor language spoken at home had statistically significant predictive effects on science achievement. Conclusions : It is important for educators to consider implementing self-concept enhancement intervention programmes by incorporating 'affect' components of academic

  7. Simultaneous inference for model averaging of derived parameters

    DEFF Research Database (Denmark)

    Jensen, Signe Marie; Ritz, Christian

    2015-01-01

    Model averaging is a useful approach for capturing uncertainty due to model selection. Currently, this uncertainty is often quantified by means of approximations that do not easily extend to simultaneous inference. Moreover, in practice there is a need for both model averaging and simultaneous...... inference for derived parameters calculated in an after-fitting step. We propose a method for obtaining asymptotically correct standard errors for one or several model-averaged estimates of derived parameters and for obtaining simultaneous confidence intervals that asymptotically control the family...

  8. Analytical expressions for conditional averages: A numerical test

    DEFF Research Database (Denmark)

    Pécseli, H.L.; Trulsen, J.

    1991-01-01

    Conditionally averaged random potential fluctuations are an important quantity for analyzing turbulent electrostatic plasma fluctuations. Experimentally, this averaging can be readily performed by sampling the fluctuations only when a certain condition is fulfilled at a reference position...

  9. Nonequilibrium statistical averages and thermo field dynamics

    International Nuclear Information System (INIS)

    Marinaro, A.; Scarpetta, Q.

    1984-01-01

    An extension of thermo field dynamics is proposed, which permits the computation of nonequilibrium statistical averages. The Brownian motion of a quantum oscillator is treated as an example. In conclusion it is pointed out that the procedure proposed to computation of time-dependent statistical average gives the correct two-point Green function for the damped oscillator. A simple extension can be used to compute two-point Green functions of free particles

  10. Laboratory studies of 2H evaporator scale dissolution in dilute nitric acid

    International Nuclear Information System (INIS)

    Oji, L.

    2014-01-01

    The rate of 2H evaporator scale solids dissolution in dilute nitric acid has been experimentally evaluated under laboratory conditions in the SRNL shielded cells. The 2H scale sample used for the dissolution study came from the bottom of the evaporator cone section and the wall section of the evaporator cone. The accumulation rate of aluminum and silicon, assumed to be the two principal elemental constituents of the 2H evaporator scale aluminosilicate mineral, were monitored in solution. Aluminum and silicon concentration changes, with heating time at a constant oven temperature of 90 deg C, were used to ascertain the extent of dissolution of the 2H evaporator scale mineral. The 2H evaporator scale solids, assumed to be composed of mostly aluminosilicate mineral, readily dissolves in 1.5 and 1.25 M dilute nitric acid solutions yielding principal elemental components of aluminum and silicon in solution. The 2H scale dissolution rate constant, based on aluminum accumulation in 1.5 and 1.25 M dilute nitric acid solution are, respectively, 9.21E-04 ± 6.39E-04 min -1 and 1.07E-03 ± 7.51E-05 min -1 . Silicon accumulation rate in solution does track the aluminum accumulation profile during the first few minutes of scale dissolution. It however diverges towards the end of the scale dissolution. This divergence therefore means the aluminum-to-silicon ratio in the first phase of the scale dissolution (non-steady state conditions) is different from the ratio towards the end of the scale dissolution. Possible causes of this change in silicon accumulation in solution as the scale dissolution progresses may include silicon precipitation from solution or the 2H evaporator scale is a heterogeneous mixture of aluminosilicate minerals with several impurities. The average half-life for the decomposition of the 2H evaporator scale mineral in 1.5 M nitric acid is 12.5 hours, while the half-life for the decomposition of the 2H evaporator scale in 1.25 M nitric acid is 10.8 hours

  11. A Multiphysics Framework to Learn and Predict in Presence of Multiple Scales

    Science.gov (United States)

    Tomin, P.; Lunati, I.

    2015-12-01

    Modeling complex phenomena in the subsurface remains challenging due to the presence of multiple interacting scales, which can make it impossible to focus on purely macroscopic phenomena (relevant in most applications) and neglect the processes at the micro-scale. We present and discuss a general framework that allows us to deal with the situation in which the lack of scale separation requires the combined use of different descriptions at different scale (for instance, a pore-scale description at the micro-scale and a Darcy-like description at the macro-scale) [1,2]. The method is based on conservation principles and constructs the macro-scale problem by numerical averaging of micro-scale balance equations. By employing spatiotemporal adaptive strategies, this approach can efficiently solve large-scale problems [2,3]. In addition, being based on a numerical volume-averaging paradigm, it offers a tool to illuminate how macroscopic equations emerge from microscopic processes, to better understand the meaning of microscopic quantities, and to investigate the validity of the assumptions routinely used to construct the macro-scale problems. [1] Tomin, P., and I. Lunati, A Hybrid Multiscale Method for Two-Phase Flow in Porous Media, Journal of Computational Physics, 250, 293-307, 2013 [2] Tomin, P., and I. Lunati, Local-global splitting and spatiotemporal-adaptive Multiscale Finite Volume Method, Journal of Computational Physics, 280, 214-231, 2015 [3] Tomin, P., and I. Lunati, Spatiotemporal adaptive multiphysics simulations of drainage-imbibition cycles, Computational Geosciences, 2015 (under review)

  12. Safety Impact of Average Speed Control in the UK

    DEFF Research Database (Denmark)

    Lahrmann, Harry Spaabæk; Brassøe, Bo; Johansen, Jonas Wibert

    2016-01-01

    of automatic speed control was point-based, but in recent years a potentially more effective alternative automatic speed control method has been introduced. This method is based upon records of drivers’ average travel speed over selected sections of the road and is normally called average speed control...... in the UK. The study demonstrates that the introduction of average speed control results in statistically significant and substantial reductions both in speed and in number of accidents. The evaluation indicates that average speed control has a higher safety effect than point-based automatic speed control....

  13. Origin of Noncubic Scaling Law in Disordered Granular Packing

    Energy Technology Data Exchange (ETDEWEB)

    Xia, Chengjie; Li, Jindong; Kou, Binquan; Cao, Yixin; Li, Zhifeng; Xiao, Xianghui; Fu, Yanan; Xiao, Tiqiao; Hong, Liang; Zhang, Jie; Kob, Walter; Wang, Yujie

    2017-06-01

    Recent diffraction experiments on metallic glasses have unveiled an unexpected non-cubic scaling law between density and average interatomic distance, which lead to the speculations on the presence of fractal glass order. Using X-ray tomography we identify here a similar non-cubic scaling law in disordered granular packing of spherical particles. We find that the scaling law is directly related to the contact neighbors within first nearest neighbor shell, and therefore is closely connected to the phenomenon of jamming. The seemingly universal scaling exponent around 2.5 arises due to the isostatic condition with contact number around 6, and we argue that the exponent should not be universal.

  14. Insights into Tikhonov regularization: application to trace gas column retrieval and the efficient calculation of total column averaging kernels

    Directory of Open Access Journals (Sweden)

    T. Borsdorff

    2014-02-01

    Full Text Available Insights are given into Tikhonov regularization and its application to the retrieval of vertical column densities of atmospheric trace gases from remote sensing measurements. The study builds upon the equivalence of the least-squares profile-scaling approach and Tikhonov regularization method of the first kind with an infinite regularization strength. Here, the vertical profile is expressed relative to a reference profile. On the basis of this, we propose a new algorithm as an extension of the least-squares profile scaling which permits the calculation of total column averaging kernels on arbitrary vertical grids using an analytic expression. Moreover, we discuss the effective null space of the retrieval, which comprises those parts of a vertical trace gas distribution which cannot be inferred from the measurements. Numerically the algorithm can be implemented in a robust and efficient manner. In particular for operational data processing with challenging demands on processing time, the proposed inversion method in combination with highly efficient forward models is an asset. For demonstration purposes, we apply the algorithm to CO column retrieval from simulated measurements in the 2.3 μm spectral region and to O3 column retrieval from the UV. These represent ideal measurements of a series of spaceborne spectrometers such as SCIAMACHY, TROPOMI, GOME, and GOME-2. For both spectral ranges, we consider clear-sky and cloudy scenes where clouds are modelled as an elevated Lambertian surface. Here, the smoothing error for the clear-sky and cloudy atmosphere is significant and reaches several percent, depending on the reference profile which is used for scaling. This underlines the importance of the column averaging kernel for a proper interpretation of retrieved column densities. Furthermore, we show that the smoothing due to regularization can be underestimated by calculating the column averaging kernel on a too coarse vertical grid. For both

  15. Bounds on Average Time Complexity of Decision Trees

    KAUST Repository

    Chikalov, Igor

    2011-01-01

    In this chapter, bounds on the average depth and the average weighted depth of decision trees are considered. Similar problems are studied in search theory [1], coding theory [77], design and analysis of algorithms (e.g., sorting) [38]. For any

  16. An average salary: approaches to the index determination

    Directory of Open Access Journals (Sweden)

    T. M. Pozdnyakova

    2017-01-01

    Full Text Available The article “An average salary: approaches to the index determination” is devoted to studying various methods of calculating this index, both used by official state statistics of the Russian Federation and offered by modern researchers.The purpose of this research is to analyze the existing approaches to calculating the average salary of employees of enterprises and organizations, as well as to make certain additions that would help to clarify this index.The information base of the research is laws and regulations of the Russian Federation Government, statistical and analytical materials of the Federal State Statistics Service of Russia for the section «Socio-economic indexes: living standards of the population», as well as materials of scientific papers, describing different approaches to the average salary calculation. The data on the average salary of employees of educational institutions of the Khabarovsk region served as the experimental base of research. In the process of conducting the research, the following methods were used: analytical, statistical, calculated-mathematical and graphical.The main result of the research is an option of supplementing the method of calculating average salary index within enterprises or organizations, used by Goskomstat of Russia, by means of introducing a correction factor. Its essence consists in the specific formation of material indexes for different categories of employees in enterprises or organizations, mainly engaged in internal secondary jobs. The need for introducing this correction factor comes from the current reality of working conditions of a wide range of organizations, when an employee is forced, in addition to the main position, to fulfill additional job duties. As a result, the situation is frequent when the average salary at the enterprise is difficult to assess objectively because it consists of calculating multiple rates per staff member. In other words, the average salary of

  17. 7 CFR 1437.11 - Average market price and payment factors.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 10 2010-01-01 2010-01-01 false Average market price and payment factors. 1437.11... ASSISTANCE PROGRAM General Provisions § 1437.11 Average market price and payment factors. (a) An average... average market price by the applicable payment factor (i.e., harvested, unharvested, or prevented planting...

  18. Anomalous behavior of q-averages in nonextensive statistical mechanics

    International Nuclear Information System (INIS)

    Abe, Sumiyoshi

    2009-01-01

    A generalized definition of average, termed the q-average, is widely employed in the field of nonextensive statistical mechanics. Recently, it has however been pointed out that such an average value may behave unphysically under specific deformations of probability distributions. Here, the following three issues are discussed and clarified. Firstly, the deformations considered are physical and may be realized experimentally. Secondly, in view of the thermostatistics, the q-average is unstable in both finite and infinite discrete systems. Thirdly, a naive generalization of the discussion to continuous systems misses a point, and a norm better than the L 1 -norm should be employed for measuring the distance between two probability distributions. Consequently, stability of the q-average is shown not to be established in all of the cases

  19. Books average previous decade of economic misery.

    Science.gov (United States)

    Bentley, R Alexander; Acerbi, Alberto; Ormerod, Paul; Lampos, Vasileios

    2014-01-01

    For the 20(th) century since the Depression, we find a strong correlation between a 'literary misery index' derived from English language books and a moving average of the previous decade of the annual U.S. economic misery index, which is the sum of inflation and unemployment rates. We find a peak in the goodness of fit at 11 years for the moving average. The fit between the two misery indices holds when using different techniques to measure the literary misery index, and this fit is significantly better than other possible correlations with different emotion indices. To check the robustness of the results, we also analysed books written in German language and obtained very similar correlations with the German economic misery index. The results suggest that millions of books published every year average the authors' shared economic experiences over the past decade.

  20. Asynchronous Gossip for Averaging and Spectral Ranking

    Science.gov (United States)

    Borkar, Vivek S.; Makhijani, Rahul; Sundaresan, Rajesh

    2014-08-01

    We consider two variants of the classical gossip algorithm. The first variant is a version of asynchronous stochastic approximation. We highlight a fundamental difficulty associated with the classical asynchronous gossip scheme, viz., that it may not converge to a desired average, and suggest an alternative scheme based on reinforcement learning that has guaranteed convergence to the desired average. We then discuss a potential application to a wireless network setting with simultaneous link activation constraints. The second variant is a gossip algorithm for distributed computation of the Perron-Frobenius eigenvector of a nonnegative matrix. While the first variant draws upon a reinforcement learning algorithm for an average cost controlled Markov decision problem, the second variant draws upon a reinforcement learning algorithm for risk-sensitive control. We then discuss potential applications of the second variant to ranking schemes, reputation networks, and principal component analysis.

  1. Benchmarking statistical averaging of spectra with HULLAC

    Science.gov (United States)

    Klapisch, Marcel; Busquet, Michel

    2008-11-01

    Knowledge of radiative properties of hot plasmas is important for ICF, astrophysics, etc When mid-Z or high-Z elements are present, the spectra are so complex that one commonly uses statistically averaged description of atomic systems [1]. In a recent experiment on Fe[2], performed under controlled conditions, high resolution transmission spectra were obtained. The new version of HULLAC [3] allows the use of the same model with different levels of details/averaging. We will take advantage of this feature to check the effect of averaging with comparison with experiment. [1] A Bar-Shalom, J Oreg, and M Klapisch, J. Quant. Spectros. Rad. Transf. 65, 43 (2000). [2] J. E. Bailey, G. A. Rochau, C. A. Iglesias et al., Phys. Rev. Lett. 99, 265002-4 (2007). [3]. M. Klapisch, M. Busquet, and A. Bar-Shalom, AIP Conference Proceedings 926, 206-15 (2007).

  2. An approximate analytical approach to resampling averages

    DEFF Research Database (Denmark)

    Malzahn, Dorthe; Opper, M.

    2004-01-01

    Using a novel reformulation, we develop a framework to compute approximate resampling data averages analytically. The method avoids multiple retraining of statistical models on the samples. Our approach uses a combination of the replica "trick" of statistical physics and the TAP approach for appr...... for approximate Bayesian inference. We demonstrate our approach on regression with Gaussian processes. A comparison with averages obtained by Monte-Carlo sampling shows that our method achieves good accuracy....

  3. High average power supercontinuum sources

    Indian Academy of Sciences (India)

    The physical mechanisms and basic experimental techniques for the creation of high average spectral power supercontinuum sources is briefly reviewed. We focus on the use of high-power ytterbium-doped fibre lasers as pump sources, and the use of highly nonlinear photonic crystal fibres as the nonlinear medium.

  4. Evolution of the Orszag-Tang vortex system in a compressible medium. I - Initial average subsonic flow

    Science.gov (United States)

    Dahlburg, R. B.; Picone, J. M.

    1989-01-01

    The results of fully compressible, Fourier collocation, numerical simulations of the Orszag-Tang vortex system are presented. The initial conditions for this system consist of a nonrandom, periodic field in which the magnetic and velocity field contain X points but differ in modal structure along one spatial direction. The velocity field is initially solenoidal, with the total initial pressure field consisting of the superposition of the appropriate incompressible pressure distribution upon a flat pressure field corresponding to the initial, average Mach number of the flow. In these numerical simulations, this initial Mach number is varied from 0.2-0.6. These values correspond to average plasma beta values ranging from 30.0 to 3.3, respectively. It is found that compressible effects develop within one or two Alfven transit times, as manifested in the spectra of compressible quantities such as the mass density and the nonsolenoidal flow field. These effects include (1) a retardation of growth of correlation between the magnetic field and the velocity field, (2) the emergence of compressible small-scale structure such as massive jets, and (3) bifurcation of eddies in the compressible flow field. Differences between the incompressible and compressible results tend to increase with increasing initial average Mach number.

  5. Eesti matemaatikaõpetajate tööstiil TIMSSi andmetel / Madis Lepik

    Index Scriptorium Estoniae

    Lepik, Madis

    2005-01-01

    Tutvustatakse 4-aastase tsükliga toimuva koolimatemaatika rahvusvahelise võrdlusuuringu TIMSS (Trends in International Mathematics and Science Style) tulemusi. Uuringu keskmes on eri riikide õpilaste matemaatikateadmised

  6. Average stress in a Stokes suspension of disks

    NARCIS (Netherlands)

    Prosperetti, Andrea

    2004-01-01

    The ensemble-average velocity and pressure in an unbounded quasi-random suspension of disks (or aligned cylinders) are calculated in terms of average multipoles allowing for the possibility of spatial nonuniformities in the system. An expression for the stress due to the suspended particles is

  7. Salecker-Wigner-Peres clock and average tunneling times

    International Nuclear Information System (INIS)

    Lunardi, Jose T.; Manzoni, Luiz A.; Nystrom, Andrew T.

    2011-01-01

    The quantum clock of Salecker-Wigner-Peres is used, by performing a post-selection of the final state, to obtain average transmission and reflection times associated to the scattering of localized wave packets by static potentials in one dimension. The behavior of these average times is studied for a Gaussian wave packet, centered around a tunneling wave number, incident on a rectangular barrier and, in particular, on a double delta barrier potential. The regime of opaque barriers is investigated and the results show that the average transmission time does not saturate, showing no evidence of the Hartman effect (or its generalized version).

  8. Average wind statistics for SRP area meteorological towers

    International Nuclear Information System (INIS)

    Laurinat, J.E.

    1987-01-01

    A quality assured set of average wind Statistics for the seven SRP area meteorological towers has been calculated for the five-year period 1982--1986 at the request of DOE/SR. A Similar set of statistics was previously compiled for the years 1975-- 1979. The updated wind statistics will replace the old statistics as the meteorological input for calculating atmospheric radionuclide doses from stack releases, and will be used in the annual environmental report. This report details the methods used to average the wind statistics and to screen out bad measurements and presents wind roses generated by the averaged statistics

  9. Control of underactuated driftless systems using higher-order averaging theory

    OpenAIRE

    Vela, Patricio A.; Burdick, Joel W.

    2003-01-01

    This paper applies a recently developed "generalized averaging theory" to construct stabilizing feedback control laws for underactuated driftless systems. These controls exponentialy stabilize in the average; the actual system may orbit around the average. Conditions for which the orbit collapses to the averaged trajectory are given. An example validates the theory, demonstrating its utility.

  10. Some scale-free networks could be robust under selective node attacks

    Science.gov (United States)

    Zheng, Bojin; Huang, Dan; Li, Deyi; Chen, Guisheng; Lan, Wenfei

    2011-04-01

    It is a mainstream idea that scale-free network would be fragile under the selective attacks. Internet is a typical scale-free network in the real world, but it never collapses under the selective attacks of computer viruses and hackers. This phenomenon is different from the deduction of the idea above because this idea assumes the same cost to delete an arbitrary node. Hence this paper discusses the behaviors of the scale-free network under the selective node attack with different cost. Through the experiments on five complex networks, we show that the scale-free network is possibly robust under the selective node attacks; furthermore, the more compact the network is, and the larger the average degree is, then the more robust the network is; with the same average degrees, the more compact the network is, the more robust the network is. This result would enrich the theory of the invulnerability of the network, and can be used to build robust social, technological and biological networks, and also has the potential to find the target of drugs.

  11. Applications of Analytical Self-Similar Solutions of Reynolds-Averaged Models for Instability-Induced Turbulent Mixing

    Science.gov (United States)

    Hartland, Tucker; Schilling, Oleg

    2017-11-01

    Analytical self-similar solutions to several families of single- and two-scale, eddy viscosity and Reynolds stress turbulence models are presented for Rayleigh-Taylor, Richtmyer-Meshkov, and Kelvin-Helmholtz instability-induced turbulent mixing. The use of algebraic relationships between model coefficients and physical observables (e.g., experimental growth rates) following from the self-similar solutions to calibrate a member of a given family of turbulence models is shown. It is demonstrated numerically that the algebraic relations accurately predict the value and variation of physical outputs of a Reynolds-averaged simulation in flow regimes that are consistent with the simplifying assumptions used to derive the solutions. The use of experimental and numerical simulation data on Reynolds stress anisotropy ratios to calibrate a Reynolds stress model is briefly illustrated. The implications of the analytical solutions for future Reynolds-averaged modeling of hydrodynamic instability-induced mixing are briefly discussed. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  12. NOAA Average Annual Salinity (3-Zone)

    Data.gov (United States)

    California Natural Resource Agency — The 3-Zone Average Annual Salinity Digital Geography is a digital spatial framework developed using geographic information system (GIS) technology. These salinity...

  13. Determinant of Household Business Scale of Moa Buffaloes at Moa Island Southwest Maluku Regency

    Science.gov (United States)

    Lainsamputty, J.; Roessali, W.; Santosa, S. I.; Eddy, B. T.

    2018-02-01

    The objective of this research was to analyze factors that affect the business scale of Moa buffaloes at Moa Island, Regency of Southwest Maluku. The research used a survey method with multistage random sampling. The location chosen was the District of Moa Lakor at Moa Island based on its largest buffalo population. Respondents were randomly drawn in a total of 120 respondents. The variables measured were years of experience in rearing animals, costs of production, farmer’s participation in group activities, animal housing systems, farmer’s income and farmer’s age. The statistical test used was the multiple linear regressions. The results showed that the mean of business scale in the area of high density of buffaloes population was 12.6 AU, in the moderate was 12.4 AU and in the low was 11.0 AU. The average of production cost was IDR 1.893.536.00/year, the average of revenue was IDR14.083.333.00/year, while the average of income was IDR 12.189.797.00/year. The independent variables simultaneously influence the business scale (Pbusiness scale (P<0.01).

  14. An approach to averaging digitized plantagram curves.

    Science.gov (United States)

    Hawes, M R; Heinemeyer, R; Sovak, D; Tory, B

    1994-07-01

    The averaging of outline shapes of the human foot for the purposes of determining information concerning foot shape and dimension within the context of comfort of fit of sport shoes is approached as a mathematical problem. An outline of the human footprint is obtained by standard procedures and the curvature is traced with a Hewlett Packard Digitizer. The paper describes the determination of an alignment axis, the identification of two ray centres and the division of the total curve into two overlapping arcs. Each arc is divided by equiangular rays which intersect chords between digitized points describing the arc. The radial distance of each ray is averaged within groups of foot lengths which vary by +/- 2.25 mm (approximately equal to 1/2 shoe size). The method has been used to determine average plantar curves in a study of 1197 North American males (Hawes and Sovak 1993).

  15. Books Average Previous Decade of Economic Misery

    Science.gov (United States)

    Bentley, R. Alexander; Acerbi, Alberto; Ormerod, Paul; Lampos, Vasileios

    2014-01-01

    For the 20th century since the Depression, we find a strong correlation between a ‘literary misery index’ derived from English language books and a moving average of the previous decade of the annual U.S. economic misery index, which is the sum of inflation and unemployment rates. We find a peak in the goodness of fit at 11 years for the moving average. The fit between the two misery indices holds when using different techniques to measure the literary misery index, and this fit is significantly better than other possible correlations with different emotion indices. To check the robustness of the results, we also analysed books written in German language and obtained very similar correlations with the German economic misery index. The results suggest that millions of books published every year average the authors' shared economic experiences over the past decade. PMID:24416159

  16. Evaluation of aesthetic abdominal surgery using a new clinical scale.

    Science.gov (United States)

    Salles, Alessandra Grassi; Ferreira, Marcus Castro; do Nascimento Remigio, Adelina Fatima; Gemperli, Rolf

    2012-02-01

    Evaluation of outcomes after aesthetic surgery still is a challenge in plastic surgery. The evaluation frequently is based on subjective criteria. This study used a new clinical grading scale to evaluate aesthetic results for plastic surgeries to the abdomen. The method scores each of the following five parameters: volume of subcutaneous tissue, contour, excess of skin, aspect of the navel, and quality of the scar on the abdominal wall. The scale options are 0 (poor), 1 (fair), and 2 (good), and the total rate can range from 0 to 10. The study included 40 women ages 18-53 years. Of these 40 women, 20 underwent traditional abdominoplasty, and 20 had liposuction alone. Preoperatively and at least 1 year later, photographic results were analyzed and scored by three independent plastic surgeons. In the abdominoplasty group, the average grade rose from 2.9±0.4 to 6.8±0.4 postoperatively. In the liposuction group, the average grade was 5.3±0.5 preoperatively and 7.7±0.4 postoperatively. In both groups, the average postoperative grade was significantly higher than the preoperative grade. The mean scores for groups A and L were significantly different, demonstrating that the scale was sensitive in identifying different anatomic abnormalities in the abdomen. The rating scale used for the aesthetic evaluation of the abdomen was effective in the analysis of two different procedures: conventional abdominoplasty and liposuction. Abdominoplasty provided the greater gain according to a comparison of the pre- and postoperative scores.

  17. A renormalization group scaling analysis for compressible two-phase flow

    International Nuclear Information System (INIS)

    Chen, Y.; Deng, Y.; Glimm, J.; Li, G.; Zhang, Q.; Sharp, D.H.

    1993-01-01

    Computational solutions to the Rayleigh--Taylor fluid mixing problem, as modeled by the two-fluid two-dimensional Euler equations, are presented. Data from these solutions are analyzed from the point of view of Reynolds averaged equations, using scaling laws derived from a renormalization group analysis. The computations, carried out with the front tracking method on an Intel iPSC/860, are highly resolved and statistical convergence of ensemble averages is achieved. The computations are consistent with the experimentally observed growth rates for nearly incompressible flows. The dynamics of the interior portion of the mixing zone is simplified by the use of scaling variables. The size of the mixing zone suggests fixed-point behavior. The profile of statistical quantities within the mixing zone exhibit self-similarity under fixed-point scaling to a limited degree. The effect of compressibility is also examined. It is found that, for even moderate compressibility, the growth rates fail to satisfy universal scaling, and moreover, increase significantly with increasing compressibility. The growth rates predicted from a renormalization group fixed-point model are in a reasonable agreement with the results of the exact numerical simulations, even for flows outside of the incompressible limit

  18. Model averaging, optimal inference and habit formation

    Directory of Open Access Journals (Sweden)

    Thomas H B FitzGerald

    2014-06-01

    Full Text Available Postulating that the brain performs approximate Bayesian inference generates principled and empirically testable models of neuronal function – the subject of much current interest in neuroscience and related disciplines. Current formulations address inference and learning under some assumed and particular model. In reality, organisms are often faced with an additional challenge – that of determining which model or models of their environment are the best for guiding behaviour. Bayesian model averaging – which says that an agent should weight the predictions of different models according to their evidence – provides a principled way to solve this problem. Importantly, because model evidence is determined by both the accuracy and complexity of the model, optimal inference requires that these be traded off against one another. This means an agent’s behaviour should show an equivalent balance. We hypothesise that Bayesian model averaging plays an important role in cognition, given that it is both optimal and realisable within a plausible neuronal architecture. We outline model averaging and how it might be implemented, and then explore a number of implications for brain and behaviour. In particular, we propose that model averaging can explain a number of apparently suboptimal phenomena within the framework of approximate (bounded Bayesian inference, focussing particularly upon the relationship between goal-directed and habitual behaviour.

  19. Bootstrapping pre-averaged realized volatility under market microstructure noise

    DEFF Research Database (Denmark)

    Hounyo, Ulrich; Goncalves, Sílvia; Meddahi, Nour

    The main contribution of this paper is to propose a bootstrap method for inference on integrated volatility based on the pre-averaging approach of Jacod et al. (2009), where the pre-averaging is done over all possible overlapping blocks of consecutive observations. The overlapping nature of the pre......-averaged returns implies that these are kn-dependent with kn growing slowly with the sample size n. This motivates the application of a blockwise bootstrap method. We show that the "blocks of blocks" bootstrap method suggested by Politis and Romano (1992) (and further studied by Bühlmann and Künsch (1995......)) is valid only when volatility is constant. The failure of the blocks of blocks bootstrap is due to the heterogeneity of the squared pre-averaged returns when volatility is stochastic. To preserve both the dependence and the heterogeneity of squared pre-averaged returns, we propose a novel procedure...

  20. Average niche breadths of species in lake macrophyte communities respond to ecological gradients variably in four regions on two continents.

    Science.gov (United States)

    Alahuhta, Janne; Virtala, Antti; Hjort, Jan; Ecke, Frauke; Johnson, Lucinda B; Sass, Laura; Heino, Jani

    2017-05-01

    Different species' niche breadths in relation to ecological gradients are infrequently examined within the same study and, moreover, species niche breadths have rarely been averaged to account for variation in entire ecological communities. We investigated how average environmental niche breadths (climate, water quality and climate-water quality niches) in aquatic macrophyte communities are related to ecological gradients (latitude, longitude, altitude, species richness and lake area) among four distinct regions (Finland, Sweden and US states of Minnesota and Wisconsin) on two continents. We found that correlations between the three different measures of average niche breadths and ecological gradients varied considerably among the study regions, with average climate and average water quality niche breadth models often showing opposite trends. However, consistent patterns were also found, such as widening of average climate niche breadths and narrowing of average water quality niche breadths of aquatic macrophytes along increasing latitudinal and altitudinal gradients. This result suggests that macrophyte species are generalists in relation to temperature variations at higher latitudes and altitudes, whereas species in southern, lowland lakes are more specialised. In contrast, aquatic macrophytes growing in more southern nutrient-rich lakes were generalists in relation to water quality, while specialist species are adapted to low-productivity conditions and are found in highland lakes. Our results emphasise that species niche breadths should not be studied using only coarse-scale data of species distributions and corresponding environmental conditions, but that investigations on different kinds of niche breadths (e.g., climate vs. local niches) also require finer resolution data at broad spatial extents.

  1. The Stanford Microsurgery and Resident Training (SMaRT) Scale: validation of an on-line global rating scale for technical assessment.

    Science.gov (United States)

    Satterwhite, Thomas; Son, Ji; Carey, Joseph; Echo, Anthony; Spurling, Terry; Paro, John; Gurtner, Geoffrey; Chang, James; Lee, Gordon K

    2014-05-01

    We previously reported results of our on-line microsurgery training program, showing that residents who had access to our website significantly improved their cognitive and technical skills. In this study, we report an objective means for expert evaluators to reliably rate trainees' technical skills under the microscope, with the use of our novel global rating scale. "Microsurgery Essentials" (http://smartmicrosurgery.com) is our on-line training curriculum. Residents were randomly divided into 2 groups: 1 group reviewed this online resource and the other did not. Pre- and post-tests consisted of videotaped microsurgical sessions in which the trainee performed "microsurgery" on 3 different models: latex glove, penrose drain, and the dorsal vessel of a chicken foot. The SMaRT (Stanford Microsurgery and Resident Training) scale, consisting of 9 categories graded on a 5-point Likert scale, was used to assess the trainees. Results were analyzed with ANOVA and Student t test, with P less than 0.05 indicating statistical significance. Seventeen residents participated in the study. The SMaRT scale adequately differentiated the performance of more experienced senior residents (PGY-4 to PGY-6, total average score=3.43) from less experienced junior residents (PGY-1 to PGY-3, total average score=2.10, P0.05). Additionally, junior residents who had access to our website showed a significant increase in their graded technical performance by 0.7 points when compared to residents who did not have access to the website who showed an improvement of only 0.2 points (P=0.01). Our SMaRT scale is valid and reliable in assessing the microsurgical skills of residents and other trainees. Current trainees are more likely to use self-directed on-line education because of its easy accessibility and interactive format. Our global rating scale can help ensure residents are achieving appropriate technical milestones.

  2. MN Temperature Average (1961-1990) - Line

    Data.gov (United States)

    Minnesota Department of Natural Resources — This data set depicts 30-year averages (1961-1990) of monthly and annual temperatures for Minnesota. Isolines and regions were created using kriging and...

  3. MN Temperature Average (1961-1990) - Polygon

    Data.gov (United States)

    Minnesota Department of Natural Resources — This data set depicts 30-year averages (1961-1990) of monthly and annual temperatures for Minnesota. Isolines and regions were created using kriging and...

  4. High average-power induction linacs

    International Nuclear Information System (INIS)

    Prono, D.S.; Barrett, D.; Bowles, E.

    1989-01-01

    Induction linear accelerators (LIAs) are inherently capable of accelerating several thousand amperes of /approximately/ 50-ns duration pulses to > 100 MeV. In this paper we report progress and status in the areas of duty factor and stray power management. These technologies are vital if LIAs are to attain high average power operation. 13 figs

  5. SEX DIFFERENCES ON THE WECHSLER INTELLIGENCE SCALE FOR CHILDREN-III IN BAHRAIN AND THE UNITED STATES.

    Science.gov (United States)

    Bakhiet, Salaheldin Farah Attallah; Lynn, Richard

    2015-12-01

    Sex differences on the Wechsler Intelligence Scale for Children-III (WISC-III) are reported for children in Bahrain and the United States. The results for the two samples were consistent in showing no significant differences in Verbal, Performance, and Full Scale IQs, higher average scores by boys on the Block design and Mazes subtests of spatial ability, and higher average scores by girls on Coding. There was also greater variability in boys than in girls.

  6. Interpreting Bivariate Regression Coefficients: Going beyond the Average

    Science.gov (United States)

    Halcoussis, Dennis; Phillips, G. Michael

    2010-01-01

    Statistics, econometrics, investment analysis, and data analysis classes often review the calculation of several types of averages, including the arithmetic mean, geometric mean, harmonic mean, and various weighted averages. This note shows how each of these can be computed using a basic regression framework. By recognizing when a regression model…

  7. Quasistatic zooming of FDTD E-field computations: the impact of down-scaling techniques

    Energy Technology Data Exchange (ETDEWEB)

    Van de Kamer, J.B.; Kroeze, H.; De Leeuw, A.A.C.; Lagendijk, J.J.W. [Department of Radiotherapy, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX, Utrecht (Netherlands)

    2001-05-01

    Due to current computer limitations, regional hyperthermia treatment planning (HTP) is practically limited to a resolution of 1 cm, whereas a millimetre resolution is desired. Using the centimetre resolution E-vector-field distribution, computed with, for example, the finite-difference time-domain (FDTD) method and the millimetre resolution patient anatomy it is possible to obtain a millimetre resolution SAR distribution in a volume of interest (VOI) by means of quasistatic zooming. To compute the required low-resolution E-vector-field distribution, a low-resolution dielectric geometry is needed which is constructed by down-scaling the millimetre resolution dielectric geometry. In this study we have investigated which down-scaling technique results in a dielectric geometry that yields the best low-resolution E-vector-field distribution as input for quasistatic zooming. A segmented 2 mm resolution CT data set of a patient has been down-scaled to 1 cm resolution using three different techniques: 'winner-takes-all', 'volumetric averaging' and 'anisotropic volumetric averaging'. The E-vector-field distributions computed for those low-resolution dielectric geometries have been used as input for quasistatic zooming. The resulting zoomed-resolution SAR distributions were compared with a reference: the 2 mm resolution SAR distribution computed with the FDTD method. The E-vector-field distribution for both a simple phantom and the complex partial patient geometry down-scaled using 'anisotropic volumetric averaging' resulted in zoomed-resolution SAR distributions that best approximate the corresponding high-resolution SAR distribution (correlation 97, 96% and absolute averaged difference 6, 14% respectively). (author)

  8. Unscrambling The "Average User" Of Habbo Hotel

    Directory of Open Access Journals (Sweden)

    Mikael Johnson

    2007-01-01

    Full Text Available The “user” is an ambiguous concept in human-computer interaction and information systems. Analyses of users as social actors, participants, or configured users delineate approaches to studying design-use relationships. Here, a developer’s reference to a figure of speech, termed the “average user,” is contrasted with design guidelines. The aim is to create an understanding about categorization practices in design through a case study about the virtual community, Habbo Hotel. A qualitative analysis highlighted not only the meaning of the “average user,” but also the work that both the developer and the category contribute to this meaning. The average user a represents the unknown, b influences the boundaries of the target user groups, c legitimizes the designer to disregard marginal user feedback, and d keeps the design space open, thus allowing for creativity. The analysis shows how design and use are intertwined and highlights the developers’ role in governing different users’ interests.

  9. Potential of high-average-power solid state lasers

    International Nuclear Information System (INIS)

    Emmett, J.L.; Krupke, W.F.; Sooy, W.R.

    1984-01-01

    We discuss the possibility of extending solid state laser technology to high average power and of improving the efficiency of such lasers sufficiently to make them reasonable candidates for a number of demanding applications. A variety of new design concepts, materials, and techniques have emerged over the past decade that, collectively, suggest that the traditional technical limitations on power (a few hundred watts or less) and efficiency (less than 1%) can be removed. The core idea is configuring the laser medium in relatively thin, large-area plates, rather than using the traditional low-aspect-ratio rods or blocks. This presents a large surface area for cooling, and assures that deposited heat is relatively close to a cooled surface. It also minimizes the laser volume distorted by edge effects. The feasibility of such configurations is supported by recent developments in materials, fabrication processes, and optical pumps. Two types of lasers can, in principle, utilize this sheet-like gain configuration in such a way that phase and gain profiles are uniformly sampled and, to first order, yield high-quality (undistorted) beams. The zig-zag laser does this with a single plate, and should be capable of power levels up to several kilowatts. The disk laser is designed around a large number of plates, and should be capable of scaling to arbitrarily high power levels

  10. GI Joe or Average Joe? The impact of average-size and muscular male fashion models on men's and women's body image and advertisement effectiveness.

    Science.gov (United States)

    Diedrichs, Phillippa C; Lee, Christina

    2010-06-01

    Increasing body size and shape diversity in media imagery may promote positive body image. While research has largely focused on female models and women's body image, men may also be affected by unrealistic images. We examined the impact of average-size and muscular male fashion models on men's and women's body image and perceived advertisement effectiveness. A sample of 330 men and 289 women viewed one of four advertisement conditions: no models, muscular, average-slim or average-large models. Men and women rated average-size models as equally effective in advertisements as muscular models. For men, exposure to average-size models was associated with more positive body image in comparison to viewing no models, but no difference was found in comparison to muscular models. Similar results were found for women. Internalisation of beauty ideals did not moderate these effects. These findings suggest that average-size male models can promote positive body image and appeal to consumers. 2010 Elsevier Ltd. All rights reserved.

  11. Scaling and the inclusive semileptonic decays of charmed particles

    International Nuclear Information System (INIS)

    Pham, X.Y.; Nabavi, R.P.

    1977-01-01

    A general formula describing the semileptonic decay of charmed particles is written in terms of structure functions. A procedure is proposed to estimate semileptonic decay widths by supposing that these structure functions may be averaged by their scaling limits

  12. Diagnosing Competency Mastery in Science: An Application of GDM to TIMSS 2011 Data

    Science.gov (United States)

    Kabiri, Masoud; Ghazi-Tabatabaei, Mahmood; Bazargan, Abbas; Shokoohi-Yekta, Mohsen; Kharrazi, Kamal

    2017-01-01

    Numerous diagnostic studies have been conducted on large-scale assessments to illustrate the students' mastery profile in the areas of math and reading; however, for science a limited number of investigations are reported. This study investigated Iranian eighth graders' competency mastery of science and examined the utility of the General…

  13. Transition physics and scaling overview

    International Nuclear Information System (INIS)

    Carlstrom, T.N.

    1996-01-01

    This paper presents an overview of recent experimental progress towards understanding H-mode transition physics and scaling. Terminology and techniques for studying H-mode are reviewed and discussed. The model of shear E x B flow stabilization of edge fluctuations at the L-H transition is gaining wide acceptance and is further supported by observations of edge rotation on a number of new devices. Observations of poloidal asymmetries of edge fluctuations and dephasing of density and potential fluctuations after the transition pose interesting challenges for understanding H-mode physics. Dedicated scans to determine the scaling of the power threshold have now been performed on many machines. A clear B t dependence is universally observed but dependence on the line averaged density is complicated. Other dependencies are also reported. Studies of the effect of neutrals and error fields on the power threshold are under investigation. The ITER threshold database has matured and offers guidance to the power threshold scaling issues relevant to next-step devices. (author)

  14. Transition physics and scaling overview

    International Nuclear Information System (INIS)

    Carlstrom, T.N.

    1995-12-01

    This paper presents an overview of recent experimental progress towards understanding H-mode transition physics and scaling. Terminology and techniques for studying H-mode are reviewed and discussed. The model of shear E x B flow stabilization of edge fluctuations at the L-H transition is gaining wide acceptance and is further supported by observations of edge rotation on a number of new devices. Observations of poloidal asymmetries of edge fluctuations and dephasing of density and potential fluctuations after the transition pose interesting challenges for understanding H-mode physics. Dedicated scans to determine the scaling of the power threshold have now been performed on many machines. A dear B t dependence is universally observed but dependence on the line averaged density is complicated. Other dependencies are also reported. Studies of the effect of neutrals and error fields on the power threshold are under investigation. The ITER threshold database has matured and offers guidance to the power threshold scaling issues relevant to next-step devices

  15. Average: the juxtaposition of procedure and context

    Science.gov (United States)

    Watson, Jane; Chick, Helen; Callingham, Rosemary

    2014-09-01

    This paper presents recent data on the performance of 247 middle school students on questions concerning average in three contexts. Analysis includes considering levels of understanding linking definition and context, performance across contexts, the relative difficulty of tasks, and difference in performance for male and female students. The outcomes lead to a discussion of the expectations of the curriculum and its implementation, as well as assessment, in relation to students' skills in carrying out procedures and their understanding about the meaning of average in context.

  16. High average-power induction linacs

    International Nuclear Information System (INIS)

    Prono, D.S.; Barrett, D.; Bowles, E.; Caporaso, G.J.; Chen, Yu-Jiuan; Clark, J.C.; Coffield, F.; Newton, M.A.; Nexsen, W.; Ravenscroft, D.; Turner, W.C.; Watson, J.A.

    1989-01-01

    Induction linear accelerators (LIAs) are inherently capable of accelerating several thousand amperes of ∼ 50-ns duration pulses to > 100 MeV. In this paper the authors report progress and status in the areas of duty factor and stray power management. These technologies are vital if LIAs are to attain high average power operation. 13 figs

  17. Serpent-COREDAX analysis of CANDU-6 time-average model

    Energy Technology Data Exchange (ETDEWEB)

    Motalab, M.A.; Cho, B.; Kim, W.; Cho, N.Z.; Kim, Y., E-mail: yongheekim@kaist.ac.kr [Korea Advanced Inst. of Science and Technology (KAIST), Dept. of Nuclear and Quantum Engineering Daejeon (Korea, Republic of)

    2015-07-01

    COREDAX-2 is the nuclear core analysis nodal code that has adopted the Analytic Function Expansion Nodal (AFEN) methodology which has been developed in Korea. AFEN method outperforms in terms of accuracy compared to other conventional nodal methods. To evaluate the possibility of CANDU-type core analysis using the COREDAX-2, the time-average analysis code system was developed. The two-group homogenized cross-sections were calculated using Monte Carlo code, Serpent2. A stand-alone time-average module was developed to determine the time-average burnup distribution in the core for a given fuel management strategy. The coupled Serpent-COREDAX-2 calculation converges to an equilibrium time-average model for the CANDU-6 core. (author)

  18. A high speed digital signal averager for pulsed NMR

    International Nuclear Information System (INIS)

    Srinivasan, R.; Ramakrishna, J.; Ra agopalan, S.R.

    1978-01-01

    A 256-channel digital signal averager suitable for pulsed nuclear magnetic resonance spectroscopy is described. It implements 'stable averaging' algorithm and hence provides a calibrated display of the average signal at all times during the averaging process on a CRT. It has a maximum sampling rate of 2.5 μ sec and a memory capacity of 256 x 12 bit words. Number of sweeps is selectable through a front panel control in binary steps from 2 3 to 2 12 . The enhanced signal can be displayed either on a CRT or by a 3.5-digit LED display. The maximum S/N improvement that can be achieved with this instrument is 36 dB. (auth.)

  19. Macro-scale turbulence modelling for flows in porous media

    International Nuclear Information System (INIS)

    Pinson, F.

    2006-03-01

    - This work deals with the macroscopic modeling of turbulence in porous media. It concerns heat exchangers, nuclear reactors as well as urban flows, etc. The objective of this study is to describe in an homogenized way, by the mean of a spatial average operator, turbulent flows in a solid matrix. In addition to this first operator, the use of a statistical average operator permits to handle the pseudo-aleatory character of turbulence. The successive application of both operators allows us to derive the balance equations of the kind of flows under study. Two major issues are then highlighted, the modeling of dispersion induced by the solid matrix and the turbulence modeling at a macroscopic scale (Reynolds tensor and turbulent dispersion). To this aim, we lean on the local modeling of turbulence and more precisely on the k - ε RANS models. The methodology of dispersion study, derived thanks to the volume averaging theory, is extended to turbulent flows. Its application includes the simulation, at a microscopic scale, of turbulent flows within a representative elementary volume of the porous media. Applied to channel flows, this analysis shows that even within the turbulent regime, dispersion remains one of the dominating phenomena within the macro-scale modeling framework. A two-scale analysis of the flow allows us to understand the dominating role of the drag force in the kinetic energy transfers between scales. Transfers between the mean part and the turbulent part of the flow are formally derived. This description significantly improves our understanding of the issue of macroscopic modeling of turbulence and leads us to define the sub-filter production and the wake dissipation. A f - f - w >f model is derived. It is based on three balance equations for the turbulent kinetic energy, the viscous dissipation and the wake dissipation. Furthermore, a dynamical predictor for the friction coefficient is proposed. This model is then successfully applied to the study of

  20. Average configuration of the geomagnetic tail

    International Nuclear Information System (INIS)

    Fairfield, D.H.

    1979-01-01

    Over 3000 hours of Imp 6 magnetic field data obtained between 20 and 33 R/sub E/ in the geomagnetic tail have been used in a statistical study of the tail configuration. A distribution of 2.5-min averages of B/sub z/ as a function of position across the tail reveals that more flux crosses the equatorial plane near the dawn and dusk flanks (B-bar/sub z/=3.γ) than near midnight (B-bar/sub z/=1.8γ). The tail field projected in the solar magnetospheric equatorial plane deviates from the x axis due to flaring and solar wind aberration by an angle α=-0.9 Y/sub SM/-2.7, where Y/sub SM/ is in earth radii and α is in degrees. After removing these effects, the B/sub y/ component of the tail field is found to depend on interplanetary sector structure. During an 'away' sector the B/sub y/ component of the tail field is on average 0.5γ greater than that during a 'toward' sector, a result that is true in both tail lobes and is independent of location across the tail. This effect means the average field reversal between northern and southern lobes of the tail is more often 178 0 rather than the 180 0 that is generally supposed

  1. Coping Strategies Applied to Comprehend Multistep Arithmetic Word Problems by Students with Above-Average Numeracy Skills and Below-Average Reading Skills

    Science.gov (United States)

    Nortvedt, Guri A.

    2011-01-01

    This article discusses how 13-year-old students with above-average numeracy skills and below-average reading skills cope with comprehending word problems. Compared to other students who are proficient in numeracy and are skilled readers, these students are more disadvantaged when solving single-step and multistep arithmetic word problems. The…

  2. Divergence of perturbation theory in large scale structures

    Science.gov (United States)

    Pajer, Enrico; van der Woude, Drian

    2018-05-01

    We make progress towards an analytical understanding of the regime of validity of perturbation theory for large scale structures and the nature of some non-perturbative corrections. We restrict ourselves to 1D gravitational collapse, for which exact solutions before shell crossing are known. We review the convergence of perturbation theory for the power spectrum, recently proven by McQuinn and White [1], and extend it to non-Gaussian initial conditions and the bispectrum. In contrast, we prove that perturbation theory diverges for the real space two-point correlation function and for the probability density function (PDF) of the density averaged in cells and all the cumulants derived from it. We attribute these divergences to the statistical averaging intrinsic to cosmological observables, which, even on very large and "perturbative" scales, gives non-vanishing weight to all extreme fluctuations. Finally, we discuss some general properties of non-perturbative effects in real space and Fourier space.

  3. Scaling for scrape-off layer plasma in tokamak

    International Nuclear Information System (INIS)

    Shimomura, Yasuo; Maeda, Hikosuke; Kimura, Haruyuki; Azumi, Masashi; Odajima, Kazuo

    1977-12-01

    Scaling for a scrape-off layer plasma in a tokamak is obtained by using DIVA (JFT-2a). The scaling gives the average electron temperature, the width and the mean electron density of the scrape-off layer. The temperature at the edge will be high in a future large tokamak with a small energy-loss by charge-exchange and radiation. The scrape-off layer plasma can easily shield the impurity influx from the wall. The fuel, however, can easily penetrate into the main plasma. (auth.)

  4. A Correlation Between the Intrinsic Brightness and Average Decay Rate of Gamma-Ray Burst X-Ray Afterglow Light Curves

    Science.gov (United States)

    Racusin, J. L.; Oates, S. R.; De Pasquale, M.; Kocevski, D.

    2016-01-01

    We present a correlation between the average temporal decay (alpha X,avg, greater than 200 s) and early-time luminosity (LX,200 s) of X-ray afterglows of gamma-ray bursts as observed by the Swift X-ray Telescope. Both quantities are measured relative to a rest-frame time of 200 s after the gamma-ray trigger. The luminosity â€" average decay correlation does not depend on specific temporal behavior and contains one scale-independent quantity minimizing the role of selection effects. This is a complementary correlation to that discovered by Oates et al. in the optical light curves observed by the Swift Ultraviolet Optical Telescope. The correlation indicates that, on average, more luminous X-ray afterglows decay faster than less luminous ones, indicating some relative mechanism for energy dissipation. The X-ray and optical correlations are entirely consistent once corrections are applied and contamination is removed. We explore the possible biases introduced by different light-curve morphologies and observational selection effects, and how either geometrical effects or intrinsic properties of the central engine and jet could explain the observed correlation.

  5. Analysis of experimental data: The average shape of extreme wave forces on monopile foundations and the NewForce model

    DEFF Research Database (Denmark)

    Schløer, Signe; Bredmose, Henrik; Ghadirian, Amin

    2017-01-01

    Experiments with a stiff pile subjected to extreme wave forces typical of offshore wind farm storm conditions are considered. The exceedance probability curves of the nondimensional force peaks and crest heights are analysed. The average force time history normalised with their peak values are co...... to the average shapes. For more nonlinear wave shapes, higher order terms has to be considered in order for the NewForce model to be able to predict the expected shapes.......Experiments with a stiff pile subjected to extreme wave forces typical of offshore wind farm storm conditions are considered. The exceedance probability curves of the nondimensional force peaks and crest heights are analysed. The average force time history normalised with their peak values...... are compared across the sea states. It is found that the force shapes show a clear similarity when grouped after the values of the normalised peak force, F/(ρghR2), normalised depth h/(gT2p) and presented in a normalised time scale t/Ta. For the largest force events, slamming can be seen as a distinct ‘hat...

  6. A more general expression for the average X-ray diffraction intensity of crystals with an incommensurate one-dimensional modulation

    International Nuclear Information System (INIS)

    Lam, E.J.W.; Beurskens, P.T.; Smaalen, S. van

    1994-01-01

    Statistical methods are used to derive an expression for the average X-ray diffraction intensity, as a function of (sinθ)/λ, of crystals with an incommensurate one-dimensional modulation. Displacive and density modulations are considered, as well as a combination of these two. The atomic modulation functions are given by truncated Fourier series that may contain higher-order harmonics. The resulting expression for the average X-ray diffraction intensity is valid for main reflections and low-order satellite reflections. The modulation of individual atoms is taken into account by the introduction of overall modulation amplitudes. The accuracy of this expression for the average X-ray diffraction intensity is illustrated by comparison with model structures. A definition is presented for normalized structure factors of crystals with an incommensurate one-dimensional modulation that can be used in direct-methods procedures for solving the phase problem in X-ray crystallography. A numerical fitting procedure is described that can extract a scale factor, an overall temperature parameter and overall modulation amplitudes from experimental reflection intensities. (orig.)

  7. Beyond KNO multiplicative cascades and novel multiplicity scaling laws

    CERN Document Server

    Hegyi, S

    1999-01-01

    The collapse of multiplicity distributions P/sub n/ onto a universal scaling curve arises when P/sub n/ is expressed as a function of the standardized multiplicity (n-c)/ lambda with c and lambda being location and scale parameters governed by leading particle effects and the growth of average multiplicity. It is demonstrated that self- similar multiplicative cascade processes such as QCD parton branching naturally lead to a novel type of scaling behavior of P/sub n/ which manifests itself in Mellin space through a location change controlled by the degree of multifractality and a scale change governed by the depth of the cascade. Applying the new scaling rule it is shown how to restore data collapsing behavior of P/sub n/ measured in hh collisions at ISR and SPS energies. (21 refs).

  8. Average of delta: a new quality control tool for clinical laboratories.

    Science.gov (United States)

    Jones, Graham R D

    2016-01-01

    Average of normals is a tool used to control assay performance using the average of a series of results from patients' samples. Delta checking is a process of identifying errors in individual patient results by reviewing the difference from previous results of the same patient. This paper introduces a novel alternate approach, average of delta, which combines these concepts to use the average of a number of sequential delta values to identify changes in assay performance. Models for average of delta and average of normals were developed in a spreadsheet application. The model assessed the expected scatter of average of delta and average of normals functions and the effect of assay bias for different values of analytical imprecision and within- and between-subject biological variation and the number of samples included in the calculations. The final assessment was the number of patients' samples required to identify an added bias with 90% certainty. The model demonstrated that with larger numbers of delta values, the average of delta function was tighter (lower coefficient of variation). The optimal number of samples for bias detection with average of delta was likely to be between 5 and 20 for most settings and that average of delta outperformed average of normals when the within-subject biological variation was small relative to the between-subject variation. Average of delta provides a possible additional assay quality control tool which theoretical modelling predicts may be more valuable than average of normals for analytes where the group biological variation is wide compared with within-subject variation and where there is a high rate of repeat testing in the laboratory patient population. © The Author(s) 2015.

  9. Regional-to-site scale groundwater flow in Romuvaara

    Energy Technology Data Exchange (ETDEWEB)

    Kattilakoski, E.; Koskinen, L. [VTT Energy, Espoo (Finland)

    1999-04-01

    The work describing numerical groundwater flow modelling at the Romuvaara site serves as a background report for the safety assessment TILA-99. The site scale can roughly be taken as the scale of detailed borehole investigations, which have probed the bedrock of Romuvaara over about 2 km{sup 2} large and 1 km deep volume. The site model in this work covers an area of about 12 km{sup 2}. The depth of the model is 2200 m. The site scale flow modelling produced characteristics of the deep groundwater flow and evaluated the impact of a spent fuel repository on the natural groundwater flow conditions. It treated the hydraulic gradient in the intact rock between the repository and the fracture zone nearest to it (about 50 m off) for the block scale model, which describes the groundwater flow on the repository scale. The result quantities were the hydraulic head h (as the base quantity) and its gradient in selected cross sections and fracture zones, the flow rates around the repository, flow paths and discharge areas of the water from the repository. Two repository layouts were discussed. The numerical simulations were performed with the FEFTRA code based on the porous medium concept and the finite element method. The regional model with a no-flow boundary condition at the bottom and on the lateral edges was firstly used to confirm the hydraulic head boundary condition on the lateral edges of an interior site model (having a no-flow boundary condition at the bottom). The groundwater table was used as the hydraulic head boundary condition at the surface of each model. Both the conductivity of the bedrock (modeled with three-dimensional elements) and the transmissivities of the fracture zones (described with two-dimensional elements in the three-dimensional mesh) decreased as a function of the depth. All the results were derived from the site model. The range of variation of the hydraulic gradient immediately outside the repository was studied in the direction of the flow

  10. High-Average, High-Peak Current Injector Design

    CERN Document Server

    Biedron, S G; Virgo, M

    2005-01-01

    There is increasing interest in high-average-power (>100 kW), um-range FELs. These machines require high peak current (~1 kA), modest transverse emittance, and beam energies of ~100 MeV. High average currents (~1 A) place additional constraints on the design of the injector. We present a design for an injector intended to produce the required peak currents at the injector, eliminating the need for magnetic compression within the linac. This reduces the potential for beam quality degradation due to CSR and space charge effects within magnetic chicanes.

  11. Statistics on exponential averaging of periodograms

    Energy Technology Data Exchange (ETDEWEB)

    Peeters, T.T.J.M. [Netherlands Energy Research Foundation (ECN), Petten (Netherlands); Ciftcioglu, Oe. [Istanbul Technical Univ. (Turkey). Dept. of Electrical Engineering

    1994-11-01

    The algorithm of exponential averaging applied to subsequent periodograms of a stochastic process is used to estimate the power spectral density (PSD). For an independent process, assuming the periodogram estimates to be distributed according to a {chi}{sup 2} distribution with 2 degrees of freedom, the probability density function (PDF) of the PSD estimate is derived. A closed expression is obtained for the moments of the distribution. Surprisingly, the proof of this expression features some new insights into the partitions and Eulers infinite product. For large values of the time constant of the averaging process, examination of the cumulant generating function shows that the PDF approximates the Gaussian distribution. Although restrictions for the statistics are seemingly tight, simulation of a real process indicates a wider applicability of the theory. (orig.).

  12. Statistics on exponential averaging of periodograms

    International Nuclear Information System (INIS)

    Peeters, T.T.J.M.; Ciftcioglu, Oe.

    1994-11-01

    The algorithm of exponential averaging applied to subsequent periodograms of a stochastic process is used to estimate the power spectral density (PSD). For an independent process, assuming the periodogram estimates to be distributed according to a χ 2 distribution with 2 degrees of freedom, the probability density function (PDF) of the PSD estimate is derived. A closed expression is obtained for the moments of the distribution. Surprisingly, the proof of this expression features some new insights into the partitions and Eulers infinite product. For large values of the time constant of the averaging process, examination of the cumulant generating function shows that the PDF approximates the Gaussian distribution. Although restrictions for the statistics are seemingly tight, simulation of a real process indicates a wider applicability of the theory. (orig.)

  13. Decreases in average bacterial community rRNA operon copy number during succession.

    Science.gov (United States)

    Nemergut, Diana R; Knelman, Joseph E; Ferrenberg, Scott; Bilinski, Teresa; Melbourne, Brett; Jiang, Lin; Violle, Cyrille; Darcy, John L; Prest, Tiffany; Schmidt, Steven K; Townsend, Alan R

    2016-05-01

    Trait-based studies can help clarify the mechanisms driving patterns of microbial community assembly and coexistence. Here, we use a trait-based approach to explore the importance of rRNA operon copy number in microbial succession, building on prior evidence that organisms with higher copy numbers respond more rapidly to nutrient inputs. We set flasks of heterotrophic media into the environment and examined bacterial community assembly at seven time points. Communities were arrayed along a geographic gradient to introduce stochasticity via dispersal processes and were analyzed using 16 S rRNA gene pyrosequencing, and rRNA operon copy number was modeled using ancestral trait reconstruction. We found that taxonomic composition was similar between communities at the beginning of the experiment and then diverged through time; as well, phylogenetic clustering within communities decreased over time. The average rRNA operon copy number decreased over the experiment, and variance in rRNA operon copy number was lowest both early and late in succession. We then analyzed bacterial community data from other soil and sediment primary and secondary successional sequences from three markedly different ecosystem types. Our results demonstrate that decreases in average copy number are a consistent feature of communities across various drivers of ecological succession. Importantly, our work supports the scaling of the copy number trait over multiple levels of biological organization, ranging from cells to populations and communities, with implications for both microbial ecology and evolution.

  14. Analytical Assessment of the Relationship between 100MWp Large-scale Grid-connected Photovoltaic Plant Performance and Meteorological Parameters

    Science.gov (United States)

    Sheng, Jie; Zhu, Qiaoming; Cao, Shijie; You, Yang

    2017-05-01

    This paper helps in study of the relationship between the photovoltaic power generation of large scale “fishing and PV complementary” grid-tied photovoltaic system and meteorological parameters, with multi-time scale power data from the photovoltaic power station and meteorological data over the same period of a whole year. The result indicates that, the PV power generation has the most significant correlation with global solar irradiation, followed by diurnal temperature range, sunshine hours, daily maximum temperature and daily average temperature. In different months, the maximum monthly average power generation appears in August, which related to the more global solar irradiation and longer sunshine hours in this month. However, the maximum daily average power generation appears in October, this is due to the drop in temperature brings about the improvement of the efficiency of PV panels. Through the contrast of monthly average performance ratio (PR) and monthly average temperature, it is shown that, the larger values of monthly average PR appears in April and October, while it is smaller in summer with higher temperature. The results concluded that temperature has a great influence on the performance ratio of large scale grid-tied PV power system, and it is important to adopt effective measures to decrease the temperature of PV plant properly.

  15. Accurate phenotyping: Reconciling approaches through Bayesian model averaging.

    Directory of Open Access Journals (Sweden)

    Carla Chia-Ming Chen

    Full Text Available Genetic research into complex diseases is frequently hindered by a lack of clear biomarkers for phenotype ascertainment. Phenotypes for such diseases are often identified on the basis of clinically defined criteria; however such criteria may not be suitable for understanding the genetic composition of the diseases. Various statistical approaches have been proposed for phenotype definition; however our previous studies have shown that differences in phenotypes estimated using different approaches have substantial impact on subsequent analyses. Instead of obtaining results based upon a single model, we propose a new method, using Bayesian model averaging to overcome problems associated with phenotype definition. Although Bayesian model averaging has been used in other fields of research, this is the first study that uses Bayesian model averaging to reconcile phenotypes obtained using multiple models. We illustrate the new method by applying it to simulated genetic and phenotypic data for Kofendred personality disorder-an imaginary disease with several sub-types. Two separate statistical methods were used to identify clusters of individuals with distinct phenotypes: latent class analysis and grade of membership. Bayesian model averaging was then used to combine the two clusterings for the purpose of subsequent linkage analyses. We found that causative genetic loci for the disease produced higher LOD scores using model averaging than under either individual model separately. We attribute this improvement to consolidation of the cores of phenotype clusters identified using each individual method.

  16. Fitting a function to time-dependent ensemble averaged data

    DEFF Research Database (Denmark)

    Fogelmark, Karl; Lomholt, Michael A.; Irbäck, Anders

    2018-01-01

    Time-dependent ensemble averages, i.e., trajectory-based averages of some observable, are of importance in many fields of science. A crucial objective when interpreting such data is to fit these averages (for instance, squared displacements) with a function and extract parameters (such as diffusion...... method, weighted least squares including correlation in error estimation (WLS-ICE), to particle tracking data. The WLS-ICE method is applicable to arbitrary fit functions, and we provide a publically available WLS-ICE software....

  17. The Effects of Scales on Autorotation of Monarch Butterfly Forewings

    Science.gov (United States)

    Dechello, Nicole; Lang, Amy

    2014-11-01

    The wings of Monarch butterflies (Danus plexippus) have scales of approximately 100 micrometers that cover their wings in a roof-shingle pattern, and these scales are hypothesized to help improve flight efficiency for their long migration. The aerodynamic effects of the scales, particularly involving the leading edge vortex formation and resulting lift, were investigated by observing the natural autorotation of forewing specimen when dropped in quiescent air. A high-speed camera recorded drop tests of 32 forewings both with scales and after removal of the scales. It was found that the scales, on average, comprised 17% of the forewing mass. Tracking software was used to analyze the videos for several parameters, including descent speed and radius of rotation. NSF ECE Grant #1358991 supported the first author as an research experience for undergraduate (REU) student.

  18. A Lifelong Learning Scale for Research and Evaluation of Teaching and Curricular Effectiveness

    Science.gov (United States)

    Wielkiewicz, Richard M.; Meuwissen, Alyssa S.

    2014-01-01

    A 16-item lifelong learning scale (LLS), appropriate for college students and others, was evaluated using a sample of 575 college students. The scale demonstrated excellent reliability and was correlated with college grade point average (GPA), agreeableness, conscientiousness, and intellect/imagination. Scores were higher for those who had studied…

  19. Determination of the Average Native Background and the Light-Induced EPR Signals and their Variation in the Teeth Enamel Based on Large-Scale Survey of the Population

    International Nuclear Information System (INIS)

    Ivannikov, Alexander I.; Khailov, Artem M.; Orlenko, Sergey P.; Skvortsov, Valeri G.; Stepanenko, Valeri F.; Zhumadilov, Kassym Sh.; Williams, Benjamin B.; Flood, Ann B.; Swartz, Harold M.

    2016-01-01

    The aim of the study is to determine the average intensity and variation of the native background signal amplitude (NSA) and of the solar light-induced signal amplitude (LSA) in electron paramagnetic resonance (EPR) spectra of tooth enamel for different kinds of teeth and different groups of people. These values are necessary for determination of the intensity of the radiation-induced signal amplitude (RSA) by subtraction of the expected NSA and LSA from the total signal amplitude measured in L-band for in vivo EPR dosimetry. Variation of these signals should be taken into account when estimating the uncertainty of the estimated RSA. A new analysis of several hundred EPR spectra that were measured earlier at X-band in a large-scale examination of the population of the Central Russia was performed. Based on this analysis, the average values and the variation (standard deviation, SD) of the amplitude of the NSA for the teeth from different positions, as well as LSA in outer enamel of the front teeth for different population groups, were determined. To convert data acquired at X-band to values corresponding to the conditions of measurement at L-band, the experimental dependencies of the intensities of the RSA, LSA and NSA on the m.w. power, measured at both X and L-band, were analysed. For the two central upper incisors, which are mainly used in in vivo dosimetry, the mean LSA annual rate induced only in the outer side enamel and its variation were obtained as 10 ± 2 (SD = 8) mGy y"-"1, the same for X- and L-bands (results are presented as the mean ± error of mean). Mean NSA in enamel and its variation for the upper incisors was calculated at 2.0 ± 0.2 (SD = 0.5) Gy, relative to the calibrated RSA dose-response to gamma radiation measured under non-power saturation conditions at X-band. Assuming the same value for L-band under non-power saturating conditions, then for in vivo measurements at L-band at 25 mW (power saturation conditions), a mean NSA and its

  20. Multiple time scale methods in tokamak magnetohydrodynamics

    International Nuclear Information System (INIS)

    Jardin, S.C.

    1984-01-01

    Several methods are discussed for integrating the magnetohydrodynamic (MHD) equations in tokamak systems on other than the fastest time scale. The dynamical grid method for simulating ideal MHD instabilities utilizes a natural nonorthogonal time-dependent coordinate transformation based on the magnetic field lines. The coordinate transformation is chosen to be free of the fast time scale motion itself, and to yield a relatively simple scalar equation for the total pressure, P = p + B 2 /2μ 0 , which can be integrated implicitly to average over the fast time scale oscillations. Two methods are described for the resistive time scale. The zero-mass method uses a reduced set of two-fluid transport equations obtained by expanding in the inverse magnetic Reynolds number, and in the small ratio of perpendicular to parallel mobilities and thermal conductivities. The momentum equation becomes a constraint equation that forces the pressure and magnetic fields and currents to remain in force balance equilibrium as they evolve. The large mass method artificially scales up the ion mass and viscosity, thereby reducing the severe time scale disparity between wavelike and diffusionlike phenomena, but not changing the resistive time scale behavior. Other methods addressing the intermediate time scales are discussed

  1. College Experience Scale (EExU

    Directory of Open Access Journals (Sweden)

    Angélica Juárez

    2017-07-01

    Full Text Available The experience of being a university student (University Experiences had been poorly studied so far. However, research in this field can provide valuable information about the quality of academic life, wellbeing or stress in this population. There is a lack of psychological tests that explore this theoretical construct. The aim of this study was to develop and validate a scale for measuring Univeristy Experiences, for that reason 314 college students were invited to participate for the validation. This students coursed different careers and reported 20 years old as average age. The University Experiences Scale (EExU has adequate psychometric properties. It has a structure of four factors: experience satisfaction, support perception, experience perception and life style adjustment. This factors explain 43.1% of the variance. The grouping of the factors of the College Experience Scale concurs with data reported in the literature about such concept, however this is the first questionnaire designed for measuring it. We anticipate that future studies will seek to verify the performance of the scale in different populations of students and analyze its psychometric properties and its possible association with other psychological variables that affect college students and their health.

  2. Universities scale like cities.

    Directory of Open Access Journals (Sweden)

    Anthony F J van Raan

    Full Text Available Recent studies of urban scaling show that important socioeconomic city characteristics such as wealth and innovation capacity exhibit a nonlinear, particularly a power law scaling with population size. These nonlinear effects are common to all cities, with similar power law exponents. These findings mean that the larger the city, the more disproportionally they are places of wealth and innovation. Local properties of cities cause a deviation from the expected behavior as predicted by the power law scaling. In this paper we demonstrate that universities show a similar behavior as cities in the distribution of the 'gross university income' in terms of total number of citations over 'size' in terms of total number of publications. Moreover, the power law exponents for university scaling are comparable to those for urban scaling. We find that deviations from the expected behavior can indeed be explained by specific local properties of universities, particularly the field-specific composition of a university, and its quality in terms of field-normalized citation impact. By studying both the set of the 500 largest universities worldwide and a specific subset of these 500 universities--the top-100 European universities--we are also able to distinguish between properties of universities with as well as without selection of one specific local property, the quality of a university in terms of its average field-normalized citation impact. It also reveals an interesting observation concerning the working of a crucial property in networked systems, preferential attachment.

  3. Universities scale like cities.

    Science.gov (United States)

    van Raan, Anthony F J

    2013-01-01

    Recent studies of urban scaling show that important socioeconomic city characteristics such as wealth and innovation capacity exhibit a nonlinear, particularly a power law scaling with population size. These nonlinear effects are common to all cities, with similar power law exponents. These findings mean that the larger the city, the more disproportionally they are places of wealth and innovation. Local properties of cities cause a deviation from the expected behavior as predicted by the power law scaling. In this paper we demonstrate that universities show a similar behavior as cities in the distribution of the 'gross university income' in terms of total number of citations over 'size' in terms of total number of publications. Moreover, the power law exponents for university scaling are comparable to those for urban scaling. We find that deviations from the expected behavior can indeed be explained by specific local properties of universities, particularly the field-specific composition of a university, and its quality in terms of field-normalized citation impact. By studying both the set of the 500 largest universities worldwide and a specific subset of these 500 universities--the top-100 European universities--we are also able to distinguish between properties of universities with as well as without selection of one specific local property, the quality of a university in terms of its average field-normalized citation impact. It also reveals an interesting observation concerning the working of a crucial property in networked systems, preferential attachment.

  4. Average Soil Water Retention Curves Measured by Neutron Radiography

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Chu-Lin [ORNL; Perfect, Edmund [University of Tennessee, Knoxville (UTK); Kang, Misun [ORNL; Voisin, Sophie [ORNL; Bilheux, Hassina Z [ORNL; Horita, Juske [Texas Tech University (TTU); Hussey, Dan [NIST Center for Neutron Research (NCRN), Gaithersburg, MD

    2011-01-01

    Water retention curves are essential for understanding the hydrologic behavior of partially-saturated porous media and modeling flow transport processes within the vadose zone. In this paper we report direct measurements of the main drying and wetting branches of the average water retention function obtained using 2-dimensional neutron radiography. Flint sand columns were saturated with water and then drained under quasi-equilibrium conditions using a hanging water column setup. Digital images (2048 x 2048 pixels) of the transmitted flux of neutrons were acquired at each imposed matric potential (~10-15 matric potential values per experiment) at the NCNR BT-2 neutron imaging beam line. Volumetric water contents were calculated on a pixel by pixel basis using Beer-Lambert s law after taking into account beam hardening and geometric corrections. To remove scattering effects at high water contents the volumetric water contents were normalized (to give relative saturations) by dividing the drying and wetting sequences of images by the images obtained at saturation and satiation, respectively. The resulting pixel values were then averaged and combined with information on the imposed basal matric potentials to give average water retention curves. The average relative saturations obtained by neutron radiography showed an approximate one-to-one relationship with the average values measured volumetrically using the hanging water column setup. There were no significant differences (at p < 0.05) between the parameters of the van Genuchten equation fitted to the average neutron radiography data and those estimated from replicated hanging water column data. Our results indicate that neutron imaging is a very effective tool for quantifying the average water retention curve.

  5. Measurement of average radon gas concentration at workplaces

    International Nuclear Information System (INIS)

    Kavasi, N.; Somlai, J.; Kovacs, T.; Gorjanacz, Z.; Nemeth, Cs.; Szabo, T.; Varhegyi, A.; Hakl, J.

    2003-01-01

    In this paper results of measurement of average radon gas concentration at workplaces (the schools and kindergartens and the ventilated workplaces) are presented. t can be stated that the one month long measurements means very high variation (as it is obvious in the cases of the hospital cave and the uranium tailing pond). Consequently, in workplaces where the expectable changes of radon concentration considerable with the seasons should be measure for 12 months long. If it is not possible, the chosen six months period should contain summer and winter months as well. The average radon concentration during working hours can be differ considerable from the average of the whole time in the cases of frequent opening the doors and windows or using artificial ventilation. (authors)

  6. Estimating unbiased economies of scale of HIV prevention projects: a case study of Avahan.

    Science.gov (United States)

    Lépine, Aurélia; Vassall, Anna; Chandrashekar, Sudha; Blanc, Elodie; Le Nestour, Alexis

    2015-04-01

    Governments and donors are investing considerable resources on HIV prevention in order to scale up these services rapidly. Given the current economic climate, providers of HIV prevention services increasingly need to demonstrate that these investments offer good 'value for money'. One of the primary routes to achieve efficiency is to take advantage of economies of scale (a reduction in the average cost of a health service as provision scales-up), yet empirical evidence on economies of scale is scarce. Methodologically, the estimation of economies of scale is hampered by several statistical issues preventing causal inference and thus making the estimation of economies of scale complex. In order to estimate unbiased economies of scale when scaling up HIV prevention services, we apply our analysis to one of the few HIV prevention programmes globally delivered at a large scale: the Indian Avahan initiative. We costed the project by collecting data from the 138 Avahan NGOs and the supporting partners in the first four years of its scale-up, between 2004 and 2007. We develop a parsimonious empirical model and apply a system Generalized Method of Moments (GMM) and fixed-effects Instrumental Variable (IV) estimators to estimate unbiased economies of scale. At the programme level, we find that, after controlling for the endogeneity of scale, the scale-up of Avahan has generated high economies of scale. Our findings suggest that average cost reductions per person reached are achievable when scaling-up HIV prevention in low and middle income countries. Copyright © 2015 Elsevier Ltd. All rights reserved.

  7. Instantaneous variance scaling of AIRS thermodynamic profiles using a circular area Monte Carlo approach

    Science.gov (United States)

    Dorrestijn, Jesse; Kahn, Brian H.; Teixeira, João; Irion, Fredrick W.

    2018-05-01

    Satellite observations are used to obtain vertical profiles of variance scaling of temperature (T) and specific humidity (q) in the atmosphere. A higher spatial resolution nadir retrieval at 13.5 km complements previous Atmospheric Infrared Sounder (AIRS) investigations with 45 km resolution retrievals and enables the derivation of power law scaling exponents to length scales as small as 55 km. We introduce a variable-sized circular-area Monte Carlo methodology to compute exponents instantaneously within the swath of AIRS that yields additional insight into scaling behavior. While this method is approximate and some biases are likely to exist within non-Gaussian portions of the satellite observational swaths of T and q, this method enables the estimation of scale-dependent behavior within instantaneous swaths for individual tropical and extratropical systems of interest. Scaling exponents are shown to fluctuate between β = -1 and -3 at scales ≥ 500 km, while at scales ≤ 500 km they are typically near β ≈ -2, with q slightly lower than T at the smallest scales observed. In the extratropics, the large-scale β is near -3. Within the tropics, however, the large-scale β for T is closer to -1 as small-scale moist convective processes dominate. In the tropics, q exhibits large-scale β between -2 and -3. The values of β are generally consistent with previous works of either time-averaged spatial variance estimates, or aircraft observations that require averaging over numerous flight observational segments. The instantaneous variance scaling methodology is relevant for cloud parameterization development and the assessment of time variability of scaling exponents.

  8. Sea Surface Temperature Average_SST_Master

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Sea surface temperature collected via satellite imagery from http://www.esrl.noaa.gov/psd/data/gridded/data.noaa.ersst.html and averaged for each region using ArcGIS...

  9. The study of scale in Persian music according to notes spectrums

    Directory of Open Access Journals (Sweden)

    A. Nadji

    2006-12-01

    Full Text Available   In this paper we have extracted the notes of Iranian scale from the traditional music played by the great musician Shahnazi on the TAR. Then, by analyzing the spectrum of the notes and by using our special averaging we have found the pitch attributed to the components’ frequency and found the interval between the notes. The results are in comple agreement with Pythagorean scale. Pitch is a subjective quantity that attribute auditory sensation in terms of which sounds maybe ordered on a scale extending from low to high. For a pure tone pitch depends mainly on the frequency of the sound stimulus, but for complex tones or musical sounds pitch depends on partials of the complex tone and when the partials of a complex tone are not harmonic however the determination of pitch is more subtle. Indeed the vibrations of string instruments give rise to overtones which are not exactly multiples of fundamental, so the pitch of musical sound that we perceive is a subjective quantity related to frequencies of the overtones. In this paper we study the effect of partials in pitch of musical notes and by averaging between partials we introduce a subjective quantity which represents the pitch of musical note which is in quite agreement with experiments. As we know there are two famous scales for music, Aristoxenuss and Pythagoraean scale. The intervals in Aristoxenuss scale are    and in Pythagorean scale are   Farabi, the well-known philosopher, based Iranian traditional music on Pythagorean scale and our measurements of pitch and intervals of the notes show this scale has remained unchanged for a thousand years.

  10. Collisionless magnetic reconnection in large-scale electron-positron plasmas

    International Nuclear Information System (INIS)

    Daughton, William; Karimabadi, Homa

    2007-01-01

    One of the most fundamental questions in reconnection physics is how the dynamical evolution will scale to macroscopic systems of physical relevance. This issue is examined for electron-positron plasmas using two-dimensional fully kinetic simulations with both open and periodic boundary conditions. The resulting evolution is complex and highly dynamic throughout the entire duration. The initial phase is distinguished by the coalescence of tearing islands to larger scale while the later phase is marked by the expansion of diffusion regions into elongated current layers that are intrinsically unstable to plasmoid generation. It appears that the repeated formation and ejection of plasmoids plays a key role in controlling the average structure of a diffusion region and preventing the further elongation of the layer. The reconnection rate is modulated in time as the current layers expand and new plasmoids are formed. Although the specific details of this evolution are affected by the boundary and initial conditions, the time averaged reconnection rate remains fast and is remarkably insensitive to the system size for sufficiently large systems. This dynamic scenario offers an alternative explanation for fast reconnection in large-scale systems

  11. Evaporation of Liquid Droplet in Nano and Micro Scales from Statistical Rate Theory.

    Science.gov (United States)

    Duan, Fei; He, Bin; Wei, Tao

    2015-04-01

    The statistical rate theory (SRT) is applied to predict the average evaporation flux of liquid droplet after the approach is validated in the sessile droplet experiments of the water and heavy water. The steady-state experiments show a temperature discontinuity at the evaporating interface. The average evaporation flux is evaluated by individually changing the measurement at a liquid-vapor interface, including the interfacial liquid temperature, the interfacial vapor temperature, the vapor-phase pressure, and the droplet size. The parameter study shows that a higher temperature jump would reduce the average evaporation flux. The average evaporation flux can significantly be influenced by the interfacial liquid temperature and the vapor-phase pressure. The variation can switch the evaporation into condensation. The evaporation flux is found to remain relative constant if the droplet is larger than a micro scale, while the smaller diameters in nano scale can produce a much higher evaporation flux. In addition, a smaller diameter of droplets with the same liquid volume has a larger surface area. It is suggested that the evaporation rate increases dramatically as the droplet shrinks into nano size.

  12. Theory-based transport simulation of tokamaks: density scaling

    International Nuclear Information System (INIS)

    Ghanem, E.S.; Kinsey, J.; Singer, C.; Bateman, G.

    1992-01-01

    There has been a sizeable amount of work in the past few years using theoretically based flux-surface-average transport models to simulate various types of experimental tokamak data. Here we report two such studies, concentrating on the response of the plasma to variation of the line averaged electron density. The first study reported here uses a transport model described by Ghanem et al. to examine the response of global energy confinement time in ohmically heated discharges. The second study reported here uses a closely related and more recent transport model described by Bateman to examine the response of temperature profiles to changes in line-average density in neutral-beam-heated discharges. Work on developing a common theoretical model for these and other scaling experiments is in progress. (author) 5 refs., 2 figs

  13. Effect of tank geometry on its average performance

    Science.gov (United States)

    Orlov, Aleksey A.; Tsimbalyuk, Alexandr F.; Malyugin, Roman V.; Leontieva, Daria A.; Kotelnikova, Alexandra A.

    2018-03-01

    The mathematical model of non-stationary filling of vertical submerged tanks with gaseous uranium hexafluoride is presented in the paper. There are calculations of the average productivity, heat exchange area, and filling time of various volumes tanks with smooth inner walls depending on their "height : radius" ratio as well as the average productivity, degree, and filling time of horizontal ribbing tank with volume 6.10-2 m3 with change central hole diameter of the ribs. It has been shown that the growth of "height / radius" ratio in tanks with smooth inner walls up to the limiting values allows significantly increasing tank average productivity and reducing its filling time. Growth of H/R ratio of tank with volume 1.0 m3 to the limiting values (in comparison with the standard tank having H/R equal 3.49) augments tank productivity by 23.5 % and the heat exchange area by 20%. Besides, we have demonstrated that maximum average productivity and a minimum filling time are reached for the tank with volume 6.10-2 m3 having central hole diameter of horizontal ribs 6.4.10-2 m.

  14. Assessing the Resolution Adaptability of the Zhang-McFarlane Cumulus Parameterization With Spatial and Temporal Averaging: RESOLUTION ADAPTABILITY OF ZM SCHEME

    Energy Technology Data Exchange (ETDEWEB)

    Yun, Yuxing [Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland WA USA; State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, Beijing China; Fan, Jiwen [Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland WA USA; Xiao, Heng [Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland WA USA; Zhang, Guang J. [Scripps Institution of Oceanography, University of California, San Diego CA USA; Ghan, Steven J. [Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland WA USA; Xu, Kuan-Man [NASA Langley Research Center, Hampton VA USA; Ma, Po-Lun [Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland WA USA; Gustafson, William I. [Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland WA USA

    2017-11-01

    Realistic modeling of cumulus convection at fine model resolutions (a few to a few tens of km) is problematic since it requires the cumulus scheme to adapt to higher resolution than they were originally designed for (~100 km). To solve this problem, we implement the spatial averaging method proposed in Xiao et al. (2015) and also propose a temporal averaging method for the large-scale convective available potential energy (CAPE) tendency in the Zhang-McFarlane (ZM) cumulus parameterization. The resolution adaptability of the original ZM scheme, the scheme with spatial averaging, and the scheme with both spatial and temporal averaging at 4-32 km resolution is assessed using the Weather Research and Forecasting (WRF) model, by comparing with Cloud Resolving Model (CRM) results. We find that the original ZM scheme has very poor resolution adaptability, with sub-grid convective transport and precipitation increasing significantly as the resolution increases. The spatial averaging method improves the resolution adaptability of the ZM scheme and better conserves the total transport of moist static energy and total precipitation. With the temporal averaging method, the resolution adaptability of the scheme is further improved, with sub-grid convective precipitation becoming smaller than resolved precipitation for resolution higher than 8 km, which is consistent with the results from the CRM simulation. Both the spatial distribution and time series of precipitation are improved with the spatial and temporal averaging methods. The results may be helpful for developing resolution adaptability for other cumulus parameterizations that are based on quasi-equilibrium assumption.

  15. Deformation-induced microstructural evolution at grain scale

    DEFF Research Database (Denmark)

    Winther, Grethe

    During plastic deformation metals develop microstructures which may be analysed on several scales,spanning from crystallographic textures averaged over the entire sample to the scale of individualgrains. Even within individual grains, intragranular phenomena in the form of orientation gradients...... aswell as dislocation patterning by formation of dislocation boundaries occur. Experimental data andassociated data analysis at the grain scale and below will be presented to illustrate our current level ofunderstanding. The basis for the analysis is the crystallographic orientation of the grain as well...... is presented for both fcc and bcc materials inseveral deformation modes, demonstrating a clear grain orientation dependence [Huang & Winther,2007]. This dependence has its origin in a dependence on the slip systems [Winther & Huang, 2007].This further implies that the dislocations in the boundaries come from...

  16. An alternative scheme of the Bogolyubov's average method

    International Nuclear Information System (INIS)

    Ortiz Peralta, T.; Ondarza R, R.; Camps C, E.

    1990-01-01

    In this paper the average energy and the magnetic moment conservation laws in the Drift Theory of charged particle motion are obtained in a simple way. The approach starts from the energy and magnetic moment conservation laws and afterwards the average is performed. This scheme is more economic from the standpoint of time and algebraic calculations than the usual procedure of Bogolyubov's method. (Author)

  17. Comparison of Single and Multi-Scale Method for Leaf and Wood Points Classification from Terrestrial Laser Scanning Data

    Science.gov (United States)

    Wei, Hongqiang; Zhou, Guiyun; Zhou, Junjie

    2018-04-01

    The classification of leaf and wood points is an essential preprocessing step for extracting inventory measurements and canopy characterization of trees from the terrestrial laser scanning (TLS) data. The geometry-based approach is one of the widely used classification method. In the geometry-based method, it is common practice to extract salient features at one single scale before the features are used for classification. It remains unclear how different scale(s) used affect the classification accuracy and efficiency. To assess the scale effect on the classification accuracy and efficiency, we extracted the single-scale and multi-scale salient features from the point clouds of two oak trees of different sizes and conducted the classification on leaf and wood. Our experimental results show that the balanced accuracy of the multi-scale method is higher than the average balanced accuracy of the single-scale method by about 10 % for both trees. The average speed-up ratio of single scale classifiers over multi-scale classifier for each tree is higher than 30.

  18. Scale transformations, the energy-momentum tensor, and the equation of state

    International Nuclear Information System (INIS)

    Carruthers, P.

    1989-01-01

    The Equation of State (EOS) relates diagonal elements of the energy-momentum tensor θ μν . The first moment of the energy-momentum tensor generates scale transformations. The virial theorem, a consequence of the behavior of the energy density under scale transformations, allows one to eliminate the kinetic energy in terms of the potential terms. The trace theorem for the energy-momentum tensor expresses ε-3p in terms of ensemble averages of scale-breaking operators, allowing a new approach to the EOS. 10 refs

  19. Influence of coma aberration on aperture averaged scintillations in oceanic turbulence

    Science.gov (United States)

    Luo, Yujuan; Ji, Xiaoling; Yu, Hong

    2018-01-01

    The influence of coma aberration on aperture averaged scintillations in oceanic turbulence is studied in detail by using the numerical simulation method. In general, in weak oceanic turbulence, the aperture averaged scintillation can be effectively suppressed by means of the coma aberration, and the aperture averaged scintillation decreases as the coma aberration coefficient increases. However, in moderate and strong oceanic turbulence the influence of coma aberration on aperture averaged scintillations can be ignored. In addition, the aperture averaged scintillation dominated by salinity-induced turbulence is larger than that dominated by temperature-induced turbulence. In particular, it is shown that for coma-aberrated Gaussian beams, the behavior of aperture averaged scintillation index is quite different from the behavior of point scintillation index, and the aperture averaged scintillation index is more suitable for characterizing scintillations in practice.

  20. Scaling in multiplicity distributions of heavy, black and grey prongs in nuclear emulsions

    International Nuclear Information System (INIS)

    Nieminen, M.; Torsti, J.J.; Valtonen, E.

    1979-01-01

    The validity of Koba-Nielsen-Olesen scaling hypothesis was examined in the case of heavy, black, and grey prongs in proton-emulsion collisions ('heavy' means 'either black or grey'). The average multiplicities of these prongs were computed in the region 0.1-400 GeV for the nuclei C, N, O, S, Br, Ag, and I. After the inclusion of the energy-dependent excitation probability of the nuclei of the form P* = b 0 + b 1 ln E 0 into the model, experimental multiplicity distributions in the energy region 6-300 GeV agreed satisfactorily with the scaling hypothesis. The ratio of the dispersion D (D = √ 2 >- 2 ) to the average multiplicity in the scaling functions of heavy, balck, and grey prongs was estimated to be 0.86, 0.84, and 1.04, respectively, in the high energy region. (Auth.)

  1. Allometric Scaling in Biology

    Science.gov (United States)

    Banavar, Jayanth

    2009-03-01

    The unity of life is expressed not only in the universal basis of inheritance and energetics at the molecular level, but also in the pervasive scaling of traits with body size at the whole-organism level. More than 75 years ago, Kleiber and Brody and Proctor independently showed that the metabolic rates, B, of mammals and birds scale as the three-quarter power of their mass, M. Subsequent studies showed that most biological rates and times scale as M-1/4 and M^1/4 respectively, and that these so called quarter-power scaling relations hold for a variety of organisms, from unicellular prokaryotes and eukaryotes to trees and mammals. The wide applicability of Kleiber's law, across the 22 orders of magnitude of body mass from minute bacteria to giant whales and sequoias, raises the hope that there is some simple general explanation that underlies the incredible diversity of form and function. We will present a general theoretical framework for understanding the relationship between metabolic rate, B, and body mass, M. We show how the pervasive quarter-power biological scaling relations arise naturally from optimal directed resource supply systems. This framework robustly predicts that: 1) whole organism power and resource supply rate, B, scale as M^3/4; 2) most other rates, such as heart rate and maximal population growth rate scale as M-1/4; 3) most biological times, such as blood circulation time and lifespan, scale as M^1/4; and 4) the average velocity of flow through the network, v, such as the speed of blood and oxygen delivery, scales as M^1/12. Our framework is valid even when there is no underlying network. Our theory is applicable to unicellular organisms as well as to large animals and plants. This work was carried out in collaboration with Amos Maritan along with Jim Brown, John Damuth, Melanie Moses, Andrea Rinaldo, and Geoff West.

  2. Mass-flux subgrid-scale parameterization in analogy with multi-component flows: a formulation towards scale independence

    Directory of Open Access Journals (Sweden)

    J.-I. Yano

    2012-11-01

    Full Text Available A generalized mass-flux formulation is presented, which no longer takes a limit of vanishing fractional areas for subgrid-scale components. The presented formulation is applicable to a~situation in which the scale separation is still satisfied, but fractional areas occupied by individual subgrid-scale components are no longer small. A self-consistent formulation is presented by generalizing the mass-flux formulation under the segmentally-constant approximation (SCA to the grid–scale variabilities. The present formulation is expected to alleviate problems arising from increasing resolutions of operational forecast models without invoking more extensive overhaul of parameterizations.

    The present formulation leads to an analogy of the large-scale atmospheric flow with multi-component flows. This analogy allows a generality of including any subgrid-scale variability into the mass-flux parameterization under SCA. Those include stratiform clouds as well as cold pools in the boundary layer.

    An important finding under the present formulation is that the subgrid-scale quantities are advected by the large-scale velocities characteristic of given subgrid-scale components (large-scale subcomponent flows, rather than by the total large-scale flows as simply defined by grid-box average. In this manner, each subgrid-scale component behaves as if like a component of multi-component flows. This formulation, as a result, ensures the lateral interaction of subgrid-scale variability crossing the grid boxes, which are missing in the current parameterizations based on vertical one-dimensional models, and leading to a reduction of the grid-size dependencies in its performance. It is shown that the large-scale subcomponent flows are driven by large-scale subcomponent pressure gradients. The formulation, as a result, furthermore includes a self-contained description of subgrid-scale momentum transport.

    The main purpose of the present paper

  3. Scalings of energy confinement and density limit in stellarator/heliotron

    International Nuclear Information System (INIS)

    Sudo, S.; Takeiri, Y.; Zushi, H.; Sano, F.; Itoh, K.; Kondo, K.; Iiyoshi, A.

    1989-04-01

    Empirical scaling of energy confinement observed experimentally in stellarator/heliotron (Heliotron E, Wendelstein 7A, L2, Heliotron DR) under the condition that plasmas are heated by ECH and/or NbI is proposed. Empirical scaling of density limit obtainable under the optimum condition is proposed. These scalings are compared with those of tokamaks. The energy confinement scaling has similar power dependence as 'L mode scaling' of tokamaks. The density limit scaling seems also to indicate the upper limit of achievable density in many tokamaks. Combining the energy confinement time and the density limit scaling a transport-limited beta value is also deduced. Thus, from the viewpoint of designing a machine, there should be some compromise in determing magnetic field strength on plasma axis, average minor radius and major radius, because their dependence on confinement time and transport-limited beta value is contradicting. (J.P.N.)

  4. A Statistical Mechanics Approach to Approximate Analytical Bootstrap Averages

    DEFF Research Database (Denmark)

    Malzahn, Dorthe; Opper, Manfred

    2003-01-01

    We apply the replica method of Statistical Physics combined with a variational method to the approximate analytical computation of bootstrap averages for estimating the generalization error. We demonstrate our approach on regression with Gaussian processes and compare our results with averages...

  5. 7 CFR 1209.12 - On average.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 10 2010-01-01 2010-01-01 false On average. 1209.12 Section 1209.12 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS... CONSUMER INFORMATION ORDER Mushroom Promotion, Research, and Consumer Information Order Definitions § 1209...

  6. Forecasting of Average Monthly River Flows in Colombia

    Science.gov (United States)

    Mesa, O. J.; Poveda, G.

    2006-05-01

    The last two decades have witnessed a marked increase in our knowledge of the causes of interannual hydroclimatic variability and our ability to make predictions. Colombia, located near the seat of the ENSO phenomenon, has been shown to experience negative (positive) anomalies in precipitation in concert with El Niño (La Niña). In general besides the Pacific Ocean, Colombia has climatic influences from the Atlantic Ocean and the Caribbean Sea through the tropical forest of the Amazon basin and the savannas of the Orinoco River, in top of the orographic and hydro-climatic effects introduced by the Andes. As in various other countries of the region, hydro-electric power contributes a large proportion (75 %) of the total electricity generation in Colombia. Also, most agriculture is rain-fed dependant, and domestic water supply relies mainly on surface waters from creeks and rivers. Besides, various vector borne tropical diseases intensify in response to rain and temperature changes. Therefore, there is a direct connection between climatic fluctuations and national and regional economies. This talk specifically presents different forecasts of average monthly stream flows for the inflow into the largest reservoir used for hydropower generation in Colombia, and illustrates the potential economic savings of such forecasts. Because of planning of the reservoir operation, the most appropriated time scale for this application is the annual to interannual. Fortunately, this corresponds to the scale at which hydroclimate variability understanding has improved significantly. Among the different possibilities we have explored: traditional statistical ARIMA models, multiple linear regression, natural and constructed analogue models, the linear inverse model, neural network models, the non-parametric regression splines (MARS) model, regime dependant Markovian models and one we termed PREBEO, which is based on spectral bands decomposition using wavelets. Most of the methods make

  7. Cloud-based design of high average power traveling wave linacs

    Science.gov (United States)

    Kutsaev, S. V.; Eidelman, Y.; Bruhwiler, D. L.; Moeller, P.; Nagler, R.; Barbe Welzel, J.

    2017-12-01

    The design of industrial high average power traveling wave linacs must accurately consider some specific effects. For example, acceleration of high current beam reduces power flow in the accelerating waveguide. Space charge may influence the stability of longitudinal or transverse beam dynamics. Accurate treatment of beam loading is central to the design of high-power TW accelerators, and it is especially difficult to model in the meter-scale region where the electrons are nonrelativistic. Currently, there are two types of available codes: tracking codes (e.g. PARMELA or ASTRA) that cannot solve self-consistent problems, and particle-in-cell codes (e.g. Magic 3D or CST Particle Studio) that can model the physics correctly but are very time-consuming and resource-demanding. Hellweg is a special tool for quick and accurate electron dynamics simulation in traveling wave accelerating structures. The underlying theory of this software is based on the differential equations of motion. The effects considered in this code include beam loading, space charge forces, and external magnetic fields. We present the current capabilities of the code, provide benchmarking results, and discuss future plans. We also describe the browser-based GUI for executing Hellweg in the cloud.

  8. Further Validation of the Coach Identity Prominence Scale

    Science.gov (United States)

    Pope, J. Paige; Hall, Craig R.

    2014-01-01

    This study was designed to examine select psychometric properties of the Coach Identity Prominence Scale (CIPS), including the reliability, factorial validity, convergent validity, discriminant validity, and predictive validity. Coaches (N = 338) who averaged 37 (SD = 12.27) years of age, had a mean of 13 (SD = 9.90) years of coaching experience,…

  9. Early Clinical Outcomes Demonstrate Preserved Cognitive Function in Children With Average-Risk Medulloblastoma When Treated With Hyperfractionated Radiation Therapy

    International Nuclear Information System (INIS)

    Gupta, Tejpal; Jalali, Rakesh; Goswami, Savita; Nair, Vimoj; Moiyadi, Aliasgar; Epari, Sridhar; Sarin, Rajiv

    2012-01-01

    Purpose: To report on acute toxicity, longitudinal cognitive function, and early clinical outcomes in children with average-risk medulloblastoma. Methods and Materials: Twenty children ≥5 years of age classified as having average-risk medulloblastoma were accrued on a prospective protocol of hyperfractionated radiation therapy (HFRT) alone. Radiotherapy was delivered with two daily fractions (1 Gy/fraction, 6 to 8 hours apart, 5 days/week), initially to the neuraxis (36 Gy/36 fractions), followed by conformal tumor bed boost (32 Gy/32 fractions) for a total tumor bed dose of 68 Gy/68 fractions over 6 to 7 weeks. Cognitive function was prospectively assessed longitudinally (pretreatment and at specified posttreatment follow-up visits) with the Wechsler Intelligence Scale for Children to give verbal quotient, performance quotient, and full-scale intelligence quotient (FSIQ). Results: The median age of the study cohort was 8 years (range, 5–14 years), representing a slightly older cohort. Acute hematologic toxicity was mild and self-limiting. Eight (40%) children had subnormal intelligence (FSIQ <85), including 3 (15%) with mild mental retardation (FSIQ 56–70) even before radiotherapy. Cognitive functioning for all tested domains was preserved in children evaluable at 3 months, 1 year, and 2 years after completion of HFRT, with no significant decline over time. Age at diagnosis or baseline FSIQ did not have a significant impact on longitudinal cognitive function. At a median follow-up time of 33 months (range, 16–58 months), 3 patients had died (2 of relapse and 1 of accidental burns), resulting in 3-year relapse-free survival and overall survival of 83.5% and 83.2%, respectively. Conclusion: HFRT without upfront chemotherapy has an acceptable acute toxicity profile, without an unduly increased risk of relapse, with preserved cognitive functioning in children with average-risk medulloblastoma.

  10. Early Clinical Outcomes Demonstrate Preserved Cognitive Function in Children With Average-Risk Medulloblastoma When Treated With Hyperfractionated Radiation Therapy

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, Tejpal, E-mail: tejpalgupta@rediffmail.com [Department of Radiation Oncology, Advanced Centre for Treatment Research and Education in Cancer and Tata Memorial Hospital, Mumbai (India); Jalali, Rakesh [Department of Radiation Oncology, Advanced Centre for Treatment Research and Education in Cancer and Tata Memorial Hospital, Mumbai (India); Goswami, Savita [Department of Clinical Psychology and Psychiatry Unit, Advanced Centre for Treatment Research and Education in Cancer and Tata Memorial Hospital, Mumbai (India); Nair, Vimoj [Department of Radiation Oncology, Advanced Centre for Treatment Research and Education in Cancer and Tata Memorial Hospital, Mumbai (India); Moiyadi, Aliasgar [Division of Neuro-Surgery, Department of Surgical Oncology, Advanced Centre for Treatment Research and Education in Cancer and Tata Memorial Hospital, Mumbai (India); Epari, Sridhar [Department of Pathology, Advanced Centre for Treatment Research and Education in Cancer and Tata Memorial Hospital, Mumbai (India); Sarin, Rajiv [Department of Radiation Oncology, Advanced Centre for Treatment Research and Education in Cancer and Tata Memorial Hospital, Mumbai (India)

    2012-08-01

    Purpose: To report on acute toxicity, longitudinal cognitive function, and early clinical outcomes in children with average-risk medulloblastoma. Methods and Materials: Twenty children {>=}5 years of age classified as having average-risk medulloblastoma were accrued on a prospective protocol of hyperfractionated radiation therapy (HFRT) alone. Radiotherapy was delivered with two daily fractions (1 Gy/fraction, 6 to 8 hours apart, 5 days/week), initially to the neuraxis (36 Gy/36 fractions), followed by conformal tumor bed boost (32 Gy/32 fractions) for a total tumor bed dose of 68 Gy/68 fractions over 6 to 7 weeks. Cognitive function was prospectively assessed longitudinally (pretreatment and at specified posttreatment follow-up visits) with the Wechsler Intelligence Scale for Children to give verbal quotient, performance quotient, and full-scale intelligence quotient (FSIQ). Results: The median age of the study cohort was 8 years (range, 5-14 years), representing a slightly older cohort. Acute hematologic toxicity was mild and self-limiting. Eight (40%) children had subnormal intelligence (FSIQ <85), including 3 (15%) with mild mental retardation (FSIQ 56-70) even before radiotherapy. Cognitive functioning for all tested domains was preserved in children evaluable at 3 months, 1 year, and 2 years after completion of HFRT, with no significant decline over time. Age at diagnosis or baseline FSIQ did not have a significant impact on longitudinal cognitive function. At a median follow-up time of 33 months (range, 16-58 months), 3 patients had died (2 of relapse and 1 of accidental burns), resulting in 3-year relapse-free survival and overall survival of 83.5% and 83.2%, respectively. Conclusion: HFRT without upfront chemotherapy has an acceptable acute toxicity profile, without an unduly increased risk of relapse, with preserved cognitive functioning in children with average-risk medulloblastoma.

  11. A depth semi-averaged model for coastal dynamics

    Science.gov (United States)

    Antuono, M.; Colicchio, G.; Lugni, C.; Greco, M.; Brocchini, M.

    2017-05-01

    The present work extends the semi-integrated method proposed by Antuono and Brocchini ["Beyond Boussinesq-type equations: Semi-integrated models for coastal dynamics," Phys. Fluids 25(1), 016603 (2013)], which comprises a subset of depth-averaged equations (similar to Boussinesq-like models) and a Poisson equation that accounts for vertical dynamics. Here, the subset of depth-averaged equations has been reshaped in a conservative-like form and both the Poisson equation formulations proposed by Antuono and Brocchini ["Beyond Boussinesq-type equations: Semi-integrated models for coastal dynamics," Phys. Fluids 25(1), 016603 (2013)] are investigated: the former uses the vertical velocity component (formulation A) and the latter a specific depth semi-averaged variable, ϒ (formulation B). Our analyses reveal that formulation A is prone to instabilities as wave nonlinearity increases. On the contrary, formulation B allows an accurate, robust numerical implementation. Test cases derived from the scientific literature on Boussinesq-type models—i.e., solitary and Stokes wave analytical solutions for linear dispersion and nonlinear evolution and experimental data for shoaling properties—are used to assess the proposed solution strategy. It is found that the present method gives reliable predictions of wave propagation in shallow to intermediate waters, in terms of both semi-averaged variables and conservation properties.

  12. Huvi või sundus - meie valik / Rein Rebane

    Index Scriptorium Estoniae

    Rebane, Rein

    2011-01-01

    Eesti õpilaste tulemused rahvusvaheliste PISA ja TIMSS-i testide põhjal on olnud head. Samadest uuringutest on aga selgunud, et nii Eesti õpilaste kui ka õpetajate rahulolu kooliga on üks madalamaid maailmas

  13. Gradient networks on uncorrelated random scale-free networks

    International Nuclear Information System (INIS)

    Pan Guijun; Yan Xiaoqing; Huang Zhongbing; Ma Weichuan

    2011-01-01

    Uncorrelated random scale-free (URSF) networks are useful null models for checking the effects of scale-free topology on network-based dynamical processes. Here, we present a comparative study of the jamming level of gradient networks based on URSF networks and Erdos-Renyi (ER) random networks. We find that the URSF networks are less congested than ER random networks for the average degree (k)>k c (k c ∼ 2 denotes a critical connectivity). In addition, by investigating the topological properties of the two kinds of gradient networks, we discuss the relations between the topological structure and the transport efficiency of the gradient networks. These findings show that the uncorrelated scale-free structure might allow more efficient transport than the random structure.

  14. FDTD calculation of whole-body average SAR in adult and child models for frequencies from 30 MHz to 3 GHz

    International Nuclear Information System (INIS)

    Wang Jianqing; Fujiwara, Osamu; Kodera, Sachiko; Watanabe, Soichi

    2006-01-01

    Due to the difficulty of the specific absorption rate (SAR) measurement in an actual human body for electromagnetic radio-frequency (RF) exposure, in various compliance assessment procedures the incident electric field or power density is being used as a reference level, which should never yield a larger whole-body average SAR than the basic safety limit. The relationship between the reference level and the whole-body average SAR, however, was established mainly based on numerical calculations for highly simplified human modelling dozens of years ago. Its validity is being questioned by the latest calculation results. In verifying the validity of the reference level with respect to the basic SAR limit for RF exposure, it is essential to have a high accuracy of human modelling and numerical code. In this study, we made a detailed error analysis in the whole-body average SAR calculation for the finite-difference time-domain (FDTD) method in conjunction with the perfectly matched layer (PML) absorbing boundaries. We derived a basic rule for the PML employment based on a dielectric sphere and the Mie theory solution. We then attempted to clarify to what extent the whole-body average SAR may reach using an anatomically based Japanese adult model and a scaled child model. The results show that the whole-body average SAR under the ICNIRP reference level exceeds the basic safety limit nearly 30% for the child model both in the resonance frequency and 2 GHz band

  15. FDTD calculation of whole-body average SAR in adult and child models for frequencies from 30 MHz to 3 GHz

    Energy Technology Data Exchange (ETDEWEB)

    Wang Jianqing [Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Fujiwara, Osamu [Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Kodera, Sachiko [Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Watanabe, Soichi [National Institute of Information and Communications Technology, Nukui-kitamachi, Koganei, Tokyo 184-8795 (Japan)

    2006-09-07

    Due to the difficulty of the specific absorption rate (SAR) measurement in an actual human body for electromagnetic radio-frequency (RF) exposure, in various compliance assessment procedures the incident electric field or power density is being used as a reference level, which should never yield a larger whole-body average SAR than the basic safety limit. The relationship between the reference level and the whole-body average SAR, however, was established mainly based on numerical calculations for highly simplified human modelling dozens of years ago. Its validity is being questioned by the latest calculation results. In verifying the validity of the reference level with respect to the basic SAR limit for RF exposure, it is essential to have a high accuracy of human modelling and numerical code. In this study, we made a detailed error analysis in the whole-body average SAR calculation for the finite-difference time-domain (FDTD) method in conjunction with the perfectly matched layer (PML) absorbing boundaries. We derived a basic rule for the PML employment based on a dielectric sphere and the Mie theory solution. We then attempted to clarify to what extent the whole-body average SAR may reach using an anatomically based Japanese adult model and a scaled child model. The results show that the whole-body average SAR under the ICNIRP reference level exceeds the basic safety limit nearly 30% for the child model both in the resonance frequency and 2 GHz band.

  16. The average covering tree value for directed graph games

    NARCIS (Netherlands)

    Khmelnitskaya, Anna Borisovna; Selcuk, Özer; Talman, Dolf

    We introduce a single-valued solution concept, the so-called average covering tree value, for the class of transferable utility games with limited communication structure represented by a directed graph. The solution is the average of the marginal contribution vectors corresponding to all covering

  17. The Average Covering Tree Value for Directed Graph Games

    NARCIS (Netherlands)

    Khmelnitskaya, A.; Selcuk, O.; Talman, A.J.J.

    2012-01-01

    Abstract: We introduce a single-valued solution concept, the so-called average covering tree value, for the class of transferable utility games with limited communication structure represented by a directed graph. The solution is the average of the marginal contribution vectors corresponding to all

  18. 18 CFR 301.7 - Average System Cost methodology functionalization.

    Science.gov (United States)

    2010-04-01

    ... 18 Conservation of Power and Water Resources 1 2010-04-01 2010-04-01 false Average System Cost... REGULATORY COMMISSION, DEPARTMENT OF ENERGY REGULATIONS FOR FEDERAL POWER MARKETING ADMINISTRATIONS AVERAGE SYSTEM COST METHODOLOGY FOR SALES FROM UTILITIES TO BONNEVILLE POWER ADMINISTRATION UNDER NORTHWEST POWER...

  19. Écoulement polyphasique dans un milieu poreux stratifié. Résultats expérimentaux et interprétation par la méthode de prise de moyenne à grande échelle Multiphase Flow in Stratified Porous Media Experimental Results and Interpretation by the Large-Scale Averaging Method

    Directory of Open Access Journals (Sweden)

    Bertin H.

    2006-11-01

    Full Text Available Nous abordons l'étude des écoulements polyphasiques en milieu poreux hétérogène d'un point de vue théorique (méthodologie de la prise de moyenne à grande échelle et expérimental. Dans une première partie nous présentons la méthodologie permettant d'obtenir les équations à grande échelle. Le point de départ de l'étude est les équations locales, analogues aux équations de Darcy généralisées obtenues par prise de moyenne des équations de Stokes à l'échelle du pore. La prise de moyenne à grande échelle de ces équations permet d'écrire un système d'équations où les coefficients de transport équivalents sont calculés à partir des données locales, par la résolution d'un problème de fermeture explicité dans le cas quasi-statique (effets capillaires dominants. La seconde partie de notre travail concerne l'étude expérimentale d'un écoulement eau-huile dans un milieu poreux stratifié constitué de deux régions de caractéristiques physiques différentes. Les champs de saturation bidimensionnels sont mesurés tout au long de l'imbibition par absorption d'un rayonnement gamma. Les résultats expérimentaux, évolution de la fraction volumique moyenne par section en fonction du temps, sont comparés aux résultats d'une simulation numérique des équations de transport où les coefficients utilisés ont été déterminés par la méthode de prise de moyenne à grande échelle. Two-phase flow in heterogeneous porous media is studied from a theoretical point of view (the large-scale averaging method and experimentally. In the first part, we present the methodology leading to the large-scale equations. The starting point of the study is the local equation, analogous to the generalized Darcy's law obtained by averaging the Stokes equation at the pore level. The large-scale averaging of these equations leads to a system where the equivalent transport coefficients are computed from the local data by solving a closure

  20. Average multiplications in deep inelastic processes and their interpretation

    International Nuclear Information System (INIS)

    Kiselev, A.V.; Petrov, V.A.

    1983-01-01

    Inclusive production of hadrons in deep inelastic proceseseus is considered. It is shown that at high energies the jet evolution in deep inelastic processes is mainly of nonperturbative character. With the increase of a final hadron state energy the leading contribution to an average multiplicity comes from a parton subprocess due to production of massive quark and gluon jets and their further fragmentation as diquark contribution becomes less and less essential. The ratio of the total average multiplicity in deep inelastic processes to the average multiplicity in e + e - -annihilation at high energies tends to unity