摘要:

An integral equation for the time‐dependent reaction is derived on the basis of the two‐group model of neutron multiplication. When the effective multiplication constant is given, the solution reduces to a determination of the mean timeTbetween consecutive generations, which is largely controlled by the circulation of neutrons in the reflector. If the steady distribution is known,Tcan be calculated from a simple formula.To illustrate the orders of magnitude which are involved,Twas calculated for a small pile surrounded by an infinite reflector. A value ofT=450 microseconds was obtained assuming a mean lifetime in the core of 50 microseconds and a mean lifetime in the reflector of 14 000 microseconds.

ISSN:0021-8979    

DOI:10.1063/1.1721575

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

Flow of two and three immiscible fluids in porous media is considered in which the various fluids are separated into different saturation zones by gravity. An equation of flow for any one fluid is derived with the condition that the other fluids must be stationary. This equation is then applied to solve the question of the maximum rate of flow of one fluid into a well from a radially symmetrical porous medium without producing the other fluid or fluids present in the formation. Different well geometries and fluid systems are considered. These problems are sometimes called ``coning'' problems.

ISSN:0021-8979    

DOI:10.1063/1.1721576

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

A new technique is reported in which silicon can be formed to provide transistor action. A suitable impurity is arced at the surface of the silicon causing the impurity to be diffused into a small region. Tests have been carried out usingn‐type andp‐type silicon with various impurities. Initial results indicated voltage gains as high as 75 and power gains between 15 and 60. Other characteristics, such as variations in current multiplication with emitter current, were examined and the mechanism of alpha was compared with the theories developed by Sittner.

ISSN:0021-8979    

DOI:10.1063/1.1721577

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

The problem of the propagation of electromagnetic energy down an infinitely long rectangular wave guide partially filled by a ferrite slab is solved. The solution is expressed in the form of a transcendental equation involving the propagation constant. Calculations are carried out for a lossless ferrite, and the phase constant is evaluated as a function of the appropriate parameters, namely, the ferrite slab thickness, the lateral position of the slab in the guide, and the applied transverse static magnetic field intensity. The results are plotted in graphic form for values of the static magnetic field in the region of ferrite saturation both above and below ferromagnetic resonance. The electromagnetic field configurations within the wave guide are plotted in detail for values of the parameters of practical interest. Two versions of the nonreciprocal phase shifter are discussed. The first consists of a single slab placed asymmetrically in the wave guide, while the second consists of two symmetrically placed slabs with antiparallel static magnetic fields imposed. The nonreciprocal nature is summarized in terms of the differential phase shift &bgr;+‐&bgr;−which is pertinent in applications of this phase shifter.

ISSN:0021-8979    

DOI:10.1063/1.1721578

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

An electrical power source can be made by exposing ap‐njunction to radioactivity or light, so that the junction field separates electron‐hole pairs produced by the radiation. Expressions for maximum power, optimum load resistance, and efficiency are derived from an equivalent circuit and rectification theory. Power and efficiency increase with source currentIgof separated charges and zero‐bias junction resistance.Igincreases with energy and intensity of radiation, but is limited by self‐absorption in the radioactive isotopes. Estimates of attainable power and efficiency for silicon cells are 3·10−3watt cm−2and 15 percent for solar radiation, averaged, allowing for night, weather, and varying angle of incidence; and 3·10−4watt cm−2and 8 percent, for beta radiation from Sr90&sngbnd;Y90of activity 32 Curie/g. However, lattice defects produced by Sr90&sngbnd;Y90beta radiation impair cell performance by increasing electron‐hole recombination. A theoretical estimate of threshold energy for radiation damage in silicon is about 0.3 Mev, about half the experimental value reported for germanium. Avoiding radiation damage by annealing, by absorbers, and by use of less energetic isotopes is discussed. The Y90beta spectrum is given; it is used in estimating damage rates in germanium, which are high, and efficiencies obtainable with absorbers, which are low. Theory and experiment are compared for Sr90&sngbnd;Y90cells of silicon and of germanium.

ISSN:0021-8979    

DOI:10.1063/1.1721579

出版商:AIP    

年代:1954

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1721581

出版商:AIP    

年代:1954

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1721582

出版商:AIP    

年代:1954

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1721583

出版商:AIP    

年代:1954

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1721584

出版商:AIP    

年代:1954

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1721585

出版商:AIP    

年代:1954

数据来源: AIP