摘要:

Apparatus for the study of friction and sliding electrical contacts is described in detail. The equipment is designed for precise atmospheric control, a feature proven to be essential in any study of sliding contact phenomena.Examples are given of the type of results obtained with this apparatus when used in frictional studies. The kinetic friction is recorded by a sensitive strain gauge system which indicates transient effects, due to the variations in surface conditions, within a single revolution of the test cylinder under the rider.

ISSN:0034-6748    

DOI:10.1063/1.1771228

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

A double diffracting x‐ray spectrometer has been developed which will be used to study the crystallographic features of irradiated materials. The design features of this instrument include: (1) a mechanism to support and align the x‐ray tube as it rotates on a conventional goniometer; (2) a remotely controlled sample holder to position and rotate radioactive samples; (3) a mechanism to adjust the position of a curved aluminum crystal which is placed in the second diffracting position in such a way that it focuses the diffracted x‐rays into the detector; and (4) sufficient lead shielding between the sample and detector to absorb the radiation emanating from the sample in order that such radiation will not influence the detector. Preliminary tests of the instrument have shown that the design features reduce the background radiation originating from the sample to a very low level, and that no serious loss in diffracted x‐ray intensities results from the double‐crystal arrangement.

ISSN:0034-6748    

DOI:10.1063/1.1771239

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

Some techniques for measuring the velocity of sound in single‐crystal materials utilize multiple internal reflections of an ultrasonic pulse between two plane parallel surfaces of the specimen. If a thin layer of cold worked material is present at these surfaces, it is possible for the initial pulse to be distorted upon successive reflections in a way which would make the apparent transit time too short. The characteristic distortion of the initial pulse is shown in an unrectified oscillogram and consists of a forerunner pulse with a dominant frequency controlled by the thickness of the cold worked layer. Velocity determinations based on the arrival time of this forerunner will be too high. In the example considered the error amounts to about ½ percent for cold worked surface layers approximately 0.005 in. thick.

ISSN:0034-6748    

DOI:10.1063/1.1771229

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

The luminescence decay times of a number of organic crystal, liquid, and plastic scintillators are reported. The scintillators were excited by pulses of x‐radiation of 7.5‐kev quantum energy. The dimensions of the specimens are given, although the effect of specimen size on decay time was not investigated.

ISSN:0034-6748    

DOI:10.1063/1.1771230

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

A new circuit for the measurement of contact differences of potential and electron temperatures of electron tubes is presented. Its basis is the retarding field equation for plane‐parallel diodes. Its use on tubes of concentric‐cylindrical geometry is discussed in conjunction with the errors involved in such measurements, indicating its applicability to most tubes of interest.

ISSN:0034-6748    

DOI:10.1063/1.1771231

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

A description of a low temperature adiabatic calorimeter for use in the 10 to 150°K range is given. Its construction is described in detail concerning the features in which it differs from calorimeters previously described in the literature. These features have resulted in an improved performance and precision. At 30°K, its precision was better than 0.1 percent, while at temperatures above 50°K, a precision of 0.03 percent or better is indicated. At the lowest temperatures, an uncertainty of 1 percent exists, largely the result of the decreasing sensitivity of the platinum resistance thermometer.

ISSN:0034-6748    

DOI:10.1063/1.1771232

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

Transformations in multicomponent analysis frequently are better represented by second‐degree simultaneous equations than by the usual linear equations. For problems requiring repetitive evaluation of a set of equations in which the coefficient terms do not change, an analog computer can be used to obtain the results both rapidly and accurately. A computer is described which will evaluate three second‐degree equations, each of ten terms, as rapidly as an operator can set the input data on the dials, and with an accuracy better than 0.2 percent of the maximum value.

ISSN:0034-6748    

DOI:10.1063/1.1771233

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

This paper gives a brief account of a calorimeter developed at the National Bureau of Standards for the measurement of microwave power with relatively high accuracy (better than 1 percent) and at low (milliwatt) power levels. The calorimeter is identifiable as an electrically (dc) calibrated, aneroid micro‐calorimeter of the Joule twin type. A bolometer mount assembly serves as a wave‐guide termination for the absorption of microwave power and constitutes the calorimetric body whose temperature rise is observed. This arrangement enables the use of a novel indirect measurement technique and tends to insure calorimetric equivalence of dc and rf heating. The equivalence error is investigated with the aid of heat flow analysis and auxiliary experiments, and an upper bound for the error is assigned.

ISSN:0034-6748    

DOI:10.1063/1.1771234

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

A high‐sensitivity, automatic recording paramagnetic resonance absorption spectrometer operating at a wavelength of 3.2 cm is described. The spectrometer is of the crystal‐heterodyne type employing a local‐oscillator and a magic tee bridge with a reflection cavity. Automatic frequency control of the signal and local‐oscillator klystrons is provided to eliminate anomalous dispersion and to reduce frequency fluctuations. The output signal can be presented as a trace of the paramagnetic absorptionversusmagnetic field on a continuous strip recorder, as a pattern on an oscilloscope of absorptionversusmagnetic field for either visual observation or photographic recording, or as a continuous recorder trace of the derivative of absorptionversusmagnetic field. Provision is made for calibration of the magnetic field by means of the proton magnetic resonance absorption. Approximately 2×10−11mole of 1, 1‐diphenyl‐2‐picryl hydrazyl can be detected with the spectrometer.

ISSN:0034-6748    

DOI:10.1063/1.1771235

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

Counting experiments were made with cylindrical counters fitted with geometry ``definers'' in order to ascertain whether it is possible to find an area of constant sensitivity in these counters. These measurements are similar to those made by Gleasonet al.with end‐window counters. It is possible to achieve this result by means of a careful choice of the dimensions of these definers. The definers also allow a great simplification of the calculation of counter efficiency for a point source. We present a formula for sources placed in any position with respect to the counter. This formula is compared with experiment and the agreement is found to be good. A comparison of absolute beta counting between one of our cylindrical counters (with definer) and an end‐window counter (with definer) is made. The agreement obtained is satisfactory.

ISSN:0034-6748    

DOI:10.1063/1.1771236

出版商:AIP    

年代:1955

数据来源: AIP