Accurate determinations of atmospheric parameters (effective temperature Teff, surface gravity log g, and metallicity Fe/H) and distances for large complete samples are of vital importance for ...various Galactic studies. We have developed a photometric method to select red giant stars and estimate their atmospheric parameters from the photometric colors provided by SkyMapper Southern Survey (SMSS) data release (DR) 1.1, using stars in common with the LAMOST Galactic spectroscopic surveys as a training set. Distances are estimated with two different approaches: one based on the Gaia DR2 parallaxes for nearby (d ≤ 4.5 kpc) bright stars and another based on the absolute magnitudes predicted by intrinsic color (g − i)0 and photometric metallicity Fe/H for distant (d > 4.5 kpc) faint stars. Various tests show that our method is capable of delivering atmospheric parameters with a precision of ∼80 K for Teff, ∼ 0.18 dex for Fe/H, and ∼0.35 dex for log g but with a significant systematic error at log g ∼ 2.3. For distances delivered from (g − i)0 and photometric Fe/H, our test with the member stars of globular clusters show a median uncertainty of 16% with a negligible zero-point offset. Using this method, the atmospheric parameters and distances of nearly one million red giant stars are derived from SMSS DR1.1. Proper motion measurements from Gaia DR2 are available for almost all of the red giant stars, and radial velocity measurements from several large spectroscopic surveys are available for 44% of these. This sample will be accessible at https://yanghuang0.wixsite.com/yangh/research.
ABSTRACT
High time resolution and accuracy are of critical importance in the studies of timing analysis and time delay localization of gamma-ray bursts (GRBs), soft gamma-ray repeaters (SGRs) and ...pulsars. The Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) consisting of two micro-satellites, GECAM-A and GECAM-B, launched on 2020 December 10, is aimed at monitoring and locating X-ray and GRBs all over the sky. To achieve its scientific goals, GECAM is designed to have the highest time resolution (0.1 $\mu {\rm s}$) among all GRB detectors ever flown. Here, we make a comprehensive time calibration campaign including both on-ground and on-orbit tests to derive not only the relative time accuracy of GECAM satellites and detectors, but also the absolute time accuracy of GECAM-B. Using the on-ground calibration with a $\rm ^{22}Na$ radioactive source, we find that the relative time accuracy between GECAM-A and GECAM-B is about 0.15 $\mu {\rm s}$ (1σ). To measure the relative time accuracy between all detectors of a single GECAM satellite, cosmic-ray events detected on orbit are utilized since they could produce many secondary particles simultaneously record by multiple detectors. We find that the relative time accuracy among all detectors onboard GECAM-B is about 0.12 $\mu {\rm s}$ (1σ). Finally, we use the novel Li-CCF method to perform the absolute time calibration with Crab pulsar and SGR J1935+2154, both of which were jointly observed by GECAM-B and Fermi/GBM, and obtain that the time difference between GECAM-B and Fermi/GBM is 3.06 ± 6.04 $\mu {\rm s}$ (1σ).
This paper reports on the observation of the sidereal large-scale anisotropy of cosmic rays using data collected by the ARGO-YBJ experiment over 5 years (2008-2012). This analysis extends previous ...work limited to the period from 2008 January to 2009 December, near the minimum of solar activity between cycles 23 and 24. With the new data sample, the period of solar cycle 24 from near minimum to maximum is investigated. A new method is used to improve the energy reconstruction, allowing us to cover a much wider energy range, from 4 to 520 TeV. Below 100 TeV, the anisotropy is dominated by two wide regions, the so-called "tail-in" and "loss-cone" features. At higher energies, a dramatic change of the morphology is confirmed. The yearly time dependence of the anisotropy is investigated. Finally, no noticeable variation of cosmic-ray anisotropy with solar activity is observed for a median energy of 7 TeV.
•A thermochemical heat storage reactor with topology optimized fins is developed.•Superior heat transfer capability of topology optimized fins is confirmed.•The enhanced heat transfer mechanisms of ...topology optimized reactor are studied.•The heat transfer rate can be further accelerated through a proper heat transfer fluid pipe distribution.
Thermochemical heat storage has a promising application prospect due to its high energy density and ability of seasonal energy storage with little heat loss. However, most of thermochemical heat storage systems suffer from very poor thermal conductivity that limit the heat transfer rate and hinder the implementation of this technology. This study presents a novel solution to the poor heat transfer problem in a multi-tube thermochemical heat storage unit through topology optimization of highly conductive fins. For the formulation of the topology optimization problem, the dehydration process of Ca(OH)2 was considered, and a density-based approach was employed. Results indicated that the topology optimized geometry had a superior heat transfer performance and a 43% improvement was achieved with respect to the normally used longitudinal design in terms of reaction time. It was found that during the dehydration process of Ca(OH)2, heat conduction was the dominant factor while convection heat transfer was only observed in a small region near the porous gas channel. Furthermore, the effects of the number of heat transfer fluid (HTF) pipes were explored. It was shown that bifurcations of intermediate branches tend to vanish with the increase of the number of HTF pipes and the charging process can be further enhanced through a more uniform HTF pipe distribution. Finally, the reconstructed model was validated, and the optimized fins were tested under the hydration process of CaO, which further confirmed the superiority of the topology design.
The Mg-Zn-RE alloy sheets always exhibit planar anisotropy in mechanical response at ambient temperature, due to the formation of ‘TD-split’ texture fabricated by ordinary rolling approach with lower ...reductions. A novel final-pass heavy reduction rolling (FHRR) approach was thus developed and performed on the as-cast ingots of Mg-1.1Zn-0.76Y-0.56Zr alloy, the composition of which was designed by thermodynamic calculation, aiming to modify the ‘TD-split’ texture. We comparatively investigate the influences of rolling routes, including light reduction rolling (LRR) and FHRR, on the microstructure, texture, mechanical properties and related stretch formability. The as-annealed LRR sheet exhibits a typical ‘TD-split’ texture, whereas the as-annealed FHRR sheets reveal a unique ‘oblique-line-split’ texture, with the basal poles tilted by about 50° from the ND towards some oblique-line with respect to about 40° of TD. Special attentions were paid on the formation of such texture and their influences on the planar anisotropy in mechanical response, mainly as a manifestation of yielding and as-followed strain hardening behavior, as well as the relationship between the mechanical anisotropy and stretch formability.
Diffuse sources of pollution such as sewer leakages, sewer overflows, illicit discharges and stormwater runoff affect the urban surface water quality but often remain unknown. Therefore, the ...development of chemical markers for identifying and characterizing the origin of diffuse sources of pollution in urban surface waters is a requisite for protecting and managing urban water resources. In this study, the occurrence of 31 emerging contaminants (ECs) in untreated wastewater, treated wastewater, urban stormwater runoff, agricultural stormwater runoff, and freshwater bodies was investigated. Artificial sweeteners (ASs), pharmaceuticals and personal care products (PPCPs) were more frequently detected in the collected water samples. In raw wastewater, 21 target ECs were detected 100% in the collected samples with median concentrations ranging from 49.6 to 77,721 ng/L, while in freshwater bodies, only 13 compounds were found with detection frequency >50%. The median concentration of the majority of detected ECs in freshwater samples was below 100 ng/L. The suitability of ECs as chemical markers of diffuse sources in an urban watershed was assessed using a suite of criteria, including the detection frequency (DF), detection ratio (DR) (i.e. the ratio between median concentration and method quantification limit of a compound) and attenuation rates (i.e., biodegradation, sorption and abiotic degradation) in wastewater treatment processes. In addition, we propose a new key criterion, the concentration ratio (CR) of labile to conservative compounds, to evaluate the applicability of suitable chemical markers for source tracking. Using this new set of criteria (i.e. CR, DF, DR and attenuation rates), our analysis showed that among the investigated ECs, only acesulfame (ACE), acetaminophen (ACT), cyclamate (CYC), saccharin (SAC) were suitable as chemical markers of diffuse sources in surface waters. For caffeine (CF), N,N-diethyl-meta-toluamide (DEET), crotamiton (CTMT), triclocarban (TCC) and triclosan (TCS), their median concentration ratio to sucralose (SUC) in water bodies was consistently higher than that in raw wastewater, suggesting that these compounds might be unsuitable as chemical markers of sewage leakage in surface waters for this study area.
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•A suite of criteria was used to evaluate ECs as chemical markers of diffuse sources.•Comprehensive data on the occurrence of 31 ECs in catchments was provided.•Artificial sweeteners (ACE, CYC, SAC, and SUC) were omnipresent in urban runoff.•Labile ECs (ACT, CYC, and SAC) were suitable chemical markers of diffuse sources.
Observation of Weyl nodes in TaAs Lv, B. Q.; Xu, N.; Weng, H. M. ...
Nature physics,
09/2015, Letnik:
11, Številka:
9
Journal Article
Recenzirano
Odprti dostop
In 1929, H. Weyl proposed that the massless solution of the Dirac equation represents a pair of a new type of particles, the so-called Weyl fermions1. However, their existence in particle physics ...remains elusive after more than eight decades. Recently, significant advances in both topological insulators and topological semimetals have provided an alternative way to realize Weyl fermions in condensed matter, as an emergent phenomenon: when two non-degenerate bands in the three-dimensional momentum space cross in the vicinity of the Fermi energy (called Weyl nodes), the low-energy excitations behave exactly as Weyl fermions. Here we report the direct observation in TaAs of the long-sought-after Weyl nodes by performing bulk-sensitive soft X-ray angle-resolved photoemission spectroscopy measurements. The projected locations at the nodes on the (001) surface match well to the Fermi arcs, providing undisputable experimental evidence for the existence of Weyl fermionic quasiparticles in TaAs.
•Pure and Co doped LaFeO3 nanofibers are synthesized by electrospinning method.•Co-doping causes a decrease in the diameters of LaFeO3 nanofibers.•Co-doping LaFeO3 nanofibers improved the gas sensing ...properties.•Co-doped LaFeO3 sensor exhibits high response and good selectivity to acetone at 130°C.
Lanthanum ferrite (LaFeO3) and Co-doped LaFeO3 nanofibers with perovskite-type structure had been synthesized via electrospinning. The structure and morphology of the nanofibers were characterized by various techniques. The as-prepared products combined the advantages of well crystallinity and the surface of samples was concave-convex and rough. In addition, the crystalline size of LaFeO3 decreased after Co doping. The gas-sensing properties of two samples were measured, Co-doped LaFeO3 presented good selectivity and high response toward acetic acid compared to pure LaFeO3 nanofibers. The results demonstrated that Co-doped LaFeO3 nanofibers could be used as a promising material for selective detection of acetic acid.
Summary
The scientific problems concerning Quaternary soil water content and the water cycle have not been researched. This study examined the soil water content and depth of distribution of ...gravitational water in the south Loess Plateau during development of the first palaeosol layer (S1) by methods such as field investigation, electron microscopy, energy spectrum analysis, chemical analysis, and so on. The purpose was to reveal the climate, water balance and vegetation type at the time when S1 developed. The depth of migration of CaCO3 and Sr were 4.2 m below the upper boundary of the S1 palaeosol, and the depth of weathered loess beneath the argillic horizon was 4.0 m. Ferri‐argillans developed well in the argillic horizon and their depth of migration was 1 m below the argillic horizon. These findings suggest that the climate during the last interglacial was subtropical and humid, and the soil‐water balance was positive. Gravitational water was present to a depth of least 4.2 m from the top of S1, and the water content was adequate for tree growth. The chemical weathering index showed that this palaeosol has been moderately weathered.
Highlights
We studied the palaeo-water content index during development of the first palaeosol.
Soil water balance during development of S1 palaeosol in the south Loess plateau was positive.
Available water content was 14% during development of S1 palaeosol.
We suggest that a subtropical climate and forest vegetation prevailed.
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