bluuebunny/crossref_metadata_2025 huggingface dataset:
Positronium Formation in Gases
Authors: Hughes Vernon W.
Published: April 2005

The formation of positronium in gases can be investigated by observing the energy spectrum of the annihilation radiation. The increase in positronium formation due to a static electric field has been measured in various gases. For the rare gases the increase has a sigmoid dependence on the ratio of electric field to pressure. The fraction of the positrons that form positronium increases by a maximum factor of 1.5, 1.4, and 2.1 for He, Ne, and A, respectively. A similar increase was observed for H2, D2, and N2. No effect of the electric field was found in the polyatomic gases CO2, CH4, C2H6, and CCl2F2, but a small anomalous decrease in positronium formation was seen in SF6.

The increase in positronium formation occurs in the presence of an electric field because low energy positrons, which die by direct annihilation with atomic electrons without positronium formation in the absence of an electric field, can gain energy from the electric field to cross the threshold energy for positronium formation in the gas. A theory based on the Boltzmann equation describes the behavior of the positrons under the combined influence of the electric field and molecular collisions, and provides the basis for obtaining from the observed data values of the elastic scattering cross section of positrons by the rare gas atoms. The cross sections are 0.023πa02, 0.12πa02, and 1.5πa02±25% for He, Ne, and A, respectively. Quantitative interpretation for the polyatomic gases is more difficult.

An optical search for the 2430 A Lyman line from positronium is described.
Effect of Structural Defects in Germanium on the Diffusion and Acceptor Behavior of Copper
Authors: Fuller C. S. , Ditzenberger J. A.
Published: April 2005

The effect of dislocations in Ge upon the diffusion of Cu has been studied using Ge crystals having different etch-pit counts as well as on Ge specimens bent on a (112) axis. The percentage of the total Cu introduced in a given time which attains the acceptor state was measured by comparing conductivity to radioactivity determinations employing Cu64. In addition, the detailed diffusion processes have been studied as a function of time and etch-pit density by means of autoradiographs taken both parallel and perpendicular to the direction of diffusion and also by delineation of p-n boundaries.

The two most important findings are: (1) the slow attainment of acceptor equilibrium especially in Ge having low concentrations of dislocations and (2) the identification of dislocations as the initial loci of acceptor copper in Ge.

The results call for a revision of our ideas on the mechanism of diffusion of Cu. The view is advanced that Cu atoms enter Ge interstitially at a high rate (>10−4 cm2/sec), but that their flow and ultimate concentration is limited by the effective rate of generation and equilibrium concentration of vacancies chiefly at dislocations.
Applications of the Electronic Probe to the Study of Turbulent Flames
Authors: Denniston D. W. , Oxendine J. R. , Knapschaefer D. H. , Burgess D. S. , Karlovitz B.
Published: April 2005

Description is given of a negatively biased bare wire probe with suitable amplification and pulse-height discrimination to be used in detecting flame fronts in turbulent motion. Typical measurements are given of a Bunsen flame's most probable position, its rms displacement from this position, and its degree of continuity during unstable burning. The treatment of data and the precision and limitations of the method are discussed.
Interaction of Nonuniform Shock Waves
Authors: Drummond W. E.
Published: April 2005

The basic interactions of nonuniform shock waves in one-dimensional unsteady and two-dimensional steady flow, are analyzed by mapping into the hodograph plane, neglecting effects of third and higher orders in the shock strength. The resulting equations are linear and can be solved by straightforward numerical calculation.
Structure of Spherulites as Revealed by Selected-Area Electron Diffraction and Electron Microscopy
Authors: Scott Robert G.
Published: April 2005

Two-dimensional spherulites in thin films of the 6–6 nylon have been studied by selected-area electron diffraction, bright-field and dark-field electron microscopy. The electron diffraction patterns were found to be comparable to studies using limited area x-ray diffraction. In this sample they showed that the molecules were arranged in sheets with the hydrogen bonds in the plane of the film. Large field areas were used and as a result no preferred direction of orientation was seen. However, in dark-field electron microscopy, by using only those Bragg electrons scattered into limited portions of the principle rings, the radical growth and branching of discrete crystalline regions was seen. Bright field electron microscopy showed the surface morphology of these structures.
Photoelastic Properties of Polystyrene in the Glassy State. II. Effect of Temperature
Authors: Rudd J. F. , Gurnee E. F.
Published: April 2005

The effect of temperature on the stress-optical coefficient of polystyrene was measured at twelve different temperatures from −195° to +24°C using samples of unoriented polystyrene sheet. The stress-optical coefficient appears to decrease with temperature from a value of about +17 brewsters at −195°C to a value of about +10 brewsters at room temperature. The elastic (Young's) modulus of polystyrene was also measured as a function of temperature using a flexural technique and was found to decrease linearly with temperature from 6.36×105 psi at −198° to 4.65×105 psi at +24°C. A curve of strain-optical coefficient vs temperature was obtained by multiplying stress-optical and modulus values; this curve increases with decreasing temperature from about +0.03 at +24° to +0.073 at −195°C.
Mechanical Behavior of Plastics
Authors: Gruntfest I. J. , Young E. M. , Kooch Walter
Published: April 2005

The applicability of Nutting's equation of the mechanical behavior of some soft plasticized polyvinyl chloride preparations noted by Dyson in creep experiments is further demonstrated by force-length measurements at constant rate of strain. This suggests new criteria for the characterization of soft plasticized PVC. For example, in a stretching experiment in which the sample is subjected to a strain (L−1) which increases linearly with time (t) at the rate (R), definition of ``modulus'' as the limit at small strains of the ratio of the force (F) to the strain is clearly inappropriate. That is, when L−1=GFmtn,lim lim L−1→0(FL−1)=(L−1)(1−n−m)/mRn/mG−1/m,which may be zero or infinite and also depends on the strain rate.

Some even more general force-length-time relationships for plastic are discussed which have been found useful for predicting the conditions of tensile failure. More complicated relationships of particular interest provide for the possibility of force-time superposition of creep curves. Published creep data are considered from this point of view.
Flow Birefringence and Stress. V. Correlation of Recoverable Shear Strains with Other Rheological Properties of Polymer Solutions
Authors: Philippoff Wladimir , Gaskins Frederick H. , Brodnyan John G.
Published: April 2005

The correlation of normal stress with the shear stress and flow birefringence of flowing solutions has been extended to include the recoverable shear strain s which can be measured directly by a rotational viscometer in ``recoil.'' This has been shown experimentally with solutions of a high-viscosity nitro-cellulose in n-butyl acetate and a viscous polyisobutylene. These results show that the principal axes of the tensors of stress, strain, and optical anistropy coincide, even when no constant shear modulus (shear compliance) exists.
Application of Radioactive Tracers to the Study of Shaped Charge Phenomena
Authors: Bryan G. M. , Eichelberger R. J. , MacDonald D. , Zigman P. E.
Published: April 2005

The problem of determining the velocity of a given element in a shaped charge jet as a function of the position of that element in the parent liner has been attacked with the help of radioactive tracers. Radioactively tagged liners were fired into stacks of steel plates, and the depth reached by the tagged element in each case was determined by radioactive assay of the plates. The resulting depth v rsus position curve was combined with emergent jet velocity data to yield velocity as a function of position. The results are in rough qualitative agreement with those previously obtained by the somewhat unwieldy method of collecting and weighing jets and slugs. The radioactive method is more direct and appears to be capable of sufficient refinement to warrant its use as a research tool.
Explicit Formulas for Tschebyscheff and Butterworth Ladder Networks
Authors: Weinberg Louis
Published: April 2005

Green found the closed-form formulas for the element values in a resistance-terminated ladder network that has a maximally flat (Butterworth) or equal-ripple (Tschebyscheff) characteristic. The Green formulas apply only when all the zeros of the reflection coefficient ρ are chosen to lie in one half-plane. In this paper we present new formulas for the element values for the case in which the zeros of ρ are chosen to alternate in the left and right half-planes. These formulas apply for n odd, where n is the degree of the dominator of the transfer function, and for any nonzero ratio of the output to the input resistance. The networks obtained are related to the symmetrical ones given by Bennett's and Belevitch's formulas for matched networks.
Equipartition of Energy and Local Isotropy in Turbulent Flows
Authors: Uberoi Mahinder S.
Published: April 2005

Homogeneous turbulence in which 〈v2〉 = 〈w2〉 ≠ 〈u2〉 was produced experimentally, where 〈u2〉, 〈v2〉, and 〈w2〉 are the mean-square turbulent velocities in x, y, and z direction, respectively. The decay of turbulence and the energy transfer between 〈u2〉 and (〈v2〉+〈w2〉) were measured, and it was found that the larger components (〈v2〉 and 〈w2〉) are losing more energy due to viscosity than by transfer to the smaller component (〈u2〉). However, 〈u2〉 is receiving enough energy by transfer to compensate for its decay and is in fact slowly increasing. The measurement of mean-square vorticity components shows that the turbulence is becoming locally isotropic at a faster rate than the equipartition of energy is taking place.

In another set of experiments it was found that when approximately isotropic turbulence is subjected to deformation, the three components of turbulent energy become widely different in magnitude and that the turbulence is not locally isotropic. This indicates that even at high Reynolds number the deformation in a shear flow may cause anisotropy. The data on the turbulent shear flow near a solid wall confirm this conjecture.

The connection of this investigation to turbulent flows in general is discussed. In particular, it follows that neither the turbulent energy nor the small-scale structure of turbulence rapidly settles down statistically to quasi-equilibrium.
Donor Diffusion in Oxide Cathodes
Authors: Peterson R. W.
Published: April 2005

The activation of oxide cathodes by chemical impurities present in the base nickel is analyzed using classical diffusion theory and a model in which the concentration of donors in the oxide particles is controlled by alkaline earth metal adsorbed on the oxide particles. Strong surface adsorption of the alkaline earth metals on the oxide crystal surfaces is indicated. To fit calculated curves of average donor concentration to experimentally observed pulse emission data obtained on Ni with Al as an impurity, surface adsorption energies of 3.2 to 3.4 ev are indicated.
Magnetic Writing on Thin Films of MnBi
Authors: Williams H. J. , Sherwood R. C. , Foster F. G. , Kelley E. M.
Published: April 2005

A study has been made of the domain structure of thin films (∼1000 A) of MnBi and their capability of storing information magnetically. It is estimated that a million bits of information could be written on a square centimeter of film. The information can be read out optically by utilizing the Faraday effect. The films have a uniaxial direction of easy magnetization normal to their surfaces and retain their magnetization after saturation along this direction in spite of the large demagnetizing factor. When magnetized in this manner, a high optical contrast is obtained between the writing and the background.
Gamma-Ray Collimator Penetration and Scattering Effects
Authors: Mather Robert L.
Published: April 2005

Expressions are developed which give the amount of unidirectional radiation from a distant radiation source passing through a cylindrical hole in a slab of material, including the amount of radiation which penetrates the edges of the hole, as a function of angle between the radiation direction and the axis of the hole. The modifications necessary for sources at finite distances are indicated. These functions are integrated over appropriate angles for distant line sources, and for extended sources. It is shown that, to a first approximation, the results are the same as the geometrical aperture for a like diameter hole in a similar slab with one mean free path of material removed from each side. The effects due to scattering from the walls of the collimator are discussed and an approximate method of calculation is presented with results for a specific collimator.
Dislocation Arrays in Germanium
Authors: Tyler W. W. , Dash W. C.
Published: April 2005

Dislocation arrays have been observed in deformed germanium using a technique based on the selective etching of lithium precipitates which prefer to nucleate on or near dislocations. Evidence is presented which indicates that both internal Frank-Read sources and surface dislocation sources are of importance in the deformation of germanium.
Hillocks, Pits, and Etch Rate in Germanium Crystals
Authors: Batterman Boris W.
Published: April 2005

Symmetric faceted etch hillocks have been observed on certain germanium surface orientations exposed to an H2O2–HF (Superoxol) etchant. Considerations of surface curvature and etch rate lead to the conclusion that the faces bounding the hillocks must be at saddle points on an etch rate vs orientation surface. A measurement of etch rate throughout the stereographic triangle has supported this conclusion. The formation of dislocation pits and hillocks is discussed in terms of the variation of surface etch rate with orientation.
Preparation of Large-Area p-n Junctions in Silicon by Surface Melting
Authors: Billig E. , Gasson D. B.
Published: April 2005

Two methods have been developed for the preparation of large-area p-n junctions in monocrystalline silicon by surface melting and overdoping of the molten material. In one method, direct rf power coupling is used to form a cylindrical p-n junction in a rod of silicon. Also, radiation heating has been used to melt the surface of thin disks of silicon. The junctions can sustain a peak inverse voltage (PIV) given approximately by PIV=40ρn or PIV=10ρp depending on the polarity of the base material, of resistivity ρn or ρp. Low-resistivity n-type base material overdoped with aluminium forms junctions exhibiting very sharp breakdown characteristics, and PIV=40ρn holds for material at least up to 15 ohm cm. Some results obtained by using a gas doping technique are also given.
Focusing in Collision Problems in Solids
Authors: Silsbee R. H.
Published: April 2005

In treating problems of sputtering and radiation damage of solids, a billiard ball model is frequently assumed. An attempt is made to indicate to what extent such a model is justified. Using this model it is noted that the lattice structure of a crystal implies a correlation between successive collisions in a damage process which can lead to the propagation of an energy pulse, or a sequence of collisions, along a close-packed line of atoms. The rate of attenuation of these pulses is estimated for a particular case and certain implications of the effect are discussed.
Surface Studies on Single-Crystal Germanium
Authors: Ellis S. G.
Published: April 2005

The condition of the surface of germanium crystals has been studied by chemical, electron microscope, electron diffraction, and other techniques after several of the standard etching procedures. The surface is often partially covered by particles believed to be germanium monoxide. An etch has been devised which gives a controlled thickness of germanium monoxide on the crystal. Another etch minimizes the oxide formation. A simple light-scattering method for checking the surface cleanliness is described. The results of surface recombination velocity and channel effect measurements on crystals treated by these methods are described as is a method for obtaining low surface recombination on n-type crystals.
Low-Temperature Thermal Conductivity of Some Commercial Coppers
Authors: Powell Robert L. , Roder H. Martin , Rogers William M.
Published: April 2005

Values are given for the thermal conductivity between 4°K and 273°K of six commercial coppers and copper alloys: coalesced, electrolytic tough-pitch, free-cutting (tellurium) and phosphorus deoxidized coppers, free-cutting leaded brass, and silicon bronze A. The first three show the conductivity maximum typical of pure metals; the last three show the monotonic increase characteristic of alloys. The intrinsic thermal resistance in the three purer coppers varies appreciably with the concentration of chemical impurities but is much less affected by physical imperfections. In the heavily worked copper alloys the lattice contribution to the conductivity is minor and the total conductivity is essentially the electronic conductivity as limited by the imperfection scattering.
Viscosity of Suspensions of Uniform Spheres
Authors: Happel John
Published: April 2005

A mathematical development of the viscosity of suspensions is presented based on the steady-state Stokes-Navier equations of motion omitting inertia terms. The disturbance due to each sphere is assumed to be confined to a frictionless envelope surrounding it similar to the stream tube for flow inside ducts.

The relationship obtained between relative viscosity and solids concentration is in good agreement with existing data over a wide concentration range without the necessity of introducing empirical constants. It is thus thought that it may be a suitable model for further theoretical study as well as furnishing a basis for empirical correlation equations of rheological properties. In very dilute systems it does not agree with the well-known Einstein formula, and possible reasons for this variation are advanced.
Semiconductor Properties of Recrystallized Silicon in Aluminum Alloy Junction Diodes
Authors: Gudmundsen Richard A. , Maserjian J.
Published: April 2005

This is a study of the basic electrical properties of thin recrystallized regions formed in the fabrication of PN junctions by the alloying of pure aluminum on N-type silicon single crystals. The average aluminum concentration is about 7×1018 cm−3, and varies by a factor of 4 to 5; being largest in the region first recrystallized and decreasing in a linear manner to the surface immediately beneath the aluminum-silicon eutectic. The average Hall-hole mobility is about 55 cm2 volt−1 sec−1 and varies from 35 to 75 cm2 volt−1 sec−1 across a region formed by precipating from 977°C to the eutectic. Across the same region the conductivity varies from 72 to 35 mho cm−1. The built-in field which is both a function of depth and total width can vary from 10 to 200 v per cm in typical cases. The minority carrier (electron) diffusion length ranges from 4 to 12 μ. The temperature dependence of the distribution coefficient corresponds to an enthalpy change (differential heat of solution) of +0.43 ev necessary for the transfer of an atom of aluminum from the liquid to the solid.
Ionization by Ultra-Speed Pellets
Authors: Hendricks Charles D.
Published: April 2005

By reflecting 10-cm microwaves from the trails of ultra-speed pellets, the ion (electron) density in the trails was found to be from 109 to 1013 electrons per cm of path length. Column diameters were from 1.0 to 7.5 cm and pellet velocities ranged from 1.48 to 2.67 km/sec. The ions appeared to come from thermal ionization behind the pellet shock waves and from oxidation reactions involving material ablated from the pellets.
Use of Scanning Slits for Obtaining the Current Distribution in Electron Beams
Authors: Harker Kenneth J.
Published: April 2005

In axially symmetric electron beams, the current density (as a function of radius) may be rather easily related to the current through a narrow slit (as a function of slit position) by means of an integral equation. A similar equation applies to scanning by a straightedge. In this paper, the solution of the integral equation is obtained and a simple technique for rapid numerical evaluation of the resulting ordinary equation is included. The relations derived are of particular interest in the large number of cases where the mechanical simplicity of slit or straightedge scanning makes these methods preferable to the more common pinhole method. The resolving powers for slit and pinhole scans are compared.
Effects of Electrode Materials and Surface Preparation on CdS-Metal Contacts
Authors: Greiner R. A. , Miller R. F. , Retherford R. C.
Published: April 2005

Experimental studies on the effects of contact materials and crystal surface preparation on the voltampere characteristics of contacts to CdS single crystals are presented. Rectifying contacts are influenced by the surface preparation prior to electrode application. An artificially roughened or naturally rough crystal surface tends to reduce the rectification ratio of a contact. Two kinds of current fluctuations that may be attributed to the contacts are observed.
Structure in Magnetically Confined Electron Beams
Authors: Webster H. F.
Published: April 2005

A number of observations have been made of structure changes that occur in hollow and solid electron beams which are confined by a magnetic field. These structure changes occur in both the density of the beam and the transverse velocity components of the beam electrons. The velocity components have been measured by use of a pinhole camera.

Some of the results obtained are as follows. The density of electron paths in a beam may become non-uniform if there is a spread in the forward component of velocity of the electrons. This may occur either because of a spread in initial angle of the electrons or because of a potential depression in the beam.

In addition, changes in beam shape and transverse velocity components of the beam electrons can occur as a result of drifting of electrons in crossed electric and magnetic fields, the electric fields in this case being provided by the space charge of the electrons themselves. Thin beams have been found to be unstable and it has been observed that they divide into an array of vortex-like current filaments when the beam current is sufficiently high. A possible connection between this occurrence and phenomena in the aurora is suggested.
Application of the Mass Spectrometer to the Study of the Upper Energy States of Molecules
Authors: Morrison J. D.
Published: April 2005

It is claimed that the poor agreement often found between the energy quantities measured by mass spectrometry, and those obtained by other methods, is due in large part to the interpretation of the experimental data. The conditions necessary for accurate measurement are summarized.

It is shown that by making certain assumptions about the probability of ionization for different processes, ionization efficiency curves can be interpreted to give the probabilities for electronic transitions from the ground state to the various ionic states of molecules. From these electronic transition probabilities, information can be deduced about the potential energy functions for these upper states.

To exploit the method fully, beams of ionizing particles with low spreads in energy are necessary. Electron and photon impact are compared, and it is shown that the latter possesses many advantages.
Formation of Negative Ions in Gases by Secondary Collision Processes
Authors: Muschlitz E. E.
Published: April 2005

Experiments on the formation of negative ions by electron bombardment of hydrogen, oxygen, and water vapor at pressures of 0–4 mm are described. The only ion observed in hydrogen is H−, formed by dissociative attachment. Pressure dependence of the O2− intensity shows that a secondary collision is involved in its formation. Data on the formation of O− and O2− at low electron energies indicate that the secondary collision leading to the formation of O2− does not involve an O− ion. The formation of O2− probably involves a stabilizing collision with a molecule of gas after the initial formation of the ion by electron attachment. From the behavior of H−, O−, and OH− intensities with H2O pressure, it is shown that the secondary process for the formation of OH− in water vapor is probably H−+H2O→OH−+H2. The cross section for this reaction is more than 10−17 cm2.
Measurements of the Effective Resonance Integral in Uranium Metal and Oxide in Different Geometries
Authors: Hellstrand Eric
Published: April 2005

A series of measurements of the effective resonance integral in uranium metal and oxide, UO2, has been made. Measurements were performed on simple rods, on a few tubes, empty or filled with a moderator, and on clusters of rods. Formulas for the effective resonance integral as a function of S/M and (S/M)½ are given for metal and UO2.

In addition the variation of the resonance absorption of neutrons as a function of depth in metal rods has been studied. The results are given in the form of curves.
Studies on the Mechanism of Operation of the L Cathode. II
Authors: Rutledge W. C. , Rittner E. S.
Published: April 2005

An experimental study of the L cathode is presented, including the chemistry of carbonate decomposition and barium generation, the origin of BaO in the evaporant, the barium transport mechanism through the porous plug, and the factors determining cathode life. Carbonate decomposition is accompanied in low porosity cathodes by the deleterious reaction BaCO3+13W=13Ba3WO6+CO. Barium is generated in the cavity at an equilibrium pressure by the reaction 2BaO+13W=13Ba3WO6+Baand is transported continuously through the porous tungsten predominantly by Knudsen flow. During transport the barium acquires oxygen from the tungsten, producing in the evaporant a large BaO content which helps to activate the surface. Termination of life coincides with completion of the BaO–W reaction and onset of the subsequent reaction 23Ba3WO6+13W=BaWO4+Ba,which is accompanied by release of a poisoning agent. Material decrease in evaporation rate and a corresponding increase in cathode life may be gained by addition of SrCO3.
Dislocation Damping at High Temperatures
Authors: Weertman J.
Published: April 2005

An unpinned dislocation damping model (based on the Mott-Nabarro solution hardening theory) was previously used to explain internal friction at room temperature and is now extended into the high-temperature range. With the model it is possible to explain the high-temperature internal friction which has been observed in the kilocycle frequency range for measurements made at very low strain amplitudes. In addition, the damping due to dislocation climb is considered.
Air Bubbles in Water
Authors: Liebermann Leonard
Published: April 2005

The solubility of air bubbles is observed in a variety of experiments. Freely rising bubbles exhibit a solution rate more than twice that of bubbles which are stationary: i.e., trapped on the walls of the container. The theory of solution of stationary bubbles is given but the theory of a free bubble is difficult and has not been solved. Stationary bubble observations lead to a determination of the coefficient of diffusivity: 2.9×10−5 cm2/sec at 27°C; the temperature dependence is considerable, obeying Einstein's equation relating diffusion and viscosity. The effect of surface contamination on diffusion is analyzed; bubble solution in the presence of contaminants is not greatly altered. Experiments are described showing that air bubbles of dimension less than 1μ lodged on hydrophobic particles are not soluble and can exist indefinitely. It is shown that hydrophobic particle residues frequently remain after bubble solution, even in relatively pure water. These residues function as bubble nuclei for boiling or for cavitation.
Ferrite Slabs in Transverse Electric Mode Wave Guide
Authors: Seidel H.
Published: April 2005

The transversely magnetized slab operating in a parallel-plane-type transverse electric mode may be examined from an operational viewpoint. Characteristics of the wave-guide mode emerge from considerations of symmetry and some results are derived that are not evident from a first-order perturbation theory. Operators are developed associated with various transverse strata of the wave-guide cross section corresponding to slabs of different media within the guide. The use of these operators is systematized in application to propagation problems in both rectangular and coaxial type transmission lines. Ferromagnetic resonance is explored in ferrites obeying a reactive Polder tensor-type description and some features of resonance are discussed.
Buildup of Electroluminescent Brightness
Authors: Haake Claus H.
Published: April 2005

The buildup of electroluminescent brightness is compared to the buildup of photoluminescence under various conditions which affect the electron population in traps. A qualitative explanation is proposed as to the mechanism of buildup and conclusions are drawn which confirm the observation that electroluminescence is confined to small regions in the phosphor crystals.
Aging Characteristics of Electroluminescent Phosphors
Authors: Roberts S.
Published: April 2005

The brightness, B, of electroluminescent light sources is observed to decay gradually as a function of operating time, t, according to the empirical formula, B=B0/(1+t/tc), where B0 is the initial brightness and tc is the time to half-brightness. At 60 cps the values of tc range in the hundreds to thousands of hours, while at 5000 cps tc is observed to be less than 100 hr for the particular phosphor used. The value of tc depends slightly, if at all, on voltage; but a very significant change in the voltage dependence of brightness occurs during the aging process. The results are interpreted on the basis of the Piper-Williams theory and are thought to be consistent with a field-induced migration of the deep donor impurity.
Ultrasonic Double Refraction in Single Crystals
Authors: Waterman P. C. , Teutonico L. J.
Published: April 2005

The phenomenon of ultrasonic double refraction and methods of observing it with pulsed echo methods are described in some detail. Two causes of ultrasonic double refraction are described. Double refraction effects were observed in three germanium single crystals. The main cause of the effects reported here seems to be a small angular difference between the propagation direction and a principal axis of the crystal.
Combustion and Detonation in Gases
Authors: Greifer B. , Cooper J. C. , Gibson F. C. , Mason C. M.
Published: April 2005

A photographic investigation of combustion in gases was undertaken to observe experimentally the mechanism of initiation and structure of detonation waves. Streak schlieren photographs of hydrogen-oxygen and carbon monoxide-oxygen explosions were made in a rectangular shock tube using precision optics and a rotating mirror camera.

The photographs show that compression waves generated during the early stages of propagation of the explosion soon steepen into a shock wave which travels ahead of the combustion wave (zone of chemical reaction). This combination of shock and combustion wave is characteristic of a nonsteady detonation state in the moments before stable detonation is initiated. The distance between the two waves narrows as the explosion progresses down the tube due to the continued formation of new combustion centers ahead of the combustion wave by means of auto-ignitions. Eventually the combustion wave overtakes the shock wave and supplies it directly with energy from the chemical reaction; at this moment stable detonation is initiated.

The internal structure of steady state detonations is found to be different from nonsteady state detonations; for example, whereas the distance between the shock and the zone of chemical reaction is of the order of several centimeters in the nonsteady state detonation, this distance in the steady state detonation is too small to be resolved by the optical system (i.e., less than 1 mm). Other structural features such as spinning detonation and a high-frequency oscillation of propagation velocity are also illustrated.
Theory of the Microstrip
Authors: Wu Tai Tsun
Published: April 2005

A procedure is presented for finding by successive approximation the current distribution, and thus the electromagnetic field, of the lowest mode of the microstrip transmission line. The approximation is valid provided that the strip is not too wide and the dielectric sheet not too thick. Each iteration consists of essentially solving two electrostatic problems.
Extension of Babinet's Principle to Absorbing and Transparent Materials, and Approximate Theory of Backscattering by Plane, Absorbing Disks
Authors: Neugebauer H. E. J.
Published: April 2005

A rigorous formulation of Babinet's Principle has been found by Copson and by Meixner for perfect conductors. A recently published theory of diffraction by holes in absorbing and transparent screens suggests a generalization of Babinet's Principle to absorbing and transparent materials. The generalized form of Babinet's Principle is not a rigorous statement; it holds only for certain approximate solutions. In this paper it is used to calculate backscattering by circular disks of various reflection coefficients from zero to unity. Experimental results by Severin and v.Baeckmann support this theory. It is expected that, in a succeeding paper, it can be shown that scattering by solid bodies may be calculated in a similar way if the bodies are bounded by plane surfaces large compared to wavelength.
Thermionic Constants and Sorption Properties of Hafnium
Authors: Hagstrum Homer D.
Published: April 2005

Thermionic emission measurements on polycrystalline hafnium in the temperature range 1250 to 1820°K have yielded a work function of 3.60 ev and a thermionic constant A of 22.9 amp cm−2 deg−2. Intermittent heating thereafter for a total of 46 hours at temperatures above 2100°K and at pressures below 1×10−9 mm Hg did not change these parameters appreciably. No gas was desorbed from the hafnium when it was flashed to 2150°K after having been cold for 64 hours. A second sample of hafnium was used as a target in apparatus for studying electron ejection by ions. It was more brittle than the first and thus more contaminated with gas. Its work function was found to be 3.91 ev and the constant A to be 20.5 amp cm−2 deg−2 after repeated flashing to 2150°K. Evidence from the electron ejection work indicates that the surface of this second hafnium sample was covered with an appreciable fraction of a monolayer immediately after cooling from high temperature. One can conclude that the work function of hafnium increases as the metal irreversibly absorbs gas on heating.
Noise in Nonlinear Oscillators
Authors: Garstens Martin A.
Published: April 2005

A method is presented for estimating the nonlinear noise contribution in an oscillator at low levels of oscillation. This involves obtaining an approximate solution of a nonhomogeneous van der Pol type of nonlinear differential equation driven by noise. The method of solution is based upon the reduction of the equation to a linear form. The nonlinear contribution can then be obtained by computing the power spectrum output of a cube law rectifier. The calculations indicate a variation of nonlinear noise with rf level. Such variation is observed in nuclear and electronic magnetic resonance devices used for the detection of magnetic absorption in paramagnetic materials.
U-Effect-III; Effect of Liquid Drop Motion in Mercury-Electrolyte Capillary Tubes
Authors: Podolsky B. , Kushevics G. , Rivers J. L.
Published: April 2005

When a glass capillary tube filled with alternating drops of mercury and electrolyte is made to vibrate mechanically, an alternating voltage is available across terminals inserted in its ends. This effect has been attributed to changes in the surface area of the interfaces [E. Yeager and F. Hovorka, J. Acoust. Soc. Am. 25, 447 (1953)]. New experimental evidence indicates that at low frequencies the output voltage depends on motion of the liquid drops with respect to the capillary tube. A first-order approximation theory which takes into account the tube compliance and the relative motion of the liquid drops with respect to the capillary tube has been obtained and is found to agree qualitatively with the experimental data relating: (1) tube output voltage to frequency at fixed amplitude of vibration; (2) tube output voltage to relative motion of the drops at fixed frequency; and (3) short-circuit current output to relative motion for fixed capillary radius, independent of mercury-electrolyte proportions for a given electrolyte. Theory indicates that the voltage is a function of the length of mercury in a tube rather than of the number of interfaces; this result seems to be in agreement with the data.
Hydrodynamics of a Reacting and Relaxing Fluid
Authors: Wood William W. , Kirkwood John G.
Published: April 2005

General equations governing the hydrodynamic behavior of an ideal compressible fluid in which chemical reactions and internal relaxations proceed are formulated. For one-dimensional flow the equations are transformed to characteristic form, in which the ``frozen'' or high-frequency sound velocity plays a role analogous to the unambiguous sound velocity in the nonreactive case.
Domain Structure Effects in an Anomalous Ferrimagnetic Resonance of Ferrites
Authors: LeCraw R. C. , Spencer E. G.
Published: April 2005

Measurements of the intrinsic tensor permeability [μ] of unsaturated Ni ferrite at 9300 mc, using cavity perturbation techniques, have revealed an anomalous resonance for negative (anti-Larmor) circularly polarized fields. The resonance has a line width of 70 oe and occurs very near the coercive force which is 13.2 oe. The usual resonance for positive (Larmor) circularly polarized fields occurs at 2750 oe. An interesting consequence of the low-field resonance is that below saturation K″ is negative, where K=K′−iK″ is the off-diagonal component of [μ]. Above saturation K″ is positive. The change in sign of K″ is shown not to violate energy considerations.

These effects are explained by a theory involving rf demagnetizing poles on Bloch walls based on a model with a physically probable domain structure. The theory extends the Polder-Smit mechanism in unmagnetized media to include applied dc fields and circularly polarized rf fields. It is applicable to all ferrites, both mono- and polycrystalline, having domain walls free to move in dc fields of the order of the coercive force. Since the anomalous resonance depends upon the domain structure and appears to occur generally, it is a probe of considerable usefulness for the study of magnetization processes and high-frequency phenomena in ferrites.
Evaporation of Impurities from Semiconductors
Authors: Lehovec K. , Schoeni K. , Zuleeg R.
Published: April 2005

Equations are derived for the impurity distribution which arises by evaporation of impurities from the surface of a homogeneously doped semiconductor. The rate of evaporation is assumed to be proportional to the surface concentration. When a rectifying metal contact is made to a semiconductor with such an impurity distribution, the dependence of capacitance on the applied voltage can be used to determine the proportionality constant between rate of evaporation and surface concentration.
Shock Sphere—An Apparatus for Generating Spherical Flows
Authors: Glass I. I. , Hall J. G.
Published: April 2005

Some experimental results are presented of the flow generated by the explosion of a sphere of high-pressure gas. Glass spheres of 1, 2, and 5-in. diam containing air, He, or SF6 at overpressures up to 21 atmos were used to produce a spherical analog of the shock tube. The results show that the shock sphere may be applied to the study of explosions, implosions, and spherical wave interaction under controlled and known initial conditions.
Diffraction by an Aperture
Authors: Keller Joseph B.
Published: April 2005

Diffraction of a wave by an aperture of any shape in a thin screen is treated by a new method—``the geometrical theory of diffraction.'' This is an extension of geometrical optics which accounts for diffraction by introducing new rays called diffracted rays. They are produced when incident rays hit the aperture edge and they satisfy the ``law of diffraction.'' A field is associated with each ray in a quantitative way, by means of the optical principles of phase variation and energy conservation. In addition ``diffraction coefficients'' are introduced to relate the field on a diffracted ray to that on the corresponding incident ray.

By this method a simple formula is obtained for the field diffracted by any aperture. It yields the field in the aperture, the diffraction pattern and the transmission cross section. Explicit formulas and numerical results are given for slits and circular apertures. The accuracy of the results increases as the wavelength decreases, but they are useful for wavelengths even as large as the aperture dimensions.
Influence of Electric Field in Diffusion Region upon Breakdown in Germanium n-p Junctions
Authors: Pell E. M.
Published: April 2005

The high current density existing at near-breakdown reverse bias of an n-p junction produces, by Ohm's law, an electric field. If the effect of this field is included in the solution for diode current, it is found that it can significantly affect the breakdown characteristic. It can, for example, produce an increase in injected photocurrent resembling multiplication, even though multiplication is not occurring in the junction itself. Alternatively, if multiplication is present, it can produce instability and breakdown before the avalanche in the space-charge region itself becomes unstable (i.e., before the multiplication factor becomes infinite). These predicted phenomena have been observed in a series of germanium n-p junctions. Closely allied with these phenomena is the observation of a region of ``soft breakdown'' in many germanium junctions, which appears to be a bulk effect.
Effects of Annealing on the Saturation Induction of Ferrites Containing Nickel and/or Copper
Authors: Van Uitert L. G.
Published: April 2005

The equilibrium distribution of copper between octahedral and tetrahedral sites in the ferrites varies appreciably with temperature. The rate at which these ions approach their equilibrium distribution at a fixed temperature, after quenching from a higher temperature, is much greater for the slightly reduced materials.

Previously unreported deviations from a smooth variation of saturation induction with annealing temperature have been observed in ferrites containing nickel and/or copper that have been prepared to achieve a high degree of homogeneity and hence to be relatively free from defects.
Magnetic Viscosity in 4–79 Molybdenum Permalloy
Authors: Van Sant Oscar J.
Published: April 2005

The dynamic behavior of 4–79 molybdenum Permalloy operating in a reversible region of its hysteresis loop is analyzed theoretically and experimentally. A useful expression is presented which relates B, H, time, and magnetic viscosity. This expression is applied to determine the behavior of the magnetic material when magnetized (1) by sinusoidal currents having frequencies in the kilocycle/second region and (2) by step-function currents producing transient voltages with time constants in the millimicrosecond region. The theoretical results show that there is a correlation between the behaviors under these two extreme cases of current excitation. This correlation is verified by measurements made on thin tapes having nominal thicknesses of ⅛, ¼, ⅓, and ½ mil and the results of these measurements agree with theory. Various effects of magnetic viscosity on the dynamic behavior of the core material are shown and an expression is derived which makes it possible to solve theoretically certain kinds of magnetic engineering problems whose theoretical solutions have not been achieved previously. These problems pertain to devices such as shift registers, high-frequency transformers, and high-frequency magnetic amplifiers which contain cores made of thin ferromagnetic tape.
Density of Color Centers in Barium Oxide as a Function of the Vapor Pressure of Barium
Authors: Timmer Cornelis
Published: April 2005

Single crystals of barium oxide were exposed at a temperature of 1423°K or 1473°K to barium vapor of different pressures ranging from 3.4×10−5 mm Hg to 7.6×10−2 mm Hg. The resulting blue coloration was measured in an absorption spectrometer, which provided estimates of the number of color centers per cm3, NF. The relation between NF and the number of barium atoms per cm3 in the vapor, Nv, was NF=1.5×1013Nv13. This relation can be tentatively explained by assuming total dissociation of the color centers into oxygen vacancies and free electrons at the temperature of formation.
Dynamic Mechanical Properties of Polyhexene-1
Authors: Kurath Sheldon F. , Passaglia Elio , Pariser Rudolph
Published: April 2005

A double electromagnetic transducer has been used to evaluate the complex shear modulus of polyhexene-1 from +70°C to −27.5°C in the 25 to 2500 cps frequency range. Real and imaginary components of the complex shear modulus as well as the mechanical loss tangent are reported over nine decades of reduced frequency. The temperature dependence of mechanical properties is discussed in terms of polymer-free volume and the glass transition temperature of −55°C. The shape of the relaxation distribution function in the transition region is similar to that of polyisobutylene. In the rubbery region the distribution function obtained from dynamic shear moduli compares favorably with that determined from stress relaxation measurements.
Fading of Radio Waves Scattered by Dielectric Turbulence
Authors: Silverman Richard A.
Published: April 2005

The fading of radio waves scattered by dielectric turbulence is shown to be the result of two effects. The first is time variation of the scattering eddies as seen in a coordinate system moving with the local wind velocity. The second is Doppler shifting produced by the convection of the scattering eddies by the mean wind and by the macro-eddies. In the troposphere, the scattering eddies lie in the inertial range of statistical turbulence theory. This makes it possible to find the envelope fading rate of the received scattered signal to within a constant of proportionality by using dimensionality and similarity arguments. The result is an expression for the fading rate as a function of carrier frequency which departs significantly from that found with ``scattering blob'' models.
Frequency Dependence of Ultrasonic Attenuation and Velocity on Plastic Deformation
Authors: Hikata Akira , Truell Rohn
Published: April 2005

The dependence of ultrasonic attenuation and velocity on plastic deformation in 2S aluminum is compared at two frequencies, five and ten megacycles, and the comparison shows agreement as regards frequency dependence with what one can expect from dislocation damping theory.
Dissipation of Energy by 2.5–10 kev Electrons in Al2O3
Authors: Young J. R.
Published: April 2005

Measurements have been made of the energy distribution of electrons penetrating thin samples of Al2O3. The observations were made using a 127° electrostatic analyzer. These results allow a determination of the dissipation of electron energy with depth when 2.5–10 kev electrons strike Al2O3. Results obtained indicate that for a given bombarding energy the average energy loss per unit thickness dW/dx remains almost constant over the entire penetration depth. However, dW/dx decreases slowly as the bombarding electron energy increases. These observations are in general agreement with those made by Ehrenberg and Franks for 10–40 kev electrons striking phosphors.