GNSS ambiguity resolution with controllable failure rate for long baseline network RTK

Many large-scale GNSS CORS networks have been deployed around the world to support various commercial and scientific applications. To make use of these networks for real-time kinematic positioning services, one of the major challenges is the ambiguity resolution (AR) over long inter-station baselines in the presence of considerable atmosphere biases. Usually, the widelane ambiguities are fixed first, followed by the procedure of determination of the narrowlane ambiguity integers based on the ionosphere-free model in which the widelane integers are introduced as known quantities. This paper seeks to improve the AR performance over long baseline through efficient procedures for improved float solutions and ambiguity fixing. The contribution is threefold: (1) instead of using the ionosphere-free measurements, the absolute and/or relative ionospheric constraints are introduced in the ionosphere-constrained model to enhance the model strength, thus resulting in the better float solutions; (2) the realistic widelane ambiguity precision is estimated by capturing the multipath effects due to the observation complexity, leading to improvement of reliability of widelane AR; (3) for the narrowlane AR, the partial AR for a subset of ambiguities selected according to the successively increased elevation is applied. For fixing the scalar ambiguity, an error probability controllable rounding method is proposed. The established ionosphere-constrained model can be efficiently solved based on the sequential Kalman filter. It can be either reduced to some special models simply by adjusting the variances of ionospheric constraints, or extended with more parameters and constraints. The presented methodology is tested over seven baselines of around 100 km from USA CORS network. The results show that the new widelane AR scheme can obtain the 99.4 % successful fixing rate with 0.6 % failure rate; while the new rounding method of narrowlane AR can obtain the fix rate of 89 % with failure rate of 0.8 %. In summary, the AR reliability can be efficiently improved with rigorous controllable probability of incorrectly fixed ambiguities.     

象山港分区水交换数值研究

在验证良好的三维斜压潮流数学模型的基础上,将象山港划分成7个海区,以7种不同的溶解态保守性物质为示踪剂,建立对流-扩散型的海湾水交换数值模型,采用关联矩阵法来描述各区之间以及各区与外海之间的水交换特性。通过不同示踪剂的浓度分布,计算了15、30、45、60和80d的水交换矩阵。由各时刻水交换矩阵可知,在象山港的7个子区中与湾外水的水交换速度最快的为Ⅰ区,最慢的为Ⅶ区。Ⅲ区(西沪港)、Ⅵ区(黄墩港)和Ⅶ区(铁港)内水体与湾外海水之间的水交换速度缓慢,但与区域外水体之间的交换速度要明显快于其他几个海区。从水交换矩阵可以看出西沪港、黄墩港和3个内港之间相互交换的海水量很小。     

乐清湾悬沙输移机制分析

以乐清湾海区特征测站实测资料为据,运用机制分解法将悬沙净输移通量分解成多个动力项并讨论不同区域悬沙输移的时空分布特征,认为潮泵输沙在湾内贡献均较大,在浅滩附近占明显优势,垂向净环流输沙在小潮期中,内湾作用显著,平流输沙在开阔水域及中湾深槽起主要作用.从余流分布、流速与含沙量的相位关系、垂向余流结构与悬沙浓度垂向梯度变化...     

乌冈栎的地理分布

利用植物地理学分布区理论与地理信息系统技术,整合相关标本信息和文献,对乌冈栎地理分布区进行研究。结果表明:1)乌冈栎水平地理分布以亚热带为主,水平分布范围在中国(23°―34°N,100°―120°E)和日本(26°―37°N,128°―140°E);垂直分布大多在海拔500m以上,少数地区可降至海拔200m,日本分布区海拔要低于中国。2)乌冈栎现代分布区可分为中国东部分布区、中国南部分布区、中国西部分布区、中国西南部分布区和日本分布区,而中国东部分布区是目前的分布中心。3)利用壳斗科化石资料,对乌冈栎起源演化及散布途径作了推断,对其起源时间、传播路线等进行了讨论。4)第三纪及第四纪气候的演变对乌冈栎现代地理分布格局有着重大影响,为适应气候变化,其形态特征与常绿硬叶栎类中的高山栎类植物有一定差别,并逐渐退出了高山分布的地理位置。乌冈栎是否传统观点认为的冬青栎东亚替代种还有待于进一步商榷。     

深海海面目标单水听器被动测距方法与验证

基于射线理论分析了在深海情况下海面声源产生声场的频率-距离干涉结构,给出了影区内声场频率-距离干涉结构的近似理论表达式,分析得到影区内声场频域干涉周期随收发距离的增加而增大、随着接收水听器深度的增加而减小。因此由单水听器记录的声场干涉结构即可实现被动声源距离估计。在南海深海实验中观测到海面宽带噪声源在声场影区形成的声场干涉结构,对实验获得声场干涉结构的处理结果验证了深海声场影区干涉结构用于被动声源距离估计的有效性。与传统的匹配场被动定位方法相比,该方法不需要已知海底声学参数和大规模的拷贝场计算。     

Hydrocarbon Generation Evolution of Permo-Carboniferous Rocks of the Bohai Bay Basin in China

<正>The Bohai Bay Basin is a Mesozoic subsidence and Cenozoic rift basin in the North China Craton.Since the deposition of the Permo-Carboniferous hydrocarbon source rock,the basin has undergone many tectonic events.The source rocks have undergone non-uniform uplift,twisting,deep burying,and magmatism and that led to an interrupted or stepwise during the evolution of hydrocarbon source rocks.We have investigated the Permo-Carboniferous hydrocarbon source rocks history of burying,heating,and hydrocarbon generation,not only on the basis of tectonic disturbance and deeply buried but also with new studies on apatite fission track analysis,fluid inclusion measurements,and the application of the numerical simulation of EASY%R_o.The heating temperature of the source rocks continued to rise from the Indosinian to Himalayan stage and reached a maximum at the Late Himalayan.This led to the stepwise increases during organic maturation and multiple stages of hydrocarbon generation.The study delineated the tectonic stages, the intensity of hydrocarbon generation and spatial and temporal distribution of hydrocarbon generations.The hydrocarbon generation occurred during the Indosinian,Yanshanian,and particularly Late Himalayan.The hydrocarbon generation during the late Himalayan stage is the most important one for the Permo-Carboniferous source rocks of the Bohai Bay Basin in China.     

Deposition of sandstorms in a vegetation-covered sand dune in Ejin Oasis and its characteristics

“Ejin Section” found in a typical vegetation-covered sand dune in Ejin Oasis was investigated. In this study, 263 samples were taken from the section for grain-size analysis, 25 for chemical analysis, 11 for 14C dating and 6 for scanning electron microscope (SEM). The results of the study indicate that 3 types of the sediments in the section can be identified, YS, LS and ST. YS, homogeneous yellow-brown dune sands, is equal to those of inland deserts, LS, loess-like sandy soils, is the same as the sandy loess in the middle Yellow River and modern falling dusts, and ST, sandy sediments interbeded with the deadwood and defoliation of Tamarix spp, represents the depositional process of the section interrupted by abrupt changes in climate. The Ejin Section has recorded the repeated dust-storms or sandstorms since 2500 yr BP and the peak periods of the dust-storms or sandstorms revealed by the section are consistent with the records of “dust rains” in historical literatures, indicating that the change of climate is a key factor to increase sandstorms or dust-storms, whereas, “artificial” factor may only be an accelerating one for desertification.     

渤海湾盆地石炭二叠系盖层及其沉积控制

在对渤海盆地石炭一二叠系盖层泥岩特征观察的基础上，通过对粘土矿物含量的相对定量分析及孔隙度、渗透率的统计分析，结合沉积控制，评价了该区盖层泥岩的封闭能力：结果表明，渤海湾盆地上、下石盒子组盖层泥岩分布范围广，保存完整，湖泊相和泛滥平原相泥岩具有较好的封闭性，可作为区域盖层，下石盆子组盖层泥岩的孔隙度和渗透率又明显低于上石盆子组，封盖性更好；太原组和山两组的泻湖相和三角洲平原相发育的泥岩也作为局部盖层。泥岩的异常压力封闭是该区盖层研究的重点。