The increasing demand on user rates in the fifth generation (5G) requires network architectures that can support high data rates with acceptable reliability. In order to increase the data rates in the presence of the current spectrum crisis, shrinking cells and reusing the spectrum is a proposed solution. Conventional implementation of dense cells requires a large number of expensive BSs to locally process and decode users’ signals. Another limiting factor that degrades the performance in a dense network is the inter-cell interference. A cloud radio access network (CRAN) is a promising solution to those cost, complexity, and interference challenges. A typical CRAN architecture consists of simplified low-cost base stations (BSs), termed radio units (RUs), that collect the radio frequency (RF) user equipments’ (UEs) signals and forward them over the fronthaul links to the central office (CO) where signal processing is done over shared resources. Besides the reduced cost and complexity of a CRAN, the joint processing at the CO enables joint interference mitigation techniques. However, the performance of CRANs depends critically on the availability of reliable fronthaul links with large bandwidth that may be expensive. Analog optical fronthaul links provide high data rates at lower cost and complexity since UEs’ signals are optically analog-modulated without digitalization, however, they suffer from other channel impairments and nonlinearities. In this thesis, analog optical fronthaul topologies are considered in which radio signals are forwarded over free-space optical (FSO) links, termed radio-over-free-space optical (RoFSO) links, and optical fiber (OF) links, termed radio-over-fiber (RoF) links. Firstly, a CRAN with mixed RF/RoFSO fronthaul is considered to investigate the performance improvement when RF fronthaul links are replaced one-by-one by RoFSO links. A novel joint optimization problem is introduced for the given architecture in which the weighted sum of UEs’ rates is maximized by jointly designing RF and RoFSO links. The optimization problem is solved over different numbers of RF and RoFSO links and under various weather conditions. Under favorable weather conditions, the replacement of 1 RF link by a RoFSO link is shown to increase the 50th percentile of UEs’ rates by 7 times. Secondly, the reliability of a CRAN with two-hop RoFSO/RoF fronthaul links is derived along with other performance metrics such as the average bit-error rate and the cumulative distribution function of UEs’ rates. For the given architecture, the Gaussian noise model of fiber nonlinearity is applied and an optimal OF average optical power is derived to minimize the outage probability. Using the optimal power, and under favorable weather conditions, the 50th percentile of user rate exceeds 1:5 Gbps. Finally, a CRAN with passive all-optical two-hop fronthaul links is considered where optical signals from the first RoFSO fronthaul hop are passively coupled into the RoF fronthaul link. The fronthaul outage probability is derived in the context of network planning to provide guidance on designing a set of system parameters. Those parameters include coverage area radius, density of RUs, RoFSO gain, RoFSO optical power and RoF length. / Thesis / Doctor of Philosophy (PhD) / The upcoming generation of wireless communications, termed fifth generation (5G), promises faster data rates and lower latency. In order to achieve this, more base stations (BSs) have to be deployed which increases the cost and complexity of the network. A solution to this challenge is to install simple BSs, i.e. radio units (RUs), that collect signals from users and forward them to a central office (CO) for joint processing which is referred to as a cloud radio access network (CRAN). The fronthaul network in a CRAN connects the RUs to the CO and it can be implemented using different kinds of links. While there are several fronthaul media (e.g., radio frequency (RF), free-space optical (FSO) links, copper lines, satellite communications, and optical fiber (OF)), optical links provide high data rates that are promising to achieve the 5G requirements. In this thesis, a novel architecture of a CRAN is considered in which analog optical links, namely FSO links and OF links, are used for fronthauling. Performance improvement in terms of rate and reliability is investigated and optimized through different design tools. In response to the challenges introduced by the proposed architecture, such as the nonlinearities of analog FSO and OF links, various design parameters are proposed in the optimization problems to tackle those challenges. Furthermore, a network planning framework is introduced to provide guidance and insights on designing the network.

The physical-layer security of a line-of-sight (LOS) free-space optical (FSO) link using orbital angular momentum (OAM) multiplexing is studied. We discuss the effect of atmospheric turbulence to OAM-multiplexed FSO channels. We numerically simulate the propagation of OAM-multiplexed beam and study the secrecy capacity. We show that, under certain conditions, the OAM multiplexing technique provides higher security over a single-mode transmission channel in terms of the total secrecy capacity and the probability of achieving a secure communication. We also study the power cost effect at the transmitter side for both fixed system power and equal channel power scenarios.

Approximately, two-thirds of earth's surface is covered by water. There is a growing interest from the military and commercial communities in having, an efficient, secure and high bandwidth underwater wireless communication (UWC) system for tactical underwater applications such as oceanography studies and offshore oil exploration. The existing acoustic and radio frequency (RF) technologies are severely limited in bandwidth because of the strong frequency dependent attenuation of sound in seawater and the high conductivity of seawater at radio frequencies, respectively. Recently, underwater wireless optical communication (UWOC) has been proposed as the best alternative or complementary solution to meet this challenge. Taking advantage of the low absorption window of seawater in blue-green (400-550 nm) regime of the electromagnetic spectrum, UWOC is expected to establish secure, efficient and high data rate communication links over short and moderate distances (< 100 m) for versatile applications such as underwater oil pipe inspection, remotely operated vehicle (ROV) and sensor networks. UWOC uses the latest gallium nitrite (GaN) visible light-emitting diode (LED) and laser diode (LD) transmitters. Although some research on LED lased UWOC is being conducted, both the military and academic 5 research communities are favoring the use of laser beams, which potentially could enhance the available bandwidth by up to three orders of magnitude. However, the underwater wireless channel is optically very challenging and difficult to predict. The propagation of laser beams in seawater is significantly affected by the harsh marine environments and suffers from severe attenuation which is a combined effect of absorption and scattering, optical turbulence, and multipath effects at high transmission rates. These limitations distort the intensity and phase structure of the optical beam leading to a decrease in signal-to-noise ratio (SNR) which ultimately degrades the performance of UWOC links by increasing the probability of error. In this dissertation, we seek to experimentally demonstrate the feasibility of short range (≤ 20 m) UWOC systems over various underwater channel water types using different modulation schemes as well as to model and describe the statistical properties of turbulence-induced fading in underwater wireless optical channels using laser beam intensity fluctuations measurements.

Made available in DSpace on 2017-07-21T18:15:37Z (GMT). No. of bitstreams: 1 Zingara Rocio Eurich.pdf: 7116862 bytes, checksum: 3aec67d482562b1faa0f2a199b297843 (MD5) Previous issue date: 2014-02-03 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / According to the importance of public spaces, especially parks, both for city population and the urban environment, this research aims to analyze the conditions of the squares of the city of Ponta Grossa-PR. For that there were used methodologies which were capable of evaluate qualitative and quantitative the afforestation and infrastructure of squares and to analyze the spatial aspects, checking the morphology, typology, distribution and functionality of these spaces, in order to promote and enhance the public open spaces of the city. Regarding the spatial distribution of the squares it was found that the concentration of them are presented in the central area of the city, and the downtown area has the highest Index for Quarter Square (IAPB), with 4.25%. While verified the morphology of the squares, it was observed that most of them 30.1% has the rectangular shape. Some areas considered as squares by the City Hall of Ponta Grossa are shown as an area without direct social function, and 83.1% could be considered effectively as squares. The most common function in the squares is the passive leisure (92.6%). In the survey of afforestation there were accounted 2,369 individuals, which 55.56% are from exotic origin. Regarding the infrastructure, the roads (85.71%), lighting (79.76%) and banks (69.05%) were the most frequent structures in squares. From the results, it is observed that there is a heterogeneous scenario in all analyzed items, since there are squares that have an extensive infrastructure and some areas have no equipment available to the population. / Em função da importância dos espaços públicos, sobretudo de praças, tanto para a população citadina como para o ambiente urbano, a presente pesquisa busca analisar as condições em que se encontram as praças da cidade de Ponta Grossa-PR. Para tanto se utilizou metodologias capazes de avaliar qualiquantitativamente a arborização e infraestrutura das praças e analisar os aspectos espaciais, verificando a morfologia, tipologia, distribuição e funcionalidade desses espaços, com o intuito de promover e valorizar os espaços livres públicos da cidade. Quanto à distribuição espacial das praças verificou-se que a concentração das mesmas apresenta-se na área central da cidade, sendo o Centro a região com maior Índice de Praças por Bairro (IAPB), com 4,25%. Quando verificado a morfologia das praças observou-se que a maioria das praças 30,1% possui o formato retangular. Algumas áreas consideradas pela Prefeitura Municipal de Ponta Grossa como praças se comportam como espaço sem função social direta, sendo que 83,1% podem ser consideradas efetivamente como praças. A função mais frequente nas praças é o lazer passivo (92,6%). No levantamento da arborização contabilizou-se 2.369 indivíduos os quais 55,56% são de origem exótica. E quanto ao levantamento da infraestrutura os caminhos (85,71%), iluminação (79,76%) e bancos (69,05%) foram as estruturas mais frequentes nas praças levantadas. A partir dos resultados observa-se um cenário heterogêneo em todos os itens analisados, visto que há praças que contam com ampla infraestrutura e algumas áreas não possuem nenhum equipamento disponível para a população.

Electroabsorption is the physical phenomenon by which the absorption of light in a medium can be controlled by applying an electric field. The Quantum–Confined Stark Effect, which makes the absorption band–edge in quantum wells very field–dependent, together with the strong absorption peak provided by excitons, are the physical foundations for the success of electroabsorption modulators based on quantum well structures in telecommunication networks. This thesis describes the design and fabrication of surface–normal electroabsorption modulation devices. The techniques needed to understand the design and fabrication of surface–normal multiple quantum well optical modulators are introduced, as are the various characterisation techniques used during and after the fabrication. Devices for several types of applications have been designed, fabricated, characterised and in some cases integrated into optical systems: – Two–dimensional arrays of 128´128 pixel amplitude modulators grown on GaAs substrates have been fabricated and characterised. Speeds of up to 11700 frames per second were demonstrated, limited by the output electronics of the computer interface. – Large–area modulators grown on GaAs substrates for free–space optical communication were developed, with an active area of 2cm2 and a modulation speed of several megahertz. Contrast ratios up to 5:1 on full modulator areas were measured. Problems limiting the yield and modulation speed of such devices have been studied, and solutions to overcome them have been demonstrated. – Large–area devices grown on InP substrates for free–space optical communication have been developed. Contrast ratios of up to 2:1 for transmissive types have been demonstrated. – Devices consisting of two rows of pixels, grown on GaAs substrates, with an active area of 22mm´5mm, divided into 64 or 128 pixels per row have been developed. These amplitude modulation devices were designed for optical signal processing applications. – One variant of these optical signal processing devices was also characterised as a ternary, binary amplitude and binary phase modulator array. – The use of GaAs multiple quantum well optical modulators in a free–space optical retro–communication system has been studied. An opto–mechanical design for a modulating retro–reflector is described, allowing a large field of view in one direction using reflecting, resonant–cavity modulators for high contrast ratios. / QC 20100802

Electromagnetic wave absorbing properties of SiC-based and alumina ceramic woven fabrics have been investigated. Electrical conductivities of SiC-based ceramic woven fabrics were modified by heat treatment in air resulting in their oxidation. Surface properties of alumina woven fabrics were altered by gold-sputtering resulting in a high conductivity layer on the surface of the wovens. Electromagnetic wave interactions of single layer and double layered combinations of these ceramic woven fabrics were determined in 17-40 GHz frequency range using &ldquo / free-space&rdquo / method. Electromagnetic wave absorption potential of ceramic woven fabrics with different chemical compositions and woven types were correlated with their material properties by X-ray diffraction, scanning electron microscopy and electrical conductivity measurements. Effects of modifications and varying woven fabric arrangements in combinations on the electromagnetic wave absorption potential of the ceramic woven fabrics have been discussed. Various double layer combinations of SiC-based and alumina woven fabrics revealed a promising potential in terms of both reduced reflection and transmission resulting in more than ~95% absorption in millimeter wavelength range, which makes them powerful candidate materials for electromagnetic wave absorption applications.

Den här uppsatsen baseras på en enkätundersökning bland lärare i en kommun i Östergötland, där lärarnas uppfattning, om det fanns plats för passion i vardagspraktiken och om det uppmuntrades och stöttades av skolledningen, undersöktes. Frågeställningarna, om lärarnas uppfattning om de har någon passion, om de får möjlighet att utöva den i sin vardagsprakrik, om de stimuleras eller hindras av styrdokumenten, samt om de upplever att skolledningen tillför inspirerande motivation i en passionerad vardagspraktik, ledde till enkätfrågorna. Detta är en kvantitativ studie i enkätform, inom det empirisk-induktiva fältet, med en kvalitativt inriktad analys då svaren i enkäten är lärares uppfattningar av bl.a. relationer till skolledning och kollegor. Den har sin grund i positivismen, med så objektiva frågeformulering som möjligt samt lärarnas uppfattningar av fenomen och företeelser som svar (Bryman, 2002). Goda exempel av lärares uppfattningar analyserades och sammanfattades utifrån den förståelse som tidigare forskning gett. Aktuell forskning undersöktes och sammanlänkades med de undersökningsresultat som erhållits. Lärarna uppfattar att de får utrymme för sina passioner i vardagspraktiken, att de uppmuntras och stöttas av skolledningen och att deras arbete med passioner är lönemeriterande. Skolledarna möter lärarna i pedagogiska diskussioner, men är mindre benägna att ge tid schemamässigt. Vad gäller styrdokumenten anser lärarna att de inte är något hinder för en passionerad vardagspraktik. Kärnan i undersökningen var ändå om lärarna ansåg att de hade någon passion och det fanns en samstämmighet runt den elevcentrerade passionen: Elevernas lärande och elevernas välmående var i fokus när de skulle ange sin passion i vardagspraktiken. / This essay is based on a survey among teachers in a municipality in Östergötland, where the teachers' opinion, if there was room for passion in everyday practice and if it was encouraged and supported by the school management, was investigated. The issues of teachers' perception if they have passion, if they are given the opportunity to exercise it in the everyday practice, if they are stimulated or hindered by the policies, and whether they interpret the school management adding inspiring motivation in a passionate everyday practice, led to the survey questions.   This is a quantitative survey in the form of a questionnaire, in the empirical-inductive field, with a qualitatively oriented analysis where the answers in the questionnaire are teachers' experiences of, inter alia, relationships with school management and colleagues. It is rooted in positivism, with objective questionnaires, as well as teachers' perceptions of phenomena and phenomena responses (Bryman, 2002).   Good examples of teachers impressions were analyzed and summarized based on the understanding that was given by previous research. Current research was studied and linked with the findings obtained. The teachers perceive they get space for their passions in everyday practice, they are encouraged and supported by the school management and that their work passions are wage meritorious. School leaders meet teachers in educational discussions, but are less likely to give time schedule-wise. As for the policy documents the teachers consider them not to be an obstacle to a passionate everyday practice.   The core of the investigation was still if the teachers perceived that they had any passion, and there was a consensus around the student-centered passion: Students' learning and students' well-being was the focus when their passion in everyday practice was to be mentioned.

This study uses the concepts of everyday politics and cultural resistance to explore how young people are experimenting with ‘free spaces’ in which to develop alternative ideas and practices within the food justice movement. Through a case study of the Spring Ridge Commons – a youth-generated free space – this research describes how youth are redefining relationships to place and to people by practicing alternative foodways like urban foraging; creating decommodified food sources; sharing skills and knowledge through peer-to-peer networks; building community through relationships of mutual support; and experimenting with non-hierarchical governance. Such practices have potential implications for child and youth care such as: reconnecting youth and adults through shared practice and meaningful work in “real life” politics and community building, reconceptualizing 'youth' and 'adult' such that both have greater access to acts of cultural production, and creating experiences of democracy in everyday life. / Graduate

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(農学) / 甲第18312号 / 農博第2037号 / 新制||農||1020(附属図書館) / 学位論文||H26||N4819(農学部図書室) / 31170 / 京都大学大学院農学研究科地域環境科学専攻 / (主査)教授 天野 洋, 教授 田中 千尋, 教授 松浦 健二 / 学位規則第4条第1項該当

Submitted by Irene Nascimento (irene.kessia@ufpe.br) on 2016-07-20T17:38:40Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) DISSERTAÇÃO FINAL - Jaciara Lopes - MDU UFPE 2016.pdf: 4397702 bytes, checksum: c5f17736093b5729caad495df535e022 (MD5) / Made available in DSpace on 2016-07-20T17:38:40Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) DISSERTAÇÃO FINAL - Jaciara Lopes - MDU UFPE 2016.pdf: 4397702 bytes, checksum: c5f17736093b5729caad495df535e022 (MD5) Previous issue date: 2016-03-14 / FACEPE / A pesquisa objetivou analisar as inter-relações e os conflitos existentes entre os usos e a gestão do espaço das calçadas, em cidades não-metropolitanas médias e pequenas, a partir das intervenções cotidianas dos indivíduos, adotando como estudo de caso, a área urbana do município de Carpina/Pernambuco, especificamente a Avenida Estácio Coimbra, localizada no Bairro São José e a Avenida Doutor Joaquim Nabuco, localizada no Bairro Centro. O interesse em investigar essa temática surgiu a partir da observação empírica da dinâmica do espaço das calçadas em cidades não-metropolitanas, nas peculiaridades, semelhanças e diferenças do espaço das calçadas das metrópoles, principalmente quanto aos usos, gestão, conflitos e inter-relações existentes nesse espaço. Sendo assim, questiona-se: Em que dimensões, os indivíduos influenciam nos usos, na gestão, nos conflitos e nas inter-relações no espaço das calçadas em cidades não-metropolitanas médias e pequenas? Há territórios no espaço das calçadas? E se há, como eles se dividem? Os procedimentos metodológicos elegidos para a execução deste trabalho consistiram: na pesquisa bibliográfica, onde foram considerados conteúdos referentes à formação e reestruturação do espaço urbano, dos espaços livres públicos e do espaço das calçadas; além da análise de leis, planos e normativas referentes ao uso e ocupação do solo no município; na observação empírica da dinâmica do espaço das calçadas na cidade; nas conversas informais com indivíduos citadinos, e; na aplicação de uma entrevista semiestruturada, realizada também, com os indivíduos citadinos, identificando inter-relações e possíveis elementos conflitantes nesse espaço. Através das informações recolhidas, almejou-se realizar um diagnóstico acerca dos usos e das funcionalidades encontradas no espaço das calçadas, analisando, por meio de um recorte físico/temporal, situações e/ou elementos conflitantes, bem como, a atuação dos usuários nesse espaço, apontando Carpina como um exemplo de cidade não-metropolitana, que pode apresentar características particulares em sua dinâmica urbana. Consolidando-se como uma temática pertinente, uma vez que busca compreender de que maneira as inter-relações e os conflitos, produzidos pelos agentes sociais, interferem nos usos e na gestão do espaço das calçadas nas cidades não-metropolitanas, a pesquisa busca contribuir para uma nova experiência urbana, reconhecendo que, embora existam leis contratuais fundamentando o desenvolvimento de um município, ao que Gomes (2002) define de nomoespaço, é possível encontrar uma realidade diferente, onde, as práticas socioespaciais, a força da amizade e os acordos de interesses, promovidos pelos citadinos, é quem define esse espaço, ao que o mesmo autor nomeia de genoespaço. Entretanto, ainda que alguns agentes sociais elejam diversos espaços nas calçadas, e, nesses espaços, firmem novos territórios, impondo sobre eles, novas regras de usos, de ocupação e de gestão, diferente dos códigos de conduta que regem o município, o espaço das calçadas necessita ser observado e apropriado, nas cidades não-metropolitanas médias e pequenas, como um espaço livre público, altamente democrático e sustentado por uma rica dinâmica urbana. / The research aimed to analyze the interrelations and conflicts among uses and space management of sidewalks, small and medium cities in non-metropolitan, through daily interventions of individuals, urban area of the municipality of Carpina/Pernambuco, specifically the Estacio Coimbra Avenue, located in Bairro São José and the Doutor Joaquim Nabuco Avenue, located in the Central District. The interest in investigating that topic it has emerged from the empirical observation of the space sidewalks in non-metropolitan cities, the peculiarities, commonalities and differences of space the sidewalks of cities, particularly as to the uses, management, conflicts and existing interrelations that space. Thus, the question is: In that dimension, the individuals influence in the use, management, conflict and on the interrelations space the sidewalks in cities small and medium non-metropolitan? Are there any territories within the sidewalks? And if there is, how did they divide? Methodological elected to perform this work consists of: in literature, in which they were considered contents related to the formation and restructuring of urban space, of public open spaces and space of the sidewalks; Apart from analysis of laws, plans and regulations concerning the use and occupation of land in the municipality; the empirical observation of dynamics of space sidewalks in the city; in informal conversations with townspeople individuals and; the application of a semi-structured interview, carried out also with the townspeople individuals, identifying inter-relationships and possible conflicting elements in that space. Through the collected information, aspired to make a diagnosis about the uses and functionality found within the sidewalks, analyzing, by means of a physical trimming / temporal positions and / or conflicting information, as well as the actions of users in that space, Carpina pointing as an example of non-metropolitan city, which may have particular characteristics in its urban dynamics. Consolidating its position as a relevant theme as it seeks to understand how the interrelations and conflicts, produced by social agents interfere in the use and management of space sidewalks in non-metropolitan cities, that research seeks to contribute to a new urban experience, recognizing that although there are contract law basing the development of a municipality, what Gomes (2002) defines nomoespaço, you can find a different reality, where the socio-spatial practices, the strength of friendship and the interests agreements, promoted by townspeople, is one who defines this space by the same author names of genoespaço. However even if some social workers may elect several spaces on the sidewalks, and in these spaces, get new territories, enforcing on them new rules of use, occupancy and management, different codes of conduct that govern the municipality, the space of sidewalks need to be observed and appropriate, in cities small and medium non-metropolitan, as a public space, highly democratic and supported by a rich urban dynamics.