Virtual wave gauges based upon stereo imaging for measuring surface wave characteristics     

Adam J. Bechle  Chin H. Wu 《Coastal Engineering》2011

A virtual wave gauge (VWG) technique based on stereo imaging is developed to remotely measure water wave height, period, and direction. VWG minimizes computational costs by directly tracking the elevation of the water surface at selected points of interest using a Eulerian based dynamic searching algorithm. Results show that the VWG technique developed in this paper dramatically improves efficiency by two orders of magnitude compared to the traditional Lagrangian–Eulerian based point cloud method of stereo image processing. VWG is tested against traditional wave wire gauges to within 98% accuracy for significant wave height. Furthermore, the flexibility of the VWG is demonstrated in two field applications. First in an offshore breaking wave case, an array of VWGs is used to efficiently measure wave directionality. Second to investigate the reflection coefficient of a rock-mounted structure interacting with nearshore waves, linear and spatial VWG arrays are designed and implemented based on a priori information of the wave field from a preliminary VWG measurement. Overall, we demonstrate that the flexible and computational efficient VWG technique has the potential to make real-time remote stereo imaging wave measurements a reality.  相似文献   

Appraisal of storm beach buffer width for cyclonic waves     

F.-C. Lee  John R.-C. Hsu  W.-H. Lin 《Coastal Engineering》2011

The loss of beach sand from berm and dune due to high waves and surge is a universal phenomenon associated with sporadic storm activities. To protect the development in a coastal hazard zone, hard structures or coastal setback have been established in many countries around the world. In this paper, the requirement of a storm beach buffer, being a lesser extent landward comparing with the coastal setback to ensure the safety of infrastructures, is numerically assessed using the SBEACH model for three categories of wave conditions in terms of storm return period, median sand grain size, berm width, and design water level. Two of the key outputs from the numerical calculations, berm retreat and bar formation offshore, are then analysed, as well as beach profile change. After having performed a series of numerical studies on selected large wave tank (LWT) test results with monochromatic waves using SBEACH, we may conclude that: (1) Berm erosion increases and submerged bar develops further offshore as the storm return period increases for beach with a specific sand grain size, or as the sand grain reduces on a beach under the action of identical wave condition; (2) Higher storm waves yield a large bar to form quicker and subsequently cause wave breaking on the bar crest, which can reduce the wave energy and limit the extent of the eroding berm; (3) A larger buffer width is required for a beach comprising small sand grain, in order to effectively absorb storm wave energy; and (4) Empirical relationships can be tentatively proposed to estimate the storm beach buffer width, from the input of wave conditions and sediment grain size. These results would benefit a beach nourishment project for shore protection or design of a recreational beach.  相似文献   

不同饵料对真蛸亲体产罗同量、受精卵孵化率及初孵幼体大小的影响     

刘兆胜  刘永胜  郑小东  曲海波 《海洋科学》2011,35(10):81-85

分别采用文蛤（Meretrix meretrix）、菲律宾蛤仔（Ruditapes philippinarum）、缢蛏（Sinonovacula constrzcta）、许氏平鲌（Sebastodes fuscescens）投喂处于产卵、护卵期的真蛸（Octopus vulgaris）亲体,通过测量亲蛸摄食量、产卵量、...  相似文献   

1990s年代际转型前后南海季风系统的季节变化     

黄菲  邢雯  李元妮  张旭  董静舒 《中国海洋大学学报(自然科学版)》2011,(Z1):9-15

利用多变量经验正交分解(MV-EOF)等方法,研究了在季节变化尺度上南海季风系统的时空分布特征。结果表明:南海夏季风的爆发时间在1993—1994年前后存在显著的年代际转型,由爆发偏晚转变成爆发偏早。第一模态表现为冬夏反位相的年周期变化,但爆发早年夏季风持续时间略长于爆发晚年,空间上都反映了南海中央海盆区的夏季强降水和850 hPa上南海北部的气旋性环流异常,但夏季风爆发早年中国华南沿海降水加强而南海南部降水偏少。相应的大范围环流场上主要反映了南海夏季风爆发后进入盛夏时节亚太地区大范围的环流特征,南海夏季风爆发偏早年索马里越赤道气流偏强,东亚季风槽位置偏北,爆发偏晚年则相反。第二模态反映了南海季风系统春秋反位相的季节变化,且秋季的振幅更强,空间降水场上对应着秋季华南沿海和南海北部与南海中南部北旱南涝的跷跷板式分布,850 hPa风场上则主要表现为异常的东北季风,该模态时空特征表明南海夏季风爆发偏早年的秋季,冬季风建立也偏早,越南及周边地区的降水偏多。相应的大范围环流场上则主要反映了冬季风的环流特征,在南海夏季风爆发偏早年的秋季,菲律宾以东的热带对流减弱,PJ波列增强,爆发晚年则相反。  相似文献   

Stream-coordinate structure of oceanic jets based on merged altimeter data     

孙澈  张林林  闫晓梅 《中国海洋湖沼学报》2011,29(1):1-9

The jet structure of the Southern Ocean front south of Australia is studied in stream-coordinate with a new altimeter product—Absolute Dynamic Topography (ADT) from AVISO. The accuracy of the ADT data is validated with the mooring data from a two-year subantarctic-front experiment. It is demonstrated that the ADT is consistent with in-situ measurements and captures the meso-scale activity of the Antarctic Circumpolar Current (ACC). Stream-coordinate analysis of ADT surface geostrophic flows finds that ACC jets exhibit large spatio-temporal variability and do not correspond to particular streamfunction values. In the circumpolar scope ACC jets display a transient fragmented pattern controlled by topographic features. The poleward shift of jet in streamfunction space, as revealed by a streamwise correlation method, indicates the presence of meridional fluxes of zonal momentum. Such cross-stream eddy fluxes concentrate the broad ACC baroclinic flow into narrow jets. Combined with a recent discovery of gravest empirical mode (GEM) in the thermohaline fields, the study clarifies the interrelationship among front, jet and streamfunction in the Southern Ocean.  相似文献   

近50a来塔里木河干流年径流量变化趋势及预测   总被引：3，自引：1，他引：2  

陈忠升  陈亚宁  徐长春 《干旱区地理》2011,34(1):43-51

根据塔里木河干流1957-2008年的年径流量监测数据,利用Mann-Kendall非参数技术检验和R/S法,对干流年径流量时间序列变化趋势进行分析,并在此基础上采用滑动t检验法和Mann-Kendall法对其突变点进行检验,最后运用方差分析外推法和叠加趋势预测模型对干流水文周期和未来径流量变化进行分析和预测.结果显示...  相似文献   

西畴县近48年来降水及气温小波分析     

刘云生  黄国平  王顺江 《云南地理环境研究》2011,23(2):90-92

利用连续小波分析1962～2009年西畴县年降水量和年平均气温序列的小波变化特征,揭示了西畴县降水量与平均气温存在多时间尺度的周期变化特征。其中降水有2个明显的特征时间尺度,分别是4年和8年,平均气温存在以准2～4年为周期的周期振荡。此外,也可以看出近48年来,平均气温存在明显升高的趋势,降水也有减少的趋势,为掌握西畴县的气候变化规律及今后的气象预报服务工作提供了一定的参考价值。  相似文献   

Re–Os and U–Pb Geochronology of Porphyry and Skarn Types Copper Deposits in Jilin Province,NE China          下载免费PDF全文

Yong Zhang  Shu–Wen Xing  Quan–Heng Song  Yan Wang  Zheng–Tao Yu  Xiao–Hui Du  Yu–Bo Ma  Zeng–Jie Zhang 《Resource Geology》2015,65(4):394-404

Jilin Province in NE China lies on the eastern edge of the Xing–Meng Orogenic Belt. Mineral exploration in this area has resulted in the discovery of numerous large, medium, and small sized Cu, Mo, Au, and Co deposits. To better understand the formation and distribution of both the porphyry and skarn types Cu deposits of the region, we examined the geological characteristics of the deposits and applied zircon U–Pb and molybdenite Re–Os isotope dating to constrain the age of the mineralization. The Binghugou Cu deposit yields a zircon U–Pb age for quartz diorite of 128.1 ± 1.6 Ma; the Chang'anpu Cu deposit yields a zircon U–Pb age for granite porphyry of 117.0 ± 1.4 Ma; the Ermi Cu deposit yields a zircon U–Pb age for granite porphyry of 96.8 ± 1.1 Ma; the Tongshan Cu deposit yields molybdenite Re–Os model ages of 128.7 to 130.2 Ma, an isochron age of 129.0 ± 1.6 Ma, and a weighted mean model age of 129.2 ± 0.7 Ma; and the Tianhexing Cu deposit yields molybdenite Re–Os model ages of 113.9 to 115.2 Ma, an isochron age of 114.7 ± 1.2 Ma, and a weighted mean model age of 114.7 ± 0.7 Ma. The new ages, combined with existing geochronology data, show that intense porphyry and skarn types Cu mineralization was coeval with Cretaceous magmatism. The geotectonic processes responsible for the genesis of the Cu mineralization were probably related to lithospheric thinning. By analyzing the accumulated molybdenite Re–Os, zircon U–Pb, and Ar–Ar ages for NE China, it is concluded that the Cu deposits formed during multiple events coinciding with periods of magmatic activity. We have identified five phases of mineralization: early Paleozoic (~476 Ma), late Paleozoic (286.5–273.6 Ma), early Mesozoic (~228.7 Ma), Jurassic (194.8–137.1 Ma), and Cretaceous (131.2–96.8 Ma). Although Cu deposits formed during each phase, most of the Cu mineralization occurred during the Cretaceous.  相似文献   

坝基软弱结构面工程特性的动态研究方法与应用     

朱雷  王小群  聂德新  黄润秋 《工程地质学报》2015,23(1):52-58

水电工程具有规模大、施工快、地质缺陷不易揭露等特点,特别是对于水电工程的安全运营至关重要的深层抗滑稳定性问题.基于上述原因,本文以金沙江观音岩水电站为例,借助坝基开挖,总结出工程地质条件软弱结构面展布特征动态评价软弱结构面参数动态取值坝基稳定性评价这一套坝基软弱结构面动态评价方法,并以软弱结构面展布特征与参数动态研究为核心,建立起合理的坝基深层抗滑稳定性评价方法.实践表明,该套方法能合理地评价重力坝抗滑稳定性问题,保证水电工程的安全运营.  相似文献   

Ostracoda during the Early Aptian (Early Cretaceous) greenhouse period on the Isle of Wight, England     

Ian P. Wilkinson 《Proceedings of the Geologists' Association. Geologists' Association》2011,122(5):809-815

The earliest Aptian marine transgression of the Lower Cretaceous across southern England resulted in the collapse of the generally freshwater Barremian environment and the initiation of marine mileux. Salinities passed from fresh-oligohaline to meso- and pliohaline, reaching fully marine conditions during the obsoletum Subzone (P. fissicostus Zone). Newly formed environmental niches were rapidly occupied by ostracod associations. In the Isle of Wight, freshwater Cypridea-rich assemblages in the lower Shepherd's Chine Member (Vectis Formation) were gradually replaced by faunas dominated by Sternbergella cornigera, Mantelliana mantelli and Theriosynoecum fittoni. Marine taxa recorded from the Atherfield Clay Formation migrated predominantly from the Paris Basin and include Asciocythere albae, Schuleridea derooi, Neocythere gottisi, N. bordeti, Cythereis geometrica, Cytheropteron stchepinskyi and Protocythere croutesensis.  相似文献