New thermal triaxial apparatus for unsaturated soils using the osmotic method     

Moulay?Sma?ne?GhembazaEmail author  Said?Ta?bi  Jean?Marie?Fleureau 《Arabian Journal of Geosciences》2015,8(6):3365-3380

The study of the temperature effects on the behaviour of saturated and unsaturated soils on triaxial paths requires the development of a new triaxial experimental device of 3.5 MPa of confining pressure and equipped with a heating collar-controlled temperature. In addition to this case of the unsaturated soils, a special pedestal is developed, so as to impose suctions up to 9 MPa using an osmotic solution of polyethylene glycol (PEG) 6000 through a permeable semi-membrane. Measurements of the degree of saturation and the variation of volume during tests induce various problems, primarily related to the thermal dilation of the osmotic solution and the cell-water system. These problems have been solved by carrying out a preliminary calibration. The applicability of this new apparatus concerns environmental geotechnics and geological engineering such as the design and behaviour of engineered barriers as well as the behaviour of the receiving layers of storage sites like radioactive waste.  相似文献   

The Ecological Impact of Conquest and Colonization on a Medieval Frontier Landscape: Combined Palynological and Geochemical Analysis of Lake Sediments from Radzyń Chełminski,Northern Poland     

Alex Brown  Rowena Banerjea  Amanda Dawn Wynne  Normunds Stivrins  Marc Jarzebowski  Lisa‐Marie Shillito  Aleks Pluskowski 《Geoarchaeology》2015,30(6):511-527

Slavic and German colonization of the southern Baltic between the 8th and 15th centuries A.D. is well‐documented archaeologically and historically. Despite the large number of pollen profiles from Poland, few palaeoecological studies have examined the ecological impact of a process that was central to the expansion of European, Christian, societies. This study aims to redress this balance through multiproxy analysis of lake sediments from Radzyń Chełminski, Northern Poland, using pollen, element geochemistry (Inductively Coupled‐Optical Emission Spectroscopy [ICP‐OES]), organic content, and magnetic susceptibility. The close association between lake and medieval settlements presents the ideal opportunity to reconstruct past vegetation and land‐use dynamics within a well‐documented archaeological, historical, and cultural context. Three broad phases of increasing landscape impact are visible in the pollen and geochemical data dating from the 8th/9th, 10th/11th, and 13th centuries, reflecting successive phases of Slavic and German colonization. This involved the progressive clearance of oak‐hornbeam dominated woodland and the development of an increasingly open agricultural landscape. Although the castles and towns of the Teutonic Order remain the most visible signs of medieval colonization, the palynological and geochemical data demonstrate that the major phase of woodland impact occurred during the preceding phase of Slavic expansion; Germans colonists were entering a landscape already significantly altered.  相似文献   

A statistical�Cdynamical scheme for reconstructing ocean forcing in the Atlantic. Part I: weather regimes as predictors for ocean surface variables     

Christophe Cassou  Marie Minvielle  Laurent Terray  Claire P��rigaud 《Climate Dynamics》2011,36(1-2):19-39

The links between the observed variability of the surface ocean variables estimated from reanalysis and the overlying atmosphere decomposed in classes of large-scale atmospheric circulation via clustering are investigated over the Atlantic from 1958 to 2002. Daily 500?hPa geopotential height and 1,000?hPa wind anomaly maps are classified following a weather-typing approach to describe the North Atlantic and tropical Atlantic atmospheric dynamics, respectively. The algorithm yields patterns that correspond in the extratropics to the well-known North Atlantic-Europe weather regimes (NAE-WR) accounting for the barotropic dynamics, and in the tropics to wind classes (T-WC) representing the alteration of the trades. 10-m wind and 2-m temperature (T2) anomaly composites derived from regime/wind class occurrence are indicative of strong relationships between daily large-scale atmospheric circulation and ocean surface over the entire Atlantic basin. High temporal correlation values are obtained basin-wide at low frequency between the observed fields and their reconstruction by multiple linear regressions with the frequencies of occurrence of both NAE-WR and T-WC used as sole predictors. Additional multiple linear regressions also emphasize the importance of accounting for the strength of the daily anomalous atmospheric circulation estimated by the combined distances to all regimes centroids in order to reproduce the daily to interannual variability of the Atlantic ocean. We show that for most of the North Atlantic basin the occurrence of NAE-WR generally sets the sign of the ocean surface anomaly for a given day, and that the inter-regime distances are valuable predictors for the magnitude of that anomaly. Finally, we provide evidence that a large fraction of the low-frequency trends in the Atlantic observed at the surface over the last 50?years can be traced back, except for T2, to changes in occurrence of tropical and extratropical weather classes. All together, our findings are encouraging for the prospects of basin-scale ocean dynamical downscaling using a weather-typing approach to reconstruct forcing fields for high resolution ocean models (Part II) from coarse resolution climate models.  相似文献   

International viewpoint and news     

Anne Marie de Grosbois 《Environmental Earth Sciences》2011,62(8):1791-1792

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Examining the assumptions of integrated coastal management: Stakeholder agendas and elite cooption in Babuyan Islands, Philippines     

Rasmus Klocker Larsen  Jo Marie Acebes 《Ocean & Coastal Management》2011,54(1):10-18

In the Philippines, Integrated Coastal Management (ICM) represents the dominant response to narratives of ecosystem decline. However, there are persistent challenges to implementation, manifested in continued resource degradation, questioning of the exercise of stakeholder involvement and rising resource conflicts. This paper examines the implementation process and how the assumptions embodied in the ICM regime meet the local reality in one group of islands in the Philippine archipelago. The evidence shows how the transformation towards a supposed equilibrium state of coastal ecosystems is undermined in the face of diverging stakeholder agendas. Expected actors are disempowered by the incoherence between the policy owners’ worldview and reality, paving the way for unethical influence from elite alliances. This is coupled with a deepening of the dominance of state, international development banks, foreign aid agencies, and NGOs in promoting their respective interests. In localities such as the Babuyan Islands, when assumptions of ICM collapse it has destructive consequences for fisherfolk and the coastal environment. We conclude that if ICM is to foster an effective and equitable correction of current unsustainable exploitation patterns, then there is a need to institute improved accountability mechanisms in the devolved governance system as well as taking seriously the espoused commitment to stakeholder involvement in determining the goals and assumptions of ICM.  相似文献   

X-ray observations of a major eruptive flare behind the limb     

Kermit L. Smith  Keith T. Strong  Zdeněk Švestka  Marie K. McCabe 《Solar physics》1994,149(2):363-380

We analyze X-ray images and spectra of a coronal structure which extended to altitudes over 130 000 km above an eruptive flare located 20° behind the western solar limb. The images were obtained by the Flat Crystal Spectrometer (FCS) and the spectra were obtained by the Bent Crystal Spectrometer (BCS) aboard the SMM spacecraft. Images in Oviii and Mgxi lines cover the period from before the flare onset (which occurred at 22:31 UT on 16 February, 1986) through 17 UT on 17 February and were used for determination of temperature and emission measure within the structure. BCS obtained Caxix spectra of the coronal event, benefiting from the occultation of the active region behind the solar limb.The BCS data show, and FCS data confirm, that the temperature, after an initial rise and decline, stayed almost constant for many hours after 04:30 UT on 17 February. This may indicate that initially we observed the rise and decay of post-flare loops, but later the X-ray emission came predominantly from a post-flare giant arch that formed above them. This has been observed in many previous cases. However, a comparison with other events characterized by very high post-flare loops, such as those that occurred on 29 July, 1973 (Skylab data) and on 14 February, 1986 (from this same region), suggests that we may be observing the same system of slowly growing groups all the time. Therefore, we suggest a third possibility, i.e., that such anomalously high loop systems first behave like post-flare loops but gradually take over some characteristics of a post-flare giant arch. The Soft X-ray Telescope aboardYohkoh, with spatial resolution improved by nearly an order of magnitude, might be able to check up on the development of such large-scale coronal structures if proper observational modes are applied after the occurrence of major eruptive flares.Deceased 1 June, 1993.  相似文献   

Rotational distortion on the surfaces of Jupiter and Saturn     

M. Marie  M. B. EL-Shaarawy 《Earth, Moon, and Planets》1994,64(3):227-242

Having formulated the Clairaut second-order differential equations up to the fourth order in superficial distortion due to Hensen's coefficients in the previous article (El-Sharawyet al., 1989 III, hereafter denotes by SM3), we are now in a position to solve them. In this paper we shall discuss the methods of solving the Clairaut theory, to give an explicit form about the distortion of the surfaces of Jupiter and Saturn, numerically up to the fourth-order.  相似文献   

Local galactic evolution     

Johan Holmberg  Birgitta NordstrÖm  Bjarne Rosenkilde Jørgensen  Johannes Andersen 《Astrophysics and Space Science》2003,284(2):685-688

The evolution of the Solar neighbourhood is followed using a unique, magnitude complete and kinematically unbiased sample of 14,000 F, G, and K dwarfs. Metallicity, age, space motion and galactic orbits have been determined for all stars. The result is a detailed view of the complex evolution of the local Milky Way, which must be matched by any model for the chemical and dynamical evolution of the Galactic disk. E.g., such models must explain the shape and large scatter in the age-metallity relation as well as the overall metallicity distribution; the evolution of stellar kinematics with age; the distribution of stars in velocity space; and the contributions from the thick and thin disks to all these relations. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Hydrodynamical simulations of the Lyα forest: data comparisons     

Avery Meiksin  Greg Bryan †  Marie Machacek ‡ 《Monthly notices of the Royal Astronomical Society》2001,327(1):296-322

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HEATING DEGREE DAY RESEARCH IN ALBERTA: RESIDENTS CONSERVE NATURAL GAS     

Marie Sanderson 《The Professional geographer》1983,35(4):437-440

A high correlation exists between monthly population-weighted heating degree days (below 18C) and the use of natural gas per household for residential heating in Alberta for the period 1962–80. The use of natural gas for residential heating per household declines since 1973 following a sharp increase in gas prices.  相似文献