bluuebunny/crossref_metadata_2025 huggingface dataset:
Calculated Frequency Spectrum of the Shot Noise from a Photo-Multiplier Tube
Authors: Sard R. D.
Published: January 2005

The mean square noise current per unit frequency range as a function of frequency, or ``power spectrum,'' of the shot noise produced by a secondary-emission multiplier tube is calculated. A general expression for it, (3), is set up and then applied to the RCA 931 family of photo-multiplier tubes. These tubes are of interest as relatively intense sources of random noise of constant intensity up to high frequencies. When an electron enters the collecting space, it initiates a pulse of current in the anode circuit. In the 931 operated with 100 volts per stage, the pulse has a total duration of about 6×10−10 sec. and a half-width of about 1.5×10−10 sec. The electrons descended from the same photon do not enter the collecting space simultaneously but are spread out over a time of the order of 6×10−10 sec. Because of the non-zero duration of the pulses and the spread in their time of occurrence, the noise spectrum is essentially flat only up to several hundred Mc, falling rapidly at higher frequencies. The paucity of data and the approximations made in the calculation make our curve of noise output versus frequency significant only as regards order of magnitude and general trend. It does seem safe to predict that the noise intensity ought to be constant from zero up to about 100 Mc, begin to fall off appreciably between 100 Mc and 1000 Mc, and become very weak at higher frequencies. Partial confirmation is provided by unpublished measurements of Jastram at the Radio Research Laboratory, Harvard University, which show that at 30 Mc the noise output is still about the same as in the range 0 to 5 Mc. There is also some experimental indication that the output is about the same at 100 Mc and that it is much smaller at higher frequencies.
The Response of Biased, Saturated Linear and Quadratic Rectifiers to Random Noise
Authors: Middleton David
Published: January 2005

Spectral distributions and powers associated with the output of biased, saturated linear and quadratic rectifiers are determined according to the method of Rice when the incoming disturbance is random noise. Three classes of input spectra are considered: (I), broad band noise, where the central frequency is equal to or less than the spectral width, (II), semi-broad band noise, for which the central frequency exceeds the width by a moderate amount, and (III), narrow band noise, where the width is much less than the central frequency. Rectification of types I and II yields spectra having roughly the same distribution as that of the incoming waves, but for type III an infinite number of separate noise bands are generated and appear in the output, centered about harmonics of the central frequency. It is found that clipping, whether at the ``top'' or ``bottom'' of the incoming wave, always spreads the spectrum and reduces the output power. Further, it is shown that clipping due to cut-off alone produces a greater spectral spread than clipping with saturation in addition, for types I and II, but not necessarily for spectra of type III. Symmetrical clipping for classes I and II yields little broadening of the spectrum, even in extreme cases, and for class III waves, the even-harmonic regions are completely missing except for a d.c. component, and only the odd-harmonic zones appear. The behavior of linear and quadratic rectifiers is qualitatively similar in most cases. The powers in the d.c. and continuous portions of the output spectrum are shown to be independent of the spectral shape of the incoming noise. Some examples of extreme clipping are considered, numerous curves are included, and a general analysis is outlined.
The Flow of Gases in Pipes at Low Pressures
Authors: Brown Gordon P. , DiNardo Albert , Cheng George K. , Sherwood Thomas K.
Published: January 2005

Data are presented on the flow of air at low pressures in copper pipes of radius 0.795 and 1.30 cm; iron pipes of radius 2.64, 5.12, and 10.1 cm; and for hydrogen in a copper pipe of radius 1.30 cm. Data are also given for the resistance to flow of air in 1½- and 3-inch nominal pipe size elbows, for 1½-inch Kinney bellows valves, and for short sections of 1-inch nominal pipe size iron pipe connecting large gas chambers. The data on straight iron and copper pipes, together with the data from the literature on glass capillaries, are correlated by the introduction of a correction factor F in Poiseuille's equation. F is correlated graphically in terms of a dimensionless group representing the ratio of mean free path to pipe radius, with separate curves for iron pipe and for copper and glass pipes or capillaries.
Absorption of Microwaves by Gases. II
Authors: Walter John E. , Hershberger W. D.
Published: January 2005

The absorption coefficients and dielectric constants of sixteen gases have been measured at the two wave-lengths λ=1.24 cm and λ=3.18 cm. The gases are H2S, COS, (CH3)2O, C2H4O, C2H5Cl, SO2, NH3, six halogenated methanes and three amines. Certain improvements in technique are described; these improvements permit detection of absorption coefficients as small as 0.2×10−4 cm−1 and measurement of larger coefficients with an accuracy of ± 5 percent. The measured dielectric constants at these wave-lengths are essentially equal to the static values. A quantitative interpretation of the absorption coefficients in terms of the known structure and spectra of the individual molecules is given. The theory indicates that all non-planar molecules which possess a permanent dipole moment should show appreciable absorption in the microwave region.
Electrical Observations of the Austenite-Martensite Transformation in Steel
Authors: McReynolds Andrew W.
Published: January 2005

A method is described for observing the austenite-martensite transformation in steel by measuring electrical resistance. Small wire samples are heated and cooled either in vacuum or in air while temperature and resistance are automatically recorded. Temperature throughout the sample is uniform enough to permit a determination of resistance as a function of temperature. It is shown that from these data a complete record of transformation during cooling can be computed. Such transformation data have been obtained on three steels of widely different compositions, representing the types of steel in which transformation is most difficult to observe.
Energy Build-Up in Magnetrons
Authors: Hunter Lloyd P.
Published: January 2005

An analysis of the operation of resonant cavity magnetrons is made without regard to the mechanism of conversion of the d.c. input power into the r-f output power. The magnetron is represented by its equivalent circuit and is assumed to be essentially in equilibrium at every point of its energy build-up curve. The last assumption is shown to be reasonable on the basis of measured starting times. From the data of load impedance charts and the rise of the r-f pulse, the relation between power generated and vane voltage is deduced. By considering the division of the energy between that stored in the resonant system, and that dissipated in the load, the law of build-up is derived. The dependence of starting time on load is calculated and agrees with experiment when the extra energy stored in the connecting line is taken into account. The starting time is affected slightly by the initial noise level and becomes infinite below a minimum Q. For high Q values the starting time can be varied only by changing the energy stored in the line, which may enable one to design a line for ``mode'' suppression.
The Measured Impedance of Cylindrical Dipoles
Authors: King D. D.
Published: January 2005

The input impedance of cylindrical dipoles is considered from the experimental point of view. Errors in measuring methods are considered and the results of a recent determination of dipole impedance are displayed.
Transient Analysis of Linear Systems, Using Underwater Explosion Waves
Authors: Osborne M. F. M. , Carter J. L.
Published: January 2005

The indicial admittance of a simple mechanical system, a tourmaline crystal hydrophone, has been determined from its response to an underwater explosion wave. The indicial admittance is simply related to the observed response to the explosion wave—the observed response is just the indicial admittance ``wrapped around'' an exponential, e−t/τ. The relative frequency calibration of two hydrophones obtained by Fourier analysis of their responses to the explosion wave is in good agreement with the direct continuous wave comparison. The peak pressure of the explosion wave is also determined from this Fourier analysis. It is suggested that the explosion wave can be used as a tool in acoustical ``circuit analysis'' in much the same way that a square wave generator is used in electrical circuit analysis.
An X-Ray Method for Measuring the Thickness of Thin Crystalline Films
Authors: Eisenstein A.
Published: January 2005

When x-rays are scattered from a thin crystalline surface film overlying a crystalline base material, diffraction lines are observed from both materials. Equations are developed for the general case of (1) a flat sample and (2) a cylindrical sample expressing the ratio of line intensities from the two materials as a function of film thickness. A usable range of 10−6 cm to 5×10−2 cm is indicated. Experimental confirmation is found in the range 10−4 cm to 6×10−3 cm.
A New Bridge Photo-Cell Employing a Photo-Conductive Effect in Silicon. Some Properties of High Purity Silicon
Authors: Teal G. K. , Fisher J. R. , Treptow A. W.
Published: January 2005

A pure photo-conductive effect was found in pyrolytically deposited and vaporized silicon films. An apparatus is described for making bridge type photo-cells by reaction of silicon tetrachloride and hydrogen gases at ceramic or quartz surfaces at high temperatures. The maximum photo-sensitivity occurs at 8400–8600A with considerable response in the visible region of the spectrum. The sensitivity of the cell appears about equivalent to that of the selenium bridge and its stability and speed of response are far better. For pyrolytic films on porcelain there are three distinct regions in the conductivity as a function of temperature. At low temperatures the electronic conductivity is given by the expression σ=Af(T) exp−(E/2kT). At temperatures between 227°C and a higher temperature of 400–500°C σ=A exp−(E/2kT), where E lies between 0.3 and 0.8 ev; and at high temperatures σ=A exp−(E/2kT), where E=1.12 ev. The value 1.12 ev represents the separation of the conducting and non-conducting bands in silicon. The long wave limit of the optical absorption of silicon was found to lie at approximately 10,500A (1.18 ev). The data lead to the conclusion that the same electron bands are concerned in the photoelectric, optical, and thermal processes and that the low values of specific conductances found (1.8×10−5 ohm−1 cm−1) are caused by the high purity of the silicon rather than by its polycrystalline structure.
The Production of High Centrifugal Fields
Authors: Beams J. W. , Young J. L. , Moore J. W.
Published: January 2005

High centrifugal fields were produced by spinning small solid steel spherical rotors up to their bursting speeds. The rotors were supported magnetically in a vacuum by an improved method and spun by rotating magnetic fields. The peripheral velocities at which the rotors of various sizes, made of the same (flaw free) steel and having the same shapes, exploded, were roughly the same and of the order of 105 cm/sec. A centrifugal field of 2.4×108 times gravity was obtained with a .795-mm spherical rotor which was the smallest diameter tried. Calculations indicate that in some cases plastic flow probably occurred in small regions near the centers of the spherical rotors somewhat below their bursting speed.
A Cathode-Ray Tube for Viewing Continuous Patterns
Authors: Johnson J. B.
Published: January 2005

A cathode-ray tube is described in which the screen of persistent phosphor is laid on a cylindrical portion of the glass. A stationary magnetic field bends the electron beam on to the screen, while rotation of the tube produces the time axis. When the beam is deflected and modulated, a continuous pattern may be viewed on the screen.
Improvements in the Stability of the FP-54 Electrometer Tube
Authors: Lafferty J. M. , Kingdon K. H.
Published: January 2005

It was found that a considerable portion of the instability in the FP-54 is caused by variations in emission from the thoriated tungsten filament. Operation of the filament at a current which neither activates nor deactivates was found to be a good criterion for adjusting the circuits employing these tubes. Large fluctuations were observed in emission immediately after activation of the filament. Greater stability was obtained by increasing the activation time from 8 to 40 minutes. Filament and shields improved the stability, showing that some rapid fluctuations in emission occur at the poorly activated end portions of the filaments. Long-time drifts were not improved by end shields. Tubes with oxide-coated filaments gave greater sensitivity and less grid current than tubes with thoriated tungsten filaments. These tubes, however, had a tendency to drift. A split type of FP-54 was constructed with a common filament and space-charge grid, but with twin control grids and plates. Both oxide-coated and thoriated tungsten filaments were used. Operation of these tubes in a bridge type circuit eliminated long-time drift and decreased the amplitude of rapid fluctuations.
A Picturesque Oxidation of Molybdenum Vacuum-Tube Leads
Authors: Liebhafsky Herman A.
Published: January 2005

A picturesque formation of MoO3 on vacuum-tube leads gains in interest and importance because of its close resemblance to a growth of W4O11 on tungsten powder in the electron microscope.
The Permeability of Different Rubbers to Gases and Its Relation to Diffusivity and Solubility
Authors: Van Amerongen G. J.
Published: January 2005

As the permeability of rubber-like substances to gases stands in relation to the solubility and rate of diffusion of the gases in those materials, these individual values should be known. The permeability of a membrane was measured manometrically and the diffusivity was derived from the time-lag of the permeation. The solubility of the gas was computed from the permeability and the diffusivity, in addition to which the solubility was also found by direct measurement. In this way eight different gases were tested with nine elastomers at different temperatures. It appeared that the permeability of a membrane to a given gas is not affected by the presence of a second gas. The differences in permeability of different elastomers to a given gas are caused mainly by differences in rate of diffusion and only in a very minor degree to differences in solubility. The differences in permeability of the same elastomer to different gases are caused not only by differences in rate of diffusion but also by differences in solubility. A linear relationship is found between the logarithm of the solubilities of different gases in natural rubber and their critical temperatures, so the higher the critical temperature of a gas, the better does it dissolve. The presence of polar groups in an elastomer reduces the solubility of non-polar gases and increases the solubility of polar gases in the elastomer. The various rubbers behave towards gases like organic liquids. The activation energy of the diffusion and the heat of solution were calculated from the temperature function of the diffusivity and the solubility. As the diameter of the molecule of the gas increases, the rate of diffusion decreases, while the activation energy of the diffusion becomes greater. The presence of polar groups and methyl groups in elastomers causes low rate of diffusion, which involves a great activation energy of diffusion. It is presumed that the activation energy of the diffusion is required to separate the rubber molecules for the displacement of the gas molecules. The attempt to elucidate the constant D0 in the equation D=D0 exp (−E/RT)—which proves to be a function of the activation energy of the diffusion E— by reference to one of the formulas published in the literature failed. An empirical formula was drawn up, by which D0 is directly related to the activation energy E.
A Machine for the Application of Sand in Making Fourier Projections of Crystal Structures
Authors: McLachlan Dan , Champaygne E. F.
Published: January 2005

This paper presents a method of using sand in building models of two-dimensional Fourier projections in crystal structure analysis. The machine for producing these models is described and the results are illustrated by projections of known structures. The mathematical principle of this method of summing Fourier series is identical to that which Bragg developed in England. The chief difference is in the use of sand instead of photographic film as the medium for producing contrasts in electronic density throughout the projection. The method herein described has a number of features which contribute to its usefulness: A two-dimensional Fourier projection comprising the addition of one hundred and fifty terms may be made in about four hours by a single worker. The time required is not determined by the size of the unit cell. The subdivisions of the projection face are sufficiently fine to assure an accuracy as great as the x-ray data from copper radiation will warrant when a scale of one angstrom to two centimeters is used. Upon embarking on a new structure problem, no changes in the equipment are necessary; as the initial set of templates suffices for all future work. The minimum interplanar spacing that the machine will accommodate is determined by the characteristics of copper radiation rather than the order (h, k, or l) by which the spacings are characterized. The resulting sand model of the projection is the same shape as the unit cell projection with regard to both the angle between the edges and the ratios of the edges of the cell. When the x-ray data warrant, a distinction can be made between heavy atoms and lighter atoms by the differences in the height of the sand. Photographs of the projections (see Figs. 7 and 9) portray atoms as distinct spots.
Radar Reflections from Long Conductors
Authors: Bloch F. , Hamermesh M. , Phillips M.
Published: January 2005

The distribution of the backscattered radiation of a long straight conductor shows a sharp return lobe perpendicular to its orientation. In horizontal observation such a ``rope'' would therefore give an appreciable echo only if it were almost exactly vertical. In practice no such effect will be observed since, because of wind and other disturbances, the rope will never be straight but actually over its whole length will pass through regions of space where the phase of the incident wave will change many times through its full range 2π. The effect of these irregularities will be to make the sharp dependence of the cross section upon the orientation of the rope disappear, and to give a cross section proportional to the total length L of the rope. In Section I, the wave-length λ is assumed to be large compared to the transverse dimensions of the rope. In Section II, the results are extended to include the case where the wave-length λ of the incident radiation is not necessarily large but is comparable with or even small compared to the width d of a ribbon-shaped rope. It is found that the cross section of such a rope can be written generally in the form σ = KAf(πd/λ), where K is a numerical constant depending upon the deviations of the rope from the vertical and where A = Ld is the area of the ribbon. The length L is assumed to be much greater than λ. The function f is evaluated by the use of a method developed by Morse and Rubenstein.
Viscometric Investigation of Dimethylsiloxane Polymers
Authors: Barry Arthur J.
Published: January 2005

The intrinsic viscosities of an extended series of linear methyl polysiloxane fluids, having dimethylsiloxane (Me2SiO) as the repeating unit, have been determined in toluene solution. These values have been correlated with their molecular weights, determined chemically and by osmotic pressure and light scattering measurements. The Staudinger equation was found applicable only for fluids of relatively low molecular weights, i.e., up to about 2500; for the higher polymers, the best correlation of intrinsic viscosity with number average molecular weight was found to be: [η]=2×10−4Mn0.66. This held reasonably well for molecular weights from 2500 to about 200,000. The bulk viscosities of the polysiloxane fluids were found to conform to the Flory relationship for melt viscosities; the expression: log visc. (cs. at 25∘C)=1.00+0.0123 Mn12appears to be reasonably valid for molecular weights above 2500.
Theory of Small Signal Bunching in a Parallel Electron Beam of Rectangular Cross Section
Authors: Feenberg Eugene , Feldman David
Published: January 2005

The phenomenon of bunching which takes place in a velocity modulated electron beam can be described in purely kinematical terms if space charge effects are negligible. However, the non-uniform distribution of charge in the bunched beam gives rise to a field which opposes the bunching process so that the kinematic solution may be validly applied only for a limited length of drift space. An accurate solution of the bunching process requires the integration of the dynamical and field equations. These reduce to a linear homogeneous system under the assumption of ``small signal'' conditions. The device of a high frequency ``surface charge'' is employed in formulating the boundary conditions at the surface of the beam. In the non-relativistic approximation the dynamical and field equations yield solutions which are classified as non-solenoidal or solenoidal accordingly as the motion produces or does not produce a high frequency charge density within the beam. There exists a non-solenoidal type of motion which generates no field outside the beam. The actual physical problem is solved by taking a suitable linear combination of both solutions. Under conditions met with in practice, a large part of the actual solution may be of the solenoidal type. The high frequency component of beam current appears as a sum of a volume current and a ``surface current,'' the latter term arising from the longitudinal motion of the high frequency ``surface charge.'' Again, under conditions met with in practice, a large part of the high frequency component of beam current may occur in the form of ``surface current.'' The theory contains three debunching wave numbers: one identical with that which occurs in Webster's debunching theory for a beam of unlimited cross section, and two which depend upon the transverse dimensions of the beam and drift tube, the current density, frequency, and beam velocity.
On Vibrations of Shallow Spherical Shells
Authors: Reissner Eric
Published: January 2005

The problem of the axi-symmetrical vibrations of a shallow spherical shell is reduced to two simultaneous differential equations for the tangential and normal components of displacement. The solution of these equations is obtained in terms of Bessel functions. With this solution the third-order determinant for the frequencies of a shell segment with clamped edge is given but not evaluated. Instead, an approximate value for the lowest frequency is calculated by means of the Rayleigh-Ritz procedure [Eq. (40)]. It is found that very little curvature is needed to modify appreciably the corresponding flat-plate frequency. The approximations which are made are those customary for shallow shells: (1) omission of the transverse shear term in the tangential force equilibrium equation, and (2) relations between couples and changes of curvatures as in the theory of flat plates.
Non-Uniform Transmission Lines and Reflection Coefficients
Authors: Walker L. R. , Wax N.
Published: January 2005

A first-order differential equation for the voltage reflection coefficient of a non-uniform line is obtained and it is shown how this equation may be used to calculate the resonant wave-lengths of tapered lines.
Resonant Frequencies of the Nosed-In Cavity
Authors: Mayer Ernest
Published: January 2005

In this paper the resonant frequency of the nosed-in cavity is studied as a function of the cavity dimensions. Maxwell's differential equations and boundary conditions are converted into an integral equation which is solved approximately by the Ritz variational method. The size and shape of the cavity are fixed by specification of the dimensions (cf. Fig. 1) r1 and r2, the inner and outer radii; εI, the post length and εII, the gap space. If the cavity is to resonate to the wave-length λ, only three of its dimensions can be given independently; the fourth will be a function of the given three and the wave number k=2π/λ. For fixed r1/r2 the dependence of kεI on kεII is calculated with a precision of 1 percent.
A Millimeter-Wave Reflex Oscillator
Authors: Lafferty J. M.
Published: January 2005

The factors which affect the frequency limitation of reflex oscillators are discussed. General design considerations are given for the construction of oscillators of the shortest possible wave-length. The performance of several tubes is given. The highest frequency obtained was 72,000 megacycles.
Resonant Circuit Modulator for Broad Band Acoustic Measurements
Authors: Hull Gordon Ferrie
Published: January 2005

A modulation method is described whereby a broad band frequency response is obtained for recording of sound. In particular low frequency sound approaching 0 c.p.s. can be recorded. The theory of the resonant circuit modulating principle is first discussed followed by a description of the apparatus which was constructed for this purpose.
Transient Temperatures around Heating Pipes Maintained at Constant Temperature
Authors: Gemant Andrew
Published: January 2005

This paper deals with the transient temperature distribution caused by conduction around cylindrical heating pipes maintained at definite constant temperatures. The theoretical equation for this case known from the literature is integrated numerically and presented in graphs. The amounts of heat dissipated are also computed and presented. As an application, the influence of pipe diameter upon temperatures obtained at given times is shown for a particular case. For practical installations, the characteristics of which usually deviate from those upon which the theoretical equation is based, the graphs may be used for obtaining close estimates as an aid in designing the installation. It is shown that on two actual installations a satisfactory agreement between measured and computed temperatures (maximum deviation about 10 degrees F) was obtained.
The Effect of Temperature on the Strength and Fatigue of Glass Rods
Authors: Vonnegut B. , Glathart J. L.
Published: January 2005

By the use of an electrodynamic quick-loading device, the strength of scratched soda-lime glass rods was measured at various temperatures between − 190°C and 520°C for load durations of 0.1 second, 10 seconds, and 100 seconds. It was found that the strength was highest at the lowest temperature, declined to a minimum at 100°–200°C, and then increased for higher temperatures. Static fatigue was exhibited at all temperatures, being maximum in the region of minimum strength. Comparisons with the results of other experimenters are made.
Plastic Flow, Creep, and Stress Relaxation: Part I. Plastic Flow
Authors: Mack Charles
Published: January 2005

Plastic substances are considered to be composed of units of flow with various yield values. It is shown that in this case the product of the strain rate and viscosity is equal to the sum of the differences between the applied stress and the yield values. This relationship can be applied to any plastic system free of elastic after-effect and expresses their mechanical properties in terms of a coefficient of viscosity which is independent of the stress applied. With the proper choice of the distribution of yield values any kind of relation between stress and strain rate can be established. This relationship is applied to plastic flow which is defined as a deformation mechanism having a curvilinear relationship between stress and rate of deformation and a constant rate of deformation at constant stress. Equations are given for the coefficient of viscosity of such systems and for the relaxation of stress at constant deformation as a function of time.
Plastic Flow, Creep, and Stress Relaxation: Part II. Creep
Authors: Mack Charles
Published: January 2005

The general equation covering the deformation of plastic substances given in Part I is applied to creep. Creep is defined as a mechanism of deformation for systems which have a curvilinear relationship between stress and strain rate and a curvilinear relationship between strain and time at constant stress. Creep is connected with changes in the internal structure of a plastic substance and results in an increase in strength of such materials through work-hardening. Equations are derived which give the stress as a function of strain rate and time (time-hardening), as a function of strain rate and strain (strain-hardening) and as a function of strain rate, strain, and time. The difference between time-hardening and strain-hardening is discussed. Expressions are given for the coefficients of viscosity of such systems which are independent of the stress applied. The relaxation of stress at constant strain is discussed, and it is shown that the stress relaxation depends upon the history of the substance under test. The concept of creep is also applied to thixotropic systems which are considered as cases of work-softening.
Plastic Flow, Creep, and Stress Relaxation: Part III. Creep and Elastic After-Effect
Authors: Mack Charles
Published: January 2005

A large number of substances show the phenomenon of elastic after-effect, and part of their deformation recovers on unloading as a function of time. This portion of the deformation at constant stress has a strain rate which decreases with time and is therefore comparable to creep. Expressions are given for the strain-time relationships of such systems, and the process of stress relaxation at constant strain is discussed. The equations given in connection with plastic flow, creep due to work-hardening, thixotropy, and creep in combination with elastic after-effect are applied to data given in the literature, and it is shown that these equations suffice to describe the deformation and relaxation mechanisms of a variety of materials such as metals, clay soil, food products, acrylic acid polymeride, polyvynil chloride, cellulose acetate, manila ropes, paper laminates, phenolic molding compounds, rubber, asphalt, and bituminous pavements.
Electron Microscope Examination of the Microphysical Properties of the Polymer Cuprene
Authors: Watson John H. L. , Kaufmann K.
Published: January 2005

The microphysical structure of cuprene is described from electron micrographs and some suggestions are made concerning the mechanism of the formation of this substance. Cuprene samples prepared by polymerization of acetylene in the presence of finely divided cuprous oxide are shown to be composed of hollow fibers characterized by both longitudinal and transverse structure. The striking appearance in electron micrographs of this type of cuprene serves to identify it in clogging deposits taken from acetylene lines. This is illustrated by a deposit taken from a reactor used in the process of hydrogenation of acetylene to ethylene. Cuprene specimens formed by alpha-ray bombardment of acetylene gas are shown to be composed of round particles joined by short, straight, thick necks which are about 500 to 1000A in length. These are samples of cuprene which have been bombarded further by alpha-particles after their initial formation. An oxidized sample has round particles of mean diameter 4900A; an unoxidized sample has a mean diameter of 3800A for the round particles. There is evidence to suggest that alpha-ray cuprene is liquid in nature. The two types of cuprene are so different physically that a change in nomenclature is in order.
Calculation of the Output from Non-Linear Mixers
Authors: Stockman Harry
Published: January 2005

The exact mathematical treatment of non-linear mixers of the type used in very-high frequency and ultra-high frequency superheterodynes is difficult. If, however, the non-linear element is simplified to the extent that it is fully described by a plotted current-voltage characteristic, several ways of determining the output become evident. Some of the most fundamental methods are described in the following, and their shortcomings pointed out. The methods are then tried out on a ``guinea pig'' characteristic and the results critically compared with respect to accuracy, amount of labor, required mathematical tools, and other factors. It is found that no ``best'' method exists and that all methods require simplifying assumptions and approximations that frequently lead the converter designer to consider practical measurements, or special methods, such as the one provided by the frequency conversion diagram technique.
Filmless Sample Mounting for the Electron Microscope
Authors: Watson John H. L.
Published: January 2005

A method is described for supporting airborne particles upon thin glass fibers where they build up in chains and may be examined in the electron microscope. With no supporting membrane, the contrast and resolution are increased in the micrographs. The specimens are particularly useful for stereoscopic studies. A special reference is made to the study of carbon particles mounted in this fashion. The carbons examined are formed by pyrolysis of acetylene and occur naturally in pronounced chains. Reproducible particle size data for the carbons can be secured by measurements made on individual particles at ×200,000. Evidence for the crystalline nature of this carbon is rendered visible in the micrographs.
Investigation of Secondary Phases in Alloys by Electron Diffraction and the Electron Microscope
Authors: Heidenreich R. D. , Sturkey L. , Woods H. L.
Published: January 2005

The application of electron diffraction reflection methods and the electron microscope to investigations of metallurgical structures is reported. It is shown that these instruments can yield valuable information concerning very small amounts of secondary phases and impurities in metals. Thus, for example, when martensite decomposes at 200°C, the slow etching component is highly dispersed Fe3N. The decomposition at 400°C yields the usual Fe3C. Further, the Fe3N formed at 200°C transforms to Fe3C when annealed at 350°C. Other examples are presented. The successful application of these instruments is dependent upon the production of clean, etched surfaces. Surface preparation is discussed and a satisfactory technique for rinsing etched surfaces is described. In some alloy systems, the etching reaction may result in the redeposition of a component onto the etched surface. In the case of a β-brass containing 0.0005–0.001 percent silver, the silver is deposited in the form of spherical particles about 1000A in diameter. Aluminum alloys appear to offer a serious problem in discovering satisfactory etchants due to the position of aluminum in the electromotive series relative to copper, silver, etc.
Problems in Non-Elastic Deformation of Metals
Authors: Zener Clarence , Hollomon J. H.
Published: January 2005

In this article an attempt is made to examine the goals of current and of possible future types of research concerned with the non-elastic deformation of metals. It is found that an understanding of non-elastic deformation would be enhanced by research upon the following topics: 1. The anelasticity associated with the viscous behavior of grain boundaries and the at least temporary viscous behavior of slip bands. 2. The mechanics of the initiation and growth of twin bands. 3. The mechanics of the initiation and growth of slip bands, including the drop in resistance to deformation which accompanies the initial slip bands. 4. The mechanics of the segregation of solute atoms in solid solution, such as of carbon and nitrogen in iron. 5. The conditions under which strain hardening is not removed by recovery or by recrystallization, and hence under which a mechanical equation of state exists, i.e., under which a relation exists between strain rate, strain, stress, and temperature. 6. Variation of the heat of activation for plastic strain rate upon stress and upon the microstructure. 7. Anisotropy introduced by deformation.
Problems in Fracture of Metals
Authors: Hollomon J. H. , Zener C.
Published: January 2005

In this report a review is made of the possible types of future research which might lead to an understanding of the fracture of metals, and hence to an increase of the strength level to which metals may be raised without danger of fracture. It is found that an understanding of fracture would be enhanced by research upon the following topics: 1. The effects of the following variables on the virtual fracture stress: (a) Strain; (b) strain rate; (c) temperature; (d) stress distribution; (e) structure; (f) mechanical history (i.e., fatigue). 2. A comparison of the fracture characteristics of metallic crystals with those of non-metallic crystals, such as rocksalt. 3. The hindrances of plastic deformation by sharp stress gradients. 4. The introduction of stress concentration by: (a) Non-metallic inclusions; (b) precipitates; (c) slip bands; (d) twin bands; (e) grain boundary deformation. 5. The effect of reversal of stresses upon the properties of slip bands.
Film-Lubrication between Spherical Surfaces: with an Application to the Theory of the Four-Ball Lubricant Testing Instrument
Authors: Howlett J.
Published: January 2005

The paper is concerned mainly with the flow of viscous liquid between the outer surfaces of two equal spheres placed in an infinite body of the liquid so that the ``minimum separation'' of the surfaces (the distance apart at the points of closest approach) is small compared with the radius; one sphere is held at rest, the other rotates at constant speed about an axis which does not pass through the center of the fixed sphere. The assumption is made that the surfaces are separated by a continuous film of liquid to which the classical theory of hydrodynamical lubrication can be applied—that is, ``boundary lubrication'' and actual contact between the surfaces are excluded; the partial differential equation (the Reynolds equation) for the pressure distribution in this film is set up, and it is shown that with a suitable choice of boundary conditions a solution can be found in very simple form. From this solution are deduced the total force exerted by the liquid on the moving sphere and the torque, about the axis of rotation, of the forces acting on the fixed sphere. The results are applied to the particular case of the four-ball lubricant testing instrument, in which a sphere is made to rotate about a vertical axis, under axial load, in the central space formed by a set of three equal spheres held stationary so as to touch one another with their centers in a horizontal plane; the whole set of spheres is immersed in the lubricant to be tested. The relations finally obtained express the load on the moving sphere and the torque on the set of fixed spheres in terms of the radius of the spheres, the velocity of rotation, and the viscosity of the liquid; they involve as a parameter the minimum separation of the moving sphere from the fixed spheres, and elimination of this gives the relation between the measurable quantities, load, and torque, which could provide a basis for the use of the instrument as a viscometer. It is found that the torque is a very slowly varying function of the load, being approximately proportional to the logarithm of the load. Further, if it is assumed that the hydrodynamical theory of lubrication is valid only for films whose thickness is greater than some agreed minimum, then the expression for the load on the moving sphere, into which the minimum separation enters, provides a criterion for the range of conditions (of which the load is much the most important) within which the theory does in fact apply to the instrument. Numerical examples are considered, and it is shown that, with allowance for wide departures from the standard size and speed of operation of the instrument, the maximum load which can be supported by the moving sphere in the hydrodynamical regime cannot be expected to exceed a few hundred grams weight; for loads of greater order the standard continuous-film theory cannot hold, and the forces on the spheres are no longer determined by the viscosity of the liquid.
The Analysis of Multicomponent Mixtures of Hydrocarbons in the Liquid Phase by Means of Infra-Red Absorption Spectroscopy
Authors: Fry D. L. , Nusbaum R. E. , Randall H. M.
Published: January 2005

This is a general method of applying infra-red absorption spectroscopy to the analysis of multicomponent hydrocarbon mixtures in the liquid phase. The procedure is calibrated by measuring optical densities of synthetic standard samples. A constant thickness cell is used for both standard and unknown samples. Two procedures for converting optical densities to concentrations are described. Examples are given for four- and five-component mixtures. Data are presented to show the reproducibility of repeated measurements of optical density on the same sample, and results are given to show the agreement between the infra-red analyses and the known composition of synthetic mixtures.
Wide Range Static Strength Testing Apparatus for Glass Rods
Authors: Baker T. C. , Preston F. W.
Published: January 2005

By adapting an electro-dynamic loudspeaker, an apparatus was assembled to test the strength of glass rods in flexure. This apparatus will apply the stress in 2 to 3 milliseconds and permit static loading for times as short as 0.01 second. Using an additional long time loading apparatus, which simultaneously tested eighteen rods, it was possible to run static fatigue tests on glass rods from 1000 seconds to 86,400 seconds. The method of testing and errors due to the apparatus are discussed.
Fatigue of Glass under Static Loads
Authors: Baker T. C. , Preston F. W.
Published: January 2005

Static loading tests were run on glass and porcelain rods732 inch in diameter for times ranging in duration from 0.01 second to 24 hours, by using specially designed apparatus. It was found that glass can support for 0.01 second about 3 times the stress that would break it in 24 hours. The effects are generally the same for all glassy materials. Porcelain showed the effect somewhat less than glass. It appeared that adsorbed moisture and gases reduced the strength.
The Effect of Water on the Strength of Glass
Authors: Baker T. C. , Preston F. W.
Published: January 2005

The strength of glass was measured in various surrounding media. It was found that glass is 20 percent stronger when dry than when wet, and two to two and a half times as strong when baked in vacuum than when tested wet (on tests of ten seconds duration). Apparently, the chief cause of the loss of strength, as compared with that in vacuum, is moisture, but gases, especially CO2, seem to have some effect. It was found that fatigue of glass disappears when the glass is tested in a vacuum.

Autoclaving tests showed that glass is rapidly etched by water at higher temperatures, and that even silica glass is considerably attacked. It appears that the attack of water on glassy surfaces produces gels, and this attack goes on inside the flaws, thus considerably complicating the problem of the strength of glass.
The Fatigue Modulus of Glass
Authors: Glathart J. L. , Preston F. W.
Published: January 2005

The decline in the breaking strength of glass with an increase in the length of time it is under stress has been noted by various experimenters. Based on the experimental results of T. C. Baker, an empirical relationship is obtained which indicates that the reciprocal of the breaking stress is a linear function of the logarithm of the duration of the stress. Certain implications of this relationship are discussed.
Induction Heating of Hollow Metallic Cylinders
Authors: Gemant Andrew
Published: January 2005

This paper deals with the heat input to hollow cylindrical metal cores subjected to induction heating. The rigorous expression for the heat input, valid for the whole frequency range, is developed and is presented by Eq. (27) of this paper. It is shown in an example how the equation is used for numerical computations. Existing approximate formulas for the low frequency and the high frequency range are checked by means of the rigorous equation; the maximum deviation between the rigorous and approximate equations is about 10 percent.
A New Electrolytic Selenium Photo-Cell
Authors: Von Hippel A. , Schulman J. H. , Rittner E. S.
Published: January 2005

A new electrolytic selenium photo-cell is described and its characteristics given as a function of operating voltage, temperature, external resistance, and time. Data are included indicative of its response to unmodulated, modulated, and monochromatic light; comparison is made with cells of similar type or possessing similar characteristics; and a method of compensating for the dark current of photo-cells is shown.

An electronic circuit is also described which can greatly improve the voltage output of the photo-element. It is generally applicable to photo-conductive and photo-voltaic cells.
Studies of Plastic Flow of Steel, Especially in Two-Dimensional Compression
Authors: Bridgman P. W.
Published: January 2005

The experimental methods are described by which rectangular blocks are subjected to two-dimensional compressional stresses and at the same time flow is maintained two-dimensional with deviations of less than one percent. Within this range of flow a rather wide range of stress conditions is possible, so that the equations of plastic flow can be examined over a correspondingly wide range of conditions. It is found that two-dimensional flow is much more sensitive than three-dimensional flow to shearing instabilities initiated at the edges where there are singularities in the mathematical solution. By proper lubrication it is, however, possible to produce approximately homogeneous deformations in two-dimensional compression at least up to shortenings to two-thirds the initial length. It is found that the transverse stress Xx required to maintain two-dimensional flow is consistently higher than the theoretical value ½Zz; for some materials the excess above the theoretical value may rise to as much as 20 percent. This excess tends to be less in the early stages of flow, and does not tend to increase beyond strains of 10 percent. The failure of Xx to be equal to ½Zz indicates a failure of the fundamental condition of isotropy of flow; this failure may be demonstrated in other ways. The time rate of primary flow is studied at various points on the strain-hardening curve. The rate of flow rises rapidly as the stress increases above the limiting strain-hardening curve. The rate of increase of the rate of flow for a given displacement from the limiting curve is much greater in the early stages of flow. It is this which makes possible the calculation of the rate of propagation of a plastic disturbance from the parameters of the static strain-hardening curve. Beyond the early stages of flow new time effects begin to appear. The flow loses its smoothness and becomes more and more inclined to be jerky. At high strains, flow may not start at once when the load is increased, but there may be an initiation period during which flow is built up. The application of the results to the generalized strain-hardening curve is discussed. In view of the failure of isotropy, strictly speaking, a generalized strain-hardening curve does not exist. Within the strain limits of this paper it is found that both the maximum shearing stress criterion and the ``significant'' stress-strain criterion apply with errors of the order of 10 percent, the maximum shearing stress criterion being on the whole perhaps somewhat better.