Estimation of critical convergence and rock load in coal mine roadways — an approach based on rock mass rating

Summary Based on field instrumentation in eight different coal mines representing varying depths and strata conditions, a relation for obtaining the critical convergence value has been established. In development heading for bord and pillar workings this relation can be used successfully to control the premature collapse of the roof. An empirical relation for rock load has been established. This can be utilized for optimum design of support system. The roofs have been categorized as stable, short-term stable and unstable. Proper attention should be provided for an unstable roof and the support design is to be changed before the convergence reaches the critical value.     

2008年8月末湖北连续大暴雨的水汽输送特征

2008年8月末湖北出现连续大暴雨,利用常规气象观测资料、自动气象站雨量资料、地基GPS可降水量资料与NCEP再分析资料探讨这次大暴雨过程水汽特征。结果发现:这次过程降雨经历了两次增强与两次减弱;GPS可降水量增加降雨加强,可降水量减小降雨减弱;暴雨发生时整层水汽输送方向是西南向,当其转变为西北向时湖北降雨减弱,整层水汽通量数值大降雨不一定就强;强降雨落区走向与整层水汽辐合中心位置走向对应较好,降雨强度变化趋势与整层水汽辐合数值变化趋势一致,但是两者尚不满足线性函数关系。对于连续大暴雨过程既要关注整层水汽辐合中心位置又要关注整层水汽辐合数值变化趋势。     

由河南\

利用常规观测资料以及区域自动站资料、多普勒天气雷达产品、卫星云图、地基GPS水汽资料、闪电定位资料以及NCEP 1°×1°再分析资料,分析了2016年7月9日豫北特大暴雨过程的环流背景与中尺度对流特征。结果表明:该过程发生在1601号台风北上、500 hPa低涡缓慢东移、200 hPa急流稳定维持的环流背景下,低层辐合、高层辐散,边界层正负温度平流对呈对称分布,对应中尺度次级环流,加强上升运动发展。大气为强对流不稳定结构,为强降水提供了能量条件。水汽输送和辐合为暴雨提供了有利的水汽条件,湿舌伸向豫北,水汽通量高值区和水汽辐合中心对应暴雨中心;GPS可降水量(PWV)在强降水发生前急升,当PWV迅速下降时降水强度明显减弱。强降水主要由低涡云系中不断生成发展的中尺度对流云团造成,其落区与云顶亮温(T_BB)梯度大值区对应且靠近其低值中心,地闪频数峰值提前于强降水峰值1~3 h。地面高温高湿环境和冷舌的侵入对中尺度对流产生有重要作用,地面辐合线为其触发机制,长时间维持导致暴雨发展;混合型回波列车效应明显,强回波伸展高度低于3 km,质心较低,不同于雹暴回波结构,类似于热带海洋型降水回波;雷达速度图上逆风区和辐合区多次出现。豫北特殊地形成为冷空气南下通道,低层维持东南气流,风向与山脉走向垂直,地形强迫抬升以及摩擦辐合作用使暴雨增幅。

     

一种新的三维地下管线衔接模型算法研究

在城市地下管网中,管线通过管件实现相交、衔接和连通等操作,然而地下管线连接方式种类繁多,管件在面对地下管线复杂多样的连接方式时存在无法完全表达的问题。文中主要研究在三维地下管网建模过程中,管件在不能完全表达管线连接方式时的衔接模型,按衔接管径不同将管线衔接建模分为等径管线衔接建模和异径管线衔接建模两类;提出采用圆管—圆球—圆管的组合进行等径管线衔接建模方法;重点研究异径管线衔接建模,提出一种利用ArcEngine组件对象构建多片圆柱体,圆柱体模拟圆环体,若干首尾相接的渐变径圆环体拟合弯管的算法。研究方法能够高效逼真地构建出等径弯管模型和异径弯管模型,解决了地下管线三维模型衔接处的光滑建模问题。     

“2009.08.13”云南省大理州强降水天气过程分析

在利用常规资料、自动站降水资料分析2009年8月12～14日大理州强降水天气过程的影响系统、物理量特征基础上,还利用大理国家气候观象台的风廓线雷达资料探讨了强降水发生前风廓线雷达各项产品的表现,结果表明此次区域性强降水过程,其主要影响系统是500 hPa上的两高辐合区和700 hPa上的切变线;强降水出现前各物理量特征表现明显;风廓线雷达资料中信噪比与强降水对应关系非常密切,垂直速度的变化对强降水有一定预示作用,强降水出现前水平风随高度存在多层切变且切变层次突然增多并抬升。     

Kinematics and strain partitioning in the southeast Hellenides (Greece)

New kinematic and structural data from the tectonic windows of eastern Crete and the Dodecanese Islands combined with strain and quartz fabric analysis have enabled us to determine a detailed structural evolution of the region and to present a plate tectonic scenario for the southeast Hellenides. During the Early Mesozoic, the southeastern part of Apulia was separated from North Africa and the adjacent microplates by WNW‐trending rift zones and NE‐trending transfer faults. Displacement along the transfer faults has locally reoriented these rift zones into an ENE–WSW direction. Finite strain and quartz fabric asymmetry data indicate that in Late Cenozoic time, NNW‐directed nappe movements caused a nearly coaxial deformation along the ENE–WSW trending rift segments and non coaxial top‐to‐the‐southeast shearing along the WNW‐trending rift segments, as well as along the pre‐existing NE‐trending transfer faults. Tectonic style along the margin varies in response to the obliquity of the principal shortening direction with respect to the margin. These variations could be due to the pre‐convergence geometry of the southern margin of Eurasia and to local strain partitioning effects. Furthermore, a tectonic model is presented in which syncompressional uplift and vertical buoyancy of the subducted crustal slice caused the rapid exhumation of metamorphic units in the south Hellenides. Copyright © 2003 John Wiley & Sons, Ltd.     

江苏地区两次强飑线天气过程的特征分析

利用常规观测资料、NCEP/NCAR再分析资料、自动气象站加密观测及多普勒雷达资料,对2006年4月28日和2009年6月14日发生在江苏及周边地区的两次典型飑线过程进行了对比分析.结果表明,两次过程发生前期,对流层低层伴有明显的暖平流,中高层出现冷平流,促进了该地区大气层结不稳定的形成和发展;在飑线移动发展过程中,地面风场中对应一条清晰的辐合线,对飑线的触发和维持起着重要的作用.两次过程中环境场的热动力结构存在明显差异:就热力条件而言,前者发生在春季,冷空气势力依然较强,对流层低层的暖平流是大气层结不稳定发展的主要原因之一,后者发生在暖湿气流相对活跃的夏季,中高层冷空气的侵袭更值得关注;动力条件分析表明,前者低层辐合抬升条件明显好于后者,而后者的热力条件占优势,一旦对流启动,更容易发展.     

Bacterial abundance and production in different water masses around South Island,New Zealand

Abstract

Bacterial numbers and production were measured in the upper water column in the winter and spring of 1993 in five water masses surrounding the South Island of New Zealand. Average bacterial numbers and production were found to be higher in spring (8.5 × 10⁵ cells ml^?1 and 0.20 mg m³ h^?1, respectively) than winter (5.5 × 10⁵ cells ml^?1 and 0.05 mg C m³ h^?1 respectively). Bacterial production was strongly correlated with chlorophyll a and primary production (P < 0.001) in spring but not in winter. Spring bacterial production and at 10 m depth averaged across 28 stations was 23% of primary production, and with a growth efficency of 40%, may have consumed up to 57% of primary production. Bacterial biomass was greater than phytoplankton biomass for 75% of the 10 m depth comparisons during winter sampling and 44% during the spring sampling. The bacterial biomass was found to represent 24.6–33.5% of the nitrogen in particulate organic matter (<200 μm) supporting the concept that in New Zealand oceanic water masses bacteria are of significant biogeochemical importance.     

一次由气旋发展与边界层东北气流触发的强对流天气分析

利用多种探测资料及NCEP/NCAR FNL 1°×1°再分析资料,对2019年4月24日发生在山西的大范围强对流天气进行了分析。结果表明:1)此次过程是在弱天气尺度强迫背景下,地面锋面气旋发展和低层偏东北气流伸入河套地区,触发了1个持续拉长状对流系统(persistent elongated convective systems,PECS)和1个β中尺度持续拉长状对流系统(meso-β-scale PECS,MβECS)发生发展造成的。2)与MβECS对应,雷达回波上表现为涡旋状的回波中镶嵌着多个对流单体,PECS则表现为4个线状回波和1个强降水单体风暴。雷达产品能更精细刻画较小尺度系统特征,但分类强对流的某些典型特征并不明显。3)物理量诊断揭示,低层锋生作用不仅使暖锋加强触发MβECS发展造成北部强对流,且使得冷锋加强和气旋发展,此背景下形成的边界层急流和地面中尺度系统导致中南部对流单体合并、加强并高度组织化。强对流范围和强度与涡旋或辐合线尺度及风场辐合强度密切相关,气旋内温压风湿场的扰动特征能更好地解释较小尺度系统形成发展的物理机制,且这些特征较强对流提前1～3 h出现,对强对流临近预报具有很好的指示意义。4)低层东北气流是干冷与暖湿空气的一个倾斜交界面,该面上各种要素并不均匀,围绕该支气流形成一个气旋式次级环流圈,是中尺度对流系统的重要触发机制;气流两侧存在较大纬向风垂直切变,是造成对流风暴传播、持续时间长的重要原因之一。     

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