Showing papers by "SRI International published in 1975"

Exceptional Paper---Probability Encoding in Decision Analysis

Abstract: This paper presents the present philosophy and practice used in probability encoding by the Decision Analysis Group at Stanford Research Institute. Probability encoding, the process of extracting and quantifying individual judgment about uncertain quantities, is one of the major functions required in the performance of decision analysis. The paper discusses the setting of the encoding process, including the use of sensitivity analyses to identify crucial state variables for which extensive encoding procedures are appropriate. The importance of balancing modeling and encoding techniques is emphasized and examples of biases and unconscious modes of judgment are reviewed. A variety of encoding methods are presented and their applicability is discussed. The authors recommend and describe a structured interview process that utilizes a trained interviewer and a number of techniques designed to reduce biases and aid in the quantification of judgment.

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.

SELECT—a formal system for testing and debugging programs by symbolic execution

Abstract: SELECT is an experimental system for assisting in the formal systematic debugging of programs. It is intended to be a compromise between an automated program proving system and the current ad hoc debugging practice, and is similar to a system being developed by King et al. of IBM. SELECT systematically handles the paths of programs written in a LISP subset that includes arrays. For each execution path SELECT returns simplified conditions on input variables that cause the path to be executed, and simplified symbolic values for program variables at the path output. For conditions which form a system of linear equalities and inequalities SELECT will return input variable values that can serve as sample test data. The user can insert constraint conditions, at any point in the program including the output, in the form of symbolically executable assertions. These conditions can induce the system to select test data in user-specified regions. SELECT can also determine if the path is correct with respect to an output assertion. We present four examples demonstrating the various modes of system operation and their effectiveness in finding bugs. In some examples, SELECT was successful in automatically finding useful test data. In others, user interaction was required in the form of output assertions. SELECT appears to be a useful tool for rapidly revealing program errors, but for the future there is a need to expand its expressive and deductive power.

SELECT---a formal system for testing and debugging programs by symbolic execution

Abstract: SELECT is an experimental system for assisting in the formal systematic debugging of programs. It is intended to be a compromise between an automated program proving system and the current ad hoc debugging practice, and is similar to a system being developed by King et al. of IBM. SELECT systematically handles the paths of programs written in a LISP subset that includes arrays. For each execution path SELECT returns simplified conditions on input variables that cause the path to be executed, and simplified symbolic values for program variables at the path output. For conditions which form a system of linear equalities and inequalities SELECT will return input variable values that can serve as sample test data. The user can insert constraint conditions, at any point in the program including the output, in the form of symbolically executable assertions. These conditions can induce the system to select test data in user-specified regions. SELECT can also determine if the path is correct with respect to an output assertion. We present four examples demonstrating the various modes of system operation and their effectiveness in finding bugs. In some examples, SELECT was successful in automatically finding useful test data. In others, user interaction was required in the form of output assertions. SELECT appears to be a useful tool for rapidly revealing program errors, but for the future there is a need to expand its expressive and deductive power.

A New N-Way Power Divider/Combiner Suitable for High-Power Applications

Abstract: Theoretical and experimental results are presented on a new N-way power divider/combiner, which is an extension of the N-way combiner by Wilkinson. The main advantages of the new design are (1) external isolation loads, permitting high-power loads, (2) easily realizable geometry, and (3) monitoring capability for imbalances at the output ports. A trial 8-way combiner with 20% bandwidth at a center frequency of 1.15 GHz fully verified the new design concept.

Proving Theorems about LISP Functions

Abstract: We describe some simple heuristics combining evaluation and mathematical induction which we have implemented in a program that automatically proves a wide variety of theorems about recursive LISP functions. The method the program uses to generate induction formulas is described at length. The theorems proved by the program include that REVERSE is its own inverse and that a particular SORT program is correct. Appendix B contains a list of the theorems proved by the program.

Flexible ultrasound coupling system

Abstract: Essentially nonreflective coupling for ultrasonic waves is provided between a fluid medium confined in a rigid container and a biological specimen, such as a human body, through a container closing bellows system which incorporates a thin, flexible closing membrane that contacts and conforms to the contours of the specimen. A supportive bellows system between rigid parts of the fluid container and the membrane gives the membrane the essential properties of conforming to the contours of a specimen having variations in curvature (concavities and convexities) while having the ability to contain the fluid medium without rupture or undue distension when it is not supported externally, as by contact with the specimen. The supportive bellows system utilizes a pair of flexible toroidal members, one tubular and one U-shaped in cross section, attached to one another in series and having internal venting so that pressure within the toroids is governed by the pressure of the fluid inside the coupling bellows system. The container closing bellows system is fluid filled, the flexible closing membrane is tautly stretched over the tubular toroid member so that it is supported by the bellows system and forms a fluid-tight closure, and a vent means is provided to adjust pressure inside the said container closing bellows system.

Shielding Effectiveness of Braided-Wire Shields

Abstract: An analysis of the shielding effectiveness of braidedwire shields is made using the parameters of the woven wire and the theory of electromagnetic coupling through small irises. The coupling through the rhombic-shaped holes in the braid is approximated by using the electric and magnetic polarizabilities of elliptical holes of the same width and length as the rhombus. The analysis develops the transfer impedance and the mutual capacitance of the shield. The transfer impedance is calculated and plotted for shields of different optical coverages. The variation of mutual capacitance and mutual inductance with the weave angle of the braid are examined.

Time optimal behavior of human saccadic eye movement

Abstract: Optimal control theory takes into account constraints such as energy and time economies which are relevant to the understanding of biological design. The versional eye tracking system responsible for the extremely rapid and precise movements called saccades, which occur, for example, during reading, seemed a likely biological system in which to test for time optimality. A homeomorphic detailed physiological model was constructed based on quantitative muscle, neuronal and oculomotor characteristcs. It is a sixth-order nonlinear representation which considers reciprocal innervation and the asymmetrical force-velocity relationship of the agonist-antagonist muscle pair that moves the eye. Simulations were done by digital computer, and responses of the model to first-, second-, and third-order time optimal control signals were observed; the major portions of the response trajectories were essentially the same. The model response was then compared with measured human saccadic eye movements, and it was found that this experimental data agreed most completely with the model driven by first-order time optimal control signals. Additionally, electromyographic studies in man and neurophysiological experiments in animals agree in showing that the nervous controller signals during saccades are also of the first-order type. Thus, we can conclude that the saccadic eye movements studied are accurately depicted by a model that yields time optimal responses.

Temperature responses of antennal receptors of the mosquito,Aedes aegypti

Abstract: 1. A pair of thermoreceptor units was identified in the sensilla coeloconica at the tip of the antennae on the mosquito,Aedes aegypti. 2. One thermoreceptor was warm-sensitive and responded with a phasic-tonic increase in spike frequency to sudden increases in temperature. The second thermoreceptor was coldsensitive, responding with a phasic-tonic increase in spike activity to sudden decreases in temperature. 3. The mean tonic spike activity of both the cold and warm receptors increased with increasing temperature to a peak of 30 imp/sec at 26‡ C for the cold receptor and 35 imp/sec at 28.5‡ C for the warm receptor. The tonic activity declined as the temperature was increased further. The maximum phasic sensitivity was observed with small temperature changes (δ T = ± 0.2‡C). This was 136 imp/sec/‡C temperature drop in the cold receptor and 130 imp/ sec/‡ C rise in the warm receptor. 4. The importance of temperature in the host-seeking and “attack” behavior of the mosquito is discussed.

The Residual-Excited Linear Prediction Vocoder with Transmission Rate Below 9.6 kbits/s

Abstract: In this paper we present a new vocoder called the residual-excited linear prediction (RELP) vocoder. The concept of the RELP vocoder combines the advantages of linear predictive coding (LPC) and voice-excited vocoding. In the RELP system, vocal tract modeling is done by the LPC technique, and the LPC residual signal is used as the excitation signal. After low-pass filtering the residual signal is coded by adaptive delta modulation and is spectrally flattened before being fed in the LPC synthesizer. The range of the transmission rate is typically between 6 and 9.6 kbits/s; the synthetic speech in this range is quite good. As the transmission rate is lowered, the synthetic speech quality degrades very gradually. Since no pitch extraction is required, the vocoder is robust in any operating environment.

Ultrasonic imaging method and apparatus

Abstract: The ultrasonic imaging method and apparatus comprises an ultrasonic wave transducer supplied with recurrent multifrequency energy pulses for pulse insonification of an object under investigation with ultrasonic waves. Resultant echo waves from the object are directed onto the transducer for converting the same to electrical signals which are supplied to a signal processor which includes a variable bandpass filter. One or more of the filter characteristics are varied as a function of depth from which the echo signals are returned for enhanced resolution and signal-to-noise ratio of the received signal. Preferably, the filter is matched to the noise and signal spectra of the system. For A scan and B scan operations wherein reverberated acoustic pulses are derived from a range of depths a time variable filter is employed for time varying operation thereof.

Structured organization of clinical data bases

Abstract: The health care delivery system is under strong pressures from several sides. Many of these pressures derive from the demand for a more comprehensive range of health services and from the increased complexity of disease and treatment patterns. Since medical science has provided tools to manage many of the once common diseases, it now has to cope with problems of less well understood origin and course. The practicing physician is faced with an information explosion of major dimensions and a gap between scientific knowledge in a basic form and its practical application at the bedside.

The possible prognostic usefulness of assessing serum proteins and cholesterol in malignancy

Abstract: Serial measurement of serum proteins, albumin, and cholesterol levels was used in attempt to assess the course and prognosis in cancer patients. This assessment is based on the fact that their declines followed first order kinetics and that these patients usually died when their levels were lower than half the initial levels. Two categories of cancer patients were identified: those in whom the initial measurements of serum albumin or cholersterol, taken soon after diagnosis, were declining (Group I), and those who showed such a decline as they entered an advanced or terminal phase (Group II). Group I included cancer of the stomach, kidney, lung (adenocarcinoma and squamous cell carcinoma), oral cavity, large intestine, breast (40%), bladder, ovary (70%), pancreas, and prostate; leukemia (acute myeloid and lymphocytic); and Hodgkin's disease (60%), all of which accounted for approximately 90% of the major causes of cancer deaths. Group II included Hodgkin's disease (40%), and cancer of the ovary (30%) and breast (60%), all of which accounted for 10% of the major causes of cancer deaths.

Measurement errors in the estimation of home value

Abstract: Home value plays an important role in a variety of fields of research. In this paper, three commonly used measures of home value are evaluated and compared using a framework developed by Joreskog and Goldberger (1975) for estimation of causal models containing unobserved variables. The paper extends ideas presented by Kain and Quigley (1972) and Kish and Lansing (1954).

Quantum yields for the production of S(1S) from OCS (1100–1700 Å)

Abstract: The quantum yield of Se(4 1S0) production from OCSe has been measured over the wavelength interval 1100–2000 A. A large yield (≳0.75) is observed between 1640 and 1800 A, which supports the assignment 1Σ+←1Σ+ to the strong absorption observed in this region. The major emission observed is the B (3Σ−u) →X (3Σ−g) band system of Se2, the upper state being produced by the reaction of Se(1S) with OCSe. This reaction has a rate coefficient of (1.6±0.2) ×10−10 cm3 molecule−1⋅sec−1 but ? (17±3) % of the reaction produces Se2B (3Σ−u). From the short wavelength threshold of the molecular emission, a value of (2.69±0.05) eV was obtained for the dissociation energy of the OC–Se bond.

A modification of the jump-flinch technique for measuring pain sensitivity in rats

Abstract: The jump-flinch procedure provides a sensitive alternative to the hot-plate and tail-flick procedures. Analysis of the components of motor responses to increasing intensity of foot shock presentation has allowed the observational discrimination of five reliably elicited categories of unlearned responses to inescapable foot shock. Morphine sulfate differentially altered response category thresholds in rats. Response category thresholds also differed between Wistar and Fisher strain rats in analgesic effects of morphine sulfate.

Luminous and chromatic flickering patterns have opposite effects.

Abstract: When stimulated in phase by a sinusoidally flickering, uniform field, the red and green cone systems tend to inhibit each other. This inhibition is minimized by (i) counterphase (luminance) patterns or (ii) red/green (chromaticity) flicker. However, when (i) and (ii) are combined, the usual flickering-pattern effect is reversed: instead of enhancing chromatic flicker, counterphase patterns tend to suppress it.

Identification by handwriting verification

Abstract: A person, who is to have his identity verified, first writes his signature or any other appropriate group of characters or symbols several times with a special pen which produces signals representative of the writing forces in the plane of the paper and the writing pressure. From these a number of different parameters are derived. These parameters may be, for example, average value, energy, timing, number of zero crossings, etc. Average values and standard deviations are obtained for each of these parameters and these are stored as components of a template vector. In order to detect whether or not a later handwriting sample is authentic, a measure of the difference between the template vector and the later handwriting sample vector is calculated. The distinction between true signatures and forgeries is then made on the basis of this difference. If it is less than an appropriately selected value the signature is judged authentic while if it is above such value it is judged a forgery. The measure of difference may be in terms of RMS difference, for example, or say, average difference. Or, a signature may be deemed a forgery if any one component of the later written signature vector, or some combination of components, deviates beyond some threshold value.

Degradation of Lindane by Escherichia coli

Abstract: Lindane was degraded by Escherichia coli isolated from rat feces. About 10% of the added lindane was metabolized by the bacterium in Trypticase soy broth containing the pesticide. A single metabolite, 2,3,4,5,6-pentachloro-1-cyclohexene, was detected and identified by gas chromatography and mass spectrometry.

Differential effects of glucocorticoids on DNA synthesis in normal and virus-transformed chick embryo cells.

Abstract: LOOSE connective tissue fibroblasts in the mouse become markedly non-motile and refractile and lose pinocytotic activity within about an hour of hydrocortisone infusion. Only minutes are required to mimic this response in culture1. These responses of fibroblasts are well correlated with the topical anti-inflammatory potency of the glucocorticoids2. Glucocorticoids inhibit the multiplication in primary cultures of rat and mouse fibroblasts and of human epithelial cells3–6. In marked contrast, they stimulate multiplication of 3T3 cells7. Some investigators regard the 3T3 cell as a prototype for the study of growth regulation in cultured fibroblasts, although this line has been identified as tumorigenic in some conditions8.

The verification and synthesis of data structures

Abstract: The concept of machine extension is a commonly used technique for implementing complex software: sets of object classes and operations on these objects are defined and used, often in a layered fashion, to construct the system. This paper addresses the adaptation of this technique to automatic programming. It discusses how such sets of data structures may be precisely specified, presents an axiomatization of a programming language suitable for machine verification, and shows how programs which realize these data structures may be proved correct. A range of data type classes is treated--including arrays, records, and pointers. Some new verification rules are presented to handle programs which use assignments and structured objects.

Radiative lifetimes of the S and D Rydberg levels of Na

Abstract: We have determined the radiative lifetimes of the $n=5\ensuremath{-}13$, $s$ and $d$ states of Na by pumping the desired level with two resonant photons derived from two dye lasers excited by the same ${\mathrm{N}}_{2}$ laser. The lifetimes increase approximately as the cube of the effective quantum number, and are in good agreement with a Coulomb-approximation calculation.