Complex magnetic oxides represent a unique intersection of immense technological importance and fascinating physical phenomena originating from interwoven structural, electronic and magnetic degrees of freedom. The resulting energetically close competing orders can be controllably selected through external fields. Competing interactions and disorder represent an additional opportunity to systematically manipulate the properties of pure magnetic systems, leading to frustration, glassiness, and other novel phenomena while finite sample dimension plays a similar role in systems with long-range cooperative effects or large correlation lengths. A rigorous understanding of these effects in strongly correlated oxides is key to manipulating their functionality and device performance, but remains a challenging task. In this dissertation, we examine a number of problems related to intrinsic and extrinsic low dimensionality, disorder, and competing interactions in magnetic oxides by applying a unique combination of standard magnetometry techniques and unconventional magnetocaloric effect and transverse susceptibility measurements. The influence of dimensionality and disorder on the nature and critical properties of phase transitions in manganites is illustrated in La0.7Ca0.3MnO3, in which both size reduction to the nanoscale and chemically-controlled quenched disorder are observed to induce a progressive weakening of the first-order nature of the transition, despite acting through the distinct mechanisms of surface effects and site dilution. In the second-order material La0.8Ca0.2MnO3, a strong magnetic field is found to drive the system toward its tricritical point as competition between exchange interactions in the inhomogeneous ground state is suppressed. In the presence of large phase separation stabilized by chemical disorder and long-range strain, dimensionality has a profound effect. With the systematic reduction of particle size in microscale-phase-separated (La, Pr, Ca)MnO3 we observe a disruption of the long-range glassy strains associated with the charge-ordered phase in the bulk, lowering the field and pressure threshold for charge-order melting and increasing the ferromagnetic volume fraction as particle size is decreased. The long-range charge-ordered phase becomes completely suppressed when the particle size falls below 100 nm. In contrast, low dimensionality in the geometrically frustrated pseudo-1D spin chain compound Ca3Co2O6 is intrinsic, arising from the crystal lattice. We establish a comprehensive phase diagram for this exotic system consistent with recent reports of an incommensurate ground state and identify new sub-features of the ferrimagnetic phase. When defects in the form of grain boundaries are incorporated into the system the low-temperature slow-dynamic state is weakened, and new crossover phenomena emerge in the spin relaxation behavior along with an increased distribution of relaxation times. The presence of both disorder and randomness leads to a spin-glass-like state, as observed in γFe2O3 hollow nanoparticles, where freezing of surface spins at low temperature generates an irreversible magnetization component and an associated exchange-biasing effect. Our results point to distinct dynamic behaviors on the inner and outer surfaces of the hollow structures. Overall, these studies yield new physical insights into the role of dimensionality and disorder in these complex oxide systems and highlight the sensitivity of their manifested magnetic ground states to extrinsic factors, leading in many cases to crossover behaviors where the balance between competing phases is altered, or to the emergence of entirely new magnetic phenomena.

No description available.

Spectrum efficiency and energy efficiency are two important attributes driving innovation in wireless communication. Efficient spectrum utilization and sharing with multiple access techniques and using under-utilized spectra by cognitive radios is the current focus due to the scarcity and cost of the available radio spectrum. Energy efficiency to increase operating time of portable handheld devices like smartphones that handle simultaneous voice/video streaming and web browsing and battery powered nodes in a sensor network where battery capacity determines the lifetime of the network is another area attracting researchers. The focus of this thesis is the spectral efficiency of multicarrier code division multiple access (CDMA) in wireless ad-hoc networks. Furthermore, energy efficiency to maximize lifetime of a network are also studied.In a multicarrier CDMA system inter-carrier interference (ICI) due to carrier frequency offset and multiple access interference (MAI) are two major factors that deteriorate the performance. Previous work in this area has been mostly focused on simulation results due to the complexity of the analysis due to the large number of random variables involved. Taking into account accurate statistical models for ICI and MAI that account for the correlation between adjacent subcarriers, this thesis presents new mathematical analysis for the spectral efficiency of multicarrier CDMA communication systems over a frequency selective Rayleigh fading environment. We analyze and compare three multicarrier CDMA schemes which are multicarrier CDMA, multicarrier direct-sequence CDMA and multitone CDMA. We also present simulation results to confirm the validity of our analysis. We also analyze the performance of three simple multiple access techniques or coexistence etiquettes in detail, which are simple to implement and do not require any central control. Accurate interference models are developed and are used to derive accurate expressions for packet error rates in the case of direct sequence CDMA and slotted packet transmission schemes. These results are then used to study the performance of the coexistence etiquettes and compare them with each other. Finally we present a new joint node selection and power allocation strategy that increases lifetime of an ad-hoc network where nodes cooperate to enable diversity in transmission.

O uso de redes sem fio no ambiente industrial está crescendo cada vez mais devido às vantagens que estas redes apresentam comparadas aos sistemas cabeados. No entanto, é necessário que as redes sem fio apresentem a mesma robustez que as redes cabeadas. Para isso, é necessário garantir o enlace de rádio frequência entre os dispositivos e também é preciso que a rede atenda aos requisitos de comunicação em tempo real. O protocolo WirelessHART foi criado em 2007, sendo o primeiro padrão aberto de comunicação sem fio especialmente desenvolvido para ambientes industriais. Esse protocolo vem ganhando cada vez mais aplicabilidade na indústria devido à sua alta confiabilidade e robustez. Por se tratar de um protocolo recente, ainda existem muitas pesquisas em andamento, sendo uma das áreas relacionada a ferramentas para análise e monitoramento da rede. Tais ferramentas têm como objetivo principal capturar as mensagens que trafegam na rede, ou seja, atuam como um sniffer. No entanto, o protocolo WirelessHART apresenta algumas peculiaridades quando comparado a outras redes sem fio, como por exemplo, o uso de 15 canais diferentes. Devido a isso, muitos sniffers já propostos para redes sem fio não podem ser utilizados, pois capturam dados em apenas uma frequência. Outra questão está relacionada ao monitoramento de redes já instaladas, onde os dispositivos podem se encontrar em locais de difícil acesso. Dessa forma, é necessário que a ferramenta tenha mobilidade, ou seja, não necessite estar conectada a um computador, por exemplo. Então, uma vez que ainda não existe uma ferramenta de monitoramento ideal para redes WirelessHART, este trabalho propõe um nova ferramenta, que apresenta vantagens, tais como: captura de dados nos 15 canais utilizando apenas um receptor de rádio, armazenamento local dos dados capturados utilizando um cartão de memória e medição da energia nos canais, para obter informações a respeito de interferências na rede. Além disso, uma aplicação offline de análise dos dados apresenta estatísticas e análises a respeito dos dados capturados. Este trabalho apresenta alguns conceitos teóricos importantes a respeito do protocolo e os detalhes da implementação da ferramenta. Os resultados obtidos mostram que a ferramenta está atuando corretamente como um sniffer e está realizando a detecção de interferências na rede. Um estudo de caso mostra o comportamento da rede WirelessHART coexistindo com o padrão IEEE 802.11. / The use of wireless networks in industrial environment is growing due to the advantages of these networks compared to wired systems. However, the wireless networks must have the same robustness that wired networks. It is necessary to ensure the link between devices and it is also necessary that the network meets the requirements of real-time communication. The WirelessHART protocol was created in 2007, and it is the first open wireless communication standard specifically designed for industrial environments. This protocol has been gaining increasing applicability in industry due to its high reliability and robustness. Because it is a recent protocol, there are still many ongoing researches. One of them is related to tools for analyzing and monitoring the network. Such tools have the main objective to capture the messages that travel on the network, acting as a sniffer. However, the WirelessHART protocol has some peculiarities as compared to other wireless networks, such as the use of 15 different channels. Because of this, many sniffers already proposed for wireless networks can not be applied, because they capture data on only one frequency. Another issue is related to the monitoring networks already installed, where devices can be found in places of difficult access. Thus, it is necessary that the tool has mobility, i.e., does not need to be connected to a computer, for example. So, since there is still no ideal monitoring tool for WirelessHART networks, this paper proposes a new tool, which has advantages such as: data capture in 15 channels using only one radio receiver, local storage of captured data using a memory card and measuring the energy in the channels for getting information about interference in the network. In addition, an offline application presents statistics and analysis about the captured data. This paper presents some important theoretical concepts about the protocol and implementation details of the tool. The results show that the tool is working properly as a sniffer and it’s performing the interference detection in the network . A case study shows the behavior of the WirelessHART network coexisting with IEEE 802.11 standard.

Orientador: Rafael Silva Oliveira / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia. / Made available in DSpace on 2018-08-22T05:52:27Z (GMT). No. of bitstreams: 1 BrumJr._Mauro_M.pdf: 3526243 bytes, checksum: 44324833dc08e57ffd87e138721c4c83 (MD5) Previous issue date: 2013 / Resumo: A partição de recursos hídricos do solo é um dos modelos plausíveis para explicar os mecanismos que promovem a coexistência e a diferenciação de nicho entre espécies em comunidades vegetais. As raízes constituem a principal interface de troca de água entre a planta e o solo, de modo que profundidade radicular é um atributo chave que pode influenciar o funcionamento hidráulico das plantas. O campo rupestre e o campo de altitude são vegetações campestres que ocorrem em montanhas ou chapadas sob diferentes regimes de água devido às diferenças climáticas e pedológicas, sendo o campo rupestre mais árido que o campo de altitude. Essas comunidades são bem conhecidas devido à alta diversidade de espécies, mas pouco se sabe a respeito da diversidade de estratégias de uso de água. Entender as estratégias hidráulicas das plantas é importante para fazer previsões das respostas das comunidades em relação às mudanças climáticas. Diante disso, o nosso objetivo foi responder: quais são os padrões de aquisição e uso de água por plantas que coexistem em uma vegetação de campo rupestre e outra de campo de altitude? Além disso, quais são as estratégias de uso de água entre as plantas com sistemas subterrâneos contrastantes nessas comunidades? Nós avaliamos a composição de isótopos estáveis da água do solo e contrastamos com a composição isotópica da água do xilema de 15 espécies de plantas em cada comunidade. A composição isotópica da água do xilema foi usada como um indicador para estimar a profundidade do solo na qual as plantas estão absorvendo a água. Também fizemos escavações das raízes para verificar qual é o tipo morfológico de cada espécie e contrastar com os resultados da composição isotópica da água do xilema. Além disso, medimos o potencial hídrico da madrugada, do meio dia e a condutância estomática máxima três vezes durante a estação seca (junho, julho e agosto). Nós demonstramos que em ambas as comunidades há uma diversidade interespecífica de formas de sistemas subterrâneos, sendo que o campo rupestre apresentou maior variação interespecífica de uso de água em perfis verticais do solo. As plantas do campo de altitude apresentam raízes mais superficiais do que no campo rupestre. Além disso, demonstramos que a profundidade do sistema radicular é um bom preditor do potencial hídrico da madrugada e do grau de regulação estomática para as plantas do campo rupestre, mas não do campo de altitude. Não encontramos relação entre a profundidade do sistema radicular e o potencial hídrico do meio dia em ambas as comunidades / Abstract: Soil water partitioning is a plausible model to explain the mechanisms that allow species coexistence and niche segregation in plant communities. Roots are the main interface of water exchange between plant and soil, so rooting depth is a key trait that affects whole-plant hydraulic function. The campos rupestres and campos de altitude are two shrubland communities that occur in mountainous plateaus under contrasting water regimes due to differences in their climatic and pedological variables, campos rupestres being more arid than campos de altitude. These communities are well known for their high species diversity but little is known about the diversity of water use strategies. Understanding plant hydraulic strategies is important for improving predictions of community responses to changes in climate. Our goal was to respond: what are the patterns of water acquisition and use in campo rupestres and campo de altitude? Furthermore, what are the water use strategies of plants with contrasting rooting depths in these plants communities? We evaluated the ?D of soil water and xylem water of 15 species in each community. The ?D of xylem water was used as proxy of rooting depth. We also excavated the roots of all species to evaluate their root morphological pattern and to compare with the isotopic data. Furthermore, we measured pre-dawn and midday water potentials and stomatal conductance three times during the dry season (June, July and August, 2012). We found a high interespecific diversity of root types in both communities and higher variance of hydraulic traits at campo rupestre. Campo de altitude plants had shallower roots than campo rupestre. Moreover, we demonstrated that pre-dawn water potential is a good predictor of rooting depth, which in turn is a good predictor of the degree of stomatal control for campo rupestre community but these patterns were not found at campo de altitude. We did not find any relationship between rooting depth and midday water potential for both communities / Mestrado / Ecologia / Mestre em Ecologia

This diploma thesis deals with the study and measurement of coexistence scenarios that can occur between the LTE and LoRa systems in the unlicensed ISM band 2.4 GHz. A common radio frequency band in which LTE and LoRa systems can coexist is defined. An appropriate laboratory measurement is proposed and realized, allowing automatized measurement of the defined coexistence scenarios. For this purpose, a personal computer, professional measurement equipment and software MATLAB are utilized. Functionality of the proposed concept is verified by extensive measurements. The obtained results are graphically shown and discussed in detail.

Mixed-ploidy populations, consisting of multiple cytotypes, are an optimal system for studying genome doubling consequences in plants. The role of frequency dependent selection, known as minority cytotype exclusion principle, is very important in them, but there are many factors limiting this selection. In my thesis, I evaluate the changes in cytotype frequencies and pattern in permanent plots in natural mixed-ploidy populations of three plant species - Butomus umbellatus, Knautia serpentinicola and Tripleurospermum inodorum and I also experimentally analyze partial aspects of frequency dependent selection towards minority cytotype in artificially established mixed-ploidy arrays of two plant species - Arabidopsis arenosa and Tripleurospermum inodorum. Varied changes in frequencies of minority cytotype ware revealed in permanent plots. Usually there was decrease, but in two plots there was increase in minority cytotype frequency and in one case it became dominant. Observed changes depend on initial frequencies of minority cytotype in populations, biological properties of species and particular environment of permanent plot. Relative indexes describing the frequency and the strength of disturbances and also the amount of soil nutrients was used to compare the environment of permanent plots across...

This research investigates the shifting political settlements between the Ugandan state and the Bunyoro and Buganda kingdoms after the discovery of oil between 2007 and 2018. It seeks to answer the following questions using a historically, theoretically, and empirically grounded investigation: What accounts for the Bunyoro kingdom’s failure to benefit substantially from the discovery of oil on its territory? What lessons can be learnt from the Buganda kingdom’s relative success in negotiating with the central government and developing its own political and economic capacity independently of the state? The Bunyoro kingdom, located in the oil-rich Albertine Graben region of western Uganda, has failed to access significant economic benefits from the country’s emerging oil sector despite its historical ownership of the land on which the resource is found. This dissertation combines political settlements theory and the concept of extraversion to explain this empirical puzzle. It finds that the ruling National Resistance Movement (NRM)’s imposition of an exclusive political settlement in Uganda, coupled with the Bunyoro kingdom’s limited holding power, accounts for the kingdom’s failure to derive financial benefits from the oil sector. The relative marginalisation of the Bunyoro from Uganda’s oil sector results from the NRM’s historical strategy of limiting the power of sub-state groups who are subsequently excluded from the governing coalition. The main beneficiaries of the oil industry in Uganda are political elites within the ruling NRM coalition and their close associates. The Buganda kingdom serves as a control case study and reveals the potential strategies and structural changes the Bunyoro kingdom could pursue to potentially bypass Uganda’s exclusive settlement and therefore benefit from the country’s nascent oil sector. This dissertation also engages with broader debates on the struggles between the state and traditional kingdoms since independence in sub-Saharan Africa and how this intersects with the politics of natural resource governance. Since the inception of the modern state in the colonial era, kingdoms have engaged in a complex and dialogic relationship of indifference, cooperation, and contention with successive governing regimes. Some of the kingdoms challenged and resisted, albeit unsuccessfully the colonial imposition of a central state primarily because it led to their loss of political and economic power. Ultimately, the state and the kingdoms represent dual forms of nationality forced to co-exist in the post-colonial era, and this produces a complex mix of cooperation, contestation and strategic coexistence. The management and exploitation of natural resources, including oil, is embedded in this political context, and is often associated with adverse outcomes, such as rent-seeking, authoritarian governance, and sectarian violence. Some of these dynamics have accompanied the emergence of Uganda’s new oil industry, with political contestation occurring between the state and the Bunyoro kingdom which has unsuccessfully attempted to capture a share of oil revenue.

Kartongbruket AB has a supplier of bale pulp which is transitioning to an RFID marking of its bales. Due to this, new perspectives are requested on an RFID implementation regarding the handling of bales. This study focuses on the inbound logistics process and the pulp bale handling process. Furthermore, traceability-related problems are noted due to the fact that the current scanning methodology does not work with sufficient precision. The coexistence between the current barcode reading system and the RFID reading system is also something that is identified as topic which needs to be studied. This study’s choice of the process industry and the cardboard industry is based on a theoretical gap regarding the above-mentioned concepts and problems in this specific industry. Purpose: The purpose of this study is to be helpful to Kartongbruket AB in their upcoming RFID implementation, and to fill the identified theoretical gaps. Method: This is a case study at Kartongbruket AB. Empirics have been collected through semi-structured interviews with relevant internal actors, where the respondents have been identified using a snowball selection method. The study is of a qualitative nature and the theoretical frame of reference has been created through a literature study. Conclusion: This study concludes that RFID can be used in the inbound logistics process to make stock balances more reliable in several potential ways. In addition to this, it can be concluded that an RFID-based system can lead to a centralized traceability system in the pulpbale handling process where internal actors can gain a greater knowledge base in customer complaints cases. The study's presented implementation model may be used as a support for the upcoming RFID implementation. The study also establishes that the merging model is the most suitable coexistence model for Kartongbruket AB when RFID and barcodes are to be run together in the pulp bale handling process.

It is widely accepted that the late Pliocene spans a time with globally warmer conditions compared to today. Regional specifics in temperature patterns from this period, however, remain poorly known. In this study, we reconstruct quantitatively late Pliocene climates for eight sites at the southeastern border of the Qinghai-Tibet Plateau (SBTP), based on palaeobotanical data compiled from published sources using the Coexistence Approach (CoA), and analyze anomalies with respect to modern climates. The reconstructed temperatures indicate that in the late Pliocene, the northwestern part of the study area was cooler than its southern part. This spatial differentiation in temperature was largely due to differences in altitude: the northwest of the SBTP probably had higher altitudes than the south at that time. Mean annual temperatures (MATs) were around 1. °C higher than today, suggesting a cooling trend since the late Pliocene. Our data show that summer temperatures have declined significantly since the late Pliocene while winter temperatures have remained similar to those of the present, different from observations in other territories. The unexpected summer and winter temperature changes can be explained by the regional orogenic uplift plus the global cooling. The eastward extrusion of the Qinghai-Tibet Plateau might have blocked the southward cold high pressure of the winter monsoon and forced it to circumvent the eastern flank of the plateau, weakening its impact on the SBTP. The post-Pliocene mountain uplift increased the overall altitude of the region, which caused the temperature decline for both summer and winter. The reconstructed summer precipitation was lower while the winter precipitation was higher than today, suggesting a weaker monsoon climate during the late Pliocene.