城市建成区遥感影像边界提取与扩张分析

针对城市建成区提取过程中,仅依赖单一数据源导致精度不够的问题,本文基于面向对象分类方法和利用土地类型信息标准差统计变量,实现遥感影像中城市建城区边界的提取,并以该建成区为依据对河南省虞城县的城区空间扩张特征作了分析。实验中首先采用均值漂移分割算法对高分一号遥感影像实现分割,然后利用决策树分类算法实现土地利用类型分类,最后基于0.1 km × 0.1 km窗口统计土地利用类型标准差信息,获取建成区边界。面向实际应用,以河南省虞城县为例,采用高分一号影像获得虞城县2017年建成区数据,并基于该数据采用多个TM影像提取城区其他年份的建成区边界,实现河南省虞城县城区空间扩张特征分析。结果表明,本文方法获取的建成区边界精度较一般的监督分类提取边界有进一步的提高,精度达到89%。进而说明结合高分辨率影像提取多个年份的建成区数据的可靠性,在城市扩张研究中,对仅利用低空间分辨率提取精度不够问题和仅利用高分辨影像提取效率低等问题提供了较好的解决方案。     

Cavity expansion in unsaturated soils exhibiting hydraulic hysteresis considering three drainage conditions

Cavity expansion theory assists in the interpretation of in situ tests including the cone penetration test and pressuremeter test. In this paper, a cavity expansion analysis is presented for unsaturated silty sand exhibiting hydraulic hysteresis. The similarity technique is used in the analysis. The soil stress–strain behaviour is described by a bounding surface plasticity model. Results of oedometric compression tests, isotropic compression tests and triaxial shear tests for both saturated and unsaturated states are used to calibrate the model. The void ratio, suction, degree of saturation and effective stress are fully coupled in the analysis. The influence of where the initial hydraulic state is located on the soil–water characteristic curve on the cavity wall pressure is investigated and found to be significant. Also, the effects of three different drainage conditions (constant suction, constant moisture content and constant contribution of suction to the effective stress) on cavity wall pressure are studied. It is found that the drainage condition in which the contribution of suction to the effective stress is constant offers a good approximation to the other two. This may simplify interpretation of in situ tests. When testing occurs quickly, meaning a constant moisture content condition prevails, a constant contribution of suction condition can be assumed without loss of significant accuracy. The contribution of suction assumed in the interpretation can be taken as being equal to the in situ value, although this discovery may not be applicable to all soil types, constitutive models and soil–water characteristic curves. Copyright © 2015 John Wiley & Sons, Ltd.     

中、新生代太平洋陆缘带的构造格局和构造转换

亚洲东部大陆边缘和北美西部大陆边缘同处于环太平洋构造带，但具有不同的构造属性。从晚白垩世到新生代，前者以构造扩张为背景，由此引起陆缘裂解，陆块漂移以及岛弧、边缘海的形成；后者以构造收缩为基础，导致陆缘增生、陆块拼贴和陆缘造山带的出现。然而，从晚侏罗世到早白垩世，亚洲东部是以构造封闭型的陆缘带为特点，北美西部则主要表现为开放型的陆缘带。构造扩张和构造收缩是环太平洋陆缘带构造环境的两种基本型式，它们在空间上呈有规律的对峙分布，在时间上成有节奏的交替转换。     

Spatio-temporal Characteristics of Residential Land Growth in Hefei of Anhui Province, China

We used the maps of urban land-use in 1978, 1991, 1994, 2000 and 2004, and softwares such as ArcGIS, Fragstats to analyze the spatio-temporal process of urban residential space quantitatively. Some methods, such as di- rection analysis and landscape pattern analysis, were employed. The results show that: 1) the residential land grew very rapidly in Hefei from 1978 to 2004, and the increased land was distributed mainly in the central city zone surrounded by a moat; however, after 1994, it was distributed mainly outside the 1th Ring Road; 2) the expansion speeds were very different in different directions: there exists a fastest expansion of residential land in the directions of NE-NNE, SW and SSE, and a slowest one in the directions of E and SEE; 3) the residential land growth went through four stages: slow circular expansion in 1978-1991, 'axes fan wings' expansion in 1991-1994, more rapid circular expansion in 1994-2000 and 'fan-wings' expansion in 2000-2004; 4) the expansion intensity was also different in all directions in the period of 1978 to 1994, and the most was in SW and then NW; and 5) there were more and more residential land area, and the spatial agglomeration was improved increasingly.     

深部大尺度单一密度界面重力异常迭代反演

对于深部大尺度单一密度界面的重力异常反演,需顾及球形观测面和重力铅垂线变化的影响。为此,本文通过球谐展开,得到重力异常的级数展开式,并推导出积分形式的反演迭代解。该迭代方法要求设法分离出单一密度界面的重力异常,已知界面上、下层的密度差和尽可能多的深度控制点。模型和实例显示其效果良好,可用于莫霍界面、岩石层底界面等深部密度界面重力异常的反演。     

Molecular dynamics interpretation of structural changes in quartz

 Constant temperature and constant pressure molecular dynamics (MD) simulations were applied to quartz to calculate the structural details which are indeterminable in usual X-ray structure studies. The dynamics of the structural changes was analyzed by means of time-dependent atomic displacement parameters. The Si-O bonds expand with increasing temperatures through the α- and β-phases, and atoms vibrate around the α₁- (or α₂-) sites at lower temperatures in the α-phase, and over the energy barriers between the α₁- and the α₂-sites at higher temperatures in the α- and the β-phases. The ratios of time lengths spent by atoms in the α₁- and α₂-sites determine the apparent atomic positions as obtained in usual structure studies of α-quartz. More frequent transfer of atoms over the α₁- and the α₂-sites contributes positively to the thermal expansions, whereas larger amplitudes of vibrations, which carry atoms more distantly and more frequently from the β-sites, contribute negatively. The well-known steep thermal expansion in the α-phase is attributed to the additive contribution from the expansions of the Si-O bond lengths, the widening of Si-O-Si angles, and the increase of the atomic transfer-frequency between the α₁- and the α₂-sites. The nearly zero or negative expansion in the β-phase is caused by balancing the negative to the positive effects. The MD crystal transforms to the β-phase via a transitional state, where the α- and β-structures appear alternately with time, or coexist. The slight and continuous expansions observed right after the steep rise(s) of the volume or cell dimensions up to the nearly horizontal curve(s) are attributed to the continuous changes within the transitional state. Received: 17 July 2000 / Accepted: 13 January 2001     

青藏、伊朗高原地区300hPa温度场异常与我国降水的关系

青藏高原、伊朗高原地区下垫面的热力异常在300hPa温度场上有明显的特征,本文利用SVD诊断方法分析了300hPa温度场异常与我国区域降水的关系。分析表明：(1)伊朗高原南部和青藏高原中东部地区4月份300hPa温度与我国黄河上游以南地区5月份降水有显著的正相关关系;(2)高原大部特别是其南部地区4～6月300hPa温度与我国长江中下游以南部分地区7月份降水存在显著的反相关关系;(3)高原大部特别是其南部地区4～8月300hPa温度与我国黄河下游以南部分地区9月份降水有显著的正相关关系;(4)高原中部前一年6～10月300hPa温度与当年我国1月份长江中下游及以南大部分地区降水存在显著的反相关关系;(5)伊朗高原特别是伊朗高原中南部前一年6～10月300hPa温度与当年我国4～5月份长江中下游部分地区降水存在显著的反相关关系;(6)高原中南部9～10月300hPa温度与我国11月份长江中下游以南部部分地区降水存在显著的反相关关系。     

天然文石-方解石的高温相变及热膨胀性质

利用高温粉末X射线衍射研究了高纯地质成因文石从室温到1 073 K的相变过程以及文石和方解石的热膨胀性质,并分析了地质成因与生物成因文石的差异和影响因素。结果表明:斜方晶系的文石在693～733 K转变为三方晶系的方解石,相变临界温度为723 K,摩尔体积增加5.97%;文石在300～663 K的体积热膨胀系数α(V)(10-5/K)随绝对温度T(K)的变化规律为:α(V)=3.59(79)+7.17(170)×10-3T,文石的热膨胀具有强烈的各向异性[轴向热膨胀系数α(c)α(b)α(a)];方解石在733～973 K的热膨胀系数α(10-5/K)为:α(V)=3.78(25),α(a)=-0.27(2),α(c)=4.31(29),a轴具有负热膨胀。生物成因的文石相变温度比合成和地质成因文石低60～140 K,粉末状文石相变温度低于单晶和未被破坏的整块文石;粉末状的生物成因文石和方解石与非生物成因的文石和方解石的热膨胀系数接近,然而整块的生物成因的文石有更小的热膨胀系数。     

重庆市直辖以来的城市空间扩展与机制

本文采用以城市土地利用年均扩展指数来表征城市空间扩展强度及其空间差异、以关联度系数来刻画要素因子对城市空间扩展影响机制的研究思路,初步构建了一种以城市土地利用面积、自然、人文、社会、经济、生态以及其他因素相结合的指标系统,以此定量揭示城市空间扩展动态演变及其影响机制的评价方法。通过对重庆市1997年直辖以来近10年的城市空间扩展实证研究表明,重庆城市由直辖初期的"极核式"空间布局逐步发展成为由"分散集团式"和"集中型同心圆式"组合成的复合式空间格局。而经济水平的持续发展是重庆市城市空间扩展的主要原因,政府引导下的大型项目建设及市场导向的乡村工业化建设过程,是改革开放以来重庆城市空间扩展的主要影响要素和扩展机制之一。     

西宁黄土状盐渍土作为回填材料的研究

通过对西宁地区黄土状盐渍土地基的分布、工程性质特点及其对建筑物危害的调查,分别从黄土状盐渍土的湿陷（溶陷）、盐胀和腐蚀性三大特点出发,对西宁黄土状盐渍土地基中回填用料土含盐量的变化对地基土性质的影响作了一些试验研究,提出了一些观点,通过实践取得了一定的社会效果和经济效益。