摘要:

Ultra‐speed pellets of the lighter metals such as aluminum and magnesium generate intensely luminous trails when fired through air. A pronounced characteristic of the luminous trails is theintermittentmanner in which the light is emitted. This effect has also been observed in meteors and in studies of conventional shaped charges. Photographs indicate that flashing is caused by yawing of the pellet.The brilliant flashes of light are associated with the ablation and subsequent burning of material from the pellet. There is evidence that the material is removed from the pellet in the form of small droplets.The brightness, luminous output, and temperature of the trail generated by an aluminum pellet have been measured. The brightness is approximately 25,000 lamberts, the luminous output is 30,000 lumen‐seconds, and the color temperature is 2900°K.

ISSN:0021-8979    

DOI:10.1063/1.1702196

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

Mechanisms in the corona discharge from a fine platinum wire at a positive potential along the axis of a hollow nickel cylinder have been investigated by using the oscilloscope to analyze the pulses caused by &agr;‐particles passed through the low field region parallel to the wire. &ggr;p, the secondary coefficient for the photo‐electric effect at the cathode in hydrogen, had values from 70×10−5at 100 mm to 5×10−5at 650 mm pressure. &ggr;ifor the hydrogen ions at the cathode was less than 10−6. The mobility of the positive ions (presumably H2+) was 13.4 (±0.4) cm2/volt×sec at 760 mm and 20°C. Adding 0.1 to 1.0 percent of oxygen to hydrogen resulted in the formation of O2−ions. &ggr;ifor the argon positive ions was about 9×10−4extrapolated to zero pressure and decreased with increasing pressure and &ggr;pwas less than110&ggr;i. Most of the ions were A2+with a mobility of 1.94 (±0.08) cm2/volt×sec. Positive wire dc current voltage data were taken in hydrogen and argon at several pressures. Sparks occurred with the positive wire in argon at relatively lower gap voltages than in hydrogen. Current‐voltage data were taken with the wire negative. In hydrogen the discharge started as a small (10−11amp) self‐supporting current (probably uniformly distributed along the wire) which changed with increasing gap voltage to a larger (microampere) discharge localized in luminous spots on the wire in analogy to Miller's observations in nitrogen. No small self‐supporting currents were observed in argon. The discharge started as a spark above 200 mm and as a glow that spread uniformly over the wire below 100 mm pressure.

ISSN:0021-8979    

DOI:10.1063/1.1702197

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

The effects of network formation of non‐Gaussian chains on the stress‐birefringence are calculated. If the birefringence is plotted against the stress, the effects make the curve deviate from a straight line. When it is plotted against the elongation, the curve will rise above that corresponding to independent Gaussian chains in agreement with the experiments.

ISSN:0021-8979    

DOI:10.1063/1.1702198

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

Values of the steady‐state dc resistance of copper oxide and selenium rectifiers as a function of temperature from 79°K to 300°K have been obtained. The maximum potentials used were 2.5 volts in the forward direction and 6.0 volts in the backward direction.It was found that a plot of the logarithm of the resistance against the reciprocal of the temperature was nearly linear for all except the reverse direction of the selenium rectifier. For the latter case at 6.0 volts the resistance went through a minimum below 200°K.

ISSN:0021-8979    

DOI:10.1063/1.1702199

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

An investigation has been made of the magnetic domain structure of Perminvar (43 percent Ni, 34 percent Fe, 23 percent Co) ring specimens having rectangular hysteresis loops after heat‐treatment in a magnetic field. Domain patterns obtained with colloidal magnetite showed curved domain boundaries extending completely around the rings, forming circles concentric with them. Changes in magnetization occur when an applied field causes the circular boundaries either to expand or contract so that there is a change in the relative values of clockwise and counter‐clockwise flux. A nucleus of reversed magnetization was formed by making a small notch in a specimen, and this decreased the coercive force and hysteresis loss by a factor of two. It was found that in a 180° domain boundary it was possible to make the change in spin orientations, which occurs in going from one side of the boundary to the other, have either a right‐ or left‐hand screw relation, by the application of a field of appropriate sign perpendicular to the surface. The effect of super‐posing an applied alternating field was also investigated, and an effective permeability of 4,000,000 was obtained.

ISSN:0021-8979    

DOI:10.1063/1.1702200

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

The technique of the new x‐ray double spectrometer method as described in a former paper1is applied to the study of angular misalignment of crystal structure in alloys.To obtain a better statistical evaluation of the x‐ray intensity data the method is extended to include arrays of spots on the Debye‐Scherrer lines at high elevations. A complete mathematical discussion of the photometric transformation of the crystallite rocking curves is presented.The specimens investigated include a low carbon alloy annealed at 850°C and three silicon ferrite samples annealed at 980°, 1100°, and 1200°C.The quantitative data obtained disclose a significant dependence of crystal perfection on annealing temperature, and demonstrate clearly that the angular misalignment of the coherently reflecting regions within the grains decreases with annealing temperature provided this temperature is not excessive.Valuable information regarding the influence of cold rolling on the subsequent annealing process is obtained. Thus, the extent of partial recrystallization of the silicon ferrite is deduced from the statistical data, and the differential grain size between the surface layers and the interior of the specimen is revealed through the study of the diffraction effects with radiation of different wavelengths.A mechanism of grain bending during plastic deformation is suggested and a relationship between magnetic properties, annealing temperature, and crystal perfection of the silicon ferrite is pointed out.

ISSN:0021-8979    

DOI:10.1063/1.1702201

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

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)‐CuK&agr;1line was used for the determinations. The lattice parametera=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)‐CrK&agr;1and &agr;2lines:a20=5.64607±0.00004kX(5.65748A) for both materials. The expansion coefficients were &agr;=6.65×10−6and 5.92 ×10−6, respectively. The density was 5.3234±0.0025 g/cm3at 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.

ISSN:0021-8979    

DOI:10.1063/1.1702202

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

The temperature diffuse scattering of x‐rays from a single crystal of &bgr;‐brass has been measured at room temperature using a Geiger counter spectrometer and crystal monochromated CuK&agr; radiation. Measurements were made throughout a large region in reciprocal space, with special attention given to thehkoplane. The results were in excellent qualitative agreement with the theory developed by Laval and James in which temperature vibrations are expressed in terms of elastic waves. From the measurements, dispersion curves are obtained giving the velocity and frequency of the elastic waves, in the [100], [110], and [111] directions, as a function of their wavelengths. An approximate frequency spectrum is then calculated on the basis of these dispersion curves. The velocities at infinite wavelength are shown to agree with those given by elastic theory using the static elastic constants.

ISSN:0021-8979    

DOI:10.1063/1.1702203

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

The reflection method for quantitative determination of pole figures, proposed by Schulz, proved to be limited with respect to the range of tilting angles in which satisfactory results can be obtained. It is shown that the previously unexplained decrease in the diffracted intensity with increasing tilting angle for specimens with random orientation distribution can be accounted for on the basis of an elementary analysis of defocusing effects. Experimental evidence is presented to show that variation of the receiving slit length and of the main slit width has the effect predicted by the analysis. The importance of accurate specimen alignment is discussed, and a satisfactory alignment check procedure is described.

ISSN:0021-8979    

DOI:10.1063/1.1702204

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

This report describes a study of dc and microsecond pulsed emission from oxide coated cathodes prepared on four different base metals. One of the base metals used was pure electrolytic nickel and the other three had impurities of 0.2 percent silicon, 4 percent silicon, and 4.7 percent tungsten added to the nickel. The flat base metal cathode was coated with equal molar barium‐strontium carbonate. The tubes were placed on life test at a cathode temperature of 1125°K with no emission current drawn. Dc and pulsed emission measurements were taken periodically. Three methods were used to measure the zero field emission current, (1) dc retarding potential, (2) dc Schottky, and (3) pulsed Schottky. These gave essentially the same Richardson plot indicating a positive correlation of dc and pulsed emission. From these Richardson plots obtained using methods (1) and (3), the work function, the emission constant, andJ0, the characteristic emission current density at 650°K, were determined. The results show that the different cathode base metals control the variation in emission with life. The emission from the tungsten‐nickel base metal is stable with life and is of much higher value than the other base metals.

ISSN:0021-8979    

DOI:10.1063/1.1702205

出版商:AIP    

年代:1952

数据来源: AIP