bluuebunny/crossref_metadata_2025 huggingface dataset:
A Method for Measuring the Total Power of Small-Angle X-Ray Scattering
Authors: Warren B. E.
Published: January 2005

Measurements of the absorption coefficients are made with a double crystal spectrometer in the parallel position, placing the sample between the two crystals, and between the second crystal and the chamber. In the first position the beam is cut down by the ordinary absorption and also by the power going into small-angle scattering; in the second position it is cut down only by the ordinary absorption. The difference in the two measured absorption coefficients gives directly the total power in small-angle scattering. From the latter, an average spherical particle size can be computed.
Ionization of Paraffin Wax by Beta-Radiation
Authors: Gemant Andrew
Published: January 2005

This is a quantitative experimental study of the primary ionization of paraffin wax by beta-radiation. Electrons emitted by uranium and carbon 14 were used. Interpretation, by means of a simple theory, of experimental data on the electrical conductivity permits evaluation of the ionic mobility in paraffin and the efficiency of ion-pair production. Only small primary ions of relatively long mean life are detected by the conductivity method. Dipolar admixtures promote secondary reactions and lower the level of conductivities attained. No ionization was detected in two hydrocarbon polymers.
Antennas and Open-Wire Lines. Part II: Measurements on Two-Wire Lines
Authors: Tomiyasu K.
Published: January 2005

The open two-wire line is investigated as a measuring instrument and difficulties in its operation are overcome. These include, in particular, the problem of balance. The impedance of antennas is shown to depend on the nature of the driving structures. A comparison of measured impedances and corresponding theoretical values shows good agreement.
Effects of Stress and Deformation on the Martensite Transformation
Authors: McReynolds Andrew W.
Published: January 2005

The relation between elastic and plastic strains and the martensite transformation from face-centered to body-centered structure has been investigated in Fe-Ni 71–29 alloy. Transformation begins at about −30°C and is of the martensite type except that it is not all completed instantaneously but continues at decreasing rate at constant temperature.

It was found that (1) There is no anomalous decrease in elastic moduli as the Ms temperature is approached, nor is Ms affected by applied elastic stresses. (2) Plastic deformation in a temperature range above Ms causes partial transformation in amounts decreasing to zero at temperature Md≈Ms+75°C, but stabilizes against further transformation by cooling. (3) Plastic yield stress increases sharply from Md to Ms then drops suddenly to a low value just below Ms. (4) The Ms temperature depends on grain size; a factor of ten increase in grain size reduces Ms about 30°C.

These results are contrary to expectations on the basis of the usual homogeneous shear model for the transformation mechanism. They indicate that the martensite phase becomes thermodynamically stable at Md but that transformation does not begin until Ms because of surface and strain energy considerations in growth of a martensite plate from a small nucleus.
A High Temperature Precision X-Ray Camera: Some Measurements of the Thermal Coefficients of Expansion of Beryllium
Authors: Gordon Paul
Published: January 2005

A high temperature precision x-ray camera has been designed and constructed by modification of the familiar back-reflection symmetrical focusing type of camera. The camera, specimen, and furnace are used within a vacuum chamber to avoid oxidation. The apparatus in its present form has been employed at temperatures up to 1000°C, but higher temperatures could be easily attained by making a few minor changes in the furnace materials.

The lattice parameters of beryllium have been measured up to 1000°C. The derived coefficients of thermal expansion, both linear and bulk, are presented as a function of temperature. In addition, the data present strong evidence that the hexagonal close packed form of beryllium which exists at room temperature is stable up to at least 1000°C, contrary to several reports in the literature.
Microwave Q Measurements in the Presence of Series Losses
Authors: Malter L. , Brewer G. R.
Published: January 2005

At very high frequencies, the effect of losses in coupling devices makes itself felt in the determinations of the various Q's and of the circuit efficiency of resonant systems. It is shown that the neglect of these losses (which appear in equivalent circuits in the form of series resistance), can lead to appreciable error. Formulas are derived and curves are plotted which permit an unambiguous determination of the Q's and of the circuit efficiency when the following items are known:

1. the standing wave ratio at resonance,

2. the standing wave ratio far from resonance, and

3. knowledge as to whether the resonant system under study is ``under'' or ``overmatched'' to the external load.
The Application of Non-Integral Legendre Functions to Potential Problems
Authors: Hall R. N.
Published: January 2005

There are a number of important potential problems having axial symmetry and involving a conical boundary whose solutions require the use of zero-order Legendre functions of real but non-integral degree. The numerical evaluation of such problems is relatively simple once the zeros of these functions have been determined and when certain integrals have been evaluated. This paper presents tables and curves giving this information, together with a number of approximate expressions for these quantities. A number of potential distributions involving conducting cones, spheres, and rings are worked out to illustrate the application of these functions.
Theory of Growth of Spherical Precipitates from Solid Solution
Authors: Zener Clarence
Published: January 2005

The radius of a spherical precipitate particle growing in a solid solution of initially uniform composition may be shown to be equal to α(Dt)½, where D is the atomic diffusion coefficient, t the time of growth, and α, the growth coefficient, is a dimensionless function of the pertinent compositions. In this paper the precise dependence is found of this function upon the pertinent concentrations. A similar computation is made for the growth coefficient corresponding to the one-dimensional growth of a plate.
Infra-Red Spectra and Structure of Hevea and Gutta Elastomers
Authors: Saunders R. A. , Smith D. C.
Published: January 2005

The infra-red absorption spectra of the purified rubber hydrocarbon fractions of several naturally occurring elastomers (hevea, guayule, kok-saghyz, gutta-percha, balata, and chicle) have been determined at room temperature over the range 2–15μ and it has been shown that the elastomers can be classified on the basis of the spectral data as belonging to one or the other of two different types, namely the hevea type or the gutta type. Both types of elastomers have also been studied over the temperature range −25 to +80°C and reference spectra for both the amorphous and the solid (crystalline) phase(s) occurring in this range have been determined for each type. At room temperature the spectral differences between the hevea (amorphous state) and gutta (α- or β-crystalline modifications) types are much more pronounced than is the case when the spectra of both types in the same (amorphous) states are compared.

The spectra of two pair of cis-trans-isomers containing the structural unit of polyisoprene have been determined and correlated with the elastomer spectra. The results indicate but do not prove that hevea- and gutta-type elastomers have the molecular structure of cis- and trans-polyisoprene, respectively.

The infra-red absorption spectra of oriented crystalline films of hevea rubber and of gutta-percha in both the α- and β-forms have also been obtained over the range 2–15μ using polarized radiation. The observed dichroic effects lead directly to the conclusion that hevea- and gutta-type elastomers are cis- and trans-polyisoprene, respectively. Although it has not been possible to deduce the exact spacial configuration of the molecules in the crystallites, it has been indicated that the planar isoprene models are unsatisfactory and that the results are in close agreement with the twisted models proposed on the basis of x-ray diffraction.

Further use has been made of the polarization data in proposing nearly complete but tentative interpretations of the spectra of both hevea- and gutta-type elastomers. The possibility of making use of the vibrational assignments for the interpretation of spectral changes produced by oxidation or other forms of degradation is pointed out.
Effect of Surface Roughness on Rolling Friction
Authors: Bikerman J. J.
Published: January 2005

The minimum tilt at which bearing balls roll down an inclined plate of stainless steel is greater for rough than for smooth surfaces. The roughest surfaces (finish No. 1, average height of elevations 3×10−4 cm, and finish No. 2D, average height 0.9×10−4 cm) gave an almost quantitative agreement between this height of elevations and the height of hills calculated from a theory attributing rolling friction to surface roughness. No similar agreement was observed for fine finishes, presumably because the balls used (radii between 0.159 and 0.635 cm) were too big for the irregularities on these surfaces. The elastic deformation of the surfaces in contact was irrelevant for coarse finishes. Capillary attraction presumably did not interfere as superficial drying of the system had no effect.

Surface roughness which is the cause of Coulomb's sliding friction thus seems to cause also rolling friction at low pressures.
Effective Use of Collimating Apertures in Small-Angle X-Ray Diffraction Cameras
Authors: Bolduan Orvil E. A. , Bear Richard S.
Published: January 2005

The use of simple, aperture-collimated cameras in x-ray diffraction studies at small angles is of value in investigating the molecularly large structural features of colloidal systems, particularly when pinhole collimation is required. To make effective use of available x-radiation one must (1) consider the initial limitations imposed on a camera by the purpose for which it is to be employed, and (2) choose remaining camera dimensions so that the registering film may receive as much radiation as possible.

The initial conditions are three in number, involving the desired pattern magnification, the necessary angular or large-spacing resolution, and the requisite guarding against beam spill-over, which together essentially limit the specimen-to-film distance, the beam diameter at the film, and the diffraction area permitted to be unguarded but covered by a beam stop. Other camera dimensions are chosen so that the film center is as close to, while viewing as much of, the radiation source as possible. In accomplishing these aims it is useful to align the camera at near grazing incidence to the x-ray tube target, though there are limitations to this procedure.

Rules for systematically accomplishing the above purposes are derived herein for the extremes of symmetrical (pinhole) and unsymmetrical (slit) aperture systems, as well as for ones employing a simple class of rectangular (unsymmetrical pinhole) aperture. Criteria are also given for evaluating the relative speeds of cameras which may depart from optimum because of mechanical limitations. Finally is described the construction of a series of cameras, found useful in studying the fibrous proteins, particularly collagen, and typical diffraction patterns obtained therefrom are reproduced.
Electron Microscope and Diffraction Study of Metal Crystal Textures by Means of Thin Sections
Authors: Heidenreich R. D.
Published: January 2005

Bethe's dynamical theory of electron diffraction in crystals is developed using the approximation of nearly free electrons and Brillouin zones.

The use of Brillouin zones in describing electron diffraction phenomena proves to be illuminating since the energy discontinuity at a zone boundary is a fundamental quantity determining the existence of a Bragg reflection. The perturbation of the energy levels at a corner of a Brillouin zone is briefly discussed and the manner in which forbidden reflections may arise at a corner pointed out. It is concluded that the kinematic theory is inadequate for interpreting electron images of crystalline films.

An electrolytic method for preparing thin metal sections for electron microscopy and diffraction is introduced and its application to the structure of cold-worked aluminum and an aluminum-copper alloy demonstrated. It is concluded that cold-worked aluminum initially consists of small, inhomogeneously strained and disoriented blocks about 200A in size. These blocks are not revealed by etching but would contribute to line broadening in the conventional diffraction experiments. By means of a reorientation of the blocks through a nucleation and growth process, larger disoriented domains about 1–3μ in size found experimentally could be accounted for. It is suggested that such a nucleation and growth reorientation phenomenon is responsible for self-recovery in cold-worked metals.

The formation of CuAl2 precipitate particles is demonstrated with both electron micrographs and diffraction patterns. A fine lamellar structure found in the quenched Al-4 percent Cu alloy is at present unexplained.
An Analysis of the Mechanics of Metal Cutting
Authors: Drucker D. C.
Published: January 2005

An attempt is made to go beyond an idealized description of the process of metal removal. The details of two-dimensional orthogonal cutting are investigated, and several concepts and hypotheses are introduced which apply equally well to the most general cutting operation. Of these, the most significant is the great importance of the small time available for the plastic deformation to occur. Ekstein's paradox is explained, and the influences of speed of cutting, depth of cut, and rake angle are correlated by the consideration of dynamic plasticity. In addition, the effect of non-homogeneity of the material is analyzed and shown to account for the gradual change from the discontinuous to the continuous type of chip as the cutting speed is increased, and for the marked increase in the specific cutting force as the depth of cut is decreased. A partial theoretical analysis of the state of stress, in the chip and the workpiece, and energy considerations are also found helpful in the description of what probably happens when metal is cut.
Antennas and Open-Wire Lines. III. Image-Line Measurements
Authors: Conley Patrick
Published: January 2005

A new type of open-wire line is described for which many disadvantages, notably radiation and unbalance, are overcome by replacing one of the physical conductors by the image of the other in a semi-infinite, highly conducting plane.

The characteristics of a line driven at both ends and loaded at the center are examined; it is shown that the impedances measured on both sides of such a line are equal and simply related to the load impedance, provided that electrical symmetry is maintained about the load point. The double-ended drive requires no dielectric supports and permits the line conductor to continue past the load.

The construction and operation of an image line with double-ended drive is described. The characteristics of the new line compare very favorably with those of a good coaxial measuring line.

Finally, use of the line in the measurement of the apparent impedance of a cylindrical dipole antenna as a function of the line spacing is described.
Convection Currents in Porous Media: II. Observation of Conditions at Onset of Convection
Authors: Morrison H. L. , Rogers F. T. , Horton C. W.
Published: January 2005

Small-scale experiments have been carried out for determining the minimum vertical thermal gradient which is required to cause convection in liquids entrapped in porous media. Observations relative to the onset of convective flow in unconsolidated sands indicate that the present theories predict minimum gradients which are excessive by considerable amounts, possibly because they neglect the temperature-dependence of viscosity. The ratio of theoretical to observed gradients is found to be roughly R=(Kh2μAV/kρα)0.51,where h2 is the thermal diffusivity, μAv is average viscosity, k is flow-permeability, ρ is density of liquid, α is the coefficient of cubical expansion of the liquid, and where K = 10−3 sec.2 per cm2 °C for c.g.s. units. By extrapolation, it is possible to strengthen the earlier conclusion that convection occurs in the Woodbine sand near the Mexia fault zone.
A Study of the Mechanism of Sintering of Metallic Particles
Authors: Dedrick J. H. , Gerds A.
Published: January 2005

An investigation has been carried out on the mechanism of sintering of metallic particles. Single layers of spherical copper particles have been sintered under varying conditions of time and temperature in a dry hydrogen atmosphere. Analysis of the rate of interface contact between the particles has shown metallic sintering to be a diffusion process, in agreement with the theory of Kuczynski. The heat of activation of self-diffusion of copper has been calculated and found to be 55,000 cal./mole. This is in close agreement with Kuczynski and also values obtained by other workers using the radioactive tracer method.
Harmonic and Subharmonic Response for the Duffing Equation ẍ+αx+βx3 = F cosωt (α>0)
Authors: Levenson Morris E.
Published: January 2005

The Duffing equation ẍ+αx+βx3 = F cosωt (α>0) is known to possess periodic solutions with frequency ω/n for all integral n, provided that β is sufficiently small. For n=1 and n≠1, these solutions are designated in the literature as harmonic and subharmonic solutions respectively. In this paper, a classification of the various types of periodic solutions is given, in which it is shown that there are two types of harmonic solutions and two types of subharmonic solutions for sufficiently small β. The perturbation method is employed to find the approximate response curves for each of the four types of periodic solutions. A comparison is made between the response curves obtained in the non-linear case (β≠0) and linear case (β=0) and some properties of the solutions in the non-linear case are discussed. A comparison is then made between the perturbation method and the Rauscher method, which is an iteration method that assumes F small instead of β. This comparison is not made in all generality, but only for one particular type of subharmonic solution. The main result obtained is that for F small, the two methods yield similar results for larger values of β than might have been anticipated.
New Interpretation of the n-Power Law in Plastic Deformation
Authors: Fusfeld Herbert I.
Published: January 2005

It is shown that the n-power law describing a true stress-strain curve, normally written as S = kδn, can be placed in the form S=S0(eδ/n)nwhere S0 is the engineering tensile strength. The application of this new expression to tensile curves is discussed.

A plot of S/S0 as a function of n, for a fixed value of the logarithmic strain δ, provides a general description of the behavior of all materials in plastic deformation. Experimental data from the literature are in good agreement with the curves.
A Technique for the Preparation of Grease or Solid Samples Dispersed in Grease-Like Media for Examination with the Electron Microscope
Authors: Mottlau A. Y.
Published: January 2005

The nature of grease as a dispersion of solid particles in oil is briefly discussed, and the value of the electron microscope in studying this solid phase is pointed out. The requirements of a satisfactory grease specimen mounting technique are outlined and a new technique fulfilling these requirements is described. Electron micrographs are presented which demonstrate the usefulness of the technique in disclosing pertinent information on grease structure. The factors involved in the preparation of powder specimens for electron micrography are discussed in relation to the adoption of a modification of the grease mounting technique for this purpose. The modified technique for powders is outlined and illustrated with micrographs.
Increasing Space-Charge Waves
Authors: Pierce J. R.
Published: January 2005

An earlier paper presented equations for increasing waves in the presence of two streams of charged particles having different velocities, and solved the equations assuming the velocity of one group of particles to be zero or small. Numerical solutions giving the rate of increase and the phase velocity of the increasing wave for a wide range of parameters, covering cases of ion oscillation and double-stream amplification, are presented here.
Application of a Variational Principle to Biconical Antennas
Authors: Tai C. T.
Published: January 2005

A theoretical examination is made of the impedance of a biconical antenna, based upon a method devised by Schwinger in studying the discontinuity problems of a wave guide. In the present analysis, an integral equation to determine the aperture field is obtained by matching the tangential electric and magnetic fields along the boundary sphere. Using this integral equation, the effective terminating admittance of the antenna can be expressed in a form that is stationary with respect to small variations in the aperture field. It is shown that the zeroth-order solution of the admittance function thus obtained is the same as the one that Smith derived by neglecting all the high order waves in the interior region except the principal mode. For small-angle cones, the present formulation yields the same exact solution obtained previously, based upon several different methods. The paper also contains a discussion of the first-order approximate solution which is applicable to both small- and wide-angle cones. The analysis includes a detailed treatment of a method by which the characteristic values and characteristic functions for a given cone may be found approximately, but very accurately; as well as certain integrals involving the product of Legendre functions.
Measurement of the Complex Conductivity of an Ionized Gas at Microwave Frequencies
Authors: Adler Fred P.
Published: January 2005

The positive column of a glow discharge is placed along the axis of a cylindrical cavity excited in the TM010 mode. The transmission of 3-cm waves through the cavity and the shift in resonant frequency are observed as a function of discharge current. It is shown that from these measurements values of the complex conductivity, σr+iσi, of the electron gas can be calculated. Curves of the measured conductivity components as functions of pressure and current are given. Using a theoretical formula for the conductivity (see reference 6) values of electron density can in turn be calculated from both σr and σi. Langmuir probe studies are carried out to check the results obtained, and adequate agreement is found.
The Calculation of X-Ray Mass Absorption Coefficients
Authors: Victoreen John A.
Published: January 2005

An empirical method of calculating mass absorption coefficients is given. Complete tables of constants are presented for calculating μ/ρ for all elements and for wave-lengths less than the K critical absorption wave-length. Partial tables give constants for wave-lengths between the L1 and M1 critical wave-lengths.

Calculated mass absorption coefficients are given for the common elements.
Bending of a Thin Circular Plate of an Aeolotropic Material under Uniform Lateral Load (Supported Edge)
Authors: Ōkubo H.
Published: January 2005

The bending problem is solved mathematically for a thin circular plate subjected to a uniform load. The material of the plate is assumed to have three symmetrical planes with respect to its elastic properties.

The solution is carried out in the case when the edge is simply supported, and it involves some numerical calculations. An empirical formula for the deflection is also given in a simpler form.
On the Torsion of a Prismatic Cylinder with a Star-Shaped Section
Authors: Ōkubo H.
Published: January 2005

The torsion problem is theoretically treated for a prismatic cylinder with a star-shaped section. To simplify the calculation, the bounding curve is assumed to be composed of logarithmic spirals. In one example the stress distributions on the boundary and on the symmetrical radial lines, and the torque are calculated. The result is confirmed by an experiment.
A Method for Studying the Distribution and Sign of Static Charges on Solid Materials
Authors: Hull Harry H.
Published: January 2005

A special powder is used to show how static electricity is distributed on materials such as paper. Red particles of this powder are attracted to positively charged areas and blue particles are attracted to negatively charged areas. Paper from heat-set printing presses shows streaks of static electricity generated by idling rollers and shifting patterns of static electricity generated in the folder, often with opposite charges on the same sheet of paper.
Study of the Sintering of Glass
Authors: Kuczynski G. C.
Published: January 2005

It has been shown experimentally that the mechanism of sintering of spherical glass particles is that of viscous flow. The viscosities of the investigated glass were determined for a range of temperatures from 575°C to 744°C. These viscosities remain in good agreement with those obtained by other methods.
Properties of Gold Deposited at Liquid Air Temperature
Authors: Wilkinson P. G. , Birks L. S.
Published: January 2005

Gold deposited in vacuum at liquid air temperature contained defects and strain. The number of defects and their characteristic decay energy increased rapidly with increasing rate of deposit in the range from 1 to 5 micrograms/cm2/min. The defects decayed with rising temperature but the relief of strain did not occur until after most of the defects had disappeared. Electron micrographs showed that the gold film was made up of aggregations of discreet particles rather than a smooth continuous film.
The Attenuation of Neutrons of Various Energies in Water
Authors: Falk C. E. , Creutz E.
Published: January 2005

Threshold detectors (In115, Ag107, and C12) were used to determine the relative intensities of neutrons at various distances inside a large water tank. Neutrons with energies up to 30 Mev were produced by (d, n) reactions. At distances in the water >20 cm the ``half-thickness'' of water was found to be almost independent of neutron energy (about 8 cm).
An Investigation of Dielectric Rod as Wave Guide
Authors: Chandler C. H.
Published: January 2005

An experimental investigation of dielectric rod as wave guide indicates that the guiding effect is retained even when the rod is only a fraction of a wave-length in diameter. The greater part of the guided energy is then outside the dielectric, so that a very low loss wave guide results. Measurements of performance made at 1.25 cm indicate attenuations down to 0.004 decibel per meter in polystyrene rod, and show good agreement with theoretical predictions. A resonator utilizing the dielectric-rod wave guide is described, in which a maximum Q of approximately 53,000 was observed.
The Traveling-Wave Tube (Discussion of Waves for Large Amplitudes)
Authors: Brillouin L.
Published: January 2005

The traveling-wave amplifier is a typical structure where E-M waves and electrons, traveling with approximately the same velocity, exhibit a strong interaction. The problem has usually been discussed for the case of weak waves with approximations corresponding to a small signal theory. It is interesting to state the limitations of this theory and to discuss the behavior of such tubes for strong signals. It seems that the amplified wave obtained in the case of small signals is progressively distorted until a final stage is reached where no further amplification is possible. The type of final distorted wave depends essentially upon all the details of the structure. In many cases where a complete investigation was possible, some strange types of shock waves were obtained, with a complete bunching of the space charge. A similar solution also applies to the linear accelerators or to the synchrotrons.
Distribution of Phases in Two-Phase Solids
Authors: Jaffe Leonard D.
Published: January 2005

The quasi-equilibrium distribution of a disperse phase, B, within a polycrystalline second phase, A, is investigated by methods of statistical thermodynamics. Phase B is assumed to consist of spherical particles of uniform size within the A crystals, and of lenticular particles of uniform size at the boundaries between two A crystals. The concentration (Mf) of B at the grain boundaries of A is found to be related to the sizes (r1 and r2) of the B particles at and away from grain boundaries, in terms of the interfacial energies (γaa and γba), the temperature (T), the over-all concentration (M), and the size of the A crystals (R), by (Mf1−Mf)(Mw1−Mw)−r13/r23=exp{−γaar12kT[9πZ−(9π/2)13(3Z3+2π)(r1/r2)3Z3−4π]},where w=1−2.66fr1R(Z−(π/3)Z−2)where Z=[2π(4(γba/γaa)+1)3(2(γba/γaa)−1]12. Temperature will significantly affect the distribution only if γaar12 is of the order of kT, or if γba/γaa∼½.
The Physical Properties of Titanium. I. Emissivity and Resistivity of the Commercial Metal
Authors: Michels Walter C. , Wilford Sally
Published: January 2005

The resistivity and the total emissivity of commerical titanium have been measured over the temperature range from room temperature to 1400°K. The resistivity at 20°C is 78.6 microhm cm. Above this temperature it increases to a flat maximum of 182 microhm cm at the temperature of the hexagonal-body-centered cubic transformation. The total emissivity is about 0.31 at low temperatures and there is some indication that it shows a maximum near the transition temperature. The spectral emissivity and the brightness temperature scale are also determined over the range of 1000°K–1400°K.
Grain Boundary Relaxation and the Mechanism of Embrittlement of Copper by Bismuth
Authors: Kê T'ing-Sui
Published: January 2005

The embrittlement of copper by small amounts of bismuth has been known for many years. Voce and Hallowes proposed recently that the agent responsible for embrittlement is bismuth present in the form of thin films at copper grain boundaries. In order to examine this picture from a different angle, internal friction and elastic modulus measurements were made on copper specimens free from and containing bismuth up to 0.01 percent with a frequency of transverse vibration of about 1000 cycles per second from −50°C to 550°C. It has been found that: (1) In the bismuth-bearing copper heat-treated to be brittle, there is no abrupt change in elastic modulus in passing through the melting point of bismuth (271°C). (2) The internal friction peak (around 500°C) associated with the stress relaxation across copper grain boundaries was reduced by the presence of bismuth, indicating that some bismuth did go to the grain boundaries. (3) Each bismuth-bearing specimen gives an internal friction peak around 290°C and the height of this peak varies approximately linearly with the bismuth content. This ``bismuth peak'' is correlated to the embrittlement of copper. It was subsequently utilized in studying the effect of cold-work, heat treatment and the rate of cooling upon the embrittlement of copper by bismuth. The effect of previous cold-work was found only to speed up the precipitation of bismuth to the grain boundaries the rate of which is very slow at low temperatures.

The data presented above corroborate the proposition that embrittlement of copper is caused by bismuth present at copper grain boundaries. However, it appears that the bismuth is distributed in a highly heterogeneous manner. Across most of the boundaries no appreciable amount of bismuth is precipitated, at least not enough to influence the grain boundary viscosity. It is these grain boundaries which give rise to that internal friction peak characteristic of pure copper. Across a few of the grain boundaries enough bismuth is precipitated to markedly decrease the grain boundary viscosity. Since no discontinuous behavior is observed as the temperature passes through the melting point of pure bismuth, it is concluded that the film of bismuth along these boundaries is not of sufficient thickness as to acquire the properties of crystalline bismuth.
Magnetite Concrete for Radiation Shielding
Authors: Creutz E. , Downes K.
Published: January 2005

A concrete containing only magnetite ore concentrate, cement, and water is found to have appreciably better shielding properties than ordinary concrete, and to possess good strength and ease of handling. Exceptionally high moisture content, although gradually lost by diffusion, decreases by only about 50 percent in thirty years in an eight-foot thick wall. Its use is desirable under certain conditions because of space economy due to its high density.
Volume Changes in the Plastic Stages of Simple Compression
Authors: Bridgman P. W.
Published: January 2005

A method has been devised by which the volume changes occurring during plastic flow in simple compression are directly measured in a dilatometer during the flow process. The great superiority of such a direct determination over an indirect determination from the alteration of dimensions is pointed out. Results are obtained for three rocks, quartz crystal, and a number of metals, including several grades of steel and iron. The volume change during plastic flow is not equal to the product of mean hydrostatic stress into the ordinary compressibility in the elastic range, but may vary in a much more complicated way. There are in the first place permanent changes of volume retained after release of stress; these have long been known and may be of either sign. In addition to the permanently retained changes there may be changes of volume during the action of stress which may be notably larger than the permanently retained part and which also may be of either sign. The most striking of these is a component of volume increase under increasing compressive stress which in the upper range of stress near the fracture point may be larger than the normal component of volume decrease, so that the total volume change is retrograde. This component is recoverable and reversible on release of stress. It would appear, therefore, that in at least some cases the irreversible phenomenon of fracture is prepared for in the region immediately below the stress of fracture by the appearance of a reversible change of volume of sign the opposite of that due to the elastic action of the stresses.
Photo-Density Method of Determining the Relative Penetration of Diffused Sodium 24 Tracer into Glass
Authors: Johnson James R.
Published: January 2005

A photo-density method for the determination of diffusion of radioactive tracer is presented and compared in detail to a thin section analysis method. The method is no doubt applicable to similar tracer problems such as metal diffusion studies. The proper analysis of an emulsion exposed by decaying Na24 which had been allowed to diffuse into glass is given. The necessity for making and using an emulsion gamma-curve for the tracer in this analysis is shown.
The Measurement of Forces Resisting Armor Penetration
Authors: Masket A. Victor
Published: January 2005

This paper summarizes the experimental and theoretical status of the optical chronograph developed in the course of ballistic research at the Naval Research Laboratory. The instrument, together with a simple procedure for analysis of data, is capable of yielding the position, velocity, and deceleration of a non-plastically deforming small arms projectile during the armor penetration process, which lasts from 30 to 150 microseconds. Decelerations have been observed up to 5×107 ft./sec.2. The longitudinal vibrations induced in projectiles during impact were observed by a shadow-photography technique which yields time-displacement curves from the motion of the trailing face of a projectile during penetration. The precision of the derived decelerations, about 4 percent, is sufficient to permit the evaluation of strain-rate and inertia effects during high speed indentation by means of conical indenters at strain-rates approaching 2×105/sec.
Probability Criterion for the Design of Servomechanisms
Authors: Ragazzini John R. , Zadeh Lotfi A.
Published: January 2005

Of the criteria that are used in the design of servomechanisms, the so-called ``minimum mean-square'' error criterion is used quite widely in cases where the undesirability of the error increases with its magnitude. There is, however, an important class of applications, particularly in the field of ballistics, where a more appropriate criterion can be defined as the probability that the error be less than some prescribed tolerance. The problem of maximization of this probability is shown to reduce to a number of implicit equations whose solution in practice must be carried out by cut and trial. It is further shown that under certain conditions the maximization of probability yields the same values for the design constants as the minimization of mean-square error. These conditions are discussed for the general case as well as for certain specific cases which are important in practice.
Measurements of the Mechanical Properties of Polymer Solutions by Electromagnetic Transducers
Authors: Smith Thor L. , Ferry John D. , Schremp Frederic W.
Published: January 2005

A concentrated polymer solution is sheared by a rod oscillating axially with a very small amplitude in a closed tube. The rod is driven by a coil in a magnetic field; from electrical measurements on the coil, the mechanical resistance and reactance of the system are calculated by transducer relationships. Equations are given for obtaining the dynamic viscosity, η′, and rigidity, G′, of the solution. In the case of some polymer solutions, the audiofrequency range covered by the present apparatus falls in the dispersion zone where η′ and G′ change rapidly with frequency. In other cases the frequency range covered appears to be at the upper end of the dispersion zone; η′ is far smaller than the viscosity in steady flow, and G′ changes very little with frequency. The advantages and limitations of the method are discussed.
Aberration Correction with Electron Mirrors
Authors: Ramberg E. G.
Published: January 2005

Both the spherical and the chromatic aberration of electron microscope objectives may, in principle, be corrected with the aid of a uniform retarding field acting as a mirror. Such an arrangement has the drawback of requiring a conducting film in the ray path and the insertion of the specimen in a region of high field strength. The employment of concave electron mirrors with concentrated field distribution, forming a real image of approximately unity magnification, is free from this drawback. The formulas for spherical and chromatic aberration, presented in a form suitable for calculation, are applied to a characteristic electron mirror field of this type (Φ = C+tanh(sinhz)). It is found that the aberration coefficients of the mirror are so large, however, that this method of aberration correction encounters serious practical difficulties.
Work Functions and Conductivity of Oxide-Coated Cathodes
Authors: Mahlman G. W.
Published: January 2005

The thermionic and photoelectric work functions and the temperature variation of coating conductivity have been measured for an oxide cathode. Thermionic and photoelectric currents were measured in both retarding and accelerating fields. The two work functions are found to be different, but not by the amount predicted by applying simple semi-conductor theory to the data. Photoelectric currents fit a Fowler plot rather well over a limited range of frequencies. The large decrease in work function with applied field, the poor ``saturation'' of thermionic currents typical of oxide cathodes, and the behavior of the photoelectric currents in accelerating fields all suggest that one is dealing with a ``patchy'' surface. Applying ``checkerboard'' patch theory to the experimental data, one finds that most of the data is accounted for by assuming patches about 3×10−4cm on a side differing in work function by about 0.2 volt.
Air Friction on Rapidly Moving Surfaces
Authors: Kuhlthau A. R.
Published: January 2005

The friction on a surface moving through air at high speed has been measured over a pressure range from 0.5 to 200 microns. A rotating cylinder type apparatus was used in which the inner cylinder was rotated at very high speed by means of an air turbine arrangement similar to that used in an air driven vacuum type ultracentrifuge. The outer cylinder completely surrounded the inner cylinder and was supported coaxially with it by means of a torsion fiber so that the frictional torque on the rotating cylinder could be measured with precision. Observations were made at rotor speeds varying from 400 r.p.s. to 1700 r.p.s. which corresponds to a linear velocity at the periphery of the rotor varying from 400 to 1700 ft./sec. It was found that at all pressures the observed torque varied in an essentially linear fashion with the rotor speed. The relationship between torque and pressure at constant speed yielded a smooth curve indicative of ordinary viscosity, and this general form held for all speeds tested. However, the results could be explained by kinetic theory treatment of viscosity only at pressures lower than 10 microns; i.e., below the point where the intermolecular collision frequency predominates over that of the collisions between the molecules and the walls.
Recent Developments in the Mathematical Theory of Plasticity
Authors: Prager William
Published: January 2005

The first part of the paper (Sections I to V) is concerned with the general technique used in the discussion of stress-strain laws for inviscid elastic-plastic materials with work hardening. It is postulated that when the ``mechanical state'' of such a material is known a given infinitesimal change of stress produces a uniquely defined infinitesimal change of strain. Once the assumption is made as to which variables determine the mechanical state, the conditions of continuity, uniqueness, irreversibility, and consistency can be used to extract rather far-reaching information regarding the structure of the stress-strain law. The procedure is applied to the case where the mechanical state is determined by the components of stress and permanent strain.

The second part of the paper (Sections VI to VIII) is concerned with various problems of plastic equilibrium. Structural stability in the plastic range is discussed and the difficulties arising in the formulation of stability problems for nonconservative systems are pointed out. Statically determinate problems in the Saint-Venant-Mises theory of plasticity are reviewed with special reference to discontinuous solutions. Finally, the ``shake-down'' problem is discussed for an elastic-plastic structure under the action of loads, each of which varies in a random manner between given extreme values.
Some Properties of Tubular Electron Beams
Authors: Wax Nelson
Published: January 2005

Approximate expressions are obtained for the potential distribution, maximum current density, and beam spread of tubular electron beams of finite thickness. Comparisons are made with previously published results for very thin tubular beams and solid cylindrical beams.
A New Solution to the Problem of Vertical Angle-of-Arrival of Radio Waves
Authors: Hamlin E. W. , Seay P. A. , Gordon W. E.
Published: January 2005

A practical mathematical solution is presented, which separates the direct and reflected components of microwave radiation when a single pair of plane waves is received. Very promising operational applications are noted when it is desired to determine elevation angles precisely, continuously, and instantaneously. The method is well suited to the measurement of very small elevation angles. The results of sample tests of the solution warrant further study in this direction.
Bending of Beams with Creep
Authors: Popov E. P.
Published: January 2005

A method of calculating stresses and deflections for beams whose material creeps is presented in this paper. Complete tension creep test data at constant temperature are used to define creep characteristics of the material. Then by using Bernoulli's hypothesis of plane sections and the techniques developed earlier for interpretation of the relaxation creep tests, a method of beam analysis is shown. Stresses and deflections may be calculated for any desired time interval. This includes the time prior to the occurrence of the steady state creep. The latter aspect appears to have been ignored by others.
Analysis of the Metal-Strip Delay Structure for Microwave Lenses
Authors: Cohn S. B.
Published: January 2005

The metal-strip delay medium is shown to be analogous to a transmission-line low pass filter. A filter analysis gives the image phase constant and image admittance of the equivalent filter section. The index of refraction of the medium is obtained from the former and the reflection coefficient from the latter. It is shown that the physical parameters may be chosen so that the strip medium is perfectly matched to space at a particular frequency. Formulas are given which hold for normal incidence even when the strips are close together. The same method may be applied to delay media consisting of thin metal obstacles of any shape arranged uniformly in parallel planes. Examples are circular disks, ellipses, and rectangles. Certain general conclusions are drawn for this class of media.
The Response of Certain Inorganic Phosphors to Far Ultraviolet Radiation
Authors: Tomboulian D. H. , Pell E. M.
Published: January 2005

The response characteristics of a number of inorganic phosphors have been investigated in the extreme ultraviolet region (∼170A) for the purpose of selecting a luminescent screen suitable for the measurement of relative intensities in conjunction with photo-multipliers. Preliminary tests indicate that in this spectral region luminescence is excited rather strongly in the tungstates. Sample screens of CaWO4 have been studied photographically in order to determine to what extent such screens give rise to a faithful reproduction of the intensity distribution of the exciting radiation. Qualitative calculations show that the luminescent intensity excited by weak soft x-ray radiation is above the noise level of the conventional photo-multiplier.
Phase Lead for A.C. Servo Mechanisms
Authors: Benner Arthur H.
Published: January 2005

General design curves for use of lead networks on log-db plots are given. A variety of parallel and bridge T networks along with d.c. networks are evaluated for use in a.c. servo mechanisms. The restrictions existing on some networks are enumerated, and suggestions on general design procedure are made.
A Grain Boundary Model and the Mechanism of Viscous Intercrystalline Slip
Authors: Kê T'ing-Sui
Published: January 2005

A study of the activation energy associated with the viscous intercrystalline slip shows that the conventional theories of grain boundary, e.g., the intercrystalline amorphous cement theory and the abrupt transitional theory, are both untenable. A grain boundary model is described in which the transition region at the boundary is considered as consisting of numerous disordered groups of atoms or diffused holes. The intercrystalline slip occurs through the atomic rearrangement by thermal agitation within each ``disordered group'' by a shear process involving as units of flow only a few atoms. This grain boundary model and slip mechanism are consistent with experimental facts and furnish, furthermore, a unified viewpoint as to the mechanism of the viscous intercrystalline slip, the volume diffusion in metals, and the constant rate creep of metal crystals under small stress. Further experiments are described concerning the influence of previous deformation and impurities on grain boundary viscosity. It has been found that the grain boundary viscosity is lower in a specimen subjected to a heavier deformation prior to its recrystallization. A very small amount of impurities was found to be able to block partially or completely the grain boundary slip in aluminum, iron, and copper. These observations are readily understood on the basis of the proposed grain boundary model and slip mechanism.