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Mendoza-Hernandez O.S.,Nagaoka University of Technology | Ishikawa H.,Nagaoka University of Technology | Ishikawa H.,Industrial Technology Institute of Ibaraki Prefecture | Nishikawa Y.,Nagaoka University of Technology | And 3 more authors.
Electrochimica Acta | Year: 2014

Li-ion insertion/deinsertion reactions of the anode of a Li-ion secondary cell incorporating a reference electrode were analyzed by electrochemical impedance spectroscopy (EIS) at different temperatures and state of charges (SOCs). The cell uses graphitized carbon as anode electroactive material. Impedance spectra fittings were carried out using an equivalent circuit, so that the reaction kinetics could be evaluated accurately. The dependencies of the Li-ion conduction (Rsl1), Li-ion solvation/desolvation (R sl2) and charge transfer (Rct) reactions on the SOC and anode potential were evaluated. The results were compared with a dQ/dE vs. E curve of graphite to analyze how the structural changes of graphite affect the Li-ion insertion process. The charge transfer process was found to be dependent on the SOC and anode potential. On the other hand, Li-ion conduction and Li-ion solvation/desolvation processes did not depend on the SOC and anode potential. © 2014 Elsevier Ltd. Source


Kitazawa H.,Japan National Food Research Institute | Funaki T.,Japan National Institute of Advanced Industrial Science and Technology | Nakao M.,Kagoshima University | Ohshiro Y.,Ibaraki Prefectural Government | And 2 more authors.
Food Science and Technology Research | Year: 2012

The purpose of this study was to clarify airflow in packaging containers with ventilation for fruit and vegetables and propose a favorable package shape for efficient ventilation. Here we investigated the influences of differences in the inlet air velocity through the ventilation port and diameter of the port on the air velocity distribution in a 1-layer packaging system container for strawberries employing computational fluid dynamic (CFD) analysis. It was suggested that the air velocity increases with a rise in the inlet air velocity or ventilation port size, i.e., the volumetric flow rate, but there were regions in which airflow could be hardly generated under any inlet condition. The results suggest that elimination of these regions is a key factor in developing a packaging container with a favorable shape for ventilation efficiency. Source


Ishikawa H.,Nagaoka University of Technology | Ishikawa H.,Industrial Technology Institute of Ibaraki Prefecture | Mendoza O.,Nagaoka University of Technology | Sone Y.,Japan Aerospace Exploration Agency | Umeda M.,Nagaoka University of Technology
Journal of Power Sources | Year: 2012

In this study, we analyzed the thermal characteristics of commercial cylindrical lithium-ion cells using an accelerated rate calorimeter (ARC) and by analyzing the electrochemical impedance spectroscopy (EIS) measurements. During the thermal runaway analysis, the cells were tested at different state of charges (SOCs) and the thermal deterioration was determined by monitoring the impedance at 1 kHz and the open circuit voltage as a function of the temperature. The mapping of the thermal runaway was obtained, ant the non-self heating, self-heating and thermal runaway regions were identified at different SOCs. The self-heating and thermal runaway behaviors showed a temperature dependence. In order to clarify the deterioration reaction in the non-self heating region, high temperature storage tests were carried out, storing the cell in the temperature range of 70-100 °C. We estimated the activation energy from the discharge capacities before and after the high temperature storage. In order to determinate the charge/discharge activation energy of the cells, EIS measurements were recorded. Based on our study, the activation energy of the deterioration was about two times greater in magnitude than the activation energy of the charge/discharge. © 2011 Elsevier B.V. All rights reserved. Source


Ishiwatari Y.,Industrial Technology Institute of Ibaraki Prefecture | Ishiwatari Y.,Ibaraki University | Mishima I.,Center for Environmental Science in Saitama | Utsuno N.,Ibaraki Kasumigaura Environmental Science Center | Fujita M.,Ibaraki University
Water Science and Technology: Water Supply | Year: 2013

To develop a method for screening ageing of water supply systems by analysing the supplied water's quality, water samples were collected from a water treatment plant, a delivery pump station, two distribution reservoirs and two feed pipes along a water pipe system. Principal component analysis of the water was conducted. In the first principal component, many elements exhibited high factor loadings, whereas the major contributor for the second principal component was iron (Fe). The unlined steel pipe, which was beyond its working lifetime, had a significantly high Fe content in suspended solids. X-ray absorption fine structure (XAFS) analysis showed differences in the abundance ratios of Fe3O4 and α-FeOOH among the sampling points. It was concluded that the concentration and speciation of Fe in supplied water can be a useful index for detecting the ageing of pipes. Copyright © IWA Publishing 2013. Source


Takahashi M.,Japan National Institute of Advanced Industrial Science and Technology | Ishikawa H.,Industrial Technology Institute of Ibaraki Prefecture | Asano T.,Industrial Technology Institute of Ibaraki Prefecture | Horibe H.,Kanazawa Institute of Technology
Journal of Physical Chemistry C | Year: 2012

In this paper, we describe the use of ozone microbubbles in photoresist removal from silicon wafers. Ozonized water has attracted much attention as an environmental friendly cleaning method in semiconductor manufacturing. However, it would be desirable to enhance the oxidative ability of ozonized water for practical application. The existence of microbubbles in ozonized water has been shown to significantly enhance the photoresist removal rate due to an elevated dissolved ozone concentration (approximately 2.5 times that of ordinary ozone bubbling) and a direct effect of the microbubbles (removal rate is approximately 1.3 times faster than water with the same concentration of dissolved ozone without microbubbles). Additionally, the ozone microbubble solution was able to effectively remove a high-dose ion-implanted photoresist, which is extremely resistant to removal by ozonized water and other wet chemicals because of its amorphous carbon-like layer, or "crust". Electron spin resonance experiments were also performed without the influence of serious metal contamination and indicated the presence of hydroxyl radicals, which are thought to be formed by interaction of ozone with hydroxide ions adsorbed at the gas-water interface upon collapse of the microbubbles. The hydroxyl radicals play an important role in photoresist removal by the ozone microbubble treatment. © 2012 American Chemical Society. Source

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