As a result of the unique geographical characteristics, pastoral lifestyle, and economic conditions in Mongolia, its fragile natural ecosystems are highly sensitive to climate change and human ...activities. The normalized difference vegetation index (NDVI) was employed in this study as an indicator of the growth status of vegetation. The Sen’s slope, Mann–Kendall test, and geographical detector modelling methods were used to assess the spatial and temporal changes of the NDVI in response to variations in natural conditions and human activities in Mongolia from 1982 to 2015. The corresponding individual and interactive driving forces, and the optimal range for the maximum NDVI value of vegetation distribution were also quantified. The area in which vegetation was degraded was roughly equal to the area of increase, but different vegetation types behaved differently. The desert steppe and the Gobi Desert both in arid regions have degraded significantly, whereas the meadow steppe and alpine steppe showed a significant upward trend. Precipitation can satisfactorily account for vegetation distribution. Changes of livestock quantity was the dominant factor influencing the changes of most vegetation types. The interactions of topographic factors and climate factors have significant effects on vegetation growth. In the region of annual precipitation between 331 mm and 596 mm, forest vegetation type and pine sandy soil type were found to be most suitable for the growth of vegetation in Mongolia. The findings of this study can help us to understand the appropriate range or type of environmental factors affecting vegetation growth in Mongolia, based on which we can apply appropriate interventions to effectively mitigate the impact of environmental changes on vegetation.
Despite the excellent photovoltaic properties achieved by perovskite solar cells at the laboratory scale, hybrid perovskites decompose in the presence of air, especially at high temperatures and in ...humid environments. Consequently, high‐efficiency perovskites are usually prepared in dry/inert environments, which are expensive and less convenient for scale‐up purposes. Here, a new approach based on the inclusion of an in situ polymerizable ionic liquid, 1,3‐bis(4‐vinylbenzyl)imidazolium chloride (bvbimCl), is presented, which allows perovskite films to be manufactured under humid environments, additionally leading to a material with improved quality and long‐term stability. The approach, which is transferrable to several perovskite formulations, allows efficiencies as high as 17% for MAPbI3 processed in air % relative humidity (RH) ≥30 (from an initial 15%), and 19.92% for FAMAPbI3 fabricated in %RH ≥50 (from an initial 17%), providing one of the best performances to date under similar conditions.
The inclusion of a novel in situ polymerizable ionic liquid, 1,3‐bis(4‐vinylbenzyl)imidazolium chloride (bvbimCl), allows perovskite films to be manufactured under humid environments, conferring improved materials quality, higher power conversion efficiency, and long‐term stability.
•Biochar (BC) was added for enhancing anaerobic digestion of complex organic wastes.•BC addition shortened lag time and raised maximum CH4 production rate.•BC showed good buffering capacity to ...mitigate pH decrease caused by VFAs accumulation.•BC addition promoted syntrophic oxidation of butyrate under high H2 partial pressure.•Electro-active Anaerolineaceae and Methanosaeta were enriched after BC addition.
Biochar was added to a mesophilic anaerobic digester to promote syntrophic volatile fatty acids (VFAs) oxidation and methane production from complex organic wastes. Compared with conventional operation, biochar addition effectively shortened the lag time by 27.5–64.4% and increased the maximum methane production rate by 22.4%–40.3%. With a biochar dosage of 15 g/L, the system performed well under an organic loading rate as high as 3 g substrate/g inoculums. Biochar showed a remarkable buffering capacity to alleviate pH decrease caused by VFAs accumulation. In order to gain knowledge on associated mechanisms, a specific experiment was conducted using butyrate as substrate. It was identified that syntrophic degradation of butyrate to acetate occurred under high H2 partial pressure. By microbial community analysis, it was further revealed that biochar addition brought about the enrichment of Anaerolineaceae and Methanosaeta, typical microorganisms for direct interspecies electron transfer.
Judicial improvement and trade structure optimization are important elements in achieving a high level of openness. This paper develops a theoretical framework on the impact of local protectionism on ...market integration and export technical complexity, and then empirically analyses the effect of judicial improvement on the technical complexity of urban product exports and its mechanism of action based on a quasi-natural experiment with the establishment of circuit courts. The study finds that the establishment of circuit courts significantly increases the technical complexity of product exports, and the findings remain valid after a series of robustness tests. Further analysis shows that the technology enhancement effect of the establishment of circuit courts is more pronounced in the group of cities with higher administrative levels, better location advantages, and less advanced rule of law. Mechanism Analysis shows that a superior institutional environment can have a two-sided effect on different types of firms. Overall, however, the productivity-enhancing effect of low-productivity firms exiting the market is lower than the productivity-reducing effect of higher-productivity firms' increased compliance costs, which in turn weakens the positive promotional effect of circuit courts. The above theoretical and empirical findings provide policy implications for maximizing the technology enhancement effect of the establishment of circuit courts on product exports, thereby promoting a high level of openness in China.
ABSTRACT
In this paper, we investigate membership and fundamental astrophysical parameters of the nearby, intermediate-age Praesepe star cluster (M44) based on the Gaia data release 2 (Gaia-DR2). ...Based on 54 425 stars within a sky area of 5.5° radius, we identify 1111 likely cluster members (≥0.6) in an 11D parameter space based on a combined machine-learning method. Of these cluster members, 1052 stars are identified as high-probability (>0.8) members. We identify 13 white dwarf (WD) candidates and one M dwarf candidate in the cluster, one of the 13 WD candidates has never been reported before. The updated member list with high-precision astrometric and photometric data allows us to more precisely determine the fundamental astrophysical parameters of the cluster. We find significant correlations between the parallaxes and proper motions of the cluster members, which may be caused by the depth effect along the line-of-sight direction. We also find clear evidence for the existence of mass segregation in the cluster. Using a Monte Carlo simulation technique, the most likely distance, proper motion, and radial velocity of the cluster are determined to be 〈D〉 = 187.0 ± 0.2 pc, (〈μαcosδ〉, 〈μδ〉) = (−36.136 ± 0.020, −12.950 ± 0.014) mas yr−1, and 〈RV〉 = + 35.0 ± 0.1 km s−1, respectively. The core and limiting radius of the cluster are determined to be 29.9 ± 1.5 (1.6 pc) and 208.1 ± 12.6 arcmin (11.3 pc), respectively. We find that the low-mass MD candidate may be escaping from the cluster according to its present spatial positions and velocity. In addition, the total mass of the cluster within the limiting radius is determined to be 568 ± 105 M⊙ using the Monte Carlo simulation technique.
Abstract
Hydrogen energy, as a new clean energy, has attracted wide attention all over the world because of its own advantages, and China is also one of the hydrogen energy plans in some countries. ...But most of the investment and energy of hydrogen energy are in other fields, such as transportation. Low carbon cities are the development model to deal with environmental deterioration and climate change in recent years. They introduce low carbon clean energy, introduce low carbon energy in small towns and construction life cycle, and establish low carbon operation system. For hydrogen valley or hydrogen energy town model to provide reference. Through the analysis and comparison of the initial utilization of hydrogen energy and other energy sources at home and abroad and the literature of energy towns, and according to the development experience at home and abroad, the feasibility and operation mode of hydrogen energy in low carbon towns are summarized.
Nowadays, the Burgers-type equations are seen in plasma astrophysics, ocean dynamics, atmospheric science, computational fluid mechanics, cosmology, condensed matter physics, statistical physics, ...nonlinear acoustics, vehicular traffic, electronic transport, and so forth. In this Letter, we investigate an extended (2+1)-dimensional coupled Burgers system in fluid mechanics. With symbolic computation and with reference to the velocity components in fluid-related problems, we construct a hetero-Bäcklund transformation and a similarity reduction, depending on the coefficients in the system.
•Burgers-type equations model oceanography, gas dynamics, shock-wave formation, etc.•We study an extended (2+1)-dimensional coupled Burgers system in fluid mechanics.•With reference to the velocity components in fluid-related problems.•We construct a hetero-Backlund transformation and a similarity reduction.•Results depend on the coefficients in the system, with symbolic computation.
This paper presents an investigation on fundamental astrophysical properties of the Pleiades cluster (M 45) using high-precision astrometric and photometric data from the Gaia Data Release 2 ...(Gaia-DR2). To obtain reliable cluster members, a machine-learning (ML) method is used to compute membership probabilities for 31462 sample stars within a radius of 6.5° from the cluster center, both the astrometric and photometric data are taken into account. We obtain a total number of 1454 likely cluster members with membership probabilities larger than 0.6, including a well-known white dwarf (LB 1497) with a high membership probability of ∼0.96. We find a well-defined relationship between the parallaxes and proper motions of the cluster members, the most likely explanation for the relationship is that the depth effect of the cluster along the line of sight must be taken into consideration. Using Monte Carlo simulations, the most likely distance, proper motion, and radial velocity of the cluster are determined to be D = 136.0 0.1 pc, ( 〈 cos δ 〉 , 〈 δ 〉 ) = (+20.141 0.093, −45.536 0.081) mas yr−1, and 〈 V r 〉 = + 5.8 0.1 km s − 1 , respectively. It is found that the likely cluster members extend outward to a limiting radius of Rlim = 310′ 12′ (12.3 0.5 pc) from the cluster center, and the total mass of the cluster within this radius is Mtot = 721 93 M . We find clear evidence for the presence of spatial mass segregation in this young cluster by analyzing the photometry and spatial positions of the likely cluster members. Interestingly, we also find that four high-mass cluster members with high membership probabilities (>0.99) are being ejected from the inner region of the cluster, they may have formed via close encounters between single and binary stars.
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