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

Conference (2015, April 16)

Detailed reference viewed: 40 (9 ULiège)
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See detailHolocene paleoclimate reconstructions from belgian continental archives
Allan, Mohammed ULiege; 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 ▲]

Detailed reference viewed: 77 (4 ULiège)
See detailHolocene paleoenvironmental reconstructions from Belgian peatbog
Allan, Mohammed ULiege; 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 ULiege; 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

Detailed reference viewed: 49 (7 ULiège)
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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)

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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 ULiège)
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See detailHolocene sediment deposition in contrasting Belgian catchments
Notebaert, Batsiaan; Houbrechts, Geoffrey ULiege; 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 ULiege

in Microscopy, Microanalysis, Microstructures (1996), 7

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See detailHolographic camera with BSO applied to microgravity fluid experiment aboard ISS
Georges, Marc ULiege; Joannes, Luc; Thizy, Cédric ULiege 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 ▲]

Detailed reference viewed: 20 (2 ULiège)
See detailHolographic Filter applied to LCD projector for improvement of laser pointer presentation
Habraken, Serge ULiege; Moreau, Vincent; Vandormael, Denis et al

in Proceedings of Spie (2000), 3951

Detailed reference viewed: 40 (6 ULiège)
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See detailHolographic interferometers based on photorefractive crystals for vibration measurements
Georges, Marc ULiege; Thizy, Cédric ULiege; 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 ULiege; 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 ▲]

Detailed reference viewed: 98 (11 ULiège)
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See detailHolographic interferometry using photorefractive crystals for quantitative phase measurement on large objects
Georges, Marc ULiege; Lemaire, Philippe ULiege

in Benton, Stephen (Ed.) Practical Holography X (1996, January)

We recently have presented a real-time holographic interferometer using sillenite crystals connected with phase-shifting for quantitative measurement of diffuse objects deformations. In our basic set-up ... [more ▼]

We recently have presented a real-time holographic interferometer using sillenite crystals connected with phase-shifting for quantitative measurement of diffuse objects deformations. In our basic set-up, the crystal, sandwiched between two polarizers, is set in front of the optical head and followed by a CCD camera with an imaging objective. With this system, for conventional objects and using 2.2 Watts of Ar3+ laser power @ 514 nm, interferograms can be observed on object fields of about 30 cm*20 cm (crystal size 1 cm*1 cm and 26 mm objective focal length). In this paper we present investigations to increase the observed field in the existing system and to be able to use lower power lasers. Since setting the object at larger distances should lead to an insufficient luminous level for hologram recording, we have proceeded by different ways. First, we use shorter focal length objectives, giving a larger field-of-view, and larger crystals have to be used in this case to avoid vignetting. Second, we use a large aperture frontal objective in order to collect more light and that images the object on the crystal, the final image being observed through relay imagery. [less ▲]

Detailed reference viewed: 16 (6 ULiège)
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See detailHolographic interferometry using photorefractive crystals: recent advances and applications
Georges, Marc ULiege; Lemaire, Philippe ULiege

in Gorecki, Christophe (Ed.) Optical Inspection and Micromeasurements (1996, June)

We present a real-time holographic interferometer using sillenite crystals for measurement of deformations of large diffusive objects. Two kind of optical heads have been investigated: a first system with ... [more ▼]

We present a real-time holographic interferometer using sillenite crystals for measurement of deformations of large diffusive objects. Two kind of optical heads have been investigated: a first system with a frontal crystal followed by a CCD camera with a short focal length objective, and a second system with imaging objective in front of the crystal, collecting light and imaging the object in its vicinity, the final image being observed with a second relay imagery. Both systems art compared with respect to their temporal behaviour and quality of interferograms. This interferometer is connected with quantitative phase-measurement systems. First, phase-shifting (PS) can be performed by translating a mirror in the reference beam, enabling acquisition of several interferograms subsequently processed leading to the object phase deformation. Nevertheless this requires stability of the object during the shifting process. Second, Fourier transform (FT) processing can be used on a single interferogram. This interferometer has been successively used in different applications: detection of defects in weakly disturbed structures using PS and monitoring of thermal deformation of an object with FT processing. [less ▲]

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See detailHolographic interferometry using two-wavelength holography for the measurement of large deformations
Ninane, Nathalie ULiege; Georges, Marc ULiege

in Applied Optics (1995), 34(11), 1923-1928

Detailed reference viewed: 12 (2 ULiège)
See detailHolographic interferometry using two-wavelength holography for the measurement of large deformations
Ninane, Nathalie ULiege; Georges, Marc ULiege

in Sirohi, R.; Hinsch, K. (Eds.) Selected papers on Holographic interferometry : Principles and technique (1998)

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See detailHolographic interferometry with a 90 degrees photorefractive crystal geometry
Georges, Marc ULiege; Pauliat, G.; Weidner, E. et al

in Delaye, Ph; Denz, C.; Mager, L. (Eds.) Photorefractive Effects, Materials, and Devices (2003, June)

Holographic interferometers are generally designed in the common geometry where both interfering waves (reference and object) enter the crystal by the same window (co-propagating configuration). The ... [more ▼]

Holographic interferometers are generally designed in the common geometry where both interfering waves (reference and object) enter the crystal by the same window (co-propagating configuration). The alternative presented here consists in using a reference beam entering the crystal by a lateral face. The crystal has to be cut adequately in order to obtain electro-optic properties similar to that of the co-propagating configuration but with a smaller optical scattering noise. Therefore higher signal-to-noise ratios are expected in the interferograms. We will present the main features and constraints of this configuration together with the experimental study of its noise characteristics. This work has been performed for sillenite and semiconductor crystals [less ▲]

Detailed reference viewed: 41 (1 ULiège)