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Improving Fatigue Detection with Feature Engineering on Physical Activity Accelerometer Data Using Large Language Models
Get PDFIn this paper, we improve the classification performance of fatigue detection on physical activity using Large Language Models (LLMs). Fatigue is a critical reminder of a person’s health condition. Currently, studies on fatigue detection solely focus on sensor data to measure body condition. However, changing sensor data for more meaningful inference and improving fatigue detection performance needed to be developed. In this study, we implement LLMs for fatigue detection in physical activity. We use LLMs in the preprocessing steps to generate meaningful features that can improve classification performance. For evaluation, we study the prompt design of LLMs to investigate their effect on improving machine learning performance, and compare evaluation metrics between traditional machine learning and LLMs-based machine learning. Using LLMs, our proposed model achieves better performance for fatigue detection, especially in physical activity, with performance improvement of 2% minimum and 4.5% maximum.journal articl
A Proposal of Fish Ladder with Triangular Strip Roughness Suitable for Anguilla Japonica Migration
Get PDFウナギが海洋から河川に遡上する際に，ダムや堰が移動阻害となり種の存続に負の影響を与えている．ウナギが遡上する際，粘膜に覆われたウナギと底面との間に大きな摩擦力の発生は期待できない．そのため，鬼束らは遡上力を支持できる，横断方向に間隙を有さない長方形桟粗度の設置を考案した．ただし，上流側隅角部ではニホンウナギの腹部と底面に隙間が生じてしまい摩擦力が低下する．これを回避する方法として三角形桟粗度の採用が挙げられる．本研究では，三角形桟粗度間隔をニホンウナギの全長の0.5倍とし，三角形桟粗度および魚道の勾配を変化させ，遡上に適した幾何学条件を模索した．その結果，全長200mmのニホンウナギの場合，本実験の条件下では桟粗度勾配16.7°，魚道勾配10°が最も遡上に適していると判明した．When eels migrate upstream from the ocean to rivers, dams and weirs act as barriers to their migration, and this has a negative impact on the survival of the species. When eels migrate upstream, no significant frictional force is expected to be generated between the eel, which is covered by a mucous membrane, and the bottom surface. Therefore, Onitsuka et al. devised the installation of rectangular strip roughness with no gaps in the transverse direction. However, the upstream corner of the rectangular strip roughness has a gap between the belly of Anguilla japonica and the bottom surface, resulting in a decrease in frictional force. One way to avoid this problem is to use triangular strip roughness. In this study, the spacing of the triangular strip roughness was set to 0.5 times the total length of Anguilla japonica, and the geometrical conditions suitable for the run were sought by varying triangular strip roughness and the slope of the fish ladder. The results showed that under the conditions of this experiment, a triangular strip roughness gradient of 16.7° and a fish ladder gradient of 10° were the most suitable for the 200mm long Anguilla japonica to migrate upstream.journal articl
Can ChatGPT Pass Modern Control Theory Exam?
Get PDFLarge language models (LLMs), such as GPT models, have been rapidly studied in recent years and are expected to be applied to academic fields such as mathematics and engineering. In this study, we examined how accurately ChatGPT (GPT-4o) can answer modern control theory questions at the undergraduate-level. A set of 98 questions on modern control theory was used to evaluate GPT-4o’s problem-solving ability on modern control theory. The results revealed that the GPT-4o showed a 49.0% correct response rate to the undergraduate-level modern control theory exercises, and that the correct response rate tended to be lower for problems involving calculations, especially those that require step-by-step thinking and complex computation. This may be attributed to the Transformer architecture of the GPT model, which generates answers based on probabilistic predictions. In this study, we proposed a method to improve response accuracy by developing a customized GPT which leverages prompt engineering methods to address these issues. In order to evaluate the proposed method, a question set consisting of 45 graduate school entrance exam questions on modern control theory was developed. The results of the evaluation showed that the correct response rate was improved by 26.6 points, yielding a 64.4% correct response rate.journal articl
Doping Dependence of Upper Critical Field of High-Tc Cuprate Bi2+xSr2−xCaCu2O8+δ Estimated from Irreversibility Field at Zero Temperature
Get PDFWe investigated the temperature (T) dependence of the irreversibility field Hirr(T) in high-critical-temperature cuprate Bi2+xSr2−xCa1−yYyCu2O8+δ (Bi-2212) single crystals over a wide range of hole doping level (p). Hirr(T) was evaluated by measuring the magnetization hysteresis loop. The value of Hirr(T) extrapolated to T = 0 K [Hirr(0)], is either equal to or sets the lower boundary for the upper critical field at T = 0 K [Hc2(0)]. Tc shows a parabolic p-dependence (peak at p = 0.16), whereas μ0Hirr(0) increases monotonically with p by approximately one order of magnitude, from 19 T for the most underdoped sample (p = 0.065, Tc = 24 K) to 209 T for the most overdoped sample (p = 0.200, Tc = 75 K). The present results qualitatively agree with Hc2(0) values evaluated from the specific heat measurements. The observed p-dependence of Hirr(0) in Bi-2212 is distinct from those in YBa2Cu3O7−δ and HgBa2CuO6+δ, in which a pronounced dip structure appears in the underdoped region. Considering that the dip structures observed in these two systems are likely associated with the formation of competing orders (most likely field-induced charge orders), the present results indicate that the influence of the competing order in Bi-2212 is less prominent than that in the other two systems.journal articl
Current-Sensor-Less Condition Monitoring of a DC-Link Capacitor Based on Analysis of a Six-Pulse Diode Rectifier Having AC and DC inductors
Get PDFCondition monitoring plays an important role in improving reliability of power electronic converters including their dc-link capacitors because it contributes to predicting converter failures. This paper presents an analysis of a six-pulse diode rectifier used in the front-end of a three-phase PWM inverter intended for current-sensor-less condition monitoring of a dc-link capacitor. The analysis reveals the ripple current flowing out of a front-end six-pulse diode rectifier having ac line and dc inductors, which allows condition monitoring of both the capacitance and equivalent-series resistance (ESR) of the capacitor without using current sensors. Theoretical analysis reveals that the capacitor current is calculated by the three-phase ac source voltage, ac line inductor, dc inductor, and output power of the inverter. Experimental results obtained from a 200-V laboratory system confirmed that both the ESR and capacitance changes were observed without any current sensors.journal articl
Study of the stabilization parameter in the virtual element method
Get PDFThe virtual element method is an approximate solution method for partial differential equations that does not require the explicit definition of interpolation functions for test and trial functions in the elements. Accordingly, it can easily handle polygonal and polyhedral elements, including nonconvex shapes, and it has begun to attract attention as a generalization of the finite element method. As one of the two terms that constitute the internal virtual work, the stabilization term has received little attention, and methods for determining the stabilization parameter have not been proposed to date. Thus, in this study, we focus on the stabilization parameter of the stabilization term. Through a series of eigenvalue analyses of the stiffness matrices, we show that the stabilization parameter corresponds to the energy of the mode not included in the consistency term. From this consideration, we propose a method for setting the stabilization parameter appropriately.journal articl
Self-Tuning of Signal Detection Level for Energy Detection-Based Carrier Sense in Low-Power Wide-Area Networks
Get PDFCarrier sense allows end devices to improve the communication quality through autonomous decentralization by consuming power. In particular, energy detection-based carrier sense can improve communication quality compared with peak detection-based carrier sense. To improve the trade-off between communication quality and energy consumption in low-power wide-area networks (LPWANs), this study proposes a self-tuning method for the signal detection level of an energy detection-based carrier sense, that is, the carrier sense level in sub-GHz band LPWANs. In the proposed method, the carrier sense level of each end device is determined based on the reception success probability of the acknowledgment packet, such that they become low carrier sense levels for an end device with low probability and high carrier sense levels for an end device with high probability. The proposed method enables autonomous decentralized derivation of the carrier sense level using only existing protocols. Numerical examples show that the proposed method can improve the performance of end devices with a high path loss to a gateway.journal articl
Automatic judgement of weld bead shape and reproduction using 3D model in welding technology competition
Get PDF溶接業界では、少子高齢化や生産年齢人口の減少にともない日本の経済基盤を支える溶接技能者の不足が深刻化しつつあり、溶接の担い手の獲得が喫緊の課題になっている1)。この課題を解決するためには、若年者を獲得して人材育成（技能伝承）を効果的に行うとともに、ロボット技術の活用を検討していく必要がある。
ロボット技術の活用にあたって、従来は少品種多量生産に対して産業ロボットを導入することが一般的であったが、近年は多品種少量生産にも対応できる協働ロボットが注目されている。協働ロボットは、人がロボットに直接触れて動作教示（ティーチング）を行うダイレクトティーチング、および高度なプログラム知識が不要な簡易設定ツールによって、ティーチングが容易になっている。また、レーザ変位計などのセンシング技術の発達により、対象物の形状を高精度に取得できるようになっている。しかしながら、協働ロボットやレーザ変位計を導入しても、溶接技能者のように溶接位置を把握し、開先形状に適した溶接を行うには、膨大な課題を解決する必要がある。その第一歩として、開先形状および溶接ビード形状の自動判定技術の確立が必要である。第1図2)に溶接ビード形状とトーチ軌道のイメージを示す。
一方、人材育成の取組みの一つに溶接技術競技会がある。溶接技術競技会は、様々な団体が主体となって開催されており、溶接技能者の技術やモチベーションの向上、溶接の普及などに寄与している。溶接技術競技会では、被覆アーク溶接法または炭酸ガスアーク溶接法によって板材の突合せ溶接を行う競技課題が多く、採点には外観判定や放射線透過試験、曲げ試験などが適用される。写真12)に溶接技術競技会の作品の外観を示す。外観判定は判定基準にもとづき熟練の評価員が手動で行う必要がある1)。また、曲げ試験を行う場合は作品の保存ができなくなる。そこで、ロボット溶接の研究過程で開発中の「開先形状と溶接ビード形状の自動判定技術」を応用して、溶接技術競技会の課題解決への取組みを行った。作品の溶接ビード形状をレーザ変位計で計測し、計測データをプログラム処理することで外観判定を自動で行うとともに、3Dモデルに変換・保存した。さらに、3Dモデルを活用することで溶接ビード形状を3Dプリンタで再現した。ここでは、これらの方法および検証結果、ならびに溶接技術競技会で実証した事例を示す。journal articl
Effect of TIG welding on ferrite content of weld metal in duplex stainless steel
Get PDF二相ステンレス鋼のティグ溶接では，シールドガスの組成や希釈などの溶接条件によって，溶接金属のフェライト量が過多または過少となり，溶接金属の耐食性が低下するおそれがある．そこで，二相ステンレス鋼の突合せ溶接（片面）にティグ溶接を適用した場合において，溶接金属のフェライト量におよぼすシールドガスの影響，ならびに初層溶接金属の断面ミクロ組織とフェライト量におよぼす二層目溶接の影響を評価した．journal articl
