Last 7 days
Bookmark and Share    
Full Text
Peer Reviewed
See detailThe strength of multi-row models
Louveaux, Quentin ULg; Poirrier, Laurent; Salvagnin, Domenico

in Mathematical Programming Computation (in press)

We develop a method for computing facet-defining valid inequalities for any mixed-integer set PJ. Our practical implementation does not return only facet- defining inequalities, but it is able to find a ... [more ▼]

We develop a method for computing facet-defining valid inequalities for any mixed-integer set PJ. Our practical implementation does not return only facet- defining inequalities, but it is able to find a separating cut whenever one exists. The separator is not comparable in speed with the specific cutting-plane generators used in branch-and-cut solvers, but it is general-purpose. We can thus use it to compute cuts derived from any reasonably small relaxation PJ of a general mixed- integer problem, even when there exists no specific implementation for computing cuts with PJ. Exploiting this, we evaluate, from a computational perspective, the usefulness of cuts derived from several types of multi-row relaxations. In particular, we present results with four different strengthenings of the two-row intersection cut model, and multi-row models with up to fifteen rows. We conclude that only fully-strengthened two-row cuts seem to offer a significant advantage over two-row intersection cuts. Our results also indicate that the improvement obtained by going from models with very few rows to models with up to fifteen rows may not be worth the increased computing cost. [less ▲]

Detailed reference viewed: 28 (3 ULg)
See detailMollino, Carlo
Prina, Daniela ULg

in Atkinson, Harriet; Kettley, Sarah; Edwards, Clive (Eds.) et al Encyclopedia of Design (in press)

Detailed reference viewed: 7 (4 ULg)
Full Text
Peer Reviewed
See detailIdentifying Semitic loanwords in Late Egyptian
Winand, Jean ULg

in Dils, Peter; Grossman, Eitan; Richter, Sebastian (Eds.) et al Language Contact and Bilingualism in antiquity: What Linguistic Borrowing into Coptic can tell us about it (in press)

Detailed reference viewed: 20 (2 ULg)
See detailSapper, Richard
Prina, Daniela ULg

in Atkinson, Harriet; Kettley, Sarah; Edwards, Clive (Eds.) et al Encyclopedia of Design (in press)

Detailed reference viewed: 9 (0 ULg)
Full Text
Peer Reviewed
See detailThe impact of transport policies on railroad intermodal freight competitiveness – The case of Belgium
Santos, Bruno F.; Limbourg, Sabine ULg; Carreira, Joana Silva

in Transportation Research. Part D : Transport and Environment (in press)

This paper discusses the impact of three freight transport policies aiming to promote railroad intermodal transport in Europe, and examines the case of Belgium as a testing ground. These policies consist ... [more ▼]

This paper discusses the impact of three freight transport policies aiming to promote railroad intermodal transport in Europe, and examines the case of Belgium as a testing ground. These policies consist in subsidizing intermodal transport operations (such as in Belgium, to stimulate rail transport), internalizing external costs (as recommended by the European Union in order to foster cleaner modes), and adopting a system perspective when optimizing the location of inland intermodal terminals. The study proposes an innovative mixed integer intermodal freight location-allocation model based on hub-location theory and deals with non-linear transport costs in order to replicate economies of distance. Our analysis suggests that subsidizing has a significant impact on the volumes transported by intermodal transport, and, to a lesser extent, that optimizing terminal location increases the competitiveness of intermodal transport. On the other hand, according to our assumptions, internalizing external costs can negatively impact the promotion of intermodality. This finding indicates that innovative last-mile transports are needed in order to reduce the external impacts of drayage operations. [less ▲]

Detailed reference viewed: 11 (3 ULg)
Full Text
Peer Reviewed
See detailEnjeux de la vannerie dans 1 les aires protégées de Madagascar
Guillaud, Sylvie; Vermeulen, Cédric ULg

in Bois et Forêts des Tropiques (in press)

Detailed reference viewed: 33 (14 ULg)
Full Text
Peer Reviewed
See detailDevelopment by the sol–gel process of highly dispersed Ni–Cu/SiO2 xerogel catalysts for selective 1,2-dichloroethane hydrodechlorination into ethylene
Pirard, Sophie ULg; Mahy, Julien ULg; Pirard, Jean-Paul ULg et al

in Microporous and Mesoporous Materials (in press)

Ni–Cu/SiO2 xerogel catalysts have been synthesized by cogelation of industrial tetraethoxysilane (Dynasil) and chelates of Ni and Cu with industrial 3-(2-aminoethylamino)propyltrimethoxysilane (Dynasylan ... [more ▼]

Ni–Cu/SiO2 xerogel catalysts have been synthesized by cogelation of industrial tetraethoxysilane (Dynasil) and chelates of Ni and Cu with industrial 3-(2-aminoethylamino)propyltrimethoxysilane (Dynasylan DAMO) in industrial ethanol denatured with diethyl phthalate. Despite the use of industrial grade reagents, highly dispersed bimetallic Ni–Cu/SiO2 xerogel catalysts were obtained. These samples are composed of completely accessible Ni–Cu alloy crystallites with sizes of 1.6–3.4 nm located inside silica particles exhibiting a monodisperse microporous distribution. It appears that the bimetallic complex acts as a nucleation agent in the formation of silica particles. The combination of results obtained from the calculation of the metal ratio in catalysts, H2 chemisorption and transmission electron microscopy allowed calculating the surface composition of the nickel–copper particles in Ni–Cu/SiO2 cogelled xerogel catalysts. Values obtained indicate a very pronounced surface enrichment with copper. While 1,2-dichloroethane hydrodechlorination over pure nickel mainly produces ethane, increasing copper content in bimetallic catalysts results in an increase in ethylene selectivity. The specific consumption rate of 1,2-dichloroethane decreases when copper loading increases. The turnover frequency, that is, the number of catalytic cycle per active site (nickel atom and its surrounding copper atoms) and per second, seems to be independent of surface composition of alloy particles. [less ▲]

Detailed reference viewed: 65 (8 ULg)
See detailDes ethnonymes aux glottonymes : enjeux de la nomination des pratiques linguistiques en Louisiane francophone
Urbain, Emilie ULg

in Jean-Michel Eloy (Ed.) Nommer des langues romanes (in press)

Detailed reference viewed: 10 (4 ULg)
Peer Reviewed
See detailLe rôle du Clergé dans la construction d’un discours « d’autorité » sur la langue en milieu francophone minoritaire : l’exemple de l’Acadie du Nouveau-Brunswick à la fin du 19e siècle
Ali-Khodja, Mourad; Urbain, Emilie ULg

in Remysen, Wim (Ed.) Les français d’ici : du discours d’autorité à la description des normes et des usages (in press)

Detailed reference viewed: 10 (0 ULg)
Peer Reviewed
See detailIntroduction
de Haro Sanchez, Magali ULg; Tissi, Lucia Maddalena

in de Haro Sanchez, Magali (Ed.) "Écrire la magie dans l'Antiquité - Scrivere la magia nell'Antichità". Actes du colloque international (Liège, 13-15 octobre 2011) (in press)

Detailed reference viewed: 21 (1 ULg)
Full Text
Peer Reviewed
See detailSimultaneous enforcement of constraints at position and velocity levels in the nonsmooth generalized-alpha scheme
Bruls, Olivier ULg; Acary, Vincent; Cardona, Alberto

in Computer Methods in Applied Mechanics & Engineering (in press)

This paper presents a formalism for the transient simulation of nonsmooth dynamic mechanical systems composed of rigid and flexible bodies, kinematic joints and frictionless contact conditions. The ... [more ▼]

This paper presents a formalism for the transient simulation of nonsmooth dynamic mechanical systems composed of rigid and flexible bodies, kinematic joints and frictionless contact conditions. The proposed algorithm guarantees the exact satisfaction of the bilateral and unilateral constraints both at position and velocity levels. Thus, it significantly differs from penalty techniques since no penetration is allowed. The numerical scheme is obtained in two main steps. Firstly, a splitting method is used to isolate the contributions of impacts, which shall be integrated with only first-order accuracy, from smooth contributions which can be integrated using a higher order scheme. Secondly, following the idea of Gear, Gupta and Leimkuhler, the equations of motion are reformulated so that the bilateral and unilateral constraints appear both at position and velocity levels. After time discretization, the equations of motion involve two complementarity conditions and it can be solved at each time step using a monolithic semi-smooth Newton method. The numerical behaviour of the proposed method is studied and compared to other approaches for a number of numerical examples. It is shown that the formulation offers a unified and valid approach for the description of contact conditions between rigid bodies as well as between flexible bodies. [less ▲]

Detailed reference viewed: 40 (3 ULg)
Full Text
Peer Reviewed
See detailInteraction between dietary protein content and the source of carbohydrates along the gastrointestinal tract of weaned piglets.
Pieper, Robert; Boudry, Christelle ULg; Bindelle, Jérôme ULg et al

in Archives of Animal Nutrition (in press)

Although fermentable carbohydrates (CHO) can reduce metabolites derived from dietary protein fermentation in the intestine of pigs, the interaction between site of fermentation and substrate availability ... [more ▼]

Although fermentable carbohydrates (CHO) can reduce metabolites derived from dietary protein fermentation in the intestine of pigs, the interaction between site of fermentation and substrate availability along the gut is still unclear. The current study aimed at determining the impact of two different sources of carbohydrates in diets with low or very high protein content on microbial metabolite profiles along the gastrointestinal tract of piglets. Thirty-six piglets (n = 6 per group) were fed diets high (26%, HP) or low (18%, LP) in dietary protein and with or without two different sources of carbohydrates (12% sugar beet pulp, SBP, or 8% lignocellulose, LNC) in a 2 × 3 factorial design. After 3 weeks, contents from stomach, jejunum, ileum, caecum, proximal and distal colon were taken and analysed for major bacterial metabolites (D-lactate, L-lactate, short chain fatty acids, ammonia, amines, phenols and indols). Results indicate considerable fermentation of CHO and protein already in the stomach. HP diets increased the formation of ammonia, amines, phenolic and indolic compounds throughout the different parts of the intestine with most pronounced effects in the distal colon. Dietary SBP inclusion in LP diets favoured the formation of cadaverine in the proximal parts of the intestine. SBP mainly increased CHO-derived metabolites such as SCFA and lactate and decreased protein-derived metabolites in the large intestine. Based on metabolite profiles, LNC was partly fermented in the distal large intestine and reduced mainly phenols, indols and cadaverine, but not ammonia. Multivariate analysis confirmed more diet-specific metabolite patterns in the stomach, whereas the CHO addition was the main determinant in the caecum and proximal colon. The protein level mainly influenced the metabolite patterns in the distal colon. The results confirm the importance of CHO source to influence the formation of metabolites derived from protein fermentation along the intestinal tract of the pig. [less ▲]

Detailed reference viewed: 6 (4 ULg)
Full Text
Peer Reviewed
See detail“How are you Vulnerable?”: Using Participation for Vulnerability Analysis in Emergency Planning
Rossignol, Nicolas ULg; Turcanu, Catrinel; Fallon, Catherine ULg et al

in Journal of Risk Research (in press)

Scientists in many fields of research have developed models, theories and concepts attempting to grasp and manage dangers that are often difficult to imagine. Among the different perspectives, the Science ... [more ▼]

Scientists in many fields of research have developed models, theories and concepts attempting to grasp and manage dangers that are often difficult to imagine. Among the different perspectives, the Science and Technology Studies (STS) Vulnerability Approach seems very promising. Relying on a constructivist paradigm, it is based on an inductive collection and analysis of a wide range of factors, with a particular focus on cultural factors and actual day-to-day practices. In this paper, we present the roots of this approach and we display findings based on three case studies exploring emergency planning in three different contexts (a city near a SEVESO plant, a school near a nuclear plant, and a city confronted to multiple catastrophic scenarios). The cases studies were realized by conducting three Focus Groups with different types of stakeholders (citizens, teachers, firemen, decision makers, etc.). After presenting the results of the case studies, we discuss how stakeholders’ participation can inform such type of vulnerability analysis in the context of emergency planning. We argue that participation fosters a deep understanding of actual safety governance practices which allows innovative results to emerge as well as it initiates a learning process among the participants. It contributes to questioning the relations between decision-makers, experts and citizens. It has the potential of bypassing the positivist and quantitative rationale of safety, and thus, of redefining the vulnerability governance. As a conclusion, we question the role of such STS vulnerability approach within the actual vulnerability governance. [less ▲]

Detailed reference viewed: 28 (10 ULg)