[pt] As tecnologias de imageamento em três dimensões (3D) vêm tendo seu uso cada vez mais disseminado no meio acadêmico e no setor industrial, especialmente na forma de nuvens de pontos, uma representação matemática da geometria e superfície de um objeto ou área. No entanto, a obtenção desses dados pode ainda ser cara e demorada, reduzindo a eficiência de muitos procedimentos que são dependentes de um grande conjunto de nuvens de pontos, como a geração de datasets para treinamento de aprendizagem de máquina, cálculo de dossel florestal e inspeção submarina. Uma solução atualmente em voga é a criação de simuladores computacionais de sistemas de imageamento, realizando o escaneamento virtual de um cenário feito a partir de arquivos de objetos 3D. Este trabalho apresenta o desenvolvimento de um simulador de sistema LiDAR (light detection and ranging) baseado em algoritmos de rastreamento de raio com paralelismo (GPU raytracing), com o sensor virtual modelado por parâmetros metrológicos e calibrado por meio de comparação com um sensor real, juntamente com um gerador flexível de cenários virtuais. A combinação destas ferramentas no simulador resultou em uma geração robusta de nuvens de pontos sintéticas em cenários diversos, possibilitando a criação de datasets para uso em testes de conceitos, combinação de dados reais e virtuais, entre outras aplicações. / [en] Three dimensional (3D) imaging technologies have been increasingly used in academia and in the industrial sector, especially in the form of point clouds, a mathematical representation of the geometry and surface of an object or area. However, obtaining this data can still be expensive and time consuming, reducing the efficiency of many procedures dependent on a large set of point clouds, such as the generation of datasets for machine learning training, forest canopy calculation and subsea survey. A trending solution is the development of computer simulators for imaging systems, performing the virtual scanning of a scenario made from 3D object files. At the end of this process, synthetic point clouds are obtained. This work presents the development of a LiDAR system simulator (light detection and ranging) based on parallel ray tracing algorithms (GPU raytracing), with its virtual sensor modeled by metrological parameters. A way of calibrating the sensor is displayed, by comparing it with the measurements of a real LiDAR sensor, in addition to surveying error models to increase the realism of the virtual scan. A flexible scenario creator was also implemented to facilitate interaction with the user. The combination of these tools in the simulator resulted in a robust generation of synthetic point clouds in different scenarios, enabling the creation of datasets for use in concept tests, combining real and virtual data, among other applications.

With the newly deployed fifth-generation telecommunications system and upcoming sixth-generation, high-gain antennas with hemispherical scanning capabilities are of high interest. Phased array antennas allow for fast scanning capabilities with electronic beam-steering. In an effort to reduce the number of antenna elements while maintaining the antenna aperture size, the element spacing is increased. However sparse arrays introduce grating lobes in the radiation pattern. An interesting solution to reduce the grating lobes is to integrate a lens with the array. Further, simulating the radiation pattern with a ray-tracing algorithm and the geometrical optics approximation makes for fast simulation times. The presented ray-tracing algorithm in this work speeds up the simulation by 43 times compared to a two-dimensional full-wave simulation. To model the full radiation pattern the rays are shot out from a single point across a set angular space. To emulate an element pattern the rays are excited with a set amplitude distribution. Here, two different methods of obtaining the amplitude are presented and compared to a two-dimensional full-wave COMSOL model. The lens is made from a dielectric, constructed from the conics equation with applied conformal matching layers. The ray path and phase distribution are calculated with Snell's law, the amplitude distribution at the lens aperture is calculated through the ray tube theory, and the radiation pattern with the Kirchhoff Diffraction formula. To optimize the lens shape and an array offset, the ray-tracing algorithm is coupled with a Particle Swarm Optimization algorithm. Two different arrays are used in this thesis, the first constructed from open-ended waveguides and the second using sub-arrays of the same waveguides. The optimized lens for the first array shows that a grating lobe suppression between 1.1-2.0 dB is achievable with a main lobe reduction between 0.2-0.3 dB for scanning to -20 degrees. For the array with sub-arrays, the main lobe suppression is between 0.3-0.9 dB, with a grating lobe suppression of up to 4.0 dB. / Med det nyligen lanserade femte generationens telekommunikationssystem och den kommande sjätte generationen är högförstärkningsantenner med halvsfäriska skanningsmöjligheter av stort intresse. Fasade array-antenner möjliggör snabb skanningskapacitet med elektronisk strålstyrning. I ett försök att minska antalet antennelement samtidigt som antennöppningens storlek bibehålls, ökas elementavståndet. Men glesa arrayer introducerar gallerlober i strålningsmönstret. En intressant lösning för att minska gallerloberna är att integrera en lins med arrayen. Vidare, simulering av strålningsmönstret med en strålspårningsalgoritm och den geometriska optiska approximationen ger snabba simuleringstider. Den presenterade strålspårningsalgoritmen i detta arbete snabbar upp simuleringen med 43 gånger jämfört med en tvådimensionell helvågssimulering. För att modellera hela strålningsmönstret skjuts strålarna ut från en enda punkt över ett fast vinkelutrymme. För att efterlikna ett elementmönster exciteras strålarna med en inställd amplitudfördelning. Här presenteras två olika metoder för att erhålla amplituden och jämförs med en tvådimensionell fullvågs-COMSOL-modell. Linsen är gjord av ett dielektrika konstruerat från koniska ekvationen med applicerade konforma matchande lager. Strålvägen och fasfördelningen beräknas med Snell-lagen, amplitudfördelningen vid linsöppningen beräknas genom strålrörsteorin och strålningsmönstret med Kirchhoff-diffraktionsformeln. För att optimera linsformen och en arrayförskjutning är strålspårningsalgoritmen kopplad med en Particle Swarm algoritm. Två olika arrayer används i denna avhandling, den första konstruerad av vågledare med öppen ände och den andra med hjälp av sub-arrayer av samma vågledare. Den optimerade linsen för den första arrayen visar att en gallerlobsundertryckning mellan 1,1-2,0 dB kan uppnås med en huvudlobsreduktion mellan 0,2-0,3 dB för skanning till -20 grader. För arrayen med sub-arrayer är undertryckningen av huvudloben mellan 0,3-0,9 dB, med en gallerlobundertryckning på upp till 4,0 dB.

No description available.

The juxtaglomerular niche occupied by renin cells (RCN) plays an important role in glomerular repair but the precise temporal and spatial interrelations remain unclear. This study proposes the hypothesis of a local intra-extraglomerular regenerative feedback system and establishes a new quantifiable system for RCN responses in individual glomeruli in vivo. A strictly intraglomerular twophoton laser-induced injury model was established. Labeled renin cells (RC) in transgenic renin reporter mice were fate-traced in healthy and injured glomeruli over several days by intravital microscopy and quantified via new three-dimensional image processing algorithms based on ray tracing. RC in healthy glomeruli demonstrated dynamic extraglomerular protrusions. Upon intraglomerular injury the corresponding RCN first increased in volume and then increased in area of dynamic migration up to threefold compared to their RCN. RC started migration reaching the site of injury within 3 hours and acquired a mesangial cell phenotype without losing physical RCN-contact. During intraglomerular repair only the corresponding RCN responded via stimulated neogenesis, a process of de novo differentiation of RC to replenish the RCN. Repeated continuous intravital microscopy provides a state-of-the-art tool to prove and further study the local intraglomerular RCN repair feedback system in individual glomeruli in vivo in a quantifiable manner.

In recent years, there has been a huge increase in the use of satellite communications. This has led to a need for more capacity, which can be solved by moving towards higher frequency bands in search of higher bandwidths. However, the use of higher frequencies entails higher link losses, which makes it essential to use highly directional and steerable antennas. Traditionally, phased array antennas have been used for this kind of application. Nevertheless, they have a limitation in the maximum scan angle due to their effective aperture, which causes a gain reduction following the cosine of the scanning angle. A way of improving the scan range is to add a dielectric radome on top of the array. However, high computational times are needed to simulate this kind of structure using full-wave simulations. For this reason, the first part of this work is focused on adapting and improving an in-house Ray Tracing tool for the particular application under study. The tool computes the path the rays follow from the array to the aperture of the radome using geometric optics, then calculates the amplitude of the electric field at the aperture using ray tube theory, and finally determines the antenna’s radiation pattern using Kirchhoff’s diffraction formula. Moreover, some features have been added to the code to be able to compute the directivity, calculate the absorption and reflection losses, simulate multilayer radomes, and change the array elements’ radiation patterns. A model in Comsol has been developed to validate the results obtained using the Ray Tracing tool and all its added features. Finally, several optimizations have been carried out to increase the scanning range while maintaining a maximum height, and ensuring it complies with the regulatory masks for satellite communications. The optimizations have been performed both using a Particle Swarm Optimizer and manually. / Under de senaste åren har det skett en stor ökning av satellitkommunikations användning. Detta har lett till ett behov för högre kapacitet, vilket kan lösas genom att flytta till högre frekvensband på jakt efter högre bandbredder. Högre bandbredder innebär dock högre länkförluster som gör det oumbärligt att utnyttja rikt- och styrbara antenner. Ursprungligen har fasstyrda antenner använts för denna typ av tillämpning. Ändå finns en begränsning av den maximala skanningsvinkeln på grund av deras effektiva yta som leder till en minskning av förstärkning som är beroende på avsökningsvinkelns cosinus. För att kunna förbättra skanningsintervallen skulle man kunna lägga till en dielektrisk radom ovanpå arrayen. Höga beräkningstider krävs dock att simulera strukturen med helvågssimuleringar. Av denna anledning fokuserar den första delen av denna uppsats att anpassa och förbättra ett internt strålspårnings verktyg för den särskilda applikationen under studie. Verktyget beräknar vägen strålarna tar ifrån arrayen till radomens öppning med hjälp av geometrisk optik, därefter kalkyleras det elektriska fältets amplitud enligt strålrörsteori och till sist fastställs antennens strålningsmönster som definieras av Kirchhoffs diffraktionsformel. Dessutom har vissa funktioner lagts till i koden för att kunna beräkna riktningen, absorptions- och reflektionsförlusterna, simulera flerskiktsradomer och ändra arrayelementens strålningsmönster. En modell i Comsol har utvecklats för att validera resultaten som producerades av strålspårning verktyget och alla dess extra funktioner. Till sist, flera optimeringar har genomförts för att öka skanningsområdet som kan bibehålla en maximal höjd och säkerställa efterlevnaden med regleringsmaskerna för satellitkommunikationerna. Optimeringarna har utförts både manuellt och med hjälp av en partikelsvärmoptimerare. / En els últims anys hi ha hagut un increment majúscul en l’ús de les comunicacions per satèl·lit. Això s’ha traduït en la necessitat de més capacitat, la qual pot ser coberta si ens movem cap a bandes de freqüència més altes, buscant un major ample de banda. Tot i això, l’ús de freqüències més elevades comporta unes majors pèrdues en l’enllaç, les quals fan essencial l’ús d’antenes altament directives i amb capacitat d’escaneig. Tradicionalment, els arranjaments d’antenes de fase gradual han estat utilitzats per aquest tipus d’aplicacions. Tanmateix, tenen una limitació del màxim angle d’escaneig a causa de la seva obertura efectiva, la qual causa una reducció del guany seguint el cosinus de l’angle d’escaneig. Una manera de millorar el rang d’escaneig és afegint un radom dielèctric al damunt de l’arranjament d’antenes. No obstant això, es necessita un alt temps de computació per simular aquest tipus d’estructures amb simuladors d’ona completa. Per aquesta raó, la primera part d’aquest treball està enfocada a adaptar i perfeccionar una eina de traçat de rajos pròpia per l’aplicació en estudi. L’eina calcula el camí que els rajos segueixen des de l’arranjament d’antenes fins a l’obertura del radom utilitzant òptica geomètrica, a continuació computa l’amplitud del camp elèctric a l’obertura mitjançant la teoria del tub de rajos i finalment determina el patró de radiació de l’antena utilitzant la fórmula de difracció de Kirchhoff. Addicionalment, algunes funcions han estat afegides al codi per tal de poder computar la directivitat, calcular les pèrdues d’absorció i reflexió, simular radoms multicapa i canviar els patrons de radiació dels elements de l’arranjament. Un model en Comsol ha estat desenvolupat per tal de validar els resultats obtinguts emprant l’eina de traçat de rajos i totes les seves funcions. Finalment, vàries optimitzacions han estat dutes a terme per tal d’incrementar el rang d’escaneig mantenint una altura màxima i assegurant que es compleix amb les màscares reguladores de comunicacions per satèl·lit. Les optimitzacions han estat realitzades utilitzant tant un optimitzador per eixam de partícules com manualment.

The objective of this work is to enhance the awareness of the indoor propagation behaviour, by a set of investigations including simulations and measurements. These investigations include indoor propagation behaviour, local mean power estimation, proposing new indoor path loss model and introducing a case study on 60 GHz propagation in indoor environments using ray tracing and measurements. A summary of propagation mechanisms and manifestations in the indoor environment is presented. This comprises the indoor localization techniques using channel parameters in terms of angle of arrival (AOA), time of arrival (TOA) and received signal strength (RSS). Different models of path loss, shadowing and fast fading mechanisms are explored. The concept of MIMO channels is studied using many types of deterministic channel modelling such as Finite Difference Time Domain, Ray tracing and Dominant path model. A comprehensive study on estimating local average of the received signal strength (RSS) for indoor multipath propagation is conducted. The effect of the required number of the RSS data and their Euclidian distances between the neighbours samples are investigated over 1D, 2D and 3D configurations. It was found that the effect of fast fading was reduced sufficiently using 2D horizontal’s arrangement with larger spacing configuration. A modified indoor path loss prediction model is presented namely effective wall loss model (EWLM). The modified model with wall correction factors is compared to other indoor path loss prediction models using simulation data (for 2.4, 5, 28, 60 and 73.5 GHz) and real-time measurements (for 2.4 and 5 GHz). Different operating frequencies and antenna polarizations are considered to verify the observations. In the simulation part, EWLM shows the best performance among other models. Similar observations were recorded from the experimental results. Finally, a detailed study on indoor propagation environment at 60 GHz is conducted. The study is supported by Line of Sight (LoS) and Non-LoS measurements data. The results were compared to the simulated ones using Wireless-InSite ray tracing software. Several experiments have confirmed the reliability of the modelling process based on adjusted material properties values from measurements.

No description available.

The aim of this work was to create a program to visualize voxel scenes in real time using ray tracing. It included the study of various methods of such a rendering with a focus on shadows. The solution was created using Unity engine and experimental packages Unity Jobs and Burst. The thesis presents multiple ray tracing passes and SVGF technique, that is used to turn a noisy input into full edge-preserving image. The final program is able to render hard shadows, soft shadows, and ambient occlusion at speed of fifty frames per second.

台灣位於環太平洋地震帶上，地形為山地居多，且地質脆弱，加上位於西太平洋副熱帶地區，使得山區常受到颱風的侵擾而發生崩塌，導致土石流和洪水等災害發生，進而影響人民的生命和財產安全。因此，如何有效地建置崩塌地區域資料庫，成為國土保育與災害防治的重要課題。以往利用遙測與航測技術於崩塌地萃取的研究中，大多是於幾何糾正後衛星影像或是航測正射影像上分析崩塌地，但產製正射影像或是糾正衛星影像時，都需要花費較多的時間，對於講求時效性的救災行動而言頗為不利。本研究之目的為發展一套不需使用正射影像萃取崩塌地的方法，以物件導向影像分類法，於DMC（Digital Mapping Camera）航測原始影像上直接萃取崩塌地資訊。首先採取多重解析影像分割的技術，將航測影像依像元光譜和形狀同質性分割成不同區塊（物件），接著利用影像光譜統計值搭配區域成長法，偵測影像中的雲覆蓋地區並過濾。其次，根據光譜亮度統計特徵值，將影像區分成陰暗地區、正常地區以及較亮地區之三種土地覆蓋類型，使用線性相關糾正法（Linear-correlation Correction）將陰暗地區光譜亮度值轉換至正常地區，並利用物件的特徵值，如光譜、面積、形狀以及相關性依序萃取此三種土地覆蓋類型內的崩塌地。最後，使用光線追蹤法 （Ray-tracing），將崩塌地區塊從影像坐標轉換至地圖坐標，使其可以套疊地形資料如坡度、坡向，並進行空間分析以提升崩塌地的判釋精度。研究結果顯示，崩塌地萃取之使用者精度和生產者精度，均有82%以上，並且整個實驗可大量批次處理影像，及快速建立崩塌地資料庫，本研究之方法和崩塌地資料庫將有助於國土保育與崩塌地的災害防治。 / Being located in a subtropical and seismic zone of the West Pacific, the geology is fragile and topography is mountainous in Taiwan. Landslides, floods and other disasters induced by typhoons occur frequently, and it cause the life-threatening and property loss of human beings in Taiwan. Therefore, how to establish landslides data effectively become an important issue of land conservation and disasters management. In recently years, most of the researchers used aerial ortho-images or satellite georeferencing images to detect landslides sites. However, it spent a lot of time generating aerial ortho-images and rectifying satellite images, and it also reduced the efficiency of landslides analysis. Thus, this study developed an object-oriented classification method, which can be directly applied in raw image data, to detect landslides sites. Firstly, this study used multi-resolution image segmentation technique to segment images acquired by Z/I DMC（Digital Mapping Camera） into individual regions （objects） according to the homogeneity of spectral and shape features, and then removed cloud areas by using brightness features depended on the spectral information of images. Secondly, the study divided the entire image into three areas, which are darker area, normal area and lighter area, according to brightness value. Next, Linear-correlation correction （LCC） method was used in this study to transform darker area to normal area so that it can easily detect the landslides sites in darker area, and the object features, such as spectral, area, shape and space correlation indices, were used to extract landslide sites in images. Finally, in order to enhance the accuracy of landslide, the initial landslides were converted from image coordinate system to map coordinate system by ray-tracing method, so the initial landslides data can be further extracted by using topographic data, including slope and aspect data. The results of this study showed that the user and producer accuracies of detecting landslides can reach up to 82%. Moreover, the entire experiments process of this study can batch analyze automatically and establish landslides database quickly. It is expected that the method and landslides data of this study may have contribution to land conservation and disasters management.

Micro-Electro-Mechanical Systems (MEMS) sensors are used in an increasing range of applications such as inertial guidance or automotive safety systems, in which damping has a significant and negative effect on the device performances. Support loss, which governs the losses from the resonator to its foundation through the supporting structure, is an important source of damping in MEMS resonators. This thesis focuses on improving an understanding of this particular damping mechanism so that efficient models can be developed to predict the amount and relative importance of support loss at the design stage. The coupling between resonator and support is of principal interest to evaluate the interaction and energy transmission between them. To quantify the stresses acting on the support, a model that predicts vibration transmission through common MEMS structures is first developed. A general wave propagation approach for the vibration analysis of networks consisting of slender, straight and curved beam elements and complete ring is presented. The analysis is based on a ray tracing method and a procedure to predict the natural frequencies and mode shapes of complex ring/beam structures is demonstrated. An analytical method is then used to model the support, approximated to a semi-infinite domain, and quantify support losses. The work focuses mainly on in-plane vibrations for single-axis gyroscopes. However, new generation of multi-axis resonators is being currently developed, and the in-plane models are extended to cope with out-of-plane vibration transmission and support loss. To illustrate the effectiveness of the models, several numerical examples are presented, by applying them first to simple beam-like structures and subsequently to structures of increasing complexity. Strategies for improving the quality factor of common MEMS sensors, and specific ring-based resonators designs that minimise support losses, are also considered.