One-step solution to local tie vector determination at co-located GNSS/VLBI sites     

Xiaping Ma  Kegen Yu  Jean-Philippe Montillet  Xiaoxing He 《Studia Geophysica et Geodaetica》2018,62(4):535-561

The local tie vector, which connects the different space geodetic techniques at a co-located site, plays an important role in the realization of the International Terrestrial Reference Frame (ITRF). This paper presents a new method to determine the tie vector between the GNSS and very long baseline interferometry tracking points. The parameters of the local tie vector and the axes offsets are introduced into constraint equations. The parameters are then resolved using the 3D constrained least squares adjustment. With the surveying data collected at two different sites (Kunming and Urumqi) in China, the proposed method can precisely determine the local tie vectors in a geocentric frame. The root mean square error (RMSE) is (1.2, 2.3 and 1.5 mm) and (1.0, 1.5 and 1.4 mm) for the three coordinate components at the sites in Kunming and Urumqi, respectively. The offset between the primary and secondary axes of the VLBI telescopes is estimated to be 7.5 mm in Kunming’s site and 4.0 mm in Urumqi’s site, and the corresponding RMSE is 1.8 mm and 2.0 mm for the two sites, respectively.  相似文献   

2013年岷县—漳县M_S6.6地震前水氡浓度的临界慢化现象研究     

王熠熙  李赫  王博  杨朋涛  王俊  向阳  王喜龙  李悦 《地震》2018,38(1):128-138

基于临界慢化理论, 以2013年7月22日甘肃岷县—漳县M_S6.6地震前南北构造带及邻区水氡浓度观测资料为例, 逐一计算了表征临界慢化现象的自相关系数和方差。 研究结果表明, 2013年岷县—漳县M_S6.6地震前, 10个台点水氡浓度资料表现出较明显的临界慢化现象, 且出现慢化现象的观测点空间分布具有一定丛集性, 慢化持续时间呈现出由南向北迁移的特征。 综合分析认为, 临界慢化方法可以有效识别水氡资料蕴含的慢化信息, 这些早期异常信号对判定前兆异常所处阶段以及深入理解前兆资料变化的物理内涵具有重要的科学意义。  相似文献   

Analysis of the Characteristics of the D.P.R. Korean Seismic Event on September 23, 2017     

Du Guangbao  Zhao Yong  Sun Li  He Shaolin  Liu Jie 《中国地震研究》2018,32(2):280-287

A M3. 4 seismic event occurred in the Punggye-ri nuclear test site,D. P. R Korea at 16∶29 p.m. on September 23,2017. We analyzed the waveforms of this event recorded by the China Earthquake Networks Center. In conclusion,this event is complex,including an explosion with a successive earthquake. Although the beginning of the event is an explosion,fault dislocation plays the main role in the event.  相似文献   

Variation in soil saturated hydraulic conductivity along the hillslope of collapsing granite gullies   总被引：2，自引：0，他引：2  

Xiaoqian Duan  Yusong Deng  Yu Tao  Yangbo He  Lirong Lin 《水文科学杂志》2018,63(5):803-817

Saturated hydraulic conductivity (K_s) affects the soil hydrological process and is influenced by many factors that exhibit strong spatial variations. To accurately measure K_s and its scale, spatial variability and relationship with collapsing gullies, we analysed four double-ring infiltrometer diameters in three soil layers during in situ experiments designed to measure K_s in two typical collapsing gullies (three slope sites) in Tongcheng County of China. The results showed that K_s increased with increasing inner ring diameter, but no significant difference existed between inner diameters of 30 and 40 cm. The K_s in red soil layers was higher than that in sandy soil layers, the transition layers had the lowest values. K_s also varied with slope position, gradually decreasing with distance from the gully head. The suggestion is that the spatial variation in K_s is affected not only by the intrinsic soil properties but also by the interaction with the collapsing gully.  相似文献   

广西土壤有机质空间变异特征及其影响因素研究   总被引：2，自引：0，他引：2  

钟聪  李小洁  何园燕  邱微文  李杰  张新英  胡宝清 《地理科学》2020,40(3):478-485

基于广西第二次土壤普查的270个土壤剖面资料,结合1∶50万数字化土壤类型图、土地利用类型图和气象监测数据等资料,利用地统计学和逐步回归分析等方法对广西表层土壤有机质空间变异特征及其影响因素进行了探究。结果表明：广西表层土壤有机质平均含量为3.11±2.19%,变异系数为70.72%,空间分布呈北高南低的趋势。广西表层土壤有机质空间分布受到自然和人为因素的共同影响,土壤类型、成土母质、海拔、土地利用、气候和坡度6个环境因子对全区土壤有机质含量变异的综合解释能力为47.9%。其中,土壤类型是最重要的影响因素,能独立解释其变异的36.0%,海拔和成土母质分别能独立解释28.5%和15.8%。气温对广西土壤有机质空间分布的影响比降水量更加显著,从而造成了广西土壤有机质整体呈南低北高的趋势。同时,土壤有机质对气温的敏感性在一定程度上受到降雨量的制约。此外,研究区农业耕作管理等因素对土壤有机质的影响也不容忽视。  相似文献   

毛乌素沙地锦鸡儿（Caragana）根系微域细菌群落多样性特征     

周子渊  于明含  丁国栋  高广磊  何莹莹 《中国沙漠》2020,40(4):128-137

基于16S rRNA高通量基因测序技术，对毛乌素沙地小叶锦鸡儿（Caragana microphylla)、柠条锦鸡儿（Caragana korshinskii）根系微域（即根系、根际土、根区土、灌丛间空白土）间的细菌群落多样性和结构差异性进行表征。本研究对各根系微域间细菌群落的Alpha多样性指数进行了单因素方差分析以及基于OTU水平的PCA分析，探究其在根系微域间Alpha和Beta多样性的层级变化，证实了有关植物根系微域生态位分化的报道，并发现锦鸡儿属植物根系微域间细菌群落的多样性和结构组成随着4个微域类型由外及内呈现出显著的层级差异性（P<0.05）。通过对优势细菌群组的结构组成分析，发现锦鸡儿属植物对特定细菌群组具有显著的向根系内筛选富集的作用（P<0.05）。这种植物通过根系微域对特定细菌群组的逐级筛选富集作用，是导致锦鸡儿属植物灌丛下不同生态位间细菌群落结构和组成发生层级变异的主要原因。  相似文献   

新疆公共服务资源空间配置与城乡互动耦合协调发展评价          下载免费PDF全文

吴文婕  韩鹤  赵艳梅  桑川  王梦珂 《干旱区地理》2020,43(4):1117-1126

公共服务资源是社会发展的“先行资本”,对于区域社会经济发展与城乡融合发展具有正面外部效应。依据公共服务资源公平性、效益性与协调性原则,结合AHP、熵值与聚类分析方法,建立新疆公共服务资源配置与城乡互动效益评价指标体系,利用协调耦合发展模型,揭示研究区公共服务、城乡互动发展以及两者耦合协调度的总体特征和空间特征。结果表明：（1） 新疆各地不同类型公共服务资源空间配置公平性有所差异,空间非公平性>人口非公平性。（2） 公共服务资源综合效益以及城乡互动发展水平呈现较低、一般（中等）、较高三个类型。（3） 公共服务效益空间分异特征呈现出东南片区>西北片区;城乡互动水平空间差异呈现出天山北坡经济带高于其他区域。（4） 新疆大部分处于城乡互动与公共服务相互影响、相互磨合的过渡发展阶段,导致公共服务损益或城乡互动损益,个别区域处在两个系统相互制约、失调衰退阶段。通过进一步提出加快建立健全城乡互动公共服务体系,构建大、中、小多层次城镇空间格局,继续完善和开拓新的公共服务增长点以满足不断增长的城乡社会发展需求等建议措施,为确保城乡居民生存发展公平与效率,促进公共服务与城乡互动耦合协调发展提供参考借鉴。  相似文献   

中国高尔夫球场时空演变、影响因素和扩散模式     

金万富  何广静  陈乐 《热带地理》2020,40(3):515-524

利用空间分析和数理统计等方法探究了1984—2016年中国高尔夫球场数量时空演变、影响因素和扩散模式。结果表明：1）球场数量变化经历了低速增长期、稳定增长期、加速增长期和紧缩期；2）球场空间分布范围经历了扩张期和收缩期，向北、向西扩散较为明显；3）目前球场主要分布在经济发展水平较高且外向型经济突出的长三角、珠三角和环渤海地区；4）人均GDP、人口规模、区域开放程度、交通优势度、气候类型和土地资源稀缺性与球场空间分布均呈显著正相关，其中交通优势度相关系数最大；5）高尔夫球场空间扩散模式兼具接触性扩散和等级性扩散。  相似文献   

A meta-analysis of the impacts of forest logging on soil CO_2 efflux     

LongFei Chen  YangZhou Xiang  ZhiBin He  Jun Du  PengFei Lin  Xi Zhu 《寒旱区科学》2020,12(3):165-179

Soil CO_2 efflux, the second largest flux in a forest carbon budget, plays an important role in global carbon cycling. Forest logging is expected to have large effects on soil CO_2 efflux and carbon sequestration in forest ecosystems. However, a comprehensive understanding of soil CO_2 efflux dynamics in response to forest logging remains elusive due to large variability in results obtained across individual studies. Here, we used a meta-analysis approach to synthesize the results of 77 individual field studies to determine the impacts of forest logging on soil CO_2 efflux. Our results reveal that forest logging significantly stimulated soil CO_2 efflux of the growing season by 5.02%. However, averaged across all studies, nonsignificant effect was detected following forest logging. The large variation among forest logging impacts was best explained by forest type, logging type, and time since logging. Soil CO_2 efflux in coniferous forests exhibited a significant increase(4.38%) due to forest logging, while mixed and hardwood forests showed no significant change. Logging type also had a significant effect on soil CO_2 efflux, with thinning increasing soil CO_2 efflux by 12.05%, while clear-cutting decreasing soil CO_2 efflux by 8.63%. The time since logging also had variable effects, with higher soil CO_2 efflux for 2 years after logging, and lower for 3-6 years after logging; when exceeded 6 years, soil CO_2 efflux increased. As significantly negative impacts of forest logging were detected on fine root biomass, the general positive effects on soil CO_2 efflux can be explained by the accelerated decomposition of organic matter as a result of elevated soil temperature and organic substrate quality. Our results demonstrate that forest logging had potentially negative effects on carbon sequestration in forest ecosystems.  相似文献   

X-ray activity from different types of stars     

Lin He  Song Wang  Xiao-Jie Xu  Roberto Soria  Ji-Feng Liu  Xiang-Dong Li  Yu Bai  Zhong-Rui Bai  Jin-Cheng Guo  Yan-Li Qiu  Yong Zhang  Ruo-Chuan Xu  Ke-Cheng Qian 《天文和天体物理学研究(英文版)》2019,(7)

X-ray emission is an important indicator of stellar activity. In this paper, we study stellar Xray activity using the XMM-Newton and LAMOST data for different types of stars. We provide a sample including 1259 X-ray-emitting stars, of which 1090 have accurate stellar parameter estimations. Our sample size is much larger than those used in previous works. We find a bimodal distribution of the X-ray to optical flux ratio(log(fX/fV)) for G and K stars. We interpret that this bimodality is due to two subpopulations with different coronal heating rates. Furthermore, using the full widths at half maxima calculated from Hα and Hβ lines, we show that these stars in the inactive peaks have smaller rotational velocities. This is consistent with the magnetic dynamo theory that presumes stars with low rotational velocities have low levels of stellar activity. We also examine the correlation between log(fX/fV) and luminosity of the excess emission in the Hα line, and find a tight relation between the coronal and chromospheric activity indicators.  相似文献