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structural engineering of graphene for high-resolution cryo-electron microscopy

SmartMat 2021年第2期2卷 202-212页

作者： Jie Xu Xiaoya Cui Nan Liu Yanan Chen Hong-Wei Wang Ministry of Education Key Laboratory of Protein Sciences Beijing Advanced Innovation Center for Structural BiologySchool of Life SciencesTsinghua UniversityBeijingChina Tsinghua-Peking Joint Center for Life Sciences Tsinghua UniversityBeijingChina School of Materials Science and Engineering Tianjin UniversityTianjinChina Joint Graduate Program of Peking-Tsinghua-NIBS School of Life SciencesTsinghua UniversityBeijingChina Beijing Frontier Research Center for Biological Structures Tsinghua UniversityBeijingChina

The revolutionary improvement of hardware and algorithm in cryogenic electron microscopy(cryo-EM)has made it a routine method to obtain structures of macromolecules at near-atomic ***,this technique still faces many *** structure-solving efficiency of cryo-EM can be significantly reduced by the biomolecules'denaturation on the air–water interfaces,the preferred orientation,strong background noise from supporting films and particle motion,and so *** overcome these problems,nanomaterials with ultrahigh electronic conductivity and ultrathin thickness are explored as promising cryo-EM specimen supporting ***,we summarize the structural engineering of graphene,for example,surface and interface modification,as supporting films for grids and the application on high-resolution cryo-EM and discuss potential future perspectives.

关键词： graphene high-resolution cryogenic electron microscopy life science liquid cell tomography

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Reduced graphene oxide membrane as supporting film for high-resolution cryo-EM

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Biophysics Reports 2021年第3期7卷 227-238页

作者： Nan Liu Liming Zheng Jie Xu Jia Wang Cuixia Hu Jun Lan Xing Zhang Jincan Zhang Kui Xu Hang Cheng Zi Yang Xin Gao Xinquan Wang Hailin Peng Yanan Chen Hong-Wei Wang Ministry of Education Key Laboratory of Protein Sciences Beijing Advanced Innovation Center for Structural BiologySchool of Life SciencesTsinghua University Tsinghua-Peking Joint Center for Life Sciences Tsinghua University Center for Nanochemistry Beijing Science and Engineering Center for NanocarbonsBeijing National Laboratory for Molecular SciencesCollege of Chemistry and Molecular EngineeringPeking University Joint Graduate Program of Peking-Tsinghua-NIBS School of Life SciencesTsinghua University Beijing Frontier Research Center for Biological Structures Tsinghua University Academy for Advanced Interdisciplinary Studies Peking University School of Materials Science and Engineering Tianjin University

Although single-particle cryogenic electron microscopy(cryo-EM) has been applied extensively for elucidating many crucial biological mechanisms at the molecular level, this technique still faces critical challenges, the major one of which is to prepare the high-quality cryo-EM specimen. Aiming to achieve a more reproducible and efficient cryo-EM specimen preparation, novel supporting films including graphene-based two-dimensional materials have been explored in recent years. Here we report a robust and simple method to fabricate EM grids coated with single-or few-layer reduced graphene oxide(RGO) membrane in large batch for high-resolution cryo-EM structural determination. The RGO membrane has decreased interlayer space and enhanced electrical conductivity in comparison to regular graphene oxide(GO) membrane. Moreover, we found that the RGO supporting film exhibited nice particle-absorption ability, thus avoiding the air–water interface problem. More importantly, we found that the RGO supporting film is particularly useful in cryo-EM reconstruction of sub-100-k Da biomolecules at near-atomic resolution, as exemplified by the study of RBD-ACE2 complex and other small protein molecules. We envision that the RGO membranes can be used as a robust graphene-based supporting film in cryo-EM specimen preparation.

关键词： 3D reconstruction Reduced graphene oxide Cryo-EM Air–water interface

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On Cyclic Finite-State Approximation of Data-Driven Systems

arXiv

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arXiv 2019年

作者： Vides, Fredy Scientific Computing Innovation Center Department of Applied Mathematics Universidad Nacional Autónoma de Honduras UNAH Honduras Graduate Program in Structural Engineering Universidad Tecnológica Centroamericana UNITEC Honduras

In this document, some novel theoretical and computational techniques for constrained approximation of data-driven systems, are presented. The motivation for the development of these techniques came from structure-preserving matrix approximation problems that appear in the fields of system identification and model predictive control, for data-driven systems and processes. The research reported in this document is focused on finite-state approximation of data-driven systems. Some numerical implementations of the aforementioned techniques in the simulation and model predictive control of some generic data-driven systems, that are related to electrical signal transmission models, are outlined.93B28, 47N70 (primary) and 93C57, 93B40 (secondary) Copyright © 2019, The Authors. All rights reserved.

关键词： Singular value decomposition

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Numerical evaluation of tubular perfobond shear connectors

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ce/papers 2021年第2-4期4卷 666-674页

作者： Souza, Keila L. da Silva, André T. Henriques, José Vellasco, Pedro C. G. Rodrigues, Monique C. PGECIV - Civil Engineering Post-Graduate Program UERJ – State University of Rio de Janeiro Brazil Structural Engineering Department UERJ – State University of Rio de Janeiro Brazil Construction Engineering Research Group IIW Faculty Hasselt University Belgium

Composite structures have been applied more frequently because they are an economical structural solution with excellent structural performance. The interaction is guaranteed with the use of elements that transfer the forces between these two materials. The most common mechanical connections between steel and concrete are made through shear connectors. Some of the connectors types used nowadays are stud bolt, U-profiles, Crestbond, Perfobond and T-Perfobond. Eurocode 4 prescribes that a connector has to possess a minimal ductility, one of the main requirements to shear connectors. The current Perfobond presents excellent resistant capacity, but low deformation capacity, contradicting what is prescribed by the code. This paper aims to study a Tubular Perforbond connector by analyzing the parameters that can influence its resistance and deformation capacity, applying FEM through Abaqus software, to simulate the composite structural, mechanical behaviour. When comparing the Tubular Perfobond connector with the Perfobond connector, it was possible to observe that the tubular connectors presented a substantial deformation capacity after peak load, while attending the connector ductility requirements. The use of Tubular connectors also decreased the concrete crushing propagation. © 2021 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.

关键词： Nonlinear analysis

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Influence of bearing coefficient in cold-formed stainless steel bolted connection

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ce/papers 2021年第2-4期4卷 148-155页

作者： Sobrinho, Kelvin da Silva, André T. Rodrigues, Monique C. Henriques, José A. Lima, Luciano R. da Vellasco, Pedro C. G. PGECIV - Civil Engineering Post-Graduate Program UERJ – State University of Rio de Janeiro Brazil Structural Engineering Department UERJ – State University of Rio de Janeiro Brazil Construction Engineering Research Group IIW Faculty Hasselt University Belgium

The connections play an important role in the overall behaviour of the structures. Therefore an adequate structural design taking into account both safe and economic criterion is necessary. The structural design of stainless steel bolted connections using actual codes can provide inadequate design capacity mainly due to the use of similar rules based on analogies from mild carbon structures. Thus, the purpose of this paper is to evaluate the structural response of stainless bolted connections considering the steel grade austenitic 304. Experimental and numerical analyses have been carried out considering bolted connection under bearing failure. In details, the study cases were subjected to two shear planes with thin-plate and thick-plate. In these cases, the occurrence of curling failures is possible. A detailed study involving the geometric parameters adopted by design equations of bolted stainless steel connections was made. The outcomes showed a reduction of the ultimate capacity characterised by out-plane deformation. In addition, the current codes led to significant difference when compared to both experimental and numerical results. © 2021 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.

关键词： structural design

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Assessment of Stainless Steel Tubular T-joints Under Chord Sidewall Failure Mode by a Semi-analytical Formulation

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ce/papers 2022年第4期5卷 574-583页

作者： Nogueira, Mateus M. de Lima, Luciano R. O. da S. Vellasco, Pedro C. G. Young, Ben PGECIV - Civil Engineering Post-Graduate Program UERJ – State University of Rio de Janeiro Brazil Structural Engineering Department UERJ – State University of Rio de Janeiro Brazil Department of Civil and Environmental Engineering The Hong Kong Polytechnic University Hong Kong

There are numerous benefits of tubular profiles that make them increasingly used in civil engineering. At the same time, stainless steel is a material with excellent properties and high corrosion resistance. However, stainless steel's high initial material cost has limited its use primarily to specialist and prestige applications, which makes it necessary to develop more accurate design rules for this material. When tubular profiles are used, it is necessary to assess the joint strengths, considering that they can fail by different mechanisms. The present work aims to develop a semi-analytical formulation to predict stainless steel tubular T-joint resistances. Joints with the brace-to-chord width ratio equal to 1 were considered in this study;therefore, the failure occurs in the chord sidewall. To assess the sidewall instability critical load, the exact stress fields were determined using Mathieu's theory, and then the Ritz energy method was applied. Considering that the joints are made of stainless steel, the next step is to transform the load found from linear to the non-linear regime. For that, a new formulation based on Ramberg-Osgood equations was developed. Finally, the results obtained from the proposed method were compared with the experimental results obtained by Feng and Young (2008) and the results from the main current standards and literature. It was observed that the proposed method presented satisfactory results, while the predictions from design codes were, in general, very conservative. © 2022 Ernst & Sohn GmbH.

关键词： Failure (mechanical)

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Numerical assessment of stainless steel tubular T-joints subjected to brace and chord axial forces

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ce/papers 2021年第2-4期4卷 2495-2503页

The utilisation of tubular sections in steel structures has increased significantly worldwide. The use of stainless steel provides several benefits for structures, including high corrosion resistance, durability, fire resistance and ease of maintenance. A significant issue in the design of tubular structures is the joints failure since they are highly susceptible to local failures that influence their actual overall behavior. The design rules of welded carbon steel tubular joints are available, such as Eurocode 3, part 1-8, NBR 16239, ISO 14346 and CIDECT guides. When stainless steel tubular joints are considered, the AS/NZS 4673 Australian/New Zealand Standard is the only available specification that can be used. An experimental and numerical analysis of these tubular joints are recommended since they enable a more accurate evaluation of their structural performance. Concerning these aspects, this work aims to investigate stainless steel tubular T-joints fabricated by SHS and RHS cold-formed profiles that focused on the effect of chord pre-loading. For this purpose, a numerical study based on finite element analysis was performed. The finite element model was developed and calibrated against experiments. The results were subsequently compared with the aforementioned design predictions. © 2021 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.

关键词： Finite element method

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NUMERICAL ANALYSIS WITH IMPLEMENTATION OF DAMAGE TO STAINLESS STEEL BOLTED CONNECTIONS SUBJECTED TO SHEAR LOAD

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ce/papers 2019年第5-6期3卷 426-435页

作者： Sobrinho, Kelvin P. Silva, André T. Rodrigues, Monique C. Henriques, José A. G. Vellasco, Pedro C. G. S. Lima, Luciano R. O. PGECIV – Post-Graduate Program in Civil Eng. State University of Rio de Janeiro – UERJ Brazil Structural Engineering Department State University of Rio de Janeiro – UERJ Brazil Faculty of Engineering Technology University Hasselt – Hasselt Belgium

In this paper, an experimental and numerical study were developed to evaluate the behavior of stainless steel bolted connections subjected to shear load until rupture, in which austenitic stainless steel 304 was used. In order to determine the material behavior, tensile coupon tests were performed. The numerical model was developed in Abaqus finite element program using dynamic explicit analysis and solid elements (C3D8) with an elastic-plastic stress-strain curve with strain hardening and damage criteria. Additionally, a comparison of the results with the recommendations given by the current standards for stainless steel structures was also accomplished. © 2020 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.

关键词： Strain hardening

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Localized microjetting in the collapse of surface macrocavities

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Physical Review E 2015年第2期91卷 022405-022405页

作者： K. L. Olney P.-H. Chiu D. J. Benson A. Higgins M. Serge V. F. Nesterenko Department of Mechanical and Aerospace Engineering University of California San Diego La Jolla California 92093 Materials Science and Engineering Graduate Program University of California San Diego La Jolla California 92093 Department of Structural Engineering University of California San Diego La Jolla California 92093 Department of Mechanical Engineering McGill University Quebec H3A 0C3 Canada

This paper focuses on the multiscale mechanism of collapse of hemicylindrical annular surface macrocavities in steel caused by high-strain, high-strain rate plastic flow of copper. Experiments and simulations revealed that a two-stage process is responsible for the observed microjetting phenomena: the formation of lateral copper microjets from the localized shear flow in copper at the interface during the filling of the cavity, and their subsequent collision at the apex of the macrocavity generating two additional horizontal microjets. The lengths of these microjets were an order of magnitude smaller than the cavity size but linearly scaled with the cavity radius. This process of microjet development is sensitive to the cavity geometry and is unlike the previously observed jetting phenomena in cavitation, impact crater collapse, or shock-induced cavity collapse.

关键词： VERY light jets SURFACES (Physics) STRAIN rate (Materials science) PLASTICITY COPPER METALS -- Mechanical properties

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THE NO FRAME CONCEPT - ITS IMPACT ON SHIPYARD COST

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NAVAL ENGINEERS JOURNAL 1984年第3期96卷 218-232页

作者： NAPPI, NS WALZ, RW WIERNICKI, CJ Natale S. Nappi:graduated from City College of New York in 1954 with a B.S. degree in civil engineering and received his M.S. in civil engineering from the Polytechnic Institute of Brooklyn in 1959. He began his professional career in 1954 at the New York Naval Shipyard as a naval architect (structures) performing detail structural design and fabrication studies for CVAs LPDs DDs and CGs and eventually became a supervisory naval architect (structures). From 1965 to 1973 he was a member of the staff of the Computer-Aided Design Division at the David Taylor Naval Ship Research and Development Center (DTNSRDC). As such he was involved in the development of the computer structural design tool the SSDP (in association with Frank M. Lev) and automated detail design programs (CASDOS). His current position is Senior Naval Architect Consultant in the structural integrity group of the Ship Structures Division Structures Department DTNSRDC. Mr. Nappi is the author and co-author of numerous technical papers and reports covering a wide spectrum of topics such as automated structural design process design for producibility and survivability material weight and cost trade-off studies and structural weight determination for high performance ships (i.e. SES SWATH HYSWAS). He has lectured on the subjects of design for survivability and ship structures at the Naval Post Graduate School and MIT. He is a member of ASNE ASCE U.S. Naval Institute Sigma Xi and is a registered Professional Engineer in the State of New York. Mr. Nappi was a member of the NAVSEA working commitee for the computer supported design planning effort and is currently a member of the DTNSRDC ASSET Advisory Committee. Ronald W. Walz:graduated in 1974 from Pennsylvania State University with a B.S. degree in civil engineering. He began his professional career in 1974 at the David Taylor Naval Ship Research and Development Center as a structural engineer in the structural design concepts group of the Ship Structures Division Structures Department.

A proposed cost effective alternative to current U.S. Navy structurally configured hulls is presented in this paper. This proposed design for producibility concept involves the elimination of structural stanchions and transverse web frames. The potential impact of this “no frame” concept on structural design, weight and construction and material costs for naval surface frigates and destroyers is reflected in 1) reduced costs for the installation of distributive systems and 2) a reduced number and complexity of structural details providing a more reliable and less costly structure. This study was performed in three parts: 1) Determine the most feasible length between bulkheads without frames; 2) Using this length perform detail weight studies and construction and material costs analysis comparison on a 72-foot long hull module, with and without frames, for a FFG-7, and 3) Estimate the saving in man hours of labor on the installation of distributive systems and shipfitting for an FFG-7. For the feasible length studies on the “no frame” structural configuration, thirty-seven strength, weight and vertical center of gravity studies were performed on two ship classes; twenty-two on the FFG-7 class and fifteen on the DD-963 class. The detailed weight studies and construction and material cost analyses were conducted for FFG-7 “no frame” and “as built” modules. Results indicating the “no frame” concept module was 6.8% heavier and 14.8% less costly than the “as built” module. For the impact of an FFG-7 “no frame” structurally configured hull on the cost of labor required for the installation of distributive systems and for other functional work such as ship fitting, welding, and electrical, this study indicated a reduction of 169,206 labor hours per ship, representing 7.12% of the total required man hours to fabricate an FFG-7 class ship. With the employment of the “no frame” concept, certain areas of significant concern and potential risk were addressed. These include: 1) t

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