一种能适应月相变化的月球图像中心提取算法   总被引：1，自引：0，他引：1  

蒲俊宇  郑勇  李崇辉  詹银虎  陈少杰  何东汉 《测绘科学技术学报》2017,(5):461-465

月球是夜间最亮的天体,测月导航可在云雾天气下有效弥补传统天文导航在夜间只能观测恒星的不足,扩大天文导航的可用范围。为实现测月导航,提出了一种能适应不同月相变化的月球敏感器图像月球中心提取算法。利用Sobel-Zernike矩算子对图像进行边缘检测,利用基于圆形性检测的搜索算法筛选月球边缘点并以此提取月球中心。经半物理仿真实验解算,该算法能够针对不同月相图像有效提取月球中心,中心提取的内符合平均精度为0.16像素,外符合平均精度为2.86″。由于在月球上观测地球也有"地相"变化,该算法同样适用于月球车地球敏感器图像中心提取。  相似文献   

世界毒品生产的地理分布及其空间扩散   总被引：2，自引：1，他引：2  

孙峰华 《世界地理研究》2002,11(3):105-111

本文首先阐述了毒品的内涵，揭示了毒品的非法生产和非法贸易给人类社会带来的严重恶果，探讨了世界毒品生产的地理分布及其新动向。着重分析了世界三大毒品生产区域“金三角”，“金新月”和“银三角”的毒品生产现状，以此基础上，描述了世界毒品的空间扩散。最后指出，由于多种原因，世界禁毒任重而道远。  相似文献   

月球地质结构及其岩石学特征   总被引：1，自引：0，他引：1  

郭迪江 Graig  JR 《地质科技情报》1995,14(4):29-32

简要介绍了美国ＮＡＳＡ阿波罗计划所获得的有关月球地质结构的一些新资料，结合笔者对月球岩石光片，薄片的镜下观察，简要介绍了月球岩石的岩石学特征，并讨论了有关月球的演化起源问题。  相似文献   

月中天与浙江中、北部沿海朔望高潮时间的探讨     

许幼明  朱志恩 《海洋湖沼通报》2000,(2):78-81

本文主要基于浙江中、北部沿海二十一个潮位站资料收集的基础上,分析和计算了水中天与各测站发生高潮的时间间隙,进一步探讨了１９９８年塑望时的高潮间隙。借古论今,从定性到定量论述了浙江中、北部沿海各测站朔望时发生高潮的时间,从而为从事海上作业的人员提供具有实用价值的图表作为参考依据。  相似文献   

Reexamination of the spawning migration of Anguilla dieffenbachii in relation to water temperature and the lunar cycle     

《新西兰海洋与淡水研究杂志》2012,46(1):131-147

ABSTRACT

The oceanic spawning migration of female Anguilla dieffenbachii eels was previously studied using pop-up satellite transmitting tags (PSAT). The swimming depths and experienced-temperature data of 3 eels released in May 2006 were re-examined in relation to water temperature data, and also lunar cycle and regional hydrography as these latter aspects were not considered in the original study. Eel 2 and Eel 3 initially experienced lower water temperature above 600?m, suggesting they remained south of the subtropical-convergence front longer than Eel 1. Their experienced nighttime minimum depths showed linear relationships with the lunar cycle, because they swam shallower during new moon than during full moon. The eels experienced narrow deep-day temperature ranges at a wide range of depths compared to experiencing narrow shallow-night depth ranges where temperatures varied more widely, indicating that several different factors determine their day and night depth ranges.  相似文献   

Xenon isotope systematics, giant impacts, and mantle degassing on the early Earth     

Robert O. Pepin  Don Porcelli   《Earth and Planetary Science Letters》2006,250(3-4):470-485

The relationships between the major terrestrial volatile reservoirs are explored by resolving the different components in the Xe isotope signatures displayed by Harding County and Caroline CO₂ well gases and mid-ocean ridge basalts (MORB). For the nonradiogenic isotopes, there is evidence for the presence of components enhanced in the light ^124–128Xe/¹³⁰Xe isotope ratios with respect to the terrestrial atmosphere. The observation of small but significant elevations of these ratios in the MORB and well gas reservoirs means that the nonradiogenic Xe in the atmosphere cannot be the primordial base composition in the mantle. The presence of solar-like components, for example U–Xe, solar wind Xe, or both, is required.For radiogenic Xe generated by decay of short-lived ¹²⁹I and ²⁴⁴Pu, the ¹²⁹Xe_rad/¹³⁶Xe₂₄₄ ratios are indistinguishable in MORB and the present atmosphere, but differ by approximately an order of magnitude between the MORB and well gas sources. Correspondence of these ratios in MORB and the atmosphere within the relatively small uncertainties found here significantly constrains possible mantle degassing scenarios. The widely held view that substantial early degassing of ¹²⁹Xe_rad and ¹³⁶Xe₂₄₄ from the MORB reservoir to the atmosphere occurred and then ended while ¹²⁹I was still alive is incompatible with equal ratios, and so is not a possible explanation for observed elevations of ¹²⁹Xe/¹³⁰Xe in MORB compared to the atmosphere. Detailed degassing chronologies constructed from the isotopic composition of MORB Xe are therefore questionable.If the present estimate for the uranium/iodine ratio in the bulk silicate Earth (BSE) is taken to apply to all interior volatile reservoirs, the differing ¹²⁹Xe_rad/¹³⁶Xe₂₄₄ ratios in MORB and the well gases point to two episodes of major mantle degassing, presumably driven by giant impacts, respectively  20–50 Ma and  95–100 Ma after solar system origin assuming current values for initial ¹²⁹I/¹²⁷I and ²⁴⁴Pu/²³⁸U. The earlier time range, for degassing of the well gas source, spans Hf–W calculations for the timing of a moon-forming impact. The second, later impact further outgassed the upper mantle and MORB source. A single event that degassed both the MORB and gas well reservoirs at the time of the moon-forming collision would be compatible with their distinct ¹²⁹Xe_rad/¹³⁶Xe₂₄₄ ratios only if the post-impact iodine abundance in the MORB reservoir was about an order of magnitude lower than current estimates. In either case, such late dates require large early losses of noble gases, so that initial inventories acquired throughout the Earth must have been substantially higher.The much larger ¹²⁹Xe_rad/¹³⁶Xe₂₄₄ ratio in the well gases compared to MORB requires that these two Xe components evolve from separate interior reservoirs that have been effectively isolated from each other for most of the age of the planet, but are now seen within the upper mantle. These reservoirs have maintained distinct Xe isotope signatures despite having similar Ne isotope compositions that reflect similar degassing histories. This suggests that the light noble gas and radiogenic Xe isotopes are decoupled, with separate long-term storage of the latter. However, without data on the extent of heterogeneities within the upper mantle, this conclusion cannot be easily reconciled with geophysical observations without significant re-evaluation of present noble gas models. Nevertheless the analytic evidence that two different values of ¹²⁹Xe_rad/¹³⁶Xe₂₄₄ exist in the Earth appears firm. If the uranium/iodine ratio is approximately uniform throughout the BSE, it follows that degassing events from separate reservoirs at different times are recorded in the currently available terrestrial Xe data.  相似文献   

Analysis of resonant curves and phase portrait in the earth–moon system by using its unperturbed solution and earth’s equatorial ellipticity     

《New Astronomy》2022

In this research article, we have investigated resonant curves due to the rate of change of earth’s equatorial ellipticity parameter $\left(\dot{\gamma }\right)$, steady-state value of the angular velocity of the moon $\left({\dot{\theta }}_{mo}\right)$, and angular velocity of barycenter $\left(\dot{{\alpha }_0}\right)$ in the Earth-Moon system. Equations of motion of the moon are determined in a spherical coordinate system with the help of the gravitational potential of the earth. By using the unperturbed solution, equations of motion of the moon reduced into the second-order differential equation. From the solution it is observed that resonance occurs due to the frequencies $\dot{\gamma }$, ${\dot{\theta }}_{m0}$, and $\dot{{\alpha }_0}$ at the resonant points ${\dot{\theta }}_{m0}=2\dot{\gamma }$, $3{\dot{\theta }}_{m0}=2\dot{\gamma }$, ${\dot{\theta }}_{m0}=\dot{\gamma }$, ${\dot{\theta }}_{m0}={\dot{\alpha }}_0$. Finally, we have analyzed the phase portrait and phase space by method of Poincaré section when the system is free from forces.  相似文献