Effect of freeze-thaw cycles on uniaxial mechanical properties of cohesive coarse-grained soils

Freeze-thaw cycles are closely related to the slope instability in high-altitude mountain regions. In this study, cohesive coarse-grained soils were collected from a high-altitude slope in the Qinghai–Tibet Plateau to study the effect of cyclic freeze-thaw on their uniaxial mechanical properties. The soil specimens were remolded with three dry densities and three moisture contents. Then, after performing a series of freeze-thaw tests in a closed system without water supply, the soil specimens were subjected to a uniaxial compression test. The results showed that the stress-strain curves of the tested soils mainly performed as strain-softening. The softening feature intensified with the increasing dry density but weakened with an increase in freeze-thaw cycles and moisture content. The uniaxial compressive strength, resilient modulus, residual strength and softening modulus decreased considerably with the increase of freeze-thaw cycles. After more than nine freeze-thaw cycles, these four parameters tended to be stable. These parameters increased with the increase of dry density and decreased with the increasing moisture content, except for the residual strength which did not exhibit any clear variation with an increase in moisture content. The residual strength, however, generally increased with an increase in dry density. The soil structural damage caused by frozen water expansion during the freeze-thaw is the major cause for the changes in mechanical behaviors of cohesive coarse-grained soils. With results in this study, the deterioration effect of freeze-thaw cycles on the mechanical properties of soils should be considered during the slope stability analysis in high-altitude mountain regions.     

大面积连续分布是页岩层系油气的标志特征——以鄂尔多斯盆地为例

非常规页岩层系油气资源大面积连续分布,是未来全球油气供应的重要接替领域。提出了页岩层系油气的地质内涵,即烃源层系生成、滞留或就近聚集在生烃层系内部或紧邻生烃层系的致密储集层中,利用新技术可实现工业开采的连续分布油气资源,包括源储一体型和源储紧邻型两种资源类型。鄂尔多斯盆地是致密油气、页岩油气等非常规页岩层系油气资源的有利发育区,中生界三叠系延长组、上古生界石炭系—二叠系源储接触面积大,页岩油气、致密油气主要在源内或近源大面积连续分布,具有“普遍含油气、储层致密、低压、低丰度”的典型地质特征,具有稳定平缓的构造面貌、较高成熟源岩广布式生排烃和大面积致密储层叠置分布的有利成藏地质背景,致密油气“甜点区(段)”主要受生烃中心和厚层砂岩分布共同控制,页岩油气“甜点区(段)”主要受富有机质页岩规模、热演化程度、天然裂缝等共同控制。随着页岩层系油气的深入勘探开发,以大面积连续分布为标志特征的页岩层系油气地质理论将深入发展,成为石油天然气地质学的下一次大飞跃。     

光源编码+PDR组合的室内行人定位方法

针对光源编码定位系统存在定位不连续、易受遮挡导致定位性能下降等问题,提出了一种光源编码/行人航迹推算(PDR)组合的室内行人定位方法。该方法采用扩展卡尔曼滤波(EKF)对PDR位置和光源编码位置进行融合处理,并运用新息滤波对光源编码位置进行抗差处理。试验结果表明,光源编码+PDR组合算法能有效改善光源编码定位不连续、非视距环境中存在粗差的问题,实现连续、高精度的室内行人定位。     

最佳波段组合的城市土地利用类型提取

针对Landsat 8陆地成像仪(OLI)遥感影像光谱特征利用率不高等问题,为排除波段间冗余信息的干扰,提高土地利用特征提取的精度,该文以2014年唐山市中心城区Landsat 8OLI遥感影像为主要数据源,开展了基于Landsat 8OLI影像的城市土地利用特征提取的最佳波段选择研究。根据最佳波段选取原则统计波段光谱信息,基于最佳指数因子以及不同土地利用类型的光谱特征曲线,确定波段1、5、7为最适合该遥感影像进行土地利用特征提取的最佳波段组合。     

基于自发地理信息的“一带一路”区域陆路交通状况分析

路网密度的研究是实施“一带一路”愿景之互联互通倡议的基础工作。“一带一路”顺应了世界经济全球化、一体化、多极化、信息化的趋势,牵连着蓬勃发展的亚太和发达的欧洲经济圈,带动中间国家的经济发展。在新形势下,如何通过交通基础设施建设推进丝绸之路经济带沿线区域间的互联互通、促进区域合作和经济发展,具有重要的现实意义。本文利用自发地理信息数据——OpenStreetMap（OSM）道路网数据,运用地理信息系统（GIS）空间分析技术,探究了“一带一路”陆路经济带辐射区域亚欧大陆的路网络密度和通行能力的空间分布格局,并分析了六大经济走廊节点城市的公路可达性空间格局。结果表明：“一带一路”陆路经济带的交通基础设施的发展存在着不平衡现象;路网密度和通行能力均呈现沿海高内陆低的空间格局;中亚、西亚地区和中南半岛地区成为道路水平落后带,限制了丝绸之路经济带资源整合与贸易畅通,建议在建设新跨国公路铁路同时,对原有老旧道路进行加宽加固等升级改造;全区域道路等级级配不合理;节点城市可达性具有明显的分异状况,六大经济走廊中83%的区域可达性在10 h以内。研究产出亚欧大陆1 km分辨率路网密度和通行能力数据集,发现了“一带一路”陆路经济带道路水平的薄弱区域,为“一带一路”陆路经济带的交通基础设施建设以及进一步的道路网研究提供了基础数据。     

IMU辅助下的单目视觉坐标传递

针对管线测量中由于GNSS RTK卫星信号遮挡或测站不易架设等原因无法提供坐标的场景,本文提出了一种IMU辅助下的单目视觉坐标传递方法,用于延伸RTK测得的精密坐标。首先在两个已知的RTK点上架设相机拍摄图像,同时采集IMU数据;然后对图像进行特征提取和匹配,恢复帧间旋转、平移及尺度;最后三角化待测点,以获得待测点在真实尺度的相机坐标系下的坐标。受IMU静基座初始对准方法的启发,本文利用重力矢量和相机光心间矢量分别在地理坐标系和相机坐标系下的投影求解这两个坐标系间的旋转矩阵,进而求得待测点在地理坐标系下的三维坐标。相对于其他测量手段,本文方法灵活便捷、设备轻便、操作简单,且一次采集即可获取相机视场中的任意共视点坐标。试验结果表明,本文提出的坐标传递方法所得的平面坐标的误差平均值为0.12 m,高程误差的平均值为0.2 m。     

典型山地降水径流时空演变及“水-热-人-地”匹配性分析

山地是中国自然生态保护与经济社会发展问题交织、矛盾突出的区域。山地水资源受气候变化和人类活动综合影响发生演变,进一步影响到其与区域气候资源、土地资源以及经济社会之间的协调匹配,研究这些问题对辨识山地发展关键短板、提供山地问题解决思路具有基础意义。根据自然环境特点和经济社会发展状况,选择太行山、横断山和黔桂喀斯特三大典型山地开展研究,基于全国水资源调查评价成果及土地利用、经济社会数据,采用Mann-Kendall检验等方法分析1956-2015年山地降水和径流时空演变特点;采用匹配距离和不平衡指数对山地的水（降水和径流）、热（积温和辐射）、地（面积和耕地）以及社会经济（人口和GDP）等4类要素匹配性进行综合对比分析。结果表明：三大典型山地中,太行山水资源禀赋最差,且2000年以来径流显著衰减,而横断山和黔桂喀斯特降水、径流丰富,且无明显变化趋势;从“水—热—人—地”对比来看,太行山以缺水问题为主,横断山多数地区土地与热资源偏少且水热空间差异大,黔桂喀斯特整体来说土地资源偏少;综合来看,水与其他要素的匹配性最差,特别是在太行山区,水的时空分布及其均衡匹配是保障山地可持续发展的关键。     

东北三省城际技术转移网络的空间演化及影响因素

从全国—本地视角,以东北三省为研究区,基于2005-2015年的专利权转移数据,融合社会网络、GIS空间分析和计量方法,定量刻画东北三省技术转移网络的空间演化规律。结果显示：① 全国视角下东北三省城际技术转移网络呈现“核心—边缘”等级层次性结构,形成了专利技术由东北辐散向全国沿海辐合的空间格局。② 本地视角下东北三省技术转移网络呈现出向心收缩结网态势,“哈长沈大”四大核心城市在本地网络中扮演“技术守门者”角色。技术转移表现出“强全国化,弱本地化”特征。③ 东北三省城际技术流动既存在路径依赖,也不断涌现路径创造。全国视角下,技术转移以东北三省核心城市为流源,基本流向以北京、上海和深圳分别为枢纽的京津冀、长三角和珠三角城市群。本地城际技术转移以哈尔滨、长春、沈阳、大连为集散中心,集中于省内转移,呈现等级、接触和跳跃式混合扩散空间模式。④ 地理距离接近度、产业结构相似度、经济水平差异度、创新能力相似度、技术吸收能力、外商直接投资对东北三省城际技术转移存在一定影响。     

Isolation and characterization of 49 polymorphic microsatellite loci for Decapterus maruadsi using SLAF-seq,and cross-amplifi cation to related species

Decapterus maruadsi is a commercially important species in China, but has been heavily exploited in some areas. There is a growing need to develop microsatellites promoting its genetic research for the adequate management of this ?shery resources. The recently developed speci?c-locus ampli?ed fragment sequencing(SLAF-seq) is an effcient and high-resolution method for genome-wide microsatellite markers discovery. In this study, 28 905 microsatellites(mono-to hexa-nucleotide repeats) were identi?ed using SLAF-seq technology, of which di-nucleotide was the most frequent(13 590, 47.02%), followed by mono-nucleotide(8 138, 28.15%), tri-nucleotide(5 727, 19.81%), tetra-nucleotide(1 104, 3.82%), pentanucleotide(234, 0.81%), and hexa-nucleotide(112, 0.39%). One hundred and thirty-two microsatellite loci(di-and tri-nucleotide) were randomly selected for ampli?cation and polymorphism, of which 49 were highly polymorphic and well-resolved. The average number of alleles per locus was 13.63, ranging from 4 to 25, and allele sizes varied between 110 bp and 309 bp. The observed heterozygosity( Ho) and expected heterozygosity( He) ranged from 0.233 to 1.000 and from 0.374 to 0.959, with mean values of 0.738 and0.836, respectively. The polymorphism information content(PIC) ranged from 0.341 to 0.941(mean=0.806).However, 12 loci deviated from Hardy-Weinberg equilibrium. Furthermore, transferability tests were also successful in validating the utility of the developed markers in ?ve phylogenetically related species of family Carangidae. A total of 48 microsatellite markers were successfully cross-ampli?ed in Decapterus macarellus, Decapterus macrosoma, Decapterus kurroides, Trachurus japonicus, and Selaroides leptolepis.The present microsatellites provided the ?rst known set of microsatellite DNA markers for D. maruadsi,D. macarellus, D. kurroides, and D. macrosoma, and would be useful for further population genetic and molecular phylogeny studies as well as help with the ?sheries management formulation and implementation of the understudied species.