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231.
文章研究一类时滞大系统 ,内部具有非线性扰动 ,同时带有时滞关联和非线性关联项。考虑到大系统的状态部分可测量 ,设计了输出反馈控制器 ,来使系统分散输出鲁棒镇定 ,仿真的结果证明了结论的有效性。 相似文献
232.
全罗盘画面反走样算法的研究和实现 总被引:8,自引:1,他引:7
在一定分辨率的屏幕上,用常规画线函数生成的静态罗盘刻度线呈现出锯齿形失真,特别当罗盘作动态旋转时,刻度线扭曲,变形,为消除这一现象,笔者根据线条的反走样原理,提出了一种实用算法,消除了静态的锯齿形失真,并从CRT屏幕上仿真的动态效果来看,罗盘刻度线旋转时不扭曲,不变形,实验证明,在光栅图形显示器中,应用此算法可消除走样,大大增强罗盘刻度线动态显示效果。 相似文献
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The problem of global geoid determination is usually solved using satellite altimetry data on the oceans, together with an
oceanographic model of sea surface topography, and gravity anomaly data on the continents. Such data, however, enable to obtain
only potential differences with respect to a reference surface whose absolute potential is unknown. This situation suggests
to modify the classical mixed boundary-value problem of physical geodesy by inserting into the boundary conditions an unknown
additive constant, that must be determined by imposing a suitable additional constraint. Yet, such formulation of the boundary-value
problem, from the point of view of its mathematical properties, is not unconditionally well-posed, and, furthermore, does
not reflect faithfully the available physical model, as the present knowledge of ocean circulation does not allow to connect
along coastlines the reference surfaces defined on the oceans and on the continents. The introduction of two different unknown
additive constants, one for the oceans and one for the earth, to be determined by imposing two additional constraints, gives
rise to a more faithful picture of the present physical knowledge, and, at the same time, to a new well-posed formulation
of the boundary-value problem.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
235.
星光折射天文导航是一种重要的地球卫星自主导航方式,量测量是影响其导航精度的重要因素。在地球卫星星光折射导航中,折射视高度、星光折射角、折射星像素坐标(折射星矢量)是3种常用的量测量,结合星光折射导航的基本原理重点介绍了这3种量测量的获取方法和量测模型,通过仿真和可观性分析比较了相同条件下3种量测量的导航性能。仿真结果表明,由于折射星像素坐标可以同时反映星光折射的大小和方向可观性高,而星光折射角和折射视高度仅能反映星光折射的大小,无法反映其方向可观性低,因此折射星像素坐标的导航性能优于星光折射角和折射视高度。此外,本文也对星敏感器精度、卫星轨道高度、星敏感器安装夹角3种因素对3种方法导航性能的影响进行了分析。 相似文献
236.
Effect of the seed perturbation amplitude on the equatorial spread F initiation during solar minimum
《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2023,71(1):255-267
The contribution of gravity wave (GW) to the initiation/development of spread F during a solar minimum year was investigated through the comparison of the observed precursory parameters and characteristics of the corresponding equatorial spread F (ESF) events. The ionospheric parameters were recorded at the magnetic equatorial station Sao Luis (2.3°S, 44°W, dip latitude 2°S) during March and October 2010. These data were used to estimate the influence of the relative gravity wave amplitude and the ambient ionospheric condition on the diurnal variation of the spread F initiation. The vertical velocity drift indicated a clear control and defines the threshold for the seasonal variability of the ESF occurrence. However, it was insufficient to solely determine or predict the day to day variation of ESF occurrence. Thus, few days with contrasting ambient ionospheric condition and magnitude of GW amplitude were analysed in order to investigate the role of the different precursory factors in the observed diurnal variation of the plasma irregularity development. The density scale length and gravity wave amplitude were shown to immensely contribute to the linear instability growth rate, especially during the days with a low post-sunset rise. Thus, the experimental observations have demonstrated the strong inter-dependence between the precursory factors and they have also highlighted the probable control of the ESF morphology. 相似文献
237.
238.
A.S. Laxmiprasad V.L.N. Sridhar Raja Surya Menon Adwaita Goswami M.V.H. Rao K.A. Lohar 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
A miniaturized in situ laser induced breakdown spectroscope-LIBS is one of the two lunar rover payloads to be flown in India’s next lunar mission Chandrayaan-2, with an objective to carry-out a precise qualitative and quantitative elemental analyses of lunar regolith at the proximity of the landing region. As per the imposed mission constraints and the executed design optimization studies, a compact and light-weight LIBS prototype model is developed at our premises. This paper mainly concerns with the estimation of theoretical aspects; especially on evaluation of elemental ablation parameters and signal-to-noise ratio (SNR) calculations for the designed instrument. Theoretical estimations and simulations yielded an incident laser power density of the order of 5 × 1010 W/cm2 on the target surface at a defined lens-to-surface distance (LTSD) of 200 mm and revealed an SNR > 100 for most of the elements under consideration. This paper also addresses the impact of LTSD variation on detection capability. The estimation of plasma-temperatures was carried out utilizing the emission spectra obtained under high vacuum environments employing the LIBS laboratory model. Experimental investigations and the performed theoretical estimations asserted the successful operation of the configured LIBS instrument for in situ elemental analyses on lunar surface. 相似文献
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240.
考虑到多学科优化设计(multidisciplinary design optimization,MDO)的效率和精度,充分发挥当前涡轮叶片各种精度分析方法的优势,提出了涡轮叶片的多重精度多学科优化设计策略.利用协同优化策略在学科解耦和协调方面的能力,引入包括流固紧密耦合分析、流固热松散耦合分析和近似方程在内的涡轮叶片设计中的多种精度模型,结合两点式标度函数和优化过程阶段性收敛后更新,改进可变复杂度建模方法处理多重精度模型的能力,研究结果表明:仅调用9次高精度流固耦合分析就能确保涡轮带冠叶片多学科优化设计的效率和精度. 相似文献