检索结果-内蒙古大学图书馆

On the comparison of three numerical methods applied to building simulation: Finite-differences, RC circuit approximation and a spectral method

引用

建筑模拟（英文版） 2020年第1期13卷 1-18页

作者： Julien Berger Suelen Gasparin Denys Dutykh Nathan Mendes Univ. Grenoble Alpes Univ. Savoie Mont Blanc CNRS LOCIE 73000 Chambéry France Univ. Grenoble Alpes Univ. Savoie Mont Blanc CNRS LAMA 73000 Chambéry France Thermal Systems Laboratory Mechanical Engineering Graduate Program Pontifical Catholic University of Paraná Rua Imaculada Concei??o 1155 CEP : 80215-901 Curitiba - Paraná Brazi

Predictions of physical phenomena in buildings are carried out by using physical models formulated as a mathematical problem and solved by means of numerical methods, aiming at evaluating, for instance, the building thermal or hygrothermal performance by calculating distributions and fluxes of heat and moisture transfer. Therefore, the choice of the numerical method is crucial since it is a compromise among (i) the solution accuracy, (ii) the computational cost to obtain the solution and (iii) the complexity of the method implementation. An efficient numerical method enables to compute an accurate solution with a minimum computational run time (CPU). On that account, this article brings an investigation on the performance of three numerical methods. The first one is the standard and widely used finite-difference approach, while the second one is the so-called RC approach, which is a particular method brought to the building physics area by means of an analogy of electric circuits. The third numerical method is the spectral one, which has been recently proposed to solve nonlinear diffusive problems in building physics. The three methods are evaluated in terms of accuracy on the assessment of the dependent variable (temperature or vapor pressure) or of density of fluxes for three different cases: (i) heat diffusion through a concrete slab, (ii) moisture diffusion through an aerated concrete slab and (iii) heat diffusion using measured temperatures as boundary conditions. Results highlight the spectral approach as the most accurate method. The RC based model with a few number of resistances does not provide accurate results for temperature and vapor pressure distributions neither to flux densities nor conduction loads.

关键词： heat transfer moisture transfer numerical methods finite differences thermal circuit model spectral method

来源：评论

学校读者我要写书评

暂无评论

Citizen science in environmental and ecological sciences

NATURE REVIEWS METHODS PRIMERS

引用

NATURE REVIEWS METHODS PRIMERS 2022年第1期2卷 1-20页

作者： Morneau, Dominique Novel Data Ecosystems for Sustainability Research Group Advancing Systems Analysis Program International Institute for Applied Systems Analysis (IIASA) Laxenburg Austria Centre d’écologie et des sciences de la conservation Muséum national d’Histoire naturelle Paris France Faculté de droit Université de Namur Namur Belgium Citizen Science Lab Leiden University Leiden Netherlands Department of Mechanical Engineering University of Bath Bath UK Nordic Foundation for Development and Ecology (NORDECO) Copenhagen Denmark Department of Biology Brandeis University Waltham MA USA Ornamental Plant Pathology Department of Plant Pathology Puyallup Research and Extension Center Washington State University Puyallup WA USA Environmental and Sustainability Participatory Information Systems Group Institute of Marine Sciences (ICM-CSIC) Barcelona Spain Electron Microscopy Science Technology Platform The Francis Crick Institute London UK Departamento de Biologia Marina Facultad Ciencias del Mar Universidad Católica del Norte Coquimbo Chile Millennium Nucleus Ecology and Sustainable Management of Oceanic Island (ESMOI) Coquimbo Chile Centro de Estudios Avanzados en Zonas Áridas (CEAZA) Coquimbo Chile Department of Geography University College London (UCL) London UK

This PrimeView highlights the utility of citizen science across a range of ecological and environmental science research.

关键词：

来源：评论

学校读者我要写书评

暂无评论

Interactions of velocity structures between large and small scales in microelectrokinetic turbulence

引用

Physical Review Fluids 2021年第7期6卷 074610-074610页

作者： Wei Zhao Weidong Su Guiren Wang State Key Laboratory of Photon-Technology in Western China Energy International Scientific and Technological Cooperation Base of Photoelectric Technology and Functional Materials and Application Institute of Photonics and Photon-technology Northwest University Xi’an 710127 China State Key Laboratory for Turbulence and Complex Systems College of Engineering Peking University Beijing China 100871 Department of Mechanical Engineering & Biomedical Engineering Program University of South Carolina Columbia South Carolina 29208 USA

Recent investigations on electrokinetic (EK) flows have indicated turbulentlike flow can be realized by applying strong and high frequency ac electric field to flows with high-conductivity-gradient interface, even though under low bulk flow Reynolds number. Relative to conventionally hydrodynamic turbulence in a high Reynolds number, the ac EK turbulent flow exhibits high randomness with stronger intermittency [Wang et al., Phys. Rev. E 93, 013106 (2016)]. The abnormally high intermittency could be attributed to the ascending probability density function of velocity gradients (dominated by small scale velocity structure function) far from the equilibrium state. By evaluating the intermittency of the ac EK turbulent flow with hierarchical structures, we astonishingly find the intermittency factor of hierarchical structures in SL94 law, i.e., β factor, which is commonly believed to be between 0 and 1, exhibits larger value than 1 in the ac EK turbulent flow. This result indicates the different hierarchical relations of flow structures in ac EK turbulence flow from that in the conventional hydrodynamic turbulence, as further illustrated by the probability density function of velocity structures among different spatial scales.

关键词： Electrokinetic flows Microfluidics Turbulence

来源：评论

学校读者我要写书评

暂无评论

Feasibility study of novel magnetic compaction force assisted additive manufacturing (MCFA-AM) methodology for continuous carbon fiber reinforced polymer (C-CFRP) composites

Feasibility study of novel magnetic compaction force assiste...

引用

SAMPE 2019 Conference and Exhibition

作者： Ranabhat, Bikash Kirmse, Sebastian Hsiao, Kaung-Ting University of South Alabama Department of Mechanical Engineering 150 Jaguar Drive Shelby Hall Suite 3130 MobileAL36608 United States Department of Mechanical Engineering United States Systems Engineering Program United States

ISBN: (纸本)9781934551301

Composite parts manufactured by the current additive manufacturing (AM) methods are inferior in strength and stiffness compared to traditional composite manufacturing. Major issues include voids, physical gaps at layer/layer interface, and low reinforcing fiber content. This paper experimentally examined the feasibility of a patent-pending novel method, Magnetic Compaction Force Assisted-Additive Manufacturing (MCFA-AM), that utilized a magnetic compaction force to print and support curve-shaped continuous carbon fiber reinforced polymer (C-CFRP) composites in free space without any mold. C-CFRP prepreg tapes were fed through a magnet-assisted roller-like-setting, which was a part of the 3D printing head, and consolidated with a magnetic compaction pressure of 0.21 MPa in this feasibility trial. Short beam shear tests (ASTM D2344) showed that the 0.21 MPa MCFA-AM samples’ interlaminar shear strength (ILSS) was 8 % and 9 % stronger and 7% weaker compared with the C-CFRP samples manufactured by the hand layup, the Tension-Tape-Placement-Without Compaction-AM, and the Out-Of-Autoclave Vacuum-Bag-Only (OOA-VBO) methods, respectively. Microscopic observations showed the size and number of voids were significantly reduced by the magnetic compaction. Finally, it demonstrated that printing stiff, strong, and complex shaped C-CFRP parts with great freedom can be done within a few minutes with this exciting AM-Composites technology advance. Copyright 2019 by Bikash Ranabhat et al. Published by Society for the Advancement of Material and Process engineering with permission.

关键词： 3D printers

来源：评论

学校读者我要写书评

暂无评论

Development of Real-time Assembly Work Monitoring System Based on 3D Skeletal Model of Arms and Fingers

Development of Real-time Assembly Work Monitoring System Bas...

引用

IEEE International Conference on systems, Man and Cybernetics

作者： Taichi Obinata Hiroaki Kawamoto Yoshiyuki Sankai Master’s Program in Intelligent and Mechanical Interaction Systems Univetsity of Tsukuba Ibaraki Japan Faculty of Engineering Information and Systems Center for Cybernics Research University of Tsukuba Ibaraki Japan

ISBN: (数字)9781728185262

ISBN: (纸本)9781728185279

Decreasing birth rates and an aging population in society often cause labor shortages in the manufacturing industry, making the development of methods to improve productivity based on limited human resources imperative. One way to achieve this is by enhancing product quality via the reduction of product losses and the consequent need for reassembly due to human error. Human error during assembly can arise from specific actions via the arms and fingers. We assumed that these errors can be captured based on the information on human skeletal models. The purpose of this study is to propose and develop a system that acquires information about assembly procedures by using human skeletal models, including the fingers of workers, and notifies them of skipped procedures and errors in part types. Further, we confirm the basic capability of the proposed system via experiments based on simulated assembly work. The proposed system monitors workers' motion based on color and depth images captured by a single RGB-D camera. In addition, we developed a function to detect the process and to point out errors with audible and visual feedbacks when errors were made by workers in assembly processes. In the experiment using simulated assembly work, the proposed system exhibited an accuracy rate of 98.3% with respect to acquisition of assembly processes. In the case of an error in an assembly process, the system was able to point out the error correctly and provide feedback to the worker before he had finished picking up the wrong part. In conclusion, we confirmed that the developed system exhibited the basic capability to acquire work procedures and efficiently point out errors in real time.

关键词： Productivity Visualization Three-dimensional displays Fingers Real-time systems Statistics Monitoring

来源：评论

学校读者我要写书评

暂无评论

Lightweight equivariant model for efficient machine learning interatomic potentials

arXiv

引用

arXiv 2023年

作者： Yang, Ziduo Wang, Xian Li, Yifan Lv, Qiujie Chen, Calvin Yu-Chian Shen, Lei Department of Mechanical Engineering National University of Singapore Singapore117575 Singapore Artificial Intelligence Medical Research Center School of Intelligent Systems Engineering Shenzhen Campus of Sun Yat-sen University Shenzhen518107 China Department of Physics National University of Singapore Singapore117551 Singapore -Preferred Program School of Electronic and Computer Engineering Peking University Shenzhen Graduate School Shenzhen518055 China State Key Laboratory of Chemical Oncogenomics School of Chemical Biology and Biotechnology Peking University Shenzhen Graduate School Shenzhen518055 China Guangdong L-Med Biotechnology Co. Ltd Guangdong Meizhou514699 China Research Institute Chongqing401123 China

In modern computational materials science, deep learning has shown the capability to predict interatomic potentials, thereby supporting and accelerating conventional simulations. However, existing models typically sacrifice either accuracy or efficiency. Moreover, lightweight models are highly demanded for offering simulating systems on a considerably larger scale at reduced computational costs. Here, we introduce a lightweight equivariant interaction graph neural network (LEIGNN) that can enable accurate and efficient interatomic potential and force predictions for molecules and crystals. Rather than relying on higher-order representations, LEIGNN employs a scalar-vector dual representation to encode equivariant features. By learning geometric symmetry information, our model remains lightweight while ensuring prediction accuracy and robustness through the equivariance. Our results show that LEIGNN consistently outperforms the prediction performance of the representative baselines and achieves significant efficiency across diverse datasets, which include catalysts, molecules, and organic isomers. Furthermore, we conduct molecular dynamics (MD) simulations using the LEIGNN force field across solid, liquid, and gas systems. It is found that LEIGNN can achieve the accuracy of ab initio MD across all examined systems. Copyright © 2023, The Authors. All rights reserved.

关键词： Prediction models

来源：评论

学校读者我要写书评

暂无评论

ARCSnake: Reconfigurable snake-like robot with Archimedean screw propulsion for multi-domain mobility

arXiv

引用

arXiv 2021年

作者： Richter, Florian Gavrilov, Peter V. Lam, Hoi Man Degani, Amir Yip, Michael C. The Department of Electrical and Computer Engineering University of California San Diego San DiegoCA92093 United States The Department of Mechanical and Aerospace Engineering University of California San Diego San DiegoCA92093 United States The Faculty of Civil and Environmental Engineering The Technion Autonomous Systems Program Technion - Israel Institute of Technology Haifa3200003 Israel

Exploring and navigating in extreme environments, such as caves, oceans, and planetary bodies, are often too hazardous for humans, and as such, robots are possible surrogates. These robots are met with significant locomotion challenges that require traversing a wide range of surface roughnesses and topologies. Previous locomotion strategies, involving wheels or ambulatory motion, such as snake platforms, have success on specific surfaces but fail in others which could be detrimental in exploration and navigation missions. In this paper, we present a novel approach that combines snake-like robots with an Archimedean screw locomotion mechanism to provide multiple, effective mobility strategies in a large range of environments, including those that are difficult to traverse for wheeled and ambulatory robots. This work develops a robotic system called ARCSnake to demonstrate this locomotion principle and tested it in a variety of different terrains and environments in order to prove its controllable, multi-domain, navigation capabilities. These tests show a wide breadth of scenarios that ARCSnake can handle, hence demonstrating its ability to traverse through extreme terrains. Copyright © 2021, The Authors. All rights reserved.

关键词： Screws

来源：评论

学校读者我要写书评

暂无评论

Cardinality compensation method based on information-weighted consensus filter using data clustering for multi-target tracking

引用

Chinese Journal of Aeronautics 2019年第9期32卷 2164-2173页

作者： Sunyoung KIM Changho KANG Changook PARK Department of Mechanical and Aerospace Engineering Seoul National UniversitySeoul 08826Republic of Korea BK21+Transformative Training Program for Creative Mechanical and Aerospace Engineers Seoul National UniversitySeoul 08826Republic of Korea Automation and Systems Research Institute Seoul 08826Republic of Korea Institute of Advanced Aerospace Technology Seoul 08826Republic of Korea

In this paper, a cardinality compensation method based on Information-weighted Consensus Filter(ICF) using data clustering is proposed in order to accurately estimate the cardinality of the Cardinalized Probability Hypothesis Density(CPHD) filter. Although the joint propagation of the intensity and the cardinality distribution in the CPHD filter process allows for more reliable estimation of the cardinality(target number) than the PHD filter, tracking loss may occur when noise and clutter are high in the measurements in a practical situation. For that reason, the cardinality compensation process is included in the CPHD filter, which is based on information fusion step using estimated cardinality obtained from the CPHD filter and measured cardinality obtained through data clustering. Here, the ICF is used for information fusion. To verify the performance of the proposed method, simulations were carried out and it was confirmed that the tracking performance of the multi-target was improved because the cardinality was estimated more accurately as compared to the existing techniques.

关键词： Cardinality compensation Cardinalized probability hypothesis density filter Data clustering Information-weighted consensus filter Multi-target tracking

来源：评论

学校读者我要写书评

暂无评论

Electromagnetic textile absorber applied to 4G and 5G bands

引用

Scientific Reports 2025年第1期15卷 1-11页

作者： Paulo H. B. Carvalho Ewaldo E. C. Santana Allan K. D. Barros Filho Paulo F. Silva Júnior Keyll C. R. Martins Talita C. Azevedo Waldemir P. Martins Mauro A. Medeiros Rubens S. Gonçalves Lourival M. Sousa Filho Gricirene S. Correia Gabrielle M. Fernandes Talita C. Pinheiro Carlos A. M. Cruz Brenda A. S. Rodrigues Graduate Program in Electrical Engineering Federal University of Maranhão (UFMA) São Luís MA Brazil Graduate Program in Computer and Systems Engineering Maranhão State University (UEMA) São Luís MA Brazil Graduate Program in Mechanical Engineering Federal Institute of Maranhão (IFMA) São Luís MA Brazil Department of Electrical Engineering Federal Institute of Paraíba (IFPB) João Pessoa PB Brazil Graduate Program in Electrical Engineering Federal University of Amazonas (UFAM) Manaus AM Brazil Department of Electronics and Computation Federal University of Amazonas (UFAM) Manaus AM Brazil

Absorber materials are developed to reduce electromagnetic radiation and ensure the compatibility of the operation of electronic equipment in environments subject to interference. This work presents the development of a low-cost textile electromagnetic absorber for 4G and 5G technologies, operating at frequencies of 2.5 GHz and 3.5 GHz. The proposed electromagnetic absorber utilizes a 1 mm-thick Denim substrate, with a graphite composite used in the agricultural and commercial polyvinyl acetate glue industry, with the relationship of 25 wt%. The measurements were carried out in a Vector Network Analyzer, model E5071C Agilent Technologies, with the characterization of the Denim substrate, the glue, and the identification of the best parameters for the construction of the absorber. In the project, three low-cost textile absorbers prototypes were fabricated, with G1 = 0.25 mm, G2 = 0.35 mm, and G3 = 0.5 mm of thickness layers of the composite deposited on a Denim fabric. The results indicate that the absorber prototypes G2 presents great results in the frequency range of 4G and 5G band, with a maximum absorption of 26.6 dB in 3.94 GHz, with a structure 98.83% thinner than the commercial absorber LF-75. The variation in absorption performance may be attributed to the different mechanisms by which the absorbers operate: the commercial absorber LF-75 primarily interacts with the magnetic field, whereas the textile prototype predominantly affects the electric field.

关键词： 4G and 5G bands Electromagnetic Low-cost Textile absorber

来源：评论

学校读者我要写书评

暂无评论

Design and Fabrication of Negative-Refractive-Index Metamaterial Unit Cells for Near-Megahertz Enhanced Acoustic Transmission in Biomedical Ultrasound Applications

引用

Physical Review Applied 2021年第2期15卷 024025-024025页

作者： Jiaying Wang Florian Allein Nicholas Boechler James Friend Oscar Vazquez-Mena Department of Nanoengineering University of California San Diego 9500 Gilman Drive La Jolla California 92093 USA Center for Memory and Recording Research University of California San Diego La Jolla California 92093 USA Calibaja Center for Resilient Materials and Systems University of California San Diego La Jolla California 92093 USA Medically Advanced Devices Laboratory Center for Medical Devices Department of Mechanical Aerospace and Engineering and the Materials Science and Engineering Program Jacobs School of Engineering University of California San Diego La Jolla California 92093 USA Department of Mechanical Aerospace and Engineering University of California San Diego 9500 Gilman Drive La Jolla California 92093 USA Materials Science and Engineering University of California San Diego 9500 Gilman Drive La Jolla California 92093 USA Medically Advanced Devices Laboratory Center for Medical Devices Department of Mechanical Aerospace and Engineering and the Materials Science and Engineering Program Jacobs School of Engineering and Department of Surgery School of Medicine University of California San Diego 9500 Gilman Drive La Jolla California 92093 USA

We present the design of negative-refractive-index acoustic metamaterials operating at near-megahertz frequencies, intended for the eventual aim of enabling enhanced acoustic transmission through high-impedance-contrast biological layers. Leveraging the concept of complementary acoustic metamaterials, the negative effective properties of the metamaterials are designed to match the magnitude of an ultrasound-blocking, high-impedance-contrast layer’s properties. The negative properties are obtained using a linear array of unit cells containing Helmholtz resonators and membranes. Using finite-element and analytical models, we calculate the band structure and the effective modulus and density of the proposed negative metamaterials. Using the full three-dimensional model of the metamaterials, we then simulate the enhancement of ultrasound transmission, through layers with high-impedance contrast to water. For instance, we see an improvement from 80% transmission through a high-impedance layer alone to 98% transmission through the metamaterial-plus-high-impedance layer combination. Scaling arguments are provided to estimate the system dimensions needed to provide higher operational frequencies appropriate for imaging and high-intensity ultrasound applications. Finally, as a proof of feasibility, a preliminary experimental realization of the unit-cell structure, created using the nanofabrication approach, is presented and tested in the near-megahertz regime. These results provide a step toward metamaterial-enhanced devices for noninvasive biomedical ultrasonic imaging and therapy.

关键词： Acoustic metamaterials Negative refraction Therapeutics Ultrasonics Semiconductor compounds Medical imaging Ultrasonography Ultrasound techniques

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：