基于回声探测监测沉水植物盖度的插值方法研究:以杭州西湖沉水植物盖度监测为例     

彭雪  张璐  黄素珍  蔺庆伟  刘碧云  张义  吴振斌 《湖泊科学》2020,32(2):472-482

沉水植物作为水生态系统的重要组成成分,在水生态系统物质循环和能量流动中发挥着重要作用,其覆盖度和生物量是评价湖泊等浅水水体系统稳定性的关键参数随着高效和无损伤监测的回声探测仪在沉水植物盖度监测中的应用,其精确度算法也受到了越来越多的关注本研究以成功恢复沉水植物的浅水湖泊杭州西湖为研究对象,利用BioSonics便携型回声探测仪——MX采集沉水植物回声样本同时结合人工样方设置,采集与回声探测对应位点的沉水植物样本,验证回声探测结果的精确性通过建立回归模型分析回声探测得到的沉水植物体积百分比(PVI)与人工样方获得的对应平均鲜重关系,结果表明二者具有较好的相关性分别采用普通克里金法、反距离权重法、径向基函数法3种插值方法对同一季节的不同湖泊和同一湖泊的不同季节未采集区域沉水植物的盖度数据进行插值分析,并对插值结果进行交叉验证,以确定方法的精确度交叉验证结果表明,插值精确度反距离权重法径向基函数法普通克里金法研究结果为回声探测与插值分析方法结合在大尺度浅水水体中沉水植物监测应用提供了技术支撑.  相似文献   

徐闻南山镇红树林沉积物及红树植物中重金属的累积特征与迁移规律     

罗松英  梁艺琼  陈碧珊  林梦婷  梁家新  邱锦坤 《热带地理》2019,39(3):347-356

为探究重金属在红树林沉积物及红树植物中的分布累积及迁移规律，选取了徐闻南山镇红树林为研究对象，通过测定红树林沉积物及红树植物不同部位（根、茎、叶）的重金属质量分数，运用富集因子、生物富集系数、转移系数及相关性分析等方法进行分析。结果表明：1）红树林沉积物重金属质量分数表现为铬（Cr）＞锌（Zn）＞镍（Ni）＞铜（Cu）＞铅（Pb）＞砷（As）＞汞（Hg）＞镉（Cd），为中等变异程度；除了镍（Ni）元素外，其余7种重金属未超过国家一级标准，除了铅（Pb）元素外，其余7种重金属均超过广东省土壤环境背景值，说明研究区沉积物中重金属具有一定的积累效应。2）沉积物中砷（As）、铜（Cu）、锌（Zn）、汞（Hg）、镍（Ni）、铬（Cr）富集因子值均＞1.5，说明受到轻微人为活动影响；各站位镍（Ni）富集因子值均＞5，结合研究区背景，反映了镍（Ni）受到自然和人为输入的共同影响。3）白骨壤体内重金属主要集中在根部，而红海榄体内重金属在根茎叶中分布相对均匀。白骨壤根茎叶部位的大多数重金属质量分数远高于红海榄，说明白骨壤对重金属的吸附能力比红海榄强。汞（Hg）集中分布在植物的叶片部位，且与其他重金属之间相关性不明显；推测汞（Hg）主要通过叶片吸收进入植物体内，与交通运输污染有关。4）不同红树植物对不同重金属富集能力各异，白骨壤对重金属的富集能力表现为：镉（Cd）＞砷（As）＞铜（Cu）＞锌（Zn）＞汞（Hg）＞铅（Pb）＞镍（Ni）＞铬（Cr），红海榄表现为：镉（Cd）＞铜（Cu）＞汞（Hg）＞锌（Zn）＞铅（Pb）＞砷（As）＞镍（Ni）＞铬（Cr）。白骨壤和红海榄对汞（Hg）的运移能力都较强；红海榄对镉（Cd）的富集能力和转运能力都较强，而白骨壤对镉（Cd）富集能力较强，转运能力却较弱，这说明红树植物对重金属元素的富集能力与转运能力不存在正比关系。  相似文献   

Effects of current climate,paleo-climate,and habitat heterogeneity in determining biogeographical patterns of evergreen broad-leaved woody plants in China   总被引：1，自引：1，他引：0  

Xu  Yue  Shen  Zehao  Ying  Lingxiao  Zang  Runguo  Jiang  Youxu 《地理学报(英文版)》2019,29(7):1142-1158

Journal of Geographical Sciences - Understanding biogeographic patterns and the mechanisms underlying them has been a main issue in macroecology and biogeography, and has implications for...  相似文献   

遗传算法优化的BP神经网络卫星钟差预报          下载免费PDF全文

孙鹏超  魏东平  孙碧娟 《天文学报》2020,61(6):67

针对BP (Back Propagation)神经网络模型预测卫星钟差中权值和阈值的最优化问题, 提出了基于遗传算法优化的BP神经网络卫星钟差短期预报模型, 给出了遗传算法优化BP神经网络的基本思想、具体方法和实施步骤. 为验证该优化模型的有效性和可行性, 利用北斗卫星导航系统(BeiDou navigation satellite system, BDS)卫星钟差数据进行钟差预报精度分析, 并将其与灰色模型(GM(1,1))和BP神经网络模型预报的结果比较分析. 结果表明: 该模型在短期钟差预报中具有较好的精度, 优于GM(1,1)模型和BP神经网络模型.  相似文献   

Body motion in liquid under ice plate with snow cover     

《Applied Ocean Research》2019

The motion of a submarine in liquid under an ice plate covered with flooded snow is considered. The ice is modelled as an elastic plate and the snow cover is modelled as a viscous layer on the top of the plate. The submarine is modelled as a slender solid of revolution with scale 1:300. The experimental and theoretical study of the influence of the viscous snow layer on deflections of the floating ice plate is conducted. The viscous layer reduces the amplitudes of flexural-gravity waves. The greatest influence of the viscous layer on the plate deflections is achieved for velocities of the submarine, where the waves of maximum amplitude are generated. Theoretical results are in good qualitative and quantitative agreement with the model experiments.  相似文献   

全球2℃温升碳约束下中国煤电搁浅资产研究     

张为荣  袁家海 《气候变化研究进展》2021,17(1):36-44

作为全球煤电装机规模最大且仍在扩张的国家,中国需要慎重评估兑现《巴黎协定》温室气体减排承诺带来的潜在煤电资产搁浅问题。研究运用“上下交互”的碳锁定曲线模型,识别不同产能扩张情景下（无新增、新增200、300和400 GW）的搁浅煤电机组。首先,从“自上而下”角度匡算中国煤电行业2℃温升目标下的碳配额。然后,从“自下而上”角度,根据高精度的燃煤电站信息核算煤电累积CO₂排放量。最后基于“上下交互”模式筛选出搁浅燃煤电站,在此基础上运用现金流量法估算其潜在的搁浅价值,并对其关键因素进行敏感性分析。结果表明,在无新增情景下,煤电搁浅资产规模约为0.38万亿元;若继续增加200~400 GW煤电装机,则搁浅价值将较无新增情景增加3.7~8.2倍。因此,建议“十四五”期间应树立煤电规模峰值意识,严控煤电新增产能,避免错过最佳减排时机。  相似文献   

鄂尔多斯盆地东北缘中侏罗统延安组植物群与古气候分析   总被引：2，自引：2，他引：0  

葛玉辉  孙春林  刘茂修 《吉林大学学报(地球科学版)》2006,36(2):164-168

鄂尔多斯盆地东北缘中侏罗统延安组为一套以河流滨湖相沉积为主的中粒中细粒长石砂岩、粉砂岩(泥质粉砂岩)、黑色页岩、粘土岩夹煤层。其中产大量的植物化石,计20属39种。经分析认为,这个植物群是一个属于我国北方区以Coniopteris-Phoenicopsis为代表的中侏罗世早期植物群,植物群组合反映鄂尔多斯盆地东北缘中侏罗世为偏潮湿的暖温带气候。  相似文献   

甘肃省重要古植物化石产地区划及保护利用     

王军  李小强  张海峰  郭兵  任文秀  彭措  冯备战  王玉玺  胡振波 《地质论评》2021,67(3):578-592

古植物化石是地质历史时期各类植物实体或遗迹的残留。对古植物化石产地进行系统的调查和区划研究是开展古生物化石保护和利用工作的基础。在资料研究和实地调查的基础上,对甘肃省24处重要古植物化石产地进行了评价和区划研究。甘肃省古植物化石产地可划分为北山地区、祁连山——河西走廊地区、鄂尔多斯和秦岭地区4个古生物化石大区以及6个古植物化石产地集中区。根据古植物化石产地的科学价值和美学价值,具体从科学性、稀有性、完整性、保存程度、可保护性5个单因素分别对24处重要古植物化石产地进行了评价。在单因素评价基础上进行了综合鉴评,共鉴评出世界级化石产地1处,国家级化石产地7处,省级化石产地16处。根据产地自然区划、行政区划等要素划分了古植物化石产地集中保护区6个。根据保护区内古植物化石产地级别及重要程度,划分出特级保护区2个,重点保护区2个和一般保护区2个。提出对重要古植物化石产地实行化石标本保护加原产地保护的建议。  相似文献   

Bragg reflection of water waves by multiple floating horizontal flexible membranes with submerged rectangular bars on the seabed     

《Applied Ocean Research》2019

Bragg reflection of water waves by multiple floating horizontal flexible membranes is investigated based on the linear wave theory and the assumption of small membrane response. Under the floating horizontal membranes, periodical submerged rectangular bars are arranged on the flat seabed. The total reflection and transmission coefficients are obtained by using the eigenfunction expansion method and the wide spacing approximation. The calculated coefficients are validated with the results available in the literature, which shows that the present method is applicable. The characteristics of Bragg reflection are systematically investigated by changing various parameters including the height of the rectangular bars, the number, the tension, the spacing, and the length of the flexible membranes. The results can help designing multiple floating horizontal flexible membranes as effective floating breakwaters by taking advantage of Bragg reflection.  相似文献   

Impacts of small cascaded hydropower plants on river discharge in a basin in Southern China     

Xu Xiao  Xiaohong Chen  Lilan Zhang  Rouyi Lai  Jie Liu 《水文研究》2019,33(10):1420-1433

The run‐off volume altered by the construction of hydropower plants affects ecohydrological processes in catchments. Although the impacts of large hydropower plants have been well documented in the literature, few studies have been conducted on the impacts of small cascaded hydropower plants (SCHPs). To evaluate the impacts of SCHPs on river flow, we chose a representative basin affected by hydropower projects and, to a lesser degree, by other human activities, that is, the Qiuxiang River basin in Southern China. The observed river discharge and climate data during the period of 1958–2016 were investigated. The datasets were divided into a low‐impact period and a high‐impact period based on the number of SCHPs and the capacities of the reservoirs. The daily river discharge alteration was assessed by applying the Indicators of Hydrologic Alteration. To separate the impact of the SCHPs on the local river discharge from that of climate‐related precipitation, the back‐propagation neural network was used to simulate the monthly average river discharge process. An abnormal result was found: Unlike large reservoirs in large watersheds, the SCHPs regulated the flows during the flood season but were not able to mitigate the droughts during the dry season due to their limited storage and the commonly occurring inappropriate interregulations of the SCHPs. The SCHPs also reduced the annual average river discharge in the research basin. The contribution of the SCHPs to the river discharge changes was 85.37%, much higher than the contributions of climate change (13.43%) and other human activities (1.20%). The results demonstrated that the impacts of the SCHPs were different from those of large dams and reservoirs that regulate floods and relieve droughts. It is necessary to raise the awareness of the impacts of these river barriers.  相似文献