Distribution and sources of organic carbon, nitrogen and their isotopes in sediments of the subtropical Pearl River estuary and adjacent shelf, Southern China   总被引：17，自引：1，他引：17  

Jianfang Hu  Ping'an Peng  Guodong Jia  Bixian Mai  Gan Zhang 《Marine Chemistry》2006,98(2-4):274-285

The isotopic composition (δ¹³C and δ¹⁵N) and organic carbon (OC) and total nitrogen (TN, organic plus inorganic) content of 37 carbonate-free surficial sediments of the subtropical Pearl River estuary and the adjacent shelf of South China Sea (SCS) was determined. The δ¹³C values indicate that the sediment organic material is a mixture from two sources, terrestrial and marine. Several of the sediments have extremely low (< 4) OC / TN ratios, which could be due to low OC contents and/or to a significant fraction of the TN present as inorganic nitrogen adsorbed on clays. In general, the spatial patterns of OC, TN, δ¹³C and δ¹⁵N are similar. Values are low at the river mouth and on the western coast, suggesting proportionally greater accumulation of terrestrial particulate organic matter relative to marine phytodetritus, which is limited by low productivity in the turbid plume of the Pearl River. Algal-derived organic carbon (al-OC) content is estimated to be low (≤ 0.06%) at the river mouth and higher (up to 0.57%) on the adjacent inner shelf based on a mixing model of end members.  相似文献   

海缆安全影响因素评述   总被引：8，自引：2，他引：8  

张效龙  徐家声 《海岸工程》2003,22(2):1-7

通过对国内外威胁海缆安全因素的研究资料和研究成果的分析，全面论述了影响海缆安全因素的种类及其对海缆的可能破坏方式和破坏的严重程度。简要说明了不同因素对海缆威胁的可能原因与相应的预防措施，为海缆安全运营提供科学的理论依据。  相似文献   

罗非鱼椭圆囊电生理学研究     

黄玉霖  贾俊成 《台湾海峡》1996,15(2):182-190

罗非鱼球状囊微音器电位是一个双峰波。峰频与刺激声频成２：１关系；在２０－８０Ｈｚ电位波形不规则。在３００－９００Ｈｚ电位波呈矩形。实验表明，球状囊不同区域对一一的声频敏感性不一样；延脑－脊髓连结处的诱发电位与球状囊微音器电位相似，但在１３０Ｈｚ电位呈单峰波；罗非鱼可闻频域在２０－９００Ｈｚ，最大敏感声频在１３０Ｈｚ，其相对敏感性为２３．０１ｄＢ；延脑－脊髓连接处诱发电位最大值在６３Ｈｚ和１３０Ｈｚ  相似文献   

春季南海南部上混合层数值模拟与数值实验   总被引：1，自引：1，他引：1  

刘秦玉  孙即霖  贾旭晶 《中国海洋大学学报(自然科学版)》2001,31(2):149-157

采用一维湍动能模式对南海南部的 SST及混合层进行数值模拟和数值试验。结果表明 :TKE模式能够模拟南海南部的海表面温度 SST以及除南海南部 5月中旬以外的上混合层深度随时间变化基本特征。在 5～ 6月 ,SST的日振荡主要依赖于短波辐射的日变化 ,风的混合作用抑制了 SST的日周期振荡。春季夏季风爆发期间 ,南海海面潜热通量和感热通量与短波辐射和风应力相比较 ,是一个对 SST和混合层影响较小的量。在春季南海南部 ,短波辐射作用能使 SST升高的最大值约为 4℃ ;潜热和感热通量能使 SST的下降的最大值为 3℃。风应力对南海混合层深度随时间变化趋势起着决定的作用 ,并能使其深度加深 2 0～ 30 m,而短波辐射则使混合层的深度变浅2～ 3m,潜热和感热通量会使混合层的深度加深 1～ 2 m。在春季南海南部 ,热通量对混合层深度的影响与风应力相比要小得多  相似文献   

波流作用下海底边界层沉积物再悬浮与影响因素研究     

文明征  陈天  胡云壮  李勇  单红仙  贾永刚 《海洋学报》2020,42(3):97-106

海底沉积物再悬浮及其分布取决于海洋水动力、沉积物类型与床面形态之间复杂的相互作用,准确地理解和确定沉积物再悬浮过程对于沉积物输运的研究具有重要的意义。本文在祥云湾海洋牧场典型海域开展现场原位观测,获取研究区波浪、海流及悬浮沉积物浓度数据;分析了波、流作用下海底边界层悬浮沉积物垂向分布特征,并探究了海洋水动力和床面形态对悬浮沉积物垂向分布的影响。结果表明,研究区波流之间的相互作用不显著,沉积物再悬浮受控于风暴浪作用,风暴浪作用下底床切应力可以达到沉积物临界切应力的10～15倍,沉积物的再悬浮滞后于风暴浪作用2～3 h。在波浪荷载微小的情况下,悬浮沉积物垂向分布呈现"I"型,波浪荷载下,悬浮沉积物垂向分布呈现幂指函数分布,表现为"L"型;床面形态随波、流作用而演化,影响沉积物的再悬浮过程,u_(?w)/u_(?c)=1.00可作为波浪和海流起主导控制作用的床面形态的判别依据,纯波浪荷载作用下的u_(?w)/u_(?c)显著高于波浪主控作用下,但二者之间的界线随着波浪荷载的增加而升高。  相似文献   

岩藻聚糖硫酸酯低聚糖降压作用的初步研究   总被引：8，自引：0，他引：8  

付雪艳  薛长湖  宁岩  李兆杰  许加超 《中国海洋大学学报(自然科学版)》2004,34(4):560-564

采用两肾—夹型建立肾血管性高血压大鼠模型。探讨岩藻聚糖硫酸酯低聚糖对肾血管性高血压大鼠的血压、呼吸及血浆中血管紧张素Ⅱ(Ang Ⅱ)含量的影响。用GY-6088型多道生理参数分析记录仪和张力传感器测定、记录血压和呼吸；用均相竞争法测定Ang Ⅱ的含量。实验表明，12．5，25，50mg／kg的岩藻聚糖硫酸酯低聚糖均能显著地降低肾血管性高血压大鼠的动脉血压。其中，高剂量(50mg／kg)的降压效果与14mg／kg的卡托普利相当；给药大鼠的呼吸频率随血压的变化呈正相关变化；12．5，25，50mg／kg剂量的岩藻聚糖硫酸酯低聚糖均能降低高血压大鼠血浆中Ang Ⅱ的含量。其中，高剂量(25，50mg／kg)组的Ang Ⅱ水平同卡托普利组(14mg／kg)相当。岩藻聚糖硫酸酯低聚糖对肾血管性高血压大鼠有显著的降压作用，抑制AngⅡ生成可能是其降压机制之一。  相似文献   

Numerical modeling of the elastoplastic damage behavior of dry and saturated concrete targets subjected to rigid projectile penetration          下载免费PDF全文

Hanbing Bian  Yun Jia  Christophe Pontiroli  Jian‐Fu Shao 《国际地质力学数值与分析法杂志》2018,42(2):312-338

The objective of the present paper is to present a numerical study on the penetration performance of concrete targets with 2 different water contents. Numerical analysis has been performed by using the finite element code Abaqus/Explicit, in which a coupled elastoplastic damage model has been developed for saturated/unsaturated concrete under a wide range of confining pressures. The performance of proposed model has been firstly verified by simulating the triaxial compression tests and penetration tests realized with saturated/dry concretes. Comparisons of available experimental results and numerical simulations show that the proposed model is able to reproduce satisfactorily the mechanical behavior of saturated and dry concretes. A higher failure stress and a more important pores closing are generally obtained in dry concrete samples with respect to saturated ones. Furthermore, the main observed patterns of penetration test realized with saturated concrete targets are also satisfactorily simulated by the numerical results. Therefore, the proposed model is used to numerically predict the penetration performance of dry concrete target, and the penetration performance of dry/saturated concrete target is discussed. We observe that in dry concrete target, the penetration of projectile is strongly declined, and a smaller damage zone is created. The numerical predictions and discussions can help engineers to enhance their understandings on the influence of hydraulic conditions on structural vulnerability of concrete structures subjected to near‐field detonations or impacts.  相似文献   

A simulation and prediction of agricultural irrigation on groundwater in well irrigation area of the piedmont of Mt. Taihang,North China     

Xuesen Mao  Jinsheng Jia  Changming Liu  Zhimin Hou 《水文研究》2005,19(10):2071-2084

Declining groundwater levels caused by irrigation is the main problem for agricultural development in Northern China. Due to both economics and increased population, surface water has become almost non‐existent and groundwater is the only water resource left. Currently the groundwater is declining at a rate between 50 and 100 cm per year. Sustainable development in Northern China requires effective management of the groundwater resources. In this study, the effect of future irrigation patterns on the decline of the groundwater table is examined with the aid of MODFLOW. MODFLOW was calibrated for five observation wells in the county. The calibrated model fitted the observed data well over a 7‐year period. The simulated results showed that the groundwater decline would be decreased, and perhaps halted, by decreasing the use of irrigation. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Sensitivity of the Weather Research and Forecasting (WRF) model to downscaling ratios and storm types in rainfall simulation     

Jia Liu  Michaela Bray  Dawei Han 《水文研究》2012,26(20):3012-3031

Accurate information of rainfall is needed for sustainable water management and more reliable flood forecasting. The advances in mesoscale numerical weather modelling and modern computing technologies make it possible to provide rainfall simulations and forecasts at increasingly higher resolutions in space and time. However, being one of the most difficult variables to be modelled, the quality of the rainfall products from the numerical weather model remains unsatisfactory for hydrological applications. In this study, the sensitivity of the Weather Research and Forecasting (WRF) model is investigated using different domain settings and various storm types to improve the model performance of rainfall simulation. Eight 24‐h storm events are selected from the Brue catchment, southwest England, with different spatial and temporal distributions of the rainfall intensity. Five domain configuration scenarios designed with gradually changing downscaling ratios are used to run the WRF model with the ECMWF 40‐year reanalysis data for the periods of the eight events. A two‐dimensional verification scheme is proposed to evaluate the amounts and distributions of simulated rainfall in both spatial and temporal dimensions. The verification scheme consists of both categorical and continuous indices for a first‐level assessment and a more quantitative evaluation of the simulated rainfall. The results reveal a general improvement of the model performance as we downscale from the outermost to the innermost domain. Moderate downscaling ratios of 1:7, 1:5 and 1:3 are found to perform better with the WRF model in giving more reasonable results than smaller ratios. For the sensitivity study on different storm types, the model shows the best performance in reproducing the storm events with spatial and temporal evenness of the observed rainfall, whereas the type of events with highly concentrated rainfall in space and time are found to be the trickiest case for WRF to handle. Finally, the efficiencies of several variability indices are verified in categorising the storm events on the basis of the two‐dimensional rainfall evenness, which could provide a more quantitative way for the event classification that facilitates further studies. It is important that similar studies with various storm events are carried out in other catchments with different geographic and climatic conditions, so that more general error patterns can be found and further improvements can be made to the rainfall products from mesoscale numerical weather models. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

综合危险性指数法在苍山县地质灾害易发区划分中的应用     

韩娟  张永伟  祁娟  魏嘉 《山东国土资源》2007,23(6):2007/4/11-2007/6/11

地质灾害的发生和发展是地质环境因素和人类工程经济活动共同作用的结果，其易发性主要受自然因素和人为因素的共同影响。以山东省苍山县地质灾害易发区划分为例，探讨性地采用了地质灾害综合危险性指数法，定量划分了苍山县地质灾害易发区，结果符合当地地质灾害发育的实际情况，为苍山县地质灾害的预防和治理工作提供了科学依据。  相似文献