In this research we attempted several modifications to microstrip ring/loop antennas to design multi-frequency antennas through systematic approaches. Such multi-frequency antennas can be useful while building compact terminals to operate at multiple wireless standards. One of the primary contributions was the use of a capacitive feed arrangement that enables simultaneous excitation of multiple concentric rings from an underlying transmission line. The combined antenna operates in the same resonant bands as the individual rings and avoids some of the bands at harmonic frequencies. A similar feeding arrangement is used to obtain dual band characteristics from just one ring, with improved bandwidth. This is made possible by widening two adjacent sides of a square ring antenna symmetrically, and attaching an open stub to the inner edge of the side opposite to the feed line. Use of fractal segments replacing the side with the stub also results in a similar performance. Use of fractal geometries has been widely associated with multi-functional antennas. It has been observed from the parametric studies that, the ratio of the resonant frequencies can range from 1.5 to 2.0. This shows some flexibility in systematically designing dual-band antennas with a desired pair of resonant frequencies. An analysis technique based on multi-port network modeling (MNM) has been proposed to accurately predict the input characteristics of these antennas. This approach can make use of the ordered nature of fractal geometries to simplify computations. Several prototype antennas have been fabricated and tested successfully to validate simulation and analytical results.

This thesis deals with the issue of power flow analysis in a medium voltage (22kV) distribution network with a focus on the influence of distributed energy generation recources. At first the issue of operation of distributed energy resources and their reverse effects on the distribution system is presented in the thesis. Furtherly there are described their operational conditions from the legislation point of view. The part dealing with calculation compares two network configurations in terms of power quality and how the power quality is impacted by distributed energy resources. The attention is given to voltage conditions, short-circuit power, power conditions, losses and flicker. The first configuration corresponds to the real situation in the network, the other one is describing the changes after the new 110/22 kV substation implementation to the power supply area and the overal change of network configuration. The network model and run simulation is done using the E-Vlivy program.

This diploma thesis analyzes the PLC communications in various scenarios. The first part of the thesis describes the principle of narrowband and broadband communication and the analysis of electrical lines. The next part describes the NS-3 framework, simulation scenarios for establishment the effect of branches and other parameters on the baud rate. The last part determines the minimum number of repeaters and their location on the extended topology.

In this paper a new equivalent circuit is presented which describes the dynamics of a prototype micro-gyro sensor. The concept takes advantage of the principles employed in vibratory gyro sensors and the ductile attributes of GalFeNOL to target high sensitivity and shock tolerance. The sensor is designed as a tuning fork structure. A GalFeNOL patch attached to the y-z surface of the drive prong causes both prongs to bending the x-z plane (about the y axis) and a patch attached to the x-z surface of the sensing prong detects Coriolis-force induced bending in the y-z plane (about the x axis). A permanent magnet is bonded on top of each prong to give bias magnetic fields. A solenoid coil surrounding the drive prong is used to produce bending in the x-z plane of both prongs. The sensing prong is surrounded by a solenoid coil with N turns in which a voltage proportional to the time rate of change of magnetic flux is induced. The equivalent circuit enables the efficient modeling of a gyro sensor and an electromechanical behavioral simulation using the circuit simulator SPICE. The prongs are modeled as wave guiding bending beams which are coupled to the electromagnetic solenoid coil transducer. In contrast to known network approaches, the proposed equivalent circuit is the first tuning fork model, which takes full account of the fictitious force in a constant rotating frame of reference. The Coriolis force as well as the centrifugal force on a concentrated mass are considered.

As opposed to public transit agencies' well-developed data generation capabilities, their utilization of their data is often overlooked. This study will tap into the potential of using the GTFS data format from an agency stakeholder perspective to assess transit performance. This format holds data for scheduled transit services, including real-time updates and network organization. The broad adaptation of GTFS by transit agencies (1240 transit networks in 672 locations worldwide) has made it a de-facto standard, making products built on top of it inherently scalable and could potentially be deployed in networks all over the world. The purpose of this thesis is two-fold; firstly, to explore how specific vulnerability features of nodes in a public transit network can be assessed using graph mining algorithms. Secondly, to develop a pipeline for aggregating GTFS data and fit it into a flow network model. The results include a data-driven framework for vulnerability characterization, a method for fitting GTFS data in a flow network model, and lastly, a definition for reduced flow capacity in a public transit context. Additionally, the results are presented in the setting of Uppsala's network (UL) and visualized with a web-based tool.

Fernkälte bietet das Potenzial, wirtschaftlich und ökologisch vorteilhaft zur Deckung des stetig zunehmenden Klimakältebedarfs beizutragen. Im Rahmen dieser Arbeit wurde ein dynamisches thermohydraulisches Netzmodell „ISENA“ entwickelt, mit dem während der Planung und des Betriebs von Fernkältesystemen auftretende Fragen, beispielsweise in Bezug auf Wirtschaftlichkeit und Energieeffizienz, beantwortet werden können. Das Netzmodell setzt sich aus einem quasistationären hydraulischen Modell und einem instationären thermischen Modell zusammen, das auf der Verfolgung von Wasserpfropfen durch das gesamte Netz basiert (Lagrange-Ansatz). Mit diesem Modellierungsansatz können numerische Fehler sowie Bilanzungenauigkeiten vermieden werden, sodass sich eine höhere Ergebnisgüte im Vergleich zu bisher bekannten Netzmodellen erreichen lässt. Ebenfalls neu entwickelt wurde das Teilmodell zur Abbildung der Wärmeströme über die Wände unterirdischer Rohrpaare (Kälteverluste und -gewinne). Dieses Modell erlaubt die Bestimmung der instationären Rohrwand-Wärmeströme für wärmegedämmte unterirdische Rohrpaare, Rohrpaare mit gedämmtem Vor- und ungedämmtem Rücklauf sowie ungedämmte Rohrpaare. Anhand von Validierungs- und Verifikationsrechnungen wird gezeigt, dass ISENA verlässliche Ergebnisse liefert und für die praktische Anwendung geeignet ist. Abschließende Beispielrechnungen geben einen Einblick in die Untersuchungsmöglichkeiten, die das neue Modell bietet – unter anderem im Hinblick auf den Vergleich von Pumpenregelungsvarianten, den Einfluss von Rohrdämmung und Erdreicheigenschaften auf Kälteverluste und -gewinne sowie die Einbindung von Hochtemperatur-Kälteverbrauchern in den Netzrücklauf.:1 Einleitung 1.1 Situation 1.2 Aufbau und Betrieb von Fernkältesystemen 1.3 Netzmodellierung und -simulation 1.4 Präzisierte Aufgabenstellung 2 Stand der Wissenschaft und Technik 2.1 Begriffe und Definitionen 2.2 Rohrleitungen 2.2.1 Technik 2.2.2 Modellierung 2.3 Peripherie 2.3.1 Kälteabnehmer 2.3.2 Durchfluss- und Differenzdruckregler 2.3.3 Erzeuger 2.3.4 Pumpen 2.3.5 Bypass 2.4 Netz 2.4.1 Netzstruktur 2.4.2 Hydraulisches Verhalten 2.4.3 Thermisches Verhalten 2.4.4 Beispielsysteme 2.5 Zwischenfazit 3 Modellerstellung 3.1 Grundlagen 3.2 Rohrleitungen 3.2.1 Hydraulisches Rohrmodell 3.2.2 Modellierung des Rohrwand-Wärmestroms 3.2.3 Thermisches Rohrmodell 3.3 Peripherie 3.3.1 Kälteabnehmer 3.3.2 Durchfluss- und Differenzdruckregler 3.3.3 Erzeuger 3.3.4 Pumpen 3.3.5 Bypass 3.3.6 Rücklaufabnehmer 3.4 Netz 3.4.1 Hydraulisches Modell 3.4.2 Thermisches Modell 3.4.3 Gesamtmodell 3.5 Programmtechnische Umsetzung 4 Modellvalidierung und -verifikation 4.1 Vorbetrachtungen 4.2 Kernmechanismen 4.2.1 Hydraulik 4.2.2 Konvektiver Energietransport 4.2.3 Wärmeübertragung über die Rohrwand 4.2.4 Wärmezufuhr bei Kälteabnehmern 4.3 Schlussfolgerungen 5 Beispielsimulationen 5.1 Vorgaben 5.2 Referenzfall 5.3 Varianten 5.3.1 Pumpenregelung 5.3.2 Netz-Vorlauftemperatur 5.3.3 Rohrgeometrie und Erdreicheigenschaften 5.3.4 Rücklaufabnehmer 6 Zusammenfassung und Ausblick Literaturverzeichnis Abbildungsverzeichnis Tabellenverzeichnis Anhang A Existierende Modelle A.1 Hydraulikberechnung mit Regelelementen A.2 Rohrwand-Wärmeströme A.3 Freie Konvektion bei Stillstand im Rohr B Numerisches Modell für Rohrwand-Wärmeströme B.1 Referenzmodell B.2 Bestimmung der Neipor-Parameter B.3 Tabellierte Neipor-Parameter C Modell ISENA C.1 Pfropfenteilung C.2 Programmtechnische Umsetzung C.3 Rohrklassen C.4 Stoffdaten / District cooling can provide economic and ecological benefits while supplying the increasing cooling demand for air conditioning. In the present thesis, a dynamic thermo-hydraulic model “ISENA” is presented which may be used in order to answer questions arising during design and operation of district cooling networks—e. g., that are related to economic and energy efficiency. The network model consists of a quasi-static hydraulic module and a transient thermal module being based on the tracking of water segments through the entire network (Lagrangian method). With this approach, numerical errors and inaccuracies in the balance of conserved quantities could be avoided, which eventually leads to a better reliability of the results as compared to that obtained from other network models. Additionally, a new sub-model has been developed for predicting the transient heat flux through the walls of buried pipes in order to model thermal gains and losses. This model covers un-insulated, insulated and combinations of insulated as well as un-insulated pipes. Calculations performed for the purpose of validation and verification are presented in order to demonstrate that ISENA provides reliable results and hence is suitable for practical applications. Finally, example simulations show the various possibilities provided by the new model—for example, concerning the comparison of different strategies for pump control, the influence of pipe insulation and soil properties on thermal gains and losses as well as the connection of buildings equipped with high temperature cooling systems to the return line of the network.:1 Einleitung 1.1 Situation 1.2 Aufbau und Betrieb von Fernkältesystemen 1.3 Netzmodellierung und -simulation 1.4 Präzisierte Aufgabenstellung 2 Stand der Wissenschaft und Technik 2.1 Begriffe und Definitionen 2.2 Rohrleitungen 2.2.1 Technik 2.2.2 Modellierung 2.3 Peripherie 2.3.1 Kälteabnehmer 2.3.2 Durchfluss- und Differenzdruckregler 2.3.3 Erzeuger 2.3.4 Pumpen 2.3.5 Bypass 2.4 Netz 2.4.1 Netzstruktur 2.4.2 Hydraulisches Verhalten 2.4.3 Thermisches Verhalten 2.4.4 Beispielsysteme 2.5 Zwischenfazit 3 Modellerstellung 3.1 Grundlagen 3.2 Rohrleitungen 3.2.1 Hydraulisches Rohrmodell 3.2.2 Modellierung des Rohrwand-Wärmestroms 3.2.3 Thermisches Rohrmodell 3.3 Peripherie 3.3.1 Kälteabnehmer 3.3.2 Durchfluss- und Differenzdruckregler 3.3.3 Erzeuger 3.3.4 Pumpen 3.3.5 Bypass 3.3.6 Rücklaufabnehmer 3.4 Netz 3.4.1 Hydraulisches Modell 3.4.2 Thermisches Modell 3.4.3 Gesamtmodell 3.5 Programmtechnische Umsetzung 4 Modellvalidierung und -verifikation 4.1 Vorbetrachtungen 4.2 Kernmechanismen 4.2.1 Hydraulik 4.2.2 Konvektiver Energietransport 4.2.3 Wärmeübertragung über die Rohrwand 4.2.4 Wärmezufuhr bei Kälteabnehmern 4.3 Schlussfolgerungen 5 Beispielsimulationen 5.1 Vorgaben 5.2 Referenzfall 5.3 Varianten 5.3.1 Pumpenregelung 5.3.2 Netz-Vorlauftemperatur 5.3.3 Rohrgeometrie und Erdreicheigenschaften 5.3.4 Rücklaufabnehmer 6 Zusammenfassung und Ausblick Literaturverzeichnis Abbildungsverzeichnis Tabellenverzeichnis Anhang A Existierende Modelle A.1 Hydraulikberechnung mit Regelelementen A.2 Rohrwand-Wärmeströme A.3 Freie Konvektion bei Stillstand im Rohr B Numerisches Modell für Rohrwand-Wärmeströme B.1 Referenzmodell B.2 Bestimmung der Neipor-Parameter B.3 Tabellierte Neipor-Parameter C Modell ISENA C.1 Pfropfenteilung C.2 Programmtechnische Umsetzung C.3 Rohrklassen C.4 Stoffdaten

[pt] Uma das características mais relevantes nos aglomerados de minério de ferro é a sua porosidade, que impacta fortemente no desempenho desses materiais nos processos siderúrgicos. O desempenho é diretamente dependente da existência de uma rede porosa que permite o fluxo de gases pelo interior desses aglomerados sem comprometer sua integridade física. Neste trabalho, amostras de diferentes tipos de aglomerados de minério de ferro foram caracterizadas com o auxílio de técnicas de microtomografia computadorizada de raios X (microCT), processamento digital de imagens e modelagem de rede de poros (PNM). Com isso, a influência da microestrutura desses aglomerados na variação da sua porosidade e permeabilidade foi avaliada. O uso de microCT permitiu uma visualização 3D da estrutura dos aglomerados, permitindo realizar uma análise da estrutura interna das amostras para a discriminação do espaço poroso. O pixel size ideal foi estipulado por meio de diversas capturas com resoluções diferentes. A PNM foi utilizada para realizar a simulação da permeabilidade absoluta das amostras, correlacionando com a porosidade, conectividade dos poros e diâmetro de poros e conexões. Foi realizada uma variação de mais ou menos 5 tons de cinza nos limiares de segmentação para estipular a sensibilidade do impacto desse parâmetro nos resultados da modelagem. Os dois aglomerados apresentaram porosidade parecida, em torno de 20 por cento. Os resultados para piores resoluções apresentaram uma inconsistência, em muitos casos não possuindo sequer permeabilidade. As imagens adquiridas com um tamanho de voxel de 2 micrômetros resultaram em cálculos consistentes de permeabilidade, em torno de 0,4 a 2,4 mD para os briquetes e 0,03 a 1,6 mD para as pelotas, sugerindo que os briquetes são levemente mais permeáveis. A variação do limiar de segmentação dos poros teve forte impacto nos resultados das modelagens, influenciando diretamente no valor do cálculo da permeabilidade absoluta. / [en] One of the most relevant features of iron ore agglomerates is their porosity, which strongly impacts the performance of these materials in steelmaking processes. Performance is directly dependent on the existence of a porous network that allows gas flow through the interior of these agglomerates without compromising their physical integrity. This study characterized samples of different iron ore agglomerates using X-ray microcomputed tomography (microCT), digital image processing, and pore network modeling (PNM). The influence of the microstructure of these agglomerates on the variation of their porosity and permeability was evaluated. MicroCT enabled a 3D visualization of the agglomerate structure, allowing for an analysis of the internal structure of the samples to discriminate the porous space. The ideal pixel size was determined through various captures at different resolutions. PNM was used to simulate the absolute permeability of the samples, correlating it with porosity, pore connectivity, and pore and connection diameter. A variation of more or less 5 gray tones in the segmentation thresholds was performed to determine the sensitivity of this parameter s impact on the modeling results. The two agglomerates had similar porosity of around 20 percent. The results for lower resolutions showed inconsistency, with many cases lacking permeability altogether. Images acquired with a pixel size of 2 micrometers resulted in consistent permeability calculations, ranging from 0.4 to 2.4 mD for briquettes and 0.03 to 1.6 mD for pellets, indicating that briquettes are slightly more permeable. The variation of pore segmentation threshold had a strong impact on the modeling results, directly influencing the value of the absolute permeability calculation.

Virtualisation is one of the underlying technologies that led to the success of cloud computing platforms (CCPs). The technology, along with other features such as multitenancy allows delivering of computing resources in the form of service through efficient sharing of physical resources. As these resources are provided through virtualisation, a robust agreement is outlined for both the quantity and quality-of-service (QoS) in a service level agreement (SLA) documents. QoS is one of the essential components of SLA, where performance is one of its primary aspects. As the technology is progressively maturing and receiving massive acceptance, researchers from industry and academia continue to carry out novel theoretical and practical studies of various essential aspects of CCPs with significant levels of success. This thesis starts with the assessment of the current level of knowledge in the literature of cloud computing in general and CCPs in particular. In this context, a substantive literature review was carried out focusing on performance modelling, testing, analysis and evaluation of Infrastructure as a Service (IaaS), methodologies. To this end, a systematic mapping study (SMSs) of the literature was conducted. SMS guided the choice and direction of this research. The SMS was followed by the development of a novel open queueing network model (QNM) at equilibrium for the performance modelling and analysis of an OpenStack IaaS CCP. Moreover, it was assumed that an external arrival pattern is Poisson while the queueing stations provided exponentially distributed service times. Based on Jackson’s theorem, the model was exactly decomposed into individual M/M/c (c ≥ 1) stations. Each of these queueing stations was analysed in isolation, and closed-form expressions for key performance metrics, such as mean response time, throughput, server (resource) utilisation as well as bottleneck device were determined. Moreover, the research was extended with a proposed open QNM with a bursty external arrival pattern represented by a Compound Poisson Process (CPP) with geometrically distributed batches, or equivalently, variable Generalised Exponential (GE) interarrival and service times. Each queueing station had c (c ≥ 1) GE-type servers. Based on a generic maximum entropy (ME) product form approximation, the proposed open GE-type QNM was decomposed into individual GE/GE/c queueing stations with GE-type interarrival and service times. The evaluation of the performance metrics and bottleneck analysis of the QNM were determined, which provided vital insights for the capacity planning of existing CCP architectures as well as the design and development of new ones. The results also revealed, due to a significant impact on the burstiness of interarrival and service time processes, resulted in worst-case performance bounds scenarios, as appropriate. Finally, an investigation was carried out into modelling and analysis of performance and security trade-offs for a CCP architecture, based on a proposed generalised stochastic Petri net (GSPN) model with security-detection control model (SDCM). In this context, ‘optimal’ combined performance and security metrics were defined with both M-type or GE-type arrival and service times and the impact of security incidents on performance was assessed. Typical numerical experiments on the GSPN model were conducted and implemented using the Möbius package, and an ‘optimal’ trade-offs were determined between performance and security, which are crucial in the SLA of the cloud computing services. / Petroleum technology development fund (PTDF) of the government of Nigeria Usmanu Danfodiyo University, Sokoto

There has been prior research on the internationalization process of retail firms. However, most of the research has investigated the developed countries' markets. There has been little research on the internationalization process of retail firms, especially in the emerging Asian markets. The emerging Asian markets are different from developed markets. Therefore, internationalization challenges and hindrances are dissimilar in this region than in developed countries' markets. Previously, there have been numerous researches on IKEA and other Swedish retail firms on the internationalization process. However, most of the research study has been done on its movement to developed markets. There has been little research done on IKEA's internationalization into emerging Asian markets. There are different challenges faced by firms, when entering into the emerging Asian market and during the business in these markets. However, the emerging Asian markets are different from other continents, especially the Western and developed markets. This research study aims to fill the existing knowledge gap by exploring the challenges that IKEA faces in emerging Asian markets. In addition to this, by the research, we seek to develop our understanding of the challenges faced by Swedish retail firms while entering emerging Asian markets. Furthermore, by exploring the challenges that retail firms face in the emerging Asian markets, we also aim to provide possible solutions on how IKEA and other retail firms can resolve or tackle the issues they face in emerging Asian markets.

Le présent travail est consacré au développement et à la validation d'un modèle hybride de propagation d'un incendie de végétation à grande échelle prenant en compte les hétérogénéités locales liées à la végétation, à la topographie du terrain et aux conditions météorologiques. Dans un premier temps, on présente différentes méthodes permettant de générer un réseau amorphe, représentatif d'une distribution réaliste de la végétation. Le modèle hybride est un modèle de réseau où les phénomènes qui se produisent à l'échelle macroscopique sont traités de façon déterministe, comme le préchauffage du site végétal provenant du rayonnement de la flamme et des braises et de la convection par les gaz chauds, mais aussi son refroidissement radiatif et son inflammation pilotée. Le rayonnement thermique provenant de la flamme est calculé en combinant le modèle de flamme solide à la méthode de Monte Carlo et en considérant son atténuation par la couche d'air atmosphérique entre la flamme et la végétation réceptive. Le modèle est ensuite appliqué à des configurations simples de propagation sur un terrain plat ou incliné, en présence ou non d'un vent constant. Les résultats obtenus sont en bon accord avec les données de la littérature. Une étude de sensibilité a été également menée permettant d'identifier les paramètres les plus influents du modèle, en termes de vitesse de propagation du feu, et de les hiérarchiser. La phase de validation a portée sur l'analyse comparative des contours de feux calculés par le modèle avec ceux mesurés lors d'un brûlage dirigé réalisé en Australie et d'un feu réel qui a lieu en Corse en 2009, montrant un très bon accord en termes de vitesse de propagation / The present work is devoted to the development of a hybrid model for predicting the rate of spread of wildland fires at a large scale, taking into account the local heterogeneities related to vegetation, topography, and meteorological conditions. Some methods for generating amorphous network, representative of real vegetation landscapes, are proposed. Mechanisms of heat transfer from the flame front to the virgin fuel are modeled: radiative preheating from the flame and embers, convective preheating from hot gases, radiative heat losses and piloted ignition of the receptive vegetation item. Flame radiation is calculated by combining the solid flame model with the Monte Carlo method and by taking into account its attenuation by the atmospheric layer between the flame and the receptive vegetation. The model is applied to simple configurations where the fire spreads on a flat or inclined terrain, with or without a constant wind. Model results are in good agreement with literature data. A sensitivity study is conducted to identify the most influential parameters of the model. Eventually, the model is validated by comparing predicted fire patterns with those obtained from a prescribed burning in Australia and from a historical fire that occurred in Corsica in 2009, showing a very good agreement in terms of fire patterns, rate of spread, and burned area.