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See detailSensitivity of the breaching process in the case of overtopping induced fluvial dike failure
Rifai, Ismail ULg; Erpicum, Sébastien ULg; Archambeau, Pierre ULg et al

in River Flow 2016 Proceedings (2016, July)

Fluvial dikes are common structures constructed for flow channelization, prevention of river bed lateral migration and for flood protection purposes. Their aging increases their vulnerability to extreme ... [more ▼]

Fluvial dikes are common structures constructed for flow channelization, prevention of river bed lateral migration and for flood protection purposes. Their aging increases their vulnerability to extreme hydro-logical events, and subsequently may cause their failure. Many laboratory studies of overtopping induced dike failure were conducted, dealing mainly on normal configurations (i.e. dam break configuration) without ac-counting for the influence of a parallel flow. The fluvial dike breaching process remains, therefore, insuffi-ciently studied. A simplified model assuming a parameterized evolution of the breach geometry has been de-veloped to evaluate the fluvial breaching process. Results showed a sensitivity of the breaching process to the main channel configuration and to the flow conditions. Also, the evolution mode that was prescribed for the breach cross-section strongly influences the breaching duration and the sediment discharge [less ▲]

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See detailAnalysis of SMOS sea surface salinity data using DINEOF
Alvera Azcarate, Aïda ULg; Barth, Alexander ULg; Parard, Gaëlle ULg et al

in Remote Sensing of Environment (2016), 180

n analysis of daily Sea Surface Salinity (SSS) at 0.15 ° × 0.15° spatial resolution from the Soil Moisture and Ocean Salinity (SMOS) satellite mission using DINEOF (Data Interpolating Empirical Orthogonal ... [more ▼]

n analysis of daily Sea Surface Salinity (SSS) at 0.15 ° × 0.15° spatial resolution from the Soil Moisture and Ocean Salinity (SMOS) satellite mission using DINEOF (Data Interpolating Empirical Orthogonal Functions) is presented. DINEOF allows reconstructing missing data using a truncated EOF basis, while reducing the amount of noise and errors in geophysical datasets. This work represents a first application of DINEOF to SMOS SSS. Results show that a reduction of the error and the amount of noise is obtained in the DINEOF SSS data compared to the initial SMOS SSS data. Errors associated to the edge of the swath are detected in 2 EOFs and effectively removed from the final data, avoiding removing the data at the edges of the swath in the initial dataset. The final dataset presents a centered root mean square error of 0.2 in open waters when comparing with thermosalinograph data at their original spatial and temporal resolution. Constant biases present near land masses, large scale biases and latitudinal biases cannot be corrected with DINEOF because persistent signals are retained in high order EOFs, and therefore these need to be corrected separately. The signature of the Douro and Gironde rivers is detected in the DINEOF SSS. The minimum SSS observed in the Gironde plume corresponds to a flood event in June 2013, and the shape and size of the Douro river shows a good agreement with chlorophyll-a satellite data. These examples show the capacity of DINEOF to remove noise and provide a full SSS dataset at a high temporal and spatial resolution with reduced error, and the possibility to retrieve physical signals in zones with high initial errors. [less ▲]

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See detailLeveraging orientation knowledge to enhance human pose estimation methods
Azrour, Samir ULg; Pierard, Sébastien ULg; Van Droogenbroeck, Marc ULg

in Articulated Motion and Deformable Objects AMDO 2016 (2016, July)

Predicting accurately and in real-time 3D body joint positions from a depth image is the cornerstone for many safety, biomedical, and entertainment applications. Despite the high quality of the depth ... [more ▼]

Predicting accurately and in real-time 3D body joint positions from a depth image is the cornerstone for many safety, biomedical, and entertainment applications. Despite the high quality of the depth images, the accuracy of existing human pose estimation methods from single depth images remains insufficient for some applications. In order to enhance the accuracy, we suggest to leverage a rough orientation estimation to dynamically select a 3D joint position prediction model specialized for this orientation. This orientation estimation can be obtained in real-time either from the image itself, or from any other clue like tracking. We demonstrate the merits of this general principle on a pose estimation method similar to the one used with Kinect cameras. Our results show that the accuracy is improved by up to 45.1 %, with respect to a method using the same model for all orientations. [less ▲]

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See detailBioclimatism in Architecture : an evolutionary perspective from vernacular architecture to eco-adaptive architecture
Nguyen, Anh Tuan; Reiter, Sigrid ULg

Conference (2016, July)

The well-known Darwinian evolutionary theory (1859) introduced natural selection as the most important mechanism of evolutionary processes at every level from biological systems, including species ... [more ▼]

The well-known Darwinian evolutionary theory (1859) introduced natural selection as the most important mechanism of evolutionary processes at every level from biological systems, including species, individual organisms… to molecules such as DNA or proteins. In architecture we observe similar evolution processes which lead to the development of various architectural movements and concepts from common primitive living structures. The study points out that the development of bioclimatism in architecture has followed the pattern of a natural evolutionary process in which “natural selection” is likely motivated by several factors, including resources and environment problems, and driven by different mechanisms including novel building design concepts and methods, new standards and codes, discoveries in building science and construction costs. Finally, this study investigates new motivations in the era of climate change whose effects are expected to introduce more challenges as well as more trends towards a sustainable built environment through the new concept of Eco-adaptive architecture. [less ▲]

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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 detailOn Generalized Hölder-Zygmund Spaces
Kreit, Damien ULg

Doctoral thesis (2016)

To study the regularity of functions, many functional spaces have been introduced during the 20th century. Among them, let us mention the Hölder-Zygmund spaces \Lambda^{\alpha}(\R^{d}) and the Besov ... [more ▼]

To study the regularity of functions, many functional spaces have been introduced during the 20th century. Among them, let us mention the Hölder-Zygmund spaces \Lambda^{\alpha}(\R^{d}) and the Besov spaces B_{p,q}^{\alpha}(\R^{d}) where \alpha>0 somehow indicates the regularity of their elements (p,q\in ]0,+\infty]). The Hölder-Zygmund spaces are particular cases of Besov spaces in the sense that \Lambda^{\alpha}(\R^{d})=B_{\infty,\infty}^{\alpha}(\R^{d}). A generalization of Besov spaces has been introduced in the middle of the seventies and is still studied nowadays. This new type of space allows a deepest study of the regularity of functions. In this thesis, we start from this generalization in order to introduce a generalization of Hölder-Zygmund spaces. The first aim of this thesis is to show that most classical properties of Hölder-Zygmund spaces can be transposed to their generalized version. Among others, a complete characterization of these spaces in terms of wavelet coefficients is proved, which opens their use in the context of the signal analysis. The second aim of this thesis is to introduce a generalized version of the pointwise Hölder spaces similarly to their global version. We then show that most properties of the global spaces can be transposed to their generalized pointwise version. Finally, we study the regularity of some financial stochastic processes. [less ▲]

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See detailMonitoring partnership networks- A graph theory approach
Faraz, Alireza ULg; Treiblmaier, Horst; Gerschberger, Markus

Conference (2016, June 17)

Recently, companies are forming strong relationships with their strategic suppliers and customers in order to maximize their profit in the global market. Such a partnership or strategic alliance is based ... [more ▼]

Recently, companies are forming strong relationships with their strategic suppliers and customers in order to maximize their profit in the global market. Such a partnership or strategic alliance is based on the mutual needs of both parties. A partnership network is formed by different strategic firms (e.g., suppliers, manufacturers, distributors, retailers) who intend to establish strong relationships together but without losing their ownership, power and control on the firm. For example, if supplier X has a strong relationship with customer Y and Y has a strong relationship with supplier Z, then X, Y and Z can form a partnership network with three nodes (X, Y and Z) and two edges (X ->Y and Z->Y). In this paper, we develop a statistical methods to study the normal behaviour of partnership networks. We furthermore develop a methodology that will help diagnose the nature of identified unusual network behavior. [less ▲]

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See detail"Madame Bovary c'est moi"
Cormann, Grégory ULg

Conference (2016, June 16)

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See detailRhodococcus erythropolis T902.1 as a bioaugmentation starter: mechanisms, constrains and potentialities for the hydrocarbon degradation
Masy, Thibaut ULg

Doctoral thesis (2016)

Since the advent of the industrial revolution in the 19th century, anthropogenic activities and lack of environmental concern gave birth to numerous contaminated areas. Amongst released pollutants ... [more ▼]

Since the advent of the industrial revolution in the 19th century, anthropogenic activities and lack of environmental concern gave birth to numerous contaminated areas. Amongst released pollutants, hydrocarbons (HC) are the most widespread in the environment but they can also constitute a carbon source for numerous microorganisms. Therefore, bioremediation (i.e. the use of microorganisms to degrade pollutants) appears as an ecologically- and cost-effective technique compared to chemical or physical treatments. This biotreatment technology often relies either on stimulating indigenous microorganisms already present in soil (biostimulation) or on adding specific microbial degraders (bioaugmentation) to enhance the natural attenuation of contaminants. However, there is a need for improved understanding of the causes that can lead to its failure or its low efficiency, such as diverse environmental constraints or poor adaptation ability of laboratory-cultivated microorganisms. Amongst bacteria studied, Rhodococcus sp. has been previously described as a potential candidate for bioaugmentation due to its ability to degrade a broad range of organic pollutants, to produce biosurfactants, which improves pollutant bioavailability, and to rapidly adapt to many environmental stresses (e.g. desiccation, low temperature, high salinity). The main objective of this work is thus to assess the potentiality and limitations in the use of a specific strain, Rhodococcus erythropolis T902.1, to degrade HC (from simple n-alkanes to polyaromatic) in diverse field conditions. The factors limiting such a process have to be identified and, as much as possible, overcome. A first bioaugmentation experiment in microcosms aimed at identifying these constrains in carbon and clay-rich soils contaminated with heating oil. This treatment was successful in strongly polluted soil, since the addition of the strain T902.1 helped in redirecting the limited quantity of available oxygen towards a higher HC degradation and also correlated with a higher proportion of degrading genes in bioaugmented soils, compared to biostimulated and control ones. However, this effect decreased with time as T902.1 development was curtailed by competition and potentially predation from the endogenous flora. In addition, HC were heterogeneously distributed and this hampered the detection of a real degradation in lowest polluted soils. As a result, inoculation should be targeted to highly polluted areas (e.g. contaminant source zones), but it requires controlling soil heterogeneity.   We thus resorted to electrical resistivity tomography (ERT), to describe this heterogeneity and to monitor bacterial HC degradation activity. This geophysical tool could discriminate lithological heterogeneities that were artificially introduced in a 2 m³ pilot. Compared to a first insufficient biostimulation phase, the introduction of R. erythropolis T902.1 in this pilot led to a HC depletion of almost 80% (6900 to 1600 ppm) in 3 months in the injection zone, where pollutants were less bioavailable. Simultaneously, HC mineralization and biosurfactant production were deduced from the monitoring of ERT, biological and physicochemical parameters. In another study, R. erythropolis T902.1 could form stable biofilms on the materials constituting draining pavement structures, which allowed its long-term survival in a real parking lot and improved the decontamination of runoff water drained through this structure during pollution tests carried out at a pilot scale. This indicates that the strain could be widely used in other decontaminating systems and not only in soil. Furthermore, this biofilm formation could be triggered by an appropriate pre-adaptation of the cells before their injection in the polluted environment, to ensure a higher ecological robustness of the inoculum, compared to the one observed in the microcosm experiment. A third constrain is the poor or slow degrading activity toward some recalcitrant compounds, such as polyaromatic HC (PAH). Metallic nanoparticles synthesized by a sol-gel process were considered as potential catalysts for the improvement of degradation kinetics. Iron nanoparticles boosted the bacterial catalytic activity of the strain T902.1 in liquid cultures containing biphenyl as the sole carbon source. Following results suggested that the iron encapsulated in the porous silica matrix, was progressively attracted by siderophores (heterobactins) produced by the strain. However, this hypothesis has still to be confirmed by further analyses. From these experiments, R. erythropolis T902.1 globally proved to compete and improve degradation rates in highly polluted soils compared to biostimulation, even under low oxygen and nutrient contents. Notably, the production of trehalolipidic biosurfactants enhances HC bioavailability for their further uptake by the strain and surrounding microorganisms. Furthermore, this strain forms stable biofilms on several supports, which increases its lifespan and paves the way for many applications in bioremediation systems. Finally, it can also be used in synergy with sol-gel iron nanoparticles to treat recalcitrant compounds such as PAH and some chlorinated aromatics, but this combination needs to be further tested in more complex media, such as soil or waste water. [less ▲]

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See detailConversion of visual post fire measurements into fire severity with the aid of thermo-plastic analysis for retrofitting
Molkens, Tom; Gernay, Thomas ULg; Van Coile, Ruben

in Proceedings of the 9th International Conference on Structures in Fire (2016, June 09)

At Koksijde in Belgium a severe fire took place in an apartment building in 2015, resulting in the death of a young man and visible structural damage to four balconies. Following the fire, experts were ... [more ▼]

At Koksijde in Belgium a severe fire took place in an apartment building in 2015, resulting in the death of a young man and visible structural damage to four balconies. Following the fire, experts were mandated to assess the damage and the need for structural repair. They estimated that the balconies had to be refurbished but that there were no other structural elements affected, in particular the slab inside the apartment could be left in place with only a surface treatment and new plaster finishing. However, the floor slab in the apartment located above the fire apartment exhibited several visual indications that the fire could have had a structural impact, such as residual deformations and cracks in the tiles. This paper presents a methodology to infer the fire severity based on post-fire measurements and non-linear thermo-plastic numerical simulations. Finally, knowing the fire severity, its effect on the structure is evaluated and a reliability-based assessment is made of the residual load bearing capacity of the slab. [less ▲]

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See detailMallarmé : le retour des choses
Durand, Pascal ULg

Conference (2016, June 09)

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See detailCritical parameters in deriving fire fragility functions for steel gravity frames
Gernay, Thomas ULg; Elhami Khorasani, Negar; Garlock, Maria

in Proceedings of the 9th International Conference on Structures in Fire (2016, June 08)

Fire fragility functions can be used to characterize the probabilistic vulnerability of buildings to fire in the context of urban resilience assessment. A methodology has been proposed to develop such ... [more ▼]

Fire fragility functions can be used to characterize the probabilistic vulnerability of buildings to fire in the context of urban resilience assessment. A methodology has been proposed to develop such functions for multi-story steel buildings. However, a large number of parameters with uncertainties play a role in the process of constructing the fragility functions. The goal of this research is to identify the critical parameters that most affect the global fire safety by investigating the sensitivity of the fragility functions to different input parameters. Sensitivity in parameters affecting the fire model, the heat transfer process and the thermo-mechanical response is examined. The effects of different design assumptions at the system level are also studied. The presented approach is useful for selecting the prevailing parameters in a fire reliability analysis and it provides important information for modeling tools that can be used to evaluate resilience for fire scenarios. [less ▲]

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See detailFire Resistance of Reinforced Concrete Columns Subjected to Standard Fire – Comparison of an Advanced and a Simplified Method
Achenbach, Marcus; Gernay, Thomas ULg; Morgenthal, Guido

in Proceedings of the 9th International Conference on Structures in Fire (2016, June 08)

For designing concrete columns subjected to a standard fire exposure, the Eurocode permits the use of simplified or advanced calculation methods. For the designer, the question of the respective ... [more ▼]

For designing concrete columns subjected to a standard fire exposure, the Eurocode permits the use of simplified or advanced calculation methods. For the designer, the question of the respective advantages of these two types of methods arises. Which situations demand the use of an advanced method? When does a simple method provide sufficient accuracy? In this paper, laboratory tests are recalculated using Finite Element Modeling (FEM) as an advanced and Extended Zone Model (EZM) as a simple method in order to investigate these questions. The recalculations indicate that the simple EZM is of sufficient accuracy for symmetric heated columns without restraints. In contrast, the mechanical behavior of columns heated on three sides demands an advanced method such as FEM to be properly described. [less ▲]

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See detailTowards a standard measure of the ability of a structure to resist a natural fire
Gernay, Thomas ULg; Franssen, Jean-Marc ULg

in Proceedings of the 9th International Conference on Structures in Fire (2016, June 08)

Fire brigades face a major threat when intervening in a building in fire: the possibility of structural collapse during the cooling phase of the fire, or soon thereafter. In the current approaches to ... [more ▼]

Fire brigades face a major threat when intervening in a building in fire: the possibility of structural collapse during the cooling phase of the fire, or soon thereafter. In the current approaches to structural fire engineering, the fire resistance rating (R) is generally the only measure taken into consideration to characterize the fire performance of structural elements, although this measure does not reflect the response in real fire conditions. In this work, a standard measure is proposed to characterize the ability of structural members to resist a natural fire including the decay phases. This measure yields information about the potential occurrence of delayed failure as a function of the duration of the fire before it started to decrease, whether by self-extinction or due to the action of the fire fighters. The paper presents the method to derive this new standard measure as well as results for different typologies of structural elements. Finally, the interpretation and practical consequences are discussed, in particular regarding the safety of fire fighters during an intervention. [less ▲]

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See detailFire fragility functions for community resilience assessment
Elhami Khorasani, Negar; Gernay, Thomas ULg; Garlock, Maria

in Proceedings of the 9th International Conference on Structures in Fire (2016, June 08)

This work provides a framework to evaluate the response of buildings in a community to fire following earthquake. As part of the framework, the paper discusses two methodologies: (1) how to develop fire ... [more ▼]

This work provides a framework to evaluate the response of buildings in a community to fire following earthquake. As part of the framework, the paper discusses two methodologies: (1) how to develop fire fragility functions; (2) how the fire fragility functions can be used in conjunction with an original fire ignition model to estimate the potential losses in a community from fire following earthquake. The paper focuses in particular on the development of fire fragility functions for an entire building to measure the probability of reaching a damage state given a fire scenario. Next, the paper proposes an ignition model to evaluate the probability of fire ignition after an earthquake. The ignition model together with fragility functions measure the probability of damage from fire following earthquake given an earthquake scenario. [less ▲]

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See detailStability in Hybrid Fire Testing
Sauca, Ana ULg; Gernay, Thomas ULg; Robert, Fabienne et al

in Proceedings of the 9th International Conference on Structures in Fire (2016, June 08)

Hybrid testing is an appealing technique to observe the behavior of an element in an experimental test while taking into account the interaction with the rest of the structure which is modelled ... [more ▼]

Hybrid testing is an appealing technique to observe the behavior of an element in an experimental test while taking into account the interaction with the rest of the structure which is modelled numerically. Being widely used in the seismic field, this technique has been recently proposed in the fire field. The purpose of this paper is to demonstrate that the loading control process may be unstable during the hybrid testing when using the methodology applied in former tests presented in the literature. The stability in the latter method depends on the stiffness ratio between the two substructures. For the purpose of discussion, a one degree-of-freedom elastic system is studied. To overcome the stability issues, a new method is presented, independent on the stiffness ratio. Finally, the hybrid testing of a 2D beam being part of a moment resisting frame is analyzed in a virtual environment (both parts being modeled numerically) using the “first generation method” and the new proposed method. [less ▲]

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