瑞雷波斜入射下层状半空间中沉积谷地周围的三维散射研究

针对层状半空间中沉积谷地对斜入射瑞雷波的三维散射问题, 采用直接刚度法计算自由场波场, 以层状半空间中移动斜线均布荷载动力格林影响函数求解三维散射波场, 建立了求解该问题的间接边界元方法. 通过与已有结果的比较, 验证了该方法的正确性, 并以均匀半空间以及弹性基岩上单一土层场地中沉积谷地为例进行了计算分析. 研究结果表明： 层状半空间与均匀半空间中沉积谷地对瑞雷波的散射存在显著差别; 层状半空间中瑞雷波的振动模态对沉积附近位移幅值有着重要影响; 土层刚度和厚度等参数也对沉积附近位移幅值大小及空间分布有着显著的影响.     

A new set of integrals of motion to propagate the perturbed two-body problem

A formulation of the perturbed two-body problem that relies on a new set of orbital elements is presented. The proposed method represents a generalization of the special perturbation method published by Peláez et al. (Celest Mech Dyn Astron 97(2):131–150, 2007) for the case of a perturbing force that is partially or totally derivable from a potential. We accomplish this result by employing a generalized Sundman time transformation in the framework of the projective decomposition, which is a known approach for transforming the two-body problem into a set of linear and regular differential equations of motion. Numerical tests, carried out with examples extensively used in the literature, show the remarkable improvement of the performance of the new method for different kinds of perturbations and eccentricities. In particular, one notable result is that the quadratic dependence of the position error on the time-like argument exhibited by Peláez’s method for near-circular motion under the $J_{2}$ perturbation is transformed into linear. Moreover, the method reveals to be competitive with two very popular element methods derived from the Kustaanheimo-Stiefel and Sperling-Burdet regularizations.     

粤北铀矿定位场

粤北铀矿区是南岭铀成矿带核心地段,也是我国花岗岩型铀矿首选突破、集中发育地区。我们用１：２０万铀矿地质编图方法、地质异常区和构造岩相域理论,从新的角度总结研究了粤北铀矿系列时空结构。得出大型地质异常区,多期次地热活动中心,岩石脆性变形产生的剪切脆裂岩相域,巨型结构和放射性元素异常场共同构成铀矿定位场,据此进行了成矿预测。     

Crystallochemical effects of heat treatment on Fe-dominant tourmalines from Dolní Bory (Czech Republic) and Vlachovo (Slovakia)

Heat treatment was performed on selected Fe-dominant tourmalines to establish the nature of any change in optical properties. Two tourmaline samples from Dolní Bory, Czech Republic (TDB) and Vlachovo, Slovakia (TVL) were heated at 450, 700 and 900°C at 0.1 mPa and ambient oxidation conditions for 8 h. EMPA study shows that tourmaline from Vlachovo has schorlitic composition and tourmaline from Dolní Bory is alkali-depleted schorl to foitite. Although the black colour remained unchanged after heating at 450°C, it changed to brown at 700°C and reddish brown at 900°C. No significant changes of chemical composition were observed during heating. X-ray diffraction, infrared and Mössbauer study showed negligible oxidation of tourmaline heated at 450°C, but a significant change in iron valency state and deprotonization at 700°C. The oxidation of Fe is the main cause of tourmaline colour change, and the substitution vector for oxidation of Fe is Fe³⁺OFe _?1 ²⁺ (OH)_?1. The predicted deprotonization of OH was confirmed by infrared spectroscopy, which documented a decrease in OH groups in both samples, mainly at the V site. The oxidation of Fe is mostly significant in the Y site as documented on the compression of the Y-site octahedra and subsequent decrease in the a lattice parameter. This feature is consistent with lattice dimensions in the transition from schorl and foitite dimensions to those consistent with fluor-buergerite. The Z-site octahedra did not compressed and were not affected by heating-induced Fe oxidation, which indicates only negligible content of ^Z Fe²⁺ in original samples. After heating at 900°C, the tourmaline structure collapsed likely due to the thermally induced weakening of bonds in Y and Z octahedra, which results in amorphization of tourmaline. Subsequently, breakdown products including Fe-oxides and mullite replaced alkali-depleted amorphized tourmaline.     

Hydrocarbon composition and distribution in a coastal region under influence of oil production in northeast Brazil

Waters and sediments from the Potiguar Basin (NE Brazilian coast) were investigated for the presence and nature of polycyclic aromatic hydrocarbons (PAH) and aliphatic hydrocarbons. The region receives treated produced waters through a submarine outfall system serving the industrial district. The total dispersed/dissolved concentrations in the water column ranged from 10-50 ng L⁻¹ for ∑16PAH and 5-10 μg L⁻¹ for total aliphatic hydrocarbons. In the sediments, hydrocarbon concentrations were low (0.5-10 ng g⁻¹for ∑16PAH and 0.01-5.0 μg g⁻¹ for total aliphatic hydrocarbons) and were consistent with the low organic carbon content of the local sandy sediments. These data indicate little and/or absence of anthropogenic influence on hydrocarbon distribution in water and sediment. Therefore, the measured values may be taken as background values for the region and can be used as future reference following new developments of the petroleum industry in the Potiguar Basin.     

大震前地震活动平静现象一种可能的机制:断层的蠕滑-匀阻化

许多大地震前地震活动存在明显的平静现象,由于其普遍性,地震平静现象被认为是具有物理意义的地震前兆并被作为地震预报的重要依据.关于大震前地震平静现象的物理机制,国内外学者从不同角度进行了研究,其中包括用破裂强度的双峰式分布、扩容硬化、震前滑动造成的应力松弛、震源体内外介质性质的差异和相互作用等机制解释强震孕育过程中短期地震活动的平静现象.尽管在一些模型中把岩石力学实验结果作为证据之一,但来自与地震活动最相似的岩石变形声发射的实验证据并不多.因为以往大量的实验结果表明,在恒定的加载条件下(等位移速率、等应力速率等),岩石破坏失稳前声发射活动多表现为加速特征,尽管一些岩石破坏前声发射活动加速现象不明显,但也难以观测到平静现象.然而,在我们开展的一系列断层结构和介质不同的中尺度标本的声发射实验中,一些标本破坏失稳前声发射活动表现出明显的相对平静现象,据此我们对大地震前地震活动平静现象的物理机制进行了讨论.     

粤北桃村坝花岗岩锆石U-Pb年代学、地球化学及成因研究

桃村坝花岗岩体位于粤北贵东复式花岗岩体中部。锆石U-Pb年龄为161.5±1.8 Ma (MSWD=1.7),属于燕山早期岩浆 活动产物。该岩体具有稍低的硅、富铝、富碱、钾大于钠、贫钙镁和高FeO*/MgO等特征。富集Rb,Th,U而亏损Ba, Sr,Ti和Nb;LREE富集(LREE/HREE=7.39~16.4, (La/Yb)N=8.79~25.5),Eu亏损较为明显(δEu=0.44~0.59);Ga/Al比值较高(平 均值为2.99),Zr+Nb+Ce+Y含量(平均为518×10-6)大于350×10-6,可归属于A2型花岗岩;εNd(t)值低,为-9.7~-8.95,Nd模式 年龄为1.66~1.76 Ga;锆石的εHf(t)值为-20.0~-14.6,相应的Hf模式年龄为2.12~2.46 Ga。综合以上特征表明桃村坝花岗岩是 在地壳伸展-减薄的构造背景下、由古元古代地壳组分部分熔融的方式形成。     

博茨瓦纳马卡迪卡迪盐湖卤水特征及找钾前景分析

马卡迪卡迪盐湖区为一现代干盐湖,盐湖以湖相碎屑沉积为主,在东侧的苏阿干盐湖赋存有高矿化孔隙卤水,通过对盐湖卤水系统的采样分析及综合研究,卤水主要化学组分为Na+和Cl-,其次为CO3^-2、HCO3^-,SO4^-2、K^+,矿化度平均为257.96g/L,卤水水化学类型为碳酸盐型;卤水组分与矿化度呈明显的正相关,表明卤水还未达到饱和阶段;受湖区构造及补给来源的影响,卤水的富集区位于研究区的西北部,同时也是矿化度最高的地区;KCl的含量在0.39%~0.99%之间,平均在0.65%,已超过液体钾盐矿的最低工业品位,分布面积约690km2,具有一定找矿前景。     

2005年南京市PM_(10)浓度时间序列分析

根据南京市2005年的PM10日均浓度和气象观测资料,利用Maflab小波分析工具,对PM10浓度的年时间序列进行分析,得出了该地区PM10日均浓度的变化规律：2—5月较大,6-9月较小,10—12月较大;并且全年共有5个突变点。结合HYSPLIT4污染扩散模式,对污染源进行追踪,结果表明：造成南京市大气污染主要有局地污染物的排放和外来污染物的输送两种类型;在垂直方向上,污染物的长距离输送一直稳定在低层。