乌兰布和沙漠西南部风况对穹状沙丘形成的影响   总被引：1，自引：0，他引：1  

杨迎  吕萍  马芳  梁准  许明静 《中国沙漠》2021,41(2):19-26

风是塑造沙丘形态的主要动力,目前对穹状沙丘的形成动力学过程尚不清楚。为探讨风况对穹状沙丘形成和演化的影响,以乌兰布和沙漠西南部穹状沙丘为例,利用吉兰泰气象站风速风向数据和Google Earth影像测量沙丘形态参数,分析风况对穹状沙丘形成的影响。结果表明：（1）乌兰布和沙漠西南部主风向为西北风,次风向为西南风和东北风,3组方向起沙风频率相当。年输沙势为172.90 VU,RDP/DP为0.39,属于低风能环境,中变率风况。（2）乌兰布和沙漠穹状沙丘长短轴之比为1.31∶1,呈椭圆形,沙丘平均走向为110.66°,与当地盛行风向大致平行,接近于合成输沙方向,盛行风向对沙丘走向有着显著影响。（3）乌兰布和沙漠西南部穹状沙丘发育在低风能、多风况条件下,春季的西北风与夏季的东北风和秋冬两季的西南风3组不同方向且强度相当的风共同作用,抑制了沙丘的滑面形成,沙丘演化过程受阻,从而使得沙丘形态长期保持稳定。  相似文献   

敏感型人工神经网络及其在水文预报中的应用   总被引：17，自引：0，他引：17       下载免费PDF全文

覃光华  丁晶  李眉眉  倪长健 《水科学进展》2003,14(2):163-166

为充分挖掘资料信息、加快收敛速度,采用一种具有敏感功能的神经网络预报模型。该模型在构造时序样本时引入遗忘因子和期望因子,以体现对前期资料的遗忘和近期预测的期望。在权值调整过程中采用指数型能量函数,以加快网络的学习收敛速度。应用实例证明:该方法可以提高当前的预测精度,并避免网络学习过程中的振荡现象。  相似文献   

广义Γ分布的特性和应用   总被引：5，自引：0，他引：5  

金光炎  董秀颖 《水文》2003,23(2):29-32

介绍了广义Γ分布———对数Γ分布和指数Γ分布的一些特性和应用。通过变数的平移和倍比变换,建立起统计参数之间的关系,并可利用三参数分布的有关表格(如模比系数KP值表)和适线方法,应用于四参数分布的频率计算上,使计算简化。  相似文献   

BP自组织神经网络在地下水动态分类中的应用   总被引：3，自引：0，他引：3  

朱雪芹  董颖  潘世兵 《水文地质工程地质》2003,30(2):62-64,73

本文是根据国内外较为流行的BP自组织神经网络方法,与区域地下水动态成因及地下水观测井历时曲线形态相结合对哈尔滨市地下水的动态型进行定量分类:波动—水文型、上升—弱水文型、上升·下降—开采型、上升—开采型,并且定位在图上。此种分类更加直观地反映本区地下水在空间和时间的变化规律,并对本区地下水的水流模型参数分区具有参考价值。  相似文献   

Quaternary reactivation of Tertiary faults in the southeastern Korean Peninsula: Age constraint by optically stimulated luminescence dating   总被引：1，自引：0，他引：1  

Jin-Han Ree  Young-Joon Lee  Ed J. Rhodes  Youngdo Park  Sung-Tack Kwon  Ueechan Chwae  Jeong-Soo Jeon  Bongjoo Lee 《Island Arc》2003,12(1):1-12

Abstract   Two groups of Quaternary faults occur in the southeastern Korean Peninsula. The first group is north-northeast-striking, high-angle dextral strike–slip faults. The second group is north-northeast-striking, low-angle reverse faults that represent the reactivation of the pre-existing normal faults. Optically stimulated luminescence dating of Quaternary sediments cut by one of the reverse faults constrains the faulting age to post-32 Ka. These faults seem to be capable of further slip under the current tectonic stress regime, as determined by recent earthquake events in northeast Asia. Therefore, the traditional concept that the southeastern Korean Peninsula is seismically stable should be reappraised.  相似文献   

Responses of distribution pattern of desert riparian forests to hydrologic process in Ejina oasis     

Zhao Wenzhi  CHANG Xueli  HE Zhibin 《中国科学D辑(英文版)》2004,47(Z1)

By using the theories and methods of landscape ecology and the technology of GIS and RS, a study has been carried out on the responses of distribution pattern of desert riparian forest to hydrologic process on the basis of the hydrologic data from 1990 to 2000 and the TM image of 2001 year. The results showed that: (1) there appears an even distribution pattern for the relative forest area in oasis, however, the degenerated forest diaplays an increasing tendency from west to east; (2) the desert riparian forest in Ejina is in completely degenerated process at the patch scale; (3) the number of patch is influenced not only by hydrologic process,but also by agricultural activity such as cultivation. The severe deterioration of the degraded vegetation in whole oasis initiates from lower reaches, and gradually impels to upstream; the fragmentation of landscape in the terminal site is more obvious, which is influenced by river shape and decreasing flux of water. It is found that the influence of surface hydrologic process to the ground hydrologic process of desert riparian forest in Ejina oasis is little for the recent ten years. The relative area of the degenerated forest increased with increasing ground water depth in the direction of parallel to river channel. On the contrary, in the direction perpendicular to river channel, there is a decreasing tendency for the average patch area of the forest and the degenerated forest with increasing ground water depth.  相似文献   

近海海域年最大波高计算方法的研究     

滕学春  吴秀杰 《海洋科学进展》1991,(2)

本文基于海上与其附近沿岸台站短期观测资料的分析,提出了水文和气象两种计算方法。用这些方法,采用附近沿岸台站的观测资料,可以得到海上累年的最大波高。检验结果表明,水文方法比气象方法好。  相似文献   

River flooding, storm resuspension, and event stratigraphy on the northern California shelf: observations compared with simulations     

Shejun Fan  Donald J. P. Swift  Peter Traykovski  Samuel Bentley  Jeffry C. Borgeld  Christopher W. Reed  Alan W. Niedoroda 《Marine Geology》2004,210(1-4):17-41

Coast-hugging surface flood plumes occur on the inner shelf of northern California during the winter season, generating dense, near-bottom suspensions which may attain fluid mud concentrations as particles settle. The period of storm-heightened waves may continue into the flood period, leading to gravity-driven seaward displacement of the bottom suspension; or the wave regime may ameliorate, leaving the suspension to consolidate as a short-lived, inner-shelf flood bed. Such beds tend to be resuspended within days or weeks by subsequent storm events that may recreate the original high concentrations. The sediment is thus dispersed seaward by gravity flows, to be deposited as a muddy flood bed on the central shelf. The locus of deposition of these “high-concentration regimes” is a function of the relative intensities of river discharge and storm wave height. Greater discharge piles thicker storm beds nearer shore, while intense wave regimes allow deposition of the fluid mud further seaward. During events with high values of both parameters, large amount of fluid mud may bypass over the shelf edge. In contrast, “low-concentration regimes” occur during storm periods when there has been no recent flood deposition on the inner shelf. The shelf floor is better consolidated than in the previous case, and the resulting suspended sediment concentrations are lower. As a consequence, low-concentration regimes are winnowing and bypassing regimes, and the beds deposited are thinner and sandier. Algorithms describing deposition by high and low-concentration regimes have been embedded in a probabilistic model. A simulation of a 400-year sequence of beds deposited by winter storms and floods suggests that on the Eel shelf, the Holocene transgressive systems tract consists of back-stepping, seaward-fining event beds, whose timelines (bedding planes) dip more gently than do their gradational facies boundaries. At these longer time scales, flood beds dominate over storm beds.  相似文献   

南沙及其西南海域的潮波系统   总被引：7，自引：1，他引：7  

曹德明  方国洪  黄企洲  于克俊  王新怡 《海洋与湖沼》1997,28(2):198-208

不同研究者所给出的南沙及其西南海域的同潮图历来有很大差别。为了给出更准确的同潮图，本文采用沿岸和岛屿200多个验潮站的调和常数给出了M2，S2，K1和O1四个主要分潮新的同潮图，同时还探讨了这些分潮之间的关系。研究表明，M2和S2在泰国湾的期波系统很相似，但在卡里马塔海峡和爪哇海差别相当大。M2潮波基本上属于驻波性质，而S2潮波则具有向西传播特征。在某些区域，如望加锡海峡的部分区域，S2的振幅可以超过M2。泰国湾中K1和O1的潮波系统也相类似。在卡里马塔海峡，这两个潮波都向南传播，但在爪哇海，O1潮波继续向东传播而K1潮波则倒过来向西传播。  相似文献   

Early life history of capelin (Mallotus villosus) in the northwest Gulf of Alaska: a historical perspective based on larval collections, October 1977-March 1979     

Doyle  Miriam J.; Busby  Morgan S.; Duffy-Anderson  Janet T.; Picquelle  Susan J.; Matarese  Ann C. 《ICES Journal of Marine Science》2002,59(5):997-1005

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