نتایج جستجو برای: ultrasonic velocity
تعداد نتایج: 167684 فیلتر نتایج به سال:
The study described herein was undertaken to determine the role of proteins, in general, and collagen, in particular, in the observed absorption and speed of ultrasound in biological tissues. It had earlier been observed that ultrasonic absorption in tissues occurs at the macromolecular level, •'z though an additional contribution to attenuation arises from tissue structural features. a Each of...
We have developed a technique in ultrasonic correlation spectroscopy called diffusing acoustic wave spectroscopy (DAWS). In this technique, the motion of the scatterers (e.g., particles or inclusions) is determined from the temporal fluctuations of multiply scattered sound. In DAWS, the propagation of multiply scattered sound is described using the diffusion approximation, which allows the auto...
Ultrasonic tissue characterization has shown promise for clinical diagnosis of diseased bone (e.g., osteoporosis) by establishing correlations between bone ultrasonic characteristics and the state of disease. Porous (trabecular) bone supports propagation of two compressional modes, a fast wave and a slow wave, each of which is characterized by an approximately linear-withfrequency attenuation c...
Both the hardening process and formation of microstructure of concrete are significantly influenced by the curing condition. The capillary absorption of concrete is closely related to the structure and distribution of the pores within the material. This paper presents an experimental study on the influence of four curing conditions, i.e., standard curing, natural curing, water curing, and seale...
The ultrasonic attenuation is evaluated at 300 K along [100], [110], and [111] directions for the characterization of bcc metal Ta. The size of the metal is considered in nanorange. Ultrasonic velocity, Grüneisen parameter and acoustic coupling constant that depend on second and third order elastic constants are calculated for determination of ultrasonic attenuation coefficient. Second and thir...
OF THE DISSERTATION Comparison of Conventional and Bayesian Analysis for the Ultrasonic Characterization of Cancellous Bone by Amber Mae Groopman Doctor of Philosophy in Physics Washington University in St. Louis, 2014 Professor James G. Miller, Chair This dissertation investigates the physics underlying the propagation of ultrasonic waves in cancellous bone. Although quantitative ultrasound ha...
The controversy as to whether Doppler ultrasonic methods should play a role in clinical decision-making in the prevention of stroke is attributable to reported disagreement between angiographic and ultrasonic results and the lack of internationally accepted ultrasound criteria for describing the degree of stenosis. Foremost among the explanations for both is the broad scatter of peak systolic v...
Quantitative ultrasonic characterization of cancellous bone can be complicated by artifacts introduced by analyzing acquired data consisting of two propagating waves (a fast wave and a slow wave) as if only one wave were present. Recovering the ultrasonic properties of overlapping fast and slow waves could therefore lead to enhancement of bone quality assessment. The current study uses Bayesian...
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