No description available.

No description available.

The increasing emphasis on teaching arithmetic meaningfully intensifies the search for materials of instruction which can effectively communicate arithmetical understandings to children. Though manipulative aids are widely approved as effective teaching media for achieving this purpose, most of the endorsements are subjective opinions rather than objective evaluations based on experimentation. This study is an attempt to determine the effectiveness of group instruction use of certain manipulative aids in teaching decimal fraction concepts to Grade VII pupils. The effectiveness was determined by comparing the achievement of two unselected groups, randomly assigned, on a test of understanding of the processes involved in decimal fractions. The two groups were given teaching treatments identical except in so far as the materials of instruction were concerned. One group used manipulative aids; the other used static representations of these aids. These materials were intended to differ only with respects to the characteristic of manipulability. Since manipulability of concepts is the most essential property of manipulative aids, it was isolated as the experimental variable. Because the groups were randomly assigned, analysis of covariance was selected to control statistically the initial differences between groups in the four variables considered likely to influence achievement on the criterion test: initial understanding of the processes involved in decimal fractions, computational ability in decimal fractions, mental ability, and reading ability. The data obtained from the investigation were analyzed and the following conclusions reached. 1. The pupils taught by means of group instruction with the manipulative aids used in this investigation did not acquire a significantly better understanding of decimal fractions than did the pupils taught with static representations of these aids. In other words, the manipulation of the concepts, performed by using the manipulative aids in group demonstrations, was not effective in contributing to the pupils’ understanding of these concepts. 2. A study of the correlations for both treatment groups between achievement on the criterion variable and achievement on each of the independent variables indicates that the manipulative aids proved to be neither more nor less effective than the static representations as media for conveying an understanding of decimal fractions to pupils of any particular ability in the areas represented by the independent variables. 3. It must not be inferred that any generalization concerning the effectiveness of these specific materials of instruction, used exclusively by the teacher for group demonstration purposes, would be applicable also to similar materials if they were used in a teaching procedure in which the pupils themselves, participated individually in the manipulative activity. It must not be inferred that any generalization concerning the effectiveness of these specific materials of instruction, which were used in a brief teaching assignment devoted exclusively to the rationalization of processes, would be applicable also to the same materials if they were used in a teaching assignment of longer duration, and/or a teaching assignment in which the emphasis on the WHY of the processes was taught concurrently with, or preceded, the emphasis on the HOW of the processes. 5. Independently of treatment groups, the achievement on the initial test of understanding of the processes involved in decimal fractions was the variable most predictive of achievement on the final test of understanding. Computational ability in decimal fractions and mental ability each shared approximately one-half the predictive capacity of the initial test of understanding. Reading ability was a negligible predictor of achievement on the final test of understanding. / Education, Faculty of / Graduate

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No description available.

International Telemetering Conference Proceedings / October 22-25, 2001 / Riviera Hotel and Convention Center, Las Vegas, Nevada / The Range Commanders Council (RCC) Range Safety Group (RSG) is conducting a study into the next generation of ground-based flight termination technology, known as the Enhanced Flight Termination System (EFTS) study. The study was initiated by the RCC in April 2000 and scheduled to be complete in March 2002. The Government is performing the study with support from contractors and academia. In addition to the RSG, the Telemetry Group, Frequency Management Group, Telecommunications and Timing Group of the RCC support the study. Additionally, the National Security Agency is providing key support along with vendors who design, build, and test range safety systems. This paper will describe the background, goals, and current status of the study.

Thesis (MEd)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: Research shows that misconceptions about calculations develop in many classrooms without being noticed and these are not corrected by repeated routine exercises. The misconceptions formed are at times the result of inappropriate models used to solve problems. An even bigger concern is that these particular models sometimes provide the correct answers by accident. This may result in the learner's belief in the models being reinforced, as described by Swan (n.d.). The aim of this study is to identify the misconceptions related to the use of decimal fractions by Grade 8 and 9 learners and then, through the use of an intervention program, to address the learners' misconceptions and attempt to correct them. Two schools were involved in this study. The group of learners from school A served as a control group to determine the success of the intervention in learners from school B. The results of school A, the frequency and nature of errors were compared with the test results of school B as well as described by interviews with learners from school B. After the diagnostic tests and interview, the learners' answers were compared with those already described in literature. The learners from school B participated voluntarily in the intervention program. Learners from both schools wrote a post-test and the results were compared with those of a pre-test. The conclusion of this study is that there are misconceptions concerning calculations with decimal fractions at Grade 8 and 9 level. These misconceptions are formed during the intermediate phase and are not suitably corrected. The intervention program, for various reasons, had limited success. These reasons are discussed and recommendations are made for future intervention programs. / AFRIKAANSE OPSOMMING: Navorsing toon dat wanbegrippe ten opsigte van berekeninge in baie klaskamers onopgemerk verbygaan en dat dit nie reggestel word deur herhaalde roetine oefeninge nie. Wanbegrippe wat kinders vorm is onder andere die gevolg van onvanpaste modelle wat gebruik word vir die oplos van probleme. 'n Groter gevaar is dat hierdie onvanpaste modelle toevallig die regte antwoord lewer. Dit kan dan veroorsaak dat die leerder se vertroue op die modelle net versterk word, soos Swan (s.j.) dit beskryf. Die doel van hierdie studie is om wanbegrippe ten opsigte van bewerkings met desimale breuke by Graad 8 en 9 leerders te identifiseer en dan deur middel van 'n intervensieprogram die leerders se wanbegrippe aan te spreek en te probeer regstel. Twee skole is by hierdie studie betrek. Die groep leerders van skool A sou dien as 'n kontrolegroep om die intervensie-sukses van die leerders van skool B te bepaal. Die skool A resultate en frekwensie van foute asook die aard daarvan is vergelyk met die toetse van skool B en beskryf op grond van onderhoude met die leerders van skool B. Ná die diagnostiese toets en onderhoud is die leerders se antwoorde vergelyk met dié wat reeds in die literatuur beskryf is. Die leerders van skool B is op vrywillige basis by 'n intervensieprogram betrek. Beide skole se leerders het daarna 'n natoets geskryf en die resultate is vergelyk met dié van die voortoets. Die gevolgtrekking wat uit hierdie studie gemaak word, is dat daar wanbegrippe ten opsigte van bewerkings met desimale breuke op graad 8 en 9 vlak aanwesig is. Hierdie wanbegrippe is in die intermediêre fase gevorm en nie reggestel nie. Die intervensieprogram het om verskeie redes slegs beperkte sukses gehad. Hierdie redes word bespreek en aanbevelings word gemaak vir toekomstige intervensieprogramme.

Although there is research into student learning on the Web and other computer-supported environments, there has been little investigation into the practice and pedagogy of university Web teachers. This qualitative study used a series of interviews of eight higher education faculty to gather data on their Web teaching practices, and an examination of their Web courses to identify their pedagogies. There was a notable difference in the way the four teachers with Web-assisted courses and the four teachers with Web-only courses used the Web in their teaching. Those with Web-assisted courses used the Web primarily as a connection to expanded resources and a supplement to their face-to-face teaching. Those who taught Web-only courses used the Web for resource access, and also used asynchronous dialogue and peer interactions to support student construction of knowledge. Moreover, the Web-only teachers reported a shift in their roles from lecturer and expert in the classroom to facilitator and co-learner as Web teachers. Four aspects of the Web teaching environment appear to be foundational in supporting an effective Web pedagogy: (1) the varied and extensive uses of e-mail, (2) the "think time" made possible by asynchronous dialogue, (3) distributed, hyperlinked learning, and (4) a reported shift from a content focus to process and issues because Web instructors are confident that the material is presented in the Web course as they wish it. The experiences of the Web teachers in the study would indicate that these four elements can be leveraged to improve university Web teaching and deepen student learning, perhaps even beyond results capable of achievement in face-to-face teaching. / Graduation date: 1999

Due to the increased consumption of energy in the modern era, many new installations of different energy solutions are required. One of the more preferred is the renewable category, which governs vast technologies ranging from wind, solar, hydro, and nuclear power. One major issue is that they are usually located up to thousands of kilometers away from the load source. Thus, a reliable transmission system is a must. For such applications, a high-voltage direct current power transmission system (HVDC) is the favorable option, most of the modern types use a modular multilevel voltage source converter (MMC) to execute the AC/DC conversion and vice versa. The control of such devices is ultimately dependent on the modulation method, it serves as a key component of the stability of the whole system. Four different variants of description for such a control method are found in the published literature, as more methods can be found, but the focus is on the four introduced. Therefore, the aim of this master's thesis is to investigate how the highlighted standard modulation methods affect the total system's behavior. Note that the implementation by the company, referred to in this context as the benchmark method, is being compared to assess its efficacy against established standard modulation methods. Detailed comparison involving this method is intentionally omitted. First, the underlying system components are described using circuit topology, which serves as the first course before the analytical derivation using dynamic modeling. By obtaining the final dynamic expression and equation for the insertion index, a detailed control strategy is displayed. The total control system is separated into two parts, one governed by the higher-level controllers and one governed by the modulation methods. As the former is predefined and given, therefore, it will be referred to as the "black box." Then a comprehensive method regarding the implementation of modulation methods is provided, serving as the most crucial part of the work. Several different studies are conducted, including harmonic analysis, fault studies, impedance scanning, and screening studies of torsional interaction. The result indicated that some degree of differences can be concluded between the modulation methods, several cases showed that controlling done in a closed loop manner is the preferred option due to its accuracy and robustness. Some of the investigated modulation methods showed severe oscillations in circumstances where the connected grids were weak. Due to the complexity of the overall system, including higher-level controllers, no direct conclusion can be drawn to definitively say whether any of the modulation methods have a clear advantage in every tested aspect. But at least, based on the results obtained in this work, in this specific simulation set-up, the closed loop method is indeed the preferred option.

Prions são agentes etiológicos das encefalopatias espongiformes transmissíveis, doenças que acometem tanto homens quanto animais. A proteína infecciosa, PrPsc, é uma isoforma de uma proteína celular normal denominada PrPc. As funções de PrPc ainda causam controvérsia na literatura, mas já foi demonstrada a participação de PrPc em uma variedade de fenômenos biológicos, como homeostase de íons cobre, proteção contra estresse oxidativo, sinalização celular e neuritogênese entre outros. A interação de PrPc com laminina, uma proteína de matriz extracelular, leva a formação e manutenção de neuritos em neurônios hipocampais. Seguindo este caminho, demonstramos no presente trabalho a interação de PrPc com outra proteína de matriz extracelular, vitronectina (Vn). Esta interação também leva ao crescimento neurítico, tanto em células do sistema nervoso central quanto do sistema nervoso periférico. No sistema nervoso periférico, a ausência de PrPc é compensada por integrinas, no fenômeno da neuritogênese. Relatamos também que a interação de PrPc com STI1, uma cochaperonina, leva tanto a neuritogênese quanto a neuroproteção por vias de sinalização distintas. A ligação de PrPc com Vn e STI1 se dá através de domínios contíguos, de modo que as interações são excludentes sendo aquela com Vn mais favorável, como observado em ensaios de ligação in vitro, quanto através do fenômeno de neuritogênese. Já a ligação de laminina se dá em um domínio distante daqueles de ligação à Vn e STI1. Assim, pode ser observada cooperatividade entre laminina e STI1 no fenômeno da neuritogênese. Por fim, demonstra-se que a interação PrPc-laminina in vivo é importante para os mecanismos de consolidação da memória. / Prions are involved in numerous neurodegenerative diseases in humans and animals called transmissible spongiform encephalopathies. PrPsc, the infectious protein, is an isoform of a normal cellular protein named PrPc. PrPc functions are still under debate, among them Cu++ homeostase, protection against oxidative stress, cell survival signaling and neuritogenesis. PrPc interaction with laminin (Ln), an extracellular matrix protein, leads to neurite growth and maintenance. PrPc interaction with another extracellular matrix protein, vitronectin (Vn) is here demonstrated. This association leads to neurite growth in hippocampal and dorsal root ganglia cells. In dorsal root ganglia cells, PrPc ablation can be compensated by integrins, at least in the neuritogenesis phenomenon. PrPc is also a cellular ligand for STI1, a co-chaperone, mediating neuritogenesis or neuroprotection, depending on the activated cell signaling pathway. Vn and STI1 binding sites at the PrPc molecule are localized in contiguous domains what makes their binding to PrPc mutually exclusive. The first is more favorable, as observed in vitro and ex vivo. On the other hand, Ln binding site at PrPc is confined to a domain distinct from those where Vn or STI1 associate. Furthermore, laminin and STI1 have additive effects on neurite outgrowth. The importance of PrPc-Ln interaction is also observed in vivo, since the complex participates in memory consolidation mechanisms.