No description available.

Hydraulic spool valves are found in most hydraulic circuits in which flow is to be modulated. Therefore their dynamic performance is critical to the overall performance of the circuit. Fundamental to this performance is the presence of flow reaction forces which act on the spool. These forces can result in the necessity of using two stage devices to drive the spool and in some cases have been directly linked to valve and circuit instabilities. As such, a great deal of research and design has concentrated on ways to reduce or compensate for flow forces. In one particular series of studies conducted on flow divider valves, it was established that a rim machined into the land of the spool reduced the flow dividing error by approximately 70-80%, and it was deduced that the main contribution to this error was flow forces. Direct verification of the claim regarding flow force reduction was not achieved and hence was the motivation for this particular study. <p> This thesis will consider the reaction (flow) force associated with a conventional spool land and one with a rim machined into it, and a modified form of the rimmed land referred to as a sharp edge tapered rim spool land. The rim and the sharp edge tapered rim were specially designed geometrical changes to the lands of the standard spool in order to reduce the large steady state flow forces (SSFF) inherent in the standard spool valve. In order to analyze the flow field inside the interior passages of the valve, three configurations of the spool were considered for orifice openings of 0.375, 0.5, 0.75 and 1.05 mm. Computational Fluid Dynamics (CFD) analysis was used to describe the fluid mechanics associated with the steady state flow forces as it provided a detailed structure of the flow through the valve, and to identify the flow mechanism whereby flow forces are reduced by the machining of a rim and tapered rim on the land of the spool. For all openings of the spool, the sharp tapered rim valve provides the largest reduction in SSFF. It was also observed that for all cases studied, the inflow SSFFs were smaller than for the outflow conditions. <p>The prediction of the steady state flow force on the rim spool was investigated in a flow divider valve configuration, and the results from the CFD analysis indicated a reduction by approximately 70%.

Hydraulic spool valves are found in most hydraulic circuits in which flow is to be modulated. Therefore their dynamic performance is critical to the overall performance of the circuit. Fundamental to this performance is the presence of flow reaction forces which act on the spool. These forces can result in the necessity of using two stage devices to drive the spool and in some cases have been directly linked to valve and circuit instabilities. As such, a great deal of research and design has concentrated on ways to reduce or compensate for flow forces. In one particular series of studies conducted on flow divider valves, it was established that a rim machined into the land of the spool reduced the flow dividing error by approximately 70-80%, and it was deduced that the main contribution to this error was flow forces. Direct verification of the claim regarding flow force reduction was not achieved and hence was the motivation for this particular study. <p> This thesis will consider the reaction (flow) force associated with a conventional spool land and one with a rim machined into it, and a modified form of the rimmed land referred to as a sharp edge tapered rim spool land. The rim and the sharp edge tapered rim were specially designed geometrical changes to the lands of the standard spool in order to reduce the large steady state flow forces (SSFF) inherent in the standard spool valve. In order to analyze the flow field inside the interior passages of the valve, three configurations of the spool were considered for orifice openings of 0.375, 0.5, 0.75 and 1.05 mm. Computational Fluid Dynamics (CFD) analysis was used to describe the fluid mechanics associated with the steady state flow forces as it provided a detailed structure of the flow through the valve, and to identify the flow mechanism whereby flow forces are reduced by the machining of a rim and tapered rim on the land of the spool. For all openings of the spool, the sharp tapered rim valve provides the largest reduction in SSFF. It was also observed that for all cases studied, the inflow SSFFs were smaller than for the outflow conditions. <p>The prediction of the steady state flow force on the rim spool was investigated in a flow divider valve configuration, and the results from the CFD analysis indicated a reduction by approximately 70%.

Optimal management of fractures, post-traumatic arthritis and instability of the distal radioulnar joint (DRUJ) requires an understanding of the forces existing across this joint as a function of the activities of daily living. However, such knowledge is currently incomplete. The goal of this research was to quantify the loads that occur at the DRUJ during forearm rotation and to determine the effect that individual muscles have on those loads. Human and cadaver studies were used to analyze the shear (A-P), transverse (M-L) and resultant forces at the DRUJ and to determine the role that 15 individual muscles had on those forces. Data for scaling the muscles forces came from EMG analysis measuring muscle activity at nine positions of forearm rotation in volunteers during isometric pronation and supination. Muscle orientations were determined from the marked muscle origin and insertion locations of nine cadaveric arms at various stages of forearm rotation. The roles that individual muscles played in DRUJ loading were analyzed by removing the muscle of interest from the analysis and comparing the results. The EMG portion of this study found that the pronator quadratus, pronator teres, brachioradialis, flexor carpi radialis and palmaris longus contribute significantly to forearm pronation. The supinator, biceps brachii, and abductor pollicis longus were found to contribute significantly to supination. The results of the DRUJ analysis affirm that large transverse forces pass from the radius to the ulnar head at all positions of forearm rotation during pronation and supination (57.5N-181.4N). Shear forces exist at the DRUJ that act to pull the radius away from the ulna in the AP direction and are large enough to merit consideration when examining potential treatment options (7.9N-99.5N). Individual muscle analysis found that the extensor carpi radialis brevis, extensor pollicis longus, extensor carpi ulnaris, extensor indicis and palmaris longus had minimal effect on DRUJ loading. Other than the primary forearm rotators (pronator quadratus, pronator teres, supinator, biceps brachii), the muscles that exhibited the largest influence on DRUJ loading were the abductor pollicis longus, brachialis, brachioradialis, extensor carpi ulnaris, flexor carpi radialis, and flexor carpi ulnaris.

Made available in DSpace on 2016-12-06T17:06:50Z (GMT). No. of bitstreams: 1 Fernanda Todeschini Viero.pdf: 1880137 bytes, checksum: 599eff8e7b843aeb1ae20b6da73a3ac0 (MD5) Previous issue date: 2011-12-12 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The main objective of this study was to analyze the kinetic characteristics of the punch in karate in natural stance and advanced where the proposed specific objectives were to verify the strength values (component orthogonal to the fixed target) generated by karate straight punch during the impact on fixed target; measuring ground reaction forces in three orthogonal directions: vertical (z), antero-posterior (y) and medio-lateral (x); compare the peak force of the punch normalized by body weight between the natural posture and stance; and compare the percentage of body weight at the time of peak force of the punch between the natural posture and stance. The study included nine practitioners of Traditional Shotokan Karate, male, graduated from the first dan, and over the age of eighteen years, all invited to participate voluntarily in the study. For the collection of ground reaction forces were used two force platforms AMTI model OR6-GT and the analysis of the punch device was developed with a fixed target instrumented. Data collection was divided into two stages, the first was rated the straight punch in front stance and the second was evaluated in a natural posture. We collected data from participants, the anthropometric characteristics taken after heating the same individual adjusted to the pre-determined position, on the force platforms in front of the column, where your equipment with the target fixed for the execution of instrumented punches average level. The kinetic parameters analyzed were interpreted with the aid of a software routine in scilab-5.3.3 (INRA, France). To present the data we used descriptive statistics. Additionally, we used the paired t-test for detecting differences in performance parameters between the punch and natural stance. All tests were carried out using SPSS 17.0 software (SPSS, USA) at a significance level of 5%. The results showed that the absolute values of impact found in this independent study confirm the stance taken karate as the art of teaching the final blow. In terms of ground reaction forces in three orthogonal directions (z, y, x), results were obtained with the forces in the orthogonal directions z and y, being that on the other hand for ortogonal direction x, the same one was rejected ahead of the necessity for a more accurate analysis. As for comparisons were obtained significant results (p <0.05) for the intensities of punches between the advanced and natural postures and non-significant results (p> 0.05) for the percentage weights at the moment of peak force between the punch advanced postures and natural. Finally, it was stressed that it seems the hip rotation is so important in the efficiency of the blow given that you can make a relationship between the intensity obtained from the impact of the blow and magnitude of the binary system generated by the actions of the feet. / O principal objetivo deste estudo foi analisar as características cinéticas do soco no Karatê em postura natural e avançada onde os objetivos específicos propostos foram verificar os valores de força (componente ortogonal ao alvo fixo) gerados pelo soco direto do karatê durante o impacto no alvo fixo; medir forças de reação do solo nas três direções ortogonais: vertical (z), ântero-posterior (y) e médio lateral (x); comparar o pico de força do soco normalizado pelo peso corporal entre a postura natural e a postura avançada; e comparar o percentual do peso corporal no momento de pico de força do soco entre a postura natural e a postura avançada. Participaram deste estudo nove praticantes de Karatê Shotokan Tradicional, do sexo masculino, graduados a partir do 1o dan, e com idade superior a dezoito anos, todos convidados a participar voluntariamente do estudo. Para as coletas das forças de reação do solo foram utilizadas duas plataformas de força AMTI modelo OR6-GT e para a análise do soco foi desenvolvido um dispositivo com o alvo fixo instrumentado. A coleta de dados foi dividida em duas etapas, na primeira foi avaliado o soco direto na postura avançada e na segunda foi avaliado na postura natural. Foram coletados os dados dos participantes, tomadas as características antropométricas e após aquecimento individual, o mesmo ajustou-se à posição pré-estabelecida nas plataformas de força em frente à coluna, onde se encontrava o aparato com o alvo fixo instrumentado para a execução dos socos a nível médio. Os parâmetros cinéticos analisados foram interpretados com auxílio de uma rotina no software Scilab-5.3.3 (INRA, França). Para apresentar os dados foi utilizada a estatística descritiva. Adicionalmente, foi utilizado o teste t pareado para verificar diferenças nos parâmetros da execução do soco entre a postura avançada e natural. Todos os testes foram realizados com auxílio do software SPSS 17.0 (SPSS, EUA) a um nível de significância de 5%. Pelos resultados verificou-se que para os valores absolutos de impacto encontrados neste estudo independente da postura adotada confirmam o karatê como sendo a arte da doutrina do golpe definitivo. No que tange às forças de reação do solo nas três direções ortogonais (z, y, x), respostas foram obtidas para as forças nas direções ortogonais z e y, sendo que em contrapartida para a direção ortogonal x, a mesma foi desprezada diante da necessidade de uma análise mais acurada. Quanto às comparações se obtiveram resultados significativos (p<0,05) para as intensidades dos socos entre as posturas avançada e natural e resultados não significativos (p>0,05) para os pesos percentuais durante o momento de pico de força do soco entre as posturas avançada e natural. Por fim, destacou-se que ao que parece o giro do quadril tem tanta importância na eficiência do golpe haja vista que se pode fazer uma relação entre a intensidade obtida através do impacto do golpe e magnitude do sistema binário gerado pelas ações dos pés.

To make a check of an contemporary balancing verification of diesel engine Zetor UŘ III with type identification 1505, the engine power 90 kW and especially friction bearing design, which could replace existing needle bearing HK 4520 type, is the aim of this diploma thesis. Bearing type modification requires constructional adjustment of engine block and balancing shaft and therefore this proposal for construction another aim in my diploma thesis. The last part of my diploma thesis is an economic balance original imposition against newly designed. Calculations are made using mathematical software MathCad, the balancing shaft is made using ProEngineer software and control calculations of bearing stresses are made with ADAMS and FEM of ANSYS system. Motivation to write this work is to prove the possibility how to decrease manufacturing costs of ZETOR TRACTORS a.s. company.

The purpose of this study was to investigate if a nine-week training intervention composed of different mobility and stability exercises intending to improve jump height, whole-body stability, and single-leg stability of junior cross-country skiers. It was also of interest to see if the test equipment could determine the study participants' potential risk of injury with a built-in injury predictor measurement, Musculoskeletal Health (MSK).  A total of 16 cross-country skiers aged 16-20 years, 8 man and 8 women, performed the following tests on a force plate; Jump Scan (i.e., to characterize an individual's dynamic movement strategy), Plank Scan (i.e., to measure the individual's ability to control global static stability across each extremity), and Balance Scan (i.e., the individual's ability to maintain their center of mass over their center of pressure). After the initial scan, participants were assigned to the same nine-week intervention program, with Group 1 performing the program three times each week and Group 2 once each week before performing a post-intervention scan. Using two-way ANOVA showed no significant between-group differences. There was no significant difference when using three-way ANOVA within both intervention groups, except higher CMJ Load scores (p=0.032) and reduction in Plank scores, Plank Left (p=0.024) in male participants. When using logistic regression tests to determine the correlation between jump height (CMJ) outcomes effect on MSK injury risk between groups and within gender, a significant correlation in females was shown (p=0.0280, R=0.46). The present study's results suggest that a 9-week training intervention is not sufficient when training either one or three times per week for improving jump height, whole-body stability, and single-leg stability in junior cross-country skiers.

An Institutional Review Board (IRB)-approved study was conducted to investigate the effects of the Tsunami Bar® (TB), a flexible barbell, on ground reaction force (GRF) production and muscle activity in the quadricep, hamstring, and gluteal muscle groups during phases of the squat exercise and compare the effects to the effects to using a rigid barbell (RB). A two-by-two repeated measures Analysis of Variance (ANOVA) test was used to compare the results. Descriptive statistics showed significantly higher GRFs for the TB during the unweighting phase, significant differences in GRFs between speeds for each phase, significantly higher forces on average with the RB during the breaking and propulsive phases at the 90 beats-per-minute (bpm) speed, and significantly higher muscle activity with the RB at the 60-bpm speed. A linkage to the beneficial effects of the TB seen in literature was seen with familiarity with the TB.

No description available.

Over one million amputees are living in the United States with major lower limb loss (Ziegler-Graham et al. 2008). Lower limb amputation leads to the functional loss of the ankle plantar flexor muscles, which are important contributors to body support, forward propulsion, and leg swing initiation during walking (Neptune et al. 2001; Liu et al. 2006). Effective prosthetic component design is essential for successful rehabilitation of amputees to return to an active lifestyle by partially replacing the functional role of the ankle muscles. The series of experimental and computer simulation studies presented in this research showed that design characteristics of energy storage and return prosthetic ankles, specifically the elastic stiffness, significantly influence residual and intact leg ground reaction forces, knee joint moments, and muscle activity, thus affecting muscle output. These findings highlight the importance of proper prosthetic foot stiffness prescription for amputees to assure effective rehabilitation outcomes. The research also showed that the ankle muscles serve to stabilize the body during turning the center of mass. When amputees turn while supported by their prosthetic components, they rely more on gravity to redirect the center of mass than active muscle generation. This mechanism increases the risks of falling and identifies a need for prosthetic components and rehabilitation focused on increasing amputee stability during turning. A proper understanding of the effects of prosthetic components on amputee walking mechanics is critical to decreasing complications and risks that are prevalent among lower-limb amputees. The presented research is an important step towards reaching this goal. / text