摘要:

A new fully automated apparatus for measuring the thermal conductivity of liquids is described. This apparatus has been developed to meet the needs of industrial applications. The principle of the measurement is based on the absolute transient hot‐wire method. All data acquisition and instrument control can be performed using a microcomputer. After filling with a sample liquid in a cell the apparatus can automatically measure the thermal conductivity at the desired temperature without any manual procedures. The automated procedures include an algorithm to determine onset time of natural convection. The applicability of the apparatus has been tested to measure the thermal conductivity of toluene at room temperature and the results have an estimated accuracy of ±1.0 to ±1.5% depending on a sample to be measured.

ISSN:0034-6748    

DOI:10.1063/1.1138095

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A thermal instrumentation assembly which uses a high‐temperature tubular reactor for conducting gas‐phase thermal decomposition studies of organic substances has been designed. This thermal reactor assembly uses a counterflow heat exchanger in conjunction with a narrow‐bore quartz tubular reactor to obtain precise control over physical factors, such as exposure temperature, mean residence time, and gas‐phase residence‐time distribution. By virtue of the design of this quartz‐ware assembly, gaseous species are subjected to essentially a square‐wave thermal pulse as they pass through the thermal reactor.

ISSN:0034-6748    

DOI:10.1063/1.1138096

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Design and performance of a cryostat with a rotatable sample stage for operation in ultrahigh vacuum is reported. The cryostat, which is designed for adsorption studies on single‐crystal metals at low temperatures, has a temperature range of 5.5≤T≤800 K. Sample cooling from 800 to 5.5 K is achieved in about 90 min.

ISSN:0034-6748    

DOI:10.1063/1.1138097

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Overvoltage protection circuits have been developed to protect oscilloscope inputs or other 50‐&OHgr; recording systems from fast (&tgr;r∼1 ns) rise‐time pulses. These circuits are voltage dividers with linear output up to a specified level, typically 1.4 V, beyond which fast switching diodes limit the output to ≲5 V for inputs as high as 5 kV. The clipping circuits are frequency compensated for flat response to several hundred megahertz.

ISSN:0034-6748    

DOI:10.1063/1.1138098

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

In this work we describe a simple measurement system that allows us to obtain the characteristic parameters (the ideality factorn, the saturation currentIs, and the series resistanceR), for nonideal Schottky barrier diodes with high series resistance. The principal features of this new system are: analog processing of the measured signal (in order to avoid large errors coming from digital differentiation) and the easy interpretation of the shape of theI0‐VAcurves obtained.

ISSN:0034-6748    

DOI:10.1063/1.1138099

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

An airborne remote sensor named GASPILS (gas pipeline leak sensor) has been developed and tested to detect leaks from natural gas pipelines by monitoring the amount of methane in the atmosphere above the leak. The sensor is a passive electro‐optical system, with two independent channels, operating in a downward‐looking profiling mode. It is designed to detect increases in the low levels of methane concentration by sensing the infrared spectral radiance signatures using a nondispersive gas filter correlation technique. This technique involves the use of a gas cell as a matched spectral filter, and it combines a high degree of sensitivity to the target gas with a high degree of specificity.

ISSN:0034-6748    

DOI:10.1063/1.1138100

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Apparatus have been designed to simulate the wear from conductors in a railway current collection system. The main features of the wear machine include a continuous monitoring of the strip wear, strip traversing, and dwell‐time test facilities for the investigation of oxidational wear on a copper disk, simulating the contact wire. Disk wear is measuredinsituby the spherical indentations method. Typical results of the specific wear rate are also presented to demonstrate the capability of the apparatus.

ISSN:0034-6748    

DOI:10.1063/1.1138101

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The conventional practice of expressing the relationship between volume flow rate,Q, and frequency,f(or pulse rate) for turbine flow meters by the ‘‘Kfactor’’ is examined. Curvature in plots ofKagainstfdue to the existence of a nonzero intercept in the linear equation relatingftoQis illustrated using calibration (water and type II hydrocarbon) data. An algorithm which enables the actual linear range of turbine flow meters to be simply and easily ascertained is presented. The very significant improvement in linearity accomplished by the use of the algorithm is illustrated for the calibration data.

ISSN:0034-6748    

DOI:10.1063/1.1138102

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Flows with coherent structures allow see‐free measurements of local velocity and velocity fluctuations. Continuous turbulent velocity histories in ionizing shock waves are obtained at a 10‐MHz sampling rate. From this, correlation profiles and frequency spectra are determined which reveal the presence of prominent high‐frequency components.

ISSN:0034-6748    

DOI:10.1063/1.1138103

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A simple device has been designed and built to protect, warm, open, and dispense cesium (Cs) contained in glass vials. The device provides the user a larger margin of safety than most other commonly used methods, while being inexpensive and simple to operate.

ISSN:0034-6748    

DOI:10.1063/1.1138518

出版商:AIP    

年代:1985

数据来源: AIP