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Satellite Link Availability Analysis using 3-Dimensional Map Data
Imaizumi, Yutaka,Ohata, Kohei,Ueba, Masazumi 통신위성우주산업연구회 2006 Joint Conference on Satellite Communications Vol.2006 No.-
We propose a method of simulating satellite link availability that uses three dimensional map data. Our method calculates the satellite signal reception level at a reception point by taking into account diffracted and/or reflected waves as well as direct waves. This paper identifies simulation parameters that enable calculations that show good agreement with measured satellite signal reception levels. Our work further shows the following. 1) To calculate satellite signal levels accurately it is necessary to take into consideration diffracted and reflected waves as well as direct waves. 2) The optimum reflection coefficient of building walls and roads was 10 dB for this evaluation environment. 3) The radius of the observation area where the reflected wave was calculated was about 150 m. This choice of area was made considering CPU time required to calculate one reception point. In future work the optimum radius will be determined by evaluating the accuracy of simulation results. The results confirmed that our satellite link availability analysis can effectively predict link conditions.
Serotonin regulates glucose-stimulated insulin secretion from pancreatic β cells during pregnancy
Ohara-Imaizumi, Mica,Kim, Hail,Yoshida, Masashi,Fujiwara, Tomonori,Aoyagi, Kyota,Toyofuku, Yukiko,Nakamichi, Yoko,Nishiwaki, Chiyono,Okamura, Tadashi,Uchida, Toyoyoshi,Fujitani, Yoshio,Akagawa, Kimio National Academy of Sciences 2013 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.110 No.48
<P>In preparation for the metabolic demands of pregnancy, beta cells in the maternal pancreatic islets increase both in number and in glucose-stimulated insulin secretion (GSIS) per cell. Mechanisms have been proposed for the increased beta cell mass, but not for the increased GSIS. Because serotonin production increases dramatically during pregnancy, we tested whether flux through the ionotropic 5-HT3 receptor (Htr3) affects GSIS during pregnancy. Pregnant Htr3a(-/-) mice exhibited impaired glucose tolerance despite normally increased cell mass, and their islets lacked the increase in GSIS seen in islets from pregnant wild-type mice. Electrophysiological studies showed that activation of Htr3 decreased the resting membrane potential in beta cells, which increased Ca2+ uptake and insulin exocytosis in response to glucose. Thus, our data indicate that serotonin, acting in a paracrine/autocrine manner through Htr3, lowers the beta cell threshold for glucose and plays an essential role in the increased GSIS of pregnancy.</P>
Reliability Consideration of a Control System Connected with the Network
Mitsuhiro Imaizumi,Mitsutaka Kimura 대한산업공학회 2015 대한산업공학회 추계학술대회논문집 Vol.2015 No.11
As the Internet technology has developed, not only the information system but also the control system which controls various devices has become connected with the Internet. The operational efficiency of a control system is improved by being connected with the Internet. However, it increases the risk of cyber attacks. This paper considers the optimal policy of a control system connected with the network. The control system consists of N units. If cyber attack cannot be detected, the system becomes failure. If the N-th operating unit cannot finish one process until a time limit T, once the process of system interrupts, and restarts again from the beginning. The mean time to system failure is derived. Further, two optimal policies which minimize the expected cost are discussed. Finally, a numerical example is given.