期刊文献+
共找到5篇文章
< 1 >
每页显示 20 50 100
中性浮力下实验体模拟对地定向控制律设计 被引量:2
1
作者 陈诗瑜 袁建平 方群 《科学技术与工程》 北大核心 2012年第8期1831-1835,共5页
中性浮力法是模拟空间微重力环境的一种常用手段,其原理是利用水的浮力平衡物体所受的重力,使物体处于漂浮状态。该方法模拟的微重力环境相似度高,持续时间长,可以提供6自由度运动模拟,因此采用该方法实现空间飞行器空间任务的地面模拟... 中性浮力法是模拟空间微重力环境的一种常用手段,其原理是利用水的浮力平衡物体所受的重力,使物体处于漂浮状态。该方法模拟的微重力环境相似度高,持续时间长,可以提供6自由度运动模拟,因此采用该方法实现空间飞行器空间任务的地面模拟演示和功能验证是可行的。研究了中性浮力下实验体模拟对地定向控制律设计问题。首先根据流体力学和动量矩定理推导出实验体的姿态动力学方程,并通过本体坐标系与参考坐标系的关系,得出用于控制的动力学方程。然后在理想状态下基于该动力学方程,使用Lyapunov方法设计实验体模拟对地定向控制律,并证明了闭环系统的渐进稳定性。最后通过仿真验证了控制算法的性能。为中性浮力环境下实验体的空间任务模拟提供理论基础。 展开更多
关键词 微重力 中性浮力 水下实验体 模拟对地定向 姿态稳定
下载PDF
基于视觉系统的双介质下目标定位 被引量:1
2
作者 王俊 朱战霞 +1 位作者 贾国华 张旭阳 《科学技术与工程》 2010年第31期7665-7669,共5页
针对传统的摄像机三角测量原理无法实现光线折射情况下物体位置准确测量的问题,在双目定位原理和折射定理的基础上,提出了一种双介质下目标定位的理论方法。运用安装在空气介质中的双目相机对玻璃水缸中实验体进行测量定位,考虑了光线... 针对传统的摄像机三角测量原理无法实现光线折射情况下物体位置准确测量的问题,在双目定位原理和折射定理的基础上,提出了一种双介质下目标定位的理论方法。运用安装在空气介质中的双目相机对玻璃水缸中实验体进行测量定位,考虑了光线通过不同介质在临界面发生一次折射的情况,建立物点双介质成像数学模型,并用该方法完成水中实验体的定位解算,求得物体质心坐标。试验结果表明该方法可用于双介质下的视觉定位测量,具有较高的测量精度和良好的稳定性。 展开更多
关键词 双介质 双目视觉 目标定位 光线折射 水下实验体
下载PDF
Calculation of wave and current loads on launching offshore jacket 被引量:6
3
作者 ZHANG Guang-fa JI Zhuo-shang LI Tie-li LIN Yan 《Journal of Marine Science and Application》 2006年第4期1-7,共7页
It’s very complicated to calculate and analyze the wave and current loads on naval architectures since the sea condition is uncertain and complicated and the determinants vary from different form types and dimensions... It’s very complicated to calculate and analyze the wave and current loads on naval architectures since the sea condition is uncertain and complicated and the determinants vary from different form types and dimensions. For calculating the wave and current loads on upright small-long-size pipe, the Morrison equation is practical and applied. Jacket platform is a kind of offshore space frame structure comprised of lots of poles that are circular cylinders with small diameter and in the oblique status relative to seabed. In this paper, based on Morrison equation, the specific method and procedure calculating the wave and current loads on launching jacket are given and applied on a typical launching jacket. The instance shows that the method and procedure are convenient and make the calculation and analysis in good agreement with actual launching. 展开更多
关键词 LAUNCHING hydrodynamic force morrison equation jacket platform
下载PDF
Influence of Magnetic Treatment on Salts Leaching: From Soils of Different Salinity Levels
4
作者 Khalida Abdul-Karim Hassan Farhad Ali Hashim Sarwar Mohammed Rasheed Ahmed 《Journal of Agricultural Science and Technology(B)》 2014年第6期434-439,共6页
Leaching behavior of individual ions from three saline soils (S1 = 85.0 dS/m, S2 = 53.92 dS/m and S3 = 38.14 dS/m) under magnetic water (MW) treatment or non-magnetized well water (WW) was investigated in column... Leaching behavior of individual ions from three saline soils (S1 = 85.0 dS/m, S2 = 53.92 dS/m and S3 = 38.14 dS/m) under magnetic water (MW) treatment or non-magnetized well water (WW) was investigated in column study. After five pore volumes, soil electrical conductivity (EC) decreased to a range between 2.99-3.29 dS/m under the two water treatments. The rate of soluble cations leached was Na+ 〉 Ca2+ 〉 Mg2+ 〉 K+ and CI- 〉 SO42- 〉 HCO3- for anions under the two water treatments. The greater amount of salt leached was during the first two pore volumes and was higher under MW treatment. Among soils, the higher the initial EC, the greater the amount of the salt leached. Measurements of the exchangeable Na~ performed at the end of leaching experiment showed a high decrease in soil exchangeable Na+ compared to the initial values of sodium adsorption ratio (SAR) and exchangeable sodium percentage (ESP) in the soil indicated that there was no prospects of soil sodification after leaching with five pore volumes. 展开更多
关键词 MW soil salinit LEACHING
下载PDF
Experimental investigation of the generation of large-amplitude internal solitary wave and its interaction with a submerged slender body 被引量:23
5
作者 WEI Gang DU Hui +4 位作者 XU XiaoHui ZHANG YuanMing QU ZiYun HU TianQun YOU YunXiang 《Science China(Physics,Mechanics & Astronomy)》 SCIE EI CAS 2014年第2期301-310,共10页
A principle of generating the nonlinear large-amplitude internal wave in a stratified fluid tank with large cross-section is pro- posed according to the 'jalousie' control mode. A new wave-maker based on the princip... A principle of generating the nonlinear large-amplitude internal wave in a stratified fluid tank with large cross-section is pro- posed according to the 'jalousie' control mode. A new wave-maker based on the principle was manufactured and the experi- ments on the generation and evolution of internal solitary wave were conducted. Both the validity of the new device and ap- plicability range of the KdV-type internal soliton theory were tested. Furthermore, a measurement technique of hydrodynamic load of internal waves was developed. By means of accurately measuring slight variations of internal wave forces exerted on a slender body in the tank, their interaction characteristics were determined. It is shown that through establishing the similarity between the model scale in the stratified fluid tank and the full scale in the numerical simulation the obtained measurement re- suits of internal wave forces are confirmed to be correct. 展开更多
关键词 internal solitary wave wave-maker stratified fluid slender body INTERACTION
原文传递
上一页 1 下一页 到第
使用帮助 返回顶部