bluuebunny/crossref_metadata_2025_split huggingface dataset:
Glass Cracking Caused by High Explosives
Authors: Pugh E. M. , Heine-Geldern R. v. , Foner S. , Mutschler E. C. 
Published: April 2005

High-speed photographs have been obtained of the fracture of glass produced by the detonation of a high explosive charge. Using photoelastic methods, the shock waves set up in the glass can also be photographed. In addition to providing a high intensity loading method, the explosive also serves as a convenient time base for determination of the rates of propagation of shock waves and cracking.
The results presented in this paper extend those obtained by other investigators who used low energy impacts to produce fracture.
The Complete Solution of the One-Velocity Diffusion Problem at Intermediate and Large Distances
Authors: Tonks Lewi 
Published: April 2005

An approximate evaluation of the branch-cut integral which occurs in the rigorous solution of the Boltzmann equation for intermediate and large distances is of importance in shielding problems. Such an evaluation leads to Eq. (20) for the point source and Eq. (24) for the plane source. Equation (20) is actually 23 percent high for zero absorption (f=0) and rσ=7, but the error decreases with increasing rσ and f. It is seen that the branch-cut term is not simply the contribution of noncollided neutrons.
Figure 2 is a plot of the region in the f−rσ plane where the two terms are comparable.
A Method of Solving the Wave Equation in a Region of Rapidly Varying Complex Refractive Index
Authors: Gibbons J. J. , Schrag R. L. 
Published: April 2005

A process is described whereby the complex wave equation is transformed into an integro-differential equation in a single real dependent variable. This makes possible a technique for obtaining wave functions, which is believed to offer definite advantages in some instances where the more standard methods are difficult to handle, e.g., in regions where the complex index is varying rapidly. The index may be entered in a tabulated form, and its exact analytical expression is not required.
The technique is then demonstrated by computing the reflection coefficient associated with an extremely critical region, that which one encounters at the ``fourth reflection condition,'' where the refractive index goes through a sharp peak (see reference 3).
The Measurement of Ultrasonic Attenuation in Solids by the Pulse Technique and Some Results in Steel
Authors: Roderick R. L. , Truell Rohn 
Published: April 2005

Pulse techniques for the measurement of attenuation in solids have been extended and refined sufficiently to obtain dependable measurements over a frequency range from 5 to 50 megacycles. Understanding of the relative importance of beam spreading, geometrical boundaries, and method of coupling has been improved. Coupling by means of water buffer and direct mounting is discussed in detail.
Attenuation measurements in the frequency range from 5 to 50 megacycles have been made on chrome molybdenum steel specimens, and these measurements have shown large differences in ultrasonic attenuation for samples of the same chemical composition but different heat treatment. The resulting differences are connected with anisotropy which appears in the photomicrographs. The attenuation measurements are quite sensitive to heat treatment and other factors. The application of the methods to metallurgical problems and the physics of solids is suggested.
Lattice Parameters, Coefficients of Thermal Expansion, and Atomic Weights of Purest Silicon and Germanium
Authors: Straumanis M. E. , Aka E. Z. 
Published: April 2005

Lattice parameter determinations of 99.97 percent pure silicon (containing 0.03 percent carbon) were carried out using the asymmetric method, a 64-mm precision camera in a thermostat at constant temperatures (10, 20, 30, 40, and 50°C). The powder mounts, about 0.12-mm in diameter, were translated and rotated during the exposure. Only the (444)-CuKα1 line was used for the determinations. The lattice parameter a=5.41991±0.00003kX (5.43086A) at 20°C, corrected for refraction, was obtained; the linear lattice expansion coefficient (between 10 and 50°C) was 4.15×10−6, the density at 20°C was 2.32831±0.00031 g/cm3 (determined by the suspension method), and the atomic weight was 28.083±0.013 (in agreement with the new chemical weight 28.09) showing that the silicon crystals used, under certain limitations, were sound although the possibility of interstitial atoms is not excluded.
The lattice parameter of purest germanium (99.99 and 99.999 percent) was measured by the same method using the (422)-CrKα1 and α2 lines: a20=5.64607±0.00004kX (5.65748A) for both materials. The expansion coefficients were α=6.65×10−6 and 5.92 ×10−6, respectively. The density was 5.3234±0.0025 g/cm3 at 25°C and the calculated atomic weight 72.593±0.037 in agreement with the present chemical weight 72.60. Thus, germanium crystals are sound; however, interstitial atoms are possible.
The precision of lattice parameter determination was about 1:200,000, but in the case of 99.999 percent germanium the precision was considerably better. This shows again that lattice constant determinations can be performed with highest precision and without use of any extrapolation method. The method of lattice parameter determination applied is an absolute one.
Statistical Errors in Measurements on Random Time Functions
Authors: Davenport W. B. , Johnson R. A. , Middleton D. 
Published: April 2005

The statistical errors in time-average measurements of various properties of (stationary) random time functions are analyzed for their dependence on the averaging interval, the method of averaging, and the statistics of the particular time function under observation. The specific averaging processes considered here are as follows:(1) The continuous time average (1T∫0TZ(t)dt),(2) The summation (by discrete sampling techniques) (1N∑n=1NZ(nT0)), and(3) The smoothing accomplished by various low-pass filters (for example, a dc meter).
Here Z(t) may represent the output of a linear or nonlinear device. As a particular example, the measurement of the power in a random noise voltage of band width ωF is analyzed in detail. The expected root-mean-square error approaches asymptotically the value (K/ωFT)½, where K is some numerical constant, depending on the device in question. For (1) and (2) T is the total observation time while for (3) it is proportional to a relevant time constant of the low-pass filter. A short discussion of the relative merits of correlators and spectrum analyzers is included, together with a brief treatment of the distribution function of the error in the measurement.
Elastic Constants of Beta-Brass Single Crystals
Authors: Artman Robert A. , Thompson Donald O. 
Published: April 2005

Measurements of Young's modulus and the rigidity modulus for a set of beta-brass single crystals of 55 atomic percent copper and for single crystals of beta-brass near the zinc-rich phase boundary reveal a dependence of the elastic constants upon composition. Comparison is made with previous results, whereby it is found that the moduli of beta-brass for different compositions may be obtained by the use of a linear interpolation in terms of the atomic ratio of copper to zinc. Derived quantities are generally related in this manner also. The value of Σ111 (Poisson's ratio) is shown to be a positive quantity, in contrast to that derivable from previous results.
Results of bending-torsion measurements are presented. The agreement between measured values and those calculated from the principal elastic constants provides assurance for the consistency of the measurements.
The Dielectric Constant of Dry Air
Authors: Hughes J. V. , Armstrong H. L. 
Published: April 2005

A sensitive and accurate method for determining the real part of the dielectric constant of gases at microwave frequencies is described. The method eliminates some possible sources of systematic error inherent in earlier methods.
The dielectric constant of dry air at N.T.P. has been determined as 1.000569, at a frequency of 3000 Mc/sec. This is in good agreement with other results, at 24,000 Mc/sec, at 9000 Mc/sec, and at low frequencies, thus verifying that the dielectric constant is independent of frequency up to nearly 30,000 Mc/sec An earlier result suggesting the contrary was found to be in error because of insufficient drying of the air.
The Radiation Pattern of an Antenna over a Circular Ground Screen
Authors: Storer James E. 
Published: April 2005

In a previous paper [The Input Impedance of an Antenna Over a Finite Ground Screen, Technical Report No. 119 (Cruft Laboratory, Harvard University, November 30, 1950)] the author treated the problem of the input impedance of an antenna erected over a large circular screen. Using the formulation developed therein, an expression is obtained for the entire radiation pattern of an antenna over a large circular screen.
The most important difference between the pattern of an antenna over a large screen and an antenna over an infinite screen is the presence of lobes over the antenna. From the expression for the radiation pattern, simple formulas are obtained for: (a) the number of lobes, (b) the angular position of the lobes, and (c) the angle, βmax, within which the lobes occur. One important result obtained is that θmax∼(1/d12),where d is the diameter of the screen. It is apparent that the effects of a finite screen decrease very slowly as the diameter of the screen is increased.
Chemical Reactions in Barium Oxide on Tungsten Emitters
Authors: Hughes R. C. , Coppola P. P. , Evans H. T. 
Published: April 2005

When barium carbonate is heated in vacuum in contact with tungsten, the following reactions may occur in sequence as progressively higher temperatures are reached: (1) WO3+BaCO3⇄BaWO4+CO2. (2) 3BaCO3+W⇄Ba3WO6+3CO. (3) BaCO3⇄BaO+CO2. (4) 6BaO+W⇄Ba3WO6+3Ba.
At a temperature of approximately 600°C, reaction (2) begins to occur with appreciable speed. Reaction (3) proceeds at 800–900°C. Reactions (2) and (3) may be made to proceed simultaneously, the preponderance of one over the other depending upon state of subdivision and intimacy of admixture of the reactants. Under favorable conditions, reaction (2) may be driven to completion with almost total absence of reaction (3). Reaction (4) progresses with appreciable speed at temperatures over approximately 1000°C.
Activated cathodes of BaO on W will have an interface of Ba3WO6 formed by reactions (2) or (4), or both, unless unusual precautions are taken to avoid this. The end result of heating the cathode is the conversion of the entire thickness of the oxide coating to the basic tungstate. The resulting coating of Ba3WO6 on W is unreactive and nonvolatile at temperatures up to 1300°C, and provides no significant thermionic emission.
Characteristics of the High Current Tungsten Arc in Argon, Helium, and Their Mixtures
Authors: Skolnik Merrill , Jones T. B. 
Published: April 2005

An experimental study was made of the properties of the high current dc electric arc in argon, helium, and their mixtures at atmospheric pressure. Tungsten-rod electrodes were used over a current range from 10 to 100 amperes. Measurements of the voltage-current and the voltage-electrode separation characteristics were made along with the plasma voltage gradients in both the pure gases and in the mixtures.
It was found that this type of arc was very stable when the system was free from oxide impurities and that the cathodic processes played a major role in the arc mechanism. The results obtained suggest that the value of the anode voltage drop for the inert gas arc over the current range studied is negligibly small. At the higher currents or with smaller diameter cathodes, tungsten was able to evaporate from the cathode in sufficient quantities to influence the character of the discharge. It was observed that the properties of the arc in mixtures of gases were in between the properties observed in the pure gases. The lower ionization potential gas, argon, had more effect on the properties of the arc in mixtures than did helium. As long as there was at least 15 percent argon present in the mixture, the arc properties and appearance were more like those observed in argon than in helium.
Specimen Charging in the Electron Microscope and Some Observations on the Size of Polystyrene Latex Particles
Authors: Ellis S. G. 
Published: April 2005

From observations in the shadow electron microscope and the standard electron microscope it is concluded that specimen charging does not significantly change the magnification of the latter, provided that the specimen is less than a few microns in thickness and the illuminating electron beam simultaneously strikes a nearby grounded conductor such as the supporting mesh.
The difference in size of shadowed and unshadowed Dow Latex 580G, lot 3584 reported by Kern and Kern (J. Appl. Phys. 21, 705 (1950)) is attributed to an added layer of material on the shadowed particles. Evidence in support of this view is presented, and the results of other workers are discussed in the light of it.
Production of Monochromatic X-Radiation for Microradiography by Excitation of Fluorescent Characteristic Radiation
Authors: Rogers T. H. 
Published: April 2005

In several types of applications of microradiography, particularly for histochemical and microchemical analysis by x-ray absorption spectroscopy, it is desirable to use monochromatic radiation of a wavelength selected specifically with reference to an absorption edge of the element of interest. An x-ray tube having as its target a material whose Kα characteristic wavelength is suitable is the most usual source of monochromatic x-radiation. In many cases, however, an otherwise desirable target is physically unsuitable for use as a target inside a vacuum tube. Hence, the possibility of producing fluorescent characteristic radiation with intensities sufficient for microradiography becomes of interest. The very high intensity of the primary x-ray beam made available by the newly developed beryllium-window x-ray tubes suggests new possibilities for the excitation of fluorescent radiation.
This paper reports the results of exploratory work attempting to establish the factors governing the intensity and degree of monochromaticity of fluorescent x-radiation. Several materials, ranging from titanium (atomic number 22) to molybdenum (42) were studied comparatively, with exciting radiations of various characteristics; titanium was studied in greater detail. It is concluded that a considerably higher degree of monochromaticity is obtainable by this method than by direct bombardment and that intensities useful for some aspects by microradiography are obtainable.
Electron Microscopy of Synthetic Latices
Authors: Maron Samuel H. , Moore Carl , Powell Allen S. 
Published: April 2005

A study has been made by electron microscopy of the size and size distribution of 22 synthetic latices. Included are GR-S latices Types II, III, and V, polystyrene latices, and several latices of special character.
Details are given on sample preparation, measurement, application of corrections, calculation of number, volume to surface, and molecular weight average diameters, as well as the number and weight average distributions.
The weight average particle size range covered was 730 to 3920A. The smallest sizes were shown by Type II latices, followed in order by Type III, polystyrene, Type V, and some of the special latices. The latices were all nonhomogeneous in size and showed size distributions both on a number and weight basis which in some instances contained single and in some cases double maxima.
The Effect of Accelerating Voltage and Specimen Morphology on Electron Diffraction Patterns
Authors: Ellis S. G. 
Published: April 2005

Using empirical relations established in the study of electron diffraction patterns of uniform thin films of aluminum, the contrast between the most intense ring and the background is calculated for other morphologies as a function of the accelerating voltage on the camera.
In all cases the contrast increases with voltage. The gain is marked if the specimen is nowhere very thick. For specimens that have very thick regions the contrast increases approximately as the square root of the voltage in the range 50 to 150 kv. The situation in reflection-diffraction in general lies between these extremes. Increasing the voltage has a more limited effect on increasing the range of specimen thicknesses that can be examined than had been previously supposed.
On the Theory of Prediction of Nonstationary Stochastic Processes
Authors: Davis R. C. 
Published: April 2005

We consider the following problem of prediction: During a finite time interval T the real valued function S(t)+N(t) is observed, in which S(t) is a signal and N(t) is a linearly superimposed noise disturbance. The problem is to predict the value of a given linear functional of S(t), the predictor formula having certain preassigned ``optimum properties'' among a certain class of predictors. In the case in which the mean value of S(t) is known, the random components of S(t) and N(t) are strictly stationary, and the time interval T is infinite, a complete solution to this problem has been given by N. Wiener. (In the case of discrete time series, the solution was given by A. Kolmogoroff.) This theory has been extended by L. Zadeh and J. Ragazzini [J. Appl. Phys. 21, 645 (1950] to the case in which T is a finite time interval and the mean value of S(t) is unknown but is restricted to be a polynomial in time. We extend the above theories to the case in which the random components of both S(t) and N(t) are nonstationary in time and merely possess finite continuous covariance and cross-covariance functions. The analytical tools of probability theory which we use are those developed independently by M. Loève and K. Karhunen in their studies of a class of stochastic processes usually termed processes of second order. Apparently these techniques are practically unknown outside of certain mathematical circles. In the opinion of the author these techniques are extremely powerful in the analysis of transient random phenomena in linear systems.
Finally we give an exposition of a method of prediction by the theory of conditional probabilities. This method is applicable when the form of the joint probability distribution of signal and noise is known and hence is applicable to many practical problems, since this distribution is often Gaussian. In this particular case the predictor formula given by the theory of conditional probabilities is identical with the usual linear predictor formula given by the theory of least squares. In case the signal is a Markoff process, the method of conditional probabilities yields a much simpler prediction formula than the usual method of least squares.
Turbulent Diffusion and Erosion
Authors: Davies Richard W. 
Published: April 2005

A new theory of turbulent diffusion is developed so as to describe the dynamics of particulate matter in fluid suspensions. In order that the statistical description be consistent with force equation dynamics of sedimentation, a new diffusion equation is derived from the postulates of a past-future stochastic process.
A steady-state suspension of particles in a turbulent stream is treated like an atomosphere. Dimensional arguments are used to retain the most relevant physical entities in a linear theory. It is shown that the bed load and mid-stream suspension of a muddy stream cannot be considered separately. Some experiments are discussed in this connection. A qualitative theory of sand rippling is explained in terms of the instability of a flat sandy bottom under certain turbulence conditions. A singular perturbation method is employed to obtain an asymptotic expansion of the solution of the equilibrium equation.
Assumptions are discussed and criticized. The advantage of the theory is that all statistical coefficients are averages of familiar dynamical quantities.
Electric Strength and Molecular Structure of Saturated Hydrocarbon Liquids
Authors: Crowe R. W. , Sharbaugh A. H. , Bragg J. K. 
Published: April 2005

A number of investigators have reported that the apparent electric strengths of straight-chain hydrocarbon liquids increase in a regular manner with increasing molecular chain length. In a recent publication we have presented evidence that this phenomenon is an illustration of a kind of Paschen's law for liquids. An observed linear dependence of the electric strengths of such hydrocarbons upon density suggested that chain length variation merely provided a means of changing the electron mean free path in the liquid.
In the present paper we describe the development of an improved technique for measuring electric strengths of liquids, and the application of this technique to a series of pure straight-chain and branched-chain liquid alkanes. As had been observed previously, the strengths of the straight-chain members of the series exhibit a linear relationship with density. The introduction of branches into the hydrocarbon chain, however, results in a definite decrease in strength. Extension of the measurements to hydrocarbons of more complicated structure has apparently introduced a kind of fine structure.
Measurement of the time dependence of electrical breakdown in liquid hydrocarbons shows that the formative time lag is relatively insensitive to changes in viscosity or molecular weight. For an electrode separation of 0.002 inch, it is approximately one microsecond.
A Definition of Passive Linear Networks in Terms of Time and Energy
Authors: Raisbeck G. 
Published: April 2005

A definition of passive linear network is made:
(a) The network is linear.
(b) If currents of any wave form are fed to the terminals of the network, the total energy delivered to the network is not negative.
(c) No voltages appear between any pair of terminals before a current is fed to the network.
When this definition is applied to two terminal networks, i.e., impedances, a necessary and sufficient condition that a two-terminal network be linear passive is that its impedance function be a positive real function.
An analysis of multiterminal networks yields as a necessary and sufficient condition from the foregoing hypotheses that a certain Hermitian quadratic form be positive definite. In the case of three-terminal networks, it reduces to 4R11R22−(R12+R21)2−(X12−X21)2≥0,where Rij+jXij=Zij are the terms of the matrix of impedances of the network. The relation of this formula to similar but not identical formulas of Gewertz and Llewellyn, and other consequences of the condition, are discussed.
On the Effect of Integration in a Pulsed Radar, Randomly Modulated Carrier
Authors: Stone W. M. 
Published: April 2005

The method of Marcum for finding the probability density function associated with a pulsed radar with integration and a square law detector is extended to include the case of a randomly modulated sinusoidal signal. Two mathematical procedures are developed, the well-known Edgeworth asymptotic series and a convergent series suggested by Varma. Sets of curves are drawn for probability of detection vs average signal-to-noise power ratio.
Some previous work has shown very high values for probability of detection resulting if it is assumed necessary to detect only one out of many pulses. Such probability levels are reduced if a slowly varying random amplitude of signal is postulated.