Academic literature on the topic 'Anisotropic surface energy'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the lists of relevant articles, books, theses, conference reports, and other scholarly sources on the topic 'Anisotropic surface energy.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Journal articles on the topic "Anisotropic surface energy":
1
KOISO, Miyuki. "Geometry of Anisotropic Surface Energy." Proceedings of Mechanical Engineering Congress, Japan 2016 (2016): jikiin04. http://dx.doi.org/10.1299/jsmemecj.2016.jikiin04.
2
PETUKHOV, A. V., and A. LIEBSCH. "SURFACE ANISOTROPY OF SECOND HARMONIC GENERATION AT Al(111)." Surface Review and Letters 01, no. 04 (December 1994): 521–23. http://dx.doi.org/10.1142/s0218625x94000576.
Abstract:
We present results of the first calculation of the surface anisotropic contribution to second harmonic generation for a realistic metal surface. Although the anisotropic second-order response has its origin at the surface, the main contribution to the surface anisotropic parameter ξ has a remarkably large penetration depth. Moreover, the long-range oscillations of the anisotropic nonlinear surface current deep inside aluminum are found. The surface anisotropic secondorder polarizability ξ is in a good qualitative agreement with recent experimental data on clean Al(111) at ħω=1.17 eV. A resonant enhancement of the SHG anisotropy is predicted for ω and 2ω close to 1.5 eV—the energy gap in bulk aluminum along the [100] directions. A significant decrease of the surface anisotropic response in comparison with the isotropic one is found for ω≥1.5 eV.
3
Koiso, Miyuki. "Uniqueness of Closed Equilibrium Hypersurfaces for Anisotropic Surface Energy and Application to a Capillary Problem." Mathematical and Computational Applications 24, no. 4 (October 10, 2019): 88. http://dx.doi.org/10.3390/mca24040088.
Abstract:
We study a variational problem for hypersurfaces in the Euclidean space with an anisotropic surface energy. An anisotropic surface energy is the integral of an energy density that depends on the surface normal over the considered hypersurface, which was introduced to model the surface tension of a small crystal. The purpose of this paper is two-fold. First, we give uniqueness and nonuniqueness results for closed equilibria under weaker assumptions on the regularity of both considered hypersurfaces and the anisotropic surface energy density than previous works and apply the results to the anisotropic mean curvature flow. This part is an announcement of two forthcoming papers by the author. Second, we give a new uniqueness result for stable anisotropic capillary surfaces in a wedge in the three-dimensional Euclidean space.
4
Vidyasagar, A., S. Krödel, and D. M. Kochmann. "Microstructural patterns with tunable mechanical anisotropy obtained by simulating anisotropic spinodal decomposition." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 474, no. 2218 (October 2018): 20180535. http://dx.doi.org/10.1098/rspa.2018.0535.
Abstract:
The generation of mechanical metamaterials with tailored effective properties through carefully engineered microstructures requires avenues to predict optimal microstructural architectures. Phase separation in heterogeneous systems naturally produces complex microstructural patterns whose effective response depends on the underlying process of spinodal decomposition. During this process, anisotropy may arise due to advection, diffusive chemical gradients or crystallographic interface energy, leading to anisotropic patterns with strongly directional effective properties. We explore the link between anisotropic surface energies during spinodal decomposition, the resulting microstructures and, ultimately, the anisotropic elastic moduli of the resulting medium. We simulate the formation of anisotropic patterns within representative volume elements, using recently developed stabilized spectral techniques that circumvent further regularization, and present a powerful alternative to current numerical techniques. The interface morphology of representative phase-separated microstructures is shown to strongly depend on surface anisotropy. The effective elastic moduli of the thus-obtained porous media are identified by periodic homogenization, and directionality is demonstrated through elastic surfaces. Our approach not only improves upon numerical tools to simulate phase separation; it also offers an avenue to generate tailored microstructures with tunable resulting elastic anisotropy.
5
Lamichhane, Shobha Kanta. "Experimental investigation on anisotropic surface properties of crystalline silicon." BIBECHANA 8 (January 15, 2012): 59–66. http://dx.doi.org/10.3126/bibechana.v8i0.4828.
Abstract:
Anisotropic etching of silicon has been studied by wet potassium hydroxide (KOH) etchant with its variation of temperature and concentration. Results presented here are temperature dependent etch rate along the crystallographic orientations. The etching rate of the (111) surface family is of prime importance for microfabrication. However, the experimental values of the corresponding etch rate are often scattered and the etching mechanism of (111) remains unclear. Etching and activation energy are found to be consistently favorable with the thermal agitation for a given crystal plane. Study demonstrate that the contribution of microscopic activation energy that effectively controls the etching process. Such a strong anisotropy in KOH allows us a precious control of lateral dimensions of the silicon microstructure.Keywords: microfabrication; activation energy; concentration; anisotropy; crystal planeDOI: http://dx.doi.org/10.3126/bibechana.v8i0.4828 BIBECHANA 8 (2012) 59-66
6
HE, L., Y. W. LIU, W. J. TONG, J. G. LIN, and X. F. WANG. "SURFACE ENERGY ENGINEERING OF Cu SURFACE BY STRAIN: FIRST-PRINCIPLES CALCULATIONS." Surface Review and Letters 20, no. 06 (December 2013): 1350054. http://dx.doi.org/10.1142/s0218625x13500546.
Abstract:
Surface energies of strained Cu surfaces were studied systematically using first-principles methods. Results showed that the strain-stabilization of Cu surface was anisotropic and strongly related to the strain distribution. This strain-induced approach could be used as an effective way to engineer the surface energies of metals.
7
KRZYSZTON, T. "SURFACE BARRIER IN THE MIXED STATE OF ANISOTROPIC SUPERCONDUCTOR." Modern Physics Letters B 07, no. 12 (May 20, 1993): 841–47. http://dx.doi.org/10.1142/s0217984993000837.
Abstract:
In the framework of London theory, the problem of equilibrium between magnetic flux density in the anisotropic superconductor and the applied external magnetic field is studied. The Gibbs free energy of a fluxoid in the presence of magnetic flux density in the sample is calculated. As a result, critical entry and exit fields are calculated and their dependence upon the angle which makes anisotropy axis and the direction of an external magnetic field.
8
Rofouie, P., Z. Wang, and A. D. Rey. "Two-wavelength wrinkling patterns in helicoidal plywood surfaces: imprinting energy landscapes onto geometric landscapes." Soft Matter 14, no. 25 (2018): 5180–85. http://dx.doi.org/10.1039/c8sm01022f.
Abstract:
We present a model to investigate the formation of two-length scale surface patterns in biological and synthetic anisotropic soft matter materials through the high order interaction of anisotropic interfacial tension and capillarity at their free surfaces.
9
Wang, Ziheng, Phillip Servio, and Alejandro D. Rey. "Complex Nanowrinkling in Chiral Liquid Crystal Surfaces: From Shaping Mechanisms to Geometric Statistics." Nanomaterials 12, no. 9 (May 4, 2022): 1555. http://dx.doi.org/10.3390/nano12091555.
Abstract:
Surface wrinkling is closely linked to a significant number of surface functionalities such as wetting, structural colour, tribology, frictions, biological growth and more. Given its ubiquity in nature’s surfaces and that most material formation processes are driven by self-assembly and self-organization and many are formed by fibrous composites or analogues of liquid crystals, in this work, we extend our previous theory and modeling work on in silico biomimicking nanowrinkling using chiral liquid crystal surface physics by including higher-order anisotropic surface tension nonlinearities. The modeling is based on a compact liquid crystal shape equation containing anisotropic capillary pressures, whose solution predicts a superposition of uniaxial, equibiaxial and biaxial egg carton surfaces with amplitudes dictated by material anchoring energy parameters and by the symmetry of the liquid crystal orientation field. The numerical solutions are validated by analytical solutions. The blending and interaction of egg carton surfaces create surface reliefs whose amplitudes depend on the highest nonlinearity and whose morphology depends on the anchoring coefficient ratio. Targeting specific wrinkling patterns is realized by selecting trajectories on an appropriate parametric space. Finally, given its importance in surface functionalities and applications, the geometric statistics of the patterns up to the fourth order are characterized and connected to the parametric anchoring energy space. We show how to minimize and/or maximize skewness and kurtosis by specific changes in the surface energy anisotropy. Taken together, this paper presents a theory and simulation platform for the design of nano-wrinkled surfaces with targeted surface roughness metrics generated by internal capillary pressures, of interest in the development of biomimetic multifunctional surfaces.
10
Wheeler, A. A., and G. B. McFadden. "A ξ-vector formulation of anisotropic phase-field models: 3D asymptotics." European Journal of Applied Mathematics 7, no. 4 (August 1996): 367–81. http://dx.doi.org/10.1017/s0956792500002424.
Abstract:
In this paper we present a new formulation of a large class of phase-field models, which describe solidification of a pure material and allow for both surface energy and interface kinetic anisotropy, in terms of the Hoffman–Cahn ξ-vector. The ξ-vector has previously been used in the context of sharp interface models, where it provides an elegant tool for the representation and analysis of interfaces with anisotropic surface energy. We show that the usual gradient-energy formulations of anisotropic phase-field models are expressed in a natural way in terms of the ξ-vector when appropriately interpreted. We use this new formulation of the phase-field equations to provide a concise derivation of the Gibbs–Thomson–Herring equation in the sharp-interface limit in three dimensions.
Dissertations / Theses on the topic "Anisotropic surface energy":
1
Li, Bin. "The variational approach to brittle fracture in materials with anisotropic surface energy and in thin sheets." Doctoral thesis, Universitat Politècnica de Catalunya, 2016. http://hdl.handle.net/10803/393861.
Abstract:
Fracture mechanics of brittle materials has focused on bulk materials with isotropic surface energy. In this situation different physical principles for crack path selection are very similar or even equivalent. The situation is radically different when considering crack propagation in brittle materials with anisotropic surface energy. Such materials are important in applications involving single crystals, extruded polymers, or geological and organic materials. When this anisotropy is strong, the phenomenology of crack propagation becomes very rich, with forbidden crack propagation directions or complex sawtooth crack patterns. Thus, this situation interrogates fundamental issues in fracture mechanics, including the principles behind the selection of crack direction. Similarly, tearing of brittle thin elastic sheets, ubiquitous in nature, technology and daily life, challenges our understanding of fracture. Since tearing typically involves large geometric nonlinearity, it is not clear whether the stress intensity factors are meaningful or if and how they determine crack propagation. Geometry, together with the interplay between stretching and bending deformation, leads to complex behaviors, restricting analytical approximate solutions to very simplified settings and specific parameter regimes.
In both situations, a rich and nontrivial experimental record has been successfully understood in terms of simple energetic models. However, general modeling approaches to either fracture in the presence of strong surface energy anisotropy or to tearing, capable of exploring new physics, have been lacking. The success of energetic simple models suggests that variational theories of brittle fracture may provide a unifying and general framework capable of dealing with the more general situations considered here.
To address fracture in materials with strongly anisotropic surface energy, we propose a variational phase-field model resorting to the extended Cahn-Hilliard framework proposed in the context of crystal growth. Previous phase-field models for anisotropic fracture were formulated in a framework only allowing for weak anisotropy. We implement numerically our higher-order phase-field model with smooth local maximum entropy approximants in a direct Galerkin method. The numerical results exhibit all the features of strongly anisotropic fracture, and reproduce strikingly well recent experimental observations. To explore tearing of thin films, we develop a geometrically exact model and a computational framework coupling elasticity (stretching and bending), fracture, and adhesion to a substrate. We numerically implement the model with subdivision surface finite elements. Our simulations qualitatively and quantitatively reproduced the crack patterns observed in tearing experiments.
Finally, we examine how shell geometry affects fracture. As suggested by previous results and our own phase-field simulations, shell shape dramatically affects crack evolution and the effective toughness of the shell structure. To gain insight and eventually develop new concepts for optimizing the design of thin shell structures, we derive the configurational force conjugate to crack extension for Koiter's linear thin shell theory. We identify the conservative contribution to this force through an Eshelby tensor, as well as non-conservative contributions arising from curvature.La mécanica de fractura frágil se ha centrado en materiales tridimensionales con una energía de superficie isotrópica. En esta situación, los diferentes principios para la selección del camino de la fisura son muy similares, o incluso equivalentes. La situación es radicalmente opuesta cuando se considera la propagación de fisuras en medios con energía de superficie anisótropa. Estos materiales son importantes en aplicaciones que involucran materiales cristalinos, polímeros extrudidos, o materiales orgánicos y geológicos. Cuando la anisotropía es fuerte, el fenómeno de la propagación de fisuras es muy rico, con direcciones de propagación prohibidas o complejos patrones de ruptura en dientes de sierra. Por tanto, esta situación plantea cuestiones fundamentales en la mecánica de la fractura, incluyendo los principios de selección de la dirección de propagación de la fractura. Igualmente, el proceso de rasgado de láminas delgadas y frágiles, comunes en la naturaleza, la tecnología y la vida diaria, desafía nuestro entendimiento de la fractura. Dado que el rasgado de estas láminas típicamente involucra grandes no linealidades geométricas, no está claro si los factores de intensidad de esfuerzos son válidos o si, y en tal caso cómo determinan la propagación de fisuras. La interacción entre la geometría, las deformaciones y la curvatura da lugar a comportamientos complejos, lo que restringe las soluciones analíticas aproximadas a ejemplos muy simplificados y a regímenes de parámetros limitados. En ambas situaciones, se han podido interpretar experimentos no triviales con modelos energéticos simples. Sin embargo, no se ha profundizado en modelos generales de fractura en presencia de energía de superficie fuertemente anisótropa o en láminas delgadas, ambas interesantes por su capacidad para explorar nueva física. El mencionado éxito de los modelos energéticos simplificados sugiere que las teorías variacionales de fractura en medios frágiles pueden proveer un marco unificador para considerar situaciones más generales, como las que se consideran en este trabajo. Para caracterizar la fractura en materiales con energía de superficie fuertemente anisótropa, proponemos un modelo variacional de campo de fase basado en el modelo extendido de Cahn-Hilliard. Los modelos de campo de fase existentes para la fractura anisótropa fueron formulados en un contexto que sólo admite anisotropía débil. En este trabajo, implementamos numéricamente nuestro modelo de campo de fase de alto orden con aproximantes locales de máxima entropía en un método directo de Garlerkin. Los resultados numéricos muestran todas las características de fractura con anisotropía fuerte, y reproducen llamativamente bien las últimas observaciones experimentales. Para explorar el rasgado de láminas delgadas, desarrollamos un modelo geométricamente exacto y un esquema computacional que acopla elasticidad (estiramiento y flexión), fractura, y la adhesión a un substrato. Implementamos numéricamente el modelo con elementos finitos basados en superficies de subdivisión. Nuestras simulaciones reproducen los patrones de ruptura, tanto cualitativamente como cuantitativamente, observados en los experimentos de rasgado. Finalmente, examinamos cómo la geometría de la lámina afecta la fractura. Como ha sido sugerido en resultados previos y en nuestras propias simulaciones de campo de fase, la forma de la lámina afecta dramáticamente la evolución de fisuras y la resistencia efectiva del material. Para comprender mejor estos fenómenos y con el objetivo de desarrollar nuevos conceptos para la optimización del diseño de estructuras de láminas delgadas, derivamos la fuerza configuracional conjugada a la extensión de la fractura para la teoría lineal de láminas delgadas de Koiter. Identificamos las contribuciones conservativas a esta fuerza a través del tensor de Eshelby, así como las contriuciones no conservativas que aparecen por el efecto de la curvatura.
2
Zhai, Xinyuan. "Crack propagation in elastic media with anisotropic fracture toughness : experiments and numerical modeling." Electronic Thesis or Diss., Institut polytechnique de Paris, 2023. http://www.theses.fr/2023IPPAE010.
Abstract:
La fabrication additive attire une attention croissante en raison de ses avantages en termes de flexibilité de modélisation et de facilité de conception de microstructures complexes. Nous avons constaté qu'en manipulant la stratégie d'impression, les échantillons imprimés par dépôt de fusion de polycarbonate peuvent présenter un comportement fortement anisotrope en termes de résistance à la rupture, tout en conservant des propriétés isotropes en termes d'élasticité.Le focus de cette thèse est d'explorer le comportement en matière de rupture dans des milieux élastiques isotropes présentant une ténacité de rupture anisotrope, en utilisant une combinaison d'investigations expérimentales et de simulations numériques. Dans la partie expérimentale, nous examinons la propagation des fissures dans diverses conditions de chargement en utilisant des géométries d'échantillons variées, englobant à la fois le Mode I et le Mode I+II. Dans la partie numérique, nous adoptons la modélisation de la fissuration fragile par champ de phase basée sur l'approche variationnelle, en utilisant des données expérimentales pour l'étalonnage et l'identification des paramètres numériques. À travers ces méthodologies complètes, notre objectif est de favoriser une compréhension plus profonde de l'interaction entre les motifs d'impression et la sélection des trajectoires de fissures. Cette compréhension a des implications significatives pour guider et gérer la propagation des fissures dans les composants fabriqués par fabrication additive. De plus, nous adoptons les critères classiques basés sur le taux de restitution d'énergie maximale généralisé pour améliorer notre compréhension de la sélection des trajectoires de fissures et de la force critique correspondante.Dans la dernière partie de cette thèse, nous présentons quelques investigations préliminaires concernant l'éventuelle émergence d'un motif de fissure en Zig-Zag dans des spécimens imprimés en 3D. De plus, nous plongeons en profondeur dans le comportement de rupture des spécimens imprimés sous chargement cyclique, offrant une comparaison exhaustive entre les observations expérimentales et les prévisions numériquesAdditive manufacturing is receiving increasing attention due to its advantages in terms of modelling flexibility and allowing to easily design complex micro-structures. Through the manipulation of the printing strategy, we observed that fused deposition of polycarbonate can result in printed samples showcasing a distinct anisotropic behavior in fracture toughness, all the while retaining isotropic properties in elasticity.This thesis is dedicated to investigating fracture behavior within isotropic elastic media with anisotropic fracture toughness. The approach involves a combination of fracture experiments and numerical simulations. In the experimental part, we examine crack propagation under various loading conditions using diverse sample geometries, encompassing both Mode I and Mode I+II loading condition. In the numerical part, we adopt the phase-field modeling of brittle fracture based on a variational approach, using experimental data for calibrating and identification of the numerical parameters. Through these comprehensive methodologies, our objective is to foster a deeper comprehension of the interplay between printing patterns and the selection of crack paths. This understanding holds significant implications for guiding and controlling crack propagation in additive manufacturing-produced components. Besides, we adopted the classical based criteria Generalized Maximum Energy Release Rate to enhance our understanding of crack path selection and the relevant critical force.In the last part of this thesis, we presents some preliminary investigations regarding the potential emergence of Zig-Zag crack patterns in 3D printed specimens. Additionally, we delve extensively into the fracture behavior of printed specimens under cyclic loading, offering a comprehensive comparison between experimental observations and numerical forecasts
3
Stevenson, Kip Patrick. "Anisotropic potential energy surfaces for atmospheric gas : unsaturated hydrocarbon molecule interactions from differential scattering experiments /." Thesis, Connect to this title online; UW restricted, 1997. http://hdl.handle.net/1773/11613.
4
Keller, A. "Evolution of Ion-Induced Ripple Patterns - Anisotropy, nonlinearity, and scaling." Forschungszentrum Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-61101.
Abstract:
This thesis addresses the evolution of nanoscale ripple patterns on solid surfaces during low-energy ion sputtering. Particular attention is paid to the long-time regime in which the surface evolution is dominated by nonlinear processes. This is explored in simulation and experiment.
In numerical simulations, the influence of anisotropy on the evolution of the surface patterns in the anisotropic stochastic Kuramoto-Sivashinsky (KS) equation with and without damping is studied. For a strong nonlinear anisotropy, a 90 rotation of the initial ripple pattern is observed and explained by anisotropic renormalization properties of the anisotropic KS equation. This explanation is supported by comparison with analytical predictions. In contrast to the isotropic stochastic KS equation, interrupted ripple coarsening is found in the presence of low damping. This coarsening seems to be a nonlinear anisotropy effect that occurs only in a narrow range of the nonlinear anisotropy parameter.
Ex-situ atomic force microscopy (AFM) investigations of Si(100) surfaces sputtered with sub-keV Ar ions under oblique ion incidence show the formation of a periodic ripple pattern. This pattern is oriented normal to the direction of the ion beam and has a periodicity well below 100 nm. With increasing ion fluence, the ripple pattern is superposed by larger corrugations that form another quasi-periodic pattern at high fluences.
This ripple-like pattern is oriented parallel to the direction of the ion beam and has a periodicity of around one micrometer. Interrupted wavelength coarsening is observed for both patterns. A dynamic scaling analysis of the AFM images shows the appearance of anisotropic scaling at large lateral scales and high fluences. Based on comparison with the predictions of different nonlinear continuum models, the recent hydrodynamic model of ion erosion, a generalization of the anisotropic KS equation, is considered as a potentially powerful continuum description of this experiment.
In further in-situ experiments, the dependence of the dynamic scaling behavior of the sputtered Si surface on small variations of the angle of incidence is investigated by grazing incidence small angle X-ray scattering (GISAXS). A transition from strongly anisotropic to isotropic scaling is observed. This indicates the presence of at least two fixed points in the system, an anisotropic and an isotropic one. The dynamic scaling exponents of the isotropic fixed point are in reasonable agreement with those of the Kardar-Parisi-Zhang (KPZ) equation. It remains to be seen whether the hydrodynamic model is able to show such a transition from anisotropic to isotropic KPZ-like scaling.
5
Zhang, Hongbin. "Relativistic Density Functional Treatment of Magnetic Anisotropy." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-25132.
Abstract:
Spin-orbit coupling (SOC) reduces the spatial symmetry of ferromagnetic solids. That is, the physical properties of ferromagnetic materials are anisotropic, depending on the magnetization direction. In this thesis, by means of numerical calculations with full-relativistic density functional theory, we studied two kinds of physical properties: surface magnetic anisotropy energy (MAE) and anisotropic thermoelectric power due to Lifshitz transitions. After a short introduction to the full-relativistic density functional theory in Chapter 2, the MAE of ferromagnetic thin films is studied in Chapter 3. For such systems, separation of different contributions, such as bulk magnetocrystalline anisotropy (MCA) energy, shape anisotropy energy, and surface/interface anisotropy energy, is crucial to gain better understanding of experiments. By fitting our calculating results for thick slabs to a phenomenological model, reliable surface MAE could be obtained. Following this idea, we have studied the MAE of Co slabs with different geometries, focusing on the effects of orbital polarization correction (OPC). We found that the surface anisotropy is mainly determined by the geometry. While OPC gives better results of orbital moments, it overestimates the MAE. In the second part of Chapter3, the effects of electric fields on the MAE of L10 ferromagnetic thin films are studied. Using a simple model to simulate the electric field, our calculations are in good agreement with previous experimental results. We predicted that for CoPt, even larger effects exist. Moreover, we found that it is the amount of screening charge that determines the magnetoelectric coupling effects. This gives us some clue about how to achieve electric field control of magnetization direction. In Chapter 4, Lifshitz transitions in L10 FePt caused by a canted magnetic field are studied. We found several Lifshitz transitions in ordered FePt with tiny features in DOS. Using a two-band model, it is demonstrated that at such transitions, the singular behaviour of kinetic properties is due to the interband scattering, and the singularity itself is proportional to the derivative of the singular DOS. For FePt, such singularity will be smeared into anomaly by chemical disorder. Using CPA, we studied the effects of energy level broadening for the critical bands in FePt. We found that for experimentally available FePt thin films, Lifshitz transitions would induce up to a 3% increase of thermopower as the magnetization is rotated from the easy axis to the hard axisSpin-Bahn-Kopplung reduziert die Symmetrie ferromagnetischer Festkörper. Das bedeutet, dass die physikalischen Eigenschaften ferromagnetischer Stoffe anisotrop bezüglich der Magnetisierungsrichtung sind. In dieser Dissertation werden mittels numerischer voll-relativistischer Dichtefunktional-Rechnungen zwei Arten physikalischer Eigenschaften untersucht: magnetische Oberflächen-Anisotropieenergie (MAE) und anisotrope Thermokraft durch Lifshitz-Übergänge. Nach einer kurzen Einführung in die relativistische Dichtefunktional-Theorie in Kapitel 2 wird in Kapitel 3 die MAE ferromagnetischer dünner Filme untersucht. In diesen Systemen ist es für ein Verständnis experimenteller Ergebnisse wichtig, verschiedene Beiträge zu separieren: Volumenanteil der magnetokristallinen Anisotropie (MCA), Formanistropie und Oberflächen bzw. Grenzflächenanisotropie. Durch Anpassen berechneter Daten für dicke Schichten an ein phänomenologisches Modell konnten verlässliche Oberflächen Anisotropien erhalten werden. In dieser Weise wurde die MAE von Co- Schichten mit unterschiedlichen Geometrien untersucht, wobei der Einfluss von Orbitalpolarisations-Korrekturen (OPC) im Vordergrund stand. Es wurde gefunden, dass die Oberflächenanisotropie hauptsächlich von der Geometrie bestimmt wird. Während OPC bessere Ergebnisse für die Orbitalmomente liefert, wird die MAE überschätzt. Im zweiten Teil von Kapitel 3 wird der Einfluss elektrischer Felder auf die MAE von dünnen ferromagnetischen Filmen mit L10-Struktur untersucht. Unter Verwendung eines einfachen Modells zur Simulation des elektrischen Feldes liefern die Rechnungen gute Übereinstimmung mit vorliegenden experimentellen Ergebnissen. Es wird vorhergesagt, dass für CoPt ein noch größerer Effekt existiert. Weiterhin wurde gefunden, dass die magnetoelektrische Kopplung von der Größe der Abschirmladung bestimmt wird. Dies ist eine wichtige Einsicht, um die Magnetisierungsrichtung durch ein elektrisches Feld kontrollieren zu können. In Kapitel 4 werden Lifshitz-Übergänge untersucht, die ein gekantetes Magnetfeld hervorruft. Es wurden mehrere Lifshitz-Übergänge in geordnetem FePt gefunden, welche kleine Anomalien in der Zustandsdichte hervorrufen. Mit Hilfe eines Zweiband-Modells wird gezeigt, dass an solchen Übergängen das singuläre Verhalten kinetischer Eigenschaften durch Interband- Streuung verursacht wird und dass die Singularität proportional zur Ableitung der singulären Zustandsdichte ist. In FePt wird durch chemische Unordnung diese Singularität zu einer Anomalie verschmiert. Der Einfluss einer Verbreiterung der Energieniveaus der kritischen Bänder in FePt wurde mittels CPA untersucht. Es wurde gefunden, dass in experimentell verfügbaren dünnen FePt-Filmen Lifshitz-Übergänge bis zu 3% Erhöhung der Thermokraft erzeugen, wenn die Magnetisierung von der leichten in die harte Richtung gedreht wird
6
Grigat, Marius [Verfasser]. "Large scale anisotropy studies of ultra high energy cosmic rays using data taken with the surface detector of the Pierre Auger Observatory / Marius Grigat." Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2011. http://d-nb.info/1018201106/34.
7
Fitton, George. "Analyse multifractale et simulation des fluctuations de l'énergie éolienne." Phd thesis, Université Paris-Est, 2013. http://tel.archives-ouvertes.fr/tel-00962318.
Abstract:
A partir des équations gouvernant le champ de vitesse, on peut non seulement s'attendre à un vent (fortement) non-gaussien, mais aussi à un vent présentant un comportement scalant. Par 'scalant' ou invariant d'échelle, nous faisons référence à un comportement statistique auto-similaire particulier; les cascades de tourbillons. Les multifractales stochastiques (avec des singularités et des co-dimensions multiples) reproduisent facilement le comportement scalant et les distributions de probabilités à queues épaisses omniprésentes dans le vent et dont la quantification est essentielle pour la communauté. Les quelques paramètres qui définissent ces modèles peuvent être déduits soit de considérations théoriques, soit de l'analyse statistique de données. Nous avons constaté que les approximations de flux basées sur le module du cisaillement du vent donnent des moments statistiques non-scalants et donc des estimations faussées des paramètres multifractals. La méthode DSF n'exige pas cette approximation et garantit un comportement scalant sur une certaine gamme d'échelles. Nous n'avons trouvé aucune estimation véritablement stable d'alpha en utilisant des méthodes standards. Ceci n'arrive plus quand nous optimisons localement (par la différenciation fractionnaire) le comportement scalant du DTM. Nous obtenons alors des estimations très stables de l'indice de multifractalité qui sont en outre en accord (alpha ≤ 2) avec des résultats publiés. Au contraire, les deux autres paramètres (C1 et H) deviennent des fonctions non-linéaires de l'ordre q des moments statistiques. Ces résultats suggèrent que le modèle UM isotrope ne peut être utilisé pour reproduire le cisaillement de vent dans la couche de surface atmosphérique. Lesdites hypothèses sont examinées en utilisant un repère tournant pour analyser l'anisotropie de la vitesse horizontale dans la couche de surface atmosphérique. Cela permet de quantifier la dépendance angulaire de l'exposant de Hurst. Les valeurs de cet exposant restent tout de même conformes aux résultats précédemment publiés. Pour des échelles de temps supérieures à quelques secondes, les deux jeux de données présentent une anisotropie scalante forte, qui décroît avec l'altitude. Nous mettons en évidence une expression analytique de la variation angulaire de l'exposant de Hurst, reposant sur les corrélations entre les composantes horizontales. Ceci pilote la formation des extrêmes du cisaillement, y compris dans le sillage d'une éolienne. Les cisaillements turbulents du vent sont si extrêmes que leur loi de probabilité est une loi de puissance. L'exposant correspondant (qD) est similaire pour les deux sites à une hauteur de 50m (4 ≤ qD ≤ 5), malgré des conditions orographiques très différentes. Nous discutons aussi de ses conséquences en analysant la stabilité de la couche limite atmosphérique et proposons une nouvelle méthode pour sa classification. Enfin, nous démontrons analytiquement que l'anisotropie augmente la probabilité des extrêmes. Ce résultat met en lumière un des nombreux mécanismes de turbulence possibles dans la couche de surface qui peut apparemment surproduire les cisaillements extrêmes du vent, s'ils sont étudiés dans le cadre des UM isotropes. Nous en analysons théoriquement les conséquences sur les estimations des paramètres multifractales par la méthode DTM. Les résultats analytiques obtenus sont en parfait accord avec les observations empiriques. Nous discutons alors de la prise en compte de toutes ces considérations pour faire des simulations multifractales des champs du vent dans la couche limite atmosphérique
8
Piovano, Paulo. "Evolution and Regularity Results for Epitaxially Strained Thin Films and Material Voids." Research Showcase @ CMU, 2012. http://repository.cmu.edu/dissertations/96.
Abstract:
In this dissertation we study free boundary problems that model the evolution of interfaces in the presence of elasticity, such as thin film profiles and material void boundaries. These problems are characterized by the competition between the elastic bulk energy and the anisotropic surface energy.
First, we consider the evolution equation with curvature regularization that models the motion of a two-dimensional thin film by evaporation-condensation on a rigid substrate. The film is strained due to the mismatch between the crystalline lattices of the two materials and anisotropy is taken into account. We present the results contained in [62] where the author establishes short time existence, uniqueness and regularity of the solution using De Giorgi’s minimizing movements to exploit the L2 -gradient flow structure of the equation. This seems to be the first analytical result for the evaporation-condensation case in the presence of elasticity.
Second, we consider the relaxed energy introduced in [20] that depends on admissible pairs (E, u) of sets E and functions u defined only outside of E. For dimension three this energy appears in the study of the material voids in solids, where the pairs (E, u) are interpreted as the admissible configurations that consist of void regions E in the space and of displacements u of the atoms of the crystal. We provide the precise mathematical framework that guarantees the existence of minimal energy pairs (E, u). Then, we establish that for every minimal configuration (E, u), the function u is C 1,γ loc -regular outside an essentially closed subset of E. No hypothesis of starshapedness is assumed on the voids and all the results that are contained in [18] hold true for every dimension d ≥ 2.
9
Walubita, Lubinda F. "Comparison of fatigue analysis approaches for predicting fatigue lives of hot-mix asphalt concrete (HMAC) mixtures." Diss., Texas A&M University, 2003. http://hdl.handle.net/1969.1/3898.
Abstract:
Hot-mix asphalt concrete (HMAC) mixture fatigue characterization constitutes a fundamental component of HMAC pavement structural design and analysis to ensure adequate field fatigue performance. HMAC is a heterogeneous complex composite material of air, binder, and aggregate that behaves in a non-linear elasto-viscoplastic manner, exhibits anisotropic behavior, ages with time, and heals during traffic loading rest periods and changing environmental conditions. Comprehensive HMAC mixture fatigue analysis approaches that take into account this complex nature of HMAC are thus needed to ensure adequate field fatigue performance. In this study, four fatigue analysis approaches; the mechanistic empirical (ME), the calibrated mechanistic with (CMSE) and without (CM) surface energy measurements, and the proposed NCHRP 1-37A 2002 Pavement Design Guide (MEPDG) were comparatively evaluated and utilized to characterize the fatigue resistance of two Texas HMAC mixtures in the laboratory, including investigating the effects of binder oxidative aging. Although the results were comparable, the CMSE/CM approaches exhibited greater flexibility and potential to discretely account for most of the fundamental material properties (including fracture, aging, healing, visco-elasticity, and anisotropy) that affect HMAC pavement fatigue performance. Compared to the other approaches, which are mechanistic-empirically based, the CMSE/CM approaches are based on the fundamental concepts of continuum micromechanics and energy theory.
10
Mekhiche, Mouhoub. "Introduction de la texture cubique {100}<001> dans les dispositifs électrotechniques : de la métallurgie à la modélisation." Grenoble INPG, 1995. http://www.theses.fr/1995INPG0019.
Abstract:
La principale plage de progression des performances magnétiques des aciers magnétiques FeSi est à l'heure actuelle la texture de ces matériaux. Il est alors important de savoir évaluer l'intérêt de telle ou telle texture pour l'électrotechnique, afin de connaître les marges de progrès existant encore dans la conception de différents dispositifs et d'estimer par là même s'il est intéressant ou non de mettre au point métallurgiquement telle texture. Le travail présenté a pour ambition de mettre en place un tel outil intégré d'étude et d'évaluation d'une texture, relativement aux contraintes du génie électrique: dans ce but nous nous sommes appliqués à l'étude et l'évaluation de la texture "cubique" {100}<001>. La synthèse métallurgique de cette texture a été obtenue à partir d'un procédé associant laminage croisé, énergie de surface et aluminium. L'étude a naturellement montré que cette association permettait d'obtenir une forte texture {100} même avec de fortes vitesses de montée en température. Après un passage nécessaire par une caractérisation magnétique 2D, un modèle d'aimantation anisotrope et anhystérétique a été élaboré pour rendre compte du comportement magnétique des tôles texturées. Enfin l'introduction de matériaux texturés dans les dispositifs électrotechniques a été étudiée sur la baseCurrently, the principal range of improvement in the magnetic performances of SiFe magnetic steels is found in the texture of these materials. It is therefore important to know how to evaluate the interest of a given texture for use in electrical engineering in order to know the margines of progress still existing in the design of different devices, and also to estimate if it is interesting or not to metallurgically develop such a texture. The present work aims to set up a tool integrated to study and evaluate a texture, relative to the constraints of electrical engineering. Towards this goal we have focused on the study and evaluation of the "cubic" texture {100}<001>. The metallugic synthesis of this texture was obtained from a procedure which associates cross rolling, surface energy and aluminium. The study showed that this association obtained a strong {100} texture even with quick rises in temperature. After a necessary phase of 2D magnetic characterization, a model of anisotropic and non hysteretic magnetization was elaborated to find the magnetic behavior of textured sheets. Finally, the introduction of such textured materials into electrical devices was studied, based on electromagnetic modeling software well adapted to the description of anisotropy
Books on the topic "Anisotropic surface energy":
1
B, McFadden Geoffrey, and National Institute of Standards and Technology (U.S.), eds. The effect of anisotropic surface energy on the Rayleigh instability. [Gaithersburg, Md.]: U.S. Dept. of Commerce, Technology Administration, National Institute of Standards and Technology, 2002.
2
B, McFadden Geoffrey, and National Institute of Standards and Technology (U.S.), eds. The effect of anisotropic surface energy on the Rayleigh instability. [Gaithersburg, Md.]: U.S. Dept. of Commerce, Technology Administration, National Institute of Standards and Technology, 2002.
Book chapters on the topic "Anisotropic surface energy":
1
Schreiner, F., J. Schmidt, B. Thorenz, M. Voigt, and F. Döpper. "Investigation of Cutting Force and Surface Quality in Frozen Wood Sawing Under Varying Influencing Factors to Improve the Energy- and Resource Efficiency of Sawing Processes." In Lecture Notes in Mechanical Engineering, 166–74. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-28839-5_19.
Abstract:
AbstractWood as a renewable material plays an important role in transforming society towards sustainability and climate neutrality. However, wood is a difficult material to saw due to its anisotropic and inhomogeneous properties. Currently, the adaption of process parameters due to varying wood temperature and moisture content are solely based on operator experience. This frequently results in unfavorable settings of process parameters leading to a drastic increase in energy consumption and poor surface quality of the sawn wood. This paper investigates the cutting force when sawing frozen spruce wood with a two tooth research saw blade and the surface quality of the resulting wood samples under varying influencing factors. The material properties temperature between 20 ℃ and −40 ℃ and moisture content as well as the kinematic factor cutting direction were observed. The results show that the cutting force of moist and wet wood increase with decreasing temperature and remain constant for dry wood. Additionally, the surface quality of wet and dry wood samples is improved when sawing wood with lower temperature values. Using these results, the operator can be supported by a data driven approach for the adaption of machining parameters, hence improving the energy- and resource-efficiency of the process.
2
Vardoulakis, I., and G. Exadaktylos. "The Asymptotic Solution of Anisotropic Gradient Elasticity with Surface Energy for a Mode-II Crack." In IUTAM Symposium on Non–Linear Singularities in Deformation and Flow, 87–98. Dordrecht: Springer Netherlands, 1999. http://dx.doi.org/10.1007/978-94-011-4736-1_9.
3
Bonzel, H. P., and K. Dückers. "Relationship Between Anisotropy of Specific Surface Free Energy and Surface Reconstruction." In Chemistry and Physics of Solid Surfaces VII, 429–54. Berlin, Heidelberg: Springer Berlin Heidelberg, 1988. http://dx.doi.org/10.1007/978-3-642-73902-6_15.
4
Handa, S. "Technology of reactive ion etching." In Plasma Etching Fundamentals and Applications, 180–211. Oxford University PressOxford, 1998. http://dx.doi.org/10.1093/oso/9780198562870.003.0005.
Abstract:
Abstract The original meaning of ‘etching’ is ‘to eat’; the process of removing something from an object. Moreover, it is impressive that another original meaning of it is ‘to feed’. In fact, reactive ion etching (RIE) consists of two processes; ‘to eat’ and ‘to feed’. The physical process of etching is to remove particles from a solid surface by the colliding energy of ions which is converted into thermal, chemical, or kinetic energy. The mechanisms of etching can be classified by forms of energy exchange: chemical and physical. The etched pattern can be classified into two types: anisotropic (directional) etching and isotropic (indirectional) etching. When thermal and chemical energies are transformed in the reaction, then indirectional etching will be processed. Liquid chemical etching is a typical example of indirectional etching.
5
Tariq, Maria, Tajamal Hussain, Adnan Mujahid, Mirza Nadeem Ahmad, Muhammad Imran Din, Azeem Intisar, and Muhammad Zahid. "Applications of Carbon Based Materials in Developing Advanced Energy Storage Devices." In Carbon Nanotubes - Redefining the World of Electronics. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.97651.
Abstract:
With the increasing pressure of population, the energy demand is growing explosively. By 2050, it is expected that the world population may reach to about 9 billion which may result in the increase of energy requirement to about 12.5 trillion watts. Due to increasing pressures of population, industries and technology, concerns to find possibilities to cope with increasing demand of energy resources, arise. Although the renewable energy resources including fossil fuels, wind, water and solar energy have been used for a long time to fulfill the energy requirements, but they need efficient conversions and storage techniques and are responsible for causing environmental pollution due to greenhouse gases as well. It is thus noteworthy to develop methods for the generation and storage of renewable energy devices that can replace the conventional energy resources to meet the requirement of energy consumption. Due to high energy demands, the sustainable energy storage devices have remained the subject of interest for scientists in the history, however, the traditional methods are not efficient enough to fulfill the energy requirements. In the present era, among other variety of advanced treatments, nano-sciences have attracted the attention of the scientists. While talking about nano-science, one cannot move on without admiring the extraordinary features of carbon nanotubes (CNTs) and other carbon based materials. CNTs are on the cutting edge of nano science research and finding enormous applications in energy storage devices. Excellent adsorption capabilities, high surface area, better electrical conductivity, high mechanical strength, corrosion resistance, high aspect ratio and good chemical and physical properties of CNTs have grabbed tremendous attention worldwide. Their charge transfer properties make them favorable for energy conversion applications. The limitation to the laboratory research on CNTs for energy storage techniques due to low specific capacitance and limited electrochemical performance can be overcome by surface functionalization using surface functional groups that can enhance their electrical and dispersion properties. In this chapter, ways CNTs employed to boost the abilities of the existing material used to store and transfer of energy have been discussed critically. Moreover, how anisotropic properties of CNTs play important role in increasing the energy storage capabilities of functional materials. It will also be discussed how various kinds of materials can be combined along CNTs to get better results.
6
Bažant, Zdeněk P., Jia-Liang Le, and Marco Salviato. "Fundamentals of Linear Elastic Fracture Mechanics." In Quasibrittle Fracture Mechanics and Size Effect, 11–52. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780192846242.003.0002.
Abstract:
The linear elastic fracture mechanics (LEFM) is the pillar of all fracture mechanics. In this chapter, it is presented in full, with complete derivations and many examples. Griffith's concept of the energy release rates is described, the elastic singular near-tip stress field is derived, and the stress intensity factors are defined. Their relation to the energy release rate, discovered by Irwin, is derived, and three different fracture modes in isotropic solids are defined. A rigorous derivation of Rice's J-integral is given and illustrated by examples. Various ways of numerical calculation of the stress intensity factors are reviewed. It is shown how the elastic compliance and deflections due to a crack or a system of cracks under external loads or crack pressure can be calculated from the known stress intensity factors. Various LEFM methods of calculating and measuring the energy release rate and fracture energy are presented and test control by a crack-mouth or crack-tip gage is explained. The complex singularities at interfacial cracks are described. The remote decay of the stress field disturbance by a crack is also derived. The chapter ends with comments on anisotropic materials and on three-dimensional singularities at the intersection of crack edge with the surface.
7
Kobayashi, Shiro, Soo-Ik Oh, and Taylan Altan. "Compaction and Forging of Porous Metals." In Metal Forming and the Finite-Element Method. Oxford University Press, 1989. http://dx.doi.org/10.1093/oso/9780195044027.003.0016.
Abstract:
Powder forming, once considered a laboratory curiosity, has evolved into a manufacturing technique for producing high-performance components economically in the metal-working industry because of its low manufacturing cost compared with conventional metal-forming processes. Generally, the powder-forming process consists of three steps: (1) compacting a precise weight of metal powder into a “green” preform with 10–30% porosity (defined by the ratio of void volume to total volume of the preform); (2) sintering the preform to reduce the metal oxides and form strong metallurgical structures; (3) forming the preform by repressing or upsetting in a closed die to less than 1% residual porosity. Powder forming has disadvantages in that the preform exhibits porosity. Because of this porosity, the ductility of the sintered preform is low in comparison with wrought materials. In forging compacted and sintered powdered-metal (P/M) preforms, where large amount of deformation and shear is involved, pores collapse and align in the direction perpendicular to that of forging and result in anisotropy. However, repressing-type deformation, where very little deformation and shear are present, does not lead to marked anisotropy. A low-density preform will result in more local flow and a higher degree of anisotropy than will a preform of high initial density. These anisotropic structures can lead to nonuniform impact resistances of the forged P/M parts. Also, in forming of sintered preforms, materials are more susceptible to fracture than in forming of solid materials, and the analysis is of particular importance in producing defect-free components by determining the effect of various parameters (preform and die geometries, sintering conditions, and the friction conditions) on the detailed metal flow. In this chapter, the plasticity theory for solid materials is extended to porous materials, applicable to the deformation analysis of sintered powdered-metal preforms. In characterizing the mechanical response of porous materials, a phenomenological approach (introducing a homogeneous continuum model) is employed. For the finite-element formulations of the equilibrium and energy equations based on the infinitesimal theory, the following assumptions are made: the elastic portion of deformation is neglected because the practical forming process involves very large amounts of plastic deformation; the normality of the plastic strain-rates to the yield surface holds; anisotropy that occurs during deformation is negligible; and thermal properties of the porous materials are independent of the temperatures.
8
Yuzevych, Volodymyr, and Bohdan Koman. "MATHEMATICAL AND COMPUTER MODELING OF INTERPHASE INTERACTION IN HETEROGENEOUS SOLID STRUCTURES." In Theoretical and practical aspects of the development of modern scientific research. Publishing House “Baltija Publishing”, 2022. http://dx.doi.org/10.30525/978-9934-26-195-4-14.
Abstract:
The aim of this work was to develop a mathematical model and computer modelling of interphase interaction, mechanical stresses and adhesion mechanisms between mechanically inhomogeneous media (different phases). Methodology. For the system "metal – dielectric" we use a macroscopic approach, which corresponds to the ratio of non-equilibrium thermodynamics and physics of solid surfaces. Let’s consider the system of equations and boundary conditions for describing the change of energy parameters (σh, γ), which characterize the thermodynamic state of the system of contacting bodies. Method for calculating the main energy parameters (interfacial energy – γm, interfacial tension – σm, work of adhesion – Aadand energy of adhesive bonds – γad) in complex solid-state structures containing boundary phases is proposed. Based on the basic equations of nonequilibrium thermodynamics and surface physics a mathematical model of the interphase boundary is designed. A comparative analysis of the features of interphase interaction in the systems "metal-metal", "metal-semiconductor" and "metal-dielectric" on the example of interacting systems "Cu – Zn", "Cu – Si" and "Cu – quartz". It is established that the most sensitive parameter in the analysis of interphase interactions is the interphase energy γm.A model of mechanical stress formation in the "condensate-substrate" system is proposed. In particular, internal stresses in metal condensates are caused by changes in the value of interphase energy parameters (primarily interfacial tension) in the substrate-nanocondensate system and due to phase-forming processes accompanied by changes in surface energy in the condensate volume during its formation. The resulting internal stresses in metal condensates are an integral result of the action of statistically distributed on the plane of the film local stresses. Such phenomena are due to the anisotropy of the energy parameters of the interphase interaction in the condensate plane. Behavior analysis of energy and adhesion parameters can be used to predict the results of interphase interaction in order to select contact pairs to create thermodynamically stable structures with predicted values of energy parameters of interphase interaction, a certain type of chemical bond and a given level of mechanical stresses.
9
Goldman, N., and R. J. Saykally. "Elucidating the role of many-body forces in liquid water. I. Simulations of water clusters on the VRT(ASP-W) potential surfaces." In Quantum Monte Carlo, 148. Oxford University PressNew York, NY, 2007. http://dx.doi.org/10.1093/oso/9780195310108.003.00152.
Abstract:
Abstract In the quest for a quantitative simulation of liquid water it appears the potential energy of the interaction of water molecules converges very rapidly and may be described adequately by only two- and three-body terms. Measurements of vibration-rotation tunneling (VRT) splittings for water dimers have provided data for fitting an anisotropic site potential with Woermer dispersion (ASPW) to provide a series of highly detailed potential energy surfaces. The expressions for these surfaces include terms corresponding to electrostatic interaction, two-body exchange repulsion, two-body dispersion, and many-body induction. In this paper the authors report an investigation of the suitability of these surfaces and several others for predicting the vibrational ground-state properties of water clusters ranging from the trimer to the hexamer. The calculations were carried out with diffusion Q:tvIC to determine cluster properties, the structures and, in particular, the vibrational average rotational constants for direct comparison with experimentally measured values. The ground-state properties were determined in runs for 1000 walkers with 15,000-20,000 time steps after equilibration. Histograms of configurations were used for calculating the internal tensors leading to the rotational constants.
10
Coker, D. F., and R. O. Watts. "Diffusion Monte Carlo simulation of condensed systems." In Quantum Monte Carlo, 48. Oxford University PressNew York, NY, 2007. http://dx.doi.org/10.1093/oso/9780195310108.003.0051.
Abstract:
Abstract This paper reports diffusion quantum Monte Carlo calculations for condensed systems, in this case for liquid 4He and for solid molecular H2. Calculations for liquid He made earlier by Whitlock et al.a using Green’s function QMC for the same potential energy surface allowed a comparison of results for this system. Coker and Watts used spherical pair potentials derived from scattering experiments for both systems, along with Axilrod-Teller-Muto three body terms. The calculations were performed with importance sampling, using a simple product of pair functions as a trial function for helium. For hydrogen a simple pair function multiplied by a single-particle term for position in the fee lattice was used. Periodic boundary conditions were employed, and calculations were carried out for several particle densities of each species. For helium, good agreement with the prior Green’s function calculations was obtained for thermodynamic and structural properties and for radial distribution functions. For hydrogen, the calculated average energies and pressures gave general agreement with experimental measurement, but they differed up to 10% in energy and 12% in pressure in a manner to be expected for neglect of molecular anisotropy. The problem treated in this paper is that of understanding xenon cluster ions at the microscopic level. Some properties of cluster anions had been measured, but these revealed no detailed information on structure and energetics. In the study reported here, diffusion QMC was used to investigate electron binding to small clusters of up to 19 atoms in fixed minimum-energy configurations. This was followed by path integral calculations to determine equilibrium distributions of cluster structures at temperatures of 10-100 K for several cluster sizes.
Conference papers on the topic "Anisotropic surface energy":
1
Sommers, Andrew D., and Anthony M. Jacobi. "Modeling the Retention of Water Droplets on Topographically-Modified, Micro-Grooved Aluminum." In ASME 2008 Heat Transfer Summer Conference collocated with the Fluids Engineering, Energy Sustainability, and 3rd Energy Nanotechnology Conferences. ASMEDC, 2008. http://dx.doi.org/10.1115/ht2008-56440.
Abstract:
In this research, a method for fabricating controlled micro-scale, anisotropic topographical features on aluminum is described for the purpose of exploiting those features to affect the surface wettability. Experimental data have shown that droplets placed on these micro-grooved aluminum surfaces using a micro-syringe exhibit an increased apparent contact angle, and for droplets condensed on these etched surfaces, up to a 50% reduction in the volume needed for the onset of droplet sliding is manifest. No chemical surface treatment is necessary to achieve this water repellency; it is accomplished solely by the anisotropic surface morphology that manipulates droplet geometry and creates and exploits discontinuities in the three-phase contact line. In an effort to provide guidance for the development of these surfaces, a mechanistic model for droplet retention on micro-grooved aluminum surfaces will also be presented. This work will show that current models, tacitly based on an assumption of isotropic wetting, do not provide reliable prediction of water retention on these new surfaces.
2
Yanson, Z. A. "On intensity of high-frequency surface waves in anisotropic elastic media. The energy approach." In Proceedings of the International Conference Days on Diffraction-2005. IEEE, 2005. http://dx.doi.org/10.1109/dd.2005.204904.
3
Tsai, Y. M. "Forced Vibrations of a Transversely Isotropic Composite Containing an External Circular Crack." In ASME 2001 Engineering Technology Conference on Energy. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/etce2001-17154.
Abstract:
Abstract The problem of a transversely isotropic composite containing an external circular crack is investigated using the method of Hankel transforms. A pair of tensile vibratory forces of equal amplitude are applied normal to the crack surface at infinity. A complete contour integration is employed to simplify the expressions of the results. An exact expression of the dynamic stress-intensity factor is obtained as a function of the force frequency and the anisotropic material constants. The normalized dynamic stress-intensity factor is shown to have different maximum values at different force frequencies for the sample fiber-reinforced and metal matrix composites. The deviation of the dynamic crack surface displacement from the associated static displacement is also shown to be dependent on the force frequency and the anisotropy of the material.
4
Zhang, Yingfan, Zhengyong Huang, Jian Li, Haohuan Wang, Run He, and Chenxin Li. "Inhibition Mechanism Under Temperature Gradient on DC Surface Flashover of 3D-Printing Anisotropic Heat Conducting Composites." In 2023 IEEE 6th International Electrical and Energy Conference (CIEEC). IEEE, 2023. http://dx.doi.org/10.1109/cieec58067.2023.10166860.
5
Pan, E. "Force Dipoles in Anisotropic Materials: Cell Orientation Guided by Substrate Anisotropy?" In ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-59138.
Abstract:
Recent studies on cell orientation have shown that cells can actively sense the elastic properties of their environment and strengthen contacts and cytoskeleton in a direction of large effective stiffness. For example, it was found that cells oriented perpendicular to clamped boundaries whilst parallel to free boundaries. It was also suggested that active mechanosensing in an elastically anisotropic medium might lead to cell orientation. In this paper, we first develop an analytical force-dipole solution in anisotropic materials. We then apply this solution to investigate the effect of substrate anisotropy on cell orientation. In our numerical examples, the substrate will be assumed to be cubic, but oriented in different orientations. The interactive energy of the cells is calculated for different boundary conditions (free and clamped) on the surface of the anisotropic substrate.
6
Tsai, Y. M. "Torsional Vibration of an External Circular Crack in a Transversely Isotropic Composite." In ASME 2002 Engineering Technology Conference on Energy. ASMEDC, 2002. http://dx.doi.org/10.1115/etce2002/cmda-29078.
Abstract:
The forced torsional vibratory motion of an external circular crack in a transversely isotropic composite is investigated by using the method of Hankel transforms. A pair of vibratory torques of equal amplitude is applied at infinity. The infinite integral involved is evaluated through a contour integration to be discontinuous in nature. An exact expression for the dynamic stress intensity factor is obtained in terms of the frequency factor and the anisotropic material constants. The maximum value of the normalized dynamic stress-intensity factor is shown to occur at different frequency factors for the sample fiber-reinforced and metal matrix composites. The distortion of the dynamic crack surface displacement from the associated static displacement depends also on the forcing frequency and the material anisotropy.
7
Zhang, Bo, Zhiwei Ma, Dongming Zheng, Rick Chalaturnyk, and Jeff Boisvert. "Machine Learning Enhanced Upscaling of Anisotropic Shear Strength for Heterogeneous Oil Sands." In SPE Canadian Energy Technology Conference. SPE, 2022. http://dx.doi.org/10.2118/208885-ms.
Abstract:
Abstract Weak shale beddings are widely distributed in the overburden and reservoir of oil sand deposits and lead to reduced anisotropic shear strength. Understanding the shear strength of the overburden and the reservoir is important in risk assessment of slope stability in open-pit mining and caprock integrity of in-situ thermal recovery of oil sands while optimizing the production of bitumen. Due to the restrictions of computational efficiency, cells used for simulation cannot be smaller enough to capture the details of heterogeneity in the reservoir. Therefore, a robust and efficient upscaling technique is important for modeling the impact of heterogeneity on the deformation and failure of oil sands during mining and in-situ recovery. However, current analytical and numerical upscaling techniques cannot provide computationally efficient geomechanical models that consider the impact of inclined shale beddings on shear strength. Therefore, we propose a machine learning enhanced upscaling (MLEU) technique that leverages the accuracy of local numerical upscaling and the efficiency of machine learning techniques. MLEU generates a fast and accurate machine learning-based proxy model using an artificial neural network (ANN) to predict the anisotropic shear strength of heterogeneous oil sands embedded with shale beddings. The trained model improves accuracy by 12%-76% compared to traditional methods such as response surface methodology (RSM). MLEU provides a reasonable estimate of anisotropic shear strength while considering uncertainties caused by different configurations of shale beddings. With the increasing demand for regional scale modeling of geotechnical problems, the proposed MLEU technique can be extended to other geological settings where weak beddings play a significant role and the impact of heterogeneity on shear strength is important.
8
Strack, Kurt M., Cesar Barajas-Olalde, Sophia Davydycheva, Yardenia Martinez, and Pantelis Soupios. "Surface-to-Borehole Electromagnetics Using an Array System: A Case Study for Co2 Monitoring and the Energy Transition." In SPE Annual Technical Conference and Exhibition. SPE, 2022. http://dx.doi.org/10.2118/209974-ms.
Abstract:
Abstract Fluid imaging technologies are used in a wide range of E&P applications. Among geophysical methods, electromagnetics (EM) determines subsurface resistivities and thus responds to fluid changes. On the path to zero carbon footprint, the most significant potential for EM lies in monitoring geothermal, carbon capture, utilization and storage (CCUS), and enhancing oil recovery (EOR). To optimize reservoir fluid monitoring, we calibrate surface measurements to well logs resulting in a 3D anisotropic model consistent with borehole data. This is done before and after depletion or injection to estimate a time-lapse reservoir response. As part of a carbon capture and storage project, we carried out baseline measurements and validated the surface EM data to the 3D anisotropic borehole model. The monitoring workflow for this project can easily be adapted for other applications to support the energy transition. From this, we learned that measurement accuracy requirements higher than 1 % because we are often imaging small anomalies. While there are always limits in acquisition set by industrial noise, we derived two ways of increasing the anomaly. One is by using, similar to a borehole focused logs, focusing methods in the acquisition setup. This is still subject to measurement accuracy limitations and limited to electric fields only. Another way is to add borehole sensors that increase the sensitivity by around a factor of 10. While shallow (around 50 m) is sufficient, they can be extended to deeper borehole sensors, bringing the measurements close to the anomaly and is thus the preferred approach. This, in combination with calibration back to the 3D anisotropic borehole log allows you to certify the data for its information content. This will give you quantifiable ways to derive risk values and significantly reduce acquisition and monitoring operations cost.
9
Hoffbauer, Mark A., Victoria J. McVeigh, and Michael J. Zuerlein. "Rotationally Anisotropic Second-Harmonic Generation Studies of the Structure and Thermal Stability of Cu(110)." In The Microphysics of Surfaces: Beam-Induced Processes. Washington, D.C.: Optica Publishing Group, 1991. http://dx.doi.org/10.1364/msbip.1991.wb2.
Abstract:
The microscopic structure and thermal stability of interfaces are of fundamental importance in determining a variety of materials properties. Order-disorder transitions on surfaces have recently received considerable attention in the scientific literature since the dynamics of such processes can impose fundamental limits on material performance at elevated temperatures. Many high-index (11n) faces (where n>2) of single-crystal metal surfaces are known to undergo this type of phasetransition. By definition, roughening of an atomically clean surface consists of the proliferation of atomic steps by thermal means at a roughening temperature, tr, where the surface free energy for creation of a step becomes zero. An unresolved question of fundamental importance is whether the roughening temperature of a low-index (110) surface can be lower than the bulk crystal melting temperature. For high index faces, a less stringent definition of roughening involving the proliferation of kinks on the already present step rows that can meander randomly has been suggested. The energy required for creation of a kink atom is lower than that required for generation of a step atom, thus roughening at temperatures lower than the bulk melting temperature can occur for stepped surfaces as opposed to low-index surfaces. Indeed, it has been shown shown both theoretically and experimentally that high-index faces of Cu, Ni, and other metals undergo roughening transitions well below the bulk melting temperatures.1
10
Bollinger, L. D., and C. B. Zarowin. "Control of Plasma Etch Rates, Selectivity and Anisotropy with Plasma Parameters." In Optical Fabrication and Testing. Washington, D.C.: Optica Publishing Group, 1987. http://dx.doi.org/10.1364/oft.1987.pdp1.
Abstract:
We discuss the experimental verification of relations derived earlier (1) between observable plasma etch rate, selectivity and anisotropy and reactor parameters for a variety of etch gases. Since the hetergeneous etch reaction is a superposition of neutral and ionic components, it can be shown that such etch chemistry exhibits enhancement and is made anisotropic by the energy transport of ions to the etch surface only when the process is ion dominated. The ion energy transport is controlled by the plasma sheath electric field-electrode area/gas pressure-collision cross section ratio, E.A./pQ, similarly controlling chemical anisotropy for ion dominated etch reactions. Under such circumstances, we show that many etch gases can yield identical ion transport, etch rate and anisotropy for a given rf current, gas pressure, ion-neutral collision cross section & electrode area, Irf/pQA.
Reports on the topic "Anisotropic surface energy":
1
Gurski, K. F., and G. B. McFadden. The effect of anisotropic surface energy on the Rayleigh instability. Gaithersburg, MD: National Institute of Standards and Technology, 2002. http://dx.doi.org/10.6028/nist.ir.6892.
2
Hart, Carl, and Gregory Lyons. A tutorial on the rapid distortion theory model for unidirectional, plane shearing of homogeneous turbulence. Engineer Research and Development Center (U.S.), July 2022. http://dx.doi.org/10.21079/11681/44766.
Abstract:
The theory of near-surface atmospheric wind noise is largely predicated on assuming turbulence is homogeneous and isotropic. For high turbulent wavenumbers, this is a fairly reasonable approximation, though it can introduce non-negligible errors in shear flows. Recent near-surface measurements of atmospheric turbulence suggest that anisotropic turbulence can be adequately modeled by rapid-distortion theory (RDT), which can serve as a natural extension of wind noise theory. Here, a solution for the RDT equations of unidirectional plane shearing of homogeneous turbulence is reproduced. It is assumed that the time-varying velocity spectral tensor can be made stationary by substituting an eddy-lifetime parameter in place of time. General and particular RDT evolution equations for stochastic increments are derived in detail. Analytical solutions for the RDT evolution equation, with and without an effective eddy viscosity, are given. An alternative expression for the eddy-lifetime parameter is shown. The turbulence kinetic energy budget is examined for RDT. Predictions by RDT are shown for velocity (co)variances, one-dimensional streamwise spectra, length scales, and the second invariant of the anisotropy tensor of the moments of velocity. The RDT prediction of the second invariant for the velocity anisotropy tensor is shown to agree better with direct numerical simulations than previously reported.
3
Friedman, Shmuel, Jon Wraith, and Dani Or. Geometrical Considerations and Interfacial Processes Affecting Electromagnetic Measurement of Soil Water Content by TDR and Remote Sensing Methods. United States Department of Agriculture, 2002. http://dx.doi.org/10.32747/2002.7580679.bard.
Abstract:
Time Domain Reflectometry (TDR) and other in-situ and remote sensing dielectric methods for determining the soil water content had become standard in both research and practice in the last two decades. Limitations of existing dielectric methods in some soils, and introduction of new agricultural measurement devices or approaches based on soil dielectric properties mandate improved understanding of the relationship between the measured effective permittivity (dielectric constant) and the soil water content. Mounting evidence indicates that consideration must be given not only to the volume fractions of soil constituents, as most mixing models assume, but also to soil attributes and ambient temperature in order to reduce errors in interpreting measured effective permittivities. The major objective of the present research project was to investigate the effects of the soil geometrical attributes and interfacial processes (bound water) on the effective permittivity of the soil, and to develop a theoretical frame for improved, soil-specific effective permittivity- water content calibration curves, which are based on easily attainable soil properties. After initializing the experimental investigation of the effective permittivity - water content relationship, we realized that the first step for water content determination by the Time Domain Reflectometry (TDR) method, namely, the TDR measurement of the soil effective permittivity still requires standardization and improvement, and we also made more efforts than originally planned towards this objective. The findings of the BARD project, related to these two consequential steps involved in TDR measurement of the soil water content, are expected to improve the accuracy of soil water content determination by existing in-situ and remote sensing dielectric methods and to help evaluate new water content sensors based on soil electrical properties. A more precise water content determination is expected to result in reduced irrigation levels, a matter which is beneficial first to American and Israeli farmers, and also to hydrologists and environmentalists dealing with production and assessment of contamination hazards of this progressively more precious natural resource. The improved understanding of the way the soil geometrical attributes affect its effective permittivity is expected to contribute to our understanding and predicting capability of other, related soil transport properties such as electrical and thermal conductivity, and diffusion coefficients of solutes and gas molecules. In addition, to the originally planned research activities we also investigated other related problems and made many contributions of short and longer terms benefits. These efforts include: Developing a method and a special TDR probe for using TDR systems to determine also the soil's matric potential; Developing a methodology for utilizing the thermodielectric effect, namely, the variation of the soil's effective permittivity with temperature, to evaluate its specific surface area; Developing a simple method for characterizing particle shape by measuring the repose angle of a granular material avalanching in water; Measurements and characterization of the pore scale, saturation degree - dependent anisotropy factor for electrical and hydraulic conductivities; Studying the dielectric properties of cereal grains towards improved determination of their water content. A reliable evaluation of the soil textural attributes (e.g. the specific surface area mentioned above) and its water content is essential for intensive irrigation and fertilization processes and within extensive precision agriculture management. The findings of the present research project are expected to improve the determination of cereal grain water content by on-line dielectric methods. A precise evaluation of grain water content is essential for pricing and evaluation of drying-before-storage requirements, issues involving energy savings and commercial aspects of major economic importance to the American agriculture. The results and methodologies developed within the above mentioned side studies are expected to be beneficial to also other industrial and environmental practices requiring the water content determination and characterization of granular materials.