bluuebunny/crossref_metadata_2025 huggingface dataset:
The Electrostatic Field of a Point Charge Inside a Cylinder, in Connection with Wave Guide Theory
Authors: Bouwkamp C. J. , De Bruijn N. G.
Published: January 2005

In this paper the field of a point charge inside a hollow, infinitely long circular cylinder is studied. The case of an axial point charge is treated in detail. Three different methods are developed. The first method shows how to calculate the induced charges at the surface of the cylinder without explicit knowledge of the potential itself. The surface charge-density function is obtained as the solution of a Fourier-type integral equation. Then the potential caused by these charges is calculated. The second method works in the opposite direction. Here the potential is obtained as solution of a boundary value problem, followed by the calculation of the corresponding charges at the surface of the cylinder.

The integral, obtained for the surface charge density, is transformed by contour integration. Although the resulting series is very useful for numerical purposes, a stronger method is necessary, in order to calculate the charge density just opposite the point source. Figure 1 shows the calculated values of the induced surface charge density. Several approximations for the charge-density function are considered, in connection with recent work of Weber (cf. Table I).

The same is done for the field inside the cylinder. Various formulas are given which allow of numerical calculations. In Table II some calculated values of the potential are shown.

The third method is based on the theory of Fourier-Bessel-Dini series. The potential is developed in terms of discrete normal solutions of the potential equation in cylindrical coordinates. The coefficients in this development can be derived from the behavior of the potential in the immediate neighborhood of the primary source.

Furthermore, it is emphasized that the study of the above potential problem can serve as a guide in questions of wave propagation in hollow circular cylinders. In this connection the third method is shown to be extremely useful, as it enables us to calculate directly the fields in the far zone from that in the immediate neighborhood of the exciting source. This new method is demonstrated in case of acoustic waves inside a cylinder, caused by a harmonically vibrating point source.
Note on Circular Loop Antennas with Non-Uniform Current Distribution
Authors: Glinski G.
Published: January 2005

In this paper are presented the approximate formulas for the components of radiation vectors of a short-circuited circular loop with non-uniform current distribution. The formulas are valid for the ratio of loop perimeter to wavelength of the order of 0.5 or less, and assume the current distribution of the hyperbolic cosine form. These formulas lead to the radiation intensity formula from which the expressions for the horizontal and vertical field patterns are derived. The latter formulas are further simplified assuming that the attenuation constant is much smaller than the phase constant. From the expression for horizontal field pattern, it follows that the pattern is symmetrical about the loop axis of symmetry. Moreover, this horizontal pattern exhibits a directional effect with maximum field in the direction of the feeder end of the loop. This directional effect is a function of loop dimensions. The theoretical horizontal pattern agrees very closely with the experimental one. From the expression for vertical field pattern, it follows that the non-uniform current distribution produces a pattern intermediate between that for horizontal dipole and horizontal small loop with uniform current distribution. The field intensity in the zenithal direction is again a function of loop dimensions. Using the expression for radiation intensity, formulas for a radius of equivalent circular horizontal field pattern, power gain, average power gain, and radiation resistance are derived. It is shown that the average power gain is essentially a function of loop radius and decreases with the increase of the latter. Finally, the approximate expression for the attenuation constant of the transmission line equivalent to the loop is derived.
Computation of the Solutions of (1+2ε cos2z)y″+θy = 0; Frequency Modulation Functions
Authors: McLachlan N. W.
Published: January 2005

This equation pertains to a loss-free frequency modulation circuit. Floquet's theory is applied to obtain stable solutions when θ, ε are outside the range of the approximation solution given by Carson in 1922. A method is described by means of which solutions may be computed to any degree of accuracy. The necessary formulae associated with the solution are derived, and convergence is discussed. A numerical example, illustrating the procedure to be followed, is worked out in detail. An appropriate normalization of the solutions is suggested in order to obtain standard frequency modulation functions. It is shown how the analysis may be extended to cover the case of the equation d2Q/dt2+(R/L)(dQ/dt)+[Q/LC0(1+2ε cos2ω1t)]=0,which applies to a frequency modulation circuit having constant resistance R.
Preliminary Analysis of Microwave Transmission Data Obtained on the San Diego Coast Under Conditions of a Surface Duct
Authors: Pekeris C. L. , Davis M. E.
Published: January 2005

The transmission data for 63 Mc and 170 Mc obtained by the U.S.N.E.L. on the San Diego coast on April 4, 1945, when a strong duct was formed near the ground, were analyzed by wave theory. The average observed M-curve was fitted with a linear-exponential term, and the electromagnetic field beyond the horizon was computed by the theory of normal modes. Good agreement between theory and experiment was obtained for both frequencies at a range of 32 miles (see Figs. 7 and 8). In the ranges between 32 and about 70 miles the observed variation of intensity with height agrees with theory, but the theoretical horizontal decrement is less than the observed by about 0.1 d.b./n. mile for 63 Mc, and by about 0.2 d.b./n. mile for 170 Mc. Beyond about 80 miles the observed field tends to assume a uniform distribution with height and shows little horizontal attenuation. Such an effect had been observed by the U.S.N.R.L. expedition to Antigua for 9-cm waves under conditions of an oceanic surface duct. Its interpretation is still wanting.
The Effect of Ground Constants on the Characteristic Values of the Normal Modes in Non-Standard Propagation of Microwaves
Authors: Pekeris C. L.
Published: January 2005

It is shown that for the case of a strongly absorbing ground (β≫1) the characteristic values D of the normal modes are given by D=Da−(U̇2/β)+[U̇3(∂U̇/∂D)/β2]+…,where βv=i(k0/q)13(ε1−1)12/ε1;  βh=βvε1,Da is the characteristic value obtained under the usual assumption that the height-gain function U vanishes at the ground, and U̇ denotes dU/dz at z=0. In the other limit of a perfectly conducting ground (β≪1) the following expansion holds D=Dc+βU2+β3U3(∂U/∂D)+…,where Dc is the characteristic value obtained under the condition U̇(0)=0. Since U̇ and U in (a) and (c), respectively, are known from the normalization condition, it is possible to determine the first correction terms to the characteristic values in each case.
A Resonant Cavity Linear Accelerator
Authors: Cullen A. B. , Greig J. H.
Published: January 2005

A folded rectangular wave guide cavity, resonant at a frequency of 2800 megacycles, is used to accelerate electrons which are injected at 2000 volts energy to an energy of 300 kilovolts. Three accelerating stages are provided, the power source being a type 4J33 radar magnetron operating on a duty cycle of 2×10−4. Power output of the magnetron is 800 kilowatts, the power consumed by the cavity being approximately 250 kilowatts. Design data for the cavity are obtained from slotted wave guide models of the cavity sections.
An Alignment Chart Giving the Polarization Correction of Equi-Inclination Weissenberg Photographic Intensities
Authors: Bond W. L.
Published: January 2005

A nomograph is presented which gives, in terms of film coordinates μ and Υ, the polarization factors to be applied to intensities taken from equi-inclination Weissenberg photographs to correct them for polarization. The remaining correction, the Lorentz factor, merely involves division by cos2μ sinΥ.
Cavity Drag in Two and Three Dimensions
Authors: Plesset Milton S. , Shaffer Philip A.
Published: January 2005

The free streamline theory has been applied to the computation of the cavity drag of symmetrical wedges of arbitrary angle. The drag coefficients and cavity widths and lengths are tabulated for a range of both cavitation parameter and internal angle. The pressure distributions computed for two-dimensional wedges have been taken to be approximately correct for cones of revolution of the corresponding internal angles. Under this assumption, drag coefficients for right circular cones of arbitrary internal angle have been computed and are tabulated for a range of both cavitation parameter and internal angle.
Probability That a Meteorite Will Hit or Penetrate a Body Situated in the Vicinity of the Earth
Authors: Grimminger G.
Published: January 2005

When a body is situated at sufficiently great altitudes (about 200 km or above) it is exposed to impact by the meteorites which enter the earth's atmosphere. A preliminary attempt is made to estimate the probability that a body situated in the vicinity of the earth will be hit by a meteorite and, when hit does occur, to estimate the metal plate thickness necessary to prevent perforation by the impact of meteorites of different sizes. For stainless steel skin thicknesses ranging from 0.05 to 0.02 inch it is necessary to consider meteorites as small as those corresponding to magnitude 8 to 11, respectively. In general, however, it is found that for meteorites which are large enough to present a perforation hazard the probability of a hit is negligibly small, particularly if the body is not exposed to meteoritic impact for excessively long periods of time.
Wave Guides for Slow Waves
Authors: Brillouin L.
Published: January 2005

The paper is devoted to a discussion of the properties of electromagnetic waves propagating with a velocity W <c. Boundary conditions are obtained for structures with very narrow slots, either closed or open, and a general method of solution of the wave equations is discussed. Fields in the free region and in the slot region are expanded in convenient Fourier series and these series joined along the border of both regions. In doing this, it can be proved that the field contains a dominant term, completed by corrections that represent the field distortion near the open end of the slots. Under favorable conditions, and for very narrow slots, the dominant terms are by far the most important. This allows for a simplified discussion of a variety of examples. The results obtained are in agreement with those of E. L. Chu and W. W. Hansen (J. App. Phys. 18, 996 (1947)).
Growth of Charged Particles in Clouds
Authors: Kunkel Wulf
Published: January 2005

In order to calculate the average growth of a charged particle in a dust cloud caused by electrostatic attraction, the following assumptions were made: the particles obey Stokes' law of motion, their velocities are small so that their motion can be considered to be in constant equilibrium with the forces acting, and the forces are effective at short ranges only or the cloud density is small enough so that not more than two particles have to be considered interacting at a time. In addition to the Coulomb force, there will appear an attraction between particles resulting from induced dipoles, but it was found that in general the effect of this force can be neglected. Straight forward integration of the equation of relative motion of two charged dust particles yields their effective cross section for aggregation from which in turn we can determine the rate of growth if the particle size and charge distribution in the cloud is known. Assuming a highly simplified distribution, one arrives at the result that aggregation is negligible if the cloud density is less than a million particles per cm3 or if the average charge of one sign is well below a thousand electrons per particle.
Electron Diffraction Study of Particle Size in Thin Bi Films Deposited by Evaporation in Vacuum
Authors: Keogh C. T. , Weber A. H.
Published: January 2005

Electron diffraction patterns of thin Bi films were studied by the method of microphotometer density curve analysis to determine changes of the film structure with aging and with increase in thickness of the films. All Bi films were deposited on Formvar by evaporation in vacuum. Analysis of the Bi diffraction patterns by comparison with the Formvar pattern as a reference standard indicate that the very thin films (about 20 atom layers or less in thickness) while initially composed of small crystals grow rapidly upon aging into larger crystals. The very thinnest film (about 5 atom layers thick) analyzed exhibited an initial increase in particle size followed by a decrease upon aging, a somewhat anomalous result requiring further confirmation.

Increase in particle size with increase in thickness of the Bi films is observed also, although the results of these latter experiments are somewhat irregular.
Bidwell's Intercept Relation and the Thermal Conductivity of Liquid Metals
Authors: Powell R. W.
Published: January 2005

A note pointing out that the claim made by Bidwell and Hogan [Journal of Applied Physics 18, 776 (1947)], that the relation k/ρC=K(1/T)+K1, where k is the thermal conductivity, ρ the density, C the specific heat, T the absolute temperature and K and K1 are constants, holds for aluminium, tin, lead and zinc with the intercept, K1, the same for the solid and liquid phase, is not so well supported by experimental evidence as the reader is led to believe.

The latest paper on aluminium makes no reference to Konno's appreciably different results for the thermal conductivity of liquid aluminium. Furthermore, adjustment appears necessary in the plotting of Bidwell and Hogan's two points for the liquid phase and this brings the intercept for the liquid phase about 30 percent above that for the solid phase.

Of the other three metals cited by Bidwell and Hogan as having been previously shown to conform to the intercept relationship, it is revealed that zinc does not on the experimental evidence of both Bidwell and Konno, lead does on the evidence of Bidwell but not on that of Konno, whilst tin does on the evidence of Konno only. Further experimental investigation is clearly necessary before any definite relationship such as that suggested can be accepted.
The Effective ``Gamma'' for Isentropic Expansions of Real Gases
Authors: Iberall Arthur S.
Published: January 2005

In an isentropic expansion of a real gas, the relationship pvγ = C (γ, C constant) is not exact. A development is given for an accurate exponent ᾱ (the effective ``gamma''), related to the ratio of specific heats, which permits the use of the relationship p0v0ᾱ = p1v1ᾱ for an isentropic expansion between any two pressures. The exponent may be computed from the initial conditions of the gas, the expansion ratio, equation of state data, and data on the variation of specific heat with temperature.
A Theory of Commercial Yarn Testing
Authors: Geyer Charles J. , Reichardt C. H. , Halsey George
Published: January 2005

A method has been devised for the application of the theory of the three-element shear model of Eyring and co-workers to textiles which does not necessitate the location of the ``basic spring line'' and thus is readily applicable to both yarn and fiber tests and to the commercial inclined-plane and pendulum-type testers. It is also applicable as a first approximation to those textiles which do not possess a ``basic spring line'' as such. The method employs the conventional spring constants or elastic moduli, but determination of the viscous constant involves the magnitude of the relaxation in constant rate of elongation experiments (or the magnitude of the creep in constant rate of loading experiments) from the upper envelope per interval of time. The relationship has been employed to establish the correlation between the viscoelastic properties of ``slashed'' and ``unslashed'' viscose tire cord rayon yarns and also to show the identity of single filament stress-strain relationships with those of yarns of normal twist of the same textile. The simplicity of technique which enables this method to be used as a routine laboratory test for the determination of the viscoelastic properties of textiles affords it an advantage over previous methods, which were often unsatisfactory from both a theoretical and an experimental viewpoint.
Theory of Plastic Flow versus Theory of Plastic Deformation
Authors: Prager W.
Published: January 2005

Typical theories of plastic flow and plastic deformation are discussed, and the concept of neutral change of stress is introduced. A neutral change of stress can be considered as a limiting case of either loading or unloading. It therefore seems reasonable to demand that the stress-strain relations for both loading and unloading should predict the same change of strain when applied to a neutral change of stress. It is shown that this condition is satisfied by the theories of plastic flow but not by the theories of plastic deformation.
The Radiation Patterns of Dielectric Rods—Experiment and Theory
Authors: Watson R. B. , Horton C. W.
Published: January 2005

A theory is developed describing the electromagnetic radiation from dielectric rods used as terminations to rectangular wave guides. The radiation patterns are computed from the fields due to equivalent magnetic and electric currents on the surfaces of the rods. These equivalent currents are determined by use of Schelkunoff's equivalence principle applied to approximate fields within the dielectric. Specific calculations are carried out for rods whose average dimensions are 0.9″×0.25″ and whose lengths vary from three to ten wave-lengths. Experimental patterns are obtained for eight polystyrene rods, some of which are variable in length. Agreement with theory is found for rods from three to six wave-lengths long; differences between experiment and theory are discussed.
The Decay of Shock Waves
Authors: Cassen B. , Stanton J.
Published: January 2005

The instantaneous rate of decay or intensification of a shock front in any fluid for which dissipative effects are localized in a shock zone is shown to be directly related to the coexisting pressure gradient in the wake of the wave adjacent to the front. The higher time derivatives of the shock velocity are also explicitly related, although in a more complicated fashion, to the higher spatial derivatives of wake pressure. Thus the experimental observation of the velocity or some related variable of a blast or ballistic shock wave can be used to ascertain properties of the fluid motion in the wake of the shock. Conversely, a knowledge of the wake profile at any instant can be employed to determine the corresponding rate of decay of the shock front. The general theory is applicable to shocks of all strengths where an equation of state can be applied graphically or analytically.
The Optical Equations of Three-Dimensional Photoelasticity
Authors: Mindlin Raymond D. , Goodman Lawrence E.
Published: January 2005

The fundamental optical problem encountered in three-dimensional photoelasticity is that of the propagation of light in a heterogeneous, aeolotropic medium. Although there is an extensive literature on the homogeneous, aeolotropic medium and the heterogeneous, isotropic medium, only a few special cases of the combined problem have been studied from the point of view of Maxwell's electromagnetic equations. With regard to approximate treatments, the most general is that of F. Neumann (1841), derived from purely kinematical considerations. In the present paper the passage from Maxwell's to Neumann's equations is executed and the nature and order of magnitude of the necessary approximations are disclosed. During the passage, there are discovered a pair of equations, of relatively simple form, which open the way to a variety of new solutions in closed form and reveal the essential parameter upon which the optical phenomena depend.
The Electron-Micrographic Structure of Shadow-Cast Films and Surfaces
Authors: Williams Robley C. , Backus Robert C.
Published: January 2005

The lower limit of size of biological objects which can be photographed with the electron microscope, by the aid of shadow-casting, is shown to depend upon the smoothness of substrate upon which they can be mounted, and upon the continuity of structure of the thin films with which they are shadowed. Numerous attempts to improve the existing deficiencies are reported, both with respect to producing smoother substrate films, and to producing films for shadow-casting of high efficiency and continuity of structure.

No success has been encountered in producing a usable substrate film perceptibly smoother than the collodion and Formvar films commonly used. It is found that the best shadow-casting material for this type of film is uranium or uranium oxide.

Verification has been obtained of the severe granulation of gold films previously used in the pre-shadowed replica process, when subjected to the electron current of a biased-beam electron gun. Attempts to reduce the granulation to a satisfactory level have failed. Various methods of preparing pre-shadowed replicas are reported. The factors affecting the tenacity of evaporated films to glass surfaces are discussed. It is found that elements which oxidize readily are relatively adherent to glass, while the elements gold, palladium, platinum, and rhodium are not. Uranium sulfide can be used as a pre-shadowed replica material, but only with some uncertainty, owing to its chemical instability. It has been found that a palladium-platinum mixture is the most satisfactory material for use in the pre-shadowed replica technique, and that films of this mixture in a thickness of about 6A produce adequate shadows in which there is no sign of granulation. The surface of clean glass is again found to have the smoothest structure of any material known, with practically no sharp discontinuities in elevation as great as 10A.

An appendix is given, in which technical details of shadow-casting and replica production are described.
An Improved Spinning Top Homogeneous Spray Apparatus
Authors: May K. R.
Published: January 2005

An apparatus is described which produces homogeneous mists or clouds of solid particles of any desired size. As in Walton's original model liquid is sprayed by a Beams high speed air-driven top, but an improved performance has been achieved by utilizing a property of high speed air films so that automatic extraction of unwanted satellite droplets, better running characteristics over a wider range, simplified construction, and low air consumption are obtained.
Distribution of Temperature and Current in Cylindrical Bodies
Authors: Muckenhoupt Carl F.
Published: January 2005

The current and temperature distributions in a conductor are affected not only by the magnetic effect of the current, i.e., skin effect, but also by the variation of resistivity with temperature. Consequently the two are interdependent, and since the resistance change amounts to between three and four percent for every 10°C rise in temperature in metals, and is still greater in insulators, its effect can be quite appreciable. A complete solution for the steady state is given herewith.
Precipitation from Solid Solutions of C and N in α-Iron
Authors: Wert Charles A.
Published: January 2005

The formation of precipitates from the solid solutions of C and N in α-iron has been studied by means of the internal friction peak associated with the stress-induced interstitial diffusion of the solute atoms. A transformation law has been found to fit the experimental data. The data are interpreted as showing the following: (1) Fe3C precipitates in the shape of spheres; (2) an intermediate phase in the precipitation of nitrogen forms in the shape of disks; and (3) within the experimental error there is indicated no continuous nucleation. Using the results of a derivation made by Zener, the mean distance between nuclei is calculated for Fe3C. For carbon concentrations of about 0.016 wt. percent, this distance is about 800, 2000, and 7000 Angstroms at 27°C, 102°C, and 312°C, respectively. With appropriate experimental conditions, the temperature dependence of the precipitation rate is found to be about the same as the temperature dependence of the diffusion rate of the solute atoms.
Magnetic Characteristics of an Oriented 50 Percent Nickel-Iron Alloy
Authors: Crede J. H. , Martin J. P.
Published: January 2005

Single crystal magnetic properties have been closely approached in a polycrystalline 50 percent nickel-iron by the development of a favorable grain orientation. The method is adapted to commercial production by careful control of processes effecting the fundamental magnetization process in the magnetic domain. Elimination of steps I and III of the normal magnetization has produced a nearly geometrically true rectangular shape of the hysteresis loop.
The Demodulation of a Frequency-Modulated Carrier and Random Noise by a Discriminator
Authors: Blachman Nelson M.
Published: January 2005

With the aid of an idealized representation of the discriminator, Middleton has shown that a frequency-modulated carrier remains intelligible for smaller carrier strengths when narrow-band f-m is used and the limiter is omitted than with a limiter and/or wide-band f-m. It is, therefore, of some interest to treat the demodulation process as it actually occurs, in the absence of a limiter. Thus, the discriminator has been taken to consist of two selective circuits, both fed by the output of the intermediate-frequency amplifier, but peaked at different frequencies, feeding rectifiers whose outputs are subtracted. Each half of the device is treated in the manner used by Rice to determine the result of passing random noise and a sine wave through a rectifier; however, there is a correlation between the noise voltages fed to the two rectifiers. The signal output and the spectral distribution of the noise output are obtained first for quadratic rectification, then in the general case, which is then specialized to linear rectification. The results are applied to a case of rectangular i-f noise spectrum, and the signal-to-noise ratio is determined for the cases of narrow-band and wide-band f-m. These results are found to be very much like those for the idealized representation of the discriminator; all are compared, along with amplitude modulation, in Table I. The optimum signal-to-noise ratio for f-m without a limiter is found to obtain with narrow-band f-m when the discriminator is designed for no wider a band than necessary; this optimum signal-to-noise ratio differs very little from that for a-m.
A Direct Method of Determining Preferred Orientation of a Flat Reflection Sample Using a Geiger Counter X-Ray Spectrometer
Authors: Schulz L. G.
Published: January 2005

A new reflection method is described for determining pole figures of flat samples with a Geiger counter x-ray spectrometer. The chief advantage of the method is that the experimental data may be used directly without corrections for changes in geometry during rotation of the sample. Beginning from an initial position identical with the usual reflection arrangement the sample is rotated about an axis defined by the intersection of the sample surface with the plane of the spectrometer. During this motion a randomly oriented sample of sufficient thickness will yield a constant counting rate because the absorption and effective scattering volume of the sample remain unchanged. As a result, no correction formula is required. The experimental arrangement requires three horizontal slits; two are used to collimate the incident beam, and the third is placed in front of the counter. A mathematical analysis of the optical elements of the arrangement is given together with the results from a practical application.
Determination of Preferred Orientation in Flat Transmission Samples Using a Geiger Counter X-Ray Spectrometer
Authors: Schulz L. G.
Published: January 2005

A method employing a diverging x-ray beam is described for the determination of preferred orientation in flat transmission samples with a Geiger counter x-ray spectrometer. It is shown that for a certain range of sample thickness the counting rate is independent of the rotation of the samples, and therefore, no correction formula is required.
Propagation of Transverse Waves in Viscoelastic Media
Authors: Adler F. T. , Sawyer W. M. , Ferry John D.
Published: January 2005

In calculating elastic constants of viscoelastic media from transverse wave propagation, it has been customary heretofore to assume a plane disturbance in a medium of infinite extent. Equations have now been derived for conditions which approach much more closely the experimental arrangement, namely, propagation from a finite source plate in a rectangular cell, and representative numerical calculations have been made. The new theory shows that the finite dimensions of cell and source should have very little influence on the wave-length as determined from observations of strain double refraction, but the attenuation should be perceptibly different from that of the plane wave case. Experimental data confirm these conclusions. Nevertheless, the simple plane theory is adequate within present experimental error for the majority of cases. Only in certain specified ranges of mechanical consistency will it be necessary to apply corrections taking into account the sizes of the cell and source.
The Effect of Cold Work in Metals on Powder Pattern Intensities
Authors: Averbach B. L. , Warren B. E.
Published: January 2005

Using crystal monochromated Cu Kα-radiation and a Geiger counter spectrometer, integrated intensity measurements have been made for powder samples of cold-worked and annealed α-brass. The effect of cold work is to increase the integrated intensity of the strong lines and make practically no change in the weak lines. The increase for the strong lines is presumably due to a reduction in extinction. Measurements were made of the (400) reflection on a cold-worked sample and on an annealed sample held at high temperature to demonstrate the difference between the effects of cold work and temperature vibration.
The Structure of Porous Materials from Gas Penetration Rates
Authors: Schwertz F. A.
Published: January 2005

Gas penetration rates have been used to study the structure of three commercial grades of sintered Pyrex glass. Specific surface areas, ``average pore diameters,'' pore population densities, average particle diameters, and particle population densities have been calculated on the basis of the data obtained.
Erosion of Electrical Contacts on Make
Authors: Germer L. H. , Haworth F. E.
Published: January 2005

When an electric current is set up by bringing two contacts together, they necessarily discharge a capacity. If the discharge takes place through an arc before the metallic circuit is established, erosion of the electrodes results. In a low voltage circuit the occurrence of an arc is dependent upon the condition of the electrode surfaces and upon the circuit inductance. For ``inactive'' surfaces, and a voltage of the order of 50, an arc does not occur if the inductance is greater than about 3 microhenries. Surfaces of various metals can be ``activated'' by vapors of certain unsaturated organic compounds, and in the active condition they give arcs even when the circuit inductance is greater than this limiting value by a factor of more than 103. The study of arcs between active metal surfaces is not yet complete, and most of this paper and all of the remainder of this abstract have to do with surfaces which are inactive.

When an arc occurs at the make of inactive metal surfaces, its energy, which in low voltage circuits of practical interest is drawn entirely from a charged condenser, is dissipated almost entirely upon the positive electrode, and melts out a crater intermediate in volume between the volume of metal which can be melted by the energy and that which can be vaporized. Some of the melted metal lands on the negative electrode and, with repeated operation, results in a mound of metal transferred from anode to cathode. This transfer is about 4×10−14 cc of metal per erg.

The arc voltage is of the order of 15. If the initial circuit potential is more than about 50 volts there may be more than one arc discharge, successive discharges being in opposite directions and resulting in the transfer of metal in opposite directions— always to the electrode which is negative.
The Scattering Cross Section of Spheres for Electromagnetic Waves
Authors: Brillouin L.
Published: January 2005

The problem discussed in this paper is that of the scattering of electromagnetic waves by a spherical obstacle. The classical theory is well known. Stratton's ``Electromagnetic Theory,'' for instance, contains a very good summary of that discussion. The computation of the scattering cross section, according to this theory, leads to some difficulties. In the case of large spheres, where geometrical optics should apply, the rigorous theory yields a scattering cross section equal to twice the actual cross section of the sphere!

The discussion presented in this paper explains this strange result and shows the role played by the shadow and by the diffraction fringes surrounding the shadow. A reasonable system of approximations yields the well known ``Babinet's principle.'' The physical interpretation is of such general character that it must certainly apply to a variety of similar problems in acoustics or wave mechanics. The spherical shape of the obstacle is essential in the present discussion, but similar results would certainly be found for other shapes of the obstacle. The case of a circular cylinder, investigated by E. B. Moullin and L. G. Reynolds, also leads to a total cross section twice as large as the actual cross section, for large cylinders. The explanation is the same as for the spheres. Experiments very carefully designed by Dr. Sinclair and Professor V. K. LaMer gave a very precise check of the theoretical predictions.
Induced Fibration of Suspensions
Authors: Winslow W. M.
Published: January 2005

This paper describes some of the phenomena found to have their origin in electrically induced fibration of small particles in fluid liquid suspension. Particular attention is given to induced shear resistances found in layers of the fluid (0.01 to 0.15 cm) when bounded by potentialized electrode surfaces. Ingredients and manner of compounding concentrated fluids capable of reversible shear resistance up to several hundred grams per cm2 are described. Dynamic induced shear resistance or the corresponding induced bulk viscosity are shown to be a parabolic function of field strength wherein parameters dependent on surface conditions of the particles are involved. Various properties of these fluids are discussed with regard to the mechanism of induced fibration, its application in slip clutches and other hydraulic devices, and some of the factors for best results. Consideration is given to the analogous magnetically induced fibration of ferromagnetic particles in fluid suspension. It is found that the observed values of induced shear resistance approximate those predictable from the well-known formulas for tractive force in both the electric and magnetic cases. Mention is also made of fluid suspensions of ferrite powders which respond to both electric and magnetic fields.
Electron Transit Time in Space-Charge Limited Current between Coaxial Cylinders
Authors: Copeland Paul L. , Eggenberger Delbert N.
Published: January 2005

From information about space-charge-limited currents, the transit time of electrons between a cylindrical cathode and an external coaxial anode has been computed. Taylor's series expansions of the functions useful in the calculations are given. These together with the tabulated values permit rapid calculation of electron transit times with an accuracy of 0.1 percent.
On the Magnitude of the Mechanical Component of Solid Friction
Authors: Strang C. D. , Lewis C. R.
Published: January 2005

An experiment was performed in order to determine the magnitude of that portion of dry, kinetic friction which is contributed by Coulomb friction, or the mechanical interlocking of surface irregularities. The results indicate that the work of the mechanical component of friction accounts for only a few percent of the work of total measured friction.
Electron Optical Mapping of Electromagnetic Fields
Authors: Marton L. , Lachenbruch S. H.
Published: January 2005

Two techniques have been devised for the exploration of electrostatic and magnetic fields where conventional methods fail. Both use electron lens systems to magnify the deflecting effect of the fields on electron beams. One technique is the electron optical analog of the ``Schlieren'' method; the other involves deformed shadows of a thin obstruction.

For several reasons the ``Schlieren'' patterns obtained experimentally thus far have been interpreted only qualitatively. The patterns obtained by the shadow method, however, have been used for quantitative evaluation of field strengths. Experimental patterns of both types, produced by the fields of magnetized recording wires, are shown.

The shadow method is theoretically applicable to the quantitative evaluation of a wide variety of electric and magnetic fields. It utilizes formulas based on relations between field distribution and electron deflection, and between the latter and the geometrical parameters of a focusing system. Such formulas are derived and applied to several simple types of field.

An application of the theory to the magnetized wires used in the experiments yields relations from which each field distribution is evaluated by fitting a line to experimentally determined points. The theory also predicts the geometrical properties of the experimental patterns.

The agreement between theory and experiment is sufficiently good to justify the underlying theoretical assumptions and approximations.
Attenuation in a Dielectric Circular Rod
Authors: Elsasser Walter M.
Published: January 2005

Analysis of the non-radiative modes propagated along a circular dielectric rod is accompanied by a discussion of dielectric loss. The attenuation for the three lowest modes in polystyrene is computed and agrees with the experimental data of Chandler given in the preceding paper.
An Aluminum-Beryllium Alloy for Substrate and Replica Preparations in Electron Microscopy
Authors: Kaye Wilbur
Published: January 2005

A technique of specimen preparation especially suited to the study of polymeric molecules and aggregates is presented. With slight modifications it is applicable to the preparation of replicas of a wide variety of surfaces where the action of heat, pressure, and solvents must be minimized. The method owes its superiority to the use of an aluminum-beryllium alloy of high strength, low scattering power and nearly amorphous structure. A layer of evaporated hydrophilic material facilitates the separation of the metal film from the mounting surface. Micrographs are presented showing certain applications of the method.
Method for the Quantitative Evaluation of X-Ray Patterns from Mixed Powders
Authors: Brentano J. C. M.
Published: January 2005

The quantitative evaluation of the constituents of mixtures from x-ray powder diffraction patterns has been highly successful in certain cases, but has been found subjected to limitations as an analytical tool of more general use. These arise from a number of effects which interfere with a simple interpretation of the patterns. The paper discusses the basic aspects of these interferences, in particular of those which result from superpositions of lines, and develops a method which takes account of them. The method is adapted to meet such cases where the constituents or impurities which interfere with the regular patterns are unknown.
Collimation Error in Small Angle X-Ray Scattering
Authors: Yudowitch K. L.
Published: January 2005

It has been shown that excessive error may be introduced in small angle x-ray scattering by the use of an incident beam of finite cross section. To account for this error the usual procedure has required multiple integrations for rays reaching a single point P on the film from all points within each slit. However, the common effect from both finite slit height and width is a range of scattering angle for rays reaching P. The integrations over each slit dimension are reduced to a single integration over scattering angle, which entails finding the limits of scattering angle.

The assumption of a constant distribution of intensity throughout the range allows the range of scattering angle δε to be taken as a measure of the collimation error. Minimization of δε permits determination of optimum values of slit height-width ratio. For two slit collimation, it further leads to determination of optimum slit spacing and optimum relative slit sizes.
Impedance of Resonant Transmission Lines and Wave Guides
Authors: Harman W. W.
Published: January 2005

The relation of the Q to the impedance of a resonant transmission line is clarified. Universal curves relating Q and resonant impedance of capacitively terminated transmission-line and wave guide sections are presented and discussed. Their use in cavity resonator design and as a method for measuring resonator shunt resistance is considered.
Density and Packing in an Aggregate of Mixed Spheres
Authors: Hudson Douglas Rennie
Published: January 2005

It is shown that in close packing of spheres, two types of interstice exist, bounded by six and by four convex spherical surfaces. These are termed ``square'' and ``triangular.'' They are connected by a continuous labyrinth through which a ball not exceeding (2/√3−1)r in radius can be threaded. In both cubic and hexagonal arrangements, their shape and size are identical, but their distribution differs. Radii R for n smaller balls, which can take up patterns with cubic symmetry within each square interstice, are calculated for values of n up to 27 and plotted. The expression (R/r)=(2−1)/n12is used as a test for efficiency of packing.

When R/r is plotted against the density increment attributable to this interstitial packing, a set of spires is obtained. At n=8 and n=9 (R/r being, respectively, 0.2289 and 0.2166) twin peaks of 13 percent and 12 percent appear, which are accentuated by first entry of a sphere into the triangular interstice at R/r = 0.22475; this contributes another 3 percent. The peak of 16 percent at n=21, R/r = 0.1782, is also reinforced by first entry of 4 spheres in a body-centered tetrahedron at 0.1716, which gives an additional 6 percent density increment. Applications to bulk storage, ceramics, and interstitial compounds and solid solutions are considered. None of the special packs gives a density increment (∂Δsquare +∂Δtriangular)/Δ even approaching the 26 percent for fine spherical filler close packed in the interstices.
Resistance of Oxide Cathode Coatings for High Values of Pulsed Emission
Authors: Danforth W. E. , Goldwater D. L.
Published: January 2005

Measurements are described of the potential variation of fine ribbon probes embedded in standard barium and strontium oxide coatings. Observations were made with 19 tubes at values of pulsed emission as high as 50 amperes/cm2. Results were as follows: (a) values of resistance were found ranging from 2 to 230 ohms-cm2; (b) potential gradients were adequate to admit dielectric breakdown as a cause of sparking; (c) the curve of resistance vs. emission passes through a maximum and, at different temperatures, this maximum occurs at the same probe potential; (d) with BaO or mixed cathodes of higher values of resistance the resistance is largely at the interface, for low resistance coatings no observations on this matter were obtained; (e) the two best tubes as regards high emission without sparking had the lowest values of coating resistance; (f) the resistance of SrO cathodes is an order of magnitude higher than that of BaO or mixed cathodes; (g) superposition of d.c. upon pulsed emission gives a pronounced decrease of resistance.
Particle Size Determination by Soft X-Ray Scattering
Authors: Yudowitch K. L.
Published: January 2005

Small angle x-ray scattering measurements are made on samples of colloidal gold of radius from 50 to 400 angstroms. Copper (1.54 angstrom wave-length) and aluminum (8.32 angstrom wave-length) radiation are used.

The usual method of analysis is shown to be valid only for particles of radius less than 120 wave-lengths. Extension of the method to larger particles is achieved, giving improved electron microscope correlation.

The use of longer wave-lengths and optimum shaped slits are shown to reduce geometry errors sufficiently to give clear evidence of predicted intensity maxima. The first three secondary shape function maxima are observed.

An additional interference maximum attributable to particle-to-particle interference is observed. The position and magnitude of this maximum are correctly predicted by an expression based on earlier fluid scattering theory.
Sweep Frequency Ionosphere Equipment
Authors: Sulzer Peter G.
Published: January 2005

A new sweep frequency ionosphere sounding equipment is described. The equipment records ionosphere virtual height as a function of frequency over the range from 1 to 25 megacycles. Special features of the device are high power output, good receiver sensitivity, and anti-jamming circuits.
A Positive-Replica Technique for Electron Microscopy
Authors: Schwartz C. M. , Austin A. E. , Weber P. M.
Published: January 2005

A positive-replica technique for electron microscopy has been developed, which reproduces the contour variations of the specimen surface, and permits direct visual interpretation of elevation. The method utilizes two resins, each mutually insoluble in the solvent for the other, specifically, polyvinyl alcohol plus Formvar. Shadow casting of the Formvar positive replica enhances detail and highlights the areas in relief in the original surface. Examples are given, in particular, applied to wear-test specimens.
A Mathematical Theory of Photo-Viscoelasticity
Authors: Mindlin Raymond D.
Published: January 2005

A phenomenological law of optical birefringence, induced by small strain in viscoelastic materials, is formulated and applied to an idealized medium. The resulting optical-stress-strain-time-temperature relations are used in finding conditions under which models made of viscoelastic materials may be employed in the photoelastic method of solving boundary value problems in the linear theory of elasticity.