Can Reinforcement Learning Be Applied to Surgery?

Background: Remarkable progress has recently been made in the field of artificial intelligence (AI).Objective: We sought to investigate whether reinforcement learning could be used in surgery in the future.Methods: We created simple 2D tasks (Tasks 1–3) that mimicked surgery. We used a neural network library, Keras, for reinforcement learning. In Task 1, a Mac OS X with an 8 GB memory (MacBook Pro, Apple, USA) was used. In Tasks 2 and 3, a Ubuntu 14. 04LTS with a 26 GB memory (Google Compute Engine, Google, USA) was used.Results: In the task with a relatively small task area (Task 1), the simulated knife finally passed through all the target areas, and thus, the expected task was learned by AI. In contrast, in the task with a large task area (Task 2), a drastically increased amount of time was required, suggesting that learning was not achieved. Some improvement was observed when the CPU memory was expanded and inhibitory task areas were added (Task 3).Conclusions: We propose the combination of reinforcement learning and surgery. Application of reinforcement learning to surgery may become possible by setting rules, such as appropriate rewards and playable (operable) areas, in simulated tasks

Applying the Burr Type XII Distribution to Decompose Remanent Magnetization Curves

Discriminating magnetic minerals of different origins in natural samples is useful to reveal their associated geological and environmental processes, which can be achieved by the analysis of remanent magnetization curves. The analysis relies on the choice of the model distribution to unmix magnetic components. Three model distributions were proposed in past studies, namely, the lognormal, skew normal, and skewed generalized Gaussian distributions, which are related to the normal distribution. In this study, the Burr type XII distribution is tested and compared with existing model distributions. An automated protocol is proposed to assign parameters necessary to initiate the component analysis, which improves the efficiency and objectivity. Results show that the new model distribution exhibits similar flexibility to the skew normal and skewed generalized Gaussian distributions in approximating skewed coercivity distributions and can fit end‐member components better than the commonly used lognormal distribution. We demonstrate that the component analysis is sensitive to model distribution as well as measurement noise. As a consequence, the decomposition is subject to bias that is hard to identify due to the lack of ground‐truth data. It is therefore recommended to compare results derived from various model distributions to identify spurious components.This work was supported by NIPR through an Advanced Project (KP7 and KP301) and JSPS KAKENHI grants (15K13581, 16H04068, 17H06321, and 18K13638). This study was also performed under the cooperative research program of the Center for Advanced Marine Core Research, Kochi University (14A037, 14B034, 15A047, and 15B042). Z. J. acknowledges Natural Science Foundation of China (grant 41504055)

An Exceptionally Difficult Binary Quadratic Optimization Problem with Symmetry: a Challenge for The Largest Unsolved QAP Instance Tai256c

Tai256c is the largest unsolved quadratic assignment problem (QAP) instance in QAPLIB. It is known that QAP tai256c can be converted into a 256 dimensional binary quadratic optimization problem (BQOP) with a single cardinality constraint which requires the sum of the binary variables to be 92. As the BQOP is much simpler than the original QAP, the conversion increases the possibility to solve the QAP. Solving exactly the BQOP, however, is still very difficult. Indeed, a 1.48\% gap remains between the best known upper bound (UB) and lower bound (LB) of the unknown optimal value. This paper shows that the BQOP admits a nontrivial symmetry, a property that makes the BQOP very hard to solve. The symmetry induces equivalent subproblems in branch and bound (BB) methods. To effectively improve the LB, we propose an efficient BB method that incorporates a doubly nonnegative relaxation, the standard orbit branching and a technique to prune equivalent subproblems. With this BB method, a new LB with 1.25\% gap is successfully obtained, and computing an LB with $1.0\%$ gap is shown to be still quite difficult.Comment: 19 pages, 7 figures. arXiv admin note: substantial text overlap with arXiv:2210.1596

多様な地質学的背景を持つ海底熱水系の磁気的研究

学位の種別: 課程博士審査委員会委員 : （主査）東京大学教授 歌田 久司, 東京大学教授 川幡 穂高, 東京大学教授 沖野 郷子, 国立極地研究所教授 野木 義史, 東京大学准教授 上嶋 誠, 東京工業大学教授 綱川 秀夫University of Tokyo(東京大学

High-resolution magnetic signature of active hydrothermal systems in the back-arc spreading region of the southern Mariana Trough

International audienceHigh-resolution vector magnetic measurements were performed on five hydrothermal vent fields of the back-arc spreading region of the southern Mariana Trough using Shinkai 6500, a deep-sea manned submersible. A new 3-D forward scheme was applied that exploits the surrounding bathymetry and varying altitudes of the submersible to estimate absolute crustal magnetization. The results revealed that magnetic-anomaly-derived absolute magnetizations show a reasonable correlation with natural remanent magnetizations of rock samples collected from the seafloor of the same region. The distribution of magnetic-anomaly-derived absolute magnetization suggests that all five andesite-hosted hydrothermal fields are associated with a lack of magnetization, as is generally observed at basalt-hosted hydrothermal sites. Furthermore, both the Pika and Urashima sites were found to have their own distinct low-magnetization zones, which could not be distinguished in magnetic anomaly data collected at higher altitudes by autonomous underwater vehicle due to their limited extension. The spatial extent of the resulting low magnetization is approximately 10 times wider at off-axis sites than at on-axis sites, possibly reflecting larger accumulations of nonmagnetic sulfides, stockwork zones, and/or alteration zones at the off-axis sites

Influence of friction stir welding conditions on joinability of oxide dispersion strengthened steel / F82H ferritic/martensitic steel joint

AbstractAs one of the joining methods for the reduced activation materials to realize the fusion reactors with high efficiency in the future, friction stir welding (FSW) is selected for fabricating the dissimilar butt joint between oxide-dispersion strengthened (ODS) alloy and F82H, and the effect of FSW conditions on joinability of this dissimilar joint was examined. The sound dissimilar joint can be produced under the condition that ODS plate is set on the advancing side and the FSW tool is plunged into F82H. As for the mild steel backside plate, the sound joint can be fabricated in the case of 150rpm rotational speed and 50mm/min traveling speed. On the other hand, by employing the silicon nitride backside plate, the total heat input should be decreased to obtain the sound joint, where the traveling speed is 100 or 150mm/min and rotational speed is 150rpm. In addition, the finite element heat conduction analyses indicate that the influence of traveling speed on the joinability with the mild steel backside plate seems to be smaller than that with the silicon nitride plate and the allowable range of the appropriate traveling speed for the joint becomes to be wider by employing the silicon nitride backside plate

Links between global magmatism and GIA -Future plan-

The Tenth Symposium on Polar Science/Special session: [S] Future plan of Antarctic research: Towards phase X of the Japanese Antarctic Research Project (2022-2028) and beyond, Tue. 3 Dec. / Entrance Hall (1st floor) at National Institute of Polar Research (NIPR

Strong ice-ocean interaction beneath Shirase Glacier Tongue in East Antarctica

Mass loss from the Antarctic ice sheet, Earth’s largest freshwater reservoir, results directly in global sea-level rise and Southern Ocean freshening. Observational and modeling studies have demonstrated that ice shelf basal melting, resulting from the inflow of warm water onto the Antarctic continental shelf, plays a key role in the ice sheet’s mass balance. In recent decades, warm ocean-cryosphere interaction in the Amundsen and Bellingshausen seas has received a great deal of attention. However, except for Totten Ice Shelf, East Antarctic ice shelves typically have cold ice cavities with low basal melt rates. Here we present direct observational evidence of high basal melt rates (7–16 m yr−1) beneath an East Antarctic ice shelf, Shirase Glacier Tongue, driven by southward-flowing warm water guided by a deep continuous trough extending to the continental slope. The strength of the alongshore wind controls the thickness of the inflowing warm water layer and the rate of basal melting