Search results for "Sound"

Direct imaging of delayed magneto-dynamic modes induced by surface acoustic waves.

2017

The magnetoelastic effect—the change of magnetic properties caused by the elastic deformation of a magnetic material—has been proposed as an alternative approach to magnetic fields for the low-power control of magnetization states of nanoelements since it avoids charge currents, which entail ohmic losses. Here, we have studied the effect of dynamic strain accompanying a surface acoustic wave on magnetic nanostructures in thermal equilibrium. We have developed an experimental technique based on stroboscopic X-ray microscopy that provides a pathway to the quantitative study of strain waves and magnetization at the nanoscale. We have simultaneously imaged the evolution of both strain and magne…

Ultrasonic detection by photo-EMF sensor and by wideband air-coupled transducer

2004

Two non-contact remote ultrasonic detection systems are compared. The first consists of a continuous wave (CW) Nd:YVO4 laser operating at 532 nm used in conjunction with a photo-induced electromotive-force (EMF) sensor. The second system employs an air-coupled capacitance transducer that has a bandwidth from 100 kHz up to 2 MHz. Both systems exhibit higher sensitivity to out-of-plane than in-plane measurements of stress wave signals. Ultrasound generation is carried out by an Nd:YAG pulsed laser at 532 nm in the thermoelastic regime in a 1.6 mm aluminum plate. A0 Lamb mode is generated at frequency-thickness product with strong out-of-plane displacements. Ultrasonic waveforms acquired are r…

Phased laser diode array permits selective excitation of ultrasonic guided waves in coated bone-mimicking tubes

2017

This paper validates simulation predictions, which state that specific modes could be enhanced in quantitative ultrasonic bone testing. Tunable selection of ultrasonic guided wave excitation is useful in non-destructive testing since it permits the mediation of energy into diagnostically useful modes while reducing the energy mediated into disturbing contributions. For instance, it is often challenging to distinguish and extract the useful modes from ultrasound signals measured in bone covered by a soft tissue. We show that a laser diode array can selectively excite ultrasound in bone mimicking phantoms. A fiber-coupled diode array (4 elements) illuminated two solid tubes (2-3mm wall thickn…

Erratum: “Enhanced acoustic pressure sensors based on coherent perfect absorber-laser effect” [J. Appl. Phys. 129, 104902 (2021)]

2021

RADICAL DISTRIBUTIONS IN AMMONIUM TARTRATE SINGLE CRYSTALS EXPOSED TO PHOTON AND NEUTRON BEAMS

2014

The radiation therapy carried out by means of heavy charged particles (such as carbon ions) and neutrons is rapidly becoming widespread worldwide. The success of these radiation therapies relies on the high density of energy released by these particles or by secondary particles produced after primary interaction with matter. The biological damages produced by ionising radiations in tissues and cells depend more properly on the energy released per unit pathlength, which is the linear energy transfer and which determines the radiation quality. To improve the therapy effectiveness, it is necessary to grasp the mechanisms of free radical production and distribution after irradiation with these …

Study of the glow curves of TLD exposed to thermal neutrons.

2007

The glow curves of thermoluminescent dosimeters (TLD600, TLD700 and MCP), exposed to a mixed field of thermal neutrons and gamma photons are analysed. The fluence values of thermal neutrons used, comparable with those used in radiotherapy, allow one to define the reliability of the TLDs, in particular the most sensitive MCP, in this radiation field and to get information on the dose absorbed values. The glow curves obtained have been deconvoluted using general order kinetics and the observed differences for the different LET components have been analysed. In particular, the ratio of the n(0) parameter of two different peaks seems to allow to discriminate the different contributions of neutr…

Modeling the influence of mineral content and porosity on ultrasound parameters in bone by using synthetic phantoms

1999

Model composite media − 10×15×80 mm3 bone tissue phantoms based on an epoxy resin with fillers—were made to study the influence of porosity and mineral content on ultrasound velocity and attenuation. The pores were simulated by ∼ 1 mm3 particles of a soft rubber, while the mineral content was imitated by a mineral residue of natural bone obtained by burning and grinding. The porosity and mineral content were varied in the range of 0–70% by volume with a step of 10%. The velocity, attenuation, and prevalent frequency of ultrasound were measured by the pulse transition method, using transducers with nominal frequencies 0.1, 0.2, 0.5, and 1.0 MHz. It was experimentally found that the ultrasoun…

Relation between bone quality values from ultrasound transmission velocity and implant stability parameters--an ex vivo study.

2011

Aim The objective of this study was to determine the relationship between bone qualities measured by ultrasound transmission velocity (UTV) and primary implant stability parameters measured by radiofrequency analysis (RFA) and push-out test (POT) in an ex-vivo model. Materials and methods Three blocks of fresh porcine bone samples were obtained from different anatomic regions, correlating to cortical, mixed and cancellous bone. Mechanical bone qualities of these samples were measured using UTV (expressed in m/s) prior to implantation. Three similar implants (4.1 × 11 mm, AstraTech OS) were inserted into each of the procured bone blocks. The evaluation of implant-bone interface stability was…

Speckle correlation technique to determine roughness in the dermatologic interval.

1988

A non-invasive method is proposed to determine human skin roughness. The technique is based on measurement of the correlation between two field distributions scattered by a metallised triafol (cellulose acetate foil) replica of the epidermal area to be analysed. The two speckle patterns are produced from the same rough surface illuminated by two coherent plane waves (He-Ne laser) under two slightly different angles. The accuracy of the method is highlighted by measurements made on a set of standard samples with roughnesses previously determined by mechanical profilometry. Analysis of the results indicates a precision of around 10%, and an applicability within the interest range of very roug…

A monte carlo study of dose rate distribution around the specially asymmetric CSM3-a 137Cs source.

2001

The CSM3 137Cs type stainless-steel encapsulated source is widely used in manually afterloaded low dose rate brachytherapy. A specially asymmetric source, CSM3-a, has been designed by CIS Bio International (France) substituting the eyelet side seed with an inactive material in the CSM3 source. This modification has been done in order to allow a uniform dose level over the upper vaginal surface when this `linear' source is inserted at the top of the dome vaginal applicators. In this study the Monte Carlo GEANT3 simulation code, incorporating the source geometry in detail, was used to investigate the dosimetric characteristics of this special CSM3-a 137Cs brachytherapy source. The absolute do…