bluuebunny/crossref_metadata_2025 huggingface dataset:
A ``Double'' Camera for Electron Diffraction
Authors: Yamaguchi Shigeto
Published: April 2005

The method of a double camera for electron diffraction here described consists in taking two diffraction patterns simultaneously so that the wavelength of electrons applied to an ``unknown'' is exactly to that for the reference.
Electron Compounds of Transition Elements
Authors: Beattie H. J.
Published: April 2005

The work of many investigators has strongly indicated that sigma phase is characterized by a certain averaged electronic structure. The characteristic was first thought to be the ``electron vacancy'' concentration in the d band, but it is now appreciated that the density of electrons outside the argon shells may also be a valid criterion. The latter characteristic is used here with the application of H. Jones' theory. The result shows a definite correlation between the homogeneity ranges and the x-ray diffraction patterns for sigma phase and several other complicated structures which occur in alloys of transition metals.
The Motion of Idealized Vacuum Tube Filaments under Shock
Authors: Thomas Harry S.
Published: April 2005

Theoretical expressions are found for the displacement of points on an ideal clamped-end string relative to the end points when the supports are given an acceleration normal to the string length at t=0. The accelerations considered have the form of (1) the Heaviside unit function, (2) the Dirac δ function, and (3) the doublet impulse function. Approximate formulas for the maximum displacement of the string are derived for each of the three cases. Possible applications of the results to the problem of filament-grid shorts in certain vacuum tubes are briefly discussed.
Pressure Response in Supersonic Wind-Tunnel Pressure Instrumentation
Authors: Ducoffe Arnold L.
Published: April 2005

In the development of high-speed aircraft, rockets, missles, etc., wind-tunnel pressure measurements at supersonic velocities are necessary to determine certain aerodynamic characteristics. Because of the lack of knowledge concerning the proper choice of parameters in the design of pressure instrumentation, the response time has been known to exceed the running time in the case of the intermittent tunnel. Pressure systems consisting of an orifice, a capillary tube, a length of connecting tubing, and a pressure-sensitive element connected in series are analyzed. The time required for the pressure in the pressure-sensitive element to reach within 1 percent of the equilibrium pressure is defined as the response time of the system. Experiments are conducted to determine the effect of the various geometric and dynamic parameters on the response time. Analytical solutions of the flow equations by numerical integration are carried out for the special case of a length of capillary tubing connected to the pressure-sensitive element for three different inside diameters.

The data indicate that the response time can be maintained within acceptable limits for present-day supersonic wind-tunnel installations by proper choice of the geometric and dynamic parameters. The agreement between theory and experiment, being quite satisfactory for the special case solved analytically, indicated that the approximations in the derived flow equations are justified.
Transient Response of the Grounded Base Transistor Amplifier with Small Load Impedance
Authors: Schaffner J. S. , Suran J. J.
Published: April 2005

An analysis of the transient response of transistor amplifiers necessitates the consideration of transit time effects. Transit time behavior of minority carriers is described by the diffusion equation. Since the diffusion equation applies to minority carriers in the base region of a transistor, a current transfer function may be derived from the diffusion equation relating the collector current to the emitter current. This transfer function is valid only when the transistor is operated as a linear amplifier with small load impedance. For these conditions, the transfer function is solved for the collector current response to a step in emitter current by use of Laplace transform techniques. The collector current rise time, as a function of the α cut-off frequency, is derived from the theoretical equations and compared to measured values.
An Influence Function for the Beta Activity of Uranium-235 Fission Products
Authors: Thornton J. Kendall , Houghton William J.
Published: April 2005

Computations have been made of the total beta activity of the fission products arising from the slow neutron fission of U235. A curve is given exhibiting the activity per unit fission, for time intervals after fission ranging from 0.01 second to 10 years. This influence function is compared with some published experimental data and with the statistical curve of Way and Wigner. A curve of its integral as a function of the upper limit is also given. This latter curve facilitates estimation of the activity in the particular case where the fission rate has been constant throughout a known time interval. Finally, an influence function for the particular group of fission products consisting of complete and partial chains having volatile first members is given.
On the Diffusion of Decaying Particles in a Radial Electric Field
Authors: Keilson Julian
Published: April 2005

The diffusion of charged particles in the presence of a radial inverse-square electric field is difficult to treat in any general manner. It is possible, however, to treat steady-state radially symmetric flow in such a field. There may then be deduced, from the radial distributions obtained, a function, γ, which provides an important description of steady-state flow from a point source in the radial field. The important point is made that the function γ obeys the differential equation adjoint to that describing time-independent diffusion in the given field.

The physical problem treated is of specific interest to transistor theory, but it is hoped that some of the techniques used in treating the problem are of more general interest.
A Study of the Propagation Mode for Metallic Vapors in Shadow-Casting by Vacuum Evaporation of Au198 and Cr51
Authors: Preuss L. E.
Published: April 2005

A special method is introduced for quantitatively determining the metal-evaporation mechanism using metallic gold and chromium tagged with pile-produced Au198 and Cr51. This tracer method provides a powerful tool for the study of the distribution of minute amounts of the evaporated metal. Propagation and deposition of the vaporized metal are analyzed under a variety of conditions both in the normal evaporation process and for shadow-casting conditions. It is shown that crucible size and shape determine the evaporation-dispersion pattern. Computation of film thickness is by quantitative tracer methods with correlating observations by electron microscopy. Structure of these metal films correlates with observations by an earlier worker [R. W. G. Wyckoff, PSA Journal 13, 12 (1947)]. The probable error of the method is ±2 percent.
Exact Interpolation of Band-Limited Functions
Authors: Kohlenberg Arthur
Published: April 2005

A general formula is derived for the spectrum of a multiply-periodic, amplitude modulated sequence of pulses. The result is used to show that a function which lies in a frequency band (W0, W0+W) is completely determined by its values at a properly chosen set of points of density 2W. This verifies a supposition commonly accepted in communication theory.

The well-known, exact interpolation formula for a function f(t) in a band (O, W) is f(t)=Σnf(n/2W)sinπ(2Wt−n)π(2Wt−n). The function is thus determined by its values at a set of evenly spaced points ½W apart.

For a function f(t) in a band (W0, W0+W) it is shown that an exact interpolation formula is f(t)=Σn[f(n/W)s(t−n/W)+f(n/W+k)s(n/W+k−t)]in which k is subject to weak restrictions and s(t)=cos[2π(W0+W)t−(r+1)πWk]−cos[2π(rW−W0)t−(r+1)πWK]2πWtsin(r+1)πWK+cos[2π(rW−W0)t−rπWk]−cos[2πW0t−rπWk]2πWtsinrπWk. Thus, the function is determined by its values at a set of points of density 2W, but the points consist of two similar groups with spacing 1/W, shifted with respect to each other.
Shapes of Floating Liquid Zones between Solid Rods
Authors: Keck P. H. , Green M. , Polk M. L.
Published: April 2005

The present paper seeks to describe the shapes of liquid floating zones between solid rods of silicon and of germanium and to discuss stability conditions. The shapes were deduced from the equation given by Laplace, p=γ(1/R1+1/R2),where p indicates the pressure difference across the surface membrane of a liquid at any point, R1 and R2 are the principal radii of curvature at that point, and γ is the surface tension of the liquid.

The floating liquid zone is analyzed within a wide stability range. Its dimensions were theoretically determined and experimentally confirmed.
The Electron Microscopy of Photographic Grains. Specimen Preparation Techniques and Applications
Authors: Hamm F. A. , Comer J. J.
Published: April 2005

Several electron microscopical specimen preparation techniques are described, including two replica techniques. The most important specimens utilize the thin film of the silver-gelatin complex which exists as a tightly fitting skin around the photographic grains. This relatively inert and insoluble complex is referred to as the combined envelope; a study of this structure is given.

Latent image centers are enlarged in several ways so as to be readily resolvable in the electron microscope. After this partial development the matrix or intergrain gelatin is removed and the grains are fixed. The final specimen consists of developed centers retained by the combined envelope.

Applications of the replica technique to grain shape, size distribution, and growth nature of photolytic silver are given. Utilization of the combined envelope in conjunction with the special development techniques to provide information which substantiates independent sensitometric data is also demonstrated.
A Coupling Analog for Nonlinear Systems with More Than One Degree of Freedom
Authors: Ludeke Carl A. , Evans Ronald T.
Published: April 2005

A simple electromechanical analog for expressing the coupling between nonlinear oscillatory systems is constructed and checked. The strength of the coupling can be easily controlled by varying the output of a dc amplifier while the type of coupling is determined by the shape of an aperture in an integrating cylinder. The device has general applicability to analogs in which the motion of a component part can be translated into the motion of a mask before an integrating cylinder with a selected aperature.
Investigation of Back Diffusion of Photoelectrons in Various Standard Gases as It Affects Secondary Electron Emission Coefficients
Authors: Theobald J. K.
Published: April 2005

The effect of back diffusion of photoelectrons of two energy distributions in standard molecular and inert gases has been measured, and the results applied to the analysis of the Thomson equation as a semi-empirical formula for correcting the measurements of the secondary emission coefficients in gaseous discharges. The method brings the results of Lauer and Molnar into satisfactory agreement. The effect of electron attachment is briefly discussed.
Time-Resolved Spectroscopy of Ultraspeed Pellet Luminosity
Authors: Allen William A. , Mayfield Earle B.
Published: April 2005

Improved optical instrumentation has resulted in high time-resolution spectrograms of the luminosity associated with ultraspeed aluminum pellets. These data indicate that in many cases the light is emitted in two phases: (1) the ballistic, or air shock, characterized by atomic metal lines and a strong continuum; (2) AlO bands that appear about 150 μsec after the metal is ablated from the pellet.
An Alternative Method of Solving Hallén's Integral Equation and Its Application to Antennas Near Resonance
Authors: King Ronold
Published: April 2005

Hallén's complex integral equation for the current in a cylindrical antenna is separated into two real integral equations for the components of current in phase and in phase-quadrature with the driving voltage. Each of these equations is solved by iteration using zeroth-order currents and vector-potential differences to define expansion parameters. It is shown that for electrical half-lengths near odd multiples of a quarter-wavelength at least a third-order solution is required in order to determine accurately the component of current in phase with the driving voltage and the conductance. Conductances for a range of radii are evaluated by the new third-order formula and compared with the King-Middleton second-order values and with the experimental data of Hartig. The new formula agrees excellently with experimental results at h=λ0/4, whereas the earlier second-order formula has by far its greatest percent error—near 8 to 10 percent—in a small range near resonance. It is concluded that for antennas near resonance, just as for very short and very long antennas, adequate account must be taken in the iteration of both components of current.
Screw Dislocations in Thin Rods
Authors: Eshelby J. D.
Published: April 2005

In connection with Galt and Herring's observation on thin whiskers of tin, the properties of a screw dislocation in a cylinder are worked out. When all boundary conditions are taken into account, the image force tends to keep the dislocation along the axis. Only when it is displaced about half-way to the surface does the image force tend to pull it out of the rod. Generators of the cylindrical rod become helices when the dislocation is introduced. The dislocation can be ejected from the rod by twisting or bending it suitably.
Quasi-Degenerated Modes in High-ε Dielectric Cavities
Authors: Schlicke H. M.
Published: April 2005

This paper deals with resonance effects in circularly cylindrical solid bodies of high-ε dielectrics such as titanates, these bodies being either not metallized or partly or fully metallized by fired-on silver. The high dielectric constant has two pronounced effects:

(a) Miniaturization, a linear reduction in size in the order of magnitude of 1/100, and

(b) Realization of boundary conditions approaching infinite wave impedance.

All four combinations of radial and axial wave impedance being zero (metallized) or infinite (interface dielectric/air) are investigated mathematically and experimentally. Special consideration is given to degenerated modes; that is, modes for which the axial dimensions of the cavity do not contribute to the resonance wavelength. Because of the inherent magnetic leakage through the dielectric, this is only conditionally true. These modes are therefore termed quasi-degenerated.

In contrast to conventional cavity theory dealing only with metallic boundaries, quasi-degenerated TE modes are realizable; namely, if the faces of the cylindrical cavities are not metallized. These cavities can be tuned by introducing magnetic rods into them or by application of conductive disks outside of them in the proper position.

A novel type of antenna can be evolved from the TE010∞∞ mode, comprising a dielectric spiral encircling a magnetic rod.

In many cases the relatively high temperature coefficient, dissipation factor, and noise level prevent for the time being the potential application of these high-ε dielectrics.
The Flexural Response of a Submerged Solid to a Pulsating Gas Bubble
Authors: Chertock George
Published: April 2005

A bubble in a liquid pulsates and generates a changing pressure field. This reacts with a submerged flexible solid and induces elastic motions. Equations are derived which show how the vibration modes and frequencies of the solid are modified by the presence of the water, and how each mode is excited by the bubble pulsation. The generalized force for each mode is proportional to the volume acceleration of the bubble. The initial analysis presupposes incompressive flow, but it is shown that the results remain applicable if the duration of any compressive phase is small compared to the pulsation period of the bubble and the vibration period of the solid.
Synthesis of Transfer Functions with Poles Restricted to the Negative Real Axis
Authors: Weinberg Louis
Published: April 2005

A procedure for the synthesis of general RC transfer functions by means of unbalanced networks is described. The transfer function need not be minimum phase but may have zeros anywhere in the complex plane except on the positive real axis. Use is made of the technique of zero shifting as in the Guillemin procedure; but the additional use of a network theorem divides the desired network into two parts, with a consequent reduction of the problem to two simpler problems. Zero shifting can now be performed in two directions from within the total network. The theorem plus a method of using fewer paralleled ladders yield a final network with fewer ladders and fewer elements than that given by the Guillemin procedure. In the illustrative example given, twenty-six elements are used, whereas the Guillemin procedure would use sixty-six.
Viscoelastic Properties as Functions of the Distribution of Activation Energies
Authors: Lyons W. James
Published: April 2005

1. Assuming that the elementary molecular deformation process conforms to the Maxwell model, and that the molecular elastic force Gi and viscous force ηi are functions (of unspecified forms) of the free energy of activation F*, the following expressions for the dynamic modulus Gd and dynamic viscosity (internal friction) ηd are obtained: Gd=1A ∫ 0∞ω2τi2Giφ(F*)ω2τi2+1dF*,and ηd=1A ∫ 0∞ηiφ(F*)ω2τi2+1dF*,where A=area of sample, τi=Gi/ηi, ω=vibration frequency, and φ(F*)dF*=the number of elementary processes having activation energies lying between F* and F*+dF*.

2. By employing an expression relating the relaxation time τi with F* for the elementary process, and adopting the so-called ``box'' distribution of relaxation times, the following explicit form for the distribution of activation energies is deduced: φ=const(1/kTF*−1/F*2),where k=Boltzmann's constant and T=absolute temperature. When the box distribution, as represented by this explicit form for φ, is introduced into the foregoing expressions for Gd and ηd, the integrated results are found to predict temperature and frequency dependencies which are in gratifying agreement with experiment.
Change of Electron Temperature in an Electron Beam
Authors: Mott-Smith H. M.
Published: April 2005

The effect of electron encounters on the velocity distribution in an electron beam after passage through an accelerating grid is calculated by direct integration of the Boltzmann equation. It is found, with electron densities and velocities typical of traveling wave tubes and diodes, that the electron encounters have a negligible effect, that the formulas of the usual kinetic theory for heat conduction do not hold, and that the longitudinal component of the electron gas pressure is negligible.
A Measurement of the Drift Velocity of Electrons in the Electrical Field in Argon-Alcohol Mixtures
Authors: Colli Laura , De Leonardis Maria Teresa
Published: April 2005

The drift velocity of electrons in an electric field in argon and alcohol mixtures has been measured. The measurement has been taken observing on the screen of a triggered sweep oscillograph the rise time of pulses as given by α-particles in an ionization chamber. The results give, for the 10 percent mixture, a behavior of the w(E/p) function, of the w=aE/p type up to E/p=2 v cm−1 mm Hg−1 values, and of the w=const type for larger values of E/p. Measurements at 0.5 and 5 percent alcohol concentrations are also reported.
Electromagnetic Field Expansions in Loss-Free Cavities Excited through Holes
Authors: Teichmann T. , Wigner E. P.
Published: April 2005

It is shown that the electromagnetic field in a loss-free cavity excited through holes cannot be completely expressed in terms of the short-circuit modes of the cavity satisfying the condition that the tangential component of the electric field is zero on the boundary of the cavity including the openings. For a complete expansion it is necessary to add an irrotational magnetic field, which contributes a term inversely proportional to the frequency, to the usual admittance matrix. If the cavity is presumed to include a reasonable portion of the guides feeding the openings, this irrotational component becomes almost diagonal.
A Note on Wave Propagation through an Inhomogeneous Medium
Authors: Hufford George A.
Published: April 2005

A few formal observations are made concerning wave propagation through an inhomogeneous medium. A modification of Kirchoff's formula is suggested and an integral equation derived which, if certain integrals can be evaluated, gives an estimate of the error made in the usual approximate methods. Applications are indicated to the equivalent earth's radius model and to the flat earth, modified index model.
Synthesis of Unbalanced RLC Networks
Authors: Weinberg Louis
Published: April 2005

A method is demonstrated for synthesizing an unbalanced RLC network with lossy coils, i.e., each inductance has an associated series resistance. The network realizes a minimum phase transfer function whose numerator and denominator are of degree not higher than the third and fourth, respectively, and whose poles and zeros may lie anywhere in the left half of the complex frequency plane. It is shown that in many cases higher degree functions may be realized as one network. For a transfer function of arbitrary degree, factoring into component transfer functions is carried out, each component having the above characteristics; the components are then realized separately and isolated from each other by vacuum tubes supplying gain.

The method makes use of the following new features:

1. A breakdown of a Hurwitz polynomial into two Hurwitz polynomials so that a division by one of them yields a sum of unity plus a positive real RLC function, each of whose partial-fraction terms (complex poles taken in pairs, or course) is positive real.

2. An application of a network theorem which divides the desired network into two networks, thus simplifying the synthesis problem.

3. A method of zero shifting to any point in the left half-plane with at least one pair of complex poles.

A further advantage of the procedure is that the network may be designed to possess input and output shunt capacitances so that tube capacitances may be automatically provided for.
Waves in an Electron Stream with General Admittance Walls
Authors: Birdsall Charles K. , Whinnery John R.
Published: April 2005

The amplifying properties of electron streams passing near nonpropagating or lossy walls have been calculated. The method of field analysis is used to obtain values of gain and phase velocity for walls of arbitrary complex admittance. It is shown how one may find easily and quickly these values for actual tube design through use of two contour maps of the complex functions encountered. The gain is found to be zero for open or short circuit, or capacitive wall impedance, low for resistive-capacitive, higher for resistive and resistive-inductive, and highest for inductive walls. The behavior of a physically realizable model of the resistive-capacitive wall is determined. In conclusion, some comment is offered concerning the usefulness of these structures in the realm of microwave tubes.
Internal Friction of Quartz
Authors: Alers George A.
Published: April 2005

The internal friction of quartz was studied by measuring the logarithmic decrement of a bar vibrating in resonance at its fundamental mode at 21 kilocycles per second and at its second harmonic mode at 42 kilo-cycles per second as a function of temperature from 200°C to 440°C. The logarithmic decrement was found to rise rapidly to a maximum of 16×10−5 at about 240°C, then fall slowly to a minimum of about 8×10−5 at about 350°C, and then rise rapidly up to and beyond 460°C. The high temperature portion shows a temperature hysteresis in which the cooling curve is lower than the heating curve. Furthermore the magnitude and, to a certain extent, the position of the peak may depend upon previous history but heating in a vacuum can reduce the logarithmic decrement curve to a reproducible one, independent of room temperature handling and thermal gradients (up to 1.5°C/cm) or stress amplitudes (up to 10 g/mm2) applied at higher temperatures.

The measured curve can be considered as the sum of two relaxation peaks and an exponential curve. One peak has an activation energy of 27.2×103 calories per mole, and the other, 12.6×103 calories per mole. The exponential curve appears to be characterized by an activation energy of about 22×103 calories per mole but may vary with heat treatment.
Stability Investigation of the Nonlinear Periodic Oscillations
Authors: Hayashi Chihiro
Published: April 2005

The stability of the nonlinear periodic oscillations is discussed by solving a variational equation which characterizes small variations from the periodic states of equilibrium. This variational equation leads to a linear equation in which the coefficient is periodic in the time. If all solutions of this equation are bounded, then the oscillation is said to be stable, otherwise it is unstable. In order to establish the stability criterion, the characteristic exponents for the unbounded solutions are calculated by Whittaker's method. Then, the generalized stability condition is derived by comparing the said characteristic exponents with the damping of the system considered. Since the solutions of the variational equation have the form: eμτ[sin (nτ−σ)+…], our stability condition is secured not only for the unbounded solutions having the fundamental frequency (n=1), but also for the unbounded solutions with higher harmonic frequencies (n=2, 3, 4, …). Hence the generalized stability condition obtained in this way is particularly effective in studying the oscillations in which the higher harmonics are excited. Finally our investigation is compared with one of the stability conditions derived by Mandelstam and Papalexi for the subharmonic oscillations.

In the Appendix, the characteristic exponents are calculated at some length for the unbounded solutions of a variational equation in which the periodic coefficient involves sine series as well as cosine series.
Attenuation in the Shock Tube
Authors: Emrich R. J. , Curtis C. W.
Published: April 2005

By timing the successive arrivals of a shock at stations placed along the channel of a shock tube, measurements have been made of the decrease in shock velocity with travel. These measurements were carried out for shocks moving into air at atmospheric pressure.

The attenuation per unit length of travel is greater for stronger shocks and in smaller tubes. Representing distance along the tube by x and using fractional increase in pressure across the shock, (P−P0)/P0=z, as a measure of shock strength, the dimensionless quantity R(dz/dx)/z is found to lie in the interval (3.5±2) ×10−4 for shocks ranging in strength 0.1<z<1.0 and in tubes of hydraulic radius 0.30<R<3.80 cm. It is believed that this attenuation is due to wall interaction rather than to nonideal rupture of the diaphragm. However, the exact physical nature of this interaction has not as yet been determined.
Statistical Criteria for the Detection of Pulsed Carriers in Noise. II
Authors: Middleton David
Published: April 2005

In Part I a statistical theory for the detection of a pulsed carrier in noise has been described, where specifically three types of observer are defined: (1) the Neyman-Pearson, (2) the Ideal, and (3) the Sequential observer. In Part II specific betting curves are determined for the weak-signal cases, and some approximate curves for strong signals are also included. The input signal-to-noise (power) ratio (a02)min corresponding to the minimum detectable signal at the output (with an arbitrary probability of a correct decision) is found, as expected, to vary as n−½ for weak signals and as n−1 for strong, where n=number of pulses integrated. Furthermore, comparison of observers on the basis of the minimum detectable signal reveals the Neyman-Pearson to be better than the Ideal, by an amount 0 (0.5 db). On the basis of the assumed approximate distribution ws(ns) of sample size, the Neyman-Pearson also appears superior to the Sequential observer, but as indicated in Part I, the latter must always be as good as, if not better than the former. The discrepancy is the result of the approximate nature of the assumed distributions. A lower bound on the errors thus introduced in the calculations of the (a02)min is accordingly provided by the extent to which the Sequential appears worse than the Neyman-Pearson observer for equal probabilities of type I and II errors α and β. For ws(ns) =δ(ns−) this error is reasonably small 0 (1.5 db), but for a Gaussian distribution of ns the effect is 0 (3.0 db) at least. Included also are an analysis of performance and some of the factors affecting it. The paper terminates with a brief account of a statistical theory of the observation process and its relation to the various observers considered here.
Optimum Nonlinear Filters
Authors: Zadeh L. A.
Published: April 2005

The theory of optimum nonlinear filters outlined in this paper is based on the consideration of a sequence of classes of nonlinear filters, designated as 𝔑1, 𝔑2, 𝔑3, …, such that each class in the sequence includes all the preceding classes and, furthermore, the class of linear filters is a subclass of every class in the sequence. A filter of class 𝔑m is described in terms of a characteristic function which involves m age variables and m values of the input time-function. The input-output relationship for a filter of class 𝔑m has the form of an m-fold integral of the characteristic function with respect to the m age variables. It is shown that the characteristic function of the optimum filter (in the least squares sense) within the class 𝔑m satisfies a linear integral equation of 2mth order. The optimization of filters of class 𝔑1 is treated in detail, and methods of approximate realization of such filters in the form of nonlinear delay line filters and power series filters are indicated. The results are extended to the case of nonstationary time series.
The Susceptance of a Circular Obstacle to an Incident Dominant Circular-Electric Wave
Authors: Sheingold L. S.
Published: April 2005

The problem of the susceptance of a circular obstacle in a circular wave guide with an incident TE01 mode is solved by a variational method. Theoretical expressions are obtained which are in good agreement with experimental results. Curves of normalized susceptance as a function of relative aperture, guide wavelength, and free-space wavelength are included.
Bulk Viscosity of the System Polystyrene—Diethyl Benzene
Authors: Bueche F.
Published: April 2005

The bulk viscosity of the system polystyrene-diethyl benzene has been measured over the concentration range from 8 to 80 weight percent polymer and a temperature range from 30 to 130°C. A single sample of polymer was used. The activation energy for viscous flow is found to vary from about 2 to 100 kcal/mole as one goes from pure solvent to pure polymer. Using a series of 15 fractions of polystyrene ranging from 50 000 to 106, the molecular weight dependence for the viscosity of this system was measured at two polymer concentrations, 14 and 44 percent. The results are compared in a qualitative way with what one would expect from existing theory.
The Effective Length of an Electrostatic Analyzer
Authors: Monahan James E.
Published: April 2005

The general formula for the effective length of an electrostatic analyzer with ``rounded'' corners is derived using a modified Schwartz transformation. For the dimensions considered the rounded corner effect introduces a correction of about 0.1 percent in the evaluation of the effective length of the analyzer.
Electrical Phenomena in Adhesion. I. Electron Atmospheres in Dielectrics
Authors: Skinner Selby M. , Savage Robert L. , Rutzler John E.
Published: April 2005

Rapid breaks of metal-polymer-metal adhesive specimens have shown the presence of a charge density on the metallic surface, provided the break occurs at the metal-polymer interface, and a much smaller charge if it occurs in the interior of the polymer. This is analyzed in terms of the electron atmosphere existing external to the metal in a dielectric region of low barrier. The barrier values in certain cases are otherwise known to be of appropriate order of magnitude. Measured experimental surface charge densities permit estimation of the maximum limit of barrier height. Because of the presence of the charge distribution in the polymer, there is an electrostatic force on the adherend metal directed toward the dielectric polymer, which represents a contribution to the total adhesive forces opposing break. Such electrostatic contributions to adhesion have not previously been considered; their order of magnitude and their relation to the thickness of the adhesive are discussed. The qualitative agreement between the theory and a number of previously unexplained experimental results in the literature is shown.
A Retarding Potential Method for Measuring Electrical Conductivity of Oxide-Coated Cathodes
Authors: Sparks I. L. , Philipp H. R.
Published: April 2005

A retarding potential method is developed for measuring the electrical conductivity of normal oxide cathode coatings. The method is limited by normal current measuring devices and can not be used for coatings which have a conductivity to thermionic emission ratio greater than 2 cm/volt. Advantages of the method are: (1) the conductivity of coatings which are in a normal state for thermionic emission may be measured without the use of probe wires or other devices which might impair the thermionic emission of the sample, and (2) conductivity and thermionic emission measurements may be made simultaneously on the same coating sample. The theory of the method is discussed in detail and experimental results obtained using this method on both BaO and (BaSr)O coatings are given.
Evaporation of Germanium Films from a Carbon Crucible
Authors: Lehovec K. , Rosen J. , MacDonald A. , Broder J.
Published: April 2005

Equipment for evaporation of germanium in vacuum at various measurable rates is described. The activation energy of evaporation is 3.5 ev, which is in close agreement with recent data by Searcy.
Subharmonic Oscillations in Nonlinear Systems
Authors: Hayashi Chihiro
Published: April 2005

This paper deals with the subharmonic oscillations which occur in systems with nonlinear restoring force. It is first shown that the order of the subharmonics has a close connection to the form of the nonlinear characteristics. The subharmonic oscillation of order ⅓, i.e., the oscillation whose fundamental frequency is one-third that of the applied force, is then particularly investigated for the cases in which the nonlinear characteristics are expressed by (1) cubic and (2) quintic functions. In both cases the stability problem of the periodic solution is discussed in detail according to the stability criterion given previously by the author. The analysis reveals that in the latter case (2) the second higher-harmonic of the subharmonic, i.e., the oscillation of order ⅔ builds up with negative damping. This is verified by experiments in which the oscillation of order ⅔ causes the collapse of the original subharmonic oscillation.
The Effect of Pressure on the Tensile Properties of Several Metals and Other Materials
Authors: Bridgman P. W.
Published: April 2005

Tension tests to fracture under superposed hydrostatic pressure reaching to nearly 30 000 kg/cm2 have been conducted on five polycrystalline metals, Ni, Ta, Cb, Mo, and W, two brittle single metallic crystals, Sb and Cu5Zn8, and two brittle amorphous materials, ``Melmac 404'' and B2O3 glass. All these materials exhibit ductility at the highest pressure; the largest increases are for the polycrystalline metals of which the largest is W, which breaks brittely at atmospheric pressure but with 81 percent reduction of area at the highest pressure. The shape of the strain hardening curves varies among the five metals from abrupt rise with long tailing off to long gradual rise with comparatively abrupt falling off, in the order W, Mo, Ta, Cb, and Ni. The character of the fracture varies continuously with pressure and is different for the different metals. Of the brittle single crystals Sb has a reduction of area of 55 percent at the highest pressure. The plastic, Melmac 404, gives the smallest increase of ductility, a reduction of area of only 14 percent at the maximum. This small value is doubtless associated with the absence of internal crystal slip planes. B2O3 glass gave a reduction of 87 percent; this is largely a phenomenon of plasticity, but there is an appreciable component of viscosity. Both amorphous materials showed an increase of density after pulling under pressure instead of a decrease.
The Field Emitter: Fabrication, Electron Microscopy, and Electric Field Calculations
Authors: Dyke W. P. , Trolan J. K. , Dolan W. W. , Barnes George
Published: April 2005

When a specially designed field cathode assembly was inserted in a commercial electron microscope which was appropriately modified for the purpose, the geometry of the needle shaped emitter was obtained from micrographs of several of its profiles at various stages of emitter fabrication and experimental use. An investigation of several methods of fabrication revealed that a smooth, simple, and relatively stable tungsten emitter geometry resulted from a refinement of the methods of Benjamin and Jenkins which combines the electrolytic etch and the smoothing action of surface migration. The electric field at any point on an emitter surface was calculated when the emitter geometry was precisely fitted with one equipotential surface from the family surrounding a charged, isolated sphere-on-orthogonal-cone. A theoretical surface distribution of current density for a typical emitter was derived from the calculated field distribution and the wave-mechanical field emission theory. From this result was calculated a value of the emitting area which was in good agreement with experiment.
Space Charge Spread of Reflected Electron Beams Studied by a Photographic Method
Authors: Wallmark J. T.
Published: April 2005

The spread of electron beams of rectangular cross section is studied (a) in a field free space, (b) in a reflection space. An experimental method is tried to trace the electron paths from the excited gas molecules left behind by directly photographing the beam in a high vacuum. The results are checked with published theoretical calculations in case (a), and with results obtained through an iterative method in case (b).
Modes in Wave Guides Containing Ferrites
Authors: Kales M. L.
Published: April 2005

When a static magnetic field is applied in the longitudinal direction to a wave guide containing a ferrite material, the medium within the guide becomes anisotropic. It has been shown by Polder that when a microwave field is propagating within such a medium, the relation between the components of B and H is given by: Bx=μHx−jμ′Hy,By=jμ′Hx+μHy,Bz=Hz, where μ and μ′ depend on the static magnetic field. Using these equations, an investigation of the wave-guide modes is made. Formal solutions are obtained for guides having circular symmetry. These solutions depend on the solution of some rather involved eigenvalue equations which determine the propagation constants, and which probably can be solved only by numerical methods.
Response of Linear Time-Dependent Systems to Random Inputs
Authors: Duncan D. B.
Published: April 2005

A nonstatistical differential equation is derived for the mean square response of linear systems to random inputs. This equation can be used to determine analytically the steady state and transient response of systems with constant coefficients. It is also applicable to time dependent systems. While the solution cannot in general be obtained analytically in this case, the equation is of the type that can be immediately mechanized on analog computers.
Temperature Dependence of Low Frequency Fluctuations in Thermionic Emitters
Authors: Tomlinson T. B.
Published: April 2005

A method is described for measuring the temperature variation of the low frequency fluctuations of emission current (flicker effect) in diodes with oxide-coated cathodes. In order to vary the cathode temperature and at the same time avoid the effects of space charge and the variation due to changes of the mean current, it is necessary to operate the test diodes under retarding field conditions. The results show that the majority of tubes exhibit minimum fluctuations at a cathode temperature in the region of 1000°K, although both rising and falling temperature characteristics are encountered. It is concluded that the flicker effect is in fact a combination of at least two separate phenomena. Finally, the various theories are examined in the light of the new information, and none is found to be completely satisfactory.
The Calibration of Photographic Emulsions for Electron Diffraction Investigations
Authors: Bartell L. S. , Brockway L. O.
Published: April 2005

A procedure for calibrating photographic emulsions has been devised which measures the deviation from linearity of the curve relating electron exposure to optical density. The experimental application of this procedure is found to give results consistent with a very simple model of the exposure process. It is also noted that the sensitivity of a photographic plate increases with increasing distance from the center of the plate. Measurements of this effect are given.
Effects of Nuclear Radiations on the Mechanical Properties of Solids
Authors: Dienes G. J.
Published: April 2005

The general nature of radiation effects in solids is reviewed briefly. Current theoretical understanding of the mechanical properties of solids is critically evaluated. The effect of nuclear radiation on the mechanical properties is discussed in detail. It is shown that the changes in the mechanical properties of crystalline substances (mostly metals) can be quite satisfactorily interpreted on the basis of the production of interstitial atoms and vacant lattice sites by fast particle irradiation. Isolated vacancies and interstitials may not be able to account for all the observations, and attention is called to the possible need of postulating the existence of aggregates of these lattice defects. In molecular solids (mostly high polymers) nuclear radiations bring about changes in the substance which are best described as chemical ones. Ions and free radicals are formed leading to subsequent chemical reactions thereby altering the properties of the substance. Drastic changes in the mechanical properties of high polymers are observed. Correlation with structural changes has hardly been started. Experiments are suggested which, in the writer's opinion, should give further insight into the fundamental processes involved.
Mechanical Investigations of Elastomers in a Wide Range of Frequencies
Authors: Philippoff Wladimir
Published: April 2005

A method has been found for measuring the shear moduli and losses of elastomers in a range of frequencies of about 1 to 106, from 10 cps down. This method provides for large cyclic shear stresses and deformations without employing resonance methods. Only one sample is needed for a complete study, the frequency of stress being the only variable. The method gives results that fit the ``box-distribution function'' developed by Kuhn and Kuenzle. Results for a series of elastomers show that such investigations are important in ascertaining the mechanical properties of elastomers in practice.
Temperature Coefficients of Non-Newtonian Viscosity at Fixed Shearing Stress and at Fixed Rate of Shear
Authors: Bestul A. B. , Belcher H. V.
Published: April 2005

Viscosity decreases with increasing shearing stress or rate of shear in the non-Newtonian flow of high polymeric systems. It is shown that it follows from this fact that the variation of viscosity with temperature is greater at fixed shearing stress than at fixed rate of shear.

For such systems, it is shown experimentally that the variation of viscosity with temperature at fixed shearing stress is independent of shearing stress. However, the variation at fixed rate of shear is always less than that at very low shearing stress, and decreases with increasing rate of shear.

This behavior is reproduced by Eyring's hyperbolic sine flow equation, which is the antecedent for most other, more adequate, non-Newtonian flow equations. However, this equation is shown to be inadequate in that it predicts incorrect values of shearing stress for the occurrence of non-Newtonian behavior.
Effects of Rate of Shear on Inherent and Intrinsic Viscosities of Polystyrene Fractions
Authors: Sharman L. J. , Sones R. H. , Cragg L. H.
Published: April 2005

Fractions of polystyrene, varying in molecular weight from 0.3×106 to 10×106 approximately, were prepared by careful tertiary fractionation. Inherent viscosities were determined at various rates of shear in the approximate range 100–20 000 sec−1, viscosity measurements being made at several different temperatures in benzene and toluene (good solvents for polystyrene), in butanone (an intermediate solvent), and in cyclohexane (a poor solvent). From these values intrinsic viscosities at various rates of shear were determined. These viscosity functions are sensitive to shear rate at high molecular weights; at a given temperature the shear effects are greater the higher the molecular weight and the better the solvent, and with increasing temperature they decrease in a good solvent and increase in a poor one This behavior is shown to be consistent with current ideas regarding the size and shape of polymer molecules in solution as affected by weight, temperature, and solvent power. It is concluded, among other things, that with flexible polymers (or polymer fractions) of very high molecular weight, measurements of intrinsic viscosity should be made in a poor solvent at a low temperature.
Anomalous Viscous Flow at Very Low Rate of Shear and Small Shearing Stress
Authors: Bergen J. T. , Patterson W.
Published: April 2005

Fluid suspensions of a solid phase in a liquid, for example, paints and printing inks, have been presumed to exhibit anomaly of flow at very low rate of shear. The consistency characteristics of such materials require an experimental shear rate and shear stress much lower than has heretofore been reported.

This paper describes a translated cylinder, or translational, viscometer of a modified Pochettino type, which possesses a shear stress sensitivity of 5×10−3 dyne/cm2, and a shear rate sensitivity of 1×10−4 sec−1. A rubber Latex of high solids content exhibited no anomaly of flow within this range of sensitivity. A rubber dissolved in organic solvent was observed to approximate a Bingham material of 0.05-dyne/cm2 yield value, while a gum tragacanth suspension in water exhibited a yield value of 0.4 dyne/cm2 with marked post-yield anomalous flow. Household paints exhibited yield value ranging from zero to 6 dyne/cm2. These yield values were related to leveling-out of brushmarks, and to sagging or ``curtain,'' except for examples exhibiting marked thixotropic behavior. Industrial organosol coatings likewise possessed yield values ranging up to 5 dyne/cm2 which were related to leveling characteristics. These yield values agree with those postulated by Waring from consideration of the forces of leveling of brushmarks. They are considerably smaller than those reported in the literature from extrapolation of flow curves from much higher rate of shear.
Space Charge Requirements in Some Ideally Focused Electron-Optical Systems
Authors: Wax Nelson
Published: April 2005

A selected set of points on the trajectories of charged particles traversing an electron-optical system may be considered to be an object space, and another set an image space. Electron-optical lenses are said to be ideally focused if the transformation of the points in object space to those in image space is one to one and continuous. A necessary condition for ideal focusing is used to prove that a number of electron-optical systems require the presence of space charge in order to be ideally focused. Expressions for some ideally focused electron-optical lenses are given, in particular those for cylindrical lenses without space charge derived from spherical lenses with space charge.