Atomistic Origins of Friction

2019 ◽  
pp. 348-388
Author(s):  
C. Mathew Mate ◽  
Robert W. Carpick
Keyword(s):  
Atomic Structure ◽  
Real Life ◽  
Static Friction ◽  
Electronic Excitations ◽  
Kinetic Friction ◽  
Dynamic Simulations ◽  
Tomlinson Model ◽  
Current State ◽  
Friction Models ◽  
Kontorova Model

This chapter covers the current state of knowledge about how the shear strength (the force needed to slide one surface over another) originates at the atomic level. For adhesive friction, friction originates from the forces needed to move the atoms on one surface over the atomic structure of the opposing surface; the simplest model for adhesive friction is the cobblestone model. The Frenkel–Kontorova model, the Prandtl–Tomlinson model, and molecular dynamic simulations are typically used to show how the atomic structure of the surfaces leads to static friction. One exciting aspect of these friction models is the prediction of superlubricity or negligible friction for incommensurate sliding surfaces, which is now being realized in experiments. Also discussed is why superlubricity is not observed in real-life situations. As atoms and molecules slide over surfaces, kinetic friction originates from phonon and electronic excitations, which are typically studied using the quartz crystal microbalance (QCM).

Friction Compensation of Geared Actuators With High Presliding Stiffness

2014 ◽  
Vol 137 (1) ◽  
Author(s):  
Myo Thant Sin Aung ◽  
Ryo Kikuuwe ◽  
Motoji Yamamoto
Keyword(s):  
Static Friction ◽  
The Other ◽  
New Method ◽  
Friction Compensation ◽  
Dynamic Friction ◽  
Kinetic Friction ◽  
Harmonic Drive ◽  
Rate Dependent ◽  
Friction Models ◽  
Three Components

Most of existing friction compensation techniques are based on friction models that uses the velocity as its input. These methods are difficult to apply to inexpensive encoder-based actuator systems that do not exhibit sufficiently large presliding displacement. This paper presents a new method of friction compensation that can be applied to geared actuators with high presliding stiffness. The compensator consists of three components that compensate: (a) static friction, (b) rate-dependent kinetic friction, and (c) dynamic friction involving presliding viscoelasticity. The first component employs dither-like torque command, and the other two are based on friction models involving precalibrated parameters. The proposed method is validated through experiments employing a harmonic drive transmission. In particular, it is suggested that the dither-like static friction compensation and the viscosity in the presliding model significantly improve the performance of the compensator.

Novel Therapeutic Approaches and Targets for Treatment of Chronic Urticaria: New Insights and Promising Targets for a Challenging Disease

2020 ◽  
Vol 22 (1) ◽  
pp. 32-45
Author(s):  
Emanuela Martina ◽  
Federico Diotallevi ◽  
Tommaso Bianchelli ◽  
Matteo Paolinelli ◽  
Annamaria Offidani
Keyword(s):  
English Language ◽  
Life Experience ◽  
Case Reports ◽  
Immunosuppressive Agents ◽  
Real Life ◽  
Chronic Spontaneous Urticaria ◽  
New Targets ◽  
Current State ◽  
Pubmed Database ◽  
Novel Drugs

Background: Chronic Spontaneous Urticaria (CSU) is a disease characterized by the onset of wheals and/or angioedema over 6 weeks. The pathophysiology for CSU is very complex, involving mast cells and basophils with a multitude of inflammatory mediators. For many years the treatment of CSU has been based on the use of antihistamines, steroids and immunosuppressive agents with inconstant and frustrating results. The introduction of omalizumab, the only licensed biologic for antihistamine- refractory CSU, has changed the management of the disease. Objective: The aim of this article is to review the current state of the art of CSU, the real-life experience with omalizumab and the promising drugs that are under development. Methods:: An electronic search was performed to identify studies, case reports, guidelines and reviews focused on the new targets for the treatment of chronic spontaneous urticaria, both approved or under investigation. The search was limited to articles published in peer-reviewed journals in the English Language in the PubMed database and trials registered in Clinicaltrials.gov. Results:: Since the advent of omalizumab, the search for new therapies for chronic spontaneous urticaria has had a new impulse. Anti-IgE drugs will probably still be the cornerstone of therapy, but new targets may prove effective in syndromic urticaria or refractory cases. Conclusion:: Although omalizumab has been a breakthrough in the treatment of CSU, many patients do not completely get benefit and even require more effective treatments. Novel drugs are under investigation with promising results.

Puzzles Unpuzzled

2021 ◽  
Vol 5 (CHI PLAY) ◽  
pp. 1-24
Author(s):  
Andrey Krekhov ◽  
Katharina Emmerich ◽  
Ronja Rotthaler ◽  
Jens Krueger
Keyword(s):  
Virtual Reality ◽  
Real Life ◽  
Basic Structure ◽  
Design Framework ◽  
Emotional Challenges ◽  
Related Research ◽  
Board Games ◽  
Current State ◽  
Prior Literature ◽  
High Level

Escape rooms exist in various forms, including real-life facilities, board games, and digital implementations. The underlying idea is always the same: players have to solve many diverse puzzles to (virtually) escape from a locked room. Within the last decade, we witnessed a rapidly increasing popularity of such games, which also amplified the amount of related research. However, the respective academic landscape is mostly fragmented in its current state, lacking a common model and vocabulary that would withstand these games' variety. This manuscript aims to establish such a foundation for the analysis and construction of escape rooms. In a first step, we derive a high-level design framework from prior literature. Then, as our main contribution, we establish an atomic puzzle taxonomy that closes the gap between the analog and digital domains. The taxonomy is developed in multiple steps: we compose a basic structure based on previous literature and systematically refine it by analyzing 39 analog and digital escape room games, including recent virtual reality representatives. The final taxonomy consists of mental, physical, and emotional challenges, thereby providing a robust and approachable basis for future works across all application domains that deal with escape rooms or puzzles in general.

Static Friction Models for Vehicle Simulation Study

2006 ◽  
Author(s):  
Xubin Song ◽  
Daniel G. Smedley
Keyword(s):  
Simulation Study ◽  
Static Friction ◽  
Friction Modeling ◽  
Stick Slip ◽  
Vehicle Simulation ◽  
Engineering Software ◽  
Variable Step ◽  
History Of ◽  
Friction Models ◽  
Smooth Dynamics

The history of the challenge of friction modeling is briefly reviewed. Then this paper focuses on the modeling and simulation study of the friction related dynamics in the Simulink® environment, because Matlab®/Simulink® are popular engineering software tools for both industry and academia. Matlab® and Simulink® are the proprietary products of MathWorks, Inc. In this paper, the static friction models are studied through Simulink® by applying fixed and variable step sizes. The comparison shows that the static Karnopp model is not only numerically tractable but also can be inclusive of the fundamental friction characteristics of both stick slip and correct friction predictions. Finally this paper presents an improved Karnopp model for clutch modeling with the use of Simulink®, and the simulation shows that this model is computationally tractable with smooth dynamics.

Numerical Investigation of the Influence of Friction Coefficient on Brake Groan

2010 ◽  
Vol 44-47 ◽  
pp. 1923-1927 ◽  
Author(s):  
Xian Jie Meng
Keyword(s):  
Nonlinear Dynamics ◽  
Friction Coefficient ◽  
Degrees Of Freedom ◽  
Equilibrium Points ◽  
Static Friction ◽  
Kinetic Friction ◽  
Dynamics Model ◽  
Excited Vibration ◽  
Nonlinear Dynamics Model ◽  
The Stability

A two degrees of freedom nonlinear dynamics model of self-excited vibration induced by dry-friction of brake disk and pads is built firstly, the stability of vibration system at the equilibrium points is analyzed using the nonlinear dynamics theory. Finally the numerical method is taken to study the impacts of friction coefficient on brake groan. The calculation result shows that with the increase of kinetic friction coefficient /or the decrease of difference value between static friction coefficient and kinetic friction coefficient can prevent or restrain self-excited vibration from happening.

scholarly journals Ethical issues on artificial intelligence in radiology: how is it reported in research articles? The current state and future directions

2021 ◽  
Vol 90 (2) ◽  
pp. e513
Author(s):  
Tomasz Piotrowski ◽  
Joanna Kazmierska ◽  
Mirosława Mocydlarz-Adamcewicz ◽  
Adam Ryczkowski
Keyword(s):  
Artificial Intelligence ◽  
Ethical Issues ◽  
Real Life ◽  
Exclusion Criteria ◽  
Future Directions ◽  
Current State ◽  
Ethical Status ◽  
The Status ◽  
Clinical Questions ◽  
Almost All

Background. This paper evaluates the status of reporting information related to the usage and ethical issues of artificial intelligence (AI) procedures in clinical trial (CT) papers focussed on radiology issues as well as other (non-trial) original radiology articles (OA). Material and Methods. The evaluation was performed by three independent observers who were, respectively physicist, physician and computer scientist. The analysis was performed for two groups of publications, i.e., for CT and OA. Each group included 30 papers published from 2018 to 2020, published before guidelines proposed by Liu et al. (Nat Med. 2020; 26:1364-1374). The set of items used to catalogue and to verify the ethical status of the AI reporting was developed using the above-mentioned guidelines. Results. Most of the reviewed studies, clearly stated their use of AI methods and more importantly, almost all tried to address relevant clinical questions. Although in most of the studies, patient inclusion and exclusion criteria were presented, the widespread lack of rigorous descriptions of the study design apart from a detailed explanation of the AI approach itself is noticeable. Few of the chosen studies provided information about anonymization of data and the process of secure data sharing. Only a few studies explore the patterns of incorrect predictions by the proposed AI tools and their possible reasons. Conclusion. Results of review support idea of implementation of uniform guidelines for designing and reporting studies with use of AI tools. Such guidelines help to design robust, transparent and reproducible tools for use in real life.

On the Static-Kinetic Friction Transition in Dry Contact of Rough Surfaces

2011 ◽  
Author(s):  
K. Farhang ◽  
D. Segalman ◽  
M. Starr
Keyword(s):  
Large Scale ◽  
Rough Surfaces ◽  
Tangential Force ◽  
Static Friction ◽  
Partial Slip ◽  
Small Scale ◽  
Asperity Contact ◽  
Kinetic Friction ◽  
Tangential Load ◽  
Asperity Contacts

This paper shows that the Mindlin problem involving two spheres in contact under the action of oscillating tangential force can lead to the account of static-kinetic friction transition. In Mindlin’s problem two spheres experience partial slip as a result of application of oscillating tangential load. When the problem is extended to multi-sphere contact, i.e. two rough surfaces, the application of tangential oscillating load results in partial slip for some asperity contacts while others experience full slip. Increase in the amplitude of the oscillating tangential force results in more contacts experiencing full slip, thereby decreasing the number of contacts in parial slip. Constitutive relation proposed by Mindlin at small scale, governing asperity interaction, is used to obtain the large scale slip function through a statistical summation of asperity scale events. The slip function establishes the fraction of asperity contact in full slip. The complement of the slip parameter is a fraction of asperities in partial slip. Through slip function it is shown that it is possible to define a slip condition for the entire surface. The derivation of the slip function allows the account of transition between static friction and kinetic friction.

Knowledge Transfer Issues in Teaching

2017 ◽  
pp. 58-78 ◽  
Author(s):  
Neeta Baporikar
Keyword(s):  
Knowledge Transfer ◽  
Management Practices ◽  
Real Life ◽  
Research Knowledge ◽  
Professional Schools ◽  
Current State ◽  
Theory To Practice ◽  
Knowledge Management Practices ◽  
Organizational Science ◽  
Practical Implications

Professional schools typically build their raison d'être on the mission of developing knowledge that can be translated into skills that advance the practice of the professions. On the other hand practitioners fail to adopt the findings of research in fields be it medicine, management or engineering. Further, knowledge created is not always in the usage mode, that too in real life practical situation. Action scientists focused on the characteristics and behaviors of researchers to explain this lack of implementation of research knowledge. Identifying the major gaps between scientific knowledge and actual knowledge transfer issues is crucial in today's scenario. Hence, the purpose of this chapter is to identify knowledge transfer issues, discuss the issues and advancements therein, and highlight practical implications of relating theory to practice with focus on management discipline. The issues discussed herein are not only of utmost importance but crucial for understanding, given the current state of management education, organizational science and knowledge management practices.

Coefficients of Friction: Static Versus Dynamic

2020 ◽  
Author(s):  
Jack Youqin Huang
Keyword(s):  
Coefficient Of Friction ◽  
Frictional Force ◽  
Inertial Force ◽  
Static Friction ◽  
Theory And Practice ◽  
Dynamic Friction ◽  
Kinetic Friction ◽  
The Coefficient Of Friction ◽  
Static Versus Dynamic ◽  
New Discovery

Abstract This paper deals with the problem of static and dynamic (or kinetic) friction, namely the coefficients of friction for the two states. The coefficient of static friction is well known, and its theory and practice are commonly accepted by the academia and the industry. The coefficient of kinetic friction, however, has not fully been understood. The popular theory for the kinetic friction is that the coefficient of dynamic friction is smaller than the coefficient of static friction, by comparison of the forces applied in the two states. After studying the characteristics of the coefficient of friction, it is found that the comparison is not appropriate, because the inertial force was excluded. The new discovery in the paper is that coefficients of static friction and dynamic friction are identical. Wheel “locked” in wheel braking is further used to prove the conclusion. The key to cause confusions between the two coefficients of friction is the inertial force. In the measurement of the coefficient of static friction, the inertial force is initiated as soon as the testing object starts to move. Therefore, there are two forces acting against the movement of the object, the frictional force and the inertial force. But in the measurement of the coefficient of kinetic friction, no inertial force is involved because velocity must be kept constant.

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