New characteristics of weighted GDOP in multi-GNSS positioning     

Yunlong Teng  Jinling Wang  Qi Huang  Bi Liu 《GPS Solutions》2018,22(3):74

In positioning, navigation and timing applications of multi-GNSS (global navigation satellite system) constellations, the geometric dilution of precision (GDOP) offers an important index for selecting satellites and evaluating positioning accuracy. However, GDOP assumes that the measurement errors of all the tracked satellites are independent and have the same accuracy level, which is impossible in practice, especially when the tracked satellites are from various constellations. Through introducing a weighted matrix describing the measurement errors of different satellites into a common GDOP, we focus on new characteristics of weighted GDOP (WGDOP) in two aspects. First, we compare the sizes of WGDOP and the common GDOP based on the range of the weights of different satellites, i.e., the diagonal elements of the weighted matrix. In addition, when the weights of different satellites increase, the change of WGDOP with the weights is also derived. Moreover, a closed-form formula for calculating WGDOP is also presented. The theoretical derivations demonstrate that the closed-form can reduce the computation burden effectively. Furthermore, numerical tests verify these analyses.  相似文献   

芦山地震和九寨沟地震台站实测震级差异性分析     

孙冬军  刘芳  毕波 《中国地震》2022,38(1):112-119

本文选取2013年芦山地震和2017年九寨沟地震波形,重新量取垂直向振幅,计算宽频带面波震级M_S（BB）,分析各台站实测震级出现方向性差异的原因。其中,通过572个宽频带台站实测芦山地震震级M_S（BB）7.1,通过603个宽频带台站实测九寨沟地震震级M_S（BB）6.9。芦山地震实测震级大于M_S（BB）7.3的台站呈现WN-ES向分布,与断层倾向一致;实测震级小于M_S（BB）7.0的台站呈现NE-WS向分布,与其所在断层走向一致。九寨沟地震实测震级大于M_S（BB）7.0的台站分布呈现NE向分布,与断层倾向一致;实测震级小于M_S（BB）6.8的台站总体分布较为离散,大体呈现NW-SE向分布,与树正断裂走向一致。实测震级偏大的台站方向性分布与多普勒效应和P波辐射花样联系不明显。对比分析芦山地震和九寨沟地震,去除场地响应和仪器自身影响,台站实测震级差异性仍然存在,因此,台站实测震级差异性是由于受到了多普勒效应、辐射花样、仪器和场地响应之外的因素影响。综合考虑地震震级涉及的影响因素,芦山地震和九寨沟地震的台站实测震级差异性可能与地震波的传播路径有关。  相似文献   

Tin-bearing minerals at the Furong tin deposit,South China: Implications for tin mineralization     

Shao-Cong Chen  Jin-Jie Yu  Min-Feng Bi  Bernd Lehmann 《Chemie der Erde / Geochemistry》2022,82(1):125856

It remains poorly constrained whether remobilization of Sn from granites and prograde skarns plays an essential role in forming economic (skarn-type) tin mineralization. Using both electron probe microanalysis and laser ablation–inductively coupled plasma–mass spectrometry methods, in-situ Sn contents, as well as major elements, were analyzed for numerous silicates and magnetite from fresh granite, altered granite, and skarn at the large Furong Sn deposit (530,000 t Sn @ 0.8% Sn) in the Nanling Range, South China. Hornblende and biotite in fresh granite are the main Sn-bearing phases (Sn = 44–321 ppm), while plagioclase and K-feldspar are poor in Sn (< 5 ppm). In altered granite, tin is hosted mainly by hydrothermal muscovite (299–583 ppm) replacing plagioclase, but rarely by chlorite (mostly <10 ppm) replacing hornblende and biotite. In contrast, most silicates (garnet, diopside, vesuvianite, pargasite and epidote) and magnetite from tin skarn are Sn-rich (47–44,241 ppm), except for Sn-poor phlogopite and scapolite (< 10 ppm). In particular, garnet, pargasite, and epidote reach tin concentrations in the percent range. Tin generally enters the stannous silicates and magnetite through substitutions for octahedral Al^vi and Fe³⁺. Comparisons of Sn contents between magmatic and hydrothermal minerals in granite, prograde and retrograde minerals related to tin skarn indicate that remobilization of Sn from granite and prograde skarn is not a pre-requisite to form tin mineralization.  相似文献   

液动潜孔锤钻进技术在潘一煤矿井下穿层钻孔中的应用          下载免费PDF全文

赵俊峰  金新  童碧  魏宏超  刘德贵  豆旭谦  张献振 《探矿工程》2015,42(6):21-23

以穿层钻孔方式进行松软煤层瓦斯预抽采极大地克服了松软煤层瓦斯治理难的问题,然而部分矿区煤层顶（底）板岩石坚硬,影响了钻孔施工效率。结合地质岩心钻探的优势,将液动潜孔锤与高强PDC钻头结合应用于煤矿井下穿层瓦斯抽采孔施工中。淮南潘一煤矿现场试验表明,该工艺方法较传统回转钻进方法,钻进效率提高了83%,钻头进尺寿命提高近5倍,具有良好的经济性能。采用清水为冲洗介质,无粉尘污染,噪声污染小,较为适合空间狭小的煤矿井下巷道施工。  相似文献   

基于年代学约束的白马雪山晚第四纪冰川作用     

张威  毕伟力  刘蓓蓓  刘啸  张兵  李超 《第四纪研究》2015,35(1)

白马雪山(5429m)地处横断山脉腹地,海拔3800m以上保存着确切的第四纪冰川遗迹,对其进行深入研究,可以为重建西南季风影响区的环境演变历史以及区域冰期-间冰期系列对比提供依据.本文采用野外地貌调查与电子自旋共振测年(ESR)相结合的方法,查明白马雪山第四纪冰川发育的地貌特点,并对研究区的冰期系列进行划分.结果显示,白马雪山晚第四纪以来至少发生5次冰川作用,分别为中梁赣冰期(475±62ka,MIS 12);倒数第二次冰期(MIS 6),年代分别为166±22ka、142±17ka、209±23ka、153±15ka、120±16ka和180±20ka;末次冰期早期(MIS 4),年代分别为57±6.8ka、67±8.7ka、81±11ka、77±11ka和64±7.7ka;末次盛冰期(19±2.5ka,LGM,MIS 2)以及全新世新冰期/小冰期(MIS 1).研究区的冰川作用与青藏高原的脉动式抬升具有一定的对应关系.  相似文献   

冷泉碳酸盐岩Sr同位素示踪研究进展     

范美彤  葛璐  朱碧  杨涛 《地质学报》2019,93(8):2081-2091

在冷泉的研究中,确定富甲烷流体的来源是非常重要的,Sr同位素对流体来源、混合模式和水岩反应等具有很好的示踪作用。近年来,国际上对冷泉碳酸盐岩Sr同位素的示踪研究越来越关注。本文系统总结了现代和古代冷泉碳酸盐岩Sr同位素的研究进展,简要归纳了Sr同位素分析测试方法,并对化学前处理过程中采用的不同酸溶液溶解样品的方法进行了对比,指出了建立标准化学前处理方法的必要性。现代和古代冷泉碳酸盐岩Sr同位素组成的变化范围较大,不同碳酸盐矿物具有不同的Sr同位素特征。冷泉碳酸盐岩Sr同位素的示踪研究集中在现代和古代冷泉流体来源的定性研究、混合流体来源的定量模型计算、以及古代冷泉碳酸盐岩的Sr同位素定年等方面。尽管取得了一系列进展,但是定量计算端元流体混合比例的准确性还有待提高,同时利用Sr同位素对古代样品进行定年存在不确定因素,其适用条件也需要进一步研究。  相似文献   

Improving Soil Enzyme Activities and Related Quality Properties of Reclaimed Soil by Applying Weathered Coal in Opencast‐Mining Areas of the Chinese Loess Plateau     

Hongbo Shao  Weixiang Li  Rutian Bi  Zhongke Bai 《洁净——土壤、空气、水》2012,40(3):233-238

There are many problems for the reclaimed soil in opencast‐mining areas of the Loess Plateau of China such as poor soil structure and extreme poverty in soil nutrients and so on. For the sake of finding a better way to improve soil quality, the current study was to apply the weathered coal for repairing soil media and investigate the physicochemical properties of the reclaimed soil and the changes in enzyme activities after planting Robinia pseucdoacacia. The results showed that the application of the weathered coal significantly improved the quality of soil aggregates, increased the content of water stable aggregates, and the organic matter, humus, and the cation exchange capacity of topsoil were significantly improved, but it did not have a significant effect on soil pH. Planting R. pseucdoacacia significantly enhanced the activities of soil catalase, urease, and invertase, but the application of the weathered coal inhibited the activity of catalase. Although the application of appropriate weathered coal was able to significantly increase urease activity, the activities of catalase, urease, or invertase had a close link with the soil profile levels and time. This study suggests that applying weathered coals could improve the physicochemical properties and soil enzyme activities of the reclaimed soil in opencast‐mining areas of the Loess Plateau of China and the optimum applied amount of the weathered coal for reclaimed soil remediation is about 27 000 kg hm^?2.  相似文献   

成岩-极低级变质作用及油气勘探意义   总被引：12，自引：3，他引：9  

张继军  毕先梅 《地学前缘》1999,6(2):251-258

采用粘土矿物学、成岩变质矿物组合、镜质体反射率及流体包裹体数据等指标,综合讨论了准噶尔盆地西北缘晚古生代地层成岩极低级变质作用的特征和油气勘探意义。变质指示矿物和古地温梯度研究确认,西北缘玛湖坳陷北段下二叠统火山岩存在极低级变质作用,具水热变质特征,变质相为葡萄石阳起石相,温度为２２０～３２０℃,压力ｐ＜２００ＭＰａ,表明极低级变质事件发生于早二叠世,未对上二叠统地层产生影响;下二叠统风城组和上二叠统地层于侏罗纪（１５０Ｍａ）达到最大古地温,为１３０～１８０℃,压力ｐ为１００～２００ＭＰａ,处于晚成岩Ａ,Ｂ期。与西准噶尔界山上古生界相比,盆地西北缘变质程度较低。因此,盆地深部上古生界仍是寻找油气、尤其是天然气的有利地带  相似文献   

含金夕卡岩矿床产出构造环境和地质地球化学评价标志   总被引：10，自引：0，他引：10  

赵一鸣  张轶男  毕承思 《地学前缘》1999,6(1):181-183

近十几年来,含金夕卡岩矿床的勘查与研究在国内外取得了很大的进展,发现了一批大型矿床,从而引人注目。含金夕卡岩矿床主要集中分布于环太平洋成矿带,按其产出构造环境可分为三类,即中（新）生代褶皱带、古生代褶皱带和地盾（台）区。控矿地层主要为石炭—二叠系和三叠系碳酸盐岩,次为第三系和寒武系等。有关岩浆岩大多为浅成钙碱性中酸性侵入岩,属Ⅰ型;时代以燕山期和喜山期为主,少数为华力西期、加里东期和印支期。含金夕卡岩绝大多数为钙夕卡岩,只有少数属镁夕卡岩,又可进一步划分为还原型和氧化型。金属矿物组合的特征是常有砷化物、铋化物和碲化物存在,Ｃｕ,Ａｕ,Ａｇ,Ａｓ,Ｂｉ,Ｔｅ,Ｃｏ和Ｓｅ等元素组合是含金夕卡岩特征性的地球化学标志。矿床（田）常具明显的交代矿化分带,并可构成一定成矿系列,其综合交代矿化分带模式,自岩体向碳酸盐围岩方向依次为：Ｃｕ（Ｍｏ）→Ｃｕ（Ｆｅ）→Ｃｕ（Ａｕ）→Ａｕ→Ａｕ（Ｐｂ,Ｚｎ,Ａｇ）。矿物共生组合和流体包裹体研究表明,夕卡岩矿物形成于６８０～３２０℃,盐度为ｗ（ＮａＣｌ）＝５９５％～１８６％,金的沉淀发生在夕卡岩期后的退化热液交代阶段,大致相当于温度为３５０～１５３℃,盐度ｗ（ＮａＣｌ）＝２４％～?  相似文献   

南极臭氧洞对全球大气辐射加热场影响的数值模拟研究   总被引：2，自引：1，他引：1  

张弘  陈月娟  毕训强 《大气科学》1999,23(3):340-348

为了探讨南极臭氧洞对全球气候的影响状况,我们用IAP_9层全球大气环流模式进行了南极臭氧洞气候效应的数值试验。本文分析了本次试验中南极臭氧洞引起的大气辐射加热场的变化,结果表明,南半球高纬和极地平流层臭氧含量的严重减少,不仅影响该地的大气辐射加热场,同时也使北半球平流层大气的辐射加热场发生改变。虽然对流层中层所受影响较少,但对流层下层南北半球的大气总辐射加热率的变化却相当明显,这些影响将使全球大气温度场产生明显变化。  相似文献