• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 10
  • 3
  • 3
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 23
  • 6
  • 6
  • 6
  • 6
  • 5
  • 4
  • 4
  • 4
  • 4
  • 4
  • 4
  • 3
  • 3
  • 3
  • 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.
11

Aplicação do controlador UPFC para o amortecimento de oscilações eletromecanicas em sistemas eletricos de potencia / Application of UPFC controller for damping electromechanical oscillations in electric power systems

Ayres, Hugo Murici 12 July 2005 (has links)
Orientador: Vivaldo Fernando da Costa / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-06T02:46:18Z (GMT). No. of bitstreams: 1 Ayres_HugoMurici_M.pdf: 1495982 bytes, checksum: e8c830648b4338fd4c90f9c0921c63d5 (MD5) Previous issue date: 2005 / Resumo: Essa dissertação apresenta um estudo que avalia a e?ciência do controlador UPFC (Uni?ed Power Flow Controller) para o amortecimento de oscilações eletromecânicas sob condições de pequenas e grandes perturbações.Um modelo de injeção de potência utilizado para representar o UPFC é implementado no Modelo de Sensibilidade de Potência (MSP). As análises no domínio do tempo são realizadas com o programa PSAT (Power System Analysis Toolbox), no qual também são implementados os modelos do UPFC e do controlador POD (Power Oscillation Damping).Diversos controladores POD são projetados para a modulação de diferentes parâmetros do UPFC. A análise da estabilidade e o projeto dos estabilizadores são baseados em técnicas de resposta em freqüência e no tempo, assim como na técnica de análise modal. Os resultados obtidos revelam que o UPFC possui um grande potencial para a manutenção da estabilidade de ângulo de sistemas de potência quando equipado com controladores POD / Abstract: This dissertation presents a study assessing the effectiveness of the Unified Power Flow Controller (UPFC) for damping electromechanical oscillation under small-signal and large disturbances. A UPFC power injection model is implemented in the Power Sensitivity Model (PSM). The time domain analysis is carried out with the Power System Analysis Toolbox (PSAT) considering the UPFC and the POD controller models implemented. A number of Power Oscillation Damping (POD) controllers are designed in order to modulate different parameters of the UPFC. The stability analysis and the design of POD controllers are based on time and frequency response techniques. Modal analysis technique is also utilized. Results obtained reveal that the UPFC has a great potential to maintain the power system angle stability when it is equipped with POD controller / Mestrado / Energia Eletrica / Mestre em Engenharia Elétrica
12

Feeding Ecology and Habitat Utilization of the Great Barracuda Sphyraena barracuda (Edwards 1771) in Southeast Florida

Hansen, Noah R. 01 January 2015 (has links)
Great barracuda Sphyraena barracuda is a large predatory teleost found circumglobally, other than the Eastern Pacific Ocean. The species is commonly caught by both recreational and commercial fishermen as bycatch while targeting other, more economically or recreationally valuable fishes. This species also exhibits an ontogenetic shift in habitat, with juveniles inhabiting mangrove and seagrass habitats, while adults live near offshore reefs and associated structure. This thesis consists of two separate studies of S. barracuda: 1) feeding ecology along an ontogenetic gradient and 2) habitat utilization of as derived through electronic tagging. The first chapter of this thesis describes the feeding ecology of great barracuda in South Florida, with an emphasis on the determination of when the ontogenetic shift in diet occurs between habitats and individual fish sizes. Specimens were collected primarily by seine net and hook-and-line fishing. The specimens were then dissected with the stomach contents examined. This study found that the ontogenetic diet shift in great barracuda begins around the second year, and that juveniles and adults are opportunistic predators with a wide diversity of teleost and crustacean prey items within the selected habitat. The second chapter of this thesis describes the habitat utilization and vertical movements of two great barracuda off of South Florida interpreted from data acquired from pop-up satellite archival tags (PSATs). This study found that large (>100 cm) great barracuda are capable of travelling hundreds of kilometers over a period of days to weeks. The results show that large great barracuda can tolerate temperatures ranging from 17.8° C to 31.3° C, and are capable of diving to depths greater than 175 m. It was also found that there was a significant difference in time spent at depth, with greater depths being inhabited more frequently at night.
13

Nonlinear Constrained Component Optimization of a Plug-in Hybrid Electric Vehicle

Yildiz, Emrah Tolga 12 1900 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / Today transportation is one of the rapidly evolving technologies in the world. With the stringent mandatory emission regulations and high fuel prices, researchers and manufacturers are ever increasingly pushed to the frontiers of research in pursuit of alternative propulsion systems. Electrically propelled vehicles are one of the most promising solutions among all the other alternatives, as far as; reliability, availability, feasibility and safety issues are concerned. However, the shortcomings of a fully electric vehicle in fulfilling all performance requirements make the electrification of the conventional engine powered vehicles in the form of a plug-in hybrid electric vehicle (PHEV) the most feasible propulsion systems. The optimal combination of the properly sized components such as internal combustion engine, electric motor, energy storage unit are crucial for the vehicle to meet the performance requirements, improve fuel efficiency, reduce emissions, and cost effectiveness. In this thesis an application of Particle Swarm Optimization (PSO) approach to optimally size the vehicle powertrain components (e.g. engine power, electric motor power, and battery energy capacity) while meeting all the critical performance requirements, such as acceleration, grade and maximum speed is studied. Compared to conventional optimization methods, PSO handles the nonlinear constrained optimization problems more efficiently and precisely. The PHEV powertrain configuration with the determined sizes of the components has been used in a new vehicle model in PSAT (Powertrain System Analysis Toolkit) platform. The simulation results show that with the optimized component sizes of the PHEV vehicle (via PSO), the performance and the fuel efficiency of the vehicle are significantly improved. The optimal solution of the component sizes found in this research increased the performance and the fuel efficiency of the vehicle. Furthermore, after reaching the desired values of the component sizes that meet all the performance requirements, the overall emission of hazardous pollutants from the PHEV powertrain is included in the optimization problem in order to obtain updated PHEV component sizes that would also meet additional design specifications and requirements.
14

Answer set programming probabilístico / Probabilistic Answer Set Programming

Morais, Eduardo Menezes de 10 December 2012 (has links)
Este trabalho introduz uma técnica chamada Answer Set Programming Probabilístico (PASP), que permite a modelagem de teorias complexas e a verificação de sua consistência em relação a um conjunto de dados estatísticos. Propomos métodos de resolução baseados em uma redução para o problema da satisfazibilidade probabilística (PSAT) e um método de redução de Turing ao ASP. / This dissertation introduces a technique called Probabilistic Answer Set Programming (PASP), that allows modeling complex theories and check its consistence with respect to a set of statistical data. We propose a method of resolution based in the reduction to the probabilistic satisfiability problem (PSAT) and a Turing reduction method to ASP.
15

Answer set programming probabilístico / Probabilistic Answer Set Programming

Eduardo Menezes de Morais 10 December 2012 (has links)
Este trabalho introduz uma técnica chamada Answer Set Programming Probabilístico (PASP), que permite a modelagem de teorias complexas e a verificação de sua consistência em relação a um conjunto de dados estatísticos. Propomos métodos de resolução baseados em uma redução para o problema da satisfazibilidade probabilística (PSAT) e um método de redução de Turing ao ASP. / This dissertation introduces a technique called Probabilistic Answer Set Programming (PASP), that allows modeling complex theories and check its consistence with respect to a set of statistical data. We propose a method of resolution based in the reduction to the probabilistic satisfiability problem (PSAT) and a Turing reduction method to ASP.
16

Telemetrický archiv družic / Satellite Telemetry Archive

Vorálek, Jan January 2020 (has links)
This thesis deals with a design of telemetry archive of PSAT, PSAT-2 and BRICSat sattelites. This telemetry data need to be extracted from SDR IQ records. The thesis contains a Doppler effect theory and description of structure of telemetry data. Then it presents a design of a program for Doppler effect correction, demodulation and decoding of these records and saving the data to telemetry archive. Thesis also deals with analysis of decoded data.
17

Simulating the contributions of local and regional sources to fine PM in megacities / Η συνεισφορά τοπικών και αποκρυσμένων περιοχών στα επίπεδα ρύπανσης των ευρωπαΐκών μεγαλουπόλεων

Σκυλλάκου, Ξακουστή 30 April 2014 (has links)
The Particulate Matter Source Apportionment Technology (PSAT) is used together with PMCAMx, a regional chemical transport model, to estimate how local emissions and pollutant transport affect primary and secondary particulate matter concentration levels in European megacities such as Paris, London and Po Valley. The case of Paris megacity was investigated in detail. During the summer and the winter period examined, only 13% of the PM2.5 is due to local Paris emissions, with 36% due to mid range (within 500 km from the center of the Paris) sources and 51% resulting from long range transport (more than 500 km from the center of the Paris). The local emissions contribution to elemental carbon (EC) is significant, with almost 60% of the EC originating from local sources during both summer and winter. Approximately 50% of the fresh primary organic aerosol (POA) originated from local sources and another 45% from areas 100-500 km from the receptor region during summer. Regional sources dominated the secondary PM components. More than 70% of the sulfate originated from SO2 emitted more than 500 km away from the center of the Paris. Also more than 45% of secondary organic aerosol (SOA) was due to the oxidation of VOC precursors that were emitted 100-500 km from the center of the Paris. Long range sources are more important during winter because the photochemical activity is lower. PSAT results for contributions of local and regional sources were also compared with observation-based estimates from field campaigns that took place during the MEGAPOLI project. PSAT predictions are in general consistent with these estimates OA and sulfate but PSAT predicts lower transported EC for both seasons. / Ο καταμεριστικός αλγόριθμος ατμοσφαιρικών σωματιδίων (PSAT, Particulate Matter Source Apportionment Technology) χρησιμοποιείται σε συνδυασμό με το τρισδιάστατο μοντέλο χημικής μεταφοράς PMCAMx με σκοπό να εκτιμήσει κατά πόσο οι τοπικές εκπομπές και η μεταφορά της ρύπανσης επηρεάζουν τα πρωτογενή και τα δευτερογενή επίπεδα σωματιδιακών συγκεντρώσεων σε Ευρωπαϊκές μεγαλουπόλεις όπως το Παρίσι, το Λονδίνο και η κοιλάδα του ποταμού Πάδου στη βόρεια Ιταλία (Po Valley). Η περίπτωση του Παρισιού μελετήθηκε λεπτομερώς. Κατά τη διάρκεια του καλοκαιριού και του χειμώνα που εξετάστηκε, μόνο το 13% των PΜ2.5 σωματιδίων προέρχονται από τοπικές πηγές, 36% προέρχεται από ενδιάμεσες πηγές (μεταξύ 500 km από το κέντρο του Παρισιού) και 51% από απομακρυσμένες περιοχές (σε αποστάσεις μεγαλύτερες των 500 km από το κέντρο του Παρισιού). Η συνεισφορά των τοπικών πηγών στο στοιχειακό άνθρακα είναι σημαντική, 60% περίπου του στοιχειακού άνθρακα προέρχεται από τοπικές πηγές κατά τη διάρκεια τόσο του καλοκαιριού όσο και του χειμώνα. Σχεδόν 50% των φρέσκων πρωτογενών οργανικών σωματιδίων (POA) προέρχονται από τοπικές πηγές και 45% από περιοχές 100-500 km από των αποδέκτη κατά τη διάρκεια του καλοκαιριού. Οι συνεισφορά από απομακρυσμένες περιοχές κυριαρχεί στα δευτερογενή σωματίδια. Περισσότερο από 70% των θεϊκών σωματιδίων προέρχεται από διοξείδιο του θείου το οποίο εκπέμπεται από αποστάσεις μεγαλύτερες των 500 km από το κέντρο του Παρισιού. Επίσης περισσότερο από το 45% των δευτερογενών οργανικών σωματιδίων οφείλεται στην οξείδωση των πτητικών οργανικών ενώσεων (VOCs) που εκπέμπονται από 100 έως 500 km μακριά από το κέντρο του Παρισιού. Οι απομακρυσμένες περιοχές είναι πιο σημαντικές κατά τη διάρκεια του χειμώνα λόγω της ελάχιστης φωτοχημείας. Τα αποτελέσματα που προέκυψαν από τον αλγόριθμο PSAT για τις συνεισφορές των τοπικών όσο και των απομακρυσμένων περιοχών επίσης συγκρίνονται με μετρήσεις πεδίου από πειραματικές διατάξεις στο πλαίσιο του διεθνούς προγράμματος MEGAPOLI. Ο αλγόριθμος PSAT προβλέπει γενικά ικανοποιητικά τις συνεισφορές σε σχέση με αυτές που υπολογίστηκαν από τις μετρήσεις πεδίου.
18

Analysis of voltage regulation and network support technologies

Rossouw, Frans Jacobus 12 1900 (has links)
Thesis (MEng)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: Recent advances in semiconductor device development pushed a large number of network devices onto the market. These devices can solve network problems more effectively and economically than ever before. Network planners need tools to analyse and implement such devices to help solve the largest network problem in South Africa: voltage regulation. Rural networks experience the majority of voltage-regulation problems in South Africa. The networks are long sub-transmission and reticulation networks and are modelled by two generic networks, namely a radial network and a two-source ring network. The equations describing voltage regulation for the generic networks are developed and implemented in PSAT, a software analysis tool. The voltage regulation for two case studies that represent the two generic networks are analysed. Four generic network devices are defined and various control methods for these devices are developed to solve the network problem. The aim of PSAT is to help the network planner to quickly evaluate a number of possible solutions and to choose the best solution for further studies. This is demonstrated with the aid of the case studies. PSAT provides a sturdy platform on which future developments, such as stability analyses, can be built. However, PSAT can already function as a stand-alone analysis tool to solve voltage regulation as a network problem. / AFRIKAANSE OPSOMMING: Onlangse vooruitgang in halfgeleier ontwikkeling het 'n groot aantal netwerktoestelle op die mark geplaas. Hierdie toestelle kan netwerk probleme doeltreffender en meer ekonomies oplos as ooit vantevore. 'n Behoefte aan 'n pakket wat netwerkbeplanners in staat stelom die netwerktoestelle te analiseer, is geïdentifiseer. So 'n pakket sal hulle help om die vernaamste netwerkprobleem in Suid-Afrika, nl. spanningsregulasie, op te los. Die oorgrote meerderheid spanningsregulasie probleme word op die platteland ondervind. Plattelandse netwerke word gekenmerk deur lang sub-transmissie en retikulasie netwerke. Hierdie netwerke word met behulp van twee generiese netwerke gemodelleer. 'n Radiale netwerk en 'n dubbelbron ringnetwerk word aangewend om enige plattelandse netwerk te analiseer. Vergelykings is vir spanningsanalise ontwikkel en in PSAT, 'n analitiese sagteware pakket, geïmplementeer. Twee gevallestudies is gedoen om die twee netwerke afsonderlik voor te stel en die vergelykings van PSAT te evalueer. Alle netwerktoestelle is in een van vier generiese kategorieë geklassifiseer. Modelle is vir elk van die kategorieë ontwikkel vtr spanningsregulasie analise. Die doel van PSAT is om die netwerk beplanner te help om vinnig en effektief soveel moontlik opsies te ondersoek as oplossings vir 'n spesifieke netwerk probleem. PSAT is reeds 'n alleenstaande pakket wat in die toekoms uitgebrei sal word om na die analise van stabilitietsprobleme te kyk.
19

An analysis of variables affecting standardized test results at the high school level

Warry, Jaye Ellen January 2003 (has links)
Thesis (Ed.D.)--Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / The purpose of this study was to determine the relative contribution to the Massachusetts Comprehensive Assessment System (MCAS) English Language Arts (ELA) of five variables: Type of Community (Urban or Suburban), Gender, Race, Preliminary Scholastic Aptitude Test (PSAT) Verbal, and PSAT Writing. MCAS is a criterion-referenced examination administered to students at various grade levels to determine their knowledge of approved curriculum. As of 2003, students must pass the mathematics and English language arts sections in order to receive a diploma. Data for the study was gathered from three urban and four suburban school districts in Massachusetts. Data about 914 students was collected from Summer 2001 - Winter 2002. Multiple regression statistical analysis was used to examine the collective and separate contributions of five independent variables; gender, race, type of community (urban or suburban), score on the verbal subtest of the PSAT, and score on the writing subtest to the findings on the dependent variab le - tenth grade language arts achievement on the MCAS. Results of the statistical analyses showed a strong relationship between MCASELA and the five independent variables, with most of the relationship attributable to the PSAT Verbal test results. Three other variables combined - PSAT Writing, Type of Community, and Gender - accounted for just 4% of the additional variance. Step-wise multiple regression analysis indicated that exclusion of Race did not diminish predictiveness, and Gender added very little to predictiveness. PSAT Verbal, PSAT Writing, and Type of Community were the principal contributions to variation in MCAS-ELA in the study. The four null hypotheses and results follow: There is no significant relationship between the dependent variable - MCAS-ELA -- and the independent variables -- Type of Community, Gender, Race, PSA T Verbal, and PSAT Writing - rejected. There is no significant relationship between each independent variable and each of the other independent variables - rejected. There is no significant relationship between the dependent variable and the other variables taken together - rejected. There is no significant additional vanance m MCAS - ELA accou nted for by an independent variable after other variable (s) - responsible for greater contributions to variance - (have) accounted for as much of the variance as possible - accepted. / 2031-01-01
20

Πιθανοτική ικανοποιησιμότητα : πολυπλοκότητα και υπολογιστικές προσεγγίσεις

Αραβαντινού, Άννα 07 July 2015 (has links)
Στην εργασία αυτή ασχοληθήκαμε με το πρόβλημα της Πιθανοτικής Ικανοποιησιμότητας. Παρουσιάσαμε ανάλυση της πολυπλοκότητας του προβλήματος και το επιλύσαμε με την βοήθεια του λογισμικού πακέτου CPLEX. Περιγράψαμε προσεγγιστικούς αλγόριθμους για το πρόβλημα της Μέγιστης Ικανοποιησιμότητας που χρησιμοποιείται στην διαδικασία της Column Generation. Τέλος, πριγράψαμε το αντίστροφο πρόβλημα των συχνών στοιχειοσυνόλων και την σχέση του με το πρόβλημα της Μέγιστης Ικανοποιησιμότητας. / This thesis is about the problem of probabilistic satisfiability. We describe its computational complexity, we solve the problem using CPLEX, we discribe some approximations on Maximum Satisfiability. Finally, we describe the connection between the problem of Probabilistic Satisfiability and the inverse frequent itemset mining.

Page generated in 0.0208 seconds