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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
441

A Line Outage Study for Prediction of Static Power Flow Redistribution

Wei, Nan 06 September 2016 (has links)
Transmission line is a crucial role in power transmission network which connects generating units to consumers. Some unpredicted failure events such as lightening or system faults can cause transmission line tripped, which may bring about a large interruption to the system and causes damage. When line outage happens, the power flow on the tripped line will be redistributed to the rest of lines in the system. It may cause risk of overload happens on other lines, and results in a cascading failure and system collapse. Reasonably, a single line outage will not affect all other lines in the system. Therefore, when a line outage happens, it is important for the system operator to have a preview of which lines will have serious impact and which lines will not, so that the operator can only focus on monitoring certain lines which will be seriously affected, rather than keeping monitoring the whole system. In this thesis, A Line Outage Distribution Factor (LODF) method is proposed and implemented in the IEEE 118 bus system to estimate active power flow redistribution after a line outage. After that, a definition of Thevenin electrical distance between two transmission lines is derived and applied to calculate electrical distances between the outage line and each line in the system. An exponential convergence tendency is found between maximum possible LODF predicted power flow variations and electrical distance, and an exponential regression method is applied to analyze this tendency. The contribution of this work is a rule has been found that starting from the outage line, the maximum possible active power flow variation on transmission lines exponentially decreases exponentially while the electrical distance increases. With only the information of system's normal operating condition and topological information, the maximum possible active power change on each lines caused by single line outage, and the margin of the impact of single line outage on power flow variations may propagate along electrical distance can be easily and quickly predicted. Ultimately, the goal of this work is to allow operators at the control center can concentrate on lines within a certain electrical distance instead of keeping monitoring the whole system when a line outage happens. / Master of Science
442

The application of simulated annealing to the mixed model, deterministic assembly line balancing problem

Edwards, Sherry L. 19 May 2010 (has links)
With the trend towards greater product customization and shorter delivery time, the use of mixed model assembly lines is increasing. A line balancing approach is needed that can address the complex nature of the mixed model line and produce near optimal solutions to problems of realistic size. Due to the combinatorial nature of the line balancing problem, exact solution techniques are limited to small problems. Heuristic methods, on the other hand, are often too simplistic to find good solutions. Furthermore, many of the existing techniques cannot be expanded to handle the mixed model problem. Simulated Annealing (SA) is a search methodology which has exhibited good results when applied to combinatorial optimization problems. In fact, researchers have found that SA is able to find near-optimal solutions while its processing time increases only as a polynomial function of problem size. However, none of the applications found in the literature fully explore the technique's ability to handle a highly-constrained problem such as line balancing. / Master of Science
443

A computerized methodology for balancing and sequencing mixed model stochastic assembly lines

Pantouvanos, John P. 21 July 2009 (has links)
A methodology for designing mixed model stochastic assembly line systems and a computer package to implement it for realistic problem sizes were developed. The methodology consists of three major steps: (1) generation of feasible sequences of feeding models into the line, (2) generation of feasible allocations (balances) of work elements to work stations, and (3) generation of combinations of sequences and allocations with the best ordering of elements within stations, calculation of total expected cost for each combination, and selection of the one with the least cost. For generating feasible balances, an exhaustive search procedure with a number of heuristic rules was used to ensure searching the whole feasible region in limited time. A cost model based on labor and incompletion costs is used to calculate the cost of each combination, and a recursive procedure to calculate incompletion probabilities for each element and incorporate them into the cost model was implemented. An example problem, its results, and the computer package listings are included. / Master of Science
444

Balancing a job shop with alternative computer-aided time standards

Hankins, Steven Lee January 1983 (has links)
This research focuses on the use of computer-aided alternative time standards to balance the workload in a job shop. An example computer-aided time standards data base is presented along with the computer software to access the data base for the calculation of alternative time standards. Three machine loading algorithms are proposed to perform the workload balance, and the effectiveness of the algorithms is tested through the results of a computer simulation. It is shown that an algorithm which is unique to the literature produces results which approach the results of a complete enumeration algorithm. / M.S.
445

Curso em ambiente virtual de aprendizagem: canteiro para germinação de comunidade de aprendizagem on line / Course offered in a LMS: garden for the sprout of an on-line community.

Queiroz, Vera Cristina 05 April 2005 (has links)
A presente pesquisa configura-se como um estudo de caso de natureza qualitativa que procurou analisar e tecer algumas considerações importantes a respeito de um curso livre experimental de inglês básico on-line - denominado Beginner Grammar Writing (BGW)-, com enfoque no desenvolvimento das habilidades de leitura e de escrita. Esse curso foi oferecido para alunos de diferentes países cuja língua materna não é o inglês, e ministrado, concomitantemente, por duas professoras da área, residentes em países distintos. Procurou-se verificar se o curso, que adotou uma metodologia de ensino-aprendizagem colaborativa/comunicacional, veio a se tornar uma comunidade de aprendizagem, a partir das características apontadas por vários teóricos, e das quais elegemos as seguintes: interesses comuns, empatia, sociabilidade colaborativa e tempo de exposição no grupo. Os dados obtidos foram coletados ao longo do curso em questão, no primeiro momento em que foi oferecido. Esses dados consistem em documentos digitais do curso (tais como e-mail dos alunos, e-mail trocados entre as professoras, registros de participação dos estudantes no fórum e em sessões de chat) e na observação participante da professora/pesquisadora ao longo de todo o curso. O estudo fundamentou-se nas teorias da comunicação escolar, comunicação on-line, de aprendizagem colaborativa e no referencial teórico a respeito de comunidades virtuais (de aprendizagem). A reflexão sobre os dados recolhidos e a análise efetuada apontaram algumas questões relevantes a respeito de ensino de inglês on-line na perspectiva de uma metodologia de ensino-aprendizagem colaborativo/ comunicacional e mostraram que o curso BGW atingiu o objetivo de promover a aprendizagem coletiva. A análise de dados confirmou ainda que uma comunidade de aprendizagem foi criada e é mantida como tal a partir do curso BGW aqui estudado. / The present study is a qualitative case study of an experimental English basic on-line course, entitled Beginner Grammar Writing (BGW), with emphasis on the development of writing and reading skills. This course was offered to students from different countries, whose native language was not English, and was delivered simultaneously by two teachers of English, resident in distinct countries. The study attempted to verify whether the students in the course, which adopted a teaching and learning collaborative/communicational methodology, became a learning community from the characteristics described by several theoreticians and from which we selected the following: common interests, empathy, collaborative sociability and time of exposure in the group. The data were collected from the course when it was first offered. Data consisted of digital documents (such as students´ e-mail, e-mail exchanged between the teachers, questionnaires, registers of students´ participation in the discussion forum and in the chat sessions, and some others) and the participative observation of the teacher/researcher throughout the course. The theoretical framework was based on the communicative theory, the collaborative learning approach and the theoretical referential on virtual learning communities. The data showed that the BGW course reached its objective of promoting a collective learning. The data also confirmed that a learning community was created and is maintained as so from the course studied.
446

Curso em ambiente virtual de aprendizagem: canteiro para germinação de comunidade de aprendizagem on line / Course offered in a LMS: garden for the sprout of an on-line community.

Vera Cristina Queiroz 05 April 2005 (has links)
A presente pesquisa configura-se como um estudo de caso de natureza qualitativa que procurou analisar e tecer algumas considerações importantes a respeito de um curso livre experimental de inglês básico on-line - denominado Beginner Grammar Writing (BGW)-, com enfoque no desenvolvimento das habilidades de leitura e de escrita. Esse curso foi oferecido para alunos de diferentes países cuja língua materna não é o inglês, e ministrado, concomitantemente, por duas professoras da área, residentes em países distintos. Procurou-se verificar se o curso, que adotou uma metodologia de ensino-aprendizagem colaborativa/comunicacional, veio a se tornar uma comunidade de aprendizagem, a partir das características apontadas por vários teóricos, e das quais elegemos as seguintes: interesses comuns, empatia, sociabilidade colaborativa e tempo de exposição no grupo. Os dados obtidos foram coletados ao longo do curso em questão, no primeiro momento em que foi oferecido. Esses dados consistem em documentos digitais do curso (tais como e-mail dos alunos, e-mail trocados entre as professoras, registros de participação dos estudantes no fórum e em sessões de chat) e na observação participante da professora/pesquisadora ao longo de todo o curso. O estudo fundamentou-se nas teorias da comunicação escolar, comunicação on-line, de aprendizagem colaborativa e no referencial teórico a respeito de comunidades virtuais (de aprendizagem). A reflexão sobre os dados recolhidos e a análise efetuada apontaram algumas questões relevantes a respeito de ensino de inglês on-line na perspectiva de uma metodologia de ensino-aprendizagem colaborativo/ comunicacional e mostraram que o curso BGW atingiu o objetivo de promover a aprendizagem coletiva. A análise de dados confirmou ainda que uma comunidade de aprendizagem foi criada e é mantida como tal a partir do curso BGW aqui estudado. / The present study is a qualitative case study of an experimental English basic on-line course, entitled Beginner Grammar Writing (BGW), with emphasis on the development of writing and reading skills. This course was offered to students from different countries, whose native language was not English, and was delivered simultaneously by two teachers of English, resident in distinct countries. The study attempted to verify whether the students in the course, which adopted a teaching and learning collaborative/communicational methodology, became a learning community from the characteristics described by several theoreticians and from which we selected the following: common interests, empathy, collaborative sociability and time of exposure in the group. The data were collected from the course when it was first offered. Data consisted of digital documents (such as students´ e-mail, e-mail exchanged between the teachers, questionnaires, registers of students´ participation in the discussion forum and in the chat sessions, and some others) and the participative observation of the teacher/researcher throughout the course. The theoretical framework was based on the communicative theory, the collaborative learning approach and the theoretical referential on virtual learning communities. The data showed that the BGW course reached its objective of promoting a collective learning. The data also confirmed that a learning community was created and is maintained as so from the course studied.
447

Zmapování vhodných pražských parků a cyklostezek pro volnočasové aktivity se zaměřením na výuku in-line bruslení pro žáky 1. stupně / Mapping appopriate Prague parks and trails for leisure activities focused on in-line skating for the pupils of a primary school

Suchý, Jan January 2011 (has links)
In the introduction of theoretical part, a sport discipline In line skating is described. Legislative aspect together with use of cycle paths is considered.The second chapter describes system of cyclopaths in the cities. Following chapters are describing the concept of parks and cyclopaths development in the rural area until 2020. Next, the work establishes criteria for evaluation of locations discussed in charter 5. Theoretical part of this work discusses in chapter six general rules for cyclopaths and park use. In chapter seven traffic signalization and in line skaters' equipment are discussed. Further chapters focus on sport and safety equipment. In the end of theoretical part of chapter ten and eleven I comment on particularities of in line skating education for children 7- 10 years old. Practical part describes mapping and evaluation of 10 selected cyclopaths located on the left side of Vltava River and close surroundings in chapter 12-13. Chapter 14 is dedicated to in-line skating and its categories. In the end of the practical part, the structure and methodology of teaching lesson of in-line skating is depicted together with description of basics of in line skating. Appendix consists of graphical comparison of results from public survey Keywords In-line skating, skating lessons, mapping of...
448

Rovibrational study of DNO3 nu5 band and collisional effect studies of CH3F microwave spectra with and without Stark effect / Etude rovibrationnelle de la bande nu5 de DNO3 et l´étude des effets collisionels dans les spectres microonde de CH3F sans et sous effet Stark

Koubek, Jindrich 15 September 2011 (has links)
Le travail qui est présenté dans ce mémoire de thèse s'inscrit dans le domaine de la Spectroscopie moléculaire en phase gazeuse théorique et expérimentale. Il comprend deux parties dédiées à des aspects relativement différents de cette discipline. La première partie présente l'analyse à haute résolution des positions et intensité des raies de la bande ν5 (ouverture angulaire du groupe NO2 dans le plan de la molécule) de DNO3 dans la région spectrale de 11 µm. Pour ce faire, nous avons utilisé un spectre infrarouge enregistré dans la région 700−1400 cm−1 à l'aide d'un spectromètre à transformée de Fourier de l'université « Bergische Universität » à Wuppertal, en Allemagne. Ce travail nous a permis de montrer que la bande ν5, centrée à 887.657 cm−1, est fortement perturbée. L'analyse prouve en effet que les niveaux d'énergie 5^1 et 7^1+9^1 sont couplés par des résonances de Coriolis de types A et B. Le schéma de résonances pour la variété isotopique DNO3 diffère donc fortement de ceux observés pour les états 5^1 et 9^2 de H14NO3 et H15NO3 qui sont majoritairement de type Fermi. Le deuxième problème abordé dans ce travail est celui des profils de raies rotationnelles pures de CH3F avec l'étude des élargissements collisionnels (collisions CH3F-CH3F et CH3F-He) des transitions optiques et de leurs composantes Stark. Des mesures microondes ont été réalisées à l'ESTC à Prague. Leur analyse a permis d'en extraire des paramètres collisionnels à l'aide de divers profils de raies (Voigt, Rautian, dépendantes de vitesse) pour les transitions J, K → J + 1, K (K = 0, …, J) avec J = 1 et J = 3 et leurs diverses composantes Stark J, K, M → J + 1, K, M' (|M| = 0, …, J ; |M − M'| = 0, 1). De plus, un modèle fondé sur l'approximation Infinite Order Sudden (IOS) a été construit pour décrire les effets d'interférences collisionnelles observés. Les résultats expérimentaux obtenus complètent et étendent des travaux précédents et sont la première démonstration de la capacité de l'approximation IOS à modéliser les couplages collisionnels entre composantes Stark / The work presented in this thesis belongs to the domain of theoretical and experimental gas phase molecular spectroscopy. It consists of two parts dedicated to two relatively different aspects in this field. The first part presents a high resolution analysis of the ν5 fundamental band (NO2 in plane bending mode) positions and intensities of D14NO3 (deuterated nitric acid) in the 11 µm spectral region. For this study, we used an infrared spectrum of D14NO3 recorded in the 700−1400 cm−1 region on a Fourier transform spectrometer at Bergische Universität in Wuppertal (Germany). Our analysis demonstrates that the fundamental ν5 band centered at 887.657 cm−1 is strongly perturbed. Indeed, it proves that 5^1 and 7^1+9^1 energy levels of DNO3 are coupled through A and B type Coriolis resonances. The resonance scheme for the isotopologue D14NO3 therefore differs substantially from the schemes of H14NO3 and H15NO3 that feature dominantly Fermi type resonances. The second theme treated in this work is devoted to the lineshapes of pure rotational transitions of CH3F with the study of collisional broadening (collisions CH3F-CH3F and CH3F-He) of optical transitions and their Stark components. The microwave measurements were realised at ICT in Prague. Their analysis enabled to provide collisional parameters using various line profiles (Voigt, Rautian, Speed dependent) for the J, K → J + 1, K (K = 0, …, J) transitions with J = 1 and J = 3 as well as for their various Stark components J, K, M → J + 1, K, M' (|M| = 0, …, J ; |M − M'| = 0, 1). Moreover, a correct use of model based on Infinite Order Sudden approximation led to very satisfactory results of the observed line-mixing effects. The retrieved experimental results complete and extend the previous studies and provide the first successful demonstration of the ability of the IOS approximation to model line-mixing effects among Stark transitions
449

Zmapování vhodných pražských parků a cyklostezek pro volnočasové aktivity se zaměřením na výuku in-line bruslení pro žáky 1. stupně / Mapping appopriate Prague parks and trails for leisure activities focused on in-line skating for the pupils of a primary school

Suchý, Jan January 2011 (has links)
In the introduction of theoretical part, a sport discipline In line skating is described. Legislative aspect together with use of cycle paths is considered.The second chapter describes system of cyclopaths in the cities. Following chapters are describing the concept of parks and cyclopaths development in the rural area until 2020. Next, the work establishes criteria for evaluation of locations discussed in charter 5. Theoretical part of this work discusses in chapter six general rules for cyclopaths and park use. In chapter seven traffic signalization and in line skaters' equipment are discussed. Further chapters focus on sport and safety equipment. In the end of theoretical part of chapter ten and eleven I comment on particularities of in line skating education for children 7- 10 years old. Practical part describes mapping and evaluation of 10 selected cyclopaths located on the left side of Vltava River and close surroundings in chapter 12-13. Chapter 14 is dedicated to in-line skating and its categories. In the end of the practical part, the structure and methodology of teaching lesson of in-line skating is depicted together with description of basics of in line skating. Appendix consists of graphical comparison of results from public survey Keywords In-line skating, skating lessons, mapping of...
450

Solving Absolute Value Equations and Inequalities on a Number Line

Curtis, Melinda A 01 September 2016 (has links)
Absolute value has often been taught procedurally. Many students struggle with solving absolute value equations and inequalities because they do not have an understanding of the underlying concepts. This study was designed to determine to what extent solving absolute value equations and inequalities by using the concept of distance on a number line is an effective method. The claim is that if students use the distance concept on a number line, they will develop the necessary conceptual understanding in addition to just a procedural knowledge that will lead to the success with and flexibility in the use of strategies for more challenging problems. The following questions were addressed in this study: How and to what extent can using a number line develop a conceptual understanding of absolute value equations and inequalities? What solution strategies do students tend to use to solve absolute value equations and inequalities? Does the strategy depend on the complexity of the problem? To what extent do they exhibit flexibility in their use of strategies? What extensions are students able to make? What misconceptions do they have? In this study, lessons and assessments were implemented based on the “best practice” of using multiple representations with a focus on conceptual understanding of absolute value. The lessons were consistent with current content standards. Students completed a pre and post assessment, and some students were selected to participate in a 15 minute interview based on their responses from their assessments. The results were analyzed qualitatively and show that students struggled with remembering the procedure for solving absolute value equations and inequalities. The results also show that students were more successful when using the distance concept on a number line.

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