An automatic transmission is a device that is connected to the back of an engine and sends the power from the engine to the drive wheels. Its job is to keep the engine within a certain angular velocity. Although there are many epicyclic-type automatic transmissions in production, the related configuration design methods are still tedious and prone to human error. A simple and analytic methodology needs to be developed. Therefore, the purpose of this research is to present an efficient methodology for the systematic design of the epicyclic gear transmissions for automobiles. First, fundamentals and gear-shifting operations of the four-speed, five-speed and six-speed epicyclic-type automatic transmissions are illustrated to establish the design requirements. Second, based on the kinematic equations of the fundamental geared entities and the corresponding basic gear ratios, a procedure is applied to execute the kinematic and mechanical-efficiency analyses for the automatic transmissions. Third, two simple clutching-sequence synthesis methods are proposed and illustrated. One is based on the speed ratio equations, and another is based on the lever diagram. Next, a planar-graph representation is presented to arrange the desired clutches for each possible clutching sequence into the epicyclic gear mechanism. Then, the number of teeth of each gear is synthesized from assigning two or three desired speed ratios by the analytic method. Finally, a computer-aided design program for the clutching-sequence synthesis is developed with the considerations of the design requirements. With the above methods, the systematic designs of the 204 epicylic gear mechanisms are given for demonstrating the feasibility of the proposed methodology. The result of this work shows that the seven-link two-DOF epicylic gear mechanisms, the eight-link two-DOF Ravigneaux gear mechanism, and the nine-link two-DOF parallel-connected epicylic gear mechanisms could reach four-, six-, and six-forward speeds at most, respectively.

The objective of the thesis was to evaluate the possibility to calculate the unloading distribution between a ventilator and a patient using a new mathematical modelling of the breathing patterns. The modelling used today is considered to lack sufficient precision for clinical use, and is a somewhat simplified model. To evaluate the possibility of a new model, a volunteer test was carried out - recording data such as Edi, pressure, volume and flow. Using this data, and by using a more complex model, tidal volume was estimated and compared to the measured data. The results did not imply any improvement compared to the simpler model regarding the accuracy and the variability. However, more work should be done in this area, as time deficiency prevented further analysis.

L’endurance aérobie est rarement mesurée à des intensités maximales, mais plutôt sous-maximales, principalement via des protocoles à puissance ou à durée constante. Or, les conditions réelles d’une épreuve sportive en compétition sont mieux représentées par le maintien de la plus haute puissance métabolique possible, et ce, le plus longtemps possible. Cela implique une autogestion de la puissance de travail de la part du participant – qui peut donc varier tout le long de l’épreuve – ainsi que l’atteinte des capacités aérobies maximales, dans certains cas. Dans cette étude, nous avons voulu comparer les variations de certains paramètres ventilatoires (ventilation, volume courant, fréquence respiratoire) et systémiques (rendement mécanique externe brut [RMEC], consommation d’oxygène [VO2]) entre deux protocoles d’effort maximal, l’un à puissance constante (100 % PAM), l’autre à puissance décrémentée (> 95 % VO2max). En effet, comparativement à un protocole d’effort classique à puissance constante, un protocole décrémenté implique l’utilisation de VO2 et non de la puissance mécanique comme critère de sélection de l’intensité d’effort, et augmente la durée de l’épreuve. En conséquence, le maintien de la consommation d’oxygène maximale (VO2max), et non de la puissance aérobie maximale (PAM), nous a permis d’observer des réponses physiologiques différentes de celles généralement décrites lors d’efforts incrémentés ou à puissance constante. Ces différences se sont traduites par une fréquence respiratoire plus élevée et un volume courant plus bas, indiquant l’existence d’une réponse tachypnéique plus prononcée lors d’un protocole décrémenté par rapport à un protocole à puissance constante, et reflétant ainsi une respiration plus superficielle, probablement due à une fatigue plus accrue des muscles ventilatoires. Cette fatigue serait caractérisée par un rendement mécanique plus bas et un VO2 plus élevé, et ce, malgré la diminution progressive de la puissance de travail lors de l’atteinte d’une consommation d’oxygène proche de VO2max. / Aerobic endurance is more commonly measured at submaximal rather than maximal work intensities, mainly through constant-power output trials, or time trials. However, real competition conditions are better represented through the ability to sustain the highest power output (PO) for the largest period of time. That implies the use of self-pacing strategies, which leads power output to vary throughout the exercise duration, and can also induce the attainment of maximal oxygen consumption (VO2max), in some cases. The aim of this study was thus to compare the variation of some ventilatory (tidal volume, breathing frequency) and systemic (gross mechanical efficiency, O2 cost) parameters, between two maximal endurance protocols, the first one consisting of a constant-load test (100% MAP) and the second one a decremental test at near-maximal aerobic capacity (> 95 % VO2max). Indeed, compared to a “classical” constant-power output test, a decremental test implies the use of VO2 rather than mechanical PO to control intensity throughout the task, and a higher effort duration. Consequently, we observed that the sustainment of maximal O2 consumption rather than maximal aerobic power (MAP) led to different physiological responses from those usually observed during constant-power output tests. These differences were caracterized by a higher breathing frequency as well as a lower tidal volume during the decremental test, which both reflect a more exagerated tachypneic response, and therefore indicate the existence of a shallower breathing pattern in this type of effort, probably due to a higher ventilatory muscle fatigue. This fatigue could also be expressed through a lower gross mechanical efficiency and a higher O2 cost, despite a progressive decrease of mechanical power as soon as oxygen consumption gets near VO2max.

Orientador: Benedito Sérgio Denadai / Banca: Renato de Sousa Almeida / Banca: Sergio Ricardo de Abreu Camarda / Banca: Fabrizio Caputo / Banca: Mauro Gonçalves / Resumo: Exercícios intensos e/ou não habituais, realizados através de contrações excêntricas, ocorrem constantemente em nossas vidas, os quais podem resultar em dores musculares imediatas ou tardias, com um marcado e prolongado efeito sobre nossa capacidade funcional. Desta forma, o presente trabalho teve como objetivo analisar o efeito do exercício excêntrico (EE), associado com dano muscular, sobre as propriedades mecânicas do músculo e índices de aptidão aeróbia. Metodologicamente o experimento foi dividido em 1 e 2. No primeiro experimento, doze homens (21,7±2,3 anos) saudáveis, não treinados, foram avaliados, através de três contrações voluntárias máximas (CVM), no pico de torque (PT) isocinético do quadríceps, e correspondente, pico da taxa de desenvolvimento de torque (pico TDT), pico da taxa de desenvolvimento de velocidade (pico TDV) e impulso contrátil (IC) a 60º.s-1 antes e após 24h e 48h de um protocolo de exercícios excêntricos de dez séries de dez repetições máximas. No segundo experimento, vinte homens (24,4±3,5 anos) saudáveis e não treinados foram divididos em dois grupos, de acordo com a cadência realizada no ciclismo (50 rpm e 100 rpm), e avaliados para a cinética de consumo de oxigênio ( O2) e eficiência mecânica bruta (EB) e de trabalho (ET), através de três transições de ciclismo com duração cada uma de 6min a 90% do limiar de lactato precedidas de 4min a 0W, antes e após 24h e 48h do protocolo de EE. Nos dois experimentos os indicadores indiretos de dano muscular de dor muscular tardia (DMT), atividade da creatina quinase (CK) plasmática e pico de torque isocinético concêntrico (PT) foram significantemente alterados 24h e 48h após o protocolo de exercícios excêntricos, em relação aos valores de base. No primeiro experimento o PT (-15,3%, p=0,002), pico TDT (-13,1%,. p=0,03) e IC (-29,3%,. p=0,01) diminuíram significantemente... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Intense and/or unusual exercises, related to eccentric contractions are constant in our lives, resulting in immediate or delayed onset muscle soreness (DOMS) and may have a marked and prolonged effect on our functional capacity. Thus, this study was to analyze the effect of eccentric exercise (EE), associated with muscle damage, on the mechanical properties of muscle and indices of aerobic fitness. Methodologically the experiment was divided into 1 and 2. In the first experiment, twelve (21.7 ± 2.3 years) healthy untrained men subjects were assessed at peak torque (PT) isokinetic quadriceps, and the corresponding peak rate of torque development (peak RTD), peak rate velocity development (peak RVD) and contractile impulse (CI) at 60o. s-1 before and after 24h and 48h isokinetic EE protocol of 10 sets of 10 repetitions. In the second experiment, twenty (24.4 ± 3.5 years) healthy and untrained men were divided into two cycling cadence groups (50 rpm and 100 rpm) and evaluated for the pulmonary oxygen uptake ( O2) kinetics and gross (GE) and work (WE) mechanical efficiency through 3 transitions cycling lasting each of 6 min at 90% lactate threshold preceded by 4min at 0W, before and after 24h and 48h protocol EE. In both experiments, DOMS (DMT), activity of creatine quinase (CK) in plasma and peak isokinetic concentric torque (PT) was significantly altered at 24h and 48h after the eccentric exercise protocol. In the first experiment, the PT (-15.3%, p = 0.002), peak RTD (-13.1%. p = 0.03) and CI (- 29.3%. p = 0.01) decreased significantly to 24h and peak RVD not changed. After 48h, PT (-7.9%, p = 0.002) and CI (-29.2%, p = 0.003) were maintained less values but RTD recovered to baseline values. RTD normalized to PT (% CVM.s-1) measured at 30 ms (24h = 580.5%, p = 0.01 and 48h = 681.3%, p = 0.006) and 100 ms (48h = 623.3 %, p = 0.009) the onset of contraction was higher than the previous... (Complete abstract click electronic access below) / Doutor

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-08-31T14:27:00Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação Mestrado LUCYANA GALINDO ARCOVERDE VAZ.pdf: 1541733 bytes, checksum: 075c4e7b9b3f5f39a8de2b68a1df2f24 (MD5) / Made available in DSpace on 2016-08-31T14:27:00Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação Mestrado LUCYANA GALINDO ARCOVERDE VAZ.pdf: 1541733 bytes, checksum: 075c4e7b9b3f5f39a8de2b68a1df2f24 (MD5) Previous issue date: 2016-03-29 / CAPEs / A ação ergogênica da cafeína sobre a capacidade anaeróbia (CAN) está relacionada à melhora do desempenho. Entretanto, os estudos que investigaram o efeito da cafeína sobre a capacidade anaeróbia utilizaram apenas o máximo déficit acumulado de oxigênio (MAOD) como método de estimativa. Avaliar o efeito do consumo agudo de cafeína sobre a CAN estimada através dos principais métodos de estimativa, MAOD, potência crítica (ponto de intercepção y da função trabalho/tempo), fase rápida de recuperação do consumo de oxigênio + concentração de lactato (3 compartimentos) e eficiência mecânica grossa (EF), que por apresentarem medidas representativas da CAN, detectam igualmente os possíveis efeitos do consumo agudo de cafeína sobre o metabolismo anaeróbio. Nove participantes realizaram um teste incremental no cicloergômetro para determinação do primeiro limiar ventilatório (LV1) e do consumo máximo de oxigênio (VO2máx). A partir da carga referente ao LV1 foram calculadas a carga de aquecimento (90% do LV1), e as cargas dos testes experimentais. Foram doze testes experimentais, sendo seis com cafeína e seis placebo, em um desenho duplo-cego, contrabalanceado e controlado por placebo. A contribuição anaeróbia foi calculada pelos principais métodos de estimativa. Os achados mostraram que os métodos não detectam a mesma medida de CAN, logo, eles não são equivalentes na estimativa. Em relação ao efeito da cafeína sobre a estimativa sim, não houve diferença entre cafeína e placebo, exceto MAOD, que teve uma medida mais alta na situação cafeína. Além disso, não houve diferença no tempo de exaustão entre cafeína e placebo na carga supramáxima. Os métodos de estimativa não são equivalentes, eles não apresentam a mesma medida da CAN. A cafeína influenciou um dos métodos, MAOD, e isso levou a uma superestimativa da medida, quando corrigido pela estimativa do placebo, não apresentou mais diferença. Além disso, a cafeína não promoveu melhora no desempenho na carga supramáxima. / The caffeine ergogenic action on anaerobic capacity (AC) is related to performance’s improvement. However, some studies used only the maximal accumulated oxygen deficit (MAOD) as estimative method to investigate the effect of caffeine on anaerobic capacity. Evaluate the effect of acute caffeine consumption over the estimated AC through the main estimative methods, MAOD, critical power (interception point y work function/time), fast recovery phase of oxygen consumption + lactate concentration (3 compartments) and gross mechanical efficiency (GME), which by presenting representative measures of AC also detect the possible effects of acute caffeine consumption on the anaerobic metabolism. Nine participants performed an incremental test on a cycle ergometer to determine the first ventilatory threshold (VT1) and the maximal oxygen uptake (VO2max). From VT1 power output were calculated warm up load (90% of VT1), and the loads of the experimental trials. Twelve experimental trails were performed, being six after caffeine and six after placebo in a double-blind, placebo-controlled and counterbalanced design. AC was calculated by main estimative methods. The findings of the present study showed that AC was not detected similarly by the estimative methods, which might assume that they are not equivalent in the estimative. However, MAOD was higher in after caffeine ingestion when compared to placebo. There were no differences between trials in the other estimative methods. In addition, the time to exhaustion was not different between caffeine and placebo in supramaximal exercise. The estimative methods are not equivalent to measure AC. However, caffeine influenced MAOD, which probably overestimate the measurement. However, when corrected by the placebo estimative, no differences between trials was observed. Furthermore, caffeine was not efficient to improve the performance at supramaximal exercise.

External gear machines (EGMs) are used in a variety of industries ranging from fluid power machinery to fluid handling systems and fuel injection applications. Energy efficiency requirements and new trends in hydraulic technology necessitate the development of novel EGMs optimized for efficiency and reliability in all of these applications. A crucial piece in the novel EGM development process is a numerical model that can simulate the operation of EGM and predict its volumetric and hydro-mechanical performance.<div><br></div><div>The EGM simulation models developed in the past have focused mostly on the challenges related to the modeling of the theoretical behavior and elementary fluid dynamics, and determining appropriate modeling schemes. Key aspects related to the flow and geometry are either considered in a simplified manner or not considered at all. In particular, the current simulation models assume the fluid to be Newtonian and the leakage flows to be laminar. However, EGMs working in fluid handling applications operate with non-Newtonian fluids. Further, in fuel injection applications, due to low fluid viscosity and high operating speed, the internal leakage flows may not remain laminar.</div><div><br></div><div>With respect to the geometric aspects, the gears in EGMs are prone to manufacturing errors that are not accounted by any simulation model. In addition, there is no method available in the literature for accurately modeling the leakage flows through curve-constricted geometries in EGMs. Further, the goal of current simulation tools is related to the prediction of the volumetric performance of EGMs. However, an equally important characteristic, hydro-mechanical performance, is often ignored. Finally, the energy flow during EGM operation can result in the variation of the fluid temperature. Thus, the isothermal assumption of current simulation tools is another major limitation.</div><div><br></div><div>The work presented in this dissertation is focused on developing numerical methodologies for the modeling of EGMs that addresses all the aforementioned limitations of the current models. In this work, techniques for evaluating non-Newtonian internal flows in EGMs is developed to permit an accurate modelling of EGMs working with non-Newtonian fluids. For fuel injection EGMs, flow regime at the tooth tips of the gears is investigated and it is shown that the flow becomes turbulent for such EGMs. A methodology for modeling this turbulent flow is proposed and its impact on the performance of EGMs is described. To include gear manufacturing errors in the simulation model, numerical techniques are developed for modeling the effects of two common gear manufacturing errors: conicity and concentricity. These two errors are shown to have an opposite impact on the volumetric efficiency of the EGM. For the evaluation of flows through curve-constricted leakage paths in EGMs, a novel flow model is developed in this work that is applicable for a wide range of geometry and flow conditions. Modeling of the hydro-mechanical efficiency of EGMs is accomplished by developing methodologies for the evaluation of torque losses at key interfaces. Finally, to account for the thermal effects in EGMs, a thermal model is developed to predict the temperature distribution in the EGM and its impact on the EGM performance.</div><div><br></div><div><div>To validate the numerical methodologies developed in this work, several experiments are conducted on commercial gear pumps as well as on a custom apparatus designed and manufactured in the course of this research work. The results from the experiments are found to match those obtained from the simulations which indicates the validity of the methodologies developed in this work. </div><div><br></div><div>These numerical methodologies are based on the lumped parameter approach to allow the coupling with mechanical models for gear micromotion and permit fast computations so that the model can be used in optimization algorithms to develop energy efficient and reliable EGMs.</div><div><br></div><div>The methodologies described in the dissertation are useful for accurate analysis of a variety of EGMs working with different types of fluids and at wide range of operating conditions. This capability will be valuable for pump designers in developing novel better performing EGM designs optimized for various applications.</div><div><br></div></div>

Made available in DSpace on 2014-06-11T19:30:53Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-04-13Bitstream added on 2014-06-13T19:40:24Z : No. of bitstreams: 1 molina_r_dr_rcla.pdf: 1580344 bytes, checksum: 7e4493046f62a81aaae554c81ae0e39c (MD5) / Exercícios intensos e/ou não habituais, realizados através de contrações excêntricas, ocorrem constantemente em nossas vidas, os quais podem resultar em dores musculares imediatas ou tardias, com um marcado e prolongado efeito sobre nossa capacidade funcional. Desta forma, o presente trabalho teve como objetivo analisar o efeito do exercício excêntrico (EE), associado com dano muscular, sobre as propriedades mecânicas do músculo e índices de aptidão aeróbia. Metodologicamente o experimento foi dividido em 1 e 2. No primeiro experimento, doze homens (21,7±2,3 anos) saudáveis, não treinados, foram avaliados, através de três contrações voluntárias máximas (CVM), no pico de torque (PT) isocinético do quadríceps, e correspondente, pico da taxa de desenvolvimento de torque (pico TDT), pico da taxa de desenvolvimento de velocidade (pico TDV) e impulso contrátil (IC) a 60º.s-1 antes e após 24h e 48h de um protocolo de exercícios excêntricos de dez séries de dez repetições máximas. No segundo experimento, vinte homens (24,4±3,5 anos) saudáveis e não treinados foram divididos em dois grupos, de acordo com a cadência realizada no ciclismo (50 rpm e 100 rpm), e avaliados para a cinética de consumo de oxigênio ( O2) e eficiência mecânica bruta (EB) e de trabalho (ET), através de três transições de ciclismo com duração cada uma de 6min a 90% do limiar de lactato precedidas de 4min a 0W, antes e após 24h e 48h do protocolo de EE. Nos dois experimentos os indicadores indiretos de dano muscular de dor muscular tardia (DMT), atividade da creatina quinase (CK) plasmática e pico de torque isocinético concêntrico (PT) foram significantemente alterados 24h e 48h após o protocolo de exercícios excêntricos, em relação aos valores de base. No primeiro experimento o PT (-15,3%, p=0,002), pico TDT (-13,1%,. p=0,03) e IC (-29,3%,. p=0,01) diminuíram significantemente... / Intense and/or unusual exercises, related to eccentric contractions are constant in our lives, resulting in immediate or delayed onset muscle soreness (DOMS) and may have a marked and prolonged effect on our functional capacity. Thus, this study was to analyze the effect of eccentric exercise (EE), associated with muscle damage, on the mechanical properties of muscle and indices of aerobic fitness. Methodologically the experiment was divided into 1 and 2. In the first experiment, twelve (21.7 ± 2.3 years) healthy untrained men subjects were assessed at peak torque (PT) isokinetic quadriceps, and the corresponding peak rate of torque development (peak RTD), peak rate velocity development (peak RVD) and contractile impulse (CI) at 60o. s-1 before and after 24h and 48h isokinetic EE protocol of 10 sets of 10 repetitions. In the second experiment, twenty (24.4 ± 3.5 years) healthy and untrained men were divided into two cycling cadence groups (50 rpm and 100 rpm) and evaluated for the pulmonary oxygen uptake ( O2) kinetics and gross (GE) and work (WE) mechanical efficiency through 3 transitions cycling lasting each of 6 min at 90% lactate threshold preceded by 4min at 0W, before and after 24h and 48h protocol EE. In both experiments, DOMS (DMT), activity of creatine quinase (CK) in plasma and peak isokinetic concentric torque (PT) was significantly altered at 24h and 48h after the eccentric exercise protocol. In the first experiment, the PT (-15.3%, p = 0.002), peak RTD (-13.1%. p = 0.03) and CI (- 29.3%. p = 0.01) decreased significantly to 24h and peak RVD not changed. After 48h, PT (-7.9%, p = 0.002) and CI (-29.2%, p = 0.003) were maintained less values but RTD recovered to baseline values. RTD normalized to PT (% CVM.s-1) measured at 30 ms (24h = 580.5%, p = 0.01 and 48h = 681.3%, p = 0.006) and 100 ms (48h = 623.3 %, p = 0.009) the onset of contraction was higher than the previous... (Complete abstract click electronic access below)

The 20 Metre Multistage Shuttle Run Test (20 MST) was modified for application to ice-sports, more specifically for ice-hockey and figure-skating. Seventy two participants in ice-sports served as the total subject group. Subjects included in the study were National and Provincial standard male ice-hockey subjects (n=67) and female figure skaters (n=5) participating in the Gauteng area of South Africa (altitude of 1497 metres above sea level and barometric pressure of 655 mmHg). The mean age for the total group was 17.44±1.33 years. The research methodology entailed a repeated measures design to determine: a) velocity of motion on-ice vs. over-ground; b) energy expenditure on-ice vs. over-ground; and c) mechanical efficiency on-ice vs. over-ground. The mean velocity of motion measured over three distances (0 to 20, 0 to 30 and 0 to 40 m) indicated a significantly (p≤0.05) faster velocity on-ice (5.99±0.72 m/s) versus over-ground (5.75±0.63 m/s). The corresponding mean time-lapsed on-ice/over-ground ratio was 0.97±0.11. Differences in mean energy expenditure whilst performing the original 20 MST over-ground as opposed to on-ice were measured at low (at 4 minutes of exercise and 10 km/h), intermediate (after 8 minutes of exercise and 12 km/h), and high intensity (after 12 min of exercise and 14 km/h). The mean of the three indicated a significantly (p≤0.05) higher energy expenditure over-ground (14.04±4.86 kcal/min) as apposed to on-ice (10.51±2.95 kcal/min). The mean energy expenditure ratio for the three different intensities on-ice vs. over-ground was 0.74±0.21. Similarly, the mechanical efficiency index over-ground (4.92±0.59) was found to be significantly (p≤0.001) poorer than on-ice (6.83±1.49). The mean mechanical efficiency ratio over-ground/over-ice was 0.74±0.13. Subsequently, based on the above results, the 20 MST was modified by: a) adapting (increasing) the velocity of motion required for each level of the test (distance of 20 m per shuttle); and b) establishing the reliability and validity of the modified 20 MST for use on-ice. The adapted 20 Metre Multistage Shuttle Skating Test (the modified (skating) 20 MST) started at a velocity of 2.8 m/s (10.1 km/h) and permitted 7.1 seconds to complete each shuttle for the first level of the test, which then decreased progressively at each level. This was based on an over-all variable-derived on-ice to over ground ratio of 0.84. Test-retest, on-ice reliability measures (n=15) for predicted VO2max (49.5±8.37 vs. 49.29±7.95 ml/kg/min) showed a highly significant (p£0.001) consistency (r=0.87). Similarly test-retest concurrent validity measures (n=10) for predicted VO2max over-ground with the original 20 MST (48.09±6.25 ml/kg/min) as designed by Léger and Lambert (1982) versus on-ice values with the adapted on-ice 20 MST (49.98±7.23 ml/kg/min), showed a very significant (p£0.01) correlation of 0.73 between the two tests. In conclusion the original 20 MST, as designed by Léger and Lambert (1982) for over-ground, proved inappropriate for use on-ice. Modification of the starting velocity as well as a progressive increase in velocity for all subsequent stages renders the modified 20 MST for ice-sports a reliable and valid test for cardiorespiratory fitness (VO2max), with surface-specific utility. The 20 Metre Multistage Shuttle Run Test (20 MST) was modified for application to ice-sports, more specifically for ice-hockey and figure-skating. Seventy two participants in ice-sports served as the total subject group. Subjects included in the study were National and Provincial standard male ice-hockey subjects (n=67) and female figure skaters (n=5) participating in the Gauteng area of South Africa (altitude of 1497 metres above sea level and barometric pressure of 655 mmHg). The mean age for the total group was 17.44±1.33 years. The research methodology entailed a repeated measures design to determine: a) velocity of motion on-ice vs. over-ground; b) energy expenditure on-ice vs. over-ground; and c) mechanical efficiency on-ice vs. over-ground. The mean velocity of motion measured over three distances (0 to 20, 0 to 30 and 0 to 40 m) indicated a significantly (p≤0.05) faster velocity on-ice (5.99±0.72 m/s) versus over-ground (5.75±0.63 m/s). The corresponding mean time-lapsed on-ice/over-ground ratio was 0.97±0.11. Differences in mean energy expenditure whilst performing the original 20 MST over-ground as opposed to on-ice were measured at low (at 4 minutes of exercise and 10 km/h), intermediate (after 8 minutes of exercise and 12 km/h), and high intensity (after 12 min of exercise and 14 km/h). The mean of the three indicated a significantly (p≤0.05) higher energy expenditure over-ground (14.04±4.86 kcal/min) as apposed to on-ice (10.51±2.95 kcal/min). The mean energy expenditure ratio for the three different intensities on-ice vs. over-ground was 0.74±0.21. Similarly, the mechanical efficiency index over-ground (4.92±0.59) was found to be significantly (p≤0.001) poorer than on-ice (6.83±1.49). The mean mechanical efficiency ratio over-ground/over-ice was 0.74±0.13. Subsequently, based on the above results, the 20 MST was modified by: a) adapting (increasing) the velocity of motion required for each level of the test (distance of 20 m per shuttle); and b) establishing the reliability and validity of the modified 20 MST for use on-ice. The adapted 20 Metre Multistage Shuttle Skating Test (the modified (skating) 20 MST) started at a velocity of 2.8 m/s (10.1 km/h) and permitted 7.1 seconds to complete each shuttle for the first level of the test, which then decreased progressively at each level. This was based on an over-all variable-derived on-ice to over ground ratio of 0.84. Test-retest, on-ice reliability measures (n=15) for predicted VO2max (49.5±8.37 vs. 49.29±7.95 ml/kg/min) showed a highly significant (p£0.001) consistency (r=0.87). Similarly test-retest concurrent validity measures (n=10) for predicted VO2max over-ground with the original 20 MST (48.09±6.25 ml/kg/min) as designed by Léger and Lambert (1982) versus on-ice values with the adapted on-ice 20 MST (49.98±7.23 ml/kg/min), showed a very significant (p£0.01) correlation of 0.73 between the two tests. In conclusion the original 20 MST, as designed by Léger and Lambert (1982) for over-ground, proved inappropriate for use on-ice. Modification of the starting velocity as well as a progressive increase in velocity for all subsequent stages renders the modified 20 MST for ice-sports a reliable and valid test for cardiorespiratory fitness (VO2max), with surface-specific utility. / Dissertation (MA (Human Movement Science))--University of Pretoria, 2005. / Biokinetics, Sport and Leisure Sciences / unrestricted

This document describes the possibilities of increasing the mechanical efficiency of the crank train of an internal-combustion engine. For this purpose, a concept with a reduced number of main bearings is chosen and its contribution is verified experimentally. The proposed solution consists of an innovative crankshaft design of a four-cylinder spark-ignition engine with only three main journal bearings and laser-welded sheet metal crank webs. The new design is compared to the mass-produced one in terms of friction losses, vibrations and loading of engine parts by means of simulations of crank train dynamics using the Multi-Body System. The increase in vibration, accompanied by a reduction in friction losses, is compensated by a torsional vibration damper and its effect is experimentally verified. Experimental research of laser welds on the crankshaft in terms of fatigue life is also described. The overall potential is also summarised and further possible development of this innovative and patented design is outlined.

Indiana University-Purdue University Indianapolis (IUPUI) / A gearless hydraulic wind energy transfer system utilizes the hydraulic power transmission principles to integrate the energy of multiple wind turbines in a central power generation location. The gearless wind power transfer technology may replace the current energy harvesting system to reduce the cost of operation and increase the reliability of wind power generation. It also allows for the integration of multiple wind turbines to one central generation unit, unlike the traditional wind power generation with dedicated generator and gearbox. A Hydraulic Transmission (HT) can transmit high power and can operate over a wide range of torque-to-speed ratios, allowing efficient transmission of intermittent wind power. The torque to speed ratios illustrates the relationship between the torque and speed of a motor (or pump) from the moment of start to when full-load torque is reached at the manufacturer recommended rated speed. In this thesis, a gearless hydraulic wind energy harvesting and transfer system is mathematically modeled and verified by experimental results. The mathematical model is therefore required to consider the system dynamics and be used in control system development. Mathematical modeling also provided a method to determine the losses of the system as well as overall efficiency. The energy is harvested by a low speed-high torque wind turbine connected to a high fixed-displacement hydraulic pump, which is connected to hydraulic motors. Through mathematical modeling of the system, an enhanced understanding of the HTS through analysis was gained that lead to a highly efficient hydraulic energy transmission system. It was determined which factors significantly influenced the system operation and its efficiency more. It was also established how the overall system operated in a multiple wind turbine configuration. The quality of transferred power from the wind turbine to the generator is important to maintaining the systems power balance, frequency droop control in grid-connected applications, and to ensure that the maximum output power is obtained. A hydraulic transmission system can transfer large amounts of power and has more flexibility than a mechanical and electrical system. However high-pressure hydraulic systems have shown low efficiency in wind power transfer when interfaced with a single turbine to a ground-level generator. HT’s generally have acceptable efficiency at full load and drop efficiency as the loading changes, typically having a peak around 60%. The efficiency of a HT is dependent on several parameters including volumetric flow rate, rotational speed and torque at the pump shaft, and the pressure difference across the inlet and outlet of the hydraulic pump and motor. It has been demonstrated that using a central generation unit for a group of wind turbines and transferring the power of each turbine through hydraulic system increases the efficiency of the overall system versus one turbine to one central generation unit. The efficiency enhancement depends on the rotational speed of the hydraulic pumps. Therefore, it is proven that the multiple-turbine hydraulic power transfer system reaches higher efficiencies at lower rotational speeds. This suggests that the gearbox can be eliminated from the wind powertrains if multiple turbines are connected to the central generation unit. Computer simulations and experimental results are provided to quantify the efficiency enhancements obtained by adding the second wind turbine hydraulic pump to the system.