Fluidic Deformation Under Hypervelocity Impacts

2014 ◽  
Author(s):  
Andrew Thurber ◽  
Javid Bayandor
Keyword(s):  
Hypervelocity Impact ◽  
Orbital Debris ◽  
Inertial Forces ◽  
Impact Event ◽  
Aerospace Materials ◽  
Computational Framework ◽  
Hypervelocity Impacts ◽  
Dramatic Rise ◽  
Impact Risk

The increased frequency of exploration into space has caused a dramatic rise in the density of debris in orbit. Orbital debris, both natural and man-made, poses an extreme impact risk to satellites and spacecraft. The relative velocities between orbital components and debris can exceed thousands of meters per second, giving rise to immense kinetic energies even for small objects. In such a hypervelocity impact event, the shock pressures exceed the strength of common aerospace materials, and brief shock-induced temperature rises cause melting and vaporization of most structural bodies. Under these extreme conditions, the failure and deformation of solids can resemble fluid flow. By using meshless Lagrangian models in an explicit computational framework, this work identifies analogous fluidic interactions and further quantifies the role of shear and inertial forces in hypervelocity impacts (HVI).

Energy Markets and Trading

2018 ◽  
Author(s):  
David Mares
Keyword(s):  
Fossil Fuels ◽  
Negative Impact ◽  
Adjustment Costs ◽  
Institutional Context ◽  
Energy Markets ◽  
Energy Resources ◽  
Trade Offs ◽  
The Social ◽  
Impact Risk

This chapter discusses the role of energy in economic development, the transformation of energy markets, trade in energy resources themselves, and the geopolitical dynamics that result. The transformation of energy markets and their expansion via trade can help or hinder development, depending on the processes behind them and how stakeholders interact. The availability of renewable, climate-friendly sources of energy, domestically and internationally, means that there is no inherent trade-off between economic growth and the use of fossil fuels. The existence of economic, political, social, and geopolitical adjustment costs means that the expansion of international energy markets to incorporate alternatives to oil and coal is a complex balance of environmental trade-offs with no solutions completely free of negative impact risk. An understanding of the supply of and demand for energy must incorporate the institutional context within which they occur, as well as the social and political dynamics of their setting.

scholarly journals Flavonoids: Potential Candidates for the Treatment of Neurodegenerative Disorders

Biomedicines ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 99
Author(s):  
Shweta Devi ◽  
Vijay Kumar ◽  
Sandeep Kumar Singh ◽  
Ashish Kant Dubey ◽  
Jong-Joo Kim
Keyword(s):  
Stress Response ◽  
Stress Responses ◽  
Neurodegenerative Disorders ◽  
Cell Damage ◽  
Cellular Stress ◽  
Clinical Manifestations ◽  
Cellular Stress Response ◽  
Dramatic Rise ◽  
Cellular Stress Responses

Neurodegenerative disorders, such as Parkinson’s disease (PD), Alzheimer’s disease (AD), Amyotrophic lateral sclerosis (ALS), and Huntington’s disease (HD), are the most concerning disorders due to the lack of effective therapy and dramatic rise in affected cases. Although these disorders have diverse clinical manifestations, they all share a common cellular stress response. These cellular stress responses including neuroinflammation, oxidative stress, proteotoxicity, and endoplasmic reticulum (ER)-stress, which combats with stress conditions. Environmental stress/toxicity weakened the cellular stress response which results in cell damage. Small molecules, such as flavonoids, could reduce cellular stress and have gained much attention in recent years. Evidence has shown the potential use of flavonoids in several ways, such as antioxidants, anti-inflammatory, and anti-apoptotic, yet their mechanism is still elusive. This review provides an insight into the potential role of flavonoids against cellular stress response that prevent the pathogenesis of neurodegenerative disorders.

Microstructural Size Dependency in Nonlinear Lateral Stability of Random Reinforced Microshells via Meshfree-Based Applied Mathematical Modeling

2021 ◽  
pp. 2150164
Author(s):  
Jie-Hua Sun ◽  
Zhi-Dong Zhou ◽  
Saeid Sahmani ◽  
Babak Safaei
Keyword(s):  
Research Work ◽  
Meshfree Method ◽  
Resin Matrix ◽  
Small Scale ◽  
Lateral Stability ◽  
Computational Framework ◽  
Probabilistic Technique ◽  
Prime Objective ◽  
Shear Deformable

The prime objective of this research work is to develop an efficient small scale-dependent computational framework incorporating microstructural tensors of dilatation gradient, rotation gradient, and deviatoric stretch gradient to analyze nonlinear lateral stability of cylindrical microshells. The numerical strategy is established based upon a mixed formation of the third-order shear deformable shell model and modified strain gradient continuum mechanics. The graphene nanoplatelet reinforcements are assumed to be randomly dispersed in a checkerboard scheme within the resin matrix. Accordingly, to extract the effective material properties, the Monte Carlo simulation together with a probabilistic technique are employed. The numerical solution for the microstructural-dependent nonlinear problem is carried out via the moving Kriging meshfree method having the capability to accommodate accurately the essential boundary conditions using proper moving Kriging shape function. It is represented that the role of the stiffening characters related to the effect of microstructural dilatation gradient, rotation gradient, and deviatoric stretch reduces continuously by going to deeper territory of the load-deflection stability path. Moreover, it is indicated that among various microstructural gradient tensors, the stiffening character of the rotation gradient is higher than deviatoric stretch gradient, and the stiffening character of the latter is more considerable than the dilatation gradient tensor.

Modeling Hypervelocity Impacts Using Smoothed Particle Hydrodynamics

2018 ◽  
Author(s):  
M. Ganser ◽  
B. van der Linden ◽  
C. G. Giannopapa
Keyword(s):  
Smoothed Particle Hydrodynamics ◽  
Large Deformations ◽  
Hypervelocity Impact ◽  
Density Fluctuations ◽  
Computational Domain ◽  
Simulation Tool ◽  
Hypervelocity Impacts ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
The Impact

Hypervelocity impacts occur in outer space where debris and micrometeorites with a velocity of 2 km/s endanger spacecraft and satellites. A proper shield design, e.g. a laminated structure, is necessary to increase the protection capabilities. High velocities result in massive damages. The resulting large deformations can hardly be tackled with mesh based discretization methods. Smoothed Particle Hydrodynamics (SPH), a Lagrangian meshless scheme, can resolve large topological changes whereas it still follows the continuous formulation. Derived by variational principles, SPH is able to capture large density fluctuations associated with hypervelocity impacts correctly. Although the impact region is locally limited, a much bigger domain has to be discretized because of strong outgoing pressure waves. A truncation of the computational domain is preferable to save computational power, but this leads to artificial reflections which influence the real physics. In this paper, hypervelocity impact (HVI) is modelled by means of basic conservation assumptions leading to the Euler equations of fluid dynamics accompanied by the Mie-Grueneisen equation of state. The newly developed simulation tool SPHlab presented in this work utilizes the discretization method smoothed particle hydrodynamics (SPH) to capture large deformations. The model is validated through a number of test cases. Different approaches are presented for non-reflecting boundaries in order to tackle artificial reflections on a computational truncated domain. To simulate an HVI, the leading continuous equations are derived and the simulation tool SPHlab is developed. The method of characteristics allows to define proper boundary fluxes by removing the inwards travelling information. One- and two-dimensional model problems are examined which show excellent absorption behaviour. An hypervelocity impact into a laminated shield is simulated and analysed and a simple damage model is introduced to model a spallation failure mode.

scholarly journals The pervasive role of pragmatics in early language

2019 ◽  
Author(s):  
Manuel Bohn ◽  
Michael C. Frank
Keyword(s):  
Language Learning ◽  
Common Ground ◽  
Social Cues ◽  
Social Reasoning ◽  
Early Language ◽  
Computational Framework ◽  
Linguistic Pragmatics ◽  
Developmental Continuity ◽  
Pragmatic Reasoning

Language is a fundamentally social endeavor. Pragmatics is the study of how speakers and listeners use social reasoning to go beyond the literal meanings of words to interpret language in context. In this review, we take a pragmatic perspective on language development and argue for developmental continuity between early non-verbal communication, language learning, and linguistic pragmatics. We link phenomena from these different literatures by relating them to a computational framework (the rational speech act framework), which conceptualizes communication as fundamentally inferential and grounded in social cognition. The model specifies how different information sources (linguistic utterances, social cues, common ground) are combined when making pragmatic inferences. We present evidence in favor of this inferential view and review how pragmatic reasoning supports children’s learning, comprehension, and use of language.

scholarly journals Functional cross-talk between allosteric effects of activating and inhibiting ligands underlies PKM2 regulation

2018 ◽  
Author(s):  
Jamie A. Macpherson ◽  
Alina Theisen ◽  
Laura Masino ◽  
Louise Fets ◽  
Paul C. Driscoll ◽  
...  
Keyword(s):  
Enzymatic Activity ◽  
High Activity ◽  
Pyruvate Kinase ◽  
Cross Talk ◽  
Glycolytic Enzyme ◽  
Computational Framework ◽  
Allosteric Inhibitor ◽  
Fructose 1,6 Bisphosphate ◽  
Low Activity

ABSTRACTAllosteric regulation is central to the role of the glycolytic enzyme pyruvate kinase M2 (PKM2) in cellular metabolism. Multiple activating and inhibitory allosteric ligands regulate PKM2 activity by controlling the equilibrium between high activity tetramers and low activity dimers and monomers. However, it remains elusive how allosteric inputs upon simultaneous binding of different ligands are integrated to regulate PKM2 activity. Here, we show that, in the presence of the allosteric inhibitor L-phenylalanine (Phe), the activator fructose 1,6-bisphosphate (FBP) can induce PKM2 tetramerisation, but fails to maximally increase enzymatic activity. Guided by a new computational framework we developed to identify residues that mediate FBP-induced allostery, we generated two PKM2 mutants, A327S and C358A, in which activation by FBP remains intact but cannot be attenuated by Phe. Our findings demonstrate a role for residues involved in FBP-induced allostery in enabling the integration of allosteric input from Phe and reveal a mechanism that underlies the co-ordinate regulation of PKM2 activity by multiple allosteric ligands.

Liquidity, Risk Premia, and the Financial Transmission of Monetary Policy

2018 ◽  
Vol 10 (1) ◽  
pp. 309-328 ◽  
Author(s):  
Itamar Drechsler ◽  
Alexi Savov ◽  
Philipp Schnabl
Keyword(s):  
Monetary Policy ◽  
Risk Sharing ◽  
Financial System ◽  
Risk Premia ◽  
New Keynesian ◽  
Liquidity Premium ◽  
Impact Risk ◽  
The Cost ◽  
Transmission Of Monetary Policy

In recent years, there has been a resurgence of research on the transmission of monetary policy through the financial system, fueled in part by empirical findings showing that monetary policy affects asset prices and the financial system in ways not explained by the New Keynesian paradigm. In particular, monetary policy appears to impact risk premia in stock and bond prices and to effectively control the liquidity premium in the economy (the cost of holding liquid assets). We review these findings and recent theories proposed to explain them, and we outline a conceptual framework that unifies them. The framework revolves around the central role of liquidity in risk sharing and explains how monetary policy governs its production and use within the financial sector.

scholarly journals The Pervasive Role of Pragmatics in Early Language

2019 ◽  
Vol 1 (1) ◽  
pp. 223-249 ◽  
Author(s):  
Manuel Bohn ◽  
Michael C. Frank
Keyword(s):  
Language Learning ◽  
Common Ground ◽  
Social Cues ◽  
Social Reasoning ◽  
Early Language ◽  
Computational Framework ◽  
Linguistic Pragmatics ◽  
Developmental Continuity ◽  
Pragmatic Reasoning

Language is a fundamentally social endeavor. Pragmatics is the study of how speakers and listeners use social reasoning to go beyond the literal meanings of words to interpret language in context. In this article, we take a pragmatic perspective on language development and argue for developmental continuity between early nonverbal communication, language learning, and linguistic pragmatics. We link phenomena from these different literatures by relating them to a computational framework (the rational speech act framework), which conceptualizes communication as fundamentally inferential and grounded in social cognition. The model specifies how different information sources (linguistic utterances, social cues, common ground) are combined when making pragmatic inferences. We present evidence in favor of this inferential view and review how pragmatic reasoning supports children's learning, comprehension, and use of language.

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