Showing papers on "Deformation (meteorology) published in 2002"
TL;DR: In this paper, a continuum model for acoustic phonons is introduced and electron-phonon interaction due to modification of band structure is derived as well as a normal deformation potential.
Abstract: Electron-phonon scattering is studied within an effective-mass theory. A continuum model for acoustic phonons is introduced and electron-phonon interaction due to modification of band structure is derived as well as a normal deformation potential. In a metallic nanotube, the deformation potential does not participate in electron scattering and a metallic nanotube becomes nearly a one-dimensional ballistic conductor even at room temperature. A resistivity determined by small band-structure interaction depends on the chirality at low temperatures. A magnetic field perpendicular to the axis induces electron scattering by the deformation potential, giving rise to huge positive magnetoresistance.
634 citations
TL;DR: In this paper, the impact of stamp deformation on the dimensional stability of the microcontact printing process is investigated. But the authors consider limitations imposed due to reversible deformation of a single stamp.
Abstract: Stamp deformation can affect the dimensional stability of the microcontact printing process. We consider limitations imposed due to reversible deformation of a single stamp. Detailed analyses of several modes of stamp deformation have been carried out. Stability criteria have been obtained for both vertical and lateral collapse of surface relief features, including buckling. The shape change of surface features imposed by surface tension has been analyzed, and the corresponding internal stresses are given in closed form. The residual stresses induced by chemical and thermal shrinkage when the elastomeric stamp is bonded to a stiff substrate are analyzed. In addition, the relation between applied load and displacement of a stamp supported by a stiff substrate is given in closed form. Contact stresses between the stamp and substrate have been analyzed both analytically and numerically by a finite element method. The role of adhesion in determining the contact area is clarified. The effect of surface roughne...
433 citations
TL;DR: In this article, the authors investigated the primal cause of widely scattered VT in this regime is not surfactant concentration but initial shape deformation, and the primal role of surfactants is to cause damping of shape oscillation, by which a contaminated bubble behaves as if it were a clean bubble with low initial shape deformations.
407 citations
312 citations
01 Jan 2002
273 citations
TL;DR: A generic methodology for estimating soft tissue deformation which integrates image-derived information with biomechanical models, and applies it to the problem of cardiac deformation estimation is presented, which provides quantitative regional 3-D estimates of heart deformation.
Abstract: The quantitative estimation of regional cardiac deformation from three-dimensional (3-D) image sequences has important clinical implications for the assessment of viability in the heart wall. We present here a generic methodology for estimating soft tissue deformation which integrates image-derived information with biomechanical models, and apply it to the problem of cardiac deformation estimation. The method is image modality independent. The images are segmented interactively and then initial correspondence is established using a shape-tracking approach. A dense motion field is then estimated using a transversely isotropic, linear-elastic model, which accounts for the muscle fiber directions in the left ventricle. The dense motion field is in turn used to calculate the deformation of the heart wall in terms of strain in cardiac specific directions. The strains obtained using this approach in open-chest dogs before and after coronary occlusion, exhibit a high correlation with strains produced in the same animals using implanted markers. Further, they show good agreement with previously published results in the literature. This proposed method provides quantitative regional 3-D estimates of heart deformation.
238 citations
TL;DR: In this article, the deformation of active rock glaciers in the Swiss Alps has been studied using borehole deformation measurements of three sites in the Alps, and it was shown that despite different internal structures, similar phenomena can be observed, and a reduction in volume can be caused by compressive flow due to the presence of air voids within permafrost.
Abstract: In order to understand the mechanical processes that influence the deformation patterns of active rock glaciers, information about local horizontal and vertical deformations as well as knowledge of the internal structure and the temperature distribution is necessary. Results from borehole deformation measurements of three sites in the Swiss Alps show that despite different internal structures, similar phenomena can be observed. In contrast to temperate glaciers, permafrost within rock glaciers has distinct shear zones where horizontal and vertical differential movements are concentrated. In addition, a reduction in volume can be caused by compressive flow due to the presence of air voids within the permafrost. The flow velocity depends on the temperature, the surface and bedrock slopes of the rock glacier, and the composition of the ice-rich frozen ground. Within degrading permafrost, the ice content decreases, the creep velocity increases and the shear zone rises towards the surface, where seasonal temperature changes and the presence of liquid water might also influence deformation. Copyright 2002 John Wiley & Sons, Ltd.
232 citations
TL;DR: In this paper, a B-spline function is used to represent the object deformation field throughout the entire image area, which is an improvement over subset-based image correlation methods by implicitly maintaining position and derivative continuity constraints among subsets up to a specified order.
Abstract: A full-field speckle pattern image correlation method is presented that will determine directly the complete, two-dimensional deformation field during the image correlation process on digital images obtained using computer vision systems. In this work, a B-Spline function is used to represent the object deformation field throughout the entire image area. This is an improvement over subset-based image correlation methods by implicitly maintaining position and derivative continuity constraints among subsets up to a specified order. The control point variables within the B-Spline deformation function are optimized iteratively with the Levenberg-Marquardt method to achieve minimum disparity between the predicted and actual deformed images. Results have shown that the proposed method is computationally efficient, accurate and robust. The general framework of this method can be applied ton-dimensional image correlation systems that solve for multi-dimension vector fields.
212 citations
TL;DR: In this paper, a theoretical framework for the inhomogeneous deformation in metallic glasses is provided, where the free volume concentration is adopted as the order parameter, which is a function of position and time.
Abstract: The present study provides a theoretical framework for the inhomogeneous deformation in metallic glasses. The free volume concentration is adopted as the order parameter, which is a function of position and time. The three processes that can change the local free volume concentration are diffusion, annihilation, and stress-driven creation. The rate functions for free volume generation and plastic flow depend on the underlying microscopic model, but the framework is generally valid for different models. A simple shear problem is solved as an example. A linear stability analysis is performed on the basis of the homogeneous solution. An inhomogeneous solution is obtained with a finite amplitude disturbance to the initial free volume distribution. Numerical simulation shows the development of the inhomogeneous deformation and strain localization.
211 citations
TL;DR: In this article, a finite element analysis for a rotating cantilever beam is presented based on a dynamic modelling method using the stretch deformation instead of the conventional axial deformation, three linear partial differential equations are derived from Hamilton's principle.
198 citations
04 Sep 2002
TL;DR: A study comparing users' ability to match a changing target value using a commercial pressure stylus and the FlexStylus' absolute deformation suggests that deformation may be a useful input method for future work considering stylus augmentation.
Abstract: FlexStylus, a flexible stylus, detects deformation of the barrel as a vector with both a rotational and an absolute value, providing two degrees of freedom with the goal of improving the expressivity of digital art using a stylus device. We outline the construction of the prototype and the principles behind the sensing method, which uses a cluster of four fibre-optic based deformation sensors. We propose interaction techniques using the FlexStylus to improve menu navigation and tool selection. Finally, we describe a study comparing users' ability to match a changing target value using a commercial pressure stylus and the FlexStylus' absolute deformation. When using the FlexStylus, users had a significantly higher accuracy overall. This suggests that deformation may be a useful input method for future work considering stylus augmentation.
TL;DR: In this paper, the superelastic behavior of polycrystalline nano-grained NiTi shape memory alloy microtube under uniaxial tension is studied. And the nominal stress-strain curve of the microtube during supererelastic deformation is recorded.
TL;DR: The ability of a digital image correlation technique to capture the heterogeneous deformation fields appearing during compression of ultra-light open-cell foams support the interpretation that the collapse of light open- cell foams occurs as a phase transition phenomenon.
TL;DR: This work studies the expansion of a dilute ultracold sample of fermions initially trapped in an anisotropic harmonic trap and predicts an inversion of the deformation of the sample, similar to what happens with Bose-Einstein condensates.
Abstract: We study the expansion of a dilute ultracold sample of fermions initially trapped in an anisotropic harmonic trap. The expansion of the cloud provides valuable information about the state of the system and the role of interactions. In particular, the time evolution of the deformation of the expanding cloud behaves quite differently depending on whether the system is in the normal or in the superfluid phase. For the superfluid phase, we predict an inversion of the deformation of the sample, similar to what happens with Bose-Einstein condensates. Vice versa, in the normal phase, the inversion of the aspect ratio is never achieved, if the mean field interaction is attractive and collisions are negligible.
TL;DR: In this paper, the apparent surface stress is defined as the energy dissipated per unit area of a solid surface in a nano-indentation test and a critical indentation depth is introduced.
Abstract: In this paper, we report on a study of the surface effect on nanoindentation and introduce the apparent surface stress that represents the energy dissipated per unit area of a solid surface in a nanoindentation test. The work done by an applied indentation load contains both bulk and surface work. Surface work, which is related to the apparent surface stress and the size and geometry of an indenter tip, is necessary in the deformation of a solid surface. Good agreement is found between theoretical first-order approximations and empirical data on depth-dependent hardness, indicating that the apparent surface stress plays an important role in depth-dependent hardness. In addition, we introduce a critical indentation depth. The surface deformation predominates if the indentation depth is shallower than the critical depth, while the bulk deformation predominates when the indentation depth is deeper than the critical depth.
TL;DR: In this article, the deformation textures that develop in aluminium during ECAE (without rotation of the billet) have been investigated experimentally and modelled using the FC-Taylor approach, for two different die angles (90 and 120°), by using actual deformation histories measured from scribed marker grids.
TL;DR: In this paper, the deformation behavior of Ti-6Al-4V alloy under hot compression conditions was characterized in the temperature range 850-1000 Â c and strain rate range 0.001 −10 Â s −1.
TL;DR: Cell deformation was associated with deformation, to a lesser degree, of the nucleus and the calculation of a stress-strain relationship for the cell with an estimated Young's modulus value of approx.
TL;DR: In this article, a selection of models built with sand and silicone putties to represent brittle and ductile lithosphere layers, respectively, are used to illustrate the effects of variations in strength profiles on deformation patterns.
Abstract: Abstract 2D deformation experiments on multilayer models of a brittle-ductile lithosphere are reviewed. The experimental method consists of simulating simplified strength profiles which incorporate brittle (frictional) and ductile (viscous) rheologies with gravity forces. A selection of models built with sand and silicone putties to represent brittle and ductile lithosphere layers, respectively, is used to illustrate the effects of variations in strength profiles on deformation patterns. Models of extension first consider lithosphere necking and the development of narrow rifts, with application to continental rifts and passive margins, and, second, lithosphere spreading with application to the development of wide rifts and core complexes. Models of compression compare sandbox-type and brittle-ductile multilayer-type experiments. Results are applied to mountain belt formation and, in particular, to the Pyrenees and the western Alps. Both extensional and compressional experiments demonstrate that the presence/absence of a sub-Moho brittle mantle and the coupling/decoupling between brittle and ductile layers play a dominant role on localized versus distributed deformation, at lithosphere scale.
TL;DR: In this paper, the authors employed a modi!ed and representative unit cell model to study the crush behavior of closed-cell metallic foams with varying spatial density distribution, where the mean through-thickness density variation was assumed to be a function of the casting process of the foam, while the in-plane variation was followed by a statistical probability distribution of the Gaussian type.
TL;DR: This paper presents an example-based method for calculating skeleton-driven body deformations using range scans of a human body in a variety of poses.
Abstract: This paper presents an example-based method for calculating skeleton-driven body deformations. Our example data consists of range scans of a human body in a variety of poses. Using markers captured...
TL;DR: In this paper, high pressure (HP) and ultra high (UHP) metamorphic rocks are exhumed from subduction zones at high rates on the order of plate velocity (cm/year).
Abstract: Abstract High pressure (HP) and ultrahigh (UHP) metamorphic rocks are exhumed from subduction zones at high rates on the order of plate velocity (cm/year). Their structural and microstructural record provides insight into conditions and physical state along the plate interface in subduction zones to depths of >100 km. Amazingly, many identified (U)HP metamorphic rocks appear not to be significantly deformed at (U)HP conditions, despite their history within a high strain rate mega-shearzone. Other (U)HP metamorphic rocks seem to be deformed exclusively by dissolution-precipitation creep. Indications of deformation by dislocation creep are lacking, apart from omphacite in some eclogites. Available flow laws for dislocation creep (extrapolated to low natural strain rates, which is equivalent to no deformation on the time scales of subduction and exhumation, i.e., 1 to 10 Ma) pose an upper bound to the magnitude of stress as a function of temperature along the trajectory followed by the rock. Although the record of exhumed (U)HP metamorphic rocks may only be representative of specific types or evolutionary stages of subduction zones, for such cases it implies: (1) strongly localized deformation; (2) predominance of dissolution-precipitation creep and fluid-assisted granular flow in the shear zones, suggesting Newtonian behaviour; (3) low magnitude of differential stress; which (4) is on the order of the stress drop inferred for earthquakes; and (5) negligible shear heating. These findings are easily reconciled with exhumation by forced flow in a low viscosity subduction channel prior to collision, implying effective decoupling between the plates.
28 Feb 2002-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the Ni-base superalloy GTD-111 is assessed by means of optical, scanning and transmission electron microscopy, and the results showed abnormal variations in tensile properties with increasing temperature.
Abstract: The Ni-base superalloy GTD-111 is widely used in manufacturing of the first stage blades of high power land-based gas turbines. In spite of its important role in increasing the performance of gas turbines, due to high temperature capability, there are little data on the microstructure, deformation mechanisms and mechanical properties of the alloy. The aim of present paper is to determine in details these properties. Microstructural characteristics of the alloy were assessed by means of optical, scanning and transmission electron microscopy. The tensile behaviour of GTD-111 has been studied in the temperature range 25–900 °C. The results showed abnormal variations in tensile properties with increasing temperature. TEM observations confirmed that these behaviours were affected by the γ′ properties and a change in the mechanism of deformation of GTD-111 at high temperatures. From creep test results, Larson–Miller and Monkman–Grant plots were produced which are used for life prediction. It was also observed that several creep deformation mechanisms operate at various combinations of temperature and stress.
TL;DR: It is found that the degree of deformation of individual grains plays a large role in determining the form of this distribution of normal contact forces, P(F), at the bottom boundary of static three-dimensional packings of compressible granular materials.
Abstract: We present an experimental investigation of the probability distribution of normal contact forces, P(F), at the bottom boundary of static three-dimensional packings of compressible granular materials. We find that the degree of deformation of individual grains plays a large role in determining the form of this distribution. For small amounts of deformation we find a small peak in P(F) below the mean force with an exponential tail for forces larger than the mean force. As the degree of deformation is increased the peak at the mean force grows in height and the slope of the exponential tail increases.
TL;DR: In this article, a finite-element software program, Marc/Mentat, was used to develop a coupled thermo-mechanical model of the deformation processes occurring during the hot rolling of planar IN718 rings.
TL;DR: In this article, the authors evaluate the machinability of typical thermoplastic and thermosetting polymers and understand the effect of their viscous properties on surface integrity, chip formation and machining forces.
TL;DR: In this paper, the influence of the degree of compression, at deformation rates of 50, 250 and 500 mm min-1, on the textural parameters in the texture profile analysis (TPA) of cylindrical samples of potato and apple tissues was examined.
Abstract: The influence of the degree of compression, at deformation rates of 50, 250 and 500 mm min–1, on the textural parameters in the texture profile analysis (TPA) of cylindrical samples of potato and apple tissues was examined. The tests were performed at up to eight different deformation levels ranging from 10% to 80%. The values of all the parameters measured in the samples of both tissues were influenced more by the degree of compression than by the deformation rate. Degrees of compression greater than 40% and 20% caused the rupture of potato and apple specimens, respectively. Regression models were fitted to express the variation of cohesiveness and chewiness with deformation rate and degree of compression. In apple and potato tissues, the degree of compression had a quadratic effect on the cohesiveness while the effect of the deformation rate was only linear. Cohesiveness was the most appropriate textural parameter for detecting effects of deformation rate and degree of compression in TPA tests of potato and apple tissues. Recoverable instantaneous springiness offers a high potential to differentiate the structural natures of different tissues.
TL;DR: In this article, constant load triaxial tests are conducted at differential stresses of 1.9-8.5 MPa, confining pressure of 12 MPa and temperature of 263 K in order to determine experimental limits on the proportion of ice in the Martian subsurface.