摘要:

Using a method which is the electromagnetic analog of the scattering matrix formalism in the theory of nuclear reactions, two ``sum rules'' are derived for the frequency independent coefficients occurring in the admittance matrix relating the currents and voltages in a loss‐free microwave junction. These are sums, respectively, over the various modes of the guides entering the junction, and over the modes of the cavity comprising the junction (suitably defined). The results are used to estimate the effect on the admittance matrix of the higher modes, both of the guides, and of the junction proper.

ISSN:0021-8979    

DOI:10.1063/1.1702286

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

Experimental methods are given for determining theQof both high and lowQresonant cavities at microwave frequencies. The emphasis is placed on the practical measurements necessary in determining the properties of ionized gases in the 3‐ and 10‐centimeter wavelength range.

ISSN:0021-8979    

DOI:10.1063/1.1702287

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

Experimental methods are given for determining the electric field within resonant cavities in the microwave region. Methods are discussed of calculating the electric field in both simple and complex structures used in gas discharge studies.

ISSN:0021-8979    

DOI:10.1063/1.1702288

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

The initial conduction interval in thyratrons, or time interval during which the major rise in current occurs, is shown to be dependent on two parameters. The first of these is dependent on tube construction and the second on circuit elements. It is shown that both factors are significant in operation of hydrogen thyratrons in millimicrosecond switching service.

ISSN:0021-8979    

DOI:10.1063/1.1702289

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

The kinetics of single‐interface motion in the diffusionless transformation of Au‐Cd single crystals containing 47.5 atomic percent Cd were studied. A diffusion‐controlled relaxation phenomenon was found with an activation energy of the order of 24,000 calories per mole. The two observed characteristics of diffusionless transformation of this alloy, that the transformation does not take place isothermally, and that the velocity of transformation on cooling is considerably and consistently larger than that on heating, can be successfully interpreted from the relaxation hypothesis.

ISSN:0021-8979    

DOI:10.1063/1.1702290

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

From observations in the shadow electron microscope and the standard electron microscope it is concluded that specimen charging does not significantly change the magnification of the latter, provided that the specimen is less than a few microns in thickness and the illuminating electron beam simultaneously strikes a nearby grounded conductor such as the supporting mesh.The difference in size of shadowed and unshadowed Dow Latex 580G, lot 3584 reported by Kern and Kern (J. Appl. Phys.21, 705 (1950)) is attributed to an added layer of material on the shadowed particles. Evidence in support of this view is presented, and the results of other workers are discussed in the light of it.

ISSN:0021-8979    

DOI:10.1063/1.1702291

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

Slotted wave‐guide arrays feeding into parallel‐plate regions have been used in some high speed scanners. Parallel‐plate regions also have been used for the suppression of second‐order beams of high gain arrays.A theoretical expression is derived for the conductance of a longitudinal shunt‐slot in a rectangular guide when the slot is radiating into a parallel‐plate region of arbitrary plate spacing. Some peculiarities of the theoretical results are discussed. There is good agreement between theory and experiment.

ISSN:0021-8979    

DOI:10.1063/1.1702292

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

Unless the primary source of noise is one of those which is theoretically tractable, the statistical properties of the noise have to be inferred from samples. We have developed some criteria to aid in the decision whether a sample can reasonably be assumed to have come from a Gaussian noise with predetermined parameters.

ISSN:0021-8979    

DOI:10.1063/1.1702293

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

The contribution of space charge to the admittance of a diode with a retarding field is calculated by computing the instantaneous electronic current induced in an external circuit. A discussion of the variation of the susceptance of a typical diode with frequency is given.

ISSN:0021-8979    

DOI:10.1063/1.1702294

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

The transient creep of single crystals prepared from 99.999 percent zinc was studied at 35°C and at strain rates of the order of 10−5/min. The results are given by the relation: creep rate=at−n, whereaandnare constants andtis the time after applying the load. This is of the form expected from Andrade's equation, but the exponentnhad only approximately the value ⅔ found by Andrade and varied from experiment to experiment. An additional instantaneous plastic strain occurs on applying the stress at the start of a creep test. It was found to be proportional to the subsequent transient creep rate (as measured byain the above equation) in a series of tests made on a given crystal. In addition to the process of recovery from strain‐hardening whereby a zinc crystal completely resoftens in a few days at 35°C, there appears to be a rapid, but very limited, stage of recovery, the effects of which quickly disappear upon further deformation. Some crystals exhibited a decrease in plasticity when allowed to rest for about two days at 35°C after a creep test. The development of this ``rest‐hardening'' is dependent to some extent on the occurrence of creep prior to the rest period. Zinc crystals were observed to contract with time after removing the load in a creep test. The extent of this contraction varied among specimens and among different tests made with the same specimen and was of the order of 10−5cm/cm or less. This appears to be the first report of such an after effect in single crystals of a pure metal. The results are discussed in relation to the findings of other workers and are interpreted in terms of recent models of the metallic state.

ISSN:0021-8979    

DOI:10.1063/1.1702295

出版商:AIP    

年代:1952

数据来源: AIP