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The research domain on the Quality of Experience (QoE) of 2D video streaming has been well established. However, a new video format is emerging and gaining popularity and availability: VR 360-degree video. The processing and transmission of 360-degree videos brings along new challenges such as large bandwidth requirements and the occurrence of different distortions. The viewing experience is also substantially different from 2D video, it offers more interactive freedom on the viewing angle but can also be more demanding and cause cybersickness. Further research on the QoE of 360-videos specifically is thus required.The first goal of this thesis is to complement earlier research by (Tran, Ngoc, Pham, Jung, and Thank, 2017) testing the effects of quality degradation, freezing, and content on the QoE of 360-videos. The second goal is to test the contribution of visual attention as influence factor in the QoE assessment. Data will be gathered through subjective tests where participants watch degraded versions of 360-videos through an HMD with integrated eye-tracking sensors. After each video they will answer questions regarding their quality perception, experience, perceptual load, and cybersickness.Results of the first part show overall rather low QoE ratings and it decreases even more as quality is degraded and freezing events are added. Cyber sickness was found not to be an issue. The effects of the manipulation on visual attention were minimal. Attention was mainly directed by content, but also by surprising elements. The addition of eye-tracking metrics did not further explain individual differences in subjective ratings. Nevertheless it was found that looking at moving objects increased the negative effect of freezing events and made participants less sensitive for quality distortions. The results of this thesis alone are not enough to successfully regard visual attention as an influence factor in 360-video.

Almost hemispherical scanning capabilities are required for modern wireless communication systems to produce broad coverage without performance degradation. Phased array antennas are commonly used as a fully-electronic beam-steering solution for its rapidity in beam switching. However, the effective aperture for high scanning angles is reduced, causing a reduction of the gain with the cosine of the elevation angle. Quasi-optical systems are used to achieve high directivity for wide scanning in combination with phased arrays. An interesting solution is the dielectric dome antenna, where rotationally symmetric dielectric lenses are used to enhance the scanning performance of an antenna with limited scanning capabilities. Using a full-wave simulator to evaluate lenses combined with arrays is very time-consuming, making the lens design inefficient and laborious. In this work is presented a Ray-Tracing tool used to simulate in a fast and efficient way the far-field of two-dimensional dielectric lenses. While a full-wave simulation of a three-dimensional lens could take approximately 3 hours, the Ray-Tracing evaluation takes less than 3 minutes, making possible the full optimization and design of these lenses. A numerical calculation of the ray path is used to evaluate the phase of the electric field at the lens aperture, while the amplitude is evaluated using ray-tube power theory. The far-field radiation pattern of the lens antenna is calculated using the Kirchhoff-Fresnel diffraction formula. In this work, it is also presented a full study of the reflection and absorption losses, which is something that was not previously done in the state of the art. Matching layers are designed and evaluated to reduce the reflection losses at each interface. To demonstrate the effectiveness of this approach, we compare the radiation patterns produced by a two-dimensional dielectric dome antenna with those computed using COMSOL, showing a significant reduction in time and computational resources. / För moderna trådlösa kommunikationssystem krävs nästan halvklotformiga skanningsmöjligheter för att åstadkomma bred täckning utan försämrad prestanda. Fasstyrda antenner används vanligen som en helt elektronisk lösning för strålstyrning på grund av dess snabbhet vid byte av strålar. Den effektiva aperturen för höga skanningsvinklar minskar dock, vilket leder till att förstärkningen minskar med cosinus av elevationsvinkeln. Kvasiooptiska system används för att uppnå hög riktningsförmåga för bred avsökning i kombination med fasade matriser. En intressant lösning är den dielektriska kupolantennen, där rotationssymmetriska dielektriska linser används för att förbättra skanningsegenskaperna hos en antenn med begränsad skanningskapacitet. Att använda en fullvågssimulator för att utvärdera linser i kombination med matriser är mycket tidskrävande, vilket gör linsdesignen ineffektiv och arbetskrävande. I detta arbete presenteras ett Ray-Tracing-verktyg som används för att på ett snabbt och effektivt sätt simulera fjärrfältet för tvådimensionella dielektriska linser. Medan en fullvågssimulering av en tredimensionell lins kan ta ungefär 3 timmar tar strålföljningssimuleringen mindre än 3 minuter, vilket gör det möjligt att optimera och konstruera dessa linser fullt ut. En numerisk beräkning av strålbanan används för att utvärdera fasen hos det elektriska fältet vid linsaperturen, medan amplituden utvärderas med hjälp av strålrörsteori. Linsantennens strålningsmönster i fjärrfältet beräknas med hjälp av Kirchhoff-Fresnel-diffraktionsformeln. I detta arbete presenteras också en fullständig studie av reflektions- och absorptionsförlusterna, vilket är något som inte tidigare har gjorts inom detta forskningsområde. Anpassningsskikt utformas och utvärderas för att minska reflektionsförlusterna vid varje gränssnitt. För att visa hur effektivt detta tillvägagångssätt är, jämför vi strålningsdiagrammen som produceras av en dielektrisk kupolantenn med dem som beräknats med COMSOL, vilket visar på en betydande minskning av beräkningsresurserna.

Optical shrink for process migration, manufacturing process variation and dynamic voltage control leads to clock skew as well as path delay variation in a manufactured chip. Since such variations are difficult to predict in pre-silicon phase, tunable clock buffers have been used in several microprocessor designs. The buffer delays are tuned to improve maximum operating clock frequency of a design. This however shifts the burden of finding tuning settings for individual clock buffers to the test process. In this project, we describe a process of using tester measurements to determine the settings of the tunable buffers for recovery of performance lost due to process variations. Then we study the impact of positioning of tunable buffers in the clock tree. In course of our study it was observed that the greatest benefit from tunable buffer placement can be derived, when the clock tree is synthesized with future tuning considerations. Accordingly, we present a clock tree synthesis procedure which offers very good mitigation against process variation, as borne out by the results. The results show that without any design intervention, an average improvement of 9% is achieved by our tuning system. However, when the clock tree is synthesized based on static timing information with tuning buffer placement considerations, much larger performance improvement is possible. In one example, performance improved by as much as 18%.

Game engines are well known for their use in the gaming industry but are starting to have an impact in other areas as well. Architecture, automotive, and the defence industry are today using these engines to visualise and, to some extent, test their products. In this thesis, we have examined how the game engine Unity could be used for simulating a radar with the purpose of detecting and measuring sea clutter. Following a pre-study examining different implementation approaches, it was decided to use ray tracing. The radar itself is simulated by using the camera to emit rays and having a plane object directly behind it act as a receiver. Rays are then individually traced for each pixel, propagating throughout the scene and saving information such as hit coordinates, distance travelled, and direction. By using the total travel distance of each ray that returned to the receiver, the phase of each ray is calculated. This is then used to compute the total amplitude, which represents the returned signal strength. Using a compute shader, most of the computations are done in parallel on the GPU, enabling millions of rays to be traced. As measuring sea clutter was an objective of the study, tests measuring the ocean were carried out. These used ocean surfaces with two different sea states, using the Phillips spectrum to generate realistic waves. A ship object was then tested in free space and on two different ocean surfaces. The calculated amplitude and the number of rays returned were used to determine the signal strength returned and the RCS of the object. The purpose of this was to compare with other results of sea clutter studied, observed both in the real world and in simulated scenarios, and determine if our approach could be a valid choice for the industry. Some results matched the findings of a similar study that used a professional radar simulation tool called OKTAL. Other results of sea clutter were found to not be realistic due to certain limitations. The current main limitation of our implementation is not being able to trace a large enough ocean surface with the finer details needed for realistic results. However, this could be solved by creating a better implementation. These findings suggest that simulating radar and sea clutter in Unity is a feasible approach worth continuing to explore. / Spelmotorer är välkända för sin användning inom spelindustrin men har också fått genomslag inom andra områden. Arkitektur, fordonsindustrin och försvarsindustrin använder idag dessa verktyg för att visualisera och till viss mån, även testa sina produkter. I detta examensarbete har vi undersökt hur spelmotorn Unity kan användas för att simulera en radar i syfte att detektera och mäta sjöklotter. Efter en förstudie där olika implementeringsmetoder undersöktes, beslutades det att använda strålspårning (eng. ray tracing). Själva radarn simuleras genom att använda kameraobjektet i Unity för att sända ut strålar. Bakom kameran finns ett planobjekt som fungerar som mottagare. Strålar spåras sedan individuellt för varje pixel och sprider sig genom en given scen. Samtidigt sparas information såsom träffkoordinater, den totala färdsträckan samt riktning. Genom att använda det totala färdavståndet för varje stråle som återvänt till mottagaren kan fasen för varje stråle beräknas. Detta kan sedan användas för att beräkna den totala returnerade amplituden, vilket motsvarar den returnerade signalstyrkan. Med hjälp av en "compute shader" kan databeräkningarna göras parallellt av GPU:n vilket underlättar när så många strålar ska spåras. Eftersom syftet med uppsatsen var mätning av simulerat sjöklotter, genomfördes tester för att mäta på ett simulerat hav. Havsytorna hade två olika sjöstadier, vilka genererades med Phillips-spektrumet för att få realistiska vågor. Ett fartygsobjekt testades sedan i frirymd och sedan även i de två olika havsytorna. Amplituden och mängden strålar som returnerades användes för att bestämma den totala returnerade signalstyrkan och "Radar Cross Section" (RCS) för objektet. Syftet med detta var att kunna jämföra med andra studier gällande sjöklotter, både simulerade som verklighetsbaserade och avgöra om vårt tillvägagångssätt kunde resultera i ett användbart verktyg för branschen. De olika amplituder och antalet strålar som vi fick tillbaka varierade beroende på vilka vinklar och havsytor som användes.Vissa resultat var inte realistiska jämfört med verkliga mätningar av sjöklotter. Det beror främst på våra nuvarande begränsningar i att inte kunna spåra en tillräckligt stor och tillräckligt detaljerad havsyta, vilket behövs för att mätningarna ska vara mer realistiska. Däremot matchade vi några resultat med de från en liknande studie, där verktyget OKTAL, som är ett professionellt radarsimuleringsverktyg, användes. Detta i kombination med möjligheterna för en förbättrad implementation tyder på att användningen av en spelmotor som Unity är ett intressant verktyg värd att vidareutforska radarsimuleringar med.

Depuis les années 1970, de nombreuses études ont rapporté l’oxydation des substrats énergétiques exogènes au repos ou pendant l’exercice. Les glucides ont gagné en popularité, puisque leur oxydation a été associée avec une amélioration de la performance. Pour étudier l’oxydation des glucides exogènes pendant l’exercice, deux techniques sont nécessaires : la calorimétrie indirecte respiratoire couplée au traçage isotopique. Ce mémoire décrit, dans un premier temps, la calorimétrie indirecte respiratoire en présentant et démontrant les équations utilisées dans cette méthode. La technique de traçage par isotope 13C ou 14C est ensuite présentée en insistant sur le développement des équations sur lesquelles elle repose. Dans un deuxième temps, les facteurs pouvant influencer le taux d’oxydation et la contribution à la fourniture d’énergie du glucose exogène pendant l’exercice prolongé sont rapportés dans les analyses de régressions multiples. L’objectif de cette analyse est d’identifier les facteurs expliquant le mieux la variation de ces deux variables. La grande variabilité existante dans les conditions expérimentales de la littérature rend difficiles les comparaisons. Par conséquent, les analyses sont effectuées sur une condition standard représentant les caractéristiques les plus communes de la littérature. La grande majorité des études ayant été effectuées sur une population semblable (hommes, entre 65 et 80 kg, âgés entre 20 et 40 ans), davantage de travaux sont nécessaires sur d’autres types de population active et sur des sujets d’âge et de masse corporelle différents. Les résultats de cette méta-analyse pourront aider à améliorer les recommandations sur l’ingestion de glucides au cours de l’exercice prolongé. / Since the 1970s, numerous studies have reported the oxidation of exogenous energy substrates at rest or during exercise. Carbohydrates have gained popularity, as their oxidation has been associated with improved performance. To study the oxidation of exogenous carbohydrates during exercise, two techniques are required: indirect respiratory calorimetry coupled with isotope tracing. This dissertation first describes the respiratory indirect calorimetry by presenting and demonstrating the equations used in this method. The 13C or 14C isotope tracing technique is then presented with emphasis on the development of the equations on which it is based. Second, factors that may influence the oxidation rate and contribution to energy supply of exogenous glucose during prolonged exercise are reported the multiple regression analysis. The objective of this analysis is to identify the factors that best explain the variation in these two variables. The large variability existing in the experimental conditions in the literature makes comparisons difficult. Therefore, the analyses are performed on a standard condition representing the most common characteristics in the literature. Because most of the studies were performed on a similar population (men, between 65 and 80 kg, aged between 20 and 40 years), more work is needed on other types of working populations and on subjects of different ages and body mass. The results of this meta-analysis may help improve recommendations for carbohydrate intake during prolonged exercise.

Taste buds are chemosensory endorgans embedded in the oral epithelium composed of cells that undergo continuous replacement. Mature taste cells live on average 10-14 days and are replaced by new cells when they die. However, the mechanism by which taste cells are produced and integrated into the taste bud as mature taste cells remains unknown. Previous studies approached this issue from either cell cycle gene expression properties or lineage tracing of precursor cells. In our study, we apply a new fate mapping technique that combines these two ideas. This technique, Mosaic Analysis with Double Markers, allows for simultaneous gene knockout and subsequent tracking of single cells. This allows us to study the potency of precursor cells supplying the taste bud while analyzing how gene function regulates the maturation pathway these taste cells take. The following experiments illustrate the initial phase of this investigation.

Bifacial photovoltaic (PV) modules have greater energy yield than traditional monofacial modules because they convert front and rear incident irradiance to electrical energy. Single-axis tracking systems can further increase energy yield and reduce the levelized cost of energy by rotating the modules throughout the day. However, racking elements in tracking systems introduce both shade and reflections on the rear face, increasing irradiance nonuniformity and fostering further electrical mismatch that reduces module power. The impact of racking, particularly that of the torque tube which spans the middle of the rear collector surface, must be accurately quantified in energy yield predictions to increase stakeholder confidence, and hasten the adoption of tracked bifacial modules. Isolating the torque-tube-reflected irradiance incident on the modules is crucial for this work. This is achieved by implementing arbitrary two-dimensional (2D) irradiance sampling on a module under test in bifacial_radiance, a ray tracing bifacial PV model, and taking the difference in rear irradiance profiles for simulations with a reflective and an absorptive torque tube at each timestamp. We calculate the TT reflection for the central one-in-portrait (1P) and two-in-portrait (2P) modules on horizontal single-axis trackers over hourly timestamps in a typical meteorological year in Livermore, California, USA. We introduce the TT reflection 2D irradiance profiles as additional light sources in DUET to quantify the TT reflection's impact on irradiance, electrical mismatch, and energy yield, as well as an incidence angle modifier's impact on TT reflection. We analyze the TT reflection based on sun zenith and diffuse fraction to group consistent illumination conditions across the year. We identify that TT reflection reduces electrical mismatch by partially offsetting TT shading, and increases annual energy yield by 0.11% and 0.18% in our particular 1P and 2P systems. While the overall impact of TT reflection is greater in the 2P system due to direct beam light incident on the TT, the TT reflection's greatest instantaneous relative contribution to total energy yield is larger for the 1P system, at high diffuse fractions and sun zeniths. For future work, we recommend validating simulation results with and without TT reflection against experimental data. The simulation method used for isolating the TT reflection may also be repurposed to help inform new TT designs that minimize electrical mismatch. Finally, instead of relying on bifacial_radiance to isolate the TT reflection, we recommend incorporating the TT as a Lambertian reflective surface in 3D view factor models with detailed shading for further TT reflection simulations.

La technique de tracé de chemins est la méthode Monte Carlo la plus populaire en infographie pour résoudre le problème de l'illumination globale. Une image produite par tracé de chemins est beaucoup plus photoréaliste que les méthodes standard tel que le rendu par rasterisation et même le lancer de rayons. Mais le tracé de chemins est coûteux et converge lentement, produisant une image bruitée lorsqu'elle n'est pas convergée. De nombreuses méthodes visant à accélérer le tracé de chemins ont été développées, mais chacune présente ses propres défauts et contraintes. Dans les dernières avancées en apprentissage profond, en particulier dans le domaine des modèles génératifs conditionnels, il a été démontré que ces modèles sont capables de bien apprendre, modéliser et tirer des échantillons à partir de distributions complexes. Comme le tracé de chemins dépend également d'un tel processus sur une distribution complexe, nous examinons les similarités entre ces deux problèmes et modélisons le processus de tracé de chemins comme un processus génératif. Ce processus peut ensuite être utilisé pour construire un estimateur efficace avec un réseau neuronal afin d'accélérer le temps de rendu sans trop d'hypothèses sur la scène. Nous montrons que notre estimateur neuronal (NPPP), utilisé avec le tracé de chemins, peut améliorer les temps de rendu d'une manière considérable sans beaucoup compromettre sur la qualité du rendu. Nous montrons également que l'estimateur est très flexible et permet à un utilisateur de contrôler et de prioriser la qualité ou le temps de rendu, sans autre modification ou entraînement du réseau neuronal. / Path tracing is one of the most popular Monte Carlo methods used in computer graphics to solve the problem of global illumination. A path traced image is much more photorealistic compared to standard rendering methods such as rasterization and even ray tracing. Unfortunately, path tracing is expensive to compute and slow to converge, resulting in noisy images when unconverged. Many methods aimed to accelerate path tracing have been developed, but each has its own downsides and limitiations. Recent advances in deep learning, especially with conditional generative models, have shown to be very capable at learning, modeling, and sampling from complex distributions. As path tracing is also dependent on sampling from complex distributions, we investigate the similarities between the two problems and model the path tracing process itself as a conditional generative process. It can then be used to build an efficient neural estimator that allows us to accelerate rendering time with as few assumptions as possible. We show that our neural estimator (NPPP) used along with path tracing can improve rendering time by a considerable amount without compromising much in rendering quality. The estimator is also shown to be very flexible and allows a user to control and prioritize quality or rendering time, without any further training or modifications to the neural network.

Three-dimensional linear ray theory is used to investigate internal waves interacting with a Lamb-Chaplygin pancake vortex dipole. These interactions involve waves propagating in the same (co-propagating) and opposite (counter-propagating) horizontal directions as the dipole translation. Co-propagating internal waves in the vertical symmetry plane between the vortices of the dipole can approach critical levels where the wave energy is absorbed by the dipole or where the waves are overturned and possibly break. As wave breaking cannot be simulated with this linear model, changes in wave steepness are calculated to aid in estimating the onset of breaking. Counter-propagating internal waves in the vertical symmetry plane can experience horizontal and vertical reflections, including turning points similar to waves in two-dimensional steady shear. Wave capture is also a possible effect of either type of interaction, depending on initial wave properties and positioning relative to the vortex dipole. Away from the vertical symmetry plane, a spanwise converging (focusing) and diverging (defocusing) of wave energy is observed in co- and counter-propagating interactions as symmetric off-center rays interact with the dipole's individual vortices. Some off-center rays experience multiple horizontal refractions similar to wave trapping.