bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulation of West African monsoon circulation in four atmospheric general circulation models forced by prescribed sea surface temperature
Authors: Moron Vincent , Philippon Nathalie , Fontaine Bernard
Published: January 2005

The mean evolution of the West African monsoon (WAM) circulation and its interannual variability have been studied using an ensemble of 21 simulations (common period 1961–1994) performed with four different atmospheric general circulation models (AGCMs) (European Center/Hamburg (ECHAM) 3, ECHAM 4, Action de Recherche Petite Echelle Grande Echelle (ARPEGE), and Goddard Institute for Space Studies (GISS)) and forced by the same observed sea surface temperature (SST) data set. The results have been compared with European Centre for Medium‐Range Weather Forecasts reanalyses (ERA‐40). The climatological means of WAM winds for the AGCMs are similar to the ERA‐40 ones. However, the AGCMs tend to underestimate the southern wind component at low levels around 10°N compared to the ERA‐40. The simulated Tropical Easterly Jet (TEJ) is usually shifted northward and also too weak for ECHAM 3 and ECHAM 4 compared to ERA‐40. The interannual variability of an atmospheric WAM index (WAMI) is quite successfully reproduced (the correlations between the mean ensemble of each AGCM and ERA‐40 time series over 1961–1994 range between 0.51 and 0.64). In particular, the four AGCMs reproduce quite well the mean teleconnection structure with El Niño–Southern Oscillation, i.e., a strong (weak) monsoon during La Niña (El Niño) events, even if the largest absolute correlations between WAMI and SST in the eastern and central equatorial Pacific are weaker than in ERA‐40. On a yearly basis, WAMI is more predictable and skillful during the cold ENSO years than during the warm ENSO ones. The unskillful warm ENSO events are associated with a significant cooling over the equatorial Atlantic and Western Pacific Ocean and a significant warming in the tropical Indian Ocean.
Creep Deflections in Columns
Authors: Marin Joseph
Published: January 2005

The determination of column deflections and column buckling loads has been considered for many years. The available theories, however, do not provide for materials which creep with time under constant loads. For the design of structural members made of these materials, a consideration of creep may be of practical importance. Plastics, concrete, and some metals creep at normal temperatures while other metals creep only at high temperatures and at stress values beyond the yield point. A consideration of creep in the design of some structures appears appropriate in view of the modern developments in plastics and the presence of high stress values which are sometimes beyond the yield stress. This paper gives a rational theory for predicting creep deflections in columns. A special case using this theory is applied to the interpretation of some preliminary tests of an aluminum alloy.
Effects of Magnetic Field on Oscillations and Noise in Hot-Cathode Arcs
Authors: Cobine J. D. , Gallagher C. J.
Published: January 2005

The voltage disturbances in hot-cathode arcs are markedly affected by a magnetic field transverse to the normal flow of current. The normal plasma oscillations can be suppressed and the noise level above 1 Mc/sec. greatly increased. The oscillations appear to be transmitted to the electrodes by electrons whose velocity is modulated by the plasma ion oscillations as they travel directly from cathode to anode. The effect of the magnetic field is to remove these electrons from the current reaching the anode. A critical value of magnetic field will suppress the oscillations and reduce the noise to a minimum. As the magnetic field is further increased the high frequency noise level increases. The high frequency noise level also increases if the pressure decreases, or if a lighter gas is used. The noise level is independent of the plasma volume. The effect of the magnetic field is to build up a region of high ion density in a narrow region near the electron source. Plasma oscillations with continuous spectrum are generated in this region of high density and high density gradient.
Numerical Solution of Axisymmetrical Problems, with Applications to Electrostatics and Torsion
Authors: Shortley George , Weller Royal , Darby Paul , Gamble Edward H.
Published: January 2005

Numerical methods are given for solution of axisymmetrical problems involving the partial differential equation ∂2ψ∂z2+∂2ψ∂ρ2+Kρ∂ψ∂ρ=0,where ρ is the radial coordinate and z the coordinate parallel to the axis. The various values of K which occur in physical situations are discussed, and common iteration methods for handling these problems are given. For Laplace's equation, K = 1. For the Stoke's stream function, K = − 1, but it is pointed out that for numerical work a new function, called the flow-disturbance function, having K = 3, is more tractable. Similarly a new function with K = 5, the stress-concentration function, is much easier to compute than the usual stress function (K = − 3) for the case of the torsion of a circular shaft of varying diameter. The methods are illustrated by computation of the equipotentials for an electron lens, and by a complete computation of the stresses and strains in a particular grooved circular shaft under torsion.
Ion Beams in High Voltage Tubes Using Differential Pumping
Authors: Lamar E. S. , Buechner W. W.
Published: January 2005

Tests on a hydrogen ion gun assembly employing differential pumping are described. Focused beam currents as high as 215 microamperes were realized at the target end of a high voltage tube 6 feet long operating in the range from 300 to 400 kilovolts. Factors which limited the current to 215 microamperes are discussed and suggestions for realizing greater beam currents are presented.
X-Ray Diffraction Studies of Color Variation of Iron Oxide Pigments
Authors: Birnbaum H. , Cohen H. , Sidhu S. S.
Published: January 2005

Samples of synthetic iron oxide (Goethite) taken at regular intervals from a twelve-day continuous process showed progressive change of color, ranging from pale yellow to dark brown. X-ray diffraction, electron microscope, and optical microscope studies lead to the conclusion that the color change in these samples is mostly caused by particle growth.
Mass Spectrometer for Leak Detection
Authors: Nier A. O. , Stevens C. M. , Hustrulid A. , Abbott T. A.
Published: January 2005

A simple low resolution mass spectrometer is described which has been used successfully in detecting small leaks in high vacuum equipment. One part of He in 200,000 parts of air can be detected.
New Developments in Vacuum Engineering
Authors: Jacobs Robert B. , Zuhr Herbert F.
Published: January 2005

Methods developed for obtaining vacuum tightness in the K-25 Gaseous Diffusion Plant for the separation of U235 are described. A general account of the vacuum engineering of the K-25 Plant also is given. The dynamics of vacuum systems are described, including the use of the mass spectrometer leak detector on rapidly responding systems. New techniques described include, among others, the helium hood method for measuring vacuum tightness and the use of calibrated leaks.
The Magnetic Electron Microscope Objective: Contour Phenomena and the Attainment of High Resolving Power
Authors: Hillier James , Ramberg E. G.
Published: January 2005

A theoretical and experimental investigation of contour phenomena observed in electron microscope images near focus has been carried out. An explanation for the apparent reversal of the Fresnel fringes at exact focus is given and a method is described for the determination of the degree of asymmetry from the fringe patterns. A procedure for empirically correcting the asymmetries usually present in magnetic electron microscope objectives is outlined and some of the results obtained with a compensated lens are shown. A number of instrumental defects which may prevent the attainment of the ultimate resolving power of an instrument, together with methods for their elimination, are listed.
An Investigation of a Method for the Analysis of Smokes According to Particle Size
Authors: Lipscomb William N. , Rubin T. R. , Sturdivant J. H.
Published: January 2005

An electrical precipitation method for the analysis of smokes according to particle size has been investigated. A thin stream of smoke particles moving under laminar conditions in a wind tunnel of rectangular cross section is electrically charged in a small region. The charged particles are then precipitated by the uniform field existing between the charged upper plate and the grounded lower plate of the wind tunnel as a long track along the lower plate. The size-frequency distributions of the particles precipitated at various points on the lower plate were determined from measurements on enlargements of electron-microscope photographs of samples of the smoke precipitated at various points. The agreement between theory and experiment is fair, but the range of sizes of the particles precipitated at a given point is rather large.
Dislocation Theory as Applied by N.A.C.A. to the Creep of Metals
Authors: Nowick A. S. , Machlin E. S.
Published: January 2005

An equation for the steady-state rate of creep of pure annealed polycrystalline metals is derived through dislocation theory and the theory of rate processes. The rate of generation of dislocations is shown to be the rate-determining process. A specific mechanism for the generation of a dislocation is presented, from which the heat and entropy of activation of the process are expressed in terms of physical constants of the material. In addition the lowering under stress of the potential energy barrier, which yields the stress-dependent term, is given in terms of constants of the material and a ``back-stress'' term. The creep equation thus obtained is found to be in good agreement with data in the literature.
Application of the Sliding Thermocouple Method to the Determination of Temperatures at the Interface of a Moving Bullet and a Gun Barrel
Authors: Armi E. L. , Johnson J. L. , Machler R. C. , Polster N. E.
Published: January 2005

Description is given of a set-up for the determination of temperatures at the frictional interface between a moving bullet and the bore in a caliber 0.50 gun barrel. Cathode-ray oscilloscope e.m.f.-time records, which were obtained from a traveling thermocouple junction formed by the bullet-bore interface, are interpreted (by use of a formula due to Jaeger) in terms of instantaneous temperatures. A calorimetrically measured value of the total frictional heat input caused by a bullet being pushed through a barrel section by means of a falling weight, is found to be in good agreement with the value of the heat input calculated from bore surface temperatures which were determined by the sliding thermocouple method.
Carbide Structures in Carburized Thoriated-Tungsten Filaments
Authors: Horsting C. W.
Published: January 2005

A wide variety of carbide structures is described, as found in the surface layer of carburized thoriated-tungsten filaments. Their origin is traced back to carburizing conditions and subsequent processing during tube making. A frequently occurring laminated carbide structure is found to contain less carbon than W2C. The thyratron relay method of carburizing control is critically reviewed. Abnormal filament current in manufactured tubes is explained as due to surface conditions which cause changes in thermal emissivity.
Fringing Flux Corrections for Magnetic Focusing Devices
Authors: Coggeshall Norman D.
Published: January 2005

When a charged particle approaches a region of uniform magnetic field its trajectory is affected by the fringing field. Compensation for the effect of the fringing field may in some cases be achieved by the use of virtual field boundaries which are outwardly displaced from the actual boundaries. A definition of the virtual boundary in terms of the effect of the fringing field upon the trajectories is formulated. A procedure for calculating the displacement d of the virtual from the actual field boundary is given using the methods previously developed for calculating ion trajectories in non-uniform magnetic fields. Using this procedure several values of the displacement for various magnet dimensions and conditions have been calculated. A method of altering the geometry of sector-type mass spectrometers to correct for the effects of the fringing fields is proposed. It is shown that the angular and spatial separations of the individual ion trajectories in an ion beam of small angular spread as it approaches a uniform field region through a fringing field are approximately the same as for the ideal case wherein the magnet field changes discontinuously at the boundary.
Quarter Wave Coupled Wave-Guide Filters
Authors: Pritchard Wilbur L.
Published: January 2005

This paper considers the theory of band-pass wave-guide filters formed by cascading rectangular cavities separated by quarter guide wave-lengths. Formulas for resonant frequency, loaded Q, and insertion loss in the pass band are derived for a single stage using matrix theory and are in a form suitable for design purposes.

The general theory of ``n'' stages is worked out using matrix algebra, and it is shown that the insertion loss and phase shift of ``n'' stages are given by: Ln=1+x2Un2(x)    φ=tan−1[Tn(x)/Un(x)],where Tn(x) and Un(x) are the first and rationalized second kind Tschebyscheff polynomials.

The specific design procedure is outlined including the design of a finite thickness inductive aperture.
A Computational Method Applicable to Microwave Networks
Authors: Dicke R. H.
Published: January 2005

A method is devised for computing the properties of a complex microwave network in terms of the properties of the circuit elements which in combination form the network. It is particularly suited to machine computation of the properties of circuits of such complexity that simpler, more direct methods fail. It is also applicable to low frequency networks. The elements of such networks may be regarded as interconnected by transmission lines of zero length. A numerical example is used to illustrate the method.
The Optics of Three-Electrode Electron Guns
Authors: Ellis S. G.
Published: January 2005

The paper is concerned primarily with the electron guns employed in electron microscopy.

The position of the image of the cathode, the magnification, and the divergence of the beam leaving the anode are calculated for a three-electrode electron gun with plane electrodes and circular apertures both for zero and battery bias. The simplifying assumption is made that the electrostatic lenses are thin. The results are compared with the experiments of Johannson. The extension of the results to the gun used in the transmission electron microscope is considered with the aid of electrolytic trough measurements. The case of a gun biased by a cathode resistor is also discussed.
On the One-Dimensional Theory of Steady Compressible Fluid Flow in Ducts with Friction and Heat Addition
Authors: Hicks Bruce L. , Montgomery Donald J. , Wasserman Robert H.
Published: January 2005

Steady, diabatic (non-adiabatic), frictional, variable-area flow of a compressible fluid is treated in differential form on the basis of the one-dimensional approximation. The basic equations are first stated in terms of pressure, temperature, density, and velocity of the fluid. Considerable simplification and unification of the equations is then achieved by choosing the square of the local Mach number as one of the variables to describe the flow.

The transformed system of equations thus obtained is first examined with regard to the existence of a solution. It is shown that, in general, a solution exists whose calculation requires knowledge only of the variation with position of any three of the dependent variables of the system. The direction of change of the flow variables can be obtained directly from the transformed equations without integration. As examples of this application of the equations, the direction of change of the flow variables is determined for two special flows.

In the particular case when the local Mach number M=1, a special condition must be satisfied by the flow if a solution is to exist. This condition restricts the joint rate of variation of heating, friction, and area at M=1. Further analysis indicates that when a solution exists at this point it is not necessarily unique.

Finally, it is shown that the physical phenomenon of choking, which is known to occur in certain simple flow situations, is related to restrictions imposed on the variables by the form of the transformed equations. The phenomenon of choking is thus given a more general significance in that the transformed equations apply to a more general type of flow than has hitherto been treated.
Crystalline Aggregation of Cobalt Powder
Authors: McCartney J. T. , Anderson R. B.
Published: January 2005

In electron microscopic studies of Fischer-Tropsch catalysts, an interesting phenomenon was observed in cobalt metal powder reduced from cobaltous oxide. The oxide particles sintered into larger smooth droplets of cobalt that were aggregated into thin hexagonal-shaped platelets. X-ray diffraction analysis showed the presence of the hexagonal crystal phase of cobalt. A possible explanation is that the aggregates are formed by forces similar to those operating in normal crystal formation, but of reduced magnitude insufficient to destroy the identity of the component particles.
Surface Studies of Glass. Part I. Contact Angles
Authors: Spitze L. A. , Richards D. O.
Published: January 2005

The water-repellent nature of glass surfaces treated with different silicones is examined by means of contact-angle measurements. Results are given showing the effect of various concentrations of silicones, types of glass, temperature of heat treatment, length of time of heat treatment, and surface roughness on the water contact angles. Silicones containing the methyl and phenyl group show good heat stability at temperatures of 500°C for short periods of time.
On the Localized Afterglows Observed with Long Sparks in Various Gases
Authors: Craggs J. D. , Hopwood W. , Meek J. M.
Published: January 2005

Simultaneous photographs, taken in two perpendicular directions, have been obtained of long sparks in various gases at 1-atmosphere pressure. The experiments were undertaken in order to decide whether the localized afterglows, noticed as long streaks in rotating mirror spark photographs, were caused by some discharge mechanism or by purely geometrical effects resulting from the tortuous nature of the spark channels. The results show that the second explanation is not feasible. Some qualitative interpretations of the effects are given.
The Field of a Microwave Dipole Antenna in the Vicinity of the Horizon. II
Authors: Pekeris C. L.
Published: January 2005

In this paper the results of a previous investigation are extended to include cases where the elevation of the transmitter z1, or of the receiver z, is less than about 1 when expressed in natural units of height. When z1 < 1 and z > 1 the electromagnetic potential ψ in the vicinity of the horizon is given, in the case of strong absorption (β≫1), by |Ψ|=[(32)13/π(rr̄)12]|(1+βz1)G(p)/β|,where βv=i(k0/q)13(ε1−1)12/ε1; βh=βvε1,and the notation of I is used. Expression (a) equals expression (B) or (C) of I multiplied by the factor |(1+βz1)|.

When both z1 and z are less than about unity the potential is given by |Ψ|=(L/r2)|(1+βz1)(1+βz)g(p′)/β2|,where L is the natural unit of horizontal distance. Expression (c) is equal to the expression for the surface wave given in (D) of I multiplied by the factor |(1+βz1)(1+βz)|.
Initial Oscillation on a Rotational Viscometer
Authors: Weltmann Ruth N.
Published: January 2005

The oscillatory system of a rotational viscometer has been investigated. The oscillation equations were checked with experimental bob deflection-time curves obtained for Newtonian liquids.

To be able to rapidly obtain correct values when taking flow curves the oscillatory system should be critically damped. Since this condition cannot be easily obtained in practice, the system should be slightly overdamped, meaning that the inertia (I) should be equal or smaller than πμ2/720KS2. It is shown that due to the higher viscosity of thixotropic materials at lower rates of shear, the flow curves at these rates of shear give an indication of rather too low than too high shearing stresses.
Stability and High Frequency
Authors: Wintner Aurel
Published: January 2005

In a linear oscillator which is not conservative, let the frequency vary so as to tend to infinity when time increases indefinitely. It seems to be evident that the oscillations must then be of stable type. Actually, this is not true. The paradox results from the circumstance that the relevant criterion of stability depends on the monotone decrease, rather than on the indefinite decrease, of the instantaneous period.
Mechanism of Fracture of Glass and Similar Brittle Solids
Authors: Taylor Nelson W.
Published: January 2005

A theory is proposed which connects the stress, f, required to break a brittle material in simple tension, with its duration of application, t. The slow process preceding fracture is shown to be the orientation of the atomic network contained in an elementary prism of length r=λ0E/f, where E is Young's modulus and λ0 is the critical elongation required for fracture. The rate-controlling factor is the activation energy, Eα/f, for the orientation or rearrangement of the atomic network under the stress, f. Moisture on glass, and moisture plus oxygen on certain metals, are important catalytic or fatigue-promoting factors because they reduce the unit activation energy, α. The theory leads to the equations t=(1/k0)eEα/fkTand logt=−logk0+(Eα/2.3kT)/f,where t is the time for fracture (duration of the stress), k is the Boltzmann constant, T the absolute temperature, and α and k0 are experimentally determined constants. The logarithmic expression has the same form as the Glathart-Preston [J. App. Phys. 17, 189 (1946)] empirical relation logt= −a/m+1/fm, which, in the case of glass, appears to be valid over a time factor of 107.

The theory shows why a solid object does not have a single characteristic breaking strength, and how it adjusts its fracture mechanism to whatever stress is applied. Quantitative tests of the theory are made, using fracture data on various glasses and on one glass at various temperatures. Applicability of the theory to certain aspects of fatigue of metals under stress-corrosion conditions, as well as to failure by fracture of the more rigid organic plastics, is indicated.

An equation, Eλ0=2γ, is proposed which connects Young's modulus and the critical fracture distance with the surface tension, γ, of the solid. Some examples are given.
Infra-Red Spectra of Hydrocarbons: II. Analysis of Octane Mixtures by the Use of Infra-Red Spectra Obtained at Low Temperatures
Authors: Avery W. H. , Morrison J. R.
Published: January 2005

Infra-red spectra in the region 2 to 22 microns were obtained for the four trimethylpentanes, at temperatures of 0°C and −195°C. In agreement with theory, the band ``widths'' at −195°C are roughly half as great as at 0°C. The spectra were observed experimentally by condensation of a film of the hydrocarbon on the reflecting bottom surface of a cell mounted vertically, with its lower end immersed in ice or liquid nitrogen. A method of forming films of reproducible dimensions and thickness is described.

To provide a quantitative estimate of the advantage for analytical purposes of the use of spactra obtained at low temperatures, an expression is derived which gives the probability (for random distribution of the band positions) that at least one band can be found for each component of a mixture, which does not ``overlap'' bands of the other components. Application of the formula, with some simplifying assumptions, to a mixture of the 18 octane isomers, indicates that reduction of the band ``width'' from 40 cm−1 to 20 cm−1 (corresponding to the temperature change from 0°C to −195°C) increases the calculated probability of the existence of a ``non-overlapped'' band for at least 17 of the isomers from 0.003 to 0.999. The importance of this result in infra-red analyses is pointed out.

The use of spectra obtained at liquid helium temperatures is suggested as offering attractive possibilities for the analysis of complex mixtures.
Magnetic Field Configurations Due to Air Core Coils
Authors: Blewett John P.
Published: January 2005

The field configurations around a circular loop of wire bearing current are discussed, and a tabulation is presented for the field component parallel to the axis of the loop. Formulae are derived for the current distribution which must obtain in cylindrical and ellipsoidal coils in order that the field inside be uniform. Several special cases are noted. The energy storage in the return flux is evaluated in each case.
Design of an Air Core Synchrotron
Authors: Blewett John P.
Published: January 2005

The analysis of the preceding paper is applied to the problem of designing a synchrotron in which the magnetic fields are produced by air core coils. The air core synchrotron is shown to be practical and to present certain advantages.
A Sound Velocity Method for Determining the Compressibility of Finely Divided Substances
Authors: Urick R. J.
Published: January 2005

A method is presented whereby the adiabatic compressibility of a finely divided material can be found from sound velocity and density measurements of a suspension of the particles in a liquid. The method is based on the assumption that the velocity of sound in a suspension is the same as it would be in an ideal solution of the two substances. This is verified experimentally by measurements of sound velocity in kaolin-water suspensions and xylene-water emulsions, and the method is illustrated by the determination of compressibility of the oil droplets in an oil emulsion and of the blood corpuscles in horse blood. Considerable accuracy is attainable for materials which are not too incompressible compared to the suspending liquid.
End-Effect in Rotational Viscometers
Authors: Lindsley Charles H. , Fischer Earl K.
Published: January 2005

In the classical equations for the traction on concentric cylinders by a viscous substance, it is assumed that traction on the top and bottom of the inner cylinder (bob) is negligible in comparison with that on the curved surface. In viscometers of practical dimensions, however, it is necessary to compensate for the end-traction or end-effect by adopting one of several expedients in design or by determining the magnitude of the effect and accounting for it in terms of increased length of bob.

In the experiments reported in this paper, the method of multiple bobs has been used, and the variation of end-effect with the following factors studied: (1) radius of bob; (2) clearance between cylindrical surfaces; (3) separation between bottom of bob and cup; and (4) viscosity.

The magnitude of the end-effect increases with radius and with clearance. For separations at the bottom greater than 1 cm and for viscosities above 1 poise the end-effect is nearly constant, but must be determined for each cup and bob combination. At lower viscosities the correction must be determined either by calibration with a standard liquid of about the same viscosity as the unknown, or by the multiple-bob method.

It is shown that trapping a layer of air beneath the bob is not effective in making the traction on the bottom negligible. The end-effect is almost as large for a bob with an open bottom as for a closed one.

When the method of multiple bobs is used, data with an accuracy of ±2 percent can be obtained without calibration. When the instrument constant is determined with standard liquids or computed from a value for the end-effect previously found, data of somewhat lower accuracy result, but the uncertainty should be within ±5 percent.
The Theory of Disk-Loaded Wave Guides
Authors: Chu E. L. , Hansen W. W.
Published: January 2005

The properties of circular wave guides loaded with apertured disks are discussed both qualitatively and quantitatively. Formulae and curves are given for various quantities including the wave and group velocities, the attenuation, and the power flow.
A Preliminary Study of a Physical Basis of Bird Navigation
Authors: Yeagley Henry L. , Whitmore F. C.
Published: January 2005

The bird navigation theory as presented implies an organ or organs in the bird's physiology which are sensitive to the effect of its motion through the vertical component of the earth's magnetic field and to the effort exerted to overcome the coriolis force, due to the earth's rotation. Both these influences involve a set of lines which together form a navigational gridwork. By correlating its instantaneous land speed with the two above effects, a bird can fly to its home which is a unique point in this gridwork, or to related companion points existing in the gridwork at positions other than its home. Experimentation with homing pigeons between the home and spurious home points (conjugate or companion points) has yielded data which supports the theory.
Inversion Applied to the Solution of 3-Dimensional Electromagnetic Problems
Authors: Bloch A.
Published: January 2005

This paper presents an extension of the method of inversion to certain electromagnetic problems and rectifies at the same time an error of long standing in the solution of an elementary problem which seems to have acted as a bar to just this extension.

If the image of a charge in a sphere is derived by the method of inversion, as is done in this paper, it becomes immediately obvious that the image of radially oriented dipole is another radial dipole plus a free charge proportional to the moment of the dipole. The potential caused by the free charge is not of negligible magnitude, and this indicates that the solution given by Sir J. Larmor and independently by S. P. Thompson and Miles Walker for the case of a magnetic dipole outside a sphere of infinite permittivity cannot be correct, for the image used therein consists of a simple dipole. However, it can be shown in addition that the latter image is not void of physical significance: the vector potential of such an image transforms in a simple manner and from this in turn follow simple laws of transformation for flux linked with loops and for mutual inductance between such loops.

This extension of the method of inversion is used in the second part of the paper to deal with a problem complementary to that of Larmor-Thompson, namely, with that of a spherical wall impermeable to magnetic flux. This problem is of practical importance as an idealization of an inductor used at radiofrequencies and placed inside a metal screen, and it has for this reason been dealt with by direct attack on several previous occasions. It is shown here that the action of such a screen on the field produced by the loop can be replaced by the introduction of a simple image loop. From this follows then a simple way of calculating the change in self and mutual inductance produced by such a screen, even in cases more general than considered heretofore. The losses caused by the screen can also be easily calculated by the use of H. A. Wheeler's concept of equivalent magnetic skin thickness.
Non-Linear Viscous Elasticity and the Eyring Shear Model
Authors: Halsey George
Published: January 2005

Attempts to analyze stress-strain-time relationships observed in experiments with textile fibers have been reported in a series of papers. This work has led to some general conclusions: First, the simplest three element model (spring in parallel with another spring and a dashpot in series) is adequate for the approximate explanation of a wide range of the data obtained. Second, the viscous element (dashpot) almost always appears to be non-Newtonian while the springs less frequently are non-Hookean. Third, the most striking deviations from simple behavior indicate, not a more complex model consisting of many simple elements, but that the assumed laws governing the viscous, or less frequently, elastic elements are themselves too simple.

Frequently a more complex law or laws will restore the three-element model to approximate agreement with the experimental facts. Finally, any system so far investigated can be made to show the presence of a number or a distribution of relaxation times by prolonging the experiment over a period of time, or more positively, by going to a point of no instantaneous relaxation, and waiting for the inevitable long period of relaxation to appear. Procedures to deal with the general situation described here are presented.

The paper begins with a condensed but essentially self-contained summary of the theoretical portions of the series of papers that preceded it. The original presentation has been clarified and recast in a form more in harmony with the present work. For experimental evidence, and supplementary information, the reader is referred to the original series.

The paper continues with a discussion of the various aspects of non-linear viscous elasticity, including the topics: Six rules for analyzing stress-strain curves (presented at the meeting of the Division of High-Polymer Physics of the American Physical Society, January 31, 1947); the thixotropic viscous element, where for convenience, complex situations, in which the populations of various states enter into a time-variable viscosity, have been gathered under the name ``thixotropy''; constant force springs, where a particularly non-Hookean behavior is described.
A Magnetron-Resonator System
Authors: Okress E. C.
Published: January 2005

The present exposition deals with the fundamental multiplet spectrum of a multi-sectorial cavity or vane-type magnetron and specific applications involving the evaluation of the π-mode wave-length thereof. The consequence of mutual coupling between the sectorial cavities through the interaction space of an infinitely long anode is evaluated for the linear case and subsequently applied to the cylindrical case. Although both the qualitative and quantitative results are reasonable in the limit for relatively very long anodes, in practice the latter are relatively short and since the mode separation, order thereof, and hence the component wave-lengths are more or less influenced by the actual relative anode and end cavity lengths at each end of the anode, the results naturally differ from ``cold'' test data. Predictions of π-mode wave-length have been obtained to about 10 percent, depending upon the degree to which the parameters of the actual vane magnetron approximate the assumptions on which the present treatment is based. With the aid of ``cold'' test data the preliminary theoretically derived resonator geometry may be appropriately ``trimmed'' to produce the exact π-mode wave-length desired.

Included in this article is a discussion of the need and function of straps of the resonator system and dimensional scaling, which preserve certain desirable properties of the prototype at the new wave-length, or operating point, in terms of magnetron performance-chart parameters. Finally, in Part III, a brief consideration is allotted to the derivation of the rectangular cavity or slot-type resonator system from the more general relation for the sectorial cavity in this article.
Gyroscopic Effects in a Vibratory System
Authors: Bennett G. S.
Published: January 2005

An analytical investigation is made to determine the influence on a vibrating elastic system of a high speed rotating element. A fundamental condition for the presence of any gyroscopic effect is that the vibration be such as to produce a tilt of the spin vector of the rotor. Equations are derived showing (a) that if precession be prevented, no gyroscopic effects are present, and (b), that if precession be permitted, the gyroscopic action contributes a force opposed to the tilt, and proportional to the angle of tilt, in effect increasing the stiffness of the elastic system. Calculations based on an arbitrarily chosen rotor intended to approximate a typical small motor armature indicate that this additive spring force is small, and that the increase in natural frequency caused by the added stiffness is exceedingly small—on the order of 0.1 percent—in the case where the precessional motion is not restrained.
The Efficiency of Thermoelectric Generators. I.
Authors: Telkes Maria
Published: January 2005

The generation of electrical energy from thermal energy by thermoelectric means cannot be accomplished with thermocouples made of the available alloys generally used for temperature measurements, their efficiency being less than one percent.

A review of the theoretical efficiency calculations shows that higher efficiencies can be attained with thermocouple materials to which the Wiedemann-Franz-Lorenz relation is applicable, when their thermoelectric power is greater than 200 microvolts/°C. Some zinc-antimony alloys with added metals approach the above conditions and have produced an experimental efficiency in excess of five percent, in accordance with the theoretical calculations.

The criteria of higher efficiency are applied to semi-conductors, deriving the optimum conditions. Lead sulfide with excess lead was found to be the only suitable material at present, which in combination with the zinc-antimony alloy produces an efficiency of seven percent.

Higher thermoelectric efficiencies can be produced only by developing new materials which can attain the theoretically required high values of thermoelectric power, low heat conductivity, and low specific resistance.
Cesium Chromate Photo-Tube Pellets
Authors: Liebhafsky H. A. , Winslow A. F.
Published: January 2005

The following results have been obtained in an exploratory investigation of the cesium chromate pellets used in the manufacture of photo-tubes: (1) hydrogen evolution or titration can be used to measure the yield of cesium with reasonable precision. Each method has limitations. (2) The theoretical yield could be obtained from cesium chromatesilicon pellets. (3) Within limits, the actual yield increases with the rate of heating; the maximum yield is not highly sensitive to composition in the range investigated. (4) No marked advantage was observed when titanium or zirconium was substituted for silicon as reducing agent. (5) An excess of hydrogen above the theoretical was consistently observed with nickel pellet holders, which points to a reaction of water vapor with reactive nickel formed during the heating and flashing of the pellet. The substitution of the less volatile molybdenum for nickel eliminated this difficulty. An excess of hydrogen was formed also when the reducing agent in the pellets was titanium.

It was suggested for purposes of further study that the complex process occurring when such pellets are induction heated be subdivided into two reactions of elementary silicon: (1) a preliminary exothermic reduction of hexavalent chromium, which initiates (2) a rapid reduction of monovalent cesium. The two reactions may proceed concurrently. This picture explains several observations made in the laboratory or in the factory.
An Effect of Electron Bombardment upon Carbon Black
Authors: Watson John H. L.
Published: January 2005

A significant change is reported in mean particle size and shape characteristics of carbon black due to specimen contamination while under examination in electron microscopes. The effect is described for a number of well-known commercial blacks and examples are given in graphical form to illustrate expected variations in mean particle size with continued bombardment at normal focusing intensities. The effect is observed in other materials but is more pronounced in carbon black. Suggestions are made for minimizing the effect.
A New Magnetic Material of High Permeability
Authors: Boothby O. L. , Bozorth R. M.
Published: January 2005

This paper describes the preparation, heat treatment, and properties of supermalloy, a magnetic alloy of iron, nickel, and molybdenum. In the form of 0.014 in. sheet it has an initial permeability of 50,000 to 150,000, a maximum permeability of 600,000 to 1,200,000, coercive force of 0.002 to 0.005 oersted, and a hysteresis loss of less than 5 ergs/cm3/cycle at B=5000. Transformer cores made of insulated 0.001 in. tape, spirally wound, have about the same initial permeability and a maximum permeability of 200,000 to 400,000. The alloy has a Curie point of 400°C and appears to have an order-disorder transformation temperature somewhat above 500°C.
Minimum Sparking Potentials of Barium, Magnesium, and Aluminum in Argon
Authors: Jacobs Harold , LaRocque Armand P.
Published: January 2005

Minimum sparking potentials of barium, magnesium, and aluminum in argon are found to be 93±½ v, 123±1 v, and 155±1 v, respectively. Utilizing the data in measuring the minimum sparking potentials, the ratios of electrons emitted from the cathode per bombarding positive ion (γm) are determined and found to be .149±.001 for barium, .089±.033 for magnesium, and .045±.002 for aluminum. A relationship is found such that, at a given field per unit pressure, a lower work function indicates a lower sparking potential and a higher γm indicates a lower sparking potential, for the case of the three metals studied. A graphical method is proposed for predicting the minimum sparking potentials for metals, whose sparking potential values have not been determined, based upon the values of γm or the work function φ.
Fatigue of Ag–Cs2O, Ag–Cs Photoelectric Surfaces
Authors: Pakswer S.
Published: January 2005

Fatigue of Ag–Cs2O, Ag–Cs surfaces has been observed in blue and red light. In blue light the long wave threshold shifts to shorter wave-length and the long wave maximum increases and sometimes shifts to shorter wave-length. Rise of temperature at the cathode counteracts the phenomena. In red light temperature effects are dominating. The observed phenomena are in line with de Boer's theory of the photoelectric effect on such surfaces as the formation of positive ions on the surface causes polarization of the neighboring Cs-atoms and a change in their selective absorption.
The Measurement of Elasticity in Fluids of Low Viscosity
Authors: Van Wazer John R. , Goldberg Herbert
Published: January 2005

By means of an apparatus applying an alternating shearing motion to a liquid, it was shown that fluids with a viscosity of around one poise have elastic properties. A discussion of the variation of the resonance maxima with the amount of damping is given, and the shear modulus and damping viscosity are calculated for some dilute solutions of high polymeric materials.
On Creep and Relaxation
Authors: Gross B.
Published: January 2005

The creep and the relaxation function of linear systems, for which the principle of superposition is valid, are mutually connected in a simple way. This makes it possible to calculate the distribution function of relaxation times of stress and the distribution function of retardation times of strain, when the relaxation function or the creep function is given. It also allows a transformation formula to be established for the conversion of one distribution function into another. The results of the theory are applied to a detailed discussion of the relaxation process in a particular case.
Parallel Plate Optics for Rapid Scanning
Authors: Myers S. B.
Published: January 2005

Rapid scanning using a paraboloid antenna is unsatisfactory; rapid movement of the antenna is mechanically impractical, while motion of the feed near the focus requires long focal length for good optical results. Another attack on the problem is to place the feed between parallel plates which produce a line source near a bifocal reflector. The energy flows along the geodesics of the mean surface between the parallel plates; the problem of shaping the plates so that a circular feed motion produces an oscillating beam at the line source becomes a problem in differential geometry and the calculus of variations. If the mean surface is assumed to consist of two developable surfaces joined along part of their boundaries, the unique solution of the optical problem is a circular disk along the edge of which the feed moves, joined to a section of a 60° cone which is straightened out at the large end to obtain a straight line source. This is the RCA solution of the problem. If the surface is assumed to consist of a surface of revolution which provides a feed circle, and attached to it a circular disk a diameter of which is the aperture, under certain natural restrictions no exact solution of the optical problem is possible, but several approximate solutions exist. Dielectric introduced between the plates of such a surface of revolution scanner effects a great improvement in the optics.
Space Charge Frequency Dependence of Magnetron Cavity
Authors: Lamb W. E. , Phillips M.
Published: January 2005

The effect on the resonant frequencies of a magnetron cavity produced by the presence of a thin layer of charge surrounding the cathode is investigated theoretically. The corresponding experimental procedure is the ``cold impedance testing'' of a magnetron with a hot cathode in the presence of a magnetic field and a low d.c. cathode-anode voltage. A small amplitude theory is used, based on the single stream steady state. The correction to the frequency of the empty cavity due to a thin cloud of charge surrounding the cathode is given by a resonance-like formula about the ``cyclotron frequency,'' eB/2πm. In the ``Rising-Sun'' tube the curve of ν vs. νc for constant d.c. voltage is asymmetric, apparently because of the presence of the ``zero'' mode. The validity of the theory is limited to low level oscillations, but the comparison of theory with experimental results seems to support the existence of the single stream steady state for non-operating magnetrons.
The Reduction of Microphonics in Triodes
Authors: Waynick A. H.
Published: January 2005

An analysis is presented showing the effect of grid displacement on the plate current of a planar triode. This is defined in terms of a new parameter called the motional transconductance. The analysis indicates that a useful mechanical displacement indicator may be constructed by moving the grid and noting the change in plate current. The analysis also indicates that the effect of certain modes of grid displacement on the plate current may be eliminated under conditions which are stipulated. Since microphonic effects are, in great part, caused by the mechanical motion of grid structures, the analysis indicates how microphonism may be reduced. It is shown that the electrical transconductance is large under these conditions, for the case investigated, so that the tube functions normally as an amplifier. Preliminary experimental results for comparison with the theory are presented.