The development and analysis of quasi-linear map projections     

Jonathan Charles Iliffe 《制图学和地理信息科学》2018,45(3):270-283

Map projections are an essential component of coordinate systems used in applications such as surveying, topographic mapping, and engineering, and care needs to be taken to select ones that minimize distortion for each case. This article explores the selection process for near-linear features on the surface of the Earth and derives limits for the extent of a project that can be projected within specified distortion tolerances. It is then demonstrated that a multifaceted set of projections of the Earth may be used to extend this concept to the mapping of features such as highways and railways that are quasi-linear but do not exactly follow a standard geometrical line (a great circle or a small circle) on the surface of the Earth. A continuous, conformal coordinate system may be derived in such situations, extending to indefinite length and applicable over a swath of several kilometers width, but it cannot be extended to cover situations with extensive variations in height. Instead, the Snake Projection is analyzed, and it is shown that this can be used to develop continuous (non-zonal) projected coordinate systems for major engineering projects extending for hundreds of kilometers and having extensive height ranges. Examples are shown of the application to railway projects.  相似文献   

Structural stability of gravity dams: a progressive assessment considering uncertainties in shear strength parameters     

Mathilde Cordier 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2018,12(2):109-122

Structural sliding stability of gravity dams is generally quantified using deterministic factor of safety, FS_det. Large FS_det (e.g. 3 in normal condition), are used in existing guidelines to guard against material and load uncertainties. Some guidelines allow an arbitrary reduction in FS_det (e.g. 2) when the knowledge in strength parameters increases from material test data. Yet, those reduced FS_det are not based on a rational consideration of uncertainties. Propagation of uncertainties could be done using probabilistic analyses, such as Monte-Carlo simulations (MC) which are complex and challenging for practical use. There is thus a need to develop simplified reliability based safety assessment procedures that could rationalise the adjustment of FS_det. This paper presents a progressive analysis methodology using four safety evaluation formats of increasing complexity: (i) deterministic, (ii) semi-probabilistic (partial coefficient), (iii) reliability based Adjustable Factor of Safety (AFS), and (iv) probabilistic. Comprehensive comparisons are made for the sliding safety evaluation of a 80 m gravity dam. Results are presented in terms of sliding factors of safety, allowable water levels, and demand/capacity ratios. It is shown that the AFS formulation, using direct integration, is simple and practical to use in complement to existing dam safety guidelines before undertaking MC simulations.  相似文献   

青海黄南地区近54年蒸发量变化特征及其影响因子     

李延林  许显花  刘义花  沈菊  陈海莲 《气象科技》2019,47(2):269-275

利用青海省黄南地区近54a(1960—2013年)蒸发量、气温、降水量、日照时数、水汽压等资料,应用地理信息系统、数理统计、线性回归和Mann-Kendall检验等方法分析了黄南地区蒸发量的空间及时间变化趋势,并对黄南地区蒸发量变化特征及其影响因子进行了诊断研究。结果表明:黄南地区年平均蒸发量呈明显的下降趋势,20世纪60—70年代为蒸发量偏多阶段,80年代及后为偏少阶段;黄南地区蒸发量最大的季节是春季和夏季,各季蒸发量均呈减少趋势;黄南地区年蒸发量在1973年发生了由多到少的突变,春、夏、秋、冬季分别发在1973、1975、1976和1974年;分析影响蒸发量的相关因子,蒸发量与日照时数呈显著的正相关关系,与水汽压和降水量呈显著的负相关关系,日照时数的减小是蒸发量减少的主要影响因子。  相似文献   

绿色交通目标下集装箱“公转铁”的CO2减排潜力评估     

陶学宗  吴琴  尹传忠 《气候变化研究进展》2019,15(6):660-669

为提高集装箱“公转铁”减排潜力评估结果的准确性,在分析“公转铁”减排原理的基础上,综合考虑空箱调运和重箱运输“门到门”运输链的干线运输、端点装卸、电力设备作业、集卡短驳、公铁中转等排放,引入反映活动类型、设备结构、能源生命周期排放的参数,对作业活动-方式结构-能耗强度-排放因子（ASIF）方法进行改进,建立“公转铁”减排潜力评估框架。以义乌—宁波港域出口集装箱运输为例,通过实地调研和公开文献获取数据,进行实证研究。结果表明,如果忽略必要因素将会导致每TEU运输需求“公转铁”的CO₂减排率被高估0.50~36.73个百分点;最佳“公转铁”情景可减排3.42万t CO₂,相应减排率为13.58%。研究结果可为政府相关部门客观评估“公转铁”的减排潜力、制定有效的“公转铁”政策措施提供理论支持。  相似文献   

那曲地区植被NDVI时空变化及成因分析     

拉巴  洛桑曲珍  次珍  平措旺丹 《气象与环境学报》2019,35(4):69-76

利用GIS和遥感技术方法分析了2000—2014年那曲地区植被归一化指数(NDVI)的时空分布特征和变化趋势,探讨了NDVI与几种气象因子的关系。结果表明:空间上,研究区植被NDVI在空间上呈自西向东、自南向北逐步增大,高海拔地区小于低海拔地区的分布特点;时间上,近15a的NDVI总体上呈不显著性下降趋势,NDVI变化可以分为3个阶段,分别为2000—2005年较好,2006—2008年略差,2009—2014年好转。植被面积变化趋势表现为西北部植被处于稳定状态的面积居多,变化较明显的区域集中在中部和东南部地区的人口密集区,改善和退化区域呈现交错出现的特点。那曲地区植被变化的主要影响因素为降水量和热量因素引起的,人类活动在较短时间尺度上对植被也有较大影响。  相似文献   

基于NCEP CFSv2模式的黑龙江省夏季降水预测研究     

班晋  王波  李永生  赵佳莹 《气象与环境学报》2019,35(6):21-27

基于1982-2017年NCEP_CFSv2（NCEP Climate Forecast System version 2）模式预测资料对黑龙江省夏季降水进行降尺度预测。通过分析黑龙江省夏季降水与同期环流因子的关系、模式对关键区环流因子的预测,选取模式模拟与再分析资料相关较好、黑龙江降水实况与再分析资料关系较好的环流因子作为预测因子,结合最优子集回归法筛选因子,建立降尺度预测模型,最后采用交叉检验法进行预测效果检验和独立样本预测。结果表明：模式降尺度预测与实况的距平符号-致率为69%,6 a独立样本预测中有5 a预测正确,优于目前的业务预测效果。进-步研究发现,在模式能够准确预测环流因子的情况下,模式降尺度可以较好地预测黑龙江省夏季降水的趋势。此外,模式降尺度在拉尼娜年预测效果较好。  相似文献   

Geological Controls on the CBM Productivity of No.15 Coal Seam of Carboniferous–Permian Taiyuan Formation in Southern Qinshui Basin and Prediction for CBM High-yield Potential Regions     

ZHANG Zheng  QIN Yong  ZHUANG Xinguo  LI Guoqing  LIU Donghai 《《地质学报》英文版》2018,92(6):2310-2332

Coalbed methane (CBM) resources in No.15 coal seam of Taiyuan Formation account for 55% of the total CBM resources in southern Qinshui Basin (SQB), and have a great production potential. This study aims at investigating the CBM production in No.15 coal seam and its influence factors. Based on a series of laboratory experiments and latest exploration and development data from local coal mines and CBM companies, the spatial characteristics of gas production of No.15 coal seam were analyzed and then the influences of seven factors on the gas productivity of this coal seam were discussed, including coal thickness, burial depth, gas content, ratio of critical desorption pressure to original coal reservoir pressure (RCPOP), porosity, permeability, and hydrogeological condition. The influences of hydrological condition on CBM production were analyzed based on the discussions of four aspects: hydrogeochemistry, roof lithology and its distribution, hydrodynamic field of groundwater, and recharge rate of groundwater. Finally, a three-level analytic hierarchy process (AHP) evaluation model was proposed for predicting the CBM potentials of the No.15 coal seam in the SQB. The best prospective target area for CBM production of the No.15 coal seam is predicted to be in the districts of Panzhuang, Chengzhuang and south of Hudi.  相似文献   

Comparative Study of Hydrogen and Carbon Isotopic Composition of Gases Generated from the Pyrolysis of a Peat under Saltwater and Freshwater Conditions     

WU Yingzhong  DUAN Yi  ZHAO Yang  CAO Xixi  MA Lanhu  QIAN Yaorong  LI Zhongping  XING Lantian 《《地质学报》英文版》2018,92(5):1879-1887

To understand the influence of the diagenetic water medium on the isotopic compositions of thermogenic coalbed gas, both hydrous and anhydrous closed-system pyrolyses were performed at temperatures of 250°C to 650°C on an herbaceous marsh peat. Compared to the results of anhydrous pyrolysis, the hydrocarbon gases generated from hydrous pyrolyses have very different hydrogen isotopic compositions. However, the carbon isotopic compositions of the hydrocarbon gases became only slightly heavier in hydrous pyrolysis, compared to that from anhydrous pyrolysis. With the progress of thermal evolution from peat to a more advanced thermal maturity of vitrinite reflectance values (Ro) of 5.5% during the pyrolysis, the difference in the average δD value increased from 52‰ to 64‰ between the hydrous pyrolysis with saltwater and anhydrous pyrolysis and increased from 18‰ to 29‰ between the hydrous pyrolysis with freshwater and anhydrous pyrolysis, respectively. The difference in the average δ13C value was only 1‰–2‰ between the hydrous and anhydrous pyrolysis. The relationships between the δD values of the generated hydrocarbon gases and Ro values as well as among δD values of the hydrocarbon gas species are established. The close relationships among these parameters suggest that the water medium had a significant effect on the hydrogen isotopic composition and a minimal effect on the carbon isotopic composition of the hydrocarbon gases. The results of these pyrolyses may provide information for the understanding of the genesis of coalbed gas from herbaceous marsh material with the participation of different diagenetic water media.  相似文献   

准噶尔腹部火山岩风化壳储层特征及其影响因素          下载免费PDF全文

李治  秦启荣  李朋波  顿雅航  付晓燕 《地质找矿论丛》2018,33(4):589-596

文章通过大量岩芯、铸体薄片观察和测井资料分析,对准噶尔腹部石西石炭系火山岩风化壳储层进行了详细地研究。研究结果表明,该火山岩风化壳储层的储集空间主要有基质溶孔、气孔或杏仁体溶孔、角砾间溶孔、微裂缝和裂缝等,其中与裂缝连通的各类溶孔占主导地位;在岩石分布上以集块岩、条带状熔岩、角砾熔岩和致密凝灰岩为主,玄武岩、安山岩和流纹岩则相对较少;储层物性主要表现为高孔低渗,只有裂缝具有较高的渗透率,且裂缝以高角度缝和直立缝为主。研究还发现,岩性岩相、裂缝和风化淋滤作用是影响该风化壳储层的主要因素。区内油层主要聚中在构造高部位、靠近断裂带和有利岩相区域;油层分布在离石炭系风化壳顶面25~150 m的范围内。  相似文献   

页岩压裂影响因素三维模型数值分析     

张健  张国祥  王金意 《江苏地质》2018,42(1):127-130

不同影响因素对页岩水力压裂效果有不同的影响。基于三维数值计算模型介绍了水力压裂的典型过程,针对水平最小主应力、页岩的弹性模量和渗透系数对压裂的影响进行了分析。结果表明:随着水平最小主应力的增加,裂缝高度也随之增加;随着页岩的弹性模量增加,裂缝的高度随之降低;随着渗透系数的增加,裂缝高度也随之增加;随着压裂液的黏度系数提高,裂缝的高度降低。  相似文献