Conical tips

An approximate model of the ISE can be developed with the aid of Figure 2.9. This figure shows a schematic cylindrical indenter with a conical tip being pushed into a specimen. The plastic zone is approximated by a segment of a sphere, and the diameter of the indent is 2r. The yield stress is Y, and the friction coefficient is a. 

Fig. 4.14 Carbon nanohorns with hydrogen condensed at the end of conical tip (a) agglomerate to form nanocarbon particles that exhibit rosette shape (b) TEM image credit http //www.phys-ics.siu.edu/migone/lab/carbon nanohoms.htm...

A pin corona discharge device consists of a stainless steel rod with a sharp conical tip as the corona emitter, a brass hollow cylinder as the corona case, and a perspex cup as the corona holder. Experimental results show that the pin corona current distribution is not uniform, which is one disadvantage of a pin corona device. 

Figure 14. The SECM approach curves for a conical tip geometry (a) positive feedback, (b) negative feedback. H is the ratio of the height to the base radius, H = hja. Adapted with permission from Ref. [13]. Copyright 2004, American Chemical Society.

Fig. 7.18 Mini-laparoscopy equipment (1.) trocar sleeve, 0 5.5 mm, with insufflation tap and magnetic-ball valve (2.) trocar, conical tip (i.) mini fibre laparoscope, 0 2 mm, angle of view 0°, working length 270 mm (4.) Veres cannula, 0 2.3 mm, with outer sheath, working length 270 mm. (autoclavable)...

Figure 1.8 A tiny plug of liquid in the conical tip of a pipette.

One of the variants of the technique involves a pendent drop on a conical tip. The reason for experimenting with this geometry is to reduce drop vibrations, always a source of error if high accuracy is required. Sessile drops and pendent drops on inclined surfaces have been investigated by Nguyen et al. ) and by Lawal and Brown ), respectively. For such systems the drops are no longer axis)rm-metric. 

FIG. 16 Schematic diagrams of thin layer cells formed by a spherical segment tip and a planar substrate (A) and by a conical tip and a planar substrate (B). (Reprinted with permission from Ref. 27. Copyright 1992 Elsevier.)... 

One can see that the different working curves have substantially different curvatures, thus a unique curve can be found to obtain the best ht with the experimental data. One can also see that the current for a conical tip tends to reach some limiting values as L — 0 and as k — 0, the working curves for a conical tip approach that computed for a disk-shaped tip. 

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