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151.
Julien Mercille 《GeoJournal》2010,75(4):327-337
This article presents an approach termed “radical geopolitics” that addresses two of critical geopolitics’ blind spots, namely, its lack of attention to the causes (the “why”) of policy and its neglect of political economy. In particular, it examines the respective roles of the geopolitical and geoeconomic factors that drive policy. The argument draws on David Harvey’s “logics of power,” modified and reformulated into a “geoeconomic logic” and a “geopolitical logic” through which postwar American foreign policy may be interpreted. The former logic arises out of capitalism’s tendency to expand geographically and the latter out of politicians’ need to maintain credibility internationally as well as from electoral pressures at home. A discussion of the Iraq War illustrates the approach and illuminates issues overlooked by critical geopolitics analyses, in particular: Why did the US invade Iraq in 2003? And what was the role of oil, if any, in motivating the invasion? It is argued that Iraq was invaded to control its oil (but much less to use it for US consumption, and still much less to generate profits from it), and to maintain American credibility. Radical geopolitics should not be seen in opposition to critical geopolitics, but rather as seeking to supplement its analyses through discussion of issues which have received less attention. 相似文献
152.
Jaffrennou C Giamarchi P Cabon JY Stephan L Burel-Deschamps L Bautin F Thomas A Dumont J Le Floch S 《Marine pollution bulletin》2007,54(12):1932-1939
Coal is currently becoming an increasingly interesting fossil energy resource and that is the reason why its maritime transport, and hence the risk of collier accidents, increase. In this work, the environmental impact of an accidental coal immersion at sea is studied: the physicochemical effects are estimated using innovative experimental setups – a laboratory seawater canal called “polludrome” is used to evaluate the behaviour of coal particles submitted to a seawater flow, and a specifically designed tub is used to study the physicochemical consequences induced when coal is introduced into continuously renewed seawater. When coal is introduced into seawater, the most easily visible consequences are physical: fine coal particles reduce the daylight penetration up to 100% and move along with the flow, and coal chunks accumulate on the floor. Chemical effects are also measured: humic matters are dissolved from coal into seawater (up to 2 mg L−1), but no release of polycyclic aromatic hydrocarbons is evidenced. Some inorganic compounds are dissolved, among which manganese, whose concentrations can reach 1 μg L−1. Fortunately, the results show that the environmental impact of this type of accident would remain limited. 相似文献
153.
Rémy Roca Jean-Claude Bergès Hélène Brogniez Michel Capderou Philippe Chambon Olivier Chomette Sophie Cloché Thomas Fiolleau Isabelle Jobard Julien Lémond Mohamed Ly Laurence Picon Patrick Raberanto André Szantai Michel Viollier 《Comptes Rendus Geoscience》2010,342(4-5):390-402
The water and energy cycles are major elements of the Earth climate. These cycles are especially active in the intertropical belt where satellites provide the most suitable observational platform. The history of Earth observations of the water cycle and of the radiation budget viewed from space reveals that the fundamental questions from the early times are still relevant for today's research. The last 2 decades have seen a number of milestones regarding the documentation of rainfall, mesoscale convective systems (MCS), water vapour and radiation at the top of the atmosphere (TOA). Beyond dedicated missions that provided enhanced characterizations of some elements of the atmospheric water cycle and field campaigns that allowed the gathering of validation data, the advent of the long record of meteorological satellites lead to new questioning on the homogenisation of the data time series, etc. The use of this record to document the tropical climate brought new results of the distribution of humidity and reinforced the understanding of some robust features of the African monsoon. Challenges for the immediate future concerns the deepening of the understanding of the role of cloud systems in the monsoon circulation, the downscaling of the documentation of the water and energy cycle at the scale of these cloud systems, the research of better adequation between the users and the satellite estimate of rainfall and finally a much needed methodological effort to build exploitable time series for the estimation of climatic trends in the water and energy cycle in the Tropics. The required observations to address these challenges are rapidly presented with emphasis on the upcoming Megha-Tropiques (MT) mission. 相似文献
154.
Julien Lesgourgues rew R. Liddle 《Monthly notices of the Royal Astronomical Society》2001,327(4):1307-1312
We use a wide range of observations to constrain cosmological models possessing a significant asymmetry in the lepton sector, which offer perhaps the best chance of reconciling a critical-density Universe with current observations. The simplest case, with massless neutrinos, fails to fit many experimental data and does not lead to an acceptable model. If the neutrinos have mass of order 1 eV (which is favoured by some neutrino observations), then models can be implemented which prove a good fit to the microwave anisotropies and large-scale structure data. However, taking into account the latest microwave anisotropy results, especially those from BOOMERANG, we show that the model can no longer accommodate the observed baryon fraction in clusters. Together with the observed acceleration of the present Universe, this puts considerable pressure on such critical-density models. 相似文献
155.
Adrianne Slyz Julien Devriendt Greg Bryan Joseph Silk 《Astrophysics and Space Science》2003,284(2):833-836
This contribution reports on our first efforts to simulate a multiphase interstellar medium on a kiloparsec scale in three
dimensions with the stars and gas modeled self-consistently. Starting from inhomogenous initial conditions, our closed box
simulations follow the gas as it cools and collapses under its own self-gravity to form stars which eventually return material
and energy back through supernovae explosions and winds.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
156.
An Improved Parallel Multiple-point Algorithm Using a List Approach 总被引:15,自引:8,他引:7
Julien Straubhaar Philippe Renard Gr��goire Mariethoz Roland Froidevaux Olivier Besson 《Mathematical Geosciences》2011,43(3):305-328
Among the techniques used to simulate categorical variables, multiple-point statistics is becoming very popular because it allows the user to provide an explicit conceptual model via a training image. In classic implementations, the multiple-point statistics are inferred from the training image by storing all the observed patterns of a certain size in a tree structure. This type of algorithm has the advantage of being fast to apply, but it presents some critical limitations. In particular, a tree is extremely RAM demanding. For three-dimensional problems with numerous facies, large templates cannot be used. Complex structures are then difficult to simulate. In this paper, we propose to replace the tree by a list. This structure requires much less RAM. It has three main advantages. First, it allows for the use of larger templates. Second, the list structure being parsimonious, it can be extended to include additional information. Here, we show how this can be used to develop a new approach for dealing with non-stationary training images. Finally, an interesting aspect of the list is that it allows one to parallelize the part of the algorithm in which the conditional probability density function is computed. This is especially important for large problems that can be solved on clusters of PCs with distributed memory or on multicore machines with shared memory. 相似文献
157.
Together with new opportunities, offshore wind farms raise new engineering challenges. An important aspect relates to the erosion of bottom material around the foundation of the wind turbines, caused by the local increase of the wave and current induced flow velocities by the pile's presence. Typically, the expected scour has a considerable impact on the stability and dynamic behavior of the wind turbine and a scour protection is placed to avoid erosion of the soil close to the foundation. Although much experience exists on the design of scour protections around bridge piers (which are placed in a current alone situation), at present, little design guidelines exist for the specific case of a scour protection around a monopile foundation subjected to a combined wave and current loading. 相似文献
158.
159.
160.
Low-level temperature inversions are a common feature of the wintertime troposphere in the Arctic and Antarctic. Inversion strength plays an important role in regulating atmospheric processes including air pollution, ozone destruction, cloud formation, and negative longwave feedback mechanisms that shape polar climate response to anthropogenic forcing. The Atmospheric Infrared Sounder (AIRS) instrument provides reliable measures of spatial patterns in mean wintertime inversion strength when compared with available radiosonde observations and reanalysis products. Here, we examine the influence of sea ice concentration on inversion strength in the Arctic and Antarctic. Correlation of inversion strength with mean annual sea ice concentration, likely a surrogate for the effective thermal conductivity of the wintertime ice pack, yields strong, linear relationships in the Arctic (r?=?0.88) and Antarctic (r?=?0.86). We find a substantially greater (stronger) linear relationship between sea ice concentration and surface air temperature than with temperature at 850?hPa, lending credence to the idea that sea ice controls inversion strength through modulation of surface heat fluxes. As such, declines in sea ice in either hemisphere may imply weaker mean inversions in the future. Comparison of mean inversion strength in AIRS and global climate models (GCMs) suggests that many GCMs poorly characterize mean inversion strength at high latitudes. 相似文献