Modeling and Simulation the Thermal Runaway Behavior of Cylindrical Li-Ion Cells—Computing of Critical Parameter

The thermal behavior of Li-ion cells is an important safety issue and has to be known under varying thermal conditions. The main objectives of this work is to gain a better understanding of the temperature increase within the cell considering different heat sources under specified working conditions. With respect to the governing physical parameters, the major aim is to find out under which thermal conditions a so called Thermal Runaway occurs. Therefore, a mathematical electrochemical-thermal model based on the Newman model has been extended with a simple combustion model from reaction kinetics including various types of heat sources assumed to be based on an Arrhenius law. This model was realized in COMSOL Multiphysics modeling software. First simulations were performed for a cylindrical 1860 cell with a -cathode to calculate the temperature increase under two various simple electric load profiles and to compute critical system parameters. It has been found that the critical cell temperature [Math Processing Error] , above which a thermal runaway may occur is approximately [Math Processing Error] , which is near the starting temperature of the decomposition of the Solid-Electrolyte-Interface in the anode at [Math Processing Error] . Furthermore, it has been found that a thermal runaway can be described in three main stages

Electrochemical-calorimetric studies on different lithium-ion cells

The lithium-ion batteries used in current electric vehicles evidently have reserves. When the capacity in each cell was optimally utilized, more energy could be put in and delivered again. Thus, the driving range of electric vehicles could be significantly increased. In this work, commercial lithium-ion pouch cells were cycled at varying C-rates under isoperibolic and adiabatic conditions in an accelerating rate calorimeter (ARC) with external battery cycler to investigate their performance and their thermal behavior. A thermal camera was also used to investigate the heat effects and the local temperature distribution during cycling in more details. Different factors that have influence on the performance of energy storage such as temperature, charging/discharging current and state of charge (SOC) have been studied. The isoperibolic investigations were performed at specific temperatures in the range from 25 to 60 °C. The results show that the applied environmental temperature did not largely influence the battery thermal behavior. Both isoperibolic and adiabatic tests were performed at different charging/discharging rates in the range from C/4 to 3C. The results show a considerable temperature rise with increasing rate. Additionally, the heat capacities and the calorimeter constant were determined to calculate the total generated heat during cycling

Temporal Integration Windows in Neural Processing and Perception Aligned to Saccadic Eye Movements

SummaryWhen processing dynamic input, the brain balances the opposing needs of temporal integration and sensitivity to change. We hypothesized that the visual system might resolve this challenge by aligning integration windows to the onset of newly arriving sensory samples. In a series of experiments, human participants observed the same sequence of two displays separated by a brief blank delay when performing either an integration or segregation task. First, using magneto-encephalography (MEG), we found a shift in the stimulus-evoked time courses by a 150-ms time window between task signals. After stimulus onset, multivariate pattern analysis (MVPA) decoding of task in occipital-parietal sources remained above chance for almost 1 s, and the task-decoding pattern interacted with task outcome. In the pre-stimulus period, the oscillatory phase in the theta frequency band was informative about both task processing and behavioral outcome for each task separately, suggesting that the post-stimulus effects were caused by a theta-band phase shift. Second, when aligning stimulus presentation to the onset of eye fixations, there was a similar phase shift in behavioral performance according to task demands. In both MEG and behavioral measures, task processing was optimal first for segregation and then integration, with opposite phase in the theta frequency range (3–5 Hz). The best fit to neurophysiological and behavioral data was given by a dampened 3-Hz oscillation from stimulus or eye fixation onset. The alignment of temporal integration windows to input changes found here may serve to actively organize the temporal processing of continuous sensory input

Composition and dynamic of benthic macroinvertebrates community in semi-arid area rivers of Burkina Faso (West Africa)

The benthic macroinvertebrates communities dynamic were investigated in rivers from Burkina Faso in the purpose to analyze the taxonomic composition, the structure of benthic macroinvertebrates community and the composite environmental variables that correspond to the major distribution patterns of this community. The results showed that a total of 132 taxa was recorded and the large majority of these (103 taxa) belonged to 57 families from 8 orders of insects that represent 95% of relative abundance. We also observed some distinct differences relative to the spatial and temporal variation in the taxonomic composition. The canonical correspondance analysis (CCA) revealed a strong correlationship between Chironomidae, Syrphidae, Culicidae, Psychodidae, as well as the Pulmonates molluscs and organic nutriments feeding dynamics. These findings showed the sensitivity of benthic macroinvertebrates at different level: sensitivity which could be attributable to man-induced activities.© 2016 International Formulae Group. All rights reserved.Keywords: Benthic macroinvertebrates, enviromental variables, dynamic, Burkina Fas

Drawing together multiple lines of evidence from assessment studies of hydropeaking pressures in impacted rivers

Hydropeaking has negative effects on aquatic biota, but the causal relationships have not been studied extensively, especially when hydropeaking occurs in combination with other environmental pressures. The available evidence comes mainly from case studies demonstrating river-specific effects of hydropeaking that result in modified microhabitat conditions and lead to declines in fish populations. We used multiple lines of evidence to attempt to strengthen the evidence base for models of ecological response to flow alteration from hydropeaking. First, we synthesized evidence of ecological responses from relevant studies published in the scientific literature. We found considerable evidence of the ecological effects of hydropeaking, but many causal pathways are poorly understood, and we found very little research on the interactive effects of hydropeaking and other pressures. As a 2nd line of evidence, we used results from analyses of large-scale data sets. These results demonstrated the extent to which hydropeaking occurs with other pressures, but did not elucidate individual or interactive effects further. Thus, the multiple lines of evidence complemented each other, but the main result was to identify knowledge gaps regarding hydropeaking and a consequent pressing need for novel approaches, new questions, and new ways of thinking that can fill them.© 2017 by The Society for Freshwater Science.publishedVersio

Manual for the application of the new European Fish Index - EFI+. A fish-based method to assess the ecological status of European running waters in support of the Water Framework Directive.

This manual describes the new European Fish Index – EFI+ - and its application software. The EFI+ software and manual have been developed within the EFI+ project. The EFI+ project was funded by the European Commission (EC) under the 6th Framework Programme, “Energy, Environment and Sustainable Development”, Key Action 1: Sustainable Management and Quality of Water of the European Commission (Specific Targeted Research Project FP6-2005-SSP-5-A, Task 4: Ecological status assessment – filling the gaps). In the year 2000, the EC adopted a new legislation, the Water Framework Directive (WFD). This new legislation, now implemented in 27 EU member countries, aims for good ecological conditions in all surface waters. Fishes are, for the first time, part of a European-wide monitoring network designed to assess the ecological status of running waters. Between 2001 and 2004 the EC funded the FAME project developed, evaluated and implemented new standardised fish-based methods to assess the ecological status of running waters in Europe (FP5, Energy, Environment and Sustainable Management. Key Action 1: Sustainable Management and Quality of Water, EVK1-CT-2001-00094, http://fame.boku.ac.at).The main output of the FAME project was the European Fish Index (EFI), the first standardised fish-based assessment method applicable across a wide range of European rivers. The EFI employs a number of environmental descriptors to predict biological reference conditions and then quantifies the deviation of the fish community structure from these reference conditions on a statistical basis. The EFI was developed mainly based on data from Western and Northern Europe and was calibrated against estimates of human pressures and impacts. Although a wide range of river types was included in the development of the EFI, some river types, e.g. very large rivers, were underrepresented. The EFI has now been tested by European countries within their national monitoring programmes and has been evaluated for use for reporting under the WFD. During this evaluation process a number of limitations were observed in the performance of the index. Therefore, the overall objective of the EFI+ project was to overcome the existing limitations of the EFI by developing a new, more accurate and pan-European fish index. The scientific and technological objectives were to (1) evaluate the applicability of the existing EFI and make necessary improvements in Central-Eastern Europe and Mediterranean ecoregions; (2) extend the scope of the existing EFI to cover large rivers; (3) analyse relationships between hydromorphological pressures (including continuity disruption) and fish assemblages to increase the accuracy of the EFI; (4) adapt the existing software to the requirements of the EFI+ to allow calculation of the ecological status for running waters. This manual is divided in two parts. Part I introduces the concepts and methods on which the EFI+ is based. This section gives an overview of the development of the new European Fish Index and its achievements to fulfil the objectives of the Water Framework Directive in terms of using fishes as indicators for assessing the ecological status of running waters. Part II is the instruction manual to the web-based software. It details the fish assemblage and environmental data required and the process for obtaining scores and classification of the ecological status of a sampling site (or set of sampling sites) using the EFI+ online software