Showing papers by "Rensselaer Polytechnic Institute published in 1982"
TL;DR: Efficient (linear time) algorithms have been developed for the Boolean operations, geometric operations,translation, scaling and rotation, N-dimensional interference detection, and display from any point in space with hidden surfaces removed.
1,185 citations
TL;DR: This paper presents a mathematical framework for discussion of large space structure (LSS) control theory, and current trends in LSS control theory and related topics in general control science are surveyed.
Abstract: This paper presents a mathematical framework for discussion of large space structure (LSS) control theory. Within this framework, current trends in LSS control theory and related topics in general control science are surveyed.
672 citations
TL;DR: In this paper, chemical interaction between molten basalt and felsic minerals of the continental crust (quartz, K-feldspar, and oligoclase) was examined in static and dynamic experiments at 1,200°-1,400° C.
Abstract: Chemical interaction between molten basalt and felsic minerals of the continental crust (quartz, K-feldspar, and oligoclase) was examined in static and dynamic experiments at 1,200°–1,400° C. Under circumstances of continuous stirring at 1,400°, β-quartz dissolves in tholeiite melt at a rate of 3.3×10−6 g/s per cm2 of contact area; at 1,300°, the solution rate is 1.5×10−6 g/cm{cm2}s. The feldspars are molten at the experimental conditions, and interact with contacting basalt melt by diffusion in the liquid state. This is a complex process characterized by rapid initial diffusion of alkalies to establish a distribution between felsic melt and basalt similar to that observed in cases of actual two-liquid equilibrium (both alkalies reach concentrations in the felsic melt 1.5–3 times those in the basalt). Alkali diffusion may be “uphill” or “downhill”, depending on which direction of net flux is required to produce a two-liquid type distribution. Once this distribution is attained, subsequent diffusion of all melt species is slow and apparently limited by the diffusivity of SiO2, which is 10−9-l0−10 cm2/s at 1,200° C. Interdiffusion experiments involving molten basalt and synthetic granite confirm the behavior illustrated by the feldspar/basalt results, and give similar SiO2 diffusivities. The solution rates and interdiffusion data can be used to model basalt contamination processes likely to occur in the continental crust. For the restricted case of solid quartzitic xenoliths, the uptake of SiO2 in a well-mixed basalt magma is quite fast: appreciable SiO2 contamination may occur over exposure times of only days to years. If basalt magma induces local melting of crustal rocks, the assimilation process becomes one of liquid-state interdiffusion. In this case, the varying diffusivities of ions and their differing preferences for silicic relative to basaltic melts can produce marked selective contamination effects. Selective contamination of ascending basaltic magmas is particularly likely in the case of K2O, which may be introduced in substantial amounts even when other elements remain unaffected. The Na2O content of mantle-derived magmas is buffered against contamination by crustal materials, and K2O is buffered against further increases once it reaches a level of 1–1.5 wt.%.
376 citations
TL;DR: Two implicit model reference adaptive control algorithms for multi-input multi-output systems are developed that ensure asymptotic stability of the output error and a bounded error under less restrictive conditions.
Abstract: Two implicit model reference adaptive control algorithms for multi-input multi-output systems are developed These algorithms do not require either satisfaction of the perfect model following conditions or explicit parameter identification The first algorithm ensures asymptotic stability of the output error provided that the output stabilized plant transfer matrix is strictly positive real The second algorithm guarantees a bounded error under less restrictive conditions The algorithms are applied to the lateral axis of an F-8 aircraft
262 citations
TL;DR: The results show very good separability of classes of movements when a learning pattern classification scheme is used, and a superposition principle seems to hold which may provide a means of decomposition of any composite motion to the six basic primitive motions.
Abstract: This paper deals with the statistical analysis and pattern classification of electromyographic signals from the biceps and triceps of a below-the-humerus amputated or paralyzed person. Such signals collected from a simulated amputee are synergistically generated to produce discrete lower arm movements. The purpose of this study is to utilize these signals to control an electrically driven prosthetic or orthotic arm with minimum extra mental effort on the part of the subject. The results show very good separability of classes of movements when a learning pattern classification scheme is used, and a superposition principle seems to hold which may provide a means of decomposition of any composite motion to the six basic primitive motions, e.g., humeral rotation in and out, elbow flexion and extension, and wrist pronation and supination. Since no synergy was detected for the hand movements, different inputs have to be provided for a grip. The method described is not limited by the location of the electrodes. For amputees with shorter stumps, synergistic signals could be obtained from the shoulder muscles. However, the presentation in this paper is limited to bicep-tricep signal classification only.
236 citations
TL;DR: In this paper, the elastic properties of apatite solids were determined from measurements of elastic wave velocities through powders under pressure, and these elastic constants were used to model the elastic behaviour of a two-phase composite material having one phase more rigid than the other by a factor of 2.4.
Abstract: One of the prime motives for studying the elastic properties of the apatites stems from the occurrence of hydroxyapatite, OHAp, in calcified tissue. In this paper the isotropic elastic contents of crystalline apatite solids are determined from measurements of elastic wave velocities through powders under pressure. Once obtained, these elastic constants are used to model the elastic behaviour of a two-phase composite material having one phase more rigid than the other by a factor of 2.4. The results are then used in a general discussion of the probable order of magnitude of the elastic constants of the organic non-crystalline phase in bones and teeth, under the assumption of a two-phase system.
201 citations
TL;DR: Evidence supports the existence of a specific effector lipid binding site on cytochrome P.450scc to which this cholesterol binding site appears to be in direct communication with the hydrophobic phospholipid milieu in which this substrate is dissolved.
Abstract: The flavoprotein NADPH-adrenodoxin reductase and the iron sulfur protein adrenodoxin function as a short electron transport chain which donates electrons one-at-a-time to adrenal cortex mitochondrial cytochromes P-450. The soluble adrenodoxin acts as a mobile one-electron shuttle, forming a complex first with NADPH-reduced adrenodoxin reductase from which it accepts an electron, then dissociating, and finally reassociating with and donating an electron to the membrane-bound cytochrome P-450 (Fig. 9). Dissociation and reassociation with flavoprotein then allows a second cycle of electron transfers. A complex set of factors govern the sequential protein-protein interactions which comprise this adrenodoxin shuttle mechanism; among these factors, reduction of the iron sulfur center by the flavin weakens the adrenodoxinadrenodoxin reductase interaction, thus promoting dissociation of this complex to yield free reduced adrenodoxin. Substrate (cholesterol) binding to cytochrome P-450scc both promotes the binding of the free adrenodoxin to the cytochrome, and alters the oxidation-reduction potential of the heme so as to favor reduction by adrenodoxin. The cholesterol binding site on cytochrome P-450scc appears to be in direct communication with the hydrophobic phospholipid milieu in which this substrate is dissolved. Specific effects of both phospholipid headgroups and fatty acyl side-chains regulate the interaction of cholesterol with its binding side. Cardiolipin is an extremely potent positive effector for cholesterol binding, and evidence supports the existence of a specific effector lipid binding site on cytochrome P.450scc to which this phospho-lipid binds.
190 citations
TL;DR: In this article, a modified Jaumann derivative based on the spin of specific material directions associated with the kinematic hardening is proposed, which eliminates the spurious oscillation. But it does not consider the effect of rotational effects.
Abstract: : Kinematic hardening represents the anisotropic component of strain hardening by a shift of the center of the yield surface in stress space. The current approach in stress analysis at finite deformation includes rotational effects by using the Jaumann derivatives of the shift and stress tensors. This procedure generates the unexpected result that oscillatory shear stress is predicated for monotonically increasing simple shear strain. A theory is proposed which calls for a modified Jaumann derivative based on the spin of specific material directions associated with the kinematic hardening. This eliminates the spurious oscillation. General anisotropic hardening is shown to require a similar approach. (Author)
188 citations
TL;DR: An evaluation is made of a new dense, nonresorbable form of hydroxylapatite for the augmentation of deficient alveolar ridges.
Abstract: An evaluation is made of a new dense, nonresorbable form of hydroxylapatite for the augmentation of deficient alveolar ridges. Surgical and prosthetic data are discussed.
183 citations
TL;DR: Fear, conditioned to apparatus cues associated with electric shock, was measured by recording freezing and the opiate antagonist naltrexone reversed this analgesia, suggesting that the analgesia has an opiate nature.
159 citations
TL;DR: A more realistic camera model which approximates the effects of a lens and an aperture function of an actual camera is extended to allow the generation of synthetic images which have a depth of field and can be focused on an arbitrary plane.
Abstract: This paper extends the traditional pinhole camera projection geometry used in computer graphics to a more realistic camera model which approximates the effects of a lens and an aperture function of an actual camera. This model allows the generation of synthetic images which have a depth of field and can be focused on an arbitrary plane; it also permits selective modeling of certain optical characteristics of a lens. The model can be expanded to include motion blur and special-effect filters. These capabilities provide additional tools for highlighting important areas of a scene and for portraying certain physical characteristics of an object in an image.
TL;DR: In this paper, a high intensity dual beam X-ray system was designed and constructed to make chordal-average void fraction measurements and used to generate probability density functions (PDF) and power spectral density (PSD) functions.
TL;DR: In this article, surface energy considerations can be used to show that a magma body in chemical and thermal equilibrium with its surroundings will tend to disperse by infiltrating the dry grain edges of the host material.
Abstract: Surface-energy considerations can be used to show that a magma body in chemical and thermal equilibrium with its surroundings will tend to disperse by infiltrating the dry grain edges of the host material. This prediction was tested in a series of “melt infiltration” experiments on a simplified basalt-peridotite analog system (forsterite-albite-anorthite). At 1290 °C and 10 kb, a melt of ∼ Fo 23 Ab 38 An 39 composition penetrates the grain edges of poly-crystalline forsterite “rock” at a rate of 1 to 2 mm/day. The infiltration mechanism probably involves chemical solution of forsterite at grain edges and simultaneous precipitation of forsterite crystals within the melt reservoir. The term “chemical sloping” is proposed to describe the operation of this process in nature, and although it may have little influence on the major-element composition of magmas, it may be effective as a zone-refining mechanism. The intergranular “mobility” of magmatic liquid in near-solidus country rock implies that (1) silicate melts may be important metasomatizing fluids under some circumstances in the upper mantle, and (2) small dikes and veins are unstable in hot surroundings and will disperse by infiltrating their wall rocks.
TL;DR: In this paper, the effects of type (m) and rate (p) of heterogeneity of heterogeneity in soil deposits were investigated for vertical and horizontal displacements due to Rayleigh waves.
Abstract: SUMMARY The paper studies certain dynamic characteristics of soil deposits with wave velocities increasing with depth according to (l+pz)'", where m = 1, 2/3, 1/2, 1/4 and 0. Analytical solutions are presented for the fundamental periods, mode shapes and amplification functions due to vertically propagating shear waves and the effects of type (m) and rate (p) of heterogeneity are systematically investigated. Then analyticalnumerical techniques are used to study the attenuation with depth in a deposit of the vertical and horizontal displacements due to travelling of Rayleigh waves. Differences attributed to different heterogeneities are discussed in connection with the machine isolation problem and the steady-state vibration technique for soil exploration. Finally, the dependence on soil heterogeneity of the time-distance response curves, obtained during seismic refraction surveys, is graphically illustrated.
TL;DR: The concept of ethos was introduced by as discussed by the authors, who argued that it is not only his own but also somebody else's, or if not his, the concept of "ethos".
Abstract: (1982). Aristotle's concept of ethos, or if not his somebody else's. Rhetoric Review: Vol. 1, No. 1, pp. 58-63.
TL;DR: In this paper, simple expressions for the equivalent horizontal spring and damping coefficients at the top of an end-bearing pile embedded in a uniform linear soil were developed for a range of Poisson's Ratios of the soil between 0.25 and 0.49.
Abstract: Simple expressions are developed for the equivalent horizontal spring and damping coefficients at the top of an end-bearing pile embedded in a uniform linear soil. Beam on elastic foundation (BEF) and dynamic finite element analyses are used for this purpose. It is demonstrated that, for long end-bearing piles, the top displacement response at high frequencies is independent of the pile length, and the pile behaves identically to a long floating pile in a half-space. A numerical criterion is presented to decide when a pile is long or short. All results are expressed as a function of the pile and soil Young’s Moduli, E\dp and E\ds, and they are valid for a range of Poisson’s Ratios of the soil between 0.25 and 0.49. Finally, expressions are also presented for the soil springs and dashpots required for more complicated BEF analyses of piles in multilayer soils. The results presented in the paper show good agreement with previous studies.
22 Nov 1982
TL;DR: In this article, a new technique for modeling 3D objects that is applicable to recog-nition tasks in advanced automation is described, where objects are represented in terms of canonic 2D models which can be used to determine the identity, location and orientation of an unknown object.
Abstract: This paper describes a new technique for modeling 3D objects that is applicable to recog-nition tasks in advanced automation. Objects are represented in terms of canonic 2D models which can be used to determine the identity, location and orientation of an unknown object. The reduction in dimensionality is achieved by factoring the space of all possible perspective projections of an object into a set of characteristic views, where each such view defines a characteristic-view domain within which all projections are topologically identical and related by a linear transformation. The characteristic views of an object can then be hierarchically structured for efficient classification. The line-junction labelling constraints are used to match a characteristic view to a given unknown-object projection, and determination of the unknown-object projection-to-characteristic view transformation then provides information about the identity as well as the location and orientation of the object.
TL;DR: To formulate recommendations for an efficient robot language of the future, this article reviews and evaluates many of the RLs now in use or under development in industrial or academic environments.
Abstract: Efficient communication with industrial robots is a key factor in the success of contemporary programmable automation, but robot languages-the means of communication-have commonly been developed in an ad hoc manner to meet the needs of a particular robot and application. Thus, we currently have almost as many robot languages as robots. To formulate recommendations for an efficient robot language of the future, this article reviews and evaluates many of the RLs now in use or under development in industrial or academic environments. Table I compares the industrial robots for which the languages were developed, and Table 2 contains background information on the 14 selected languages, * which are identified below.
TL;DR: The diffusivity of dissolved carbonate in sodium aluminosilicate (SiO2, 30% Na2O, 10% Al2O3) and iron-free “basalt” melts was measured by a 14C thin-source tracer technique at conditions of combined high temperature and high pressure, ranging from 800°C to 1350°C and 0.5 to 18 kbar for the simple melt and 1350 to 1500°C at 15 k bar for the haplobasalt melt.
TL;DR: It is shown that for regular graphs of order n the expected value of the total length of a minimum fundamentalcycle set does not exceed O(n2).
Abstract: The following problem is considered: Given an undirected, connected graph G, find a spanning tree in G such that the sum of the lengths of the fundamental cycles (with respect to this tree) is minimum. This problem, besides being interesting in its own right, is useful in a variety of situations It is shown that this problem is NP-complete. A number of polynomial-time, heuristic algorithms which yield "good" suboptimal solutions are presented and their performances are discussed. Finally, it is shown that for regular graphs of order n the expected value of the total length of a minimum fundamentalcycle set does not exceed O(n2).
TL;DR: The effects of the opiate antagonist naloxone (NX) on fluid preference and intake were determined in rats drinking with chronically indwelling gastric fistulas, supporting the idea that NX modifies affective reactivity to palatable solutions, and that NX's antidipsogenic actions are not due to feedback from post- absorptional events.
TL;DR: The crystalline lens of the age 11 human eye has been modelled mathematically, using simplified assumptions about lens curvature, internal organization and elasticity, and it becomes clear that the vitreous body provides an essential support function during the accommodative process.
TL;DR: In this article, a practical model of phase shifter has been described and a simplified real power flow control algorithm by phase shifters is described, which has also been used to solve the problems of overloads in contingency analysis and minimizing line losses in transmission systems.
Abstract: In this paper a practical model of phase shifter has been described. By using this model a symmetrical Y-bus matrix can be preserved in the load flow calculation. On this basis a simplified real power flow control algorithm by phase shifter is described. This model has also been used to solve the problems of overloads in contingency analysis and minimizing line losses in transmission systems.
TL;DR: A model for fluid flow in bone in vitro and a result that suggests that the electromechanical effect in wet (fluid saturated) bone is not due to a piezoelectric effect is presented is presented.
TL;DR: In this paper, the authors investigated the relationship among variables defined by the Fishbein-Ajzen model, situational factors, and energy consumption measures, and concluded that given the complex nature of energy consumption, multiple treatments are probably necessary to increase conservation.
Abstract: Summary One hundred and thirteen students and 506 consumers in a statewide sample participated in two studies which investigated the relationship among variables defined by the Fishbein-Ajzen model, situational factors, and energy consumption measures. Correlational analyses with the student sample indicated that one of the situational variables, knowledge, predicted energy usage relatively accurately. In addition, the standard Fishbein-Ajzen model appeared to be moderately useful in understanding energy consumption. With the statewide sample, similar results were found except that the situational variable of income rather than knowledge was the most potent predictor. A manipulation attempting to alter the information level of the students yielded a change in knowledge, but no change in the Fishbein-Ajzen measures. It was concluded that given the complex nature of energy consumption, multiple treatments are probably necessary to increase conservation.
01 Jan 1982
TL;DR: This note presents a more efficient algorithm for finding the largest element in a circular list of processors when messages can be passed in either direction.
Abstract: This note presents a more efficient algorithm for finding the largest element in a circular list of processors when messages can be passed in either direction. It passes 2N*floor(lg N) + 3N messages in the worst case, compared to Chang and Roberts' N(N + 1)/2 and Hirschberg and Sinclair's 8N + 8*ceiling(N lg N) messages. The technique is a selective elimination of possible processes, which then merely relay future messages between the remaining contenders.
TL;DR: In this paper, a combined theoretical and experimental study of deposition of colloidal particles in packed beds is presented, and it is shown experimentally that the rate of deposition declines rapidly with surface coverage even when the surface forces are favorable for deposition and that this decline is largely due to an excluded-area effect introduced by the surface-borne particles.
TL;DR: In this article, the radial distribution of the volumetric vapour fraction in steady, fully developed turbulent two-phase flow is described for vertical low-quality bubbly flows in a circular pipe.
Abstract: The radial distribution of the volumetric vapour (or void) fraction in steady, fully developed turbulent two-phase flow is described for vertical low-quality bubbly flows in a circular pipe The analysis is based on the phasic equations of conservation of momentum in the axial and radial directions Mixing-length theory is used to model the turbulent stresses in the continuous phase The predicted flow structure shows three distinct regions The ‘outer’ region, that is, the region away from the wall and the centre-line, has a uniform void distribution For upflow, a bubble layer is predicted near the wall, while for downflow, vapour coring is predicted, with a peak in void fraction at the centre-line These predictions are in agreement with observed void profiles
TL;DR: In this article, the effect of soil cross-anistropy on surface displacements and stress distributions in a homogeneous thick soil deposit (halfspace) subjected to axisymmetric parabolic vertical surface loading is analyzed.
Abstract: An analytic investigation is presented on the effect of soil cross-anistropy on surface displacements and stress distributions in a homogeneous thick soil deposit (halfspace) subjected to axisymmetric parabolic vertical surface loading. Rigorous treatment is given to deformational soil anisotropy and particular emphasis is accorded to the sensitivity of calculated stresses and deformations to assumed realistic values of the five independent material constants, under both drained and undrained loading conditions. For a given vertical Young's modulus, it is found that the horizontal Young's modulus, the shear modulus on vertical planes and the Poisson's ratio for horizontal due to vertical strain have a profound effect on all stress and displacement components, especially under undrained conditions. The dependence of normal vertical stresses on material properties and particularly on one of the Poisson's ratios disproves the opposite conclusion of isotropic elasticity.