摘要:

Empirical evidence obtained for CO at room temperature, which supports the use of average absorption coefficients for entire vibration‐rotation bands, is examined. In Sec. II the existence of an average apparent absorption coefficient for data obtained with inadequate spectral resolution is demonstrated. In Sec. III semiquantitative evidence at elevated total pressures and small optical densities for the use of a constant absorption coefficient equal to the ratio of integrated absorption to effective band width is described. These results serve as direct support for a proposed simplified method for radiant‐heat‐transfer calculations.

ISSN:0021-8979    

DOI:10.1063/1.1700125

出版商:AIP    

年代:1951

数据来源: AIP

摘要:

The evaporation products of BaO heated on ribbon filaments of Pt, Ta, Ni, Mo, and W, and of SrO on Pt have been studied using a high resolution mass spectrometer for positive ion analyses. The ratio Ba+/BaO+, was measured for each base material as a function of temperature and of the energy of the ionizing electrons to determine the origin of each ion peak observed. The results indicate: (a) Only on systems BaO on Pt and BaO on Ni, and SrO on Pt were the evaporation processes reproducible without particular attention to procedure. (b) The two systems BaO on Pt and SrO on Pt differ markedly in their evaporation mechanisms. (c) At high temperatures peaks are found due to Ba2O++, Ba2O+, Ba2O2+, and other barium compounds depending on the base metals used. (d) A measurable ion current was found due to Sr+ions evaporated from Pt.

ISSN:0021-8979    

DOI:10.1063/1.1700126

出版商:AIP    

年代:1951

数据来源: AIP

摘要:

The existence of an allotropic transformation in hafnium, suggested by Zwikker in 1926, has been confirmed. The transformation temperature is 1310±10°C. The high temperature beta‐form is probably body‐centered cubic.

ISSN:0021-8979    

DOI:10.1063/1.1700127

出版商:AIP    

年代:1951

数据来源: AIP

摘要:

Measurements on charge storage in polystyrene capacitors over a period of months indicate that exceptionally fine capacitors may be made of polystyrene film when sufficient care is taken. Very small charge ``soakage'' occurs in such a capacitor, and charges may be retained for times of the order of one hundred years and possibly longer. The specific resistance approaches 1022ohm cm when measured over a period of months. The power factor of polystyrene is about 10−4for frequencies of 10−1to 10−6cycle per sec with a tendency to increase at the lowest frequencies and with a possible peak at still lower frequencies. The difference between charge soakage during charging and the charge recovery after shorting indicates some nonreversible current flow when measurements are made over several months' time.

ISSN:0021-8979    

DOI:10.1063/1.1700128

出版商:AIP    

年代:1951

数据来源: AIP

摘要:

The effects produced by small cylindrical charges that were detonated on the surfaces of heavy steel plates are discussed. Particular attention is paid to (a) shapes of crater, (b) changes in hardness, (c) flow patterns, (d) fractures, and (e) changes in microstructure. The distribution of stress appears in some respects to correspond to that which might be set up by a static load. The mechanisms of the inelastic deformation, however, differ very greatly between the static case and the dynamic case. Dynamic loading produces numerous shock twins and fractures that undoubtedly occur because of the very high strain rates involved.

ISSN:0021-8979    

DOI:10.1063/1.1700129

出版商:AIP    

年代:1951

数据来源: AIP

摘要:

Reported values for the heat of activation,H, for volume chemical diffusion, as obtained from the slope of the best straight line in a semilogarithmic plot of diffusion data againstT−1, may often be greatly in error. These values will be too low whenever diffusion along internal surfaces plays a significant role at the lower temperatures of measurement. A method is presented which attempts to avoid such errors inHby using the calculated values of Zener for the intercept of the straight line. When the data is reconsidered in the light of this method, the widely accepted belief thatHfor chemical diffusion in dilute solid solutions is generally considerably less thanHfor self‐diffusion of the solvent is brought to question. In fact, it is found that the chemical diffusion activation energy is generally within 15 percent of that for self‐diffusion. It is further concluded that the process of diffusion under a chemical gradient may itself produce internal surfaces which act as short‐circuiting diffusion paths.

ISSN:0021-8979    

DOI:10.1063/1.1700130

出版商:AIP    

年代:1951

数据来源: AIP

摘要:

Judgment of the performance of automatic control systems often involves a consideration of the behavior of such systems in the presence of random noise. The noise may be of an undesirable nature, such as receiver noise, or it may represent an ensemble of statistical inputs which the system is to follow. Analytical techniques exist for determining the response of linear systems to noise inputs. However, no general methods are available for analyzing nonlinear systems subject to noise inputs. An electric analog computer, together with a suitable source of noise, may be used to study nonlinear systems. This paper describes an electronic noise generator designed for analog computer or simulator use. Methods are discussed for measuring the important characteristics of low frequency noise, such as the mean value, spectral density, amplitude distribution, and autocorrelation. Particular attention is devoted to the length of time necessary to establish satisfactory estimates of the properties of low frequency noise.

ISSN:0021-8979    

DOI:10.1063/1.1700131

出版商:AIP    

年代:1951

数据来源: AIP

摘要:

Several Chilean coppers used in cuprous‐oxide rectifier work have been analyzed for carbon, oxygen, and sulfur. The carbon determinations were in agreement with published solubility data. Large differences were found in the oxygen and sulfur content which could be correlated with the refining data of the copper and the reverse leakage currents of the rectifiers. The change in sulfur content caused by various heat treatment also was investigated.

ISSN:0021-8979    

DOI:10.1063/1.1700132

出版商:AIP    

年代:1951

数据来源: AIP

摘要:

Existing theories of the static magnetron do not predict violation of the Hull cut‐off condition or cathode bombardment. Measurements made at anode voltages and magnetic fields much larger than those used by earlier investigators revealed violations of the Hull cut‐off condition considerably more pronounced than those previously reported, and much greater amounts of cathode bombardment. When sufficient cathode bombardment takes place, emission may be enhanced (through secondary emission) by a factor of ∼103over the thermionic value. When enhanced emission occurs in magnetrons employing pure metal cathodes, it is found that maximum current limits exist for each magnetic field. These limits form a maximum current boundary on a voltage‐current plot. The maximum current boundary depends on secondary emission properties of the cathode surface and on geometry. Experimental observations on enhanced emission, cathode bombardment, the maximum current boundary, and flow of anode current in violation of the Hull cut‐off condition are combined into a self‐consistent picture in static magnetrons employing pure metal cathodes. Although cathode bombardment and flow of anode current are still unexplained, their existence can account for the observed enhanced emission and maximum current boundary. In this it is unnecessary to endow the cathodes with anomalous thermionic or secondary emission properties.The process causing cathode bombardment, enhanced emission, and flow of anode current in violation of the Hull cut‐off condition is believed to be an electronic interaction which occurs almost entirely in the relatively dense region of space charge surrounding the cathode. The significant factors influencing the interaction appear to be applied electric and magnetic fields, space charge density, and thickness of the space charge sheath. The basic problem of electronic interaction in the static magnetron is partially defined. It is expected that when a realistic solution to this problem exists, including a correct account of cathode bombardment, the occurrence of enhanced emission would be automatically predicted.

ISSN:0021-8979    

DOI:10.1063/1.1700133

出版商:AIP    

年代:1951

数据来源: AIP

摘要:

Apparatus has been designed and tested which makes possible the identification of the positive ions in the beam of a cathode‐ray tube. A hollow cathode construction allows the positive ions to pass through the conventional part of the electron gun and be studied as a positive ion beam by another set of focusing electrodes and deflection magnets. Curves of ion yield and bucking potential measurements indicate that most of the ions are formed in the early stages of electron acceleration.

ISSN:0021-8979    

DOI:10.1063/1.1700134

出版商:AIP    

年代:1951

数据来源: AIP