Effects of reactant crossover and electrode dimensions on the performance of a microfluidic based laminar flow fuel cell

A mathematical model is developed to simulate the performance of a laminar flow fuel cell with reactant crossover using the Poisson-Nernst-Plank (PNP) equations. The model includes a more general treatment of reactant (fuel or oxidant) crossover than the common method where it is assumed that the crossover flux is fully utilized as crossover current. This new model allows for the analysis of very narrow channels and estimation of parasitic crossover current at both the anode and the cathode. It also allows for the consideration of a laminar flow fuel cell with a significant amount of reactant crossover where the crossover species are not fully consumed by the crossover current. Moreover, the combination of the PNP equations and the general reactant crossover treatment reveal the two-dimensional developing region for electrode mixed potentials which is a novel result. The parameters considered in this study are electrode length and separation (channel height). Numerical results show that the reactant crossover, transport limitations, and Ohmic losses are the primary performance limitation factors. The current distributions along the anode and cathode are presented as well as the reactant concentrations at the anode as evidence of these performance limitations. It is also shown that the fluid velocity field, as it changes with channel height, plays a small role in the development of the depletion boundary layer.     

A 0.18-μm CMOS IA-32 processor with a 4-GHz integer executionunit

This paper describes the main features and functions of the Pentium(R) 4 processor microarchitecture. We present the front-end of the machine, including its new form of instruction cache called the trace cache, and describe the out-of-order execution engine, including a low latency double-pumped arithmetic logic unit (ALU) that runs at 4 GHz. We also discuss the memory subsystem, including the low-latency Level 1 data cache that is accessed in two clock cycles. We then describe some of the key features that contribute to the Pentium(R) 4 processor's floating-point and multimedia performance. We provide some key performance numbers for this processor, comparing it to the Pentium(R) III processor     

On the reticulation problem in multivariable control systems

The problem of reticulating (partitioning) a multivariable control problem is investigated. An iterative process is suggested, where each subprogram is solved successively under the conditions imposed by the solutions of the other subproblems through the interactions of the original control problem. For a special case, it is shown that the rate of convergence of this process is a function of how the reticulation is made. This yields a quantitative measure of reticulating which is then used to determine the optimal reticulation.     

Resealable Superfluid Valve

Recently it has been shown that Torlon may be used to construct a resealable superfluid bellows valve with a hard seat, soft stem configuration. We present a modification on this design incorporating a thin BeCu diaphragm to produce a valve having a dead volume of 0.02 cm ³. The valve may be actuated using a high pressure gas handling system or electrically using a sealed expansion volume.     

Spatialization design: comparing points and landscapes

Spatializations represent non-spatial data using a spatial layout similar to a map. We present an experiment comparing different visual representations of spatialized data, to determine which representations are best for a non-trivial search and point estimation task. Primarily, we compare point-based displays to 2D and 3D information landscapes. We also compare a colour (hue) scale to a grey (lightness) scale. For the task we studied, point-based spatializations were far superior to landscapes, and 2D landscapes were superior to 3D landscapes. Little or no benefit was found for redundantly encoding data using colour or greyscale combined with landscape height. 3D landscapes with no colour scale (height-only) were particularly slow and inaccurate. A colour scale was found to be better than a greyscale for all display types, but a greyscale was helpful compared to height-only. These results suggest that point-based spatializations should be chosen over landscape representations, at least for tasks involving only point data itself rather than derived information about the data space.