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406 results on '"Kosaka, Ryo"'

13. Relationship Between Propagation Angle of Dislocations in β-Ga2O3 (001) Bulk Wafers and Their Etch Pit Shapes.

Author

Isaji, Sou, Maeda, Issei, Ogawa, Naoya, Kosaka, Ryo, Hasuike, Noriyuki, Isshiki, Toshiyuki, Kobayashi, Kenji, Yao, Yongzhao, and Ishikawa, Yukari

Subjects
SCANNING transmission electron microscopy, FOCUSED ion beams, CRYSTAL defects, SCANNING electron microscopy, ANGLES, ETCHING
Abstract

In this study, we examined the etch pits formed by molten alkali etching on beta-gallium oxide (β-Ga2O3) (001) bulk wafers and their dislocations to understand the behavior of crystal defects in β-Ga2O3. For this, we used focused ion beam (FIB), scanning transmission electron microscopy (STEM), and scanning electron microscopy (SEM). The FIB–STEM observation shows that the etch pits, named Cannonball type, correspond to dislocation propagation on the (100) plane, and the asymmetry of etch pit shapes is proportional to the propagation angle of dislocations. These findings allow for the determination of the propagation angles of dislocation in β-Ga2O3 without using any FIB preprocessing of cross-sectional STEM observations. SEM was used to examine more than 100 Cannonball-type etch pits, and the propagation angle distribution of the associated dislocations was derived using the deviation of the core of each etch pit. Our results show that the propagation angle distribution is almost flat regardless of its angle; however, with lower occurrences at around 20° and 70°, the core deviation ratio was 1:2 in the ± [010] direction. [ABSTRACT FROM AUTHOR]

Published
2023
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23. Evaluating Plasma Skimming with Different Groove Shapes of Hydrodynamic Bearings for Applying to Blood Pumps by Cells Visualization

Author

Hijikata Wataru, Jiang Ming, Sakota Daisuke, and Kosaka Ryo

Subjects
Bearing (mechanical), Materials science, medicine.diagnostic_test, Fluid bearing, Rotational speed, Hematocrit, Volumetric flow rate, law.invention, law, medicine, Shear flow, Spiral, Groove (music), Biomedical engineering
Abstract

As a potential solution for solving the hemolysis problem inside the narrow bearing clearance of hydrodynamically levitated blood pumps, plasma skimming has been observed and verified with spiral groove bearings. The objective of this study is to investigate and improve the plasma skimming effect by including the consideration of the red blood cells (RBCs) flow for the hydrodynamic bearing groove shape design. We designed a test rig to imitate the shear flow conditions inside the hydrodynamic bearing clearance. By visualizing RBCs inside the bearing clearance, plasma skimming efficiency with three different designs of groove shapes, referring to PlateA, PlateB, and PlateC, were evaluated and compared under a clearance size of 25 μm, a rotational speed of 2400 rpm, and a flow rate of 150 ml/min conditions. The flow of RBCs inside the clearance was photographed by a high-speed camera with a magnification lens. The plasma skimming efficiency was evaluated by comparing the measured hematocrit using the camera and the measured hematocrit of blood in the circuit. The in vitro blood tests were repeated three times for each designed groove shape with 1%-5% hematocrit human blood as the working fluid. The Student's t-test result of plasma skimming efficiency among three designed shapes showed that there was a significant difference between PlateA and PlateC at hematocrit of 5%, 4%, 3% and 2%, respectively. It is testified that the groove shapes of hydrodynamic bearings have a significant influence on the plasma skimming effect occurring in the bearing clearance.

Published
2021

46. A Study on the Introduction of Environmental Cooperative Tax in Okinawa Prefecture

Author

Shimoji, Yoshiro, Uchiyama, Yuta, Fujihira, Yoshinori, Kohsaka, Ryo / Kosaka, Ryo, Matsumoto-Oda, Akiko, and Hirano, Norio

Subjects
財政悪化, Island municipalities, Environmental cooperative tax, Financial deterioration, Tourism tax, 観光税, 離島自治体, 環境協力税
Abstract

Three island villages in the Okinawa prefecture, Izena, Iheya and Tokashiki, have introduced "environmental cooperative tax" to obtain the budget to conserve the landscape as tourism resources and to maintain their tourism facilities. In this paper, the current trend and process of the introduction of the environmental cooperative tax are investigated by reviewing the existing survey and statistical information. Further, the socio-economic characteristics of the 3 villages are examined in order to explore the possibilities of the applying the taxation to the other island municipalities. Overall purpose of this study is to rethink the tourism tax in the whole Okinawa prefecture and explore future direction of the tourism management in the Okinawa in terms of the tourism tax system. The revenues from the tax are stable in Izena and Iheya, increasing in Tokashiki. Izena has introduced the tax in year 2005 earlier than other two villages. By the introducing the tax, environmental conservation activities have been facilitated by the revenues of the tax in Izena. As the indirect effects of the taxation, environmental management activities by the residents have been reinforced in Izena. The tax introduced by the villages has characteristics as environmental tax and tourist tax, because the tax is used for environmental conservation and imposed on the residents and tourists who come from the outside of the villages. The population amounts in the 3 villages are relatively small in the Okinawa. By examining the demographic and economic structures of the 3 villages and the other islands municipalities in the Okinawa, similarity and uniqueness of the islands municipalities are identified. Based on the results, several municipalities which may have potentials to introduce the environmental cooperative tax are detected. The taxation can be a tool for the tourism management in the Okinawa by appropriate gainsharing and synergistic collaboration among municipalities., 紀要論文

Published
2016

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