摘要:

The Rouse theory for viscoelastic properties of very dilute solutions is modified for application to undiluted linear polymers. With the effective segment mobility expressed in terms of steady‐flow viscosity, the theory is applied to polymers of rather low molecular weight essentially without further change. In high molecular weight polymers, it is assumed that for modes of motion with relaxation times above a critical value the effective segment mobility drops abruptly, in accordance with the effect of entanglement coupling on steadyflow viscosity as described by Bueche. Properties in both the transition region between glasslike and rubberlike consistency and the rubberlike or plateau region are predicted semiquantitatively with no arbitrary parameters. In an alternative application to the transition region, the average effective friction coefficient per monomer unit can be calculated for both linear and lightly cross‐linked systems.

ISSN:0021-8979    

DOI:10.1063/1.1721997

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

The rate of atmospheric corrosion of Cu&sngbnd;Zn and Cu&sngbnd;Mg alloys are retarded by Al or Mn, and the law of the growth of film in the case of Cu&sngbnd;Zn alloys changes over from the parabolic to the logarithmic law on the addition of Al or Mn. For Cu&sngbnd;Mg alloys under a given set of conditions the law of the growth of film is governed byx12=k1logt+k2,wherexis the film thickness,tis time, andk1andk2are constants. It has been indicated that some experimental data on the corrosion of metals and alloys may be quantitatively represented if two or more functions, representing different mechanisms of the growth of film, are taken into consideration simultaneously.

ISSN:0021-8979    

DOI:10.1063/1.1721998

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

The effect of cyclotron irradiation by 38‐Mev alpha particles on the steady‐state creep rate (ca10−6per second) of aluminum has been measured at beam densities up to 1.2×1013particles per cm2per second. The data, which were taken on a 0.016‐inch thick aluminum specimen for a stress range of 600 to 2500 psi and over a temperature range of 160° to 330°C, showed a slight decrease in rate (up to 19 percent) during irradiation. Since the effect is small, apparently independent of beam density, and is comparable to the usual deviations in the absence of radiation, it can be considered a null result.

ISSN:0021-8979    

DOI:10.1063/1.1721999

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

Solutions of Maxwell's equations are presented which satisfy the boundary conditions for corrugated and dielectric‐clad circular conducting cylinders. These solutions have the physical interpretation of leaky azimuthal surface waves. Values of the complex propagation constant are given as functions of the geometry. For large cylinders the leakage is small and the transmission properties are approximately those of a trapped wave on a flat surface. A coarse experiment gives reasonable agreement with the theory. Some possible applications to transmission lines and antennas are indicated.

ISSN:0021-8979    

DOI:10.1063/1.1722000

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

Data are given on the thermoelectric power and on the resistivity of the dilute alloys, Cu&sngbnd;Si, Ni&sngbnd;Si, and Fe&sngbnd;Si, from −195° to +500°C (and higher for some of the alloys). The Cu&sngbnd;Si thermopower at first decreases with increasing Si content and then again increases, the minimum being at about 2 or 3 atomic percent Si, depending on the temperature. The Cu&sngbnd;Si resistivity is typical of Cu‐base alloys, the resistivity increases per atomic percent Si changing from 7.2 &mgr;&OHgr; cm at −190°C to 8.7 &mgr;&OHgr; cm at 840°C. The thermopower and resistivity curves for Ni&sngbnd;Si show a characteristic knick at the Curie temperature of each alloy. The Fe&sngbnd;Si thermopowers are positive at lower temperatures and become negative at a temperatureT0which decreases with increasing Si content. Furthermore,T0changes from about 300°C for pure iron to about +70°C for 2 atomic percent Si. The resistivity of Fe&sngbnd;Si alloys increases faster than linearly with temperature, and this is also the case for the Ni&sngbnd;Si alloys below the Curie temperature. Above the Curie temperature, the Ni&sngbnd;Si resistivities vary linearly with temperature. The increase in resistivity per atomic percent Si in Fe is 10.5 &mgr;&OHgr; cm at all temperatures within the measured range.

ISSN:0021-8979    

DOI:10.1063/1.1722001

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

With both surface and volume recombination taken into account, time‐dependent and steady‐state Green's functions are obtained for a point source of added carriers in a semi‐infinite semiconductor, and for infinite line and plane sources parallel to the surface. Small‐signal theory is employed, and a compact Stieltjes‐integral derivation is given. The Green's functions are specialized to provide: the time dependence of surface concentration following the instantaneous injection of carriers at a point on the surface; that following instantaneous injection which is uniform over the surface; and the distance dependences for steady point, infinite‐line, semi‐infinite plane, and semi‐infinite line surface sources. Steady flows of minority carriers from these sources into ap—njunction perpendicular to the surface are also calculated. Analytical approximations are found for the steady‐source cases. Theoretical and experimental aspects of the determination of lifetimes and surface recombination velocities from data by means of these results are discussed.

ISSN:0021-8979    

DOI:10.1063/1.1722002

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

In the rigorous theory of diffraction by a conducting wedge as developed by Sommerfeld and extended by Pauli, the total field is represented by the terms given by geometrical optics plus a contour integral which represents the diffracted waves. If the faces of the wedge form a dihedral angle of &pgr;/m, m=1, 2, 3 … the contour integral vanishes identically and the solution given by geometrical optics is exact. This prediction has been tested and checked by measurements and calculations of the diffraction patterns of wedges whose dihedral angles were 90° and 30°. The measurements were made at a wavelength of 1.25 cm.

ISSN:0021-8979    

DOI:10.1063/1.1722003

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

The spatial distributions of indium resonance neutrons about a ``point'' Ra‐Be source have been measured in pure CaCO3(limestone) and SiO2(sand) out tor2≈9&tgr;. Both media show nearly Gaussian distributions corresponding to Fermi ages &tgr;(SiO2)=1906±90 cm2and &tgr;(CaCO3)=461±23 cm2over most of the range observed. Excess resonance flux near the source, more pronounced in CaCO3than in SiO2, appears to be due to inelastic scattering although such interpretation is not unambiguous. Space integrals indicate ∼10 percent more absorption in CaCO3than in SiO2during moderation. Data were corrected for 4.5‐hr activity, 54‐min activation by high energy neutrons, and edge effects; consideration was given to the 3.9‐ and 9‐ev In levels in defining the mean detection energy and to the nonmonoenergetic nature of the Ra‐Be source in affecting the shape of the indium resonance spatial distribution.

ISSN:0021-8979    

DOI:10.1063/1.1722004

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

A new type of analysis is applied to observations on jets from lined cavity charges in order to test the nonsteady‐state hydrodynamic theory of a jet formation. The results support previous findings that the theory is qualitatively accurate, but give evidence of departures from the ideal situation assumed in the theory. An attempt is made to assess one of the more likely sources of error, the neglect of acceleration of the liner.

ISSN:0021-8979    

DOI:10.1063/1.1722005

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

The absorption in thin layers of nickel, aluminum, and cobalt of beta rays from Co60was measured in connection with the use of the surface counting method of determining diffusion coefficients. Data was obtained for foils and for evaporated and electroplated layers. In all cases the activity increased between 0 and 4 mg/cm2. A discrepancy was noted between the data for foils and those for evaporated and electroplated layers. It is shown that this general behavior is predicted by simple scattering and absorption expressions. The implications of these data for the use of the surface counting method are discussed.

ISSN:0021-8979    

DOI:10.1063/1.1722006

出版商:AIP    

年代:1955

数据来源: AIP