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Precise Orbit Determination (POD) of Satellite Laser Ranging (SLR)-tracked satellites is stepping towards millimeter-level precision, which requires further refinement of satellite perturbation models and consideration of more detailed perturbation force models that were not previously taken into accounted. Atmospheric drag is one of the main perturbative forces acting on a Low Earth Orbit (LEO) satellite, however, the atmospheric wind speed associated with atmospheric drag has not been considered in International Laser Ranging Service (ILRS) regular data processing. Therefore, in order to analyze the magnitude of atmospheric wind speed influence on POD of SLR satellites, this paper applies HWM14 (Horizontal Wind Model 14) atmospheric wind speed model to perform POD of LARES, Ajisai, Starlette, Stella, Larets satellites and analyses the results. The results show that after applying HWM14 atmospheric wind speed model, the SLR observation residual WRMS (Weighted Root Mean Square) value for LARES, Starlette, Stella, Larets satellites reach 1.04 cm, 2.13 cm, 1.73 cm, 3.36 cm, respectively, which are reduced by 0.10 cm, 0.30 cm, 0.00 cm, 0.05 cm, respectively. However, for Ajisai, one has an almost the same orbit residual WRMS value of 2.88 cm. The 3D (three-dimensional) orbit overlapping arcs error for LARES is 17.53 cm, which is reduced by 1.75 cm; for Starlette it is 19.12 cm, which is reduced by 0.96 cm; for Stella there is almost same orbit overlapping arcs error of 34.9 cm. The accuracy of orbit forecast for 1 day and 3 days for LARES reaches 147.57 cm and 163.96 cm, respectively, which is improved by 0.04 cm and 20.73 cm in the T (Tangential) direction, respectively. The accuracy of orbit forecast for 1 day and 3 days for Stella reaches 191.77 cm and 308.52 cm, respectively, which is improved by 1.95 cm and 6.74 cm in the T direction, respectively. The accuracy of orbit forecast for 1 day and 3 days for Larets reaches 6.18 m and 145.26 m, respectively, which is improved by 7.81 m and 473.61 m in the T direction, respectively. Above results display that considering HWM14 atmospheric wind speed model has a certain improvement for POD of LARES, Starlette, Stella and Larets. Therefore, the influence of atmospheric wind speed should be considered in the SLR POD and regular data processing. [ABSTRACT FROM AUTHOR]

• Three sequential processes occur, including coalescence, spreading, retraction. • Spreading diameter and time are normalized by impact and stationary droplets. • Effects of Weber number, droplet volume ratio, surface wettability are clarified. • Maximum spreading coefficient elevates at larger Weber number or drop volume ratio. • An accurate theoretical model of the maximum spreading diameter is proposed. In numerous applications related to droplet impact, impacting droplets often interact with solid surfaces with adhesive droplets rather than dry surfaces, but the former is significantly less studied than the latter. Here, for the fundamental process of droplet impact on a stationary droplet on the surface, we investigate droplet dynamics and maximum spreading under various conditions. The spreading diameter and time are reasonably nondimensionalized as the spreading coefficient and dimensionless time by considering both the impacting and stationary droplets, and the complex influence of diameters of two droplets is reduced to the effect of a single droplet volume ratio. The proposed dimensionless framework provides a method to simplify influencing factors and facilitates the study of droplet dynamics under different Weber numbers, surface wettabilities, and droplet volume ratios. The maximum spreading coefficient increases with the increase of the Weber number or the droplet volume ratio, while it is nearly independent of surface wettability. A theoretical model of the maximum spreading diameter is established through energy analysis. By considering the coupled effects of various factors and modifying the viscous dissipation, the model has the merits of high prediction accuracy and broad applicability. Our findings can not only advance the basic understanding of the ubiquitous droplet impact phenomena, but also provide useful guidance for applications such as spraying cooling and inkjet printing. [Display omitted] [ABSTRACT FROM AUTHOR]

Green infrastructure (GI) could reduce surface runoff and provide essential ecosystem service (ES) in flood management. More frequent flooding necessitated GI intervention to promote flood regulation and mitigation service. This study presented the Supply-Demand-Intervention framework of ES for flood mitigation in Nanjing, and aimed to explore flood interventions of GI that improve ES supply and satisfy ES demand from the perspective of landscape pattern. This study quantified ES supply by runoff reduction capacity and assessed ES demand by flood risk index, respectively. Stepwise regression analysis revealed the association between landscape pattern and ES supply and demand. We found the mismatch between ES supply and demand in Nanjing, as well as the spatial heterogeneity between ES supply and demand during various design storms. Urban central areas showed the low ES supply, high ES demand and high priority rank of intervention. Current GI conditions had the difficulty in dealing with more severe floods in Nanjing. And landscape elongation, shape, fragmentation, and segmentation were found to have significant effect on ES supply and demand. More elongated and segmented landscape, with less continuity and connectedness, could promote ES supply, while less fragmentated landscape, with complex shape, could reduce ES demand. Different intervention strategies were proposed to adapt to different areas for promoting ES delivered by GI. In Gulou and Qinhuai district, it was suggested to apply well-shaped elongated cropland and water areas to segment and disperse the built-up land. These findings could provide critical implications for reasonable GI planning and management in flood mitigation and adaption. [Display omitted] • This study proposed Supply-Demand-Intervention framework of ecosystem service. • Ecosystem service supply and demand showed spatial heterogeneity and unmatched relationship. • Green infrastructure with more irregular shape promoted ecosystem service supply and satisfy demand. • More segmented and less fragmented landscape was more than essential. [ABSTRACT FROM AUTHOR]

Most studies, employing ignition temperature as the ignition criterion, utilized surface absorption of radiant incident heat flux in analytical models when investigating the ignition mechanism of solid combustibles. However, in-depth absorption exerts its influence on ignition time significantly for translucent solid, especially at high radiant heat flux. In this work, we extend the previous researches from surface absorption to in-depth absorption to develop an approximate analytical ignition model using critical mass flux instead of critical temperature. An approximation methodology is proposed during derivation to study the in-depth absorption scenario. The comparison among this model, available experimental data of black PMMA in the literature and previous numerical simulations indicates that the proposed model provides relatively high accuracy in predicting ignition time. Furthermore, the pure surface absorption circumstance is also reexamined and compared with the classical ignition theory. The results show that surface absorption hypothesis accelerates the total mass flux, which consequently shortens the ignition time. However, in-depth absorption assumption eliminates the heat accumulation on surface and results in good prediction for ignition time at high heat flux. For in-depth absorption, the absorption coefficient affects the heat penetration depth and temperature distribution in this layer which consequently affects the thermal degradation reaction rate, mass flux and finally ignition time. Meanwhile, the ignition time considering both surface and in-depth absorption is discussed, and the relationship with pure surface and in-depth absorption conditions is obtained. [ABSTRACT FROM AUTHOR]

Baiyin city, which is located upstream of the Yellow River and in the central part of Gansu province, China, is severely contaminated by heavy metals such as chromium. A Gram-positive bacterium BYCr-1 capable of reducing hexavalent chromium (Cr(VI)) to trivalent (Cr(III)) aerobically was isolated from a rare-earth ore in Baiyin, Gansu, China. 16S rRNA analysis revealed that it was closely related to Bacillus subtilis. It can reduce 0.2 mM Cr(VI) to Cr(III) in M9 medium after 48 h incubation. Transmission electron microscopy (TEM) image showed that Cr(III) precipitates were located both inside and outside the cells. An nfrA gene was upregulated by 5.3 folds upon Cr(VI) treatment. Furthermore, E. coli-NfrA demonstrated elevated chromate-reducing ability. Our results indicate that BYCr-1 is able to resist and reduce high concentrations of Cr(VI), which makes it a potentially suitable candidate for bioremediation of Cr(VI) contamination. This study also reveals that nfrA confers Cr(VI)-reducing ability in Bacillus subtilis. [ABSTRACT FROM AUTHOR]

Abstract: Mercury (Hg) contaminants are widespread in Lanzhou and cause environmental pollution. Mercury pollution is harmful to environments and human health. Microbes are able to reduce Hg (II) to less toxic form elemental Hg which could be a potential alternative for mercury remediation. We've isolated a strain named Lzu-02 from sediments of the Lanzhou Reach of the Yellow River which is able to resist Hg (II). It was also able to reduce Hg (II) to elemental Hg aerobically when incubated in M9 medium with 40 μM HgCl2. The optimum condition of resisting and reducing Hg (II) for Lzu-02 was pH 6 and 37 °C. Lzu-02 was identified to be most similar to Staphylococcus epidermidis by 16S sequencing analysis and Vitek phenotype identification. We also found that Lzu-02 had a mer operon consisting of SmerR, SmerC, SmerT and SmerA genes. The relative expressions of three genes (SmerC, SmerT and SmerA) were upregulated when Lzu-02 was cultivated in M9 medium with 40 μM HgCl2. These results suggested that strain Lzu-02 could be useful for the bioremediation of Hg (II) in Lanzhou reach of the Yellow River. [Copyright &y& Elsevier]