•A photovoltaic/thermal system was used in indoor and outdoor of greenhouse.•The experiments were carried out by using the pure water and nanofluids.•The results showed that the use of hybrid ...nanofluids was the best efficiency.•Using of pure water caused high efficiency difference at indoor and outdoor.•Using of nanofluids reduced the efficiency difference between indoor and outdoor.
Invoked by a rising demand for energy in greenhouse production, the industry has adopted a new approach by incorporating photovoltaic panels. A photovoltaic/thermal (PVT) system was used both inside and outside of a greenhouse to simultaneously supply electricity and heating. The experiments were carried out in both indoor and outdoor conditions using pure water cooling, single nanofluids (0.1, 0.3, and 0.5 wt%), and hybrid nanofluids (SiO2-Al2O3; 0.1–0.1, 0.3–0.3 and 0.5–0.5 %wt). The highest electrical and thermal efficiency values were 13.17% and 65.05% for the outdoor PV panel , and 11.47% and 56.08% for the indoor panel using hybrid nanofluid with the 0.5–0.5 concentration of (wt%). The results also indicated that the overall efficiency of the indoor and outdoor systems were 48.54% and 63.26%, respectively, when using pure water. Hybrid nanofluid, however, increased the overall efficiency of both indoor and outdoor systems by 68.09% and 75.26%. This finding revealed the larger effect of the nanofluid on the indoor system than on the outdoor greenhouse. Accordingly, the efficiency gap of the two systems was dropped from 14.72% to 7.17% when working with nanofluid, instead of pure water. Additionally, the results showed that the overall efficiency of the indoor system had the closest efficiency to that of the outdoor system when using the single and hybrid (Al2O3-SiO2) water-based nanofluids.
The prime Kepler mission detected 34,032 transit-like signals, out of which 8054 were identified as likely due to astrophysical planet transits or eclipsing binaries. We manually examined 306 of the ...remaining 25,978 detections, and found six plausible transiting or eclipsing objects, five of which are plausible planet candidates (PCs), and one stellar companion. One of our new PCs is a possible new second planet in the KOI 4302 system. Another new PC is a possible new planet around the KOI 4246, and when combined with a different possible planet rescued by the False Positive Working Group, we find that KOI 4246 may be a previously unrecognized three-planet system.
Modeling of CO Rovibrational Line Emission of HD 141569 Jensen, Stanley K.; Brittain, Sean D.; Najita, Joan R. ...
Publications of the Astronomical Society of the Pacific,
10/2021, Letnik:
133, Številka:
1028
Journal Article
Recenzirano
HD 141569 is a Herbig Ae/Be star that straddles the boundary between the transition disks and debris disks. It is a low dust mass disk that reveals numerous structural elements (e.g., gaps and rings) ...that may point to young planets. It also exhibits a reservoir of CO gas observed at both millimeter and IR wavelengths. Previous observations reported a possible asymmetry in the CO gas emission. Herein the IR rovibrational emission lines are analyzed and modeled both spectroscopically and spectroastrometrically. We find emission features from both 12CO and 13CO isotopologues heated to a temperature of approximately 200 K in the radial extent of 13–60 au. We do not see evidence of the previously reported asymmetry in CO emission, our results being consistent with a Keplerian, axisymmetric emitting region. This raises the question of whether the emission profile may be evolving in time, possibly as a result of an orbiting feature in the inner disk such as a planet.
Common features of all carbonaceous chondrite groups are invariant refractory element ratios, depletions of moderately volatile elements as a function of their condensation temperature (TC), and ...strongly depleted highly volatile element concentrations independent of TC. The depletion of volatile elements with respect to the bulk solar system composition requires a separation of gas from solids in the solar nebula. Several models have been proposed to explain the decoupling of gas and solids, but not all are compatible with astrophysical, chemical, and petrologic constraints. Here existing physical models are integrated with measured element concentrations, measured and modeled physical properties of protoplanetary disks, and planetary-scale nucleosynthetic and stable isotope variations to establish a conceptual model for the condensation and accretion of elements into planetesimals. In this model, the chemical composition of chondrites is established by element condensation in a cooling solar nebula that changed its surface density as a function of time and temperature. The model predicts peak temperatures at the condensation sites of about 1400 K that consequently decreased due to a diminishing heat source originating from viscous heating and radiation, accompanied by continuous removal of gas from the nebula surface by photoevaporation. The coupled evolution of condensing solids from a nebula of diminishing surface density resulted in a pattern of decreasing moderately volatile abundances with decreasing TC. The reduction of nebula opacity due to the chondrule-forming process significantly increased nebula cooling rates and led to the near-chondritic relative abundances of highly volatile elements observed in carbonaceous chondrites.
The mineralogy and geochemistry of Ceres, as constrained by Dawn's instruments, are broadly consistent with a carbonaceous chondrite (CM/CI) bulk composition. Differences explainable by Ceres’s more ...advanced alteration include the formation of Mg‐rich serpentine and ammoniated clay; a greater proportion of carbonate and lesser organic matter; amounts of magnetite, sulfide, and carbon that could act as spectral darkening agents; and partial fractionation of water ice and silicates in the interior and regolith. Ceres is not spectrally unique, but is similar to a few other C‐class asteroids, which may also have suffered extensive alteration. All these bodies are among the largest carbonaceous chondrite asteroids, and they orbit in the same part of the Main Belt. Thus, the degree of alteration is apparently related to the size of the body. Although the ammonia now incorporated into clay likely condensed in the outer nebula, we cannot presently determine whether Ceres itself formed in the outer solar system and migrated inward or was assembled within the Main Belt, along with other carbonaceous chondrite bodies.
Solar system objects with perihelia beyond the orbit of Jupiter (q > 5 au) are too cold for water ice to generate an appreciable coma via sublimation. Despite this, numerous high-perihelion objects ...(HPOs) including many comets and recently escaped Kuiper Belt objects (Centaurs) are observed to be active out at least to the orbit of Saturn (q ∼ 10 au). Peak equilibrium temperatures at 10 au (∼125 K), while far too low to sublimate water ice, are sufficient to sublimate supervolatiles such as CO and CO2 ice. Temperatures at 10 au are also high enough to trigger the rapid crystallization of exposed amorphous ice, thus constituting another possible driver of distant activity. While supervolatile ices can sublimate strongly (as ) to at least Kuiper Belt (30 au) distances, crystallization is an exponential function of temperature that cannot be sustained much beyond ∼10 au. The heliocentric dependence of the activity thus suggests an observational test. If activity in high-perihelion objects is triggered by crystallization, then no examples of activity should be found with perihelia of q > 10 au. If, on the other hand, activity is due to free sublimation of exposed supervolatile ices, or another cause, then distant activity might be detected. We obtained sensitive, high-resolution Hubble Space Telescope observations of HPOs to search for activity beyond the crystallization zone. No examples of activity were detected in 53 objects with q > 15 au, consistent with the crystallization trigger hypothesis. However, sensitivity limits are such that we cannot reject the alternative hypothesis that mass loss is driven by the sublimation of supervolatile ices. We also searched for binary companions in our sample, finding none and setting an empirical 3 limit to the binary fraction of <8%.
Planet Nine has been proposed to potentially be a black hole (BH) in the outer solar system. We investigate the accretion flares that would result from impacts of small Oort Cloud objects, and find ...that the upcoming Legacy Survey of Space and Time (LSST) observing program will be able to either rule out or confirm Planet Nine as a BH within a year. We also find that LSST could rule out or confirm the existence of trapped planet-mass BHs out to the edge of the Oort Cloud, indirectly probing the dark matter fraction in subsolar mass BHs and potentially improving upon current limits by orders of magnitude.
•Angrites and eucrites exhibit nucleosynthetic anomalies in Nd and Zr isotopes.•These isotopic signatures are consistent with deficits in s-process nuclides.•This is similar to previously reported ...deficits for chondritic meteorites.•Distribution of s-process matter could be linked to heliocentric distance.•This creates potential for ‘cosmolocating’ feeding zones of Solar System materials.
The significant reorganization of the early Solar System due to giant planet migration has hampered our understanding of where planetary bodies formed. Previously employed proxies for reconstructing the primordial planetary architecture, such as water content or oxidation state, are complicated by post-accretionary processes. Here we investigate basaltic achondrites for their nucleosynthetic isotope signatures in the elements neodymium (Nd) and zirconium (Zr) and show that they are—similar to previously investigated chondritic meteorites—characterized by a relative deficit in isotopes produced by the s-process of nucleosynthesis. Importantly, these data are well correlated with nucleosynthetic signatures observed in other elements, demonstrating that s-process matter was heterogeneously distributed throughout the early Solar System. By comparing these isotopic signatures with potential proxies for Solar System reconstruction and computer modeling, we here argue that this isotopic heterogeneity in bulk meteoritic materials is linked to the original heliocentric distance of formation. Such scaling of nucleosynthetic signatures with heliocentric distance could permit reconstruction of the primordial architecture of the Solar System by ‘cosmolocating’ the accretion orbits of meteoritic parent bodies as a function of incorporated s-process matter.
Abstract
The NASA New Horizons Venetia Burney Student Dust Counter (SDC) measures dust particle impacts along the spacecraft’s flight path for grains with mass ≥10
−12
g, mapping out their spatial ...density distribution. We present the latest SDC dust density, size distribution, and flux measurements through 55 au and compare them to numerical model predictions. Kuiper Belt objects (KBOs) are thought to be the dominant source of interplanetary dust particles in the outer solar system due to both collisions between KBOs and their continual bombardment by interstellar dust particles. Continued measurements through 55 au show higher than model-predicted dust fluxes as New Horizons approaches the putative outer edge of the Kuiper Belt (KB). We discuss potential explanations for the growing deviation: radiation pressure stretches the dust distribution to further heliocentric distances than its parent body distribution; icy dust grains undergo photosputtering that rapidly increases their response to radiation pressure forces and pushes them further away from the Sun; and the distribution of KBOs may extend much further than existing observations suggest. Ongoing SDC measurements at even larger heliocentric distances will continue to constrain the contributions of dust production in the KB. Continued SDC measurements remain crucial for understanding the Kuiper Belt and the interpretation of dust disks around other stars.
•A review on spectral beam splitting (SBS) CPVT technologies is presented.•SBS methods including interference, liquid absorptive and other filters are discussed.•The researches of SBS CPVTs are ...reviewed comprehensively and summarized.•Recent research status and system performance characteristics are analysed.•Suggestions on the development of SBS CPVT technologies are proposed.
This article presents a review on the research and development of spectral beam splitting concentrated photovoltaic/thermal (SBS CPVT) hybrid solar systems. The investigations on the SBS CPVT hybrid technologies had begun in the 1980s and were aimed at complete utilization of the solar irradiation over the whole solar spectrum using both PV cells and thermal absorbers. Several different SBS approaches were employed to achieve better conversion efficiencies, including the interference filter, liquid absorptive filter, holographic filter, luminescent filter, diffractive filter, combined interference and liquid absorptive filter, combined liquid and solid absorptive filter, and photovoltaics itself as a solid absorptive filter. The SBS CPVT systems were proposed or assembled in various system configurations for numerous purposes, such as domestic hot water, thermochemical reaction, hydrogen production, or even power generation. These researches and developments are comprehensively reviewed in this article, and the advantages and disadvantages of different SBS methods are presented and concluded. This paper also aims to provide a global point of view on research trends, market potential, technical obstacles, and the future work required for the development of SBS CPVT technology.
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