Backus — Gilbert’s method in gravity and magnetic inversion     

Xiwen Wang 《地震科学（英文版）》1992,5(1):133-143

In this paper, the application of Backus—Gilbert’s inversion method to the potential field anomalies for evaluating gravity and magnetic inversion solutions is discussed. Errors in data and singularity of kernels in the equations result in difficulties in solving equations. The application of regularization method similar to spectral expansion method makes calculation fast and easily. To make solution stable, constraints are used, which make the spread of solutions become narrow, standard deviation become small and iterative computations of inversion become fast. Finally, the author analyses specifically two profiles of Yunchen basin and calculated the Moho interface and the Curie isotherm of these two profiles.  相似文献   

Suppression of Vortex-Induced Vibration by Fairings on Marine Risers     

Yongtian Kang  Wensheng Xiao  Quanbin Wang  Dagang Zhang  Jun Zhao 《中国海洋大学学报(英文版)》2020,19(2):298-306

Vortex-induced vibration is quite common during the operation of offshore risers or umbilical cables,commonly leading to serious damage to risers and reduced service life.Vortex-induced vibration of the offshore risers could be effectively suppressed by fairing devices.In this paper,a newly developed vortex-induced vibration fairing and large eddy simulation model of the FLUENT software were used for numerical analysis,experimental research and stimulating vortex-induced vibration at 0.1–2 ms^-1.The data of the numerical model with fairing was compared and analyzed to study the vortex shedding frequency at different Reynolds numbers and changes in drag and lift coefficients.The displacement state of 12 in risers with and without fairing was experimentally tested using a five degree-of-freedom balance.The vortex-induced vibration effect of the fairing was tested at different velocities.The result shows the drag reduction effect of the fairing is more obvious when the flow velocity is 0.4–1.2 ms^-1 and the maximum drag reduction reaches 55.6%when the flow velocity is 0.6 ms^-1.Additionally,the drag reduction effect was obvious when the flow velocity was greater than 1.3 ms^-1 and less than 0.3.The result indicates that the developed 12 in fairing,with good potential in engineering applications,has good vortex-induced vibration-suppression effects.  相似文献   

旋翼无人机单目视觉障碍物径向光流检测法   总被引：1，自引：0，他引：1  

张小东  郝向阳  孙国鹏  徐亚丽 《测绘学报》2017,46(9):1107-1115

针对旋翼无人机在室外复杂环境下传统金字塔LK光流法检测障碍物准确性不高,适应性差的问题,提出了一种基于径向光流的单目视觉自主实时障碍物检测方法。该方法通过融合金字塔LK光流与切向光流求解径向光流,并基于径向光流设计了一种新的障碍物判定策略检测障碍物。试验表明,与传统金字塔LK光流法相比,在不增加算法复杂度的情况下,该方法具有更高的准确性和更强的适应性,可满足工程实践中无人机自主避障要求。  相似文献   

How does law make place? Localisation,translocalisation and thing-law at the world’s first factory     

《Geoforum》2016

This article examines how law is implicated in the formation of place, and how place in turn can shape law. It is an empirical explication of Latour’s call for researchers to study the global through its local instantiations. Drawing upon recent theoretical work in both material culture studies and legal geography the article examines the interplay of law and material formations at one originating site, Sir Richard Arkwright’s Cromford Mills in Derbyshire in order to examine the creation and circulation of a new form of place in the late eighteenth century: the industrial scale cotton mill. It shows how a diverse range of legal elements ranging across patent law, the Calico Acts and ancient local Derbyshire lead mining laws all helped to shape that place-form, its proliferation across the United Kingdom, and ultimately further afield. In doing so the article conceptualises processes of localisation, translocalisation and thing-law by which the abstractions of both place-forms and law elements become activated through their pragmatic local emplacement. Whilst the case study concerns 200 year old place-making machinations, many of the spatio-legal articulations of Arkwright and his opponents have a surprisingly modern feel about them. The paper therefore advocates the benefits of a longitudinal, historical approach to the study of place-making, and in particular, calls for a greater attentiveness in legal geography to law’s role in the intentional formation of (work)places by their owners.  相似文献   

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范昊鹏  王庆宾  吴晓平 《大地测量与地球动力学》2015,35(2):326-330

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近十年北京气溶胶光学特性及直接辐射强迫研究     

唐利琴  胡波  刘慧  赵舒曼  刘俊卿 《气候与环境研究》2021,26(2):155-168

利用SBDART（Santa Barbara DISORT Atmospheric Radiative Transfer）辐射传输模式,结合AERONET（Aerosol Robotic Network）北京站观测的气溶胶光学特性数据,评估北京地区近十年气溶胶以及黑碳气溶胶的辐射强迫,主要研究结果如下:北京近十年气溶胶平均光学厚度（aerosol optical depth, AOD_440nm）为0.61±0.56,?ngstr?m波长指数均值为1.09,单次散射反照率（single scattering albedo, SSA_440nm）的均值为0.888±0.045;AOD呈现下降趋势,SSA呈上升趋势,表明该区域气溶胶污染有所改善。晴空条件下,大气层顶、地面和大气的气溶胶直接辐射强迫多年均值分别为?24.91±19.80 W m?2、?65.52±43.78 W m?2、40.61±28.62 W m?2,即气溶胶对大气层顶和地表为冷却效应,对大气产生加热作用。气溶胶和黑碳气溶胶的直接辐射强迫绝对值的年际变化表现为微弱的下降趋势,季节变化特征为春夏季高,冬季低,这与AOD的变化规律一致。并且黑碳气溶胶的直接辐射强迫下降趋势与SSA的上升趋势呈现较好的反位相关系。  相似文献   

2021年青海玛多M_S7.4地震序列精定位与震源机制研究          下载免费PDF全文

张志朋  李君  冯兵  王文青  柴旭超 《地震工程学报》2022,44(1):218-226

利用双差定位法对2021年5月22日玛多M_S7.4地震序列中1 434个地震进行重新定位,使用TDMT矩张量反演方法求解玛多地震序列M≥4.5地震的震源机制解,综合分析得到如下结论:(1)玛多地震序列震中整体走向为NWW-SEE向,与昆仑山口—江错断裂展布方向相吻合,序列总长度170 km,呈NWW向和SEE向双侧破裂,主震西北侧存在NW向条带,可能是此次地震的分支断裂活动,在南东侧存在余震稀疏段以及横穿玛多—甘德断裂的余震分布带,推测可能是地下速度结构差异所致;(2)主震附近地震序列以左旋走滑型地震为主,优势走向为NWW向,倾向NE,倾角较高,与昆仑山口—江错断裂性质基本一致,结合余震定位结果推断昆仑山口—江错断裂为本次地震的发震断层;(3)主震附近地震序列P轴平均方位角为237°,P轴,T轴平均倾角分别为15°、16°,N轴平均倾角为65°,结合研究区构造特征推断,本次地震是由NEE-SWW向水平挤压应力推动NWW-SEE向断裂发生左旋走滑错动所致。  相似文献   

武汉市商业中心空间特征及影响因素分析     

马志勇  常迎辉  孙立坚  王涛涛 《测绘通报》2021,(12):60-65

本文以武汉市主城区为研究对象,首先基于手机信令的居民出行OD数据识别商业中心的势力范围和腹地,并分析了研究区商业中心的空间特征;然后构建了影响腹地规模的指标体系;最后通过熵权法对影响因子赋权,计算得到各商业中心的综合水平。研究结果表明:①研究区商业中心呈多核心分布特征,其影响范围沿地铁分布,长江对其具有明显分隔作用;②POI多样性与商业中心腹地规模有较强相关性(0.879 8),商业中心吸引力更多取决于其服务水平和交通发达程度;③汉街和街道口虽为区级商业中心,但由于位置较好、交通便捷,仍是附近居民消费、游憩的首选。  相似文献   

Applicative limitations of sediment transport on predictive modeling in geomorphology     

WEI Xiang  LI Zhanbin 《地理学报》2004,14(1):94-104

Sources of uncertainty or error that arise in attempting to scale up the results of laboratory-scale sediment transport studies for predictive modeling of geomorphic systems include: (i) model imperfection, (ii) omission of important processes, (iii) lack of knowledge of initial conditions, (iv) sensitivity to initial conditions, (v) unresolved heterogeneity, (vi) occurrence of external forcing, and (vii) inapplicability of the factor of safety concept. Sources of uncertainty that are unimportant or that can be controlled at small scales and over short time scales become important in large-scale applications and over long time scales. Control and repeatability, hallmarks of laboratory-scale experiments, are usually lacking at the large scales characteristic of geomorphology. Heterogeneity is an important concomitant of size, and tends to make large systems unique. Uniqueness implies that prediction cannot be based upon first-principles quantitative modeling alone, but must be a function of system history as well. Periodic data collection, feedback, and model updating are essential where site-specific prediction is required.  相似文献   

高温影响下西安市人口脆弱性评估及其空间分异     

黄晓军  祁明月  赵凯旭  郑殿元  刘萌萌 《地理研究》2021,40(6):1684-1700

高温给城市人口健康和社会发展带来的脆弱性后果愈发严重,如何科学量化与评估城市高温人口脆弱性,为制定更具针对性的高温适应对策提供科学依据成为当前国际研究热点。在城市高温人口脆弱性分析框架基础上,以西安市为例,整合遥感影像、手机信令、POI、社会经济等多源数据,从高温暴露、敏感性、适应能力3个维度构建高温影响下人口脆弱性评估指标体系和脆弱性测度模型,揭示高温人口脆弱性等级分布特征和空间异质性,识别人口脆弱性空间地域及其致脆因子类型。结果表明：① 西安市高温暴露、敏感性和适应能力都表现出显著的空间集聚特征,且总体上均呈现出“中心-边缘”结构,即城市中心地区形成“高暴露、高敏感、高适应”,城市边缘表现为“低暴露、低敏感、低适应”。② 西安市人口脆弱性以低值和较低水平为主,脆弱性也具有显著的空间集聚性,脆弱性较高地区主要集中在城市三环以内,形成断续的“岛状”分布形态,脆弱性低值和较低值地区分布在城市边缘。③ 不同致脆类型的面积占比依次为综合主导型（37.3%）>高温暴露主导型（33.3%）>适应能力不足主导型（23.6%）>人口敏感主导型（5.8%）;高温暴露主导型广泛分布在城市中心、北部和西部等地,人口敏感主导型相对集中在城市中心偏南地区,适应能力不足主导型主要分布在城市边缘,综合主导型主要集中在城市南部,北部也有大量分散式分布。本研究可在城市高温人口脆弱性评估方法,城市高温人口脆弱性的减缓与治理等方面提供借鉴和启示。  相似文献