Efeito Agudo em Parâmetros Cinéticos em Tarefas Estáticas e Dinâmicas devido ao Uso de Palmilhas Proprioceptivas

Pós-graduação em Engenharia Mecânica - FEG

Force and displacement transmissibility of a nonlinear isolator with high-static-low-dynamic-stiffness

Engineers often face the challenge of reducing the level of vibrations experienced by a given payload or those transmitted to the support structure to which a vibrating source is attached. In order to increase the range over which vibrations are isolated, soft mounts are often used in practice. The drawback of this approach is the static displacement may be too large for reasons of available space for example. Ideally, a vibration isolator should have a high-static stiffness, to withstand static loads without too large a displacement, and at the same time, a low dynamic stiffness so that the natural frequency of the system is as low as possible which will result in an increased isolation region. These two effects are mutually exclusive in linear isolators but can be overcome if properly configured nonlinear isolators are used. This paper is concerned with the characterisation of such a nonlinear isolator comprising three springs, two of which are configured to reduce the dynamic stiffness of the isolator. The dynamic behaviour of the isolator supporting a lumped mass is investigated using force and displacement transmissibility, which are derived by modelling the dynamic system as a single-degree-of-freedom system. This results in the system dynamics being approximately described by the Duffing equation. For a linear isolator, the dynamics of the system are the same regardless if the source of the excitation is a harmonic force acting on the payload (force transmissibility) or a harmonic motion of the base (displacement transmissibility) on which the payload is mounted. In this paper these two expressions are compared for the nonlinear isolator and it is shown that they differ. A particular feature of the displacement transmissibility is that the response is unbounded at the nonlinear resonance frequency unless the damping in the isolator is greater than some threshold value, which is not the case for force transmissibility. An explanation for this is offered in the paper. (C) 2011 Elsevier Ltd. All rights reserved.

Parâmetros do controle postural em mulheres idosas com ou sem histórico de quedas associadas ou não à osteoartrite de joelhos

OBJETIVOS: Comparar parâmetros estabilométricos de mulheres idosas com ou sem histórico de quedas associadas ou não à osteoartrite (OA) de joelhos. MÉTODOS: Cinquenta e seis idosas apresentando ou não histórico de quedas (Q) e OA de joelho unilateral e bilateral foram distribuídas da seguinte maneira: grupo QOA (n = 10), idosas com histórico de queda e OA de joelho; grupo QSOA (n = 11), idosas com histórico de queda e sem OA de joelho; grupo SQOA (n = 14), idosas sem histórico de quedas (SQ) e com OA de joelho; e grupo SQSOA (n = 21), idosas sem histórico de quedas e sem OA de joelho. Para análise do equilíbrio semiestático usando uma plataforma de força, foram avaliados os deslocamentos anteroposterior (DAP) e mediolateral (DML), as velocidades de oscilação anteroposterior (VAP) e mediolateral (VML) em quatro situações na postura ereta. As situações avaliadas foram as seguintes: 1) PFOA: sobre superfície fixa e olhos abertos; 2) PFOF: sobre superfície fixa e olhos fechados; 3) PIOA: sobre superfície instável e olhos abertos; 4) PIOF: sobre superfície instável e os olhos fechados. RESULTADOS: As idosas com OA de joelho apresentaram maior DAP em todas as situações analisadas (P < 0,05), ao passo que idosas com histórico de quedas apresentaram maior DML (P < 0,05). Não houve diferenças entre os grupos para VAP e VML (P > 0,05). CONCLUSÕES: A OA de joelho, por si, é um fator prejudicial no aumento de oscilação do centro de pressão (COP) na direção anteroposterior, enquanto o histórico de quedas, independente da presença de OA de joelhos, traz prejuízos ao controle postural na direção mediolateral.

On the dynamical properties of an elliptical-oval billiard with static boundary

Some dynamical properties for a classical particle confined inside a closed region with an elliptical-oval-like shape are studied. The dynamics of the model is made by using a two-dimensional nonlinear mapping. The phase space of the system is of mixed kind and we have found the condition that breaks the invariant spanning curves in the phase space. We have discussed also some statistical properties of the phase space and obtained the behaviour of the positive Lyapunov exponent. (C) 2009 Elsevier B.V. All rights reserved.

Static potential in scalar QED(3) with non-minimal coupling

Here we compute the static potential in scalar QED(3) at leading order in 1/Nf. We show that the addition of a non-minimal coupling of Pauli-type (is an element of(mu nu alpha)j(mu)partial derivative(nu)A(alpha)), although it breaks parity, it does not change the analytic structure of the photon propagator and consequently the static potential remains logarithmic ( confining) at large distances. The non-minimal coupling modifies the potential, however, at small charge separations giving rise to a repulsive force of short range between opposite sign charges, which is relevant for the existence of bound states. This effect is in agreement with a previous calculation based on Moller scattering, but differently from such calculation we show here that the repulsion appears independently of the presence of a tree level Chern-Simons term which rather affects the large distance behaviour of the potential turning it into a constant.

Análise do equilíbrio postural de indivíduos diabéticos por meio de baropodometria

Objective of this study was to analyze the postural balance of neuropathic diabetic individuals through baropodometry, related to losses in the sensorimotor system. Twenty-eight healthy and 25 diagnosed with diabetic neuropathy were subjected to static evaluation (measurement of displacement of body center of pressure) and dynamic (temporal analysis of the stance phase of gait cycle). The tactile sensitivity of the feet was assessed by Semmes Weinstein monofilaments and isometric muscle strength of ankle dynamometry. Analyses of multivariânvia (MANOVAs) and variance (ANOVAs) indicated lower performance in tactile sensitivity, muscle strength and dynamic balance, but showed no difference for static equilibrium of diabetic neuropathy. With this study by regression analysis, one can infer that the equilibrium differences in gait of neuropathic insensitivity may result from tactile and muscle strength. © FTCD/FIP-MOC.

Instabilidade postural em indivíduos obesos com deficiência intelectual

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Influência de calços na orientação postural de indivíduos com escoliose idiopática

INTRODUCTION: The relationship between the orientation of the segments and the adjustments that can be triggered by shoe lift and insoles in scoliotic patients during maintenance of standing position is unclear. OBJECTIVE: To verify static changes and those associated with unilateral manipulations of shoe lift in the postural orientation in people with idiopathic scoliosis. MATERIALS AND METHODS: Experimental group composed of ten patients with idiopathic scoliosis with double curve (less 10°) and control group with ten participants without scoliosis (aging from 13 to 24 years). Participants were videotaped in upright stance, standing with no, low (1 cm), and high (3 cm) shoe lift, which were placed under right and left shoe. In each condition, the participant maintain upright stance for 15 seconds and reflective markers were affixed on specific anatomical places. Postural angles were obtained: high thoracic; medium thoracic; thoracolumbar; and lumbar, as well segmental angles: shoulder; scapula; pelvis; and knee. RESULTS: In the no shoe lift condition, differences were observed between groups for high and medium thoracic angles and for shoulder. With low and high shoe lift under the right foot, difference was observed between shoe lift heights for high thoracic, for pelvis and knee angles. With low and high shoe lift under the left foot, differences between groups were observed for thoracolumbar angle and between shoe lift heights for pelvis and knee angles. CONCLUSIONS: The shoe lift promotes reorientation in the lower regions of the spine and segments of pelvis and knee. It might be suggested that in the scoliosis with double curves, manipulation in the basis of support changes the alignment of the trunk that might promote structural reorganization and the search of new adjustments among segments in individuals with idiopathic scoliosis.

Relação entre a disparidade de força entre membros inferiores e estabilidade postural em atletas de voleibol

Volleyball is a sport in which the laterality dominant limb shows superior strength and coordination because of its preferential use. Asymmetrical tendencies during the landing after the jump when striking or blocking actions are predominant for most part of game (ARRUDA; EDUARDO, 2008). Adaptations include imbalance of forces in static and dynamic motions at the knee joint, which increases risk for injury. Also, asymmetries in balance control during jumping and landing associate with a general postural instability that can be observed during static balance tasks. The purpose of this study was to investigate relationship between unequal lower limb strength (muscle imbalance) and postural stability levels in volleyball athletes and non-athletes. Nine female volleyball athletes and 10 active non-athletes participated in this study. Four encouters with participants were scheduled: three encounters in the bodybuilding gymnasium to collect anthropometric measures (weight, height for BMI, thigh circumference, which provided an initial diagnosis about asymmetry), and to perform the isometric strength test (i.e., leg press using a load cell and a force transducer to calculate uni an bilateral strength). The last encounter was in the laboratory where a balance test on a force platform was administered under five test conditions, with three repetitions each: baseline (natural standing position), one-leg standing, right side, with full vision (D_CV), and blindfolded (D_SV), one-leg standing, left side, with full vision (E_CV), and blindfolded (E_SV). The stability levels were evaluated using the path length parameters which was based on the total displacement of the center of pressure (DTCP). . Both groups shows asymmetric strength levels between legs, with better performance for the right leg. An ANOVA three way using the DTCP for the CV condition, legs (D x E), trials (3) with repeated measures for the first two factors and with a between (three)...

Challenging postural tasks increase asymmetry in patients with parkinson's disease

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Assimetria no controle postural em idosos caidores e não caidores neurologicamente sadios e com doenã de Parkinson em diferentes posições estáticas

Individuals with Parkinson's disease (PD) seem to present asymmetric postural control, and the commitment to postural control that is a big factor of falls in this population. However, the asymmetry in the postural control of fallers and non fallers with PD and neurologically healthy elderly is not too much studied. The objective of the study is to analyze the asymmetry in postural control in different static positions of elderly patients with PD and healthy elderly fallers and non fallers. The study included 70 older adults with PD and 70 neurologically healthy (CG). The groups were matched for age, gender, height, weight and cognitive condition. It was evaluated the clinical, cognitive status and incidence of falls among its participants through weekly prospective follow-up of 4 months. Then, for each group, CG and PD, it was selected 12 elderly fallers and 12 elderly non fallers to evaluate postural control. Participants were evaluated through two force platforms in conditions of bipedal support, unipedal and tandem position. It was realized 3 attempts of 30s for each condition. For unipedal and tandem condition it was made 3 attempts for each lower limb. The parameters of interest of the center of pressure (CoP), were analyzed for each condition and compared by MANOVAs with factor group, fall and asymmetry. Post hoc Tukey tests were used to determine the relationships between them. The results show that CG individuals showed greater velocity and CoP area in relation to PD. It was verified that at the control group that non fallers individuals (CGN) had more displacement and RMS in the average lateral direction in the dominant limb when compared to the less affected limb of non fallers with PD (PDN). Faller individuals in the control group (CGF) had larger area in the non dominant limb when compared to the most affected leg of fallers individuals with PD (PDF). Still, the PDF individuals had higher RMS in anteroposterior feeling....

Tribocorrosion behaviour of hot pressed CoCrMo−Al2O3 composites for biomedical applications

Alumina/alumina wear couple can lower the wear rates and thus metallic ion releasing on load bearing metallic implant materials. However, the low fracture toughness of ceramics is still a major concern. Therefore, the present study aims to process and to triboelectrochemically characterise the 5 and 10 vol.-%Al2O3 reinforced CoCrMo matrix composites. Corrosion and tribocorrosion behaviour of the composites were investigated in 8 g L−1 NaCl solution at body temperature. Corroded and worn surfaces were investigated by a field emission gun scanning electron microscope equipped with energy dispersive X-ray spectroscopy. After tribocorrosion experiments, wear rates were calculated using a profilometer. Results suggest that Al2O3 particle addition decreased the tendency of CoCrMo alloy to corrosion under both static and tribocorrosion conditions. However, no significant influence on the corrosion and wear rates was observed in composites mainly due to increased porosity and insufficient matrix/reinforcement bonding.