摘要:

A Lorentz field is generated when moving free carriers in semiconductors interact with a crossed magnetic field. A set of computer results show a strong interaction with high‐order transverse modes in a parallelplate wave guide. As a result of this interaction, unstable solutions which lead to the generation of growing waves have been found.

ISSN:0021-8979    

DOI:10.1063/1.1657870

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

It is shown by use of image converter photographs and probe data, that a Q‐switched laser can produce blast waves at relatively low gas pressures (p≳0.6 mm Hg). The gas density and time dependence of the laser produced blast waves are found to be in close agreement with predictions based on ideal blast‐wave theory. The data were taken using argon gas and laser delivered energies of approximately 0.5 J.

ISSN:0021-8979    

DOI:10.1063/1.1657871

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Practical results for the pressure amplification in the right angle between two planes can be obtained by combining the known solutions of the problems of oblique and normal shock reflection. The results so obtained have been checked for various shock strengths and two angles of incidence by experiments carried out in an explosively driven shock tube.

ISSN:0021-8979    

DOI:10.1063/1.1657872

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

A method is proposed for designing an x‐ray spectrometer which can scan a limited wavelength region without movement of the concave grating or the electronic counter. Spectrometers widely used in the past have consisted of a fixed x‐ray source and a movable counter. This method is to use a fixed counter and a scanning x‐ray source to avoid undesirable movement of the sensitive electronic counter with its delicate and complex cooling system. The scanning x‐ray source will be obtained by scanning the cathode ray beam of an x‐ray tube. Two cases are analyzed theoretically; the Rowland circle (or Paschen‐Runge) mounting, and a new arrangement which will be designated as the Sawada mounting. In the latter, the concave grating and the middle point of the scanning region of the x‐ray source lie on the circumference of a circle with the same radius as that of the grating. It will be useful for constructing an x‐ray grating spectrometer in the future. The length of a spectral line is shorter in the case of the Sawada mounting than in the case of the Rowland circle mounting, and the width of the line is broader in the case of the Sawada mounting than in the case of the Rowland circle mounting, owing to various abberations. The other advantages and disadvantages of the Sawada mounting are discussed in comparison with the Rowland circle mounting.

ISSN:0021-8979    

DOI:10.1063/1.1657873

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The time required for the evaporation in a vacuum of a given amount of tungsten from a round tungsten filament heated by constant current is computed and experimentally verified. Tables of time vs normalized wire diameter for initial temperatures between 2000° and 2950°K, in steps of 50°K are presented. The results are valid for any initial wire diameter. The increasing electric field is also computed and tabulated. From the results, the ultimate life of the heated filament can be obtained. For example, at an initial temperature of 2400°K, it is found that when the mass of the wire has diminished 10%, the filament has attained about 98% of its life. The life of the wire under constant‐current conditions is shown to be substantially less than that under constant‐temperature conditions.

ISSN:0021-8979    

DOI:10.1063/1.1657874

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The specific heats of some stainless steels (AISI types 304, 304L, 310, and 321; and US Steel ``Tenelon'') have been measured between 1.7°K and 4.2°K. The results could not be fitted to the usual relationc=&ggr;T+BT3, but rather toC=A+&ggr;T+BT3. Moreover, the value of &ggr; was extremely high. These results are discussed in terms of magnetic contributions to the specific heat.

ISSN:0021-8979    

DOI:10.1063/1.1657875

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The excess entropy measured in dilute solid solutions of Al&sngbnd;Ag, Al&sngbnd;Zn, and Pb&sngbnd;Tl is compared to a theoretical vibrational entropy model. This theoretical model is based upon the localized influences which solute atoms produce in dilute solid solutions. The excess entropy, of vibrational origin, is found to arise principally from the mass and valence differences between solute and solvent atoms. Use of various types of potentials is made to calculate the ``force constants'' between the impurity atoms and the nearest‐neighbor atoms in the solid solutions.

ISSN:0021-8979    

DOI:10.1063/1.1657876

出版商:AIP    

年代:1969

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1657878

出版商:AIP    

年代:1969

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1657879

出版商:AIP    

年代:1969

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1657880

出版商:AIP    

年代:1969

数据来源: AIP