The general refractivity formula applied to densified silicate glasses

Concomitant changes of refractive index (n) with density (ϱ) of isochemical series comprizing several densified silicate glasses were analyzed. The data include glasses of the systems SiO₂, TiO₂-SiO₂, Na₂O-SiO₂, and NaAlSi₃O₈-CaAl₂Si₂O₈. Extending the ideal point dipole theory, an electronic overlap parameter (b) accounting for the non-ideal behaviour of solids was refined using the general refractivity formula , where α is the molar polarizability. Statistical analyses assuming α=constant within each isochemical series showed no systematic variation of b with chemical composition. A constrained refinement of b using all data converged at b=1.3. Applying this common overlap parameter and appropriate polarizability constants, recalculated refractive index values fit excellently the experimental results within the entire n−ϱ range. Furthermore, the additivity of polarizabilities, often assumed for oxide components, is derived for TiO₂-SiO₂ glasses and for glasses of plagioclase composition.     

Diaplectic labradorite glass from the manicouagan impact crater: II. X-ray diffraction studies and structural model

The structural state of diaplectic labradorite glass (≈An₅₈) from the Manicouagan impact crater and of its fusion-formed glass analog have been investigated by X-ray diffraction studies. The experimental X-ray intensity distribution patterns indicate that the diaplectic and fusion-formed glasses are structurally rather similar, the former being apparently slightly less disordered. Theoretical X-ray distribution curves have been calculated using the structure of high albite as a quasi-crystalline model of the glass structure. The experimental and theoretical curves show fair similarity when the calculations are based on the complete unit cell. It is inferred therefore, that the structures of both kinds of glasses possess an average short range order comparable to that in high albite and extending to about the dimensions of the unit cell. In addition, the experimental X-ray scattering pattern and X-ray Debye-Scherrer transmission photographs of the diaplectic glass reveal the presence of relics up to about 8 nm in size of the previous crystalline lattice of the primary labradorite. The present results support Grady's shear band model according to which diaplectic glass may represent the quench product of a shock-generated high-density melt frozen in prior to total pressure release.     

极端干旱条件下策勒绿洲引种植物水分生理特征研究

在塔克拉玛干沙漠南缘的中国科学院策勒沙漠研究站植物引种筛选实验区内,以3 a生文冠果、花棒和紫叶小檗为实验材料,研究三种植物经历持续干旱到短期复水过程中的生理生态响应。结果表明：（1）干旱复水后花棒和紫叶小檗的chla、chlb、叶绿素总量以及chla/b值均随土壤含水量的增加而显著增加,文冠果的叶绿素及其组分含量减少。水分变化对chla含量影响较大。（2）三种植物的MDA含量、SS含量在复水后并没有减少,而是显著的增加,文冠果的增加量最大;各物种的脯氨酸的含量降低,紫叶小糪减少的最多。（3）三种植物的清晨水势和正午水势随土壤水分含量的增加而降低,花棒和紫叶小檗的水势变化较小,水分亏缺迹象不显著。文冠果和花棒的抗逆性较强,而紫叶小檗对水分变化比较敏感。本研究结果可为研究区引种植物的适应性及防护林建设中的植物种选择提供理论参考。     

Cooling and exhumation of the oldest Sanqiliu uranium ore system in Motianling district,South China Block

The Sanqiliu uranium deposit belongs to a uranium ore system in Motianling district. It is the oldest uranium deposit in South China. Primary uranium mineralization occurred almost simultaneously with the emplacement of the host granites and subsequent dykes, and it has a relatively high grade of uranium (0.421%). We clarify the age of mineralization and investigate the cooling history through new pitchblende U–Pb and apatite fission‐track thermochronology. The pitchblende U–Pb results indicate that uranium mineralization occurred at ~801–759 Ma. Fractionation of uranium and lead at ~374–295 Ma is interpreted as remobilization and resetting of the original uranium. The Motianling area has apatite fission‐track ages of 57 to 18 Ma. By combining our results with previous work, we conclude that the deposit cooled slowly and was exposed at the surface during the Cenozoic. The timing and depth of exhumation helped to preserve and avoid erosion of the uranium deposit, and highlight the potential for regional uranium exploration.     

Turbulent Flow Properties Around a Staggered Wind Farm

The fundamental properties of turbulent flow around a perfectly staggered wind farm are investigated in a wind tunnel. The wind farm consisted of a series of 10 rows by 2–3 columns of miniature wind turbines spaced 5 and 4 rotor diameters in the streamwise and spanwise directions respectively. It was placed in a boundary-layer flow developed over a smooth surface under thermally neutral conditions. Cross-wire anemometry was used to obtain high resolution measurements of streamwise and vertical velocity components at various locations within and above the wind farm. The results show that the staggered configuration is more efficient in terms of momentum transfer from the background flow to the turbines compared to the case of an aligned wind turbine array under similar turbine separations in the streamwise and spanwise directions. This leads to improved power output of the overall wind farm. A simplified analysis suggests that the difference in power output between the two configurations is on the order of 10%. The maximum levels of turbulence intensity in the staggered wind farm were found to be very similar to that observed in the wake of a single wind turbine, differing substantially with that observed in an aligned configuration with similar spacing. The dramatic changes in momentum and turbulence characteristics in the two configurations show the importance of turbine layout in engineering design. Lateral homogenization of the turbulence statistics above the wind farm allows for the development of simple parametrizations for the adjustment of flow properties, similar to the case of a surface roughness transition. The development of an internal boundary layer was observed at the upper edge of the wind farm within which the flow statistics are affected by the superposition of the ambient flow and the flow disturbance induced by the wind turbines. The adjustment of the flow in this layer is much slower in the staggered situation (with respect to its aligned counterpart), implying a change in the momentum/power available at turbine locations. Additionally, power spectra of the streamwise and vertical velocity components indicate that the signature of each turbine-tip vortex structure persists to locations deep within the wind farm.     

Modeling and Simulation of Supercavity with Inertial Force in the Horizontal Curvilinear Motion简

To make a curvilinear motion in the horizontal plane is one of the most contents for realizing the maneuverability of the supercavitating vehicle. It is significant to achieve the controllability and maneuverability of the vehicle in three dimensions both theoretically and practically on research. Models of angle of attack, gravity and inertial force effects on the supercavity in the horizontal curvilinear motion are established, respectively. The supercavity is simulated based on these models in combination with Logvinovich model and the unsteady gas-leakage rate model at the given ventilation rate, and the effect of the inertial force on it is analyzed numerically. Results show that the maximum deviation of the center line of the cross section of supercavity towards the outward normal direction of its trajectory increases as the cavitation number or curvature radius decrease and always occur in the tail because of the increase of inertial effects along the axis of supercavity from the cavitator when other models and flow parameters are constant for the given trajectory curvature. For the variable curvature, the supercavity sheds due to its instability caused by the time-varying angle of attack. The deviation increases along the length of supercavity if the curvature remains the same sign.     

GAUGE: the GrAnd Unification and Gravity Explorer

The GAUGE (GrAnd Unification and Gravity Explorer) mission proposes to use a drag-free spacecraft platform onto which a number of experiments are attached. They are designed to address a number of key issues at the interface between gravity and unification with the other forces of nature. The equivalence principle is to be probed with both a high-precision test using classical macroscopic test bodies, and, to lower precision, using microscopic test bodies via cold-atom interferometry. These two equivalence principle tests will explore string-dilaton theories and the effect of space–time fluctuations respectively. The macroscopic test bodies will also be used for intermediate-range inverse-square law and an axion-like spin-coupling search. The microscopic test bodies offer the prospect of extending the range of tests to also include short-range inverse-square law and spin-coupling measurements as well as looking for evidence of quantum decoherence due to space–time fluctuations at the Planck scale.