Glucocorticoids are an important cause of secondary osteoporosis in humans, which decreases bone quality and leads to fractures. Mechanical stimulation in the form of low-intensity and high-frequency vibration seems to be able to prevent bone loss and to stimulate bone formation. The objective of this study was to evaluate the effects of mechanical vibration on bone structure in rats treated with glucocorticoids. Thirty 3-month-old adult male Wistar rats were randomized to three groups: control (C), glucocorticoid (G), and glucocorticoid with vibration (CV). The G and GV groups received 3.5 mg/kg/day of methylprednisolone 5 days/week for a duration of 9 weeks, and the C group received vehicle (saline solution) during the same period. The CV group was vibrated on a special platform for 30 min per day, 5 days per week during the experiment. The platform was set to provide a vertical acceleration of 1 G and a frequency of 60 Hz. Skeletal bone mass was evaluated by total body densitometry (DXA). Fracture load threshold, undecalcified bone histomorphometry, and bone volume were measured in tibias. Glucocorticoids induced a significantly lower weight gain (-9.7%) and reduced the bone mineral content (-9.2%) and trabecular number (-41.8%) and increased the trabecular spacing (+98.0%) in the G group...

Uma vibração aplicada a um tendão muscular aumenta a freqüência de disparos de aferentes, como os de fusos neuromusculares Ia e II, cujas terminações afetam circuitos da medula espinhal e com isto podem influenciar o controle motor. O objetivo deste estudo foi analisar o efeito de vibrações a duas freqüências (15 e 80Hz) e amplitudes de 1 e 2,5mm aplicadas ao tendão calcâneo direito sobre o sistema de controle postural e sobre a circuitaria neural associada a reflexos monosinápticos da perna. A hipótese era de que a vibração de alta freqüência ativasse preferencialmente os aferentes de fuso neuromuscular de tipo Ia enquanto a vibração a 15 Hz ativasse preferencialmente os aferentes de tipo II. Isto significaria que a vibração a 80 Hz teria forte efeito sobre o reflexo H, enquanto a vibração a 15 Hz teria um efeito significativo sobre a postura. Participaram deste estudo 14 sujeitos sãos. Na postura ereta quieta, foi realizada a aquisição do reflexo H enquanto o tendão calcâneo era vibrado. Após um intervalo de descanso, foi realizada a aquisição do Centro de Pressão (COP) tanto na direção Ântero-Posterior (AP) quanto na Médio-Lateral (ML) em paralelo à aquisição bilateral do EMG dos músculos (SO...

O objetivo do estudo foi verificar a ocorrência da potencialização pós-ativação (PPA) e o efeito do treinamento de força (TF) sem e com a plataforma vibratória na capacidade de sprints repetidos (CSR). O estudo foi divido em duas partes: a primeira analisou o efeito do TF associado à plataforma vibratória na CSR; e a segunda verificou a ocorrência da PPA na CSR. No primeiro estudo participaram 29 sujeitos, os quais foram divididos em 3 grupos: TF, TF+vibração a 30 Hz e amplitude de 2-4 mm (TF+V30) e TF+vibração a 50 Hz e amplitude de 4-6 mm (TF+V50). Os sujeitos realizaram inicialmente análise da área de secção transversa do quadríceps (ASTQ), teste de uma repetição máxima (1RM) no exercício agachamento e o teste de CSR. Após isso, os sujeitos foram submetidos a 10 semanas de treinamento de força, de acordo com o seu respectivo grupo e, ao final da intervenção, realizaram as mesmas avaliações aplicadas antes das sessões de treinamento. No segundo estudo, 12 jogadores de handebol realizaram teste de 1RM, e em sequência, de maneira aleatória o teste de CSR sem e com a atividade condicionante. A atividade condicionante foi realizada no exercício agachamento e consistiu de cinco séries de uma repetição a 90% de 1RM. O treinamento de força sem e com a vibração aumentou na mesma magnitude a força muscular e a ASTQ. Para o grupo TF+V30...

A incidência da fibromialgia na população é relativamente alta, cerca de 2%, o que implica em gastos públicos consideráveis principalmente devido a sua etiologia indefinida. Os sintomas mais comumente relatados são dor muscular, fadiga, estresse e distúrbios do sono. Considerando a escassez bibliográfica envolvendo o treinamento vibratório a pacientes com fibromialgia, bem como a possibilidade de ocorrência de lesão em grandes amplitudes de vibração e a necessidade de tratamento dessa população por toda a vida, a principal finalidade deste estudo foi avaliar a eficácia do treinamento vibratório em plataforma de baixa amplitude sobre a composição corporal, os sintomas, a qualidade de vida e o estresse oxidativo de mulheres com fibromialgia. Partiparam do estudo 38 mulheres, sendo 28 com diagnóstico de fibromialgia e 10 saudáveis. Elas foram divididas em 4 grupos: grupo controle (C), composto por pacientes com fibromialgia que não realizaram tratamento, grupo vibração e exercício I (VE I), composto por pacientes com fibromialgia que realizaram exercícios sobre a plataforma, grupo vibração e exercício II (VE II), composto por mulheres saudáveis que realizaram exercícios sobre a plataforma e grupo vibração (V)...

Este trabalho apresenta um estudo de medição e avaliação da exposição humana à vibração transmitida ao sistema mão-braço durante a atividade ciclística. Medições de vibração são realizadas para três diferentes tipos de pavimento, asfalto (AS), placas moldadas “in loco” de concreto (PC) e blocos intertravados de concreto (BI), utilizando-se dois modelos de bicicleta, speed (S) e mountain bike (MB), e ciclistas com diferentes características físicas. Segundo uma análise objetiva, para cada configuração – tipo de pavimento x modelo de bicicleta x ciclista –, avalia-se a exposição diária à vibração A(8), como definido pela norma ISO 5349- 1, para uma duração diária de exposição à vibração de 2 h, e também avalia-se os tempos máximos de exposição diária à vibração, para que os limites de exposição definidos pela Diretiva 2002/44/EC sejam atingidos. Segundo uma análise subjetiva, avalia-se o grau de conforto oferecido por cada tipo de pavimento quanto à exposição à vibração, de acordo com a opinião dos ciclistas. Ao final, os resultados são comparados e verifica-se, tanto pela análise objetiva quanto pela subjetiva, que o tipo de pavimento mais adequado para a atividade ciclística é o asfalto (AS)...

O uso de automóveis vem crescendo atualmente, sendo de suma importância que estes propiciem bem-estar ao motorista e a seus passageiros. O trabalho busca avaliar o grau de conforto do motorista em relação à vibração através de medições realizadas em quatro veículos de mesma categoria disponíveis no mercado brasileiro. São eles: Volkswagen Gol, Ford Fiesta, Renault Sandero e Fiat Palio. Para avaliação são colocados como condições de comparação o tipo de pavimento, velocidade e local de medição. A medição da vibração é feita através da inserção de acelerômetros em partes de contato do motorista com o veículo. Utiliza-se um acelerômetro para medir o nível de vibração no volante (vibração transmitida ao sistema mão-braço) e outro acoplado ao banco do motorista através de um seatpad para medir a vibração transmitida ao corpo inteiro. Ainda, para a situação de motoristas profissionais avalia-se a exposição diária à vibração A(8) para diferentes situações de trabalho e compara-se com os limites de exposição definidos pelas normas vigentes. Faz-se ainda, um estudo estatístico a fim de comprovar a influência de parâmetros como a velocidade e tipo de pavimento, na vibração interna dos veículos. Segundo a análise de conforto...

Este trabalho consiste no estudo da vibração de corpo inteiro como resultado da realização de exercícios em plataformas vibratórias. Tem por objetivo avaliar os níveis vibratórios a que os usuários dessas plataformas estão submetidos e para tanto foram realizadas medições em três diferentes plataformas com dois indivíduos de massas diferentes a fim de verificar como se da a variação da aceleração com a freqüência de operação e se existe diferença nos níveis de aceleração conforme a massa do usuário para o mesmo regime de operação. Cada plataforma foi avaliada conforme seus regimes usuais e as acelerações obtidas em cada regime de operação foram então compiladas para a simulação de rotinas de treino equivalentes a 20 minutos de exposição diária. Cada uma das rotinas foi então confrontada com as curvas que determinam os valores limite de exposição diário (VLE) de acordo com a norma ISO 2631-1 (1997) a fim de classificar qual o potencial de riscos a saúde que a exposição às vibrações pode oferecer. Os resultados obtidos mostram que a utilização das plataformas deve ter algum tipo de controle, já que as rotinas simuladas obtiveram acelerações que segundo a norma, em longo prazo, tem grande potencial de oferecer riscos à saúde.; This work is a study of whole body vibration as a result of exercises on vibration plates. Aims to asses the vibration levels that users of these plates are submitted and for such were made measurements on three different vibration plates with two individuals of different masses in order to verify how occurs the variation of acceleration with the frequency of operation and if differing levels of acceleration to users with different masses exposed to the same regime of operation. Each plate was evaluated according to their usual regimes and the acceleration obtained in each operating regime was then compiled for the simulation of daily routines of 20 minutes of exposure. Each routine was confronted with the curves that determine the daily exposure limit values in accordance with ISO 2631-1 (1997) in order to classify which the potential health risks that exposure to vibration can offer. The results shows that the use of the plates must have some kind of control...

Introduction The use of whole-body vibration (WBV) appears to influence in a positive way the performance of athletes in certain characteristics such as muscular strength, power and body balance. The aim of this study was to compare the acute neuromuscular activity caused by different vibration frequencies (15Hz and 25Hz), and different knee flexion angles (120° and 150°). Methods A total of 19 male university students underwent 4 sessions of WBV. The subjects were exposed randomly to four different WBV protocols using a vibration platafform (Galileu 2000).The amplitude allowed by the vibration platform was (peak-to-peak) 3 mm. Each vibration session lasted 6 min and they accomplish a rest period of one day between sessions. The protocols used were: 15 Hz of vibration and 120º of knee flexion; 15 Hz and 150º; 25 Hz and 120º; and 25 Hz and 150º. Muscle activity exerted by the muscles Vastus Intermedius (VI), Vastus Lateralis (VL), Vastus Medialis (VM) and Biceps Femoris (BF) were evaluated by electromyographic analysis (Biopac MP 100, Biopac Systems Inc. Goleta, CA, EUA). Paired Samples T test with repeated measures was used to compare the main effects of muscle activity of each test. Results When comparing the two angles of knee flexion (120° vs 150°) with the 15Hz frequency...

INTRODUCTION: The cycling activity has increased in recent years, either as a means of leisure or physical activity or as means of transport. Discomfort is one of the main complaints for cyclists, especially when related to the type o pavement they use while riding. This work presents a study of measurement and evaluation of human exposure to hand-arm vibration in the leisure cyclist activity in different pavements in order to classify according to vibration discomfort and to vibration injury risk. METHODS: Vibration measurements are performed for three pavement types, asphalt (AS), precast concrete slab (PC), and interlocking concrete blocks (BI), using two bicycle models (time trial speed racing bike, S and mountain bike, MB), and cyclists with different physical characteristics. It is performed a quantitative analysis of each configuration - pavement type × bike model × cyclist - where the daily vibration exposure A(8) is evaluated, as defined in ISO 5349-1 Standard, for 2h daily exposure. It is also evaluated the maximum daily exposure in order to reach limit values, as defined by Directive 2002/44/EC. RESULTS: Based on a subjective analysis (survey), it is evaluated the comfort degree for vibration exposure for each tested pavement...

Vortex-induced vibration of bridges happens at a relatively low wind speed and while vehicles often run on a bridge at that wind speed. Thus, it is necessary to study how the vehicles influence vortex-induced vibration of vehicle-bridge systems. Based on the project of Shanghai Bridge over Yangtse River, the wind tunnel test for vortex-induced vibrations of vehicle-bridge system of a 1:60 model is presented. The wind tunnel test is introduced in detail including the equipments, test procedures and discussion of results. The results show that the vehicles have much influence on vortex-induced vibration of vehicle-bridge system for the Shanghai Bridge over Yangtse River. With speed increasing, the displacement of the bridge with vehicles fluctuates larger than that of the bridge without vehicles. The frequencies of vibration could be divided into three stages, vertical vibration frequency for the first stage, torsional vibration frequency for the second stage, and suspension system vibration frequency for the third stage. For the bridge with vehicles, vertical vortex-induced vibration was accompanied with torsional vibration and the frequencies of the two vibrations are equal. The displacement of vortex-induced vibration for the bridge with vehicles was larger than that of vortex-induced vibration for the bridge without vehicles. Due to the disturbance of vehicles...

Vibration absorbers, also called vibration neutralizers, are mechanical systems to be attached to another mechanical system, or structure, called the primary system, with the purpose of reducing vibration and sound radiation. The simplest form of a vibration absorber is that of a single degree of freedom system, where the "spring" is made of a viscoelastic material, perhaps with some metallic inserts. This paper sets out to describe how to design a best possible system of viscoelastic vibration absorbers for an available viscoelastic material, known by its four fractional parameter model, by using a novel objective function, defined through a Frobenius norm. A real example is presented and discussed.

Cette thèse vise à répondre à trois questions fondamentales: 1) La diminution de l’excitabilité corticospinale et le manque d’inhibition intracorticale observés suite à la stimulation magnétique transcrânienne (SMT) du cortex moteur de la main atteinte de sujets hémiparétiques sont-ils aussi présents suite à la SMT du cortex moteur de la jambe atteinte? 2) Est-ce que les altérations dans l’excitabilité corticomotrice sont corrélées aux déficits et incapacités motrices des personnes ayant subi un accident vasculaire cérébral depuis plus de 6 mois? 3) La vibration musculaire, étant la source d’une forte afférence sensorielle, peut-elle moduler l’excitabilité corticomotrice et améliorer la performance motrice de ces personnes? Premièrement, afin d’appuyer notre choix d’intervention et d’évaluer le potentiel de la vibration mécanique locale pour favoriser la réadaptation des personnes ayant une atteinte neurologique, nous avons réalisé une révision en profondeur de ses applications et intérêts cliniques à partir d’informations trouvées dans la littérature scientifique (article 1). La quantité importante d’information sur les effets physiologiques de la vibration contraste avec la pauvreté des études qui ont évalué son effet thérapeutique. Nous avons trouvé que...

Active control of vibration in structures has been investigated by an increasing number of researchers in recent years. There has been a great deal of theoretical work and some experiment examining the use of point forces for vibration control, and more recently, the use of thin piezoelectric crystals laminated to the surfaces of structures. However, control by point forces is impractical, requiring large reaction masses, and the forces generated by laminated piezoelectric crystals are not sufficient to control vibration in large and heavy structures. The control of flexural vibrations in stiffened structures using piezoceramic stack actuators placed between stiffener flanges and the structure is examined theoretically and experimentally in this thesis. Used in this way, piezoceramic actuators are capable of developing much higher forces than laminated piezoelectric crystals, and no reaction mass is required. This thesis aims to show the feasibility of active vibration control using piezoceramic actuators and angle stiffeners in a variety of fundamental structures. The work is divided into three parts. In the first, the simple case of a single actuator used to control vibration in a beam is examined. In the second, vibration in stiffened plates is controlled using multiple actuators...

Vibrating machinery must be isolated from a supporting structure if the vibration is likely to cause fatigue of components or annoyance to people due to direct vibration exposure or from the noise radiated by the vibrating structure. Active vibration isolation can be applied in these situations to extend the low frequency performance of passive vibration isolators. In this thesis, theoretical and experimental investigations are described for a vibrating rigid body that is passively and actively isolated from a beam and a cylinder, respectively. The focus of the work is to investigate the vibrational power transmitted by translational forces and rotational moments into the support structure. For the investigation of the simply supported beam, a classical mathematical model is examined and finite element modelling is used to predict the power transmission into the beam when active vibration control is used. The results show that power transmission by moments is significant and cannot be ignored when the vibrational power transmission into the support structure is actively controlled. To control the power transmission by translational forces and rotational moments, a novel six axis active vibration isolator and a novel six axis force transducer were constructed to be used in the experimental investigations. Using vibrational power transmission as a cost function to be minimized in active control experiments presents unique problems because negative values of translational power transmission are possible when power transmission from rotational moments is ignored or when phase errors occur in the transducer outputs. Active control attempts which converge the cost function to a negative value of power transmission along a particular axis can result in overall vibration levels in the structure which are greater than without active control. To prevent the increase in vibration levels...

Vibration is recognised as one of the most significant disturbances to the operation of mechanical systems. Many traditional vibration isolator designs suffer from the trade-off between load capacity and isolation performance. Furthermore, in providing sufficient stiffness in the vertical direction to meet payload weight requirements, isolators are generally overly stiff in the remaining five degrees of freedom (DOF). In order to address the limitations of traditional isolator designs, this thesis details the development of a 6-DOF active vibration isolation approach. The proposed solution is based on a magnetic levitation system, which provides quasi-zero stiffness payload support in the vertical direction, and inherent zero stiffness in the other five DOFs. The introduced maglev isolator also allows the static force and moment inputs from the payload to be adaptive-passively balanced using permanent magnets. In this thesis, the theoretical background of the proposed maglev vibration isolation method is presented, which demonstrates the ability of the maglev system to achieve the intended vertical payload support and stiffness in the six degrees of freedom. Numerical models for calculating the forces and torques in the proposed maglev system are derived...

http://trove.nla.gov.au/work/32491263; Machine derived contents note: CHAPTER 1: PERCEPTION THRESHOLDS FOR LOW FREQUENCY NOISE 1 ulnpleasantness and acceptable limits of low frequency sound Ki o inukai, Norio Nakamura and Hideto Taya 7 1 1 An investigation of the perception thresholds of band-limited low frequency noises: influence of bandwidth ,jsunao Matsumoto, Yukio Takahashi, Setsuo Maeda, Hiroki Yamaguchi, Kauhiro Yamada and Jishnu K Subedi 15 1.3. Masked perception thresholds of low frequency tones under background noises and their estimation by loudness model Jishnu K. Subedi, Hiroki Yamaguchi, Yasunao Matsumoto 27 1.4. Thresholds and acceptability of low frequency pure tones by sufferers Yukio Inukai, Hideto Taya and Shinji Yamada 45 CHAPTER 2: EFFECT OF LOW FREQUENCY NOISE ON PEOPLE IN TERMS OF ANNOYANCE AND SLEEP DEPRIVATION 2.1. Unpleasantness and acceptable limits of low frequency sound Yukio Inukai, Norio Nakamura and Hideto Taya 7 2.2. Low frequency noise and annoyance in classroom Pir Axelsson, Kjell Holmberg and U/​f Landstr6m 61 2.3. A Structured approach to LFS-complaints in the Rotterdam region of the Netherlands /​ng. Piet Sloven 71 2.4. Annoyance of low frequency noise and traffic noise Frank Rysgaard Qistdorff and Torben Poulsen 87 2.5. Perceptions of the public of low frequency noise D.M. J...

This thesis investigated the monitoring and analysis of signals related to the vibration of large rotary blasthole drills. The research focused on a machine with electric drilling actuators: such machines are used as primary production equipment in the drill‐and‐blast cycle of the surface (open‐pit) mining process. The performance of such machines is limited by the onset of severe vibrations, which can arise due to the interaction of geology, bit, drill string, machine structure, and control settings. Experimental data for the thesis were obtained during field periods at an iron ore mine in Minnesota’s Mesabi Iron Range. The data acquisition and signal analysis techniques which were utilized are presented, including smoothing of signals and calculated variables such as specific energy. Ambient vibration sources and vibration aliasing issues are investigated. Results from analyzing structural response tests indicate that, as expected, the natural frequency of the drill mast decreases with increasing bit depth – although the mounting position of accelerometers distorts this trend. The pull down force (weight on bit) is shown to have no appreciable impact on the mast’s natural frequency, nor on the mast’s damping ratio. A strong relationship between rotary speed and the dominant vibration frequency peaks at 3x and 6x rotary speed is demonstrated...

Este trabalho consiste em avaliar os níveis de vibração em um trator agrícola no qual o operador está exposto a uma situação normal de trabalho. Com este intuito, são colocados como situações de trabalho, o deslocamento do veículo em terreno não pavimentado, estrada asfaltada e a operação de plantio. A medição da vibração é feita através da instalação de acelerômetros em partes de contato do motorista com o veículo. Utilizou-se um acelerômetro para medir o nível de vibração no volante (vibração transmitida ao sistema mão-braço) e outro acoplado ao assento do motorista e na base do assento através de um seat pad para medir a vibração transmitida ao corpo inteiro. Também, avalia-se a exposição diária à vibração A(8) para situações normais de trabalho e comparando com os limites de exposição diária, definidas pelas normas vigentes. Com base nos resultados obtidos, observa-se que para determinadas condições, as vibrações ultrapassam os limites de exposição permitidos pela norma.; This work aims at assessing the vibration levels in an agricultural tractor whose driver is exposed in a normal working situation. The evaluated work situations are driving on unpaved terrain, driving on a paved road (asphalt) and in planting operation. The vibration measurement is evaluated by installing accelerometers in contact parts of the driver with the vehicle. It is used an accelerometer to measure the vibration levels in the steering wheel (vibration transmitted to the hand-arm system) and other one to measure the whole body vibration that is coupled to the driver's seat and seat back. In addition...

In the present work in situ sound insulation measurements were performed, according to the applicable standards of ISO 140 series, and vibration measurements of the separator elements in question (floor, ceiling, side walls). We intend to compare the results of direct measure-ments of sound insulation with the results of the predictions of sound insulation, based on the vibration measurements, to verify the feasibility of using vibration measurements to determine the most suitable locations of sound propagation (floor, ceiling, side walls) to act in order to improve, where it is needed, sound insulation in buildings. The principles of sound propaga-tion considered in EN 12354 series standards are used, e.g., 5 major structural paths, depend-ing on the sound radiating element in the receiver compartment [1) partition wall, 2) ceiling, 3) floor, 4) wall left side, 5) wall right side] and 2 major airborne path [1) openings in the par-tition element, 2) openings in other elements]. Different Radiation Factors, to convert vibra-tion of elements in sound are also considered, depending on the radiation element type and on the frequency in question.