Showing papers by "Georgia Institute of Technology published in 1976"

Nationwide assessment of potential output from wind-powered generators

Abstract: A method for computing the actual expected power for a wind-powered generator from a given observed speed distribution is described and applied to estimate the potential output for different locations in the continental U.S. A contour map of generator capacity factor values (fraction of the rated output realizable) is obtained for wind-powered generator systems with a cut-in speed of 3.6 m/sec and a rated speed of 8.0 m/sec, and for a unit with hypothetical values for the 1 MW class (cut-in speed, 6.7 m/sec; rated speed, 13.4 m/sec). Results indicate that in the central U.S. and in certain areas of the New England coast at a height of 61 m, over 60% of the rated output power could be obtained on an annual average. In these areas capacity factors of over 20% could be obtained with the 1MW system.

Real-time digital hardware pitch detector

Abstract: A high-quality pitch detector has been built in digital hard-ware and operates in real time at a 10 kHz sampling rate. The hardware is capable of providing energy as well as pitch-period estimates. The pitch and energy computations are performed 100 times/s (i.e., once per 10 ms interval). The algorithm to estimate the pitch period uses center clipping, infinite peak clipping, and a simplified autocorrelation analysis. The analysis is performed on a 300 sample section of speech which is both center clipped and infinite peak clipped, yielding a three-level speech signal where the levels are -1, 0, and +1 depending on the relation of the original speech sample to the clipping threshold. Thus computation of the autocorrelation function of the clipped speech is easily implemented in digital hardware using simple combinatorial logic, i.e., an up-down counter can be used to compute each correlation point. The pitch detector has been interfaced to the NOVA computer facility of the Acoustics Research Department at Bell Laboratories.

Organic complexes of iron and aluminium in natural waters

Abstract: IN natural waters throughout the world1, iron concentrations are commonly several orders of magnitude greater than the equilibrium solubility of iron hydroxide2. Highly coloured waters (which have relatively high concentrations of organic matter) commonly have even greater iron concentrations. Two of the chemical species postulated to account for this phenomenon are: (1) fine colloidal particles of iron hydroxide (possibly associated with colloidal organic matter) and (2) dissolved complexes of iron with naturally occurring organic substances. While the existence of colloidal iron hydroxide in natural waters is widely accepted3, there is little conclusive evidence for or against the existence of dissolved organic complexes of iron. We wish to present evidence which suggests that dissolved organic matter forms complexes not only with iron but also with aluminium, with competition between Fe and Al for available complexing sites determining the relative abundances of the two metals in natural waters.

The Viking Biological Investigation: Preliminary Results

Abstract: Three different types of biological experiments on samples of martian surface material ("soil") were conducted inside the Viking lander. In the carbon assimilation or pyrolytic release experiment, 14CO2 and 14CO were exposed to soil in the presence of light. A small amount of gas was found to be converted into organic material. Heat treatment of a duplicate sample prevented such conversion. In the gas exchange experiment, soil was first humidified (exposed to water vapor) for 6 sols and then wet with a complex aqueous solution of metabolites. The gas above the soil was monitored by gas chromatography. A substantial amount of O2 was detected in the first chromatogram taken 2.8 hours after humidification. Subsequent analyses revealed that significant increases in CO2 and only small changes in N2 had also occurred. In the labeled release experiment, soil was moistened with a solution containing several 14C-labeled organic compounds. A substantial evolution of radioactive gas was registered but did not occur with a duplicate heat-treated sample. Alternative chemical and biological interpretations are possible for these preliminary data. The experiments are still in process, and these results so far do not allow a decision regarding the existence of life on the plonet Mars.

Phytoplankton production in the Great Salt Lake, Utah, and a laboratory study of algal response to enrichment1

Abstract: The annual production by phytoplankton in the southern basin of the Great Salt Lake as estimated at two stations in 1973 averaged 145 g C m−2. The majority of the production occurred during March and April and was due to an unidentified species of Dunaliella. Daily carbon fixation rates averaged 2.13 g C m−2 at both locations during this period. A minor phytoplankton bloom in August, due to a small, unidentified green flagellate contributed 5% of the total annual phytoplankton production. Phytoplankton production was probably limited during April by self-shading and during the remainder of the year by the availability of nitrogen, as shown by laboratory bioassays. Grazing by Artemia salina reduces the phytoplankton population in late summer when nutrient levels have partially increased due to regeneration. The meromictic character of the lake was indicated by profiles of temperature and density. The monimolimnion is postulated to act as a nutrient sink, reducing the rate of nutrient release to the mixolimnion.

A Unified Operator Theory of Generalized Inverses

Abstract: The main purpose of this paper is to develop a unified approach to generalized inverses of linear operators, with particular emphasis on algebraic, topological, extremal, and proximinal properties.

Numerical Boundary Conditions for Viscous Flow Problems

Abstract: A method for treating certain troublesome boundary conditions in the numerical solution of time-dependent incompressible viscous flow problems is presented. This method is developed on the basis of an integral representation for the velocity vector which contains the entire kinematics of the problem, including the boundary conditions of concern. It is shown that for the exterior flow problem the freestream condition is satisfied at infinity exactly, and the need to treat a farfield condition is removed by the use of the integral representation. The distribution of a nonvelocity variable on the solid boundary, i.e., the "extraneous" boundary condition needed for both the exterior and the interior flows, are shown to be governed by the kinematics of the problem. The method is shown to accurately follow the local generation of vorticity on the solid boundary computationally.

The relationship of microstructure to monotonic and cyclic straining of two age hardening aluminum alloys

Abstract: The effect of microstructure on the monotonic and low cycle fatigue properties of a high purity, large grain, ternary aluminum-zinc, magnesium (Al-Zn-Mg) alloy and a high strength 7050 aluminum alloy was investigated. The best combination of fatigue life, strength, and ductility for the ternary alloy resulted when aged to produce a microstructure containing predominately η′ having a Guinier radius of approximately 65a and a small amount of incoherent η (MgZn2). Superior fatigue life, strength, and ductility were found when the 7050 alloy was aged to produce the maximum number of partially coherent η′ precipitates having a Guinier radius of approximately 35a. Aging the 7050 alloy to produce particles larger than 50a gave a microstructure that had lower fatigue properties at the low plastic strain amplitudes, δep/2 <1.0 pct. The empirical CoffinManson relationship was found to hold for a given deformation process, however changes in deformation character resulted in changes in the Coffin-Manson parameters.

Perturbations and Approximations for Generalized Inverses and Linear Operator Equations

Abstract: Publisher Summary This chapter explains the problems of perturbations and approximations of generalized inverses of linear operators. The approximation theory of generalized inverses of linear operators has many subtle points involving several modes of convergence, analytic and computational tractability, and techniques that are not merely extensions of those used in the matrix case. Often the study of approximations for a given mathematical object leads to a deeper understanding of the properties of that object, as suggested by Bertrand Russell. Resolution of the difficulties arising in the approximations leads to sharper insight into the properties of the exact object. The approximation methods include projectional and iterative methods and collectively-compact operator approximations. The chapter discusses these methods.

Infrared Temperature Mapping in Elastohydrodynamic Lubrication

Abstract: An improved technique for the measurement of temperature distributions in an EHD conjunction is presented. The technique reported here employs the infrared radiation emitted by the EHD conjunction and appears more rigorous, more reliable, and less cumbersome than that reported previously by the authors. Detailed mapping of fluid temperature (averaged through the thickness) and the ball surface temperature can be obtained. These temperature distributions have been reported for a naphthenic mineral oil for peak Hertz pressures of 1.05 and 1.51 GN/sq m (148 and 219 kpsi), at sliding speeds ranging from 0.35 to 12.7 m/s (13.4 to 500 ips) and a bath temperature of 40 C.

Stability of channel beds by armoring

Abstract: An experimental study of channel armoring formed the basis for an empirical technique to determine, for a given logarithmic-normal sediment distribution and for given hydraulic flow properties: (1)If the sediment bed will armor; and (2)if the sediment bed should armor, what will be the geometric mean diameter and standard deviation of the armored surface particles? Conversely, from this technique stable armored channels can be designed for a given earth material by the proper choice of channel dimensions that affect hydraulic parameters.

A Stochastic Model for an Optimal Priority Bed Distribution Problem in a Hospital Ward

Abstract: Ward beds are a primary resource under the control of hospital management. We develop a method for determining an optimum distribution of beds in a ward by assuming that ward patients can be classified into two categories, that admissions follow Poisson distribution, and that length of stay in the ward follows the negative exponential distribution. After defining a cut-off level as "the number of beds beyond which type 2 non-serious patients are not admitted," we develop a system of differential and difference birth and death process equations for the process. An objective function made up of shortage and holding costs is then developed and optimized for various values of cut-off priority level. An application of this model to a university teaching hospital in Cleveland is illustrated. The model is then extended to a situation where overflows are temporarily housed in a buffer accommodation or inappropriate ward.

The bilinear programming problem

Abstract: The paper deals with bilinear programming problems and develops a finite algorithm using the “piecewise strategy” for large-scale systems. It consists of systematically generating a sequence of expanding polytopes with the global optimum within each polytope being known. The procedure then stops when the final polytope contains the feasible region.

Ion identity and transport properties in CO2 over a wide pressure range

Abstract: We have investigated in drift tube mass spectrometers the identity and the transport properties of ions formed in CO2 gas at pressures ranging from 10−4 to 762 torr. Under bombardment by low energy (20–100 eV) electrons in the ion source, the primary positive ion is predominantly CO+2, with traces of C+, O+, and CO+. The predominant ion becomes O+2 at pressures above 100 μ (0.1 torr), and clustering of CO2 molecules to the O2+ occurs even at pressures below 1 torr. Break‐up of the clusters also occurs, the ion identity changing many times in the drift region. The zero‐field reduced mobility of the O+2⋅ (CO2)n charge carrier is a function of pressure, and varies from (1.30±0.03) cm2/V⋅sec at 0.2 torr to (1.18±0.03) cm2/V⋅sec at 1 torr. The sole negative ion produced directly by the electron bombardment is O−, which clusters to form the stable ion CO−3, whose reduced mobility is (1.27±0.06) cm2/V⋅sec for E/N ?60 Td at all pressures below 1 torr. At much higher pressures and under somewhat different conditio...

Use of dynamic theory to describe experimental results from volume holography

Abstract: The general applicability of dynamic theory to the description of the recording and readout characteristics of volume (thick) hologram gratings is indicated. In dynamic theory (as opposed to static theory), the volume nature of the thick holographic grating allows the interference of an incident light beam with its own diffracted beam inside the recording medium. This effect causes the continuous recording of another grating that alters the initial one, producing a resultant grating that is not uniform through the thickness of the recording material and a grating whose writing and reading characteristics may vary dramatically depending on the recording material and the experimental conditions. A large number of diverse types of writing, reading, and angular selectivity behavior have been reported in the published literature. The dynamic theory of thick hologram writing and reading is shown to predict qualitatively all of these various types of experimental behavior.

Aspects of Generalized Inverses in Analysis and Regularization

Abstract: This paper provides glimpses into some aspects of generalized inverses in analysis and some aspects of regularization of ill-posed linear operator equations. The paper consists of three parts. Part I, which deals with linear analysis, is devoted primarily to generalized inverses of integral operators of the first and second kinds and to related topics. Part II provides some uses of generalized inverses in nonlinear analysis (nonlinear alternative problems, inverse mapping and open mapping theorems, nonlinear operator equations and constrained optimization problems). Part III deals briefly with regularization methods in which generalized inverses play a role. Reference citations in this paper are to the Bibliography at the end of this volume. Also, the reader may refer to Section 2 of the paper on “Perturbations and Approximations…” in this volume for notation and results on generalized inverses that are used in the present paper.

The viking carbon assimilation experiments: interim report.

Abstract: A synthesis of organic matter from atmospheric carbon monoxide or carbon dioxide, or both, appears to take place in the surface material of Mars at a low rate. The synthesis appears to be thermolabile and to be inhibited by moisture.

Thermocouple time constant measurement by cross power spectra

Abstract: A method of measuring thermocouple time constants is outlined which requires Fourier signal processing. In this method, two thermocouples of differing time constants are placed in a gas flow as closely as possible to one another, and the time constant of the first thermocouple is determined directly from the extremum of the imaginary part of the ratio of the ensemble averaged cross-power spectrum to the ensemble averaged auto-power spectrum of that thermocouple. A coherence function is given for assuring the quality of the data, and results are presented for an experimental test of the method. Some problems with the method are briefly noted.

Determining Ambulance—Hospital Locations for On-Scene and Hospital Services

Abstract: Network models, incorporating several new impedance measures, for the location of ambulances and hospitals are introduced. Although the minimization of average impedance is frequently stated as a criterion in location models, the impedance does not usually embrace more than a single link, such as the time taken from a facility to a demand point. Here the impedance is extended to include not only the primary link between facility and demand but also the link from the point of rescue to the point of ultimate service. The return link between the service point and dispatching station is considered as well. Models for the simultaneous location of ambulance dispatching points and hospitals are framed. /Author/ /TRRL/

The Traveling Salesman Location Problem

Abstract: The problem of locating a single new facility relative to m existing facilities has been studied extensively under the assumption that trips are always made between the new facility and a single existing facility each time a trip occurs A variation of the problem is the traveling salesman location problem, which involves a traveling salesman who services m customers Each time a trip occurs the salesman visits one or more customers during the trip Thus, 2m-1 different itineraries can be formed, each occurring with a given probability The new facility, which is the starting and ending point of each itinerary, is to be located such that the expected distance traveled per unit time is minimized An iterative procedure is presented for solving the traveling salesman location problem; computational experience with the procedure is provided

Space and Time Hierarchies for Classes of Control Structures and Data Structures

Abstract: Control structures and data structures are modeled by directed graphs. In the control case nodes represent executable statements and arcs represent possible flow of control; in the data case nodes represent memory locations and arcs represent logical adjacencies in the data structure. Classes of graphs are compared by a relation ≤S.T where G ≤S.TH if G can be embedded in H with at most a T-fold increase in distance between embedded nodes by making at most S “copies” of any node in G. For both control structures and data structures, S and T are interpreted as space and time constants, respectively. Results are presented that establish hierarchies with respect to ≤S.T for (1) data structures, (2) sequential program schemata normal forms, and (3) sequential control structures.

Process failure mechanisms and optimal design of fraction defective control charts

Abstract: This note continues the study of various probability models for the duration of the process in the in-control state in the economic design of control charts. The fraction defective control chart is investigated, using both a discrete-time Markov model and two non-Markov models. Numericalexamples are presented which indicate that the process failure mechanism is an important consideration in optimum control chart design.

Effect of toroidal field ripple on particle and energy transport in a tokamak

Abstract: The azimuthal asymmetry introduced in tokamaks by the use of a finite number of toroidal field coils can lead to anomalously large particle and energy losses. The diffusion and ion heat transport coefficients associated with the ripple-induced drift of particles trapped in the usual banana orbits have been calculated and the results compared with the coefficients for neoclassical banana transport in axisymmetric tokamaks, transport governed by the dissipative trapped-ion instability, and the transport associated with particles trapped between the coil planes by the ripple field itself. The calculations were performed for an Experimental Power Reactor design and show that the losses due to the ripple-induced banana drifts can be a major limit on fusion reactor magnet design.