摘要:

A powerful data‐acquisition and processing system, which retains the low per‐station cost of a microcomputer‐based system while providing the resources for easy data reduction, is presented. The system uses microcomputer‐based real‐time data‐collection stations and a larger central computer for data‐reduction tasks. An application to the control of a continuous‐wave ultrasonic spectrometer is shown. In particular, the precision measurement of acoustic velocity as a function of temperature is presented for single‐crystal vanadium with a low concentration of interstitial hydrogen.

ISSN:0034-6748    

DOI:10.1063/1.1137459

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

A resonant transformer pulse generator for the pumping of high repetition rate rare‐gas halide discharge lasers is described. Since with this design a low‐voltage dc power supply is needed, command charging can easily be achieved by using a thyristor as the switching element. The pulse generator has been tested driving a thyratron‐switched laser operating up to 100 pps free running and up to 200 pps in the burst mode.

ISSN:0034-6748    

DOI:10.1063/1.1137460

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Applying a damped oscillating discharge to a dielectric‐electrode TE (transversely excited) CO2laser, we obtain a high‐power and long‐pulse CO2laser output. With a decreasing value of the inductance inserted in parallel with the discharge load so as to make the discharge condition damped oscillating, laser output energy increased remarkably. When the inductance was 500 nH, a uniform glow discharge was obtained up to gas pressures of 500–600 Torr without any preionization. At a total pressure of 700 Torr (CO2/N2/He=1/2/8), a maximum CO2laser output energy of 270 mJ/pulse (7.3 J/l atm) was obtained with an electrical efficiency of 4.3% and with a pulse duration of 7 &mgr;s.

ISSN:0034-6748    

DOI:10.1063/1.1137461

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

A nondispersive photometer has been developed featuring a novel harmonic signal analysis for application oriented choice of functional components. These consist of rotating gas filters and interference filters as well as solid‐state and optoacoustic detectors. Applications include direct measurement of concentration ratios. Simple models explaining the features of functional components as well as calibration procedures are given. Experimental data are presented, in comparison.

ISSN:0034-6748    

DOI:10.1063/1.1137462

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

A method for fabricating the improved version of an integrated transducer for color distinction is proposed. It consists of three SnO2(n)–Si(n) photodiodes on a Si wafer and a trichromatic filter prepared by arranging filters of the three primary colors (Eastman Kodak gelatin filters; Nos. 47B, 58, and 25) on an infrared glass filter (Hoya Glass; B‐460). Its photoelectric characteristics and dependence of error of color distinction on the dimension of the transducer are reported. The photodiodes employed in this conversion assembly are produced by the simple spray method and are most suitable for detecting the low illumination. Since this transducer adapts the trichromatic color resolution method, highly accurate color distinction is possible. With this type of transducer, three photodiodes sensitive to the primary colors, red, green, and blue, respectively, are arranged on a plane. An error in color distinction can occur due to the differences in the strength of the light incident upon the respective photodiodes. This problem is reduced by making the transducer more compact. Finally, 11 kinds of colors are discerned in this experiment as an application of the transducer.

ISSN:0034-6748    

DOI:10.1063/1.1137463

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Two specific problems associated with a triple hot wire probe are discussed and analyzed here, namely, the problem of nonorthogonality of the three wires and the variation of the directional sensitivity coefficientsk2andh2with the pitch and yaw angles. Both problems can cause significant errors in the measured turbulence quantities. In particular,v¯2andw¯2can be drastically affected. The present results confirm thatv¯2andw¯2can be measured rather inaccurately with a triple wire, if  ‘‘overall’’ values ofk2andh2are used, where ‘‘overall’’ denotes a mean integral value over a wide range of angles. It was found here that if these coefficients, in particularh2, are left to vary with the angles,v¯2andw¯2can be measured more accurately. It is strongly recommended to take this effect into account when high‐velocity fluctuations are expected. Two numerical schemes have been proposed as remedies to these problems. They were found to work effectively although the data processing time is significantly increased. It is believed that these algorithms improve the performance of a triple wire, and can be applied to any three‐dimensional flow with high turbulence level for which the mean velocity vector is unknown beforehand.

ISSN:0034-6748    

DOI:10.1063/1.1137464

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Measuring errors due to hot‐wire temperature sensitivity are expressed in terms of measurable parameters. Examples show that such errors can be significant, often excessive.

ISSN:0034-6748    

DOI:10.1063/1.1137465

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The transient hot‐strip (THS) method has been developed for experimental situations with two different materials kept against the sides of the strip. Based on this development THS probes, with known or separately measured thermal properties, have been designed and used successfully in a series of reported experiments. If the thermal diffusivity of the probe is less than that of the material under study and good contact is established between the probe and the sample, the accuracy of the measurements turns out to be as good as with the ordinary transient hot‐strip method.

ISSN:0034-6748    

DOI:10.1063/1.1137466

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

A method is presented for measuring mechanical resonant frequencies of heavy structures. This method employs only one electromechanical transducer which alternates as driver and receiver. We present results obtained with a superconducting magnet to demonstrate the applicability of the method: The resonant frequencies of the magnet shift with current, which affects stress.

ISSN:0034-6748    

DOI:10.1063/1.1137467

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

A third‐sound helium film resonator using a capacitive thickness detector suitable for high‐resolution studies of third sound in4He and3He–4He mixtures is described. The sensitivity to changes in the helium film thickness is observed to be &bartil;0.1 pm.

ISSN:0034-6748    

DOI:10.1063/1.1137468

出版商:AIP    

年代:1983

数据来源: AIP