Conceptual modeling and analysis of a solar receiver for thermochemical hydrogen generation

Hydrogen has the potential to revolutionize the way we live our everyday lives in the near future. With the global demand for oil increasing and pumping capabilities running at, or almost at full capacity, the world will eventually have to turn to alternative energy sources to satisfy the need for fuel in the near future; The processes involved in designing a system capable of hydrogen production include many different components. For the generation of hydrogen through a solar process, one of these components is the design and analysis of the solar receiver. The solar receiver is the component of the solar system where the concentrated solar heat flux is focused on, which provides heat for such things as a working fluid (such as in the case of a Stirling engine), or a heat transfer fluid (in the case of a indirect receiver/reactor or where heat must be transported from one location to another); The focus of this study is to design and analyze a conceptual design of a solar receiver for an indirect receiver/reactor system on a solar dish concentrator and to show schematically a design of a receiver/reactor layout with dimensions for a scale commensurate with typical dish concentrator geometry. A CFD analysis will be presented using the STAR-CD program to examine velocity distribution, pressure drop and heat transfer behavior of the receiver component. A macro analysis of the receiver/reactor thermal system is also presented. The CFD analysis will be looked at for the case of midrange thermochemical cycles (max ∼ 600°C), where molten nitrate salt can be employed as the heat transfer fluid

Temperature measurement in the convective and segregated vibrated bed of powder : A numerical study

In numerically simulated vibrated beds of powder, we measure temperature under convection by the generalized Einstein's relation. The spatial temperature distribution turns out to be quite uniform except for the boundary layers. In addition to this, temperature remains uniform even if segregation occurs. This suggests the possibility that there exists some "thermal equilibrium state" even in a vibrated bed of powder. This finding may lead to a unified view of the dynamic steady state of granular matter.Comment: Granular Matter, in press (Revised for the publication

Initial incorporation of phytoplankton into young ice in Saroma Ko lagoon, Hokkaido, Japan

The initial incorporation of phytoplankton into young ice was examined on February 25-28,1998 in Saroma Ko lagoon, Hokkaido, Japan to test our hypothesis that some physical selection would occur to establish the ice algal assemblages during the formation of young sea ice and the development of fast sea ice. An open pool (2×2m) was employed for the experiment. Young sea ice was collected for a 24hr experiment. Relative brine volume in the young sea ice might be related to air temperature. Incorporated contents of chlorophyll α, biogenic silica, particulate organic carbon and nitrogen were directly related to the relative brine volume. The larger than 2μm fractions of chlorophyll α and biogenic silica were 95% and 78%, respectively. The most abundant species incorporated into the young sea ice were Navicula transitans (33%) and Achnanthes taeniata (12%). Those species were originated from a water column where they were released from the bottom surface of seasonal sea ice in the vicinity of the experimental pool. Cell density of the incorporated phytoplankton ranged from 46 to 154 cells ml^ into the young sea ice and 17±5 cells ml^ in the sea water under the young sea ice. Those microscopic observations suggested the selective incorporation of phytoplankton into the young sea ice at the beginning of ice formation and it might accelerate selective development of establish the ice algal assemblages with the growth of fast sea ice

Respiration of adult female Calanus hyperboreus (Copepoda) during spring in the North Water Polynya

The respiration rate of adult female Calanus hyperboreus was determined in order to assess physiological activity and its relationship to food availability during spring in the North Water Polynya, northern Baffin Bay. The respiration rate increased hyperbolically with increasing ambient chlorophyll α (Chl. α) concentration regardless of the reproductive status. The increase of respiration with Chl. α concentration may be caused by activated feeding behavior. This suggests that all adult females during spring were physiologically active individuals. Possible advantages of the rapid response to food concentration in adult female copepods are discussed

膀胱癌に対するIL-12発現型がん治療用ウイルスとiPS細胞由来樹状細胞の併用療法の開発

学位の種別: 課程博士審査委員会委員 : （主査）東京大学教授 大須賀 穣, 東京大学特任教授 井川 靖彦, 東京大学准教授 深柄 和彦, 東京大学准教授 森川 鉄平, 東京大学講師 山田 大介University of Tokyo(東京大学

Effect of ice algal community on the increase of chlorophyll a concentration during spring in coastal water of the Sea of Okhotsk

A seasonal study of size fractionated chlorophyll α concentration was conducted weekly in Monbetsu Harbor from October 1996 to November 1997 to investigate the annually persistent occurrence of the spring peak of the chlorophyll α concentration in the >10μm size fraction immediately after the retreat of sea ice, as described by K. Hamasaki et al. (Plankton Biol. Ecol., 45,151,1998). Species composition of natural phytoplankton assemblages was also investigated to study whether phytoplankton or ice algae were responsible for the spring peak in the coastal water. The spring peak occurred immediately after the retreat of sea ice but timing of the occurrence was different between the stations occupied in the present study. The spatial heterogenity in occurrence of the spring peak seemed to be related to the sea ice distribution between the stations. New sea ice provided only a small supply of ice algae due to the relatively short growth period inside of the harbor. Large ice floes provided for a large supply of ice algae due to the long growth period outside of the harbor. The magnitude of the spring peak was related to sea ice growth. However, those ice algae seemed to sink to the bottom with little contribution to phytoplankton assemblage in the harbor, while ice algae contributed significantly to the spring peak outside of the harbor. Species composition revealed relatively fast response of phytoplankton to the environmental change after the disappearance of sea ice. Surface assemblages of phytoplankton including ice algae seemed to respond fully to the regional optical condition by changing in the species composition

Size dependent nanomechanics of coil spring shaped polymer nanowires

Direct laser writing (DLW) via two-photon polymerization (TPP) has been established as a powerful technique for fabrication and integration of nanoscale components, as it enables the production of three dimensional (3D) micro/nano objects. This technique has indeed led to numerous applications, including micro- and nanoelectromechanical systems (MEMS/NEMS), metamaterials, mechanical metamaterials, and photonic crystals. However, as the feature sizes decrease, an urgent demand has emerged to uncover the mechanics of nanosized polymer materials. Here, we fabricate coil spring shaped polymer nanowires using DLW via two-photon polymerization. We find that even the nanocoil springs follow a linear-response against applied forces, following Hooke’s law, as revealed by compression tests using an atomic force microscope. Further, the elasticity of the polymer material is found to become significantly greater as the wire radius is decreased from 550 to 350 nm. Polarized Raman spectroscopy measurements show that polymer chains are aligned in nanowires along the axis, which may be responsible for the size dependence. Our findings provide insight into the nanomechanics of polymer materials fabricated by DLW, which leads to further applications based on nanosized polymer materials

The effect of pCO2 on size-fractionated phytoplankton community in the Southern Ocean

第3回極域科学シンポジウム　横断セッション「南極海季節的海氷域における生物地球化学」11月26日（月） 統計数理研究所 セミナー