The Orbital Evolution of Two Sounding Satellites and Analysis of the Accuracy of Orbit Determination

The satellites TC-1 and TC-2 are the two Chinese satellites with great elliptical orbits which are still in orbit around the earth at present. Since the launch the orbits of the two satellites have continuously evolved, which has a certain effect on the orbit determination and prediction precision. The regularities of the orbital evolution of the two sounding satellites are qualitatively and quantitatively analyzed. Under the current tracking mode the corresponding prediction precision of orbit determination is analyzed based on the different stages of the orbital evolution, thereby providing the basis for the adjustment of planning mode by the satellite application departments and the guarantee of normal satellite payload. Finally, the orbital lifetimes of the two satellites are predicted through the trend of the orbital evolution.     

电离层赤道异常两日振荡的数值模拟

近20年来,国外学者对电离层赤道异常问题的数值模拟研究未考虑到大气行星波对潮汐发电机电场的调制效应,因而不能解释赤道异常峰值的逐日变化.本文结果表明二日波对F_2区电子浓度的输运有很大影响.这一方法可以推广到赤道异常各种长周期行星波振荡的数值研究. 本文从非定常等离子体连续方程出发,建立包含行星波振荡对E×B漂移的调制效应的方程,并给出数值模拟的方法以及可与实际观测进行比较的结果.文中取二日波漂移振幅为U_p=0 m/s、5m/s、10m/s,而初位相分别为φ=0°、90°共四种情形进行了模拟,结果表明,二日波的调制可使赤道异常的时空分布以及异常峰值产生明显的逐日变化.在所选取的模型中,取U_p=5m/s,φ=0°所得到的f_0F_2t的二日分布特征与观测较吻合.而u_p约5m/s的变化能引起异常峰值f_0F_2约1-2MHz的起伏,而二天之内f_0F_2的二个峰值表现出约2-4MHz的起伏.     

随机森林模型在遥感水深反演中的应用

随着我国浅海测绘需求的日益增长,文中利用四波段的WorldView-2高分辨率遥感影像,选取我国南海西沙群岛中的甘泉岛和台湾南湾地区作为典型试验区,开展水深反演研究。引入随机森林算法构建了随机森林水深反演模型,并同常用的3种水深反演模型进行精度对比。结果表明,在甘泉岛和南湾地区随机森林模型反演的水深值和真实水深值的RMSE分别为0.85 m和1.59 m,MRE分别为8%和12%,均优于其他3种模型。     

“MgO/AC”复合材料对水溶液中Cu~(2+)和Cr(Ⅵ)的吸附性能研究

用造纸草浆黑液和氯化镁为原料制得氧化镁/活性炭("MgO/AC")复合材料,分别测定了该复合材料对水溶液中Cu2+与Cr(Ⅵ)的脱除性能。Cu2+的吸附随pH值的升高而增大,pH=3时基本达到平衡;在实验考察的pH范围内(1~8),Cr(Ⅵ)的吸附呈单调递减趋势。动力学拟合结果表明,"MgO/AC"复合材料对Cu2+和Cr(Ⅵ)的吸附过程均符合伪二级动力学方程;两过程的吸附速率均随吸附温度的升高而增大,表现为吸热吸附;吸附活化能Ea分别为50.19,51.42 kJ.mol-1;"MgO/AC"复合材料对Cu2+的吸附优于对Cr(Ⅵ)的吸附。Cu2+在"MgO/AC"复合材料上的吸附过程用Langmuir模型描述更为合适,在293~323 K范围内,Cu2+的饱和吸附量为19.46~90.91 mg.g-1;Cr(Ⅵ)的吸附过程则更符合Freundlich模型。     

Unveiling controls of the latitudinal gradient of surface pCO2 in the Kuroshio Extension and its recirculation regions（northwestern North Pacific） in late spring

In the northwestern North Pacific, annual net air-sea CO₂ flux is greatest in the Kuroshio Extension（KE） zone,owing to its low annual mean partial pressure of CO₂（pCO₂）, and it decreases southward across the basin. To quantify the influences of factors controlling the latitudinal gradient in CO₂ uptake, sea surface pCO₂ and related parameters were investigated in late spring of 2018 in a study spanning the KE, Kuroshio Recirculation（KR）, and...     

The bimodal rift-related Juscelândia volcanosedimentary sequence in central Brazil: Mesoproterozoic extension and Neoproterozoic metamorphism

The Barro Alto Complex and Juscelândia volcanosedimentary sequence are exposed in the central part of the Neoproterozoic Brasília belt of central Brazil. The former is a large (approximately 150 km long), boomerang-shaped, mafic-ultramafic, layered complex formed by two different intrusions metamorphosed under granulite facies. These rocks are tectonically overlain by rocks of the Juscelândia volcanosedimentary sequence, represented mainly by biotite-gneiss and amphibolite, or amphibolite facies metamorphic equivalents of rhyolite and basalt, respectively. New SIMS U–Pb zircon data and Sm–Nd isochron data presented herein help clarify the igneous and metamorphic evolution of the Juscelândia volcanosedimentary sequence, as well as its relationship with the Barro Alto Complex. Zircon grains from two biotite gneisses were analyzed by SIMS (SHRIMP) and indicate Mesoproterozoic dates, approximately 1.28 Ga, interpreted as the time of bimodal volcanism in a tectonic setting transitional between a continental rift and an ocean basin. Metamorphism is constrained by Sm–Nd garnet-whole-rock isochrons for garnet amphibolite and pelitic schists of the Juscelândia sequence, as well as for clinopyroxene-garnet amphibolite and garnet granulite of the Barro Alto Complex, which give ages between 0.74 and 0.76 Ga, in agreement with SIMS dates for metamorphic zircon rims. These new data are significant, because they establish that a single metamorphic event affected both the Barro Alto Complex and the Juscelândia sequence. Based on these new data, we present a modified tectonic model for the Brasília belt.     

沉淀-陈化-返溶作用和压力对热液中氟钛络合物高温水解的影响及地质意义

钛是自然界中最不活泼的金属元素之一,然而越来越多的证据显示钛可以在特定条件下能进入热液流体中发生迁移,其中氟可能在其中扮演着重要的角色。本文研究了300℃和50~400MPa压力条件下氟钛络合物(K2Ti F6)的稳定性以及沉淀-陈化-返溶作用和压力对氟钛络合物水解行为的影响。研究结果显示,氟钛络合物水解的过程中,由于Ti O2沉淀物的陈化作用,在稳定的温度和压力条件下,沉淀物的返溶很难发生;但在缓慢降温和机械性振荡过程中,沉淀物的返溶会明显发生。而且,在温度不变的情况下,压力的改变对K2Ti F6水解并没有显著的影响,显示氟钛络合物不管在高压还是低压环境下均遵循近似的水解规律。本文认为主要的原因在于压力的增高会促进水解反应沉淀物的陈化,进而抑制沉淀物的返溶,但并不破坏水解反应的平衡。最后,本文提出金属络合物的形成-水解-沉淀/返溶-陈化过程是水-岩作用或热液成矿过程中高场强元素活化、迁移和成矿的主要机制。     

基于SWMM-CCHE2D耦合模型的海绵城市内涝管控效果评价

为了解决暴雨导致的城市内涝,为应急管理提供技术支撑,考虑城市暴雨过程及海绵地表特性,结合城市水文学及水力学原理和芝加哥雨型,建立了SWMM-CCHE2D耦合模型。结合高精度地形数据和降雨、径流实时监测数据,采用SWMM雨洪模型模拟暴雨条件下海绵城市的产流,耦合高精度的二维水动力模型CCHE2D模拟相应的内涝情况。结果表明：暴雨条件下通州海绵区的产汇流具有缓慢下渗和汇流的特性,主要海绵措施的加入对径流削减率会有9.0%~40.6%不同程度的提高,从而减缓内涝,其中,对5年一遇暴雨的效果最显著;在100年一遇暴雨下设计的各种海绵措施中,生物滞留带对径流削减率的提高程度最明显,高达28.4%,透水铺装和绿地也具有较好的效果。     

东亚季风气候对Heinrich2事件的响应:来自石笋的高分辨率记录

据湖北省神农架天鹅洞一支石笋11个230Th年龄和254个δ18O数据,建立了28.5～22.0kaB.P.同位素分辨率平均约30a的东亚季风气候变化序列。该石笋δ18O曲线与南京葫芦洞石笋记录在重叠时段基本一致,说明本区石笋δ18O反映了区域性东亚季风经向环流特征。在24.3kaB.P.左右,石笋δ18O明显正偏,持续时间近1ka,指示一次显著的弱夏季风事件,与北大西洋倒数第二次冰漂碎屑事件(Heinrich2)同步发生,可视为东亚季风气候对H2事件的响应。高分辨率的δ18O序列揭示了H2事件的内部结构特征:(1)事件发生的突变性,石笋δ18O记录指示事件发生时在100a内δ18O从-8.59‰迅速正偏为-6.75‰,振幅达1.84‰;(2)事件结束的渐变性,δ18O正偏到-6.75‰后便以阶梯状缓慢负偏到-8.86‰至事件结束,持续时间近900a。这一过程与末次盛冰期东亚季风气候H1事件表现的季风强弱转换方式基本一致,说明末次盛冰期东亚季风气候H型事件具有共同的内部结构特征。研究表明,末次盛冰期东亚季风气候H事件的突变可能受北大西洋驱动并经青藏高原冰川变化放大。     

珠江流域碳酸盐岩与硅酸盐岩风化对大气CO_2汇的效应

对珠江流域11个测站的河水1个水文年4次取样进行水化学和同位素测试分析,揭示无论是碳酸盐岩区还是硅酸盐岩区,岩石风化均使河流的离子成分以HCO3-、Ca2+、Mg2+为主,碳酸盐岩风化溶蚀速率和由碳酸盐岩风化溶蚀引起的大气CO2消耗量分别为27.60 mm/ka和540.21x103mol/(km2·a-1),是硅酸盐岩风化速率和由硅酸盐岩风化引起的大气CO2消耗量的10.8倍和6.7倍,说明碳酸盐岩风化是流域碳汇过程及效应的主体。由于有利的水热条件和高的碳酸盐岩面积比例,珠江流域平均岩石风化速率和由岩石风化作用引起的大气CO2消耗量分别为30.15mm/ka和620.36×103mol/(km2·a-1),为全球60条河流平均值的2.6倍。