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RECLAIMING SALIENCY: RHYTHMIC PRECISION-MODULATED ACTION AND PERCEPTION

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arXiv 2022年

作者： Meera, Ajith Anil Novicky, Filip Parr, Thomas Friston, Karl Lanillos, Pablo Sajid, Noor Department of Cognitive Robotics Faculty of Mechanical Maritime and Materials Engineering Delft University of Technology Delft2628 CN Netherlands Donders Institute for Brain Cognition and Behavior Department of Neurophysiology Radboud University Netherlands Wellcome Centre for Human Neuroimaging University College London LondonWC1N 3AR United Kingdom Donders Institute for Brain Cognition and Behavior Department of Artificial Intelligence Radboud University Netherlands

Computational models of visual attention in artificial intelligence and robotics have been inspired by the concept of a saliency map. These models account for the mutual information between the (current) visual information and its estimated causes. However, they fail to consider the circular causality between perception and action. In other words, they do not consider where to sample next, given current beliefs. Here, we reclaim salience as an active inference process that relies on two basic principles: uncertainty minimisation and rhythmic scheduling. For this, we make a distinction between attention and salience. Briefly, we associate attention with precision control, i.e., the confidence with which beliefs can be updated given sampled sensory data, and salience with uncertainty minimisation that underwrites the selection of future sensory data. Using this, we propose a new account of attention based on rhythmic precision-modulation and discuss its potential in robotics, providing numerical experiments that showcase advantages of precision-modulation for state and noise estimation, system identification and action selection for informative path planning. Copyright © 2022, The Authors. All rights reserved.

关键词： Free energy

A recurrent neural network approach to roll estimation for needle steering

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arXiv 2021年

作者： Emerson, Maxwell Ferguson, James M. Ertop, Tayfun Efe Rox, Margaret Granna, Josephine Lester, Michael Maldonado, Fabien Gillaspie, Erin A. Alterovitz, Ron Webster, Robert J. Kuntz, Alan Department of Mechanical Engineering Vanderbilt University United States Department of Medicine and Thoracic Surgery Vanderbilt University Medical Center United States Department of Computer Science University of North Carolina at Chapel Hill United States Robotics Center School of Computing University of Utah United States

Steerable needles are a promising technology for delivering targeted therapies in the body in a minimally invasive fashion via controlled, actively steered insertions. These robotically actuated needles usually leverage an asymmetric tip [1] to take curved paths through the body, avoiding anatomical obstacles and honing in on a target (see Fig. 1, left). Methods such as duty cycling and sliding mode control enable safe, accurate, and automatic controlled steering of these needles to anatomical targets or along predetermined trajectories in the body [2,3]. These controllers require knowledge of the full 6 degrees of freedom (DOF) pose of the steerable needle’s tip as it is steered through the body. To acquire this information for feedback during control, electromagnetic sensors can be embedded in the tip of the needle. However, these sensors typically fill the internal working channel of the needle, precluding the use of the needle for therapy delivery. External sensors, such as ultrasound and bi-plane fluoroscopy (a type of continuous X-ray) can sense the needle tip’s position and heading (5 DOF), but are not able to sense its axial orientation (roll angle) [4]. Without full 6-DOF state measurement, an alternative method is needed to estimate the full state of the needle tip for effective steering. © 2021, CC BY.

关键词： Needles

A novel computational chemistry approach of narrow bandgap perovskite Cs 3 Sb 2 H 9 material for sustainable energy harvesting devices

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Materials Chemistry and Physics 2025年 345卷

作者： Waqar Azeem Shoukat Hussain Abhinav Kumar Dhouha Choukaier Jayanti Makasana M.M. Rekha G. Senthil Kumar Sankar Narayan Das Parveen Kumar Ankit D. Oza Muhammad Khuram Shahzad Faculty of Resilience Rabdan Academy Abu Dhabi United Arab Emirates Institute of Physics Khwaja Fareed University of Engineering and Information Technology Rahim Yar Khan 64200 Pakistan Department of Nuclear and Renewable Energy Ural Federal University Named after the First President of Russia Boris Yeltsin Ekaterinburg 620002 Russia Department of Mechanical Engineering and Renewable Energy Technical Engineering College The Islamic University Najaf Iraq Centre for Research Impact & Outcome Chitkara University Institute of Engineering and Technology Chitkara University Rajpura 140401 Punjab India Department of Basic Health Sciences in the Foundation Year for Health Colleges Program College of Languages Princess Nourah bint Abdulrahman University P.O. Box 84428 Riyadh 11671 Saudi Arabia Marwadi University Research Center Department of Mechanical Engineering Faculty of Engineering & Technology Marwadi University Rajkot 360003 Gujarat India Department of Chemistry and Biochemistry School of Sciences JAIN (Deemed to be University) Bangalore Karnataka India Department of Mechanical Engineering Sathyabama Institute of Science and Technology Chennai Tamil Nadu India Department of Mechanical Engineering Siksha ‘O' Anusandhan (Deemed to be University) Bhubaneswar Odisha 751030 India Department of Mechanical Engineering Chandigarh Engineering College Chandigarh Group of Colleges-Jhanjeri Mohali 140307 Punjab India University Centre for Research and Development Chandigarh University Mohali Punjab 140413 India

Perovskite materials are essential to materials science because they may be used in both theoretical as well as experimental investigations. The hydride perovskite Cs 3 Sb 2 H 9 based on cesium is computed in this work by utilizing a density functional theory. The current compound has a trigonal structure with 164 (P-3m1) space groups and is constructed on the Cambridge-serial-total-energy-package program by using generalized gradient-approximation and Perdew-Burke-Ernzerhof exchange-correlation functional. According to the results, the structural characteristics indicate that Cs 3 Sb 2 H 9 has a semiconductor and indirect bandgap of 0.81 eV. The structure stability is confirmed by the compound Cs 3 Sb 2 H 9 formation energy (−2.906 eV/atom), cohesive energy (2.906 eV/atom), electron density difference, and tolerance factor (0.87). The partial density of states and density of states validate the extent of electron localization in discrete bands. By fitting the damping ratio for the hypothetical dielectric function scaling to the proper peaks, the optical transitions are investigated. The compound's strong conductivity and absorption make it ideal for hydrogen storage applications, which boost productivity and function. Cs 3 Sb 2 H 9 compound is novel and achieved a better gravimetric hydrogen quantity percentage of about 3.438 wt percent. We found that the Cs 3 Sb 2 H 9 has potential applications in the fields of sustainable optoelectronics and hydrogen storage devices.

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Design of concentrated solar thermal powered heat exchanger completed with energy storage material

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AIP Conference Proceedings 2023年第1期2719卷

作者： Shafira Riskina Adi Setiawan Gunawati Gunawati Rozanna Dewi Magister Program in Renewable Engineering Faculty of Engineering Universitas Malikussaleh Bukit Indah 24352 Lhokseumawe Indonesia Mechanical Engineering Department Faculty of Engineering Universitas Malikussaleh Bukit Indah 24352 Lhokseumawe Indonesia Department of Physics Faculty of Mathematics and Natural Sciences Universitas Syiah Kuala Darussalam 23111 Banda Aceh Indonesia Chemical Engineering Department Faculty of Engineering Universitas Malikussaleh Bukit Indah 24352 Lhokseumawe Indonesia

Indonesia is a tropical area and located under the equator line with more than six hours of sunlight a day or about 2400 hours a year. Solar energy has an intensity between 0.6-0.7 kW/m2 and has a potential of 207.8 GWe (electric). This potential can be utilized to reduce the use of fossil energy by harvesting solar energy and transferring it in a helical coil heat exchanger (HCHE) type. This study aims to develop a special proposed heat exchanger design to collect solar thermal energy. As the energy supply is intermittent, a thermal energy storage system is installed. The design of HCHE has coil diameter of 10 mm with thickness of the tube 0.5 mm. HCHE performance test was performed by feeding water to the heat exchanger at a flow rate of 0.006 kg/s where the inlet water temperatures was 27.2˚C. At the outlet, the average temperature was 32.3˚C. During the test, the maximum temperature can be reached by the system was 269.4˚C. This indicates that the solar thermal collector design is working and potentially can be scale-up for energy generating system.

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Can I lift it? Humanoid robot reasoning about the feasibility of lifting a heavy box with unknown physical properties

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arXiv 2020年

作者： Han, Yuanfeng Li, Ruixin Chirikjian, Gregory S. Department of Mechanical Engineering Johns Hopkins University BaltimoreMD United States Department of Mechanical Engineering National University of Singapore Singapore Laboratory for Computational Sensing and Robotics Johns Hopkins University BaltimoreMD United States

A robot cannot lift up an object if it is not feasible to do so. However, in most research on robot lifting, "feasibility" is usually presumed to exist a priori. This paper proposes a three-step method for a humanoid robot to reason about the feasibility of lifting a heavy box with physical properties that are unknown to the robot. Since feasibility of lifting is directly related to the physical properties of the box, we first discretize a range for the unknown values of parameters describing these properties and tabulate all valid optimal quasi-static lifting trajectories generated by simulations over all combinations of indices. Second, a physical-interaction-based algorithm is introduced to identify the robust gripping position and physical parameters corresponding to the box. During this process, the stability and safety of the robot are ensured. On the basis of the above two steps, a third step of mapping operation is carried out to best match the estimated parameters to the indices in the table. The matched indices are then queried to determine whether a valid trajectory exists. If so, the lifting motion is feasible;otherwise, the robot decides that the task is beyond its capability. Our method efficiently evaluates the feasibility of a lifting task through simple interactions between the robot and the box, while simultaneously obtaining the desired safe and stable trajectory. We successfully demonstrated the proposed method using a NAO humanoid robot. Copyright © 2020, The Authors. All rights reserved.

关键词： Trajectories

Modeling the Neuromuscular Control System of an Octopus Arm

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arXiv 2022年

作者： Wang, Tixian Halder, Udit Gribkova, Ekaterina Gazzola, Mattia Mehta, Prashant G. Department of Mechanical Science and Engineering United States Coordinated Science Laboratory United States Neuroscience Program United States National Center for Supercomputing Applications United States Carl R. Woese Institute for Genomic Biology University of Illinois at Urbana-Champaign ChampaignIL61820 United States

The octopus arm is a neuromechanical system that involves a complex interplay between peripheral nervous system (PNS) and arm musculature. This makes the arm capable of carrying out rich maneuvers. In this paper, we build a model for the PNS and integrate it with a muscular soft octopus arm. The proposed neuromuscular architecture is used to qualitatively reproduce several biophysical observations in real octopuses, including curled rest shapes and target-directed arm reaching motions. Two control laws are proposed for target-oriented arm motions, and their performance is compared against a benchmark. Several analytical results, including rest-state characterization and stability properties of the proposed control laws, are provided. © 2022, CC BY-NC-ND.

关键词： Benchmarking

Impacts of Grid Frequency Variation on Dynamic Performance of DFIG Based Wind Turbine 5

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Impacts of Grid Frequency Variation on Dynamic Performance o...

5th International Symposium on Material, Mechatronics and Energy 2018, ISMME 2018

作者： Shiddiq Yunus, A.M. Energy Conversion Study Program Mechanical Engineering Department Politeknik Negeri Ujung Pandang Indonesia

Wind energy is one of popular sources of renewable energy that massively used to generate electric power nowadays. Among wind generator technologies, Doubly Fed Induction Generator (DFIG) is placed as the first dominant wind generator type that is installed worldwide since 2004. Its popularity is due to the advantages of its capability to extract more energy compare to the fixed speed type. Moreover, it uses only one-third converter size which reduced the total construction cost compared to its closest rival, Full Converter Wind Turbine Generator Type. Although DFIG widely installed worldwide, it is in fact, very sensitive to the grid disturbances such as frequency variation. Based on IEEE standard for 60 Hz system, a power system should not be allowed to work in less than 59.3 Hz or more than 60.5 Hz. In this paper, DFIG-grid connected is extensively simulated in the condition of frequency variation that is carried out using Matlab/Simulink. The results show that some important parameters such as power output of the generator, voltage at point of common coupling, voltage at DC link and generator speed are experiencing significant rise/drop which in turn might damage the wind turbine generator. © Published under licence by IOP Publishing Ltd.

关键词： Wind Turbine Generators

Deep potentials for materials science

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材料展望（英文）

材料展望（英文） 2022年第2期 89-115页

作者： Tongqi Wen Linfeng Zhang Han Wang Weinan E David J Srolovitz Department of Mechanical Engineering The University of Hong KongHong KongHong Kong Special Administrative Region of China DP Technology BeijingPeople's Republic of China AI for Science Institute BeijingPeople's Republic of China Laboratory of Computational Physics Institute of Applied Physics and Computational MathematicsBeijingPeople's Republic of China HEDPS CAPTCollege of EngineeringPeking UniversityBeijingPeople's Republic of China AI for Science Institute BeijingPeople's Republic of China School of Mathematical Sciences Peking UniversityBeijingPeople's Republic of China Department of Mathematics and Program in Applied and Computational Mathematics Princeton UniversityPrincetonNJUnited States of America Department of Mechanical Engineering The University of Hong KongHong KongHong Kong Special Administrative Region of China International Digital Economy Academy(IDEA) ShenzhenPeople's Republic of China

To fill the gap between accurate(and expensive)ab initio calculations and efficient atomistic simulations based on empirical interatomic potentials,a new class of descriptions of atomic interactions has emerged and been widely applied;*** learning potentials(MLPs).One recently developed type of MLP is the deep potential(DP)*** this review,we provide an introduction to DP methods in computational materials *** theory underlying the DP method is presented along with a step-by-step introduction to their development and *** also review materials applications of DPs in a wide range of materials *** DP Library provides a platform for the development of DPs and a database of extant *** discuss the accuracy and efficiency of DPs compared with ab initio methods and empirical potentials.

关键词： deep potential atomistic simulation machine learning potential neural network

Development of a Hand Exoskeleton System for Quantitative Analysis of Hand Functions

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Journal of Bionic engineering 2018年第5期15卷 783-794页

作者： Jeongsoo Lee Minhyuk Lee Joonbum Bae Bio-Robotics and Control (BiRC) Laboratory Department of Mechanical Engineering UNIST Ulsan Republic of Korea

This paper proposes a hand exoskeleton system for evaluating hand functions. To evaluate hand functions, the hand exoskeleton system must be able to pull each finger joint, measure the finger joint angle and exerted force on the finger simultaneously. The proposed device uses serially connected 4-bar linkage structures, which have two embedded actuators with encoders and two loadcells per finger, to move each phalanx independently and measure the finger joint angles. A modular design was used for the exoskeleton, to facilitate the removal of unnecessary modules in different experiments and improve convenience. Silicon was used on the surface of the worn part to reduce the skin irritation that results from prolonged usage. This part was also designed to be compatible with various finger thicknesses. Using the proposed hand exoskeleton system, finger independence, multi-finger synergy, and finger joint stiffness were determined in five healthy subjects. The finger movement and force data collected in the experiments were used for analyzing three hand functions based on the physical and physiological phenomena.

关键词： evaluation of hand function hand rehabilitation wearable system exoskeleton