一种功率谱相关的基元域近场强干扰抑制方法

针对影响拖曳线列阵声纳系统目标检测性能的两种典型近场强干扰源,由宽带近场阵列模型,提出了基于功率谱相关的干扰抵消方法,通过比较基元域频域信号与干扰波束信号功率谱之间的相似关系,找到与每路基元信号相匹配的干扰分量信号,最后通过频域块自适应滤波算法实现每路基元域信号中的干扰抵消。宽带仿真结果与海试表明,这种方法在强干噪比和低信噪比条件下,比最小方差无失真响应和传统基元域干扰抵消方法在阵增益方面提高约10dB。相比传统基元域干扰抵消方法,这种方法能够实现抵消拖船干扰的同时抵消邻近目标强干扰。     

The ocean/continent transition along a profile through the Lofoten basin,Northern Norway

The Cenozoic margins of the Norwegian-Greenland Sea offer ideal conditions for passive margin studies. A series of structural elements, first observed on these margins, led to the concept of volcanic passive margins. Questions still remain about the development of such features and the location of the boundary between oceanic and continental crust. Despite the thin sediment cover of the margins, seismic reflection data are not able to image the deeper structures due to the occurrence of igneous rocks at shallow depth.This paper presents a 320-km long profile perpendicular to the strike of the main structural units of the Lofoten Margin in Northern Norway. A geological model is proposed, based on observations made with ocean bottom seismographs, which recorded seismic refraction data and wide angle reflections, along with a seismic reflection profile covering the same area. Ray-tracing was used to calculate a geophysical model from the shelf area into the Lofoten basin. The structures typical of a volcanic passive margin were found, showing that the Lofoten Margin was influenced by increased volcanic activity during its evolution. The ocean/continent transition is located in a 30-km wide zone landwards of the Vøring Plateau escarpment.The whole margin is underlain by a possibly underplated, high velocity layer. Evidence for a pre-rift sediment basin landwards of the escarpment, overlain by basalt flows, was seen. These structural features, related to extensive volcanism on the Lofoten Margin, are not as distinct as further south along the Norwegian Margin. Viewed in the light of the hot-spot theory of White and McKenzie (1989) the Lofoten Margin can be interpreted as a transitional type between volcanic and non-volcanic passive margin.     

热带海表风速与海表温度日变化关系分析

星载可见光/红外仪器因其波长缺乏穿透云的能力,只能观测到云顶及其下部有限深度的信息,而星载被动微波仪器则因其波长较长,具有穿透云的能力而能获得云体信息,因此星载被动微波仪器较可见光/红外仪器观测云和降水更具有优势。自20世纪70年代末至今,美国投入了大量星载被动微波仪器,服务于天气预报等领域,促进了云和降水等参数的被动微波遥感反演算法的快速发展。本文聚焦星载被动微波遥感反演洋面云液态水研究的进展,旨在提升我国的星载被动微波仪器遥感应用能力。文章首先简介了几种微波辐射传输模式形式,其次介绍了被动微波通道（频率）对洋面参数和云液态水的敏感性研究,然后介绍了被动微波反演洋面云液态水的统计反演算法、物理反演算法、物理与统计相结合的反演算法、被动微波多通道多参数的同步反演算法、被动微波与可见光/红外相结合的反演算法,最后探讨了未来该领域研究的发展方向。

     

Post‐orogenic thermal history and exhumation of the northern Appalachian Basin: Low‐temperature thermochronologic constraints

Apatite fission‐track (AFT) thermochronology and (U‐Th)/He (AHe) dating, combined with paleothermometers and independent geologic constraints, are used to model the thermal history of Devonian Catskill delta wedge strata. The timing and rates of cooling determines the likely post‐orogenic exhumation history of the northern Appalachian Foreland Basin (NAB) in New York and Pennsylvania. AFT ages generally young from west to east, decreasing from ~185 to 120 Ma. AHe single‐grain ages range from ~188 to 116 Ma. Models show that this part of the Appalachian foreland basin experienced a non‐uniform, multi‐stage cooling history. Cooling rates vary over time, ~1–2 °C/Myr in the Early Jurassic to Early Cretaceous, ~0.15–0.25 °C/Myr from the Early Cretaceous to Late Cenozoic, and ~1–2 °C/Myr beginning in the Miocene. Our results from the Mesozoic are broadly consistent with earlier studies, but with the integration of multiple thermochronometers and multi‐kinetic annealing algorithms in newer inverse thermal modeling programs, we constrain a Late Cenozoic increase in cooling which had been previously enigmatic in eastern U.S. low‐temperature thermochronology datasets. Multi‐stage cooling and exhumation of the NAB is driven by post‐orogenic basin inversion and catchment drainage reorganization, in response to changes in base level due to rifting, plus isostatic and dynamic topographic processes modified by flexure over the long (~200 Myr) post‐orogenic period. This study compliments other regional exhumation data‐sets, while constraining the timing of post‐orogenic cooling and exhumation in the NAB and contributing important insights on the post‐orogenic development and inversion of foreland basins along passive margins.     

Passive revolution: A church‐military partnership in the Philippines

In the Philippines, a Catholic social movement for local development and broad structural transformation, referred to as Basic Ecclesial Communities, offers a counter‐narrative to state development. Predicated on the power of networked local groups, the Diocese of San Carlos has taken the original concept and rescaled it, operating a variety of social‐action programmes at the diocese level. The focus of this paper is a unique partnership between the diocese and the Armed Forces of the Philippines, which has produced a number of measurable positive changes in under‐serviced areas. We remain uncertain, however, about the extent to which the church is cooperating with, or being co‐opted by, the military as it enters into partnership, and many members of the clergy share our scepticism. In this paper we draw upon Gramsci's concept of passive revolution (1971) as a means to conceptualize both the efforts of the church to reform society from within, and the reaffirmation of the hegemonic discourse that seems inevitable.     

An alternative methodology for designing tuned mass dampers to reduce seismic vibrations in building structures

It is well established that small tuned mass dampers (TMDs) attached to structures are very effective in reducing excessive harmonic vibrations induced by external loads but are not as interesting within the context of earthquake engineering problems. For this reason, large mass ratio TMDs have been proposed with the objective of adding a significant amount of damping to structures, thus constituting a good means of reducing structural response in these cases. This solution has other important and attractive dynamic features such as robustness to system uncertainties and reduction of the motion of the inertial mass. In this context, this paper aims to describe an alternative methodology to existing procedures used to tune these devices to earthquake loads and to present some additional considerations regarding its performance in controlling seismic vibrations. The main feature of the proposed method consists of establishing a direct proportion between the damping ratios of the structure's first two vibration modes and the adopted mass ratio. By equalizing the damping ratios of the system's main vibration modes, this proposal also facilitates the use of simplified methods, such as modal analysis based on response spectra. To demonstrate the usefulness of this alternative methodology, an application example is presented, which was also used to perform a parametric study involving other tuning methods and to estimate mass ratio values from which there is no significant advantage in increasing the TMD mass. Copyright © 2012 John Wiley & Sons, Ltd.     

浙西北二叠,三叠纪浊积岩系及其大地构造意义

对浙西北上二叠统长兴组，大隆组及下三叠统政棠组沉积特征，生物生态等的研究表明，长兴组，大隆组和政棠组为一套浊积岩系沉积，沉积背影为一向东南倾斜的被动大陆边缘，印支期造山作用使其发生了强烈的前陆褶皱－冲断变形，岩石地球化学分析结果表明在浊积岩沉积时期，推测可能存在的部分来来源于晚元古代岛弧和晚元古代造山带的物源。     

2017年夏季北极中央航道海冰观测特征及海冰密集度遥感产品评估

2017年夏季中国第八次北极科学考察期间,"雪龙"号极地考察船首次成功穿越北极中央航道,期间全程开展了海冰要素的人工观测。中央航道走航期间的平均海冰密集度和平均冰厚分别为0.64和1.5 m,海冰密集度时空变化大且以厚当年冰为主,高纬密集冰区的浮冰大小显著高于海冰边缘区。基于"雪龙"号的船基走航观测海冰密集度评估比较了国际上常用的5种常用的微波遥感反演海冰密集度产品,同走航目测海冰密集度点对点的比较,误差最大的为德国不来梅大学AMSR2基于Bootstrap算法的产品,平均误差和均方根误差分别为0.19和0.28;误差最小的为欧洲气象卫星应用组织基于AMSR2数据和OSHD和TUD两种不同算法的产品,平均误差分别为-0.02和0.01,均方根误差均为0.20。从日平均比较来看,AMSR2基于Bootstrap算法的误差最大,平均误差和均方根误差分别为0.15和0.20;AMSR2/OSI SAF（TUD）的误差最小,平均误差和均方根误差分别为0.0和0.11,OSI SAF产品更接近人工观测结果。     

基于多维度遥感影像的洪河国家级自然保护区沼泽湿地分类方法研究

以洪河国家级自然保护区为研究区,选取了多时相的Sentinel-1B和Sentinel-2A影像为数据源,制定出9种多时相主被动遥感数据组合方案,用于沼泽湿地遥感分类;分别对根据9种方案整合的多维数据集,进行基于尺度继承的多尺度分割,得到面向对象的分割影像,建立与不同方案对应的特征数据集;采用随机森林机器学习算法,对多...     

南羌塘侏罗纪盆地的沉积－构造转换与烃源岩

沉积盆地层序地层和岩相古地理研究以及沉积-构造转换过程分析，是探讨沉积体系时空演化的重要思路。通过沉积-构造转换的分析。指出羌南地区在侏罗纪经历了从被动大陆边缘到夭折前陆，最后隆升剥蚀的演化历史；初步厘定了南羌塘地区烃源岩形成环境。在经历4次海侵的过程中。相应发育了两个陆源碎屑岩-碳酸盐岩沉积旋回。在这4次沉积-构造转换过程中．发育3套黑色页岩沉积：分别属于被动大陆边缘烃源岩和前陆盆地两个阶段烃源岩。是南羌塘侏罗纪盆地的油气评价的物质基础。