基于改进LM-GN算法的磁性目标定位方法研究

利用三轴磁传感器阵列对水下磁性目标进行定位是典型的非线性最小二乘优化问题,传统高斯– 牛顿（GN）法和列文伯格–马夸尔特（LM）算法在求解该问题时具有初值敏感性问题。通过引入信赖域搜索技术,对 LM 算法进行改进,并基于改进的 LM 算法实现磁性目标定位,又通过设置判断阈值来评估迭代点与最优解的距离,提出一种结合改进 LM 算法和高斯–牛顿法特点的改进 LM-GN 算法,既降低了算法对初始值的依赖性,又提高了运行效率。仿真实验结果表明：该方法可以克服现有方法中受初始值影响较大的问题,对目标特征参数的估计更精确,且收敛速度快,具有一定的实际应用价值。     

Application of an optical nitrate profiler to high- and low-turbidity coastal shelf waters

Here, we report the results of high-resolution nitrate measurements using an optical nitrate profiler(in situ ultraviolet spectrophotometer, ISUS) along transect across a high-turbidity shelf(East China Sea) and a lowturbidity shelf(Chukchi Sea). The ISUS-measured nitrate concentrations closely reproduced the results measured by conventional bottle methods in low-turbidity waters. However, for high-turbidity waters of the East China Sea(salinity<30), a correction factor of 1.19 was required t...     

完全非线性波浪与二维固定结构物作用的IGN-BEM耦合分析模型

为高效准确地对完全非线性波浪与二维固定结构物的相互作用进行模拟分析,建立了二维完全非线性时域耦合模型。耦合模型将计算域划分为靠近结构物的内域和远离结构物的外域,每个区域均采用满足完全非线性自由水面边界条件的波浪模型进行求解。在内域使用Laplace方程描述流体运动并采用高阶边界元法（BEM）对其进行求解;而在没有结构物的外域,波浪运动的控制方程为Irrotational Green-Naghdi（IGN）方程并采用有限元法（FEM）对其进行求解。内域和外域通过一段重叠区域进行耦合,从而实现模型间变量的传递。首先利用耦合模型分别对规则波的传播、直墙前立波的生成以及相关物理模型试验进行模拟,数值结果与精确解和试验结果的良好吻合验证了耦合模型耦合方式的合理性以及处理非线性问题的准确性;然后使用耦合模型模拟分析了波浪与固定结构物间的相互作用,并将结果与线性解析解以及完全非线性BEM模型的结果进行了对比分析,进一步证明了耦合模型的正确性与高效性。     

Application of chemometric methods to analyze the distribution and chemical fraction patterns of metals in sediment from a metropolitan river

Rivers in metropolitan areas are often highly polluted with materials that pose a threat to a large number of residents. Human influences lead to contaminants in metropolitan rivers having more complex sources than those in rural rivers. This complexity results in contamination that is unstable and rapidly changing. Here, the contents and chemical fractionation patterns of eleven toxic elements (As, Cd, Co, Cu, Cr, Mn, Ni, Pb, Zn, Y, and Hg) were evaluated in 13 samples collected from along the Beiyunhe River in Beijing, China. The results revealed that the metal contents were unevenly distributed along the river, with higher levels being observed in the downriver sites and the rendezvous sites. Additionally, more than 80% of the metals were found to be in the residual phase. The organic and sulfide phases were the most important extractable phases of most metals, with Ni, Co, Cu, and Cr primarily being associated with these phases and As, Cd, and Zn having a strong association with the iron/manganese oxide and hydroxide phases. Additionally, Mn was associated with the exchangeable and carbonate phases, with the lowest concentrations being observed in the organic and sulfide phases. Conversely, the metal exchangeable and carbonate phases were uniformly distributed throughout the river. Analysis of the metal sources revealed that particles input from the atmosphere comprised a considerable amount of the metals in the Beiyunhe River. However, these metals likely do not enter the sediment via atmospheric deposition directly, but rather through rainwater runoff into the river. The methods used in the present study will be useful in other studies that require analysis of complex data.     

地震前兆台网观测数据质量分析——中国地震背景场探测项目实施

地震前兆台网的运行直接影响产出的观测数据质量。观测数据平均连续率和平均数据完整率可以反映地震前兆台网的运行质量。对中国地震背景场探测项目试行期间(2014年)及正式启动后2015年度的观测数据质量,从以上2个指标进行分析,并对比原有仪器运行质量,可知背景场项目试运行期间,各学科台网投入仪器运行稳定,观测数据符合相关要求,总体质量良好,观测仪器可以投入正式运行。     

城市浅层地震勘探过障碍变观设计

在城市浅层地震勘探数据采集中,地震测线经常会遇到河流、桥、交叉路口等地表障碍。为了尽量减小地表障碍造成的影响,需要对观测系统作变观设计。作者分析总结了城市浅层地震勘探中常见障碍以及过障碍变观模式,并开发了浅层地震过障碍变观设计软件,利用此软件可在采集现场快捷地进行过障碍变观。将这种方法应用于实际工作中,有效减小了资料缺失造成的影响,提高了资料的信噪比。该软件能够根据实际工作环境和设备条件在野外现场对观测系统进行灵活变观,设计出合理的过障碍观测系统,有效地提高了变观设计的效率。     

Processes of initial collision and suturing between India and Asia

The initial collision between Indian and Asian continents marked the starting point for transformation of land-sea thermal contrast, uplift of the Tibet-Himalaya orogen, and climate change in Asia. In this paper, we review the published literatures from the past 30 years in order to draw consensus on the processes of initial collision and suturing that took place between the Indian and Asian plates. Following a comparison of the different methods that have been used to constrain the initial timing of collision, we propose that the tectono-sedimentary response in the peripheral foreland basin provides the most sensitive index of this event, and that paleomagnetism presents independent evidence as an alternative, reliable, and quantitative research method. In contrast to previous studies that have suggested collision between India and Asia started in Pakistan between ca. 55 Ma and 50 Ma and progressively closed eastwards, more recent researches have indicated that this major event first occurred in the center of the Yarlung Tsangpo suture zone (YTSZ) between ca. 65 Ma and 63 Ma and then spreading both eastwards and westwards. While continental collision is a complicated process, including the processes of deformation, sedimentation, metamorphism, and magmatism, different researchers have tended to define the nature of this event based on their own understanding, an intuitive bias that has meant that its initial timing has remained controversial for decades. Here, we recommend the use of reconstructions of each geological event within the orogenic evolution sequence as this will allow interpretation of collision timing on the basis of multidisciplinary methods.     

地震槽波的数学-物理模拟初探

针对地震槽波在低速层的传播特性,开展了煤层内地震槽波勘探的数值模拟和物理模拟研究的初探工作.在数值模拟研究方面,采用交错网格有限差分法对煤层中的地震槽波进行三分量全波场模拟.基于波场快照和人工合成地震记录研究了不同模型中的波场特征和各种波型的传播规律.在物理模拟方面,通过选用不同配比的环氧树脂和硅橡胶类材料构建地震槽波物理模型,利用透射法和反射法观测系统获得了清晰的地震槽波记录以研究槽波的地震学特征.研究表明,在煤层内槽波的地震波场中,Love型槽波的能量小于Rayleigh型槽波的SV分量,大于Rayleigh型槽波的SH分量.相对于Love型槽波和Rayleigh型槽波的SH分量,Rayleigh型槽波的SV分量在围岩中的泄露能量较强.在煤层界面附近的围岩中,地震波仍以槽波形式传播,随着距离的增加能量逐渐衰减.随着煤层变薄,煤层槽波主频向高频方向移动,频散现象增强,传播速度增大.     

宾川地区的地壳厚度和泊松比分布特征研究

This paper presents the changes of crust thickness and Poissons ratios distribution in the Binchuan region,where the first air-gun transmitting station and its a small dense array were deployed.From September 2011 to January 2014,more than 239 teleseismic events of M≥6.0 were recorded in 16 stations in the Binchuan region.Their P-wave receiver functions were analyzed respectively.The high spatial resolution result shows that the average crust thickness of Binchuan region is 45.3km,it follows the rule of"deeper in the north and east part,shallower in the south and west part."The deepest region is in Xiaoyindian Station;the crust thickness is 47.9km;the shallowest region is in Paiying Station,it has the thickness of 42.1km.It shows that the deeper Moho surface nearby the Chenghai fault and shallower nearby the Honghe fault;the isoline distribution of thickness changes greatly nearby the Chenghai fault and slowly nearby the Honghe fault.From the distribution of Poissons ratios,it is unevenly in the study area with a great difference from the north part to the south part,which shows a characteristic of"lower in the north,higher in the south".The Poissons ratio nearby the Honghe fault is medium too high(0.26≤σ≤0.29);lower nearby the Chenghai fault(σ≤0.26).This paper concludes the possible reason of different characteristic between Poissons ratio and crust thickness is thicker in the upper crust in the Binchuan region.     

三维复杂地壳结构非线性走时反演

中国大陆中西部乃至全球造山带普遍具有复杂地壳结构.随着矿产资源勘探和深部探测研究的深入,探测造山带及盆山耦合区下方地壳精细结构正逐渐成为当前面临的巨大挑战.人工源深地震测深方法正越来越清晰地揭示出不同构造域地壳速度结构的基本特征,然而传统的层状结构模型参数化方法难以准确描述复杂地质模型,通常情况下多忽略速度结构的精细间断面且采用层边界平滑处理,难以满足地壳精细结构成像的发展要求.针对上述困难,本文采用最近发展的块状结构建模方案构建三维复杂地壳模型,基于逐段迭代射线追踪正演走时计算方法,推导了走时对三角形界面深度以及网格速度的偏导数,开展了非线性共轭梯度走时反演方法研究.发展了利用直达波和反射波等多震相走时数据对界面深度和网格速度的多参数联合反演方法,并引人不同种类震相数据的权系数和不同类型参数偏导数归一化的方法.数值算例表明,基于块状结构的非线性共轭梯度走时反演方法适用于复杂地壳结构模型,在利用人工源走时数据反演复杂地壳精细结构领域具有良好的应用前景.