摘要:

In view of the recent interest in the introduction of stacking faults in crystals during plastic deformation, the x‐ray diffraction effects have been calculated for face‐centered cubic crystals with deformation faults (as distinct from growth faults, the expressions for which are given in an appendix for comparison). Explicit expressions are derived for the reciprocal lattice intensity distribution, and it is shown how the intensity of faulting can be determined from measurements on the breadths of the reciprocal lattice streaks or the displacements of their peaks. It is then shown how these effects will be revealed in the x‐ray powder pattern and some practical aspects are discussed.

ISSN:0021-8979    

DOI:10.1063/1.1702312

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

Electron beam oscillators are placed in one of two groups depending on whether or not they employ resonant energy‐extractors. A natural upper frequency limit exists for the group which does. This limit depends chiefly on the ac beam current density and the noise level in the resonant structure. For practical values of these parameters, the maximum frequency is below the range of visible light.

ISSN:0021-8979    

DOI:10.1063/1.1702313

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

This paper presents a mathematical analysis of the fundamental circuit on which the operation of dielectric amplifiers depends. The analysis is based on the assumption that the effective hysteresis curve of the amplifier's dielectric material may be represented by a hyperbolic sine function. The case of resistive load is analyzed and expressions for the steady‐state input and output currents are calculated. From a consideration of the transient response of the amplifier, an estimate of its time constant is obtained.

ISSN:0021-8979    

DOI:10.1063/1.1702314

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

Simplified expressions have been developed for the engineering emissivity of uniformly distributed diatomic gases for nonoverlapping rotational lines with a resonance contour. Unfortunately the rotational half‐widths for spectral lines arising from transitions between excited vibrational energy levels are generally not known. For this reason it was necessary to make the assumption that the rotational half‐widths for transitions of the formn→n+v,v=1 or 2, are identical. The theoretical analysis is, however, sufficiently general to be useful without modification when accurate data concerning the dependence of line‐width on vibrational excitation become available. Explicit expressions have been obtained for the contributions to the total emissivity associated with individual vibration‐rotation bands.Representative emissivity calculations have been carried out for CO and HCl. Comparison of the calculated emissivities of CO with experimental data shows only fair agreement, suggesting either that the assumed description of rotational half‐widths is inadequate or else that the empirical emissivity data are not reliable at elevated temperatures.

ISSN:0021-8979    

DOI:10.1063/1.1702315

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

The question is treated whether in the study of linear visco‐elastic behavior of a material change of temperature is completely equivalent to a shift of the logarithmic time scale or not. If it is, the material is termed ``thermo‐rheologically simple'' (classA).It is shown that, by plotting the results of a similar rheological experiment (for instance, a creep experiment) performed at different temperatures and comparing the curves obtained, one can decide whether the materials considered belongs to classAor not, by seeing whether the curves can be made to fit by shifting them along the axis of logarithmic time. Once the material has been decided to behave thermo‐rheologically simple, one can plot the function describing the time‐shift as function of the temperature.Some examples of thermo‐rheologically simple materials are quoted from the literature.The micro‐rheological conditions for thermo‐rheologically simple behavior are discussed. It turns out that this behavior implies that in similar deformations at different temperatures always the same sequence of molecular events follows, whereas in materials not belonging to classA, not only the speed, but also the sequence of molecular processes changes when the temperature of the experiment changes. This implies, that materials of classAcannot from a heat treatment assume a special structure which could not be obtained by one temperature, whereas for materials of classBa heat treatment can indeed result in a special structure. It is reasonable to expect that thermo‐rheologically simple materials will be found only among polymers containing no crystallites and no pronounced polar groups.

ISSN:0021-8979    

DOI:10.1063/1.1702316

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

An attempt has been made to measure the energies with which positive ions arrive at the cathode of a negative point‐to‐plane corona in N2. A hairpin thermocouple was used as the point electrode. It was heated by the corona current, and its thermal emf was recorded by a galvanometer. After appropriate calibration, the potential across the Crookes darkspace was determined to be about 300 volts, and the average energy with which ions arrive at the corona point to be about 15 ev.

ISSN:0021-8979    

DOI:10.1063/1.1702317

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

The diffraction pattern of an aperture with amplitude distributionA(x) and phase function &psgr;(x) is examined for two cases: (1) controlled variation of the amplitude distribution with known uniform phase; (2) controlled variation of phase with known amplitude distribution. For Case 1, it is shown that a symmetrically tapered amplitude distribution produces a diffraction pattern with reduced secondary lobes, while an asymmetric amplitude distribution produces a shaped pattern. Thus, antenna beam shaping may be achieved by controlled variation of amplitude distribution in an aperture in which there is uniform phase. For Case 2, it is shown that a specified beam shape may be approximated by controlled variation of phase in the aperture when the amplitude distribution is known. The method of calculation is an extension of the method originally formulated by Chu for calculating cylindrical reflectors to transform a given primary radiation pattern to a specified shaped pattern. A general formulation of Chu's method for an amplitude distribution on a curved surface is developed. The theoretical results are applied to the design of progressive‐phase antennas and experimental results given.

ISSN:0021-8979    

DOI:10.1063/1.1702318

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

A point focusing x‐ray monochromator was designed and constructed for low angle scattering studies. The anastigmatic point focus is achieved by means of two cylindrically bent quartz crystals whose focal circles are mutually perpendicular. The beam, emanating from the copper target of an x‐ray tube, is reflected in succession, first from the crystal defining the horizontal focal circle, and second from the crystal defining the vertical focal circle following which it comes to a monochromatic point focus of wavelength 1.537A (CuK&agr;1). The sample to be studied is placed between the second crystal and the point focus, and the scattered beam is detected by means of a photographic film placed at the point focus, at right angles to the undeviated beam, the latter being suppressed by means of an absorber, or allowed to pass through a hole in the film.Mathematical analysis, in which a ray was traced through the two‐crystal system, revealed correctly the shape and size of the point focus, and the possibility of reducing the latter in size by stopping down the beam emerging from the target.

ISSN:0021-8979    

DOI:10.1063/1.1702319

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

We describe the results of experiments we have made, using the point focusing monochromator as the primary tool, to determine the particle size of latex spheres. The suitability of the instrument for this particular study is described and the experimental data obtained are tabulated, these data coming from our experiments with three physically distinct samples of Dow latex. We attempt to make a critical interpretation of the data by considering separately several possible space arrangements which the latex spheres might assume when the water, which is initially the suspending fluid, is evaporated. Corrections for the finite size and shape of the ``point'' focus are described. The absence of a significant difference in the mean particle sizes of the three samples considered is established.The data from all three samples is combined to yield a mean particle diameter under an external pressure of one atmosphere of 2687.5A with a statistical standard deviation of 1.2A and a fixed (systematic) error estimated to be not more than ±7A.

ISSN:0021-8979    

DOI:10.1063/1.1702320

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

Anelastic properties of zinc single crystal of high purity (99.996 percent) have been studied, using bars vibrating transversely at audio frequencies in free‐free modes. Internal friction, effective elasticity, and shape of resonance curve were determined against the strain amplitude. When the driving force exceeds a critical value, the internal friction increases, its maximum‐amplitude‐frequency decreases, and its resonance curve becomes asymmetrical. Furthermore, under this conditiona discontinuous phenomenon, which is supposed to be closely correlated with slips occurring in the crystal, has been found. This discontinuous phenomenon was recorded under different stresses.

ISSN:0021-8979    

DOI:10.1063/1.1702321

出版商:AIP    

年代:1952

数据来源: AIP