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Freeze‐thaw cycles are most common at the beginning or near the end of the winter season. These cycles have various effects on the ecosystems of Eastern Canada, affecting both biotic and abiotic components of temperate cold environments. Using air temperature minima and maxima from four meteorological stations close to Québec City, we determined the frequency of daily freeze‐thaw cycles for the last 30 years. The results show no significant increase in the number of freeze‐thaw cycles despite a small increase in air temperature. Polynomial curves describing the relationship between mean air temperatures and the number of freeze‐thaw cycles were calculated. Based on these equations and anticipating a climate change scenario, we projected future freeze‐thaw cycles. Assuming a 5 °C increase in mean air temperatures by 2100, we estimated that the number of days with a freeze‐thaw cycle could increase by approximately 20 days per winter. The increase in the number of such cycles will be concentrated during the coldest months of the winter (January and February).  相似文献   

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《Acta Archaeologica》2012,83(1):200-200
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Christophorus Clavius' Theory of the Elements and the Idea of the Terraqueous Globe. The need to reconcile Aristotle's theory of elementary spheres with the evidence of earth above sea level – the so‐called ‘terra firma’ – induced an important conceptual shift. As a consequence anti‐Aristotelian arguments were brought to the fore in order to be incorporated into the very same Aristotelian tradition. The German Jesuit Christophorus Clavius played a momentous role in this process. He introduced the idea of the terraqueous globe into the Scholastic cosmology, modifying the logical frame of Aristotelian physics. The present work analyses Clavius' theory as well as the procedures he considers to reach his purpose. He used a combinatorial approach to study the relations occurring between the four elements – earth, water, air and fire – and analysed their relations from a physical perspective, proposing a possible structure of the sublunary world.  相似文献   

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Beyond the material forms that constitute public space, it is subject to representations or images that shape the types of use, forms of appropriation, and general perception that people have of it. Following a centre‐periphery gradient that allows us to compare three zones of the Montreal region (pericentral, periurban, and the northern ring), we analyzed photographs available within cyberspace (from different municipalities and boroughs, local newspapers, and social media) to draw out representations of public space. What can photographs available online tell us about how space is perceived? We have established a typology of images of public space (idyllic nature, urban scene, festive space, empty space, family portrait) that are representative of the overall corpus studied. We have compared these results with a correspondence analysis to clarify the structure of interaction between the variables. The analysis demonstrates that the representations are more differentiated between neighbourhoods than between regions, and that while newspapers and municipalities represent more themes of sociability and family life, social media shows more empty spaces, whether they be monumental spaces, or spaces of daily life.  相似文献   

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Based on the case of the Mohawk territory of Akwesasne, wedged between Ontario, Quebec, and New York state, this paper provides an analysis of the links between the affirmation of indigenous culture and the implementation of security policies on borderlands. The focus extends beyond political conflicts over border issues to encompass the ways in which Aboriginal sovereignty is affirmed within processes of negotiation and cooperation in the matters of identification requirements, border agents’ cultural sensitivity, and law enforcement. We find that the enhancement of border security can paradoxically be a political opportunity for local leaders to reaffirm indigenous sovereignty, and that this reaffirmation through cooperation is, at the same time, emerging as a key factor in the implementation of border security policies.  相似文献   

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Depuis plus d'un siècle, l'agriculture québécoise en général, et la production maraîchère en particulier, ont subi d'importantes transformations. Cette étude historique vise à comprendre comment la production maraîchère a évolué par rapport aux changements dans l'environnement décisionnel général de l'agriculture entre 1940 et 1990. L'analyse des données statiques de superficie, de production et de rendement pour 12 légumes ont permis d'identifier trois périodes, intercalées d'années transitoires, dans l'évolution de la production maraîchère référant chacune à une stratégie agricole particulière. La première (1940–1957) correspond à une stratégie agricole de type familial traditionnel; la seconde (1963–1975), à une agriculture marchande spécialisée fondée sur la maximisation des revenus à court terme par intensification; la troisième (1980–1990), à une agriculture marchande diversifiée fondée également sur une maximisation à court terme. Les facteurs externes de l'environnement décisionnel qui ont entraîné ces changements sont identifiés et discutès. For more than a century, Quebec agriculture in general, and market-gardening production in particular, have experienced important changes. This study, using a historical perspective, seeks to understand how market gardening evolved in relation to changes in the broad decision environment for agriculture between 1940 and 1990. Statistical analysis of data on the areas cultivated, production levels, and yields for 12 vegetable crops revealed three distinct periods, separated by periods of transition, in the evolution of market gardening. Each period is characterized by a particular type of agricultural development strategy. The first period (1940–1957) is characterized by a focus on the traditional family form; the second (1963–1975), by a specialized market agriculture driven by short-term income-maximization intensification; the third (1980–1990), by a diversified marketoriented agriculture, also based on short-term income maximization. External environmental factors that stimulated these changes are identified and discussed.  相似文献   

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Films carry an original geographic discourse. Beyond the vision of an author, they often reflect a society's perspective on territories. The goal of this research is to study the geographic discourse developed by Canadian cinema through an analysis of the places structuring Canadian cinematographic narratives. This analysis is based on the systematic study of a selection of 46 contemporary Canadian films. These films have been transformed into a database of 2200 places using an original geographic reading grid. Analysis of these places identifies the existence of territories under‐ and over‐represented by Canadian cinema, as well as territories of consensus and divergence that exist between different categories of Canadian cinema such as Quebecois, anglophone, and hybrid. Some interesting results include the general lack of interest in the southern hemisphere—notably Latin America—as well as in the Nordic territories (outside of First Nations cinema). It is also interesting to note the quasi‐absence of Vancouver on the screen, while Toronto and the United States appear recurrently. But the most striking result is probably the profound divergence in the way Canadian cinema treats the province of Quebec in general, and the city of Montreal in particular. Montreal is indeed the perfect example of a space of divergence: the city is heavily represented in Quebecois films, but completely ignored in the rest of Canadian cinematographic production. This deep opposition illustrates the importance of downtown Montreal as a symbolic space of Quebec national identity.  相似文献   

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Starting from an econometric model of local employment growth, applied to Canada (1971–2001), residuals—relative to model predictions—are analyzed over time and over space, in turn allowing us to draw a distinction between general explanatory variables and factors of a more local, cyclical or accidental nature. The model's explanatory power grows over time, founded on variables such as urban size, market access and industrial structure, allowing us to conclude that local employment growth in Canada follows an increasingly geographically predictable pattern. However, an examination of the residuals reveals more localized processes. Growth volatility is most manifest in Alberta and British Columbia, home to the most erratic local economies. Emerging patterns are visible in the last period, most notably the underperformance of Northern Ontario and of non‐metropolitan communities between Windsor and Québec City, lying along the Great Lakes and the Saint Lawrence. The over‐performance—compared to model predictions — of small and mid‐sized towns in south‐eastern Québec can, on the other hand, be interpreted as a sign of truly local social processes, generally associated with a particularly dynamic local entrepreneurial class.  相似文献   

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