Design methodology for barrier‐based two phase flow distributor

The barrier‐based distributor is a multiphase flow distributor for a multichannel microreactor which assures flow uniformity and prevents channeling between the two phases. For N number of reaction channels, the barrier‐based distributor consists of a gas manifold, a liquid manifold, N barrier channels for the gas, N barrier channels for the liquid, and N mixers for mixing the phases before the reaction channels. The flow distribution is studied numerically using a method based on the hydraulic resistive networks (RN). The single phase hydraulic RN model (Commenge et al., 2002;48:345–358) is extended for two phases gas‐liquid Taylor flow. For Re_GL <30, the accuracy for the model was above 90%. The developed‐model was used to study the effects of fabrication tolerance and barrier channel dimensions. A design methodology has been proposed as an algorithm to determine the required hydraulic resistance in the barrier channels and their dimensions. This methodology is demonstrated using a numerical example. © 2012 American Institute of Chemical Engineers AIChE J, 2012     

Characterisation of Fuel Cell Membranes as a Function of Drying by Means of Contact Angle Measurements

In another paper in this volume, it is demonstrated that the electrochemical interface in MEAs, and thus the polarization performance of the resulting fuel cells, can be improved by optimising the hot‐pressing procedure in the MEA preparation. In particular, the extent of drying of the membrane during MEA preparation was shown to be critical. In the present investigation, the effect of the drying process, and thus water content, on the hydrophilicity, wetting, and surface energies of some fuel cell membranes is examined. Wetting and surface energies are well known to influence the bonding behaviour of materials. Conclusions about how membrane drying and changes in water content influence membrane bonding and the relative importance of these surface effects are drawn.     

Synthesis and Structure of Hg1−xCrxSr2CuO4+δ Mercurocuprates

We report preliminary results concerning the synthesis and structural characterisation of the chromium stabilised 1201 phases: Hg_1?xCr_xSr₂CuO_4+δ. A systematic study of the formation of phases in this system has been undertaken, together with a combined powder neutron and synchrotron x-ray diffraction study, to address the issue of chromium clustering and ordering in this system.     

Fluorination of Underdoped Mercurocuprate Superconductors

We present the results of a study into the incorporation of fluorine into the mercurocuprate superconductors. In all cases, the effect of fluorination has been to increase the T_c of underdoped superconductors to the maxima reported. This has important ramifications for the role of the interstitial oxygen in the mercurocuprate superconductors. To assist us in our study, we have, additionally, developed a novel synthetic procedure for preparing HgBa₂CuO₄₊ in a highly underdoped state. Remarkably, this material shows an increase in T_c, upon fluorination, of 60K!     

Integrating perceptual level of detail with head-pose estimation and its uncertainty

Immersive virtual environments with life-like interaction capabilities can provide a high fidelity view of the virtual world and seamless interaction methods to the user. High demanding requirements, however, raise many challenges in the development of sensing technologies and display systems. The focus of this study is on improving the performance of human–computer interaction by rendering optimizations guided by head pose estimates and their uncertainties. This work is part of a larger study currently being under investigation at NASA Ames, called “Virtual GloveboX” (VGX). VGX is a virtual simulator that aims to provide advanced training and simulation capabilities for astronauts to perform precise biological experiments in a glovebox aboard the International Space Station (ISS). Our objective is to enhance the virtual experience by incorporating information about the user’s viewing direction into the rendering process. In our system, viewing direction is approximated by estimating head orientation using markers placed on a pair of polarized eye-glasses. Using eye-glasses does not pose any constraints in our operational environment since they are an integral part of a stereo display used in VGX. During rendering, perceptual level of detail methods are coupled with head-pose estimation to improve the visual experience. A key contribution of our work is incorporating head pose estimation uncertainties into the level of detail computations to account for head pose estimation errors. Subject tests designed to quantify user satisfaction under different modes of operation indicate that incorporating uncertainty information during rendering improves the visual experience of the user.     

Autonomous Self‐Healing of Epoxy Thermosets with Thiol‐Isocyanate Chemistry

Thiol‐isocyanate chemistry, combined with a dual capsule strategy, is used for the development of extrinsic self‐healing epoxy materials. It is shown that the amine groups present in the matrix both serve as a catalyst for the addition reaction between a thiol and an isocyanate and as a way to covalently link the healed network structure to the surrounding resin. The tapered double cantilever beam (TDCB) geometry is used for evaluating the recovery of the fracture toughness at room temperature after different healing times. Using manual injection of the healing agents into the crack, a healing efficiency up to 130% is obtained for the EPIKOTE 828/DETA epoxy material. On the other hand, when two types of microcapsules, one containing a tetrathiol reagent and the other a low toxic isocyanate reagent, are incorporated into this epoxy thermoset (20 wt%), a recovery of more than 50% is reached. The influence of parameters such as the amount and core content of the microcapsules on the healing efficiency is investigated. Furthermore, the thiol‐isocyanate chemistry is also tested for an industrial cold‐curing epoxy resin (RIM 135/RIMH 137).     

Scanning electron microscopy of cyclosporine-induced gingival overgrowth

Overgrown human gingival specimens were examined histologically and by scanning electron microscopy (SEM) to study structural changes caused by cyclosporine. The biopsy specimens were from organ transplant recipients receiving cyclosporine to suppress the rejection of the transplanted organ. The epithelium of the overgrown gingiva was thickened, acanthotic and parakeratotic. Retepegs were anastomosing and extending into connective tissue. The SEM examination of the outer surface of the attached gingival showed loss of cellular attachments and cells were exfoliating. The normal honeycomb structure formed by interconnecting microvilli surrounding the pits was distorted. Outer gingival cell surface showed numerous round, ovoid and dome-like structures instead of parallel, reticular or fingerprint-like microridges. It was concluded that cyclosporine not only caused hyperplasia but also changed the structure of the outer epithelial cell surface.