Solar radiation is a primary driver for many physical, chemical, and biological processes on the earth’s surface. Solar energy engineers, architects, agriculturists, hydrologists, etc. often require ...a reasonably accurate knowledge of the availability of the solar resource for their relevant applications at their local. In solar applications, one of the most important parameters needed is the long-term average daily global irradiation. For regions where no actual measured values are available, a common practice is to estimate average daily global solar radiation using appropriate empirical correlations based on the measured relevant data at those locations. These correlations estimate the values of global solar radiation for a region of interest from more readily available meteorological, climatological, and geographical parameters. The main objective of this study is to chronologically collect and review the extensive global solar radiation models available in the literature and to classify them into four categories, i.e., sunshine-based, cloud-based, temperature-based, and other meteorological parameter-based models, based on the employed meteorological parameters as model input.
Furthermore, in order to evaluate the accuracy and applicability of the models reported in this paper for computing the monthly average daily global solar radiation on a horizontal surface, the geographical and meteorological data of Yazd city, Iran was used. The developed models were then evaluated and compared on the basis of statistical error indices and the most accurate model was chosen in each category. Results revealed that all the proposed correlations have a good estimation of the monthly average daily global solar radiation on a horizontal surface in Yazd city, however, the El-Metwally sunshine-based model predicts the monthly averaged global solar radiation with a higher accuracy.
•Energy and exergy analysis of a thermoelectric assisted solar still are conducted.•The rate of components’ exergy destructions are proportional to the solar intensity.•The largest exergy destruction ...happened in the thermoelectric module.•Unlike the energy, the daily exergy efficiency of this active solar still is very low.
The present study is devoted to a comprehensive thermodynamic modeling of a novel portable solar still through the first and second laws analysis. In this new solar still, a thermoelectric module is employed to elevate the temperature difference between evaporating and condensing zones. Energy and exergy balance equations have been written for all components of the solar still including glass cover, thermoelectric module, saline water, and basin-liner. A new approach is used to evaluate evaporative heat transfer coefficients. Comparison of distilled water calculated by the present approach and the results obtained by employing various semi-experimental models proved the accuracy of the proposed thermodynamic modeling. It is also found that the exergy stored within the body of saline water, which was neglected in the most previous studies, is important and should be considered.
It is shown that the daily average energy and exergy efficiencies of the solar still are 19.8% and 0.95%, respectively. It is seen that the exergy efficiency is much lower than the energy efficiency. Furthermore, it is found that the rate of exergy destructions in solar still components is proportional to the incident solar intensity. The largest exergy destruction belongs to the thermoelectric module, which is 63.4% of the total exergy destruction, while the glass cover has the smallest share. It is concluded that although the energy efficiency associated with this type of thermoelectrically assisted solar still is higher than its counterpart simple passive solar still one, however, its exergy efficiency is lower.
Background
Emergence of coronavirus disease 2019 (COVID‐19) is a major healthcare threat. Apparently, the novel coronavirus (SARS‐CoV‐2) is armed by special abilities to spread and dysregulate the ...immune mechanisms. The likelihood of oropharyngeal candidiasis (OPC) development in COVID‐19 patients with a list of attributable risk factors for oral infections has not yet been investigated.
Objectives
We here aim to investigate the prevalence, causative agents and antifungal susceptibility pattern of OPC in Iranian COVID‐19 patients.
Patients and Methods
A total of 53 hospitalised COVID‐19 patients with OPC were studied. Relevant clinical data were mined. Strain identification was performed by 21‐plex PCR and sequencing of the internal transcribed spacer region (ITS1‐5.8S‐ITS2). Antifungal susceptibility testing to fluconazole, itraconazole, voriconazole, amphotericin B, caspofungin, micafungin and anidulafungin was performed according to the CLSI broth dilution method.
Results
In 53 COVID‐19 patients with OPC, cardiovascular diseases (52.83%) and diabetes (37.7%) were the principal underlying conditions. The most common risk factor was lymphopaenia (71%). In total, 65 Candida isolates causing OPC were recovered. C albicans (70.7%) was the most common, followed by C glabrata (10.7%), C dubliniensis (9.2%), C parapsilosis sensu stricto (4.6%), C tropicalis (3%) and Pichia kudriavzevii (=C krusei, 1.5%). Majority of the Candida isolates were susceptible to all three classes of antifungal drugs.
Conclusion
Our data clarified some concerns regarding the occurrence of OPC in Iranian COVID‐19 patients. Further studies should be conducted to design an appropriate prophylaxis programme and improve management of OPC in critically ill COVID‐19 patients.
•Energetic and exergetic performance of two circular and square solar ponds are studied.•Solar ponds may be used as effective thermal storage in Yazd with a desired efficiency.•Circular solar pond ...shows superior thermal performance than the square one.•Energy efficiencies are higher than exergy efficiencies for both solar ponds.
Solar energy is a free, clean and widely available renewable energy. Various kinds of solar systems provide scope for several studies on energy and exergy analysis. Solar ponds are one of applications for collecting and storing solar energy simultaneously and are usable in regions with readily available land, much sunlight, and access to low-priced salt.
In the present work, an experimental investigation of the energetic and exergetic performance of two prototype solar ponds with square and circular cross sections has been carried out. The solar ponds were built at Bafgh city, a city near Yazd in the central part of Iran. The cross sectional area and depth of both prototype solar ponds are 3m2 and 1.5m, respectively. During 11months of energy storage operation, a data acquisition system was used to measure the temperature variations along the height of the solar ponds and to capture the development of thermal stratification. Data collection is done with 10min intervals.
Thermal analysis of an experimental solar pond is usually a complicated task due to variations of many involved factors such as solar radiation, thermophysical properties of operating fluid, climatic changes etc. The energy performances of the solar ponds under investigation are carried out by modeling the solar incident radiation on the ponds surface, calculating energy exchange within each zone and thermal energy losses to the environment. Although the data are collected for almost one year of operation, however, the energy analysis is performed for some warmer months of the year during which the ponds are in the charging or energy storing period.
An exergy balance model is also developed to investigate the exergetic performance of solar ponds. Monthly averaged exergy efficiencies are obtained for different regions of the ponds and compared with the corresponding energy efficiencies. The monthly average temperature of ambient is considered as the reference environment temperature for the exergy analysis. It was demonstrated that the circular solar pond has superior thermal performance than the square one. Stored water in the storage zone of the circular solar pond reaches to a higher temperature in comparison with the square one. It is attributed to the different shading effect in the two solar ponds. The maximum energy efficiencies for NCZ and HSZ of circular solar pond are found to be 17.25% and 25.8%, respectively while the corresponding values for the square solar pond are 17.39% and 23.65%. Maximum exergy efficiency for NCZ and HSZ are 0.86% and 2.44% for circular solar pond and 0.71% and 1.91% for the square solar pond.
•An experimental study of the Trombe wall with a new design is studied.•The new design increases maximum absorber temperature 10°C more than traditions.•Weekly results imply that the room temperature ...is in range of 15–30°C.•Proposed system reduces the difference of maximum and minimum temperature of room.•The new design increases the stored energy of the Trombe wall.
This paper presents an experimental study of a new designed Trombe wall, which is a part of the southern wall of a test room, in terms of energy performance and heating comfort during winter operation for Yazd city (Iran) desert climate. The area of the Trombe wall is 50% of that of the southern wall of the test room. Hence, it occupies less space and reduces the implementation costs. Contrary to the traditional Trombe walls in which the absorber receives solar radiation from one direction, this innovative design enables the absorber to receive solar radiation from three directions (East, South and West), therefore, the absorbing surface of the wall is subject to the solar irradiation during the all day time (from sunrise to sunset). The experimental results revealed that the range of room temperature on the coldest winter days and weeks in Yazd is kept within 15–30°C, and this implies that the present Trombe wall design is able to provide a comfortable indoor temperature with lower difference between the maximum and minimum temperatures due to the increased stored energy of the Trombe wall. Furthermore, the present innovative design of the Trombe wall channel causes the absorber temperature to reach around 47°C on the coldest winter days, indicating the highest possible solar intensity received by the absorber. Analysis of the hourly stored energy of the Trombe wall reveals that the more solar intensity leads to the more energy absorption and the higher Trombe wall back surface temperature, which in turn causes the hourly stored energy to reach to a maximum of 5800kJ/h in February.
Vitamin C is an essential water-soluble nutrient that functions as a key antioxidant and has been proven to be effective for boosting immunity. In this study, we aimed to assess the efficacy of ...adding high-dose intravenous vitamin C (HDIVC) to the regimens for patients with severe COVID-19 disease.
An open-label, randomized, and controlled trial was conducted on patients with severe COVID-19 infection. The case and control treatment groups each consisted of 30 patients. The control group received lopinavir/ritonavir and hydroxychloroquine and the case group received HDIVC (6 g daily) added to the same regimen.
There were no statistically significant differences between two groups with respect to age and gender, laboratory results, and underlying diseases. The mean body temperature was significantly lower in the case group on the 3rd day of hospitalization (p = 0.001). Peripheral capillary oxygen saturations (SpO
) measured at the 3rd day of hospitalization was also higher in the case group receiving HDIVC (p = 0.014). The median length of hospitalization in the case group was significantly longer than the control group (8.5 days vs. 6.5 days) (p = 0.028). There was no significant difference in SpO
levels at discharge time, the length of intensive care unit (ICU) stay, and mortality between the two groups.
We did not find significantly better outcomes in the group who were treated with HDIVC in addition to the main treatment regimen at discharge. Trial registration irct.ir (IRCT20200411047025N1), April 14, 2020.
Counting short cycles in bipartite graphs is a fundamental problem of interest in the analysis and design of low-density parity-check codes. The vast majority of research in this area is focused on ...algorithmic techniques. Most recently, Blake and Lin proposed a computational technique to count the number of cycles of length <inline-formula> <tex-math notation="LaTeX">\boldsymbol {g} </tex-math></inline-formula> in a bi-regular bipartite graph, where <inline-formula> <tex-math notation="LaTeX">\boldsymbol {g} </tex-math></inline-formula> is the girth of the graph. The information required for the computation is the node degree and the multiplicity of the nodes on both sides of the partition, as well as the eigenvalues of the adjacency matrix of the graph (graph spectrum). In this paper, the result of Blake and Lin is extended to compute the number of cycles of length <inline-formula> <tex-math notation="LaTeX">\boldsymbol {g} + \textbf {2}, \ldots, \textbf {2}\boldsymbol {g}-\textbf {2} </tex-math></inline-formula>, for bi-regular bipartite graphs, as well as the number of 4-cycles and 6-cycles in irregular and half-regular bipartite graphs, with <inline-formula> <tex-math notation="LaTeX">\boldsymbol {g} \geq \textbf {4} </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">\boldsymbol {g} \geq \textbf {6} </tex-math></inline-formula>, respectively.
This paper proposes two solutions based on angle diversity receivers (ADRs) to mitigate inter-cell interference (ICI) in underground mining visible light communication (VLC) systems, one of them is a ...novel approach. A realistic VLC system based on two underground mining scenarios, termed as mining roadway and mine working face, is developed and modeled. A channel model based on the direct component in line-of-sight (LoS) and reflections of non-line-of-sight (NLoS) links is considered, as well as thermal and shot noises. The design and mathematical models of a pyramid distribution and a new hemi-dodecahedral distribution are addressed in detail. The performances of these approaches, accompanied by signal combining schemes, are evaluated with the baseline of a single photo-diode in reception. Results show that the minimum lighting standards established in both scenarios are met. As expected, the root-mean-square delay spread decreases as the distance between the transmitters and receivers increases. Furthermore, the hemi-dodecahedron ADR in conjunction with the maximum ratio combining (MRC) scheme, presents the best performance in the evaluated VLC system, with a maximum user data rate of 250 Mbps in mining roadway and 120 Mbps in mine working face, received energy per bit/noise power of 32 dB and 23 dB, respectively, when the bit error rate corresponds to 10 - 4 , and finally, values of 120 dB in mining roadway and 118 dB in mine working face for signal-to-interference-plus-noise ratio are observed in a cumulative distribution function.
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