SAR image coregistration using fringe definition detection

In order to overcome the limitation of cross correlation coregistration method for Synthetic Aperture Radar(SAR) interferometric pairs with low coherence,a new image coregistration algorithm based on Fringe Definition Detection(FDD) is presented in this paper.The Fourier transformation was utilized to obtain spectrum characteristics of interferometric fringes.The ratio between spectrum mean and peak was proposed as the evaluation index for identifying homologous pixels from interferometric images.The satellites ERS-1/2 C-band SAR acquisitions covering the Yangtze River plain delta,eastern China and ALOS/PALSAR L-band images over the Longmen Shan mountainous area,southwestern China were respectively employed in the experiment to validate the proposed coregistration method.The testing results suggested that the derived Digital Elevation Model(DEM) from FDD method had good agreement with that from the cross correlation method as well as the reference DEM at high coherence area.However,The FDD method achieved a totally improved topographic mapping accuracy by 24 percent in comparison to the cross correlation method.The FDD method also showed better robustness and achieved relatively higher performance for SAR image coregistration in mountainous areas with low coherence.     

A generalized limit equilibrium method for the solution of active earth pressure on a retaining wall

In this paper, a generalized limit equilibrium method of solving the active earth pressure problem behind a retaining wall is proposed. Differing from other limit equilibrium methods, an arbitrary slip surface shape without any assumptions of pre-defined shapes is needed in the current framework, which is verified to find the most probable failure slip surface. Based on the current computational framework, numerical comparisons with experiment, discrete element method and other methods are carried out. In addition, the influences of the inclination of the wall, the soil cohesion, the angle of the internal friction of the soil, the slope inclination of the backfill soil on the critical pressure coefficient of the soil, the point of application of the resultant earth pressure and the shape of the slip surface are also carefully investigated. The results demonstrate that limit equilibrium solution from predefined slip plane assumption, including Coulomb solution, is a special case of current computational framework. It is well illustrated that the current method is feasible to evaluate the characteristics of earth pressure problem.     

基于陆态网络GPS数据的电离层空间天气监测与研究

中国大陆构造环境监测网络(简称陆态网络)是以全球卫星导航定位系统(GNSS)为主,辅以多种空间观测技术,实时动态监测大陆构造环境变化,探求其对资源、环境和灾害的影响的地球科学综合观测网络.基于陆态网络约200个基准站的GPS观测数据,本文探讨了其在电离层空间天气监测与研究方面的应用.包括磁暴期间电离层暴扰动形态,大尺度电离层行进式扰动,太阳耀斑引起的电离层骚扰和低纬电离层不规则体结构等.研究结果表明:陆态网络布局合理,观测数据质量良好,完全可用于中国及周边地区电离层空间天气监测与研究,为进一步开展我国电离层空间天气预警和预报奠定了观测基础.     

特高压输电线路塔线耦联体系非线性振动响应振动台试验研究

为了研究地震作用下特高压塔线耦联体系导线、地线的非线性振动响应,文中以单向和双向一致激励为主,通过输入不同加速度幅值的El Centro波、Taft波、Pasadena波及上海人工波,对某型特高压输电塔线耦联体系进行了缩尺模型振动台试验.试验主要分2种工况:将导线作为集中质量进行计算的方法以及挂有实际分裂导线模型的方法.试验结果表明:两种体系中塔体结构动力特性存在差别;地震作用下,挂线单塔各项动力反应峰值比相应的单塔悬挂集中质量有不同程度的降低,8度罕遇地震时较为显著,导线的非线性振动效应有利于该型输电塔动力反应幅值的降低.挂线单塔与挂集中质量单塔不同方向的加速度能量谱分布规律存在较大差异.     

An analytical study on turbulence with mixed-flow model and two-phase model

Suspended sediment is carried by turbulent water flows in rivers.Traditional sediment-laden flow analysis treats the suspension as a mixed liquid,and recent two-phase flow model enables separate velocity measurement of the two coupling phases.A simplified theoretical analysis was presented to discuss the differences between the two models in reporting turbulence intensity in experimental research.The turbulence intensity of the mixture is lower than the weighted average of those of the two phases in mixed-flow experiments.The mixture’s turbulence intensity becomes higher than the average of the two phases in two-phase experiments due to the presence of velocity lag.The same set of data may lead to either an underestimation or an overestimation of actual turbulence levels when different models are used.     

YRY-4型钻孔应变观测抽水影响分析

分析泰安基准地震台YRY-4型钻孔应变仪仪器受不同位置抽水的影响,就地下岩石含水变化所产生的地形变干扰,简要分析地下水与地下岩石间的相互作用。这对地震前兆的研究有重要实用意义。     

基于地震对应概率谱分析的定点形变前兆异常探索

利用地震对应概率谱和累计滑动平均概率方法,选取精河水平摆卡尔曼滤波差值进行中强地震前兆定量的异常识别探索。探索中先是对精河水平摆卡尔曼滤波差值数据进行数据分布及各区间参数有震对应分布的研究,然后利用累计滑动平均方法得到滑动平均概率,从而检验地震对应概率谱在定点形变前兆异常的预报效能。     

DEM-based numerical modelling of runoff and soil erosion processes in the hilly–gully loess regions

For sake of improving our current understanding on soil erosion processes in the hilly–gully loess regions of the middle Yellow River basin in China, a digital elevation model (DEM)-based runoff and sediment processes simulating model was developed. Infiltration excess runoff theory was used to describe the runoff generation process while a kinematic wave equation was solved using the finite-difference technique to simulate concentration processes on hillslopes. The soil erosion processes were modelled using the particular characteristics of loess slope, gully slope, and groove to characterize the unique features of steep hillslopes and a large variety of gullies based on a number of experiments. The constructed model was calibrated and verified in the Chabagou catchment, located in the middle Yellow River of China and dominated by an extreme soil-erosion rate. Moreover, spatio-temporal characterization of the soil erosion processes in small catchments and in-depth analysis between discharge and sediment concentration for the hyper-concentrated flows were addressed in detail. Thereafter, the calibrated model was applied to the Xingzihe catchment, which is dominated by similar soil erosion processes in the Yellow River basin. Results indicate that the model is capable of simulating runoff and soil erosion processes in such hilly–gully loess regions. The developed model are expected to contribute to further understanding of runoff generation and soil erosion processes in small catchments characterized by steep hillslopes, a large variety of gullies, and hyper-concentrated flow, and will be beneficial to water and soil conservation planning and management for catchments dealing with serious water and soil loss in the Loess Plateau.     

Influence of Three Gorges Dam on streamflow and sediment load of the middle Yangtze River, China

Using updated hydrological datasets from three stations, including Cuntan, Yichang and Hankou, covering the period of January 1992–December 2008, the influence of Three Gorges Dam (TGD) on streamflow and sediment load of the Yangtze River was investigated. Results indicated that TGD did not seem to exert a significant influence on streamflow occurring at three stations and changes in streamflow can be mainly attributed to streamflows of tributaries. However, a sharp decrease in the sediment load after the impoundment of TGD was observed. Clear water after the impoundment caused erosion of riverbed and resulted in more sediment at the Hankou station than at the Yichang station. No distinct changes in the annual and monthly maximum sediment loads were observed before and after the impoundment. Therefore, annual and monthly maximum sediment load changes should be subjected mainly to river hydraulics. This study has practical relevance for understanding the influence of large hydraulic structures on the hydrological processes of large rivers.     

高原地区农作物水热指标与特点的研究进展

通过对作物农业气象条件鉴定、作物农业气象试验研究、作物生态气候适应性分析和作物农业气候区划以及农业气象灾害调查记载对比评估分析等手段, 整理和总结了髙原地区7种粮食作物、6种经济作物、6种特色作物、7种瓜果作物和4种中药材等共计30种农作物水热指标以及冬小麦和春小麦土壤水分指标. 高原地区作物水热指标具有4个明显特点, 釆用不同积温界限值来确定不同作物属性热量指标, 喜凉、中性、喜温和喜热作物分別釆用≥0 ℃、≥5 ℃、≥10 ℃和≥15 ℃积温界限值作热量指标. 不同温度带作物适宜的热量指标差异明显, 有随温度带愈冷凉作物热量指标呈偏低的趋势. 不同水分气候区作物水分指标差异较大, 有随湿润度增加作物水分指标呈递减的趋势. 作物水热指标随气候变化而发生缓慢变化, 气候变暖使作物全生长期延长, 对同一熟性品种而言, 需要热量指标比变暖前有提高趋势; 气候变干使作物水分指标有增加趋势. 农作物水热指标是衡量作物适生种植的重要标准, 是引种、作物布局、栽培管理、髙产优质安全生产的重要科学依据, 是气象为农业服务必不可少的基础资料, 也是服务工作的前提.