• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 594
  • 182
  • 175
  • 73
  • 59
  • 36
  • 25
  • 18
  • 16
  • 14
  • 11
  • 10
  • 10
  • 9
  • 9
  • Tagged with
  • 1437
  • 188
  • 164
  • 126
  • 108
  • 104
  • 95
  • 94
  • 85
  • 82
  • 77
  • 76
  • 64
  • 60
  • 58
  • 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.
91

Effects of Metal Ions and Loop Stability on the Structure and Function of the T Box Antiterminator RNA and its complex with Model tRNA

Muchenditsi, Abigael M. 21 September 2009 (has links)
No description available.
92

Evaluating Grey-box Models in Highly and Slightly Correlated Imbalanced Data Sets

Khandelwal, Aashish S. January 2010 (has links)
No description available.
93

Effect of elevated embryonic incubation temperature on the temperature preference of juvenile lake (Coregonus clupeaformis) and round whitefish (Prosopium cylindraceum)

Harman, Adam January 2020 (has links)
Lake (Coregonus clupeaformis) and round (Prosopium cylindraceum) whitefish are two species of cold-adapted freshwater fish that spawn in shallow (<10m) cobble beds in the Laurentian great lakes. Developing whitefish embryos are potentially exposed to various anthropogenic sources of warming, including climate change and thermal effluents discharged in the nearshore environment. Several studies have investigated the effects of elevated incubation temperatures on whitefish embryos (particularly lake whitefish) but little work has been done to examine post-hatch effects. Thermal preferenda (temperature preference) describe the range of temperatures an organism will occupy when given a choice and are traditionally thought to be species-specific. Temperature preference can be modulated by a variety of abiotic and biotic factors including environmental temperature and is typically correlated with optimal growth temperature for a species. Assays for thermal preferenda require at least 24 hours, which includes a long tank-acclimation period that limits throughput and thus impacts replication in the study. A shuttle box thermal preference assay was optimized from 24-hours to 4-hours; length of acclimation time and trial length had no significant impact on thermal preference. Whitefish were incubated at natural and elevated temperatures until hatching; all groups were moved to common garden conditions (15°C) during the post-hatching stage. Temperature preference was determined at 12 months of age; lake whitefish were also tested at 8 months. Round whitefish displayed a significant decrease in temperature preference when incubated at 2°C and 6°C compared to 0.5°C. Lake whitefish had similar temperature preferences regardless of age and incubation temperature. This suggests that there is a difference in thermal tolerance between these species, as round whitefish were more sensitive to elevated incubation treatments. This thesis identified a persistent effect of elevated incubation treatments on the thermal preference of juvenile round whitefish, lasting up to 12 months post-hatch, which highlights the importance of examining sub-lethal thermal effects and thermal plasticity of cold-adapted species. / Thesis / Master of Science (MSc) / Lake and round whitefish are cold-adapted freshwater species that spawn in shallow coastal water in the Laurentian great lakes. Anthropogenic warming from various sources (e.g. climate change, thermal effluent) has been shown to reduce survival of whitefish embryos, but few studies have investigated the effects of elevated embryonic incubation temperatures on surviving juveniles. Fish typically prefer a small range of temperatures (temperature preference) that they will occupy if given a choice, which can be affected by a variety of factors including early life thermal exposure. This thesis shows round whitefish incubated at elevated temperatures (2°C, 6°C) display decreased temperature preference up to 12 months post-hatch, while lake whitefish had similar temperature preference regardless of incubation temperature. Therefore, this thesis provides more evidence that round whitefish are a more thermally sensitive species.
94

An investigation of wood box columns to determine formulas for their design

Kinzey, Bertram York January 1950 (has links)
The strength of 102 wood box columns of air-dry dense select southern pine was investigated in order to determine formulas for their design. Constructional variables such as column slenderness; plank thickness, fastening, and arrangement; and the use of spacers for individual plank stiffening were studied as to their effects on column strength. The analysis shows that those formulas currently used for the design of other column types are suitable for box column design if properly modified. Short box columns develop (1) a strength equal to that of solid columns of equal slenderness if of 2-in. Lumber and (20 85 percent of the solid column load if of 1-in. Lumber. The Euler formulas for long columns and the constant (K) in the fourth-power Forest Products Laboratory formula for intermediate columns must be revised to account for the load capacity of long box columns which is less than that of equivalent solid columns as a result of the lower stiffness of a nailed cross-section. The incorporation of box columns rather than solid columns in timber frameworks results in savings of material. Furthermore, with standard lumber sizes a wider variety of cross-sectional areas for box columns can be built than is possible with standard timber sizes for solid columns. / Master of Science
95

The Effect of the Stiffness of Unit Load Components on Pallet Deflection and Box Compression Strength

Phanthanousy, Samantha 08 June 2017 (has links)
Currently, pallets are designed assuming that the load is distributed evenly on the top of the pallet. When pallets are loaded with packages such as corrugated boxes or returnable plastic containers, due to their physical shape, packages, are not capable of deforming freely with the pallet and a bridging phenomenon occurs. During this load bridging phenomenon, a portion of the vertical forces are redistributed as horizontal forces which causes the redistribution of the vertical compression stresses on the pallet towards the support. As a result, the deflection of the pallet can decrease and the load capacity of the pallet can increase significantly. The second chapter of this paper investigates the effect of package content on pallet deflection. The study concluded that package content did not have a significant effect on pallet deflection within the boundary conditions of the experiment. The third part of this paper considers how a specific pallet characteristic could affect the way a corrugated box performs. Standard box design procedures include adjustments of estimated compression strength for relative humidity, overhang on pallets, vibration, and alignment of boxes. However, there is no adjustment factor for pallet stiffness. The objective of the study described in this thesis is to find an answer for how the compression strength of a box is affected by pallet stiffness and top deckboard twist. The study concluded that the pallet stiffness and top deckboard twist do not have an effect on the compression strength of the box until less than 12% of the area box is supported. / Master of Science
96

Ett flervariabelt feldetekteringssystem för övervakning av bärlagertemperaturen i vattenkraftturbiner

Fredlund, Henrik January 2004 (has links)
<p>The purpose of this thesis work was to develop an automatic fault detection system for surveillance of bearing temperature in hydropower turbines. The parameters used except the bearing temperature were cooling water temperature and cooling water flow. A simple static model based on data sampled every minute was developed to estimate the bearing temperature. Then a detector for detection of change in bearing temperature based on the CUSUM-algorithm was designed. Since the amount of data was very small the developed model was too uncertain to be used in a working system.</p><p>The designed fault detection system showed to work well for the available data. It is, however, recommended that the performance of the system should be evaluated using more data. Another model based on data sampled once every minute for at least a year has to be developed before the system can be fully evaluated. The results shown were:</p><p>• The fault detection system can discover fast and slow changes in bearing temperature.</p><p>• No false alarms were given for measuring faults and sensor faults of the types used in this thesis. If a measuring fault occurs for too long there will be an alarm.</p><p>The fault detection algorithm was also implemented in Delphi to be used in a working system over the Internet where for example trends and alarms will be presented.</p> / <p>Syftet med examensarbetet var att utveckla ett automatiskt feldetekteringssystem för övervakning av bärlagertemperaturen i vattenkraftturbiner. De ingående parametrarna förutom bärlagertemperaturen var kylvattentemperaturen och kylvattenflödet. En enkel statisk modell baserad på data samplat en gång per minut togs fram för att estimera bärlagertemperaturen. Därefter utvecklades en detektor för att upptäcka avvikelser i bärlagertemperaturen baserad på CUSUM-algoritmen. På grund av en för liten mängd data var den framtagna modellen alltför osäker för att kunna implementeras i ett fungerande system.</p><p>Det framtagna feldetekteringssystemet visade sig fungera bra för de data som fanns tillgängliga. Det är däremot rekommenderat att utvärdera systemets prestanda med längre dataserier. En ytterligare modell baserad på minutdata över ett år måste tas fram innan systemet kan fungera på riktigt. De resultat som erhölls var:</p><p>• Feldetekteringssystemet klarar av att upptäcka abrupta och långsamma avvikelser av bärlagertemperaturen.</p><p>• Inga falsklarm ges då det är enstaka mätfel eller givarfel av sådan typ som tagits upp i arbetet. Pågår ett mätfel alltför länge ges dock ett larm.</p><p>Feldetekteringsalgoritmen implementerades även i Delphi för att kunna användas i ett fungerande system över Internet där t.ex. trendkurvor och larmsignaler skall kunna presenteras.</p>
97

Sécurisation par dynamiques chaotiques des réseaux locaux sans fil au niveau de la couche MAC / Security by chaotic dynamics of wireless LANs at the MAC layer

Zaïbi, Ghada 06 December 2012 (has links)
Les travaux de recherche de cette thèse s’inscrivent dans le cadre de la sécurité par chaos des réseaux locaux sans fil, en particulier les réseaux de capteurs sans fil. L’originalité de cette thèse consiste à proposer des cryptosystèmes à base de chaos plus adaptés aux réseaux de capteurs, en termes de consommation d’énergie, que les algorithmes conventionnels et à réaliser une implémentation sur une plateforme réelle. Nous présentons en premier lieu un état de l’art des réseaux, les menaces, les contraintes limitant le processus de sécurité des informations ainsi que les principales techniques de cryptographie. Nous donnons un aperçu sur la théorie de chaos et nous validons l’aspect aléatoire de plusieurs suites chaotiques par les tests statistiques du NIST. Nous proposons ensuite des nouvelles méthodes de construction de S-Box chaotiques tout en prouvant leur robustesse contre les attaques traditionnelles. Nous proposons enfin un nouvel algorithme de cryptage d’image dédié au réseau de capteurs sans fil. La validation de nos contributions est effectuée par simulation et par des mesures expérimentales sur une plateforme de réseaux de capteurs réels (SensLab). / The security of wireless sensor network is a growing field of research hampered by limited battery life time and computing constraints. The originality of this thesis is to provide Low Power chaotic cryptosystems for sensor networks more suitable than conventional algorithms and achieve an implementation on a real platform.. We present first a state of the art of wireless networks, threats and constraints of the security process as well as conventional cryptographic techniques. We give an overview of the chaos theory and we validate the randomness of several chaotic maps by the NIST statistical tests. Then, we propose new methods of chaotic S-Box construction, while demonstrating their robustness against traditional attacks. Finally, we propose a new image encryption algorithm dedicated to wireless sensor network. Validation of our contributions is performed by simulation and experimental measurements on a platform of real sensor networks (SensLab).
98

Optimalizace založená na bezderivačních a metaheuristických metodách / Optimization using derivative-free and metaheuristic methods

Márová, Kateřina January 2016 (has links)
Evolutionary algorithms have proved to be useful for tackling many practical black-box optimization problems. In this thesis, we describe one of the most powerful evolutionary algorithms of today, CMA- ES, and apply it in novel way to solve the problem of tuning multiple coupled PID controllers in combustion engine models. Powered by TCPDF (www.tcpdf.org)
99

Documentário e ficção: o registro audiovisual como recurso na pesquisa científica da atualidade em ciências da comunicação / Documentary and Fiction: Audiovisual registration as a resource in nowadays scientific research in Communication Science

Perez, Cesar Bargo 25 March 2015 (has links)
Esta tese reflete em seu contexto gerador, um processo profissional contínuo aplicado à academia que se desenvolve com a aplicação de teorias fílmicas e oportunidades de captação e registro de imagens em depoimentos testemunhais. Valendo-se da experiência acumulada, este trabalho tem a intenção de evidenciar o registro audiovisual de cunho testemunhal como ferramenta-chave na pesquisa científica em Ciências da Comunicação da atualidade, mostrando o potencial de interação entre o pesquisador e seu público, entre o condutor da captação testemunhal, líder do processo de registro, e seu objeto de pesquisa, com todas as articulações e preceitos de ficcionalidade e atualização de discurso que a oportunidade audiovisual suscita na instância ao vivo. O trabalho explicita e detalha o Processo de tomada dessas entrevistas e os experimentos de contato público-pesquisador conduzidos em um período de dois anos para defender sua relevância e essencialidade na pesquisa em Ciências da Comunicação. / This thesis reflects, in its generating context, a continuous professional process applied to the Academia that develops with the application of filmic theories and opportunities for the registration and recording of images and testimonials. Backed by such accumulated work experience, this document has the purpose of evidencing the testimonial-style audiovisual record as a key tool in the scientific research in current Communication Sciences. The thesis wants to show the interaction potential between the researcher and his public, between the one conducting the testimonial, the leader of the process, and his subject, with all the articulations and precepts of fictionality and speech revision and updating that the audiovisual opportunity has raised in the live instance. The paper makes explicit and details the Process behind those interviews and the public-researcher experiments conducted within a time span of 2 years to defend its relevance and the essentiality in the research in Communication Sciences.
100

Modelo de previsão aplicado ao mercado de transporte rodoviário do açúcar no estado de São Paulo / Prediction model applied to the road transport market of sugar in the State of São Paulo

Costa, Gilberto Fernandes da 29 April 2014 (has links)
A pesquisa tem como objetivo obter previsões para o mercado de fretes do açúcar para exportação no Estado de São Paulo. Para cumprir tal objetivo, utilizou-se a metodologia Box- Jenkins de séries temporais. O período compreendido na pesquisa foi janeiro de 2006 a setembro de 2013. Foram delimitadas no Estado de São Paulo nove regiões para análise: Ribeirão Preto, Jaú, Araraquara, Presidente Prudente, Araçatuba, Piracicaba, São José do Rio Preto, Pirassununga e Assis. Essas regiões também foram agregadas com o objetivo de obter previsões para o Estado de São Paulo. As previsões foram realizadas fora da amostra correspondendo ao período de outubro de 2012 a setembro de 2013. Os modelos estimados, de forma geral, obtiveram um bom desempenho considerando os cinco primeiros meses de previsão, como o ocorrido nas regiões de Jaú, Araraquara, Piracicaba, Pirassununga e Assis. Dentre as nove regiões analisadas, os modelos ajustados para as Regiões de Piracicaba e Assis apresentaram melhores desempenhos, fato este comprovado pelos menores valores do Erro Quadrático Médio e Soma do Quadrado dos Desvios. Considerando os resultados gerais das nove regiões e da análise do Estado de São Paulo de forma agregada, houve predomínio do emprego do modelo ARIMA como melhor método para a realização de previsões para o mercado de fretes do açúcar. Não obstante, as previsões geradas pela metodologia Box- Jenkins, no curto prazo, constituem em boa ferramenta de auxílio para tomada de decisões e planejamento dos agentes envolvidos no mercado do açúcar. / The research aims to obtain predictions for the freights market of sugar for export in the State of São Paulo in Brazil. A Box-Jenkins time series methodology was used to fulfill this objective. The survey was performed from January 2006 through September 2013. Nine regions in São Paulo State were placed for analysis: Ribeirão Preto, Jaú, Araçatuba, Araraquara, Piracicaba, São José do Rio Preto, Pirassununga, Presidente Prudente and Assis and also these regions were aggregated in order to obtain estimates for the State of São Paulo. The predictions were made out of the sample corresponding to the period from October 2012 to September 2013. The estimated models generally presented good performance considering the five first months of forecast, as occurred in the regions of Jaú, Araraquara, Piracicaba, Pirassununga and São José do Rio Preto. Out of the nine regions analyzed, the models adjusted for the regions of Piracicaba and Assis showed better performances, proven by the lowest average square error and Sum of Squares of deviations. Considering the overall results of the nine regions and the analysis of the state of São Paulo aggregated, employment ARIMA model predominated as the best method for performing predictions for the freight market sugar. Nevertheless, the forecasts generated by the Box-Jenkins methodology, in a short term, constitute good tool to aid decision-making and planning of the agents involved in the sugar market.

Page generated in 0.0351 seconds