摘要:

An active bandpass filter has been developed with the desirable feature of wideQcontrol over the range of frequencies extending to ∼4 kc. TheQhas been made as high as 250 with good stability characteristics over this range. The flexibility of the filter has been illustrated by the construction of a filter bank tuned to select Fourier components of a 50‐cps periodic wave in a typical noise environment and recombine them with no added relative phase shift and with equal gain to improve the signal‐to‐noise ratio.

ISSN:0034-6748    

DOI:10.1063/1.1717383

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

A new technique is described for measuring microwave dielectric constants which overcomes several disadvantages of currently standard methods. Perturbation techniques are used with thin rod samples placed in aTM012cylindrical cavity in such a manner that all undesirable effects of the ends of the rod are eliminated. A considerable increase in repeatability and ease of measurement is obtained.

ISSN:0034-6748    

DOI:10.1063/1.1717384

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

It is shown that large errors due to long wavelength harmonics can occur in the determination of integrated intensities and halfwidths with a double crystal spectrometer. For example, in measuring the integrated intensity of the (333) reflection of silicon with MoK&agr; radiation, an error of a factor of 4 is possible due to 3&lgr; radiation from the white spectrum which is simultaneously diffracted by the (111) planes. The amount of error is dependent upon the particular experimental arrangement (tube voltage and allowed horizontal divergence being the most important factors), and can be reduced, and in most cases eliminated, by use of an appropriate filter.

ISSN:0034-6748    

DOI:10.1063/1.1717385

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

A molecular beam electron bombardment detector that detects approximately 1/40 of a neutral beam falling into an area of 3×10−2cm2is described. Molecular beams of sulfur dioxide and argon have been detected with signal‐to‐noise ratios of 2000/1 and 500/1, respectively. An improved design is discussed.

ISSN:0034-6748    

DOI:10.1063/1.1717386

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

This paper describes a method of measuring the electrical resistivities of metals by ac induction methods, in which the specimen is in bulk form, and no direct contact to it is required. Theoretical expressions are given for a sphere and for an infinite circular cylinder in a uniform applied ac field, and an experimental method is described which is applicable to any shape or applied field configuration.

ISSN:0034-6748    

DOI:10.1063/1.1717387

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

It is shown that the active material obtained in the use of Victawet as a parting layer for electron microscope replicas is the inorganic decomposition product sodium metaphosphate (S.M.P.). The results of an investigation of the parting layer characteristics of S.M.P. suggest its use in applications which have previously employed Victawet. Measurements with radioactive tracers indicate that on smooth surfaces reproducible stripping can be realized with parting layers of S.M.P. a few molecular dimensions in thickness. The use of a ribbon filament source with this material is recommended to minimize shadowing effects and thus reduce the thickness of S.M.P. required for successful stripping.

ISSN:0034-6748    

DOI:10.1063/1.1717388

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

Accurately determined pressures can be produced in a vacuum gauge calibration chamber by means of repeated injections of small, precisely metered masses of air. The apparatus is simple and the pressures obtained are highly repeatable.

ISSN:0034-6748    

DOI:10.1063/1.1717389

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

Methods are described to produce thin foils suitable for transmission electron microscopy from ordinary tensile specimens. The specimens were cylindrical single crystals of &agr;‐brass of diameter ¼ in. and gauge length ¾ in. All the procedures are electrolytic in order to avoid introduction of mechanical strains.

ISSN:0034-6748    

DOI:10.1063/1.1717390

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

A small internal optical cell which can be used to study the infrared absorption of pure liquids to 12 000 atmospheres is described. The sample is sealed in a small plastic bag which is held between two sapphire plates. The distance between the plates can be set to accommodate the different absorptive capacities of various liquids.

ISSN:0034-6748    

DOI:10.1063/1.1717391

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

A device which can be used in conjunction with a tensile testing machine to determine the birefringence of a polymer sample as a function of stress, strain, and temperature is described. A chamber is provided so that the sample may be held at a controlled temperature during the measurement.

ISSN:0034-6748    

DOI:10.1063/1.1717392

出版商:AIP    

年代:1961

数据来源: AIP