摘要:

It is shown how a non‐homogeneous, non‐isotropic, electrically conductive, two‐dimensional continuum can be replaced by a network of resistors whereby the nodes of the network are situated at any arbitrarily selected points, and how Southwell's relaxation method can be applied to this network for the solution of potential problems.

ISSN:0021-8979    

DOI:10.1063/1.1698395

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

The electronic transadmittances, transmodulation functions, and other characteristics of a planar, multigrid high frequency tube are expressed in terms of four fundamental admittance and modulation functions which are sufficient for the description of the low level r‐f properties of the electron beam. A matrix representation is introduced based on the successive velocity moments of the beam which leads to the formulation of the characteristics as products involving excitation, grid transmission, modulation, and modulation admittance matrices. The electronic equations obtained are a formulation in which the Llewellyn approximation that the second and all higher velocity moments are zero is not made. Thus the theory allows for higher order velocity effects but is dependent on the knowledge of the fundamental admittance and modulation functions.

ISSN:0021-8979    

DOI:10.1063/1.1698397

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

An analysis is made of the operation of magnetic amplifiers or non‐linear transformers. Open circuit output voltages are calculated for transformers driven by a sinusoidal primary current, and also for sinusoidal primary current plus a direct current bias. The case of a loaded secondary is also considered and it is shown that there exist conditions for instability or resonance. A subsequent paper will consider Barkhausen noise as a limiting condition on the sensitivity of these devices.

ISSN:0021-8979    

DOI:10.1063/1.1698399

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

Using the method of steepest descents the far field and the asymptotic form of the current distribution is obtained for an infinitely long, perfectly conducting cylindrical antenna excited by a localized electromotive force. The low frequency value of the radiation conductance is determined by integrating the radiated energy flux over a large sphere.

ISSN:0021-8979    

DOI:10.1063/1.1698401

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

Image contrast in electron microscope images may arise from absorption, scattering, or phase changes impressed on the illuminating electron wave. In the present paper the intensity distribution in the in‐focus and out‐of‐focus image of an edge of a transparent thin film introducing a prescribed phase change in the incident beam is calculated. It is found that the resulting ``phase contrast'' increases both with the film thickness (i.e., magnitude of phase change) and with the degree of defocusing and, for thin specimens, exceeds other sources of contrast in magnitude. The model is too schematic to permit a quantitative comparison with measured intensity distributions.

ISSN:0021-8979    

DOI:10.1063/1.1698403

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

A procedure is outlined for calculating the maximum changes in the exhaust velocity of gases which can be introduced during flow through a rocket nozzle as the result of vibrational time lags. Representative calculations have been carried out for a number of propellant systems. These calculations indicate that the vibrational time lags cannot produce changes in exhaust velocity which exceed a few percent. The numerical values of the changes are found to depend not only on the nature of the gases but also on the occurrence or non‐occurrence of chemical reaction during flow.

ISSN:0021-8979    

DOI:10.1063/1.1698405

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

The Substitution Principle established by Munk and Prim for flows of a gas having constant specific heats is extended to the wider class of fluids having a state equation of the form &rgr;=P(p)S(s). The equations of motion for this class of fluids is reduced to a canonical form involving only the reduced velocity vector and the pressure. It is shown that explicit elimination of the pressure from these equations is possible only for those fluids whose state equation has the form &rgr;=pkS(s) withk<1. Relations between the Mach number and stagnation pressure and the reduced velocity field are discussed for the class of fluids under investigation.

ISSN:0021-8979    

DOI:10.1063/1.1698406

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

This paper describes a special technique by which it is possible to stabilize the breakdown voltage of a glow tube having zirconium electrodes in pure argon at a pressure of 8.5 mm Hg. A brief account is also given of some experimental methods by which it is possible to find the order of magnitude of two critical currents, whose concepts have been used in the theory of spark discharge at low pressures. One of these critical currents is the ``threshold current,'' which is defined as the maximum steadystate current in a glow tube just before a spark. The other critical current is the maximum electronic current (attained during the development of a spark) at cathode before space‐charge distortion becomes appreciable. The methods described below were confined to two tubes having zirconium cathodes of area 0.3 sq. cm, the electrode spacing being 3.5 mm. One of these two tubes had a zirconium anode, and the other one had a thorium anode. The tubes contained pure argon at a pressure of 8.5 mm Hg. For both the tubes, the order of the ``threshold current'' was found to be 10−8amp., and the order of the other critical current (electronic current at cathode) was estimated as 10−8amp.

ISSN:0021-8979    

DOI:10.1063/1.1698407

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

An expression is derived for the total emission conductance produced by the electrons returned to the cathode of a diode operating with a retarding off‐cathode field. For the retarding voltage and diode spacing used, the assumption of a linear potential distribution is justified. Examples of the variation of the total emission conductance with retarding voltage and frequency are illustrated.

ISSN:0021-8979    

DOI:10.1063/1.1698408

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

A visual method for studying the path of ultrasonic waves through thin plates of material has been devised, and a set of photographs showing the complexity of ultrasonic reflection and transmission by metal plates has been obtained. An attempt has also been made to estimate the critical angles of total reflection for dilatation and shear waves by visual examination of the reflection of a supersonic beam. Using these data, Young's modulus and the shear modulus for a116‐inchaluminum sheet have been determined and the values are compared with those obtained using a previously described electrical method and with published data.

ISSN:0021-8979    

DOI:10.1063/1.1698409

出版商:AIP    

年代:1949

数据来源: AIP