bluuebunny/crossref_metadata_2025 huggingface dataset:
Spectral Emissivity and Electron Emission Constants of Thoria Cathodes
Authors: Hanley T. E.
Published: January 2005

A method is described for forming cathodes by means of a cataphoresis process wherein a thin layer of thoria is deposited over an underlying metal. A temperature scale determination yields for the relation between true temperature (°K) and brightness temperature (°C) at λ = 0.65 micron: Tt = 1.172Tb + 177.5. Electron emission studies yield for the constants of the Richardson equations: A=2.63 amp./cm2/deg.2; Φ=2.67 volts for d.c. emission,A=5.62 amp./cm2/deg.2; Φ=2.55 volts for pulsed emission.Information was also obtained regarding the resistivity of thoria at high temperatures.
Irradiation of Biological Materials by High Energy Roentgen Rays and Cathode Rays
Authors: Trump J. G. , Van De Graaff R. J.
Published: January 2005

In this work roentgen rays and cathode rays of several million-volts energy have been applied to an investigation of their biological, photo-chemical, and germicidal effects, particularly as they are related to the processing of foods and biological materials. A constant-potential electrostatic generator, together with an acceleration tube, was used to produce continuous streams of electrons with homo-geneous and controllable energy. [R. J. Van de Graaff, K. T. Compton, and L. C. Van Atta, Phys. Rev. 43, 149 (1943).] These high energy electrons were utilized both for the production of penetrating roentgen rays and for the direct irradiation of materials. The mechanism of the biological action of both roentgen rays and cathode rays is discussed, as well as the energy considerations in their application to various absorbers. The companion paper [C. G. Dunn, W. L. Campbell, H. Fram, and A. Hutchins, J. App. Phys. 19, 605 (1948)] reports on measurements of the lethal action of these radiations on a wide variety of micro-organisms and also on the effect of the radiations on enzymes, vitamins, and certain whole food products. Both investigations have been conducted cooperatively by the Departments of Electrical Engineering and Food Technology at the Massachusetts Institute of Technology.

The systematic and quantitative study of the effects of roentgen and cathode rays on various elementary forms of living matter is regarded as an essential prelude to their possible widespread application to the preservation of foods and the sterilization of various biological materials. It was realized that the mechanisms of biological action of high energy roentgen rays and cathode rays are similar and depend closely upon the ionization energy absorbed per gram of material. The studies were begun with roentgen rays since these were immediately available and permitted quantitative measurement of the energy absorbed in the biological materials. Later, the water-cooled gold x-ray target was replaced with an aluminum cathode-ray window, and corresponding studies were begun on the direct application of high energy electrons to these materials. During the period of these biological studies the x-ray source was also used in a daily clinical program of deep cancer therapy under the medical direction of Dr. Richard Dresser and also in the investigation of the physical properties of high energy radiations. [R. Dresser, Radiology, in publication.]
The Analysis of Retarded Control Systems
Authors: Pipes Louis A.
Published: January 2005

This paper presents a mathematical discussion of retarded control systems. The analysis presented is applicable to general control systems and is based on the solution of a linear differential equation of infinite order. The mathematical investigation is performed by operational methods, and the question of stability is studied by the use of the complex variable.
Rising Sun Magnetrons with Large Numbers of Cavities
Authors: Hollenberg A. V. , Kroll N. , Millman S.
Published: January 2005

Studies of the rising sun design for magnetron oscillators have been extended to large numbers of cavity resonators. Successful operation of pulsed magnetrons having as many as 38 cavity resonators has been achieved in the 1.25-cm wave-length region. The open cavity resonators heretofore used in rising sun magnetrons were found unsuited for oscillators containing a large number of cavities. The extension to higher numbers was made possible by the use of closed-end resonators. This modification in cavity geometry produces a favorable redistribution of the spectrum of the resonant modes of the rising sun structure, thereby making possible the operation of the magnetron in the desired π-mode without disturbance from other modes. The increase in the number of cavity resonators for magnetrons should serve to facilitate the extension of present magnetron techniques to the millimeter range and to increase the radiofrequency power obtainable from magnetrons at 1 cm and at longer wave-lengths.
Transmission Losses in 2n-Terminal Networks
Authors: Belevitch Vitold
Published: January 2005

The semipositive character of the dissipation function of any physical 2n-terminal network imposes some restrictions on the realizability of prescribed transmission losses between the various pairs of terminals when they are connected to given impedances. These restrictions are most easily expressed in terms of elements of the efficiency matrix of the network, which is defined in the first part of this paper. Discussions of the application of matrix calculus to the solution of reactive and resistive, transformer-type, and general 2n-terminal networks are presented.

A very useful tool in solving telephone transmission problems is the conventional theory of 4-terminal transducers, often called 4-pole networks. Although this theory is sufficient for the study of most circuits, some problems involve networks with a larger number of terminals, which are often referred to as 2n-terminal, or 2n-pole networks. This paper is a contribution to their theory.

The particular point that will be considered in this paper is the restriction imposed by physical realizability on the arbitrary choice of transmission losses between various pairs of terminals connected to a given set of terminating (generator or receiver) impedances.
Transmission of Monoenergetic Slow Neutrons through Solid Solutions and Mechanical Mixtures of TiC and WC
Authors: Sidhu S. S.
Published: January 2005

TiC and WC form continuous substitutional solid solutions at least up to 25 percent TiC+75 percent WC by weight when heated to 4000°F, TiC being the solvent and WC the solute. Total neutron scattering cross sections of a series of finely powdered solid solutions and corresponding mechanical mixtures of the two carbides were determined as a function of the mole percent of WC from the measured transmission of monoenergetic neutrons with energies 0.08138, 0.03479, 0.02056, and 0.01526 ev or wave-lengths λ=1.004A, λ=1.536A, λ=1.998A and λ=2.319A, respectively. The cross sections of both the solutions and the mixtures increase with increasing mole percent of WC. For mixtures they are the same as the additive cross sections, each constituent scattering independently of the other. They are analogous to x-ray scattering for the mixtures in which each constituent gives its own diffraction pattern and the patterns of the two constituents are superimposed. The neutron cross sections of solid solutions are lower than those of the mixtures at low percentages of WC but increase rapidly with the concentration of the solute molecules. They appear to be sensitive both to the structure of the solvent and the concentration of the substituting atoms.
Experimental Results on Standing Wave Type Linear Accelerators for Electrons
Authors: Lawton Elliott J. , Hahn W. C.
Published: January 2005

The work that was done in this laboratory on the development of a resonant cavity type linear accelerator is briefly described. The experimental results demonstrate that electrons entering at low energies will accelerate to a higher energy in passing through a group of cavities of equal β(λ0/2) spacing and along which appears a standing wave field distribution. Starting at 57 kv, an energy of 0.345 Mev was attained with two cavities. An 8-cavity accelerator of cavity length corresponding to β=0.75 had a maximum output of 0.57 Mev. Experimentally determined energies were in fair agreement with theoretical values at equal axial gradients. Excitation power was found to be proportional to [(Mev)2/Length](1/Q)×coupling coefficient. The power required for an axial gradient of 1 Mev/ft., even for the most favorable design, was high and would require the full output of one HK7 type magnetron for each foot of accelerator length. Energy spread in the accelerated beam was large for the two cavity tubes but small for the longer 8-cavity tube. It is believed that the apparent low energy spread observed in the 8-cavity case resulted from a limited range in entering angle brought about by the reduced axial gradient. There was little evidence of radial defocusing. A change in resonance wave-length amounting to +0.000225 cm per degree centigrade was observed. There was indication that the magnetron would follow a resonance change of approximately 5°C.
A Method for Measuring the Complex Dielectric Constant of Gases at Microwave Frequencies by Using a Resonant Cavity
Authors: Jen C. K.
Published: January 2005

A sensitive method has been developed for the measurement of the complex dielectric constant of low pressure gases at X-band microwave frequencies. The gas, whose complex dielectric properties are to be determined, is contained in a resonant cavity which is a part of the microwave circuit. With the introduction of the gas, the real part of the dielectric constant changes the resonant frequency of the cavity, while the imaginary part changes the amplitude and breadth of the cavity response curve. By a rapid variation of the frequency across the cavity resonance, the real and imaginary parts can be conveniently and accurately determined from measurements on an oscilloscope. Tests on such a system have been performed with satisfactory results. Sample data are presented for methylchloride and deuterated ammonia. This method can be used for the measurement of the resonant dispersion and absorption of microwaves by gas molecules. Also, the same method can be used for the measurement of loaded and unloaded Q-values of a cavity.
Carbon Film Formation and Commutator Brush-Wear As Revealed by the Electron Microscope
Authors: Fullam Ernest F. , Savage Robert H.
Published: January 2005

The faces of carbon or graphite brushes, polished by rubbing against a rotating copper disk and subsequently examined with the electron microscope by means of surface replicas, are found to consist of many tilted ``fingers,'' which are the projecting portions of the large and irregular graphite plates composing the brush. These graphite projections show a directional overlap, which is determined by the direction of motion of the disk, and when viewed stereoscopically they are found to be inclined at various angles up to nearly 90° with reference to the plane of the rotating base. They account for a previously observed ``directional memory'' of graphited surfaces and they show that such surfaces in general cannot be regarded as consisting simply of graphite plates oriented with the hexagonal planes flat and parallel to the plane of motion.

The brush track on the rotating copper base is found to contain small islands of carbon deposited from the brush. These islands consist of large numbers of graphite wear-fragments, which are individually of very small size in comparison with the projections of the brush face. These fragments are clearly derived from the projections by a tearing apart of their edges and are packed tightly and with random arrangement into the tool marks of the copper smoothing over the irregularities of the latter. It is not determined whether this ``carbon film'' of the brush track is continuous.

The wear-dust of unlubricated graphite is found to consist of particles which are very small in average size compared with those from which brushes are manufactured. The size of these wear-fragments extends below the resolving power of the electron microscope, and this is consistent with recent data on similar particles of a size determined independently by adsorption measurements.
The Attenuation of Spherical Shock Waves in Air
Authors: Stoner Richard G. , Bleakney Walker
Published: January 2005

The peak pressure of spherical shock waves from small explosive charges has been determined as a function of distance by measuring the velocity of propagation and applying the velocity-pressure relation derived from the Rankine-Hugoniot equations. The charges were composed of TNT or pentolite (TNT/PETN 50/50 by weight), weighed from 1.45 to 8 lb., and were spherical or cylindrical in shape, except for one series of small rectangular blocks. Measurements on the non-spherical charges were made in the plane through the center of the charge, perpendicular to the axis.

The pressure-distance relations for the four principle charge types are given by the following fitted equations, in which Π represents excess peak pressure in atmospheres, and the distance, scaled according to charge weight, is given by the non-dimensional variable Z=R/(ρτ)⅓ where R is the distance from a charge of volume τ and specific gravity ρ:

½-lb. rectangular blocks, TNT, ΠQ=13.50/Z−769.9/Z2+36280/Z3;8-lb. cylinders, Pentolite, ΠA=10.49/Z−135.5/Z2+21070/Z3;4-lb. cylinders, TNT, ΠB=11.34/Z−185.9/Z2+19210/Z3;3.75-lb. spheres, Pentolite, ΠC=8.63/Z+295.1/Z2+7823/Z3. These equations are valid for values of Z between approximately 18 and 110. The indicated probable error of the fitted curves is of the order of one percent for intermediate distances, increasing to from two to seven percent at the extremes of the distance range covered.

The curve for spherical charges is in agreement with the Kirkwood theory, and the results for cylinders having various length/diameter ratios indicate large dependence of pressure on charge shape for values of Z up to 50 at least.
Chromatic Aberration and Resolving Power in Electron Microscopy
Authors: Ramberg E. G. , Hillier J.
Published: January 2005

Contrast difficulties in the observation of fine detail in thin specimens may be overcome by employing dark-field observation. This introduces the added complication, however, that the imaging electrons are now inhomogeneous, having experienced a most probable energy loss of the order of 20 volts. The present calculations of the effect of chromatic aberration and diffraction show that with an objective aperture smaller than the ``optimum aperture,'' and centered optics, such inhomogeneities do not appreciably affect the resolution, even in the extreme case that the electrons are uniformly distributed in energy.
The Young's Modulus and Strain Coefficient of Resistivity of Some Bismuth Rich Alloys
Authors: Kuczynski G. C. , Norton J. T.
Published: January 2005

The Young's modulus and strain coefficient of electrical resistivity were determined for some Bi–Pb, Bi–Sn, Bi–Se, and Bi–Ni alloys. It was found that the modulus of elasticity decreases rapidly in the regions of solid solution contrary to the predictions of Guillet. The strain coefficient of resistivity was found to increase rapidly within the limits of solid solubility while the stress coefficient of electrical resistivity remained constant.
The Theory of the Radio Detection of Meteors
Authors: Manning Laurence A.
Published: January 2005

The methods of observation are described both for ``bursts'' of signal strength and ``whistles'' caused by reflection of radio waves from meteoric ionization. Consideration is given to the geometry of reflection, and it is shown that meteoric velocity and range can be accurately determined by combined pulse and whistle observations. The possibility of determining the direction and position of a meteor path by observations at three receiving locations is examined, and a method for interpreting such data is developed. An investigation is made of the fraction of meteors capable of producing bursts, and the important effect of the meteoric radiant is emphasized.
Aids to Analysis of Patterns Obtained in the Diffraction of Electrons by Gases
Authors: Yearian H. J. , Barss W. M.
Published: January 2005

Three techniques have been found particularly useful in the analysis of the electron diffraction patterns produced in the scattering of electrons by gases. The first is the use of a continuously rotating shutter which is placed directly in front of the photographic plate used to record the patterns. The shutter has an angular opening proportional to the third power of the distance from the center of the pattern and serves to reduce greatly the high background intensity gradient which is characteristic of electron scattering. The second is the application of a Fourier computing scheme to the transformation from intensity curves, derived from observed patterns, to the ``radial distribution function'' which is of value in selecting a model for the molecule whose structure is being determined by the analysis. The third technique is the computation of patterns corresponding to various molecular models by means of a graphical synthesizer in (sinx)/x. This synthesizer has advantages over the usual numerical computing schemes in that it takes account of the angular variation of atomic structure factor for electron scattering and also makes evident the contributions of scattering by specific atom pairs to the complete synthesized intensity curve.
Some Observations on the Formvar Replica Method, with a Note on Glass Surfaces
Authors: Deacon Beatrice M. , Ellis S. G. , Cross W. G. , Sennett R. S.
Published: January 2005

A study of the capabilities and limitations of the Formvar replica method has been made with more particular reference to shadow cast Formvar replicas. Observations have been made on the dependence of the deduced surface structure on the method of replication of the surface and the method of shadow casting the replica. The most suitable thickness of Formvar and evaporated metal film has been studied for various surfaces. Other replica methods have been summarized and compared with Formvar replica methods.

The structure of glass surfaces, both polished and fractured, is briefly discussed on the basis of observations made from Formvar replicas.
Pseudostructures in Electron Microscope Specimens
Authors: Watson John H. L.
Published: January 2005

Pseudostructures, which are not real properties of electron microscope specimens but are introduced by the action of the electron beam, are described. Examples are given from samples of tetracopper calcium oxychloride, precipitates from slowly hydrolized ferric chloride solutions, and tungsten oxide to illustrate some of the effects which may occur. The polymorphism of these substances, particularly of tungsten oxide, is discussed.

The major effects which contribute to the pseudostructure formation are melting, evaporation, change of crystalline states, increase in degree of crystallinity, and migration of material. Reasons are given for concluding that the primary cause of specimen changes is to be found in the heating effect of the beam. The possibilities of secondary causes are also considered.

Artifacts may also be introduced into bacterial specimens. Observed changes in such samples are described briefly and examples are given.
A Range-Finder Testing Laboratory
Authors: Gardner Irvine C.
Published: January 2005

A laboratory for testing optical range finders constructed under the sponsorship of the Ordnance Department, U. S. Army is described. The central piece of the equipment, specially designed and constructed for the purpose, is a testing instrument that optically simulates targets at ranges from 855 yards to infinity, introducing the corresponding angular parallax between two beams of light at a separation of 15 feet, with angular errors not exceeding one second. This instrument is installed in a room with temperature control equipment and also provision for applying directed radiation to simulate extremes of temperature substantially as great as those encountered under service conditions. Such a laboratory provides convenient means of rapidly acquiring exact information regarding the behavior of a range finder and localization of the sources of error. It also enables one to predict how a given range finder will perform at any point on the earth's surface without the necessity of maintaining laboratories in the different temperature zones.
The Testing of Range Finders
Authors: Gardner Irvine C.
Published: January 2005

The errors of a range or height finder are divided, on the basis of origin, into four groups, namely: 1. External errors that originate from the lack of homogeneity in the air column between the instrument and target. 2. Instrumental errors that arise from defective performance of the instrument. 3. Physiological errors that are caused by physiological limits upon the performance of the observer's eye. 4. Psychological errors that have their origin in the psychological limitations of the ability of the observer to judge the range setting correctly.

Of these classes of errors, the designer can exert direct control, within limits, upon the instrumental errors. The three other classes cannot be controlled directly, but, given a qualitative and quantitative knowledge of their characteristics, it is possible to design a range finder or height finder in such manner as to lessen their detrimental effects. A brief discussion is given of the different known sources of error in each of the four classes, with typical values of the resulting errors as obtained by measurements made in the range-finder testing laboratory established at the National Bureau of Standards under the sponsorship of the Ordnance Department of the Army.
A Method for the Evaporation of Alloys
Authors: Harris Louis , Siegel Benjamin M.
Published: January 2005

We have developed a method for the evaporation of alloys in high vacuum which from the nature of the procedure used should be applicable to all alloys which are not refractory. The method has been tested on α-brass and β-brass and on a gold-cadmium alloy. These alloys have components whose vapor pressures are very different and yet chemical and electron diffraction analyses on the evaporated brass alloys and chemical analysis on the evaporated cadmium-gold alloy show that the composition of the original alloy is held to within close limits.
Statistical Factors Affecting the Intensity of X-Rays Diffracted by Crystalline Powders
Authors: Alexander Leroy , Klug Harold P. , Kummer Elizabeth
Published: January 2005

The Laplacian probability equation can be used to predict the reproducibility of the intensities of x-rays diffracted by crystalline powders. If absorption is neglected, and N is the number of particles irradiated, p the proportion of particles which are oriented so as to diffract, and q=1 − p, the relative mean deviation to be expected in repeated intensity measurements is given by Um=0.798 (q/Np)½. When absorption and the actual distribution of particle sizes are taken into account, the expression becomes Um=0.798(qμve/pA)12,where μ is the linear absorption coefficient of the material, ve the effective volume per particle, and A the cross-sectional area of the incident beam.

The theory is confirmed by measurements on four size fractions of quartz powder using a Norelco Geiger-counter x-ray spectrometer. For typical experimental conditions and powders of medium absorbing power for x-rays, it is demonstrated that good reproducibility can be expected only if the effective particle dimension is less than approximately five microns.
Methods for Measuring Dynamic Mechanical Properties of Rubber-Like Materials
Authors: Nolle A. W.
Published: January 2005

Five methods are described for measuring the complex differential dynamic Young's modulus of rubber-like materials, under conditions of very small sinusoidal strain variations, at frequencies from 10−1 to 105 cycles per second and in a temperature range which at its widest limits extends from minus 60 to plus 100 degrees centigrade. These methods are (1) measurement of the frequency of oscillation and the decrement of a ``rocking-beam oscillator'' in which the restoring force is supplied by rubber (0.1 to 25 c.p.s.); (2) measurement of the frequency of resonance and the band width of a rubber reed which executes forced oscillation (10 to 500 c.p.s.); (3) measurement of the phase velocity and the attenuation of longitudinal waves in a thin rubber strip in the absence of standing waves (1 to 40 Kc); (4) measurement of the frequency of longitudinal-wave resonance and the band-width of a half-wave transmission line (below 300 c.p.s.); (5) measurement of the change in the frequency of resonance and the change in the band width of a magnetostrictive rod against whose end a rubber sample is pressed (12 to 120 Kc). Equations are developed for calculating the complex modulus from the results of each experiment, and the practical advantages and limitations of the methods are described.
Nucleation
Authors: Fisher J. C. , Hollomon J. H. , Turnbull D.
Published: January 2005

Based on Turnbull's concept of the importance of transient nucleation during phase transformations in solids, a general theory of nucleation has been developed. The nucleation mechanism for reactions where stable nuclei appear only during cooling or plastic deformation has been clarified. The general theory makes possible quantitative description of the rates of nucleation of all phase transformations as well as of fracture cracks, slip bands, and magnetic transformations in solids.
An Analytical Discussion of the Construction of Pole Figures
Authors: Wood John K.
Published: January 2005

The construction of pole figures of crystal orientation data obtained by means of x-rays can be made quickly and accurately if the angular relationships between planes or ``poles'' are known and if all of the data from a diffraction pattern are used. A flexible set of equations is derived from which these relationships can be found starting with customary crystallographic information. Data for an hypothetical case of diffraction are computed to illustrate the method. Although the examples refer, for the most part, to cubic crystals, the method can be extended to cover other types.
An Electron Microscope Study of Gold Smoke Deposits
Authors: Harris Louis , Jeffries David , Siegel Benjamin M.
Published: January 2005

Gold smoke deposits have been examined at high resolution with the electron microscope, and the size and distribution of the unit particles determined. The smokes were produced by evaporating gold from a hot tungsten filament in a partial atmosphere of nitrogen, and the samples were collected on thin collodion films. It was found that the size of the unit colloidal gold particles varied with the pressure of the atmosphere and the rate of evaporation. The manner of aggregation of the particles was found to be independent of the nitrogen atmosphere pressure and rate of evaporation over a relatively wide range. The aggregations, however, changed markedly when a small amount of oxygen was present during the evaporation. Measurements in the visible and infra-red regions of the spectrum were correlated with the electron microscope investigations, and it was found that the optical properties of the deposits depend strikingly upon the manner in which the smoke particles aggregate and how the aggregates are distributed.
Surface Currents on a Conducting Sphere Excited by a Dipole
Authors: Papas C. H. , King Ronold
Published: January 2005

This paper treats the problem of determining the current distribution on the surface of a perfectly conducting sphere when driven by a dipole antenna erected on its surface. Curves of the real and imaginary parts of the surface currents are given for the case of a half-wave dipole and various radii of the sphere.
Spurious Signals Caused by Noise in Triggered Circuits
Authors: Middleton David
Published: January 2005

The expected number of peaks/sec. (nσ+N), caused by noise or by a signal and noise, in excess of a given amplitude, or triggering level, is determined for broad-band noise (a) and for the envelope of a narrow-band disturbance (b). The signals considered here are pulses of various shapes (rectangular, triangular, trapezoidal), or a carrier modulated by these pulses. The expected number of peaks per second is directly proportional to the band width of the noise, and depends in some degree (20–30 percent) on filter shape, the gaussian response yielding a larger value of nσ+N than the rectangular, for the same total input power. Further, nσ+N is greatest when the triggering level is the most probable amplitude. Pulse shape is not significant when the pulses are on only a small fraction of the total period of observation, but becomes so if (1) the time of observation is comparable to the pulse length, and (2) the pulses have sharp leading edges. The latter gives rise to a transient effect which is not ignorable. This transient contribution does not appear in the envelope of narrow-band waves, as long as the maximum time-rate of change of the wave form of the envelope is much less than the central or resonant frequency of the IF, i.e., as long as the concept of ``envelope'' is meaningful. Rectification does not change nσ+N, provided that there is no appreciable distortion of the envelope by video- or audio-filters and that the triggering level of the input is passed by the detector.

Improvement, defined in ways appropriate to the systems in question, of one circuit which can tolerate A1 spurious signals/sec. in excess of a given triggering level over another circuit, which can tolerate only A2 such signals (A1>A2), is calculated for broad-band signal and noise, and for narrow-band waves following half-wave linear or quadratic rectification. In general, the improvement is slight (a few db) if the trigger levels of the two circuits are not close to the most probable value of the amplitude and if the ratio of the number of spurious signals allowed/sec. to the band width of the disturbance is small. Significant improvement follows only when the maximum tolerable number of triggering peaks/sec. is the same order of magnitude as the band width of the noise. Tables and figures illustrating the above are included in Part I; the mathematical derivations are contained in Part II.
Frequency Stabilization of Microwave Oscillators by Spectrum Lines. II
Authors: De Quevedo José L. García , Smith William V.
Published: January 2005

The design of both narrow band high stabilization and broad band lower stabilization spectrum line discriminators is developed in a generalized form applicable to various spectrum lines and cavity designs. Comparison with experiment is made for two broad band discriminators utilizing the NH3 3,3-absorption line at 23,870 megacycles as the frequency determining element. These discriminators used with an amplifier of 2000 gain, reduce drifts by factors of 250 and 1000, respectively, compared to an unstabilized tube.
On the Calculation of Radiation Patterns of Dielectric Rods
Authors: Watson R. B. , Horton C. W.
Published: January 2005

A previous paper described the radiation field of a dielectric rod used as a termination for a wave guide. The theory therein made use of a standing wave distribution of equivalent currents over the surface of the rod to describe its radiation effect. It is shown in this paper that the equivalent currents may be expressed in terms of traveling waves without appreciably changing the computed radiation patterns.
Heat Transfer from a Rotating Disk to Ambient Air
Authors: Wagner Carl
Published: January 2005

The coefficient of heat transfer from a rotating disk to ambient air in case of a laminar boundary layer is theoretically calculated on the basis of von Kármán's calculation of flow conditions.
An Interferometric Method for the Calibration of Electron Microscope Magnification
Authors: Farrant J. L. , Hodge A. J.
Published: January 2005

Interferometric methods have been used to measure uniform cylindrical silica and glass fibers as small as 5μ in diameter with better than 1 percent accuracy. Such fibers yield sharp images when examined in the electron microscope and constitute a convenient and rugged specimen for accurate direct calibration of the instrument for magnifications up to 10,000 diameters. Higher magnification ranges are then readily determined by means of an internal calibration obtained by taking micrographs of glass spheres about 0.5 micron in diameter. Such spheres are also convenient specimens for determining the image distortions which must be known to correct the widths of the fiber images. This method appears to be capable of greater accuracy than any employed hitherto.
Electronic Radiography and Microradiography
Authors: Trillat Jean-Jacques
Published: January 2005

Two techniques of radiography by means of secondary photoelectrons liberated by hard x-rays (180 kv), one by reflection and one by transmission, are described. Special fine-grained photographic emulsions of the Lippmann type are required which will not be affected by x-rays traversing the film, but are sensitive to photoelectrons liberated from the surface of a specimen in intimate contact with the photographic film or paper. In this way photographic negatives may be reproduced (from the silver of the image), microradiographs prepared by enlargement of any area of the radiograph, surface topography studied, ores analyzed, etc. For electronic radiography by transmission, instead of the specimen being its own electron generator, a thin metal foil (usually lead) pressed against the specimen generates the electrons which then traverse the thin specimens, and register on the photographic film or paper. Applications are papers, insect wings, varnish or rubber films, plant leaves, tissue sections, plastics, and alloys.
A Temperature-Controlled Frevel Focusing X-Ray Powder Camera
Authors: Vand V.
Published: January 2005

A focusing x-ray powder camera of Frevel type is described, suitable for the study of large cells of organic crystals. It uses a convergent x-ray beam collimated by a multiple slit system and records transmitted reflections only.
The Absorption of Incident Quanta by Atoms as Defined by the Mass Photoelectric Absorption Coefficient and the Mass Scattering Coefficient
Authors: Victoreen John A.
Published: January 2005

Evidence presented indicates that the absorption of quanta as defined by the mass photoelectric absorption coefficient τ/ρ and the mass scattering coefficient σ/ρ of any element may be represented by a simple expression.

Tabulated values of the calculated mass absorption coefficients μ/ρ are given for wave-lengths from 0.01 to 40 angstroms for hydrogen and carbon and from 0.01 to λK and λK to λL for aluminum, copper, tin, and lead. Graphs are given showing agreement with observed values.
A Solution of the Problem of Rapid Scanning for Radar Antennae
Authors: Rinehart R. F.
Published: January 2005

The problem of devising a rapid scanning focusing antenna based on wave-guide principles has been solved only approximately and not too satisfactorily. In the present paper, a known property of a plane optical system with variable index of refraction is shown to satisfy the requirements of such an antenna system. By a suitable transformation, the plane variable refractive index system can be transformed into a surface of revolution of constant refractive index which reproduces the optical properties of the plane system. This surface provides an apparently practicable solution to the scanning problem. It is shown that the diameter of the feed circle can be made arbitrarily small by judicious use of an ellipsoidal reflector.
The Determination of Stresses in Plastic Regions in Problems of Plane Flow
Authors: Symonds P. S.
Published: January 2005

A simple numerical-graphical method for the calculation of stresses in plastic zones adjacent to boundaries of arbitrary shape is outlined, applicable to problems of plane plastic flow in ideally plastic materials. For illustration, the method is applied to determine the stresses in plastic zones near elliptic free boundaries. The yield load of a tensile bar containing elliptic notches is obtained for a series of notches of varying sharpness. Some related problems are discussed briefly.
Heat Transfer in Sweat-Cooled Porous Metals
Authors: Weinbaum Sidney , Wheeler H. L.
Published: January 2005

Heat transfer inside sweat-cooled metals is analyzed and formulas showing the temperature distributions along the length of a sweat-cooled bar and across a sweat-cooled hollow cylinder are derived.
Stress-Strain Rate Relations for Anisotropic Plastic Flow
Authors: Dorn John E.
Published: January 2005

A simple theory for stress-strain rate analyses during plastic flow of anisotropic sheet metals is proposed for the work hardening range. The effect of orientation on the yield strength in simple tension and biaxial tension was discussed for various types of symmetry. The theory appears to be approximately correct for mild steel plates that exhibit planar isotropy.
The Structure of Extremely Thin Layers Evaporated in Kinetic Vacuum Systems
Authors: Stahl H. A.
Published: January 2005

In a commercial electron diffraction camera some alkaline earth metals (from Be to Sr) or Al, Ni, or Mo were evaporated onto outgassed metal sheets or glass slides, using the starting pressure of 0.1μ of mercury. The diffraction patterns of the thinnest layers (to about 103A) presented, regardless of the evaporation speed used, the pattern of the oxide of the evaporated metal exclusively. The diffraction pattern of the metal space lattice itself was growingly observed with Be, Al, Ni, and Mo only after uninterrupted evaporation until layer thicknesses of about 1μ were reached. When Mg, Ca, and Sr were evaporated, no patterns without, at least, the most intensive oxide rings could be attained under the vacuum conditions given in the apparatus.

The results are in accord with some earlier findings of Langmuir, Beeching, Darbyshire, and Beischer, and clear up some hitherto not fully explained effects with stepwise evaporated layers. The appearance of oxide patterns is always accompanied by strong improvements of the vacuum in the evaporation compartment by the arising metal vapors, i.e., by the well-known gettering effect.
The Theoretical Resolution Limit of the Electron Microscope
Authors: Scherzer O.
Published: January 2005

The resolving power of the electron microscope and the contrast in the image are calculated for different conditions of focusing, illumination and aperture. These conditions can change the limit of resolution by a factor of about 3. The contrast in the image of an atom is appreciably increased by defocusing and spherical aberration. Nevertheless, the contrast improves when the numerical value of the aberration constant is diminished. The effect of different methods of spherical correction is discussed briefly.
The Internal Friction of Zinc Single Crystals
Authors: Wert Charles A.
Published: January 2005

This paper presents typical data on the internal friction of twelve single crystals of zinc oscillating longitudinally. The measurements of decrement were made at frequencies of 41 kc and 57 kc. (a) Zinc of three grades of purity was used. The behavior of decrement as a function of stress amplitude for these different materials was found to depend less on the purity of the metal than has been reported previously (see references 1 and 2). (b) For one crystal the decrement showed little rise from its initial value of 2×10−5 at very low stress amplitudes up to stress amplitudes nearly three times the static elastic limit. Considerable similarity of behavior of the decrement as a function of stress amplitude resolved into the basal plane has been found for a number of crystals with a wide range of orientation. The obtaining of these consistent results depended on the use of appropriate annealing and etching techniques. (c) The decrement of a well annealed crystal increased with rising temperature at all stress amplitudes throughout the temperature range −75°C to 150°C. (d) The prior application of static stress far below the static elastic limit has been found to increase the decrement at high stress amplitudes without affecting that at very low stress amplitudes. This increase was a function of the stress amplitude at which the decrement was measured, and of the prior static stress, L. The observations fitted a relation of the form logΔ=C1+C2L, where C1 depended on the amplitude of measurement and C2 was approximately constant.
The Demodulation of an F-M Carrier and Random Noise by a Limiter and Discriminator
Authors: Blachman Nelson M.
Published: January 2005

Certain mathematical representations of a limiter and discriminator are postulated. On this basis, and on the basis of the statistics of narrow-band random noise, the output signal voltage and r.m.s. noise output voltage are calculated for a limiter and discriminator fed by an f-m carrier and narrow-band random noise. The output signal-to-noise ratio can thus be expressed as a function of the input signal-to-noise ratio. The former is plotted versus the latter in Fig. 5, for several different degrees of limiting. A sharp increase in the output signal-to-noise ratio from far below the input signal-to-noise ratio to only 0.9 db below it is found to occur as the latter increases through the range 0 db to 6 db. For the sake of comparison, Fig. 5 also shows the corresponding curve for square law detection of an a-m carrier, as well as that for f-m without a limiter. It is to be emphasized that these results pertain to the unfiltered discriminator output; consideration of filtering, which is generally present in a receiver to a considerable extent, requires a determination of the spectral distribution of the discriminator output noise.
Determination of the Elastic Constants of Solids by Ultrasonic Methods
Authors: Schneider William C. , Burton Charles J.
Published: January 2005

The application of ultrasonic methods to the determination of the elastic constants of solids is considered in some detail. It is shown that a rotating plate technique in which ultrasonic transmission is plotted as a function of the angle of incidence of the waves allows determination of the velocities of dilatation and shear waves in the plate. From these data, Poisson's ratio and the mechanical moduli may be determined. Details of an apparatus for making such measurements are given. The elastic constants of several metals have been measured with this equipment and the values obtained are shown to be in agreement with previous published data. In addition, measurements of a number of thermoplastic and thermosetting resins have been made successfully. It has been found that in the case of Melmac Resin 26–8B there is no variation in the elastic constants as a function of cure time.
The Effect of Current Magnitude upon the Behavior of a Superconducting Bolometer in Its Transition Region
Authors: Fuson Nelson
Published: January 2005

A simple theoretical analysis of the superconducting bolometer in transition is shown to be useful in predicting phenomena such as the shape of the transition curve and the dependence of the bolometer time constant upon the current magnitude. The analysis holds for bolometer currents smaller than a critical value which is equal to the square root of the ratio of the bolometer cooling constant to the bolometer dR/dT. For bolometers constructed in this laboratory this critical current value falls between 15 and 30 ma.

Qualitative extension of the theory to the case of large bolometer currents is made by considering the presence of regions at different temperatures within the bolometer and by summarizing the possible effects of the magnetic field due to the bolometer current upon the transition. Experimentally obtained transition curves are given for both small and large bolometer currents.
The Effect of Uplift and Denudation on Underground Temperatures
Authors: Benfield A. E.
Published: January 2005

This paper gives calculations and computations, based on simple ideal conditions, of the possible disturbances of underground temperatures caused by uplift and denudation. The effects of the speed of denudation, the rate of uplift, and the time during which these two processes may have been operating, are illustrated by numerical tables applying to some specific ideal situations. The resulting disturbance of the heat flow in the earth (which is evaluated by making use of underground temperature gradients) is discussed. It is shown that uplift and denudation increase the heat flow above its equilibrium value, but that no very large increase is likely to occur unless the equilibrium heat flow is small and the speed of denudation is large.
An Experimental Investigation of Formulas for the Prediction of Horn Radiator Patterns
Authors: Woonton G. A. , Hay D. R. , Vogan E. L.
Published: January 2005

The E-plane radiation pattern has been measured at short distances and both E and H-plane patterns at relatively great distances from the mouths of several electromagnetic horns. Measured values are compared with values calculated by the Kirchhoff formula and in addition the distant patterns are compared with values calculated by the corrected formula due to Stratton and Chu.

For the range of horn length and aperture considered, the Kirchhoff formula gives satisfactory agreement in the E-plane for angles as great as twenty degrees and at distances as short as one foot from the mouth of the horn; the H-plane predictions are not as satisfactory.
The Incremental Friction Coefficient—a Non-Hydrodynamic Component of Boundary Lubrication
Authors: Burwell J. T. , Strang C. D.
Published: January 2005

In investigations of lubricated sliding friction between two crossed cylinders it is found that for hard, smooth surfaces the friction force is a straight-line function of the applied load, although this line does not generally pass through the origin. The slope of this line defines a friction coefficient, designated as the incremental friction fΔ, which is thought to have certain advantages in the study of non-fluid lubricated friction. It is obviously independent of the load. It is found to be independent of viscous fluid effects and hence permits investigation of non-fluid friction at reasonable speeds. In spite of being devoid of any viscous component, it is found in a great many cases to decrease with increasing speed, U, over at least part of the range, and this variation often appears to be a linear function of the logarithm of the speed. The curve of fΔ vs. ln U seems to be characteristic of the chemical structure of the lubricant and of the rubbing surfaces. It is not contended that viscous effects are absent under the conditions of these experiments but simply that the value of fΔ, which is not the total friction coefficient, does not, because of its method of determination, include such effects.
The Thermal Behavior of Evaporated Layers in Vacuum Devices
Authors: Stahl H. A.
Published: January 2005

Some layers presenting the space lattice pattern of the metal (Be, Mg, Al, Mo, or Ni) were heated for constant periods. Beginning with a distinctly marked threshold temperature, the interference rings of the oxide space lattice appeared while, simultaneously, the metal space lattice pattern diminished, entirely disappearing with another higher lying temperature. The oxidation temperature ranges (for ten-minute heating periods) of Be, Mg, and Al were measured. With glucinum it is equal to that within which, Kollath stated, there was a strong increase of the emissivity of beryllium secondary emission cells.

An elementary calculation gives an inferior time limit to oxidation of the observable surface layer. The surface layer of polished metals is considered; the high secondary emissivity in the case of glucinum, together with the usually supposed Beilby layer giving only two broad diffuse diffraction rings, points to the existence of a random liquid-like network of BeO molecules on the surface of polished beryllium secondary emission cells.