Thesis (M.S.)--University of Nevada, Reno, 2006. / "December, 2006." Includes bibliographical references (leaves 82-85). Online version available on the World Wide Web.

Thesis (M.S.)--Brigham Young University. Dept. of Mechanical Engineering, 2006. / Includes bibliographical references (p. 107-109).

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Μία από τις σημαντικότερες Ανανεώσιμες Πηγές Ενέργειας θεωρείται η ηλιακή ενέργεια. Η μετατροπή της σε ηλεκτρική ενέργεια επιτυγχάνεται με τα φωτοβολταϊκά συστήματα. Η ολοένα και μεγαλύτερη διάδοσή τους κάνει επιτακτική την ανάγκη για την εις βάθος μελέτη τους και τη βελτίωση της απόδοσής τους. Στην παρούσα διπλωματική εργασία εξετάζεται η αρχή λειτουργίας και η τεχνολογία των συστημάτων αυτών, ενώ γίνεται μοντελοποίηση και βέλτιστη προσαρμογή διαφόρων περιπτώσεων φορτίων συνδεδεμένων σε ένα αυτόνομο σύστημα. Παράλληλα, εξετάζονται οι παράμετροι που επηρεάζουν τη μέγιστη μεταφορά ισχύος από τη φωτοβολταϊκή συστοιχία στο φορτίο, ενώ δίνεται βάρος στην κατανόηση της επίδρασης της προσπίπτουσας ακτινοβολίας και της θερμοκρασίας / One of the major Renewable Energies Sources is solar energy. Its conversion to electricity is achieved by photovoltaic systems. Their increasing dissemination makes both in-depth study and improvement of their performance necessary. This thesis examines the working principle and technology of these systems, while modeling and optimal adjustment of different cases of loads connected to an off-grid system are researched. In addition, the parameters affecting the maximum transfer of power from the photovoltaic array to the load are analyzed and the impact of the incident radiation and temperature is explained.

Because of high fuel costs and rising concern over controlling motor vehicle emissions, there has been a surge in the number of hybrid passenger vehicles on roads in recent years. This transition has not yet been seen with agricultural vehicles. With this in mind, this study created a test scheme to characterize and replicate agricultural loads, and design of a hybrid drivetrain that is suitable for agricultural purposes. Torque and power data were recorded from the controller area network of a tractor performing a baling operation. The recorded data was characterized using statistical and time series analyses, and converted into a simplified torque profile that could be run on a common type of dynamometer. The prototype series hybrid drivetrain was subjected to the simplified profile developed, and drivetrain efficiency was compared to the efficiency under constant load. The effect of battery pack, and engine size was also tested. On average, the prototype developed was not more efficient than a similarly sized standard geared vehicle, but there is significant room for further optimization.

O controle da carga de treinamento é apontado como um desafio na atualidade, principalmente no esporte coletivo, onde existe uma busca pelo avanço nessa área de conhecimento em diferentes centros de pesquisa no mundo. Esses pesquisadores se utilizam da aplicação de ferramentas biomecânicas, fisiológicas, bioquímicas, imunológicas e psicobiológicas para visando esse controle, apesar de pouco entendimento efetivo ter sido alcançado até o presente momento, justificando a continuidade dessa busca. Baseando-se nessa lacuna presente no estado da arte traçamos uma estratégia onde inicialmente devido à existência de pontos conflitantes na literatura em relação ao uso do salto com contramovimento (SCM), foi realizada uma meta-análise para verificar qual deveria ser a estratégia para aplicação dessa ferramenta biomecânica. A partir desse ponto, os demais estudos experimentais da presente tese foram conduzidos com o objetivo de verificar as possibilidades da aplicação de ferramentas biomecânicas para o controle de carga de treinamento em atletas. Os três experimentos foram realizados com a participação de atletas de futsal (n = 18; idade: 15,2 ± 0,9 anos; massa corporal: 62,3 ± 13,1 kg; estatura: 1,71 ± 0,1 m). Os voluntários realizaram o processo de familiarização com o SCM e, em seguida, foi verificada a confiabilidade do desempenho, utilizada para determinar a diferença mínima individual (DMI) do mesmo. Todos os voluntários realizaram as coletas iniciais (T0), avaliando o desempenho do SCM, por intermédio de medidas cinemáticas (tapete de contato e câmeras optoeletrônicas), dinâmicas (plataforma de força), além das antropométricas (balança com estadiômetro e antropômetros). Após a primeira etapa experimental, os voluntários foram distribuídos de maneira aleatória em dois grupos: Grupo Regulação (GR; n = 9) e Grupo Controle (GC; n = 9). Os voluntários realizaram quatro semanas de intensificação do treinamento, logo em seguida foi realizada a avaliação intermediária (T1), com mais duas semanas para o tapering e a reavaliação (T2). O monitoramento semanal ocorreu no início de cada microciclo a partir da DMI do SCM com o tapete de contato, assim todos os voluntários eram avaliados, mas os ajustes ocorriam somente para o GR. A meta-análise revelou que altura média do SCM foi a variável mais sensível e adequada para acompanhar os efeitos da fadiga e supercompensação. Para o experimento 01, o treinamento autorregulado no GR resultou em uma carga de treinamento significantemente mais elevada na semana 3 (tamanho de efeito \"TE\" = 0,6) e semana 4 (TE = 2,3) comparando com o GC. Entretanto, a carga de treinamento final não foi significativamente diferente entre os grupos (p = 0,082). Como resultado do aumento de carga durante a indução ao overreaching, o GR reduziu a altura do SCM entre T0-T1 (TE = -0,31). Entre T1-T2, o GR teve um aumento significativo na altura do SCM (TE = 0,61), e da mesma forma, outro aumento significativo na altura do SCM entre T0-T2 foi observado (TE = 0,30). As alterações na altura do SCM para o GC não foram significativas: T0-T1 (TE = -0,19); T1-T2 (TE = 0,41) e T0-T2 (TE = 0,07). No experimento 02, as alterações na altura do SCM foram acompanhadas pelas seguintes alterações nos parâmetros dinâmicos; durante a redução de desempenho ocorreu um aumento do momento de quadril na rotação externa/interna e durante o aumento de desempenho ocorreu um aumento da energia e do momento de quadril na flexão/extensão. Quanto ao experimento 03, durante a flexão/extensão; a energia de quadril (r² = 56%), o pico de potência de quadril (r² = 46%), a média do momento de joelho (r² = 50%) e o pico de potência de joelho (r² = 43%) foram correlacionados significativamente com as alterações na altura do SCM. Com esses achados, podemos concluir que o uso de ferramentas biomecânicas permitiu o controle de carga de treinamento de atletas de futsal, utilizando a altura média do SCM com a DMI para regular o treino e alcançar o overreaching funcional. Além disso, as alterações ocorridas nos parâmetros dinâmicos do SCM respaldam a utilização dessa abordagem / The training load control is identified as a challenge today, especially in team sports, where there is a search for the breakthrough in the area of knowledge in different research centers in the world. These researchers are using biomechanical markers, physiological markers, biochemical markers, immunological markers and psychobiological markers for its implementation, although little understanding and effectiveness be achieved to date. Thus we performed a strategy which initially due to the existence of conflicting points in the literature regarding the use of the countermovement jump (CMJ), a meta-analysis was performed to determine which should be the approach to application of biomechanical markers: From that point, the experimental studies of this thesis were conducted in order to verify the possibilities of application of biomechanical markers for training load control in athletes. The three experiments were carried out with the participation of futsal athletes (n = 18; age: 15.2 ± 0.9 years; body mass: 62.3 ± 13.1 kg; height: 1.71 ± 0.1 m). The volunteers perform the familiarization process with the CMJ and then its reliability was verified and used to determine the minimal individual differences (MID). All volunteers performed the initial assessment (T0) for evaluating the performance of CMJ, through kinematic measurements (contact mat and optoelectronic cameras), dynamic (force plate), and anthropometric (scale with stadiometer and anthropometers). After the first experimental stage, volunteers were randomly distributed into two groups: regulated group (RG; n = 9) and control group (CG, n = 9). The volunteers performed four weeks of intensified training, an intermediate evaluation (T1), then two weeks for tapering and finally the reassessed (T2). The weekly monitoring occurred at the beginning of each microcycle from the MID of CMJ with the jump mat, all volunteers performed this assessment, but the adjustments were performed just for RG. The meta-analysis showed that average of CMJ height was the most sensitive and appropriate variable to monitor the effects of fatigue and supercompensation. For the experiment 01, the auto-regulated training in RG resulted in a significantly higher training load at week 3 (effect size \"ES\" = 0.6) and week 4 (ES = 2.3) compared to the CG. However, the final training load was not significantly different between the groups (p = 0.082). As a result of the increased load during the induction overreaching, RG reduced CMJ height between T0-T1 (ES = -0.31). Between T1-T2, RG had a significant increase in the CMJ height (ES = 0.61), and similarly, another significant increase in the CMJ height between T0-T2 was observed (ES = 0.30). Changes in the height of the CMJ for CG were not significant: T0-T1 (ES = -0.19); T1-T2 (ES = 0.41) and T0-T2 (ES = 0.07). In the experiment 02, we found that changes in the CMJ height were followed by the following changes in dynamic parameters; reduction performance by increasing the hip moment (external/internal rotation) and increase performance by increasing hip energy and moment (flexion/extension). For experiment 03, during flexion/extension; hip energy (r² = 56%), peak hip power (r² = 46%), mean knee moment (r² = 50%) and peak knee power (r² = 43%) were correlated significantly with changes in the CMJ height. With these findings, we conclude that the use of biomechanical markers allowed the training load control of the futsal players using the average of CMJ height with MID to regulate the training and achieve functional overreaching. Moreover, the changes in the dynamic parameters of the CMJ support the use of this approach

In engineering practice, there is no clear reference or guidance for the computation of the superimposed parapet load distributed to each girder of a bridge. The purpose of this study is to determine the distribution of the parapet wall weight load to prestressed concrete girders for simple span bridges. The focus is on the reactions at the bearings of simple span bridges. It was found in this study that the exterior girder takes about fifty percent of the parapet load distribution in a case with five girders. This study presents background, introduction, data, and results pertaining to this research. Care is made to fully explain all procedures and terminology for complete understanding of the topic. This study implements the finite element analysis program NISA to test simple span bridge models and collect the data of the reactions at the bearings of these models. Multiple models are created that use AASHTO Types III prestressed concrete girders. The lengths of the girders as well as the cantilever span lengths of the deck will vary. The focus of this research is to determine the distribution of the parapet weight loading on the prestressed concrete girders of simple span bridges. The results are provided in table form showing the reactions on the bridge models. The ratios of the load distribution of the exterior beams to the load distribution of the interior beams are also shown. This data provides a reference for the load distribution of the parapet wall weight to the girders.

In response to the global concerns towards oil scarcity and climate change, the automotive industry is currently focusing on improving fuel economy and reducing exhaust emissions. Modern downsized gasoline engines that come with a package that includes a boosting system, variable valve train and direct fuel injection system is effective for fuel economy improvement and emission reduction. However, the knocking issue becomes severe at high load operations as a result of the high intake boosting pressure. In regard to the part load conditions, the gas exchange process requires extra work to draw in air into the cylinder due to a lower amount of pressure in the intake manifold caused by the restriction of the throttle plate. The Miller cycle is regarded as a potential strategy of knock control for downsized gasoline engines. Extensive works have sought to examine the performance improvement via the Miller cycle, yet only limited research has been conducted on the manner in which it can influence knock suppression. The focus of this thesis is to investigate early and late intake valve closing timings in terms of how they affect the compression process, the ability to suppress engine knock and meet the power output required at high loads for spark-ignited gasoline engines. Apart from that, this research also demonstrates the Miller cycle potential by utilising fully variable valve timing in controlling the load at the part load condition without using a throttle. The early intake valve closing with different valve lifts was tested in order to investigate the impact during the gas exchange process, particularly the pumping losses and the potential to improve fuel economy. This study includes both experimental and simulation studies. A Lotus single-cylinder research engine referred to as SCORE was mainly used for the experimental component of the study. The simulation work was conducted using a one-dimensional spark ignition engine model built in the Ricardo WAVE software for naturally-aspirated and downsized engines. The engine model values are validated against the experimental values from the Lotus SCORE and Lotus SABRE engines. The combustion model with a reduced kinetics mechanism was validated using a Rover K-series engine. A broad matrix of the engine operations has been investigated combining a variety of engine speeds and engine loads. The Miller cycle effects on knock suppression in a downsized engine environment have been investigated in three parts, namely the Miller cycle at different speed-load, knock suppression with extreme Miller cycle, and knock analysis with combustion kinetics. Through the works, the Miller cycle has demonstrated its capability to suppress engine knocking in a more efficient manner as opposed to the standard engine operation. This is contributed by the fact that early and late intake valve closings could affect the end gas condition at the end of the compression stroke, thus making it possible to suppress the engine knocking. The experimental study for controlling load without using throttle under the naturally-aspirated condition found that the Miller cycle with an early intake calve closing strategy able to improve fuel consumption by reducing pumping losses. The downsized engine condition, which has been evaluated via modelling work, also showed an improved performance trend using the unthrottled Miller cycle strategy. The open cycle and close cycle efficiencies have improved through the Miller cycle implementation. The contribution of this work is made in order to establish the comparison of the Miller cycle strategy in suppressing knocking between the early intake valve closing and late intake valve closing under a boosted environment. For the part load condition of the downsized engine, the research contributes to the existing body of knowledge by comparing the throttle-less Miller cycle and the standard throttled operation as a load control strategy.