摘要:

A selected set of points on the trajectories of charged particles traversing an electron‐optical system may be considered to be an object space, and another set an image space. Electron‐optical lenses are said to be ideally focused if the transformation of the points in object space to those in image space is one to one and continuous. A necessary condition for ideal focusing is used to prove that a number of electron‐optical systems require the presence of space charge in order to be ideally focused. Expressions for some ideally focused electron‐optical lenses are given, in particular those for cylindrical lenses without space charge derived from spherical lenses with space charge.

ISSN:0021-8979    

DOI:10.1063/1.1721366

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

Mixtures of boron and carbon were heated at approximately 2000°C; the reaction products have been studied by x‐ray diffraction and by density and electrical measurements. The existance of a wide range of homogeneity of ``boron carbide'' has been established. No evidence of compound formation corresponding to B4C could be detected. Similarities between the structures of boron and ``boron carbides'' indicate that the latter may best be described as solutions of varying amounts of carbon in a slightly distorted boron lattice.

ISSN:0021-8979    

DOI:10.1063/1.1721367

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

Room temperature measurements on very pure specimens verify the Tyndall law,s=atm, which was determined by tensile measurements. The value ofmis approximately 0.6. Discrepancies in tensile creep tests reported by other observers are shown experimentally to be caused most probably by bending of the specimen during the creep process. The Bauschinger effect has also been investigated and creep at the very small stresses needed appears to follow the same creep law.

ISSN:0021-8979    

DOI:10.1063/1.1721368

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

A method is presented for the calculation of the departure of actual network behavior from design characteristics attributable to the use of nonideal components. The method yields a set of tolerance coefficients relating percentage changes in the positions of the zeros and poles of the network function to percentage changes in the network components. Once this information is available, changes in gain or phase are easily determined.

ISSN:0021-8979    

DOI:10.1063/1.1721369

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

The formula for mutual impedance by the generalized circuit method is reduced to a form which greatly reduces the number of integrations required in determining the mutual impedance of various combinations of open wire and terminated wire antennas. The application is illustrated by finding the mutual impedance of the legs of an open wireX‐antenna, the latter being equivalent to the radiation impedance of a biconical antenna, and for small angle cones reduces to a form from which Schelkunoff's inverse terminal impedance may be determined.

ISSN:0021-8979    

DOI:10.1063/1.1721370

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

Upon examining the formulas for self‐ and mutual impedances of antennas, it is found that while the mutual impedance formula for separately driven collinear standing wave antennas may be used directly in determining the radiation impedance when such antennas are connected in cascade, certain modifications must be made in the case of traveling wave antennas under similar circumstances. Accordingly, formulas are derived for rhombic antennas spaced in tandem and are modified to permit the determining of the radiation impedance of two identical rhombic antennas connected in cascade.

ISSN:0021-8979    

DOI:10.1063/1.1721371

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

A dominant‐mode wave guide radiating through a slot into a half‐space may be regarded from a network viewpoint, with the half‐space represented by a number of spherical transmission lines, the wave‐guide feed by a single uniform transmission line and the slot by a coupling network. This paper contains (a) an investigation of how many spherical transmission lines are necessary to represent adequately the far field (gain pattern) of the slot antenna, and (b) an approximate theoretical evaluation (by a variational calculation) and experimental check of the equivalent circuit parameters of a slot‐coupled junction of a rectangular and spherical wave guide, when the far field can be well represented by the dominant spherical mode. The results are useful in connection with a method of measuring the electromagnetic scattering properties of obstacles located in a half‐space illuminated by a wave‐guide‐fed slot antenna.

ISSN:0021-8979    

DOI:10.1063/1.1721372

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

Drag coefficients for a cylinder were measured at Reynolds numbers from 0.06 to 6.0 by observing the deflections of thin wires suspended in an air stream. The results confirm a theoretical equation proposed by Lamb and are consistent with experimental data of other investigators.

ISSN:0021-8979    

DOI:10.1063/1.1721373

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

The mixed boundary value problem of the potential inside a cylindrical conducting box of radiusaand height 2cin which is mounted coaxially and concentrically a thin flat charged conducting disk of radiusbis solved approximately. A formula for the coefficients in the Bessel function potential series is derived which is valid forc>¼aandb<¾a. The boundary conditions are met rigorously except that the disk is not quite flat. Figures show its deviation for twelve parameter values. A formula for narrow gaps is derived. Upper and lower limits for the capacitance for twelve parameter values are tabulated.

ISSN:0021-8979    

DOI:10.1063/1.1721374

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

Any RLC transfer function with an even or odd numerator is realized as the transfer voltage ratio of a Darlington network, where such a network is defined as one containing lossless elements plus onlyoneresistance. The single resistance appearswithinthe network, and the termination is thus lossless. An unbalanced network that contains no mutual inductance is achieved by the procedure. The method makes use of Norton's theorem, zero shifting, and the paralleling of ladder networks. The number of ladders and elements required in the realization is kept small by a technique demonstrated in the paper.

ISSN:0021-8979    

DOI:10.1063/1.1721375

出版商:AIP    

年代:1953

数据来源: AIP