无人船运动控制方法综述   总被引：1，自引：1，他引：0  

裴志远  戴永寿  李立刚  金久才  邵峰 《海洋科学》2020,44(3):153-162

为实现无人船海上自主作业,无人船运动控制的快速性、准确性以及鲁棒性亟待提高。首先从全驱动控制和欠驱动控制角度,分别概括了国内外无人船航向控制、航速控制、轨迹跟踪控制以及路径跟踪控制的主流控制方法。其次,归纳总结了处理海洋环境不确定扰动的研究进展,包括扰动的建模和消除、抑制扰动的主流方法。最后,总结了无人船运动控制现状与存在的问题,并从工程应用和理论研究两个角度对未来的研究方向进行了展望。  相似文献   

2008年汶川MS8.0地震电离层图像信息长时程演化初探     

宋程  张永仙  夏彩韵  张小涛 《地震》2019,39(2):135-146

应用改进的图像信息方法, 结合DEMETER电磁卫星的电子温度数据, 对2008年汶川M_S8.0地震进行了长时程的回溯性预测研究。 与以往的地震电离层演化图像提取异常的研究相比, 将其回溯的时程延长至震前近11个月, 并向震后延长48 d。 在长期连续的异常扰动演化图中, 出现了两个明显的异常时段, 且在震前2个月短期内异常扰动明显减弱并趋于背景值。 两个时段出现的异常扰动分布位置及其形态以及持续时间皆不重复, 这体现了前兆异常的不易确定, 难以定性及定量识别的特点。 电离层异常扰动特征的长时程研究, 有评估其预测参数和模型可靠性的实际作用, 也为应用中国卫星观测数据服务于地震预报等研究积累经验, 具有借鉴意义。  相似文献   

塘沽地电阻率观测轻轨干扰降噪处理     

王晓蕾  谷国梁  马义山  刘传军  徐小远  杨建思 《地震地磁观测与研究》2019,40(4):81-88

随着地铁轻轨的迅速发展，我国大多数地电阻率测项受到不同程度干扰，诸多学者为此提出采用小波方法进行滤波的建议。文中拟采用小波和HHT滤波方法，以受津滨轻轨干扰严重的塘沽地电阻率观测资料为例，进行降噪处理，对比2种方法的滤波效果，以获得更好的滤波方法。  相似文献   

河北广平地震台数字电扰动异常分析     

贾华  乔子云  贾立峰  张国苓  寇海川  张双凤  张小涛 《地震地磁观测与研究》2019,40(4):95-101

自2018年1月11日，河北广平地震台数字电扰动仪NS、EW测道每日北京时间18时至次日06时出现规律性高值变化。通过观测系统检测、测区环境调查、现场实验分析、周边台站观测对比、其他台干扰形态分析及震例总结等手段，并对各种可能的影响因素进行分析论证，综合分析认为，该变化为干扰的可能性较大，非地震前异常。  相似文献   

人为干扰对越冬后期稻田中小天鹅(Cygnus columbianus)昼间能量消耗的影响     

于超  周立志  宋昀微 《湖泊科学》2019,31(1):195-201

能量的消耗模式是动物适合度的重要体现，动物的日常行为和栖息地特征共同影响日能量消耗.稻田生境是越冬水鸟重要的觅食场所之一，同时又容易受到人为干扰，越冬水鸟应对日间不同的人为干扰因素而合理进行能量消耗配置，对于在越冬后期为迁徙而贮备能量的水鸟来说尤为迫切和重要.本文采用焦点动物取样法，观测越冬后期稻田中小天鹅（Cygnus columbianus）在干扰和非干扰环境中昼间行为的时间分配，推算其能量消耗.结果表明，小天鹅在干扰环境中警戒行为的时间分配和能量消耗、单次警戒时间和警戒频次均显著大于非干扰环境，游泳频次也是如此；在稻田中的昼间警戒能耗随干扰时间增加而增加，随干扰距离增加而降低.干扰造成小天鹅减少高能耗的取食行为，增加低能耗的警戒行为，降低昼间总能量的消耗.  相似文献   

扰动方式对水华微囊藻(Microcystis flos-aquae)群体大小的影响     

芮政  杨桂军  刘玉  韩丽华  秦伯强  杨宏伟  钟春妮 《湖泊科学》2019,31(2):355-364

风浪扰动是影响湖泊生态系统的重要环境因素之一.为了解扰动方式对微囊藻群体大小的影响，在实验室可控条件下，模拟不同扰动方式（持续扰动和间歇扰动）对太湖水华微囊藻（Microcystis flos-aquae）群体大小的影响.结果显示，间歇扰动组水华微囊藻群体从35.09 μm迅速增大至43.73 μm，实验第17天时为59.00 μm；而持续扰动组水华微囊藻群体大小先从35.07 μm增大到43.51 μm，实验第17天时减小至13.95 μm；不扰动组整个实验期间群体大小相对稳定，实验初为35.38 μm，实验第17天时为33.67 μm.方差分析显示，间歇扰动组群体大小显著大于持续扰动组和不扰动组，持续扰动组显著小于不扰动组.实验第17天时间歇扰动组藻细胞密度（1.675×10⁶ cells/ml）显著高于持续扰动组（0.344×10⁶ cells/ml）和不扰动组（1.461×10⁶ cells/ml）.研究结果表明，适当强度下的间歇扰动能促使水华微囊藻群体显著增大和生长，而长时间的持续扰动则会抑制水华微囊藻群体的聚集和生长，该结果有助于人们对太湖微囊藻水华暴发机理的认识.  相似文献   

基于三维激光扫描技术的钢结构扰度检测及应用     

宋云记  王晓民  王智 《测绘通报》2020,(12):160-163

钢结构在长期荷载及不均匀受力的作用下会产生空间变形，其中扰度是其重要的衡量指标。通常采用全站仪采集钢结构轴线上若干特征点进行分析、计算，由于钢结构特征点难以捕捉，测量存在误差，并且有限的空间离散点难以全面反应钢结构空间变形。本文采用徕卡RTC360三维激光扫描进行钢结构扰度测量；介绍了其作业流程及数据处理方法；利用标靶将各个测站的三维点云拼接成一个整体；采用拟合的方法提取空间特征点及轴线；利用三维点云构建空间模型，并与设计模型进行碰撞分析；可全面地反映钢结构的空间变形情况。  相似文献   

Shenandoah Watershed Study-Virginia Trout Stream Sensitivity Study (SWAS-VTSSS): Stream water quality and hydrologic monitoring data for mid-Appalachian headwater streams     

Ami L. Riscassi  Todd M. Scanlon  Suzanne W. Maben  James N. Galloway 《水文研究》2021,35(4):e14164

The Shenandoah Watershed Study (established in 1979) and the Virginia Trout Stream Sensitivity Study (established in 1987) serve to increase understanding of hydrological and biogeochemical changes in western Virginia mountain streams that occur in response to acidic deposition and other ecosystem stressors. The SWAS-VTSSS program has evolved over its 40+ year history to consist of a temporally robust and spatially stratified monitoring framework. Currently stream water is sampled for water quality bi-hourly during high-flow events at three sites and weekly at four sites within Shenandoah National Park (SHEN), and quarterly at 72 sites and on an approximately decadal frequency at ~450 sites within the wider western Virginia Appalachian region. Stream water is evaluated for pH, acid neutralizing capacity (ANC), base cations (calcium, magnesium, sodium and potassium ion), acid anions (sulphate, nitrate and chloride), silica, ammonium, and conductivity with a subset of samples evaluated for monomeric aluminium and dissolved organic carbon. Hourly stream discharge (four sites) and in-situ measurements of conductivity, water and air temperature (three sites) are also measured within SHEN. Here we provide an overview and timeline of the SWAS-VTSSS stream water monitoring program, summarize the field and laboratory methods, describe the water chemistry and hydrologic data sets, and document major watershed disturbances that have occurred during the program history. Website links and instructions are provided to access the stream chemistry and time-series monitoring data in open-access federal databases. The purpose of this publication is to promote awareness of these unique, long-term data sets for wider use in catchment studies. The water chemistry and hydrologic data can be used to investigate a wide range of biogeochemical research questions and provide key inputs for models of these headwater stream ecosystems. SWAS-VTSSS is an ongoing program and quality assured data sets are uploaded to the databases annually.  相似文献   

中国大陆密度和地震波速扰动异常的年龄属性研究     

杨文采 《地质学报》2021,95(1):227-237

大陆动力学研究需要物质随空间和时间的变化的信息。三维密度和地震波速度扰动图像反映岩石圈物质的空间分布,要和大地构造学中的时间尺度信息综合起来,才能恢复动力学作用的过程。本文通过对比不同构造期的构造图和地壳不同深度的地球物理性质图像,研究中国大陆密度以及地震波速度扰动和构造事件的相关度。研究表明,岩石圈地幔的密度和波速扰动和现今板块构造的相关度是高的,说明岩石圈地幔的密度大黏度高,不仅地震波速快得多,物质蠕动的速度也比下地壳慢得多,板块运动产生的变形保存时间比较久。中国大陆中地壳的密度扰动和白垩纪以来的构造事件的相关度是高的,说明中地壳的密度扰动主要反映了白垩纪以来的构造事件。中国大陆上地壳结晶基底的密度扰动和侏罗纪以来的构造事件的相关度是高的,说明上地壳的密度扰动可以反映燕山期的构造事件。对于中国大陆而言,下地壳的波速变化和板块构造没有明显的相关性;不过下地壳深层的密度扰动也反映新构造期的构造事件。其原因可能是因为下地壳的物质黏度比较低,物质蠕动的速度比岩石圈地幔快得多,板块运动产生的变形不容易保存。总之,应用不同深度的密度扰动图像分别推测不同地质时期的地壳构造运动发生的地点和范围是可行的,地壳深层的三维密度扰动成像有可能提供180Ma以来中国大陆地质作用事件的有关信息。  相似文献   

Legacies of 19th century land use shape contemporary forest cover     

《Global Environmental Change》2015

Historic land use can exert strong land-use legacies, i.e., long-lasting effects on ecosystems, but the importance of land-use legacies, alongside other factors, for subsequent forest-cover change is unclear. If past land use affects rates of forest disturbance and afforestation then this may constrain land use planning and land management options, and legacies of current land management may constrain future land use. Our goal was to assess if and how much land-use legacies affect contemporary forest disturbance, and the abundance of different forest types in the Carpathian region in Eastern Europe (265,000 km², encompassing parts of Poland, Slovakia, Ukraine, Romania, Hungary, and Czech Republic). We modeled contemporary forest disturbance (based on satellite image analysis from 1985 to 2010) as a function of historic land use (based on digitized topographic maps from 1860 and 1960). Contemporary forest disturbance was strongly related to historic land use even when controlling for environmental, accessibility and socio-political variation. Across the Carpathian region, the odds of forest disturbance were about 50% higher in areas that were not forested in 1860 (new forests) compared to areas that were forested then (old forests). The forest disturbance in new forests was particularly high in Poland (88% higher odds), Slovakia (69%) and Romania (67%) and persisted across the entire range of environmental, accessibility and socio-political variation. Reasons for the observed legacy effects may include extensive plantations outside forest ranges, predominantly spruce, poplar, and black locust, which are prone to natural disturbances. Furthermore, as plantations reach harvestable age of about 70 years for pulp and 120 year for saw-timber production, these are likely to be clear-cut, producing the observed legacy effects. Across the Carpathians, forest types shifted towards less coniferous cover in 2010 compared to the 1860s and 1960s likely due to extensive historic conifer harvest, and to recent natural disturbance events and clear-cuts of forest plantations. Our results underscore the importance of land-use legacies, and show that past land uses can greatly affect subsequent forest disturbance for centuries. Given rapid land use changes worldwide, it is important to understand how past legacies affect current management and what the impact of current land management decisions may be for future land use.  相似文献