摘要:

Progress in cloud physics has been seriously limited because of the impossibility of conducting controlled cloud experiments on a sufficiently large scale. To meet the requirements, a laboratory has been built in which thick artificial expansion type clouds may be produced under controlled and measurable conditions.A mine shaft 0.210 kilometer deep and 2.2×2.2 meters in cross section has been sealed and adapted to the production of thick artificial clouds. The shaft and its principal auxiliaries necessary for the study of some of the basic problems of clouds and precipitation are described. Dense, thick clouds completely filling the shaft are now being produced on a routine basis. Some preliminary illustrative data are presented.

ISSN:0021-8979    

DOI:10.1063/1.1701971

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

An analysis of the ratios of the di‐ and tri‐atomic ions of hydrogen, deuterium, and H—D mixtures obtained from a hot‐cathode arc discharge in a magnetic field was used to examine the nature of ionic collision and displacement processes. Ion mobility, and consequently the rate of ion‐molecule collisions, at constant pressure, were controlled by varying the intensity of the magnetic field. Statistical treatment of mass spectrograph data indicates that the formation of H3+is due to the reactionH2++H2→H3++Hand that the ion rather than the molecule undergoes dissociation on collision.

ISSN:0021-8979    

DOI:10.1063/1.1701981

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

The radiation patterns were measured for three series of dielectric rod antennas of circular cross section excited in theTM01mode at a frequency of 9275 mcps. Only one parameter was changed in each series of rods so that the effect of this parameter on the pattern could be studied. Dielectric antennas excited in theTM01mode have a null in the radiation pattern in the forward direction. It was found that maximum attenuation of secondary lobes was obtained using large diameter rods but sharper and deeper central nulls were obtained with small diameter rods. It was also noted that the deepest central null was obtained using a rod of uniform cross section. For uniformly tapered rods of various lengths, the maximum secondary lobe attenuation as well as the sharpest and deepest central null was obtained using the longest rod. The radiation patterns of the antennas excited in theTE01mode were of the same nature as those obtained using theTM01mode. Measurements were made also of the electric field strength on the surfaces of the radiating rods and these measurements were correlated with the radiation patterns.

ISSN:0021-8979    

DOI:10.1063/1.1701955

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

The velocity and pressure field in a slightly compressible liquid resulting from the collapse of a spherical bubble is computed as a function of the pressure at the bubble wall, using the acoustic approximation. The results are accurate as long as the liquid velocities are small compared to the sonic velocity in the liquid; they agree with the results previously obtained by C. Herring.The following bubble model is then investigated. The bubble is supposed filled with inviscid perfect non‐conducting gas; special emphasis is given to the gas motion which involves a series of shock waves. A fraction of the energy of compression is thus degraded so that the radius of the bubble after the first rebound is somewhat less than the original radius. The pressure variation at the bubble wall is virtually the same as if the gas were compressed uniformly and isentropically.

ISSN:0021-8979    

DOI:10.1063/1.1701962

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

Careful measurements have been made of the wear of rubbing steel surfaces as a function of load, distance of travel, and hardness under controlled conditions which eliminated the effect of all factors except adhesion. At normal pressures averaged over the apparent contact area which are less than one third the hardness of the softer material the amount of wear was found to depend linearly on the distance of travel and on the load but was independent of the apparent area of contact. At average pressures greater than one third of the hardness, the depth of wear varied linearly with the distance of travel, was independent of the apparent area of contact for a given average normal stress, but increased many fold for small increases in stress. These findings rationalize the familiar observations on the running‐in of machine surfaces. The results are discussed in the light of the current adhesion theory of dry friction.

ISSN:0021-8979    

DOI:10.1063/1.1701970

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

The resonance of a small spheroidal object in a large spheroidal cavity is investigated. This approximates the case of a thin needle‐like antenna in a large cavity. It is shown that this needle, if thin enough, shows marked resonant properties, in that when the cavity is tuned to a resonant frequency defined by the needle, the magnetic field on the surface of the needle is greatly enhanced. This property can be used in a practical way, in measuring surface impedance of the material of which the needle is composed: at resonance most of the loss in the cavity is located at the surface of the needle and depends on the material of which it is composed.

ISSN:0021-8979    

DOI:10.1063/1.1701972

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

The electron microscope has been used to study the structure of sputtered silver films. When compared with evaporated silver films which are prepared at the same rate, the sputtered films are observed to have a more continuous structure. When compared with evaporated silver films which are produced at much faster rates, the sputtered films exhibit a crossover phenomenon in which the thinner films are the more continuous and the thicker films less continuous than evaporated films of the same thickness. These properties are in agreement with resistivity measurements. A possible explanation for the results is proposed.

ISSN:0021-8979    

DOI:10.1063/1.1701973

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

A ball rolling on a rotating surface is shown to simulate the motion of a charged particle in a magnetic field. The theory is given for the case of a warped surface undergoing arbitrary rotation about a fixed axis and translation perpendicular thereto, while the system from which the ball is observed partakes of similar but independent motion. With approximations based on not too large departure of the surface from flatness, the following cases can be simulated: (a) The magnetic field is homogeneous and constant. The electric field is perpendicular to the magnetic field, and irrotational, but otherwise arbitrarily spatially dependent, and arbitrarily time dependent within certain limits. (b) The magnetic field is homogeneous but arbitrarily time dependent. The electric field is perpendicular to the magnetic field and may have a variety of space and time dependences, including a part which encircles the axis and has just the right magnitude to produce acceleration in a circular orbit as in the betatron.Results of rudimentary experiments are presented which indicate that the method is capable of good accuracy.

ISSN:0021-8979    

DOI:10.1063/1.1701974

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

Tests in a small hypersonic wind tunnel have determined critical temperature and pressure conditions for the condensation of pure dry nitrogen and have indicated that in the range of pressure (0.5–2.8 mm Hg) and temperature (52°–64°R) obtained in the tests, there is a supersaturation of about 30 Fahrenheit degrees.

ISSN:0021-8979    

DOI:10.1063/1.1701975

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

A method is described by which the stress‐strain curve of a wire tensile specimen can be derived from measurements of its changes of electrical resistance as a function of strain. The method can be applied only to a selected group of metals that have experimentally been shown to be suitable. A material is suitable when its resistance changes per unit of elastic and per unit of plastic strain are each constant and different from each other. The method assumes uniform strain throughout the length of the specimen, which limits conditions studied to those prior to necking. Examples are shown illustrating the linear resistance‐strain relations and the applications of the method for several suitable materials. The resistance‐strain characteristics of several materials that are not suitable are given, together with a statement of some mechanisms responsible.

ISSN:0021-8979    

DOI:10.1063/1.1701976

出版商:AIP    

年代:1952

数据来源: AIP