Há uma tendência para a prescrição de restrições cada vez mais severas para o isolamento da envolvente nos edifícios nas regulamentações europeias, particularmente devido à recente Directiva sobre o Desempenho Energético dos Edifícios. O objectivo desta pesquisa é investigar a influência do aumento do isolamento da envolvente no desempenho térmico dos edifícios em Portugal e em climas do Sul Europeu, com ênfase no período do Verão. Os benefícios com o aumento da espessura do isolamento são evidentes numa situação típica de Inverno. No entanto, no Verão, em certas condições, uma envolvente altamente isolada pode dificultar a dissipação do calor para o exterior, causando um aumento da temperatura interior acima do limite de conforto. A metodologia desenvolvida compreende estudos paramétricos obtidos em simulações computacionais. São considerados distintos modelos de edifícios, com diferentes espessuras de isolamento da envolvente, e distintos ganhos internos, padrões de ventilação e taxas de sombreamento. Dessa forma, é possível investigar a interdependência de vários parâmetros no desempenho térmico e fazer análises comparativas. São avaliadas as condições nas quais o sobreaquecimento ocorre, e as suas consequências, tanto em termos do conforto dos ocupantes, quanto do aumento do consumo de energia para arrefecimento e a correspondente potencial eliminação das poupanças de Inverno. Para a análise do conforto, utiliza-se uma metodologia baseada na Abordagem Adaptativa.Os resultados mostraram que, quando o isolamento da envolvente é aumentado, a fim de que se possa evitar o sobreaquecimento excessivo, no Verão, é necessário controlar rigorosamente os ganhos internos e solares. Finalmente, foi desenvolvido um modelo teórico simplificado, que possibilita a previsão da temperatura média do ar no interior de edifícios multizona, sem condicionamento artificial. Esse modelo foi aplicado para casos representativos dentre os simulados e apresentou resultados fidedignos. Através dele, é possível determinar-se se a temperatura interior aumenta ou diminui, com o aumento do isolamento da envolvente, permitindo, portanto, optimizar o processo de especificação deste importante parâmetro do edifício. / FCT - Fundação para a Ciência e a Tecnologia

Over recent years considerable advances have taken place in the field of space geodesy, resulting in a number of highly precise global positioning techniques. The increased resolution of many of the scientific products from the new observational techniques has stimulated the interest of not only geodesists but also geophysicists. Furthermore, their potential to determine the orientation of the earth's axis of rotation (polar motion) and the variations of the rate of rotation of the earth about that axis, was recognised by the scientific community. The result was the establishment of Project MERIT, to intercompare these new observational techniques. Satellite Laser Ranging, a method of measuring the distance from a point on the earth's surface to an artificial satellite by means of timing the flight of a short pulse of laser light, is currently the most accurate available means of tracking near earth satellites. However, in order to reach the accuracy requirements of current geodetic applications dedicated satellites, such as the NASA LAser GEOdynamic Satellite (LAGEOS), must be tracked and specialised processing software must be used. This Thesis describes the basic theory behind the analysis of Satellite Laser Ranging Observations, with a special emphasis on the determination of earth rotation parameters (the polar motion and the variations in the rate of rotation). The development and testing, at Nottingham, of the Satellite Orbit Determination and Analysis Package Of Programs, SODAPOP, for the processing of laser range data, is described. The thesis also presents and discusses the results of the analysis of laser range observations the LAGEOS satellite, from the short and main campaigns of project MERIT.

In the last three decades there have been major changes in how surveying is practiced, and what surveyors have been trained and educated to do with the new expertise that technological advancements offer. Within surveying communities it is generally acknowledged that the changes in the profession have brought about an urgent need for change in educational programmes if they are to have relevance to contemporary practice. The thesis reports on a research study which explored the nature and impact of the educational strategies used in university surveying courses. The study employed a nested case study approach at two levels. Firstly, fifteen initial case studies of university programmes from thirteen countries provided a broad perspective of surveying education across the world. Secondly, two of these programmes were selected for in-depth comparative case studies to provide deeper understandings of the educational systems in two distinct contexts. The inquiry methods for the initial case studies included documentary analysis and interviews of senior academics and representatives of professional surveying bodies. For the two in-depth case studies, the inquiry methods included observations of pedagogical activities, focussed group discussions and interviews of university staff and students as well as professional surveyors. The interviews were recorded and thematically analysed. Some concepts from Bourdieu’s theory of practice were useful in coming to understandings about the interrelationship between the field of surveying education and the field of surveying practice. The study identified tensions and prospects within and between the programmes studied and between them and the profession. The key issues that emerged were: the predominance of highly discipline specific curricula with some indication of a shifting to a more broad-based education; tensions between industry expectations and the academic focus; a high level of interest in the university courses from the profession and uncertainty about the real meaning of geomatics and its relevance to local surveying communities. The findings have critical implications for how surveying/geomatics educational courses are developed in the future. The empirical evidence led to the development of a proposed improved model for contemporary surveying/geomatics education.

A Mobile Laser Scanning System (MLSS) is a kinematic platform combining different sensors, namely: GPS, IMU and laser scanner. These sensors are integrated and synchronised to a common time base providing 3D geo-referenced data. MLSS is used in several areas; such as 3D urban and landscape modelling for visualisation in planning and road design, simulations for environmental management, and to support land use decision-making. The accuracy of 3D geo-referenced points, achieved via Mobile Laser Scanning (MLS) under normal conditions, can reach the level of 3cm. However, this accuracy tends to be degraded in urban areas, because of trajectory errors of the laser scanner (IMU drift due to the limited availability of GPS signal). This, also, can be attributed to the difficulty of matching natural features in the point cloud. Previous researches have tried to overcome the problems in urban laser scanning by focusing on enhancing the performance of the navigation system (NGS). This can be costly and may not achieve the high accuracy level required for some engineering application. When the navigation solution is degraded, the accuracy of the point cloud results will be degraded. Using different data sources is another way to improve accuracy in urban areas. For example using airborne LiDAR, terrestrial imagery, and unmanned aerial vehicle (UAV) but these are very time consuming as well as costly compared to MLS systems. Targets are used in a number of ways in MLS and are often chosen from natural detail points. These can be difficult to define, particularly when high accuracy requirements need to be met, for example, when matching scans together or fitting scans to existing surveys as used in this project, and calibrating the system. The accuracy of MLS in the urban area was tested using three methods, namely ground control points (GCPs), surface to surface comparing, and additional source of data. Also, the effect of range, incidence angle (IA), resolution and brightness on different types of targets (sphere, cone, pyramid and flat target) was studied to explore the optimal target design. Moreover, an algorithm for automatic target detection was developed to detect the optimal target. Then, for each target in the point cloud, the centre/apex was calculated using least squares surface fitting. Tests show that the accuracy of 3D coordinates, obtained from MLS in an urban area is about 2-5 cm. Tests also show that using targets with MLS can improve the quality of results reaching 5 mm levels of accuracy even in the urban area, based on the use of check points to assess the quality and reliability of the outputs Almost all work on this project was carried out using the software packages available at the Nottingham Geospatial Institute (NGI) and MLS data provided by 3D Laser Mapping Ltd. (3DLM). Two terrestrial laser scanners, namely: HDS 3000 and Faro Focus3D have been used for testing the designed targets. The findings of this research will contribute easy, cost effective and improved accuracies in MLS data. This enhances usefulness in applications, such as change detection, deformation monitoring, cultural heritage and the process of 3D modelling, particularly in urban areas.

This thesis is dedicated to the development of two new tropospheric mapping functions for GNSS data processing, based on a high resolution mesoscale numerical weather model (NWM). NWMs have proven to be beneficiary in the processing of GNSS and VLBI data, both for deriving mapping functions and for providing a priori information such as zenith hydrostatic delay (ZHD). The mapping functions derived here make a greater use of the NWM information than the mapping functions currently recommended by the International GNSS Service. In addition to using a single vertical pro¯le at the site in order to derive mapping functions under the assumption of an azimuthally symmetric atmosphere, the NWM was also ray traced every thirty degrees in azimuth. This way, a complete volume of the atmosphere is sensed, and better modelling is expected if the NWM does indeed provide an accurate representation of the atmosphere, by accounting for azimuthal variations. An emphasis was put in this thesis on assessing the mathematical models used to vertically interpolate meteorological information, as they play a key role in computing the refractivities in the ray tracing algorithm. Error sources were identified and quantified. As expected, water vapour is the major source of error. However, the results showed that the model used for the total pressure induced a systematic bias. To derive an azimuth dependent mapping function, the Marini model traditionally used had to be left in favor of a cubic spline interpolation (CSI). This new approach was validated by comparing the performance of the new azimuthally symmetric mapping functions against the updated Vienna mapping functions (VMF1), the best mapping functions currently available. Similar positioning performances were obtained, therefore validating the CSI based approach. The performance of new azimuth dependent mapping functions (AMF) in handling the troposphere asymmetry were compared to those obtained when estimating horizontal tropospheric gradients with an azimuthally symmetric mapping function. Results show a good agreement in the modelling of the asymmetry, and that estimating gradients is justified. The gradient solution performed better overall, although it failed for some sites, and better inter-station consistency was obtained with the AMF. This thesis also investigated the role of the tropospheric modelling in the retrieval of the atmospheric pressure loading (APL) in GNSS data processing, which is now part of the IGS 2008 recommendations. The results show that differential height time series obtained with different tropospheric modelling can correlate with the APL signal to a level up to 0.7. In other words, the choice of tropospheric modelling strategy does greatly influence the retrieval of the APL.

Oil-air separation is a key function in aero engines with closed-loop oil systems. Aero-engine separators are employed to separate oil from air before being released overboard. Typically, these devices make use of a porous medium such as an open-cell metal foam, in order to enhance oil separation. Although quite scarce, there has been some research aimed at developing a suitable modelling framework for aero-engine separators. However, numerical modelling of the air/oil flow through the open-cell metal foams employed in aero-engine separators has never been properly addressed. This thesis presents the development of a pore-scale numerical modelling approach to determine the transport properties of fluid flow through open-cell metal foams. Micro-computer tomography scans were used to generate 3D digital representations of several commercial open-cell metal foams. A code was developed in Matlab to render the CT images into 3D volumes and perform morphological measurements on the samples. Subsequently, conventional finite volume simulations are carried out in order to obtain the airflow and compute the pressure gradient across the investigated samples. Simulations were performed for a wide range of Reynolds numbers and the feasibility of using Reynolds-averaged Navier-Stokes (RANS) turbulence models is investigated. Validation was done by comparing the pore-scale pressure gradient results against experimental measurements. Further simulations were carried out to isolate and analyse particular effects in more detail, such as wall and entrance effects, fluid compressibility, time-dependent flow features, anisotropy of the foam structure and the impact of porosity and surface area on the pressure gradient. The oil phase within aero-engine separators has the form of disperse droplets. Thus, the oil phase in the pore-scale simulations was modelled using a Lagrangian particle tracking approach. Lagrangian simulations were run in steady state and one-way coupled, due to the low mass fraction of oil normally present within aero-engine separators Converged airflow pore-scale solutions were employed as the base flow for the Lagrangian tracking approach. A simplified oil capture criterion assumed the droplet trajectory to be terminated upon collision against the foam solid ligaments. The focus of the present work was on separation of small droplets with a diameter smaller than 10 microns. Hence, a series of calculations were performed using a representative droplet diameter range, and multiple flow velocities. The outcome of such approach was a qualitative evaluation of the oil separation effectiveness for several commercial open-cell metal foams under a representative range of flow regimes. Furthermore, rotational effects which are experienced by the metal foams within aero-engine separators were modelled using a moving frame of reference (MRF) approach. Finally, a methodology for upscaling the results obtained by the detailed pore-scale simulations into a simple macroscopic porous medium model is described, showing promising results. One of the aims of this work was to develop a numerical modelling framework able to provide an accurate representation of the airflow and a qualitative assessment of the oil capture within aero-engine separators. The feasibility of using the current state-of-the-art modelling framework is assessed. The separator design and geometry are based on the oil separation test rig located at the Karlsruhe Institute of Technology (KIT). Experimental measurements of the overall pressure drop and oil capture performed at KIT are used to validate the simulations. The methodology presented here overcomes some limitations and simplifications present in previous similar studies. The upscaled macroscopic porous medium model was applied to full aero-engine separator CFD simulations. Experiments and simulations were conducted for three different separator configurations, one without a metal foam, and two with metal foams of different pore sizes. For each configuration, a variation of air flow, shaft rotational speed and droplet size was conducted. The focus was on the separation of droplets with a diameter smaller than 10 \textmu m. Single-phase air flow simulation results showed that overall pressure drop increases with both increased shaft speed and air flow, largely in agreement with the experiments. Oil capture results proved to be more difficult to be captured by the numerical model and indicate that droplet re-atomization might play a significant role in the oil separation phenomena. Re-atomization, droplet-droplet collisions and droplet breakup were not considered at the present stage, but could be subject of future work. The modelling framework described here should not be seen as a definite answer but as an improvement upon the current state-of-the-art methodology, providing important lessons and recommendations for future work on aero-engine separators.

Considering the gap in available information and the need of the industries such as oil and gas production, energy, and food processing, this study focuses on the two phase flows around bends in process pipe lines. The aim of this study is to investigate the influence of 90° bends on the gas-liquid two phase flow behaviour in vertical and horizontal orientations using advanced two-phase flow measuring techniques. An experimental study has been conducted using silicone oil with a viscosity of 5 mPa.s and air to examine the transitional flows around 90° bends of 68 mm internal diameter (ID) with different configurations. Experiments were conducted at ambient conditions in an open system which consists of a 68 mm ID riser of 4.5 m long, vertical upward 90° bend and two horizontal sections of a 9.2m and 5.5m long in series with a horizontal 90° bend in between. The experimental matrix comprises 60 combinations of gas and liquid superficial velocities, ranging from 0.045 m.s-1 to 3.21 m.s-1 and 0.15 m.s-1 to 0.53 m.s-1 respectively. The phase distributions within the pipes were measured using Electrical Capacitance Tomography (ECT) and Wire Mesh Sensors (WMS). The behaviour of the flow was examined qualitatively using high speed imaging. To study the flow development in the riser, both ECT and WMS were placed in series and moved along three axial locations downstream of the mixing section. During the experiments at the bends, the ECT was kept immediately upstream while the WMS was moved to different positions downstream of the bend. The cross-sectional void fraction time series from the ECT and the WMS were used to quantify the main hydrodynamic parameters of the flow including cross-sectional averaged void fraction, bubble size distribution, radial void fraction profiles, slug length, slug frequency, void fraction in liquid slugs, and the slug bubble velocity. Results were compared against the available slug flow correlations. The results show that the phases separate shortly after the vertical to horizontal bend leading to stratified or wavy stratified flow. Beyond a certain threshold of the gas flow rate and liquid level, onset of slugs can be observed at a certain distance downstream of the vertical upward bend. This work suggests that the formation of hydrodynamic slugs downstream of the vertical upward bend is independent of the inlet conditions upstream. The horizontal bend, unlike the vertical upward bend, has a minor influence on the flow evolution, particularly slug flow. This is due to the influence of gravitational force on phase separation and its subsequent effect on the change of momentum in the vertical bend. The flow structures, mainly slugs and disturbance waves, are slightly accelerated as they pass through the horizontal bend with minimum change to the structure frequency and gas holdup within liquid slugs. Most of the existing correlations do not predict the measured void fractions in this work as those correlations were essentially limited to the conditions they were developed for as the basis of them lies in the curve fitting. In this work, the higher viscosity and lower surface tension led to higher gas holdup in liquid slugs causing the discrepancy.

This work contained in this thesis is the result of an industrial and academic collaboration, designed to investigate and further the present knowledge of dense turbulent dispersions. Experiments were conducted to provide support and experimental validation to a CFD code being simultaneously developed, which was able to give insight into these types of flows. Additional to this support, the aim of this thesis was to also further knowledge of key topics in this field. The experimental methodology chosen was to use a mixture of Particle Image Velocimetry and Particle Tracking Velocimetry. To discriminate between particle and liquid phases, two approaches were adopted, depending upon the experiment. In one approach, fluorescent dyes were used to tag one phase, whilst optical filters were applied to the camera lenses. In the second approach, a size-based binary mask was applied to a single image, in order to remove phase information and produce two sets of images. A number of different analysis techniques were researched and developed as part of this thesis. The performance of particle tracking algorithms was assessed to ascertain their most suitable usage. A number of different algorithms, designed to characterise particle positions, were validated against known test cases. These included the Box Counting Method, a Voronoi analysis, and Radial Distribution Functions. A further technique, known as the Particle Potential method, was also developed to characterise local clustering. Two experiments were undertaken throughout this project, both of which were developed from scratch so that full control was assured over all experimental parameters. A vertical channel experiment was designed to assess the injections of particles into a rectangular channel. These experiments allowed for an ideal test case of highly concentrated particles, without the need to achieve optical visibility through a dense solution. The experiments also provided an early test of a Refractive Index Matching candidate pair; hydrogel particles and water. The second experiment was known as the Circulating Dispersion Rig, which was designed to pump a slurry in a continuous loop in a cylindrical pipe. These experiments, due to the geometry used and dense nature of the slurry, were reliant upon trying to achieve optimum optical visibility, and so hydrogel/water mixtures were tested in advance against other, more well-utilised pairings. The experiments conducted have provided some insight into the nature of particles in turbulent flows, in particular their clustering properties. Clustering was assessed under various concentrations. Key results included analysis of these clusters using a Voronoi diagram technique, which identified four key types of cluster structure, and the parameters under which these form. Collision probabilities of particle pairs were also assessed, using Particle Tracking data and computation of relative velocities. Such information is of importance for experimental validation of CFD codes relating to dispersed two-phase flows, where particle-particle coupling must be assessed in order to provide accurate solutions. The key drive towards the future, should further experiments be desirable, would be to investigate the improvement of optically matching liquids and solids, which was felt to be the limiting factor towards achieving measurements at even higher concentrations. However, these experiments show some progress can be made in making measurements of four-way coupled turbulent flows.

In this work, two (La,Sr)(Al,Ta) O3 single crystals were grown by the conventional Czochralski pulling method by using different rotation rates and pull rates to find out the optimal growth conditions. The total length of the first (La,Sr)(Al,Ta) O3 crystal is about 8.5cm, and the shape is not symmetrical. The small thermal conductivity of the crystal would lead to small temperature gradient, so the growth rate was slow. The shape of the second crystal was improved by adjusting the thermal field. But, the bottom of the residual has blue color. The blue residual was analysed by x-ray and Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Besides, the crystal structure was analyzed and the second phase had been found in crystals by high angle x-ray spectrum and polarizer microscope.

Creating three dimensional digital representations of urban areas, also known as 3D city modelling, is essential in many applications, such as urban planning, radio frequency signal propagation, flight simulation and vehicle navigation, which are of increasing importance in modern society urban centres. The main aim of the thesis is the development of a semi-automated, innovative workflow for creating 3D city models using aerial photographs and LiDAR data collected from various airborne sensors. The complexity of this aim necessitates the development of an efficient and reliable way to progress from manually intensive operations to an increased level of automation. The proposed methodology exploits the combination of different datasets, also known as data fusion, to achieve reliable results in different study areas. Data fusion techniques are used to combine linear features, extracted from aerial photographs, with either LiDAR data or any other source available including Very Dense Digital Surface Models (VDDSMs). The research proposes a method which employs a semi automated technique for 3D city modelling by fusing LiDAR if available or VDDSMs with 3D linear features extracted from stereo pairs of photographs. The building detection and the generation of the building footprint is performed with the use of a plane fitting algorithm on the LiDAR or VDDSMs using conditions based on the slope of the roofs and the minimum size of the buildings. The initial building footprint is subsequently generalized using a simplification algorithm that enhances the orthogonality between the individual linear segments within a defined tolerance. The final refinement of the building outline is performed for each linear segment using the filtered stereo matched points with a least squares estimation. The digital reconstruction of the roof shapes is performed by implementing a least squares-plane fitting algorithm on the classified VDDSMs, which is restricted by the building outlines, the minimum size of the planes and the maximum height tolerance between adjacent 3D points. Subsequently neighbouring planes are merged using Boolean operations for generation of solid features. The results indicate very detailed building models. Various roof details such as dormers and chimneys are successfully reconstructed in most cases.