Range Of Wire Diameters Research Articles

Passive mass deposition control of cryogen sprays through the use of wire meshes.

Cryogen spray cooling (CSC) is used for epidermal protection during laser dermatologic surgery. However, further research is necessary to optimize the use of CSC for many applications, particularly in patients with darker skin types, and in procedures with deep-targeted chromophores. With the objective to enhance cryogen spray atomization and introduce a passive mass deposition control, stainless steel wire meshes of various sizes were positioned in the spray path of two nozzles of different diameters (0.7 and 1.4 mm). A temperature sensor placed at a fixed distance below the nozzle tips measured variations in temperature as a function of time. Calculations for heat flux (q), and overall heat extraction (Q) were done through an inverse heat conduction problem (IHCP) algorithm. The use of wire meshes reduced maximum q and thus cooling efficiency for both nozzles. However, for the larger diameter nozzle (1.4 mm), cooling duration was prolonged significantly when compared to the case without mesh, which led to an increase in Q. Wire meshes, within the range of wire diameters used, are not desirable for use with the smaller diameter nozzle because they reduce cooling efficiency. For the larger diameter nozzle, however, the prolonged cooling duration and increase in Q may be beneficial for laser dermatological procedures directed towards deeper targeted chromophores, such as hair removal.

HTS conductors for magnets

We have successfully improved the J/sub c/ value of Bi-2212 round wire to 500 kA/cm/sup 2/ at 4.2 K in self-field. The J/sub c/ value strongly depended on the filament size, aspect ratio, and geometry. Adjusting the filament size made it possible to obtain wires with J/sub c/ values higher than 450 kA/cm/sup 2/ in a range of wire diameters from 0.8 to 1.3 mm. The J/sub c/ value remained constant up to an applied tensile strength of 150 MPa. A 1 + 6 stranded cable fabricated using 1.02 mm diameter wires carried an I/sub c/ value of 4.5 kA at 4.2 K in self-field. A 16-strand Rutherford cable could also be fabricated using this wire.

Observation of Quantized Circulation in Superfluid Helium

An experimental study has been made of the circulation of the superfluid component of liquid helium II around a fine wire. The method used was that of Vinen, in which the circulation is measured by means of the influence it has on the transverse vibrations of the wire. The present work extends Vinen's original work in several ways. Measurements were made over a range of temperatures from 1.2 to 1.9\ifmmode^\circ\else\textdegree\fi{}K and a range of wire diameters from 25 to 100 \ensuremath{\mu}. In addition, measurements of the direction of the apparent circulation were made as well as of the magnitude. The experiments have two principal results. The first is that motion of the superfluid around the wire could persist for many hours after any motion of the containing vessel had stopped. However, this motion was not steady; smooth changes in apparent circulation could take place throughout an experimental run, changes which could include reversals in direction. The second principal result is that the apparent circulation tended to show markedly greater stability at the anticipated quantum levels than at other values. Long periods of stability were observed at the levels of 0, 1, 2, and 3 quantum units. An additional significant result is that as the wire diameter was increased the maximum value of metastable circulation observed also increased.

The electric strength of air. — VII

In view of the variation among the values obtained by different observers, this paper aims to make a careful determination of corona-forming voltages for alternating and for positive and negative continuous voltages in the same apparatus and under the same conditions. Within the range of wire diameters used, corona appears at a lower value when the wire is positive than when it is negative, although the two curves converge for increasing diameters. The maximum excess of negative over positive, as observed, was 6.3 per cent. The values with alternating voltage coincide with those of negative continuous voltage. Positive continuous voltage therefore forms corona at the lowest value. The observations on the negative corona give values higher than any heretofore obtained. Other experiments are described, giving qualitative indications of the correctness of Townsend's theory of ionization by collision.

The Electric Strength of Air.-VII

In view of the variation among the values obtained by different observers, this paper aims to make a careful determination of corona-forming voltages for alternating and for positive and negative continuous voltages in the same apparatus and under the same conditions. Within the range of wire diameters used, corona appears at a lower value when the wire is positive than when it is negative, although the two curves converge for increasing diameters. The maximum excess of negative over positive, as observed, was 6.3 per cent. The values with alternating voltage coincide with those of negative continuous voltage. Positive continuous voltage there-fore forms corona at the lowest value. The observations on the negative corona give values higher than any heretofore obtained. Other experiments are described, giving qualitative indications of the correctness of Townsend's theory of ionization by collision.