摘要:

The spectral emissivity for &lgr;=6700A has been determined for Fe‐Ni alloys and shows changes with temperature which indicate that in the temperature range of 1200°K to 1600°K abnormal behaviors exist which hitherto have not been suspected. A correlation of emissivity change with change in density of metals is suggested.

ISSN:0021-8979    

DOI:10.1063/1.1701950

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

A new derivation of Nyquist's equation, relative to the amount of thermal fluctuations generated in an electrical conductor, is presented. A generalization of the new proof to include any arbitrary impedance function shows that the original equation as derived by Nyquist is valid only for physically realizable impedances of the minimum reactance type. This is followed by a new and short derivation of the shot noise formula for temperature limited diodes.

ISSN:0021-8979    

DOI:10.1063/1.1701951

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

The postulated problem of heat transfer in a stationary isotropic turbulence under constant small temperature gradient is examined from both Lagrangian and Eulerian points of view. By combination of Taylor's ``diffusion by continuous movements'' and a new temperature fluctuation equation somewhat like the wellknown turbulent energy equation, it is possible to obtain (1) an expression for the turbulent heat transfer coefficient which depends only on velocity field, and (2) an approximate expression for the corresponding correlation coefficient which depends only on velocity field and fluid physical properties.A preliminary result is given for ``turbulent Prandtl Number'' in a homogeneous shear flow in terms of the shear and heat transfer correlation coefficients.

ISSN:0021-8979    

DOI:10.1063/1.1701952

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

In investigating the order‐disorder transformation in CuPt, cell parameters were determined from specimens quenched at intervals from 25°C to 890°C. The rhombohedral deformation of the ordered, layered structure was found to diminish with increasing temperature, disappearing at a critical temperature of 815°C. Integrated intensity measurements of superstructure reflections from quenched powder and briquette samples determined that the long range order,S, decreases slowly with increasing temperature to a value of 0.77 atTc, where it changes abruptly to zero, with the transformation belowTcbeing homogeneous. A simple theory is developed relating the rhombohedral deformation toS.Cold working an ordered sample was found to transform the alloy almost completely from the ordered rhombohedral cell to the disordered cubic cell. From measurements of diffuse intensities diffracted by briquettes aboveTc, Fourier transform methods determined parameters which fixed the local order as being local layering configurations, in contrast to the usualA‐likes‐Btype of order.

ISSN:0021-8979    

DOI:10.1063/1.1701954

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

The wave motion in an elastic solid given by the theory of reflection at a free surface is evanescent for certain conditions—aP(plane irrotational) wave at grazing incidence and also anSV(plane equivoluminal) wave at grazing incidence. It is shown that by the application of suitable limiting processes wave motions can be obtained for these critical circumstances. The relation of these motions to the noncritical motions is analogous to the relation of critically damped to noncritically damped vibrations.

ISSN:0021-8979    

DOI:10.1063/1.1701956

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

The analogy between the difference equations of a wave‐equation boundary‐value problem and the current‐law equations of a direct‐current network is developed. This theory permits construction of a dc network analyzer for solution of the wave equation. Some of the network parameters are necessarily negative. These ``negative resistors'' are simulated by active dc circuits. The determination of characteristic frequencies, characteristic functions, and response to simple harmonic forces is illustrated by solution of an irregularly shaped membrane. Methods are discussed for solving problems involving inhomogeneous or anisotropic media or various types of boundary conditions.

ISSN:0021-8979    

DOI:10.1063/1.1701957

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

Small metallic pellets have been fired at velocities up to 6 km/sec by means of modified shaped charges. Previous work in this field has been confined largely to observations of meteors and conventional shaped charges. Data obtained on ballistic phenomena verify the conventional drag force determinations extrapolated to large Mach numbers. Steel pellets at velocities of 2.5 km/sec lose little mass in flight. Pellets composed of lighter metals, such as aluminum at a velocity of 5 km/sec, burn vigorously with the emission of much light and heat. It has been found that the motion of both nonburning and burning pellets can be represented within experimental error by the empirical equationv=v0e−&agr;s,wherev0is the initial velocity of the pellet,vis its velocity after it has traveled a distancesthrough the air, and &agr; is a constant.

ISSN:0021-8979    

DOI:10.1063/1.1701958

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

Formulas, tables, and graphs are given of the cumulative probability distribution of a function frequently occurring in the theory and practice of radio wave propagation as well as in the study of the influence of noise in phase modulation systems.

ISSN:0021-8979    

DOI:10.1063/1.1701959

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

Solutions are presented for the problem of gas flow in a solid propellant rocket motor using combined numerical and graphical methods. The character of the problem, sources of information, and method of solution are described, and solutions for the case of JPN ballistite propellant are presented. These solutions give the equilibrium distributions of pressure, density, velocity, and temperature of the gas stream and burning rate of the solid propellant as functions of two characteristic parameters &bgr; andJ. These parameters are descriptive of the charge geometry and flow channel geometry, respectively. The solutions cover the entire range of nozzle, charge‐size combinations, including the case of no nozzle.

ISSN:0021-8979    

DOI:10.1063/1.1701960

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

A method is proposed for the direct determination of the rate of shear‐shearing stress curve of a fluid from data obtained in concentric cylinder viscometers. The method involves the use of a viscometer in which the ratio of outer to inner cylinder radii can be varied. It is further shown that to a close approximation two such radius ratios are sufficient to define the flow curve.Data for two non‐Newtonian systems are presented to show that the proposed method is valid.

ISSN:0021-8979    

DOI:10.1063/1.1701961

出版商:AIP    

年代:1952

数据来源: AIP