bluuebunny/crossref_metadata_2025_split huggingface dataset:
Small Particle X-Ray Scattering by Fibers, Size and Shape of Microcrystallites
Authors: Heyn A. N. J. 
Published: April 2005

A theoretical and experimental analysis is given of small particle x-ray scattering by fibers.
The scattering by different fibers of high orientation is compared with the theoretical scattering curves derived for independent scattering by an assemblage of parallel cylinders. Under certain conditions of swelling, excellent agreement is obtained between experimental and theoretical curves. From this agreement it is concluded that under these conditions, independent particle scattering is realized and that interparticle interference and multiple scattering do not play a part.
Under all other conditions (dry fiber and other conditions of swelling) interparticle interference plays an important role in the scattering by these ``densely packed'' materials as can be concluded from the different distributions of intensity. The swelling method offers a means for separating independent and nonindependent scattering.
An analysis of the influence of various conditions of swelling is made, and the correct experimental conditions for obtaining independent scattering are derived from the results.
From the scattering under such conditions, the particle size in different fibers is determined on the basis of the theoretical formulas for independent scattering.
Viscoelasticity of Poly Methacrylates
Authors: Bueche F. 
Published: April 2005

This paper presents an intensive study of the viscous and elastic properties of the poly methacrylates. Variation of these properties is studied as a function of temperature in the range 60&lt;T&lt;160°C, as a function of molecular weight in the range 5×103&lt;M&lt;5×106, and as a function of plasticizer concentration over the range 0–100 percent. Capillary viscometers were used in the low-viscosity systems and tensile creep and recovery measurements under very small loads were used to study the less fluid systems. Principal effort was confined to polymethyl methacrylate but enough work was done using the butyl and decyl esters to show that the whole series of these polymers fits into a relatively simple picture. Consequently, given a certain minimum amount of data, it is now possible to predict the viscoelastic behavior of these polymers in the range of variables given above.
The theory of viscoelasticity previously given has been extended so as to take account of the effects of chain entanglements and distributions in molecular weight. Moderately good agreement is found between theory and experiment.
Vibroscope Measurements of the Elastic Moduli of Nylon 66 and Dacron Filaments of Various Draw Ratios
Authors: Wakelin J. H. , Voong E. T. L. , Montgomery D. J. , Dusenbury J. H. 
Published: April 2005

By use of the electrostatic vibroscope method, dynamic measurements have been made of the Young's modulus derived from bending and the torsional modulus of nylon 66 and Dacron filaments ranging in draw ratio from one (undrawn) to six. Quasistatic measurements have also been made to obtain the Young's modulus derived from extension. The dynamic values of the Young's modulus increase from draw ratio one to draw ratio six by a factor of 3.5 for nylon 66 and 5.8 for Dacron. The torsional moduli of both filament types exhibit no appreciable changes with increasing draw ratio.
The ratio of the Young's modulus to three times the torsional modulus, which ratio is unity for a homogeneous isotropic material with a Poisson's ratio of ½, is about three for nylon 66 and greater than five for Dacron at a draw ratio of six. These results, along with those obtained at lower draw ratios, indicate that both filaments become progressively anisotropic with drawing, the extent of the anisotropy reflecting mainly the changes in the Young's modulus. As a check on the experimental procedures, the elastic moduli have also been measured for a 1-mil drawn tungsten wire.
A Rheological Equation of State which Predicts Non-Newtonian Viscosity, Normal Stresses, and Dynamic Moduli
Authors: DeWitt T. W. 
Published: April 2005

An equation of state is formulated from the classical Maxwell assumptions of superposition of the effects due to strain and rate of deformation in a strained fluid. Except for the form of the time derivative, these assumptions result in the usual expression for a Maxwell element. The time derivative of the stress, however, is computed with respect to a set of axes in the fluid which are rotating (with respect to fixed axes) at a rate measured by the vorticity of the assumed velocity distribution. The usual transformation between rotating and fixed reference axes introduces cross terms between the stress and vorticity components.
The resulting equation of state predicts non-Newtonian behavior and the simultaneous appearance of normal stresses. It reduces to the Newtonian case for low rates of shear (or for small relaxation times) and, if the cross terms are sufficiently small (but not otherwise), to the usual Maxwell element expression in the dynamic case. A common origin is thus assigned to these several phenomena. Reduced variable and distribution function procedures, at least in principle, should be as applicable to the viscosity and pressure phenomena as to dynamic data.
Domain Configurations and Crystallographic Orientation in Grain-Oriented Silicon Steel
Authors: Paxton W. S. , Nilan T. G. 
Published: April 2005

The magnetic domain structure of polycrystalline grain-oriented 3¼% silicon steel has been investigated by the magnetic-powder-pattern technique and the orientation of individual grains determined by the etchpit optical-goniometer technique. A semiquantitative relationship has been found between the domain patterns and crystalline orientation. The observed powder patterns can be grouped into five types, depending upon the angle, φ, between the rolling plane and the &lt;100&gt; direction lying closest to the rolling plane. When the rolling direction is known and φ is &lt;10°, semiquantitative grain-by-grain orientation information can be obtained solely from the domain patterns.
The behavior of two of the types of patterns in an applied magnetic field is shown, and on the basis of this behavior, a three-dimensional domain configuration is proposed for one of the less complicated surface patterns.
Apparatus for Making Simultaneous Stress and Birefringence Measurements on Polymers
Authors: Gurnee E. F. , Patterson L. T. , Andrews R. D. 
Published: April 2005

An instrument has been constructed to allow simultaneous measurements of stress and birefringence in polymer samples to be made as a function of time and temperature. The stress is measured by attaching one end of the sample to a cantilever beam near the fulcrum; the small deflection of the beam is indicated by means of a differential transformer, which in turn is attached to an automatic recorder.
The birefringence is measured with a Senarmont compensator (quarter-wave plate method). Measurements can be made either manually or with a continuously rotating analyzer. This latter method permits the automatic recording of the birefringence and is also adaptable to the study of rapid birefringence changes. The sample is housed in a copper pipe surrounded by a thermostatically controlled liquid bath.
Some data are presented showing the use of this apparatus in measuring birefringence and stress changes during stress relaxation experiments (sample held at constant elongation), birefringence changes during creep under constant load, and stress-optical coefficients.
Small Particle X-Ray Scattering by Fibers. II. Radial Distribution of Microcrystallites
Authors: Heyn A. N. J. 
Published: April 2005

Radial distribution functions of the microcrystalline particles in fibers are derived from the x-ray scattering at small angles. Particle distribution functions are obtained by application of the method of Fourier synthesis to the x-ray data, by inversion of the intensity scattered under conditions where interparticle interference plays a part.
Different distribution curves are obtained with different fibers, investigated under the same conditions.
The distribution curves obtained with the same fiber investigated under different conditions of swelling, are consistent with the wider separation of the particles at higher degrees of swelling. A quantitative explanation is thus given of the differences between the scattered intensities at different degrees of swelling.
The degree of crystallinity is calculated from the distribution curves, so obtained, in combination with the particle sizes determined in preceding papers.
Tensile Strength of Plastics above the Glass Temperature
Authors: Bueche F. 
Published: April 2005

A theory is presented for the tensile strength of rubbery plastics under dynamic test conditions. It is found that a nearly universal curve may be plotted relating the tensile strength of rubbers to the time of application of the load in a simple creep test or to the shear rate in a conventional type tensile test. The dependence on chain length, degree of cross linking, and temperature is also predicted.
Experimental results for the tensile strength of poly butyl methacrylate in the range 30–95°C are presented. These are shown to agree with the theory within the experimental error. The experimental testing scale extends over a range of eight decades when use is made of a temperature—time superposition principle predicted by the theory.
By comparing the tensile creep and tensile strength curves for poly butyl methacrylate, it is possible to find the size of a segment as defined in the theory of viscoelasticity. One segment is found to contain about six monomer units.
On Chemical Surface Reactions in Laminar Boundary Layer Flows
Authors: Chambré Paul L. , Acrivos Andreas 
Published: April 2005

The progress of an isothermal chemical reaction on a catalytic surface, which is located in a laminar hydrodynamic flow field of large Reynolds number, is analyzed. Past analytical investigations have been restricted primarily to chemical reactions in fully velocity developed flow fields subject frequently to one or both of the following approximations. (i) The actual velocity distribution is replaced by a flow of uniform velocity. (ii) The concentrations of the reactants on the catalytic surface are prescribed subject to certain hypotheses concerning the rate controlling mechanism.
In this investigation the principal aim has been to calculate the actual surface concentration in a laminar boundary layer flow without unduly sacrificing the hydrodynamic features or introducing unnecessary assumptions about the effective over-all reaction mechanism. The method presented, which is related to an analysis of convective heat transfer from a nonisothermal surface, is applicable to arbitrary catalytic reaction mechanisms in a certain class of laminar boundary layer type flow fields.
Invariants in Experimental Data on Linear Kinetics and the Formulation of Models
Authors: Berman Mones , Schoenfeld Robert 
Published: April 2005

A new mathematical approach for the analysis of radioactive tracer experiments on compartmentalized systems in steady states is presented. The experimental measurements of the amounts of tracer in one or more compartments are approximated by a sum of exponential functions of time. The coefficients and exponential factors of these functions are shown to represent a set of invariants of the data. These are then related in a concise matrix equation to the compartmental model parameters, which are defined as the transition probabilities per unit time per unit quantity (turn-over rates) of molecules from one compartment (or state) into another.
When measurements are incomplete, the freedom in choosing a model is expressed in turns of a minimum number of variables equal to the difference between the number of model parameters and the number of invariants found in the data. It is shown how other information regarding the model parameters or the amounts of material in steady state may be combined with the tracer data to reduce the degrees of freedom of a proposed model.
Matrix transformations are worked out to allow the mapping of all mathematically consistent models in the configuration space of the minimum variables. The boundaries in this space corresponding to the limits for physically realizable models are found. Thus, a model is expressed by a set of coordinates and the values of all the parameters are obtained by substituting the values of the coordinates. Investigation of the range of variation of each parameter over the bounded region is also possible.
Ultrasonic Attenuation Caused by Thermoelastic Heat Flow
Authors: Lücke Kurt 
Published: April 2005

Expressions for the attenuation of sound waves in a standard linear viscoelastic body have been derived and have been applied to the attenuation due to the thermoelastic effect.
The thermoelastic attenuation for sound waves has been computed for single crystals and polycrystalline materials under application of the high-frequency approximation of sound propagation. For single crystals the attenuation in the main propagation directions have been computed explicitly for cubic and hexagonal crystals taking into account the anisotropy of the elastic properties and thermal expansion.
Comparison with experiments in the megacycle region shows that the attenuation caused by heat flow between the grains of a polycrystalline specimen is usually overpowered by scattering at the grain structure. Also the computed attenuation caused by heat flow between the regions of compressions and rarefaction of the wave is for many materials much smaller than the measured values.
For single crystals of certain metals, however, the computed and the measured values have the same order of magnitude. It can be shown that in these cases the attenuation is composed of a thermoelastic component and of a component resulting from dislocations. In zinc the two components can be separated experimentally and the agreement between the measured and the computed thermoelastic damping is very good.
Donor Concentration Changes in Oxide-Coated Cathodes Resulting from Changes in Electric Field
Authors: Krusemeyer H. J. , Pursley M. V. 
Published: April 2005

Large reproducible changes in work function of oxide cathodes have been observed following step-like changes in dc current drawn from, as well as to, the coating. One type, with a time constant in the range of 10−2 to 1 second, has been reported by others. It appears to be caused by a redistribution of donors by the field set up in the coating. We studied this phenomenon further as a function of temperature, dc current density, coating composition, and barium deposition.
We also discovered a second type of transient which follows the first. It has a time constant, in the range from 100 to 104 seconds. The amplitude of this change is of the same order as that of the first. The time dependence is in most cases given by a simple exponential. Both amplitude and time constant are a function of the cathode itself as well as its environment. This transient is thought to be caused by a change of the total number of donors. A simple analysis accounting for the exponential form yields values for the donor loss rate.
Motion of the Interface between Two Immiscible Liquids of Unequal Density in a Porous Solid
Authors: Kidder Ray E. 
Published: April 2005

A general solution is obtained to a two-dimensional problem of the movement of the interface between two immiscible liquids of unequal density in a porous solid, the interface motion being the result of the force of gravity acting on the two liquids. The solution is obtained by direct potential theory methods and employs a method of approximation similar to that used in the linear theory of water waves.
It is shown that the elevation of the interface above its equilibrium position satisfies a ``nonoscillatory'' wave equation, i.e., the classical wave equation in which the wave velocity is pure imaginary.
The solution of the special case of an initially plane tilted interface is included.
Analysis of the Plasma of Fluorescent Lamps
Authors: Waymouth John F. , Bitter Francis 
Published: April 2005

An attempt has been made to explain the properties of the ``plasma'' of fluorescent lamps in considerable detail, using the ambipolar diffusion theory of Schottky, modified to include ionization by multiple electron impacts. Ionization is assumed to occur by electron collisions with excited and metastable atoms. The cross section for this process is one of two inaccurately known parameters, which we treat as adjustable constants, occurring in the calculations. The other is the effective diffusion constant for quanta of the resonance line, in the presence of a high-temperature electron gas.
Qualitative agreement of the foregoing theory with experiment is demonstrated for all the derived quantities as functions of the several parameters of the discharge. The magnitudes of the calculated electron temperature, electric field, total light output, and efficiency are also in sufficiently good agreement with experimental values for the lamps of greatest commercial interest to permit extrapolations to be made with reasonable confidence. Optimum agreement of theory with experiment for T-12 lamps is obtained using a mean life time of ultraviolet photons in the discharge 3.6 times that employed by Kenty for diffusion in un-ionized vapor, and with a value 3.3 for the ratio of cross section for ionization of excited state to that of the ground state.
Atmospheric Attenuation of Solar Millimeter Wave Radiation
Authors: Theissing H. H. , Caplan P. J. 
Published: April 2005

A lumped attenuation figure for the solar millimeter wave radiation in the water vapor of the atmosphere was measured with a thermal detection apparatus. The corresponding theoretical attenuation figure was computed from the solar millimeter spectrum known from previous measurements of the authors and from the Van Vleck-Weisskopf equation and turned out smaller than the first experimental figure by a factor of about 3 in terms of decibels per kilometer. With the general structure of an absorption spectrum considered well traced by theory this disagreement can only mean a failure of the computation to yield the correct absolute absorption level in the window regions to which the experiment predominantly refers. The fault may lie either in the equation itself or in inadequately known constants required in the computation.
Regardless, however, of the cause and magnitude of this discrepancy, the novel method of this paper lies in a combination of the above-mentioned experimental and computed figures to furnish a well-supported spectral attenuation function in the window region. This function, which constitutes the final result, turns out largely independent of the shortcomings in the computation part, inasmuch as theory was used to furnish merely its structure and experiment to provide its absolute level.
Convergent-Beam X-Ray Analysis of Mosaic Structure in Polycrystals
Authors: Berry Chester R. 
Published: April 2005

A simple x-ray diffraction method was used to measure the mosaic misalignment and the number of dislocations in the grains of silver halide precipitates and of nickel foils where the grain sizes were in the range from a few tenths of a micron to a few microns. The experimental arrangement is such that separate diffraction spots are produced by each grain and the width of a spot is determined primarily by the mosaic nature of the grain.
It appears that measurements of angular misalignment can be made down to the limit imposed by the natural width of the x-ray spectrum lines. In general, either cold work or the presence of a substitutional impurity causes broadening of the diffraction spots. However, it is possible to incorporate impurities without producing broadening or dislocations. In spite of a 1% substitution of iodide impurity in silver bromide, grains were produced which appear to have no edge dislocations.
On the Transient Behavior of Semiconductor Rectifiers
Authors: Gossick B. R. 
Published: April 2005

The time dependent behavior of semiconductor surface barrier and point contact diodes has been calculated for small variations. (It is assumed here that the surface barrier lies on a semiconducting pellet with uniform cross section. If, on the contrary, the contact area is small compared with the semiconducting surface, like the case considered by Borneman, Schwartz, and Stickler [J. Appl. Phys. 26, 1021–1028 (1955)], then the analysis given for a point contact applies.) It is pointed out that these rectifying barriers have an ac admittance of the form Y(jω)=G0(1−Γ)+ΓG0(1+jωτ)12+jωCbin which G0 is the slope of the dc characteristic curve, Cb the barrier capacitance, ω and j the angular frequency and √−1, respectively, and τ the recombination time of minority carriers. The dimensionless constant Γ equals the injection ratio γ with surface barriers, but represents γr0(L+r0)−1 with point contacts where r0 is the effective contact radius, and L the diffusion length of minority carriers. The constant conductance G0(1−Γ) is related only to electrons with surface barriers (it is assumed that the semiconductor is n-type and that the rectifying contact emits holes), but with point contacts it is associated with both electrons and holes. The frequency dependent conductance ΓG0(1+jωτ)12 is due only to holes in either case. Compared with the conductance ΓG0(1+jωτ)12 the barrier capacitance Cb ordinarily plays a more dominant role in the frequency dependence of point contacts than with surface barriers, because the value of Γ is r0(L+r0)−1 times its value with surface barriers, and normally r0≪L.
The barrier voltage response f(t) to an impulse current has been calculated. Although the expression f(t) is complicated, it may be approximated under representative conditions (depending on bias and nature of the contact) by one of the following functions: e−t, et erfct½, or {[1–2C(t)] cost+[1–2S(t)] sint} with time t in appropriate units. The functions C(t) and S(t) are the Fresnel integrals defined by the equation C(t)−jS(t)= ∫ 0te−jxdx(2πx)12.
A special case of large amplitude behavior, the open circuit voltage decay following the interruption of forward current is also treated. It is found that with surface barriers, the open circuit decay time depends on recombination time of minority carriers, their penetration depth beyond the barrier in the semiconductor, and the injection ratio. With point contacts the decay time depends primarily on the product of the injection ratio and contact radius.
Dynamic Properties of Various Rubbers at High Frequencies
Authors: Cunningham J. R. , Ivey D. G. 
Published: April 2005

The shear wave velocity and attenuation of GR-S, Butyl, Hevea, Hycar, and Paracril rubbers have been measured in the frequency range 0.2–7 Mc/sec and the temperature range −60°C to 20°C. To minimize errors arising from interfaces in the acoustic path, a double path technique was used. By combining the shear wave data with bulk wave data the dynamic shear, bulk, and Young's moduli, and their associated viscosities, were calculated. The results were coupled with low-frequency Young's modulus data on the same materials to give information over many decades of logarithmic frequency, and from this the distribution of relaxation times was determined.
To a fair approximation, in the range investigated, it was found that the real and imaginary parts of the dynamic Young's modulus could be taken as equal to three times the corresponding values of the dynamic shear modulus. It was found that the classical Stokes assumption, that the bulk viscosity is negligible in comparison to the shear viscosity, was reasonable for some of the rubbers, but not for all of them.