基于连续帧间差分的抛弃式探头三维下沉运动处理方法研究     

陈振涛  刘凤  王晓蕾  罗文 《海洋技术学报》2018,(2):7-12

抛弃式探头由无人机装载,能够在较远目标区域和危险海域开展海洋水文环境剖面参数的测量。通过安装不同传感器,可以实现对温度、盐度的剖面测量,其深度的测量采用数学方法计算得到。针对双摄像机水箱实验获得的5个不同攻角实验结果,分析了常用的运动目标的检测方法,最终选择基于连续帧间差分法,确定探头的三维坐标位置,进而得到探头下沉运动的三维运动轨迹和速度曲线等信息。探头从水面释放后攻角在下沉过程中不断调整,改变运动姿态,同时伴随自身的旋转,抵消水平方向阻力作用,初始攻角产生的深度测量误差主要体现在加速过程,探头达到匀速运动后测量误差不变,在不考虑横流的情况下,探头最后以匀速垂直下落运动。  相似文献   

基于PSR-WSVM模型的边坡位移预测     

李建新  刘小生  肖钢  周文  刘仁志 《大地测量与地球动力学》2020,40(6):577-580

为建立高精度的边坡位移预测模型，采用相空间重构（PSR）将边坡位移时间序列数据转换为多维数据，同时构造小波核函数改进的支持向量机模型，建立PSR-WSVM模型并应用于边坡位移预测。将PSR-WSVM模型预测结果与传统支持向量机（SVM）模型、小波支持向量机（WSVM）模型和基于相空间重构的支持向量机（PSR-SVM）模型预测结果进行对比，通过平均绝对误差（MAE）、平均绝对误差百分比（MAPE）和均方根误差（RMSE）3个精度评价指标验证PSR-WSVM模型的可行性。工程实例结果表明，PSR-WSVM模型预测结果的3个精度评价指标都优于另外3种模型，边坡位移预测的精度明显提升。  相似文献   

广州城市流浪乞讨者的空间管治与日常生活实践   总被引：2，自引：0，他引：2  

尹铎  蔡慕言  梁金多  朱竑  高权 《地理科学》2019,39(3):450-458

以广州流浪乞讨者为研究对象,通过深度访谈等质性研究方法,解读针对流浪乞讨者的空间管治政策与手段,分析流浪乞讨者的日常生活实践与生境协商。研究发现：在地方城市政策对流动性与公共秩序限制的双重压力下,在流浪乞讨者的日常生活实践中,不仅有针对管治行动者而刻意为之的特殊营建,亦有基于程式化生活流程对自我身份认同的重塑与真情实感的展演。地方政府基于空间目标的救助与真实存在的日常生活实践存在着一种张力。研究关注了城市边缘群体日常生活对地理意义的主动塑造过程,对全面理解并规范管理中国城市流浪乞讨现象具有借鉴意义。  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   

张掖盆地地下水硝酸盐污染与人体健康风险评价     

盛丹睿  温小虎  冯起  武君  司建华  吴敏 《中国沙漠》2019,39(5):37-44

地下水是张掖盆地的重要水资源，其硝酸盐污染尚未得到足够重视。对张掖盆地2004、2015年地下水硝酸盐浓度进行了系统分析，并采用美国环境保护署（USEPA）推荐的健康风险评价模型评估了地下水硝酸盐的健康风险。结果表明：自2004年以来张掖盆地地下水硝酸盐污染日趋严重。2015年硝酸盐浓度最高已达到283.32 mg·L^-1，17.61%的采样点硝酸盐氮浓度超过GB5749-2006《生活饮用水卫生标准》中饮用地下水限量值（20 mg·L^-1）。研究区人群经皮肤接触途径摄入硝酸盐的健康风险在可接受水平，而饮水摄入硝酸盐的健康风险较高，总风险中饮水途径引起健康风险的贡献率占99.40%，远大于皮肤接触途径。儿童经饮水摄入和皮肤接触两种途径的健康风险均显著高于成人，分别为成人的1.544倍和1.039倍。32.39%的采样点地下水硝酸盐对儿童的健康风险超出了可接受水平，14.79%的采样点地下水硝酸盐对成人的健康风险不可接受。甘州区城区、临泽县北部边缘及高台县城区周围硝酸盐浓度最高，这些区域内所有人群都面临硝酸盐引发的高健康风险，其余区域硝酸盐引发的健康风险相对较低。  相似文献   

Implementation of a coupled plastic damage distinct lattice spring model for dynamic crack propagation in geomaterials          下载免费PDF全文

Chao Jiang  Gao‐Feng Zhao 《国际地质力学数值与分析法杂志》2018,42(4):674-693

This paper studies dynamic crack propagation by employing the distinct lattice spring model (DLSM) and 3‐dimensional (3D) printing technique. A damage‐plasticity model was developed and implemented in a 2D DLSM. Applicability of the damage‐plasticity DLSM was verified against analytical elastic solutions and experimental results for crack propagation. As a physical analogy, dynamic fracturing tests were conducted on 3D printed specimens using the split Hopkinson pressure bar. The dynamic stress intensity factors were recorded, and crack paths were captured by a high‐speed camera. A parametric study was conducted to find the influences of the parameters on cracking behaviors, including initial and peak fracture toughness, crack speed, and crack patterns. Finally, selection of parameters for the damage‐plasticity model was determined through the comparison of numerical predictions and the experimentally observed cracking features.  相似文献   

海洋卫星军民融合发展现状及几点思考          下载免费PDF全文

李科  张靓  魏兰  赵忠东 《海洋测绘》2018,(3):78-82

对比分析了国内外海洋卫星军民融合发展现状,指出了我国存在的主要差距,并分析造成这些差距和障碍的主要问题和症结所在,从标准体系融合、技术融合和数据融合三个方面提出我国海洋卫星军民融合发展思路,并结合发展思路提出了科学统筹、科技引领、开放协作、以人为本的军民融合发展举措,为海洋卫星军民融合发展提供了借鉴作用和决策支持。  相似文献   

铜藻(Sargassum horneri)在营养限制胁迫后对NH₄-N的超补偿吸收研究     

李大鹏  马增岭  李慧  丁刚  辛美丽  吴海一  郭文 《海洋与湖沼》2018,49(4):904-909

以经济马尾藻铜藻(Sargassum horneri)为研究材料,研究了其在营养限制胁迫后对NH_4-N的超补偿吸收情况。实验分营养限制和恢复营养两个阶段进行,每个阶段均设置饥饿处理组、饱和处理组和正常对照组。铜藻在低营养限制胁迫(饥饿)下培养10天后,恢复营养盐培养3天,分别采用次溴酸盐氧化法和锌镉还原法测定培养液中的NH_4-N和NO_3-N的浓度。本文研究发现,饥饿处理组中铜藻吸收氨氮的速率远高于正常对照组和饱和处理组,在恢复培养第一天时,饥饿处理组对NH_4-N的吸收速率最高为14.94μmol/(g·h),与正常对照组及饱和处理组间差异显著。在恢复培养的后两天,三个处理组中铜藻对NH_4-N的吸收速率差异慢慢变小,直至最后几乎相同。三组对NO_3-N没有表现出较高的吸收,最高仅为6.15μmol/(g·h),结果表明:氮源包括NH_4-N和NO_3-N时,铜藻优先选择吸收NH_4-N。实验后称重测定生长速率:对照组、饥饿处理组和饱和组生长率(SGR)分别为8.48%、8.86%、8.01%,ANOVA方差分析表明,三者存在显著差异(P=0.0320.05),从而证实了铜藻也存在超补偿生长的现象。  相似文献   

Assessment of alternative adsorption models and global sensitivity analysis to characterize hexavalent chromium loss from soil to surface runoff          下载免费PDF全文

Chuan‐An Xia  Juxiu Tong  Bill X. Hu  Xiujie Wu  Alberto Guadagnini 《水文研究》2018,32(20):3140-3157

We investigate our ability to assess transfer of hexavalent chromium, Cr(VI), from the soil to surface runoff by considering the effect of coupling diverse adsorption models with a two‐layer solute transfer model. Our analyses are grounded on a set of two experiments associated with soils characterized by diverse particle size distributions. Our study is motivated by the observation that Cr(VI) is receiving much attention for the assessment of environmental risks due to its high solubility, mobility, and toxicological significance. Adsorption of Cr(VI) is considered to be at equilibrium in the mixing layer under our experimental conditions. Four adsorption models, that is, the Langmuir, Freundlich, Temkin, and linear models, constitute our set of alternative (competing) mathematical formulations. Experimental results reveal that the soil samples characterized by the finest grain sizes are associated with the highest release of Cr(VI) to runoff. We compare the relative abilities of the four models to interpret experimental results through maximum likelihood model calibration and four model identification criteria (i.e., the Akaike information criteria [AIC and AIC_C] and the Bayesian and Kashyap information criteria). Our study results enable us to rank the tested models on the basis of a set of posterior weights assigned to each of them. A classical variance‐based global sensitivity analysis is then performed to assess the relative importance of the uncertain parameters associated with each of the models considered, within subregions of the parameter space. In this context, the modelling strategy resulting from coupling the Langmuir isotherm with a two‐layer solute transfer model is then evaluated as the most skilful for the overall interpretation of both sets of experiments. Our results document that (a) the depth of the mixing layer is the most influential factor for all models tested, with the exception of the Freundlich isotherm, and (b) the total sensitivity of the adsorption parameters varies in time, with a trend to increase as time progresses for all of the models. These results suggest that adsorption has a significant effect on the uncertainty associated with the release of Cr(VI) from the soil to the surface runoff component.  相似文献   

Area usage estimation and spatiotemporal variability in distribution patterns of southern right whales,Eubalaena australis,of southern Brazil          下载免费PDF全文

Eduardo Pires Renault‐Braga  Karina Rejane Groch  Paulo A. de Carvalho Flores  Eduardo R. Secchi  Luciano Dalla‐Rosa 《Marine Ecology》2018,39(3)

Southern right whales—Eubalaena australis (Desmoulins, 1822)—migrate seasonally from high‐latitude feeding grounds to coastal breeding and calving grounds at lower latitudes such as the southern coast of Brazil. Understanding how these whales are distributed along the coast is important for monitoring their postwhaling recovery and defining management strategies. In this study, we applied Kernel density estimators to aerial survey data to determine main occurrence and concentration areas of right whales in southern Brazil and investigate inter‐ and intra‐annual distribution patterns between 2003 and 2012. Our results show considerable variation in area usage within and among years, and changes in the general distribution pattern of right whales in the last years of the study. Intra‐annually, higher concentration area tended to expand from July to September and decrease in November. Some areas stood out as high‐density areas for right whales: Ribanceira/Ibiraquera, Itapirubá Sul/Sol, and from Arroio to Gaivota. Some evidences also suggest preferential areas for mother–calf pairs. The higher concentration area of right whales in southern Brazil was estimated at 52,541 km² and the occurrence area was 682.69 km², which is the whole study area. As right whale distribution in the region is likely expanding due to this population's current recovery, our study provides essential information for management plan of the Right Whale Environmental Protection Area.  相似文献