摘要:

Application of thermodynamics of irreversible processes to a thermocouple of which (a) the bars have an arbitrary shape, (b) the properties of the materials are arbitrary functions of temperature, and (c) the composition is, under certain restrictions, inhomogeneous and anisotropic, leads through introduction of a single place coordinate to two nonlinear differential equations describing the stationary distribution of temperature and electrical potential. Output powers and efficiencies are expressed in terms of the temperature gradients in the bars. The maximal values of the efficiencies obtained by variation of the shape of the bars are independent of the shape. Upper bounds of the efficiencies attainable by stationary thermoelectric conversion are derived. If the shape of the bars is restricted to general cylinders and truncated wedges or cones the transient behavior is described by two partial differential equations which contain two independent variables only. A periodic ripple in the electrical current has the same effect as a decrease of the electrical conductivities of the materials.

ISSN:0021-8979    

DOI:10.1063/1.1776982

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Electron metallographs evidenced rupture and blistering of the exterior tin surface of containers which had failed prematurely due to excessive hydrogen formation by corrosion processes within the container when packed with grapefruit juice. The enlargement of grain boundaries of the base steel of tin plate due to hydrogen diffusion has been illustrated.

ISSN:0021-8979    

DOI:10.1063/1.1776983

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Dissociation of solid SrO by impact of electrons having energy below 400 v was measured by a mass spectrometer method. Positively and negatively charged dissociation products were observed with equal sensitivity; no uncharged products were observed with an arrangement having poorer sensitivity. Thefundamentaldissociation products are Sr+, Sr++, and O+with essentially no O−. Surface impurities such as CO, Cl, F, and H were also abundant. The only source of chlorine found was an impurity in the original SrCO3, of about 1 part in 105. However, its abundance in the ion current is about equal to that of oxygen, and the yields of Cl+and Cl−are about equal. All particles must come essentially only from the surface layers.Yields of Sr+and Sr++increase with the square of electron density; yields of O+, Cl+, and Cl−increase, respectively, with the 1.5, 1.0, and 1.0 power of electron current density. The process is quite inefficient, the impact of 107electrons giving about 1 fundamental dissociation product for 20 to 30 ma per cm2of bombarding current. Yields are independent of electron energy from slightly above threshold to beyond 200 v, above which they decline slowly. Yields increase slightly with temperature, corresponding to activation energies of a few tenths of a volt.At least some of the chlorine on the surface probably exists in the uncharged form; threshold energies are too low to convert a Cl−on the surface to a Cl+in the vacuum. Removal of O+, Sr+, and Sr++ions is discussed in terms of a crystal composed of singly charged Sr+and O−ions; a process involving two incoming electrons in rapid succession on a minute area is apparently required for removal of an O+, Sr+, or Sr++ion.

ISSN:0021-8979    

DOI:10.1063/1.1776984

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Experimental evidence is presented that electron mirror microscopy is particularly well suited for direct visual observation of magnetic stray fields at grain boundaries in magnetic materials. Silicon‐iron disks were used as specimens. By mounting these specimens on a special magnetic stage of axial symmetry, the appearance and the growth of magnetic stray fields with increasing external applied magnetic fields could be observed directly, and motion picture recordings were taken from the viewing screen of the microscope. A series of electron mirror micrographs shown demonstrates that grain boundaries behave quite differently stray field‐wise. The fact that magnetic stray fields on grain boundaries are now accessible to direct visual observation is considered valuable for many magnetic investigations. The still controversial subject of grain size effects on the magnetic properties of such important magnetic materials as silicon‐iron is one subject which might profit from these potentialities inherent in electron mirror microscopy. This electronic observation method might also be helpful in grain boundary studies concerned with the basic physics of magnetics in such narrow regions of distorted order.

ISSN:0021-8979    

DOI:10.1063/1.1776985

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Studies have been made of the effect of neutron irradiation on the resistivity and magnetoresistivity of the alloy AuCu when subjected to various pre‐irradiation thermal and mechanical treatments. The specimens were exposed to estimated fast neutron fluxes up to 7.3×1018neutrons/cm2in the Brookhaven pile. In the case of thermally disordered specimens, the effect of the irradiation was to decrease the resistivity in completely disordered states and to increase the resistivity in completely ordered states;viz., there was some tendency for specimens to reach intermediate degrees of order. The effect on mechanically disordered specimens was to increase the resistivity in all cases. The irradiation effected a larger percentage change in in the coefficient of magnetoresistivity than in the resistivity.

ISSN:0021-8979    

DOI:10.1063/1.1776986

出版商:AIP    

年代:1959

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1776988

出版商:AIP    

年代:1959

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1776989

出版商:AIP    

年代:1959

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1776990

出版商:AIP    

年代:1959

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1776991

出版商:AIP    

年代:1959

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1776993

出版商:AIP    

年代:1959

数据来源: AIP