Dissertations / Theses on the topic 'Hybrid input-output'

This thesis involves construction of input-output models measuring the economic impact of a farming innovation organisation (The Birchip Cropping Group) on the Victorian regional economy of Buloke Shire. The input-output modeling undertaken is of two forms; the first being a simple naïve top-down model, and the second a more sophisticated hybrid model. The naïve top-down model is based on input-output coefficients drawn from the Australian national input-output tables, and is regarded as naïve because these input-output coefficients are not adjusted to take account of local economic factors. The hybrid model uses the same national input-output coefficients as a base, and then modifies these coefficients to better reflect industrial conditions in the Shire using a location quotients-adjustment technique, as well as using original survey data collected from entities operating in Buloke Shire. One of the aims of the thesis is to determine whether the simpler naïve top-down approach produces results consistent with the theoretically more accurate hybrid methodology, and thus whether the naïve top-down approach represents a reliable method of conducting regional economic impact analysis. That is, can such studies be undertaken accurately using a naïve top down approach, or is it necessary to adopt the more resource intensive methodology of a hybrid model. The results of the analysis suggest construction of a hybrid model is advisable, as generally the naïve top-down approach produces over-estimates of the economic effects of the Birchip Cropping Group. That is, it appears the economic impact multipliers estimated with the naïve top-down model are too large, suggesting the time and effort involved in constructing the hybrid model was worthwhile. Using the hybrid model, the conclusion is that the Birchip Cropping Group has a significant affect on the regional economy of Buloke Shire, with the economic impact being estimated at close to $600,000 in additional output, $61,000 in additional income, and 3.5 additional jobs per year.

More and more local governments (municipalities and county councils) include the indirect climate impacts of consumption in their environmental work. Life Cycle Assessment (LCA) is an established tool for inventorying both direct and indirect impacts of a product or service, but when the climate impact of an entire organization's consumption of products and services is of interest, the inventory of data can easily become excessive. Through the years, various methods for enabling life cycle inventory on the organizational level have been developed. Hybrid-LCA is one of them where the term "hybrid" comes from that the method combines a so-called bottom up with a top down approach of the data inventory. The practical application of hybrid-LCA and the usefulness of the assessment results for local governments are not self-evident. This study aims to investigate the practical application of hybrid-LCA as a tool for inventorying climate impact for municipalities’ and county councils’ consumption. The purpose includes identifying the challenges associated with the practical procedure when conducting a hybrid-LCA and evaluating the inventory results’ usefulness in municipalities and county councils’ climate work. The results of the study are based on semi-structured interviews, a case study in which hybrid LCA is applied and a workshop where the case study is evaluated. The results show that the hybrid-LCA enables both a holistic approach to the climate impact and a level of detail for selected areas, making it possible to prioritize areas and identify measures to reduce the climate impact from consumption. The main challenges that arise in the practical procedure of the hybrid-LCA are associated with inventory and verification of foreground data and matching purchases of product groups to standardized classifications. To simplify the execution, increase transparency and facilitate monitoring, local governments are recommended to investigate the possibility of coordinating purchasing system and labeling product groups, in accordance with standardized classifications. It is also recommended to request information about a products weight and material content from suppliers. The uncertainties associated with the outcome of a hybrid-LCA are and remain large, therefore it is important that the results are communicated in terms of potential environmental impacts.

This thesis lays the foundation for the creation of an economic database for the counties of Devon and Cornwall in the form of a regional input-output table. The thesis reconsiders the popular hybrid approach to the construction of such tables. In particular, the nonsurvey-to-survey ordering of procedure is questioned. The thesis attempts to restore a more logical preference-order which begins with first-best (survey) estimation methods and extends to second-best (survey-based-nonsurvey) methods. The third-best methods of estimation (pure nonsurvey i.e. location quotient) are excluded from the process altogether. The thesis is largely concerned with the development of the second-best method. The second-best method is derived from an empirical analysis of the nature of nonsurvey estimation error. The analysis is able to reject the Stevens et al. (1983) hypothesis that differences in regional and national production functions are insignificant. Nevertheless, the strategy of developing 'trade-only' nonsurvey estimation methods is found to be valid since, whilst the error associated with regional trade misspecification can be reduced within a broad method of estimation, the error attributable to the misspecification of regional production functions remains largely intractable to such an approach. Survey resources must therefore be devoted to the specification of these functions. The second-best methodology extends the Stevens et al. (1983) by deriving equations that specify the RAS algorithm and local expenditure propensities for households from empirical data for Scotland. These equations have general application within the new hybrid methodology. By restoring a more logical preference-order of approach to estimating hybrid regional input-output tables, emphasis is placed on the analytical strength afforded by a good data set, and not on the analytical 'strength' of magic-box mathematics. This should encourage the regional input-output table to be implemented as an evolving local economic database, which will improve the general quality of regional analysis and, in the long-run, offer cost-savings in data collection and collation.

A rapidly growing share of global agricultural areas is devoted to the production of biomass for non-food purposes. The expanding non-food bioeconomy can have far-reaching social and ecological implications; yet, the non-food sector has attained little attention in land footprint studies. This paper provides the first assessment of the global cropland footprint of non-food products of the European Union (EU), a globally important region regarding its expanding bio-based economy. We apply a novel hybrid land flow accounting model, combining the biophysical trade model LANDFLOW with the multi-regional input-output model EXIOBASE. The developed hybrid approach improves the level of product and country detail, while comprehensively covering all global supply chains from agricultural production to final consumption, including highly-processed products, such as many non-food products. The results highlight the EU's role as a major processing and the biggest consuming region of cropland-based non-food products while at the same time relying heavily on imports. Two thirds of the cropland required to satisfy the EU's non-food biomass consumption are located in other world regions, particularly in China, the US and Indonesia, giving rise to potential impacts on distant ecosystems. With almost 39% in 2010, oilseeds used to produce for example biofuels, detergents and polymers represented the dominant share of the EU's non-food cropland demand. Traditional non-food biomass uses, such as fibre crops for textiles and animal hides and skins for leather products, also contributed notably (22%). Our findings suggest that if the EU Bioeconomy Strategy is to support global sustainable development, a detailed monitoring of land use displacement and spillover effects is decisive for targeted and effective EU policy making.

Due to the rapid development of wireless communications together with the inflexibility of the current spectrum allocation policy, radio spectrum becomes more and more exhausted. One of the critical challenges of wireless communication systems is to efficiently utilize the limited frequency resources to be able to support the growing demand of high data rate wireless services. As a promising solution, cognitive radios have been suggested to deal with the scarcity and under-utilization of radio spectrum. The basic idea behind cognitive radios is to allow unlicensed users, also called secondary users (SUs), to access the licensed spectrum of primary users (PUs) which improves spectrum utilization. In order to not degrade the performance of the primary networks, SUs have to deploy interference control, interference mitigating, or interference avoidance techniques to minimize the interference incurred at the PUs. Cognitive radio networks (CRNs) have stimulated a variety of studies on improving spectrum utilization. In this context, this thesis has two main objectives. Firstly, it investigates the performance of single hop CRNs with spectrum sharing and opportunistic spectrum access. Secondly, the thesis analyzes the performance improvements of two hop cognitive radio networks when incorporating advanced radio transmission techniques. The thesis is divided into three parts consisting of an introduction part and two research parts based on peer-reviewed publications. Fundamental background on radio propagation channels, cognitive radios, and advanced radio transmission techniques are discussed in the introduction. In the first research part, the performance of single hop CRNs is analyzed. Specifically, underlay spectrum access using M/G/1/K queueing approaches is presented in Part I-A while dynamic spectrum access with prioritized traffics is studied in Part I-B. In the second research part, the performance benefits of integrating advanced radio transmission techniques into cognitive cooperative radio networks (CCRNs) are investigated. In particular, opportunistic spectrum access for amplify-and-forward CCRNs is presented in Part II-A where collaborative spectrum sensing is deployed among the SUs to enhance the accuracy of spectrum sensing. In Part II-B, the effect of channel estimation error and feedback delay on the outage probability and symbol error rate (SER) of multiple-input multiple-output CCRNs is investigated. In Part II-C, adaptive modulation and coding is employed for decode-and-forward CCRNs to improve the spectrum efficiency and to avoid buffer overflow at the relay. Finally, a hybrid interweave-underlay spectrum access scheme for a CCRN is proposed in Part II-D. In this work, the dynamic spectrum access of the PUs and SUs is modeled as a Markov chain which then is utilized to evaluate the outage probability, SER, and outage capacity of the CCRN.

A new communication paradigm is foreseen for beyond 2020 society, due to the emergence of new broadband services and the Internet of Things era. The set of requirements imposed by these new applications is large and diverse, aiming to provide a ubiquitous broadband connectivity. Research community has been working in the last decade towards the definition of the 5G mobile wireless networks that will provide the proper mechanisms to reach these challenging requirements. In this framework, three key research directions have been identified for the improvement of capacity in 5G: the increase of the spectral efficiency by means of, for example, the use of massive MIMO technology, the use of larger amounts of spectrum by utilizing the millimeter wave band, and the network densification by deploying more base stations per unit area. This dissertation addresses densification as the main enabler for the broadband and massive connectivity required in future 5G networks. To this aim, this Thesis focuses on the study of the UDN. In particular, a set of technology enablers that can lead UDN to achieve their maximum efficiency and performance are investigated, namely, the use of higher frequency bands for the benefit of larger bandwidths, the use of massive MIMO with distributed antenna systems, and the use of distributed radio resource management techniques for the inter-cell interference coordination. Firstly, this Thesis analyzes whether there exists a fundamental performance limit related with densification in cellular networks. To this end, the UDN performance is evaluated by means of an analytical model consisting of a 1-dimensional network deployment with equally spaced BS. The inter-BS distance is decreased until reaching the limit of densification when this distance approaches 0. The achievable rates in networks with different inter-BS distances are analyzed for several levels of transmission power availability, and for various types of cooperation among cells. Moreover, UDN performance is studied in conjunction with the use of a massive number of antennas and larger amounts of spectrum. In particular, the performance of hybrid beamforming and precoding MIMO schemes are assessed in both indoor and outdoor scenarios with multiple cells and users, working in the mmW frequency band. On the one hand, beamforming schemes using the full-connected hybrid architecture are analyzed in BS with limited number of RF chains, identifying the strengths and weaknesses of these schemes in a dense-urban scenario. On the other hand, the performance of different indoor deployment strategies using HP in the mmW band is evaluated, focusing on the use of DAS. More specifically, a DHP suitable for DAS is proposed, comparing its performance with that of HP in other indoor deployment strategies. Lastly, the presence of practical limitations and hardware impairments in the use of hybrid architectures is also investigated. Finally, the investigation of UDN is completed with the study of their main limitation, which is the increasing inter-cell interference in the network. In order to tackle this problem, an eICIC scheduling algorithm based on resource partitioning techniques is proposed. Its performance is evaluated and compared to other scheduling algorithms under several degrees of network densification. After the completion of this study, the potential of UDN to reach the capacity requirements of 5G networks is confirmed. Nevertheless, without the use of larger portions of spectrum, a proper interference management and the use of a massive number of antennas, densification could turn into a serious problem for mobile operators. Performance evaluation results show large system capacity gains with the use of massive MIMO techniques in UDN, and even greater when the antennas are distributed. Furthermore, the application of ICIC techniques reveals that, besides the increase in system capacity, it brings significant energy savings to UDNs.
A partir del año 2020 se prevé que un nuevo paradigma de comunicación surja en la sociedad, debido a la aparición de nuevos servicios y la era del Internet de las cosas. El conjunto de requisitos impuesto por estas nuevas aplicaciones es muy amplio y diverso, y tiene como principal objetivo proporcionar conectividad de banda ancha y universal. En las últimas décadas, la comunidad científica ha estado trabajando en la definición de la 5G de redes móviles que brindará los mecanismos necesarios para garantizar estos requisitos. En este marco, se han identificado tres mecanismos clave para conseguir el necesario incremento de capacidad de la red: el aumento de la eficiencia espectral a través de, por ejemplo, el uso de tecnologías MIMO masivas, la utilización de mayores porciones del espectro en frecuencia y la densificación de la red mediante el despliegue de más estaciones base por área. Esta Tesis doctoral aborda la densificación como el principal mecanismo que permitirá la conectividad de banda ancha y universal requerida en la 5G, centrándose en el estudio de las Redes Ultra Densas o UDNs. En concreto, se analiza el conjunto de tecnologías habilitantes que pueden llevar a las UDNs a obtener su máxima eficiencia y prestaciones, incluyendo el uso de altas frecuencias para el aprovechamiento de mayores anchos de banda, la utilización de MIMO masivo con sistemas de antenas distribuidas y el uso de técnicas de reparto de recursos distribuidas para la coordinación de interferencias. En primer lugar, se analiza si existe un límite fundamental en la mejora de las prestaciones en relación a la densificación. Con este fin, las prestaciones de las UDNs se evalúan utilizando un modelo analítico de red unidimensional con BSs equiespaciadas, en el que la distancia entre BSs se disminuye hasta alcanzar el límite de densificación cuando ésta se aproxima a 0. Las tasas alcanzables en redes con distintas distancias entre BSs son analizadas, considerando distintos niveles de potencia disponible en la red y varios grados de cooperación entre celdas. Además, el comportamiento de las UDNs se estudia junto al uso masivo de antenas y la utilización de anchos de banda mayores. Más concretamente, las prestaciones de ciertas técnicas híbridas MIMO de precodificación y beamforming se examinan en la banda milimétrica. Por una parte, se analizan esquemas de beamforming en BSs con arquitectura híbrida en función de la disponibilidad de cadenas de radiofrecuencia en escenarios exteriores. Por otra parte, se evalúan las prestaciones de ciertos esquemas de precodificación híbrida en escenarios interiores, utilizando distintos despliegues y centrando la atención en los sistemas de antenas distribuidos o DAS. Además, se propone un algoritmo de precodificación híbrida específico para DAS, y se evalúan y comparan sus prestaciones con las de otros algoritmos de precodificación utilizados. Por último, se investiga el impacto en las prestaciones de ciertas limitaciones prácticas y deficiencias introducidas por el uso de dispositivos no ideales. Finalmente, el estudio de las UDNs se completa con el análisis de su principal limitación, el nivel creciente de interferencia en la red. Para ello, se propone un algoritmo de control de interferencias basado en la partición de recursos. Sus prestaciones son evaluadas y comparadas con las de otras técnicas de asignación de recursos. Tras este estudio, se puede afirmar que las UDNs tienen gran potencial para la consecución de los requisitos de la 5G. Sin embargo, sin el uso conjunto de mayores porciones del espectro, adecuadas técnicas de control de la interferencia y el uso masivo de antenas, las UDNs pueden convertirse en serios obstáculos para los operadores móviles. Los resultados de la evaluación de prestaciones de estas tecnologías confirman el gran aumento de la capacidad de las redes mediante el uso masivo de antenas y la introducción de mecanismos de I
A partir de l'any 2020 es preveu un nou paradigma de comunicació en la societat, degut a l'aparició de nous serveis i la era de la Internet de les coses. El conjunt de requeriments imposat per aquestes noves aplicacions és ampli i divers, i té com a principal objectiu proporcionar connectivitat universal i de banda ampla. En les últimes dècades, la comunitat científica ha estat treballant en la definició de la 5G, que proveirà els mecanismes necessaris per a garantir aquests exigents requeriments. En aquest marc, s'han identificat tres mecanismes claus per a aconseguir l'increment necessari en la capacitat: l'augment de l'eficiència espectral a través de, per exemple, l'ús de tecnologies MIMO massives, la utilització de majors porcions de l'espectre i la densificació mitjançant el desplegament de més estacions base per àrea. Aquesta Tesi aborda la densificació com a principal mecanisme que permetrà la connectivitat de banda ampla i universal requerida en la 5G, centrant-se en l' estudi de les xarxes ultra denses (UDNs). Concretament, el conjunt de tecnologies que poden dur a les UDNs a la seua màxima eficiència i prestacions és analitzat, incloent l'ús d'altes freqüències per a l'aprofitament de majors amplàries de banda, la utilització de MIMO massiu amb sistemes d'antenes distribuïdes i l'ús de tècniques distribuïdes de repartiment de recursos per a la coordinació de la interferència. En primer lloc, aquesta Tesi analitza si existeix un límit fonamental en les prestacions en relació a la densificació. Per això, les prestacions de les UDNs s'avaluen utilitzant un model analític unidimensional amb estacions base equidistants, en les quals la distància entre estacions base es redueix fins assolir el límit de densificació quan aquesta distància s'aproxima a 0. Les taxes assolibles en xarxes amb diferents distàncies entre estacions base s'analitzen considerant diferents nivells de potència i varis graus de cooperació entre cel·les. A més, el comportament de les UDNs s'estudia conjuntament amb l'ús massiu d'antenes i la utilització de majors amplàries de banda. Més concretament, les prestacions de certes tècniques híbrides MIMO de precodificació i beamforming s'examinen en la banda mil·limètrica. D'una banda, els esquemes de beamforming aplicats a estacions base amb arquitectures híbrides és analitzat amb disponibilitat limitada de cadenes de radiofreqüència a un escenari urbà dens. D'altra banda, s'avaluen les prestacions de certs esquemes de precodificació híbrida en escenaris d'interior, utilitzant diferents estratègies de desplegament i centrant l'atenció en els sistemes d' antenes distribuïdes (DAS). A més, es proposa un algoritme de precodificació híbrida distribuïda per a DAS, i s'avaluen i comparen les seues prestacions amb les de altres algoritmes. Per últim, s'investiga l'impacte de les limitacions pràctiques i altres deficiències introduïdes per l'ús de dispositius no ideals en les prestacions de tots els esquemes anteriors. Finalment, l' estudi de les UDNs es completa amb l'anàlisi de la seua principal limitació, el nivell creixent d'interferència entre cel·les. Per tractar aquest problema, es proposa un algoritme de control d'interferències basat en la partició de recursos. Les prestacions de l'algoritme proposat s'avaluen i comparen amb les d'altres tècniques d'assignació de recursos. Una vegada completat aquest estudi, es pot afirmar que les UDNs tenen un gran potencial per aconseguir els ambiciosos requeriments plantejats per a la 5G. Tanmateix, sense l'ús conjunt de majors amplàries de banda, apropiades tècniques de control de la interferència i l'ús massiu d'antenes, les UDNs poden convertir-se en seriosos obstacles per als operadors mòbils. Els resultats de l'avaluació de prestacions d' aquestes tecnologies confirmen el gran augment de la capacitat de les xarxes obtingut mitjançant l'ús massiu d'antenes i la introducci
Giménez Colás, S. (2017). Ultra Dense Networks Deployment for beyond 2020 Technologies [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/86204
TESIS

Ce mémoire propose une stratégie de contrôle sans commutation d’algorithme pour un système hybride constituée d’une pile à combustible comme source principale et d’un pack de supercondensateurs comme source auxiliaire. Trois structures de système hybride ont été étudiées. Après avoir évoqué les différentes structures des systèmes hybrides électriques et des techniques utilisées pour les contrôler, deux approches sont traitées. La première est basée sur la notion de platitude permettant d’assurer la gestion des flots d’énergie dans une source hybride et plus généralement dans un système multi sources/multi charges. La stratégie proposée repose sur la génération d’un modèle d’ordre réduit du système et la gestion des flots d’énergie via des trajectoires de référence de certaines grandeurs énergétiques du système. L’impact de ce mode de contrôle sur le dimensionnement des éléments passifs (inductances, condensateurs) de la source hybride a été expliqué. Dans la deuxième stratégie, l’énergie totale stockée dans les hacheurs est prise en compte dans l’élaboration de la commande du système multi sources/multi charges en utilisant une linéarisation entrée/sortie sur les convertisseurs des charges. Un observateur non linéaire a été proposé pour estimer la variation de la caractéristique statique de pile à combustible et permet de garantir un fonctionnement optimal du système hybride. Les architectures de puissance et les modes de commande proposés ont été validés par des résultats simulés et/ou expérimentaux
This work deals with a nonlinear control strategy of an electrical hybrid system which is composed of a fuel cell as the main source and a supercapacitor bank as the auxiliary source. Any algorithm commutation is not used in the proposed control strategy whereas the system works in different operating modes. After a review of various structures of the electrical hybrid systems and different control methods of these systems, two new approaches are developed. The first one is flatness-based method to ensure the energy management in the proposed hybrid systems and generally in a multi source / multi loads system. The proposed strategy is based on generation of a reduced-order model of the system. The energy management is carried out through the reference trajectories of the stored electrostatic energy of the system. The effect of the proposed control method on design of the system components (inductors and capacitors) is explained. In the second approach, the total energy stored in the choppers is taken into account to control the load converters of a multi-source/multi load system by use of the input/output linearization method. A nonlinear observer is proposed to estimate the variation of voltage-power output characteristic of the fuel cell which leads to an optimal performance of the hybrid system. The simulation and experimental results prove validity of the proposed control strategy

碩士
國立臺北大學
資源管理研究所
90
The “Ecological Footprint” which was proposed by Wackernagel and Rees in 1996 is viewed as an index of sustainability and it means the area of land and water required for resource provision and environmental assimilation in order to support the final consumption of a defined human population. The ecological footprint (EF) provides an evaluation regarding the dependence of humanity on the ecosystem and then justifies whether the human population survives within the carrying capacity of a defined territory. This research attempted to release one of the assumptions in the EF calculation- the current harvest practices are sustainable. Using agricultural footprint as an example, this research obtained the picture of sustainable yield of paddy rice based on statistics and relevant literature. With regard to the EF calculation, this research adopted hybrid input-output analysis in order to take into account the raw material embodied in the imported and exported manufactured products. The contribution of this research is to make the EF calculation more reasonable such that the results can reveal the extent to which the human consumption depends on ecological systems from the perspective of sustainable yield. The results show that the area of farmland required by the Taiwan residents is larger when the assumption of current sustainable yield is released. This justifies the necessity and importance of examining whether the current harvest is sustainable in the EF calculation.

碩士
國立成功大學
電機工程學系碩博士班
101
A modified nonlinear autoregressive moving average with exogenous inputs (NARMAX) model-based state-space self-tuner with fault tolerance is proposed in this thesis for unknown nonlinear stochastic hybrid systems with a direct transmission matrix from input to output. Through the off-line observer/Kalman filter identification method, one has a good initial guess of modified NARMAX model to reduce the on-line system identification process time. Then, based on the modified NARMAX-based system identification, a corresponding adaptive digital control scheme is presented for the unknown continuous-time nonlinear system, with an input-output direct transmission term, which also has measurement and system noises and inaccessible system states. Besides, an effective state space self-turner with fault tolerance scheme is presented for the unknown multivariable stochastic system. A quantitative criterion is suggested by comparing the innovation process error estimated by the Kalman filter estimation algorithm, so that a weighting matrix resetting technique by adjusting and resetting the covariance matrices of parameter estimate obtained by the Kalman filter estimation algorithm is utilized to achieve the parameter estimation for faulty system recovery. Finally, applying the proposed anti-windup scheme according to these models establishes decentralized trajectory trackers for unknown interconnected large-scale systems with input constraints and state delay. The illustrative example is given to demonstrate the effectiveness of the proposed method.

碩士
中原大學
土木工程研究所
100
Traditionally, most studies used two-stage approach to solve block layout problem with I/O points design. In order to make planning results more practical and measure distance between facilities more precisely, this thesis integrates block layout problem and I/O points design using a contour distance metric. In this thesis, ant colony optimization (ACO) and clonal selection algorithm (CSA) are combined and a hybrid ant colony algorithm (HACO) is proposed to solve unequal-area facility layout problem with I/O points design. Operations of CSA are embedded in the ACO to improve the solution quality of initial ant solutions and increase differences among ant solutions, so search capability of HACO is enhanced. Several international benchmark problems are used to test the algorithm efficiency of HACO. Compared with preview researches, HACO can obtain the close or better solutions.

碩士
國立成功大學
環境工程學系碩博士班
99
Rapid industrialization and population growth have increased the rate of depletion of various scarce natural resources, such as freshwater, forest, and oil. The depletion of natural freshwater is an issue of particular importance because freshwater is indispensable both for human well-being and for ecological systems. The development of water use (WU) inventories for many human activities has thus received increasing attention. For example, the International Organization for Standardization (ISO) is working on the establishment of a standard for the assessment of a water footprint of a product. And, compared to other environmental impact categories such as greenhouse gas emissions, freshwater consumption is relatively new and no consistent standard. Therefore, it is difficult for industries to conduct a water footprint study on their products in a consistent and comprehensive manner. In this study, a comprehensive business water footprint (BWF) framework for companies is developed. Using this framework, companies can combine their financial data and direct water used with the national economic input-output (IO) table to construct environmentally extended IO table to evaluate their BWF. A Taiwanese crystalline silicon solar cells company is taken as a case study to verify this framework. The results show that the company had a BWF of 26.4 billion L for its production of crystalline silicon solar cells in 2006. The indirect (upstream supply chain) BWF associated with the silicon materials, such as ingots and wafers, had the largest contribution. The IO table is compiled every five years (ex. the most recent update is made for 2006); therefore, there is no input-output table available in other years (such as 2008). Using the methodology described in the framework, the BWFs for companies were calculated. Under the proposed framework, product water footprints (PWFs) can also be estimated from the BWF for company. The framework provides a simple yet comprehensive means of calculating BWFs in a company, especially where related data are not widely available or accessible for a process-based product-specific water footprint.

Tese de doutoramento em Sistemas de Energia Sustentável, apresentada ao Departamento de Engenharia Mecânica da Faculdade de Ciências e Tecnologia da Universidade de Coimbra
As relações entre o consumo de energia, o crescimento econômico e os impactos ambientais são determinantes para o processo de formulação de políticas. A Análise Input-Output (AIO) tem sido usada para estudar inter/intra-relações entre os diferentes setores económicos, bem como estendida para a análise dos sistemas energético e ambiental. Modelos de Programação Linear Multi-objetivo (PLMO) utilizando a estrutura Input-Output (IO) também vêm sendo desenvolvidos para estudar os compromissos (trade-offs) entre os sistemas económico, energético e ambiental. Os modelos IO-PLMO são capazes de captar a complexidade e natureza conflituosa dos problemas do mundo real, permitindo a obtenção de um informação relevante que não seria possível conseguir com uma aplicação separada de ambas as metodologias. Esta combinação de modelos de PLMO e AIO desempenha um papel complementar na compreensão das interações entre os sistemas económicos e energéticos, e os correspondentes impactos ambientais, oferecendo um quadro consistente para avaliar os efeitos de políticas distintas sobre estes sistemas. Um modelo de PLMO baseado em uma estrutura IO híbrida com unidades monetárias e físicas é apresentado nesta tese. Este modelo tem como objetivo avaliar os trade-offs entre objectivos económicos, energéticos, ambientais e sociais no sistema económico brasileiro. Primeiramente, as tabelas IO para o Brasil são reorganizadas para incluir o Balanço Energético Nacional, criando uma estrutura IO híbrida com unidades físicas e monetárias. Este quadro é estendido para avaliar diferentes Gases de Efeito Estufa (GEE), que são então agregados em um único indicador (CO2eq), e o nível de emprego. Duas versões do modelo de PLMO são definidas: uma versão com valores determinísticos e outra em que a programação intervalar é usada para tratar a incerteza em alguns coeficientes do modelo. A versão determinística do modelo tem 443 variáveis (incluindo a produção dos setores e produtos energéticos e várias variáveis econômicas) e um conjunto de 490 restrições (definidoras e limitadoras). As funções objetivo consideradas são a maximização dos níveis do PIB e do emprego, bem como a minimização do consumo de energia e emissões de GEE. Os métodos interativos STEM e o TRIMAP são aplicados para tratar a versão determinística do modelo, permitindo a exploração de soluções de compromisso de acordo com as informações de preferência emitidas pelo decisor. O STEM permitiu um processo de busca de solução interativa através da redução da região admissível baseada na especificação de quantidades de relação para as função objetivo com valores já satisfatórios, fornecendo informações sobre os trade-offs entre os objetivos conflitantes em diferentes regiões da região admissível. O método interativo TRIMAP ofereceu uma pesquisa flexível de soluções através de um ambiente gráfico amigável baseada na visualização das regiões de indiferença associadas a soluções vértices eficientes no diagrama paramétrico, permitindo uma exploração progressiva e seletiva de soluções de compromisso. Ambos os métodos forneceram informações de apoio à decisão relevante para um decisor hipotético, ajudando-o na compreensão dos trade-offs em jogo e na identificação de soluções de compromisso para os modelos de PLMO. A versão intervalar do modelo IO-PLMO híbrido, que inclui 518 restrições e 473 variáveis, é analisada com uma abordagem interativa que envolve a formulação de modelos determinísticos substitutos para o modelo de PLMO intervalar (baseado na minimização do pior desvio possível das funções objetivo intervalar em relação as suas soluções ideais intervalares correspondentes) e de uma fase interativa em que a sinergia entre o algoritmo (prestando informações ao decisor) e o decisor (processando as informações e fornecendo orientações para o processo de cálculo) facilitando um processo de pesquisa com base na proximidade dos valores da solução intervalar em relação à solução intervalar ideal. Perspectivas otimistas e pessimistas foram consideradas a fim de procurar soluções com diferentes alternativas de decisão. Finalmente, os impactos de diferentes processos de cultivo de cana de açúcar e de produção de bioetanol de primeira (1G) e segunda geração (2G) sobre o sistema económico brasileiro e a oferta doméstica de bioetanol em cenários prospetivos foram analisados com a versão determinística do modelo de PLMO. Coeficientes técnicos para diferentes configurações de usinas de bioetanol de produção combinada de 1G + 2G e sistemas de cultivo da cana foram estimados e introduzidos na matriz de coeficientes técnicos. As funções objetivo foram a maximização do PIB e do emprego, e a minimização do consumo de energia e das emissões totais de GEE. A maximização da produção total de bioetanol no país em cada cenário também foi considerado. Soluções não-dominadas foram calculadas através da minimização da distância de Tchebycheff para a solução ideal em cada cenário. A extensão da análise envolvendo todo o sistema económico veio complementar o desenho e a análise baseada em processos potenciais de produção de bioetanol, contribuindo para identificar efeitos indiretos que podem contrabalançar os benefícios. Esta tese fornece modelos, metodologias e conhecimento baseado na avaliação das soluções obtidas com diferentes processos de cálculo, que é essencial para o desenvolvimento de abordagens integradas para a análise prospetiva dos trade-offs económico-energético-ambiental em um país e em um setor específico.
The study and assessment of the relationships between energy consumption, economic growth and environmental impacts is determinant for the policy making process. Input-Output Analysis (IOA) has been used to study inter/intra-relationships among different sectors in the economic system and extended to account for energy and environmental impacts. Multi-objective Linear Programming (MOLP) models using the Input-Output (IO) framework has also been developed to study economic-energy-environment trade-offs. The IO-MOLP models are able to capture the complexity and conflicting nature of real world problems allowing obtaining insightful information that would not be possible to achieve with a separated application of both methodologies. This combination of multi-objective models with IOA plays a supplementary role in understanding the interactions between the economic and energy systems, and the corresponding impacts on the environment, offering a consistent framework for assessing the effects of distinct policies. A MOLP model based on a hybrid IO framework with monetary and physical units is presented in this thesis. This model aims at assessing the trade-offs between economic, energy, environmental and social objectives in the Brazilian economic system. Firstly, the IO tables for Brazil are reorganized to include the National Energy Balance, creating a hybrid IO framework. This framework is extended to assess different Greenhouse Gas (GHG) emissions, which are then aggregated into a single indicator (CO2eq), and the employment level. Two versions of the MOLP model are defined: a version with deterministic values and another one in which interval programming techniques are used for tackling the uncertainty in some coefficients of the model. The deterministic version of the model has 443 variables (including the total output of sectors and energy commodities and several economic variables) and a set of 490 (defining and bound) constraints. The objective functions considered are the maximization of GDP and employment levels, and the minimization of energy consumption and GHG emissions. The STEM and TRIMAP interactive methods are applied to the deterministic version of the model, allowing the exploration of compromise solutions according to the preference information issued by the decision maker (DM). STEM allows an interactive solution search process through the reduction of the feasible region based on the specification of relaxation quantities for the already satisfactory objective functions, thus providing information about the trade-offs that are at stake between the competing objectives in different regions of the search space. The TRIMAP interactive method offers a flexible search for solutions in a user-friendly graphical environment based on the display of indifference regions associated with vertex efficient solutions on the parametric diagram, allowing a progressive and selective exploration of compromise solutions. Both methods have provided relevant decision support information to a hypothetical DM assisting him/her in understanding the trade-offs at stake and identifying compromise solutions to the MOLP models. The interval version of the hybrid IO-MOLP model, which includes 518 constraints and 473 variables, is analyzed with an interactive approach involving the formulation of surrogate deterministic models for the interval MOLP model (based on the minimization of the worst possible deviation of the interval objective functions to their corresponding interval ideal solutions) and an interactive phase in which a synergy between the algorithm (providing information to the DM) and the DM (processing the information and providing guidelines for the computation process). This approach has allowed a reference point searching process based on the closeness of the values of the interval solution in relation to the ideal interval solution. Optimistic and pessimistic perspectives have been considered in order to search for solutions using different decision alternatives. Finally, impacts of different sugarcane cultivation and first-generation (1G) and second-generation (2G) bioethanol production processes on the Brazilian economic system and domestic bioethanol supply in prospective scenarios are analyzed with the deterministic version of the MOLP model. Technical coefficients for different configurations of combined 1G+2G bioethanol plants and sugarcane cultivation are estimated and introduced into the Brazilian technical coefficient matrix. The objective functions are the maximization of GDP and employment level, and the minimization of total energy consumption and GHG emissions. The maximization of the total bioethanol production in the country in each scenario is also considered. Non-dominated solutions are computed by minimizing a Tchebycheff distance to the ideal solution in each scenario. Extending the analysis to the whole economic system has complemented the process design and process-based analysis of prospective bioethanol production, contributing to identify indirect effects that can counterbalance the benefits. This thesis provides models, methodologies and knowledge based on the assessment of the solutions obtained in the different computation processes that is essential for the development of integrated approaches for prospective analysis of economic-energy-environmental trade-offs in a country and a specific sector.
FCT - SFRH/BD/42960/2008

IEEE 802.11n Wireless Local Area Networks (WLANs) employ Multiple-Input-Multiple-Output (MIMO), which significantly boosts the raw data rate at the Physical layer (PHY). But the potential of enhancing Medium Access Control (MAC) layer efficiencies by MIMO is still in its early stage and is the aim of the research in this thesis. Many existing works in this field mainly employ distributed MIMO spatial multiplexing/Multi-User Detection (MUD) technique and stream sharing to enable multiple simultaneous transmissions. Most works require synchronization among multiple transmissions, split the channel, and aim for single-hop networks. In this thesis, a novel Hybrid Carrier Sense (HCS) framework is proposed, mainly at the MAC layer to exploit the power of MIMO. HCS senses the channel availability jointly by the virtual carrier sense and physical carrier sense. HCS does not require synchronization among nodes; each node independently and locally determines when to start its transmission. HCS not only shares the channel, but also exploits the bi-directional handshakes of the wireless transmissions and increases the number of simultaneous stream transmissions. For a network with M antennas in each node, HCS can accommodate 2x(M-1) streams instead of M streams achieved by all other existing works. Moreover, HCS is aimed for multi-hop wireless ad hoc networks, in which the hidden terminal, exposed terminal, and deafness problems greatly degrade network performance. The HCS framework incorporates solutions to these problems. HCS is implemented in an NS2 network simulator and the performance evaluation shows that HCS significantly outperforms MIMO-enabled IEEE 802.11 (in which MIMO is only used for enhancing the raw data rate in the physical layer), resulting in higher aggregate throughput, packet delivery ratio and fairness in multi-hop wireless ad hoc networks. The HCS framework will be in wide use in the future generation of wireless networks and opens up more research possibilities. Some ideas in the HCS framework can be applied not only for MIMO, but also for many other techniques surveyed in this thesis; or we may combine them with HCS to further boost the network performance.
Thesis (Ph.D, Electrical & Computer Engineering) -- Queen's University, 2013-10-15 21:46:15.983

The main goal of this dissertation thesis is to quantify the environmental burden associated with household consumption in the Czech Republic. Emissions of three groups of gases were selected to express the burden on the environment, namely emissions causing climate change, acidification and the formation of photosmog. These emissions arise from the consumption of fuels in households, and they are usually referred to as direct household emissions. Or they arise in the production and distribution of goods and services, and they are usually referred to as indirect household emissions. Although indirect emissions come from combustion in energy production and other industrial processes and agricultural activities, not from households, they are a consequence of household demand for final products. Therefore, such emissions are considered to be a consequence of household consumption. The resulting emission values are given for the average household and households divided into expenditure deciles. Emissions increase with expenditure per household member in total consumption and in individual consumption groups across all deciles. In the case of climate change-related emissions, more than half come from heating (41%) and electricity (21%). For acidification, heating (31%) and food (24%) are the dominant...

This thesis exploits index modulation techniques to design energy- and spectrum-efficient system models to operate in future wireless networks. In this respect, index modulation techniques are studied considering two different media: mapping the information onto the frequency indices of multicarrier systems, and onto the antenna array indices of a platform that comprises multiple antennas. The index modulation techniques in wideband communication scenarios considering orthogonal and generalized frequency division multiplexing systems are studied first. Single cell multiuser networks are considered while developing the system models that exploit the index modulation on the subcarriers of the multicarrier systems. Instead of actively modulating all the subcarriers, a subset is selected according to the index modulation bits. As a result, there are subcarriers that remain idle during the data transmission phase and the activation pattern of the subcarriers convey additional information. The transceivers for the orthogonal and generalized frequency division multiplexing systems with index modulation are both designed considering the uplink and downlink transmission phases with a linear combiner and precoder in order to reduce the system complexity. In the developed system models, channel state information is required only at the base station. The linear combiner is designed adopting minimum mean square error method to mitigate the inter-user-interference. The proposed system models offer a flexible design as the parameters are independent of each other. The parameters can be adjusted to design the system in favor of the energy efficiency, spectrum efficiency, peak-to-average power ratio, or error performance. Then, the index modulation techniques are studied for large-scale multiple-input multiple-output systems that operate in millimeter wave bands. In order to overcome the drawbacks of transmission in millimeter wave frequencies, channel properties should be taken in to account while envisaging the wireless communication network. The large-scale multiple-input multiple-output systems increase the degrees of freedom in the spatial domain. This feature can be exploited to focus the transmit power directly onto the intended receiver terminal to cope with the severe path-loss. However, scaling up the number of hardware elements results in excessive power consumption. Hybrid architectures provide a remedy by shifting a part of the signal processing to the analog domain. In this way, the number of bulky and high power consuming hardware elements can be reduced. However, there will be a performance degradation as a consequence of renouncing the fully digital signal processing. Index modulation techniques can be combined with the hybrid system architecture to compensate the loss in spectrum efficiency to further increase the data rates. A user terminal architecture is designed that employs analog beamforming together with spatial modulation where a part of the information bits is mapped onto the indices of the antenna arrays. The system is comprised a switching stage that allocates the user terminal antennas on the phase shifter groups to minimize the spatial correlation, and a phase shifting stage that maximizes the beamforming gain to combat the path-loss. A computationally efficient optimization algorithm is developed to configure the system. The flexibility of the architecture enables optimization of the hybrid transceiver at any signal-to-noise ratio values. A base station is designed in which hybrid beamforming together with spatial modulation is employed. The analog beamformer is designed to point the transmit beam only in the direction of the intended user terminal to mitigate leakage of the transmit power to other directions. The analog beamformer to transmit the signal is chosen based on the spatial modulation bits. The digital precoder is designed to eliminate the inter-user-interference by exploiting the zero-forcing method. The base station computes the hybrid beamformers and the digital combiners, and only feeds back the digital combiners of each antenna array-user pair to the related user terminals. Thus, a low complexity user architecture is sufficient to achieve a higher performance. The developed optimization framework for the energy efficiency jointly optimizes the number of served users and the total transmit power by utilizing the derived upper bound of the achievable rate. The proposed transceiver architectures provide a more energy-efficient system model compared to the hybrid systems in which the spatial modulation technique is not exploited. This thesis develops low-complexity system models that operate in narrowband and wideband channel environments to meet the energy and spectrum efficiency demands of future wireless networks. It is corroborated in the thesis that adopting index modulation techniques both in the systems improves the system performance in various aspects.:1 Introduction 1 1.1 Motivation 1 1.2 Overview and Contribution 2 1.3 Outline 9 2 Preliminaries and Fundamentals 13 2.1 Multicarrier Systems 13 2.2 Large-scale Multiple Input Multiple Output Systems 17 2.3 Index Modulation Techniques 19 2.4 Single Cell Multiuser Networks 22 3 Multicarrier Systems with Index Modulation 27 3.1 Orthogonal Frequency Division Multiplexing 28 3.2 Generalized Frequency Division Multiplexing 40 3.3 Summary 52 4 Hybrid Beamforming with Spatial Modulation 55 4.1 Uplink Transmission 56 4.2 Downlink Transmission 74 4.3 Summary 106 5 Conclusion and Outlook 109 5.1 Conclusion 109 5.2 Outlook 111 A Quantization Error Derivations 113 B On the Achievable Rate of Gaussian Mixtures 115 B.1 The Conditional Density Function 115 B.2 Tight Bounds on the Differential Entropy 116 B.3 A Bound on the Achievable Rate 118 C Multiuser MIMO Downlink without Spatial Modulation 121 Bibliography

This thesis presents a parallel-series two-bridge DC/DC converter topology with the ability to operate with ZVS over a wide input and load range. The intended application is power conditioning systems (PCS) of photovoltaic (PV) arrays used in hybrid renewable energy system architectures. The proposed topology provides two degrees of freedom which allows the PV-PCS to regulate the DC-link voltage, while tracking the maximum power point (MPP) of the PV array. This topology distributes the main power into two bridges and the phase-shift between the two bridges and provides another degree of freedom for the PCS to track the MPP. The proposed topology is also able to achieve soft-switching over a wide range. The power conditioning system shows a modular structure to efficiently transfer the power to the load as the main power is divided between two bridges. In addition, the proposed control scheme provides complete decoupling between the input side controller from the output side controller in order to perform MPPT and regulate the the DC-link voltage simultaneously. A 2kW Experimental prototype has been provided to validate the feasibility and performance of the converter. Experimental results prove that the converter is able to regulate the DC-link voltage and track the maximum power extracted from the PV array simultaneously.
Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2012-04-18 19:51:43.405

Due to the highly-varying wireless channels over time, frequency, and space domains, statistical QoS provisioning, instead of deterministic QoS guarantees, has become a recognized feature in the next-generation wireless networks. In this dissertation, we study the adaptive wireless resource allocation problems for statistical QoS provisioning, such as guaranteeing the specified delay-bound violation probability, upper-bounding the average loss-rate, optimizing the average goodput/throughput, etc., in several typical types of mobile wireless networks. In the first part of this dissertation, we study the statistical QoS provisioning for mobile multicast through the adaptive resource allocations, where different multicast receivers attempt to receive the common messages from a single base-station sender over broadcast fading channels. Because of the heterogeneous fading across different multicast receivers, both instantaneously and statistically, how to design the efficient adaptive rate control and resource allocation for wireless multicast is a widely cited open problem. We first study the time-sharing based goodput-optimization problem for non-realtime multicast services. Then, to more comprehensively characterize the QoS provisioning problems for mobile multicast with diverse QoS requirements, we further integrate the statistical delay-QoS control techniques — effective capacity theory, statistical loss-rate control, and information theory to propose a QoS-driven optimization framework. Applying this framework and solving for the corresponding optimization problem, we identify the optimal tradeoff among statistical delay-QoS requirements, sustainable traffic load, and the average loss rate through the adaptive resource allocations and queue management. Furthermore, we study the adaptive resource allocation problems for multi-layer video multicast to satisfy diverse statistical delay and loss QoS requirements over different video layers. In addition, we derive the efficient adaptive erasure-correction coding scheme for the packet-level multicast, where the erasure-correction code is dynamically constructed based on multicast receivers’ packet-loss statuses, to achieve high error-control efficiency in mobile multicast networks. In the second part of this dissertation, we design the adaptive resource allocation schemes for QoS provisioning in unicast based wireless networks, with emphasis on statistical delay-QoS guarantees. First, we develop the QoS-driven time-slot and power allocation schemes for multi-user downlink transmissions (with independent messages) in cellular networks to maximize the delay-QoS-constrained sum system throughput. Second, we propose the delay-QoS-aware base-station selection schemes in distributed multiple-input-multiple-output systems. Third, we study the queueaware spectrum sensing in cognitive radio networks for statistical delay-QoS provisioning. Analyses and simulations are presented to show the advantages of our proposed schemes and the impact of delay-QoS requirements on adaptive resource allocations in various environments.