三维航标监测与管理系统的设计与实现

设计了三维航标监测与管理系统的整体框架和功能结构,研究了其涉及的若干关键技术,开发实现了系统功能.     

Searching for tidal tails – investigating galaxy harassment

Galaxy harassment has been proposed as a physical process that morphologically transforms low surface density disc galaxies into dwarf elliptical galaxies in clusters. It has been used to link the observed very different morphology of distant cluster galaxies (relatively more blue galaxies with 'disturbed' morphologies) with the relatively large numbers of dwarf elliptical galaxies found in nearby clusters. One prediction of the harassment model is that the remnant galaxies should lie on low surface brightness tidal streams or arcs. We demonstrate in this paper that we have an analysis method that is sensitive to the detection of arcs down to a surface brightness of 29 B μ and we then use this method to search for arcs around 46 Virgo cluster dwarf elliptical galaxies. We find no evidence for tidal streams or arcs and consequently no evidence for galaxy harassment as a viable explanation for the relatively large numbers of dwarf galaxies found in the Virgo cluster.     

The Morávka meteorite fall: 3. Meteoroid initial size,history, structure,and composition

Abstract— The properties and history of the parent meteoroid of the Morávka H5–6 ordinary chondrites have been studied by a combination of various methods. The pre‐atmospheric mass of the meteoroid was computed from fireball radiation, infrasound, seismic signal, and the content of noble gases in the meteorites. All methods gave consistent results. The best estimate of the pre‐atmospheric mass is 1500 ± 500 kg. The fireball integral bolometric luminous efficiency was 9%, and the acoustic efficiency was 0.14%. The meteoroid cosmic ray exposure age was determined to be (6.7 ± 1.0) × 10⁶ yr. The meteorite shows a clear deficit of helium, both ³He and ⁴He. This deficit can be explained by solar heating. Numerical backward integration of the meteoroid orbit (determined in a previous paper from video records of the fireball) shows that the perihelion distance was probably lower than 0.5 AU and possibly as low as 0.1 AU 5 Ma ago. The collision which excavated Morávka probably occurred while the parent body was on a near‐Earth orbit, as opposed to being confined entirely to the main asteroid belt. An overview of meteorite macroscopic properties, petrology, mineralogy, and chemical composition is given. The meteorites show all mineralogical features of H chondrites. The shock level is S2. Minor deviations from other H chondrites in abundances of trace elements La, Ce, Cs, and Rb were found. The ablation crust is enriched with siderophile elements.     

基于Erdas2013的Pleiades卫星影像区域网平差设计与实现

介绍了Pleiades卫星影像数据及基于Erdas 2013的Pleiades卫星影像应用的可行性和区域网平差技术,为该卫星影像应用于相关测绘工程提供了技术依据。     

Minimum control for spacecraft formations in a J2 perturbed environment

Large ΔV amounts are often required to maintain the relative geometry which is needed to implement a formation flying concept. A wise use of the orbital environment makes the orbit keeping phase easier, reducing the overall propellant consumption. A first important step in this direction is the selection of formation configurations and orbits which, while still satisfying the mission requirements, are less subject to perturbations resulting naturally in closed relative motion. Within this frame, a number of studies have been recently carried out in order to identify possible sets of invariant relative orbits under the effects of the Earth oblateness, a conservative force commonly referred to as J2 which is also the most important perturbation for Low Earth Orbit. These efforts clearly marked the difficulties connected with achieving genuine periodic relative motion under J2 effect, but they also showed the existence of a set of conditions on the orbital parameters which allow for quasi-periodic J2 trajectories. This paper presents these particular trajectories, by means of deeper theoretical explanations, showing the dependency of the shape of the relative configurations on the orbital inclination. Since the quasi-periodic trajectories cannot be written analytically, and moreover, they are very sensitive with respect to the initial conditions, difficulties arise when trying to exploit these paths as reference for the control of a formation. This paper proposes a novel approach to find, from the actual quasi periodic natural trajectories, minimal control periodic reference trajectories. Next, it evaluates quantitatively the amount of propellant which is needed to control a spacecraft formation along these paths. The choice of Hill’s classical circular projected configuration as a nominal trajectory is considered as a comparison, showing the clear advantages of the proposed guidance design, which assumes low-perturbed periodic reference orbits as nominal trajectories.     

Habitat suitability curves for benthic macroinvertebrates from a small New Zealand river

We developed habitat suitability curves (HSC) using generalised additive models (GAMs) for nine benthic macroinvertebrate taxa from a small New Zealand river for hydraulic-habitat modelling assessments of instream flow requirements. We included interaction terms between the primary variables (water depth, velocity, substrate) when significant, to address a longstanding criticism of univariate HSC. To date, only large-river univariate HSC have been available and these have been used in hydraulic-habitat applications on small rivers, despite doubt over the transferability of HSC between rivers of different size and type. We tested the outcome on the predicted abundance–flow relationship of applying the small-river habitat suitability GAMs versus large-river GAMs for two taxa on the same small river. We found the effects of flow allocation were overestimated by the large-river GAMs relative to the small-river GAMs. Further research to develop general HSC for categories of river size and type is needed to better inform hydraulic-habitat modelling applications.     

基于Wallis滤波器的异源遥感影像匀光方法

针对异源遥感影像由于辐射水平差异导致地物在相邻图像上亮度值存在差异的现象,分析了造成影像间色调差异的各种原因以及现有处理方法在进行影像间色彩平衡处理时存在的问题,实现了基于Wallis滤波器进行匀光的相关算法,并通过多组匀光实验取得了较好的色彩平衡效果。     

藏西北革吉县雄巴乡场镇冻土灾害特征及防治措施

近年来,藏西北革吉县雄巴乡场镇内的冻土灾害日趋严重,研究该区冻土灾害的特征、成因及危害,对制定相应的防灾减灾政策具有重要意义.从基本特征、成因条件、风险性及防治措施等方面对雄巴乡场镇的冻土灾害开展了综合研究,认为加剧该区冻土灾害的主要原因是全球气候变暖导致的降雨量增加和气温升高,使场镇内透水性差、不均匀分布的土体含水率...