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[en] In this work, the performances of two optimized reflective secondary optics elements a CPC (Compound Parabolic Concentrator) and a Cone for use in a CPV concentrator system are studied using ray-tracing simulation for the same primary optical element: a Fresnel lens. These optical elements are compared in terms of concentration, acceptance angle, exit angle and output light distribution. Our results show that the power distribution at the end of the concentrator is more uniform in the case of the cone. The optical efficiency is higher when the secondary element is placed at a distance with f the focal length; R the input radius of the secondary optical element and θ the acceptance angle of the secondary optical element. Also, we found that the length and the input radius of each optical element decrease when the Fresnel lens diameter increases but the input radius of the CPC stills the larger. Finally, our calculation show that the CPC is longer than the cone while the Fresnel lens diameter is less than 200 mm and beyond this value both the cone and the CPC mostly present the same length. (paper)
[en] Highlights: • Development of an analytical model for assessing the well-mixing length of a tracer in a duct airflow. • Validation on data from in situ experiments. • Model simplification for proposing correlations more suitable for the industrial issue. - Abstract: The aim of this study is to propose an analytical model for assessing the well-mixing length of a tracer in a ventilation duct. The first part of the article is devoted to describe an experimental bench developed for validating the proposed model. This bench allows to follow the evolution of a tracer injected at a source point in the center of a duct by using an original optical measurement technique. In a second part, an analytical model for the spatial evolution of a tracer concentration in a circular duct is developed, taking into account an eddy viscosity model. The difficulty for applying this model to industrial cases led us to propose a simplified version that can be used for a non-dimensional distance greater than 20 diameters. The latter was then inverted in order to access to two criteria: the coefficient of variation in the duct section and the difference between the local measured concentration and the expected homogeneous concentration. Each one has its interest depending on whether a global information on the duct section or a local information (on the axis for example) at a given distance is required.
[en] Highlights: • Outdoor radon levels can cause departure from lognormal indoor radon distribution. • An analytical method is proposed to evaluate and correct outdoor impact for every radon distribution. • Results of this study can be useful for a correct classification of radon areas. - Abstract: Outdoor radon concentration contributes to indoor radon levels, generally causing a shift from lognormal distribution of measured radon concentration data distribution, and it makes more challenging the estimation of radon distribution parameters on the basis of the lognormal assumption. In particular, lognormal assumption with no correction could lead to a significantly biased estimate of the percentage of dwellings exceeding a certain level, e.g. a reference level (RL), since this is based on biased estimates of geometric mean (GM) and geometric standard deviation (GSD) of radon concentration distribution. Subtracting to each measured data a constant outdoor radon level can usually compensate data distribution departure from log-normality (except for low radon levels), if the appropriate outdoor level value is chosen by means of a lognormal fit of the data. This approach – already (but not always) used in literature – cannot be applied in cases where all the data of radon concentrations are not available (e.g., for a review study). For these cases, this work presents an analytical method to quantitatively evaluate and correct the impact of outdoor on the lognormal distribution parameter estimates and, in particular, on the percentages of dwellings exceeding radon reference levels. The proposed method is applied to a number of possible situations, with different values of outdoor radon level, GM and GSD. The results show that outdoor radon levels generally produce an underestimation of the actual GSD parameter, which increases as the outdoor level increases, and in the worse cases, could lead to an underestimation higher than 50%. Consequently, if the outdoor contribution is not properly taken into account, the percentage of dwellings exceeding a certain RL is almost always underestimated, even by 80%–90% for RL equal to 300 Bq/m3. This could have implications for the classification of areas as regards radon concentration and for the estimation of avertable lung cancers attributable to radon levels higher than some possible RLs.
[en] Highlights: • Indoor radon was measured in randomly selected newly built houses in 2008 and 2016. • New building regulations with preventive measures on radon was introduced in 2010. • A significant reduction of radon concentrations was found in detached houses. - Abstract: Results from two national surveys of radon in newly built homes in Norway, performed in 2008 and 2016, were used in this study to investigate the effect of the 2010 building regulations introducing limit values on radon and requirements for radon prevention measures upon construction of new buildings. In both surveys, homes were randomly selected from the National Building Registry. The overall result was a considerable reduction of radon concentrations after the implementation of new regulations, but the results varied between the different dwelling categories. A statistically significant reduction was found for detached houses where the average radon concentration was almost halved from 76 to 40 Bq/m3. The fraction of detached houses which had at least one frequently occupied room with a radon concentration above the Action Level (100 Bq/m3) fell from 23.9% to 6.4%, while the fraction above the Upper Limit Value (200 Bq/m3) was reduced from 7.6% to 2.5%. In 2008 the average radon concentration measured in terraced and semi-detached houses was 44 and in 2016 it was 29 Bq/m3, but the reduction was not statistically significant. For multifamily houses, it was not possible to draw a conclusion due to insufficient number of measurements.
[en] Highlights: Efficient dimerization of protonated ellipticine (EH+) is found in water. The long-lived fluorescence decay component of EH+ in H2O is due to dimer emission. Dimerization is enthalpically driven and entropically disfavored process. Dimer formation must be taken into account even at μM EH+ concentrations. Absorption and fluorescence spectroscopic measurements, as well as isothermal calorimetric titrations showed that the biexponential decay kinetics of protonated ellipticine (EH+) fluorescence in water originates from dimerization. Due to the high equilibrium constant for the association of two EH+ and the intense fluorescence of the dimer, deviation from the exponential emission intensity decay commences below micromolar concentrations. Dimerization must be taken into account when EH+ concentration is determined by spectrophotometry, and when EH+ binding to substrates are studied. The molar absorption coefficients of the monomer and dimer were determined.
[en] In order to investigate the corrosion behavior and impact toughness of 105SS drill pipe steel in the wet H2S environment, the impact and corrosion testing were carried out. The results show that the diffusible hydrogen concentration is mainly influenced by the morphology of the corrosion scales and the dynamic fracture toughness loss of 105SS drill pipe steels increases with the increase of diffusible hydrogen concentration. However, when hydrogen was released, the impact energy increases. The area of quasi-cleavage features on the fracture surfaces increases with the increase of hydrogen concentration. (paper)
[en] Highlights: • Nationwide indoor radon survey in Montenegro. • Distribution of radon concentrations deviates from log-normality. • Log-normality obtained by subtracting contribution from radon in outdoor air. • Fraction of homes with high radon levels estimated using transformed data set. • National reference level, “urgent action level” and radon priority areas proposed. - Abstract: The first nationwide indoor radon survey in Montenegro started in 2002 and year-long radon measurements with CR-39 track-etch detectors, within the national grid of 5 km × 5 km and local grids in urban areas of 0.5 km × 0.5 km, were performed in homes in half of the country's territory. The survey continued in 2014 and measurements in the rest of the country were completed at the end of 2015. The 953 valid results, obtained in the national radon survey, give an average radon activity concentration in Montenegrin homes of 110 Bq/m3. Assuming a log-normal distribution of the experimental results, geometric mean GM = 58.3 Bq/m3 and geometric standard deviation GSD = 2.91 are calculated. However, normality tests show that the experimental data are not log-normal, and that they become closest to a log-normal distribution after subtracting from them radon concentration in the outdoor air of 7 Bq/m3, which is theoretically calculated. Such a transformed distribution has GMtr = 46.7 Bq/m3 and GSDtr = 3.54. The estimations derived from positing a priory that the experimental results conform to a log-normal distribution underestimate the percentage of homes with radon concentrations at the thresholds of 300 Bq/m3 and above, which is better estimated by using GMtr and GSDtr. Based on the results of radon survey, a new national radon reference level of 300 Bq/m3 and an “urgent action level” of 1000 Bq/m3 are suggested, with estimated fractions of the national dwelling stock above these levels of 7.4% and 0.8% respectively. Fractions of homes with radon concentrations above the suggested levels are also estimated for each of the 23 municipalities in Montenegro, using appropriate GMtr and GSDtr. The six municipalities which have more than 10% of homes with radon concentration above 300 Bq/m3 are recommended as radon priority areas.
[en] In this paper, we have used detailed balance limit model in order to achieve optimum single junction solar cell for different outdoor conditions. Also, maximum achievable efficiency for GaAs-based double junction solar cells has been calculated and effects of the concentration ratio on optimum point have been investigated. Although 1.9/1.0 eV is achieved as the optimum combination of band gaps for double junction solar cells, but simulation results show some changes in value of top cell’s optimum band gap when the GaAs is used as bottom cell. Finally, effect of changing temperature on behavior of GaAs-based double junction solar cell has been studied under 1sun black body, AM0 and AM1.5 spectrums. (author)
[en] Based on the skeleton sand body analysis in planar and spatial distribution rules of lower member of Xishanyao Formation, the key blocks of sedimentary microfacies are shown in detail in the article, and the relationship between sedimentary microfacies and uranium mineralization is explored. It is suggested that two large sedimentary bodies of the lower member of Xishanyao Formation control two key ore-concentrated areas (Ku-Hong and Men-Zha-Wu) at the southern margin of Yili basin. Skeleton sand body in ore-concentration areas has good reservoir properties due to its large thickness and strong connectivity. Fan delta sedimentary system which includes delta plain facies and delta front facies developed in the lower member of Xishanyao Formation. The main ore-controlling microfacies are distributary channel, underwater distributary channel and front sheet sand. Ore bodies of distributary channel are enriched in the coarse sand body and ore bodies of underwater distributary channel are enriched in the nearby shale, especially carbonaceous shale and coal line in general. Ore bodies of front sheet sand are enriched in the middle-coarse sand body that connected to the channel transition. (authors)