bluuebunny/crossref_metadata_2025 huggingface dataset:
Considerations Regarding the Distribution of Radiation Damage in Matter Bombarded by Light Ions and a Method of Making it Uniform
Authors: Schwed Philip , Groetzinger Gerhart
Published: April 2005

If a beam of high energy particles impinges on a solid, radiation damage is produced only in a very thin layer at the end of the range of the particles. Computations determining the extent of this inhomogeneity of damage are outlined and carried out for the specific case of 20-Mev deuterons impinging on a copper sample. A simple method is discussed for producing uniform damage in a thickness corresponding to the range of the particles.
Space-Charge-Limited Currents between Inclined Plane Electrodes
Authors: Ivey Henry F.
Published: April 2005

The method of attack devised by Walker has been applied to the problem of current flow between inclined plane electrodes. It is assumed that the initial velocities of emission are negligible. Solutions for the potential distribution, the space-charge characteristic (``perveance''), the particle trajectories, and the transit time in such diodes under conditions of complete space-charge limitation are given. The trajectories and transit time have also been determined for the space-charge-free case. The results are presented in both graphical and tabular form. In most cases the solutions are given for angles between the electrodes as great as 180°.

For an angle between the electrodes of approximately 118° the transit time in the space-charge-free case is equal to that for complete space charge limitation. The effect of accidental electrode tilt on the perveance of a diode, which presumably has parallel electrodes, has also been investigated. A rectangular electrode whose width is 1.24 times the interelectrode spacing is relatively insensitive to tilt about a line passing through its center and parallel to its side. A disk-shaped electrode is insensitive to tilt about any axis passing through its center if its diameter is 1.42 times the interelectrode spacing.
Secondary Electron Emission from Metals under Positive Ion Bombardment in High Extractive Fields
Authors: Webster E. W. , Van de Graaff R. J. , Trump J. G.
Published: April 2005

In the further study of breakdown mechanisms in high vacuum, experiments show that secondary electron emission from metals under positive hydrogen ion bombardment is small and increases only slowly with the electric field strength at the bombarded surface. Although more significant emission may yet be found with the heavier ions obtained in an actual vacuum gap, the particle interchange component of the breakdown process appears to be quantitatively inadequate on the basis of present measured electron and positive ion emission coefficients. The possible importance of negative ion emission deserves consideration in the particle exchange process.
Phenomena Associated with the Flight of Ultra-Speed Pellets. Part III. General Features of Luminosity
Authors: Rinehart John S. , Allen William A. , White W. C.
Published: April 2005

Ultra-speed pellets of the lighter metals such as aluminum and magnesium generate intensely luminous trails when fired through air. A pronounced characteristic of the luminous trails is the intermittent manner in which the light is emitted. This effect has also been observed in meteors and in studies of conventional shaped charges. Photographs indicate that flashing is caused by yawing of the pellet.

The brilliant flashes of light are associated with the ablation and subsequent burning of material from the pellet. There is evidence that the material is removed from the pellet in the form of small droplets.

The brightness, luminous output, and temperature of the trail generated by an aluminum pellet have been measured. The brightness is approximately 25,000 lamberts, the luminous output is 30,000 lumen-seconds, and the color temperature is 2900°K.
Mechanisms of Positive and Negative Corona in Hydrogen and Argon between Coaxial Cylindrical Electrodes over an Extended Pressure Range
Authors: Lauer Eugene J.
Published: April 2005

Mechanisms in the corona discharge from a fine platinum wire at a positive potential along the axis of a hollow nickel cylinder have been investigated by using the oscilloscope to analyze the pulses caused by α-particles passed through the low field region parallel to the wire. γp, the secondary coefficient for the photo-electric effect at the cathode in hydrogen, had values from 70×10−5 at 100 mm to 5×10−5 at 650 mm pressure. γi for the hydrogen ions at the cathode was less than 10−6. The mobility of the positive ions (presumably H2+) was 13.4 (±0.4) cm2/volt×sec at 760 mm and 20°C. Adding 0.1 to 1.0 percent of oxygen to hydrogen resulted in the formation of O2− ions. γi for the argon positive ions was about 9×10−4 extrapolated to zero pressure and decreased with increasing pressure and γp was less than 110γi. Most of the ions were A2+ with a mobility of 1.94 (±0.08) cm2/volt×sec. Positive wire dc current voltage data were taken in hydrogen and argon at several pressures. Sparks occurred with the positive wire in argon at relatively lower gap voltages than in hydrogen. Current-voltage data were taken with the wire negative. In hydrogen the discharge started as a small (10−11 amp) self-supporting current (probably uniformly distributed along the wire) which changed with increasing gap voltage to a larger (microampere) discharge localized in luminous spots on the wire in analogy to Miller's observations in nitrogen. No small self-supporting currents were observed in argon. The discharge started as a spark above 200 mm and as a glow that spread uniformly over the wire below 100 mm pressure.
Study of Imperfections of Crystal Structure in Polycrystalline Materials: Low Carbon Alloy and Silicon Ferrite
Authors: Slade J. J. , Weissmann Sigmund
Published: April 2005

The technique of the new x-ray double spectrometer method as described in a former paper1 is applied to the study of angular misalignment of crystal structure in alloys.

To obtain a better statistical evaluation of the x-ray intensity data the method is extended to include arrays of spots on the Debye-Scherrer lines at high elevations. A complete mathematical discussion of the photometric transformation of the crystallite rocking curves is presented.

The specimens investigated include a low carbon alloy annealed at 850°C and three silicon ferrite samples annealed at 980°, 1100°, and 1200°C.

The quantitative data obtained disclose a significant dependence of crystal perfection on annealing temperature, and demonstrate clearly that the angular misalignment of the coherently reflecting regions within the grains decreases with annealing temperature provided this temperature is not excessive.

Valuable information regarding the influence of cold rolling on the subsequent annealing process is obtained. Thus, the extent of partial recrystallization of the silicon ferrite is deduced from the statistical data, and the differential grain size between the surface layers and the interior of the specimen is revealed through the study of the diffraction effects with radiation of different wavelengths.

A mechanism of grain bending during plastic deformation is suggested and a relationship between magnetic properties, annealing temperature, and crystal perfection of the silicon ferrite is pointed out.
Correlation of DC and Microsecond Pulsed Emission from Oxide Coated Cathodes
Authors: Horak Frank A.
Published: April 2005

This report describes a study of dc and microsecond pulsed emission from oxide coated cathodes prepared on four different base metals. One of the base metals used was pure electrolytic nickel and the other three had impurities of 0.2 percent silicon, 4 percent silicon, and 4.7 percent tungsten added to the nickel. The flat base metal cathode was coated with equal molar barium-strontium carbonate. The tubes were placed on life test at a cathode temperature of 1125°K with no emission current drawn. Dc and pulsed emission measurements were taken periodically. Three methods were used to measure the zero field emission current, (1) dc retarding potential, (2) dc Schottky, and (3) pulsed Schottky. These gave essentially the same Richardson plot indicating a positive correlation of dc and pulsed emission. From these Richardson plots obtained using methods (1) and (3), the work function, the emission constant, and J0, the characteristic emission current density at 650°K, were determined. The results show that the different cathode base metals control the variation in emission with life. The emission from the tungsten-nickel base metal is stable with life and is of much higher value than the other base metals.
Physical Structure and Magnetic Anisotropy of Alnico 5. Part II
Authors: Nesbitt E. A. , Heidenreich R. D.
Published: April 2005

As a result of measurements of magnetic anisotropy and coercive force on single crystals of Alnico 5 and the electron metallography of Part I, the following conclusions were obtained. When the crystals are heat treated in a field in the principal crystallographic directions, the easy direction of magnetization is the field direction, and magnetically the crystals have twofold symmetry. However, there is a strong tendency because of crystal forces for the precipitate to grow in 〈100〉 directions; and, therefore, the crystal has the highest anisotropy when the heat-treating field and a 〈100〉 direction are parallel. The large increase in residual induction of Alnico 5 which results from the magnetic field heat treatment is caused by the easy directions of the crystal changing from the 〈111〉 directions to a single easy direction approximately parallel to the field. Domain rotations rather than boundary movements account for the coercive force of the alloy, since the dimensions of the individual particles are approximately 200 angstroms. The present physical picture of the alloy is one of single domains of precipitate material in parallel with single domains of matrix material, the observed coercive force being the resultant of this parallel combination.
The Elastic Constants of Nickel
Authors: Neighbours J. R. , Bratten F. W. , Smith Charles S.
Published: April 2005

The elastic constants of nickel have been determined by the pulsed ultrasonic method. Wave velocity measurements on four nickel single crystals of general orientation which were magnetically saturated were combined by the approximation method leading to values of the elastic constants C11=2.53, C12=1.52, C44=1.24, all in units of 1012 dyne cm−2.
Deformation and Fracturing of Thick-Walled Steel Cylinders under Explosive Attack
Authors: Pearson John , Rinehart John S.
Published: April 2005

Tests have been conducted on annealed heavy-walled cylinders of low carbon (1020) steel internally loaded by explosive charges. The purpose of these tests was to obtain basic information on the manner and type of fracturing and plastic flow obtained by extremely high pressures acting for short durations. It was observed that all of the cylinders tended to fracture in long fragments in the same basic pattern, but with variations because of wall thickness and manner of loading. Experimental results indicate that the radial cleavage type of fracture is initiated within the cylinder wall and propagated to the surface, while the shear type fracture associated with the inner portion of the cylinder wall appears as an independent energy relieving process.

Microstructure analysis of the cylinder fragments shows a definite relationship between the type of fracture and the amount of distortion of the grain boundary. Considerable shock twinning is present in the cylinder fragments, and the grain structure near the inner surface shows severe distortion and flow. Strain measurements indicate that considerable plastic strain occurs during the explosive loading and cleavage fractures were always observed to occur in association with considerable plastic deformation.
Influence of Cold-Work on the Hall Effect of a Metal
Authors: Wiener Bernard , Groetzinger Gerhart
Published: April 2005

Cold-work in copper to the extent of 75 percent reduction in the cross-sectional area resulted in an increase in the Hall constant of 0.01±0.002 times the Hall constant for annealed copper. The value obtained for the Hall constant for annealed copper was minus 5.33×10−13 volt-cm/ampere-gauss.
Interferometric Analysis of Airflow about Projectiles in Free Flight
Authors: Bennett F. D. , Carter W. C. , Bergdolt V. E.
Published: April 2005

A description is given of the adaptation to the ENIAC of the interferogram reduction problem for axisymmetric flows. Isopycnal charts from interferograms of projectiles in free flight are presented, and comparison is made with similar studies by other workers using fixed models in a wind tunnel or a circular jet. In general, good agreement is found between density fields obtained by the two methods. Sources of error are discussed; and in particular, it is found that random errors accumulate to effect adversely the density values near the axis of the flow.
Radiation Field of a Square, Helical Beam Antenna
Authors: Knudsen H. Lottrup
Published: April 2005

Rigorous formulas have been derived for the field from a square, helical antenna with a uniformly progressing current wave of constant amplitude. These formulas that have the advantage of great simplicity are of direct use for helical antennas in the meter band, where for practical reasons only square helices are used. Further, in connection with corresponding rigorous formulas for the field from a circular, helical antenna with a uniformly progressing current wave of constant amplitude the present formulas may be used for an investigation of the magnitude of the error introduced in Kraus' approximate calculation of the field from a circular, helical antenna by replacing this antenna with an ``equivalent'' square helix. This investigation is carried out by means of a numerical example. The investigation shows that Kraus' approximate method of calculation yields results in fair agreement with the results obtained from the rigorous formulas. A statement to the contrary made recently in the literature is shown to rest on a trivial error.
Contribution to the Theory of the Silicon Carbide Contact
Authors: Holm Else
Published: April 2005

1. The high limiting contact voltage of 40 to 50 volts in contacts between silicon carbide members (single crystals of the black-green variety) is explained on the basis of the known temperature-voltage relation.

2. Practically clean silicon carbide possesses a superficial layer which functions as a potential hill for the electrons. Because of its thinness the hill is penetrable for the electric current by means of the tunnel effect. The tunnel resistance per unit area was investigated with terminal areas of the order of 2 mm2. Being constant at small voltages, it drops down through some orders of magnitude within the voltage range of 0.5 to 5 volts, showing that the work function for emission of electrons into the barrier material from the adjacent metal is of the order of 3 electron volts. From the amount of the tunnel resistance it is concluded that the thickness of the potential hill is of the order of 10 to 20 Angstrom units. The simultaneity of applied voltage and tunnel current is demonstrated.
Eddy-Currents in Solid Cylindrical Cores Having Non-Uniform Permeability
Authors: Aspden Harold
Published: April 2005

A method of estimating magnetization losses due to eddy-currents in solid cylindrical cores of ferromagnetic material is given. The conception of complex permeability is introduced to show the effects which hysteresis has upon the degree of flux penetration. A formula is given for the effective permeability which should be used in the classical treatment in which nonlinearities have been ignored.

An arbitrary case in which the permeability changes across the core section is considered and the solution is extended to a core which is homogeneous, but whose permeability changes with the degree of magnetization. In this way errors due to a nonlinear B-H curve are reduced and the complex permeability notation is shown to lead to a more reasonable Steinmetz relationship.

The eddy-current anomaly is mentioned and it is noted that the theory developed is suited to a consideration of the anomaly as explained in terms of time-lag effects.
The Condition for the Creeping of a Liquid Past a Mercury Seal
Authors: Jessup R. S.
Published: April 2005

An observation of the creeping of a liquid past a mercury seal is reported. The conditions under which such a phenomenon might be expected to occur are discussed in terms of the thermodynamics of surfaces.
Electromagnetic Levitation of Solid and Molten Metals
Authors: Okress E. C. , Wroughton D. M. , Comenetz G. , Brace P. H. , Kelly J. C. R.
Published: April 2005

The subject is an unconventional method of heating and melting metals without a crucible, by suspension in space with an electromagnetic field. Operating conditions for certain cases are given. The results obtained by means of the new technique encourage the thought of melting, purifying, alloying, and agitating of inert and reactive metals without resort to crucibles, and thereby avoiding the contamination of reactive metals by crucible materials. Preliminary results with various forms and masses of metal are described. Considerations concerning the atmosphere in which levitation occurs are included.
The Effect of Velocity Distribution in a Modulated Electron Stream
Authors: Watkins Dean A.
Published: April 2005

A method of solving electron beam problems is described which takes into account the thermal velocity spread. The method is based on the Liouville theorem. Two such problems are solved by means of a power series. In the case of small-signal velocity modulation of a drifting stream, the velocity spread distorts the shape of the standing wave of current which is produced, in addition to lengthening the plasma wavelength and the electronic wavelength. For a drifting stream with full shot noise in each velocity class at the input, a standing wave of noise current is produced with deep minima. The size of the first minimum is found to increase as the square of frequency and with increasing velocity spread. That full uncorrelated shot noise can produce a standing wave of convection current is somewhat surprising. The present analysis demonstrates that space charge is the important factor in determining the behavior of noise currents in electron streams even at high frequencies, and that velocity spread plays a less important role.
The Radiation Resistance of Resonant Transmission Lines
Authors: Chipman R. A. , Carr E. F. , Hoy N. A. , Yurko M.
Published: April 2005

For resonant sections of a transmission line consisting of parallel silver rods extending vertically above a metal ground plane, the resonance curves of input admittance as a function of line length have been drawn by a synchronized recording meter apparatus, and the effective total resistance of each resonant line calculated. This has been done for frequencies between 300 Mcps and 1400 Mcps, for resonant line lengths up to several wavelengths, for line sections with both open-circuit and short-circuit termination at the top, and in each case with and without a large metal pipe shielding the test line. Radiation resistance is obtained as the difference between the resistance calculations for any one resonant line section unshielded and shielded.

With a probable error of about 5 percent the radiation resistance is found to be proportional to the square of the frequency, and to be independent of line length and of whether the top termination is an open circuit or a short circuit. The absolute values agree reasonably well with the theory of Storer and King [Proc. Inst. Radio Engrs. 39, 1408 (1951)] and disagree conclusively with some predictions of earlier theories.
Physical Processes in the L Cathode
Authors: Schaefer D. L. , White John E.
Published: April 2005

The activity of this barium-on-tungsten cathode is maintained by dispensing barium from a pellet of barium compound. The dispensing mechanism is shown to be controlled by surface diffusion of barium over tungsten. Despite incomplete coverage of the emitting surface with barium, and almost complete absence of streaming of active material out through pores in the surface material, evaporation of barium is sufficient to be of concern in certain applications.
Determination of the Transverse Permeabilities of Large Core Samples from Petroleum Reservoirs
Authors: Collins R. E.
Published: April 2005

The solution of the problem of determining the permeabilities of petroleum reservoir rocks from measurements employing the flow of a gas through large cylindrical cores, transverse to the axis of the cores, is presented. This solution is obtained by solving the corresponding problem in potential theory, the method of conformal transformations of complex variables being employed. An electrolytic model study of this problem is described and a comparison of the theoretical and experimental solutions presented.
Radiation Characteristics of a Turnstile Antenna Shielded by a Section of a Metallic Tube Closed at One End
Authors: Baños Alfredo , Saxon David S. , Bailin Louis L.
Published: April 2005

Radiation characteristics are established for a turnstile antenna in a cylindrical shield. The antenna consists of perpendicularly crossed wires driven by a sinusoidal current distribution, harmonic in time, and differing in phase by 90° between members of the cross. The shield is assumed to be a perfectly conducting cylindrical can open at one end and its diameter is taken to be of the order of a fraction of the driving wavelength. The axis of the shield is perpendicular to the plane of the antenna, passing through its center. The excitation of an infinitely long circular wave guide by the above current distribution is considered first, and conditions under which only the dominant (TE11) mode is important are determined. The essential radiation problem can then be regarded as one in which a semi-infinite circular guide, excited by a TE11 mode, radiates into free space. This problem has been formally solved by Levine and Schwinger and, using their results, values of the reflection coefficient and gain function have been computed by the National Bureau of Standards, Institute for Numerical Analysis, University of California, Los Angeles. The results of this theory are compared with experiment and with the Kirchhoff method.
Completeness Relations for Loss-Free Microwave Junctions
Authors: Teichmann T.
Published: April 2005

Using a method which is the electromagnetic analog of the scattering matrix formalism in the theory of nuclear reactions, two ``sum rules'' are derived for the frequency independent coefficients occurring in the admittance matrix relating the currents and voltages in a loss-free microwave junction. These are sums, respectively, over the various modes of the guides entering the junction, and over the modes of the cavity comprising the junction (suitably defined). The results are used to estimate the effect on the admittance matrix of the higher modes, both of the guides, and of the junction proper.
On Diffusionless Transformation in Au-Cd Single Crystals Containing 47.5 Atomic Percent Cadmium: Characteristics of Single-Interface Transformation
Authors: Chang Lo-Ching
Published: April 2005

The kinetics of single-interface motion in the diffusionless transformation of Au-Cd single crystals containing 47.5 atomic percent Cd were studied. A diffusion-controlled relaxation phenomenon was found with an activation energy of the order of 24,000 calories per mole. The two observed characteristics of diffusionless transformation of this alloy, that the transformation does not take place isothermally, and that the velocity of transformation on cooling is considerably and consistently larger than that on heating, can be successfully interpreted from the relaxation hypothesis.
Theory of Wave-Guide-Fed Slots Radiating into Parallel-Plate Regions
Authors: Gruenberg Harry
Published: April 2005

Slotted wave-guide arrays feeding into parallel-plate regions have been used in some high speed scanners. Parallel-plate regions also have been used for the suppression of second-order beams of high gain arrays.

A theoretical expression is derived for the conductance of a longitudinal shunt-slot in a rectangular guide when the slot is radiating into a parallel-plate region of arbitrary plate spacing. Some peculiarities of the theoretical results are discussed. There is good agreement between theory and experiment.
On the Evaluation of Noise Samples
Authors: Siegert Arnold J. F.
Published: April 2005

Unless the primary source of noise is one of those which is theoretically tractable, the statistical properties of the noise have to be inferred from samples. We have developed some criteria to aid in the decision whether a sample can reasonably be assumed to have come from a Gaussian noise with predetermined parameters.
Axial Motion of an Electron in a Constant Wave Velocity Section of a Linear Accelerator
Authors: Caplan David , Akeley Edward
Published: April 2005

The relativistic differential equations for the axial motion of an electron in a wave guide, excited by a progressive, sinusoidal, longitudinal, electric wave of constant speed less than that of light in vacuum, have been integrated. The first integral yields the results of J. C. Slater and gives the energy-phase relationship, which is periodic. A second integration yields the phase distance relationship and thus completes the determination of the orbits. All separatrices are exactly integrable in terms of trigonometric and hyperbolic functions, while the general case requires elliptic integrals of the first and third kinds. The former are obtainable from tables, while the latter are evaluated by series expansions, or in the case of particles near the self-crossing point of the separatrices where the convergence of the series expansion is slow, by the use of the addition theorem for elliptic integrals of the third kind.

These results are applied to the case of the proposed new Purdue Linear Accelerator. Energy distribution of the particles coming out of the end of the first two sections of this accelerator is in this way obtained.
The Emission of Radiation from Diatomic Gases. IV. Emissivity Calculations for CO and HCl for Nonoverlapping Rotational Lines as a Function of Temperature and Optical Density
Authors: Penner S. S.
Published: April 2005

Simplified expressions have been developed for the engineering emissivity of uniformly distributed diatomic gases for nonoverlapping rotational lines with a resonance contour. Unfortunately the rotational half-widths for spectral lines arising from transitions between excited vibrational energy levels are generally not known. For this reason it was necessary to make the assumption that the rotational half-widths for transitions of the form n→n+v, v=1 or 2, are identical. The theoretical analysis is, however, sufficiently general to be useful without modification when accurate data concerning the dependence of line-width on vibrational excitation become available. Explicit expressions have been obtained for the contributions to the total emissivity associated with individual vibration-rotation bands.

Representative emissivity calculations have been carried out for CO and HCl. Comparison of the calculated emissivities of CO with experimental data shows only fair agreement, suggesting either that the assumed description of rotational half-widths is inadequate or else that the empirical emissivity data are not reliable at elevated temperatures.
Time-Temperature Dependence of Linear Viscoelastic Behavior
Authors: Schwarzl F. , Staverman A. J.
Published: April 2005

The question is treated whether in the study of linear visco-elastic behavior of a material change of temperature is completely equivalent to a shift of the logarithmic time scale or not. If it is, the material is termed ``thermo-rheologically simple'' (class A).

It is shown that, by plotting the results of a similar rheological experiment (for instance, a creep experiment) performed at different temperatures and comparing the curves obtained, one can decide whether the materials considered belongs to class A or not, by seeing whether the curves can be made to fit by shifting them along the axis of logarithmic time. Once the material has been decided to behave thermo-rheologically simple, one can plot the function describing the time-shift as function of the temperature.

Some examples of thermo-rheologically simple materials are quoted from the literature.

The micro-rheological conditions for thermo-rheologically simple behavior are discussed. It turns out that this behavior implies that in similar deformations at different temperatures always the same sequence of molecular events follows, whereas in materials not belonging to class A, not only the speed, but also the sequence of molecular processes changes when the temperature of the experiment changes. This implies, that materials of class A cannot from a heat treatment assume a special structure which could not be obtained by one temperature, whereas for materials of class B a heat treatment can indeed result in a special structure. It is reasonable to expect that thermo-rheologically simple materials will be found only among polymers containing no crystallites and no pronounced polar groups.
Anelasticity of Zinc
Authors: Takahashi Shuichiro
Published: April 2005

Anelastic properties of zinc single crystal of high purity (99.996 percent) have been studied, using bars vibrating transversely at audio frequencies in free-free modes. Internal friction, effective elasticity, and shape of resonance curve were determined against the strain amplitude. When the driving force exceeds a critical value, the internal friction increases, its maximum-amplitude-frequency decreases, and its resonance curve becomes asymmetrical. Furthermore, under this condition a discontinuous phenomenon, which is supposed to be closely correlated with slips occurring in the crystal, has been found. This discontinuous phenomenon was recorded under different stresses.
Measurement of the Internal Energy in Copper Introduced by Cold Work
Authors: Welber Benjamin
Published: April 2005

A determination was made of the ratio of the stored energy to the energy expended in cold-working copper by twisting. Ratios of about 0.03 were found in three cylindrical samples which were cold-worked to the extent of 8 to 12 cal/g.
Longitudinal and Transverse Ultrasonic Waves in a Synthetic Rubber
Authors: Nolle A. W. , Sieck P. W.
Published: April 2005

Velocity and attenuation of both transverse and longitudinal ultrasonic waves are measured in a buna-N vulcanizate at 2, 5, and 10 megacycles, over a range of temperatures. The method involves use of solid transmission media to conduct pulsed signals into a thin flat specimen. Values of the bulk modulus and of the complex shear modulus are computed from the measurements. It is found that longitudinal-wave losses in this particular synthetic rubber are substantially accounted for by the relaxation phenomena measured in shear, but this conclusion is subject to considerable quantitative uncertainty arising from experimental errors estimated to be as large as 5 percent for longitudinal-wave acoustic data and 10 percent for transverse-wave acoustic data. It is found that below approximately −25°C the shear-modulus loss tangent becomes relatively independent of temperature and frequency in the present range.
Space Charge Reduction of Low Frequency Fluctuations in Thermionic Emitters
Authors: Tomlinson T. B.
Published: April 2005

The methods of measuring the space charge reduction factor for shot noise are briefly reviewed, and attention is drawn to the difficulties of making a similar measurement for flicker noise. An indirect qualitative test is described in which a triode is used both in normal manner and as a diode under retarding field conditions. Noise measurements at a high and a low frequency show that the effect of space charge on flicker noise exceeds that for shot noise. The diode results are used to estimate the value of the flicker noise reduction factor which is then seen to have a value less than the corresponding shot noise reduction factor at all current levels.
The Dirac Delta-Function and the Summation of Fourier Series
Authors: Spiegel M. R.
Published: April 2005

The summation of Fourier series is attained by use of ordinary linear differential equations with constant coefficients having inputs that depend on certain combinations of the Dirac delta-function. The method is illustrated by several examples representative of those series that arise in applications.
Free Molecular Flow in the Sample Inlet to the Mass Spectrometer
Authors: Zemany Paul D.
Published: April 2005

The aspects of free molecular flow in the sample inlet to the mass spectrometer are pointed out and the conditions under which such flow can occur are described. Methods for calculating the leak diameter and sample pressure for various flow rates are developed. These principles are illustrated by consideration of the flow characteristics in the mass spectrometer leak detector, and by an example from reaction kinetic studies.

The decrease in pressure in the sample reservoir is also described. This is applied to a determination of molecular weights. The effect of the pressure decrease on apparent fragmentation patterns is pointed out and a rational expression for spectrometer sensitivity is suggested which is based on the fraction of molecules which flow through the spectrometer which appear as ions.
The Conductivity Change in Polyethylene During γ-Irradiation
Authors: Mayburg S. , Lawrence W. L.
Published: April 2005

The effect of Co60 γ-irradiation on the direct current conductivity σ of polyethylene has been determined up to an intensity I of 4000 roentgens per hour at room temperature. The equation σ/σ00=1+(I/I0)34describes the data where σ00 is the conductivity without radiation and is the order of 10−18 (ohm cm)−1 and I0 is 20 roentgen/hr. Measurements at liquid nitrogen temperatures give a factor of 20 decrease in the normal conductivity and a factor of 25 decrease in the radiation induced conductivity below their respective room temperature values.

The temperature data serves to suggest an ionic mechanism for electrical conduction in polyethylene as opposed to an electronic mechanism. In fact, the ion contributing most to the conduction in the polyethylene may well be the proton.
Metal Transfer and Wear
Authors: Feng I.-Ming
Published: April 2005

A new theory of metal transfer and wear is suggested in this paper. The essence of the theory is as follows: Metal transfer and wear take place at points of actual contact. The interfaces of the high spots that actually make contact are roughened as the result of plastic deformation when they carry normal load. The mechanical interlocking effect of these roughened interfaces is the primary cause of metal transfer and wear. Due to the mechanical interlocking effect of the roughened interface, and the strain-hardening that accompanies plastic deformation, the application of a tangential force will break one of the pair of the contacting high spots a certain distance away from the interface rather than at the original interface. A secondary cause of metal transfer is the adhesion or the diffusion process which takes place during the temperature flash that occurs during breakage. If the adhesive force is very weak and the diffusion process is not rapid enough to cause the sheared-off peak of the high spot to become a blob of transferred metal, the small piece of metal sheared from the high spot can leave as a loose wear particle. This proposed theory explains the welding of the sheared-off peak to its opponent high spot as the consequence of friction, whereas, in the ``welding'' theory of friction, welding is considered as the cause of friction. Most metallic surfaces in ordinary atmosphere are always covered by a surface film. The effect of surface contamination on metal transfer, wear, and the shear component of friction is discussed. Difficulties encountered in applying the ``welding'' theory to explain the friction of and metal transfer between contaminated surfaces where metallic adhesion is absent, are obvious. Experimental support of this new theory is given here. It includes as direct evidence (1) the roughening of the interface as the result of the plastic deformation, (2) the perfect matching at the roughened interface, which gives a strong mechanical interlocking effect, and (3) a definite region of severely strain-hardened metal near the interface.
Dimensional Changes Normal to the Direction of Diffusion
Authors: Balluffi R. W. , Alexander B. H.
Published: April 2005

Silver from the vapor phase was diffused into thin gold wires and foils at 940°C. Measurements were made of the resulting dimensional changes which occurred normal and parallel to the direction of diffusion. The linear percentage expansion normal to the diffusion direction was always found to be only slightly less than the corresponding expansion parallel to the diffusion stream. The results are best explained by the creation of new lattice sites at dislocations and support both the vacancy and interstitial mechanisms of diffusion in substitutional solutions.
The Temperature Dependence of the Viscosity of Liquids
Authors: Gutmann F. , Simmons L. M.
Published: April 2005

The equation logη=A+B/(T+C) is obtained as a simple modification of Andrade's viscosity equation by treating the activation energy as a function of temperature, A, B, and C being free parameters. This is shown statistically to express adequately the temperature dependence of viscosity over substantial ranges of temperature for all the liquids examined, viz., n-heptane; n-nonane; n-undecane; n-tridecane; n-heptadecane; benzene; viscous mineral oil; ethanol; 1,2-dibromopropane; water; mercury; molten gallium; potassium; sodium; sodium nitrate; silver bromide; lead chloride; bromine; 98–100 percent sulfuric acid.
On the Calorimetric Heat Exchange Correction
Authors: Vasileff H. D.
Published: April 2005

A method has been developed for determining the low temperature heat capacity of a cylindrical sample from heating and cooling curves. The effect of temperature gradient in the sample is included.
Propagation of Elastic Waves in a Cylindrical Bore Containing a Fluid
Authors: Biot M. A.
Published: April 2005

The paper deals with the propagation of unattenuated elastic waves in a cylindrical bore through an elastic material of infinite extent filled with a fluid. The phase and group velocity dispersion curves are plotted for axial symmetric waves in the coupled fluid-solid system.
Analysis of Short-Time Tracer Injection in Underground Formations
Authors: Wallick G. C. , Jenkins R.
Published: April 2005

A proposed method of determining average underground formation characteristics by means of short-time tracer injection has been investigated both theoretically and experimentally. Streamline travel times for the passage of either an ideal gas or an incompressible fluid through a homogeneous permeable formation, from an injection well to a production well, have been calculated using an electronic digital computer. With only minor modifications, the methods of solution employed could be used in the investigation of more complex well systems. For a fixed ratio of injection well pressure to production well pressure the streamline travel times, expressed in terms of a dimensionless time parameter θ, are approximately independent of the well spacing to well radius ratio. A procedure has been devised for predicting the produced tracer concentration as a function of time using the calculated streamline travel times. Preliminary field tests indicate that the short-time tracer injection method is of practical value, but that additional study is necessary before the method can be used most advantageously.
X-Ray Study of the Graphitization of Carbon Black
Authors: Houska C. R. , Warren B. E.
Published: April 2005

A picture of the early stage of graphitization of a carbon black has been obtained from an x-ray study of a Fine Thermal (FT) carbon black heated for two hours at 2300°C. Nearest neighbor pairs of layers take on the graphite relation independently, producing both ABA and ABC sequences. There are two nearest neighbor layer spacings 3.35 A and 3.44 A corresponding to pairs with the graphite relation and pairs with random orientation. The (00l) peaks must be corrected for the distortion broadening resulting from the two spacings, to obtain the parallel layer group thickness Lc. The probability for the ordering of nearest neighbor layers P1 is defined as the ``degree of graphitization.'' A logarithmic plot is used for a rapid determination of P1 and the layer diameter La from the modulated two dimensional (hk) reflections.
Growth of Silicon Crystals Free from Dislocations
Authors: Dash William C.
Published: April 2005

The dislocations which occur in silicon crystals grown by the Czochralski method with and without a crucible are studied by etching and copper decoration techniques. A representative crystal with about 500 dislocations per cm2 is examined in detail to provide general information about their distribution. Sources of dislocations which are important at particular stages of growth are isolated and means found to minimize or eliminate them. The sources include generation by thermal shock from surface damage or residual dislocations in the seed; poor epitaxy at the seed; plastic generation in the bulk of the crystal; effects of segregation of impurities. Plastic generation is the only source found in the bulk of a crystal. ``Spontaneous'' formation of dislocations from excess vacancies is not found. Impurity segregation causes some generation at the tip end of crystals. For certain crystallographic directions it is possible to eliminate residual dislocations and thenceforth grow a dislocation-free crystal. This is interpreted in terms of climb. In a super-saturation of vacancies, an edge dislocation can be forced completely out of a crystal; a screw will remain straight or may be distorted into a coaxial helix. By growth along 〈100〉 or 〈111〉 axes under conditions which favor a vacancy supersaturation, screw as well as edge and mixed dislocations can propagate to the surface and be eliminated. The observations are consistent with this interpretation. When the dislocations are eliminated, the growing crystal can withstand large temperature fluctuations without further generation of dislocations. A procedure is outlined for the growth of dislocation-free silicon crystals. Germanium crystals free of dislocations have been grown by a direct application of the method. It is believed that the conclusions reached during the course of this investigation may be applied to the development of methods for growing dislocation-free crystals of other substances.
Measurements of the Dember Potential in Bulk Germanium
Authors: Stubbe L. , Gossick B.
Published: April 2005

The potential difference across a semiconducting sample, which arises from a gradient of excess carrier density, and which depends on the mobilities of holes and electrons being unequal, has been observed. Measurements of this voltage and photoconductivity permit a determination of the ratio (mobility of electrons/mobility of holes) by a relation given by van Roosbroeck. The ratio 2.1 was obtained for germanium.
X-Ray Integrated Intensity of Germanium Effect of Dislocations and Chemical Impurities
Authors: Batterman Boris W.
Published: April 2005

The absolute values of x-ray integrated intensities from germanium single crystals were measured with CuKα radiation. Dislocation densities below 105 cm−2 did not significantly affect intensities for the first three orders of (111). The observed absolute intensities of all reflections agreed with the prediction of the Darwin-Prins theory within the estimated errors of the measurements and the theoretical calculations. To investigate the effect of chemical impurities on intensities, crystals with one part in 104 of indium or lithium atoms and less than 105 dislocations/cm2 were studied. Regions of the indium doped specimen had (444) intensities 30% higher than the high resistivity specimens, while the crystals in which lithium had precipitated gave an increase of about 40% for this reflection. The precipitated lithium broadened the reflection curves and produced a diffuse scattering in the neighborhood of the Bragg reflection. It is presumably the strains caused by the impurity atoms that are responsible for the increased intensity.
Dislocation Contribution to the Temperature Dependence of the Internal Friction and Young's Modulus of Copper
Authors: Thompson D. O. , Holmes D. K.
Published: April 2005

A study of the amplitude-independent internal friction and Young's modulus in copper from 14°K to room temperature, both before and after neutron irradiation, indicates that there are two dislocation components in these quantities. These have been tentatively identified as a relaxation component studied in detail theoretically by Seeger and a background component which appears to be characteristic of Koehler's bowing mechanism. It is felt that these two components are probably quite intimately related, for the background internal friction rises at just slightly higher temperatures than the maximum of the individual relaxation processes, and the activation energy of the background process is about twice the kink energy obtained from Seeger's theory. Moreover, the Bordoni, or relaxation spectrum, is shown to be considerably more complex than has been previously indicated in that there appear to be at least four principal relaxations. As a result of the analysis attempted in the present work, it appears that the more obvious difficulties of Seeger's theoretical treatment are alleviated.
Capacitance and Barrier Height in Grain Boundaries
Authors: Mueller Rolf K.
Published: April 2005

It is shown that the capacitance of a grain boundary depends on the height of the potential barrier φ only if φ is smaller than 2kT ln (Nd/ni) (ev). For higher barrier potentials the capacitance is in good approximation a function of the bulk properties only. The capacitance as a function of applied bias and temperature (100–250°K) has been measured on tilt boundaries of 4°, 6°, and 25°, with donor concentrations ranging from 1014 to 1016 per cm3. It was found that in all cases the barrier height was larger than 2kT ln (Na/ni). This gives for the highest doped samples at 100°K a lower limit for the barrier height of 0.66(ev).
Contact Potential Measurements on Cleaned Germanium Surfaces
Authors: Fowler Alan B.
Published: April 2005

The contact potential of the (110) face of the n and p regions of an n-p germanium crystal was measured in a vacuum of less than 10−9 mm Hg using a Kelvin bridge technique. The n and p regions were so doped that their resistivities were 0.058 and 0.33 ohm-cm, respectively. If there had been no surface states the difference in work function would have been 0.34 ev. The argon-cleaned surface exhibited a difference of 0.002(±0.004) ev. An exposure of as little as 0.4×10−7 mm-min of oxygen increased the difference to 0.013 ev. A difference as large as 0.018 ev was observed after a 28×10−7 mm-min exposure. After 56×10−7 mm-min the difference was reduced to 0.000(±0.005) ev. These results are discussed in terms of several surface state distributions.
Hugoniot Equation of State of Aluminum and Steel from Oblique Shock Measurement
Authors: Katz Samuel , Doran D. G. , Curran D. R.
Published: April 2005

A method using an explosive-produced oblique shock in a wedge-shaped specimen has been developed for determining the Hugoniot equation of state of solids. Simultaneous measurements of shock and free-surface velocities along the wedge face permit calculation from a single shot of pressure and density over a pressure range exceeding 2:1. Aluminum has been studied over the range 40–180 kb, good agreement being obtained with the normal-shock method. The data for low-carbon steel may be qualitatively interpreted in terms of a double-shock system, associated with the polymorphic transition from α- to γ-iron proposed by Minshall and Bancroft. The present method may provide a means for measuring the pressure at which a solid undergoes a polymorphic transition under dynamic conditions. Preliminary results for antimony indicate a dynamic phase transition at 95 kb corresponding to the one observed statically at 84 kb.