检索结果-内蒙古大学图书馆

Alternative method for assessing the effectiveness of heat exchangers

Measurement: Sensors 2021年 18卷

作者： Mauricio N. Frota Edgardo R. Castro-Pacheco José Daniel Hernández-Vásquez Rui Pitanga Marques da Silva Pontifical Catholic University of Rio de Janeiro Metrology Programme Brazil Universidad Antonio Nariño FIMEB Mechanical Engineering Program Colombia Mechanical Engineering Department Centro Federal de Educação Rio de Janeiro Brazil

This article discusses an automated system for monitoring the thermal effectiveness of hydrogenerator heat exchangers (water-air). The proposed calculation methodology eliminates the need to measure the outlet air temperature (the heat exchanger hot working fluid) and allows for continuous monitoring of the exchanger even during online cleaning interventions not requiring interruption of the generation. A computational code is proposed to solve the non-linear equations governing the mechanisms of heat transfer between the working fluids. The technique was validated based on analysis of the uncertainties associated with measurements performed over an 11-month monitoring period. The results of the study reveal that the conventional method, which does require measurement of the outlet air temperature, can introduce errors of the order of 30% in the calculation of the exchanger effectiveness. The suggested procedure proved to be an effective tool for managing the cooling system of hydrogenerators.

关键词： Heat exchanger effectiveness Hydrogenerator Measurement uncertainty

来源：评论

学校读者我要写书评

暂无评论

Energy Shaping Control of a CyberOctopus Soft Arm

arXiv

引用

arXiv 2020年

作者： Chang, Heng-Sheng Halder, Udit Shih, Chia-Hsien Tekinalp, Arman Parthasarathy, Tejaswin Gribkova, Ekaterina Chowdhary, Girish Gillette, Rhanor Gazzola, Mattia Mehta, Prashant G. Department of Mechanical Science and Engineering Coordinated Science Laboratory United States Neuroscience Program United States Department of Agricultural and Biological Engineering United States Department of Molecular and Integrative Physiology United States National Center for Supercomputing Applications United States Carl R. Woese Institute for Genomic Biology University of Illinois Urbana-Champaign United States

This paper entails the application of the energy shaping methodology to control a flexible, elastic Cosserat rod model. Recent interest in such continuum models stems from applications in soft robotics, and from the growing recognition of the role of mechanics and embodiment in biological control strategies: octopuses are often regarded as iconic examples of this interplay. The dynamics of the Cosserat rod, here modeling a single octopus arm, are treated as a Hamiltonian system and the internal muscle actuators are modeled as distributed forces and couples. The proposed energy shaping control design procedure involves two steps: (1) a potential energy is designed such that its minimizer is the desired equilibrium configuration;(2) an energy shaping control law is implemented to reach the desired equilibrium. By interpreting the controlled Hamiltonian as a Lyapunov function, asymptotic stability of the equilibrium configuration is deduced. The energy shaping control law is shown to require only the deformations of the equilibrium configuration. A forward-backward algorithm is proposed to compute these deformations in an online iterative manner. The overall control design methodology is implemented and demonstrated in a dynamic simulation environment. Results of several bio-inspired numerical experiments involving the control of octopus arms are reported. Copyright © 2020, The Authors. All rights reserved.

关键词： Lyapunov functions

来源：评论

学校读者我要写书评

暂无评论

Suitability of type-II fiber Bragg gratings in silica optical fiber for temperature sensing in treat 11

Suitability of type-II fiber Bragg gratings in silica optica...

引用

11th Nuclear Plant Instrumentation, Control, and Human-Machine Interface Technologies, NPIC and HMIT 2019

作者： McCary, Kelly M. Wilson, Brandon A. Birri, Anthony H. Blue, Thomas E. Petrie, Christian Department of Mechanical and Aerospace Engineering Nuclear Engineering Program Ohio State University 201 W. 19th Ave ColumbusOH43210 United States Oak Ridge National Laboratory P.O. Box 2008 Oak RidgeTN37831 United States

ISBN: (纸本)9780894487835

Optical fibers provide a variety of options for instrumentation in reactor environments. Optical fibers can be used to measure multiple physical phenomena including, temperature, strain, pressure, and fluid level. In addition to the various sensing applications, optical fibers are immune to electromagnetic interference, have a small footprint (~100 µm), and a fast response. The department of Energy and Idaho National Laboratory have considered optical fibers for use as in-pile instrumentation in the Transient Reactor Test Facility (TREAT). TREAT was designed to test reactor fuels under accident conditions by replicating accident conditions for a variety of reactor transients, such as those associated with a loss of coolant accident (LOCA). This work investigates silica fiber optic temperature sensors with inscribed type-II fiber Bragg gratings (FBGs) under conditions similar to those that would be experienced in a TREAT transient. Separate effects testing was used to test the sensors under high-temperature step transients and under irradiation up to a total fluence similar to that of TREAT. Specifically, this work investigates distributed temperature measurements, using the Optical Frequency Domain Reflectometry (OFDR) sensing technique, using a Luna Innovations Optical Backscatter Reflectometer (OBR) 4600, with silica optical fibers inscribed with type-II fiber Bragg gratings (FBGs). In conclusion, separate effects testing of type-II FBGs in silica optical fiber, to high temperature and to neutron fluences that are an order of magnitude larger than fluences that are anticipated for TREAT tests, demonstrate that type-II FBGs in silica optical fiber hold great promise for high-temperature reactor instrumentation in TREAT. © 2018 Westinghouse Electric Company LLC All Rights Reserved

关键词： Fiber Bragg gratings

来源：评论

学校读者我要写书评

暂无评论

Rationally designed chimeric solid-binding peptides for tailoring solid interfaces

引用

Medical Devices and Sensors 2020年第3期3卷

作者： Yucesoy, Deniz T. Khatayevich, Dimitry Tamerler, Candan Sarikaya, Mehmet GEMSEC Genetically Engineered Materials Science and Engineering Center University of Washington SeattleWA United States Department of Materials Science and Engineering University of Washington SeattleWA United States Department of Mechanical Engineering Bioengineering Program Institute for Bioengineering Research University of Kansas Lawrence LawrenceKS United States Department of Chemical Engineering University of Washington SeattleWA United States Department of Oral Health Sciences University of Washington SeattleWA United States Impossible Foods Redwood CityCA United States

Joining biology with materials science requires the ability to design, engineer and control biology/solid-state materials interfaces at the molecular level. The specific molecular interactions that take place among biomolecules, known as molecular recognition, enable all aspects of molecular processes in living systems prerequisite to the biological functions. Having the ability to establish specific biological interactions between the solid materials and biological constituents is essential for precise design of biologically viable soft interfaces that are molecularly tailored at solid surfaces. Solid-binding peptides offer excellent opportunities in surface biofunctionalization over the traditionally utilized chemical approaches which generally make use of covalent bonds for surface molecular attachments with limited flexibility. Solid-binding peptides are selected using directed evolution techniques using genotype to phenotype relationships and therefore referred also as genetically engineered peptides for inorganics (GEPI) and exclusively bind to solid materials using molecular recognition. Here, the peptide has weak interactions at multiple contact points that are established between the biomolecule and the solid lattice, and then folds into a conformation coherent with the underlying solid lattice through self-organization on the surface. Solid-binding peptides provide an unprecedented biological advantage as modular building blocks to couple biological and synthetic entities at the bio–solid interfaces. Taking full advantage of biology's versatility, they can easily be engineered to form chimeric molecules with inherent multifunctionality displaying biofunctional molecular entities, such as enzymes, co-factors, antimicrobial peptides, antibodies, nucleic acids and molecular probes that target biomarkers. This minireview provides an insight into the key principles of solid-binding peptides for advancing surfaces biofunctionalization by a selected set of exampl

关键词： Biomolecules

来源：评论

学校读者我要写书评

暂无评论

Inter-laboratory and inter-operator reproducibility in gait analysis measurements in pediatric subjects

引用

International Biomechanics 2019年第1期6卷 19-33页

作者： Scalona, Emilia Di Marco, Roberto Castelli, Enrico Desloovere, Kaat Van Der Krogt, Marjolein Cappa, Paolo Rossi, Stefano Department of Mechanical and Aerospace Engineering (DIMA) “Sapienza” University of Rome Rome Italy Laboratory of Movement Analysis and Robotics (MARlab) “Bambino Gesù” Children Hospital Passoscuro Fiumicuno (RM) Italy KU Leuven Department of Rehabilitation Sciences Laboratory for Clinical Motion Analysis University Hospital Leuven Pellenberg Belgium Department of Rehabilitation Medicine VU University Medical Center Amsterdam Movement Sciences Amsterdam Netherlands Department of Economics Engineering Society and Business Organization (DEIM) University of Tuscia Viterbo Italy

The intra-subject, the inter-operator, and the inter-laboratory variabilities are the main sources of uncertainties in gait analysis, and their effects have been partially described in the literature for adult populations. This study aimed to extend the repeatability and reproducibility analysis to a pediatric population, accounting for the effects induced by the intra-subject variations, the measurement setup, the marker set configuration, and the involved operators in placing markers and EMG electrodes. We evaluated kinematic, kinetic and EMG outputs collected from gait analyses performed on two healthy children in two laboratories, by two operators, and with two marker placement protocols. The two involved centers previously defined a common acquisition procedure based on their routine pipelines. The similarity of kinematic, kinetic, and EMG curves were evaluated by means of the coefficients of the Linear Fit Method, and the Mean Absolute Variability with and without the offset among curves. The inter-operator variability was found to be the main contribution to the overall reproducibility of kinematic and kinetic gait data. On the contrary, the main contribution to the variability of the EMG signals was the intra-subject repeatability that is due to the physiological stride to stride muscle activation variability. © 2019, © 2019 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.

关键词： electromyography Gait analysis inter-laboratory reproducibility inter-operator reproducibility intra-subject repeatability pediatric subjects

来源：评论

学校读者我要写书评

暂无评论

Optimal Tuning of Cascade Controllers for Feed Drive Systems using Particle Swarm Optimization

Optimal Tuning of Cascade Controllers for Feed Drive Systems...

引用

IEEE International Conference on Industrial Informatics (INDIN)

作者： Milica Petrović Alberto Villalonga Zoran Miljković Fernando Castaño Stanisław Strzelczak Rodolfo Haber Department of Production Engineering University of Belgrade Faculty of Mechanical Engineering Belgrade Serbia Centre for Automation and Robotics UPM-CSIC Madrid Spain University of Technology Warsaw Poland

Cascade control configurations are one of the widely used control solutions for improving dynamic response of the feed drive systems in the manufacturing industry. However, optimal tuning of cascade controllers in presence of hard nonlinearities such as backlash and friction is still a complex and time-consuming task. This paper presents a computational procedure for tuning P-PI cascade controller by using particle swarm optimization (PSO) for a feed drive system of machine tools in the presence of friction and backlash. The minimizing of the maximum position error during the reversal of the axes is used as an objective function for optimization. The performance of the PSO method is compared in simulations and real-time experiments with the fine tune (FT) method, which is one of the standard methods applied in industry. Both, simulation and real-time experimental studies carried out on a test platform with 8070 Fagor controller show a remarkable improvement in the performance of the cascade control system using the proposed PSO-based strategy.

关键词：

来源：评论

学校读者我要写书评

暂无评论

Consistent approximation of optimal control problems using Bernstein polynomials

Consistent approximation of optimal control problems using B...

引用

IEEE Annual Conference on Decision and Control

作者： Venanzio Cichella Isaac Kaminer Claire Walton Naira Hovakimyan Antonio M. Pascoal Department of Mechanical Engineering University of Iowa Iowa City IA Department of Mechanical and Aerospace Engineering Naval Postgraduate School Monterey CA Department of Mechanical Science and Engineering University of Illinois at Urbana-Champaign Urbana IL Institute for Systems and Robotics (ISR) Instituto Superior Tecnico (IST) Univ. Lisbon Portugal

ISBN: (数字)9781728113982

ISBN: (纸本)9781728113999

We present a direct method for the solution of nonlinear optimal control problems based on Bernstein polynomial approximations. We show, using a rigorous setting, that the proposed method yields consistent approximations of time continuous optimal control problems. We demonstrate that the method can also be used for the estimation of optimal control problems costates. This result leads to the formulation of the Covector Mapping Theorem for Bernstein polynomial approximation. Finally, we exploit the numerical and geometric properties of Bernstein polynomials, and illustrate the advantages of the method through numerical examples.

关键词： Optimal control Convergence Approximation methods Optimization Robots Conferences Estimation

来源：评论

学校读者我要写书评

暂无评论

High-entropy boride-carbide two-phase ultrahigh temperature ceramics fabricated by reactive spark plasma sintering

arXiv

引用

arXiv 2020年

作者： Qin, Mingde Gild, Joshua Hu, Chongze Wang, Haoren Bin Hoque, Md Shafkat Braun, Jeffrey L. Harrington, Tyler J. Hopkins, Patrick E. Vecchio, Kenneth S. Luo, Jian Program of Materials Science and Engineering University of California San Diego La JollaCA92093 United States Department of NanoEngineering University of California San Diego La JollaCA92093 United States Department of Mechanical and Aerospace Engineering University of Virginia CharlottesvilleVA22904 United States Department of Materials Science and Engineering University of Virginia CharlottesvilleVA22904 United States Department of Physics University of Virginia CharlottesvilleVA22904 United States

A series of high-entropy boride-carbide two-phase ultrahigh temperature ceramics (UHTCs) are fabricated via a novel reactive spark plasma sintering (SPS) based route, each from five individual commercial powders, including N metal diborides and (5 − N) metal carbides, of equimolar amounts. Greater than ~99% of the theoretical densities have been achieved with virtually no native oxides. These two-phase UHTCs consist of a hexagonal high-entropy boride (HEB) phase and a cubic high-entropy carbide (HEC) phase, where a chemical equilibrium between the two phases that drive them away from equimolar compositions. A thermodynamic relation that governs the compositions of the HEB and HEC phases in equilibrium is discovered and a thermodynamic model is proposed. These two-phase high-entropy UHTCs exhibit tunable grain size (4.2-11.4 μm), Vickers’ microhardness (23-27 GPa), Young’s modulus (462-525 GPa), shear modulus (193-232 GPa), and thermal conductivity (13.2-26.2 Wm-1K-1). A new observation is that the high-entropy two-phase UHTCs have higher hardness than the weighted linear average of the two single-phase HEB and HEC, which are already harder than the rule-of-mixture (RoM) averages of individual UHTCs. Several intriguing observations about the moduli are revealed with accurate acoustic waves measurements. On the one hand, the Young’s moduli of high-entropy two-phase UHTCs are always higher than the theoretical RoM averages. On the other hand, the shear modulus of HEC is higher, but that of HEB is lower, than the theoretical RoM average. The latter unexpected observation is explained by the unique layered structure of the HEB, where an expansion in lattice parameter c is confirmed by X-ray diffraction. This study extends the state of the art by introducing two-phase high-entropy ceramics, which provide a new platform to tailor various properties via changing the phase fraction and microstructure. Copyright © 2020, The Authors. All rights reserved.

关键词： Entropy

来源：评论

学校读者我要写书评

暂无评论

Determination of feasible sites for wind farm using WAsP in Uttaradit, Thailand

引用

IOP Conference Series: Materials Science and engineering 2021年第1期1163卷

作者： T Khan J Taweekun T Theppaya Energy Technology Program Faculty of Engineering Prince of Songkla University Hat Yai Songkhla 90112 Thailand. Department of Mechanical and Mechatronics Engineering Faculty of Engineering Prince of Songkla University Hat Yai Songkhla 90112 Thailand.

Electricity production from the wind plays the potential role to reduce conventional way of electricity generation to reduce the negative impacts on the environment. In this study the data is collected from Uttaradit, the northern province of Thailand. The calculation in this study is based on ten-minutes interval data at 10 m observed during the year 2017-2019 by Thai meteorological department. Weibull distribution is applied to extract the monthly and yearly wind in the selected area by using wind atlas analysis and application program (WAsP). Moreover, in WAsP a stimulation was created to observe the comparison of potential of wind energy between three windiest sites located in the study area. The results generated show that the mean wind speed is 2.35m/s and the gradient wind direction from north and south are quite distinct. The annual energy production calculation of three sites in Uttaradit by WAsP estimates about 2125.815MWh, 3379.621MWh and 3369.235MWh respectively by using Bonus 300kW Mk III wind turbine. This paper suggests and supports the suitable sites and wind turbine for the electricity generation in Uttaradit. Hence, it will not only reduce the stress on conventional methods but also create awareness regarding the potential of wind energy.

关键词：

来源：评论

学校读者我要写书评

暂无评论

The effects of camshaft modification on engine performance in automatic transmission motorcycle

引用

AIP Conference Proceedings 2021年第1期2403卷

作者： Rinasa Agistya Anugrah Akmal Irfan Majid 1Department of Mechanical Technology Faculty of Vocational Program Universitas Muhammadiyah Yogyakarta Indonesia 2Department of Mechanical and Industrial Engineering Faculty of Engineering Universitas Gadjah Mada Indonesia 3Centre for Energy Studies Universitas Gadjah Mada Indonesia

Automatic transmission motorcycles have become a popular transportation choice in many countries. One of the methods to improve engine performance is by modifying the camshaft. In this report, we characterized the engine performance (power and torque) after modifying the camshaft’s Lobe Separation Angle (LSA). The valve opening duration and the overlapping process became the main variables to be adjusted. The experiments used a 4-strokes engine with SOHC (Single Over Head Camshaft) taken from an automatic transmission motorcycle with 110 cc type. The actual engine capacity was 108 cc (with a bore of 50 mm and stroke of 55 mm), and the compression ratio was 9.2:1. This engine has a maximum torque of 13.28 Nm and a power of 9.1 HP (at 5393 RPM). To evaluate engine power and torque for both compared camshafts, a dynamometer was used. From this study, we can conclude that LSA plays a vital role in determining valve timing diagrams, thus influences engine performance. Power and torque curve peaks of the modified camshafts are obtained at a lower speed than that of the standard camshafts.

关键词：

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：