A Multi-Angle Averaging Theorem Applied to the J2 Problem

A particular multi-angle averaging theorem for systems admitting a finite Fourier expansion of the field is presented, together with its application to the problem of motion around an oblate planet (the J₂ problem), in harmonic oscillator formulation. This method of approximate integration has the advantage of working with (close on) directly measurable elements. This revised version was published online in July 2006 with corrections to the Cover Date.     

高空槽脊对台风“天兔”（0705）变性过程中非对称降水的影响

本文基于NCEP再分析资料、TRMM卫星降水资料和RSMC最佳路径集（Best-track Dataset）资料,分析了热带气旋（TC）“天兔”变性过程中降水分布和大尺度环流的演变,并结合片段位涡反演进行修改槽脊的数值试验,研究了环流调整对TC变性过程中非对称降水的影响。结果表明:（1）“天兔”变性前降水集中在路径左侧,伴随着纬向型向经向型调整的背景环流,副热带高压南退的同时减弱西进;（2）TC降水的非对称分布与冷暖锋的相对强弱、水汽输送情况以及高空冷空气下传的落区有直接关系;（3）加强环流调整后,系统斜压性加强,与LOT（降水集中于TC路径左侧）型降水相关的环流指数增大过程随之加强,有利于LOT型降水分布进一步加强。     

Seismically induced changes in groundwater levels and temperatures following the ML5.8 (ML5.1) Gyeongju earthquake in South Korea

Hydrogeological responses to earthquakes such as changes in groundwater level, temperature, and chemistry, have been observed for several decades. This study examines behavior associated with M_L 5.8 and M_L 5.1 earthquakes that occurred on 12 September 2016 near Gyeongju, a city located on the southeast coast of the Korean peninsula. The M_L 5.8 event stands as the largest recorded earthquake in South Korea since the advent of modern recording systems. There was considerable damage associated with the earthquakes and many aftershocks. Records from monitoring wells located about 135 km west of the epicenter displayed various patterns of change in both water level and temperature. There were transient-type, step-like-type (up and down), and persistent-type (rise and fall) changes in water levels. The water temperature changes were of transient, shift-change, and tendency-change types. Transient changes in the groundwater level and temperature were particularly well developed in monitoring wells installed along a major boundary fault that bisected the study area. These changes were interpreted as representing an aquifer system deformed by seismic waves. The various patterns in groundwater level and temperature, therefore, suggested that seismic waves impacted the fractured units through the reactivation of fractures, joints, and microcracks, which resulted from a pulse in fluid pressure. This study points to the value of long-term monitoring efforts, which in this case were able to provide detailed information needed to manage the groundwater resources in areas potentially affected by further earthquakes.

     

3种经典机器学习算法在火山岩测井岩性识别中的对比

岩性识别一直是火山岩油气勘探中的重要课题,基于测井数据的岩性识别也逐渐成为火山岩研究的需要,大数据背景下的机器学习算法为测井岩性识别提供了一个新方向。为提高某研究区火山岩岩性识别符合率,本文采用K近邻、支持向量机和自适应增强3种经典机器学习算法,对研究区内的粗面岩、非致密粗面岩、辉绿岩、辉长岩、玄武岩和非致密玄武岩等6类中基性火山岩进行岩性识别。从常规测井系列中优选对研究区岩性敏感的自然伽马、声波时差、补偿中子、深侧向电阻率和补偿密度等5种测井参数作为岩性识别模型的输入向量,从研究区内5口有岩心样品或薄片鉴定资料的目标层中选取测井数据点1 440个,其中960个作为训练样本,其余480个作为测试样本。以识别符合率和时间作为评价指标,对3种算法的识别结果进行对比分析,实验表明：自适应增强算法的分类准确率最高,6类岩性平均识别符合率达到82.10%;支持向量机算法表现良好,平均识别符合率为81.04%;K近邻算法平均识别符合率为76.04%。     

多时相MODIS指数提取东北三省水稻种植面积

为准确提取水稻面积,以东北为研究区域,采用多时相16d合成MODIS增强型植被指数数据和8d合成MODIS地表反射率数据提取水稻种植分布。选取水稻代表样点利用IDL编程提取物候曲线,利用归一化植被指数(NDVI)将水稻与其他明显地类区分,然后建立水稻增强型植被指数(EVI)、地表水体指数(LSWI)之间的相关关系,结合最新2015年土地利用数据提取东北三省2015年水稻种植面积。同时运用运筹学理论建立省级尺度水稻判别条件最优化模型,分析其在空间分布上的差异性和相关性,并将结果与统计年鉴进行对比分析,分析表明MODIS数据适合大区域省级范围水稻面积的提取,精度可达90%以上。由此得出,MODIS数据在省级尺度提取水稻种植面积上有着较大的优势。     

贵阳市空气质量预报方法与效果检验

2012年环境保护部发布的《环境空气质量标准》实施后,贵阳市空气质量状况发生了变化。利用贵阳市空气质量指数和常规气象要素等资料,分析空气质量特征及其与气象要素的关系,通过多元线性逐步回归和BP神经网络方法,分季节建立空气质量指数预报模型,并同CUACE模式进行对比检验。结果表明:近3年贵阳市空气质量状况良好,优良天数增多,污染天数减少且污染天气多出现在冬季,首要污染物为PM_2.5、PM₁₀和O_3;各季相关因子不同,但主要与相对湿度和风速有关;两种模型预报效果均表现为夏季评价最高,等级TS评分超过85%,指数准确率近99%,冬季预报效果相对最差,TS评分接近或达到70%,指数准确率超过或接近80%,而春、秋季效果指标差距不大;对2015—2016年AQI的预报效果回归模型的优于CUACE模式的,TS评分和预报准确率分别相差16.2%和20.0%。     

北黄海盆地东部坳陷下白垩统砂岩成岩作用及其储层意义

通过对取芯井砂岩镜下特征及孔隙度渗透率变化的分析,研究了北黄海盆地东部坳陷下白垩统砂岩的成岩作用及其储层意义。结果显示,储层砂岩类型以长石砂岩、长石石英砂岩和岩屑石英砂岩为主,处于中成岩作用阶段的A亚期末期至B亚期早期。主要的成岩作用类型有压实作用、压溶作用、胶结作用、交代作用、蚀变作用、溶蚀作用和重结晶作用,主要孔隙类型有粒间孔隙、粒内孔隙、填隙物内孔隙和次生裂缝。长石砂岩是主要储层。压实作用、压溶作用、胶结作用和重结晶作用使砂岩孔隙度减小,降低了储层物性,起到破坏性作用;交代作用、蚀变作用和溶蚀作用使砂岩孔隙度增大,改善了储层物性,起到建设性作用。孔隙度和渗透率整体上由浅变深而呈现由大到小趋势,在深度为3 000~3 020 m和3 140~3 250 m时出现异常高值,孔隙度与渗透率的异常高值带是次生孔隙发育带。     

冻结砂土体积变形影响因素的敏感性分析

为了分析三轴试验中冻土体积变形影响因素的敏感性,选定包括内因和外因在内的6种影响因素,选用青海省德令哈的砂土按照正交试验方案进行常规三轴试验,并采用灰色关联分析法对试验结果进行分析,给出各影响因素的敏感性排序。结果表明,在选定的6种影响因素中,含水率、加载速率及温度的敏感性超过70%,需重点考虑。在较小含水率条件下,冻结砂土先体缩再体胀,且应力峰值点和应变峰值点所对应的轴向应变基本一致,而在饱和条件下仅发生体积膨胀。加载速率对冻土的影响主要表现为对其力学特性和破坏形态的改变,随着加载速率的增加冻土的体缩量、切线模量和峰值强度增加,但峰值应变却表现为减小趋势,冻结砂土性质趋近脆性。土样温度降低,土颗粒间的黏结力增加,孔隙压力转变为有效应力,从而导致冻结砂土的强度增加、体积膨胀量增加。分析结果可为相关试验及工程优化设计提供一定的参考。     

Grounding mobile policies: Ad hoc networks and the creative city in Bandung,Indonesia

This paper explores the ad hoc networks that form to move policies to new sites by examining the process through which the city of Bandung, Indonesia adopted a creative city policy. As revealed through the Bandung case, attention to the formation of these networks highlights the way that power operates within them, privileging certain ideas and structuring the ways in which information flows through their channels. This insight suggests that the concept of policy mobilities would be enriched by a closer attention to the way power is used to construct networks that promote specific policies and places as sites of ‘best practice’. Furthermore, this paper extends the concept of policy mobilities to a city ‘off the map’. In contrast to most existing policy mobilities research that tends to focus on the stable, large‐scale networks through which policies travel and on the high‐profile cities constructed as policy models, the case of Bandung provides a study of how policy mobilities may occur differently outside of its well‐established locations.     

环北极国家与地区的北极航道通行政策及其发展趋势分析

全球变暖加快了北冰洋融化的速度,从而使得北极航道全面开通的时间将比预期大大提前,北极航道的交通价值也日益凸显。在这种情况下,环北极国家与地区纷纷提出了对北极航道通行的政策和主张。中国虽不是环北极国家,但北极航道能缩短中国国际贸易的海运距离,节约货物海上运输的时间和成本,并降低传统航线的海盗和恐怖主义袭击风险,所以从维护中国在北极航道通行问题上的"潜在利益"的角度出发,中国应该加强对北极航道通行问题的关注。本文首先介绍了北极航道问题的由来,逐一阐述了俄罗斯、加拿大、美国和欧盟在北极航道通行问题上的政策和主张,最后分析了北极航道通行政策的发展趋势。