bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.
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.
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.
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.
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.
Modification of Silica Replica Technique for Study of Biological Membranes and Application of Rotary Condensation in Electron Microscopy
Authors: Heinmets F. 
Published: January 2005

A modified silica replica technique for electron microscopy has been developed involving direct condensation of silica upon the object. For improvement of the silica replica technique in general, the following new procedures are introduced:
(a) The undesirable effects of brittleness of silica replica is largely obviated by use of a thin plastic supporting film.
(b) A working method is introduced which completely avoids manual manipulation of the unsupported replicas.
(c) A better definition of small structural elements of the specimen is obtained when a new method of condensing metallic vapors on a rotating replica is introduced; when compared to the usual shadowcasting, an improved two-dimensional definition of the objects is achieved; also the combined use of rotary condensation and shadowcasting provides a better general definition of objects than would be obtainable by either method alone.
Reproducibility of the morphology of crystals and particles by the modified silica replica is demonstrated with the electron micrographs.
The Enumeration of Fourier Phase Permutations Using Electronic Analog Machines
Authors: Booth A. D. 
Published: January 2005

An automatic method is proposed for recording systematically the density distributions resulting from all permutations of sign of a given set of Fourier coefficients.
It is suggested that the device could be used in conjunction with analog computers of the type now being built by Pepinski, and relay circuits for this purpose are given.
Scattering by an Inhomogeneous Solid
Authors: Debye P. , Bueche A. M. 
Published: January 2005

A general treatment of the scattering of radiation by an inhomogeneous material is developed. It is shown how scattering measurements can be used to obtain the average square of the fluctuations in refractive index or electron density and a correlation function which measures the degree of correlation between two fluctuations as a function of their distance of separation.
The scattering of visible light by Lucite and two glass samples has been investigated. The data are analyzed in terms of the quantities mentioned above. It is found that the extensions in space of the inhomogeneities in the Lucite sample are much greater than those in the optical glass samples investigated. The magnitudes of the fluctuations in refractive index are found to be dependent on the composition of the sample.
The Compatibility, Efficiency and Permanence of Plasticizers
Authors: Boyer Raymond F. 
Published: January 2005

This paper attempts to interrelate three important aspects of plasticizer behavior: compatibility or how much plasticizer can be added without causing phase separation; efficiency, or how much a given amount of plasticizer lowers the brittle temperature; and permanence, or how well a plasticizer is retained by the polymer on heat aging or solvent treatment.
Compatibility is discussed in terms of the Flory-Huggins theory of the thermodynamics of polymer solutions, which relates the activity of the plasticizer to its concentration in the polymer. Efficiency is measured by how the plasticizer lowers the melt viscosity of the polymer. An empirical relationship between efficiency and μ (the Huggins polymer-solvent interaction constant) is shown. Loss of plasticizer at elevated temperatures depends in part on the effective vapor pressure of the plasticizer, and in part on how rapidly diffusion of plasticizer from the interior of the sample replenishes that lost from the surface. From the fact that diffusion constant times viscosity is a constant, it is possible to correlate measured diffusion rates with plasticizer content and with plasticizer efficiency. A linear relationship is predicted and found experimentally between logarithm of the diffusion constant and the brittle temperature. In this sense, the more efficient a plasticizer is, the more rapidly it can diffuse out of the polymer and be lost. Consideration is given to the effect of plasticizer on electrical resistance and tensile strength. A preliminary discussion of polymeric plasticizers is presented.
X-Ray Diffraction Studies of the Stretching and Relaxing of Polyethylene
Authors: Brown Alexander 
Published: January 2005

The orientation of the crystallites when polyethylene is stretched at 96°C is normal in that, from the onset of stretching, the preferred orientation is that wherein the long chain axis is parallel to the direction of stretch. At low extensions the preference for this orientation is weak, but it progressively becomes stronger as stretching proceeds.
When polyethylene is stretched at room temperature, the crystallite behavior is more complicated. The first 20 percent extension produces no preferred orientation of the crystallites. From 30 percent to 200 percent extension the preferred orientation is that wherein the 011 ``axis'' is parallel to the direction of stretch, and the long chain axis therefore inclined to this direction at an angle of 64°. From 200 percent extension to the break (about 600 percent extension), the tilt of the crystallites in the preferred orientation progressively lessens and almost vanishes at the break. The stress-strain diagram of polyethylene is interpreted in the light of these findings. The preferred orientation of the crystallites in the region of the shoulder in necked-down polyethylene is also that wherein the 011 ``axis'' aligns with the stretching direction.
When stretched polyethylene is relaxed by shrinking at elevated temperatures, the crystallites become disoriented but in a non-random manner. This behavior is described qualitatively.
Infra-Red Absorption Spectra of Some Polymers at Liquid-Helium Temperatures
Authors: King Gilbert W. , Hainer R. M. , McMahon H. O. 
Published: January 2005

Infra-red absorption spectra of polythene, rubber, polystyrene and polyvinyl chloride have been obtained at 4° absolute, in the rocksalt region, in a specially designed transmission cell containing liquid helium. No unusual changes occur on cooling which considerably alter the absorption. Some sharpening and improvement in resolution occurs, but the widths of most bands in polymers remain wide.
In polythene one component of the doublet at 720 cm−1 becomes very sharp (possibly even less than the experimental value of the slit width, 1 cm−1). Its companion remains broad, about 4 cm−1. The two components are interpreted as CH2 wagging in trans- and cis-configurations of the hydro-carbon chain.
Elasticity of Zinc Crystals
Authors: Wert C. A. , Tyndall E. P. T. 
Published: January 2005

Young's modulus, E, has been measured by dynamic and static methods for 25 zinc single crystals. The results fit a parabolic curve when 1/E is plotted against the square of the cosine of the orientation. From the constants of this curve and earlier data on linear compressibility by Bridgman, are derived numerical values for the coefficients of compliance of the zinc crystal, as follows: S11=8.38, S12=0.5, S13=−7.31, S33=28.4, S44=26.1, all ×10−13 cm2/dyne.
Data on three crystals were taken from room temperature to 375°C. From these may be computed Young's modulus for any orientation and any temperature in the range given. Young's modulus decreases for all orientations with increasing temperature.
A Resonance Effect in the Synchrotron
Authors: Courant E. D. 
Published: January 2005

The effect of the resonance occurring at n=−d(logH)/d(logr)=¾ between the second harmonic of the frequency of radial oscillations and the frequency of revolution of the particles in a synchrotron is analyzed. It is shown that this resonance will lead to an increase in the amplitude of the radial oscillations if the first Fourier coefficient of the azimuthal variation of n is too large. The effect may occur even if the value of n at the equilibrium orbit is different from ¾, because the orbit will drift back and forth periodically due to the phase oscillations and may cross the place where n=¾.
A criterion is derived for the condition that the increase in the amplitude of the oscillations per unit time due to this resonance be less than the decrease in the amplitude due to the magnetic damping, i.e. that there be a net damping effect. It turns out that this condition reduces to the requirement that the first Fourier component of the azimuthal inhomogeneities of the magnetic field be less than about 10−3. If this condition is not satisfied the resonance effect will reduce the intensity of the beam unless the equilibrium value of n is sufficiently far from ¾.
An Apparatus to Depict the Load-Elongation Diagram of Yarn at Five Cycles per Second
Authors: Breazeale Francis , Whisnant John 
Published: January 2005

An apparatus is described which presents on a cathode-ray oscilloscope the load-elongation hysteresis diagram, loading and unloading, of a length of yarn. The frequency may be adjusted from 1.7 to 5 cycles per second, the constant minimum load per cycle at any value from several grams to several thousand grams, and the percent extension per cycle from several percent down to several tenths of one percent. The growth of the sample as a function of time is automatically plotted, and, in addition, the stretch modulus of the sample at any time may be determined from the setting of an amplifier dial.
As way of illustration of the type of data which may be obtained with this apparatus, there are shown both the absolute and percent energy losses exhibited by tire cords of widely different constructions. For the somewhat arbitrary condition of load increment 2 kilograms over a minimum load of 0.6 kilogram, at a frequency of 5 cycles/second, both the percent and absolute energy losses increase very rapidly with increasing twist in the plies, less rapidly with increasing twist in the cord. Of interest, also, is the extremely high energy losses shown by cords which are made by plying together two plies of originally zero twist, thus giving a cord whose ply and cord twist are approximately the same, and in the same direction. Some other interesting features regarding energy losses in cords are pointed out.
Dust—An Active Meteorological Factor in the Atmosphere of Northern Africa
Authors: El-Fandy M. G. 
Published: January 2005

In subtropical Africa dust is shown to be an active meteorological element, particularly below the T-inversions common at 2000–3000 feet under Etesian conditions. Actual instability of the lower atmosphere is then not necessary for dust to rise, and mere mechanical stirring by day by winds of about 20 miles per hour or more is sufficient to produce severe sand storms over desert areas under such conditions.
A dust particle suspended in the atmosphere has been assumed to possess an ``air-pocket'' or ``surrounding eddy'' of its own. The radius of the ``air-pocket'' of a particle of radius ``a'' cm (less than 5 micron) is shown to be about 10a cm. It is doubtful whether one can assume the persistence of one and the same ``eddy,'' but with such an assumption made the average radius of the ``eddy'' is found to be 6a by observation, but on rejecting the assumption there appears to be a close agreement between theory and observation. The particles also share their excess of heat with their environment in a very small time, of the order of 10−2–10−3 second.
The amount of heat that can be directly supplied to the lower atmosphere by baked dust blown in a dust storm may, by itself, be sufficient to produce convection up to a height of 3000 feet or more. The same range of height of convection is also attainable in a cloud of dust by the absorption of solar radiation scattered or diffusely reflected within the cloud. In this respect it is suggested, though not fully verified, that the effect of suspended dust should be taken into account when discussing problems of upper-layer instability in subtropical Africa.
It has also been observed that in the special cases of ``squalls'' the intensity of the storm, notably the poorness of visibility, is proportional to the time during which the squall reaches its maximum. The feature has been given a mathematical explanation.
The conclusion is that owing to increased absorption of solar radiation within dusty atmospheres, or to direct heating of the air by baked dust that may be blown by day in the warm season of the region, dust is found to play a part that cannot be ignored in modifying the processes of water vapor and heat transfer, by altering turbulent and radiative processes, and in modifying the properties of air masses invading the deserts.
Thermionic Emission from Sintered Cathode of Thoria and Tungsten Mixture
Authors: Fan H. Y. 
Published: January 2005

To obtain suitable conductivity for direct heating, tungsten powder is added to sintered thoria cathodes. The thermionic properties of a cathode, sintered from a mixture of 67 percent thoria and 33 percent tungsten, were investigated. Emission constants were determined and the emission was found to be somewhat lower than that of cathodes sintered from pure thoria.
Change of cathode activity with temperature was observed and studied in detail. The cathode showed high activity at temperatures which would bring about deactivation of ordinary thoriated tungsten and decreased its activity when the temperature was lowered to the range where thoriated tungsten would be activated. A theory is proposed for the mechanism of the change in activity, involving the production of free thorium due to reduction of thoria by tungsten, diffusion and evaporation of thorium from thoria. Evaporation of thorium as well as thoria was proved by the use of a tungsten filament probe which detected evaporation of materials from the cathode by the change of its own emission. The energy of evaporation of free thorium from thoria is estimated from the experiments to be 46600 cal./g-atom. The energy of evaporation of thoria is found to be 184000 cal./g-molecule. The behavior of the cathode is satisfactorily explained by the proposed theory.
Magnetic Properties of Iron Compacts in Relation to Sintering Temperature
Authors: Steinitz Robert 
Published: January 2005

Previous experiments have indicated that the magnetic permeability of sintered iron compacts is to a large extent determined by the final density of the compact. The permeability of five different iron powders has proved to be independent of the origin of the powder, if the compacts were sintered at the same temperature. The results were compared with the theory of Polder and Van Santen and agreed very well with their predicted curve, if the residual pores were assumed to be flat disks. It could be expected that at higher sintering temperatures, the disk-shaped pores would change into a more equiaxed or spherical shape.
Experiments to check this theory have been made, and the results are in good agreement. Compared for identical densities, the permeability of different iron powders is appreciably higher if sintering is done at 1250–1350°C and for 24 hours, instead of at 1150°C for one hour. Different powders, however, now show quite different permeabilities, which could be explained by a different inclination of the powder to form spheroidal pores.
It is shown that coining after high temperature sintering brings the permeability values back to the curve of the disk-shaped flat pores. The effect of the increase in permeability at higher temperature cannot, therefore, be due to a purification process, but must be attributed to a change in the pore shape.
The Precision Determination of Lattice Constants by the Powder and Rotating Crystal Methods and Applications
Authors: Straumanis M. E. 
Published: January 2005

A method that makes possible the attainment of a very high degree of precision in the determination of lattice constants (in some cases more than 1:200,000, even with crystals of lower symmetry) is described. The method and its applications, which has been in steady development since 1934 (in Riga, University of Latvia), tries to eliminate the errors of the Debye-Scherrer-Hull and rotating crystal methods by a careful experimental technique, based on:
(1) Very exactly built cameras of a reasonable diameter (64 mm);
(2) Elimination of all well-known errors of the powder and rotating crystal methods (e.g., elimination of film shrinkage errors by a new method of putting the film into the camera);
(3) Locating the camera in a specially constructed thermostat so that the temperature some hours before and during exposure is kept constant.
The films obtained in this way are very clear, especially in the important back-reflection region, with distinct lines (or spots) that can be measured exactly. As no standard substances are necessary and the absorption corrections are negligible (using very thin samples), the method must be regarded absolute. Of course, the sample (crystal) must be prepared, mounted, and centered under the microscope, a procedure that is not difficult.
Applications: lattice constants and expansion coefficients (even within the range of 10°C); quantitative solubility determinations; appearance of new phases and transition points; the determination of the exact value of Avogadro's number; molecular and atomic weight determinations (if the exact density values are known); statement of imperfections in crystals.