大连石庙鲍育苗池冬!春季底栖藻类组成初探     

王起华  林碧琴  丁明进  何信  程爱华 《海洋科学》1998,22(1):51-54

对大连石庙鲍育苗池冬,春季底栖藻类的组成作了调研,共发现藻类５７种（含变种）,其中有２４种及变种为辽宁省新记录。藻类组成有如下特点：硅藻种类比较丰富;冬、春季藻类群落组成有一定的主次,演替表现十分明显,种类的重现率不高。  相似文献   

西南岩溶区岩溶基本特征与资源、环境、社会、经济综述   总被引：15，自引：3，他引：12  

吴应科  毕于远  郭纯青 《中国岩溶》1998,17(2):141-150

西南岩溶区跨越黔、滇、桂、川、渝、湘、鄂、粤8省(市) ,面积54万km2 , 236个岩溶县, 1亿多人口,是国内外最大的连片岩溶区之一,也是全球岩溶之瑰宝。但对其整体性、系统性的综合研究,目前基本上还处于空白。本文从区域岩溶特征到资源、环境、社会、经济进行较为系统的综述,以期引起更多的关注。   相似文献   

Climate and extrema of ocean waves in the East China Sea     

Hailun He  Jinbao Song  Yefei Bai  Yao Xu  Juanjuan Wang  Fan Bi 《中国科学:地球科学(英文版)》2018,61(7):980-994

Wave climate plays an important role in the air-sea interaction over marginal seas. Extreme wave height provides fundamental information for various ocean engineering practices, such as hazard mitigation, coastal structure design, and risk assessment. In this paper, we implement a third generation wave model and conduct a high-resolution wave hindcast over the East China Sea to reconstruct a 15-year wave field from 1988 to 2002 for derivation of monthly mean wave parameters and analysis of extreme wave conditions. The numerical results of the wave field are validated through comparison with satellite altimetry measurements, low-resolution reanalysis, and the ocean wave buoy record. The monthly averaged wave height and wave period show seasonal variation and refined spatial patterns of surface waves in the East China Sea. The climatological significant wave height and mean wave period decrease from the open ocean in the southeast toward the continental area in the northwest, with the pattern generally following the bathymetry. Extreme analysis on the significant wave height at the buoy station indicates the hindcast data underestimate the extreme values relative to the observations. The spatial pattern of extreme wave height shows single peak emerges at the southwest of Ryukyu Island although a wind forcing with multi-core structure at the extreme is applied.  相似文献   

大地电场观测中干扰变化的特征分析     

胡小静  毕青  付虹 《地震》2017,37(2):157-166

针对云南省地电场观测中常见的路灯漏电、 雷电及降雨3种典型干扰因素, 分别讨论了干扰变化的形态特征、 功率谱分析结果、 干扰产生的过程和机理以及地电场地架设时的注意事项, 最后阐述了干扰识别的原理和依据, 得到以下认识: 路灯漏电引起的干扰变化以阶跃型周期变化为主要形态, 变化幅度主要受漏电产生的入地电流强度和土壤介质导电性能的影响; 雷电引起的干扰变化以典型的大幅畸变为主要形态, 主要与放电场强和雷区距离有关; 降雨引起的干扰变化以大幅上升或下降为主要形态, 持续过程与降雨量和电极自身性能有较大关系。  相似文献   

A forecasting model for wave heights based on a long short-term memory neural network     

Song Gao  Juan Huang  Yaru Li  Guiyan Liu  Fan Bi  Zhipeng Bai 《海洋学报(英文版)》2021,40(1):62-69

To explore new operational forecasting methods of waves, a forecasting model for wave heights at three stations in the Bohai Sea has been developed. This model is based on long short-term memory(LSTM) neural network with sea surface wind and wave heights as training samples. The prediction performance of the model is evaluated,and the error analysis shows that when using the same set of numerically predicted sea surface wind as input, the prediction error produced by the proposed LSTM model at Sta. N01 is 20%, 18% and 23% lower than the conventional numerical wave models in terms of the total root mean square error(RMSE), scatter index(SI) and mean absolute error(MAE), respectively. Particularly, for significant wave height in the range of 3–5 m, the prediction accuracy of the LSTM model is improved the most remarkably, with RMSE, SI and MAE all decreasing by 24%. It is also evident that the numbers of hidden neurons, the numbers of buoys used and the time length of training samples all have impact on the prediction accuracy. However, the prediction does not necessary improve with the increase of number of hidden neurons or number of buoys used. The experiment trained by data with the longest time length is found to perform the best overall compared to other experiments with a shorter time length for training. Overall, long short-term memory neural network was proved to be a very promising method for future development and applications in wave forecasting.  相似文献   

Mechanism of Suspended Kaolinite Particle Clogging in Porous Media During Managed Aquifer Recharge     

Xueyan Ye  Ruijuan Cui  Xinqiang Du  Sijia Ma  Jingtong Zhao  Ying Lu  Yuyu Wan 《Ground water》2019,57(5):764-771

Managed aquifer recharge is an effective strategy for urban stormwater management. Chemical ions are normally retained in stormwater and groundwater and may accelerate clogging during the recharge process. However, the effect of water chemistry on physical clogging has not previously been investigated. In this study, we investigated the hydrogeochemical mechanism of saturated porous media clogging in a series of column experiments. The column was packed with river sand and added suspensions of kaolinite particles. Calcium chloride and sodium chloride are used as representative ions to study chemical effects. We found that an increase in ionic strength resulted in retention of kaolinite solids in the column, with a breakthrough peak of C/C₀ value of 1 to 0.2. The corresponding hydraulic conductivity decreased with increased solids clogging. Divalent cations were also found to have a greater influence on kaolinite particle clogging than monovalent cations. The enhanced hydrochemical-related clogging was caused by kaolinite solids flocculating and increasing the deposition rate coefficient by 1 to 2 times in high ionic strength conditions. Three clogging mechanisms of kaolinite solids are proposed: surface filtration, inner blocking, and attachment. This study further deepens the understanding of the mechanisms of solids clogging during aquifer recharge and demonstrates the significance of ionic strength on recharge clogging risk assessments.  相似文献   

蓝藻光合氮同化的特征与分子调控机理研究进展     

杨小龙  刘莉华  毕永红  王洵  董薇  邓自发  王寿兵 《湖泊科学》2023,35(3):766-779

水华蓝藻的生物学特性及其竞争优势、蓝藻水华的形成与维持机制等科学问题,一直是国内外研究的热点。氮素是诱发蓝藻水华暴发的重要营养盐,蓝藻对氮素的同化与其光合作用密切偶联。然而,水体中氮素存在多种形态,不同形态氮素对蓝藻生长和水华发生的影响具有显著差异。因此,了解蓝藻光合作用特征及其同化不同形态氮素的机制和策略,对深入理解蓝藻水华的发生机理具有重要意义。本文在蓝藻的光能捕获与激发能转移、光合电子传递、碳浓缩机制及CO₂同化等光合作用过程及其特征综述的基础上,对蓝藻摄取、同化5种主要氮素形态(NO₃^-、NO₂^-、NH₄⁺、尿素和N₂)的分子机制及其特征进行了解读,总结了蓝藻细胞光合碳、氮同化的耦合关系及调控机制;并指出了该领域的未来发展方向,以推动该方向的深入研究。  相似文献   

断层圈闭形成机制及时空配置有效性评价——以歧口凹陷歧南斜坡为例     

汪顺宇  孙晓军  王海学  李静  姜文亚  曹晓峰  毕晨阳  种健 《地质科学》2020,(1):93-108

断层的分段生长和连接控制着断层圈闭的形成,为了研究断层形成过程对圈闭形成的控制作用,应用位移/离距法和位移梯度比法判别断层相互作用阶段,落实断层圈闭的空间匹配有效性。针对空间匹配的断层圈闭,应用最大断距相减法开展断层圈闭形成时期的研究,在成藏关键时期前形成的断层圈闭是油气有利聚集的部位。本文以歧口凹陷歧南斜坡的南大港同向断层与扣村反向断层为例,开展断层圈闭时空配置有效性评价,研究结果表明油气多分布在同时具备空间和时间匹配有效的断层圈闭内,仅具备空间或时间匹配有效性的断层圈闭中未见油气聚集。因此,通过对未钻探断层圈闭开展时空匹配有效性评价,能够有效地降低勘探开发的风险。  相似文献   

北京地区沙尘天气气溶胶飞机观测特征   总被引：5，自引：0，他引：5  

马新成  毕凯  田海军  金华  张磊  黄梦宇 《气象科技》2016,44(1):95-103

利用3次沙尘天气期间的气溶胶飞机观测资料,分析了北京地区在3种沙尘天气下气溶胶垂直分布特征。结果显示:逆温层的存在对扬沙个例的垂直分布有影响。数密度谱的分布基本呈单调递减,但边界层内扬沙、浮尘和沙尘暴个例都在0.13~0.3μm间存在峰值,而扬沙个例在0.8μm,浮尘个例在6.5μm以及沙尘暴个例在2.8和6.5μm处出现次峰值。沙尘中细粒子的有效直径是人为源气溶胶粒子的4到10倍。浮尘天气整个粒子谱宽从近地面层开始随高度先增大后减小,到3000m达到最大,这与高空输送有关;扬沙个例沙尘粒子谱分布显示近地面层大于50μm段粒子谱无论数浓度还是谱宽都明显高于浮尘和沙尘暴个例,这与扬沙是局地大风扬尘引起有关;沙尘暴个例谱宽在接近云底达到最大,说明大粒子已经被携带到一定高度,与蒙古气旋云系的上升运动有关。  相似文献   

Genesis of the Wulong gold deposit,Liaoning Province,NE China:Constrains from noble gases,radiogenic and stable isotope studies     

Peng Zhang  Linlin Kou  Yan Zhao  Zhongwei Bi  Deming Sha  Renping Han  Zhumin Li 《地学前缘(英文版)》2020,(2):547-563

TheWulong lode deposit contains over 80 tonnes of gold with an average grade of 5.35 g/t.It is one of the largest deposits in Dandong City,Liaoning Province in northeast China.Previous studies on the deposit focused on its geological characteristics,geochemistry,fluid inclusions,and the timing of gold mineralization.However,controversy remains regarding the origin of the ore-forming fluids and metals,and the genesis of the gold deposit.This paper presents zircon UePb and pyrite RbeSr ages and S,Pb,He,and Ar isotopic results along with quartz H and O isotopic data for all litho-units associated with the deposit.Laser ablation inductively coupled mass spectrometry measurements yielded zircon UePb dates for samples of pre-mineralization rocks like granite porphyry dike,the Sanguliu granodiorite,fine-grained diorite,and syn-mineralization diorite,as well as post-mineralization dolerite,and lamprophyre;their emplacement ages are 126
1 Ma,124
1 Ma,123
1 Ma,120
1 Ma,119
2 Ma,and 115
2 Ma,respectively.The pyrite RbeSr isochron age is 119
1 Ma,indicating that both magmatism and mineralization occurred during the Early Cretaceous.The d18OH2O values of ore-forming hydrothermal fluids from the quartzepolymetallic sulfide vein stage vary from 4.8&to 6.5&,and the dDV-SMOW values are between67.7&and75.9&,indicating that the ore-forming fluids were primarily magmatic.The noble gas isotope compositions of fluid inclusions hosted in pyrite suggest that the ore-forming fluids were dominantly derived from crustal sources with minor mantle input.Sulfur isotopic values of pyrite vary between 0.2&and 3.5&,suggesting that S was derived from a homogeneous magmatic source or possibly from fluids derived from the crust.The Pb isotopic compositions of sulfides(207Pb/204Pb?15.51 e15.71,206Pb/204Pb?17.35e18.75,208Pb/204Pb?38.27e40.03)indicate that the Pb of the Wulong gold deposit is a mixture of crust and mantle components.Geochronological and geochemical data,together with the regional geological history,indicate that Early Cretaceous magmatism and mineralization of the Wulong gold deposit occurred during the rollback of the subducting Paleo-Pacific Plate,which resulted in lithospheric thinning and the destruction of the North China Craton(NCC),which indicates that the deposit is of magmaticehydrothermal origin.  相似文献