科学卫星有效载荷EGSE平台的研究与应用

为提高科学卫星有效载荷地面测试的准确性和效率,分析了国内外现有卫星地面电测系统平台及其应用,设计并实现了一个基于CCSDS 660.0标准的通用EGSE综合开发平台.基于该平台分别设计并实现了空间用CCD相机的性能定标和星上科学数据处理单元(DPU)的功能验证实验.结果表明,该平台具有很好的通用性与可扩展性,能够适应载荷的子单元、子系统以及系统的测试配置要求.为国内EGSE通用平台的研制及科学卫星有效载荷EGSE平台化开发提供了参考.     

Palaeogeothermal response and record of the effusing of Emeishan basalts in the Sichuan basin

Thermal history of the Sichuan basin is reconstructed based on vitrinite reflectance from boreholes in the basin using a paleo-heat flow method.The results show that the Sichuan basin experienced a relatively low heat flow period in the Early Paleozoic,and an elevated paleo-heat flow,ranging 60-80 mW/m2 with a maximum as high as 100 mW/m2 around 259 Ma,from the beginning of the Late Paleozoic to the end of the early Permian,and a decreased paleo-heat flow from the late Permian to the late Triassic,and then ...     

High-resolution carbon isotope record for the Paleocene-Eocene thermal maximum from the Nanyang Basin,Central China

The Paleocene-Eocene thermal maximum (PETM) was a transient episode of global warming, associated with massive atmospheric greenhouse gas input that occurred at the Paleocene/Eocene boundary. Biostratigraphic and isotope stratigraphic studies indicate that the PETM event is well documented in the marl deposits of the Yuhuangding section in the Nanyang Basin, Central China, with a carbon isotope negative excursion of ~6.1‰ within 19-m-thick marl deposits. This is the highest resolution record of the PETM so far found in the world. The PETM event was triggered within 2-cm-thick marl sediments, with a decrease of δ¹³C (stable carbon isotope ratio) from –3.2‰ to –5.2‰, suggesting a massive methane hydrate release for a transient period that was possibly caused by a catastrophic event. A comparison between marine and terrestrial records indicates a “Three-Phase Model” for the PETM event. Initially there is a rapid negative excursion in the δ¹³C record, followed by a slowly decreasing trend, and then a gradual positive recovery, corresponding respectively to a rapid dissociation of oceanic methane hydrate, followed by a slow release of methane and then the consumption of the released methane.     

Yaw attitude of eclipsing GPS satellites and its impact on solutions from precise point positioning

During the period when a GPS satellite, the Earth and the Sun are approximately collinear, the phenomenon of eclipsing the satellite occurs, when the satellite yaw attitude deviates from its nominal case, i.e. the body X-axis cannot point towards the Sun for Block II&IIA or away from it for Block IIR satellites. The yaw attitude of the eclipsing satellites has a significant influence on both the satellite clock estimation at each International GNSS Service (IGS) Analysis Center (AC) and for users of the precise point positioning (PPP) implementations. It is known that, during the eclipsing periods, inconsistent yaw attitude models among the ACs will contribute to the errors of the IGS combined clock products. As for the PPP user, the influence of the eclipsing satellite is two-fold. First, as the satellite clocks are always kept fixed during PPP implementation, the above-mentioned problematic IGS clocks will inevitably be passed on to the PPP estimates. Second, the improper yaw attitude modeling of the eclipsing satellite will cause a correction bias exceeding 1 dm for the two kinds of attitude-related systematic errors, namely the phase wind-up and satellite antenna phase center offset, which will further deteriorate the accuracy of the PPP solutions. A yaw attitude model is introduced in this paper with the aim of improving the reliability of PPP solutions during the satellite eclipsing period.     

Estimating possible impact of human activity on the warm season temperature in Beijing since the industrial era

Global surface temperature shows an increasing trend over the past 100 years.Anthropogenic and natural factors have been invoked to explain this warming, but their relative contribution and the spatial variability remain controversial.Based on a 2650-year temperature record from a stalagmite near Beijing, we explore the possible impacts of human activity on the warm season temperature in Beijing since the industrial era using the method of singular spectrum analysis (SSA).The results suggest that the warm s...     

First observation of mesospheric and thermospheric winds by a Fabry-Perot interferometer in China

A Fabry-Perot interferometer, funded by the Meridian Project in China, was deployed at the Xinglong station (40.2°N,117.4°E) of the National Astronomical Observatories in Hebei Province, China. The instrument has been operating since April 2010, measuring mesospheric and thermospheric winds. The first observational data of winds at three heights in the mesosphere and thermosphere were analyzed, demonstrating the capacity of this instrument to aid basic scientific research. The wavelengths of three airglow emissions were OH892.0, OI 557.7, and OI 630.0 nm, which corresponded to heights of 87, 98, and 250 km, respectively. Three 38-day data sets of horizontal winds, from April 5, 2010 to May 12, 2010, show clear day-to-day variations at the same height. The minimum and maximum meridional winds at heights of 87, 98, and 250 km were –16.5 to 8.7 m/s, –24.4 to 15.9 m/s, and –43.6 to 1.5 m/s. Measurements of zonal winds were –5.4 to 7.6 m/s, 2.3 to 23.0 m/s, and –22.6 to 49.3 m/s. The average data from the observations was consistent with the data from HWM93. The wind data at heights of 87 and 98 km suggest a semi-diurnal oscillation, clearly consistent with HWM93 results. Conversely there was a clear discrepancy between the observations and the model at 250 km. In general, this Fabry-Perot interferometer is a useful ground-based instrument for measuring mesospheric and thermospheric winds at middle latitudes.     

Carbon isotopic compositions of pore and matrix carbonates in carbonate nodules, and origin of carbonate formation

Carbon isotopes of pedogenic carbonate are often used to study paleoenvironments, but the existence of detrital carbonate changes the carbon isotopic composition. To develop an experimental method to determine existence of detrital carbonate in carbonate nodules, and to avoid it during isotope analysis, 23 pedogenic carbonate nodules in Miocene loess from the Loess Plateau of China were studied through micromorphology and carbon isotope analysis. The difference in carbon isotopic composition between matrix carbonate (B) and pore carbonate (A) (δ¹³C_(B-A)) ranges from 0.27‰ to 0.44‰ in nodules containing detrital carbonate and –0.16‰ to 0.13‰ in nodules where detrital carbonate is absent. The latter is within measurement error, but the former is beyond it. Here we propose an isotopic approach to determine if nodules contain detrital carbonate: if δ¹³C_(B-A) is within the measurement error, the nodules do not contain detrital carbonate, and vice versa. We suggest that it is better to analyze pore carbonate instead of matrix carbonate when using carbon isotope of carbonate nodules to reconstruct paleoenvironments.     

Temperature variability since A.D. 1837 inferred from tree-ring maximum density of <Emphasis Type="Italic">Abies fabri</Emphasis> on Gongga Mountain,China

Two tree-ring MXD (maximum latewood density) chronologies of Abies fabri were developed from the eastern slopes of Gongga Mountain, and a regional chronology (RC) was established based on the two MXD chronologies. There were significant positive correlations between the three MXD chronologies and August–September temperature, and the RC had the highest correlation (r=0.733, n=48, P<0.001) with mean August–September temperature. Based on growth-climate analyses, we reconstructed mean August–September temperature during the past 171 years for the study area. The reconstruction explained 53.5% of the instrumental temperature variance during the period 1960–2007 (F=52.8, R²_adj =52.4%). In the past 171 years, there were 22 very warm years and 23 very cold years, four cold periods (1837–1842, 1884–1891, 1899–1905 and 1984–1989) and three warm periods (1966–1973, 1916–1924 and 1876–1881). Our reconstruction was validated by other tree ring-based temperature reconstructions from the surrounding area and documented climate disaster events.     

放大-转发OFDMA中继系统多业务资源分配方案

针对独立功率限制、放大–转发OFDMA中继系统的多业务资源分配问题,提出一种在满足实时用户要求前提下,非实时用户数据速率最大化的资源分配方案. 根据业务的不同将问题分解为实时和非实时用户的资源分配两个子问题. 对于实时用户的资源分配,利用Lagrange方法计算. 对于非实时用户的资源分配,每个子载波分配给信道条件最好的用户,针对功率分配提出两步功率分配方法. 首先按照总功率约束进行初始功率分配,然后对各子载波的功率进行调整以满足独立功率约束. 对于子载波分配提出一种低复杂度的子载波集合分配算法. 仿真结果表明,该方案在满足多业务用户要求的同时使系统性能得到优化,且计算复杂度低.     

家庭基站网络分布式资源分配算法

针对具有自组织特性的家庭基站(home eNodeB, HeNB) 网络,提出了一种分布式资源分配算法. 该方法首先使HeNB 根据网络状况选择分量载波,而当接收到邻小区的重选请求时,可以重新选择备用载波列表中的载波,释放当前使用的载波给邻居使用,从而提高HeNB 获得可行载波的可能性. 使HeNB 根据优化目标函数自主地进行功率优化,以减少小区间干扰并提高系统容量. 通过蒙特卡罗方法分析该算法的性能,仿真结果表明：该资源分配算法能够提高用户的平均吞吐量并降低中断概率.