摘要:

This article, the final one of a series on the design of electrostatic electron microscopes, contains a description of an instrument which illustrates the principles previously discussed. The microscope described is believed to be the first constructed with the object of providing the greatest of simplicity in construction, operation, and maintenance with the design parameters balanced to give a particular range of resolving power. The range chosen is about ten times the light microscope. The instrument is permanently aligned and utilizes external photography. The over‐all size and weight of the instrument, as well as the number and complexity of components, are materially less than previously described instruments.

ISSN:0021-8979    

DOI:10.1063/1.1714968

出版商:AIP    

年代:1943

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1714969

出版商:AIP    

年代:1943

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1714970

出版商:AIP    

年代:1943

数据来源: AIP

摘要:

A review of the literature has shown that there was no reliable method of measuring the flow properties of fluids in the range of viscosity 106to 1012poises where the flow is ``generally viscous.'' The theory of the penetrometer has been developed in this paper to a point where absolute viscosities may be determined both for viscous flow (viscosity independent of rate of shear) and generally viscous flow (viscosity dependent on rate of shear). The new penetrometer method was checked (1) with the capillary viscometer for viscous flow using coal tar pitch, and (2) with the revised axially moving cylinder method for generally viscous flow using a high melting blown asphalt. For any one temperature, the flow properties of a generally viscous material are defined by the straight line relationship between log shearing stress and log rate of shear. From this relationship viscosity may be calculated at any desired rate of shear. The slopenof this line is required in the calculation of rate of shear both for the penetrometer method and for any other type of standard viscometer method. An independent means for observingnwas developed for the penetrometer and for the moving cylinder method. It is shown that earlier formulas for standard instruments based on viscous flow are invalid when applied to fluids showing generally viscous flow properties. The power function law relating shearing stress and rate of shear has been found to hold for the asphalt studied over the range of rate of shear from 10−5to 10 reciprocal seconds. In addition to speed of operation and precision, the penetrometer has the advantages of minimizing the elastic effects and reproducibility without extensive heat treatment and preworking. Entire shearing stress‐rate of shear curves can be determined with one load and one penetration using a succession of time intervals.

ISSN:0021-8979    

DOI:10.1063/1.1714971

出版商:AIP    

年代:1943

数据来源: AIP

摘要:

A method is suggested for determining either the indicial admittance of a linear system, when the response to a known transient is observed, or the shape of the transient, when the admittance is known. A method is also outlined for obtaining the impedance operators, and in particular the impedance coefficients (stiffness, resistance, and inertia). Corrections due to the reaction of the instrument used in measuring the response of the system, or of a restraint to insure stability of the system, can be taken into account when appreciable. Suggested applications are to acoustical and aerodynamical problems.

ISSN:0021-8979    

DOI:10.1063/1.1714972

出版商:AIP    

年代:1943

数据来源: AIP

摘要:

Formulas are derived for the inductance per unit length of square tubular conductors. A numerical example illustrates use of these formulas. A comparison is effected with other formulas advanced earlier by Dwight and Wang.

ISSN:0021-8979    

DOI:10.1063/1.1714973

出版商:AIP    

年代:1943

数据来源: AIP

摘要:

Formulas are derived, by direct integration of the defining definite integrals, for the general geometric mean distance between (i) a point and a line segment; (ii) a point and a rectangular area; (iii) two parallel line segments; (iv) two orthogonal line segments; (v) a line segment and a parallel‐sided rectangular area; (vi) two parallel‐sided rectangular areas. Certain useful identities of the formula for the last‐named case are presented.

ISSN:0021-8979    

DOI:10.1063/1.1714974

出版商:AIP    

年代:1943

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1714975

出版商:AIP    

年代:1943

数据来源: AIP