基于AIS数据的船舶排放估测模型与实船验证     

王直欢  王维勋  施欣 《上海海事大学学报》2019,40(4):12-16

为提升船舶能耗和排放估测的准确性和灵活性,提出面向船舶自动识别系统(automatic identification system, AIS)大数据的完全自下而上的船舶能耗和排放估测新方法。该方法视船舶为一种基于船舶航迹的线排放源,在构建船舶网格化轨迹模型的基础上,考虑每个网格航段的持续时间和发动机负载,实现船舶能耗和排放的精细化建模,统一船舶排放总量和空间分布计算。实船应用表明,该方法可提供更加准确的船舶能耗估计,并可灵活计算各种航行状态、船队规模和时空尺度的能耗和排放清单。  相似文献   

Digital Module 16: Longitudinal Data Analysis     

Jeffrey R. Harring  Tessa L. Johnson 《Educational Measurement》2020,39(3):137-138

In this digital ITEMS module, Dr. Jeffrey Harring and Ms. Tessa Johnson introduce the linear mixed effects (LME) model as a flexible general framework for simultaneously modeling continuous repeated measures data with a scientifically defensible function that adequately summarizes both individual change as well as the average response. The module begins with a nontechnical overview of longitudinal data analyses drawing distinctions with cross-sectional analyses in terms of research questions to be addressed. Nuances of longitudinal designs, timing of measurements, and the real possibility of missing data are then discussed. The three interconnected components of the LME model—(1) a model for individual and mean response profiles, (2) a model to characterize the covariation among the time-specific residuals, and (3) a set of models that summarize the extent that individual coefficients vary—are discussed in the context of the set of activities comprising an analysis. Finally, they demonstrate how to estimate the linear mixed effects model within an open-source environment (R). The digital module contains sample R code, diagnostic quiz questions, hands-on activities in R, curated resources, and a glossary.  相似文献   

基于DE-SVM的船舶航迹预测模型     

刘娇  史国友  杨学钱  朱凯歌 《上海海事大学学报》2020,41(1):34-39

为提高船舶航迹预测精度,解决准确建模难度大和神经网络易陷入局部最优的问题,考虑实时获取目标船AIS数据较少的特点,提出一种基于支持向量机(support vector machine,SVM)的航迹预测模型。选择AIS数据中的航速、航向和船舶经纬度作为样本特征变量;采用小波阈值去噪的方法处理训练数据;采用差分进化(differential evolution,DE)算法对模型内部参数寻优以提高模型收敛速度和预测精度。选取天津港实船某段航迹的AIS数据,比较基于DE-SVM与基于BP神经网络的航迹预测模型的仿真结果。结果表明,基于DE-SVM的航迹预测模型具有更高的预测精度,简单、可行、高效,且耗时少。  相似文献   

基于隐马尔科夫模型的VLCC目的港预测     

杨春  王一丹  徐晖  胡勤友  潘亚兰 《上海海事大学学报》2020,41(4):42-49

超大型油船(very large crude carrier，VLCC)目的港预测对海运原油流向预测以及货源地未来运力估计具有重要作用。针对VLCC的AIS目的港信息存在缺失、更新不及时、不准确等现象，提出一种基于隐马尔科夫模型的VLCC目的港预测方法。分析船舶AIS轨迹数据，得到油船历史停靠港口序列；根据VLCC轨迹提取习惯航路，以航路中的交叉点为依据设置观测线；利用船舶航行轨迹数据判断船舶是否经过观测线以及经过观测线的方向，对不同方向分别计算船舶在挂靠港间的转移概率矩阵和船舶挂靠港与观测线间的输出概率矩阵，建立VLCC目的港预测模型并进行预测。研究结果表明：在大多数情况下VLCC目的港预测的准确率可以达到70%以上；航线越固定、运行越规律的船舶，预测准确率越高；船舶越靠近目的港，预测越准确；重载状态下的船舶目的港预测更准确。  相似文献   

HyperSnap-DX软件在科技期刊图形与图像处理中的应用     

朱伟 《编辑学报》2006,18(2):133-133

北大方正书版排版系统支持的图形、图像格式有限,仅支持.tif等少数图形文件格式,因此,在很多情况下,如格式为.doc、,dwg等的图形一般采用扫描的方法,通过photoshop软件处理后,再存为.tif格式文件为北大方正书版所利用,但有时效果不佳.  相似文献   

Early stages in building hybrid activity between school and work: the case of PénArt     

Sylvie Barma  Thérèse Laferrière  Bruno Lemieux  Julie Massé-Morneau  Marie-Caroline Vincent 《Journal of Education & Work》2017,30(6):669-687

This formative intervention documents the emergence of a hybrid activity aiming at student engagement and academic achievement. In this context-bound study, early stages of this activity consisted in establishing PénArt meant to enable high school students with difficulties to start up their own business at school. It involved reaching agreements between a high school and a youth centre so that high school students engage in the production and selling of their branded t-shirt. At the frontiers of their respective activity system, students, youth workers, special education teachers and members of the school board took actions to cross boundaries and redefine their interrelations. Cultural historical activity theory was fruitful to document the development of a new object-oriented activity. Tensions and contradictions revelaled to be the key moments in the emergence of the hybrid activity. Expansive learning led us to understand that, in a conflicting situation, a collective’s agentive actions create an expansive form of learning and leads to a successful entrepreneurship experience. Change laboratory capacity to foster change for cooperative education in Quebec was successful. The students enrolled in a regional entrepreneurship contest and won it. That was a significant event for students with low self-esteem linked with their performance at school.  相似文献   

水松扦插繁殖技术的研究   总被引：2，自引：0，他引：2  

李博  李火根 《桂林师范高等专科学校学报》2008,22(3):151-156

水松为我国特有的珍稀濒危树种。本研究对水松扦插繁殖技术进行了探讨。通过研究母树年龄,采条部位,扦插基质,激素种类、浓度与处理时间,基因型等因素对水松扦插成活率的影响,初步总结出一套水松扦插繁殖技术。以1a生或2a生实生苗顶部枝条为插穗,用2000ppmIBA速蘸处理30s或用100ppmNAA浸泡插穗基部2h,然后扦插在混合基质（草炭：珍珠岩=7：3）中,可以获得较为理想的结果,扦插成活率可达85％以上。试验还发现,不同基因型间生根能力差异显著,表明通过优良单株选择可改良水松的生根特性。  相似文献   

圆盘薄壁零件车削中夹具的优化   总被引：1，自引：0，他引：1  

万余仙 《邢台职业技术学院学报》2008,25(5):30-32

圆盘薄壁零件在普通卧式车床的生产加工过程中,因没有足够的刚性,容易产生变形、尺寸精度起差、甚至工件脱落于夹具,导致工件报废的现象。通过优化装夹方法,改进夹具,完全能够达到零件加工的技术要求。  相似文献   

数控车床切削直螺纹编程方法初探     

孟涛 《常熟理工学院学报》2004,18(4):99-101

在目前的数控车床加工中,螺纹切削有多种方法,如直进式螺纹切削和斜进式螺纹切削等,文中针对直螺纹的加工介绍几种常见的切削方式和编程.  相似文献   

基于移动趋势的轨迹隐私保护研究综述     

张璐 《教育技术导刊》2021,20(1):245-248

移动设备的普及为基于位置的服务应用带来新的发展机遇,但在使用LBS时造成的轨迹隐私泄露问题成为LBS普及的隐患。轨迹泛化法是一种轨迹隐私保护技术,在保护轨迹隐私的同时还可提高服务质量。基于组的轨迹隐私保护技术特点,对不考虑移动趋势的轨迹泛化法进行分析,总结基于移动趋势的轨迹隐私保护方法并对未来研究方向进行展望。  相似文献