データ駆動型意思決定のための目的指向モデリング

京都大学新制・課程博士博士(情報学)甲第23542号情博第772号新制||情||132(附属図書館)京都大学大学院情報学研究科知能情報学専攻(主査)教授 鹿島 久嗣, 教授 山本 章博, 教授 下平 英寿学位規則第4条第1項該当Doctor of InformaticsKyoto UniversityDGA

Improving imbalanced classification using near-miss instances

The class imbalance is a major issue in classification, i.e., the sample size of a rare class (positive) is often a performance bottleneck. In real-world situations, however, “near-miss” positive instances, i.e., negative but nearly-positive instances, are sometimes plentiful. For example, natural disasters such as floods are rare, while there are relatively plentiful near-miss cases where actual floods did not occur but the water level approached the bank height. We show that even when the true positive cases are quite limited, such as in disaster forecasting, the accuracy can be improved by obtaining refined label-like side-information “positivity” (e.g., the water level of the river) to distinguish near-miss cases from other negatives. Conventional cost-sensitive classification cannot utilize such side-information, and the small size of the positive sample causes high estimation variance. Our approach is in line with learning using privileged information (LUPI), which exploits side-information for training without predicting the side-information itself. We theoretically prove that our method reduces the estimation variance, provided that near-miss positive instances are plentiful, in exchange for additional bias. Results of extensive experiments demonstrate that our method tends to outperform or compares favorably to existing approaches

Effect of Specimen Thickness on Aging and Fatigue Strength of Al-Zn Alloys

Repeated tensile fatigue strength of the low temperature age-hardened Al-Zn alloys is investigated varying the specimen thickness. Fatigue strength of the age-hardened specimens decreases with the specimen thickness when the specimen is thinner than a certain thickness, whereas fatigue strength of non age-hardened specimens, i.e., pure aluminum and dilute Al-Zn alloy, does not depend the specimen thickness. The dependence of fatigue strength on the thickness of age-hardened specimen is considered to be caused by the decrease of the strength of specimen as a whole, as a result of increase in volume ratio of the soft surface layer formed after age-hardening with decreasing specimen thickness

高圧充填層の伝熱機構に関する研究

金沢大学工学部研究課題/領域番号:X42440-----59706, 研究期間(年度):1967出典：研究課題「高圧充填層の伝熱機構に関する研究」課題番号X42440-----59706（KAKEN：科学研究費助成事業データベース（国立情報学研究所）） （https://kaken.nii.ac.jp/ja/grant/KAKENHI-PROJECT-X42440-----59706/）を加工して作

固液間における熱と物質との同時移動に関する基礎的研究

金沢大学工学部研究課題/領域番号:X40440-----59560, 研究期間(年度):1965出典：研究課題「固液間における熱と物質との同時移動に関する基礎的研究」課題番号X40440-----59560（KAKEN：科学研究費助成事業データベース（国立情報学研究所）） （https://kaken.nii.ac.jp/ja/grant/KAKENHI-PROJECT-X40440-----59560/）を加工して作

Enhancement of electrolytic mass transfer around spheres by applying static magnetic fields

金沢大学大学院自然科学研究科エコサイクルシステム金沢大学工学部The effect of applying a static magnetic field on mass transfer rate in diffusion-controlled electroreduction was studied experimentally around single spheres of diameters 8 to 14 mm under the condition of laminar natural convection. The electrolytic solution of the system K"SUB 3" Fe(CN)"SUB 6" -K"SUB 4" Fe(CN)"SUB 6" with a supporting electrolyte was employed and the magnetic field was applied to the cathode in the horizontal or vertical direction and up to 336 mT in flux density. By applying the magnetic field in every direction, the mass transfer rate was enhanced more than 50% at the highest magnetic flux density, compared to the simple natural convection case. (from Authors)

The physiological response during optogenetic-based cardiac pacing in awake freely moving mice

There are several methods to control a heart rate, such as electrical stimulation and drug administration. However, these methods may be invasive or affect other organs. Recently, an optogenetic-based cardiac pacing method has enabled us to stimulate the cardiac muscle in non-contact. In many previous studies, the pacing was applied ex vivo or in anesthetized animals. Therefore, the physiologic response of animals during optogenetic pacing remains unclear. Here, we established a method of optogenetic-based cardiac pacing in awake, freely moving mice and simultaneously measured electrocardiogram, blood pressure, and respiration. As a result, light-induced myocardial contraction produces blood flow and indirectly affects the respiration rhythm. Additionally, light illumination enabled heart rate recovery in bradycardic mice. These findings may be employed for further research that relates a heartbeat state to animal behavior. Together, this method may drive the development of less invasive pacemakers without pacing leads

Effects of pulsating magnetic fields on electrolytic mass transfer around cylindrical cathodes

金沢大学大学院自然科学研究科エコサイクルシステム金沢大学工学部The influence of pulsating magnetic fields on mass transfer was studied experimentally in the electroreduction of ferrocyanide ions around an inclined cylindrical cathode under diffusion-controlled conditions. The mass transfer rate is increased by applying the pulsating magnetic field as well as the static one. The time-averaged enhancement of the mass transfer rate is dependent markedly on duty cycle (ON-time ratio), peak magnetic flux density of the applied pulsating magnetic fields in a range of 20 to 200 mHz, and slightly on its frequency. The mass transfer coefficient was correlated well by two types of non-dimensional regression equations with and without a duty-cycle factor, by using the "magneto-diffusion factor" to express the contribution of the applied magnetic flux density