摘要:

An earlier paper presented equations for increasing waves in the presence of two streams of charged particles having different velocities, and solved the equations assuming the velocity of one group of particles to be zero or small. Numerical solutions giving the rate of increase and the phase velocity of the increasing wave for a wide range of parameters, covering cases of ion oscillation and double‐stream amplification, are presented here.

ISSN:0021-8979    

DOI:10.1063/1.1698275

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

Using crystal monochromated CuK&agr;‐radiation and a Geiger counter spectrometer, integrated intensity measurements have been made for powder samples of cold‐worked and annealed &agr;‐brass. The effect of cold work is to increase the integrated intensity of the strong lines and make practically no change in the weak lines. The increase for the strong lines is presumably due to a reduction in extinction. Measurements were made of the (400) reflection on a cold‐worked sample and on an annealed sample held at high temperature to demonstrate the difference between the effects of cold work and temperature vibration.

ISSN:0021-8979    

DOI:10.1063/1.1698276

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

Gas penetration rates have been used to study the structure of three commercial grades of sintered Pyrex glass. Specific surface areas, ``average pore diameters,'' pore population densities, average particle diameters, and particle population densities have been calculated on the basis of the data obtained.

ISSN:0021-8979    

DOI:10.1063/1.1698277

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

A theoretical examination is made of the impedance of a biconical antenna, based upon a method devised by Schwinger in studying the discontinuity problems of a wave guide. In the present analysis, an integral equation to determine the aperture field is obtained by matching the tangential electric and magnetic fields along the boundary sphere. Using this integral equation, the effective terminating admittance of the antenna can be expressed in a form that is stationary with respect to small variations in the aperture field. It is shown that the zeroth‐order solution of the admittance function thus obtained is the same as the one that Smith derived by neglecting all the high order waves in the interior region except the principal mode. For small‐angle cones, the present formulation yields the same exact solution obtained previously, based upon several different methods. The paper also contains a discussion of the first‐order approximate solution which is applicable to both small‐ and wide‐angle cones. The analysis includes a detailed treatment of a method by which the characteristic values and characteristic functions for a given cone may be found approximately, but very accurately; as well as certain integrals involving the product of Legendre functions.

ISSN:0021-8979    

DOI:10.1063/1.1698278

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

When an electric current is set up by bringing two contacts together, they necessarily discharge a capacity. If the discharge takes place through an arc before the metallic circuit is established, erosion of the electrodes results. In a low voltage circuit the occurrence of an arc is dependent upon the condition of the electrode surfaces and upon the circuit inductance. For ``inactive'' surfaces, and a voltage of the order of 50, an arc does not occur if the inductance is greater than about 3 microhenries. Surfaces of various metals can be ``activated'' by vapors of certain unsaturated organic compounds, and in the active condition they give arcs even when the circuit inductance is greater than this limiting value by a factor of more than 103. The study of arcs between active metal surfaces is not yet complete, and most of this paper and all of the remainder of this abstract have to do with surfaces which are inactive.When an arc occurs at the make of inactive metal surfaces, its energy, which in low voltage circuits of practical interest is drawn entirely from a charged condenser, is dissipated almost entirely upon the positive electrode, and melts out a crater intermediate in volume between the volume of metal which can be melted by the energy and that which can be vaporized. Some of the melted metal lands on the negative electrode and, with repeated operation, results in a mound of metal transferred from anode to cathode. This transfer is about 4×10−14cc of metal per erg.The arc voltage is of the order of 15. If the initial circuit potential is more than about 50 volts there may be more than one arc discharge, successive discharges being in opposite directions and resulting in the transfer of metal in opposite directions— always to the electrode which is negative.

ISSN:0021-8979    

DOI:10.1063/1.1698279

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

The problem discussed in this paper is that of the scattering of electromagnetic waves by a spherical obstacle. The classical theory is well known. Stratton's ``Electromagnetic Theory,'' for instance, contains a very good summary of that discussion. The computation of the scattering cross section, according to this theory, leads to some difficulties. In the case of large spheres, where geometrical optics should apply, the rigorous theory yields a scattering cross section equal to twice the actual cross section of the sphere!The discussion presented in this paper explains this strange result and shows the role played by the shadow and by the diffraction fringes surrounding the shadow. A reasonable system of approximations yields the well known ``Babinet's principle.'' The physical interpretation is of such general character that it must certainly apply to a variety of similar problems in acoustics or wave mechanics. The spherical shape of the obstacle is essential in the present discussion, but similar results would certainly be found for other shapes of the obstacle. The case of a circular cylinder, investigated by E. B. Moullin and L. G. Reynolds, also leads to a total cross section twice as large as the actual cross section, for large cylinders. The explanation is the same as for the spheres. Experiments very carefully designed by Dr. Sinclair and Professor V. K. LaMer gave a very precise check of the theoretical predictions.

ISSN:0021-8979    

DOI:10.1063/1.1698280

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

The positive column of a glow discharge is placed along the axis of a cylindrical cavity excited in the TM010mode. The transmission of 3‐cm waves through the cavity and the shift in resonant frequency are observed as a function of discharge current. It is shown that from these measurements values of the complex conductivity, &sgr;r+i&sgr;i, of the electron gas can be calculated. Curves of the measured conductivity components as functions of pressure and current are given. Using a theoretical formula for the conductivity (see reference 6) values of electron density can in turn be calculated from both &sgr;rand &sgr;i. Langmuir probe studies are carried out to check the results obtained, and adequate agreement is found.

ISSN:0021-8979    

DOI:10.1063/1.1698281

出版商:AIP    

年代:1949

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1698283

出版商:AIP    

年代:1949

数据来源: AIP