References of "Chene, Grégoire"
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See detailDe bois, de pierre, de terre…et de verre. Approche de l’approvisionnement des chantiers alto-médiévaux à travers le cas de la mosaïque du baptistère de Nevers.
Van Wersch, Line ULiege; Neri, Elisabetta; Chene, Grégoire ULiege et al

Conference (2018)

Les découvertes de verre architectural qui se sont multipliées ces dernières années lèvent peu à peu le voile sur le rôle joué par de ce matériau dans les édifices alto-médiévaux. Les églises possédaient ... [more ▼]

Les découvertes de verre architectural qui se sont multipliées ces dernières années lèvent peu à peu le voile sur le rôle joué par de ce matériau dans les édifices alto-médiévaux. Les églises possédaient de véritables vitraux et le verre pouvait être incrusté dans les murs et les sols où il jouait un rôle dans la réflexion de la lumière. Dès lors, le besoin croissant de verre architectural a pu contribuer aux innovations techniques dans l’artisanat verrier du nord-ouest de l’Europe ainsi qu’à la mise en place de réseaux d’approvisionnement spécifiques en fonction des chantiers de construction. Attribuées au décor VIe siècle, les tesselles mises au jour lors des fouilles de la cathédrale de Nevers, dans le baptistère, sont un témoignage du début de ce processus. Les cubes sont majoritairement réalisés en verre, opaque et coloré ou incolore et recouvert d’une feuille d’or. Comme certains d’entre eux étaient encore insérés dans du mortier portant des traces de polychromie, leur attribution a une mosaïque pariétale est assurée. L’étude de ces objets et leur analyse en PIXE-PIGE et en raman, nous a permis d’identifier les matières premières et les techniques utilisées pour leur mise en œuvre. La comparaison avec des édifices contemporains a mis en exergue des points communs et les particularismes propres au site de Nevers, nous permettant de proposer une hypothèse pour l’approvisionnement des matériaux nécessaires à la décoration du baptistère. Cette étude révèle ainsi l’importance d’un chantier de mosaïque pariétale et la complexité des relations qu’il demande. [less ▲]

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See detailInter-techniques comparison of PIXE and XRF for Lake sediments
El Ouahabi, Meriam ULiege; Chene, Grégoire ULiege; Strivay, David ULiege et al

in Journal of Analytical Atomic Spectrometry (2018), 33(883 - 892),

In this paper we describe a validation procedure for chemical analysis of major elements and some minor elements as Sr, Cr, Ni, Zn and Zr in heterogeneous geological sediments. The procedure applies two ... [more ▼]

In this paper we describe a validation procedure for chemical analysis of major elements and some minor elements as Sr, Cr, Ni, Zn and Zr in heterogeneous geological sediments. The procedure applies two distinct techniques (PIXE and XRF) to the analysis of sediments. In this work an inter-technique comparison of the heterogeneous lacustrine sediments from the Amik Lake in the vicinity of the Roman city of Antioch (SE, Turkey) was carried out. Dried raw samples and with the addition of linking powder were analyzed using PIXE performed on the “Arkeo” beam line of the University of Liège AVF-Cyclotron and XRF (University of Liège). The aim of this work was to compare PIXE and XRF analysis with the set-ups routinely in use in the two laboratories. The purpose was also to determine the best combination of techniques and sample preparation protocol to be applied for heterogeneous sediments and the main elements of interest for each specific technique. The results are in agreement among the two techniques, with discrepancies concerning almost lighter and minor elements. These differences are related mainly to the texture of the sediments and the intrinsic features of the XRF and PIXE techniques. Major and selected minor elements are sensitive to the grain-size and the porosity of the samples. However, the accuracy of both XRF and PIXE requires the reduction of the grain-size or addition of linking powder to the sediments to fill the voids in order to increase the intensities of both lighter and minor elements. The results demonstrate the critical importance of sample treatment prior to analysis as well as the necessity of several measurement points and replicates to ensure the accuracy of the PIXE results. [less ▲]

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See detailLight Induced Super-Hydrophilicity in Niobium and Tantalum Oxides Thin Films
Henry, Théo ULiege; Bonsague, Fabio; Dubreuil, Olivier ULiege et al

Poster (2017, July)

Since its discovery at the end of the nineties by Wang et al.,[1] the interest for light-induced superhydrophilicity is ever growing. The application fields for materials displaying such a property are ... [more ▼]

Since its discovery at the end of the nineties by Wang et al.,[1] the interest for light-induced superhydrophilicity is ever growing. The application fields for materials displaying such a property are wide and numerous:[2] self-cleaning surfaces, anti-fogging, anti-bacterial, water and air purification, microfluidics…Nowadays, a research emphasis is on relatively low energy bandgap semiconductors, targeting a higher efficiency under solar irradiation or more precisely in the near UV and low-end of the visible spectral range. Here, however, we report UV-induced superhydrophilicity in metal oxides thin films showing a relatively high transparency in the UV. Reactive ion beam sputtering (IBS) was used to deposit niobium, tantalum and titanium oxides thin films with thickness ranging from 10 nm to 120 nm on fused silica substrates at room temperature. Contact angle measurements were performed for progressively increasing UV doses and also as function of elapsed time after the termination of the exposure in order to investigate the UV-induced hydrophilicity and recovery behavior of tantalum and niobium oxide thin films in comparison to that of titanium oxide deposited in analogous conditions. [less ▲]

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See detailAssessment of natural radioactivity and associated radiation hazards in sand building material used in Douala Littoral Region of Cameroon, using gamma spectrometry
Guembou Shouop, Cébastien Joel ULiege; Ndontchueng Moyo, Maurice; Chene, Grégoire ULiege et al

in Environmental Earth Sciences (2017), 76(164),

Twenty-four sand samples were collected from different sand quarries from Douala Littoral Region (Wouri, Dibamba, Mungo and Docteur Anse rivers and Atlantic Sea) along the Guinea Golf. These samples were ... [more ▼]

Twenty-four sand samples were collected from different sand quarries from Douala Littoral Region (Wouri, Dibamba, Mungo and Docteur Anse rivers and Atlantic Sea) along the Guinea Golf. These samples were investigated using gamma-ray spectrometry system. Highest values of 226Ra, 232Th and 40K measured specific activities expressed in Bq Kg−1 units were, respectively, 146.7 (in Youpoue–Bamenda 2) 102.9 (in Village 1) and 928 (in Northern Akwa 6) while the lowest values were found to be, respectively, 11.8 (in Northern Akwa 6), 8.0 (in Bonaberi–Bonamikano 4) and 54.0 (Youpoue 3). The potential radiological hazards parameters were assessed by calculating successively radium equivalent activity (Raeq), outdoor absorbed gamma dose rate (Dout), annual effective dose rate, internal hazard (Hin) and external hazard (Hex) indices and alpha and gamma index from using those sand in the construction of dwellings and large buildings. Results obtained show that annual dose absorbed by inhabitants due to sand construction use in Douala is below 1.0 mSv year−1. Therefore, most of the types of sands studied and incorporated in constructions appear to be safe as building material. The outputs from this research will be useful to assess the radiation hazards of sand building material in humans and to initiate a sand database together with a radiological map of the area at stake. [less ▲]

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See detailOptimal measurement counting time and statistics in gamma spectrometry analysis: The time balance
Guembou Shouop, Cébastien Joel ULiege; Penabei, Samafou; Ndontchueng Moyo, Maurice et al

Scientific conference (2017, January 04)

The optimal measurement counting time for gamma-ray spectrometry analysis using HPGe detectors was determined in our laboratory by comparing twelve hours measurement counting time at day and twelve hours ... [more ▼]

The optimal measurement counting time for gamma-ray spectrometry analysis using HPGe detectors was determined in our laboratory by comparing twelve hours measurement counting time at day and twelve hours measurement counting time at night. The day spectrum does not fully cover the night spectrum for the same sample. It is observed that the perturbation come to the sun-light. After several investigations became clearer: to remove all effects of radiation from outside (earth, the sun, and universe) our system, it is necessary to measure the background for 24, 48 or 72 hours. In the same way, the samples have to be measured for 24, 48 or 72 hours to be safe to be purified the measurement (equality of day and night measurement). It is also possible to not use the background of the winter in summer. Depend on to the energy of radionuclide we seek, it is clear that the most important steps of a gamma spectrometry measurement are the preparation of the sample and the calibration of the detector. [less ▲]

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See detailPrecision measurement of radioactivity in Gamma-rays spectrometry using two HPGe detectors (BEGe-6530 and GC0818-7600SL models) comparison techniques: Application to the soil measurement.
Guembou Shouop, Cébastien Joel ULiege; Samafou Penabei; NDONTCHUENG MOYO, Maurice et al

in MethodsX (2017), 4(42-54), 2017

To obtain high quality of results in gamma spectrometry, it is necessary to select the best HPGe detector for particular measurements, to calibrate energy and efficiency of gamma detector as accurate as ... [more ▼]

To obtain high quality of results in gamma spectrometry, it is necessary to select the best HPGe detector for particular measurements, to calibrate energy and efficiency of gamma detector as accurate as possible. To achieve this aim, the convenient detector model and gamma source can be very useful. The purpose of this study was to evaluate the soil specific activity using two HPGe model (BEGe-6530 and GC0818-7600SL) by comparing the results of the two detectors and the technics used according to the detector type. The relative uncertainty activity concentration was calculated for 226Ra, 232Th and 40K. For broad energy germanium detector, BEGe-6530, the relative uncertainty concentration ranged from 2.85 to 3.09% with a mean of 2.99% for 226Ra, from 2.29 to 2.49% with a means of 2.36% for 232Th and from 3.47 to 22.37% with a mean of 12.52% for 40K. For GC0818-7600SL detector, it was ranged from 10.45 to 25.55% with a mean of 17.10% for 226Ra, from 2.54 to 3.56% with a means of 3.10% for 232Th and from 3.42 to 7.65% with a mean of 5.58% for 40K. The average report between GC0818-7600SL model and BEGe-6530 model was calculated and showed the mean value of 3.36. The main study was based on the following points: • Determination of The relative uncertainty activity concentration of 226Ra, 232Th and 40K • Determination of the relative uncertainty related to the radium equivalent activity to compare the performance of the two detection systems • Proved that the activity concentration determination in gamma spectrometry depended on the energy range emitted by a radionuclide. This study showed that the standard deviation measurement was less important to the result realized with BEGe-6530 HPGe model. Our findings were demonstrated that the results of the Broad Energy Germanium detector were more reliable. [less ▲]

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See detailThe scientific analyses of glass vessels
Van Wersch, Line ULiege; Biron, Isabelle; Mathis, François et al

in Theuws, F.; Kars, M. (Eds.) The Saint-Servatius complex in Maastricht. The Vrijthof excavations (1969-1970) (2017)

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See detailGamma-Ray Spectrometry: Experimental Measurement and Monte Carlo Simulation using GEANT4 toolkit
Guembou Shouop, Cébastien Joel ULiege; Ndontchueng Moyo, Maurice; Chene, Grégoire ULiege et al

Poster (2016, July 13)

Nowadays the precision in the measurement has become a challenge for physicists. That is why in recent decades, the interest is very granted to simulation. Since 1940, the method Monte Carlo is more ... [more ▼]

Nowadays the precision in the measurement has become a challenge for physicists. That is why in recent decades, the interest is very granted to simulation. Since 1940, the method Monte Carlo is more useful for validation and even for prediction of the results of the experiment. The aim of this study is to validate experimental models. Our laboratories are equipped with HPGe gamma spectrometers for measuring the natural radioactivity, it becomes interesting to compare and even to improve the performance of our system. Geant4 is used for the construction of the geometry of detection, the physics processes and the primary particles. First and prliminary result was prsented in this paper. [less ▲]

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See detailCounting time measurement and statistics in gamma spectrometry: the balance
Guembou Shouop, Cébastien Joel ULiege; Ndontchueng Moyo, Maurice; Chene, Grégoire ULiege et al

Poster (2016, July 11)

Nuclear counting statistics at high count rate are assessed on a γ-ray spectrometer set-up. Our typical gamma spectrometry system consists of a High Purity Germanium (HPGe) detector, liquid nitrogen ... [more ▼]

Nuclear counting statistics at high count rate are assessed on a γ-ray spectrometer set-up. Our typical gamma spectrometry system consists of a High Purity Germanium (HPGe) detector, liquid nitrogen cooling system, preamplifier, detector bias supply, linear amplifier, analog-to-digital converter (ADC), multichannel storage of the spectrum, and data readout devices. Although the system is powerful enough for background measurements, it is important, nowadays, to have a great statistical in short time measurement: which is a challenge for scientists. The purpose of this study was to determine the average time for gamma spectrometry measurement. To detect Uranium, Thorium and their respective daughters and Potassium series with a relative related error less than 1%, it was found that it is necessary to count during a minimum of 24 Hours (86,400 s). This result is in accordance to the literature with planar geometry detector. These results conduct us to make the following three guidelines for selecting the detector best suited for an application: 1. The more detector material available (germanium semi-conductor), the higher the full-energy peak efficiency. 2. The smaller the distance between the detector and the source material, the higher the full- energy peak efficiency. 3. While better resolution gives a better MDA, the resolution contributes only as the square root to the MDA value, whereas the MDA is proportional to the full-energy peak efficiency. This idea came to us by comparing the spectra of measuring radioactivity lasts for 12 hours in the day that does not fully covered the night spectra for the same sample. The conclusion after several investigations became clearer: to remove all effects of radiation from outside (earth, sun and universe) our system, it is necessary to measure the background for 24, 48 or 72 hours. In the same way, the samples have to be measures for 24, 48 or 72 hours to be safe to be purified the measurement (equality of day and night measurement). It is also possible to not use the background of the winter in summer. Depend to the energy of radionuclide we seek, it is clear that the most important steps of a gamma spectrometry measurement are the preparation of the sample and the calibration of the detector. [less ▲]

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See detailPIXE-PIGE analysis of Early Medieval Glass Artefacts at IPNAS cyclotron external beam line
Chene, Grégoire ULiege; Van Wersch, Line ULiege; Biron, Isabelle et al

Poster (2016, July 05)

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See detailGeochemistry and mineralogy approaches to characterize brick and its lake sediments sources: Antioch Roman City (Southern Turkey)
El Ouahabi, Meriam ULiege; Hubert, Aurelia ULiege; Benjelloun, Yacine et al

Poster (2016, July)

The Roman aqueduct of Antioch-on-the-Orontes (Southern Turkey) is situated close to the Antioch city. This last is located near the Amik Lake (Lake of Antioch) and close to the junction between the active ... [more ▼]

The Roman aqueduct of Antioch-on-the-Orontes (Southern Turkey) is situated close to the Antioch city. This last is located near the Amik Lake (Lake of Antioch) and close to the junction between the active Dead Sea fault and the East Anatolian fault. During the Roman period, the Amik Plain was more densely occupied than at any time in its history [1]. The study focuses on the bricks and the lake sediments characterization in order to determine the source area as well as the technical production used at this period. For this purpose, several bricks were sampled on different parts of the city's aqueducts. Furthermore, a core of about 6 m of sediments was also collected from the dried Amik Lake. The bricks were characterized through a mineralogical (XRD) and chemical (PIXE-PIGE) approaches. Unfired clay fraction remained as inclusion in the brick was separated and then analysed using XRD. Geochemical composition and clay mineralogy were performed on the raw sediments from the Amik Lake in order to compare the source area. Technological test will be performed on the raw clay sediments from the Amik Lake in the purpose to understand the production techniques used at this time. The age of the brick production was previously dated to the Roman Period [2]. The synthesis of all the data attested the Amik Lake sediment as the raw material for the bricks of the aqueduct. Clay mineral composition from the Roman period deposited in the lake is smectite, illite, kaolinite and small amount of mixed-layer clays. The similar clays composition is found in the remained clays on the brick used for the aqueduct construction. Fast and heterogeneous firing practice characterized the manufacturing of these materials due to the rapid need for the materials during the post-seismic repairs after earthquakes that are mentioned in historical written works. [1] J. Casana, Geomorphology, 101, 429-442 (2008) [2] Y. Benjelloun, J. de Sigoyer, J. Carlut, A. Hubert-Ferrari, H. Dessales, H. Pamir, V. Karabacak, Comptes Rendus Geoscience, 347, 170-180 (2015) [less ▲]

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See detailNatural radioactivity and elemental composition of sands in the Douala region, Littoral of Cameroon Using Portable XRF and HPGe detector
Guembou Shouop, Cébastien Joel ULiege; Ndontchueng Moyo, Maurice; Chene, Grégoire ULiege et al

Poster (2016, June 21)

Twenty four sand samples from seven sand quarries alone the Gulf of Guinea, Douala Littoral region of Cameroon, were analyzed using high purity germanium detector and a portable X-ray fluorescence (PXRF ... [more ▼]

Twenty four sand samples from seven sand quarries alone the Gulf of Guinea, Douala Littoral region of Cameroon, were analyzed using high purity germanium detector and a portable X-ray fluorescence (PXRF) spectrometer. A comprehensive study was conducted to determine the natural radioactivity concentrations and the geological provenience of sand samples from seven different quarries sites of the Douala, a popular city, and its surroundings. The radioactivity investigation was performed by using high resolution gamma-ray spectrometry. From the measured gamma-spectra, the average activity concentrations were determined for 226Ra, 232Th, 40K and 235U for a depth of 5–25 cm. Results of this study were compared to values from other locations around the world. X-ray fluorescence spectrometry (XRF) measurements were performed for the quantitative elemental analysis of the sands, revealing the major, minor and trace elements present in the investigated samples. Reference marine and geological sample are used to check precision and accuracy of the equipment for major and minor components. From XRF experimental results it was possible to estimate the geological provenience of the analyzed sands. These data record the radioactivity background levels in sands and could be used as reference information in Cameroon. The comparison of major (Si, Al), minor (K, Ca,Fe), and trace (Ti, Mn, Zr, Rb, Sr) element ratios was made. The results indicate that the levels of Si and Al can be very helpful in subgroup definition and provide useful clues to the raw materials used for glassmaking in Cameroon. [less ▲]

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See detailRecent technical developments of non-invasive cultural heritage analysis at the University of Liège
Strivay, David ULiege; Chene, Grégoire ULiege; Calvo Del Castillo, Helena ULiege et al

Conference (2015, December 07)

The University of Liège has more than twenty years of experience in the use of ion beam analysis techniques for cultural heritage research. We will present here some of the recent developments. First, we ... [more ▼]

The University of Liège has more than twenty years of experience in the use of ion beam analysis techniques for cultural heritage research. We will present here some of the recent developments. First, we have developed a high energy extracted beamline up to 20 MeV on our cyclotron with a good energy resolution of a few keV. These last years Ion Beam Analysis users show an interest in High Energy Alpha beam. These beams can be used for on-site analysis by means of radioactive sources e.g. for space application but they also offer a powerful combination of properties for the analysis of thick layers (about 10 to 20 µm). This kind of layers are often met in cultural heritage applications but can be also present on new materials. Contrary to this kind of materials where the principal information needed is the in-depth profiles as the sample are of known composition, for cultural heritage materials the combination of elemental analysis and their in-depth distribution is essential as the nature of the material is a-priori not known. We will also present the development around our first extracted beamline. We have indeed improved the automatic scanning system for macro-PIXE. Some examples will be shown. Finally we will show other non-invasive analysis developments related to cultural heritage. [less ▲]

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See detailTiO2 templated films used as photoelectrode for solid-state DSSC applications: Study of the solid electrolyte infiltration by Rutherford Backscattering Spectrometry
Dewalque, Jennifer ULiege; Colson, Pierre ULiege; Mathis, François et al

Poster (2015, May 10)

Liquid-state dye-sensitized solar cells can suffer from electrolyte evaporation and leakage. Therefore solid-state hole transporting materials are investigated as alternative electrolyte materials ... [more ▼]

Liquid-state dye-sensitized solar cells can suffer from electrolyte evaporation and leakage. Therefore solid-state hole transporting materials are investigated as alternative electrolyte materials. However, in solid-state dye-sensitized solar cells, optimal TiO2 films thickness is limited to a few microns allowing the adsorption of only a low quantity of photoactive dye and thus leading to poor light harvesting and low conversion efficiency. In order to overcome this limitation, high surface area templated films are investigated as alternative to nanocrystalline films prepared by doctor-blade or screen-printing. Moreover, templating is expected to improve the pore accessibility what would promote the solid electrolyte penetration inside the porous network, making possible efficient charge transfers. In this study, films prepared from different structuring agents are discussed in terms of microstructural properties (porosity, crystallinity) as well as effect on the dye loading and Spiro-OMeTAD (2,2',7,7'-tetrakis-(N,N-di-p-methoxyphenylamine)9,9'-spirobifluorene) solid electrolyte filling. Different techniques such as transmission electron microscopy (TEM), atmospheric poroellipsometry (AEP) and UV-visible absorption spectroscopy (UV-vis.) have been used to describe the microstructural features of the films. Besides, we have implemented Rutherford backscattering spectrometry (RBS) as an innovative non-destructive tool to characterize the hole transporting materials infiltration. Templated films show dye loading more than two times higher than nanocrystalline films prepared by doctor-blade or screen-printing and solid electrolyte infiltration up to 88%. [less ▲]

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See detailPore-filling of Spiro-OMeTAD determined by Rutherford backscattering spectrometry in templated TiO2 photoelectrodes
Dewalque, Jennifer ULiege; Colson, Pierre ULiege; Thalluri, Venkata Visveswara Gopala Kris ULiege et al

in Organic Electronics (2014), 15

Liquid-state dye-sensitized solar cells can suffer from electrolyte evaporation and leakage. Therefore solid-state hole transporting materials are investigated as alternative electrolyte materials ... [more ▼]

Liquid-state dye-sensitized solar cells can suffer from electrolyte evaporation and leakage. Therefore solid-state hole transporting materials are investigated as alternative electrolyte materials. However, in solid-state dye-sensitized solar cells, optimal TiO2 films thickness is limited to a few microns allowing the adsorption of only a low quantity of photoactive dye and thus leading to poor light harvesting and low conversion efficiency. In order to overcome this limitation, high surface area templated films are investigated as alternative to nanocrystalline films prepared by doctor-blade or screen-printing. Moreover, templating is expected to improve the pore accessibility what would promote the solid electrolyte penetration inside the porous network, making possible efficient charge transfers. In this study, films prepared from different structuring agents are discussed in terms of microstructural properties (porosity, crystallinity) as well as impact on the dye loading and Spiro-OMeTAD (2,2',7,7'-tetrakis-(N,N-di-p-methoxyphenylamine)9,9'-spirobifluorene) solid electrolyte filling. We first report Rutherford backscattering spectrometry as an innovative non-destructive tool to characterize the hole transporting materials infiltration. Templated films show dye loading more than two times higher than nanocrystalline films prepared by doctor-blade or screen-printing and solid electrolyte infiltration up to 88%. [less ▲]

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