Search results for " vibration"

Neck Muscle Vibration and Spatial Orientation During Stepping in Place in Humans

2002

Unilateral long-lasting vibration was applied to the sternomastoid muscle to assess the influence of asymmetric neck proprioceptive input on body orientation during stepping-in-place. Blindfolded subjects performed 3 sequences of 3 trials, each lasting 60 s: control, vibration applied during stepping (VDS), and vibration applied before stepping (VBS). VDS caused clear-cut whole body rotation toward the side opposite to vibration. The body rotated around a vertical axis placed at about arm's length from the body. The rotation did not begin immediately on switching on the vibrator. The delay varied from subject to subject from a few seconds to about 10 s. Once initiated, the angular velocity…

Acute effects of transient vertical whole-body vibration

1991

The question as to whether shock-type whole-body vibration causes increasingly acute strain was investigated. Random vibrations were superimposed with shocks differing in amplitude and in number per unit of time in a systematic manner. The weighted root mean square (rms) acceleration was kept constant in all over the varied experiments. A total of 17 men were exposed to vibration from an electrohydraulic simulator. The following strain criteria were used: biodynamic behavior of the trunk and the head, electrical activity of the muscles of the back and the neck, subjective sensation, skin temperature in the lumbar area and visual and tracking performance. It was found that increasing shock a…

Socio-medicinal aspects of vibration-induced white finger disease

2008

The influence of vibration-induced white finger disease on the quality of life and possible social consequences is the subject of the study presented herein.The data acquisition was carried out by means of a standardized questionnaire. Parameters such as quality of life, professional practice, prevention and social security were assessed among other things.Nearly three quarters of the interviewees (n = 115) did not consult a physician with the occurrence of the first complaints. Physicians frequently made the correct diagnosis only with delay. From the first occurrence of symptoms to the acknowledgment as an occupational disease 0.5-34.5 years had usually elapsed. The quality of life affect…

Whole-body vibration and disorders of the spine

1987

This cross-sectional study is based on interviews and medical examinations of 352 operators of earth-moving machines who had been exposed to whole-body vibrations for at least three years. In addition, available X-rays showing different parts of the spines of 251 machine operators who had been exposed to vibration for at least ten years were used for evaluation. One hundred and forty-nine of the operators were asked about discomfort occurring immediately after an eight-hour work shift. The group of exposed persons was compared with a control group of 215 non-exposed persons. The percentage of subjects reporting spinal discomfort was much higher for the exposed group than for the non-exposed…

A NUMERICAL APPROACH FOR THE PREDICTION OF SOUND GENERATED BY A MISTUNED ROTOR CASCADE

2012

A numerical investigation on the effects of blade frequency mistuning on the acoustic emission of a rotor cascade in subsonic flow is shown. A numerical method has been developed and implementd to obtain the mistuned rotor aeroelastic response and the associated acoustic waves. Both the aeroelastic and acoustic models are based on a linear unsteady small perturbations theory. The dynamic aeroelastic coupling between bending and torsional responses of each blade and the aerodynamic coupling among the blades are included in the formulation.

PRODROMI SULLE STIME CATASTALI

2012

Worker safety in agriculture 4.0: A new approach for mapping operator's vibration risk through Machine Learning activity recognition

2022

While being a fundamental driver of competitiveness in agroindustry, technological innovation has also introduced new critical elements related, for example, to the sustainability of the production processes as well as to the safety of workers. In such regard, the advent of the 4th industrial revolution (Agriculture 4.0) based on digitalization, is an unprecedented opportunity of rethinking the role of innovation in a new human-centric perspective. In particular, the establishment of an interconnected work environment and the augmentation of the operator’s physical, sensorial, and cognitive capabilities, are two technologies which can be effectively employed for substantially improving the …

Aminoacid zwitterions in solution : Geometric, energetic, and vibrational analysis using density functional theory-continuum model calculations

1998

Glycine and alanine aminoacids chemistry in solution is explored using a hybrid three parameters density functional (B3PW91) together with a continuum model. Geometries, energies, and vibrational spectra of glycine and alanine zwitterions are studied at the B3PW91/6-31+G∗∗ level and the results compared with those obtained at the HF and MP2/6-31+G∗∗ levels. Solvents effects are incorporated by means of an ellipsoidal cavity model with a multipolar expansion (up to sixth order) of the solute’s electrostatic potential. Our results confirm the validity of the B3PW91 functional for studying aminoacid chemistry in solution. Taking into account the more favorable scaling behavior of density funct…

The Boson Peak of Amyloid Fibrils: Probing the Softness of Protein Aggregates by Inelastic Neutron Scattering

2014

Proteins and polypeptides are characterized by low-frequency vibrations in the terahertz regime responsible for the so-called "boson peak". The shape and position of this peak are related to the mechanical properties of peptide chains. Amyloid fibrils are ordered macromolecular assemblies, spontaneously formed in nature, characterized by unique biological and nanomechanical properties. In this work, we investigate the effects of the amyloid state and its polymorphism on the boson peak. We used inelastic neutron scattering to probe low-frequency vibrations of the glucagon polypeptide in the native state and in two different amyloid morphologies in both dry and hydrated sample states. The dat…

Stochastic linearization of MDOF systems under parametric excitations

1992

Abstract The stochastic linearization approach is examined for non-linear systems subjected to parametric type excitations. It is shown that, for these systems too, stochastic linearization and Gaussian closure are two equivalent approaches if the former is applied to the coefficients of the Ito differential rule. A critical review of other stochastic linearization approaches is also presented and discussed by means of simple examples.