The disintegrating old open cluster Czernik 3 Sharma, Saurabh; Ghosh, Arpan; Ojha, D K ...
Monthly Notices of the Royal Astronomical Society,
10/2020, Letnik:
498, Številka:
2
Journal Article
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ABSTRACT
We have performed a detailed analysis of the Czernik 3 (Cz3) open cluster by using deep near-infrared photometry taken with TIRCAM2 on the 3.6 m Devasthal optical telescope along with the ...recently available high-quality proper motion data from the Gaia DR2 and deep photometric data from Pan-STARRS1. The cluster has a highly elongated morphology with fractal distribution of stars. The core and cluster radii of the cluster are estimated as 0.5 and 1.2 pc, respectively. We have identified 45 stars as cluster members using the Gaia proper motion data. The distance and age of the cluster are found to be 3.5 ± 0.9 kpc and $0.9^{+0.3}_{-0.1}$ Gyr, respectively. The slope of the mass function `Γ′ in the cluster region, in the mass range ∼0.95 <M/M⊙ < 2.2, is found to be −1.01 ± 0.43. The cluster shows the signatures of mass segregation and is dynamically relaxed (dynamical age = 10 Myr). This along with its small size, big tidal radius, low density/large separation of stars, and elongated and distorted morphology indicates that the Cz3 is a loosely bound disintegrating cluster under the influence of external tidal interactions.
•The performance of evacuated tube collector with/without storage was investigated.•Evacuated tube collector with phase change material showed better performance.•Designed system is suitable for ...day/night time utilization of hot water.•Thermal cycle test of SA-67 has been studied for long term stability.
This manuscript presents an experimental investigation of heat pipe evacuated tube solar collector with and without phase change material for water heating application under the same weather conditions. In this study, a comparative analysis of two systems has been done in the same weather condition. Where evacuated tubes of the first system (evacuated tube collector-A) were left without phase change material and second system (evacuated tube collector-B) was integrated with SA-67 as phase change material. In order to ensure the thermal and chemical stability of the selected phase change material, thermal cycling treatment was carried out. The results showed that SA-67 has excellent chemical and thermal stability even after 1500 thermal cycling treatment.
In order to analyze the thermal performance of the designed systems, the experiment was conducted with five different water flow rates (8, 12, 16, 20 and 24 L per hour). The daily thermal efficiency of evacuated tube solar collector with and without phase change material was varied in the range of 42–55% and 79–87% respectively. Although, the daily energy efficiency of evacuated tube collector integrated with phase change material was 37.56%, 35.31%, 36.69%, 32.34%, and 32.73% higher than evacuated tube collector without phase change material for water flow rates of 8, 12, 16, 20 and 24 L per hour respectively. The daily thermal efficiency for both systems was maximum at the flow rate of 20 L per hour. The heat transfer parameters for the designed systems have also been evaluated and compared.
Increasing anthropogenic and biogenic emissions of precursor compounds have led to high tropospheric ozone concentrations in India particularly in Indo-Gangetic Plains, which is the most fertile and ...cultivated area of this rapidly developing country. Current ozone risk models, based on European and North American data, provide inaccurate estimations for crop losses in India. During the past decade, several ozone experiments have been conducted with the most important Indian crop species (e.g. wheat, rice, mustard, mung bean). Experimental work started in natural field conditions around Varanasi area in early 2000's, and the use of open top chambers and EDU (ethylene diurea) applications has now facilitated more advanced studies e.g. for intra-species sensitivity screening and mechanisms of tolerance. In this review, we identify and discuss the most important gaps of knowledge and future needs of action, e.g. more systematic nationwide monitoring for precursor and ozone formation over Indian region.
Tropospheric ozone is an increasing threat to food production in India.
This paper reviews dissimilatory nitrate reduction to ammonium (DNRA) in soils - a newly appreciated pathway of nitrogen (N) cycling in the terrestrial ecosystems. The reduction of NO3− occurs in two ...steps; in the first step, NO3− is reduced to NO2−; and in the second, unlike denitrification, NO2− is reduced to NH4+ without intermediates. There are two sets of NO3−/NO2− reductase enzymes, i.e., Nap/Nrf and Nar/Nir; the former occurs on the periplasmic-membrane and energy conservation is respiratory via electron-transport-chain, whereas the latter is cytoplasmic and energy conservation is both respiratory and fermentative (Nir, substrate-phosphorylation). Since, Nir catalyzes both assimilatory- and dissimilatory-nitrate reduction, the nrfA gene, which transcribes the NrfA protein, is treated as a molecular-marker of DNRA; and a high nrfA/nosZ (N2O-reductase) ratio favours DNRA. Recently, several crystal structures of NrfA have been presumed to producee N2O as a byproduct of DNRA via the NO (nitric-oxide) pathway. Meta-analyses of about 200 publications have revealed that DNRA is regulated by oxidation state of soils and sediments, carbon (C)/N and NO2−/NO3− ratio, and concentrations of ferrous iron (Fe2+) and sulfide (S2−). Under low-redox conditions, a high C/NO3− ratio selects for DNRA while a low ratio selects for denitrification. When the proportion of both C and NO3− are equal, the NO2−/NO3− ratio modulates partitioning of NO3−, and a high NO2−/NO3− ratio favours DNRA. A high S2−/NO3− ratio also promotes DNRA in coastal-ecosystems and saline sediments. Soil pH, temperature, and fine soil particles are other factors known to influence DNRA. Since, DNRA reduces NO3− to NH4+, it is essential for protecting NO3− from leaching and gaseous (N2O) losses and enriches soils with readily available NH4+-N to primary producers and heterotrophic microorganisms. Therefore, DNRA may be treated as a tool to reduce ground-water NO3− pollution, enhance soil health and improve environmental quality.
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•DNRA is a novel and shortest biological pathway of N-cycling in terrestrial ecosystems where NO3- is reduced to NH4+ in soils•This pathway has potential to reduce N2O emissions and protect NO3- from leaching losses•It outcompetes the denitrification process under limited NO3- availability in the system•It enriches soil with NH4+-N and make available to primary producers as N-fertilizer•Meta-analyse revealed that DNRA is mainly regulated by C/N ratio, NO2- / NO3- ratio and S2-
•Compendium on switching from Pt based CE to naturally available materials for CE.•Systematically reviews on the CE in DSSCs with special focus on Pt-TCO free CE.•Synthesis and fabrication methods of ...various CE has been presented.
Among all PV devices, DSSCs are believed to be one of the most promising devices, owing to their low cost, facile methods of fabrication and eco-friendly nature. Several components such are titanium dioxide/metal oxide-based photoanode, platinum/composite material based counter electrode and sensitizing dye along with the electrolyte are the basic components which effects the performance of DSSCs. Counter electrode collects the electron from an external circuit and helps in the regeneration of dye by oxidation-reduction of electrolyte, which significantly effects the overall performance of PV devices. Several materials such as carbonaceous materials, conducting polymers, oxides, and sulfides have been investigated as the low cost and highly stable material for the potential replacement for an expensive Pt-based counter electrode in DSSCs. In this Review, an attempt has been made to present recent achievements to replace Platinum (Pt) counter electrode with other inexpensive and earth abundant materials for DSSCs. This article systematically reviews the counter electrodes in DSSCs and provides review focused on Pt-TCO free counter electrodes. The main problems and challenges such as synthesis and fabrication of various CE, commercialization of DSSCs are addressed in detail with a conclusion and proposition section.
Abstract
Deep optical photometric data on the NGC 7538 region were collected and combined with archival data sets from the Chandra, 2MASS and Spitzer surveys to generate a new catalogue of young ...stellar objects (YSOs) including those not showing infrared excess emission. This new catalogue is complete down to 0.8 M⊙. The nature of the YSOs associated with the NGC 7538 region and their spatial distribution are used to study the star-formation process and the resultant mass function (MF) in the region. Out of the 419 YSOs, ∼91 per cent have ages between 0.1 and 2.5 Myr and ∼86 per cent have masses between 0.5 and 3.5 M⊙, as derived by the spectral energy distribution fitting analysis. Around 24, 62 and 2 per cent of these YSOs are classified to be class I, class II and class III sources, respectively. The X-ray activities for the class I, class II and class III objects are not significantly different from each other. This result implies that the enhanced X-ray surface flux due to the increase in the rotation rate may be compensated for by the decrease in the stellar surface area during the pre-main-sequence evolution. Our analysis shows that the O3V type high-mass star IRS 6 may have triggered the formation of young low-mass stars up to a radial distance of 3 pc. The MF shows a turn-off at around 1.5 M⊙ and the value of its slope Γ in the mass range 1.5 < M/M⊙ < 6 is −1.76 ± 0.24, which is steeper than the Salpeter value.
•Experimental performance has been carried for developed solar water heater.•Stearic acid as phase change material has been investigated under both modes.•Proposed system is suitable for domestic & ...industrial applications.•Phase change material integrated manifold is designed for thermal energy storage.•System was investigated with different mass flow rates under both modes.
In this study, the thermal performance of a novel solar collector integrated with stearic acid as phase change material has been investigated. In this design, the solar radiation was collected by heat pipe equipped evacuated tubes and then stored in manifold integrated with phase change material. The stored thermal energy of phase change material then transferred to water flowing through bundle of finned copper pipes placed inside the manifold. In present study, the design, the operating principle and the experimental investigation of the developed system have been presented. The developed system was investigated with different mass flow rates and also discussed the influence of varying mass flow rate on the thermal performance of system. The experimental investigation of designed and developed system has been carried out for two modes i.e. mid-day charging mode and full-day charging mode. It has been observed that for considered mass flow rates, thermal efficiency of the system was varied in the range of approximately 52–62% for full-day charging mode while for mid-day charging mode, it was varied between 55 and 72%. The maximum value of thermal efficiency was approximately 72.52% at mass flow rate of 24 LPH for mid-day charging mode. The efficiency of phase change material for both modes was varied in the range of approximately 61–64%. The annual cost and annual fuel cost of the developed system are much lower than conventional system. Also, the initial capital cost for the developed system can be recovered after 6 years of operation. However, there is no recovery of initial investment for electricity based water heating system.
The proposed system overcomes two problems associated with conventional heat pipe evacuated tube solar collector: elimination of heat pipe overheating problem and low thermal conductivity of phase change materials. By this novel design of manifold, the influence of thermal stratification on the thermal performance of solar collectors can be completely eradicated.
Dry anaerobic digestion (DAD) is an attractive method for the stabilization of solid organic waste with high solid concentration (22–40%). This article provides different aspects for bio-energy ...production through dry anaerobic digestion suggested by different researchers. Basic fundamental aspects like reactions occurring in the process, microbial species involved in the process, effect of feedstocks and operational parameters like pH, temperature, C/N ratio, VFA concentration, etc. with types of reactors are summarized. A number of scenarios and the effect of changing individual parameters of the environmental impacts of dry anaerobic digestion process for biogas production are considered. Mobility of mass nutrient and energy flow in the above said process are also parts of this review article. We conclude that long term research and development for improvement and optimization of operational parameters in dry anaerobic digestion is necessary.
Phase change materials (PCMs) utilized for thermal energy storage applications are verified to be a promising technology due to their larger benefits over other heat storage techniques. Apart from ...the advantageous thermophysical properties of PCM, the effective utilization of PCM depends on its life span. Moreover, PCMs which are utilized for different solar thermal energy storage applications are required longer thermal and chemical stability for the extended performance of a system. This review shows the in-depth details on thermal stability and reliability of different PCMs such as organic, inorganic, eutectics, and composites materials for heat storage applications. Different methods for measuring the thermophysical properties along with the classification of PCMs based on applications and temperature ranges have been discussed. This paper also covers the selection criteria and commercial viability of PCMs for different domestic and industrial applications. In addition to this, the effect of thermal cycle testing on the properties of different organic, inorganic, eutectic, and composite PCMs has been summarized. The present article can be highly useful for researchers and practice engineers in the areas related to thermal energy storage applications.
•Comprehensive summary on several factors affecting the solar panel efficiencies.•Compendium on different self-cleaning methods for PV panels.•Superhydrophobic based self-cleaning method is most ...suitable for PV applications.•Presents the future trend and move in self-cleaning based research on PV panels.
Photovoltaic (PV) installations in desert areas such as Middle East, Africa, four-season countries and industrial areas suffers from loss in efficiency due to accumulation of dust, snowfall and airborne dirt (both organic and inorganic) from factories. The resultant soiling through dirt accumulation hinders the conversion of light into electricity, consequently degrading the PV performance. Hence, in order to maintain a steady performance, PV panels must be cleaned regularly. However, traditional manual cleaning of the panels is an energy and time consuming process. Moreover, manual cleaning can also create cracks on the PV panel surface due to harsh brushing which will further deteriorate PV performance. In addition, very small particles cannot be removed effectively by manual cleaning process. Therefore, researchers around the globe are promoting the self-cleaning methods, viz., electrostatic method, mechanical method and coating method for PV panel surface cleaning. In this article, attempt has been made to review the progress and achievements in all kinds of self-cleaning methods for PV panels with special focus on super hydrophobic coating based methods for self-cleaning. In this connection, future focus research areas such as development of mini robots and spray coating on self-cleaning have been pointed out.
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