Showing papers by "Massachusetts Institute of Technology published in 1980"
TL;DR: The theory of edge detection explains several basic psychophysical findings, and the operation of forming oriented zero-crossing segments from the output of centre-surround ∇2G filters acting on the image forms the basis for a physiological model of simple cells.
Abstract: A theory of edge detection is presented. The analysis proceeds in two parts. (1) Intensity changes, which occur in a natural image over a wide range of scales, are detected separately at different scales. An appropriate filter for this purpose at a given scale is found to be the second derivative of a Gaussian, and it is shown that, provided some simple conditions are satisfied, these primary filters need not be orientation-dependent. Thus, intensity changes at a given scale are best detected by finding the zero values of delta 2G(x,y)*I(x,y) for image I, where G(x,y) is a two-dimensional Gaussian distribution and delta 2 is the Laplacian. The intensity changes thus discovered in each of the channels are then represented by oriented primitives called zero-crossing segments, and evidence is given that this representation is complete. (2) Intensity changes in images arise from surface discontinuities or from reflectance or illumination boundaries, and these all have the property that they are spatially. Because of this, the zero-crossing segments from the different channels are not independent, and rules are deduced for combining them into a description of the image. This description is called the raw primal sketch. The theory explains several basic psychophysical findings, and the operation of forming oriented zero-crossing segments from the output of centre-surround delta 2G filters acting on the image forms the basis for a physiological model of simple cells (see Marr & Ullman 1979).
6,893 citations
Book•
01 Jan 1980TL;DR: Hornstein this article discusses the Biological Basis of Language Capacities and Language and Unconscious Knowledge Notes Index (LUCI) for language and unconscious knowledge in the context of natural language processing.
Abstract: Foreword by Norbert Hornstein Preface Part I 1 Mind and Body 2 Structures, Capacities, and Conventions 3 Knowledge of Grammar 4 Some Elements of Grammar Part II 5 On the Biological Basis of Language Capacities 6 Language and Unconscious Knowledge Notes Index
2,930 citations
TL;DR: In this article, the detection of NMR spectra of less sensitive nuclei coupled to protons was improved by a 2-dimensional Fourier transform technique involving a double transfer of polarization.
2,449 citations
TL;DR: In this article, three models of equilibrium expected market returns which reflect the dependence of the market return on the interest rate were analyzed and the non-negativity restriction of the expected excess return was explicity included as part of the specification.
2,330 citations
01 Jul 1980
TL;DR: The work described herein involves the user commanding simple shapes about a large-screen graphics display surface, and because voice can be augmented with simultaneous pointing, the free usage of pronouns becomes possible, with a corresponding gain in naturalness and economy of expression.
Abstract: Recent technological advances in connected-speech recognition and position sensing in space have encouraged the notion that voice and gesture inputs at the graphics interface can converge to provide a concerted, natural user modalityThe work described herein involves the user commanding simple shapes about a large-screen graphics display surface Because voice can be augmented with simultaneous pointing, the free usage of pronouns becomes possible, with a corresponding gain in naturalness and economy of expression Conversely, gesture aided by voice gains precision in its power to reference
1,524 citations
TL;DR: This work provides a tutorial introduction to certain numerical computations both in linear algebra and linear systems in the context of bounded arithmetic and the singular value decomposition (SVD).
Abstract: We provide a tutorial introduction to certain numerical computations both in linear algebra and linear systems in the context of bounded arithmetic. The essential characteristics of bounded arithmetic are discussed in an introductory section followed by a review of the fundamental concepts of numerical stability and conditioning. The singular value decomposition (SVD) is then presented along with some related comments on the numerical determination of rank. A variety of applications of the SVD in linear algebra and linear systems is then outlined. A final section discusses some details of the implementation of the SVD on a digital computer. An Appendix is provided which contains a number of useful illustrative example.
1,448 citations
TL;DR: The distinction between representational and computational theories of mind is explored in this article, where it is argued that rational psychologists accept a formality condition on the specification of mental processes; naturalists do not.
Abstract: The paper explores the distinction between two doctrines, both of which inform theory construction in much of modern cognitive psychology: the representational theory of mind and the computational theory of mind. According to the former, propositional attitudes are to be construed as relations that organisms bear to mental representations. According to the latter, mental processes have access only to formal (nonsemantic) properties of the mental representations over which they are defined.The following claims are defended: (1) That the traditional dispute between “rational” and “naturalistic” psychology is plausibly viewed as an argument about the status of the computational theory of mind. Rational psychologists accept a formality condition on the specification of mental processes; naturalists do not. (2) That to accept the formality condition is to endorse a version of methodological solipsism. (3) That the acceptance of some such condition is warranted, at least for that part of psychology which concerns itself with theories of the mental causation of behavior. This is because: (4) such theories require nontransparent taxonomies of mental states; and (5) nontransparent taxonomies individuate mental states without reference to their semantic properties. Equivalently, (6) nontransparent taxonomies respect the way that the organism represents the object of its propositional attitudes to itself, and it is this representation which functions in the causation of behavior.The final section of the paper considers the prospect for a naturalistic psychology: one which defines its generalizations over relations between mental representations and their environmental causes, thus seeking to account for the semantic properties of propositional attitudes. Two related arguments are proposed, both leading to the conclusion that no such research strategy is likely to prove fruitful.
1,156 citations
TL;DR: In this article, the polymer network of a gel undergoes a discrete transition in equilibrium volume with changes in solvent composition or temperature, and the volume collapse is also observed when the p\mathrm{H}$ within the gel is varied.
Abstract: The polymer network of a gel, under certain conditions, undergoes a discrete transition in equilibrium volume with changes in solvent composition or temperature. This Letter demonstrates that ionization of the gel network plays an essential role in the phase transition. The volume collapse is also observed when the $p\mathrm{H}$ within the gel is varied.
1,101 citations
TL;DR: Stratified squamous epithelia of internal organs do not form a typical stratum corneum and do not make the large keratins characteristic of epidermis, implying that they have embarked on an alternate route of terminal keratin synthesis.
1,042 citations
TL;DR: The physiocochemical, biochemical, and mechanical considerations that form the basis for two-stage design of a membrane useful as an experimental wound closure of patients who suffer extensive loss of skin are described.
Abstract: Individuals who suffer extensive loss of skin, commonly in fires, are acutely ill, in danger of succumbing either to massive infection of to severe fluid loss. Patients who survive these early threats must often cope with problems of rehabilitation arising from deep, disfiguring scars and crippling contractures. In this report we describe the physiocochemical, biochemical, and mechanical considerations that form the basis for two-stage design of a membrane useful as an experimental wound closure. Stage I of the design, applicable to short-term acute use, calls for a membrane which displaces efficiently air pockets from a carefully prepared woundbed, free of weak boundary layers, and maintains the moisture flux through the wound at an optimal level. Optimization of the surface energy, modulus of elasticity, energy to fracture and moisture permeability of the membrane are among the essential attributes of Stage I design. Stage 2 of the design, applicable to long-term, chronic use, focuses on a nonantigenic membrane which performs as a biodegradable template for synthesis of neodermal tissue. A survey of candidate materials suggests reasons for selection of a porous, crosslinked collagen-glycosaminoglycan coprecipitate as the chemical basis of an evolving design which was initiated 10 years ago. Over the past several years a set of membranes has been iteratively designed on this basis and has been used to cover satisfactorily large experimental full-thickness skin wounds in guinea pigs. Such membranes have effectively protected these wounds from infection and fluid loss for over 25 days without rejection and without requiring change or other invasive manipulation. When appropriately designed for the purpose, the membranes have also strongly retarded wound contraction and have become replaced by newly synthesized, stable connective tissue. Several rules relating the molecular structure and morphology of these membranes to cellular response of adjacent tissue have also been derived. This report is the first in a series which details the methodology of preparation and the record of performance.
1,035 citations
01 Dec 1980
TL;DR: The extension of classical detection theory to the case of distributed sensors is discussed, based on the theory of statistical hypothesis testing, and theoretical results concerning the form of the optimal decision rule are presented.
Abstract: The extension of classical detection theory, based on the theory of statistical hypothesis testing, to the case of distributed sensors is discussed. The development is based on the formulation of a decentralized or team hypothesis testing problem. Theoretical results concerning the form of the optimal decision rule, examples, application to data fusion, and open problems are presented.
TL;DR: In this paper, a spectral decomposition of a frame of noisy speech is used to attenuate a particular spectral line depending on how much the measured speech plus noise power exceeds an estimate of the background noise.
Abstract: One way of enhancing speech in an additive acoustic noise environment is to perform a spectral decomposition of a frame of noisy speech and to attenuate a particular spectral line depending on how much the measured speech plus noise power exceeds an estimate of the background noise. Using a two-state model for the speech event (speech absent or speech present) and using the maximum likelihood estimator of the magnitude of the speech spectrum results in a new class of suppression curves which permits a tradeoff of noise suppression against speech distortion. The algorithm has been implemented in real time in the time domain, exploiting the structure of the channel vocoder. Extensive testing has shown that the noise can be made imperceptible by proper choice of the suppression factor.
TL;DR: The algorithm has the feature that when it determines a number composite then the result is always true, but when it asserts that a number is prime there is a provably small probability of error.
TL;DR: In this paper, it was shown that all parallel inviscid shear flows of constant density are unstable to a wide class of initial infinitesimal three-dimensional disturbances in the sense that, according to linear theory, the kinetic energy of the disturbance will grow at least as fast as linearly in time.
Abstract: It is shown that all parallel inviscid shear flows of constant density are unstable to a wide class of initial infinitesimal three-dimensional disturbances in the sense that, according to linear theory, the kinetic energy of the disturbance will grow at least as fast as linearly in time This can occur even when the disturbance velocities are bounded, because the streamwise length of the disturbed region grows linearly with time This finding may have implications for the observed tendency of turbulent shear flows to develop a longitudinal streaky structure
TL;DR: In this article, an assessment of flat triangular plate bending elements with displacement degrees-of-freedom at the three comer nodes only is presented, with the purpose of identifying the most effective for thin plate analysis.
Abstract: SUMMARY An assessment of flat triangular plate bending elements with displacement degrees-of-freedom at the three comer nodes only is presented, with the purpose of identifying the most effective for thin plate analysis. Based on a review of currently available elements, specific attention is given to the theoretical and numerical evaluation of three triangular 9 degrees-of-freedom elements; namely, a discrete Kirchhoff theory (DKT) element, a hybrid stress model (HSM) element and a selective reduced integration (SRI) element. New and efficient formulations of these elements are discussed in detail and the results of several example analyses are given. It is concluded that the most efficient and reliable three-node plate bending elements are the DKT and HSM elements.
TL;DR: In this paper, the authors used a two-dimensional model with sediment units of varying thickness, radioactive heat production, and conductivity to calculate the temperature distribution within the sediments.
TL;DR: In this article, the authors defined a bomb as an extratropical surface cyclone whose central pressure fall averages at least 1 mb h−1 for 24 hours, and studied this explosive cyclogenesis in the Northern Hemisphere during the period September 1976-May 1979.
Abstract: By defining a “bomb” as an extratropical surface cyclone whose central pressure fall averages at least 1 mb h−1 for 24 h, we have studied this explosive cyclogenesis in the Northern Hemisphere during the period September 1976–May 1979. This predominantly maritime, cold-season event is usually found ∼400 n mi downstream from a mobile 500 mb trough, within or poleward of the maximum westerlies, and within or ahead of the planetary-scale troughs. A more detailed examination of bombs (using a 12 h development criterion) was performed during the 1978–79 season. A survey of sea surface temperatures (SST's) in and around the cyclone center indicates explosive development occurs over a wide range of SST's, but, preferentially, near the strongest gradients. A quasi-geostrophic diagnosis of a composite incipient bomb indicates instantaneous pressure falls far short of observed rates. A test of current National Meteorological Center models shows these products also fall far short in attempting to capture ob...
TL;DR: An algorithm is described for computing the edit distance between two strings of length n and m, n ⪖ m, which requires O(n · max(1, mlog n) steps whenever the costs of edit operations are integral multiples of a single positive real number and the alphabet for the strings is finite.
TL;DR: High-resolution determinations of crustal properties along the spreading center were made to gain knowledge of the source of new oceanic crust and marine magnetic anomalies, the nature of the axial magma chamber, and the depth of hydrothermal circulation.
Abstract: Hydrothermal vents jetting out water at 380° ± 30°C have been discovered on the axis of the East Pacific Rise. The hottest waters issue from mineralized chimneys and are blackened by sulfide precipitates. These hydrothermal springs are the sites of actively forming massive sulfide mineral deposits. Cooler springs are clear to milky and support exotic benthic communities of giant tube worms, clams, and crabs similar to those found at the Galapagos spreading center. Four prototype geophysical experiments were successfully conducted in and near the vent area: seismic refraction measurements with both source (thumper) and receivers on the sea floor, on-bottom gravity measurements, in situ magnetic gradiometer measurements from the submersible Alvin over a sea-floor magnetic reversal boundary, and an active electrical sounding experiment. These high-resolution determinations of crustal properties along the spreading center were made to gain knowledge of the source of new oceanic crust and marine magnetic anomalies, the nature of the axial magma chamber, and the depth of hydrothermal circulation.
TL;DR: In this paper, a new iteration procedure is introduced to solve the full matrix equations resulting from spectral approximations to nonconstant coefficient boundary-value problems in complex geometries, and the work required to solve these spectral equations exceeds that of solving the lowest-order finite-difference approximation to the same problem by only O(N log N).
TL;DR: In this article, the authors compared laboratory, in situ, and inferred values of permeability, k, of crystalline and argillaceous rocks, and found that in situ k ranged from about 1 μd (10−14 cm2) to 100 md; this is close to the permeability of many sandstones and about 103 times greater than laboratory measurements for intact crystalline rocks.
TL;DR: To determine if water labeled with the stable isotope 18O can yield faster and more accurate results, total body water was measured simultaneously using waterlabeled with both 18O and 2H and the H2(18)O dilutions were measured by mass spectrometry.
TL;DR: In this article, the output of the plant is shown to be bounded by expressing the plant feedback loop as an exponentially stable system with a time-varying gain in the feedback path.
Abstract: The paper presents a proof of stability of model reference adaptive control systems using direct control. The structure of the adaptive system is similar to that considered by Monopoli [1] and Narendra and Valavani [2] but contains an additional feedback term which ensures that the time derivative of the parameter error vector belongs to the L2space. The output of the plant is shown to be bounded by expressing the plant feedback loop as an exponentially stable system with a time-varying gain \dot{\phi}(\cdot)\in L^{2} in the feedback path.
TL;DR: The results suggest a new approach to dynamic time warping for isolated words in which both the reference and test patterns are linearly warped to a fixed length, and then a simplified dynamic time Warping algorithm is used to handle the nonlinear component of the time alignment.
Abstract: The technique of dynamic programming for the time registration of a reference and a test pattern has found widespread use in the area of isolated word recognition. Recently, a number of variations on the basic time warping algorithm have been proposed by Sakoe and Chiba, and Rabiner, Rosenberg, and Levinson. These algorithms all assume that the test input is the time pattern of a feature vector from an isolated word whose endpoints are known (at least approximately). The major differences in the methods are the global path constraints (i.e., the region of possible warping paths), the local continuity constraints on the path, and the distance weighting and normalization used to give the overall minimum distance. The purpose of this investigation is to study the effects of such variations on the performance of different dynamic time warping algorithms for a realistic speech database. The performance measures that were used include: speed of operation, memory requirements, and recognition accuracy. The results show that both axis orientation and relative length of the reference and the test patterns are important factors in recognition accuracy. Our results suggest a new approach to dynamic time warping for isolated words in which both the reference and test patterns are linearly warped to a fixed length, and then a simplified dynamic time warping algorithm is used to handle the nonlinear component of the time alignment. Results with this new algorithm show performance comparable to or better than that of all other dynamic time warping algorithms that were studied.
TL;DR: In this article, the authors determined the frequency dependence of shear-waves in the crust and upper mantle of the Earth using band-pass filtered records of about 900 earthquakes occurring in the central Japan area with focal depths from 0 to 150 km.
TL;DR: In this paper, two general classes of explanations for such non-Ohmic effects are presented: thermal and electronic. But, as discussed in Section 2.1, the use of the terminology electrothermal encompasses predominantly thermal and predominantly electronic processes as well as all intermediate cases, and therefore should not prejudice the casual observer into concluding that both effects are necessarily important.
Abstract: The application of sufficiently high electric fields to any material eventually results in deviations from linearity in the observed current-voltage I(V) characteristic. There are two general classes of explanations for such non-Ohmic effects— thermal and electronic. Thermal effects arise because the electrons accelerated by the field always emit phonons in an attempt to return to equilibrium. Electronic effects are due to changes in the response of the charged carriers to high applied fields. In general, both effects must be considered in any quantitative analysis, and the two can produce a coupled response ofter called “electrothermal.” The use of the terminology electrothermal encompasses predominantly thermal and predominantly electronic processes as well as all intermediate cases, and therefore should not prejudice the casual observer into concluding that both effects are necessarily important. In a discussion of the physical mechanism in a particular sample, the major parameters controlling its operation must be identified and separated out from the less significant features.
TL;DR: An investigation of the single-vehicle, many-to-many, immediate-request dial-a-ride problem is developed, with a Dynamic Programming approach which exhibits a computational effort which is asymptotically lower than the corresponding effort of the classical Dynamic Programming algorithm applied to a Traveling Salesman Problem of the same size.
Abstract: An investigation of the single-vehicle, many-to-many, immediate-request dial-a-ride problem is developed in two parts I and II Part I focuses on the “static” case of the problem In this case, intermediate requests that may appear during the execution of the route are not considered A generalized objective function is examined, the minimization of a weighted combination of the time to service all customers and of the total degree of “dissatisfaction” experienced by them while waiting for service This dissatisfaction is assumed to be a linear function of the waiting and riding times of each customer Vehicle capacity constraints and special priority rules are part of the problem A Dynamic Programming approach is developed The algorithm exhibits a computational effort which, although an exponential function of the size of the problem, is asymptotically lower than the corresponding effort of the classical Dynamic Programming algorithm applied to a Traveling Salesman Problem of the same size Part II extends this approach to solving the equivalent “dynamic” case In this case, new customer requests are automatically eligible for consideration at the time they occur The procedure is an open-ended sequence of updates, each following every new customer request The algorithm optimizes only over known inputs and does not anticipate future customer requests Indefinite deferment of a customer's request is prevented by the priority rules introduced in Part I Examples in both “static” and “dynamic” cases are presented
TL;DR: Collagen--GAG membranes appear to be useful as chemically well-characterized, solid macromolecular probes of biomaterial--tissue interactions.
Abstract: Detailed methodology is described for the reproducible preparation of collagen--glycosaminoglycan (GAG) membranes with known chemical composition. These membranes have been used to cover satisfactorily large experimental full-thickness skin wounds in guinea pigs over the past few years. Such membranes have effectively protected these wounds from infection and fluid loss for over 25 days without rejection and without requiring change or other invasive manipulation. When appropriately designed for the purpose, the membranes have also strongly retarded wound contraction and have become replaced by newly synthesized, stable connective tissue. In our work, purified, fully native collagen from two mammalian sources is precipitated from acid dispersion by addition of chondroitin 6-sulfate. The relative amount of GAG in the coprecipitate varies with the amount of GAG added and with the pH. Since coprecipitated GAG is generally eluted from collagen fibers by physiological fluids, control of the chemical composition of membranes is arrived at by crosslinking the collagen--GAG ionic complex with glutaraldehyde, or, alternately, by use of high-temperature vacuum dehydration. Appropriate use of the crosslinking treatment allows separate study of changes in membrane composition due to elution of GAG by extracellular fluid in animal studies from changes in composition due to enzymatic degradation of the grafted or implanted membrane in these studies. Exhaustive in vitro elution studies extending up to 20 days showed that these crosslinking treatments insolubilize in an apparently permanent manner a fraction of the ionically complexed GAG, although it could not be directly confirmed that glutaraldehyde treatment covalently crosslinks GAG to collagen. By contrast, the available evidence suggests strongly that high-temperature vacuum dehydration leads to formation of chemical bonds between collagen and GAG. Procedures are described for control of insolubilized and "free" GAG in these membranes as well as for control of the molecular weight between crosslinks (Mc). The insolubilized GAG can be controlled in the range 0.5--10 wt. % while "free" GAG can be independently controlled up to at least 25 wt. %; Mc can be controlled in the range 2500--40,000. Studies by infrared spectroscopy have shown that treatment of collagen--GAG membranes by glutaraldehyde or under high-temperature vacuum does not alter the configuration of the collagen triple helix in the membranes. Neither do these treatments modify the native banding pattern of collagen as viewed by electron microscopy. Collagen--GAG membranes appear to be useful as chemically well-characterized, solid macromolecular probes of biomaterial--tissue interactions.