梅州市城镇化发展若干问题的探讨   总被引：3，自引：0，他引：3  

罗迎新 《热带地理》2006,26(4):339-343,348

通过专家咨询与调研,运用定性与定量综合分析方法,阐述了梅州市城镇化发展经历起步、波动徘徊、恢复、提高发展4个阶段基本特征,分析了规划认识不足,基础设施建设滞后,产业结构不合理,城镇管理水平低等不利因素对梅州市城镇化发展的影响,认为实施城镇化发展战略是创新"开放梅州"的环境基础,是创新"工业梅州"的重要载体,是创新"生态梅州"的重要途径,是创新"文化梅州"的孕育温床,提出了梅州市城镇化发展的思路,包括制订城镇发展规划;优化城镇空间结构,建立城镇体系;创新城市管理制度,实施"经营城市"策略;重视文化遗产承传与  相似文献   

An application of problem and product ontologies for the revision of beach nourishments     

D. Van de Vlag  B. Vasseur  A. Stein  R. Jeansoulin 《International journal of geographical information science》2013,27(10):1057-1072

An ontological approach in GIS serves as a framework for the conceptualization of processes in the real world. In this paper, we examine an application in coastal change in the Netherlands, whereby beaches are subject to artificial nourishment to offset the effect of severe erosion. The use of ontologies helps to define two scenarios: S_I determined by the regulations from the Ministry for Public Works; S_II grounded on the abilities from an existing spatial dataset. A comparison between S_I and S_II shows that 72.8% of the objects suitable and unsuitable for nourishment are correctly classified. A higher overlap is found in areas where actual beach nourishments were carried out. Inaccuracies in attributes influence the determination of the objects. A sensitivity analysis applied to altitude illustrates a significant increase of objects suitable for nourishment for both scenarios, when altitude is decreased within the lower limit of the root mean square error for the 95% confidence interval. Moreover, the sensitivity of altitude shows that artificial boundaries for beach nourishment objects are not reasonable and consequently should be treated as vague objects.  相似文献   

宝鸡黄土区滑坡遥感调查中遥感数据尺度问题探讨     

徐刚 《地质力学学报》2017,23(1):88-96

遥感数据的尺度效应决定了可识别内容与识别精度,同一区域内的遥感数据尺度不同,同样的遥感处理模型或者方法将得到不同的处理结果。以宝鸡黄土区滑坡遥感调查为基础,对不同遥感数据源的滑坡体的最小可识别面积、图斑面积精度测算、最佳及最大成图比例尺、遥感地质灾害解译对比性分析、滑坡遥感解译精度评价等等与遥感尺度有密切关系的问题进行了探讨。研究结果表明,在宝鸡黄土区,调查大、中型以上滑坡的信息,可以采用SPOT-5(2.5 m)融合图像数据,比例尺为1∶25000或1∶50000;调查中型、小型滑坡及较大滑坡体内部结构定量信息,可以采用Quick Bird(0.61 m)融合图像数据,比例尺为1∶5000。  相似文献   

Research on ground fissure origins and mechanisms in Hebei Plain,P. R. China     

QI Jian-feng  TIAN Meng-ke  CHI Xiu-cheng  WANG Cheng-zhen 《地下水科学与工程》2016,4(3):188-196

In order to assess the geological environment impact of a city landfill by the Yangtze River, soils from different depths in the dumpsite were sampled and analyzed. It was found that pollutants content at the site was distinctly higher than that in nearby environments. The content of heavy metals, such as Cd, Hg, As, Pb and Cu, reduces as depth increases; the content of elements F, Cl and N is the contrary. Pollutants migration driven by underground water flow was analyzed, considering the hydro-geological conditions of the site. It is believed that, due to leaching after rainfall infiltration, pollutants in the garbage layer migrates deeper, the cohesive soil in the underlying surface prevents them from spreading to the deeper aquifer; additionally, the high pressure tolerance of the deep groundwater is a key factor in preventing pollutants from entering the aquifer. Furthermore, human control has reduced the annual fluctuation range of water level in nearby rivers, weakening the hydrodynamic relations with phreatic water, and thus reducing the spreading of pollutants to nearby surface waters.  相似文献   

珠江源区生态地质环境安全体系构建研究     

白海霞  王嘉学  普荣 《地质灾害与环境保护》2011,22(1):76-79

珠江源区森林生态系统严重退化,湿地遭到破坏,导致石漠化和水土流失严重,水旱灾害频繁。生态地质环境问题制约了该区经济和社会的发展,影响了整个珠江流域。应在加强全民教育的基础上,坚持科技引导,推进制度建设,以退耕还林为切入点,调整产业结构,改善农村能源结构,建立生态地质环境监测网,以此构建一个珠江源区生态地质环境安全体系。  相似文献   

定点在日-地(月)系L1点附近的探测器的发射及维持   总被引：1，自引：0，他引：1  

侯锡云  刘林 《天文学报》2007,48(3):364-373

在限制性三体问题中共线平动点附近的运动虽然是不稳定的,但可以是有条件稳定的,该动力学特征使得一些有特殊目的的探测器只需消耗较少的能量即可定点在这些点附近(如ISEE-3、SOHO).以日-地(月)系的L1点为例,根据其附近的运动特征,探讨定点探测器的发射与轨道控制问题,给出了相应的数值模拟结果,为工程上的实现提供理论依据.  相似文献   

对青海省水文地质工程地质环境地质勘查工作的几点思考     

罗银飞  赵振  陈惠娟 《城市地质》2013,(3):6-9

根据青海省国有地勘队伍和行业工作近年来呈现的主要特点,分析了青海省水工环地质勘查队伍建设,行业工作相对于经济社会发展需求间存在的问题,为进一步做好水工环地质工作提出了参考建议。  相似文献   

Experimental and numerical evaluation of the effectiveness of a stiff wave barrier in the soil     

《Soil Dynamics and Earthquake Engineering》2015

This paper discusses the design, the installation, and the experimental and numerical evaluation of the effectiveness of a stiff wave barrier in the soil as a mitigation measure for railway induced vibrations. A full scale in situ experiment has been conducted at a site in El Realengo (Spain), where a barrier consisting of overlapping jet grout columns has been installed along a railway track. This barrier is stiff compared to the soil and has a depth of 7.5 m, a width of 1 m, and a length of 55 m. Geophysical tests have been performed prior to the installation of the barrier for the determination of the dynamic soil characteristics. Extensive measurements have been carried out before and after installation of the barrier, including free field vibrations during train passages, transfer functions between the track and the free field, and the track receptance. Measurements have also been performed at a reference section adjacent to the test section in order to verify the effect of changing train, track, and soil conditions over time. The in situ measurements show that the barrier is very effective: during train passages, a reduction of vibration levels by 5 dB is already obtained from 8 Hz upwards, while a peak reduction of about 12 dB is observed near 30 Hz immediately behind the barrier. The performance decreases further away from the jet grouting wall, but remains significant. The experimental results are also compared to numerical simulations based on a coupled finite element–boundary element methodology. A reasonable agreement between experiments and predictions is found, largely confirming the initially predicted reduction. This in situ test hence serves as a ‘proof of concept׳, demonstrating that stiff wave barriers are capable of significantly reducing vibration levels, provided that they are properly designed.  相似文献   

现代气象服务体系若干问题研究   总被引：4，自引：1，他引：4  

汤绪  张洪广 《气象与减灾研究》2001,24(4):5-8

在分析有关国家建立现代气象服务体系做法的基础上,结合我国气象服务工作实际,提出了现代气象服务体系的基本概念和我国建立现代气象服务体系的必要性和紧迫性,并对现代气象服务体系的运行机制、组织结构、技术支撑和如何建立现代气象服务体系进行了探讨和研究。  相似文献   

Confidence regions for GPS baselines by Bayesian statistics     

B. Gundlich  K.-R. Koch 《Journal of Geodesy》2002,76(1):55-62

 The global positioning system (GPS) model is distinctive in the way that the unknown parameters are not only real-valued, the baseline coordinates, but also integers, the phase ambiguities. The GPS model therefore leads to a mixed integer–real-valued estimation problem. Common solutions are the float solution, which ignores the ambiguities being integers, or the fixed solution, where the ambiguities are estimated as integers and then are fixed. Confidence regions, so-called HPD (highest posterior density) regions, for the GPS baselines are derived by Bayesian statistics. They take care of the integer character of the phase ambiguities but still consider them as unknown parameters. Estimating these confidence regions leads to a numerical integration problem which is solved by Monte Carlo methods. This is computationally expensive so that approximations of the confidence regions are also developed. In an example it is shown that for a high confidence level the confidence region consists of more than one region. Received: 1 February 2001 / Accepted: 18 July 2001  相似文献