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517 results on '"Shimizu, Seiichi"'

8. Satellite Constellation Pattern Optimization for Complex Regional Coverage

Author

Lee, Hang Woon, Shimizu, Seiichi, Yoshikawa, Shoji, and Ho, Koki

Subjects
Mathematics - Optimization and Control, Electrical Engineering and Systems Science - Systems and Control, Physics - Space Physics
Abstract

The use of regional coverage satellite constellations is on the rise, urging the need for an optimal constellation design method for complex regional coverage. Traditional constellations are often designed for continuous global coverage, and the few existing regional constellation design methods lead to suboptimal solutions for periodically time-varying or spatially-varying regional coverage requirements. This paper introduces a new general approach to design an optimal constellation pattern that satisfies such complex regional coverage requirements. To this end, the circular convolution nature of the repeating ground track orbit and common ground track constellation is formalized. This formulation enables a scalable constellation pattern analysis for multiple target areas and with multiple sub-constellations. The formalized circular convolution relationship is first used to derive a baseline constellation pattern design method with the conventional assumption of symmetry. Next, a novel method based on binary integer linear programming is developed, which aims to optimally design a constellation pattern with the minimum number of satellites. This binary integer linear programming method is shown to achieve optimal constellation patterns for general problem settings that the baseline method cannot achieve. Five illustrative examples are analyzed to demonstrate the value of the proposed new approach., Comment: 47 pages, 23 figures, Journal of Spacecraft and Rockets (Published)

Published
2019
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11. Optimal Satellite Constellation Spare Strategy Using Multi-Echelon Inventory Control

Author

Jakob, Pauline C. M., Shimizu, Seiichi, Yoshikawa, Shoji, and Ho, Koki

Subjects
Mathematics - Optimization and Control, Computer Science - Computational Engineering, Finance, and Science, Electrical Engineering and Systems Science - Systems and Control, Physics - Space Physics
Abstract

The recent growing trend to develop large-scale satellite constellations (i.e., mega-constellation) with low-cost small satellites has brought the need for an efficient and scalable maintenance strategy decision plan. Traditional spare strategies for satellite constellations cannot handle these mega-constellations due to their limited scalability in number of satellites and/or frequency of failures. In this paper, we propose a novel spare strategy using an inventory management approach. We consider a set of parking orbits at a lower altitude than the constellation for spare storage, and model satellite constellation spare strategy problem using a multi-echelon (s,Q)-type inventory policy, viewing Earth's ground as a supplier, parking orbits as warehouses, and in-plane spare stocks as retailers. This inventory model is unique in that the parking orbits (warehouses) drift away from the orbital planes over time due to orbital mechanics' effects, and the in-plane spare stocks (retailers) would receive the resupply from the closest (i.e., minimum waiting time) available warehouse at the time of delivery. The parking orbits (warehouses) are also resupplied from the ground (supplier) with stochastic lead time caused by the order processing and launch opportunities, leveraging the cost saving effects by launching many satellites in one rocket (i.e., batch launch discount). The proposed analytical model is validated against simulations using Latin Hypercube Sampling. Furthermore, based on the proposed model, an optimization formulation is introduced to identify the optimal spare strategy, comprising the parking orbits characteristics and all locations policies, to minimize the maintenance cost of the system given performance requirements. The proposed model and optimization method are applied to a real-world case study of satellite mega-constellation to demonstrate their value., Comment: 32 pages, 7 figures, Published

Published
2018
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13. Early dynamics of chronic myeloid leukemia on nilotinib predicts deep molecular response

Author

Okamoto, Yuji, Hirano, Mitsuhito, Morino, Kai, Kajita, Masashi K., Nakaoka, Shinji, Tsuda, Mayuko, Sugimoto, Kei-ji, Tamaki, Shigehisa, Hisatake, Junichi, Yokoyama, Hisayuki, Igarashi, Tadahiko, Shinagawa, Atsushi, Sugawara, Takeaki, Hara, Satoru, Fujikawa, Kazuhisa, Shimizu, Seiichi, Yujiri, Toshiaki, Wakita, Hisashi, Nishiwaki, Kaichi, Tojo, Arinobu, and Aihara, Kazuyuki

Published
2022
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16. Living‐donor liver transplantation for methylmalonic acidemia patient with hepatocellular carcinoma: A case report and literature review

Author

Deguchi, Harunori, primary, Sakamoto, Seisuke, additional, Shimizu, Seiichi, additional, Fukuda, Akinari, additional, Uchida, Hajime, additional, Yanagi, Yusuke, additional, Nakao, Toshimasa, additional, Kodama, Tasuku, additional, Komine, Ryuji, additional, Nishi, Kentaro, additional, Kamei, Koichi, additional, Haga, Chizuko, additional, Yoshioka, Takako, additional, Matsumoto, Kimikazu, additional, Horikawa, Reiko, additional, and Kasahara, Mureo, additional

Published
2024
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21. Living-donor liver transplantation providing an adequate chemotherapy for a pediatric patient with anaplastic large cell lymphoma complicated with liver failure due to the aggravation of biliary hepatopathy by secondary hemophagocytic lymphohistiocytosis

Author

Sakamoto, Kenichi, Osumi, Tomoo, Yoshimura, Satoshi, Shimizu, Seiichi, Kato, Motohiro, Tomizawa, Daisuke, Fukuda, Akinari, Sakamoto, Seisuke, Nakano, Noriyuki, Yoshioka, Takako, Miyazaki, Osamu, Nosaka, Syunsuke, Deguchi, Takao, Kiyokawa, Nobutaka, Kasahara, Mureo, and Matsumoto, Kimikazu

Published
2020
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23. Female and preserved platelet count subgroups of myelodysplastic syndrome patients benefit from standard‐dose azacitidine

Author

Ogawa, Shinichi, primary, Sakamoto, Tatsuhiro, additional, Matsuoka, Ryota, additional, Ishitsuka, Kantaro, additional, Ogino, Yasuko, additional, Sootome, Ayano, additional, Makishima, Kenichi, additional, Yoshida, Chikashi, additional, Ito, Yufu, additional, Shimizu, Seiichi, additional, Suyama, Takuya, additional, Shinagawa, Atsushi, additional, Ito, Takayoshi, additional, Obara, Naoshi, additional, Kusakabe, Manabu, additional, Sakata‐Yanagimoto, Mamiko, additional, Miyazaki, Yasushi, additional, Nannya, Yasuhito, additional, and Chiba, Shigeru, additional

Published
2023
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24. The role of liver transplantation in COACH syndrome (Joubert syndrome with congenital hepatic fibrosis): A review of the literature

Author

Chen, Lijian, primary, Uchida, Hajime, additional, Komine, Ryuji, additional, Kodama, Tasuku, additional, Nakao, Toshimasa, additional, Okada, Noriki, additional, Yanagi, Yusuke, additional, Shimizu, Seiichi, additional, Abbas, Syed, additional, Fukuda, Akinari, additional, Sakamoto, Seisuke, additional, and Kasahara, Mureo, additional

Published
2023
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27. The role of portal hemodynamics in pediatric living donor liver transplantation

Author

Verma, Sapana, primary, Sakamoto, Seisuke, additional, Abdelwahed, Mohamed Sami, additional, Shimizu, Seiichi, additional, Uchida, Hajime, additional, Okada, Noriki, additional, Nakao, Toshimasa, additional, Kodama, Tasuku, additional, Komine, Ryuji, additional, Fukuda, Akinari, additional, Rela, Mohamed, additional, and Kasahara, Mureo, additional

Published
2023
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29. The role of living‐donor liver transplantation in children with an advanced malignant rhabdoid tumor of the liver in the era of transplant oncology: Case report and literature review

Author

Yanagi, Yusuke, primary, Sakamoto, Seisuke, additional, Nakao, Toshimasa, additional, Kodama, Tasuku, additional, Uchida, Hajime, additional, Shimizu, Seiichi, additional, Fukuda, Akinari, additional, Yamada, Masaki, additional, Kiyotani, Chikako, additional, Matsumoto, Kimikazu, additional, Yoshioka, Takako, additional, Miyazaki, Osamu, additional, Nosaka, Shunsuke, additional, and Kasahara, Mureo, additional

Published
2023
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30. The role of liver transplantation in COACH syndrome (Joubert syndrome with congenital hepatic fibrosis): A review of the literature.

Author

Chen, Lijian, Uchida, Hajime, Komine, Ryuji, Kodama, Tasuku, Nakao, Toshimasa, Okada, Noriki, Yanagi, Yusuke, Shimizu, Seiichi, Abbas, Syed, Fukuda, Akinari, Sakamoto, Seisuke, and Kasahara, Mureo

Subjects
JOUBERT syndrome, LITERATURE reviews, LIVER transplantation, HEPATIC fibrosis, PATIENT portals, ESOPHAGEAL varices
Abstract

Background: COACH syndrome is a rare autosomal recessive genetic disease characterized by liver fibrosis, which leads to severe complications related to portal hypertension. However, only a few patients with COACH syndrome undergoing liver transplantation (LT) have been reported. Materials and Methods: We herein report the outcomes of four children who underwent LT for COACH syndrome at our institute and review three previously reported cases to elucidate the role of LT in COACH syndrome. Results: All four patients in our institute were female, and three received living donors LT. All patients were diagnosed with COACH syndrome by genetic testing. LT was performed in these patients at 3, 7, 9, and 14 years old. The indication for LT was varices related to portal hypertension in all patients. One showed an intrapulmonary shunt. Blood tests revealed renal impairment due to nephronophthisis in three patients, and one developed renal insufficiency after LT. The liver function was maintained in all patients. A literature review revealed detailed information for three more patients. The indication for LT in these three cases was portal hypertension, such as bleeding from esophageal varices. One patient had chronic renal failure on hemodialysis at LT and underwent combined liver and kidney transplantation. Of these three previous patients, one died from hepatic failure due to de novo HCV infection 3 years after LT. Conclusions: LT should be considered an effective treatment for COACH syndrome in patients with severe portal hypertension. However, a detailed follow‐up of the renal function is necessary. [ABSTRACT FROM AUTHOR]

Published
2024
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31. Female and preserved platelet count subgroups of myelodysplastic syndrome patients benefit from standard‐dose azacitidine.

Author

Ogawa, Shinichi, Sakamoto, Tatsuhiro, Matsuoka, Ryota, Ishitsuka, Kantaro, Ogino, Yasuko, Sootome, Ayano, Makishima, Kenichi, Yoshida, Chikashi, Ito, Yufu, Shimizu, Seiichi, Suyama, Takuya, Shinagawa, Atsushi, Ito, Takayoshi, Obara, Naoshi, Kusakabe, Manabu, Sakata‐Yanagimoto, Mamiko, Miyazaki, Yasushi, Nannya, Yasuhito, and Chiba, Shigeru

Published
2024
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42. Optimal liver transplant procedure in progressive familial intrahepatic cholestasis type 1 treated with biliary diversion or intestinal transplantation: Lessons learned from three cases treated with different approaches.

Author

Uchida, Hajime, Sakamoto, Seisuke, Komine, Ryuji, Kodama, Tasuku, Nakao, Toshimasa, Yanagi, Yusuke, Shimizu, Seiichi, Abbas, Syed Hasnain, Fukuda, Akinari, and Kasahara, Mureo

Subjects
SHORT bowel syndrome, LIVER transplantation, ADULT respiratory distress syndrome, CHOLESTASIS, GROWTH disorders, DISEASE progression, URINARY diversion, LIVER histology
Abstract

Background: Progressive familial intrahepatic cholestasis type 1 (PFIC1) is an autosomal recessive cholestatic liver disorder caused by ATP8B1 gene mutations. Although liver transplantation (LT) is indicated for progressive liver disease, postoperative complications, including severe diarrhea and graft steatohepatitis leading to graft loss, have been reported. Cases: The first patient had jaundice, pruritus, diarrhea, and growth retardation (weight z‐score: −2.5; height z‐score: −3.7). She underwent LT with total internal biliary diversion (TIBD) to the colon at 2 years of age. Graft biopsy at the 7‐year follow‐up examination revealed microvesicular steatosis (60%). Her diarrhea improved, and her growth failure was recovering (weight z‐score: −1.0; height z‐score: −1.7). The second patient underwent sequential intestine–liver transplantation at 8 years of age due to end‐stage liver disease (ESLD) and short bowel syndrome caused by massive bowel resection for internal hernia after partial external biliary diversion (PEBD) at 21 months of age. She developed severe pancreatitis induced by steroid–bolus therapy for rejection after transplantation. She died 1.7 years after intestinal transplantation due to an uncontrollable pancreatic abscess and acute respiratory distress syndrome. The third patient underwent PEBD at 15 months of age and received LT with TEBD at 15 years of age due to ESLD with hepatic encephalopathy. Throughout the perioperative period, she showed no abdominal symptoms, including diarrhea and pancreatitis. Graft biopsy at the 2‐year follow‐up examination revealed macrovesicular steatosis (60%) with inflammation. Conclusions: The patients showed different outcomes. Effective therapeutic options to mitigate post‐LT complications in patients with PFIC1 must be considered individually. [ABSTRACT FROM AUTHOR]

Published
2023
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44. Successful pediatric liver transplantation case with a positive SARS‐CoV‐2 test at the time of transplant

Author

Shimizu, Seiichi, primary, Sakamoto, Seisuke, additional, Yamada, Masaki, additional, Funaki, Takanori, additional, Fukuda, Akinari, additional, Uchida, Hajime, additional, Okada, Noriki, additional, Nakao, Toshimasa, additional, Kodama, Tasuku, additional, Komine, Ryuji, additional, Shoji, Kensuke, additional, Baba, Chiaki, additional, Suzuki, Yasuyuki, additional, Nakagawa, Satoshi, additional, Ogimi, Chikara, additional, and Kasahara, Mureo, additional

Published
2023
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