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See detailTrajectory-Based Supplementary Damping Control for Power System Electromechanical Oscillations
Wang, Da ULg; Glavic, Mevludin ULg; Wehenkel, Louis ULg

in IEEE Transactions on Power Systems (2014), 29(6), 2835-2845

This paper considers a trajectory-based approach to determine control signals superimposed to those of existing controllers so as to enhance the damping of electromechanical oscillations. This approach is ... [more ▼]

This paper considers a trajectory-based approach to determine control signals superimposed to those of existing controllers so as to enhance the damping of electromechanical oscillations. This approach is framed as a discrete-time, multi-step optimization problem which can be solved by model-based and/or by learning-based methods. This paper proposes to apply a model-free tree-based batch mode Reinforcement Learning (RL) algorithm to perform such a supplementary damping control based only on information collected from observed trajectories of the power system. This RL-based supplementary damping control scheme is first implemented on a single generator and then several possibilities are investigated for extending it to multiple generators. Simulations are carried out on a 16-generators medium size power system model, where also possible benefits of combining this RL-based control with Model Predictive Control (MPC) are assessed. [less ▲]

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See detailWhy and how to repair concrete? Compatibility assessment
Courard, Luc ULg

Scientific conference (2014, October 27)

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See detailThe marauder's map or the use of non-intrusive range laser scanners in the context of smart rooms
Pierard, Sébastien ULg

Scientific conference (2014, October 24)

Dans cette présentation, je vais expliquer comment des capteurs laser peuvent être utilisés pour réaliser différentes fonctionnalités importantes pour les environnements intelligents. Je montrerai comment ... [more ▼]

Dans cette présentation, je vais expliquer comment des capteurs laser peuvent être utilisés pour réaliser différentes fonctionnalités importantes pour les environnements intelligents. Je montrerai comment créer une carte précise et y représenter le mouvement de toutes les personnes, en particulier les trajectoires de leurs pieds. Celles-ci peuvent servir à identifier la personne observée, car chacune a sa propre démarche. Ceci ouvre des voies dans les domaines de la domotique, des environnements intelligents et de la sécurité. Les trajectoires de pieds ont également de nombreuses applications dans le domaine médical, en particulier pour la gériatrie, la kinésithérapie et la neurologie, ce que je détaillerai. Je démontrerai également que cette technologie permet de détecter les situations de piggybacking et de tailgating. Tout ceci étant rendu possible par une chaîne de traitement de signal minutieusement étudiée et par des techniques d'apprentissage automatique. [less ▲]

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See detailModelling serial offenders’ spatial behaviours: new assumptions for geographic profiling
Trotta, Marie ULg

Doctoral thesis (2014)

The geographic profiling is amethodology of investigation which uses the crime sites of a criminal series in order to delineate prior areas for searching the offender. Its implementation is currently ... [more ▼]

The geographic profiling is amethodology of investigation which uses the crime sites of a criminal series in order to delineate prior areas for searching the offender. Its implementation is currently limited by too simplistic assumptions that are difficult to assess during an investigation or even not corroborated at an individual level of observation. This thesis studies the predictive capacities of geographic profiling in the context of Belgium, a dense country where the road network is not suitable for classical algorithmimplemented with Euclidean or Manhattan distances. More precisely, the thesis has for first objective to integrate space anisotropy with two improvements: (1) the integration of the road network in the journey-to-crime and (2) the integration of the structure of opportunities for series of sexual offences. Beyond this objective, the thesis questions a hypothesis underlying this type of research methodology: the kind of spatial relationship between the offender’s residence and the crime sites. An alternative to the distance decay effect is developed, minimising the variance in travelled distances between the offender anchor point and the initial contact sites of the offences (MOV hypothesis). The sensitivity of this methodology is measured and its effectiveness is compared to the one of the distance decay effect. A major result of the thesis is that the share of behaviours than can be modelled by this new hypothesis is similar to the one of the distance decay effect. However, a large number of series did not meet the required conditions to implement an efficientmethodology given the multiplicity of offender’s residences or the scarcity of sites composing the series; those applicability criteria are analysed in this work. Nevertheless, theMOV hypothesis is particularly valuable for long series of offences. Then, the thesis analyses the impact of the geometry of crime series locations on the effectiveness of the chosen spatial assumption (distance decay effect orMOV) with graph theory. It highlights the superiority of the MOV hypothesis for offenders travelling in some preferred direction. The analysis also shows that both hypotheses are not mutually exclusive but can be combined to build offender geographic profiles. Finally, this thesis focuses on the modelling of neutral areas in terms of criminal attractiveness on the Belgian territory. The work presents the originality of analysing data on a whole country, integrating both urban and non-urban areas. The objective of the modelling is the integration of the opportunity structure of sexual offences in the geographic profile and the estimation of the perturbing effect of a differentiated attractiveness. In order to assess this perturbation, we propose a two-steps process. Firstly, a regression model combining factors fromthe crime pattern and social disorganisation theories models the spatial distribution of crimes. The regression model identifies a centre-periphery relationship in the spatial distribution of crime locations. Still, the model underestimates the number of positive sectors, omitting some attractors. Then, the impact of attractive location (i.e. presenting the favourable factors for crime concentration)is evaluated for the series of sexual offences. In fine, the two spatial hypotheses do not seem affected by the attractors identified by the modelling except when the contact sites are clustered in attractive areas. In addition, the share of serial offenders committing their offences in the most attractive locations is smaller than that of single offenders. This observation strengthens the need for working on spatial distribution models instead of calibrated functions with solved cases. [less ▲]

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See detailDroit constitutionnel belge - Plan général du cours (année 2014-2015)
Behrendt, Christian ULg

Learning material (2014)

Le document constitue le Plan général de l'enseignement de Droit constitutionnel dispensé à l'Université de Liège en 2e année de bachelier en droit et en 2e année de bachelier en science politique.

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See detailDebatte über Kollaboration. Tristes Spektakel
Brüll, Christoph ULg

Article for general public (2014)

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See detailManaging understory light to maintain the coexistence of forest tree species with different shade tolerances
Ligot, Gauthier ULg

Doctoral thesis (2014)

Similar to the management of the other environmental resources, forest management has been questioned and more sustainable practices of forest management are being sought. New close-to-nature practices ... [more ▼]

Similar to the management of the other environmental resources, forest management has been questioned and more sustainable practices of forest management are being sought. New close-to-nature practices aim to favor natural processes over human interventions. Particularly, continuous-cover forestry has the goal of relying on natural regeneration, and maintaining irregular stand structure and tree species mixture. However, maintaining mixture of species with different shade tolerances appears arduous with such a silvicultural system. Successfully managing irregular and mixed forests, relying on natural processes, requires a strong knowledge of the ecology of natural regeneration. In particular, strong knowledge is required to predict the result of the interspecific competition in the understory depending upon light availability. The amount of radiation transmitted to the understory is indeed a critical factor determining regeneration dynamics. It determines, at least in part, regeneration composition because of interspecific differences of growth and survival under shade. Moreover, our quantitative understanding of understory light in uneven-aged and mixed stands remains incomplete. A better quantitative understanding of understory light is needed to provide quantitative guidelines for the management of understory light in uneven-aged and mixed stands and, hence, for the management of natural regeneration. The purpose of this thesis is to determine how close-to-nature forest management can maintain mixtures of species with contrasting shade tolerances. I consider ecological conditions with good water and nutrient supplies. In these conditions, partially closed canopy limits the amount of light that reaches the understory, and light is the major factor driving regeneration composition. Consequently, I study the dynamics of natural regeneration with regards to light availability as well as the interception of light by the canopy of heterogeneous stands. Studying the regeneration ecology of two species with contrasting shade tolerances (Fagus sylvatica L. and Quercus petraea (Matt.) Liebl.), I find that the shade-tolerant species outgrow the less shade-tolerant species in all light conditions. Even though the control of understory light with continuous-cover silviculture is required to sustain the growth of less shade-tolerant regenerations, it might not be sufficient to maintain the coexistence of species with contrasting shade tolerances. In order to examine the effects of canopy structure and composition on understory light availability, I use a model of light interception by heterogeneous canopies after synthesizing and discussing the approaches reported in the literature. The model predicts satisfactorily measures of transmitted light even though it is a relatively simple radiative transfer model. I next explore how various silvicultural treatments can be manipulated to provide favorable understory light conditions for natural regeneration. These silvicultural strategies correspond to selective thinnings of five different types, e.g., harvesting preferentially small trees, large trees, or trees of shade-tolerant species or creating circular gaps. The results underline that creating favorable understory light conditions for natural regeneration can be achieved with various regeneration treatments. However, the adequate reduction of stand density depends upon the chosen silvicultural strategies. In particular, creating gaps of about 500 m2 provides adequate light for small regeneration clumps. Harvesting preferentially small and trees of shade-tolerant species are also appropriate but required higher harvest intensity. Harvesting preferentially large trees slightly increases understory light and promotes more shade-tolerant species than less shade-tolerant species. In order to maintain the coexistence of species with contrasting shade tolerances, forest manager must control understory light and manually suppress the regeneration of the shade-tolerant species. The outcome of this study provides foresters with the necessary tools to evaluate how silvicultural treatments can be manipulated to create or maintain favorable light conditions for the regeneration of species of different shade tolerances. Guidelines are additionally proposed for forest managers wanting to maintain the coexistence of species with contrasting shade tolerances. [less ▲]

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See detailCombined holography and thermography in a single sensor through image-plane holography at thermal infrared wavelengths
Georges, Marc ULg; Vandenrijt, Jean-François ULg; Thizy, Cédric ULg et al

in Optics Express (2014), 22(21), 25517-25529

Holographic interferometry in the thermal wavelengths range, combining a CO2 laser and digital hologram recording with a microbolometer array based camera, allows simultaneously capturing temperature and ... [more ▼]

Holographic interferometry in the thermal wavelengths range, combining a CO2 laser and digital hologram recording with a microbolometer array based camera, allows simultaneously capturing temperature and surface shape information about objects. This is due to the fact that the holograms are affected by the thermal background emitted by objects at room temperature. We explain the setup and the processing of data which allows decoupling the two types of information. This natural data fusion can be advantageously used in a variety of nondestructive testing applications. [less ▲]

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See detailSensitivity of Greenland Ice Sheet surface mass balance to perturbations in sea surface temperature and sea ice cover: a study with the regional climate model MAR
Noel, Brice; Fettweis, Xavier ULg; van de Berg, W.J. et al

in Cryosphere (The) (2014), 8

During recent summers (2007–2012), several surface melt records were broken over the Greenland Ice Sheet (GrIS). The extreme summer melt resulted in part from a persistent negative phase of the North ... [more ▼]

During recent summers (2007–2012), several surface melt records were broken over the Greenland Ice Sheet (GrIS). The extreme summer melt resulted in part from a persistent negative phase of the North Atlantic Oscillation (NAO), favoring warmer atmospheric conditions than normal over the GrIS. Simultaneously, large anomalies in sea ice cover (SIC) and sea surface temperature (SST) were observed in the North Atlantic, suggesting a possible connection. To assess the direct impact of 2007–2012 SIC and SST anomalies on GrIS surface mass balance (SMB), a set of sensitivity experiments was carried out with the regional climate model MAR forced by ERA-Interim. These simulations suggest that perturbations in SST and SIC in the seas surrounding Greenland do not considerably impact GrIS SMB, as a result of the katabatic wind blocking effect. These offshore-directed winds prevent oceanic near-surface air, influenced by SIC and SST anomalies, from penetrating far inland. Therefore, the ice sheet SMB response is restricted to coastal regions, where katabatic winds cease. A topic for further investigation is how anomalies in SIC and SST might have indirectly affected the surface melt by changing the general circulation in the North Atlantic region, hence favoring more frequent warm air advection towards the GrIS. [less ▲]

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See detailA Riemannian approach to large-scale constrained least-squares with symmetries
Mishra, Bamdev ULg

Doctoral thesis (2014)

This thesis deals with least-squares optimization on a manifold of equivalence relations, e.g., in the presence of symmetries which arise frequently in many applications. While least-squares cost ... [more ▼]

This thesis deals with least-squares optimization on a manifold of equivalence relations, e.g., in the presence of symmetries which arise frequently in many applications. While least-squares cost functions remain a popular way to model large-scale problems, the additional symmetry constraint should be interpreted as a way to make the modeling robust. Two fundamental examples are the matrix completion problem, a least-squares problem with rank constraints and the generalized eigenvalue problem, a least-squares problem with orthogonality constraints. The possible large-scale nature of these problems demands to exploit the problem structure as much as possible in order to design numerically efficient algorithms. The constrained least-squares problems are tackled in the framework of Riemannian optimization that has gained much popularity in recent years because of the special nature of orthogonality and rank constraints that have particular symmetries. Previous work on Riemannian optimization has mostly focused on the search space, exploiting the differential geometry of the constraint but disregarding the role of the cost function. We, on the other hand, propose to take both cost and constraints into account to propose a tailored Riemannian geometry. This is achieved by proposing novel Riemannian metrics. To this end, we show a basic connection between sequential quadratic programming and Riemannian gradient optimization and address the general question of selecting a metric in Riemannian optimization. We revisit quadratic optimization problems with orthogonality and rank constraints by generalizing various existing methods, like power, inverse and Rayleigh quotient iterations, and proposing novel ones that empirically compete with state-of-the-art algorithms. Overall, this thesis deals with exploiting two fundamental structures, least-squares and symmetry, in nonlinear optimization. [less ▲]

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See detailThe Airline Container Loading Problem with Pickup and Delivery
Lurkin, Virginie ULg; Schyns, Michael ULg

Conference (2014, October 19)

The present paper looks into the problem of optimizing the loading of a set of containers and pallets into cargo aircraft serving multiple airports. Due to the pickup and delivery operations occurring at ... [more ▼]

The present paper looks into the problem of optimizing the loading of a set of containers and pallets into cargo aircraft serving multiple airports. Due to the pickup and delivery operations occurring at intermediate airports, this problem is simultaneously a weight and balance problem and a sequencing problem. Our objective is to minimize fuel and handling operations costs. This problem is shown to be NP-hard. We resort to a mixed integer linear program. On the basis of a professional partner's real-world data, TNT Airways, we perform numerical experiments using a standard B&C library. This approach yields better solutions than traditional manual planning, which results in substantial cost savings. [less ▲]

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See detailThe Effect of Urtica dioica Supplements on Egg Quality
Touazi, Leghel; Moula, Nassim ULg

Poster (2014, October 17)

Eggs are a rich source of lipids and proteins. Because of their low production cost, they represent a cheap source of animal proteins and lipids. recently, in Algeria, consumers’ interest are oriented of ... [more ▼]

Eggs are a rich source of lipids and proteins. Because of their low production cost, they represent a cheap source of animal proteins and lipids. recently, in Algeria, consumers’ interest are oriented of healthiness and dietetic values food. The purpose of this study was to investigate the effects a dietary supplement of Urtica dioica on laying hen's performance and egg quality. The study was conducted from may to june 2014 in the area of Chemini (Algeria). Sixty, 25-wk-old Lohmann Brown layers were randomly divided into 3 groups with 20 hens in each group. Group 1 was the control group fed a standard commercial diet based on corn and soybean, whereas the groups 2 and 3 were fed the control diet supplemented with 1% and 1.5% of nettle respectively. The hens were housed in cages in the same local and fed ad libitum. Fifty five eggs were sampled 4 times in each group from 25 to 27 weeks. A total of 220 eggs were examined. A series of measurements were carried out on each egg, namely egg weight, form index (egg shape), yolk to albumen ratio (Y:A), Yolk color, egg shell thickness, Haugh’s units. Egg weight, yolk color and Haugh Units (HU) were affected by age. Significant differences (P<0.05) were recorded between feeding type in total egg weight, yolk color and Haugh Units. The egg from group 2 proved to have a higher egg weight (57.67g; group 1: 55.41g; group 3: 56.70g; P<0.05), (33.4%), intermediate Yolk color (8.53; group 1: 9.03 ; group 3: 9.38; P<0.05) and HU (79.81; group 1: 80.85; group 3: 76.92). The results showed that the use of 1% and 1.5% of Urtica dioica, had positive effects on the color of yolk of laying hens. Using different levels of Urtica dioica could change the characteristics of egg and could meet the preferences of consumers for the intense color of the yolk. [less ▲]

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See detailL'evidence-based practice en psychologie et en logopédie
Durieux, Nancy ULg

Conference (2014, October 17)

L’evidence-based practice (EBP) est une approche qui recommande d’optimiser les soins de santé en intégrant les meilleures données actuelles issues de la recherche scientifique, l’expertise des cliniciens ... [more ▼]

L’evidence-based practice (EBP) est une approche qui recommande d’optimiser les soins de santé en intégrant les meilleures données actuelles issues de la recherche scientifique, l’expertise des cliniciens ainsi que la situation et les préférences de chaque patient (Sackett et al., 1996). L’EBP fait couler beaucoup d’encre en médecine, où elle prend sa source, mais également dans d’autres disciplines. Certains praticiens ne jurent que par elle, d’autres la décrient… Quoiqu’il en soit, le recours à l’EBP est de plus en plus encouragé en logopédie et en psychologie. Les principaux objectifs de cette conférence seront de définir l’EBP, d’en décrire les étapes et d’exposer les bénéfices et les obstacles à son application. Des perspectives d’avenir seront également discutées afin que l’EBP puisse intégrer le quotidien des logopèdes et des psychologues en Belgique. [less ▲]

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See detailDépression, niveau d'engagement dans des activités et processus psychologiques : Nouvel axe de lecture et nouveaux outils d'évaluation
Wagener, Aurélie ULg

Conference (2014, October 17)

Cet atelier aura pour objectif de présenter un modèle théorique, testé auprès de 500 personnes, des liens entre la dépression, le niveau d’engagement dans des activités et différentes familles de ... [more ▼]

Cet atelier aura pour objectif de présenter un modèle théorique, testé auprès de 500 personnes, des liens entre la dépression, le niveau d’engagement dans des activités et différentes familles de processus psychologiques (image de soi, pensées négatives répétitives, évitement expérientiel, satisfaction environnementale, régulation émotionnelle et tendance à l’approche). Plus précisément, nous menons actuellement une étude dont les résultats nous permettront d’identifier les processus psychologiques médiateurs de la relation entre la dépression et le niveau d’engagement dans des activités. Ces processus psychologiques médiateurs pourront donc devenir des cibles précises et identifiées du traitement psychothérapeutique. Pour mener à bien cette étude, nous avons réalisé une revue de la littérature des outils évaluant spécifiquement ces processus psychologiques. Certains questionnaires ont été traduits de l’Anglais au Français et sont en cours de validation. L’ensemble des échelles utilisées, leur utilité et leur cotation, seront présentées lors de l’atelier. Elles seront également mises à disposition des cliniciens intéressés. Une discussion concernant les patients avec lesquels les utiliser sera également proposée. [less ▲]

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See detailRéflexions sur les outils d'évaluation de la phonologie et de la morphosyntaxe dans le diagnostic de dysphasie
Devault, Cecilia; Labbé, Amandine; Leclercq, Anne-Lise ULg

Scientific conference (2014, October 17)

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See detailEBP en logopédie : Exemples de rééducations issues de la recherche et appliquées en clinique
Martinez Perez, Trecy ULg; Leclercq, Anne-Lise ULg

Scientific conference (2014, October 17)

L'Evidence-Based Practice (EBP) se définit comme l'utilisation consciencieuse et judicieuse des meilleures données (preuves) issues de la recherche clinique pour une prise en charge personnalisée de ... [more ▼]

L'Evidence-Based Practice (EBP) se définit comme l'utilisation consciencieuse et judicieuse des meilleures données (preuves) issues de la recherche clinique pour une prise en charge personnalisée de chaque patient (Sackett, 1996). Initié en médecine, l'EBP touche désormais d'autres pratiques cliniques telles que la logopédie. Lors de cet atelier, nous illustrerons comment transposer dans notre pratique clinique des rééducations qui ont montré leur efficacité via des recherches dans le domaine du langage oral et du bégaiement. [less ▲]

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See detailLocal goat in Kabylie (Chemini and Bouzeguene)
Moula, Nassim ULg; Michaux, Charles ULg; Philippe, François-Xavier ULg et al

Poster (2014, October 17)

The livestock sector plays a dynamic role in the economic development of rural areas in Algeria. Due to its adaptation to harsh environments, goat breeding is practiced in many areas of the country. To ... [more ▼]

The livestock sector plays a dynamic role in the economic development of rural areas in Algeria. Due to its adaptation to harsh environments, goat breeding is practiced in many areas of the country. To the north, it is confined to mountainous areas, but the bulk of the workforce is left in the steppe and semi-desert areas. The goat population in Algeria reached 3.8 million heads, ranking second after sheep. The present work contributes to a better characterisation of local goat in Kabylie for production and reproduction traits. The study was conducted in the regions of Chemini (Bejaia province) and Bouzeguene (Tizi-Ouzou province). A survey was conducted in 29 herds. The results revealed that the overall mean of goats per households was 6.69 ± 2.97. The purposes of keeping goat in Chemini and Bouzguene was private consumption of milk (82.76%) and meat (68.97%) as well as for commercial exchange (62.07%). The Kabyle goat is small (male: 62.23 cm and female: 58.41 cm) with long hair. Its ears are drooping, its convex profile has a slightly pronounced nasal split and its coat colour ranges from dark brown to black. However, the crossbreeding with exotic breeds (mainly with Saanen goat), controlled or uncontrolled, increased the frequency of white coat. The average age at puberty in males was 6.93 ± 1.04 and 7.38 ± 0.94 months in females. The reported age at first kidding and kidding interval were 13.03 ± 0.87 months and 7.83 ± 1.29 months, respectively. [less ▲]

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See detailThe effect of the inclusion of Urtica dioica leaves meal in diets on growth performances and carcass characteristics of broiler
Moula, Nassim ULg; Philippe, François-Xavier ULg; Michaux, Charles ULg et al

Poster (2014, October 17)

The objective of this study was to evaluate the effects of the inclusion of Urtica dioica leaves meal in diets on growth performances and carcass characteristics of broiler chicken. The study was ... [more ▼]

The objective of this study was to evaluate the effects of the inclusion of Urtica dioica leaves meal in diets on growth performances and carcass characteristics of broiler chicken. The study was conducted from May to June 2014 in the area of Chemini (Algeria). In a completely randomized design, a total of 100 one-day-old broilers (industrial strain) were divided into 2 groups and 2 repetitions with 25 chickens each. Group 1 was the control group fed a standard commercial diet based on corn and soybean purchased on the local market, whereas the birds in group 2 were fed the nettle diet (control diet with addition of 2% of nettle). The animals were housed inside in experimental pens and fed ad libitum. The results showed that nettle inclusion significantly promotes growth performance of broilers at 42 days of age (1644.8 ± 45.5 vs. 1565.1 ± 45.5g; P<0.05). The broilers fed the nettle diet had higher thigh yield (26.0 ± 0.3 vs. 25.2 ± 0.3%; P<0.05) but lower abdominal fat yield (4.39 ± 0.16 vs. 3.90 ± 0.16%; P<0.05). No significant effect of the diet was observed for carcass yield (around 71.1%) and breast percentage (around 32.40%). The overall mortality was not significantly different (P>0.05) for any of the dietary regimens (around 20%). Feed conversion ratio of the two groups were very close (around 2.17). This experiment showed that dietary inclusion of Urtica dioica has positive effects on growth performance and carcass quality of broilers. [less ▲]

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