S-wave velocity of the crust around Tianshan Mountains inverted from seismic ambient noise tomography

We process ambient noise data from seismic stations deployed in central Asia to determine the crustal shear wave velocity structure beneath the Tianshan Mountians and surrounding area. About 748 inter-station Rayleigh wave empirical Green’s functions have been recovered to estimate the phase velocity dispersions over periods from 6 to 50 s using the image transformation technique. Results show that for short periods (6–20 s), the distribution of Rayleigh wave phase velocities is generally consistent with surface geology, with high velocities corresponding to mountain ranges and low velocities to sedimentary basins. Along two profiles, which trend from NE-SW and NW-SE, the shear wave velocity shows a pair of high velocity anomalies dipping in opposite directions beneath the Tianshan Mountains. At shallow depths, those high velocity anomalies roughly correlate with areas where the mountain front and the surrounding basin are connected. The profiles also show a narrow zone beneath the Tianshan Mountains, which may represent a route for the upwelling from upper mantle. Those observations suggest that the underthrusting of the Tarim Basin and Kazakh Shield combine with the weakness of the crust, which is heated by the upwelling from upper mantle, may play an important role on the reactivation of the Tianshan Mountains associated with the India-Eurasia collision.     

本影变换与灰值形态变换

在二值形态变换的基础上,通过引入本影和表面算子,给出了灰值形态变换的定义,较为全面地讨论了本影变换和表面算子的相关性质以及以此为基础所建立的灰值形态学变换的相关性质,并给出了详尽的证明过程.     

基于离散指数函数优化GM(1,1)模型的重新优化

分析了已存两种基于离散指数函数优化的GM(1,1)模型存在的问题,结合两者的优化思想对已存的背景值构造形式添加动态修正项,建立了适合于近似指数序列建模的重新优化模型,实例应用结果显示重新优化的模型大幅度提高了已存优化模型的精度.     

填充床/沿面复合放电等离子体降解苯的研究

研究填充床/沿面复合放电等离子体反应器,用于对挥发性有机化合物(volatile organic compounds,VOCs)的降解.该反应器以置于石英介质管内的不锈钢弹簧为高压电极,以附着在有机玻璃管内壁的不锈钢网为低压电极,将石英介质管放于有机玻璃管中央,并于石英介质管外与低压电极间填充玻璃珠.采用交流高压电源供电,实现在石英介质管内发生沿面放电,同时在石英介质管外发生填充床放电.含污染物的气体首先通过沿面放电区域,然后经填充床放电区域排出.以苯为目标物,考察了高压电极弹簧外径、玻璃珠尺寸对苯降解的影响,通过引入MnO2/γ-Al2O3催化剂参与反应,进一步提高了苯的去除率.结果表明:在玻璃珠直径6 mm、高压电极弹簧外径12 mm、放电间距12 mm、放电电压27 kV、苯的初始体积分数为0.011 4%的条件下,苯的处理效率高达75%.MnO2负载量为MnO2/γ-Al2O3催化剂质量的10%,并填充于反应器底部,苯的降解率达85%,去除效果提高.     

p-完美凸集和绝对p-完美凸集

给出p-完美凸集、绝对p-完美凸集的定义,讨论了Banach空间中p-凸集、p-完美凸集、绝对p-完美凸集三者之间的关系, 同时给出了p-完美凸集和绝对p-完美凸集的若干性质(0相似文献   

苯-乙醇-水混合液的分离提纯

在大学物理化学实验教学中,《苯-乙醇-水三组分体系相图的绘制》实验将产生大量的苯-乙醇-水混合废液,并分层为上层苯液(含有少量水和乙醇),下层乙醇-水溶液(含有大量乙醇和水,以及少量苯).文章根据苯、乙醇在水中的溶解度不同,对上层苯液进行多次水萃取乙醇,最后用无水CaCl2干燥处理得到纯苯(98.9%).对于下层乙醇-水溶液,由于苯与乙醇、水形成三元恒沸物,通过蒸馏除去苯,继续蒸馏得到乙醇-水的二元恒沸物(乙醇95.6%,水4.4%)和纯乙醇(99.7wt%).将乙醇-水的二元恒沸物通过CaCl2脱水处理,得到99.4wt%以上的乙醇.     

Fast motion estimation algorithm for H.264/AVC based on centered prediction

H.264/AVC video coding standard can achieve roughly half of the bit-savings over MPEG2 and MPEG4 for a given quality. However, this comes at a cost in considerably increased complexity at the encoder and thus increases the difficulty in hardware implementation. The high redundancy that exists between the successive frames of a video sequence makes it possible to achieve a high data compression ratio. Motion estimation (ME) plays an important role in motion compensated video coding. A fast motion estimation algorithm for H.264/AVC is proposed based on centered prediction, called centered prediction based fast mixed search algorithm (CPFMS). It makes use of the spatial and temporal correlation in motion vector (MV) fields and feature of all-zero blocks to accelerate the searching process. With the initialized searching point prediction, adaptive search window changing and searching direction decision, CPFMS is provided to reduce computation in block-matching process. The experimental results show that the speed of CPFMS is nearly 12 times of FS with a negligible peak signal-noise ratio (PSNR) loss. Also, the efficiency of CPFMS outperforms some popular fast algorithms such as hybrid unsymmetrical cross multi-hexagongrid search and a novel multidirectional gradient descent search evidently.     

U-Pb dating of detrital zircons from the Wudangshan Group in the South Qinling and its geological significance

U-Pb dating was made by the LA-ICP-MS method for detrital zircons from the Wudangshan volcanic-sedimentary succession in the South Qinling. Samples comprise quartz sandstones of the Wudangshan Group collected from the base of the Yangping Formation and an upper layer of the Shuangtai Formation overlain its volcanic sequence, and two river-sand collections from the drainage systems cutting across the two formations, respectively. The results show that the Yangping detrital zircons are dominated by 830–780 Ma grains with a minor population of ~1.0–0.84 Ga and sporadic grains of ~2.6, ~2.4 and 2.0 Ga, whereas the Shuangtai zircons yield an upper intercept age of 763±33 Ma, identical to the timing of the Wudangshan volcanism within error, with few concordant grains of 1.9 and 0.86 Ga. Age spectra for the two river-sand samples are similar to those of the Yangping and Shuangtai Formations, respectively. It thus suggests that the Wudangshan strata are less than 780 Ma, whereas their major detrital zircon populations of 1.0–0.85 Ga and 830–780 Ma are consistent with timing of the Hannan magmatic activities along the northwestern margin of the South China Block. This suggests a Hannan or adjacent area provenance for the Wudangshan strata. The Wudang area is characterized by rift-related igneous events at ~755 and ~680 Ma, respectively, pointing to a tectono- magmatic history different from the Hannan area. It is inferred that the ~755 Ma magmatism is likely to indicate a separation of the South China Block from the supercontinent Rodinia, while the ~680 Ma event suggests a further split between the South Qinling and some unknown continent.     

Temperature variability since A.D. 1837 inferred from tree-ring maximum density of <Emphasis Type="Italic">Abies fabri</Emphasis> on Gongga Mountain,China

Two tree-ring MXD (maximum latewood density) chronologies of Abies fabri were developed from the eastern slopes of Gongga Mountain, and a regional chronology (RC) was established based on the two MXD chronologies. There were significant positive correlations between the three MXD chronologies and August–September temperature, and the RC had the highest correlation (r=0.733, n=48, P<0.001) with mean August–September temperature. Based on growth-climate analyses, we reconstructed mean August–September temperature during the past 171 years for the study area. The reconstruction explained 53.5% of the instrumental temperature variance during the period 1960–2007 (F=52.8, R²_adj =52.4%). In the past 171 years, there were 22 very warm years and 23 very cold years, four cold periods (1837–1842, 1884–1891, 1899–1905 and 1984–1989) and three warm periods (1966–1973, 1916–1924 and 1876–1881). Our reconstruction was validated by other tree ring-based temperature reconstructions from the surrounding area and documented climate disaster events.     

关于当前战略性新兴产业发展阶段的初步判断

当前,发展战略性新兴产业成为产业结构调整的重要举措。2010年国家政府工作报告再次提出要大力发展新能源、新材料、节能环保、生物医药、信息网络、高端制造产业,以及新能源汽车、物联网等战略性新兴产业．作为抢占经济科技制高点、确定国家未来发展走向的战略任务．予以更大地投入和政策支持。