摘要:

A system consisting of two photomultipliers viewing one scintillating crystal is given for resolving peaks in a scintillation spectrum which otherwise would overlap because of photomultiplier statistics. A differential discriminator accepts pulses from a fixed portion of the spectrum from one of the tubes. Another differential discriminator scans the spectrum from the second tube and is coincidence gated by the first. Experimental results are presented which show that this method can separate monoenergetic lines not otherwise resolved.

ISSN:0034-6748    

DOI:10.1063/1.1770661

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

The stress required for the plastic deformation of a metal at elevated temperatures depends on both temperature and strain rate. In order to determine mechanical properties at high temperatures, both these quantities must be known and controlled. Otherwise stress cannot be expressed as a unique function of strain. The machine described in this paper performs short time tensile tests at constant temperature and constant true strain rate. It automatically measures and controls the minimum diameter of a cylindrical specimen which is pulled in a constant temperature furnace. A cam drive establishes the required exponential variation of diameter with time, and, by means of an optical comparator and error‐operated servo, the testing machine pulls the specimen at the required rate. Load is determined by measuring the deflection of weigh‐bars in series with the specimen. Since true strain increases linearly with time, a true stress, true strain curve can be plotted from yield to fracture.The information obtainable with this machine should be of considerable value in hot‐working research, and will complement that available from creep and stress rupture tests.

ISSN:0034-6748    

DOI:10.1063/1.1770662

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

A recording mercurial manometer which covers the range 0–760 mm of Hg is presented. A NichromeVor ChromelAresistance wire is concentrically positioned in the mercury column of a large bulb manometer. The resistance of this wire is part of a direct current bridge circuit with a recording potentiometer as the balance indicating device. An electrical circuit which is designed to handle a variety of experimental conditions is presented.

ISSN:0034-6748    

DOI:10.1063/1.1770663

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

Apparatus and methods are described for the measurement of the vapor pressure of materials, especially corrosive liquid, over the entire liquid range. The first method consisted of measuring the pressure registered on a mercury manometer by helium, which acted as a buffer between the manometer and a single boiling point tube. In the second method, two metal boiling point tubes were connected to a common pressure system. The boiling temperature of the test liquid in one tube was compared directly with the boiling temperature of water in the other. Pressure values were interpolated from steam tables. The data obtained with both systems were compared with accepted data.

ISSN:0034-6748    

DOI:10.1063/1.1770664

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

A method of employing the components of a high speed analog computer to evaluate product integrals is presented. Kernel functions of two variables are obtained with time as the variable of integration and the position of ganged potentiometers as the parametric variable. High speed multipliers, function generators, adders, and integrators permit the evaluation of a one‐hundred point product integral curve every 1.67 seconds. This curve is displayed on a cathode‐ray tube screen having a long persistence P‐7 phosphor. Examples of sine and cosine transforms evaluated with the product integrator are given. The observed errors range from 1 to 10 percent, depending upon the problem.

ISSN:0034-6748    

DOI:10.1063/1.1770665

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

The manufacturing yield of acceptable external‐cathode counters has been found to be 67 percent with ethylene‐argon filling and 94 percent with ethyl alcohol‐argon filling. Over 90 percent of the tubes that did not perform well with ethylene‐argon performed well when refilled with alcohol‐argon. A total of 444 counters enter into these statistics. Twenty rejected ethylene tubes were alternately refilled and tested with alcohol‐argon and ethylene‐argon. Results of several of such test cycles showed repeated success with alcohol and failure with ethylene. Deterioration of quality with counting‐age was extremely nonuniform for ethylene tubes, and at the end of their useful lifetime they displayed extreme multiple‐pulsing but no serious damage to the plateau slope. A temporary return to normal operating characteristics was observed for these tubes after inactive periods. This behavior is explained in terms of the Paetow effect.

ISSN:0034-6748    

DOI:10.1063/1.1770666

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

An instrument for the measurement of photocurrents is described. It has the advantage of an inherent time response of 0.1 second with an accompanying sensitivity of 2.0×10−13ampere per inch deflection on the oscillograph screen. These characteristics are shown to be desirable for the evaluation of transient photocurrents.A short discussion of the application of the instrument to the measurement of transient photocurrents in photographic emulsions is presented. These currents require two seconds to reach a maximum amplitude for a variety of emulsions. Thus the process giving rise to these currents may be electrolytic rather than electronic.

ISSN:0034-6748    

DOI:10.1063/1.1770667

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

A thin sheet of a temperature‐sensitive phosphor has been used to show the distribution of temperature on the surface of a flat plate in supersonic flow. Calibration of the phosphor is described, and a photograph is shown. Use of a photomultiplier tube permits one to determine the temperature as a function of time, from which recovery temperatures and heat transfer coefficients may be deduced.

ISSN:0034-6748    

DOI:10.1063/1.1770668

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

The conventional Cockcroft‐Walton voltage multiplying circuit is studied considering it as a transmission line. It is shown that, even when no direct current is drawn from the high voltage electrode, there is an important loss in output voltage caused by circulating currents in the stray capacitances. This loss of voltage is independent of the supply frequency. Formulas are developed for the voltage efficiency resulting from a given choice of capacitor size and number of stages.Two modifications of the Cockcroft‐Walton circuit which improve the voltage efficiency are suggested and analyzed. The first of these involves a loading coil at the high voltage end of the line. The second involves the addition of inductors in series with each of the capacitors of the circuit.

ISSN:0034-6748    

DOI:10.1063/1.1770669

出版商:AIP    

年代:1953

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1770670

出版商:AIP    

年代:1953

数据来源: AIP