Calibration of estuarine current crosses     

Björn Kjerfve 《Estuarine, Coastal and Shelf Science》1982,15(5):553-559

Tethered current crosses are simple, reliable tools in making measurements of estuarine currents in the absence of surface waves. The standard error of the estimate of current speed is less than 5 cm s^?1 for the particular crosses and weights used in a calibration experiment. The useful velocity range of these current crosses was 8–147 cm s^?1, corresponding to a measured angle, α, from 2° to 30°. Regression of the independently measured current speed on $\text{(tan α)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ yielded coefficients of determination greater than 0·94, indicating that the drag coefficient is not a function of current speed. However, the calculated drag coefficients varied widely from 0·66 to 2·55, depending on the particular combination of cross and weight, varying drastically from the commonly assumed drag coefficient value of 1·12. Thus, in using current crosses, it is imperative to calibrate each cross against a current meter reading to determine an appropriate value for the drag coefficient for a particular current cross and weight.  相似文献   

Stresses due to vertical subsurface loading for an inhomogeneous cross‐anisotropic half‐space     

Cheng-Der Wang  Ernian Pan 《国际地质力学数值与分析法杂志》2004,28(12):1233-1255

In this article, we present the solutions for the stresses induced by four different loads associated with an axially loaded pile in a continuously inhomogeneous cross‐anisotropic half‐space. The planes of cross‐anisotropy are parallel to the horizontal surface of the half‐space, and the Young's and shear moduli are assumed to vary exponentially with depth. The four loading types are: an embedded point load for an end‐bearing pile, uniform skin friction, linear variation of skin friction, and non‐linear parabolic variation of skin friction for a friction pile. The solutions for the stresses due to the pile load are expressed in terms of the Hankel integral and are obtained from the point load solutions of the same inhomogeneous cross‐anisotropic half‐space which were derived recently by the authors (Int. J. Rock Mech. Min. Sci. 2003; 40 (5):667–685). A numerical procedure is proposed to carry out the integral. For the special case of homogeneous isotropic and cross‐anisotropic half‐space, the stresses predicted by the numerical procedure agree well with the solutions of Geddes and Wang (Geotechnique 1966; 16 (3):231–255; Soils Found. 2003; 43 (5):41–52). An illustrative example is also given to investigate the effect of soil inhomogeneity, the type and degree of soil anisotropy, and the four different loading types on the vertical normal stress. The presented solutions are more realistic in simulating the actual stratum of loading problem in many areas of engineering practice. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

BOOK REVIEWS     

《The Professional geographer》1982,34(4):458-490

Books reviewed in this article: Aerial Photography and Remote Sensing. Terrain Analysis and Remote Sensing . JOHN R. G. TOWNSHEND , ed. Environmental Data Use in Computer-assisted Data Handling Systems: The Results of a Survey of Applications in the Pacific Northwest States . KENNETH E. GORDON . Applied Land Use: A Spatial Approach . JOHN F. LOUNSBURY , LAWRENCE M. SOMMERS , AND EDWARD A. FERNALD , eds. The Second Battle of New Orleans: A History of the Vieux Carre Riverfront-Expressway Controversy . RICHARD O. BAUMBACH , JR. AND WILLIAM E. BORAH . Cultural Environmental Archaeology . MYRA SHACKLEY . The Immoral landscape: Female Prostitution in Western Societies . RICHARD SYMANSKI . life Among the Poor in Cairo . UNNI WIKAN , translated by Ann Henning. Women, Work and Property in Northwest India . URSULA SHARMA . The Domestication of Women: Discrimination in Developing Societies . BARBARA ROGERS Economic Optimization in Locational and Transport Analysis . A. G. WILSON , J. D. COELHO , S. M. MACGILL , H. C. W. L. WILLIAMS . New Tools for Economic Development: The Enterprise Zone, Development Bank, and RFC . GEORGE STERNLIEB AND DAVID LISTOKIN , eds. Regional Wage Inflation . R. L. MARTIN , ed. Finding A Place For Energy-Siting Coal Conversion Facilities . FRANK J. CALZONETTI WITH MARK S. ECKERT . Environmental Management, Resources, and Systems Environmentalism. Second Edition . T. O'RIORDAN . Countryside Conservation . BRYN GREEN . Medical Spatial Diffusion: An Historical Geography of Epidemics in an Island Community . A. D. CLIFF , P. HAGGETT , J. K. ORD , AND G. R. VERSEY . Philosophy and Geographic Thought Order and Skepticism: Human Geography and the Dialectic of Science . RICHARD SZYMANSKI AND JOHN A. AGNEW . Measurement of Subjective Phenomena . D. F. JOHNSTON , ed. Conceptions of Space in Social Thought: A Geographic Perspective . ROBERT DAVID SACK . The Association of American Geographers: The First Seventy-five Years: 1904-1979 . PRESTON E. JAMES AND GEOFFREY J. MARTIN . The Life and Thought of Isaiah Bowman . GEOFFREY J. MARTIN . Physical River Basin Planning: Theory and Practice . SURANJIT K. SAHA AND CHRISTOPHER J. BARROW , eds. Soils and landforms: An Integration of Ceomorphology and Pedology . A. I. GERRARD Climatic Change and Society. Consequences of Increasing Atmospheric Carbon Dioxide . WILLIAM W. KELLOGG AND ROBERT SCHWARE . Political Political Redistrictings and Geographic Theory . RICHARD L. MORRILL . Population Studies in Spanish American Population History: Dell Plain Latin American Studies NO. 8 . DAVID J. ROBINSON , ed. Population Redistribution in the Midwest . CURTIS C. ROSEMAN , ANDREW J. SOFRANKO , AND JAMES D. WILLIAMS , eds. Geographical Perspectives on the Elderly . A. M. WARNES , ed. Regional Perspective On the American South . MERLE BLACK AND JOHN SHELTON REED , eds. The Prairies and Plains: Prospects for the 80s . JOHN R. ROGGE , ed. Rural Rural Settlement in an Urban World . MICHAEL BUNCE . Social Accident at Three Mile Island: The Human Dimensions . DAVID L. SILLS , C. P. WOLF , AND VIVIEN B. SHELANSKI , eds. The American Small Town: Twentieth-Century Place Images . JOHN JAKLE . Urban A House of My Own . SUSAN LOBO . The City: Patterns and Processes in the Urban Ecosystem . CHRISTOPHER H. EXLINE , GARY L. PETERS , AND ROBERT P. LARKIN . Movement in Cities . P. W. DANIELS AND A. M. WARNES . Urbanization and Urban Planning in Capitalist Society . MICHAEL DEAR AND ALLEN J. SCOT , eds.  相似文献   

位温、等熵位涡与锋和对流层顶的分析方法   总被引：10，自引：2，他引：8  

陶祖钰  郑永光 《气象》2012,38(1):17-27

等熵位涡分析是位涡理论的分析基础。此文的目的是介绍等熵位涡分析所必需掌握的基本概念和方法。文中从位温和位涡、对流层和平流层、锋和对流层顶的基本性质出发,讨论了锋和对流层顶在剖面图、等压面图及等位温面（即等熵面）图上的特征。文中给出了各种分析实例图形,并通过分析和对比指出：平流层的高位涡是对流层顶以上位温随高度急剧增加位温垂直梯度特别大的结果;位温垂直梯度是决定位涡分布的主要因子;等熵位涡图主要反映极地气团的活动,同时也是与极地气团密切关联的锋、急流、对流层顶的综合反映。最后提出了等熵位涡分析中需要避免的一些错误认识,特别是不能将等位温面上的流线当成轨迹的错误,并由此得出平流层空气侵入对流层下部的错误推论。  相似文献   

2007/2008年冬季雨雪冰冻灾害的副热带高压环流背景与变异特征     

张韧  洪梅  刘科峰  陈奕德 《大气科学学报》2012,35(1):1-9

基于NCEP/NCAR提供的1958—2008年逐日再分析资料,对2007/2008年冬季我国雨雪冰冻灾害期间副高指数特征与El Nino/La Nina年平均冬半年副高指数特征以及50a平均冬半年副高指数特征进行对比分析。采用交叉小波和小波相干分析方法,进一步分析了它们之间的相关性和异同性以及对大气环流的影响,揭示了2007/2008年我国南方雨雪冰冻灾害期间副热带高压活动与环流变异特性的一些基本特征,如La Nina事件冬季(尤其是中等强度La Nina事件年份的冬季),副高通常比一般年份副高的平均位置偏北。  相似文献   

Autolisp语言在测量工作中的应用     

王湘文 《东北测绘》2012,(10):216-218

通过两个实例介绍了Autolisp语言编程在工程测量中的应用,通过实践证明,该应用可以明显地提高工作效率。  相似文献   

在数字化地形图中图摘纵横断图形     

周荣  刘玉善 《北京测绘》2012,(2):47-50,70

对传统纸质图摘纵横断数据采集的一般流程进行分析,从相关步骤环节入手,分析缺点。编写的图摘纵横断软件对步骤环节进行改进,作业人员完成对数字化电子地形图中图摘纵横断的数据采集过程,从而完成了传统纸质图摘纵横断数据采集的成果要求,同时进一步提供了为检验人员对数据的完整性、正确性加以核对的便利性。通过作业人员的实践,取得了良好的效果。  相似文献   

印度洋偶极子与热带太平洋海洋表面温度异常多时间尺度相互作用初析   总被引：1，自引：0，他引：1  

肖莺  张祖强  何金海 《大气科学》2010,34(3):483-494

本文利用交叉谱方法, 将印度洋偶极子 (简称IOD) 与ENSO的相关关系分解到不同的时间尺度上来分析, 进而通过对海气耦合过程的初步分析, 讨论了不同时间尺度上IOD与ENSO的相互作用。结果表明, IOD与ENSO在准1～2年、 准3年、 准4年等三个时间尺度上存在显著相关, 同时, IOD还存在一个独立于ENSO的模态, 主要表现在准8个月时间尺度上。从海气相互作用的角度看, 在与ENSO相关的三个特征时间尺度上, IOD年际变率主要通过引发热带印度洋纬向风异常并且东传到太平洋, 从而引起热带中东太平洋海温的年际变率。与ENSO相对独立的IOD模态则没有类似的纬向风异常东传过程。此外, 在上述四个不同时间尺度上, 产生IOD变率的印度洋海气耦合过程不尽相同, 各具特点。  相似文献   

Seismic constraints on rock damaging related to a failing mountain peak: the Hochvogel,Allgäu     

M. Dietze  M. Krautblatter  L. Illien  N. Hovius 《地球表面变化过程与地形》2021,46(2):417-429

Large rock slope failures play a pivotal role in long-term landscape evolution and are a major concern in land use planning and hazard aspects. While the failure phase and the time immediately prior to failure are increasingly well studied, the nature of the preparation phase remains enigmatic. This knowledge gap is due, to a large degree, to difficulties associated with instrumenting high mountain terrain and the local nature of classic monitoring methods, which does not allow integral observation of large rock volumes. Here, we analyse data from a small network of up to seven seismic sensors installed during July–October 2018 (with 43 days of data loss) at the summit of the Hochvogel, a 2592 m high Alpine peak. We develop proxy time series indicative of cyclic and progressive changes of the summit. Modal analysis, horizontal-to-vertical spectral ratio data and end-member modelling analysis reveal diurnal cycles of increasing and decreasing coupling stiffness of a 260,000 m³ large, instable rock volume, due to thermal forcing. Relative seismic wave velocity changes also indicate diurnal accumulation and release of stress within the rock mass. At longer time scales, there is a systematic superimposed pattern of stress increased over multiple days and episodic stress release within a few days, expressed in an increased emission of short seismic pulses indicative of rock cracking. Our data provide essential first order information on the development of large-scale slope instabilities towards catastrophic failure. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.  相似文献   

云贵高原斜坡地带典型地下水富硫酸盐地区“越层找水”模式及其机理研究          下载免费PDF全文

曹建文  夏日元  方尚武  赵良杰  王喆  王若凡  易瑞 《中国地质》2019,46(2):235-243

地下水是中国西南云贵高原斜坡地带重要的饮用水源,其中黔中镇宁县北部存在大面积地下水中硫酸盐超标地区,导致了当地出现水质性缺水问题。本次研究通过岩相古地理分析、水化学分析、D、18O、34S同位素测试、岩样测试、岩心观察等技术手段,查明了研究区内地下水的补给源主要为大气降水,地下水中硫酸盐(SO_4~(2-))浓度在30～1100 mg/L,平均值为221.78 mg/L,呈现高度富集SO_4~(2-)的特点;在区域相对隔水层以上,不同类型地下水中SO_4~(2-)浓度大体具有机井上升泉下降泉溶潭地下河出口基岩裂隙泉表层岩溶泉的规律;探讨了地表水、地下水中SO_4~(2-)的来源,表层岩溶泉中硫酸根的来源主要为大气降水,高硫酸盐样品中硫酸根的来源主要为石膏溶解。在此基础上,结合钻井资料,掌握了研究区膏岩层分布及含水层结构特征,通过建立"越层找水"模式,采取下层低硫酸盐含水层,获取合格饮用水源,可有效解决当地水质性缺水问题。  相似文献