bluuebunny/crossref_metadata_2025 huggingface dataset:
Disk-Loaded Wave Guides
Authors: Chu E. L. , Hansen W. W.
Published: January 2005

Dimensions of disk-loaded wave guide suitable for use in a linear electron accelerator are calculated with high accuracy using Schwinger's method. A qualitative explanation of the method is given.
Visual Methods for Studying Ultrasonic Phenomena
Authors: Barnes R. Bowling , Burton Charles J.
Published: January 2005

After a brief review of various applications of ultrasonic techniques, considerable attention is paid to the established methods employed for making sound waves visible. It is shown that these methods are primarily modifications of the technique of ``schlieren photography'' originally developed by Foucault and used frequently for photographing phenomena (e.g., air flow analysis) in which refractive index gradients are set up. The advantages and disadvantages of the various techniques are discussed in some detail and it is shown that a technique employed by Willard is particularly well adapted to the visualization of ultrasonic waves. A modification of this method is discussed, the experimental apparatus is described and typical photographs of ultrasonic wave patterns are shown. In particular, the close analogy existing between light waves and ultrasonic waves with respect to the wave phenomena of refraction, diffraction, and interference is demonstrated in a number of photographs.
Investigations of a Bearing for Small Angular Deflections without Any Friction and with Negligible Restoring Torque
Authors: Schlitt Helmut
Published: January 2005

This paper deals with bearings supported on metal beams under mechanical stress in the axial direction. Because of a phenomenon related to the bending of long columns under axial compression the torque of the total arrangement can be made zero or even negative. Such a bearing can be designed with two decisive advantages, absolutely no friction, and practically no restoring torque as far as small angles of rotation are concerned. Two different types of beam bearings are treated, and their equations for precalculation are derived. Furthermore, the influences of temperature, external forces, and the angle of rotation on the torque of the bearing are investigated. Finally, a combination of two different beam bearings is shown to offer a possible compensation for these unfavorable effects.
On Supersonic Flow Patterns
Authors: Munk M. M.
Published: January 2005

For a definite Mach number, given by M2 = 4/(3−γ), all Mach lines in a steady plane two-dimensional potential flow of a perfect gas with expansion exponent γ have zero curvature. The use and significance of this relation are discussed, and the hypothetical expansion law consistent with straight Mach lines is deduced.
Use of a Mechanical Harmonic Synthesizer in Electrical Network Analysis
Authors: Brown S. Leroy , McKinney Chester M.
Published: January 2005

A method is described for determining the variation of the resistance (R) and the reactance (X) of an electrical network from mechanical plots of the numerators and denominators (both functions of the angular frequency ω) occurring in the expressions for R and X. From the expressions, R = N(ω)/D(ω) and X = N′(ω)/D(ω), mechanical plots of N, N′, and D versus ω can be obtained with a mechanical harmonic synthesizer, and the values of R or X corresponding to any value of ω may then be determined by taking the ratios of the ordinates of N and D, or N′ and D, corresponding to the desired value of ω.
Theory of Hardness and Measurements Applicable to Contact Problems
Authors: Holm Else , Holm Ragnar , Shobert Erle I.
Published: January 2005

The theory of the hardness is reviewed and measurements are made with respect to the application of hardness data to contact problems, particularly for the determination of the real contact area. The ball indentation method is recommended, with hardness H defined as the ratio P/Sm between the contact load P and the mouth area Sm of the indentation. This hardness is not a single valued material constant but is a function of the specific depth D of the indentation, where D is the ratio between the actual depth and the radius of curvature of the indentation. The variation of H with geometric and metallurgical conditions is discussed together with some empirical formulae to describe the experimental results. The relation between the hardness and the yield point is discussed. A comparison with Brinell and Rockwell hardness numbers is also made. The indentation which two crossed cylindrical rods produce in each other is found to give nearly the same hardness as the ball indentation tests if D exceeds a certain value.
Radiation Resistances of Loaded Antennas
Authors: Raymond Richard C. , Webb Wayne
Published: January 2005

Short cylindrical antennas have been loaded to resonate at frequencies lower than their natural frequencies by means of dielectric sheaths of cylindrical and conical form. These loadings are compared experimentally with loading by means of metal disks at the ends of the antennas. Resistances at resonance calculated by the Poynting vector method for two assumed current distributions are compared with the experimental results. It is shown that for a given current distribution at resonance, the antenna radiation resistance depends only on the antenna length in wave-lengths. Particular loading methods alter the current distributions. Those which produce more nearly uniform current distributions yield higher radiation resistances.
Current Distributions on Some Simple Antennas
Authors: Webb Wayne , Raymond Richard C.
Published: January 2005

A method is described for measuring the amplitude distribution of high frequency current along some simple types of antennas. Measured curves for some cases are given and compared with some frequently assumed curves. Some of the measured distributions were integrated numerically to determine the driving point resistances. The driving point resistances were measured for geometrically similar antennas in some cases. Deviations from usually assumed curves are significant, but do not bring about large errors in the calculated resistances.
On Theoretical Signal-to-Noise Ratios in F-M Receivers: A Comparison with Amplitude Modulation
Authors: Middleton David
Published: January 2005

Signal-to-noise ratios at the output of an f-m receiver are determined as functions of the input signal-to-noise ratio, clipping level, and i-f and audio filter characteristics when random (fluctuation) noise accompanies the signal to be observed. Both narrow and broad band f-m are examined. Specific calculations are made for sinusoidal frequency modulation, and it is indicated how data for this simple type of signal may be related to the more complex phenomenon of speech. The concept of the signal-to-noise ratio is redefined to describe more accurately the sensing of a signal in noise, since the conventional definition for f-m proves inadequate and misleading, except for strong carriers. Extensive comparisons are made with a-m reception employing a half-wave linear rectifier, and it is found that for moderate and weak (<3 db) signals a-m requires less input signal power against the same noise background than does f-m to achieve the same desired output. This is particularly evident for weak signals. Only when the signal is strong (>10 db) is f-m superior to a-m; here broad band f-m with very heavy limiting is needed. Narrow band f-m at its best (no limiting) is comparable with or inferior to a-m at high signal levels. Limiting proves to be detrimental in narrow-band operation for all cases involving fluctuation noise, whereas heavy limiting is essential for successful broad-band performance. Furthermore, the shape of the i-f response becomes important in the latter, while it is not in the former. A large number of curves illustrating the average and mean-square signal and noise outputs, etc., and signal-to-noise ratios for various conditions of operation are included.
Effect of Surface Roughness on Eddy Current Losses at Microwave Frequencies
Authors: Morgan Samuel P.
Published: January 2005

A theoretical investigation has been made of the power dissipation by eddy currents in a metallic surface at microwave frequencies in the presence of regular parallel grooves or scratches whose dimensions are comparable to the eddy current skin depth. The eddy current equation has been integrated numerically for grooves of various shapes and sizes transverse to the direction of induced current flow, and the corresponding losses are calculated and plotted. The power dissipation is increased by about 60 percent over its value for a smooth surface when the root-mean-square deviation of the grooved surface from an average plane is equal to the skin depth; the exact shape of the grooves is not critical. The increase in eddy current losses caused by grooves parallel to the current is shown in a particular case to be only about one-third as great as the increase caused by transverse grooves of similar size. The effect on losses of an isolated narrow crack or fissure transverse to the current is briefly discussed.
Flash Radiography Applied to Ordnance Problems
Authors: Clark J. C.
Published: January 2005

Flash radiographic techniques as applied to Army Ordnance problems are discussed. The feasibility of using microsecond x-ray bursts in the study of internal ballistic and explosive phenomena is discussed and illustrated by selected flash radiographs.
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.
Reflection and Transmission of Electromagnetic Waves by a Spherical Shell
Authors: Keller Herbert B. , Keller Joseph B.
Published: January 2005

Exact, explicit expressions are obtained for the field of a radiating periodic point dipole located in medium 1 at the center of a spherical shell of medium 2, which is bounded by medium 3. The values of ε, μ, σ and the shell radii are arbitrary. The reflected and transmitted fields are examined in various special cases. When the shell radii become infinite, the fields agree with those obtained by R. K. Luneberg for the case of plane waves normally incident on a flat plate of medium 2 between media 1 and 3. When the radii are infinite and media 2 and 3 identical, the Fresnel formulas for normal incidence of plane waves on a plane interface between two half-infinite media are obtained. When the radii are finite, media 2 and 3 identical and μ1 = μ3, the results of C. T. Tai are obtained. For finite radii, media 1 and 3 identical, and shell thickness small compared to a wave-length, the fields check the approximate results of J. B. Keller for the fields reflected and transmitted by a thin shell of any shape, when his results are specialized to the present case.
Microwave Antennas and Dielectric Surfaces
Authors: Redheffer R. M.
Published: January 2005

For a plane dielectric sheet near a receiving antenna the power varies sinusoidally with distance, having a half-wave period and an average proportional to the transmission coefficient. This is explained by assuming an equivalent antenna reflection, an assumption checked by special experiments. The theory includes phase and arbitrary incidence, for which the wave may be elliptically polarized. The reciprocal of received amplitude vs. polarization then gives a similar ellipse with 90° shift in orientation. Corresponding theory for transmitters shows that the reflection varies sinusoidally with half-wave period and with average proportional to the reflection coefficient. For a distant sheet there is inverse-distance attenuation. The effect of initial antenna mismatch is fully investigated. For any cylindrical surface, including corrugations or a plane, amplitude reflection varies with angle as the secondary power pattern. With a paraboloidal antenna of radius a at wave-length λ, the reflection from a circular cylinder of radius ρ and reflection coefficient R is 6R(λp)½/13a; that from a narrow strip of width 2aq is (7Rq/80)(15−10q2+3q4); that from a narrow strip distant aq′ from the axis is proportional to R(1−q′2)4. If the initial mismatch gives a reflection r, and if the surfaces make an angle θ with the axis, the above are multiplied by (1−r2) exp (4θ2 ln2/w) where w is the antenna pattern half-width. Corresponding results are given for corrugated surfaces and series of strips. Applications to radomes are discussed, and to pressurizing seal design and tolerances. All results are extensively verified experimentally.
Statistical Aspects of Fracture Problems
Authors: Epstein Benjamin
Published: January 2005

In recent years there has been an increasing interest in the development of statistical theories of strength. A main aim of these theories is to explain in a reasonable way such things as the dependence of the strength of specimens on their volume or length. In this paper it is pointed out that the problems posed by these models are equivalent to an important problem in mathematical statistics, namely, the distribution of the smallest value in samples of size n drawn from a population having some probability density function f(x). The calculations made by mathematical statisticians give a far more complete description of the results to be expected than do the estimates to be found up to now in the technical literature.
An Electronic Differential Analyzer
Authors: Koehler J. S.
Published: January 2005

An electrical device is designed which will solve ordinary, non-linear, non-homogeneous differential equations or the boundary value problems based on such differential equations. The device is based on the fact that the charge on the condenser in a series resonant circuit varies with the time in a manner described by a linear second-order differential equation. The desired variations of the coefficients with time are fed into the apparatus by using a variable voltage generator. This generator provides a small voltage which varies with time in accordance with any given curve. The variable voltage generator has been constructed and operates satisfactorily. The resulting solution is drawn by an oscillograph. The instrument is designed to furnish a solution which does not deviate from the true solution by more than four percent.
The Resonant Modes of the Rising Sun and Other Unstrapped Magnetron Anode Blocks
Authors: Kroll Norman M. , Lamb Willis E.
Published: January 2005

In this paper an electromagnetic field theory is developed for unstrapped magnetron anode blocks of rather general symmetry, from which the wave-length spectrum and associated electromagnetic fields can be computed. The method is a generalization of that developed by Clogston (A. M. Clogston, Ph.D. thesis, Massachusetts Institute of Technology, 1941) for the simple case in which all of the side resonators are alike. The characteristics of the rising sun type anode block are discussed in some detail. In addition, the general features of anode blocks having any kind of symmetry are discussed in the limiting case of small anode diameter.
Measurement of Stress by Means of X-Rays
Authors: Thomas D. E.
Published: January 2005

The article shows how the formulae used in stress measurement by x-rays are derived and points out an error in a recently published book.
Measured Impedances of Helical Beam Antennas
Authors: Glasser Otto J. , Kraus John D.
Published: January 2005

Experimentally determined impedance characteristics are presented for helical antennas. At frequencies too low for the axial or beam mode, the terminal impedance changes greatly with small variations in frequency. However, in the frequency range of the fundamental axial mode, the impedance is relatively constant, especially if the number of turns and the pitch angle of the helix are not too small. This characteristic is an advantage in wide frequency-band applications. For example, the resistance variation of a 5-turn, 18-degree helix over a frequency band of about 1.7 to 1 is only 105 to 145 ohms, and the reactance variation only 0±15 ohms. The effect of the pitch angle and number of turns is discussed.
The Triangulation of a Two-Dimensional Continuum for the Purpose of the Approximate Solution of Second-Order Partial Differential Equations
Authors: Tasny-Tschiassny L.
Published: January 2005

It is shown how a non-homogeneous, non-isotropic, electrically conductive, two-dimensional continuum can be replaced by a network of resistors whereby the nodes of the network are situated at any arbitrarily selected points, and how Southwell's relaxation method can be applied to this network for the solution of potential problems.
Dark-Field Electron Microscopy. I. Studies of Crystalline Substances in Dark-Field
Authors: Hall C. E.
Published: January 2005

Dark-field images in the electron microscope were studied by means of an objective aperture system fixed to the object rather than to the objective lens. The resolution in images produced by the diffusely scattered component is in the range 100 to 200A, but the resolution in images produced by Bragg reflections approaches that obtainable in bright-field operation. A resolution of about 50A was obtained with test objects consisting of evaporated films containing small crystallites, but it is estimated that crystallites having dimensions down to about 20A can be recorded with conditions prevailing in this work. Substances studied in dark-field include evaporated films of metals and compounds and finely divided substances. It is concluded that the dark-field method is of value for studying the size, location, and other characteristics of crystalline components in a specimen. Some of the theoretical factors influencing resolution in dark-field are discussed.
Tensile Properties of Rolled Silver Chloride
Authors: Axilrod B. M. , Lamb J. J.
Published: January 2005

Tensile tests were made at 25° and 93°C on specimens taken from a rolled silver chloride sheet which was prepared from a single crystal. Tensile strengths of approximately 2500 and 1500 lb./in.2 were obtained at 25° and 93°C, respectively; the corresponding elongations at failure were about 15 and 40 percent, respectively. For specimens annealed at 200°C and tested at 25°C, the tensile strength was 75 percent and the elongation about twice that of the corresponding values for unannealed specimens. The stress-strain diagram of the rolled material was determined at 25°C with optical strain gauges while loading and unloading two specimens to maximum strains of 0.0015 and 0.0037, respectively; no effect of this moderate strain on the infra-red transmissivity was observed.
Barkhausen Noise and Magnetic Amplifiers. I. Theory of Magnetic Amplifiers
Authors: Krumhansl J. A. , Beyer R. T.
Published: January 2005

An analysis is made of the operation of magnetic amplifiers or non-linear transformers. Open circuit output voltages are calculated for transformers driven by a sinusoidal primary current, and also for sinusoidal primary current plus a direct current bias. The case of a loaded secondary is also considered and it is shown that there exist conditions for instability or resonance. A subsequent paper will consider Barkhausen noise as a limiting condition on the sensitivity of these devices.
On the Infinitely Long Cylindrical Antenna
Authors: Papas Charles H.
Published: January 2005

Using the method of steepest descents the far field and the asymptotic form of the current distribution is obtained for an infinitely long, perfectly conducting cylindrical antenna excited by a localized electromotive force. The low frequency value of the radiation conductance is determined by integrating the radiated energy flux over a large sphere.
Phase Contrast in Electron Microscope Images
Authors: Ramberg E. G.
Published: January 2005

Image contrast in electron microscope images may arise from absorption, scattering, or phase changes impressed on the illuminating electron wave. In the present paper the intensity distribution in the in-focus and out-of-focus image of an edge of a transparent thin film introducing a prescribed phase change in the incident beam is calculated. It is found that the resulting ``phase contrast'' increases both with the film thickness (i.e., magnitude of phase change) and with the degree of defocusing and, for thin specimens, exceeds other sources of contrast in magnitude. The model is too schematic to permit a quantitative comparison with measured intensity distributions.
Flow through a Rocket Nozzle with and without Vibrational Equilibrium
Authors: Penner S. S.
Published: January 2005

A procedure is outlined for calculating the maximum changes in the exhaust velocity of gases which can be introduced during flow through a rocket nozzle as the result of vibrational time lags. Representative calculations have been carried out for a number of propellant systems. These calculations indicate that the vibrational time lags cannot produce changes in exhaust velocity which exceed a few percent. The numerical values of the changes are found to depend not only on the nature of the gases but also on the occurrence or non-occurrence of chemical reaction during flow.
A Note on the Substitution Principle for Steady Gas Flow
Authors: Prim R. C.
Published: January 2005

The Substitution Principle established by Munk and Prim for flows of a gas having constant specific heats is extended to the wider class of fluids having a state equation of the form ρ=P(p)S(s). The equations of motion for this class of fluids is reduced to a canonical form involving only the reduced velocity vector and the pressure. It is shown that explicit elimination of the pressure from these equations is possible only for those fluids whose state equation has the form ρ=pkS(s) with k<1. Relations between the Mach number and stagnation pressure and the reduced velocity field are discussed for the class of fluids under investigation.
High Frequency Total Emission Loading in Diodes
Authors: Begovich Nicholas A.
Published: January 2005

An expression is derived for the total emission conductance produced by the electrons returned to the cathode of a diode operating with a retarding off-cathode field. For the retarding voltage and diode spacing used, the assumption of a linear potential distribution is justified. Examples of the variation of the total emission conductance with retarding voltage and frequency are illustrated.
A Visual Method for Demonstrating the Path of Ultrasonic Waves through Thin Plates of Material
Authors: Burton Charles J. , Barnes R. Bowling
Published: January 2005

A visual method for studying the path of ultrasonic waves through thin plates of material has been devised, and a set of photographs showing the complexity of ultrasonic reflection and transmission by metal plates has been obtained. An attempt has also been made to estimate the critical angles of total reflection for dilatation and shear waves by visual examination of the reflection of a supersonic beam. Using these data, Young's modulus and the shear modulus for a 116-inch aluminum sheet have been determined and the values are compared with those obtained using a previously described electrical method and with published data.
The High Current Carbon Arc and Its Mechanism
Authors: Finkelnburg Wolfgang
Published: January 2005

The high current carbon arc with maximum crater brightness of 2000 candles per mm2, axial intensity of 1.2×106 candles, power inputs up to 200 kw, light efficiencies exceeding 90 lumens per watt, radiation efficiency of 73 percent, crater temperatures up to 8000°K, and arc stream temperatures of the order of 12,000°K is the most powerful and one of the most interesting radiation sources known. The rising voltage characteristic, the anodic vapor stream which causes its excellent radiation properties, and the contracted arc stream distinguish the high current carbon arc from the well-known normal low current carbon arc. The properties of the contracted arc stream are discussed and a general theory of arc streams is presented. Starting from the anodic mechanism for the low current carbon arc, the anodic mechanism of the high current arc is developed. The rising voltage characteristic, the anodic vapor stream, and the high crater brightness are explained as a consequence of an abnormal voltage drop in front of the anode which increases with increased current density and is caused by a very rapid evaporation of the anodic material. The important role which the magnetic field of the arc current plays in the stabilization of all high current arcs is pointed out. The author believes that this unique high temperature arc has bearing on other arc and spark discharges, and also will play an important role in future developments of high temperature physics and chemistry.
Radio Doppler Investigation of Meteoric Heights and Velocities
Authors: Manning L. A. , Villard O. G. , Peterson A. M.
Published: January 2005

A continuous-wave Doppler method of determining meteoric velocities and heights was tested during the 1948 Perseid meteor shower. The accuracy of the technique was found to compare very favorably with optical and other radio methods. Doppler measurements have the advantage of relatively great sensitivity.
Propagation of Audiofrequency Sound in High Polymers
Authors: Witte R. S. , Mrowca B. A. , Guth E.
Published: January 2005

Velocity and attenuation measurements were made in thin strips of rubber from 0.5 to 5 kc and from −5°C to 90°C to obtain the dynamic viscoelastic constants of butyl and GR-S gum stocks. Above room temperature velocity and attenuation are higher in butyl gum than in GR-S. In all cases, the velocity increases with decreasing temperature and increasing frequency. The attenuation shows a peak with temperature. For butyl the peaks are broad and occur at higher temperatures than for GR-S. For both stocks an increase in frequency gives peaks which are higher and sharper, and shifted to higher temperatures. In some instances, there are indications of peaks in the attenuation versus frequency at frequencies beyond our range of measurement. The behavior of the dynamic modulus in the temperature and frequency range studied is similar to that of the velocity. These results combined with low temperature static measurements and very low frequency dynamic measurements indicate a U-shaped modulus-temperature curve whose minimum broadens and shifts to higher temperatures with increasing frequency. This may be explained by a generalization of the kinetic theory of rubber elasticity, taking into account intra- and intermolecular forces, and considering time effects.
Propagation of Ultrasonic Bulk Waves in High Polymers
Authors: Ivey Donald G. , Mrowca B. A. , Guth Eugene
Published: January 2005

The propagation of supersonic waves in bulk rubbers has been studied from 40 kc/sec. to 10 Mc/sec. and from −60°C to 60°C. The wave velocity was found to increase with decreasing temperature, leveling off both at high and low temperatures, and was found to increase slightly with frequency. Peaks in attenuation as a function of either temperature or frequency were observed, the peaks occurring at lower temperatures for lower frequencies. The peaks for butyl, a high loss rubber, are broader and higher than those for GR-S and Hevea, which are lower loss rubbers. The results are in qualitative agreement with data obtained by strip methods at audiofrequencies. However, for bulk waves the real and imaginary parts of two elastic constants, the bulk and shear moduli, determine wave velocity and attenuation; hence, independent measurements of shear wave properties are necessary to evaluate these constants. A three constant theory is discussed, assuming a shear viscosity only, so that an effective modulus K+4μ/3 is obtained, where K and μ are the bulk and shear moduli. Relaxation times of the order 10−6 to 10−8 second are indicated. Approximate values of the dynamic Young's modulus are obtained from the effective modulus by assuming that the high frequency dispersion is due to the appearance of a ``crystalline'' shear elasticity. These results are correlated with low frequency data, and the dynamic Young's modulus and the loss factor are plotted. The loss factor exhibits a maximum in the dispersion region. Results are plotted in the range from 1 c.p.s. to 107 c.p.s., which covers a wider range of frequency than earlier investigations. The necessary distribution of relaxation times is discussed.
Equation of State for Polystyrene
Authors: Spencer R. S. , Gilmore G. D.
Published: January 2005

Practical considerations emphasize the desirability of formulating an adequate equation of state for polystyrene. A fairly satisfactory one is this simplified version of van der Waals' equation, (P+π)(V−ω)=nRT,where π is the internal pressure (or cohesive energy density) and ω is the volume at absolute zero, by extrapolation. Evaluating constants from thermal expansion data and expressing P in p.s.i., V in cc per gram, and T in degrees Kelvin, this becomes (P+27,000)(V−0.822)=11.6T.Agreement with compressibility measurements, which are described in some detail, is good. Discrepancies with room temperature values of sound velocity and cohesive energy density by swelling measurements are discussed briefly.
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.
Relationship between Gough-Joule Coefficients and Moduli of Vulcanized Rubbers
Authors: Conant F. S. , Hall G. L. , Thurman G. R.
Published: January 2005

The Gough-Joule coefficients (a) at constant stress and (b) at constant strain are defined and methods of measurement of each on vulcanized rubbers are given. It is shown mathematically and experimentally that the ratio of (b) to (a) is equal to the ``tangent'' modulus. The quotient of the Gough-Joule coefficient at constant stress divided by the stress and the quotient of the Gough-Joule coefficient at constant strain divided by the strain are shown to be constants which are independent of the stress-strain-temperature conditions of the test. Experimental data are given for stocks based on Hevea, GR-S, Neoprene GN, Butyl Rubber, and Butaprene.
Polymerization in the Solid State
Authors: Miller E. , Fankuchen I. , Mark H.
Published: January 2005

The melting point of ε-carbobenzoxy-α-carboxyl-l-lysine anhydride stored at room temperature for one year (I) rises considerably above that of the freshly prepared compound (II) (m.p. 100°). X-ray diffraction studies indicate: (II) is probably monoclinic, a≃90A, b=5A, c≃10A; (I) suffered disorientation giving diagrams similar to those of bulk polymer (III); threshold conditions for the disorientation process are heat-treatment of (II) at 70° for 24 hours; the change appears to be complete when (II) is heat-treated at 85° for 24 hours since the diagrams are similar to those of (III) and no further change is observed in the diagrams of samples treated under more severe conditions below the melting point. The largest Bragg spacing of 29A observed for (II) is of the same order of magnitude as the over-all length of a fully extended hydrogen-bonded dimer of (II). The smallest refractive index of (II) is parallel to the b axis. The structure of (II) is concluded to be a triple dimer layer arrangement which would involve a relatively small entropy change on polymerizing in the solid state to give (I) and (III).
Time and Stress Effects in the Behavior of Rubber at Low Temperature
Authors: Beatty J. R. , Davies J. M.
Published: January 2005

The stiffening of rubber-like materials at low temperature involves several different phenomena, sometimes with their effects superimposed. One of these is crystallization. This is a rate process which is generally very fast at high stresses and very slow at zero stress. In these experiments at temperatures near −25°C and under a shear stress of about 148 p.s.i. the dynamic modulus of the rubber increased at a rate convenient to study. Correlation with x-ray data showed that crystallization was very likely responsible for the increase in stiffness. The rate of change of stiffness increased rapidly with increase in applied stress, and there was no optimum rate at −25°C as has been found for unstressed rubber. The degree of vulcanization influenced the rate of change, tighter cures giving smaller changes. Neoprene FR, GR-S and polybutadiene, which ordinarily show little evidence of crystallization showed very definite, but small increases in stiffness. Mixing GR-S with natural rubber seems to limit the crystallization of the natural rubber rather effectively, but apparently Neoprene FR does not mix intimately enough with natural rubber to affect the crystallization of the latter appreciably.
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.
Dilatometric Studies of High Polymers. I. Second-Order Transition Temperature
Authors: Kolb Harry J. , Izard Emmette F.
Published: January 2005

By means of a density balance, the relationship between intrinsic viscosity and dilatometric properties is established for polyethylene terephthalate. The most pronounced property change associated with increasing intrinsic viscosity was observed to be the second-order transition temperature. The relationship between crystallinity and dilatometric properties is presented for 3 aromatic polyesters. In every case, increased crystallinity in the polymers is associated with higher second-order transition temperatures, larger transition range, higher density, and lower volume coefficients of expansion. Second-order transition temperatures, densities at 0°C, and volume of coefficients of expansion are presented for a number of polyesters and vinyl polymers to illustrate the effects of chemical structure as well as physical state on these dilatometric properties. Illustration of the effect of copolymerization on second-order transition temperatures is made with a copolyester system.
Dilatometric Studies of High Polymers. II. Crystallization of Aromatic Polyesters
Authors: Kolb Harry J. , Izard Emmette F.
Published: January 2005

By means of both a density balance and gradient tube, experimental density data are obtained to illustrate the thermal crystallization behavior of 3 aromatic polyesters at temperatures from 90°C to 150°C. The data are discussed with reference to both amount and rate of crystallization and density curves are presented to show qualitative similarity between kinetics of polymer crystallization and the kinetics of chemical reactions. From the experimental data, a temperature, for convenience labeled the minimum crystallization temperature, is described and is shown to be 30° to 50° above the second-order transition temperature for the polyesters. In addition to thermal crystallization, data are presented to show that immersion media may initiate crystallization below the minimum temperature associated with thermal crystallization of polymers. Liquids used as immersion media for polyethylene terephthalate were water, methyl alcohol, acetone, benzene, nitromethane, and nitric acid. The last four liquids initiate crystallization of the polymer at room temperature.
Notes on the Excitation of Electromagnetic Waves in Cylindrical Metallic Wave Guides
Authors: Colino A.
Published: January 2005

In this paper very simple formulas are deduced for calculating the amplitude of modes produced in a cylindrical guide when the currents distribution is known. One example is included.
Use of a Mechanical Harmonic Synthesizer in Electric Wave Filter Analysis
Authors: Brown S. Leroy , Sharp James M.
Published: January 2005

A mechanical method is described for graphing the effect of the variation with frequency of the series reactance (X1) and the shunt reactance (X2) of a filter section. This method permits the quantities X1/−4X2, X1X2{(X1/−4X2)−1} and X1X2/{(X1/−4X2)−1}, from which the characteristics of an electric wave filter are calculated, to be graphed easily as a function of frequency. The cut-off frequencies are located directly from the graphs of N and D (where N/D is either the ratio X1/−4X2 or (X1/−4X2)) as functions of frequency, and the calculation of the attenuation and phase shift at any frequency is readily made from the ratio of corresponding ordinates of the N and D curves. The image impedance is determined from the ratio of corresponding ordinates from two additional curves which are mechanical plots of the numerator and the denominator of the expression for the square of the image impedance, X1X2{(X1/−4X2)−1} for the mid-series image impedance, and X1X2/{(X1/−4X2)−1} for the mid-shunt image impedance.
Barkhausen Noise and Magnetic Amplifiers. II. Analysis of the Noise
Authors: Krumhansl J. A. , Beyer R. T.
Published: January 2005

The Barkhausen noise is calculated for ferromagnetic cores used in magnetic amplifiers. The method of analysis follows that used in the analysis of the shot effect. The signal-to-noise ratio for a typical magnetic amplifier circuit is calculated and compared with experiment.
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.
Electric-Field Modulation of Ultrasonic Signals in Liquids
Authors: Nolle A. W.
Published: January 2005

An experiment is performed to determine whether the presence of a periodic transverse electric field produces modulation, either of amplitude or of phase, of a continuous progressive ultrasonic wave train passing through the liquid. One object of the experiment is to ascertain whether the application of an electric field to a polar liquid influences either the compressibility or the viscosity of the liquid through molecular orientation. The results of a related investigation in which an electric field was applied in the direction of wave travel, published in 1945 by Barone and Giacomini, were inconclusive. The present experiments reveal phase modulation in a number of conducting liquids. This is explained as a thermal effect involving the temperature dependence of velocity of sound. No evidence is found of phase modulation resulting from dipole orientation in non-conducting polar liquids. Amplitude modulation, which would result from change of attenuation, is not found in any liquid. A variety of organic liquids is investigated. Limits of sensitivity of the apparatus are given.
Inter-Particle Interference Effects in the Small Angle X-Ray Scattering from Fine Powders
Authors: Lund Louis H. , Vineyard George H.
Published: January 2005

Simple formulas for calculating the small angle x-ray scattering from aggregates of identical spherical particles, taking into account the interference between different particles, are given. The case of independent clumps of particles and the case of a more general arrangement describable by a radial density function are considered. Calculated curves of scattered intensity vs. angle for likely arrangements of both types are presented. The assumption that each particle scatters independently is seen to be a poor approximation whenever there is a significant amount of clumping or whenever the average density of the sample is as much as one third of the density corresponding to close packing. Estimates of particle size from the small angle scattering are shown to be seriously affected.
Synthesis ofn-Reactance Networks for Desired Transient Response
Authors: Aigrain Pierre R. , Williams Everard M.
Published: January 2005

This paper deals with the problem of synthesizing a network with n-reactances and an associated necessary number of resistances which will have a transient response most nearly equal, in the least square sense, to a desired transient response when excited with some particular input voltage or current impulse. A method is derived for this synthesis in the cases for which the Laplace transform of the input impulse contains no poles or one pole at s=0. The significance of this method with relation to synthesis techniques based on steady-state considerations is discussed, and the method is illustrated for a simple case.
An Electro-Mechanical Device for Solving Non-Linear Differential Equations
Authors: Ludeke Carl A.
Published: January 2005

This paper introduces an electro-mechanical device for solving some non-linear differential equations. Solutions are obtained with sufficient accuracy and speed so that an entire domain of solutions can be quickly investigated. The procedure not only avoids the limited point of view inherent in the solutions obtained by most mechanical means, but also retains sufficient accuracy so that its solutions can be used as a starting point for numerical methods if further accuracy is desired. Examples are given of results obtained on some non-linear differential equations.