系统偏差常数弧段估计策略对多系统静态精密单点定位的影响

为探讨系统偏差最优估计策略,利用IGS提供的GPS、BDS、GLONASS和Galileo 四系统的观测数据以及GFZ提供的精密卫星钟差和精密轨道产品,将系统偏差（ISB）按照高斯白噪声、20 min、30 min、1 h、2 h分段常数进行单天静态解,分别获得E、N、U方向上的坐标偏差,分析不同系统偏差求解策略下多系统融合PPP的收敛时间和定位精度。结果表明,在多系统融合静态PPP中,从观测模型强度与定位结果稳定性和可靠性角度综合考虑,对ISB采用20 min分段常数估计策略是最优的,静态PPP收敛时间在30 min左右,收敛后的定位精度E方向优于2 cm、N方向优于1 cm、U方向优于5 cm。     

Thickness distribution and extent of sea ice and snow in Prydz Bay and surrounding waters observed in 2012/2013 austral summer

Three ship-based observational campaigns were conducted to survey sea ice and snow in Prydz Bay and the surrounding waters(64.40°S–69.40°S, 76.11°E–81.29°E) from 28 November 2012 to 3 February 2013. In this paper, we present the sea ice extent and its variation, and the ice and snow thickness distributions and their variations with time in the observed zone. In the pack ice zone, the southern edge of the pack ice changed little, whereas the northern edge retreated significantly during the two earlier observation periods. Compared with the pack ice, the fast ice exhibited a significantly slower variation in extent with its northernmost edge retreating southwards by 6.7 km at a rate of 0.37 km?d-1. Generally, ice showed an increment in thickness with increasing latitude from the end of November to the middle of December. Ice and snow thickness followed an approximate normal distribution during the two earlier observations(79.7±28.9 cm, 79.1±19.1 cm for ice thickness, and 11.6±6.1 cm, 9.6±3.4 cm for snow thickness, respectively), and the distribution tended to be more concentrated in mid-December than in late November. The expected value of ice thickness decreased by 0.6 cm, whereas that of snow thickness decreased by 2 cm from 28 November to 18 December 2012. Ice thickness distribution showed no obvious regularity between 31 January and 3 February, 2013.     

Revisiting the Relationship Between Urbanization and Economic Development in China Since the Reform and Opening-up

The relationship between urbanization and economic development has become a hot topic in the scientific community due to its great practical significance,and economic and social value.However,this relationship continues to change dynamically.In the new stage of urbanization,it is urgent to reveal the causal relationship quantitatively and diagnose the future direction systematically.Based on this,this paper calculates the contribution rate of China’s urbanization to economic development from 1978 to 2019 and uses the panel data cointegration test method to explore the causal relationship between urbanization and economic development in China.The study has three principal results.First,the contribution rate of urbanization to economic growth has maintained the overall growth trend from1978 to 2019,but the growth rate of urbanization’s contribution to economic growth has been relatively low since 2012.It is an important reason that the real estate sector has moved into a new stage of transformation.Second,the cointegration test shows that economic development is a significant factor in advancing urbanization and the urbanization is the product of economic development.Urbanization has a positive feedback effect on economic development,but this effect does not pass the 5%significance level test.The impulse response function shows that the impact of urbanization on economic development is relatively small and stable,indicating that it is limited that the boost of economic development by land-centered urbanization.Third,China’s urbanization and economic development have both shown rapid growth for some time,but their relationship is still the low level of coordination,which has also led to a downward trend in the contribution of new-type,people-oriented urbanization to economic growth in recent years.In the future,China’s urbanization and economy need to maintain relatively medium-low speed growth in the medium-long term,and we should boost the coordinated development of urbanization and economy from low level to high level.     

排序对模糊度解算中降相关性能的影响分析

针对不同排序算法对模糊度解算存在降相关性能影响的问题,从理论上分析了自然升序法、对称旋转法及扰动升序法的降相关原理,并基于模拟数据和实测数据,从降相关时间、搜索时间、总体耗时、Bootstrapping成功率及条件数5个方面对3种算法进行对比分析。结果表明,降相关效率与搜索椭球压缩程度呈负相关关系,搜索椭球压缩程度越高,降相关效率越低;对于不同的排序算法,提高降相关性能的关键在于减少降相关时间及对条件方差按一定方向排序,进而提高搜索效率。     

加快信息产业化 促进社会经济持续发展

以构建高效信息传输网络为代表的全球信息化浪潮正在蓬勃兴起。这是现代科学技术发展对人类社会的一次革命性变革,对人类社会生产方式、产业结构、价值观和行为规范都将产生深刻的影响。从世界范围看,信息产业从传统的第三产业中分离出来,成为一种独立的新兴产业的趋势已日益明显。信息产业可以成为中国跨世纪发展的支柱产业和具有持久效能的高效经济增长点。而将汽车工业作为全国2/3省区“九五”期间的支柱产业是不适宜的。加快发展信息产业,也是中国根据自身的国情,建立资源节约型的国民经济体系,实现“两个转变”和社会经济可持续发展目标的必然选择。     

基于级配方程的粗粒料压实特性试验研究

级配显著影响着堆石料的压实特性,定量表述级配对堆石料压实特性的影响至关重要。基于连续级配土的级配方程,设计了16组不同级配的试验粗粒料,进行了表面振动压实试验和侧限压缩试验,定量研究了级配对粗粒料压实特性的影响。研究表明:由表面振动压实(动应力)试验和侧限压缩(静应力)试验得到的干密度与级配曲线面积之间均呈二次函数关系,且干密度中的最大值对应的级配曲线面积均在0.9附近;无论是表面振动压实试验还是侧限压缩试验,堆石料都存在干密度最优(最大)的级配。依据试验成果,给出了所试验堆石料的最优级配区间(级配上、下包络线);同时,利用相似级配法论证了实际级配粗粒料的最优级配区间,并根据国内外多座土石坝粗粒料的设计级配验证了该最优级配区间的普遍适用性,为土石坝粗粒料的级配设计提供了理论依据。     

河床透-阻型岩溶塌陷形成机理

由岩溶引发的地面塌陷具有灾害性大,隐蔽性高等特点,为了对其进行有效预报及治理,以某岩溶塌陷强烈发育地区为研究对象,提出采用等值反磁通瞬变电磁法（Opposing Coils Transient Electromagnetics Method,OCTEM）与工程地质钻探相结合的方法,对地层界面进行地球物理方法探测,由覆盖层埋深、电阻率大小、等值线变化等因素确定地层产状,并通过物探反演图及钻孔信息进行验证。结果表明,在岩溶塌陷强烈发育地段,等值反磁通瞬变电磁法可以有效查明地下溶蚀发育情况,在周围环境因素干扰强等常规物探方法无法开展的情况下,可以达到较好的应用效果。等值反磁通瞬变电磁法在岩溶、地面塌陷等地质灾害发育地区提供了有效的预测,为相似情况下的研究分析工作提供理论及实践基础。     

基于自适应核密度的贝叶斯概率模型岩性识别方法研究

准确地刻画岩石类型及其结构关系可以为能源矿产勘探、深部结构与构造等研究提供重要信息.目前利用地球物理技术可以通过不同岩石对应的物性参数(如密度、磁化率、电阻率、速度等)之间的差异进行岩性识别,但是不同岩石物性往往存在一定程度的重合,利用单一物性进行岩性识别的结果不够准确,因此利用多源数据进行岩性识别具有重要的意义.贝叶斯方法属于统计分类方法,依靠概率进行分类,概率密度的计算依靠样本属性之间的相互联系.基于此,我们将基于自适应核密度估计的贝叶斯概率模型引入到岩性识别中.该方法对于多类不同物性参数具有良好的适应能力,预测的岩性分类结果带有概率参数,可以存在模糊区间,提供多种岩性分类结果.该方法具有较强可扩展性,可以同时处理参数和非参数信息,使得已知地质信息以及物性参数得到最大化的利用.实验证明该方法的岩性识别结果较好,相比于传统高斯算法和固定带宽核密度估计,自适应带宽的核密度估计获得的分类结果更稳定、更准确.     

小秦岭地区矿田构造深部探测初步认识

通过地震剖面、钻孔资料对比,利用1∶5万重力资料和广域电磁测深资料对小秦岭地区矿田构造深部特征进行了探讨。初步认为:小秦岭地区太华群埋深1 500、2 500、3 500 m处是重要的构造界面,特别是1 500 m处可能限制了大多数的石英脉矿体就位,1 500～2 500 m网格状电磁剖面南倾、北倾视电阻率交汇部位有可能形成较大规模金矿体;巡马道断裂结构复杂,其上盘可能以构造片岩、碎裂岩为主,3 500 m深部可能存在燕山期侵入岩体,具有寻找石英脉型金矿的前景,又具备形成构造蚀变岩型金矿的条件;太要断裂呈"阶梯状"北倾,其北1.5～3 km范围内,第四系下伏太华群埋深在800～1 500 m,该断裂西宽东窄,东西两段断距存在差异;提出了该地区深部找矿应重点关注巡马道断裂中西段两侧电性结构特征复杂地段的认识。