Showing papers by "SRI International published in 1978"

Design and Testing of a Generalized Reduced Gradient Code for Nonlinear Programming

Abstract: : The purpose of this paper is to describe a Generalized Reduced Gradient (GRG) algorithm for nonlinear programming, its implementation as a FORTRAN program for solving small to medium size problems, and some computational results. Our focus is more on the software implementation of the algorithm than on its mathematical properties. This is in line with the premise that robust, efficient, easy to use NLP software must be written and made accessible if nonlinear programming is to progress, both in theory and in practice.

A Model and an Algorithm for the Dynamic Traffic Assignment Problems

Abstract: A discrete time model is presented for dynamic traffice assignment with a single destination. Congestion is treated explicitly in the flow equations. The model is a nonlinear and nonconvex mathematical programming problem. A piecewise linear version of the model, with additional assumptions on the objective function, can be solved for a global optimum using a one-pass simplex algorithm---branch-and-bound is not required. The piecewise linear program has a staircase structure and can be solved by decomposition techniques or compactification methods for sparse matrices.

Developing a natural language interface to complex data

Abstract: Aspects of an intelligent interface that provides natural language access to a large body of data distributed over a computer network are described. The overall system architecture is presented, showing how a user is buffered from the actual database management systems (DBMSs) by three layers of insulating components. These layers operate in series to convert natural language queries into calls to DBMSs at remote sites. Attention is then focused on the first of the insulating components, the natural language system. A pragmatic approach to language access that has proved useful for building interfaces to databases is described and illustrated by examples. Special language features that increase system usability, such as spelling correction, processing of incomplete inputs, and run-time system personalization, are also discussed. The language system is contrasted with other work in applied natural language processing, and the system's limitations are analyzed.

SIFT: Design and analysis of a fault-tolerant computer for aircraft control

Abstract: SIFT (Software Implemented Fault Tolerance) is an ultrareliable computer for critical aircraft control applications that achieves fault tolerance by the replication of tasks among processing units. The main processing units are off-the-shelf minicomputers, with standard microcomputers serving as the interface to the I/O system. Fault isolation is achieved by using a specially designed redundant bus system to interconnect the proeessing units. Error detection and analysis and system reconfiguration are performed by software. Iterative tasks are redundantly executed, and the results of each iteration are voted upon before being used. Thus, any single failure in a processing unit or bus can be tolerated with triplication of tasks, and subsequent failures can be tolerated after reconfiguration. Independent execution by separate processors means that the processors need only be loosely synchronized, and a novel fault-tolerant synchronization method is described. The SIFT software is highly structured and is formally specified using the SRI-developed SPECIAL language. The correctness of SIFT is to be proved using a hierarchy of formal models. A Markov model is used both to analyze the reliability of the system and to serve as the formal requirement for the SIFT design. Axioms are given to characterize the high-level behavior of the system, from which a correctness statement has been proved. An engineering test version of SIFT is currently being built.

On-the-fly garbage collection: an exercise in cooperation

Abstract: As an example of cooperation between sequential processes with very little mutual interference despite frequent manipulations of a large shared data space, a technique is developed which allows nearly all of the activity needed for garbage detection and collection to be performed by an additional processor operating concurrently with the processor devoted to the computation proper. Exclusion and synchronization constraints have been kept as weak as could be achieved; the severe complexities engendered by doing so are illustrated.

Atomic and Molecular Polarizabilities-A Review of Recent Advances

Abstract: Publisher Summary This chapter focuses on the recent developments in the experimental and theoretical determination of the polarizabilities of simple atoms and molecules. Polarizability values (related to the “quadratic Stark effect”) are accurately known for the noble gas atoms and for hydrogen, in theory, but the remainder of the periodic table has proven much more difficult to deal with, both theoretically and experimentally. The static electric dipole polarizability of the ground-state hydrogen atom is almost exactly 4.5a30, where a0 is the Bohr radius. Across rows of the periodic table, polarizabilities range from hundreds (of a30 units) for the alkali metal atoms generally monotonically down to a few for noble gas atoms. Excited atoms have much larger polarizabilities; recent polarizability measurements for atoms in Rydberg orbits have yielded values on the order of 1010a30. Further research on molecular polarizabilities can help in the determination of polarizability anisotropies whether through state selection or with beams of different temperatures. Supersonic molecular beams are found to have low internal energies, and the internal energy can be controlled somewhat in “seeded” beams.

Optimality Conditions for a Dynamic Traffic Assignment Model

Abstract: We consider a dynamic traffic assignment model formulated as a nonlinear and noneonvex mathematical program. Necessary optimality conditions require equalization of certain marginal costs for all the paths that are being used, and these optimality conditions are shown to be a generalization of the optimality conditions of a conventional static traffic assignment problem. We also examine the behavior of the dynamic model under static demand conditions and show that in this case our model is a generalized version of a standard static model. Our model suggests a promising refinement of the objective function for the static case.

Doubly Excited Autoionizing Rydberg States of Sr

Abstract: We report the observation of doubly excited autoionizing Rydberg states of Sr, belonging to the configuration $5{p}_{\frac{1}{2}}$, $\mathrm{nl}$. Our procedure involves a three-step optical excitation process which incorporates Stark switching to reach higher $l$ states not normally accessible because of dipole selection rules. Quantum defects are reported for several $5{p}_{\frac{1}{2}}$, $\mathrm{ns}$ and $5{p}_{\frac{1}{2}}$, $\mathrm{nd}$ states. The lifetimes of the $5{p}_{\frac{1}{2}}$, $\mathrm{ns}$ states are shown to scale as ${({n}^{*})}^{3}$, and the lifetimes of the $5{p}_{\frac{1}{2}}$, $16l$ states are shown to increase dramatically with increasing $l$.

Application of Bioassay to the Characterization of Diesel Particle Emissions

Abstract: A wide variety of combustion sources produce soot, i.e., carbon aerosols containing variable quantities of organic matter. The most significant transportation-related sources of such materials are diesel engines. Diesel power has been used for railway locomotives, long haul trucks, and earthmoving equipment for many years. However, recently a strong trend has developed toward use of diesel engines in urban service vehicles and also taxicabs. In the near future substantial numbers of diesel-powered automobiles may be used by the general public.

Pituitary-adrenal response to separation in mother and infant squirrel monkeys.

Abstract: Pituitary-adrenal response in mother and infant squirrel monkeys following brief separation was assessed. Each mother and infant pair was tested under each of 3 conditions: (1) Basal; (2) Separation-Reunion; and (3) Separation. Samples were obtained from mothers and infants in the Separation and Separation-Reunion conditions 30 min following the initial disturbance. A similar paradigm was used to assess the effects of separation in surrogate-reared animals. The results indicate that mothers, infants, and surrogate-reared infants respond to 30-min separation with a substantial increase in plasma cortisol. The values obtained in the Separation-Reunion condition did not differ significantly from Basal values in any of the 3 groups, suggesting that the effect of separation on the pituitary-adrenal system is not due to the disturbance involved in the separation procedure. The response of surrogate-reared infants suggests that these infants develop similar attachments to the surrogate as normal infants to their own mothers.

Kinetics of Oxidation of Hot‐Pressed Silicon Nitride Containing Magnesia

Abstract: The oxidation of NC 132 hot-pressed silicon nitride in dry oxygen was studied at 1521 to 1731K. The rate of O2 uptake and N2 release, as a function of time, was measured volumetrically. The ratio of N2 released to O2 consumed was smaller than expected from the stoichiometry of the oxidation reaction for Si3N4. The low value was attributed to impurities in the material. The oxidation rate followed the parabolic law with an activation energy of 440 kJ/mol. The corrosion scales (examined by microsurface techniques) were porous due to bubbles of released N2. The scales consisted of a mixture of unoxidized silicon nitride grains, crystalline oxides (SiO2 and MgSiO3containing other elements), and a glass phase. Reoxidation showed that the oxide scale was not protective. The magnesium profile in the subsurface layers indicated that the diffusion of magnesium in the unoxidized material was the rate-limiting step in the oxidation.

An algorithm for reasoning about equality

Abstract: A simple technique for reasoning about equalities that is fast and complete for ground formulas with function symbols and equality is presented. A proof of correctness is given as well.

The estimation of labor supply models using experimental data

Abstract: For many years there has been interest in replacing the existing complex transfer system in the United States with a nationwide negative income tax (NIT) program.' The feasibility and desirability of an NIT, however, depend on its effects on aggregate labor supply (and its cost). Interest in predicting these aggregate effects has motivated considerable empirical research on labor supply. The first studies used existing data, usually cross-sectional, to estimate the parameters of labor supply functions.2 Unfortunately, the range of estimates in these studies is disturbingly large and of limited usefulness to policymakers.3 Consequently, a new approach to labor supply research has been followed social experimentation.4 Several experiments have been funded by the federal government to test the effects of alternative NIT programs on labor supply. The first experiment, the New Jersey Experiment, was conducted in New Jersey and Pennsylvania from 1968 to 1972.5 Other experiments have taken place in Gary, Indiana from 1970 to 1974, and in rural areas of Iowa and North Carolina from 1969 to 1973. The largest and most comprehensive of these experiments began in 1971 in Seattle, Washington and Denver, Colorado and is still taking place. In principle, a controlled experiment affords the opportunity to overcome most of the problems inherent in nonexperimental research, because in an experiment, the budget constraints of individuals are exogenously shifted in a measurable way. In practice, however, the experiments have been beset with their own unique set of econometric problems. These problems include the nonrandom assignment of experimental treatment, small samples, truncation of response, limited duration, participation in other welfare programs both before and during the experiment by sample members, and the selection of nonrepresentative samples.6 In this paper, a methodology is presented that attempts to deal with these problems. Experimental data from the Seattle and *Economists, SRI International. The research reported in this paper was performed under contracts with the states of Washington and Colorado, prime contractors for the Department of Health, Education, and Welfare, under contract numbers SRS-70-53 and SRS-71-18, respectively. The opinions expressed in the paper are our own and should not be construed as representing the opinions or policies of the states of Washington or Colorado, or any agency of the U.S. government. An earlier version of this paper was presented at the Summer 1976 meetings of the Econometric Society and in seminars at the National Bureau of Economic Research and Mathematica Policy Research. Jodie Allen, Yoram Barzel, David Betson, Michael Boskin, Glen Cain, Joseph Corbett, Irwin Garfinkel, David Greenberg, Terry Johnson, Richard Kaluzny, Richard Kasten, Robert Lerman, Stanley Masters, Myles Maxfield, Robert Moffit, Larry Orr, Harold Watts, and Robert Willis provided valuable comments on various drafts of this paper. We are, of course, solely responsible for the views presented and for any remaining errors. Helen Cohn, Diane Hollenbeck, Paul McElherne, Gary Stieger, and Steven Spickard provided expert programming assistance. I Milton Friedman is usually credited with developing the concept of a negative income tax. Robert Lampman and James Tobin (1965) among others also made early contributions to the concept. 2An excellent collection of such studies is presented in Glen Cain and Harold Watts. 3See Keeley for a survey of these studies and a discussion of some of the econometric difficulties that lead to such a wide range of estimates. 4Heather Ross (1966) is credited with first conceiving the idea of an NIT experiment. Guy Orcutt and Alice Orcutt (1968) first published a paper outlining an experimental design. 5The New Jersey Experiment is described in David Kershaw and Jerilyn Fair. Watts and Albert Rees (1977a, b) and Joseph Pechman and P. Michael Timpane present the results from this experiment. 6See Henry Aaron, Keeley, and Keeley and Robins for a critical discussion of many of these problems.

Opposing effects of tumor promoters on erythroid differentiation.

Abstract: TUMOUR promoters are compounds which are not carcinogens but which can induce tumours in mice treated with a subcarcinogenic dose of a chemical carcinogen1,2. The mechanism of action of tumour promoters in vivo is unknown, although recent reports suggest that they may inhibit terminal differentiation of certain cells in vitro. Myogenesis of chick embryo myoblasts3, spontaneous and induced erythroid differentiation of Friend virus-transformed proerythroid cells4,5 and lipogenesis in a clone of BALB/c 3T3 preadipocyte cells are examples of in vitro differentiation processes inhibited by tumour promoters. Unfortunately, inhibition of differentiation by tumour promoters has not yet been shown to occur in vivo. It is also uncertain whether the cells used in the above studies are representative of the actual target cells for tumour promoters in vivo. We report here that tumour promoters can induce as well as inhibit differentiation of virus-transformed proerythroid cells in vitro. Detection of the opposing effects depends on measuring tumour promoter action in more than one virus-transformed proerythroid cell line.

Application of RRKM theory to the reactions OH + NO2 + N2 → HONO2 + N2 (1) and ClO + NO2 + N2 → ClONO2 + N2 (2); a modified gorin model transition state

Abstract: Rate constants as a function of both temperature and pressure were calculated for the title reactions using RRKM theory in conjunction with a modified Gorin transition state. The modification introduces a hindrance parameter which accounts for repulsive interactions between the rotating fragments. At the highest stratospheric pressures (∼50 torr) and at stratospheric temperature (∼220°K), the extent of “falloff” from first-order [N2] dependence is ∼70% for reaction (1) and ∼35% for reaction (2).

Charge-state dependence of electron loss from h by collisions with heavy, highly stripped ions

Abstract: Theoretical calculations, confirmed by experimental measurements, are used to obtain a new scaling for electron loss from a hydrogen atom in collision with a heavy, highly stripped ion. The calculations cover the energy range 50 to 5000 keV/amu and charge states q from 1 to 50. The experiments are in the range 108 to 1140 keV/amu and charge states 3 to 22. A simple analytic expression that describes the electron-loss cross section for 1 < or = q < or = 50 in the energy range 50 to 5000 keV/amu is presented.

Maternal discrimination of infant vocalizations in squirrel monkeys

Abstract: Responses of mother squirrel monkeys to vocalizations of their own and other infants were examined to determine whether mothers could discriminate their infants on the basis of auditory cues. Thirty mothers, whose infants ranged in age from one to seven months were tested in three conditions in which their own infant, a different infant, and no infant served as the stimulus. Mothers were tested in an enclosed alleyway with opaque end panels behind which stimuli were placed. The quantity and quality of maternal responses clearly differed in the three conditions and indicated that mothers recognized their own infants. Differences in maternal vocalizations were the most pronounced. All but one type of vocalization increased in the own-infant condition; the exception, a high-pitched shrill, decreased. Mothers also spent more time near the stimulus and were more active when tested with their own infants.

Three-dimensional visual stimulus deflector

Abstract: A 3-D visual stimulus deflector has been designed so that a subject can view any stimulus pattern or object through it, and the pattern (up to 25° in diameter) can be moved over a range of 40° horizontally and 30° vertically. The optical distance of the object being viewed can be changed over a 15-diopter range, while the brightness and visual angle subtended by the object remain fixed. Further, the observer can view the object through a pupil of any desired shape and transmittance. Horizontal and vertical movements are independent, with time delays of 1 msec and a response range from dc to 200 Hz. Focus change is independent of lateral field motion and has a time delay of 12 msec and a maximum slewing rate of approximately 40 diopters/sec. Two such devices can be aligned side by side in a binocular configuration for independent 3-D control of the fixation of each eye.

Interactions of Δ9-tetrahydrocannabinol with d-Amphetamine, cocaine, and nicotine in rats ☆ ☆☆

Abstract: The acute, reciprocal dose-response interactions between Δ9-tetrahydrocannabinol (Δ9 - THC; 2.5, 5.0 and 10.0 mg/kg; IG) and each of three stimulants - d-amphetamine (dA; 1, 2 and 4 mg/kg; IP), cocaine (COC; 10, 20 and 30 mg/kg; IP), and nicotine (NIC; 0.25, 0.5 and 1.0 mg/kg; IP) were studied for their effects on performance of a conditioned avoidance response (CAR), photocell activity, heart rate, body temperature, and rotarod performance. Δ9 - THC impaired CAR and rotarod performance, depressed photocell activity, and decreased heart rate and body temperature. None of the three stimulants influenced CAR performance, but dA and COC increased the number of intertrial responses, and this latter effect was partially antagonized by Δ9 - THC. dA and COC, but not NIC, stimulated photocell activity. Δ9-THC completely blocked this effect of dA, whereas there was mutual antagonism between Δ9 - THC and COC on this measure and NIC markedly potentiated the depression caused by Δ9 - THC. dA and COC tended to offset the impairment of rotarod performance caused by Δ9 - THC, whereas NIC augmented it. The bradycardia and hypothermia caused by Δ9 - THC tended to be augmented by these stimulants, especially NIC. The interactions were also studied after subacute treatment for six days with Δ9 - THC and/or each of the three stimulants. There was evidence for tolerance to the effects of Δ9-THC on all measures and this tolerance generally resulted in less interactive effects between Δ9 - THC and the stimulants. Little or no tolerance was seen for the effects of the three stimulants of their interaction with Δ9 - THC. The time course of radioactivity derived from 14C-Δ9-THC and each of the radiolabelled stimulants was determined in plasma and brain. Only minor interactive effects were found and, in general, they could not account for the functional interactions.

Is “sometime” sometimes better than “always”?: intermittent assertions in proving program correctness

Abstract: This paper explores a technique for proving the correctness and termination of programs simultaneously. This approach, the intermittent-assertion method, involves documenting the program with assertions that must be true at some time when control passes through the corresponding point, but that need not be true every time. The method, introduced by Burstall, promises to provide a valuable complement to the more conventional methods.The intermittent-assertion method is presented with a number of examples of correctness and termination proofs. Some of these proofs are markedly simpler than their conventional counterparts. On the other hand, it is shown that a proof of correctness or termination by any of the conventional techniques can be rephrased directly as a proof using intermittent assertions. Finally, it is shown how the intermittent-assertion method can be applied to prove the validity of program transformations and the correctness of continuously operating programs.

Evaluation of a Fundamental Approach for the Statistical Analysis of Fracture

Abstract: Generalized relations between the strength distribution function and derivatives of the fracture probability are developed for five widely used testing methods for measuring the strengths of ceramic materials. The derived relations for three of these methods are used to analyze room-temperature fracture strength data for hot-pressed silicon nitride. Fracture of this material is shown to be controlled by internal flaws at strength levels up to and including the range where the tensile and flexural distributions overlap, but it is primarily surface-flaw-controlled toward the upper end of the flexural distribution.

Theory of flicker and transient responses. III. An essential nonlinearity

Abstract: From our stead-state flicker data, Kelly's (1971) model correctly predicts the transient thresholds for rectangular pulses of variable duration when the (flickering or flashed) stimulus is a 4 cycle/deg grating, but the same prediction fails for a uniform (8 degrees) field. However, if we augment the model with a "hard" nonlinearity, we can fit both types of transient thresholds as well as the steady-state thresholds. The most plausible embodiment of this essential nonlinearity is an asymmetric recifier, which seems to represent the behavior of retinal ganglion cells. Unlike the symmetric models of Roufs and Rashbass, this asymmetry also correctly predicts that the decrement thresholds for some stimuli are smaller than the corresponding increment thresholds.

Semiclassical perturbation theory of electron-molecule collisions

Abstract: The theory of the classical or semiclassical S matrix is combined with the use of perturbation dynamics to derive an approximately unitary expression for the scattering matrix for a very general class of potential interactions. The S matrix takes the form of a sum over products of Bessel functions whose orders are related to the changes in quantum numbers occurring in the transition, and whose arguments depend on the dynamical variables of the problem, including the unperturbed quantum numbers. In the general case, these arguments can be expressed as simple integrals over the unperturbed trajectory, and for well-behaved potentials they can be explicitly evaluated in terms of the modified Bessel functions K/sub 0/ and K/sub 1/. The connection between the semiclassical perturbation scattering theory and other approximations, such as the Born and eikonal approximations is demonstrated. The general theory is illustrated by applications to electron- (or ion-) polar-molecule scattering, including quadrupole as well as dipole interactions and including coupling to vibrations in both harmonic and anharmonic approximations. The more complicated interactions involve lengthier products of Bessel functions in the sum-and-product representation, but these are easily and systematically evaluated, and they reduce smoothly to the appropriate simpler expressions when the couplingmore » coefficients of the higher-order terms become small. More complicated potentials, including interactions between polyatomic molecules, can be handled by a simple systematic extension of the same principles. For electron-molecule scattering, these expressions can be used in their present form since the sums are dominated by Bessel functions of comparatively low order which can be evaluated directly; extensions to molecule-molecule scattering and ion-molecule scattering are equally valid formally, but their practical application will often require the use of asymptotic approximations to the Bessel functions.« less

Functional Cerebral Asymmetry and Performance III. Reaction Time as a Function of Task, Hand, Sex, and EEG Asymmetry

Abstract: To determine whether fluctuations of EEG asymmetry in the human cerebral hemispheres influenced overt performance, 14 male and 14 female subjects were tested in verbal and nonverbal target detection tasks and reaction time (RT) was recorded. RT was longest in both word and pattern tasks when the hand used for responding was contralateral to the hemisphere presumably most relevant to the task. The task variable did not affect EEG asymmetry, but females had lower R/L alpha ratios than males and EEG power increased and frequency decreased over the course of testing in association with decreased RT. RT also varied as a function of EEG asymmetry. In contrast to original expectations, RT was longest to verbal targets when R/L alpha power ratios were highest and longest to nonverbal targets when R/L ratios were lowest. The results were compatible with the notion of an inverted U function relating performance and arousal, and supported previous studies indicating that alpha asymmetry influences overt performance.

Axisymmetric compression of a Mohr–Coulomb medium around a circular hole

Abstract: An analytical solution is presented for the stress and strain fields in a Mohr–Coulomb material in plane strain around a circular hole when it is compressed by an axisymmetric far-field pressure. It is shown that several solutions arise involving one to three plastic zones depending on the values of Poisson's ratio and the friction angle. The solution chosen for presentation was obtained and used to validate the functioning of the Mohr–Coulomb yield condition that was added to the NONSAP finite element code. Stress and strain field comparisons are made.