A two-phase flow model for hydrogen evolution in an electrochemical cell

Hydrogen evolution, flow field and current density distribution in an electrochemical cell are investigated with a two-phase flow model. The mathematical model involves solutions of transport equations for the variables of each phase with allowance for inter-phase transfer of mass and momentum. The buoyancy force generated due to density difference between two phases modifies flow profile and increases fluid velocity at the vicinity of the electrode. The current density decreases over the electrode mainly because of the decrease in effective conductivity of electrolyte. It is found that the hydrogen generation significantly increases at higher electrolyte flow by reducing the residence time of bubbles over the electrode. The predicted results satisfactorily agree with data available in the literature.National Science FoundationThe Authors would like to acknowledge the financial support from TUBITAK of Turkey and the National Science Foundation (NSF) of the USA through the US-Turkey Cooperative Research Agreement under Contract number MISAG-NSF-4

2Mm Catheter Design For Endoscopic Optical Coherence Tomography

A biophotonics catheter was conceived with collimation optics, an axicon lens, and custom design imaging optics yielding a 360 degree scan aimed at imaging within concave structures such as arteries and lung lobes. The large depth of focus is necessary to image a long-depth-range sample with constant transverse resolution in optical coherence tomography (OCT). There are two approaches to achieving constant invariant resolution in OCT: Dynamic focusing or Bessel beam formation. This paper focuses on imaging with Bessel beams. The Bessel beams may be created with axicon optics which can be used instead of a conventional focusing lens in the sample arm of the OCT interferometer. In this paper we present the design of a 2mm catheter for optical coherence endoscopy with resolution of about 5 micron across a depth of focus of about 1.6mm. Importantly, we investigated the fabrication of a 800μm diameter axicon lens and the associated lateral resolution obtained over a long depth range in our OCT system, compared to the same OCT system using a conventional lens. © 2006 SPIE-OSA