Predictions of the hydrodynamic performance of the wave rotor wave energy device

This paper provides a linear solution for the Wave Rotor, a wave energy device that comprises two parallel counter rotating cylinders in orbital motion. Theoretical results are obtained for the radiated waves generated by the device, and for its efficiency. Comparisons with earlier measurements of radiated waves show very promising agreement.     

东北冷涡过程对江淮梅雨期降水的影响机制

利用1954--2003年中国740站逐日降水资料以及NCEP／NCAR再分析资料,对东北冷涡影响江淮梅雨的机制进行了研究。结果发现,东北冷涡出现以后,随着它的东移南压与西伸的副热带高压之间相互作用,使我国江淮地区南侧对流层中上层的气压梯度力加强,气压梯度力做功使得动能增大,随后动能向下输送,导致江淮以南地区的西南低空急流形成;低空急流引导的北上暖湿气流与东北冷涡引导的南下干冷空气相互作用,有利于梅雨锋的形成和维持,激发江淮地区低层对流不稳定增加,上升运动出现,从而导致江淮梅雨期降水活跃。     

Sr–Nd isotopic systematics and geochemistry of intermediate plutonic rocks from Ikoma Mountains, Southwest Japan: evidence for a sequence of Mesozoic magmatic activity in the Ryoke Belt

Abstract The Ryoke Belt in the Ikoma Mountains, Nara Prefecture, Japan, is composed mainly of various granitic, intermediate and gabbroic rocks. Igneous activity in this area is divided into two periods, early–middle Jurassic and late Cretaceous, based on isotopic dating. The intermediate plutonic rocks in the Fukihata area are composed of two rock types: Kyuanji quartz diorite and Fukihata tonalite. Rb–Sr whole-rock isochron ages have been determined for both plutonic rocks. Their ages and initial ⁸⁷Sr/⁸⁶Sr ratios are as follows: the Kyuanji quartz diorite has an age of 161.0 ± 17.9 Ma with an initial ⁸⁷Sr/⁸⁶Sr ratio of 0.70727 ± 0.00007, while the Fukihata tonalite has an age of 121.4 ± 24.6 Ma with an initial ⁸⁷Sr/⁸⁶Sr ratio of 0.70753 ± 0.00020. Our chronological results indicate that the Kyuanji quartz diorite belongs to the Jurassic mafic rocks, such as the Ikoma gabbroic mass, while the Fukihata tonalite belongs to the early Cretaceous granitic rocks. Both these intermediate plutonic rocks have different chemical characteristics and were derived from different magmas.     

1971—2010年中亚低涡活动特征

利用1971—2010年NCEP/NCAR逐日再分析资料,对中亚低涡的活动规律及不同移动路径对新疆天气的影响进行分析。结果表明:40年共出现305次中亚低涡过程,低涡成熟期维持日数共1166 d;中亚低涡随纬度分布有两个高频活动区域:47.5°~55°N (北涡) 和35°~47.5°N (南涡),北涡表现出明显的季节变化,夏季所占比例最大为52%,而南涡活动四季差别不明显。中亚低涡的成熟期生命史2~3 d占56%,4~5 d占27.5%,5 d以上占16.5%。低涡活动具有明显的月、季节、年际和年代际变化,且呈显著的年代际增加趋势。南、北涡均出现东北、偏东和东南向移动路径,并影响新疆不同区域的天气。中亚低涡可造成新疆出现低温大风天气 (干涡) 和强降水天气 (湿涡),干涡占60%,且季节分布比较均匀;湿涡占40%,季节分布差异大,其中,夏季最多占57%,秋、春季次之。     

塔里木盆地西南部下白垩统克孜勒苏群沉积特征与成矿成藏作用*

通过对塔里木盆地西南部(塔西南)江格结尔地区下白垩统克孜勒苏群地层剖面测量,该地区的克孜勒苏群分为5个岩性段,岩性主要为泥质粉砂岩、岩屑砂岩、含砾砂岩、砾岩等,沉积相主要为辫状河三角洲相;其上覆的上白垩统库克拜组为介壳灰岩、膏质泥岩,沉积相为浅海相、滨海潟湖相; 下伏的上侏罗统库孜贡苏组岩性主要为杂砾岩、含砂杂砾岩和石英砂岩等,沉积相为冲积扇相;三者呈整合接触。从该区下白垩统克孜勒苏群的沉积特征来看,早白垩世为陆源碎屑沉积环境,在晚白垩世转入海相沉积环境。对比该区北侧陆内造山带中的拉分断陷盆地(萨热克巴依盆地)中下白垩统克孜勒苏群的地层层序,该区仅沉积了下白垩统克孜勒苏群下部3个岩性段而缺失上部岩性段,表明在早白垩世后期塔里木盆地北侧西南天山发生过一次抬升作用。下白垩统克孜勒苏群是铜铅锌铀矿等金属矿产的赋矿层位,同时也是塔里木盆地石油和天然气的重要储集层位,在铜铅锌等矿石中常可见大量的沥青等有机质,这些有机质主要源于下伏侏罗系的煤系烃源岩,并通过成矿流体参与了金属矿产的成矿作用,因而这种多矿种“同盆共存”的现象,在沉积盆地的研究中作为整体的成矿系统来研究将更有意义。     

高原涡东移与东亚夏季风的关系分析

本文对1979～2017年6月1～5日有无高原涡东移年份从东亚夏季风的高低空环流系统进行对比分析表明：同一较短时间段,有长生命尺度东移高原涡与无高原涡东移的年份,东亚季风区的高低空环流系统有较明显差异,且不同路径东移高原涡高低空环流系统也有异同。(1)高度场：有高原涡东移年份,西风急流大值区较无高原涡东移年份明显偏东,南亚高压中心纬度大致相同,东北移、东南移路径南亚高压中心分别偏北、偏南。有高原涡东移年份东亚大槽较无高原涡东移年份偏东。东北移、东移、东南移的西太平洋副热带高压西伸脊点依次偏南,偏东。(2)水汽条件：有高原涡东移年份均伴随有贝加尔湖东南部输送至我国东北的宽的水汽带,不同东移路径与纬向风分量关系密切。(3)海平面气压场：有高原涡东移年份海陆气压差较大,且海平面气压随着高原涡东移出现一个向东逐渐减小的过程。     

西南地区农业旱情的气象干旱指数适应性研究

利用西南地区60站1961—2011年的日平均气温、降水量资料求得半年尺度的气象干旱指数值,包括帕尔默干旱指数、标准化降水干旱指数、Z指数、降水距平百分率指数。采用超前相关、相似和技巧评分两种计算方法检测与西南地区农业灾情最适宜的气象干旱指数。基于最适宜的干旱指数,给出西南地区农业干旱灾害可能发生的风险分布。结果表明:Z指数定义的冬半年气象干旱对西南地区农业旱情的指示性较其他3种气象干旱指标更优。冬半年Z指数小于等于-0.84时引发的西南地区农业干旱灾害成灾率大于8%的风险平均达0.53,农业干旱绝收率大于5%的风险平均达0.37,风险最大地区位于贵州西北部。结论有助于深入认识气象干旱指数与农业干旱灾情的联系,对于西南地区农业干旱的检测预测有一定的应用价值。     

Segmentation and Morphotectonic Variations Along a Super Slow-Spreading Center: The Southwest Indian Ridge (57° E-70° E)

Bathymetric data along the Southwest Indian Ridge (SWIR) between 57°E and 70° E have been used to analyze the characteristics of thesegmentation and the morphotectonic variations along this ridge. Higheraxial volcanic ridges on the SWIR than on the central Mid-Atlantic Ridge(MAR) indicate that the lithosphere beneath the SWIR axis that supportsthese volcanic ridges, is thicker than the lithosphere beneath the MAR. Astronger/thicker lithosphere allows less along-axis melt flow andenhances the large crustal thickness variations due to 3D mantle upwellings.Magmatic processes beneath the SWIR are more focused, producing segmentsthat are shorter (30 km mean length) with higher along-axis relief (1200 mmean amplitude) than on the MAR. The dramatic variations in the length andamplitude of the swells (8–50 km and 500–2300 m respectively),the height of axial volcanic ridges (200–1400 m) and the number ofvolcanoes (5–58) between the different types of segments identifiedon the SWIR presumably reflect large differences in the volume, focusing andtemporal continuity of magmatic upwelling beneath the axis. To the east ofMelville fracture zone (60°42 E), the spreading center isdeeper, the bathymetric undulation of the axial-valley floor is less regularand the number of volcanoes is much lower than to the west. The spreadingsegments are also shorter and have higher along-axis amplitudes than to thewest of Melville fracture zone where segments are morphologically similar tothose observed on the central MAR. The lower magmatic activity together withshorter and higher segments suggest colder mantle temperatures withgenerally reduced and more focused magma supply in the deepest part of thesurvey area between 60°42 E and 70° E. The non-transformdiscontinuities show offsets as large as 70 km and orientations up toN36° E as compared to the N0° E spreading direction. We suggest thatin regions of low or sporadic melt generation, the lithosphere neardiscontinuities is laterally heterogeneous and mechanically unable tosustain focused strike-slip deformation.     

Ore genesis of the Tianbaoshan carbonate-hosted Pb–Zn deposit,Southwest China: geologic and isotopic (C–H–O–S–Pb) evidence

The Tianbaoshan Pb–Zn deposit, part of the Sichuan–Yunnan–Guizhou (SYG) Pb–Zn metallogenic province, is located in the western Yangtze Block and contains 2.6 million tonnes of 10–15 wt.% Pb + Zn metals. Ore bodies occur as vein or tubular types and are hosted in Sinian (late Proterozoic) carbonate rocks and are structurally controlled by the SN-trending Anninghe tectonic belt and NW-trending concealed fractures. The deposits are simple in mineralogy, with sphalerite, galena, pyrite, chalcopyrite, arsenopyrite, freibergite, and pyrargyrite as ore minerals and dolomite, calcite, and quartz as gangue minerals. These phases occur as massive, brecciated, veinlet, and dissemination in dolostone of the upper Sinian Dengying Formation. Hydrogen and oxygen isotope compositions of hydrothermal fluids range from –47.6 to –51.2‰ and –1.7 to +3.7‰, respectively. These data suggest that H₂O in hydrothermal fluids had a mixed origin of metamorphic and meteoric waters. Carbon and oxygen isotope compositions range from –6.5 to –4.9‰ and +19.3 to +20.2‰, respectively. These compositions plot in the field between mantle and marine carbonate rocks with a negative correlation, suggesting that CO₂ in the ore-forming fluids had multiple sources, including the Permian Emeishan flood basalts, Sinian-to-Permian marine carbonate rocks, and organic matters in Cambrian-to-Permian sedimentary rocks. Sulphur isotope compositions range from –0.4 to +9.6‰, significantly lower than Cambrian-to-Permian seawater sulphate (+15 to +35‰) and sulphate (+15 to +28‰) from evaporates in Cambrian-to-Permian strata, implicating that the S was derived from host-strata evaporates by thermal–chemical sulphate reduction. ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb, and ²⁰⁸Pb/²⁰⁴Pb ratios range from 18.110 to 18.596, 15.514 to 15.878, and 38.032 to 39.221, respectively, which plot in field of the upper crust Pb evolution curve, unlike those of Proterozoic basement rocks, Sinian dolostone, Devonian-to-Permian carbonate rocks, and the Permian Emeishan flood basalts, implying complex derivation of Pb metal in the ore-forming fluids. Geological and isotopic studies of the Tianbaoshan Pb–Zn deposit reveal that constituents in the hydrothermal fluids were derived from multiple sources and that fluid mixing was a possible metallogenic mechanism. The studied deposit is not distal magmatic–hydrothermal, sedimentary exhalative (SEDEX), or Mississippi Valley (MVT) types, rather, it represents a unique ore deposit type, named in this article the SYG type.     

秦岭大巴山地形对陕南强降水的影响研究

2021年4月23日陕西东南部出现了大范围暴雨天气,共有18站日降雨量超过4月日雨量极值,较为罕见。利用常规高空、地面观测资料及ERA5再分析资料(0.25°×0.25°)对该暴雨过程成因及极端性进行诊断,结果表明：500 hPa高原槽前强西南气流带来的正涡度平流有利于低空急流的增强以及低涡的发展和维持。该过程有两支强水汽输送带,一支为偏南风水汽输送带,另一支为热带气旋外围的偏东风水汽输送带,700 hPa切变线以及850 hPa西南低涡给陕南带来显著的水汽辐合,持续充沛的水汽供应及辐合使得强降雨维持较长时间,从而形成暴雨。探空上有明显锋面逆温,锋区由南向北呈倾斜结构,锋生主要由辐合项和水平变形项贡献,其中水平变形项以伸缩变性项为主。西南暖湿气流沿着层冷垫爬升,中低层大气的风速、风向切变以及锋生造成强烈水汽辐合上升,同时偏南急流沿着秦岭和大巴山迎风坡的强迫抬升进一步增强了降水。标准化异常(SD)诊断显示,700 hPa、850 hPa超过3σ的异常偏强偏南风水汽输送以及850 hPa超过3σ异常偏强的偏东风水汽输送,造成陕西整层水汽含量异常偏大,同时由于中层辐合加上锋生造成的垂直环流,使得陕西东南部上升运动较气候态异常偏强3σ,造成4月份陕西极端暴雨过程。