On Plane-Parallel Separated Flows of an Incompressible Fluid near Flat Boundaries

On the basis of Stokes separated flows, examples of separated flows described by the Navier-Stokes equations of a viscous incompressible fluid are constructed. These flows are represented by series convergent in a certain non-zero neighborhood of a flat contour immersed in the flow. In this neighborhood, the series have the same structure as those for the basic Stokes flows. Examples of the regions in which the series segments chosen give only a slight deviation from the numerical solutions of the Navier-Stokes equations are presented. The comparison between inviscid separated flows (without the no-slip condition on the contour) and viscous flows of the same structure (with the no-slip condition) shows that the viscosity does not play a decisive role in the formation of separation or the type of streamline approach to or departure from the contour.     

层间剪切带法向空间分布定量预报

本文讨论了层间剪切带法向空间分布定量预报问题。文中首先对层间剪切带发育的力学机制进行了再认识, 提出了基于变形破坏程度的分类方案; 引进了构造地质学中的尺度概念; 讨论了影响层间剪切带在法向空间发育分布的因素并建议了相应的考虑方法。之后, 建立了两个模型分别讨论岩石地层“软硬相间”的组合特征和完善型剪切带分区段预报。由此提出了一套实用性强比较可靠的定量预报方法, 最后用该方法对清江高坝洲坝基层间剪切带的分布进行了验证性预报, 取得了较高的精度(精度在70%左右)。     

同步辐射X射线衍射光谱在地带性土壤粘粒矿物研究中的应用

X射线衍射（XRD）光谱是分析土壤粘粒矿物组成的重要手段,但常规XRD分析存在前处理复杂、耗时较长、光谱分辨率低、扫描不充分等问题。为此,该研究依托北京同步辐射装置（BSRF）的4B9A衍射实验站,以我国东部不同气候带（即温带、亚热带、热带）的7种地带性森林土壤（棕色针叶林、暗棕壤、棕壤、黄棕壤、黄壤、赤红壤和砖红壤）为研究对象,利用同步辐射X射线衍射（SR-XRD）光谱对土壤粘粒矿物组成特征进行分析。结果表明：（1）温带土壤（棕色针叶林、暗棕壤和棕壤）质地以粘壤土为主,而亚热带土壤（黄棕壤、黄壤和赤红壤）分布在粘土和粘壤土的分界线上;从亚热带到热带,土壤质地呈现出粘土→壤土→砂土的变化趋势。（2）土壤硅铝率（Sa）表现为温带土壤（5.22）>热带土壤（4.53）>亚热带土壤（4.49）;同样地,硅铝铁率（Saf）也呈现出温带土壤（4.06）>热带土壤（3.53）>亚热带土壤（3.36）的变化规律。（3）从温带到热带,土壤粘粒矿物中高岭石的含量增加、结晶度提高,而伊利石的含量则逐渐减少;温带土壤以2∶1型粘粒矿物为主,而热带土壤则以1∶1型矿物为主;在SR-XRD光谱中鉴定出了伊蒙混层、长石两种粘粒矿物的存在,而这两种矿物在常规XRD光谱中未被识别。（4）与常规XRD法相比,利用SR-XRD法分析土壤粘粒矿物组成具有以下优势：一是前处理工作量较少,常规XRD法需将粘粒样品制成不同类型的载玻片再进行测定,而SR-XRD法直接测定粘粒样品即可;二是光谱分辨率高,SR-XRD法的分辨率可达到≤100 nm,从而能够检测到更多的衍射峰;三是实验效率提高,SR-XRD法的优化扫描步长可达0.04°,比常规XRD法增加1倍,从而提高了测试效率;四是扫描辨识度增加,SR-XRD法的看光时间可优化为4 min,是常规XRD法的2倍,使得样品的扫描更加充分。     

杏六区薄差储层有效动用界限研究

大庆长垣内部油田已进入高含水期,目前的水驱开发对象已由中高渗透层逐渐转变为薄差储层,这类储层油藏地质条件复杂,开发效益较差,已探明的储量中却有数亿吨储量主要存在于低渗透的薄差储层中.由于其微观孔隙结构和物性特征与厚油层存在差异,有些物性较差的储层甚至无法动用.以大庆油田杏六区的薄差储层为研究对象,运用压力数法和非线性渗流指数法确定有效动用的渗透率下限,利用双管并联实验确定级差上限,结合核磁共振技术与压汞实验结果给出孔喉动用的下限,得出:杏六区薄差储层有效动用的渗透率下限为1×10~(-3)μm~2;级差上限为5;流动孔喉半径下限为0.288μm,该结果为薄差储层的有效开发提供了一定的参考和借鉴.     

On periodically isotonic climate change

In a view of the past two millennia, is the recent 160-year global warmth an anomaly or a continuation of past climate pattern? In this work, we present two non-parametric χ² tests based on the U-test for the isotonic change-point problem proposed in an unpublished work by G. Shen and H. Xu (henceforth abbreviated as SX (unpublished)) and apply them to the global warming data. Our tests do not require any structure assumption on the underlying the deterministic mean process {μ_t} under the periodically isotonic alternative, but accommodate a large class of the models for the random error process. Being more attractive, the two tests obviate estimation of {μ_t} and possess explicit asymptotic distributions for short-range dependence data, and have asymptotic power 1 even under the local alternative.     

Experimental study on the Karst area fracture zones of the synthesizing geophysical methods

岩溶地区地形、地质情况相对复杂,各种物探方法的应用都受到一定条件限制,进行岩溶断裂破碎带勘察时,应进行综合物探勘察,为设计和施工提供可靠的原始资料;本文采用综合物探方法对广州地铁九号线工程田美断裂进行探测,详细查明田美断裂的走向、破碎带宽度、构造破碎特征、断裂的性质、规模和产状等;同时辅以少量勘察验证孔施工对断裂做验证,以便有效地揭示断裂特征,通过实验取得较理想的成果,并意外地发现了田美断裂的次一级断裂。     

Crack-tip-opening displacement for four symmetrically situated cracks with coalesced interior yield zones

Crack-tip opening displacements are obtained for four collinear straight cracks, weakening an unbounded homogeneous and isotropic elastic-perfectly plastic plate. The cracks are so configured that two symmetrically situated and interiorly lying cracks are of equal-lengths. Other two exteriorly lying, collinear straight cracks (surrounding the interiorly lying straight cracks) are of mutually equal-lengths. Thus an exterior and an interior crack-set are symmetrically oriented with respect to the other interior–exterior collinear cracks-set configuration. Uniform constant load prescribed at remote boundary of the plate, opens the crack in self-similar fashion developing a strip-yield zone ahead each tip of the cracks. It is assumed that the strip-yield zone developed at each of interior tips of an exteriorly and interiorly lying crack-set configuration gets coalesced. The developed yield zones are subjected to normal cohesive yield stress to arrest the crack from further opening. The solution of the problem is obtained by superposing the solutions of the two auxiliary problems, appropriately derived from the given problem. Each of the auxiliary problems, in turn, is solved using complex variable technique. Expressions are derived for quantities of interest viz. crack-tip opening displacement (CTOD), length of each developed yield zone. The effect of applied load and closing load on the parameters CTOD and strip yield zone affecting the crack arrest is presented graphically and concluded.     

一维光子晶体非线性色散特性的分析

从无限周期一维光子晶体的色散关系和有限周期光子晶体的透射系数两个方面,对有限和无限周期光子晶体有效折射率的实部和虚部特性曲线分别进行了计算和分析.结果表明一维光子晶体的色散曲线与弹性电偶极子的经典色散曲线类似,在光子晶体的导带为正常色散,而在禁带呈现反常色散.并且用简约布里渊和扩展布里渊区色散曲线对文献报道中存在的两种矛盾的计算结果进行了理论的探讨.解释了导致对一维光子晶体有效折射率计算存在两种不同结果的原因.