Showing papers by "Georgia Institute of Technology published in 1975"
TL;DR: In this paper, three types of linear feedback control schemes are considered: joint angle and velocity feedback with (GRC) and without (IJC) cross joint feedback, and feedback of flexible state variables (FFC).
Abstract: The control of the flexible motion in a plane of two pinned beams is addressed with application to remote manipulators. Three types of linear feedback control schemes are considered: joint angle and velocity feedback with (GRC) and without (IJC) cross joint feedback, and feedback of flexible state variables (FFC). Two models of the distributed flexibility are presented along with some results obtained from them. The relative merit of the three control schemes is discussed.
395 citations
TL;DR: In this article, five sources of feedback (the formal organization, supervisor, co-workers, the task, one's own self) were investigated for their "informativeness" as providers of information about what the job requirements are (referent) and the extent to which they were met (feedback).
241 citations
01 Apr 1975
TL;DR: This paper presents several digital signal processing methods for representing speech, including simple waveform coding methods; time domain techniques; frequency domain representations; nonlinear or homomorphic methods; and finaIly linear predictive coding techniques.
Abstract: This paper presents several digital signal processing methods for representing speech. Included among the representations are simple waveform coding methods; time domain techniques; frequency domain representations; nonlinear or homomorphic methods; and finaIly linear predictive coding techniques. The advantages and disadvantages of each of these representations for various speech processing applications are discussed.
238 citations
TL;DR: In this paper, the layout problem is formulated as a quadratic set covering problem, and a branch and bound method for optimizing the resulting problem is devised, which can be provided to the layout engineer for consideration and modification.
Abstract: This paper presents a computerized procedure for layout design. The layout problem is formulated as a quadratic set covering problem. A branch and bound method for optimizing the resulting problem is devised. As a result, optimal and suboptimal layouts can be provided to the layout engineer for consideration and modification.
170 citations
01 Sep 1975
TL;DR: This correspondence presents a procedure for generating correlated random variables with specified non-Gaussian probability distribution functions (pdf's) such as might be required for Monte Carlo simulation studies.
Abstract: This correspondence presents a procedure for generating correlated random variables with specified non-Gaussian probability distribution functions (pdf's) such as might be required for Monte Carlo simulation studies. Specifically, a method is presented for generating an arbitrary number of pseudorandom numbers each with a prescribed probability distribution and with a prescribed correlation coefficient matrix for the collection of random numbers. Collections of typical numbers generated with the method are evaluated with chi-squared tests for the distribution functions and with confidence intervals for the correlation coefficients derived from maximum likelihood estimates. In all cases tested the generated numbers passed the tests.
139 citations
TL;DR: In this article, the elastic stress intensity factors for arbitrary-shaped cracks in plane stress and plane strain problems were calculated using an assumed displacement hybrid finite element model, where the unknowns in the final algebraic system of equations are the nodal displacements and the elastic tensor intensity factors.
Abstract: This paper deals with a procedure to calculate the elastic stress intensity factors for arbitrary-shaped cracks in plane stress and plane strain problems. An assumed displacement hybrid finite element model is employed wherein the unknowns in the final algebraic system of equations are the nodal displacements and the elastic stress intensity factors. Special elements, which contain proper singular displacement and stress fields, are used in a fixed region near the crack tip; and the interelement displacement compatibility is satisfied through the use of a Lagrangean multiplier technique. Numerical examples presented include: central as well as edge cracks in tension plates and a quarter-circular crack in a tension plate. Excellent correlations were obtained with available solutions in all the cases. A discussion on the convergence of the present solution is also included.
120 citations
TL;DR: In this paper, a model based on fluid flow in fractures is proposed for modeling hot springs in continental geothermal areas, thermal springs which are not associated with known high-temperature areas, and hot springs associated with hydrothermal circulation on ocean ridge crests.
Abstract: Summary
Hot springs in continental geothermal areas, thermal springs which are not associated with known high-temperature areas, and hot springs associated with hydrothermal circulation on ocean ridge crests are described by models based on fluid flow in fractures. A steady state model shows that fractures of the order of a few millimetres wide can carry a substantial convective flow and that the convective flow depends upon the third power of the fracture width. The steady state model also furnishes estimates of conductive temperature losses in springs and gives estimates of the depths of circulation for thermal springs in the southeastern United States which are in good agreement with available field data.
In many cases the temperature and flow rate of springs is non-stationary. This is particularly true of hot springs in high temperature geothermal areas and it is expected to be true of springs on mid-ocean ridge crests. Time-dependent models for springs show that the main effect of the circulation is to lower the regional geothermal gradient. Non-stationary convection controlled by fractures can explain the variability of heat flow data obtained near ocean ridge crests. A numerical example shows that convection in a block 3 km wide, containing fractures 3 mm wide and 5 km deep, and circulating for 104 years gives rise to a hot spring with a temperature of 125 °C and a flow rate of 0.14 kg m−1 s−1. Such a spring discharging at the sea floor would give rise to an unmeasurably small temperature anomaly in the sea water. The convective heat transfer due to such a circulation system is roughly 200 times greater than the heat transfer that would have been achieved by conduction alone.
112 citations
TL;DR: In this paper, the authors propose to weight the test vectors, giving maximum weights to those likely to be near the primary axes, intermediate weights for those near hyperplanes but not near primary axes and near zero weights for almost collinear with or almost orthogonal to the first initialF-axis.
Abstract: Kaiser's iterative algorithm for the varimax rotation fails when (a) there is a substantial cluster of test vectors near the middle of each bounding hyperplane, leading to non-bounding hyperplanes more heavily overdetermined than those at the boundaries of the configuration of test vectors, and/or (b) there are appreciably more thanm (m factors) tests whose loadings on one of the factors of the initialF-matrix, usually the first, are near-zero, leading to overdetermination of the hyperplane orthogonal to this initialF-axis before rotation. These difficulties are overcome by weighting the test vectors, giving maximum weights to those likely to be near the primary axes, intermediate weights to those likely to be near hyperplanes but not near primary axes, and near-zero weights to those almost collinear with or almost orthogonal to the first initialF-axis. Applications to the Promax rotation are discussed, and it is shown that these procedures solve Thurstone's hitherto intractable “invariant” box problem as well as other more common problems based on real data.
107 citations
TL;DR: In this article, a nonlinear autonomous parabolic partial differential equation in one space variable subject to Neumann boundary conditions on a compact interval is investigated and conditions under which a solution has a nonempty ω-limit set.
105 citations
TL;DR: In this article, the (n, 6, 4) model of ion-neutral-molecule interactions as functions of effective ion temperature for eight values of n and several values of a parameter γ that measures the relative strengths of the r−6 and r−4 attraction terms.
96 citations
TL;DR: For a large class of linear continuous-time systems including delay-differential systems, an algebraic theory is presented in terms of Noetherian operator rings generated from a finite number of elements belonging to a convolution algebra of distributions.
Abstract: For a large class of linear continuous-time systems including delay-differential systems, an algebraic theory is presented in terms of Noetherian operator rings generated from a finite number of elements belonging to a convolution algebra of distributions. The external behavior of these systems is given by a finite set of input/output (convolution) operator equations which are solved in a novel manner by constructing an operational transfer function matrix and then applying an extension of the Mikusinski operational calculus. After the formulation of an internal representation consisting of a finite set of scalar operational-differential equations, the problem of realizing an operational transfer function matrix by such an internal description is considered. Results on the existence and construction of realizations are given.
TL;DR: In this paper, the layer structure of fire-clay and kaolinite was studied by high-resolution electron microscopy after embedding in Spurr low-viscosity Epoxy media and thin sectioning normal to the (001) planes by an ultramicrotome.
Abstract: The layer structure of kaolinite from Twiggs, Georgia and fire-clay type kaolinite (Frantex B, from France), particle size separates 2–0·2 μm was studied by high resolution electron microscopy after embedment in Spurr low-viscosity Epoxy media and thin sectioning normal to the (001) planes by an ultramicrotome. Images of the (001) planes (viewed edge-on) of both kaolinites were spaced at 7 A and generally aligned in parallel, with occasional bending into more widely spaced images of about 10 A interval. Some of the 10 A images converged to 7 A at one or both ends, forming ellipse-shaped islands 80 to 130 A thick and 300 to 500 A long. The island areas and interleaved 10 A layers between 7 A layers may represent a residue of incomplete weathering of mica to kaolinite. The proportions of micaccous occlusions were too small and the layer sequences too irregular to be detected by X-ray diffraction. The lateral continuity of the layers through the 7-10-7 A sequence in a kaolinite particle would partially interrupt or prevent expansion in dimethyl sulfoxide (DMSO) and other kaolinite intercalating media. Discrete mica particles were also observed with parallel images at 10 A, as impurities in both kaolinites. The small K content of the chemical analyses of the kaolinite samples is accounted for as interlayer K, not only in discrete mica particles but also in the micaceous occlusions.
TL;DR: The result does indicate some caution is necessary in interpreting age-recognition interactions, and two hypotheses, storage and retrieval, which account for the adult age decrement seen in recall, are tested.
Abstract: A recognition-memory paradigm was used to test two hypotheses, storage and retrieval, which account for the adult age decrement seen in recall. Partial storage was minimized by using items in the recognition list which were similar to the to-be-remembered items. Recognition performance was unaffected by adult age differences, thereby supporting the retrieval hypothesis. However, older persons made a greater number of semantic errors in the recognition test list supporting the storage hypothesis. While the error difference did not affect overall recognition performance, the result does indicate some caution is necessary in interpreting age-recognition interactions.
TL;DR: Chimpanzees have the capacity to match-to-sample even when the sample and matching stimuli are presented to different modalities, and cross-modal matching- to-sample can be performed even when a delay is imposed between the sampling response and matching response.
TL;DR: In this article, the results of various computer experiments performed on the two-particle unequal-mass Toda lattice are discussed, and it is shown that this system exhibits a transition from near-integrable to macroscopically observable stochastic behavior at a critical value of the total energy, which depends on the mass ratio of the two particles.
Abstract: In this paper, the results of various computer experiments performed on the two-particle, unequal-mass Toda lattice are discussed. These experiments indicate that this system exhibits a transition from near-integrable to macroscopically observable stochastic behavior at a critical value of the total energy ${E}_{c}$ which depends on the mass ratio of the two particles ($\frac{{m}_{2}}{{m}_{1}}$). This transition appears to occur for every mass ratio in the open interval $0l\frac{{m}_{2}}{{m}_{1}}l1$. Details of trajectory behavior at selected energies and mass ratios are exposed through presentation of a number of Poincar\'e surfaces of section. The transition discussed herein will likely prove to be significant for both mathematics and physics.
TL;DR: In this article, a ten-channel eikonal treatment of the excitations of atomic helium, initially in the $2,1,3}S$ metastable states, by incident electrons with energy $E$ (eV) in the range
Abstract: We present a ten-channel eikonal treatment of the $2^{1,3}P$, $3^{1,3}S$, $3^{1,3}P$, and $3^{1,3}D$ excitations of atomic helium, initially in the $2^{1,3}S$ metastable states, by incident electrons with energy $E$ (eV) in the range $5\ensuremath{\le}E\ensuremath{\le}100$. Integral and differential inelastic cross sections are obtained. Also, the angular-correlation parameters $\ensuremath{\lambda}$ and $\ensuremath{\chi}$, which respectively provide the relative population and relative phase of the collisionally excited $P$ magnetic substates, and the circular polarization fraction $\ensuremath{\Pi}$ of radiation emitted from these $P$ states, are determined as functions of scattering angle $\ensuremath{\theta}$ and $E$. No measurements exist to date. The principle of detailed balance is explicitly demonstrated for the $2^{1}S\ensuremath{-}1^{1}S$ superelastic collision.
TL;DR: It is demonstrated that the human leukocyte enzyme is distinct from the porcine pancreatic enzyme, and the structural features necessary for an effective inhibitor are defined, which may lead to a treatment for emphysema and related diseases.
TL;DR: Acyl carbazates with appropriate substituents are analogs of acyl amino acids in which the α-methine group has been replaced by a nitrogen atom and should find utility as inhibitors and active site titrants for serine proteases.
TL;DR: In this paper, a method for calculating arbitrary-order diffraction efficiencies of thick, lossless transmission gratings with arbitrary periodic grating shapes has been developed, along with a coupled-mode theory of diffraction.
Abstract: A method for calculating arbitrary-order diffraction efficiencies of thick, lossless transmission gratings with arbitrary periodic grating shapes has been developed. A Fourier-series representation of the grating is employed, along with a coupled-mode theory of diffraction. For illustration, numerical values of the diffraction efficiencies at the first three Bragg angles are calculated for sinusoidal, square-wave, triangular, and saw-tooth gratings. Numerical results for the same grating shapes with the same parameters are also calculated for comparison, by extending Burckhardt's numerical method for analyzing thick sinusoidal gratings. The comparison shows that the coupled-mode theory provides results with relative computational ease and results that are in agreement with calculations obtained by extending the more-rigorous Burckhardt theory to nonsinusoidal grating shapes and to higher-order Bragg angles.
01 Jan 1975
TL;DR: In this paper, the results of 103 tests on the noise generation capability of bunsen burner type premixed hydrocarbon-air turbulent flames were presented, and the results for sound power output, reacting volume and spectral content were correlated with the burner diameter, flow velocity, fuel mass fraction and laminar flame speed.
Abstract: The results are presented of 103 tests on the noise generation capability of bunsen burner type premixed hydrocarbon-air turbulent flames. The fuels used have been propane, propylene, acetylene and ethylene, all burning at 1 atmosphere in an anechoic chamber.The results for sound power output, reacting volume and spectral content are correlated with the burner diameter, flow velocity, fuel mass fraction and laminar flame speed; these variables are sufficient to produce correlations with respect to the Reynolds number, Mach number, fuel mass fraction and the first Damkohler similarity group. Introducing a new simplified version of the theory of combustion noise, known turbulent flame speed correlations, and the theory of isotropic turbulence decay downstream of the burner lip, it is shown that the correlations for frequency content and radiated sound power have a rational basis.
TL;DR: In this paper, a theory measuring a decision maker's aversion to temporal risks is developed in the context of a simple choice framework that admits the interpretation of time varying utility of wealth, and a relation "more temporally risk averse" is defined and characterized in terms of instantaneous risk aversion (the usual single variable case) and impatience.
TL;DR: The conclusion that the mode of substrate binding severely moderates the inherent chemical reactivity of the activated oxygen in this system of Pseudomonas oleovorans is supported.
TL;DR: An application of second-order response-surface de signs to a digital simulator of a street network is presented; the object is to find optimal settings for the traffic signals during the morning peak of traffic flow.
Abstract: Computer simulation models are frequently used to determine the combination of levels for a set of independent variables at which a response variable is optimized. This process leads to problems of experi mental design, i.e., the choice of levels of the independent variables at which the simulation model is to be run and at which the model's responses are to be observed. This paper considers second-order response-surface designs and optimization procedures for use in this situation. Several classes of designs are constructed and applied to surfaces typically generated by computer simulation models. Results are obtained which should assist in the selection of de signs in general or for use on specific surfaces. An application of second-order response-surface de signs to a digital simulator of a street network is presented; the object is to find optimal settings for the traffic signals during the morning peak of traffic flow.
TL;DR: The problem of estimating the admittance parameters of an external equivalent network using internal system operating data and static state estimator data is considered and the algorithm for performing this type of parameter estimation is derived.
Abstract: The problem of estimating the admittance parameters of an external equivalent network using internal system operating data is considered. By utilizing information available from monitoring scheduled or forced internal system outages, together with static state estimator data, external network equivalents can be estimated. The algorithm for performing this type of parameter estimation is derived. Its effectiveness and Computer requirements are demonstrated by simulating a representative system. Application for this algorithm is foreseen to be in the off-line estimation and model validity assessment of network equivalent models which are used in several on-line applications.
TL;DR: In this article, an assumed displacement hybrid finite-element procedure was developed for treating a general class of problems involving mixed-mode behavior of cracks is used to solve some two-dimensional, fracture mechanics problems involving rectilinear-anisotropic materials.
Abstract: An assumed displacement hybrid finite-element procedure developed for treating a general class of problems involving mixed-mode behavior of cracks is used to solve some two-dimensional, fracture mechanics problems involving rectilinear-anisotropic materials. This finite-element program uses four "singular" elements which surround the crack tip and "regular" elements which occupy the remaining region. The singular element has a built-in displacement field of the r type with the two modes of stress intensity factors, K 1 and K I I , as unknowns. Displacement compatibility between singular and regular elements is also maintained. Isoparametric transformations are used to derive the stiffness matrix of quadrilateral curved elements. Rectilinear anisotropic, nonhomogeneous, but linear elastic, material properties are considered. The program was checked out by analyzing a bimaterial tension plate with an eccentric crack and a centrally-cracked orthotropic tension plate. The results thus obtained agreed well with those by Erdogan and Biricikoglu, and Bowie and Freese, respectively. The program was then used to analyze two fracture test specimens for which analytical solutions do not exist. The first specimen was the doubly edge-notched tension plate with material principal directions oriented 0°-90° or ′45° to the geometric axes of symmetry and with varying crack length. The second specimen was the three-point bend specimen with material principal directions oriented 0°-90° to the geometric axes of symmetry. Finally, an orthotropic tension plate with an oblique center crack was analyzed. Finite-element solutions of most of these problems do not seem to have appeared in prior literature.
TL;DR: In this article, the frequency and mode shapes of circular rings on rigid and elastic supports were determined for in-plane vibration by using a transfer matrix approach, where the transfer matrices were obtained by numerical integration of differential equations of the elements.
TL;DR: In this article, the influence of wire processing variables on the formation of subgrain structures and strengthening in three aluminum conductor materials is described, and the yield strengths of these wires were found to obey a a = σ0 +k(•L) m relationship, with an exponentm = -1 independent of the processing sequence used to arrive at the structure.
Abstract: The influence of wire processing variables on the formation of subgrain structures and strengthening in three aluminum conductor materials is described. Electrical conductor grade aluminum, an Al-Fe-Mg alloy and an Al-Fe-Co alloy each develop subgrain structures with mean linear intercepts (•L) in the range of 0.4 to 1.5 μm with several sequences of wiredrawing and partial annealing. The yield strengths of these wires were found to obey a a = σ0 +k(•L) m relationship, with an exponentm = -1 independent of the processing sequence used to arrive at the structure. The role of precipitate particles in the alloys is to raisek above that for EC-A1 while Mg in solid solution increases σ0. The precipitates also affect the development of the substructure during the wiredrawing and annealing.
TL;DR: The base composition is shown to influence the conformations adopted by dinucleoside phosphates, and comparison of calculations with experimetal data, where available, show good agreement.
Abstract: Synopsis Classical potential energy calculations have been made for the ribodinucleoside monophosphates ApA, CpC, GpG, and UpU. Van der Waals’, electrostatic, and torsional contributions to the energy were calculated, and the energy was minimized with the seven backbone conformational angles as simuitaneously variable parameters. At the global minimum, ApA and CpC have conformations like double helical RNA: the angles w’ and w are g-g-, the sugar pucker is C3’-endo, and the bases are anti. GpG and UpU, on the other hand, have the w’,w angle pair g-t at the global minimum, and for GpG the bases are syn. Energy contour maps for w’ and w show two broad, low energy regions for ApA, CpC, and UpU: one is g-g-, and the second encompasses g-t and g+g+ within a single lowenergy contour. The two regions are connected by a path at 10-13 kcal./mole. For GpG, with bases syn, however, only a small low-energy region at g-t is found. The helical ‘A’ RNA conformation is 8.5 kcal/mole higher for this molecule. Thus, the base composition is shown to influence the conformations adopted by dinucleoside phosphates. Comparison of calculations with experimental data, where available, show good agreement.
TL;DR: In chemotactic studies employing countercurrent separation the nematode aenorhabditis elegans was found to avoid D-tryptophan with a threshold in the range 10(-4) to 10(-3) M.
Abstract: In chemotactic studies employing countercurrent separation the nematode aenorhabditis elegans was found to avoid D-tryptophan with a threshold in the range 10(-4) to 10(-3) M. There was no response to L-tryptophan up to 10(-2) M although it appeared to partially inhibit the response to D-tryptophan.