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形態: カラー図版あり, Physical characteristics: Original contains color illustrations, Accepted: 2021-07-12, 資料番号: PA2210028000

The science operations of the spacecraft and remote sensing instruments for the Martian Moon eXploration (MMX) mission are discussed by the mission operation working team. In this paper, we describe the Phobos observations during the first 1.5 years of the spacecraft’s stay around Mars, and the Deimos observations before leaving the Martian system. In the Phobos observation, the spacecraft will be placed in low-altitude quasi-satellite orbits on the equatorial plane of Phobos and will make high-resolution topographic and spectroscopic observations of the Phobos surface from five different altitudes orbits. The spacecraft will also attempt to observe polar regions of Phobos from a three-dimensional quasi-satellite orbit moving out of the equatorial plane of Phobos. From these observations, we will constrain the origin of Phobos and Deimos and select places for landing site candidates for sample collection. For the Deimos observations, the spacecraft will be injected into two resonant orbits and will perform many flybys to observe the surface of Deimos over as large an area as possible. Graphical Abstract

The orbital motion of spacecraft around asteroids is strongly disturbed primarily because of solar radiation pressure (SRP) and higher-order gravitational forces. To achieve stable orbits in such a...

This paper describes the orbit design of the deployable payload Rover 2 of MINERVA-II, installed on the Hayabusa2 spacecraft. Because Rover 2 did not have surface exploration capabilities, the operation team decided to experiment with a new strategy for its deployment to the surface. The rover was ejected at a high altitude and made a semi-hard landing on the surface of the asteroid Ryugu after several orbits. Based on the orbital analysis around Ryugu, the expected collision speed was tolerable for the rover to function post-impact. Because the rover could not control its position, its motion was entirely governed by the initial conditions. Thus, the largest challenge was to insert the rover into a stable orbit (despite its large release uncertainty), and avoid its escape from Ryugu due to an environment strongly perturbed by solar radiation pressure and gravitational irregularities. This study investigates the solution space of the orbit around Ryugu and evaluates the orbit’s robustness by utilizing Monte Carlo simulations to determine the orbit insertion policy. Upon analyzing the flight data of the rover operation, we verified that the rover orbited Ryugu for more than one period and established the possibility of a novel method for estimating the gravity of an asteroid.

The deep-space multi-object orbit determination system (DMOODS) and its application in the asteroid proximity operation of the Hayabusa2 mission are described. DMOODS was developed by the Japan Aerospace Exploration Agency (JAXA) for the primary purpose of determining the trajectory of deep-space spacecraft for JAXA’s planetary missions. The weighted least-squares batch filter is used for the orbit estimator of DMOODS. The orbit estimator supports more than 10 data types, some of which are used for relative trajectory measurements between multiple space objects including natural satellites and small bodies. This system consists of a set of computer programs running on Linux-based consumer PCs on the ground, which are used for orbit determination and the generation of radiometric tracking data, such as delta differential one-way ranging and doppler tracking data. During the asteroid proximity phase of Hayabusa2, this system played an essential role in operations that had very strict navigation requirements or operations in which few optical data were obtained owing to special constraints on the spacecraft attitude or distance from the asteroid. One example is orbit determination during the solar conjunction phase, in which the navigation accuracy is degraded by the effect of the solar corona. The large range bias caused by the solar corona was accurately estimated with DMOODS by combining light detection and ranging (LIDAR) and ranging measurements in the superior solar conjunction phase of Hayabusa2. For the orbiting operations of target markers and the MINERVA-II2 rover, the simultaneous estimation of six trajectories of four artificial objects and a natural object was made by DMOODS. This type of simultaneous orbit determination of multi-artificial objects in deep-space has never been accomplished before.

This paper describes the guidance and navigation technique used by Hayabusa2 for the asteroid rendezvous operation to reach Ryugu. The operation results, including the achieved guidance and navigation performance, are also summarized. Multiple assessment and navigation teams worked closely to provide reliable navigation solutions with a short solution delivery cycle. Although the uncertainty of the Ryugu’s ephemeris was considerable before Hayabusa2’s arrival, a combination of radiometric-optical hybrid navigation and a stochastic-constrained optimum guidance method was able to achieve an accuracy of less than 100 m and 1 cm/s, and the arrival was precisely timed.

In late 2018, the asteroid Ryugu was in the Sun’s shadow during the superior solar conjunction phase. As the Sun-Earth-Ryugu angle decreased to below 3°, the Hayabusa2 spacecraft experienced 21 days of planned blackout in the Earth-probe communication link. This was the first time a spacecraft had experienced solar conjunction while hovering around a minor body. For the safety of the spacecraft, a low energy transfer trajectory named Ayu was designed in the Hill reference frame to increase its altitude from 20 to 110 km. The trajectory was planned with the newly developed optNEAR tool and validated with real time data. This article shows the results of the conjunction operation, from planning to flight data.

Nonalcoholic fatty liver disease (NAFLD) is often associated with insulin resistance and glucose intolerance. Postprandial hypoglycemia frequently occurs in NAFLD patients; however, the details remain unclear.The 75-g oral glucose tolerance test (75gOGTT) in 502 patients with biopsy-proven NAFLD and continuous glucose monitoring (CGM) in 20 patients were performed, and the characteristics and causes of postprandial hypoglycemia were investigated.The proportion of patients in the Hypo subgroup [plasma glucose (PG) at 180 minfasting-PG (FPG)] among patients with normal glucose tolerance was significantly higher than that with diabetes mellitus and impaired glucose tolerance or impaired fasting glucose. FPG and hemoglobin A1c (HbA1c) were lower, and area under the curve of total insulin secretion within 120 min (120 min) was higher in Hypo than Hyper in overall patients. Although FPG and PG at 30 min were higher in Hypo than Hyper, HOMA-IR and the insulinogenic index were not different in normal glucose tolerance and impaired glucose tolerance or impaired fasting glucose. In multivariate logistic regression analysis, low HbA1c, low fasting immunoreactive insulin, and high area under the curve of total insulin secretion (120 min) were found to be independent factors associated with hypoglycemia. CGM showed postprandial hypoglycemia until lunch in 70% of NAFLD patients. However, no remarkable relationship in terms of hypoglycemia was identified between the 75gOGTT and CGM.Postprandial hypoglycemia was identified in many NAFLD patients detected by 75gOGTT and CGM. It was clarified that important causes of postprandial hypoglycemia were related to low HbA1c, an early elevation of PG, low fasting and relatively low early insulin secretion, and delayed hyperinsulinemia.

Accepted: 2017-12-12, 資料番号: SA1170267000

著者人数: 120名(所属. 宇宙航空研究開発機構宇宙科学研究所 (JAXA)(ISAS): 澤田, 弘崇; 横田, 康弘; 坂谷, 尚哉; 岡田, 達明; 田中, 智; 飯島, 祐一; 早川, 雅彦; 松岡, 萌; R.-L. Ballouz; 嶌生, 有理; 水野, 貴秀; 石原, 吉明; 長谷川, 直; 藤本, 正樹; 吉川, 真; 山本, 幸生; 白井, 慶; R. Noguchi; 尾川, 順子; 照井, 冬人; 菊地, 翔太; 山口, 智宏; 竹内, 央, 三桝, 裕也; 高橋, 忠輝; 竹井, 洋; 藤井, 淳; 中澤, 暁; 細田, 聡史; 森, 治; 嶋田, 貴信; Soldini, Stefania; 岩田, 隆浩; 安部, 正真; 矢野, 創; 月崎, 竜童; 尾崎, 正伸; 西山, 和孝; 佐伯, 孝尚; 渡邊, 誠一郎; 津田, 雄一), Accepted: 2019-03-12, 資料番号: SA1180387000

資料番号: SA1170276000

The article “Orbit insertion strategy of Hayabusa2’s rover with large release uncertainty around the asteroid Ryugu” written by Yusuke Oki, Kent Yoshikawa, Hiroshi Takeuchi et al., was originally published electronically on the publisher’s internet portal (currently SpringerLink) on 05 November 2020 without open access. After publication in Volume 4, Issue 4, page 309–329, the author(s) decided to opt for Open Choice and to make the article an open access publication. Therefore, the copyright of the article has been changed to © The Author(s) 2020 and the article is forthwith distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits use, duplication, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

It is greatly important to restrict power consumption of running trains for reducing power consumption cost. This study aims to control the train’s "power demand", average power consumption in 30 minutes, utilizing decentralized control scheme. This control system is a server-less system and is advantageous from the view point of plug & play and capital investment. In this work, it was verified that this control scheme can achieve the power demand control by the fundamental train running experiment.

The present case report presents a rare case of Epstein-Barr virus (EBV)-associated early gastric carcinoma with lymphoid stroma, accompanied by lymph node metastasis. A 61-year-old woman was referred to our hospital following observation of a gastric mass lesion that was initially diagnosed at a medical check-up. Esophagogastroduodenoscopy revealed a slightly elevated lesion with a central irregular depression in the middle third of the stomach. Endoscopic ultrasonography revealed a well-circumscribed hypoechoic mass located predominantly within the submucosa and the mucosa. Biopsy specimens of the lesion indicated the possibility of carcinoma with lymphoid stroma with a lymphoepithelial lesion. Abdominal contrast-enhanced computed tomography (CT) revealed a well-defined mass with homogeneous enhancement approximately 1.2 cm in diameter in the middle part of the stomach, demonstrating lymphadenopathy in the perigastric area at a maximum size of 1.4 cm in diameter. The patient underwent laparoscopic distal gastrectomy with regional lymphadenectomy due to suspicion of a gastric carcinoma with lymphoid stroma. Histopathological and immunohistochemical findings verified the diagnosis of carcinoma with lymphoid stroma, which were positive for EBV-encoded RNA (EBER-ISH) by in situ hybridization. There was one lymph node metastasis, which was in line with the CT imaging. Marked infiltration of lymphoid cells was observed in the tumor stroma, which were negative for EBER-ISH. The present case is informative of the pathological characteristics of this condition, and clinicians should recognize the features of this disease to make an accurate diagnosis and select the appropriate treatment.

New hydrofluoroethers (HFEs), 2-trifluoromethyl-3-methoxy-perfluoro-pentane (TMMP) and 2-(trifluoro-2-fluoro-3-difluoropropoxy)-3-difluoro-4-fluoro-5-trifluoropentane (TPTP) were investigated as nonflammable electrolyte solvents for lithium ion batteries. Activation energies (ΔG∗dep) for desolvation of lithium ion (Li+) and lithium-solvation number (Ns) were evaluated for 1 M LiBETI/EC+DEC electrolytes with and without TMMP or TPTP in order to understand the mechanism of rate-capability improvement. The ΔG∗dep for the carbonate-mixed electrolyte (0.01–2 M of LiBETI/EC+DEC (50:50 in volume)) increased from 45.7 to 98.3 kJ mol−1 with a decrease in the LiBETI concentration. In comparison, ΔG∗dep was found lower (ΔG∗dep≈35 kJ mol−1) for TPTP-mixed electrolytes (LiBETI/EC+DEC+TPTP (5:45:50)) and much lower (ΔG∗dep≈25 kJ mol−1) for TMMP-mixed electrolytes (LiBETI/EC+DEC+TMMP (5:45:50)). Adding 60 vol% TPTP in EC+DMC (50:50) reduced both NEC and NDMC by 40%, exemplified by Raman spectroscopy with different concentrations of LiBETI (0.05–1.5 M) and DFT calculation. Thus, the rate-capability improvement by adding TMMP or TPTP is exerted by both enhancements of the intercalation kinetics and Li+ diffusion at the LiCoO2 interface, where HFEs preferentially exist by their affinity with the hydrophilic LiCoO2 cathode surface.

For two series of API 5L X65 linepipes (Pipes A and B), the critical condition for ductile cracking of the linepipe steel and the applicability of the critical condition to an axially notched linepipe were investigated. Static 3-point bending tests for Charpy V-notch specimens were conducted in order to evaluate the critical condition of ductile cracking from the notch tip by using FE- analyses. At the position of ductile cracking from the notch tip for the Charpy type specimens, the stress triaxiality was approx. 0.6 for both linepipe steels, however the equivalent plastic strain (ep) was different on each linepipe; the ep for the ductile cracking was approx. 0.65 for Pipe A and approx. 1.47 for Pipe B. Hydraulic burst tests were then conducted for internally patched linepipes with an axial through-wall (TW) notch. The results of the FE-analyses for the hydraulic burst tests indicated the following: 1) the position of the ductile cracking at the TW notch tip was not the center of the wall-thickness (WT), but a slightly shifted position to the inner surface from the center of WT, 2) the equivalent plastic strain at the position where a ductile crack was initiated for the TW notched linepipe was almost the same as that obtained from the 3-point bending test result for the Charpy V-notch specimen. The present study revealed that the critical strain for ductile cracking from a notch tip for a Charpy type specimen was in good agreement with that for an axially notched linepipe. It was therefore clarified that the critical condition for ductile cracking for linepipes with an actual flaw could be predicted from the results of a small-scale test and FE-analysis to evaluate the relationship between the stress triaxiality and the equivalent plastic strain at the position of the ductile cracking.

This paper investigates an iterative algorithm to control weighting coefficients of transmit/receive spatial filters in a frequency-division duplex (FDD) based eigen-mode space division multiplexing (E-SDM/FDD) system. In this system, weighting matrices of transmit/receive spatial filters are optimized using an iterative algorithm that minimizes the mean square error (MSE) of the virtual received signal, where the receiver feeds back relative channel characteristic information of the forward-link to the transmitter. This paper also presents an alternative feedback control method for optimizing the weighting coefficients of the transmit spatial filter in presence of feedback bit errors; the receiver determines the weighting coefficients at the transmitter and sends back relative information of them to the transmitter. This method will be able to mitigate the performance degradation caused by the feedback bit error. Simulation results of bit error rate (BER) performance proves the effectiveness of the proposed algorithm in the E-SDM/FDD 4 × 2 MIMO systems.

A 65-year-old man with back pain showed a hypovascular lesion of the head of the pancreas on dynamic computed tomography and abdominal ultrasonography. The distal portion of the pancreas was not visible. Endoscopic retrograde cholangiopancreatography revealed pancreatic duct obstruction, and the duodenal minor papilla was not visible. Therefore, we diagnosed the patient's condition as stage IVa pancreatic cancer with congenital agenesis of the dorsal pancreas. The patient underwent successful chemotherapy with 3 courses of gemcitabine and S-1, which was followed by pancreaticoduodenectomy. Pathological staging revealed invasive ductal carcinoma, pT3, pN0, pM0, stage III. We report a rare case of pancreatic cancer with congenital agenesis of the dorsal pancreas.

資料番号: SA1160306000