Factors Influencing the Wear Behavior of Sintered Steels

A review was made on the research progress of wear behavior of sintered steels in recent years.Wear is not an intrinsic property of sintered steels,which is strongly influenced by the wear test conditions.Howerver,many other factors that determine the mechanical properties of sintered steels also affect the wear behavior.Porosity has different effects on the wear of sintered steels depending on the application conditions.Under dry sliding condition ,higher porosity results in lower wear resistance.The influence of microstructures on wear resistance is in the order;Carbide,martensite,bainite and lamellar pearlite,The wear resistance increases with hardness,but this relationship changes with the porosity and microstructures of sintered steels.     

What Paves the Way to Conventional Language? The Predictive Value of Babble,Pointing, and Socioeconomic Status

A child's first words mark the emergence of a uniquely human ability. Theories of the developmental steps that pave the way for word production have proposed that either vocal or gestural precursors are key. These accounts were tested by assessing the developmental synchrony in the onset of babbling, pointing, and word production for 46 infants observed monthly between the ages of 9 and 18 months. Babbling and pointing did not develop in tight synchrony and babble onset alone predicted first words. Pointing and maternal education emerged as predictors of lexical knowledge only in relation to a measure taken at 18 months. This suggests a far more important role for early phonological development in the creation of the lexicon than previously thought.     

Individually Weighted-Average Models: Testing a Taxonomic SEM Approach Across Different Multidimensional/Global Constructs Because the Weights “Don’t Make No Nevermind”

From the time of William James, psychologists have posited individually importance-weighted-average models (IWAMs) in which weighting specific attributes by individual measures of importance improves prediction of the global outcome measures. Because IWAMs cause much confusion, we briefly review a general taxonomic paradigm and structural equation models for testing IWAMs, and demonstrate its application for 2 simulated and 3 diverse “real” data applications (multidimensional measures of self-concept, quality of life, and job satisfaction). Consistent across the real data applications and previous research more generally, there is surprisingly little support for IWAMs when tested appropriately. In these diverse tests of IWAMs we integrate new approaches such as exploratory structural equation modeling (SEM), alternative approaches to constructing latent interactions, application of bifactor models, modeling method and item-wording effects, and the juxtaposition of model evaluation in relation to goodness of fit (typically used in SEM studies) and variance explained (typically used in multiple regression tests of IWAMs).     

A Comparison of Techniques for Handling and Assessing the Influence of Mobility on Student Achievement

Conventional multilevel modeling works well with purely hierarchical data; however, pure hierarchies rarely exist in real datasets. Applied researchers employ ad hoc procedures to create purely hierarchical data. For example, applied educational researchers either delete mobile participants' data from the analysis or identify the student only with the last school attended while including an explanatory variable indicating whether a student is mobile. This simulation study compared the parameter and standard error estimates of these two ad hoc procedures for handling and assessing the influence of mobility on outcomes with results based on use of the multiple membership random effects model. Substantial bias was found for some parameters when multiple membership data structures were ignored.     

Academic resilience and its psychological and educational correlates: A construct validity approach

This study examines educational and psychological correlates of academic resilience using within‐network and between‐network validity approaches. Based on a sample of 402 Australian high‐school students, a newly developed unidimensional academic resilience construct found within‐network validity by way of sound item and factor properties. In terms of between‐network validity, correlation, path analysis, and cluster analysis showed that five factors predict academic resilience: self‐efficacy, control, planning, low anxiety, and persistence. Hence, a 5‐C model of academic resilience is proposed: confidence (self‐efficacy), coordination (planning), control, composure (low anxiety), and commitment (persistence). Path analysis also showed that academic resilience subsequently predicts three educational and psychological “outcomes”: enjoyment of school, class participation, and general self‐esteem. © 2006 Wiley Periodicals, Inc. Psychol Schs 43: 267–281, 2006.     

Agriculture as a subject in primary school

Many countries have included agriculture as a subject in primary school for a number of reasons. The present article briefly presents five rationales for including agriculture and offers three main approaches which seem to emerge from current practice. The main results of the subsequent discussion can be summarized as follows: integrating education with rural development most of the time would mean including agriculture as a subject in primary schools in rural areas and compensating it in core curriculum with some sort of practical subject taught in urban areas. It becomes clear that narrow vocational and extension-support approaches to school agriculture should be avoided in favour of a more general approach which relates agriculture to science. Unless these problems — curricular, technical, and organizational — are tackled, the results of school agriculture and its acceptance by those concerned will remain far behind expectations and possibilities.

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Zusammenfassung Zahlreiche Länder haben aus einer Vielzahl von Gründen Landwirtschaftskunde als Primarschulfach eingeführt. Die vorliegende Studie unterbreitet verschiedene Grundprinzipien für das Einbeziehen von Landwirtschaftskunde ins Curriculum und bietet drei Hauptansätze, die anscheinend aus derzeit üblichen Praktiken entstehen. Die wichtigsten Ergebnisse der damit zusammenhängenden Diskussion können folgendermaßen zusammengefaßt werden: Die Verknüpfung von Erziehung mit ländlicher Entwicklung bedeutet meistens, Landwirtschaft als ein Primarschulfach in ländlichen Gebieten einzubeziehen und im Kerncurriculum durch ein in städtischen Bereichen unterrichtetes praktisches Fach zu ersetzen. Es wird klar, daß Ansätze zur Landwirtschaft als Schulfach, die im engeren Sinne berufsbezogen sind oder die landwirtschaftliche Beratung fördern, zugunsten eines allgemeineren, Landwirtschaft mit Wissenschaft verknüpfenden Ansatzes vermieden werden sollten. Wenn diese Probleme curricularer, technischer und organisatorischer Art nicht gelöst werden können bleiben die Erfolge der Schullandwirtschaft und ihre Anerkennung durch die Betroffenen nicht nur weit hinter den Erwartungen anderer, sondern auch hinter ihrer, Möglichkeiten zurück.

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Résumé Plusieurs raisons ont améné de nombreux pays à introduire l'agriculture en tant que matière dans le contenu du programme d'études, de l'école primaire. Cet article présente brièvement cinq raisons d'être de l'introduction de cette nouvelle matière et trois approches principales qui semblent émerger de pratiques courantes. Les principaux résultats de la discussion subséquente peuvent être résumés de la façon suivante; l'intégration de l'éducation dans le développement rural signifie presque toujours introduire l'agriculture en tant que matière dans le plan d'études des écoles primaires des zones rurales et compenser cet enseignement par celui d'un sujet pratique dans les zones urbaines. Il apparaît évident que les approches purement professionnelles ou d'aide au développment de cette matière doivent être évitées en faveur d'une approche plus générale qui établirait une relation entre l'agriculture et la science. Les résultats de cette matière enseignée à l'école et sa réception par les personnes concernées resteront bien au-delà des espérances et des possibilités, si ces problèmes curriculaires, techniques et organisationnels ne sont pas résolus.

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For materials published by GTZ please write to: GTZ (Deutsche Gesellschaft für Technische Zusammenarbeit GmbH), Postfach 5180, D-6236 Eschborn 1, Federal Republic of Germany.     

美德

甜美的白昼,如此凉爽、安宁、明媚! 天地间完美的匹配-- 今宵的露珠儿将为你的消逝而落泪; 因为你必须离去.     

Quality of education and the demand for education — Evidence from developing countries

The relationship between quality and demand is analysed using data from various countries, with special emphasis on Burkina Faso, Mali, and Tanzania. Four types of educational quality are postulated: value, output, process and input quality. The relative importance of quality compared to external efficiency and costs is assessed. The paper is a reanalysis of existing studies. Qualitative data are complemented by simple analysis of educational statistics. The studies had different though over-lapping foci: one study explored reasons for non-enrolment, drop-out and exclusion from school under the umbrella theme of the quality of education. Another one emphasised social demand in rural areas, with quality one of a number of topics. A third study looked at attitudes towards education and educational strategies, restricting itself to parents. A primary level, the quality of education influences the demand for education. The relative importance of quality varies from one context to another. Quality influences the decision to enrol less than the decision to carry on. However, it affects enrolment to such an extent that moderate correlations have been observed between pass rates and repeater rates on the one hand, and enrolment rates on the other. Value quality is mainly related to enrolment. Output quality is the criterion for selecting a school or a school system. Output, process and input quality affect dropping out and irregular attendance. Repetition, justified on unsatisfactory output quality, is related to input quality. The decision to participate in education combines considerations of educational quality with an evaluation of costs, both direct costs and opportunity costs.