Dissertations / Theses on the topic 'Slat'

Parallel-hole collimators are the most widely used collimators in clinical SPECT imaging. However the performances of these collimators are limited in terms of efficiency and resolution, 0.01% and 1cm at 10cm distance from the detector face, respectively. Simultaneous optimisation is not possible due to existence of a fundamental trade-off between resolution and efficiency. Hence an alternative method of increasing efficiency without compromising resolution is necessary. Slit-slat collimator provides a better alternative to parallel-hole, due to their magnification power. The aim and objectives of this PhD work was to design and optimise a clinical brain SPECT system based on slit-slat collimation and a novel detector with silicon drift diodes (SDDs) readout providing 1mm intrinsic resolution. The system efficiency can be improved by increasing the number of slits, however as the number of slits increases, so does the multiplexing, which is the overlapping of the projections on the detector plane. We hypothesize that the reconstruction of multiplexed (MX) projections can be improved by addition of non-MX projections. We have proved this using simulation and shown that a gain in signal to noise ratio (SNR) (25.5%) corresponding to 43% reduction in acquisition time was achievable when non-MX projections were available. Several novel system designs that utilise the SDDs technology with mixed degrees of multiplexing have been evaluated. To enable experimental validation of the simulation work, a prototype slit-slat collimator was designed and built for a conventional gamma camera. Full calibration of the system was performed, the efficiency and resolution profiles were measured and studies of point sources, Jaszczak and Striatal phantoms were completed. The results of these studies confirmed the potential for multiplexing to improve image quality when used in conjunction with non-multiplexed projections with a maximum gain in SNR equivalent to of 50.6%.

In the case of civil transport aircraft, engines were the dominant noise source until the advent of the high-bypass ratio engines in the early 1970s. Since then, airframe noise has become more important, particularly during the approach-to-landing stage of aircraft operations. The main components of airframe noise are the flap side edge, leading edge slat, and the landing gear. Experiments in both the wind tunnel and via fly-over measurements have shown that the slat noise is a major contributor to the overall airframe noise during the landing approach for a commercial aircraft. To achieve the goal of reducing slat noise significantly without adversely affecting the aerodynamic performance of the wing, it is obligatory to improve the understanding of the mechanism of slat noise generation. Experiments and numerical simulations were performed to investigate the phenomena of slat noise. It was found that the slat broadband noise generation is governed by two kinds of mechanism. At a low angle of attack of the wing, the typical circulation region is not formed in the slat cove and the slat noise level is low. As the angle of attack increases to a certain value, vortical structures are intermittently generated due to flow interaction occuring between the shear layer originating from the slat cusp and the flow convected from the stagnation line on the main element. Intense slat noise is produced as the vortical structures approach the slat cove surface. With the angle of attack increasing further, the slat noise becomes weak again. The interaction effect tends to become weaker as the shear layer deviates away from the surface of the main element. Two approaches with the aim of attenuating the slat noise were experimentally and numerically studied. The first approach was to reduce the slat noise using air blown on the suction surface of the slat near its trailing edge. A numerical simulation showed that the slat noise levels over most of the frequencies, especially above a St number of 7, were obviously attenuated. In the second approach, a strip mounted on the pressure surface of the main element model was experimentally proven to be an effective method for reducing the broadband slat noise at an angle of attack of 8 degrees and a freestream velocity of 25 m/s. The position and height of the strip also influenced the level of the reduction. Several tonal noise components appear in the slat noise spectrum at an angle of attack of 4 degrees and a freestream velocity of 25 m/s. The dominant tone is associated with the vortex shedding off the slat cusp through the Kelvin-Helmholtz instability. This tone was successfully suppressed using a plasma actuator employing an open-loop control. A maximum reduction of 11 dB was achieved at a St number of approximately 19.7. A quasi-static feedback control system was also developed, wherein a controller is responsible for calculating the control inputs in terms of ii feedback signals. The experimental results show that the controller can work effectively to suppress the slat noise.

ABSTRACTThe purpose of this thesis is to design and analyze the new generation leading edge slat of a commercial jet to reduce the structural noise with the application of new conceptual design approaches. Recent scientific research show that the leading edge slats account for the structural noise during the flight operation therefore, when the leading edge slat is deployed under different flight conditions, an open gap/slot is formed between the high lift device and the wing box. However, since the leading edge slat includes flexible sections, it is assumed that defining an adaptive system inside the leading edge slat may reduce the structural noise by utilizing bending properties of these flexible sections. Hence, electromechanical actuator designing gains also great importance in the whole process. In this study, we have used, finite element modelling of the slat structure to examine the required structural deformations and strengths; our work is based on the software ANSYS/Workbench. To be realistic in deciding the right geometry in the follow up steps, we have first studied a generic geometry having no aerodynamics or actuator forces application. The whole simulation was performed by defining dummy forces and dummy material properties. The simulation lead to having a global overview of the mechanical behaviour of the structure; further, once the influent parameters were tested, realistic aerodynamic forces and material properties were defined, and as a result of bending of the flexible sections the required gap closure was formed between the trailing edge of the slat and the wing box. Subsequently, the suitable actuator design and required strength analysis are also performed on the last section. This study has also proved that the use of adaptive systems on the leading edge slats improves flight comfort by reducing the structural noise and provides less fuel consumption; this is significant for the long run considerations of aeroplane manufacturers.
es Zentrum für Luft- und Raumfahrt e. V. (DLR)

This study was conducted to examine the potential of plastic slats as flooring material for maintenance of broiler breeders. Although plastic slats are more expensive than wood slats, plastic slats are more durable and easier to clean. Wood and plastic slats were tested as full and partial flooring to determine the ideal proportion of slats for broiler breeder floors. Space allotment was 2040 cm²/bird on all floor treatments. . Arbor Acres broiler breeders, one of the more common strains in British Columbia, were raised to 58 weeks of age to monitor the influence of slat material and slat coverage on egg production and progeny growth over one production cycle. Since the pens were not set up to determine the number of eggs lost through slats, "egg production" values were actually egg recovery values. Over-all egg recovery was significantly higher on partial wood (PWS) and partial plastic slats (PPS) than on either of the full slat treatments. Breeders on full wood slats (FWS) had higher over-all egg production than those on full plastic slats (FPS). Differences were significant for three biweekly periods, but slats did not influence the over-all incidence of floor eggs and cracked floor eggs. The incidence of cracked nest eggs was significantly higher in FWS and FPS than in PWS and PPS pens during four lay periods and overall. The proportion of non-cracked nest eggs, which was taken as an approximation of the proportion of settable eggs, was higher for partial slat pens than full slat pens, and FWS pens had a higher proportion of non-cracked nest eggs than FPS pens. To monitor fertility and hatchability, eggs were incubated at 37, 42, 46, 50 and 56 weeks of breeder age. Fertility, hatchability of total eggs set and hatchability of fertile eggs was not affected by type of slats. Progeny from the hatch at 37, 46 and 56 week of breeder age were grown in Petersime battery cages to three weeks of age. The progeny of breeders on FPS had lower first week weight gain than the other progeny groups due to moisture loss when 7 FPS progeny were lost during the second growth trial. Weekly and over-all feed conversion of progeny was not affected by types of slats used by parents. The 56th week progeny were grown in Petersime battery cages to market age (six weeks). PWS and FPS progeny had higher third week weight gain than PPS progeny. During the sixth week, FWS and PWS progeny had higher weight gain than FPS and PPS progeny. The sixth week feed conversion of FPS progeny was higher than that of the other three progeny groups. No other differences were seen. As long as slats were used as partial flooring, there were no differences in egg production on wood or plastic slats. The proportion of "settable" eggs, fertility, and hatchability of eggs of plastic slat breeders were comparable with that of wood slat breeders regardless of slat coverage. There were significant differences in the 3-week growth of 37th, 46th and 56th week progeny and the 6-week growth of 56th week progeny on the different slat types, but the differences were not due to slat treatments. There was no interaction between breeder age and slat material, therefore the influence of slat material on egg production and progeny growth did not vary with breeder age. Although egg recovery and the number of settable eggs were lower for FPS breeders, breeders on plastic slats performed as well as those on wood slats in the present study.
Land and Food Systems, Faculty of
Graduate

This study primarily investigated the flow and aeroacoustics associated with the slat of a three-element aerofoil in approach conditions. The study assessed importance of several factors and examined their aerodynamic impacts. The factors investigated were aerofoil incidence, slat angle, slat cusp geometry, fixing transition and blowing in the slat cove. A combination of experimental and computational techniques investigated the factors selected. The experimental work employed PIV, pressure tap, a force balance, flush mounted microphones and an acoustic array. The computational work used DES along with the FW-H acoustic analogy to obtain the far-field directivity. Tonal features occurred at high incidence and originated at the slat trailing edge, due to the blunt trailing edge and gap, and at the reattachment point. Fixing transition removes the tone at the reattachment point and reduces the slat gap tone at the trailing edge but does not remove the tone generated by the blunt trailing edge. All of the tones found, only occurred at certain slat and wing settings. Broadband sound was present in all conditions but had a strong dependence on the incidence of the wing. The sound was loudest with the wing at  = 5o with a reduction as the wing incidence was increased. The broadband sound also reduced as the slat angel decreased from S = 23o. The shear incidence angle was a good indicator of the impact of these two factors on the sound generated. Extending the slat cusp reduced the broadband sound at low aerofoil incidence. However, for   10o the extension led to increased broadband sound. Neither blowing nor fixing transition had a significant impact on the broadband sound generated by the slat system. The aerodynamic loads generated by the wing were mainly dependent on the aerofoil incidence. However, other factors did influence the forces generated. Reducing the slat angle increased the lift generated by the wing especially at low aerofoil incidence but the lift to drag ratio was unaltered. At high aerofoil incidence, extending the slat cusp reduced the lift generated. Blowing and fixing transition did not significantly alter the forces generated by the wing.

International Telemetering Conference Proceedings / October 26-29, 1987 / Town and Country Hotel, San Diego, California
This paper describes telemetry used in the Supersonic Low Altitude Target (SLAT) built for the U.S. Navy by Martin Marietta. Feeding digital inputs directly to a pulse code modulation (PCM) encoder, bypassing the analog-to-digital (A/D) converter, and injecting into the output PCM wavetrain is well known. Various techniques for accomplishing this have been reported; however, they all have time correlation and synchronization problems. The system to be described involves asynchronous data transfer from the digital computer to the PCM encoder. The system uses a dual-port random-access memory (RAM) to effectively decouple the computer output, which is running synchronously on its 6 MHz clock, from the PCM wavetrain, which is running at 128 kilobits per second. Data from the computer is being "written into" the RAM simultaneously while data is being "read out." Contention arbitration prevents loss of data when read and write ports of the same address are activated. A "forbidden code" provides a special code when the computer is not connected or is producing all zeros.

Mecanismo é um conjunto de elos, ligados por juntas, que se movem relativamente uns aos outros. A análise de mecanismos consiste em verificar o funcionamento do sistema mecânico a fim de entender o comportamento e a viabilidade para uma determinada função. Nesta dissertação será feito um estudo de um tipo específico de mecanismo usado em um slat. Slats, ou flapes de bordo de ataque são sistemas aerodinâmicos de hipersustentação localizados no bordo de ataque de aeronaves, utilizados para aumentar o desempenho em fases de decolagem e pouso. O trabalho apresenta uma série de dispositivos de hipersustentação com intuito de mostrar os tipos de mecanismos mais utilizados em aeronaves. O projeto tridimensional do sistema será feito, serão calculados parâmetros aerodinâmicos do mesmo e finalmente uma simulação computacional será feita. Esta análise consistirá em modelar o funcionamento do sistema considerando o sistema de multicorpos rígidos com e sem folga. O objetivo é estimar os esforços no atuador quando o sistema está condicionado aos esforços aerodinâmicos e verificar se há travamento do sistema. Além disso, a contribuição de folgas no desempenho do sistema será avaliada.

Abstract Noise generated by high-lift devices such as slats on a wing is a major contributor to the overall airframe noise during the landing approach of a commercial aircraft. In this work the concept of attenuating slat noise using absorptive acoustic lin- ers in the slat/main element gap is explored using a time domain computational aeroacoustic (CAA) technique. The aims of the development and application of the computational method are to reveal the mechanism of the slat noise generation and demonstrate the feasibility of controlling the slat noise using acoustic liners. A model scale three-element high-lift airfoil comprising a main element, a leading edge slat and trailing edge °ap geometry is employed in the investigation. Numerical simulations are performed to investigate the generation and far ¯eld propagation of the slat noise. A numerical approach is developed that combines near ¯eld °ow computation with an integral radiation model to predict the far ¯eld acoustic signal. A time domain impedance boundary condition (TDIBC) is implemented to simulate the e®ect of the liner material directly. Both the high frequency tonal noise and low frequency broadband noise generated from the slat are investigated. For the high frequency tonal noise, an unsteady Reynolds-averaged Navier-Stokes (URANS) simulation using high-order spatial and temporal schemes for the wing without acoustic liners shows the presence of vortex shedding and associated high frequency acoustic sources behind the slat trailing edge. To evaluate the mitigating performance of liners on the generated noise and ¯nd an optimized liner impedance value, an exercise is conducted on a range of liner impedance values by solving the linearized Euler equations (LEE) for a modeled acoustic source located at the trailing edge of the slat to ¯nd a optimized one. Using the optimized impedance value, URANS computations for the wing with liner treatment are conducted. The results show that acoustic liners on the slat cove and on the main element can provide useful attenuation of the high frequency slat trailing edge noise. For the low frequency broadband noise, the noise sources are calculated by both the pseudo-laminar zonal method and the stochastic noise generation and radiation i (SNGR) approach. The pseudo-laminar zonal calculation is basically an URANS calculation with the two-equation shear stress transport (SST) · ¡ ! model to model the e®ect of turbulence and a region in the slat cove is set as laminar zone. In the SNGR approach broadband sources of noise are modeled using stochastic noise generation method from a numerical solution of the steady Reynolds-averaged Navier-Stokes (RANS) equations using the · ¡ ! closure and then the acoustic ¯eld is calculated by solving the acoustic perturbation equations (APE) using high- order spatial and temporal schemes. By comparing the results of pseudo-laminar method and that of SNGR approach, the SNGR method has been shown to be a potentially useful method to model the generation of broadband slat noise and to investigate the attenuation of slat gap acoustic liners, for which the interest is in changes of noise level rather than the absolute value. The broadband noise attenuation e®ect of the acoustic liner treatment is studied by applying a broadband TDIBC to the acoustic ¯eld obtained by the SNGR method. The far-¯eld directivity is obtained through an integral surface solution of Ffowcs Williams and Hawkings (FW-H) equation. Predictions for a non-optimized acoustic liner show a moderate amount of attenuation. To accurately simulate the broadband noise generation and radiation, a LES using a high-order spatial scheme and implicit temporal integration is conducted for the high-lift con¯guration with slat deployed and the calculated results show the characteristic of the unsteady °ow and the mechanisms of the broadband noise generation. The recorded noise sources are then used to drive the APE to simulate the noise propagation and the attenuation by acoustic liners. The source driven APE results agree well with that of LES in term of far ¯eld directivity and sound pressure level. Similar to the SNGR simulation, a moderate amount of attenuation is achieved by the acoustic liner treatment.

As one of the major contributors to aircraft noise, the noise generated by high-lift devices has been explored for many years. However, the noise related to the slat track system, which includes all the extrusive components connecting the slat and the main element, is still generally studied through experimentation due to the complex geometry. In this project, the aerodynamics and aeroacoustics of the slat track and cut-out, especially the main element cut-out, were investigated through numerical simulations for the first time. Two methods were employed in this work. Noise propagation is first studied via a compact source model to evaluate the contribution of each source individually and to investigate the influence of the slat track system on the noise propagation in the slat region. The APE-IV system was employed but modified by using a more accurate expression of enthalpy perturbation to calculate the acoustic fields. The results show that both the slat track system and the background flow modify the sound propagation path. The energy radiated towards the ground is increased due to the interaction of sound waves with the slat track system and the background flow. Detached eddy simulations were run to investigate the mechanisms of the slat track and cut-out noise generation. Major noise sources in the slat cove region are identified and a noise generation feedback loop is proposed. The results show that the increment of noise levels due to the existence of the slat track system is two-fold. The slat track and the cut-out generate noise individually and they also amplify the noise generated within the slat region when the sound waves propagate though the slat cove area and interact with the slat track and cut-out. The dominant frequencies of the spectrum are seen to shift towards the high frequencies due to these added on components. In this work, two kinds of possible noise attenuation approaches were proposed and studied. Geometries based on replacing the sharp cut-out on the main element leading edge with an edge-rounded or a sealed cut-out have been proved to be able to reduce the cut-out noise significantly. Application of acoustic bulk absorbing material can also attenuate the cut-out noise efficiently for a certain range of frequencies.

The main sources of airframe noise in commercial aircrafts are the landing gear and the highlift devices. Among the high-lift devices, the slat deserves special attention since it represents a distributed source along the wing span. During approach and landing the noise generated by the slat can be comparable to the engine generated noise. For the design of quieter high-lift systems, it is important to understand the physics responsible for the slat noise generation. The objective of the work described in this thesis is to correlate the dynamics of large scale turbulent structures at different airfoil configurations with the characteristics of the noise generated by these structures. Four different configurations were investigated, ranging two airfoil angles of attack and three slat positions relative to the main element. The unsteady flow data was provided by a Lattice-Boltzmann based computational code. The Proper Orthogonal Decomposition technique was used for the objective identification of large scale structures in the slat region. Two different metrics were considered for the eduction of the coherent structures: one based on the Turbulent Kinetic Energy of the structures; and one based on their correlation to the noise emitted by the slat. The results of the transient simulations showed good agreement with wind tunnel measurements, providing confidence on the relevance of the analysis. The noise spectra of three of the cases simulated were dominated by a series of narrowband peaks at low frequency, while the spectrum of the remaining case was broadband in nature. Analysis of the averaged flow showed a large variation of the size and shape of the recirculating zone inside the slat cove and on the reattachment position of the mixing layer, between the simulated cases. The results indicated that, as the reattachment point approximates the region of the gap between the slat and the main element, the noise emission power increases. The large scale structures most correlated to the noise were typically two-dimensional and their shape suggests they resulted from the growth of disturbances in the mixing layer due to the inflectional instability. The dynamics of the noise correlated structures at the frequencies of the peaks was consistent with the existence of an acoustic feedback mechanism acting inside the slat cove. Based on the observation of the educed structures a model to predict the frequencies of peaks was proposed, showing good agreement with the frequencies computed from the unsteady flow data.
As principais fontes de ruído não propulsivo em aeronaves comerciais são os trens-de-pouso e os dispositivos híper-sustentadores. Entre os dispositivos híper-sustentadores, o eslate se destaca por constituir uma fonte distribuída ao longo da envergadura da asa. Durante a fase de aproximação e aterrissagem, o eslate pode gerar ruído com níveis comparáveis ao gerado pelos motores. Para viabilizar projetos de aerofólios com eslates menos ruidosos, é importante compreender os fenômenos fluidodinâmicos responsáveis pela geração desse ruído. O trabalho descrito neste texto tem por objetivo verificar se existe correlação entre o comportamento de grandes estruturas turbulentas em diferentes configurações do aerofólio com as características do ruído aeroacústico gerado por elas. O escoamento em quatro configurações diferentes foi estudado, abrangendo dois ângulos de ataque e três posições do eslate em relação ao elemento principal. Os dados do escoamento para análise foram gerados através de simulações numéricas não estacionárias utilizando um código comercial baseado no Método Lattice-Boltzmann. O método da Decomposição Ortogonal Apropriada foi utilizado para a identificação das estruturas de grande escala baseada em critérios objetivos. Duas métricas distintas foram utilizadas, uma baseada na energia cinética turbulenta e outra baseada na correlação com as ondas acústicas geradas a partir do eslate. Os resultados das simulações transientes apresentaram boa concordância com resultados experimentais. O espectro de ruído de três casos simulados são dominados por picos de baixa frequência, enquanto o espectro do quarto caso é tipicamente de banda larga. A análise do escoamento indica uma tendência de aumento do ruído à medida que o recolamento se aproxima do bordo de fuga do eslate. As estruturas mais correlacionadas com o ruído são tipicamente bi-dimensionais e seu formato indica que são resultado do crescimento de perturbações na camada de mistura devido à instabilidade inflexional. A dinâmica das estruturas correlecionadas com o ruído na frequência dos picos é consistentes com a existência de uma retro-alimentação das perturbações da camada de mistura por ondas acústica na cova do eslate. Um modelo para previsão das frequências dos picos foi proposto a partir da observação das estruturas identificadas pela Decomposição Ortogonal Apropriada, mostrando boa concordância com as frequências observadas nos espectros calculados com base nos dados transientes das simulações.

Thesis (M.S.)--West Virginia University, 2002.
Title from document title page. Document formatted into pages; contains viii, 46 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 29-31).

Tato diplomová práce se zaměřuje na stanovení geometrických a materiálových parametrů konstrukce slotu letadla B737-200. V této práci je vypracovaný návrh kompozitového slotu s ohledem na dané zatěžovací případy, včetně tzv. “bird strike”. Analytické výpočty jsou ověřené metodou konečných prvků (MKP) v programech MSC.Nastran/Patran, MSC.Dytran

Thesis (PhD)--Stellenbosch University, 2011.
ENGLISH ABSTRACT: Natural draught wet-cooling tower rain zone performance can be significantly enhanced by reducing the mean drop size in the rain zone with the installation of specially designed grids below the cooling tower fill. Drops enter the rain zone in the form of a polydisperse drop distribution, dripping from below the cooling tower fill, comprising relatively large drops. In order to design and optimize a grid for breaking up these drops, the mechanisms of drop break-up after impingement on the grid surface, referred to as splashing, straddling and dripping, need to be clearly understood. Two of these mechanisms, splashing and straddling, are therefore investigated experimentally using high speed video cameras to measure initial drop sizes, mass fractions and drop size distributions after impingement on different horizontal slats covered with a thin layer of water. The following parameters are varied independently for these experiments: drop fall distance, initial drop size, slat width and the water film thickness on the slats. Dripping from below the grid, is investigated theoretically. The effect of drop interaction on the drop size distribution in the rain zone is also investigated experimentally by measuring the drop distributions at the top and bottom of rain zones with a height of approximately 7.05 m to 7.65 m for different inlet distributions. The experimental drop break-up data, numerically obtained splash drop trajectory data and drop interaction data found in literature are used to develop a theoretical model of a purely counter flow cooling tower rain zone with and without installed grids. The model is compared to experimental data and theoretical data from literature and the predicted thermal and dynamic behaviour of the rain zone are generally found to be in good agreement with these results. Ultimately, this model is used for the optimization of the grid layout in terms of variables such as distance between the grid and the fill, slat width, slat spacing and slat height. It is found that the best drop break-up is achieved for grids comprising narrower slats with lower grid porosities as opposed to grids comprising wider slats. For the determined optimal grid layout it is found that a significant improvement in cooling tower performance can be achieved.
AFRIKAANSE OPSOMMING: Nat-koeltoringreënsonevermoë kan aansienlik verhoog word deur die druppelgrootte in hierdie gebied te verklein deur roosters, wat spesifiek vir hierdie doel ontwerp is, onder die pakkingsmateriaal te installeer. Die inlaatdruppelverdeling aan die bokant van die reënsone bestaan uit ‘n verdeling van relatief groot druppels wat drip van die onderkant van die pakkingsmateriaal. Ten einde ‘n rooster te ontwerp en te optimeer wat hierdie druppels kan opbreek moet die meganismes van druppelopbreking, bekend as spatting, vurking en drip goed verstaan word. Spatting en vurking is om hierdie rede eksperimenteel ondersoek, met behulp van hoëspoed videokameras. Die volgende veranderlikes is onafhanklik verander tydens hierdie eksperimente: valafstand van die druppel, aanvanklike druppelgrootte, latwydte en die dikte van die lagie water bo-op die lat. Die dripmeganisme aan die onderkant van die rooster is slegs teoreties ondersoek. Die effek wat druppelinteraksie in die reënsone het op die druppelgrootte is ondersoek deur die druppelgroottes aan die bo- en onderkant van ‘n 7.05 m tot 7.65 m reënsone te meet vir verskillende druppelinlaatverdelings. Die eksperimentele druppeldata, sowel as numeries berekende data wat die snelheid en trajek van spatdruppels beskryf, tesame met data vir druppelinteraksies wat uit die literatuur verkry is word gebruik om ‘n teoretiese model te ontwikkel vir ‘n suiwer teenvloei koeltoringreënsone met en sonder roosters. Hierdie model word vergelyk met eksperimentele data en data wat uit die literatuur verkry is en daar is gevind dat daar oor die algemeen ‘n goeie ooreenstemming is tussen die voorspelde en gemete termiese en dinamiese gedrag van die reënsone. Uiteindelik word die model gebruik vir die optimering van die rooster in terme van die volgende veranderlikes: afstand tussen rooster en pakkingsmateriaal, latwydte, latspasiëring en lathoogte. Daar word gevind dat beter druppelopbreking verkry word deur gebruik te maak van smaller latte en ‘n laer roosterporeusiteit. Daar is gevind dat die bepaalde optimale roosteruitleg in die reënsone van ‘n koeltoring ‘n wesenlike verbetering in koeltoringvermoë tot gevolg kan hê.

O presente trabalho refere-se a um estudo aeroacústico experimental visando caracterizar o ruído de eslate sob a presença de excrescências instaladas no interior de sua cova, e em ângulos de ataque extremos (entre -4 e 18 [º]). O eslate é um dispositivo hipersustentador posicionado no bordo de ataque do perfil aerodinâmico que objetiva a operação da aeronave em voo com uma menor velocidade. Desta maneira, é proporcionado um maior ângulo de estol e consequente maior sustentação, permitindo que os procedimentos de pouso e decolagem sejam mais seguros e que uma pista menor para ambas as operações possa ser utilizada, por exemplo. Este estudo contempla um modelo de perfil MDA 30P30N, com as excrescências no formato de selos de seção transversal bidimensional, circular e quadrada, presentes em diferentes posições na cova do eslate e ao longo de toda a sua envergadura. Foram compreendidos diferentes ângulos de ataque do modelo e velocidades de escoamento livre. O trabalho experimental utilizou-se de um túnel de vento de seção de testes e circuito fechados da USP-EESC, o modelo MDA 30P30N pré-existente na universidade e equipamentos de medições acústicas (microfones, sistemas de aquisição de dados e etc.), e de pressão (escâneres, manômetros, etc.). O pós-processamento dos dados aeroacústicos adquiridos nos ensaios realizados é uma etapa que objetiva a caracterização do ruído a partir de espectros de frequência e mapas acústicos, para localização e determinação da intensidade das fontes sonoras. Este processo é efetivado com códigos de beamforming implementados pelo grupo de pesquisa contendo o método de deconvolução DAMAS. A técnica de beamforming é um método para localização e estimativa da amplitude de fontes de ruído utilizando medidas realizadas a partir de uma antena de microfones, baseando-se em um modelo matemático que descreve a propagação de ondas acústicas em um meio com propriedades físicas bem definidas. Estes modelos são simplificados em relação à complexidade dos fenômenos de geração e propagação do som. O cálculo basicamente resolve a contribuição relativa das fontes provindas de diferentes direções no campo sonoro de interesse. O método DAMAS almeja compensar a influência das características da antena de microfones empregada para aquisição dos dados do resultado proveniente do cálculo efetuado com a técnica de beamforming convencional, resolvendo um problema de deconvolução. Os espectros de ruído obtidos neste trabalho apresentam o ruído de eslate bem definido em três componentes principais, que são os múltiplos picos tonais de baixa frequência, banda larga e pico tonal de alta frequência. Para a configuração de referência, sem a presença de selos na cova do eslate, verifica-se que ângulos de ataque extremos, muito baixos ou muito altos, apresentam o espectro de frequências quase que inteiramente como de banda larga e de intensidade muito próxima ao ruído de fundo do túnel. Também há um ângulo de ataque em que a emissão sonora é máxima. Quando há a presença de um selo na cova do eslate, existe um grande impacto em seu espectro acústico. Dependo da posição em que o selo se encontra, este pode atenuar ou intensificar os múltiplos picos tonais de baixa frequência, trocar o pico dominante, suprimir a componente de múltiplos picos, modificar o comportamento da componente da banda larga e ainda amplificar ou reduzir o ruído global do eslate.
The present work refers to an experimental aeroacoustic study aiming to characterize slat noise over the presence of excrescences installed at the interior of its cove, and at very high and very low angles of attack (between -4 e 18 [º]). A slat is a high-lift device located at the leading edge of an airfoil which target to maintain the aircraft in flight at a lower speed by providing a greater stall angle and consequently greater lift coefficient, allowing safer landing and take-off procedures. Therefore, a smaller airport runaway for both operations may be used. This study includes a model of a MDA 30P30N airfoil, with a seal excrescence of two-dimensional cross-section shape, circular or square, positioned at different locations at slat cove throughout the extent of its span. Different models angles of attack and some free-stream velocities were tested. The experimental work employed a closed-section wind tunnel situated at USP-EESC, a preexisting MDA 30P30N model, and acoustic measurement equipments (microphones, data acquisition systems, etc.), and pressure measurement equipments (scanners, pressure gauges, etc.). The data post-processing of aeroacoustics experiments intend to characterize the slat noise due to frequency spectrums and acoustic maps to locate and evaluate the intensity of the noise sources. This process is made with beamforming in-house codes, implemented by the research group, containing a deconvolution method named DAMAS. Beamforming technique is a method to localize and assess noise sources amplitude using measurements from an antenna of microphones, based on a mathematical model that describes the propagation of acoustic waves in a medium with well defined physical properties. Such models are simplified compared to the complexity of the phenomena of generation and propagation of sound. The calculation basically resolves the relative contribution of sources emanating from different directions at the sound field of interest. DAMAS method aim to extract the characteristics of the microphones antenna employed to acquire data, from the result of the calculation performed with conventional beamforming algorithm, solving a deconvolution problem. The noise spectrum obtained at this work shows that the slat noise can be well defined in three main components, which are the multiple tonal peaks of low frequency, broadband and high-frequency tonal peak. For the baseline configuration, without seals at slat cove, it is possible to notice that for extreme angles of attack, very low or very high, the noise spectrum is almost entire of broadband type. Its noise intensity is very near to the background wind tunnel noise. There is an angle of attack which has a maximum sound emission. A seal at MDA 30P30N slat cove has a huge impact on slat noise spectrum. Depending on the seal position, it can mitigate or enhance the multiple low-frequency tonal peaks, change the dominant peak, suppress multiple tonal peaks, modify the behavior of the broadband component and reduce or amplify the overall slat noise.

This thesis is dedicated to a study of manufacturing of aluminum parts at Alfa company. A complete analysis of the company's main product which are roller doors for commercial vehicles is elaborated. The thesis is based on a existing operation of the company and tries to find the optimal solution for the future. The result is the definition of a new solution and determination it’s operating costs, economic impacts and suggestions for improvement. Key words roller door, aluminum profiles, slat, roller shutter, manufacturing of aluminum parts.

The goal of this diploma work is a proposal and structural survey of wooden bridge for pedestrians and cyclists over the water area. The bridge is situated into the area of town Jihlava. A clingy slat wood and steel construction elements have been used for construction proposal. Bridge span is being used as 50 metres. Generally two variations of bridge constructions have been elaborated, variation A and variation B, of which variation A has been elaborated in more details.

The purpose of a multi-element high lift device is to increase lift dramatically while controlling the stall limit. The fluid flow over a multi-element high lift device has been explored widely both experimentally and numerically at high Reynolds numbers (O(10^6 )). The numerical simulations use turbulence models and hence details of the flow are not yet available. Low Reynolds number (O(10^4 )) flows over high lift devices have not been explored until recently. These lower Reynolds number flows have applications in the development of small aerial vehicles. The present work discusses both two-dimensional and three-dimensional direct numer- ical simulations of fluid flow over a 30P30N three-element high lift system using a high-order spectral element method code, Nek5000, that solves the incompressible Navier-Stokes equations. The intricate geometry of the multi-element device poses a challenge for the high-order spectral element method. We study the complex flow physics in the slat cove region and the wake/shear layer interaction over a 30P30N three-element high lift device. The targeted cases are at Reynolds num- bers based on stowed chord lengths (Rec ) of 8.32 × 10^3 , 1.27 × 10^4 , and 1.83 × 10^4 at angle of attack of 4. A critical interval for Rec has previously been found between 1.27 × 10^4 and 1.38 × 10^4 in experiments. This divides the flow into two types: when Rec is below the critical interval, no roll-up is observed in the slat cove and Görtler vortices dominate the slat wake; however when the Rec is above the critical interval, a roll-up is observed in the slat cove and co-existence of streamwise and spanwise vortices is confirmed in the slat wake. We confirm the presence of the critical interval from the simulations performed at three values of Rec . Lift and drag analysis is provided along with pressure coefficient plots for each element of the multi-element airfoil. Different vortical structures are also identified in the transition of flow from two dimensions to three dimensions. The relevant validation is performed with the available experimental data.

This diploma thesis deals with the static assessment of selected parts of the panel building of the former boarding school, for which adaptation to separate housing units and extension of one floor is planned. Upon the planned change of layout, extensions of the original door openings and new openings are proposed. The work assesses the object in its original state with the included unprofessional interference in statics during its use, and the object in the final state with planned modifications of the openings and proposes solutions to secure unsatisfactory areas to suit the new state loads

A redução do ruído externo gerado por aeronaves operando nas proximidades de grandes centros urbanos é apontada como uma questão vital para a manutenção e expansão sustentável das atividades da aviação civil. Nas últimas décadas, reduções significativas no ruído gerado pelos sistemas de propulsão da aeronave tornaram relevantes as contribuições do trem de pouso e dos dispositivos de hiper-sustentação (flapes e eslates) para o ruído global da aeronave. A caracterização do espectro acústico de cada componente hiper-sustentador é necessária para o desenvolvimento de métodos preditivos de ruído e projetos aerodinâmicos que viabilizem a redução de ruído sem penalizações severas para o desempenho e a segurança da aeronave. Experimentos com modelos em escalas mostram que a contribuição de cada elemento hiper-sustentador para o ruído global é determinada pelo tamanho e modelo da aeronave. Tal fato dificulta a generalização dos resultados experimentais e determina a caracterização do espectro acústico de cada componente de um aerofólio em termos de sua geometria e configuração operacional. Este trabalho tem como objetivo principal a caracterização do ruído do eslate a partir de medições experimentais com um aerofólio hiper-sustentador McDonnell Douglas (30P30N), composto por flape, eslate e elemento principal. Os experimentos foram realizados em túnel de vento de seção fechada, e as medições acústicas contaram com o uso de uma antena composta por 62 microfones. Os dados acústicos foram processados com algoritmos de beam-forming convencional e deconvolução DAMAS (Deconvolution Approach for the Mapping of Acoustic Sources). A aplicação de técnicas de beam-forming permite representar uma distribuição espacial de fontes na forma de um mapa acústico e determinar o nível de ruído gerado por fontes que concorrem de forma independente para o ruído global. A base de dados experimentais permite o estudo do ruído do eslate sob diferentes configurações operacionais e geométricas do aerofólio. A análise do espectro acústico do eslate revela a ocorrência de ruído tonal em baixa e alta frequências, e ruído de banda larga em média frequência. Os mapas de beam-forming obtidos associam o ruído de banda larga com uma distribuição bidimensional de fontes ao longo da envergadura do eslate. O ruído do eslate aumenta com a velocidade de escoamento livre, enquanto que os picos tonais de baixa frequência e o ruído de banda larga decrescem com o aumento do ângulo de ataque do aerofólio de 2° para 10°. Os espectros de ruído do eslate colapsam quando reescalados pelo número de Mach do escoamento livre elevado a uma potência entre 4 e 5, e o ruído tonal colapsa em Strouhal dado pela corda do eslate e pela velocidade do escoamento base. Os resultados mostram que o ruído do eslate é fortemente dependente da geometria do aerofólio, particularmente para variações de overlap. Uma boa correspondência quantitativa foi obtida comparando-se espectros experimentais de ruído do eslate com espectros numéricos, obtidos a partir de um modelo com a mesma geometria e em condições de teste idênticas, o que indica a viabilidade do uso de túneis de vento de secção fechada para a realização de experimentos aeroacústicos.
The reduction in the noise produced by aircraft operating in the vicinity of large urban centers is an important issue for a sustainable growth in the civil aviation activities. Over the last decades, from a signicant reduction achieved in the noise generated by aircraft propulsion systems, the contribution of both landing gears and high-lift devices (flaps and slats) has become important to the aircraft overall noise. The identication of the noise signature of each high-lift component is required for the development of both noise prediction methods and new aerodynamic design concepts toward achieving a noise reduction without severe penalty over the aircraft performance and safety. Scaled model experiments have shown that the importance of each airframe component to the overall noise is determined by particularities in both aircraft geometry and size. Such noise model dependence hampers the generalization of experimental results from a reference testing model and leads to the necessity of assessing noise generation according to the testing model geometry and operational condition. This study focuses mainly on the characterization of slat noise from experimental measurements on a high-lift Mcdonnell Douglas (30P30N) airfoil, composed of a slat, a ap and a main element. Measurements were performed in a closed-section wind tunnel by a 62-microphone array and the acoustic data were processed with in-house codes based on conventional beam-forming and DAMAS (Deconvolution Approach for theMapping of Acoustic Sources) algorithms. Beam-forming techniques potentially enable the representation of a spatial source distribution as an acoustic map, from which the contribution of independent sources to the overall noise can be estimated. The experimental database enables the study of the slat noise from dierent airfoil operational conditions and geometrical settings. The slat noise spectral signature reveals the occurrence of tonal noise over both low- and high-frequency bands and also broadband noise over a mid-frequency range. Beam-forming maps indicate the slat broad-band noise originates from a source spatially distributed along the slat span. The slat noise increases in function of the ow speed, whereas low-frequency tonal peaks and the broadband noise decrease as the airfoil angle of attack increases from 2 to 10. The slat noise spectra scalle when the Mach number is raised to a power between 4 and 5, and the tonal noise collapses with Strouhal based on the slat chord and the ow speed. Results show the slat noise is strongly in uenced by the airfoil geometry, particularly for variations in the overlap. A good quantitative agreement was achieved through the comparison between the experimental and numerical slat noise spectra for the same model geometry and test conditions, which indicates the viability of performing aeroacoustic experiments in closed-section wind tunnels.

Com o desenvolvimento para aeronaves de propulsores turbo-fan com elevada razão de derivação, componentes da estrutura do avião passaram a ter relevância na geração de ruído aerodinâmico, principalmente durante a aproximação e o pouso. Dentre esses componentes, o eslate se destaca por ser uma fonte que se estende ao longo de praticamente toda a envergadura da asa. Neste trabalho, simulações numéricas foram feitas no intuito de considerar configurações práticas nas análises do ruído aeroacústico gerado pelo eslate. Um código comercial baseado no Método Lattice-Boltzmann foi usado no cálculo do escoamento transiente em torno do aerofólio MD30P30N. O domínio computacional simulado imitou a configuração geométrica de um túnel de vento. Foi levado em consideração o efeito da presença de duas formas de excrescência que são comuns na cova do eslate de aeronaves comerciais. Uma delas foi um selo que fica posicionado na parede da cova e a outra, um tubo do sistema anti-gelo. Tanto o escoamento transiente na região da cova quanto as características do ruído aeroacústico propagado para o campo distante foram analisados. Uma metodologia que impõe condição de parede com escorregamento livre no es- late e elemento principal, permitindo assim uma redução do custo computacional, foi usada. A abordagem foi ainda testada para a condição de um aerofólio submetido a escoamento cruzado, simulando uma asa infinita com enflechamento. Também uma modificação na metodologia, para que ela possa ser empregada em aerofólios com elevados ângulos de ataque, foi proposta e testada. O código híbrido MSES foi usado para o cálculo da espessura de deslocamento na camada limite do aerofólio. A modificação na geometria baseada em \'delta\'* causou uma melhora da solução aeroacústica de uma simulação empregando paredes com escorregamento livre, tomando como base de comparação a solução com paredes sem escorregamento. Simulações com selo dentro da cova, perto do recolamento, mostraram que, em certas circunstâncias, há um bloqueio dos vórtices da camada de mistura, intensificando picos tonais no espectro do ruído. A variação da posição do selo mostrou um efeito significativo no ruído do eslate, de forma que um selo suficientemente afastado do recolamento modificou o espectro do ruído do eslate. Os resultados com o aerofólio enflechado indicam que, também neste caso, o ruído do eslate não depende diretamente da camada limite na cúspide, mas da circulação do aerofólio. Por sua vez, a presença do tubo na cova aumenta significativamente a intensidade do ruído de banda larga produzido pelo eslate. Em uma asa sem enflechamento, o tubo causa também um aumento substancial na intensidade de picos tonais de baixa frequência.
The development of high by-pass ratio turbo-fan engine turned the airframe noise into an important component in a commercial airplanes\' noise characteristics. Between the airframe noise sources the slat can be highlighted as it extends almost along the whole wing span. Numerical simulation was carried out in order to consider practical configuration in the aeroacoutic noise generated by the slat. The effects of two different excrescences, which are normally present in commercial airplanes\' slat cove, were taken into account. One of them was a seal attached to the cove wall and the outher one was a tube that compose the anti-icing system. Both unsteady flow in cove region and far-field noise characteristics were analysed. A methodology that impose free-slip wall boundary condition on slat and main element surfaces was employed, which allowed the reduction of computational requirements. This approach was also tested for airfoil with crossflow, which simulates an infinite swept wing. Also a modification of the methodology was proposed and tested to extend its application in high-lift airfoils under higher angle of attack. A commercial code based on the Lattice-Boltzmann Method was used to compute the unsteady flow over the MD30P30N airfoil. The simulated computational domain imitates the geometry of a wind tunnel. The hybrid Euler/IBL code MSES was employed to calculate the displacement thickness of the airfoil\'s boundary layers. The geometry modification based on \'delta\'* caused a improvement on the aeroacoustic solution of a free-slip simulation, the no-slip simulation results being taken as reference. Simulations of geometries with relatively small seal close to the reattachment point showed that a blockage of the mixing layer vortices hapens and tonal peaks are intensified in the far-field noise spectrum. The variation of the seal position showed a significant effect on the slat noise, so that a seal farther from the reattachment modified affected both the shape and intensity of the noise spectrum. Results with the swept airfoil indicates that, even in the presence of crossflow, the slat noise does not depend on the cusp boundary layer, namely it is more sensitive to the airfoil circulation. The tube crossing the slat cove augmented significantly the broadband noise generated by the slat. In an unswept wing it also caused a substantial increase in the low-frequency tonal peaks.

Esta dissertação apresenta o desenvolvimento e otimização de uma metodologia baseada em código comercial para previsão de ruído em um eslate, além do estudo da dependência do ruído ao variar a camada limite do aerofólio. Com a contínua redução do ruído produzido por motores em aeronaves e as sucessivas restrições nos níveis de certificação, o ruído produzido por dispositivos aerodinâmicos tem ganhado importância no projeto de uma aeronave. Durante o pouso, o ruído gerado pelos dispositivos hiper-sustentadores é classificado dentre os mais relevantes, sendo o eslate um de seus componentes. Este trabalho busca criar e otimizar uma metodologia baseada no código PowerFLOW, assim como estudar a influência das camadas limite do aerofólio na geração de ruído. Tal código é baseado na formulação de Lattice- Boltzmann. As fontes acústicas simuladas são propagadas utilizando uma analogia acústica de Ffowcs-Williams e Hawkings e, então, analisadas utilizando métodos estatísticos de análise de sinais. Estudos de validação e verificação do código baseados em soluções analíticas são apresentados, tais como uma camada de mistura periódica no espaço e a solução dos vórtices de Taylor-Green. A seguir, o aerofólio 30P30N é utilizado em todo o estudo relacionado a eslates, analisando primeiramente a independência da solução em relação ao nível de refinamento da malha e do tamanho do domínio empregados. Baseado nas recomendações de tal estudo, o resultado é comparado com simulações disponíveis na literatura. Com uma maior confiança na metodologia, o trabalho então apresenta estudos variando a camada limite em regiões do eslate, assim como removendo-a completamente em certas regiões do aerofólio ao empregar condições de contorno de livre-escorregamento. O trabalho mostra que a influência das camadas limite do aerofólio é desprezível em relação ao erro do método. Isso é causado pela aparente independência do ruído do eslate em relação ao escoamento perto de sua cúspide. Tal independência permite que a malha computacional seja otimizada, reduzindo o custo da simulação em até 60%.
This dissertation presents the development and optimization of a methodology based on a commercial software to predict slat noise, also studying noise dependency when varying airfoil boundary layers. Due to continuous reduction on aircraft engine noise and successive restrictions on noise certification levels, airframe noise has been gaining importance on aircraft design. During landing, high-lift noise is ranked as one of the most relevant ones, being slat noise one of its components. This work focuses on creating and optimizing a noise prediction methodology based on the software PowerFLOW, and also on studying the influence of airfoil boundary layers on noise generation. Such software is based on Lattice-Boltzmann formulation. The simulated sound sources are propagated using Ffowcs-Williams and Hawkings acoustic analogy and then analyzed by signal analysis methods. Code validation and verification studies based on analytical solutions are presented, such as the spacially-periodic mixing layer and the Taylor-Green vortices solutions. Following, the 30P30N airfoil is employed through the rest of this work, firstly studying the solution independency related to mesh refinement level and computational domain size. Based on recommendations from this study, the results are compared to simulations from the literature. With higher confidence levels on this methodology, the work then presents studies varying the slat boundary layer and also removing it completely by employing free-slip boundary conditions on certain airfoil regions. This work presents that the airfoil boundary layer influence is neglectable when compared to the method error. This is caused by the apparent slat noise independency related to the flowfield near the slat cusp. Such independency allows the computational mesh to be optimized, reducing the simulation cost by up to 60%.

PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
FUNDAÇÃO DE APOIO À PESQUISA DO ESTADO DO RIO DE JANEIRO
PROGRAMA DE EXCELENCIA ACADEMICA
BOLSA NOTA 10
Atualmente, sistemas de visão computacional em computadores portáteis estão se tornando uma importante ferramenta de uso pessoal. Sistemas de visão para localização de objetos é uma área de pesquisa muito ativa. Essa dissertação propõe um algoritmo para localizar posições no espaço e objetos em ambientes não instrumentados com o uso de uma câmera web e um computador pessoal. Para isso, são usados dois algoritmos de rastreamento de marcadores para reinicializar frequentemente um algoritmo de Visual Simultaneous Localisation and Mapping. Essa dissertação também apresenta uma implementação e um conjunto de testes para validar o algoritmo proposto.
Nowadays, vision systems in portable computers are becoming an important tool for personal use. Vision systems for object localization are an active area of research. This dissertation proposes an algorithm to locate position and objects in a regular environment with the use of a simple webcam and a personal computer. To that end, we use two algorithms of marker tracking to reboot often a Visual Simultaneous Localisation and Mapping algorithm. This dissertation also presents an implementation and a set of tests that validate the proposed algorithm.

GREY SLATE is a collection of poems that focuses on the natural world in order to explore the mysteries of life with the intent to create a meditation on what it means to be a human being interacting with this world. Inspired by John Keats’ theory of Negative Capability, GREY SLATE does not seek to explain, but to dwell in the mysteries it explores. The poems are tied together through similar images or ideas in order to mimic the way the mind works as it jumps from thought to thought. GREY SLATE also mixes different types of poems: from haiku to sonnet to paradelle, and from lyric to narrative to prose poem. GREY SLATE hopes to inspire readers to take a break from searching for truths and indulge in the beautiful mystery that is life with no need for answers.

Catchwords and catchphrases denoting crucial ideological concepts or disqualifying an opponent serve as indices pointing to the line of demarcation between political camps. Using the example of three catchwords (Patriotyzm genetyczny genetic patriotism, pka kulturowa cultural shelf, Palikotyzacja X-a Palikotization of X) emerging in the aggravated political debate in Poland between 2000 and 2009, and mainly signaling affiliation with the national conservative PiS-party, a twofold approach combining methods from discourse analysis and cognitive linguistics is proposed. On the one hand, the lexical items are analyzed as keywords in statu nascendi which are disputed, quoted or ridiculed and serve as intertextual hinges which still have the potential to evoke the communicative situation in which they have been created. On the other hand, the selected newly created lexical items are analyzed as conceptual integration networks within the framework of blending theory. The blending analysis reveals the underlying logic of the novel conceptual structure and displays the explanative and argumentative pattern suggested by the blend and condensed in the catchword. By tracing the disputes elicited by these catchwords and analyzing sequences in which these newly created concepts are contested or maintained from a cognitive perspective, we can see how the logic suggested by the blend is either perpetuated or perverted in the process of the ongoing dissemination of the catchword.

A core problem that must be solved by any practical visual SLAM system is the need to obtain correspondences throughout the image stream captured by a moving camera. Correspondences enable joint estimation of a moving camera's trajectory together with a 3D map of the observed scene. Visual SLAM pipelines commonly obtain correspondence through sparse feature matching techniques and construct maps using a composition of point, line or other simple primitives. The resulting sparse feature map representations provide sparsely furnished, incomplete reconstructions of the observed scene. Related techniques from multiple view stereo (MVS) achieve high quality dense reconstruction by obtaining dense correspondences over calibrated image sequences. Despite the usefulness of the resulting dense models, these techniques have been of limited use in visual SLAM systems. The computational complexity of estimating dense surface geometry has been a practical barrier to its use in real-time SLAM. Furthermore, MVS algorithms have typically required a fixed length, calibrated image sequence to be available throughout the optimisation --- a condition fundamentally at odds with the online nature of SLAM. With the availability of massively-parallel commodity computing hardware, we demonstrate new algorithms that achieve high quality incremental dense reconstruction within online visual SLAM. The result is a live dense reconstruction (LDR) of scenes that makes possible numerous applications that can utilise online surface modelling, for instance: planning robot interactions with unknown objects, augmented reality with characters that interact with the scene, or providing enhanced data for object recognition. The core of this thesis goes beyond LDR to demonstrate fully dense visual SLAM. We replace the sparse feature map representation with an incrementally updated, non-parametric, dense surface model. By enabling real-time dense depth map estimation through novel short baseline MVS, we can continuously update the scene model and further leverage its predictive capabilities to achieve robust camera pose estimation with direct whole image alignment. We demonstrate the capabilities of dense visual SLAM using a single moving passive camera, and also when real-time surface measurements are provided by a commodity depth camera. The results demonstrate state-of-the-art, pick-up-and-play 3D reconstruction and camera tracking systems useful in many real world scenarios.

Thesis: Sc. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2016.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 151-162).
The ability to construct an accurate model of the environment is an essential capability for mobile autonomous systems, enabling such fundamental functions as planning, navigation, and manipulation. However, the general form of this problem, simultaneous localization and mapping (SLAM), is typically formulated as a maximum-likelihood estimation (MLE) that requires solving a nonconvex nonlinear program, which is computationally hard. Current state-of-the-art SLAM algorithms address this difficulty by applying fast local optimization methods to compute a critical point of the MLE. While this approach has enabled significant advances in SLAM as a practical technology by admitting the development of fast and scalable estimation methods, it provides no guarantees on the quality of the recovered estimates. This lack of reliability in existing SLAM algorithms in turn presents a serious barrier to the development of robust autonomous systems generally. To address this problem, in this thesis we develop a suite of algorithms for SLAM that preserve the computational efficiency of existing state-of-the-art methods while additionally providing explicit performance guarantees. Our contribution is threefold. First, we develop a provably reliable method for performing fast local optimization in the online setting. Our algorithm, Robust Incremental least-Squares Estimation (RISE), maintains the superlinear convergence rate of existing state-of-the-art online SLAM solvers while providing superior robustness to nonlinearity and numerical ill-conditioning; in particular, we prove that RISE is globally convergent under very mild hypotheses (namely, that the objective is twice-continuously differentiable with bounded sublevel sets). We show experimentally that RISE's enhanced convergence properties lead to dramatically improved performance versus alternative methods on SLAM problems exhibiting strong nonlinearities, such as those encountered in visual mapping or when employing robust cost functions. Next, we address the lack of a priori performance guarantees when applying local optimization methods to the nonconvex SLAM MLE by proposing a post hoc verification method for computationally certifying the correctness of a recovered estimate for pose-graph SLAM. The crux of our approach is the development of a (convex) semidefinite relaxation of the SLAM MLE that is frequently exact in the low to moderate measurement noise regime. We show that when exactness holds, it is straightforward to construct an optimal solution Z* for this relaxation from an optimal solution X* of the SLAM problem; the dual solution Z* (whose optimality can be verified directly post hoc) then serves as a certificate of optimality for the solution X* from which it was constructed. Extensive evaluation on a variety of simulated and real-world pose-graph SLAM datasets shows that this verification method succeeds in certifying optimal solutions across a broad spectrum of operating conditions, including those typically encountered in application. Our final contribution is the development of SE-Sync, a pose-graph SLAM inference algorithm that employs a fast purpose-built optimization method to directly solve the aforementioned semidefinite relaxation, and thereby recover a certifiably globally optimal solution of the SLAM MLE whenever exactness holds. As in the case of our verification technique, extensive empirical evaluation on a variety of simulated and real-world datasets shows that SE-Sync is capable of recovering globally optimal pose-graph SLAM solutions across a broad spectrum of operating conditions (including those typically encountered in application), and does so at a computational cost that scales comparably with that of fast Newton-based local search techniques. Collectively, these algorithms provide fast and robust inference and verification methods for pose-graph SLAM in both the online and offline settings, and can be straightforwardly incorporated into existing concurrent filtering smoothing architectures. The result is a framework for real-time mapping and navigation that preserves the computational speed of current state-of-the-art techniques while delivering certifiably correct solutions.
by David M. Rosen.
Sc. D.

Two models able to predict Time-Temperature-Transformation (TTT) diagrams for liquid oxides and oxyfluorides have been developed. One on the basis of the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation and the other – using Classical Nucleation Theory (CNT). The most recent FactSage database was used for calculating the thermodynamic properties of the liquid and solid phases. The model based on the JMAK equation provided much better agreement with experimental data than the CNT model. The model developed in this study was used to successfully predict TTT diagrams for binary, ternary and multicomponent oxide slags containing no more than 50 wt% SiO2 and for some of the oxyfluoride slags.
Deux modèles capables de prédire les diagrammes temps-température-transformation (TTT) pour des oxydes et oxyfluorures liquides ont été développés. Un des modèles est basé sur l'équation de Johnson-Mehl-Avrami-Kolmogorov (JMAK), et l'autre – utilisant la théorie classique de la nucléation (TCN). La base de données la plus récente a été utilisée pour calculer les propriétés thermodynamiques des phases liquides et solides. Le modèle basé sur l'équation JMAK a démontré un accordement avec les données expérimentales bien meilleur que la TCN. Le modèle développé dans cette étude peut être utilisé pour prédire des diagrammes TTT pour les oxydes contenant pas plus que 50 % massique de SiO2 et pour quelques oxyfluorures.

Localização e Mapeamento Simultâneos (SLAM) é uma das tarefas mais difíceis em robótica móvel, uma vez que existe uma dependência mútua entre a estimativa da localização do robô e a construção do mapa de ambiente. As estratégias de SLAM mais bem sucedidas focam na construção de um mapa métrico probabilístico empregando técnicas de filtragem Bayesiana. Embora tais métodos permitam a construção de soluções localmente consistentes e coerentes, o SLAM continua sendo um problema crítico em operações em ambientes grandes. Para contornar esta limitação, muitas estratégias dividem o ambiente em pequenas regiões, e formulam o problema de SLAM como uma combinação de múltiplos submapas métricos precisos associados em um mapa topológico. Este trabalho propõe um método de SLAM baseado nos algoritmos DP-SLAM (Distributed Particle SLAM) e SegSlam (Segmented SLAM). SegSLAM é um algoritmo que cria múltiplos submapas para cada região do ambiente, e posteriormente constrói o mapa global selecionando combinações de submapas. Por sua vez, DP-SLAM é um algoritmo de filtro de particulas Rao-Blackwellized que utiliza uma representação distribuída eficiente dos mapas das partículas, juntamente com a árvore de ascendência das partículas. A característica distribuída destas estruturas é favorável para a combinação de diferentes segmentos de mapa localmente precisos, o que aumenta a diversidade de soluções. O algoritmo proposto nesta dissertação, chamado SDP-SLAM, segmenta e combina diferentes hipóteses de trajetórias do robô, a fim de reconstruir o mapa do ambiente. Nossas principais contribuições são o desenvolvimento de novas estratégias para o casamento de submapas e para a estimativa de boas combinações de submapas. O SDP-SLAM foi avaliado através de experimentos realizados por um robô móvel operando em ambientes reais e simulados.
Simultaneous Localization and Mapping (SLAM) is one of the most difficult tasks in mobile robotics, since there is a mutual dependency between the estimation of the robot pose and the construction of the environment map. Most successful strategies in SLAM focus in building a probabilistic metric map employing Bayesian filtering techniques. While these methods allow the construction of consistent and coherent local solutions, the SLAM remains a critical problem in operations within large environments. To circumvent this limitation, many strategies divide the environment in small regions, and formulate the SLAM problem as a combination of multiple precise metric submaps associated in a topological map. This work proposes a SLAM method based on the Distributed Particle SLAM (DPSLAM) and the Segmented SLAM (SegSLAM) algorithms. SegSLAM is an algorithm that generates multiple submaps for every region of the environment, and then build the global map by selecting combinations of submaps. DP-SLAM is a Rao-Blackwellized particle filter algorithm that uses an efficient distributed representation of the particles maps associated with an ancestry tree of the particles. The distributed characteristic of these structures favors the combination of locally accurate map segments, that can increase the diversity of global level solutions. The algorithm proposed in this dissertation, called SDP-SLAM, segments and combines different hypotheses of robot trajectories to reconstruct the environment map. Our main contributions are the development of novel strategies for the matching of submaps and for the estimation of good submaps combinations. SDP-SLAM was evaluated through experiments performed by a mobile robot operating in real and simulated environments.

Svensson, L. Tar empatin slut? En litteraturstudie om empatitrötthet. Examensarbete i omvårdnad 15 högskolepoäng. Malmö högskola: Fakulteten för hälsa och samhälle, institutionen för vårdvetenskap, 2018. Bakgrund: Sjuksköterskor ställs inför fler traumatiska upplevelser under kort tid än en individ utanför det vårdande yrket gör under en livstid. Empatitrötthet är för den svenska sjukvården ett nytt myntat begrepp. För att förstå empatitrötthet har även fenomenet empati beskrivits kort i bakgrunden. En vidare och djupare förståelse för fenomenet empatitrötthet presenteras i resultatet. Syfte: Syftet med studien är att utforska fenomenet empatitrötthet ur ett omvårdnadsperspektiv.Metod: En icke systematisk litteraturstudie har gjorts baserad på kvalitativa, kvantitativa och mixade ansatser för att få ett helhetsperspektiv på fenomenet empatitrötthet. Resultat: Fenomenet empatitrötthet påverkar omvårdnaden av patienter och anhöriga. Sjuksköterskor med kort erfarenhet drabbas lättare av empatitrötthet än sjuksköterskor med lång erfarenhet. Det finns inga riktlinjer för hur en sjuksköterska ska motverka empatitrötthet, utan sjuksköterskor använder egna strategier för att inte drabbas av empatitrötthet.Konklusion: Litteraturstudien visar att begreppet empatitrötthet är högst aktuellt i dagens sjukvård då hög arbetsbelastning och stress hos sjuksköterskan ofta är ett faktum. Nyckelord: Empatitrötthet, Omvårdnad, Utbrändhet, Sekundär traumatisk stress, Sjuksköterska.
Svensson, L. Does empathy ever end? A literature review about compassion fatigue. Degree project in nursing 15 credit points. Malmö University: Faculty of Health and Society, Department of Care Science, 2018. Background: Nurses today are exposed to more traumatic events under a short period of time than a person outside the caring environment experiences in a lifetime. Compassion fatigue is a new concept in Swedish health care. To understand compassion fatigue the concept empathy further been discussed in the background. A deeper understanding for the phenomena compassion fatigue is presented in the result. Aim: The aim for this study is to further explore the phenomena of compassion fatigue from a nursing perspective.Method: A non-systematic literature review has been used in this study based on literature using different approaches to get a holistic view on the phenomena compassion fatigue. Result: The phenomenon of compassion fatigue affects the care of patients and relatives. Nurses with short experience are more easily affected by compassion fatigue than nurses with long experience. There are no guidelines for how a nurse should counteract comapssion fatigue, but nurses use their own strategies to not suffer from compassion fatigue.Conclusion: The review shows that the concept of compassion fatigue is highly topical in today's medical care when high workload and stress in the nurse is often a fact. Keywords: Burnout, Compassion fatigue, Nursing, Nurses, Secondary traumatic stress.

This paper explores the influences, ideas and motivations behind my MFA thesis exhibition. It primarily focuses on how I developed my work for the show in connection to my previous work as well as work created by other artists who explored the impacts of new media in the last decade. With the advancement of social media, digital technologies no longer have their infamous coldness. Our perceptions and the metaphors in language are all reflected onto the machines we create while in return they also shape and redefine our lives. It becomes increasingly difficult to talk about dialectics such as machine-human, virtual-real, and nature-culture. With the aid of some humor, I attempted to reflect on the marriage of these old oppositions and this paper will discuss the foundations of these ideas as well as my practice in general.

Simultaneous Localisation and Mapping (SLAM) began as a technique to enable real-time robotic navigation on previously unexplored environments. The created maps however were designed for the sole purpose of localising the robot (i.e. what is the position and orientation of the robot in relation to the map) and several systems demonstrated the increasing descriptive power of map representations, which on vision-only SLAM solutions consisted of simple sparse corner-like features as well as edges, planes and most recently fully dense surfaces that abandon the notion of sparse structures altogether. Early sparse representations enjoyed the benefit of being simple to maintain as features could be added, optimised and removed independently while being memory and compute efficient, making them suitable for robust real-time camera tracking that relies on a consistent map. However, sparse representations are limiting when it comes to interaction, as for example, a robot aiming to safely navigate in an environment would need to sense complete surfaces in addition to empty space. Furthermore, sparse features can only be detected on highly-textured areas and during slow motion. Recent dense methods overcome the limitations of sparse methods as they can work in situations where corner features would fail to be detected due to blurry images created during rapid camera motion and also enable to correctly reason about occlusions and complete 3D surfaces, thus raising the interaction capabilities to new levels. This is only possible thanks to the advent of commodity parallel processing power and large amount of memory on Graphic Processing Units (GPUs) that needs careful consideration during algorithm design. However, increasing the map density makes creating consistent structures more challenging due to the vast amount of parameters to optimise and the interdependencies amongst them. More importantly, our interest is in making interaction even more sophisticated by abandoning the idea that an environment is a dense monolithic structure in favour of one composed of discrete detachable objects and bounded regions having physical properties and metadata. This work explores the development of a new type of visual SLAM system representing the map with semantically meaningful objects and planar regions which we call Dense Semantic SLAM, enabling new types of interaction where applications that can go beyond asking the question of "where am I" towards "what is around me and what can I do with it". In a way it can be seen as a return to lightweight sparse-based representations while keeping the predictive power of dense methods with added scene understanding at the object and region levels.

Abstract Composition Adjustment by Sealed argon bubbling – Oxygen Blowing (CAS-OB) process is a ladle treatment process that was developed for chemical heating and alloying of steel. The main stages of the process are heating, (possible) alloying and reduction of slag. The CAS-OB process aims for homogenization and control of the composition and temperature of steel. In this dissertation, a mathematical reaction model was developed for the slag reduction stage of the CAS-OB process. Slag reduction is carried out by applying vigorous bottom stirring from porous plugs at the bottom of the ladle. Due to the bottom stirring a circular steel flow is induced which disrupts top slag layer and due to shear stress at the steel-slag interface small slag droplets are detached. This induces an immense increase in the interfacial area between steel and slag which provides favourable conditions for the reduction reactions. In order to model reduction reactions, a sub-model for describing the interfacial area was needed. For this the slag droplet formation was studied using computational fluid dynamics (CFD) and based on these studies, a sub-model for droplet formation was developed. The model for the reduction stage of the CAS-OB process takes into account not only the reaction during the reduction but also the heat transfer between the phases, ladle and surroundings. The reduction stage model was validated using validation data obtained from the CAS-OB station of the SSAB Raahe steel plant in Finland. It was concluded that the model was able to predict steel and slag compositions as well as the steel temperature very well
Tiivistelmä CAS-OB -prosessi on sulametallurgiassa käytettävä senkkakäsittelyprosessi, joka on kehitetty teräksen kemialliseen lämmittäseen ja seostukseen. CAS-OB-prosessin pääprosessivaiheet ovat lämmitysvaihe, mahdollinen seostusvaihe ja kuonan pelkistysvaihe. CAS-OB -prosessilla tavoitellaan teräksen koostumuksen homogenisointiin ja lämpötilan kontrollointiin. Tässä tutkimuksessa kehitettiin matemaattinen reaktiomalli CAS-OB -prosessin kuonan pelkistysvaiheen kuvaamiseen. Kuonan pelkistys tapahtuu senkan pohjassa olevien huuhtelutiilien avulla suoritettavan voimakkaan kaasuhuuhtelun avulla. Pohjahuuhtelu aiheuttaa kiertävän teräsvirtauksen senkassa. Teräsvirtaus irrottaa teräksen päällä olevasta kuonakerroksesta pisaroita ja kuonan ja teräksen välinen reaktiopinta-ala kasvaa voimakkaasti. Tämä tarjoaa suotuisat olosuhteet pelkistysreaktiolle senkassa. Pelkistysreaktioiden mallintamiseksi tässä työssä kehitettiin CFD-simulaatioiden avulla alimalli, jonka avulla voidaan kuvata teräksen ja kuonan välisen pinta-alan suuruutta. Pelkistysvaiheen mallissa huomioidaan reaktioiden lisäksi myös systeemissä tapahtuva lämmösiirto. Pelkistysmalli validoitiin mittausdatalla, joka hankittiin SSAB Raahen terässulaton CAS-OB -asemalla järjestetyssä validointikampanjassa. Tutkimuksessa havaittiin, että malli kykenee hyvin ennustamaan teräksen ja kuonan koostumuksen sekä teräksen lämpötilan

During the pyrometallurgical extraction of copper, a significant part of the copper is lost with discard slag, which decreases profits, overall copper recovery, and efficiency of raw material usage. Smelting furnace slag usually has a copper content that is close to or higher than that of copper ores. The investigation of copper losses to slag is thus a task of practical significance, as the ore grades are depleting. Slag cleaning, e.g., a settling furnace, can reduce copper losses to slag as the mechanically suspended copper-containing droplets separate from slag under the action of gravity and can hence be recovered.  An industrial trial was conducted in an electric settling furnace with slag originating from an electric smelting furnace and processed in a zinc fuming furnace. The trial was conducted to increase the understanding of copper losses to slag and how the process parameters temperature and settling time influence the slag copper content. The obtained slag samples were also evaluated to gain better insights as to the settling mechanism and, if any, factors that hinder the copper phases from settling. Slag modification with CaO was also evaluated to investigate how the modification influences the settling of copper phases and, thus, the final slag copper content.  Samples collected during the industrial trial were the basis for the evaluation in the current work. The samples came from batches with varying temperatures, settling times, and CaO content collected at four different sample positions. Instrumental techniques, including XRF, FAAS, ICP-SFMS, and SEM-EDS, were used to analyze the chemical compositions of the samples and the appearance of copper and associated phases.  The results indicated that the copper content of outgoing slag increased with increasing temperature in the evaluated interval. The copper content was also concluded to be more strongly affected by the temperature compared to the settling time. Regulating the temperature to the lower temperature interval in the settling furnace could thus decrease the final slag copper content. During the slag characterization, it was found that suspended copper-containing phases were hindered from settling, due to the attachment to solid phases and gas bubbles in the slag. By controlling and minimizing the presence of the bottom buildup and thus solid phases in the slag, the copper content can be decreased. The results indicated that the CaO slag modification decreased the final slag copper content, and can thus be used as a modifier for increased settling.

Archaeological investigations into the whereabouts of the Alder Creek Donner family campsite yielded a number of artifacts. One type of artifact collected was writing slate fragments, the topic of this thesis. Why were writing slate fragments found at the Alder Creek camp? An investigation into writing slate in the historical record had to be conducted to address this question. The lack of pertinent research associated with writing slate posed a major obstacle, as it has been disregarded as a diagnostic artifact in historical archaeological literature. This paper addresses this problem by a history of writing slate and its uses, as well as including a discussion of precursors to writing slate, to provide a context for materials recovered from the Alder Creek site. It was first thought that writing slate was only used in the context of education, as might have provided a means of keeping the children busy during the Donner Partys snowbound experience. However, this research indicates that a number of other activities can be associated with writing slate; including messages and notes, record keeping and accounting, gaming and gambling. The writing slate recovered from the Donner family camp is analyzed here using the results of the historical overview of this material and a cognitive archaeological approach.

Methodology The basis of the research was to identify those physical, chemical and geological attributes of slate which make it a good roofing material. These were often related to specific Scottish quarries in order to select those which showed the best potential for resumed production. However, as no fresh samples of Scottish slate were available, the work was based initially on slate of known and reliable quality from producing quarries elsewhere. The parameters examined were mineral composition, metamorphic grade, fabric and weathering properties. When the parameters most closely related to the quality of finished slates were established then the Scottish slate was examined for these same parameters. Mineral Composition Recent progress in the determination of the chemical formulae of the phyllosilicates of fine-grained material has enabled the mineral composition of slate to be calculated from its total oxide composition. Calculations based on representative samples from each group of quarries gave good results when taken from sites in close proximity, but application to samples from more remote sites gave a weaker correlation. Metamorphic Grade Metamorphic grade affects the crystallinity and the grain size of a material. Traditionally for sedimentary rocks both properties were evaluated by the sharpness of peaks in XRD analysis, using Full Width at Half Magnitude (FWHM) as the criterion. However, this method is not effective when applied to slate, and an alternative method of determining its crystallinity was developed, based on the intensities of peaks of the main minerals.

Visual Simultaneous Localisation and Mapping (SLAM) is concerned with simultaneously estimating the pose of a camera and a map of the environment from a sequence of images. Traditionally, sparse maps comprising isolated point features have been employed, which facilitate robust localisation but are not well suited to advanced applications. In this thesis, we present map representations that allow a more dense description of the environment. In one approach, planar features are used to represent textured planar surfaces in the scene. This model is applied within a visual SLAM framework based on the Extended Kalman Filter. We presents solutions to several challenges which arise from this approach.

A 1/12 scale tank was constructed to physically simulate the metallurgical skimming process in order to gain a better insight of the skimming of fluid slag from copper anode furnaces. 1-decanol and water were used to represent the slag and the underlying liquid metal respectively. It was observed that slag skimming was comprised of two steps, a transportation step to carry slag to the skimming lip, and a removal step to move the slag across the lip. The efficiency of the transportation by bath surface circulation was strongly affected by the method of creation of the surface movement. Submerged gas injection failed to carry slag to the lip effectively because of the uncontrollable circulation pattern generated on the bath surface. On the other hand, three impinging gas jets in glancing contact with the bath surface were able to carry slag to the lip effectively. The Re of the jets (I.D. 0.01m) inclined 50° to the horizontal was 6100. The jet configuration was two of the jets were placed close and parallel to the rear wall of the model and faced each other. The third jet was parallel to the model short axis and was directed at the skimming mouth. With the same amount of time, 70% of the slag originally charged to the tank was skimmed with the assistance from the impinging gas jets in comparison to 20% when no jet was used. Detailed analysis of the skimming process revealed that the underlying liquid bath level continuously decreased as the slag was skimmed and resulted in continuous reduction of the skimming rate. In order to compensate the reduction of skimming rate due to bath level reduction, a control strategy was proposed for rotating the furnace continuously to maximize the skimming effectively.

Iron and steel production is a rapidly growing industry with global outputs increasing 65% over the last ten years (World Steel Association, 2012). Unfortunately, it is also the largest industrial source of atmospheric CO2, accounting for a quarter of the CO2 emissions from industrial sources (International Energy Agency (IEA), 2007).Mineral carbonation provides a robust method for permanent sequestration of CO2 that is environmentally inert. Larnite (Ca2SiO4), the major constituent of steel slag, reacts readily with aqueous CO2 (Santos et al., 2009). Consequently, its carbonation offers an important opportunity to reduce CO2 emissions at source. A potential added benefit is that this treatment may render steel slag suitable for recycling. This study investigates the impact of temperature, fluid flux and reaction gradient on the dissolution and carbonation of steel slag, and is part of a larger study designed to determine the conditions under which conversion of larnite, and other calcium silicates, to calcite is optimized. Experiments were conducted on 2 – 3 mm diameter steel slag grains supplied by Tata Steel RD&T. A CO2-H2O mixture was pumped through a steel flow-through reactor containing these grains. For a given experiment, temperature was fixed at a value between 120°C and 200°C, pressure was 250 bar, and the fluid flux was fixed at 0.8 mL/cm2min or 6 mL/cm2min. Reactions were also carried out in a batch reactor at 180°C and 250 bar, corresponding to a condition of zero flux. The duration of experiments ranged from 3 to 7 days. The CO2-H2O fluid reacted with the steel slag grains to form phosphorus-bearing Ca-carbonate phases. At high fluid flux, 6 mL/cm2min, these phases dissolved at the edges of slag grains, leaving behind a porous rind of aluminum and iron oxides. Increasing temperature increased the rate of this reaction. At low fluid flux, 0.8 mL/cm2min, the extent of carbonation was increased. At the edge of grains, instead of being transformed to porous rinds, primary Ca minerals were replaced by phosphorus-bearing Ca-carbonate phases. As a result of the greater length of reactor used in these experiments, a reaction gradient was observed along which the fluid remained supersaturated with respect to the calcium carbonate, coating the surfaces of the slag grains. Steel slag exposed to the CO2-H2O fluid in the batch reactor was less carbonated; incongruent dissolution of the slag followed by surface coating of the grains by calcium carbonate inhibited further interaction of the slag with the fluid, limiting the extent of possible carbonation.The results of this study show that carbonation of steel slag by aqueous CO2 is feasible using relatively large grains, and that it can be optimised by varying fluid flux. Experiments of the type described above will contribute to the eventual global reduction of industrial CO2 emissions.
L'industrie du fer et de l'acier est en pleine croissance et sa production mondiale a augmenté de 65% au cours des dix dernières années (World Steel Association, 2012). Malheureusement, elle est également responsable d'un quart des émissions industrielles de CO2 ce qui en fait la plus importante source industrielle de CO2 atmosphérique (International Energy Agency (IEA), 2007).La carbonatation minérale fournit une méthode robuste pour la séquestration permanente du CO2 sous une forme écologiquement inerte. La larnite (Ca2SiO4), constituant principal des scories d'acier, réagit aisément avec le CO2 aqueux (Santos et al., 2009). Par conséquent, sa carbonatation offre une importante occasion de réduire à la source les émissions de CO2. Un avantage potentiel supplémentaire de ce traitement est de rendre les scories d'acier convenables pour le recyclage. Cette étude examine l'impact de la température, le flux molaire surfacique du fluide carbonaté, et d'un gradient de réaction sur la dissolution et la carbonatation des scories d'acier. Elle s'inscrit dans une étude plus large visant à déterminer les conditions optimisant la conversion de la larnite, et d'autres silicates de calcium, à la calcite.Des expériences ont été menées sur des grains de scories d'acier d'un diamètre de 2 à 3 mm fournis par Tata Steel RD&T. Un mélange de CO2-H2O a été pompé à travers un réacteur continu contenant ces grains et maintenu à une température entre 120°C et 200°C, une pression de 250 bar et à des flux molaires surfaciques de 0.8 à 6 mmol/cm2min. Chaque expérience a duré de 3 à 7 jours. Le fluide CO2-H2O a réagi avec les grains de scories d'acier et a formé des minéraux de carbonate de calcium contenant du phosphore. À flux molaire surfacique élevé, soit 6 mL/cm2min, ces phases sont dissoutes aux bords des grains, laissant place à une bordure poreuse d'oxydes d'aluminum et de fer. Une augmentation de la température a augmenté la vitesse de cette réaction. A valeur intermédaire de flux molaire surfacique, 0.8 mL/cm2min, le degré de carbonatation a augmenté. Au lieu laisser des bordures poreuses d'oxydes, les minéraux de calcium primaires en marge des grains ont plutôt été remplacés par des phases de calcium carbonate contenant du phosphore. En plus, l'usage d'un réacteur plus long a créé un gradient de réaction et maintenu la supersaturation du fluide relative au carbonate de calcium qui a enrobé les grains. Les scories d'acier exposées au fluide dans un réacteur discontinu (sans flux de fluide) ont été moins carbonatées; la dissolution non-congruente de la scorie a pris place suivie par l'enrobage des grains de scories par le carbonate, et ce dernier a réduit la surface de réaction de la scorie avec le fluide.Les résultats de cette étude démontrent que la carbonatation par le CO2 aqueux des scories d'acier à granulométrie relativement grossière est possible et qu'elle peut être optimisée en variant le flux molaire surfacique du fluide. Les expériences de ce type contribueront à la réduction éventuelle des émissions industrielles globales de CO2.

SLAM (Simulatenous Localization and Mapping) es quizá el problema más importante a solucionar en robótica para construir robots móviles verdaderamente autónomos. El SLAM es acerca de cómo un robot móvil opera en un entorno a priori desconocido, utilizando únicamente sus sensores de abordo, mientras construye un mapa de dicho entorno que al mismo tiempo utiliza para localizarse. Los sensores del robot tienen un gran impacto en los algoritmos usados en SLAM. Los primeros enfoques se centraron en el uso de sensores de rango como sonares o láseres. Sin embargo hay algunas desventajas relacionadas con su utilización: La asociación de datos es difícil, son costosos, habitualmente están limitados a mapas 2D y tienen alto costo computacional debido al gran número de características (features) que producen. Lo anterior ha propiciado que enfoques recientes se estén moviendo hacia el uso de cámaras como sensor principal. Estas se han vuelto muy atractivas para los investigadores de la robótica, dado que generan mucha información, facilitan la asociación de datos, están bien adaptadas para sistemas embebidos: son ligeras, baratas y ahorran energía. Usando visión, un robot puede localizarse así mismo usando objetos comunes como landmarks. Sin embargo, a diferencia de los sensores de rango, que proveen información angular y de rango, una cámara es un sensor proyectivo que mide el bearing (ángulo) respecto a objetos de la imagen. Por lo que la profundidad (range) no puede ser obtenida en una sola toma. Este hecho ha motivado la aparición de una nueva familia de métodos de SLAM: Los Bearing-Only SLAM methods, los cuales están basados en técnicas especiales para la inicialización de features, permitiendo el uso de sensores de bearing en SLAM. Esta tesis se centra en el estudio de la problemática del Bearing-Only SLAM: da una descripción extensa del tema, recapitula los retos actuales a resolver y propone nuevos métodos y algoritmos enfocados a tratar diferentes sub problemas concernientes esta problemática en general. Estos sub problemas deben de ser tratados, de manera que sea posible construir sistemas capaces de operar en entornos diversos y complejos. La investigación descrita en esta disertación ha sido dividida en tres partes: 3DOF Bearing-Only SLAM: El proceso de inicialización de nuevas features es quizá el sub problema más importante a tratar en Bearing-Only SLAM. En esta parte de la tesis se introduce un nuevo método llamado Delayed Inverse Depth Features Initialization (para 3DOF y asumiendo odometría). Este método utiliza una parametrización inversa, donde la profundidad e incertidumbre iníciales de cada feature son dinámicamente estimadas previamente a que una feature sea declarada como un nuevo landmark en el mapa estocástico. También se presenta un sistema de SLAM basado en sonido, llamado SSLAM el cual usa fuentes de sonido como features del mapa. La contribución del SSLAM es demostrar la viabilidad de la inclusión del sentido auditivo en SLAM y mostrar que es factible utilizar sensores alternativos en Bearing-Only SLAM. Métodos de asociación de datos para SLAM basado en visión: El problema de la asociación de datos es quizá uno de los problemas más difíciles en robótica y también uno de los sub problemas más importantes a tratar en SLAM. Consiste en determinar si las mediciones de un sensor tomadas en tiempos diferentes, corresponden al mismo objeto físico del mundo. En esta parte de la tesis, se proponen diferentes métodos que tratan el problema de la asociación de datos en un contexto de SLAM basado en visión. SLAM monocular de 6DOF: El SLAM monocular de 6DOF quizá representa la variante más extrema del SLAM, dado que una cámara en mano es utilizada como la única entrada sensorial del sistema. En esta parte de la tesis, se extiende el algoritmo de 2DOF Bearing-Only SLAM para ser aplicado en un contexto de SLAM monocular. También se propone un nuevo esquema llamado SLAM Monocular Distribuido, enfocado en el problema de construir y mantener mapas consistentes de grandes entornos en tiempo real. La idea es dividir la estimación total del sistema en dos procesos de estimación concurrentes. Primero un método actual de SLAM monocular (Virtual Sensor) es modificado como un complejo sensor virtual que emula sensores típicos, como el laser para medición de rango y encoders para odometría. Después otro método tradicional de SLAM (Global SLAM) es acoplado para construir y mantener el mapa final. Numerosas referencias bibliográficas, graficas, comparaciones, simulaciones y experimentos con datos reales de sensores, son presentador con el fin de mostrar el desempeño de los métodos propuestos.
Simultaneous Localization and Mapping (SLAM) is perhaps the most fundamental problem to solve in robotics in order to build truly autonomous mobile robots. SLAM is about on how can a mobile robot operate in an a priori unknown environment and use only onboard sensors to simultaneously build a map of its surroundings and use it to track its position. The robot’s sensors have a large impact on the algorithm used for SLAM. Early SLAM approaches focused on the use of range sensors as sonar rings or lasers. Nevertheless there are some disadvantages with the use of range sensors in SLAM: Correspondence or data association is difficult. They are expensive. They are generally limited to 2D maps and computational overhead due to large number of features. The aforementioned issues have propitiated that recent work is moving towards the use of cameras as the primary sensing modality. Cameras have become more and more interesting for the robotic research community, because it yield a lot of information allowing reliable data association. Cameras are well adapted for embedded systems: they are light, cheap and power saving. Using vision, a robot can localize itself using common objects as landmarks. On the other hand, at difference of range sensors (i.e. sonar or laser) which provides range and angular information, a camera is a projective sensor which measures the bearing of images features. Therefore depth information (range) cannot be obtained in a single frame. This fact has propitiated the emergence of a new family of SLAM methods: The Bearing-Only SLAM methods, which mainly relies in especial techniques for features system-initialization in order to enable the use of bearing sensors (as cameras) in SLAM systems. This thesis is focused on the study of the Bearing-Only SLAM problematic: It gives an extensive overview of the subject. It point out the principal challenges nowadays. And it presents new methods and algorithms which address different sub problems concerning to the Bearing-Only SLAM problematic. These sub problems must be solved, in order to build systems capable of operating in extremely diverse and complex environments. The research described in this dissertation has been divided into three parts: 3DOF Bearing-Only SLAM: The initialization process for new features is perhaps the most important sub problem for addressing in Bearing-Only SLAM. In this part of the thesis we introduce a novel method called Delayed Inverse Depth Features Initialization for a 3DOF odometry-available context. In this method, which uses an inverse depth parameterization, initial depth and uncertainty of each feature are dynamically estimated priors to add the new landmark in the stochastic map. We also present a Sound-based SLAM system, called SSLAM, which uses “Sound Sources” as map’s features. The main contributions of the SSLAM are demonstrating the viability on the inclusion of the hearing sense in SLAM and show that is straightforward to use alternative bearing in SLAM systems. Data association methods for camera-based SLAM: the data association problem is possibly one of the hardest problems in robotic and also one of the most important sub problems to solve in SLAM. The correspondence problem is the problem of determining if sensor measurements taken at different points in time correspond to the same physical object in the world. In this part of the thesis, we propose different methods for addressing the data association problem in a context of vision-based SLAM. 6DOF Monocular SLAM: 6-DOF monocular SLAM possibly represents the harder variant of SLAM, since a low cost hand-held camera is used as the only sensory input to the system. In this part of the thesis, we extend our 2DOF Bearing-Only SLAM algorithm for being used in a monocular SLAM context. Also a novel framework called Distributed Monocular SLAM is proposed for addressing the problem of building and maintaining a global and consistent map of large environments at real time. The key idea is to divide the whole estimation into two concurrent estimation processes. First a state of the art monocular SLAM method (Called Virtual Sensor) is modified as a complex virtual sensor that emulates typical sensors such as laser for range measurement and encoders for dead reckoning. Afterward, a classic SLAM method (called Global SLAM) is plugged in for building and maintaining the final map. Several references, graphics, comparisons, simulations and experiments with real data are presented in order to demonstrate the performance of the methods.

A classic Computer Vision task is the estimation of a 3D map from a collection of images. This thesis explores the online simultaneous estimation of camera poses and map points, often called Visual Simultaneous Localisation and Mapping [VSLAM]. In the near future the use of visual information by autonomous cars is likely, since driving is a vision dominated process. For example, VSLAM could be used to estimate the position of the car in relation to objects of interest, such as the road, other cars and pedestrians. Aimed at the creation of a real-time, robust, loop closing, single camera SLAM system, the properties of several state-of-the-art VSLAM systems and related techniques are studied. The system goals cover several important, if difficult, problems, which makes a solution widely applicable. This thesis makes two contributions: A rigorous qualitative analysis of VSLAM methods and a system designed accordingly. A novel tracking by matching scheme is proposed, which, unlike the trackers used by many similar systems, is able to deal better with forward camera motion. The system estimates general motion with loop closure in real time. The system is compared to a state-of-the-art monocular VSLAM algorithm and found to be similar in speed and performance.

MARINHA DO BRASIL
Os sistemas que operam em banda larga necessitam de radiadores que atendam eletricamente a banda de freqüência utilizada. As antenas com características de independência da freqüência, em particular as antenas espirais, têm encontrando cada vez mais utilização nesses sistemas, seja em aplicações comercias ou militares. Esta dissertação tem por objetivo a análise de desempenho de antenas espirais do tipo fenda em cavidades, pela aplicação do método dos momentos. Serão consideradas cavidades com a face oposta à antena constituída por um condutor perfeito ou acoplada a uma estrutura de microondas com matriz de espalhamento conhecida. Essa estrutura de microondas, poderá simular, por exemplo, uma ou mais camadas de material absorvente.Um modelo numérico foi desenvolvido, e a partir dele foi elaborado um programa de computador, para determinar as características de radiação de antenas espirais em cavidade. São apresentados e comparados os resultados obtidos para três configurações de antenas espirais de Arquimedes do tipo fenda: sem cavidade, com cavidade condutora e com um material absorvente colocado sobre a face da cavidade oposta a abertura da antena.
Broad band systems need radiators to operate over the entire frequency band. Frequency independent antennas, in particular spiral antennas, are finding increasing application in such systems, for commercial or military purposes. This dissertation has for objective the analysis of performance of cavity-backed slot spiral antenna, by applying the moment method . For this study it will be taken into account cavities with the face opposing to the antenna consisting of a perfect conductor or connected to a structure of microwaves with known scattering matrix. This microwave structure will be able to simulate, for example, one or more layers of absorbing material. A numerical model was developed, and based on it, it was elaborated a computer program to determine the radiation characteristics of cavity-backed spiral antennas. The results surveyed for three configurations of slot Archimedean spiral antenna are presented and compared: without cavity, with conducting cavity, and with an absorbing material placed on the cavity opposite to the antenna.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 161-173).
This thesis solves the classical problem of simultaneous localization and mapping (SLAM) in a fashion which avoids linearized approximations altogether. Based on creating virtual synthetic measurements, the algorithm uses a linear time-varying (LTV) Kalman observer, bypassing errors and approximations brought by the linearization process in traditional extended Kalman filtering (EKF) SLAM. Convergence rates of the algorithm are established using contraction analysis. Different combinations of sensor information can be exploited, such as bearing measurements, range measurements, optical flow, or time-to-contact. As illustrated in simulations, the proposed algorithm can solve SLAM problems in both 2D and 3D scenarios with guaranteed convergence rates in a full nonlinear context. A novel distributed algorithm SLAM-DUNK is proposed in the thesis. The algorithm uses virtual vehicles to achieve information exclusively from corresponding landmarks. Computation complexity is reduced to 0(n), with simulations on Victoria Park dataset to support the validity of the algorithm. In the final section of the thesis, we propose a general framework for cooperative navigation and mapping. The frameworks developed for three different use cases use the null space terms of SLAM problem to guarantee that robots starting with unknown initial conditions could converge to a shared consensus coordinate system with estimates reflecting the truth.
by Feng Tan.
Ph. D.