Showing papers in "Journal of Applied Physics in 1936"
TL;DR: In this article, a method is described for studying the flow of gas-liquid mixtures through unconsolidated sands and a relation between permeability and liquid-saturation of the sand is found which permits the correlation of saturation and the steady state flow of the gas and liquid components.
Abstract: A method is described for studying the flow of gas‐liquid mixtures through unconsolidated sands. Results are given for experiments on four sands of widely different permeabilities using carbon dioxide and water as the fluids. A relation between permeability and liquid‐saturation of the sand is found which permits the correlation of saturation and the steady state flow of the gas and liquid components. Generalization of these results for all unconsolidated sands seems permissible. The phenomena of equilibrium permeability and equilibrium liquid‐saturation are described and their significance discussed. It is believed that the experimental attack and type of analysis is applicable to the general problem of the flow of gas‐liquid mixtures through porous media.
244 citations
TL;DR: In this paper, the thermal sensitivity of skin to radiation has been studied with a new technique and the temperature changes in the skin surface have been accurately measured, and the change in skin response of both whites and negroes to visible, infrared radiation and sunlight has been measured.
Abstract: The thermal sensitivity of skin to radiation has been studied with a new technique and the temperature changes in the skin surface have been accurately measured. The change in skin response of both whites and negroes to visible, infrared radiation, and sunlight has been measured. Results show that the sensation evoked by the radiations depends upon the optical properties of the skin. White subjects were found to be more sensitive to heat than negroes. The effect of the exposed area upon the sensitivity was observed. The postulate that the magnitude of the sensation depends upon two factors, nerve impulse frequency and central association, was found to fit the present data. A formula for calculating the degree of association is proposed. The results show that the sensitivity to radiation increases as the exposed area is increased up to the point where the stimulus has dropped to 0.0004 gram cal./sec.·cm2. A radiation weaker than this will evoke no sensation regardless of the size of the area exposed. This was taken to be the threshold of the excitation of an end organ. The temperature change in the skin surface with this radiation rate was measured to be a rise in temperature at the rate of 0.0008°C per second; sensation is perceived after 3 seconds of exposure. The relationship of the temperature change of the skin was studied. It was found that neither the change (ΔT) nor rate of change (ΔT/Δt) of skin temperature is adequate to explain the sensory effect. An hypothesis is proposed which attributes the sensation to a differential change in the temperature of the blood vessel net work within 0.1 mm of the skin surface and another at 0.3 mm.
19 citations
TL;DR: In this paper, an asphalt viscosity index is established which is defined by the relationship: A.V.I.=100(10a−1), where ''a'' is the slope of the log viscoity versus temperature plot.
Abstract: A review is given of the work which has been done on the temperature‐viscosity relations of bituminous materials and it is pointed out that the methods commonly used for evaluating the changes of consistency with temperature are empirical and unsatisfactory. Viscosity measurements at temperatures ranging from 15° to 35°C have been made on fourteen asphalts of paving consistency by means of the alternating stress method described by Bingham and Stephens. It has been found that for these asphalts and temperatures a plot of the logarithm of viscosity against temperature gives essentially a straight line. An asphalt viscosity index is established which is defined by the relationship: A.V.I.=100(10a−1), where ``a'' is the slope of the log viscosity versus temperature plot. To obtain numerical values for the A.V.I. it is only necessary to determine experimentally the viscosity at two temperatures (in the range where the straight line relation holds) and substitute in the expression: A.V.I.=100[(ηcηd)1/(tc−td)−1...
12 citations
TL;DR: In this paper, the behavior of resistance-capacity coupled amplifiers is studied with regard to their behavior as resonant networks and the optimum value of circuit constants and the design procedure developed.
Abstract: The behavior of resistance‐capacity coupled amplifiers is studied with regard to their behavior as resonant networks. Expressions are obtained for the optimum value of circuit constants and the design procedure developed. Tuning at one cycle per second has been successfully applied to low noise amplifiers.
10 citations
TL;DR: In this article, the thermal stress developed by unequal heating of a flat strip is investigated, the temperature varying along the length and through the thickness of the strip, but not across the width.
Abstract: The thermal stress developed by unequal heating of a flat strip is investigated, the temperature varying along the length and through the thickness, but not across the width. The problem is reduced to one of edge tractions only, for which general solutions are already known. From the properties of these solutions it is shown that for heating local to a narrow transverse band across the width, as might occur in welding processes, there is a concentration of stress near the edge of the strip, at the hottest part, and a maximum tensile stress of magnitude EαTmax., when the temperature is constant through the thickness. The corresponding quantity is found also for temperatures varying through the thickness. For steel EαTmax,= lim ··350Tmax, pounds per in.2, the temperature being measured in centigrade degrees above that of the cool parts of the strip, and this approaches the yield point of mild steel for a maximum temperature (rise) of the order of 150°C. For a given maximum temperature, the maximum stress is...
9 citations
TL;DR: The average life of the rubber bands was about 33 weeks as mentioned in this paper and no correlation was found between the magnitude of the load and the time that the specimen could bear its load, and the drift rate was proportional to the log of the time.
Abstract: Similar vulcanized rubber bands were subjected to four different tensions which produced immediate strains of approximately two to five times their original length. During the life of the bands this elongation was augmented an additional one to two hundred percent by the so‐called after‐strain or drift. Observations were taken at constant temperature. The average life of the bands was about 33 weeks. No correlation was found between the magnitude of the load and the time that the specimen could bear its load. Drift for all stresses continued to the breaking point. In all cases the initial time rate of drift was comparatively high. It declined with time to a positive minimum, passed through an inflection, and then steadily increased for the remaining life of the band. The inflection occurred after some weeks or months of drift. No correlation was found between the magnitude of the load and the time of inflection in the drift rate. During the interval between one and eighty minutes, the magnitude of the drift in at least one specimen was directly proportional to the log of the time. It then deviated from the log law and for three weeks closely followed a decreasing power law.
9 citations
TL;DR: In this paper, an oscillographic study of the short a.c. arc between pure graphite electrodes was conducted, and it was shown that the reignition potential is a linear function of the gas pressure for air, N2, O2, and CO2.
Abstract: The results of an oscillographic study of the short a.c. arc between pure graphite electrodes show that the reignition potential is a linear function of the gas pressure for air, N2, O2, and CO2. The relation is expressed by Vr=A+Bp. The constant A follows the minimum sparking potential of the gas, increases with the rate of rise of the impressed voltage, and is independent of the arc current, except for CO2. The constant B depends on the gas, arc current, and rate of rise of impressed voltage. The reignition potential is closely related to the glow discharge and is shown to approach the sparking potential of the gas as the r.m.s. value of the current approaches zero. The factors that affect reignition are indicated, and a reasonable mechanism of the phenomenon is stated.
9 citations
TL;DR: In this article, the authors measured the capacity frequency of a single cell under carefully controlled conditions for a period of about six months and found that the capacity is less subject to variations at the higher than the lower frequencies.
Abstract: In order to determine the relative effects of electrode condition, electrolyte and a number of physical parameters on electrolytic capacity, the capacity‐frequency characteristics of a single cell, kept under carefully controlled conditions, were measured for a period of about six months. Some conclusions to be drawn are: (1) While the magnitude of the capacity can be varied over a wide range by change in electrode condition, the general shape of the capacity frequency characteristic is determined mostly by the concentration of the active ion in the electrolyte. (2) The capacity can be decreased greatly by exposing the electrodes to catalytic poisons such as H2S and CO and can be subsequently increased by exposure to either electrolytic oxygen or hydrogen. These effects can be alternated. (3) The capacity is less subject to variations at the higher than the lower frequencies.
8 citations
TL;DR: In this article, a simple method of analyzing lightning photographs taken with moving film cameras is described, and the results of analysis of two air discharges with some interesting features and one very unusual type of discharge are presented.
Abstract: A simple method of analyzing lightning photographs taken with moving film cameras is described. The results of analysis of two air discharges with some interesting features and one very unusual type of discharge are presented. Certain discharges at the close of storms and the correlation of electrical and photographic measurements are discussed.
6 citations
TL;DR: In this paper, the theory of the heat losses from an electrically heated wire, as given by Roberts and Kannuluik, has been extended to include a wire supported by springs.
Abstract: The theory of the heat losses from an electrically heated wire, as given by Roberts and Kannuluik, has been extended to include a wire supported by springs. The results obtained have been used in a measurement of the thermal conductivity of commercial tungsten wire in the temperature range from 78°K to 273°K. There are definite indications that the Wiedemann‐Franz law breaks down badly in this region.
4 citations
TL;DR: In this article, a new apparatus was developed which permits the determination of jelly strength in terms of load versus compression, where the impression made in this manner within the gelatin specimen is compensated for by lifting it against the motion of a plunger with the aid of a calibrated micrometer screw.
Abstract: In view of the importance of simple and precise methods for the determination of jelly strength, a new apparatus has been developed which permits the determination of jelly strength in terms of load versus compression. Chain weight loading is used for the gradual application or reduction of weight. The impression made in this manner within the gelatin specimen is compensated for by lifting it against the motion of a plunger with the aid of a calibrated micrometer screw. In this manner, it is possible to determine the load versus compression characteristics to better than three significant figures. The preparation of the sample has been standardized in such a manner that jelly strength determinations can be carried out at room temperature. Samples of load versus penetration diagrams are given. Also, the formation of hysteresis loops is described. The introduction of the term, jell factor, is suggested (A = ½·breaking load·penetration (gram centimeters).
TL;DR: In this article, a method of arriving analytically at a pair of gear tooth curves which will fulfill certain prescribed conditions is presented, e.g., the mating curve for a circular pin tooth.
Abstract: This paper sets forth a method of arriving analytically at a pair of gear tooth curves which will fulfill certain prescribed conditions. The method may also be used to find a curve which will mesh with a given curve and produce a constant angular velocity ratio, e.g., the mating curve for a circular pin tooth.
TL;DR: In this article, a boundary value problem which may be applied to certain cases of heat transfer is worked out, and the solution is applied to the investigation of the lags occurring in a medium of finite thermal conductivity enclosed in an infinitely long cylindrical case of infinite thermal conductivities.
Abstract: A boundary value problem which may be applied to certain cases of heat transfer is worked out. The solution is applied to the investigation of the lags occurring in a medium of finite thermal conductivity enclosed in an infinitely long cylindrical case of infinite thermal conductivity when heat is introduced uniformly into the case, and when heat is evolved uniformly within the medium.
TL;DR: In this paper, the effects of variations in the size and shape of the obstacles on the stress concentration were investigated and an explanation offered for the stiffiening of rubber by pigments based on the change in slope of the rubber stress strain curve.
Abstract: The stresses around large obstacles in strained rubber were studied with the assumption that the effects would be similar with actual pigment particles. The effects of variations in the size and shape of the obstacles on the stress concentration were investigated and an explanation offered for the stiffiening of rubber by pigments based on the change in slope of the rubber stress strain curve. The various average diameters of a series of zinc oxide samples were measured and their relationship with some physical properties of rubber compounds determined.
TL;DR: In this article, the steady state concentration field was determined for cases of constant inflow over the surfaces of two external spheres, or two long parallel cylinders, both when the bodies were in an inactive environment, and when they were aligned with an external gradient.
Abstract: Some diffusion problems arising in biophysics are discussed for simple two‐body cases. The steady state concentration field is determined, by a method of images, for cases of constant inflow over the surfaces of two external spheres, or two long parallel cylinders; both when the bodies are in an inactive environment, and when they are aligned with an external gradient. As an application, there is calculated the resultant force on each body arising from a normal surface pressure proportional to the concentration. The numerical value of these forces is of the same order of magnitude as that approximately estimated previously by N. Rashevsky.3
TL;DR: In this article, the Rasch and Hinrichson equation was found valid for fresh samples over the range of temperatures used, but the presence of these layers caused distinct changes in the characteristics of this relationship.
Abstract: Some effects upon current‐voltage and temperature relationships as caused by the formation of ``impregnated'' layers in the vicinity of the electrodes are described. For ``unimpregnated'' samples, Ohm's law appeared to be valid. Upon ``impregnation'' various current‐voltage relationships from I=AVN to that of Poole were observed, the nature of the function apparently depending upon the characteristics of the layers produced. The Rasch and Hinrichson equation was found valid for fresh samples over the range of temperatures used, but the presence of these layers caused distinct changes in the characteristics of this relationship. The possible importance of such layers upon the electrical properties of glass and other insulating materials at the higher fields and temperatures and their possible effect in causing some of the apparent discrepancies in existing data is pointed out. The importance of much further detailed study of their properties is suggested.