A Comparison of Fick and Maxwell-Stefan Diffusion Formulations in PEMFC Cathode Gas Diffusion Layers

This paper explores the mathematical formulations of Fick and Maxwell-Stefan diffusion in the context of polymer electrolyte membrane fuel cell cathode gas diffusion layers. Formulations of diffusion combined with mass-averaged Darcy flow are considered for three component gases. Fick formulations can be considered as approximations of Maxwell-Stefan in a certain sense. For this application, the formulations can be compared computationally in a simple, one dimensional setting. We observe that the predictions of the formulations are very similar, despite their seemingly different structure. Analytic insight is given to the result. In addition, it is seen that for both formulations, diffusion laws are small perturbations from bulk flow. The work is also intended as a reference to multi-component gas diffusion formulations in the fuel cell setting.Comment: 12 pages, submitted to the Journal of Power Source

Second-Order Convergence of a Projection Scheme for the Incompressible Navier–Stokes Equations with Boundaries

A rigorous convergence result is given for a projection scheme for the Navies–Stokes equations in the presence of boundaries. The numerical scheme is based on a finite-difference approximation, and the pressure is chosen so that the computed velocity satisfies a discrete divergence-free condition. This choice for the pressure and the particular way that the discrete divergence is calculated near the boundary permit the error in the pressure to be controlled and the second-order convergence in the velocity and the pressure to the exact solution to be shown. Some simplifications in the calculation of the pressure in the case without boundaries are also discussed

What Are the Barriers Which Discourage 15-16 Year-Old Girls from Participating in Team Sports and How Can We Overcome Them?

Given the clear benefits of regular physical activity (such as reduced risks of cardiovascular disease and obesity, as well as other benefits including those related to mental health), exploration of the reasons that adolescent girls give for not taking part in team sports may be particularly valuable for enhancing later rates of participation. We combined questionnaires and semistructured interviews to assess the barriers that prevent 15-16-year-old girls from participating in extracurricular team games and what can be done to overcome these barriers and improve physical activity levels. Four barriers became prominent as to why girls in this sample do not participate: Internal Factors, Existing Stereotypes, Other Hobbies and Teachers. Methods to overcome these barriers were identified; changing teachers’ attitudes and shifting the media’s focus away from male sport. Following the successful summer Olympics and Paralympics in the UK, and the resulting positive focus on some of the nation’s female athletes, a shift in focus may be possible. However, this needs to be maintained to allow girls more opportunities, role models and motivation to participate in sport

A proposal for a development platform for microcontroller-based devices

This thesis is concerned with designing, implementing and testing a miniaturised temperature data logging device. Investigations demonstrated that a microcontroller could provide a low-cost single-chip solution to this problem and after a detailed review of 8-bit microcontrollers, the MC68HCll was chosen for this task. This document also includes discussion on an environment that was developed for creating and testing MC68HC11 software and the use of Motorola\u27s evaluation boards. To ensure that the device was designed to software engineering standards an investigation into software engineering analysis techniques took place. This resulted in the Jackson Structured Programming (JSP) methodology being adapted to produce a proposed development platform suitable for microcontroller-based design

Stable Fourth Order Stream-Function Methods for Incompressible Flows with Boundaries

Fourth-order stream-function methods are proposed for the time dependent, incompressible Navier-Stokes and Boussinesq equations. Wide difference stencils are used instead of compact ones and the boundary terms are handled by extrapolating the stream-function values inside the computational domain to grid points outside, up to fourth-order in the noslip condition. Formal error analysis is done for a simple model problem, showing that this extrapolation introduces numerical boundary layers at fifth-order in the stream-function. The fourth-order convergence in velocity of the proposed method for the full problem is shown numerically

Aspects of the biology of a house sparrow (Passer domesticus) colony

Morphological, biochemical and minisatellite DNA variation was investigated at the colour ringed Brackenhurst House Sparrow population. Measurements and blood samples were collected from 584 nestlings and 692 other birds between 1985 and 1989. Six loci (6PGD, IDH, PEPD2, PEPD3, PEPT and transferrin) which had been the subject of a previous report (Burke, 1984) were investigated by starch gel electrophoresis. All followed Mendelian inheritance patterns, were in Hardy Weinberg equilibria and displayed temporal stability in allele frequencies. No evidence was found of the previously reported segregation distortion at PEPD3 and transferrin but artefact bands were encountered when scoring the latter. Family groups identified by observing colour ringed adults during feeding visits were examined using both enzyme and minisatellite DNA markers. Z chromosome linkage of several fingerprint bands was implicated, though most segregate independently. The probability of detecting an extra-pair fertilization was estimated as 0.5454 using starch gels and 0.9998 by fingerprinting. 51 out of 420 nestlings from 144 broods possessed several bands absent from the attendants' fingerprints. All nestlings with multiple mismatches shared many bands with the attendant female but a number consistent with band sharing between unrelateds with the male, i.e. nonparentage, was the result of cuckoldry. 24% of broods and 37% of males were affected. A correlation between the presence of extra-pair offspring and poor hatching success was noted. Cuckoldry was twice as successful in broods which contained infertile eggs. Metric variation was examined in the confirmed families. Significant heritabilities were demonstrated for weight, tarsus and tail length but environmentally induced variance was considerable. Yearlings were smaller than full adults in plumage length. This may be due to levels of protein reserves at critical growth periods. Some evidence of assortative mating for tail length was found which was unrelated to age associated changes

A predictive hazard perception paradigm differentiates driving experience cross-culturally

Hazard perception (HP) tests are used in several developed countries as part of the driver licensing process, where they are believed to have improved road safety; however, relatively little HP research has been conducted in developing countries, which account for 80% of the world’s road fatalities. Previous research suggests that drivers in these countries may be desensitized to hazardous road situations and thus have increased response latencies to hazards, creating validity issues with the typical HP reaction time paradigm. The present study compared Malaysian and UK drivers’ HP skills when watching video clips filmed in both countries, using a predictive paradigm where hazard criterion could not affect performance. Clips filmed in the UK successfully differentiated experience in participants from both countries, however there was no such differentiation in the Malaysian set of videos. Malaysian drivers also predicted hazards less accurately overall, indicating that exposure to a greater number of hazards on Malaysian roads did not have a positive effect on participants’ predictive hazard perception skill. Nonetheless the experiential discrimination noted in this predictive paradigm may provide a practical alternative for hazard perception testing in developing countries

Defining end user requirements for a field-based molecular detection system for wildlife forensic investigations

The increasing use of non-laboratory-based DNA and protein detection methods promise to provide rapid investigative intelligence and support sample prioritisation. Primarily developed for human forensic or medical applications, current systems may also show utility in the field of wildlife forensic science. However, it is currently unknown whether the requirements of the wildlife forensic community can be met by current non-laboratory based tools. Given the diverse array of stakeholders and sample types commonly encountered, it is necessary to first identify the needs of the community and then try and map their needs to current instrumentation. By using a market research style questionnaire, this study identified key requirements for a non-laboratory-based system following feedback from the wildlife forensic community. Data showed that there is strong support for field-based detection methods while highlighting concerns including contamination risks and reduced quality assurance associated with non-laboratory testing. Key species and applications were identified alongside hurdles to implementation and adoption. Broadly, the requirements align with many of the developmental drivers that have led to the rise of in-field portable detection instrumentation, specifically rapid detection within one hour, ease-of-use, and ≥95% accuracy. Several existing platforms exist that met some of the identified requirements but not all. With further collaboration between industry partners and the wildlife forensic community it is possible that new field-based systems can be developed and applied routinely