Low multipath antennas for GNSS-based attitude determination systems applied to high-altitude platforms   总被引：1，自引：1，他引：0  

Luigi Boccia  Pasquale Pace  Giandomenico Amendola  Giuseppe Di Massa 《GPS Solutions》2008,12(3):163-171

High-altitude platforms (HAPs) are a flexible and attractive technology for providing innovative wireless services. These aerial platforms can be successfully employed for mobile or broadband communications and for disaster monitoring or response. However, one of the open issues is whether HAP stations can provide reliable services without temporal outages owing to stratospheric winds that can cause positional and attitude instabilities thus affecting the communication system operation. To counteract this issue, one possible solution is to use reconfigurable antennas whose pointing direction can be adjusted depending on the platform spatial orientation. However, this would require real-time three-axial attitude data. As a possible solution, this paper will review the potential of GNSS-based attitude determination systems with reference to HAP stations. In particular, it will be shown how the use of a particular class of low multipath and lightweight antennas can provide a high degree of accuracy without altering the avionic ballast.  相似文献   

Evidence of magmatic CO2-rich fluids in peraluminous graphite-bearing leucogranites from Deep Freeze Range (northern Victoria Land,Antarctica)     

Maria Luce Frezzotti  Gianfranco Di Vincenzo  Claudio Ghezzo  Ernst A. J. Burke 《Contributions to Mineralogy and Petrology》1994,117(2):111-123

Fine-grained peraluminous synkinematic leuco-monzogranites (SKG), of Cambro-Ordovician age, occur as veins and sills (up to 20–30 m thick) in the Deep Freeze Range, within the medium to high-grade metamorphics of the Wilson Terrane. Secondary fibrolite + graphite intergrowths occur in feldspars and subordinately in quartz. Four main solid and fluid inclusion populations are observed: primary mixed CO₂+H₂O inclusions + Al₂SiO₅ ± brines in garnet (type 1); early CO₂-rich inclusions (± brines) in quartz (type 2); early CO₂+CH₄ (up to 4 mol%)±H₂O inclusions + graphite + fibrolite in quartz (type 3); late CH₄+CO₂+N₂ inclusions and H₂O inclusions in quartz (type 4). Densities of type 1 inclusions are consistent with the crystallization conditions of SKG (750°C and 3 kbar). The other types are post-magmatic: densities of type 2 and 3 inclusions suggest isobaric cooling at high temperature (700–550°C). Type 4 inclusions were trapped below 500°C. The SKG crystallized from a magma that was at some stage vapour-saturated; fluids were CO₂-rich, possibly with immiscible brines. CO₂-rich fluids (±brines) characterize the transition from magmatic to post-magmatic stages; progressive isobaric cooling (T<670°C) led to a continuous decrease off _{O 2} can entering in the graphite stability field; at the same time, the feldspars reacted with CO₂-rich fluids to give secondary fibrolite + graphite. Decrease ofT andf _{O 2} can explain the progressive variation in the fluid composition from CO₂-rich to CH₄ and water dominated in a closed system (in situ evolution). The presence of N₂ the late stages indicates interaction with external metamorphic fluids.Contribution within the network Hydrothermal/metamorphic water-rock interactions in crystalline rocks: a multidisciplinary approach on paleofluid analysis. CEC program: Human Capital and Mobility  相似文献   

Far-infrared observations of main sequence stars surrounded by dust shells     

P. M. Harvey  B. Smith  J. Di Francesco 《Astrophysics and Space Science》1995,224(1-2):475-476

We present 50 and 100µm photometry and size information for several main sequence stars surrounded by dust shells. The observations from NASA's Kuiper Airborne Observatory include the Vega-like stars, Beta Pic, Fomalhaut, as well as four stars suggested by Walker and Wolstencroft to belong possibly to the same class. The results of our observations are best interpreted as upper limits to the far-infrared sizes of the dust clouds around all of the stars except Fomalhaut and Beta Pic. We have also fit simple, optically thin models to the Beta Pic data to explore the range of shell parameters consistent with our limits and with previous observations.  相似文献   

Observation of MKN 501 at gamma-ray energies     

L. Bassani  R. C. Butler  A. J. Dean  G. Di Cocco  A. Della Ventura  F. Perotti  G. Villa 《Astrophysics and Space Science》1982,82(2):311-316

During a balloon flight in September 1979 of the MISO low-energy -ray telescope, the BL Lac-object MkN 501 was studied in the hard X-ray range above 30 keV and in the low energy -ray range up to 19 MeV. No statistically significant X- and -ray fluxes were detected. The implications of the upper limits obtained are discussed in the light of the relativistic jet theories recently proposed.  相似文献   

Response to the comment by V. Neck on “Hydrolysis of neptunium(V) at variable temperatures (10-85 °C)”, Geochimica et Cosmochimica Acta 68, 4821-4830     

Linfeng Rao  Thandankorai G. Srinivasan  PierLuigi Zanonato  Plinio Di Bernardo 《Geochimica et cosmochimica acta》2006,70(17):4556-4562

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松溪县域城镇体系发展研究     

翁清光林皆敏  伍世代白晓 《福建地理》2006,21(2):20-22,27

城镇体系建设是当今加快城市化进程的重要组成部分。本文通过对松溪县域城镇现状的调查,从城镇体系的等级规模结构、空间布局结构、职能结构3个方面剖析其发展中存在的一些问题。从建设社会主义新农村、改善人居环境的角度出发,提出相应的发展思路和建议,为松溪县“十一五”期间制定城镇发展战略提供一定的参考。  相似文献   

内蒙古西辽河流域特种玉米品种特性及气候区划   总被引：3，自引：0，他引：3  

白美兰刘兴汉  邸瑞琦杨丽桃 冯晓晶 《气象科技》2005,33(5):437-441

基于玉米本身的特性和用途的不同,将玉米分为高油型玉米、高淀粉型玉米、高赖氨酸型玉米和甜玉米四大类型.根据每种玉米品种对气候条件、土壤类型、地形特征等的不同需求,以通辽地区作为内蒙古东部西辽河流域玉米主产区的示范区,提出了特种玉米的区划指标,并利用GIS技术进行适宜种植区域划分.内蒙古通辽地区大部分农区适宜种植特种玉米,最适宜区、适宜区基本上均位于通辽南部和中部农业区.  相似文献   

K 近邻非参数回归概率预报技术及其应用   总被引：7，自引：1，他引：7       下载免费PDF全文

翟宇梅赵瑞星  肖仁春王力维 《应用气象学报》2005,16(4):453-460

针对参数回归技术制作概率预报存在拟合好、但预报结果不稳定的现象, 提出了用K近邻非参数回归技术制作概率预报的新途径。K 近邻非参数回归技术包括历史样本数据库、近邻子集生成和优化以及预报量估计4 个主要部分。利用该技术进行了单要素概率预报(主要包括云量和降水)和多维联合概率预报(降水、总云量、风速和气温)试验, 并对试验结果进行了检验。实例研究结果表明:该文所给出的计算方案预报稳定性好, 准确率较高,具有良好的业务应用价值。  相似文献   

地震作用下的灰坝液化特征及其动力稳定性分析--以安阳电厂为例   总被引：1，自引：0，他引：1  

李永乐  陈宇  彭成山  刘宪亮 《地质科技情报》2002,21(1):83-86

根据安阳电厂灰坝岩土工程性质及其动力学特性,建立了适合灰坝工程的动力分析模型并采用有限元法进行了动力分析.在此基础上,在不同工况条件下对灰坝进行了抗液化安全评价及抗震稳定性分析.研究表明,在不设碎石桩、无排渗体条件下,粉煤灰子坝的抗液化安全系数Ks＜1.25,将发生液化;在设碎石桩、有排渗体条件下,粉煤灰子坝的抗液化安全系数明显提高,Ks≥1.25,不会发生液化.抗震稳定性分析表明,在上述两种工况条件下灰坝是稳定的.  相似文献   

河南省洛阳—三门峡铝土矿地质特征及其勘查开发前景   总被引：8，自引：0，他引：8       下载免费PDF全文

陈全树  何文平  周迪 《地质找矿论丛》2002,17(4):252-256,270

河南省洛阳-三门峡的铝土矿，是赋存于中石炭统本溪组的一水硬铝石型沉积铝土矿。本区不仅蕴藏量多，而且有相当数量的富铝土矿，勘查开发潜力大，前景广阔。  相似文献