Showing papers by "Georgia Institute of Technology published in 1980"

In Vivo Probe Measurement Technique for Determining Dielectric Properties at VHF through Microwave Frequencies

Abstract: A novel probe technique for the determination of dielectric properties of semisolid materials and living tissues in situ is described experimentally and theoretically. This method, based on an antenna modeling theorem, offers unique advantages over conventional dielectric measurements techniques including 1) an ability to perform living (in vivo) tissue dielectric measurements, 2) elimination of the need for tedious sample preparation, 3) the ability to obtain continuous dielectric property data from below 0.1 GHz to above 10 GHz, and 4) the ability to process data on a real time basis. Results of system performance evaluation via measurements of standard liquid dielectric and in vivo tissue data are presented.

Organizational Effectiveness: A Multiple-Constituency Approach

Abstract: Current approaches to organizational effectiveness are conceptually conflicting and empirically arid. They appear handicapped by a desire to produce a single effectiveness statement about any given organization. We propose a “multiple-constituency” approach to avoid this requirement, explicitly assuming that an organization's different constituencies will form different assessments of its effectiveness. We also suggest several conceptual and empirical implications of this reorientation.

The Economic Design of Control Charts: A Review and Literature Survey

Abstract: The design of control charts with respect to economic criteria has been the subject of considerable study during the last three decades. Several different process models have been developed and applied to most of the major types of control charts. this ..

Iodine: Its possible role in tropospheric photochemistry

Abstract: A detailed study of the photochemistry of iodine and its oxides indicates that iodine species may play an important role in the tropospheric photochemical system. Methyl iodide, often observed in the marine troposphere with an average concentration of 5-10 ppt, is photolyzed and thereby produces I atoms. Chemical interactions with O3, HxOy, and NOx cause I to be converted to other inorganic compounds such as IO, HOI, IONO2, and I2. The production of these species and their subsequent recycling back to I can lead to the catalytic removal of tropospheric O3, the enhancement of the NO2/NO ratio, the destruction of HxOy free radicals, and the conversion of HO2 to OH. Ultimately, tropospheric inorganic iodine is removed by heterogeneous processes. Calculations using a numerical model to simulate tropospheric photochemistry indicate that iodine may have a strong impact upon the atmospheric O3-NOx-HxOy system. The magnitude of these effects is dependent upon the value of several uncertain rate constants and the primary source distributions of CH3I and other organic and inorganic iodine compounds.

Thermal decomposition of human tooth enamel

Abstract: Further insight into human tooth enamel, dense fraction (TE), has been obtained by following the change and loss of CO3 2−, OH−, structurally incorporated H2O, Cl−, and, indirectly, HPO4 2− after TE had been heated in N2 or vacuum in the range 25–1000°C. Quantitative infrared spectroscopic, lattice parameter, and thermogravimetric measures were used. Loss of the CO3 2− components begins at much lower temperature (e.g., 100°C) than previously recognized, which has implications for treatments in vitro and possibly in vivo. CO3 2− in B sites is lost continuously from the outset; the amount in A sites first decreases and then increases above 200° to a maximum at ∼800°C (>10% of the possible A sites filled), where it is responsible for an increase ina lattice parameter. A substantial fraction of the CO3 2− in B sites moves to A sites before being evolved, apparently via a CO2 intermediary. This implies an interconnectedness of the A and B sites which may be significant in vivo. No loss of Cl− was observed at temperatures below 700–800°C. Structural OH− content increases ∼70% to a maximum near 400°C. Structurally incorporated water is lost continuously up to ∼800°C with a sharp loss at 250–300°C. The “sudden”a lattice parameter contraction, ∼0.014A, occurs at a kinetics-dependent temperature in the 250–300°C range and is accompanied by reordering and the “sharp” loss of ∼1/3 of the structurally incorporated H2O. The hypothesis that structurally incorporated H2O is the principal cause of the enlargement of thea lattice parameter of TE compared to hydroxyapatite (9.44 vs 9.42A) is thus allowed by these experimental results.

On the use of the I 0 -sinh window for spectrum analysis

Abstract: Closed form expressions for main-lobe width, modified main-lobe width, and relative sidelobe amplitude are given for the I_{0}- \sinh window function. These formulas facilitate exploring the tradeoff between record length, spectral resolution, and leakage in digital spectrum analysis. An especially simple empirical approximation relating main-lobe width and relative sidelobe amplitude is given.

On the relationship between zero criteria for two-variable polynomials and asymptotic stability of delay differential equations

Abstract: Asymptotic stability of delay differential equations of the retarded type is studied in terms of zero criteria for polynomials in two independent complex variables. The major new result of this note is that asymptotic stability independent of delay can be expressed in terms of a (finitely) implementable algebraic criterion involving a two-variable polynomial.

Post-Occupancy Evaluation An Overview

Abstract: Post-occupancy evaluation (POE) is defined as examination of the effectiveness for human users of occupied, designed environments. POEs generally focus on a single type of designed setting, tend to describe rather than manipulate, and are usually aimed at application. Within this wide focus, POEs vary considerably, and three conceptual dimensions-generality, breadth of focus, and applicability-are useful in cataloguing them. These dimensions are described and their implications for POE sponsorship and methods are discussed. Suggestions are proposed for future developments of the field.

Theoretical and empirical studies on using program mutation to test the functional correctness of programs

Abstract: In testing for program correctness, the standard approaches [11,13,21,22,23,24,34] have centered on finding data D, a finite subset of all possible inputs to program P, such that1) if for all x in D, P(x) = f(x), then P* = fwhere f is a partial recursive function that specifies the intended behavior of the program and P* is the function actually computed by program P. A major stumbling block in such formalizations has been that the conclusion of (1) is so strong that, except for trivial classes of programs, (1) is bound to be formally undecidable [23].There is an undeniable tendency among practitioners to consider program testing an ad hoc human technique: one creates test data that intuitively seems to capture some aspect of the program, observes the program in execution on it, and then draws conclusions on the program's correctness based on the observations. To augment this undisciplined strategy, techniques have been proposed that yield quantitative information on the degree to which a program has been tested. (See Goodenough [14] for a recent survey.) Thus the tester is given an inductive basis for confidence that (1) holds for the particular application. Paralleling the undecidability of deductive testing methods, the inductive methods all have had trivial examples of failure [14,18,22,23].These deductive and inductive approaches have had a common theme: all have aimed at the strong conclusion of (1). Program mutation [1,7,9,27], on the other hand, is a testing technique that aims at drawing a weaker, yet quite realistic, conclusion of the following nature:(2) if for all x in D, P(x) = f(x), then P* = f OR P is "pathological."To paraphrase,3) if P is not pathological and P(x) = f(x) for all x in D then P* = f.Below we will make precise what is meant by "P is pathological"; for now it suffices to say that P not pathological means that P was written by a competent programmer who had a good understanding of the task to be performed. Therefore if P does not realize f it is "close" to doing so. This underlying hypothesis of program mutation has become known as the competent programmer hypothesis: either P* = f or some program Q "close" to P has the property Q* = f.To be more specific, program mutation is a testing method that proposes the following version of correctness testing:Given that P was written by a competent programmer, find test data D for which P(D) = f(D) implies P* = f.Our method of developing D, assuming either P or some program close to P is correct, is by eliminating the alternatives. Let p be the set of programs close to P. We restate the method as follows:Find test data D such that:i) for all x in D P(x) = f(x) andii) for all Q in p either Q* = P* or for some x in D, Q(x) ≠ P(x).If test data D can be developed having properties (i) and (ii), then we say that D differentiates P from p, alternatively P passes the p mutant test.The goal of this paper is to study, from both theoretical and experimental viewpoints, two basic questions:Question 1: If P is written by a competent programmer and if P passes the p mutant test with test data D, does P* = f?Note that, after formally defining p for P in a fixed programming language L, an affirmative answer to question 1 reduces to showing that the competent programmer hypothesis holds for this L and p.We have observed that under many natural definitions of p there is often a strong coupling between members of p and a small subset µ. That is, often one can reduce the problem of finding test data that differentiates P from p to that of finding test data that differentiates P from µ. We will call this subset µ the mutants of P and the second question we will study involves the so-called coupling effect [9]:Question 2 (Coupling Effect): If P passes the µ mutant test with data D, does P pass the p mutant test with data D?Intuitively, one can think of µ as representing the programs that are "very close" to P.In the next section we will present two types of theoretical results concerning the two questions above: general results expressed in terms of properties of the language class L, and specific results for a class of decision table programs and for a subset of LISP. Portions of the work on decision tables and LISP have appeared elsewhere [5,6], but the presentations given here are both simpler and more unified. In the final section we present a system for applying program mutation to FORTRAN and we introduce a new type of software experiment, called a "beat the system" experiment, for evaluating how well our system approximates an affirmative response to the program mutation questions.

Benders' partitioning scheme applied to a new formulation of the quadratic assignment problem

Abstract: In this paper we present a new formulation of the quadratic assignment problem. This is done by transforming the quadratic objective function into a linear objective function by introducing a number of new variables and constraints. The resulting problem is a 0-1 linear integer program with a highly specialized structure. This permits the use of the partitioning scheme of Benders where only the original variables need be considered. The algorithm described thus iterates between two problems. The master problem is a pure 0-1 integer program, and the subproblem is a transportation problem whose optimal solution is shown to be readily available from the master problem in closed form. Computational experience on problems available in the literature is provided.

On generalized balanced realizations

Abstract: The class of analytic time-varying linear systems is considered. Different balanced realizations of such systems are defined, and their existence and properties are analyzed. The results are then used to derive reduced order approximations (also for unstable systems). A method is suggested to determine the order of a "good" approximation.

Identification and Interpretation of First Order Space-Time ARMA Models

Abstract: The effect of system size and shape on the theoretical space-time autocorrelation function is described for first order STARMA models. Figures and tables are presented to assist in identification considerations which include model interpretation, patterns of the theoretical spacetime autocorrelation and partial autocorrelation functions, and initial estimation for the STAR(11) and STMA(11) models.

Leachate Recycle as Landfill Management Option

Abstract: Leachate production from shredded municipal soil wastes and its stabilization and associated gas production monitored over a 699-day test period have indicated that once leachate is generated and recycled, rapid conversion of readily available organic constituents occurs. The landfill thereby serves as an anaerobic biochemical stabilization process which promotes sequential conversion of complex materials through intermediates to final end products. The overall results indicate that leachate recycle will enhance predictability and accelerate stabilization of readily available organic constituents with increased rates of gas production. Decreasing the time required for stabilization to a matter of months rather than years provides attractive alternatives for better operational control, energy recovery and rapid realization of potentials for land reclamation and ultimate use without some of the uncertainties associated with conventional landfill management practices.

Numerical Modeling of Dynamic Crack Propagation in Finite Bodies, by Moving Singular Elements—Part 1: Formulation

Abstract: An efficient numerical (finite element) method is presented for the dynamic analysis of rapidly propagating cracks in finite bodies, of arbitrary shape, wherein linear-elastic material behavior and two-dimensional conditions prevail. Procedures to embed analytical asymptotic solutions for singularities in stresses/strains near the propagating crack-tip, to account for the spatial movement of these singularities along with the crack-tip, and to directly compute the dynamic stress-intensity factor, are presented. Numerical solutions of several problems and pertinent discussions are presented in Part II of this paper.

Vapor Pressure and Heats of Vaporization and Sublimation of Liquids and Solids of Interest in Cryogenics below 1-atm Pressure

Abstract: A series of research reports were prepared several years ago for the National Bureau of Standards in which the vapor pressure and heats of vaporization and sublimation of liquids and solids of cryogenic interest below 1-atm pressure were computed as functions of the thermodynamic temperature from appropriate thermodynamic relations using what was then considered to be the best available physical property data. The results of these calculations were presented in tabular form as a function of absolute temperature from approximately the normal boiling point of the condensed gas to approximately the temperature at which the vapor pressure of the solid is about 10−15 torr. The original reports referred to in the references for this paper should be consulted for details.

Global measurements of aerosols in remote continental and marine regions: Concentrations, size distributions, and optical properties

Abstract: The phase I Gametag (Global Atmospheric Measurements Experiment of Tropospheric Aerosols and Gases) aerosol measurements were designed to provide an initial assessment of the levels, types, and optical effects of tropospheric aerosols in remote marine and continental regions and to examine the possible causal relationships between the observed distributions and the dominant factors controlling aerosol population: chemical and physical transformations, source and sink strengths, and transport. We used size-number data to determine mass concentrations and to estimate extinction, using nominal optical properties. Filter and impactor data have been used to determine aerosol composition, and correlative aircraft measurements have been used to aid in our data interpretation. Our data have been used to generate latitudinal profiles along our Pacific flight tracks. Our continental measurements, in general, show bimodal aerosol size distributions that reflect different source for each mode. The aerosol population consists primarily of crustal aerosols with r ≥ 0.5 μm and sulfate and combustion aerosols with r < 0.5 μm, with only a minor sea salt component. Owing to vertical mixing, there are no qualitative differences between the boundary layer and the free troposphere. Our data indicate that crustal aerosols represent a significant component of a background tropospheric aerosol in western North America and suggest that the possible contribution of the crustal aerosol to extinction should not be ignored. Pacific marine measurements show a qualitative difference between the boundary layer and the free troposphere. The boundary-layer aerosol population is dominated by a bimodal sea spray aerosol; optical effects and mass concentration are dominated by a mode with a volume mean radius of ∼1 μm. Our measurements show only a small crustal component of the marine boundary-layer aerosol. Our data indicate a loss of Cl from the sea spray aerosol, with the greatest loss in the small particles. We have inferred a background concentration of 0.2 ppbm for our measured particles that does not appear to be directly related to the sea spray aerosol. We have identified some of these particles as locally produced secondary aerosols; simultaneous measurements of gaseous species support this interpretation. Our Pacific free tropospheric aerosol measurements show a highly variable aerosol component, with local variations in concentration by 1 order of magnitude within a few kilometers. Our measured total aerosol and crustal component concentrations show a general decrease from north to south. Our lowest mean mid tropospheric concentration was seen south of 20°S; we have identified this mean concentration of 0.08 ppbm as a midtropospheric background aerosol.

Three-stage birefringent filter tuning smoothly over the visible region: theoretical treatment and experimental design.

Abstract: The Jones transformation matrix, which describes the arbitrary incidence of polarized light on a thin uniaxial birefringent plate, is determined. With the optic axis presumed to lie in the plane of the plate, digital solutions to the resulting formulas are presented for several different quartz plates to depict the tuning characteristics of a birefringent plate functioning as a single-stage birefringent filter. A simplified model is used to generalize these results to describe a multistage birefringent filter. This theoretical study forms the basis for the design and construction of a three stage, quartz, birefringent filter to be used as the coarse tuning element in a visible cw dye laser. A relatively simple and straightforward procedure for the assembly of the three-stage filter is given. The performance of this newly constructed filter is found to be superior to currently available commercial models, tuning smoothly over the 4400-6600-A wavelength region.

Long-Period Oscillations in the Meteor Region

Abstract: Meteor wind data taken over Atlanta (34°N, 84°W) during the three-year interval 1974–77 are analyzed for periodic fluctuations of a recurrent nature. Power spectra and cross spectra of the zonal and meridional velocities between 80 and 100 km are constructed for several samples. Ensemble statistics indicate the regular appearance of periods near 17, 8, 5, 2, 1.6 and 1.2 days. Most of these display smaller spectral values near 90 km. The general seasonal behavior has maximum values in winter and minimum values in summer, paralleling the observed variation of traveling wave energy flux in the stratosphere. The regularity with which these oscillations appear, tempts an association with the periods of atmospheric normal modes.

Turbulence measurements in a constricted tube

Abstract: Measurements of turbulent flow through a constricted tube with a contoured 75% constriction have been performed with a laser-Doppler anemometer. One motivation for these studies was the problem of flow through arterial stenoses and consequently a range of relatively low Reynolds numbers (5000–15000) was employed. Velocity profiles, r.m.s. turbulence velocities, and energy spectra were recorded along with determinations of the wall pressure variation and length of recirculation region. Results show extremely high levels of turbulence and considerable turmoil within the so-called recirculation region. A method for determining the reattachment point in an intensely turbulent flow is given which should offer improvement over flow visualization techniques. Similarity in turbulence energy spectra measured at various radial positions is found at several axial locations, but does not occur in the region immediately downstream of separation. The downstream recovery of the turbulence velocity to upstream values takes place slowly. A secondary motivation of providing experimental data useful in evaluating turbulence models for computational fluid dynamics led to extensive measurements of radial and axial r.m.s. turbulence velocity components at a Reynolds number of 15000.

On Some New General and Complementary Energy Theorems for the Rate Problems in Finite Strain. Classical Elastoplasticity

Abstract: General variational theorems for the rate problem of classical elastoplasticity at finite strains, in both Updated Lagrangian (UL) and Total Lagrangian (TL) rate forms, and in terms of alternate measures of stress-rate and conjugate strain-rates, are critically studied from the point of view of their application. Attention. is primarily focused on the derivation of consistent complementary energy rate principles which could form the basis of consistent and rational assumed stress-type finite element methods, and two such principles, in both UL and TL forms, are newly stated. Systematic procedures to exploit these new principles in the context of a finite element method are discussed. Also discussed are certain general modified variational theorems which permit an accurate numerical treatment of near incompressible behavior at large plastic strains

A finitely convergent algorithm for bilinear programming problems using polar cuts and disjunctive face cuts

Abstract: A finite algorithm is presented in this study for solving Bilinear programs. This is accomplished by developing a suitable cutting plane which deletes at least a face of a polyhedral set. At an extreme point, a polar cut using negative edge extensions is used. At other points, disjunctive cuts are adopted. Computational experience on test problems in the literature is provided.

Responses of the nematode Caenorhabditis elegans to controlled chemical stimulation.

Abstract: A new method is described for studying the behavioral responses of nematodes to controlled chemical stimulation. The worm is held by the tail with a suction pipet. Behavior is recorded by an array of light sensors connected to a multichannel recorder. Several types of behavior can be detected in addition to the normal backward propagating waves of about 2 Hz that propel untethered worms forward. The most dramatic of these is the reversal bout, consisting of forward propagating waves of about 0.7 Hz, that propel untethered worms backward. The latter waves are easily distinguished from the former by the large amplitude motion caused by the fact that they contain a sharper bend at the tail. This technique was used to demonstrate that a purely temporal change in chemical stimulation can cause a large change in the probability of occurrrence of a reversal bout. These altered probabilities adapt back to the basal level in about one minute. Increased probabilities adapt faster than decreased. Stronger stimulation causes slower adaptation. Since the reversal bout is associated with changes in direction of locomotion, these observations suggest that klinokinesis with adaptation plays a role in the movement of nematodes in chemical gradients.