An effective mesh strategy for CFD modelling of polymer electrolyte membrane fuel cells

Computational fluid dynamics (CFD) is a major tool in PEM fuel cell research. Typical three-dimensional PEM fuel cell models involve more than 106 mesh elements. This makes the computation very intense and necessitates a methodology to mesh the computational domain that can keep the number of elements to a minimum while maintaining good accuracy. In this study, the effect of computational mesh in each direction on the accuracy of the solution is investigated in a systematic way. It is found that the mesh in different directions has a different degree of influence on the solution suggesting that the mesh in one direction can be coarser than the other. The proposed mesh strategy is capable of greatly reducing the number of mesh elements, hence computation time, while preserving the characteristics of important flow-field variables. Moreover, it is applicable to a wide range of cell sizes and flow-field configurations and should be used as a guideline for mesh generation

Transient performance investigation of different flow-field designs of automotive polymer electrolyte membrane fuel cell (PEMFC) using computational fluid dynamics (CFD)

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.Transient performance of a polymer electrolyte membrane (PEM) fuel cell in terms of the time-dependent current density profile that responds to the varying cell potential is of critical importance for an automotive PEM fuel cell. A step change in cell potential is applied to the cell terminals to simulate a sudden change in load demand due to an engine startup or very high acceleration. The transient responses of the three most commonly used flow-fields, namely, parallel, single-serpentine, and interdigitated designs in terms of the magnitude of current overshoot and time taken to adjust to the new equilibrium state are compared. The results suggest the serpentine flow-field outperforms its two counterparts as it balances the satisfactory transient performance with an expense of acceptable pressure drop across the cell and hence it is the most appropriate design to be used in automotive PEM fuel cells.dc201

Motivations and barriers to uptake and use of female-initiated, biomedical HIV prevention products in sub-Saharan Africa: an adapted meta-ethnography

Abstract: Background: Women bear a disproportionate burden of HIV throughout the world prompting extensive research into HIV prevention products for women which has met with varied success. With an aim of informing future policy and programming, this review examines the barriers and motivations to the uptake and use of female initiated products in sub-Saharan countries. Methods: We conducted a systematic review as an adapted meta-ethnography of qualitative data focused on actual use of products. After deduplication, 10,581 and 3861 papers in the first and second round respectively were screened. Following the PRISMA guidance, 22 papers were selected and synthesized using Malpass’s definitions of first, second, and third order constructs. First order constructs, consisting of participant data published in the selected papers, were extracted and categorised by second and third order constructs for analysis. A weight of evidence review was conducted to compare and assess quality across the papers. Results: The 22 papers selected span 11 studies in 13 countries. We derived 23 s order constructs that were translated into seven overarching third order constructs: Sexual Satisfaction, Trust, Empowerment and Control, Personal Well-being, Product use in the social-cultural environment, Practical Considerations, Risk Reduction, and Perceptions of Efficacy. Relationships and trust were seen to be as or more important for product use as efficacy. These constructs reveal an inherent inter-relationality where decision making around HIV prevention uptake and use cannot be binary or mono-faceted, but rather conducted on multiple levels. We developed a framework illustrating the central and proximal natures of constructs as they relate to the decision-making process surrounding the use of prevention products. Conclusions: Health systems, structural, and individual level HIV prevention interventions for women should adopt a holistic approach. Interventions should attend to the ways in which HIV prevention products can serve to reduce the likelihood of HIV transmission, as well as help to protect partnerships, enhance sexual pleasure, and take into account woman’s roles in the social environment. Stigma, as well as sexuality, is likely to continue to influence product uptake and use and should be prominently taken into account in large-scale interventions. Trial registration: Not applicable

Acceptability of an open-label wait-listed trial design: Experiences from the PROUD PrEP study

Background PROUD participants were randomly assigned to receive pre-exposure prophylaxis (PrEP) immediately or after a deferred period of one-year. We report on the acceptability of this open-label wait-listed trial design. Methods Participants completed an acceptability questionnaire, which included categorical study acceptability data and free-text data on most and least liked aspects of the study. We also conducted in-depth interviews (IDI) with a purposely selected sub-sample of participants. Results Acceptability questionnaires were completed by 76% (415/544) of participants. After controlling for age, immediate-group participants were almost twice as likely as deferred-group participants to complete the questionnaire (AOR:1.86;95%CI:1.24,2.81). In quantitative data, the majority of participants in both groups found the wait-listed design acceptable when measured by satisfaction of joining the study, intention to remain in the study, and interest in joining a subsequent study. However, three-quarters thought that the chance of being in the deferred-group might put other volunteers off joining the study. In free-text responses, data collection tools were the most frequently reported least liked aspect of the study. A fifth of deferred participants reported ‘being deferred’ as the thing they least liked about the study. However, more deferred participants disliked the data collection tools than the fact that they had to wait a year to access PrEP. Participants in the IDIs had a good understanding of the rationale for the open-label wait-listed study design. Most accepted the design but acknowledged they were, or would have been, disappointed to be randomised to the deferred group. Five of the 25 participants interviewed reported some objection to the wait-listed design. Conclusion The quantitative and qualitative findings suggest that in an environment where PrEP was not available, the rationale for the wait-listed trial design was well understood and generally acceptable to most participants in this study

Spending of HIV resources in Asia and Eastern Europe: systematic review reveals the need to shift funding allocations towards priority populations

Introduction: It is increasingly important to prioritize the most cost-effective HIV interventions. We sought to summarize the evidence on which types of interventions provide the best value for money in regions with concentrated HIV epidemics. Methods: We conducted a systematic review of peer-reviewed and grey literature reporting measurements of cost-effectiveness or cost-benefit for HIV/AIDS interventions in Asia and Eastern Europe. We also collated HIV/AIDS spending assessment data from case-study countries in the region. Results: We identified 91 studies for inclusion, 47 of which were from peer-reviewed journals. Generally, in concentrated settings, prevention of mother-to-child transmission programmes and prevention programmes targeting people who inject drugs and sex workers had lower incremental cost-effectiveness ratios than programmes aimed at the general population. The few studies evaluating programmes targeting men who have sex with men indicate moderate cost-effectiveness. Collation of prevention programme spending data from 12 countries in the region (none of which had generalized epidemics) indicated that resources for the general population/non-targeted was greater than 30% for eight countries and greater than 50% for five countries. Conclusions: There is a misalignment between national spending on HIV/AIDS responses and the most affected populations across the region. In concentrated epidemics, scarce funding should be directed more towards most-at-risk populations. Reaching consensus on general principles of cost-effectiveness of programmes by epidemic settings is difficult due to inconsistent evaluation approaches. Adopting a standard costing, impact evaluation, benefits calculation, analysis and reporting framework would enable cross comparisons and improve HIV resource prioritization and allocation.Andrew P Craig, Hla-Hla Thein, Lei Zhang, Richard T Gray, Klara Henderson, David Wilson, Marelize Gorgens, and David P Wilso