Takeuchi S.,Japan Central Research Institute of Electric Power Industry
Journal of Geophysical Research: Solid Earth | Year: 2011
Using a compilation of melt compositions, meltwater contents, temperatures, and phenocryst contents, the preeruptive viscosities under magma reservoir conditions are calculated for 83 erupted magmas. The basaltic-to-rhyolitic magmas have preeruptive viscosities over the range 101 to 10 8 Pa s. Although bulk SiO2 content has often been used as a qualitative measure of preeruptive magma viscosity, the bulk SiO2 content shows a weak correlation with magma viscosity (correlation coefficient r = 0.5). Because of a wide range of phenocryst contents from 0 to ∼50 vol %, andesitic magmas have viscosities ranging from 102 to 107 Pa s, which are lower or higher than those of phenocryst-poor rhyolitic magmas with 105 to 106 Pa s. Focusing on andesitic to rhyolitic magmas, the r between bulk SiO2 contents and magma viscosities changes to -0.1. In contrast, the melt-only SiO2 content from a basaltic-to-rhyolitic melt shows a good linear correlation with melt-only viscosity (r = 0.9). Although most of the calculated viscosities of erupted magmas fall below ∼106 Pa s, as consistent with the previous compilation study, this paper describes 20 examples of highly viscous magmas with >106 Pa s, in most cases, composed of mixtures of high-silica rhyolitic melt (75-79 wt % SiO2) and abundant phenocrysts (30-55 vol %). In these highly viscous magmas, 9 examples have erupted following the precursory eruption of less viscous magma, suggesting that precursory dike propagation and conduit formation by the less viscous magma with <10 6 Pa s induced the following eruption of less eruptible, highly viscous magmas. Copyright © 2011 by the American Geophysical Union.
Yokoyama T.,Japan Central Research Institute of Electric Power Industry
Separation and Purification Technology | Year: 2012
There are several technology options for energy sectors that could reduce the amount of CO 2 emissions. At present amine-based absorption processes are most promising as CO 2 capture technologies. However amine-based CO 2 capture technologies are energy intensive and high in cost. There is continuous research and development for more effective solvents for CO 2 capture focusing mainly on lower heat requirement for regeneration. Although many studies for solvent development usually focus on solvents with low reaction heat, the regeneration heat of a solvent is interpreted approximately into three heat components (heat of reaction, sensible heat, and heat of vaporization). The heat energy for the regeneration process is usually supplied from the reboiler in the form of steam and the distribution of the heat energy to the three components depends on the key process parameters such as circulation rate and steam supply rate. In this study the overall performance of the MEA process in terms of CO 2 removal efficiency is examined at various process parameters through experimental work. There are negligible degradation and corrosion problems exhibited. Based on the results the distribution of regeneration heat is analyzed, in terms of the three heat components using an equilibrium-staged model. The model reaction process between CO 2 with MEA solvent in the CO 2 capture system was addressed based on CO 2-H 2O-MEA equilibrium. However for simplicity, the vapor-liquid equilibrium of H 2O-MEA system and the vapor-liquid equilibrium of CO 2-MEA are considered separately and then the two systems are coupled assuming they come into existence simultaneously. It is shown that focusing only on the heat of reaction which is an inherent property of a solvent is not sufficient to reduce the reboiler heat duty and that the sensible heat and the heat of vaporization must be taken into consideration to reduce the reboiler heat duty as they are strongly affected by operational parameters. © 2011 Elsevier B.V. All rights reserved.
Goto M.,Japan Central Research Institute of Electric Power Industry
Decision Support Systems | Year: 2010
This study investigates the financial performance of the world telecommunications industry by DEA-DA (Data Envelopment Analysis-Discriminant Analysis). The proposed use of DEA-DA has a linkage with Altman's Z score that has long served as a methodological and conceptual basis in finance. Based upon the Z score of telecommunications companies, we rank them for financial assessment. After evaluating their financial performance of the firms, this study pays attention to the financial performance of AT&T (American Telephone & Telegraph) and NTT (Nippon Telegraph and Telephone) after their divestiture. This study finds that AT&T outperformed NTT because AT&T changed itself to an IT (Information Technology) company that provides wireless communications services and other IT services, but NTT separated IT and wireless services into the other companies after the breakup. © 2009 Elsevier B.V. All rights reserved.
Hamada N.,Japan Central Research Institute of Electric Power Industry
Radiation Research | Year: 2014
Exactly a century after Röntgen's discovery of X rays, I entered a university to major in radiological sciences. At that time, I felt that, despite extensive use and indispensable roles of ionizing radiation in medicine and industry, many fascinating questions have yet to be answered concerning its biological mechanisms of action, and thus I decided to get into the field of radiation research. Fifteen years have passed since I started radiobiological studies in 1998, during which time various basic tenets I initially learned in my late teens and early twenties have been challenged by recent observations. Of these, this brief overview particularly focuses on the following five different albeit non mutually exclusive questions: (i) "Is nuclear DNA the only intracellular target for radiation effects?"; (ii) "What is the significance of delayed cell death in clonogenic survival?"; (iii) "Does an irradiated cell become a cancer cell?"; (iv) "Are cataracts tissue reactions?"; and (v) "Why is high-LET radiation biologically effective?". © 2014 by Radiation Research Society.
Sueyoshi T.,New Mexico Institute of Mining and Technology |
Goto M.,Japan Central Research Institute of Electric Power Industry
Energy Economics | Year: 2011
This study discusses a new DEA (Data Envelopment Analysis) approach to measure the unified (operational and environmental) efficiency of energy firms. It is widely known that they produce not only desirable (good) outputs (e.g., electricity) but also undesirable (bad) outputs (e.g., CO2) as a result of their plant operations. The proposed approach incorporates an output separation (desirable and undesirable outputs) for the performance evaluation of energy firms. In addition to the output separation, this study separates inputs into energy and non-energy inputs. Consequently, the proposed approach incorporates not only the output separation but also the input separation within a computational framework of DEA non-radial measurement. This study compares the proposed approach with other previous DEA approaches used for the performance evaluation of energy firms. After the methodological comparison, this study applies the proposed approach for measuring the unified efficiency of Japanese fossil fuel power generation. This empirical study confirms that the implementation of Kyoto Protocol (2005) has not been effective on the unified efficiency of Japanese fossil fuel power generation during the observed period (2004-2008). Although the empirical result is inconsistent with the current Japanese environmental policy under Kyoto Protocol, it contains policy implications for guiding the future direction of Japanese environmental policy on the electric power industry. © 2010 Elsevier B.V.