bluuebunny/crossref_metadata_2025 huggingface dataset:
Theory of Radar Reflection from Wires or Thin Metallic Strips
Authors: Van Vleck J. H. , Bloch F. , Hamermesh M.
Published: January 2005

Knowledge of the radar response of wires or thin metallic strips, as a function of their length and thickness, and of the radar frequency is important in the design of reflectors for radar. In view of the difficulty of this theoretical problem and the necessity of making approximations, as well as the dearth of adequate experimental data, two independent procedures for solution are presented. Detailed quantitative results are obtained for the angular dependence of the cross section, and also for the mean cross section, of randomly-oriented wires or, more generally, of metallic strips, which behave electromagnetically like cylindrical wires of a certain ``equivalent radius.'' When expressed in terms of a unit of area equal to the square of the wave-length, these cross sections depend on the dimensions of the wire only through the two ratios 2la=length of wireequivalent radius of wire, 2lλ=length of wirewave−length.>The mean cross section is shown to take on maximum values when 4l/λ is slightly less than an integer (n = 1, 2, etc.). The shift of these ``resonances'' from integral values depends on the ratio 2l/a, becoming greater as 2l/a decreases. The value of σ̄/λ2 at resonance increases slowly with the order n of the resonance; it depends only very slightly on the ratio 2l/a, increasing as 2l/a decreases. For values of 4l/λ away from resonance, σ̄/λ2 decreases rapidly, reaching minimum values near 4l/λ = 3/2, 5/2, etc. The value of σ̄/λ2 at these minima is strongly dependent on 2l/a, increasing as 2l/a decreases. Also as 4l/λ increases, the heights of the minima increase and approach the height of the resonance peaks. A brief comparison with preliminary experimental results is given.
Excess Noise in Cavity Magnetrons
Authors: Sproull Robert L.
Published: January 2005

The magnetron oscillator of some frequency-modulation radars also furnishes the ``local oscillator'' excitation for the crystal mixer of the receiver. Excess noise generation by the magnetron was observed to reduce greatly the receiver sensitivity. This noise exhibited a strong dependence upon anode voltage and current, and changed with time in a perplexing manner. After many experiments, a hypothesis of the cause of excess noise was developed, and further experiments confirmed this hypothesis. The noise is thought to be caused by ionization of atoms of the cathode oxide coating, which atoms are removed from the cathode by electron bombardment. In order to reduce the generation of excess noise, and still preserve the advantages of an oxide-coated cathode, a special shape of cathode has been developed. The coated regions of this cathode are sheltered from electron bombardment, and the noise is much reduced. Use of cathodes of this general type should also produce magnetrons with longer operating lives than present tubes.
A Semi-Polar Form of Fourier Series and Its Use in Crystal Structure Analysis
Authors: Lukesh Joseph S.
Published: January 2005

A new form of Fourier series for crystal structure analysis is developed and a graphical method of summation described. The procedure is designed to permit simple and fairly rapid computation and recording of the density contributions of all planes at all points in the unit cell. Its particular advantage is in the case of centrosymmetrical projections where phases must be assigned experimentally. Adjustment of phases involves only re-addition of numbers rather than a complete new summation. The method also requires a minimum of equipment which is easily constructed at negligible expense.
Preparation and Uses of Silica Replicas in Electron Microscopy
Authors: Gerould Charles H.
Published: January 2005

A detailed description of the preparation of silica replicas and substrates and their many and varied uses is presented with photographs and electron micrographs. A method of preparing silica replicas of specimens which cannot be subjected to the temperatures and pressures of the ordinary technique is described. It consists of applying a polystyrene lacquer to the specimen surface in place of the conventional molding. The question of ``up and down'' in stereo pictures of silica replicas is definitely settled by adding a metal oxide smoke (MgO) to the polystyrene replica before the silica evaporation. A successful powder dispersing technique consists of dispersing the powder in an ethyl cellulose lacquer and depositing upon a silica substrate. Several other techniques are also included.
A Flux Plotting Method for Obtaining Fields Satisfying Maxwell's Equations, with Applications to the Magnetron
Authors: Crout Prescott D.
Published: January 2005

In this report the flux plotting methods which have previously been applied to fields satisfying Laplace's and Poisson's equations are extended to fields satisfying Maxwell's equations. Application is made to the hole and slot, and vane types of magnetron tubes.
A Magnetron Oscillator for Dielectric Heating
Authors: Nelson R. B.
Published: January 2005

Magnetron oscillators can provide very high frequency power for dielectric heating. Factors determining the choice of frequency for particular jobs are discussed. The design of a magnetron having 5 kw continuous output at 1050 megacycles is described, and performance data on the tube are given.
An Approximate Solution of the Differential Equation of the Ultracentrifuge
Authors: Archibald W. J.
Published: January 2005

In determining molecular weights with the ultracentrifuge by the equilibrium method, it is necessary to drive the rotor at relatively high speeds for very long periods of time. It would be a real advantage to be able to deduce molecular weights from the distribution of concentration within a cell placed in a rotor without waiting for equilibrium. The solution of a certain differential equation gives the theoretical distribution within the cell at any time, and a comparison of the experimentally determined concentrations with those deduced from theory should yield molecular weights without waiting for equilibrium. The exact solution of this differential equation is known, but it is not suitable for numerical work. The present paper presents an approximate solution from which numerical results can be obtained with ease.
The Motion of a Conical Coil Spring
Authors: Epstein I.
Published: January 2005

The elongations and natural frequencies of conically-shaped coil springs are derived theoretically for several dynamic boundary conditions. Frequencies are verified experimentally on nickel and piano wire springs, attesting the reliability of the computations.
An Introduction to the Mathematical Theory of Plasticity
Authors: Prager W.
Published: January 2005

The paper aims at introducing the reader to the principal theories of plasticity. Since a presentation of the general stress-strain relations used in these theories would require too much space, the discussion is restricted to the mechanical behavior of plastic materials under shear. Theories of plastic deformation (Hencky, Nadai) and theories of plastic flow (Saint Venant-Lévy-Mises, Prandtl-Reuss, Prager) are illustrated by the example of a prismatic bar under torsion.
On the Theory of Noise in Radio Receivers with Square Law Detectors
Authors: Kac Mark , Siegert A. J. F.
Published: January 2005

For the video output V of a receiver, consisting of an i-f stage, a quadratic detector, and a video amplifier, the probability density P(V) has been obtained for noise alone and for noise and signal. The results are expressed in terms of eigenvalues and eigenfunctions of the integral equation ∫ 0∞K(t)ρ(s−t)f(t)dt=λf(s),where ρ(τ) is the i-f correlation function (i.e., the Fourier transform of the i-f power spectrum) and K(t) is the response function of the video amplifier (i.e., the Fourier transform of the video amplitude spectrum). Two special cases are discussed in which the integral equation can be solved explicitly. Approximations for general amplifiers are given in the limiting cases of wide and narrow videos. Some applications of the method to other problems are shown in Sections 7B and 9.
Heating and Cooling of Bolometer Elements
Authors: Shive J. N.
Published: January 2005

The analogy between thermal and electrical networks is used to obtain solutions to problems relating to the heating and cooling of air-backed and solid-backed bolometer elements exposed to radiation of periodically fluctuating intensity. From the equations derived, thermal response-frequency characteristics are computed for ``typical'' bolometer elements. Features of these characteristics are discussed, and the physical influences of the various thermal properties of the bolometer material and of the backing material are pointed out.
A Note on a Paper by Faust and Beck
Authors: Stone William M.
Published: January 2005

An infinite sum transformation is defined and applied to a system of linear difference equations discussed by Faust and Beck in their paper on single tuned amplifiers. Some transforms of the more common functions are given and points of superiority of the transform method over the classical methods of solution of difference equations are emphasized.
Internal Friction of Zinc Single Crystals
Authors: Swift Irvin H. , Richardson John E.
Published: January 2005

Measurements were made of the internal friction of single crystal rods when vibrating longitudinally at 45 kilocycles per second. The decrement, or ratio of energy dissipated per cycle to twice the total vibrational energy, was used as a measure of the internal friction. At strain amplitudes below about 10−5 or 10−6 the decrement was independent of strain amplitude. The value of the constant decrement at low amplitudes, and the changes which occurred as the amplitude was increased, were both greatly dependent on the history of the specimen. The constant decrement for different crystals ranged from 7×10−5 to values higher than could be measured (about 200×10−5). For some of the initially high-decrement crystals, values decreased with time (room temperature anneal). In general, for annealed crystals the decrement, measured as a function of increasing strain amplitude, remained almost constant up to and beyond the static elastic limit and then rose rapidly. It returned to the initial value when the strain amplitude was again reduced. On a second run, however, the rise in decrement occurred at much lower amplitude than on the initial one. It is concluded that the decrement is the result of two separate processes. The changing decrement at higher strain amplitudes is qualitatively explained with the use of dislocation theory.
Measurements of the Refractive Index of Films
Authors: Billmeyer Fred W.
Published: January 2005

The refractive index of a film of transparent or translucent material may be determined by immersing the film in a suitable liquid mixture and observing the intensity of light reflected from the surface of the specimen. The composition of the immersion liquid is varied, and a record is made of its refractive index (measured on a refractometer) and of the reflected light intensity. The refractive index of the film is the same as that of the immersion liquid giving the lowest reflected intensity. This has been confirmed by experiments with a glass plate, whose refractive index was known. According to Fresnel's laws of reflection, the experimental data should fit a parabola with its minimum at the refractive index of the film. On fitting the data by the method of least squares, the minimum is obtained with a standard deviation of the order of 0.002 refractive index units. The method has been applied to several plastic materials.
A Sound Velocity Method for Determination of Molecular Weight of Liquid Polymers
Authors: Weissler Alfred , Fitzgerald James W. , Resnick Irving
Published: January 2005

A new method is presented for determining number average molecular weights of liquid polymers, by means of easily performed measurements. The molecular weight is an explicit function M=Bdv13−A(n2−1n2+2)of the sound velocity v, density d, refractive index n, and the two empirical constants A and B. Accuracy of about 2 parts per hundred was attained for the lower polyethylene glycols. The method seems suitable for molecular weights up to several thousand. Sound velocities were measured by an acoustic interferometer, at one megacycle frequency.
An Instrument for Measuring Particle Diameters and Constructing Histograms from Electron Micrographs
Authors: Hanson E. E. , Daniel J. H.
Published: January 2005

An instrument for shortening the time and labor required in constructing particle size histograms from electron micrographs is described. Representative histograms obtained with the instrument for GR-S latices are shown. Linear, surface, and volume-equivalent diameters of non-spherical particles are defined, and variations in the instrument for plotting such diameters are proposed.
Elastic Losses in Some High Polymers as a Function of Frequency and Temperature
Authors: Sack H. S. , Motz J. , Raub H. L. , Work R. N.
Published: January 2005

The frequency and temperature dependence of the elastic losses of polyvinyl chlorides (0° to 80°C, 60 to 1400 c.p.s.) and of natural rubber and butadiene-styrene copolymers (GRS) of different relative concentration (−50° to 35°C, 20 to 3500 c.p.s.) was studied by 3 methods, in which the motion of a reed in free or forced vibration is observed. Natural rubber at temperatures above 20°C, and polyvinyl chloride exhibit frequency independent losses, the mechanism of which is not yet clear. The results for rubber below 20° and for GRS can be explained by a relaxation theory. The behavior of the elastic losses also reflects the existence of a second-order transition, below which rotation of chain segments is hampered.
Elastic Properties of Cork: II. Stress-Temperature Relationship of Compressed Cork
Authors: Dart S. L. , Guth Eugene
Published: January 2005

In the first paper of this series it was shown that for cork, held at constant compression, the stress as a function of compression, temperature, and time was separable into two factors, one factor representing the load-compression curve and the other describing the decay of stress with time. In the present paper the dependence of the load-compression curve upon temperature is studied. After the sample has relaxed at constant temperature and compression for a time sufficiently long so that the change of stress with time may be neglected, stress-temperature curves were obtained. These curves showed a linear dependence of the stress upon the temperature. From the stress-temperature curves the resolution of the stress into its additive components due to internal energy and entropy was carried out. The physical significance of this resolution is discussed. The experiments were carried out with a refined version of the apparatus described in the first paper. In particular, the apparatus was corrected for rate of thermal expansion.
Elastic Properties of Cork: III. Hydrostatic and Ordinary Load-Compression Curves for Cork
Authors: Dart S. L. , Robinson Howard A. , Guth Eugene
Published: January 2005

Load-compression curves were taken for natural cork. The S-shape of the curves is discussed and a theoretical fit is made for the high end of the curve, assuming an initial stiffness and an incompressible part of the cork material. A comparison is made between repeated compressions, with and without a recovery period of time.

Pressure-volume curves were also taken and their significance discussed in connection with the load-compression curves leading to an evaluation of Poisson's ratio.
A Cold Cathode Rectifier
Authors: Bennett Willard H.
Published: January 2005

A cold cathode rectifier is described in which corona discharge is used at atmospheric and higher pressures in hydrogen and nitrogen free of electron-attaching impurities. This kind of tube has advantages where the current demands upon a rectifier are small.
The Hydrodynamic Lubrication of Finite Sliders
Authors: Boegli Charles P.
Published: January 2005

Two approximations are made in the solution of Reynolds' lubrication equation for the case of a finite slider. These approximations lead to a series of equations that are easy and rapid to use for flat sliders, and which are also applicable to curved sliders. Examples of their use are presented, and a number of calculations are made to determine the range of slider proportions to which they may be applied with sufficient accuracy. The method is of special value for wide sliders which are difficult or impossible to analyze by other methods.
Crystal Pattern Synthesis by an Approximate Summation of Fourier Series
Authors: Lukesh Joseph S.
Published: January 2005

A faithful representation of the locations of the peaks of electron density maps can be obtained rapidly by determining for each point in the projected unit cell the algebraic sum of the amplitudes of those reflections which are contributing either a maximum or a minimum at each point. Since maxima and minima do not, in general, fall at the specific points of the grid, an approximation must be introduced. Using the semi-polar form of Fourier series, the approximate summation can be accomplished with the use of one hundred and fifty strips. The method was tested by determining the peak locations in the structure of diopside projected on 001. Potential applications of the approximate summation include rapid checking of the validity of assumed crystal structures.
Single Crystal Electron Diffraction by Micro-Crystalline Materials
Authors: Davidson Norman , Hillier James
Published: January 2005

It is shown that the double lens probe-type electron diffraction camera described earlier is capable of producing useful electron diffraction patterns of single microscopic crystals in the size range 200–2000A; the formation of an opaque carbonaceous deposit, which occurs when an electron probe is focused on a specimen, is prevented in the diffraction camera by previously exposing the specimen chamber to an electron spray. A number of examples of two-dimensional grating patterns and Kikuchi-line patterns obtained from such crystals are shown. From either type of pattern it is possible to obtain accurate values for some of the lattice spacings, while from the Kikuchi-line patterns it is possible to deduce accurately the orientation of the crystals relative to the electron beam. The results are shown to agree reasonably well with the predictions of the dynamical theory as presented by MacGillavry. It is concluded that a two-dimensional grating pattern is to be expected from a crystal oriented with an important lattice vector approximately parallel to the electron beam independent of slight disorders or warping of the crystal. Kikuchi-line patterns are to be expected for most other crystals which are not excessively thick or disordered. The theory also shows that both types of patterns may be obtained simultaneously.
Microsecond Measurement of the Phosphorescence of X-Ray Fluorescent Screens
Authors: Marshall Fitz-Hugh
Published: January 2005

Microsecond square-wave x-ray pulses, repeated a thousand times a second, were obtained by operating an x-ray tube directly from a radar pulser. The phosphorescent build-up and decay of light emitted by fluorescent materials when irradiated by the x-ray pulses was observed with a multiplier phototube connected to an oscilloscope. Oscillograms of CaWO4 (radiographic intensifying screen) and BaSO4 indicate simple exponential response, with decay to 1/eth intensity in 6 and 0.8 microseconds, respectively. MgWO4 and Patterson B (fluoroscopic) and D (photofluorographic) screens were found to complete their main response to microsecond excitation in 10 to 100 microseconds, but their decay is not exponential.
X-Ray Diffraction Studies of Chrome-Steel Slags
Authors: Chatterjee G. P. , Sidhu S. S.
Published: January 2005

X-ray diffraction studies of the crystalline constituents in the acid open hearth chrome-steel samples showed that chromium exists in these samples as a chrome-iron spinel of the form, FeO·Cr2O3. Its density was 5.109 g/cc and its melting 2160°C. It crystallized in the face-centered cubic structure with a0=8.348A and Z=8.
Spherical Aberration of Compound Magnetic Lenses
Authors: Marton L. , Bol K.
Published: January 2005

A reduction of the spherical aberration of strong electron lenses can be achieved by a strong lens as a virtual image former and by a transformation of the image in a real one by means of one or more weak lenses. Calculations are carried out for bell-shaped magnetic fields of the axial field distribution H(z)=H01+(z/a)2,and numerical values of the achieved reduction of the aberration are given for different lens strength, magnification, and image distance of the compound system.
Physical Properties of Calcium Tungstate X-Ray Screens
Authors: Coltman J. W. , Ebbighausen E. G. , Altar W.
Published: January 2005

The absolute energy of the light from a fluorescent calcium tungstate x-ray screen, its spectral distribution, and the efficiency of conversion from x-rays to light have been determined. The absolute energy and its spectral distribution were obtained spectrographically by comparison with a standard tungsten filament lamp. Equations are given for determining the distribution of light in the diffusing screen material, and calculation of the light losses are made for varying screen thickness and x-ray absorption. The data for energy distribution of the ingoing x-rays were taken from measurements obtained in this laboratory by a new method to be published elsewhere. Allowance for scattering and secondary x-radiation was made and a conversion efficiency of 5.0 percent was obtained for this calcium tungstate phosphor.
Pressure and Oil Flow in Oil-filled Cables at Load Variations
Authors: Knudsen Hans Lottrup
Published: January 2005

This paper presents a method for calculating pressure and oil flow in a section of an oil-filled cable at load variations with due regard to both the hydraulic resistance of the oil canals and the elasticity of the sheath and the pressure armor, if any, and the compressibility of the oil. The present article restricts itself to cable sections terminated with oil reservoirs in which the pressure is constant; in a forthcoming paper this restriction will be dropped. Formulas are given for pressure, oil current, and amount of oil which flows through a cross section of the cable for an arbitrarily prescribed oil expansion per unit length. These formulas are applied to the following oil expansion functions: S0·1, d/dt(N0·1), e−t/T·1, and 1/√t·1, which represent the oil expansion or terms occurring in the series giving the oil expansion in some important cases. Generalized functions are plotted for the pressure at the midpoint, the oil current at the endpoints, and the amount of oil which passes the endpoints for the above mentioned oil expansion functions. Using these generalized functions, the calculation of pressure and oil flow, with the simplifying assumptions made here, is reduced to elementary operations. Numerical examples illustrate the use of the given formulas and curves.
The Elastic Constants of Materials Loaded with Non-Rigid Fillers
Authors: Dewey Jane M.
Published: January 2005

General expressions are given for the modulus of rigidity, λ̄2, and compressibility, k̄, of a medium of Lame's constants, λ1 and λ2, loaded with a volume fraction, φ, of a filler of constants λ1′ and λ2′. To terms in the first power of φ λ̄2=λ̄2(1+15(λ2′−λ2)(λ1−2λ2)2λ2′(3λ1+8λ2)+λ2(9λ1+14λ2)φ)k̄=k+3+4λ2k′3+4λ2k(k′−k)φ.If the ``filler'' is a gas at a pressure, p, in a nearly incompressible medium, these give Young's modulusĒ=E(1−E9p+4Eφ).Modulus of rigidityλ̄2=λ2(1−53φ).Compressibilityk̄=k+33p+4λ2φ.Poisson's ratioσ̄=σ(1−3E9p+4Eφ),where φ is the volume loading, p is the pressure within the spherical cavities in the deformed state. Barred symbols refer to the properties of the loaded material; unbarred, to the medium alone. Expressions for the displacements and stresses within the medium and the particles, neglecting interactions between particles, are also given.
Heat Transfer between a Fluid and a Porous Solid Generating Heat
Authors: Brinkley Stuart R.
Published: January 2005

The theory, due to Anzelius, of the transfer of heat between a fluid flowing with constant velocity through a porous solid is extended to include the case where the solid generates heat. Expressions are obtained for the temperatures of solid and fluid as functions of position and time, it being assumed that the heat source function is a linear function of the temperature of the solid with coefficients independent of position and time. The application of the theory to a description of the temperature in catalytic reactions is indicated.
The Nucleation of Ice Formation by Silver Iodide
Authors: Vonnegut B.
Published: January 2005

Silver iodide particles have been found to serve as nuclei for the formation of ice crystals in super-cooled water and in water vapor super-saturated with respect to ice. It is believed that silver iodide serves as a very effective nucleus because it very closely resembles ice in crystal structure. Both dimensions of the unit cell of ice and silver iodide are the same to within approximately one percent. The maximum temperature at which the silver iodide particles serve as nuclei is approximately −4°C for particles one micron in diameter, and −8°C for particles 100 Angstrom units in diameter. A silver iodide smoke generator has been constructed which consumes 1 mg of silver iodide per second and produces 1013 effective nuclei per second.
Waves in Elastic Tubes: Velocity of the Pulse Wave in Large Arteries
Authors: King Allen L.
Published: January 2005

An equation for waves in elastic tubes is developed and applied to cylindrical tubes with Hookian and with elastomeric walls. The former application yields the Moens-Korteweg formula, which has been found inadequate. The latter application leads to a rather complicated equation for the pulse-wave velocity.

Values of pulse-wave velocities are computed for the thoracic aorta by means of the foregoing equation, and the results are compared with measured mean velocities for the entire aorta. Graphs and tables are given, so that a graphical analysis of this velocity equation can be applied to any large artery; and the method is illustrated by computing the pulse-wave velocity in the left common carotid. The relation l÷∫0lds/v, for the mean velocity over a tube of length l, is shown to be valid for the aorta and large arteries.
An Electronic Computer for X-Ray Crystal Structure Analyses
Authors: Pepinsky R.
Published: January 2005

An electronic synthesizer is described for determination of atomic positions in crystals. The synthesizer sums the two-dimensional Fourier series representing planar, centro-symmetric projections of electron densities in a crystal unit cell; and the projection is presented by a television scan on the screen of a cathode ray oscilloscope. The specific advantage of the device is the immediate observability of effects on the projection of alterations in signs of one or any number of Fourier coefficients.
Resonant Cavities for Dielectric Measurements
Authors: Works C. N.
Published: January 2005

Fixed and variable length re-entrant resonant cavities designed for the measurement of dielectric constant and dissipation factor are described. These cavities operate in the frequency decade of 108 to 109 cycles per second, a region avoided by many experimenters because the frequency is too high for the application of circuit techniques and not high enough for the convenient use of coaxial lines or wave guides. The theoretical considerations in the design of these cavities are presented. The well-known susceptance variation method, widely used in the frequency range of 104 to 108 cycles per second, was extended to apply to these cavities; it yields a rapid measuring technique and very simple expressions for calculating the values of the dielectric properties. The performance of this apparatus is discussed and the results of the measurements of a few typical dielectrics are given.
A Variable Capacitor for Measurements of Pressure and Mechanical Displacements; A Theoretical Analysis and Its Experimental Evaluation
Authors: Lilly John C. , Legallais Victor , Cherry Ruth
Published: January 2005

A variable capacitor is described for measuring (1) small displacements, (2) small volume changes, and (3) pressure differences. The capacitor consists of a deflectable diaphragm and a fixed electrode. The diaphragm is metallic, plane-parallel, clamped at the edges, and at ground potential; the electrode, at an a.c. potential, has a plane surface parallel to the undeflected plate across an air gap. For use in displacement measurements, the diaphragm's center is deflected by a point contact from a mechanical link to the observed system, or by a uniform pressure load from a fluid link to the system. The fluid link is used also when measuring volume changes and pressure differences. The plate deflection results in a change in the air gap, and thus generates a capacitance signal. This signal is measured by electrical methods.

A theoretical analysis of this variable capacitor is presented; sensitivity and alinearity factors for the three uses of the device are derived. The experimental performance shows reasonably satisfactory agreement with the derived theory. The displacement of the plate's center was measured with an interferometric method, using a yellow He line as a standard of reference; the applied pressure, with a liquid manometer; and the capacitance signal, with a standard capacitor substitution procedure. The gauge can be used so as to give quantitative electrical indications of displacement, volume change, or pressure difference; or can be used as a null indicator device in which an unknown pressure is balanced against a known one on opposite sides of the diaphragm. In order to achieve large volume an displacement sensitivities, small air gaps (5.10–4 cm) are employed. Details of a construction method to assure small values are presented.
Conductivity of Metallic Surfaces at Microwave Frequencies
Authors: Maxwell E.
Published: January 2005

Methods of measuring effective conductivities at microwave frequencies are described. These consist of either measuring the transmission loss in a long waveguide, or in measuring the Q's of resonant cavities. Both methods have been applied to measurements at 1.25 cm. Results for a number of metals are presented. Deviations from d.c. conductivity are thought to be due to surface roughness.
High Speed Compression Tests on Copper
Authors: Greenfield M. , Habib E. T.
Published: January 2005

Dynamic shortening of one-half inch long copper cylinders is achieved by striking them with a hardened steel projectile at high velocities. The average strain rate was about 1200 per second. Energy per unit volume absorbed by the copper is plotted against strain. A true stress-logarithmic strain curve is computed. This curve is compared with a similar curve derived from high speed tests on copper in tension.
TM
0,1 Mode in Circular Wave Guides with Two Coaxial Dielectrics
Authors: Frankel Sidney
Published: January 2005

Field components for a transverse magnetic wave in a wave guide with two coaxial dielectrics are computed. A typical example is given to show the calculation of guide dimensions to reduce phase velocity to a preassigned value.
Graphical Methods for Evaluating Fourier Integrals
Authors: Cunningham W. J.
Published: January 2005

The Fourier transform method of determining the response of a linear system to an arbitrary input signal often has its practical usefulness impaired because of difficulties in evaluating the necessary integrals. One possibility of overcoming these difficulties lies in the application of graphical methods to the transformations. Three such graphical procedures are described, all based upon fundamental properties of the transforms. Each method involves an analysis of the curves of the function to be transformed as a sum of curves of simpler functions whose transforms are known. The methods are useful in cases where the problem is too complicated for a simple analytic solution, or where part of the necessary data is available only in the form of a curve obtained, say, from experimental measurements of transmission characteristics or wave shapes. The accuracy of the methods is restricted only by that of the graphical plotting and curve fitting. If only approximate results are required, they may be obtained relatively quickly by these methods.
Two Calculating Machines for X-Ray Crystal Structure Analysis
Authors: Booth A. D.
Published: January 2005

The calculation of structure factors in x-ray structure analysis is one of the most laborious operations. Two mechanisms are described which have proved of great service in several analyses. The simpler of the devices is of general application and can be constructed with comparatively limited workshop facilities.
Infinite-Rejection Filters
Authors: Stone Albert M. , Lawson James L.
Published: January 2005

The characteristics of certain bridged-T filter structures have been investigated theoretically and an experimental confirmation of this theory at u.h.f. has been obtained. In theory it is possible to obtain infinite attenuation at a designated frequency, while retaining essentially the same band width as that for the uncompensated filter. A model has been constructed which has a band width of ½ Mc/sec. at 3000 Mc/sec. with an attenuation at center frequency of over 70 db. This is to be compared with the attenuation from a similar uncompensated filter of 20 db. Certain other known filter expressions have also been reduced to forms readily utilizable at these frequencies. Their utility for u.h.f. applications is discussed. The distortion produced in otherwise rectangular pulses of short duration has been investigated both theoretically and experimentally. Curves are presented which show the resultant wave form as a function of the tuning of the filter.
Theory of Automatic Control Systems
Authors: Melvin M. Avramy
Published: January 2005

The theory of robots or reproducing power-amplifying systems is considered. After a general terminological orientation the study in the first part is confined to simple robots, the theory of which is equivalent to that of non-linear springs with inertia and friction. The alacrity and fidelity of control are well exhibited by studying the behavior of a robot under constant tracking. Special emphasis is placed on the specification of conditions for optimum performance, i.e., minimum deviation or maximum fidelity after any given time. Curves are given for both proportional and on-off robots, from which the parameter values for optimum performance may be read.

In Part II the theory of proportional robots is analyzed in detail, especially from the point of view of conditions for optimum performance. Two subsequent papers will contain the theory for the on-off case and the general non-linear robot case. The paper is organized as follows:

Part I. Descriptive account

A. Terminology and kinematic description

B. Dynamical equation of robots with usual load

C. Optimum performance curves. Practical examples

Part II. Theory of simple robots with proportional control

A. Complete solutions as functions of time. Optimum performance curves

B. Path curves in the position-velocity plane
The Sensitized Luminescence of Manganese-Activated Calcite
Authors: Schulman James H. , Evans Lyle W. , Ginther Robert J. , Murata K. J.
Published: January 2005

Synthetic manganese-activated calcites are shown to be practically inert to ultraviolet excitation in the range 2000–3500A, while they are luminescent under cathode-ray excitation. The incorporation of small amounts of an auxiliary impurity along with the manganese produces the strong response to ultraviolet radiation hitherto ascribed to CaCO3:Mn itself. Three such impurities have been studied: lead, thallium, and cerium. The first two induce excitation in the neighborhood of the mercury resonance line, while the cerium introduces a response principally to longer wave ultraviolet. The strong response to 2537A excitation shown by some natural calcites is likewise found to be due to the presence of lead along with the manganese, rather than to the manganese alone. The data do not warrant ascribing the longer wave-length ultraviolet-excited luminescence of all natural calcites to the action of an auxiliary impurity. The essential identity of the cathode-ray excited luminescence spectra of CaCO3:Mn, CaCO3: (Pb+Mn), CaCO3:(Tl+Mn), and CaCO3:(Ce+Mn) with the 2537A-excited spectra of the latter three is evidence that the luminescent center in all cases is the manganese ion or the MnO6 group. It is shown that a ``cascade'' mechanism for the action of the auxiliary impurities, lead, thallium, and cerium, is incorrect; and that the phenomenon must be considered as a case of sensitized luminescence. Owing to the nature of cathode-ray excitation, the manganese activator can be excited by this agent even in the absence of a second impurity. For optical excitation, however, an absorption band for the ultraviolet must be established by building into the CaCO3:Mn a second impurity or ``sensitizer.''
Electron Beam Deflection: Part I. Small-Angle Deflection Theory
Authors: Hutter R. G. E.
Published: January 2005

Two general mathematical methods are discussed which may be used to study the effects of electric and/or magnetic deflection fields on electron beams. The basic equations for the ``path method'' are the equations of motion of Newton or Euler-Lagrange. The ``iconal method'' makes use of certain properties of the Hamiltonian function.

These methods are then applied to describe the action of balanced, two-dimensional electric deflection fields on electron beams. It is shown that both methods yield essentially the same results. Expressions are derived describing the magnitude of deflection and the distortions of an electron beam.

Only the path method is used in a similar investigation of magnetic-type deflection fields.
Electrostatic Dischargers for Aircraft
Authors: Hall Wayne C.
Published: January 2005

Methods of discharging static electricity from aircraft in flight so as to reduce or eliminate corona interference, commonly known as precipitation static, are discussed. These methods have been classified into those employing either gaseous ions (high mobility), or those employing charge carriers such as water spray or dust particles (low mobility). Devices within the first classification offer the better solution to the problem from a practical standpoint. A discharger invented and developed at the Naval Research Laboratory is described.
Slow Transverse Magnetic Waves in Cylindrical Guides
Authors: Bruck G. G. , Wicher E. R.
Published: January 2005

The fundamental physical phenomenon upon which linear electron accelerators and traveling beam tubes depend is the fact that the phase velocity of guided TM waves can be reduced to a fraction of the velocity of light. There are various practical ways of achieving these reduced velocities, such as diaphragms or spiral grooves in the guide wall. An open helix has been used by Pierce.

An accurate knowledge of the field pattern would greatly facilitate an understanding of these devices. It is of particular importance to have exact information about the field in the region in which the charge actually travels, namely, in a region located at least a considerable fraction of a wave-length from the guide walls. Because of the complex shapes assumed by actual guide walls calculations of the field are inevitably somewhat inexact and complicated.

The authors propose that, for the purposes of theory, the well-established proposition concerning the equivalence of true and simulated dielectrics in producing a slow field be used. We propose to think of slowing down the phase velocity by lining the guide walls with a natural dielectric. The essential properties of the slow field, particularly in the important region referred to above, will not be affected by this method of obtaining it while, on the other hand, the field calculation becomes quite easy and exact.

Although this procedure is intended in the main as a device to facilitate the theoretical calculation of the field, the authors believe that such a step—replacement of periodic metallic structures by dielectrics—might prove useful in some actual applications.
Incandescent Lamps as Electrical Load for Testing
Authors: Keilien S.
Published: January 2005

Because of the positive coefficient of resistivity of tungsten, incandescent lamps permit a current considerably greater than the normal lamp current to flow for a short initial period. When lamps are used as load for testing electrical apparatus, the factors affecting this inrush must be considered. Size of power source, its distance from the load (lamps), and frequency of switching the lamps (employing repetitive operations for endurance testing) are evaluated.

From the given curve the necessary cooling time for the desired current inrush may be determined, and thus the frequency with which the lamps could be switched ``on'' and ``off'' may be calculated. Practical means for obtaining the required cooling time are described.
The Capacity per Unit Length and Characteristic Impedance of Coaxial Cables with One Slightly Non-Circular Conductor
Authors: Parzen Philip
Published: January 2005

It is possible to calculate approximately the electrostatic field in a coaxial line with one slightly non-circular conductor as a perturbation of that existing in the usual coaxial line. General expressions are then derived for the capacity per unit length and the characteristic impedance of such lines. In particular, these results are applied to the coaxial line with outer square conductor.
Thermal Conductivity of Aluminum; Solid and Liquid States
Authors: Bidwell C. C. , Hogan C. L.
Published: January 2005

Thermal conductivity measurements on lead, tin, and zinc extending over the liquid as well as the solid states were reported by one of the authors in 1940. The present report extends this work to cover aluminum in both the liquid and solid phases. An improved technique is described. The law k/ρC=K(1/T) + K′ is found to hold for aluminum also, with the intercept, K′, the same for both states. The thermal conductivity (k) decreases with rise of temperature as it does for lead, tin, and zinc. On this point previous workers have published very conflicting data.
Microwave Dielectric Measurements
Authors: Dakin T. W. , Works C. N.
Published: January 2005

The method of measurement of the dielectric properties of solid dielectrics described by S. Roberts and A. von Hippel has been applied with 3-cm wave-length waves in a rectangular wave guide. In this method the dielectric sample is placed at a short circuited end of the transmission line, and the dielectric properties of the sample, calculated from the position of a minimum of the standing wave and the ratio of the minimum field strength to the maximum field strength of the standing wave. A simplified procedure for calculating the dielectric properties from the measurements is presented. Values are given of the dielectric properties of some common plastic and ceramic materials at 10-cm wave-length and 3-cm wave-length, which were measured with this method.
Electron Beam Deflection: Part II. Applications of the Small-Angle Deflection Theory
Authors: Hutter R. G. E.
Published: January 2005

The theory developed in Part I is applied to a number of typical deflection fields such as the fields produced by parallel plates, parallel cylinders, semi-infinite co-planar sheets, and bent-plates. Graphs for the magnitude of deflection are given. An electrolytic tank potential-plotting device is described which was used for the determination of the potential distribution of some of the deflection fields.

The theory shows that the deflection is a function of the initial conditions of the electron beam before entering the field and that it is a slightly non-linear function of the field strength. It follows that the fluorescent spot and the pattern produced on the screen of cathode-ray tubes will show distortions. These distortions were calculated for several deflection fields and electron beam shapes; the results are shown graphically.

The problem of the reduction of these distortion effects is discussed.
A 70-Mev Synchrotron
Authors: Elder F. R. , Gurewitsch A. M. , Langmuir R. V. , Pollock H. C.
Published: January 2005

A synchrotron for the production of 70-Mev x-rays has been built and tested. The general mode of operation, and various features of its design and construction, are discussed. Some preliminary information on the characteristics of the electron and x-ray beams is included. This work has been supported by the Office of Naval Research.
Cathode-Ray Presentation of Three-Dimensional Data
Authors: Schmitt Otto H.
Published: January 2005

The cathode-ray oscilloscope is usually regarded as a means for displaying data in one or two variables as a function of time. By means of simple transformations which are easily performed electrically, it is possible to present three variable electrical data in the form of isometric or other conventional projections or as true perspective drawings. It is further possible to change the observer's viewpoint in the presentation coordinate system at will by turning range, elevation, and azimuth controls.

A more elaborate but similar set of transformations permits presentation of separate pictures to the two eyes. These pictures are optically superimposed but differ in such a way as to yield stereoscopically correct perspective pictures. These pictures are fully acceptable to the eye as patterns in space.
A Least-Square Application to Relaxation Methods
Authors: Bowie O. L.
Published: January 2005

A least-square application to relaxation techniques is presented wherein the mean-square error is minimized in considering any corrections to a given set of values for the unknown function. A systematic procedure is, therefore, devised for weighting errors at various points of the lattice. The process has general applicability to various forms of equations and definitions of corresponding difference equations. As illustrations, Laplace's and the biharmonic equations are considered.
An X-Ray Diffraction Study of the Silver-Magnesium Alloy System
Authors: Letner Harold R. , Sidhu S. S.
Published: January 2005

Four homogeneous solid solutions were found in the silver-magnesium alloy system. The α-primary solid solution of magnesium in silver has a f.c.c. structure. The β-solid solution has a b.c.c. structure. The γ-solid solution appears to have a complicated structure. While others have identified it as hexagonal, no definite structure could be assigned to it from our diffraction data. The δ-solid solution has a h.c.p. structure of magnesium.

The lattic parameter a0 in the α-solid solution increases with increasing magnesium concentration but exhibits a marked negative deviation from Vegard's Law. The a0 in the β-solid solution, however, increases linearly with increasing magnesium concentration.

Silver and magnesium atoms are distributed at random in the α-phase but take up preferred positions in the β-phase. The ordering process takes place throughout the β-phase, but is most nearly complete in the region of 50 atomic percent Mg.
A Study on Anaeroid Capsules
Authors: Pike Eugene W. , Gibbs Norman E.
Published: January 2005

The analysis of anaeroid capsule performance by the expansion of the observed pressure-deflection curve in Gram summation-orthogonal polynomials is illustrated on a series of fifteen runs on five typical capsules.

All of the deflection curves examined contained significant cubic and quartic terms while a few showed fifth-order terms. These high order terms are very unstable in magnitude and sign for successive deflections of the same capsule, and this accounts for the very complex hysteresis curves which have been observed.

The relationship of these high order terms in the deflection characteristic to the accuracy and cost of precise anaeroid barometers is brought out, and it is suggested that barometric systems free of elastic redundancies must be devised if accurate barometers for radiosondes and similar instruments are to be mass produced.