The Experts below are selected from a list of 75 Experts worldwide ranked by ideXlab platform
Juan Manuel Madariaga - One of the best experts on this subject based on the ideXlab platform.
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spectroscopic speciation and thermodynamic modeling to explain the degradation of weathering steel surfaces in so2 rich urban atmospheres
Microchemical Journal, 2014Co-Authors: Julene Aramendia, Leticia Gomeznubla, Kepa Castro, Juan Manuel MadariagaAbstract:Abstract The characteristic protection ability of weathering steel can be affected by the environment in SO 2 rich urban atmospheres. Although sulphur dioxide can partially be oxidised to sulphur trioxide, both acid gases can be dissolved either in the atmosphere or in the Moisture Film present on the steel surface, forming sulphurous and/or sulphuric acid, and accelerating the corrosion of the material. Thermodynamic simulations, based on experimental data obtained by Raman and SEM–EDS techniques on different weathering steel sculptures located outside in Bilbao (Basque Country), were done to probe the role of SO 2 in the formation of several soluble sulphates, such as, rozenite (FeSO 4 ·4H 2 O) and retgersite (NiSO 4 ·6H 2 O). According to the results, it was confirmed that the presence of atmospheric particles of calcium carbonate does not have an outstanding negative role in the metal decaying process. However, the presence of high magnesium calcite (HMC) plays an important role in the formation of magnesioferrite, another decaying product present in the surface of the weathering steel . As all these sulphates are soluble, rain water can dissolve them leading into a continuous decaying and material loss process.
D. Zirkelbach - One of the best experts on this subject based on the ideXlab platform.
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Hygrothermal Performance and Damage Risk of Green Roofs
Hygrothermal Behavior Building Pathology and Durability, 2012Co-Authors: D. Zirkelbach, B. Schafaczek, Hartwig M. KünzelAbstract:Green roofs become more and more popular especially in cities where they can help to improve the microclimate by reduced peak temperatures compared to conventional roof surfaces. They also reduce the gutter loads by rain water retention and save both heating energy in winter and cooling energy in summer. On the other hand, the cooler temperatures in summer may reduce the drying potential of the load bearing structure beneath the green roof. In inverted roofs the permanently humid conditions can lead to Moisture accumulation in the foam insulation slabs. Due to a multitude of influencing factors like Moisture storage, freezing, evaporation, shading and reduced radiation absorption through the plant cover etc. a simulation of the hygrothermal behaviour of green roofs represents a challenge. Therefore, the hygrothermal conditions of green roofs on wooden structures and on inverted concrete roofs at different locations has been measured and evaluated for several locations in Europe. Based on these experimental results a new approach was developed to calculate in a realistic way the hygrothermal performance of green roofs including the important influencing factors mentioned before. This contribution first investigates the conditions beneath the growth medium layers and the water content of the insulation boards and of the wooden sheathing by field tests in Holzkirchen, Vienna and Leipzig. In the second part a new approach to simulate green roofs including the growth medium layer is shown. In the case of inverted green roofs, the Moisture Film beneath the insulation boards is a dominant factor too that must be taken into account in the simulation. Finally, the results of simulations and experiments are compared in order to validate and fine-tune the new approaches that have been developed to model the behaviour of vegetated wooden structures and inverted concrete roofs in South, Central and North Europe.
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Long-Term Hygrothermal Performance of Green Roofs
2010Co-Authors: D. Zirkelbach, B. Schafaczek, H. KünzelAbstract:Green roofs are becoming more and more popular because their thermal inertia, combined with latent heat effects, saves energy both in summer and winter and helps improve the microclimate in cities. Due to a multitude of influencing factors like Moisture storage, freezing, evaporation, shading, reduced radiation absorption through the plant cover, etc., a simulation of the hygrothermal behavior of green roofs is still difficult. In Germany, green roofs are often applied on so-called inverted roofs, where a vapor-retarding foam insulation is used above the roofing membrane in direct contact with the growth medium. Due to a more or less permanent Moisture Film beneath the insulation panels and a mostly Moisture-saturated growth medium above, these insulation boards experience a continuous Moisture accumulation during their service life. In numerous in-situ investigations of inverted green roofs, the accumulation of Moisture was determined by periodical probing over a period of 10 years. Temperature and humidity sensors at several positions in the roofs served to monitor the transient behavior. Based on these tests, new models for the hygrothermal performance of inverted green roofs have been developed to simulate the Moisture behavior of the foam insulation boards, depending on material properties and boundary conditions. Together with further experimental investigations, this model allows a detailed analysis of the longterm hygrothermal and energy performance of green roofs.
Julene Aramendia - One of the best experts on this subject based on the ideXlab platform.
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spectroscopic speciation and thermodynamic modeling to explain the degradation of weathering steel surfaces in so2 rich urban atmospheres
Microchemical Journal, 2014Co-Authors: Julene Aramendia, Leticia Gomeznubla, Kepa Castro, Juan Manuel MadariagaAbstract:Abstract The characteristic protection ability of weathering steel can be affected by the environment in SO 2 rich urban atmospheres. Although sulphur dioxide can partially be oxidised to sulphur trioxide, both acid gases can be dissolved either in the atmosphere or in the Moisture Film present on the steel surface, forming sulphurous and/or sulphuric acid, and accelerating the corrosion of the material. Thermodynamic simulations, based on experimental data obtained by Raman and SEM–EDS techniques on different weathering steel sculptures located outside in Bilbao (Basque Country), were done to probe the role of SO 2 in the formation of several soluble sulphates, such as, rozenite (FeSO 4 ·4H 2 O) and retgersite (NiSO 4 ·6H 2 O). According to the results, it was confirmed that the presence of atmospheric particles of calcium carbonate does not have an outstanding negative role in the metal decaying process. However, the presence of high magnesium calcite (HMC) plays an important role in the formation of magnesioferrite, another decaying product present in the surface of the weathering steel . As all these sulphates are soluble, rain water can dissolve them leading into a continuous decaying and material loss process.
Jean-pierre Celis - One of the best experts on this subject based on the ideXlab platform.
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Effect of relative humidity and full immersion in water on friction, wear and debonding of unidirectional carbon fiber reinforced epoxy under reciprocating sliding
Composites Part B: Engineering, 2016Co-Authors: Houcine Dhieb, Josephus Gerardus Buijnsters, Khaled Elleuch, Jean-pierre CelisAbstract:Abstract Unidirectional carbon fiber reinforced epoxy was tested in ambient air at three different levels of relative humidity and under full immersion in demineralized water. Reciprocating sliding tests were performed at 23 °C against either stainless steel or alumina balls moving in parallel or anti-parallel direction to the fibers. We demonstrate in this work that humidity and water immersion affect significantly the fiber debonding. Under sliding against stainless steel or alumina at low relative humidity, fiber debonding is more pronounced than at high relative humidity and at water immersion. The wear depth increases with increasing relative humidity when sliding against stainless steel, whereas it remains practically constant against alumina. For all test conditions, the wear depth is larger when tested against stainless steel than against alumina. It was found that the thin Moisture Film formed at the surface of the stainless steel counter body leads to a higher corrosive risk than water immersion. More precisely, we demonstrate that high humidity leads to the production of oxide debris originated from the stainless steel ball which increases markedly the wear by abrasion. These debris lead to a high fluctuation of the coefficient of friction measured on carbon fiber reinforced epoxy composite sliding against stainless steel at 85% RH, whereas a steady state coefficient of friction is noticed against alumina.
Michael P. Doyle - One of the best experts on this subject based on the ideXlab platform.
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Internalization and fate of Escherichia coli O157:H7 in leafy green phyllosphere tissue using various spray conditions.
Journal of food protection, 2014Co-Authors: Marilyn C. Erickson, Cathy C. Webb, Lindsey E. Davey, Alison S. Payton, Ian D. Flitcroft, Michael P. DoyleAbstract:In the past decade, leafy greens have been implicated in several outbreaks of foodborne illness, and research has focused on contamination during preharvest operations. Concerns have been raised that internalization of pathogens into the edible tissue occurs where postharvest chemical interventions would be ineffective. This study was initiated to measure the degree and fate of Escherichia coli O157:H7 internalized in the phyllosphere tissue of leafy greens when spray conditions, inoculum level, and type of leafy green were varied. Two spraying treatments were applied: (i) spraying individual spinach or lettuce leaves on plants once with a high dose (7 to 8 log CFU/ml) of E. coli O157:H7 and (ii) spraying spinach, lettuce, or parsley plants repeatedly (once per minute) with a low dose (2.7 to 4.2 log CFU/ml) of E. coli O157:H7 over a 10- to 20-min period. With the high-dose spray protocol, no significant differences in the prevalence of internalization occurred between Shiga toxin-negative E. coli O157:H7 isolates and virulent isolates (P > 0.05), implying that the Shiga toxin virulence factors did not influence internalization or the subsequent fate of those populations under these test conditions. Significantly greater internalization of E. coli O157:H7 occurred in spinach leaves compared with lettuce leaves when leaves were sprayed once with the high-dose inoculum (P < 0.05), whereas internalization was not observed in lettuce leaves but continued to be observed in spinach and parsley leaves following repeated spraying of the low-dose inoculum. Based on these results, it is surmised that a Moisture Film was generated when spraying was repeated and this Film assisted in the mobilization of pathogen cells to plant apertures, such as stomata. E. coli O157:H7 cells that were internalized into spinach tissue using a low-dose repeat-spray protocol were temporary residents because they were not detected 2 days later, suggesting that plant-microbe interactions may be responsible.