Search results for "VIBRATION"
showing 10 items of 823 documents
The Effects of Low-frequency Vibration on Aligner Treatment Duration: A Clinical Trial
2021
Objectives: The aim of this study was to investigate the effectiveness of an orthodontic tooth movement acceleration device (AcceleDent, OrthoAccel Technologies, Houston, Texas) when used during an aligner treatment. Materials and Methods: Adult patients who began an aligner treatment (Lineo, Micerium Lab, Avegno, Italy) were allocated to two treatment groups. The first one (Group A), with a 7-day aligner change regimen, used the AcceleDent device for 20 min per day, whereas the second one (Group B) changed the aligners every 14 days and did not use any device. The registered outcomes were the possibility of completing the treatment, the number of aligners needed and treatment duration in t…
Machine Learning approach towards real time assessment of hand-arm vibration risk
2021
In industry 4,0, the establishment of an interconnected environment where human operators cooperate with the machines offers the opportunity for substantially improving the ergonomics and safety conditions of the workplace. This topic is discussed in the paper referring to the vibration risk, which is a well-known cause of work-related pathologies. A wearable device has been developed to collect vibration data and to segment the signals obtained in time windows. A machine learning classifier is then proposed to recognize the worker’s activity and to evaluate the exposure to vibration risks. The experimental results demonstrate the feasibility and effectiveness of the methodology proposed.
A SYMMETRIC AND POSITIVE DEFINITE BEM FOR 2-D FORCED VIBRATIONS
1997
A BEM formulation for 2D elastodynamics in the time domain has been presented. The formulation gives a resolving system that involves boundary displacements only. The stiffness and mass matrices of the boundary discretized body are frequency independent, symmetric and positive definite
Complex power distribution analysis in plates covered with passive constrained layer damping patches
2012
International audience; The vibration of a plate partially covered with a passive constrained layer damping (PCLD) patch is studied from an energetic point of view. The damped plate is excited by an acoustic plane wave. The study is done with a numerical two-dimensional multilayer plate model. Results of the present model are compared to those obtained with three-dimensional finite element models. It is shown that the present model gives accurate results, even for the layer's inner behavior. It is less expansive in terms of computational cost; hence, it can simulate efficiently the structure for higher frequencies. Mathematical formulas for complex mechanical power are presented, and the li…
Dynamic stability of plane elastic frames
1982
Abstract The stability of plane elastic frames subjected to a vertical foundation motion of the stationary, ergodic type is investigated. The equations of motion are obtained in modal co-ordinates, with account taken of many modes of vibration. The problem is subsequently reduced to the study of only the first mode of vibration. By considering a particular case, the stability domains are sketched as functions of the variation of the rigidities of the beam-column connecting joints and as functions of the number of stories.
Neuromuscular and mobility responses to a vibration session in hypoxia in multiple sclerosis
2020
AbstractThe aim of this study was to investigate the acute effects of vibration training (WBVT) under hypoxic and normoxic conditions on the voluntary rate of force development (RFD), balance and muscle oxygen saturation (SMO2) in persons with Multiple Sclerosis (MS). 10 participants completed the study (30% males, 44.4±7.7 years, 164.3±8.9 cm, 65.2±11.1 kg, 2.5±1.3 Expanded Disability Status Scale, 24.1±4.0 kg.m−2 BMI). Maximal force, RFD during isometric knee extension, static balance with eyes open and closed and sit-to-stand test were evaluated before and immediately after one session of WBVT (12 60-s bout of vibration; frequency 35 Hz; amplitude 4 mm; 1-min rest intervals) under both n…
Acute Effects of Mechanical Vibration
1986
We know that man possesses a highly developed ability to adjust to different environmental conditions. For this function there are physiological regulatory systems, which release reactions in him for protection against such influences. Thus, receptors for light, smell, taste, temperature, sound, touch, position change, pressure, and tension are at hand which, as parts of the cybernetics system, can release physiologically meaningful protective reactions.
Chronic Effects of Whole-Body Vibration
1986
The reactions of the body to stress from mechanical vibration, presented in the section “Acute Effects of Mechanical Vibration” (see p. 12), deal with individual organs and functions. It is now time for the following question to be asked: Are these physiological or pathophysiological changes in reality the external symptoms of a vibration-induced illness of the whole organism? Above all, some Soviet scientists are of this opinion. Andreeva-Galanina (1967) has especially called this concept “vibration illness” and has used it in the sense that the totality of vibration-induced changes in the human organism can be characterized (Rublack 1978). In this systemic “vibration illness,” Andreeva-Ga…
In vivo vibrational wave propagation in human tibiae at different ages
1989
Vibrational wave propagation was tested in vivo on the tibial bone of both legs of 56 female volunteers. The impact was produced by a hammer with a force strain gauge and the response was monitored by two accelerometers. The peak amplitude of the accelerations, the velocity of the acceleration wave propagation and damping were analysed for comparison among the different age groups. The results showed significant negative correlations between age and the peak amplitude of acceleration, and the velocity of acceleration wave propagation (p less than 0.01). The damping time of the acceleration wave also had a negative correlation with age. These findings suggested that age differences were rela…
Correlates of vibrotactile thresholds in men of different ages
1986
— As a part of a larger gerontological research project vibrotactile thresholds on the inner malleolus of the ankle were studied in 355 men aged 31–35, 51–55 and 71–75 years. The groups studied were random samples of men living in the town of Jyvaskyla in Finland in the year 1981. The thresholds were assessed at three frequencies: 50 Hz, 100 Hz and 250 Hz. The thresholds were associated with age at all frequencies, the means of the threshold values being significantly higher in the older age groups. Within the age groups the thresholds correlated positively with height. In addition, reaction and movement time, leg extension velocity, and postural sway were associated with the thresholds. Ne…