Study of the cause of the temperature rise at the muscle-bone interface during ultrasound hyperthermia

Undesirable temperature rise at the muscle-bone interface has been one of the major problems during ultrasound hyperthermia treatment. In this study, we examined by both computer calculation and phantom experiment the cause of this problem. Ultrasound penetrates a bone in two different waveforms, longitudinal and transversal. The transmission coefficient of these two waves vary greatly with the incident angle. From both theoretical and experimental results, the incident angle dependency of the interface heat was confirmed. When the incident angle is less than the critical angle of the longitudinal wave, the main cause of the temperature elevation is the absorption of the longitudinal wave in the bone. When the incident angle is larger than the critical angle of the longitudinal wave, the transversal wave becomes the major cause of the heat generation. At the incident angles larger than the critical angle of the transversal wave, no temperature rise is produced by the absorption of the ultrasound at the bone; the incident longitudinal wave, strengthened by the reflected wave, is absorbed in the muscle just in front of the bone. The heat generated in the muscle is transported to the interface so that the temperature of the interface and bone increases slightly.     

Binary genetic algorithm-based pattern LUT for grayscale digital half-toning

Grayscale digital half-toning is a popular technique to reproduce grayscale images with devices that can support only two levels at output, i.e., black and white. Printers, LCD displays, etc. are some common examples of such devices. Considering 0 and 1 as black and white, respectively, this can be represented as an image-wise binary pattern generation process. The binary patterns are aimed to retain the local tonal and structural characteristics of grayscale image for a faithful illusion of the original grayscale image. Apart from tonal and structural characteristics retention, desired blue-noise characteristics also contribute significantly toward eye pleasant appearance of half-tone images. The paper presents a binary genetic algorithm-based approach to generate such binary patterns through optimizing randomly generated binary strings against a visual cost function. Paper also presents a pattern look-up-table (LUT)-based approach toward conventional clustered dot ordered dithering which is suitable for devices like laser or offset printers that cannot recognize individual pixels. The pattern LUT approach is driven toward green-noise characteristics instead of the blue-noise characteristics. The results obtained with test images are presented pictorially and evaluated through half-tone quality evaluation metrics. The evaluation results and comparison with state-of-art techniques shows the potential of presented technique for practical implementations.     

Measurement and numerical simulation of a small centrifugal compressor characteristics at small or negative flow rate

For centrifugal compressors used in automotive turbochargers,the extension of the surge margin is demanded because of lower engine speed.In order to estimate the surge line exactly,it is required to acquire the compressor characteristics at small or negative flow rate.In this paper,measurement and numerical simulation of the characteristics at small or negative flow rate are carried out.In the measurement,an experimental facility with a valve immediately downstream of the compressor is used to suppress the surge.In the numerical work,a new boundary condition that specifies mass flow rate at the outlet boundary is used to simulate the characteristics around the zero flow rate region.Furthermore,flow field analyses at small or negative flow rate are performed with the numerical results.The separated and re-circulated flow fields are investigated by visualization to identify the origin of losses.     

Determination of nequinate and buquinolate in livestock products using liquid chromatography-tandem mass spectrometry

We studied the simultaneous determination of nequinate and buquinolate, which are used as feed additives to prevent coccidiosis, by means of liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). The sample was extracted with acetonitrile, then loaded onto an HLB mini-column with 20% methanol. After clean-up with 20% methanol, the analytes were eluted with acetonitrile-methanol (1 : 1). The coccidiostats in the purified samples were determined using ESI-MRM mode LC-MS/MS with a sample matrix calibration curve. Mean recoveries of nequinate and buquinolate from 8 kinds of livestocks samples (chicken muscle, chicken liver, chicken heart, swine muscle, swine heart, cattle muscle, sheep muscle, egg) were in the range of 89.5% to 108.6%, and the relative standard deviation values were <20% (n=10) at the levels of 0.01 μg/g and 0.05 μg/g, respectively. The limits of quantification of these compounds were 0.001 μg/g in each sample.     

Early construction and operation of the highly contaminated water treatment system in Fukushima Daiichi Nuclear Power Station (IV) - Assessment of hydrogen behavior in stored Cs adsorption vessel

Hydrogen diffusion behavior in a cesium adsorption vessel is assessed. The vessel is used to remove radioactive substance from contaminated water, which is proceeded from Fukushima accident. Experiment and numerical calculation are conducted to clarify the characteristics of natural circulation in the vessel. The natural circulation arising from the temperature difference between inside and outside the vessel is confirmed. We develop an evaluation model to predict the natural circulation and its prediction agrees well with the results obtained by the experiment and the calculation. Using the model, we predict steady and transient behavior of hydrogen concentration. Results indicate that hydrogen concentration is kept lower than the flammability limit when the short vent pipe is open.