bluuebunny/crossref_metadata_2025_split huggingface dataset:
Particle-Size Effects in Explosives at Finite and Infinite Diameters
Authors: Malin M. E. , Campbell A. W. , Mautz C. W. 
Published: April 2005

The effect of particle-size variations on the detonation velocity of the two-component solid explosive, Composition B, has been studied at various diameters and shown to be important. An attempt has been made to apply the diameter-effect theory of Eyring and that of Jones to explain the experimental data, but without complete success.
Certain particle-size effects in Composition B have been shown to persist to infinite diameter, and a plausibility argument in terms of the Kirkwood-Wood theory has been offered.
The presence of large crystals in low-density RDX has been shown to lead to a ``super velocity'' which still prevails at infinite diameter. Experiments using large spheres of Composition B have been performed which also demonstrate a ``super velocity'' which may be related to the effect found in RDX.
Formation of High-Density Electron Beams
Authors: Brewer George R. 
Published: April 2005

The physical principles underlying the design and performance of electron guns suitable for the generation of high-density electron beams (beam current density of the order of 200 amp/cm2) are discussed. Initiation of the flow of a cylindrical electron beam focused by a uniform magnetic field is described, with emphasis on the design of the electron gun. The principles underlying the Pierce design procedure for space-charge limited electron guns is treated, including the limitations and the modifications necessary when used for very high-density beams. Means are suggested for partial compensation of the electric field distortion due to the anode aperture of the gun. The effects on the beam and resulting limitations in gun design due to thermal velocities of emission are described.
The experimental techniques for study of gun and beam performance are described, together with some results of these studies. These techniques include detailed measurement of beam characteristics, such as current density and transverse velocity distributions, both with and without a magnetic field. These measurements illustrate a number of deviations of actual electron flow from that usually considered in the simple theories.
Nuclear Magnetic Resonance, Radiation Damage, and Rigidity in Branched Polyethylene as a Function of Temperature
Authors: Fuschillo N. , Sauer J. A. 
Published: April 2005

Molecular motions and microstructure are studied as a function of irradiation damage and temperature in branched polyethylene. The methods of proton magnetic resonance, specific volume and density percent crystallinity, mechanical rigidity and loss, and x-ray determined crystallinities are employed. The samples were subjected to irradiation doses ranging from 0 to 8.3×1018 nvt in the Brookhaven reactor. Significant changes in the proton resonance line shape at 295°K occur for an irradiation of 0.3×1018 nvt. Second moments and intensity ratios indicate that the first effect of irradiation on the line shape can be interpreted as due to the destruction of crystallinity or order. This effect however is offset at higher doses by the restrictive influence of radiation induced crosslinks on molecular chain motion. Estimates of the percent crosslinking aid in the interpretation of the temperature variation of proton resonance line shapes and allow some estimate to be made of the lengths of chain associated with a given type of molecular motion. Activation energies are calculated from NMR and mechanical loss data for these molecular motions.
With increasing temperature the proton resonance and mechanical properties are associated first with rotational oscillations, over energy barriers, of short segments (of the order four methylene groups in length) of a chain (activation energy ∼6 kcal/mole) and also with the γ peak of the mechanical loss data. At temperatures exceeding the ``glass transition temperature'' the molecular movements are also described by neo-Brownian diffusional motions involving chain lengths of about 10 methylene groups (activation energy ∼12 kcal/mole). These latter ``neo-Brownian'' motions are associated to some extent with the β peak of the mechanical loss data and probably also involve some branch point motion. The majority of the motion occurs principally in the amorphous regions of the branched polyethylene until temperatures above 290°K are reached and the microstructure begins to change due to the ``melting'' of crystallites.
The intensity ratio for the complex line shape exhibited by polyethylene at temperatures greater than 200°K are associated with the high-frequency rigidity of the sample.
Contribution to the Theory of the Contact between a Carbon Brush and a Copper Collector Ring
Authors: Holm Else 
Published: April 2005

The main subject is the interpretation of the fluctuations, ΔU, (0.3 to 0.6 v), in the contact voltage U between a carbon brush sliding smoothly on a copper ring. A special method was used and proved very informative. Within a fraction of a second, voltage or current was varied from an initial value (often zero) to a higher value and back again. Thereby voltage vs current or time were registered by means of an oscilloscope. It is shown that the sudden negative ΔU's are essentially due to electrical breakdowns—frittings at about 1 v—of the collector films, which are necessary in order to let the current through. The proof is given with stationary as well as sliding contacts by comparing the features involved with those of model diagrams, the design of which is based on the concept of fritting. Besides typical frittings of the type studied earlier, the concept of widening the area of conducting spots (generated through the collector films) by frittings as the current is increased, has been worked out. It is shown that every fritting of the collector films leads to a metallic junction by proving that consecutive records with decreasing voltage exhibit the character prescribed by the electrical and thermal constants of the electrode material used.
Experimental proofs were obtained showing that ``frictional oxidation'' provided a noticeable contamination (of fritted spots) during one revolution between leaving the brush and meeting it again.
Study of Phase Transitions in WO3 with a High-Temperature X-Ray Diffractometer
Authors: Perri J. A. , Banks E. , Post B. 
Published: April 2005

WO3 undergoes a phase transformation from monoclinic to orthorhombic at approximately 320°C and from orthorhombic to tetragonal at 720°C. A detailed study of the variation of the unit cell dimensions over the range from room temperature to 1000°C has been carried out using high-temperature x-ray diffraction techniques. Some unique features of the apparatus are described in this paper.
Between the 320°C and 720°C transformations, the a and c axes increase uniformly in length while the b axis decreases. There is a marked increase in the volume of the unit cell below the orthorhombic to tetragonal transformation; the volume decreases sharply in the transformation and resumes its ``normal'' increase above 720°C.
Measurement of Minority Carrier Lifetimes with the Surface Photovoltage
Authors: Johnson E. O. 
Published: April 2005

The surface photovoltage method uses the junction-like properties of a semiconductor surface as a means for studying the decay of excess carriers. No more than capacitive contact with the specimen is required to detect the surface photovoltage which, in the millivolt range, is a linear function of the excess carrier density. Theoretically, the surface method yields exactly the same carrier decay constant as the photoconductivity method when the lowest diffusion mode prevails in the specimen. This has been quantitatively confirmed for Ge: only qualitative confirmation has been made with Si.
For surfaces tending toward inversion, the surface method gives larger signals than the photoconductivity method, particularly for semiconductors with low intrinsic carrier density. On the other hand, for accumulation layer surfaces the surface method usually gives smaller output signals.
Study of Boiling in Short Narrow Channels and Its Application to Design of Magnets Cooled by Liquid H2 and N2
Authors: Sydoriak S. G. , Roberts T. R. 
Published: April 2005

A study has been made of the critical heat input, Q̇c, to liquid H2 and N2 boiling in an annular gap, of cross-section area, A, between a vertical cylindrical heater of height, Z, and various concentric plugs. The data are in approximate agreement with calculations based on an assumption of homogeneous and frictionless two phase flow. The pressure drop across the channel is spent primarily to accelerate the vapor being formed and the liquid carried with it. The derived relation does not contain any empirical coefficients or exponents. For ρv,2≪ρL the general equation reduces to Q̇=AL(ρV,2 ρLZegf2)12,where L is the latent heat of vaporization, ρv,2 the exit vapor density, ρL the liquid density, g the gravitational acceleration, Ze the hydrostatic head equivalent to the pressure drop across the heater, and f2 the mass fraction of vapor in the fluid leaving the heater.
Forced flow experiments give f2. At Q̇c equal to that found in natural convection boiling, f2=̇0.5 for both liquids. For Z=3 or 6 in. and a channel thickness of 0.022 in. the ratio of observed to calculated Q̇ is 0.95 for N2 and 0.70 for H2. The calculation is equally good for critical natural convection experiments, Ze=Z, and for subcritical as well as critical forced flow measurements, which extend up to Ze=70 Z.
The optimum operating vapor pressure is discussed for magnets cooled by ideal natural convection boiling. A simple roll-type of coil is discussed and is shown to be superior in some respects to more conventional windings.
Linear Dissipation in Solids
Authors: Lomnitz C. 
Published: April 2005

In solid materials the properties of transient creep, internal friction and dispersion can be correlated on the basis of a linear theory, if the strains are small throughout. The theory, first given by Boltzmann, is developed in some detail. Dissipative properties of the material are shown to depend on a function of time called the ``creep function'' φ(t).
The general condition 1/Q≅constant is examined. This condition is compatible with a creep function of logarithmic type. Velocity dispersion of plane or spherical waves is very small in such a medium. Graphs of 1/Q, phase and group velocities vs frequency are given, and a quantitative relationship between creep and internal friction constants is derived. The results are substantially applicable to the problem of losses in dielectrics, by carrying out the electromechanical analogy.
Deposit Spot Patterns from Low-Index Planes of Metal Single Crystals in a New Theory of Cathode Sputtering
Authors: Henschke Erich B. 
Published: April 2005

The generation of the deposit spot patterns from low-index planes at lower and higher ion energy is explained by mechanical double and triple collisions of the perpendicularly incident ions with lower and upper surface atoms of the target plane. The effective collision spheres are assumed to be determined by the largest closed electronic shells of the ion and the target atom with radii smaller than the radii of the largest electronic orbits of these shells. A second factor has to be taken into account for the explanation of the shape and other features of the single spots of the patterns. This is the attenuating influence of the different electron densities in the paths of the ion within the lattice, because the largest closed electronic shells exceed the size of the collision spheres and produce the highest electron density in close-packed rows of the lattice.
These two concepts are sufficient to explain the number and arrangements of the spots in the patterns of low-index planes, the specific shape of the single spots, the alterations of the spot patterns connected with higher ion energy or with accidental deviations of the prepared crystal plane from the ideal crystallographic plane, the deviation of the symmetry axis of the single spots in (110) fcc patterns from the diagonal direction of the unit area, and finally the different shape and size of the single spots in (111) spot patterns of silver and copper.
Exact Current-Voltage Relation for the Metal-Insulator-Metal Junction with a Simple Model for Trapping of Charge Carriers
Authors: Suits Gwynn H. 
Published: April 2005

The exact solution to the diffusion equation for one kind of charge carrier is obtained for the metal-insulator-metal junction where trapping of the charge carriers may occur in the body of the insulator. The effect of surface states is not considered. The electric potential distribution is given in closed form and the exact dc current-voltage relation is given in parametric form for any degree of trapping. A graph of the current-voltage relation is shown for the special case where the two boundary metals are the same.
A brief description of some experimental difficulties is given when test junctions were prepared entirely by the vacuum evaporation method.
Microwave Gas Discharge Breakdown in Air, Nitrogen, and Oxygen
Authors: Rose D. J. , Brown Sanborn C. 
Published: April 2005

The microwave breakdown electric field has been measured for pure air uncontaminated by discharge products (presumably oxides of nitrogen), and for nitrogen and oxygen separately. The breakdown field for pure air is significantly higher than that previously observed, in which cases such contamination could be suspected.
The breakdown field for pure air lies between those for nitrogen and oxygen. A calculation of the high-frequency breakdown field in air is made from dc data, using the measured Townsend ionization coefficient, electron attachment coefficient, and average electron energy. The present data agree well with this calculation.
Infrared Emissivities and Absorptivities of Gases
Authors: Penner S. S. , Thomson A. 
Published: April 2005

Approximate analytic expressions are obtained for the ``effective band widths'' and emissivities of diatomic molecules at elevated pressures.
The absorptivities of molecular vibration-rotation bands are evaluated for radiation emitted by similar molecular vibration-rotation bands and for radiation emitted by blackbodies. The results obtained for the absorptivity calculations compare favorably with available empirical correlations for H2O.
The postulated model does not apply to CO2 and, therefore, no satisfactory theoretical formula has been derived for the absorptivities of this molecule. The appendix (by A. Thomson) is devoted to a critical examination of the limits of validity of the effective band-width concept for different molecules.
Glow-Arc Transition in Current-Stabilized Electrical Discharges
Authors: Jenkins Jobe , Jones T. Benjamin 
Published: April 2005

The purpose of this investigation was to measure the limits with regard to currents and time duration of the glow and arc modes for the low current discharge at atmospheric pressure. In addition, some indications were obtained as to the conditions at the cathode which lead to such transitions. Accurate measurements in the normally unstable transition region were made possible through the use of a current stabilized power supply, together with special instrumentation for determining the magnitude and duration of the arc or glow voltage for periods as short as 0.02 microsecond.
It is shown that glow-arc transitions can occur for currents as low as 0.002 amp and for currents at least as high as 1.0 amp in the atmospheric pressure argon discharge. The duration of the arc mode at low currents is usually less than 5 microseconds. These low current transitions occur only when an oxide film is present on the cathode and are caused by the action of high fields created by positive ions across the bulk of the thin oxide films.
Small Signal Power Theorem for Electron Beams
Authors: Haus H. A. , Bobroff D. L. 
Published: April 2005

An analysis is presented of a filament beam in arbitrary dc electric and magnetic fields. The trajectory of the filament beam in the absence of ac fields may thus follow an arbitrary curve. It is shown that the electromagnetic power delivered by the filament beam is, within the assumptions of small signal theory, balanced by a decrease in the beam of a quantity, the ``generalized ac power'' in the beam. This ac power involves products of the small signal beam-excitation amplitudes.
The ac power theorem for a filament beam can be extended to a thick beam. This is done to find the small signal ac power theorem for a two-dimensional rectilinear beam of finite thickness. The power theorem presented here is applicable to M-type and E-type traveling-wave devices. Applications to the noise theory and signal analysis of electron beams are indicated.
Rotational Model of Flux Reversal in Square Loop Ferrites
Authors: Gyorgy E. M. 
Published: April 2005

The present paper analyzes a rotational model of flux reversal in ferromagnetic materials. A brief review of the experimentally established details of the flux reversal process in square loop ferrites is given. The discrepancies between the experimental results and the predictions of the domain wall motion theory are discussed. The switching coefficient Sw is examined in detail.
The rotational model is based on the solution of the modified Landau and Lifshitz equation and predicts the shape of the output voltage pulse, the relationship between the flux reversal time and the applied field, and the minimum switching coefficient that can be obtained for a given ferrite. The switching coefficients determined experimentally are within a factor of three of the minimum value of Sw predicted by this model.
The Reaction Field and Its Use in Some Solid-State Amplifiers
Authors: Anderson P. W. 
Published: April 2005

It is shown that the theory of the maser can be simply presented in terms of the concept of the radiation reaction field. This is the radiation field produced in a cavity or wave guide by the presence of the sample's electromagnetic moment. Its reaction back on the sample causes coherence effects such as those called ``superradiance'' by Dicke.
Two amplifiers using the radiation reaction field in different ways from the usual solid-state maser are discussed. One of them takes advantage of the nonlinearity of the equations of motion to make a modulated coupling between two cavity modes by means of a sample with three energy levels such as is used in Bloembergen's maser. The resulting amplifying mixer behaves the same as (but is different in principle from) Suhl's ferromagnetic amplifier. A second type of amplifier employs the reaction field to destroy the circular polarization of a paramagnetic resonance. It is then possible to make an amplifier from this using the principle of the subharmonic generator.
Dynamic Mechanical Behavior of Irradiated Polyethylene
Authors: Deeley C. W. , Sauer J. A. , Woodward A. E. 
Published: April 2005

Samples of a ``high-density'' polyethylene (ρ=0.964 g/cc) irradiated in a nuclear reactor to thermal neutron doses as high as 2.9×1018 nvt and of ``low-density'' polyethylene (ρ=0.915 g/cc) subjected to gammaray bombardment from a Co60 source up to a dosage of 1×109 rep have been investigated by dynamic mechanical methods from 80°K to 450°K at audio-frequencies. Degrees of cross-linking were estimated from the observed changes in resonance frequency at temperatures where the specimens were ``rubber-like.'' Densities and x-ray crystallinities at 25°C were also measured.
For the pile-irradiated ``high-density'' polyethylene the γ peak found around 165°K shows a marked increase in height and area at dosages above 1018 nvt. The α peak at about 390°K decreases markedly upon receiving a thermal neutron dose of 0.6×1018 nvt. Further changes in this absorption with higher dosages are obscured by the appearance of a β peak around 330°K which is almost absent in the unirradiated material; the appearance of the β region is attributed to the creation of branch points and cross-link points in the essentially linear polymer by the irradiation.
The irradiated ``low-density'' specimens exhibit three damping peaks. Over the dosage range studied the γ peak (165°K) increases in height and area, the β peak (270°K) shifts to higher temperatures, and the α peak (360°K) shifts to lower temperatures with increasing dose. The cross-linking degree is not proportional to dose and to the highest dosages studied, there is very little, if any, reduction in x-ray crystallinity.
Magnetic Writing with an Electron Beam
Authors: Mayer Ludwig 
Published: April 2005

Experimental evidence is presented that magnetic writing with an electron beam is possible. The method is based on Curie-point writing which permits local reversal of the direction of magnetization in suitable, premagnetized magnetic films by temporarily elevating the temperature above the Curie point. By utilizing the dissipation energy of a focused electron beam for this purpose, quite well-defined traces of reversed magnetization could be recorded on MnBi films. The traces were erasable magnetically. Writing speeds corresponding to 3·104 bits/sec and information densities corresponding to 105 bits/cm2 could be achieved in these first experiments. Considerably higher writing speeds and some increase in information density should be feasible.
By means of an electron mirror micrograph of the electronically recorded magnetic trace, evidence is presented which shows that, in addition to read-in with an electron beam, electronic read-out of the magnetically stored information is also possible.
Electronic writing of magnetic half-tone images by controlling the size of the spots of reversed magnetization appears to be feasible also.
Diffusion of Gallium in Silicon
Authors: Kurtz A. D. , Gravel C. L. 
Published: April 2005

The diffusion of gallium into silicon has been investigated over a temperature range of 1130°C–1358°C using an open-tube vapor-solid diffusion technique at atmospheric pressure. A p-n junction method combined with incremental conductivity measurements of the diffused layer was used to determine the diffusion constant. Lower diffusivities and a somewhat higher activation energy, (ΔH=95 kcal) were obtained than those reported previously.
The difference is attributed to variation of diffusivity with surface concentration and is discussed on the basis of substitutional diffusion proceeding by a vacancy mechanism.
Arc Cathode Movement in a Magnetic Field
Authors: Guile A. E. , Secker P. E. 
Published: April 2005

An arc cathode spot in a transverse magnetic field may move either in the Amperian (forward) direction, or in the opposite (retrograde) direction. Experiments are described which show that forward continuous motion is caused by magnetic fields at the cathode surface, as is the case with retrograde motion, and that both of these motions depend upon the material and surface condition of the cathode. Forward cathode velocity both when continuous and when moving in a stepping process is independent of arc current over a wide range.
The theories so far suggested for retrograde motion do not appear to be able to account for the dependence of retrograde cathode movement on the nature of the cathode surface.