• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 77
  • 50
  • 10
  • 8
  • 6
  • 5
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 177
  • 54
  • 29
  • 26
  • 25
  • 21
  • 19
  • 19
  • 17
  • 17
  • 16
  • 15
  • 14
  • 14
  • 13
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
161

Tax Avoidance, Aggressive Tax Planning, and the United States’ Tax Cuts and Jobs Act of 2017 : An Investigation into Anti-Base Erosion and Anti-Profit Shifting Strategies

Rosato, Andrea January 2022 (has links)
No description available.
162

Donors’ priorities when reducing HMA allocation : Are the needs of people the criteria of decision-making when it comes to budget cuts in Humanitarian Mine Action?

Frei, Michael January 2023 (has links)
There is always competition between regions when it comes to their needs after facing a conflict, disaster, or long-term crisis. Donors allocating ODA or Humanitarian Assistance must decide to whom they want to allocate their support. While the literature broadly identifies the motivation for sending allocation to specific recipients and not to others, it has not yet researched the processes of the opposite, the reduction or break-off of aid allocation. This thesis researches the topic at the level of Humanitarian Mine Action (HMA). The question focuses on donors of bilateral HMA allocation and their motives of decision-making, when under financial pressure and forced to shorten their overall HMA budget. Using a most-different in-depth case study based on two steps on the cases of Australia and Germany, the question is researched, if the donors base their decisions and priorities on the needs of people when they have to reduce HMA budgets. The findings show that HMA rarely is documented separately and mostly connected either with ODA or Humanitarian Assistance. To get clear answers about the thoughts and motivations of decision-makers when it comes to the reduction or cut of HMA allocation, deeper research including interviews is needed.
163

L’investissement en santé publique dans les provinces canadiennes de 1975 à 2018 : un désengagement à géométrie variable?

Ben Jelili, Emna 08 1900 (has links)
Au-delà de la capacité des systèmes à faire face aux crises sanitaires, investir en prévention devrait se lire « investir pour la santé » dans la perspective plus large d’une amélioration du bien-être des populations. Plusieurs études démontrent que les programmes de santé publique contribuent à prévenir la mortalité, améliorent la qualité de vie et réduisent les coûts des soins de santé sur le court et long terme (Dyakova et al. 2017 ; Masters et al. 2017). Pourtant, le portrait des dépenses de santé dans la plupart des pays suggère un sous-financement inquiétant des dépenses préventives en santé. Ce mémoire propose un cadre formel pour démystifier les dynamiques politiques et financières sous-jacentes à la prise de décision des gouvernements en place en matière d’investissement en santé préventive. Plus précisément, il est question d’analyser les variations des dépenses en santé publique dans les provinces canadiennes de 1975 à 2018. En s’intéressant à l’organisation du système de santé dans son ensemble et au gré des réformes politiques et structurelles des provinces, les résultats de l’analyse qualitative montrent que l’émergence du nouveau management public (NMP) dans les années 1990 a globalement contribué à la diminution accordée à la prévention. L’analyse quantitative quant à elle, énonce les éléments conjoncturels et structurels financiers qui participent à la variation des dépenses en santé publique. En considérant le financement en santé publique comme un investissement à long terme, il a été démontré que les dépenses préventives ne sont pas aussi largement soutenues et constituent des investissements à long terme discrets avec peu d’appuis dans la société. Cela implique, du point de vue financier, que ce type de dépenses est plus propice aux coupures budgétaires, surtout en période de récession et de crise économique. / Beyond the capacity of systems to deal with health crises, investing in prevention should read “investing for health” in the broader perspective of improving the well-being of populations. Several studies demonstrate that public health programs help prevent mortality, improve quality of life and reduce health care costs in the short and long term (Dyakova et al. 2017; Masters et al. 2017). However, the portrait of health expenditure in most countries suggests a worrying underfunding of preventive health expenditure. This thesis proposes a formal framework to demystify the political and financial dynamics underlying the decision-making of governments in place in terms of investment in public health. More specifically, we analyze the variations in public health expenditure in the Canadian provinces from 1975 to 2018. By focusing on the organization of the health system as a whole, according to political and structural reforms over time, the results of the qualitative analysis show that the emergence of new public management (NPM) in the early 1990 contributed overall to the reduction granted to prevention. The quantitative analysis, for its part, sets out the economic and structural financial elements that contribute to the variation in public health expenditure. Viewing public health funding as a long-term investment, it has been shown that preventive spending is not as widely supported and is a discrete long-term investment with little support in society. This implies, from a financial point of view, that this type of spending is more prone to budget cuts, especially in times of recession and economic crisis.
164

Ekonomistyrning i PostNord AB Region Växjö : Budget i kombination med prestationsmätning och dess styreffekter i organisationen

Mattelin, Martin, Andersson, Emelie January 2014 (has links)
Bakgrund: I en konkurrenskraftig miljö med föränderliga villkor krävs en tillämpning av sofistikerade styrverktyg inom ett företags ekonomistyrsystem. Verksamheten PostNord AB har i och med en bolagisering och avreglering genomgått en strukturomvandling men har fortfarande ett statligt uppdrag samtidigt som de konkurrerar med helt kommersiella företag. Problemdiskussion: PostNord AB får i dagsläget inte önskad effekt på styrning i verksamheten då det brister i förhållning till budgeten. Detta har utmynnat i en diskussion kring relationen mellan budget och prestationsmätning och dess styreffekter i organisationen. Syfte: Studiens syfte är att kartlägga PostNord ABs ekonomistyrsystem med särskilt fokus på budget och prestationsmätningar och dess styreffekter i organisationen. Vidare är syftet att ge rekommendationer på förändringar av dagens styrsystem, vilka kan ge en förbättrad styreffekt inom PostNord AB - Region Växjö. Metod: Studien innefattar en fallstudie som forskningsdesign. Insamlingen av empiriskt material har skett genom intervjuer, dokument och observationer. Intervjuerna har utförts semi-strukturerat och respondenturvalet har skett utifrån ett kedje- samt lämplighetsurval. Resultat: Problemområden beträffande ekonomistyrsystemets styreffekter har identifierats där förbättringsförslag rörarande företagets mest kritiska områden har rekommenderats. Dessa innefattar en nedtoning av budgeten till förmån för prestationsmätningar, mål kopplade till mått, ökad kommunikation mellan nivåerna samt förhöjd motivation genom ökat deltagande. Slutsats: Marknaden som PostNord AB verkar på kännetecknas av tämligen fasta spelregler med en likartad infrastruktur för distribution. Avgörandet för företagets framgång beror på hur det på mest fördelaktiga sätt kan anpassa och maximera sin verksamhet efter rådande villkor. Detta talar för en ökad användning av processinriktade prestationsmätningar. / Background: In a competitive environment with changing conditions the use of sophisticated management tool are required within a company’s management control system. The company Post Nord AB has, with corporatisation and deregulation undergone a structural change, but still has a state-mandated while competing with fully commercial enterprises. Problems Discussion: Post Nord AB is in the current situation not receiving the desired effect on the control of the business when because of imperfections in the attitude to the budget. This has led to a discussion on the relationship between budget and performance measurement and its control effects in the organization. Purpose: The aim of the study is to map Post Nord AB’s management control system with particular focus on the budget and performance measurements and its control effects in the organization. A further purpose is to provide recommendations on changes to the current control system, which can enhance the control effect in Post Nord AB - Region Växjö. Method: The study includes a case study research design. The collection of empirical data were collected through interviews, documents and observations. The interviews were conducted semi- structured and the selection were based on a chain and suitability selection. Results: Issues concerning control effects of the management control system have been identified and improvement proposals have been recommended. These include a dimming of the budget in favor of performance measurements, goals related to measurement, increased communication between levels and enhanced motivation through increased participation. Conclusion: PostNord AB acts on a market characterized by fairly fixed rules with a similar distribution infrastructure. The essential for the company’s success depends on how it in most beneficial ways can customize and maximize their business to the prevailing conditions. This suggests an increased use of process-oriented performance measurements.
165

Impact des coupes partielles sur l’activité de coléoptères phloeophages et xylophages en forêt boréale

Bélanger Morin, Mathieu 12 1900 (has links)
Ce projet de recherche évalue la réponse à court terme de coléoptères phloeophages et xylophages (Cerambycidae et Scolytinae) à différentes intensités de coupes partielles (0, 25 et 40% de la surface terrière prélevée) afin de déterminer la viabilité de cette méthode sylvicole en forêt boréale. Disposant de 12 parcelles expérimentales (4 répétitions pour chaque intensité de coupe) dans une sapinière à bouleau blanc située au sud de la forêt boréale (Québec, Canada), nous avons évalué l’abondance, la diversité ainsi que l’établissement (taux d’attaque) de ces deux groupes d’insectes, et ce dès la première année suivant la coupe. L’échantillonnage a été réalisé à l’aide de pièges à interception multidirectionnelle et de l’écorçage de sections de 3 espèces d’arbres exposées dans l’ensemble des parcelles. Nos résultats montrent une plus grande activité/abondance des deux taxons (abondance 5 à 6 fois plus élevée) ainsi qu’une composition en espèces différente et plus diversifiée dans les peuplements partiellement coupés (25 et 40%). De plus, la présence et la distribution d’espèces colonisant habituellement des hôtes affaiblis (e.g., Trypodendron lineatum, Rhagium inquisitor) – et pouvant donc réduire la valeur économique d’arbres résiduels – a été recensée et semble être favorisée entres autres par l’ouverture de la canopée et des blessures physiques faites aux arbres pendant les opérations sylvicoles. Par ailleurs, l’approche combinant différentes techniques d’échantillonnage a permis une meilleure compréhension des mécanismes de localisation/sélection d’hôte (variant en fonction de l’espèce), un aspect important de la dynamique des insectes pour l’évaluation des risques suite aux coupes forestières. Sur la base de cette étude à court terme, il ne semblerait pas y avoir de différence significative sur les risques pour le milieu quant à l’augmentation d’activité des Cerambycidae et Scolytinae entre les deux traitements de coupe appliqués. Il reste cependant indispensable de vérifier la validité de ces résultats sur une plus longue période afin d’établir des plans d’aménagement forestier durables pour la forêt boréale. / To evaluate the viability of partial cuts, short-term responses of phloeophagous and xylophagous beetles (Cerambycidae and Scolytinae) following different partial cut treatments (0, 25 and 40% of basal area cut) were determined in a balsam fir–white birch boreal forest in Quebec, Canada. Each treatment was replicated 4 times totaling 12 experimental stands. The summer following treatments, abundance and diversity of targeted beetle groups along with their establishment (attack rates) in partially cut stands were assessed with passive flight- interception traps and bark dissection of exposed, freshly cut boles from three tree species. Greater activity/abundance from both taxa were detected (abundance 5 to 6 times larger) along with a different and more diversified species composition in partially cut stands (25 and 40%). The presence and distribution of species that usually colonize weakened host trees (e.g., Trypodendron lineatum, Rhagium inquisitor) – and can thus reduce stands economic value for future harvest operations – were influenced by canopy openness and injuries on residual trees made during silvicultural operations. Furthermore, combining diverse sampling techniques allowed us to observe different host-selection patterns (random landing vs. primary attraction) given our multi-scale experimental approach, which we found to vary between insect species. Understanding these mechanisms for such beetle groups are important to evaluate stand vulnerability following partial cuts and predict impacts and risks in a given environment. While the 40% partial cuts remove additional wood volume, we found no significant increase in beetle activity between the 25 and 40% treatment. Though partial cuts render treated stands more vulnerable to greater Cerambycidae and Scolytinae attacks, further studies must be done to confirm this trend in longer term if proper boreal forest management plans are to be drawn.
166

Développement de modèles graphiques probabilistes pour analyser et remailler les maillages triangulaires 2-variétés / Development of probabilistic graphical models to analyze and remesh 2-manifold triangular meshes

Vidal, Vincent 09 December 2011 (has links)
Ce travail de thèse concerne l'analyse structurelle des maillages triangulaires surfaciques, ainsi que leur traitement en vue de l'amélioration de leur qualité (remaillage) ou de leur simplification. Dans la littérature, le repositionnement des sommets d'un maillage est soit traité de manière locale, soit de manière globale mais sans un contrôle local de l'erreur géométrique introduite, i.e. les solutions actuelles ne sont pas globales ou introduisent de l'erreur géométrique non-contrôlée. Les techniques d'approximation de maillage les plus prometteuses se basent sur une décomposition en primitives géométriques simples (plans, cylindres, sphères etc.), mais elles n'arrivent généralement pas à trouver la décomposition optimale, celle qui optimise à la fois l'erreur géométrique de l'approximation par les primitives choisies, et le nombre et le type de ces primitives simples. Pour traiter les défauts des approches de remaillage existantes, nous proposons une méthode basée sur un modèle global, à savoir une modélisation graphique probabiliste, intégrant des contraintes souples basées sur la géométrie (l'erreur de l'approximation), la qualité du maillage et le nombre de sommets du maillage. De même, pour améliorer la décomposition en primitives simples, une modélisation graphique probabiliste a été choisie. Les modèles graphiques de cette thèse sont des champs aléatoires de Markov, ces derniers permettant de trouver une configuration optimale à l'aide de la minimisation globale d'une fonction objectif. Nous avons proposé trois contributions dans cette thèse autour des maillages triangulaires 2-variétés : (i) une méthode d'extraction statistiquement robuste des arêtes caractéristiques applicable aux objets mécaniques, (ii) un algorithme de segmentation en régions approximables par des primitives géométriques simples qui est robuste à la présence de données aberrantes et au bruit dans la position des sommets, (iii) et finalement un algorithme d'optimisation de maillages qui cherche le meilleur compromis entre l'amélioration de la qualité des triangles, la qualité de la valence des sommets, le nombre de sommets et la fidélité géométrique à la surface initiale. / The work in this thesis concerns structural analysis of 2-manifold triangular meshes, and their processing towards quality enhancement (remeshing) or simplification. In existing work, the repositioning of mesh vertices necessary for remeshing is either done locally or globally, but in the latter case without local control on the introduced geometrical error. Therefore, current results are either not globally optimal or introduce unwanted geometrical error. Other promising remeshing and approximation techniques are based on a decomposition into simple geometrical primitives (planes, cylinders, spheres etc.), but they generally fail to find the best decomposition, i.e. the one which jointly optimizes the residual geometrical error as well as the number and type of selected simple primitives. To tackle the weaknesses of existing remeshing approaches, we propose a method based on a global model, namely a probabilistic graphical model integrating soft constraints based on geometry (approximation error), mesh quality and the number of mesh vertices. In the same manner, for segmentation purposes and in order to improve algorithms delivering decompositions into simple primitives, a probabilistic graphical modeling has been chosen. The graphical models used in this work are Markov Random Fields, which allow to find an optimal configuration by a global minimization of an objective function. We have proposed three contributions in this thesis about 2-manifold triangular meshes : (i) a statistically robust method for feature edge extraction for mechanical objects, (ii) an algorithm for the segmentation into regions which are approximated by simple primitives, which is robust to outliers and to the presence of noise in the vertex positions, (iii) and lastly an algorithm for mesh optimization which jointly optimizes triangle quality, the quality of vertex valences, the number of vertices, as well as the geometrical fidelity to the initial surface.
167

Study of analytical methods for electron track detection from heavy quark decays generated by sqrt(s)=8TeV pp collisions at ALICE / Estudo de métodos analíticos para detecção de traços de elétrons oriundos do decaimento de quarks pesados por colisões pp a raiz(s)=8TeV no ALICE

Luzio, Marco Aurelio 03 May 2017 (has links)
A study of the usage of ALICEs time of flight (TOF), time projection chamber (TPC), and electromagnetic calorimeter (EMCal), aiming at detecting and separating electrons and positrons (e±) originated from different sources, was carried out. To accomplish the objectives of the research, data gathered from the 2012 proton-proton (pp) collision experiment were used. At a center of mass energy of sqrt(s)=8TeV, the collision of the proton beams liberates heavy quarks, charm and bottom, with approximate lifetimes of approximately 10^13s and 10^12s, respectively. The e± generated through weak semileptonic heavy flavor decays are of interest for studying quarks, therefore it served solely as motivation and incentive for the research carried out and described herein. The introduction of carefully selected cuts, with the purpose of separating partial data collected in the three detectors, permitted the understanding of their effect on the results. Furthermore, due to the fact that the TOFs design was not meant to separate e± from the other heavier particles, only the general effects of introducing a simple cut in the beta=v/c values were analyzed. The more specific cuts were only used for the data generated by the events detected by the TPC and the EMCal. A combination of cuts based on the particles energy loss as a function of traveled distance (dE/dx), with the ratio of energy to momentum (E/p) of the particle, was adopted to enable the separation process, thus allowing for the isolation of e± from the other particles, namely pi±, K±, and p/p. The analysis was performed for values of total particle momentum in the range 0<=p<=6GeV/c. A comparison of the raw data with the results obtained by applying this procedure, indicated a substantial increase in the e± yield and efficiency, reaching average values above 90% over the entire momentum range. / Um estudo do uso dos detetores de tempo de voo (TDV), câmara de projeção de tempo (CPT), e calorímetro eletromagnético (CalEM) do ALICE, visando detectar elétrons e pósitrons (e±) originados por diferentes fontes, foi realizado. Para atingir os objetivos da pesquisa, dados coletados durante o experimento de colisões próton-próton em 2012 foram utilizados. Com um nível de enegia do centro de mass igual a raiz(s)=8TeV, a colisão dos feixes de prótons libera quarks pesados, charm e bottom, com tempo de vida de aproximadamente 10^13s e 10^12s, respectivamente. Os e± gerados pelo decaimento fraco semileptônico de sabores pesados é de interesse para o estudo dos quarks, portanto, o conceito serviu somente como motivação e incentivo para a pesquisa realizada e descrita nesta dissertação. A introdução de cortes específicos, com a finalidade de parcialmente separar dados coletados nos três detectores, permitiu adquirir entendimento sobre os efeitos do cortes nos resultados. Adicionalmente, em virtude do projeto do TDV não ter sido feito visando separar e± oriundos do decaimento dos sabores pesados das demais partículas mais massivas, somente os efeitos gerais de introduzir um corte simples nos valores de beta=v/c, foram analisados. Os cortes mais específicos foram somente nos dados detectados pelo CPT e pelo CalEM. Uma combinação de cortes baseados na perda de energia da partícula em função da distância percorrida (dE/dx), com a razão entre a energia e o momento da partícula (E/p), foi adotada para viabilizar o processo de separação, desta forma permitindo a separação dos e± das demais partículas, ou seja, dos pi±, K±, and p/p. A análise foi realizada para valores de momento total das partículas na faixa 0<=p<=6GeV/c. Uma comparação dos dados originais com os resultados obtidos pela aplicação do procedimento, indicou um aumento substancial do rendimento e eficiência dos e±, atingindo valores médios acima de 90% na faixa inteira de momento.
168

Specialized models for the long-term transmission network expansion planning problem /

Escobar Vargas, Laura Mónica January 2018 (has links)
Orientador: Rubén Augusto Romero Lázaro / Resumo: A análise de sistemas altamente complexos quando e analizado o problema de planejamento de expansão de redes de transmissão de longo prazo, é o foco principal deste trabalho. Os modelos e metodos propostos são aplicados ao problema de planejamento estático tradicional, que é um problema de otimização matemática classificado como NP-completo, não-linear inteiro misto. O qual envolve no investimento, variáveis operacionais contínuas e variáveis inteiras. O comportamento normal de cada sistema pode conter informação essencial para a criação de novos métodos, como os planos de corte baseados em cortes de diferença de ângulos para problemas de grande escala, o que é a base é o ponto de partida deste trabalho, derivando em desigualdades válidas é ciclos críticos. Os cortes angulares básicos reduzem o espaço de busca do problema e o tempo total de cálculo deste problema, enquanto ao método de inequações válidas que pode ser usado para fornecer limites inferiores sólidos no investimento ótimo do planejamento de transmissão, já que a diferença entre o modelo DC (modelo exato) e o modelo de transporte (modelo mais relaxado) são as restrições angulares. Os ciclos críticos têm sido desenvolvidos para melhoraralguns dos modelos tradicionais do problemas de planejamento da expansão da rede de transmissão de longo prazo. A razão por trás disso é a ausência da segunda lei de Kirchhoff, que completa a representação do sistema, mas aumenta a complexidade. Para resolver os problemas resultantes... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The analysis of highly complex systems when solving the long-term transmission network expansion planning problem is the main focus of this work. The proposed improved models and methodology are applied to the traditionalstatic planning problem, which is a mathematical optimization problem classified as NP-complete and mixed-integer nonlinear problem. It involves continuousoperating variables and integer investment variables. The normal behavior of each system can be shown essential information to the creation of new methods, as the cutting-planes based in bus-angle difference cuts for large-scale problems which were the starting point of this work, deriving in valid inequalities and critic cycles. The angular cuts aim to reduce the search space of the problem and the total computation time of this NP-hard problem as for the valid inequalities methodthat can be used to provide strong lower bounds on the optimal investment of the transmissionplanning, since the difference between the DC model (exact model) and the transport model (more relaxed model) are the angular constraints. Critic cycles has been develop in order to improve some of the traditional long-term transmission network expansion planning problem models. The reason behind it is the absence of second Kirchhoff’s law which completes the representationof the system, but increase the complexity. In order to solve the resulting problems, this work uses the modeling language AMPL with the solver CPLEX. In test systems w... (Complete abstract click electronic access below) / Doutor
169

Indexation et recherche de similarités avec des descripteurs structurés par coupes d'images sur des graphes / Indexing and Searching for Similarities of Images with Structural Descriptors via Graph-cuttings Methods

Ren, Yi 20 November 2014 (has links)
Dans cette thèse, nous nous intéressons à la recherche d’images similaires avec des descripteurs structurés par découpages d’images sur les graphes.Nous proposons une nouvelle approche appelée “bag-of-bags of words” (BBoW) pour la recherche d’images par le contenu (CBIR). Il s’agit d’une extension du modèle classique dit sac-de-mots (bag of words - BoW). Dans notre approche, une image est représentée par un graphe placé sur une grille régulière de pixels d’image. Les poids sur les arêtes dépendent de caractéristiques locales de couleur et texture. Le graphe est découpé en un nombre fixe de régions qui constituent une partition irrégulière de l’image. Enfin, chaque partition est représentée par sa propre signature suivant le même schéma que le BoW. Une image est donc décrite par un ensemble de signatures qui sont ensuite combinées pour la recherche d’images similaires dans une base de données. Contrairement aux méthodes existantes telles que Spatial Pyramid Matching (SPM), le modèle BBoW proposé ne repose pas sur l’hypothèse que des parties similaires d’une scène apparaissent toujours au même endroit dans des images d’une même catégorie. L’extension de cette méthode ` a une approche multi-échelle, appelée Irregular Pyramid Matching (IPM), est ´ également décrite. Les résultats montrent la qualité de notre approche lorsque les partitions obtenues sont stables au sein d’une même catégorie d’images. Une analyse statistique est menée pour définir concrètement la notion de partition stable.Nous donnons nos résultats sur des bases de données pour la reconnaissance d’objets, d’indexation et de recherche d’images par le contenu afin de montrer le caractère général de nos contributions / Image representation is a fundamental question for several computer vision tasks. The contributions discussed in this thesis extend the basic bag-of-words representations for the tasks of object recognition and image retrieval.In the present thesis, we are interested in image description by structural graph descriptors. We propose a model, named bag-of-bags of words (BBoW), to address the problems of object recognition (for object search by similarity), and especially Content-Based Image Retrieval (CBIR) from image databases. The proposed BBoW model, is an approach based on irregular pyramid partitions over the image. An image is first represented as a connected graph of local features on a regular grid of pixels. Irregular partitions (subgraphs) of the image are further built by using graph partitioning methods. Each subgraph in the partition is then represented by its own signature. The BBoW model with the aid of graphs, extends the classical bag-of-words (BoW) model by embedding color homogeneity and limited spatial information through irregular partitions of an image. Compared to existing methods for image retrieval, such as Spatial Pyramid Matching (SPM), the BBoW model does not assume that similar parts of a scene always appear at the same location in images of the same category. The extension of the proposed model to pyramid gives rise to a method we named irregular pyramid matching (IPM).The experiments demonstrate the strength of our approach for image retrieval when the partitions are stable across an image category. The statistical analysisof subgraphs is fulfilled in the thesis. To validate our contributions, we report results on three related computer vision datasets for object recognition, (localized)content-based image retrieval and image indexing. The experimental results in a database of 13,044 general-purposed images demonstrate the efficiency and effectiveness of the proposed BBoW framework.
170

Impact des coupes partielles sur l’activité de coléoptères phloeophages et xylophages en forêt boréale

Bélanger Morin, Mathieu 12 1900 (has links)
Ce projet de recherche évalue la réponse à court terme de coléoptères phloeophages et xylophages (Cerambycidae et Scolytinae) à différentes intensités de coupes partielles (0, 25 et 40% de la surface terrière prélevée) afin de déterminer la viabilité de cette méthode sylvicole en forêt boréale. Disposant de 12 parcelles expérimentales (4 répétitions pour chaque intensité de coupe) dans une sapinière à bouleau blanc située au sud de la forêt boréale (Québec, Canada), nous avons évalué l’abondance, la diversité ainsi que l’établissement (taux d’attaque) de ces deux groupes d’insectes, et ce dès la première année suivant la coupe. L’échantillonnage a été réalisé à l’aide de pièges à interception multidirectionnelle et de l’écorçage de sections de 3 espèces d’arbres exposées dans l’ensemble des parcelles. Nos résultats montrent une plus grande activité/abondance des deux taxons (abondance 5 à 6 fois plus élevée) ainsi qu’une composition en espèces différente et plus diversifiée dans les peuplements partiellement coupés (25 et 40%). De plus, la présence et la distribution d’espèces colonisant habituellement des hôtes affaiblis (e.g., Trypodendron lineatum, Rhagium inquisitor) – et pouvant donc réduire la valeur économique d’arbres résiduels – a été recensée et semble être favorisée entres autres par l’ouverture de la canopée et des blessures physiques faites aux arbres pendant les opérations sylvicoles. Par ailleurs, l’approche combinant différentes techniques d’échantillonnage a permis une meilleure compréhension des mécanismes de localisation/sélection d’hôte (variant en fonction de l’espèce), un aspect important de la dynamique des insectes pour l’évaluation des risques suite aux coupes forestières. Sur la base de cette étude à court terme, il ne semblerait pas y avoir de différence significative sur les risques pour le milieu quant à l’augmentation d’activité des Cerambycidae et Scolytinae entre les deux traitements de coupe appliqués. Il reste cependant indispensable de vérifier la validité de ces résultats sur une plus longue période afin d’établir des plans d’aménagement forestier durables pour la forêt boréale. / To evaluate the viability of partial cuts, short-term responses of phloeophagous and xylophagous beetles (Cerambycidae and Scolytinae) following different partial cut treatments (0, 25 and 40% of basal area cut) were determined in a balsam fir–white birch boreal forest in Quebec, Canada. Each treatment was replicated 4 times totaling 12 experimental stands. The summer following treatments, abundance and diversity of targeted beetle groups along with their establishment (attack rates) in partially cut stands were assessed with passive flight- interception traps and bark dissection of exposed, freshly cut boles from three tree species. Greater activity/abundance from both taxa were detected (abundance 5 to 6 times larger) along with a different and more diversified species composition in partially cut stands (25 and 40%). The presence and distribution of species that usually colonize weakened host trees (e.g., Trypodendron lineatum, Rhagium inquisitor) – and can thus reduce stands economic value for future harvest operations – were influenced by canopy openness and injuries on residual trees made during silvicultural operations. Furthermore, combining diverse sampling techniques allowed us to observe different host-selection patterns (random landing vs. primary attraction) given our multi-scale experimental approach, which we found to vary between insect species. Understanding these mechanisms for such beetle groups are important to evaluate stand vulnerability following partial cuts and predict impacts and risks in a given environment. While the 40% partial cuts remove additional wood volume, we found no significant increase in beetle activity between the 25 and 40% treatment. Though partial cuts render treated stands more vulnerable to greater Cerambycidae and Scolytinae attacks, further studies must be done to confirm this trend in longer term if proper boreal forest management plans are to be drawn.

Page generated in 0.0426 seconds