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  • 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.
21

The Effects of Message Matching in Climate Change Persuasion

Penner, Matthew R. 01 April 2019 (has links)
Public opinions of climate change are not consistent with the reality that climate change is occurring. Effective persuasive messages must be created to ensure that irreparable damage to the environment is prevented. This study investigated the cognitive processes that occur when an individual is exposed to a persuasive message regarding environmental concerns that is matched to an individual’s personality characteristics like right wing authoritarianism and purity. Messages on two environmental topics (solar panels and the Environmental Protection Agency) were created. Each topic was framed in multiple ways to test hypotheses about personality-based message matching. Participants completed a thought listing task after reading about each of the topics, and then indicated their attitudes toward the message topics. Participants were also asked to complete several individual difference scales. Reported attitudes were regressed on individual differences and message frame type in order to determine the effects of message matching on attitudes. While the results do not support a matching effect for purity, an effect of right wing authoritarianism was found after controlling for environmental apathy. This suggests that individual difference matching effects do exist, although they may be more complex than initially hypothesized.
22

Mechanisms to Reduce Routing Information Inaccuracy Effects: Application to MPLS and WDM Networks

Masip Bruin, Xavier 07 October 2003 (has links)
Les xarxes IP tradicionals utilitzen el model de transmissió "best-effort" per transportar tràfic entre clients de la xarxa. Aquest model de transmissió de tràfic no és el més adequat per les aplicacions en temps real com per exemple, vídeo sota demanda, conferències multimedia o realitat virtual que per altra banda tenen cada cop més adeptes entre els clients de la xarxa. A fi de garantir el correcte funcionament d'aquest tipus d'aplicacions, l'estructura de la xarxa ha de ser substancialment modificada amb l'objectiu final de poder optimitzar els seus propis recursos i així poder fer front a aquells tipus de tràfics i de clients que requereixen certes garanties de "Qualitat de Servei" (QoS) per a la seva correcta transmissió.Aquestes modificacions o millores de la xarxa poden ser perfectament realitzades sota l'entorn d'Enginyeria de Tràfic (Traffic Engineering, TE). Dos són els principals aspectos relacionats amb el funcionament de la xarxa en aquest entorn de TE: els mecanismes de commutació i els mecanismes d'encaminament. Així, per una banda es necessita un mecanisme de commutació molt ràpid en els nodes interns de la xarxa a fi de que els paquets de dades puguin ser processats amb el menor temps possible. En xarxes IP aquest objectiu s'aconsegueix amb el Multiprotocol Label Switching (MPLS). Per altra banda, a fi de garantir certa QoS, les decisions d'encaminament s'han de realitzar tenint en compte quines són les restriccions de QoS sol·licitades per el node client que origina el tràfic. Aquest objectiu s'aconsegueix modificant els esquemes d'encaminament tradicionals, incorporant-hi els paràmetres de QoS en les decisions d'encaminament, generant el que es coneix com algorismes d'encaminament amb QoS (QoS routing).Centrant-nos en aquest darrer aspecte, la majoria dels algorismes d'encaminament amb QoS existents, realitzen la selecció de la ruta a partir de la informació d'estat de l'enllaç emmagatzemada en les bases de dades d'estat de l'enllaç contingudes en els nodes. Per poder garantir que els successius canvis en l'estat de la xarxa estiguin perfectament reflectits en aquesta informació d'encaminament, el protocol d'encaminament ha d'incloure un mecanisme d'actualització que faci possible garantir que la selecció de les rutes es fa a partir d'informació acurada de l'estat real de la xarxa. En un entorn IP tradicional, el qual inicialment no inclou paràmetres de QoS, els canvis produïts en la informació d'encaminament són tan sols deguts a modificacions en la topologia i connectivitat de la xarxa. En aquest entorn, donat que la freqüència en la qual s'espera rebre missatges advertint d'aquestes modificacions no és elevada, la majoria dels mecanismes d'actualització es basen en la inclusió d'un cert període de refresc. Així, les bases de dades s'actualitzen periòdicament mitjançant la distribució d'uns missatges que informen a la resta de nodes de l'estat de la xarxa,a fi de que cada node pugui actualitzar la seva base de dades.No obstant això, hem de tenir en compte que en aquelles xarxes IP/MPLS altament dinàmiques amb requeriments de QoS, aquest mecanisme d'actualització basat en un refresc periòdic no serà útil. Això és degut a la rigidesa que presenta aquest mecanisme, la qual fa que no sigui aplicable a un entorn que presenti contínues variacions del paràmetres dels enllaços cada cop que s'estableixi o s'alliberi una connexió (ara a més de la topologia i connectivitat, s'inclouen paràmetres de QoS, com ampla de banda, retard, variació del retard, etc.). Per tot això, s'haurà de generar un mecanisme d'actualització molt més eficient que sigui capaç de mantenir les bases de dades dels nodes perfectament actualitzades reflectint els continus canvis en l'estat de la xarxa. L'alta granularitat d'aquest mecanisme provocarà una sobrecàrrega de la xarxa, degut a l'enorme quantitat de missatges d'actualització que seran necessaris per poder mantenir informació actualitzada en les bases de dades d'estat de l'enllaç en cada node.Per reduir aquesta sobrecàrrega de senyalització apareixen les polítiques d'activació (triggering policies) que tenen per objectiu determinar en quin moment un node ha d'enviar un missatge d'actualització a la resta de nodes de la xarxa advertint-los de les variacions produïdes en els seus enllaços. Desafortunadament, l'ús d'aquestes polítiques d'activació produeix un efecte negatiu sobre el funcionament global de la xarxa. En efecte, si l'actualització de la informació de l'estat de l'enllaç en els nodes no es fa cada cop que aquesta informació es veu modificada, sinó que es fa d'acord a una certa política d'activació, no es podrà garantir que aquesta informació representi de forma acurada l'esta actual de la xarxa en tot moment. Això pot provocar una selecció no òptima de la ruta seleccionada i un increment en la probabilitat de bloqueig de noves connexions a la xarxa. / Las redes IP tradicionales utilizan el modelo de transmisión best-effort para transportar tráfico entre clientes de la red. Es bien sabido que este modelo de transmisión de tráfico no es el más adecuado para las aplicaciones en tiempo real, tales como video bajo demanda, conferencias multimedia o realidad virtual, que cada vez son más de uso común entre los clientes de la red. Para garantizar el correcto funcionamiento de dichas aplicaciones la estructura de la red debe ser modificada a fin de optimizar la utilización de sus propios recursos y para poder hacer frente a aquellos tráficos que requieran ciertas garantías de Calidad de Servicio (QoS) para su correcta transmisión.Estas modificaciones o mejoras de la red pueden ser perfectamente realizadas bajo el entorno de Traffic Engineering (TE). Dos son los principales aspectos relacionados con el funcionamiento de la red en el entorno de TE: los mecanismos de conmutación y los mecanismos de encaminamiento. Así, por una parte, se necesita un mecanismo de conmutación muy rápido en los nodos intermedios de la red a fin de que los paquetes de datos puedan ser procesados con el menor tiempo posible. En redes IP este objetivo se consigue con el Multiprotocol Label Switching (MPLS). Por otra parte a fin de garantizar cierta QoS, las decisiones de encaminamiento se deben realizar acorde con los parámetros de QoS requeridos por el cliente que origina tráfico. Este objetivo se consigue modificando los esquemas de encaminamiento tradicionales e incorporando parámetros de QoS en las decisiones de encaminamiento, lo que deriva en la generación de encaminamiento con QoS (QoS routing).Centrándonos en este último aspecto de encaminamiento, la mayoría de los algoritmos de QoS routing existentes realizan la selección de la ruta a partir de la información de estado del enlace que está almacenada en las bases de datos de estado del enlace contenidas en los nodos. A fin de garantizar que los sucesivos cambios en el estado de la red estén perfectamente reflejados en dicha información, el mecanismo de encaminamiento debe incorporar un mecanismo de actualización cuyo objetivo sea garantizar que las decisiones de encaminamiento se realizan a partir de información fidedigna del estado de la red. En un entorno IP tradicional, el cual no incluye parámetros de QoS, los cambios producidos en dicha información son los debidos a modificaciones en la topología y conectividad. En dicho entorno dado que no son esperadas frecuentes variaciones de la topología de la red, la mayoría de los mecanismos de actualización están basados en la inclusión de un cierto periodo de refresco.Sin embargo, en redes IP/MPLS altamente dinámicas con requerimientos de QoS, este mecanismo de actualización no será adecuado debido a su rigidez y a las continuas variaciones de los parámetros de los enlaces (que ahora incluirá parámetros de QoS, tales como, ancho de banda, retardo, variación del retado, etc.) que se producirán cada vez que se establezca/libere una conexión. Por tanto, se deberá generar un mecanismo de actualización mucho más eficiente que sea capaz de actualizar las bases de datos de los nodos a fin de reflejar las constantes variaciones del estado de la red. La alta granularidad de este mecanismo provocará una sobrecarga de la red, debido a la enorme cantidad de mensajes de actualización necesarios para mantener información actualizada del estado de la red. Para reducir esta sobrecarga de señalización aparecen las políticas de disparo (triggering policies), cuyo objetivo es determinar en qué momento un nodo debe enviar un mensaje de actualización al resto de nodos de la red advirtiéndoles de las variaciones producidas en sus enlaces.Desafortunadamente el uso de dichas políticas de disparo produce un efecto negativo sobre el funcionamiento global de la red. En efecto, si la actualización de la información de estado del enlace en los nodos no se realiza cada vez que dicha información es modificada sino de acuerdo con cierta política de disparo, no se puede garantizar que dicha información represente fielmente el estado de la red. Así, la selección de la ruta, podrá ser realizada basada en información inexacta o imprecisa del estado de lo red, lo cual puede provocar una selección no óptima de la ruta y un incremento en la probabilidad de bloqueo de la red.Esta Tesis se centra en definir y solucionar el problema de la selección de rutas bajo información inexacta o imprecisa de la red (routing inaccuracy problem). Se consideran dos escenarios de trabajo, las actuales redes MPLS y las futuras redes WDM, para los cuales se propone un nuevo mecanismo de encaminamiento: BYPASS Based Routing (BBR) para redes IP/MPLS y BYPASS Based Optical Routing (BBOR) para redes WDM. Ambos mecanismos de encaminamiento se basan en un concepto común denominado "bypass dinámico".El concepto de "bypass dinámico" permite que un nodo intermedio de la red encamine el mensaje de establecimiento que ha recibido del nodo fuente, a través de una ruta distinta a la calculada por el nodo fuente (y explícitamente indicada en el mensaje de establecimiento), cuando detecte que inesperadamente el enlace de salida no dispone de recursos suficientes para soportar las garantías de QoS requeridas por la conexión a establecer. Estas rutas alternativas, denominadas bypass-paths, son calculadas por el nodo fuente o de entrada a la red simultáneamente con la ruta principal para ciertos nodos intermedios de la misma. En redes IP/MPLS el mecanismo BBR aplica el concepto de "bypass dinámico" a las peticiones de conexión con restricciones de ancho de banda. En cambio, en redes WDM, el mecanismo BBOR aplica el concepto de "bypass dinámico" a la hora de asignar una longitud de onda por la cual se va a transmitir el trafico. / Traditional IP networks are based on the best effort model to transport traffic flowsbetween network clients. Since this model cannot properly support the requirements demanded by several emerging real time applications (such as video on demand, multimedia conferences or virtual reality), some modifications in the network structure, mainly oriented to optimise network performance, are required in order to provide Quality of Service (QoS) guarantees.Traffic Engineering is an excellent framework to achieve these network enhancements.There are two main aspects in this context that strongly interact with network performance: switching mechanisms and routing mechanisms. On one hand, a quick switching mechanism is required to reduce the processing time in the intermediate nodes. In IP networks this behaviour is obtained by introducing Multiprotocol Label Switching (MPLS). On the other hand, a powerful routing mechanism that includes QoS attributes when selecting routes (QoS Routing) is also required.Focusing on the latter aspect, most QoS routing algorithms select paths based on the information contained in the network state databases stored in the network nodes. Because of this, routing mechanisms must include an updating mechanism to guarantee that the network state information perfectly represents the current network state. Since network state changes (topology) are not produced very often, in conventional IP networks without QoS capabilities, most updating mechanisms are based on a periodic refresh.In contrast, in highly dynamic large IP/MPLS networks with QoS capabilities a finer updating mechanism is needed. This updating mechanism generates an important and nondesirablesignalling overhead if maintaining accurate network state information is pursued. To reduce the signalling overhead, triggering policies are used. The main function of a triggering policy is to determine when a network node must advertise changes in its directly connected links to other network nodes. As a consequence of reduced signalling, the information in the network state databases might not represent an accurate picture of the actual network state.Hence, path selection may be done according to inaccurate routing information, which could cause both non-optimal path selection and an increase in connection blocking frequency.This Thesis deals with this routing inaccuracy problem, introducing new mechanisms to reduce the effects on global network performance when selecting explicit paths under inaccurate routing information. Two network scenarios are considered, namely current IP/MPLS networks and future WDM networks, and one routing mechanism per scenario is suggested:BYPASS Based Routing (BBR) for IP/MPLS and BYPASS Based Optical Routing (BBOR) for WDM networks. Both mechanisms are based on a common concept, which is defined as dynamic bypass.According to the dynamic bypass concept, whenever an intermediate node along the selected path (unexpectedly) does not have enough resources to cope with the incoming MPLS/optical-path demand requirements, it has the capability to reroute the set-up message through alternative pre-computed paths (bypass-paths). Therefore, in IP/MPLS networks the BBR mechanism applies the dynamic bypass concept to the incoming LSP demands under bandwidth constraints, and in WDM networks the BBOR mechanism applies the dynamic bypass concept when selecting light-paths (i.e., selecting the proper wavelength in both wavelength selective and wavelength interchangeable networks). The applicability of the proposed BBR and the BBOR mechanisms is validated by simulation and compared with existing methods on their respective network scenarios. These network scenarios have been selected so that obtained results may be extrapolated to a realistic network.
23

Genetická variabilita a fylogeografie mšice zhoubné \kur{Diuraphis noxia} (Aphididae) / Genetic variability and phylogeography of Russian wheat aphid, \kur{Diuraphis noxia} (Aphididae)

SATTRANOVÁ, Anna January 2013 (has links)
Genetic analysis of 433 samples of serious crop pest aphid Diuraphis noxia was conducted with the use of 8 microsatellites loci. Statistical analysis revealed sexual reproduction of D. noxia in temperate regions. The linkage disequilibrium was detected because of the excess of heterozygotes. These results support the theory of RNDr. Starý about the invasion of D. noxia to American continent via states of North Africa, Spain and France.
24

Estratégias Para Sobrevivência Em Redes Ópticas Considerando Penalidades da Camada Física

FREITAS, Rodrigo Choji de 13 December 2012 (has links)
Submitted by Eduarda Figueiredo (eduarda.ffigueiredo@ufpe.br) on 2015-03-06T15:47:00Z No. of bitstreams: 2 Tese_Rodrigo_Choji_de_Freitas.pdf: 3582270 bytes, checksum: de853c11feb70926d05f9cb458e258c2 (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) / Made available in DSpace on 2015-03-06T15:47:00Z (GMT). No. of bitstreams: 2 Tese_Rodrigo_Choji_de_Freitas.pdf: 3582270 bytes, checksum: de853c11feb70926d05f9cb458e258c2 (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Previous issue date: 2012-12-13 / FAPEAM e CAPES / Nesta tese é investigado um importante tópico concernente às redes totalmente ópticas: sobrevivência à ocorrência de falhas. Garantir tolerância a falhas é um requisito indispensável para as atuais redes ópticas de alta capacidade, principalmente porque elas transportam um grande volume de dados e, caso alguma interrupção no tráfego ocorra e que não possa ser solucionada imediatamente, uma perda significativa de informação é inevitável, provocando transtornos técnicos e, sobretudo, econômicos. Um outro tema tratado neste trabalho diz respeito às penalidades impostas a um sinal, oriundas de uma rede totalmente óptica. Nestas infraestruturas de rede, o sinal óptico não é regenerado a cada nó. Portanto, é importante que as soluções que garantem resiliência à rede óptica levem em consideração também a degradação do sinal óptico. A pesquisa desenvolvida neste trabalho visa a contribuir com a área de sobrevivência em redes totalmente ópticas, a partir da proposição de novos algoritmos de restauração e proteção que, além de garantir a resiliência de uma chamada contra falhas, também encontrem uma rota que seja adequada.
25

Estudo de algoritmos RWA em redes GMPLS sobre DWDM

Feres, Mariana Massimino 08 June 2009 (has links)
Made available in DSpace on 2016-06-02T19:05:45Z (GMT). No. of bitstreams: 1 3190.pdf: 9507279 bytes, checksum: 8c55bfbb567b6057f6f56e7a27fb7164 (MD5) Previous issue date: 2009-06-08 / Financiadora de Estudos e Projetos / The increase in the number of users and the emergence of sophisticated network applications motivate the research to improve the data-communication technologies, and thus to meet the requirement for bandwidth. In optical networks, one of the main advances is wavelength division multiplexing (WDM). An essential issue in designing of optical networks is how the network will be controlled, that is, which type of signaling will be used for resources reservation, routing and wavelength assigning, and how physical impairments will be dealfish. This implies in the necessity of several devices to guarantee the good functioning of the network. The diversity and complexity of administration of these devices stimulate the creation of GMPLS (Generalized Multiprotocol Label Switching), in order to provide control, for domains not only based on packages (as it makes the MPLS - Multiprotocol Label Switching), but also on time slots, wavelength and fiber. However, the labels switching on the wavelength multiplexing can generate a NP-complete problem involving the routing and wavelength assignment: if both do no succeed, the connection blocking will occur with and loss of network performance. Another relevant question is that, in all-optical networks, there is some physical impairment that influence the blocking probability e must be taken in consideration in algorithms RWA. This work presents the study of the control plan GMPLS and RWA algorithms for the setting up of connections in alloptical WDM networks. Moreover, the study of two physical impairments (polarization mode dispersion and optical signal noise rate) was done, inserting them in RWA algorithm to reduce the blocking probability due them. The results had shown that the MostUsed algorithm has better performance than the BestFit and the Random one when considered the connection blocking due to resources (lambdas). Moreover, the use of impairments-aware algorithms influence significantly in the reduction of the blocking probability. Therefore, the more advantageous performance was observed in the use of impairment-aware algorithms simultaneously with the MostUsed algorithm. / O aumento de usuários e o surgimento de aplicações de redes sofisticadas impulsionam as pesquisas para aprimorar as tecnologias de transmissão de dados, e assim suprir a exigência por largura de banda. Em redes ópticas, um dos principais avanços é o surgimento da multiplexação de comprimento de onda (WDM). Desta forma, uma questão essencial no projeto de redes ópticas compreende na definição de como a rede será controlada, isto é, qual tipo de sinalização será utilizado para reserva de recursos, definição de rotas, tratamento de falhas, entre outras funções formadoras do plano de controle. Isso implica na necessidade de diversos dispositivos para garantir o bom funcionamento da rede. A diversidade e complexidade de administração desses dispositivos incentivam a criação do GMPLS (Generalized Multiprotocol Label Switching), a fim de prover controle, não somente para domínios baseados em pacotes (como faz o MPLS - Multiprotocol Label Switching), mas também em tempo, comprimento de onda e fibra. Porém, a comutação de rótulos sobre a multiplexação de comprimento de onda pode gerar um problema NP-Completo envolvendo o roteamento e a associação de comprimento de onda, uma vez que se ambas não obtiverem sucesso, ocorrerá o bloqueio da conexão e perda de desempenho da rede. Outra questão relevante é que, em redes totalmente ópticas, existem problemas inerentes da camada física os que influenciam na probabilidade de bloqueio e devem ser levados em consideração em algoritmos RWA (roteamento por associação de comprimento de onda). O presente trabalho realiza o estudo do plano de controle GMPLS e de algoritmos RWA para o estabelecimento de conexões em redes WDM transparentes. Além disso, é feito um estudo de duas restrições da camada física (dispersão por modo de polarização e relação sinal ruído óptica) inserindo-as no algoritmo RWA para diminuir a probabilidade de bloqueio devido a elas. Os resultados mostraram que o algoritmo MostUsed possui melhor desempenho em relação ao BestFit e ao Random quando considerado bloqueio por falta de recursos (lambdas). Além disso, o uso de algoritmos cientes de restrições da camada física influencia significamente na diminuição da probabilidade de bloqueio. Portanto, o melhor desempenho foi observado no uso de algoritmos cientes de restrições físicas juntamente com o algoritmo MostUsed.
26

Δρομολόγηση και ανάθεση μήκους κύματος σε οπτικά δίκτυα βασισμένη στα φυσικά χαρακτηριστικά του δικτύου

Μανουσάκης, Κωνσταντίνος 26 October 2007 (has links)
Ο πιο σύγχρονος και περισσότερα υποσχόμενος τύπος οπτικών δικτύων, είναι τα οπτικά δίκτυα πολυπλεξίας διαίρεσης μήκους κύματος (Wavelength Division Multiplexing – WDM). Τα δίκτυα αυτά διαθέτουν τεράστια χωρητικότητα και αναμένεται να αποτελέσουν τα μελλοντικά δίκτυα κορμού για τη μεταφορά μεγάλου όγκου δεδομένων. Η πλήρης αξιοποίηση της χωρητικότητας των WDM δικτύων, όμως, απαιτεί την επίλυση ειδικών θεμάτων που σχετίζονται µε τις ιδιαιτερότητες και τη φύση των WDM οπτικών δικτύων. Το σημαντικότερο ίσως από αυτά είναι το πρόβλημα της δρομολόγησης και ανάθεσης μήκους κύματος (Routing and Wavelength Assignment – RWA), πάνω στο οποίο έχει αναπτυχθεί έντονη ερευνητική δραστηριότητα τα τελευταία χρόνια, το οποίο είναι NP-πλήρες. Ένα άλλο θέμα που χρήζει ιδιαίτερης προσοχής είναι οι εξασθενήσεις που υφίσταται ένα σήμα μέσα στο οπτικό δίκτυο. Όταν λοιπόν κάποιο σήμα διαδίδεται κατά μήκος ενός οπτικού μονοπατιού πέφτει η ποιότητα του εξαιτίας των φυσικών επιδράσεων που δέχεται. Οι φυσικές επιδράσεις κατά κανόνα μειώνουν τον λόγο σήματος προς θόρυβο (SNR), με αποτέλεσμα να αυξηθεί σημαντικά και η συχνότητα εμφάνισης λαθών (BER) στον κόμβο προορισμού. Αν η παραπάνω συχνότητα εμφάνισης λαθών είναι μεγαλύτερη από ένα καθορισμένο όριο, τότε το αίτημα δρομολόγησης θα πρέπει να απορριφθεί. Επομένως κατά την επίλυση του RWA προβλήματος θα πρέπει να ληφθούν υπόψη οι επιδράσεις που προκαλούνται στο σήμα λόγω των φυσικών χαρακτηριστικών του δικτύου. Στην παρούσα διπλωματική εργασία έχει υλοποιηθεί ένας αλγόριθμος για την επίλυση του στατικού RWA, που βασίζεται στην μοντελοποίηση ενός γραμμικού προβλήματος (Linear Programming – LP). Κατά την μοντελοποίηση λαμβάνονται υπόψη οι πιο σημαντικές επιδράσεις, όπως η χρωματική διασπορά (Chromatic Dispersion – CD), η διασπορά τρόπου πόλωσης (Polarization Mode Dispersion – PMD), η ενισχυμένη αυθόρμητη εκπομπή (Amplifier Spontaneous Emission – ASE) και η αλληλεπίδραση γειτονικών καναλιών (crosstalk). Η επίδραση των τριών πρώτων παραμέτρων εξαρτάται αποκλειστικά από τα χαρακτηριστικά των συνδέσμων και μοντελοποιούνται σύμφωνα με αναλυτικούς τύπους, ενώ η επίδραση του crosstalk εξαρτάται από τον αριθμό των οπτικών μονοπατιών που διατρέχουν ένα σύνδεσμο. Προτείνεται επίσης μία συνάρτηση βελτιστοποίησης ώστε να προκύπτουν ακέραιες λύσεις με πολύ μεγάλη πιθανότητα από την επίλυση του LP (Linear Program) προβλήματος. Αυτός ο αλγόριθμος εφαρμόζεται σε ένα μητροπολιτικό δίκτυο και λαμβάνονται συγκριτικά αποτελέσματα για διάφορες παραμέτρους των φυσικών στοιχείων του δικτύου. / Wavelength division multiplexing (WDM) is a promising technology for faster and more reliable data communication networks. In a WDM network several optical signals are sent on the same fiber using different wavelength channels. Multiple WDM channels from different end users may be multiplexed on the same fiber. Traditionally only a small fraction of the fiber capacity is in use, but by using WDM it is possible to exploit this huge capacity more efficiently. Under WDM, the optical transmission spectrum is curved up into a number of non-overlapping wavelength bands, with each wavelength supporting a single communication channel operating at whatever rate one desires. WDM technology has been recognized as one of the key components of the future networks. Routing and wavelength assignment (RWA) is a crucial issue for WDM optical network designers. In wavelength routed WDM optical networks connections between terminal stations are established through the use of lightpaths. Given a WDM optical topology and a set of connection requests between pairs of source-destination terminal nodes, the problem of how to route all the lightpaths simultaneously, one per connection, and which wavelength should be assigned to each one of them, subject to minimizing network resources or maximizing traffic characteristics, arises; this is known as the Routing and Wavelength Assignment problem RWA. In transparent networks, the signal quality is subject to a variety of physical impairments, such as polarization mode dispersion (PMD), amplified spontaneous emission (ASE) noise and chromatic dispersion (CD) and crosstalk. These impairments are linearly modeled and handled effectively by a set of analytical formulas as additional constraints on RWA. We apply our algorithm to perform impairment-constraint based RWA, in order to obtain comparative results of a typical metropolitan network's performance under various network and impairment parameters, such as bit rate, amplifier gain and type, modulation format used, etc.
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Analytical investigations and numerical experiments for singularly perturbed convection-diffusion problems with layers and singularities using a newly developed FE-software

Ludwig, Lars 14 March 2014 (has links) (PDF)
In the field of singularly perturbed reaction- or convection-diffusion boundary value problems the research area of a priori error analysis for the finite element method, has already been thoroughly investigated. In particular, for mesh adapted methods and/or various stabilization techniques, works have been done that prove optimal rates of convergence or supercloseness uniformly in the perturbation parameter epsilon. Commonly, however, it is assumed that the exact solution behaves nicely in that it obeys certain regularity assumptions although in general, e.g. due to corner singularities, these regularity requirements are not satisfied. So far, insufficient regularity has been met by assuming compatibility conditions on the data. The present thesis originated from the question: What can be shown if these rather unrealistic additional assumptions are dropped? We are interested in epsilon-uniform a priori estimates for convergence and superconvergence that include some regularity parameter that is adjustable to the smoothness of the exact solution. A major difficulty that occurs when seeking the numerical error decay is that the exact solution is not known. Since we strive for reliable rates of convergence we want to avoid the standard approach of the "double-mesh principle". Our choice is to use reference solutions as a substitute for the exact solution. Numerical experiments are intended to confirm the theoretical results and to bring further insights into the interplay between layers and singularities. To computationally realize the thereby arising demanding practical aspects of the finite element method, a new software is developed that turns out to be particularly suited for the needs of the numerical analyst. Its design, features and implementation is described in detail in the second part of the thesis.
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Αλγόριθμοι δρομολόγησης και ανάθεσης μηκών κύματος με βάση την ενέργεια σε οπτικά δίκτυα

Αγγελέτου, Αρχοντούλα 06 October 2011 (has links)
Η αλματώδης ανάπτυξη που παρατηρείται τα τελευταία χρόνια στον τομέα των οπτικών δικτύων τηλεπικοινωνιών, έχει ως συνέπεια την αύξηση της κατανάλωσης ενέργειας. Σήμερα υπολογίζεται ότι η ενέργεια που οφείλεται σε IT τεχνολογίες αποτελεί το 1%-2% της παγκόσμιας κατανάλωσης. Ωστόσο, τα ποσοστά αυτά αναμένεται να αυξηθούν δραματικά μιας και όλο και περισσότερες εφαρμογές, που απαιτούν μεγάλο εύρος ζώνης (π.χ. video streaming, HDTV), αναπτύσσονται ταχύτατα. Μέχρι πρόσφατα ο κύριος περιορισμός στην ανάπτυξη των δικτύων ήταν το κόστος εξοπλισμού και μετάδοσης. Σήμερα το μεγαλύτερο πρόβλημα είναι η όλο και αυξανόμενη κατανάλωση ενέργειας. Έτσι λοιπόν πιο energy-aware προσεγγίσεις για το σχεδιασμό, την υλοποίηση και τη λειτουργία των οπτικών δικτύων κρίνονται πλέον απαραίτητες. Για την αντιμετώπιση του προβλήματος της κατανάλωσης ενέργειας σε οπτικά δίκτυα υπάρχουν δυο προσεγγίσεις: η ανάπτυξη ενεργο-αποδοτικών συσκευών δικτύου ή η ανάπτυξη αλγορίθμων δρομολόγησης και ανάθεσης μήκους κύματος (RWA) που να λαμβάνουν υπόψη τους και την ενέργεια που καταναλώνει το δίκτυο. Στην παρούσα διπλωματική εργασία επιλέχθηκε η δεύτερη προσέγγιση όπου και αναπτύχθηκαν Energy Aware RWA αλγόριθμοι για τον σχεδιασμό WDM οπτικών δικτύων με στόχο την ελαχιστοποίηση της ενέργειας που καταναλώνεται. Αυτό επιτυγχάνεται μειώνοντας τον αριθμό των συσκευών του δικτύου, όπως αναγεννητές, ενισχυτές, add/drop τερματικά κ.τ.λ. που είναι γνωστό ότι καταναλώνουν αρκετή ενέργεια κατά τη λειτουργία τους. Αρχικά αναπτύχθηκε ένας αλγόριθμος σε Ακέραιο Γραμμικό Ακέραιο Προγραμματισμό (Integer Linear Programming - ILP) που ελαχιστοποιεί από κοινού όλες εκείνες τις συσκευές του δικτύου που καταναλώνουν ενέργεια. Έπειτα το πρόβλημα χωρίζεται σε δυο υπο-προβλήματα: την κατανομή αναγεννητών σε κόμβους του δικτύου όπου η αναγέννηση είναι απαραίτητη και στο Energy Aware RWA. Σε αυτή τη περίπτωση εκτός από ILP προγραμματισμό εφαρμόζεται επίσης και χαλάρωση των περιορισμών ακεραιότητας (LP προγραμματισμός) ώστε να μπορούν να προκύψουν λύσεις και για μεγαλύτερες τοπολογίες. Για τον υπολογισμό της απόδοσης των προτεινόμενων αλγορίθμων διεξάγονται μια σειρά από πειράματα εξομοιώσεων σε Matlab, με τη βοήθεια του LINDO API για την επίλυση των (I)LP προβλημάτων σε ένα μικρό δίκτυο αλλά και στο ευρωπαϊκό δίκτυο Geant-2. Oι προτεινόμενοι αλγόριθμοι συγκρίνονται με τυπικούς RWA αλγορίθμους που δεν λαμβάνουν υπόψη την ενέργεια ή ελαχιστοποιούν κάποιες από τις συνιστώσες του δικτύου. Οι υπολογισμοί δείχνουν ότι η κατανάλωση της ενέργειας του δικτύου μπορεί να μειωθεί μέχρι και 45% σε δίκτυο με συνδέσμους μονής ίνας και μέχρι και 65% σε συνδέσμους διπλής ίνας. / The continuing deployment and upgrade of optical telecommunication networks drive up power and energy consumption, in a way that makes operators worry that future energy consumption levels may pose constraints on communications growth that are more significant than those posed by bandwidth considerations. As community concerns about global energy consumption grow, the power consumption of the optical networks is becoming an issue of increasing importance. Even though energy consumption of IT-related infrastructure currently represents between 1% and 2% of global energy consumption, such values are destined to rise, as more bandwidth-hungry applications (such as video streaming, and HDTV in particular) continue to be developed. Thus, it seems that an energy-aware approach is increasingly needed during the design, implementation and operation of optical networks. Two different approaches can be explored to reduce energy consumption in optical networks: the improvement of the energy efficiency of the equipment and the energy awareness of the Routing and Wavelengths Assignment (RWA) algorithms. In this work the energy minimization problem in optical networks is considered from an algorithmic perspective. The objective of the proposed algorithms is to plan optical WDM networks so as to minimize the energy consumed, by minimizing the number of the most energy-consuming components. Such components can be amplifiers, regenerators, add/drop terminals, optical fibers, etc. Firstly an Integer Linear Programming (ILP) formulation is given that aims at jointly minimizing the energy consuming modules present in an optical network, such as the regenerators, amplifiers, wavelength selective switches, etc. Then the problem for a general (translucent network) is decomposed into a regeneration placement problem, and an energy-aware RWA for transparent networks problem, where again ILP formulations are given to minimize energy consumption. The ILP of the decomposed problem is solved as an LP problem, by relaxing the integer constraints, in order to obtain solutions for larger network topologies. In order to evaluate the performance of the proposed Energy Aware (EA)-RWA algorithms a number of simulation experiments is carried out. All the RWA algorithms are implemented in Matlab and LINDO API is used to solve the corresponding (I)LP problems. The proposed algorithms are compared with RWA algorithms that do not consider energy minimization techniques or RWA algorithms that partially take into account energy consuming components. The simulation results showed that the energy consumption in the optical layer can be reduced by up to 45% in single fiber networks and by up to 65% in multi-fiber networks.
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Planejamento de redes WDM com proteção para caminhos opticos

Steiner, Renato Miranda 08 October 2004 (has links)
Orientador: Raul Vinhas Ribeiro / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-04T00:10:39Z (GMT). No. of bitstreams: 1 Steiner_RenatoMiranda_M.pdf: 2911331 bytes, checksum: f37192c3e00e737a230072ffd04287be (MD5) Previous issue date: 2004 / Resumo: Esta dissertação trata do dimensionamento inicial de tráfego em redes de caminhos ópticos WDM (Wavelength Division Multiplexing) comutadas por comprimento de onda com proteção de caminhos. Fazemos uma introdução das tecnologias chave e dos principais aspectos de planejamento da rede. Apresentamos algumas opções de provisionamento de transporte para diversas arquiteturas de redes clientes. O problema de roteamento e designação de comprimento de onda (RWA ¿ Routing and Wavelength Assignment) é apresentado, e são comparados modelos de programação inteira mista (MILP ¿ Mixed Integer Linear Program) com formulações nó-arco e arco-caminho. A formulação arco-caminho é expandida para incorporar capacidade para proteção compartilhada e dedicada no RWA, em mais dois MILPs. Um algoritmo gerador de rotas alternativas conveniente ao problema foi elaborado. Comparamos diferentes esquemas de restauração de tráfego: pré-configurado 1+1, pré-configurado 1:1, e pré planejado 1:1 e 1:N. A modelagem de proteção/restauração é aplicada a uma rede de 15 nós. Todos os algoritmos foram implementados na linguagem de modelagem AMPL/CPLEX / Abstract: This dissertation is a study about the initial traffic deployment in wavelength-routed WDM (Wavelength Division Multiplexing) optical networks with path protection. We make an introduction of the key technologies and the major network planning aspects. We introduce some architectures for transport provisioning to various client network architectures. The RWA (Routing and Wavelength Assignment) problem is introduced, and node-link and link-path MILP (Mixed Integer Linear Program) formulations are compared. The link-path formulation is expanded to incorporate dedicated and spare capacity in the RWA, in more two MILPs. An algorithm for generation of alternative routes convenient to the problem was elaborated. Different traffic restoration schemes are compared: 1+1, pre-configured 1:1, and pre-planned 1:1 and 1:N. The protection/restoration framework is applied to a 15 nodes network. All the algorithms were implemented on the AMPL/CPLEX modelling language / Mestrado / Automação / Mestre em Engenharia Elétrica
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Authoritariansim and Collectivism: Antecedents and Consequences Among College Students

Samuel, Jasmine, Ms. 01 January 2016 (has links)
Moral Foundations Theory (MFT) suggests there are five distinct moral dimensions, which define morality as a whole. MFT can be broken down into two groups binding: in group/loyalty, authority/respect, and purity/sanctity-which encompass group morality. Harm/Care, fairness/reciprocity are individualizing dimensions, which highlight individual morality. Recent work has found MFT predicts sociopolitical ideologies, as well as sociopolitical attitudes. In an effort to better understand the existing relationships we investigate MFT as a predictor of sociopolitical parties, and attitudes Right-Wing Authoritarianism (RWA) and Social Dominance Orientation (SDO). We also draw on similarities between Individualism/Collectivism and MFT. Specifically we demonstrate individualizing foundations, and dimensions of individualism predict SDO, where as Binding dimensions and dimensions of Collectivism relate to RWA.

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