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Nonlinear Value Function Approximation Method with Easy Hyperparameter Tuning and Convergence Guarantee

IEEE Access 2025年 13卷 30117-30126页

作者： Watabe, Yuuya Shibuya, Takeshi University of Tsukuba Master's Program in Intelligent and Mechanical Interaction Systems Ibaraki305-8577 Japan University of Tsukuba Institute of Systems and Information Engineering Ibaraki305-8577 Japan

Reinforcement Learning is a branch of machine learning to learn control strategies that achieve a given objective through trial-And-error in the environment. Because this can be applicable even when the state transition function of the control object is unknown or it is difficult to create its model properly, this can reduce the designer's burden. Reinforcement learning repeats evaluating a policy and improving it based on that evaluation. An algorithm called value function approximation is used in this evaluation. Value function approximation is a general term for algorithms of approximating a function called value function, which maps an arbitrary state to how much reward can be obtained in the future when acting according to a policy from that state. Value function approximation should have high approximation accuracy and hyperparameter easy to tune. Although various value function approximation methods have been proposed so far, some of them does not have convergent guarantee and the others' hyperparameter tuning is difficult. The purpose of this paper is to propose a value function approximation method that have convergence guarantee even with nonlinear function approximator and whose hyperparameter tuning is easy and to verify its performance through numerical experiments. To this end, we focused on GTD2 method, which is one of the value function approximation methods that has convergence guarantee even with a nonlinear function approximator. GTD2 method has the drawback that its hyperparameter is difficult to tune appropriately so that the approximation does not diverge during learning. Therefore, we firstly clarified the cause of the divergence of GTD2 method. Secondly, based on this cause, we proposed Normalized and Regularized GTD2 (NRGTD2) method, that incorporates a method for suppressing divergence into GTD2 method. Finally, through numerical experiments, it was clarified that the proposed method suppresses the divergence and can achieve better approxim

关键词： Reinforcement learning

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Throughput and Quality Optimized Down-Selection of Overlay Measurement Markers for Robust Control of the Maximum Overlay Error in a Pattern Layer in Photolithography Processes

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IEEE Transactions on Semiconductor Manufacturing 2025年第2期38卷 251-262页

作者： Graff, Noah Djurdjanovic, Dragan The University of Texas at Austin Graduate Program in Dynamic Systems & Controls Walker Department of Mechanical Engineering AustinTX78712 United States The University of Texas at Austin Walker Department of Mechanical Engineering AustinTX78712 United States

This paper presents a metaheuristic optimization-based approach for selecting a pre-determined number of measurement markers from the set of available markers that optimizes the performance of the recently introduced robust L∞ norm overlay control algorithm, which robustly minimizes the worst overlay error across a given pattern layer. This optimization is then used in a Design of Experiments (DOE) setting to build a tractable regression model of a customizable objective function encompassing cost effects of quality losses and throughput benefits resulting from the down-selection of markers selected for robust overlay control. Using this model, one can rapidly determine the optimal proportion of markers for any set of cost parameters, and the optimal subset forming this proportion of available markers can be down-selected to maximize performance of the resulting robust overlay controller. Overlay data and models from a semiconductor manufacturing fab were used to evaluate the newly proposed inspection and control strategy. Results clearly indicate that the novel strategic down-selection of measurement markers coupled with robust overlay control could lead to vastly improved throughputs without decreasing quality relative to what can be achieved using traditional Run-to-Run (R2R) control. Feasibility of the novel DOE-based optimization was demonstrated for two scenarios of cost-effect parameters. © 1988-2012 IEEE.

关键词： Throughput

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Three-dimensional surface topography analysis of die-sinking electrical discharge machined eco-friendly beryllium-free copper alloys

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International Journal of Advanced Manufacturing Technology 2025年第7期138卷 2911-2953页

作者： Vijayan, Vipin Saju, Kaiprappady Kunchu Sundaresan, Jithin Division of Mechanical Engineering School of Engineering Cochin University of Science and Technology Thrikkakkara Kerala Kochi682022 India Department of Mechanical Engineering Muthoot Institute of Technology and Science Varikoli Kerala Ernakulam682308 India Business Information Systems Program Information Systems Department School of Computing and Creative Arts Bina Nusantara University Senayan DKI Jakarta Jakarta10270 Indonesia

Beryllium-copper alloys, the most widely used copper alloys, are utilised extensively in diverse sectors, including the electrical, electronics, instrumentation, metallurgy, aerospace, automotive, petrochemical, machinery manufacturing, and die and mould-making industries. The main drawback of these alloys is that they produce the toxic component, beryllium oxide, which can lead to a chronic lung disease known as berylliosis. Beryllium-free copper alloys, such as copper-nickel-silicon-chromium, are eco-friendly, less costly, and possess properties similar to those of beryllium-copper alloys. Hence, they are now replacing beryllium-copper alloys in the applications mentioned earlier. Due to their high strength and hardness, these alloys are often fabricated into components using unconventional machining techniques, such as electrical discharge machining. Electrical discharge machining is particularly advantageous in industrial applications where precisely controlled random surface textures on these alloys are required. However, despite the industrial significance, research on the electrical discharge machining process of copper-nickel-silicon-chromium alloys is scarce. Therefore, the current work aims to address this research gap by conducting an experimental investigation of the random surfaces generated on copper-nickel-silicon-chromium alloy components after the die-sinking electrical discharge machining process through a comprehensive three-dimensional surface topography analysis. Three-dimensional surface topography parameters overcome the drawbacks of two-dimensional roughness parameters by considering the majority of surface points. This work investigates the effects of input factors, including electrode material, dielectric fluid material, flushing condition, and current on nearly all relevant areal texture (3D) parameters. ANOVA is performed to study the level of significance of each input parameter. The regression analyses reveal that current is the most si

关键词： Beryllium powder metallurgy

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Texture development and surface reconstruction of BiVO_(4)photoanode via one-pot hydrothermal reaction for enhanced photoelectrochemical water splitting

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Journal of Advanced Ceramics 2025年第3期14卷 133-141页

作者： Sung Won Hwang Yoo Jae Jeong Runfa Tan Indhujasri Saravanan Hyun Soo Han Dong Hoe Kim In Sun Cho Department of Energy Systems Research Ajou UniversitySuwon 16499Republic of Korea Department of Material Science&Engineering Ajou UniversitySuwon 16499Republic of Korea Department of Mechanical Engineering Stanford UniversityStanford 94305USA Department of Material Science&Engineering Korea UniversitySeoul 02841Republic of Korea Materials Science and Engineering Program University of Colorado BoulderBoulder 80303USA

The simultaneous optimization of the bulk and surface characteristics of photoelectrodes is essential to maximize their photoelectrochemical(PEC)*** report a novel one-pot hydrothermal synthesis of textured and surface-reconstructed BiVO_(4)photoanodes(ts-BVO),achieving significant improvements in PEC water *** controlling precursor molarity and ethylene glycol(EG)addition,we developed a stepwise dual reaction(SDR)mechanism,which enables simultaneous bulk texture development and surface *** optimized CoBi/ts-BVO photoanode exhibited a photocurrent density of 4.3 mA∙cm^(−2)at 1.23 V *** hydrogen electrode(RHE)with a high Faradaic efficiency of 98%under one sun *** with nontextured BiVO_(4),the charge transport efficiency increased from 8%to 70%,whereas the surface charge transfer efficiency improved from 9%to 85%.These results underscore the critical role of both bulk and surface engineering in enhancing PEC *** findings offer a streamlined approach for improving the intrinsic properties of photoanodes in solar water splitting.

关键词： BiVO_(4) hydrothermal texture surface reconstruction ethylene glycol(EG) photoelectrochemical water splitting

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The Centrifugal Nuclear Thermal Rocket: Foundations, Challenges, and Progress

The Centrifugal Nuclear Thermal Rocket: Foundations, Challen...

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AIAA Science and Technology Forum and Exposition, AIAA SciTech Forum 2025

作者： Thomas, Dale Houts, Michael Wang, Dean Hollingsworth, Keith Frederick, Robert Cassibry, Jason Department of Industrial & Systems Engineering and Engineering Management The University of Alabama in Huntsville HuntsvilleAL35899 United States Space Nuclear Propulsion Program Office NASA Marshall Space Flight Center HuntsvilleAL35812 United States Department of Mechanical & Aerospace Engineering The Ohio State University ColumbusOH43210 United States Department of Mechanical & Aerospace Engineering and Interim Dean of the Honors College The University of Alabama in Huntsville HuntsvilleAL35899 United States Department of Mechanical & Aerospace Engineering Propulsion Research Center The University of Alabama in Huntsville HuntsvilleAL35899 United States Department of Mechanical & Aerospace Engineering The University of Alabama in Huntsville HuntsvilleAL35899 United States

ISBN: (数字)9781624107238

ISBN: (纸本)9781624107238

The Centrifugal Nuclear Thermal Rocket (CNTR) is a Nuclear Thermal Propulsion (NTP) concept designed to heat propellant directly by the reactor fuel. The primary difference between the CNTR concept and traditional NTP systems is that rather than using traditional solid fuel elements, the CNTR uses liquid fuel with the liquid contained in rotating cylinders by centrifugal force. If the concept can be successfully realized, the CNTR would have a high specific impulse (up to 1800 s) at high thrust, which may enable (i) viable near-term human Mars exploration by reducing round-trip times to 420 days and (ii) direct injection orbits for scientific rendezvous missions to the Solar System outer planets and Kuiper Belt objects. Research is presently underway to determine resolutions for the significant engineering challenges that the CNTR concept presents. These challenges, the study plans to address them, and progress have been described previously;this paper provides an update on progress to date for the overall research effort, including strategies and key results on revision of a reference configuration, definition of key parameters which allows integration of the results of various analyses, and reviews strategies to mitigate the problem of Uranium vapor saturating the propellant exhaust and significantly impacting the CNTR’s specific impulse. Analyses and experiments, both underway and planned, to update estimates of engine key performance parameters including specific impulse, thrust and thrust to weight ratio along with the identification of selected design margins within the engine itself are described – all toward the goal of enabling plans for a laboratory demonstration of a single Centrifugal Fuel Element. © 2025, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.

关键词： Rockets

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Effect of Sn addition on electrochemical activity of ribbons of Mg-Al-Ca anode material for rechargeable magnesium batteries fabricated by rapid solidification

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Keikinzoku/Journal of Japan Institute of Light Metals 2025年第1期75卷 9-13页

作者： Fukuta, Yoshitaka Kikura, Kensei Tsukeda, Tadayoshi Aida, Tetsuo Tabata, Hironobu Kurihara, Hideki Suzuki, Mayumi Program of Materials Science and Engineering Studies in Science and Engineering Graduate School of Science and Engineering University of Toyama 3190 Gofuku Toyama-shi Toyama930-8555 Japan Graduate School of Science and Engineering University of Toyama Toyama-shi Toyama Japan Faculty of Sustainable Design Academic Assembly University of Toyama Toyama-shi Toyama Japan CHUETSU METAL WORKS CO. LTD. Nakaniikawagun Toyama Japan Saitama Industrial technology Center Kawaguchi-shi Saitama Japan Department of Mechanical Systems Engineering Faculty of Engineering Toyama Prefectural University Imizu-shi Toyama Japan

Magnesium-based batteries are potential candidates for next-generation rechargeable batteries due to the divalent nature of magnesium cations and the natural abundance of magnesium resources. In this study, the electrochemical activity of Mg-6mass%Al-3mass%Ca anodes combined with Sn was investigated. Thin ribbons of the anode specimens were prepared by a single-roll rapid solidification method. The results showed that the electrochemical activity increased upon adding 1 mass% Sn, while it decreased for 3 mass% Sn. Based on the results of an X-ray diffraction analysis, the addition of Sn led to the formation of Mg2Sn and Ca2Sn phases, which increased the lattice distortion. Scanning electron microscopy observations indicated that these secondary phases were homogeneously distributed for 1 mass% Sn addition, while they were coarsely distributed for 3 mass% Sn. © 2025 The Japan Institute of Light Metals.

关键词： X ray diffraction analysis

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Response of unsteady thermocapillary convection to local heating at specific depths in a thin liquid film

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Chemical engineering Science 2025年 314卷

作者： Kudo, Masaki Igarashi, Keita Mechanical Systems Engineering Program Monozukuri Engineering Department Tokyo Metropolitan College of Industrial Technology 10-40 Higashi-oi 1-chome Tokyo Shinagawa City140-0011 Japan

A hydrothermal wave (HTW) refers to a flow pattern that arises during unsteady thermocapillary convection, negatively impacting the purity of single crystals during zone melting. This study utilized active control through localized heating to reduce HTW amplitude, akin to noise cancellation. The effectiveness of this method was evaluated both experimentally and numerically by adjusting the heating depth in a thin liquid film. Silicone oil served as the test fluid, and the liquid film was rectangular in shape. In the case of linear time-periodic heating, a line-shaped heater applied a constant maximum heat input, synchronized with the HTW's period. Experimental results indicated that HTW amplitude significantly depends on the heating depth of the liquid film. Downstream of the HTW, temperature amplitude could be reduced by up to 60%, whereas upstream, it could be amplified. In numerical simulations, HTW reduction and amplification were linked to substantial changes in the streamwise temperature gradient on the free surface, rather than to local cancellation of the temperature disturbance. Unlike the results from single-pulse heating control, the amplitude ratio showed a strong dependence on whether the heat input significantly affected the streamwise thermal and flow fields. © 2025 Elsevier Ltd

关键词： Liquid films

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Evaluation of Cuffless Blood Pressure Estimation Accuracy at Each Heartbeat During Exercise 6th

Evaluation of Cuffless Blood Pressure Estimation Accuracy a...

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6th International Conference on Biomedical and Health Informatics, ICBHI 2024

作者： Ono, Kouki Maeda, Yuka Yoshimura, Takumi Huang, Ming Tamura, Toshiyo Master’s Program in Intelligent and Mechanical Interaction Systems University of Tsukuba Tsukuba305-8577 Japan Institute of Systems and Information Engineering University of Tsukuba Tsukuba305-8577 Japan Medical and Welfare Engineering Tokyo Metropolitan College of Industrial Technology Tokyo116-8523 Japan School of Data Science Nagoya City University Nagoya467-8501 Japan Future Robotics Organization Waseda University Tokyo169-8050 Japan

ISBN: (纸本)9783031863226

Continuous blood pressure monitoring is crucial because of its dynamic nature, influenced by factors such as physical activity and mental stress. Although cuffless blood pressure estimation is a promising technique for continuous monitoring, its accuracy during drastic fluctuations, especially during exercise, remains insufficiently validated. In this study, we evaluated a simple Pulse Arrival Time based blood pressure estimation method and several improved methods for sharp fluctuations induced by exercise. Sixteen subjects in the experiment, with data from 13 valid for analysis. The proposed method achieved an average correlation of 0.527 in systolic blood pressure, suggesting that cuffless blood pressure estimation could be applied to estimate continuous blood pressure variability during exercise. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2025.

关键词： Blood pressure

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Extension-type flexible pneumatic actuator with a large extension force using a cross-link mechanism based on pantographs

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Sensors and Actuators A: Physical 2025年 390卷

作者： Shimooka, So Tadachi, Kazuma Kamegawa, Tetsushi Faculty of Environmental Life Natural Science and Technology Okayama University 3-1-1 Tsushima-naka Kita-ku Okayama Japan Mechanical and Systems Engineering Program School of Engineering Okayama University 3-1-1 Tsushima-naka Kita-ku Okayama Japan

In this study, we propose an extension-type flexible pneumatic actuator (EFPA) with a high extension force and no buckling. In a previous study, soft actuators that extended in the axial direction by applying a supply pressure were unable to generate the extension's pushing force because the actuators buckled owing to their high flexibility. To generate a pushing force, the circumferential stiffness of an extension-type flexible soft actuator must be reinforced. Therefore, a cross-linked EFPA (CL-EFPA) was developed, inspired by a pantograph that restrains the EFPA three-dimensionally using the proposed link mechanism. The proposed CL-EFPA consists of three EFPAs and a cross-linking mechanism for integrating each EFPA circumference. The pushing force of the CL-EFPA is approximately 3.0 times compared with that generated by the previous EFPA with plates to restrain its plane. To perform various bending motions, attitude control was performed using an analytical model and a system that included valves, sensors, and controllers. © 2025 The Authors

关键词： Buckling

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Wind speed forecasting approach using conformal prediction and feature importance selection

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International Journal of Electrical Power and Energy systems 2025年 168卷

作者： Zuege, Cesar Vinicius Stefenon, Stefano Frizzo Yamaguchi, Cristina Keiko Mariani, Viviana Cocco Gonzalez, Gabriel Villarrubia Coelho, Leandro dos Santos Graduate Program in Electrical Engineering Federal University of Parana PR Curitiba Brazil Postgraduate Program in Productive Systems in Association with UNIPLAC UNC UNESC and UNIVILLE SC Brazil Department of Electrical Engineering Federal University of Parana PR Curitiba Brazil Graduate Program in Mechanical Engineering Federal University of Parana PR Curitiba Brazil Expert Systems and Applications Lab Faculty of Science University of Salamanca Salamanca37008 Spain

Wind energy is a rising renewable energy source that plays an important role in the transition to a more sustainable energy system. Variation in wind power generation is one of the main challenges facing this energy source. Wind forecasting approaches are essential for planning and operating wind farms, but are complex due to the dynamic nature of the wind and the influence of local factors. This paper evaluates short-term forecasting of time series with a measure of uncertainty associated with wind speeds. The proposed method considers the conformal prediction approach and, based on Shapley values, uses optimal selection of features given their importance. Furthermore, a Bayesian Optimization with Tree-structured Parzen Estimators (BO-TPE) will be used to tune the hyperparameters of the models. The results showed that using Variational Mode Decomposition (VMD) allied with Singular Spectrum Analysis (SSA) to feed into a conformal prediction model improved the performance of the model. Taking into account a Beutenberg data set, Germany, the best model was Light Gradient Boosting Machine (LGBM)-VMD-SSA without partial fit, resulting in a root mean squared error (RMSE) criterion of 0.25031, coverage measure of 94.4%, and width measure of 1.008. When considering a dataset from Limoeiro, Brazil, the best model was also LGBM-VMD-SSA without partial fit, resulting in an RMSE of 0.21597, a coverage of 90.3%, and a width of 0.678. SHapley Additive exPlanations (SHAP) bring explainability to the model results. The models proposed in this study, hypertuned by BO-TPE with interpretable results based on SHAP, can be useful in predicting wind speed and power generation. © 2025 The Authors

关键词： Windmill

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