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710
Dynamic Simulation and Virtual Control of a Deformable Fingertip
 Proceedings of IEEE International Conference on Robotics and Automation
, 1996
"... An efficient computational model for the dynamics of a deformable robot fingertip is presented. The dynamic model is based on a discretization of the fingertip's volume into a lattice of masses locally interconnected by damped springs. The lattice's parameters are adjusted in correspondenc ..."
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An efficient computational model for the dynamics of a deformable robot fingertip is presented. The dynamic model is based on a discretization of the fingertip's volume into a lattice of masses locally interconnected by damped springs. The lattice's parameters are adjusted in correspondence with bulk properties of the fingertip's deformable material (rubber). In the task studied, the fingertip moves toward a rigid flat surface, contacts it, and presses against it. This motion is commanded by an external feedback controller which communicates with the dynamic model through a virtual control interface: The controller applies forces and torques to the dynamic model and the dynamic model responds in realtime with position /velocity/force feedback information. In this fashion, the controller interacts with the fingertip's model in the same way it would interact with the actual physical system. This type of paradigm is envisioned as a prototyping/testing tool in the design of control system...
On Topology, Size and Generalization of Nonlinear FeedForward Neural Networks
 Neurocomputing
, 1997
"... . The use of similarity transforms in the design and the interpretation of feedforward neural networks is proposed. The method is based on the socalled BuckinghamTheorem or PiTheorem and is valid for all neural network function approximation problems which belong to the class of dimensionally h ..."
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. The use of similarity transforms in the design and the interpretation of feedforward neural networks is proposed. The method is based on the socalled BuckinghamTheorem or PiTheorem and is valid for all neural network function approximation problems which belong to the class of dimensionally homogeneous equations. The new design method allows the a priori determination of a minimal topology size of the first and last network layer. Finally, the correct and unique pointwise generalization capability of the new socalled similarity network topology is proved and illustrated using two examples. Keywords: PiTheorem, similarity transforms, similarity functions, dimensional homogeneity, neural network generalization, neural network topology. 1 Introduction The potential of feedforward neural networks to approximate the functional relationship g implicitly encoded in a certain number of p training patterns fx 1 ; : : : ; x n g p has originated much research in the understanding, the...
Composition modulation and nanophase separation in a binary epilayer
, 1999
"... When a thin binary layer grows epitaxially on an elemental substrate, the composition often modulates in the plane of the layer. The layer may even demix when the bulk of the same composition is miscible. Sometimes the layer separates into two phases, forming periodic stripes or other regular patter ..."
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When a thin binary layer grows epitaxially on an elemental substrate, the composition often modulates in the plane of the layer. The layer may even demix when the bulk of the same composition is miscible. Sometimes the layer separates into two phases, forming periodic stripes or other regular patterns. The size of the separated phases may be in the range 1±100 nm, and stable against coarsening on annealing. This paper develops a thermodynamic framework to study these remarkable phenomena. For an epilayer less than a few monolayers thick, the excess energy cannot be attributed to individual sources of super®cial mis®t. Instead, we lump the epilayer and adjacent monolayers of the substrate into a single super®cial object, and specify the excess surface energy for the object. The variation of the surface energy density with the variation of the strain de®nes surface stress. When the composition modulates in the epilayer, the surface stress is nonuniform, deforms the substrate, and reduces the total energy. Consequently, the compositiondependent surface stress tends to re®ne phases, resisting coarsening. In a stability analysis, we perturb a uniform concentration ®eld into a sinusoidal ®eld with a small amplitude and an arbitrary
Numerical Methods for HighDimensional Warps
 in Chapter in Brain Warping
, 1998
"... Introduction The fundamental problem in brain warping is to define the class of admissible spatial transformations, which must be sufficiently broad to enable a reference anatomy to fit all subject anatomies, and to develop efficient, automated algorithms for the calculation of the appropriate tran ..."
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Introduction The fundamental problem in brain warping is to define the class of admissible spatial transformations, which must be sufficiently broad to enable a reference anatomy to fit all subject anatomies, and to develop efficient, automated algorithms for the calculation of the appropriate transformation. In this chapter, we focus on numerical methods for inferring spatial warps that are very high in dimension in order to accommodate the complex ways in which the neuroanatomy of normal individuals can vary. Specifically, the elastic matching technique described in a previous chapter is implemented. The warps therefore correspond to deformations in the continuum mechanics, and we require methods for solving boundaryvalue problems. Two approaches are standard and each involves a different way of discretizing the problem. The finite difference method , which operates directly on the motion equations, is easy to code and computationally fast, but the fi
Thermal stresses in the oceanic lithosphere: Evidence from geoid anomalies at fracture zones
 J. Geophys. Res
, 1986
"... Models for the thermal and mechanical evolution of the oceanic lithosphere predict he progressive development of large thermal stresses in the thickening plate. However, there has so far been little direct evidence for the magnitude and distribution of thermal stresses. We present heoretical models ..."
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Models for the thermal and mechanical evolution of the oceanic lithosphere predict he progressive development of large thermal stresses in the thickening plate. However, there has so far been little direct evidence for the magnitude and distribution of thermal stresses. We present heoretical models which examine the effect of thermal stresses at fracture zones and show that an anomaly of the predicted form can be observed in geoid profiles which cross fracture zones. Specifically, our models predict he development of thermal bending moments which depend on lithosphere thickness or age and therefore change across fracture zones. Including the effect of varying thermal bending moments, thin plate theory predicts vertical, nonisostatic displacements of the lithosphere by plate flexure. The predicted amplitude of the resulting geoid anomaly is large enough to be observed in Seasat altimeter profiles. Furthermore, the general form of this anomaly differs ufficiently from other predicted components ofthe geoid anomaly at fracture zones to be discernable. The anomaly due to thermal stresses has been clearly identified in geoid profiles across the Clarion and the Udintsev fracture zones. The amplitude of this observed anomaly is well predicted if cooling lithosphere begins to accumulate lastic stresses at a temperature of 700øC, consistent with the maximum depth of seismicity in the oceanic lithosphere. The distribution of thermal stresses with depth is also consistent with focal mechanisms of intraplate earthquakes.
Crosssectional Structural Analysis for 3D Printing Optimization
"... We propose a novel crosssectional structural analysis technique that efficiently detects critical stress inside a 3D object. We slice the object into crosssections and compute stress based on bending momentum equilibrium. Unlike traditional approaches based on finite element methods, our method do ..."
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We propose a novel crosssectional structural analysis technique that efficiently detects critical stress inside a 3D object. We slice the object into crosssections and compute stress based on bending momentum equilibrium. Unlike traditional approaches based on finite element methods, our method does not require a volumetric mesh or solution of linear systems, enabling interactive analysis speed. Based on the stress analysis, the orientation of an object is optimized to increase mechanical strength when manufactured with 3D printing.
Analysis of circular torsion bar with circular holes using nullfield approach, Comput Modelling Eng Sci 12
, 2006
"... Abstract: In this paper, we derive the nullfield integral equation for a circular bar weakened by circular cavities with arbitrary radii and positions under torque. To fully capture the circular geometries, separate forms of fundamental solution in the polar coordinate and Fourier series for boun ..."
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Abstract: In this paper, we derive the nullfield integral equation for a circular bar weakened by circular cavities with arbitrary radii and positions under torque. To fully capture the circular geometries, separate forms of fundamental solution in the polar coordinate and Fourier series for boundary densities are adopted. The solution is formulated in a manner of a semianalytical form since error purely attributes to the truncation of Fourier series. Torsion problems are revisited to demonstrate the validity of our method. Torsional rigidities for different number of holes are also discussed.
Hydromechanical modeling of tectonically driven groundwaterflow with application to the Arkoma Foreland Basin
 Journal of Geophysical ResearchSolid Earth
, 1992
"... Deep groundwater flow can be driven by several mechanisms in sedimentary basins. In the case of evolving foreland basins, largescale compression and thrusting could develop abnormally high pressures in the foreland sag that would initiate transient fluid flow. The socalled tectonic "squeegee& ..."
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Deep groundwater flow can be driven by several mechanisms in sedimentary basins. In the case of evolving foreland basins, largescale compression and thrusting could develop abnormally high pressures in the foreland sag that would initiate transient fluid flow. The socalled tectonic "squeegee" effect is thought to have caused basinwide migration of oreforming brines and hydrocarbons (Oliver, 1986). Twodimensional numerical models are developed here to quantify the role of cmnpressional tectonics in driving regional fluid flow in the later stages of thrusting in a foreland basin. Poroelasticity theory coupled with regional groundwater flow form the basic elements of the mathematical model. We use the mathematical model to predict deformation and pressure dissipation in the unfaulted and nonfolded part of a foreland basin in front of a thrust belt as it is subjected to an instantaneous loading event. Sets of numerical experiments show that overpressure zones develop along the leading edge of the thrust belt near the loading front. Stressinduced flow rates of the order of centimeters to meters per year are possible soon after compression of the foreland, and transient flow fields dissipate in about 103 and 10 4 years. Longer transients can exist in very low permeability strata. Large overpressures may be unable to buildup under conditions of gradual thrusting, as fluid pressures may dissipate too quickly. The general features of tectonically driven flow are also explored through a sensitivity study
Split singularities: Stress field near the edge of a silicon die on a polymer substrate.” Acta Materialia 47(1
, 1999
"... AbstractÐIn current design the circuitry is extended very close to the edges of a silicon die to maximize useful surface area. When the die is bonded to a polymer substrate, with the circuitry facing the polymer, thermal mis®t stress concentrates at the die edges and may damage the circuitry. The st ..."
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AbstractÐIn current design the circuitry is extended very close to the edges of a silicon die to maximize useful surface area. When the die is bonded to a polymer substrate, with the circuitry facing the polymer, thermal mis®t stress concentrates at the die edges and may damage the circuitry. The stress distribution near a die edge is quanti®ed using a combination of asymptotic analysis and ®nite element calculation. The asymptotic ®eld consists of two modes of singular stresses, scaling with the distance from the edge r as, respectively, r � 1 and r � 2, where 1> 2. It is shown that the more singular ®eld (i.e. the l1singularity) prevails in an exceedingly small zone, smaller than 10 �6 times the die thickness. Once both modes are included, however, the asymptotic ®eld matches the full ®eld in a zone about 10 �1 times the die thickness. This ®nding resolves several controversies in the literature on electronic packaging. The nearedge stress distribution is presented for various substrate thicknesses, elastic moduli and thermal expansion coe�cients. The results can be used to explore design options. # 1998 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved. 1.
Finite Element Stress Analysis of a Restored Axisymmetric First Molar. J Dent Res 53: 859866. REFERENCES 132
 in Class 11 Prepared and Restored Premolars, J Prosthet Dent 55 184185 GIOVANOLA, J H and FINNIE, I 1984) The Crack Opening Displacement (COD) as a Fracture Parameter and a Comparative Assessment of the COD and Jintegral Concepts, 5M Archiv q 227257 GO
, 1974
"... A first molar with full crown preparation and three marginal configurationschamfer, chisel, and shoulder with a bevelwas analyzed by the finite element method. The maximum, minimum, and shear stresses were plotted as a function of the radius along various horizontal planes. The chamfer geometry ..."
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A first molar with full crown preparation and three marginal configurationschamfer, chisel, and shoulder with a bevelwas analyzed by the finite element method. The maximum, minimum, and shear stresses were plotted as a function of the radius along various horizontal planes. The chamfer geometry exhibited the most uniform stress distribution. Experimental stress analysis of dental structures has been a topic of interest during the past quarter century. The object of such research was the determination of stress distribution and improvement of the mechanical strength of these structures. Most of the stress analysis of dental structures was carried out using the photoelastic technique.18 A more recent method of stress analysis, originally developed in 19569 in the aircraft industry, is the finite element method. This technique has since been in widespread use not only in aerospace engineering, but also in civil engineering. The finite element method has proved to be extremely effective for the treatment of problems of plane stress and plane strain.10,11 The purpose of this study was to examine the distribution of the stresses in a first molar with three marginal configurations using the finite element method. Materials and Methods The concept of the finite element method involves the idealization of the actual conThis investigation was supported by USPHS Re