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[en] We have analyzed the transport regimes and the asymptotic forms of the impurity concentration in a randomly inhomogeneous fractal medium in the case when an impurity source is surrounded by a weakly permeable degrading barrier. The systematization of transport regimes depends on the relation between the time t0 of emergence of impurity from the barrier and time t* corresponding to the beginning of degradation. For t0 < t*, degradation processes are immaterial. In the opposite situation, when t0 > t*, the results on time intervals t < t* can be formally reduced to the problem with a stationary barrier. The characteristics of regimes with t* < t < t0 depend on the scenario of barrier degradation. For an exponentially fast scenario, the interval t* < t < t0 is very narrow, and the transport regime occurring over time intervals t < t* passes almost jumpwise to the regime of the problem without a barrier. In the slow power-law scenario, the transport over long time interval t* < t < t0 occurs in a new regime, which is faster as compared to the problem with a stationary barrier, but slower than in the problem without a barrier. The asymptotic form of the concentration at large distances from the source over time intervals t < t0 has two steps, while for t > t0, it has only one step. The more remote step for t < t0 and the single step for t > t0 coincide with the asymptotic form in the problem without a barrier.
[en] Using the closed-can technique, radon exhalation rate, radon concentration and effective radium content have been carried out for soil samples collected from triple-junction of the North Anatolian Fault System and East Anatolian Fault System. The measured maximum values of the exhalation rate and radon concentration in the system were 400.7 (mBqm-2 h-1) and 8.10 Bqkg-1, respectively. However, effective radium concentration in soil samples has been found to vary from 0.02 to 0.80 Bqkg-1. Linear correlation was observed between soil-gas radon concentration, effective radium content and radon exhalation rate. The linear correlation coefficient between radium content and radon concentration was found to be 0.91. Nevertheless, it was found that there is a linear correlation (R2=0.99) between the radon concentration and exhalation rate
[en] The aim of this study was to survey the radon concentrations at 21 elementary schools in Gyeongju, Republic of Korea, to identify those schools with high radon concentrations. Considering their geological characteristics and the preliminary survey results, three schools were finally placed under close scrutiny. For these three schools, continuous measurements over 48 h were taken at the principal's and administration office. The radon concentrations at one school, Naenam, exceeded the action level (148 Bq/m3) established by the U.S. EPA, while those at the other two schools were below that level. - Highlights: • Preliminary measurements of the indoor radon concentrations were performed at the auditoriums in 23 elementary schools in Gyeongju. • Considering the geological characteristics and preliminary survey results, three elementary schools were screened for closer scrutiny. • For the three schools, continuous measurements were made at their principal's and administration offices over 48-h period. • The scrutiny revealed one elementary school of high radon concentration much higher than the U.S. EPA action level
[en] Highlights: •Theoretical net solar-to-electric efficiency of 51.5% is attainable. •Design of efficient PVT systems is governed by at least 5 key considerations. •Concentration ratio has the most pronounced influence on PVT system efficiency. •Efficient PV, low emissivity and high concentration deliver the best performance. -- Abstract: Performance limit of a solar hybrid power generation system integrating efficient photovoltaic (PV) cells and methanol thermal (T) decomposition is explored from a thermodynamic perspective within the capability of state-of-the-art technologies. This type of PVT system features potentially high “net solar-to-electric efficiency” in general, primarily resulting from a key difference in the design of the thermal part compared with conventional PVT systems, i.e. replacing heat engines by a thermochemical power generation module for thermal energy utilization. Key design parameters of the system, including PV cell type, emissivity, solar concentration ratio and solar concentrator type, are individually studied. A system combining all such optimized aspects is projected to achieve net solar-to-electric efficiencies up to 51.5%, after taking all major (e.g. optical, radiative) losses into consideration. This study reveals important insights and enriches understanding on design principles of efficient PVT systems aimed at comprehensive and effective utilization of solar energy.
[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] A compact, low-cost and high-output-power silicon-wafer solar strip-cells-array module (SCAM) was experimentally demonstrated. The proposed SCAM consisted mainly of a silicon-wafer strip-cell sparse array and low-concentration-ratio array concentrator based on an epoxy resin polymer (ERP) cylindrical plano-convex lens. A polymer replication process based on a polydimethylsiloxane mold was used to fabricate the ERP lens array concentrator. The results show that 46.94% of the silicon-wafer cell was saved in the designed SCAM. Moreover, the output power of the SCAM with a low concentration ratio of 8 suns was improved by 8.6%, compared with a whole piece of a conventional silicon-wafer solar cell with the same area as the module. The proposed method encapsulating solar cells provides a means to reduce the usage of silicon cells in modules as well as improving the output power of modules. (paper)
[en] We have suggested a complexity measure based method for studying the dependence of measured 222Rn concentration time series on indoor air temperature and humidity. This method is based on the Kolmogorov complexity (KL). We have introduced (i) the sequence of the KL, (ii) the Kolmogorov complexity highest value in the sequence (KLM) and (iii) the KL of the product of time series. The noticed loss of the KLM complexity of 222Rn concentration time series can be attributed to the indoor air humidity that keeps the radon daughters in air. - Highlights: • We proposed a complexity measure to study the dependence of 222Rn time series on indoor parameters. • We have introduced spectrum and maximal Kolmogorov complexity and the product of time series. • We used indoor 222Rn time series measured in 2009 in the Low-Background Laboratory in Belgrade. • Loss of complexity of 222Rn time series comes from indoor air humidity keeping 222Rn daughters in air
[en] The hygroscopic growth of aerosols is controlled by the relative humidity (RH) and changes the aerosols’ physical and hence optical properties. Observational studies of aerosol–cloud interactions evaluate the aerosol concentration using optical parameters, such as the aerosol optical depth (AOD), which can be affected by aerosol humidification. In this study we evaluate the RH background and variance values, in the lower cloudy atmosphere, an additional source of variance in AOD values beside the natural changes in aerosol concentration. In addition, we estimate the bias in RH and AOD, related to cloud thickness. This provides the much needed range of RH-related biases in studies of aerosol–cloud interaction. Twelve years of radiosonde measurements (June–August) in thirteen globally distributed stations are analyzed. The estimated non-biased AOD variance due to day-to-day changes in RH is found to be around 20% and the biases linked to cloud development around 10%. Such an effect is important and should be considered in direct and indirect aerosol effect estimations but it is inadequate to account for most of the AOD trend found in observational studies of aerosol–cloud interactions. (letter)
[en] The Kuril Islands region is considered promising for development of salmon aquaculture. There are 41 salmon fish hatcheries in the Sakhalin Island and the Kuril Islands, 34 of them are hatcheries of the chum. Therefore, concentrations of six elements (Zn, Cu, Cd, Pb, As, and Hg) were determined in chum salmon were caught in this region. The contents of toxic elements (Cd, Pb, As, and Hg) don't exceed their maximum permissible concentrations (MPC) according to the Russian sanitary standards, but concentration of Pb are closely to MPC. Increased concentrations of Pb in wild chum have the natural origin. The unusual conditions of the Western Pacific are formed under the influence such factors as volcanism and upwelling. - Highlights: • High content of Pb, found in chum from the Kuril Islands, is caused by natural sources. • The content of elements do not exceed maximum permissible concentrations in Russia. • Kuril region is considered as promising zone for development of salmon aquaculture. - Kuril region is suitable for aquaculture development of Pacific salmon.