《海洋数值模拟》课程建设的探索

《海洋数值模拟》是淮海工学院面向海洋技术专业本科生开设的专业选修课程。以培养海洋科学专业学生的数值模拟技能为目标,以研究海洋环境动力机制为导向,研究了《海洋数值模拟》课程的教学案例,提出了关于该课程建设上的思考,教学实践表明,学生的基本技能得到明显提高,学习兴趣普遍增强。     

利用数值投影变换构建全球六边形离散格网

本文针对全球离散格网构建过程中从平面格网到球面格网的关键步骤进行讨论,提出了一种新型的评价球面离散格网几何属性最优化的目标函数,使用遗传算法优化,得到了球面上有限层次内最优化条件下的直接剖分格网。利用有限层次内最优化格网提供的控制点数据,结合数值投影变换理论,成功地构建了几何属性更加均匀的全球六边形离散格网系统。实验表明,相对于现有Snyder等积投影建立的全球格网,在格网单元的均匀度上更优;在运算效率方面,速度大约是Snyder投影的2.5-3倍。     

利用MATLAB实现图像处理与分析

本文通过对图像的均衡操作、二值图像的处理、小波去噪等实例，介绍了MATLAB进行图像处理和分析的实用方法与技巧，它对各种软钉包、进行图像处理和分析等，提供了高效便捷的方法。     

海岸海洋潮流模拟可视化与虚拟现实建模

潮流数值模拟的科学可视化与虚拟现实是海岸海洋科学研究重要的现代技术手段之一。首先从地理信息系统的角度对潮流数值模拟系统的数据模型进行了论述，提出了适合水文数值模拟的对象模型方法；其次探讨了空间流场的可视化技术，阐述了虚拟现实在潮流数值模拟中的作用；最后设计并实现了一个海岸海洋潮流模拟虚拟现实的原型软件系统VRO－cean,并在南黄海辐射沙洲等的潮流数值模拟试验中进行了实际对比检验。     

Development of a 3-D urbanization index using digital terrain models for surface urban heat island effects

This study assesses surface urban heat island (SUHI) effects during heat waves in subtropical areas. Two cities in northern Taiwan, Taipei metropolis and its adjacent medium-sized city, Yilan, were selected for this empirical study. Daytime and night time surface temperature and SUHI intensity of both cities in five heat wave cases were obtained from MODIS Land-Surface Temperature (LST) and compared. In order to assess SUHI in finer spatial scale, an innovated three-dimensional Urbanization Index (3DUI) with a 5-m spatial resolution was developed to quantify urbanization from a 3-D perspective using Digital Terrain Models (DTMs). The correlation between 3DUI and surface temperatures were also assessed. The results obtained showed that the highest SUHI intensity in daytime was 10.2 °C in Taipei and 7.5 °C in Yilan. The SUHI intensity was also higher than that in non-heat-wave days (about 5 °C) in Taipei. The difference in SUHI intensity of both cities could be as small as only 1.0 °C, suggesting that SUHI intensity was enhanced in both large and medium-sized cities during heat waves. Moreover, the surface temperatures of rural areas in Taipei and Yilan were elevated in the intense heat wave cases, suggesting that the SUHI may reach a plateau when the heat waves get stronger and last longer. In addition, the correlation coefficient between 3DUI and surface temperature was greater than 0.6. The innovative 3DUI can be employed to assess the spatial variation of temperatures and SUHI intensity in much finer spatial resolutions than measurements obtained from remote sensing and weather stations. In summary, the empirical results demonstrated intensified SUHI in large and medium-sized cities in subtropical areas during heat waves which could result in heat stress risks of residents. The innovative 3DUI can be employed to identify vulnerable areas in fine spatial resolutions for formulation of heat wave adaptation strategies.     

引潮位的Doodson规格化展开及其精度评定

基于引潮位Doodson规格化展开的基本原理以及ELP/MPP02月球历表、Newcomb太阳历表的结构,设计了一个用以代表三角函数的数据结构;并由此自定义了三角函数的乘法与加法算法,将月球、太阳引潮位分别展开至5阶、3阶,振幅绝对值截断阈值为10-7,在展开过程中对"伪波"进行"滤波"处理后,最终得到包含4 686项展开式的引潮位展开表(其中振幅绝对值超过10-6的展开式有2 441项)。以德国BFO(Black Forest Observatory)测站为例,基于DE431历表,通过天球参考系变换计算得到1950—2050年间时间间隔为1 h的法向引潮力基准序列BFDE431;并根据各个引潮位展开表计算得到相应的法向引潮力序列;通过与BFDE431基准序列求差,得到各个差值序列的统计值。计算结果表明,文中给出的展开表对应的差值序列数值在±58×10~(-11)m·s~(-2)(nGal)以内,均方差为12.5×10~(-11)m·s~(-2),与XI89展开表的精度相当。但由于没有考虑行星及地球扁率的影响,仍未达到HW95和RATGP95展开表的精度水平。     

GPS卫星轨道数值积分与广播星历及IGS精密星历的比较

本文采用作者自编的SPPORB IT程序,对GPS卫星轨道的运动方程进行Adam s数值积分求解,同时利用广播星历计算卫星轨道坐标,然后将两者结果同IGS精密星历提供的卫星坐标进行比较,并探讨其轨道误差,计算结果显示广播星历与精密星历差值在2m左右,而数值积分与精密星历的差值在2 cm左右,进一步的分析表明前者误差较大是没有考虑卫星所受的太阳光压、日月引力等影响,而后者考虑了这些影响。鉴于IGS提供的是地固系坐标,而本文数值积分是在惯性系坐标系下进行的,因此本文还举例对惯性坐标系和地固系之间的坐标转换进行了描述。最后,通过实例说明SPPORB IT程序的稳定性以及Adam s数值积分方法的有效性。     

DInSAR技术对不同方位形变的敏感性研究

以DEM数据为假想的地面目标,只考虑距离对相位的影响,模拟竖直向、距离向和方位向形变的干涉纹图,从而研究DInSAR技术对空间不同方位形变的敏感性。在所有模拟参数和形变位移大小都相同的情况下,三个不同方位形变所产生的相位从0到2π变化的完整干涉环的数目是各不相同的,揭示DInSAR技术对不同方位地表形变的敏感性存在差异,且敏感性由大到小依次为:竖直向、距离向和方位向。     

略论珠穆朗玛峰重力值的推估

仅根据邻近点的重力与高程资料,采用了4种有关公式,有效地推估了珠穆朗玛峰顶上的重力值,该值为(976970±7)×10^-5m·s^-2。这一结果为精确推求珠峰大地水准面和正高提供了必要的数据     

Diurnal Variation of Gravity Wave Activity at Midlatitudes in the Ionospheric F Region

We investigate the short-term fluctuations in the period range from 15 to 180 minutes in the electron density variations of the F region ionosphere. Electron density profiles obtained at the ionospheric stations of Pruhonice (49.9° N, 14.5° E) and Ebro (40.8° N, 0.5° E) at five minute time sampling have been used for this analysis. The diurnal changes of the activity of the acoustic gravity wave fluctuations (AGW) show a clear enhancement during and several hours after sunrise. The periods of such AGW's are about 60 to 75 minutes and these waves propagates vertically through the ionosphere from a source located at an altitude of 180-220 km. The most likely source for these events seems to be passage of the Solar terminator.