摘要:

It is shown that the scattered field and the field inside the body can be expressed formally as power series in the above ratio, the calculation of successive terms in the series requiring the solution of standard problems in potential theory, together with the evaluation of certain potential integrals, so that the process can be carried as far as desired if Laplace's equation can be solved in the coordinate system appropriate for the body. The convergence of the series for the scattered field becomes progressively worse as we recede from the body, but an alternative expression for the field, also proceeding in powers of the same parameter, gives a representation which is valid everywhere except in the immediate neighborhood of the body (in particular, in the wave zone) and which does not suffer from this defect. The case of a perfect conductor, or diffraction through a hole in a perfectly conducting screen, can be treated as particular cases of the general theory. The paper can be regarded as an extension of Rayleigh's work, which confines itself to the first terms in the series.

ISSN:0021-8979    

DOI:10.1063/1.1721461

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

The method previously described of solving electromagnetic scattering problems as power series inkis here applied to the ellipsoid, the first three terms in the series being obtained. The second term in the series for the wave zone field (that proportional tok3) vanishes, and the same is true of any body possessing a center of symmetry. Thus the terms ink2,k4in the wave zone field are here obtained. The direction and polarization of the incident wave, and the electromagnetic constants of the ellipsoid, are arbitrary. The final results are expressed in terms of certain elliptic integrals which are functions of the three principal axes of the ellipsoid. These integrals can all be expressed simply in terms of just two such integrals; they become elementary integrals in the case of a spheroid. Various special cases are considered, including that of a perfectly conducting elliptical disk and the complementary problem of diffraction through an elliptical hole in a perfectly conducting screen.

ISSN:0021-8979    

DOI:10.1063/1.1721462

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

The statistical definition of information is compared with Boltzmann's formula for entropy. The immediate result is that informationIcorresponds to a negative term in the total entropySof a system.S=S0−I.A generalized second principle states thatSmust always increase. If an experiment yields an increase &Dgr;Iof the information concerning a physical system, it must be paid for by a larger increase &Dgr;S0in the entropy of the system and its surrounding laboratory. Theefficiency &egr; of the experimentis defined as &egr; = &Dgr;I/&Dgr;S0≤1. Moreover, there is a lower limitkln2 (k, Boltzmann's constant) for the &Dgr;S0required in an observation. Some specific examples are discussed: length or distance measurements, time measurements, observations under a microscope. In all cases it is found that higher accuracy always means lower efficiency. The information &Dgr;Iincreases as the logarithm of the accuracy, while &Dgr;S0goes up faster than the accuracy itself. Exceptional circumstances arise when extremely small distances (of the order of nuclear dimensions) have to be measured, in which case the efficiency drops to exceedingly low values. This stupendous increase in the cost of observation is a new factor that should probably be included in the quantum theory.

ISSN:0021-8979    

DOI:10.1063/1.1721463

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

A duality between the two types of negative resistance is noted. It is demonstrated that with series or parallel ``resonant circuits'' one can form either class by using either a nonlinear choke or nonlinear condenser. This ac characteristic can be converted to a similar dc one by using a bridge rectifier. With such an arrangement one can excite oscillations in a resonant circuit or produce relaxation oscillations. Several quite general oscillatory circuits are described, as are some multistable and counter circuits. The interaction with mechanical systems are considered.

ISSN:0021-8979    

DOI:10.1063/1.1721464

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

The method of Kac and Siegert for finding the output probabi ity density characteristic function for receivers with square law envelope detections is discussed, and a parallel development is given for the square law rectifier. Procedures are then outlined for determining the probability density functions directly, i.e., without solving the eigenvalue problem or inverting the characteristic function. The method depends on expanding the density function in an orthonormal series, the coefficients of which are expressed in terms of cumulants, which in turn are obtained from the system kernel by straightforward quadratures.As an example to illustrate the procedure, a receiver with Gaussian IF and Gaussian audio‐frequency pass characteristics is treated in detail, and the output probability density functions are found for various sinusoidal input signal strengths and IFvsaudio band‐width ratios.

ISSN:0021-8979    

DOI:10.1063/1.1721465

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

Chips of a gold‐silver alloy were made by orthogonal cutting with apparatus which permitted the determination of the chip geometry and cutting forces. From these data the stresses and strains and the shear and friction energies were calculated. Three rake angles were used to obtain different shear strains. The energy stored in the chips was determined as the difference in the heat effects associated with the dissolution in liquid tin of samples of cold worked and annealed chips in an isothermal calorimeter of high precision. With increasing strain the stored energy increased, but the ratio of the stored energy to the shear energy decreased.

ISSN:0021-8979    

DOI:10.1063/1.1721466

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

An optical technique, reported in a previous paper, has been used to measure surface oscillations on a series of thick 5.5‐in. diam steel plates of different thicknesses while they deform under explosive attack. Data obtained from the four 1025 steel specimens illustrated in the previous paper, and data obtained from two additional specimens have been analyzed partially. Results are compared with predictions from the theory of elasticity for the case of a diverging pulse. Elementary theory, known to be incorrect in the physical regime studied, is shown to give many satisfactory predictions for large distances from the charge.

ISSN:0021-8979    

DOI:10.1063/1.1721467

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

A noniterative numerical method has been found for solving a partial differential equation when its boundary conditions are not known on the entirety of a closed boundary. Under such conditions, the iterative numerical methods which are generally used, such as the relaxation technique, are not applicable. As an example, this noniterative numerical method has been used to calculate the shapes of a pair of beam forming electrodes for use in an electron gun in which rectilinear flow is desired. The calculated shapes are in almost complete agreement with Pierce's experimental results. Equipotential surfaces calculated by this method have been checked by means of an electrolytic trough which employs a semiautomatic detecting and plotting system.

ISSN:0021-8979    

DOI:10.1063/1.1721468

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

The dielectric constant &egr;´/&egr;0and loss tangent tan&dgr; of barium‐strontium titanate ceramics were measured as a function of temperature and static electric field at frequencies of 10 kc, 500 kc, and 3000 Mc. No frequency dependence of &egr;´/&egr;0was apparent at temperatures above the Curie point. An increase in tan&dgr; was observed in going from the low frequencies to 3000 Mc, but above the Curie point the values were not excessively large. A description of the 3000 Mc bridge construction and operation is given.

ISSN:0021-8979    

DOI:10.1063/1.1721469

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

Previous treatments of the linearized equations describing hole and electron flow in a homogeneous semiconductor have not been wholly satisfying mathematically. An exact treatment of these equations is undertaken and it is demonstrated that the departure from complete local charge neutrality implicit in the equations corresponds to a polarization attributable to local variations of conductivity. The dielectric relaxation is described and exact expressions for the effective mobility and diffusion coefficients are obtained. The corrections to the older values are of magnitude &tgr;r/&tgr;, where &tgr;ris the relaxation time and &tgr; the lifetime. For semiconductors, these corrections are negligible.

ISSN:0021-8979    

DOI:10.1063/1.1721470

出版商:AIP    

年代:1953

数据来源: AIP