312 research outputs found
Evaluation and Inter-Comparison of Oxygen-Based OC-EC Separation Methods for Radiocarbon Analysis of Ambient Aerosol Particle Samples
No full textRadiocarbon analysis is a widely-used tool for source apportionment of aerosol particles. One of the big challenges of this method, addressed in this work, is to isolate elemental carbon (EC) for 14C analysis. In the first part of the study, we validate a two-step method (2stepCIO) to separate total carbon (TC) into organic carbon (OC) and EC against the EUSAAR_2 thermal-optical method regarding the recovered carbon concentrations. The 2stepCIO method is based on the combustion of OC in pure oxygen at two different temperature steps to isolate EC. It is normally used with a custom-built aerosol combustion system (ACS), but in this project, it was also implemented as a thermal protocol on a Sunset OC-EC analyzer. Results for the recovered EC mass concentration showed poor agreement between the 2stepCIO method on the ACS system and on the Sunset analyzer. This indicates that the EC recovery is sensitive not only to the temperature steps, but also to instrument-specific parameters, such as heating rates. We also found that the EUSAAR_2 protocol itself can underestimate the EC concentration on untreated samples compared to water-extracted samples. This is especially so for highly loaded filters, which are typical for 14C analysis. For untreated samples, the EC concentration on long-term filter samples (two to five days sampling time) was 20–45% lower than the sum of EC found on the corresponding 24-h filter samples. For water-extracted filter samples, there was no significant difference between long-term and the sum of daily filter samples. In the second part of this study, the 14C was measured on EC isolated by the 2stepCIO method and compared to methods from two other laboratories. The different methods agree well within their uncertainty estimates
High Contribution of Biomass Combustion to PM2.5 in the City Centre of Naples (Italy)
No full textA better knowledge of the local and regional sources of the atmospheric particulate matter provides policy makers with the proper awareness when acting to improve air quality, in order to protect public health. A source apportionment study of the carbonaceous aerosol in Naples (Italy) is presented here, in order to improve this understanding in a vulnerable urban area. The aim of this study is quantifying directly fossil and non-fossil contributions to carbonaceous aerosol, by means of radiocarbon measurements. This is the first time that such an approach is implemented in this area. Fine particles with diameter ≤ 2.5 μm (PM2.5) were collected daily on top of a building in the city center, from November 2016 until January 2017. The carbonaceous aerosol was separated into organic carbon (OC) and elemental carbon (EC), by a two-step thermal desorption method. Subsequent radiocarbon analysis enabled the partitioning of the major sources of carbonaceous aerosol into fossil and non-fossil ones by applying radiocarbon isotopic mass balance. The PM2.5 concentration was on average 29 ± 3 μg/m3 (mean ± standard error; n = 18), with a maximum of 68.6 ± 0.7 μg/m3 on a day when air masses back-trajectories suggest a local origin and stagnant airflow conditions in the region. The carbonaceous component accounts for roughly half of the PM2.5 mass. Fossil fuel emissions are a minor source of OC (23%), but the dominant source of EC (66%), which is directly emitted during combustion processes. However, overall only 30% of the total carbon is of fossil origin, accounting for 14% of PM2.5 mass. Surprisingly, a comparable contribution is due to primary biomass burning carbon, which accounts in total for 15% of PM2.5 mass. Traffic pollution, the main cause of fossil fuel emissions in urban areas, is a significant, but not the predominant source of carbonaceous particle concentration. These findings support the conclusion of a predominant contribution from non-fossil sources to the carbon in airborne particulate matter, which policy makers should take into account when planning mitigation strategies to improve urban air quality
Secondary Organic Aerosol - Formation Mechanisms and Source Contributions in Europe
No full textFine particulate matter (PM2.5) as an atmospheric pollutant is strongly related to increased mortality and morbidity. The empirically established link between aerosol concentration and human health compels increased efforts to reduce the atmospheric concentrations of fine particles. Organic material accounts for about 20-60% of the total PM2.5 and contains substances of known toxicity. It has been shown that in some areas secondary organic aerosol (SOA) accounts for 20% of the total organic aerosol throughout the year but can contribute up to 70% in smog episodes. The estimation of the sources and concentrations of organic aerosol is therefore crucial to the proper assessment of related health effects
Part of this work attempts a critical review of the literature on SOA. The goal is to describe formation mechanisms, to identify likely precursor gases, and to estimate the SOA contribution to PM2.5. SOA forms by oxidation of volatile organic compounds (VOC). The aerosol yield varies significantly among different VOC species as well as source sectors and the contribution of SOA to the total particulate organic material is dependent on the time of the day and the season. The consequences of these findings for reduction strategies are discussed.
The knowledge gained in the literature review is further used to exemplify a possible procedure to assess and compare the aerosol formation potential of some source sectors used in the RAINS model. It is found that traffic and solvent use in the printing industry and paint are important sectors for SOA production
Problems of complex indicators of smart cities
No full texthttps://kmf.uz.ua/wp-content/uploads/2020/09/final_1_kotet-foldrajzfkonf-2020-07-14.pdf https://opac3.brff.monguz.hu:443/hu/record/-/record/bibBRF00008119Abstract. As the popularity of smart city research is increasing, the “measurement” of “smartness” became
also a popular research topic. The paper deals with the problem of creating composite index numbers for the evaluation of smart city projects and for the comparison of “smartness” of cities. These
composite indicators are popular tools of technocrats and bureaucrats, but the transformation of a
multi-indicator system into a one-dimensional metric scale is a highly questionable practice.Az okosváros-kutatások népszerűségével együtt az okosvárosság mérésére
irányuló próbálkozások szintén népszerűvé váltak a közelmúltban. A mutatószámok kifejlesztése kutatói közösségek, kutatóintézetek részéről is megfigyelhető és az okosváros-projekteket tervezők, beruházók, finanszírozók hatásvizsgálatra, adatvezérelt döntéshozatalra és elemzésre irányuló igényével is
egybeesik. A mérések során jellemzően nem egy vagy néhány alapindikátort
használnak, hanem nagyon sok, olykor száznál is több alapmutatóból képzett
komplex mutatószámot vagy mutatószámokat. A tanulmány ezeknek a tartalmi
problémáit vázolja. A különféle javasolt indikátorok megvizsgálása ugyanis azt
mutatja, hogy ezekben többségben vannak a teljesen hagyományos gazdasági-társadalmi jelzőszámok, a nem hagyományos, de a digitalizációval semmilyen
kapcsolatban nem lévő mutatók és kisebbségben a valódi digitális mutatók,
amelyek kapcsolatban állhatnak az okosváros-fejlesztésekkel.A tanulmány a „Nemzetköziesítés, oktatói, kutatói és hallgatói utánpótlás megteremtése, a tudás- és technológiai transzfer fejlesztése mint az intelligens szakosodás eszközei a Széchenyi István Egyetemen” elnevezésű, EFOP-3.6.1-16-2016-00017 azonosítóval ellátott projekt keretében készült
δ13C signatures of organic aerosols: Measurement method evaluation and application in a source study
No full textAnalysis of the stable carbon isotope 13C in organic carbon (OC) can give insight into sources and atmospheric processing of carbonaceous aerosols, provided the 13C source signatures are known. However, only few data on 13C signatures of OC emitted by common sources of carbonaceous aerosol are available in Europe. We present and evaluate an improved version of a measurement method to obtain δ13C signatures on organic aerosols desorbed from filter samples at three different desorption temperatures (200 °C, 350 °C and 650 °C) and apply it in a source study. With our calibration approach, the reproducibility of a L-Valine reference material desorbed at a single temperature step of 650 °C shows a standard deviation of 0.19‰ over a period of more than one year. The average δ13C value for this reference material over 248 measurements is −24.10‰, which shows only a slight bias to the nominal value of −24.03‰. Repeated analysis of ambient filter samples desorbed at three temperature steps show typical standard deviations of about 0.3‰ for all temperature steps (200 °C, 350 °C and 650 °C). Isotopic fractionation due to partial thermal desorption during the individual temperature steps was tested on single compound reference materials. It showed significant isotopic fractionation only at temperature steps, in which a very minor fraction of the compound was desorbed. Possible isotope effects caused by charring of organic material were investigated and found to be not significant. The thermal desorption method was applied to various source filter samples from the region of Naples, Italy. We analyzed two different biomass burning sources, exhaust from a city bus and traffic emissions collected in a tunnel and compared these to ambient filter samples from the same region. δ13C signatures of the total OC show values in a narrow range of about −28‰ to −26‰ for all sources, which does not allow a source apportionment only based on 13C. Nevertheless, the results add information to a source inventory of δ13C, where information of 13C in organic aerosol from specific emission sources are rare. City bus emissions show little variation of δ13C over the temperature steps, whereas biomass burning aerosol is enriched in 13C for OC desorbed at 650 °C. For PM10 samples in the urban tunnel an enrichment in δ13C at the 650 °C temperature steps was observed, which is likely caused by the contribution of carbonate carbon to the carbonaceous material desorbed at this temperature step
Thermal separation and purification of organic and elemental carbon from small aerosol samples for 14C analysis
No full textAn Investigation of Experimenter Bias in the Performance of Children at Asimple Motor Task Under Conditions of Social Reinforcement and Nonreinforcement
No full textMade available in DSpace on 2014-12-08T23:02:08Z (GMT). No. of bitstreams: 1
7013295.pdf: 2401603 bytes, checksum: 25ae5295a561c74cc6f247f502b7f2d3 (MD5)
Previous issue date: 1969Embargo set by: Seth Robbins for item 60234
Lift date: Forever
Reason: Restricted to the U of I community idenfinitely during batch ingest of legacy ETDsRestricted to the U of I community idenfinitely during batch ingest of legacy ETDsU of I Only74 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1969
Studium cyklizace a solvolyzy acylovanych amidoximu
No full textReaction of substituted amidoximes with acyl chlorides and chloroformates have been used to prepare series of substituted amidoximecarbonates and O-benzoylbenzamidoximes. The kinetics of methanolysis of substituted arylbenzamidoximecarbonates has been studied in methanolic sodium methoxide at 25 C. This reaction proceeds in two stepsSummary in EnglishAvailable from STL Prague, CZ / NTK - National Technical LibrarySIGLECZCzech Republi
Simulation d'écoulements tridimensionnels autour d'objets cylindriques infinis
No full textLa thèse clarifie les mécanismes de la transition à la tridimensionnalité apparaissant dans le sillage d'objets cylindriques infinis. La première partie se concentre sur l'étude du sillage d'un cylindre circulaire par des simulations tridimensionnelles. Elle montre que le caractère sous-critique de la bifurcation déclenchant la tridimensionnalité est à l'origine d'effets non-linéaires extrêmement forts limitant considérablement la pertinence de la théorie linéaire. La dynamique de l'écoulement est fortement chaotique et contient de très grandes échelles dans la direction de l'envergure du cylindre qu'il est nécessaire de prendre en compte afin de reproduire d'une manière fiable les résultats expérimentaux. Les résultats numériques obtenus mettent en évidence la limite inférieure de l'intervalle de bi-stabilité sous-critique au nombre de Reynolds de 170 et montrent que les modes A et B coexistent dès ce nombre de Reynolds. La même méthode d'étude est ensuite appliquée à une aile NACA0012 infinie placée dans un écoulement à des angles d'incidence variables. L'apparition de la tridimensionnalité est étudiée pour des angles d'incidence allant de 8 à 12 degrés. La bifurcation correspondante est supercritique. Les échelles spatiales prédites peuvent être utiles pour la mise en place de simulations numériques directes efficaces.The thesis sheds light on the onset of three-dimensionality in the wake of infinite cylindrical bodies. The first part of thesis consists in an investigation of the wake of a straight infinite circular cylinder by 3D simulations. It shows that the subcriticality of the bifurcation giving rise to the onset of three-dimensionality triggers very strong non-linear effects limiting considerably the relevance of the linear theory. The flow dynamics is shown to be chaotic and to contain very large spanwise scale that must be taken into account to reproduce reliably experimental observations. The obtained numerical results set the subcritical bi-stability interval down to the Reynolds number of 170 and show that the well-known modes A and B co-exist in all regimes since the very onset of the three-dimensionality. The method of investigation of the cylinder wake is further applied to a NACA0012 airfoil with variable angle of incidence. The onset of three-dimensionality is investigated for angles of incidence from 8 to 12 degrees. The corresponding bifurcation is supercritical. The obtained spanwise scales might be of use in designing efficient direct numerical simulations.STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF
Une Méthode de frontière immergée pour la simulation d'écoulements autour d'objets de forme arbitraire
No full textUne methode de frontiere immergee pour la simulation des ecoulements autour d'objets de forme arbitraire est presentee.Elle est basee sur une discretisation par differences finies d'ordre deux sur un maillage cylindrique regulier.La discretisation temporelle suit une methode a pas fractionne,avec un schema de Runge-Kutta pour les termes convectifs et un schema de Crank-Nicholson pour les termes diffusifs.La geometrie de l'objet est decrite gr^ace a une fonction courbe de niveau (level set).Pres de l'interface fluide-objet,ces termes sont interpoles a l'ordre deux sans pour autant inffluencer le critere de stabilite de la methode.Le probleme de Stokes est resolu a l'aide de l'algorithme d'Uzawa permettant une precision temporelle d'ordre deux pour la pression.Une approche de type volumes-finis pour le traitement de la divergence assure une conservation de la masse m^eme pres de la paroi.La formulation faible du probleme reliant la pression et la divergence permet de symetriser l'operateur d'Uzawa.Le probleme de Stokes est resolu numeriquement par une methode de gradients conjugues alliee a un preconditionnement par l'inverse du laplacien qui permet une resolution efficace des equations de Navier-Stokes.Le calcul de la force et du moment exerces par le fluide sur l'objet est effectue par l'utilisation d'un volume de contr^ole.La methode a ete comparee aux resultats d'un code spectral-elements spectraux d'ordre 6 deja valide dans d'autres travaux.Le cas test est une sphere placee dans un ecoulement uniforme pour les regimes axisymetrique stationnaire, non axisymetrique stationnaire et instationnaire.Tant qualitativement que quantitativement,la methode donne des resultats en tres bon accord avec les resultats du code spectral-elements spectraux d'ordre plus eleve.An immersed boundary method for the simulation of uid ow around arbitrarily shaped objects is presented. It is based on a second order _nite di_erence discretization in a regular cylindrical mesh. Temporal advancement is achieved with a fractional step method using a Runge-Kutta scheme for the non-linear terms and a Crank-Nicholson scheme for the linear terms. Object's geometry is described with a level set method. Near the uid-object interface, linear and non-linear terms are interpolated with second order precision to match wall boundary conditions without a_ecting the stability criteria. The arising Stokes problem is resolved using Uzawa algorithm to ensure second order temporal precision for the pressure. Velocity divergence is calculated with a nite-volume method to ensure mass conservation even near the object wall. The weak formulation of the problem linking the pressure to the divergence makes the Uzawa operator symmetric. The Stokes problem is then numerically solved using a preconditioned conjugate gradient method where the preconditioner is the inverse of the Laplacian which allows an e_cient resolution of the Navier-Stokes equations. The force and the momentum exerted by the uid on the body are computed using a control volume approach. The developed method is compared to a spectral-spectral elements code of sixth order precision previously validated in various works. The case of a sphere in a uniform ow is tested at di_erent ow regimes: stationary axisymmetric regime, stationary non axisymmetric regime and instationary regime. The method is qualitatively as well as quantitatively in good agreement with the results of the higher order spectral code.STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF
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