Showing papers by "Virginia Tech published in 1969"

Fitting the task to the man

Abstract: Muscular work nervous control of movements improving work efficiency body size the design of work stations heavy work handling loads skilled work human-machine systems mental activity fatigue occupational stress boredom job design in monotonous tasks working hours and eating habits nightwork and shiftwork vision ergonomic principles of lighting noise and vibration indoor climate daylight, colours and music for a pleasant work environment.

Multiproject Scheduling with Limited Resources: A Zero-One Programming Approach

Abstract: A zero-one 0-1 linear programming formulation of multiproject and job-shop scheduling problems is presented that is more general and computationally tractable than other known formulations. It can accommodate a wide range of real-world situations including multiple resource constraints, due dates, job splitting, resource, substitutability, and concurrency and nonconcurrency of job performance requirements. Three possible objective functions are discussed; minimizing total throughput time for all projects: minimizing the time by which all projects are completed i.e., minimizing makespan; and minimizing total lateness or lateness penalty for all projects.

Anaerobic bacteria of the gastrointestinal flora and their occurrence in clinical infections.

Abstract: Within the last few years, knowledge concerning anaerobic bacteria of man and other monogastric animals has increased and changed a great deal. With the development of improved culture techniques for the cultivation of the more sensitive anaerobes, it has become possible to study more effectively the anaerobic flora of man and other animals. Studies carried out with these methods have shown that no area of the gastrointestinal tract is sterile, that the predominant kinds of bacteria in the different areas of the tract are not the same, that the bacteria in the tract are metabolically active, and that the same species of anaerobic bacteria are also found, rather frequently, in infected tissue.

Federalism: Problems of scale

Abstract: The modern explanation of Democratic government is based firmly on the theory of economic externalities. Individual choices in a situation in which externalities are important may lead to highly inefficient resource use. Government is one way, and frequently the most convenient way, to deal with this problem. This approach also gives a idea of the optimal size of the government or governments. It may be said that the governmental unit chosen to deal with any given activity should be large enough to "internalize" all of the externalities which that activity generates. It would appear that most students do not really aim at totally internalizing all external effects of the given action, but merely internalizing most of them, say 90 per cent. The reason that I am confident that this is so is that they almost never discuss local border effects. Any geographically delimited governmental unit must have a border, and if its function is to deal with an externality producing activity, then its actions just inside the border will normally produce an externality just outside the boundary. Thus total internalization would normally require boundaries which ran along some very impressive natural barrier. Such a minor matter as street-cleaning might require a continental or even world-wide governmental unit to totally internalize its effects.

Some Applications of the Singular Decomposition of a Matrix

Abstract: It is emphasized that the singular decomposition of a matrix has a variety of uses, especially in statistics, although it is seldom mentioned in books on either matrices or statistics. Some applications are surveyed and some new ones are given.

Optimal Redundancy for Reliability in Series Systems

Abstract: This paper considers the problem of determining the optimal number of redundant components in order to maximize the reliability of a series system subject to multiple resource restrictions. After formulating and solving an associated zero-one programming problem by a branch-and-bound procedure, the paper shows that the optimal solution to the associated problem is equivalent to the optimal solution for the optimal redundancy problem. Finally, the paper shows that this technique solves fairly large problems with multiple constraints without excessive storage-space requirements.

Classical and Inverse Regression Methods of Calibration in Extrapolation

Abstract: In an earlier paper (Krutchkoff, 1967) the Inverse Method of calibration is compared to the Classical Method by a Monte Carlo technique and found to have a uniformly smaller average squared error in the range of the controlled variable. This note presents some results obtained when using these procedures for extrapolation. Situations are shown to exist in extrapolation in which the Classical Method is superior to the Inverse Method.

Atomic movements in plagioclase feldspars: Kinetic interpretation

Abstract: The diffraction, n.q.r. and optical data on plagioclase feldspars are used to derive kinetic interpretations of structural changes induced by laboratory heat treatment and by geological processes. For anorthite, the Si, Al configuration is essentially ordered except for unusual transient processes. Cooperation between Ca atoms, and random nucleation, produces a domain texture in the primitive structure which is highly sensitive to temperature. The rapid inversion from the primitive to the body-centered structure is explained by increasingly rapid “rattling” of the Ca ions in the interstices of the semi-flexible alumino-silicate framework. The weakening of “b” reflections at higher temperatures is ascribed to incipient Si, Al disorder associated with irregular vibration of the alumino-silicate framework and the Ca atoms. Quenching phenomena are explained by variation of the domain boundary texture inherited from disorder at high temperature. For albite, the Si, Al configuration changes sluggishly from an ordered to a disordered pattern, and vice versa. Kinetic data are reinterpreted using a model in which the cell dimensions depend on local rather than distant order: the major change in distant order is deduced to occur at 450–600° C. Sodic plagioclase grown at high temperature shows distant disorder of the atoms, but cell dimensions suggest development of strong local order for calcic compositions. Low-entropy plagioclases of intermediate composition show complex intergrowths and domain structures because of kinetic barriers to atomic diffusion. X-ray diffraction data for slowly-cooled specimens are consistent with nucleation of albite- and anorthite-like regions from a high-temperature disordered phase. Electrostatic energy calculations show that Na and Ca atoms, although they face smaller energy barriers for diffusion, cannot form domains until the Si and Al atoms have moved jointly. The Si, Al ordering patterns of low albite and anorthite are topologically incompatible in a continuous framework if oxygen is not to be bonded to two Al. Therefore domains of low-albite and anorthite must be separated by disordered boundaries. For intermediate compositions, An15-An75, domains remain small. The anorthite-like domains probably form at higher temperatures than the albite-like domains. The latter tend to be about the same size for all bulk compositions. The atomic positions are influenced by neighboring atoms. Upon heating rapidly, Si and Al atoms remain in position and provide a memory for reformation of an identical structure upon cooling. The framework changes shape, and some Na, Ca atoms inter-diffuse to yield a quasi-homogeneous structure with a diffraction pattern which qualitatively approaches that of high albite. Upon prolonged heating at high temperature, Si, Al atoms inter-diffuse producing nonquenchable changes to the high-albite structure. At Na-rich bulk compositions, some domains of low albite grow into large lamellae while others remain small in contact with anorthite domains producing alternate lamellae of intermediate structure type; hence the peristerite intergrowth. A similar but opposite process could cause an intergrowth of lamellae of anorthite structure interposed with an intermediate type structure. A unique low plagioclase series is not expected. Plagioclases of intermediate composition trend towards slightly different endproducts depending on the details of the cooling history. Breaks and bends in plots of physical properties, and intergrowths for certain specimens, depend on special compositional, growth and annealing factors. The intergrowth responsible for iridescence of intermediate plagioclase is ascribed to Na, K segregation prior to development of the complex domain structure. Prolonged annealing at high temperature in a dry environment is suggested. It is futile to attempt to describe low entropy plagioclases in terms of classical thermodynamics: only a kinetic interpretation based on atomic and sub-microscopic textural factors can be viable.

Effect of Sublethal and Lethal Temperature on Plant Cells

Abstract: Soybean, Glycine max L., and elodea, Elodea canadensis Michx, leaves were exposed to sublethal and lethal temperatures and examined by light microscopy. Loss of chlorophyll and swollen chloroplasts were observed in cells of elodea leaves exposed to sublethal temperatures. At the thermal death point of leaf cells of elodea and soybean, there was a disorganization of the tonoplast membrane, plasmalemma, and chloroplast membranes. Approximately 40% of the cells in elodea and 50% of the cells in soybean leaves exhibited oriteria of cell death when exposed to a temperature which induced necrotic leaf tissue. Plasmolysis of leaf cells of elodea and soybean occurred at lethal temperatures, but did not appear to be the primary cause of cellular death. The primary effect of lethal temperatures on the leaf cells used in these experiments is disintegration of the cellular membranes.Following exposure of attached elodea leaves to lethal temperatures, changes in leaf cells were periodically observed with a light microscope. In low temperature treatments, (43 through 52 degrees ), the percentages of cells exhibiting criteria of death 12 days after treatment did not change from the percentages determined immediately after treatment. All treatments above 52 degrees resulted in 40% or more of the cells exhibiting criteria of cell death immediately after treatment. In these treatments, this resulted in all cells exhibiting criteria of death on the fourth day after treatment.

Potassium release from muscovite as influenced by particle size

Abstract: Completeness of exchange of K from muscovite by Ba 2+ ions decreased with particle size below 20/~. Accompanying K exchange at 120~ using a repeated batch technique, was a marked loss of Si and the formation of boehmite in the finer fractions. Several possible explanations for the unexpected high K retention of fine mica fractions are discussed. The formation of a diffusion-inhibiting surface "skin" is discounted, because equilibrium was obtained more rapidly with the fine fractions than with coarser fractions. The average degree of bending of unit mica layers due to peripheral expansion is probably greater in large particles. With bending, rotation of tetrahedra and shifting of adjacent layers with respect to each other may induce greater release of K and a lower selectivity for this ion. Fault planes may induce preferential expansion of individual layers and initiate interstrati- fication and splitting of particles. Splitting of particles may reduce bending and increase K selectivity.

Thermally induced solid state polycondensation of nylon 66, nylon 6‐10 and polyethylene terephthalate

Abstract: The mechanism of solid state polycondensation has been subjected to a fundamental analysis. Equations were formulated for combined diffusion and chemical reaction for two separate situations. One was for solid state polycondensation in polymer flakes or chips. The other dealt with polymer powders. The resultant solutions related molecular weight changes to rate functions. A technique for deriving the rate functions from experimental data is described. Solid state polycondensations were then studied for nylon 66, nylon 6-10, and polyethylene terephthalate. These data which ranged from 120 to 200°C. were tested with various mechanisms. The most appropriate one was found to be that developed in the present work. Chemical reaction was found to be the rate controlling step in solid state polycondensation in nylon 66, polyethylene terephthalate, powders of nylon 6-10 and larger particles of nylon 6-10 at and above 160°C. Diffusion of byproduct through the solid was the rate controlling step for larger particles of nylon 6-10 at temperatures below 160°C. Thermograms of nylon 6-10 indicated morphological changes which possibly influenced the behavior of the larger nylon 6-10 particles. The Arrhenius relation was fitted to the situations where chemical reaction controlled.

Lethality of Radio‐Frequency Energy upon Microorganisms in Liquid, Buffered, and Alcoholic Food Systems

Abstract: SUMMARY This work was done to determine if 60 mc/sec R-F energy has a selective killing effect on microorganisms other than that attributable to heat. The organisms studied were Saccharomyces cerevisiae, Escherichia coli, and Bacillus subtilis, An aqueous buffer medium was used to suspend the microorganisms for the irradiation treatments. No killing effect of the R-F energy per se on the organisms was observed at any of the various buffer pH values, nor was there an obsevable synergistic killing effect of R-F energy and heat on the microorganisms in any of the buffer. However, a synergistic killing effect of ethanol and heat at 48.8°C was demonstrated on S. cerevisiae. Irradiating S. cerevisiae and E. coli in several liquid foods also failed to show a selective killing effect of R-F energy.

Organizational Identification of Scientists

Abstract: The article presents a discussion of occupational sociology and reports on the growth and development in the field of study. Beginning in the 1930's, social psychologists began evaluating the way e...

Central efferent processes and autonomic‐behavioral integration

Abstract: Neurophysiological and psychophysiological studies have provided a substantial amount of data concerning the integration of autonomic and somatic responses. It is clear that this integration is primarily achieved within the central nervous system and that coordinated autonomic-behavioral activity is reflected, at the periphery, in the anticipatory and preparatory phases of movement. It is suggested that the central efferent organization of these preparatory responses is directly responsible for emotional experience. The demonstration that autonomic events are highly correlated with behavioral responses is regarded as providing further support for the view that the primary concern of the central nervous system is the production of adaptive behavior.

A Subjective Evaluation of Bode's Law and an ‘Objective’ Test for Approximate Numerical Rationality

Abstract: Bode's law has usually been evaluated subjectively by means of overall judgment and opinions differ regarding its significance. Here we analyze it in some detail, with use of the axioms of probability, but still subjectively. The subjective Bayes factor in favor of Bode's law's being not a mere accident is given as between about 300 and 700. More tentatively, the existence of Bode's law seems to provide a factor of about 20 in favor of a non-cataclysmic origin of the solar system and hence in favor of there being an extremely large number of planetary systems in the galaxy. These factors would I think be much increased by taking into account “Dabbler's Law,” which is concerned with the mean distances of the saturnine satellites. It is pointed out that Dabbler's law has had predictive value and can be used for a further prediction. An “objective” test is given for whether a number is “nearly rational”. The ratios of the sidereal periods of pairs of solar bodies, for a given primary, are found not ...

The crystal structures of the humite minerals: I. Norbergite

Abstract: The crystal structure of norbergite, MgrSi9r.MgFr a(OH)o z from Franklin, New Jersey (a:4.7rca(); b:10.2718(3); c:8.7a76$) A; Pbnm, para:3.177 g/cc) was refined by Ieast-squares techniques to R:0.052 using 867 intensities weighted by the range-estimate method (weighted R:0.024). The structure is based on a slightly distorted hexagonal close-packed array of anions with one-half the octahedral sites occupied by Mg and onetu,'elfth the tetrahedral sites occupied by Si. F is ordered in the array and bonded to three Mg; its temperature factor is twice that of four-coordinated O. Comparable bond lengths involving F and O indicate that the radius of li is -0.11 A smaller than that of O. As in forsterite, the dominant structural unit in norbergite is a zigzag chain of edgesharing octahedra lying parallel to z. A detaiied study of the structure in terms of bondangle strains shows that the distortions from an ideal hexagonal close-packed model can be explained qualitatively in terms of ca-tion-cation repulsion across shared polyhedral edges. The Si-O bond lengths (1.635, 1.638 A) opposite shared edges are significantly longer than that (1.612 A) opposite the unshared edges of the tetrahedron.

Petrology of clinopyroxene-amphibole inclusions from the roque nublo volcanics, gran canaria, canary islands. Petrology of roque nublo volcanics I

Abstract: Inclusions consisting of clinopyroxene, amphibole, Fe-Ti oxides and apatitc are abundant in the Roque Nublo volcanics, a unit of Late Tertiary age that is widespread on Gran Canaria Island. The unit includes alkalic basalts and breccias. Mafic minerals in several inclusions and in one basalt host have been analysed with the electron microprobe.

Glaciation on the Continental Margin off New England

Abstract: The Pleistocene glacial limit in the marine environment off New England can be traced by plotting the seaward limit of abundant sandy gravel and the position of shoals. Maximum limit of the last glaciation was probably along an irregular line extending through Nantucket Shoals, across Great South Channel, northern Georges Bank, and at least to the edge of the Scotian Shelf. If, as we assume, glaciers lowered sea level approximately 130 m, the ice margin was probably a subaerial one on Nantucket Shoals and Georges Bank, and it was bordered by outwash and meltwater channels leading away from the ice front. On the Scotian Shelf, the margin may have bordered directly on the ocean, to judge by the lack of shoals and the widespread dispersion of gravel out to the shelf edge. The glaciofluvial nature of the original deposits and marine reworking during the eustatic rise in sea level have made it difficult to recognize ice-contact deposits near the limit of maximum glacial advance. The gravel on shallow banks and ledges is in a bimodal mixture with sand. Association of coarse gravel and sand suggests postdepositional reworking of till by marine processes and removal of silt and clay. Gravel in the Gulf of Maine is mixed with sand, silt, and clay, a mixture characteristic of till.

An empirical Bayes smoothing technique

Abstract: In the empirical situation we assume that a random parameter ( occurs according to an unknown distribution G(O). We then observe the value of a random variable X according to a conditional distribution F(x I), where 0 is the unknown value of 0. We require an estimator for 0 which has small expected squared error. We assume further that this is a routinely reoccurring situation and that this is its nth occurrence. We can therefore base our estimate on the values of all n observations, xl, x2, ..., Xn. It should be emphasized here that we require an estimate of fn which is the parameter in the distribution of only the last observation. The empirical Bayes approach to the problem was introduced by Robbins (1955) and neatly summarized by Rutherford & Krutchkoff (1969). One obtains the Bayes estimator for the situation, the mean of the posterior distribution, in a form which does not contain the prior distribution explicitly. Generally, the form contains marginal density or mass functions which can be estimated using xj, x2, ..., xn. As was shown by Clemmer & Krutchkoff (1968), available estimators for density functions afford the empirical Bayes procedures excellent small sample properties. On the other hand, Maritz (1966) showed that for the discrete case the usual estimator for mass functions gives the empirical Bayes procedures poor small sample properties. He suggests smoothing the estimates for discrete probabilities. Here we present a simple general procedure for smoothing estimates of discrete probabilities and demonstrate its effect on the small sample properties of the empirical Bayes procedure for the Poisson situation.