bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaporation Rate of Liquid Helium. I
Authors: Wexler Aaron
Published: April 2005

In connection with a study of the emissivity of metals at low temperatures, a quantitative analysis has been made of the factors involved in the design of storage containers for liquid helium. Experiments confirm the analysis, which has resulted in an exceedingly simple liquid-nitrogen-protected liquid helium container having a helium evaporation rate of 1 percent per day.

The hemispherical emissivity of mechanically polished copper at 4.23°K was determined for blackbody radiation. For radiation corresponding to that emitted by a blackbody at 77.1°K and 297.1°K, the measured emissivities are 6.9×10−3 and 1.29×10−2, respectively. These data are discussed in relation to the recent theoretical work of Reuter and Sondheimer.

The heat of vaporization of helium at 4.228°K was determined to be 4.93 cal g−1, in substantial agreement with the data of Dana and Kamerlingh Onnes. Kistemaker's thermodynamic considerations questioning the accuracy of these data are evaluated in terms of the new determination.
Convection Currents in Porous Media. IV. Remarks on the Theory
Authors: Rogers F. T. , Schilberg L. E. , Morrison H. L.
Published: April 2005

Differential equations for critical stability of a fluid in a porous medium and heated from below are solved by an approximate method not hitherto used. A single formula is obtained for the thermal environment at critical stability, apparently valid over a wide range of conditions, which allows for temperature dependence of viscosity and nonlinear temperature distributions. New experiments are reported in which initial convection has been detected by visual, thermal, and radioactive-trace means. Experimental mean thermal gradients for critical stability deviated from values predicted by the new solution of theory by the following average amounts: visual, 150 percent; thermal, 32 percent; radioisotopic, 11 percent.
Propagation of Disturbances in One-Dimensional Accelerated Electron Streams
Authors: Smullin L. D.
Published: April 2005

The propagation of small sinusoidal modulations in the infinite, parallel-plane diode is studied. A second-order differential equation is obtained for the ac convection current. Solutions are found in closed form for the cases of a drift-stream, space-charge-limited acceleration, and acceleration with an arbitrary current density less than the space-charge-limited value.
Propagation Characteristics in a Coaxial Structure with Two Dielectrics
Authors: Baños Alfredo , Saxon David S. , Gruen H.
Published: April 2005

The propagation characteristics for circularly symmetric TM modes in a coaxial structure with two dielectrics offer many points of interest. For a given mode, the pertinent parameters are the ratio of the dielectric constants of the two media involved, the ratio of the two radii, and the operating frequency, expressed, say, in terms of the cut-off frequency for the empty guide. Among the results of special interest are the facts, previously pointed out by Frankel and by Bruck and Wicher, that the phase velocity for a given propagating mode may lie between the phase velocities corresponding to each of the two unbounded dielectrics and that, by proper choice of parameters, it is always possible to obtain a phase velocity of a preassigned value higher, of course, than the lower of the two velocities for the unbounded media. This suggests the possibility of using such structures in linear accelerators. The results of an extensive computational program are presented in the form of families of curves showing the dependence of the propagation constant and of the phase velocity on the parameters of interest. Some discussion of the power flow and field distribution is also given.
Asymptotic Approximation for the Normal Modes in Sound Channel Wave Propagation
Authors: Haskell N. A.
Published: April 2005

Asymptotic methods are used to find approximate solutions of the acoustic wave equation in a medium in which the velocity is a continuously variable function of one coordinate. It is shown that, when the velocity function has a minimum, undamped normal mode solutions exist and are closely analogous to the internally reflected waves in the case of a medium made up of discrete layers. By converting the sum of the high order normal modes into an equivalent integral, it is shown that superposition of these modes leads to geometrical ray theory modified by diffraction in a manner that may be computed from the incomplete fresnel and airy integrals.
Density Measurements in Supersonic Flow by Means of the X-Ray Absorption Method
Authors: Winkler Eva M.
Published: April 2005

The density in supersonic flow was measured by the absorption of soft x-rays. The equipment is briefly described. Data obtained in undisturbed flow at M=2.83 are compared with values computed from Pitot pressure measurements. Measurements of the density distribution across a shock wave on a wedge-shaped model are presented. The suitability of the method, its limitations, and improvements of the technique are briefly discussed.
Latex Particle Size from X-Ray Diffraction Peaks
Authors: Yudowitch K. L.
Published: April 2005

A high resolution camera was constructed for small angle x-ray scattering. Measurements with this camera on Dow latex 580G exhibit a number of concentric rings. Each ring is associated with a theoretical maximum of scattered intensity predicted by the spherical x-ray form factor corrected for packing.

The particle diameter is then computed from the position of each ring. Twenty measurements yield a diameter of 2780A with a probable error of less than ±1 percent.
Calculation of the Electrical Capacitance of a Cube
Authors: Reitan Daniel Kinseth , Higgins Thomas James
Published: April 2005

The basic theory of calculation of the capacitance of a given geometrical configuration by the use of subareas is advanced and applied to solve the long-standing problem of the accurate evaluation of the capacitance C of a cube of side a. The best previously published determination is 0.62211a<C<0.71055a. The value obtained of C≈0.655a esu is both a lower limit and very close to the exact value.
The Properties of Evaporated Gold and Tungsten Oxides
Authors: Wilkinson P. G.
Published: April 2005

Gold blacks, prepared by evaporating gold from a tungsten filament in tank nitrogen at several mm pressure, were found to contain tungsten oxides which greatly affected the optical and electrical properties. Deposits containing more than 0.5 mole percent of tungsten oxides were black and showed resistivities 103 to 108 times that of bulk gold. The resistivities of gold blacks increased on exposure to oxygen. On the other hand, oxide-free deposits were yellow and possessed a low stable resistivity, unaffected by exposure to oxygen. Exposure to air or oxygen caused an increase in the electrical resistance, and optical transmission of films of tungsten dioxide and tungsten trioxide evaporated in high vacuum. It was concluded that evaporated films of pure gold are unaffected by exposure to air and that the changes in optical and electrical characteristics, often observed in evaporated gold films exposed to air, may be attributed to contamination by oxides of tungsten. It was also concluded that so-called gold blacks are black because of the presence of tungsten oxides, since gold evaporated in pressures of several millimeters of oxygen-free nitrogen formed bright reflecting films rather than black absorbing deposits.
A Note on Reflection and Transmission
Authors: Lengyel Bela A.
Published: April 2005

The quantities characterizing wave propagation through the interface of two media or through a transmission line containing obstacles are the two reflection coefficients r1 and r2 and the two transmission coefficients t1 and t2. It is shown that for any lossless discontinuity |r1| = |r2|, argt1 = argt2, and that argr1+argr2 −2 argt1 = ±π. These relations are applied to the calculation of reflections from sheets of dielectric and metal-plate media, the latter being distinguished by the fact that argt1≠0.
Experimental Determination of the Reflection Coefficient of Metal-Plate Media
Authors: Ruze J. , Young M.
Published: April 2005

A method of measuring the reflection coefficient of metal-plate media at 3 cm is described. The technique differs from that presented in the preceding paper in that the measurements are made in a closed system and back reflections are eliminated by an absorbing wedge. Angle of incidence and the plate thickness are varied. The agreement with the Carlson-Heins theory is excellent for very thin plates. For plates of moderate thickness near normal incidence the measured reflection is higher than that predicted for an infinitely thin set of plates with identical index of refraction.
Long-Range Order in Beta-Brass and Cu3Au
Authors: Keating D. T. , Warren B. E.
Published: April 2005

Measurements have been made on single crystals of CuZn and Cu3Au held at various temperatures below Tc to decide whether there is a single-ordered phase whose order changes with temperature, or whether there is an ordered and a disordered phase the relative amounts changing with temperature. Precision measurements were made of the position and width of the (222) CuZn and (400) Cu3Au reflections. The disordered phase has a larger cell dimension, so that reflections from the ordered and disordered phases are slightly displaced from one another. For both materials, a single peak was observed which was too narrow to correspond to the existence of two phases. At the stoichiometric compositions, it is concluded that below Tc there is only an ordered phase whose long-range order varies with temperature. Measurements of the long-range order in Cu3Au have been made on briquets of filings, using quenched samples, and on a sample held at temperature.
Transmission-Line Equivalent of Electronic Traveling-Wave Systems
Authors: Mathews W. E.
Published: April 2005

It is well known that the small-signal behavior of long electron beams may be analyzed in terms of propagating space-charge waves, suggesting an equivalence between such beams and longitudinally moving transmission lines. This in turn suggests the analysis of such electronic devices as the traveling-wave amplifier, double-stream or electron-wave amplifier, and multicavity magnetron, in terms of coupled distributed-parameter transmission lines moving relative to each other. It is shown that this approach is equivalent to a rigorous field-theory analysis in certain cases of particular interest, and the procedure for calculating the significant distributed parameters is indicated. Final results for the idealized helix and thin cylindrical electron beam are presented.
Thickness-Shear and Flexural Vibrations of Crystal Plates
Authors: Mindlin Raymond D.
Published: April 2005

The theory of flexural motions of elastic plates, including the effects of rotatory inertia and shear, is extended to crystal plates. The equations are solved approximately for the case of rectangular plates excited by thickness-shear deformation parallel to one edge. Results of computations of resonant frequencies of rectangular, AT-cut, quartz plates are shown and compared with experimental data. Simple algebraic formulas are obtained relating frequency, dimensions, and crystal properties for resonances of special interest in design.
Maxwell's Demon Cannot Operate: Information and Entropy. I
Authors: Brillouin L.
Published: April 2005

In an enclosure at constant temperature, the radiation is that of a ``blackbody,'' and the demon cannot see the molecules. Hence, he cannot operate the trap door and is unable to violate the second principle. If we introduce a source of light, the demon can see the molecules, but the over-all balance of entropy is positive. This leads to the consideration of a cycle Negentropy→Information→Negentropyfor Maxwell's demon as well as for the scientist in his laboratory. Boltzmann's constant k is shown to represent the smallest possible amount of negative entropy required in an observation.
Scattering and Absorption of Gamma-Rays
Authors: Plesset M. S. , Cohen S. T.
Published: April 2005

A formulation is presented of the scattering and absorption of gamma-rays in different materials. The range of gamma-ray energies considered is from 1 to 10 mc2. Results are given for the transmission of gamma-rays through air and lead.
Diffraction Errors in an Optical Measurement at Radio Wavelengths
Authors: Woonton G. A. , Carruthers J. A. , Elliott H. A. , Rigby E. Caroline
Published: April 2005

The errors arising in the measurement of antenna patterns by means of a lens are examined. The effect of the lens aperture is separated from the effect of lens aberrations and only the effect of the aperture is discussed. Theoretical solution of the problem is obtained for a uniformly illuminated aperture and for short electromagnetic horns. The theory is found to be in agreement with experimental measurements. The phenomenon of mutilation due to the aperture is examined with the help of both computed results and experimental measurements. The systematic errors due to mutilation have been found and have been shown as precision limits. An extrapolation of the data suggests that a lens forty wavelengths wide can be used for the precision measurement of the patterns of antennas ten to twenty wavelengths wide. The technique is entering its range of usefulness at a wavelength of 3.2 cm and should increase in value as the wavelength is decreased.
Internal Friction of Ferromagnetic Materials
Authors: Ferro A. , Montalenti G.
Published: April 2005

It is common knowledge that in cyclically stressed ferromagnetic materials an energy loss due to internal friction is observed; this part of loss disappears when the material is brought to saturation or above the Curie temperature. It is also known that a stress, applied to a ferromagnetic material, produces a motion of Weiss domains from their rest position.

The scope of this paper is to verify experimentally the following hypothesis: in cyclically stressed ferromagnetic materials, energy loss because of magneto-elastic internal friction is induced by a domain motion due to the applied stress itself.

The ratio Ir/Is (where Ir=residual induction, and Is=saturation intrinsic induction) has been chosen as an index of the domain position; its measure has been carried out by normal ballistic method on a permeameter rigged with a torsion applying device.

Energy loss was measured by means of a torsion pendulum; a coil allowed the saturation of specimen in order to separate magneto-elastic from purely mechanical losses. Plotting curves of Ir/Is and of magneto-elastic losses as a function of applied stress and comparing them for each tested material, it has been found that they, besides having the same shape, show abrupt slope variations at practically the identical value of stress. It has further been observed that a specimen presenting only a low percent variation of Ir/Is ratio (i.e., in which domains had slightly moved from their rest position) showed also moderate magneto-elastic losses. These results appear to confirm assumptions made about the magneto-elastic internal friction in ferromagnetic materials. The reason why motion of domains takes place in an essentially irreversible way still remains unknown.
On the Accuracy of the Long-Range Ballistic Rocket
Authors: Frye W. E.
Published: April 2005

The accuracy of a V-2 type ballistic rocket which is guided to the termination of propulsion and is in free flight thereafter is investigated. The effect of the rotation of the earth and the re-entry into the atmosphere on the accuracy is considered and the errors due to lack of thrust control are analyzed.
Electrode Reactions in the Glow Discharge
Authors: Haworth F. E.
Published: April 2005

The reactions which occur at silver electrodes in a normal glow discharge in air have been determined. These are: (1) formation of AgNO2 and some Ag2O at the anode at the rate of 3.4 μg/coulomb; (2) loss of metal from the cathode by chemical action at the rate of 3.5 μg/coulomb (probably the same reaction as (1) with subsequent loss of the reaction products by the greater heating of the cathode, but this hypothesis has not been established); and (3) normal sputtering loss at the cathode at the rate of 0.4 μg/coulomb. These processes result in building a conducting layer on the anode. If the electrode separation is so small that the anode extends into the region of the cathode fall, then the high electric field pulls the newly formed and not very coherent growth upon the anode across into a bridge between the electrodes.
Reflecting Surface to Simulate an Infinite Conducting Plane
Authors: Raff S. J.
Published: April 2005

In measuring small microwave reflections back to the transmitting antenna, a finite reflecting surface which simulates the reflection of an infinite plane is desirable for calibration. Treating a flat reflecting surface by the methods of physical optics, the reflection can be represented as the sum of the contributions of Fresnel zones. Owing to the slow rate of decrease of reflections from successive zones, the shape of the surface has considerable effect on the accuracy with which its reflection simulates that of an infinite plane.

By means of the calculus of variations, an optimum shape is designed which, for a given antenna pattern, reflector size, and range of antenna to reflector distances, will give the closest simulation of the reflection of an infinite plane. Such an optimum surface of 23 wavelengths extreme dimensions has been constructed for use at 25 wavelengths from a dipole antenna. The maximum simulation error was calculated to be ±3 percent. The reflection from this surface has been measured and is within ±4 percent of that of an infinite plane over the range of 15 to 35 wavelengths from the antenna.
Mechanical Properties of Substances of High Molecular Weight. X. The Relaxation Distribution Function in Polyisobutylene and Its Solutions
Authors: Ferry John D. , Fitzgerald Edwin R. , Johnson Myrle F. , Grandine Lester D.
Published: April 2005

Previous twin transducer measurements of the dynamic rigidity and viscosity of a polyisobutylene sample of viscosity-average molecular weight 1.2 million have been extended over a wider temperature range, and previous wave propagation data on solutions of this polymer in xylene have been extended by transducer measurements at lower concentrations. Values of the relaxation distribution function are derived from all these data and are compared with values obtained from stress relaxation measurements on solutions of the same polymer in Decalin, as well as stress relaxation data of Andrews and Tobolsky on solid polyisobutylene and dynamic measurements on butyl rubber from several sources. When reduced to a common reference state at 25°C by the assumption that all relaxation processes depend identically on temperature, the data for solid polyisobutylene provide a picture of the distribution function over eleven cycles of logarithmic time. It appears to have a plateau from 0.1 to 104 sec with a sharp rise at shorter times and a sharp drop at longer times. From 10−5 to 0.1 sec the functions for polyisobutylene and butyl rubber are similar in shape, the latter being somewhat higher. When data for polyisobutylene solutions from 5 to 25 percent concentration are reduced to the reference state of the solid polymer by the assumption that all relaxation processes depend identically on concentration, a single distribution function is obtained which from 10 to 106 sec is similar in shape to that derived from direct measurements on the solid polymer but lies somewhat below it.
Electron Plasma Oscillations
Authors: Wehner Gottfried
Published: April 2005

Electron plasma oscillations are excited by a beam of fast electrons in a stabilized low-pressure mercury discharge. Probe measurements reveal that the uhf fields are localized in thin layers, the plasma density and frequency of which follow Langmuir's law. The beam of fast electrons traversing such an oscillation layer becomes velocity modulated, and excitation conditions result from drift time and bunching considerations similar to those in a klystron. A sealed-off tube described covers a frequency range between 800 and 4000 Mc (five modes) without changing or matching any resonance circuit.
The Cascaded Binary Counter with Feedback
Authors: Montgomery G. Franklin
Published: April 2005

The count of a cascade of binary pulse counters having any arrangement of feedback connections can be calculated. The calculation is simplified for two special connection patterns. For a particular count, one or the other of these patterns, or a modification of the two, requires a least number of connections.
Initial Conditions in Linear Varying-Parameter Systems
Authors: Zadeh Lotfi A.
Published: April 2005

The problem considered in this paper is that of determining the response of an initially excited linear varying-parameter system to a given input. Mathematically, this problem reduces to solving a linear differential equation (with time-dependent coefficients) subject to prescribed initial conditions. It is shown that these conditions may be satisfied by superposing upon the given input a linear combination of delta-functions and treating the system as if it were initially at rest. Based on this fact and employing the concept of a system function, a general and yet simple expression for the response is developed. The result is similar in form to that obtained by the use of conventional laplace transformation techniques in the case of a linear differential equation with constant coefficients.
The Epitaxy of Alkali Chlorides on Metals
Authors: Johnson G. W.
Published: April 2005

The alkali chlorides were crystallized from solution on single crystals and on polycrystalline specimens of various metals. Oriented growth was obtained on Ag, Au, Cu, Zn, Pb, Sb, Bi, and Fe. Since oxide films were present on all metals except Ag and Au, it was concluded that the oxides were oriented with respect to the metallic substrate. From results with Ag and Au, it was found that the permissible misfit for epitaxy to occur was of the same order (∼10 percent) as for ionic pairs.
Applications of Polystyrene Particles in Conjunction with Shadow Casting to the Study of Polished Metallic Surfaces
Authors: Feng I-Ming
Published: April 2005

This is a report of a study of polished metallic surfaces with the electron microscope. Negative collodion replicas were used in this experiment. The determination of width and depth of scratches by means of polystyrene particles and shadow casting is briefly discussed. Experimental results are summarized as follows: The effect of polishing pressure applied is that greater pressure gives wider and deeper scratches and also causes severer flow and distortion of metal near the scratch. In comparison with unidirectional polishing, multidirectional polishing gives better surface finish with fewer scratches: these scratches run in all directions and have a wide range of width and depth; mostly they are shallower and narrower than would be the case with unidirectional polishing. The average widths and depths of scratches on surfaces polished with various conditions are also given here. Harder abrasives give a higher depth/width ratio.
Radiation Field of Helical Antennas with Sinusoidal Current
Authors: Kornhauser E. T.
Published: April 2005

A rigorous formula for the radiation field of a helical antenna is derived on the assumption of an empirical current distribution obtained experimentally by Kraus. For a helix of several turns this formula yields results very nearly the same as those obtained from an approximate method by Kraus, and it has the additional advantages of greater simplicity of computation and applicability to helices of nonintegral numbers of turns. It appears that this empirical current distribution is of a most fortuitous form, but no theoretical basis for it has yet been found.
Recovery of Selenium Rectifiers after a Voltage Pulse in the Blocking Direction
Authors: Lehovec K.
Published: April 2005

The capacitance of selenium rectifiers which have been subjected to a voltage pulse in the blocking direction is found to be temporarily decreased after the pulse has ceased. The recovery of the changed capacity to its original value is investigated as a function of pulse height, pulse duration, and temperature. The speed of the recovery can be greatly increased by illumination (through a transparent electrode) with light of the same spectral range which is effective in causing the photoeffect in selenium photovoltaic cells. This is an indication that the phenomenon is of electronic and not of ionic nature.

As an explanation it is proposed that an electric pulse in blocking direction removes electrons from elevated energy states in the electrode-selenium boundary. Recovery occurs because electrons are returned to the elevated energy states by thermal agitation and also by photoelectric effect if the selenium is illuminated.
Measurement of Carbon Diffusion in Metallic Carbides
Authors: Kuczynski G. C. , Landauer R.
Published: April 2005

A method for measuring the diffusion coefficient of carbon in metallic carbides is proposed. The rate at which excess metallic inclusions are consumed by carbon diffusing in from a surface is used to indicate the extent to which diffusion has taken place. Conditions are derived under which the results are susceptible to simple analytic treatment.
Arcing at Electrical Contacts on Closure. Part I. Dependence upon Surface Conditions and Circuit Parameters
Authors: Germer L. H.
Published: April 2005

In a low voltage circuit the occurrence of an arc between approaching electrodes is dependent upon the nature of the surfaces and upon the circuit inductance. For carbon surfaces, or noble metal surfaces which have been ``activated'' by operation in various organic vapors resulting in a carbonaceous layer, the limiting circuit inductance is somewhat above 10−3h, which is much higher than the limiting inductance for clean noble metal surfaces. This activation by organic vapors occurs for noble metals only and for certain vapors; for example, benzene derivatives. In the case of silver and benzene vapor, it has been shown that the activation is due to adsorption of benzene onto a greasy surface layer and its decomposition there by the heat of subsequent closures. A metal surface, which has been activated by organic vapor, remains active indefinitely if there is no arcing at the surfaces; but with continued operation and accompanying arcing, the activating material is burned away, and the surface returns to the inactive condition if no activating vapor is supplied.

Arc voltages, which are independent of current and of ambient gas, as far as tested, have been measured for a number of metals and for carbon; the arc voltage for carbon is quite erratic in the range between 20 and 30 volts, but for each of a number of metals the arc voltage is steady.

Arcing at noble metal surfaces, similar to that induced by carbonaceous material from organic vapors, can be produced also by insulating particles or insulating films. The active condition gradually disappears with continued arcing, unless there is a steady supply of insulating material to the surface.

The minimum arc current has been measured to be 0.6 amp for active silver and for carbon, and 0.03 amp for inactive silver. These are the currents at which an established arc is extinguished.
Pulse-Annealing for the Study of Relaxation Processes in Solids
Authors: Parkins W. E. , Dienes G. J. , Brown F. W.
Published: April 2005

A new experimental technique is presented for studying rate processes in solids. The method, termed ``pulse-annealing,'' involves direct heating of a very small sample to a chosen annealing temperature for a short period, followed by rapid cooling to some fixed temperature for an in-place physical property measurement. The method is a very flexible one, as the above cycle may be repeated to obtain any desired time-temperature history. General experimental techniques are described and specific application to graphite and metals noted.

The annealing process is examined theoretically. A method is described for deriving the activation energy of the fundamental relaxation process from the isothermal annealing curves of a physical property, the physical property being used as an index of the annealing process. It is shown that the activation energy is derivable without knowledge of the relation between the measured physical property and the fundamental kinetic variable. For further kinetic analysis (determination of rate constants and orders of reaction), however, it is necessary to know this relation. The analysis of isothermal and tempering experiments is compared.
Kinetics of Ordering in the Alloy AuCu
Authors: Dienes G. J.
Published: April 2005

The kinetics of ordering in AuCu has been studied using electrical resistivity as the index of order. A purely phenomenological analysis of isothermal resistivity-time curves showed that ordering in this alloy is a process characterized by a single constant activation energy of 29 kcal. For further kinetic analysis, it is necessary to transform the raw data into isothermal order parameter-time curves. This was accomplished via Muto's theoretical relation between resistivity and the Bragg-Williams order parameter, S. A consistent kinetic picture was obtained in terms of S, with the ordering process accurately described by a simple third-order rate equation with all the kinetic constants fully evaluated. The usual ln (rate constant) versus 1/T plot gave an activation energy of 28.5 kcal in excellent agreement with the phenomenological activation energy. Further experiments showed that the proposed kinetics predicts correctly the response to complex time temperature sequences.
Flow of Gases in Porous Media
Authors: Wilson L. H. , Sibbitt W. L. , Jakob M.
Published: April 2005

This paper presents a brief theoretical review of the viscous and free molecular flow phenomena. The equations which describe these two types of flow are applied to flow through porous media and are combined to yield a semi-empirical equation which may be used not only for the viscous and free molecular flow, but also for the transition region between these. Experimentally determined limiting values of the ratio of molecular mean free path to pore diameter are reported. These ratios may be used to indicate the nature of flow in a porous media provided the pore size is known, or they may be used to determine pore size experimentally.
Elastic Energy of an Ellipsoidal Inclusion in an Infinite Solid
Authors: Robinson Kenneth
Published: April 2005

An exact solution in closed form is presented for the displacements, stresses and total elastic energy for the problem of an ellipsoidal isotropic inclusion bonded to an isotropic body of infinite extent when the inclusion and the infinite solid have uniformly distributed changes in their stress-free specific volumes. The physically important details of the dependence of the total strain energy of the two materials upon the shape and volume of the inclusion, the elastic moduli of the two isotropic materials and the changes of specific volume, are included. The solution is indicated for the stresses and displacements for the case where the material at infinity is, in addition to the above condition, in a homogeneous state of stress whose principal directions are parallel to the axes of the cavity.
Air Condensation in Hypersonic Flow
Authors: Wegener P. , Reed S. , Stollenwerk E. , Lundquist G.
Published: April 2005

The NOL 12×12-cm hyperballistics wind tunnel No. 4, which operates in a Mach number range up to eleven, is briefly described. Experiments performed in this tunnel indicate that a fraction of the air condenses at or shortly after reaching the dew line for air condensation unless the supply air is preheated. The measured effects of air condensation on the flow at high Mach numbers for a variety of supply temperatures and pressures are given. It is found that of the flow parameters commonly measured in supersonic wind tunnels, only static-pressure and shock-angle measurements are sensitive to liquefaction effects. A simple thermodynamic analysis assuming a reversible condensation process allows interpretation of some of the observations.
Axially Symmetric Systems for Generating and Measuring Magnetic Fields. Part I
Authors: Garrett Milan Wayne
Published: April 2005

This is Part I of a systematic discussion of axially symmetric magnetic fields, both central and remote from the origin, search coils reporting the field or gradient at a single point, and mutual inductances. Here the central uniformity of symmetrical fields and gradients is analyzed by zonal harmonic expansion. Laplace's equation and symmetry restrict these fields to a few types, regardless of the detailed geometry of the generating system. Universal error-contour maps are derived for the central field or gradient in systems having errors of second, fourth, or sixth order, and for hybrid types combining second and fourth. One hybrid has an oblate error field suitable for cloud-chamber and orbital applications.

Source systems include circular filaments, cylindrical or plane circular current sheets, and thick solenoids of rectangular or notched section. Each type of source may be designed to produce any of the field patterns. To this end, source constants derived for the particular source type are combined into a set of over-all coefficients that express the field constants for a complete system. Rapid methods are given for computing the source constants and from them all the field derivatives, using recurrence relations or tables of Legendre functions. In particular, computing time for thick-solenoid fields or gradients is greatly reduced, using a new series with a recurrence formula. The text includes tabular aids and reference formulas, and discusses the rate of convergence of series for central and remote fields, and for mutual inductances.

Special systems briefly described include several infinite series of systems like that which starts with Ampere's loop, the Helm-holtz pair, and Maxwell's three-loop system. These have integral numbers of circular filaments from two to infinity. More practical are the thin solenoids. Those that produce a fourth-order (Helm-holtz) field by omission of central turns are fully tabulated for all lengths. A short solenoid with double-wound ends and sixth-order error may realize greater uniformity in actual practice than any previously described system. Still greater (theoretical) uniformity is achieved in two eighth-order combinations of a short solenoid with a loop pair; these are described and depicted, with error limits.
The Offset Wave-Guide Junction as a Reactive Element
Authors: Smullin L. D. , Glass W. G.
Published: April 2005

A new type of wave-guide circuit element has been described that has a number of desirable electrical and mechanical properties. These include ease and accuracy of adjustment, and simple analytical expressions for some of the more important properties.

The capacitive junction allows the practical construction of capacitively coupled resonant cavities. Such cavities have a relatively constant band width over their tuning range, as compared with the more commonly used inductively coupled cavities.
X-Ray Absorption in a Crystal Set at the Bragg Angle
Authors: Campbell H. N.
Published: April 2005

Whereas extinction effects would be expected to decrease the x-ray transmission through a crystal when it is set at a reflecting angle, it is shown experimentally that in many cases the transmission increases at the Bragg angle.

This is believed to be due to the fact that the decrease in the effective absorption coefficient overshadows the losses due to reflection.

A reconsideration of Darwin's presentation of extinction allowing for variable μ shows that the transmission may increase or decrease depending on the values of μ and p. Thus the earlier observations of Bragg and co-workers are reconciled with the observations reported here.

The importance, to crystal structure workers, of determining how μ varies with direction in periodic media is obvious.
Emission of Radiation from Diatomic Gases. II. Experimental Determination of Effective Average Absorption Coefficients of CO
Authors: Penner S. S. , Weber D.
Published: April 2005

Empirical evidence obtained for CO at room temperature, which supports the use of average absorption coefficients for entire vibration-rotation bands, is examined. In Sec. II the existence of an average apparent absorption coefficient for data obtained with inadequate spectral resolution is demonstrated. In Sec. III semiquantitative evidence at elevated total pressures and small optical densities for the use of a constant absorption coefficient equal to the ratio of integrated absorption to effective band width is described. These results serve as direct support for a proposed simplified method for radiant-heat-transfer calculations.
The Evaporation Products of Barium Oxide from Various Base Metals and of Strontium Oxide from Platinum
Authors: Aldrich L. T.
Published: April 2005

The evaporation products of BaO heated on ribbon filaments of Pt, Ta, Ni, Mo, and W, and of SrO on Pt have been studied using a high resolution mass spectrometer for positive ion analyses. The ratio Ba+/BaO+, was measured for each base material as a function of temperature and of the energy of the ionizing electrons to determine the origin of each ion peak observed. The results indicate: (a) Only on systems BaO on Pt and BaO on Ni, and SrO on Pt were the evaporation processes reproducible without particular attention to procedure. (b) The two systems BaO on Pt and SrO on Pt differ markedly in their evaporation mechanisms. (c) At high temperatures peaks are found due to Ba2O++, Ba2O+, Ba2O2+, and other barium compounds depending on the base metals used. (d) A measurable ion current was found due to Sr+ ions evaporated from Pt.
Thermal and Shot Fluctuations in Electrical Conductors and Vacuum Tubes
Authors: Solomon Salim S.
Published: April 2005

A new derivation of Nyquist's equation, relative to the amount of thermal fluctuations generated in an electrical conductor, is presented. A generalization of the new proof to include any arbitrary impedance function shows that the original equation as derived by Nyquist is valid only for physically realizable impedances of the minimum reactance type. This is followed by a new and short derivation of the shot noise formula for temperature limited diodes.
An Experimental Investigation of the Dielectric Rod Antenna of Circular Cross Section Excited in Rotationally Symmetrical Modes
Authors: McKinney C. M.
Published: April 2005

The radiation patterns were measured for three series of dielectric rod antennas of circular cross section excited in the TM01 mode at a frequency of 9275 mcps. Only one parameter was changed in each series of rods so that the effect of this parameter on the pattern could be studied. Dielectric antennas excited in the TM01 mode have a null in the radiation pattern in the forward direction. It was found that maximum attenuation of secondary lobes was obtained using large diameter rods but sharper and deeper central nulls were obtained with small diameter rods. It was also noted that the deepest central null was obtained using a rod of uniform cross section. For uniformly tapered rods of various lengths, the maximum secondary lobe attenuation as well as the sharpest and deepest central null was obtained using the longest rod. The radiation patterns of the antennas excited in the TE01 mode were of the same nature as those obtained using the TM01 mode. Measurements were made also of the electric field strength on the surfaces of the radiating rods and these measurements were correlated with the radiation patterns.
Phenomena Associated with the Flight of Ultra-Speed Pellets. Part I. Ballistics
Authors: Allen William A. , Rinehart John S. , White W. C.
Published: April 2005

Small metallic pellets have been fired at velocities up to 6 km/sec by means of modified shaped charges. Previous work in this field has been confined largely to observations of meteors and conventional shaped charges. Data obtained on ballistic phenomena verify the conventional drag force determinations extrapolated to large Mach numbers. Steel pellets at velocities of 2.5 km/sec lose little mass in flight. Pellets composed of lighter metals, such as aluminum at a velocity of 5 km/sec, burn vigorously with the emission of much light and heat. It has been found that the motion of both nonburning and burning pellets can be represented within experimental error by the empirical equation v=v0e−αs,where v0 is the initial velocity of the pellet, v is its velocity after it has traveled a distance s through the air, and α is a constant.
Direct Determination of the Flow Curves of Non-Newtonian Fluids
Authors: Krieger Irvin M. , Maron Samuel H.
Published: April 2005

A method is proposed for the direct determination of the rate of shear-shearing stress curve of a fluid from data obtained in concentric cylinder viscometers. The method involves the use of a viscometer in which the ratio of outer to inner cylinder radii can be varied. It is further shown that to a close approximation two such radius ratios are sufficient to define the flow curve.

Data for two non-Newtonian systems are presented to show that the proposed method is valid.
The Structure of Sputtered Silver Films
Authors: Ells C. E. , Scott G. D.
Published: April 2005

The electron microscope has been used to study the structure of sputtered silver films. When compared with evaporated silver films which are prepared at the same rate, the sputtered films are observed to have a more continuous structure. When compared with evaporated silver films which are produced at much faster rates, the sputtered films exhibit a crossover phenomenon in which the thinner films are the more continuous and the thicker films less continuous than evaporated films of the same thickness. These properties are in agreement with resistivity measurements. A possible explanation for the results is proposed.
Determination of Field Strength in a Linear Accelerator Cavity
Authors: Maier L. C. , Slater J. C.
Published: April 2005

One theoretical and two experimental methods are described for finding the accelerating field in the M.I.T. linear accelerator cavity, in terms of the input power. One of the experimental methods is based on measuring the power leaking out through a calibrated hole in an end wall closing the cavity, the hole being located where the field strength is to be determined. The other method is based on the perturbation of the resonant frequency of the cavity by a small conducting sphere located on the axis. All three methods of determination check satisfactorily. In terms of the resulting relations, we discuss the probable field actually existing in the accelerator under operating conditions.
Forced Thickness-Shear and Flexural Vibrations of Piezoelectric Crystal Plates
Authors: Mindlin Raymond D.
Published: April 2005

An approximate theory is given for the vibrations of piezoelectric crystal plates in thickness-shear and flexural modes, including the interaction between the elastic and electric fields. The problem of the rectangular, AT, quartz plate is solved and computed frequencies are compared with measurements by Sykes. Algebraic formulas are obtained relating resonant frequencies with dimensions, elastic and electric constants, and orientation of cut.
The Thermal Dependence of the Elastic Moduli of Polycrystalline Graphite
Authors: Faris F. E. , Green L. , Smith C. A.
Published: April 2005

Young's modulus and the shear modulus of grade SA-25 molded graphite and grade AUF extruded graphite were measured as functions of temperature in the range from 25°C to 2000°C. In the case of the extruded material, variations of the two moduli with position and direction relative to the axis of extrusion were also investigated. The moduli were found to increase with temperature, a behavior in contrast with that exhibited by most materials. Maxima in the low frequency shear modulus values and increases in the internal friction of both graphites observed in the range from 1550–1750°C may possibly be interpreted in terms of grain boundary relaxation. The bulk modulus and Poisson's ratio at room temperature were calculated from the data for the nominally isotropic SA-25 graphite to be 6×1010 dynes/cm2 and 0.27, respectively.
The Temperature Dependence of Viscosity for Water and Mercury
Authors: Kampmeyer Preston M.
Published: April 2005

Smoothed values for the viscosities of water and mercury, as reported in the literature, show surprisingly large percentage deviations from the experimental data. Because water is frequently used as the calibrating fluid in viscometry, it was of interest to apply expressions, suggested by the theory of Eyring, for smoothing experimental data. It was of further interest to apply the Arrhenius expression for the variation of viscosity with temperature to the data for both water and mercury and to compare the closeness of fit with that obtained by the use of the aforementioned expressions. As judged by the Gaussian criterion of fit, an expression suggested by the Eyring theory provides smoothed values for the viscosities of both water and mercury which are believed to be more reliable than those in common use. This is especially true for the viscosity of water, for which relative viscosity data were first smoothed and then pinned to the recent value of 10.019±0.003 millipoises at 20°C as reported by Swindells and Coe.

From other empirical equations relating densities and energies of vaporization to temperature, equations are derived for expressing the activation energies for viscous flow as a function of temperature.
On the Use of the Joule-Thomson Effect to Measure the Work Equivalent of Heat. Thermodynamic Theory
Authors: Roebuck John R.
Published: April 2005

The Joule-Thomson porous plug experiment is described, its quantitative aspects indicated, and the constant enthalpy condition set up. The experimental plan for the proposed measurement is described and a short analysis of the physical situation in the fluid given. The standard equation for the Joule-Thomson coefficient is applied to the situation and details are given of how this equation may be integrated for two special physical situations. The information necessary for these integrations is discussed and physical means described for obtaining it. A numerical integration may be used for obtaining the work equivalent of heat (J) with a high precision corresponding to the high precision with which these various data may be measured.
Electrical Conductivity and Thermoelectric Power of (BaSr)O and BaO
Authors: Young J. R.
Published: April 2005

A study has been made of the thermoelectric power, the electrical conductivity, and the thermionic emission of (BaSr)O and BaO at different states of activation and on different base metals over a temperature range of 1100°K to 300°K. A plot of the logarithm of the conductivity vs reciprocal temperature showed two straight line regions. The temperature dependence of the thermionic emission was found to be the same as the temperature dependence of the conductivity in the temperature range 700°K to 1100°K. The slope of a plot of the thermoelectric power vs reciprocal temperature was also similar to the thermionic work function and the conductivity activation energy in this temperature range.

The thermoelectric power varied with temperature from a value of about 2.0 mv/° at 1100°K, increasing to about 2.5 mv/° at 800°K, reducing to between 1.0 and 0.5 mv/° at about 500°K, and remaining practically constant or increasing slowly at still lower temperatures. In all thermoelectric power measurements the hot junction was positive indicating negative charge carriers.

The simple semiconductor theory does not adequately account for these results which seem to be in good agreement with the pore conduction hypothesis.