Preliminary Study on the Translunar Halo Orbits of the Real Earth–Moon System     

Miquel A. Andreu 《Celestial Mechanics and Dynamical Astronomy》2003,86(2):107-130

The computation of translunar Halo orbits of the real Earth–Moon system (REMS) has been an open problem for a long time, but now, it is possible to compute Halo orbits of the REMS in a systematic way. In this paper, we describe the method used for the numerical computation of Halo orbits for a time span longer than 41 years. Halo orbits of the REMS are computed from quasi-periodic Halo orbits of the quasi-bicircular problem (QBCP). The QBCP is a model for the dynamics of a spacecraft in the Earth–Moon–Sun system. It is a Hamiltonian system with three degrees of freedom and depending periodically on time. In this model, Earth, Moon and Sun are moving in a self-consistent motion close to bicircular. The computed Halo orbits of the REMS are compared with the family of Halo orbits of the QBCP. The results show that the QBCP is a good model to understand the main features of the Halo family of the REMS.  相似文献   

Particulate barium fluxes and export production in the northwestern Mediterranean   总被引：1，自引：0，他引：1  

Erika Sternberg  Catherine Jeandel  Juan-Carlos Miquel  Beat Gasser  Marc Souhaut  Roseanna Arraes-Mescoff  Roger Francois 《Marine Chemistry》2007,105(3-4):281-295

Biogenic barium, mostly in the barite (BaSO₄) form, has been proposed as a tracer for export production in the ocean. Here we report on biogenic barium (Ba_xs) and particulate organic carbon (POC) fluxes from sediment traps deployed at the DYFAMED site in the Northwestern Mediterranean Sea. Ba_xs fluxes display average values of 37 ± 45 and 50 ± 58 μg/m²/d at 200 and 1000 m respectively, and are linearly correlated to POC fluxes (mean values of 7.9 ± 9.3 and 6.8 ± 6.8 mg C/m²/d at 200 and 1000 m). Export production estimates, calculated using published Ba_xs- or POC-based algorithms, all fall below or close to the lower limit of potential export values proposed in the literature. This work clearly demonstrates the usefulness of Ba_xs as a tracer of oceanic export production in the Northwestern Mediterranean Sea. However, development of a quantitative export production proxy requires a clear understanding of the underlying cause(s) for the observed spatial variations in the relationship between Ba_xs and POC fluxes. The present study confirms that the processes leading to barite formation differ between margin and open-ocean sites and probably account for much of the regional variability in the POC/Ba_xs ratio.  相似文献   

Multi-scale spatial variability in fish assemblages associated with Posidonia oceanica meadows in the Western Mediterranean Sea     

Joan Moranta  Miquel Palmer  Gabriel Morey  Ana Ruiz  Beatriz Morales-Nin 《Estuarine, Coastal and Shelf Science》2006,68(3-4):579

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Image analysis applied to quantitative evaluation of chromatic impact generated by open-pit quarries and mines     

Victor Pinto  Xavier Font  Miquel Salgot  Jose Tapias  Tomas Mañá 《Environmental Geology》2002,41(5):495-503

One of the most important environmental impacts resulting from opencast mining, and especially quarries, is the visual impact. Evaluation of this impact considers two aspects: first, the area occupied by the quarry as seen by an observer from a specific place, and, second, the chromatic contrast existing between landscape and exploitation. In this study we develop a methodology to assess the chromatic impact in an objective and comparable form. To assess this impact we developed a method based on image analysis that allows us to obtain from a picture or image its equivalent as a function of chromatic impact, according to the sensibility of the human eye to different wavelengths. The methodology was applied to the Martinenca limestone quarry (Alcanar, Tarragona) and to Cerro Kori Kollo mine, La Joya district (Bolivia).  相似文献   

Clinoform architecture and along‐strike facies variability through an exhumed erosional to accretionary basin margin transition     

Miquel Poyatos‐Mor  George D. Jones  Rufus L. Brunt  Daniel E. Tek  David M. Hodgson  Stephen S. Flint 《Basin Research》2019,31(5):920-947

Exhumed basin margin‐scale clinothems provide important archives for understanding process interactions and reconstructing the physiography of sedimentary basins. However, studies of coeval shelf through slope to basin‐floor deposits are rarely documented, mainly due to outcrop or subsurface dataset limitations. Unit G from the Laingsburg depocentre (Karoo Basin, South Africa) is a rare example of a complete basin margin scale clinothem (>60 km long, 200 m‐high), with >10 km of depositional strike control, which allows a quasi‐3D study of a preserved shelf‐slope‐basin floor transition over a ca. 1,200 km² area. Sand‐prone, wave‐influenced topset deposits close to the shelf‐edge rollover zone can be physically mapped down dip for ca. 10 km as they thicken and transition into heterolithic foreset/slope deposits. These deposits progressively fine and thin over tens of km farther down dip into sand‐starved bottomset/basin‐floor deposits. Only a few km along strike, the coeval foreset/slope deposits are bypass‐dominated with incisional features interpreted as minor slope conduits/gullies. The margin here is steeper, more channelized and records a stepped profile with evidence of sand‐filled intraslope topography, a preserved base‐of‐slope transition zone and sand‐rich bottomset/basin‐floor deposits. Unit G is interpreted as part of a composite depositional sequence that records a change in basin margin style from an underlying incised slope with large sand‐rich basin‐floor fans to an overlying accretion‐dominated shelf with limited sand supply to the slope and basin floor. The change in margin style is accompanied with decreased clinoform height/slope and increased shelf width. This is interpreted to reflect a transition in subsidence style from regional sag, driven by dynamic topography/inherited basement configuration, to early foreland basin flexural loading. Results of this study caution against reconstructing basin margin successions from partial datasets without accounting for temporal and spatial physiographic changes, with potential implications on predictive basin evolution models.  相似文献   

The impacts of climate change in Europe (the PESETA research project)   总被引：1，自引：1，他引：0  

Juan-Carlos Ciscar 《Climatic change》2012,112(1):1-6

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The Westerly Index as complementary indicator of the North Atlantic oscillation in explaining drought variability across Europe   总被引：1，自引：0，他引：1  

Sergio M. Vicente-Serrano  Ricardo García-Herrera  David Barriopedro  Cesar Azorin-Molina  Juan I. López-Moreno  Natalia Martín-Hernández  Miquel Tomás-Burguera  Luis Gimeno  Raquel Nieto 《Climate Dynamics》2016,47(3-4):845-863

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A method to estimate intensity occurrence probabilities in low seismic activity regions     

J. J. Egozcue  A. Barbat  J. A. Canas  J. Miquel  E. Banda 《地震工程与结构动力学》1991,20(1):43-60

The estimation of site intensity occurrence probabilities in low seismic activity regions has been studied from different points of view. However, no method has been definitively established because several problems arise when macroseismic historical data are incomplete and the active zones are not well determined. The purpose of this paper is to present a method that estimates site occurrence probabilities and at the same time measures the uncertainties inherent in these probabilities in low activity regions. The region to be studied is divided into very broad seismic zones. An exponential intensity probability law is adjusted for each zone and the degree of uncertainty in the assumed incompleteness of the catalogue is evaluated for each intensity. These probabilities are used to establish what may be termed ‘prior site occurrence models’. A Bayesian method is used to improve ‘prior models’ and to obtain the ‘posterior site occurrence models’. Epicentre locations are used to recover spatial information lost in the prior broad zoning. This Bayesian correction permits the use of specific attenuation for different events and may take into account, by means of conservative criteria, epicentre location errors. Following Bayesian methods, probabilities are assumed to be random variables and their distribution may be used to estimate the degree of uncertainty arising from (a) the statistical variance of estimators, (b) catalogue incompleteness and (c) mismatch of data to prior assumptions such as Poisson distribution for events and exponential distribution for intensities. The results are maps of probability and uncertainty for each intensity. These maps exhibit better spatial definition than those obtained by means of simple, broad zones. Some results for Catalonia (NE of Iberian Peninsula) are shown.  相似文献   

Growth of Daphnia magna males and females fed with the cyanobacterium Microcystis aeruginosa and the green alga Scenedesmus obliquus in different proportions     

Miquel Lürling  Wendy Beekman 《洁净——土壤、空气、水》2006,34(4):375-382

Laboratory experiments were used to study the sensitivity of both male and female Daphnia magna to a toxic cyanobacterium, Microcystis aeruginosa. Male and female D. magna were fed with M. aeruginosa and a green alga (Scenedesmus obliquus) in different mixtures that included 0%, 25%, 50%, 75% and 100% Microcystis. Growth of both males and females declined with increasing proportion of Microcystis in the diet. Males were slightly less sensitive to Microcystis than females with EC₅₀ for growth inhibition at 72% and 63% Microcystis in the diet, respectively. On monospecific Microcystis diet, mortality rates for males (0.16 d^–1) and females (0.17 d^–1) were similar. The reproductive rate of females was the most sensitive endpoint with an EC₅₀ of 42% Microcystis in the diet, whereas population growth rates were the least sensitive (EC₅₀ of 74% Microcystis). Microcystis in the diet severely depressed growth and reproduction in Daphnia and poses a severe threat to its survival in which only a switch in reproductive strategy might provide Daphnia a refuge to a Microcystis environment that gradually becomes uninhabitable.  相似文献   

GIOVE-A initial signal analysis     

Oliver Montenbruck  Christoph Günther  Sebastian Graf  Miquel Garcia-Fernandez  Johann Furthner  Hanspeter Kuhlen 《GPS Solutions》2006,10(2):146-153

In late December 2005 the GIOVE-A test satellite was launched by the European Space Agency (ESA) to secure the frequencies for the Galileo system and to provide a platform for testing the new navigation signals. We performed an initial assessment of these signals using the 30 m deep space antenna of the DLR ground station in Weilheim (Germany). The antenna gain raised the signals above the noise level, thus allowing a detailed analysis even without knowledge of the ranging codes. The present paper covers the analysis of the L1/E1 signals, which includes a discussion of the spectrum, the time domain signal and a decoding of the spreading codes for the Open Service.  相似文献