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排序方式: 共有196条查询结果,搜索用时 31 毫秒
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In this study we applied a multidisciplinary approach, coupling geophysical and geochemical measurements, to unveil the provenance of 170 obsidian flakes, collected on the volcanic island of Ustica (Sicily). On this island there are some prehistoric settlements dated from the Neolithic to the Middle Bronze Age. Despite not having geological outcrops of obsidian rocks, the countryside of Ustica is rich in fragments of this volcanic glass, imported from other source areas. The study of obsidian findings was carried out first through visual observations and density measurements. At least two different obsidian families have been distinguished, probably imported from Lipari and Pantelleria islands. Analysing the magnetic properties of the samples, these two main sources were confirmed, but the possibility of other provenances was inferred. Finally, we characterized the geochemical signature of the Ustica obsidians by performing microchemical analyses through electron microprobe (EMPA) and laser ablation (LA–ICP–MS). The results were compared with literature data, confirming the presence of the Lipari and Pantelleria sources (Sicily) and indicating for the first time in this part of Italy a third provenance from Palmarola island (Latium). Our results shed new light on the commercial exchanges in the peri‐Tyrrhenian area during the prehistoric age.  相似文献   
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Brexit means that regions of the United Kingdom will lose access to the EU Cohesion Policy. Have EU funds been effective, and what might be the consequences of an interruption of EU financial support? This paper studies the impact of “Objective 1” funding—the highest form of EU aid—in Cornwall and South Yorkshire, two of the U.K.’s most subsidized regions. Counterfactual methodologies assessing their labor market and economic performance provide evidence of a positive effect of EU Objective 1 funds. When in 2006 South Yorkshire lost Objective 1 eligibility, this massively reduced its share of EU funds and the region was unable to sustain the gains obtained in previous years. This suggests that while Structural Funds may be effectively improving socio‐economic conditions of poorer regions, the performance of subsidized areas could be deeply affected by a reduction (or worse, an interruption) of EU aid.  相似文献   
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Italian district small and medium enterprises (SMEs) developed aggressive strategies to extend their sales networks and supply chains abroad. Literature on districts offered alternative explanations about the impacts of internationalization on local manufacturing systems. The authors consider the evolution of Italian districts in the framework of global value chain approach, focusing on the role of leading firms. Based on a survey of 650 Italian SMEs and financial indicators, the paper describes the rise of a new district firm model, the open network, which becomes a key node of global value chains. The paper also analyses the relationships among internationalization, innovation strategies and performance of SMEs.  相似文献   
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王笛 《史学月刊》2006,(11):93-101
在第二次世界大战以前,来到美国的中国移民基本上被华人社区中的中国传统的社会组织所控制。华人社区有四种基本的社会组织,即宗族、会馆、秘密社会和行会,这些组织的扩张是由于社区生活的需要和外部的压力。它们也强烈影响到华人社会的形成和发展,并在延缓中国移民的同化过程中扮演了一个重要角色。排华运动、组织的束缚和内部的争斗使中国移民与主流社会隔离了几十年,宗族的条规、方言的区别、利益的冲突等又破坏了中国移民的内部团结,这也导致了处于相对封闭状态的中国移民的同化过程非常缓慢。  相似文献   
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The Aterian has a huge geographic extension covering all North Africa, although it was not supposed to exist in the mountain ranges of the central Sahara. Its chronological context is not yet definitively determined and it is still difficult to say whether the Aterian tools are technological, typological, functional, or chronological markers. Recent surveys and excavations at Uan Tabu and Uan Afuda, two rock-shelters located in the central Tadrart Acacus, provide the first chronological, environmental and archaeological indications on this Late Pleistocene human occupation in the area. The lack of organic matter led us to perform OSL and TL analyses on sand. L'Atérien a une énorme extension géographique qui couvre tout le Nord de l'Afrique, tandis qu'on ne pensait pas qu'il existait dans les montagnes du Sahara central. Son contexte culturel n'est pas définitivement déterminé et il est encore difficile de dire si les instruments atériens sont des indicateurs téchnologiques, typologiques, fonctionels ou culturels. Reconnaissances et fouilles récentes à Uan Tabu et Uan Afuda, deux abris situés dans l'Acacous central, fournissent les premières indications sur la chronologie, l'environnement et l'archéologie de l'Atérien dans la région. L'absence de la substance organique, nous a porté à faire des déterminations OSL et TL sur les sables.  相似文献   
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In this paper, we propose a recursive approach to estimate the spatial error model. We compare the suggested methodology with standard estimation procedures and we report a set of Monte Carlo experiments which show that the recursive approach substantially reduces the computational effort affecting the precision of the estimators within reasonable limits. The proposed technique can prove helpful when applied to real-time streams of geographical data that are becoming increasingly available in the big data era. Finally, we illustrate this methodology using a set of earthquake data.  相似文献   
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Here we show the results of two morpho-bathymetric surveys carried out on the underwater archaeological area of the Pozzuoli Bay (Naples, Italy). Such area is enclosed in the Campi Flegrei active volcanic complex, where bradyseism and recent volcanic activity strongly influenced the coastline shape over the last 2 Ka. The Digital Elevation Model (DTM) of the seafloor allowed to draw the main archaeological features of the Bay, that also include the military complex of Portus Iulius and the ancient thermal and villa complex of Baianus Lacus. The extraction of archaeological features from DTM was achieved thanks to the use of a GIS-derived tool based on the profile curvature algorithm. Thus, the Villa dei Pisoni (1st Century B.C.) and the thermal complex of Secca delle Fumose were investigated by using ultra-high resolution DTMs, that show the presence of Roman pilae for the protection of coastal buildings and also the inner planimetry of the Villa dei Pisoni complex. The observation of coastal engineering structures give also the opportunity to formulate some hypothesis on the evolution of morphology and of the sedimentary pattern of the area, while depth of archaeological remains allowed a rough computation of the rate of subsidence, resulted to be 2.55 (±0.5) mm/y for the Eastern sector (Pozzuoli) and 2.90 (±0.5) mm/y for the western (Baia).  相似文献   
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