bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.
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.
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.
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.
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.
Dynamic Method for Measuring the Pyroelectric Effect with Special Reference to Barium Titanate
Authors: Chynoweth A. G. 
Published: April 2005

A dynamic method has been developed for the study of the pyroelectric effect. Transient currents produced in single crystals of barium titanate when subjected to flashes of light are shown to be pyroelectric in origin. The illumination results in a small change in the temperature of the crystal which, in turn, causes the polarization to change. This change is recorded as a current in the external circuit. It is shown that from room temperature up to the Curie point, the pyroelectric current is consistent with the polarization as a function of temperature, as determined from hysteresis loop measurements. The technique proves to be a sensitive and nondestructive method for studying the state of polarization of a crystal.
The technique is used to study the pyroelectric effect induced by applied static electric fields at temperatures above the Curie point. The results are consistent with Devonshire's theory of the ferroelectricity of BaTiO3, and they confirm that the Curie point transition is of the first order.
Uses of Carbon Replicas in Electron Microscopy
Authors: Bradley D. E. 
Published: April 2005

Some of the early techniques for the preparation of carbon films and replicas for the electron microscope are compared with the method of vacuum evaporation developed by the author. The basic techniques for the production of replicas from evaporated carbon are described, and the high resolution obtainable is demonstrated and discussed. Some properties of evaporated carbon replicas are mentioned.
Descriptions are given of the carbon replica methods used in metallurgy and some applications are illustrated. Applications of carbon replicas in the following fields of research are also described: microbiology, biology, botany, entomology, chemistry, and industrial applications including the study of fibers.
It is concluded that evaporated carbon can be used as the final replica in any multistage replica process, and that it can be applied with advantage in almost every field of research in which the electron microscope is employed.
Vapor Pressure of Plastic Materials
Authors: Jensen Niels 
Published: April 2005

A method is presented of measuring the equivalent nitrogen vapor pressure of polymeric materials over a range of temperatures. It is found that, for the range of temperatures investigated (300–450°K), the vapor pressure-temperature characteristics of the polymeric materials studied are described by the empirical relation logP=A−B/T.
The values of the constants A and B in this equation are determined for a number of materials including nylon, Teflon, saran, polyethylene, and mylar.
Formative Time Lags in the Electric Breakdown of Liquid Hydrocarbons
Authors: Crowe R. W. 
Published: April 2005

Recent investigations of the time dependence of electrical breakdown in liquid hydrocarbons have led to a disagreement regarding the influence of molecular structure upon the formative time lag. This paper represents an attempt to resolve the discrepancy, and to determine if possible the significance of the time lag in the breakdown process. The experiments involve the application of rectangular pulses of voltage of variable duration and amplitude to the liquids between hemispherical electrodes.
The results of the investigation show definitely that the formative time lag is insensitive to changes in the molecular weight of the hydrocarbon liquid. Consequently, it cannot be associated with the time required for positive ions to cross the spark gap, as has been suggested by recent investigators. Its characteristic dependence upon the electrode separation, however, suggests that it may be mainly a measure of the transit time of an electron or an electron avalanche.
Space Charge Effects in Dense, Velocity-Modulated Electron Beams
Authors: Weinstein M. , Von Foerster H. M. 
Published: April 2005

By assuming the bunching process of electrons in the drift region of a klystron as being space periodic, rather than time periodic, it is possible to describe the debunching mechanism in a finite diameter beam on a large signal basis. It is shown that such beams have a discrete spectrum of oscillations with the plasma frequency as series limits. This makes it impossible to assign a unique bunching parameter to all electrons.
These results check with a velocity-phase analysis of high-density electron beams carried out with a beam analyzer at a frequency of 3000 Mc.
Hypo-Elastic Shear
Authors: Truesdell C. 
Published: April 2005

Part I reproduces the lecture given at the meeting of the Society of Rheology and furnishes a nonmathematical introduction to the theory of hypo-elasticity. Hypo-elasticity is a smooth, simple theory of elastic response based on time rates. For small strains it agrees with the classical linear theory of elasticity. To determine stress-strain relations for large deformation is a mathematical problem, the answer to which varies from one special case to another. Simple shear is taken as an example. Here it turns out that hypo-elastic materials may soften or stiffen in shear, depending on the value of a dimensionless constant which has no effect when the strain is small. For bodies which soften, a theoretical prediction of ``hypo-elastic yield'' is obtained.
Part II concerns a new special type of hypo-elastic body in some ways more general, in other ways more special than that considered in Part I. According to this theory, yield of the von Mises type appears to follow if the stress intensity is sufficiently great. The equations of this theory are solved for the case of simple shear. It is shown that if von Mises yield occurs, hypo-elastic yield must occur at a lesser stress. For large values of a certain parameter, von Mises yield is imaginary and only hypo-elastic yield occurs. For moderate values of the parameter, hypo-elastic yield appears as primary yield, with von Mises yield as secondary yield at infinite strain. For small values of the parameter, hypo-elastic yield and von Mises yield are indistinguishable, and the stress-strain curve is similar to the idealized forms assumed at the outset in the conventional Prandtl-Reuss theory.
Transient Behavior in a Ferroresonant Circuit
Authors: Skalnik J. G. 
Published: April 2005

Several physical systems are described approximately by Duffing's equation d2φdt2+adφdt+bφ+cφ3=Fcosω1t,where a, b, and c are constants of the system and F and ω1 are constants of the applied forcing function. This is a second-order nonlinear differential equation whose complete exact solution is unknown.
Approximate solutions for the steady-state behavior of the systems represented by the above equation are well known. The present work investigates the transient behavior in the region of the steady-state response. The theory developed is supported by solutions using an analog computer and by experiment with an actual electrical circuit whose behavior is approximated by the foregoing equation.
Theory of the Non-Newtonian Rheology of Raw Rubbers Consisting of Supermolecular Rheological Units
Authors: Mooney M. 
Published: April 2005

A theory of the viscosity of raw rubbers is developed on the postulate that raw rubbers, when subjected to continuous shear in the non-Newtonian region of flow, consist of microscopic rheological units which are semipermanent aggregates of many rubber molecules [M. Mooney and W. E. Wolstenholme, J. Appl. Phys. 25, 1098 (1954)]. The theory treats these units as tacky, elastic solids, whose relative movement and slippage constitute the macroscopic flow of the rubber. The resulting theoretical flow curve differs little from that given by H. M. Smallwood [J. Appl. Phys. 8, 505 (1937)], but the interpretation of the parameters is radically different. The new theory leads to expressions for the number of temporary point attachments per unit area between two touching rheological units and for the mean life of these attachments.
Agreement with experimental data is slightly better than in Smallwood. Two types of observed deviation from the theory can be interpreted as due to two plausible phenomena not included in the mathematical treatment.
Investigations on Barium Ferrite Magnets
Authors: Sixtus K. J. , Kronenberg K. J. , Tenzer R. K. 
Published: April 2005

Barium ferrite (BaO:6Fe2O3) has been investigated magnetically to test the predictions of fine particle theory in the region of grain sizes larger than the critical one for which no satisfactory theory exists as yet. Grain size and coercive force of polycrystalline magnets (nonoriented and crystal oriented) were closely related to sintering temperatures. A comparison of theoretical and observed temperature dependence of coercive force is made and shows a close fit when certain reasonable assumptions are made.
Susceptibilities showed values attributed to rotation of the magnetization vector for samples of high coercive force only (4000 oe), while wall movements contribute more or less to the susceptibility of all other samples.
Domain patterns show wall movements in applied fields on samples with particle thickness down to 10×10−4 cm. Patterns on grains below 5×10−4 cm thickness (IHC more than 2000 oe) indicate reversals of magnetization by the rotation process. On magnets of the transition particle size both processes can be observed side by side, the walls being less movable for higher coercive forces.
Monte Carlo Calculation of Noise Near the Potential Minimum of a High-Frequency Diode
Authors: Tien P. K. , Moshman J. 
Published: April 2005

Noise near the potential-minimum of a high-frequency diode has been calculated in this paper using a high speed electronic, digital computer. Random numbers were generated and used to simulate the emission of electrons at the cathode. Electrons emitted were continuously fed into the calculating process and those collected on the anode or returned to the cathode were automatically erased. In this way the electron motions computed by numerical integration followed the actual operation of a one-dimensional space-charge limited diode.
The results of this paper are based upon data obtained in the course of 3000 unit time intervals. In each case current and velocity fluctuations near the potential minimum were computed. This basic information permitted the calculation of the reduction in noise current caused by space-charge smoothing. The results were then applied for a calculation of the minimum noise figure for microwave beam-type amplifiers and show a sharp minimum of less than 2 db around 2500 Mc and a maximum of about 7.5 db near 4000 Mc. At very low frequencies the noise figure is small and agrees with existing low-frequency theories. At very high frequencies it approaches the figure corresponding to full shot noise, namely 6.3 db. Within the accuracy of calculation, correlation between current and velocity fluctuations has not been found nor the smoothing in velocity fluctuation.
Permeation of Gases through Solids
Authors: Norton Francis J. 
Published: April 2005

The permeation process consists of the steps: adsorption, solution, diffusion, and desorption. These are discussed for glasses, polymers, and metals. There are two generalizations: (1) All gases go through all polymers. (2) No rare gas permeates any metal. Criteria are given for measurements of the permeation process.
In glasses the permeation rate depends on atomic size and glass composition. Some special processes which may simulate permeation in vacuum devices are discussed: oxide dissociation, electrolysis in ceramic materials, nuclear reactions, and ionic impact.
Nuclear Magnetic Resonance Studies of Polyethylene
Authors: Rempel R. C. , Weaver H. E. , Sands R. H. , Miller R. L. 
Published: April 2005

Nuclear magnetic resonance (NMR) studies of three polyethylenes have been made over the temperature range −190°C to 120°C. Two components of the NMR line are observed—a narrow one identified with the ``amorphous'' regions and a broad one identified with the ``crystalline'' regions. Differences between polyethylenes in the shape of the narrow component are observed and discussed.
The variation of line width of the two components with temperature indicates two motional transitions occurring in the ``amorphous'' regions and one in the ``crystalline'' regions over the temperature range studied. Energies of activation inferred for one of the ``amorphous'' transitions agree well with those determined from melt viscosity studies implying a similarity of molecular processes controlling the two measurements and allowing an interpretation of the one observed by NMR to be made.
The NMR data are used to interpret (in terms of molecular motions) the three dispersion regions observed by dynamic mechanical measurements, with the following results: in the vicinity of −100°C, the amorphous regions undergo a transition involving mainly the onset of rotation of linear segments of the polymer chains. Between −35°C and 0°C (depending on the sample), the motion of amorphous chain segments containing branch points leads to a transition. In the neighborhood of 60–100°C (depending on the sample), there are the beginnings of observable motion of the chain segments within crystallites.
Using a new method of decomposing the NMR line into its two components (based on the experimental line shape at low temperatures), the relative intensities of the two components (hence, the relative amounts of fixed and moving nuclei) are determined. This ratio, previously held to be identical with the ``percentage crystallinity,'' is shown to be inconsistent with this view and to support the molecular interpretation presented.
Motion of an Arc in a Magnetic Field
Authors: Smith Charles G. 
Published: April 2005

A magnetic field transverse to an arc tends to move the cathode spot in either the direction of the electromagnetic force (the Amperian sense) or in the opposite direction (the retrograde sense). The theory of A. E. Robson and A. von Engle assumes that an arc, bent over in the Amperian direction forms a loop in which the magnetic field of the arc opposes the applied field to yield the retrograde motion. Calculations herein presented indicate that the arc field is too weak to uphold the theory. Retrograde motion proceeds continuously against a blast of vapor, while Amperian motion proceeds in the direction of the blast and is often discontinuous. These phenomena are recalled in giving an alternative explanation of the data.
Examination of the ``ball of fire'' discharge, which can display retrograde motion, shows the excitation phenomena in the region between dark and bright plasma yields information about retrograde motion. Studies of the corresponding dark space and negative glow of an arc and a better knowledge of electron liberation at the cathode give promise of yielding information about the retrograde motion.