The Experts below are selected from a list of 201 Experts worldwide ranked by ideXlab platform
R. Mahdavi - One of the best experts on this subject based on the ideXlab platform.
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Application of Ultrasonic Velocity Measurement for flow stress determination of TWIP steel
Materials Science and Technology, 2012Co-Authors: P. Behjati, Ghasem Dini, H V Dastjerdi, R. MahdaviAbstract:In the present work, the Ultrasonic Velocity Measurement was used as a non-destructive technique for flow stress determination of a twinning induced plasticity steel. For this purpose, first, a relationship between mechanical twinning and Ultrasonic Velocity was found out and then, it was used in the flow stress model previously suggested by the authors. Comparison of the obtained results with the experimental values revealed a good agreement.
Kiyotaka Sato - One of the best experts on this subject based on the ideXlab platform.
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Ultrasonic Velocity Measurement of crystallization rates of palm oil in oil-water emulsions
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 1997Co-Authors: Y. Hodate, Satoru Ueno, Junko Yano, Toshiya Katsuragi, Y. Tezuka, T. Tagawa, Noriyuki Yoshimoto, Kiyotaka SatoAbstract:Abstract The xrystallization behaviour of palm oil dispersed in oil-in-water emulsion (oil, 30 wt.%; water, 70 wt.%) was studied by Ultrasonic Velocity Measurement under cooling and heating processes. Na caseinate, as a major surfactant, and hydrophilic sucrose polyesters, as minor components, were employed for emulsification. The rates of crystallization of palm oil were monitored by the changes in the Ultrasonic Velocity values, which increasing amount of fat crystals in the palm oil phase. Effects of the addition of highly hydrophobic food emulsifiers of sucrose polyesters with HLB values of around 1, added in palm oil, were examined, in an attempt to modify the rate of crystallization of palm oil. Comparing the results in the emulsion systems with those in neat palm oil liquid, we have obtained the following results: (a) the rates of crystallization, particularly of nucleation, were retarded in the emulsion systems compared with the neat liquid; (b) the addition of hydrophobic sucrose polyesters increased the nucleation rates in the emulsion systems, whereas it retarded the rates of crystal growth; (c) this opposing effect was most manifest for the sucrose polyesters with a stearic acid moiety, yet minimized for those with an oleic acid moiety. A mechanistic argument is given for the experimental results in terms of emulsifier-fat interactions.
R. Strelitzki - One of the best experts on this subject based on the ideXlab platform.
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Aspects of Ultrasonic Velocity Measurement in trabecular bone
Medical Physics, 1997Co-Authors: R. StrelitzkiAbstract:Osteoporosis is a major health problem in modern society. Different techniques are used to discriminate people at risk of this disease. One of them, ultrasound, has advantages compared to the more established densitometric methods. Two parameters, the Velocity and the Broadband Ultrasonic Attenutation (BUA) are most often assessed on the oscalcis. The thesis examines the errors in Measurement of Velocity and attenuation. To confirm and demonstrate this, Measurements of BUA on several commercial devices were carried out using bone phantom materials and these showed significant (up to 33 dB MHz-1) variations. The errors in Velocity Measurements include those due to frequency dependence of attenuation and Velocity and these factors are evaluated separately. Time and frequency domain methods are used as well as theoretical modeling. It is shown that phase Velocity is more resilient and accurate than commonly used methods and provides an opportunity to measure dispersion which may be an additional and useful parameter. The use of low frequency methods, utilizing bar wave propagation is also examined. It is concluded that the way is now clear to develop alternative clinical equipment based largely on Velocity Measurements, which should give a closer estimate of bone strength than existing Ultrasonic techniques.
G Van Der Perre - One of the best experts on this subject based on the ideXlab platform.
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a comparison of time domain and frequency domain approaches to Ultrasonic Velocity Measurement in trabecular bone
Physics in Medicine and Biology, 1996Co-Authors: Phf Nicholson, G Lowet, Christian M Langton, Jan Dequeker, G Van Der PerreAbstract:Different methods for Ultrasonic Velocity determination using broad-band pulse transmission have been investigated in 70 human calcanae in vitro. The work took place within the context of the EC BIOMED1 concerted action Assessment of Quality of Bone in Osteoporosis. Ultrasonic velocities were determined using three different transit time definitions: first arrival (TTV1), thresholding (TTV2), and first zero crossing (TTV3). Phase Velocity (PV) was determined over a range of frequencies from 200 to 800 kHz using a new phase spectral analysis technique. The different Velocity Measurements were compared in terms of their magnitudes and their inter-correlations. There were significant differences of up to between different transit time velocities (p < 0.0001), indicating the sensitivity of the Measurement to the arrival criteria used. Phase velocities were lower than all of the transit time velocities (p < 0.0001) and decreased with increasing frequency (p < 0.005). A strong correlation was observed between PV at 400 kHz (PV400) and TTV3, with much weaker correlations between PV and the other transit time velocities. Reproducibility for transit time Velocity Measurement was optimal for TTV3 (coefficient of variation, cv = 0.41%), and for PV it was optimal at 600 kHz (cv = 0.34%). These data indicate that transit time Measurements may be subject to errors due to the modification of the pulse shape during propagation through bone by attenuation and dispersion. Velocity Measurement by phase spectral analysis appears to offer advantages over the transit time approach, and should be the method of choice for Velocity Measurement in trabecular bone. Where transit time Velocity Measurements are made, the first-zero-crossing criterion appears to be have some advantages over other arrival criteria. We also note that PV Measurements provide new information on dispersion which could prove to be relevant to the structural and mechanical characterization of trabecular bone.
P. Behjati - One of the best experts on this subject based on the ideXlab platform.
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Application of Ultrasonic Velocity Measurement for flow stress determination of TWIP steel
Materials Science and Technology, 2012Co-Authors: P. Behjati, Ghasem Dini, H V Dastjerdi, R. MahdaviAbstract:In the present work, the Ultrasonic Velocity Measurement was used as a non-destructive technique for flow stress determination of a twinning induced plasticity steel. For this purpose, first, a relationship between mechanical twinning and Ultrasonic Velocity was found out and then, it was used in the flow stress model previously suggested by the authors. Comparison of the obtained results with the experimental values revealed a good agreement.
