摘要:

A theory describing polarization reversal in BaTiO3c‐domain crystals based on observed time and field dependence of polarizationP=f(E,t) is presented, and the activation field &agr; as well as mobility &mgr; are related to the constants appearing in the basic differential equation. The theory gives time and field dependence of the switching current at constant temperature. Although the theory does not imply restriction on the applied fieldE(t), results are given only for pulsed and sinusoidal fields. The effect of skin properties on the bulk crystal has been considered. Dependence of coercive field on applied field and frequency are readily obtained. Switching resistance is calculated.

ISSN:0021-8979    

DOI:10.1063/1.1723435

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

The variable parameter (or parametric) principle of amplification is characterized by a typical arrangement in which a variable energy storage element, such as an inductor or a capacitor, is suitably coupled to two resonant circuits. If the value of the energy storage element is made to vary in the proper way, energy is fed from the source which drives the element (that is, the pump) to the fields of both the resonant circuits. This paper describes the behavior relative to gain, band width, and noise of this type of amplifier.Specifically, it is shown that to increase gain, theQof one of the resonant circuits, the one commonly called the idling circuit, must be increased or the variation in the variable reactance must be increased. The band width is inversely proportional to thisQand to the voltage gain. Hence, for high gain, the amplifier is normally a narrow band device. One of the most important sources of noise is the thermal noise originating in the idling circuit. However, in principle this source can be reduced indefinitely by making the idling frequency approach the pumping frequency or by artificially cooling the idling circuit. In this fashion very low noise figures should be possible.The parametric principle can also be applied to producing frequency conversion with large conversion gain. The appendix presents the expressions for gain, band width, and noise figure for this application. The behavior of the converter relative to gain, band width, and noise is quite similar to that of the amplifier.

ISSN:0021-8979    

DOI:10.1063/1.1723436

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

Spheres of copper, lead, tin, iron, aluminum, zinc, silver, and lead‐tin alloys were accelerated to velocities of 0.75 to 2.25 km/sec and impacted normally upon targets of the same material as the pellets. Conditions were maintained so that pellets lost no mass before striking the target. The target mass was large compared to the mass of the pellet, so the targets could be considered semi‐infinite.The volume of the crater produced was found to be directly proportional to the kinetic energy of the pellet in the energy range investigated.The penetration varied linearly with the velocity or momentum of the pellet. The area of the crater as measured in the plane of the original surface of the target was found to be directly proportional to the momentum of the pellet at the time of the impact.In the case of the lead‐tin alloy series, a correlation was observed between the crater parameters, the phase diagram of the alloys, and various functions of the pellet mass and velocity for the following series of alloys: 100% lead; 90% lead, 10% tin;...; 10% lead, 90% tin; 100% tin.

ISSN:0021-8979    

DOI:10.1063/1.1723437

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

Permeability, coercive force, remanence, and hysteresis and core losses of a 3% singly oriented silicon‐iron alloy are measured in the temperature range of 30° to 700°C. Their temperature dependence is interpreted in terms of either the intrinsic properties of a ferromagnetic or domain theory. The magnetization curve is analyzed on the basis of the crystallographic characteristics of the texture in the material. Domain distribution is discussed at each stage of magnetization. Application of the analysis leads to the establishment of the relationship between the temperature coefficient of permeability and the magnetization processes.

ISSN:0021-8979    

DOI:10.1063/1.1723438

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

Analytical equations have been derived for the transmission factor applicable to the case of a rather weakly absorbing sample of circular cross section and larger than the x‐ray beam. Calculations are presented for liquid nitrogen and it is shown that under certain practicable conditions the transmission factor is constant for a rather wide range of the scattering angle.

ISSN:0021-8979    

DOI:10.1063/1.1723439

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

When two circuits such as filters or transmission lines are coupled together by means of distributed reactances which can vary sinusoidally in time and space, energy can be converted between waves of different frequencies in a variety of ways. If the waves on the two transmission lines are characterized by frequencies &ohgr;1and &ohgr;2and phase constants &bgr;1and &bgr;2, while the coupling reactances vary as &ohgr;=&ohgr;1−&ohgr;2and &bgr;=&bgr;1−&bgr;2+&Dgr;&bgr;, powerP1at &ohgr;1is converted into powerP2at &ohgr;2and vice versa in a manner reminiscent of waves on coupled passive circuits, except that a relationship (P2/&ohgr;2)=(P1/&ohgr;1) is obeyed. If the group velocities on both transmission lines are in the same direction, the direction of power transfer reverses periodically with distance. If they are not in the same direction, the power transfer increases monotonically with distance for small &Dgr;&bgr; but reverses periodically for &Dgr;&bgr; larger than a certain limit.When the coupling reactance varies as given by &ohgr;=&ohgr;1+&ohgr;2and &bgr;=&bgr;1+&bgr;2, parametric amplification is possible in the form of exponentially growing waves at frequencies &ohgr;1and &ohgr;2if the group velocities are in the same direction, and in a form reminiscent of the backward wave amplifier when the group velocities are not in the same direction. In both cases the excess energy is supplied by the variable coupling reactance and can be indefinitely large.Possible applications of new principles of these coupled circuits to broad‐band frequency converters, frequency‐channel selectors, wide‐band amplifiers, tunable narrow‐band amplifiers, and oscillators are described. Noise performances of the circuits are also discussed.

ISSN:0021-8979    

DOI:10.1063/1.1723440

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

The general solution is obtained for the index of refraction of a variable‐index, spherical lens which will form perfect geometrical images of the points of two given concentric spheres on each other. One conjugate sphere is assumed to be outside the lens or at its surface, while the other may be either inside, outside, or at the surface. If one of the spheres is of infinite radius, the lens will focus a parallel beam perfectly at a point on the other sphere.It is shown that the index of refraction may be specified arbitrarily, subject to two simple conditions, in an outer shell of any desired thickness less than the radius of the lens. The index of the central portion is then expressed in terms of a function which is tabulated, and of an integral involving the index of the outer shell. Some properties of the general solution are discussed, and various special solutions are derived.

ISSN:0021-8979    

DOI:10.1063/1.1723441

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

The collection of a minority gas species at the cathode in a glow discharge, termed cataphoresis, appears not to have been completely successfully explained. Observation indicates that in all cases, the minority gas segregated at the cathode, must be capable of being very effectively ionized by the vehicular gas. The recent discovery of the effective creation of ion complexes such as NeHe+and NeA+in pressure dependent reactions above some mm of Hg pressure by Oskam, the independent direct observation of these ions and the production of ions such as HeH+, NeH+, and AH+with 1% H2in the inert gas by Weimer, using the effusion mass spectrometer of Pahl, render a basis for the extension of the Druyvesteyn theory developed for metallic ions in inert gas to the general process, aid in the explanation of the Hg‐Xe anomaly observed by Kenty, and indicate certain needed corrections which are acting to make the process more efficient.

ISSN:0021-8979    

DOI:10.1063/1.1723442

出版商:AIP    

年代:1958

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1723443

出版商:AIP    

年代:1958

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1723445

出版商:AIP    

年代:1958

数据来源: AIP