bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies in Newtonian Flow. I. The Dependence of the Viscosity of Liquids on Temperature
Authors: Doolittle Arthur K.
Published: April 2005

It is shown that the Walther and Andrade equations, while very satisfactory for moderate ranges of temperature, are not adequate to define the dependence of the viscosity of liquid normal paraffins on temperature over extended ranges. One method of developing a viscosity-temperature relationship is presented that gives equations defining this dependence with satisfactory validity. The purpose of this paper is to show that the precise dependence of the viscosity of liquids on temperature is complicated. This is in contrast to the relatively simple relation for the precise dependence of the viscosity of liquids on free-space which will be presented in subsequent papers.
The One-Sided Green's Function
Authors: Miller Kenneth S.
Published: April 2005

Let L be a linear differential operator of the nth order whose coefficients pi(x) are continuous in a semi-infinite interval I: [a, ∞). A function H(x, ζ) is said to be a one-sided Green's function for the operator L if it satisfies the four conditions: (1) H is continuous and its first n derivatives with respect to x are continuous in I. (2) Hα(ζ, ζ)=0 for α=0, 1, …, n−2. (3) Hn−1(ζ, ζ)=1/p0(ζ). (4) LH=0. (The subscript on the H refers to partial differentiation with respect to the first argument, and p0(x) is the coefficient of dn/dxn in the expression for L.) It is shown that H is unique and if u(x)=∫ax H(x, ζ)f(ζ)dζ, then Lu=f(x) and u(α)(a)=0, α=0, 1, …, n−1. Furthermore, if H is given, a fundamental system of solutions of Lu=0 can be written down explicitly in terms of H and its derivatives evaluated at the end point a. The converse problem is trivial. Other properties of H are also considered, for example, its relation to the impulsive response of a network.
The Impedance of an Antenna over a Large Circular Screen
Authors: Storer James E.
Published: April 2005

In the performance of antenna measurements the antenna is usually placed over a large conducting screen. The assumption is then made that the measurements are in close agreement with those that would be obtained if the screen were of infinite size. Recent experimental work, however, indicates that the finiteness of the ground screen may influence the measurements to a considerable extent.

It is therefore desirable to solve this problem theoretically in order to determine the extent of the change introduced by the use of a finite screen. This paper treats the problem of an antenna erected vertically in the center of a circular screen. An integral equation is obtained for the electric field in the plane of the screen, outside the screen. This equation is solved approximately by the use of a variational principle, and a formula is obtained for the change of antenna impedance as a function of the diameter of the screen. The formula may be used to give a simple and accurate estimate of the changes introduced by the use of a finite screen.
Microwave Filters Employing a Single Cavity Excited in More than One Mode
Authors: Lin Wei-guan
Published: April 2005

A cavity resonator with input and output couplings represents a two-terminal-pair network with an infinite number of natural modes of oscillation. In some cavities of special shape, a number of degenerate modes with identical natural frequencies can be found. In a single cavity, various numbers of these degenerate modes can be coupled together to form a chain of coupled circuits by perturbing the otherwise ideal geometrical configuration of the cavity. The filter behavior is prescribed, and the two-terminal-pair network realizing this is obtained by a process of synthesis.
On the Stress-Function Approaches of Boussinesq and Timpe to the Axisymmetric Problem of Elasticity Theory
Authors: Sternberg E. , Eubanks R. A. , Sadowsky M. A.
Published: April 2005

In the first part of this note the stress-function approaches of Boussinesq and Timpe to the rotationally symmetric problem in the classical theory of elasticity are referred to general orthogonal axisymmetric curvilinear co-ordinates. Although the underlying computations are of a routine character, it is felt that the presentation of the final results may serve a useful purpose. In the second part of the note, a connection between the two stress-function approaches is established.
Mathematical Data for Electron Drain on Positive Ion Sources
Authors: Rauch S. E.
Published: April 2005

A study of the motion of electrons moving in the presence of crossed electric and magnetic fields is presented. Special electromagnetic regions are selected for discussion which assist in the controlling of electron discharge on positive ion sources when used with large mass-spectrograph units. The article compares the components of motion parallel and perpendicular to the magnetic field in the following regions: uniform crossed electric and magnetic fields; electric field produced by nonparallel plane condenser plates, uniform H parallel to one plate; electric field produced by coaxial circular cylindrical condensers, uniform magnetic field normal to axis of cylinders; uniform electric field, circularly bowed magnetic field. The components of motion are expressed in terms of mathematical functions, and where it is deemed useful, additional results are presented in graphical form so that the conclusions can be applied with a minimum of calculations.
Arcing at Electrical Contacts on Closure. Part II. The Initiation of an Arc
Authors: Germer L. H.
Published: April 2005

The capacity of the plates of an oscilloscope charged to 35 or 40 volts is discharged repeatedly by approaching electrodes of carbon, active silver, and inactive silver. Facts about the discharges, which are arcs of very short duration, are inferred from resulting open circuit potentials and calculated electrode separations.

The separation at the first arc varies in different experiments but corresponds on the average to a nominal electric field of 0.6×106 volts/cm for carbon or active silver and to 2×106 volts/cm for inactive silver. Each arc is initiated by a very small number of field emission electrons. The hypothesis that a single electron may perhaps be sufficient is consistent with observations at later stages of each closure when the electrodes are closer and the field much higher.

The earlier observation, that the potential across a short arc is constant and independent of current, is not true if the arc time is sufficiently short. For active silver a time comparable with 2×10−8 sec is required to establish the steady arc voltage characteristic of later stages of arcs which last longer than this. The initial time during which the potential is decreasing toward its final steady value is 100 times the transit time of a silver ion across the gap.
On the Theory of Random Noise. Phenomenological Models. II
Authors: Middleton David
Published: April 2005

Part II is devoted to the detailed evaluation of the first and second (second-order) moments, namely, average values and the cross- and autocorrelation functions for stationary random noise waves for models I–III, whose statistical description is given in Part I. From these in turn are determined the cross- and auto-spectral intensities governing the distribution of energy in the random disturbances. Finally, the asymptotically normal distributions characteristic of the high density poisson noise (III) are evaluated, together with higher order correction terms and their associated characteristic functions.
Electrical Charge Storage in Polystyrene Capacitors
Authors: Matheson L. A. , Caldecourt V. J.
Published: April 2005

Measurements on charge storage in polystyrene capacitors over a period of months indicate that exceptionally fine capacitors may be made of polystyrene film when sufficient care is taken. Very small charge ``soakage'' occurs in such a capacitor, and charges may be retained for times of the order of one hundred years and possibly longer. The specific resistance approaches 1022 ohm cm when measured over a period of months. The power factor of polystyrene is about 10−4 for frequencies of 10−1 to 10−6 cycle per sec with a tendency to increase at the lowest frequencies and with a possible peak at still lower frequencies. The difference between charge soakage during charging and the charge recovery after shorting indicates some nonreversible current flow when measurements are made over several months' time.
Some Experimental Indications of the Stresses Produced in a Body by an Exploding Charge
Authors: Rinehart John S.
Published: April 2005

The effects produced by small cylindrical charges that were detonated on the surfaces of heavy steel plates are discussed. Particular attention is paid to (a) shapes of crater, (b) changes in hardness, (c) flow patterns, (d) fractures, and (e) changes in microstructure. The distribution of stress appears in some respects to correspond to that which might be set up by a static load. The mechanisms of the inelastic deformation, however, differ very greatly between the static case and the dynamic case. Dynamic loading produces numerous shock twins and fractures that undoubtedly occur because of the very high strain rates involved.
The Generation and Measurement of Low Frequency Random Noise
Authors: Bennett R. R. , Fulton A. S.
Published: April 2005

Judgment of the performance of automatic control systems often involves a consideration of the behavior of such systems in the presence of random noise. The noise may be of an undesirable nature, such as receiver noise, or it may represent an ensemble of statistical inputs which the system is to follow. Analytical techniques exist for determining the response of linear systems to noise inputs. However, no general methods are available for analyzing nonlinear systems subject to noise inputs. An electric analog computer, together with a suitable source of noise, may be used to study nonlinear systems. This paper describes an electronic noise generator designed for analog computer or simulator use. Methods are discussed for measuring the important characteristics of low frequency noise, such as the mean value, spectral density, amplitude distribution, and autocorrelation. Particular attention is devoted to the length of time necessary to establish satisfactory estimates of the properties of low frequency noise.
Enhanced Emission from Magnetron Cathodes
Authors: Jepsen Robert L. , Muller Marcel W.
Published: April 2005

Existing theories of the static magnetron do not predict violation of the Hull cut-off condition or cathode bombardment. Measurements made at anode voltages and magnetic fields much larger than those used by earlier investigators revealed violations of the Hull cut-off condition considerably more pronounced than those previously reported, and much greater amounts of cathode bombardment. When sufficient cathode bombardment takes place, emission may be enhanced (through secondary emission) by a factor of ∼103 over the thermionic value. When enhanced emission occurs in magnetrons employing pure metal cathodes, it is found that maximum current limits exist for each magnetic field. These limits form a maximum current boundary on a voltage-current plot. The maximum current boundary depends on secondary emission properties of the cathode surface and on geometry. Experimental observations on enhanced emission, cathode bombardment, the maximum current boundary, and flow of anode current in violation of the Hull cut-off condition are combined into a self-consistent picture in static magnetrons employing pure metal cathodes. Although cathode bombardment and flow of anode current are still unexplained, their existence can account for the observed enhanced emission and maximum current boundary. In this it is unnecessary to endow the cathodes with anomalous thermionic or secondary emission properties.

The process causing cathode bombardment, enhanced emission, and flow of anode current in violation of the Hull cut-off condition is believed to be an electronic interaction which occurs almost entirely in the relatively dense region of space charge surrounding the cathode. The significant factors influencing the interaction appear to be applied electric and magnetic fields, space charge density, and thickness of the space charge sheath. The basic problem of electronic interaction in the static magnetron is partially defined. It is expected that when a realistic solution to this problem exists, including a correct account of cathode bombardment, the occurrence of enhanced emission would be automatically predicted.
The Power Spectrum of a Narrow Band Noise Passed through a Nonlinear Impedance Element
Authors: McLucas John L. , Raymond Richard C.
Published: April 2005

The power spectrum of the current flowing through a nonlinear impedance element excited by a narrow band of noise centered at 1.6 mc has been measured experimentally from the audio range through the sixth harmonic band. A noise having the spectral shape of an error function with a standard deviation of 3.8 kc was generated by passing the current from a photomultiplier tube through several tuned amplifier stages. The noise was applied through an attenuator of 50 ohms characteristic impedance to a type 1N34 crystal diode. The current flowing in the diode passed through attenuators of 50 ohms characteristic impedance to the spectrum analyzer. In the audio range, a conventional wave analyzer was used, and in the remaining ranges, a calibrated radio receiver was used to measure the spectral distribution of output power. The results are in qualitative agreement with the theory of Middleton. A possible reason for the poor agreement is the difficulty of expressing the diode characteristic in a simple form for the computations.
The Spectral Emissivity of Iron-Nickel Alloys
Authors: Wahlin H. B. , Zentner Robert , Martin James
Published: April 2005

The spectral emissivity for λ=6700A has been determined for Fe-Ni alloys and shows changes with temperature which indicate that in the temperature range of 1200°K to 1600°K abnormal behaviors exist which hitherto have not been suspected. A correlation of emissivity change with change in density of metals is suggested.
Heat Transfer in Isotropic Turbulence
Authors: Corrsin Stanley
Published: April 2005

The postulated problem of heat transfer in a stationary isotropic turbulence under constant small temperature gradient is examined from both Lagrangian and Eulerian points of view. By combination of Taylor's ``diffusion by continuous movements'' and a new temperature fluctuation equation somewhat like the wellknown turbulent energy equation, it is possible to obtain (1) an expression for the turbulent heat transfer coefficient which depends only on velocity field, and (2) an approximate expression for the corresponding correlation coefficient which depends only on velocity field and fluid physical properties.

A preliminary result is given for ``turbulent Prandtl Number'' in a homogeneous shear flow in terms of the shear and heat transfer correlation coefficients.
X-Ray Measurement of Order in CuPt
Authors: Walker C. B.
Published: April 2005

In investigating the order-disorder transformation in CuPt, cell parameters were determined from specimens quenched at intervals from 25°C to 890°C. The rhombohedral deformation of the ordered, layered structure was found to diminish with increasing temperature, disappearing at a critical temperature of 815°C. Integrated intensity measurements of superstructure reflections from quenched powder and briquette samples determined that the long range order, S, decreases slowly with increasing temperature to a value of 0.77 at Tc, where it changes abruptly to zero, with the transformation below Tc being homogeneous. A simple theory is developed relating the rhombohedral deformation to S. Cold working an ordered sample was found to transform the alloy almost completely from the ordered rhombohedral cell to the disordered cubic cell. From measurements of diffuse intensities diffracted by briquettes above Tc, Fourier transform methods determined parameters which fixed the local order as being local layering configurations, in contrast to the usual A-likes-B type of order.
A Note on Critical Reflections of Elastic Waves at Free Surfaces
Authors: Goodier J. N. , Bishop R. E. D.
Published: April 2005

The wave motion in an elastic solid given by the theory of reflection at a free surface is evanescent for certain conditions—a P (plane irrotational) wave at grazing incidence and also an SV (plane equivoluminal) wave at grazing incidence. It is shown that by the application of suitable limiting processes wave motions can be obtained for these critical circumstances. The relation of these motions to the noncritical motions is analogous to the relation of critically damped to noncritically damped vibrations.
Steady-State One-Dimensional Flow in Rocket Motors
Authors: Price E. W.
Published: April 2005

Solutions are presented for the problem of gas flow in a solid propellant rocket motor using combined numerical and graphical methods. The character of the problem, sources of information, and method of solution are described, and solutions for the case of JPN ballistite propellant are presented. These solutions give the equilibrium distributions of pressure, density, velocity, and temperature of the gas stream and burning rate of the solid propellant as functions of two characteristic parameters β and J. These parameters are descriptive of the charge geometry and flow channel geometry, respectively. The solutions cover the entire range of nozzle, charge-size combinations, including the case of no nozzle.
The Collapse and Rebound of a Gas Bubble
Authors: Trilling Leon
Published: April 2005

The velocity and pressure field in a slightly compressible liquid resulting from the collapse of a spherical bubble is computed as a function of the pressure at the bubble wall, using the acoustic approximation. The results are accurate as long as the liquid velocities are small compared to the sonic velocity in the liquid; they agree with the results previously obtained by C. Herring.

The following bubble model is then investigated. The bubble is supposed filled with inviscid perfect non-conducting gas; special emphasis is given to the gas motion which involves a series of shock waves. A fraction of the energy of compression is thus degraded so that the radius of the bubble after the first rebound is somewhat less than the original radius. The pressure variation at the bubble wall is virtually the same as if the gas were compressed uniformly and isentropically.
On the Empirical Law of Adhesive Wear
Authors: Burwell J. T. , Strang C. D.
Published: April 2005

Careful measurements have been made of the wear of rubbing steel surfaces as a function of load, distance of travel, and hardness under controlled conditions which eliminated the effect of all factors except adhesion. At normal pressures averaged over the apparent contact area which are less than one third the hardness of the softer material the amount of wear was found to depend linearly on the distance of travel and on the load but was independent of the apparent area of contact. At average pressures greater than one third of the hardness, the depth of wear varied linearly with the distance of travel, was independent of the apparent area of contact for a given average normal stress, but increased many fold for small increases in stress. These findings rationalize the familiar observations on the running-in of machine surfaces. The results are discussed in the light of the current adhesion theory of dry friction.
A Vertical Shaft for the Production of Thick Artificial Clouds and for the Study of Precipitation Mechanics
Authors: Gunn Ross
Published: April 2005

Progress in cloud physics has been seriously limited because of the impossibility of conducting controlled cloud experiments on a sufficiently large scale. To meet the requirements, a laboratory has been built in which thick artificial expansion type clouds may be produced under controlled and measurable conditions.

A mine shaft 0.210 kilometer deep and 2.2×2.2 meters in cross section has been sealed and adapted to the production of thick artificial clouds. The shaft and its principal auxiliaries necessary for the study of some of the basic problems of clouds and precipitation are described. Dense, thick clouds completely filling the shaft are now being produced on a routine basis. Some preliminary illustrative data are presented.
The Supersaturation of Nitrogen in a Hypersonic Wind Tunnel
Authors: Faro I. , Small T. R. , Hill F. K.
Published: April 2005

Tests in a small hypersonic wind tunnel have determined critical temperature and pressure conditions for the condensation of pure dry nitrogen and have indicated that in the range of pressure (0.5–2.8 mm Hg) and temperature (52°–64°R) obtained in the tests, there is a supersaturation of about 30 Fahrenheit degrees.
Investigation of Stress-Strain Relations of Metal Wires by Electrical Resistance Changes
Authors: Vigness Irwin
Published: April 2005

A method is described by which the stress-strain curve of a wire tensile specimen can be derived from measurements of its changes of electrical resistance as a function of strain. The method can be applied only to a selected group of metals that have experimentally been shown to be suitable. A material is suitable when its resistance changes per unit of elastic and per unit of plastic strain are each constant and different from each other. The method assumes uniform strain throughout the length of the specimen, which limits conditions studied to those prior to necking. Examples are shown illustrating the linear resistance-strain relations and the applications of the method for several suitable materials. The resistance-strain characteristics of several materials that are not suitable are given, together with a statement of some mechanisms responsible.
The M.I.T. Linear Electron Accelerator
Authors: Demos P. T. , Kip A. F. , Slater J. C.
Published: April 2005

The M.I.T. linear electron accelerator consists of a circular wave guide fitted with uniformly spaced irises, and sustains a standing-wave, transverse magnetic π-mode oscillation at a resonant frequency of 2800 Mc/sec. The phase velocity is equal to the velocity of light. Electrons are injected into the accelerating tube at an energy of 2 Mev by a standard Van de Graaff generator. Acceleration up to an energy of at least 18 Mev has been obtained, using the 21-foot length of the accelerator. Peak accelerated currents of the order of 10 ma, and average currents of the order of 1 μa, are obtained. The accelerator is fed by 21 tunable magnetrons (Raytheon RK5586), phased in synchronism. In this paper, the principles of design, constructional features, and operation are discussed. The accelerator is now being used for nuclear experimentation.
Particle Dynamics in the Linear Accelerator
Authors: Terrall J. R. , Slater J. C.
Published: April 2005

Hamilton's equations for the motion of an electron in a linear accelerator are integrated to find the final kinetic energy and phase of an electron injected with arbitrary initial kinetic energy and phase, after traveling down a fixed length of accelerator. The results are expressed in the form of a map of the initial energy-phase space onto a final energy-phase space. This map proves in practice to be very convenient for discussing the actual operation of the accelerator. The curves presented are calculated for numerical values appropriate for the M.I.T. accelerator.
Mass-Spectrographic Study of Ionic Reactions in Hydrogen
Authors: Murray Raymond L.
Published: April 2005

An analysis of the ratios of the di- and tri-atomic ions of hydrogen, deuterium, and H—D mixtures obtained from a hot-cathode arc discharge in a magnetic field was used to examine the nature of ionic collision and displacement processes. Ion mobility, and consequently the rate of ion-molecule collisions, at constant pressure, were controlled by varying the intensity of the magnetic field. Statistical treatment of mass spectrograph data indicates that the formation of H3+ is due to the reaction H2++H2→H3++Hand that the ion rather than the molecule undergoes dissociation on collision.
A Nonsteady Heat Diffusion Problem with Spherical Symmetry
Authors: Plesset M. S. , Zwick S. A.
Published: April 2005

A solution in successive approximations is presented for the heat diffusion across a spherical boundary with radial motion. The approximation procedure converges rapidly provided the temperature variations are appreciable only in a thin layer adjacent to the spherical boundary. An explicit solution for the temperature field is given in the zero order when the temperature at infinity and the temperature gradient at the spherical boundary are specified. The first-order correction for the temperature field may also be found. It may be noted that the requirements for rapid convergence of the approximate solution are satisfied for the particular problem of the growth or collapse of a spherical vapor bubble in a liquid when the translational motion of the bubble is neglected.
The Condensation of Nitrogen in a Hypersonic Nozzle
Authors: Willmarth W. W. , Nagamatsu H. T.
Published: April 2005

A small, stainless steel, two-dimensional source flow nozzle supplied with bottled nitrogen was used for the condensation investigation. It was found that the nitrogen supersaturates approximately 15°K or 1.2 Mach numbers when expanded from stagnation conditions of 70°F and pressures of 8.21 and 16.15 atmos. A numerical method for solving the equations of motion with the aid of the experimental data allows the computation of the fluid temperature during the condensation process. The addition of small amounts of carbon dioxide reduced the degree of supersaturation obtainable with bottled nitrogen.
Effect of Internal Strains on Linear Expansion, X-Ray Lattice Constant, and Density of Crystals
Authors: Miller P. H. , Russell B. R.
Published: April 2005

General formulas are derived for the shift in x-ray diffraction maxima due to small distortions in simple cubic crystals. The special case of radial distortions due to lattice defects is considered in detail; it is found that the relative change in lattice constant computed from the shift in diffraction maxima is of the order of magnitude of the defect concentration and larger by as much as 100 percent than the linear expansion when the concentration of defects is of the order of one percent or less. A comparison is made of lattice constant, linear expansion, and density expected in crystals containing Frenkel defects, Schottky defects, or F centers.
Bonding of Thin Films
Authors: Meissner H. P. , Byrne J.
Published: April 2005

Unsupported films of nitrocellulose of 0.25 micron and less in thickness bonded immediately and spontaneously in air to solid surfaces which they were made to touch. Bond strength increased with diminishing film thickness. Similar behavior was shown by films of gold, regenerated cellulose, polymethyl methacrylate, and gelatin. This bonding power of nitrocellulose films, which was apparently not attributable to static electricity or to mechanical joint formation, was lost while immersed in water, benzene, or hexane, but was regained upon removal and drying.
Theory of Electrically Short Transmitting and Receiving Antennas
Authors: King Ronold
Published: April 2005

Complete and quantitatively accurate solutions of the properties of electrically short transmitting and receiving antennas (of length 2h such that 2πh/λ0≦1) are obtained by determining the distributions of current that actually satisfy the integral equations. Components of current in phase and in phase-quadrature with the driving voltage or the incident electric field are evaluated together with the impedance, the effective length, and the gain. It is shown that when the King-Middleton method of solving Hallén's integral equation by iteration is applied correctly, quite accurate results are obtained even in a first-order solution. The greatest error in the first-order formulas is shown to be in the resistance, a small quantity of higher order compared with the reactance. The newly determined values are combined with the King-Middleton second-order results to obtain more complete and more accurate impedances and effective lengths in the range of 0≦2πh/λ≦1.4.
Mechanism for Self-Diffusion in Graphite
Authors: Dienes G. J.
Published: April 2005

The mechanism for self-diffusion in single crystals of graphite has been examined theoretically. Calculations for vacancy and direct interchange mechanisms are based on atomic interactions within the graphite hexagonal layers. These interactions are obtained from the known systematic change of carbon-carbon bond strength with interatomic distance. In order to be able to calculate the energy of formation of an interstitial carbon atom, a potential function has been devised to account for interaction between the planes. This potential function consists of two terms, a van der Waals' attraction and an exponential type repulsion. The adjustable constants have been evaluated from known physical data. The interplanar cohesive energy of graphite is calculated to be 4.36 kcal/mole.

Comparison of the total activation energies for self-diffusion via vacancies, direct interchange, and interstitial atoms indicates that direct interchange is the preferred mechanism. The activation energy for self-diffusion by means of direct interchange is estimated to be 90 kcal/mole. The present theoretical treatment is not applicable to diffusion along grain boundaries or pores.
Studies of Self-Diffusion in Graphite Using C-14 Tracer
Authors: Feldman M. H. , Goeddel W. V. , Dienes G. J. , Gossen W.
Published: April 2005

Self-diffusion in graphite was measured over the temperature range from 1835°C to 2370°C by observing the penetration of C-14 tracer initially applied to one end of a graphite rod.

The experimental data were found to be in agreement with a diffusion mechanism consisting of concurrent volume and grain boundary processes. Activation energies for both processes (EV and EB) could not be uniquely obtained from the data, however. An independent determination of either is required in order to evaluate the other. On the basis of recent theoretical work, EV may be taken to be 90 kcal/mole. From the present experiments and the above value of EV, the activation energy for grain boundary diffusion, EB, is calculated to be 75.4 kcal/mole.
A New Permanent Magnet from Powdered Manganese Bismuthide
Authors: Adams Edmond , Hubbard William M. , Syeles Albert M.
Published: April 2005

Permanent magnets in present use consist chiefly of alloys containing cobalt or nickel, or both. Because these elements are currently scarce, possible substitute materials were examined. The intermetallic compound manganese bismuthide was chosen for this investigation because it has the highest recorded magnetic crystal anisotropy. The new permanent magnet was prepared by hot pressing finely pulverized MnBi in the presence of a strong magnetic field to facilitate particle alignment. Some of these compacts showed a maximum energy product (BH)max as high as 4.3×106 gauss-oersteds, a coercive force (Hc) of 3400 oersteds and a residual flux density (Br) of 4300 gauss. This preliminary work shows that aside from its possibilities as a substitute for magnets requiring cobalt, this new magnet material has a value which exceeds present materials for special applications where a high coercive force is desirable, e.g., where one cannot use a magnet that is long compared to the air gap required. There is also theoretical possibility of further improvement in maximum energy product.
Application of Fluorescence X-Rays to Metallurgical Microradiography
Authors: Splettstosser H. R. , Seemann H. E.
Published: April 2005

Fluorescence x-rays may be more useful analytically in metallurgical microradiography than the line emission from a tube target because of the greater homogeneity of the former radiation. Although the intensity of fluorescence is very low, exposure times are not prohibitive for some applications. In the present report, the method and apparatus are described and illustrative examples are shown.
An X-Ray Diffraction Study of the Hafnium-Hydrogen System
Authors: Sidhu S. S. , McGuire J. C.
Published: April 2005

The hafnium-hydrogen system at room temperature consists of three phases. The lattice parameters of the hafnium metal used in this investigation and of the three phases are as follows: hafnium, a0=3.200A, c0=5.061A, and c=1.58; deformed cubic phase, a0=4.702±0.012A, c0=4.678±0.012A, and c=0.995; face-centered cubic phase, a0=4.708±0.002A; and face-centered tetragonal phase, a0=4.882±0.002A, c0=4.384±0.002A, and c=0.898. The deformed cubic phase extends up to HfH1.53 and converts into the face-centered cubic phase between HfH1.53 and HfH1.70. The face-centered cubic phase transforms into the tetragonal phase between HfH1.80 and HfH1.87. The tetragonal phase extends up to HfH1.98.
Bariated Tungsten Emitters
Authors: Hughes Ray C. , Coppola Patrick P.
Published: April 2005

Thermionic emitters consisting of barium oxide dispersed throughout a body of porous tungsten can be successfully made if suitable compounds of barium are employed as the source of the oxide. Compounds such as the carbonate, which can oxidize tungsten and react to form Ba3WO6: 3BaCO3+W→Ba3WO6+3CO,are unsuitable. However, if by various means, BaO is dispersed in tungsten, reaction occurs at operating temperature of the cathode to slowly generate free barium: 6BaO+W→Ba3WO6+3Ba, which diffuses to the surface and lowers the work function.

Cathodes consisting of approximately 5 percent of BaO in W are capable of supplying continuous emission in excess of 100 amp/cm2, give equivalent dc and pulsed emission, and are highly resistant to damage by arcing, temporary poor vacuum, ion bombardment, and high temperatures.

Emission current of approximately 8 amp/cm2 was obtained at an operating temperature of 1000°C from a typical cathode of this type. The life of this cathode, at 1100°C, was in excess of 650 hours. Constants of the Richardson equation for a relatively inactive cathode were φ=1.56 ev, A=0.6 amp/cm2/deg2.
Creep of Copper under Deuteron Bombardment
Authors: Witzig Warren F.
Published: April 2005

The creep rate of copper under deuteron bombardment has been investigated using the 16-Mev external beam of the University of Pittsburgh cyclotron. Measurements were made of the second stage creep rate of a copper wire under deuteron bombardment at a temperature of 260°C and a loading of 10,000 psi. Within the precision of the experiment ±20 percent, the creep rate during and after bombardments of 10 to 20 hours duration was unchanged from the creep rate preceding bombardment. Theoretical considerations of the type discussed by Slater, predict that with the available deuteron flux of 1012 particles per cm2 per sec there should be no appreciable change in creep rate. The available deuteron flux cannot displace enough atoms from their normal lattice sites to produce a dislocation involving a hundred atoms or more; further, the steady-state density of displaced atoms is not enough to impede the motion of those dislocations present in the crystals. While regions of increased local temperature are produced during bombardment, these also should not affect the creep rate. Thus, apparently the considerations of solid-state theory are confirmed and creep rates should not be expected to increase for all metals under bombardment.
Diffraction of a Shock or an Electromagnetic Pulse by a Right-Angled Wedge
Authors: Keller Joseph B.
Published: April 2005

Graphs of the theoretical pressure distribution resulting from diffraction of a weak shock by a rigid right-angled corner are presented and compared with graphs of measured pressure distributions. The agreement is found to be satisfactory. A graph of the electric field resulting from diffraction of an electromagnetic pulse by a perfectly conducting right-angled corner is also presented.
Fast Jets from Collapsing Cylinders
Authors: Koski W. S. , Lucy F. A. , Shreffler R. G. , Willig F. J.
Published: April 2005

A method is described for producing fast jets from the collapse of metal-lined cavities in high explosives. The behavior of these jets suggests that they cannot be accounted for by the simple hydrodynamical considerations that have in the past been successful when applied to slower type jets. Various experiments, including time-resolved spectrographic observations, show the jets to be, at least in part, of a gaseous nature. Velocities as high as 90 km/sec have been observed for beryllium jets, with heavier elements exhibiting lower velocities in inverse order of their atomic weights.
Solubility and Diffusion Coefficient of Carbon in Nickel: Reaction Rates of Nickel-Carbon Alloys with Barium Oxide
Authors: Lander J. J. , Kern H. E. , Beach A. L.
Published: April 2005

Experimental values for the solubility of carbon in nickel in the range 700°C to 1300°C yield the equation lnS=2.480−4,880/T, where S is the solubility in grams of carbon per 100 grams of nickel. Values obtained for the diffusion coefficient in the same range fit the equation lnD=0.909−20,200/T, where D is in cm2 per second. These results are of some interest in the problem of the activation of thermionic oxide coated cathodes, and the experimental method used to measure the diffusion coefficients is related to phenomena occurring in vacuum tubes. To extend the usefulness of the results in this direction, rates of reaction between diffused carbon and barium oxide coatings on nickel have been measured. It was found that the rates are diffusion limited over a wide range of conditions of interest.
A Method for the Measurement of Spherical Aberration of an Electrostatic Electron Lens
Authors: Shipley Daryl W.
Published: April 2005

A relatively simple method for the experimental determination of spherical aberration of electrostatic electron lenses is described. This method uses an effective point source of electrons at the center of deflection of a magnetic deflection yoke; the yoke deflects the beam through any desired aperture angle. From the measurement of the displacement of the electron beam in the Gaussian image plane as a function of the aperture angle, the coefficient of spherical aberration can be calculated. The value for this coefficient obtained from the measurement of a unipotential lens and that calculated for this lens by numerical integration are compared; the agreement is within twelve percent. An effective method for the detection of axial astigmatism (which is due to an ellipticity of the lens field) of a lens is described. Diagrams and photographs are given which qualitatively substantiate the method.
The Mechanism of the Ring Discharge in Negative Point-to-Plane Corona
Authors: Greenwood Allan
Published: April 2005

Conditions favoring the formation of the ring discharge, and changes in the electrical characteristics which it brings about, are discussed. A theory is developed which seeks to explain the formation of the ring in terms of field distortion caused by negative space charges in the gap. This requires a change of view on the subject of space charge transit times, but this is justified by theoretical and experimental considerations. The paper concludes with a description of two experiments designed to test the theory, and analyzes the results of these tests.
The Scattering of Radio Waves by Meteorological Particles
Authors: Labrum N. R.
Published: April 2005

The scattering of electromagnetic waves by clouds of small spheroidal obstacles is considered from a theoretical standpoint. Numerical data are obtained for the case of clouds composed of partly melted ice particles. These results are applied to the interpretation of ``bright band'' radar echoes from meteorological formations.

It is also shown that these echoes may contain a component with polarization at right angles to that of the transmitted beam. It is suggested that this property could be utilized in certain cases to provide additional information as to the nature of the scattering particles.
Potential Distribution for Space-Charge Limited Current between a Plane Accelerating Grid and Parallel Anode
Authors: Ramberg E. G. , Malter L.
Published: April 2005

Expressions are derived for the potential distribution between a plane accelerating grid and parallel anode under conditions of space-charge limitation, taking account of the Maxwellian velocity distribution of the electrons. The distribution is determined by Langmuir's diode functions in combination with a function depending on the current transmission of the grid-anode space, which is represented graphically.
Contribution to the Theory of Impulse Breakdown
Authors: Dickey Frank R.
Published: April 2005

The experiments of R. C. Fletcher on impulse breakdown are discussed and a simple theory for these experiments is developed by assuming that the breakdown consists of ionization and charge separation in a uniform field. The theory accounts reasonably well for the time lags and also explains the shapes of the breakdown voltage transients. It indicates also that measurement of the mean ionizing time for electrons in the gap should be possible.
Film Boiling Termination Mechanism
Authors: Marx J. W. , Davis B. I.
Published: April 2005

It is suggested that free molecule heat conduction provides the critical energy transfer that just precedes the collapse of the vapor blanket in the film boiling process. An expression for the extreme possible values of the heat transfer coefficient, as a function of pressure, is derived for solid-boiling liquid systems and numerically evaluated for water. The wetting temperature is given in terms of measurable parameters of the system, and experiments are suggested.
On the Magnetic Resonance Absorption in Conductors
Authors: Bloembergen N.
Published: April 2005

The electromagnetic losses in conductors are analyzed in terms of magnetic absorption and conduction losses. The quantities observed in a magnetic resonance experiment have a different meaning depending on whether the dimensions of the sample are large or small compared to the skin depth. Explicit formulas for electric and magnetic losses are given for the case of a plane sheet and a sphere. The influence of the conductivity on the line shape and saturation effects is discussed both for nuclear and ferromagnetic resonance.
On the Accumulation of Errors in the Numerical Solution of Differential Equations
Authors: Papoulis A.
Published: April 2005

The following gives a method for the evaluation of errors in the numerical solution of systems of differential equations.

Under certain assumptions the errors can be obtained by finding the difference r(x) between the computed solution y(x) passing through the given initial point, and the solution Y(x) passing through a neighboring point—that is, by solving the same equations repeatedly with different initial conditions.
The Thermal Conductivity of Metals at High Temperature
Authors: Hogan C. L. , Sawyer R. B.
Published: April 2005

The Forbes bar method has been modified and adapted to the problem of measuring the thermal conductivity of metals and alloys in the temperature range from 25°C to 1000°C. A mathematical analysis is presented which indicates the error involved by assuming plane isothermals in the sample. The electrical and thermal conductivities of commercial ``A'' nickel, inconel, several stainless steel alloys, and 1010 steel are reported, and the results are compared, qualitatively at least, with the theory presented by Wilson1 and Makinson.2
Unsteady-State Separation Performance of Cascades. I
Authors: Montroll Elliott W. , Newell Gordon F.
Published: April 2005

This paper concerns the exact solution of the nonlinear differential equations which describe the time dependent behavior of multistage cascade separating processes for separation of two very similar molecular species. The Rayleigh separation law is postulated for each stage.

The main questions of interest in the nonstationary operation of cascades involve (a) their behavior while the concentration of the required component is being built up to the desired value; (b) the behavior of the cascade during the transition from one stationary mode of operation to another; and (c) the manner in which local concentration fluctuations are propagated through the cascade. We have derived analytical expressions that are suitable for the discussion of all of these points in square cascades. The cases of finite, half infinite, and infinite cascades are considered with and without product withdrawal.

A brief discussion of the linearization of a class of nonlinear second-order partial differential equations is given in Appendix I.
An Iterative Method for the Solution of Eigenvalue Problems
Authors: Berry V. J. , De Prima C. R.
Published: April 2005

A simple iterative procedure is developed for the determination of eigenvalues and eigenfunctions associated with the solution of Sturm-Liouville problems in a finite interval. Both the frequency and the displacement for a given mode may be determined with an accuracy which is independent of the accuracy involved in the calculation of other modes. Convergence of the iteration process is rapid, and the successive approximations to a given eigenvalue are shown to form a monotone sequence. The method is particularly useful when the coefficients of the differential equation are not expressed in analytical form.
The Reversion Method for Solving Nonlinear Differential Equations
Authors: Pipes Louis A.
Published: April 2005

The subject considered in this paper is the presentation of a method for the solution of ordinary nonlinear differential equations of a certain type. The method is based on the algebraic procedure used in reverting power series. By the use of this method, ordinary differential equations having certain type of nonlinearity are reduced to systems of linear differential equations. The resulting linear differential equations are then solved by the Laplace transform or operational method. The general procedure is illustrated by means of examples, and the method is applied to nonlinear electric circuits.
The Structure of Tetragonal Tungsten Trioxide
Authors: Kehl W. L. , Hay R. G. , Wahl D.
Published: April 2005

A study of tungsten trioxide (WO3) by differential thermal analysis and x-ray diffraction at temperatures up to 980°C showed a new tetragonal form to exist at temperatures of 740°C and higher. This form has a distorted ReO3 structure. There are two molecules in a unit cell of dimensions a0=5.25A, c0=3.91A. All atoms lie in the 2- or 4-fold special positions of the space group P4/nmm. The tungsten atoms are alternately displaced in opposite directions from the center of charge of the oxygen atoms so as to resemble the antiferroelectric structure proposed by Kittel.
The Dielectric Constant of Water Vapor in the Microwave Region
Authors: Birnbaum George , Chatterjee S. K.
Published: April 2005

The dielectric constant of water vapor was determined at 9280 Mc by a cavity comparison method at 10 temperatures ranging from 32 to 103°C. In addition, observations were made at 24,800 Mc at the single temperature of 24.5°C. Although the vapor pressure was raised to within 10 percent of the saturation value at 24.5°C and 103°C, the variation of (ε′−1)/(ε′+2) with pressure remained linear, contrary to observations made at radiofrequencies. These data are discussed in relation to the questions of association and adsorption of the vapor. The present results are in agreement with those obtained at radiofrequencies (sufficiently below saturation pressures) and do not show the dispersion reported in an early microwave experiment. Results obtained here and those obtained by others are used to determine mean values for the constants in the Debye equation: namely, P=[3.96±0.32]+[(2.077±0.016)104/T]. This gives a dipole moment of (1.846±0.005)10−18 esu.