Nonlinear model predictive control methodology for efficiency and durability improvement in a fuel cell power system

The main contribution of this work is the improvement of the efficiency of a PEMFC power system while guaranteeing conditions that also improve its durability. Adopting the NMPC scheme with the distributed parameter model and the nonlinear observer, the efficiency of the PEMFC-based system can be maximized guaranteeing at the same time the appropriate internal gas concentration profiles to avoid global and local hydrogen and oxygen starvation and proper membrane humidification.Peer ReviewedPostprint (author's final draft

Social preferences in bargaining games

In einer Vielzahl von Experimenten erwies sich, dass eine signifikante Zahl von Entscheidungsträgern sich nicht wie der üblicherweise angenommene Homo Oeconomicus verhält. Diese Arbeit untersucht, vor allem anhand des Ultimatum Spiels, verschiedene Modelle sozialer Präferenzen: Ungleichheitsaversion, Reziprozität sowie Modelle, die beide Prinzipien vereinen. Ungleichheitsaversionsmodelle haben eine simple Struktur und sind leicht anzuwenden. Das Fehr-Schmidt Modell (1999) ist dem Bolton-Ockenfels Modell (2000) meist vorzuziehen. Beide können aber nicht alle beobachteten Phänomene erklären, weil sie die Rolle von Intentionen vernachlässigen. Modelle, die auf Reziprozität basieren, modellieren explizit wie Menschen auf wahrgenommene Intentionen reagieren. Dies ist, von einem psychologischen Standpunkt betrachtet, schlüssiger, birgt aber den Nachteil größerer Komplexität der Modelle und multipler Gleichgewichte. Doch auch reine Reziprozitäts-Modelle können das in Experimenten beobachtete Verhalten nicht vollständig erklären. Die höchste Erklärungsrelevanz erzielen Modelle, die sowohl distributive Aspekte als auch aus Aktionen abgeleitete Intentionen miteinbeziehen. Beispiele dafür sind das Falk und Fischbacher Modell (2006) sowie das Charness und Rabin Modell (2002). Beide überzeugen durch größere Vollständigkeit und psychologische Schlüssigkeit, sind aber ob ihrer hohen Komplexität in konkreten Spielen schwer anwendbar.Self-regarding preferences cannot always account for empirically observed behavior. Concerns for fairness seem to affect how people behave e.g. in bargaining games. This paper focuses on the ultimatum game and examines models of reciprocity, inequality aversion and models that combine intentional and distributional aspects. The Fehr and Schmidt model of inequality aversion (1999) is more accurate than the Bolton and Ockenfels model (2000), because it is often in line with minimax preferences. However, the concept of inequality aversion does not capture the whole story since it neglects the importance of perceived intentions. Reciprocity based models explicitly model people's reactions to infered intentions. Doing so is more intuitive from a psychological point of view, but on the other hand reduces the simplicity of the models and allows for multiple equilibria. Experimental testing shows that even (pure) reciprocity models cannot explain all the behavior empirically observed. A more complete model must combine distributional concerns and reciprocity motivation, as found in the Falk and Fischbacher model (2006) or the Charness and Rabin model (2002). They are most convincing in the context of completeness and psychological plausibility, but due to their highly complex structure they are hardly applicable to concrete game-theoretic situations

Nonlinear predictive control for durability enhancement and efficiency improvement in a fuel cell power system

© . This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/In this work, a nonlinear model predictive control (NMPC) strategy is proposed to improve the efficiency and enhance the durability of a proton exchange membrane fuel cell (PEMFC) power system. The PEMFC controller is based on a distributed parameters model that describes the nonlinear dynamics of the system, considering spatial variations along the gas channels. Parasitic power from different system auxiliaries is considered, including the main parasitic losses which are those of the compressor. A nonlinear observer is implemented, based on the discretised model of the PEMFC, to estimate the internal states. This information is included in the cost function of the controller to enhance the durability of the system by means of avoiding local starvation and inappropriate water vapour concentrations. Simulation results are presented to show the performance of the proposed controller over a given case study in an automotive application (New European Driving Cycle). With the aim of representing the most relevant phenomena that affects the PEMFC voltage, the simulation model includes a two-phase water model and the effects of liquid water on the catalyst active area. The control model is a simplified version that does not consider two-phase water dynamics.Peer ReviewedPostprint (author's final draft

Evaluation of the Dawson College shooting psychological intervention: moving toward a multimodal extensive plan

In 2006, following the shooting at Dawson College, the authorities implemented an intervention plan. This provided an opportunity to analyze the responses to services offered, and afforded a learning opportunity, which led to the proposal of an extensive multimodal short- and long-term psychological plan for future needs. Both quantitative and qualitative data were gathered 18 months after the event, involving the participation of 948 students and staff. Mental health problems and the perception of services offered after the shooting were investigated, using standardized measures. Second, focus groups and individual interviews were conducted among a subgroup of participants (support team members; teachers and employees; students and parents) and permitted to gather data on services received and services required. Individual report of events, the extent of psychological impact and services offered and received were analyzed in terms of the following dimensions: intervention philosophy, training, ongoing offer of services and finally, detection and outreach. A significant incidence of disorders and a high rate of exacerbation of preexisting mental disorders were observed within the 18 months following the shooting. Postimmediate and short-term intervention appeared adequate, but the long-term collective vision toward community support and availability of mental health services were lacking. Lessons learned from this evaluation and other school shootings suggest that preparedness and long-term community responses are often overlooked. A multimodal extensive plan is proposed based on a theoretical model from which interventions strategies could be drawn

Proton exchange membrane fuel cell degradation prediction based on Adaptive Neuro-Fuzzy Inference Systems .

International audienceThis paper studies the prediction of the output voltage reduction caused by degradation during nominal operating condition of a PEM fuel cell stack. It proposes a methodology based on Adaptive Neuro-Fuzzy Inference Systems (ANFIS) which use as input the measures of the fuel cell output voltage during operation. The paper presents the architecture of the ANFIS and studies the selection of its parameters. As the output voltage cannot be represented as a periodical signal, the paper proposes to predict its temporal variation which is then used to construct the prediction of the output voltage. The paper also proposes to split this signal in two components: normal operation and external perturbations. The second component cannot be predicted and then it is not used to train the ANFIS. The performance of the prediction is evaluated on the output voltage of two fuel cells during a long term operation (1000 hours). Validation results suggest that the proposed technique is well adapted to predict degradation in fuel cell systems

Analyse des mécanismes de dégradation dans un système pile à combustible

International audienceLes systèmes pile à combustible (SPàC) sont considérés comme une solution viable et une alternative prometteuse autant pour des applications embarquées que stationnaires. Cela dit, ces systèmes doivent répondre à des critères essentiels à leur large développement, à savoir, coût, durabilité et fiabilité. Le présent travail se focalise sur l’aspect fiabilité du système pile à combustible. En effet, une meilleure compréhension des mécanismes de dégradation dans le SPàC permettra de développer les stratégies nécessaires à la réduction des dégradations au sein du SPàC et augmenter sa durée de vie utile. Une analyse des mécanismes de dégradation et leurs effets au niveau du SPàC a été faite dans le but de construire un arbre de défaillances le plus complet possible. Le SPàC étudié comprend le stack (membrane, couche catalytique, plaques bipolaires, couche de diffusion des gaz) le système d’alimentation en air (compresseur, capteurs, régulateurs, électrovannes), le système d’alimentation en hydrogène (capteurs, régulateurs, électrovannes) et le système de refroidissement (pompe de circulation, capteurs, électrovannes, régulateurs). Cette étude permettra de déduire les lois de propagation des défauts dans le SPàC qui permettront une meilleure estimation de sa durée de vie

Electrophysiological correlates of the brain-derived neurotrophic factor (BDNF) Val66Met polymorphism

The brain-derived neurotrophic factor (BDNF) protein is essential for neuronal development. Val66Met (rs6265) is a functional polymorphism at codon 66 of the BDNF gene that affects neuroplasticity and has been associated with cognition, brain structure and function. The aim of this study was to clarify the relationship between BDNF Val66Met polymorphism and neuronal oscillatory activity, using the electroencephalogram (EEG), in a normative cohort. Neurotypical (N = 92) young adults were genotyped for the BDNF Val66Met polymorphism and had eyes open resting-state EEG recorded for four minutes. Focal increases in right fronto-parietal delta, and decreases in alpha-1 and right hemispheric alpha-2 amplitudes were observed for the Met/Met genotype group compared to Val/Val and Val/Met groups. Stronger frontal topographies were demonstrated for beta-1 and beta-2 in the Val/Met group versus the Val/Val group. Findings highlight BDNF Val66Met genotypic differences in EEG spectral amplitudes, with increased cortical excitability implications for Met allele carriers

Advancing research for seamless Earth system prediction

Whether on an urban or planetary scale, covering time scales of a few minutes or a few decades, the societal need for more accurate weather, climate, water, and environmental information has led to a more seamless thinking across disciplines and communities. This challenge, at the intersection of scientific research and society’s need, is among the most important scientific and technological challenges of our time. The “Science Summit on Seamless Research for Weather, Climate, Water, and Environment” organized by the World Meteorological Organization (WMO) in 2017, has brought together researchers from a variety of institutions for a cross-disciplinary exchange of knowledge and ideas relating to seamless Earth system science. The outcomes of the Science Summit, and the interactions it sparked, highlight the benefit of a seamless Earth system science approach. Such an approach has the potential to break down artificial barriers that may exist due to different observing systems, models, time and space scales, and compartments of the Earth system. In this context, the main future challenges for research infrastructures have been identified. A value cycle approach has been proposed to guide innovation in seamless Earth system prediction. The engagement of researchers, users, and stakeholders will be crucial for the successful development of a seamless Earth system science that meets the needs of society

Fine Scale Analysis of Crossover and Non-Crossover and Detection of Recombination Sequence Motifs in the Honeybee (Apis mellifera)

BACKGROUND: Meiotic exchanges are non-uniformly distributed across the genome of most studied organisms. This uneven distribution suggests that recombination is initiated by specific signals and/or regulations. Some of these signals were recently identified in humans and mice. However, it is unclear whether or not sequence signals are also involved in chromosomal recombination of insects. METHODOLOGY: We analyzed recombination frequencies in the honeybee, in which genome sequencing provided a large amount of SNPs spread over the entire set of chromosomes. As the genome sequences were obtained from a pool of haploid males, which were the progeny of a single queen, an oocyte method (study of recombination on haploid males that develop from unfertilized eggs and hence are the direct reflect of female gametes haplotypes) was developed to detect recombined pairs of SNP sites. Sequences were further compared between recombinant and non-recombinant fragments to detect recombination-specific motifs. CONCLUSIONS: Recombination events between adjacent SNP sites were detected at an average distance of 92 bp and revealed the existence of high rates of recombination events. This study also shows the presence of conversion without crossover (i. e. non-crossover) events, the number of which largely outnumbers that of crossover events. Furthermore the comparison of sequences that have undergone recombination with sequences that have not, led to the discovery of sequence motifs (CGCA, GCCGC, CCGCA), which may correspond to recombination signals