bluuebunny/crossref_metadata_2025_split huggingface dataset:
Etching of Dislocations on the Low-Index Faces of GaAs
Authors: Abrahams M. S. , Buiocchi C. J. 
Published: April 2005

A new etchant for GaAs consisting of CrO3, HF, AgNO3, and H2O is described which selectively attacks dislocations on the following planes: Ga {111}, As {111}, {100}, and {110}. Dislocations normal, inclined, and parallel to the plane of observation are revealed. The etching figures were correlated with dislocations by equating (a) the etch pits produced on {111} surfaces with those produced by a known dislocation etchant, (b) the {111} etch pits with the linear structure appearing on {100}, and (c) the pits on two matched {110} cleavage planes. Supporting evidence obtained from plastic indentation experiments on {111} and {100} is also presented. It is observed that long, straight dislocations tend to lie in 〈110〉 and 〈112〉 directions. It was established by reverse bending experiments that the etchant produces pits only at As or β dislocations, if no impurity segregation has occurred. If decoration of the dislocations has occurred, as in Bridgman-grown GaAs, pits are produced at both α (Ga) and β dislocations.
The relative etching rates for the {100}, Ga {111}, {110}, and As {111} faces are 1.0, 0.71, 0.69, and 0.50, respectively.
Stacking faults on {100} are also revealed by the etchant on epitaxial films. A second etchant is reported which reveals stacking faults on the As {111} faces of GaAs. This etchant is the same as the dislocation etchant but with the CrO3 absent.
Theory of the Single-Wire Transmission Line
Authors: Roberts T. E. 
Published: April 2005

Equations are derived for the current induced in an infinitely long, thin, straight wire of nonzero surface impedance when the wire is connected to a flanged coaxial line. Also, radiation field patterns are computed and the input conductance determined. It is found that the current (and likewise the input conductance) can be separated into two components, one of which is a propagating or modal current. Graphs are presented from which the efficiency of excitation of the propagating current can be computed.
A second structure consisting of a single wire between perfectly conducting parallel plates is solved as a boundary-value problem. The solution is used in the discussion of the physical behavior of a finite single-wire transmission line. In particular it is found that the usual transmission line concepts are valid under certain restricting conditions.
Attenuation of Gamma Rays. I. Transmission Values for Finite Slabs of Lead, Iron, and the Compton Scatterer
Authors: Peebles Glenn H. 
Published: April 2005

An approximate integral recursion formula is developed which gives a relation between the probability that a photon will be transmitted through a slab of finite thickness with exactly k+1 collisions and the probability that it will be transmitted with exactly k collisions, where the latter probability is known for suitable ranges of slab thickness, of incident energy, and of incident angle. A similar formula also exists for the expected energy transmitted. The two recursion formulas have been used to calculate the transmissions with one, two, and three scatterings for photons incident on slabs of lead and of iron, and from these calculated transmissions the ``build-up'' factors have been estimated. The build-up factor for normally incident photons of 1 to 20 mc2 are given for lead slabs and for iron slabs having a thickness of 0 to 20 mfp.
A second method, which considers the transmission through a thick slab as a succession of transmissions through thin slabs, is used to check the estimates of the build-up factor obtained by the first method. This second method provides additional information in the form of the distributions of the transmitted photons.
Finally, some transmission and reflection values for thin slabs of the Compton scatterer are presented along with some results for air which are obtained by the second (thin-slab) method.
Attenuation of Gamma Rays. II. Transmission Values for Various Materials and Geometries
Authors: Peebles Glenn H. 
Published: April 2005

A discussion of the effect of variation of the total absorption coefficient on gamma-ray transmission probabilities is given, which leads to estimates of the build-up factors for a material of arbitrary atomic number Z.
Estimates are made of the photon and energy densities arising from a plane of sources, a line of sources, and a point source in an infinite homogeneous medium, where the material of the medium is (1) iron and (2) lead.
Microwave Diffraction Measurements in a Parallel-Plate Region
Authors: Row Ronald V. 
Published: April 2005

Many infinite two-dimensional electromagnetic-scattering problems are strictly equivalent to the configuration obtained from the image principle by placing a finite-scattering obstacle between two parallel, infinite, and perfectly conducting planes and illuminating it with a plane or cylindrical incident wave confined to the parallel-plate region.
An experimental approximation to this arrangement is described for use in the 3-centimeter wavelength region. Finite rectangular parallel metal plates support a transverse incident electromagnetic wave with the electric field oriented perpendicular to the plates. Absorbing wedges at the boundary of the region reduce reflections from this discontinuity. The electromagnetic field scattered from any particular obstacle may be investigated by means of a dipole probe introduced into the region through a moveable section of one of the plates.
The success of this technique is demonstrated by comparing measurements of the total field scattered by infinite conducting wedges of included angle 0, 45, and 90 degrees with the known theoretical expressions, for perpendicular incidence. Agreement with theory is good.
The effect of finite thickness of the diffracting screen (case of 0° wedge) in increasing the amplitude of the scattered wave is noted and compared to theoretical results derived for scattering from a thin conducting half-plane with a cylinder superimposed on the edge.
Theory of the Formation of Bubbles
Authors: Takagi Shunsuke 
Published: April 2005

We have not yet obtained a perfect theory of bubble formation. In this paper the perfect theory of the formation of bubbles in the case where the bubbles of vapor are nucleated spontaneously in pure liquid is presented. This is done by the systematization of the classical theory of M. Volmer (Kinetik der Phasenbildung, 1939) and the theory of D. Turnbull and J. C. Fisher [J. Chem. Phys. 17, 71 (1949)] and it coincides satisfactorily with the experiment of K. L. Wismer [J. Phys. Chem. 26, 301 (1922)].
Theory must be advanced further so as to afford a perfect explanation of the processes of boiling, cavitation and the critical phenomena of the movement of soil moisture [S. Takagi, Monographs on Theoretical Soil Physics; Theoretical Considerations on the Thermodynamical and Kinematic Properties of Soil Moisture (not yet published)]. To effect this object, the author has calculated the rate of formation of bubbles at a surface. The theoretical value, however, of the negative pressure at which the liquid fractures does not coincide by any means with the atmospheric pressure in the process of boiling. This is true also in the process of cavitation and in the process of critical phenomena of the movement of soil moisture. Some other factors must be introduced in order to bring the theory to a state of practical value.
The Effect of the Rate of Cooling on the Allotropic Transformation Temperatures of Uranium
Authors: Duwez Pol 
Published: April 2005

Allotropic transformation in uranium has been studied over a range of cooling rates from 5 to about 8000°C/sec. The transformation temperatures of both gamma-to-beta and beta-to-alpha were found to decrease continuously with increasing rates of cooling. The extent of the beta-range increased with increasing cooling rates. For rates of cooling up to 1000°C/sec, recalescence was observed in both transformations. For higher cooling rates, there was usually no recalescence.
In most of the recorded cooling curves, a small but definite thermal arrest was observed, between the two main arrests which correspond to the two known phase transformations. This additional thermal arrest was also present in a heating curve, where it occurred at about 740°C, compared with 666 and 771°C for the two known phase transformations. Possible explanations of the additional arrest are discussed.
A Thermoelectric Study of the Electrical Forming of Germanium Rectifiers
Authors: Kikuchi Makoto , Onishi Tomio 
Published: April 2005

The electrical forming phenomena on the etched surfaces of n-type Ge crystals by ac voltages were studied thermoelectrically. Remarkable improvements in the i-v characteristics were obtained by applying appropriate forming voltages. The thermoelectric current observed on the etched surface showed n-type direction but it was converted to p-type by the forming. It has also been found out that the thermo-emf depends sensitively on the pressure of the whisker contact after the forming (and on the polished surface), while the dependence is small before the forming on the etched surface.
Experimental results seem to show that some substance of relatively high resistivity and of p-type thermo-emf is produced by the forming between the whisker metal and the Ge surface.
Forced Oscillations with Nonlinear Restoring Force
Authors: Hayashi Chihiro 
Published: April 2005

Forced oscillations with nonlinear restoring force are studied in transient states as well as in steady states. The original differential equation characterized by a nonlinear term is transformed under certain restrictions to the following differential equation of the first order: dy/dx=Y(x,y)/X(x,y).
Following Poincaré and Bendixson, the singularities and the integral curves of the above equation are discussed, the former being correlated with the periodic states of oscillations, the latter with the transient states of oscillations. The stability of the periodic solutions is determined in accordance with that of the singular points, viz., according to the roots of the characteristic equation. The integral curves yield the relationship between the given initial conditions and the periodic solutions. Thus, once the initial conditions are prescribed, we can foresee the final periodic states which are started with those conditions.
With this method of investigation, we have first studied the harmonic oscillations presented in Part I and then the subharmonic oscillation of order ⅓ given in Part II. In both cases the theoretical results are compared with the experimental measurements carried out for an electric circuit containing a saturable iron core, and the satisfactory agreement is found between them.
An Operational Analysis of Traffic Dynamics
Authors: Pipes Louis A. 
Published: April 2005

The dynamics of a line of traffic composed of n vehicles is studied mathematically. It is postulated that the movements of the several vehicles are controlled by an idealized ``law of separation.'' The law considered in the analysis specifies that each vehicle must maintain a certain prescribed ``following distance'' from the preceding vehicle. This distance is the sum of a distance proportional to the velocity of the following vehicle and a certain given minimum distance of separation when the vehicles are at rest. By the application of this postulated law to the motion of the column of vehicles, the differential equations governing the dynamic state of the system are obtained.
The solution of the dynamical equations for several assumed types of motion of the leading vehicle is effected by the operational or Laplace transform method and the velocities and accelerations of the various vehicles are thus obtained. Consideration is given to the use of an electrical analog computer for studying the dynamical equations of the system.
Elasticity and Thermal Expansion of Germanium Between −195 and 275°C
Authors: Fine Morris E. 
Published: April 2005

Young's moduli (E) of the directions 〈100〉 and 〈111〉 and the shear modulus (G) for 〈100〉 were determined in germanium from −195 to 255, 275, and 140°C, respectively. From these moduli, the elastic parameters, the compressibility, and Poissons's ratio were calculated.
The thermal expansion was measured from −196 to 275°C.
Limiting Conditions for Jet Formation in High Velocity Collisions
Authors: Walsh J. M. , Shreffler R. G. , Willig F. J. 
Published: April 2005

The high velocity collision of two solids is discussed as a problem in compressible fluid hydrodynamics. Such collisions may conveniently be divided into jetless and jet-forming categories. A theory is presented which describes flow in the collision region for the jetless case and determines a critical collision angle (as a function of material velocities and equation-of-state properties of the materials) above which a jet must arise from the collision.
The experimental study of solid collisions utilizes metal plates driven by high explosives, the impact of the plates being recorded with a high speed smear camera. Two experimental arrangements are used, and data for collisions employing Dural, mild steel, brass and lead are presented. Jetless and jet-forming collisions are observed, and critical angles separating the two types are compared with theoretical predictions. Agreement seems sufficiently good to indicate that the theory is valid.
Positive and Negative Ions in Cathode-Ray Tubes
Authors: Bachman C. H. , Hall G. L. , Silberg P. A. 
Published: April 2005

The positive and negative ions accompanying the operation of a cathode-ray tube contribute in a number of ways to tube failure. These ions have been studied in standard sealed-off tubes. The identities of the most persistent ions have been determined and ion currents measured. Some attempts to limit or control the ions at their sources have been made.
The greatest offender is hydrogen which is present as both negative and positive ions. It is shown that aluminized screens offer little protection to the ion bombarded phosphor. Uncertainty in the literature as to whether negative m/e, 26 is C2H2 or CN seems resolved in favor of C2H2.
The Limiting Negative Pressure of Mercury in Pyrex Glass
Authors: Briggs Lyman J. 
Published: April 2005

It is generally considered that mercury does not ``wet'' glass, as evidenced by the convex surface of the mercury meniscus in a manometer. If this were true under all conditions, the development of a negative pressure in a mercury column would be impossible. But pure mercury in a clean evacuated degassed tube shows a flat meniscus. In other words, when the tube is degassed, mercury does adhere to the glass wall.
A U-tube manometer of 5-mm bore with one leg sealed off was evacuated and degassed at 500°C with a mercury-vapor pump, and then filled with pure mercury by distillation. The vertical height of the mercury column from the meniscus in the open tube to the top of the closed leg was 52 cm. When the manometer was again evacuated, the mercury column remained suspended from the top of the tube, withstanding a negative pressure of two-thirds of an atmosphere.
In extending the measurements, short mercurial thermometers were first used. Each thermometer was cemented to the spinner of a variable-speed motor, with the spin axis bisecting the distance from the end of the bulb to the meniscus. The maximum centrifugal stress on the free capillary column was consequently at the spin axis. Measurement of nine thermometers gave negative pressures ranging from 2 to 17 bars.
Finally, freshly drawn capillary tubes with fine bores were evacuated, degassed by heating, sealed off and filled by breaking one end under pure mercury. The negative pressure which these mercury columns could withstand under centrifugal stress increased rapidly as the degassing improved. The highest negative pressure observed for mercury was 425 bars at 28°C. In this case, the furnace temperature during degassing was raised to the point where the capillary tube started to deform.
The Gas Flow Past Slender Bodies
Authors: Munk Max M. 
Published: April 2005

The following relates to moving objects immersed in a perfect gas otherwise at rest. The momentum of the resulting gas flow is defined. It is shown that it ultimately approaches a definite magnitude as the object assumes a steady motion, said magnitude being independent of the history of the previous motion.
This result is applied to the two-dimensional flows of airship theory, and thus the airship theory is extended to include compressibility effects to a limited extent.
Axial Motion of Electrons in a Linear Accelerator with β=1
Authors: Swihart James , Akeley Edward 
Published: April 2005

Complete integrated solutions have been found in terms of elementary functions for the motion of an electron on the axis of a progressive wave linear accelerator with a constant wave speed, β=1. The character of the solutions has been discussed and asymptotic relations found.
Calculations have been made for the third section of the Purdue linear accelerator, in which the curves for the first two sections where β&lt;1 have been extended. The energy distribution of the emergent beam was computed. It was found possible to design a linear accelerator with constant wave speed sections which, without preliminary bunching, would produce a beam of greater homogeneity in energy than might have been expected.
A Test of the Theory of Secondary Viscoelastic Stress
Authors: Mooney M. 
Published: April 2005

Experimental data published by Garner, Nissan, and Wood on secondary stresses in a viscoelastic liquid have been analyzed in terms of the superelasticity theory of secondary stresses as developed by Mooney. The theory was slightly modified to be consistent with the reported viscosity rate of shear behavior of the test liquid. With this modification the theory agreed within experimental error with observed normal stresses at various radii on a stationary circular plate mounted parallel to a rotating plate.
One reported qualitative experimental result is in disagreement with the theory, but this particular result is questioned. Other theories of secondary stress are briefly discussed.
Viscoelastic Properties of Dilute Polymer Solutions
Authors: Rouse P. E. , Sittel K. 
Published: April 2005

The viscoelastic properties of dilute solutions of chain polymers have been measured at frequencies in the range from 200 cps to 60 kc. The data are compared with theoretical curves calculated from the steady-flow viscosities of the solution and solvent, the molecular weight and concentration of the polymer, and the absolute temperature; this calculation made use of equations obtained from a recently developed theory. The equations contain no adjustable constants. The theory is shown to be at least a good first approximation to the viscoelastic properties of the solutions studied.
The agreement of the data and the theory implies that, up to 60 kc at least, the viscoelastic properties of dilute solutions of polystyrene and polyisobutylene are the result of the thermal motions of the segments of the polymer molecules. These segmental motions coordinate with one another to produce changes in the configurations of the molecules. The configurational changes have associated with them a series of relaxation times. These relaxation times are shown to depend upon molecular weight of the polymer, concentration, type of solvent, and viscosity of solvent.
Transmission of Electromagnetic Waves through Pairs of Parallel Wire Grids
Authors: Groves Willice E. 
Published: April 2005

The control and direction of electromagnetic waves is accomplished, in general, by the use of boundary materials and structures which produce desired effects on such waves when irradiated by them. An important class of boundary structure for this purpose is a surface having alternate areas of conducting and nonconducting material. Grids formed of a large number of parallel cylindrical conductors of circular cross section, uniformly spaced and lying in a common surface, are among the most generally useful of this class of boundary structure. Single layer parallel wire grids have received considerable study in the past. However, little information is available concerning the characteristics of multiple layers of such grids
An analytical solution is obtained for the power transmission coefficient of a double grid system. Power transmission coefficients for various combinations of system parameters are computed from the analytical solution and tested experimentally. The solution is found to yield excellent correlation with experiment until the interwire spacing approaches the wavelength.
Determination of the Surface Stress by Means of Electroplating
Authors: Ōkubo H. 
Published: April 2005

This paper presents a new method for the measurement of surface stress. By the use of test pieces plated with copper, the stress is measured by observing the flecks on the surface produced by cyclic stress. The variation in the appearance of flecks which is due to the change of load is very sensitive at a proper load, so an accurate determination of the surface stress is feasible.
The stress concentration factor in torsion is obtained experimentally by the method described for circular shafts with a circumferential notch in each. The results are compared with theoretical values, calculated from two different formulas previously derived by the author and Sonntag, respectively. It is confirmed that the experimental results obtained here are in good agreement with those calculated by the author's formula.
Electron Flow Through Small Tubes With Magnetic Focusing
Authors: Stewart John L. 
Published: April 2005

When a uniform finite magnetic field passing through the cathode is used for focusing a beam of electrons, random emission at the cathode results in the electrons traveling down the beam in a helical manner. Such a rotational motion severely limits the amount of current that can be made to travel through a small tube or between closely spaced parallel plates. The amount of current transmitted through such structures is calculated in this paper and presented in the form of normalized curves. It is assumed that the current initially fills the tube or the region between the parallel plates.
If an alternating electric field having a frequency comparable to the rotational frequency of the electrons is applied normal to the beam, the average electron radius of motion is increased. Should the electron beam be made to flow through a tube after the application of such an alternating electric field, the current transmission through the tube will be reduced over that when no electric field exists. The first-order correction term for this case is calculated and presented in the form of normalized curves. The fact that the average electron radius is increased when an electric field is present implies added energy and leads to the formulation of a conductance expression relating the power in the rotational motion of the beam to the electric field normal to the beam.
The current interception and the equivalent beam conductance are important in many electronic devices such as traveling-wave tubes. The beam conductance may be quite large in some cases—on the order of that present off the axis of a helix.