bluuebunny/crossref_metadata_2025_split huggingface dataset:
Non-Linear Viscous Elasticity and the Eyring Shear Model
Authors: Halsey George 
Published: January 2005

Attempts to analyze stress-strain-time relationships observed in experiments with textile fibers have been reported in a series of papers. This work has led to some general conclusions: First, the simplest three element model (spring in parallel with another spring and a dashpot in series) is adequate for the approximate explanation of a wide range of the data obtained. Second, the viscous element (dashpot) almost always appears to be non-Newtonian while the springs less frequently are non-Hookean. Third, the most striking deviations from simple behavior indicate, not a more complex model consisting of many simple elements, but that the assumed laws governing the viscous, or less frequently, elastic elements are themselves too simple.
Frequently a more complex law or laws will restore the three-element model to approximate agreement with the experimental facts. Finally, any system so far investigated can be made to show the presence of a number or a distribution of relaxation times by prolonging the experiment over a period of time, or more positively, by going to a point of no instantaneous relaxation, and waiting for the inevitable long period of relaxation to appear. Procedures to deal with the general situation described here are presented.
The paper begins with a condensed but essentially self-contained summary of the theoretical portions of the series of papers that preceded it. The original presentation has been clarified and recast in a form more in harmony with the present work. For experimental evidence, and supplementary information, the reader is referred to the original series.
The paper continues with a discussion of the various aspects of non-linear viscous elasticity, including the topics: Six rules for analyzing stress-strain curves (presented at the meeting of the Division of High-Polymer Physics of the American Physical Society, January 31, 1947); the thixotropic viscous element, where for convenience, complex situations, in which the populations of various states enter into a time-variable viscosity, have been gathered under the name ``thixotropy''; constant force springs, where a particularly non-Hookean behavior is described.
A Magnetron-Resonator System
Authors: Okress E. C. 
Published: January 2005

The present exposition deals with the fundamental multiplet spectrum of a multi-sectorial cavity or vane-type magnetron and specific applications involving the evaluation of the π-mode wave-length thereof. The consequence of mutual coupling between the sectorial cavities through the interaction space of an infinitely long anode is evaluated for the linear case and subsequently applied to the cylindrical case. Although both the qualitative and quantitative results are reasonable in the limit for relatively very long anodes, in practice the latter are relatively short and since the mode separation, order thereof, and hence the component wave-lengths are more or less influenced by the actual relative anode and end cavity lengths at each end of the anode, the results naturally differ from ``cold'' test data. Predictions of π-mode wave-length have been obtained to about 10 percent, depending upon the degree to which the parameters of the actual vane magnetron approximate the assumptions on which the present treatment is based. With the aid of ``cold'' test data the preliminary theoretically derived resonator geometry may be appropriately ``trimmed'' to produce the exact π-mode wave-length desired.
Included in this article is a discussion of the need and function of straps of the resonator system and dimensional scaling, which preserve certain desirable properties of the prototype at the new wave-length, or operating point, in terms of magnetron performance-chart parameters. Finally, in Part III, a brief consideration is allotted to the derivation of the rectangular cavity or slot-type resonator system from the more general relation for the sectorial cavity in this article.
The Efficiency of Thermoelectric Generators. I.
Authors: Telkes Maria 
Published: January 2005

The generation of electrical energy from thermal energy by thermoelectric means cannot be accomplished with thermocouples made of the available alloys generally used for temperature measurements, their efficiency being less than one percent.
A review of the theoretical efficiency calculations shows that higher efficiencies can be attained with thermocouple materials to which the Wiedemann-Franz-Lorenz relation is applicable, when their thermoelectric power is greater than 200 microvolts/°C. Some zinc-antimony alloys with added metals approach the above conditions and have produced an experimental efficiency in excess of five percent, in accordance with the theoretical calculations.
The criteria of higher efficiency are applied to semi-conductors, deriving the optimum conditions. Lead sulfide with excess lead was found to be the only suitable material at present, which in combination with the zinc-antimony alloy produces an efficiency of seven percent.
Higher thermoelectric efficiencies can be produced only by developing new materials which can attain the theoretically required high values of thermoelectric power, low heat conductivity, and low specific resistance.
Cesium Chromate Photo-Tube Pellets
Authors: Liebhafsky H. A. , Winslow A. F. 
Published: January 2005

The following results have been obtained in an exploratory investigation of the cesium chromate pellets used in the manufacture of photo-tubes: (1) hydrogen evolution or titration can be used to measure the yield of cesium with reasonable precision. Each method has limitations. (2) The theoretical yield could be obtained from cesium chromatesilicon pellets. (3) Within limits, the actual yield increases with the rate of heating; the maximum yield is not highly sensitive to composition in the range investigated. (4) No marked advantage was observed when titanium or zirconium was substituted for silicon as reducing agent. (5) An excess of hydrogen above the theoretical was consistently observed with nickel pellet holders, which points to a reaction of water vapor with reactive nickel formed during the heating and flashing of the pellet. The substitution of the less volatile molybdenum for nickel eliminated this difficulty. An excess of hydrogen was formed also when the reducing agent in the pellets was titanium.
It was suggested for purposes of further study that the complex process occurring when such pellets are induction heated be subdivided into two reactions of elementary silicon: (1) a preliminary exothermic reduction of hexavalent chromium, which initiates (2) a rapid reduction of monovalent cesium. The two reactions may proceed concurrently. This picture explains several observations made in the laboratory or in the factory.
Elastic Properties of Cork: III. Hydrostatic and Ordinary Load-Compression Curves for Cork
Authors: Dart S. L. , Robinson Howard A. , Guth Eugene 
Published: January 2005

Load-compression curves were taken for natural cork. The S-shape of the curves is discussed and a theoretical fit is made for the high end of the curve, assuming an initial stiffness and an incompressible part of the cork material. A comparison is made between repeated compressions, with and without a recovery period of time.
Pressure-volume curves were also taken and their significance discussed in connection with the load-compression curves leading to an evaluation of Poisson's ratio.
Waves in Elastic Tubes: Velocity of the Pulse Wave in Large Arteries
Authors: King Allen L. 
Published: January 2005

An equation for waves in elastic tubes is developed and applied to cylindrical tubes with Hookian and with elastomeric walls. The former application yields the Moens-Korteweg formula, which has been found inadequate. The latter application leads to a rather complicated equation for the pulse-wave velocity.
Values of pulse-wave velocities are computed for the thoracic aorta by means of the foregoing equation, and the results are compared with measured mean velocities for the entire aorta. Graphs and tables are given, so that a graphical analysis of this velocity equation can be applied to any large artery; and the method is illustrated by computing the pulse-wave velocity in the left common carotid. The relation l÷∫0lds/v, for the mean velocity over a tube of length l, is shown to be valid for the aorta and large arteries.
A Variable Capacitor for Measurements of Pressure and Mechanical Displacements; A Theoretical Analysis and Its Experimental Evaluation
Authors: Lilly John C. , Legallais Victor , Cherry Ruth 
Published: January 2005

A variable capacitor is described for measuring (1) small displacements, (2) small volume changes, and (3) pressure differences. The capacitor consists of a deflectable diaphragm and a fixed electrode. The diaphragm is metallic, plane-parallel, clamped at the edges, and at ground potential; the electrode, at an a.c. potential, has a plane surface parallel to the undeflected plate across an air gap. For use in displacement measurements, the diaphragm's center is deflected by a point contact from a mechanical link to the observed system, or by a uniform pressure load from a fluid link to the system. The fluid link is used also when measuring volume changes and pressure differences. The plate deflection results in a change in the air gap, and thus generates a capacitance signal. This signal is measured by electrical methods.
A theoretical analysis of this variable capacitor is presented; sensitivity and alinearity factors for the three uses of the device are derived. The experimental performance shows reasonably satisfactory agreement with the derived theory. The displacement of the plate's center was measured with an interferometric method, using a yellow He line as a standard of reference; the applied pressure, with a liquid manometer; and the capacitance signal, with a standard capacitor substitution procedure. The gauge can be used so as to give quantitative electrical indications of displacement, volume change, or pressure difference; or can be used as a null indicator device in which an unknown pressure is balanced against a known one on opposite sides of the diaphragm. In order to achieve large volume an displacement sensitivities, small air gaps (5.10–4 cm) are employed. Details of a construction method to assure small values are presented.
Theory of Automatic Control Systems
Authors: Melvin M. Avramy 
Published: January 2005

The theory of robots or reproducing power-amplifying systems is considered. After a general terminological orientation the study in the first part is confined to simple robots, the theory of which is equivalent to that of non-linear springs with inertia and friction. The alacrity and fidelity of control are well exhibited by studying the behavior of a robot under constant tracking. Special emphasis is placed on the specification of conditions for optimum performance, i.e., minimum deviation or maximum fidelity after any given time. Curves are given for both proportional and on-off robots, from which the parameter values for optimum performance may be read.
In Part II the theory of proportional robots is analyzed in detail, especially from the point of view of conditions for optimum performance. Two subsequent papers will contain the theory for the on-off case and the general non-linear robot case. The paper is organized as follows:
Part I. Descriptive account
A. Terminology and kinematic description
B. Dynamical equation of robots with usual load
C. Optimum performance curves. Practical examples
Part II. Theory of simple robots with proportional control
A. Complete solutions as functions of time. Optimum performance curves
B. Path curves in the position-velocity plane
Electron Beam Deflection: Part I. Small-Angle Deflection Theory
Authors: Hutter R. G. E. 
Published: January 2005

Two general mathematical methods are discussed which may be used to study the effects of electric and/or magnetic deflection fields on electron beams. The basic equations for the ``path method'' are the equations of motion of Newton or Euler-Lagrange. The ``iconal method'' makes use of certain properties of the Hamiltonian function.
These methods are then applied to describe the action of balanced, two-dimensional electric deflection fields on electron beams. It is shown that both methods yield essentially the same results. Expressions are derived describing the magnitude of deflection and the distortions of an electron beam.
Only the path method is used in a similar investigation of magnetic-type deflection fields.
Slow Transverse Magnetic Waves in Cylindrical Guides
Authors: Bruck G. G. , Wicher E. R. 
Published: January 2005

The fundamental physical phenomenon upon which linear electron accelerators and traveling beam tubes depend is the fact that the phase velocity of guided TM waves can be reduced to a fraction of the velocity of light. There are various practical ways of achieving these reduced velocities, such as diaphragms or spiral grooves in the guide wall. An open helix has been used by Pierce.
An accurate knowledge of the field pattern would greatly facilitate an understanding of these devices. It is of particular importance to have exact information about the field in the region in which the charge actually travels, namely, in a region located at least a considerable fraction of a wave-length from the guide walls. Because of the complex shapes assumed by actual guide walls calculations of the field are inevitably somewhat inexact and complicated.
The authors propose that, for the purposes of theory, the well-established proposition concerning the equivalence of true and simulated dielectrics in producing a slow field be used. We propose to think of slowing down the phase velocity by lining the guide walls with a natural dielectric. The essential properties of the slow field, particularly in the important region referred to above, will not be affected by this method of obtaining it while, on the other hand, the field calculation becomes quite easy and exact.
Although this procedure is intended in the main as a device to facilitate the theoretical calculation of the field, the authors believe that such a step—replacement of periodic metallic structures by dielectrics—might prove useful in some actual applications.
Incandescent Lamps as Electrical Load for Testing
Authors: Keilien S. 
Published: January 2005

Because of the positive coefficient of resistivity of tungsten, incandescent lamps permit a current considerably greater than the normal lamp current to flow for a short initial period. When lamps are used as load for testing electrical apparatus, the factors affecting this inrush must be considered. Size of power source, its distance from the load (lamps), and frequency of switching the lamps (employing repetitive operations for endurance testing) are evaluated.
From the given curve the necessary cooling time for the desired current inrush may be determined, and thus the frequency with which the lamps could be switched ``on'' and ``off'' may be calculated. Practical means for obtaining the required cooling time are described.
Electron Beam Deflection: Part II. Applications of the Small-Angle Deflection Theory
Authors: Hutter R. G. E. 
Published: January 2005

The theory developed in Part I is applied to a number of typical deflection fields such as the fields produced by parallel plates, parallel cylinders, semi-infinite co-planar sheets, and bent-plates. Graphs for the magnitude of deflection are given. An electrolytic tank potential-plotting device is described which was used for the determination of the potential distribution of some of the deflection fields.
The theory shows that the deflection is a function of the initial conditions of the electron beam before entering the field and that it is a slightly non-linear function of the field strength. It follows that the fluorescent spot and the pattern produced on the screen of cathode-ray tubes will show distortions. These distortions were calculated for several deflection fields and electron beam shapes; the results are shown graphically.
The problem of the reduction of these distortion effects is discussed.
Cathode-Ray Presentation of Three-Dimensional Data
Authors: Schmitt Otto H. 
Published: January 2005

The cathode-ray oscilloscope is usually regarded as a means for displaying data in one or two variables as a function of time. By means of simple transformations which are easily performed electrically, it is possible to present three variable electrical data in the form of isometric or other conventional projections or as true perspective drawings. It is further possible to change the observer's viewpoint in the presentation coordinate system at will by turning range, elevation, and azimuth controls.
A more elaborate but similar set of transformations permits presentation of separate pictures to the two eyes. These pictures are optically superimposed but differ in such a way as to yield stereoscopically correct perspective pictures. These pictures are fully acceptable to the eye as patterns in space.
An X-Ray Diffraction Study of the Silver-Magnesium Alloy System
Authors: Letner Harold R. , Sidhu S. S. 
Published: January 2005

Four homogeneous solid solutions were found in the silver-magnesium alloy system. The α-primary solid solution of magnesium in silver has a f.c.c. structure. The β-solid solution has a b.c.c. structure. The γ-solid solution appears to have a complicated structure. While others have identified it as hexagonal, no definite structure could be assigned to it from our diffraction data. The δ-solid solution has a h.c.p. structure of magnesium.
The lattic parameter a0 in the α-solid solution increases with increasing magnesium concentration but exhibits a marked negative deviation from Vegard's Law. The a0 in the β-solid solution, however, increases linearly with increasing magnesium concentration.
Silver and magnesium atoms are distributed at random in the α-phase but take up preferred positions in the β-phase. The ordering process takes place throughout the β-phase, but is most nearly complete in the region of 50 atomic percent Mg.
A Study on Anaeroid Capsules
Authors: Pike Eugene W. , Gibbs Norman E. 
Published: January 2005

The analysis of anaeroid capsule performance by the expansion of the observed pressure-deflection curve in Gram summation-orthogonal polynomials is illustrated on a series of fifteen runs on five typical capsules.
All of the deflection curves examined contained significant cubic and quartic terms while a few showed fifth-order terms. These high order terms are very unstable in magnitude and sign for successive deflections of the same capsule, and this accounts for the very complex hysteresis curves which have been observed.
The relationship of these high order terms in the deflection characteristic to the accuracy and cost of precise anaeroid barometers is brought out, and it is suggested that barometric systems free of elastic redundancies must be devised if accurate barometers for radiosondes and similar instruments are to be mass produced.
The Conical Dipole of Wide Angle
Authors: Smith P. D. P. 
Published: January 2005

The following report deals with a method of calculating the admittance of dipoles that consist of complete cones of wide angle. The theory makes use of the orthogonal properties of Legendre's functions and of their derivatives in order to make the outside field's tangential component vanish over the spherical end surfaces of the dipoles, and to make the inside and outside fields fit at the boundary sphere. This is a surface of the same radius as the dipole, extending from the upper to the lower end surface.This leads to a set of Eqs. (10) for the infinite set of coefficients bk, and an Eq. (3) that expresses the effective load admittance yt in terms of the coefficients bk. If a sufficient number of these coefficients is considered, there should be no appreciable discontinuities in field at the boundary sphere, and the tangential field should vanish on all the surfaces of the dipole.On the assumption that only the first two outside waves, and the internal T.E.M. and first higher order inside wave are important for dipoles whose radius is less than a half-wave-length, an approximate formula for yt is found, and the results are shown in Figs. 4 and 6. It is unnecessary to evaluate the solutions of Legendre's equation Ln(θ), because the integrals that involve them are expressed in terms of n(μ1) and dn(μ1)/dμ1, n being the root of Ln(A)=0, and μ1=cosA.The solutions are transformed to the center of the dipole, and plotted in Fig. 6, while the relative terminating admittances, K·yt, are plotted on an impedance diagram in Fig. 7.
Graphite Lubrication
Authors: Savage Robert H. 
Published: January 2005

The slipperiness of graphite is not inherent in the crystal structure alone but depends upon adsorption films, especially water, which cover the carbon atoms and provide surfaces of low cohesion. In vacuum graphite rods or brushes seize upon a moving base (copper or graphite) and wear away as a fine dust. This wear and accompanying high friction are instantly stopped by some condensible vapors at low pressures (H2O, C6H6, NH3, etc.) which apparently effect the coverage of the graphite by a reversible adsorption governed by the pressure and surface temperature. Under conditions of optimum coverage (zero wear) the graphite friction is still appreciable but may be accounted for as the heat of cohesion of water monolayers attached to the carbon atoms and undergoing successive makes-and-breaks. From the measured frictional energy and an assigned heat of cohesion based upon surface energy data, the area of molecular contact is estimated to be 4×10−6 cm2 under a real pressure 2×104 kg/cm2.
The wear dust of unlubricated graphite shows a unique adsorptive power at room temperature, greater for hydrogen than that of activated charcoal by five orders of magnitude. This and other characteristics may throw new light upon the mechanism of friction in general and upon the structure of stroked graphite surfaces in particular.
Theory of Formation of Metal Chips
Authors: Piispanen Väinö 
Published: January 2005

In this article values for the angles β and ν have been deduced (compare Fig. 3 and Eqs. (2) and (3)). New values have been deduced for the shear angle φ, Eqs. (16), (20), and (21). The increasing of the internal friction and the strain hardening have been considered.
Equations for the work done in cutting per unit of length (6) and (13) have been deduced. For the cutting force Eqs. (14), (15), and (19) have been deduced. A high cutting speed decreases the friction angle τ between the chip and the face of the tool, by which the forces loading the machine tool steeply may be decreased. These forces are very highly dependent on the friction angle τ, since the rake angle α is negative.
A new theory of the formation of a discontinuous chip is presented.