Ince-Strutt Stability Charts for Ship Parametric Roll Resonance in Irregular Waves

Ince-Strutt stability chart of ship parametric roll resonance in irregular waves is conducted and utilized for the exploration of the parametric roll resonance in irregular waves. Ship parametric roll resonance will lead to large amplitude roll motion and even wreck. Firstly, the equation describing the parametric roll resonance in irregular waves is derived according to Grim’s effective theory and the corresponding Ince-Strutt stability charts are obtained. Secondly, the differences of stability charts for the parametric roll resonance in irregular and regular waves are compared. Thirdly, wave phases and peak periods are taken into consideration to obtain a more realistic sea condition. The influence of random wave phases should be taken into consideration when the analyzed points are located near the instability boundary. Stability charts for different wave peak periods are various. Stability charts are helpful for the parameter determination in design stage to better adapt to sailing condition. Last, ship variables are analyzed according to stability charts by a statistical approach. The increase of the metacentric height will help improve ship stability.     

郑和牵星图导航技术研究

《1421:中国发现世界》作者加文·孟希斯(Gavin Menzies)将中国的海洋文明推向15世纪初,这个历史命题令世界震惊,"郑和航海图"就是证据之一。"郑和航海图"记录了郑和舰队巡航南海,远航印度洋国家的探索过程。该地图发现于明《武备志》240卷,是一种传统的中国导航牵星图和针路图,充满了许多待解之谜。本文对郑和航海图中"更数"所代表的现代概念的距离和速度进行了研究,发现帆船航行"更数"的距离和速度在不同的地区存在差异;牵星图中的星座只能用来确定纬度坐标。将郑和航海图和现代地图做了实验对比,在进行大气折射校正后,郑和航海图的纬度坐标能够准确显示在现代Google地图中。在郑和航海图的许多航点上,我们可以在现代地图中准确找到带有明显中国特点的航海基地。     

使用MATLAB绘制常用海洋要素图件

利用MATLAB软件强大的图形制作功能,结合海洋水文资料的特点,介绍了海洋水文资料的检查、处理、分析及应用中常用图形的快捷绘制方法。     

海洋测绘数据库维护的问题与改进设想

分析了海洋测绘数据库维护存在的几个问题,提出了调整海洋测绘产品生产体系、建立海洋测绘数据库维护更新机制等设想和建议,以提高海洋测绘数据库的数据质量,更好地为国家经济建设和国防建设服务。     

矩法计算粒度参数在计算机上的应用

矩法计算粒度参数首先需将薄片粒度换算成筛析粒度，然后根据各次矩公式进行计算。该方法使得整个粒度分布都投入计算，因而具有图算法无法比拟的优越性；借助于计算机，使得这一方法适用范围更为广阔，使用起来更为快速、准确。     

降雨对陕西山洪灾害的触发作用

本文分析了近年来5月～9月晋中市出现飑线天气的高空背景形势,通过对晋中市区域小天气图客观分析以及进行物理量诊断分析,找出了晋中市飑线落区预报技术指标。     

双坐标系组合图在地球信息图谱化中的应用

文章选择新颖的斜角坐标系量化图形中的双坐标系组合图形用于展现地球信息图谱。通过筛选多种多样的组合形式选择适合于不同地球信息展示的最佳图形样式,高效、美观地传递信息,使地球复杂系统的统计数据中蕴藏的时空规律跃然纸上,为研究地学信息图谱引进了一种新的表达方法。     

Trend analysis of Climatic Research Unit temperature dataset for Gangotri glacier,India

The absence of continuous long term meteorological dataset has led to limited knowledge of glaciers’ response to climate change over Himalayas. This study presents an open source long term temperature dataset Climatic Research Unit (CRU) available since 1901 to study trend analysis of temperature (T_max, T_min and T_mean) for Gangotri basin in Himalayas. The study first establishes close agreement between CRU time series data and observed temperature dataset available from National Institute of Hydrology (NIH), Roorkee for a period of 11 years from 2005 to 2015 using standard anomaly, Wilcoxon Signed-Rank (WSR) and correlation tests. The close agreement of CRU with NIH data validate the use of CRU time series to study variation in meteorological parameter for hilly terrain of Himalayas. The second part includes application of different statistical tests such as Mann-Kendall (MK), Sen’s slope and CUSUM technique on CRU data to detect existence of any possible trends and identification of change points in T_max, T_min and T_mean on long term scale. On annual scale, significant increasing trends for T_mean and T_min were observed with no significant trend for T_max. On seasonal and monthly scale, T_max showed significant decreasing trend for monsoon season and increasing trend for winters while T_min show significant increasing trend for all months (except May) and seasons. CUSUM technique identified 8 change points from 3 annual time series with 2 for T_mean (1974 and 1999), 3 each for T_max (1941, 1975 and 1999) and T_min (1941, 1965 and 1999) respectively. Overall, significant increase in T_min with no significant trend for T_max has been identified over the study area.