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Hokkaido, Japan

Oya T.,Hokkaido UniversitySapporo | Nomura T.,Hokkaido UniversitySapporo | Tsubota M.,Hokkaido University | Okinaka N.,Hokkaido University | Akiyama T.,Hokkaido University
Applied Thermal Engineering

We developed new phase change composites (PCC) using erythritol as a phase change material (PCM) and graphite and nickel particles as highly thermal conductive fillers. Their effective thermal conductivities became two orders of magnitude larger than that of the original PCM. The PCC was prepared by using a conventional dispersion technique and its effective thermal conductivity was measured by the laser flash method at room temperature. We interpreted the results based on percolation theory, for which the effects of the graphite structure and the volumetric ratio on the effective thermal conductivity were examined. The results showed that the effective thermal conductivity increased gradually with increasing filler content and aspect ratio of filler. Of significance, they increased remarkably when we used 20 vol% spherical graphite. Moreover, among the three samples that we prepared, the greatest thermal conductivity, 4.72 W(m K)-1, was recorded for the PCC with 15 vol% expanded graphite content. This was 6.4 times higher than the thermal conductivity of pure erythritol. © 2012 Elsevier Ltd. Source

Matsumura S.,Hokkaido UniversitySapporo | Yamazaki K.,Hokkaido UniversitySapporo | Yamazaki K.,Japan National Institute of Polar Research | Sato T.,Hokkaido UniversitySapporo
Journal of the Meteorological Society of Japan

We investigate the formation mechanism of the summer Okhotsk High (OH) in terms of the land-atmosphere coupling in Siberia. A reanalysis data indicates that the formation mechanism of the OH clearly differs between early and late summer because it changes from a nearly barotropic to a baroclinic structure with seasonal changes. Then, we assess the influence of springtime snow cover on the formation of the late summer OH with the baroclinicity using a regional climate model. The model performs well in reproducing the land-atmosphere coupling in eastern Siberia and the OH in August 2008, when abnormal weather prevails in Japan, in conjunction with the intensively developed OH. The August OH develops with a distinct baroclinic structure owing to increased surface heating, which is related to land-atmosphere coupling in response to reduced spring snow cover in eastern Siberia. The land-atmosphere coupling can help to reinforce and maintain the baroclinic structure through surface heating, forming strong surface anticyclone to the southeast over the Sea of Okhotsk. Our results suggest that the late summer OH is a regional climate system that involves coupling among the atmosphere, the cool ocean, and the warm land surface. © 2015, Meteorological Society of Japan. Source

Sato M.,Hokkaido UniversitySapporo | Tojo Y.,Hokkaido UniversitySapporo | Matsuo T.,Hokkaido UniversitySapporo | Matsuto T.,Hokkaido UniversitySapporo
Sustainable Environment Research

Long-term safety is essential for sustainable landfills, which should be operated and managed without environmental pollution caused by the release of hazardous compounds. However, knowledge of the long-term fate of compounds such as polycyclic aromatic hydrocarbons (PAHs) remains insufficient. This study determined the concentrations of 18 PAHs in bottom ash samples obtained from municipal solid waste incinerators in Japan and calculated their fate in a landfill using a simple model that accounted for the biodegradation of PAHs and their distribution in three phases. Naphthalene, phenanthrene, and fluoranthene were major compounds identified in all samples, in concentrations ranging from 10 to 1000 µg kg-1. The concentrations of other PAHs were lower than 100 µg kg-1. Although the total concentrations of the 18 PAHs varied by up to three orders of magnitude, the concentrations were not high relative to those of other environmental media. In particular, the PAH concentrations were similar to those of soil and sediment reported in previous studies. The simple calculation procedure applied in this study showed that the fate of PAHs was dominated by the presence of organic carbon in the modelled landfill. PAHs of high molecular weight remained long term because of their affinity for organic carbon. However, when conditions favouring biodegradation were achieved, the PAH concentrations diminished on a shorter timescale. © 2010, Chinese Institute of Environmental Engineering. All rights reserved. Source

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