Showing papers by "Rensselaer Polytechnic Institute published in 1989"
TL;DR: It is shown that readily obtained prior knowledge can be used to obtain good-quality imagery with reduced data and the effect of noise on the reconstruction process is considered.
Abstract: We consider the problem of reconstructing remotely obtained images from image-plane detector arrays. Although the individual detectors may be larger than the blur spot of the imaging optics, high-resolution reconstructions can be obtained by scanning or rotating the image with respect to the detector. As an alternative to matrix inversion or least-squares estimation [Appl. Opt. 26, 3615 (1987)], the method of convex projections is proposed. We show that readily obtained prior knowledge can be used to obtain good-quality imagery with reduced data. The effect of noise on the reconstruction process is considered.
719 citations
14 May 1989
TL;DR: An algorithm for the generation of mechanical assembly sequences and a proof of its correctness and completeness is presented, which uses a relational model which describes the geometry of the assembly and the attachments that bind one part to another.
Abstract: The authors present an algorithm for the generation of mechanical assembly sequences and a proof of its correctness and completeness. The algorithm uses a relational model which describes the geometry of the assembly and the attachments that bind one part to another. The problem of generating the assembly sequences is transformed into the problem of generating disassembly sequences, in which the disassembly tasks are the reverse of feasible assembly tasks. This transformation leads to a decomposition approach in which the problem of disassembling one assembly is decomposed into distinct subproblems, each involving the disassembly of one subassembly. It is assumed that at each assembly task exactly two subassemblies are mated and that all contacts between the parts in the two subassemblies are established. The algorithm yields an AND/OR graph representation of assembly sequences. The correctness of the algorithm is based on the assumption that it is always possible to decide correctly whether two subassemblies can be joined based on geometrical and physical criteria. An approach to compute this decision is given, and bounds for the amount of computation required are presented. >
654 citations
TL;DR: The complete electrode model, which includes the effects of discretization of the current pattern, the shunt effect due to the highly conductive electrode material, and the effect of an effective contact impedance, allows calculation of the voltages due to any current pattern applied to a homogeneous resistivity field.
Abstract: A mathematical model for the physical properties of electrodes suitable for use in electric current computed tomography is discussed. The model includes the effects of discretization, shunt, and contact impedance. The complete model was validated by experiment. Bath resistivities of 284.0, 139.7, 62.3, and 29.5 Omega -cm were studied. Values of effective contact impedance used in the numerical approximations were 58.0, 35.0, 15.0, and 7.5 Omega -cm/sup 2/, respectively. Agreement between the calculated and experimentally measured values was excellent throughout the range of bath conductivities studied. It is desirable in electrical impedance imaging systems to model the observed voltages to the same precision as they are measured in order to be able to make the highest-resolution reconstructions of the internal conductivity that the measurement precision allows. The complete electrode model, which includes the effects of discretization of the current pattern, the shunt effect due to the highly conductive electrode material, and the effect of an effective contact impedance, allows calculation of the voltages due to any current pattern applied to a homogeneous resistivity field. >
591 citations
TL;DR: In this paper, a quantitative petrogenetic grid for pelitic schists in the system KFMASH that includes the phases garnet, chlorite, biotite, chloritoid, cordierite, staurolite, talc, kyanite, andalusite, sillimanite, pyrophyllite (with quartz, H2O and muscovite or K-feldspar in excess) is presented.
Abstract: A quantitative petrogenetic grid for pelitic schists in the system KFMASH that includes the phases garnet, chlorite, biotite, chloritoid, cordierite, staurolite, talc, kyanite, andalusite, sillimanite, and pyrophyllite (with quartz, H2O and muscovite or K-feldspar in excess) is presented. The grid is based on thermodynamic data of Berman et al. (1985) and Berman (1988) for endmember KFASH and KMASH equilibria and natural Fe-Mg partitioning for the KFMASH system. Calculation of P-T slopes and the change in Fe/(Fe+Mg) along reactions in the KFMASH system were made using the Gibbs method. In addition, the effect on the grid of MnO and CaO is evaluated quantitatively. The resulting grid is consistent with typical Buchan and Barrovian parageneses at medium to high grades. At low grades, the grid predicts an extensive stability field for the paragenesis chloritoid+biotite which arises because of the unusual facing of the reaction chloritoid+biotite + quartz+H2O = garnet+chlorite+muscovite, which proceeds to the right with increasing T in the KFMASH system. However, the reaction proceeds to the left with increasing T in the MnKFASH system so the assemblage chloritoid + biotite is restricted to bulk compositions with high Fe/(Fe+Mg+Mn). Typical metapelites will therefore contain garnet+chlorite at low grades rather than chloritoid + biotite.
522 citations
TL;DR: The characteristic length of a heterogeneous brittle material such as concrete represents a material property that governs the minimum possible width of a zone of strain softening damage in nonlocal areas as mentioned in this paper.
Abstract: The characteristic length of a heterogeneous brittle material such as concrete represents a material property that governs the minimum possible width of a zone of strainsoftening damage in nonlocal...
412 citations
TL;DR: In this article, the optical phase conjugation is enhanced from each nonlinear region because the optical field can be concentrated in both the interior and the exterior neighborhoods of the particle and magnified at the surface-mediated plasmon resonance.
Abstract: Calculations of the nonlinear-optical behavior are developed for model composites of nanospheres with a metallic core and nonlinear shell or with a nonlinear core and metallic shell suspended in a nonlinear medium. Optical phase conjugation is shown to be enhanced from each nonlinear region because the optical field can be concentrated in both the interior and the exterior neighborhoods of the particle and magnified at the surface-mediated plasmon resonance. For the model composite with a metallic core, a limited range of resonance tunability can be achieved by adjustment of shell thickness; the frequency range is dependent on the dielectric dispersion of the metal. For the composite with a metallic shell instead of a metallic core, this restriction is reduced so that tunability from ultraviolet to infrared can be attained. Enhancement of the phase-conjugate signal is calculated for the electrostrictive mechanism dominant in the microsecond time scale and for the electronic mechanism dominant in the picosecond time scale. Calculations based on the dielectric functions for gold and for aluminum indicate that phase-conjugate reflectivity enhancements of 108 can be achieved. The imaginary components of the composite dielectric functions are shown to limit the magnitude of the field enhancement at the surface-plasmon resonance and determine the absorption and figure of merit of the composite.
410 citations
TL;DR: In a series of experimental social dilemmas, subjects were instructed to make single, anonymous choices about whether or not to contribute money for a shared "bonus" that would be provided only if enough other people in the group also contributed their money as discussed by the authors.
Abstract: Social dilemmas occur when the pursuit of self-interest by individuals in a group leads to less than optimal collective outcomes for everyone in the group. A critical assumption in the human sciences is that people's choices in such dilemmas are individualistic, selfish, and rational. Hence, cooperation in the support of group welfare will only occur if there are selfish incentives that convert the social dilemma into a nondilemma. In recent years, inclusive fitness theories have lent weight to such traditional views of rational selfishness on Darwinian grounds. To show that cooperation is based on selfish incentives, however, one must provide evidence that people do not cooperate without such incentives. In a series of experimental social dilemmas, subjects were instructed to make single, anonymous choices about whether or not to contribute money for a shared “bonus” that would be provided only if enough other people in the group also contributed their money. Noncontributors cited selfish reasons for their choices; contributors did not. If people are allowed to engage in discussion, they will contribute resources at high rates, frequently on irrational grounds, to promote group welfare. These findings are consistent with previous research on ingroup biasing effects that cannot be explained by “economic man” or “selfish gene” theories. An alternative explanation is that sociality was a primary factor shaping the evolution of Homo sapiens. The cognitive and affective mechanisms underlying such choices evolved under selection pressures on small groups for developing and maintaining group membership and for predicting and controlling the behavior of other group members. This sociality hypothesis organizes previously inexplicable and disparate phenomena in a Darwinian framework and makes novel predictions about human choice.
405 citations
TL;DR: A conceptual framework that links manufacturing to business unit strategy and focuses on developing the notion of ‘generic manufacturing strategies’ at the strategic business unit (SBU) level is provided.
Abstract: This paper provides a conceptual framework that links manufacturing to business unit strategy and focuses on developing the notion of 'generic manufacturing strategies' at the strategic business unit (SBU) level Specifically, an explicit conceptual link is drawn between 'generic' business unit strategies and 'generic' functional structures in manufacturing It is proposed that the alternate manufacturing structures implicitly represent 'generic manufacturing strategies' Drawing on ideas and concepts from the business strategy literature and manufacturing literature the paper links Porter's generic strategy framework to a complementary manufacturing structure framework that uses three dimensions: process structure complexity, product line complexity, and organizational scope Viewed from different perspectives, the 'manufacturing contingency theory' concepts presented implicitly in the paper can be viewed as an extension of classic research on the interdependence between strategy and structure The frameworks developed here provide a partial synthesis of knowledge in the broader disciplines of engineering and management without sacrificing academic rigor and practitioner relevance
371 citations
TL;DR: This paper argues that the authors should think of citations first as rhetoric and second as reward, and some implications for quantitative modeling of the citation process are drawn.
Abstract: Because of the widespread use of citations in evaluation, we tend to think of them primarily as a form of colleague recognition. This interpretation neglects rhetorical factors that shape patterns of citations. After reviewing sociological theories of citation, this paper argues that we should think of citations first as rhetoric and second as reward. Some implications of this view for quantitative modeling of the citation process are drawn.
249 citations
01 Jan 1989
TL;DR: In this paper, an attempt is made to construct a simple model of the evolution of the asteroid belt from the data available about the individual asteroids, showing how it takes into account condensation locations, heating, collisional evolution, and delivery of asteroids to earth.
Abstract: An attempt is made to construct a simple model of the evolution of the asteroid belt from the data available about the individual asteroids. Data on the meaning of taxonomic types, the stratigraphy of the asteroid belt, the compositional meaning of Tholen space, collisional and dynamical history, and asteroid shapes are reviewed. Two main paradoxes concerning asteroids, called the ordinary chondrite mystery and the olivine problems, are briefly described. Finally, the tentative model is presented, showing how it takes into account condensation locations, heating, collisional evolution, and delivery of asteroids to earth.
245 citations
TL;DR: This constellation of findings indicates that the human lens grows throughout adult life while the globe does not, that thickening of the lens completely accounts for shallowing of the anterior chamber with age, but that the posterior surface of the Lens remains fixed in position relative to the cornea and retina.
TL;DR: In this article, a micromechanics model is presented for the prediction of stress fields in coated fiber composites, based on the "average stress in the matrix" concept of Mori and Tanaka and formulated for the case of thermoelastic loading.
TL;DR: Elemental analyses, Mössbauer, and EPR data show that endonuclease III of Escherichia coli is unique in being both a DNA repair enzyme and an iron-sulfur protein.
Abstract: Elemental analyses, Mossbauer, and EPR data are reported to show that endonuclease III of Escherichia coli is an iron-sulfur protein. Mossbauer spectra of protein freshly prepared from E. coli grown on 57Fe-enriched medium demonstrate that the native enzyme contains a single 4Fe-4S cluster in the 2+ oxidation state, with a net spin of zero. Upon treatment with ferricyanide, a fraction (less than 25%) of the clusters is oxidized into a state which yields an EPR spectrum near g = 2.01 typical of a 3Fe-4S cluster. The magnetic field dependence of the linear electric field effect verifies this assignment. Electron spin echo modulation on the g = 2.01 form of the protein in deuterated solvent indicates the presence of exchangeable protons in the vicinity of the 3Fe-4S cluster. The data obtained show that the [4Fe-4S]2+ cluster of the native enzyme is resistant to either oxidation or reduction, although photoreduction elicited a g = 1.94 type EPR signal characteristic of a [4Fe-4S]1+ cluster. These studies show that endonuclease III is unique in being both a DNA repair enzyme and an iron-sulfur protein. The function of the 4Fe-4S cluster remains to be established.
TL;DR: The objective of this study is to establish and verify the set of boundary conditions at the interface between a biphasic mixture and a Newtonian or non-Newtonian fluid (synovial fluid) such that a set of well-posed mathematical problems may be formulated to investigate joint lubrication problems.
Abstract: The objective of this study is to establish and verify the set of boundary conditions at the interface between a biphasic mixture (articular cartilage) and a Newtonian or non-Newtonian fluid (synovial fluid) such that a set of well-posed mathematical problems may be formulated to investigate joint lubrication problems. A "pseudo-no-slip" kinematic boundary condition is proposed based upon the principle that the conditions at the interface between mixtures or mixtures and fluids must reduce to those boundary conditions in single phase continuum mechanics. From this proposed kinematic boundary condition, and balances of mass, momentum and energy, the boundary conditions at the interface between a biphasic mixture and a Newtonian or non-Newtonian fluid are mathematically derived. Based upon these general results, the appropriate boundary conditions needed in modeling the cartilage-synovial fluid-cartilage lubrication problem are deduced. For two simple cases where a Newtonian viscous fluid is forced to flow (with imposed Couette or Poiseuille flow conditions) over a porous-permeable biphasic material of relatively low permeability, the well known empirical Taylor slip condition may be derived using matched asymptotic analysis of the boundary layer at the interface.
TL;DR: Spectra of ten additional asteroids, located beyond the outer edge of the main belt, show no discernible absorption features, suggesting that aqueous alteration did not always operate at these heliocentric distances.
Abstract: Absorption features having depths up to 5% are identified in high-quality, high-resolution reflectance spectra of 16 dark asteroids in the main belt and in the Cybele and Hilda groups. Analogs among the CM2 carbonaceous chondrite meteorites exist for some of these asteroids, suggesting that these absorptions are due to iron oxides in phyllosilicates formed on the asteroidal surfaces by aqueous alteration processes. Spectra of ten additional asteroids, located beyond the outer edge of the main belt, show no discernible absorption features, suggesting that aqueous alteration did not always operate at these heliocentric distances.
TL;DR: Some important theoretical issues associated with the treatment of the spin-3/2 baryons in the effective Lagrangian theory are investigated, including the form of thespin- 3/2 particle propagator, off-shell parameters involving the spins, strategies of implementing gauge invariance, and unitarity, and the experience on theelta..(1232) resonance are invoked.
Abstract: We investigate some important theoretical issues associated with the treatment of the spin-(3/2 baryons in the effective Lagrangian theory. These are the form of the spin-(3/2 particle propagator, off-shell parameters involving the spin-(3/2 field; strategies of implementing gauge invariance, and unitarity. We comment on previous works by Peccei, Nath et al., Williams, and Adelseck et al., the last three works being in the context of recent revival of interest of baryon resonance structure in quantum chromodynamics. Our experience on the \ensuremath{\Delta}(1232) resonance is invoked as a concrete example of dealing with these problems. Examples of some related problems in theories of massive vector and spin-(3/2 particles, in pion decay and supersymmetry, respectively, are also discussed. These discussions should trigger new theoretical and experimental investigations in the study of baryon resonances excited from free hadrons and in complex nuclei.
TL;DR: It is proposed that the conformational changes in the floor of the HRV-14 canyon induced by these compounds substantially decrease adsorption of the virion to its receptor.
Abstract: A series of eight antiviral compounds complexed with human rhinovirus 14 (HRV-14) were previously shown to displace segments of polypeptide chains in the floor of the "canyon" by as much as 0.45 nm in C-alpha positions from the native conformation (J. Badger, I. Minor, M. J. Kremer, M. A. Oliveira, T. J. Smith, J. P. Griffith, D. M. A. Guerin, S. Krishnaswamy, M. Luo, M. G. Rossman, M. A. McKinlay, G. D. Diana, F. J. Dutko, M. Fancher, R. R. Rueckert, and B. A. Heinz, Proc. Natl. Acad. Sci. USA 85:3304-3308, 1988). Because the canyon is thought to serve as the viral receptor-binding site (M. G. Rossmann, E. Arnold, J. W. Erickson, E. A. Frankenberger, J. P. Griffith, H. J. Hecht, J. E. Johnson, G. Kamer, M. Luo, A. G. Mosser, R. R. Rueckert, B. Sherry, and G. Vriend, Nature [London] 317:145-153, 1985; M. G. Rossmann and R. R. Rueckert, Microbiol. Sci. 4:206-214, 1987), these compounds were assessed for their ability to block adsorption of HRV-14 to HeLa cell membrane receptors. In parallel experiments, the compounds were assessed directly for antiviral activity in an in vitro plaque reduction assay in intact HeLa cells. All eight compounds blocked the adsorption of 50% of HRV-14 at approximately the same concentration required to reduce the number of visible plaques by 50% (MIC). A structurally related compound which was inactive in the plaque reduction assay had no effect on HRV-14 binding. A drug-resistant mutant of HRV-14 (Leu-1188), which was less sensitive to the eight compounds in plaque reduction assays was similarly less sensitive in the adsorption assay. We propose that the conformational changes in the floor of the HRV-14 canyon induced by these compounds substantially decrease adsorption of the virion to its receptor. These results provide further evidence for the role of the HRV canyon in receptor binding.
TL;DR: A class of algorithms for the generation of curves and surfaces encompass some well-known methods of subdivision for Bernstein-Bezier curves and B -spline curves and Lane and Riesenfeld's algorithm is proposed.
TL;DR: This work deals with the analytic formulation of the principle of increasing precision with decreasing intelligence; the fundamental principle of hierarchically intelligent control; a three-level structure representing the organization, coordination and execution of such a system.
01 Sep 1989
TL;DR: Four basic PetriNet augmentation methods for error recovery are investigated and it is demonstrated that when these methods are used to augment the Petri net controller, some important properties of the controller are guaranteed to be preserved.
Abstract: The concept of Petri net controllers is extended to include automatic error recovery and adaptive design. In the Petri net controller considered, a place that represents an operation or a state of a machine is attached to two functions and a constant so that it can represent a system working with both normal states and abnormal states. In addition, it is possible to detect an error with the controller using watchdog timers. Four basic Petri net augmentation methods for error recovery are investigated: input conditioning, alternate path, feedback error recovery, and forward error recovery. The authors demonstrate that when these methods are used to augment the Petri net controller, some important properties of the controller are guaranteed to be preserved. These properties include boundedness or safety, liveness, reversibility and the essentially decision-free property. An example of augmentations for error recovery for a piston insertion cell with two robots is given. >
01 Jan 1989
TL;DR: In this article, the spectral interpretive procedures used in the investigations of asteroid mineralogy are described, together with some still unresolved issues such as the source of ordinary chondrites.
Abstract: Information available from reflectance spectroscopy on the surface mineralogy of asteroids is discussed. Current spectral interpretive procedures used in the investigations of asteroid mineralogy are described. Present understanding of the nature and history of asteroids is discussed together with some still unresolved issues such as the source of ordinary chondrites.
TL;DR: This article found that Type As and low self-monitors would report a higher frequency of conflict with others and weaker preferences for cooperative modes of conflict resolution than Type Bs and high self-monitoring.
TL;DR: Several attempts to model both steady one and two phase flows and unsteady flows in membrane filtration are described, including both oscillating flows and flows with centrifugal instabilities.
TL;DR: A quantitative comparison of the fluctuation-induced energy flux with the total energy flux has been made in the edge region of the TEXT tokamak using fluctuation measurements from Langmuir, heavy-ion-beam, and magnetic probes.
Abstract: A quantitative comparison of the fluctuation-induced energy flux with the total energy flux has been made in the edge region of the TEXT tokamak using fluctuation measurements from Langmuir, heavy-ion-beam, and magnetic probes. At all but the lowest densities the convected energy flux due to electrostatic fluctuations dominates the energy losses caused by plasma transport. Energy loss through magnetic fluctuations is insignificant in the edge.
17 Jul 1989
TL;DR: This paper considers projective problems, that is, the polynomials are homogeneous and the solutions are sought in n-dimensional projective space, and shows that the solutions of an affine system are specializations of the solution rays of its homogenized projective version.
Abstract: Finding the solution to a system of n non-linear polynomial equations in n unknowns over a given field, say the algebraic closure of the coefficient field, is a classical and fundamental problem in computational algebra. For algebraic reasons (refer to footnote 1 in van der Waerden (1953, $80)) one considers projective problems, that is, the polynomials are homogeneous and the solutions are sought in n-dimensional projective space. Note also that the solutions of an affine system are specializations of the solution rays of its homogenized projective version. Going back to Cayley and Bezout in the last century, solvability of such a projective system is determined by the vanishing of a certain invariant, its resultant. This invariant generalizes the Sylvester resultant of two polynomials in a single variable (Knuth 1981) and the determinant of the coefficient matrix on a homogeneous linear system. In 1916 Macaulay (1916) showed that the resultant can be expressed by a quotient of two determinants whose corresponding matrices have coefficients of the input polynomials as their entries. These matrices have dimension exponential in the number of variables, but since there is an easy reduction to an
TL;DR: An emerging paradigm, dissipative structure, provides an alternative perspective on transformation by proposing that non-equilibrium conditions provide the opportunity for a new organizational order, resulting in an increased ability to manage complexity.
Abstract: Organizational transformation, qualitative and fundamental changes in an organization, occurs as a result of an organization's adaptive mechanisms being overwhelmed by internally or externally induced contingencies. Current approaches to change derived from equilibrium models are not adequate to describe the transformation phenomena. An emerging paradigm, dissipative structure, provides an alternative perspective on transformation by proposing that non-equilibrium conditions provide the opportunity for a new organizational order, resulting in an increased ability to manage complexity. Conditions, processes, and functioning of organizations from this perspective are discussed.
TL;DR: In this paper, the authors measured the diffusion of water into silica glass in the temperature range of 200° to 750°C by treating the glass in air containing a constant water vapor pressure and analyzing the concentration profile using a Fourier transform infrared spectrometer.
Abstract: Diffusion of water into silica glass was measured in the temperature range of 200{degrees} to 750{degrees}C by treating the glass in air containing a constant water vapor pressure and analyzing the concentration profile using a Fourier transform infrared spectrometer. In the short-time diffusion heat treatments, the surface concentration was lower and the apparent diffusion coefficient was higher than the corresponding steady-state values. The temperature dependence of the steady-state diffusion coefficient showed two different activation energies. Above {approximately}550{degrees}C the diffusion coefficients were similar to the published results with an activation energy of {approximately}80 kJ/mol, while below {approximately}550{degrees}C, the diffusion coefficient was higher than the value obtained by extrapolation from higher temperatures, and the activation energy was {approximately}40kJ/mol. Correspondingly, the water solubility- temperature relation showed a sudden change at around the same temperature: at temperatures above this temperature the solubility increased with decreasing temperature, while at lower temperatures the trend was reversed. It is suggested that this observed peculiarity was caused by the initial nonequilibrium reaction between water and SiO{sub 2} glass and a change in enthalpy of the glass-water reaction.
TL;DR: This paper provides guidance on the choice between change from baseline or percentagechange from baseline as the analysis variable by means of plots of these variables versus baseline.
Abstract: Clinical trials data often include baseline and response measurements on each patient. Comparisons of treatments commonly employ either change from baseline or percentage change from baseline as the analysis variable. This paper provides guidance on the choice between these two by means of plots of these variables versus baseline. I provide two examples that illustrate the problem and I discuss the impact of use of the wrong adjusted response.
TL;DR: The least storage and node computation required by a breadth-first tree or trellis decoder that corrects t errors over the binary symmetric channels is calculated.
Abstract: The least storage and node computation required by a breadth-first tree or trellis decoder that corrects t errors over the binary symmetric channels is calculated. Breadth-first decoders work with code paths of the same length, without backtracking. The Viterbi algorithm is an exhaustive trellis decoder of this type; other schemes look at a subset of the tree or trellis paths. For random tree codes, theorems about the asymptotic number of paths required and their depth are proved. For concrete convolutional codes, the worst case storage for t error sequences is measured. In both cases the optimal decoder storage has the same simple dependence on t. The M algorithm and algorithms proposed by G.J. Foschini (ibid., vol.IT-23, p.605-9, Sept. 1977) and by S.J. Simmons (PhD. diss., Queens Univ., Kingston, Ont., Canada) are optimal, or nearly so; they are all far more efficient than the Viterbi algorithm. >
TL;DR: The behavioral effects of cost and social influence on warning compliance were examined in this paper, where participants in several studies performed a chemistry laboratory task using a set of instructions that contained a warning directing them to wear a safety mask and gloves.
Abstract: The behavioral effects of cost and social influence on warning compliance were examined. Participants in several studies performed a chemistry laboratory task using a set of instructions that contained a warning directing them to wear a safety mask and gloves. Cost was manipulated by locating the masks and gloves in either an accessible location (low cost) or a less accessible location (high cost); social influence was manipulated by the presence of a confederate who either did or did not comply with the warning. The results showed reduced compliance with the warning when the cost was high and that the compliance rate was biased up or down depending on the behavior of the confederate. The results from a field study confirmed the social influence effect. Implications of this research for facilitating warning effectiveness and safety are discussed.