Failure mode and effect analysis, and fault tree analysis of polymer electrolyte membrane fuel cells

Hydrogen fuel cells have the potential to dramatically reduce emissions from the energy sector, particularly when integrated into an automotive application. However there are three main hurdles to the commercialisation of this promising technology; one of which is reliability. Current standards require an automotive fuel cell to last around 5000 h of operation (equivalent to around 150,000 miles), which has proven difficult to achieve to date. This hurdle can be overcome through in-depth reliability analysis including techniques such as Failure Mode and Effect Analysis (FMEA) and Fault Tree Analysis (FTA) amongst others. Research has found that the reliability field regarding hydrogen fuel cells is still in its infancy, and needs development, if the current standards are to be achieved. In this work, a detailed reliability study of a Polymer Electrolyte Membrane Fuel Cell (PEMFC) is undertaken. The results of which are a qualitative and quantitative analysis of a PEMFC. The FMEA and FTA are the most up to date assessments of failure in fuel cells made using a comprehensive literature review and expert opinion

Fault Tree Analysis of Polymer Electrolyte Fuel Cells to predict degradation phenomenon

Hydrogen Fuel Cells are an electro-chemical, zero-emission energy conversion and power generation device. Their only products are heat and electrical energy, and water vapour. One of the major hurdles to the uptake of this technology is the reliability of the fuel cell system. This hurdle can be overcome through in depth reliability analysis including Failure Mode and Effect Analysis (FMEA) and Fault Tree analysis (FTA) amongst others. Research has found that the reliability research area regarding hydrogen fuel cells is still in its infancy, and needs development. This paper looks at the current state of the art in reliability analysis regarding Polymer Electrolyte Fuel Cells (PEMFC). A recent fault tree (FT) from the literature is qualitatively analysed to ascertain its practicality in relation to PEMFC degradation analysis. The fault tree was found to harbour certain aspects that could be improved upon. There was no FMEA undertaken to precede the FT which would have given a greater understanding of the possible failure modes in a PEMFC system and their relationships. The FT was found to be lacking dependant relationships which are apparent in a PEMFC system. The data from the literature was also analysed to check its relevance in today’s fast moving PEMFC research. Conclusions are given to the way forward for future reliability evaluation of PEMFCs

Advanced reliability analysis of Polymer Electrolyte Membrane Fuel Cells using Petri-Net analysis and fuel cell modelling techniques

Reliability issues with fuel cells have held back the commercialisation of this new technology, and as such are required to be studied further. Current reliability standards for automotive applications require an operational life- time of 150,000 miles or 5,000 hours. These standards are hard to achieve; therefore in depth reliability analysis and degradation studies can help allude towards the key areas of improvement in fuel cell technology to meet these standards. Previous Failure Mode and Effect Analysis (FMEA) work has shown that the multi-component system of a Polymer Electrolyte Membrane Fuel Cell (PEMFC) is inherently complex. Dependencies exist between multiple failure modes which discounts Fault Tree Analysis (FTA) as a feasible reliability modelling technique. Therefore, in this study, Petri-Net simulation and fuel cell modelling techniques have been adopted to develop an accurate degradation model. Operational parameters such as water content, temperature and current density and their effects on the occurrence of failure modes can be modelled through this technique. The work will improve previous fuel cell reliability studies by taking into consideration; operating parameters (water content, temperature), fuel cell voltage based on demand (drive cycles) and dependencies between failure modes

Biotic and Abiotic Associations with Westslope Cutthroat Trout (Oncorhynchus clarkii lewisi) in the North Fork Flathead River Basin in northwestern Montana, USA and southeastern British Columbia, CAN under current and future climate scenarios.

Westslope Cutthroat Trout (Oncorhynchus clarkii lewisi; WCT) populations are declining across much of their native range due to threats such as habitat degradation, competition with non-native species, and climate change. Understanding how habitat characteristics impact distributions of nonhybridized WCT populations throughout a relatively pristine core conservation area is needed to inform management and conservation efforts. We investigated whether abiotic (e.g., gradient) and biotic (i.e., Bull Trout – Salvelinus confluentus) variables predicted WCT presence and predicted how future stream temperature projections for the area might be expected to alter distributions. We compared logistic regression models of WCT presence throughout tributaries of the North Fork Flathead River in Montana, USA and British Columbia, CAN models using a variety of metrics (e.g., Akaike Information Criterion). WCT were widespread throughout the 293 reaches analyzed (present in 69.3% of reaches). Their presence was predicted by gradient, summer temperature, and an interaction of pool density and Bull Trout. Using this regression model and climate projections under both moderate and extreme emissions scenarios, WCT presence is predicted to increase by 13.0% and 14.1% respectively in 2075 from current distributions based on changes in temperature alone. When changes in Bull Trout distributions and temperatures are considered, WCT distributions are predicted to increase by 13.4% and 17.5% under the moderate and high emissions scenario, respectively. This conservation area is predicted to continue to serve as a WCT stronghold, if other threats can be contained

Targets for Transformation: a strategic plan for the Syracuse University Library, 2000-2005

A strategic plan is a tool that enables an organization to revitalize itself and focus on a set of mission-critical goals over a period of time. A well-crafted plan intentionally implemented and consistently monitored promotes success in strategic areas and provides a foundation for transforming services, technology, collections, and infrastructure to meet the constantly evolving needs and demands of teaching, research, and scholarly communication. A strategic plan: articulates commonly held values and a shared sense of purpose and mission proposes goals and assesses progress to those goals informs decision-making enables action within a larger context that is known and understood by all establishes a continuous planning process A strategic plan is a starting point in an ongoing process. The Syracuse University Library strategic plan, “Targets for Transformation: a strategic plan for the Syracuse University Library, 2000-2005” was submitted to University Librarian Peter Graham in July 2000. According to Graham, a strategic plan was necessary “to shape our University’s future information services and environment.” The Library undertook a strategic planning process to enhance its effectiveness within the University’s intellectual and cultural life. The planning process began in July 1999 with a Library management team retreat, focused on understanding the planning process, identifying aspirations, establishing planning assumptions, and conducting an environmental scan. In August 1999 the Library held staff town meetings based on two questions: 1) in 2004, what do we want our users to say about the Library? and 2) in 2004, what do we want to say about the Library

Advanced reliability analysis of Polymer Electrolyte Membrane Fuel Cells using Petri-Net analysis and fuel cell modelling techniques

This is the author’s version of a work that was accepted for publication in International Journal of Hydrogen Energy. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published at: http://dx.doi.org/10.1016/j.ijhydene.2015.01.154Reliability issues with fuel cells have held back the commercialisation of this new technology, and as such are required to be studied further. Current reliability standards for automotive applications require an operational life- time of 150,000 miles or 5,000 hours. These standards are hard to achieve; therefore in depth reliability analysis and degradation studies can help allude towards the key areas of improvement in fuel cell technology to meet these standards. Previous Failure Mode and Effect Analysis (FMEA) work has shown that the multi-component system of a Polymer Electrolyte Membrane Fuel Cell (PEMFC) is inherently complex. Dependencies exist between multiple failure modes which discounts Fault Tree Analysis (FTA) as a feasible reliability modelling technique. Therefore, in this study, Petri-Net simulation and fuel cell modelling techniques have been adopted to develop an accurate degradation model. Operational parameters such as water content, temperature and current density and their effects on the occurrence of failure modes can be modelled through this technique. The work will improve previous fuel cell reliability studies by taking into consideration; operating parameters (water content, temperature), fuel cell voltage based on demand (drive cycles) and dependencies between failure modes

Distress and satisfaction with research participation: Impact on retention in longitudinal disaster research

© 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/BY-NC-ND/4.0/).Previous studies of the impact of post-trauma research participation indicate that while the research experience may be emotional, it can still be valued by participants. This paper describes participant experiences of the Australian post-bushfire research study–Beyond Bushfires. It examines the relationships between distress during research participation, probable mental health conditions, and satisfaction with the research experience over time. A range of strategies was incorporated into the study, including a distress and risk assessment and referral protocol, to minimise any risk of harm for people who had experienced the 2009 bushfires and their aftermath. Participants included 1056 respondents (Wave 1) interviewed via telephone and web-based survey between December 2011 through January 2013, and 736 (76.1%) of the participants were re-surveyed between July and November 2014 (Wave 2). Research impact was monitored through two questions about survey experience on each occasion. Reported distress at completing the survey was generally low, while overall satisfaction was relatively high. Participants’ reported satisfaction was not associated with their reported level of distress as a result of the survey; and reported participation distress at Wave 1 did not predict whether a respondent would return to complete the survey at Wave 2. Fire-related Posttraumatic stress symptoms were associated with increased satisfaction and likelihood to return at Wave 2. These findings suggest that for Beyond Bushfires survey respondents the perceived benefits outweighed the costs of participation over time

Risk of intracerebral haemorrhage with alteplase after acute ischaemic stroke : a secondary analysis of an individual patient data meta-analysis

Background Randomised trials have shown that alteplase improves the odds of a good outcome when delivered within 4.5 h of acute ischaemic stroke. However, alteplase also increases the risk of intracerebral haemorrhage; we aimed to determine the proportional and absolute effects of alteplase on the risks of intracerebral haemorrhage, mortality, and functional impairment in different types of patients. Methods We used individual patient data from the Stroke Thrombolysis Trialists' (STT) meta-analysis of randomised trials of alteplase versus placebo (or untreated control) in patients with acute ischaemic stroke. We prespecified assessment of three classifications of intracerebral haemorrhage: type 2 parenchymal haemorrhage within 7 days; Safe Implementation of Thrombolysis in Stroke Monitoring Study's (SITS-MOST) haemorrhage within 24-36 h (type 2 parenchymal haemorrhage with a deterioration of at least 4 points on National Institutes of Health Stroke Scale [NIHSS]); and fatal intracerebral haemorrhage within 7 days. We used logistic regression, stratified by trial, to model the log odds of intracerebral haemorrhage on allocation to alteplase, treatment delay, age, and stroke severity. We did exploratory analyses to assess mortality after intracerebral haemorrhage and examine the absolute risks of intracerebral haemorrhage in the context of functional outcome at 90-180 days. Findings Data were available from 6756 participants in the nine trials of intravenous alteplase versus control. Alteplase increased the odds of type 2 parenchymal haemorrhage (occurring in 231 [6.8%] of 3391 patients allocated alteplase vs 44 [1.3%] of 3365 patients allocated control; odds ratio [OR] 5.55 [95% CI 4.01-7.70]; absolute excess 5.5% [4.6-6.4]); of SITS-MOST haemorrhage (124 [3.7%] of 3391 vs 19 [0.6%] of 3365; OR 6.67 [4.11-10.84]; absolute excess 3.1% [2.4-3.8]); and of fatal intracerebral haemorrhage (91 [2.7%] of 3391 vs 13 [0.4%] of 3365; OR 7.14 [3.98-12.79]; absolute excess 2.3% [1.7-2.9]). However defined, the proportional increase in intracerebral haemorrhage was similar irrespective of treatment delay, age, or baseline stroke severity, but the absolute excess risk of intracerebral haemorrhage increased with increasing stroke severity: for SITS-MOST intracerebral haemorrhage the absolute excess risk ranged from 1.5% (0.8-2.6%) for strokes with NIHSS 0-4 to 3.7% (2.1-6.3%) for NIHSS 22 or more (p=0.0101). For patients treated within 4.5 h, the absolute increase in the proportion (6.8% [4.0% to 9.5%]) achieving a modified Rankin Scale of 0 or 1 (excellent outcome) exceeded the absolute increase in risk of fatal intracerebral haemorrhage (2.2% [1.5% to 3.0%]) and the increased risk of any death within 90 days (0.9% [-1.4% to 3.2%]). Interpretation Among patients given alteplase, the net outcome is predicted both by time to treatment (with faster time increasing the proportion achieving an excellent outcome) and stroke severity (with a more severe stroke increasing the absolute risk of intracerebral haemorrhage). Although, within 4.5 h of stroke, the probability of achieving an excellent outcome with alteplase treatment exceeds the risk of death, early treatment is especially important for patients with severe stroke.Peer reviewe

Effects of alteplase for acute stroke according to criteria defining the European Union and United States marketing authorizations : Individual-patient-data meta-analysis of randomized trials

Background The recommended maximum age and time window for intravenous alteplase treatment of acute ischemic stroke differs between the Europe Union and United States. Aims We compared the effects of alteplase in cohorts defined by the current Europe Union or United States marketing approval labels, and by hypothetical revisions of the labels that would remove the Europe Union upper age limit or extend the United States treatment time window to 4.5h. Methods We assessed outcomes in an individual-patient-data meta-analysis of eight randomized trials of intravenous alteplase (0.9mg/kg) versus control for acute ischemic stroke. Outcomes included: excellent outcome (modified Rankin score 0-1) at 3-6 months, the distribution of modified Rankin score, symptomatic intracerebral hemorrhage, and 90-day mortality. Results Alteplase increased the odds of modified Rankin score 0-1 among 2449/6136 (40%) patients who met the current European Union label and 3491 (57%) patients who met the age-revised label (odds ratio 1.42, 95% CI 1.21-1.68 and 1.43, 1.23-1.65, respectively), but not in those outside the age-revised label (1.06, 0.90-1.26). By 90 days, there was no increased mortality in the current and age-revised cohorts (hazard ratios 0.98, 95% CI 0.76-1.25 and 1.01, 0.86-1.19, respectively) but mortality remained higher outside the age-revised label (1.19, 0.99-1.42). Similarly, alteplase increased the odds of modified Rankin score 0-1 among 1174/6136 (19%) patients who met the current US approval and 3326 (54%) who met a 4.5-h revised approval (odds ratio 1.55, 1.19-2.01 and 1.37, 1.17-1.59, respectively), but not for those outside the 4.5-h revised approval (1.14, 0.97-1.34). By 90 days, no increased mortality remained for the current and 4.5-h revised label cohorts (hazard ratios 0.99, 0.77-1.26 and 1.02, 0.87-1.20, respectively) but mortality remained higher outside the 4.5-h revised approval (1.17, 0.98-1.41). Conclusions An age-revised European Union label or 4.5-h-revised United States label would each increase the number of patients deriving net benefit from alteplase by 90 days after acute ischemic stroke, without excess mortality.Peer reviewe

Impact of vaccination on the association of COVID-19 with cardiovascular diseases:An OpenSAFELY cohort study

Infection with SARS-CoV-2 is associated with an increased risk of arterial and venous thrombotic events, but the implications of vaccination for this increased risk are uncertain. With the approval of NHS England, we quantified associations between COVID-19 diagnosis and cardiovascular diseases in different vaccination and variant eras using linked electronic health records for ~40% of the English population. We defined a 'pre-vaccination' cohort (18,210,937 people) in the wild-type/Alpha variant eras (January 2020-June 2021), and 'vaccinated' and 'unvaccinated' cohorts (13,572,399 and 3,161,485 people respectively) in the Delta variant era (June-December 2021). We showed that the incidence of each arterial thrombotic, venous thrombotic and other cardiovascular outcomes was substantially elevated during weeks 1-4 after COVID-19, compared with before or without COVID-19, but less markedly elevated in time periods beyond week 4. Hazard ratios were higher after hospitalised than non-hospitalised COVID-19 and higher in the pre-vaccination and unvaccinated cohorts than the vaccinated cohort. COVID-19 vaccination reduces the risk of cardiovascular events after COVID-19 infection. People who had COVID-19 before or without being vaccinated are at higher risk of cardiovascular events for at least two years.</p