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41.
《Marine Policy》2016
Most of the fishers of coastal East Africa particularly among the Bajuni, Kojani, Macua and Vezo ethnic communities have historically practiced migration. This study explores the strategies used by migrant fishers’ of Pemba in the Western Indian Ocean region. By adopting a modified sustainable livelihoods framework (SLF), the study uses in-depth interviews and questionnaires to explore the life histories of the fishers in migrant communities, their motivations to migrate, and their associated socioeconomic and ecological implications. Results point out to a complexity of factors contributing to migration including natural, to economic and social factors. Interaction of such factors is instrumental in shaping fisher migration as an activity into an important livelihood strategy. The study concludes that SLF provides holistic understanding of migration. However the incorporation of the ‘livelihood spaces’ extends this knowledge by integrating the spectrum of spatial aspects. This understanding is critical in the design of policies and interventions necessary to ensure resource sustainability and secure fishers livelihoods. This multi-method approach is critical in empirical study of fisher migration. 相似文献
42.
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
43.
施洞口断裂位于贵州东部,曾作为贵州大地构造的分界,但马号段构造样式历有争议,为了探讨施秉县金钟山非典型丹霞地貌成因,即金钟山白垩纪断陷盆地及其“红层”非典型丹霞山体地貌形成的控制因素,对施洞口断裂带马号段、台盘段和舟溪段等多个重要剖面进行调查研究,结合区域地质资料,否定“巴团飞来峰构造”,认同1:20万镇远幅区域地质图划定的构造透镜体形式,同时查明了金钟山白垩系南东边界的沉积关系其实是断层接触,构成施洞口断裂马号地区较大规模构造透镜体的南东边界,使施洞口断裂在整体的平剖结构展布上呈现分支联合的构造透镜状普遍规律特征,另外认为马号—金钟山公路沿线寒武系白云岩为不整合沉积覆盖于青白口系之上,而东侧一带的青白口系又以逆冲断层“推覆”于寒武系白云岩之上,从而成为导致施洞口断裂带在马号段构造特征较为复杂的主要原因,据此本文对施洞口断裂构造特征进行了再次调查梳理,具有较重要的基础地质科学意义,并从地质演化角度解释了施秉金钟山白垩纪断陷盆地及其“红层”非典型丹霞地貌山体的形成,可为金钟山的旅游开发提供地学科普参考依据。 相似文献
44.
Seanpaul La Selle Bruce M. Richmond Bruce E. Jaffe Alan R. Nelson Frances R. Griswold Maria E. M. Arcos Catherine Chagué James M. Bishop Piero Bellanova Haunani H. Kane Brent D. Lunghino Guy Gelfenbaum 《Sedimentology》2020,67(3):1249-1273
Over the past 200 years of written records, the Hawaiian Islands have experienced tens of tsunamis generated by earthquakes in the subduction zones of the Pacific ‘Ring of Fire’ (for example, Alaska–Aleutian, Kuril–Kamchatka, Chile and Japan). Mapping and dating anomalous beds of sand and silt deposited by tsunamis in low-lying areas along Pacific coasts, even those distant from subduction zones, is critical for assessing tsunami hazard throughout the Pacific basin. This study searched for evidence of tsunami inundation using stratigraphic and sedimentological analyses of potential tsunami deposits beneath present and former Hawaiian wetlands, coastal lagoons, and river floodplains. Coastal wetland sites on the islands of Hawai΄i, Maui, O΄ahu and Kaua΄i were selected based on historical tsunami runup, numerical inundation modelling, proximity to sandy source sediments, degree of historical wetland disturbance, and breadth of prior geological and archaeological investigations. Sand beds containing marine calcareous sediment within peaty and/or muddy wetland deposits on the north and north-eastern shores of Kaua΄i, O΄ahu and Hawai΄i were interpreted as tsunami deposits. At some sites, deposits of the 1946 and 1957 Aleutian tsunamis are analogues for deeper, older probable tsunami deposits. Radiocarbon-based age models date sand beds from three sites to ca 700 to 500 cal yr bp , which overlaps ages for tsunami deposits in the eastern Aleutian Islands that record a local subduction zone earthquake. The overlapping modelled ages for tsunami deposits at the study sites support a plausible correlation with an eastern Aleutian earthquake source for a large prehistoric tsunami in the Hawaiian Islands. 相似文献
45.
“一带一路”沿线重点省份旅游经济高质量发展研究 总被引：1，自引：1，他引：0
从旅游资源转换效率的视角，以“一带一路”沿线18个重点省份为研究靶区，运用修正的DEA模型等方法探究2008—2017年的旅游经济增长质量的时空演变及发展趋势。研究结论有：① 10 a间，18个重点省份旅游资源转换效率均值仅为0.312，远未达到生产前沿面。② 经过邹检验（Chow test），2014年为“一带一路”沿线18个重点省份旅游资源转换效率时间序列的突变点。③ 18个重点省份的旅游资源转换效率均存在σ收敛、绝对β收敛和条件β收敛；开放先行区、战略支点区未通过σ收敛检验、战略支点区未通过绝对β收敛。 相似文献
46.
Tovi Fenster 《Urban geography》2019,40(1):37-57
This paper examines the language and phraseology of ‘creative destruction‘ (‘renewal‘ and ‘exploitation’) expressed in urban planning procedures concerning one particular house in West Jerusalem: 28 Radak Street. Through a forensic examination of the planning-related communications about this address, the work analyzes the various stages of the ’destruction’ and ’renewal’ of the property. It demonstrates how each of the various actors involved (Municipality, planning committees, legal courts, private entrepreneur and local residents) uses different language and phraseology to present their argument, while the voice of the original Palestinian owners of the house is entirely absent from the planning battle. 相似文献
47.
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
48.
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
49.
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
50.
《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