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Molecular dynamics simulation of the Stribeck curve: Boundary lubrication, mixed lubrication, and hydrodynamic lubrication on the atomistic level

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摩擦:英文版 2023年第12期11卷 2342-2366页

作者： Simon STEPHAN sebastian SCHMITT Hans HASSE Herbert M.URBASSEK Laboratory of Engineering Thermodynamics(LTD) Department of Mechanical and Process EngieeringTU KaiserslauternRheinland-Pfalz 67663Germany Physics Department and Research Center(OPTIMAS) TU KaiserslauternRheinland-Pfalz 67663Germany

Lubricated contact processes are studied using classical molecular dynamics simulations for determining the entire range of the Stribeck ***,the lateral movement of two solid bodies at different gap height are *** each simulation,a rigid asperity is moved at constant height above a flat iron surface in a lubricating *** methane and decane are considered as *** three main lubrication regimes of the Stribeck curve and their transition regions are covered by the study:Boundary lubrication(significant elastic and plastic deformation of the substrate),mixed lubrication(adsorbed fluid layer dominates the process),and hydrodynamic lubrication(shear flow is set up between the surface and the asperity).We find the formation of a tribofilm in which lubricant molecules are immersed into the metal surface—not only in the case of scratching,but also for boundary lubrication and mixed *** formation of a tribofilm is found to have important consequences for the contact ***,the two fluids are found to show distinctly different behavior in the three lubrication regimes:For hydrodynamic lubrication(large gap height),decane yields a better tribological performance;for boundary lubrication(small gap height),decane shows a larger friction coefficient than methane,which is due to the different mechanisms observed for the formation of the tribofilm;the mixed lubrication regime can be considered as a transition regime between the two other ***,it is found that the nature of the tribofilm depends on the lubricant:While methane particles substitute substrate atoms sustaining mostly the crystalline structure,the decane molecules distort the substrate surface and an amorphous tribofilm is formed.

关键词： boundary lubrication mixed lubrication hydrodynamic lubrication molecular dynamics simulation tribofilm

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Metabolic control of adult neural stem cell behavior

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Frontiers in Biology 2015年第2期10卷 100-106页

作者： Marlen Knobloch sebastian Jessberger Brain Research Institute Faculty of Medicine and Science University of Zurich 8057 Zurich Switzerland

Neural stem cells generate new neurons throughout life in distinct regions of the mammalian brain. This process, called adult neurogenesis, is important for tissue homeostasis and physiological brain function. In addition, failing or altered neurogenesis has been associated with a number of diseases such as major depression and epilepsy. Thus, understanding the molecular mechanisms governing the neurogenic process in the adult brain may enable future therapeutic approaches to target neural stem/progenitor cells （NSPCs） and their progeny to ameliorate disease symptoms and/or disease progression. Recently, the control of cellular metabolism has emerged as a regulator of NSPC activity in the adult brain. Here we review recent findings that attempt to describe stage-specific modulations of metabolism to ensure proper neurogenesis and suggest future avenues of research aiming to understand how metabolism affects NSPC behavior.

关键词： adult neurogenesis metabolic switch quiescence proliferation differentiation

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How single-cell immunology is benefiting from microfluidic technologies

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Microsystems & Nanoengineering 2020年第1期6卷 728-741页

作者： Fabien C.Jammes sebastian J.Maerkl Institute of Bioengineering School of EngineeringEcole Polytechnique Federale de LausanneLausanneSwitzerland

The immune system is a complex network of specialized cells that work in concert to protect against invading pathogens and tissue *** in this network often result in excessive or absent immune responses leading to allergies,autoimmune diseases,and *** of the mechanisms and their regulation remain poorly *** cells are highly diverse,and an immune response is the result of a large number of molecular and cellular interactions both in time and *** bulk methods are often prone to miss important details by returning population-averaged *** is a need in immunology to measure single cells and to study the dynamic interplay of immune cells with their *** in the fields of microsystems and microengineering gave rise to the field of microfluidics and its application to *** systems enable the precise control of small volumes in the femto-to nanoliter *** controlling device geometries,surface chemistry,and flow behavior,microfluidics can create a precisely defined microenvironment for single-cell studies with spatio-temporal *** features are highly desirable for single-cell analysis and have made microfluidic devices useful tools for studying complex immune *** addition,microfluidic devices can achieve high-throughput measurements,enabling in-depth studies of complex *** has been used in a large panel of biological applications,ranging from single-cell genomics,cell signaling and dynamics to cell–cell interaction and cell migration *** this review,we give an overview of state-of-the-art microfluidic techniques,their application to single-cell immunology,their advantages and drawbacks,and provide an outlook for the future of single-cell technologies in research and medicine.

关键词： fluid network details

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Indentation Size Effect inβCuAlBe and Cu-2Be Alloys

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Acta Metallurgica Sinica(English Letters) 2021年第12期34卷 1669-1678页

作者： Susana Montecinos sebastian Tognana Walter Salgueiro IFIMAT Facultad de Ciencias ExactasUniversidad Nacional del Centro de La Provincia de Buenos AiresPinto 3997000 TandilArgentina Consejo Nacional de Investigaciones Científicas y Técnicas CONICET Av.Rivadavia 1917C1033AAJ Buenos AiresArgentina CIFICEN(UNCPBA-CICPBA-CONICET) Pinto 3997000 TandilArgentina Comisión de Investigaciones Científicas de la Provincia de Bs.As Calle 526 entre 10 y 111900 La PlataArgentina

The indentation size effect(ISE)was studied by instrumented nanoindentation and Vickers hardness measurements on polycrystalline copper,βCuAlBe pseudoelastic and age-hardenable CuBe *** in the load-depth curves at different loads would suggest a change in the behavior of the materials as the load *** was estimated at different loads taking into account the pile-up in each case,which was estimated from the images of the topography obtained by atomic force microscopy(AFM).The effect of the microstructure of Cu-2Be(wt%)samples on the ISE was also *** each copper alloy,the Nix and Gao model was applied to the hardness-depth curves,and significant differences were found for the parameters *** is in the constant nanohardness regime for depths below 500 nm,while microhardness exhibits the ISE *** behavior of the nanohardness and the plastic strain with the depth is almost *** presents the lowest values of plastic strains due to the pseudoelastic effect,while Cu presents an almost constant value around 8%,which corresponds to the highest plastic strain obtained.

关键词： Hardness Pseudoelasticity Copper alloys Plasticity Indentation size effect

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Coupling between fluids and rock deformation in the continental crust:Preface

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Geoscience Frontiers 2019年第6期10卷 2085-2092页

作者： Silvia Japas sebastian Oriolo Vinod Samuel Instituto de Geociencias Básicas Aplicadas y Ambientales(IGeBA)CONICETUniversidad de Buenos AiresCiudad UniversitariaBuenos AiresArgentina Department of Earth System Sciences Yonsei UniversitySeoulRepublic of Korea

*** Fluids are essential and widespread components of the Earth *** regulate the main process of mass and energy transport,conditioning the geochemical and geophysical evolution of the crust(Bredehoeft and Norton.1990)and,consequently,its properties and mechanical *** coupling between fluids,rock deformation,and heat are crucial engines for plate tectonics,playing a leading role in the rheology and evolution of the lithosphere(*** et al.,2000;Kennedy and van Soest,2007;Thompson,2010;Miller.2013;Yardley and Bodnar,2014:Hirauchi et al.,2016:Menzies et al.,2016;Plümper et al.,2017;Vizán et al.,2017).

关键词： rock crust continental

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Why are COVID-19 travel bubbles a tightrope walk?An investigation based on the Trans-Tasmanian case

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Communications in Transportation Research 2023年第1期3卷 37-43页

作者： Xiaoqian Sun sebastian Wandelt Anming Zhang National Key Laboratory of CNS/ATM School of Electronic and Information EngineeringBeihang UniversityBeijing100191China Sauder School of Business University of British ColumbiaVancouverBCCanada

The COVID-19 pandemic has hit the transportation sector hard;particularly air transportation,as a major mode of long-distance transportation,has been affected *** the dawn of COVID-19,politicians and policy makers have discussed the idea of introducing travel bubbles between countries(or counties),to allow for a continued exchange of people and *** eponymous Trans-Tasmanian travel bubble is a major example,involving quarantine-free travel between Australia and New *** both countries have tried to form a travel bubble various times,recurring setbacks and difficulties were *** October 2021,this ambitious project presumably has come to an end,with both countries announcing the essential capitulation of their COVIDZero strategies and a planned opening towards broader international *** this study,we perform a close investigation of the history behind the Trans-Tasmanian travel bubble as an on-off relationship,identifying a set of drivers for the serious problems involving a sustainable setup and *** develop a framework which represents important factors for successful travel bubbles and believe that the satisfaction of all factors at once is extremely *** results and insights are not specific to the Trans-Tasmanian case only,although it is taken as a running example,but can be generalized to various scales and *** hope that our study contributes to the literature by improving our understanding of the highly buzzed travel bubble concept,while providing empirical evidence for the troubles that inherently make such bubbles a tightrope walk.

关键词： COVID-19 Travel bubble Australia New Zealand

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Recent advances in crystalline and amorphous particulate protein formulations for controlled delivery

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Asian Journal of Pharmaceutical Sciences 2016年第4期11卷 469-477页

作者： sebastian Puhl Lorenz Meinel Oliver Germershaus Institute for Pharmacy and Food Chemistry University of WuerzburgAm Hubland97074 WuerzburgGermany Institute for Pharma Technology University of Applied Sciences Northwestern SwitzerlandGruendenstrasse 404132 MuttenzSwitzerland

The number of particulate delivery systems for biologics is negligible compared to liquid dosage forms, signifying the complications associated with development of solid protein delivery systems. Particulate protein delivery systems can improve stability, reduce viscosity of suspensions at high protein concentration and allow for controlled drug release. This review discusses current advances in controlled delivery of particulate protein formulations. While the focus lies on protein crystals and delivery systems employing protein crystals,amorphous protein particles will also be addressed. Crystallization and precipitations methods and modifications allowing controlled delivery with and without encapsulation are summarized and discussed.

关键词： Protein crystals Protein particles Protein delivery Controlled release

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APPROACHES FOR SUSTAINABLE MANUFACTURING

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Chinese Journal of Mechanical Engineering 2007年第1期20卷 86-90页

作者： GüNTHER Seliger sebastian Kernbaum MARCO Zettl Department Assembly Technology and Factory Management Institute for Machine Tools and Factory Management Technical University Berlin Berlin 10587 Germany

Sustainable development is a holistic approach harmonizing ecological, economical and socio-political needs with respect to the superior objective of enhancing human living standards. Thereby the availability of natural resources and the conservation of the ecosystems have to be considered that future generations have the possibility to meet their own needs. A long-term economical development demands the transition from a souree-sink economy to a cycle economy as a result of limited resources, limited environmental capacities to absorb waste and emissions as well as increasing needs of a growing population. A reference model for snstainability in manufacturing is presented and used to illustrate sustainable approaches with respect to management, technology, process and product. Adaptation of products and components is a vital element for supporting efficient reuse of products and components. Consequently adaptation contributes to the ambitions goals of snstainability. Technological enablers for adaptation as modularity, information and communication technology are exemplarily introduced. Moreover, approaches for disseminating knowledge in sustainability are given.

关键词： Sustainability Manufacturing Adaptation Modularization Life cycle unit

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Robustness and efficiency of voting consensus protocols within byzantine infrastructures

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Blockchain(Research and Applications) 2021年第1期2卷 1-14页

作者： Angelo Capossele sebastian Müller Andreas Penzkofer IOTA Foundation 10405BerlinGermany Aix-Marseille Universitae CNRSCentrale MarseilleI2MUMR 737313453MarseilleFrance

This paper investigates several voting consensus protocols with low computational complexity in noisy Byzantine *** computer simulations,we show that explicit randomization of the consensus protocol can significantly increase the robustness towards faulty and malicious *** identify the optimal amount of randomness for various Byzantine attack strategies on different kinds of network topologies.

关键词： Distributed systems Consensus protocols Byzantine infrastructures Simulation studies

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Design and Robust Performance Evaluation of a Fractional Order PID Controller Applied to a DC Motor

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IEEE/CAA Journal of Automatica Sinica 2017年第2期4卷 304-314页

作者： J.Viola L.Angel J.M.sebastian Universidad Pontificia Bolivariana Universidad Politecnica de Madrid Centre for Automation and Robotics (CAR) UPM-CSIC

This paper proposes a methodology for the quantitative robustness evaluation of PID controllers employed in a DC motor. The robustness analysis is performed employing a 2~3 factorial experimental design for a fractional order proportional integral and derivative controller(FOPID), integer order proportional integral and derivative controller(IOPID)and the Skogestad internal model control controller(SIMC). The factors assumed in experiment are the presence of random noise,external disturbances in the system input and variable load. As output variables, the experimental design employs the system step response and the controller action. Practical implementation of FOPID and IOPID controllers uses the MATLAB stateflow toolbox and a NI data acquisition system. Results of the robustness analysis show that the FOPID controller has a better performance and robust stability against the experiment factors.

关键词： Factorial experimental design fractional-order PID controller robustness analysis SIMC PID controller

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