Interaction of uniform current with a circular cylinder submerged below an ice sheet

The problem of a uniform current passing through a circular cylinder submerged below an ice sheet is considered. The fluid flow is described by the linearized velocity potential theory, while the ice sheet is modelled through a thin elastic plate floating on the water surface. The Green function due to a source is first derived, which satisfies all the boundary conditions apart from that on the body surface. Through differentiating the Green function with respect to the source position, the multipoles are obtained. This allows the disturbed velocity potential to be constructed in the form of an infinite series with unknown coefficients which are obtained from the boundary condition. The result shows that there is a critical Froude number which depends on the physical properties of the ice sheet. Below this number there will be no flexural waves propagating to infinity and above this number there will be two waves, one on each side of the body. When the depth based Froude number is larger than 1, there will always be a wave at far upstream of the body. This is similar to those noticed in the related problem and is different from that in the free surface problem without ice sheet. Various results are provided, including the properties of the dispersion equation, resistance and lift, ice sheet deflection, and their physical features are discussed.     

中国城市群土地利用互补性比较研究——以14个城市群为例

互补性指基于区域间禀赋差异,借助“流”要素促进区域间优势互补,使得总体效益大于个体之和。从互补性概念出发,以中国14个城市群为案例研究区,借助SPSS对应分析及ArcGIS平台,结合能够反映互补性的统计量指标总惯量,对中国城市群土地利用互补性进行时空分析。结果表明：① 中国城市群土地利用互补性差异较大,以长江经济带为轴,向北向南土地利用互补性增加;② 中国超大型城市群城市用地类型综合化特征显著,土地利用互补性低于全国重要地区城市群;③ 大多数城市群5年间互补性呈现下降趋势,城市间产业同构,缺乏特色。未来在合理的城市群规划基础上,加快相关民生政策跨行政区合作,打破行政壁垒,协调区域间土地供求关系,明确城市功能定位,形成协调互补的城市发展格局。     

ENVISAT测高卫星沿轨大地水准面梯度的海洋垂线偏差法研究

研究了利用沿轨大地水准面梯度数据计算海洋垂线偏差的最小二乘法,首先对ENVISAT测高数据进行各项地球物理改正得到近似测高大地水准面,然后计算沿轨大地水准面的梯度,接着用最小二乘法计算格网垂线偏差东西分量和南北分量的平均值。最后,用该方法计算了南中国海区域及其邻近海域(4°N～25°N,104°E～120°E)的5′×5′垂线偏差南北分量和东西分量,其精度优于7″,并与EGM96模型计算的垂线偏差值进行了比较,证明了该方法的有效性。     

Active faults and magnitudes of left-lateral displacement along the northern margin of the Tibetan Plateau

The northern margin of the Tibetan Plateau (NMTP) is a major intracontinental Cenozoic transpressional zone that comprises a series of active strike-slip faults and thrust faults. It is important to document cumulative horizontal displacements along the NMTP in order to understand quantitatively strain partitioning in East Asia since the India–Eurasia collision. Based on an analysis of horizontal slip along major active faults, the total amount of horizontal displacements is estimated up to 700 km between the Tibetan Plateau and the Tarim Basin since the convergence of India and Eurasia. Along the western and middle segment of the Altyn Tagh fault to the northern margin of the Qaidam Basin, there are abundant evidence that show that the net displacement is 400 km since 40–35 Ma, and along the Shulenan Shan and southeast of middle Qilian Shan since 25–17 Ma, the amount of offset is 150 km. The largest horizontal slip in Qilian Shan–Hexi Corridor to the northeast of the Altyn Tagh fault is also 150 km since late Oligocene to early Miocene. It decreases to only 60 km along the Haiyuan fault (since late Miocene) and to 25 km along the Zhongwei–Tongxin fault since the Pliocene (about 5.3–3.4 Ma), at the northeast margin of the Tibetan Plateau. This clearly implies northeastward diminishing of the total horizontal displacement and temporal getting younger of the fault slip along the NMTP. However, this tendency is very complicated at different times and different segments as a result of the uplift, growth and rotation of different segments of the NMTP at different stages during the convergence of India and Eurasia.     

软弱地层深挖基坑中工程桩偏位分析

某软土地基上建造多栋毗邻的小高层住宅,在地下车库基坑的开挖过程中,软土流动推挤坑内桩基导致偏位。文章以上述工程为背景,借助三维有限差分程序FLAC3D,选取简化计算模型,对基坑开挖流动土体作用下工程桩的反应性状进行了模拟与分析,并与实测值进行了比较,最后讨论了影响桩基变形的相关因素,可为分析软土地区基坑开挖对坑内工程桩影响时提供一定的理论指导。     

启封透孔偏斜的原因及处理措施

煤田地质钻探对已竣工钻孔进行启封透孔取心可揭露封孔的真实情况,对封闭段质量作出全面评价。但由于竣工钻孔到启封透孔施工间隔时间较长,如果施工方法不当易造成将孔透斜。为提高启封透孔成功率,应根据实际情况进行分析研究,制订预防透孔偏斜的措施。在分析启封透孔偏斜的主要原因的基础上提出了预防措施,总结了处理透孔偏斜的技术措施,并用实例说明了这些措施的可行性。     

不对称钢骨混凝土梁抗弯刚度的试验研究

文章在5根不对称钢骨混凝土梁试验研究的基础上，利用现行规范[1]中对称钢骨混凝土梁截面抗弯刚度的计算公式，提出了不对称钢骨混凝土梁截面抗弯刚度的计算方法，建立了相应的计算公式。结果表明，按照本文公式得到的计算值与实测值吻合良好。     

从物理大地测量角度分析重力异常用于重力反演时所存在的误差及其改正

从重力异常△g的原始定义出发，对将其用于反演地球内部密度结构时，本身所存在的不合理性及其造成的误差进行分析和估算，并给出相应的公式。主要内容包括以下3个方面。1．重力异常中所包含的两个界面所造成的物理上的不确定性分析及其所造成的几何差异估计。2．当将实际重力与模型正常重力严格地视作为矢量，传统的重力异常或重力扰动由于未考虑垂线偏差所造成的误差分析和计算。3．对试图以具有确定物理意义的地球物理模型（如PREM）代替大地测量中的正常椭球作为正常场源时，共合理性及存在的问题进行分析，并分析对其对应的正常重力之间的差异进行估算。     

地球重力场参数计算程序的设计与应用

根据地球重力场参数的计算模型,借助全球地球重力场模型EGM2008,利用Microsoft Visual Studio 2010面向对象的功能,设计和开发了可以计算任意点重力异常、高程异常、垂线偏差分量的计算程序,以德国地学中心(GFZ)研制的相关软件对程序的正确性进行了验证,以吉林省各城市的经纬度数据计算了对应的重力异常、高程异常、垂线偏差分量。     

微波干涉测量技术及其在桥梁变形观测中的应用

将步进频率连续波技术和干涉测量技术相结合而构成的地面微波干涉雷达系统GB-radar,可用于获取高精度、高分辨率的变形信息,以实现对地面目标的静动态高精度监测.本文介绍了基于该技术的IBIS-S系统在桥梁变形观测中的应用,分析了测量误差,通过实例验证了地面微波干涉雷达技术可以精细地测量桥梁挠度的动态变化,精度高,可以真实地反映结构物的动力特性.