bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermoelectric Power and Electrical Resistivity of Dilute Alloys of Silicon in Copper, Nickel, and Iron
Authors: Domenicali C. A. , Otter F. A.
Published: April 2005

Data are given on the thermoelectric power and on the resistivity of the dilute alloys, Cu–Si, Ni–Si, and Fe–Si, from −195° to +500°C (and higher for some of the alloys). The Cu–Si thermopower at first decreases with increasing Si content and then again increases, the minimum being at about 2 or 3 atomic percent Si, depending on the temperature. The Cu–Si resistivity is typical of Cu-base alloys, the resistivity increases per atomic percent Si changing from 7.2 μΩ cm at −190°C to 8.7 μΩ cm at 840°C. The thermopower and resistivity curves for Ni–Si show a characteristic knick at the Curie temperature of each alloy. The Fe–Si thermopowers are positive at lower temperatures and become negative at a temperature T0 which decreases with increasing Si content. Furthermore, T0 changes from about 300°C for pure iron to about +70°C for 2 atomic percent Si. The resistivity of Fe–Si alloys increases faster than linearly with temperature, and this is also the case for the Ni–Si alloys below the Curie temperature. Above the Curie temperature, the Ni–Si resistivities vary linearly with temperature. The increase in resistivity per atomic percent Si in Fe is 10.5 μΩ cm at all temperatures within the measured range.
Injected Current Carrier Transport in a Semi-Infinite Semiconductor and the Determination of Lifetimes and Surface Recombination Velocities
Authors: Van Roosbroeck W.
Published: April 2005

With both surface and volume recombination taken into account, time-dependent and steady-state Green's functions are obtained for a point source of added carriers in a semi-infinite semiconductor, and for infinite line and plane sources parallel to the surface. Small-signal theory is employed, and a compact Stieltjes-integral derivation is given. The Green's functions are specialized to provide: the time dependence of surface concentration following the instantaneous injection of carriers at a point on the surface; that following instantaneous injection which is uniform over the surface; and the distance dependences for steady point, infinite-line, semi-infinite plane, and semi-infinite line surface sources. Steady flows of minority carriers from these sources into a p—n junction perpendicular to the surface are also calculated. Analytical approximations are found for the steady-source cases. Theoretical and experimental aspects of the determination of lifetimes and surface recombination velocities from data by means of these results are discussed.
Moderation of Neutrons in SiO2 and CaCO3
Authors: Tittman Jay
Published: April 2005

The spatial distributions of indium resonance neutrons about a ``point'' Ra-Be source have been measured in pure CaCO3 (limestone) and SiO2 (sand) out to r2≈9τ. Both media show nearly Gaussian distributions corresponding to Fermi ages τ(SiO2)=1906±90 cm2 and τ(CaCO3)=461±23 cm2 over most of the range observed. Excess resonance flux near the source, more pronounced in CaCO3 than in SiO2, appears to be due to inelastic scattering although such interpretation is not unambiguous. Space integrals indicate ∼10 percent more absorption in CaCO3 than in SiO2 during moderation. Data were corrected for 4.5-hr activity, 54-min activation by high energy neutrons, and edge effects; consideration was given to the 3.9- and 9-ev In levels in defining the mean detection energy and to the nonmonoenergetic nature of the Ra-Be source in affecting the shape of the indium resonance spatial distribution.
X-Ray Diffraction Study of Silver Iodide Aerosols
Authors: Manson James E.
Published: April 2005

A source of silver iodide aerosols has been studied to determine the effect of the temperature of generation on the crystal structure of the particles in the aerosol output. Sampling was done by use of a novel thermal precipitator which gave samples in the proper form for direct analysis in a Debye-Scherrer x-ray diffraction camera. Patterns were obtained indicating the presence of both cubic and hexagonal modifications (ZnS and ZnO type). As the source temperature was raised, an increase of the proportion of hexagonal particles was observed, 95 percent hexagonal particles resulted when the source was operated at 800°C. An explanation of this behavior is proposed.
Measurement of Detonation Velocity by Doppler Effect at Three-Centimeter Wavelength
Authors: Cook Melvin A. , Doran Ray L. , Morris Glen J.
Published: April 2005

This article describes the application of the Doppler principle to the measurement of detonation velocity with three-centimeter electromagnetic radiation. The method makes use of the ionized wave front in detonation as a moving reflecting surface for electromagnetic waves. Detonation velocities for four different solid explosives were calculated from the observed Doppler frequencies and the indices of refraction, which were measured by a microwave interferometer. Complexities in the observed Doppler patterns come about because the cylindrical charges act as multimode dielectric wave guides.
Reflection of Sound in the Ocean from a Continuous Stratum Containing a Velocity Extremum
Authors: Cook E. O. , Heaps H. S.
Published: April 2005

The reflection of a plane wave of sound from a layer separating regions of different sound velocities, the layer itself containing a velocity variation through an extremum, is considered in terms of its dependence upon the angle of incidence, the layer thickness, and the velocity variation through the layer. It is found that the power reflection coefficient may differ significantly from its value for the corresponding abrupt or monotonic velocity transition. Numerical results are tabulated for various types of layers of thickness from zero to ten wavelengths and with a total velocity transition of ±5 and ±10 ft/sec.
Dependence of the Electric Strengths of Liquids on Electrode Spacing
Authors: Sharbaugh A. H. , Bragg J. K. , Crowe R. W.
Published: April 2005

Using a reproducible pulsed voltage technique, the electric strengths of liquid hexane, heptane, and tetradecane have been measured with small electrode spacings (approximately 2 to 200 microns). The electric strengths are found to change inversely with the logarithm of the separation in accord with theoretical expectation. On the basis of an approximate model of the breakdown process, the measurements on heptane yield values of 9×10−7 cm for the electron mean free path in the liquid and 9 for the number of multiplications per electron required for breakdown.
Barium Getters in Carbon Monoxide
Authors: Morrison J. , Zetterstrom R. B.
Published: April 2005

The effects of pressure, temperature, and physical state on the ability of a barium getter to sorb carbon monoxide are presented. At pressures in the 10−5-mm range, a five-milligram getter is exhausted in about one thousand hours. Temperatures ranging from room temperature to 150°C did not affect greatly the rate of gettering or the capacities of the getters. The observed gettering rates or capacities do not obey any simple law over an extended time.
Properties of Elastic and Plastic Waves Determined by Pin Contactors and Crystals
Authors: Minshall Stanley
Published: April 2005

Experimental techniques are described by which one can observe the separation of a shock wave in a metal into an elastic wave and a slower plastic wave. The plastic-wave velocity was about 15 percent less in steel and 10 percent less in tungsten than the elastic-wave velocity, at pressures imparted by Composition B explosive. Elastic-wave velocities were the same, within experimental error, as the measured sound velocities. The pressure in the elastic wave in SAE 1020 steel, deduced from the material and wave velocities, is independent of the plastic-wave pressure within experimental accuracy, and is about 12 kilobars. SAE 1040 steel, however, does not exhibit a single characteristic elastic-wave pressure. The pressure initially is about 6 kilobars, and increases to about 12 kilobars before the arrival of the plastic wave.
Note on the Kramers-Kronig Relations
Authors: Brachman Malcolm K.
Published: April 2005

The explicit form of the relationship between the real and imaginary parts of a physically realizable network function is correlated with the alternate conventions available for such problems. The transformation from a linear frequency scale to a logarithmic one is simply effected by considering the Mellin transforms of the appropriate functions.
Plasma Ion Oscillations in Electron Beams
Authors: Hernqvist K. G.
Published: April 2005

The frequency of the oscillations observed in ion-neutralized electron streams such as that of an ion-trapping gun or of a tetrode has been shown to agree well with the Langmuir-Tonks theory for plasma ion oscillations. The existence of a dipole mode of oscillation in addition to the longitudinal mode has been observed for a plasma column. A mechanism is proposed for the excitation of these self-sustained oscillations by which the secondary electron current from electrodes bounding the plasma is modulated by the vibration of the ions in such a way as to deliver energy to the ac field associated with the ion oscillations. Experimental observations verify this picture as far as the source of energy is concerned.
Propagation of Shock Waves in Aluminum
Authors: Mallory H. Dean
Published: April 2005

The velocity of shock waves in aluminum and the associated translational motions, produced by metal-metal impact, have been determined by an electrical contact technique. The results obtained have been used to evaluate an equation of state for the metal.
Multiple Coincidence Magnetic Storage Systems
Authors: Minnick Robert C. , Ashenhurst Robert L.
Published: April 2005

In existing magnetic matrix storage systems a given location is selected by applying to two intersecting wires a current equivalent to one-half of the selecting field. This situation is generalized so that any core is selected by energizing p wires each with a current equivalent to 1/p of the selecting field. The advantages gained are in the correspondingly smaller fields applied to the nonselected cores, or alternatively, in the faster switching times obtainable by applying a total field greater than the coercive force to the selected core. To obtain the increased selection ratio p—2, additional sets of wires must be introduced into the matrix. Methods for accomplishing this are developed with the aid of a system analogous to plane analytic geometry for a finite set of points. Utilizing the increased selection ratio new fabrication techniques may be employed. Specifically, a storage matrix is illustrated in which the cores are toroids etched from a continuous sheet of magnetic material.
Nucleation of Ammonium Iodide Crystals from Aqueous Solutions
Authors: Newkirk J. B. , Turnbull D.
Published: April 2005

Ammonium iodide crystals nucleate at a sensible rate in small drops (10–50 micron diameter) of solution only if the supersaturation ratio S equals or exceeds a value of 1.21. This critical supersaturation ratio corresponds to an interfacial energy σ between ammonium iodide crystals and solution equal to or greater than 15.4 ergs/cm2. However, for sensible nucleation of NH4I on a freshly cleaved surface of one of the mica minerals, S is related to the disregistry δ between atom sites on the mica surface and the atom sites on a {111} plane of NH4I. This dependence can be described by the equation lnS=3.8δ2+0.0059. This equation is in agreement with the theory of Turnbull and Vonnegut relating disregistry to the potency of nucleation catalysts. However, the coefficient of δ2 is about 1 to 2 orders of magnitude smaller than the theoretical expectation.

Our results are consistent with Bradley's hypothesis that S, for sensible 2-dimensional nucleation of NH4I on its own perfect {111} planes, is remarkably small, viz. S≃1.01.
Self-Propagating Intermittent Discharge
Authors: Boyle W. S.
Published: April 2005

When a constant current pulse is applied to a pair of electrodes at small separations in air a series of electrical discharges takes place. These are characterized by a fixed distance between successive discharges. The intermittent nature of the discharge is determined by the local circuit and the spatial distribution of a series of discharges results from the blast wave which is propagated from each discharge. Measurements of the propagation distance as a function of the time interval between discharges and the energy released in each discharge are in qualitative agreement with those predicted from the theory of an intense explosion. The voltage transients across the electrodes show that during a series of discharges the breakdown voltages remain substantially constant and equal to the minimum breakdown voltage in air. This is attributed to the fact that the discharge can always find a low-density region which is quite near the front of the blast wave where the conditions for minimum breakdown voltage can be satisfied.
Variation of Magnetoresistivity of AuCu with Degree of Order
Authors: Wiener Bernard , Schwed Philip , Groetzinger Gerhart
Published: April 2005

The room temperature resistivity and the magnetoresistivity of AuCu have been investigated as a function of the degree of order. Measurements were made first of all on samples quenched to room temperature after reaching equilibrium at temperatures below the Curie point. In addition measurements were made on samples which were first disordered by quenching from a temperature above the Curie point, were then annealed for various lengths of time at 265°C, and were finally quenched to room temperature. The coefficient of magnetoresistivity equals 1.8×10−12 and 6×10−14 gauss−2, respectively, for the completely ordered and completely disordered alloy. The equilibrium curve for the magnetoresistivity shows a minimum at 365°C and a pronounced maximum at 388°C which is close to the transition temperature for the phase change of AuCu I to AuCu II. No such extremes in the value of the coefficient of magnetoresistivity occur during the annealing of a thermally disordered sample.
Equivalent-Radius Method for Determination of Non-Newtonian Flow Curves from Viscometric Data
Authors: Cram K. H. , Whitwell J. C.
Published: April 2005

A rapid and precise method is presented for approximating absolute flow curves (shear rate vs shear stress) of non-Newtonian liquids from data obtained with rotational or capillary viscometers. It is shown that the apparent Newtonian flow curve computed from a single measurement (i.e., a single flow rate) in either type of viscometer crosses the true flow curve at a shear stress corresponding to some intermediate radius between the bob and cup radii or less than the capillary radius. If shear rate and stress are computed at the common point using the ordinary Newtonian relations for shear stress and shear rate, the point so calculated will lie on the absolute flow curve. An ``equivalent radius'' rather than a wall radius is used in the conventional Newtonian equations.

The position of the equivalent radius is fairly insensitive to changes in the form of the flow curve, particularly in the case of the rotational viscometer. A method for determining the proper intermediate radius is developed and graphs are presented to facilitate this determination and permit estimation of the accuracy of the method. An example is given using data from the literature [I. M. Krieger and S. H. Maron, J. Appl. Phys. 25, 72 (1954)] for a 62.2 percent GR-S Latex slurry. Within the range of the data (slope of the log-log flow curve varying from 1.5 to 3.0), the maximum error incurred by use of a single equivalent radius for each of two rotational viscometers was 0.1 percent for the instrument with a cup/bob radius ratio of 1.064, and 0.4 percent for the instrument with a ratio of 1.113. Accuracy can be increased by use of an iterative procedure.

The method has been developed in detail only for the case of pseudo-plastic flow, but the principle can be applied to other types of flow.
Wide-Angle Radiation in Pencil Beam Antennas
Authors: Carter David
Published: April 2005

This paper is concerned with theoretical estimates of wide-angle radiation in pencil beam antennas. In reflector-type antennas this energy consists of direct radiation from the feed and scattered energy from the reflector. Approximate methods for the evaluation of these contributions are discussed, together with their simplifying assumptions. To get some numerical indications, calculations were made for paraboloidal reflectors of different f/D ratios and a class of primary patterns which provide an approximate representation of a great many common feeds. The results are presented in graphical form to provide useful design information. They show the dependence of the wide-angle radiation level on feed and dish parameters.
Effect of Reactor Irradiation on the White-to-Grey Tin Transformation
Authors: Fleeman Jerome , Dienes G. J.
Published: April 2005

The effect of low-temperature (liquid nitrogen) reactor irradiation on the white-to-grey tin transformation has been investigated. It was found that, compared to an unirradiated pure sample, the transformation, measured by dilatometry, is drastically accelerated by prior irradiation. The irradiation apparently eliminates the normally very long induction period. The kinetic behavior of reactor irradiated samples and of samples seeded with grey tin were found to be qualitatively similar. These results indicate that the defects introduced into white tin by reactor irradiation serve as nuclei, or at least embryos of nucleation, for the subsequent phase transformation. Whether point defects, their aggregates, or the strains surrounding the displaced atoms are responsible for the artificial ``seeding'' cannot yet be decided. Reactor irradiation appears to be a promising new tool for studying nucleation and growth processes since quite uniform artificial nucleation can be accomplished this way.
Theoretical and Experimental Study of Electromagnetic Scattering by Two Identical Conducting Cylinders
Authors: Row R. V.
Published: April 2005

The scattering of a cylindrical TEM wave by two parallel, identical conducting circular cylinders is developed as a special case of a theoretical analysis which treats the scattering by an arbitrary array of cylinders. Only the case with the incident E-vector parallel to the axes of the cylinders is considered, and attention is focused on the mutual effects present when the cylinder diameter and spacing are comparable to a wavelength.

The approximations made in the theory are tested experimentally using 3 cm microwaves in a parallel plate region. Significant departures from the results of the independent scattering hypothesis as predicted by the theory have been confirmed experimentally.
Trajectory-Tracer Study of Helix- and Band-Type Postdeflection Acceleration
Authors: Sponsler George C.
Published: April 2005

A high-speed automatic electron-trajectory tracer was employed to study the relative loss in deflection sensitivity and linearity caused by continuous resistive helical and conventional band-type cathode-ray tube postdeflection accelerators. A total of 144 trajectories was traced for six different electrode configurations immersed in a wedge-type electrolytic tank that simulated a particular tube envelope. Beam-deflection angles of 5.5°, 13.5°, 21.5°, and 30° were employed with maximum potential differences of 0, 2.3, 4.8, 7.3, 9.8, and 12.3-kv postdeflection acceleration and a 2.7-kv initial electron energy. The relative error of the resultant trajectories plotted is estimated at one percent. Of the configurations tested, the performance of the continuous resistive helix was far superior in deflection sensitivity and slightly better in deflection linearity. The results also indicate that a linear, stepped voltage distribution [(V0/N)·n], although poorer than the continuous-helix distribution, may give better performance than that resulting from a stepped, geometrical voltage distribution (V0, V0/2, V0/4, etc.).
Performance of the Nonmagnetic Radio-Frequency Mass Spectrometer Tube
Authors: Wherry T. C. , Karasek F. W.
Published: April 2005

The nonmagnetic radio-frequency principle of mass selection appears attractive because it promises to result in a mass spectrometer of simple construction and rugged nature. Accurate evaluation of the use of this principle is difficult because of the lack of published performance data. In an effort to obtain performance data a 5-stage Bennett-type tube with stage separation of 5–9-4–7 cycles has been constructed and operational variables studied theoretically and experimentally.

The experimental results are encouraging. They indicate the tube is capable of sufficient stability, resolving power, and sensitivity to be used for many analytical and research problems. Electronic circuits required to achieve a reasonable stability are relatively simple.
Silicon n-p-n Grown Junction Transistors
Authors: Tanenbaum M. , Valdes L. B. , Buehler E. , Hannay N. B.
Published: April 2005

Silicon n-p-n junction transistors have been made from rate-grown single crystals. Using gallium and antimony as doping agents, single crystals of n-type silicon have been grown containing up to five p-regions from 0.0005 to 0.002 inches wide which are suitable for the production of transistors. The ohmic contact to the p-type base region was made by alloying an aluminum wire using techniques similar to those employed in the fabrication of aluminum-silicon diodes.

The electrical evaluation of n-p-n transistors produced from these single crystals is described. Alphas in excess of 0.9 at −1 ma emitter current have been obtained, and collector saturation currents of 10−6ampere/cm2 are common. With base-layer widths of about 0.0005 inch, the alpha cutoff occurs at approximately 5 megacycles. The units (approximately 0.04×0.04×0.5 inches in size) have been operated at power levels in excess of 1.5 watts in air with no special provision for heat dissipation.
Magnetic Materials for Digital Computer Components. II. Magnetic Characteristics of Ultra-Thin Molybdenum-Permalloy Cores
Authors: Menyuk Norman
Published: April 2005

Measurements of the flux-reversal time τ as a function of the applied magnetic field H have been made for ⅛-mil, ¼-mil, ½-mil, and 1-mil 4–79 molybdenum-Permalloy tape cores. There measurements have been taken at seven temperatures, ranging from −196°C to 270°C. From these measurements, the switching coefficient Sw=(H−H0)τ is found, where H0 is the threshold field value for irreversible domain-wall motion. Determination of the switching coefficient as the tape thickness is varied permits a separation of the spin-relaxation and eddy-current contributions to switching delay. These contributions are studied individually as functions of temperature. Upon increasing the temperature over the range considered, the eddy-current contribution and the threshold field value H0 are approximately halved, and the spin-relaxation contribution is reduced by 20 percent. All these factors lead to a faster flux reversal at higher temperature for a given applied field. This behavior is in agreement with theoretical predictions.
Energy Relations in Cold Working an Alloy at 78°K and at Room Temperature
Authors: Leach J. S. L. , Loewen E. G. , Bever M. B.
Published: April 2005

The energy relations associated with the plastic deformation by cold working of a 75 percent gold—25 percent silver alloy at two temperatures were investigated. The samples were produced by drilling under controlled conditions, which is a suitable method of deformation. The energy stored in the chips was measured by tin solution calorimetry and the total energy expended in the deformation was determined from dynamometer measurements.

The results for cutting with a drill having the most suitable geometry were as follows. The energy stored at room temperature was 0.50 cal/g and the corresponding value for 78°K was 1.48 cal/g. The values of the total energy of deformation were 53.5 cal/g at room temperature and 109 cal/g at 78°K. The true stress-true strain curve at room temperature was normal for a nonferrous metal and the curve for 78°K showed the behavior expected at low temperature from a face-centered cubic metal.
Work Function of Tungsten Single Crystal Planes Measured by the Field Emission Microscope
Authors: Müller Erwin W.
Published: April 2005

The work functions of the low emitting crystallographic planes of tungsten, (011) and (112), are not well known. In previous experiments scattered secondaries and some other disturbing effects covered the small emission particularly of the (011) plane. A method combining the field emission microscope with a probe collector has been applied. The current density in the (011) plane turned out to be 4 to 5 orders of magnitude smaller than in strongly emitting planes. Applying the Fowler-Nordheim theory, φ011 was found between 5.70 and 5.99 ev and φ112 between 4.65 and 4.88 ev depending on the temperature at which the tungsten crystal has been annealed previously. This is not a temperature effect of the work function, but the result of freezing in thermal imperfections of the planes. The work function of the ideal (011) plane appears to be as high as 5.99 ev. The existence of such a high value is further suggested by the ionization of aluminum on a hot polycrystalline tungsten wire, indicating that a part of the surface has a work function as high as the 5.96 ev ionization energy of aluminum.
Thermionic Emission Microscopy of Metals. Part I. General
Authors: Heidenreich R. D.
Published: April 2005

An electrostatic emission microscope operating with an accelerating voltage of 10–25 kv is briefly described. Factors determining image quality, particularly contrast and resolution, are discussed and the interpretation of images on the basis of the Schottky emission equation is considered. The instrument can be operated at magnifications of 250, 1000, 2500, and 4000× with a resolution consistently better than 1000 A.

It has been found that the iron group metals can be activated easily using barium formate rather than evaporated Ba or Sr. The level of thermionic emission from such surfaces is determined primarily by the partial pressure of chemical reducing agent at the surface (such as carbon) to reduce BaO to free barium. The effect of various impurities and alloying metals is discussed from the standpoint of interpretation of emission images. The most important single agent for promoting emission from Ni, Cu, and Fe, etc., is carbon.

Examples of emission images include nickel, stainless steel, and plain carbon steel. Complications such as surface roughness are demonstrated with micrographs and the limitations of the technique pointed out.
Theory of Non-Newtonian Flow. I. Solid Plastic System
Authors: Ree Taikyue , Eyring Henry
Published: April 2005

The relaxation process of viscous flow may be visualized as the sudden shifting of some small patch on one side of a shear surface with respect to the neighboring material on the other side of the shear surface. Any shear surface will divide a mosaic of such patches lying on the two sides of the surface. Except for the simplest systems, this mosaic of patches will be heterogeneous and can be described by groups each characterized by its mean relaxation time βn, by xn the fractional area of the shear surface which the group occupies and by αn, a characteristic shear volume divided by kT. The resulting generalized expression for viscosity is η= ∑ n=1nxnβnαnsinh−1βnṡβnṡ,where ṡ is the rate of shear. This equation is applied to masticated natural rubber, polystyrene, X-672 GR-S, X-518 GR-S rubber, and Vistanex LM-S polyisobutylene. All applications give good agreement with experiment. The known criticisms of Eyring's simple relaxation theory for viscous flow are reviewed, and are apparently taken care of in this general treatment.
Application of the Superposition Principle and Theories of Mechanical Equation of State, Strain, and Time Hardening to Creep of Plastics under Changing Loads
Authors: Findley William N. , Khosla Gautam
Published: April 2005

The superposition principle and the theories of mechanical equation of state, strain, and time hardening were applied to the creep under changing loads of four unfilled thermoplastics—polyethylene; monochlorotrifluoroethylene (Kel-F), crystalline; polyvinylchloride (Geon-404), annealed; and polystyrene.

A comparison of the theoretical results predicted by these theories with the experimental results indicated the accuracy with which these theories described the creep behavior under changing loads for the above materials.
Diffusion Controlled Stress Relaxation
Authors: McMickle R. H. , Kubu E. T.
Published: April 2005

The action of water solutions of dimethyl formamide on Dinitrile A fibers was studied using the stress-relaxation technique. After prior conditioning and stress relaxation in water, the addition of dimethyl formamide-water solutions produced an exponential stress relaxation. It was found that the rate and extent of stress relaxation in dimethyl formamide-water solutions is dependent on the dimethyl formamide concentration. The rate of stress relaxation in dimethyl formamide-water solutions is also dependent on the cross-sectional area and the state of orientation of the fiber. These data can best be explained by postulating that the rate of diffusion of the dimethyl formamide-water solution into the fiber controls the rate of stress relaxation. The diffusion coefficient is found to be concentration dependent, and the diffusion process has an activation energy of 14 kcal.
Viscosity and Elasticity of Oil Surfaces and Oil-Water Interfaces
Authors: Criddle D. W. , Meader A. L.
Published: April 2005

A study of the rheological properties of lubricating oils was made by means of semiquantitative measurements of the viscosity and elasticity of surface and interfacial films. A torsion-pendulum type, surface viscometer was used. A refined, uncompounded mineral oil was shown to possess neither surface nor interfacial viscosity or elasticity. One additive in mineral oil showed surface viscosity and elasticity, and two additives developed these properties at an oil-water interface. The aged, viscous surface and interfacial films studied were found to be non-Newtonian.
Contribution to the Study of Transport Phenomena in Gases at High Densities
Authors: Michels A. , Cox J. A. M. , Botzen A. , Friedman Abraham S.
Published: April 2005

The results of recent measurements of the viscosity and thermal conductivity of argon have shown the importance of studying these transport phenomena over a large density range in different regions of the reduced temperature. It appears that the Chapman-Enskog theory cannot give an adequate description of the new experiments. It has not yet been possible to give a full account of the observations. However, a less rigorous theoretical discussion demonstrates the relevant physical features of the problem. For the moment it serves to indicate a new experimental program. This research may contribute to a more clear understanding of the transport properties in different states of a material, including the difficult intermediate region between the gas and liquid state.
Elastic-Plastic Instability Caused by the Size Effect and Its Influence on Rubbing Wear
Authors: Hunt Frederick V.
Published: April 2005

The yield strength of many materials is much higher for minute specimens than for bulk samples. The region around the point of highest shear stress in a solid undergoing deformation by a small spherical indenter can be regarded as such a minute specimen which may be ``protected'' by the size effect against plastic yielding if it is small enough. Formulating the effective yield strength and the elastic stress under the indenter in terms of a common parameter provides a basis for assessing the influence of size scale on the plastic yield threshold. Four size categories are identified, including a critical case for which a small change of loading may cause a discontinuous transition from the elastic to the plastic regime throughout the region of contact, and another, more frequently encountered, in which the supportable pre-yield elastic stress is materially enhanced. The latter effect may exert an important influence on the rate of rubbing wear since it can make available a wider range of loading for which a low wear rate prevails. Reported wear tests on steel riders and on sapphire phonograph styli confirm these predictions qualitatively.
Specification of Thermally and Mechanically Induced Nonequilibrium States in AuCu by the Resistivity and Magnetoresistivity
Authors: Wiener Bernard , Groetzinger Gerhart , McCollum Rathuel
Published: April 2005

Studies were made of the change in the resistivity and magnetoresistivity of samples of AuCu, which had been thermally disordered, while annealed at 150°C, of samples, completely disordered by cold work, while annealed at 150°C and 265°C, and of initially ordered samples when subjected to varying amounts of cold work. The curves of magnetoresistivity against resistivity for the last three cases agree with one another, but differ from that for the thermally disordered sample annealed at 150°C and from a previously obtained curve for the annealing of a thermally disordered sample at 265°C. These last two curves are also markedly different from each other. All five curves appear distinct from the previously obtained curve for AuCu in equilibrium. An interpretation of the results in terms of the production of a more or less pronounced admixture of AuCu II during certain stages of the cold working or annealing process is presented.
Elastic Constants of Germanium between 1.7° and 80°K
Authors: Fine M. E.
Published: April 2005

The elastic constants of germanium (c11, c12, and c44) increase on cooling and approach constant values for very low temperatures.
Electron Microscopy of Monodisperse Latexes
Authors: Bradford E. B. , Vanderhoff J. W.
Published: April 2005

A series of monodisperse polystyrene latexes has been prepared by carefully controlled emulsion polymerizations. The particle diameters of three of these latexes were determined by electron microscopy. The latex particles were dispersed on collodion membranes supported by copper grids. The microscopes had previously been calibrated with collodion replicas of a 30 000 line/inch diffraction grating. In general, the reproducibility of measurements from many photographic exposures was good; however, a few exposures yielded particle diameters considerably higher than the averages.

An investigation of this technique indicated that: (1) polystyrene latex particle diameters (collodion membranes—copper grid supports) increased considerably on electron irradiation, (2) collodion diffraction grating replicas (copper grid supports) shrank slightly on electron irradiation, and (3) the magnification of the electron microscope varied slightly from exposure to exposure. It was found that variations of particle diameter resulting from the foregoing sources of error were negligible when the particles were dispersed directly on a silicon monoxide diffraction grating replica supported by a stainless steel grid.

The particle diameters of the latexes determined in this manner ranged from 880 to 11 720 A. Many photographic exposures of each latex were used for these measurements. The monodispersity of the latex particles is evident from the small values of the standard deviations of the over-all particle-size distributions. The reproducibility of particle diameters determined from different exposures is evident from the small values of the standard deviations of the means of the exposure averages.
Thermionic Emission Microscopy of Metals. II. Transformations in Plain Carbon Steels
Authors: Heidenreich R. D.
Published: April 2005

The direct observation of transformations in plain carbon steels at temperatures above about 625°C is demonstrated for both the A3 and A1 transformations.

It is concluded from emission studies of the decomposition of austenite below the A3 line that the transformation is of a diffusionless type rather than carbon diffusion controlled. It is shown that carbon is associated with ``memory'' in the austenite grain structure, the memory improving with increasing carbon content. The emission images also indicate that the growth of a ferrite grain in austenite induces a recrystallization of the surrounding austenite. A model to account for the memory is advanced based on thin sheets of retained austenite in newly transformed ferrite.

Studies of a 0.77 percent carbon steel below the A1 line illustrate the formation of pearlite. The images suggest that these decompositions take place in two distinct steps. The first is the formation of a metastable crystal which subsequently decomposes by carbon diffusion to the final ferrite-carbide products. Austenite recrystallization about a growing pearlite nodule is demonstrated. A model for the transformation based on a diffusionless type reaction followed by a diffusion decomposition is suggested to explain the emission images.
Condition of High-Velocity Ductile Fracture
Authors: Orowan E.
Published: April 2005

The Griffith energy criterion, dW = −dU (dW = crack propagation work, −dU = released elastic energy), cannot be applied to essentially ductile fractures. In particular, it does not represent the condition of rapid ductile fracture propelled by the elastic energy of the specimen. The condition of such fractures is d2W/dx2=−d2U/dx2 where x is the plastic extension accompanying the propagation of the crack.
Slowing Down Distribution of U235 Fission Neutrons from a Point Source in Light Water
Authors: Hill J. E. , Roberts L. D. , Fitch T. E.
Published: April 2005

The results of a measurement of the slowing down distribution in water of neutrons from a point fission source to indium resonance energy, 1.458 ev, are given. The second, fourth, sixth, and eighth moments of the measured distribution are calculated and have the values, r̄2=184.7 cm2, r̄4=1.222×105 cm4, r̄6=2.27×108 cm6, and r̄8=8.6×1011 cm8.
Slowing Down Distribution to Indium Resonance of U235 Fission Neutrons from a Point Fission Source in Two Aluminum Light Water Mixtures
Authors: Roberts L. D. , Hill J. E. , Fitch T. E.
Published: April 2005

The mean square slowing down length, r̄2, has been measured for two aluminum light water mixtures, the aluminum-to-water volume ratios being 1:1 and 1:2 by volume. The values of r̄2 obtained are 460.7 cm2 and 297.4 cm2, respectively.
Radiation Induced Changes in the Electrical Resistivity of α Brass
Authors: Rosenblatt D. B. , Smoluchowski R. , Dienes G. J.
Published: April 2005

Nucleon irradiation of metallic solid solutions may lower their resistivity by changing the degree of randomness (tendency to order or to cluster) or by a change of elastic moduli. Measurements of resistivity of brasses containing 10, 20, and 30% zinc have been performed at room temperature, at 80°K and at 4°K. The alloys were irradiated in a reactor at +50°C and at 80°K. It appears that the results can be best interpreted in terms of the formation of lattice defects upon low temperature exposure and increase of short-range order upon irradiation at +50°C. The change of residual resistivity is negative while the change of resistivity due to thermal scattering is positive for the samples irradiated at +50°C. The former depends upon irradiation flux and upon annealing time in a different manner from the latter. Short-range order appears to be produced also by proper heat treatment.
Tracer Diffusion of Iron in Stainless Steel
Authors: Linnenbom V. , Tetenbaum M. , Cheek C.
Published: April 2005

The tracer diffusion of iron in 18−8 stainless steel has been measured over a wide temperature range by the surface activity decrease method, using radioactive Fe55. The results show that the lattice diffusion coefficients can be described by the equation D=0.58 exp(−67 100/RT) cm2 sec−1. The effect of variations in grain size has been determined, and it has been shown that when the grain size is small, grain boundary diffusion contributes appreciably to the over-all diffusion process, this effect decreasing with increasing temperature.
Forward Characteristic of Germanium Point Contact Rectifiers
Authors: Cutler Melvin
Published: April 2005

A quantitative discussion of the forward characteristic is given for point contact rectifiers. It shows that the theoretical value of d lnI/dV in the exponential region is nearly q/kT, and that the experimental slopes which are a fraction of this value cannot be the result of the spreading voltage. Recombination of injected carriers has little effect except at large currents beyond the exponential region. Relations are derived for the limit of very large currents, which show that γ approaches a value smaller than (1+b)−1, the hole concentration at the contact approaches a maximum value proportional to the equilibrium concentration of holes at the surface, and the spreading voltage becomes a linear function of the current.
Preparation of Thin Magnetic Films and Their Properties
Authors: Blois M. S.
Published: April 2005

Techniques for the preparation by vacuum evaporation of single thin layers and laminated structures of ferromagnetic alloys (principally in the iron-nickel system) are described. The magnetic properties are related to those parameters of the process which may be chosen to yield materials having desired characteristics. A method for producing films with extreme hysteresis loop rectangularity is described. Questions of suitable substrate materials, evaporable dielectrics for use in insulating multilayer deposits, and control of alloy composition, are considered in detail.
Retraction of Oriented Polystyrene Monofilaments
Authors: Andrews R. D.
Published: April 2005

When oriented polystyrene monofilaments are heated to temperatures in the neighborhood of the transition temperature they retract to an unoriented state at conveniently measurable rates. Curves of length as a function of time have been measured at five different temperatures (75°–95°C, at 5° intervals) for two filaments with different initial amounts of orientation.

When the retraction curves are plotted as length vs log time, it is found that the curves at different temperatures are not superposable by lateral shift along the logarithmic time scale, as would be true for simple viscoelastic behavior. Activation energies calculated from these curves are a function of time as well as of temperature; the activation energy at any given temperature tends to level out to a final constant value with increasing time, however. The rate of change of activation energy with time increases with increasing temperature, so that the final value is attained more quickly; the final value also decreases systematically with increasing temperature.

Final activation energy values increase rapidly with decreasing temperature in this region and are very high (300 kcal at 75°). It is postulated that specific volume changes are responsible for the time-dependent activation energies observed in these experiments. It is also of interest that these experiments appear to isolate the viscoelastic mechanism involving molecular configuration change from that involving local molecular distortions.
Extension of the Hertz Theory of Impact to the Viscoelastic Case
Authors: Pao Yoh-Han
Published: April 2005

The problem considered is that of two bodies coming into normal contact over smooth curved surfaces. The initial relative velocity and the total kinetic energy involved is low. Contact is, however, confined to such small volumes of the objects involved that very high concentrations of energies are obtained at those places. The rates of application of stress are correspondingly high. The Hertz solution to this type of problem provides a useful approximation in the case of elastic objects.

In the present treatment one of the impinging bodies is of viscoelastic material. Two viscoelastic bodies may also be treated if they are of the same material. The Laplace transform method is used to obtain the viscoelastic expression for the force developed between the two surfaces. This expression is then applied to the impact case. The expression can also be applied to other truly static cases; e.g., contact between gear tooth surfaces.

The results are of technological interest, since it is not possible to say if a plastic is suitable for a certain category of impact applications, unless the rates of straining or stressing obtained in those applications can be estimated.
Glass Transitions in Polymer-Plasticizer Systems
Authors: Breitman L.
Published: April 2005

Glass temperatures (Tg) of pure and plasticized elastomers have been obtained from dilatometric measurements and from the temperature dependence of angular response to torsional stress. The depression of Tg by a diluent, determined by either method, is a convenient measure of its plasticizing ability. Some compounds which are normally crystalline above Tg of the pure polymer, but nevertheless compatible with the polymer, depressed the glass temperature. The polymer-diluent compatibility at low temperatures results either from supercooling, the depression of the melting point of diluent by polymer, or possibly a combination of both phenomena. Tg decreased as the diluent loading increased to a more or less well defined limit, beyond which further dilution had negligible effect. For diester type plasticizers both ΔTgmax and the limiting diluent concentration were linear functions of compatibility, as defined by the extent to which standard polymer vulcanizates were swollen by plasticizer. The viscosities and apparent activation energies for flow (Ev) of hydrocarbon oils correlated with their low temperature plasticizing efficiencies. Pour points and glass temperatures may also be significant properties of the diluents. It is concluded that low Ev and high solvency for polymer are desirable properties for low temperature plasticizers.
Proton Magnetic Resonance in Polyamides
Authors: Slichter W. P.
Published: April 2005

The proton magnetic resonance absorption has been observed in several linear polyamides from 77°K to 400°K. The absorption line narrows gradually with increasing temperature up to about 280°K. A marked decrease in line width with increasing temperature occurs over a span of 20 or 30 degrees within the range of 280 to 400°K, and is presumed to result from the onset of rotation of chain segments. In a series of polyamides possessing an even number of carbon atoms between polar groups, this transition occurs at a lower temperature as the hydrocarbon portions are made longer (polydecamethylene octadecanediamide compared to polyhexamethylene adipamide). In the copolymer polyhexamethylene adipamide-sebacamide, the transition region is at a lower temperature than in the pure adipamide or pure sebacamide. The x-ray diffraction studies on polyamide fibers show that the chain packing becomes more symmetrical over these same temperatures. The resonance results are interpreted in terms of simple models.
A Semiempirical Expression for the First Townsend Coefficient of Molecular Gases
Authors: Crowe R. W. , Bragg J. K. , Devins J. C.
Published: April 2005

The general utility of an approximate expression for the first Townsend coefficient of a gas, derived several years ago by Druyvesteyn and Penning, has been tested by introducing into the theoretical treatment somewhat more realistic assumptions regarding the relevant scattering cross sections of the gas molecule. It has been demonstrated by numerical calculations that the functional dependence of the Townsend α upon the electric field and the gas pressure is, within certain limits, insensitive to the assumed energy dependence of the elastic and inelastic cross sections. The functional form of the inelastic cross section does, however, influence the way in which the ionization energy of the gas molecule enters in the exponential part of the expression.