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Search Results: 1 - 10 of 227477 matches for " Felix R. Vogel "
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Can we evaluate a fine-grained emission model using high-resolution atmospheric transport modelling and regional fossil fuel CO2 observations?
Felix R. Vogel,Balendra Thiruchittampalam,Jochen Theloke,Roberto Kretschmer
Tellus B , 2013, DOI: 10.3402/tellusb.v65i0.18681
Abstract: Quantifying carbon dioxide emissions from fossil fuel burning (FFCO2) is a crucial task to assess continental carbon fluxes and to track anthropogenic emissions changes in the future. In the present study, we investigate potentials and challenges when combining observational data with simulations using high-resolution atmospheric transport and emission modelling. These challenges concern, for example, erroneous vertical mixing or uncertainties in the disaggregation of national total emissions to higher spatial and temporal resolution. In our study, the hourly regional fossil fuel CO2 offset (ΔFFCO2) is simulated by transporting emissions from a 5 min×5 min emission model (IER2005) that provides FFCO2 emissions from different emission categories. Our Lagrangian particle dispersion model (STILT) is driven by 25 km×25 km meteorological data from the European Center for Medium-Range Weather Forecast (ECMWF). We evaluate this modelling framework (STILT/ECMWF+IER2005) for the year 2005 using hourly ΔFFCO2 estimates derived from 14C, CO and 222Radon (222Rn) observations at an urban site in south-western Germany (Heidelberg). Analysing the mean diurnal cycles of ΔFFCO2 for different seasons, we find that the large seasonal and diurnal variation of emission factors used in the bottom-up emission model (spanning one order of magnitude) are adequate. Furthermore, we show that the use of 222Rn as an independent tracer helps to overcome problems in timing as well as strength of the vertical mixing in the transport model. By applying this variability correction, the model-observation agreement is significantly improved for simulated ΔFFCO2. We found a significant overestimation of ΔFFCO2 concentrations during situations where the air masses predominantly originate from densely populated areas. This is most likely caused by the spatial disaggregation methodology for the residential emissions, which to some extent relies on a constant per capita-based distribution. In the case of domestic heating emissions, this does not appear to be sufficient.
The Slowdowns of Water Dynamics when Approaching a Glass Transition or a Solid Interface: A Common Rationale
Felix Klameth,Michael Vogel
Physics , 2015,
Abstract: Performing molecular dynamics simulations, we investigate the enormous slowdowns of water dynamics when approaching a glass transition or a solid interface. We show that both effects can be described on common grounds within a theoretical framework, which was recently proposed by Schweizer et al. and considers coupled local hopping and elastic distortion. For confined water, we correctly describe the variation of the alpha-relaxation time tau_alpha as a function of both temperature and position with respect to the interface. Exploiting our knowledge of a cooperative length scale xi(T) from the confinement studies, we quantitatively rationalize the glassy slowdown, tau_alpha(T), and the Stokes-Einstein breakdown of bulk water. For both confined and bulk liquid, variations of the alpha-relaxation time are intimately related to changes of the cage-rattling amplitude.
Evaluation of Selected Control Programming Languages for Process Engineers by Means of Cognitive Effectiveness and Dimensions  [PDF]
Gülden Bayrak, Felix Ocker, Birgit Vogel-Heuser
Journal of Software Engineering and Applications (JSEA) , 2017, DOI: 10.4236/jsea.2017.105026
Abstract: Different programming languages can be used for discrete, abstract and process-oriented programming. Depending on the application, there exist additional requirements, which are not fulfilled by every programming language. Flexible programming and maintainability are especially important requirements for process engineers. In this paper, the programming languages Activity Diagram, State Chart Diagram and Sequential Function Chart are compared and evaluated with regard to these requirements. This evaluation is based on the principles of cognitive effectiveness and cognitive dimensions. The aim of this paper is to identify the programming language suited best for controlling sequential processes, e.g. thermomechanical or batch processes.
Neutrino Masses and Oscillations: Triumphs and Challenges
R. D. McKeown,P. Vogel
Physics , 2004, DOI: 10.1016/j.physrep.2004.01.003
Abstract: The recent progress in establishing the existence of finite neutrino masses and mixing between generations of neutrinos has been remarkable, if not astounding. The combined results from studies of atmospheric neutrinos, solar neutrinos, and reactor antineutrinos paint an intriguing picture for theorists and provide clear motivation for future experimental studies. In this review, we summarize the status of experimental and theoretical work in this field and explore the future opportunities that emerge in light of recent discoveries.
Double Beta Decay
Steven R. Elliott,Petr Vogel
Physics , 2002, DOI: 10.1146/annurev.nucl.52.050102.090641
Abstract: The motivation, present status, and future plans of the search for the neutrinoless double beta decay are reviewed. It is argued that, motivated by the recent observations of neutrino oscillations, there is a reasonable hope that neutrinoless double beta decay corresponding to the neutrino mass scale suggested by oscillations, of about 50 meV, actually exists. The challenges to achieve the sensitivity corresponding to this mass scale, and plans to overcome them, are described.
Analyse de sensibilité du modèle mathématique
Felix R.,Xanthoulis D.
Biotechnologie, Agronomie, Société et Environnement , 2005,
Abstract: Sensitivity analysis of the mathematical model “Erosion Productivity Impact calculator” (EPIC) by approach One-Factor-At-A-Time (OAT). Nowadays, mathematical models are very complex and have many input parameters. Moreover, all do not have the same level of influence on the outputs. In order to identify the most significant parameters of EPIC that will guide the user on the field and in the process of calibration of the model, a sensitivity analysis by the approach One- Factor-At-A-Time was carried out on two data files: one coming from the Programme-Action-Hesbaye” (PAH, 1996) a n d the other of the INCO project (2000). The method used consists in modifying each input parameter of the model by -10% and +10% around its initial value. The effect of each operated modification is analysed on 6 outputs of the model (nitrate leached, water percolation, water consumption, biomass, yield and mineralised humus) of which their sensitivity was quantified by calculation of an index called “Sensitivity Index” and by a percentage of variation. The outputs considered showed particularly sensitive to the parameters “Potential Heat Units” (PHU), “Fraction of nitrogen in plant at 50% of maturity” (BN2) but especially to the “Second point of the evolution of the LAI curve” (DLAP2). A variation of 10% of this parameter causes average changes of approximately 14% and 85% in the six outputs, respectively for the data files of the PAH and the Inco project.
Plasmons in disordered nanoparticle chains: Localization and Transport
Felix Rüting
Physics , 2011, DOI: 10.1103/PhysRevB.83.115447
Abstract: Disorder-induced effects on plasmon coupling in chains of metallic nanoparticles are studied within a dipole model, by considering two types of disorder: fluctuations of the particles' shapes and fluctuations of their positions. Typical localization effects are found both in the eigenmodes and in the transport behavior of the system, and an estimate of the localization length is made. It is argued that chains with deliberately introduced disorder constitute promising systems for studying localization effects of electromagnetic waves at optical frequencies under well controllable and manipulable conditions.
Water Dynamics at Rough Interfaces
Markus Rosenstihl,Kerstin K?mpf,Felix Klameth,Matthias Sattig,Michael Vogel
Physics , 2014,
Abstract: We use molecular dynamics computer simulations and nuclear magnetic resonance experiments to investigate the dynamics of water at interfaces of molecular roughness and low mobility. We find that, when approaching such interfaces, the structural relaxation of water, i.e., the $\alpha$ process, slows down even when specific attractive interactions are absent. This prominent effect is accompanied by a smooth transition from Vogel to Arrhenius temperature dependence and by a growing importance of jump events. Consistently, at protein surfaces, deviations from Arrhenius behavior are weak when free water does not exist. Furthermore, in nanoporous silica, a dynamic crossover of liquid water occurs when a fraction of solid water forms near 225 K and, hence, the liquid dynamics changes from bulk-like to interface-dominated. At sufficiently low temperatures, water exhibits a quasi-universal $\beta$ process, which is characterized by an activation energy of $E_a\!=\!0.5$ eV and involves anisotropic reorientation about large angles. As a consequence of its large amplitude, the faster $\beta$ process destroys essentially all orientational correlation, rendering observation of a possible slower $\alpha$ process difficult in standard experiments. Nevertheless, we find indications for the existence of structural relaxation down to a glass transition of interfacial water near 185 K. Hydrated proteins show a highly restricted backbone motion with an amplitude, which decreases upon cooling and vanishes at comparable temperatures, providing evidence for a high relevance of water rearrangements in the hydration shell for secondary protein relaxations.
Weekly periodicities of Aerosol Optical Thickness over Central Europe – evidence of an anthropogenic direct aerosol effect
D. B umer, R. Rinke,B. Vogel
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2008,
Abstract: Statistical analyses of data from ground-based sun photometer stations in Central Europe are presented. All stations are part of the Aerosol Robotic Network (AERONET), and only data of the highest data quality level 2.0 has been applied. The averages by weekday of Aerosol Optical Thickness (AOT) at a wavelength of 440 nm of 12 of the 14 stations in the investigation area show a weekly periodicity with lowest values on Sunday and Monday, but greatest values from Wednesday until Saturday, that is significant at least on a 90% level. The stations in Germany and in Greater Paris show weekly cycles with ranges of about 20% on average. In Northern Italy and Switzerland this range is about 10% on average. By applying several checks, we exclude that the weekly cycles were caused by a maintenance effect or by different retrieval conditions as a consequence of a weekly cycle in cloud cover. The corresponding weekly cycle of anthropogenic gaseous and particulate emissions leads us to the conclusion of the anthropogenic origin of the weekly AOT cycle. Since these AOT patterns are derived from the reduction of the direct sun radiation by the columnar atmospheric aerosol, this result represents strong evidence for an anthropogenic direct aerosol effect on shortwave radiation. Furthermore, this study makes a first contribution to the understanding and explanation of recently observed weekly periodicities in meteorological variables as temperature in Germany.
Sense of belonging and social cohesion in a desegregated former House of Delegates School
R Tabane, S Human-Vogel
South African Journal of Education , 2010,
Abstract: The ideal of creating a non-racial and equitable school environment is embedded in the South African Constitution. This ideal is informed by a desire to overcome the divisions of the apartheid past by pursuing policies and strategies that will promote the achievement of social cohesion, without denying space for various identities. Schools are seen as im portant vehicles for driving social cohesion amongst learners and it is therefore important that all learners, irrespective of their race, experience a sense of belonging in the school. Using a case study and an interactive qualitative analysis research methodology, we explored the experiences of black and Indian learners in a desegregated former House of Delegates school to determine the successes and possible challenges of ensuring racial integration at the school level and therefore its contribution to social cohesion. The study demonstrates the importance of eight concepts (namely, the school as a welcoming space; belonging; respect; security; equality in the way we socialise; tender loving care; motivation; and freedom) to the study of racial integration and social cohesion. This article focuses on the contribution that sense of belonging has on creating a school environment that is enabling, contributing to learner achievement and concludes that sense of belonging, integration, and social cohesion are intertwined and important in creating an environment that is welcoming and a “home” to diverse learners and educators.
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