Browsing
     by title


0-9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

or enter first few letters:   
OK
Full Text
Peer Reviewed
See detailIonic adsorption of ammonium and nitrate on some animal litters and their role in ammonia volatilization
Nimenya, H.; Delaunois, A.; Bloden, Serge ULg et al

in Annals of Zootechnology (2000), 49

Two experiments were carried out to determine the adsorption of ammonium and nitrate on litters (Exp. 1) and the volatilization of ammonia in their presence (Exp. 2). In Exp. 1, glass tubes containing 15 ... [more ▼]

Two experiments were carried out to determine the adsorption of ammonium and nitrate on litters (Exp. 1) and the volatilization of ammonia in their presence (Exp. 2). In Exp. 1, glass tubes containing 15 mi of a buffered solution enriched with NH4Clcalculated as 10.59 mg.l(-1) of NH4+ or KNO3 calculated as 50 mg.l(-1) of NO3- were used. Graded amounts (0 [control], 25, 50, 100 mg) of litters (wheat straw, nax straw (Equi-lin(R)), zeolite (Zeolite Stall Fresh(R)), spruce sawdust and beech sawdust) were added to the tubes which were incubated for 24 h. Ammonium and nitrate concentrations, and pH, were checked on the supernatant. A preliminary experiment was carried out with zeolite to come to an ammonium balance. After adsorption of ammoniumby graded amounts of zeolite, [0 (control), 0.25, 1, 2, 4 g], ammonium balance was assessed after two elutions with 1 N HCl. In Exp. 2, Woulff flasks were used and ammonia was trapped in a solution of 0.1 N HCl. The preliminary experiment showed that the ammonium added and adsorbed by different amounts of zeolite was completely recovered after 2 elutions. All litters, except beech sawdust, were effective in ammonium adsorption. Especially, the straws were required in very small amounts to immobilize the added ammonium or nitrate. Furthermore, with straws the pH value decreased from pH 7.5-7.60 to pH 6.90, and this effect was related to the amounts of material added. For each pH group, ammonia volatilization was significantly decreased (P <0.05) with straw (wheat straw, Equi-lino) as compared with their blank pH group. However, no significant decrease was observed with sawdust (spruce, beech) and zeolite [less ▲]

Detailed reference viewed: 90 (8 ULg)
Full Text
Peer Reviewed
See detailIonic end-capping of (semi)telechelic polymers by mesogens
Gohy, Jean-François; Sobry, Roger ULg; Van den Bossche, Guy ULg et al

in Polymer International (2000), 49(11), 1293-1301

Two methods have been used to end-cap linear polymer chains at one end or at both ends by a mesogen through ionic bonding. These polymers are designated as liquid-crystalline halato(semi)telechelic ... [more ▼]

Two methods have been used to end-cap linear polymer chains at one end or at both ends by a mesogen through ionic bonding. These polymers are designated as liquid-crystalline halato(semi)telechelic polymers (LC H(S)TPs). The first method relies on the ion exchange reaction between the metal counterion of halato(semi)telechelic polymers and an ionic mesogen. The second method is based on the proton transfer from a sulfonic or carboxylic acid end-group to a tertiary aliphatic amine, this approach being controlled by the relative pKa values of the acidic and basic groups. If the pKa difference is not large enough, strong hydrogen-bonding is observed by Fourier-transform infrared (FTIR) spectroscopy rather than proton transfer. The resulting materials have been characterized by differential scanning calorimetry (DSC), polarized optical microscopy (POM) and small-angle X-ray scattering (SAXS). [less ▲]

Detailed reference viewed: 22 (3 ULg)
Full Text
Peer Reviewed
See detailIonic end-capping of (semi)telechelic polymers by mesogens: a novel route to liquid crystalline polymers
Gohy, Jean-François; Jérôme, Robert ULg

in Progress in Polymer Science (2001), 26(7), 1061-1099

A mesogenic cation has been associated with low molecular weight carboxylato- and sulfonato-(semi)telechelic polymers to form liquid crystalline halato(semi)telechelic polymers (LC H(S)TPs). Two methods ... [more ▼]

A mesogenic cation has been associated with low molecular weight carboxylato- and sulfonato-(semi)telechelic polymers to form liquid crystalline halato(semi)telechelic polymers (LC H(S)TPs). Two methods have been used to end-cap the linear polymer chains at one (or both) end(s) by a mesogen through ionic bonding. The first method relies on the ion-exchange reaction between the metal counterion of halato(semi)telechelic polymers and an ionic mesogen. The second method is based on the proton-transfer from a sulfonic or carboxylic acid end-group to a tertiary aliphatic amine, this approach being controlled by the relative pKa's of the acid and basic groups. The resulting materials have been characterized by differential scanning calorimetry (DSC), polarized optical microscopy (POM), small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS). On the basis of these experimental results, a model for the supramolecular organization of the LC H(S)TPs has been proposed. The final morphology results from the interplay of two competitive effects: the dipolar interaction of the ion-pairs known for multiplets formation and the propensity of the mesogenic moiety to form mesophases. The outcome of this competition depends on the mobility of the mesogenic counterion, i.e. on the strength of the dipolar interactions, the mobility of the polymer backbone and the mesogen/polymer ratio, which is controlled by the polymer molecular weight. A rod-like organization of the multiplets and a stretching of the polymer chains in the very close vicinity of the mesogenic core has been found in sulfonate polystyrenes, in agreement with the Eisenberg, Hird and Moore model for ionomers. The thickness of this region of restricted mobility has been estimated to 1 nm, which is the order of magnitude of the persistence length of polystyrene. Finally, LC H(S)TPs have been tested as interfacial agents in polystyrene/liquid crystal dispersions. The dipolar interactions of the ion pairs are clearly favorable to the additive localization at the polymer/LC interface. The higher polarity of the ammonium sulfonate pairs compared to the parent ammonium carboxylate ion pairs accordingly accounts for a higher interfacial activity. [less ▲]

Detailed reference viewed: 47 (1 ULg)
See detailIonic Liquids: Past, Present and Future
Robert, Thierry ULg

Scientific conference (2011, August 24)

Detailed reference viewed: 68 (6 ULg)
Full Text
Peer Reviewed
See detailIonic or non-ionic contrast media during coronary intervention: does it make a difference?
Legrand, Victor ULg

in European heart journal (2001), 22(5), 353-4

Detailed reference viewed: 1 (0 ULg)
Full Text
Peer Reviewed
See detailIonization fronts in RCW 107 (NGC 6164/5).
Danks, A. C.; Manfroid, Jean ULg

in Astronomy and Astrophysics (1977), 56

Abstract image available at: http://cdsads.u-strasbg.fr/abs/1977A&A....56..443D

Detailed reference viewed: 7 (0 ULg)
Peer Reviewed
See detailIonization potentials of atoms and ions from lithium to tin (Z = 50)
Biémont, Emile ULg; Frémat, Y.; Quinet, Pascal ULg

in At. Data Nucl. Data Tables (1999), 71

Detailed reference viewed: 9 (1 ULg)
See detailIono slab monitoring service
Stankov, Stanimir; Warnant, René ULg; Stegen, Koen

Conference (2009)

Detailed reference viewed: 9 (0 ULg)
Full Text
Peer Reviewed
See detailIonoluminescence characterization of microwave and hot-filament CVD diamonds
Calvo Del Castillo, Helena ULg; Ruvalcaba Sil, Jose Luis; Belmont, Ernesto et al

in Physica Status Solidi A. Applications and Materials Science (2008), 205(9), 2221-2225

Detailed reference viewed: 15 (0 ULg)
Full Text
Peer Reviewed
See detailIonoluminescence of diamond, synthetic diamond and simulants
Calvo Del Castillo, Helena ULg; Ruvalcaba Sil, Jose Luis; Álvarez, M A[ et al

in Nuclear Instruments & Methods in Physics Research Section A (2007), 387

Detailed reference viewed: 8 (0 ULg)
Full Text
Peer Reviewed
See detailIonoluminescence of trivalent rare ion doped strontium barium niobate
Calvo Del Castillo, Helena ULg; Ruvalcaba-Sil, Jose Luis; Bettinelli, Marco et al

in Journal of Luminescence (2008), 128

Detailed reference viewed: 3 (0 ULg)
Peer Reviewed
See detailIonoluminiscencia en minerales de interés gemológico
Calvo Del Castillo, Helena ULg; Ruvalcaba Sil, Jose Luis; Millán Chagoyén, Asunción et al

Poster (2007)

Detailed reference viewed: 9 (0 ULg)
See detailIonoluminiscencia: Aplicaciones en Bienes Culturales (Gemas y minerales)
Calvo Del Castillo, Helena

in del Egido, Marián; Calderón, Tomás (Eds.) La Ciencia y el Arte (2008)

Detailed reference viewed: 4 (0 ULg)
Full Text
See detailIonosphere Crossing of GALILEO Signals
Bidaine, Benoît ULg

Master's dissertation (2006)

The ionosphere plays a crucial role in Global Navigation Satellite Systems (GNSS) accuracy. This electrically charged part of the atmosphere can lead to errors in positioning up to several tens of meters ... [more ▼]

The ionosphere plays a crucial role in Global Navigation Satellite Systems (GNSS) accuracy. This electrically charged part of the atmosphere can lead to errors in positioning up to several tens of meters for single frequency receivers. Therefore its modelling constitutes an important field of study. An empirical model called NeQuick has been chosen to evaluate the ionospheric contribution in GALILEO single frequency users correction. It generates electron densities for given space, time and solar activity conditions from a minimum set of anchor points characteristics. Its use with integration methods allows to calculate total electron contents (TEC) which are directly related to the ionospheric delay. The current GALILEO baseline version of NeQuick is the one published by the Radiocommunication Sector of the International Telecommunication Union (ITU-R) in 2000. From that time, several improvements have been proposed and some problems have been discovered leading to the need of a better understanding and comparison of these different versions and an analysis of the weaknesses. For example research about new topside formulations is currently performed - a new simple proposal has been tested - and the consequences of the daily effective use of NeQuick, which is designed to work with monthly median situations, have to be better known. A software tool with a Graphical User Interface (GUI) has then been developed for the analysis and a comparison between different versions and also between modelled and measured data has been performed. Structuring and analysis of the above-mentioned issues and results of the comparison are detailed in the present document. Solutions or possible paths to investigate solutions are also proposed. [less ▲]

Detailed reference viewed: 234 (41 ULg)
Full Text
See detailIonosphere Modelling Based on the NeQuick Model and GNSS Data Ingestion
Bidaine, Benoît ULg; Warnant, René ULg

in Second International Colloquium - Scientific and Fundamental Aspects of the Galileo Programme (2009, October)

As for other GNSS, the ionospheric effect remains one of the main factors limiting Galileo accuracy. For single frequency users, this contribution to the error budget will be mitigated by a global ... [more ▼]

As for other GNSS, the ionospheric effect remains one of the main factors limiting Galileo accuracy. For single frequency users, this contribution to the error budget will be mitigated by a global algorithm based on the NeQuick model. This quick-run empirical model provides flexible solutions for combining ionospheric information obtained from various systems, from GNSS to ionosondes and topside sounders thanks to which NeQuick has been designed. Hence it constitutes an interesting simulation tool not only serving Galileo needs for mitigation of the ionospheric effect but also widening the use of new data available thanks to the future European system. NeQuick provides the electron density as a function of location, time and solar activity. Thanks to numerical integration, the total content in free electrons of the ionosphere (Total Electron Content, TEC) can be deduced as well as the ionospheric propagation delay depending linearly on TEC on satellite-to-receiver path. The model is particularly suited to be used within an optimization procedure called ingestion. In this framework, an “effective ionization level” Az plays the role of the solar activity input in order to fit a specific dataset. For Galileo single frequency operation, daily Az values will be computed from slant TEC measurements performed within the ground segment. In this study, we perform slant TEC ingestion for a dozen of locations around the world where both an ionosonde and a GPS receiver are installed. These collocated instruments allow us to compare measured and modelled vertical TEC in different ways showing for example global statistics or dependence towards latitude. We analyze such results for the year 2002 (high solar activity level) giving an interesting insight in the situation we could observe when Galileo reach its Full Operation Capability, during the next solar maximum. [less ▲]

Detailed reference viewed: 236 (27 ULg)
Full Text
See detailIonosphere Modelling for Galileo Single Frequency Users
Bidaine, Benoit ULg

Doctoral thesis (2012)

Nowadays the ionosphere constitutes one of the most often modelled natural media. Indeed each GPS receiver among nearly two million units sold daily throughout the world runs a model to mitigate the ... [more ▼]

Nowadays the ionosphere constitutes one of the most often modelled natural media. Indeed each GPS receiver among nearly two million units sold daily throughout the world runs a model to mitigate the ionospheric effect affecting the signal propagation from the satellites. This propagation is delayed by the free electrons in the atmosphere so that the navigation signals appear to travel distances larger than actual ones by 7 m on average. Hence this delayed propagation deteriorates the positioning accuracy deemed on a 10−m level for mass-market applications mainly involving single frequency users. Tomorrow the European navigation system Galileo will offer a new mitigation strategy to single frequency users. This strategy will rely on the NeQuick ionospheric model and associated broadcast information. To be properly implemented, it must be extensively described to future Galileo users. These users will also wonder about its effectiveness in accounting for the ionospheric delay. The PhD research covered by the present thesis has built on Belgian expertise in ionosphere monitoring to investigate the NeQuick model and its use for Galileo. It began with the collection and handling of ionosphere measurements including GPS data. It analysed various situations at different places in the world encompassing a whole year (2002). This PhD thesis provides the ins and outs of the Galileo Single Frequency Ionospheric Correction Algorithm. It gathers an algorithm description, a performance evaluation and a variant investigation. In the shape of a paper collection, it discloses many figures as visual entry-points into the juxtaposed text and includes many references allowing to dig into the details. The algorithm performances are usefully characterised both in terms of delay mitigation and positioning accuracy. On the one hand, the residual ionospheric delay reaches 31% for the chosen sites and year. On the other hand, the positioning accuracy amounts to 6 m horizontally and 9.3 m vertically. The performance evaluation allowed to emphasise several aspects of the Galileo ionospheric correction. This correction depends largely on the modelling of the topside, the upper part of the ionosphere, which hosts more complex physical processes. It owes its good performances to data ingestion, the model adaptation technique to actual measurements underlying the Galileo algorithm. It does not necessarily provide highly correlated correction levels in terms of delay on the one hand and positioning on the other. It enables the definition of alternative regional procedures following a compatible design but coping with its weaknesses. The present thesis paves the way for future work related to ionosphere modelling for Galileo single frequency users. It supplies comparative information for the algorithm assessment in the framework of successive phases of Galileo deployment. It establishes a conceptual basis for an Assisted Ionospheric Correction Algorithm (A-ICA) disseminating more flexible ionospheric information thanks to the integration of Global Navigation Satellite Systems and telecommunications. [less ▲]

Detailed reference viewed: 429 (38 ULg)
Full Text
See detailIonosphere Modelling for GALILEO Single Frequency Users
Bidaine, Benoît ULg; Warnant, René ULg

Poster (2007, October 17)

Detailed reference viewed: 116 (18 ULg)
Full Text
Peer Reviewed
See detailIonosphere modelling for Galileo single frequency users: illustration of the combination of the NeQuick model and GNSS data ingestion
Bidaine, Benoît ULg; Warnant, René ULg

in Advances in Space Research (2011), 47(2), 312-322

The ionospheric effect remains one of the main factors limiting the accuracy of Global Navigation Satellite Systems (GNSS) including Galileo. For single frequency users, this contribution to the error ... [more ▼]

The ionospheric effect remains one of the main factors limiting the accuracy of Global Navigation Satellite Systems (GNSS) including Galileo. For single frequency users, this contribution to the error budget will be mitigated by an algorithm based on the NeQuick global ionospheric model. This quick-run empirical model provides flexible solutions for combining ionospheric information obtained from various sources, from GNSS to ionosondes and topside sounders. Hence it constitutes an interesting simulation tool not only serving Galileo needs for mitigation of the ionospheric effect but also widening the use of new data. In this study, we perform slant TEC data ingestion - the optimisation procedure underlying the Galileo single frequency ionospheric correction algorithm - into NeQuick for a dozen locations around the world where both an ionosonde and a GPS receiver are installed. These co-located instruments allow us to compare measured and modelled vertical TEC showing for example global statistics or dependence towards latitude. We analyse measurements for the year 2002 (high solar activity level) giving an insight into the situation we could observe when Galileo reaches its Full Operation Capability, during the next solar maximum. At last we compare Galileo and GPS ionospheric corrections. For Galileo, we end up with an underestimation of 11% and 4% depending on the version of NeQuick embedded in the algorithm, as well as a 22% standard deviation. This means respectively twice, five and 1.5 times better than GPS. [less ▲]

Detailed reference viewed: 197 (47 ULg)
Full Text
Peer Reviewed
See detailIonospheric and geomagnetic conditions during periods of degraded GPS position accuracy : 2. RTK events during disturbed and quiet geomagnetic conditions
Warnant, René ULg; Kutiev, Ivan; Marinov, Pencho et al

in Advances in Space Research (2007), 39(5), 881-888

Detailed reference viewed: 30 (7 ULg)