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Real Conditions (real + condition)

Distribution by Scientific Domains

Engineering	50%

Selected Abstracts

Run Out of Landslides , Continuum Mechanics versus Discontinuum Mechanics Models

GEOMECHANICS AND TUNNELLING, Issue 5 2008
Rainer Poisel a.o.Univ.-Prof.
In general, a rock slope failure leads to the detachment of a rock mass consisting of a mass of blocks. During the last few years continuum mechanics as well as discontinuum mechanics numerical codes have been developed for modelling the run out of these masses. In order to compare both methods, Punta Thurwieser Rock Avalanche and Frank Slide were modelled by the continuum mechanics numerical code DAN3D as well as by the distinct element method PFC3D modified for run out modelling. The simulations showed that the parameters necessary to get results coinciding with observations in nature are completely different and that Frank run out was a real "slide" of a coherent mass, whereas Punta Thurwieser run out was a rock mass fall with much internal movement. The parameters for a run out simulation, therefore, have to be chosen in such a way that the simulation gives a rock mass fall in one particular case and a slide of a coherent mass in another, corresponding to the real conditions. Therefore, the prediction of the run out kinematics and the fixing of the parameters is a demanding task in each case when modelling run outs. Bergstürze , Vergleich kontinuumsmechanische und diskontinuumsmechanische Rechenmodelle Das Versagen von Felsböschungen und Talflanken führt meist zur Ablösung einer Masse von Blöcken. In den letzten Jahren wurden sowohl kontinuumsmechanische als auch diskontinuumsmechanische Rechenmodelle für die Simulation des Absturzvorgangs solcher Massen entwickelt. Anhand der Modellierung der Bergstürze Punta Thurwieser und Frank Slide mittels DAN3D und PFC3D werden die genannten Ansätze verglichen. Die Ergebnisse zeigen, dass sich die für eine realitätsnahe Modellierung erforderlichen Parameter stark unterscheiden. Während der Frank Slide als weitgehend kohärente Masse abging, war der Bergsturz Punta Thurwieser ein stark turbulenter Trümmerstrom. Die Parameter für die rechnerische Modellierung eines Bergsturzes müssen daher im einen Fall so gewählt werden, dass sich , je nach realen Verhältnissen , eine "laminare" Bewegung, im anderen Fall aber so, dass sich eine turbulente Bewegung ergibt. Die Vorhersage der Kinematik eines Bergsturzes und die darauf aufbauende Auswahl von Rechenparametern stellt daher eine anspruchsvolle Aufgabe dar. [source]

Computational energy analysis of an innovative isothermal chamber for testing of the special equipment used in the transport of perishable products

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 10 2004
S. K. Chatzidakis
Abstract This paper describes an improved numerical simulation study of an isothermal chamber recently constructed at Zografou Campus of the National Technical University of Athens (NTUA) for the testing of special equipment used for transporting perishable foodstuffs in accordance with the United Nations ATP agreement. Using a transient finite difference model, a simulation is developed for a modern ATP test chamber and a typical specimen refrigerated vehicle to be tested. The simulation results are compared to experimental measurements taken under real conditions by a data acquisition system and a refrigerated semi-trailer as specimen. Proportional,integral control is employed for the regulation of the cooling and heating system. The impact of various parameters on the time required to reach the set-point temperature (tset) is investigated and the energy consumption is simulated for a period of 22 h. In particular, the impact of specimen insulation thickness and the thickness of the chamber insulation floor are considered in detail. The total energy consumption increases by approximately 16% when the concrete floor layer thickness is increased from 8 to 16 cm for typical initial conditions and desired chamber and specimen temperatures of 32.5 and 7.5°C, respectively. Using a floor insulation of 6 cm extruded heavy strain-resistant polystyrene reduces the energy consumption by at least 13%. Specimen insulation thickness increase from U -value of 0.35 W m,2 K to 0.75 W m,2 K result to an increase in energy consumption by a percentage of 28%. Thermal capacity, temperature of car body and specimen dimensions are also treated as variables that affect the total duration of an ATP test and its total energy consumption. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Influence of water activity and temperature on conidial germination and mycelial growth of ochratoxigenic isolates of Aspergillus ochraceus on grape juice synthetic medium.

JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 10 2005
Predictive models
Abstract The first stages in the development of Aspergillus ochraceus, an ochratoxin A-producing fungus that infects grapes and may grow on them, have been studied on a synthetic nutrient medium similar to grape in composition. Spore germination and mycelial growth have been tested over a water activity (aw) and temperature range which could approximate to the real conditions of fungal development on grapes. Optimal germination and growth were observed at 30 °C for all three isolates tested. Maximal germination rates were detected at 0.96,0.99 aw at 20 °C, while at 10 and 30 °C the germination rates were significantly higher at 0.99 aw. Although this abiotic factor (aw) had no significant influence on mycelial growth, growth rates obtained at 0.98 aw were slight higher than those at other aw levels. Predictive models for the lag phase before spore germination as a function of water activity and temperature have been obtained by polynomial multiple linear regression, and the resulting response surface models have been plotted. Copyright © 2005 Society of Chemical Industry [source]

Clinical evidence of benefits of a dietary supplement containing probiotic and carotenoids on ultraviolet-induced skin damage

BRITISH JOURNAL OF DERMATOLOGY, Issue 3 2010
D. Bouilly-Gauthier
Summary Background,Lactobacillus johnsonii (La1) has been reported to protect skin immune system homeostasis following ultraviolet (UV) exposure. Objectives, To assess the effects of a dietary supplement (DS) combining La1 and nutritional doses of carotenoids on early UV-induced skin damage. Methods, Three clinical trials (CT1, CT2, CT3) were performed using different UV sources: nonextreme UV with a high UVA irradiance (UV-DL, CT1), extreme simulated solar radiation (UV-SSR, CT2) and natural sunlight (CT3). All three clinical trials were carried out in healthy women over 18 years of age with skin type II,IV. In CT1, early markers of UV-induced skin damage were assessed using histology and immunohistochemistry. In CT2, the minimal erythemal dose (MED) was determined by clinical evaluation and by chromametry. Chromametry was also used to evaluate skin colour. Dermatologists' and subjects' assessments were compiled in CT3. Results, A 10-week DS intake prevented the UV-DL-induced decrease in Langerhans cell density and the increase in factor XIIIa+ type I dermal dendrocytes while it reduced dermal inflammatory cells. Clinical and instrumental MED rose by 20% and 19%, respectively, and skin colour was intensified, as shown by the increase in the ,E* parameter. The efficacy of DS was confirmed by dermatologists and subjects under real conditions of use. Conclusions, Nutritional supplementation combining a specific probiotic (La1) and nutritional doses of carotenoids reduced early UV-induced skin damage caused by simulated or natural sun exposure in a large panel of subjects (n = 139). This latter result might suggest that DS intake could have a beneficial influence on the long-term effects of UV exposure and more specifically on skin photoageing. [source]