摘要:

Measurements of the white noise of transistors (principally, diffused‐base structures) and diodes have been made at temperatures ranging from ∼77°K to 300°K for a range of about two decades in injection level, and from 10 kc to 10 Mc. Comparisons of the noise measurements with calculated levels are presented. The germanium transistors show a progressively increasing deviation from the theory as the temperature is decreased, and most of the silicon transistors exhibited excess white noise at room temperature and below.

ISSN:0021-8979    

DOI:10.1063/1.1735079

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

A theoretical description of sinusoidal oscillation of an incompressible viscoelastic medium between fixed infinite parallel planes is presented. The mechanical properties of the viscoelastic medium under sinusoidal shear are expressed by a complex viscosity coefficient. The general equation for oscillatory motion of an incompressible viscoelastic medium is developed. The solution to this equation is obtained for rectilinear motion parallel to a pair of infinite planes. The equation for the velocity distribution between the planes is developed and several typical profiles are presented graphically. The equation for the acoustic impedance per unit area of plane is obtained. Functions from which the acoustic resistance and acoustic reactance may be determined are presented in graphical form for media which range from a perfect viscous fluid to a perfect elastic solid. The applicability of the theoretical results to oscillatory flow in rectangular tubes is discussed.

ISSN:0021-8979    

DOI:10.1063/1.1735080

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

The operation of a cesium plasma thermocouple is described for a range of hot‐junction temperatures from 1600°K to 2600°K and for a range of cesium pressures from 10−5mm Hg to 2 mm Hg. Electromotive force and short‐circuit current data are presented for cells containing three different emitter substances: Ta, ZrC, and (ZrC) (UC). In the range of pressure and temperature variation studied, the observed electromotive forces are between 1 and 4.5 volts. Short‐circuit current depends markedly on the current emission properties of the hot electrode. The largest short‐circuit current density observed for the (ZrC) (UC) emitter, is 62 amperes per square centimeter.

ISSN:0021-8979    

DOI:10.1063/1.1735081

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Some experimental studies of a cold cathode discharge in a strong magnetic field are described. Current densities of the order of half an ampere per square centimeter in various gases were used. For such a discharge, the current to the cathodes is about 75% ionic. Positive ions leaving the discharge by moving across the magnetic field were observed with a mass spectrometer and showed a temperature of about 1 v. Fast electrons from the cathode escape from the discharge across the magnetic field without losing the greater part of their energy. By considering the rate of ion production it is shown that the slow electrons in the discharge have a temperature less than about three volts. Fluctuations in charge densities must play a very important role in the mechanism of the discharge.

ISSN:0021-8979    

DOI:10.1063/1.1735082

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

A new method is described for recording electrical signals. Information is written at extremely high density by means of an electron beam on a film consisting of a low melting thermoplastic material. This can be projected as a full color image, or can be converted to an electrical signal. The tape, which is processed by quick heating, can be readily erased and reused.

ISSN:0021-8979    

DOI:10.1063/1.1735083

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

A very low friction, about 10−2, has been unexpectedly observed in reciprocating sliding with gold, silver, copper, and platinum. It was found that the characteristics common to those metals were soft metal substrate and no surface oxide or soft oxide. Some discussion is given on this phenomenon.

ISSN:0021-8979    

DOI:10.1063/1.1735084

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

The characteristics of noise propagation through a multi‐velocity region with linearly increasing dc potential have been calculated using the density‐function formulation of Siegman, Watkins, and Hsieh. [J. Appl. Phys.28, 1138 (1957)]. This type of noise transducer approximates that found experimentally in electron guns which have produced noise figures of 3 db and less atSband. It is shown that arbitrarily low values of beam noisiness can be obtained by reducing the slope of the potential profile and that adjustment of this parameter provides the practical possibility of attaining very low noise figures in slow space‐charge wave amplifiers as frequency is increased. The calculated results are compared with experimental data atSband andXband.

ISSN:0021-8979    

DOI:10.1063/1.1735085

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Studies are presented showing the electrical properties of the highly ionized, detonation‐generated plasmas ejected into various gaseous media at the bare surfaces of high explosives. Theseexternalplasmas are shown to originate from chemionization in the reactions of high explosive at free surfaces and are not produced by thermal ionization in the shock wave propagated in the surrounding gaseous medium. The initial external‐plasma lengthLp* was found to be directly proportional to the lengtha0of the reaction zone of the high explosive‐generating source. Conduction measurements in plasmas propagating in chlorine, oxygen, argon, nitrogen, helium, and air showed that the electron affinity of the gaseous medium is important in determining the rate of decay of the plasma and its ultimate disintegration. The lifetime of external plasmas are substantial in media of low electron affinity, exceeding appreciably 250 &mgr;sec in such media as argon, helium, and nitrogen. Free electrons contribute practically the entire conductivity of these plasmas. Interesting pulsations occur when the external plasmas are generated by a charge of diameter smaller than the constraining tube and upon passing from a smaller into a larger constraining tube. A striking confirmation of the quasi‐lattice or metallic‐like model of plasmas is the observation that the plasma finally ``explodes'' into a gas cloud many times larger when its ion density decays to a critical low level.

ISSN:0021-8979    

DOI:10.1063/1.1735086

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

By exposing with light flashes delayed by short time intervals after the application of electric field pulses, it is possible to measure ionic conduction on large silver bromide grains from a photographic emulsion. Values of conductivity were obtained by an analysis of the transient decay of internal field pulses resulting from the application of known pulses of the external field. The internal field was measured by means of its effect in causing displacement of latent‐image centers formed by the exposure flashes. The room‐temperature ionic conductance of these grains was found to be the equivalent of about 9×10−6&OHgr;−1cm−1with an activation energy of about 0.42 ev. This conductance is several powers of ten higher than that reported for large silver bromide crystals of high purity and is thought to be primarily the result of surface effects. The implications of this result in terms of modern theories of photographic latent‐image formation are discussed.

ISSN:0021-8979    

DOI:10.1063/1.1735087

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Pulses of electric field applied to silver bromide grains of a photographic emulsion at short time intervals after the application of short light flashes cause displacement of photoelectrons and holes if their lifetimes are greater than the delay interval. The asymmetry in the location of the photoproducts—microscopically visible silver and bromine or developable latent‐image specks—is an indication of the fraction of carriers free at the time the electric field is applied. As the delay interval is varied, the decay of the number of free carriers may be followed. In the emulsion system studied, the number of photoelectrons was found to decay approximately according to a 1/(1+&agr;t) law, falling to half the initial value in 0.25 &mgr;sec. The lack of a dependence on intensity or temperature is taken to indicate temporary trapping in a distribution of shallow traps, perhaps at the grain surface. The number of free holes decays by an exponential law, with a mean lifetime of about 15 &mgr;sec. Indications are that hole mobility is very low, owing either to temporary trapping or self‐trapping. The implications of these results in terms of modern theories of latent‐image formation are discussed.

ISSN:0021-8979    

DOI:10.1063/1.1735088

出版商:AIP    

年代:1959

数据来源: AIP