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  • 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.
1

The Effects of Rotation Around Two Axes of the Body Upon Static Balance

Gill, Sherry A. 08 1900 (has links)
The problem of this study was to investigate the effect of the rotation around two axes of the body upon static balance as measured by the stork stand, the headstand, and the one foot balance.
2

A Study of the Relationship between Balance on Stationary and Moving Objects

Nolen, Carlyle A. 01 1900 (has links)
This study investigated the relationship between balance on a moving base and balance on a stationary base. The hypothesis chosen for this investigation was that the correlation between the two types of balance would be zero.
3

Influências das posturas abertas e fechadas no equilíbrio estático e na autoestima / Influences of open and closed in postures static balance and self-esteem

Colaciti, Larissa Delmont [UNESP] 26 February 2016 (has links)
Submitted by LARISSA DELMONT COLACITI null (larissadelaciti@yahoo.com.br) on 2016-03-24T18:37:11Z No. of bitstreams: 1 Dissertação Larissa (texto e pré-textual)1.pdf: 1132631 bytes, checksum: 90947c8e89157bc2af02930316e36ae6 (MD5) / Approved for entry into archive by Ana Paula Grisoto (grisotoana@reitoria.unesp.br) on 2016-03-24T19:53:07Z (GMT) No. of bitstreams: 1 colaciti_ld_me_bauru.pdf: 1132631 bytes, checksum: 90947c8e89157bc2af02930316e36ae6 (MD5) / Made available in DSpace on 2016-03-24T19:53:07Z (GMT). No. of bitstreams: 1 colaciti_ld_me_bauru.pdf: 1132631 bytes, checksum: 90947c8e89157bc2af02930316e36ae6 (MD5) Previous issue date: 2016-02-26 / A postura corporal é um dos indícios mais relevantes que a comunicação não verbal exerce no ser humano, podendo revelar até mesmo estados emocionais. As posturas abertas ou expansivas, com cabeça erguida e membros em extensão sugerem dominância, autoridade e poder sobre uma situação; e as posturas fechadas ou retraídas, com cabeça baixa e membros em flexão suscitam sentimentos mais depressivos, inseguros e negativos. Esta pesquisa tem o objetivo de verificar a influência das posturas abertas e fechadas sobre o equilíbrio estático, a autoestima, a frequência cardíaca e a saturação de oxigênio. Participaram 40 universitários, média de idade 21,25 anos, que realizaram as posturas abertas (dois minutos), aferiram a frequência cardíaca e a saturação de oxigênio, subiram na plataforma de força para verificar o equilíbrio estático, e responderam o escala de autoestima de Rosenberg, depois permaneciam em posturas fechadas (dois minutos) e realizaram as mesmas tarefas descritas. Os resultados mostraram que as posturas abertas e fechadas afetaram significantemente a autoestima, a frequência cardíaca e o equilíbrio estático, sendo que, os participantes realizando as posturas abertas tiveram maior escore na autoestima, na frequência cardíaca e também melhoram a estabilidade postural nas variáveis, área e deslocamento total do centro de pressão. Realizando-se as posturas fechadas diminuíram o escore da autoestima, da frequência cardíaca e menor estabilidade postural. / The body posture is one of the most important evidence that non-verbal communication exercises in humans may reveal even emotional states. Open or expansive postures, with raised head and limbs in extension suggests dominance, authority and power over a situation; and postures closed or retracted, with head and limbs in flexion raise more depressive, insecure and negative feelings. This research aims to investigate the influence of the open and closed positions on the static balance, self-esteem, heart rate and oxygen saturation. Attended by 40 students, average age 21.25 years, who underwent open positions (two minutes), measured the heart rate and oxygen saturation, they were up on the force platform to check the static equilibrium, and responded to the self-esteem scale Rosenberg, then remained in closed positions (two minutes) and performed the same tasks described. The results showed that the open and closed positions significantly affected the self-esteem, heart rate and static balance, with the participants holding open positions had higher scores on self-esteem, heart rate and also improve postural stability in variable area and total displacement of the center of pressure. By performing the closed postures decreased the score of self-esteem, heart rate and less postural stability.
4

Static Balancing of Rigid-Body Linkages and Compliant Mechanisms

Sangamesh Deepak, R January 2012 (has links) (PDF)
Static balance is the reduction or elimination of the actuating effort in quasi-static motion of a mechanical system by adding non-dissipative force interactions to the system. In recent years, there is increasing recognition that static balancing of elastic forces in compliant mechanisms leads to increased efficiency as well as good force feedback characteristics. The development of insightful and pragmatic design methods for statically balanced compliant mechanisms is the motivation for this work. In our approach, we focus on a class of compliant mechanisms that can be approximated as spring-loaded rigid-link mechanisms. Instead of developing static balancing techniques directly for the compliant mechanisms, we seek analytical balancing techniques for the simplified spring–loaded rigid–link approximations. Towards that, we first provide new static balancing techniques for a spring-loaded four-bar linkage. We also find relations between static balancing parameters of the cognates of a four-bar linkage. Later, we develop a new perfect static balancing method for a general n-degree-of-freedom revolute and spherical jointed rigid-body linkages. This general method distinguishes itself from the known techniques in the following respects: 1 It adds only springs and not any auxiliary bodies. 2 It is applicable to linkage shaving any number of links connected in any manner. 3 It is applicable to both constant(i.e., gravity type) and linear spring loads. 4 It works both in planar and spatial cases. This analytical method is applied on the approximated compliant mechanisms as well. Expectedly, the compliant mechanisms would only be approximately balanced. We study the effectiveness of this approximate balance through simulations and a prototype. The analytical static balancing technique for rigid-body linkages and the study of its application to approximated compliant mechanisms are among the main contributions of this thesis.
5

A influência da escoliose idiopática do adolescente e do seu tratamento cirúrgico sobre o equilíbrio semi-estático / The influence of adolescent idiopathic scoliosis and its surgical treatment on the semi-static balance

Santiago, Hildemberg Agostinho Rocha de 15 December 2011 (has links)
A escoliose idiopática do adolescente (EIA) é uma deformidade da coluna vertebral que acomete indivíduos entre 10 e 19 anos de idade, caracteriza-se por desvios das curvas nos planos frontal e sagital, e rotação intervertebral no plano axial. Devido a sua natureza tridimensional apresenta alterações biomecânicas que geram adaptações em músculos e ligamentos da coluna vertebral, alterando suas funções no controle postural. O tratamento cirúrgico visa corrigir os desvios e manter as curvas no plano sagital, através de artrodeses. Com base nesses conceitos, o objetivo do estudo foi avaliar a influência da escoliose idiopática do adolescente, e da sua correção cirúrgica, sobre o equilíbrio semi-estático. Participaram do estudo 30 adolescentes divididas em dois grupos: Grupo Controle (GC) [n=15], idade média de 15,13 ± 1,59 anos, massa corporal de 51,22 ± 2,5Kg e estatura de 159 ± 3cm, e Grupo Escoliose (GE) [n=15] com média de idade de 15 ± 1,64 anos, massa corporal de 46,1 ± 3,26Kg e estatura de 156 ± 3cm; das quais foi mesurada a oscilação do centro de pressão a partir de uma plataforma de força avaliando as variáveis: desvio ântero-posterior (DAP); desvio médio-lateral (DML); velocidade ântero-posterior (VAP); velocidade médio-lateral (VML) e área (A²). O GC realizou a avaliação do equilíbrio semi-estático em um único momento, enquanto o GE realizou a avaliação do equilíbrio semi-estático no momento pré-operatório (PRÉ) e no 7°, 30°, 60° e 90° dia de pós-operatório (PO). Foi avaliado o grau de correção da curvatura e a relação entre número de vértebras artrodesadas e a oscilação corporal. O equilíbrio semi-estático foi avaliado nas 4 posições de Romberg (P1 - pés separados, P2 - pés unidos, P3 - série parcial e P4 - série completa) nas condições olhos abertos (AO) e olhos fechado (OF). Os resultados mostram que o GE apresentou uma redução média de 49,8° para a curva torácica e 18,14° para as lombares. O número de vértebras artrodesadas foi de 11,26 ± 1,7. O GE apresentou maior oscilação que o GC, com diferença significativa nas quatro variáveis estudadas (DAP, DML, VAP, VML e A²) e em todas as posições/condições. Com base nos resultados verificou-se que o GE oscila mais que o GC tanto no pré-operatório como nos momentos pós-operatório. Na comparação entre as posições, GE oscilou mais no sentido AP em P1 e no sentido ML em P4, também obteve maior valor para a A². Para a VAP P2 foi a mais desafiadora e para VML foi P4. Os dados apontam para uma diminuição gradativa da oscilação com o passar dos dias de PO, porém no 90° dia o GE ainda apresenta valores superiores ao momento PRÉ. Portanto, os resultados mostram que a escoliose afeta o controle postural e que no 90° dia pós-cirúrgico a oscilação postural ainda se apresenta superior ao período pré-operatório, e que pode estar associado a um comprometimento sensório-motor ou a um problema de integração sensorial pré-existente, também relacionado as alterações biomecânicas decorrentes da cirurgia e seu efeito agudo. / The adolescent idiopathic scoliosis (AIS) is a spinal deformity that affects individuals between 10 and 19 years of age, characterized by deviations of the curves in the frontal and sagittal planes, and intervertebral rotation in the axial plane. Due to its three-dimensional nature presents biomechanical changes that cause changes in muscles and ligaments of the spinal column, altering their functions in postural control. Surgical treatment aims to correct the deviations and maintain the curves in the sagittal plane through arthrodesis. Based on these concepts, the study aimed to evaluate the influence of adolescent idiopathic scoliosis and its surgical correction on the semi-static balance. The study included 30 adolescents divided into two groups: control group (CG) [n = 15], mean age 15.13 ± 1.59 years, body mass 51.22 ± 2.5kg and height 159 ± 3cm, and scoliotic group (SG) [n = 15] mean age 15 ± 1.64 years, body mass index of 46.1 ± 3.26kg and height 156 ± 3cm, which was gauged from the oscillation the center of pressure from a force platform to evaluate the variables: anteroposterior deviation (APD); average-lateral devitation (MLD); anteroposterior speed (APS); average-lateral speed (MLS) and area (A²). CG carried out the assessment of the semi-static balance in a single moment, while the SG was evaluated at the preoperative period (PRE) and at the 7th, 30th, 60th and 90th days post operative (PO). We assessed the degree of curvature correction and the relationship between number of vertebrae arthrodesed and body sway. The static balance was assessed in 4 Romberg\'s positions (P1 - feet apart, P2 - feet together, P3 - partial series P4 and - full series) in eyes open conditions (EO) and eyes closed (EC). The results show that the SG had an average reduction of 49.8 degrees for the thoracic curve and 18.14 degrees for the lumbar. The number of vertebrae arthrodesed was 11.26 ± 1.7. The SG showed greater sway than the CG, with a significant difference in the four variables (APD; MLD; APS; MLS and A²) and in all positions/conditions. Based on the results it was found that the SG oscillates more than the CG (preoperatively and postoperatively). Comparing the positions of the SG volunteers ranged more towards AP in P1 and P4 in the ML direction, which also had higher values for the A². For the APS P2 was the most challenging and MLS was P4. The data indicate a gradual decrease of the oscillation over the postoperative days, but in the 90th day the GE still has higher values when the PRE. Therefore, the results show that scoliosis affects postural control and at the 90th day after the surgery the postural oscillation still superior tham postsurgery period, and maybe it can be associated with an impaired sensorimotor or a sensory integration problem pre-existing, related to the biomechanical changes followed from the surgery and its acute effect.
6

The relationship between postural stability sway, balance, and injury in adolescent female soccer players in the eThekwini district of KwaZulu-Natal

Koenig, Jean-Pierre 24 July 2014 (has links)
Submitted in partial compliance with the requirements for the Master of Technology: Chiropractic, Durban University of Technology, 2014. / Background: Poor balance is a risk factor for injury in adolescent sport including soccer. Despite the rapid growth in female adolescent soccer especially in South Africa, the association between balance and injury in this population has not been fully explored. This study aimed to determine the relationship between injury and balance. Static and dynamic balance was monitored as sway index (SI) and limits of stability direction control (LOSDC). Objectives: The objectives of this study were to determine the body mass index of adolescent female soccer players; to determine the prevalence of injury in adolescent female soccer players; to determine static balance as revealed by the sway index (SI); to determine dynamic stability as revealed by limits of stability direction control (LOSDC) and to correlate body mass index (BMI) to sway index and limits of stability. Method: Eighty adolescent female soccer players, between the ages of fourteen and eighteen, were recruited through convenience sampling from schools in the eThekwini district of KwaZulu-Natal. After obtaining informed consent and assent, participants completed questionnaires and were scheduled for the balance and BMI assessments. The objective data for each participant consisted of height, weight, Sway Index (SI) and Limits of Stability Direction Control (LOSDC) readings, measured using a stadiometer, electronic scale and Biodex Biosway Balance System (Biodex Medical Systems Inc., Shirley, New York) respectively. The subjective and objective data were analyzed using SPSS version 21.0 (SPSS Inc. Chicago, Ill, USA). Statistical tests included descriptive statistics using frequency and cross-tabulation. Inferential statistics using t-tests and Pearson’s correlations at a significance level of 0.05 was also incorporated. The testing of hypotheses was performed using Fisher’s Exact tests for nominal data and ordinal data. A p value of < 0.05 was considered as statistically significant. The statistical analysis also included Odds Ratio calculations. Results: The mean body mass index of the injured participants was 23.54±3.56 kg/m2 and the mean body mass index of the uninjured participants was 23.00±4.63. Only 27.5% of the participants sustained an injury. Injured participants performed poorly on average in the SI assessment involving their eyes open when standing on a soft surface. The results were similar for the LOSDC in the overall, right, left, backward-right and backward-left directions. However, there were no significant correlations calculated. Significant relationships existed between BMI and the SI assessments in the injured participants which involved standing on a firm surface with their eyes open (p = 0.05), their eyes closed when also standing on a firm surface (p = 0.05), their eyes open when standing on a soft surface (p = 0.02), and their eyes closed when standing on a soft surface (p = 0.04). A significant relationship also existed between BMI and LOS right direction control (p = 0.02). Conclusion: This research paper revealed that the body mass index as investigated in this study is similar to other studies involving female adolescents; soccer injury as investigated in this study is similar to other studies involving female adolescents; poor static and dynamic balance is not associated with injury in adolescent female soccer players and lastly, body mass index is linked to the balance of an individual.
7

A influência da escoliose idiopática do adolescente e do seu tratamento cirúrgico sobre o equilíbrio semi-estático / The influence of adolescent idiopathic scoliosis and its surgical treatment on the semi-static balance

Hildemberg Agostinho Rocha de Santiago 15 December 2011 (has links)
A escoliose idiopática do adolescente (EIA) é uma deformidade da coluna vertebral que acomete indivíduos entre 10 e 19 anos de idade, caracteriza-se por desvios das curvas nos planos frontal e sagital, e rotação intervertebral no plano axial. Devido a sua natureza tridimensional apresenta alterações biomecânicas que geram adaptações em músculos e ligamentos da coluna vertebral, alterando suas funções no controle postural. O tratamento cirúrgico visa corrigir os desvios e manter as curvas no plano sagital, através de artrodeses. Com base nesses conceitos, o objetivo do estudo foi avaliar a influência da escoliose idiopática do adolescente, e da sua correção cirúrgica, sobre o equilíbrio semi-estático. Participaram do estudo 30 adolescentes divididas em dois grupos: Grupo Controle (GC) [n=15], idade média de 15,13 ± 1,59 anos, massa corporal de 51,22 ± 2,5Kg e estatura de 159 ± 3cm, e Grupo Escoliose (GE) [n=15] com média de idade de 15 ± 1,64 anos, massa corporal de 46,1 ± 3,26Kg e estatura de 156 ± 3cm; das quais foi mesurada a oscilação do centro de pressão a partir de uma plataforma de força avaliando as variáveis: desvio ântero-posterior (DAP); desvio médio-lateral (DML); velocidade ântero-posterior (VAP); velocidade médio-lateral (VML) e área (A²). O GC realizou a avaliação do equilíbrio semi-estático em um único momento, enquanto o GE realizou a avaliação do equilíbrio semi-estático no momento pré-operatório (PRÉ) e no 7°, 30°, 60° e 90° dia de pós-operatório (PO). Foi avaliado o grau de correção da curvatura e a relação entre número de vértebras artrodesadas e a oscilação corporal. O equilíbrio semi-estático foi avaliado nas 4 posições de Romberg (P1 - pés separados, P2 - pés unidos, P3 - série parcial e P4 - série completa) nas condições olhos abertos (AO) e olhos fechado (OF). Os resultados mostram que o GE apresentou uma redução média de 49,8° para a curva torácica e 18,14° para as lombares. O número de vértebras artrodesadas foi de 11,26 ± 1,7. O GE apresentou maior oscilação que o GC, com diferença significativa nas quatro variáveis estudadas (DAP, DML, VAP, VML e A²) e em todas as posições/condições. Com base nos resultados verificou-se que o GE oscila mais que o GC tanto no pré-operatório como nos momentos pós-operatório. Na comparação entre as posições, GE oscilou mais no sentido AP em P1 e no sentido ML em P4, também obteve maior valor para a A². Para a VAP P2 foi a mais desafiadora e para VML foi P4. Os dados apontam para uma diminuição gradativa da oscilação com o passar dos dias de PO, porém no 90° dia o GE ainda apresenta valores superiores ao momento PRÉ. Portanto, os resultados mostram que a escoliose afeta o controle postural e que no 90° dia pós-cirúrgico a oscilação postural ainda se apresenta superior ao período pré-operatório, e que pode estar associado a um comprometimento sensório-motor ou a um problema de integração sensorial pré-existente, também relacionado as alterações biomecânicas decorrentes da cirurgia e seu efeito agudo. / The adolescent idiopathic scoliosis (AIS) is a spinal deformity that affects individuals between 10 and 19 years of age, characterized by deviations of the curves in the frontal and sagittal planes, and intervertebral rotation in the axial plane. Due to its three-dimensional nature presents biomechanical changes that cause changes in muscles and ligaments of the spinal column, altering their functions in postural control. Surgical treatment aims to correct the deviations and maintain the curves in the sagittal plane through arthrodesis. Based on these concepts, the study aimed to evaluate the influence of adolescent idiopathic scoliosis and its surgical correction on the semi-static balance. The study included 30 adolescents divided into two groups: control group (CG) [n = 15], mean age 15.13 ± 1.59 years, body mass 51.22 ± 2.5kg and height 159 ± 3cm, and scoliotic group (SG) [n = 15] mean age 15 ± 1.64 years, body mass index of 46.1 ± 3.26kg and height 156 ± 3cm, which was gauged from the oscillation the center of pressure from a force platform to evaluate the variables: anteroposterior deviation (APD); average-lateral devitation (MLD); anteroposterior speed (APS); average-lateral speed (MLS) and area (A²). CG carried out the assessment of the semi-static balance in a single moment, while the SG was evaluated at the preoperative period (PRE) and at the 7th, 30th, 60th and 90th days post operative (PO). We assessed the degree of curvature correction and the relationship between number of vertebrae arthrodesed and body sway. The static balance was assessed in 4 Romberg\'s positions (P1 - feet apart, P2 - feet together, P3 - partial series P4 and - full series) in eyes open conditions (EO) and eyes closed (EC). The results show that the SG had an average reduction of 49.8 degrees for the thoracic curve and 18.14 degrees for the lumbar. The number of vertebrae arthrodesed was 11.26 ± 1.7. The SG showed greater sway than the CG, with a significant difference in the four variables (APD; MLD; APS; MLS and A²) and in all positions/conditions. Based on the results it was found that the SG oscillates more than the CG (preoperatively and postoperatively). Comparing the positions of the SG volunteers ranged more towards AP in P1 and P4 in the ML direction, which also had higher values for the A². For the APS P2 was the most challenging and MLS was P4. The data indicate a gradual decrease of the oscillation over the postoperative days, but in the 90th day the GE still has higher values when the PRE. Therefore, the results show that scoliosis affects postural control and at the 90th day after the surgery the postural oscillation still superior tham postsurgery period, and maybe it can be associated with an impaired sensorimotor or a sensory integration problem pre-existing, related to the biomechanical changes followed from the surgery and its acute effect.
8

Balansbrädans effekt på balansen jämfört med styrketräning, och balansbräda i kombination med styrketräning, vibrationer, samt kinesiotejp, hos individer med kronisk fotledsinstabilitet : En litteraturstudie / The wobble-board’s effect on balance compared to strength training, and wobble board in combination with strength training, vibrations, and kinesio tape, in individuals with chronic ankle instability : A Literature study

Molin, Axel, Svensson, Samuel January 2023 (has links)
Bakgrund: Tio till tjugo procent av akuta skador på ligamenten kring fotleden resulterar ikronisk fotledsinstabilitet, vilket innebär en instabilitetskänsla, stukningstendens, smärta ochsvullnad i fotleden. Det är värdefullt att som fysioterapeut ha kunskap om vilkenrehabiliteringsmetod som förbättrar balans i syfte att öka stabiliteten i foten. Syfte: Sammanställa litteraturen och bedöma det vetenskapliga underlaget gällande effektenpå balansen hos individer med kronisk fotledsinstabilitet genom träning med balansbräda.Detta ställs upp i två sammanvägningar: balansbräda jämfört med styrketräning, ochbalansbräda jämfört med ingen behandling. Metod: En systematisk litteratursökning efter randomiserade kontrollerade studier utfördes idatabaserna PubMed, Uppsala universitetsbibliotek, samt Cochrane Library. Totaltinkluderades åtta studier med sammanlagt 286 deltagare. Samtliga studier kvalitetsgranskadesenligt PEDro-skalan, och GRADEstud användes för bedömning av det sammanvägdaresultatets tillförlitlighet. Resultat: Signifikant förbättring av balans kopplat till styrketräning samt balansträning medbalansbräda, men liten fördel för en kombination för de båda kopplat till statisk balans. Kvalitetsgranskning enligt PEDro visade på att sex studier hade en måttlig kvalité och tvåstudier hade hög kvalité. Utifrån evidensbedömningen anses det föreligga en lågtillförlitlighet till det vetenskapliga underlaget för styrketräning med motståndsband förfotleden samt balansträning med balansbräda. Konklusion: Både styrketräning för relevant muskulatur och balansträning med balansbrädaförbättrar balansen efter ett ≥4 veckor långt protokoll med ≥3 träningssessioner/vecka.Evidensen talar för att båda rehabiliteringsmetoder ger liknande utfall, men fler studierbehövs för att bekräfta resultatet då de sammanvägda resultaten har låg tillförlitlighet. / Background: Ten to twenty percent of acute ankle injuries result in chronic ankle instability,which results in instability in the foot, distorsion tendency, and pain and swelling around theankle. Thus it´s valuable for physiotherapists to have knowledge regarding whichrehabilitation methods yield the most positive effect on balance in order to increase stabilityin the foot. Purpose: To compile the literature and assess the evidence regarding the effects on balanceof people diagnosed with chronic ankle instability through rehabilitation with awobble-board. This is set up in two comparisons: wobble-board compared tostrength-training, and wobble-board compared to no treatment. Method: A systematic literature search for randomized controlled trials was done inPubMed, Uppsala University Library, and CochraneLibrary. A total of eight studies wereincluded in this review, with a total of 286 participants. Study quality was judged by using the PEDro-scale, and GRADEstud was used to assess the reliability of the combined results. Results: Significant improvement in balance related to resistance training and balancetraining with wobble-board, with a small advantage to training with a combination of the twowhen measuring static balance. Quality according to PEDro showed six studies of moderatequality and two studies of high quality. Grading of the evidence is deemed insufficient whenit comes to training with resistance bands and training with a wobble-board. Conclusion: Both strength-training for the relevant muscles and balance-training using thewobble-board improves the balance after a ≥4 week-long protocol with ≥3 sessions/week.The evidence shows that both methods give similar results, however further research isrequired to confirm the results because the reliability of the combined results was deemedinsufficient.
9

Controle de válvulas de sucção de compressores de refrigeração usando limitador de abertura /

Cavalheiro Júnior, Milton Cesar. January 2017 (has links)
Orientador: José Luiz Gasche / Resumo: A maioria dos sistemas de refrigeração por compressão de vapor utiliza compressores alternativos, considerados mecanismos importantes na era moderna. O ciclo de operação de um compressor alternativo é descrito por uma série de fenômenos complexos ocorrendo em um curto período de tempo. Dentre os fatores considerados importantes para e ciência termodinâmica dos compressores, destacam-se as válvulas que controlam os processos de sucção e de descarga, que são responsáveis por grandes perdas termodinâmicas no ciclo. Parte das perdas ocorre no sistema de válvulas, particularmente na válvula de sucção, onde as instabilidades do seu movimento reduzem a e ciência do processo de sucção. Como uma forma de reduzir os problemas gerados pelas instabilidades no funcionamento da válvula de sucção, propomos a utilização de um esbarro para limitar a abertura máxima da válvula, reduzindo sua instabilidade e aumentando a e ciência do compressor. Mostramos experimentalmente que existe uma posição de equilíbrio que mantém a válvula aberta sem instabilidades e que esta posição varia, aproximadamente, linearmente com o número de Reynolds. / Mestre
10

Balance control in dance positions

Huh, Ravina (Eunhye) January 2016 (has links)
The purpose of this thesis is to develop and understand dance balance characteristics on various kinds of dance, related positions and shoe types which contribute to dance performance and to understand different balance controls in various groups. The first study was conducted to examine balance into ballet 2nd position between Ballet shoes and Pointe shoes. Eight dancers performed five different conditions in ballet 2nd position (Ballet Flat, Ballet Demi, Pointe Flat, Pointe Demi, and Pointe Toe) and Centre of Pressure (COP) was used to assess balance. The second study was testing balance control and response to perturbations whilst standing on double leg stance dance positions using a moving platform. Four dance positions were performed by eight subjects (Normal Flat, Turnout Flat, Normal Demi and Turnout Demi) and the platform was moved in two different directions (Forward and Backward) at two different speeds (slow and fast). Kinetics, Kinematics and EMG data was taken from this study. The third study was taken to compare balance control and response to perturbations in single leg standing dance positions between eight dancers and eight gymnasts. The subjects performed static single leg balance in Normal Flat, Turnout Flat, Normal Demi and Turnout Demi. Also, perturbed stance trials were collected in anterior, posterior, right and left directions for two dance positions (Normal Flat and Turnout Flat) at two different speeds (slow and fast) on the moving platform. The results from the studies indicate that dancers move in Medial - Lateral direction more than in Anterior - Posterior direction on Demi-pointe and Toe standing by performing plantar flexion during ballet 2nd position. Demi-pointe position may cause longer delay of EMG latencies because CNS is probably sending information already to keep correcting balance on Demi-pointe. Dancers and Gymnasts have different balance controls due to their ways of training in their performance. Dancers generally reacted faster with slow perturbation in Turnout stance than Gymnasts because this is the particular condition which Dancers are training in.

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