• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 133
  • 45
  • 32
  • 27
  • 13
  • 8
  • 8
  • 8
  • 4
  • 4
  • 4
  • 3
  • 2
  • 1
  • 1
  • Tagged with
  • 335
  • 335
  • 180
  • 173
  • 30
  • 29
  • 28
  • 28
  • 27
  • 26
  • 26
  • 25
  • 24
  • 24
  • 21
  • 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

Efecto de la gestión de la cubierta vegetal en el control biológico de Tetranychus urticae en mandarino clementino

Aguilar Fenollosa, Ernestina 15 April 2011 (has links)
Tetranychus urticae es una especie plaga importante en cítricos que puede también alimentarse de otras especies asociadas a la cubierta vegetal de este cultivo. Para determinar el efecto de la gestión de la cubierta vegetal en el control biológico de este ácaro, hemos estudiado la dinámica tanto de ácaros Tetranychidae como Phytoseiidae en cuatro parcelas comerciales de mandarino clementino en las que se aplicó tres estrategias diferentes de gestión de la cubierta vegetal: (1) suelo desnudo, (2) cubierta espontánea y (3) cubierta sembrada de Festuca arundinacea. Los resultados apuntan a que tanto los enemigos naturales (mecanismos "top-down") como la planta huésped (mecanismos "bottom-up") juegan un papel importante en la regulación de los ácaros Tetranychidae. Por un lado, la selección de dos razas de T. urticae especializadas en F. arundinacea y en Citrus clementina, en la cubierta y en el árbol respectivamente, cuando esta gramínea se utiliza como cubierta podría explicar en parte los resultados obtenidos (regulación "bottom-up") ya que esto impediría a los especímenes de una planta huésped colonizar con éxito la otra. Los ensayos de trasplante recíproco realizados muestran que las dos demos de T. urticae recogidas de clementina y F. arundinacea difieren considerablemente en su éxito en el desarrollo en el huésped alternativo y esto indica la existencia de fenómenos de adaptación local. Esta adaptación se traduciría en mecanismos "bottom-up" que evitarían que los ácaros que habitan en la cubierta colonicen con éxito la copa de los árboles. Por otro lado, la composición cualitativa de las comunidades de Phytoseiidae asociados a las diferentes cubiertas podría ser clave en la regulación de las poblaciones de T. urticae y Panonychus citri (regulación "top-down"). Los ácaros Phytoseiidae tipo I y II, depredadores especializados en Tetranychidae, se encuentran de manera consistente en la cubierta de F. arundinacea y esto puede explicar la mejor regulación de las poblaciones de ácaros Tetranychidae en los árboles asociados a esta cubierta. Por el contrario, la disposición más regular de fuentes de alimentación alternativas (polen) en la cubierta natural en relación con la cubierta de F. arundinacea, podría explicar la mayor abundancia de Phytoseiidae tipo IV en la primera. Como consecuencia, los Phytoseiidae tipo I y II, más eficaces en el control de Tetranychidae, podrían sufrir las consecuencias de ser competitivamente inferiores que el Phytoseiidae generalista tipo IV que explota el polen en la cubierta espontánea. Este hecho, en combinación con los períodos de escasez de presa, podría dar lugar a su desaparición del agroecosistema y resultar en un deficiente control de los ácaros Tetranychidae en los árboles asociados a una cubierta natural. Haciendo balance de gastos e ingresos, la cubierta más favorable fue la de F. arundinacea (entre 44,4 y 74,5% de reducción de costes en relación con la más cara). Festuca arundinacea como cubierta vegetal es una estrategia de control biológico por conservación muy recomendable para los productores de clementina. Aunque su uso no redujo las poblaciones de ácaros en los árboles por debajo del umbral económico, la disminución en la necesidad de tratamientos, hace que la adopción de esta táctica sea una alternativa beneficiosa tanto ecológica como económicamente. Nuestros resultados apuntan a la cubierta de F. arundinacea, que no permitió el establecimiento de Tetranychus evansi y ofrece una mejor regulación de P. citri y T. urticae que en suelo desnudo o cubierta natural, como la más adecuada para un control más sostenible de los ácaros Tetranychidae en cítricos.
162

Practical Applications of Extended Deductive Databases in DATALOG*

Seipel, Dietmar January 2010 (has links)
A wide range of additional forward chaining applications could be realized with deductive databases, if their rule formalism, their immediate consequence operator, and their fixpoint iteration process would be more flexible. Deductive databases normally represent knowledge using stratified Datalog programs with default negation. But many practical applications of forward chaining require an extensible set of user–defined built–in predicates. Moreover, they often need function symbols for building complex data structures, and the stratified fixpoint iteration has to be extended by aggregation operations. We present an new language Datalog*, which extends Datalog by stratified meta–predicates (including default negation), function symbols, and user–defined built–in predicates, which are implemented and evaluated top–down in Prolog. All predicates are subject to the same backtracking mechanism. The bottom–up fixpoint iteration can aggregate the derived facts after each iteration based on user–defined Prolog predicates.
163

En kristisk studie av metoder för skattningar av CO2 från vägtrafik med diesel som drivmedel.

Rannamaa, Jonas January 2014 (has links)
Det finns nu ingen tvekan om att det är vi människor, och vårt användande av fossila bränslen, som bidrar till den förstärkta växthuseffekten. Rättvisande metoder till att mäta växthusgasutsläpp är nödvändiga för att kunna fatta framtida beslut. Vägtrafiken är en av de största källorna till utsläpp av växthusgaser och den ökar hela tiden i omfattning. Den här studien fokuserar på olika metoder som används för att uppskatta koldioxidemissioner från vägtrafiken genom att först uppskatta mängderna diesel, från ett kritiskt perspektiv. Som hjälp till detta har en alternativ metod, för att uppskatta dieselkonsumtionen från vägtrafiken i Sverige, skapats. Resultaten visar skillnader mellan olika metoders uppskattningar, några av dessa i motsättning till varandra. Studien visar att resultat från modellen HBEFA 3.1 samvarierar med statistiken över levererad diesel i Sverige men visar lägre volymer. De alternativa metoderna, som skapats för den här studien, kan förklara sänkningarna av dieselkonsumtionen år 2008-2009 men kan inte förklara sänkningarna år 1999-2000 och 2011-2012. Mera studier som undersöker skillnaderna mellan resultaten från National inventory report Sweden och statistisk information över levererade mängder diesel i Sverige, och vad som orsakar dessa, behövs. / There is now no doubt about that it is humans, and our usage of fossil fuels, that contributes to the global warming. Accurate methods of measuring greenhouse gases are vital for future decision making. Road traffic is one of the major sources for greenhouse gases and it is increasing in volume. This study focus on different methods, used to estimate carbon dioxide emissions from road traffic by first estimating the quantity of diesel, from a critical point of view. For that purpose an alternative method used to estimate diesel consumption from road traffic in Sweden is created. The results show differences between methods estimates, some of them in contradiction to each other. The study shows that the results from the model HBEFA 3.1 covariate with both sources of statistics on delivered diesel in Sweden but show lower volumes. The alternative methods created in this study can explain the decrease of diesel consumption in the year 2008-2009 but can’t explain the decrease in the years 1999-2000 and 2011-2012. More studies on differences between the results in the National inventory report Sweden and statistical information on deliveries of diesel, and what is causing them, are needed.
164

Political culture and socialisation responses to integrated water resources management (IWRM) : the case of Thabo Mofutsanyane District Municipality / Sysman Motloung

Motloung, Sysman January 2010 (has links)
This study looks at political culture and socialisation responses to Integrated Water Resource Management (IWRM). It identifies political culture and socialisation as part of a process, the development of a political culture with specific attitudes, cognitions, and feelings towards the political system. Political culture and socialisation impart the knowledge of how to act politically, i.e. how to apply values in formulating demands and making claims on the political system. They form a connecting link between micro- and macro-politics. The study maintains that political orientations are handed down from one generation to another, through the process of political socialisation. Top-down and bottom-up influences come into play to augment a discourse on the global nature of political socialisation and the political culture of international societies with regard to IWRM and governance ideologies. It is argued that these international ideas become relevant in the national political agenda, civil society organisations and trans-national networks. The IWRM aspects of water as an economic good and a basic human right have become a two-edged sword in the South African context. The study reveals that politics stand at the epicentre of water problems, and that IWRM is a political-ethical issue which challenges power bases in many communities. The IWRM global norms of equitable, efficient and sustainable use of water resources have become a major problem in a water-scarce country burdened with economic inequalities and abject poverty. This is a pressing issue because there is an increasing demand for water to sustain the development necessary to redress the draconian ills of the apartheid past. This becomes evident in the fundamental legislative overhaul that has taken place since 1994, embracing a transformation culture that glorifies the norm of water not only as a fundamental human right, but also as a commodity that is necessary to sustain human dignity. It is here that water is politicised. Violent protests have erupted in reaction to perceived neo-liberal attempts to deny the poor their access to this resource. The political culture and socialisation responses as far as IWRM is concerned appear within fragmented lines, i.e. mainly black and poor communities embrace a culture of non-payment for services and resort to violent protests as a viable method to raise their concerns. In contrast, the white and middle-class communities manifest a tendency to form parallel local government structures; they then withhold rate payments and provide services for themselves through ratepayer associations. Finally, the study considers the South African context with regard to the manifestations of political culture, and how this influences water resources. It is evident that there is too much emphasis on politics at the expense of discussions on IWRM. Civil society organisations make very little attempt to encourage public participation in water management structures. It also appears that political elites who are disillusioned with civil society organisations tend to derail their efforts to educate the public on water management structures. / MA, Political Studies, North-West University, Vaal Triangle Campus, 2011
165

Le incerte vie della sostenibilità: energia, acqua e rifiuti tra azioni strategiche d'impresa e percorsi di partecipazione / The uncertain ways for sustainability. Energy, water and waste between entrepreneurial strategy and participation paths

CORRADI, VALERIO 19 February 2010 (has links)
Le modalità attuali di produzione, distribuzione e consumo dei servizi elettrico, idrico e d’igiene urbana sono largamente insostenibili. Alla luce del crescente impatto ambientale di tali attività, aziende di servizio, istituzioni e cittadini-consumatori si dichiarano preoccupati e disponibili a riorientare strategie, politiche e pratiche sulla base di principi di sostenibilità ambientale. Il presente lavoro si propone di analizzare i processi di trasformazione in senso ecologico di alcune filiere della produzione e del consumo di servizi pubblici locali secondo una prospettiva disciplinare di sociologia dell’ambiente, attraverso uno studio di caso avente per oggetto le politiche ambientali della maggiore local utility italiana e una indagine qualitativa delle pratiche sociali di consumo di servizi di un campione di stakeholders/clienti della medesima Società. La ricerca assegna ampio spazio all’analisi dell’attuale scenario socio-ambientale nel quale trovano posto discorsi e strategie ambientali di multiutilities orientate a un incremento della complessità organizzativa e delle performance sociali, economiche, ambientali, e cambiamenti nelle modalità di consumo/fruizione finale dei servizi che ridefiniscono, sul piano simbolico e pratico, gli importanti nessi tra produzione e consumo e tra fattori come tecnologia e stile di vita. In particolare dalla ricerca sembrano emergere con insistenza due percorsi che si propongono come obiettivo la sostenibilità ambientale. Uno di tipo istituzionale che prospetta cambiamenti secondo uno schema di intervento dall’alto verso il basso (top-down), e un altro, animato da priorità molto diverse, che è portatore di un rinnovamento partecipativo dal basso. A fronte di queste contrastanti vie della sostenibilità, il modello teorico più noto e diffuso nell’ambito della sociologia dell’ambiente per la lettura del mutamento in senso ecologico nel campo dei servizi pubblici locali mostra la propria inadeguatezza e l’esigenza di una riformulazione. Sul piano delle risultanze empiriche la separazione e il difficile riconoscimento tra i soggetti portatori di strategie top-down e quelli che elaborano percorsi bottom up mostra la problematica presenza di logiche di azione molto diverse in campo ambientale che sembrano difficili da conciliare. A un’ultima analisi emerge come nel conseguimento di principi di sostenibilità ambientale sia la via dall’alto che quella dal basso, accanto e indubbie potenzialità, possiedono rilevanti elementi di incertezza e ambiguità che per il momento sembrano rendere indefinibile da parte dei produttori e consumatori dei servizi elettrico, idrico e ambientale un percorso efficace e condiviso per la transizione verso un futuro sostenibile. / The sustainable management of common-pool resources will be among the main challenges that people will have to solve in the next years. In spite of all that, unsustainability of the current energy, water and waste production–consumption models are evident. In the last years socio-technical utility systems such as electricity, water and waste, have been subjected to many transformation in managerial (liberalization), organizational (multiutility model) and socio-cultural (new orientation for consumption) dimensions. Since the utility systems are closely intertwined with society and nature their transformation to play a leading role in the making of environmental sustainable future for society. In the first section this paper introduces an analysis of theoretic position on utility system’s transformation, and highlight weak point and perspective of this dynamic change’s riding. In the second section the paper proposes a sociological integrated framework for interpretation of the ecological transformation of the energy and water consumption and waste management. The sociological analysis shows that in socio-environmental field there are two sustainable paths (top down strategy versus bottom up way) but they seem weak and uncertain and don’t enough for building a sustainable future.
166

Estimating measurement uncertainty in the medical laboratory

Placido, Rui January 2016 (has links)
Medical Laboratories Accreditation is covered by ISO 15189:2012 - Medical Laboratories — Requirements for Quality and Competence. In Portugal, accreditation processes are held under the auspices of the Portuguese Accreditation Institute (IPAC), which applies the Portuguese edition (NP EN ISO 15189:2014). Accordingly, Medical Laboratories accreditation processes now require the estimate of measurement uncertainty (MU) associated to the results. The Guide to the Expression of Uncertainty in Measurement (GUM) describes the calculation of MU, not contemplating the specific aspects of medical laboratory testing. Several models have been advocated, yet without a final consensus. Given the lack of studies on MU in Portugal, especially on its application in the medical laboratory, it is the objective of this thesis to reach to a model that fulfils the IPAC’s accreditation regulations, in regards to this specific requirement. The study was based on the implementation of two formulae (MU-A and MU-B), using the Quality Management System (QMS) data of an ISO 15189 Accredited Laboratory. Including the laboratory’s two Cobas® 6000–c501 (Roche®) analysers (C1 and C2) the work focused three analytes: creatinine, glucose and total cholesterol. The MU-B model formula, combining the standard uncertainties of the method’s imprecision, of the calibrator’s assigned value and from the pre-analytical variation, was considered the one best fitting to the laboratory's objectives and to the study's purposes, representing well the dispersion of values reasonably attributable to the measurand final result. Expanded Uncertainties were: Creatinine - C1 = 9,60%; C2 = 5,80%; Glucose - C1 = 8,32%; C2 = 8,34%; Cholesterol - C1 = 4,00%; C2 = 3,54 %. ...[cont.].
167

Vliv biomanipulací s účelovou rybí obsádkou na vývoj kvality vody vodárenské nádrže Hamry

Jurek, Lukáš January 2016 (has links)
I have dealt in my thesis with biomanipulation on the water reservoir Hamry. The reservoir is located near the village Hamry in the Bohemian-Moravian Highlands, it is meso-eutrofního character and its size (about 42 ha of water surface) and an average depth of 2 m is ranked among the smaller, shallow tank. Biomanipulation measures are there implementation and monitored in the long term (since 2008).Biomanipulation implemented in 2015, which mainly consist of removing unwanted species of fish from the reservoir were implemented by different methods at all ontogenetic levels of fish. That means collecting eggs perch Perca fluviatilis, L., seinings of juvenile stages panktivorous species of fish, as well as seinings and elimination of adult unwanted fish species. Part of the seinings were catching spawning shoals of bream Abramis brama, L. and roach Rutilus rutilus, L. With those biomanipalition actions was carried collection and evaluation of samples of zooplankton, phytoplankton, hydrochemical analyzes and physico-chemical parameters of water. Also were investigated phosphorus content in sediments. Some of the data I obtained and evaluated actively (especially zooplankton), other data were evaluated by specialists from ÚBO AV ČR Brno, or employees of the Department of Fisheries and Hydrobiology at the Institute of Zoology, Fisheries, Hydrobiology and Apiculture MENDELU Brno and I have only used this data to compare the efficiency of the imlpemented biomanipulation.
168

Formalisation of edit operations for structure editors

Holmquist, Johan January 2005 (has links)
Although several systems with structure editors have been built, no model exist to formally describe the edit operations used in such editors. This thesis introduces such a model --- a formalism to describe general structure edit operations for text oriented documents. The model allows free bottom-up editing for any tree-based structural document with a textual content. It can also handle attribute and erroneous structures. Some classes of common structures have been identified and structure editor specifications constructed for them, which can be used and combined in the creation of other structure editors.
169

Modulateur sigma-delta complexe passe-bande à temps continu pour la réception multistandard

Jouida, Nejmeddine 18 February 2010 (has links)
Le travail de recherche que nous présentons dans cette thèse s’inscrit dans le domaine de la conception des circuits et systèmes pour la numérisation des signaux radio large bande multistandard. La finalité de ces travaux est l’établissement de nouvelles méthodologies de conception des circuits analogiques et mixtes VLSI, et à faible consommation pour le convertisseur analogique numérique (CAN). Nous proposons l’utilisation d’un CAN de type S? complexe passe-bande à temps-continu pour l’architecture Low-IF. Ce qui permet de simplifier l’étage analogique en bande de base en esquivant le besoin de circuits tels que le contrôleur de gain automatique, le filtre anti-repliement et les filtres de rejection d’images. Le récepteur est plus linéaire et présente un degré d’intégrabilité adéquat pour les applications multistandard de type Radio logicielle Restreinte (SDR). La première contribution consiste à proposer une méthodologie originale et complètement automatisée de dimensionnement du modulateur ?? pour la réception SDR. Une nouvelle stratégie de stabilisation, basée sur le placement des zéros et des pôles du filtre de boucle, est élaborée permettant ainsi de simplifier le passage du temps-discret vers le temps-continu par une simple correspondance entre les domaines pour les intégrateurs et les résonateurs du filtre de boucle. La deuxième contribution concerne la construction d’une architecture générique du modulateur ?? complexe à temps-continu en suivant une méthodologie originale. Les éléments de base de cette architecture sont les deux modulateurs ?? passe-bas pour les voies I et Q à temps-continu. Les deux filtres de boucles sont en couplage croisé en structure polyphase, ce qui permet le décalage vers la fréquence intermédiaire du récepteur. Nous avons conçu un outil de dimensionnement sous MATLAB pour les modulateurs S? multistandard stables d’ordre élevés à temps-continu, passe bas, passe-bande réel et complexe. La troisième contribution de ces travaux concerne la proposition d’une méthodologie de conception avancée de circuits mixtes VLSI pour les CANs de type ??. Cette méthodologie de conception permet une combinaison des approches descendante ‘Top-down’ et montante ‘Bottom-up’, ce qui rend possible l’analyse des compromis de conception par l’utilisation concurrente des circuits au niveau transistor et des modèles comportementaux. Cette approche permet de faire allier à la fois la précision et la vitesse de processus de simulation lors de la conception des CANs de type ??. La modélisation comportementale du modulateur S?, en utilisant le langage VHDL-AMS, nous a permis de développé une bibliothèque de modèles permettant la prise en compte des imperfections tels que le bruit, le jitter, le retard de boucle au niveau comportemental. Afin d’illustrer la méthodologie de conception proposée, un exemple de la vérification par la simulation mixte est fourni à travers la conception d’un quantificateur en technologie CMOS. L’extraction des paramètres des imperfections du schéma au niveau transistor a permit d’enrichir le modèle comportemental et de prévenir les anomalies causant la dégradation des performances du modulateur S?. / Abstract
170

A comparison of the rate and accuracy of symbol location on visual displays using colour-coded alphabetic and categorisation strategies in Grade 1 to 3 children

Herold, M.P. (Marina Patricia) 14 October 2012 (has links)
The ability to locate symbols on a visual display forms an integral part of the effective use of AAC systems. Characteristics of display design and perceptual features of symbols have been shown to influence rate and accuracy of symbol location (Thistle&Wilkinson, 2009; Wilkinson, Carlin,&Jagaroo, 2006). The current study endeavoured to compare the use of two colour-coded organisational strategies (alphabetical order and categorisation) for their effectiveness in symbol location and to investigate if some bottom-up features influenced the performance of the participants in these tasks. 114 learners in Grade 1 to 3 in a mainstream school were randomly divided into two groups. Both of the groups were exposed to two visual search tests in alternating order. The tests involved searching for 36 visual targets amongst 81 coloured Picture Communication Symbols on a computer screen in one of two colour-coded organizational methods, namely alphabetical order or categorisation. The data from the research task was collected through computer logging of all mouse selections. Findings showed that locating symbols on a computer screen with a categorisation strategy was significantly faster and more accurate than with an alphabetical strategy for the Grade 1 to 3 participants. The rate and accuracy of target symbol location in both the strategies decreased significantly as grade increased, as did the differences between rate and accuracy of target location when using the two strategies. It was also found that although the tests in this study placed heavy top-down processing demands on the participants, there was still evidence of bottom-up factors influencing their performance. Implications for display design in AAC clinical practice were discussed. / Thesis (PhD)--University of Pretoria, 2012. / Centre for Augmentative and Alternative Communication / unrestricted

Page generated in 0.0192 seconds