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arXiv 2020年

作者： Yang, Wenchao Masroor, Emad Stremler, Mark A. Department of Mechanical and Materials Engineering Queen's University KingstonONK7L 3N6 Canada Engineering Mechanics Program Virginia Tech BlacksburgVA24061 United States Department of Biomedical Engineering and Mechanics Virginia Tech BlacksburgVA24061 United States

An inclined gravity-driven soap film channel was used to study the wake patterns formed behind a transversely oscillating cylinder at Re = 235 ± 14. The natural frequency of vortex shedding from a stationary cylinder, fSt, was used to identify the oscillation frequencies of interest. The (dimensionless) frequency, f∗= f/fSt, and amplitude, A∗= A/D, of the cylinder's motion was varied over a large portion of the fundamental synchronization region (i.e., for f∗≈ 1), and a 'map' of wake patterns was constructed in (f∗, A∗) space. Lock-on between the frequency of the cylinder's motion and the dominant frequency of the resulting vortex wake was observed for a large range of this parameter space, predominantly manifested as synchronized '2S' and '2P' wake modes. Synchronized 'P+S', '2T', and 'transitional' wakes were also found in smaller regions of parameter space. Unsynchronized 'coalescing' and 'perturbed von Kármán' wakes were observed as the oscillation frequency became sufficiently different from fSt. The wake patterns and vortex formation processes found in this study, particularly the 2P mode wakes, bear a strong resemblance to previous three-dimensional experimental results, despite the physical constraint from the soap film that limits three-dimensional effects in the wake. © 2020, CC BY-NC-ND.

关键词： Vortex flow

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Development of modeling framework for high-temperature heat pipes in micro reactors 18

Development of modeling framework for high-temperature heat ...

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18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2019

作者： Shi, Shanbin Liu, Yang Sabharwall, Piyush Department of Mechanical Aerospace and Nuclear Engineering Rensselaer Polytechnic Institute 110 8th Street TroyNY12180 United States Nuclear Engineering Program Department of Mechanical Engineering Virginia Tech 635 Price Fork Road BlacksburgVA24061 United States Idaho National Laboratory 2525 Fremont Ave Idaho FallsID83402 United States

Heat pipes as well as two-phase thermosyphons are highly efficient heat transfer devices utilizing continuous evaporation and condensation of a proper working fluid for two-phase heat transport in a closed system. Because of nearly isothermal and fully passive phase-change heat transfer mechanism, heat pipes and thermosyphons have found many applications in space technologies and other energy systems. High temperature heat pipes could potentially be used as a heat removal device from the primary system and be coupled with power conversion system or process heat application. In this study, a comprehensive one dimensional three-field model has been developed for analysis of high-temperature heat pipes in normal operation conditions and transients. The conservation or field equations of mass, momentum, and energy were presented for the liquid film, vapor, and droplet. In addition, constitutive equations or correlations were reviewed thoroughly for the closure of the three-field equations. Specific constitutive equations regarding interfacial mass and heat transfer at two interfaces, namely film-gas interface and gas-droplet interface, were reviewed for droplet entrainment and deposition rates as well as film and droplet evaporation rates. Additionally, mechanistic correlations of annular flow film thickness were recommended for the modeling of the thermosyphons without a wick as a critical constitutive correlation. Furthermore, experimental data needs from new experiments using a prototype working fluid for the model validation of high-temperature heat pipes in micro reactors were recommended for the future research. © 2019 American Nuclear Society. All rights reserved.

关键词： Liquid films

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A joint optimization approach of LiDAR-camera fusion for accurate dense 3D reconstructions

arXiv

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arXiv 2019年

作者： Zhen, Weikun Hu, Yaoyu Liu, Jingfeng Scherer, Sebastian Department of Mechanical Engineering Carnegie Mellon University Robotics Institute Carnegie Mellon University

Fusing data from LiDAR and camera is conceptually attractive because of their complementary properties. For instance, camera images are higher resolution and have colors, while LiDAR data provide more accurate range measurements and have a wider Field Of View (FOV). However, the sensor fusion problem remains challenging since it is difficult to find reliable correlations between data of very different characteristics (geometry vs. texture, sparse vs. dense). This paper proposes an offline LiDAR-camera fusion method to build dense, accurate 3D models. Specifically, our method jointly solves a bundle adjustment (BA) problem and a cloud registration problem to compute camera poses and the sensor extrinsic calibration. In experiments, we show that our method can achieve an averaged accuracy of 2.7mm and resolution of 70 points/cm2 by comparing to the ground truth data from a survey scanner. Furthermore, the extrinsic calibration result is discussed and shown to outperform the state-of-the-art method. Copyright © 2019, The Authors. All rights reserved.

关键词： Textures

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Agriculture 4.0 and its Barriers in the Agricultural Production Chain Development in Southern Brazil

SSRN

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SSRN 2022年

作者： Silveira, Franco da Silva, Sabrina Letícia Couto da Machado, Filipe Molinar Barbedo, Jayme Garcia Arnal Amaral, Fernando Gonçalves Graduate Program of Industrial Engineering Federal University of Rio Grande do Sul Av. Osvaldo Aranha 99 RS Porto Alegre90035-190 Brazil Federal Institute of Education Science Technology of Rio Grande do Sul Campus Porto Alegre RS Brazil Embrapa Agricultural Digital Av. André Tosello 209 - C.P. 6041 SP Campinas13083-886 Brazil Department of Mechanical Engineering Regional Integrated University of Alto Uruguay and the Missões Av. Universidade das Missões 464 RS Santo Ângelo98802-470 Brazil

Agriculture 4.0 can drive the growth of the agricultural production chain in emerging countries like Brazil, which is known as one of the primary food and meat producers worldwide, by implementing a range of advanced technologies such as Internet of Things (IoT), Artificial Intelligence (AI), Blockchain, and Machine Learning. However, the development of agriculture 4.0 in Brazil is a complex process, and little is known about the real barriers that impact its adoption among the actors of the agricultural production chain. There is a lack of empirical studies about the perception of Brazilian farmers regarding the barriers that may compromise the successful path of agriculture 4.0. This article aims to identify and validate the barriers that hinder the development of agriculture 4.0 in the agricultural production chain of Southern Brazil. Twenty-five barriers were chosen for validation based on a Systematic Review of the existing Literature. A confirmatory factor analysis was performed using the statistical tests of Kaiser-Meyer-Olkin and Bartlett . Validation was performed through the perception of farmers ( N = 347 ) distributed among the states of Rio Grande do Sul, Santa Catarina, and Paraná. The data were collected from an online questionnaire that identified the importance of the barriers for the farmers in the sample. The most frequent and important barriers mentioned by the farmers were: lack of infrastructure , lack of solutions accessible to farmers, need to foster R&D and innovative business models , age group risk , and lack of efficacy in the data on the rural environment. © 2022, The Authors. All rights reserved.

关键词： Digital storage

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Methods for Measuring the Just Noticeable Difference for Variable Stimuli: Implications for Perception of Metabolic Rate with Exoskeleton Assistance

Methods for Measuring the Just Noticeable Difference for Var...

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IEEE/RAS-EMBS International Conference on Biomedical robotics and Biomechatronics (BioRob)

作者： Roberto L. Medrano Gray C. Thomas Elliott Rouse Department of Mechanical Engineering Robotics Institute University of Michigan Ann Arbor MI USA Neurobionics Lab University of Michigan Ann Arbor MI USA Neurobionics and Locomotor Control Systems Labs University of Michigan

ISBN: (数字)9781728159072

ISBN: (纸本)9781728159089

The reduction of metabolic rate has become a pillar for quantifying the success of exoskeletons for performance augmentation, but how well can humans perceive these metabolic benefits? Measuring human perceptual ability in this context presents a unique challenge, since the stimulus of metabolic rate is not directly controllable. In this paper we introduce and compare two methods for addressing indirect stimuli: conventional method of constant stimuli (MOCS) with binning, and single presentation (SP). Both methods are based on a maximum likelihood estimation for a sigmoidal psychometric curve, under the assumption of a constant Weber fraction. Using Monte Carlo simulations, we conclude that while conventional MOCS with binning performs better for low actuation noise levels, single presentation strategies are better otherwise. We additionally present a pilot result for one subject using the single presentation strategy, which quantified the Just Noticeable Difference (JND) of changes to metabolic rate of 25.2 ± 23.2%.

关键词：

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Finite-time Frequency Estimator for Harmonic Signal

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IFAC-PapersOnLine 2020年第2期53卷 584-589页

作者： Alexey A. Bobtsov Anastasiia O. Vediakova Nikolay A. Nikolaev Olga V. Slita Anton A. Pyrkin Alexey A. Vedyakov Department of Control Systems and Robotics ITMO University Saint Petersburg Russia Laboratory “Control of Complex Systems” Institute of Problems of Mechanical Engineering V.O. Bolshoj pr. 61 St. Petersburg 199178 Russia Center for Technologies in Robotics and Mechatronics Components Innopolis University Innopolis Russia Department of Computer Applications and Systems Saint Petersburg State University Saint Petersburg Russia

This paper is devoted to a frequency estimation of a pure sinusoidal signal in finite-time. The parameterization is based on applying delay operators to a measurable signal. The result is the first-order linear regression model with one parameter, which depends on the signal frequency. The proposed method of finite-time estimation consists of two steps. On the first step, the standard gradient descent method is used to estimate the regression model parameter. On the next step using algebraic equations, finite-time frequency estimate is found. The described method does not require measuring or calculating derivatives of the input signal and uses one integrator for the gradient method and another one for the finite-time estimation. The efficiency of the proposed approach is demonstrated through the set of numerical simulations.

关键词： parameter estimation observers frequency estimation finite-time estimation

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Dynamic Research on Low-Frequency Vibration Isolation Tables

Research Square

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Research Square 2020年

作者： Jurevicius, Mindaugas Viselga, Gintas Turla, Vytautas Jurkonis, Eugenijus Tetsman, Ina Vilnius Gediminas Technical University Department of Mechanical and Materials Engineering Basanaviciaus 28 VilniusLT-03224 Lithuania Vilnius Gediminas Technical University Department of Mechatronics Robotics and Digital Manufacturing Basanaviciaus 28 VilniusLT-03224 Lithuania

In the paper, an establishment of dynamic characteristics of tabletops of the newly-developed optical tables is being discussed upon. Low-frequency vibration isolation systems are reviewed. Theoretical and experimental tests have been performed. Dynamic models of an optical table on a vibrating platform at different excitations have been developed, the dynamic displacement and the resonance frequencies of the system have been established and vibration transmissibility curves have been presented. The obtained dynamic characteristics of the mechanical passive low-frequency vibration isolation system show that such a system is able to isolate the vibrations effectively. The results of the performed experimental tests confirm the data of the theoretical research. © 2020, CC BY.

关键词： Stiffness

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Carbon footprint of coffee production: the case study of Indian Robusta coffee

Energy Nexus

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Energy Nexus 2025年 18卷

作者： Sandra P. Iglesias Paraskevi Karka John A. Posada Ralph E.F. Lindeboom Machteld van den Broek Girigan Gopi Manju Mathew TD John Vipin Champatan P.V. Aravind Energy Conversion Group Energy and Sustainability Research Institute Groningen Faculty of Science and Engineering University of Groningen Nijenborgh 6 9747AG Groningen the Netherlands Engineering and Technology Institute Groningen Faculty of Science and Engineering University of Groningen Nijenborgh 3 9747AG Groningen the Netherlands Department of Biotechnology Delft University of Technology Building 58 Van der Maasweg 9 2629 HZ Delft the Netherlands Universidad ECCI Postgraduate Department Bogotá 111311 Colombia CITG Section Sanitary Engineering Department of Water Management Faculty of Civil Engineering and Geosciences Delft Stevinweg 1 2628 CN Delft the Netherlands Delft University of Technology Faculty of Technology Policy and Management Jaffalaan 5 2628 BX Delft the Netherlands MS Swaminathan Research Foundation Climate Smart Coffee Program- KDISC Mechanical Engineering Dept Govt. Engg. College Wayanad Kerala India

Coffee processing encompasses the conversion of coffee cherries into marketable products, including the removal of outer layers to produce green coffee and, in extended chains, their roasting into roasted coffee, and grinding into ground coffee. Calculating the carbon footprint (CF) in coffee processing is crucial for identifying and mitigating key sources of greenhouse gas (GHG) emissions. Utilizing the Life Cycle Assessment (LCA) methodology, the current study quantifies the CF associated with Robusta dry coffee processing by collecting primary data through interviews with coffee producers and visits to coffee processing units, roasting, and grinding facilities in Wayanad, India. The study identifies GHG emission hotspots across two scenarios. Scenario A includes transportation of dried coffee beans from farm to coffee processing unit, green coffee production, packaging, roasting, and grinding at a local unit, while Scenario B covers local transportation of green coffee beans from India to The Netherlands, green coffee production, packaging, and its transportation from India to The Netherlands. Cultivation and harvesting of coffee cherries, consumer-level preparation and use, and disposal of coffee products are outside the scope of this study. The functional unit is defined as 1 kg of green coffee for both scenarios. Findings show that the CF equals 0.62 and 0.38 kg CO 2eq per kg of green coffee for scenarios A and B, respectively. Roasting (78 % of CF), and sea transportation (66 % of CF) emerged as the main hotspots of GHG emissions for scenario A, and scenario B, respectively.

关键词： Carbon footprint LCA Robusta coffee Green coffee Roasted coffee Ground coffee

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A Variable Stiffness Soft Continuum Robot Based on Pre-charged Air, Particle Jamming, and Origami

A Variable Stiffness Soft Continuum Robot Based on Pre-charg...

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IEEE International Conference on robotics and Automation (ICRA)

作者： Yujia Li Tao Ren Yonghua Chen Michael Z. Q. Chen School of Mechatronic Engineering Southwest Petroleum University Chengdu China Robotics Research Center Xihua University Chengdu China Department of Mechanical Engineering The University of Hong Kong Pok Fu Lam Hong Kong School of Automation Nanjing University of Science and Technology Nanjing China

ISBN: (数字)9781728173955

ISBN: (纸本)9781728173962

Soft continuum robots have many applications such as medical surgeries, service industries, rescue tasks, and underwater exploration. Flexibility and good accessibility of such robots are the key reasons for their popularity. However, the complexity of their structural design and control systems limit their broader applications. In this paper, a novel variable stiffness soft continuum robot based on pre-charged air, particle jamming, and origami is proposed. The robot is a bellow-like origami structure with internal chambers. A spine-like chamber is filled with particles, and three identical chambers surrounding the spine chamber are filled with pressurized air. When the origami structure is compressed, the particles are jammed by the compression force and the increased pressure of the three air chambers, thus increasing the overall stiffness of the robot. The robot expansion-contraction and bending are controlled by three tendons. An analytical model of the proposed stiffness variation mechanism has been developed. The effects of various parameters on the lateral and axial stiffness of the soft continuum robot have been investigated by experimental studies. A prototype robot has been fabricated to demonstrate grasping operations.

关键词： Robots Jamming Force Tendons Electron tubes Wires Valves

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Real-time liquid pouring motion generation: End-to-end sensorimotor coordination for unknown liquid dynamics trained with deep neural networks

Real-time liquid pouring motion generation: End-to-end senso...

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2019 IEEE International Conference on robotics and Biomimetics, ROBIO 2019

作者： Saito, Namiko Dai, Nguyen Ba Ogata, Tetsuya Mori, Hiroki Sugano, Shigeki Waseda University Department of Modern Mechanical Engineering Tokyo Japan Waseda University National Institute of Advanced Industrial Science and Technology Department of Intermedia Art and Science Tokyo Japan Waseda University Future Robotics Organization Tokyo Japan

ISBN: (纸本)9781728163215

We propose a sensorimotor dynamical system model for pouring unknown liquids. With our system, a robot holds and shakes a bottle to estimate the characteristics of the contained liquid, such as viscosity and fill level, without calculating to determine their parameters. Next, the robot pours a specified amount of the liquid into another container. The system needs to integrate information on the robot's actions, the liquids, the container, and the surrounding environment to perform the estimation and execute a continuous pouring motion using the same model. We use deep neural networks (DNN) to construct the system. The DNN model repeats prediction and execution of the actions to be taken in the next time step based on the input sensorimotor data, including camera images, force sensor data, and joint angles. At the same time, the DNN model acquires liquid characteristics in the internal state. We confirmed that the DNN model can control the robot to pour a desired amount of liquid with unknown viscosity and fill level. © 2019 IEEE.

关键词： Liquids

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