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21.
全站仪似水准法和对向法高程测量的比较研究   总被引:1,自引:0,他引:1  
魏东升  李星照 《测绘科学》2008,33(1):152-154
通过对似水准法和对向法高程测量原理、误差来源及精度的比较分析,我们发现随着距离和竖直角度的增大,对向法高程测量中误差的变化大于似水准法高程测量中误差的变化;当两观测点间的水平距离小于等于1km时,对向法高程测量精度一般高于似水准法高程测量精度,但是当两观测点间的水平距离大于1km时,似水准法高程测量精度一般高于对向法高程测量精度。  相似文献   
22.
针对目前常规水准测量在山区公路高程控制测量中的局限性,本文提出了一种三角高程与常规水准测量相结合的混合构网方法,并通过实例得出,这种方法充分利用了两者的优势,在保证成果的可靠性和精度的同时,大大提高了工作效率,缩短了生产周期。  相似文献   
23.
We have reinvestigated the mid-Cretaceous plume pulse in relation to paleo-oceanic plateaus from accretionary prisms in the circum-Pacific region, and we have correlated the Pacific superplume activity with catastrophic environmental changes since the Neoproterozoic. The Paleo-oceanic plateaus are dated at 75–150 Ma; they were generated in the Pacific superplume region and are preserved in accretionary prisms. The volcanic edifice composed of both modern and paleo-oceanic plateaus is up to 10.7 × 106 km2 in area and 19.1 × 107 km3 in volume. The degassing rate of CO2 (0.82 − 1.1 × 1018 mol/m.y.) suggests a significant impact on Cretaceous global warming. The synchronous occurrence of paleo-oceanic plateaus in accretionary complexes indicates that Pacific superplume pulse activities roughly coincided at the Permo-Triassic boundary and the Vendian–Cambrian boundary interval. The CO2 expelled by the Pacific superplume probably contributed to environmental catastrophes. The initiation of the Pacific superplume contributed to the snowball Earth event near the Vendian–Cambrian boundary; this was one of the most dramatic events in Earth's history. The scale of the Pacific superplume activity roughly corresponds to the scale of drastic environmental change.  相似文献   
24.
本文概要介绍了我国21世纪发展白皮-《中国21世纪议程》;全面列举了国际社会对西北地区第一批优先项目支持的承诺,勾勒了西北地区“可持续发展之路”的轮廓。  相似文献   
25.
Erratum to: GeoJournal 62: 51–58 DOI 10.1007/s10708-005-8562-2 The erroneous version of this article was originally published in GeoJournal 62: 51–58. This amended version corrects the formatting errors which are evident in the original version.Abstract It is universally accepted that the need for defining precise lines of separation and points of contacts between states is the byproduct of the emergence of nation-states and ‘world economy’ in the nineteenth century Europe. Nevertheless, it is hard to overlook the fact that these modern notions are rooted in periods prior to the emergence in Europe of nation-states. There are indications that ancient civilizations were familiar with the notion of ‘state’ in connection with the concepts of territory and boundary. Ancient texts reveal that this basic principle existed in ancient Persian literature in respect of matters of state, territory, and boundary. Similarly, the likelihood exists that these Persian notions could have influenced Roman civilization. It is widely believed that a combination of ancient Greco-Roman and Persian civilizations is a major contributor to what culturally constitutes ‘West’. Later in the Sassanid period the inter-linked notions of state, territory, and boundary developed substantially, coming quite close to their contemporary forms. On the other hand, considering that ‘justice’ was the corner stone of ancient Persian Political philosophy, the idea that ancient␣Iranian spatial arrangement might have contributed to the evolution of the concept of democracy in the West may not be too difficult to contemplate.The online version of the original article can be found at  相似文献   
26.
This article discusses the involvement of older women and men in voluntary work in rural communities in the Netherlands. Gender, ageing and civil society form the core concepts in the article. Politicians and policy makers in the Netherlands are worried about the perceived decline of civil society and about the consequences of this decline for specific categories of older women in terms of well-being and social exclusion. The paper presents the results of two surveys of involvement of older women and men in civic organisations, voluntary work and local actions. The surveys indicate high levels of involvement of both women and men. No gender differences are found in activity level. However, the data demonstrate the gendered nature of civil society. Women are more engaged in informal voluntary work and informal local actions, while men are more active in formal organisations and functions. This gender segmentation is not absolute, however. Many older women and men transgress the traditional feminine–masculine boundaries. The surveys highlight the involvement of women and men in rural communities, but indicate lower activity levels in urban areas.  相似文献   
27.
库车坳陷侏罗系煤成气动力学模拟研究   总被引:1,自引:0,他引:1  
应用黄金管—高压釜封闭体系热模拟实验与GC、GC-IRMS分析技术,结合KINETICS专用软件,对库车坳陷侏罗系煤成气进行了动力学模拟研究。库车坳陷侏罗系煤具有高的产气性,在高演化阶段主要产甲烷气;侏罗系煤热解气甲烷碳同位素为-36‰~-25‰,乙烷碳同位素为-28‰~-16‰;甲烷、C2-C5气态烃的生成活化能分别为(47~64k)calm/ol、(55~72k)calm/ol,频率因子各为5.265×1013s-1、5.388×1018s-1。在此基础上,进一步探讨了克拉2气田天然气的成因。研究认为,克拉2气田天然气属阶段捕获的煤成气,主要聚集了5~1Ma时期的天然气,其成熟度Ro分布范围为1.3%~2.5%。  相似文献   
28.
The influences of exposure to the atmosphere on ammonium cycle in the intertidal surface sediments were in situ studied with a geochemical approach at a typical station in the Yangtze Estuary during three tidal cycles in September 2003. During an about 8-h emersion period of each diurnal tide, six high-resolution vertical profiles of adsorbed and dissolved ammonium were measured. It was observed that both adsorbed and dissolved ammonium generally had an increasing trend in sediment cores during the exposure. The rate of ammonium regeneration in sediments was estimated using the accumulation amount of ammonium including adsorbed and soluble fractions during the daytime emersion. The calculation result showed that there was relatively high ammonification rate (˜500 nmol N cm−3 day−1), which reflected that organic nitrogen in sediments was quickly decomposed with a residence time of ˜52.7 days. Due to the dramatic temperature difference observed in sediment profiles, free convection was considered an important mechanism of regulating the efflux of produced ammonium into overlying waters. The total estimated amount of regenerated ammonium was ˜1.35×105 t N year−1 in the intertidal flat of the Yangtze Estuary, which occupied 7.6% of the total inorganic nitrogen annually transported to the estuarine ecosystem.  相似文献   
29.
东准噶尔巴塔玛依内山组是典型陆相火山.沉积体系(盆地),主体由基性及中酸性火山熔岩组成,火山碎屑岩及火山碎屑沉积岩较少,通过对纸房地区晚石炭世巴塔玛依内山组陆相火山岩的岩石化学、地球化学特征进行系统研究,认为它属于造山期后固结初期,新陆壳裂谷向高原火山岩演化的同岩浆源、同沉积盆地、同火山作用的钙碱系列双峰式火山岩.  相似文献   
30.
 以图像处理、GIS为平台,对哈萨克斯坦阿克纠宾地区的重、磁、电、遥感及地震资料进行了综合分析。指出,该地区重、磁力资料信息含量较高,对于确定盐下构造分布具有积极意义。使用遥感资料对小断层及裂隙发育状况进行研究,有助于裂隙孔隙型碳酸盐岩油藏开发注水效率的提高。同时可对扎纳若尔、阿里别克莫拉等油田的井网状况进行监控和地面设施进行调查。  相似文献   
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