bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Origin Flaw Characteristics on Glass Strength
Authors: Levengood W. C. 
Published: April 2005

Glass breakage experiments were made which indicate two different mechanisms of fracture. The breaking process is dependent on the widths as well as the depth of the origin flaws. When the fracture is of the large, open type, the reciprocal of the breaking stress is a linear function of the depth of flaw; when the flaw is minute, the reciprocal of the breaking stress is a linear function of the square root of fracture depth.
A pronounced strength increase was observed in cuts formed under various liquids and aged for various lengths of time. This increase took place about one hour after cutting and was interpreted as a rehealing phenomenon. Cuts made in air did not show the rapid strength increase.
Cycle fatigue tests were also made on laths of glass and it was observed that there was an initial decrease in strength followed by an increase. This was interpreted as rehealing effect in the minute type of flaw.
Dislocations, Point-Defect Clusters, and Cavities in Neutron Irradiated LiF Crystals
Authors: Gilman J. J. , Johnston W. G. 
Published: April 2005

Micrographic techniques have been used to study dislocations, point defect clusters, and cavities in neutron-irradiated LiF crystals.
No evidence of inhomogeneous damage caused by ``thermal or displacement spikes'' was found. However, a uniform etching effect was found for doses greater than ∼1015 nvt. The etching is believed to be caused by clusters of point defects greater than 2 A but less than 50 A in size. This agrees with previous x-ray results. The defect clusters decrease in number and increase in size with increasing annealing temperatures. At temperatures greater than ∼400°C only (110) dislocation loops remain and these disappear above ∼600°C. Electron bombardment causes a similar effect.
The as-grown dislocation structure of LiF is not affected by neutron bombardment. However, it becomes increasingly difficult to move fresh dislocations in crystals given neutron doses greater than ∼1012 nvt. The hardening is independent of dislocation velocity and temperature and hence cannot be caused by Cottrellpinning of dislocations. The color changes that accompany hardening suggest that it is caused by defect clusters rather than single defects.
At annealing temperatures above ∼600°C crystallographic cavities appear in LiF crystals. They are rectangular parallelepipeds with (100) sides. Evidence is presented to show that the cavities are not caused by fission gases but probably by loss of fluorine from the crystals.
On the Quality of Gray Tin Crystals and Their Rate of Growth
Authors: Becker J. H. 
Published: April 2005

Various methods of preparing samples of gray tin suitable for electrical and optical investigations are described. Attempts to deposit atoms of tin directly into the gray tin lattice by vapor- and electrodeposition and by chemical reactions at low temperatures have all yielded crystals of white tin; however, by transformation of white tin under suitable conditions it is possible to obtain large coherent crystals of gray tin. These include samples several cm long showing single crystal regions up to 2 mm, as well as flat thin films as large as 25×25 mm2.
The temperature at which the transformation takes place, the purity of the initial white tin specimen, its size, and the method of attaching a sample to a substrate are important factors for determining both the quality and the rate of transformation. Investigations were carried out over a wide range of temperatures for several sources of high purity tin, as well as with additions of In, Ga, Al, As, and Sb. Effects of mechanical and thermal treatment are also included. A careful distinction is made between the time for nucleation and the rate of growth after nucleation.
Results are analyzed in the light of absolute rate theory and a reasonable explanation is obtained for many of the observed phenomena. The heat of activation for the white to gray tin reaction is determined as (8.7±1.5)×103 cal/mole at 0°K.
Some Effects of Nonuniform Fields on Dielectrics
Authors: Pohl Herbert Ackland 
Published: April 2005

Some of the more interesting effects of nonuniform electric fields are described in this report. Experimental and theoretical studies show the effects to be rather striking for particles larger than molecular size. The results show that the effect can be used to produce a fairly efficient pumping action of nonconducting liquids, to cause continuous and easily measureable separations in coarse suspensions, to cause selective precipitation, and to produce mixing.
By this means, liquids may be thrown several feet into the air with an electromechanical efficiency of about 25%. A separation factor of at least 2.5 in continuous separatory operation may be produced in a suspension of polyvinyl chloride in carbon tetrachloride-benzene mixture. Suspensions of polar materials in less polar liquids may be either dispersed or precipitated. In one interesting ``demonstration'' type experiment, drops were ``hung'' in mid-air.
Note on Diffusive Separation of Gas Mixtures in Flow Fields
Authors: Liu V. C. 
Published: April 2005

This paper discusses the effect of pressure-diffusion flux upon the concentration distribution of gas mixtures in flow fields. The equation of concentration is formulated for a binary gas mixture in which the mass ratio is large and the concentration of the lighter gas is very small. An asymptotic solution to the steady-state equation of concentration is given for an irrotational and incompressible flow.
As an illustration, the diffusive separation (i.e., deviation from the original homogeneous state) of a mixture of helium and nitrogen along streamlines at the entrance to a long straight channel is calculated. It is assumed that the pressure inside the channel is 90% of that in the free stream, and that the diffusion coefficient of the mixture corresponds with the atmospheric conditions at 80-km altitude.
Crater Formation in Metallic Targets
Authors: Partridge William S. , Vanfleet Howard B. , Whited C. R. 
Published: April 2005

Spheres of copper, lead, tin, iron, aluminum, zinc, silver, and lead-tin alloys were accelerated to velocities of 0.75 to 2.25 km/sec and impacted normally upon targets of the same material as the pellets. Conditions were maintained so that pellets lost no mass before striking the target. The target mass was large compared to the mass of the pellet, so the targets could be considered semi-infinite.
The volume of the crater produced was found to be directly proportional to the kinetic energy of the pellet in the energy range investigated.
The penetration varied linearly with the velocity or momentum of the pellet. The area of the crater as measured in the plane of the original surface of the target was found to be directly proportional to the momentum of the pellet at the time of the impact.
In the case of the lead-tin alloy series, a correlation was observed between the crater parameters, the phase diagram of the alloys, and various functions of the pellet mass and velocity for the following series of alloys: 100% lead; 90% lead, 10% tin;...; 10% lead, 90% tin; 100% tin.
Parametric Amplification and Frequency Mixing in Propagating Circuits
Authors: Tien P. K. 
Published: April 2005

When two circuits such as filters or transmission lines are coupled together by means of distributed reactances which can vary sinusoidally in time and space, energy can be converted between waves of different frequencies in a variety of ways. If the waves on the two transmission lines are characterized by frequencies ω1 and ω2 and phase constants β1 and β2, while the coupling reactances vary as ω=ω1−ω2 and β=β1−β2+Δβ, power P1 at ω1 is converted into power P2 at ω2 and vice versa in a manner reminiscent of waves on coupled passive circuits, except that a relationship (P2/ω2)=(P1/ω1) is obeyed. If the group velocities on both transmission lines are in the same direction, the direction of power transfer reverses periodically with distance. If they are not in the same direction, the power transfer increases monotonically with distance for small Δβ but reverses periodically for Δβ larger than a certain limit.
When the coupling reactance varies as given by ω=ω1+ω2 and β=β1+β2, parametric amplification is possible in the form of exponentially growing waves at frequencies ω1 and ω2 if the group velocities are in the same direction, and in a form reminiscent of the backward wave amplifier when the group velocities are not in the same direction. In both cases the excess energy is supplied by the variable coupling reactance and can be indefinitely large.
Possible applications of new principles of these coupled circuits to broad-band frequency converters, frequency-channel selectors, wide-band amplifiers, tunable narrow-band amplifiers, and oscillators are described. Noise performances of the circuits are also discussed.
A Comparison of Theory and Experiment for a Thermoelectric Cooler
Authors: Norwood M. H. 
Published: April 2005

The performance of single-stage Peltier thermocouples was calculated using the experimentally measured values of thermoelectric power, electrical resistivity, and thermal conductivity as functions of temperature. These calculations were made by solving numerically the differential equation for the temperature distributions in the thermoelements. The boundary conditions were the hot junction temperature and the heat flow at the cold junction. The calculated behavior of the thermocouples agreed well with the measured performance in the three cases studied. The measured thermocouple figure of merit agreed with that calculated from the material properties.
The effect of temperature variations of the material properties on thermocouple performance was studied by comparing exact calculations with calculations involving one temperature-averaged constant material property. This type of calculation showed that the Thomson effect caused about 4°K of the maximum ΔT of 66°K for one couple studied. The temperature variation of resistivity was found to be the major cause of disagreement between exact calculations and the simpler theory (Ioffe equations).
Harmonic Generation and Frequency Mixing in Ferromagnetic Insulators
Authors: Jepsen R. L. 
Published: April 2005

When a transverse rf magnetic field is applied to a ferromagnetic insulator, a second harmonic frequency term arises in mz (the axial or longitudinal component of the rf magnetization). If in addition an axial component of the rf field is applied, then a second harmonic frequency term appears in mt (the transverse component of the rf magnetization) as well. It happens further that mt exhibits two dc magnetic field resonances. One resonance occurs when the material is biased to the fundamental, and the other arises when the material is biased to the second harmonic.
In a similar way, application of two frequencies having both axial and transverse components results in sum and difference frequency terms appearing in mt, in addition to the usual mz. The mixed frequency terms in mz are resonant for the two values of dc magnetic field corresponding to the two applied frequencies. The mixed frequency terms in mt exhibit additional resonances for dc magnetic fields corresponding to the sum and difference frequencies.
The present paper describes calculations of second harmonic generation and second-order frequency mixing under the assumption of uniform precession of the magnetization, for small and ellipsoidally shaped samples of material and with loss included in the Landau-Lifshitz form. A simple case of third harmonic generation is also discussed. Results of the calculations are applied to a simple example of second harmonic generation. The detailed calculations and results are contained elsewhere in a rather lengthy report.
Low-Angle X-Ray Diffraction of Crystalline Nonoriented Polyethylene and Its Relation to Crystallization Mechanisms
Authors: Mandelkern L. , Posner A. S. , Diorio A. F. , Roberts D. E. 
Published: April 2005

X-ray diffraction maxima at low angles have been observed in crystalline but nonoriented linear polyethylene, the crystallization process being conducted from the melt of the pure undiluted polymer. Several orders of diffraction are observed in favorable cases, and the spacings corresponding to the first-order reflections range from 150–850 A. The values of the maxima depend on the mode of crystallization. Previous assertions that in such systems the maxima are limited to 100–200 A are shown to be very restrictive and typical only of crystallization processes conducted at very large undercooling. Major attention is focused on the properties of specimens crystallized isothermally at relatively low values of the undercooling. The spacings are very sensitive to the crystallization temperature in this range. The highest values are observed at low undercooling, and substantial decreases occur as the temperature is lowered. Concomitantly, the density observed after isothermal crystallization significantly decreases with a lowering of the crystallization temperature.
The fact that a periodicity can be developed in such systems, the magnitude of the maxima, and their dependence on the crystallization temperature, is explicable by the application of nucleation theory. It is assumed that subsequent to the formation of critical-size nuclei from a bundle of polymer chains, crystal growth along the chain direction is severely retarded, while in the transverse direction essentially unimpeded crystallization occurs. From the observed temperature coefficient of the low-angle spacings, the ratio of the excess free energy (resulting from the junction of crystalline and amorphous regions at the crystallite ends) to the bulk enthalpy of fusion is found to be 2.6. The magnitude of this ratio receives confirmation from another type of experiment.
Nonbasal Glide in Dislocation-Free Cadmium Crystals. II. The (112̄2) [1̄1̄23] System
Authors: Price P. B. 
Published: April 2005

The (112̄2) [1̄1̄23] glide system was studied in thin, dislocation-free cadmium platelets by transmission electron microscopy and compared with observations on zinc platelets. Screw dislocations with a ⅓&lt;1̄1̄23&gt; Burgers vector were formed at the edges of the crystal and moved primarily on {112̄2} planes. Elongated, sessile dislocation loops were formed on basal planes when screws developed large jogs during cross-glide. Smaller numbers of secondary ⅓&lt;1̄1̄20&gt; dislocations were also formed and moved on basal planes. Observations in the temperature range −150° to +25°C showed that the behavior of the long loops and of the other dislocations in cadmium and zinc varied with temperature as follows: (1) At temperatures lower than ∼−120° in Cd and ∼−80° in Zn, the long loops were stable and practically no recovery took place. High densities of loops and networks of secondary dislocations were built up and hardened the crystal. (2) In the intermediate temperature range −120° to −40° for Cd and −80° to +10° for Zn, the long loops split up into rows of circular loops, which were then stable. The process involved the pipe-diffusion of material around the long loops and required a lower activation energy than that for climb. Some of the circular loops were found to contain stacking faults. (3) At high temperature, above ∼−40° for Cd and ∼+10° for Zn, circular loops annealed out by climb with an activation energy ∼0.8 ev for Cd and ∼0.95 ev for Zn; secondary dislocation networks dispersed by climb; and the dislocation density, and therefore the work-hardening, was small.
At high beam intensities dislocation loops often grew by climb, probably as a result of the formation of point defects by ion bombardment, the ions being formed by the interaction between electrons and residual gas molecules.
Circuit Theory of Coupled Transmission Systems
Authors: Kino G. S. , Paik S. F. 
Published: April 2005

A method of obtaining an exact circuit equivalence of a class of coupled transmission systems from Maxwell's equations is described. The solution for the propagating characteristics of the coupled transmission system can be readily obtained from the circuit analog. The process of reducing field equations to circuit equations is carried out for a particular coupled structure, a coupled helix system. The circuit theory yields frequencies of the coupled modes as functions of the propagation constant, rather than the propagation constant in terms of frequency. The circuit theory has the great advantage that it is as valid for strongly coupled systems as it is for weakly coupled systems. The usefulness of the approach is demonstrated by applying the theory to several slightly different propagating systems.
Expressions for the energy and the power flow derived from the circuit theory are compared to the true power flow and the energy in the transmission system. It is shown that the energy of the system in the equivalent transmission line corresponds to the true energy, if the circuit is assumed to propagate slow waves. The power flow relation obtained from the circuit analog differs from the true power flow by the factor of (vp/vg) which is attributed to the dispersive nature of the circuit. Important relationships between impedances of the transmission system defined in various ways are obtained from the power flow relation.
Calcium Tungstate: Czochralski Growth, Perfection, and Substitution
Authors: Nassau K. , Broyer A. M. 
Published: April 2005

The conditions for the Czochralski growth of calcium tungstate to give crystals of quality suitable for continuous optical maser operation at room temperature are described.
Purity, growth direction, and perfection considerations are discussed. Optical examination in polarized light, the presence of gas bubbles, solid inclusions and Tyndal scattering haze, and interferometer measurements provide estimates of the degree of imperfection present.
Transition and rare-earth metal ion additions were studied, and data on distribution coefficients, valency, and charge compensation are given.
Among miscellaneous data measured are the thermal expansion coefficients in the a- and c-axis directions up to 1030°C, and redeterminations of the solubility and optical transmission curve.
Stacking Fault Energy in Silicon
Authors: Aerts E. , Delavignette P. , Siems R. , Amelinckx S. 
Published: April 2005

In hexagonal networks in the (111) plane of silicon both families of nodes are ``extended.'' This implies that intrinsic as well as extrinsic stacking faults have small energy. The two stacking fault energies are ∼50 ergs/cm2 and ∼60 ergs/cm2. It is not possible at present to decide which energy belongs to which stacking fault.
Both the etch pits, and the dislocations on which they are centered, can be revealed in the electron microscope.
Magnetic Transitions in Cubic Spinels
Authors: Menyuk N. , Wold A. , Rogers D. , Dwight K. 
Published: April 2005

Magnetization curves of the cubic spinels MnCr2O4, CoCr2O4, MnV2O4, and CoV2O4 have been obtained between 4.2°K and their Curie points. With the possible exception of MnV2O4, all the curves indicate the presence of a magnetic transition within this temperature range. Although all these materials have been reported to be normal spinels, inconsistencies between our results and the recent theory of spin configurations in normal cubic spinels led to further experiments which established that CoV2O4 is not, in general, normal.
Theory suggests the presence of two types of transition in MnCr2O4 and CoCr2O4, but only one has been observed in each case. The temperatures at which the observed break in the magnetization curves of these materials occurs can be interpreted by ascribing them to different types of transitions. The interpretation of the MnCr2O4 magnetization curve is compatible with the neutron diffraction results of Corliss and Hastings.
Anisotropy in Rolled Permalloy Tape
Authors: Gyorgy E. M. , Treves D. 
Published: April 2005

The anisotropy induced in gold-doped Permalloy by cold rolling and subsequent heat treatments has been investigated using a recording torque magnetometer. The material was cold rolled from 0.014 in. to 0.000125 in. and then heat treated for 2 hr in a dry hydrogen atmosphere. The torque curves obtained could be decomposed into a hard and soft component. For fields below 200 oe, the torque curves due to the hard component have a tangent-like shape with the peak a few degrees from the hard direction, while the torque curves due to the soft component have the regular shape corresponding to uniaxial magnetocrystalline anisotropy. Both components are uniaxial with the easy direction along the roll direction.
The hard component is independent of the heat treatments up to about 900°C and has an equivalent anisotropy field of the order of several hundred oersteds. The high apparent anisotropy of the hard component and its independence of the heat treatment suggest that this component arises from a magnetostatic effect. By etching the tape it has been shown that the hard component is due to the surface structure of the tape. The surface structure is probably the result of the rolling process.
The soft component is strongly dependent upon the heat treatment subsequent to the cold work and almost vanishes at an annealing temperature of about 650°C. This decrease is consistent with the ordered pair mechanism suggested by Chikazumi. The small residual soft component at high annealing temperatures is very sensitive to the rate of quenching. This behavior may indicate the presence of partial ordering and some degree of crystal orientation. The value of the anisotropy field due to the soft component is approximately equal to the measured value of the threshold for rapid rotational flux reversal.
Grain-Size Effects in Oriented 48% Nickel-Iron Cores at 400 Cycles
Authors: Littmann M. F. , Harris E. S. , Ward C. E. 
Published: April 2005

The constant-current, flux-reset test at 400 cycles has been used widely to evaluate core material for magnetic amplifier applications. An important criterion by this test is the ``gain'' or ratio of flux change to change in dc control magnetizing force. It is well known that gain is related to the squareness ratio Br/Bm of the hysteresis loop.
This study shows that gain is also very sensitive to the grain structure as well as the crystal orientation of the core material. Material having a homogeneous structure has high gain, whereas if partial secondary grain growth has occurred, resulting in a large difference in grain size for the material, the gain can be reduced by a factor 1.5 to 3 times. The effect was artificially simulated by combining two cores of different grain size. Individually, the cores had high gain but together they had very low gain. The cause is ascribed to the difference in coercive force between the large and small grains. The conclusion is reached that high gain is obtainable from material consisting entirely of either large or small grains of proper crystal orientation.