Showing papers by "SRI International published in 1979"
TL;DR: Many large sequential computers execute operations in a different order than is specified by the program, and a correct execution by each processor does not guarantee the correct execution of the entire program.
Abstract: Many large sequential computers execute operations in a different order than is specified by the program. A correct execution is achieved if the results produced are the same as would be produced by executing the program steps in order. For a multiprocessor computer, such a correct execution by each processor does not guarantee the correct execution of the entire program. Additional conditions are given which do guarantee that a computer correctly executes multiprocess programs.
2,301 citations
TL;DR: The spatio-temporal threshold surface for stabilized vision is constructed, and its properties are displayed in terms of the usual frequency parameters; e.g., at low spatial frequencies, the temporal response becomes nearly independent of spatial frequency, while at low temporal frequency, the spatial response becomes independent of temporal frequency.
Abstract: The stabilized contrast-sensitivity function measured at a constant retinal velocity is tuned to a particular spatial frequency, which is inversely related to the velocity chosen The Fourier transforms of these constant-velocity passbands have the same form as retinal receptive fields of various sizes At low velocities, in the range of the natural drift motions of the eye, the stabilized contrast-sensitivity function matches the normal, unstablized result At higher velocities (corresponding to motions of objects in the environment), this curve maintains the same shape but shifts toward lower spatial frequencies The constant-velocity passband is displaced across the spatio-temporal frequency domain in a manner that is almost symmetric about the constant-velocity plane at v = 2 deg/s Interpolating these diagonal profiles by a suitable analytic expression, we construct the spatio-temporal threshold surface for stabilized vision, and display its properties in terms of the usual frequency parameters; eg, at low spatial frequencies, the temporal response becomes nearly independent of spatial frequency, while at low temporal frequencies, the spatial response becomes independent of temporal frequency
761 citations
TL;DR: In this paper, formal definitions are given for several coherence relations, based on the operations of an inference system; that is, the relations between successive portions of a discourse are characterized in terms of the inferences that can be drawn from each.
751 citations
Book•
01 Jan 1979TL;DR: The dynamics of explosion and its use as mentioned in this paper, the dynamics of exploding objects and their use, and their dynamics of their use in the context of explosion detection and its application in military applications.
Abstract: The dynamics of explosion and its use , The dynamics of explosion and its use , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی
379 citations
TL;DR: In this article, four types of carbon were observed to form on an alumina-supported nickel methanation catalyst on exposure to carbon monoxide at 550 ± 50 K. In order of their reactivity toward hydrogen, the carbon species may be classified as: chemisorbed carbon atoms (α), bulk nickel carbide, amorphous carbon (β), and crystalline elemental carbon.
356 citations
TL;DR: It is shown that for stratospheric measurements below about 25 km, molecular density uncertainties are the dominant source of error for wavelengths shorter than about 1.1 microm during nonvolcanic conditions.
Abstract: A methodology is presented for objective and automated determination of the uncertainty in lidar aerosol measurements. This methodology is based on standard error-propagation procedures, a large data base on atmospheric behavior, and long experience in lidar data processing. Algebraic expressions for probable error are derived as a function of the relevant parameters. The validity of these expressions is then tested by making simulated measurements and analyses in which random errors of appropriate size are injected at proper steps of the measurement and analysis process. An illustrative example is given where the methodology is applied to a new lidar system now being used for airborne measurements of the stratospheric aerosol.
225 citations
TL;DR: The global distribution of fluorocarbon-12 and fluorcarbon-11 is used to establish a relatively fast interhemispheric exchange rate of 1 to 1.2 years and the rapid growth of methyl chloroform causes it to be a potentially significant depleter of stratospheric ozone.
Abstract: The global distribution of fluorocarbon-12 and fluorocarbon-11 is used to establish a relatively fast interhemispheric exchange rate of 1 to 1.2 years. Atmospheric residence times of 65 to 70 years for fluorocarbon-12 and 40 to 45 years for fluorocarbon-l1 best fit the observational data. These residence times rule out the possibility of any significant missing sinks that may prevent these fluorocarbons from entering the stratosphere. Atmospheric measurements of methyl chloroform support an 8-to 10-year residence time and suggest global average hydroxyl radical (HO) concentrations of 3 x 10 5 to 4 x 10 5 molecules per cubic centimeter. These are a factor of 5 lower than predicted by models. Additionally, methyl chloroform global distribution supports Southern Hemispheric HO levels that are a factor of 1.5 or more larger than the Northern Hemispheric values. The long residence time and the rapid growth of methyl chloroform cause it to be a potentially significant depleter of stratospheric ozone. The oceanic sink for atmospheric carbon tetrachloride is about half as important as the stratospheric sink. A major source of methyl chloride (3 x 10 12 grams per year), sufficient to account for nearly all the atmospheric methyl chloride, has been identified in the ocean.
211 citations
TL;DR: In this article, the authors report the calculation and experimental observation of a manifestation of the former, the threefold reduction of the Na √ n ϵ$ radiative lifetimes by 300-K blackbody-radiation-induced stimulated emission and absorption.
Abstract: Blackbody radiation affects low-frequency (${h}_{\ensuremath{
u}}\ensuremath{\ll}\mathrm{kT}$) atomic transitions both by inducing transitions and producing ac frequency shifts, important effects that have previously been ignored. Here we report the calculation and experimental observation of a manifestation of the former, the threefold reduction of the Na $\mathrm{np}$ radiative lifetimes by 300-K blackbody-radiation-induced stimulated emission and absorption. Estimates of ac frequency shifts for Rydberg and ground-state atoms are given.
196 citations
TL;DR: A practical procedure is presented for an extension of quantifier-free Presburger arithmetic that permits arbitrary unmterpreted predicate and function symbols and is powerful enough to encode the semantics of array operators as well as MAX, MIN, and ABSVALUE.
Abstract: A practical procedure is presented for an extension of quantifier-free Presburger arithmetic that permits arbitrary unmterpreted predicate and function symbols This theory includes many of the formulas one tends to encounter in program venficatlon and is powerful enough to encode the semantics of array operators as well as MAX, MIN, and ABSVALUE An implementation of the procedure has proved to be of great value in a program verlficauon system developed at SRI for the United States Air Force
194 citations
TL;DR: Under optimum conditions, image stabilization elevates the subject's contrast threshold by a factor of about 20; it also produces after-images with resolution greater than 12 c/deg; these results compare favorably with those obtained by other methods.
Abstract: To demonstrate that eye movements have profound effects on the sine-wave contrast threshold, the author uses a new method of stabilizing the retinal image, in which the Purkinje reflections from the eye move the stimulus pattern displayed on a CRT screen. Calibration of this compensatory motion is very critical; a gain error greater than 1% may produce significant destabilization. Under optimum conditions, image stabilization elevates the subject’s contrast threshold by a factor of about 20; it also produces after-images with resolution greater than 12 c/deg. These results compare favorably with those obtained by other methods.
178 citations
TL;DR: In this paper, the thermal cell (25°C) as a function of the concentration of and temperature are reported, combined with isothermal potentials for the silver-silver chloride electrode at elevated temperatures to calibrate external electrodes as pseudothermodynamic standards for the investigation of electrochemical processes in high temperature aqueous systems.
Abstract: Potentials for the thermal cell (25°C) as a function of the concentration of and temperature are reported. The thermal cell potentials are combined with isothermal potentials for the silver‐silver chloride electrode at elevated temperatures to calibrate external electrodes as pseudothermodynamic standards for the investigation of electrochemical processes in high temperature aqueous systems.
TL;DR: In this article, the authors showed that backscatter from field-aligned irregularities (FAI) is spatially collocated with the upper wall of plasma bubbles, and used the spatial displacement of a field aligned back-scatter region to estimate the upward bubble velocity, which is in better agreement with the bubble velocity predicted by theoretical models using flux-tube-integrated values of electron density and Pedersen conductivity.
01 Apr 1979
TL;DR: Some of the basic principles of ultrasonic propagation in tissue and how those principles impact the design of imaging devices are presented and some new research developments in this rapidly emerging technology are described.
Abstract: Recent advances in electronics and digital processing techniques have significantly improved conventional ultrasonic imaging systems and allowed the development of new and sophisticated scanning methods. As a result, ultrasonic imaging devices have become an important modality for the clinical radiologist, complimenting the images obtained from X-ray and nuclear cameras. A particular advantage of ultrasonic waves is that they are nonionizing, thus presenting less risk to both patient and examiner. This paper presents some of the basic principles of ultrasonic propagation in tissue and how those principles impact the design of imaging devices. The characteristics of both the B- scan and C-scan techniques are described along with a summary of various scan formats that are currently available. Examples of B-scan and C-scan instruments are presented along with their relative advantages, limitations, and current usage;representative images are presented whenever possible. This paper concludes with a description of some new research developments in this rapidly emerging technology.
Proceedings Article•
20 Aug 1979TL;DR: In this paper, planning models developed in artificial intelligence are applied to the kind of planning that must be carried out by participants in a conversation and a planning mechanism is defined, and a short fragment of a free-flowing videotaped conversation is described.
Abstract: In this paper, planning models developed in artificial intelligence are applied to the kind of planning that must be carried out by participants in a conversation. A planning mechanism is defined, and a short fragment of a free-flowing videotaped conversation is described. The bulk of the paper is then devoted to an attempt to understand the conversation in terms of the planning mechanism. This microanalysis suggests ways in which the planning mechanism must be augmented, and reveals several important conversational phenomena that deserve further investigation.
TL;DR: In this article, coal was converted by methanol/KOH systems to a product which was extractable by pyridine fully, and 15-25% of the mixture was enriched in hydrogen relative to the starting coal.
04 Jun 1979
TL;DR: PSOS has been designed according to a set of formal techniques embodying the SRI Hierarchical Development Methodology, which has been described elsewhere, but is only summarized here.
Abstract: PSOS has been designed according to a set of formal techniques embodying the SRI Hierarchical Development Methodology (HDM). HDM has been described elsewhere, 1 – 3 and thus is only summarized here. The influence of HDM on the security of PSOS is also discussed elsewhere. 4 In addition, Linden 5 gives a general discussion of the impact of structured design techniques on the security of operating systems (including capability systems).
TL;DR: A novel, closed-loop drug delivery system was developed where the presence or absence of an external compound controls drug delivery from a bioerodible polymer that accelerated polymer erosion and drug release.
TL;DR: The electrochemical results suggest a correlation between the diminished generation of Superoxide anion by 5-iminodaunorubicin and its observed suppressed cardiotoxicity relative to other anthracyclines.
TL;DR: Preliminary afternoon and predawn ionospheric profiles at 12� south latitude and near the equator have topside plasma scale heights changing to 960 kilometers above an altitucde of 3500 kilometers for the dayside, and about 960 kilomneters at all measured heights above the peak for the nightside.
Abstract: A preliminary profile of the atmosphere of Jupiter in the South Equatorial Belt shows (1) the tropopause occurring at a pressure level of 100 millibars and temperature of about 113 K, (2) a higher warm inversion layer at about the 35-millibar level, and (3) a lower-altitude constant lapse rate matching the adiabatic value of about 2 K/km, with the temperature reaching 150 K at the 600-millibar level. Preliminary afternoon and predawn ionospheric profiles at 12 deg and near the equator, respectively, have topside plasma scale heights of 590 km changing to 960 km above an altitude of 3500 km for the dayside, and about 960 km at all measured heights above the peak for the nightside. The higher value of scale height corresponds to a plasma temperature of 1100 K under the assumption of a plasma of protons and electrons in ambipolar diffusive equilibrium. The peak electron concentration in the upper ionosphere is approximately 200,000/cu cm for the dayside and about a factor of 10 less for the nightside. These peaks occur at altitudes of 1600 and 2300 km, respectively. Continuing analyses are expected to extend and refine these results, and to be used to investigate other regions and phenomena.
TL;DR: In this article, a computer method was developed to analyze digital records of lidar backscatter in a manner that reveals the presence and heights of significant aerosol layers and the depth of the mixed layer.
TL;DR: In this article, an adaptive antenna array can achieve an angular resolution of uncorrelated interference sources substantially greater than the aperture of diffraction limit by using adaptive techniques, where the antenna beam is scanned over the interference source locations and for each scan condition the adaptive processor is allowed to reach its steady state.
Abstract: By using adaptive techniques an antenna array can achieve an angular resolution of uncorrelated interference sources substantially greater than the aperture of diffraction limit. The antenna beam is scanned over the interference source locations, and for each scan condition the adaptive processor is allowed to reach its steady state. It is shown that for realistic ratios of interference strengths to system thermal noise, resolutions in excess of 0.25 times the Rayleigh limit can be achieved.
TL;DR: A new, nonassertional approach to proving multiprocess program correctness is described by proving the correctness of a new algorithm to solve the mutual exclusion problem, an improved version of the bakery algorithm, specified and proved correct without being decomposed into indivisible, atomic operations.
Abstract: A new, nonassertional approach to proving multiprocess program correctness is described by proving the correctness of a new algorithm to solve the mutual exclusion problem. The algorithm is an improved version of the bakery algorithm. It is specified and proved correct without being decomposed into indivisible, atomic operations. This allows two different implementations for a conventional, nondistributed system. Moreover, the approach provides a sufficiently general specification of the algorithm to allow nontrivial implementations for a distributed system as well.
TL;DR: The power of the new methodology to detect differences between drug formulations, when, in fact, such differences exist, is shown to be superior to that of conventional bioavailability tests.
Abstract: A new methodology for comparative bioavailability testing is described in which each drug formulation is compared with a stable isotope-labeled variant of the drug that is consumed orally in solution at the same time the tested formulation is ingested. The methodology is used to determine the comparative bioavailabilities of two commercially available brands of imipramine hydrochloride. The power of the new methodology to detect differences between drug formulations, when, in fact, such differences exist, is shown to be superior to that of conventional bioavailability tests.
10 Oct 1979
TL;DR: A technique that uses the relative positions and orientations of the features to determine the correspondence between features of an object model and features observed in a picture and is a robust, general-purpose way to match structures.
Abstract: A crucial step in the recognition or location of an object in an image is the proper identification of object features. If the features are not uniquely characterized by their local appearances, as is often the case in programmable assembly, the matching technique must base its decisions on the relative structure of the features. In this paper we describe a technique that uses the relative positions and orientations of the features to determine the correspondence between features of an object model and features observed in a picture. A graph is constructed in which maximal cliques (i.e., completely connected subgraphs) represent mutually consistent assignments of model features to observed features. The technique is a robust, general-purpose way to match structures. However, in practical applications its use is restricted to moderately sized graphs because the algorithm that locates maximal cliques is apparently exponential. For tasks that require the analysis of large graphs a few techniques are presented to reformulate them so that smaller graphs are sufficient.© (1979) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
TL;DR: The collisional reaction probabilities of several atmospheric species on bulk sulfuric acid surfaces indicate that heterogeneous processes may be important in tropospheric chemistry.
Abstract: The collisional reaction probabilities of several atmospheric species on bulk sulfuric acid surfaces indicate that heterogeneous processes may be important in tropospheric chemistry.
TL;DR: In this paper, the initial state thermal liquid junction potentials (..delta..T(=T-298.15/sup 0/K) Ag-AgCl/NaCl/AgCl-Ag(T/sup, 0.005 to 0.5 mol/Kg) and for temperatures as high as 548.
Abstract: Potentials for the thermocell (298.15/sup 0/K) Ag-AgCl/NaCl/ AgCl-Ag(T/sup 0/K) have been determined for NaCl concentrations ranging from 0.005 to 0.5 mol/Kg and for temperatures as high as 548.15/sup 0/K. Thermodynamic analysis of the cell has permitted evaluation of the initial state thermal liquid junction potentials (..delta../theta/ /SUB TLJP/ ) over the same range of conditions, and it was found that ..delta../theta/ /SUB TLJP/ increases in an approximately parabolic manner with ..delta..T(=T-298.15/sup 0/K). The entropy of transport function tS /SUB Na/ - tS /SUB C1/ has also been calculated.
TL;DR: New experiments designed to test the origins of the LERG are reported, including regional retinal recordings, Fourier waveform analysis, and spectral sensitivity data, which support the earlier conclusion that the low-amplitude LERG obtained with sinusoidal flicker is dominated by the LRP.
TL;DR: The use of nonlinear optical processes expands the flexibility of excimer systems in the study of a wide range of atomic and molecular phenomena and materials as mentioned in this paper, which has already allowed for the selective excitation of states in the 10 to 20 eV range involving bound state excitation, ionization and molecular dissociation.
Abstract: The use of nonlinear optical processes expands the flexibility of excimer systems in the study of a wide range of atomic and molecular phenomena and materials. These mechanisms have already allowed for the selective excitation of states in the 10 to 20 eV range involving bound state excitation, ionization, and molecular dissociation. Specific examples involving the electronic excitation of H 2 , Kr, and Xe, the production of Xe+for the analysis of the molecular properties of XeF*, and nonlinear photodissociation of N 2 O and OCS are discussed.
TL;DR: The value and limitations of transition state theory (TSTT) are reviewed in detail in this paper, and other examples of TST usefulness are discussed for bimolecular processes in terms of 'complex' vs. 'direct' mechanisms.
Abstract: Value and limitations of transition-state theory (TST) are reviewed. TST analyses of the temperature dependence of the 'direct' reactions CH3 + CH3CHO yields CH4 + CH3CO(1) and O + CH4 yields OH + CH3(2) are presented in detail, and other examples of TST usefulness are recalled. Limitations are discussed for bimolecular processes in terms of 'complex' vs. 'direct' mechanisms. The reaction OH + CO yields CO2 + H is discussed in this context. Limitations for unimolecular processes seem to arise only for simple bond fission processes, and recent advances are noted.
TL;DR: Voyager 2 radio signals were observed essentially continuously during a grazing occultation of the spacecraft by the southern limb of Jupiter, showing a classic atmospheric occultation profile and the effects of turbulence and ionospheric focusing and defocusing.
Abstract: About 22 hours after its closest approach to Jupiter, Voyager 2 passed behind the planet as viewed from the earth. Although the spacecraft was geometrically occulted for nearly two hours, the radio links between it and the earth were maintained almost continuously because of the refraction of the signals in Jupiter's south polar atmosphere. A figure shows the plane-of-the-sky geometry of this grazing occultation and preliminary data on the intensity of the spacecraft radio signals as received by the tracking station at Goldstone, California. The intensity data indicate a classic atmospheric occultation profile and the effects of turbulence and ionospheric focusing and defocusing. Analysis of the dispersive ionospheric refraction data yields preliminary profiles for the topside ionosphere at 66.7 deg S (entry in the evening) and 50.1 deg S (exit in the morning) that are reversed with respect to corresponding Voyager 1 profiles in terms of plasma concentration at a fixed altitude. Preliminary reduction of the preencounter occultation of Voyager 1 by the Io torus gives an average plasma density of about 1000 e/cu cm.