Comparison of measured and predicted nearshore sediment grain-size distribution patterns,southwestern Lake Michigan,U.S.A.     

Juli Badal Graf 《Marine Geology》1976,22(4):253-270

Comparison of calculated grain sizes with those found in a part of the shoaling zone of south western Lake Michigan reveals that existing quantitative expressions yield sizes which are much larger than those of the natural sediments, but that many aspects of the pattern of size distribution are predictable. An empirical and a theoretical expression were each used to calculate grain sizes in equilibrium with several different wave states for the measured bathymetry. For each wave state, the theoretical equation yields sizes which are closer to those found in the field over most of the shoaling zone, but sizes predicted by each of the two equations approach each other as the shore is approached and natural slopes increase toward the slope used in formulating the empirical expression. Grain-size trends predicted by the calculations include coarsening toward shore and to the south near shore. The calculations with the theoretical expression reveal more detail and predict an anomalously coarse area in the deeper part of the field area and elongate areas of fine sediments close to shore. Some support for the existence of these areas was found in the field.  相似文献   

The role of small prey in human subsistence strategies from Early Upper Palaeolithic sites in Iberia: the rabbits from the Evolved Aurignacian level of Arbreda Cave          下载免费PDF全文

Lluís Lloveras  Julià Maroto  Joaquim Soler  Richard Thomas  Marta Moreno‐García  Jordi Nadal  Narcís Soler 《第四纪科学杂志》2016,31(5):458-471

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Numerical Study on the Impacts of the Bogus Data Assimilation and Sea Spray Parameterization on Typhoon Ducts   总被引：1，自引：0，他引：1       下载免费PDF全文

FEI Jianfang  DING Juli  HUANG Xiaogang  CHENG Xiaoping  HU Xiaohua 《Acta Meteorologica Sinica》2013,27(3):308-321

The Weather Research and Forecasting model version 3.2 (WRF v3.2) was used with the bogus data assimilation (BDA) scheme and sea spray parameterization (SSP), and experiments were conducted to assess the impacts of the BDA and SSP on prediction of the typhoon ducting process induced by Typhoon Mindule (2004). The global positioning system (GPS) dropsonde observations were used for comparison. The results show that typhoon ducts are likely to form in every direction around the typhoon center, with the main type of ducts being elevated duct. With the BDA scheme included in the model initialization, the model has a better performance in predicting the existence, distribution, and strength of typhoon ducts. This improvement is attributed to the positive effect of the BDA scheme on the typhoon’s ambient boundary layer structure. Sea spray affects typhoon ducts mainly by changing the latent heat (LH) flux at the air-sea interface beyond 270 km from the typhoon center. The strength of the typhoon duct is enhanced when the boundary layer under this duct is cooled and moistened by the sea spray; otherwise, the typhoon duct is weakened. The sea spray induced changes in the air-sea sensible heat (SH) flux and LH flux are concentrated in the maximum wind speed area near the typhoon center, and the changes are significantly weakened with the increase of the radial range.  相似文献   

Applicability of Newmark method at regional, sub-regional and site scales: seismically induced Bullas and La Paca rock-slide cases (Murcia, SE Spain)     

Martín Jesús Rodríguez-Peces  José Luis Pérez-García  Julián García-Mayordomo  José Miguel Aza?ón  Juan Miguel Insua-Arévalo  Jorge Delgado-García 《Natural Hazards》2011,59(2):1109-1124

In this paper, the applicability of the Newmark method at regional, sub-regional and site scales has been investigated in the Lorca Basin (Murcia). This basin is located in one of the most seismically active regions of Spain. The area is very interesting for studying earthquake-induced slope instabilities as there are well-known cases associated with specific earthquakes. For the regional and sub-regional scales, a geographic information system has been used to develop an implementation of Newmark sliding rigid block method. Soil and topographic amplification effects have been particularly considered. Subsequently, ‘Newmark displacement’ maps for deterministic seismic scenarios have been produced. Some specific studies have also been performed using limit equilibrium methods to estimate the safety factor and the critical acceleration of certain slope instabilities at a site scale. These instabilities were the rock slides related to recent seismic series at the Lorca Basin: 2002 Bullas (M _w = 5.0) and 2005 La Paca (M _w = 4.8). Finally, the safety factor, critical acceleration and Newmark displacement values estimated at different scales have been compared to determine which scale is most suitable for the Newmark method.  相似文献   

A Comparison of Random Field Models Beyond Bivariate Distributions     

Xavier Emery  Julián M. Ortiz 《Mathematical Geosciences》2011,43(2):183-202

In order to determine to what extent a spatial random field can be characterized by its low-order distributions, we consider four models (specifically, random spatial tessellations) with exactly the same univariate and bivariate distributions and we compare the statistics associated with various multiple-point configurations and the responses to specific transfer functions. The three- and four-point statistics are found to be the same or experimentally hardly distinguishable because of ergodic fluctuations, whereas change of support and flow simulation produce very different outcomes. This example indicates that low-order distributions may not discriminate between contending random field models, that simulation algorithms based on such distributions may not reproduce the spatial properties of a given model or training image, and that the inference of high-order distribution may require very large training images.  相似文献   

新疆胜利达坂金矿区金矿化特征   总被引：2，自引：0，他引：2  

王居里  王润三  刘养杰 《新疆地质》1993,(2)

胜利达坂金矿区,发育近EW向的韧性剪切带。该剪切带是区内金矿的主要控矿构造,控制了矿床、矿体及矿化体的分布。矿体主要沿韧性剪切带糜棱面理分布。矿石的主要类型是浸染糜棱岩型和变形石英脉型。成矿的最有利部位是剪切带内应力梯度大的地带。区内乳白色变形石英脉具有很大的找金潜力。该区金矿属韧性剪切带型金矿。  相似文献   

Detecting the order of spatial dependence via symbolic analysis     

Mariano Matilla-García  Julián Rodríguez Ruiz  Manuel Ruiz Marín 《International journal of geographical information science》2013,27(6):1015-1029

In this article, we have proposed a simple diagnostic statistical procedure for testing the order of dependence of a spatial process. The proposed test is of nonparametric nature, and it is able to deal with potential nonlinear spatial dependencies. An added value is that from a methodological point of view, the new test is based on symbolic dynamics and hence on information theory. We characterized the behavior of a symbolic entropy measure in the presence of spatial dependencies of order higher than 1. The good power performance of the new method in detecting higher order spatial lags is notable and gives rise to an expectation that it may form a suitable basis for constructive specification searches.  相似文献   

红海湾水产养殖示范区水质综合评价   总被引：3，自引：0，他引：3  

贾晓平  林钦  甘居利  蔡文贵  李纯厚  王小平  王增焕  贾颋 《广东海洋大学学报》2002,22(4):37-43

红海湾是广东省非常重要的海水养殖示范区。为了维系和保护红海湾规模化水产养殖示范区的优良生态环境 ,1 997年 4月至 1 998年 1 2月对红海湾水域水质的时空变化趋势和质量状况进行了研究与评价。结果表明 ,红海湾海水综合质量总体上处于相对清洁水平 ,但浅海养殖区和长沙湾养殖区有机污染明显 ,分别达富营养化和高富营养化程度。DIN和IP是水质富营养化的主要因素 ,而石油类、Cu、COD是重点控制的优先污染物。  相似文献   

粤东沿海养殖水域浮游植物的生态特征     

李纯厚  贾晓平  林钦  蔡文贵  甘居利  王增焕  高东阳 《广东海洋大学学报》2002,22(1):24-29

粤东至珠江口近海是广东重要的海水养殖水域 ,同时也是赤潮多发区 ,为了研究养殖水域赤潮发生的机理及防治对策 ,维护海水养殖的健康发展 ,对该海域浮游植物的生态特征进行了初步研究。结果表明 ,1 999年浮游植物样品中共鉴定出 1 3 0种 ,组成以广布种和暖水性种类为主 ;出现赤潮生物 3 6种 ,占种类组成的 2 8%。细胞数量 1 0 3 91× 1 0 4 m 3～ 40 3 6 80× 1 0 4 m 3,平均 1 648 1 4× 1 0 4 m 3;多样性指数在 2 68(3 75范围内变化 ,平面分布呈现自柘林湾向深圳湾递减的趋势 ;而种类组成均匀度则以柘林湾和深圳湾为高 ,中部水域较低。尽管养殖水域不同 ,优势种表现明显差异 ,但Nitzschiadelicatissima和Skeletonemacostatum在各养殖水域均出现较高数量  相似文献   

Statistical characteristics and mechanistic analysis of suddenly reversed tropical cyclones over the western North Pacific Ocean     

Xia Luo  Jianfang Fei  Xiaogang Huang  Xiaoping Cheng  Juli Ding  Yiqiang He 《大气科学进展》2015,32(4):565-576

Based on best track data of tropical cyclones(TCs) from the Japan Meteorological Agency, the characteristics of suddenly reversed TCs(SRTCs), which have turning angles usually approaching 180°, are statistically analyzed from 1949 to 2011 over the western North Pacific Ocean. The typical large-scale circulation patterns of SRTCs are investigated using reanalysis data and dynamical composite analysis. Results show that turnings mainly occur in low latitudes between 10°N and 20°N,and mainly west of 135°E. The majority of SRTCs reach their peak intensity at, or slightly before, the turning time and subsequently decrease at some variable rate. Specifically, SRTCs are divided into four types, each containing two groups(i.e.eight groups in total) in terms of the moving-direction changes. The moving speed of all SRTC types except the south–north type decreases to its lowest during the 24 h, corresponding to a significant reduction in the primary steering components.According to the analysis of the 13 typical flow patterns found in this study, we suggest that sudden track changes are caused by the reversal steering flow. The original balance of the background flow patterns are broken up by new systems, e.g. binary TCs or dispersion-induced anticyclones. Additionally, sudden track changes are often due to double ridge variations of the subtropical high or weakened/strengthened high pressure in the east and west, respectively.  相似文献