84 research outputs found
PM2.5 dispersion in Venice area: a model validation
No full textA multidisciplinary project was developed with the aim of better understand PM2.5 primary sources and secondary aerosol formation and compositions. A model system was used to simulate four periods during different seasons in 2009 for which both organic and inorganic measured data were available. Input data were estimated and formatted as requested by models. Measured and predicted data were compared for the three stations and during different seasons in order to test model performance
An integrated approach for the chemical characterization and oxidative potential assessment of indoor PM2.5
No full textAn integrated approach has been developed for the multi-component analysis of indoor PM2.5 collected onto the same quartz fiber filter (QFF) by using an innovative combination of techniques such as inductively coupled sector field plasma mass spectrometry (ICP-SF-MS) with vapor-phase microwave-assisted aqua regia or sonication-assisted water extraction, ion chromatography, thermal-optical transmittance as well as high performance liquid chromatography and enzyme-linked 5,5'-dithio-bis(2-nitrobenzoic acid) assay for the determination of elemental composition, major inorganic ions, elemental/organic carbon (EC/OC) as well as oxidative potential (OP) through ascorbate (AA) and reduced glutathione (GSH) depletion, respectively. The low mass of PM2.5 collectable indoors, the elemental blank values of the QFFs and the sample volume/acidity requirements of the ICP-SF-MS represented a challenge for elemental determination. Finally, this approach was successfully applied for determination of 15 elements (Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Rb, Sr, Mo, Cd, Sn and Pb) at the ngm-3 level in more than two-thirds of indoor PM2.5 (n=25) collected in mechanically ventilated offices within the European Union project OFFICAIR at increased sampling flow rates (0.6m3h-1-2.3m3h-1) and sampling time (cca. 100h) in the acidic/aqueous extracts. The concentration of Cl-, NO3 -, SO4 2-, Na+, NH4 +, K+, Ca2+, Mg2+, OC and EC was at the μgm-3 level in the aqueous extracts. This new approach aiming at the comprehensive characterization of low mass indoor PM2.5 samples allowed assessment of OPAA and OPGSH in all samples. The PM2.5 critical sample mass to achieve elemental determination was approximately 400μ
Axial and transverse momentum balance in subchannel analysis.
No full textThesis. 1975. M.S.--Massachusetts Institute of Technology. Dept. of Nuclear Engineering.Includes bibliographical references.M.S
Hydrodynamic behavior of a bare rod bunle
No full textTemperature distributions within the rod bundle of a nuclear reactor is of major importance in nuclear reactor design. However temperature information presupposes knowledge of the hydrodynamic behavior of the coolant which is the most difficult part of the problem due to complexity of the turbulence phenomena. In the present work a 2-equation turbulence model - a strong candidate for analyzing actual three dimensional turbulent flows - has been used to predict fully developed flow of infinite bare rod bundle of various aspect ratios (P/D). The model has been modified to take into account anisotropic effects of eddy viscosity. Secondary flow calculations have been also performed although the mo^el seems to be too rough to predict the secondary flow correctly. Heat Transfer calculations have been performed to confirm the importance of anisotropic viscosity in temperature predictions. All numerical calculations for flow and heat have been performed by two computer codes developed in the present work which were based on the TEACH code [71]· Also experimental measurements of the distribution of axial velocity, turbulent axial velocity, turbulent kinetic energy and radial Reynoldsstresses were performed in the developing and fully developed regions. A 2-channel Laser Doppler Anemometer working on the Reference mode with forward scattering was used to perform the measurements in a simulated interior subchannel of a triangular rod array with P/D=1.124. Comparisons between the analytical results and the results of this experiment as well as other experimental data in rod bundle array available in literature are presented. The predictions are in good agreement with the results for the high Reynolds numbers
Personal control of the indoor environment in offices: Relations with building characteristics, influence on occupant perception and reported symptoms related to the building-the officair project
No full textPersonal control over various indoor environment parameters, especially in the last decades, appear to have a significant role on occupants’ comfort, health and productivity. To reveal this complex relationship, 7441 occupants of 167 recently built or retrofitted office buildings in eight European countries participated in an online survey about personal/health/work data as well as physical/psycho-social information. The relationship between the types of control available over indoor environments and the perceived personal control of the occupants was examined, as well as the combined effect of the control parameters on the perceived comfort using multilevel statistical models. The results indicated that most of the occupants have no or low control on noise. Half of the occupants declared no or low control on ventilation and temperature conditions. Almost one-third of them remarked that they do not have satisfactory levels of control for lighting and shading from sun conditions. The presence of operable windows was shown to influence occupants’ control perception over temperature, ventilation, light and noise. General building characteristics, such as floor number and floor area, office type, etc., helped occupants associate freedom positively with control perception. Combined controlling parameters seem to have a strong relation with overall comfort, as well as with perception regarding amount of privacy, office layout and decoration satisfaction. The results also indicated that occupants with more personal control may have less building-related symptoms. Noise control parameter had the highest impact on the occupants’ overall comfor
Divine abandonment of Christ and the soul in Byzantine exegesis and ascetic literature
No full textThis thesis examines the role that the motif of divine abandonment played in the exegetical and ascetical literature of late antiquity. Divine abandonment of the soul was an integral part of the spiritual life. Its "normativeness" was related to the notion of divine paideia: God instructed the soul by abandoning the soul to ethical trials. This paideia had eschatological implications: divine abandonment highlighted the eschatological orientation of the Christian faith. Divine abandonment of Christ, however, is treated in Christological, rather than ascetical, terms. The experience of abandonment by the ascetics was not based on a "Christ-like" ethical model: Christ's abandonment was only connected to the ascetical abandonment within the scope of divine providence. The first part introduces the Patristic exegesis on the Song of Songs. It shows that Patristic exegesis related divine abandonment of the soul to ethical trials and highlights the role of the motif as part of divine paideia that leads the soul to an eschatological ethical perfection. The second part discusses Christ's abandonment on the cross, which Patristic literature handled with a certain hesitancy, even uncertainty. The last part examines the ascetical tradition. The motif illustrated God’s providential care for the ascetic soul where God remedied the soul's weakness and led her to the ethical fulfilment in the eschaton. This part also addresses the subtle way in which ascetical literature envisaged Christ as a spiritual model. The conclusion that this thesis draws is that it is within the theological framework of divine paideia and eschatology that the Patristic literature understood the notion of divine abandonment. Furthermore, it suggests that it is in this framework of their common tradition that the Eastern and Western spiritual traditions might mutually approach and understand each other
Spatial and temporal variation of particulate matter characteristics within office buildings — The OFFICAIR study
No full textIn the frame of the OFFICAIR project, office buildings were investigated across Europe to assess how the office workers are exposed to different particulate matter (PM) characteristics (i.e. PM2.5 mass concentration, particulate oxidative potential (OP) based on ascorbate and reduced glutathione depletion, trace element concentration and total particle number concentration (PNC)) within the buildings. Two offices per building were investigated during the working hours (5 consecutive days; 8 h per day) in two campaigns. Differences were observed for all parameters across the office buildings. Our results indicate that the monitoring of the PM2.5 mass concentration in different offices within a building might not reflect the spatial variation of the health relevant PM characteristics such as particulate OP or the concentration of certain trace elements (e.g., Cu, Fe), since larger differences were apparent within a building for these parameters compared to that obtained for the PM2.5 mass concentration in many cases. The temporal variation was larger for almost all PM characteristics (except for the concentration of Mn) than the spatial differences within the office buildings. These findings indicate that repeated or long-term monitoring campaigns are necessary to have information about the temporal variation of the PM characteristics. However, spatial variation in exposure levels within an office building may cause substantial differences in total exposure in the long term. We did not find strong associations between the investigated indoor activities such as printing or windows opening and the PNC values. This might be caused by the large number of factors affecting PNC indoors and outdoors
New Approaches on Prediction of Maximum Individual Exposure from Airborne Hazardous Releases
No full textModeling Short-Term Maximum Individual Exposure from Airborne Hazardous Releases in Urban Environments. Part I: Validation of a Deterministic Model with Field Experimental Data
No full textThe release of airborne hazardous substances in the atmosphere has a direct effect on human health as, during the inhalation, an amount of concentration is inserted through the respiratory system into the human body, which can cause serious or even irreparable damage in health. One of the key problems in such cases is the prediction of the maximum individual exposure. Current state of the art methods, which are based on the concentration cumulative distribution function and require the knowledge of the concentration variance and the intermittency factor, have limitations. Recently, authors proposed a deterministic approach relating maximum individual exposure to parameters such as the fluctuation intensity and the concentration integral time scale. The purpose of the first part of this study is to validate the deterministic approach with the extensive dataset of the MUST (Mock Urban Setting Test) field experiment. This dataset includes 81 trials, which practically cover various atmospheric conditions and stability classes and contains in total 4004 non-zero concentration sensor data with time resolutions of 0.01–0.02 s. The results strengthen the usefulness of the deterministic model in predicting short-term maximum individual exposure. Another important output is the estimation of the methodology uncertainty involved
Personal exposure to ambient and indoor ozone: the effect of different commuting modes in Athens, Greece.
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