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Spatiotemporal Variations of Fine Particulate Organic and Elemental Carbons in Greater Tokyo
Hiroshi Hayami,Shinji Saito,Shuichi Hasegawa 한국대기환경학회 2019 Asian Journal of Atmospheric Environment (AJAE) Vol.13 No.3
Hourly concentrations of fine particulate OC and EC are monitored for more than one year by optical monitors at three sites in and out of Tokyo, Japan. Distances between the sites are 20 to 50 km. SOC concentrations are estimated from the OC and EC concentrations by an EC tracer method. Site A in an industrial site shows higher EC concentrations than site B in a residential area, but differences between the sites are much reduced for OC. Site C in a rural area, where measurements are available in colder months, shows pronounced seasonal variations with high peaks in October and December and characteristic diurnal variations in OC with the highest in the evening in October, due probably to open field burning. Photochemical formation of SOC is suggested but does not rise up so much OC concentrations in summer, which are quite lower than other seasons. A comparison between relative concentrations of EC among the sites and local emissions amounts indicates missing or considerable underestimation of EC emissions near the rural site C. Time lag correlations suggest transport of OC produced by open field burning around site C to site A. These findings would be useful for improving model performances in OC/EC predictions.
Electron heating experiment using the high harmonic fast wave on LHD
hiroshi Kasahara,K. Saito,N. Takeuchi,R. Kumazawa,T. Seki,T. Mutoh,T. Oosako,Y. Takase 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.49 No.III
Electron heating experiments using the High Harmonic Fast Wave (HHFW) were performed on the Large Helical Device (LHD). An electron temperature increase from 2.5 keV to 3.6 keV by 1.2 MW of HHFW was observed when both ECH and NBI were used to create a target plasma with high stored energy and electron temperature. When ECH works effectively, the electron density is pumped out, but the rate of decrease of the electron density is reduced when HHFW heating is applied. This result indicates that HHFW is absorbed effectively when the central electron temperature and electron beta are high enough, and suggests that parallel heating of electrons by HHFW reduces electron density pump out caused by perpendicular electron heating by ECH. According to a 1-D calculation, raising the density is more effective for improving singlepass damping than raising the temperature. According to a 2-D full-wave calculation, electron damping occurs in an off-axis region at low density, but wave fields become more concentrated in the core and absorption becomes more centrally localized at high density.e
Saito, Kimiaki,Mikami, Satoshi,Andoh, Masaki,Matsuda, Norihiro,Kinase, Sakae,Tsuda, Shuichi,Sato, Tetsuro,Seki, Akiyuki,Sanada, Yukihisa,Wainwright-Murakami, Haruko,Yoshimura, Kazuya,Takemiya, Hiroshi The Korean Association for Radiation Protection 2019 방사선방어학회지 Vol.44 No.4
Massive environmental monitoring has been conducted continuously since the Fukushima Daiichi Nuclear Power accident in March of 2011 by different monitoring methods that have different features together with migration studies of radiocesium in diverse environments. These results have clarified the characteristics of radiological environments and their temporal change around the Fukushima site. At three months after the accident, multiple radionuclides including radiostrontium and plutonium were detected in many locations; and it was confirmed that radiocesium was most important from the viewpoint of long-term exposure. Radiation levels around the Fukushima site have decreased greatly over time. The decreasing trend was found to change variously according to local conditions. The air dose rates in environments related to human living have decreased faster than expected from radioactive decay by a factor of 2-3 on average; those in pure forest have decreased more closely to physical decay. The main causes of air dose rate reduction were judged to be radioactive decay, movement of radiocesium in vertical and horizontal directions, and decontamination. Land-use categories and human activities have significantly affected the reduction tendency. Difference in the air dose rate reduction trends can be explained qualitatively according to the knowledge obtained in radiocesium migration studies; whereas, the quantitative explanation for individual sites is an important future challenge. The ecological half-lives of air dose rates have been evaluated by several researchers, and a short-term half-life within 1 year was commonly observed in the studies. An empirical model for predicting air dose rate distribution was developed based on statistical analysis of an extensive car-borne survey dataset, which enabled the prediction with confidence intervals. Different types of contamination maps were integrated to better quantify the spatial data. The obtained data were used for extended studies such as for identifying the main reactor that caused the contamination of arbitrary regions and developing standard procedures for environmental measurement and sampling. Annual external exposure doses for residents who intended to return to their homes were estimated as within a few millisieverts. Different forms of environmental data and knowledge have been provided for wide spectrum of people. Diverse aspects of lessons learned from the Fukushima accident, including practical ones, must be passed on to future generations.