摘要:

A new flume is described which contains a rotating laminar flow with a linearly varying temperature distribution from top to bottom, making it useful for a number of model experiments in geophysics. Some experimental results in selective withdrawal from this apparatus are presented as examples of the types of problems that can be addressed.

ISSN:0034-6748    

DOI:10.1063/1.1136467

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

An automated methane/total hydrocarbon analyzer was developed and flight tested that produced alternate methane/total hydrocarbon measurements every 7 s, providing the spatial resolution needed for regional hydrocarbon measurements at aircraft speeds. The sensitivity of the analyzer to oxygen and water vapor interference was characterized at appropriate concentrations. A technique to periodically measure atmospheric oxygen was determined to be necessary for accurate hydrocarbon measurements and incorporated into the analyzer. A data collection methodology was developed to minimize errors resulting from changes in flame ionization detector sensitivity at different altitudes (pressures). Selected aircraft data acquired during the 1979 Southeastern Virginia Urban Plume Study are presented to illustrate instrument performance.

ISSN:0034-6748    

DOI:10.1063/1.1136468

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

In order to monitor perfusion during certain surgical operations a simple instrument for measuring the rate of flow of a liquid in the range 2–20 ml/min was developed and has proved useful in the laboratory. A miniature thermistor is used as the measuring probe and a pulse technique to reduce heat dissipation in the liquid. The circuit described is self‐oscillating and its frequency is proportional to the liquid flow. A frequency‐to‐voltage converter allows a recorder to be driven directly but the response is not linear, the sensitivity being much higher for the lower rates of flow (i.e., recorder scale expanded at the lower end). The dimensions of the measuring cell and methods of temperature compensation are discussed. Calibration curves are shown as well as a typical flow recording. The same circuit may be adapted to measure flow in a gas.

ISSN:0034-6748    

DOI:10.1063/1.1136469

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

An automatic temperature controller and data acquisition system for use with a dilution refrigerator is described. The unit is controlled by a 16‐bit home microcomputer and operates and reads a resistance bridge, capacitance bridge, and temperature controller. Interfacing is achieved with common components and minimum additional wiring. Flexibility is retained in the software to allow application to several types of measurements.

ISSN:0034-6748    

DOI:10.1063/1.1136470

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

This paper describes a new technique for the capacitive measurement of high dc voltages, based on the principle of consecutive differentiation and integration. A measuring electrode acts as the differentiating high‐voltage capacitor; the electric flux to the measuring electrode can be intercepted by a movable shield. The signal is integrated with a commerically available integrator. The method has excellent accuracy and linearity, while the long‐term stability is determined by the drift of the integrator. Calibration is only necessary after a change in the high‐voltage circuit. The system is sensitive to corona, but the onset of corona can easily be observed by the operator. The described principle can also be used to measure 60 Hz and impulse voltages.

ISSN:0034-6748    

DOI:10.1063/1.1136471

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A computer‐based system has been developed to control the timing sequence in multilaser experiments. In particular, it has been used to compensate for the long‐term drift, ∼50 ns/4 h, associated with thyratron‐switched excimer lasers.

ISSN:0034-6748    

DOI:10.1063/1.1136463

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A design for a high temperature coaxial flashlamp is presented. This device has proved very useful in optical pumping studies of high temperature metal vapors. It is easily constructed, and provides high power ultraviolet irradiation of samples at up to 950° C. 5000 pulses of 2 &mgr;s length and 500 J of energy have been produced without apparent degradation of the lamp.

ISSN:0034-6748    

DOI:10.1063/1.1136489

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A simple oscillator–amplifier system has been constructed. The system allows the amplification of short (300 ps), intense (40 &mgr;J) pulses from an atmospheric pressure nitrogen laser. Pulses of up to 0.5 mJ energy, ≊1.7 MW peak power, were routinely obtained.

ISSN:0034-6748    

DOI:10.1063/1.1136458

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A method for correcting for the inductance in a fast pulsed discharge circuit yields accurate discharge voltage and power input waveforms. An economic fast current shunt is described.

ISSN:0034-6748    

DOI:10.1063/1.1136459

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A servo amplifier is described which increases the stability of the series 213 and series 216 Granville–Phillips servo controlled leak valve. The amplifier provides increased immunity from 60 Hz noise through filtering, negative feedback via a rate sensing circuit, and adjustable gain.

ISSN:0034-6748    

DOI:10.1063/1.1136460

出版商:AIP    

年代:1981

数据来源: AIP