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1 Dec 1948

Volume 19, Issue 12, pp. 1097-1192


Transformations in Organic Pigments

F. A. Hamm and Earl Van Norman

J. Appl. Phys. 19, 1097 (1948); http://dx.doi.org/10.1063/1.1715026 (13 pages) | Cited 19 times

Online Publication Date: 28 April 2004

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Organic pigments are often recrystallized in various ways to effect purification and to control the particle size of the new crop of crystals. Copper phthalocyanine and indanthrene blue RS have been observed to yield crystals of varying shades, ranging from a light greenish blue to a dark reddish blue (purple). These shades have in the past been attributed only to differences in particle size because the elementary analyses strongly indicated that the samples were chemically identical. This investigation shows that both these pigments are polymorphic, and each can exist in at least two different physical forms. The shade differences, therefore, may be due to the differences in the light absorption exhibited by the structurally different polymorphic forms.
The polymorphic transformations can, for both pigments, be readily observed to take place in the electron microscope. The new form of both pigments, completely stable to the illuminating beam after the transformation, can be seen to grow from the vapor state at the expense of the original metastable solid material. The ``red'' shade of indanthrene blue RS and the ``hard'' powder of copper phthalocyanine have been labeled ``metastable'' because they transform in the electron microscope. The ``red'' shade of indanthrene blue RS can also be made to transform during its molecular distillation; the ``blue'' shade did not transform under any circumstances. The ``hard'' and ``soft'' powders of copper phthalocyanine can both be made to transform during their molecular distillations (not in the electron microscope) to give the same new form which is identical with the form that grew in the electron microscope at the expense of the original ``hard'' powder.
Electron diffraction patterns prove that the newly formed phases are structurally different from the original samples. Both these commercially important pigments are therefore at least dimorphic.

Drag Coefficients of Steel Spheres Entering Water Vertically

Albert May and Jean C. Woodhull

J. Appl. Phys. 19, 1109 (1948); http://dx.doi.org/10.1063/1.1715027 (13 pages) | Cited 15 times

Online Publication Date: 28 April 2004

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Drag coefficients have been determined from high speed motion pictures for ¼‐inch to 1☒‐inch steel spheres shot into water vertically with speeds from 25 to 208 ft.∕sec. These drag coefficients correspond to the entrance cavity phase and to the v‐squared‐law drag forces only, the immediate effects on the spheres of other forces being eliminated in the calculations. It is found that CD is a function of both the Reynolds and Froude Numbers. Within the range investigated, the dependence may be expressed by CD=0.0174 ln(RF☒).

Homing and Navigational Courses of Automatic Target‐Seeking Devices

Luke Chia‐Liu Yuan

J. Appl. Phys. 19, 1122 (1948); http://dx.doi.org/10.1063/1.1715028 (7 pages) | Cited 7 times

Online Publication Date: 28 April 2004

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A graphical and mathematical analysis of homing and navigational courses of automatic target‐seeking devices is presented.
Homing courses for a seeker‐to‐target speed ratio of over two are likely to be impractical for target interception.
A method for obtaining a constant bearing course (navigational course) is developed. Some special cases of navigational courses have been studied graphically. It is shown that an optimum navigational ratio exists between that which leads to too slow an approach to the desired course and that which leads to instability.
Graphical analysis of navigational courses for straight as well as circular target motion is also given.

Use of an Electron Diffraction Camera as an Ultraoscilloscope, and Suggested Application to Contact Erosion

J. J. Lander

J. Appl. Phys. 19, 1128 (1948); http://dx.doi.org/10.1063/1.1715029 (2 pages) | Cited 1 time

Online Publication Date: 28 April 2004

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A high speed oscilloscope, obtained by adaptation of an electron diffraction camera, is described and a preliminary account is given of the use of this oscilloscope in a study of the ``short arc'' which occurs on opening mechanical contacts under certain conditions.
FREE

Erratum: The Attenuation of Spherical Shock Waves in Air

Richard G. Stoner and Walker Bleakney

J. Appl. Phys. 19, 1129 (1948); http://dx.doi.org/10.1063/1.1715031 (1 page)

Online Publication Date: 28 April 2004

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Abstract Unavailable

Dielectric Measurement Methods for Solids at Microwave Frequencies

W. H. Surber and G. E. Crouch

J. Appl. Phys. 19, 1130 (1948); http://dx.doi.org/10.1063/1.1715032 (10 pages) | Cited 9 times

Online Publication Date: 28 April 2004

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An experimental method of measuring the dielectric constants of solids is described for the case of medium and high loss materials. The dielectric sample is enclosed within a section of wave guide terminated by a reflecting plane, and measurements are made of the standing wave ratio and position of the voltage minimum for both a short‐circuit and an open‐circuit termination. The equations for the dielectric properties of the substance may then be expressed in a relatively simple form in terms of elementary functions for media having tanδ ≥ 0.03.
In order to obtain reasonable accuracy for the determination of the loss factor of low loss materials using only standard wave‐guide components, it was found to be necessary to adjust the operating conditions to obtain maximum power absorption by the dielectric sample. A frequency variation method of obtaining this maximum loss sensitivity is described, the apparatus being the same as that used for the medium and high loss materials.
A set of experimental values is given for the dielectric constants of a group of common plastics at 24,000 mega‐cycles. A brief analysis of the effect of certain of the equipment losses is included.
FREE

Erratum: Twinning in Tetragonal Alloys of Copper and Manganese

Francis T. Worrell

J. Appl. Phys. 19, 1139 (1948); http://dx.doi.org/10.1063/1.1715033 (1 page)

Online Publication Date: 28 April 2004

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Abstract Unavailable

Properties of a Long Antenna

Erik Hallén

J. Appl. Phys. 19, 1140 (1948); http://dx.doi.org/10.1063/1.1715034 (8 pages) | Cited 4 times

Online Publication Date: 28 April 2004

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Although exact integral expressions for the outgoing current waves on a long antenna have long existed, they have never been brought in such a form that a numerical or graphical description of the wave has been possible. The author shows how to transform them into good series expansions valid for all distances from the feeding point. Graphs show the result. The traveling current waves can also be extracted from the author's expression for the current on a finite transmitting antenna published in Nova Acta Upsal, 1938. Both ways give identical series.

The Dissipation of Heat by Free Convection from Vertical and Horizontal Cylinders

W. Elenbaas

J. Appl. Phys. 19, 1148 (1948); http://dx.doi.org/10.1063/1.1715035 (7 pages) | Cited 13 times

Online Publication Date: 28 April 2004

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This paper gives a simpler deduction of formulas given previously [W. Elenbaas, Physica 9, 285, 665, (1942)] for the dissipation of heat of horizontal and vertical cylinders with natural cooling.

On the Theory of Biconical Antennas

C. T. Tai

J. Appl. Phys. 19, 1155 (1948); http://dx.doi.org/10.1063/1.1715036 (6 pages) | Cited 8 times

Online Publication Date: 28 April 2004

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The investigation contained in this paper gives a general treatment of the theory of biconical antennas based upon Smith's formulation of the problem. For the case of small‐angle cones, an expression of the effective load admittance is obtained which is the same one that Schelkunoff derived based upon two rather ingenious methods, both of which, however, are not as rigorous as the present one. As an illustration of another application of the analysis, a treatment is given of the characteristics of biconical antennas where the space between the cones is filled with a dielectric other than air.

Measurement by Radioactive Tracers of Diffusion in Liquids

Andrew Gemant

J. Appl. Phys. 19, 1160 (1948); http://dx.doi.org/10.1063/1.1715037 (4 pages) | Cited 2 times

Online Publication Date: 28 April 2004

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A method, using a radioactive tracer technique, for the measurement of diffusion coefficients in liquids is described. Results for uranyl nitrate solutions, revealing the diffusion of Th‐234, in water and dioxane are presented.

Physical Limitations of Omni‐Directional Antennas

L. J. Chu

J. Appl. Phys. 19, 1163 (1948); http://dx.doi.org/10.1063/1.1715038 (13 pages) | Cited 205 times

Online Publication Date: 28 April 2004

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The physical limitations of omni‐directional antennas are considered. With the use of the spherical wave functions to describe the field, the directivity gain G and the Q of an unspecified antenna are calculated under idealized conditions. To obtain the optimum performance, three criteria are used, (1) maximum gain for a given complexity of the antenna structure, (2) minimum Q, (3) maximum ratio of G∕Q. It is found that an antenna of which the maximum dimension is 2a has the potentiality of a broad band width provided that the gain is equal to or less than 4a∕λ. To obtain a gain higher than this value, the Q of the antenna increases at an astronomical rate. The antenna which has potentially the broadest band width of all omni‐directional antennas is one which has a radiation pattern corresponding to that of an infinitesimally small dipole.

A Technique for Quantitative Determination of Texture of Sheet Metals

John T. Norton

J. Appl. Phys. 19, 1176 (1948); http://dx.doi.org/10.1063/1.1715039 (3 pages) | Cited 11 times

Online Publication Date: 28 April 2004

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A method is described for making a pole figure of rolled sheet employing an x‐ray unit equipped with a G‐M counter for measuring intensities. Small rods are cut from the sheet with their axes parallel to the plane of the sheet and making various angles with the rolling direction. With the counter tube set at the correct diffraction angle for the desired crystallographic plane, each rod in turn is placed in the beam and rotated continuously about its axis. The recorder chart, synchronized with the rod rotation, plots a curve of intensity vs. angular position. Thus the record for each rod provides information for a specific diameter of the pole figure and all have a common point at the center. Since all rods are cylindrical and of the same diameter, there is no absorption correction to be applied. Contours for the pole figures may be drawn as closely together as desired. For special purposes where the complete pole figure is not required but quantitative comparisons are to be made between specimens, certain simplified techniques based on the same principle have proved useful.

Drag of an Airfoil in Accelerated, Supersonic Flight

C. S. Gardner, H. F. Ludloff, and F. Reiche

J. Appl. Phys. 19, 1179 (1948); http://dx.doi.org/10.1063/1.1715040 (2 pages) | Cited 1 time

Online Publication Date: 28 April 2004

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Abstract Unavailable

Remarks on ``The Efficiency of Thermoelectric Generators''

Robert M. Papet

J. Appl. Phys. 19, 1180 (1948); http://dx.doi.org/10.1063/1.1715041 (1 page) | Cited 5 times

Online Publication Date: 28 April 2004

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Abstract Unavailable

Calculation of the Temperature Development in a Contact Heated in the Contact Surface, and Application to the Problem of the Temperature in a Sliding Contact

W. J. Oosterkamp

J. Appl. Phys. 19, 1180 (1948); http://dx.doi.org/10.1063/1.1715042 (2 pages) | Cited 5 times

Online Publication Date: 28 April 2004

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Abstract Unavailable

On the Possibility of Hg Type Arcs with Hot Refractory Cathodes

Jerome Rothstein

J. Appl. Phys. 19, 1181 (1948); http://dx.doi.org/10.1063/1.1715043 (2 pages) | Cited 1 time

Online Publication Date: 28 April 2004

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Abstract Unavailable

The Application of Electron Multiplier Tubes in the Measurement of X‐Ray Beam Intensities and in the Determination of Crystal Structure

G. Papp and K. Sasvári

J. Appl. Phys. 19, 1182 (1948); http://dx.doi.org/10.1063/1.1715044 (2 pages)

Online Publication Date: 28 April 2004

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Abstract Unavailable

Homing Pigeon in Electromagnetic Fields

C. L. Clark, R. A. Peck, and W. F. Hollander

J. Appl. Phys. 19, 1183 (1948); http://dx.doi.org/10.1063/1.1715045 (1 page) | Cited 1 time

Online Publication Date: 28 April 2004

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Abstract Unavailable

PROGRAM OF THE E. F. BURTON MEMORIAL MEETING OF THE ELECTRON MICROSCOPE SOCIETY OF AMERICA

J. Appl. Phys. 19, 1186 (1948); http://dx.doi.org/10.1063/1.1715046 (7 pages) | Cited 12 times

Online Publication Date: 28 April 2004

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Abstract Unavailable
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