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546 results on '"Hozumi, N."'

78. Breakdown strength of biodegradable dielectric liquid: The effect of temperature and viscosity.

Author

Kurnianto, Rudi, Taufan, M., Nawawi, Zainuddin, Nagao, M., and Hozumi, N.

Abstract

The investigation of temperature effect connected with viscosity changes on the breakdown strength of virgin coconut oil (VCO) has been studied by AC voltage and sphere gap electrode system of 2.5 mm distance. The results showed that temperature affected the viscosity and breakdown strength of VCO. The viscosity was inversely proportional to temperature and breakdown strength. The increase of temperature was followed by the increase of breakdown strength. It is considered that the increase of temperature would decrease the fat content in VCO. The same reason could also be used to explain the increase of temperature would decrease the viscosity. However, in a part of experiment, in the range of temperature 55°C and 60°C, we still have no basic reason to conclude, due to the limitation of our data. Thus, this investigation opens the chance for further research and discussion concerning the effect of temperature on the breakdown strength of VCO. [ABSTRACT FROM PUBLISHER]

Published
2012

85. Development of Ultrasonic Nano-imaging System for Visualization of Cells.

Author

Kim, Sun I., Suh, Tae Suk, Magjarevic, R., Nagel, J. H., Saijo, Yoshifumi, Hozumi, N., Kobayashi, K., Okada, N., Lee, C. K., Sasaki, H., Yambe, T., and Tanaka, M.

Abstract

As the frequency of ultrasound is inversely proportional to the wave length and beam width, GHz range ultrasound realizes the nano-level ultrasonic imaging. In the present study, a prototype of ultrasonic nano-level imaging system using a single pulsed ultrasound is proposed. A 500-ps width single electric pulse was input into an ultrasonic transducer made of ZnO with the central frequency of 500 MHz, which corresponded to 2-µm focal spot. The reflections were captured by 2GSa/s analogue-digital converter. The transducer was driven by two linear servo motors to scan XY-plane above the specimen. The scanning field was available from 2.4 × 2.4 mm to 40 × 40 µm with 300 × 300 pixels. The waveform from the tissue area contains two reflections at the surface and at the interface between the tissue and slide glass. Frequency domain analysis was performed by analyzing the interference between the two reflections in order to calculate the thickness and sound speed of the specimen. Normal and atherosclerotic human coronary arteries were frozen, sliced approximately 5-µm and mounted on a glass slides. Pure water was used for the coupling medium between the transducer and tissue. Three layered structure of coronary artery was clearly visualized by the system. Especially, calcification and lipid core showed a significant difference of sound speed. The values of speed of sound were within same range as our previous measurements. In visualization of cultured nerve cells, saline was used for the coupling medium. The resolution was enough to visualize a single cell and the process of the cell was clearly seen. A prototype of ultrasonic nano-imaging system which was able to visualize a single cell was developed. The system is useful for intraoperative pathological examination, study of low-frequency ultrasonic images, and assessment of biomechanics of the tissues at a nano-level. [ABSTRACT FROM AUTHOR]

Published
2007
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94. Carrier mobility in ethylene-vinylacetate copolymer estimated by transient space charge

Author

Hozumi, N., Muramoto, Y., Nagao, M., and Zhang, Yewen

Subjects
Electric insulators -- Testing, Dielectrics -- Research, Business, Electronics, Electronics and electrical industries
Abstract

Carrier mobility in an ethylene vinyl acetate (EVA) copolymer film was measured by a new technique. The time-dependent charge distribution was monitored by the pulsed-electroacoustic method when a pulse voltage was superposed on a dc bias voltage. A positive charge packet was injected from the anode soon after the pulse application, and moved towards the cathode. It was suggested from the movement of the charge packet that the mobility of the positive carrier at 10 to 60 MV/m was in the order of [10.sup.-13] [m.sup.2]/Vs at room temperature. When the pulse voltage was very high, a charge packet appeared within the bulk, suggesting that carrier dissociation takes place.

Published
2001

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