大定源瞬变电磁均匀层状介质正演计算

大定源回线瞬变电磁法以其高效的工作方式,一直备受野外工作者青睐。这里从基本理论出发,给出了大定源回线发射源在均匀层状介质的电磁响应计算公式,利用Quadrature With Extrapolation(QWE)算法计算了线框内、外的垂向磁场响应,并将其与传统的Fast Hankel Transform(FHT)算法进行了对比分析,两者对于虚部的计算都比较准确。当发射线框位于地表以上一定高度时,两者的计算结果吻合的较好。在发射线圈位于地表的时候,QWE算法的计算结果比较稳定,适用性优于FHT。     

大理岩单轴蠕变模型参数

采用分级加载方式进行单轴压缩蠕变试验,获得大理岩的单轴压缩蠕变曲线。对比发现五元件Kelvin模型能较好的拟合蠕变试验曲线,取其作为大理岩蠕变模型。对同一应力水平下的蠕变曲线,取10 h、20 h、40 h和50 h四个蠕变时间段,用五元件Kelvin模型进行拟合,分别获得蠕变模型参数。拟合结果表明,蠕变模型参数在不同的应力水平下和不同的加载时间下都是变化的。当应力水平足够大(58 MPa),E2随加载时间的变化规律和E1刚好相反;当加载时间足够长(20 h)时,E2随应力水平的变化规律和E1刚好相同。当应力水平足够大(58 MPa),蠕变模型参数η1和η2始终随着加载时间的增加而增加。当加载时间足够长(=50 h),蠕变模型参数η1和η2始终随着应力水平的增加而增加。     

川东北元坝地区须家河组储层特征与超致密成因探讨

元坝地区须家河组砂岩的致密化程度极高,以超低孔、超低渗储层为主,属于超致密砂岩。本文基于铸体薄片、阴极发光、扫描电镜和物性等资料,在对砂岩的岩石组分、孔隙类型及物性特征分析的基础上,通过与国内外典型致密砂岩对比,揭示研究区砂岩较其他砂岩致密化程度高的原因,分析超致密砂岩的勘探潜能。结果表明,研究区砂岩具有较高的塑性岩屑、碳酸盐岩岩屑和黏土杂基含量;填隙物以黏土杂基和钙质胶结物为主,较强的硅质胶结作用仅发育于石英砂岩中。孔隙多为黏土杂基晶间微孔,喉道呈窄缝状或不发育,孔喉分选差,偏细歪度。砂岩致密化程度高主要有两方面的原因:一是原始组构差,成分成熟度低,含有较高的塑性岩屑、碳酸盐岩岩屑和黏土杂基含量,导致砂岩在早成岩阶段既已经历了很强的压实作用和钙质胶结作用,致密化时间早,溶蚀作用不发育;二是成岩演化阶段高,砂岩经历了中成岩阶段的压溶及进一步的钙质/硅质胶结,使得砂岩超致密化。与国内外典型致密砂岩气藏对比表明,超致密砂岩有效孔隙少,对天然气的富集能力有限。元坝地区须家河组只有孔隙度近于8%(如长石岩屑砂岩)的砂岩才可成为有利的致密气储层。     

A novel decomposition of the quadratic transfer function (QTF) for the time-domain simulation of non-linear wave forces on floating bodies

In the present study, a novel method is proposed for the separation of the second-order sum- and difference-frequency wave forces—that is, quadratic transfer functions (QTFs)—on a floating body into three components due to wave–wave, wave–motion, and motion–motion action. By applying the new QTF components, the second-order wave forces on a floating body can be strictly computed in the time domain. In this work, the boundary value problems (BVPs) corresponding to the three kinds of QTF components were derived, and non-homogeneous boundary conditions on the free surface and the body surface were obtained. The second-order diffraction potentials were determined using the boundary integral equation method. In the solution procedure, the highly oscillatory and slowly converging integral on the free surface was evaluated in an accurate and effective manner. Furthermore, the application of the QTF components in the time domain was demonstrated. The second-order exciting forces in the time domain were divided into three parts. Each part of these forces was computed via a two-term Volterra series model based on the incident waves, the first-order motion response, and the QTF components. This method was applied to several numerical examples. The results demonstrated that this decomposition yields satisfactory results.     

Elastic reverse time migration based on vector wavefield decomposition

Prestack elastic reverse time migration ( RTM) requires multicomponent seismic data .But for multi-component elastic Kirchhoff migration , there is a limitation that ray theory no longer applies if thegeology be-comes complicated .In this paper, the authors have created a new 2D migration context for isotropic , elastic RTM, which included decomposition of the elastic source and receiver wavefields into P and S wave vectors by decoupled elastodynamic extrapolation , which retained the same stress and particle velocity components as the input data .Then we appliedsource-normalized crosscorrelation imaging condition in elastic reverse time migra-tion to compensate the energy of deep strata .We found that the resulting images were nearly identical to the ve-locity model , and the resolution has been improved .Our method is a wavefielddecomposition based on vector , and we can alsoavoid the problem of polarity reversal of converted shear wave imaging .It proved the applicabili-ty of the method proposed in our paper .     

人工林伐区不同集材方式对林地土壤的影响

选择福建人工林伐区5种常用集材方式进行作业试验,分析不同集材方式对林地土壤理化性质的影响,结果表明:5种集材方式作业后,土壤理化性质指标都发生了明显的变化,且各种土壤指标的变化值因集材方式的不同而异。经主成分分析,5种集材方式对林地土壤理化性质的干扰影响由大到小依次为土滑道集材、手扶拖拉机集材、手板车集材、人力担筒集材和全悬空索道集材。从生态采运角度出发提出减少集材作业对林地土壤破坏影响的技术措施。     

干旱胁迫对甘肃中部春小麦生理性状及灌水利用效率的影响

为研究干旱胁迫对春小麦生长发育阶段生理性状和灌水利用效率的影响,以高产优质抗旱春小麦新品种‘定丰18号’和‘定丰19号’为材料,对其分蘖期到成熟期进行正常供水(WW)、轻度土壤干旱(MD)和重度土壤干旱(SD) 3种不同水分处理,研究3种处理对小麦叶片水势、光合速率、籽粒灌浆速率、产量构成因素以及灌水利用效率的影响。结果表明,与WW处理比较,MD和SD处理显著降低了叶片水势(p <0. 05),MD处理通过夜间恢复其叶片水势可达到正常水平,SD处理不能恢复; SD处理显著抑制了叶片光合作用,MD处理与WW处理无显著差异(p> 0. 05);与WW处理相比,MD处理籽粒灌浆速率、粒重、穗粒数、千粒重和产量显著增加,而SD处理则显著降低(p <0. 05),不同处理间容重无显著差异(p> 0. 05)。两个不同小麦品种的两年试验结果基本一致,适度的水分亏缺有利于小麦增产,从而可提高其灌水利用效率。     

A METHOD FOR PREDICTING SHORT-AND MID-RANGE TURNING AND ACCELERATION MOTION TREND OF TROPICAL CYCLONES OVER THE SOUTH CHINA SEA

An approach is proposed for predicting turning and acceleration motion trend of the tropicalcyclones over the South China Sea for 72 h in the extrapolated track coordinates.Cross-track(CT)and along-track(AT)components are defined according to the persistently extrapolatedtrack coodinates based on observed positions at the initial and past 24 h times.A kind of straight-forward measure may be provided with CT and AT components for typhoon turning motion and ac-celeration motion.Canonical correlation analysis(CCA)is performed to reveal the correlaotions be-tween tropical cyclone tracks and environmental 500 hPa geopotential height fields.A stepwise dis-criminate analysis technique is adopted to derive the classification functions of the respective threecategories for AT and CT components.Especially,categorical combinations of CT and AT compo-nents are divided into possible 9 regions corresponding with tropical cyclone behaviors.Not onlycan 9 motion trends of a tropical cyclone be predicted,but also the location and its maximum errorat least in certain direction are available.The perfect prediction(PP)verifications indicate that thepercent corrects for the CT and AT categories are 67% and 69% in the independent samples,73%and 53% in the dependent samples,respectively,higher than that of 33.3% for random chance;moreover,the rate for successfully forecasting that in which one of the nine regions the tropical cy-clones will fall at 72 h is about 40%,also higher than the stochastic probability of 11%.Themethod has been proved to be skillful and promising.     

石笋微层物质组成的二次离子质谱初步分析及其气候意义

我国北方洞穴石笋中发育双重光性微层(透光微层和发光微层),两种微层可以相互对应,但也存在不相匹配的现象。运用二次离子质谱分析微层内物质组分,发现透光微层的浅色段含有相对丰度较高的Mg和Sr元素以及小分子有机质,而Ba和Fe及大分子有机质主要赋存于微层内暗色段,层内暗色物质包含有机质和粘土物质。微层物质组成和成因等方面的研究可以反映气候变化的高分辨率信息。     

玻璃熔片制样X射线荧光光谱法测定矾土中主次量组分

建立了玻璃熔片-X射线荧光光谱测定进出口矾土中主、次量组分的分析方法,用可变α系数校正元素基体效应,同时进行谱线重叠校正。利用高纯化学试剂配制合成标准参考物质,球磨机混匀,熔融玻璃片法制备系列校准样片,用X射线荧光光谱法对样品中的二氧化硅、三氧化二铁、三氧化二铝、氧化钙、氧化镁、氧化钾、五氧化二磷、二氧化钛进行测定。方法回收率为98.1%~111.0%,经国家铝矾土标准物质GBW 07178、GBW 07179验证,结果与标准值基本一致。建立的方法解决了测试过程中标准样品种类和数量不足的难题。