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11.
CLAUDE FROESCHLÉ ELENA LEGA ROBERT GONCZI 《Celestial Mechanics and Dynamical Astronomy》1997,67(1):41-62
We present a very simple and fast method to separate chaotic from regular orbits for non-integrable Hamiltonian systems. We
use the standard map and the Hénon and Heiles potential as model problems and show that this method appears to be at least
as sensitive as the frequency-analysis method. We also study the chaoticity of asteroidal motion.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
12.
ABSTRACT. In this article we explore the relationships between public parks and a broad interpretation of sustainability, taking as a case study the city of Barcelona, Spain. Recent official discourses in Barcelona insist on sustainability as one of the fundamental assets of public parks. Yet whether these urban artifacts actually contribute to sustainability objectives in environmental and social terms remains to be examined. We compare two public parks in Barcelona‐the Parc Joan Miró (1983), and the Parc de Diagonal Mar (2002)–and show how, in the former, the integration of the social, political, and environmental dimensions of sustainability was largely achieved, whereas in the latter, only the environmental dimension appears to have been considered. 相似文献
13.
ALEXANDER V. KIRDYANOV FRANK HAGEDORN ANASTASIA A. KNORRE ELENA V. FEDOTOVA EUGENE A. VAGANOV MUHTAR M. NAURZBAEV PAVEL A. MOISEEV ANDREAS RIGLING 《Boreas: An International Journal of Quaternary Research》2012,41(1):56-67
Kirdyanov, A. V., Hagedorn, F., Knorre, A. A., Fedotova, E. V., Vaganov, E. A., Naurzbaev, M. M., Moiseev, P. A. & Rigling, A. 2012 (January): 20th century tree‐line advance and vegetation changes along an altitudinal transect in the Putorana Mountains, northern Siberia. Boreas, Vol. 41, pp. 56–67. 10.1111/j.1502‐3885.2011.00214.x. ISSN 0300‐9483. Ongoing climatic changes potentially affect tree‐line ecosystems, but in many regions the observed changes are superimposed by human activities. We assessed how the forest‐tundra ecotone has changed during the last century in the Putorana Mountains, northern Siberia, an extremely remote and untouched area in Eurasia. A space‐for‐time approach was used to determine the spatio‐temporal dynamics of forest structure and biomass along an altitudinal transect. From the closed larch forest to the upper tree line, the mean age of Larix gmelinii (Rupr.) decreased considerably from 220 to 50 years ago. At the current upper species line, there is a strong and successful germination of larch, with 1500 saplings per hectare, indicating an ongoing filling‐in, a densification of a formerly open forest and an upslope shift of the tree‐line position (approximately 30 to 50 m in altitude during the last century). The forest expansion coincided with large increases in winter precipitation during the 20th century. In contrast, tree growth rates were significantly positively related to summer temperatures, neither of which increased markedly. The total aboveground biomass decreased from approximately 40 t ha?1 in the closed larch forest to 5 t ha?1 at the tree line. Our study demonstrates that ongoing climatic changes lead to an upslope expansion of forests in the remote Putorana Mountains, which alters the stand structure and productivity of the forest‐tundra ecotone. These vegetation changes are very probably of minor importance for aboveground carbon sequestration, but soil carbon data are needed to estimate the impact of the forest expansion on the total ecosystem carbon storage. 相似文献