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RISS 인기검색어
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- 저자 : ( Tetsuji Okuda ) (검색결과 8 건)
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Low-temperature Thermoelectric Properties of the Electron-doped Perovskites Sr1−xCaxTi1−yNbyO3
Tetsuji Okuda,Junichi Fukuyado,Kurahito Narikiyo,Mitsuru Akaki,Hideki Kuwahara 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.3
We have investigated the thermoelectric (TE) properties for single crystals of the perovskitesSr1−xCaxTi1−yNbyO3 for 0 ≤ x ≤ 0.4 and 0 ≤ y ≤ 0.03 at temperatures below room temperature(RT). We found that SrTi0.99Nb0.01O3 showed a large power factor at low temperatures (PF =50 µW/K2cm at 100 K 90 µW/K2cm at 50 K) and the largest dimensionless TE figure-ofmeritat temperatures below 40 K (ZT 0.07) among the reported materials. Such a large lowtemperatureTE response around a carrier concentration of 1020 cm−3 is due to a distinct phonondrag effect. We also found that the Ca2+ substitution for Sr2+ increased the ZT at 300 K forSr1−xCaxTi0.97Nb0.03O3 from 0.08 to 0.105. The enhancement of the ZT around RT originatesboth from a large reduction of a thermal conductivity due to a randomness introduced into thecrystal structure and from an unexpected enhancement of a Seebeck coefficient.
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Behavior of Steel Slag used as Sand Alternative in the Marine Environment
( Tetsuji Okuda ),( Satoshi Asaoka ),( Hitomi Yano ),( Satoshi Nakai ),( Wataru Nishijima ) 한국폐기물자원순환학회(구 한국폐기물학회) 2015 한국폐기물자원순환학회 3RINCs초록집 Vol.2015 No.-
Tidal flats and seagrass beds were decreased in Japan by landfilling and others. So in recent years, coast regeneration projects have been progressed in order to recover tidal flats and seagrass beds. A sand-alternative material for creation of land is needed which could have safety, environmental friendly and stable supply, then steel slag meets these requirements. However, steel slag normally doesn't have silt faction and solidification is happen by the elution of Ca and Fe from slag in sea water. In our previous butch experiment, dredged soils obtained from sea sediment has a possibility to supply silt fraction and reduce the solidification. In this paper, we reviled the solidification behavior of steel slag in seawater during 10 months, and the effect of the addition of dredged soil to steel slag and there mechanism. The slag were bonded to each other with iron oxide, and shear stress was 3 times increased in slag only. The addition of dredged soil decrease the shear stress, and also interfere the solidification of slag. ORP or/and embrittlement effect as impurities by the components in dredge soil were the reason of these inhibition of the formation of the bridge between slags by the dredge soil.
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Tetsuji Okuda,Satoshi Oozono,Takumi Kihara,Masashi Tokunaga 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.12
The magnetotransport property of a hole-doped delafossite CuCr0.97Mg0.03O2 with a spin-3/2antiferromagnetic (AF) triangular sublattice was investigated by using a pulsed high magneticfield. A dramatic change of magnetoresistance was observed with a variation of temperature, whichindicates that a spin fluctuation due to a competition between the AF and the ferromagnetic Hund’sinteractions is enhanced at temperatures around the N´eel temperatures (TN). The competitionmay lead to a partially-disordered state at temperatures below TN which may cause a nontrivialpromotion of a 120˚ Neel state.
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Sugimoto, Kenji,Nakano, Yoichi,Okuda, Tetsuji,Nakai, Satoshi,Nishijima, Wataru,Okada, Mitsumasa The Ecological Society of Korea 2017 Journal of Ecology and Environment Vol.41 No.3
Background: There have been many studies on the growth conditions of Zostera marina and Zostera japonica, but few studies have examined how spatial and temporal factors affect growth in established seagrass beds or the distribution range and shoot density. This study aims to clarify the factors that determine the temporal and spatial distribution of Zostera marina and Zostera japonica in the Seto Inland Sea east of Yamaguchi Prefecture. Methods: The study site is in Hiroshima Bay of the Seto Inland Sea, along the east coast of Yamaguchi Prefecture, Japan. We monitored by diving observation to confirm shoot density, presence or absence of both species and observed water temperature, salinity by sensor in study sites. Results: The frequency of occurrence of Zostera marina was high in all seasons, even in water depths of D.L. + 1 to -5 m ($80{\pm}34%$ to $89{\pm}19%$; mean ${\pm}$ standard deviation), but lower (as low as $43{\pm}34%$) near the breakwall, where datum level was 1 to 2 m, and it was further reduced in datum level -5 m and deeper. The frequency of occurrence of Zostera japonica was highest in water with a datum level of +1 to 0 m. However, in datum level of 0 m or deeper, it became lower as the water depth became deeper. Datum level +1 m to 0 m was an optimal water depth for both species. The frequency of occurrence and the shoot density of both species showed no negative correlation. In 2011, the daily mean water temperature was $10^{\circ}C$ or less on more days than in other years and the feeding damage by S. fuscescens in the study sites caused damage at the tips. Conclusions: We considered that the relationship between these species at the optimal water depth was not competitive, but due to differences in spatial distribution, Zostera marina and Zostera japonica do not influence each other due to temperature conditions and feeding damage and other environmental conditions. Zostera japonica required light intensity than Zostera marina, and the water depth played an important role in the distribution of both species.
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Kenji Sugimoto,Yoichi Nakano,Tetsuji Okuda,Satoshi Nakai,Wataru Nishijima,Mitsumasa Okada 한국생태학회 2017 Journal of Ecology and Environment Vol.41 No.3
Background: There have been many studies on the growth conditions of Zostera marina and Zostera japonica, but few studies have examined how spatial and temporal factors affect growth in established seagrass beds or the distribution range and shoot density. This study aims to clarify the factors that determine the temporal and spatial distribution of Zostera marina and Zostera japonica in the Seto Inland Sea east of Yamaguchi Prefecture. Methods: The study site is in Hiroshima Bay of the Seto Inland Sea, along the east coast of Yamaguchi Prefecture, Japan. We monitored by diving observation to confirm shoot density, presence or absence of both species and observed water temperature, salinity by sensor in study sites. Results: The frequency of occurrence of Zostera marinawas high in all seasons, even in water depths of D.L. + 1 to −5 m (80 ± 34% to 89 ± 19%; mean ± standard deviation), but lower (as low as 43 ± 34%) near the breakwall, where datum level was 1 to 2 m, and it was further reduced in datum level −5 m and deeper. The frequency of occurrence of Zostera japonica was highest in water with a datum level of +1 to 0 m. However, in datum level of 0 m or deeper, it became lower as the water depth became deeper. Datum level +1 m to 0 m was an optimal water depth for both species. The frequency of occurrence and the shoot density of both species showed no negative correlation. In 2011, the daily mean water temperature was 10 °C or less on more days than in other years and the feeding damage by S. fuscescens in the study sites caused damage at the tips. Conclusions: We considered that the relationship between these species at the optimal water depth was not competitive, but due to differences in spatial distribution, Zostera marina and Zostera japonica do not influence each other due to temperature conditions and feeding damage and other environmental conditions. Zostera japonica required light intensity than Zostera marina, and the water depth played an important role in the distribution of both species.
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Mallampati, Srinivasa Reddy,Mitoma, Yoshiharu,Okuda, Tetsuji,Simion, Cristian,Lee, Byeong Kyu Elsevier 2015 JOURNAL OF ENVIRONMENTAL RADIOACTIVITY Vol.139 No.-
<P><B>Abstract</B></P> <P>Although direct radiation induced health impacts were considered benign, soil contamination with <SUP>137</SUP>Cs, due to its long-term radiological impact (30 years half-life) and its high biological availability is of a major concern in Japan in the aftermath of the Fukushima nuclear power plant disaster. Therefore <SUP>137</SUP>Cs reduction and immobilization in contaminated soil are recognized as important problems to be solved using suitable and effective technologies. One such thermal treatment/vitrification with nanometallic Ca/CaO amendments is a promising treatment for the ultimate immobilization of simulated radionuclide <SUP>133</SUP>Cs in soil, showing low leachability and zero evaporation. Immobilization efficiencies were 88%, 95% and 96% when the <SUP>133</SUP>Cs soil was treated at 1200 °C with activated carbon, fly ash and nanometallic Ca/CaO additives. In addition, the combination of nanometallic Ca/CaO and fly ash (1:1) enhanced the immobilization efficiency to 99%, while no evaporation of <SUP>133</SUP>Cs was observed. At lower temperatures (800 °C) the leachable fraction of Cs was only 6% (94% immobilization). Through the SEM–EDS analysis, decrease in the amount of Cs mass percent detectable on soil particle surface was observed after soil vitrified with <I>n</I>Ca/CaO + FA. The <SUP>133</SUP>Cs soil was subjected to vitrified with <I>n</I>Ca/CaO + FA peaks related to Ca, crystalline phases (CaCO<SUB>3</SUB>/Ca(OH)<SUB>2</SUB>), wollastonite, pollucite and hematite appeared in addition to quartz, kaolinite and bentonite, which probably indicates that the main fraction of enclosed/bound materials includes Ca-associated complexes. Thus, the thermal treatment with the addition of nanometallic Ca/CaO and fly ash may be considered potentially applicable for the remediation of radioactive Cs contaminated soil at zero evaporation, relatively at low temperature.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Vitrification with nanometallic Ca/CaO is a promising treatment for Cs in soil. </LI> <LI> Dynamic Cs immobilization and zero evaporation were done by nanometallic Ca/CaO. </LI> <LI> By SEM analysis the amount of cesium detectable on soil particle surface decreases. </LI> <LI> Leachable cesium concentrations reduced, lower than the standard regulatory limit. </LI> <LI> Nanometallic Ca/CaO is unique amendment for the remediation of Cs in soil. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>SEM–EDS element maps of <SUP>133</SUP>Cs contaminated soil before and after thermal treatment at 1200 °C with different addictives. Color intensity for Cs is from 0 to 100 (low to high).</P> <P>[DISPLAY OMISSION]</P>
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Shun Yamanouchi,Eri Nasuno,Masaki Ohno,Chigusa Okano,Ken-ichi Iimura,Tetsuji Okuda,Wataru Nishijima,Norihiro Kato 한국생물공학회 2017 Biotechnology and Bioprocess Engineering Vol.22 No.3
The model cationic molecule prodigiosin interacted with a polyamide/polysulfone composite reverse osmosis (RO) membrane, resulting in a reduction of the membrane permeation rate. Prodigiosin is an antibacterial agent produced by Serratia marcescens that is frequently isolated from activated sludge of domestic or industrial wastewater. Such molecules respectively secreted or leaked from live or dead cells are thought to affect membrane biofouling. In this study, a cell suspension containing prodigiosin-producing S. marcescens AS-1 wild-type or the non-producing AS-1ΔspnI strain was fed to the thin RO membrane to determine the occlusion ratio on the membrane. Cationic prodigiosin enhanced membrane biofouling by clogging the pores and enhanced the accumulation of the cake layer. The effects remarkably recovered the occlusion ratio after removing the cake layer by feeding with water. After temporary pressure relief, the occlusion ratios for AS-1 and AS-1ΔspnI were recovered to stable levels from approximately 70 to 49% and 23%, respectively. Zetapotential analysis supported the neutralization effects leading to the accumulation of bacterial cells under applied high pressure for RO membrane permeation.
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