Study on Hydrodynamic Characteristics of Wave Turbulent Bottom Boundary Layer Using A Large-Sized Wave Flume

China Ocean Engineering - Experimental studies were conducted in a super-large wave flume, aiming at uncovering the hydrodynamic characteristics involved in the turbulent wave boundary layer of...     

Main Cause of the Poloidal Plasma Motion Inside a Magnetic Cloud Inferred from Multiple-Spacecraft Observations

Although the dynamical evolution of magnetic clouds (MCs) has been one of the foci of interplanetary physics for decades, only few studies focus on the internal properties of large-scale MCs. Recent work by Wang et al. (J. Geophys. Res. 120, 1543, 2015) suggested the existence of the poloidal plasma motion in MCs. However, the main cause of this motion is not clear. In order to find it, we identify and reconstruct the MC observed by the Solar Terrestrial Relations Observatory (STEREO)-A, Wind, and STEREO-B spacecraft during 19?–?20 November 2007 with the aid of the velocity-modified cylindrical force-free flux-rope model. We analyze the plasma velocity in the plane perpendicular to the MC axis. It is found that there was evident poloidal motion at Wind and STEREO-B, but this was not clear at STEREO-A, which suggests a local cause rather than a global cause for the poloidal plasma motion inside the MC. The rotational directions of the solar wind and MC plasma at the two sides of the MC boundary are found to be consistent, and the values of the rotational speeds of the solar wind and MC plasma at the three spacecraft show a rough correlation. All of these results illustrate that the interaction with ambient solar wind through viscosity might be one of the local causes of the poloidal motion. Additionally, we propose another possible local cause: the existence of a pressure gradient in the MC. The significant difference in the total pressure at the three spacecraft suggests that this speculation is perhaps correct.     

Numerical Modeling of the Undertow Structure and Sandbar Migration in the Surfzone

A process-based 3D numerical model for surfzone hydrodynamics and beach evolution was established. Comparisons between the experimental data and model results proved that the model could effectively describe the hydrodynamics, sediment transport feature and sandbar migration process in the surfzone with satisfactory precision. A series of numerical simulations on the wave breaking and shoaling up to a barred beach were carried out based on the model system. Analyzed from the model results, the wave-induced current system in the surfzone consists of two major processes, which are the phase-averaged undertow caused by wave breaking and the net drift caused by both of the nonlinear wave motion and surface roller effect. When storm waves come to the barred beach, the strong offshore undertow along the beach suppresses the onshore net drift, making the initial sandbar migrate to the seaside. Under the condition of calm wave environment, both the undertow and net drift flow to the shoreline at the offshore side of the sandbar, and then push the initial sandbar to the shoreline. The consideration of surface roller has significant impact on the modeling results of the sandbar migration. As the roller transfer rate increases, the sandbar moves onshore especially under the storm wave condition.     

Application of GIS to Geo-anomaly-Based Delineation of Mineral Resources

The geo-anomaly-based delineation of mineral resourcesusing GIS (Zhao et al.,1 996,1 995;Zhao and Chi,1 991 )takes the geological anomalous ore-forming theory as its theo-retical basis,the conceptual model of geology and mineral re-sources and the corresponding spatial analysis model as its ge-ological foundation,the GIS as its basic tool for the analysisof mineral resources prediction,and the analyses of favorableprospecting index and the spatial correlation of geologicalanomalies assemblag…     

核形石研究现状与展望

核形石作为微生物岩的一种重要颗粒结构类型,长期受到地质学家的广泛关注.通过广泛的文献资料调研,分别从核形石相关的定义、分类、成因环境、微生态系统、物质结构组成、生长机制、控制因素等7个方面总结了核形石的研究进展.并通过野外观测和室内综合分析,在山东微山寒武系馒头组中发现了一种核形石新类型,以无核心、无纹层、无定形、茵类...     

铂族元素地球化学标准物质的研制

ＧＰｔ＿１～７系列标准物质由土壤、水系沉积物、富镁超基性岩、富铁超基性岩、含铜镍贫铂矿石及铬铁矿等不同类型７个样品组成。铂族元素的含量范围从土壤和岩石的背景含量到矿石达４～５个数量级。经方差检验样品均匀度良好。标准物质的定值分析采用了不同类型的试金和湿化学法分离富集,以原子吸收、催化比色、催化极谱、等离子体质谱、发射光谱和中子活化等方法进行测定。定值的元素为Ｐｔ、Ｐｄ、Ｏｓ、Ｒｕ、Ｉｒ、Ｒｈ６个铂族元素及Ａｕ。该系列标准物质主要适于作铂族元素地球化学勘查和铂矿勘查中铂族元素分析的量值标准与测试的质量监控。     

华北地台太古宙主要变质岩的平均化学组成

在华北地台太古宙高级变质区和花岗岩，绿岩带内系统采集了变质杂岩体和变质火山岩样品２７７５个，组合成３３９件分析样，采用１５种分析方法对样品进行测试，同时由国际公认的国家一级地球化学标准物质监控分析质量，提出了华北地台长英质片麻岩、变粒岩、麻粒岩和斜长角闪岩２６种变质岩类１３个主成分和６４种微量元素的平均含量     

三类高空冷涡的划分及其动态合成分析

结合地理分布将中国北方高空冷涡划分为东北冷涡(120°—145°E,35°—60°N),华北冷涡(100°—130°E,30°—45°N)以及东蒙冷涡(100°—130°E,40°—55°N)三类,根据2000—2018年NCEP/NCAR 1°×1°再分析资料和日降水资料对19 a冷涡个例进行筛选对比,统计分析三类冷涡的活动规律,利用动态合成分析方法分析三类冷涡的结构和降水特征。结果表明:在490例高空冷涡个例中,遗漏的冷涡个例有2个,重复的个例有13个,剩下475例个例都能较好的被选出和归类,给出的三类冷涡定义较为合理。东北冷涡和东蒙冷涡在全年皆可生成,而华北冷涡在12月和2月没有发现。东北冷涡在4、5月生成最多,在3月和8月生成较少。华北冷涡在5月生成最多,冬季生成较少。东蒙冷涡在5、6、9三个月生成较多,在2、3和11月生成较少。对三类冷涡的动态合成分析表明:在结构方面,考察位势高度、温度、涡度、和等熵位涡分布,得到东北冷涡平均强度最强,东蒙冷涡次之,华北冷涡最弱;在降水方面,冷涡强度最强的时段,冷涡降水主要出现在高空急流出口区以北,对应有强的高层辐散。由于低层湿度分布以及水汽输送强度的不同,三类冷涡的降水大值中心位置有所差别,并且华北冷涡平均降水强度最大,东北冷涡次之,东蒙冷涡相对较小。     

Observational climatology and characteristics of wintertime atmospheric blocking over Ural–Siberia

This study investigates the climatological aspects and temporal characteristics of wintertime Ural-Siberian blocking (USB, centered over 30°–100°E), for the period 1980/1981–2009/2010. Sixty-eight events are identified and their physical structure is diagnosed using thermodynamic and geostrophic vorticity tendency equations. In climatology, horizontal advections play a fundamental role in constructing a USB event, in which the anticyclonic center is a warm core in the troposphere and a cold core in the lower stratosphere. The decay of the thermal structure is related to diabatic cooling along the vertical structure and warm advection in the lower stratosphere. Meanwhile, the collapse of the height structure is caused primarily by cyclonic vorticity advection. A strong interrelationship exists between the intensity and extension of USB events. The temporal characteristics of USB events are analyzed by examining strong and weak events, which are of high and low intensity. The strong events are probably preceded by an open ridge over Europe and a cyclogenesis over the Mediterranean Sea, and their formation is followed by the stronger amplification of a Rossby wave packet across Eurasia. On the other hand, the weak events are likely to be triggered by surface cold anomalies over Siberia. Overall, the evolution of a USB event forms a dynamic linkage with the Siberian high, in which the decay stage of the USB event is accompanied by a southeastward migration of the Siberian high and a subsequent cold air outbreak in East Asia. These results advance our understanding of USB and its relationship with East Asian winter monsoon activities.     

查明地质异常：成矿预测的基础

一成矿有关的条件都表现为地质演化过程中的地质异常事件。与成矿有关的地质异常都是“成矿可能地段”，可能找到预期类型矿床的地质异常或异常带可以称为“找矿可行地段”，而其中有更多的直接和间接找矿信息的部位则称之为“找矿有利地段”。地质异常在不同尺度水平上具有自相似性，在空间上具有复杂扰因机制－－混沌动力学机制，在表现形式上，包含显式和隐式两大类型的地质体或地质体组成。它们与成矿的关系是内在的成因联系和空