A cost-benefit analysis for the implementation of riparian buffer strips in the Shihmen reservoir watershed

The Shihmen reservoir is an important water source for about 3.4 million people in northern Taiwan. To protect reservoir water quality,it is necessary to conserve and manage the associated watersheds. Riparian buffer strips can trap pollutants emitted near a watershed.The location and design of a buffer strip can influence its pollutant-trapping efficiency.Any commitment of land for use as a riparian buffer strip must consider the project’s economic effectiveness.The present research is a cost-benefit analysis of various possible land developments in the Shihmen reservoir watershed.This study has applied a regression equation to evaluate pollutant-trapping efficiency levels of riparian buffer strips of various widths.Planned buffer strips have been evaluated in terms of net economic effectiveness and benefit-cost ratio.Results indicate that the optimal buffer strip width is 30 m for the Shihmen reservoir watershed.     

地幔热柱动力学研究的新进展

由于地幔热柱对我们了解地球动力学和地幔动力学过程具有非常重要的科学意义，因此受到国际地学界的广泛关注，近年来，随着一系列国际研究计划的展开和实施，热柱动力学的研究取得了很大的研究。本文拟合“国际热柱－岩石圈相互作用研讨会”的讨论内容，对热柱领域已取得的进展和存在的问题作一简要的回顾，以期待进我国热柱动力学研究的发展有所埤益。     

Impact melting of lunar meteorite Dhofar 458: Evidence from polycrystalline texture and decomposition of zircon

Abstract– Dhofar 458 is a lunar meteorite consisting mainly of olivine‐plagioclase intergrowths, pyroxene‐plagioclase intergrowths, and plagioclase fragments. Pyroxene‐plagioclase globules are also common. In this study, we report the discovery of a polycrystalline zircon in this lunar meteorite. The polycrystalline zircon contains small vesicles and rounded baddeleyite grains at its margin. The polycrystalline and porous texture of the zircon indicates high‐pressure shock‐induced melting and degassing. Baddeleyite grains are derived from decomposition of zircon under high postshock temperature. The shock features in zircon indicates that the shock pressure in Dhofar 458 was greater than approximately 60 GPa and the postshock temperature greater than approximately 1700 °C. The polycrystalline and degassing texture and decomposition zircon also strongly indicates that Dhofar 458 is a clast‐rich impact melt rock. During this shock event, most components were melted and grains of mafic minerals are interstitial to lath‐like plagioclase grains. Large fragments of olivine and chromite also formed polycrystalline texture at margins and chemically reequilibrated with surrounding melts. We suggest that pyroxene‐plagioclase globules could be remains of melted target clasts, whereas vesicles may form during shock‐induced degassing of the rock. The U‐Pb isotopic data plot on a well‐defined discordant line, yielding the age of the zircon of 3434 ± 15 Ma (2σ). This age is interpreted as the time of the impact event that melted Dhofar 458 and caused decomposition and recrystallization of this zircon in Dhofar 458, which reset this zircon’s U‐Pb age.     

复合加载下考虑接触作用的地基承载特性数值分析

港口、海洋工程结构物基础一般处于复合加载状态,其极限承载力通常采用近来引入的极限荷载图进行评价.对位于地基表面的重力式海洋基础,需要考虑基础与地基间的接触特性对极限承载力的影响.以大型通用有限元软件ABAQUS为计算平台,建立了复合加载模式的地基极限承载力数值分析方法;针对饱和黏土地基上的表面基础,利用在ABAQUS平台上开发的接触计算模块,模拟基础与地基间竖向可分离、切向完全粘结的接触作用;进而基于建立的分析方法,进行系统的有限元计算,分析地基的破坏模式随荷载条件的变化,给出地基的极限荷载包络图,并与经典承载力计算公式结果进行对比.研究结果表明,经典承载力计算公式低估了三维荷载条件下的地基极限承载力,有限元计算模型及数值分析方法,可以较好地分析研究地基的失稳机理及承载力特性,并可考虑基础与地基不同的接触条件对破坏模式及组合极限承载力的影响.     

Interactions of nonlinear gravity waves and uniform current in Lagrangian system

The particle trajectory on a weakly nonlinear progressive surface wave obliquely interacting with a uniform current is studied by using an EulerLagrange transformation. The thirdorder asymptotic solution is a periodic bounded function of Lagrangian labels and time, which imply that the entire solution is uniformlyvalid. The explicit parametric solution highlights the trajectory of a water particle and mass transport associated with a particle displacement can now be obtained directly in Lagrangian form. The angular frequency and Lagrangian mean level of the particle motion in Lagrangian form differ from those of the Eulerian. The variations in the water particle orbits resulting from the oblique interaction with a steady uniform current of different magnitudes are also investigated.     

NWA 13943(CK5型)碳质球粒陨石的矿物岩石学和稳定同位素组成研究

CK型陨石是一类高度氧化的碳质球粒陨石, 金属/磁铁矿的比值接近零. 与其它类型的碳质球粒陨石(岩石类型: 1-3)不同, 大多数CK型陨石在母体上经历了强烈的热变质过程(550--1270K), 以4-6型为主. 多项证据表明, CK和CV3型陨石具有成因联系. 但是, 两者在岩相结构和化学组成方面仍存在微小差异. 因此, 精细地区分和比较两者的地球化学特征对于验证CK-CV单一母体假说非常重要. Northwest Africa (NWA) 13943是一块新发现的陨石, 经历过较强烈的热变质作用. 利用扫描电子显微镜和电子探针, 确定了NWA 13943的岩石类型. 并运用质谱分析技术, 重点测定了NWA 13943陨石的全岩氧同位素和铬同位素组成. 综合岩石结构、矿物化学成分、氧同位素异常(△¹⁷O,△代表同位素分馏值)和铬同位素异常(ε⁵⁴Cr, ε表示样品中的同位素比值与标样中的同位素比值的相对偏差的10⁴倍),CK和CV型陨石的母体可能形成于原行星盘中两个相似但不同的化学源区.     

测高-重力边值问题的局部剪裁解

给出了基于最小方差原理的测高-重力超定边值问题解的局部建模剪裁解法,并采用由卫星测高资料计算的6′×6′海洋重力异常和30′×30′大地水准面数据,计算了展开到1 800阶次的中国南海及邻近海域的测高-重力试验模型.与其他模型比较表明,这种由超定剪裁法解得到的局部模型能够较好地改善重力场模型中波长部分的精度.     

地震发生时间的概率预报（一）

概率预报的基本思想是利用地震历史中表现出来的统计规律去推测未来。在一定概率意义下,给出下次地震可能发生的时间界限,或是在指定时间内,给出地震发生的概率,对于研究地震区域划分,提供抗震烈度等问题都是有一定意义的。这里仅从地震序列本身提取预报信息,没有考虑发震时间与各种前兆观测的关系,也没有考虑时间与地点和强度的相关。     

香港地区重力固体潮和海潮负荷特征研究

介绍了在香港地区重力固体潮合作观测成果, 获得了该地区完整的重力固体潮实测模型. 利用全球和近海海潮模型以及岛屿验潮站数据较系统地研究了海潮负荷特征, 反演了全球海潮模型的适定性. 数值结果说明周日频段内的海潮模型要比半日频段内的模型更加稳定, 实施验潮站潮位高变化改正对精密确定重力固体潮相位滞后起重要作用. 文章还研究了重力观测残差和台站背景噪声水平. 本项研究填补了中国地壳运动观测网络在该地区重力固体潮观测空白, 为地表和空间大地测量提供有效参考和服务.     

Ion Probe Study of Silicate Inclusions from Colomera （IIE） Iron Meteorite： the Rare Earth Element Perspective

Coupled with a petrographical study, I carried out an ion probe study of rare earth element microdistributions in mineral phases of silicate inclusions from the Colomera IIE iron meteorite. Most mineral grains have homogeneous REEs, but show considerable inter-grain variations by a factor of 2 to 100. The whole rock REE abundances for Colomera,estimated by combining REE data with modal abundances, are relatively LREE-enriched with REEs of～10’CI, which suggest that Colomera silicates were highly differentiated and might represent a low degree partial melt (-10%) of a chondritic source. REE geochemistry of Colomera silicate inclusions points to an origin that involves differentiation,dynamic mixing, remelting, reduction, recrystallization, and subsequent rapid cooling near the surface of a planetary body.