Showing papers by "Rensselaer Polytechnic Institute published in 1987"
TL;DR: In this article, the authors present a review of continuous-time random walk theory for diffusion of single particles on lattices with frozen-in disorder, including models with regular transition rates and irregular lattices.
835 citations
TL;DR: The new technique of x-ray microtomography nondestructively generates three-dimensional maps of the x-rays attenuation coefficient inside small samples with approximately 1 percent accuracy and with resolution approaching 1 micrometer.
Abstract: The new technique of x-ray microtomography nondestructively generates three-dimensional maps of the x-ray attenuation coefficient inside small samples with approximately 1 percent accuracy and with resolution approaching 1 micrometer. Spatially resolved elemental maps can be produced with synchrotron x-ray sources by scanning samples at energies just above and below characteristic atomic absorption edges. The system consists of a high-resolution imaging x-ray detector and high-speed algorithms for tomographic image reconstruction. The design and operation of the microtomography device are described, and tomographic images that illustrate its performance with both synchrotron and laboratory x-ray sources are presented.
722 citations
TL;DR: In this article, the authors measured the dihedral wetting angle, θ, resulting from 5-day annealing periods at 950-1150°C and 1 GPa.
595 citations
TL;DR: In this paper, the authors investigated the properties of rutile-saturated melts ranging from basalt to rhyodacite and found that dissolved TiO 2 is positively correlated with T and not strongly dependent on P total.
590 citations
420 citations
TL;DR: In this article, the authors measured important flow quantities such as local void fraction, liquid velocity and the Reynolds stresses using both single-sensor and three-Sensor hot-film anemometer probes, and found that the observed wall peaking and coring phenomena in up and down flows could be predicted by considering the turbulence structure of the continuous phase and lateral lift force acting on the dispersed phase.
399 citations
TL;DR: In this article, the authors calculate the force s-exercant sur a sphere unique en accelation par rapport a un fluide non visqueux soumis a une deformation pure and une rotation loin de the sphere.
357 citations
TL;DR: On montre, en generalisant l'equation d'etat du gaz d'electrons afin d'inclure les effets des gradients de densite, que cette description peut etre etendue pour inclure le comportement quantique observe dans des couches d' inversion forte.
Abstract: The diffusion-drift description of electrons and holes in a semiconductor is frequently used to obtain a detailed understanding of the physics and engineering of semiconductor devices. We show that, by generalizing the equation of state of the electron gas to include density-gradient dependences, this standard description can be extended to describe much of the quantum-mechanical behavior exhibited by strong inversion layers.
316 citations
TL;DR: In this article, the authors report on the early results from a research program that is combining the research on both new products and new ventures, to come up with a more comprehensive evaluation of relative success factors.
311 citations
TL;DR: In this article, the volume fraction distribution of fiber misalignment angle in the range of ±10°, with an estimated resolution of ±0·25°, is presented for carbon fiber composites, which includes both in-plane and out-of-plane misalignments.
287 citations
TL;DR: Visible and near IR reflectance spectra for anhydrous carbonate minerals are presented, and the use of the spectra to determine the mineralogy and gain information for the carbonate mineral is examined.
Abstract: Visible and near IR reflectance spectra for anhydrous carbonate minerals are presented, and the use of the spectra to determine the mineralogy and gaining information for the carbonate minerals is examined. Seven strong absorption bands at wavelengths greater than 1.6 microns are observed in all the spectra of anhydrous end-member carbonate minerals. The band position, intensity, and width for the carbonate bands are studied. The iron and maganese bands for the carbonate minerals are analyzed. The potential causes of spectral differences between carbonate minerals are investigated.
TL;DR: In this paper, the mechanics of transverse cracking in an elastic fibrous composite ply was explored for the case of low crack density, where cracks are assumed to initiate from a nucleus created by localized fiber debo...
Abstract: The mechanics of transverse cracking in an elastic fibrous composite ply is explored for the case of low crack density. Cracks are assumed to initiate from a nucleus created by localized fiber debo...
TL;DR: The algorithmic changes made do ensure the robustness of the approach, but introduce additional algorithmic difficulties, the solutions of which are also presented.
Abstract: A technical description of the algorithms employed in the modified quadtree mesh generator is given. Although the basis of the mesh generator is the same as the original version developed by Yerry and Shephard,1,2 the actual algorithms on which it is built have been entirely changed for the purpose of ensuring the robustness of the technique. As demonstrated in the paper the algorithmic changes made do ensure the robustness of the approach, but introduce additional algorithmic difficulties, the solutions of which are also presented. In addition to examples showing the capability of the mesh generator, the linear computational growth rate of the mesh generator is demonstrated.
TL;DR: In this paper, the alumina-silica phase relations of samples annealed in oxygen and quenched were studied by optical microscopy, image analysis, X-ray diffraction, and the electron microprobe.
Abstract: The alumina-silica phase relations of samples annealed in oxygen and quenched were studied by optical microscopy, image analysis, X-ray diffraction, and the electron microprobe. The solid solution boundaries of mullite changed with increasing temperature and joined at 1890°C and a composition of 77.15 wt% alumina. The melting point of mullite was 189°C with a peritectic between 76.5 and 77.0 wi% alumina.
TL;DR: In this article, a two-site theory is presented that can explain the features of the potential/pH response of both silicon nitride and borosilicate glass ISFETs.
Abstract: Ion-sensitive field-effect transistors (ISFET's) with silicon dioxide, silicon nitride, and borosilicate glass as the active gate material were fabricated and tested for pH-sensing applications. The borosilicate glass and silicon nitride devices were found to have a linear potential/pH response and previous theories of ISFET function were inadequate to explain this. A two-site theory is presented that can explain the features of the potential/pH response of both silicon nitride and borosilicate glass ISFETs. The model is easily extended to any two-site system.
TL;DR: In this paper, the authors focus on theoretical methods for estimating the dynamic response of earth dams to earthquake ground excitation and discuss the major phenomena associated with, and factors influencing, the response.
TL;DR: In this paper, the authors introduce the concept of fault diameter of interconnection networks and derive fault diameter for specific classes of commonly used interconnection network and various types of product graphs.
Abstract: We introduce the concept of fault diameter of interconnection networks. The motivation is to estimate the degradation of performance under maximally fault conditions. We derive fault diameter of specific classes of commonly used interconnection networks and various types of product graphs.
TL;DR: In this article, a dimensionless model for growth of equiaxed dendrites in alloys under small Peclet number conditions is presented, and the behavior of this model is compared with that of Karma and Langer and to experiments of Chopra.
Abstract: A dimensionless model for growth of equiaxed dendrites in alloys under small Peclet number conditions is presented. The behavior of this model is compared with that of Karma and Langer and to experiments of Chopra. Good agreement between both models and with experiments is found. It is shown that the maximum in growth rate,viz., minimum in tip radius with composition, depends strongly on the ratio of heat-to-solute diffusivity and on the solute distribution coefficient.
TL;DR: This hypothesis is consistent with what is known of the α‐crystallin molecule and aggregate, and can be tested experimentally, and if shown to be true, then α‐ Crystallin will be the first example of a naturally occurring protein micelle.
TL;DR: Trace-element zoning has been measured in an amphibolite garnet from the Tauern window, Austria, by using an ion microprobe as discussed by the authors, and the humps correspond to a part of the major element zoning profile that is interpreted as a P-T reversal.
Abstract: Trace-element zoning has been measured in an amphibolite garnet from the Tauern window, Austria, by using an ion microprobe. Humps in the zoning profiles of Na, Sc, V, Y, and the heavy rare-earth elements mark a period of open-system behavior. These humps correspond to a part of the major-element zoning profile that is interpreted as a P-T reversal. The source of the mass excesses of these elements remains ambiguous: they were derived either on a thin-section scale by the breakdown of trace-element-enriched refractory minerals or externally from unusual trace-element-enriched fluids. P-T paths determined from garnet zoning may require modification if open-system behavior is important during garnet growth.
TL;DR: Mesure de microdurete de verre de silice dans divers liquides aqueux ou non L'initiation de la fissure ne depend du temps que dans l'eau L'etude est faite par spectrometrie IR a transformee de Fourier as discussed by the authors.
Abstract: Mesure de la microdurete de verre de silice dans divers liquides aqueux ou non L'initiation de la fissure ne depend du temps que dans l'eau L'etude est faite par spectrometrie IR a transformee de Fourier On separe la microdurete selon deux facteurs: la contribution de la surface et celle du volume
TL;DR: In modeling the anisotropic properties of hydroxyapatite (HAp), Katz found that two kinds of phenomenological relationships held among the elastic stiffness coefficients, which play a significant role in characterizing the elastic anisotropy in bone.
TL;DR: In this paper, the compositional stability of monazite in "granitic" melts ranging from peraluminous to metaluminous compostions was investigated under water-saturated conditions between 850-1000°C, at 8 Kb.
Abstract: A major host for LREE and the heat producing elements Th and U in peraluminous granites is monazite, and the stability of monazite will affect the redistribution of these elements within the crust during anatexis. The compositional stability of monazite in "granitic" melts ranging from peraluminous to metaluminous compostions has been investigated under water-saturated conditions between 850-1000°C, at 8 Kb. Monazite solubility (concentration of LREE's in saturated melts) increases with the values of M > 1.3 [=(2Ca+Na+K)/(AlXSi) in the melt], and is constant for M < 1.3. The temperature dependence of monazite saturation has been determined by Rapp and Watson [1986] for a melt of M = 1.3 and model should be applicable to all peraluminous magmas. Application of the monazite solubility model to crustal anatexis indicates that for fusion temperatures at or below 800°C, anatexis producing peraluminous magmas may lead to an enrichment of monazite in the restitic lower crust depending upon the initial LREE concentration in the source. At temperatures approaching 850°C, enrichment of monazite in the lower crust by anatexis is unlikely due to the high monazite-saturation concentrations.
TL;DR: The decidability of the sufficient completeness property of equational specifications satisfying certain conditions is shown and the related concept of quasi-reducibility of a term with respect to a set of rules is proved.
Abstract: The decidability of the sufficient completeness property of equational specifications satisfying certain conditions is shown. In addition, the decidability of the related concept of quasi-reducibility of a term with respect to a set of rules is proved. Other results about irreducible ground terms of a term rewriting system also follow from a key technical lemma used in these decidability proofs; this technical lemma states that there is a finite bound on the substitutions of ground terms that need to be considered in order to check for a given term, whether the result obtained by any substitution of ground terms into the term is irreducible. These results are first shown for untyped systems and are subsequently extended to typed systems.
TL;DR: In this article, two modeles, tous les deux bases sur la definition de trois regions de transfert thermique, have been proposed, and experimentally evaluated.
Abstract: On propose deux modeles, tous les deux bases sur la definition de trois regions de transfert thermique. Etude experimentale mettant en evidence les effets des differents parametres sur le coefficient de transfert thermique
TL;DR: Data from 166 general hospitals in New York State (1981) is used to estimate a quadratic and logarithmic long-run cost function and Ramsey's RESET test isused to discriminate between the two models and the Quadratic is clearly rejected as a misspecification.
TL;DR: In this article, the elastic-plastic response of metal matrix composites reinforced by aligned continuous fibers can be described in terms of two distinct modes: the matrix-dominated and the fiber-dominated modes.
Abstract: It is shown that elastic-plastic response of metal matrix composites reinforced by aligned continuous fibers can be described in terms of two distinct modes. In the matrix-dominated mode, the composite deforms primarily by plastic slip in the matrix, on planes which are parallel to the fiber axis. In the fiber-dominated mode, both phases deform together in the elastic and plastic range. Constitutive equations are derived for the matrix-dominated mode of deformation in composites with elastic-perfectly plastic matrices. Response in the fiber-dominated mode is approximated by the self-consistent and Voigt models. The two deformation modes give different branches of the overall yield surface which identify the state of stress that activates a particular mode, and indicate the conditions for mode transition in a given composite system. The matrix-dominated mode is found to exist in systems reinforced by fibers of large longitudinal shear stiffness, such as boron or silicon carbide. Systems reinforced by more compliant fibers, such as graphite, appear to deform exclusively in the fiber-dominated mode. The results show good agreement with experimental data, and with predictions obtained from a more accurate material model. They also help to reconcile several different plasticity theories of fibrous composites, and suggest limits of their validity.
TL;DR: In this article, the authors presented an efficient procedure for analyzing naturally curved and twisted beams undergoing large displacements and rotations but small strains. But they did not consider the elastic couplings of composite beams.
Abstract: This paper presents an efficient procedure for analyzing naturally curved and twisted beams undergoing large displacements and rotations but small strains. Special care is taken to accurately model the structural behavior of the beam: shearing deformations as well as torsion-related warping are taken into account. The various elastic couplings (e.g., bending-twisting or extention-twisting) that can arise in composite beams are also modeled in a rational fashion. The equations are derived in curvilinear material coordinates, and Euler angles are used to represent the arbitrarily large rotations. The strain energy in the beam is reduced to a quadratic expression by means of a quasilinearization procedure. This expression of the strain energy is the basis for a finite-element analysis of the structure, and standard iteration techniques are used to obtain nonlinear solutions to the problem. The predictions of this model are found to be in good agreement with the experimental results, and the computational efficiency is greatly improved as compared with other available analyses.
TL;DR: When extrapolated back to the non-accommodated resting state, the data indicate that the lens thickens, both its surfaces become more sharply curved, and the anterior chamber shallows with age in adult greater than 5 years, while opposite trends are seen in younger animals.
TL;DR: It is found that large local variation exist in the manner with which human knee joint cartilage swells, including anisotropic effects, inhomogeneities, and dependence on local biochemical composition and pathological condition.