土体约束对海底管道整体屈曲的影响机理研究     

李成凤  刘润  彭碧瑶  王秀妍 《海洋科学》2018,42(2):56-63

高温高压下海底管道的整体屈曲稳定性分析是管道设计的重要组成部分,而选取多长的管道进行分析对其整体屈曲稳定性结果影响显著。依据临界管长将管道分为"长管"与"短管",基于动力显式分析方法,揭示了长管与短管在发生整体屈曲过程中,屈曲幅值与波长、管壁轴向压力、轴向应变及轴向位移的变化规律;研究了土体约束力影响管道临界长度的规律性,分析了土体约束力系数对长管与短管整体屈曲变形的影响。研究发现,土体约束力对短管的整体屈曲行为影响显著,短管的整体屈曲幅值随土体约束力系数的增大呈现先增大后减小的趋势。该项研究对区分不同长度管道的整体屈曲类型进而采取有效防控措施具有重要参考价值。  相似文献   

Long‐term monitoring of a mercury contaminated estuary (Ria de Aveiro,Portugal): the effect of weather events and management in mercury transport          下载免费PDF全文

J. P. Coelho  P. Pato  B. Henriques  A. Picado  A. I. Lillebø  J. M. Dias  A. C. Duarte  M. E. Pereira  M. A. Pardal 《水文研究》2014,28(2):352-360

The main aim of this research was to assess the mercury transport from an estuarine basin with a background of anthropogenic contamination during a spring tidal cycle (year 2009) and compare it with two previous tidal cycles (years 1994 and 1999), as part of a long‐term monitoring program. Results showed that effective mercury transport occurs both in the dissolved and particulate fractions (0.18 and 0.20 kg per tidal cycle, respectively), and despite an overall decrease in environmental contamination, results more than double previous findings on particulate transport in the system. These findings result essentially from changes in the tidal prism (net export of 2 million m³ of water), given that both dissolved and particulate concentrations did not increase over time. Hydrodynamic simulations were performed to evaluate the effect of physical disturbance (dredging) and weather events (increased freshwater flow) in these processes, and results suggest the increased freshwater flow into the system as the main forcing function for the mercury transport increment. These results highlight the importance of long‐term monitoring programs, since despite an overall improvement in local contamination levels, the enhancement of transport processes through hydrological changes increases environmental pressure away from the contamination source. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

A 10-year wave energy resource assessment and trends of Indonesia based on satellite observations     

Amiruddin  Ribal Agustinus  Khaeruddin  Thamrin Sri Astuti 《海洋学报(英文版)》2019,38(8):86-93

Wave energy resource assessment and trends around Indonesian's ocean has been carried out by means of analyzing satellite observations. Wave energy flux or wave power can be approximated using parameterized sea states derived from satellite data. Unfortunately, only some surface parameters can be measured from remote sensing satellites, for example for ocean surface waves: significant wave height. Others, like peak wave period and energy period are not available, but can instead be estimated using empirical models. The results have been assessed by meteorological season. The assessment shows clearly where and when the wave power resource is promising around Indonesian's ocean. The most striking result was found from June to August, in which about 30–40 kW/m(the 90 th percentile: 40–60 kW/m, the 99th percentile: 50–70 kW/m) wave power energy on average has been found around south of the Java Island. The significant trends of wave energy at the 95% level have also been studied and it is found that the trends only occurred for the extreme cases, which is the 99th percentile(i.e.,highest 1%). Wave power energy could increase up to 150 W/m per year. The significant wave heights and wave power have been compared with the results obtained from global wave model hindcast carried out by wave model WAVEWATCH III. The comparisons indicated excellent agreements.  相似文献   

月球交会对接VLBI差分时延研究          下载免费PDF全文

郑鑫  刘庆会  吴亚军  马俊武  邓涛 《天文学报》2020,61(3):22

中国探月3期任务中,月球交会对接技术是任务成功的重要保障.利用嫦娥3号(CE03)绕月飞行的VLBI (Very Long Baseline Interferometry)时延数据,模拟仿真绕月交会对接过程中,同波束VLBI观测模式下,差分群时延的变化情况.仿真结果显示,在远程导引段,轨道器和上升组合体轨道距离保持100 km,持续半小时,差分群时延很好地反映了两者的轨道信息,可以用于定轨定位;自主控制段,上升组合体靠近轨道器,在轨道距离从5 km减小到20 m过程中,上升组合体加速追赶轨道器时,差分群时延快速趋近于0,上升组合体减速远离轨道器时,差分群时延绝对值快速变大.最后,利用嫦娥3号奔月段同时发射两个DOR (Differential One-Ranging)信号的VLBI时延数据,计算差分相时延,初步展示了月球交会对接过程中同波束VLBI差分相时延的误差情况.  相似文献   

辽东湾海洋工程可靠性设计的海冰参数选取     

马玉贤  关湃  许宁  许有良  袁帅  刘永青  于福祥 《海洋工程》2019,37(3):136-142

海冰参数的合理取值是海洋工程海冰灾害风险评估的重要内容。利用1950—2018年的冰情等级(5个等级)数据,进行了1950—2018、1950—1990、1991—2018三种情景下的回归分析,确定了不同时期的冰情等级概率分布密度函数。利用鲅鱼圈雷达观测站2002—2017年的海冰现场实测资料,分别对鲅鱼圈附近海域一般冰厚、最大冰厚、最小冰厚进行概率分布拟合。基于上述概率分布结果,给出不同冰情等级的重现期,进而对海冰作业条件给出的设计参考值进行评价。结果表明:1990年以后2级、3级冰情重现期相对1990年之前变小,4级、5级冰情重现期相对1990年之前变大,规范给出重现期范围已不能代表辽东湾冬季海冰情况。本研究成果可为辽东湾海洋工程可靠性设计提供重要数据支撑。  相似文献   

Some statistical characteristics of large deepwater waves around the Korean Peninsula     

Kyung-Duck Suh  Hyuk-Dong Kwon  Dong-Young Lee 《Coastal Engineering》2010

The relationship between significant wave height and period, the variability of significant wave period, the spectral peak enhancement factor, and the directional spreading parameter of large deepwater waves around the Korean Peninsula have been investigated using various sources of wave measurement and hindcasting data. For very large waves comparable to design waves, it is recommended to use the average value of the empirical formulas proposed by Shore Protection Manual in 1977 and by Goda in 2003 for the relationship between significant wave height and period. The standard deviation of significant wave periods non-dimensionalized with respect to the mean value for a certain significant wave height varies between 0.04 and 0.21 with a typical value of 0.1 depending upon different regions and different ranges of significant wave heights. The probability density function of the peak enhancement factor is expressed as a lognormal distribution, with its mean value of 2.14, which is somewhat smaller than the value in the North Sea. For relatively large waves, the probability density function of the directional spreading parameter at peak frequency is also expressed as a lognormal distribution.  相似文献   

Developing millennial tree ring chronologies in the fire‐prone North American boreal forest     

DOMINIQUE ARSENEAULT  BENJAMIN DY  FABIO GENNARETTI  JULIA AUTIN  YVES BÉGIN 《第四纪科学杂志》2013,28(3):283-292

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新疆东天山地区土屋和延东铜矿床斑岩叠加改造成矿作用   总被引：2，自引：0，他引：2  

王云峰  陈华勇  肖兵  韩金生  杨俊 《矿床地质》2016,35(1):51-68

土屋和延东铜矿床位于东天山大南湖-头苏泉岛弧带南部,是中亚成矿带的重要组成部分。文章根据脉次穿插关系、蚀变矿物组合及矿物共生关系,将土屋和延东铜矿床均划分为斑岩成矿期、叠加改造期和表生期3个期次。土屋铜矿床的铜矿化形成于斑岩成矿期和叠加改造期,而延东铜矿床的铜矿化主要形成于叠加改造期;土屋和延东铜矿床伴生的钼矿化主要形成于叠加改造期。因此,笔者认为前人获得的辉钼矿Re-Os年龄(326.2~322.7 Ma)代表叠加改造期的成矿年龄,该期矿化与石英钠长斑岩((323.6±2.5)Ma)的侵入相关,而斑岩成矿期的矿化与斜长花岗斑岩(339~332 Ma)相关,成矿年龄为341.2~333.9 Ma。叠加改造期的存在,使得斑岩成矿期的蚀变分带可能受到了叠加和破坏。  相似文献   

依兰-伊通断裂新构造活动规律分析          下载免费PDF全文

翟明见  朱光  刘备  顾承串  张帅  林少泽  宋利宏 《地质科学》2016,(2):594-618

作为郯庐断裂带北段主干的依兰-伊通断裂, 其新构造活动性与活动规律仍然存在不同的认识.本次工作通过详细的野外调查, 发现该断裂内活断层广泛存在, 由东、西两支北东走向的主干活断层构成, 沿着古近纪地堑边界断层发育.这些活断层主要呈破碎型结构, 多为逆右行平移活动.通过对这些活断层一系列实测擦痕反演应力场, 显示它们多是在东西向挤压中活动的, 而现今应力场转变为北东东-南西西向区域性挤压.依据本次野外观察与¹⁴ C定年, 并结合前人定年结果与近代地震分布, 表明依兰-伊通西支活断层的最新活动时代为全新世与晚更新世相间, 而东支活断层的最新活动时代主要为早-中更新世.依兰-伊通断裂内活断层显示了明显的差异性活动, 表现为西支的活动强度明显大于东支, 西支的最新活动时代皆晚于东支, 沿走向上活动性强、弱相间与最新活动时代不断变化, 以及近代地震活动不均一分布.它们沿走向上的分段性、差异性活动主要是因为被一系列北西向断层切断所致.  相似文献   

基于均一化资料的中国大陆极端温度的长期趋势   总被引：1，自引：0，他引：1  

肖冰霜  马玉霞  赵天保  颜书豪 《气象》2016,42(3):339-346

近百年来,全球气候变暖。这与暖日和暖夜增加,冷日和冷夜减少相关联。文章研究结果进一步证实了这一发现。本文基于1960-2012年中国大陆542个台站均一化气温资料,通过将中国大陆划分为8个次区域,利用百分位定义法计算了极端温度指数序列,同时,运用时间趋势分析法,对中国大陆各区域极端温度和极端温度指数的时空分布及变化趋势特征进行了分析。结果表明:在全球变暖的背景下,从地理分布而言,中国大陆在过去53年除西南地区外,大部分地区最低和最高温度有显著的升高趋势,其中,东北温度升高最为明显;从季节而言,冬季极端温度升高最为明显,夏季升高最少;最低温度明显升高,最高温度也有所升高,但是最低温度的升高幅度更大。冷夜和冷日出现频率呈减少趋势,暖夜和暖日出现频率呈增加趋势,其中以冷夜指数变化最为突出,均呈现一种区域差异的现象。本文利用更新的资料验证了前人的工作,也进一步分区分析,结果可为更多地区评估以及进一步的相关研究提供参考。  相似文献