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See detailHolocene evolution of the coastal system of Sfax (SE Tunisia)
Lamourou, Ali ULg; Touir, jamel; Fagel, Nathalie ULg

Poster (2014, July 07)

This study aims to identify the depositional environments along the Tunisian coastal system and to follow their evolution over the Holocene. The material consists in three marine sediment cores retrieved ... [more ▼]

This study aims to identify the depositional environments along the Tunisian coastal system and to follow their evolution over the Holocene. The material consists in three marine sediment cores retrieved at 3 meter depth from the Northern coastal system of Sfax («Société d'Étude et d'Aménagement des Côtes Nord de la Ville de Sfax", site TAPARURA). The identification of the different depositional paleoenvironments was mainly based on field campaigns and laboratory mineralogical and sedimentological analyses of sediments. The vertical succession analysis of depositional facies allows to identify 2 main environments. First a fluviatile depositional environment (coastal plain) is characterized by fluviatile channels facies and inundation plains at the bottom of the cores. Second, at the top of the cores, we observed a marine sandy sedimentation with numerous bioclasts of gasteropods, lamellibranches and algae. This facies evolution is consistent with a relative sea level rise, responsible for the flooding of the fluviatile system at the level of the coastal plain. The main factor controlling the facies evolution and the sediment thickness variation is the local sea-floor morphology. The Holocene seabed is mainly inherited from the last glacial maximum morphology. Resulting from an important fluviatile digging that occurred, the relative sea-level fluctuations, the hydro-isostatic rebound and the climate. [less ▲]

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See detailHolocene floodplain deposition and scale effects in a typical European upland catchment : A case study from the Amblève catchment, Ardennes (Belgium)
Notebaert, Bastiaan; Verstraeten, Gert; Houbrechts, Geoffrey ULg et al

in Holocene (2013), 23(8), 1184-1197

This study quantifies Holocene alluvial sediment deposition in the Belgian Amblève catchment (1080 km2), situated in the Ardennes uplands. An extended coring data set is used for a quantitative ... [more ▼]

This study quantifies Holocene alluvial sediment deposition in the Belgian Amblève catchment (1080 km2), situated in the Ardennes uplands. An extended coring data set is used for a quantitative description and a quantification of the alluvial depositions. The floodplains fall into three main types: the upper and lower floodplains and the steep reaches. Total Holocene alluvial sediment deposition amounts to 32 Tg, or 0.029 Tg/km2. Dating of sediments using iron slag as tracer shows that on average 42% of contemporary storage was accumulated during the last 600 years. Radiocarbon dating of fluvial deposits at eight sites in the catchment confirms that the majority of the sediment is relatively recent. The increased sedimentation rates for this period are related to anthropogenic land use, possibly enhanced by climatic variations. A fluvial sediment budget was constructed for this 600 yr time period and shows that export from the catchment has about the same importance as storage in the floodplains, while lateral reworking of existing floodplain deposits only affects half the quantity of sediments. Overall, floodplain sediment storage in the Amblève catchment, comparable with other upland catchments, is of lesser importance compared with catchments dominated by loess. This can mainly be explained by lower sediment supply resulting from less intense anthropogenic land use, despite the higher sediment transport efficiency through the fluvial system. Floodplain sediment storage is scale-dependent, with initially a sharp increase in catchment area-specific sediment deposition, followed by a steady decrease with increasing catchment area. [less ▲]

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See detailHolocene instabilities in GIN sea overflows based on mineralogical and Nd/Pb isotopic sedimentary records
Simon, Q.; Fagel, Nathalie ULg; Mattielli et al

Conference (2007)

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See detailHolocene instabilities in GIN sea overflows based on mineralogical and Nd/Pb isotopic sedimentary records
Simon, Q.; Fagel, Nathalie ULg; Jennings, A. et al

Poster (2008)

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See detailHolocene palaoenvironmental records in PN speleothem (Han-sur-Lesse cave, southern Belgium
Allan, Mohammed ULg; Fagel, Nathalie ULg; Verheyden, Sophie

Conference (2015, April 16)

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See detailHolocene paleoclimate reconstructions from belgian continental archives
Allan, Mohammed ULg; VERHEYDEN, sophie; CRUCIFIX, Michel et al

Poster (2016, June 28)

Speleothems and peatbogs presented in Belgium are interesting archives for atmospheric pollution record and climate variability. Both archives are reliable continental environmental archives of high ... [more ▼]

Speleothems and peatbogs presented in Belgium are interesting archives for atmospheric pollution record and climate variability. Both archives are reliable continental environmental archives of high interest due to their dating possibilities and their possibility to preserve multi-proxy records of environmental and climatic dynamics. Combining studies on speleothems and peatbogs from the same area will provide an age-constrained reconstruction of climatic variability at annual resolution for key intervals of the Holocene. The reconstructed precipitation and temperature curves in NW European settings, as proposed in HOPES, are essential to better constrain the Northern Hemisphere climatic record and to test climate models. Our strategy is derived from a comparative study of two continental archives speleothems and peatbogs. Time series of elemental and stable isotope geochemistry will be established for the 2 archives. For peatbog, the reconstructions of temperature (derived from stable C and O isotope), precipitation (derived from humification) and dust flux (from elementary geochemical signature) would track climate changes with subdecadal resolution. As an innovative part, Laser Ablation analyse of elemental geochemistry on impregnated peat section will allow to reach an annual resolution in the dust flux. For speleothems, records of temperature (derived from oxygen and carbon isotopic composition of calcite) and effective rainfall (derived from geochemical ratios) would reach a seasonal resolution. [less ▲]

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See detailHolocene paleoenvironmental reconstructions from Belgian peatbog
Allan, Mohammed ULg; VERHEYDEN, sophie; Le roux, gael et al

Conference (2016, January 27)

Atmospheric deposition is an important part of the global climate system, and plays a key role in the marine and terrestrial biogeochemical cycles as a source for major and trace nutrient elements ... [more ▼]

Atmospheric deposition is an important part of the global climate system, and plays a key role in the marine and terrestrial biogeochemical cycles as a source for major and trace nutrient elements. Reconstruction of atmospheric deposition is crucial to understand the effects of the increased atmospheric depositions induced by humans on the environment and to help understanding Holocene climate variability. This study investigated potential paleoenvironmental proxies provided by major and trace elements and stable isotopes compositions of peat bogs. Peat bog cores were collected from Hautes-Fagnes plateau (Misten bog) (SE-Belgium). The analyses of Rare Earth Elements (REE) and lithogenic element concentrations as well as Nd isotopes were performed by HR-ICP-MS and MC-ICP-MS respectively, in a  7 m peat section representing 7300 years, dated by 210Pb and 14C methods. The Misten bog is highly affected by atmospheric supplies (natural and anthropogenic) and can be used to establish the changes in atmospheric dust during the Mid-Late Holocene. Dust fluxes show pronounced increase at 3200-2800BC, 600BC, AD600, 1000AD, 1200AD and from 1700 AD corresponding to local and regional human activities combined with climate change. Peat humification and testate amoebae were used to evaluate hydroclimatic conditions. The Nd values show large variability, between -5 and –13, identifying three major sources of dust: local soils, distal volcanic and desert particles. Our results provide evidence that climate forcing may be detected in ombrotrophic peat, even for the historical period that is characterised by a mixed climate-human control. [less ▲]

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See detailHolocene paleoenvironmental reconstructions from speleothem and peat bog archives
Allan, Mohammed ULg; VERHEYDEN; CRUCIFIX, Michel et al

Poster (2016, January 28)

The geological materials (speleothems and peatbogs) presented in Belgium (Hautes-Fagnes Plateau, Ardennes caves) are interesting archives for atmospheric pollution record and climate variability. Both ... [more ▼]

The geological materials (speleothems and peatbogs) presented in Belgium (Hautes-Fagnes Plateau, Ardennes caves) are interesting archives for atmospheric pollution record and climate variability. Both archives are easily dated (U/Th and counting for laminated speleothems, 210Pb and 14C for peatbogs), have a high temporal resolution (decadal to seasonal), contain multiple measurable parameters (elemental geochemistry, stable isotopes, radiogenic Nd and Pb isotopes, pollens, rates of peat humification, luminescence and thickness of laminated speleothems) and depending on environmental conditions of temperature and / or humidity. The aim of this study is to determine the sensitivity of both archives (speleothems and peatbogs) to human perturbations and climate changes. Our ultimate goal is to contribute to a better understanding of natural interglacial climate variability by generating and confronting high resolution paleoclimate reconstructions from 2 continental archives. [less ▲]

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See detailHolocene record of atmospheric flux by geochemical and Pb isostopes signatures in a Belgian Hautes Fagnes peat bog: Preliminary results
Gerard; De Vleeschouwer, F.; Mattielli, N. et al

in Geochimica et Cosmochimica Acta (2004), 68(11), 485-485

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See detailHolocene Records of Aerosols in Continental Environments (HoRACE)
Le Roux; De Vleeschouwer, F.; Cherbukin et al

Conference (2008)

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See detailHolocene records of regional dust deposition using peat bogs
Le Roux, G.; De Vleeschouwer, F.; Cheburkin, A. et al

Poster (2008)

Detailed reference viewed: 16 (1 ULg)
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See detailHolocene records of regional dust deposition using peat bogs
Le Roux, G.; De Vleeschouwer, François; Cheburkin, A. et al

in Geochimica et Cosmochimica Acta (2008), 72(12), 535-535

Detailed reference viewed: 34 (0 ULg)
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See detailHolocene sediment deposition in contrasting Belgian catchments
Notebaert, Batsiaan; Houbrechts, Geoffrey ULg; Verstraeten, Gert et al

in LUCIFS Workshop December 2008: Programme and Abstracts (2008)

Holocene alluvial sediment deposition was studied in several contrasting Belgian catchments: the Geul (380 km2) and its tributary the Gulp (47 km2), the Amblève (1070 km2) and its tributary the Lienne ... [more ▼]

Holocene alluvial sediment deposition was studied in several contrasting Belgian catchments: the Geul (380 km2) and its tributary the Gulp (47 km2), the Amblève (1070 km2) and its tributary the Lienne (148 km²), and the Dijle (750 km2). These catchments have a comparable Holocene climatic evolution, but they differ largely in land use history. Detailed total Holocene sediments deposition was assessed for each catchment using more then 1000 hand augerings. Detailed radiocarbon dating of fluvial deposits was performed in the Dijle catchment, while iron slag was used as a tracer for sediments deposited after 1350 AD in the Lienne catchment. For the Geul River the presence of lead contamination, originating from 19th century mining activities, were used as a tracer. Results show that sediment deposition is much largest in the Dijle catchment (4.6 Mg/ha catchment area) then in the Gulp catchment (1.3 Mg/ha catchment area), while the lowest deposition is found in the Amblève catchment (0.2 Mg/ha catchment area). It is clear that these differences are mainly due to historical land use differences, although it can not be excluded that part of these differences are due to physical factors, especially for the Amblève catchment. For the latter catchment, the distribution of iron slags in the floodplain sediments showed that large parts of the alluvial plane were eroded after 1350 AD, and thus that there is no net aggradation as for the Dijle and Gulp floodplain. Remobilization of floodplain sediment in the Amblève makes it also difficult to estimate Holocene erosion rates. Nevertheless it is clear that an important part of the sedimentation took place after the Middle Ages, and that during Medieval times the river changed from a system with two or more channels to a system with one single channel. This is probably related to increasing deforestation after 1350 AD. Dating results of the Dijle floodplain show that the sedimentation rates are largely influenced by land use with main deposition after the Middle Ages. There is a gradual increase in sedimentation rate since Neolithic times and each new cultural period is recognized by an increase in sedimentation rate related to the intensification of land use. Several sites show that sedimentation rates have recently decreased, probably due to a reduction in cropland area. 12 Dating of the Geul River floodplain suggests a high sedimentation rate during the 19th century and lower rates for more recent times, which can be related to the more intense 19th century land combined with mobilization of sediments by the mining activities, which ended at the end of that century. From the data collected in these catchments it is clear that land use changes are the main driving factors for accelerated alluvial sediment deposition rates, although climate fluctuations can have influenced the impact of land use changes. [less ▲]

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See detailThe holodisc distance transform and its applications in image analysis
Pirard, Eric ULg

in Microscopy, Microanalysis, Microstructures (1996), 7

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See detailHolographic camera with BSO applied to microgravity fluid experiment aboard ISS
Georges, Marc ULg; Joannes, Luc; Thizy, Cédric ULg et al

in Nolte, D.; Salamo, G.; Siahmakoun, A. (Eds.) et al Photorefractive Effects, Materials, and Devices (2001, July)

We present the preliminary development steps of a holographic interferometer using a BSO crystal for the monitoring of fluids experiments under microgravity conditions. This set-up could be included in ... [more ▼]

We present the preliminary development steps of a holographic interferometer using a BSO crystal for the monitoring of fluids experiments under microgravity conditions. This set-up could be included in the Fluid Science Laboratory (FSL, a module dedicated to fluid physics experiment onboard the International Space Station-ISS). Some preliminary studies have been carried out. An optimized configuration has been found allowing a fast recording (50 milliseconds) and large number of readouts (>1000) for analysis of events over a long period without reducing the measurement resolution. We present examples of Rayleigh-Benard convection quantitative measurement performed with a laboratory instrument prototype. [less ▲]

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See detailHolographic Filter applied to LCD projector for improvement of laser pointer presentation
Habraken, Serge ULg; Moreau, Vincent; Vandormael, Denis et al

in Proceedings of Spie (2000), 3951

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See detailHolographic interferometers based on photorefractive crystals for vibration measurements
Georges, Marc ULg; Thizy, Cédric ULg; Ryhon, Sébastien et al

Conference (2002, June)

Photorefractive crystals offer many advantages over other classical holographic recording media. They allow fast in-situ processable holographic recording as well as indefinite reusability. Moreover high ... [more ▼]

Photorefractive crystals offer many advantages over other classical holographic recording media. They allow fast in-situ processable holographic recording as well as indefinite reusability. Moreover high signal-to-noise ratio can be reached as well as high resolutions. We present several types of holographic instruments using such materials. Here we will emphasize their applications in vibration measurements. A first one is based on the classical stroboscopic technique, a second one uses a pulsed laser. [less ▲]

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See detailHolographic interferometry based on photorefractive crystal to measure 3D thermo-elastic distortion of composite structures and comparison with finite element models
Thizy, Cédric ULg; Eliot, F.; Olympio, K.R. et al

in Lehmann, Peter (Ed.) Proc. SPIE Vol 8788 on Optical Measurement Systems for Industrial Inspection VIII (2013, May)

Thermo-elastic distortions of composite structures have been measured by a holographic camera using a BSO photorefractive crystal as the recording medium. The first test campaign (Phase 1) was performed ... [more ▼]

Thermo-elastic distortions of composite structures have been measured by a holographic camera using a BSO photorefractive crystal as the recording medium. The first test campaign (Phase 1) was performed on CFRP struts with titanium end-fittings glued to the tips of the strut. The samples were placed in a vacuum chamber. The holographic camera was located outside the chamber and configured with two illuminations to measure the relative out-of-plane and in-plane (in one direction) displacements. The second test campaign (Phase 2) was performed on a structure composed of a large Silicon Carbide base plate supported by 3 GFRP struts with glued Titanium end-fittings. Thermo-elastic distortions have been measured with the same holographic camera used in phase 1, but four illuminations, instead of two, have been used to provide the three components of displacement. This technique was specially developed and validated during the phase 2 in CSL laboratory. The system has been designed to measure an object size of typically 250x250 mm²; the measurement range is such that the sum of the largest relative displacements in the three measurement directions is maximum 20 μm. The validation of the four-illuminations technique led to measurement uncertainties of 120 nm for the relative in-plane and out-of-plane displacements, 230 nm for the absolute in-plane displacement and 400 nm for the absolute out-of-plane displacement. For both campaigns, the test results have been compared to the predictions obtained by finite element analyses and the correlation of these results was good [less ▲]

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