摘要:

The basic interactions of nonuniform shock waves in one‐dimensional unsteady and two‐dimensional steady flow, are analyzed by mapping into the hodograph plane, neglecting effects of third and higher orders in the shock strength. The resulting equations are linear and can be solved by straightforward numerical calculation.

ISSN:0021-8979    

DOI:10.1063/1.1722577

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

Equations have been derived for velocity, temperature, and pressure distribution in a two‐dimensional compressible viscous vortex with a steady state component of radial flow. Radial velocity has been assumed small compared with the tangential component, and heat transfer has been neglected. The equations have been based upon the Navier‐Stokes equation in its most general form, the First Law of Thermodynamics, and the Gas Laws. A reference radius has been defined where viscous stress is zero; from this, nondimensional forms have been set up and generalized charts prepared for ready visualization and numerical applications. Because of the classical concept of viscosity as used in the Navier‐Stokes equation, results are strictly applicable to laminar flow only; a discussion is presented regarding possible application to turbulent flow.

ISSN:0021-8979    

DOI:10.1063/1.1722578

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

The effects of sample size on the apparent properties of ferrites observed by microwave cavity perturbation methods are treated. Retardation effects associated with the propagation of electromagnetic waves in the specimen are considered. Results are given for the idealized cases of rods of infinite length and disks of infinite extent. Methods of adaptation to finite rods and disks are suggested. An approximate solution is given for the sphere which is in qualitative agreement with some aspects of the experimental observations. A formula relating the shift in resonance field to the sphere size is presented:HR−H0=4&pgr;M&egr;·(16&pgr;2/45)(R/&lgr;)2.

ISSN:0021-8979    

DOI:10.1063/1.1722579

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A semiempirical method for the determination of mass absorption coefficients for the very soft x‐ray region of 5 to 50 A is described. A universal function for the absorption byK‐shell electrons and another for absorption byLand extra‐Lshell electrons are given in table form to permit the calculation of mass absorption coefficients for elements of atomic number up to 36. Calculated and observed values from available absorption data are compared with those predicted by quantum theory. Tables are given for the mass absorption coefficients for nine useful wavelengths in the ultra‐soft region, 8.34, 13.3, 17.6, 21.7, 23.7, 27.4, 31.6, 36.3, and 44 A.

ISSN:0021-8979    

DOI:10.1063/1.1722580

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

Techniques are described for the preparation of multiple junction structures in semiconductors by solid state diffusion of impurities from a region of a doubly doped crystal into an adjacent region of different impurity concentrations. The change in impurity concentrations from one region to the other is achieved initially by surface melting and regrowth, and is later modified by diffusion. Conditions which must be imposed on the doping levels, segregation coefficients, and diffusion constants of the doping materials employed will be discussed.p‐n‐p, n‐p‐n, andn‐p‐n‐pstructures have been fabricated in germanium.

ISSN:0021-8979    

DOI:10.1063/1.1722558

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

The electrical resistances of thin films of 24 metals, deposited on glass substrates (near room temperature) by evaporation, sputtering, or electroplating, have been measured before and after artificial aging by heatingin vacua. Reductions in resistance of 25 to 50% as a result of aging were commonly noted. Evaporated films were reduced from approximately 2&rgr;bto 1.3&rgr;b(resistivity of the bulk metal) and sputtered films from 4–10&rgr;bto 1.5–1.8&rgr;b. A preferred aging temperature, specific to each metal but influenced somewhat by film thickness, was noted. This temperature agreed closely with the temperature of recrystallization of the metal. Thin metal films, as usually deposited, appear to be in a state of strain not associated with the bulk metal as it crystallizes from the melt. The application of heat energy to the film promotes the removal of strains, occluded and adsorbed gas, and the growth of the crystallites of the film. These concurrent actions reduce the electrical resistance of films of 1000 A thickness to a value usually in the range 25–75% above that of the bulk metal.

ISSN:0021-8979    

DOI:10.1063/1.1722559

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

Secondary waves of electroluminescence exhibit specific trends with varying frequency and temperature. As has been assumed before, secondary waves are caused by effects of charge polarization inside the phosphor crystals; however, there has been no previous theoretical approach to this problem which leads to a description of the behavior of secondary waves with respect to frequency and temperature. An attempt has therefore been made to treat this phenomenon mathematically, using a simple model of charge polarization. During electroluminescent excitation conduction electrons are drawn to the anodic crystal parts where they become trapped. When the alternating field externally applied passes zero these electrons, under the influence of a polarization field, may return to luminescence centers and thus give rise to light emission. The return process depends on the trap depth, the temperature, the applied external field, and its frequency. This model can indeed describe the observed behavior, so that there seems to be little doubt as to the actual origin of secondary waves. As an interesting corollary of these considerations, the occurrence of secondary waves may be a means for determining electron trap depths and for detecting shallow traps where ``glow curves'' fail.

ISSN:0021-8979    

DOI:10.1063/1.1722560

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A semigraphical scheme is presented for the synthesis of a linear, finite, discrete network, in which the desired network response is prescribed in the time domain. The method is based on the approximation of the real part of a desired system function by a sequence of impulses along a contour parallel to the imaginary axis of the complex‐frequency plane. A simple scheme of error evaluation is proposed. Examples illustrating the synthesis procedure are also considered.

ISSN:0021-8979    

DOI:10.1063/1.1722561

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A criterion is presented for the applicability of cavity perturbation theory for measuring permeabilities and dielectric constants of materials. In the literature, the perturbation criterion is usually stated as: the rf fields in the cavity with and without the sample are approximately equal. This is the same as stating that changes in the stored energy in the cavity, upon introduction of the sample, are small. This criterion is shown to be too strong, and usually violated in experiments. A weaker but sufficient criterion, for all commonly encounteredQvalues, is that changes in the over‐all geometrical configuration of the rf fields must be small upon introduction of the sample. Experimentally, this means that for small sample measurements only the percentage change in the real part of the frequency must be small. Data are presented to demonstrate the above ideas.

ISSN:0021-8979    

DOI:10.1063/1.1722562

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

The investigation of excess currents on silicon and germanium diodes has shown that inversion layers give an approximate logarithmic increase of excess current with applied voltage. Approximately ohmic excess currents are observed not only in the presence of water vapor but also in the presence of vapors of certain organic liquids. These excess currents can be shown to be due to a surface conductance which has a different bias voltage dependence from that exhibited by inversion layers. Evidence is presented which indicates that the holes induced in the liquid film (outer surface states) move in an applied field much like holes in a molten semiconductor, provided the liquid film is coherent. This added conductance is responsible for the ohmic behavior in the presence of condensable vapors.

ISSN:0021-8979    

DOI:10.1063/1.1722563

出版商:AIP    

年代:1957

数据来源: AIP