排序方式: 共有306条查询结果,搜索用时 15 毫秒
241.
242.
Measurements of photosynthetically active radiation(PAR),which are indispensable for simulating plant growth and productivity,are generally very scarce.This study aimed to compare two extrapolation and one interpolation methods for estimating daily PAR reaching the earth surface within the Poyang Lake national nature reserve,China.The daily global solar radiation records at Nanchang meteorological station and daily sunshine duration measurements at nine meteorological stations around Poyang Lake were obtain... 相似文献
243.
244.
本文对上海市规划和国土资源行业指挥监测中心的总体情况、系统框架、运行环境、特色功能等内容进行了简要的介绍,对指挥监测中心系统建设中的涉及数据仓库建设及更新机制、车辆实时指挥调度、海量数据存储、快速浏览展示等实现方式进行了详细的介绍。 相似文献
245.
246.
WANG Siyi WANG Qingyan .College of Construction Engineering Jilin University Changchun China .Key Laboratory of Underground Information Detecting Technology Education Ministry China 《东北亚地学研究》2009,12(1):22-27
This study presented the specified steps of comprehensively analyzing the hydraulic-driven hammer system with the application of the Virtual Prototype Technology. By comparing the simulation results with experimental phenomena and data, the correctness of simulation analysis conclusion is verified. Meanwhile, by -means of its perfect visualization, the internal work process which can not be seen before is simulated. The mechanism of some abnormal phenomena encountered during the experiment is explained. 相似文献
247.
ZHOU Xianchun LIN Yihua WANG Hui MO Jiaqi College of Electronic Information Engineering Nanjing University of information Science Technology Nanjing China Division of Computational Science E-Institutes of Shanghai Universities at SJTU Shanghai China State Key Laboratory of Numerical Modeling for Atmospheric Sciences Geophysical Fluid Dynamics 《海洋学报(英文版)》2009,(3)
A class of coupled system of the El Nino/La Nina-Southern Oscillation (ENSO) mechanism is studied. Using the perturbed theory, the asymptotic expansions of the solution for ENSO model are obtained and the asymptotic behavior of solution for corresponding problem is considered. 相似文献
248.
A deep-sea Manned Submarine Vehicle (MSV) is usually required to move at a low forward speed and a low rotational speed when it executes investigation tasks. In this condition, the motion is in large drift angles, and the maneuverability hydrodynamic forces cannot be expressed properly in the conventional mathematical model of submersible motion. In this paper, firstly, a general equation of MSV with six-freedom motion is presented, and the numerical simulation of descent/ascent motion and helix motion is c... 相似文献
249.
Feedback and Feedforward Optimal Control for Offshore Jacket Platforms 总被引:18,自引:0,他引:18
The optimal control is investigated for linear systems affected by external harmonic disturbance and applied to vibration control systems of offshore steel jacket platforms. The wave-induced force is the dominant load that offshore structures are subjected to, and it can be taken as harmonic excitation for the system. The iineafized Morison equation is employed to estimate the wave loading. The main result concerns the existence and design of a realizable optimal regulator, which is proposed to damp the forced oscillation in an optimal fashion. For demonstration of the effectiveness of the control scheme, the platform performance is investigated for different wave states. The simulations axe based on the tuned mass damper (TMD) and the active mass damper (AMD) control devices. It is demonstrated that the control scheme is useful in reducing the displacement response of jacket-type offshore platforms. 相似文献
250.
Zheng Zhizhen Robert K. Vincent Shen Ping and Yang XuanhuiCenter for Seismic Data Information CSB Beijing China Bowling Green State University Ohio - USA Institute of Geophysics CSB Beijing China 《中国地震研究》1999,(4)
In this paper, the observation networks of precursory geosound and observation instruments are introduced first. Then it is mentioned, in particular, that audible precursory geosound was instrumentally recorded for the first time. The following section discussed the relation between the geosound and earthquake. Finally, the Nucleation time in earthquake preparation process is discussed. 相似文献