Precise orbit determination for the GRACE mission using only GPS data

The GRACE (gravity recovery and climate experiment) satellites, launched in March 2002, are each equipped with a BlackJack GPS onboard receiver for precise orbit determination and gravity field recovery. Since launch, there have been significant improvements in the background force models used for satellite orbit determination, most notably the model for the geopotential. This has resulted in significant improvements to orbit accuracy for very low altitude satellites. The purpose of this paper is to investigate how well the orbits of the GRACE satellites (about 470 km in altitude) can currently be determined using only GPS data and based on the current models and methods. The orbit accuracy is assessed using a number of tests, which include analysis of orbit fits, orbit overlaps, orbit connecting points, satellite Laser ranging residuals and K-band ranging (KBR) residuals. We show that 1-cm radial orbit accuracy for the GRACE satellites has probably been achieved. These precise GRACE orbits can be used for such purposes as improving gravity recovery from the GRACE KBR data and for atmospheric profiling, and they demonstrate the quality of the background force models being used.     

几何精度因子对GRACE卫星几何轨道精度影响分析

分析了GDOP值与GRACE卫星几何轨道精度之间的关系,发现定轨精度较差的历元其GDOP值普遍较大甚至异常,进一步研究发现GDOP值异常现象是因剔除个别含有粗差的卫星而导致的,进而通过设置GDOP值阈值的方式剔除发生GDOP值异常的历元。实验结果表明,GDOP值阈值设置为50,将大于该阈值的历元剔除,能够有效抑制个别历元精度较差的情况,最终的RMS在地固系X,Y,Z3个方向分别为0.029m,0.043m,0.029m,实现了几何法厘米级精密定轨的目标。     

盐胁迫下梭梭幼苗膜脂过氧化和保护酶活性

使用0、50、100、200、350、500 mmol/L NaCl处理梭梭幼苗,分三次取样,并测其相应指标,结果表明梭梭幼苗细胞膜透性在10天时保持稳定;当胁迫到20天、30天时,同化枝膜透性随盐浓度的增加及胁迫时间的延长逐渐增加.整个试验过程中,丙二醛含量逐渐增加,但前期增加幅度不大,后期梭梭幼苗同化枝的丙二醛含量在NaCl胁迫30天时为2.569 μmol·g-1.SOD和POD活性在整个试验过程中相对于对照而言整体呈增加趋势,但在前期增加得较快,后期较慢.CAT活性在整个过程中则一直呈增加趋势.     

96孔酶标板法测定对虾血淋巴的过氧化物酶相对活性的初步研究

过过氧氧化化物物酶酶（（ＰＰＯＯＤＤ））广广泛泛存存在在于于真真核核生生物物体体内内 ,,在在清清除除自自由由基基 ((ＯＯ - - )) ,,防防止止生生物物分分子子损损伤伤方方面面有有十十分分重重要要的的作作用用。。因因此此通通过过测测量量对对虾虾血血淋淋巴巴的的过过氧氧化化物物酶酶活活性性大大小小可可以以推推测测对对虾虾的的生生理理状状态态 ,,甚甚至至可可用用其其辅辅助助检检测测或或诊诊断断对对虾虾病病害害的的生生理理指指标标。。丁丁美美丽丽等等采采用用改改良良的的连连苯苯三三酚酚自自氧化化法法测测定定中…     

An Ensemble-Based Three-Dimensional Variational Assimilation Method for Land Data Assimilation

Land surface models are often highly nonlinear with model physics that contain parameterized discontinuities. These model attributes severely limit the application of advanced variational data assimilation methods into land data assimilation. The ensemble Kalman filter （EnKF） has been widely employed for land data assimilation because of its simple conceptual formulation and relative ease of implementation. An updated ensemble-based three-dimensional variational assimilation （En3-DVar） method is proposed for land data assimilation This new method incorporates Monte Carlo sampling strategies into the 3-D variational data assimilation framework. The proper orthogonal decomposition （POD） technique is used to efficiently approximate a forecast ensemble produced by the Monte Carlo method in a 3-D space that uses a set of base vectors that span the ensemble. The data assimilation process is thus significantly simplified. Our assimilation experiments indicate that this new En3-DVar method considerably outperforms the EnKF method by increasing assimilation precision. Furthermore, computational costs for the new En3-DVar method are much lower than for the EnKF method.     

用于控制高柔结构振动的POD技术

本文通过模型试验和理论分析研究了一种控制高柔结构振动的新方法－－－ＰＯＤ（摆、油阻尼器）减振系统。文中详细分析了其减震原理,并提出了与试验结果相吻合的三角形非缄性滞回模型。试验结果表明,在接近调谐状态下ＰＯＤ法可减振４８％。数据计算的结果也表明,ＰＯＤ不仅减振效果比ＴＭＤ高得多,而且有效频带也宽得多。ＰＯＤ系统具有造价低、易安装、占用空间小、免维护等优点,可用于风可于震等荷载引起的电视塔、悬索桥塔     

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基于随机森林算法的广州白云机场终端区雷暴潜势预报

利用2014-2015年夏季雷达资料获取雷暴发生有无数据, 计算探空资料的对流指数与雷暴发生有无数据的灰色关联度, 发现雷暴产生跟抬升凝结高度气压、850~700 hPa的温度和露点温度、风切变的关系最紧密。接着建立广州白云机场终端区内3类区域(离塔台中心8 km、50 km、100 km)的12小时随机森林分类模型, 对不同区域的雷暴潜势进行预报和评估, 发现终端区区域面积越大, 雷暴发生样本比例越高, 临界成功指数CSI、预报准确率AF、探测概率POD越来越高, 虚假报警率FAR越来越低, 表明预报出来的准确率越来越高。离塔台中心50 km和100 km区域的预报准确率AF和探测概率POD超过70%, 对航空重要天气MDRS通报业务有指示作用。同时袋外错误率均低于1/3, 随机森林算法的泛化性能好。      

Acute toxicity of organochlorine insecticide endosulfan to the giant freshwater prawn Macrobrochium rosenbergii

Endosulfan, an organochlorine pesticide, is highly toxic and effective at controlling pests in agriculture, horticulture, and public health programs. In this study, static bioassays were used to evaluate the toxicity of endosulfan to freshwater prawns( Macrobrachium rosenbergii) of various lengths(1.5±0.03,4±0.08, and 7±0.06 cm). Additionally, the activities of peroxidase(POD), acid phosphatase(ACP),alkaline phosphatase, acetylcholinesterase(AChE), and Na + /K +-ATPase were analyzed to refl ect the effects of endosulfan exposure. The 96 h LC 50 of endosulfan for prawns 1.5, 4, and 7 cm long were 1.86, 4.53,and 6.09μg/L, respectively, improved tolerance to endosulfan with growth. The POD activities of test organisms exposed to low concentrations of endosulfan were inhibited, indicating the presence of oxygen damaged tissue. Moreover, a notable decrease in AChE activity was observed due to overstimulation of neurotransmission, which might result in abnormal behavior. The effect caused by endosulfan on phosphatase production in the hepatopancreas of prawns 1.5, 4, and 7 cm long was different because the ability of nonspecifi c immune regulation increased with growth. The 96 h LC 50 values obtained in this study could be used in the formulation of water-quality criteria in China. Moreover, the changes in enzymes activities of M. rosenbergii under stress of endosulfan could be applied in the establishment of early warning indicators for bio-safety.     

Effect of a polybrominated diphenyl ether congener (BDE-47) on growth and antioxidative enzymes of two mangrove plant species, Kandelia obovata and Avicennia marina, in South China

The effects of BDE-47 on the growth and antioxidative responses of the seedlings of Kandelia obovata (Ko) and Avicennia marina (Am) were compared in an 8-week hydroponic culture spiked with different levels of BDE-47, 0.1, 1, 5 and 10 mg l⁻¹. The two highest BDE-47 levels significantly suppressed the growth and increased the activities of three antioxidative enzymes, superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), of Ko in week 1. However, SOD and POD activities at high levels of BDE-47 became lower than the control in week 8. On the contrary, growth of Am was not affected at all contamination levels, and the activities of three enzymes were enhanced by BDE-47 in weeks 1 and 4, but such stimulatory effect became insignificant in week 8. Avicennia was more tolerant to BDE-47 toxicity than Kandelia, as its antioxidative enzymes could better counter-balance the oxidative stress caused by BDE-47.