摘要:

A simple electromechanical analog for expressing the coupling between nonlinear oscillatory systems is constructed and checked. The strength of the coupling can be easily controlled by varying the output of a dc amplifier while the type of coupling is determined by the shape of an aperture in an integrating cylinder. The device has general applicability to analogs in which the motion of a component part can be translated into the motion of a mask before an integrating cylinder with a selected aperature.

ISSN:0021-8979    

DOI:10.1063/1.1721222

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

The effect of back diffusion of photoelectrons of two energy distributions in standard molecular and inert gases has been measured, and the results applied to the analysis of the Thomson equation as a semi‐empirical formula for correcting the measurements of the secondary emission coefficients in gaseous discharges. The method brings the results of Lauer and Molnar into satisfactory agreement. The effect of electron attachment is briefly discussed.

ISSN:0021-8979    

DOI:10.1063/1.1721223

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

A procedure involving autocorrelation is described which, for long averaging time and incoming signals with continuous spectrum, has a detection threshold equal to that of a corresponding conventional system consisting of band pass filter, rectifier, and low pass filter. The autocorrelation procedure is quite complex; a full autocorrelation function is computed and then subjected to a ``filtering'' operation. A simpler procedure, such as computing autocorrelation coefficients for only one or a few delay times, will in general be less effective. A third process, involving multiplication by a local sinusoidal signal, is also discussed and shown to be closely parallel to the conventional system.

ISSN:0021-8979    

DOI:10.1063/1.1721224

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

Improved optical instrumentation has resulted in high time‐resolution spectrograms of the luminosity associated with ultraspeed aluminum pellets. These data indicate that in many cases the light is emitted in two phases: (1) the ballistic, or air shock, characterized by atomic metal lines and a strong continuum; (2) AlO bands that appear about 150 &mgr;sec after the metal is ablated from the pellet.

ISSN:0021-8979    

DOI:10.1063/1.1721225

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

Another method has been developed for obtaining the rate of shearvsshearing stress curves of non‐Newtonian fluids from concentric cylinder viscometer data. The mathematical expression developed is a rapidly converging power series in lns, wheresis the cup to bob radius ratio. An estimate of error shows that under favorable conditions only two terms of the series are significant, and that terms past the third will hardly ever be needed.

ISSN:0021-8979    

DOI:10.1063/1.1721226

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

The modern theory of the friction between dry metal surfaces ascribes it to local minute welds or adhesions between the surfaces and suggests that for a given pair of surfaces the friction force is uniquely defined by the normal load alone. Herein it is demonstrated that this cannot in general be true and that some further condition of operation must also be defined. Experiments are reported indicating that one such possible condition is the sliding speed so that the friction force is actually a function of the normal load and the sliding speed. It is pointed out that the speed can influence the friction force in two ways—one, by the resulting shear strain rate in the vicinity of the welded junction, and the other by the length of time taken for a junction of full strength to form.

ISSN:0021-8979    

DOI:10.1063/1.1721227

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

Halle´n's complex integral equation for the current in a cylindrical antenna is separated into two real integral equations for the components of current in phase and in phase‐quadrature with the driving voltage. Each of these equations is solved by iteration using zeroth‐order currents and vector‐potential differences to define expansion parameters. It is shown that for electrical half‐lengths near odd multiples of a quarter‐wavelength at least a third‐order solution is required in order to determine accurately the component of current in phase with the driving voltage and the conductance. Conductances for a range of radii are evaluated by the new third‐order formula and compared with the King‐Middleton second‐order values and with the experimental data of Hartig. The new formula agrees excellently with experimental results ath=&lgr;0/4, whereas the earlier second‐order formula has by far its greatest percent error—near 8 to 10 percent—in a small range near resonance. It is concluded that for antennas near resonance, just as for very short and very long antennas, adequate account must be taken in the iteration of both components of current.

ISSN:0021-8979    

DOI:10.1063/1.1721228

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

The motion of a rigid sphere moving through an incompressible, homogeneous, nonviscous fluid in the presence of a rigid, infinite plane boundary is examined. The direction of motion of the sphere is assumed to be parallel to the plane boundary. It is assumed that the motion is irrotational and that the sphere velocity is small. An exact treatment is presented. Several curves of the pressure variation on the plane boundary are plotted for different values of the ratio of sphere radius to the perpendicular distance from the center of the sphere to the plane boundary.

ISSN:0021-8979    

DOI:10.1063/1.1721229

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

Allotropic transformation in uranium has been studied over a range of cooling rates from 5 to about 8000°C/sec. The transformation temperatures of both gamma‐to‐beta and beta‐to‐alpha were found to decrease continuously with increasing rates of cooling. The extent of the beta‐range increased with increasing cooling rates. For rates of cooling up to 1000°C/sec, recalescence was observed in both transformations. For higher cooling rates, there was usually no recalescence.In most of the recorded cooling curves, a small but definite thermal arrest was observed, between the two main arrests which correspond to the two known phase transformations. This additional thermal arrest was also present in a heating curve, where it occurred at about 740°C, compared with 666 and 771°C for the two known phase transformations. Possible explanations of the additional arrest are discussed.

ISSN:0021-8979    

DOI:10.1063/1.1721230

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

A brief discussion of proposed explanations for the electret effect is presented. Plexiglas, Lucite, and Nylon electrets were prepared under fields ranging from 19 to 36 kv/cm and observed for as long as 2000 hours. The surface charge densities were measured by electrostatic induction using a commercial electronic electrometer and a shunt capacitance to reduce the readings to a maximum of 20 volts. The initial state was a heterocharge or a homocharge depending on the strength of the forming field. The steady state was a homocharge in every case. Charge densities as high as 5.5×10−9coulomb/cm2(16.5 esu) were observed. A Plexiglas disk was charged at room temperature under a strong field and its subsequent decaying homocharge recorded. The experimental results support the ideas of Mikola and Gross, i.e., the existence of two decaying polarizations of opposite sense due to ionic migration, one occurring within the dielectric, the other, across the electrode‐dielectric interface.

ISSN:0021-8979    

DOI:10.1063/1.1721231

出版商:AIP    

年代:1953

数据来源: AIP