Relative radial mass and rigidity of some warped product manifolds

We give a Riccati type formula adapted for two metrics having the same geodesics rays starting from a fixed point or orthogonal to a special fixed hypersurface. We assume that one of these metrics is a warped product if the dimension n is greater than or equal to 3. This formula has non-trivial geometric consequences such as a positive mass type theorem and other rigidity results. We also apply our result to some standard models.     

电感耦合等离子体质谱法测定土壤中24种元素

采用电感偶合等离子体质谱法同时测定环境土壤样品中锂、铍、硼、铝、镁、钛、铁、锰、砷、硒、锶、锑、钒、铬、铜、锌、镍、钼、钴、镉、银、铅、钡、铊等24种元素.试验采用动态反应池,考察了影响测定的因素,结果表明:引入动态反应气NH3可有效消除多原子离子干扰.优化了NH3的流速,确定了分析矾、铬、铜和砷等易受干扰元素的最佳流速分别为0.70,0.72,0.30,0.30 mL·min-1.检出限(3σ)在0.005～0.1μg·L-1之间,加标回收率在94.0%～104.5%之间.     

Investigation of cavitation noise using Eulerian-Lagrangian multiscale modeling

We have employed the large eddy simulation (LES) approach to investigate the cavitation noise characteristics of an unsteady cavitating flow around a NACA66 (National Advisory Committee for Aeronautics) hydrofoil by employing an Eulerian-Lagrangian based multiscale cavitation model. A volume of fluid (VOF) method simulates the large cavity, whereas a Lagrangian discrete bubble model (DBM) tracks the small bubbles. Meanwhile, noise is determined using the Ffowcs Williams-Hawkings equation (FW-H). Eulerian-Lagrangian analysis has shown that, in comparison to VOF, it is more effective in revealing microscopic characteristics of unsteady cavitating flows, including microscale bubbles, that are unresolvable around the cloud cavity, and their impact on the flow field. It is also evident that its evolution of cavitation features on the hydrofoil is more consistent with the experimental observations. The frequency of the maximum sound pressure level corresponds to the frequency of the main cavity shedding for the noise characteristics. Using the Eulerian-Lagrangian method to predict the noise signal, results show that the cavitation noise, generated by discrete bubbles due to their collapse, is mainly composed of high-frequency signals. In addition, the frequency of cavitation noise induced by discrete microbubbles is around 10 kHz. A typical characteristic of cavitation noise, including two intense pulses during the collapsing of the cloud cavity, is described, as well as the mechanisms that underlie these phenomena. The findings of this work provide for a fundamental understanding of cavitation and serve as a valuable reference for the design and intensification of hydrodynamic cavitation reactors.     

Digital capacity and employment outcomes: Microdata evidence from pre- and post-COVID-19 Europe

This paper examines the relationship between employment outcomes and broadband Internet access, education and digital skills using the pre- and post-COVID-19 survey waves of the Eurostat Community Statistics on Information Society from 2017, 2019, and 2021 in 27 European countries. Joint estimates of individuals’ employment status and skills employ external controls based on Eurostat and COVID-19 European Regional Tracker NUTS1-level regional statistics and Oxford COVID-19 Government Response Tracker information on governments’ containment and economic support measures. Broadband access, digital skills and educational attainment combine to raise employment outcomes, but COVID-19 has changed these relationships in distinct ways. It has increased employment benefits from formal education and roughly tripled the labor market advantages from having household members with tertiary education. The pandemic has increased the employment value of having at least some digital skills, while the relative benefits of more advanced digital skills shrank.     

Improved Single Crystal Growth of the Boron Sillenite “Bi24B2O39” and Investigation of the Crystal Structure

The boron sillenite, up to now known as the 12:1 compound Bi₂₄B₂O₃₉ in the system Bi₂O₃ – B₂O₃ andcrystallizing in the space group I23, melts incongruently at 655 °C only about 25 K above the eutectic tie line and corresponding to a steep liquidus line. Single crystals with dimensions larger then 1 cm ³ have been successfully grown in [100], [110], and [111] direction by an improved Top Seeded Solution Growth (TSSG) technique equipped with crucible weighing, accelerated crystal rotation technique and air‐cooled pulling rod. The structure of the boron sillenite was analyzed by X‐ray diffraction method, which was possible due to the high crystalline quality achieved. A defect‐free sublattice corresponding to a Bi‐O framework is isostructural with all sillenites, but a 2 Å environment around the origin is occupied by different cations with different population coefficients. The best calculation results in the formula Bi_24.5BO_38.25 which is more Bi‐rich than the 12:1 assumption.