排序方式： 共有55条查询结果，搜索用时 31 毫秒
41.
图像信息学(PI)算法已经成为了地震较活跃地区研究中长期地震危险趋势的重要算法,近年来已被应用于多个国家和地区的地震预测工作中.为进一步探索PI算法在地震活动相对较弱地区的预测效能以及其对地区性差异的依赖情况,本文以山东及邻区为研究区,通过遍历计算模型中网格大小、预测时间窗起点及长度三种参数下的预测结果,并以定量检验算法效能的"ROC值"为统计检验方法,在目标震级ML4.0、ML4.5、ML5.0情况下分别分析不同参数组合下的预测结果,得到了针对本研究区PI算法对几种参数的依赖关系.进一步选取优势参数分布中的参数组合,以回溯性和"向前"预测两种情况分别给出了在相应预测时间窗口内发生目标地震的"热点"分布,最后针对算法的技术及物理问题进行了讨论.本工作探索了不同计算参数对算法预测效能的影响以及PI算法在地震活动相对较弱地区的适用性,简要讨论了不同震级范围表现出来的自相似特征对算法的影响,可为将算法引入到山东地区的地震危险性研究工作提供参考. 相似文献
42.
汽车产业集群网络演化与驱动机制研究——以奇瑞汽车集群为例 总被引：4，自引：2，他引：2
产业集群的理论本质在于专业化集聚基础上的地方化结网。基于对奇瑞汽车集群跟踪研究,获取了2005年、2010年、2014年的企业关系数据,刻画了企业网络演化过程及驱动机制。发现：① 1997~2014年,奇瑞汽车集群网络经历了“松散型网络-紧凑型网络-开放型网络”演化过程,网络密度和聚类系数不断增强,平均最短路径不断缩小,其中产业联系网络发育最为成熟,社会交流网络次之,创新合作网络发育最不完善;② 奇瑞汽车集群网络演化机制本质上是路径依赖机制（政府作用、关系资源）,关系选择机制（战略择定、市场选择）及学习创新机制（技术交流）共同作用的结果。在松散型网络、紧凑型网络和开放型网络阶段,路径依赖机制、关系选择机制和学习创新机制分别发挥主导性作用;③ 奇瑞主导型集群网络正逐渐从地方集群网络向跨区域、跨集群网络发展,这与全球汽车产业网络整体发展相一致。 相似文献
43.
《Norsk geografisk tidsskrift. Norwegian journal of geography》2012,66(4):248-258
The mountain areas of Europe have been of vital importance in the system of summer farming whereby the movement of livestock between different altitudinal levels is a key element. However, summer farming has been downscaled considerably during the 20th century. The article describes two areas where summer farming is still practised: Forollhogna in Norway, and Asturias in Spain. The authors document the transhumance system in the two areas, and investigate how farmers view the summer farming system and landscape, how they relate to nature protection, and whether specific value orientations can be detected in their views. The findings show that the logic behind summer farming is the same in both areas: economic motivation and access to grazing grounds. With regard to nature and landscape protection, the opinion that wild nature is given priority and that ‘managed nature’ of transhumance is overlooked was found in both areas, although it was expressed more strongly in Asturias than in Forollhogna. Opinions and ideals related to ‘good farming’ were found in both contexts, and were reflected in well-kept fields and productive and healthy livestock. 相似文献
44.
经贸视角下中国台湾“新南向政策”分析——基于SNA和VAR方法 总被引：2，自引：1，他引：1
中国台湾“新南向政策”倍受社会关注。基于经贸视角及2001~2015年贸易数据,在分析经济依赖度及国际竞争力基础上,通过社会网络分析（SNA）方法探讨中国大陆在贸易网络中的地位及其对中国台湾的影响,利用VAR脉冲响应函数对比分析中国台湾与中国大陆、新南向国家的对外贸易对中国台湾经济发展的影响。研究结果表明：新南向国家对中国大陆的经济依赖度远高于其对中国台湾的经济依赖度,中国大陆对其的贸易地位是中国台湾难以替代的;中国台湾对中国大陆的经济依赖度明显高于其对新南向国家的经济依赖度,中国大陆对其的贸易地位是新南向国家难以替代的;中国大陆在贸易网络格局中处于核心地位,对于提升中国台湾贸易网络地位起着重要促进作用;中国大陆与中国台湾的对外贸易对中国台湾经济发展的正向效应明显高于新南向国家。中国台湾当局应秉承“九二共识”,抓住机遇,积极推进“新南向政策”与“一带一路”倡议融合,加强同中国大陆的经贸合作与交流,促进其经济稳定持续发展。 相似文献
45.
Zhenghua Hu Guofeng Wang Jiye Wang Lingkui Meng 《International journal of geographical information science》2017,31(11):2216-2233
This paper introduces a robust method for computing the optimal route with hierarchy. We convert a planar road network into its Voronoi-based counterpart with multiple levels of detail (LoDs), which is subsequently assigned travel times that are estimated for different times of day using taxicab trajectory data. On the basis of this network structure, we model the path-finding process in travel, as the optimal route with hierarchy is computed in a ‘coarse-to-fine’ manner. In other words, the route is iteratively constructed from roads in a low LoD network to roads in a high LoD network. To confirm the efficiency and effectiveness of our method, comparative experiments were conducted using randomly selected pairs of origins/destinations in Wuhan, China. The results indicate that our travel lengths are on average 12% longer than those computed by the Dijkstra algorithm and 15% shorter than those computed by the hierarchical algorithm (in ArcGIS). Our travel times are on average 29% longer than those computed by the Dijkstra algorithm and 31% shorter than those computed by the hierarchical algorithm (in ArcGIS). Hence, we argue that our method is situated in terms of performance between the Dijkstra algorithm and the hierarchical algorithm (in ArcGIS). Moreover, road usage patterns confirm that our algorithm is cognitively equivalent to the hierarchical algorithm (in ArcGIS) by favoring high-class roads and outperforms the Dijkstra algorithm by avoiding choosing low-class roads. Computationally, our method outperforms the Dijkstra algorithm but is on the same level as the hierarchical algorithm (in ArcGIS) in terms of efficiency. Therefore, it has the potential to be used in real-time routing applications or services. 相似文献
46.
R. A. Callen 《Australian Journal of Earth Sciences》2013,60(3-4):393-410
A late‐Tertiary age, as well as the commonly accepted mid‐Tertiary age, is proved for widespread silcretes in S.A. This is demonstrated by stratigraphic relationships with palynologically dated sequences, and evidence of erosion of silcretes. The age limits are Early Eocene to Early Miocene and Medial Miocene to Early Pleistocene, probably Late Pliocene. The late‐Tertiary silcrete dominates the duricrusted landscape flanking the north of the Willouran and Flinders Ranges, and forms patches throughout the Tarkarooloo Lobe (Lake Frome area). Silica type varies according to the material cemented; chalcedony and opal are more common in finer grained, less permeable, clayey clastics, and micro‐ to crypto‐crystalline quartz ('grey billy’ or ‘terrazzo') in porous permeable arenites and regoliths. ‘Grey billy’ silcretes with pedogenic features resembling massive nodular calcretes were probably formed close to phreatic surfaces or in the soil zone, and result from deposition of silica and titania from surface waters near ground level. They can be used to mark unconformities. Those without such features were formed at depths of several to tens of metres in the phreatic zone, beyond the effects of a fluctuating groundwater table. The varying composition of groundwaters and fluctuations of the phreatic surface probably occurred as the result of climatic changes from wet to arid to wet, causing alternate solution and redeposition of silica. Silcrete was essentially a late Mesozoic‐Cainozoic phenomenon, this being a time of general uplift of the Australian continent during intervals of climatic fluctuation. However, the time spans of Australian silcretes are not sufficiently known to make correlations with major climatic events, which are on a finer time‐scale. 相似文献
47.
经济地理学视角下中国经济新常态的格局与类型划分 总被引：2，自引：2，他引：0
面对外部国际需求萎缩,内部支撑经济高速增长的传统人口红利、资源环境红利等逐渐衰减,中国经济增长将面临逐步回落到中低增速的“新常态”。从经济地理学角度开展针对中国经济新常态这一新事像及其格局研究具有重要意义。以全国31个省区单元（港澳台除外）为研究尺度,通过关键指标,分析了中国经济新常态的格局态势,开展了类型划分。结果表明：近年来,中国财政收入、电力消费量、铁路货运量指标,主要行业门类,以及投资、出口和消费的增速均呈现明显下降,绝大多数省区与全国发展态势保持一致。将全国31个省区划分为较快增长、下行压力较小和下行压力较大3类区域,下行压力较大区域细分发展阶段型、整体衰退型、能源原材料型以及其他等4种类型,不同类型区域具有明显的地理集聚特征。针对这一轮经济下行风险,不同地区应采取不同的对策,重点关注东北区域的整体衰退风险,以及山西等省能源原材料省区的经济下行风险。 相似文献
48.
In the western Ahaggar shield, the transition between the Precambrian and the Ordovician units is characterised by thick volcano-sedimentary series (‘Série pourprée’ of the Ahnet). This series, in part of Cambrian age, results from the demolition of the Panafrican belt. Similar series were known in grabens located between the West African craton and the Ahaggar, from the ‘Adrar des Iforas’, in the south, to the Ougarta belt, in the north. We describe in this study a new formation identical to the ‘Série pourprée’ of the Ahnet, but cropping out in the far Southeast of the Ahaggar (In Guezzam). This new datum improves the Panafrican belt configuration. To cite this article: H. Djellit et al., C. R. Geoscience 334 (2002) 789–794. 相似文献
49.
New data about the ‘Sables fauves’ clearly show two different kinds of organisations: stratigraphic superposition of Langhian and Serravallian units to the south and embankment of Serravallian sediments in Langhian deposits to the north. The result consists in two different palaeogeographic schemes. The Langhian Sea is widely extended, forming the ‘Lectoure Gulf’, whereas the Serravallian Sea is much more reduced, with valleys fillings to the north and a little gulf to the south. This involves a tectonic activity along a structure which orientation is N120°E (‘flexure de la Douze’) and a relative rising of the northern part, of about 30 m. To cite this article: P. Gardère et al., C. R. Geoscience 334 (2002) 987–994. 相似文献
50.
以发展较为成功的中国?印尼经济贸易合作区（简称“中印合作区”）为例,讨论“一带一路”背景下中国境外经贸合作区的成功发展经验与“园中园”发展模式。中印合作区是中国企业在印度尼西亚设立的第一批国家级境外经贸合作区之一,采用“园中园”发展模式。通过实地调研与访谈的方法,构建“园中园”发展模式分析框架,从构建多主体间的合作网络、根植地方的制度文化环境、提供优质的园区环境这3个维度重点分析了中印合作区的发展过程与特征。归纳总结境外经贸合作区发展的成功经验,为未来境外经贸合作区的建设提供案例借鉴与理论参考。 相似文献