摘要:

The essential construction features of a piston actuated shock tube are described, and its advantages relative to the conventional use of diaphragm ruptures for shock initiation are listed. Typical operational parameters are presented to illustrate the levels of reproducibility achieved. Tests with He and N2drivers into ∼99% Ar (1.0%–0.1% reagent) covered shock speeds from 1.539±0.002–0.8143±0.002 mm/&mgr;s, corresponding to 2390–847K incident shock temperatures. Application of this tube for recording postshock front density gradients of the endoergic dissociation of ethane and the exoergic condensation of iron atoms via the laser–Schlieren technique is described.

ISSN:0034-6748    

DOI:10.1063/1.1144090

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

A rotating piezoelectric device, which uses the so‐called slip‐stick mechanism for micropositioning is presented. The device is especially designed for use in point‐contact experiments at very low temperatures in high magnetic fields. Two typical applications are presented.

ISSN:0034-6748    

DOI:10.1063/1.1144091

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

We have developed an accurate, inexpensive translator utilizing the thermal expansion of an electrically heated wire. The resistance of the wire, measured in a Wheatstone bridge, provides a readout of the length of the wire based on its temperature coefficient of resistance.

ISSN:0034-6748    

DOI:10.1063/1.1144092

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

A modified high‐pressure, stopped‐flow apparatus has been developed to enable kinetic experiments to be monitored spectrophotometrically to 200 MPa, with efficient mixing of the reactant solutions. This apparatus is compact, relatively inexpensive to construct, and the solutions are only exposed to inert materials, such as Kel‐F, Teflon, quartz (low‐pressure windows), and glass or Viton. The drive‐syringe pistons are propelled by a step motor housed on top of the stopped‐flow unit inside the pressure vessel, resulting in a dead time for the system of ∼10 ms at 25 °C.  

ISSN:0034-6748    

DOI:10.1063/1.1144466

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

An improved, spring‐loaded thermocouple rake, suitable for studying flame structure, has been designed. This design keeps the thermocouple under tension thereby ensuring that the thermocouple does not droop due to the thermal expansion of the sensing wire when inserted in the flame. The present design allows the usage of thermocouple wire as small as 0.0508 mm and relative ease in changing thermocouple wire.

ISSN:0034-6748    

DOI:10.1063/1.1144093

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

A quartz tube is propelled horizontally along a quartz track by the stick‐slip inertial slider method, activated by the longitudinal mode of a piezoelectric tube mounted inside the quartz tube. Two‐dimensional motion is achieved by rotation of the quartz tube, activated by the bending mode of the piezo. With a sample attached to the quartz tube, the device is an excellent replacement for the electrostatic‐clamp type of walker used as the coarse approach mechanism in scanning probe microscopes (SPMs). Alternatively, by attaching the tip (or sample) to the piezo tube, the device can function as a very simple SPM in which the same piezo tube is used for coarse approach and for scanning. The device performs reliably in air and high vacuum, and is ultrahigh vacuum compatible. Step sizes from 10 to 1000 nm, and speeds up to 0.2 mm/s are possible.  

ISSN:0034-6748    

DOI:10.1063/1.1144094

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Two, inexpensive, easily constructed vessels are described which can be used to prepare and deliver measured volumes of parts per million concentrations of gaseous mixtures.

ISSN:0034-6748    

DOI:10.1063/1.1144095

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The magnetic susceptibility of polychlorotrifluoroethylene, commonly named as Kel’f, has been measured in a magnetic field of 2 T from 2 to 300 K. The susceptibility is diamagnetic above 3 K with a small Curie contribution at low temperature.  

ISSN:0034-6748    

DOI:10.1063/1.1144096

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Temperature control of furnaces to be used with the PARC vibrating sample magnetometer can be greatly improved if a separate temperature controller is utilized. A control circuit that allows easy temperature programming and ramping is described, as well as sample holder modifications which permit accurate measurement of the sample temperature.  

ISSN:0034-6748    

DOI:10.1063/1.1144097

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

A simple technique for measuring the relative extension or response of a piezoelectric tube as a function of frequency is presented. The method clearly identifies resonant modes of the system. This information is useful in tuning feedback control systems in scanned probe microscopes.

ISSN:0034-6748    

DOI:10.1063/1.1144098

出版商:AIP    

年代:1993

数据来源: AIP