摘要:

The amplitude and period of the limit cycle of the Van Der Pol equation,y¨+y=vy˙(1−y2), are found for all values ofvby joining graphically the results of solutions aboutv=0 andv=∞.

ISSN:0021-8979    

DOI:10.1063/1.1721623

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

For the purpose of extending the usefulness of a Geiger counter to higher radiation intensities, it has been suggested that the voltage applied to its electrodes be a periodically repeated pulse rather than the usual dc. If the duration of the pulse is of the order of the spread time of the discharge in the tube, the output currentvsradiation intensity relation will differ from the usual linear one, largely because the resulting current surge may not reach its maximum before the end of the applied pulse. This relation will therefore depend, among other factors, on the not fully understood mechanism by which the discharge spreads. Using probability considerations, we here calculate this relation as a function of the response of the tube under ordinary operation. If the discharge spreads rapidly (e.g., exponentially) initially, an approximate general relationship not involving the detailed spread mechanism may be established. The response to be expected in two types of tubes is discussed in detail, using models for the spread mechanism which are mathematically simplified though probably physically adequate.

ISSN:0021-8979    

DOI:10.1063/1.1721624

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

Formulas are developed which define the profile of the electrostatic potential distribution in the semi‐infinite, space‐charge‐filled region between a plane emitter of secondary electrons and a parallel retarding‐field control grid. The calculation assumes a known secondary‐electron energy distribution and a cosine angular distribution. In practical application, the formulas must be evaluated numerically or graphically since the energy distribution cannot be expressed analytically except over limited regions. A method of determining the critical spacing between electrodes which will prevent formation of a space‐charge‐induced minimum in the potential distribution between the emitter and control grid is presented.

ISSN:0021-8979    

DOI:10.1063/1.1721625

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

In order to prepare a good secondary electron emitting surface from a silver‐magnesium alloy, it was found that baking in dry oxygen would not form the desired surface as originally believed, whereas baking in the presence of water vapor did yield a good secondary emitter. Subsequent experiments showed that, because of the rapid diffusion of oxygen through heated silver, the magnesium in the alloy was oxidized in situ without diffusing to the surface to form the required magnesium oxide layer. With water vapor as an oxidizing medium, the diffusion rate of magnesium through the silver greatly exceeded that of the water vapor, and a satisfactory surface layer was formed. A new technique was then devised in which an original water‐vapor process formed the desired surface, followed by an oxygen process to oxidize the remanent magnesium throughout the volume of the alloy. With the new technique, good secondary emitters are possible which will withstand severe overheating without the evaporation of magnesium found with earlier techniques.

ISSN:0021-8979    

DOI:10.1063/1.1721626

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

The effect of symmetry of the solutions to the finite difference diffusion equation upon the stability criterion is discussed. A simple example is included to illustrate the discussion.

ISSN:0021-8979    

DOI:10.1063/1.1721627

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

The relationships between certain approximations that have been proposed recently in connection with the linear viscoelastic behavior of noncrosslinked amorphous polymers are discussed. The approximations reviewed here are applicable with slight modifications to other types of linear response, for example, dielectric behavior.

ISSN:0021-8979    

DOI:10.1063/1.1721628

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

Foster's reactance theorem synthesizes the class of lossless networks in a so‐called canonic form. This idea is here generalized in order to show that there is a distinct class of RLC networks possessing a canonic form. It will be shown that when an RLC driving‐point impedance or admittance possesses a canonic form, its poles and zeros must alternate on each and every ``separate part'' of an algebraic curve (c) of a special nature located in the left half of the frequency planes=&sgr;+j&ohgr;, belonging to one of the following two families:a0+1nak(&sgr;+&agr;k)(&sgr;+&agr;k)2+&ohgr;2=0;  a0  1nak(&sgr;2+&ohgr;2+&agr;k&sgr;)(&sgr;+&agr;k)2+&ohgr;2=0.A corollary of this theorem, in the case (c) is a straight line or circle, symmetrically placed with respect to the real axis, unifies the three known cases of LC networks, RL‐RC networks, and networks with slight dissipation.Analysis and synthesis of RLC networks possessing a canonic form is introduced in the light of a more general approach to the problem based on the class consideration. The problem of the driving‐point impedances which contain mutual coupling in their Brune configuration has been clarified by outlining their generating functions and their network structure. (The latter part is omitted here and shall be presented in another article.)

ISSN:0021-8979    

DOI:10.1063/1.1721629

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

A solution of Maxwell's equations is obtained in a resonant cavity with a center post of arbitrary electrical properties. The solution gives the dielectric coefficient and the conductivity of the center post in terms of the natural frequency andQof the cavity. The theory is of particular use in the study of semiconductors where perturbation theories are of little value. It is shown that a transition from a cylindrical mode to a coaxial mode occurs as the conductivity of the center post is varied. This transition occurs for a relatively small change in conductivity. The present results are compared with those of perturbation theory, and it is shown that the latter are valid over a greater range than the conditions imposed in their derivation indicate.

ISSN:0021-8979    

DOI:10.1063/1.1721630

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

The methods of fabricating 16 percent Al‐Fe from cast slab to thin‐gauge sheet are described in some detail. The melting, casting, homogenizing, hot rolling, and cold rolling at 575°C and room temperature are described. Particular attention is focused upon the 575°C cold rolling from the standpoint of the possible beneficial effects derived from an ordering reaction which occurs in this alloy. The technique of cold reduction from 0.007 in. to 0.0005 in. at room temperature is discussed.Magnetic data on a limited number of heat‐treated laminated cores are given. Useful physical properties, other than magnetic, of previous limited interest because of the inability to fabricate the alloy into ductile strong thin sheets, are discussed. These properties include excellent oxidation resistance at high temperatures, good wet‐corrosion resistance to certain chemical solutions, and high electrical resistivity.

ISSN:0021-8979    

DOI:10.1063/1.1721631

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

Classical diode theory, as applied to metal point contacts made to ann‐type semiconductor, is adequate only for small forward voltages at which, under certain conditions, hole current may be negligible. The shape of the theoretically predicted diode characteristic is not affected by the hole injection process at low voltages, no matter what the composition of the current. However, for voltages in excess of a certain value, dependent only on the resistivity of the material (on the order of 0.1 volt for 5 ohm‐centimeter germanium), the spreading resistance is comparable to the barrier resistance, and it is the hole injection process which accounts for continued rectification. The extent to which the spreading resistance is decreased by hole injection depends on the ratio, &ggr;, of hole current to total current. The present paper includes a theory of the effect of this ratio on the diode characteristic at higher forward voltages. A method of measuring &ggr; from V‐I characteristics alone is indicated.

ISSN:0021-8979    

DOI:10.1063/1.1721632

出版商:AIP    

年代:1954

数据来源: AIP