摘要:

Schilieren spark snapshots spaced at electronically controlled intervals of several hundredths of a millisecond show the emergence of the shock wave and the formation of the vortex ring at the end of a cylindrical shock tube, open to the atmosphere. The axial positions of the vortex ring and shock front are plotted as a function of time for the first millisecond, in which time the vortex forms and is accelerated to about three‐quarters of the theoretical particle velocity of the mass flow following the initial plane shock. The diameter of the vortex ring increases nonlinearly with time and distance.

ISSN:0021-8979    

DOI:10.1063/1.1701987

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

A method of expanding expressions of the typeJ(&xgr;)Y(&sgr;)−J(&sgr;)Y(&xgr;) andJ′(&xgr;)Y(&sgr;)−J′(&sgr;)Y(&xgr;) is given. HereJandYare Bessel functions of the first and second kind. These forms occur frequently in physical problems with cylindrical symmetry. The type of expansion used here can be used with other functions that are solutions of second‐order differential equations. The use of these expansions allows the development of theories for two rheometers used for determining dynamic mechanical properties of liquids. In these mathematical treatments, the inertia of the sample is taken into account.

ISSN:0021-8979    

DOI:10.1063/1.1701988

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

A generalization of ordinary circuit theory which enables one to define impedances in any periodic structure is developed, based on the concept of expansion of electromagnetic fields in terms of a set of linearly independent basis fields. Techniques for measurement of impedances in a periodic structure are described, involving a determination of the parameters of a coupling system by an extension of the well‐known nodal shift method.

ISSN:0021-8979    

DOI:10.1063/1.1701989

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

An approximate evaluation of the branch‐cut integral which occurs in the rigorous solution of the Boltzmann equation for intermediate and large distances is of importance in shielding problems. Such an evaluation leads to Eq. (20) for the point source and Eq. (24) for the plane source. Equation (20) is actually 23 percent high for zero absorption (f=0) andr&sgr;=7, but the error decreases with increasingr&sgr; andf. It is seen that the branch‐cut term is not simply the contribution of noncollided neutrons.Figure 2 is a plot of the region in thef−r&sgr; plane where the two terms are comparable.

ISSN:0021-8979    

DOI:10.1063/1.1701990

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

A small, stainless steel, two‐dimensional source flow nozzle supplied with bottled nitrogen was used for the condensation investigation. It was found that the nitrogen supersaturates approximately 15°K or 1.2 Mach numbers when expanded from stagnation conditions of 70°F and pressures of 8.21 and 16.15 atmos. A numerical method for solving the equations of motion with the aid of the experimental data allows the computation of the fluid temperature during the condensation process. The addition of small amounts of carbon dioxide reduced the degree of supersaturation obtainable with bottled nitrogen.

ISSN:0021-8979    

DOI:10.1063/1.1701991

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

The transit time spread due to difference in initial velocity in a planar diode has been calculated for the case of nonhomogeneous velocity distribution. The spread is given as a function of the current for two practical cases, the normal diode and an inverted diode (a beam reflected in a diode space). The spread is also given as a function of anode voltage within certain limits. The method may be used to estimate the influence of transit time spread on transit time devices. A special application is described.

ISSN:0021-8979    

DOI:10.1063/1.1701992

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

The formal multiple scattering solution obtained previously for the scattering of a plane wave by an arbitrary configuration of parallel cylinders is applied to the finite grating of cylinders and to the reflection grating of semicylindrical bosses on a perfectly conducting infinite plane. A far field solution in closed form for spacing large compared to wavelength and radius is obtained on neglecting the ``end effects.'' It is found that for the transmission grating both polarizations may be markedly affected by multiple scattering; for the reflection grating, however, the effects are much more pronounced for polarization perpendicular to the elements. The case of radii≪&lgr; is investigated in detail; the &lgr;'s for which the effects are greatest are determined, and various intensity curves are presented. The bright and dark bands appearing on these curves (overlaying the usual continuous spectra observed with broadband radiation) are similar to the ``grating anomalies'' discovered by Wood in 1902. The present analysis provides a simple physical interpretation of their presence in terms of the magnitudes and phases of the various orders of scattering. Simple relations for their dependence on the parameters are derived which agree in general with experimental results. Both the electromagnetic and acoustic cases are treated.

ISSN:0021-8979    

DOI:10.1063/1.1701993

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

The Joule‐Thomson porous plug experiment is described, its quantitative aspects indicated, and the constant enthalpy condition set up. The experimental plan for the proposed measurement is described and a short analysis of the physical situation in the fluid given. The standard equation for the Joule‐Thomson coefficient is applied to the situation and details are given of how this equation may be integrated for two special physical situations. The information necessary for these integrations is discussed and physical means described for obtaining it. A numerical integration may be used for obtaining the work equivalent of heat (J) with a high precision corresponding to the high precision with which these various data may be measured.

ISSN:0021-8979    

DOI:10.1063/1.1701994

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

It has been proposed that the conductivity of a porous semiconductor, such as oxide‐coated cathode, may be influenced by the presence of an electron gas in the pores of the aggregate. In this paper calculations for the magnitude of this component of the conductivity are made on the basis of two simplified models approximating the geometry of a pore. The conditions under which such a component of the conductivity can appreciably modify the total conductivity are analyzed. It is further shown that such a porous semiconductor will possess two sources of thermoelectric emf. A simple theory for the thermoelectric power of the electron gas in a pore is developed, and the manner in which it will combine with the normal thermoelectric power of the crystals is shown.

ISSN:0021-8979    

DOI:10.1063/1.1701995

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

A study has been made of the thermoelectric power, the electrical conductivity, and the thermionic emission of (BaSr)O and BaO at different states of activation and on different base metals over a temperature range of 1100°K to 300°K. A plot of the logarithm of the conductivityvsreciprocal temperature showed two straight line regions. The temperature dependence of the thermionic emission was found to be the same as the temperature dependence of the conductivity in the temperature range 700°K to 1100°K. The slope of a plot of the thermoelectric powervsreciprocal temperature was also similar to the thermionic work function and the conductivity activation energy in this temperature range.The thermoelectric power varied with temperature from a value of about 2.0 mv/° at 1100°K, increasing to about 2.5 mv/° at 800°K, reducing to between 1.0 and 0.5 mv/° at about 500°K, and remaining practically constant or increasing slowly at still lower temperatures. In all thermoelectric power measurements the hot junction was positive indicating negative charge carriers.The simple semiconductor theory does not adequately account for these results which seem to be in good agreement with the pore conduction hypothesis.

ISSN:0021-8979    

DOI:10.1063/1.1701996

出版商:AIP    

年代:1952

数据来源: AIP