Spencer, A J M
2004-01-01
The mechanics of fluids and the mechanics of solids represent the two major areas of physics and applied mathematics that meet in continuum mechanics, a field that forms the foundation of civil and mechanical engineering. This unified approach to the teaching of fluid and solid mechanics focuses on the general mechanical principles that apply to all materials. Students who have familiarized themselves with the basic principles can go on to specialize in any of the different branches of continuum mechanics. This text opens with introductory chapters on matrix algebra, vectors and Cartesian ten
A continuum mechanics analysis of shear characterisation methods
Akkerman, Remko
2018-01-01
The shear response of fabrics and fabric reinforced materials is primarily characterised by means of Picture Frame and Bias Extension experiments. Normalisation methods have been proposed earlier to enable comparison between different measurement results. Here, a continuum mechanics based analysis
Continuum Damage Mechanics A Continuum Mechanics Approach to the Analysis of Damage and Fracture
Murakami, Sumio
2012-01-01
Recent developments in engineering and technology have brought about serious and enlarged demands for reliability, safety and economy in wide range of fields such as aeronautics, nuclear engineering, civil and structural engineering, automotive and production industry. This, in turn, has caused more interest in continuum damage mechanics and its engineering applications. This book aims to give a concise overview of the current state of damage mechanics, and then to show the fascinating possibility of this promising branch of mechanics, and to provide researchers, engineers and graduate students with an intelligible and self-contained textbook. The book consists of two parts and an appendix. Part I is concerned with the foundation of continuum damage mechanics. Basic concepts of material damage and the mechanical representation of damage state of various kinds are described in Chapters 1 and 2. In Chapters 3-5, irreversible thermodynamics, thermodynamic constitutive theory and its application ...
Computational Continuum Mechanics
Shabana, Ahmed A
2011-01-01
This text presents the theory of continuum mechanics using computational methods. Ideal for students and researchers, the second edition features a new chapter on computational geometry and finite element analysis.
BOOK REVIEW: Nonlinear Continuum Mechanics for Finite Element Analysis
Bialek, James M.
1998-05-01
Nonlinear continuum mechanics of solids is a fascinating subject. All the assumptions inherited from an overexposure to linear behaviour and analysis must be re-examined. The standard definitions of strain designed for small deformation linear problems may be totally misleading when finite motion or large deformations are considered. Nonlinear behaviour includes phenomena like `snap-through', where bifurcation theory is applied to engineering design. Capabilities in this field are growing at a fantastic speed; for example, modern automobiles are presently being designed to crumple in the most energy absorbing manner in order to protect the occupants. The combination of nonlinear mechanics and the finite element method is a very important field. Most engineering designs encountered in the fusion effort are strictly limited to small deformation linear theory. In fact, fusion devices are usually kept in the low stress, long life regime that avoids large deformations, nonlinearity and any plastic behaviour. The only aspect of nonlinear continuum solid mechanics about which the fusion community now worries is that rare case where details of the metal forming process must be considered. This text is divided into nine sections: introduction, mathematical preliminaries, kinematics, stress and equilibrium, hyperelasticity, linearized equilibrium equations, discretization and solution, computer implementation and an appendix covering an introduction to large inelastic deformations. The authors have decided to use vector and tensor notation almost exclusively. This means that the usual maze of indicial equations is avoided, but most readers will therefore be stretched considerably to follow the presentation, which quickly proceeds to the heart of nonlinear behaviour in solids. With great speed the reader is led through the material (Lagrangian) and spatial (Eulerian) co-ordinates, the deformation gradient tensor (an example of a two point tensor), the right and left Cauchy
Continuum mechanics of anisotropic materials
Cowin, Stephen C
2013-01-01
Continuum Mechanics of Anisotropic Materials(CMAM) presents an entirely new and unique development of material anisotropy in the context of an appropriate selection and organization of continuum mechanics topics. These features will distinguish this continuum mechanics book from other books on this subject. Textbooks on continuum mechanics are widely employed in engineering education, however, none of them deal specifically with anisotropy in materials. For the audience of Biomedical, Chemical and Civil Engineering students, these materials will be dealt with more frequently and greater accuracy in their analysis will be desired. Continuum Mechanics of Anisotropic Materials' author has been a leader in the field of developing new approaches for the understanding of anisotropic materials.
Chaves, Eduardo W V
2013-01-01
This publication is aimed at students, teachers, and researchers of Continuum Mechanics and focused extensively on stating and developing Initial Boundary Value equations used to solve physical problems. With respect to notation, the tensorial, indicial and Voigt notations have been used indiscriminately. The book is divided into twelve chapters with the following topics: Tensors, Continuum Kinematics, Stress, The Objectivity of Tensors, The Fundamental Equations of Continuum Mechanics, An Introduction to Constitutive Equations, Linear Elasticity, Hyperelasticity, Plasticity (small and large deformations), Thermoelasticity (small and large deformations), Damage Mechanics (small and large deformations), and An Introduction to Fluids. Moreover, the text is supplemented with over 280 figures, over 100 solved problems, and 130 references.
Fundamentals of continuum mechanics
Rudnicki, John W
2014-01-01
A concise introductory course text on continuum mechanics Fundamentals of Continuum Mechanics focuses on the fundamentals of the subject and provides the background for formulation of numerical methods for large deformations and a wide range of material behaviours. It aims to provide the foundations for further study, not just of these subjects, but also the formulations for much more complex material behaviour and their implementation computationally. This book is divided into 5 parts, covering mathematical preliminaries, stress, motion and deformation, balance of mass, momentum and energ
Introduction to continuum mechanics
Lai, W Michael; Rubin, David
1996-01-01
Introduction to Continuum Mechanics is a recently updated and revised text which is perfect for either introductory courses in an undergraduate engineering curriculum or for a beginning graduate course.Continuum Mechanics studies the response of materials to different loading conditions. The concept of tensors is introduced through the idea of linear transformation in a self-contained chapter, and the interrelation of direct notation, indicial notation, and matrix operations is clearly presented. A wide range of idealized materials are considered through simple static and dynamic problems, a
Continuum mechanics for engineers
Mase, G Thomas; Mase, George E
2009-01-01
Continuum TheoryContinuum MechanicsStarting OverNotationEssential MathematicsScalars, Vectors and Cartesian TensorsTensor Algebra in Symbolic Notation - Summation ConventionIndicial NotationMatrices and DeterminantsTransformations of Cartesian TensorsPrincipal Values and Principal DirectionsTensor Fields, Tensor CalculusIntegral Theorems of Gauss and StokesStress PrinciplesBody and Surface Forces, Mass DensityCauchy Stress PrincipleThe Stress TensorForce and Moment Equilibrium; Stress Tensor SymmetryStress Transformation LawsPrincipal Stresses; Principal Stress DirectionsMaximum and Minimum Stress ValuesMohr's Circles For Stress Plane StressDeviator and Spherical Stress StatesOctahedral Shear StressKinematics of Deformation and MotionParticles, Configurations, Deformations and MotionMaterial and Spatial CoordinatesLangrangian and Eulerian DescriptionsThe Displacement FieldThe Material DerivativeDeformation Gradients, Finite Strain TensorsInfinitesimal Deformation TheoryCompatibility EquationsStretch RatiosRot...
Introduction to continuum mechanics
Rubin, David; Lai, W Michael
1994-01-01
Continuum mechanics studies the response of materials to different loading conditions. The concept of tensors is introduced through the idea of linear transformation in a self-contained chapter, and the interrelation of direct notation, indicial notation and matrix operations is clearly presented. A wide range of idealized materials are considered through simple static and dynamic problems, and the book contains an abundance of illustrative examples and problems, many with solutions. Through the addition of more advanced material (solution of classical elasticity problems, constitutive e
Multiscale methods coupling atomistic and continuum mechanics: analysis of a simple case
Blanc , Xavier; Le Bris , Claude; Legoll , Frédéric
2007-01-01
International audience; The description and computation of fine scale localized phenomena arising in a material (during nanoindentation, for instance) is a challenging problem that has given birth to many multiscale methods. In this work, we propose an analysis of a simple one-dimensional method that couples two scales, the atomistic one and the continuum mechanics one. The method includes an adaptive criterion in order to split the computational domain into two subdomains, that are described...
Song, Kyonchan; Li, Yingyong; Rose, Cheryl A.
2011-01-01
The performance of a state-of-the-art continuum damage mechanics model for interlaminar damage, coupled with a cohesive zone model for delamination is examined for failure prediction of quasi-isotropic open-hole tension laminates. Limitations of continuum representations of intra-ply damage and the effect of mesh orientation on the analysis predictions are discussed. It is shown that accurate prediction of matrix crack paths and stress redistribution after cracking requires a mesh aligned with the fiber orientation. Based on these results, an aligned mesh is proposed for analysis of the open-hole tension specimens consisting of different meshes within the individual plies, such that the element edges are aligned with the ply fiber direction. The modeling approach is assessed by comparison of analysis predictions to experimental data for specimen configurations in which failure is dominated by complex interactions between matrix cracks and delaminations. It is shown that the different failure mechanisms observed in the tests are well predicted. In addition, the modeling approach is demonstrated to predict proper trends in the effect of scaling on strength and failure mechanisms of quasi-isotropic open-hole tension laminates.
Kukudzhanov, Vladimir N
2013-01-01
This work focuses on computational methods in continuum thermomechanics. The text is based on the author's lectures, which ensures a didactical and coherent buildup.The main emphasis is put on the presentation of ideas and qualitative considerations, illustrated by specific examples and applications. Conditions and explanations that are essential for the practical application of methods are discussed thoroughly.
Nonlocal Theories in Continuum Mechanics
Directory of Open Access Journals (Sweden)
M. Jirásek
2004-01-01
Full Text Available The purpose of this paper is to explain why the standard continuum theory fails to properly describe certain mechanical phenomena and how the description can be improved by enrichments that incorporate the influence of gradients or weighted spatial averages of strain or of an internal variable. Three typical mechanical problems that require such enrichments are presented: (i dispersion of short elastic waves in heterogeneous or discrete media, (ii size effects in microscale elastoplasticity, in particular with the size dependence of the apparent hardening modulus, and (iii localization of strain and damage in quasibrittle structures and with the resulting transitional size effect. Problems covered in the examples encompass static and dynamic phenomena, linear and nonlinear behavior, and three constitutive frameworks, namely elasticity, plasticity and continuum damage mechanics. This shows that enrichments of the standard continuum theory can be useful in a wide range of mechanical problems.
Elementary Continuum Mechanics for Everyone
DEFF Research Database (Denmark)
Byskov, Esben
numerical method, the finite element method, including means of mending inherent problems •An informal, yet precise exposition that emphasizes not just how a topic is treated, but discusses why a particular choice is made The book opens with a derivation of kinematically nonlinear 3-D continuum mechanics...
Solernou, Albert; Hanson, Benjamin S; Richardson, Robin A; Welch, Robert; Read, Daniel J; Harlen, Oliver G; Harris, Sarah A
2018-03-01
Fluctuating Finite Element Analysis (FFEA) is a software package designed to perform continuum mechanics simulations of proteins and other globular macromolecules. It combines conventional finite element methods with stochastic thermal noise, and is appropriate for simulations of large proteins and protein complexes at the mesoscale (length-scales in the range of 5 nm to 1 μm), where there is currently a paucity of modelling tools. It requires 3D volumetric information as input, which can be low resolution structural information such as cryo-electron tomography (cryo-ET) maps or much higher resolution atomistic co-ordinates from which volumetric information can be extracted. In this article we introduce our open source software package for performing FFEA simulations which we have released under a GPLv3 license. The software package includes a C ++ implementation of FFEA, together with tools to assist the user to set up the system from Electron Microscopy Data Bank (EMDB) or Protein Data Bank (PDB) data files. We also provide a PyMOL plugin to perform basic visualisation and additional Python tools for the analysis of FFEA simulation trajectories. This manuscript provides a basic background to the FFEA method, describing the implementation of the core mechanical model and how intermolecular interactions and the solvent environment are included within this framework. We provide prospective FFEA users with a practical overview of how to set up an FFEA simulation with reference to our publicly available online tutorials and manuals that accompany this first release of the package.
FE Analysis of Rock with Hydraulic-Mechanical Coupling Based on Continuum Damage Evolution
Directory of Open Access Journals (Sweden)
Yongliang Wang
2016-01-01
Full Text Available A numerical finite element (FE analysis technology is presented for efficient and reliable solutions of rock with hydraulic-mechanical (HM coupling, researching the seepage characteristics and simulating the damage evolution of rock. To be in accord with the actual situation, the rock is naturally viewed as heterogeneous material, in which Young’s modulus, permeability, and strength property obey the typical Weibull distribution function. The classic Biot constitutive relation for rock as porous medium is introduced to establish a set of equations coupling with elastic solid deformation and seepage flow. The rock is subsequently developed into a novel conceptual and practical model considering the damage evolution of Young’s modulus and permeability, in which comprehensive utilization of several other auxiliary technologies, for example, the Drucker-Prager strength criterion, the statistical strength theory, and the continuum damage evolution, yields the damage variable calculating technology. To this end, an effective and reliable numerical FE analysis strategy is established. Numerical examples are given to show that the proposed method can establish heterogeneous rock model and be suitable for different load conditions and furthermore to demonstrate the effectiveness and reliability in the seepage and damage characteristics analysis for rock.
Continuum mechanics elasticity, plasticity, viscoelasticity
Dill, Ellis H
2006-01-01
FUNDAMENTALS OF CONTINUUM MECHANICSMaterial ModelsClassical Space-TimeMaterial BodiesStrainRate of StrainCurvilinear Coordinate SystemsConservation of MassBalance of MomentumBalance of EnergyConstitutive EquationsThermodynamic DissipationObjectivity: Invariance for Rigid MotionsColeman-Mizel ModelFluid MechanicsProblems for Chapter 1BibliographyNONLINEAR ELASTICITYThermoelasticityMaterial SymmetriesIsotropic MaterialsIncompressible MaterialsConjugate Measures of Stress and StrainSome Symmetry GroupsRate Formulations for Elastic MaterialsEnergy PrinciplesGeometry of Small DeformationsLinear ElasticitySpecial Constitutive Models for Isotropic MaterialsMechanical Restrictions on the Constitutive RelationsProblems for Chapter 2BibliographyLINEAR ELASTICITYBasic EquationsPlane StrainPlane StressProperties of SolutionsPotential EnergySpecial Matrix NotationThe Finite Element Method of SolutionGeneral Equations for an Assembly of ElementsFinite Element Analysis for Large DeformationsProblems for Chapter 3Bibliograph...
Static nonlinear analysis of piles cap based on the Continuum Damage Mechanics
Directory of Open Access Journals (Sweden)
Luiz Antonio Farani de Souza
2015-10-01
Full Text Available The piles cap is an important structural element whose function is to transfer the actions of the superstructure for a group of piles. The visual inspection of the piles cap behavior under service conditions is not possible and, in addition, the knowledge of its actual structural performance is a vital necessity for the constructions overall stability. In this paper, a two-dimensional nonlinear analysis is carried out, by means of Finite Element Method, of a reinforced concrete pile caps with two piles found in the literature. It adopts for the material concrete a constitutive model based on the Continuum Damage Mechanics, with the possibility to provide a tensile and compression differentiated behavior. The steel is described by an elastoplastic bilinear model. The equilibrium path is achieved by Arc Length iteration technique in association with the Newton - Raphson Method. The numerical results obtained with the developed computational code are compared with the available experimental and numerical results and the analytical solution, and have the objective of evaluate the potential of the proposed modeling as an investigation numerical tool to determine the rupture force and the damage distribution in the piles cap.
Tensor Algebra and Tensor Analysis for Engineers With Applications to Continuum Mechanics
Itskov, Mikhail
2013-01-01
There is a large gap between the engineering course in tensor algebra on the one hand and the treatment of linear transformations within classical linear algebra on the other hand. The aim of this modern textbook is to bridge this gap by means of the consequent and fundamental exposition. The book primarily addresses engineering students with some initial knowledge of matrix algebra. Thereby the mathematical formalism is applied as far as it is absolutely necessary. Numerous exercises are provided in the book and are accompanied by solutions, enabling self-study. The last chapters of the book deal with modern developments in the theory of isotropic and anisotropic tensor functions and their applications to continuum mechanics and are therefore of high interest for PhD-students and scientists working in this area. This third edition is completed by a number of additional figures, examples and exercises. The text and formulae have been revised and improved where necessary.
Tensor algebra and tensor analysis for engineers with applications to continuum mechanics
Itskov, Mikhail
2015-01-01
This is the fourth and revised edition of a well-received book that aims at bridging the gap between the engineering course of tensor algebra on the one side and the mathematical course of classical linear algebra on the other side. In accordance with the contemporary way of scientific publications, a modern absolute tensor notation is preferred throughout. The book provides a comprehensible exposition of the fundamental mathematical concepts of tensor calculus and enriches the presented material with many illustrative examples. In addition, the book also includes advanced chapters dealing with recent developments in the theory of isotropic and anisotropic tensor functions and their applications to continuum mechanics. Hence, this monograph addresses graduate students as well as scientists working in this field. In each chapter numerous exercises are included, allowing for self-study and intense practice. Solutions to the exercises are also provided.
Geometric continuum mechanics and induced beam theories
R Eugster, Simon
2015-01-01
This research monograph discusses novel approaches to geometric continuum mechanics and introduces beams as constraint continuous bodies. In the coordinate free and metric independent geometric formulation of continuum mechanics as well as for beam theories, the principle of virtual work serves as the fundamental principle of mechanics. Based on the perception of analytical mechanics that forces of a mechanical system are defined as dual quantities to the kinematical description, the virtual work approach is a systematic way to treat arbitrary mechanical systems. Whereas this methodology is very convenient to formulate induced beam theories, it is essential in geometric continuum mechanics when the assumptions on the physical space are relaxed and the space is modeled as a smooth manifold. The book addresses researcher and graduate students in engineering and mathematics interested in recent developments of a geometric formulation of continuum mechanics and a hierarchical development of induced beam theories.
Continuum mechanics of single-substance bodies
Eringen, A Cemal
1975-01-01
Continuum Physics, Volume II: Continuum Mechanics of Single-Substance Bodies discusses the continuum mechanics of bodies constituted by a single substance, providing a thorough and precise presentation of exact theories that have evolved during the past years. This book consists of three parts-basic principles, constitutive equations for simple materials, and methods of solution. Part I of this publication is devoted to a discussion of basic principles irrespective of material geometry and constitution that are valid for all kinds of substances, including composites. The geometrical notions, k
Teaching Continuum Mechanics in a Mechanical Engineering Program
Liu, Yucheng
2011-01-01
This paper introduces a graduate course, continuum mechanics, which is designed for and taught to graduate students in a Mechanical Engineering (ME) program. The significance of continuum mechanics in engineering education is demonstrated and the course structure is described. Methods used in teaching this course such as topics, class…
Continuum mechanics concise theory and problems
Chadwick, P
1998-01-01
Written in response to the dearth of practical and meaningful textbooks in the field of fundamental continuum mechanics, this comprehensive treatment offers students and instructors an immensely useful tool. Its 115 solved problems and exercises not only provide essential practice but also systematically advance the understanding of vector and tensor theory, basic kinematics, balance laws, field equations, jump conditions, and constitutive equations.Readers follow clear, formally precise steps through the central ideas of classical and modern continuum mechanics, expressed in a common, effici
Sendova, T.
2010-02-15
In this paper we focus on the analysis of the partial differential equations arising from a new approach to modeling brittle fracture based on an extension of continuum mechanics to the nanoscale. It is shown that ascribing constant surface tension to the fracture surfaces and using the appropriate crack surface boundary condition given by the jump momentum balance leads to a sharp crack opening profile at the crack tip but predicts logarithmically singular crack tip stress. However, a modified model, where the surface excess property is responsive to the curvature of the fracture surfaces, yields bounded stresses and a cusp-like opening profile at the crack tip. Further, two possible fracture criteria in the context of the new theory are discussed. The first is an energy-based crack growth condition, while the second employs the finite crack tip stress the model predicts. The classical notion of energy release rate is based upon the singular solution, whereas for the modeling approach adopted here, a notion analogous to the energy release rate arises through a different mechanism associated with the rate of working of the surface excess properties at the crack tip. © The Author(s), 2010.
Finsler-Geometric Continuum Mechanics
2016-05-01
general than classical approaches and can reproduce phase field solutions when certain simplifying assumptions are imposed. Upon invoking a conformal or...curvature, and so forth) may in turn depend on position and direction or in- ternal state. This generality is in contrast to classical Riemannian...general relativity,1 gravitation,2 quantum mechan- ics,3 electrodynamics ,4 heat conduction,5 and the mechanics of solids.6 The latter topic (i.e
Continuum damage and fracture mechanics
Öchsner, Andreas
2016-01-01
This textbook offers readers an introduction to damage and fracture mechanics, equipping them to grasp the basic ideas of the presented approaches to modeling in applied mechanics. In the first part, the book reviews and expands on the classical theory of elastic and elasto-plastic material behavior. A solid understanding of these two topics is the essential prerequisite to advancing to damage and fracture mechanics. Thus, the second part of this course provides an introduction to the treatment of damage and fractures in the context of applied mechanics. Wherever possible, the one-dimensional case is first introduced and then generalized in a following step. This departs somewhat from the more classical approach, where first the most general case is derived and then simplified to special cases. In general, the required mathematics background is kept to a minimum. Tutorials are included at the end of each chapter, presenting the major steps for the solution and offering valuable tips and tricks. The supplem...
Continuum mechanics the birthplace of mathematical models
Allen, Myron B
2015-01-01
Continuum mechanics is a standard course in many graduate programs in engineering and applied mathematics as it provides the foundations for the various differential equations and mathematical models that are encountered in fluid mechanics, solid mechanics, and heat transfer. This book successfully makes the topic more accessible to advanced undergraduate mathematics majors by aligning the mathematical notation and language with related courses in multivariable calculus, linear algebra, and differential equations; making connections with other areas of applied mathematics where parial differe
The geometrical language of continuum mechanics
Epstein, Marcelo
2010-01-01
This book presents the fundamental concepts of modern differential geometry within the framework of continuum mechanics. It is divided into three parts of roughly equal length. The book opens with a motivational chapter to impress upon the reader that differential geometry is indeed the natural language of continuum mechanics or, better still, that the latter is a prime example of the application and materialization of the former. In the second part, the fundamental notions of differential geometry are presented with rigor using a writing style that is as informal as possible. Differentiable manifolds, tangent bundles, exterior derivatives, Lie derivatives, and Lie groups are illustrated in terms of their mechanical interpretations. The third part includes the theory of fiber bundles, G-structures, and groupoids, which are applicable to bodies with internal structure and to the description of material inhomogeneity. The abstract notions of differential geometry are thus illuminated by practical and intuitivel...
Nonlinear continuum mechanics and large inelastic deformations
Dimitrienko, Yuriy I
2010-01-01
This book provides a rigorous axiomatic approach to continuum mechanics under large deformation. In addition to the classical nonlinear continuum mechanics - kinematics, fundamental laws, the theory of functions having jump discontinuities across singular surfaces, etc. - the book presents the theory of co-rotational derivatives, dynamic deformation compatibility equations, and the principles of material indifference and symmetry, all in systematized form. The focus of the book is a new approach to the formulation of the constitutive equations for elastic and inelastic continua under large deformation. This new approach is based on using energetic and quasi-energetic couples of stress and deformation tensors. This approach leads to a unified treatment of large, anisotropic elastic, viscoelastic, and plastic deformations. The author analyses classical problems, including some involving nonlinear wave propagation, using different models for continua under large deformation, and shows how different models lead t...
Sensitivity filtering from a continuum mechanics perspective
DEFF Research Database (Denmark)
Sigmund, Ole; Maute, Kurt
2012-01-01
In topology optimization filtering is a popular approach for preventing numerical instabilities. This short note shows that the well-known sensitivity filtering technique, that prevents checkerboards and ensures mesh-independent designs in density-based topology optimization, is equivalent to min...... to minimizing compliance for nonlocal elasticity problems known from continuum mechanics. Hence, the note resolves the long-standing quest for finding an explanation and physical motivation for the sensitivity filter....
Non-classical continuum mechanics a dictionary
Maugin, Gérard A
2017-01-01
This dictionary offers clear and reliable explanations of over 100 keywords covering the entire field of non-classical continuum mechanics and generalized mechanics, including the theory of elasticity, heat conduction, thermodynamic and electromagnetic continua, as well as applied mathematics. Every entry includes the historical background and the underlying theory, basic equations and typical applications. The reference list for each entry provides a link to the original articles and the most important in-depth theoretical works. Last but not least, every entry is followed by a cross-reference to other related subject entries in the dictionary.
On nonlocal modeling in continuum mechanics
Directory of Open Access Journals (Sweden)
Adam Martowicz
2018-01-01
Full Text Available The objective of the paper is to provide an overview of nonlocal formulations for models of elastic solids. The author presents the physical foundations for nonlocal theories of continuum mechanics, followed by various analytical and numerical techniques. The characteristics and range of practical applications for the presented approaches are discussed. The results of numerical simulations for the selected case studies are provided to demonstrate the properties of the described methods. The paper is illustrated with outcomes from peridynamic analyses. Fatigue and axial stretching were simulated to show the capabilities of the developed numerical tools.
Polymer quantum mechanics and its continuum limit
International Nuclear Information System (INIS)
Corichi, Alejandro; Vukasinac, Tatjana; Zapata, Jose A.
2007-01-01
A rather nonstandard quantum representation of the canonical commutation relations of quantum mechanics systems, known as the polymer representation, has gained some attention in recent years, due to its possible relation with Planck scale physics. In particular, this approach has been followed in a symmetric sector of loop quantum gravity known as loop quantum cosmology. Here we explore different aspects of the relation between the ordinary Schroedinger theory and the polymer description. The paper has two parts. In the first one, we derive the polymer quantum mechanics starting from the ordinary Schroedinger theory and show that the polymer description arises as an appropriate limit. In the second part we consider the continuum limit of this theory, namely, the reverse process in which one starts from the discrete theory and tries to recover back the ordinary Schroedinger quantum mechanics. We consider several examples of interest, including the harmonic oscillator, the free particle, and a simple cosmological model
Continuum Mechanics of Beam and Plate Flexure
DEFF Research Database (Denmark)
Jönsson, Jeppe
This text has been written and used during the spring of 1995 for a course on flexural mechanics of beams and plates at Aalborg University. The idea has been to concentrate on basic principles of the theories, which are of importance to the modern structural engineer. Today's structural engineer...... must be acquainted with the classic beam and plate theories, when reading manuals and using modern software tools such as the finite element method. Each chapter includes supplementary theory and derivations enabling consultation of the notes also at a later stage of study. A preliminary chapter...... introduces the modern notation used in textbooks and in research today. It further gives an introduction to three-dimensional continuum mechanics of elastic bodies and the related principles of virtual work. The ideas to give the students a basic understanding of the stresses and strains, the equilibrium...
Hu, M.; Rutqvist, J.
2017-12-01
The disposal of heat-generating nuclear waste in salt host rock establishes a thermal gradient around the waste package that may cause brine inclusions in the salt grains to migrate toward the waste package. In this study, a dual-continuum model is developed to analyze such a phenomenon. This model is based on the Finite Volume Method (FVM), and it is fully thermal-hydro-mechanical (THM) coupled. For fluid flow, the dual-continuum model considers flow in the interconnected pore space and also in the salt grains. The mass balance of salt and water in these two continua is separately established, and their coupling is represented by flux associated with brine migration. Together with energy balance, such a system produces a coupled TH model with strongly nonlinear features. For mechanical analysis, a new formulation is developed based on the Voronoi tessellated mesh. By relating each cell to several connected triangles, first-order approximation is constructed. The coupling between thermal and mechanical fields is only considered in terms of thermal expansion. And the coupling between the hydraulic and mechanical fields in terms of pore-volume effects is consistent with Biot's theory. Therefore, a fully coupled THM model is developed. Several demonstration examples are provided to verify the model. Last the new model is applied to analyze coupled THM behavior and the results are compared with experimental data.
Advanced methods of continuum mechanics for materials and structures
Aßmus, Marcus
2016-01-01
This volume presents a collection of contributions on advanced approaches of continuum mechanics, which were written to celebrate the 60th birthday of Prof. Holm Altenbach. The contributions are on topics related to the theoretical foundations for the analysis of rods, shells and three-dimensional solids, formulation of constitutive models for advanced materials, as well as development of new approaches to the modeling of damage and fractures.
Continuum mechanics methods in the theory of phase transformations
Grinfel'D, Mikhail A.
A theory for phase transformations in solids is developed on the basis of the variational principles of thermodynamics. The discussion focuses on the fundamental concepts of the theory, detailed classification of phase transformations at the phenomenological level, and statement of essentially new boundary value problems for continuum mechanics equations. General solutions are illustrated by the equilibrium and stability analysis of specific two-phase systems and solution of problems of practical importance. The methods and results discussed here are relevant to various problems in rigid body mechanics, hydrodynamics, materials science, geomechanics, and other fields.
SEACAS Theory Manuals: Part II. Nonlinear Continuum Mechanics
Energy Technology Data Exchange (ETDEWEB)
Attaway, S.W.; Laursen, T.A.; Zadoks, R.I.
1998-09-01
This report summarizes the key continuum mechanics concepts required for the systematic prescription and numerical solution of finite deformation solid mechanics problems. Topics surveyed include measures of deformation appropriate for media undergoing large deformations, stress measures appropriate for such problems, balance laws and their role in nonlinear continuum mechanics, the role of frame indifference in description of large deformation response, and the extension of these theories to encompass two dimensional idealizations, structural idealizations, and rigid body behavior. There are three companion reports that describe the problem formulation, constitutive modeling, and finite element technology for nonlinear continuum mechanics systems.
Elementary continuum mechanics for everyone with applications to structural mechanics
Byskov, Esben
2013-01-01
The book opens with a derivation of kinematically nonlinear 3-D continuum mechanics for solids. Then the principle of virtual work is utilized to derive the simpler, kinematically linear 3-D theory and to provide the foundation for developing consistent theories of kinematic nonlinearity and linearity for specialized continua, such as beams and plates, and finite element methods for these structures. A formulation in terms of the versatile Budiansky-Hutchinson notation is used as basis for the theories for these structures and structural elements, as well as for an in-depth treatment of structural instability.
Hyperbolic theories and problems of continuum mechanics
Directory of Open Access Journals (Sweden)
Yuri N. Radayev
2015-03-01
Full Text Available Theories and problems of that part of continuum thermomechanics which can not be properly formulated without partial differential equations of hyperbolic analytical type are considered. Special attention is paid to comparatively new hyperbolic continuum theories: the theory of three-dimensional perfect plasticity and the theory of micropolar thermoelasticity. The latter is accepted as type-II thermoelasticity. Three-dimensional statical and kinematical equations of the perfect plasticity theory by Ishlinskii and Ivlev are studied in order to elucidate their analytical type and opportunity to obtain integrable equations along some special lines. A new approach to hyperbolic formulations of thermoelasticity presumes consideration of referential gradients of thermodynamic state variables and extra field variables (rapid variables as independent functional arguments in the action density. New hyperbolic thermomechanics of micropolar thermoelastic media is developed within the framework of classical field theory by the variational action integral and the least action principle.
Elementary Continuum Mechanics for Everyone - And Some More
DEFF Research Database (Denmark)
Byskov, Esben
Quite trivially, Continuum mechanics per se deals with the description of deformations of three-dimensional continua i.e. models whose properties are independent of scale in that the continuum does not possess a structure. Thus, continuum mechanics does not try to model the atomic structure...... of the involved materials- perhaps not even the crystalline or spongy, or lumpy structure- but offers a "smeared-out" version of the real world. Also, the desired description depends very much on the needs of the dicipline in question....
Elementary Continuum Mechanics for Everyone - and Some More
DEFF Research Database (Denmark)
Byskov, Esben
Quite trivially, Continuum mechanics per se deals with the description of deformations of three-dimensional continua i.e. models whose properties are independent of scale in that the continuum does not possess a structure. Thus, continuum mechanics does not try to model the atomic structure...... of the involved materials- perhaps not even the crystalline or spongy, or lumpy structure- but offers a "smeared-out" version of the real world. Also, the desired description depends very much on the needs of the discipline in question....
Continuum mechanics using Mathematica fundamentals, methods, and applications
Romano, Antonio
2014-01-01
This textbook's methodological approach familiarizes readers with the mathematical tools required to correctly define and solve problems in continuum mechanics. Covering essential principles and fundamental applications, this second edition of Continuum Mechanics using Mathematica® provides a solid basis for a deeper study of more challenging and specialized problems related to nonlinear elasticity, polar continua, mixtures, piezoelectricity, ferroelectricity, magneto-fluid mechanics, and state changes (see A. Romano, A. Marasco, Continuum Mechanics: Advanced Topics and Research Trends, Springer (Birkhäuser), 2010, ISBN 978-0-8176-4869-5). Key topics and features: * Concise presentation strikes a balance between fundamentals and applications * Requisite mathematical background carefully collected in two introductory chapters and one appendix * Recent developments highlighted through coverage of more significant applications to areas such as wave propagation, fluid mechanics, porous media, linear elasticity....
ICMS Workshop on Differential Geometry and Continuum Mechanics
Grinfeld, Michael; Knops, R
2015-01-01
This book examines the exciting interface between differential geometry and continuum mechanics, now recognised as being of increasing technological significance. Topics discussed include isometric embeddings in differential geometry and the relation with microstructure in nonlinear elasticity, the use of manifolds in the description of microstructure in continuum mechanics, experimental measurement of microstructure, defects, dislocations, surface energies, and nematic liquid crystals. Compensated compactness in partial differential equations is also treated. The volume is intended for specialists and non-specialists in pure and applied geometry, continuum mechanics, theoretical physics, materials and engineering sciences, and partial differential equations. It will also be of interest to postdoctoral scientists and advanced postgraduate research students. These proceedings include revised written versions of the majority of papers presented by leading experts at the ICMS Edinburgh Workshop on Differential G...
Theoretical Analysis of a Modified Continuum Model
Ge, Hong-Xia; Wu, Shu-Zhen; Cheng, Rong-Jun; Lo, Siu-ming
2011-09-01
Based on the optimal velocity (OV) model, a new car-following model for traffic flow with the consideration of the driver's forecast effect (DFE) was proposed by Tang et al., which can be used to describe some complex traffic phenomena better. Using an asymptotic approximation between the headway and density, we obtain a new macro continuum version of the car-following model with the DFE. The linear stability theory is applied to derive the neutral stability condition. The Korteweg—de Vries equation near the neutral stability line is given by nonlinear analysis and the corresponding solution for the traffic density wave is derived.
Boyina, Gangadhara Rao T.; Rayavarapu, Vijaya Kumar; V. V., Subba Rao
2017-02-01
The prediction of ultimate strength remains the main challenge in the simulation of the mechanical response of composite structures. This paper examines continuum damage model to predict the strength and size effects for deformation and failure response of polymer composite laminates when subjected to complex state of stress. The paper also considers how the overall results of the exercise can be applied in design applications. The continuum damage model is described and the resulting prediction of size effects are compared against the standard benchmark solutions. The stress analysis for strength prediction of rotary wing aircraft cabin door is carried out. The goal of this study is to extend the proposed continuum damage model such that it can be accurately predict the failure around stress concentration regions. The finite element-based continuum damage mechanics model can be applied to the structures and components of arbitrary configurations where analytical solutions could not be developed.
Continuum mechanical and computational aspects of material behavior
Energy Technology Data Exchange (ETDEWEB)
Fried, Eliot; Gurtin, Morton E.
2000-02-10
The focus of the work is the application of continuum mechanics to materials science, specifically to the macroscopic characterization of material behavior at small length scales. The long-term goals are a continuum-mechanical framework for the study of materials that provides a basis for general theories and leads to boundary-value problems of physical relevance, and computational methods appropriate to these problems supplemented by physically meaningful regularizations to aid in their solution. Specific studies include the following: the development of a theory of polycrystalline plasticity that incorporates free energy associated with lattice mismatch between grains; the development of a theory of geometrically necessary dislocations within the context of finite-strain plasticity; the development of a gradient theory for single-crystal plasticity with geometrically necessary dislocations; simulations of dynamical fracture using a theory that allows for the kinking and branching of cracks; computation of segregation and compaction in flowing granular materials.
From cells to tissue: A continuum model of epithelial mechanics
Ishihara, Shuji; Marcq, Philippe; Sugimura, Kaoru
2017-08-01
A two-dimensional continuum model of epithelial tissue mechanics was formulated using cellular-level mechanical ingredients and cell morphogenetic processes, including cellular shape changes and cellular rearrangements. This model incorporates stress and deformation tensors, which can be compared with experimental data. Focusing on the interplay between cell shape changes and cell rearrangements, we elucidated dynamical behavior underlying passive relaxation, active contraction-elongation, and tissue shear flow, including a mechanism for contraction-elongation, whereby tissue flows perpendicularly to the axis of cell elongation. This study provides an integrated scheme for the understanding of the orchestration of morphogenetic processes in individual cells to achieve epithelial tissue morphogenesis.
Growth limit of carbon onions – A continuum mechanical study
DEFF Research Database (Denmark)
Todt, Melanie; Bitsche, Robert; Hartmann, Markus A.
2014-01-01
The growth of carbon onions is simulated using continuum mechanical shell models. With this models it is shown that, if a carbon onion has grown to a critical size, the formation of an additional layer leads to the occurrence of a structural instability. This instability inhibits further growth o...... model gives insight into mechanisms which are assumed to limit the size of carbon onions and can serve as basis for further investigations, e.g., of the formation of nanodiamonds in the center of carbon onions. © 2013 Elsevier Ltd. All rights reserved....
Directory of Open Access Journals (Sweden)
Zhi Yan
2017-01-01
Full Text Available Piezoelectric nanomaterials (PNs are attractive for applications including sensing, actuating, energy harvesting, among others in nano-electro-mechanical-systems (NEMS because of their excellent electromechanical coupling, mechanical and physical properties. However, the properties of PNs do not coincide with their bulk counterparts and depend on the particular size. A large amount of efforts have been devoted to studying the size-dependent properties of PNs by using experimental characterization, atomistic simulation and continuum mechanics modeling with the consideration of the scale features of the nanomaterials. This paper reviews the recent progresses and achievements in the research on the continuum mechanics modeling of the size-dependent mechanical and physical properties of PNs. We start from the fundamentals of the modified continuum mechanics models for PNs, including the theories of surface piezoelectricity, flexoelectricity and non-local piezoelectricity, with the introduction of the modified piezoelectric beam and plate models particularly for nanostructured piezoelectric materials with certain configurations. Then, we give a review on the investigation of the size-dependent properties of PNs by using the modified continuum mechanics models, such as the electromechanical coupling, bending, vibration, buckling, wave propagation and dynamic characteristics. Finally, analytical modeling and analysis of nanoscale actuators and energy harvesters based on piezoelectric nanostructures are presented.
Yan, Zhi; Jiang, Liying
2017-01-26
Piezoelectric nanomaterials (PNs) are attractive for applications including sensing, actuating, energy harvesting, among others in nano-electro-mechanical-systems (NEMS) because of their excellent electromechanical coupling, mechanical and physical properties. However, the properties of PNs do not coincide with their bulk counterparts and depend on the particular size. A large amount of efforts have been devoted to studying the size-dependent properties of PNs by using experimental characterization, atomistic simulation and continuum mechanics modeling with the consideration of the scale features of the nanomaterials. This paper reviews the recent progresses and achievements in the research on the continuum mechanics modeling of the size-dependent mechanical and physical properties of PNs. We start from the fundamentals of the modified continuum mechanics models for PNs, including the theories of surface piezoelectricity, flexoelectricity and non-local piezoelectricity, with the introduction of the modified piezoelectric beam and plate models particularly for nanostructured piezoelectric materials with certain configurations. Then, we give a review on the investigation of the size-dependent properties of PNs by using the modified continuum mechanics models, such as the electromechanical coupling, bending, vibration, buckling, wave propagation and dynamic characteristics. Finally, analytical modeling and analysis of nanoscale actuators and energy harvesters based on piezoelectric nanostructures are presented.
Yan, Zhi; Jiang, Liying
2017-01-01
Piezoelectric nanomaterials (PNs) are attractive for applications including sensing, actuating, energy harvesting, among others in nano-electro-mechanical-systems (NEMS) because of their excellent electromechanical coupling, mechanical and physical properties. However, the properties of PNs do not coincide with their bulk counterparts and depend on the particular size. A large amount of efforts have been devoted to studying the size-dependent properties of PNs by using experimental characterization, atomistic simulation and continuum mechanics modeling with the consideration of the scale features of the nanomaterials. This paper reviews the recent progresses and achievements in the research on the continuum mechanics modeling of the size-dependent mechanical and physical properties of PNs. We start from the fundamentals of the modified continuum mechanics models for PNs, including the theories of surface piezoelectricity, flexoelectricity and non-local piezoelectricity, with the introduction of the modified piezoelectric beam and plate models particularly for nanostructured piezoelectric materials with certain configurations. Then, we give a review on the investigation of the size-dependent properties of PNs by using the modified continuum mechanics models, such as the electromechanical coupling, bending, vibration, buckling, wave propagation and dynamic characteristics. Finally, analytical modeling and analysis of nanoscale actuators and energy harvesters based on piezoelectric nanostructures are presented. PMID:28336861
On Mathematical Aspects of Dual Variables in Continuum Mechanics. Part 1 : Mathematical Principles
Giessen, E. van der; Kollmann, F.G.
1996-01-01
In this paper consisting of two parts we consider mathematical aspects of dual variables appearing in continuum mechanics. Tensor calculus on manifolds as introduced into continuum mechanics is used as a point of departure. This mathematical formalism leads to additional structure of continuum
Wetting in the nanoscale: a continuum mechanics approach.
Barberis, F; Capurro, M
2008-10-01
A continuum mechanics model has been developed to study the equilibrium shape of nanometric droplets on a planar solid substrate and how, in this scale, the contact angle depends on the drop size. The drop is modeled as a liquid volume enclosed in an inextensible membrane, subject to an isotropic tension (the surface tension) and to a field of surface forces including, in the proximity of the solid, the liquid-to-solid interactions, envisaged as a generic potential force per unit surface directed normally to the solid surface (i.e. vertically). The only conditions required to solve the problem are those of mechanical and thermodynamic equilibrium. The predictions of the model are discussed in comparison with data on nanodrops retrieved by a special AFM device for a number of different liquid-solid systems.
Non-coherent continuum scattering as a line polarization mechanism
Energy Technology Data Exchange (ETDEWEB)
Del Pino Alemán, T.; Manso Sainz, R.; Trujillo Bueno, J., E-mail: tanausu@iac.es, E-mail: rsainz@iac.es, E-mail: jtb@iac.es [Instituto de Astrofísica de Canarias, E-38205 La Laguna, Tenerife (Spain)
2014-03-20
Line scattering polarization can be strongly affected by Rayleigh scattering at neutral hydrogen and Thomson scattering at free electrons. Often a depolarization of the continuum results, but the Doppler redistribution produced by the continuum scatterers, which are light (hence, fast), induces more complex interactions between the polarization in spectral lines and in the continuum. Here we formulate and solve the radiative transfer problem of scattering line polarization with non-coherent continuum scattering consistently. The problem is formulated within the spherical tensor representation of atomic and light polarization. The numerical method of solution is a generalization of the Accelerated Lambda Iteration that is applied to both the atomic system and the radiation field. We show that the redistribution of the spectral line radiation due to the non-coherence of the continuum scattering may modify the shape of the emergent fractional linear polarization patterns significantly, even yielding polarization signals above the continuum level in intrinsically unpolarizable lines.
Harik, V. M.
2001-01-01
Limitations in the validity of the continuum beam model for carbon nanotubes (NTs) and nanorods are examined. Applicability of all assumptions used in the model is restricted by the two criteria for geometric parameters that characterize the structure of NTs. The key non-dimensional parameters that control the NT buckling behavior are derived via dimensional analysis of the nanomechanical problem. A mechanical law of geometric similitude for NT buckling is extended from continuum mechanics for different molecular structures. A model applicability map, where two classes of beam-like NTs are identified, is constructed for distinct ranges of non-dimensional parameters. Expressions for the critical buckling loads and strains are tailored for two classes of NTs and compared with the data provided by the molecular dynamics simulations. copyright 2001 Elsevier Science Ltd. All rights reserved.
A continuum mechanics constitutive framework for transverse isotropic soft tissues
Garcia-Gonzalez, D.; Jérusalem, A.; Garzon-Hernandez, S.; Zaera, R.; Arias, A.
2018-03-01
In this work, a continuum constitutive framework for the mechanical modelling of soft tissues that incorporates strain rate and temperature dependencies as well as the transverse isotropy arising from fibres embedded into a soft matrix is developed. The constitutive formulation is based on a Helmholtz free energy function decoupled into the contribution of a viscous-hyperelastic matrix and the contribution of fibres introducing dispersion dependent transverse isotropy. The proposed framework considers finite deformation kinematics, is thermodynamically consistent and allows for the particularisation of the energy potentials and flow equations of each constitutive branch. In this regard, the approach developed herein provides the basis on which specific constitutive models can be potentially formulated for a wide variety of soft tissues. To illustrate this versatility, the constitutive framework is particularised here for animal and human white matter and skin, for which constitutive models are provided. In both cases, different energy functions are considered: Neo-Hookean, Gent and Ogden. Finally, the ability of the approach at capturing the experimental behaviour of the two soft tissues is confirmed.
Chen, Xi; Cui, Qiang; Tang, Yuye; Yoo, Jejoong; Yethiraj, Arun
2008-07-01
A hierarchical simulation framework that integrates information from molecular dynamics (MD) simulations into a continuum model is established to study the mechanical response of mechanosensitive channel of large-conductance (MscL) using the finite element method (FEM). The proposed MD-decorated FEM (MDeFEM) approach is used to explore the detailed gating mechanisms of the MscL in Escherichia coli embedded in a palmitoyloleoylphosphatidylethanolamine lipid bilayer. In Part I of this study, the framework of MDeFEM is established. The transmembrane and cytoplasmic helices are taken to be elastic rods, the loops are modeled as springs, and the lipid bilayer is approximated by a three-layer sheet. The mechanical properties of the continuum components, as well as their interactions, are derived from molecular simulations based on atomic force fields. In addition, analytical closed-form continuum model and elastic network model are established to complement the MDeFEM approach and to capture the most essential features of gating. In Part II of this study, the detailed gating mechanisms of E. coli-MscL under various types of loading are presented and compared with experiments, structural model, and all-atom simulations, as well as the analytical models established in Part I. It is envisioned that such a hierarchical multiscale framework will find great value in the study of a variety of biological processes involving complex mechanical deformations such as muscle contraction and mechanotransduction.
Applicability of the Continuum-Shell Theories to the Mechanics of Carbon Nanotubes
Harik, V. M.; Gates, T. S.; Nemeth, M. P.
2002-01-01
Validity of the assumptions relating the applicability of continuum shell theories to the global mechanical behavior of carbon nanotubes is examined. The present study focuses on providing a basis that can be used to qualitatively assess the appropriateness of continuum-shell models for nanotubes. To address the effect of nanotube structure on their deformation, all nanotube geometries are divided into four major classes that require distinct models. Criteria for the applicability of continuum models are presented. The key parameters that control the buckling strains and deformation modes of these classes of nanotubes are determined. In an analogy with continuum mechanics, mechanical laws of geometric similitude are presented. A parametric map is constructed for a variety of nanotube geometries as a guide for the applicability of different models. The continuum assumptions made in representing a nanotube as a homogeneous thin shell are analyzed to identify possible limitations of applying shell theories and using their bifurcation-buckling equations at the nano-scale.
Analysis of thermodiffusive cellular instabilities in continuum combustion fronts
Azizi, Hossein; Gurevich, Sebastian; Provatas, Nikolas
2017-01-01
We explore numerically the morphological patterns of thermodiffusive instabilities in combustion fronts with a continuum fuel source, within a range of Lewis numbers and ignition temperatures, focusing on the cellular regime. For this purpose, we generalize the recent model of Brailovsky et al. to include distinct process kinetics and reactant heterogeneity. The generalized model is derived analytically and validated with other established models in the limit of infinite Lewis number for zero-order and first-order kinetics. Cellular and dendritic instabilities are found at low Lewis numbers. These are studied using a dynamic adaptive mesh refinement technique that allows very large computational domains, thus allowing us to reduce finite-size effects that can affect or even preclude the emergence of these patterns. Our numerical linear stability analysis is consistent with the analytical results of Brailovsky et al. The distinct types of dynamics found in the vicinity of the critical Lewis number, ranging from steady-state cells to continued tip splitting and cell merging, are well described within the framework of thermodiffusive instabilities and are consistent with previous numerical studies. These types of dynamics are classified as "quasilinear" and characterized by low-amplitude cells that may be strongly affected by the mode selection mechanism and growth prescribed by the linear theory. Below this range of Lewis number, highly nonlinear effects become prominent and large-amplitude, complex cellular and seaweed dendritic morphologies emerge.
Modular Continuum Manipulator: Analysis and Characterization of Its Basic Module
Directory of Open Access Journals (Sweden)
Anand Kumar Mishra
2018-02-01
Full Text Available We present the basic module of a modular continuum arm (soft compliant manipulator for broad applications (SIMBA. SIMBA is a robotic arm with a hybrid structure, namely a combination of rigid and soft components, which makes the arm highly versatile, dexterous, and robust. These key features are due to the design of its basic module, which is characterized by a three-dimensional workspace with a constant radius around its rotation axis, large and highly repeatable bending, complete rotation, and passive stiffness. We present an extensive analysis and characterization of the basic module of the SIMBA arm in terms of design, fabrication, kinematic model, stiffness, and bending behavior. All the theoretical models presented were validated with empirical results. Our findings show a positional typical error of less than ≈6% in module diameter (highly repeatable with a passive stiffness of 0.8 N/mm (≈1 kg load. Our aim is to demonstrate that this kind of robotic element can be exploited as an elementary module of a more complex structure, which can be used in any application requiring high directional stiffness but without the need for an active stiffness mechanism, as is the case in daily activities (e.g., door opening, water pouring, obstacle avoidance, and manipulation tasks.
Temperature Dependences of Mechanisms Responsible for the Water-Vapor Continuum Absorption
Ma, Qiancheng
2014-01-01
The water-vapor continuum absorption plays an important role in the radiative balance in the Earth's atmosphere. It has been experimentally shown that for ambient atmospheric conditions, the continuum absorption scales quadratically with the H2O number density and has a strong, negative temperature dependence (T dependence). Over the years, there have been three different theoretical mechanisms postulated: far-wings of allowed transition lines, water dimers, and collision-induced absorption. The first mechanism proposed was the accumulation of absorptions from the far-wings of the strong allowed transition lines. Later, absorption by water dimers was proposed, and this mechanism provides a qualitative explanation for the continuum characters mentioned above. Despite the improvements in experimental data, at present there is no consensus on which mechanism is primarily responsible for the continuum absorption.
Continuum vibration analysis of dielectric elastomer membranes
Nalbach, S.; Rizzello, G.; Seelecke, S.
2017-04-01
Dielectric Elastomer (DE) transducers are well known for the possibility of responding to an applied voltage with relatively large actuation strains, often larger than 100%, and for their relatively high actuation bandwidth (order of several kHz). However, up to date there are relatively few applications which use the dynamic behavior of DEs. Some relevant examples include loudspeakers and fluid dispensers. Motivated by the potentialities of DEs in high-frequency applications, the aim of this work is the investigation of the continuous vibrations observed when DE membranes are actuated electrically. The system under analysis consists of a circular DE membrane pre-loaded with a spring. While exciting the DE membrane actuator with high-voltage, high-frequency signals, the motion of the membrane is detected with a 3D laser vibrometer which uses Doppler effect to reconstruct the system spectrum and vibration modes. An extensive experimental investigation is performed to study the influence of system parameters, such as membrane geometry and pre-stress, on the membrane frequency spectrum and vibrational modes.
Energy Technology Data Exchange (ETDEWEB)
Zimmerman, Jonathan A.; Jones, Reese E.; Templeton, Jeremy Alan; McDowell, David L.; Mayeur, Jason R.; Tucker, Garritt J.; Bammann, Douglas J.; Gao, Huajian
2008-09-01
Materials with characteristic structures at nanoscale sizes exhibit significantly different mechani-cal responses from those predicted by conventional, macroscopic continuum theory. For example,nanocrystalline metals display an inverse Hall-Petch effect whereby the strength of the materialdecreases with decreasing grain size. The origin of this effect is believed to be a change in defor-mation mechanisms from dislocation motion across grains and pileup at grain boundaries at mi-croscopic grain sizes to rotation of grains and deformation within grain boundary interface regionsfor nanostructured materials. These rotational defects are represented by the mathematical conceptof disclinations. The ability to capture these effects within continuum theory, thereby connectingnanoscale materials phenomena and macroscale behavior, has eluded the research community.The goal of our project was to develop a consistent theory to model both the evolution ofdisclinations and their kinetics. Additionally, we sought to develop approaches to extract contin-uum mechanical information from nanoscale structure to verify any developed continuum theorythat includes dislocation and disclination behavior. These approaches yield engineering-scale ex-pressions to quantify elastic and inelastic deformation in all varieties of materials, even those thatpossess highly directional bonding within their molecular structures such as liquid crystals, cova-lent ceramics, polymers and biological materials. This level of accuracy is critical for engineeringdesign and thermo-mechanical analysis is performed in micro- and nanosystems. The researchproposed here innovates on how these nanoscale deformation mechanisms should be incorporatedinto a continuum mechanical formulation, and provides the foundation upon which to develop ameans for predicting the performance of advanced engineering materials.4 AcknowledgmentThe authors acknowledge helpful discussions with Farid F. Abraham, Youping Chen, Terry J
Maugin, Gérard A
2016-01-01
Mixing scientific, historic and socio-economic vision, this unique book complements two previously published volumes on the history of continuum mechanics from this distinguished author. In this volume, Gérard A. Maugin looks at the period from the renaissance to the twentieth century and he includes an appraisal of the ever enduring competition between molecular and continuum modelling views. Chapters trace early works in hydraulics and fluid mechanics not covered in the other volumes and the author investigates experimental approaches, essentially before the introduction of a true concept of stress tensor. The treatment of such topics as the viscoelasticity of solids and plasticity, fracture theory, and the role of geometry as a cornerstone of the field, are all explored. Readers will find a kind of socio-historical appraisal of the seminal contributions by our direct masters in the second half of the twentieth century. The analysis of the teaching and research texts by Duhem, Poincaré and Hilbert on cont...
Modeling stock price dynamics by continuum percolation system and relevant complex systems analysis
Xiao, Di; Wang, Jun
2012-10-01
The continuum percolation system is developed to model a random stock price process in this work. Recent empirical research has demonstrated various statistical features of stock price changes, the financial model aiming at understanding price fluctuations needs to define a mechanism for the formation of the price, in an attempt to reproduce and explain this set of empirical facts. The continuum percolation model is usually referred to as a random coverage process or a Boolean model, the local interaction or influence among traders is constructed by the continuum percolation, and a cluster of continuum percolation is applied to define the cluster of traders sharing the same opinion about the market. We investigate and analyze the statistical behaviors of normalized returns of the price model by some analysis methods, including power-law tail distribution analysis, chaotic behavior analysis and Zipf analysis. Moreover, we consider the daily returns of Shanghai Stock Exchange Composite Index from January 1997 to July 2011, and the comparisons of return behaviors between the actual data and the simulation data are exhibited.
Stress, deformation, conservation, and rheology: a survey of key concepts in continuum mechanics
Major, J.J.
2013-01-01
This chapter provides a brief survey of key concepts in continuum mechanics. It focuses on the fundamental physical concepts that underlie derivations of the mathematical formulations of stress, strain, hydraulic head, pore-fluid pressure, and conservation equations. It then shows how stresses are linked to strain and rates of distortion through some special cases of idealized material behaviors. The goal is to equip the reader with a physical understanding of key mathematical formulations that anchor continuum mechanics in order to better understand theoretical studies published in geomorphology.
Lehoucq, R B; Sears, Mark P
2011-09-01
The purpose of this paper is to derive the energy and momentum conservation laws of the peridynamic nonlocal continuum theory using the principles of classical statistical mechanics. The peridynamic laws allow the consideration of discontinuous motion, or deformation, by relying on integral operators. These operators sum forces and power expenditures separated by a finite distance and so represent nonlocal interaction. The integral operators replace the differential divergence operators conventionally used, thereby obviating special treatment at points of discontinuity. The derivation presented employs a general multibody interatomic potential, avoiding the standard assumption of a pairwise decomposition. The integral operators are also expressed in terms of a stress tensor and heat flux vector under the assumption that these fields are differentiable, demonstrating that the classical continuum energy and momentum conservation laws are consequences of the more general peridynamic laws. An important conclusion is that nonlocal interaction is intrinsic to continuum conservation laws when derived using the principles of statistical mechanics.
Hindcasting the Continuum of Dansgaard-Oeschger variability: Mechanisms, Patterns and Timing
Timmermann, A.; Menviel, L.; Friedrich, T.; England, M. H.
2013-12-01
Millennial-scale variability associated with Dansgaard-Oeschger (DO) and Heinrich events (HE) is arguably one of the most puzzling climate phenomena ever discovered in paleoclimate archives of the last glacial period. With similar variability occurring during other glacial periods, it is very timely to identify the underlying mechanisms. Here, we set out to elucidate the dynamics of millennial-scale climate variability by conducting a transient global hindcast simulation with a 3-dimensional intermediate complexity Earth system model covering the period 50 ka B.P. to 30 ka B.P. The model is forced by time-varying external boundary conditions (greenhouse gases, orbital forcing, and ice-sheet orography and albedo) and anomalous North Atlantic freshwater fluxes, which capture the effects of Northern Hemisphere ice-sheet calving on millennial timescales. Together these forcings generate a realistic global climate trajectory, as demonstrated by an extensive model/paleo data comparison. Our analysis is consistent with the simple idea that variations in ice-sheet calving and related changes of the Atlantic Meridional Overturning Circulation were the main driver for the continuum of MIS3 DO and HE variability seen in paleorecords across the globe. According to this scenario, timescale and abruptness of millennial-scale variability are primarily determined by the ice-sheet/ice-shelf calving processes, rather than by the thermohaline circulation. Using a number of high-resolution paleo records from other glacial periods we demonstrate that the proposed ice-sheet calving/AMOC response mechanism can universally explain the continuum of millennial-scale glacial variability during the Late Pleistocene.
Continuum analysis of biological systems conserved quantities, fluxes and forces
Suraishkumar, G K
2014-01-01
This book addresses the analysis, in the continuum regime, of biological systems at various scales, from the cellular level to the industrial one. It presents both fundamental conservation principles (mass, charge, momentum and energy) and relevant fluxes resulting from appropriate driving forces, which are important for the analysis, design and operation of biological systems. It includes the concept of charge conservation, an important principle for biological systems that is not explicitly covered in any other book of this kind. The book is organized in five parts: mass conservation; charge conservation; momentum conservation; energy conservation; and multiple conservations simultaneously applied. All mathematical aspects are presented step by step, allowing any reader with a basic mathematical background (calculus, differential equations, linear algebra, etc.) to follow the text with ease. The book promotes an intuitive understanding of all the relevant principles and in so doing facilitates their applica...
Cammi, Roberto
2013-01-01
This Brief presents the main aspects of the response functions theory (RFT) for molecular solutes described within the framework of the Polarizable Continuum Model (PCM). PCM is a solvation model for a Quantum Mechanical molecular system in which the solvent is represented as a continuum distribution of matter. Particular attention is devoted to the description of the basic features of the PCM model, and to the problems characterizing the study of the response function theory for molecules in solution with respect to the analogous theory on isolated molecules.
Spencer Operator and Applications: From Continuum Mechanics to Mathematical physics
Pommaret, Jean-François
2011-01-01
Though a few of the results presented are proved in the recent references provided, the way they are combined with others and patched together around the three books quoted is new. In view of the importance of the full paper, the present version is only a summary of the definitive version to appear later on. Finally, the reader must not forget that "each formula" appearing in this new general framework has been used explicitly or implicitly in (C), (M) and (W) for a mechanical, mathematical o...
Continuum Mechanical Modelling of Skin-pass Rolling
DEFF Research Database (Denmark)
Kijima, Hideo; Bay, Niels
2007-01-01
The special contact conditions in skin-pass rolling of steel strip is analyzed by studying plane strain upsetting of thin sheet with low reduction applying long narrow tools and dry friction conditions. An extended sticking region is estimated by an elasto-plastic FEM analysis of the plane strain...
Acoustofluidics 3: Continuum mechanics for ultrasonic particle manipulation.
Dual, Jurg; Schwarz, Thomas
2012-01-21
Although ultrasonic particle manipulation is performed in fluids, the adjacent solid material and its modelling play an important part in the design of such devices, as the impedance difference between liquids and solids is not very large. The modelling of the solid is done in the framework of linear elastodynamics, which is described by the displacement field, the strain field and the stress field. These quantities are related by kinematical relations, local linear momentum conservation and constitutive laws. Also material damping is important and can be modelled in the framework of linear viscoelasticity. Because of the finite size of the devices, resonant modes are important to analyse. In addition some of the elements behave as mechanical structures obeying specific equations that take into account the structural boundaries. A practical example is given, which shows the full complexity of device modelling, which is preferably done using the Finite Element Method.
Stress transfer modeling in CNT reinforced composites using continuum mechanics
International Nuclear Information System (INIS)
Chaboki Khiabani, A.; Sadrnejad, S. A.; Yahyaeii, M.
2008-01-01
Because of the substantial difference in stiffness between matrix and nano tube in CNT composite, the stress transfer between them controls their mechanical properties. This paper investigates the said issue, analytically and numerically, in axial load using representative volume element. The analytical model was established based on the modified Cox's shear lag model with the use of some simplified assumptions. Some, in the developed shear lag model, the CNT assumes hollow fiber. Solving the governing differential equation. led the high shear stress, in interface especially in the CNT cap. In addition, some finite element models were performed with different aspect ratios and the shear stress pattern especially in interface was calculated numerically. Despite some simplified assumptions that were performed with these two models such as elastic behavior and full connectivity, and the comparison of their results with other numerical models show adequate agreement
Continuum Mechanics using Mathematica® Fundamentals, Applications and Scientific Computing
Romano, Antonio; Marasco, Addolorata
2006-01-01
This book's methodological approach familiarizes readers with the mathematical tools required to correctly define and solve problems in continuum mechanics. The book covers essential principles and fundamental applications, and provides a solid basis for a deeper study of more challenging and specialized problems related to elasticity, fluid mechanics, plasticity, materials with memory, piezoelectricity, ferroelectricity, magneto-fluid mechanics, and state changes. Key topics and features: * Concise presentation strikes a balance between fundamentals and applications * Requisite mathematical background carefully collected in two introductory chapters and two appendices * Recent developments highlighted through coverage of more significant applications to areas such as porous media, electromagnetic fields, and phase transitions Continuum Mechanics using Mathematica® is aimed at advanced undergraduates, graduate students, and researchers in applied mathematics, mathematical physics, and engineering. It may ser...
Song, Jie; Dong, Mei; Koltuk, Serdar; Hu, Hui; Zhang, Luqing; Azzam, Rafig
2017-12-01
Construction works associated with the building of reservoirs in mountain areas can damage the stability of adjacent valley slopes. Seepage processes caused by the filling and drawdown operations of reservoirs also affect the stability of the reservoir banks over time. The presented study investigates the stability of a fractured-rock slope subjected to seepage forces in the lower basin of a planned pumped-storage hydropower (PSH) plant in Blaubeuren, Germany. The investigation uses a hydro-mechanically coupled finite-element analyses. For this purpose, an equivalent continuum model is developed by using a representative elementary volume (REV) approach. To determine the minimum required REV size, a large number of discrete fracture networks are generated using Monte Carlo simulations. These analyses give a REV size of 28 × 28 m, which is sufficient to represent the equivalent hydraulic and mechanical properties of the investigated fractured-rock mass. The hydro-mechanically coupled analyses performed using this REV size show that the reservoir operations in the examined PSH plant have negligible effect on the adjacent valley slope.
Directory of Open Access Journals (Sweden)
Jun Liu
2002-01-01
Full Text Available Thin sections from human breast biopsies were employed to perform a differential analysis of the ultrasound spectral responses from invasive ductal carcinoma and normal tissue. A non-destructive testing methodology was employed, yielding the reflection coefficients as function of frequency in the clinical ultrasound range. The spectral responses were simulated both in the context of continuum and nano-biomechanics, with the objective of quantifying the physical properties that determine the differences in the spectral signature of normal vs. malignant tissue. The properties that were employed for the theoretical reconstruction of the spectra were: the density, the continuum and the nanomechanical elastic constants, and the nanomechanical theory internodal distance. The latter is a measure of the depth-of-penetration of mechanical actions between contiguous tissue elements. Together with vectorial descriptors of the tissue spatial arrangement, the internodal distance variable affords the quantitative incorporation of tissue architectural data in the theoretical model.
A continuum mechanics-based musculo-mechanical model for esophageal transport
Kou, Wenjun; Griffith, Boyce E.; Pandolfino, John E.; Kahrilas, Peter J.; Patankar, Neelesh A.
2017-11-01
In this work, we extend our previous esophageal transport model using an immersed boundary (IB) method with discrete fiber-based structural model, to one using a continuum mechanics-based model that is approximated based on finite elements (IB-FE). To deal with the leakage of flow when the Lagrangian mesh becomes coarser than the fluid mesh, we employ adaptive interaction quadrature points to deal with Lagrangian-Eulerian interaction equations based on a previous work (Griffith and Luo [1]). In particular, we introduce a new anisotropic adaptive interaction quadrature rule. The new rule permits us to vary the interaction quadrature points not only at each time-step and element but also at different orientations per element. This helps to avoid the leakage issue without sacrificing the computational efficiency and accuracy in dealing with the interaction equations. For the material model, we extend our previous fiber-based model to a continuum-based model. We present formulations for general fiber-reinforced material models in the IB-FE framework. The new material model can handle non-linear elasticity and fiber-matrix interactions, and thus permits us to consider more realistic material behavior of biological tissues. To validate our method, we first study a case in which a three-dimensional short tube is dilated. Results on the pressure-displacement relationship and the stress distribution matches very well with those obtained from the implicit FE method. We remark that in our IB-FE case, the three-dimensional tube undergoes a very large deformation and the Lagrangian mesh-size becomes about 6 times of Eulerian mesh-size in the circumferential orientation. To validate the performance of the method in handling fiber-matrix material models, we perform a second study on dilating a long fiber-reinforced tube. Errors are small when we compare numerical solutions with analytical solutions. The technique is then applied to the problem of esophageal transport. We use two
Research on the deformation of a confined aquifer based on Cosserat continuum mechanics
Directory of Open Access Journals (Sweden)
Y. S. Xu
2015-11-01
Full Text Available Recent monitoring of land subsidence and soil deformation indicates a new phenomenon where excessive and continuous deformation occurs in the sandy aquifers in Shanghai and the Su-Xi-Chang region of China. It is hard to explain factors contributing to this phenomenon with traditional Cauchy continuum mechanics in which low normal stress in the ground could not cause such large deformation. Steep hydraulic gradient would be formed in the aquifer if groundwater is pumped from densely distributed wells, and shear stresses would develop then. Accumulated shear stress could then lead to deformation of the aquifer or even land subsidence. Accumulated shear stress due to the drawdown of groundwater level is one of the main factors that contribute to deformation within an aquifer. Traditional Cauchy continuum mechanics cannot consider this shear stress because of the hypothesis of equal shear stress in the aquifer unit. Cosserat continuum mechanics can be applied to analyse the mechanism of aquifer deformation controlled by accumulated shear stress by considering the scale effect and the asymmetric distribution of shear stress in the aquifer unit.
Ivaneyko, Dmytro; Toshchevikov, Vladimir; Saphiannikova, Marina; Heinrich, Gert
2014-04-07
A new theoretical formalism is developed for the study of the mechanical behaviour of magneto-sensitive elastomers (MSEs) under a uniform external magnetic field. This formalism allows us to combine macroscopic continuum-mechanics and microscopic approaches for complex analysis of MSEs with different shapes and with different particle distributions. It is shown that starting from a model based on an explicit discrete particle distribution one can separate the magnetic field inside the MSE into two contributions: one which depends on the shape of the sample with finite size and the other, which depends on the local spatial particle distribution. The magneto-induced deformation and the change of elastic modulus are found to be either positive or negative, their dependences on the magnetic field being determined by a non-trivial interplay between these two contributions. Mechanical properties are studied for two opposite types of coupling between the particle distribution and the magneto-induced deformation: absence of elastic coupling and presence of strong affine coupling. Predictions of a new formalism are in a qualitative agreement with existing experimental data.
Effect of continuum damage mechanics on spring back prediction in metal forming processes
International Nuclear Information System (INIS)
Nayebi, Ali; Shahabi, Mehdi
2017-01-01
The influence of considering the variations in material properties was investigated through continuum damage mechanics according to the Lemaitre isotropic unified damage law to predict the bending force and spring back in V-bending sheet metal forming processes, with emphasis on Finite element (FE) simulation considerations. The material constants of the damage model were calibrated through a uniaxial tensile test with an appropriate and convenient repeating strategy. Holloman’s isotropic and Ziegler’s linear kinematic hardening laws were employed to describe the behavior of a hardening material. To specify the ideal FE conditions for simulating spring back, the effect of the various numerical considerations during FE simulation was investigated and compared with the experimental outcome. Results indicate that considering continuum damage mechanics decreased the predicted bending force and improved the accuracy of spring back prediction.
A morphing approach to couple state-based peridynamics with classical continuum mechanics
Han, Fei
2016-01-04
A local/nonlocal coupling technique called the morphing method is developed to couple classical continuum mechanics with state-based peridynamics. State-based peridynamics, which enables the description of cracks that appear and propagate spontaneously, is applied to the key domain of a structure, where damage and fracture are considered to have non-negligible effects. In the rest of the structure, classical continuum mechanics is used to reduce computational costs and to simultaneously satisfy solution accuracy and boundary conditions. Both models are glued by the proposed morphing method in the transition region. The morphing method creates a balance between the stiffness tensors of classical continuum mechanics and the weighted coefficients of state-based peridynamics through the equivalent energy density of both models. Linearization of state-based peridynamics is derived by Taylor approximations based on vector operations. The discrete formulation of coupled models is also described. Two-dimensional numerical examples illustrate the validity and accuracy of the proposed technique. It is shown that the morphing method, originally developed for bond-based peridynamics, can be successfully extended to state-based peridynamics through the original developments presented here.
Morphing continuum analysis of energy transfer in compressible turbulence
Cheikh, Mohamad Ibrahim; Wonnell, Louis B.; Chen, James
2018-02-01
A shock-preserving finite volume solver with the generalized Lax-Friedrichs splitting flux for morphing continuum theory (MCT) is presented and verified. The numerical MCT solver is showcased in a supersonic turbulent flow with Mach 2.93 over an 8∘ compression ramp. The simulation results validated MCT with experiments as an alternative for modeling compressible turbulence. The required size of the smallest mesh cell for the MCT simulation is shown to be almost an order larger than that in a similar direct numerical simulation study. The comparison shows MCT is a much more computationally friendly theory than the classical Navier-Stokes equations. The dynamics of energy cascade at the length scale of individual eddies is illuminated through the subscale rotation introduced by MCT. In this regard, MCT provides a statistical averaging procedure for capturing energy transfer in compressible turbulence, not found in classical fluid theories. Analysis of the MCT results show the existence of a statistical coupling of the internal and translational kinetic energy fluctuations with the corresponding eddy rotational energy fluctuations, indicating a multiscale transfer of energy. In conclusion, MCT gives a new characterization of the energy cascade within compressible turbulence without the use of excessive computational resources.
Serebrennikov, Aleksey M.
2014-09-01
Here, we introduce a nonlinear continuum mechanical theoretical model of dissipative plasmonic oscillations relying on the principle of least action. The proposed theory has allowed obtaining the expression of a stress tensor for an “electron gas-ionic frame” system. In parallel, an initial boundary value problem for nonlinear integrodifferential equations constituting the model has been formulated. On the basis of a finite-difference approach the iterative solution method, algorithm and solver have been worked out. Thereby we have investigated the phenomena of harmonic multiples generation by a cluster of metal nanoparticles. Also by using these tools the estimate of the density function parameter satisfying the requirement of regular oscillations has been obtained numerically. On the ground of extensive numerical runs it was found that for a given set of parameters the system response turned out to be mainly linear, however the contributions of the closest odd harmonic multiples (third and fifth) were well resolved under quantitative analysis. This result allows the nonlinearity governable by the principal equation of motion to be associated with Kerr's type nonlinearity.
The archetype-genome exemplar in molecular dynamics and continuum mechanics
Greene, M. Steven; Li, Ying; Chen, Wei; Liu, Wing Kam
2014-04-01
We argue that mechanics and physics of solids rely on a fundamental exemplar: the apparent properties of a system depend on the building blocks that comprise it. Building blocks are referred to as archetypes and apparent system properties as the system genome. Three entities are of importance: the archetype properties, the conformation of archetypes, and the properties of interactions activated by that conformation. The combination of these entities into the system genome is called assembly. To show the utility of the archetype-genome exemplar, this work presents the mathematical ingredients and computational implementation of theories in solid mechanics that are (1) molecular and (2) continuum manifestations of the assembly process. Both coarse-grained molecular dynamics (CGMD) and the archetype-blending continuum (ABC) theories are formulated then applied to polymer nanocomposites (PNCs) to demonstrate the impact the components of the assembly triplet have on a material genome. CGMD simulations demonstrate the sensitivity of nanocomposite viscosities and diffusion coefficients to polymer chain types (archetype), polymer-nanoparticle interaction potentials (interaction), and the structural configuration (conformation) of dispersed nanoparticles. ABC simulations show the contributions of bulk polymer (archetype) properties, occluded region of bound rubber (interaction) properties, and microstructural binary images (conformation) to predictions of linear damping properties, the Payne effect, and localization/size effects in the same class of PNC material. The paper is light on mathematics. Instead, the focus is on the usefulness of the archetype-genome exemplar to predict system behavior inaccessible to classical theories by transitioning mechanics away from heuristic laws to mechanism-based ones. There are two core contributions of this research: (1) presentation of a fundamental axiom—the archetype-genome exemplar—to guide theory development in computational
International Nuclear Information System (INIS)
Thellamurege, Nandun M.; Si, Dejun; Cui, Fengchao; Li, Hui
2014-01-01
A combined quantum mechanical/molecular mechanical/continuum (QM/MM/C) style second order Møller-Plesset perturbation theory (MP2) method that incorporates induced dipole polarizable force field and induced surface charge continuum solvation model is established. The Z-vector method is modified to include induced dipoles and induced surface charges to determine the MP2 response density matrix, which can be used to evaluate MP2 properties. In particular, analytic nuclear gradient is derived and implemented for this method. Using the Assisted Model Building with Energy Refinement induced dipole polarizable protein force field, the QM/MM/C style MP2 method is used to study the hydrogen bonding distances and strengths of the photoactive yellow protein chromopore in the wild type and the Glu46Gln mutant
Continuum mechanical model for cross-linked actin networks with contractile bundles
Ferreira, J. P. S.; Parente, M. P. L.; Natal Jorge, R. M.
2018-01-01
In the context of a mechanical approach to cell biology, there is a close relationship between cellular function and mechanical properties. In recent years, an increasing amount of attention has been given to the coupling between biochemical and mechanical signals by means of constitutive models. In particular, on the active contractility of the actin cytoskeleton. Given the importance of the actin contraction on the physiological functions, this study propose a constitutive model to describe how the filamentous network controls its mechanics actively. Embedded in a soft isotropic ground substance, the network behaves as a viscous mechanical continuum, comprised of isotropically distributed cross-linked actin filaments and actomyosin bundles. Trough virtual rheometry experiments, the present model relates the dynamics of the myosin motors with the network stiffness, which is to a large extent governed by the time-scale of the applied deformations/forces.
The existence of a symmetric stress tensor in a non-local description of continuum mechanics
Schwarz, G.
1993-12-01
Among the foundations of continuum mechanics is the description of the constitutive forces in terms of a symmetric tensor. Noll showed that this is a consequence of the axiom of material frame indifference, what in turn means a local invariance of the system under the Euclidean group. Here we will prove, in order to obtain the same result, that the assumption of locality in this axiom is redundant. We model a non-local system by means of a virtual work principle. Under the global demand that the corresponding functional does not respond on rigid infinitesimal motions, we show the existence of a symmetric stress tensor as a local result.
Chen, Yunxia; Cui, Yuxuan; Gong, Wenjun
2017-11-15
Static fatigue behavior is the main failure mode of optical fibers applied in sensors. In this paper, a computational framework based on continuum damage mechanics (CDM) is presented to calculate the crack propagation process and failure time of optical fibers subjected to static bending and tensile loads. For this purpose, the static fatigue crack propagation in the glass core of the optical fiber is studied. Combining a finite element method (FEM), we use the continuum damage mechanics for the glass core to calculate the crack propagation path and corresponding failure time. In addition, three factors including bending radius, tensile force and optical fiber diameter are investigated to find their impacts on the crack propagation process and failure time of the optical fiber under concerned situations. Finally, experiments are conducted and the results verify the correctness of the simulation calculation. It is believed that the proposed method could give a straightforward description of the crack propagation path in the inner glass core. Additionally, the predicted crack propagation time of the optical fiber with different factors can provide effective suggestions for improving the long-term usage of optical fibers.
1993-01-01
Modern continuum mechanics is the topic of this book. After its introduction it will be applied to a few typical systems arising in the environmental sciences and in geophysics. In large lake/ocean dynamics peculiar effects of the rotation of the Earth will be analyzed in linear/nonlinear processes of a homogenous and inhomogenous water body. Strong thermomechanical coupling paired with nonlinear rheology affects the flow of large ice sheets (such as Antarctica and Greenland) and ice shelves. Its response to the climatic forcing in an environmental of greenhouse warming may significantly affect the life of future generations. The mechanical behavior of granular materials under quasistatic loadings requires non-classical mixture concepts and encounters generally complicated elastic-plastic-type constitutive behavior. Creeping flow of soils, consolidation processes and ground water flow are described by such theories. Rapid shearing flow of granular materials lead to constitutive relations for the stresses whic...
State stability analysis for the fermionic projector in the continuum
Energy Technology Data Exchange (ETDEWEB)
Hoch, Stefan Ludwig
2008-07-01
The principle of the fermionic projector in the continuum gives an indication that there might be a deeper reason why elementary particles only appear with a few definite masses. In this thesis the existence of approximately state-stable configurations is shown. In order to achieve that, we make use of a variational principle for the fermionic projector in the continuum which contains certain contributions supported on the light cone. In a certain sense, these extra terms contain the structure of the underlying discrete spacetime. Lorentz invariant distributions and their convolutions are studied. Some of these are well-defined because the convolution integrals have compactly supported integrands. Other convolutions can be regularized such that the property of being ill-defined only plays a role on the light cone. These results are used to analyze the variational principle and to give criteria for state stability, which can be numerically analyzed. Some plots are presented to allow a decision about state stability and to show how possible configurations could look like. (orig.)
State stability analysis for the fermionic projector in the continuum
International Nuclear Information System (INIS)
Hoch, Stefan Ludwig
2008-01-01
The principle of the fermionic projector in the continuum gives an indication that there might be a deeper reason why elementary particles only appear with a few definite masses. In this thesis the existence of approximately state-stable configurations is shown. In order to achieve that, we make use of a variational principle for the fermionic projector in the continuum which contains certain contributions supported on the light cone. In a certain sense, these extra terms contain the structure of the underlying discrete spacetime. Lorentz invariant distributions and their convolutions are studied. Some of these are well-defined because the convolution integrals have compactly supported integrands. Other convolutions can be regularized such that the property of being ill-defined only plays a role on the light cone. These results are used to analyze the variational principle and to give criteria for state stability, which can be numerically analyzed. Some plots are presented to allow a decision about state stability and to show how possible configurations could look like. (orig.)
A Monte Carlo and continuum study of mechanical properties of nanoparticle based films
Energy Technology Data Exchange (ETDEWEB)
Ogunsola, Oluwatosin; Ehrman, Sheryl [University of Maryland, Department of Chemical and Biomolecular Engineering, Chemical and Nuclear Engineering Building (United States)], E-mail: sehrman@eng.umd.edu
2008-01-15
A combination Monte Carlo and equivalent-continuum simulation approach was used to investigate the structure-mechanical property relationships of titania nanoparticle deposits. Films of titania composed of nanoparticle aggregates were simulated using a Monte Carlo approach with diffusion-limited aggregation. Each aggregate in the simulation is fractal-like and random in structure. In the film structure, it is assumed that bond strength is a function of distance with two limiting values for the bond strengths: one representing the strong chemical bond between the particles at closest proximity in the aggregate and the other representing the weak van der Waals bond between particles from different aggregates. The Young's modulus of the film is estimated using an equivalent-continuum modeling approach, and the influences of particle diameter (5-100 nm) and aggregate size (3-400 particles per aggregate) on predicted Young's modulus are investigated. The Young's modulus is observed to increase with a decrease in primary particle size and is independent of the size of the aggregates deposited. Decreasing porosity resulted in an increase in Young's modulus as expected from results reported previously in the literature.
A Monte Carlo and continuum study of mechanical properties of nanoparticle based films
International Nuclear Information System (INIS)
Ogunsola, Oluwatosin; Ehrman, Sheryl
2008-01-01
A combination Monte Carlo and equivalent-continuum simulation approach was used to investigate the structure-mechanical property relationships of titania nanoparticle deposits. Films of titania composed of nanoparticle aggregates were simulated using a Monte Carlo approach with diffusion-limited aggregation. Each aggregate in the simulation is fractal-like and random in structure. In the film structure, it is assumed that bond strength is a function of distance with two limiting values for the bond strengths: one representing the strong chemical bond between the particles at closest proximity in the aggregate and the other representing the weak van der Waals bond between particles from different aggregates. The Young's modulus of the film is estimated using an equivalent-continuum modeling approach, and the influences of particle diameter (5-100 nm) and aggregate size (3-400 particles per aggregate) on predicted Young's modulus are investigated. The Young's modulus is observed to increase with a decrease in primary particle size and is independent of the size of the aggregates deposited. Decreasing porosity resulted in an increase in Young's modulus as expected from results reported previously in the literature
A continuum constitutive model for the mechanical behavior of woven fabrics
Energy Technology Data Exchange (ETDEWEB)
King, M.J.; Jearanaisilawong, P.; Socrate, S. [Massachusetts Institute of Technology, Cambridge, MA (United States). Dept. of Mechanical Engineering
2005-06-01
We propose a new approach for developing continuum models for the mechanical behavior of woven fabrics in planar deformation. We generate a physically motivated continuum model that can both simulate existing fabrics and predict the behavior of novel fabrics based on the properties of the yarns and the weave. The approach relies on the selection of a geometric model for the fabric weave, coupled with constitutive models for the yarn behaviors. The fabric structural configuration is related to the macroscopic deformation through an energy minimization method, and is used to calculate the internal forces carried by the yarn families. The macroscopic stresses are determined from the internal forces using equilibrium arguments. Using this approach, we develop a model for plain weave ballistic fabrics, such as Kevlar, based on a pin-joined beam geometry. We implement this model into the finite element code ABAQUS and simulate fabrics under different modes of deformation. We present comparisons between model predictions and experimental findings for quasi-static modes of in-plane loading. (author)
Directory of Open Access Journals (Sweden)
Giuseppe Guzzetta
2013-06-01
Full Text Available In order to treat deformation as one of the processes taking place in an irreversible thermodynamic transformation, two main conditions must be satisfied: (1 strain and stress should be defined in such a way that the modification of the symmetry of these tensorial quantities reflects that of the structure of the actual material of which the deforming ideal continuum is the counterpart; and (2 the unique decomposition of the above tensors into the algebraic sum of an isotropic and an anisotropic part with different physical meanings should be recognized. The first condition allows the distinction of the energy balance in irrotational and rotational deformations; the second allows the description of a thermodynamic transformation involving deformation as a function of both process quantities, whose values depend on the specific transition, or path, between two equilibrium states, and of state quantities, which describe equilibrium states of a system quantitatively. One of the main conclusions that can be drawn is that, dealing with deformable materials, the quantities that must appear in thermodynamic equations cannot be tensorial quantities, such as the stress tensor and the infinitesimal or finite strain tensor usually considered in continuum mechanics (or, even worse, their components. The appropriate quantities should be invariants involved by the strain and stress tensors here defined. Another important conclusion is that, from a thermodynamic point of view, the consideration of the measurable volume change occurring in an isothermal deformation does not itself give any meaningful information.
Bergan, Andrew C.; Leone, Frank A., Jr.
2016-01-01
A new model is proposed that represents the kinematics of kink-band formation and propagation within the framework of a mesoscale continuum damage mechanics (CDM) model. The model uses the recently proposed deformation gradient decomposition approach to represent a kink band as a displacement jump via a cohesive interface that is embedded in an elastic bulk material. The model is capable of representing the combination of matrix failure in the frame of a misaligned fiber and instability due to shear nonlinearity. In contrast to conventional linear or bilinear strain softening laws used in most mesoscale CDM models for longitudinal compression, the constitutive response of the proposed model includes features predicted by detailed micromechanical models. These features include: 1) the rotational kinematics of the kink band, 2) an instability when the peak load is reached, and 3) a nonzero plateau stress under large strains.
Ulerich, J.; Göktepe, S.; Kuhl, E.
This manuscript presents a continuum approach towards cardiac growth and remodeling that is capable to predict chronic maladaptation of the heart in response to changes in mechanical loading. It is based on the multiplicative decomposition of the deformation gradient into and elastic and a growth part. Motivated by morphological changes in cardiomyocyte geometry, we introduce an anisotropic growth tensor that can capture both hypertrophic wall thickening and ventricular dilation within one generic concept. In agreement with clinical observations, we propose wall thickening to be a stress-driven phenomenon whereas dilation is introduced as a strain-driven process. The features of the proposed approach are illustrated in terms of the adaptation of thin heart slices and in terms overload-induced dilation in a generic bi-ventricular heart model.
Continuum mechanics and thermodynamics in the Hamilton and the Godunov-type formulations
Peshkov, Ilya; Pavelka, Michal; Romenski, Evgeniy; Grmela, Miroslav
2018-01-01
Continuum mechanics with dislocations, with the Cattaneo-type heat conduction, with mass transfer, and with electromagnetic fields is put into the Hamiltonian form and into the form of the Godunov-type system of the first-order, symmetric hyperbolic partial differential equations (SHTC equations). The compatibility with thermodynamics of the time reversible part of the governing equations is mathematically expressed in the former formulation as degeneracy of the Hamiltonian structure and in the latter formulation as the existence of a companion conservation law. In both formulations the time irreversible part represents gradient dynamics. The Godunov-type formulation brings the mathematical rigor (the local well posedness of the Cauchy initial value problem) and the possibility to discretize while keeping the physical content of the governing equations (the Godunov finite volume discretization).
Creep Tests and Modeling Based on Continuum Damage Mechanics for T91 and T92 Steels
Pan, J. P.; Tu, S. H.; Zhu, X. W.; Tan, L. J.; Hu, B.; Wang, Q.
2017-12-01
9-11%Cr ferritic steels play an important role in high-temperature and high-pressure boilers of advanced power plants. In this paper, a continuum damage mechanics (CDM)-based creep model was proposed to study the creep behavior of T91 and T92 steels at high temperatures. Long-time creep tests were performed for both steels under different conditions. The creep rupture data and creep curves obtained from creep tests were captured well by theoretical calculation based on the CDM model over a long creep time. It is shown that the developed model is able to predict creep data for the two ferritic steels accurately up to tens of thousands of hours.
A nonlocal continuum damage mechanics approach to simulation of creep fracture in ice sheets
Duddu, Ravindra; Waisman, Haim
2013-06-01
We present a Lagrangian finite element formulation aimed at modeling creep fracture in ice-sheets using nonlocal continuum damage mechanics. The proposed formulation is based on a thermo-viscoelastic constitutive model and a creep damage model for polycrystalline ice with different behavior in tension and compression. In this paper, mainly, we detail the nonlocal numerical implementation of the constitutive damage model into commercial finite element codes (e.g. Abaqus), wherein a procedure to handle the abrupt failure (rupture) of ice under tension is proposed. Then, we present numerical examples of creep fracture under four-point bending, uniaxial tension, and biaxial tension in order to illustrate the viability of the current approach. Finally, we present simulations of creep crack propagation in idealized rectangular ice slabs so as to estimate calving rates at low deformation rates. The examples presented demonstrate the mesh size and mesh directionality independence of the proposed nonlocal implementation.
Wrist-Powered Partial Hand Prosthesis Using a Continuum Whiffle Tree Mechanism: A Case Study.
Xu, Kai; Liu, Huan; Zhang, Zhaoyu; Zhu, Xiangyang
2018-03-01
Among the advances in upper extremity prostheses in the past decades, only a small portion of the results were obtained for partial hand prostheses, possibly due to the highly diverse partial hand presentations and limited space for component integration. In an attempt to address these challenges, this paper presents the design, construction, installation, and experimental characterization of a wrist-powered partial hand prosthesis developed in Shanghai Jiao Tong University (hereafter referred to as the JTP hand), customized for a specific amputee. The JTP hand possesses: 1) a continuum whiffle tree mechanism to allow adaptive grasping; 2) a force-magnifying partial gear pair to enhance the power of the grip; and 3) a phalange-embedded disengageable ratchet to enable or disable backdrivability. Various grasps and gestures were formed using the JTP hand. The obtained results suggest that the proposed design might be a viable option for patients with transmetacarpal amputation.
International Nuclear Information System (INIS)
JianPing, Jing; Guang, Meng; Yi, Sun; SongBo, Xia
2003-01-01
A nonlinear Continuum Damage Mechanics model is proposed to assess the creep-fatigue life of a steam turbine rotor, in which the effects of complex multiaxial stress and the coupling of fatigue and creep are taken into account. The nonlinear evolution of damage is also considered. The model is applied to a 600 MW steam turbine under a practical start-stop operation. The results are compared with those from the linear accumulation theory that is dominant in life assessment of steam turbine rotors at present. The comparison show that the nonlinear continuum damage mechanics model describes the accumulation and development of damage better than the linear accumulation theory
Dumbser, Michael; Peshkov, Ilya; Romenski, Evgeniy; Zanotti, Olindo
2017-11-01
In this paper, we propose a new unified first order hyperbolic model of Newtonian continuum mechanics coupled with electro-dynamics. The model is able to describe the behavior of moving elasto-plastic dielectric solids as well as viscous and inviscid fluids in the presence of electro-magnetic fields. It is actually a very peculiar feature of the proposed PDE system that viscous fluids are treated just as a special case of elasto-plastic solids. This is achieved by introducing a strain relaxation mechanism in the evolution equations of the distortion matrix A, which in the case of purely elastic solids maps the current configuration to the reference configuration. The model also contains a hyperbolic formulation of heat conduction as well as a dissipative source term in the evolution equations for the electric field given by Ohm's law. Via formal asymptotic analysis we show that in the stiff limit, the governing first order hyperbolic PDE system with relaxation source terms tends asymptotically to the well-known viscous and resistive magnetohydrodynamics (MHD) equations. Furthermore, a rigorous derivation of the model from variational principles is presented, together with the transformation of the Euler-Lagrange differential equations associated with the underlying variational problem from Lagrangian coordinates to Eulerian coordinates in a fixed laboratory frame. The present paper hence extends the unified first order hyperbolic model of Newtonian continuum mechanics recently proposed in [110,42] to the more general case where the continuum is coupled with electro-magnetic fields. The governing PDE system is symmetric hyperbolic and satisfies the first and second principle of thermodynamics, hence it belongs to the so-called class of symmetric hyperbolic thermodynamically compatible systems (SHTC), which have been studied for the first time by Godunov in 1961 [61] and later in a series of papers by Godunov and Romenski [67,69,119]. An important feature of the
Energy Technology Data Exchange (ETDEWEB)
Ghadiani, S.R.
2005-07-01
In this thesis, the new concept of the German Aerospace Center (DLR) for an effusion-cooled ceramic rocket combustion chamber is investigated. Using effusion cooling, the porous inner liner of the chamber is cooled by passing the coolant through its pores. The theoretical treatment of the fluid-saturated deformable porous construction under non-isothermal conditions leads to a coupled solid fluid model which is formulated in this thesis within the framework of the Theory of Porous Media (TPM). The multiphasic continuum mechanical model created allows for the definition of mechanical loads, thermal loads as well as a fluid mass flow across the boundary. All necessary constitutive equations are physically expedient conclusions resulting from the evaluation of the determining entropy inequality. The FE-tool PANDAS from the Institute of Mechanics (civil engineering) at University of Stuttgart is used as numerical solver. The numerical simulations discussed in this work are restricted to the qualitative demonstration of the most important physical effects occurring in the construction under study. For a real design study, material parameters have to be determined by experiments which are not the subject of this thesis. Corresponding experiments are being performed in ongoing activities at the DLR. The model presented in this work has to be understood as a general tool for the design investigation of actively cooled porous constructions. (orig.)
Varshney, Swati; Song, Juha; Li, Yaning; Boyce, Mary C; Ortiz, Christine
2015-12-01
Many armored fish scale assemblies use geometric heterogeneity of subunits as a design parameter to provide tailored biomechanical flexibility while maintaining protection from external penetrative threats. This study analyzes the spatially varying shape of individual ganoid scales as a structural element in a biological system, the exoskeleton of the armored fish Polypterus senegalus (bichir). X-ray microcomputed tomography is used to generate digital 3D reconstructions of the mineralized scales. Landmark-based geometric morphometrics is used to measure the geometric variation among scales and to define a set of geometric parameters to describe shape variation. A formalism using continuum mechanical strain analysis is developed to quantify the spatial geometry change of the scales and illustrate the mechanisms of shape morphing between scales. Five scale geometry variants are defined (average, anterior, tail, ventral, and pectoral fin) and their functional implications are discussed in terms of the interscale mobility mechanisms that enable flexibility within the exoskeleton. The results suggest that shape variation in materials design, inspired by structural biological materials, can allow for tunable behavior in flexible composites made of segmented scale assemblies to achieve enhanced user mobility, custom fit, and flexibility around joints for a variety of protective applications. Copyright © 2015. Published by Elsevier Inc.
Directory of Open Access Journals (Sweden)
Epstein M.
2006-12-01
Full Text Available In this paper certain basic concepts of continuum mechanics are presented and discussed in a manner that may be suggestive for applications in geophysics. In particular, ideas such as Cosserat media, continuous distribution of inhomogeneities, and the role of material symmetries are emphasized. In the spirit of a live meeting, the style of the presentation has been kept informal. Ce document présente et discute de certains concepts de base de la mécanique du continuum de façon à permettre d'envisager des applications dans le domaine de la géophysique. Il aborde en particulier les concepts tels que les milieux de Cosserat, la répartition continue d'hétérogénéités et le rôle des symétries matérielles. Dans l'esprit de notre communication orale, la présentation garde un style informel.
Yuan, Xuebo; Wang, Youshan
2017-10-01
The radial deformation of carbon nanotubes (CNTs) adhering to a substrate may prominently affect their mechanical and physical properties. In this study, both classical atomistic simulations and continuum analysis are carried out, to investigate the lateral adhesion of single-walled CNTs (SWCNTs) and multi-walled CNTs (MWCNTs) to a silicon substrate. A linear elastic model for analyzing the adhesion of 2D shells to a rigid semi-infinite substrate is constructed in the framework of continuum mechanics. Good agreement is achieved between the cross-section profiles of adhesive CNTs obtained by the continuum model and by the atomistic simulation approach. It is found that the adhesion of a CNT to the silicon substrate is significantly influenced by its initial diameter and the number of walls. CNTs with radius larger than a certain critical radius are deformed radially on the silicon substrate with flat contact regions. With increasing number of walls, the extent of radial deformation of a MWCNT on the substrate decreases dramatically, and the flat contact area reduces—and eventually vanishes—due to increasing equivalent bending stiffness. It is analytically predicted that large-diameter MWCNTs with a large number of walls are likely to ‘stand’ on the silicon substrate. The present work can be useful for understanding the radial deformation of CNTs adhering to a solid planar substrate.
Sedov, L
1968-01-01
At its meeting on April 23, 1965 in Paris the Bureau of IUTAM decided to have a Symposium on the Irreversible Aspects of Continaum Mechanics held in June 1966 in Vienna. In addition, a Symposium on the Transfer of Physical Characteristics in Moving Fluids which, orig inally, had been scheduled to take place in Stockholm was rescheduled to be held in Vienna immediately following the Symposium on the Irre versible Aspects of Continuum Mechanics. It was felt that the subjects of the two symposia were so closely related that participants should be given an opportunity to attend both. Both decisions were unanimously approved by the members of the General Assembly of IUTAM. Prof. H. PARKUS, Vienna, was appointed Chairman of the Symposium on the Irreversible Aspects, and Prof. L. I. SEDOV, Moscow, was appointed Chairman of the Symposium on the Transfer of Physical Characteristics, with Prof. P ARKUS being re sponsible for the local organization of both symposia. In accordance with the policy set forth by IUTAM...
Fracture simulation of restored teeth using a continuum damage mechanics failure model.
Li, Haiyan; Li, Jianying; Zou, Zhenmin; Fok, Alex Siu-Lun
2011-07-01
The aim of this paper is to validate the use of a finite-element (FE) based continuum damage mechanics (CDM) failure model to simulate the debonding and fracture of restored teeth. Fracture testing of plastic model teeth, with or without a standard Class-II MOD (mesial-occusal-distal) restoration, was carried out to investigate their fracture behavior. In parallel, 2D FE models of the teeth are constructed and analyzed using the commercial FE software ABAQUS. A CDM failure model, implemented into ABAQUS via the user element subroutine (UEL), is used to simulate the debonding and/or final fracture of the model teeth under a compressive load. The material parameters needed for the CDM model to simulate fracture are obtained through separate mechanical tests. The predicted results are then compared with the experimental data of the fracture tests to validate the failure model. The failure processes of the intact and restored model teeth are successfully reproduced by the simulation. However, the fracture parameters obtained from testing small specimens need to be adjusted to account for the size effect. The results indicate that the CDM model is a viable model for the prediction of debonding and fracture in dental restorations. Copyright © 2011 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.
Theoretical analysis of the density wave in a new continuum model and numerical simulation
Lai, Ling-Ling; Cheng, Rong-Jun; Li, Zhi-Peng; Ge, Hong-Xia
2014-05-01
Considered the effect of traffic anticipation in the real world, a new anticipation driving car following model (AD-CF) was proposed by Zheng et al. Based on AD-CF model, adopted an asymptotic approximation between the headway and density, a new continuum model is presented in this paper. The neutral stability condition is obtained by applying the linear stability theory. Additionally, the Korteweg-de Vries (KdV) equation is derived via nonlinear analysis to describe the propagating behavior of traffic density wave near the neutral stability line. The numerical simulation and the analytical results show that the new continuum model is capable of explaining some particular traffic phenomena.
Energy Technology Data Exchange (ETDEWEB)
Choi, Myungseok; Olshevskiy, Alexander; Kim, Chang-Wan [Konkuk University, Seoul (Korea, Republic of); Eom, Kilho [Sungkyunkwan University, Suwon (Korea, Republic of); Gwak, Kwanwoong [Sejong University, Seoul (Korea, Republic of); Dai, Mai Duc [Ho Chi Minh City University of Technology and Education, Ho Chi Minh (Viet Nam)
2017-05-15
Carbon nanotube (CNT) has recently received much attention due to its excellent electromechanical properties, indicating that CNT can be employed for development of Nanoelectromechanical system (NEMS) such as nanomechanical resonators. For effective design of CNT-based resonators, it is required to accurately predict the vibration behavior of CNT resonators as well as their frequency response to mass adsorption. In this work, we have studied the vibrational behavior of Multi-walled CNT (MWCNT) resonators by using a continuum mechanics modeling that was implemented in Finite element method (FEM). In particular, we consider a transversely isotropic hollow cylinder solid model with Finite element (FE) implementation for modeling the vibration behavior of Multi-walled CNT (MWCNT) resonators. It is shown that our continuum mechanics model provides the resonant frequencies of various MWCNTs being comparable to those obtained from experiments. Moreover, we have investigated the frequency response of MWCNT resonators to mass adsorption by using our continuum model with FE implementation. Our study sheds light on our continuum mechanics model that is useful in predicting not only the vibration behavior of MWCNT resonators but also their sensing performance for further effective design of MWCNT- based NEMS devices.
A Micro-Mechanically Based Continuum Model for Strain-Induced Crystallization in Natural Rubber
Mistry, Sunny Jigger
Recent experimental results show that strain-induced crystallization can substantially improve the crack growth resistance of natural rubber. While this might suggest superior designs of tires or other industrial applications where elastomers are used, a more thorough understanding of the underlying physics of strain-induced crystallization in natural rubber has to be developed before any design process can be started. The objective of this work is to develop a computationally-accessible micro-mechanically based continuum model, which is able to predict the macroscopic behavior of strain crystallizing natural rubber. While several researchers have developed micro-mechanical models of partially crystallized polymer chains, their results mainly give qualitative agreement with experimental data due to a lack of good micro-macro transition theories or the lack of computational power. However, recent developments in multiscale modeling in polymers provide new tools to continue this early work. In this thesis, a new model is proposed to model strain-induced crystallization in natural rubber. To this end, a micro-mechanical model of a constrained partially crystallized polymer chain with an extended-chain crystal is derived and connected to the macroscopic level using the non-affine micro-sphere model. On the macroscopic level, a thermodynamically consistent framework for strain-crystallizing materials is developed, and a description of the crystallization kinetics is introduced. For that matter, an evolution law for crystallization based on the gradient of the macroscopic Helmholtz free energy function (chemical potential) in combination with a simple threshold function is used. A numerical implementation of the model is proposed and its predictive performance assessed using published data.
Molecular-To-Continuum Fracture Analysis of Thermosetting Polymer/Solid Interfaces
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KENT,MICHAEL S.; REEDY JR.,EARL DAVID; STEVENS,MARK J.
2000-01-01
This report focuses on the relationship between the fundamental interactions acting across an interface and macroscopic engineering observable such as fracture toughness or fracture stress. The work encompasses experiment, theory, and simulation. The model experimental system is epoxy on polished silicon. The interfacial interactions between the substrate and the adhesive are varied continuously using self-assembling monolayer. Fracture is studied in two specimen geometries: a napkin-ring torsion geometry and a double cantilevered beam specimen. Analysis and modeling involves molecular dynamics simulations and continuum mechanics calculations. Further insight is gained from analysis of measurements in the literature of direct force measurements for various fundamental interactions. In the napkin-ring test, the data indicate a nonlinear relationship between interface strength and fracture stress. In particular, there is an abrupt transition in fracture stress which corresponds to an adhesive-to-cohesive transition. Such nonlinearity is not present in the MD simulations on the tens-of-nanometer scale, which suggests that the nonlinearity comes from bulk material deformation occurring on much larger length scales. We postulate that the transition occurs when the interface strength becomes comparable to the yield stress of the material. This postulate is supported by variation observed in the fracture stress curve with test temperature. Detailed modeling of the stress within the sample has not yet been attempted. In the DCB test, the relationship between interface strength and fracture toughness is also nonlinear, but the fracture mechanisms are quite different. The fracture does not transition from adhesive to cohesive, but remains adhesive over the entire range of interface strength. This specimen is modeled quantitatively by combining (i) continuum calculations relating fracture toughness to the stress at 90 {angstrom} from the crack tip, and (ii) a relationship
Leone, Frank A., Jr.
2015-01-01
A method is presented to represent the large-deformation kinematics of intraply matrix cracks and delaminations in continuum damage mechanics (CDM) constitutive material models. The method involves the additive decomposition of the deformation gradient tensor into 'crack' and 'bulk material' components. The response of the intact bulk material is represented by a reduced deformation gradient tensor, and the opening of an embedded cohesive interface is represented by a normalized cohesive displacement-jump vector. The rotation of the embedded interface is tracked as the material deforms and as the crack opens. The distribution of the total local deformation between the bulk material and the cohesive interface components is determined by minimizing the difference between the cohesive stress and the bulk material stress projected onto the cohesive interface. The improvements to the accuracy of CDM models that incorporate the presented method over existing approaches are demonstrated for a single element subjected to simple shear deformation and for a finite element model of a unidirectional open-hole tension specimen. The material model is implemented as a VUMAT user subroutine for the Abaqus/Explicit finite element software. The presented deformation gradient decomposition method reduces the artificial load transfer across matrix cracks subjected to large shearing deformations, and avoids the spurious secondary failure modes that often occur in analyses based on conventional progressive damage models.
Zhang, Y Y; Wang, C M; Duan, W H; Xiang, Y; Zong, Z
2009-09-30
This paper presents an assessment of continuum mechanics (beam and cylindrical shell) models in the prediction of critical buckling strains of axially loaded single-walled carbon nanotubes (SWCNTs). Molecular dynamics (MD) simulation results for SWCNTs with various aspect (length-to-diameter) ratios and diameters will be used as the reference solutions for this assessment exercise. From MD simulations, two distinct buckling modes are observed, i.e. the shell-type buckling mode, when the aspect ratios are small, and the beam-type mode, when the aspect ratios are large. For moderate aspect ratios, the SWCNTs buckle in a mixed beam-shell mode. Therefore one chooses either the beam or the shell model depending on the aspect ratio of the carbon nanotubes (CNTs). It will be shown herein that for SWCNTs with long aspect ratios, the local Euler beam results are comparable to MD simulation results carried out at room temperature. However, when the SWCNTs have moderate aspect ratios, it is necessary to use the more refined nonlocal beam theory or the Timoshenko beam model for a better prediction of the critical strain. For short SWCNTs with large diameters, the nonlocal shell model with the appropriate small length scale parameter can provide critical strains that are in good agreement with MD results. However, for short SWCNTs with small diameters, more work has to be done to refine the nonlocal cylindrical shell model for better prediction of critical strains.
A Continuum Damage Mechanics Model for the Static and Cyclic Fatigue of Cellular Composites
Huber, Otto
2017-01-01
The fatigue behavior of a cellular composite with an epoxy matrix and glass foam granules is analyzed and modeled by means of continuum damage mechanics. The investigated cellular composite is a particular type of composite foam, and is very similar to syntactic foams. In contrast to conventional syntactic foams constituted by hollow spherical particles (balloons), cellular glass, mineral, or metal place holders are combined with the matrix material (metal or polymer) in the case of cellular composites. A microstructural investigation of the damage behavior is performed using scanning electron microscopy. For the modeling of the fatigue behavior, the damage is separated into pure static and pure cyclic damage and described in terms of the stiffness loss of the material using damage models for cyclic and creep damage. Both models incorporate nonlinear accumulation and interaction of damage. A cycle jumping procedure is developed, which allows for a fast and accurate calculation of the damage evolution for constant load frequencies. The damage model is applied to examine the mean stress effect for cyclic fatigue and to investigate the frequency effect and the influence of the signal form in the case of static and cyclic damage interaction. The calculated lifetimes are in very good agreement with experimental results. PMID:28809806
Continuum damage growth analysis using element free Galerkin ...
Indian Academy of Sciences (India)
This paper presents an elasto-plastic element free Galerkin formulation based on Newton–Raphson algorithm for damage growth analysis. Isotropic ductile damage evolution law is used. A study has been carried out in this paper using the proposed element free Galerkin method to understand the effect of initial damage ...
Continuum damage growth analysis using element free Galerkin ...
Indian Academy of Sciences (India)
using the proposed element free Galerkin method to understand the effect of initial damage and its growth on structural ... Effect of material discontinuity on damage growth analysis is also presented. Keywords. Damage ... 1996), Lagrange multiplier technique (Dolbow & Belytschko 1998), penalty method (Liu. 2002), full ...
Continuum soil modeling in the static analysis of buried structures
International Nuclear Information System (INIS)
Julyk, L.J.; Marlow, R.S.; Moore, C.J.; Day, J.P.; Dyrness, A.D.
1993-10-01
Soil loading traditionally has been modeled as a hydrostatic pressure, a practice acceptable for many design applications. In the analyses of buried structure with predictive goals, soil compliance and load redistribution in the presence of soil plasticity are important factors to consider in determining the appropriate response of the structure. In the analysis of existing buried waste-storage tanks at the US Department of Energy's Hanford Site, three soil-tank interaction modeling considerations are addressed. First, the soil interacts with the tank as the tank expands and contracts during thermal cycles associated with changes in the heat generated by the waste material as a result of additions and subtractions of the waste. Second, the soil transfers loads from the surface to the tank and provides support by resisting radial displacement of the tank haunch. Third, conventional finite-element mesh development causes artificial stress concentrations in the soil associated with differential settlement
Analysis of adult patients with epilepsy in the age continuum
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V. A. Karlov
2016-01-01
Full Text Available Objective: to study the presence of comorbidities and to investigate quality of life in patients with main types of epilepsy in relation to age.Patients and methods. The investigation enrolled 150 patients aged 17 to 64 years with idiopathic, cryptogenic, and symptomatic types of epilepsy. The investigators studied the presence of sleep disorders using the questionnaires designed by the Somnology Center, Ministry of Health of Russia, and that of daytime sleepiness by the Epworth Sleepiness Scale, determined the level of anxiety and depression by the Hospital Anxiety and Depression Scale, and assessed the severity of seizures by the National Hospital Seizure Severity Scale. Quality of life was investigated using the QOLIE-89 questionnaire. A cluster analysis was carried out to divide all the patients into three age groups (mean age, 27.3; 30.7; and 37.7 years.Results and discussion. A positive relationship was obtained between some indicators of sleep disorders, level of anxiety, and age. There were significant differences between the above three age groups in the following indicators: sleep disorders; daytime sleepiness; level of anxiety, severity of seizures, and scores of the QOLIE-89 questionnaire (p<0.001. Since the patients suffer from different basic types of epilepsy (cryptogenic, idiopathic, and symptomatic, the findings testify to age as an independent factor that modifies quality of life in epileptic patients.
International Nuclear Information System (INIS)
Kalman, Z.H.; Chaudhuri, J.; Weng, G.J.; Weissmann, S.
1980-01-01
The strain distribution in the vicinity of the notches of a double-notched, elastically bent silicon crystal was determined by measuring the diffracted X-ray intensities. The measurements were carried out on traverse-oscillation topographs of a crystal section extending through both notches. Strain distributions were determined by measuring the local densities of silver deposits (measurements of 'opacities') with a scanning electron microscope. It was shown that both the density range and spatial resolution of X-ray densitometry were larger by an order of magnitude than those of optical densitometry. The strain concentration factors associated with the notches were measured experimentally and calculated by continuum mechanics. The results were in satisfactory agreement. Also, the experimentally found rise of strains, to a maximum in the critical area adjacent to the notch root, followed the trend predicted by continuum mechanics. (Auth.)
A morphing strategy to couple non-local to local continuum mechanics
Lubineau, Gilles
2012-06-01
A method for coupling non-local continuum models with long-range central forces to local continuum models is proposed. First, a single unified model that encompasses both local and non-local continuum representations is introduced. This model can be purely non-local, purely local or a hybrid depending on the constitutive parameters. Then, the coupling between the non-local and local descriptions is performed through a transition (morphing) affecting only the constitutive parameters. An important feature is the definition of the morphing functions, which relies on energy equivalence. This approach is useful in large-scale modeling of materials that exhibit strong non-local effects. The computational cost can be reduced while maintaining a reasonable level of accuracy. Efficiency, robustness and basic properties of the approach are discussed using one- and two-dimensional examples. © 2012 Elsevier Ltd.
Deissler, Robert G.
1996-01-01
Background material on Fourier analysis and on the spectral form of the continuum equations, both averaged and unaveraged, are given. The equations are applied to a number of cases of homogeneous turbulence with and without mean gradients. Spectral transfer of turbulent activity between scales of motion is studied in some detail. The effects of mean shear, heat transfer, normal strain, and buoyancy are included in the analyses.
Herrendoerfer, R.; Gerya, T.; van Dinther, Y.
2016-12-01
The convergent plate motion in subduction zones is accommodated by different slip modes: potentially dangerous seismic slip and imperceptible, but instrumentally detectable slow slip transients or steady slip. Despite an increasing number of observations and insights from laboratory experiments, it remains enigmatic which local on- and off-fault conditions favour slip modes of different source characteristics (i.e., slip velocity, duration, seismic moment). Therefore, we are working towards a numerical model that is able to simulate different slip modes in a consistent way with the long-term evolution of the fault system. We extended our 2D, continuum mechanics-based, visco-elasto-plastic seismo-thermo-mechanical (STM) model, which simulated cycles of earthquake-like ruptures, albeit only at plate tectonic slip rates (van Dinther et al, JGR, 2013). To model a wider slip spectrum including seismic slip rates, we, besides improving the general numerical approach, implemented an invariant reformulation of the conventional rate-and state dependent friction (RSF) and an adaptive time-stepping scheme (Lapusta and Rice, JGR, 2001). In a simple setup with predominantly elastic plates that are juxtaposed along a predefined fault of certain width, we vary the characteristic slip distance, the mean normal stress and the size of the rate-weakening zone. We show that the resulting stability transitions from decaying oscillations, periodic slow slip, complex periodic to seismic slip agree with those of conventional RSF seismic cycle simulations (e.g. Liu and Rice, JGR, 2007). Additionally, we will present results of the investigation concerning the effect of the fault width and geometry on the generation of different slip modes. Ultimately, instead of predefining a fault, we simulate the spatio-temporal evolution of a complex fault system that is consistent with the plate motions and rheology. For simplicity, we parametrize the fault development through linear slip-weakening of
Yuan, Xuebo; Wang, Youshan
2018-02-01
Carbon nanotubes (CNTs) can undergo collapse from the ordinary cylindrical configurations to bilayer ribbons when adhered on substrates. In this study, the collapsed adhesion of CNTs on the silicon substrates is investigated using both classical molecular dynamics (MD) simulations and continuum analysis. The governing equations and transversality conditions are derived based on the minimum potential energy principle and the energy-variational method, considering both the van der Waals interactions between CNTs and substrates and those inside CNTs. Closed-form solutions for the collapsed configuration are obtained which show good agreement with the results of MD simulations. The stability of adhesive configurations is investigated by analyzing the energy states. It is found that the adhesive states of single-walled CNTs (SWCNTs) (n, n) on the silicon substrates can be categorized by two critical radii, 0.716 and 0.892 nm. For SWCNTs with radius larger than 0.892 nm, they would fully collapse on the silicon substrates. For SWCNTs with radius less than 0.716 nm, the initial cylindrical configuration is energetically favorable. For SWCNTs with radius between two critical radii, the radially deformed state is metastable. The non-contact ends of all collapsed SWCNTs are identical with the same arc length of 2.38 nm. Finally, the role of number of walls on the adhesive configuration is investigated quantitatively. For multi-walled CNTs with the number of walls exceeding a certain value, the cylindrical configuration is stable due to the increasing bending stiffness. The present study can be useful for the design of CNT-based nanodevices.
Wang, John T.; Pineda, Evan J.; Ranatunga, Vipul; Smeltzer, Stanley S.
2015-01-01
A simple continuum damage mechanics (CDM) based 3D progressive damage analysis (PDA) tool for laminated composites was developed and implemented as a user defined material subroutine to link with a commercially available explicit finite element code. This PDA tool uses linear lamina properties from standard tests, predicts damage initiation with an easy-to-implement Hashin-Rotem failure criteria, and in the damage evolution phase, evaluates the degradation of material properties based on the crack band theory and traction-separation cohesive laws. It follows Matzenmiller et al.'s formulation to incorporate the degrading material properties into the damaged stiffness matrix. Since nonlinear shear and matrix stress-strain relations are not implemented, correction factors are used for slowing the reduction of the damaged shear stiffness terms to reflect the effect of these nonlinearities on the laminate strength predictions. This CDM based PDA tool is implemented as a user defined material (VUMAT) to link with the Abaqus/Explicit code. Strength predictions obtained, using this VUMAT, are correlated with test data for a set of notched specimens under tension and compression loads.
Nonlinear Analysis on Cross-Correlation of Financial Time Series by Continuum Percolation System
Niu, Hongli; Wang, Jun
We establish a financial price process by continuum percolation system, in which we attribute price fluctuations to the investors’ attitudes towards the financial market, and consider the clusters in continuum percolation as the investors share the same investment opinion. We investigate the cross-correlations in two return time series, and analyze the multifractal behaviors in this relationship. Further, we study the corresponding behaviors for the real stock indexes of SSE and HSI as well as the liquid stocks pair of SPD and PAB by comparison. To quantify the multifractality in cross-correlation relationship, we employ multifractal detrended cross-correlation analysis method to perform an empirical research for the simulation data and the real markets data.
Babenko, Oksana; Koppula, Sudha; Daniels, Lia; Nadon, Lindsey; Daniels, Vijay
2017-10-01
Lifelong learning is an integral part of health professionals' maintenance of competence. Several studies have examined the orientation toward lifelong learning at various stages of the education and career continuum; however, none has looked at changes throughout training and practice. The objective of the present study was to determine if there are differences between groups defined by their places on the education and career continuum. The authors performed a group-level meta-analysis on studies that used the 14-item Jefferson Scale of Physician Lifelong Learning or its variants. Eleven published articles, which reported on studies with post-secondary health professions students, residents, and practicing health professionals met the inclusion criteria. In total, there were 12 independent data sets, with four data sets per group. In total, over seven thousand students, residents, and practicing health professionals responded to the Jefferson Scale (N=7.269). Individual study means tendency to be high, suggesting a high orientation toward lifelong learning among the trainees (students and residents) and practicing health professionals. Meta-analysis results indicated that the orientation toward lifelong learning tended to increase gradually along the education and career continuum. Significant differences in the group means were found between the trainees and practicing health professionals. In the reviewed studies, the orientation toward lifelong learning among students, residents, and practicing professionals was high. Nonetheless, although based on separate cohorts, it appears that the orientation toward lifelong learning continues to develop even after the completion of formal training.
International Nuclear Information System (INIS)
Hobler, Gerhard
2015-01-01
Many experiments indicate the importance of stress and stress relaxation upon ion implantation. In this paper, a model is proposed that is capable of describing ballistic effects as well as stress relaxation by viscous flow. It combines atomistic binary collision simulation with continuum mechanics. The only parameters that enter the continuum model are the bulk modulus and the radiation-induced viscosity. The shear modulus can also be considered but shows only minor effects. A boundary-fitted grid is proposed that is usable both during the binary collision simulation and for the spatial discretization of the force balance equations. As an application, the milling of a slit into an amorphous silicon membrane with a 30 keV focused Ga beam is studied, which demonstrates the relevance of the new model compared to a more heuristic approach used in previous work
Directory of Open Access Journals (Sweden)
Charles M. Reinke
2011-12-01
Full Text Available Recent work has demonstrated that nanostructuring of a semiconductor material to form a phononic crystal (PnC can significantly reduce its thermal conductivity. In this paper, we present a classical method that combines atomic-level information with the application of Bloch theory at the continuum level for the prediction of the thermal conductivity of finite-thickness PnCs with unit cells sized in the micron scale. Lattice dynamics calculations are done at the bulk material level, and the plane-wave expansion method is implemented at the macrosale PnC unit cell level. The combination of the lattice dynamics-based and continuum mechanics-based dispersion information is then used in the Callaway-Holland model to calculate the thermal transport properties of the PnC. We demonstrate that this hybrid approach provides both accurate and efficient predictions of the thermal conductivity.
Computational performance of Free Mesh Method applied to continuum mechanics problems
YAGAWA, Genki
2011-01-01
The free mesh method (FMM) is a kind of the meshless methods intended for particle-like finite element analysis of problems that are difficult to handle using global mesh generation, or a node-based finite element method that employs a local mesh generation technique and a node-by-node algorithm. The aim of the present paper is to review some unique numerical solutions of fluid and solid mechanics by employing FMM as well as the Enriched Free Mesh Method (EFMM), which is a new version of FMM, including compressible flow and sounding mechanism in air-reed instruments as applications to fluid mechanics, and automatic remeshing for slow crack growth, dynamic behavior of solid as well as large-scale Eigen-frequency of engine block as applications to solid mechanics. PMID:21558753
Testing a continuum structure of self-determined motivation: A meta-analysis.
Howard, Joshua L; Gagné, Marylène; Bureau, Julien S
2017-12-01
Self-determination theory proposes a multidimensional representation of motivation comprised of several factors said to fall along a continuum of relative autonomy. The current meta-analysis examined the relationships between these motivation factors in order to demonstrate how reliably they conformed to a predictable continuum-like pattern. Based on data from 486 samples representing over 205,000 participants who completed 1 of 13 validated motivation scales, the results largely supported a continuum-like structure of motivation and indicate that self-determination is central in explaining human motivation. Further examination of heterogeneity indicated that while regulations were predictably ordered across domains and scales, the exact distance between subscales varied across samples in a way that was not explainable by a set of moderators. Results did not support the inclusion of integrated regulation or the 3 subscales of intrinsic motivation (i.e., intrinsic motivation to know, to experience stimulation, and to achieve) due to excessively high interfactor correlations and overlapping confidence intervals. Recommendations for scale refinements and the scoring of motivation are provided. (PsycINFO Database Record (c) 2017 APA, all rights reserved).
Rahimi, Mohammad; Karimi-Varzaneh, Hossein Ali; Böhm, Michael C; Müller-Plathe, Florian; Pfaller, Sebastian; Possart, Gunnar; Steinmann, Paul
2011-04-21
A scheme is described for performing molecular dynamics simulations on polymers under nonperiodic, stochastic boundary conditions. It has been designed to allow later the embedding of a particle domain treated by molecular dynamics into a continuum environment treated by finite elements. It combines, in the boundary region, harmonically restrained particles to confine the system with dissipative particle dynamics to dissipate energy and to thermostat the simulation. The equilibrium position of the tethered particles, the so-called anchor points, are well suited for transmitting deformations, forces and force derivatives between the particle and continuum domains. In the present work the particle scheme is tested by comparing results for coarse-grained polystyrene melts under nonperiodic and regular periodic boundary conditions. Excellent agreement is found for thermodynamic, structural, and dynamic properties.
Directory of Open Access Journals (Sweden)
Wang X.-S.
2008-04-01
Full Text Available The main purpose of this paper is to seek a mechanical interpretation of electromagnetic phenomena. We suppose that vacuum is filled with a kind of continuously distributed material which may be called Omega(1 substratum. Further, we speculate that the Omega(1 substratum might behave like a fluid with respect to translational motion of large bod- ies through it, but would still posses elasticity to produce small transverse vibrations. Thus, we propose a visco-elastic constitutive relation of the Omega(1 substratum. Further- more, we speculate that electric charges are emitting or absorbing the Omega(1 substratum continuously and establish a fluidic source and sink model of electric charges. Thus, Maxwell’s equations in vacuum are derived by methods of continuum mechanics based on this mechanical model of vacuum and the singularity model of electric charges.
Directory of Open Access Journals (Sweden)
Xiao-Song Wang
2008-04-01
Full Text Available The main purpose of this paper is to seek a mechanical interpretation of electromagnetic phenomena. We suppose that vacuumis filled with a kind of continuously distributed material which may be called $Omega (1$ substratum. Further, we speculate that the $Omega (1$ substratum might behave like a fluid with respect to translational motion of large bodies through it, but would still posses elasticity to produce small transverse vibrations. Thus, we propose a visco-elastic constitutive relation of the $Omega (1$ substratum. Furthermore, we speculate that electric charges are emitting or absorbing the $Omega (1$ substratum continuously and establish a fluidic source and sink model of electric charges. Thus,Maxwell's equations in vacuum are derived by methods of continuum mechanics based on this mechanical model of vacuum and the singularity model of electric charges.
Hertel, Peter
2012-01-01
This small book on the properties of continuously distributed matter covers a huge field. It sets out the governing principles of continuum physics and illustrates them by carefully chosen examples. These examples comprise structural mechanics and elasticity, fluid media, electricity and optics, thermoelectricity, fluctuation phenomena and more, from Archimedes' principle via Brownian motion to white dwarfs. Metamaterials, pattern formation by reaction-diffusion and surface plasmon polaritons are dealt with as well as classical topics such as Stokes' formula, beam bending and buckling, crystal optics and electro- and magnetooptic effects, dielectric waveguides, Ohm's law, surface acoustic waves, to mention just some. The set of balance equations for content, flow and production of particles, mass, charge, momentum, energy and entropy is augmented by material, or constitutive equations. They describe entire classes of materials, such as viscid fluids and gases, elastic media, dielectrics or electrical con...
Analysis of the population of continuum states in wave packet propagation calculations
Sjakste, J.; Borisov, A. G.; Gauyacq, J. P.; Kazansky, A. K.
2004-04-01
We present a 'virtual detector' method which allows the extraction of the momentum distributions in continuum states from time-dependent wave packet propagation studies with explicitly time-dependent Hamiltonians. It is based on the approach developed by Balint-Kurti et al (1990 J. Chem. Soc. Faraday Trans. 86 1741) for quantum chemistry applications and consists in measuring a signal in the asymptotic region. In that sense, it is close to the semiclassical method proposed recently in this journal (Feuerstein and Thumm 2003 J. Phys. B: At. Mol. Opt. Phys. 36 707). The advantage of the present approach is that it is based on a rigorous quantum mechanical treatment, robust, easy to handle and requires a much smaller grid size. The method is illustrated with the 3D example of electron detachment from the H- ion colliding with a free-electron metal surface.
Analysis of the population of continuum states in wave packet propagation calculations
International Nuclear Information System (INIS)
Sjakste, J; Borisov, A G; Gauyacq, J P; Kazansky, A K
2004-01-01
We present a 'virtual detector' method which allows the extraction of the momentum distributions in continuum states from time-dependent wave packet propagation studies with explicitly time-dependent Hamiltonians. It is based on the approach developed by Balint-Kurti et al (1990 J. Chem. Soc. Faraday Trans. 86 1741) for quantum chemistry applications and consists in measuring a signal in the asymptotic region. In that sense, it is close to the semiclassical method proposed recently in this journal (Feuerstein and Thumm 2003 J. Phys. B: At. Mol. Opt. Phys. 36 707). The advantage of the present approach is that it is based on a rigorous quantum mechanical treatment, robust, easy to handle and requires a much smaller grid size. The method is illustrated with the 3D example of electron detachment from the H - ion colliding with a free-electron metal surface
A continuum damage mechanics approach to simulation of creep and fracture in ice sheets
Duddu, R.; Bassis, J. N.; Waisman, H.; Tuminaro, R.
2011-12-01
We investigate iceberg calving from grounded tidewater and outlet glaciers using a novel creep continuum damage model for polycrystalline ice, which is valid for low stresses or strain rates. The proposed three-dimensional model is based on a thermo-viscoelastic constitutive law for ice creep and a local damage accumulation law for tension, compression and shear loadings. The model has been validated by published experimental data and is implemented in the commercially available finite element code ABAQUS by adopting a strain-based algorithm in a Lagrangian description. The model is then used to investigate conditions that enable surface, englacial and basal crevasse formation resulting from different boundary conditions applied to an idealized rectangular slab of ice in contact with the ocean. Preliminary simulations, based on imposed stress fields, suggest that a low tensile stress is required for crevasse (crack) opening and propagation to the bottom of the ice slab. In all the subsequent simulations the internal stress field is explicitly calculated. Basal boundary condition of the ice slab is varied from free slip to Newtonian frictional slip to study its effect on crack growth. The simulation results suggest that in the case of deeper (thicker) ice sheets compression failure of ice at the bottom is a possible mode of failure and that the height of the sea water level influences the depth of the crevasses.
Duddu, R.; Bassis, J. N.; Waisman, H.
2012-12-01
We investigate iceberg calving from grounded tidewater and outlet glaciers using a novel creep continuum damage model for polycrystalline ice, which is valid for low stresses or strain rates. The proposed three-dimensional model is based on a thermo-viscoelastic constitutive law for ice creep and a nonlocal damage accumulation law for tension, compression and shear loadings. The model has been validated by published experimental data and is implemented in the commercially available finite element code ABAQUS by adopting a strain-based algorithm using a Lagrangian description. The model is then used to investigate conditions that enable surface crevasse propagation resulting from different boundary conditions applied to an idealized rectangular slab of ice in contact with the ocean. The basal boundary condition of the ice slab is varied from free slip to fixed (no slip) to study its effect on surface crack (crevasse) growth. The depth varying ice flow velocities lead to tensile stresses in the top region of the ice slab that leads to surface crevasse propagation. The simulation results suggest that if the ice slab is thick enough and the water depth small enough, surface crevasses will penetrate the entire ice thickness. On the other hand, if the ice slab is thin and water depth sufficiently large, crevasses will not penetrate the ice thickness.
Nonlinear analysis of an improved continuum model considering headway change with memory
Cheng, Rongjun; Wang, Jufeng; Ge, Hongxia; Li, Zhipeng
2018-01-01
Considering the effect of headway changes with memory, an improved continuum model of traffic flow is proposed in this paper. By means of linear stability theory, the new model’s linear stability with the effect of headway changes with memory is obtained. Through nonlinear analysis, the KdV-Burgers equation is derived to describe the propagating behavior of traffic density wave near the neutral stability line. Numerical simulation is carried out to study the improved traffic flow model, which explores how the headway changes with memory affected each car’s velocity, density and energy consumption. Numerical results show that when considering the effects of headway changes with memory, the traffic jams can be suppressed efficiently. Furthermore, research results demonstrate that the effect of headway changes with memory can avoid the disadvantage of historical information, which will improve the stability of traffic flow and minimize car energy consumption.
Maugin, Gérard A
2014-01-01
Conceived as a series of more or less autonomous essays, the present book critically exposes the initial developments of continuum thermo-mechanics in a post Newtonian period extending from the creative works of the Bernoullis to the First World war, i.e., roughly during first the “Age of reason” and next the “Birth of the modern world”. The emphasis is rightly placed on the original contributions from the “Continental” scientists (the Bernoulli family, Euler, d’Alembert, Lagrange, Cauchy, Piola, Duhamel, Neumann, Clebsch, Kirchhoff, Helmholtz, Saint-Venant, Boussinesq, the Cosserat brothers, Caratheodory) in competition with their British peers (Green, Kelvin, Stokes, Maxwell, Rayleigh, Love,..). It underlines the main breakthroughs as well as the secondary ones. It highlights the role of scientists who left essential prints in this history of scientific ideas. The book shows how the formidable developments that blossomed in the twentieth century (and perused in a previous book of the author in...
A Mathematical Analysis of Atomistic-to-Continuum (AtC) Multiscale Coupling Methods
Energy Technology Data Exchange (ETDEWEB)
Gunzburger, Max
2013-11-13
We have worked on several projects aimed at improving the efficiency and understanding of multiscale methods, especially those applicable to problems involving atomistic-to-continuum coupling. Activities include blending methods for AtC coupling and efficient quasi-continuum methods for problems with long-range interactions.
Wetzel, Angela P
2012-08-01
Instrument development consistent with best practices is necessary for effective assessment and evaluation of learners and programs across the medical education continuum. The author explored the extent to which current factor analytic methods and other techniques for establishing validity are consistent with best practices. The author conducted electronic and hand searches of the English-language medical education literature published January 2006 through December 2010. To describe and assess current practices, she systematically abstracted reliability and validity evidence as well as factor analysis methods, data analysis, and reported evidence from instrument development articles reporting the application of exploratory factor analysis and principal component analysis. Sixty-two articles met eligibility criteria. They described 64 instruments and 95 factor analyses. Most studies provided at least one source of evidence based on test content. Almost all reported internal consistency, providing evidence based on internal structure. Evidence based on response process and relationships with other variables was reported less often, and evidence based on consequences of testing was not identified. Factor analysis findings suggest common method selection errors and critical omissions in reporting. Given the limited reliability and validity evidence provided for the reviewed instruments, educators should carefully consider the available supporting evidence before adopting and applying published instruments. Researchers should design for, test, and report additional evidence to strengthen the argument for reliability and validity of these measures for research and practice.
Zheng, Zhenzhen; Chou, Ching-Shan; Yi, Tau-Mu; Nie, Qing
2011-10-01
Cell polarization, in which substances previously uniformly distributed become asymmetric due to external or/and internal stimulation, is a fundamental process underlying cell mobility, cell division, and other polarized functions. The yeast cell S. cerevisiae has been a model system to study cell polarization. During mating, yeast cells sense shallow external spatial gradients and respond by creating steeper internal gradients of protein aligned with the external cue. The complex spatial dynamics during yeast mating polarization consists of positive feedback, degradation, global negative feedback control, and cooperative effects in protein synthesis. Understanding such complex regulations and interactions is critical to studying many important characteristics in cell polarization including signal amplification, tracking dynamic signals, and potential trade-off between achieving both objectives in a robust fashion. In this paper, we study some of these questions by analyzing several models with different spatial complexity: two compartments, three compartments, and continuum in space. The step-wise approach allows detailed characterization of properties of the steady state of the system, providing more insights for biological regulations during cell polarization. For cases without membrane diffusion, our study reveals that increasing the number of spatial compartments results in an increase in the number of steady-state solutions, in particular, the number of stable steady-state solutions, with the continuum models possessing infinitely many steady-state solutions. Through both analysis and simulations, we find that stronger positive feedback, reduced diffusion, and a shallower ligand gradient all result in more steady-state solutions, although most of these are not optimally aligned with the gradient. We explore in the different settings the relationship between the number of steady-state solutions and the extent and accuracy of the polarization. Taken together
Higher order point and continuum mechanics from phase-space action
Energy Technology Data Exchange (ETDEWEB)
Shamanna, J.; Talukdar, B.; Das, U
2002-12-02
It is pointed out that use of phase-space action provides an elegant method to study the canonical structure of problems in mechanics. Higher order Lagrangian systems are Hamiltonized by employing the variational principle in phase space. Studies are envisaged for both particle dynamics and field theory. Hamilton's equations are expressed in terms of appropriate Poisson brackets.
Corni, Federico; Fuchs, Hans U.; Savino, Giovanni
2018-01-01
This is a description of the conceptual foundations used for designing a novel learning environment for mechanics implemented as an "Industrial Educational Laboratory"--called Fisica in Moto (FiM)--at the Ducati Foundation in Bologna. In this paper, we will describe the motivation for and design of the conceptual approach to mechanics…
Analysis of Thermo-Diffusive Cellular Instabilities in Continuum Combustion Fronts
Azizi, Hossein; Gurevich, Sebastian; Provatas, Nikolas; Department of Physics, Centre Physics of Materials Team
We explore numerically the morphological patterns of thermo-diffusive instabilities in combustion fronts with a continuum solid fuel source, within a range of Lewis numbers, focusing on the cellular regime. Cellular and dendritic instabilities are found at low Lewis numbers. These are studied using a dynamic adaptive mesh refinement technique that allows very large computational domains, thus allowing us to reduce finite size effects that can affect or even preclude the emergence of these patterns. The distinct types of dynamics found in the vicinity of the critical Lewis number. These types of dynamics are classified as ``quasi-linear'' and characterized by low amplitude cells that may be strongly affected by the mode selection mechanism and growth prescribed by the linear theory. Below this range of Lewis number, highly non-linear effects become prominent and large amplitude, complex cellular and seaweed dendritic morphologies emerge. The cellular patterns simulated in this work are similar to those observed in experiments of flame propagation over a bed of nano-aluminum powder burning with a counter-flowing oxidizer conducted by Malchi et al. It is noteworthy that the physical dimension of our computational domain is roughly close to their experimental setup. This work was supported by a Canadian Space Agency Class Grant ''Percolating Reactive Waves in Particulate Suspensions''. We thank Compute Canada for computing resources.
Directory of Open Access Journals (Sweden)
Ramesh S. Kanwar
2011-07-01
Full Text Available This study applied a broad continuum of risk analysis methods including mean-variance and coefficient of variation (CV statistical criteria, second-degree stochastic dominance (SSD, stochastic dominance with respect to a function (SDRF, and stochastic efficiency with respect to a function (SERF for comparing income-risk efficiency sustainability of conventional and reduced tillage systems. Fourteen years (1990–2003 of economic budget data derived from 35 treatments on 36 experimental plots under corn (Zea mays L. and soybean (Glycine max L. at the Iowa State University Northeast Research Station near Nashua, IA, USA were used. In addition to the other analyses, a visually-based Stoplight or “probability of target value” procedure was employed for displaying gross margin and net return probability distribution information. Mean-variance and CV analysis of the economic measures alone provided somewhat contradictive and inconclusive sustainability rankings, i.e., corn/soybean gross margin and net return showed that different tillage system alternatives were the highest ranked depending on the criterion and type of crop. Stochastic dominance analysis results were similar for SSD and SDRF in that both the conventional and reduced tillage system alternatives were highly ranked depending on the type of crop and tillage system. For the SERF analysis, results were dependent on the type of crop and level of risk aversion. The conventional tillage system was preferred for both corn and soybean for the Stoplight analysis. The results of this study are unique in that they highlight the potential of both traditional stochastic dominance and SERF methods for distinguishing economically sustainable choices between different tillage systems across a range of risk aversion. This study also indicates that the SERF risk analysis method appears to be a useful and easily understood tool to assist farm managers, experimental researchers, and potentially policy
International Nuclear Information System (INIS)
Dumbser, Michael; Peshkov, Ilya; Romenski, Evgeniy; Zanotti, Olindo
2016-01-01
Highlights: • High order schemes for a unified first order hyperbolic formulation of continuum mechanics. • The mathematical model applies simultaneously to fluid mechanics and solid mechanics. • Viscous fluids are treated in the frame of hyper-elasticity as generalized visco-plastic solids. • Formal asymptotic analysis reveals the connection with the Navier–Stokes equations. • The distortion tensor A in the model appears to be well-suited for flow visualization. - Abstract: This paper is concerned with the numerical solution of the unified first order hyperbolic formulation of continuum mechanics recently proposed by Peshkov and Romenski [110], further denoted as HPR model. In that framework, the viscous stresses are computed from the so-called distortion tensor A, which is one of the primary state variables in the proposed first order system. A very important key feature of the HPR model is its ability to describe at the same time the behavior of inviscid and viscous compressible Newtonian and non-Newtonian fluids with heat conduction, as well as the behavior of elastic and visco-plastic solids. Actually, the model treats viscous and inviscid fluids as generalized visco-plastic solids. This is achieved via a stiff source term that accounts for strain relaxation in the evolution equations of A. Also heat conduction is included via a first order hyperbolic system for the thermal impulse, from which the heat flux is computed. The governing PDE system is hyperbolic and fully consistent with the first and the second principle of thermodynamics. It is also fundamentally different from first order Maxwell–Cattaneo-type relaxation models based on extended irreversible thermodynamics. The HPR model represents therefore a novel and unified description of continuum mechanics, which applies at the same time to fluid mechanics and solid mechanics. In this paper, the direct connection between the HPR model and the classical hyperbolic–parabolic Navier
Qi, Fei; Ju, Feng; Bai, Dong Ming; Chen, Bai
2018-02-01
For the outstanding compliance and dexterity of continuum robot, it is increasingly used in minimally invasive surgery. The wide workspace, high dexterity and strong payload capacity are essential to the continuum robot. In this article, we investigate the workspace of a cable-driven continuum robot that we proposed. The influence of section number on the workspace is discussed when robot is operated in narrow environment. Meanwhile, the structural parameters of this continuum robot are optimized to achieve better kinematic performance. Moreover, an indicator based on the dexterous solid angle for evaluating the dexterity of robot is introduced and the distal end dexterity is compared for the three-section continuum robot with different range of variables. Results imply that the wider range of variables achieve the better dexterity. Finally, the static model of robot based on the principle of virtual work is derived to analyze the relationship between the bending shape deformation and the driven force. The simulations and experiments for plane and spatial motions are conducted to validate the feasibility of model, respectively. Results of this article can contribute to the real-time control and movement and can be a design reference for cable-driven continuum robot.
Nims, Robert J; Durney, Krista M; Cigan, Alexander D; Dusséaux, Antoine; Hung, Clark T; Ateshian, Gerard A
2016-02-06
This study presents a damage mechanics framework that employs observable state variables to describe damage in isotropic or anisotropic fibrous tissues. In this mixture theory framework, damage is tracked by the mass fraction of bonds that have broken. Anisotropic damage is subsumed in the assumption that multiple bond species may coexist in a material, each having its own damage behaviour. This approach recovers the classical damage mechanics formulation for isotropic materials, but does not appeal to a tensorial damage measure for anisotropic materials. In contrast with the classical approach, the use of observable state variables for damage allows direct comparison of model predictions to experimental damage measures, such as biochemical assays or Raman spectroscopy. Investigations of damage in discrete fibre distributions demonstrate that the resilience to damage increases with the number of fibre bundles; idealizing fibrous tissues using continuous fibre distribution models precludes the modelling of damage. This damage framework was used to test and validate the hypothesis that growth of cartilage constructs can lead to damage of the synthesized collagen matrix due to excessive swelling caused by synthesized glycosaminoglycans. Therefore, alternative strategies must be implemented in tissue engineering studies to prevent collagen damage during the growth process.
Representative volume size: A comparison of statistical continuum mechanics and statistical physics
Energy Technology Data Exchange (ETDEWEB)
AIDUN,JOHN B.; TRUCANO,TIMOTHY G.; LO,CHI S.; FYE,RICHARD M.
1999-05-01
In this combination background and position paper, the authors argue that careful work is needed to develop accurate methods for relating the results of fine-scale numerical simulations of material processes to meaningful values of macroscopic properties for use in constitutive models suitable for finite element solid mechanics simulations. To provide a definite context for this discussion, the problem is couched in terms of the lack of general objective criteria for identifying the size of the representative volume (RV) of a material. The objective of this report is to lay out at least the beginnings of an approach for applying results and methods from statistical physics to develop concepts and tools necessary for determining the RV size, as well as alternatives to RV volume-averaging for situations in which the RV is unmanageably large. The background necessary to understand the pertinent issues and statistical physics concepts is presented.
Predicition of the first spinning cylinder test using continuum damage mechanics
International Nuclear Information System (INIS)
Lidbury, D.P.G.; Sherry, A.H.; Bilby, B.A.; Howard, I.C.; Li, Z.H.; Eripret, C.
1993-01-01
For many years large-scale experiments have been performed world-wide to validate aspects of fracture mechanics methodology. Special emphasis has been given to correlations between small- and large-scale specimen behaviour in quantifying the structural behaviour of pressure vessels, piping and closures. Within this context, the first three Spinning Cylinder Tests, performed by AEA Technology at its Risley Laboratory, addressed the phenomenon of stable crack growth by ductile tearing in contained yield and conditions simulating pressurized thermal shock loading in a PWR reactor pressure vessel. A notable feature of the test data was that the effective resistance to crack growth, as measured in terms of the J R-curve, was appreciably greater than that anticipated from small-scale testing, both at initiation and after small amounts (a few millimeters) of tearing. In the present paper, two independent finite element analyses of the First Spinning Cylinder Test (SC 1) are presented and compared. Both involved application of the Rousselier ductile damage theory in an attempt to better understand the transferability of test data from small specimens to structural validation tests. In each instance, the parameters associated with the theory's constitutive equation were calibrated in terms of data from notched-tensile and (or) fracture mechanics tests, metallographic observation and (or) chemical composition. The evolution of ductile damage local to the crack tip during SC 1 was thereby calculated and, together with a crack growth criterion based on the maximization of opening-mode stress, used as the basis for predicting cylinder R-Curves (angular velocity vs. Δa, J-integral vs. Δa). The results show the Rousselier model to be capable of correctly predicting the enhancement of tearing toughness of the cylinder relative to that of conventional test specimens, given an appropriate choice of finite element cell size in the region representing the crack tip
On equivalence of discrete-discrete and continuum-discrete design sensitivity analysis
Choi, Kyung K.; Twu, Sung-Ling
1989-01-01
Developments in design sensitivity analysis (DSA) method have been made using two fundamentally different approaches as shown. In the first approach, a discretized structural finite element model is used to carry out DSA. There are three different methods in the discrete DSA approach: finite difference, semi-analytical, and analytical methods. The finite difference method is a popular one due to its simplicity, but a serious shortcoming of the method is the uncertainty in the choice of a perturbation step size of design variables. In the semi-analytical method, the derivatives of stiffness matrix is computed by finite differences, whereas in the analytical method, the derivatives are obtained analytically. For the shape design variable, computation of analytical derivative of stiffness matrix is quite costly. Because of this, the semi-analytical method is a popular choice in discrete shape DSA approach. However, recently, Barthelemy and Haftka presented that the semi-analytical method can have serious accuracy problems for shape design variables in structures modeled by beam, plate, truss, frame, and solid elements. They found that accuracy problems occur even for a simple cantilever beam. In the second approach, a continuum model of the structure is used to carry out DSA.
Turan, Başak; Selçuki, Cenk
2014-09-01
Amino acids are constituents of proteins and enzymes which take part almost in all metabolic reactions. Glutamic acid, with an ability to form a negatively charged side chain, plays a major role in intra and intermolecular interactions of proteins, peptides, and enzymes. An exhaustive conformational analysis has been performed for all eight possible forms at B3LYP/cc-pVTZ level. All possible neutral, zwitterionic, protonated, and deprotonated forms of glutamic acid structures have been investigated in solution by using polarizable continuum model mimicking water as the solvent. Nine families based on the dihedral angles have been classified for eight glutamic acid forms. The electrostatic effects included in the solvent model usually stabilize the charged forms more. However, the stability of the zwitterionic form has been underestimated due to the lack of hydrogen bonding between the solute and solvent; therefore, it is observed that compact neutral glutamic acid structures are more stable in solution than they are in vacuum. Our calculations have shown that among all eight possible forms, some are not stable in solution and are immediately converted to other more stable forms. Comparison of isoelectronic glutamic acid forms indicated that one of the structures among possible zwitterionic and anionic forms may dominate over the other possible forms. Additional investigations using explicit solvent models are necessary to determine the stability of charged forms of glutamic acid in solution as our results clearly indicate that hydrogen bonding and its type have a major role in the structure and energy of conformers.
Wang, Q; Wang, C M
2007-02-21
In this paper, the constitutive relations of nonlocal elasticity theory are presented for application in the analysis of carbon nanotubes (CNTs) when modelled as Euler-Bernoulli beams, Timoshenko beams or as cylindrical shells. In particular, the shear stress and strain relation for the nonlocal Timoshenko beam theory is discussed in great detail due to a misconception by some researchers that the nonlocal effect should appear in this constitutive relation. Different theories for proposing the value of the small scale parameter are also introduced and a recommendation for the value from the standpoint of wave propagation of CNTs is given.
Hiermaier, Stefan
2007-01-01
Required reading for those in the relevant areas of work, this book examines the testing and modeling of materials and structures under dynamic loading conditions.Readers get an in-depth analysis of the current mathematical modeling and simulation tools available for a variety of materials, alongside discussions of the benefits and limitations these tools pose in industrial design.The models discussed are also available in commercial codes such as LS-DYNA and AOTODYN.Following a logical and well organized structure, this volume uniquely combines experimental procedures with numerical simulatio
Directory of Open Access Journals (Sweden)
D. A. Eliseev
2015-01-01
Full Text Available The solution stability of an initial boundary problem for a linear hybrid system of differential equations, which models the rotation of a rigid body with two elastic rods located in the same plane is studied in the paper. To an axis passing through the mass center of the rigid body perpendicularly to the rods location plane is applied the stabilizing moment proportional to the angle of the system rotation, derivative of the angle, integral of the angle. The external moment provides a feedback. A method of studying the behavior of solutions of the initial boundary problem is proposed. This method allows to exclude from the hybrid system of differential equations partial differential equations, which describe the dynamics of distributed elements of a mechanical system. It allows us to build one equation for an angle of the system rotation. Its characteristic equation defines the stability of solutions of all the system. In the space of feedback-coefficients the areas that provide the asymptotic stability of solutions of the initial boundary problem are built up.
Dumbser, Michael; Peshkov, Ilya; Romenski, Evgeniy; Zanotti, Olindo
2016-06-01
This paper is concerned with the numerical solution of the unified first order hyperbolic formulation of continuum mechanics recently proposed by Peshkov and Romenski [110], further denoted as HPR model. In that framework, the viscous stresses are computed from the so-called distortion tensor A, which is one of the primary state variables in the proposed first order system. A very important key feature of the HPR model is its ability to describe at the same time the behavior of inviscid and viscous compressible Newtonian and non-Newtonian fluids with heat conduction, as well as the behavior of elastic and visco-plastic solids. Actually, the model treats viscous and inviscid fluids as generalized visco-plastic solids. This is achieved via a stiff source term that accounts for strain relaxation in the evolution equations of A. Also heat conduction is included via a first order hyperbolic system for the thermal impulse, from which the heat flux is computed. The governing PDE system is hyperbolic and fully consistent with the first and the second principle of thermodynamics. It is also fundamentally different from first order Maxwell-Cattaneo-type relaxation models based on extended irreversible thermodynamics. The HPR model represents therefore a novel and unified description of continuum mechanics, which applies at the same time to fluid mechanics and solid mechanics. In this paper, the direct connection between the HPR model and the classical hyperbolic-parabolic Navier-Stokes-Fourier theory is established for the first time via a formal asymptotic analysis in the stiff relaxation limit. From a numerical point of view, the governing partial differential equations are very challenging, since they form a large nonlinear hyperbolic PDE system that includes stiff source terms and non-conservative products. We apply the successful family of one-step ADER-WENO finite volume (FV) and ADER discontinuous Galerkin (DG) finite element schemes to the HPR model in the stiff
International Nuclear Information System (INIS)
2016-01-01
International Conference - Gravitation, Cosmology and Mechanics of Continuous Environments (devoted to the 100th anniversary K.P. Stanyukovich's birth) was held in Bauman Moscow State Technical University on the 3th and 4th of March. More than 100 papers were presented by K.P. Stanyukovich's students, faculty, various universities staff and representatives of the Russian Academy of Sciences. Kirill Petrovich Stanyukovich (3 March, 1916 - 4 June, 1989) - an outstanding physicist, mathematician and engineer made a significant contribution to the development of various fields of science: gas dynamics, physics of explosion, magnetic hydrodynamics, astronomy. He developed a hydrodynamic model of gravity, the theory of gravity with a variation of the effective gravitational constant, with a variable number of particles, he offered one of the first Universe evolution scenarios from the initial vacuum stage. Kirill Petrovich was the author of a number of inventions and of 330 scientific and popular-science works. He came from an old noble family - the Stanyukovich. (The famous writer and marine painter Konstantin Stanyukovich was his granduncle). Not yet having finished school, K.P. Stanyukovich got seriously interested in astronomy and became a member of the observers’ team of the Moscow Society of Astronomy Fanciers (MSAF) where he met Leonid Alekseevich Kulik, the famous Tunguska meteorite investigator and one of the national meteoritics founders. In 1932 the first K.P. Stanyukovich's research article on meteor astronomy (in co-authorship with I.E. Vasilyev) “Lyrids in 1930” was published in the 'Bulletin of MSAF Observers. In 1931 K.P. Stanyukovich took part in the MSAF meteors observation expedition on the Karadag scientific station in the Crimea, and in 1932 proposed a new method for estimating the meteor extinction height, based on an empirical relationship between meteor brightness and path length. In the same year he was involved in the
DEFF Research Database (Denmark)
Hansen, Jesper S; Dyre, Jeppe C; Daivis, Peter
2015-01-01
This paper introduces the fundamental continuum theory governing momentum transport in isotropic nanofluidic systems. The theory is an extension of the classical Navier-Stokes equation, and includes coupling between translational and rotational degrees of freedom as well as nonlocal response...
Hyperbolic conservation laws in continuum physics
Dafermos, Constantine M
2016-01-01
This is a masterly exposition and an encyclopedic presentation of the theory of hyperbolic conservation laws. It illustrates the essential role of continuum thermodynamics in providing motivation and direction for the development of the mathematical theory while also serving as the principal source of applications. The reader is expected to have a certain mathematical sophistication and to be familiar with (at least) the rudiments of analysis and the qualitative theory of partial differential equations, whereas prior exposure to continuum physics is not required. The target group of readers would consist of (a) experts in the mathematical theory of hyperbolic systems of conservation laws who wish to learn about the connection with classical physics; (b) specialists in continuum mechanics who may need analytical tools; (c) experts in numerical analysis who wish to learn the underlying mathematical theory; and (d) analysts and graduate students who seek introduction to the theory of hyperbolic systems of conser...
Saha, Punam K.; Xu, Yan; Liang, Guoyuan; Duan, Hong
2009-02-01
Trabecular bone (TB) is a complex quasi-random network of interconnected struts and plates. TB constantly remodels to adapt dynamically to the stresses to which it is subjected (Wolff's Law). In osteoporosis, this dynamic equilibrium between bone formation and resorption is perturbed, leading to bone loss and structural deterioration, both increasing fracture risk. Bone's mechanical competence can only be partly explained by variations in bone mineral density, which led to the notion of bone structural quality. Previously, we developed digital topological analysis or DTA which classifies plates, rods, profiles, edges and junctions in a TB skeletal representation. Although the method has become quite popular, a major limitation is that DTA produces hard classifications only, failing to distinguish between narrow and wide plates. Here, we present a new method called volumetric topological analysis or VTA for quantification of regional topology in complex quasi-random TB networks. At each TB voxel, the method uniquely classifies the topology on the continuum between perfect plates and rods. Therefore, the method is capable of detecting early alterations of trabeculae from plates to rods according to the known etiology of osteoporotic bone loss. Here, novel ideas of geodesic distance transform, geodesic scale and feature propagation have been introduced and combined with DTA and fuzzy distance transform methods conceiving the new VTA technology. The method has been applied to MDCT and μCT images of a cadaveric distal tibia specimen and the results have been quantitatively evaluated. Specifically, intra- and inter-modality reproducibility of the method has been examined and the results are found very promising.
VizieR Online Data Catalog: MgII line vs 3000Å continuum analysis in 68 QSOs (Zhu+, 2017)
Zhu, D.; Sun, M.; Wang, T.
2018-02-01
We investigate the relationship between the MgIIλ2798 emission line and the 3000Å continuum variations using a sample of 68 intermediate-redshift (z~0.65-1.50) broad-line quasars spanning a bolometric luminosity range of 44.49erg/s=10; and (b) for narrow lines, S/N>=5. All our quasar spectra are recalibrated based on the assumption of constant narrow emission- line fluxes. In an analysis of spectrum-to-spectrum variations, we find a fairly close correlation (Spearman {rho}=0.593) between the variations in broad MgII and in the continuum. This is consistent with the idea that MgII is varying in response to the continuum emission variations. Adopting the modified weighted least squares regression method, we statistically constrain the slopes (i.e., the responsivity α of the broad MgII) between the variations in both components for the sources in different luminosity bins after eliminating intrinsic biases introduced by the rescaling process itself. It is shown that the responsivity is quite small (average {bar}α~0.464) and anti- correlates with the quasar luminosity. Our results indicate that high signal- to-noise flux measurements are required to robustly detect the intrinsic variability and the time lag of the MgII line. (2 data files).
Continuum modelling of pantographic sheets for out-of-plane bifurcation and vibrational analysis
Giorgio, I.; Rizzi, N. L.; Turco, E.
2017-11-01
A nonlinear two-dimensional (2D) continuum with a latent internal structure is introduced as a coarse model of a plane network of beams which, in turn, is assumed as a model of a pantographic structure made up by two families of equispaced beams, superimposed and connected by pivots. The deformation measures of the beams of the network and that of the 2D body are introduced and the former are expressed in terms of the latter by making some kinematical assumptions. The expressions for the strain and kinetic energy densities of the network are then introduced and given in terms of the kinematic quantities of the 2D continuum. To account for the modelling abilities of the 2D continuum in the linear range, the eigenmode and eigenfrequencies of a given specimen are determined. The buckling and post-buckling behaviour of the same specimen, subjected to two different loading conditions are analysed as tests in the nonlinear range. The problems have been solved numerically by means of the COMSOL Multiphysics finite element software.
Directory of Open Access Journals (Sweden)
Kimiyo Kikuchi
Full Text Available Continuum of care has the potential to improve maternal, newborn, and child health (MNCH by ensuring care for mothers and children. Continuum of care in MNCH is widely accepted as comprising sequential time (from pre-pregnancy to motherhood and childhood and space dimensions (from community-family care to clinical care. However, it is unclear which linkages of care could have a greater effect on MNCH outcomes. The objective of the present study is to assess the effectiveness of different continuum of care linkages for reducing neonatal, perinatal, and maternal mortality in low- and middle-income countries.We searched for randomized and quasi-randomized controlled trials that addressed two or more linkages of continuum of care and attempted to increase mothers' uptake of antenatal care, skilled birth attendance, and postnatal care. The outcome variables were neonatal, perinatal, and maternal mortality.Out of the 7,142 retrieved articles, we selected 19 as eligible for the final analysis. Of these studies, 13 used packages of intervention that linked antenatal care, skilled birth attendance, and postnatal care. One study each used packages that linked antenatal care and skilled birth attendance or skilled birth attendance and postnatal care. Four studies used an intervention package that linked antenatal care and postnatal care. Among the packages that linked antenatal care, skilled birth attendance, and postnatal care, a significant reduction was observed in combined neonatal, perinatal, and maternal mortality risks (RR 0.83; 95% CI 0.77 to 0.89, I2 79%. Furthermore, this linkage reduced combined neonatal, perinatal, and maternal mortality when integrating the continuum of care space dimension (RR 0.85; 95% CI 0.77 to 0.93, I2 81%.Our review suggests that continuous uptake of antenatal care, skilled birth attendance, and postnatal care is necessary to improve MNCH outcomes in low- and middle-income countries. The review was conclusive for the
Energy Technology Data Exchange (ETDEWEB)
Wang, Chi-Jen [Iowa State Univ., Ames, IA (United States)
2013-01-01
In this thesis, we analyze both the spatiotemporal behavior of: (A) non-linear “reaction” models utilizing (discrete) reaction-diffusion equations; and (B) spatial transport problems on surfaces and in nanopores utilizing the relevant (continuum) diffusion or Fokker-Planck equations. Thus, there are some common themes in these studies, as they all involve partial differential equations or their discrete analogues which incorporate a description of diffusion-type processes. However, there are also some qualitative differences, as shall be discussed below.
Energy Technology Data Exchange (ETDEWEB)
Pradhan, S.C. [Department of Aerospace Engineering Indian Institute of Technology, Kharagpur West Bengal, 721 302 (India)], E-mail: scp@aero.iitkgp.ernet.in; Phadikar, J.K. [Department of Aerospace Engineering Indian Institute of Technology, Kharagpur West Bengal, 721 302 (India)
2009-03-09
In the present work, vibration analysis of multilayered graphene sheets embedded in polymer matrix has been carried out employing nonlocal continuum mechanics. Governing equations have been derived using the principle of virtual work. It has been shown that nonlocal effect is quite significant and needs to be included in the continuum model of graphene sheet.
Tarver, Will L; Menachemi, Nir
2016-03-01
Health information technology (HIT) has the potential to play a significant role in the management of cancer. The purpose of this review is to identify and examine empirical studies that investigate the impact of HIT in cancer care on different levels of the care continuum. Electronic searches were performed in four academic databases. The authors used a three-step search process to identify 122 studies that met specific inclusion criteria. Next, a coding sheet was used to extract information from each included article to use in an analysis. Logistic regression was used to determine study-specific characteristics that were associated with positive findings. Overall, 72.4% of published analyses reported a beneficial effect of HIT. Multivariate analysis found that the impact of HIT differs across the cancer continuum with studies targeting diagnosis and treatment being, respectively, 77 (P = .001) and 39 (P = .039) percentage points less likely to report a beneficial effect when compared to those targeting prevention. In addition, studies targeting HIT to patients were 31 percentage points less likely to find a beneficial effect than those targeting providers (P = .030). Lastly, studies assessing behavior change as an outcome were 41 percentage points less likely to find a beneficial effect (P = .006), while studies targeting decision making were 27 percentage points more likely to find a beneficial effect (P = .034). Based on current evidence, HIT interventions seem to be more successful when targeting physicians, care in the prevention phase of the cancer continuum, and/or decision making. An agenda for future research is discussed. © The Author 2015. Published by Oxford University Press on behalf of the American Medical Informatics Association. All rights reserved. For Permissions, please email: journals.permissions@oup.com.
Duives, Dorine C.; Daamen, Winnie; Hoogendoorn, Serge P.
2016-04-01
In recent years numerous pedestrian simulation tools have been developed that can support crowd managers and government officials in their tasks. New technologies to monitor pedestrian flows are in dire need of models that allow for rapid state-estimation. Many contemporary pedestrian simulation tools model the movements of pedestrians at a microscopic level, which does not provide an exact solution. Macroscopic models capture the fundamental characteristics of the traffic state at a more aggregate level, and generally have a closed form solution which is necessary for rapid state estimation for traffic management purposes. This contribution presents a next step in the calibration and validation of the macroscopic continuum model detailed in Hoogendoorn et al. (2014). The influence of global and local route choice on the development of crowd movement phenomena, such as dissipation, lane-formation and stripe-formation, is studied. This study shows that most self-organization phenomena and behavioural trends only develop under very specific conditions, and as such can only be simulated using specific parameter sets. Moreover, all crowd movement phenomena can be reproduced by means of the continuum model using one parameter set. This study concludes that the incorporation of local route choice behaviour and the balancing of the aptitude of pedestrians with respect to their own class and other classes are both essential in the correct prediction of crowd movement dynamics.
Directory of Open Access Journals (Sweden)
Gabriela Rezende Fernandes
2009-01-01
Full Text Available In this work, non-linear analyses of reinforced concrete plates are performed by using a BEM formulation, based on Kirchhoff’s theory, which has already proved to be a robust technique to deal with plate problems. The non-linear behavior of concrete is modeled by theMazars model, which is based on continuum damage mechanics (CDM and has an easy parametric identification, while the reinforcement is governed by the uniaxial elasto-plastic model with constant hardening. Initially, the different types of damage models and their parametric identification are discussed and the Mazars model is presented. Then the BEM formulation is discussed, which is based on the initial moment technique, where the remaining domain integralsare evaluated by approaching the initial moment field over internal cells. The stress distribution over the plate thickness is obtained by using a Gauss scheme in which the adopted criterion is verified ineach Gauss point defined along the plate. Then, the internal values of moments are approached by numerical integrals along the plate thickness. Finally, some numerical examples of reinforced concrete plates are analyzed, where the potentiality of the Mazars model is verified despite the difficulties of the parametric identification.Nesse trabalho são feitas análises nãolineares de placas de concreto armado,utilizando-se uma formulação do MEC (método dos elementos de contorno baseada nas hipóteses de Kirchhoff. O modelo constitutivo adotado para o concreto é o modelo proposto por Mazars baseado na Mecânica do da Dano Contínuo (MDC, sendo o comportamento não-linear das armaduras governado pelo modelo elastoplástico comencruamento isótropo. Justifica-se a escolha de tal modelo numérico pela simplicidade paramétrica do modelo de dano e pela robustez do MEC, que já provou ser eficiente na análise de placas. Inicialmente, apresenta-se uma revisão dos tipos de modelos de dano e suas implicações na identifica
Generalized Continuum: from Voigt to the Modeling of Quasi-Brittle Materials
Directory of Open Access Journals (Sweden)
Jamile Salim Fuina
2010-12-01
Full Text Available This article discusses the use of the generalized continuum theories to incorporate the effects of the microstructure in the nonlinear finite element analysis of quasi-brittle materials and, thus, to solve mesh dependency problems. A description of the problem called numerically induced strain localization, often found in Finite Element Method material non-linear analysis, is presented. A brief historic about the Generalized Continuum Mechanics based models is presented, since the initial work of Voigt (1887 until the more recent studies. By analyzing these models, it is observed that the Cosserat and microstretch approaches are particular cases of a general formulation that describes the micromorphic continuum. After reporting attempts to incorporate the material microstructure in Classical Continuum Mechanics based models, the article shows the recent tendency of doing it according to assumptions of the Generalized Continuum Mechanics. Finally, it presents numerical results which enable to characterize this tendency as a promising way to solve the problem.
International Nuclear Information System (INIS)
Welz, Bernhard; Borges, Daniel L.G.; Lepri, Fabio G.; Vale, Maria Goreti R.; Heitmann, Uwe
2007-01-01
The literature about applications of high-resolution continuum source atomic absorption spectrometry (HR-CS AAS) with electrothermal atomization is reviewed. The historic development of HR-CS AAS is briefly summarized and the main advantages of this technique, mainly the 'visibility' of the spectral environment around the analytical line at high resolution and the unequaled simultaneous background correction are discussed. Simultaneous multielement CS AAS has been realized only in a very limited number of cases. The direct analysis of solid samples appears to have gained a lot from the special features of HR-CS AAS, and the examples from the literature suggest that calibration can be carried out against aqueous standards. Low-temperature losses of nickel and vanadyl porphyrins could be detected and avoided in the analysis of crude oil due to the superior background correction system. The visibility of the spectral environment around the analytical line revealed that the absorbance signal measured for phosphorus at the 213.6 nm non-resonance line without a modifier is mostly due to the PO molecule, and not to atomic phosphorus. The future possibility to apply high-resolution continuum source molecular absorption for the determination of non-metals is discussed
Modeling flow in fractured medium. Uncertainty analysis with stochastic continuum approach
International Nuclear Information System (INIS)
Niemi, A.
1994-01-01
For modeling groundwater flow in formation-scale fractured media, no general method exists for scaling the highly heterogeneous hydraulic conductivity data to model parameters. The deterministic approach is limited in representing the heterogeneity of a medium and the application of fracture network models has both conceptual and practical limitations as far as site-scale studies are concerned. The study investigates the applicability of stochastic continuum modeling at the scale of data support. No scaling of the field data is involved, and the original variability is preserved throughout the modeling. Contributions of various aspects to the total uncertainty in the modeling prediction can also be determined with this approach. Data from five crystalline rock sites in Finland are analyzed. (107 refs., 63 figs., 7 tabs.)
A continuum damage analysis of hydrogen attack in 2.25 Cr-1Mo vessel
DEFF Research Database (Denmark)
van der Burg, M.W.D.; van der Giessen, E.; Tvergaard, Viggo
1998-01-01
A micromechanically based continuum damage model is presented to analyze the stress, temperature and hydrogen pressure dependent material degradation process termed hydrogen attack, inside a pressure vessel. Hydrogen attack (HA) is the damage process of grain boundary facets due to a chemical...... reaction of carbides with hydrogen, thus forming cavities with high pressure methane gas. Driven by the methane gas pressure, the cavities grow, while remote tensile stresses can significantly enhance the cavitation rate. The damage model gives the strain-rate and damage rate as a function...... of the temperature, hydrogen pressure and applied stresses. The model is applied to study HA in a vessel wall, where nonuniform distributions of hydrogen pressure, temperature and stresses result in a nonuniform damage distribution over the vessel wall. Stresses inside the vessel wall first tend to accelerate...
DEFF Research Database (Denmark)
Skov, V.; Thomassen, Mads; Kruse, T.A.
2012-01-01
The recent discovery of the Janus activating kinase 2 V617F mutation in most patients with polycythemia vera (PV) and half of those with essential thrombocythemia (ET) and primary myelofibrosis (PMF) has favored the hypothesis of a biological continuum from ET over PV to PMF. We performed gene...... expression profiling of whole blood from control subjects (n = 21) and patients with ET (n = 19), PV (n = 41), and PMF (n = 9) using DNA microarrays. Applying an unsupervised method, principal component analysis, to search for patterns in the data, we demonstrated a separation of the four groups...... with biological relevant overlaps between the different entities. Moreover, the analysis separates Janus activating kinase 2-negative ET patients from Janus activating kinase 2-positive ET patients. Functional annotation analysis demonstrates that clusters of gene ontology terms related to inflammation, immune...
Valdiviezo, Laura Alicia
2010-06-01
This essay addresses Katherine Richardson Bruna's paper: Mexican Immigrant Transnational Social Capital and Class Transformation: Examining the Role of Peer Mediation in Insurgent Science, through five main points . First, I offer a comparison between the traditional analysis of classism in Latin America and Richardson Bruna's call for a class-first analysis in the North American social sciences where there has been a tendency to obviate the specific examination of class relations and class issues. Secondly, I discuss that a class-first analysis solely cannot suffice to depict the complex dimensions in the relations of schools and society. Thus, I suggest a continuum in the class-first analysis. Third, I argue that social constructions surrounding issues of language, ethnicity, and gender necessarily intersect with issues of class and that, in fact, those other constructions offer compatible epistemologies that aid in representing the complexity of social and institutional practices in the capitalist society. Richardson Bruna's analysis of Augusto's interactions with his teacher and peers in the science class provides a fourth point of discussion in this essay. As a final point in my response I discuss Richardson Bruna's idea of making accessible class-first analysis knowledge to educators and especially to science teachers.
Valentin, J; Sprenger, M; Pflüger, D; Röhrle, O
2018-02-10
Investigating the interplay between muscular activity and motion is the basis to improve our understanding of healthy or diseased musculoskeletal systems. To be able to analyze the musculoskeletal systems, computational models are employed. Albeit some severe modeling assumptions, almost all existing musculoskeletal system simulations appeal to multi-body simulation frameworks. Although continuum-mechanical musculoskeletal system models can compensate for some of these limitations, they are essentially not considered due to their computational complexity and cost. The proposed framework is the first activation-driven musculoskeletal system model, in which the exerted skeletal muscle forces are computed using three-dimensional, continuum-mechanical skeletal muscle models and in which muscle activations are determined based on a constraint optimization problem. Numerical feasibility is achieved by computing sparse grid surrogates with hierarchical B-splines, and adaptive sparse grid refinement further reduces the computational effort. The choice of B-splines allows the use of all existing gradient-based optimization techniques without further numerical approximation. This paper demonstrates that the resulting surrogates have low relative errors (less than 0.76%) and can be used within forward simulations that are subject to constraint optimization. To demonstrate this, we set up several different test scenarios in which an upper limb model consisting of the elbow joint, the biceps and triceps brachii and an external load is subjected to different optimization criteria. Even though this novel method has only been demonstrated for a two-muscle system, it can easily be extended to musculoskeletal systems with three or more muscles. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
Houedanou, Koffi Wilfrid
2017-01-01
This paper presents an a posteriori error analysis for a coupled continuum pipe-flow/Darcy model in karst aquifers. We consider a unified anisotropic finite element discretization (i.e. elements with very large aspect ratio). Our analysis covers two-dimensional domains, conforming and nonconforming discretizations as well as different elements. Many examples of finite elements that are covered by analysis are presented. From the finite element solution, the error estimators are constructed an...
2007-04-30
of papers containing this body of work have described this as a highly innovative approach at the cutting edge of international geomechanics research...for publication in world-leading journals in granular media mechanics, multi-scale modelling, and experimental and theoretical geomechanics research...international geomechanics research” “an innovative direction for modelling particulate systems” “should be very useful, enriching the knowledge
Wetzel, Angela Payne
Previous systematic reviews indicate a lack of reporting of reliability and validity evidence in subsets of the medical education literature. Psychology and general education reviews of factor analysis also indicate gaps between current and best practices; yet, a comprehensive review of exploratory factor analysis in instrument development across the continuum of medical education had not been previously identified. Therefore, the purpose for this study was critical review of instrument development articles employing exploratory factor or principal component analysis published in medical education (2006--2010) to describe and assess the reporting of methods and validity evidence based on the Standards for Educational and Psychological Testing and factor analysis best practices. Data extraction of 64 articles measuring a variety of constructs that have been published throughout the peer-reviewed medical education literature indicate significant errors in the translation of exploratory factor analysis best practices to current practice. Further, techniques for establishing validity evidence tend to derive from a limited scope of methods including reliability statistics to support internal structure and support for test content. Instruments reviewed for this study lacked supporting evidence based on relationships with other variables and response process, and evidence based on consequences of testing was not evident. Findings suggest a need for further professional development within the medical education researcher community related to (1) appropriate factor analysis methodology and reporting and (2) the importance of pursuing multiple sources of reliability and validity evidence to construct a well-supported argument for the inferences made from the instrument. Medical education researchers and educators should be cautious in adopting instruments from the literature and carefully review available evidence. Finally, editors and reviewers are encouraged to recognize
Thermoforming Finite Element Analysis of Continuum Fiber Reinforced Plastics using ABAQUS
Piera Höppner, Sergi
2013-01-01
Thermoforming simulations are an essential part in engineering design of components made of Continuous Fiber Reinforced Plastics (CFRP) with thermoplastic matrix known as Organic Sheets (OS). Through the simulations, the post-deformed fiber orientation can be calculated, which is essential for the determination of the mechanical properties of the component. Furthermore, draping problems can be detected, which may be corrected by adjusting the geometry of the tools or reinforcin...
First amplitude analysis of resonant structures in the 5-pion continuum at COMPASS
International Nuclear Information System (INIS)
Neubert, Sebastian
2012-01-01
The study of hadronic scattering amplitudes and in particular the spectroscopy of light mesons provide a unique tool to investigate the strong interaction. At very lowenergies the meson spectrum is governed by the spontaneous breakdown of the chiral symmetry of the QCD vacuum. At higher masses a series of resonances appears. Their origin and their relation to chiral symmetry breaking is only partly understood. In particular for masses above ∝ 1.6 GeV/c 2 while a large number of states have been reported they are still poorly known experimentally. One complication are multi-body final states into which heavy mesons can decay. In this thesis a method for the amplitude analysis of the π - π + π - π + π - system is being developed. The COMPASS experiment at CERN uses the diffractive dissociation of a 190 GeV pion beam as a source of meson resonances up to masses of about 3 GeV/c 2 . A partial wave decomposition of the 5π system is presented here which for the first time allows to search for mesonic 5-body resonances. A novel technique based on an evolutionary algorithm is developed to solve the problem of finding a reliable truncation of the partial wave expansion of the hadronic amplitude. The method for the first time allows the investigation of systematic uncertainties introduced by the use truncated isobar model amplitudes. The well known π 2 (1670) and π(1800) states are found with good agreement to measurements in other channels. In addition there is evidence for several other resonant contributions, among them the controversial π 2 (1880) which is being discussed as a hybrid-meson candidate. In the course of the analysis a new software-framework for amplitude analysis has been developed, which is now being used by the COMPASS collaboration for the analysis of several hadronic channels. Future experiments in particle physics will have to collect large amounts of data in order to search for the subtle effects that would indicate new physics beyond the
First amplitude analysis of resonant structures in the 5-pion continuum at COMPASS
Energy Technology Data Exchange (ETDEWEB)
Neubert, Sebastian
2012-07-06
The study of hadronic scattering amplitudes and in particular the spectroscopy of light mesons provide a unique tool to investigate the strong interaction. At very lowenergies the meson spectrum is governed by the spontaneous breakdown of the chiral symmetry of the QCD vacuum. At higher masses a series of resonances appears. Their origin and their relation to chiral symmetry breaking is only partly understood. In particular for masses above {proportional_to} 1.6 GeV/c{sup 2} while a large number of states have been reported they are still poorly known experimentally. One complication are multi-body final states into which heavy mesons can decay. In this thesis a method for the amplitude analysis of the {pi}{sup -}{pi}{sup +}{pi}{sup -}{pi}{sup +}{pi}{sup -} system is being developed. The COMPASS experiment at CERN uses the diffractive dissociation of a 190 GeV pion beam as a source of meson resonances up to masses of about 3 GeV/c{sup 2}. A partial wave decomposition of the 5{pi} system is presented here which for the first time allows to search for mesonic 5-body resonances. A novel technique based on an evolutionary algorithm is developed to solve the problem of finding a reliable truncation of the partial wave expansion of the hadronic amplitude. The method for the first time allows the investigation of systematic uncertainties introduced by the use truncated isobar model amplitudes. The well known {pi}{sub 2}(1670) and {pi}(1800) states are found with good agreement to measurements in other channels. In addition there is evidence for several other resonant contributions, among them the controversial {pi}{sub 2}(1880) which is being discussed as a hybrid-meson candidate. In the course of the analysis a new software-framework for amplitude analysis has been developed, which is now being used by the COMPASS collaboration for the analysis of several hadronic channels. Future experiments in particle physics will have to collect large amounts of data in order to
A Continuum-Atomistic Analysis of Transgranular Crack Propagation in Aluminum
Yamakov, V.; Saether, E.; Glaessgen, E.
2009-01-01
A concurrent multiscale modeling methodology that embeds a molecular dynamics (MD) region within a finite element (FEM) domain is used to study plastic processes at a crack tip in a single crystal of aluminum. The case of mode I loading is studied. A transition from deformation twinning to full dislocation emission from the crack tip is found when the crack plane is rotated around the [111] crystallographic axis. When the crack plane normal coincides with the [112] twinning direction, the crack propagates through a twinning mechanism. When the crack plane normal coincides with the [011] slip direction, the crack propagates through the emission of full dislocations. In intermediate orientations, a transition from full dislocation emission to twinning is found to occur with an increase in the stress intensity at the crack tip. This finding confirms the suggestion that the very high strain rates, inherently present in MD simulations, which produce higher stress intensities at the crack tip, over-predict the tendency for deformation twinning compared to experiments. The present study, therefore, aims to develop a more realistic and accurate predictive modeling of fracture processes.
Pereira, Éderson R.; Castilho, Ivan N. B.; Welz, Bernhard; Gois, Jefferson S.; Borges, Daniel L. G.; Carasek, Eduardo; de Andrade, Jailson B.
2014-06-01
This work reports a simple approach for Br determination in coal using direct solid sample analysis in a graphite tube furnace and high-resolution continuum source molecular absorption spectrometry. The molecular absorbance of the calcium mono-bromide (CaBr) molecule has been measured using the rotational line at 625.315 nm. Different chemical modifiers (zirconium, ruthenium, palladium and a mixture of palladium and magnesium nitrates) have been evaluated in order to increase the sensitivity of the CaBr absorption, and Zr showed the best overall performance. The pyrolysis and vaporization temperatures were 800 °C and 2200 °C, respectively. Accuracy and precision of the method have been evaluated using certified coal reference materials (BCR 181, BCR 182, NIST 1630a, and NIST 1632b) with good agreement (between 98 and 103%) with the informed values for Br. The detection limit was around 4 ng Br, which corresponds to about 1.5 μg g- 1 Br in coal, based on a sample mass of 3 mg. In addition, the results were in agreement with those obtained using electrothermal vaporization inductively coupled plasma mass spectrometry, based on a Student t-test at a 95% confidence level. A mechanism for the formation of the CaBr molecule is proposed, which might be considered for other diatomic molecules as well.
Analysis of kinetic reaction mechanisms
Turányi, Tamás
2014-01-01
Chemical processes in many fields of science and technology, including combustion, atmospheric chemistry, environmental modelling, process engineering, and systems biology, can be described by detailed reaction mechanisms consisting of numerous reaction steps. This book describes methods for the analysis of reaction mechanisms that are applicable in all these fields. Topics addressed include: how sensitivity and uncertainty analyses allow the calculation of the overall uncertainty of simulation results and the identification of the most important input parameters, the ways in which mechanisms can be reduced without losing important kinetic and dynamic detail, and the application of reduced models for more accurate engineering optimizations. This monograph is invaluable for researchers and engineers dealing with detailed reaction mechanisms, but is also useful for graduate students of related courses in chemistry, mechanical engineering, energy and environmental science and biology.
Jiang, Lijian
2010-08-01
In this paper, we discuss a numerical multiscale approach for solving wave equations with heterogeneous coefficients. Our interest comes from geophysics applications and we assume that there is no scale separation with respect to spatial variables. To obtain the solution of these multiscale problems on a coarse grid, we compute global fields such that the solution smoothly depends on these fields. We present a Galerkin multiscale finite element method using the global information and provide a convergence analysis when applied to solve the wave equations. We investigate the relation between the smoothness of the global fields and convergence rates of the global Galerkin multiscale finite element method for the wave equations. Numerical examples demonstrate that the use of global information renders better accuracy for wave equations with heterogeneous coefficients than the local multiscale finite element method. © 2010 IMACS.
Shao, Z.; Li, N.; Lin, J.
2017-09-01
The hot stamping and cold die quenching process has experienced tremendous development in order to obtain shapes of structural components with great complexity in automotive applications. Prediction of the formability of a metal sheet is significant for practical applications of forming components in the automotive industry. Since microstructural evolution in an alloy at elevated temperature has a large effect on formability, continuum damage mechanics (CDM)-based material models can be used to characterise the behaviour of metals when a forming process is conducted at elevated temperatures. In this paper, two sets of unified multi-axial constitutive equations based on material’s stress states and strain states, respectively, were calibrated and used to effectively predict the thermo-mechanical response and forming limits of alloys under complex hot stamping conditions. In order to determine and calibrate the two material models, formability tests of AA6082 using a developed novel biaxial testing system were conducted at various temperatures and strain rates under hot stamping conditions. The determined unified constitutive equations from experimental data are presented in this paper. It is found that both of the stress-state based and strain-state based material models can predict the formability of AA6082 under hot stamping conditions.
Continuum regularized Yang-Mills theory
International Nuclear Information System (INIS)
Sadun, L.A.
1987-01-01
Using the machinery of stochastic quantization, Z. Bern, M. B. Halpern, C. Taubes and I recently proposed a continuum regularization technique for quantum field theory. This regularization may be implemented by applying a regulator to either the (d + 1)-dimensional Parisi-Wu Langevin equation or, equivalently, to the d-dimensional second order Schwinger-Dyson (SD) equations. This technique is non-perturbative, respects all gauge and Lorentz symmetries, and is consistent with a ghost-free gauge fixing (Zwanziger's). This thesis is a detailed study of this regulator, and of regularized Yang-Mills theory, using both perturbative and non-perturbative techniques. The perturbative analysis comes first. The mechanism of stochastic quantization is reviewed, and a perturbative expansion based on second-order SD equations is developed. A diagrammatic method (SD diagrams) for evaluating terms of this expansion is developed. We apply the continuum regulator to a scalar field theory. Using SD diagrams, we show that all Green functions can be rendered finite to all orders in perturbation theory. Even non-renormalizable theories can be regularized. The continuum regulator is then applied to Yang-Mills theory, in conjunction with Zwanziger's gauge fixing. A perturbative expansion of the regulator is incorporated into the diagrammatic method. It is hoped that the techniques discussed in this thesis will contribute to the construction of a renormalized Yang-Mills theory is 3 and 4 dimensions
Extension versus Bending for Continuum Robots
Directory of Open Access Journals (Sweden)
George Grimes
2008-11-01
Full Text Available In this paper, we analyze the capabilities of a novel class of continuous-backbone ("continuum" robots. These robots are inspired by biological "trunks, and tentacles". However, the capabilities of established continuum robot designs, which feature controlled bending but not extension, fall short of those of their biological counterparts. In this paper, we argue that the addition of controlled extension provides dual and complementary functionality, and correspondingly enhanced performance, in continuum robots. We present an interval-based analysis to show how the inclusion of controllable extension significantly enhances the workspace and capabilities of continuum robots.
Directory of Open Access Journals (Sweden)
Eugeniy A. Lukashev
2017-11-01
Full Text Available The occurrence of convective currents and their development from regular forms with the subsequent transition to irregular turbulent currents draw attention to the fact that they are responsible for the efficiency of many technological processes of heat and mass transfer. Such technological processes are basic in the chemical, petrochemical, power, metallurgical and other industries. Convective flows arise in liquids and gases in the gravitational field in the presence of spatial inhomogeneity of the density created by the inhomogeneity of the temperature and the concentration of components arising during, for example, chemical reactions or other causes. With increasing temperature difference, the resting liquid loses its stability, which then leads to the appearance of a convective flow (Rayleigh–Bénard instability. A further increase in the temperature difference leads to an instability of the primary convective flow, and the hydrodynamic crisis leads to a heat transfer crisis. The paper reconstructs the early stage of the Rayleigh–Bénard convective instability considered as a nonequilibrium phase transition with the spinodal decomposition (diffusion separation mechanism.
Yuan, Jinliang; Yu, Jong-Sung; Sundén, Bengt
2015-03-01
During recent years intensive research activities involving both experimental and modeling approaches have appeared for different aspects of Lithium-air (Li-air) battery. Multi-phase transport phenomena including dissolved oxygen and lithium ions (Li+) in the liquid electrolyte, as well as electrons in the solid materials, are strongly coupled with the porous structures and various reactions, particularly the solid product grown in the porous cathode during battery discharge. Understanding the mechanisms of transport phenomena and accurate evaluation of effective transport properties are significant for improving the battery capacities and design, especially at high rate conditions. In this paper, the transport governing equations commonly used for macroscopic continuum models at porous-average level are outlined and highlighted, with a purpose to provide a general overview of the validity and the limitation of these approaches. The most often used models in the open literature are reviewed and discussed focusing on the effective properties involving tortuosity factors, solid product morphologies, as well as effects on the void space clogging, surface area reduction and passivation. Comments and suggestions are also provided for better understanding of multi-phase transport phenomena and implementation of the detailed models for solid product generation and morphology growth in Li-air battery cathodes.
A continuum damage analysis of hydrogen attack in a 2.25Cr–1Mo pressure vessel
Burg, M.W.D. van der; Giessen, E. van der; Tvergaard, V.
1998-01-01
A micromechanically based continuum damage model is presented to analyze the stress, temperature and hydrogen pressure dependent material degradation process termed hydrogen attack, inside a pressure vessel. Hydrogen attack (HA) is the damage process of grain boundary facets due to a chemical
Mechanical tolerance stackup and analysis
Fischer, Bryan R
2011-01-01
Use Tolerance Analysis Techniques to Avoid Design, Quality, and Manufacturing Problems Before They Happen Often overlooked and misunderstood, tolerance analysis is a critical part of improving products and their design processes. Because all manufactured products are subject to variation, it is crucial that designers predict and understand how these changes can affect form, fit, and function of parts and assemblies--and then communicate their findings effectively. Written by one of the developers of ASME Y14.5 and other geometric dimension and tolerancing (GD&T) standards, Mechanical Tolerance
An expedition to continuum theory
Müller, Wolfgang H
2014-01-01
This book introduces field theory as required in solid and fluid mechanics as well as in electromagnetism. It also presents the necessary mathematical framework, namely tensor algebra and tensor calculus, by using an inductive approach, which makes it particularly suitable for beginners. In general, the book can be used in undergraduate classes on continuum theory and, more specifically, in courses on continuum mechanics, for students of physics and engineering alike. The benefits for the readers consist of providing a sound basis of the subject as a whole and of training their ability for solving specific problems in a rational manner. For this purpose the general laws of nature in terms of the balances for mass, momentum, and energy are applied and combined with constitutive relations, which are material specific. Various examples and homework problems illustrate how to use the theory in daily practice. Numerous mini-biographies have been added to the mathematical text for diversion and amusement.
Mills, R.; Lotoski, J.; Lu, Y.
2017-09-01
EUV continuum radiation (10-30 nm) arising only from very low energy pulsed pinch gas discharges comprising some hydrogen was first observed at BlackLight Power, Inc. and reproduced at the Harvard Center for Astrophysics (CfA). The source was determined to be due to the transition of H to the lower-energy hydrogen or hydrino state H(1/4) whose emission matches that observed wherein alternative sources were eliminated. The identity of the catalyst that accepts 3 · 27.2 eV from the H to cause the H to H(1/4) transition was determined to HOH versus 3H. The mechanism was elucidated using different oxide-coated electrodes that were selective in forming HOH versus plasma forming metal atoms as well as from the intensity profile that was a mismatch for the multi-body reaction required during 3H catalysis. The HOH catalyst was further shown to give EUV radiation of the same nature by igniting a solid fuel comprising a source of H and HOH catalyst by passing a low voltage, high current through the fuel to produce explosive plasma. No chemical reaction can release such high-energy light. No high field existed to form highly ionized ions that could give radiation in this EUV region that persisted even without power input. This plasma source serves as strong evidence for the existence of the transition of H to hydrino H(1/4) by HOH as the catalyst and a corresponding new power source wherein initial extraordinarily brilliant light-emitting prototypes are already producing photovoltaic generated electrical power. The hydrino product of a catalyst reaction of atomic hydrogen was analyzed by multiple spectroscopic techniques. Moreover, the mH catalyst was identified to be active in astronomical sources such as the Sun, stars and interstellar medium wherein the characteristics of hydrino match those of the dark matter of the Universe.
Finch, Peter Dallas
2010-01-01
The continuum of learning walks can be viewed in stages with various dimensions including frequency, participants, purpose and the presence of an instructional framework within which the instructional practice is viewed. Steps in the continuum progress as the learning walks are conducted more frequently. One way to ensure this is accomplished is…
Theoretical Calculation and Validation of the Water Vapor Continuum Absorption
Ma, Qiancheng; Tipping, Richard H.
1998-01-01
The primary objective of this investigation is the development of an improved parameterization of the water vapor continuum absorption through the refinement and validation of our existing theoretical formalism. The chief advantage of our approach is the self-consistent, first principles, basis of the formalism which allows us to predict the frequency, temperature and pressure dependence of the continuum absorption as well as provide insights into the physical mechanisms responsible for the continuum absorption. Moreover, our approach is such that the calculated continuum absorption can be easily incorporated into satellite retrieval algorithms and climate models. Accurate determination of the water vapor continuum is essential for the next generation of retrieval algorithms which propose to use the combined constraints of multi-spectral measurements such as those under development for EOS data analysis (e.g., retrieval algorithms based on MODIS and AIRS measurements); current Pathfinder activities which seek to use the combined constraints of infrared and microwave (e.g., HIRS and MSU) measurements to improve temperature and water profile retrievals, and field campaigns which seek to reconcile spectrally-resolved and broad-band measurements such as those obtained as part of FIRE. Current widely used continuum treatments have been shown to produce spectrally dependent errors, with the magnitude of the error dependent on temperature and abundance which produces errors with a seasonal and latitude dependence. Translated into flux, current water vapor continuum parameterizations produce flux errors of order 10 W/ml, which compared to the 4 W/m' magnitude of the greenhouse gas forcing and the 1-2 W/m' estimated aerosol forcing is certainly climatologically significant and unacceptably large. While it is possible to tune the empirical formalisms, the paucity of laboratory measurements, especially at temperatures of interest for atmospheric applications, preclude tuning
Energy Technology Data Exchange (ETDEWEB)
Fried, Eliot; Gurtin, Morton E.
2001-04-20
The central focus of the research carried out under this grant is the application of continuum mechanics to materials science, specifically to the macroscopic characterization of material behavior at small length scales. Specifically, research was carried out in the following general areas: dislocations in solids; point defects in liquid crystals; dynamic fracture; diffusional phase transitions in deformable solids; incoherent phase interfaces; phase field simulations of twinning and coarsening in solids; crystal plasticity; microforce theories for diffusion and recrystallization; granular flow.
Sudo, Felipe Kenji; Amado, Patricia; Alves, Gilberto Sousa; Laks, Jerson; Engelhardt, Eliasz
2017-01-01
ABSTRACT. Background. Subcortical Vascular Cognitive Impairment (SVCI) is a clinical continuum of vascular-related cognitive impairment, including Vascular Mild Cognitive Impairment (VaMCI) and Vascular Dementia. Deficits in Executive Function (EF) are hallmarks of the disorder, but the best methods to assess this function have yet to be determined. The insidious and almost predictable course of SVCI and the multidimensional concept of EF suggest that a temporal dissociation of impairments in EF domains exists early in the disorder. Objective: This study aims to review and analyze data from the literature about performance of VaMCI patients on the most used EF tests through a meta-analytic approach. Methods: Medline, Web of Knowledge and PsycINFO were searched, using the terms: “vascular mild cognitive impairment” OR “vascular cognitive impairment no dementia” OR “vascular mild neurocognitive disorder” AND “dysexecutive” OR “executive function”. Meta-analyses were conducted for each of the selected tests, using random-effect models. Results: Systematic review showed major discrepancies among the results of the studies included. Meta-analyses evidenced poorer performance on the Trail-Making Test part B and the Stroop color test by VaMCI patients compared to controls. Conclusion: A continuum of EF impairments has been proposed in SVCI. Early deficits appear to occur in cognitive flexibility and inhibitory control. PMID:29354217
Directory of Open Access Journals (Sweden)
Shoba Ramanadhan
2015-07-01
Full Text Available Understanding the heterogeneity of groups along the vaccine hesitancy continuum presents an opportunity to tailor and increase the impact of public engagement efforts with these groups. Audience segmentation can support these goals, as demonstrated here in the context of the 2009 H1N1 vaccine. In March 2010, we surveyed 1569 respondents, drawn from a nationally representative sample of American adults, with oversampling of racial/ethnic minorities and persons living below the United States Federal Poverty Level. Guided by the Structural Influence Model, we assessed knowledge, attitudes, and behaviors related to H1N1; communication outcomes; and social determinants. Among those who did not receive the vaccine (n = 1166, cluster analysis identified three vaccine-hesitant subgroups. Disengaged Skeptics (67% were furthest from vaccine acceptance, with low levels of concern and engagement. The Informed Unconvinced (19% were sophisticated consumers of media and health information who may not have been reached with information to motivate vaccination. The Open to Persuasion cluster (14% had the highest levels of concern and motivation and may have required engagement about vaccination broadly. There were significant sociodemographic differences between groups. This analysis highlights the potential to use segmentation techniques to identify subgroups on the vaccine hesitancy continuum and tailor public engagement efforts accordingly.
Experimental and mechanical analysis of cement–nanotube ...
Indian Academy of Sciences (India)
Introduction Researchers have attempted to estimate the mechanical properties of multi- and single-walled nanotubes (MWNTs and SWNTs, respectively) in manyways, including experimental, molecular dynamics (MD) and elastic continuum modelling methods. The discovery of carbon nanotubes (CNTs) brings with it the ...
Energy Technology Data Exchange (ETDEWEB)
None
2015-08-01
This issue of Continuum Magazine covers the depth and breadth of NREL's ever-expanding analytical capabilities. For example, in one project we are leading national efforts to create a computer model of one of the most complex systems ever built. This system, the eastern part of the North American power grid, will likely host an increasing percentage of renewable energy in years to come. Understanding how this system will work is important to its success - and NREL analysis is playing a major role. We are also identifying the connections among energy, the environment and the economy through analysis that will point us toward a 'water smart' future.
Continuum representations of cellular solids
Energy Technology Data Exchange (ETDEWEB)
Neilsen, M.K.
1993-09-01
Cellular materials consist of interconnected struts or plates which form cells. The struts or plates are constructed from a variety of metals, polymers, ceramics and wood products. Cellular materials are often used in impact limiters for shipping containers to protect the contents from accidental impact events. These materials exhibit a variety of complex behavior when subjected to crushing loads. This research focuses on the development of continuum representations of cellular solids that can be used in the finite element analysis of shipping container accidents. A significant portion of this work is the development of a new methodology to relate localized deformations to appropriate constitutive descriptions. This methodology provides the insight needed to select constitutive descriptions for cellular solids that capture the localized deformations that are observed experimentally. Constitutive relations are developed for two different cellular materials, aluminum honeycomb and polyurethane foam. These constitutive relations are based on plasticity and continuum damage theories. Plasticity is used to describe the permanent deformation exhibited by both aluminum honeycomb and polyurethane foam. Continuum damage is needed to capture the change in elastic parameters due to cracking of the polyurethane cell wall materials. The new constitutive description of polyurethane foam is implemented in both static and dynamic finite element codes, and analytical and numerical predictions are compared with available experimental data.
Gimelshein, Sergey; Lilly, Taylor; Moskovets, Eugene
2015-11-01
A multi-step numerical approach is used to analyze the efficiency of an ion-funnel to transport ions over a wide range of m/z. A continuum approach based on the solution of the Navier-Stokes equations is applied to model the gas flow through a capillary connecting the atmospheric and subatmospheric sections of a mass spectrometer. A microscopic, fully kinetic approach based on the solution of the Boltzmann equation is used to examine the ion and gas transport through an ion-funnel kept at a 0.1-3 Torr pressure to the quadrupole section kept at a 0.01 Torr pressure. In addition to aerodynamic drag, the developed approach takes into account the combined effect of the DC field driving the ions downstream toward the funnel exit, the rf field confining the ions in radial direction, and the space charge causing ion repulsion. The sensitivity of the ion transmission to the gas pressure in the ion-funnel, the rf, and the total ion current injected to the funnel from capillary nozzle is shown. Graphical Abstract ᅟ.
Hoover, Wm G; Hoover, Carol G
2010-04-01
Guided by molecular dynamics simulations, we generalize the Navier-Stokes-Fourier constitutive equations and the continuum motion equations to include both transverse and longitudinal temperatures. To do so we partition the contributions of the heat transfer, the work done, and the heat flux vector between the longitudinal and transverse temperatures. With shockwave boundary conditions time-dependent solutions of these equations converge to give stationary shockwave profiles. The profiles include anisotropic temperature and can be fitted to molecular dynamics results, demonstrating the utility and simplicity of a two-temperature description of far-from-equilibrium states.
Energy Technology Data Exchange (ETDEWEB)
Block, G I; Rubin, M B; Morris, J P; Berryman, J G
2006-08-23
Experimental data indicates that the limiting crack speed in brittle materials is less than the Rayleigh wave speed. One reason for this is that dynamic instabilities produce surface roughness and microcracks that branch from the main crack. These processes increase dissipation near the crack tip over a range of crack speeds. When the scale of observation (or mesh resolution) becomes much larger than the typical sizes of these features, effective-medium theories are required to predict the coarse-grained fracture dynamics. Two approaches to modeling these phenomena are described and used in numerical simulations. The first approach is based on cohesive elements that utilize a rate-dependent weakening law for the nodal cohesive forces. The second approach uses a continuum damage model which has a weakening effect that lowers the effective Rayleigh wave speed in the material surrounding the crack tip. Simulations in this paper show that while both models are capable of increasing the energy dissipated during fracture when the mesh size is larger than the process zone size, only the continuum damage model is able to limit the crack speed over a range of applied loads. Numerical simulations of straight-running cracks demonstrate good agreement between the theoretical predictions of the combined models and experimental data on dynamic crack propagation in brittle materials. Simulations that model crack branching are also presented.
The MUPPLE competence continuum
Wild, Joanna; Wild, Fridolin; Kalz, Marco; Specht, Marcus; Hofer, Margit
2009-01-01
Wild, J., Wild, F., Kalz, M., Specht, M., & Hofer, M. (2009). The MUPPLE competence continuum. In F. Wild, M. Kalz, M. Palmér & D. Müller (Eds.), Proceedings of 2nd Workshop Mash-Up Personal Learning Envrionments (MUPPLE'09). Workshop in conjunction with 4th European Conference on Technology
Thermo mechanical buckling analysis of carbon nanotubes on ...
Indian Academy of Sciences (India)
Carbon nanotubes are cylindrical macromolecules consisting of carbon atoms arranged in a peri- odic hexagonal structure and were invented by Iijima (1991). This started a new field of research for the accurate analysis of nano-size structures. Recently there has been growing interest for application of non-local continuum ...
Shape Modeling of a Concentric-tube Continuum Robot
DEFF Research Database (Denmark)
Bai, Shaoping; Xing, Charles Chuhao
2012-01-01
Concentric-tube continuum robots feature with simple and compact structures and have a great potential in medical applications. The paper is concerned with the shape modeling of a type of concentric-tube continuum robot built with a collection of super-elastic NiTiNol tubes. The mechanics...
Nonlocal continuum field theories
2002-01-01
Nonlocal continuum field theories are concerned with material bodies whose behavior at any interior point depends on the state of all other points in the body -- rather than only on an effective field resulting from these points -- in addition to its own state and the state of some calculable external field. Nonlocal field theory extends classical field theory by describing the responses of points within the medium by functionals rather than functions (the "constitutive relations" of classical field theory). Such considerations are already well known in solid-state physics, where the nonlocal interactions between the atoms are prevalent in determining the properties of the material. The tools developed for crystalline materials, however, do not lend themselves to analyzing amorphous materials, or materials in which imperfections are a major part of the structure. Nonlocal continuum theories, by contrast, can describe these materials faithfully at scales down to the lattice parameter. This book presents a unif...
A NEW LOOK AT THE INTEGRATED RADIO/MICROWAVE CONTINUUM SPECTRUM OF GALACTIC SUPERNOVA REMNANT IC 443
Energy Technology Data Exchange (ETDEWEB)
Onić, D.; Urošević, D. [Department of Astronomy, Faculty of Mathematics, University of Belgrade (Serbia); Leahy, D., E-mail: donic@matf.bg.ac.rs [Department of Physics and Astronomy, The University of Calgary (Canada)
2017-01-01
Recent observations of the microwave sky, by space telescopes such as the Wilkinson Microwave Anisotropy Probe and Planck , have opened a new window into the analysis of continuum emission from supernova remnants (SNRs). In this paper, different emission models that can explain the characteristic shape of currently known integrated radio/microwave continuum spectrum of the Galactic SNR IC 443 are tested and discussed. In particular, the possibility is emphasized that the slight bump in the integrated continuum of this remnant around 20–70 GHz is genuine and that it can be explained by the contribution of an additional emission mechanism such as spinning dust. We find that adding a spinning dust component to the emission model improves the fit of the integrated spectrum of this SNR while at the same time preserving the physically probable parameter values. Finally, models that include the high-frequency synchrotron bending of the IC 443 radio to microwave continuum are favored.
Mechanical tolerance stackup and analysis
Fischer, Bryan R
2004-01-01
BackgroundDimensioning and TolerancingTolerance Format and Decimal PlacesConverting Plus/Minus Dimensions and Tolerances into Equal Bilaterally Toleranced DimensionsVariation and Sources of VariationTolerance AnalysisWorst-case Tolerance StackupsStatistical Tolerance StackupsGeometric Dimensioning and Tolerancing (GD&T)Converting Plus/Minus Tolerancing to Positional Tolerancing and Projected Tolerance ZonesDiametral and Radial Tolerance StackupsSpecifying Material Condition Modifiers and Their Effect on Tolerance Stackups The Tolerance Stackup SketchThe Tolerance Stackup Report FormTolerance S
Czech Academy of Sciences Publication Activity Database
Zapiór, Maciej; Kotrč, Pavel; Oliver, R.; Procházka, O.; Heinzel, Petr
2016-01-01
Roč. 337, č. 10 (2016), s. 1078-1081 ISSN 0004-6337. [Dynamic Sun - Exploring the Many Facets of Solar Eruptive Events. Potsdam, 26.10.2015-29.10.2015] Institutional support: RVO:67985815 Keywords : Sun * activity * chromosphere Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 0.916, year: 2016
Continuum Fitting HST QSO Spectra
Tytler, David; Oliversen, Ronald J. (Technical Monitor)
2002-01-01
The Principal Component Analysis (PCA) method which we are using to fit and describe QSO spectra relies upon the fact that QSO continuum are generally very smooth and simple except for emission and absorption lines. To see this we need high signal-to-noise (S/N) spectra of QSOs at low redshift which have relatively few absorption lines in the Lyman-a forest. We need a large number of such spectra to use as the basis set for the PCA analysis which will find the set of principal component spectra which describe the QSO family as a whole. We have found that too few HST spectra have the required S/N and hence we need to supplement them with ground based spectra of QSOs at higher redshift. We have many such spectra and we have been working to make them suitable for this analysis. We have concentrated on this topic since 12/15/01.
Continuum treatment of electronic polarization effect.
Tan, Yu-Hong; Luo, Ray
2007-03-07
A continuum treatment of electronic polarization has been explored for in molecular mechanics simulations in implicit solvents. The dielectric constant for molecule interior is the only parameter in the continuum polarizable model. A value of 4 is found to yield optimal agreement with high-level ab initio quantum mechanical calculations for the tested molecular systems. Interestingly, its performance is not sensitive to the definition of molecular volume, in which the continuum electronic polarization is defined. In this model, quantum mechanical electrostatic field in different dielectric environments from vacuum, low-dielectric organic solvent, and water can be used simultaneously in atomic charge fitting to achieve consistent treatment of electrostatic interactions. The tests show that a single set of atomic charges can be used consistently in different dielectric environments and different molecular conformations, and the atomic charges transfer well from training monomers to tested dimers. The preliminary study gives us the hope of developing a continuum polarizable force field for more consistent simulations of proteins and nucleic acids in implicit solvents.
Continuum treatment of electronic polarization effect
Tan, Yu-Hong; Luo, Ray
2007-03-01
A continuum treatment of electronic polarization has been explored for in molecular mechanics simulations in implicit solvents. The dielectric constant for molecule interior is the only parameter in the continuum polarizable model. A value of 4 is found to yield optimal agreement with high-level ab initio quantum mechanical calculations for the tested molecular systems. Interestingly, its performance is not sensitive to the definition of molecular volume, in which the continuum electronic polarization is defined. In this model, quantum mechanical electrostatic field in different dielectric environments from vacuum, low-dielectric organic solvent, and water can be used simultaneously in atomic charge fitting to achieve consistent treatment of electrostatic interactions. The tests show that a single set of atomic charges can be used consistently in different dielectric environments and different molecular conformations, and the atomic charges transfer well from training monomers to tested dimers. The preliminary study gives us the hope of developing a continuum polarizable force field for more consistent simulations of proteins and nucleic acids in implicit solvents.
Continuum radiation of argon plasma
International Nuclear Information System (INIS)
D'Yachkov, L.G.
1995-01-01
A simple completely analytical method of the calculation of radiative continuum of plasmas is derived and an analysis of experimental data on continuum radiation of argon plasma is made. The method is based on the semiclassical quantum defect theory. To calculate radial matrix elements of dipole transitions the asymptotic expansion in powers of E c /ω 2/3 , with an accuracy to the linear term, where E, is the arithmetic mean of the initial and final energies of the transition, is used. This expansion has the same form for free-free, free-bound and bound-bound transitions. If the quantum defects are also approximated by a linear function of energy, the integration over the electron energy (the Maxwell-Boltzmann distribution is assumed) can be performed in analytical form. For Rydberg states the sum of photoionization continua can be replaced by an integral. We have calculated the absorption coefficient pf argon plasma. The photoionization cross section is calculated for all the states of 4s, 5s, 6s, 4p, 5p, 3d, 4d, 4s', 5s', 6s', 4p', 5p', 3d' and 4d' configurations taking into account P-coupling and multiplet splitting (56 states). Other excited states are allowed for by the integral formula together with free-free transitions
Noomen, M.F.; Skidmore, A.K.; Meer, van der F.D.; Prins, H.H.T.
2006-01-01
It is known that natural gas in the soil affects vegetation health, which may be detected through analysis of reflectance spectra. Since natural gas is invisible, changes in the vegetation could potentially indicate gas leakage. Although it is known that gas in soil affects plant reflectance, the
Valdiviezo, Laura Alicia
2010-01-01
This essay addresses Katherine Richardson Bruna's paper: "Mexican Immigrant Transnational Social Capital and Class Transformation: Examining the Role of Peer Mediation in Insurgent Science", through five main points. First, I offer a comparison between the traditional analysis of classism in Latin America and Richardson Bruna's call for…
Control Engineering Analysis of Mechanical Pitch Systems
Bernicke, Olaf; Gauterin, Eckhard; Schulte, Horst; Zajac, Michal
2014-12-01
With the help of a local stability analysis the coefficient range of a discrete damper, used for centrifugal forced, mechanical pitch system of small wind turbines (SWT), is gained for equilibrium points. - By a global stability analysis the gained coefficient range can be validated. An appropriate approach by Takagi-Sugeno is presented in the paper.
Kapania, Rakesh K.; Liu, Youhua
1998-01-01
The use of continuum models for the analysis of discrete built-up complex aerospace structures is an attractive idea especially at the conceptual and preliminary design stages. But the diversity of available continuum models and hard-to-use qualities of these models have prevented them from finding wide applications. In this regard, Artificial Neural Networks (ANN or NN) may have a great potential as these networks are universal approximators that can realize any continuous mapping, and can provide general mechanisms for building models from data whose input-output relationship can be highly nonlinear. The ultimate aim of the present work is to be able to build high fidelity continuum models for complex aerospace structures using the ANN. As a first step, the concepts and features of ANN are familiarized through the MATLAB NN Toolbox by simulating some representative mapping examples, including some problems in structural engineering. Then some further aspects and lessons learned about the NN training are discussed, including the performances of Feed-Forward and Radial Basis Function NN when dealing with noise-polluted data and the technique of cross-validation. Finally, as an example of using NN in continuum models, a lattice structure with repeating cells is represented by a continuum beam whose properties are provided by neural networks.
Energy Technology Data Exchange (ETDEWEB)
Huber, Charles S. [Instituto Federal Sul-rio-grandense, Câmpus Pelotas, Pelotas, RS (Brazil); Universidade Federal do Rio Grande do Sul, Instituto de Química, Porto Alegre, RS (Brazil); Vale, Maria Goreti R. [Universidade Federal do Rio Grande do Sul, Instituto de Química, Porto Alegre, RS (Brazil); Instituto Nacional de Ciência e Tecnologia do CNPq, INCT de Energia e Ambiente, Universidade Federal da Bahia, Salvador, BA (Brazil); Welz, Bernhard [Instituto Nacional de Ciência e Tecnologia do CNPq, INCT de Energia e Ambiente, Universidade Federal da Bahia, Salvador, BA (Brazil); Universidade Federal de Santa Catarina, Departamento de Química, Florianópolis, SC (Brazil); Andrade, Jailson B. [Instituto Nacional de Ciência e Tecnologia do CNPq, INCT de Energia e Ambiente, Universidade Federal da Bahia, Salvador, BA (Brazil); Dessuy, Morgana B., E-mail: mbdessuy@ufrgs.br [Universidade Federal do Rio Grande do Sul, Instituto de Química, Porto Alegre, RS (Brazil); Instituto Nacional de Ciência e Tecnologia do CNPq, INCT de Energia e Ambiente, Universidade Federal da Bahia, Salvador, BA (Brazil)
2015-06-01
High-resolution continuum source graphite furnace molecular absorption spectrometry has been applied for sulfur determination in diesel fuel. The sharp rotational lines of the carbon monosulfide molecule (formed during the vaporization step) were used to measure the absorbance. The analytical line at 258.056 nm was monitored using the sum of three pixels. Different chemical modifiers were investigated and the mixture of palladium and magnesium was used as chemical modifier in combination with iridium as permanent modifier. L-Cysteine was chosen as sulfur standard and the calibration was done against aqueous standard solutions. The proposed method was applied for the analyses of four diesel samples: two S10 samples and two S500 samples. The trueness of the method was checked with a certified reference material (CRM) of sulfur in diesel fuel (NIST 2724b). Accurate results, for samples and CRM, were achieved after a dilution with propan-1-ol. The following figures of merit were obtained: characteristic mass of 17 ± 3 ng, limit of detection and limit of quantification of 1.4 mg kg{sup −1} and 4.7 mg kg{sup −1}, respectively. - Highlights: • Ir, Ru and Zr were investigated as permanent modifiers. • Ca, Mg, Pd and Pd/Mg were investigated as modifiers in solution. • Indirect determination of sulfur monitoring the molecular absorbance of the CS • Direct analysis of diesel samples using a dilution in propan-1-ol.
Primo de Carvalho Alves, Lucas; Pio de Almeida Fleck, Marcelo; Boni, Aline; Sica da Rocha, Neusa
2017-01-01
Melancholic features of depression (MFD) seem to be a unidimensional group of signs and symptoms. However, little importance has been given to the evaluation of what features are related to a more severe disorder. That is, what are the MFD that appear only in the most depressed patients. We aim to demonstrate how each MFD is related to the severity of the major depressive disorder. We evaluated both the Hamilton depression rating scale (HDRS-17) and its 6-item melancholic subscale (HAM-D6) in 291 depressed inpatients using Rasch analysis, which computes the severity of each MFD. Overall measures of model fit were mean (±SD) of items and persons residual = 0 (±1); low χ2 value; p>0.01. For the HDRS-17 model fit, mean (±SD) of item residuals = 0.35 (±1.4); mean (±SD) of person residuals = -0.15 (±1.09); χ2 = 309.74; pdepressed mood, work and activities, somatic symptoms, psychic anxiety, guilt feelings, and psychomotor retardation. Depressed mood is less severe, while guilt feelings and psychomotor retardation are more severe MFD in a psychiatric hospitalization. Understanding depression as a continuum of symptoms can improve the understanding of the disorder and may improve its perspective of treatment.
Ostuzzi, Giovanni; Benda, Laura; Costa, Enrico; Barbui, Corrado
2015-09-01
Patients with cancer are particularly vulnerable to depressive experiences, ranging from severe emotional reactions to proper depressive syndromes, including major depression. These experiences may deeply affect the course and outcome of the disease. The aim of this study was to assess the efficacy acceptability of antidepressants on the continuum of depressive experiences in patients suffering from cancer. MEDLINE, EMBASE, PsycINFO, CENTRAL, as well as websites of regulatory agencies, clinical trial repositories and pharmaceutical companies, were systematically searched for published and unpublished randomised trials assessing the efficacy of antidepressants versus placebo in patients with cancer. Efficacy of antidepressants at the end of the study was the primary outcome. The review protocol was registered with PROSPERO (CRD42014013440). A total of 19 studies contributed to the analysis. Antidepressants (particularly the selective serotonin-reuptake inhibitors and mianserin) were more effective than placebo in relieving depressive experiences in both patients with major depression or depressive symptoms (standardised mean difference -0.596, 95% confidence interval -1.041 to -0.150), as well as in patients with other cancer-related distressing symptoms (standardised mean difference -0.229, 95% confidence interval -0.419 to -0.039). We found evidence that efficacy was positively associated with length of treatment. No differences between antidepressants and placebo were found in terms of overall acceptability. Antidepressants should be considered as one treatment option for relieving the burden of depressive experiences in patients with cancer. Copyright © 2015 Elsevier Ltd. All rights reserved.
Osis, Sean T; Hettinga, Blayne A; Ferber, Reed
2016-05-01
An ongoing challenge in the application of gait analysis to clinical settings is the standardized detection of temporal events, with unobtrusive and cost-effective equipment, for a wide range of gait types. The purpose of the current study was to investigate a targeted machine learning approach for the prediction of timing for foot strike (or initial contact) and toe-off, using only kinematics for walking, forefoot running, and heel-toe running. Data were categorized by gait type and split into a training set (∼30%) and a validation set (∼70%). A principal component analysis was performed, and separate linear models were trained and validated for foot strike and toe-off, using ground reaction force data as a gold-standard for event timing. Results indicate the model predicted both foot strike and toe-off timing to within 20ms of the gold-standard for more than 95% of cases in walking and running gaits. The machine learning approach continues to provide robust timing predictions for clinical use, and may offer a flexible methodology to handle new events and gait types. Copyright © 2016 Elsevier B.V. All rights reserved.
Laursen, Tod A
2003-01-01
This book comprehensively treats the formulation and finite element approximation of contact and impact problems in nonlinear mechanics. Intended for students, researchers and practitioners interested in numerical solid and structural analysis, as well as for engineers and scientists dealing with technologies in which tribological response must be characterized, the book includes an introductory but detailed overview of nonlinear finite element formulations before dealing with contact and impact specifically. Topics encompassed include the continuum mechanics, mathematical structure, variational framework, and finite element implementations associated with contact/impact interaction. Additionally, important and currently emerging research topics in computational contact mechanics are introduced, encompassing such topics as tribological complexity, conservative treatment of inelastic impact interaction, and novel spatial discretization strategies.
Buckling of graded coatings: A continuum model
Chiu, Tz-Cheng
2000-12-01
Requirements for the protection of hot section components in many high temperature applications such as earth-to-orbit winged planes and advanced turbine systems have led to the application of thermal barrier coatings (TBCs) that utilize ceramic coatings on metal substrates. An alternative concept to homogeneous ceramic coatings is the functionally graded materials (FGM) in which the composition of the coating is intentionally graded to improve the bonding strength and to reduce the magnitude of the residual and thermal stresses. A widely observed failure mode in such layered systems is known to be interface cracking that leads to spallation fracture. In most cases, the final stage of the failure process for a thin coating appears to be due to buckling instability under thermally or mechanically induced compressive stress. The objective of this study is to develop a solution to the buckling instability problem by using continuum elasticity rather than a structural mechanics approach. The emphasis in the solution will be on the investigation of the effect of material inhomogeneity in graded coatings on the instability load, the postbuckling behavior, and fracture mechanics parameters such as the stress intensity factors and strain energy release rate. In this analysis, a nonlinear continuum theory is employed to examine the interface crack problem. The analytical solution of the instability problem permits the study of the effect of material inhomogeneity upon the inception of buckling and establishes benchmark results for the numerical solutions of related problems. To study the postbuckling behavior and to calculate the stress intensity factors and strain energy release rate a geometrically nonlinear finite element procedure with enriched crack-tip element is developed. Both plane strain and axisymmetric interface crack problems in TBCs with either homogeneous or graded coating are then considered by using the finite element procedure. It is assumed that the
Silva, Arlene S; Brandao, Geovani C; Matos, Geraldo D; Ferreira, Sergio L C
2015-11-01
The present work proposed an analytical method for the direct determination of chromium in infant formulas employing the high-resolution continuum source electrothermal atomic absorption spectrometry combined with the solid sample analysis (SS-HR-CS ET AAS). Sample masses up to 2.0mg were directly weighted on a solid sampling platform and introduced into the graphite tube. In order to minimize the formation of carbonaceous residues and to improve the contact of the modifier solution with the solid sample, a volume of 10 µL of a solution containing 6% (v/v) H2O2, 20% (v/v) ethanol and 1% (v/v) HNO3 was added. The pyrolysis and atomization temperatures established were 1600 and 2400 °C, respectively, using magnesium as chemical modifier. The calibration technique was evaluated by comparing the slopes of calibration curves established using aqueous and solid standards. This test revealed that chromium can be determined employing the external calibration technique using aqueous standards. Under these conditions, the method developed allows the direct determination of chromium with limit of quantification of 11.5 ng g(-1), precision expressed as relative standard deviation (RSD) in the range of 4.0-17.9% (n=3) and a characteristic mass of 1.2 pg of chromium. The accuracy was confirmed by analysis of a certified reference material of tomato leaves furnished by National Institute of Standards and Technology. The method proposed was applied for the determination of chromium in five different infant formula samples. The chromium content found varied in the range of 33.9-58.1 ng g(-1) (n=3). These samples were also analyzed employing ICP-MS. A statistical test demonstrated that there is no significant difference between the results found by two methods. The chromium concentrations achieved are lower than the maximum limit permissible for chromium in foods by Brazilian Legislation. Copyright © 2015. Published by Elsevier B.V.
Gu, L.; Pallardy, S. G.; Hosman, K. P.; Sun, Y.
2015-01-01
Using decade-long continuous observations of tree mortality and predawn leaf water potential (ψpd) at the Missouri Ozark AmeriFlux (MOFLUX) site, we studied how the mortality of important tree species varied along the isohydric to anisohydric continuum and how such variations may be predicted. Water stress determined inter-annual variations in tree mortality with a time delay of one year or more, which was predicted by predawn leaf water potential integral (PLWPI), mean effective precipitation interval (a time period with no daily precipitation rates exceeding a threshold) with a daily threshold precipitation at 5 mm day-1 (MEPI5), and precipitation variability index (PVI). Positive temperature anomaly integral (PTAI) and vapor pressure deficit integral (VPDI) also worked reasonably well, particularly for moderate droughts. The extreme drought of the year 2012 drastically increased the mortality of all species in the subsequent year. Regardless of the degree of isohydry and drought intensity, the ψpd of all species recovered rapidly after sufficiently intense rain events. This, together with a lack of immediate leaf and branch desiccation, suggests that hydraulic disconnection in the xylem was absent even during extreme drought and tree death was caused by significant but indirect effects of drought. We also found that species occupying middle positions along the isohydric to anisohydric continuum suffered less mortality than those at either extremes (i.e. extremely isohydric or extremely anisohydric). Finally, our study suggested that species differences in mortality mechanisms can be overwhelmed and masked in extreme droughts and should be examined in a broad range of drought intensity.
International Nuclear Information System (INIS)
Stora, R.
1976-09-01
The mathematics of gauge fields and some related concepts are discussed: some corrections on the principal fiber bundles emphasize the idea that the present formulation of continuum theories is incomplete. The main ingredients used through the construction of the renormalized perturbation series are then described: the Faddeev Popov argument, and the Faddeev Popov Lagrangian; the Slavnov symmetry and the nature of the Faddeev Popov ghost fields; the Slavnov identity, with an obstruction: the Adler Bardeen anomaly, and its generalization to the local cohomology of the gauge Lie algebra. Some smooth classical configurations of gauge fields which ought to play a prominent role in the evaluation of the functional integral describing the theory are also reviewed
Continuum robots and underactuated grasping
Directory of Open Access Journals (Sweden)
N. Giri
2011-02-01
Full Text Available We discuss the capabilities of continuum (continuous backbone robot structures in the performance of under-actuated grasping. Continuum robots offer the potential of robust grasps over a wide variety of object classes, due to their ability to adapt their shape to interact with the environment via non-local continuum contact conditions. Furthermore, this capability can be achieved with simple, low degree of freedom hardware. However, there are practical issues which currently limit the application of continuum robots to grasping. We discuss these issues and illustrate via an experimental continuum grasping case study.
This paper was presented at the IFToMM/ASME International Workshop on Underactuated Grasping (UG2010, 19 August 2010, Montréal, Canada.
Continuum limbed robots for locomotion
Mutlu, Alper
This thesis focuses on continuum robots based on pneumatic muscle technology. We introduce a novel approach to use these muscles as limbs of lightweight legged robots. The flexibility of the continuum legs of these robots offers the potential to perform some duties that are not possible with classical rigid-link robots. Potential applications are as space robots in low gravity, and as cave explorer robots. The thesis covers the fabrication process of continuum pneumatic muscles and limbs. It also provides some new experimental data on this technology. Afterwards, the designs of two different novel continuum robots - one tripod, one quadruped - are introduced. Experimental data from tests using the robots is provided. The experimental results are the first published example of locomotion with tripod and quadruped continuum legged robots. Finally, discussion of the results and how far this technology can go forward is presented.
A mechanical energy analysis of gait initiation
Miller, C. A.; Verstraete, M. C.
1999-01-01
The analysis of gait initiation (the transient state between standing and walking) is an important diagnostic tool to study pathologic gait and to evaluate prosthetic devices. While past studies have quantified mechanical energy of the body during steady-state gait, to date no one has computed the mechanical energy of the body during gait initiation. In this study, gait initiation in seven normal male subjects was studied using a mechanical energy analysis to compute total body energy. The data showed three separate states: quiet standing, gait initiation, and steady-state gait. During gait initiation, the trends in the energy data for the individual segments were similar to those seen during steady-state gait (and in Winter DA, Quanbury AO, Reimer GD. Analysis of instantaneous energy of normal gait. J Biochem 1976;9:253-257), but diminished in amplitude. However, these amplitudes increased to those seen in steady-state during the gait initiation event (GIE), with the greatest increase occurring in the second step due to the push-off of the foundation leg. The baseline level of mechanical energy was due to the potential energy of the individual segments, while the cyclic nature of the data was indicative of the kinetic energy of the particular leg in swing phase during that step. The data presented showed differences in energy trends during gait initiation from those of steady state, thereby demonstrating the importance of this event in the study of locomotion.
Cocheret de la Morinière, E.; Pollux, B.J.A.; Nagelkerken, I.; Hemminga, M.A.; Huiskes, A.H.L.; Van der Velde, G.
2003-01-01
Juveniles of a number of reef fish species develop in shallow-water 'nursery' habitats such as mangroves and seagrass beds, and then migrate to the coral reef. This implies that some reef fish species are distributed over the mangrove-seagrass-reef continuum in subpopulations with different size
Hansen, N.; Krishna, R.; van Baten, J.M.; Bell, A.T.; Keil, F.J.
2009-01-01
A continuum model based on the Maxwell−Stefan (M-S) equations in combination with the ideal adsorbed solution theory has been used to analyze the influence of adsorption thermodynamics and intraparticle diffusional transport on the overall kinetics of benzene alkylation with ethene over H-ZSM-5. The
Electromagnetic field and mechanical stress analysis code
International Nuclear Information System (INIS)
1978-01-01
Analysis TEXMAGST is a two stage linear finite element code for the analysis of static magnetic fields in three dimensional structures and associated mechanical stresses produced by the anti J x anti B forces within these structures. The electromagnetic problem is solved in terms of magnetic vector potential A for a given current density anti J as curl 1/μ curl anti A = anti J considering the magnetic permeability as constant. The Coulombian gauge (div anti A = o) was chosen and was implemented through the use of Lagrange multipliers. The second stage of the problem - the calculation of mechanical stresses in the same three dimensional structure is solved by using the same code with few modifications - through a restart card. Body forces anti J x anti B within each element are calculated from the solution of the first stage run and represent the input to the second stage run which will give the solution for the stress problem
Validation of a Perturbed-Continuum Model for Shear Localization
National Research Council Canada - National Science Library
Iyer, K; Schoenfeld, S; Casem, D; Wright, T
2004-01-01
.... Experiments and continuum analysis (Wright, 2002) have shown sudden stress collapse via shear localization may be related to velocity or strain rate perturbations in the vicinity of shear band initiation...
Equivalent-Continuum Modeling With Application to Carbon Nanotubes
Odegard, Gregory M.; Gates, Thomas S.; Nicholson, Lee M.; Wise, Kristopher E.
2002-01-01
A method has been proposed for developing structure-property relationships of nano-structured materials. This method serves as a link between computational chemistry and solid mechanics by substituting discrete molecular structures with equivalent-continuum models. It has been shown that this substitution may be accomplished by equating the vibrational potential energy of a nano-structured material with the strain energy of representative truss and continuum models. As important examples with direct application to the development and characterization of single-walled carbon nanotubes and the design of nanotube-based devices, the modeling technique has been applied to determine the effective-continuum geometry and bending rigidity of a graphene sheet. A representative volume element of the chemical structure of graphene has been substituted with equivalent-truss and equivalent continuum models. As a result, an effective thickness of the continuum model has been determined. This effective thickness has been shown to be significantly larger than the interatomic spacing of graphite. The effective thickness has been shown to be significantly larger than the inter-planar spacing of graphite. The effective bending rigidity of the equivalent-continuum model of a graphene sheet was determined by equating the vibrational potential energy of the molecular model of a graphene sheet subjected to cylindrical bending with the strain energy of an equivalent continuum plate subjected to cylindrical bending.
Müser, Martin H
2014-01-01
In this work, single-asperity contact mechanics is investigated for positive and negative work of adhesion Δγ. In the latter case, finite-range repulsion acts in addition to hard-wall constraints. This constitutes a continuum model for a contact immersed in a strongly wetting fluid, which can only be squeezed out in the center of the contact through a sufficiently large normal load F N. As for positive work of adhesion, two stable solutions can coexist in a finite range of normal loads. The competing solutions can be readily interpreted as contacts with either a load-bearing or a squeezed-out fluid. The possibility for coexistence and the subsequent discontinuous wetting and squeeze-out instabilities depend not only on the Tabor coefficient μT but also on the functional form of the finite-range repulsion. For example, coexistence and discontinuous wetting or squeeze-out do not occur when the repulsion decreases exponentially with distance. For positive work of adhesion, the normal displacement mainly depends on F N, Δγ, and μT but - unlike the contact area - barely on the functional form of the finite-range attraction. The results can benefit the interpretation of atomic force microscopy in liquid environments and the modeling of multi-asperity contacts.
Jackson, Karen E.; Fasanella, Edwin L.; Littell, Justin D.
2017-01-01
This paper describes the development of input properties for a continuum damage mechanics based material model, Mat 58, within LS-DYNA(Registered Trademark) to simulate the response of a graphite-Kevlar(Registered Trademark) hybrid plain weave fabric. A limited set of material characterization tests were performed on the hybrid graphite-Kevlar(Registered Trademark) fabric. Simple finite element models were executed in LS-DYNA(Registered Trademark) to simulate the material characterization tests and to verify the Mat 58 material model. Once verified, the Mat 58 model was used in finite element models of two composite energy absorbers: a conical-shaped design, designated the "conusoid," fabricated of four layers of hybrid graphite-Kevlar(Registered Trademark) fabric; and, a sinusoidal-shaped foam sandwich design, designated the "sinusoid," fabricated of the same hybrid fabric face sheets with a foam core. Dynamic crush tests were performed on components of the two energy absorbers, which were designed to limit average vertical accelerations to 25- to 40-g, to minimize peak crush loads, and to generate relatively long crush stroke values under dynamic loading conditions. Finite element models of the two energy absorbers utilized the Mat 58 model that had been verified through material characterization testing. Excellent predictions of the dynamic crushing response were obtained.
Department of Housing and Urban Development — The purpose of the Continuum of Care (CoC) Homeless Assistance Programs is to reduce the incidence of homelessness in CoC communities by assisting homeless...
Experiments and video analysis in classical mechanics
de Jesus, Vitor L B
2017-01-01
This book is an experimental physics textbook on classical mechanics focusing on the development of experimental skills by means of discussion of different aspects of the experimental setup and the assessment of common issues such as accuracy and graphical representation. The most important topics of an experimental physics course on mechanics are covered and the main concepts are explored in detail. Each chapter didactically connects the experiment and the theoretical models available to explain it. Real data from the proposed experiments are presented and a clear discussion over the theoretical models is given. Special attention is also dedicated to the experimental uncertainty of measurements and graphical representation of the results. In many of the experiments, the application of video analysis is proposed and compared with traditional methods.
Links between annual, Milankovitch and continuum temperature variability.
Huybers, Peter; Curry, William
2006-05-18
Climate variability exists at all timescales-and climatic processes are intimately coupled, so that understanding variability at any one timescale requires some understanding of the whole. Records of the Earth's surface temperature illustrate this interdependence, having a continuum of variability following a power-law scaling. But although specific modes of interannual variability are relatively well understood, the general controls on continuum variability are uncertain and usually described as purely stochastic processes. Here we show that power-law relationships of surface temperature variability scale with annual and Milankovitch-period (23,000- and 41,000-year) cycles. The annual cycle corresponds to scaling at monthly to decadal periods, while millennial and longer periods are tied to the Milankovitch cycles. Thus the annual, Milankovitch and continuum temperature variability together represent the response to deterministic insolation forcing. The identification of a deterministic control on the continuum provides insight into the mechanisms governing interannual and longer-period climate variability.
ANSYS mechanical APDL for finite element analysis
Thompson, Mary Kathryn
2017-01-01
ANSYS Mechanical APDL for Finite Element Analysis provides a hands-on introduction to engineering analysis using one of the most powerful commercial general purposes finite element programs on the market. Students will find a practical and integrated approach that combines finite element theory with best practices for developing, verifying, validating and interpreting the results of finite element models, while engineering professionals will appreciate the deep insight presented on the program's structure and behavior. Additional topics covered include an introduction to commands, input files, batch processing, and other advanced features in ANSYS. The book is written in a lecture/lab style, and each topic is supported by examples, exercises and suggestions for additional readings in the program documentation. Exercises gradually increase in difficulty and complexity, helping readers quickly gain confidence to independently use the program. This provides a solid foundation on which to build, preparing readers...
Topics in Applied Continuum Mechanics : Symposium
Ziegler, F
1974-01-01
THE FOUNDATIONS OF THERMOELASTICITY-EXPERIMENTS AND THEORY (A. PHILLIPS) 1. Introduction 2. The initial yield surface 4 3. The subsequent yield surface 6 4. Some theoretical consequences 10 References 13 ON THE PHYSICS AND MATHEMATICS OF SELF-STRESSES (E. KRONER) 1. Introduction 22 2. The physical origin of the self-stresses 23 3. Formulation of the mathematical problem of self-stresses 27 4. The method of modified Green's functions 30 5. Concluding remarks 35 References 38 DISTORTION IN MICROPOLAR ELASTICITY (W. NOWACKI) 1. Fundamental relations and equations 39 2. Principle of virtual work 42 3. Theorem of minimum of the complimentary work 43 • 4. Reciprocity theorem 44 5. Equations in displacements and rotations 47 6. Compatibility equations 51 References 57 THE YIELD CRITERION IN THE GENERAL CASE OF NONHOMOGENEOUS STRESS AND DEFORMATION FIELDS (J. A. KONIG and W. OLSZAK) 1. Introduction 58 2. The plasticity condition 61 3. Special cases of the yield condition 62 4. Example: Pure bending 63 5. Criteria f...
Molecular mechanics conformational analysis of tylosin
Ivanov, Petko M.
1998-01-01
The conformations of the 16-membered macrolide antibiotic tylosin were studied with molecular mechanics (AMBER∗ force field) including modelling of the effect of the solvent on the conformational preferences (GB/SA). A Monte Carlo conformational search procedure was used for finding the most probable low-energy conformations. The present study provides complementary data to recently reported analysis of the conformations of tylosin based on NMR techniques. A search for the low-energy conformations of protynolide, a 16-membered lactone containing the same aglycone as tylosin, was also carried out, and the results were compared with the observed conformation in the crystal as well as with the most probable conformations of the macrocyclic ring of tylosin. The dependence of the results on force field was also studied by utilizing the MM3 force field. Some particular conformations were computed with the semiempirical molecular orbital methods AM1 and PM3.
Recognition and Analysis of Corrosion Failure Mechanisms
Directory of Open Access Journals (Sweden)
Steven Suess
2006-02-01
Full Text Available Corrosion has a vast impact on the global and domestic economy, and currently incurs losses of nearly $300 billion annually to the U.S. economy alone. Because of the huge impact of corrosion, it is imperative to have a systematic approach to recognizing and mitigating corrosion problems as soon as possible after they become apparent. A proper failure analysis includes collection of pertinent background data and service history, followed by visual inspection, photographic documentation, material evaluation, data review and conclusion procurement. In analyzing corrosion failures, one must recognize the wide range of common corrosion mechanisms. The features of any corrosion failure give strong clues as to the most likely cause of the corrosion. This article details a proven approach to properly determining the root cause of a failure, and includes pictographic illustrations of the most common corrosion mechanisms, including general corrosion, pitting, galvanic corrosion, dealloying, crevice corrosion, microbiologically-influenced corrosion (MIC, corrosion fatigue, stress corrosion cracking (SCC, intergranular corrosion, fretting, erosion corrosion and hydrogen damage.
Asinari, Pietro
2009-11-01
A finite difference lattice Boltzmann scheme for homogeneous mixture modeling, which recovers Maxwell-Stefan diffusion model in the continuum limit, without the restriction of the mixture-averaged diffusion approximation, was recently proposed [P. Asinari, Phys. Rev. E 77, 056706 (2008)]. The theoretical basis is the Bhatnagar-Gross-Krook-type kinetic model for gas mixtures [P. Andries, K. Aoki, and B. Perthame, J. Stat. Phys. 106, 993 (2002)]. In the present paper, the recovered macroscopic equations in the continuum limit are systematically investigated by varying the ratio between the characteristic diffusion speed and the characteristic barycentric speed. It comes out that the diffusion speed must be at least one order of magnitude (in terms of Knudsen number) smaller than the barycentric speed, in order to recover the Navier-Stokes equations for mixtures in the incompressible limit. Some further numerical tests are also reported. In particular, (1) the solvent and dilute test cases are considered, because they are limiting cases in which the Maxwell-Stefan model reduces automatically to Fickian cases. Moreover, (2) some tests based on the Stefan diffusion tube are reported for proving the complete capabilities of the proposed scheme in solving Maxwell-Stefan diffusion problems. The proposed scheme agrees well with the expected theoretical results.
Lagrangian continuum dynamics in ALEGRA.
Energy Technology Data Exchange (ETDEWEB)
Wong, Michael K. W.; Love, Edward
2007-12-01
Alegra is an ALE (Arbitrary Lagrangian-Eulerian) multi-material finite element code that emphasizes large deformations and strong shock physics. The Lagrangian continuum dynamics package in Alegra uses a Galerkin finite element spatial discretization and an explicit central-difference stepping method in time. The goal of this report is to describe in detail the characteristics of this algorithm, including the conservation and stability properties. The details provided should help both researchers and analysts understand the underlying theory and numerical implementation of the Alegra continuum hydrodynamics algorithm.
The geometry of continuum regularization
International Nuclear Information System (INIS)
Halpern, M.B.
1987-03-01
This lecture is primarily an introduction to coordinate-invariant regularization, a recent advance in the continuum regularization program. In this context, the program is seen as fundamentally geometric, with all regularization contained in regularized DeWitt superstructures on field deformations
Babaei, H.; Shahidi, A. R.
2011-12-01
Free vibration analysis of quadrilateral multilayered graphene sheets (MLGS) embedded in polymer matrix is carried out employing nonlocal continuum mechanics. The principle of virtual work is employed to derive the equations of motion. The Galerkin method in conjunction with the natural coordinates of the nanoplate is used as a basis for the analysis. The dependence of small scale effect on thickness, elastic modulus, polymer matrix stiffness and interaction coefficient between two adjacent sheets is illustrated. The non-dimensional natural frequencies of skew, rhombic, trapezoidal and rectangular MLGS are obtained with various geometrical parameters and mode numbers taken into account, and for each case the effects of the small length scale are investigated.
Set theory and the continuum hypothesis
Cohen, Paul J
2008-01-01
This exploration of a notorious mathematical problem is the work of the man who discovered the solution. The independence of the continuum hypothesis is the focus of this study by Paul J. Cohen. It presents not only an accessible technical explanation of the author's landmark proof but also a fine introduction to mathematical logic. An emeritus professor of mathematics at Stanford University, Dr. Cohen won two of the most prestigious awards in mathematics: in 1964, he was awarded the American Mathematical Society's Bôcher Prize for analysis; and in 1966, he received the Fields Medal for Logic.
Koshiyama, Kenichiro; Nishimoto, Keisuke; Ii, Satoshi; Sera, Toshihiro; Wada, Shigeo
2018-01-20
The pulmonary acinus is a dead-end microstructure that consists of ducts and alveoli. High-resolution micro-CT imaging has recently provided detailed anatomical information of a complete in vivo acinus, but relating its mechanical response with its detailed acinar structure remains challenging. This study aimed to investigate the mechanical response of acinar tissue in a whole acinus for static inflation using computational approaches. We performed finite element analysis of a whole acinus for static inflation. The acinar structure model was generated based on micro-CT images of an intact acinus. A continuum mechanics model of the lung parenchyma was used for acinar tissue material model, and surface tension effects were explicitly included. An anisotropic mechanical field analysis based on a stretch tensor was combined with a curvature-based local structure analysis. The airspace of the acinus exhibited nonspherical deformation as a result of the anisotropic deformation of acinar tissue. A strain hotspot occurred at the ridge-shaped region caused by a rod-like deformation of acinar tissue on the ridge. The local structure becomes bowl-shaped for inflation and, without surface tension effects, the surface of the bowl-shaped region primarily experiences isotropic deformation. Surface tension effects suppressed the increase in airspace volume and inner surface area, while facilitating anisotropic deformation on the alveolar surface. In the lungs, the heterogeneous acinar structure and surface tension induce anisotropic deformation at the acinar and alveolar scales. Further research is needed on structural variation of acini, inter-acini connectivity, or dynamic behavior to understand multiscale lung mechanics. Copyright © 2018 Elsevier Ltd. All rights reserved.
Ultrafine Cohesive Powders: From Interparticle Contacts to Continuum Behaviour.
Tykhoniuk, Rostyslav; Tomas, Jürgen; Luding, Stefan; Kappl, Michael; Heim, Lars; Butt, Hans-Jürgen
2007-01-01
Continuum mechanical models and appropriate measuring methods to determine the material parameters are available to describe the flow behaviour of cohesive powders. These methods are successfully applied to design process equipment as silos. In addition, “microscopic” studies on the particle
Continuum description for jointed media
International Nuclear Information System (INIS)
Thomas, R.K.
1982-04-01
A general three-dimensional continuum description is presented for a material containing regularly spaced and approximately parallel jointing planes within a representative elementary volume. Constitutive relationships are introduced for linear behavior of the base material and nonlinear normal and shear behavior across jointing planes. Furthermore, a fracture permeability tensor is calculated so that deformation induced alterations to the in-situ values can be measured. Examples for several strain-controlled loading paths are presented
Whitham, Hilary K; Sansom, Stephanie L; Wejnert, Cyprian; Finlayson, Teresa; Huang, Ya-Lin A; An, Qian; Paz-Bailey, Gabriela
2018-03-01
Using National HIV Behavioral Surveillance (NHBS) cross-sectional survey and HIV testing data in 21 U.S. metropolitan areas, we identify sex practices among sexually active men who have sex with men (MSM) associated with: (1) awareness of HIV status, and (2) engagement in the HIV care continuum. Data from 2008, 2011, and 2014 were aggregated, yielding a sample of 5079 sexually active MSM living with HIV (MLWH). Participants were classified into HIV status categories: (1) unaware; (2) aware and out of care; (3) aware and in care without antiretroviral therapy (ART); and (4) aware and on ART. Analyses were conducted examining sex practices (e.g. condomless sex, discordant condomless sex, and number of sex partners) by HIV status. Approximately 30, 5, 10 and 55% of the sample was classified as unaware, aware and out of care, aware and in care without ART, and aware and on ART, respectively. Unaware MLWH were more likely to report condomless anal sex with a last male partner of discordant or unknown HIV status (25.9%) than aware MLWH (18.0%, p value aware MLWH (17.3 and 5.6%, p-value HIV status (ranging from 17.7 to 21.3%), and median number of both male and female sex partners were similar. In conclusion, awareness of HIV and engagement in care was not consistently associated with protective sex practices, highlighting the need for continued prevention efforts.
Continuum deformation of multi-agent systems
Rastgoftar, Hossein
2016-01-01
This monograph presents new algorithms for formation control of multi-agent systems (MAS) based on principles of continuum mechanics. Beginning with an overview of traditional methods, the author then introduces an innovative new approach whereby agents of an MAS are considered as particles in a continuum evolving in ℝn whose desired configuration is required to satisfy an admissible deformation function. The necessary theory and its validation on a mobile-agent-based swarm test bed are considered for two primary tasks: homogeneous transformation of the MAS and deployment of a random distribution of agents on a desired configuration. The framework for this model is based on homogeneous transformations for the evolution of an MAS under no inter-agent communication, local inter-agent communication, and intelligent perception by agents. Different communication protocols for MAS evolution, the robustness of tracking of a desired motion by an MAS evolving in ℝn, and the effect of communication delays in an MAS...
On frame indifferent Lagrangians of micropolar thermoelastic continuum
Directory of Open Access Journals (Sweden)
Vladimir A. Kovalev
2015-06-01
Full Text Available A non-linear mathematical model of type-II thermoelastic continuum with fine microstructure is developed. The model is described in terms of 4-covariant field theoretical formalism attributed to field theories of continuum mechanics. Fine microstructure is introduced by d-vectors and tensors playing role of extra field variables. A Lagrangian density for type-II thermoelastic continuum with fine microstructure is proposed and the least action principle is formulated. Virtual microstructural inertia is added to the considered action density. It is also valid for the thermal inertia. Corresponding 4-covariant field equations of type-II thermoelasticity are obtained. Constitutive equations of type-II microstructural thermoelasticity are discussed. Following the usual procedure for type-II micropolar thermoelastic Lagrangians functionally independent rotationally invariant arguments are obtained. Those are proved to form a complete set. Objective forms of the Lagrangians satisfying the frame indifference principle are given. Those are derived by using extrastrain vectors and tensors.
On the design of the NIF Continuum Spectrometer
Thorn, D. B.; MacPhee, A.; Ayers, J.; Galbraith, J.; Hardy, C. M.; Izumi, N.; Bradley, D. K.; Pickworth, L. A.; Bachmann, B.; Kozioziemski, B.; Landen, O.; Clark, D.; Schneider, M. B.; Hill, K. W.; Bitter, M.; Nagel, S.; Bell, P. M.; Person, S.; Khater, H. Y.; Smith, C.; Kilkenny, J.
2017-08-01
In inertial confinement fusion (ICF) experiments on the National Ignition Facility (NIF), measurements of average ion temperature using DT neutron time of flight broadening and of DD neutrons do not show the same apparent temperature. Some of this may be due to time and space dependent temperature profiles in the imploding capsule which are not taken into account in the analysis. As such, we are attempting to measure the electron temperature by recording the free-free electron-ion scattering-spectrum from the tail of the Maxwellian temperature distribution. This will be accomplished with the new NIF Continuum Spectrometer (ConSpec) which spans the x-ray range of 20 keV to 30 keV (where any opacity corrections from the remaining mass of the ablator shell are negligible) and will be sensitive to temperatures between ˜ 3 keV and 6 keV. The optical design of the ConSpec is designed to be adaptable to an x-ray streak camera to record time resolved free-free electron continuum spectra for direct measurement of the dT/dt evolution across the burn width of a DT plasma. The spectrometer is a conically bent Bragg crystal in a focusing geometry that allows for the dispersion plane to be perpendicular to the spectrometer axis. Additionally, to address the spatial temperature dependence, both time integrated and time resolved pinhole and penumbral imaging will be provided along the same polar angle. The optical and mechanical design of the instrument is presented along with estimates for the dispersion, solid angle, photometric sensitivity, and performance.
Mechanical vibration and shock analysis, sinusoidal vibration
Lalanne, Christian
2014-01-01
Everything engineers need to know about mechanical vibration and shock...in one authoritative reference work! This fully updated and revised 3rd edition addresses the entire field of mechanical vibration and shock as one of the most important types of load and stress applied to structures, machines and components in the real world. Examples include everything from the regular and predictable loads applied to turbines, motors or helicopters by the spinning of their constituent parts to the ability of buildings to withstand damage from wind loads or explosions, and the need for cars to m
The application of single particle hydrodynamics in continuum models of multiphase flow
Decker, Rand
1988-01-01
A review of the application of single particle hydrodynamics in models for the exchange of interphase momentum in continuum models of multiphase flow is presented. Considered are the equations of motion for a laminar, mechanical two phase flow. Inherent to this theory is a model for the interphase exchange of momentum due to drag between the dispersed particulate and continuous fluid phases. In addition, applications of two phase flow theory to de-mixing flows require the modeling of interphase momentum exchange due to lift forces. The applications of single particle analysis in deriving models for drag and lift are examined.
International Nuclear Information System (INIS)
Ababou, Rachid; Canamon, Israel; Poutrel, Adrien
2012-01-01
to a coupled system of equivalent tensorial HM equations governing the HM processes in an equivalent continuum. The underlying hypotheses are (i) low Reynolds number for water flow; (ii) quasi-elastic deformations; and (iii) quasi-static mechanics. The equivalent up-scaled coefficients are symmetric tensors of rank 0, rank 2, and rank 4. The up-scaling procedure is decomposed in 3 independent steps, as follows: (Step 1) Hydraulic up-scaling, based on a flux superposition approach. This step leads to an equivalent Darcy equation with macro-permeability tensor Kij(x,y,z). (Step 2) Mechanical up-scaling step: this step leads to non-orthotropic equivalent compliance Cijmn(x,y,z) and equivalent stiffness Rijmn(x,y,z), the latter being the inverse of the former in the sense of symmetric 4. rank tensors. (Step 3) Hydro-Mechanical up-scaling step: this step leads to the coupling coefficients M(x,y,z) and Bij(x,y,z), where M is the scalar Biot modulus, and Bij is the tensorial Biot coefficient. The HM coupling coefficients M and Bij, as well as the Cijmn and Rijmn tensors, appear in a non-orthotropic version of Biot's poro-elastic law, obtained as a result of the up-scaling procedure. These coefficients contain explicit information on the properties of the matrix and on the systems of cracks. The visual representation of spatially distributed 4. rank tensor fields like Cijmn(x,y,z) and Rijmn(x,y,z) with 3x3x3x3 components is a problem in itself, even when the symmetries are taken into account. Several methods have been considered. One of the methods, used in this work, consists in representing the 3x3x3x3 compliance Cijmn with the 6x6 Kelvin-Voigt index notation, and then, isolating two symmetric 3x3 submatrices Nij and Sij. Stiffness Rijmn is treated similarly after inverting it from Cijmn. The 3x3 normal and shear matrices are then represented by ellipsoids. Another method consists in 'isotropizing' the tensorial coefficients to obtain equivalent spherical coefficients
Methods of stability analysis in nonlinear mechanics
International Nuclear Information System (INIS)
Warnock, R.L.; Ruth, R.D.; Gabella, W.; Ecklund, K.
1989-01-01
We review our recent work on methods to study stability in nonlinear mechanics, especially for the problems of particle accelerators, and compare our ideals to those of other authors. We emphasize methods that (1) show promise as practical design tools, (2) are effective when the nonlinearity is large, and (3) have a strong theoretical basis. 24 refs., 2 figs., 2 tabs
1968-01-01
5 The symposium was held in Freudenstadt from 28\\h to 31 \\ ofAugust st nd 1967 and in Stuttgart from 1 to 2 of September 1967. The proposal to hold this symposium originated with the German Society of Applied Mathematics and Mechanics (GAMM) late in 1964 and was examined by a committee of IUTAM especially appointed for this purpose. The basis of this examination was a report in which the present situation in the field and the possible aims of the symposium were surveyed. Briefly, the aims of the symposium were stated to be 1. the unification of the various approaches developed in recent years with the aim of penetrating into the microscopic world of matter by means of continuum theories; 2. the bridging of the gap between microscopic (or atomic) research on mechanics on one hand, and the phenomenological (or continuum mechanical) approach on the other hand; 3. the physical interpretation and the relation to actual material behaviour of the quantities and laws introduced into the new theories, together with ap...
Embodiment design of soft continuum robots
Directory of Open Access Journals (Sweden)
Rongjie Kang
2016-04-01
Full Text Available This article presents the results of a multidisciplinary project where mechatronic engineers worked alongside biologists to develop a soft robotic arm that captures key features of octopus anatomy and neurophysiology. The concept of embodiment (the dynamic coupling between sensory-motor control, anatomy, materials and environment that allows for the animal to achieve adaptive behaviours is used as a starting point for the design process but tempered by current engineering technologies and approaches. In this article, the embodied design requirements are first discussed from a robotic viewpoint by taking into account real-life engineering limitations; then, the motor control schemes inspired by octopus nervous system are investigated. Finally, the mechanical and control design of a prototype is presented that appropriately blends bio-inspiration and engineering limitations. Simulated and experimental results show that the developed continuum robotic arm is able to reproduce octopus-like motions for bending, reaching and grasping.
Analysis of Costs and Returns of Mechanized Fishing Boat ...
African Journals Online (AJOL)
Administrator
Analysis of Costs and Returns of Mechanized Fishing Boat Operations in India. EJBE Vol. 1, No. 2/2010. Page 129 effective management of this economically backward sector in India. Mechanized fishing boat ... economics of operation of the 17.5 m indigenous mechanized fishing boat along the Kerala Coast and ...
Thermo-mechanical finite element analysis of bolted cask lid structures
International Nuclear Information System (INIS)
Wieser, G.; Qiao, L.; Eberle, A.; Voelzke, H.
2004-01-01
Analysis of complex bolted cask lid structures under mechanical or thermal accident conditions is important for the evaluation of cask integrity and leak tightness in package design assessment according to the transport regulations or in aircraft crash scenarios. In this context BAM is developing methods based on finite elements (FE) to calculate the effects of mechanical impacts onto the bolted lid structures as well as effects caused by severe fire scenarios. In the case of fire it might not be enough to perform only a thermal heat transfer analysis. A complex cask design together with a severe hypothetical time-temperature curve representing an accident fire scenario will create a strong transient heating up of the cask body and its lid system. This causes relative displacements between the seals and their counterparts that can be analysed by a so-called thermomechanical calculation. Although it is currently not possible to directly correlate leakage rates with results from deformation analyses, an appropriate finite element model of the considered type of metallic lid seal has been developed. For the present it is possible to estimate the behaviour of the seal based on the calculated relative displacements at its seating and the behaviour of the lid bolts under the impact load or the temperature field, respectively. Except for the lid bolts, the geometry of the cask and the mechanical loading is axisymmetric which simplifies the analysis considerably, and a two-dimensional finite-element model with substitute lid bolts may be used. The substitute bolts are modelled as one-dimensional truss or beam elements. An advanced two-dimensional bolt submodel represents the bolts with plane stress continuum elements. This paper discusses the influence of different bolt modellings on the relative displacements at the seating of the seals. The influence of bolt modelling, thermal properties and the detailed geometry of the two-dimensional finite-element models on the
Continuum theory for nanotube piezoelectricity.
Michalski, P J; Sai, Na; Mele, E J
2005-09-09
We develop and solve a continuum theory for the piezoelectric response of one-dimensional nanotubes and nanowires, and apply the theory to study electromechanical effects in boron-nitride nanotubes. We find that the polarization of a nanotube depends on its aspect ratio, and a dimensionless constant specifying the ratio of the strengths of the elastic and electrostatic interactions. The solutions of the model as these two parameters are varied are discussed. The theory is applied to estimate the electric potential induced along the length of a boron-nitride nanotube in response to a uniaxial stress.
Continuum-regularized quantum gravity
International Nuclear Information System (INIS)
Chan Huesum; Halpern, M.B.
1987-01-01
The recent continuum regularization of d-dimensional Euclidean gravity is generalized to arbitrary power-law measure and studied in some detail as a representative example of coordinate-invariant regularization. The weak-coupling expansion of the theory illustrates a generic geometrization of regularized Schwinger-Dyson rules, generalizing previous rules in flat space and flat superspace. The rules are applied in a non-trivial explicit check of Einstein invariance at one loop: the cosmological counterterm is computed and its contribution is included in a verification that the graviton mass is zero. (orig.)
Directory of Open Access Journals (Sweden)
Milašinović Dragan D.
2015-01-01
Full Text Available A new analytical model for the prediction of concrete response under uniaxial compression and its experimental verification is presented in this paper. The proposed approach, referred to as the rheological-dynamical continuum damage model, combines rheological-dynamical analogy and damage mechanics. Within the framework of this approach the key continuum parameters such as the creep coefficient, Poisson’s ratio and damage variable are functionally related. The critical values of the creep coefficient and damage variable under peak stress are used to describe the failure mode of the concrete cylinder. The ultimate strain is determined in the post-peak regime only, using the secant stress-strain relation from damage mechanics. The post-peak branch is used for the energy analysis. Experimental data for five concrete compositions were obtained during the examination presented herein. The principal difference between compressive failure and tensile fracture is that there is a residual stress in the specimens, which is a consequence of uniformly accelerated motion of load during the examination of compressive strength. The critical interpenetration displacements and crushing energy are obtained theoretically based on the concept of global failure analysis. [Projekat Ministarstva nauke Republike Srbije, br. ON 174027: Computational Mechanics in Structural Engineering i br. TR 36017: Utilization of by-products and recycled waste materials in concrete composites for sustainable construction development in Serbia: Investigation and environmental assessment of possible applications
Directory of Open Access Journals (Sweden)
Mega Hayuningtyas Erwanti
2015-12-01
Full Text Available This study is conducted to examine the portrayal of a lesbian continuum in Sarah Waters’ Fingersmith. To conduct the analysis, there are two research questions: first, how is the construction of lesbian continuum portrayed in the relationship between Susan Trinder and Maud Lilly and how does lesbian continuum become a strategy to negotiate compulsory heterosexuality. In doing the analysis, the theory of lesbian continuum which is proposed by Adrienne Rich will be used to elaborate the novel. This study is a qualitative research where the data are taken from the novel Fingersmith, library research, journals, and other relevant sources. To gain the comprehensive analysis, this study uses some methods which are: close reading, postulation the statements of the problems, data classification, and analysis using the lesbian continuum theory, supporting analysis through library research, books, and academic journals. This study finds that the characters of Susan Trinder and Maud Lilly can be identified as having a double life which constructs the lesbian continuum. Moreover, the lesbian continuum becomes a strategy to negotiate compulsory heterosexuality with denial and negotiation of women’s oppression. Abstrak: Artikel ini mengkaji representasi lesbian continuum dalam novel Sarah Waters yang berjudul Fingersmith. Dua pertanyaan utama penelitian ini adalah (1 bagaimana konstruksi lesbian continuum direpresentasikan dalam hubungan antara tokoh Susan Trinder dan Maud Lily dalam novel Fingersmith dan (2 bagaimana lesbian continuum menjadi strategi untuk menghadapi compulsory heterosexuality dalam novel Fingersmith. Teori lesbian continuum oleh Adrienne Rich akan menjadi teori utama untuk menjawab pertanyaan penelitian. Menggunakan teknik pembacaan novel dan analisis pustaka yang bersumber dari jurnal dan sumber lain yang mendukung. Untuk mendapatkan data yang komprehensip, metode yang dipakai adalah close reading, menjabarkan pertanyaan, klasifikasi
Handbook of mathematical analysis in mechanics of viscous fluids
Novotný, Antonín
2018-01-01
Mathematics has always played a key role for researches in fluid mechanics. The purpose of this handbook is to give an overview of items that are key to handling problems in fluid mechanics. Since the field of fluid mechanics is huge, it is almost impossible to cover many topics. In this handbook, we focus on mathematical analysis on viscous Newtonian fluid. The first part is devoted to mathematical analysis on incompressible fluids while part 2 is devoted to compressible fluids.
Cellular Automata in Topology Optimization of Continuum Structures ...
African Journals Online (AJOL)
In this paper, an optimization algorithm based on cellular automata (CA) is developed for topology optimization of continuum structures with shear and flexural behavior. The design domain is divided into small triangle elements and each cell is considered as a finite element. The stress analysis is performed by the Constant ...
Analysis of Mechanical Properties for GEM Foil
Chin, Yuk Ming
2016-01-01
In view of new assembly technique of the GEM detector; in which three foils stack is stretched to get the uniform gaps among the foils. We studied the mechanical properties of the foil material. We conditioned the samples in different environments to make them extra dry and wet. As holes are the major source of the charge amplification their deformation can effect the detector performance. Therefore in our studies we also studied at which level of the stress the holes deformation is seen. These tensile and holes deformation studies can help to optimize the stress during detector assembly.
Schifferle, Andreas; Dommann, Alex; Neels, Antonia
2017-01-01
New methods are needed in microsystems technology for evaluating microelectromechanical systems (MEMS) because of their reduced size. The assessment and characterization of mechanical and structural relations of MEMS are essential to assure the long-term functioning of devices, and have a significant impact on design and fabrication. Within this study a concept for the investigation of mechanically loaded MEMS materials on an atomic level is introduced, combining high-resolution X-ray diffraction (HRXRD) measurements with finite element analysis (FEA) and mechanical testing. In situ HRXRD measurements were performed on tensile loaded single crystal silicon (SCSi) specimens by means of profile scans and reciprocal space mapping (RSM) on symmetrical (004) and (440) reflections. A comprehensive evaluation of the rather complex XRD patterns and features was enabled by the correlation of measured with simulated, 'theoretical' patterns. Latter were calculated by a specifically developed, simple and fast approach on the basis of continuum mechanical relations. Qualitative and quantitative analysis confirmed the admissibility and accuracy of the presented method. In this context [001] Poisson's ratio was determined providing an error of less than 1.5% with respect to analytical prediction. Consequently, the introduced procedure contributes to further going investigations of weak scattering being related to strain and defects in crystalline structures and therefore supports investigations on materials and devices failure mechanisms.
Analysis of WWER 1000 collector cracking mechanisms
Energy Technology Data Exchange (ETDEWEB)
Matocha, K.; Wozniak, J. [Vitkovice J.S.C., Ostrava (Switzerland)
1997-12-31
The presentation reviews the large experimental program, started in 1993 in Vitkovice, where the main aim was: (1) a detailed study of strain and thermal ageing, dissolved oxygen content and temperature on subcritical crack growth in 10NiMo8.5 (10GN2MFA) steel, (2) a detailed study of the effect of high temperature water and tube expansion technology on fracture behaviour of ligaments between holes for heat exchange tubes, and (3) a detailed study of the effect of drilling, tube expansion technology and heat treatment on residual stresses on the surface of holes for heat exchange tubes. The aim of all these investigations was to find a dominant damage mechanism responsible for collector cracking to be able to judge the efficiency of implemented modifications and suggested countermeasures and to answer a very important question whether proper operation conditions (mainly water chemistry) make the operation of steam generators made in Vitcovice safe throughout the planned lifetime. 10 refs.
Control and Modeling of Extensible Continuum Robots
National Aeronautics and Space Administration — The goal of this research is to develop fundamental control theory, dynamic modeling, and control technology for extensible continuum robotic manipulators. These...
Passing waves from atomistic to continuum
Chen, Xiang; Diaz, Adrian; Xiong, Liming; McDowell, David L.; Chen, Youping
2018-02-01
Progress in the development of coupled atomistic-continuum methods for simulations of critical dynamic material behavior has been hampered by a spurious wave reflection problem at the atomistic-continuum interface. This problem is mainly caused by the difference in material descriptions between the atomistic and continuum models, which results in a mismatch in phonon dispersion relations. In this work, we introduce a new method based on atomistic dynamics of lattice coupled with a concurrent atomistic-continuum method to enable a full phonon representation in the continuum description. This permits the passage of short-wavelength, high-frequency phonon waves from the atomistic to continuum regions. The benchmark examples presented in this work demonstrate that the new scheme enables the passage of all allowable phonons through the atomistic-continuum interface; it also preserves the wave coherency and energy conservation after phonons transport across multiple atomistic-continuum interfaces. This work is the first step towards developing a concurrent atomistic-continuum simulation tool for non-equilibrium phonon-mediated thermal transport in materials with microstructural complexity.
Recognition and Analysis of Corrosion Failure Mechanisms
Steven Suess
2006-01-01
Corrosion has a vast impact on the global and domestic economy, and currently incurs losses of nearly $300 billion annually to the U.S. economy alone. Because of the huge impact of corrosion, it is imperative to have a systematic approach to recognizing and mitigating corrosion problems as soon as possible after they become apparent. A proper failure analysis includes collection of pertinent background data and service history, followed by visual inspection, photographic documentation, materi...
Kinematics Analysis of Two Parallel Locomotion Mechanisms
2010-08-27
1998, "Design Considerations of New Six Degrees-of-Freedom Parallel Robots," Leuven, Belgium, 2, pp. 1327-1333. [19] Angeles, J., Guilin , Y., and...Parallel Manipulators: Identification and Elimination," Minneapolis, MN, USA, 72, pp. 459-466. [25] Dash, A. K., Chen, I. M., Song Huat, Y., and Guilin ...28] Guilin , Y., Chen, I. M., Wei, L., and Angeles, J., 2001, "Singularity Analysis of Three-Legged Parallel Robots Based on Passive-Joint Velocities
A constitutive model of soft tissue: From nanoscale collagen to tissue continuum
Tang, Huang
2009-04-08
Soft collagenous tissue features many hierarchies of structure, starting from tropocollagen molecules that form fibrils, and proceeding to a bundle of fibrils that form fibers. Here we report the development of an atomistically informed continuum model of collagenous tissue. Results from full atomistic and molecular modeling are linked with a continuum theory of a fiber-reinforced composite, handshaking the fibril scale to the fiber and continuum scale in a hierarchical multi-scale simulation approach. Our model enables us to study the continuum-level response of the tissue as a function of cross-link density, making a link between nanoscale collagen features and material properties at larger tissue scales. The results illustrate a strong dependence of the continuum response as a function of nanoscopic structural features, providing evidence for the notion that the molecular basis for protein materials is important in defining their larger-scale mechanical properties. © 2009 Biomedical Engineering Society.
de Babos, Diego Victor; Bechlin, Marcos André; Barros, Ariane Isis; Ferreira, Edilene Cristina; Gomes Neto, José Anchieta; de Oliveira, Silvana Ruella
2016-05-15
A new method is proposed for the simultaneous determination of Mo and Ni in plant materials by high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GFAAS), employing direct solid sample analysis (DSS) and internal standardization (IS). Cobalt was used as internal standard to minimize matrix effects during Ni determinations, enabling the use of aqueous standards for calibration. Correlation coefficients for the calibration curves were typically better than 0.9937. The performance of the method was checked by analysis of six plant certified reference materials, and the results for Mo and Ni were in agreement with the certified values (95% confidence level, t-test). Analysis was made of different types of plant materials used as renewable sources of energy, including sugarcane leaves, banana tree fiber, soybean straw, coffee pods, orange bagasse, peanut hulls, and sugarcane bagasse. The concentrations found for Mo and Ni ranged from 0.08 to 0.63 ng mg(-1) and from 0.41 to 6.92 ng mg(-1), respectively. Precision (RSD) varied from 2.1% to 11% for Mo and from 3.7% to 10% for Ni. Limits of quantification of 0.055 and 0.074 ng were obtained for Mo and Ni, respectively. Copyright © 2016 Elsevier B.V. All rights reserved.
International Nuclear Information System (INIS)
Kreider, J.F.
1985-01-01
This book is an introduction on fluid mechanics incorporating computer applications. Topics covered are as follows: brief history; what is a fluid; two classes of fluids: liquids and gases; the continuum model of a fluid; methods of analyzing fluid flows; important characteristics of fluids; fundamentals and equations of motion; fluid statics; dimensional analysis and the similarity principle; laminar internal flows; ideal flow; external laminar and channel flows; turbulent flow; compressible flow; fluid flow measurements
Molecular thermal transistor: Dimension analysis and mechanism
Behnia, S.; Panahinia, R.
2018-04-01
Recently, large challenge has been spent to realize high efficient thermal transistors. Outstanding properties of DNA make it as an excellent nano material in future technologies. In this paper, we introduced a high efficient DNA based thermal transistor. The thermal transistor operates when the system shows an increase in the thermal flux despite of decreasing temperature gradient. This is what called as negative differential thermal resistance (NDTR). Based on multifractal analysis, we could distinguish regions with NDTR state from non-NDTR state. Moreover, Based on dimension spectrum of the system, it is detected that NDTR state is accompanied by ballistic transport regime. The generalized correlation sum (analogous to specific heat) shows that an irregular decrease in the specific heat induces an increase in the mean free path (mfp) of phonons. This leads to the occurrence of NDTR.
Analysis and control of underactuated mechanical systems
Choukchou-Braham, Amal; Djemaï, Mohamed; Busawon, Krishna
2014-01-01
This monograph provides readers with tools for the analysis, and control of systems with fewer control inputs than degrees of freedom to be controlled, i.e., underactuated systems. The text deals with the consequences of a lack of a general theory that would allow methodical treatment of such systems and the ad hoc approach to control design that often results, imposing a level of organization whenever the latter is lacking. The authors take as their starting point the construction of a graphical characterization or control flow diagram reflecting the transmission of generalized forces through the degrees of freedom. Underactuated systems are classified according to the three main structures by which this is found to happen—chain, tree, and isolated vertex—and control design procedures proposed. The procedure is applied to several well-known examples of underactuated systems: acrobot; pendubot; Tora system; ball and beam; inertia wheel; and robotic arm with elastic joint. The text is illustrated with MATL...
Analytical kinematics analysis and synthesis of planar mechanisms
Gans, Deborah
2013-01-01
Using computational techniques and a complex variable formulation, this book teaches the student of kinematics to handle increasingly difficult problems in both the analysis and design of mechanisms all based on the fundamental loop closure equation.
The Analysis and Development of a Mechanical Breadboard Structure
National Research Council Canada - National Science Library
Mikes, James A
2006-01-01
.... Following this analysis, a development team created a new novel structural system for a mechanical breadboard as the research indicated these components were both important to the overall system...
International Nuclear Information System (INIS)
Videla, F. A.; Schinca, D. C.; Scaffardi, L. B.; Torchia, G. A.; Moreno, P.; Mendez, C.; Giovanetti, L. J.; Ramallo Lopez, J. M.; Roso, L.
2010-01-01
Studies of fragmentation process of gold nanoparticles (Nps) in deionized water after generation by femtosecond laser ablation were performed. To analyze the fragmentation process, direct IR ultrafast pulses or super-continuum (SC) radiation focused in the colloidal solution were used in separate steps. IR pulses and SC generated externally in a sapphire crystal or directly inside the water were applied under low fluence regime. In the latter cases, to evaluate the effect on fragmentation of the different spectral bands present in the SC, we have determined different efficiency regions characterized by means of the product between the spectral response and the optical extinction spectrum corresponding to the initial Nps solution. From the analysis of this product function, we can conclude that the main fragmentation mechanism is due to linear absorption in the visible region. Likewise, the SC generated in water resulted more efficient than the SC obtained externally by a sapphire crystal. This fact may be attributed to the blue broadening of the water SC spectrum (as compared with the sapphire SC) due to the large intensity used for its generation. Transmission electron microscopy and small angle x-ray scattering measurements support the results found from optical extinction spectroscopy.
Analysis of costs and returns of mechanized fishing boat operations ...
African Journals Online (AJOL)
Analysis of costs and returns of mechanized fishing boat operations in India. KS Bose, PV Sarma. Abstract. This article makes an attempt to analyze the cost and returns of Mechanized Fishing Boat Operators (MFBO's) and the determinants of the selected MFBOs. The study is based on a sample of 180 MFBOs operating ...
Stress analysis in a functionally graded disc under mechanical loads ...
Indian Academy of Sciences (India)
Stress analysis in a functionally graded disc under mechanical loads and a steady state temperature distribution. HASAN ÇALLIO ˘GLU. Department of Mechanical Engineering, Pamukkale University, 20070,. Denizli, Turkey e-mail: hcallioglu@pau.edu.tr. MS received 25 November 2009; revised 12 August 2010; accepted.
Giant resonances in the deformed continuum
International Nuclear Information System (INIS)
Nakatsukasa, T.; Yabana, K.
2004-01-01
Giant resonances in the continuum for deformed nuclei are studied with the time-dependent Hartree-Fock (TDHF) theory in real time and real space. The continuum effect is effectively taken into account by introducing a complex Absorbing Boundary Condition (ABC). (orig.)
Physics of the continuum of borromean nuclei
Energy Technology Data Exchange (ETDEWEB)
Vaagen, J.S.; Rogde, T. [Dept. of Physics, Univ. of Bergen (Norway); Danilin, B.V. [RRC The Kurchatov Inst., Kurchatov, Moscow (Russian Federation); Ershov, S.N. [JINR, Dubna, Moscow (Russian Federation); Thompson, I.J. [Dept. of Physics, Univ. of Surrey, Guildford (United Kingdom); Zhukov, M.V. [Chalmers Univ. of Technology and Goeteborg Univ., Goeteborg (Sweden); RNBT Collaboration
1998-06-01
The continuum states of two-neutron halo nuclei are calculated in the method of hyperspherical harmonics. Using DWIA theory appropriate for dilute halo matter we have probed the structure of the low-lying {sup 6}He continuum via calculations of charge-exchange and inelastic scattering. (orig.)
Physical-Mechanisms Based Reliability Analysis For Emerging Technologies
2017-05-05
AFRL-AFOSR-VA-TR-2017-0095 PHYSICAL -MECHANISMS BASED RELIABILITY ANALYSIS FOR EMERGING TECHNOLOGIES Ron Schrimpf VANDERBILT UNIVERSITY 110 21ST...SUBTITLE PHYSICAL -MECHANISMS BASED RELIABILITY ANALYSIS FOR EMERGING TECHNOLOGIES 5a. CONTRACT NUMBER 5b. GRANT NUMBER FA9550-11-1-0307 5c. PROGRAM...which reliability models can be built. Thus, it is important to develop more predictive reliability models for advanced technologies, based on physical
From discrete particles to continuum fields near a boundary
Weinhart, Thomas; Thornton, Anthony Richard; Luding, Stefan; Bokhove, Onno
2012-01-01
An expression for the stress tensor near an external boundary of a discrete mechanical system is derived explicitly in terms of the constituents’ degrees of freedom and interaction forces. Starting point is the exact and general coarse graining formulation presented by Goldhirsch in [I.Goldhirsch, Gran.Mat., 12(3):239-252, 2010], which is consistent with the continuum equations everywhere but does not account for boundaries. Our extension accounts for the boundary interaction forces in a self...
Properties of warm nuclei in the quasi-continuum
Directory of Open Access Journals (Sweden)
Voinov A.
2010-03-01
Full Text Available Nuclear thermodynamic quantities are extracted from nuclear level densities measured with the CACTUS detector array at the Oslo Cyclotron Laboratory. The experiments are performed with light-particle inelastic or transfer reactions. A simple combinatorial model is used to describe the underlying mechanisms responsible for the exponential increasing level density as function of excitation energy. The calculated number of broken Cooper pairs and the parity distribution in continuum are discussed.
A quantum informed continuum model for ferroelectric and flexoelectric materials
Oates, William S.
2013-04-01
Correlations between quantum mechanics and continuum mechanics are investigated by exploring relations based on the electron density and electrostatic forces within an atomic lattice in ferroelectric materials. Theoretically, it is shown that anisotropic stress is dependent upon electrostatic forces that originate from the quadrupole density. This relation is directly determined if the nuclear charge and electron density are known. The result is an extension of the Hellmann-Feynman theory used to quantify stresses based on electrostatics. Further, flexoelectricity is found to be proportional to the next two higher order poles. These relations are obtained by correlating a nucleus-nucleus potential and nucleus-electron potential with the deformation gradient and second order gradient. An example is given for barium titanate by solving the electron density using density function theory (DFT) calculations. Changes in energy and stress under different lattice geometric constraints are modeled and compared to nonlinear continuum mechanics to understand differences in formulating a model directly from DFT calculations versus a nonlinear continuum model that uses polarization versus the quadrupole density as the order parameter.
Chemolli, Emanuela; Gagné, Marylène
2014-06-01
Self-determination theory (SDT) proposes a multidimensional conceptualization of motivation in which the different regulations are said to fall along a continuum of self-determination. The continuum has been used as a basis for using a relative autonomy index as a means to create motivational scores. Rasch analysis was used to verify the continuum structure of the Multidimensional Work Motivation Scale and of the Academic Motivation Scale. We discuss the concept of continuum against SDT's conceptualization of motivation and argue against the use of the relative autonomy index on the grounds that evidence for a continuum structure underlying the regulations is weak and because the index is statistically problematic. We suggest exploiting the full richness of SDT's multidimensional conceptualization of motivation through the use of alternative scoring methods when investigating motivational dynamics across life domains.
The quest for truth, particularly in mechanics
Czech Academy of Sciences Publication Activity Database
Okrouhlík, Miloslav
2013-01-01
Roč. 19, č. 4 (2013), s. 253-272 ISSN 1736-6038 Institutional support: RVO:61388998 Keywords : continuum mechanics of solids * finite element analysis * validity of models * definitions of terms Subject RIV: BI - Acoustics http://www.kirj.ee/23324/
Directory of Open Access Journals (Sweden)
Yao Yu
2010-01-01
Full Text Available The kinematics analysis method of a novel 3-DOF wind tunnel mechanism based on cable-driven parallel mechanism is provided. Rodrigues' parameters are applied to express the transformation matrix of the wire-driven mechanism in the paper. The analytical forward kinematics model is described as three quadratic equations using three Rodridgues' parameters based on the fundamental theory of parallel mechanism. Elimination method is used to remove two of the variables, so that an eighth-order polynomial with one variable is derived. From the equation, the eight sets of Rodridgues' parameters and corresponding Euler angles for the forward kinematical problem can be obtained. In the end, numerical example of both forward and inverse kinematics is included to demonstrate the presented forward-kinematics solution method. The numerical results show that the method for the position analysis of this mechanism is effective.
International Nuclear Information System (INIS)
Lee, T.D.
1985-01-01
This paper reviews the role of time throughout all phases of mechanics: classical mechanics, non-relativistic quantum mechanics, and relativistic quantum theory. As an example of the relativistic quantum field theory, the case of a massless scalar field interacting with an arbitrary external current is discussed. The comparison between the new discrete theory and the usual continuum formalism is presented. An example is given of a two-dimensional random lattice and its duel. The author notes that there is no evidence that the discrete mechanics is more appropriate than the usual continuum mechanics
Parallel algorithms for continuum dynamics
International Nuclear Information System (INIS)
Hicks, D.L.; Liebrock, L.M.
1987-01-01
Simply porting existing parallel programs to a new parallel processor may not achieve the full speedup possible; to achieve the maximum efficiency may require redesigning the parallel algorithms for the specific architecture. The authors discuss here parallel algorithms that were developed first for the HEP processor and then ported to the CRAY X-MP/4, the ELXSI/10, and the Intel iPSC/32. Focus is mainly on the most recent parallel processing results produced, i.e., those on the Intel Hypercube. The applications are simulations of continuum dynamics in which the momentum and stress gradients are important. Examples of these are inertial confinement fusion experiments, severe breaks in the coolant system of a reactor, weapons physics, shock-wave physics. Speedup efficiencies on the Intel iPSC Hypercube are very sensitive to the ratio of communication to computation. Great care must be taken in designing algorithms for this machine to avoid global communication. This is much more critical on the iPSC than it was on the three previous parallel processors
Continuum methods in lattice perturbation theory
International Nuclear Information System (INIS)
Becher, Thomas G
2002-01-01
We show how methods of continuum perturbation theory can be used to simplify perturbative lattice calculations. We use the technique of asymptotic expansions to expand lattice loop integrals around the continuum limit. After the expansion, all nontrivial dependence on momenta and masses is encoded in continuum loop integrals and the only genuine lattice integrals left are tadpole integrals. Using integration-by-parts relations all of these can be expressed in terms of a small number of master integrals. Four master integrals are needed for bosonic one loop integrals, sixteen in QCD with Wilson or staggered fermions
Area Regge calculus and continuum limit
International Nuclear Information System (INIS)
Khatsymovsky, V.M.
2002-01-01
Encountered in the literature generalisations of general relativity to independent area variables are considered, the discrete (generalised Regge calculus) and continuum ones. The generalised Regge calculus can be either with purely area variables or, as we suggest, with area tensor-connection variables. Just for the latter, in particular, we prove that in analogy with corresponding statement in ordinary Regge calculus (by Feinberg, Friedberg, Lee and Ren), passing to the (appropriately defined) continuum limit yields the generalised continuum area tensor-connection general relativity
A Concentric Tube Continuum Robot with Piezoelectric Actuation for MRI-Guided Closed-Loop Targeting
Su, Hao; Li, Gang; Rucker, D. Caleb; Webster, Robert J.; Fischer, Gregory S.
2016-01-01
This paper presents the design, modeling and experimental evaluation of a magnetic resonance imaging (MRI)-compatible concentric tube continuum robotic system. This system enables MRI-guided deployment of a precurved and steerable concentric tube continuum mechanism, and is suitable for clinical applications where a curved trajectory is needed. This compact 6 degree-of-freedom (DOF) robotic system is piezoelectrically-actuated, and allows simultaneous robot motion and imaging with no visually...
Nano-Continuum Modeling of a Nuclear Glass Specimen Altered for 25 Years
Energy Technology Data Exchange (ETDEWEB)
Steefel, Carl
2014-01-06
The purpose of this contribution is to report on preliminary nano-continuum scale modeling of nuclear waste glass corrosion. The focus of the modeling is an experiment involving a French glass SON68 specimen leached for 25 years in a granitic environment. In this report, we focus on capturing the nano-scale concentration profiles. We use a high resolution continuum model with a constant grid spacing of 1 nanometer to investigate the glass corrosion mechanisms.
Resilience among patients across the cancer continuum: diverse perspectives.
Molina, Yamile; Yi, Jean C; Martinez-Gutierrez, Javiera; Reding, Kerryn W; Yi-Frazier, Joyce P; Rosenberg, Abby R
2014-02-01
Each phase of the cancer experience profoundly affects patients' lives. Much of the literature has focused on negative consequences of cancer; however, the study of resilience may enable providers to promote more positive psychosocial outcomes before, during, and after the cancer experience. The current review describes the ways in which elements of resilience have been defined and studied at each phase of the cancer continuum. Extensive literature searches were conducted to find studies assessing resilience during one or more stages of the adult cancer continuum. For all phases of the cancer continuum, resilience descriptions included preexisting or baseline characteristics, such as demographics and personal attributes (e.g., optimism, social support), mechanisms of adaptation, such as coping and medical experiences (e.g., positive provider communication), as well as psychosocial outcomes, such as growth and quality of life. Promoting resilience is a critical element of patient psychosocial care. Nurses may enable resilience by recognizing and promoting certain baseline characteristics and optimizing mechanisms of adaptation.
Multigrid treatment of implicit continuum diffusion
Francisquez, Manaure; Zhu, Ben; Rogers, Barrett
2017-10-01
Implicit treatment of diffusive terms of various differential orders common in continuum mechanics modeling, such as computational fluid dynamics, is investigated with spectral and multigrid algorithms in non-periodic 2D domains. In doubly periodic time dependent problems these terms can be efficiently and implicitly handled by spectral methods, but in non-periodic systems solved with distributed memory parallel computing and 2D domain decomposition, this efficiency is lost for large numbers of processors. We built and present here a multigrid algorithm for these types of problems which outperforms a spectral solution that employs the highly optimized FFTW library. This multigrid algorithm is not only suitable for high performance computing but may also be able to efficiently treat implicit diffusion of arbitrary order by introducing auxiliary equations of lower order. We test these solvers for fourth and sixth order diffusion with idealized harmonic test functions as well as a turbulent 2D magnetohydrodynamic simulation. It is also shown that an anisotropic operator without cross-terms can improve model accuracy and speed, and we examine the impact that the various diffusion operators have on the energy, the enstrophy, and the qualitative aspect of a simulation. This work was supported by DOE-SC-0010508. This research used resources of the National Energy Research Scientific Computing Center (NERSC).
Yan, J. W.; Tong, L. H.; Xiang, Ping
2017-12-01
Free vibration behaviors of single-walled boron nitride nanotubes are investigated using a computational mechanics approach. Tersoff-Brenner potential is used to reflect atomic interaction between boron and nitrogen atoms. The higher-order Cauchy-Born rule is employed to establish the constitutive relationship for single-walled boron nitride nanotubes on the basis of higher-order gradient continuum theory. It bridges the gaps between the nanoscale lattice structures with a continuum body. A mesh-free modeling framework is constructed, using the moving Kriging interpolation which automatically satisfies the higher-order continuity, to implement numerical simulation in order to match the higher-order constitutive model. In comparison with conventional atomistic simulation methods, the established atomistic-continuum multi-scale approach possesses advantages in tackling atomic structures with high-accuracy and high-efficiency. Free vibration characteristics of single-walled boron nitride nanotubes with different boundary conditions, tube chiralities, lengths and radii are examined in case studies. In this research, it is pointed out that a critical radius exists for the evaluation of fundamental vibration frequencies of boron nitride nanotubes; opposite trends can be observed prior to and beyond the critical radius. Simulation results are presented and discussed.
Loop quantization as a continuum limit
International Nuclear Information System (INIS)
Manrique, Elisa; Oeckl, Robert; Weber, Axel; Zapata, Jose A
2006-01-01
We present an implementation of Wilson's renormalization group and a continuum limit tailored for loop quantization. The dynamics of loop-quantized theories is constructed as a continuum limit of the dynamics of effective theories. After presenting the general formalism we show as a first explicit example the 2D Ising field theory, an interacting relativistic quantum field theory with local degrees of freedom quantized by loop quantization techniques
Isogeometric Analysis and Shape Optimization in Fluid Mechanics
DEFF Research Database (Denmark)
Nielsen, Peter Nørtoft
This thesis brings together the fields of fluid mechanics, as the study of fluids and flows, isogeometric analysis, as a numerical method to solve engineering problems using computers, and shape optimization, as the art of finding "best" shapes of objects based on some notion of goodness. The flow...... unites the power to solve complex engineering problems from finite element analysis (FEA) with the ability to effectively represent complex shapes from computer aided design (CAD). The methodology is appealing for flow modeling purposes also due to the inherent high regularity of velocity and pressure...... approximations, and for shape optimization purposes also due to its tight connection between the analysis and geometry models. The thesis is initiated by short introductions to fluid mechanics, and to the building blocks of isogeometric analysis. As the first contribution of the thesis, a detailed description...
Mechanical Property Analysis of Circular Polymer Membrane under Uniform Pressure
Jianbing, Sang; Xiang, Li; Sufang, Xing; Wenjia, Wang
2017-01-01
Mechanical property analysis of circular hyperelastic polymer membrane under uniform pressure has been researched in this work. The polymer membrane material is assumed to be homogeneous and isotropic and incompressibility of materials has been considered. Based on the modified stain energy function from Gao and nonmomental theory of axial symmetry thin shell, finite deformation analysis of polymer membrane under uniform pressure has been proposed in current configuration and governing equati...
Time-dependent reliability sensitivity analysis of motion mechanisms
International Nuclear Information System (INIS)
Wei, Pengfei; Song, Jingwen; Lu, Zhenzhou; Yue, Zhufeng
2016-01-01
Reliability sensitivity analysis aims at identifying the source of structure/mechanism failure, and quantifying the effects of each random source or their distribution parameters on failure probability or reliability. In this paper, the time-dependent parametric reliability sensitivity (PRS) analysis as well as the global reliability sensitivity (GRS) analysis is introduced for the motion mechanisms. The PRS indices are defined as the partial derivatives of the time-dependent reliability w.r.t. the distribution parameters of each random input variable, and they quantify the effect of the small change of each distribution parameter on the time-dependent reliability. The GRS indices are defined for quantifying the individual, interaction and total contributions of the uncertainty in each random input variable to the time-dependent reliability. The envelope function method combined with the first order approximation of the motion error function is introduced for efficiently estimating the time-dependent PRS and GRS indices. Both the time-dependent PRS and GRS analysis techniques can be especially useful for reliability-based design. This significance of the proposed methods as well as the effectiveness of the envelope function method for estimating the time-dependent PRS and GRS indices are demonstrated with a four-bar mechanism and a car rack-and-pinion steering linkage. - Highlights: • Time-dependent parametric reliability sensitivity analysis is presented. • Time-dependent global reliability sensitivity analysis is presented for mechanisms. • The proposed method is especially useful for enhancing the kinematic reliability. • An envelope method is introduced for efficiently implementing the proposed methods. • The proposed method is demonstrated by two real planar mechanisms.
Mechanisms of subsidence for induced damage and techniques for analysis
International Nuclear Information System (INIS)
Drumm, E.C.; Bennett, R.M.; Kane, W.F.
1988-01-01
Structural damage due to mining induced subsidence is a function of the nature of the structure and its position on the subsidence profile. A point on the profile may be in the tensile zone, the compressive zone, or the no-deformation zone at the bottom of the profile. Damage to structures in the tension zone is primarily due to a reduction of support during vertical displacement of the ground surface, and to shear stresses between the soil and structure resulting from horizontal displacements. The damage mechanisms due to tension can be investigated effectively using a two-dimensional plane stress analysis. Structures in the compression zone are subjected to positive moments in the footing and large compressive horizontal stresses in the foundation walls. A plane strain analysis of the foundation wall is utilized to examine compression zone damage mechanisms. The structural aspects affecting each mechanism are identified and potential mitigation techniques are summarized
Mechanical property analysis of kenaf–glass fibre reinforced ...
Indian Academy of Sciences (India)
... to predict the mechanical properties by using NX Nastran 9.0 software. The experimental results were compared with the predicted values and a high correlation between the results was observed. The morphology of the fractured surfaces of the composites was analysed using a scanning electron microscopy analysis.
Experimental analysis of nonlinear problems in solid mechanics
International Nuclear Information System (INIS)
1982-01-01
The booklet presents abstracts of papers from the Euromech Colloqium No. 152 held from Sept. 20th to 24th, 1982 in Wuppertal, Federal Republic of Germany. All the papers are dealing with Experimental Analysis of Nonlinear Problems in Solid Mechanics. (RW)
An Analysis of the Waste Water Treatment Maintenance Mechanic Occupation.
Clark, Anthony B.; And Others
The general purpose of the occupational analysis is to provide workable, basic information dealing with the many and varied duties performed in the waste water treatment mechanics occupation. The document opens with a brief introduction followed by a job description. The bulk of the document is presented in table form. Twelve duties are broken…
Analysis of a Pediatric Home Mechanical Ventilator Population.
Amirnovin, Rambod; Aghamohammadi, Sara; Riley, Carley; Woo, Marlyn S; Del Castillo, Sylvia
2018-03-06
The population of children requiring home mechanical ventilation has evolved over the years and has grown to include a variety of diagnoses and needs that have led to changes in the care of this unique population. The purpose of this study was to provide a descriptive analysis of pediatric patients requiring home mechanical ventilation after hospitalization and how the evolution of this technology has impacted their care. A retrospective, observational, longitudinal analysis of 164 children enrolled in a university-affiliated home mechanical ventilation program over 26 years was performed. Data included each child's primary diagnosis, date of tracheostomy placement, duration of mechanical ventilation during hospitalization that consisted of home mechanical ventilator initiation, total length of pediatric ICU stay, ventilator settings at time of discharge from pediatric ICU, and disposition (home, facility, or died). Univariate, bivariate, and regression analysis was used as appropriate. The most common diagnosis requiring the use of home mechanical ventilation was neuromuscular disease (53%), followed by chronic pulmonary disease (29%). The median length of stay in the pediatric ICU decreased significantly after the implementation of a ventilator ward (70 d [30-142] vs 36 d [18-67], P = .02). The distribution of subjects upon discharge was home (71%), skilled nursing facility (24%), and died (4%), with an increase in the proportion of subjects discharged on PEEP and those going to nursing facilities over time ( P = 0.02). The evolution of home mechanical ventilation has allowed earlier transition out of the pediatric ICU and with increasing disposition to skilled nursing facilities over time. There has also been a change in ventilator management, including increased use of PEEP upon discharge, possibly driven by changes in ventilators and in-patient practice patterns. Copyright © 2018 by Daedalus Enterprises.
Failure analysis and seal life prediction for contacting mechanical seals
Sun, J. J.; He, X. Y.; Wei, L.; Feng, X.
2008-11-01
Fault tree analysis method was applied to quantitatively investigate the causes of the leakage failure of mechanical seals. It is pointed out that the change of the surface topography is the main reasons causing the leakage of mechanical seals under the condition of constant preloads. Based on the fractal geometry theory, the relationship between the surface topography and working time were investigated by experiments, and the effects of unit load acting on seal face on leakage path in a mechanical seal were analyzed. The model of predicting seal life of mechanical seals was established on the basis of the relationship between the surface topography and working time and allowable leakage. The seal life of 108 mechanical seal operating at the system of diesel fuel storage and transportation was predicted and the problem of the condition monitoring for the long-period operation of mechanical seal was discussed by this method. The research results indicate that the method of predicting seal life of mechanical seals is feasible, and also is foundation to make scheduled maintenance time and to achieve safe-reliability and low-cost operation for industrial devices.
Diagnostic Reasoning across the Medical Education Continuum
Directory of Open Access Journals (Sweden)
C. Scott Smith
2014-07-01
Full Text Available We aimed to study linguistic and non-linguistic elements of diagnostic reasoning across the continuum of medical education. We performed semi-structured interviews of premedical students, first year medical students, third year medical students, second year internal medicine residents, and experienced faculty (ten each as they diagnosed three common causes of dyspnea. A second observer recorded emotional tone. All interviews were digitally recorded and blinded transcripts were created. Propositional analysis and concept mapping were performed. Grounded theory was used to identify salient categories and transcripts were scored with these categories. Transcripts were then unblinded. Systematic differences in propositional structure, number of concept connections, distribution of grounded theory categories, episodic and semantic memories, and emotional tone were identified. Summary concept maps were created and grounded theory concepts were explored for each learning level. We identified three major findings: (1 The “apprentice effect” in novices (high stress and low narrative competence; (2 logistic concept growth in intermediates; and (3 a cognitive state transition (between analytical and intuitive approaches in experts. These findings warrant further study and comparison.
International Nuclear Information System (INIS)
Zorski, Henryk; Bazanski, Stanislaw; Gutowski, Roman; Slawianowski, Jan; Wilmanski, Krysztof; Wozniak, Czeslaw
1992-01-01
In the last 3 decades the field of mechanics has seen spectacular progress due to the demand for applications in problems of cosmology, thermonuclear fusion, metallurgy, etc. This book provides a broad and thorough overview on the foundations of mechanics. It discusses theoretical mechanics and continuum mechanics, as well as phenomenological thermodynamics, quantum mechanics and relativistic mechanics. Each chapter presents the basic physical facts of interest without going into details and derivations and without using advanced mathematical formalism. The first part constitutes a classical exposition of Lagrange's and Hamiltonian's analytical mechanics on which most of the continuum theory is based. The section on continuum mechanics focuses mainly on the axiomatic foundations, with many pointers for further research in this area. Special attention is given to modern continuum thermodynamics, both for the foundations and applications. A section on quantum mechanics is also included, since the phenomenological description of various quantum phenomena is becoming of increasing importance. refs.; figs.; tabs
Identification of a transcriptional signature for the wound healing continuum.
Peake, Matthew A; Caley, Mathew; Giles, Peter J; Wall, Ivan; Enoch, Stuart; Davies, Lindsay C; Kipling, David; Thomas, David W; Stephens, Phil
2014-01-01
There is a spectrum/continuum of adult human wound healing outcomes ranging from the enhanced (nearly scarless) healing observed in oral mucosa to scarring within skin and the nonhealing of chronic skin wounds. Central to these outcomes is the role of the fibroblast. Global gene expression profiling utilizing microarrays is starting to give insight into the role of such cells during the healing process, but no studies to date have produced a gene signature for this wound healing continuum. Microarray analysis of adult oral mucosal fibroblast (OMF), normal skin fibroblast (NF), and chronic wound fibroblast (CWF) at 0 and 6 hours post-serum stimulation was performed. Genes whose expression increases following serum exposure in the order OMF healing phenotype (the dysfunctional healing group), whereas genes with the converse pattern are potentially associated with a positive/preferential healing phenotype (the enhanced healing group). Sixty-six genes in the enhanced healing group and 38 genes in the dysfunctional healing group were identified. Overrepresentation analysis revealed pathways directly and indirectly associated with wound healing and aging and additional categories associated with differentiation, development, and morphogenesis. Knowledge of this wound healing continuum gene signature may in turn assist in the therapeutic assessment/treatment of a patient's wounds. © 2014 The Authors. Wound Repair and Regeneration published by Wiley Periodicals, Inc. on behalf of Wound Healing Society.
Applications of Digital Image Analysis in Experimental Mechanics
DEFF Research Database (Denmark)
Lyngbye, J. : Ph.D.
The present thesis "Application of Digital Image Analysis in Experimental Mechanics" has been prepared as a part of Janus Lyngbyes Ph.D. study during the period December 1988 to June 1992 at the Department of Building technology and Structural Engineering, University of Aalborg, Denmark....... In this thesis attention will be focused on optimal use and analysis of the information of digital images. This is realized during investigation and application of parametric methods in digital image analysis. The parametric methods will be implemented in applications representative for the area of experimental...
Haro 11: Where is the Lyman Continuum Source?
Energy Technology Data Exchange (ETDEWEB)
Keenan, Ryan P.; Oey, M. S. [Department of Astronomy, University of Michigan, 1085 South University Avenue, Ann Arbor, MI 48109 (United States); Jaskot, Anne E. [Department of Astronomy, Smith College, Northampton, MA 01063 (United States); James, Bethan L. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
2017-10-10
Identifying the mechanism by which high-energy Lyman continuum (LyC) photons escaped from early galaxies is one of the most pressing questions in cosmic evolution. Haro 11 is the best known local LyC-leaking galaxy, providing an important opportunity to test our understanding of LyC escape. The observed LyC emission in this galaxy presumably originates from one of the three bright, photoionizing knots known as A, B, and C. It is known that Knot C has strong Ly α emission, and Knot B hosts an unusually bright ultraluminous X-ray source, which may be a low-luminosity active galactic nucleus. To clarify the LyC source, we carry out ionization-parameter mapping (IPM) by obtaining narrow-band imaging from the Hubble Space Telescope WFC3 and ACS cameras to construct spatially resolved ratio maps of [O iii]/[O ii] emission from the galaxy. IPM traces the ionization structure of the interstellar medium and allows us to identify optically thin regions. To optimize the continuum subtraction, we introduce a new method for determining the best continuum scale factor derived from the mode of the continuum-subtracted, image flux distribution. We find no conclusive evidence of LyC escape from Knots B or C, but instead we identify a high-ionization region extending over at least 1 kpc from Knot A. This knot shows evidence of an extremely young age (≲1 Myr), perhaps containing very massive stars (>100 M {sub ⊙}). It is weak in Ly α , so if it is confirmed as the LyC source, our results imply that LyC emission may be independent of Ly α emission.
Wang, Xiaoling; Meng, Shuo; Han, Jingshi
2017-10-03
The Bacterial flagellar filament can undergo a polymorphic phase transition in response to both mechanical and chemical variations in vitro and in vivo environments. Under mechanical stimuli, such as viscous flow or forces induced by motor rotation, the filament changes its phase from left-handed normal (N) to right-handed semi-coiled (SC) via phase nucleation and growth. Our detailed mechanical analysis of existing experiments shows that both torque and bending moment contribute to the filament phase transition. In this paper, we establish a non-convex and non-local continuum model based on the Ginzburg-Landau theory to describe main characteristics of the filament phase transition such as new-phase nucleation, growth, propagation and the merging of neighboring interfaces. The finite element method (FEM) is adopted to simulate the phase transition under a displacement-controlled loading condition (rotation angle and bending deflection). We show that new-phase nucleation corresponds to the maximum torque and bending moment at the stuck end of the filament. The hysteresis loop in the loading and unloading curves indicates energy dissipation. When the new phase grows and propagates, torque and bending moment remain static. We also find that there is a drop in load when the two interfaces merge, indicating a concomitant reduction in the interfacial energy. Finally, the interface thickness is governed by the coefficients of the gradient of order parameters in the non-local interface energy. Our continuum theory and the finite element method provide a method to study the mechanical behavior of such biomaterials. Copyright © 2017 Elsevier Ltd. All rights reserved.
Multiscale synchrony behaviors of paired financial time series by 3D multi-continuum percolation
Wang, M.; Wang, J.; Wang, B. T.
2018-02-01
Multiscale synchrony behaviors and nonlinear dynamics of paired financial time series are investigated, in an attempt to study the cross correlation relationships between two stock markets. A random stock price model is developed by a new system called three-dimensional (3D) multi-continuum percolation system, which is utilized to imitate the formation mechanism of price dynamics and explain the nonlinear behaviors found in financial time series. We assume that the price fluctuations are caused by the spread of investment information. The cluster of 3D multi-continuum percolation represents the cluster of investors who share the same investment attitude. In this paper, we focus on the paired return series, the paired volatility series, and the paired intrinsic mode functions which are decomposed by empirical mode decomposition. A new cross recurrence quantification analysis is put forward, combining with multiscale cross-sample entropy, to investigate the multiscale synchrony of these paired series from the proposed model. The corresponding research is also carried out for two China stock markets as comparison.
Error analysis of mechanical system and wavelength calibration of monochromator
Zhang, Fudong; Chen, Chen; Liu, Jie; Wang, Zhihong
2018-02-01
This study focuses on improving the accuracy of a grating monochromator on the basis of the grating diffraction equation in combination with an analysis of the mechanical transmission relationship between the grating, the sine bar, and the screw of the scanning mechanism. First, the relationship between the mechanical error in the monochromator with the sine drive and the wavelength error is analyzed. Second, a mathematical model of the wavelength error and mechanical error is developed, and an accurate wavelength calibration method based on the sine bar's length adjustment and error compensation is proposed. Based on the mathematical model and calibration method, experiments using a standard light source with known spectral lines and a pre-adjusted sine bar length are conducted. The model parameter equations are solved, and subsequent parameter optimization simulations are performed to determine the optimal length ratio. Lastly, the length of the sine bar is adjusted. The experimental results indicate that the wavelength accuracy is ±0.3 nm, which is better than the original accuracy of ±2.6 nm. The results confirm the validity of the error analysis of the mechanical system of the monochromator as well as the validity of the calibration method.
Scaling analysis for the investigation of slip mechanisms in nanofluids.
Savithiri, S; Pattamatta, Arvind; Das, Sarit K
2011-07-26
The primary objective of this study is to investigate the effect of slip mechanisms in nanofluids through scaling analysis. The role of nanoparticle slip mechanisms in both water- and ethylene glycol-based nanofluids is analyzed by considering shape, size, concentration, and temperature of the nanoparticles. From the scaling analysis, it is found that all of the slip mechanisms are dominant in particles of cylindrical shape as compared to that of spherical and sheet particles. The magnitudes of slip mechanisms are found to be higher for particles of size between 10 and 80 nm. The Brownian force is found to dominate in smaller particles below 10 nm and also at smaller volume fraction. However, the drag force is found to dominate in smaller particles below 10 nm and at higher volume fraction. The effect of thermophoresis and Magnus forces is found to increase with the particle size and concentration. In terms of time scales, the Brownian and gravity forces act considerably over a longer duration than the other forces. For copper-water-based nanofluid, the effective contribution of slip mechanisms leads to a heat transfer augmentation which is approximately 36% over that of the base fluid. The drag and gravity forces tend to reduce the Nusselt number of the nanofluid while the other forces tend to enhance it.
Scaling analysis for the investigation of slip mechanisms in nanofluids
Directory of Open Access Journals (Sweden)
Savithiri S
2011-01-01
Full Text Available Abstract The primary objective of this study is to investigate the effect of slip mechanisms in nanofluids through scaling analysis. The role of nanoparticle slip mechanisms in both water- and ethylene glycol-based nanofluids is analyzed by considering shape, size, concentration, and temperature of the nanoparticles. From the scaling analysis, it is found that all of the slip mechanisms are dominant in particles of cylindrical shape as compared to that of spherical and sheet particles. The magnitudes of slip mechanisms are found to be higher for particles of size between 10 and 80 nm. The Brownian force is found to dominate in smaller particles below 10 nm and also at smaller volume fraction. However, the drag force is found to dominate in smaller particles below 10 nm and at higher volume fraction. The effect of thermophoresis and Magnus forces is found to increase with the particle size and concentration. In terms of time scales, the Brownian and gravity forces act considerably over a longer duration than the other forces. For copper-water-based nanofluid, the effective contribution of slip mechanisms leads to a heat transfer augmentation which is approximately 36% over that of the base fluid. The drag and gravity forces tend to reduce the Nusselt number of the nanofluid while the other forces tend to enhance it.
Error analysis of mechanical system and wavelength calibration of monochromator.
Zhang, Fudong; Chen, Chen; Liu, Jie; Wang, Zhihong
2018-02-01
This study focuses on improving the accuracy of a grating monochromator on the basis of the grating diffraction equation in combination with an analysis of the mechanical transmission relationship between the grating, the sine bar, and the screw of the scanning mechanism. First, the relationship between the mechanical error in the monochromator with the sine drive and the wavelength error is analyzed. Second, a mathematical model of the wavelength error and mechanical error is developed, and an accurate wavelength calibration method based on the sine bar's length adjustment and error compensation is proposed. Based on the mathematical model and calibration method, experiments using a standard light source with known spectral lines and a pre-adjusted sine bar length are conducted. The model parameter equations are solved, and subsequent parameter optimization simulations are performed to determine the optimal length ratio. Lastly, the length of the sine bar is adjusted. The experimental results indicate that the wavelength accuracy is ±0.3 nm, which is better than the original accuracy of ±2.6 nm. The results confirm the validity of the error analysis of the mechanical system of the monochromator as well as the validity of the calibration method.
Mechanical and Spectroscopic Analysis of Retrieved/Failed Dental Implants
Directory of Open Access Journals (Sweden)
Umer Daood
2017-11-01
Full Text Available The purpose of this study was to examine surface alterations and bone formation on the surface of failed dental implants (Straumann [ST] and TiUnite [TiUn] removed due to any biological reason. In addition, failure analysis was performed to test mechanical properties. Dental implants (n = 38 from two manufacturers were collected and subjected to chemical cleaning. The presence of newly formed hydroxyapatite bone around failed implants was evaluated using micro-Raman spectroscopy. Scanning electron microscopy was used to identify surface defects. Mechanical testing was performed using a Minneapolis servo-hydraulic system (MTS along with indentation using a universal testing machine and average values were recorded. A statistical analysis of mechanical properties was done using an unpaired t test, and correlation between observed defects was evaluated using Chi-square (p = 0.05. Apatite-formation was evident in both implants, but was found qualitatively more in the ST group. No significant difference was found in indentation between the two groups (p > 0.05. The percentage of “no defects” was significantly lower in the ST group (71%. Crack-like and full-crack defects were observed in 49% and 39% of TiUn. The ST group showed 11,061 cycles to failure as compared with 10,021 cycles in the TiUnite group. Implant failure mechanisms are complex with a combination of mechanical and biological reasons and these factors are variable with different implant systems.
Dynamic Response of Linear Mechanical Systems Modeling, Analysis and Simulation
Angeles, Jorge
2012-01-01
Dynamic Response of Linear Mechanical Systems: Modeling, Analysis and Simulation can be utilized for a variety of courses, including junior and senior-level vibration and linear mechanical analysis courses. The author connects, by means of a rigorous, yet intuitive approach, the theory of vibration with the more general theory of systems. The book features: A seven-step modeling technique that helps structure the rather unstructured process of mechanical-system modeling A system-theoretic approach to deriving the time response of the linear mathematical models of mechanical systems The modal analysis and the time response of two-degree-of-freedom systems—the first step on the long way to the more elaborate study of multi-degree-of-freedom systems—using the Mohr circle Simple, yet powerful simulation algorithms that exploit the linearity of the system for both single- and multi-degree-of-freedom systems Examples and exercises that rely on modern computational toolboxes for both numerical and symbolic compu...
Mechanical Analysis Of Limestone In Jaya, Lhong, And Lhoknga
Directory of Open Access Journals (Sweden)
Raihan .
2012-09-01
Full Text Available Research about mechanical analysis of limestone in District Jaya, Lhong, and Lhoknga has been done from Dec. 2011 to Mei 2012. This study aim is to classify the limestones based on physical and mechanical tests as well as identify opportunities limestone utilization in accordance with the SII 0378-80 as a condition of quality natural stone for building. Research have been done by testing compressive strength, modulus Young, wear, specific gravity, porosity, and absorption. The result shows that the limestones are qualified natural stone for building the foundation, curbstone, stone and ornamental stone or paste.
Terahertz mechanical vibrations in lysozyme: Raman spectroscopy vs modal analysis
Carpinteri, Alberto; Lacidogna, Giuseppe; Piana, Gianfranco; Bassani, Andrea
2017-07-01
The mechanical behaviour of proteins is receiving an increasing attention from the scientific community. Recently it has been suggested that mechanical vibrations play a crucial role in controlling structural configuration changes (folding) which govern proteins biological function. The mechanism behind protein folding is still not completely understood, and many efforts are being made to investigate this phenomenon. Complex molecular dynamics simulations and sophisticated experimental measurements are conducted to investigate protein dynamics and to perform protein structure predictions; however, these are two related, although quite distinct, approaches. Here we investigate mechanical vibrations of lysozyme by Raman spectroscopy and linear normal mode calculations (modal analysis). The input mechanical parameters to the numerical computations are taken from the literature. We first give an estimate of the order of magnitude of protein vibration frequencies by considering both classical wave mechanics and structural dynamics formulas. Afterwards, we perform modal analyses of some relevant chemical groups and of the full lysozyme protein. The numerical results are compared to experimental data, obtained from both in-house and literature Raman measurements. In particular, the attention is focused on a large peak at 0.84 THz (29.3 cm-1) in the Raman spectrum obtained analyzing a lyophilized powder sample.
Energy Technology Data Exchange (ETDEWEB)
Resano, Martín, E-mail: mresano@unizar.es [Department of Analytical Chemistry, Aragón Institute of Engineering Research (I3A), University of Zaragoza, Pedro Cerbuna 12, 50009 Zaragoza (Spain); Flórez, María del Rosario [Department of Analytical Chemistry, Aragón Institute of Engineering Research (I3A), University of Zaragoza, Pedro Cerbuna 12, 50009 Zaragoza (Spain); Queralt, Ignasi [Institute of Earth Sciences Jaume Almera ICTJA-CSIC, Sole Sabarís s/n, 08028 Barcelona (Spain); Marguí, Eva [Department of Chemistry, Faculty of Sciences, Universitat de Girona, Campus Montilivi s/n, 17071 Girona (Spain)
2015-03-01
This work investigates the potential of high-resolution continuum source graphite furnace atomic absorption spectrometry for the direct determination of Pd, Pt and Rh in two samples of very different nature. While analysis of active pharmaceutical ingredients is straightforward and it is feasible to minimize matrix effects, to the point that calibration can be carried out against aqueous standard solutions, the analysis of used automobile catalysts is more challenging requiring the addition of a chemical modifier (NH{sub 4}F·HF) to help in releasing the analytes, a more vigorous temperature program and the use of a solid standard (CRM ERM®-EB504) for calibration. However, in both cases it was possible to obtain accurate results and precision values typically better than 10% RSD in a fast and simple way, while only two determinations are needed for the three analytes, since Pt and Rh can be simultaneously monitored in both types of samples. Overall, the methods proposed seem suited for the determination of these analytes in such types of samples, offering a greener and faster alternative that circumvents the traditional problems associated with sample digestion, requiring a small amount of sample only (0.05 mg per replicate for catalysts, and a few milligrams for the pharmaceuticals) and providing sufficient sensitivity to easily comply with regulations. The LODs achieved were 6.5 μg g{sup −1} (Pd), 8.3 μg g{sup −1} (Pt) and 9.3 μg g{sup −1} (Rh) for catalysts, which decreased to 0.08 μg g{sup −1} (Pd), 0.15 μg g{sup −1} (Pt) and 0.10 μg g{sup −1} (Rh) for pharmaceuticals. - Highlights: • Solid sampling HR CS GFAAS permits the fast and direct determination of Pd, Pt and Rh. • 2 determinations suffice for the 3 elements (2 of them can be measured simultaneously). • Samples as different as car catalysts and pharmaceuticals can be accurately analyzed. • Aqueous standards (pharmaceuticals) or a solid CRM (catalysts) is used for calibration.
A Geometry Deformation Model for Braided Continuum Manipulators
Directory of Open Access Journals (Sweden)
S. M. Hadi Sadati
2017-06-01
Full Text Available Continuum manipulators have gained significant attention in the robotic community due to their high dexterity, deformability, and reachability. Modeling of such manipulators has been shown to be very complex and challenging. Despite many research attempts, a general and comprehensive modeling method is yet to be established. In this paper, for the first time, we introduce the bending effect in the model of a braided extensile pneumatic actuator with both stiff and bendable threads. Then, the effect of the manipulator cross-section deformation on the constant curvature and variable curvature models is investigated using simple analytical results from a novel geometry deformation method and is compared to experimental results. We achieve 38% mean reference error simulation accuracy using our constant curvature model for a braided continuum manipulator in presence of body load and 10% using our variable curvature model in presence of extensive external loads. With proper model assumptions and taking to account the cross-section deformation, a 7–13% increase in the simulation mean error accuracy is achieved compared to a fixed cross-section model. The presented models can be used for the exact modeling and design optimization of compound continuum manipulators by providing an analytical tool for the sensitivity analysis of the manipulator performance. Our main aim is the application in minimal invasive manipulation with limited workspaces and manipulators with regional tunable stiffness in their cross section.
Analysis of the mechanical behaviour of the ITER magnet system
Energy Technology Data Exchange (ETDEWEB)
Jong, C.T.J.
1996-03-01
The International Thermonuclear Experimental Reactor (ITER) is a tokamak fusion device with the objective of demonstrating controlled ignition and an extended burn for a duration sufficient to achieve stationary conditions. The design of ITER will be based on extensive new design work supported by new physical and technological results. As part of the ITER Engineering Design Activities, the mechanical behaviour of the toroidal field coil (TF coil) system during normal operating conditions and fault conditions has to be analyzed. The displacements and/or stresses in the components must be limited to prevent mechanical failure of parts of the overall structure. These Engineering Design Activities are supported by R and D programs in the European Union. This final report describes the work carried out by ECN to develop a finite element model (FE model) of the TF-coil system which is suitable for the analysis of the mechanical behaviour and presents results obtained with this model. For the analysis of the mechanical behaviour, a large three dimensional (3D) non-linear finite element model has been developed. With this FE model a large number of load cases has been analyzed which correspond with several time points during multiple pulses. (orig./WL).
Lattice gravity near the continuum limit
International Nuclear Information System (INIS)
Feinberg, G.; Friedberg, R.; Lee, T.D.; Ren, H.C.
1984-01-01
We prove that the lattice gravity always approaches the usual continuum limit when the link length l -> 0, provided that certain general boundary conditions are satisfied. This result holds for any lattice, regular or irregular. Furthermore, for a given lattice, the deviation from its continuum limit can be expressed as a power series in l 2 . General formulas for such a perturbative calculation are given, together with a number of illustrative examples, including the graviton propagator. The lattice gravity satisfies all the invariance properties of Einstein's theory of general relativity. In addition, it is symmetric under a new class of transformations that are absent in the usual continuum theory. The possibility that the lattice theory (with a nonzero l) may be more fundamental is discussed. (orig.)
Stiffness Control of Surgical Continuum Manipulators.
Mahvash, Mohsen; Dupont, Pierre E
2011-04-01
This paper introduces the first stiffness controller for continuum robots. The control law is based on an accurate approximation of a continuum robot's coupled kinematic and static force model. To implement a desired tip stiffness, the controller drives the actuators to positions corresponding to a deflected robot configuration that produces the required tip force for the measured tip position. This approach provides several important advantages. First, it enables the use of robot deflection sensing as a means to both sense and control tip forces. Second, it enables stiffness control to be implemented by modification of existing continuum robot position controllers. The proposed controller is demonstrated experimentally in the context of a concentric tube robot. Results show that the stiffness controller achieves the desired stiffness in steady state, provides good dynamic performance, and exhibits stability during contact transitions.
Integrated Information Systems Across the Weather-Climate Continuum
Pulwarty, R. S.; Higgins, W.; Nierenberg, C.; Trtanj, J.
2015-12-01
The increasing demand for well-organized (integrated) end-to-end research-based information has been highlighted in several National Academy studies, in IPCC Reports (such as the SREX and Fifth Assessment) and by public and private constituents. Such information constitutes a significant component of the "environmental intelligence" needed to address myriad societal needs for early warning and resilience across the weather-climate continuum. The next generation of climate research in service to the nation requires an even more visible, authoritative and robust commitment to scientific integration in support of adaptive information systems that address emergent risks and inform longer-term resilience strategies. A proven mechanism for resourcing such requirements is to demonstrate vision, purpose, support, connection to constituencies, and prototypes of desired capabilities. In this presentation we will discuss efforts at NOAA, and elsewhere, that: Improve information on how changes in extremes in key phenomena such as drought, floods, and heat stress impact management decisions for resource planning and disaster risk reduction Develop regional integrated information systems to address these emergent challenges, that integrate observations, monitoring and prediction, impacts assessments and scenarios, preparedness and adaptation, and coordination and capacity-building. Such systems, as illustrated through efforts such as NIDIS, have strengthened the integration across the foundational research enterprise (through for instance, RISAs, Modeling Analysis Predictions and Projections) by increasing agility for responding to emergent risks. The recently- initiated Climate Services Information System, in support of the WMO Global Framework for Climate Services draws on the above models and will be introduced during the presentation.
Continuum modeling and numerical simulation of cell motility.
Hodge, Neil; Papadopoulos, Panayiotis
2012-06-01
This work proposes a continuum-mechanical model of cell motility which accounts for the dynamics of motility-relevant protein species. For the special case of fish epidermal keratocytes, the stress and cell-substrate traction responses are postulated to depend on selected protein densities in accordance with the structural features of the cells. A one-dimensional version of the model is implemented using Arbitrary Lagrangian-Eulerian finite elements in conjunction with Lagrange multipliers for the treatment of kinematic constraints related to surface growth. Representative numerical tests demonstrate the capacity of the proposed model to simulate stationary and steady crawling states.
Physical quantities and dimensional analysis: from mechanics to quantum gravity
Trancanelli, Diego
2015-01-01
Physical quantities and physical dimensions are among the first concepts encountered by students in their undergraduate career. In this pedagogical review, I will start from these concepts and, using the powerful tool of dimensional analysis, I will embark in a journey through various branches of physics, from basic mechanics to quantum gravity. I will also discuss a little bit about the fundamental constants of Nature, the so-called "cube of Physics", and the natural system of units.
Conformation analysis of trehalose. Molecular dynamics simulation and molecular mechanics
International Nuclear Information System (INIS)
Donnamaira, M.C.; Howard, E.I.; Grigera, J.R.
1992-09-01
Conformational analysis of the disaccharide trehalose is done by molecular dynamics and molecular mechanics. In spite of the different force fields used in each case, comparison between the molecular dynamics trajectories of the torsional angles of glycosidic linkage and energy conformational map shows a good agreement between both methods. By molecular dynamics it is observed a moderate mobility of the glycosidic linkage. The demands of computer time is comparable in both cases. (author). 6 refs, 4 figs
Parametric Design and Mechanical Analysis of Beams based on SINOVATION
Xu, Z. G.; Shen, W. D.; Yang, D. Y.; Liu, W. M.
2017-07-01
In engineering practice, engineer needs to carry out complicated calculation when the loads on the beam are complex. The processes of analysis and calculation take a lot of time and the results are unreliable. So VS2005 and ADK are used to develop a software for beams design based on the 3D CAD software SINOVATION with C ++ programming language. The software can realize the mechanical analysis and parameterized design of various types of beams and output the report of design in HTML format. Efficiency and reliability of design of beams are improved.
Correlation between the variation of the ionizing continuum and broad absorption lines
Lu, Wei-Jian; Lin, Ying-Ru; Qin, Yi-Ping
2018-01-01
In this Letter, we present an analysis of the relation between the variability of broad absorption lines (BALs) and that of the continuum. Our sample is multi-epoch observations of 483 quasars by the Sloan Digital Sky Survey-I/II/III (SDSS-I/II/III). We derive the fractional flux variations of the continuum and fractional equivalent width (EW) variations for C IV and Si IV BALs, and explore the correlations between the three. Our results reveal moderate anticorrelations with high significance level between the fractional flux variations of the continuum and fractional EW variations for both C IV and Si IV BALs. We also prove a significant positive correlation between the fractional EW variations for C IV and Si IV BALs, which is in agreement with several previous studies. Our discoveries can serve as evidence for the idea: Change of an ionizing continuum is the primary driver of BAL variability.
SEACAS Theory Manuals: Part III. Finite Element Analysis in Nonlinear Solid Mechanics
Energy Technology Data Exchange (ETDEWEB)
Laursen, T.A.; Attaway, S.W.; Zadoks, R.I.
1999-03-01
This report outlines the application of finite element methodology to large deformation solid mechanics problems, detailing also some of the key technological issues that effective finite element formulations must address. The presentation is organized into three major portions: first, a discussion of finite element discretization from the global point of view, emphasizing the relationship between a virtual work principle and the associated fully discrete system, second, a discussion of finite element technology, emphasizing the important theoretical and practical features associated with an individual finite element; and third, detailed description of specific elements that enjoy widespread use, providing some examples of the theoretical ideas already described. Descriptions of problem formulation in nonlinear solid mechanics, nonlinear continuum mechanics, and constitutive modeling are given in three companion reports.
Finite continuum quasi distributions from lattice QCD
Monahan, Christopher; Orginos, Kostas
2018-03-01
We present a new approach to extracting continuum quasi distributions from lattice QCD. Quasi distributions are defined by matrix elements of a Wilson-line operator extended in a spatial direction, evaluated between nucleon states at finite momentum. We propose smearing this extended operator with the gradient flow to render the corresponding matrix elements finite in the continuum limit. This procedure provides a nonperturbative method to remove the power-divergence associated with the Wilson line and the resulting matrix elements can be directly matched to light-front distributions via perturbation theory.
Coupling of nonlocal and local continuum models by the Arlequinapproach
Han, Fei
2011-08-09
The objective of this work is to develop and apply the Arlequin framework to couple nonlocal and local continuum mechanical models. A mechanically-based model of nonlocal elasticity, which involves both contact and long-range forces, is used for the \\'fine scale\\' description in which nonlocal interactions are considered to have non-negligible effects. Classical continuum mechanics only involving local contact forces is introduced for the rest of the structure where these nonlocal effects can be neglected. Both models overlap in a coupling subdomain called the \\'gluing area\\' in which the total energy is separated into nonlocal and local contributions by complementary weight functions. A weak compatibility is ensured between kinematics of both models using Lagrange multipliers over the gluing area. The discrete formulation of this specific Arlequin coupling framework is derived and fully described. The validity and limits of the technique are demonstrated through two-dimensional numerical applications and results are compared against those of the fully nonlocal elasticity method. © 2011 John Wiley & Sons, Ltd.
Qin, Zhiwei; McNee, David; Gleisner, Heike; Raab, Andrea; Kyeremeh, Kwaku; Jaspars, Marcel; Krupp, Eva; Deng, Hai; Feldmann, Jörg
2012-07-17
Driven by increasing demand for the monitoring of industrial perfluorinated compounds (PFCs), the identification of novel fluorine containing compounds (FOCs) and the tracking of organofluorine drugs and their degradation products, there is a clear need for sensitive, fluorine-specific detection of unknown FOCs. Here we report the first ever direct fluorine-specific (speciation) method; capable of individually detecting untargeted FOCs in environmental and biological samples through the application of continuum source molecular absorption spectrometry (CS-MAS) using a commercial CS-AAS. Two model FOCs (2,4,6, trifluorobenzoic acid (TFBA) and 5-fluoroindol-5-carboxylic acid (FICA)) were used, achieving fluorine-specific detection across a range of 0.1 to 300 ng/mL fluorine, corresponding to a limit of detection of 4 pg F and 5.26 nM for both compounds. Both TFBA and FICA showed a similar response to CS-MAS detection, potentially enabling the quantification of fluorine content in novel FOCs without having molecular standards available. This paper also reports the use of reverse-phase high performance liquid chromatography (RP-HPLC) coupled off-line with CS-MAS for the identification of single organofluorines in a mixture of FOCs via fraction collection. The linear range of both FOCs was determined to be from 1 to 500 ng/mL. The limits of detection of those species were just above 1 ng/mL (100 pg) and can therefore compete with targeted analytical methods such as ESI-MS. Finally, as a proof of principle the analysis of a fluoride-containing groundwater sample from Ghana demonstrated that this method can be used in the detection of novel FOCs, with identification achieved through parallel ESI-MS. Coupled HPLC-CS-MAS/ESI-MS is the first analytical methodology capable of selectively detecting and identifying novel FOCs, making possible the quantification of all fluorine containing compounds in one sample. This is the necessary analytical requirement to perform
Continuum and computational modeling of flexoelectricity
Mao, Sheng
Flexoelectricity refers to the linear coupling of strain gradient and electric polarization. Early studies of this subject mostly look at liquid crystals and biomembranes. Recently, the advent of nanotechnology revealed its importance also in solid structures, such as flexible electronics, thin films, energy harvesters, etc. The energy storage function of a flexoelectric solid depends not only on polarization and strain, but also strain-gradient. This is our basis to formulate a consistent model of flexoelectric solids under small deformation. We derive a higher-order Navier equation for linear isotropic flexoelectric materials which resembles that of Mindlin in gradient elasticity. Closed-form solutions can be obtained for problems such as beam bending, pressurized tube, etc. Flexoelectric coupling can be enhanced in the vicinity of defects due to strong gradients and decay away in far field. We quantify this expectation by computing elastic and electric fields near different types of defects in flexoelectric solids. For point defects, we recover some well-known results of non-local theories. For dislocations, we make connections with experimental results on NaCl, ice, etc. For cracks, we perform a crack-tip asymptotic analysis and the results share features from gradient elasticity and piezoelectricity. We compute the J integral and use it for determining fracture criteria. Conventional finite element methods formulated solely on displacement are inadequate to treat flexoelectric solids due to higher order governing equations. Therefore, we introduce a mixed formulation which uses displacement and displacement-gradient as separate variables. Their known relation is constrained in a weighted integral sense. We derive a variational formulation for boundary value problems for piezeo- and/or flexoelectric solids. We validate this computational framework against exact solutions. With this method more complex problems, including a plate with an elliptical hole
Outgas analysis of mechanical cryocoolers for long lifetime
Sato, Yoichi; Shinozaki, Keisuke; Sawada, Kenichiro; Sugita, Hiroyuki; Mitsuda, Kazuhisa; Yamasaki, Noriko Y.; Nakagawa, Takao; Tsunematsu, Shoji; Otsuka, Kiyomi; Kanao, Kenichi; Yoshida, Seiji; Narasaki, Katsuhiro
2017-12-01
Mechanical cryocoolers for space applications are required to have high reliability to achieve long-term operation in orbit. ASTRO-H (Hitomi), the 6th Japanese X-ray astronomy mission, has a major scientific instrument onboard-the Soft X-ray Spectrometer (SXS) with several 20K-class two-stage Stirling (2ST) coolers and a 4K-class Joule Thomson (JT) cooler, which must operate for 3 years to ensure the lifetime of liquid helium as a cryogen for cooling of its detectors [1,2]. Other astronomical missions such as SPICA [3,4], LiteBIRD [5], and Athena [6] also have top requirements for these mechanical cryocoolers, including a 1K-class JT cooler to be operated for more than 3-5 years with no cryogen system. The reliability and lifetime of mechanical cryocoolers are generally understood to depend on (1) mechanical wear of the piston seal and valve seal, and (2) He working gas contaminated by impurity outgases, mainly H2O and CO2 released from the materials in the components of the cryocoolers. The second factor could be critical relative to causing blockage in the JT heat exchanger plumbing and the JT orifice or resulting in blockage in the Stirling regenerator and thereby degrading its performance. Thus, reducing the potential for outgassing in the cryocooler design and fabrication process, and predicting the total amount of outgases in the cryocooler are very important to ensure cryocooler lifetime and cooling performance in orbit. This paper investigates the outgas analysis of the 2ST and the 1K/4K-JT coolers for achieving a long lifetime. First, gas analysis was conducted for the materials and components of the mechanical cryocoolers, focusing on non-metallic materials as impurity gas sources. Then gas analysis of the mechanical wear effect of the piston seal materials and linear ball bearings was investigated. Finally, outgassing from a fully assembled cryocooler was measured to evaluate whether the outgas reduction process works properly to meet the requirement
Multi technical analysis of wear mechanisms in axial piston pumps
Schuhler, G.; Jourani, A.; Bouvier, S.; Perrochat, J.-M.
2017-05-01
Axial piston pumps convert a motor rotation motion into hydraulic or pneumatic power. Their compactness and efficiency of approximately 0.9 make them suitable for actuation applications especially in aeronautics. However, they suffer a limited life due to the wear of their components. In the literature, studies of axial piston pumps deal with contact between its different elements under lubrication conditions. Nevertheless, they are more focused on analytic or numerical approaches. This study consists in an experimental analysis of worn pump components to highlight and understand wear mechanisms. Piston shoes are central components in the axial piston pump since they are involved in three tribological contacts. These three contacts are thereby studied: piston shoes/swashplate, piston shoes/pistons and piston shoes/shoes hold down plate (SHDP). To perform this analysis, helicopter hydraulic pumps after different operating times have been studied. The wear damage mechanisms and wear debris are analysed using SEM observations. 3D surface roughness measurements are then used to characterize worn surfaces. The observations reveal that in the contact between shoes and swashplate, the main wear mechanism is three-body abrasive wear due to coarse carbides removal. Between shoes and pistons, wear occurs in a less severe way and is mainly due to the debris generated in the first contact and conveyed by the lubricating fluid. In the third contact, the debris are also the prime cause of the abrasive wear and the generation of deep craters in the piston shoes.
Statistical mechanical analysis of LMFBR fuel cladding tubes
International Nuclear Information System (INIS)
Poncelet, J.-P.; Pay, A.
1977-01-01
The most important design requirement on fuel pin cladding for LMFBR's is its mechanical integrity. Disruptive factors include internal pressure from mixed oxide fuel fission gas release, thermal stresses and high temperature creep, neutron-induced differential void-swelling as a source of stress in the cladding and irradiation creep of stainless steel material, corrosion by fission products. Under irradiation these load-restraining mechanisms are accentuated by stainless steel embrittlement and strength alterations. To account for the numerous uncertainties involved in the analysis by theoretical models and computer codes statistical tools are unavoidably requested, i.e. Monte Carlo simulation methods. Thanks to these techniques, uncertainties in nominal characteristics, material properties and environmental conditions can be linked up in a correct way and used for a more accurate conceptual design. First, a thermal creep damage index is set up through a sufficiently sophisticated clad physical analysis including arbitrary time dependence of power and neutron flux as well as effects of sodium temperature, burnup and steel mechanical behavior. Although this strain limit approach implies a more general but time consuming model., on the counterpart the net output is improved and e.g. clad temperature, stress and strain maxima may be easily assessed. A full spectrum of variables are statistically treated to account for their probability distributions. Creep damage probability may be obtained and can contribute to a quantitative fuel probability estimation
Analysis of Mechanical Stresses/Strains in Superconducting Wire
Barry, Matthew; Chen, Jingping; Zhai, Yuhu
2016-10-01
The optimization of superconducting magnet performance and development of high-field superconducting magnets will greatly impact the next generation of fusion devices. A successful magnet development, however, relies deeply on the understanding of superconducting materials. Among the numerous factors that impact a superconductor's performance, mechanical stress is the most important because of the extreme operation temperature and large electromagnetic forces. In this study, mechanical theory is used to calculate the stresses/strains in typical superconducting strands, which consist of a stabilizer, a barrier, a matrix and superconducting filaments. Both thermal loads and mechanical loads are included in the analysis to simulate operation conditions. Because this model simulates the typical architecture of major superconducting materials, such as Nb3Sn, MgB2, Bi-2212 etc., it provides a good overall picture for us to understand the behavior of these superconductors in terms of thermal and mechanical loads. This work was supported in part by the U.S. Department of Energy, Office of Science, Office of Workforce Development for Teachers and Scientists (WDTS) under the Science Undergraduate Laboratory Internship (SULI) program.
Strategic management of a continuum of care.
Evashwick, C J
1993-01-01
Why would an organization want to undertake the changes required to be a continuum of care? Because providers of residential and long-term nursing care that continue to function in isolation may survive, but they will not thrive in the 21st century.
Continuum Modeling in the Physical Sciences
Groesen, van E.; Molenaar, J.
2007-01-01
Mathematical modeling—the ability to apply mathematical concepts and techniques to real-life systems—has expanded considerably over the last decades, making it impossible to cover all of its aspects in one course or textbook. Continuum Modeling in the Physical Sciences provides an extensive
Analysis of Environmental Law Enforcement Mechanism Based on Economic Principle
Cao, Hongjun; Shao, Haohao; Cai, Xuesen
2017-11-01
Strengthening and improving the environmental law enforcement mechanism is an important way to protect the ecological environment. This paper is based on economical principles, we did analysis of the marginal management costs by using Pigou means and the marginal transaction costs by using Coase means vary with the quantity growth of pollutant discharge Enterprises. We analyzed all this information, then we got the conclusion as follows. In the process of strengthening the environmental law enforcement mechanism, firstly, we should fully mobilize all aspects of environmental law enforcement, such as legislative bodies and law enforcement agencies, public welfare organizations, television, newspapers, enterprises, people and so on, they need to form a reasonable and organic structure system; then we should use various management means, such as government regulation, legal sanctions, fines, persuasion and denounce, they also need to form an organic structural system.
Mechanical Properties for Reliability Analysis of Structures in Glassy Carbon
Garion, Cédric
2014-01-01
Despite its good physical properties, the glassy carbon material is not widely used, especially for structural applications. Nevertheless, its transparency to particles and temperature resistance are interesting properties for the applications to vacuum chambers and components in high energy physics. For example, it has been proposed for fast shutter valve in particle accelerator [1] [2]. The mechanical properties have to be carefully determined to assess the reliability of structures in such a material. In this paper, mechanical tests have been carried out to determine the elastic parameters, the strength and toughness on commercial grades. A statistical approach, based on the Weibull’s distribution, is used to characterize the material both in tension and compression. The results are compared to the literature and the difference of properties for these two loading cases is shown. Based on a Finite Element analysis, a statistical approach is applied to define the reliability of a structural component in gl...
Nonlinear analysis of collapse mechanism in superstructure vehicle
Nor, M. K. Mohd; Ho, C. S.; Ma'at, N.
2017-04-01
The EU directive 2001/85/EC is an official European text which describes the specifications for "single deck class II and III vehicles" required to be approved by the regulation UN/ECE no.66 (R66). To prevent the catastrophic consequences by occupant during an accident, the Malaysian government has reinforced the same regulation upon superstructure construction. This paper discusses collapse mechanism analysis of a superstructure vehicle using a Crash D nonlinear analysis computer program based on this regulation. The analysis starts by hand calculation to define the required energy absorption by the chosen structure. Simple calculations were then performed to define the weakest collapse mechanism after undesirable collapse modes are eliminated. There are few factors highlighted in this work to pass the regulation. Using the selected cross section, Crash D simulation showed a good result. Generally, the deformation is linearly correlates to the energy absorption for the structure with low stiffness. Failure of critical members such as vertical lower side wall must be avoided to sustain safety of the passenger compartment and prevent from severe and fatal injuries to the trapped occupant.
Collapse Mechanism Analysis in the Design of Superstructure Vehicle
Mohd Nor, M. K.
2016-11-01
The EU directive 2001/85/EC is an official European text which describes the specifications for “single deck class II and III vehicles” required to be approved by the regulation UN/ECE no.66 (R66). To prevent the catastrophic consequences by occupant during an accident, the Malaysian government has reinforced the same regulation upon superstructure construction. This paper discusses collapse mechanism analysis of a superstructure vehicle using a Crash D nonlinear analysis computer program based on this regulation. The analysis starts by hand calculation to define the required energy absorption by the chosen structure. Simple calculations were then performed to define the weakest collapse mechanism after undesirable collapse modes are eliminated. There are few factors highlighted in this work to pass the regulation. Using the selected cross section, Crash D simulation showed a good result. Generally, the deformation is linearly correlates to the energy absorption for the structure with low stiffness. Failure of critical members such as vertical lower side wall must be avoided to sustain safety of the passenger compartment and prevent from severe and fatal injuries to the trapped occupant.
Keralavarma, Shyam Mohan
The objective of this dissertation is to further the understanding of inelastic behavior in metallic materials. Despite the increasing use of polymeric composites in aircraft structures, high specific strength metals continue to be used in key components such as airframe, fuselage, wings, landing gear and hot engine parts. Design of metallic structures subjected to thermomechanical extremes in aerospace, automotive and nuclear applications requires consideration of the plasticity, creep and fracture behavior of these materials. Consideration of inelasticity and damage processes is also important in the design of metallic components used in functional applications such as thin films, flexible electronics and micro electro mechanical systems. Fracture mechanics has been largely successful in modeling damage and failure phenomena in a host of engineering materials. In the context of ductile metals, the Gurson void growth model remains one of the most successful and widely used models. However, some well documented limitations of the model in quantitative prediction of the fracture strains and failure modes at low triaxialities may be traceable to the limited representation of the damage microstructure in the model. In the first part of this dissertation, we develop an extended continuum model of void growth that takes into account details of the material microstructure such as the texture of the plastically deforming matrix and the evolution of the void shape. The need for such an extension is motivated by a detailed investigation of the effects of the two types of anisotropy on the materials' effective response using finite element analysis. The model is derived using the Hill--Mandel homogenization theory and an approximate limit analysis of a porous representative volume element. Comparisons with several numerical studies are presented towards a partial validation of the analytical model. Inelastic phenomena such as plasticity and creep result from the collective
Market mechanisms for compensating hazardous work: a critical analysis
International Nuclear Information System (INIS)
Shakow, D.
1984-01-01
Adam Smith's theory that the marketplace can compensate workers for social inequities (i.e., hazards, boredom, etc.) in the work place is applied to the nuclear industry. The author argues that market mechanisms are unlikely to ensure adequate compensation for work-related hazards. He summarizes and critiques the neoclassical compensating-wage hypothesis, then reviews empirical evidence in support of the hypothesis in light of an alternative hypothesis derived from the literature on labor market segmentation. He challenges the assumption of perfect labor mobility and perfect information. A promising direction for further research would be a structural analysis of the emerging market for temporary workers. 13 references, 2 figures
Groups as units of functional analysis, individuals as proximate mechanisms.
Wilson, David Sloan
2014-06-01
Whenever selection operates at a given level of a multitier hierarchy, units at that level should become the object of functional analysis, and units at lower levels should be studied as proximate mechanisms. This intuition already exists for the study of genes in individuals, when individuals are the unit of selection. It is only beginning to be applied for the study of individuals in groups, when groups are the unit of selection. Smaldino's target article is an important step in this direction with an emphasis on human cultural evolution, but the same algorithm applies to all multilevel evolutionary processes.
Analysis of mechanical fabrication experience with CEBAF's production SRF cavities
International Nuclear Information System (INIS)
Mammosser, J.; Kneisel, P.; Benesch, J.
1993-06-01
CEBAF has received a total of 360 five-cell niobium cavities, the largest group of industrially fabricated superconducting cavities so far. An extensive data base exists on the fabrication, surface treatment, assembly and cavity performance parameters. Analysis of the mechanical features of the cavities includes the following: the spread in fabrication tolerances of the cells derived from field profiles of the ''as fabricated'' cavities and the ''as fabricated'' external Q-values of the fundamental power coupler compared to dimensional deviations. A comparison is made of the pressure sensitivity of cavities made of materials from different manufacturers between 760 torr (4.2 K) and 23 torr (2 K)
Hybrid molecular–continuum methods: From prototypes to coupling software
Neumann, Philipp
2014-02-01
In this contribution, we review software requirements in hybrid molecular-continuum simulations. For this purpose, we analyze a prototype implementation which combines two frameworks-the Molecular Dynamics framework MarDyn and the framework Peano for spatially adaptive mesh-based simulations-and point out particular challenges of a general coupling software. Based on this analysis, we discuss the software design of our recently published coupling tool. We explain details on its overall structure and show how the challenges that arise in respective couplings are resolved by the software. © 2013 Elsevier Ltd. All rights reserved.
A κ-generalized statistical mechanics approach to income analysis
International Nuclear Information System (INIS)
Clementi, F; Gallegati, M; Kaniadakis, G
2009-01-01
This paper proposes a statistical mechanics approach to the analysis of income distribution and inequality. A new distribution function, having its roots in the framework of κ-generalized statistics, is derived that is particularly suitable for describing the whole spectrum of incomes, from the low–middle income region up to the high income Pareto power-law regime. Analytical expressions for the shape, moments and some other basic statistical properties are given. Furthermore, several well-known econometric tools for measuring inequality, which all exist in a closed form, are considered. A method for parameter estimation is also discussed. The model is shown to fit remarkably well the data on personal income for the United States, and the analysis of inequality performed in terms of its parameters is revealed as very powerful
Ezzedine, S. M.; Vorobiev, O.; Herbold, E. B.; Glenn, L. A.; Antoun, T.
2013-12-01
This work is focused on analysis of near-field measurements (up to 100 m from the source) recorded during Source Physics Experiments in a granitic formation. One of the main goals of these experiments is to investigate the possible mechanisms of shear wave generation in the nonlinear source region. SPE experiments revealed significant tangential motion (up to 30 % of the magnitude in the radial direction) at many locations. Furthermore, azimuthal variations in radial velocities were also observed which cannot be generated by a spherical source in isotropic materials. Understanding the nature of this non-radial motion is important for discriminating between the natural seismicity and underground explosions signatures. Possible mechanisms leading to such motion include, but not limited to, heterogeneities in the rock such as joints, faults and geologic layers as well as surface topography and vertical motion at the surface caused by material spall and gravity. We have performed a three dimensional computational studies considering all these effects. Both discrete and continuum methods have been employed to model heterogeneities. In the discrete method, the joints and faults were represented by cohesive contact elements. This enables us to examine various friction laws at the joints which include softening, dilatancy, water saturation and rate-dependent friction. Yet this approach requires the mesh to be aligned with joints, which may present technical difficulties in three dimensions when multiple non-persistent joints are present. In addition, the discrete method is more computationally expensive. The continuum approach assumes that the joints are stiff and the dilatancy and shear softening can be neglected. In this approach, the joints are modeled as weakness planes within the material, which are imbedded into and pass through many finite elements. The advantage of this approach is that it requires neither sophisticated meshing algorithms nor contact detection
Steam Generator Analysis Tools and Modeling of Degradation Mechanisms
International Nuclear Information System (INIS)
Yetisir, M.; Pietralik, J.; Tapping, R.L.
2004-01-01
The degradation of steam generators (SGs) has a significant effect on nuclear heat transport system effectiveness and the lifetime and overall efficiency of a nuclear power plant. Hence, quantification of the effects of degradation mechanisms is an integral part of a SG degradation management strategy. Numerical analysis tools such as THIRST, a 3-dimensional (3D) thermal hydraulics code for recirculating SGs; SLUDGE, a 3D sludge prediction code; CHECWORKS a flow-accelerated corrosion prediction code for nuclear piping, PIPO-FE, a SG tube vibration code; and VIBIC and H3DMAP, 3D non-linear finite-element codes to predict SG tube fretting wear can be used to assess the impacts of various maintenance activities on SG thermal performance. These tools are also found to be invaluable at the design stage to influence the design by determining margins or by helping the designers minimize or avoid known degradation mechanisms. In this paper, the aforementioned numerical tools and their application to degradation mechanisms in CANDU recirculating SGs are described. In addition, the following degradation mechanisms are identified and their effect on SG thermal efficiency and lifetime are quantified: primary-side fouling, secondary-side fouling, fretting wear, and flow-accelerated corrosion (FAC). Primary-side tube inner diameter fouling has been a major contributor to SG thermal degradation. Using the results of thermalhydraulic analysis and field data, fouling margins are calculated. Individual effects of primary- and secondary-side fouling are separated through analyses, which allow station operators to decide what type of maintenance activity to perform and when to perform the maintenance activity. Prediction of the fretting-wear rate of tubes allows designers to decide on the number and locations of support plates and U-bend supports. The prediction of FAC rates for SG internals allows designers to select proper materials, and allows operators to adjust the SG maintenance
Electromagnetic analysis of control element drive mechanism for KSNP
International Nuclear Information System (INIS)
Kim, H. M.; Kim, I. G.; Kim, I. Y.
2002-01-01
The magnetic jack type Control Element Drive Mechanism (CEDM) for Korean Standard Nuclear Power Plant (KSNP) is an electromechanical device which provides controlled linear motion to the Control Element Assembly (CEA) through the Extension Shaft Assembly (ESA) in response to operational signals received from the Control Element Drive Mechanism Control System (CEDMCS). The CEDM is operated by applying localized magnetic flux fields to movable latch and lift magnets, which are in the coolant pressure boundary. The CEDM design had been developed through electromechanical testing of the system including the magnetic force lifting the ESA. But it will be inefficient if parametric studies should be performed to improve the CEDM by test due to the consumption of high cost and long duration. So it becomes necessary to develop a computational model to simulate the electromagnetic characteristics of the CEDM to improve the CEDM design efficiently. In this paper, the electromagnetic analysis using a 2D finite element model has been carried out to simulate magnetic force of the lift magnet of the CEDM, to provide effective evaluation between leakage flux and lift force and to compare with test results. Analysis results show the lift force satisfied the test results and design requirement and the lift force depend on the shape of the components, leakage flux and B-H curve
Directory of Open Access Journals (Sweden)
Gustavo Cabrera
2017-11-01
Full Text Available The procedure for the synthesis of 3-cyano-4-hydroxycoumarin is presented along with the results from the analysis of its tautomeric equilibrium using Density Functional Theory (DFT and Polarizable Continuum Model (PCM. The geometry of the compounds was optimized with Gaussian 03 and from the resulting structures, a group of thermodynamic and kinetic parameters were determined. It was found that 3-cyano-4-hydroxycoumarin was the most stable tautomer, as was also shown by spectroscopic techniques. Other parameters, such as: transition state energy, equlibrium constant, kinetic constant, bond orders and bond angles, were also calculated.
Harnessing the Interaction Continuum for Subtle Assisted Living
Directory of Open Access Journals (Sweden)
Xavier Alamán
2012-07-01
Full Text Available People interact with each other in many levels of attention, intention and meaning. This Interaction Continuum is used daily to deal with different contexts, adapting the interaction to communication needs and available resources. Nevertheless, computer-supported interaction has mainly focused on the most direct, explicit and intrusive types of human to human Interaction such as phone calls, emails, or video conferences. This paper presents the results of exploring and exploiting the potentials of undemanding interaction mechanisms, paying special attention to subtle communication and background interaction. As we argue the benefits of this type of interaction for people with special needs, we present a theoretical framework to define it and propose a proof of concept based on Augmented Objects and a color codification mechanism. Finally, we evaluate and analyze the strengths and limitations of such approach with people with cognitive disabilities.
Continuum analogues of contragredient Lie algebras
International Nuclear Information System (INIS)
Saveliev, M.V.; Vershik, A.M.
1989-03-01
We present an axiomatic formulation of a new class of infinite-dimensional Lie algebras - the generalizations of Z-graded Lie algebras with, generally speaking, an infinite-dimensional Cartan subalgebra and a contiguous set of roots. We call such algebras ''continuum Lie algebras''. The simple Lie algebras of constant growth are encapsulated in our formulation. We pay particular attention to the case when the local algebra is parametrized by a commutative algebra while the Cartan operator (the generalization of the Cartan matrix) is a linear operator. Special examples of these algebras are the Kac-Moody algebras, algebras of Poisson brackets, algebras of vector fields on a manifold, current algebras, and algebras with differential or integro-differential Cartan operator. The nonlinear dynamical systems associated with the continuum contragredient Lie algebras are also considered. (author). 9 refs
Mesoscopic and continuum modelling of angiogenesis
Spill, F.
2014-03-11
Angiogenesis is the formation of new blood vessels from pre-existing ones in response to chemical signals secreted by, for example, a wound or a tumour. In this paper, we propose a mesoscopic lattice-based model of angiogenesis, in which processes that include proliferation and cell movement are considered as stochastic events. By studying the dependence of the model on the lattice spacing and the number of cells involved, we are able to derive the deterministic continuum limit of our equations and compare it to similar existing models of angiogenesis. We further identify conditions under which the use of continuum models is justified, and others for which stochastic or discrete effects dominate. We also compare different stochastic models for the movement of endothelial tip cells which have the same macroscopic, deterministic behaviour, but lead to markedly different behaviour in terms of production of new vessel cells. © 2014 Springer-Verlag Berlin Heidelberg.
On the Continuum of Eating Disorders
Hawkins, Lana Lee Munro
2007-01-01
Theorists and researchers have long debated as to whether the differences between subthreshold levels of eating disturbances and diagnosable eating disorders are a difference of degree (the continuum hypothesis) or a difference of kind (the discontinuity hypothesis). The present study investigated the relationship between level of eating disordered behaviour and the psychopathology associated with, and thought by some to be prodromal factors in, the development of clinically diagnosable eatin...
Continuum angular distributions in the transition regions
International Nuclear Information System (INIS)
Kalbach, C.
1993-01-01
One of the open questions from the 1988 published systematics of continuum angular distributions in light particle reactions is addressed. Evidence for a smooth transition in the systematics at incident energies of ∼125 MeV is summarized, and appropriate revisions to the global parameterization are proposed. Applying similar changes to the second-order term helps to remove problems noted in the literature with low-energy (N,α) reactions
New examples of continuum graded Lie algebras
International Nuclear Information System (INIS)
Savel'ev, M.V.
1989-01-01
Several new examples of continuum graded Lie algebras which provide an additional elucidation of these algebras are given. Here, in particular, the Kac-Moody algebras, the algebra S 0 Diff T 2 of infinitesimal area-preserving diffeomorphisms of the torus T 2 , the Fairlie, Fletcher and Zachos sine-algebras, etc., are described as special cases of the cross product Lie algebras. 8 refs
International Nuclear Information System (INIS)
Cornwall, J.M.
1986-01-01
The nonperturbative aspects of continuum QCD are so complex that one can only hope to approach them through well-motivated models. The author reviews the general properties that any such model must have, based on the understanding of the gluon condensate in the QCD vacuum. A specific, practical model is proposed motivated by a picture of the condensate as made of thick vortex sheets self-consistently constructed from dynamically massive gluons. (author)
Game Play Schemas: From Player Analysis to Adaptive Game Mechanics
Directory of Open Access Journals (Sweden)
Craig A. Lindley
2008-01-01
Full Text Available Schema theory provides a foundation for the analysis of game play patterns created by players during their interaction with a game. Schema models derived from the analysis of play provide a rich explanatory framework for the cognitive processes underlying game play, as well as detailed hypotheses for the hierarchical structure of pleasures and rewards motivating players. Game engagement is accounted for as a process of schema selection or development, while immersion is explained in terms of levels of attentional demand in schema execution. However, schemas may not only be used to describe play, but might be used actively as cognitive models within a game engine. Predesigned schema models are knowledge representations constituting anticipated or desired learned cognitive outcomes of play. Automated analysis of player schemas and comparison with predesigned target schemas can provide a foundation for a game engine adapting or tuning game mechanics to achieve specific effects of engagement, immersion, and cognitive skill acquisition by players. Hence, schema models may enhance the play experience as well as provide a foundation for achieving explicitly represented pedagogical or therapeutic functions of games.
International Nuclear Information System (INIS)
Daeinabi, Khadijeh; Korayem, Moharam Habibnejad
2011-01-01
Atomic force microscopy is applied to measure intermolecular forces and mechanical properties of materials, nano-particle manipulation, surface scanning and imaging with atomic accuracy in the nano-world. During nano-manipulation process, contact forces cause indentation in contact area between nano-particle and tip/substrate which is considerable at nano-scale and affects the nano-manipulation process. Several nano-contact mechanics models such as Hertz, Derjaguin–Muller–Toporov (DMT), Johnson–Kendall–Roberts–Sperling (JKRS), Burnham–Colton–Pollock (BCP), Maugis–Dugdale (MD), Carpick–Ogletree–Salmeron (COS), Pietrement–Troyon (PT), and Sun et al. have been applied as the continuum mechanics approaches at nano-scale. In this article, indentation depth and contact radius between tip and substrate with nano-particle for both spherical and conical tip shape during nano-manipulation process are analyzed and compared by applying theoretical, semiempirical, and empirical nano-contact mechanics models. The effects of adhesion force, as the main contrast point in different nano-contact mechanics models, on nano-manipulation analysis is investigated for different contact radius, and the critical point is discussed for mentioned models.
Improvements in continuum modeling for biomolecular systems
Yu, Qiao; Ben-Zhuo, Lu
2016-01-01
Modeling of biomolecular systems plays an essential role in understanding biological processes, such as ionic flow across channels, protein modification or interaction, and cell signaling. The continuum model described by the Poisson- Boltzmann (PB)/Poisson-Nernst-Planck (PNP) equations has made great contributions towards simulation of these processes. However, the model has shortcomings in its commonly used form and cannot capture (or cannot accurately capture) some important physical properties of the biological systems. Considerable efforts have been made to improve the continuum model to account for discrete particle interactions and to make progress in numerical methods to provide accurate and efficient simulations. This review will summarize recent main improvements in continuum modeling for biomolecular systems, with focus on the size-modified models, the coupling of the classical density functional theory and the PNP equations, the coupling of polar and nonpolar interactions, and numerical progress. Project supported by the National Natural Science Foundation of China (Grant No. 91230106) and the Chinese Academy of Sciences Program for Cross & Cooperative Team of the Science & Technology Innovation.
Directory of Open Access Journals (Sweden)
R. Sussmann
2016-09-01
Full Text Available Quantitative knowledge of water vapor radiative processes in the atmosphere throughout the terrestrial and solar infrared spectrum is still incomplete even though this is crucial input to the radiation codes forming the core of both remote sensing methods and climate simulations. Beside laboratory spectroscopy, ground-based remote sensing field studies in the context of so-called radiative closure experiments are a powerful approach because this is the only way to quantify water absorption under cold atmospheric conditions. For this purpose, we have set up at the Zugspitze (47.42° N, 10.98° E; 2964 m a.s.l. a long-term radiative closure experiment designed to cover the infrared spectrum between 400 and 7800 cm−1 (1.28–25 µm. As a benefit for such experiments, the atmospheric states at the Zugspitze frequently comprise very low integrated water vapor (IWV; minimum = 0.1 mm, median = 2.3 mm and very low aerosol optical depth (AOD = 0.0024–0.0032 at 7800 cm−1 at air mass 1. All instruments for radiance measurements and atmospheric-state measurements are described along with their measurement uncertainties. Based on all parameter uncertainties and the corresponding radiance Jacobians, a systematic residual radiance uncertainty budget has been set up to characterize the sensitivity of the radiative closure over the whole infrared spectral range. The dominant uncertainty contribution in the spectral windows used for far-infrared (FIR continuum quantification is from IWV uncertainties, while T profile uncertainties dominate in the mid-infrared (MIR. Uncertainty contributions to near-infrared (NIR radiance residuals are dominated by water vapor line parameters in the vicinity of the strong water vapor bands. The window regions in between these bands are dominated by solar Fourier transform infrared (FTIR calibration uncertainties at low NIR wavenumbers, while uncertainties due to AOD become an
Morphing continuum theory for turbulence: Theory, computation, and visualization
Chen, James
2017-10-01
A high order morphing continuum theory (MCT) is introduced to model highly compressible turbulence. The theory is formulated under the rigorous framework of rational continuum mechanics. A set of linear constitutive equations and balance laws are deduced and presented from the Coleman-Noll procedure and Onsager's reciprocal relations. The governing equations are then arranged in conservation form and solved through the finite volume method with a second-order Lax-Friedrichs scheme for shock preservation. A numerical example of transonic flow over a three-dimensional bump is presented using MCT and the finite volume method. The comparison shows that MCT-based direct numerical simulation (DNS) provides a better prediction than Navier-Stokes (NS)-based DNS with less than 10% of the mesh number when compared with experiments. A MCT-based and frame-indifferent Q criterion is also derived to show the coherent eddy structure of the downstream turbulence in the numerical example. It should be emphasized that unlike the NS-based Q criterion, the MCT-based Q criterion is objective without the limitation of Galilean invariance.
Reproducing the nonlinear dynamic behavior of a structured beam with a generalized continuum model
Vila, J.; Fernández-Sáez, J.; Zaera, R.
2018-04-01
In this paper we study the coupled axial-transverse nonlinear vibrations of a kind of one dimensional structured solids by application of the so called Inertia Gradient Nonlinear continuum model. To show the accuracy of this axiomatic model, previously proposed by the authors, its predictions are compared with numeric results from a previously defined finite discrete chain of lumped masses and springs, for several number of particles. A continualization of the discrete model equations based on Taylor series allowed us to set equivalent values of the mechanical properties in both discrete and axiomatic continuum models. Contrary to the classical continuum model, the inertia gradient nonlinear continuum model used herein is able to capture scale effects, which arise for modes in which the wavelength is comparable to the characteristic distance of the structured solid. The main conclusion of the work is that the proposed generalized continuum model captures the scale effects in both linear and nonlinear regimes, reproducing the behavior of the 1D nonlinear discrete model adequately.
A survey of infrared continuum versus line radiation from metal halide lamps
International Nuclear Information System (INIS)
Kato, M; Herd, M T; Lawler, J E
2008-01-01
Near-infrared radiation (near-IR) losses from the arcs of six commercial metal halide high intensity discharge (MH-HID) lamps with various power levels and with both Na/Sc and rare earth doses were surveyed in this paper. A radiometrically calibrated Fourier transform infrared spectrometer was used. Lamps with rare earth doses have appreciably better color rendering indices (CRIs) than lamps with Na/Sc doses. The ratios of near-IR continuum emission over near-IR line emission from these six lamps were compared. The near-IR continuum dominates near-IR losses from lamps with rare earth doses and the continuum is significant, but not dominant, from lamps with Na/Sc doses. There was no strong dependence of this ratio on input power or color temperature (T c ). Total near-IR losses were estimated using absolutely calibrated, horizontal irradiance measurements. Estimated total near-IR losses were correlated with CRI. The lamps with rare earth doses yield the best CRIs, but have appreciably higher near-IR losses due primarily to continuum processes. One of these rare earth MH-HID lamps was used in a more detailed study of the microscopic physics of the continuum mechanism (Herd M T and Lawler E 2007 J. Phys. D: Appl. Phys. 40 3386)
Preliminary core mechanics analysis for KALIMER by CRAMP code
International Nuclear Information System (INIS)
Lee, Byoung Oon; Hwang, Woan; Ian, Slater; John, Duthie; Kim, Young Jin
1999-08-01
CRAMP code is designed to solve the problem of mutually interacting and distorting sub-assemblies in a fast breeder reactor. It is the UK's main core mechanics design tool and is currently being used in the design of EFR. This report contains the results of preliminary core mechanics calculations for KALIMER core configuration by the updated version of CRAMP code. The base case calculation s on KALIMER core, and the sensitivity studies (to investigate effect of main design parameter) are carried out by the code which was updated with material subroutine in CRAMP to model the characteristics of HT9. Sensitivity studies include following cases; (1) with gaps at LRP and URP reduced to 0.4 mm at 386 dg C (2) with 0.2 mm radial clearance around both nosepiece at seals (3) with flexibility at LRP reduced by a factor of 2 (4) with stiffness of nosepiece increased by a factor of 2 (5) with reduced creep (6) combined with gap reduced 0.4 mm and 0.2 mm clearance at seals (7) with IVS position replaced to dummy ducts (8) with initial bow at every duct except S/A 1. From each calculation, the data obtained and compared are as follows; (a) contact forces between pads (b) gaps between pads (c) duct dynamic behavior of duct bowing and dilation i.e. the variation of bowing and dilation with time) (d) reactivity change (e) maximum LRP contact force, maximum URP contact force and maximum nosepiece force vs interval number for the base case. The design requirements and the specifications for KALIMER assembly ducts are reviewed, and preliminary core mechanics analysis for KALIMER core configuration are carried out. (Author). 7 refs., 2 tabs., 50 figs
A dynamic mechanical analysis technique for porous media.
Pattison, Adam Jeffry; McGarry, Matthew; Weaver, John B; Paulsen, Keith D
2015-02-01
Dynamic mechanical analysis (DMA) is a common way to measure the mechanical properties of materials as functions of frequency. Traditionally, a viscoelastic mechanical model is applied and current DMA techniques fit an analytical approximation to measured dynamic motion data by neglecting inertial forces and adding empirical correction factors to account for transverse boundary displacements. Here, a finite-element (FE) approach to processing DMA data was developed to estimate poroelastic material properties. Frequency-dependent inertial forces, which are significant in soft media and often neglected in DMA, were included in the FE model. The technique applies a constitutive relation to the DMA measurements and exploits a nonlinear inversion to estimate the material properties in the model that best fit the model response to the DMA data. A viscoelastic version of this approach was developed to validate the approach by comparing complex modulus estimates to the direct DMA results. Both analytical and FE poroelastic models were also developed to explore their behavior in the DMA testing environment. All of the models were applied to tofu as a representative soft poroelastic material that is a common phantom in elastography imaging studies. Five samples of three different stiffnesses were tested from 1-14 Hz with rough platens placed on the top and bottom surfaces of the material specimen under test to restrict transverse displacements and promote fluid-solid interaction. The viscoelastic models were identical in the static case, and nearly the same at frequency with inertial forces accounting for some of the discrepancy. The poroelastic analytical method was not sufficient when the relevant physical boundary constraints were applied, whereas the poroelastic FE approach produced high quality estimates of shear modulus and hydraulic conductivity. These results illustrated appropriate shear modulus contrast between tofu samples and yielded a consistent contrast in
Analysis and modeling of coupled thermo-hydro-mechanical phenomena in 3D fractured media
International Nuclear Information System (INIS)
Canamon Valera, I.
2006-11-01
This doctoral research was conducted as part of a joint France-Spain co-tutelage PhD thesis in the framework of a bilateral agreement between two universities, the Institut National Polytechnique de Toulouse (INPT) and the Universidad Politecnica de Madrid (UPM). It concerns a problem of common interest at the national and international levels, namely, the disposal of radioactive waste in deep geological repositories. The present work is devoted, more precisely, to near-field hydrogeological aspects involving mass and heat transport phenomena. The first part of the work is devoted to a specific data interpretation problem (pressures, relative humidities, temperatures) in a multi-barrier experimental system at the scale of a few meters - the 'Mock-Up Test' of the FEBEX project, conducted in Spain. Over 500 time series are characterized in terms of spatial, temporal, and/or frequency/scale-based statistical analysis techniques. The time evolution and coupling of physical phenomena during the experiment are analyzed, and conclusions are drawn concerning the behavior and reliability of the sensors. The second part of the thesis develops in more detail the 3-Dimensional (3D) modeling of coupled Thermo-Hydro-Mechanical phenomena in a fractured porous rock, this time at the scale of a hundred meters, based on the data of the 'In-Situ Test' of the FEBEX project conducted at the Grimsel Test Site in the Swiss Alps. As a first step, a reconstruction of the 3D fracture network is obtained by Monte Carlo simulation, taking into account through optimization the geomorphological data collected around the FEBEX gallery. The heterogeneous distribution of traces observed on the cylindrical wall of the tunnel is fairly well reproduced in the simulated network. In a second step, we develop a method to estimate the equivalent permeability of a many-fractured block by extending the superposition method of Ababou et al. [1994] to the case where the permeability of the rock matrix is not
Development of test methodology for dynamic mechanical analysis instrumentation
Allen, V. R.
1982-01-01
Dynamic mechanical analysis instrumentation was used for the development of specific test methodology in the determination of engineering parameters of selected materials, esp. plastics and elastomers, over a broad range of temperature with selected environment. The methodology for routine procedures was established with specific attention given to sample geometry, sample size, and mounting techniques. The basic software of the duPont 1090 thermal analyzer was used for data reduction which simplify the theoretical interpretation. Clamps were developed which allowed 'relative' damping during the cure cycle to be measured for the fiber-glass supported resin. The correlation of fracture energy 'toughness' (or impact strength) with the low temperature (glassy) relaxation responses for a 'rubber-modified' epoxy system was negative in result because the low-temperature dispersion mode (-80 C) of the modifier coincided with that of the epoxy matrix, making quantitative comparison unrealistic.
Mechanical Characteristics Analysis of Surrounding Rock on Anchor Bar Reinforcement
Gu, Shuan-cheng; Zhou, Pan; Huang, Rong-bin
2018-03-01
Through the homogenization method, the composite of rock and anchor bar is considered as the equivalent material of continuous, homogeneous, isotropic and strength parameter enhancement, which is defined as reinforcement body. On the basis of elasticity, the composite and the reinforcement are analyzed, Based on strengthening theory of surrounding rock and displacement equivalent conditions, the expression of reinforcement body strength parameters and mechanical parameters is deduced. The example calculation shows that the theoretical results are close to the results of the Jia-mei Gao[9], however, closer to the results of FLAC3D numerical simulation, it is proved that the model and surrounding rock reinforcement body theory are reasonable. the model is easy to analyze and calculate, provides a new way for determining reasonable bolt support parameters, can also provides reference for the stability analysis of underground cavern bolting support.
The modelling and analysis of the mechanics of ropes
Leech, C M
2014-01-01
This book considers the modelling and analysis of the many types of ropes, linear fibre assemblies. The construction of these structures is very diverse and in the work these are considered from the modelling point of view. As well as the conventional twisted structures, braid and plaited structures and parallel assemblies are modelled and analysed, first for their assembly and secondly for their mechanical behaviour. Also since the components are assemblies of components, fibres into yarns, into strands, and into ropes the hierarchical nature of the construction is considered. The focus of the modelling is essentially toward load extension behaviour but there is reference to bending of ropes, encompassed by the two extremes, no slip between the components and zero friction resistance to component slip. Friction in ropes is considered both between the rope components, sliding, sawing and scissoring, and within the components, dilation and distortion, these latter modes being used to model component set, the p...
Mechanical analysis of ceramic head for modular hip prosthesis
International Nuclear Information System (INIS)
Ravagli, E.
1995-03-01
A study, performed with the department of orthopaedics of the Rome Catholic University, has found out the two possible parameters mainly responsible for head breaking, i. e. errors in conical mating between head and stem, and cracks in the heads. This study has been continued in the frame of the STRIDE-CETMA project, aimed at founding and developing a centre for technologically advanced materials in Brindisi Technology Park (Italy). This report starts a systematic mechanical analysis of the above mentioned head, with the purpose of characterizing it exhaustively. The evaluations made lead to the conclusion that in nomimal conditions, the head is largely overdimensioned, taking into account the maximum load applied to the prosthesis
Bacterial Biogeography across the Amazon River-Ocean Continuum
Energy Technology Data Exchange (ETDEWEB)
Doherty, Mary; Yager, Patricia L.; Moran, Mary Ann; Coles, Victoria J.; Fortunato, Caroline S.; Krusche, Alex V.; Medeiros, Patricia M.; Payet, Jérôme P.; Richey, Jeffrey E.; Satinsky, Brandon M.; Sawakuchi, Henrique O.; Ward, Nicholas D.; Crump, Byron C.
2017-05-23
Spatial and temporal patterns in microbial biodiversity across the Amazon river-ocean continuum were investigated along ~675 km of the lower Amazon River mainstem, in the Tapajos River tributary, and in the plume and coastal ocean during low and high river discharge using amplicon sequencing of 16S rRNA genes in whole water and size-fractionated samples (0.2-2.0 μm and >2.0 μm). River communities varied among tributaries, but mainstem communities were spatially homogeneous and tracked seasonal changes in river discharge and co-varying factors. Co-occurrence network analysis identified strongly interconnected river assemblages during high (May) and low (December) discharge periods, and weakly interconnected transitional assemblages in September, suggesting that this system supports two seasonal microbial communities linked to river discharge. In contrast, plume communities showed little seasonal differences and instead varied spatially tracking salinity. However, salinity explained only a small fraction of community variability, and plume communities in blooms of diatom-diazotroph assemblages were strikingly different than those in other high salinity plume samples. This suggests that while salinity physically structures plumes through buoyancy and mixing, the composition of plume-specific communities is controlled by other factors including nutrients, phytoplankton community composition, and dissolved organic matter chemistry. Co-occurrence networks identified interconnected assemblages associated with the highly productive low salinity nearshore region, diatom-diazotroph blooms, and the plume edge region, and weakly interconnected assemblages in high salinity regions. This suggests that the plume supports a transitional community influenced by immigration of ocean bacteria from the plume edge, and by species sorting as these communities adapt to local environmental conditions. Few studies have explored patterns of microbial diversity in tropical rivers and
Correlation between videogame mechanics and executive functions through EEG analysis.
Mondéjar, Tania; Hervás, Ramón; Johnson, Esperanza; Gutierrez, Carlos; Latorre, José Miguel
2016-10-01
This paper addresses a different point of view of videogames, specifically serious games for health. This paper contributes to that area with a multidisciplinary perspective focus on neurosciences and computation. The experiment population has been pre-adolescents between the ages of 8 and 12 without any cognitive issues. The experiment consisted in users playing videogames as well as performing traditional psychological assessments; during these tasks the frontal brain activity was evaluated. The main goal was to analyse how the frontal lobe of the brain (executive function) works in terms of prominent cognitive skills during five types of game mechanics widely used in commercial videogames. The analysis was made by collecting brain signals during the two phases of the experiment, where the signals were analysed with an electroencephalogram neuroheadset. The validated hypotheses were whether videogames can develop executive functioning and if it was possible to identify which kind of cognitive skills are developed during each kind of typical videogame mechanic. The results contribute to the design of serious games for health purposes on a conceptual level, particularly in support of the diagnosis and treatment of cognitive-related pathologies. Copyright © 2016 Elsevier Inc. All rights reserved.
Mechanical analysis of the DSB cross-section
International Nuclear Information System (INIS)
Chen, Yanping.
1993-05-01
This paper presents the preliminary mechanical finite element analysis for the SSCL designed DSB dipole magnet. This SSCL version 50 mm aperture dipole magnet is for the SSCL High Energy Booster with nineteen turns, three wedges for inner coil and twenty six turns, one wedge for outer coil, the round collar is nineteen mm thick, the yoke and the shell are adopted from the design for quadrupole QSElO1. The main purposes of this mechanical study are to ensure that there are no excessive stresses in the cold mass under different loading, to avoid coils unloading from the collar at excitation of 6500 A, to ensure collar-to-yoke, line-to-line fit after welding the shell, and also to ensure the yoke midplane gaps are closed at an operating current of 6500 A. Therefore, the analyses performed include magnet assembly (collaring) to 69 Mpa azimuthal stress at the inner coil pole and 55 Mpa azimuthal stress at the outer coil pole; shell welding to 207 Mpa azimuthal stress in the shell; magnet cooldown to 4.25 K; and Lorentz excitation at a current of 6500 A
Mechanical analysis of UMo/Al dispersion fuel
International Nuclear Information System (INIS)
Jeong, Gwan Yoon; Kim, Yeon Soo; Sohn, Dong-Seong
2015-01-01
Deformation of fuel particles and mass transfer from the transverse end of fuel meat toward the meat center was observed. This caused plate thickness peaking at a location between the meat edge and the meat center. The underlying mechanism for this fuel volume transport is believed to be fission induced creep of the U–Mo/Al meat. Fuel meat swelling was measured using optical microscopy images of the cross sections of the irradiated test plates. The time-dependent meat swelling was modeled for use in numerical simulation. A distinctive discrepancy between the predicted and measured meat thickness was found at the meat ends, which was assumed to be due to creep-induced mass relocation from the meat end to the meat center region that was not considered in the meat swelling model. ABAQUS FEA simulation was performed to reproduce the observed phenomenon at the meat ends. Through the simulation, we obtained the effective creep rate constants for the interaction layers (IL) and aluminum matrix. In addition, we obtained the corresponding stress and strain analysis results that can be used to understand mechanical behavior of U–Mo/Al dispersion fuel.
Mechanical and Thermal Analysis of Classical Functionally Graded Coated Beam
Directory of Open Access Journals (Sweden)
Toudehdehghan Abdolreza
2018-01-01
Full Text Available The governing equation of a classical rectangular coated beam made of two layers subjected to thermal and uniformly distributed mechanical loads are derived by using the principle of virtual displacements and based on Euler-Bernoulli deformation beam theory (EBT. The aim of this paper was to analyze the static behavior of clamped-clamped thin coated beam under thermo-mechanical load using MATLAB. Two models were considered for composite coated. The first model was consisting of ceramic layer as a coated and substrate which was metal (HC model. The second model was consisting of Functionally Graded Material (FGM as a coated layer and metal substrate (FGC model. From the result it was apparent that the superiority of the FGC composite against conventional coated composite has been demonstrated. From the analysis, the stress level throughout the thickness at the interface of the coated beam for the FGC was reduced. Yet, the deflection in return was observed to increase. Therefore, this could cater to various new engineering applications where warrant the utilization of material that has properties that are well-beyond the capabilities of the conventional or yesteryears materials.
Stability Analysis for Compliant Constant-Force Compression Mechanisms
Directory of Open Access Journals (Sweden)
Ikechukwu Celestine UGWUOKE
2009-12-01
Full Text Available Stability analysis in compliant mechanism (CM design is of utmostimportance. From a practical point of view, a CM that is unstable is of nosignificance (has no practical value. Three useful plots were considered in theevaluation of each of the dynamic models of nine configurations of compliantconstant-force compression mechanisms (CCFCMs for their stabilitycharacteristics, which includes the polar plot based on the Routh-Hurwitzstability criterion, the Bode plot, and the Nyquist diagram which considersstability in the real frequency domain. Frequency-domain stability criterion isvery useful for determining suitable approaches to adjusting the CCFCMparameters in order to increase its relative stability. The results obtained showthat the CCFCMs investigated do exhibit higher relative stability for highervalues of damping ratio, and for zero damping ratio, all the CCFCMsinvestigated were unstable. The result also show that for the CCFCMsinvestigated to be stable, damping ratio must be greater than 0.03 (ξ > 0.03and depending on what attributes are most desirable, the CCFCM parameterscan be optimized to achieve the desired results. Nyquist criterion provides uswith suitable information concerning the absolute stability and furthermore,can be utilized to define and ascertain the relative stability of a system.
Video analysis of concussion injury mechanism in under-18 rugby
Hendricks, Sharief; O'Connor, Sam; Lambert, Michael; Brown, James C; Burger, Nicholas; Mc Fie, Sarah; Readhead, Clint; Viljoen, Wayne
2016-01-01
Background Understanding the mechanism of injury is necessary for the development of effective injury prevention strategies. Video analysis of injuries provides valuable information on the playing situation and athlete-movement patterns, which can be used to formulate these strategies. Therefore, we conducted a video analysis of the mechanism of concussion injury in junior-level rugby union and compared it with a representative and matched non-injury sample. Methods Injury reports for 18 concussion events were collected from the 2011 to 2013 under-18 Craven Week tournaments. Also, video footage was recorded for all 3 years. On the basis of the injury events, a representative ‘control’ sample of matched non-injury events in the same players was identified. The video footage, which had been recorded at each tournament, was then retrospectively analysed and coded. 10 injury events (5 tackle, 4 ruck, 1 aerial collision) and 83 non-injury events were analysed. Results All concussions were a result of contact with an opponent and 60% of players were unaware of the impending contact. For the measurement of head position on contact, 43% had a ‘down’ position, 29% the ‘up and forward’ and 29% the ‘away’ position (n=7). The speed of the injured tackler was observed as ‘slow’ in 60% of injurious tackles (n=5). In 3 of the 4 rucks in which injury occurred (75%), the concussed player was acting defensively either in the capacity of ‘support’ (n=2) or as the ‘jackal’ (n=1). Conclusions Training interventions aimed at improving peripheral vision, strengthening of the cervical muscles, targeted conditioning programmes to reduce the effects of fatigue, and emphasising safe and effective playing techniques have the potential to reduce the risk of sustaining a concussion injury. PMID:27900149
Video analysis of concussion injury mechanism in under-18 rugby.
Hendricks, Sharief; O'Connor, Sam; Lambert, Michael; Brown, James C; Burger, Nicholas; Mc Fie, Sarah; Readhead, Clint; Viljoen, Wayne
2016-01-01
Understanding the mechanism of injury is necessary for the development of effective injury prevention strategies. Video analysis of injuries provides valuable information on the playing situation and athlete-movement patterns, which can be used to formulate these strategies. Therefore, we conducted a video analysis of the mechanism of concussion injury in junior-level rugby union and compared it with a representative and matched non-injury sample. Injury reports for 18 concussion events were collected from the 2011 to 2013 under-18 Craven Week tournaments. Also, video footage was recorded for all 3 years. On the basis of the injury events, a representative 'control' sample of matched non-injury events in the same players was identified. The video footage, which had been recorded at each tournament, was then retrospectively analysed and coded. 10 injury events (5 tackle, 4 ruck, 1 aerial collision) and 83 non-injury events were analysed. All concussions were a result of contact with an opponent and 60% of players were unaware of the impending contact. For the measurement of head position on contact , 43% had a 'down' position, 29% the 'up and forward' and 29% the 'away' position (n=7). The speed of the injured tackler was observed as 'slow' in 60% of injurious tackles (n=5). In 3 of the 4 rucks in which injury occurred (75%), the concussed player was acting defensively either in the capacity of 'support' (n=2) or as the 'jackal' (n=1). Training interventions aimed at improving peripheral vision, strengthening of the cervical muscles, targeted conditioning programmes to reduce the effects of fatigue, and emphasising safe and effective playing techniques have the potential to reduce the risk of sustaining a concussion injury.
Petsev, Nikolai D.; Leal, L. Gary; Shell, M. Scott
2017-12-01
Hybrid molecular-continuum simulation techniques afford a number of advantages for problems in the rapidly burgeoning area of nanoscale engineering and technology, though they are typically quite complex to implement and limited to single-component fluid systems. We describe an approach for modeling multicomponent hydrodynamic problems spanning multiple length scales when using particle-based descriptions for both the finely resolved (e.g., molecular dynamics) and coarse-grained (e.g., continuum) subregions within an overall simulation domain. This technique is based on the multiscale methodology previously developed for mesoscale binary fluids [N. D. Petsev, L. G. Leal, and M. S. Shell, J. Chem. Phys. 144, 084115 (2016)], simulated using a particle-based continuum method known as smoothed dissipative particle dynamics. An important application of this approach is the ability to perform coupled molecular dynamics (MD) and continuum modeling of molecularly miscible binary mixtures. In order to validate this technique, we investigate multicomponent hybrid MD-continuum simulations at equilibrium, as well as non-equilibrium cases featuring concentration gradients.
Mofrad, Mohammad R. K.; Kamm, Roger D.
2011-08-01
1. Introduction and the biological basis for cell mechanics Mohammad R. K. Mofrad and Roger Kamm; 2. Experimental measurements of intracellular mechanics Paul Janmey and Christoph Schmidt; 3. The cytoskeleton as a soft glassy material Jeffrey Fredberg and Ben Fabry; 4. Continuum elastic or viscoelastic models for the cell Mohammad R. K. Mofrad, Helene Karcher and Roger Kamm; 5. Multiphasic models of cell mechanics Farshid Guuilak, Mansoor A. Haider, Lori A. Setton, Tod A. Laursen and Frank P. T. Baaijens; 6. Models of cytoskeletal mechanics based on tensegrity Dimitrije Stamenovic; 7. Cells, gels and mechanics Gerald H. Pollack; 8. Polymer-based models of cytoskeletal networks F. C. MacKintosh; 9. Cell dynamics and the actin cytoskeleton James L. McGrath and C. Forbes Dewey, Jr; 10. Active cellular motion: continuum theories and models Marc Herant and Micah Dembo; 11. Summary Mohammad R. K. Mofrad and Roger Kamm.
Analysis of transient fuel failure mechanisms: selected ANL programs
International Nuclear Information System (INIS)
Deitrich, L.W.
1975-01-01
Analytical programs at Argonne National Laboratory related to fuel pin failure mechanisms in fast-reactor accident transients are described. The studies include transient fuel pin mechanics, mechanics of unclad fuel, and mechanical effects concerning potential fuel failure propagation. (U.S.).
Zeidi, Mahdi; Kim, Chun I. L.
2018-01-01
A continuum-based model is presented for the mechanics of bidirectional composites subjected to finite plane deformations. This is framed in the development of a constitutive relation within which the constraint of material incompressibility is augmented. The elastic resistance of the fibers is accounted for directly via the computation of variational derivatives along the lengths of bidirectional fibers. The equilibrium equation and necessary boundary conditions are derived by virtue of the principles of virtual work statement. A rigorous derivation of the corresponding linear theory is developed and used to obtain a complete analytical solution for small deformations superposed on large. The proposed model can serve as an alternative 2D Cosserat theory of nonlinear elasticity.
Comparative analysis reveals the underlying mechanism of vertebrate seasonal reproduction.
Ikegami, Keisuke; Yoshimura, Takashi
2016-02-01
Animals utilize photoperiodic changes as a calendar to regulate seasonal reproduction. Birds have highly sophisticated photoperiodic mechanisms and functional genomics analysis in quail uncovered the signal transduction pathway regulating avian seasonal reproduction. Birds detect light with deep brain photoreceptors. Long day (LD) stimulus induces secretion of thyroid-stimulating hormone (TSH) from the pars tuberalis (PT) of the pituitary gland. PT-derived TSH locally activates thyroid hormone (TH) in the hypothalamus, which induces gonadotropin-releasing hormone (GnRH) and hence gonadotropin secretion. However, during winter, low temperatures increase serum TH for adaptive thermogenesis, which accelerates germ cell apoptosis by activating the genes involved in metamorphosis. Therefore, TH has a dual role in the regulation of seasonal reproduction. Studies using TSH receptor knockout mice confirmed the involvement of PT-derived TSH in mammalian seasonal reproduction. In addition, studies in mice revealed that the tissue-specific glycosylation of TSH diversifies its function in the circulation to avoid crosstalk. In contrast to birds and mammals, one of the molecular machineries necessary for the seasonal reproduction of fish are localized in the saccus vasculosus from the photoreceptor to the neuroendocrine output. Thus, comparative analysis is a powerful tool to uncover the universality and diversity of fundamental properties in various organisms. Copyright © 2015 Elsevier Inc. All rights reserved.
Mechanical behavior analysis on electrostatically actuated rectangular microplates
Li, Zhikang; Zhao, Libo; Jiang, Zhuangde; Ye, Zhiying; Dai, Lu; Zhao, Yulong
2015-03-01
Microplates are widely used in various MEMS devices based on electrostatic actuation such as MEMS switches, micro pumps and capacitive micromachined ultrasonic transducers (CMUTs). Accurate predictions for the mechanical behavior of the microplate under electrostatic force are important not only for the design and optimization of these electrostatic devices but also for their operation. This paper presents a novel reduced-order model for electrostatically actuated rectangular and square microplates with a new method to treat the nonlinear electrostatic force. The model was developed using Galerkin method which turned the partial-differential equation governing the microplates into an ordinary equation system. Using this model and cosine-like deflection functions, explicit expressions were established for the deflection and pull-in voltage of the rectangular and square microplates. The theoretical results were well validated with the finite element method simulations and experimental data of literature. The expressions for the deflection analysis are able to predict the deflection up to the pull-in position with an error less than 5.0%. The expressions for the pull-in voltage analysis can determine the pull-in voltages with errors less than 1.0%. Additionally, the method to calculate the capacitance variation of the electrostatically actuated microplates was proposed. These theoretical analyses are helpful for design and optimization of electrostatically actuated microdevices.
Mechanical behavior analysis on electrostatically actuated rectangular microplates
International Nuclear Information System (INIS)
Li, Zhikang; Zhao, Libo; Jiang, Zhuangde; Ye, Zhiying; Zhao, Yulong; Dai, Lu
2015-01-01
Microplates are widely used in various MEMS devices based on electrostatic actuation such as MEMS switches, micro pumps and capacitive micromachined ultrasonic transducers (CMUTs). Accurate predictions for the mechanical behavior of the microplate under electrostatic force are important not only for the design and optimization of these electrostatic devices but also for their operation. This paper presents a novel reduced-order model for electrostatically actuated rectangular and square microplates with a new method to treat the nonlinear electrostatic force. The model was developed using Galerkin method which turned the partial-differential equation governing the microplates into an ordinary equation system. Using this model and cosine-like deflection functions, explicit expressions were established for the deflection and pull-in voltage of the rectangular and square microplates. The theoretical results were well validated with the finite element method simulations and experimental data of literature. The expressions for the deflection analysis are able to predict the deflection up to the pull-in position with an error less than 5.0%. The expressions for the pull-in voltage analysis can determine the pull-in voltages with errors less than 1.0%. Additionally, the method to calculate the capacitance variation of the electrostatically actuated microplates was proposed. These theoretical analyses are helpful for design and optimization of electrostatically actuated microdevices. (paper)
Mechanical analysis of a shear-cracked RC beam
Directory of Open Access Journals (Sweden)
Shahriar Shahbazpanahi
2017-07-01
Full Text Available Shear crack analysis is essential for engineers to estimate repair work in concrete structures. So far, conventional theoretical and numerical analyses in fracture mechanics have been applied to study concrete flexural beams, but there is still little knowledge regarding the shear capacity for beams with a diagonal initial notch. In this study, a theoretical analysis is presented to obtain fracture resistance in a four-point RC beam with two inclined initial notch on supports. Here, a fictitious crack approach is adopted for estimating the equivalent effect of the fracture process zone of concrete in shear-cracked. Based on equilibrium equation in the beam notch cross section, shear force was expressed in terms of fracture process zone length. Then, in a double notch four-point beam, Mode II of the stress intensity factor due to the external load is determined. Finally, this process presents the relationship between the shear capacity and the fracture process zone length and expresses the fracture resistance as a function of fracture process zone length.The predicted results of loading capacities are then shown.
Continuum and micro-mechanics treatment of constraint in fracture
International Nuclear Information System (INIS)
Dodds, R.H. Jr.; Shih, C.F.
1993-01-01
This paper explores the fundamental concepts of the J-Q description of crack-tip fields, the fracture toughness locus and micromechanics approaches to predict the variability of macroscopic fracture toughness with constraint under elastic-plastic conditions. While these concepts derived from plane-strain considerations, initial applications in fully 3-D geometries are very promising. Computational results are presented for a surface cracked plate containing a 6:1 semi-elliptical, a=t/4 flaw subjected to remote uniaxial and biaxial tension. Crack-tip stress fields consistent with the J-Q theory are demonstrated to exist at each location along the crack front. The micromechanics model employs the J-Q description of crack-front stresses to interpret fracture toughness values measured on laboratory specimens for fracture assessment of the surface cracked plate. The computational results suggest only a minor effect of the biaxial loading on the crack tip stress fields and, consequently, on the propensity for fracture relative to the uniaxial loading. 45 refs., 19 figs., 3 tabs
Continuum Mechanical and Computational Aspects of Material Behavior
Energy Technology Data Exchange (ETDEWEB)
Fried, Eliot [McGill Univ., Montreal, QC (Canada)
2015-02-11
Fluid flows are typically classified as laminar or turbulent. While the glassy, regular flow of water from a slightly opened tap is laminar, the sinuous, irregular flow of water from a fully opened tap is turbulent. In a laminar flow, the velocity and other relevant fields are deterministic functions of position and time. Photos taken at different times, no matter how far removed, of steady laminar flow from a tap will be identical. In a turbulent flow, the velocity and other relevant fields manifest complex spatial and temporal fluctuations. A video of steady turbulent flow from a tap will exhibit a constantly changing pattern and many length and time scales. In nature and technology, laminar flows are more the exception than the rule. Fluvial, oceanic, pyroclastic, atmospheric, and interstellar flows are generally turbulent, as are the flows of blood through the left ventricle and air in the lungs. Flows around land, sea, and air vehicles and through pipelines, heating, cooling, and ventilation systems are generally turbulent, as are most flows involved in industrial processing, combustion, chemical reactions, and crystal growth. Over the past year, a significant portion of our research activity has focused on numerical studies of Navier-Stokes-αβ model and extensions thereof. Our results regarding these and other approaches to turbulence modeling are described below.
Kinetic analysis of the multistep aggregation mechanism of monoclonal antibodies.
Nicoud, Lucrèce; Arosio, Paolo; Sozo, Margaux; Yates, Andrew; Norrant, Edith; Morbidelli, Massimo
2014-09-11
We investigate by kinetic analysis the aggregation mechanism of two monoclonal antibodies belonging to the IgG1 and IgG2 subclass under thermal stress. For each IgG, we apply a combination of size exclusion chromatography and light scattering techniques to resolve the time evolution of the monomer, dimer, and trimer concentrations, as well as the average molecular weight and the average hydrodynamic radius of the aggregate distribution. By combining the detailed experimental characterization with a theoretical kinetic model based on population balance equations, we extract relevant information on the contribution of the individual elementary steps on the global aggregation process. The analysis shows that the two molecules follow different aggregation pathways under the same operating conditions. In particular, while the monomer depletion of the IgG1 is found to be rate-limited by monomeric conformational changes, bimolecular collision is identified as the rate-limiting step in the IgG2 aggregation process. The measurement of the microscopic rate constants by kinetic analysis allows the quantification of the protein-protein interaction potentials expressed in terms of the Fuchs stability ratio (W). It is found that the antibody solutions exhibit large W values, which are several orders of magnitude larger than the values computed in the frame of the DLVO theory. This indicates that, besides net electrostatic repulsion, additional effects delay the aggregation kinetics of the antibody solutions with respect to diffusion-limited conditions. These effects likely include the limited efficiency of the collision events due to the presence of a limited number of specific aggregation-prone patches on the heterogeneous protein surface, and the contribution of additional repulsive non-DLVO forces to the protein-protein interaction potential, such as hydration forces.
Atom depth analysis delineates mechanisms of protein intermolecular interactions
International Nuclear Information System (INIS)
Alocci, Davide; Bernini, Andrea; Niccolai, Neri
2013-01-01
Highlights: •3D atom depth analysis is proposed to identify different layers in protein structures. •Amino acid contents for each layers have been analyzed for a large protein dataset. •Charged amino acids in the most external layer are present at very different extents. •Atom depth indexes of K residues reflect their side chains flexibility. •Mobile surface charges can be responsible for long range protein–protein recognition. -- Abstract: The systematic analysis of amino acid distribution, performed inside a large set of resolved protein structures, sheds light on possible mechanisms driving non random protein–protein approaches. Protein Data Bank entries have been selected using as filters a series of restrictions ensuring that the shape of protein surface is not modified by interactions with large or small ligands. 3D atom depth has been evaluated for all the atoms of the 2,410 selected structures. The amino acid relative population in each of the structural layers formed by grouping atoms on the basis of their calculated depths, has been evaluated. We have identified seven structural layers, the inner ones reproducing the core of proteins and the outer one incorporating their most protruding moieties. Quantitative analysis of amino acid contents of structural layers identified, as expected, different behaviors. Atoms of Q, R, K, N, D residues are increasingly more abundant in going from core to surfaces. An opposite trend is observed for V, I, L, A, C, and G. An intermediate behavior is exhibited by P, S, T, M, W, H, F and Y. The outer structural layer hosts predominantly E and K residues whose charged moieties, protruding from outer regions of the protein surface, reorient free from steric hindrances, determining specific electrodynamics maps. This feature may represent a protein signature for long distance effects, driving the formation of encounter complexes and the eventual short distance approaches that are required for protein
ANALYSIS OF THE MECHANICAL STRENGTH OF A DRIVING MECHANISM CALLED SHOCK
Directory of Open Access Journals (Sweden)
Dan ILINCIOIU
2015-05-01
Full Text Available It evaluates the maximum static and dynamic stresses produced in the elements of a quadrilateral mechanism transporting a vehicle in the storage in an urban park. Determine multiplier shock hazard if the mechanism freezes and increases mechanical stress.
A 3D steady-state model of a tendon-driven continuum soft manipulator inspired by the octopus arm.
Renda, F; Cianchetti, M; Giorelli, M; Arienti, A; Laschi, C
2012-06-01
Control and modelling of continuum robots are challenging tasks for robotic researchers. Most works on modelling are limited to piecewise constant curvature. In many cases they neglect to model the actuators or avoid a continuum approach. In particular, in the latter case this leads to a complex model hardly implemented. In this work, a geometrically exact steady-state model of a tendon-driven manipulator inspired by the octopus arm is presented. It takes a continuum approach, fast enough to be implemented in the control law, and includes a model of the actuation system. The model was experimentally validated and the results are reported. In conclusion, the model presented can be used as a tool for mechanical design of continuum tendon-driven manipulators, for planning control strategies or as internal model in an embedded system.
A 3D steady-state model of a tendon-driven continuum soft manipulator inspired by the octopus arm
International Nuclear Information System (INIS)
Renda, F; Cianchetti, M; Giorelli, M; Arienti, A; Laschi, C
2012-01-01
Control and modelling of continuum robots are challenging tasks for robotic researchers. Most works on modelling are limited to piecewise constant curvature. In many cases they neglect to model the actuators or avoid a continuum approach. In particular, in the latter case this leads to a complex model hardly implemented. In this work, a geometrically exact steady-state model of a tendon-driven manipulator inspired by the octopus arm is presented. It takes a continuum approach, fast enough to be implemented in the control law, and includes a model of the actuation system. The model was experimentally validated and the results are reported. In conclusion, the model presented can be used as a tool for mechanical design of continuum tendon-driven manipulators, for planning control strategies or as internal model in an embedded system. (paper)
Computational aspects of the continuum quaternionic wave functions for hydrogen
Energy Technology Data Exchange (ETDEWEB)
Morais, J., E-mail: joao.pedro.morais@ua.pt
2014-10-15
Over the past few years considerable attention has been given to the role played by the Hydrogen Continuum Wave Functions (HCWFs) in quantum theory. The HCWFs arise via the method of separation of variables for the time-independent Schrödinger equation in spherical coordinates. The HCWFs are composed of products of a radial part involving associated Laguerre polynomials multiplied by exponential factors and an angular part that is the spherical harmonics. In the present paper we introduce the continuum wave functions for hydrogen within quaternionic analysis ((R)QHCWFs), a result which is not available in the existing literature. In particular, the underlying functions are of three real variables and take on either values in the reduced and full quaternions (identified, respectively, with R{sup 3} and R{sup 4}). We prove that the (R)QHCWFs are orthonormal to one another. The representation of these functions in terms of the HCWFs are explicitly given, from which several recurrence formulae for fast computer implementations can be derived. A summary of fundamental properties and further computation of the hydrogen-like atom transforms of the (R)QHCWFs are also discussed. We address all the above and explore some basic facts of the arising quaternionic function theory. As an application, we provide the reader with plot simulations that demonstrate the effectiveness of our approach. (R)QHCWFs are new in the literature and have some consequences that are now under investigation.
Nonlinear mechanics a supplement to theoretical mechanics of particles and continua
Fetter, Alexander L
2006-01-01
In their prior Dover book, Theoretical Mechanics of Particles and Continua, Alexander L. Fetter and John Dirk Walecka provided a lucid and self-contained account of classical mechanics, together with appropriate mathematical methods. This supplement-an update of that volume-offers a bridge to contemporary mechanics.The original book's focus on continuum mechanics-with chapters on sound waves in fluids, surface waves on fluids, heat conduction, and viscous fluids-forms the basis for this supplement's discussion of nonlinear continuous systems. Topics include linearized stability analysis; a det
Nonlinear modeling of crystal system transition of black phosphorus using continuum-DFT model
Setoodeh, A. R.; Farahmand, H.
2018-01-01
In this paper, the nonlinear behavior of black phosphorus crystals is investigated in tandem with dispersion-corrected density functional theory (DFT-D) analysis under uniaxial loadings. From the identified anisotropic behavior of black phosphorus due to its morphological anisotropy, a hyperelastic anisotropic (HA) model named continuum-DFT is established to predict the nonlinear behavior of the material. In this respect, uniaxial Cauchy stresses are employed on both the DFT-D and HA models along the zig-zag and armchair directions. Simultaneously, the transition of the crystal system is recognized at about 4.5 GPa of the applied uniaxial tensile stress along the zig-zag direction on the DFT-D simulation in the nonlinear region. In order to develop the nonlinear continuum model, unknown constants are surveyed with the optimized least square technique. In this regard, the continuum model is obtained to reproduce the Cauchy stress–stretch and density of strain–stretch results of the DFT-D simulation. Consequently, the modified HA model is introduced to characterize the nonlinear behavior of black phosphorus along the zig-zag direction. More importantly, the specific transition of the crystal system is successfully predicted in the new modified continuum-DFT model. The results reveal that the multiscale continuum-DFT model is well defined to replicate the nonlinear behavior of black phosphorus along the zig-zag and armchair directions.
Nonlinear modeling of crystal system transition of black phosphorus using continuum-DFT model.
Setoodeh, A R; Farahmand, H
2018-01-24
In this paper, the nonlinear behavior of black phosphorus crystals is investigated in tandem with dispersion-corrected density functional theory (DFT-D) analysis under uniaxial loadings. From the identified anisotropic behavior of black phosphorus due to its morphological anisotropy, a hyperelastic anisotropic (HA) model named continuum-DFT is established to predict the nonlinear behavior of the material. In this respect, uniaxial Cauchy stresses are employed on both the DFT-D and HA models along the zig-zag and armchair directions. Simultaneously, the transition of the crystal system is recognized at about 4.5 GPa of the applied uniaxial tensile stress along the zig-zag direction on the DFT-D simulation in the nonlinear region. In order to develop the nonlinear continuum model, unknown constants are surveyed with the optimized least square technique. In this regard, the continuum model is obtained to reproduce the Cauchy stress-stretch and density of strain-stretch results of the DFT-D simulation. Consequently, the modified HA model is introduced to characterize the nonlinear behavior of black phosphorus along the zig-zag direction. More importantly, the specific transition of the crystal system is successfully predicted in the new modified continuum-DFT model. The results reveal that the multiscale continuum-DFT model is well defined to replicate the nonlinear behavior of black phosphorus along the zig-zag and armchair directions.
Distributions of self-trapped hole continuums in silica glass
International Nuclear Information System (INIS)
Wang, R. P.; Saito, K.; Ikushima, A. J.
2006-01-01
Photobleaching of self-trapped holes (STH) in low temperature UV-irradiated silica glass has been investigated by the electron spin resonance method. The bleaching time dependence of the decay of two kinds of STH, STH 1 , and STH 2 , could be well fitted by the stretched exponential function, and STH 2 has a quicker decay than STH 1 . On the other hand, the decay becomes significant large when the photon energy increases from 1.5 to 2.0 eV, and then keeps constant with a further increase of photon energy. The distributions of the STH continuums are estimated at the positions on top of the valence band, being 1.66±0.27 eV for STH 1 and 1.63±0.33 eV for STH 2 . A possible recombination mechanism is proposed to explain the decay of STH signals
Pathway Analysis and the Search for Causal Mechanisms
Weller, Nicholas; Barnes, Jeb
2016-01-01
The study of causal mechanisms interests scholars across the social sciences. Case studies can be a valuable tool in developing knowledge and hypotheses about how causal mechanisms function. The usefulness of case studies in the search for causal mechanisms depends on effective case selection, and there are few existing guidelines for selecting…
Continuum modeling an approach through practical examples
Muntean, Adrian
2015-01-01
This book develops continuum modeling skills and approaches the topic from three sides: (1) derivation of global integral laws together with the associated local differential equations, (2) design of constitutive laws and (3) modeling boundary processes. The focus of this presentation lies on many practical examples covering aspects such as coupled flow, diffusion and reaction in porous media or microwave heating of a pizza, as well as traffic issues in bacterial colonies and energy harvesting from geothermal wells. The target audience comprises primarily graduate students in pure and applied mathematics as well as working practitioners in engineering who are faced by nonstandard rheological topics like those typically arising in the food industry.
Continuum description of avalanches in granular media.
Energy Technology Data Exchange (ETDEWEB)
Aranson, I. S.; Tsimring, L. S.
2000-12-05
A continuum theory of partially fluidized granular flows is proposed. The theory is based on a combination of the mass and momentum conservation equations with the order parameter equation which describes the transition between flowing and static components of the granular system. We apply this model to the dynamics of avalanches in chutes. The theory provides a quantitative description of recent observations of granular flows on rough inclined planes (Daerr and Douady 1999): layer bistability, and the transition from triangular avalanches propagating downhill at small inclination angles to balloon-shaped avalanches also propagating uphill for larger angles.
Histidine in Continuum Electrostatics Protonation State Calculations
Couch, Vernon; Stuchebruckhov, Alexei
2014-01-01
A modification to the standard continuum electrostatics approach to calculate protein pKas which allows for the decoupling of histidine tautomers within a two state model is presented. Histidine with four intrinsically coupled protonation states cannot be easily incorporated into a two state formalism because the interaction between the two protonatable sites of the imidazole ring is not purely electrostatic. The presented treatment, based on a single approximation of the interrelation between histidine’s charge states, allows for a natural separation of the two protonatable sites associated with the imidazole ring as well as the inclusion of all protonation states within the calculation. PMID:22072521
Lyman Continuum Leakage in the Local Universe
Leitherer, Claus; Hernandez, Svea; Lee, Janice; Oey, Sally
2015-08-01
Star-forming galaxies are viable candidates for providing the ionizing photon supply accounting for the reionization of the early universe. However, direct determination of the fraction of ionizing photons that can escape the optically thick galaxy ISM is challenging. I will discuss Lyman continuum observations of a sample of massive young star clusters in local galaxies which take advantage of a new capability of HST's Cosmic Origins Spectrograph. The derived photon leakages are compared to values found at high redshift and discussed in the context of cosmological models.
Quasi-bound states in continuum
International Nuclear Information System (INIS)
Nakamura, Hiroaki; Hatano, Naomichi; Garmon, Sterling; Petrosky, Tomio
2007-08-01
We report the prediction of quasi-bound states (resonant states with very long lifetimes) that occur in the eigenvalue continuum of propagating states for a wide region of parameter space. These quasi-bound states are generated in a quantum wire with two channels and an adatom, when the energy bands of the two channels overlap. A would-be bound state that lays just below the upper energy band is slightly destabilized by the lower energy band and thereby becomes a resonant state with a very long lifetime (a second QBIC lays above the lower energy band). (author)
Importance of Coulomb interactions in bound-to-continuum THz quantum cascade lasers
Energy Technology Data Exchange (ETDEWEB)
Jirauschek, C; Matyas, A [Emmy Noether Research Group ' Modeling of Quantum Cascade Devices' , Technische Universitaet Muenchen, D-80333 Munich (Germany); Lugli, P, E-mail: jirauschek@tum.d [Institute for Nanoelectronics, Technische Universitaet Muenchen, D-80333 Munich (Germany)
2009-11-15
We demonstrate the importance of Coulomb interactions in bound-to-continuum THz quantum cascade lasers, employing an ensemble Monte-Carlo analysis. In such structures, the electron-electron interactions between the closely spaced energy levels in the minibands tend to play a more important role than in resonant-phonon depopulation designs, where the energy levels are more energetically separated and LO phonon scattering prevails. Also a significant conduction band bending due to space charge effects is observed. Thus, especially for bound-to-continuum structures careful modelling of Coulomb interactions is crucial to obtain good agreement with experiment.
Analysis of barosensitive mechanisms in yeast for Pressure Regulated Fermentation
Nomura, Kazuki; Iwahashi, Hitoshi; Iguchi, Akinori; Shigematsu, Toru
2013-06-01
Introduction: We are intending to develop a novel food processing technology, Pressure Regulated Fermentation (PReF), using pressure sensitive (barosensitive) fermentation microorganisms. Objectives of our study are to clarify barosensitive mechanisms for application to PReF technology. We isolated Saccharomyces cerevisiae barosensitive mutant a924E1 that was derived from the parent KA31a. Methods: Gene expression levels were analyzed by DNA microarray. The altered genes of expression levels were classified according to the gene function. Mutated genes were estimated by mating and producing diploid strains and confirmed by PCR of mitochondrial DNA (mtDNA). Results and Discussion: Gene expression profiles showed that genes of `Energy' function and that of encoding protein localized in ``Mitochondria'' were significantly down regulated in the mutant. These results suggest the respiratory deficiency and relationship between barosensitivity and respiratory deficiency. Since the respiratory functions of diploids showed non Mendelian inheritance, the respiratory deficiency was indicated to be due to mtDNA mutation. PCR analysis showed that the region of COX1 locus was deleted. COX1 gene encodes the subunit 1 of cytochrome c oxidase. For this reason, barosensitivity is strongly correlated with mitochondrial functions.
Analysis of the partnership network in the clean development mechanism
International Nuclear Information System (INIS)
Kang, Moon Jung; Park, Jihyoun
2013-01-01
The clean development mechanism (CDM) is a global collaborative action proposed at the Kyoto Protocol in response to climate change issues. The CDM contributes to cost-efficient reduction of greenhouse gas emissions in industrialized countries and promotes sustainable development in developing countries. Its fundamental framework is based on partnerships between industrialized and developing countries. This study employs social network analysis to investigate the dynamics of the partnership networks observed in 3816 CDM projects registered in the database of the United Nations Framework Convention on Climate Change over the period of 2005 to 2011. Our three main findings can be summarized as follows. First, the CDM partnership network is a small world; however, its density tends to decrease as the number of participants for a CDM project decreases. Second, the partnership networks’ leading groups tend to shift from partner countries into host countries. Third, a host country that pursues more partnership-based projects takes better control of resources and knowledge-flow in the ego-network formed around that country, and can thus better utilize global resources for its CDM projects. - Highlights: ► We investigate dynamics of the international partnership networks of CDM projects. ► The density of CDM networks tends to decrease by time. ► The partnership networks’ leading groups tend to shift into host countries. ► A host country with more partnerships better utilizes global knowledge resources.
Dissipation consistent fabric tensor definition from DEM to continuum for granular media
Li, X. S.; Dafalias, Y. F.
2015-05-01
In elastoplastic soil models aimed at capturing the impact of fabric anisotropy, a necessary ingredient is a measure of anisotropic fabric in the form of an evolving tensor. While it is possible to formulate such a fabric tensor based on indirect phenomenological observations at the continuum level, it is more effective and insightful to have the tensor defined first based on direct particle level microstructural observations and subsequently deduce a corresponding continuum definition. A practical means able to provide such observations, at least in the context of fabric evolution mechanisms, is the discrete element method (DEM). Some DEM defined fabric tensors such as the one based on the statistics of interparticle contact normals have already gained widespread acceptance as a quantitative measure of fabric anisotropy among researchers of granular material behavior. On the other hand, a fabric tensor in continuum elastoplastic modeling has been treated as a tensor-valued internal variable whose evolution must be properly linked to physical dissipation. Accordingly, the adaptation of a DEM fabric tensor definition to a continuum constitutive modeling theory must be thermodynamically consistent in regards to dissipation mechanisms. The present paper addresses this issue in detail, brings up possible pitfalls if such consistency is violated and proposes remedies and guidelines for such adaptation within a recently developed Anisotropic Critical State Theory (ACST) for granular materials.
Missing links in the root-soil organic matter continuum
Energy Technology Data Exchange (ETDEWEB)
O' Brien, Sarah L. [Argonne National Laboratory (ANL); Iversen, Colleen M [ORNL
2009-01-01
wide range of soil processes, from the exudation of labile C compounds to the development of fungal associations. For example, Zoe Cardon demonstrated that the root-mediated redistribution of deep soil water to relatively dry shallower soil, increased soil CO{sub 2} efflux and nutrient cycling near the surface in an arid ecosystem. Andrew Kulmatiski also discussed the importance of rooting distribution throughout the soil profile for strategies of water uptake by different species in an African savanna. Later, Julie Jastrow demonstrated that living roots shape soil physical structure by promoting the formation of soil aggregates, which facilitated accrual of SOM in restored grasslands. Taken together, the evidence is compelling that living roots, and organic matter derived from root detritus, are important parts of the continuum of organic matter in the soil. Larger soil organisms (i.e. 50 {micro}m to many cm in body size) play an important role in the root-SOM continuum by grazing on roots and microbes, comminuting organic matter and aggregating soil in fecal pellets. However, litterbag and soil incubation studies necessarily exclude invertebrates, and research on faunal activity and trophic dynamics tends to be independent from research on the biogeochemistry of SOM cycling. Tim Filley used plant-derived biomarkers in invertebrate residues to bridge the gap between larger soil organisms, such as earthworms and beetle larvae, and SOM distribution. He found that larger soil organisms help to stabilize root-derived organic matter in soil aggregates. Similar coupling of biogeochemistry with food web studies could prove fruitful for describing mechanisms that underlie critical ecosystem processes. Despite considerable research efforts, the breadth of the microbial role in the root-SOM continuum remains unresolved. Using advanced pyrosequencing techniques, David Nelson demonstrated the importance of archea as nitrifiers in agricultural systems exposed to elevated [CO{sub 2
Caltagirone, Jean-Paul
2014-01-01
This book presents the fundamental principles of mechanics to re-establish the equations of Discrete Mechanics. It introduces physics and thermodynamics associated to the physical modeling. The development and the complementarity of sciences lead to review today the old concepts that were the basis for the development of continuum mechanics. The differential geometry is used to review the conservation laws of mechanics. For instance, this formalism requires a different location of vector and scalar quantities in space. The equations of Discrete Mechanics form a system of equations where the H
Continuum damage modeling and simulation of hierarchical dental enamel
Ma, Songyun; Scheider, Ingo; Bargmann, Swantje
2016-05-01
Dental enamel exhibits high fracture toughness and stiffness due to a complex hierarchical and graded microstructure, optimally organized from nano- to macro-scale. In this study, a 3D representative volume element (RVE) model is adopted to study the deformation and damage behavior of the fibrous microstructure. A continuum damage mechanics model coupled to hyperelasticity is developed for modeling the initiation and evolution of damage in the mineral fibers as well as protein matrix. Moreover, debonding of the interface between mineral fiber and protein is captured by employing a cohesive zone model. The dependence of the failure mechanism on the aspect ratio of the mineral fibers is investigated. In addition, the effect of the interface strength on the damage behavior is studied with respect to geometric features of enamel. Further, the effect of an initial flaw on the overall mechanical properties is analyzed to understand the superior damage tolerance of dental enamel. The simulation results are validated by comparison to experimental data from micro-cantilever beam testing at two hierarchical levels. The transition of the failure mechanism at different hierarchical levels is also well reproduced in the simulations.
On the continuum limit of a Z4 lattice gauge theory
International Nuclear Information System (INIS)
Pena, A.; Socolovsky, M.
1983-01-01
The continuum limit of a Z 4 gauge plus matter lattice theory is identified with massless scalar and vector fields with quartic self-interactions phi 4 and (AμAμ) 2 , respectively. The analysis is based on the mean field approximation after gauge fixing. (orig.)
Multiple Temperature Model for Near Continuum Flows
International Nuclear Information System (INIS)
XU, Kun; Liu, Hongwei; Jiang, Jianzheng
2007-01-01
In the near continuum flow regime, the flow may have different translational temperatures in different directions. It is well known that for increasingly rarefied flow fields, the predictions from continuum formulation, such as the Navier-Stokes equations, lose accuracy. These inaccuracies may be partially due to the single temperature assumption in the Navier-Stokes equations. Here, based on the gas-kinetic Bhatnagar-Gross-Krook (BGK) equation, a multitranslational temperature model is proposed and used in the flow calculations. In order to fix all three translational temperatures, two constraints are additionally proposed to model the energy exchange in different directions. Based on the multiple temperature assumption, the Navier-Stokes relation between the stress and strain is replaced by the temperature relaxation term, and the Navier-Stokes assumption is recovered only in the limiting case when the flow is close to the equilibrium with the same temperature in different directions. In order to validate the current model, both the Couette and Poiseuille flows are studied in the transition flow regime
A continuum-based model capturing size effects in polymer bonds
International Nuclear Information System (INIS)
Diebels, S; Johlitz, M; Steeb, H; Chatzouridou, A; Batal, J; Possart, W
2007-01-01
It is known from applications that the mechanical behaviour of polymer bonds does not only depend on the properties of the polymer itself but also on the substrate. Therefore, the mechanical behaviour, i.e. the stiffness, of a polymer joint becomes thickness dependent. In the present work we describe experiments performed on polymer joints and we develop a continuum-based model which is able to describe the experimentally observed size effects without suggesting the microstructure in detail. The continuum mechanical model is enhanced by a scalar-valued structure parameter which describes all the effects taking place in the boundary layer which arises near the substrate. It is shown that the model parameters can be determined on the basis of simple shear experiments performed on polymer layers of different thickness
Paes, S.S.; Yakimets, I.; Wellner, N.; Hill, S.E.; Wilson, R.H.; Mitchell, J.R.
2010-01-01
The aim of this study was to provide a detailed description of the fracture mechanisms in three different biopolymer thin materials: gelatin, hydroxypropyl cellulose (HPC) and cassava starch films. That was achieved by using a combination of fracture mechanics methodology and in situ visualization
Gao, B. C.; Meng, X. K.; Shen, M. X.; Peng, X. D.
2016-05-01
A transient thermal-mechanical coupling model for a contacting mechanical seal during start-up has been developed. It takes into consideration the coupling relationship among thermal-mechanical deformation, film thickness, temperature and heat generation. The finite element method and multi-iteration technology are applied to solve the temperature distribution and thermal-mechanical deformation as well as their evolution behavior. Results show that the seal gap transforms from negative coning to positive coning and the contact area of the mechanical seal gradually decreases during start-up. The location of the maximum temperature and maximum contact pressure move from the outer diameter to inside diameter. The heat generation and the friction torque increase sharply at first and then decrease. Meanwhile, the contact force decreases and the fluid film force and leakage rate increase.
Analysis of health promotion and prevention financing mechanisms in Thailand.
Watabe, Akihito; Wongwatanakul, Weranuch; Thamarangsi, Thaksaphon; Prakongsai, Phusit; Yuasa, Motoyuki
2017-08-01
In the transition to the post-2015 agenda, many countries are striving towards universal health coverage (UHC). Achieving this, governments need to shift from curative care to promotion and prevention services. This research analyses Thailand's financing system for health promotion and prevention, and assesses policy options for health financing reforms. The study employed a mixed-methods approach and integrates multiple sources of evidence, including scientific and grey literature, expenditure data, and semi-structured interviews with key stakeholders in Thailand. The analysis was underpinned by the use of a well-known health financing framework. In Thailand, three agencies plus local governments share major funding roles for health promotion and prevention services: the Ministry of Public Health (MOPH), the National Health Security Office, the Thai Health Promotion Foundation and Tambon Health Insurance Funds. The total expenditure on prevention and public health in 2010 was 10.8% of the total health expenditure, greater than many middle-income countries that average 7.0-9.2%. MOPH was the largest contributor at 32.9%, the Universal Coverage scheme was the second at 23.1%, followed by the local governments and ThaiHealth at 22.8 and 7.3%, respectively. Thailand's health financing system for promotion and prevention is strategic and innovative due to the three complementary mechanisms in operation. There are several methodological limitations to determine the adequate level of spending. The health financing reforms in Thailand could usefully inform policymakers on ways to increase spending on promotion and prevention. Further comparative policy research is needed to generate evidence to support efforts towards UHC. © The Author 2016. Published by Oxford University Press.
Analysis of early-stage sintering mechanisms of mechanically activated BaTiO3
Directory of Open Access Journals (Sweden)
Nikolić M.V.
2006-01-01
Full Text Available Barium-titanate powder was mechanically activated in a planetary-ball mill for 60 and 120 minutes. Non-isothermal sintering of non-activated and activated powder samples was investigated using a dilatometer in the temperature interval from room to 1380oC with three different heating rates (10, 20 and 30oC/min. Early-stage sintering mechanisms for all three types of samples were analyzed, showing significant differences between the non-activated and mechanically activated samples.
Mechanical property analysis of kenaf–glass fibre reinforced ...
Indian Academy of Sciences (India)
mechanical properties and are used as reinforcing materials in polymer composites [3–5]. However, the products made from natural fibre composite are still limited to the structural applications, owing to their poor mechanical prop- erties [6]. To solve this issue, the natural fibres are hybridized with synthetic fibres to make the ...
A Comparative Analysis Of The Technical Efficiency Of Mechanized ...
African Journals Online (AJOL)
mechanized cassava farmers in Egor and Oredo Local Government Areas of Edo State, ... cultivated had negative significant (P<0.01) effect on their inefficiency while for the non-mechanized farmers, all the above variables except educational level ...
An experimental analysis of fracture mechanisms by acoustic ...
African Journals Online (AJOL)
Afin d'analyser le comportement mécanique globale de l'assemblage, des essais de traction .... named as Groups A, B and C (Tab. 5). Table.1: Mechanical properties of epoxy matrix Vicotex 914. Table.2: Mechanical properties of fibers T300. Young. 's modul us. E. Poisson's ratio. Ν shear modulus. G. Tensile strength yield.
Experimental Analysis of Tensile Mechanical Properties of Sprayed FRP
Directory of Open Access Journals (Sweden)
Zhao Yang
2016-01-01
Full Text Available To study the tensile mechanical properties of sprayed FRP, 13 groups of specimens were tested through uniaxial tensile experiments, being analyzed about stress-strain curve, tensile strength, elastic modulus, breaking elongation, and other mechanical properties. Influencing factors on tensile mechanical properties of sprayed FRP such as fiber type, resin type, fiber volume ratio, fiber length, and composite thickness were studied in the paper too. The results show that both fiber type and resin type have an obvious influence on tensile mechanical properties of sprayed FRP. There will be a specific fiber volume ratio for sprayed FRP to obtain the best tensile mechanical property. The increase of fiber length can lead to better tensile performance, while that of composite thickness results in property degradation. The study can provide reference to popularization and application of sprayed FRP material used in structure reinforcement.
Adaptive spacetime method using Riemann jump conditions for coupled atomistic-continuum dynamics
Kraczek, B.; Miller, S. T.; Haber, R. B.; Johnson, D. D.
2010-03-01
We combine the Spacetime Discontinuous Galerkin (SDG) method for elastodynamics with the mathematically consistent Atomistic Discontinuous Galerkin (ADG) method in a new scheme that concurrently couples continuum and atomistic models of dynamic response in solids. The formulation couples non-overlapping continuum and atomistic models across sharp interfaces by weakly enforcing jump conditions, for both momentum balance and kinematic compatibility, using Riemann values to preserve the characteristic structure of the underlying hyperbolic system. Momentum balances to within machine-precision accuracy over every element, on each atom, and over the coupled system, with small, controllable energy dissipation in the continuum region that ensures numerical stability. When implemented on suitable unstructured spacetime grids, the continuum SDG model offers linear computational complexity in the number of elements and powerful adaptive analysis capabilities that readily bridge between atomic and continuum scales in both space and time. A special trace operator for the atomic velocities and an associated atomistic traction field enter the jump conditions at the coupling interface. The trace operator depends on parameters that specify, at the scale of the atomic spacing, the position of the coupling interface relative to the atoms. In a key finding, we demonstrate that optimizing these parameters suppresses spurious reflections at the coupling interface without the use of non-physical damping or special boundary conditions. We formulate the implicit SDG-ADG coupling scheme in up to three spatial dimensions, and describe an efficient iterative solution scheme that outperforms common explicit schemes, such as the Velocity Verlet integrator. Numerical examples, in 1d×time and employing both linear and nonlinear potentials, demonstrate the performance of the SDG-ADG method and show how adaptive spacetime meshing reconciles disparate time steps and resolves atomic-scale signals
Coupled Mechanical-Electrochemical-Thermal Analysis of Failure Propagation in Lithium-ion Batteries
Energy Technology Data Exchange (ETDEWEB)
Zhang, Chao; Santhanagopalan, Shriram; Pesaran, Ahmad
2016-07-28
This is a presentation given at the 12th World Congress for Computational Mechanics on coupled mechanical-electrochemical-thermal analysis of failure propagation in lithium-ion batteries for electric vehicles.
Performance analysis of spectrum sharing mechanisms in cognitive radio networks
Directory of Open Access Journals (Sweden)
Peipei Chen
2011-01-01
Full Text Available Abstract In this article, a non-preemptive (NP mechanism is proposed to improve the quality-of-service (QoS of secondary users (SUs in joint leasing and sensing-based cognitive radio networks (CRNs. In this spectrum-sharing mechanism, a primary user (PU could not forcibly terminate a SU with ongoing transmission. Both the typical preemptive and the proposed NP mechanisms are modeled by multi-dimensional Markov chains with three state variables. A decomposition-approximated method is used to derive the closed-form solutions of the steady-state probabilities in the Markov chains. The analytical results are verified by numerical results. System parameters that affect performance metrics are also investigated in these two mechanisms. The simulation results show that in the proposed mechanism the performance metrics of SUs such as force-termination probability and mean system delay are improved significantly, with an acceptable loss of PUs' QoS in terms of mean waiting time and blocking probability. A QoS tradeoff can be achieved between the primary and the secondary systems. For QoS improvement of SUs, the proposed NP mechanism outperforms the preemptive mechanism in joint leasing and sensing-based CRNs.
A Structural Analysis of a Mechanical Heart Valve Prosthesis with Flat Leaflet
Kwon, Young Joo
This paper addresses the basic concept of MDO methodology and the structural analysis that should be performed in the design process of a mechanical heart valve prosthesis with flat leaflet using MDO methodology. In the structural design of the mechanical heart valve (MHV) prosthesis, the fluid mechanics analysis is executed for the blood flow passing through the leaflets of a mechanical heart valve prosthesis. Thereafter, the rigid body dynamics analysis of the leaflet motion is performed to obtain the structural condition for the structural mechanics analysis of the deformed leaflet. Then the structural mechanics analysis of the deformed leaflet follows to confirm the minimum thickness of the leaflet for the structural durability of the mechanical heart valve prosthesis. This paper shows that the minimum leaflet thickness can be evaluated to be 0.6mm among the suggested thicknesses.
Toward the Development of a Flexible Mesoscale MRI-compatible Neurosurgical Continuum Robot.
Kim, Yeongjin; Cheng, Shing Shin; Diakite, Mahamadou; Gullapalli, Rao P; Simard, J Marc; Desai, Jaydev P
2017-12-01
Brain tumor, be it primary or metastatic, is usually life threatening for a person of any age. Primary surgical resection which is one of the most effective ways of treating brain tumors can have tremendously increased success rate if the appropriate imaging modality is used for complete tumor resection. Magnetic resonance imaging (MRI) is the imaging modality of choice for brain tumor imaging because of its excellent soft-tissue contrast. MRI combined with continuum soft robotics has immense potential to be the next major technological breakthrough in the field of brain cancer diagnosis and therapy. In this work, we present the design, kinematic, and force analysis of a flexible spring-based minimally invasive neurosurgical intracranial robot (MINIR-II). It is comprised of an inter-connected inner spring and an outer spring and is connected to actively cooled shape memory alloy spring actuators via tendon driven mechanism. Our robot has three serially connected 2-DoF segments which can be independently controlled due to the central tendon routing configuration. The kinematic and force analysis of the robot and the independent segment control were verified by experiments. Robot motion under forced cooling of SMA springs was evaluated as well as the MRI compatibility of the robot and its motion capability in brainlike gelatin environment.
Thermal mechanical analysis of applications with internal heat generation
Govindarajan, Srisharan Garg
control blade, spatial variations in temperature within the control blade occur from the non-uniform heat generation within the BORAL as a result of the non-uniform thermal neutron flux along the longitudinal direction when the control blade is partially withdrawn. There is also variation in the heating profile through the thickness and about the circumferential width of the control blade. Mathematical curve-fits are generated for the non-uniform volumetric heat generation profile caused by the thermal neutron absorption and the functions are applied as heating conditions within a finite element model of the control blade built using the commercial finite element code Abaqus FEA. The finite element model is solved as a fully coupled thermal mechanical problem as in the case of the annular target. The resulting deflection is compared with the channel gap to determine if there is a significant risk of the control blade binding during reactor operation. Hence, this dissertation will consist of two sections. The first section will seek to present the thermal and structural safety analyses of the annular targets for the production of molybdenum-99. Since there hasn't been any detailed, documented, study on these annular targets in the past, the work complied in this dissertation will help to understand the thermal-mechanical behavior and failure margins of the target during in-vessel irradiation. As the work presented in this dissertation provides a general performance analysis envelope for the annular target, the tools developed in the process can also be used as useful references for future analyses that are specific to any reactor. The numerical analysis approach adopted and the analytical models developed, can also be applied to other applications, outside the Mo-99 project domain, where internal heat generation exists such as in electronic components and nuclear reactor control blades. The second section will focus on estimating the thermally induced deflection and hence
Understanding the mechanism(s) of mosaic trisomy 21 by using DNA polymorphism analysis
Energy Technology Data Exchange (ETDEWEB)
Pangalos, C.; Abazis, D.; Avramopoulos, D.; Blouin, J.L.; Antonaraksi, S.E. (Univ. of Patras Medical School (Greece)); Raoul, O.; deBlois, M.C.; Prieur, M. (Cytogenetics Laboratory, Paris (France)); Schinzel, A.A.
1994-03-01
In order to investigate the mechanism(s) underlying mosaicism for trisomy 21, the authors genotyped 17 families with mosaic trisomy 21 probands, using 28 PCR-detectable DNA polymorphic markers that map in the pericentromeric region and long arm of chromosome 21. The percentage of cells with trisomy 21 in the probands' blood lymphocytes was 6%-94%. There were two classes of autoradiographic results: In class I, a third allele' of lower intensity was detected in the proband's DNA for at least two chromosome 21 markers. The interpretation of this result was that the proband had inherited three chromosomes 21 after meiotic nondisjunction (NDJ) (trisomy 21 zygote) and subsequently lost one because of mitotic (somatic) error, the lost chromosome 21 being that with the lowest-intensity polymorphic allele. The parental origin and the meiotic stage of NDJ could also be determined. In class II, a third allele' was never detected. In these cases, the mosaicism probably occurred either by a postzygotic, mitotic error in anormal zygote that followed a normal meiosis (class IIA mechanism); by premeiotic, mitotic NDJ yielding an aneusomic zygote after meiosis, and subsequent mitotic loss (class IIB mechanism); or by a meiosis II error with lack of crossover in the preceding meiosis I, followed by mitotic loss after fertilization (class IIC mechanism). Among class II mechanisms, the most likely is mechanism IIA, while IIC is the least likely. There were 10 cases of class I and 7 cases of class II results. Within class I, there were nine cases with maternal meitoic errors (six meiosis I and three meiosis II errors, on the basis of pericentromeric markers) and one with paternal meiosis I error. The postzygotic loss of chromosome 21 was determined in eight maternal class I cases, and it was maternally derived in five cases and paternally derived in three; this suggests that the postzygotic loss of chromosome 21 is probably random. 28 refs., 1 fig., 2 tabs.
Variational continuum multiphase poroelasticity theory and applications
Serpieri, Roberto
2017-01-01
This book collects the theoretical derivation of a recently presented general variational macroscopic continuum theory of multiphase poroelasticity (VMTPM), together with its applications to consolidation and stress partitioning problems of interest in several applicative engineering contexts, such as in geomechanics and biomechanics. The theory is derived based on a purely-variational deduction, rooted in the least-Action principle, by considering a minimal set of kinematic descriptors. The treatment herein considered keeps a specific focus on the derivation of most general medium-independent governing equations. It is shown that VMTPM recovers paradigms of consolidated use in multiphase poroelasticity such as Terzaghi's stress partitioning principle and Biot's equations for wave propagation. In particular, the variational treatment permits the derivation of a general medium-independent stress partitioning law, and the proposed variational theory predicts that the external stress, the fluid pressure, and the...
Continuum Reverberation Mapping of AGN Accretion Disks
Energy Technology Data Exchange (ETDEWEB)
Fausnaugh, Michael M. [Department of Astronomy, Ohio State University, Columbus, OH (United States); MIT Kavli Institute for Astrophysics and Space Research, Cambridge, MA (United States); Peterson, Bradley M. [Department of Astronomy, Ohio State University, Columbus, OH (United States); Center for Cosmology and AstroParticle Physics, Ohio State University, Columbus, OH (United States); Space Telescope Science Institute, Baltimore, MD (United States); Starkey, David A. [SUPA Physics and Astronomy, University of St. Andrews, Scotland (United Kingdom); Department of Astronomy, University of Illinois at Urbana-Champaign, Urbana, IL (United States); Horne, Keith, E-mail: faus@mit.edu [SUPA Physics and Astronomy, University of St. Andrews, Scotland (United Kingdom); Collaboration: the AGN STORM Collaboration
2017-12-05
We show recent detections of inter-band continuum lags in three AGN (NGC 5548, NGC 2617, and MCG+08-11-011), which provide new constraints on the temperature profiles and absolute sizes of the accretion disks. We find lags larger than would be predicted for standard geometrically thin, optically thick accretion disks by factors of 2.3–3.3. For NGC 5548, the data span UV through optical/near-IR wavelengths, and we are able to discern a steeper temperature profile than the T ~ R{sup −3/4} expected for a standard thin disk. Using a physical model, we are also able to estimate the inclinations of the disks for two objects. These results are similar to those found from gravitational microlensing of strongly lensed quasars, and provide a complementary approach for investigating the accretion disk structure in local, low luminosity AGN.
PREFACE: Continuum Models and Discrete Systems Symposia (CMDS-12)
Chakrabarti, Bikas K.
2011-09-01
The 12th International Symposium on Continuum Models and Discrete Systems (CMDS-12) (http://www.saha.ac.in/cmp/cmds.12/) took place at the Saha Institute of Nuclear Physics in Kolkata from 21-25 February 2011. Previous CMDS symposia were held in Kielce (Poland, 1975), Mont Gabriel (Canada, 1977), Freudenstadt (Federal Republic of Germany, 1979), Stockholm (Sweden, 1981), Nottingham (United Kingdom, 1985), Dijon (France, 1989), Paderborn (Germany, 1992), Varna (Bulgaria, 1995), Istanbul (Turkey, 1998), Shoresh (Israel, 2003) and Paris (France, 2007). The broad interdisciplinary character, limited number of participants (not exceeding 100) and informal and friendly atmosphere of these meetings has made them a well-acknowledged place to make highly fruitful contacts and exchange ideas, methods and results. The purpose of CMDS is to bring together scientists with different backgrounds who work on continuum theories of discrete mechanical and thermodynamical systems in the fields of mathematics, theoretical and applied mechanics, physics, material science, and engineering. The spirit of the CMDS meetings is to stimulate extensive and active interdisciplinary research. The International Scientific Committee members of this conference were: David J Bergman (Chairman CMDS 10), Tel Aviv University, Israel; Bikas K Chakrabarti (Chairman CMDS 12), Saha Institute of Nuclear Physics, India; Alex Hansen, Norwegian University of Science and Technology, Norway; Hans Jürgen Herrmann, Institute for Building Materials, ETH, Switzerland; Esin Inan (Chairman CMDS 9), Istanbul Technical University, Turkey; Dominique Jeulin (Chairman CMDS 11), Ecole des Mines de Paris, France; Frank Juelicher, Max-Planck-Institute for the Physics of Complex Systems, Germany; Hikaru Kawamura, University of Osaka, Japan; Graeme Milton, University of Utah, USA; Natalia Movchan, University of Liverpool, UK; and Ping Sheng, The Hong Kong University of Science and Technology, Hong Kong. At CMDS-12 the topics
Morphological and mechanical analysis of electrospun shape memory polymer fibers
Energy Technology Data Exchange (ETDEWEB)
Budun, Sinem [Institute of Pure and Applied Science, Marmara University, 34722 Istanbul (Turkey); İşgören, Erkan [Textile Technology, Technical Education Faculty, Marmara University, 34722 Istanbul (Turkey); Erdem, Ramazan, E-mail: ramazanerdem@akdeniz.edu.tr [Textile Technologies, Serik G-S. Sural Vocational School of Higher Education, Akdeniz University, 07500 Antalya (Turkey); Yüksek, Metin [Textile Engineering, Technology Faculty, Marmara University, 34722 Istanbul (Turkey)
2016-09-01
Highlights: • Fiber morphology of PU based shape memory fibers varied especially with polymer concentration and applied voltage. • The smallest diameter (381 ± 165 nm) and almost uniform (without bead) fibers were belonged to the sample Y10K30 with a feeding rate of 1 ml/h and an applied voltage of 30 kV at 24.5 cm distance. • All calculated shape fixity results were above 80% and the best value (92 ± 4%) was obtained for Y10K30. • All gained shape recovery results were determined above 100% and the highest measurement (130 ± 4%) was belonged to Y15K39. • The greatest tensile property was obtained for Y10K30 (14.7 ± 3.2 MPa) in machine direction and for Y10K39 (12.9 ± 0.8 MPa) in transverse direction. Y15K39 (411 ± 24%) and Y20K30 (402 ± 34%) possessed the highest elongation results compared with the other electrospun webs. - Abstract: Shape memory block co-polymer Polyurethane (PU) fibers were fabricated by electrospinning technique. Four different solution concentrations (5 wt.%, 10 wt.%, 15 wt.% and 20 wt.%) were prepared by using Tetrahydrofuran (THF)/N,N-dimethylformamide (DMF) (50:50, v/v) as solvents, and three different voltages (30 kV, 35 kV and 38.9 kV) were determined for the electrospinning process. Solution properties were explored in terms of viscosity and electrical conductivity. It was observed that as the polymer concentration increased in the solution, the conductivity declined. Morphological characteristics of the obtained fibers were analyzed through Scanning Electron Microscopy (SEM) measurements. Findings indicated that fiber morphology varied especially with polymer concentration and applied voltage. Obtained fiber diameter ranged from 112 ± 34 nm to 2046 ± 654 nm, respectively. DSC analysis presented that chain orientation of the polymer increased after electrospinning process. Shape fixity and shape recovery calculations were realized. The best shape fixity value (92 ± 4%) was obtained for Y10K30 and the highest shape
An experimental analysis of fracture mechanisms by acoustic ...
African Journals Online (AJOL)
This work is focused on the study of the evolution of damage mode and failure mechanisms of woven composite bolted assembly carbon fiber/epoxy. In the present paper three configurations are studied [0°,45°,0°,45°], [0°,45°,0°,45°]s and [0°,45°,0°,45,0°]s. In order to analyze a global mechanical behavior of the assembly, ...
Analysis of the Lifecycle of Mechanical Engineering Products
Gubaidulina, Rauza Khamidovna; Gruby, S. V.; Davlatov, G. D.
2016-01-01
Principal phases of the lifecycle of mechanical engineering products are analyzed in the paper. The authors have developed methods and procedures to improve designing, manufacturing, operating and recycling of the machine. It has been revealed that economic lifecycle of the product is a base for appropriate organization of mechanical engineering production. This lifecycle is calculated as a minimal sum total of consumer and producer costs. The machine construction and its manufacturing techno...
A Threshold Continuum for Aeolian Sand Transport
Swann, C.; Ewing, R. C.; Sherman, D. J.
2015-12-01
The threshold of motion for aeolian sand transport marks the initial entrainment of sand particles by the force of the wind. This is typically defined and modeled as a singular wind speed for a given grain size and is based on field and laboratory experimental data. However, the definition of threshold varies significantly between these empirical models, largely because the definition is based on visual-observations of initial grain movement. For example, in his seminal experiments, Bagnold defined threshold of motion when he observed that 100% of the bed was in motion. Others have used 50% and lesser values. Differences in threshold models, in turn, result is large errors in predicting the fluxes associated with sand and dust transport. Here we use a wind tunnel and novel sediment trap to capture the fractions of sand in creep, reptation and saltation at Earth and Mars pressures and show that the threshold of motion for aeolian sand transport is best defined as a continuum in which grains progress through stages defined by the proportion of grains in creep and saltation. We propose the use of scale dependent thresholds modeled by distinct probability distribution functions that differentiate the threshold based on micro to macro scale applications. For example, a geologic timescale application corresponds to a threshold when 100% of the bed in motion whereas a sub-second application corresponds to a threshold when a single particle is set in motion. We provide quantitative measurements (number and mode of particle movement) corresponding to visual observations, percent of bed in motion and degrees of transport intermittency for Earth and Mars. Understanding transport as a continuum provides a basis for revaluating sand transport thresholds on Earth, Mars and Titan.
Dynamic mechanical thermal analysis of hypromellose 2910 free films.
Cespi, Marco; Bonacucina, Giulia; Mencarelli, Giovanna; Casettari, Luca; Palmieri, Giovanni Filippo
2011-10-01
It is common practice to coat oral solid dosage forms with polymeric materials for controlled release purposes or for practical and aesthetic reasons. Good knowledge of thermo-mechanical film properties or their variation as a function of polymer grade, type and amount of additives or preparation method is of prime importance in developing solid dosage forms. This work focused on the dynamic mechanical thermal characteristics of free films of hypromellose 2910 (also known as HPMC), prepared using three grades of this polymer from two different manufacturers, in order to assess whether polymer chain length or origin affects the mechanical or thermo-mechanical properties of the final films. Hypromellose free films were obtained by casting their aqueous solutions prepared at a specific concentrations in order to obtain the same viscosity for each. The films were stored at room temperature until dried and then examined using a dynamic mechanical analyser. The results of the frequency scans showed no significant differences in the mechanical moduli E' and E″ of the different samples when analysed at room temperature; however, the grade of the polymer affected material transitions during the heating process. Glass transition temperature, apparent activation energy and fragility parameters depended on polymer chain length, while the material brand showed little impact on film performance. Copyright © 2011 Elsevier B.V. All rights reserved.
Bacterial Biogeography across the Amazon River-Ocean Continuum
Directory of Open Access Journals (Sweden)
Mary Doherty
2017-05-01
Full Text Available Spatial and temporal patterns in microbial biodiversity across the Amazon river-ocean continuum were investigated along ∼675 km of the lower Amazon River mainstem, in the Tapajós River tributary, and in the plume and coastal ocean during low and high river discharge using amplicon sequencing of 16S rRNA genes in whole water and size-fractionated samples (0.2–2.0 μm and >2.0 μm. River communities varied among tributaries, but mainstem communities were spatially homogeneous and tracked seasonal changes in river discharge and co-varying factors. Co-occurrence network analysis identified strongly interconnected river assemblages during high (May and low (December discharge periods, and weakly interconnected transitional assemblages in September, suggesting that this system supports two seasonal microbial communities linked to river discharge. In contrast, plume communities showed little seasonal differences and instead varied spatially tracking salinity. However, salinity explained only a small fraction of community variability, and plume communities in blooms of diatom-diazotroph assemblages were strikingly different than those in other high salinity plume samples. This suggests that while salinity physically structures plumes through buoyancy and mixing, the composition of plume-specific communities is controlled by other factors including nutrients, phytoplankton community composition, and dissolved organic matter chemistry. Co-occurrence networks identified interconnected assemblages associated with the highly productive low salinity near-shore region, diatom-diazotroph blooms, and the plume edge region, and weakly interconnected assemblages in high salinity regions. This suggests that the plume supports a transitional community influenced by immigration of ocean bacteria from the plume edge, and by species sorting as these communities adapt to local environmental conditions. Few studies have explored patterns of microbial diversity in
Bacterial Biogeography across the Amazon River-Ocean Continuum.
Doherty, Mary; Yager, Patricia L; Moran, Mary Ann; Coles, Victoria J; Fortunato, Caroline S; Krusche, Alex V; Medeiros, Patricia M; Payet, Jérôme P; Richey, Jeffrey E; Satinsky, Brandon M; Sawakuchi, Henrique O; Ward, Nicholas D; Crump, Byron C
2017-01-01
Spatial and temporal patterns in microbial biodiversity across the Amazon river-ocean continuum were investigated along ∼675 km of the lower Amazon River mainstem, in the Tapajós River tributary, and in the plume and coastal ocean during low and high river discharge using amplicon sequencing of 16S rRNA genes in whole water and size-fractionated samples (0.2-2.0 μm and >2.0 μm). River communities varied among tributaries, but mainstem communities were spatially homogeneous and tracked seasonal changes in river discharge and co-varying factors. Co-occurrence network analysis identified strongly interconnected river assemblages during high (May) and low (December) discharge periods, and weakly interconnected transitional assemblages in September, suggesting that this system supports two seasonal microbial communities linked to river discharge. In contrast, plume communities showed little seasonal differences and instead varied spatially tracking salinity. However, salinity explained only a small fraction of community variability, and plume communities in blooms of diatom-diazotroph assemblages were strikingly different than those in other high salinity plume samples. This suggests that while salinity physically structures plumes through buoyancy and mixing, the composition of plume-specific communities is controlled by other factors including nutrients, phytoplankton community composition, and dissolved organic matter chemistry. Co-occurrence networks identified interconnected assemblages associated with the highly productive low salinity near-shore region, diatom-diazotroph blooms, and the plume edge region, and weakly interconnected assemblages in high salinity regions. This suggests that the plume supports a transitional community influenced by immigration of ocean bacteria from the plume edge, and by species sorting as these communities adapt to local environmental conditions. Few studies have explored patterns of microbial diversity in tropical rivers and
Motion interference analysis and optimal control of an electronic controlled bamboo-dance mechanism
Liu, Xiaohong; Xu, Liang; Hu, Xiaobin
2017-08-01
An electric bamboo-dance mechanism was designed and developed to realize mechanism of automation and mechanization. For coherent and fluent motion, ANSYS finite element analysis was applied on movement interference. Static structural method was used for analyzing dynamic deflection and deformation of the slender rod, while modal analysis was applied on frequency analysis to avoid second deformation caused by resonance. Therefore, the deformation in vertical and horizontal direction was explored and reasonable optimization was taken to avoid interference.
Probabilistic Analysis of Failures Mechanisms of Large Dams
Shams Ghahfarokhi, G.
2014-01-01
Risk and reliability analysis is presently being performed in almost all fields of engineering depending upon the specific field and its particular area. Probabilistic risk analysis (PRA), also called quantitative risk analysis (QRA) is a central feature of hydraulic engineering structural design.
Quantum control mechanism analysis through field based Hamiltonian encoding
International Nuclear Information System (INIS)
Mitra, Abhra; Rabitz, Herschel
2006-01-01
Optimal control of quantum dynamics in the laboratory is proving to be increasingly successful. The control fields can be complex, and the mechanisms by which they operate have often remained obscure. Hamiltonian encoding (HE) has been proposed as a method for understanding mechanisms in quantum dynamics. In this context mechanism is defined in terms of the dominant quantum pathways leading to the final state of the controlled system. HE operates by encoding a special modulation into the Hamiltonian and decoding its signature in the dynamics to determine the dominant pathway amplitudes. Earlier work encoded the modulation directly into the Hamiltonian operators. This present work introduces the alternative scheme of field based HE, where the modulation is encoded into the control field and not directly into the Hamiltonian operators. This distinct form of modulation yields a new perspective on mechanism and is computationally faster than the earlier approach. Field based encoding is also an important step towards a laboratory based algorithm for HE as it is the only form of encoding that may be experimentally executed. HE is also extended to cover systems with noise and uncertainty and finally, a hierarchical algorithm is introduced to reveal mechanism in a stepwise fashion of ever increasing detail as desired. This new hierarchical algorithm is an improvement over earlier approaches to HE where the entire mechanism was determined in one stroke. The improvement comes from the use of less complex modulation schemes, which leads to fewer evaluations of Schroedinger's equation. A number of simulations are presented on simple systems to illustrate the new field based encoding technique for mechanism assessment
Points-Based Safe Path Planning of Continuum Robots
Directory of Open Access Journals (Sweden)
Khuram Shahzad
2015-07-01
Full Text Available Continuum robots exhibit great potential in a number of challenging applications where traditional rigid link robots pose certain limitations, e.g., working in unstructured environments. In order to enable the usage of continuum robots in safety-critical applications, such as surgery and nuclear decontamination, it is extremely important to ensure a safe path for the robot's movement. Existing algorithms for continuum robot path planning have certain limitations that need to be addressed. These include the fact that none of the algorithms provide safety assurance parameters and control for path planning. They are computationally expensive, applicable to a specific type of continuum robots, and mostly they do not incorporate design and kinematics constraints. In this paper, we propose a points-based path planning (PoPP algorithm for continuum robots that computes the path by imposing safety constraints and improves upon the limitations of existing approaches. In the algorithm, we exploit the constant curvature-bending property of continuum robots in their path planning process. The algorithm is computationally efficient and provides a good tradeoff between accuracy and efficiency that can be implemented to enable the safety-critical application of continuum robots. This algorithm also provides information regarding path volume and flexibility in movement. Simulation results confirm that the algorithm possesses promising potential for all types of continuum robots (following the constant curvature-bending property. We believe that this effectively balances the desired safety and efficiency requirements.
The urban watershed continuum: evolving spatial and temporal dimensions
Sujay S. Kaushal; Kenneth T. Belt
2012-01-01
Urban ecosystems are constantly evolving, and they are expected to change in both space and time with active management or degradation. An urban watershed continuum framework recognizes a continuum of engineered and natural hydrologic flowpaths that expands hydrologic networks in ways that are seldom considered. It recognizes that the nature of hydrologic connectivity...
Bursts and shocks in a continuum shell model
DEFF Research Database (Denmark)
Andersen, Ken Haste; Bohr, Tomas; Jensen, M.H.
1998-01-01
We study a burst event, i.e., the evolution of an initial condition having support only in a finite interval of k-space, in the continuum shell model due to Parisi. We show that the continuum equation without forcing or dissipation can be explicitly written in characteristic form and that the right...
Continuum Thinking and the Contexts of Personal Information Management
Huvila, Isto; Eriksen, Jon; Häusner, Eva-Maria; Jansson, Ina-Maria
2014-01-01
Introduction: Recent personal information management literature has underlined the significance of the contextuality of personal information and its use. The present article discusses the applicability of the records continuum model and its generalisation, continuum thinking, as a theoretical framework for explicating the overlap and evolution of…
Continuum of Counseling Goals: A Framework for Differentiating Counseling Strategies.
Bruce, Paul
1984-01-01
Presents counseling goals in a developmental continuum similar in concept to Maslow's hierarchy of needs. Discusses ego development goals, socialization goals, developmental goals, self-esteem goals, and self-realization goals and describes characteristics and implications of the continuum. (JAC)
Mechanics of advanced materials analysis of properties and performance
Matveenko, Valery
2015-01-01
The last decades have seen a large extension of types of materials employed in various applications. In many cases these materials demonstrate mechanical properties and performance that vary significantly from those of their traditional counterparts. Such uniqueness is sought – or even specially manufactured – to meet increased requirements on modern components and structures related to their specific use. As a result, mechanical behaviors of these materials under different loading and environmental conditions are outside the boundaries of traditional mechanics of materials, presupposing development of new characterization techniques, theoretical descriptions and numerical tools. The book presents interesting examples of recent developments in this area. Among the studied materials are bulk metallic glasses, metamaterials, special composites, piezoelectric smart structures, nonwovens, etc.
Characterization of esophageal physiology using mechanical state analysis
Directory of Open Access Journals (Sweden)
Richard Eduard Leibbrandt
2016-02-01
Full Text Available The esophagus functions to transport swallowed fluids and food from the pharynx to the stomach. The esophageal muscles governing bolus transport comprise circular striated muscle of the proximal esophagus and circular smooth muscle of the distal esophagus. Longitudinal smooth muscle contraction provides a mechanical advantage to bolus transit during circular smooth muscle contraction. Esophageal striated muscle is directly controlled by neural circuits originating in the central nervous system, resulting in coordinated contractions. In contrast, the esophageal smooth muscle is controlled by enteric circuits modulated by extrinsic central neural connections resulting in neural relaxation and contraction. The esophageal muscles are modulated by sensory information arising from within the lumen. Contraction or relaxation, which changes the diameter of the lumen, alters the intraluminal pressure and ultimately inhibits or promotes flow of content. This relationship that exists between the changes in diameter and concurrent changes in intraluminal pressure has been used previously to identify the ‘mechanical states’ of the circular muscle; that is when the muscles are passively or actively, relaxing or contracting. Detecting these changes in the mechanical state of the muscle has been difficult and, as the current interpretation of esophageal motility is based largely upon pressure measurement (manometry, subtle changes in the muscle function during peristalsis can be missed. We hypothesized that quantification of mechanical states of the esophageal circular muscles and the pressure-diameter properties that define them, would allow objective characterization of the mechanisms that govern esophageal peristalsis. To achieve this we analyzed barium swallows captured by simultaneous videofluoroscopy and pressure with impedance recording. From these data we demonstrated that intraluminal impedance measurements could be used to determine changes in the
Marya eGwadz; Marya eGwadz; Rebecca ede Guzman; Robert eFreeman; Alexandra eKutnick; Elizabeth eSilverman; Noelle Regina Leonard; Noelle Regina Leonard; Amanda Spring Ritchie; Corrine eMunoz-Plaza; Nadim eSalomon; Hannah eWolfe; Christopher eHilliard; Christopher eHilliard; Charles eCleland
2016-01-01
Drug use is associated with low uptake of HIV antiretroviral therapy (ART), an under-studied step in the HIV care continuum, and insufficient engagement in HIV primary care. However, the specific underlying mechanisms by which drug use impedes these HIV health outcomes are poorly understood. The present qualitative study addresses this gap in the literature, focusing on African American/Black and Hispanic persons living with HIV (PLWH) who had delayed, declined, or discontinued ART and who al...
New Observations of Balmer Continuum Flux in Solar Flares Instrument Description and First Results
Czech Academy of Sciences Publication Activity Database
Kotrč, Pavel; Procházka, O.; Heinzel, Petr
2016-01-01
Roč. 291, č. 3 (2016), s. 779-789 ISSN 0038-0938 R&D Projects: GA ČR GAP209/12/1652 Grant - others:EC(XE) 295272; EC(XE) 606862 Program:FP7; FP7 Institutional support: RVO:67985815 Keywords : flares * spectrum * Balmer continuum Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 2.682, year: 2016
The structure of protostellar dense cores: a millimeter continuum study
International Nuclear Information System (INIS)
Motte, Frederique
1998-01-01
A comprehensive theoretical scenario explains low-mass star formation and describes the gravitational collapse of an isolated 'ideal' dense core. The major aim of this thesis is to check the standard model predictions on the structure of protostellar dense cores (or envelopes). The earliest stages of star formation remain poorly known because the protostars are still deeply embedded in massive, opaque circumstellar cocoons. On the one hand, sensitive bolometer arrays very recently allow us to measure the millimeter continuum emission arising from dense cores. Such observations are a powerful tool to constrain the density structure of proto-stellar dense cores (on large length scale). In particular, we studied the structure of isolated proto-stellar envelopes in Taurus and protostars in the ρ Ophiuchi cluster. In order to accurately derive their envelope density power law, we simulated the observation of several envelope models. Then we show that most of the Taurus protostars present a density structure consistent with the standard model predictions. In contrast, dense cores in ρ Ophiuchi main cloud are highly fragmented and protostellar envelope have finite size. Moreover fragmentation appears to be essential in determining the final stellar mass of ρ Oph forming stars. In clusters, fragmentation may thus be at the origin of the stellar initial mass function (IMF). On the other hand, our interferometric millimeter continuum observations are tracing (with higher angular resolution) the inner part of protostellar envelopes. Our study show that disks during protostellar stages are not yet massive and thus do not perturb the analysis of envelope density structure. (author) [fr
Analysis of Diversity-Preserving Mechanisms for Global Exploration
DEFF Research Database (Denmark)
Friedrich, Tobias; Oliveto, Pietro S.; Sudholt, Dirk
2009-01-01
Maintaining diversity is important for the performance of evolutionary algorithms. Diversity-preserving mechanisms can enhance global exploration of the search space and enable crossover to find dissimilar individuals for recombination. We focus on the global exploration capabilities of mutation......-based algorithms. Using a simple bimodal test function and rigorous runtime analyses, we compare well-known diversity-preserving mechanisms like deterministic crowding, fitness sharing, and others with a plain algorithm without diversification. We show that diversification is necessary for global exploration...
Directory of Open Access Journals (Sweden)
Erica H Layer
Full Text Available Progression through the HIV continuum of care, from HIV testing to lifelong retention in antiretroviral therapy (ART care and treatment programs, is critical to the success of HIV treatment and prevention efforts. However, significant losses occur at each stage of the continuum and little is known about contextual factors contributing to disengagement at these stages. This study sought to explore multi-level barriers and facilitators influencing entry into and engagement in the continuum of care in Iringa, Tanzania. We used a mixed-methods study design including facility-based assessments and interviews with providers and clients of HIV testing and treatment services; interviews, focus group discussions and observations with community-based providers and clients of HIV care and support services; and longitudinal interviews with men and women living with HIV to understand their trajectories in care. Data were analyzed using narrative analysis to identify key themes across levels and stages in the continuum of care. Participants identified multiple compounding barriers to progression through the continuum of care at the individual, facility, community and structural levels. Key barriers included the reluctance to engage in HIV services while healthy, rigid clinic policies, disrespectful treatment from service providers, stock-outs of supplies, stigma and discrimination, alternate healing systems, distance to health facilities and poverty. Social support from family, friends or support groups, home-based care providers, income generating opportunities and community mobilization activities facilitated engagement throughout the HIV continuum. Findings highlight the complex, multi-dimensional dynamics that individuals experience throughout the continuum of care and underscore the importance of a holistic and multi-level perspective to understand this process. Addressing barriers at each level is important to promoting increased engagement throughout
Mechanical property analysis of kenaf–glass fibre reinforced ...
Indian Academy of Sciences (India)
Department of Mechanical Engineering, Sri Sai Ram Engineering College, Chennai 600 044, Tamil Nadu, India. MS received 29 June 2015; accepted 29 ... contributes to a healthier environment [13]. Kenaf fibre is a good reinforcement ..... From the figure, it is observed that there is the grad- ual increase in the displacement, ...
Analysis of Deformation Characteristics and Stability Mechanisms of ...
Indian Academy of Sciences (India)
21
deformation and inclinometer monitoring of internal deformation over 7 years, we find that the displacement of a typical ... Stability mechanisms; The field monitoring. 1. Introduction. Completed in 2009, the Three ..... rainfall infiltrates into the landslide mass, which increases the self-weight of the landslide mass and forms the ...
Analysis of mechanical-hydraulic bedload deposition control measures
Schwindt, S.; Franca, M. J.; De Cesare, G.; Schleiss, A. J.
2017-10-01
During floods, the bedload transport of steep headwaters can exceed the hydraulic transport capacity of milder downstream reaches where settlements are often situated. Therefore, sediment retention barriers are typically installed upstream of such sensible areas. These barriers trigger bedload trapping via two control mechanisms, either hydraulic or mechanical. Both deposition controls, pertaining to instream sediment trapping structures, are analyzed experimentally in this study. Bedload trapping by hydraulically controlled barriers is prone to sediment flushing, i.e., the remobilization of formerly deposited sediment, in particular when the barrier is simultaneously under- and overflown. In this case, the remobilization rate is close to the bedload transport capacity of the nonconstricted channel. Mechanical deposition control by screens is in turn sensible to the grain size. Thus, both deposition control concepts may fail, and bedload may be transported downstream at a rate corresponding to the transport capacity of headwaters, thereby endangering urban areas. This study shows that the combination of both deposition control concepts is suitable for improving the control of bedload retention. With this combination, undesired sediment flushing of upstream deposits in the channel caused by insufficient hydraulic control is prevented. Furthermore, the uncertainty related to the estimation of the representative grain size in the design of mechanical control barriers is reduced.
Mechanics, analysis and geometry 200 years after Lagrange
1991-01-01
Providing a logically balanced and authoritative account of the different branches and problems of mathematical physics that Lagrange studied and developed, this volume presents up-to-date developments in differential goemetry, dynamical systems, the calculus of variations, and celestial and analytical mechanics.
Failure analysis fundamentals and applications in mechanical components
Otegui, Jose Luis
2014-01-01
This book addresses the failures of structural elements, i.e. those components whose primary mission is to withstand mechanical loads. The book is intended as a self-contained source for those with different technical grades, engineers and scientists but also technicians in the field can benefit from its reading.
An Analysis of Knowledge Management Mechanisms in Healthcare Portals
Lee, Chei Sian; Goh, Dion Hoe-Lian; Chua, Alton Y. K.
2010-01-01
Healthcare portals are becoming increasingly popular with Internet users since they play an important role in supporting interaction between individuals and healthcare organizations with a Web presence. Additionally, many of these organizations make use of knowledge management mechanisms on their healthcare portals to manage the abundance of…
Hartog, J P Den
1961-01-01
First published over 40 years ago, this work has achieved the status of a classic among introductory texts on mechanics. Den Hartog is known for his lively, discursive and often witty presentations of all the fundamental material of both statics and dynamics (and considerable more advanced material) in new, original ways that provide students with insights into mechanical relationships that other books do not always succeed in conveying. On the other hand, the work is so replete with engineering applications and actual design problems that it is as valuable as a reference to the practicing e
comparison of elastic-plastic FE method and engineering method for RPV fracture mechanics analysis
International Nuclear Information System (INIS)
Sun Yingxue; Zheng Bin; Zhang Fenggang
2009-01-01
This paper described the FE analysis of elastic-plastic fracture mechanics for a crack in RPV belt line using ABAQUS code. It calculated and evaluated the stress intensity factor and J integral of crack under PTS transients. The result is also compared with that by engineering analysis method. It shows that the results using engineering analysis method is a little larger than the results using FE analysis of 3D elastic-plastic fracture mechanics, thus the engineering analysis method is conservative than the elastic-plastic fracture mechanics method. (authors)
Comprehensive mechanisms for combustion chemistry: Experiment, modeling, and sensitivity analysis
Energy Technology Data Exchange (ETDEWEB)
Dryer, F.L.; Yetter, R.A. [Princeton Univ., NJ (United States)
1993-12-01
This research program is an integrated experimental/numerical effort to study pyrolysis and oxidation reactions and mechanisms for small-molecule hydrocarbon structures under conditions representative of combustion environments. The experimental aspects of the work are conducted in large diameter flow reactors, at pressures from one to twenty atmospheres, temperatures from 550 K to 1200 K, and with observed reaction times from 10{sup {minus}2} to 5 seconds. Gas sampling of stable reactant, intermediate, and product species concentrations provides not only substantial definition of the phenomenology of reaction mechanisms, but a significantly constrained set of kinetic information with negligible diffusive coupling. Analytical techniques used for detecting hydrocarbons and carbon oxides include gas chromatography (GC), and gas infrared (NDIR) and FTIR methods are utilized for continuous on-line sample detection of light absorption measurements of OH have also been performed in an atmospheric pressure flow reactor (APFR), and a variable pressure flow (VPFR) reactor is presently being instrumented to perform optical measurements of radicals and highly reactive molecular intermediates. The numerical aspects of the work utilize zero and one-dimensional pre-mixed, detailed kinetic studies, including path, elemental gradient sensitivity, and feature sensitivity analyses. The program emphasizes the use of hierarchical mechanistic construction to understand and develop detailed kinetic mechanisms. Numerical studies are utilized for guiding experimental parameter selections, for interpreting observations, for extending the predictive range of mechanism constructs, and to study the effects of diffusive transport coupling on reaction behavior in flames. Modeling using well defined and validated mechanisms for the CO/H{sub 2}/oxidant systems.
Wooden, Diane H.; Rank, David M.; Bregman, Jesse D.; Witteborn, Fred C.; Tielens, A. G. G. M.; Cohen, Martin; Pinto, Philip A.; Axelrod, Timothy S.
1993-01-01
Spectrophotometric observations of SN 1987A from the Kuiper Airborne Observatory are presented for five epochs at 60, 260, 415, 615, and 775 days after the explosion. The low-resolution (lambda/Delta lambda = 50-100) spectra of SN 1987A are combined with data from other wavelengths to model the continuum, subtract the continuum from the spectra to determine line strengths and reveal molecular bands, separate the atomic continuum radiation from the dust continuum, and derive constraints on the grain temperatures and optical depths. A scenario for the evolution of SN 1987A and that of the ejecta from which it arises is obtained on the basis of the analysis of the continuum emission.
Analysis of the Lifecycle of Mechanical Engineering Products
Gubaydulina, R. H.; Gruby, S. V.; Davlatov, G. D.
2016-08-01
Principal phases of the lifecycle of mechanical engineering products are analyzed in the paper. The authors have developed methods and procedures to improve designing, manufacturing, operating and recycling of the machine. It has been revealed that economic lifecycle of the product is a base for appropriate organization of mechanical engineering production. This lifecycle is calculated as a minimal sum total of consumer and producer costs. The machine construction and its manufacturing technology are interrelated through a maximal possible company profit. The products are to be recycled by their producer. Recycling should be considered as a feedback phase, necessary to make the whole lifecycle of the product a constantly functioning self-organizing system. The principles, outlined in this paper can be used as fundamentals to develop an automated PLM-system.
Analysis of Drag Reduction Methods and Mechanisms of Turbulent
Directory of Open Access Journals (Sweden)
Gu Yunqing
2017-01-01
Full Text Available Turbulent flow is a difficult issue in fluid dynamics, the rules of which have not been totally revealed up to now. Fluid in turbulent state will result in a greater frictional force, which must consume great energy. Therefore, it is not only an important influence in saving energy and improving energy utilization rate but also an extensive application prospect in many fields, such as ship domain and aerospace. Firstly, bionic drag reduction technology is reviewed and is a hot research issue now, the drag reduction mechanism of body surface structure is analyzed, such as sharks, earthworms, and dolphins. Besides, we make a thorough study of drag reduction characteristics and mechanisms of microgrooved surface and compliant wall. Then, the relevant drag reduction technologies and mechanisms are discussed, focusing on the microbubbles, the vibrant flexible wall, the coating, the polymer drag reduction additives, superhydrophobic surface, jet surface, traveling wave surface drag reduction, and the composite drag reduction methods. Finally, applications and advancements of the drag reduction technology in turbulence are prospected.
Analysis of mechanical behavior and hysteresis heat generating mechanism of PDM motor
Energy Technology Data Exchange (ETDEWEB)
Shi, Changshuai; Zhu, Xiaohua; Tang, Liping [Southwest Petroleum University, Chengdu (China); Deng, Juan [Avic Chengdu Engine (Group) Co.,Ltd, Chengdu (China)
2017-03-15
Positive displacement motor (PDM), which is prone to high temperature fatigue failure, can be weakened in its application in deep and superdeep well. In order to study the forced state, deformation regularity and thermal hysteresis of PDM motor, the paper established the three-dimensional thermal-mechanical coupled Finite element model (FEM). Based on the theoretical research, experimental study and numerical simulation, the study found that the displacement of stator lining shows a sinusoidal variation under internal pressure, when adapting the general form of sine function to fitting inner contour line deformation function. Then the paper analyzed the hysteresis heat generating mechanism of the motor, learning that hysteresis thermogenous of stator lining occurs due to the viscoelastic of rubber material and cyclic loading of stator lining. A heartburn happens gradually in the center of the thickest part of the stator lining as temperature increases, which means work efficiency and service life of PDM will be decreased when used in deep or superdeep well. In this paper, we established a theory equation for the choice of interference fit and motor line type optimization design, showing hysteresis heat generating analyzing model and method are reasonable enough to significantly improve PDM’s structure and help better use PDM in deep and surdeep well.
Analysis of Mechanical Seals for High-Speed Centrifugal Gas Compressors
K.N. Nwaigwe; P.E. Ugwuoke; E.E. Anyanwu; D.P.S. Abam
2012-01-01
A study aimed at seal selection efficiency for centrifugal pumps in the oil and gas industry is presented. A detailed analysis of mechanical seals in use in exploration and production activities of the oil and gas sector was undertaken. The approach of analysis was using seal design equations as mathematical models for simulating the performance of the mechanical seal. The results showed a mechanical seal with balance value of 0.5, an increased surface area between mating surfaces; provided w...
Optical continuum generation on a silicon chip
Jalali, Bahram; Boyraz, Ozdal; Koonath, Prakash; Raghunathan, Varun; Indukuri, Tejaswi; Dimitropoulos, Dimitri
2005-08-01
Although the Raman effect is nearly two orders of magnitude stronger than the electronic Kerr nonlinearity in silicon, under pulsed operation regime where the pulse width is shorter than the phonon response time, Raman effect is suppressed and Kerr nonlinearity dominates. Continuum generation, made possible by the non-resonant Kerr nonlinearity, offers a technologically and economically appealing path to WDM communication at the inter-chip or intra-chip levels. We have studied this phenomenon experimentally and theoretically. Experimentally, a 2 fold spectral broadening is obtained by launching ~4ps optical pulses with 2.2GW/cm2 peak power into a conventional silicon waveguide. Theoretical calculations, that include the effect of two-photon-absorption, free carrier absorption and refractive index change indicate that up to >30 times spectral broadening is achievable in an optimized device. The broadening is due to self phase modulation and saturates due to two photon absorption. Additionally, we find that free carrier dynamics also contributes to the spectral broadening and cause the overall spectrum to be asymmetric with respect to the pump wavelength.
Mean colors of stellar flare continuum
International Nuclear Information System (INIS)
Mullan, D.J.
1976-01-01
Shmeleva and Syrovatskii have shown that under certain circumstances the temperature structure in the hotter regions (T>2 x 10 4 K) of a solar flare is characterized by two universal functions: one for constant density conditions, the second for constant pressure conditions. Here we show that the U--B, B--V colors of optically thin thermal bremsstrahlung emitted by both of these temperature structures are consistent with the mean colors of stellar flares near maximum light and also with the observed evolution of flare light in the two-color diagram during flare cooling. We suggest that the transition which occurs in the character of stellar flare light from mostly continuum emission near flare maximum to mostly line emission later in the flare is related to the transition which must occur from the constant density regime to the constant pressure regime on a time scale of order 1--2 minutes. The two types of flares (spike flares and slow flares) identified by Moffett are ascribed to these two different regimes. The flare light-curve model described here resembles in some respects a model previously proposed by Andrews, but there are differences in detail
Performance-based shape optimization of continuum structures
International Nuclear Information System (INIS)
Liang Qingquan
2010-01-01
This paper presents a performance-based optimization (PBO) method for optimal shape design of continuum structures with stiffness constraints. Performance-based design concepts are incorporated in the shape optimization theory to achieve optimal designs. In the PBO method, the traditional shape optimization problem of minimizing the weight of a continuum structure with displacement or mean compliance constraints is transformed to the problem of maximizing the performance of the structure. The optimal shape of a continuum structure is obtained by gradually eliminating inefficient finite elements from the structure until its performance is maximized. Performance indices are employed to monitor the performance of optimized shapes in an optimization process. Performance-based optimality criteria are incorporated in the PBO method to identify the optimum from the optimization process. The PBO method is used to produce optimal shapes of plane stress continuum structures and plates in bending. Benchmark numerical results are provided to demonstrate the effectiveness of the PBO method for generating the maximum stiffness shape design of continuum structures. It is shown that the PBO method developed overcomes the limitations of traditional shape optimization methods in optimal design of continuum structures. Performance-based optimality criteria presented can be incorporated in any shape and topology optimization methods to obtain optimal designs of continuum structures.
Nano Scale Mechanical Analysis of Biomaterials Using Atomic Force Microscopy
Dutta, Diganta
The atomic force microscope (AFM) is a probe-based microscope that uses nanoscale and structural imaging where high resolution is desired. AFM has also been used in mechanical, electrical, and thermal engineering applications. This unique technique provides vital local material properties like the modulus of elasticity, hardness, surface potential, Hamaker constant, and the surface charge density from force versus displacement curve. Therefore, AFM was used to measure both the diameter and mechanical properties of the collagen nanostraws in human costal cartilage. Human costal cartilage forms a bridge between the sternum and bony ribs. The chest wall of some humans is deformed due to defective costal cartilage. However, costal cartilage is less studied compared to load bearing cartilage. Results show that there is a difference between chemical fixation and non-chemical fixation treatments. Our findings imply that the patients' chest wall is mechanically weak and protein deposition is abnormal. This may impact the nanostraws' ability to facilitate fluid flow between the ribs and the sternum. At present, AFM is the only tool for imaging cells' ultra-structure at the nanometer scale because cells are not homogeneous. The first layer of the cell is called the cell membrane, and the layer under it is made of the cytoskeleton. Cancerous cells are different from normal cells in term of cell growth, mechanical properties, and ultra-structure. Here, force is measured with very high sensitivity and this is accomplished with highly sensitive probes such as a nano-probe. We performed experiments to determine ultra-structural differences that emerge when such cancerous cells are subject to treatments such as with drugs and electric pulses. Jurkat cells are cancerous cells. These cells were pulsed at different conditions. Pulsed and non-pulsed Jurkat cell ultra-structures were investigated at the nano meter scale using AFM. Jurkat cell mechanical properties were measured under