京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第18938号 / 工博第3980号 / 新制||工||1613(附属図書館) / 31889 / 京都大学大学院工学研究科都市社会工学専攻 / (主査)教授 松岡 俊文, 教授 後藤 仁志, 准教授 村田 澄彦 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

Partial enclosures are commonly used to reduce machinery noise. However, it is well known in industry that enclosures sometimes amplify the sound at low frequencies due to strong acoustic resonances compromising the performance. These noise issues are preventable if predicted prior to prototyping and production. Though boundary and finite element approaches can be used to accurately predict partial enclosure insertion loss, modifications to the model require time for remeshing and solving. In this work, partial enclosure performance at low frequencies is simulated using a plane wave transfer matrix approach. Models can be constructed and the effect of design modifications can be predicted rapidly. Results are compared to finite element analysis and measurement with good agreement. The approach is then used to design and place resonators into a sample enclosure. Improvements in enclosure performance are predicted using plane wave simulation, compared with acoustic finite element analysis, and then validated via measurement.

WiFi can provide network coverage for users on land at anytime and anywhere, but on the sea, the wireless communication scenes change dramatically due to the signals are non-existence. Although some techniques (e.g. satellite, undersea fiber, microwave communication) have been used in marine communication, they are either too expensive with very small bandwidth, or too limited in its coverage range. We propose to develop a marine wireless mesh network which is formed by low cost buoyed wireless base stations to provide broadband connectivity for users on the sea. Ocean wave simulation and prediction are key technologies in developing marine mesh network, because marine environments are dramatically different from terrestrial environment. The ocean waves have characteristics of rhythmic oscillations and the line of sight between two communication nodes is often blocked by them. Therefore, we have to develop a new wave-state-aware networking protocol which is suitable for marine environments. Ocean wave simulation technology can simulate this kind of dynamic environments and provide a test platform for the development of marine mesh network. Ocean wave prediction technology can improve the throughput of marine wireless network. Thus, they are indispensable technologies in developing marine mesh network. In this thesis, we designed an ocean wave measurement method, two ocean wave prediction methods, and an ocean wave simulation method. Firstly, we designed an accelerometer-based ocean wave measurement method. It can measure the real time wave height accurately. Secondly, we designed an Elman-neural-network-based ocean wave prediction method for nonlinear waves. It has a higher prediction accuracy than other neural network methods in nonlinear wave prediction. Thirdly, we designed a multiple-linear-regression-based ocean wave prediction method for linear waves. It has a higher prediction accuracy and less time consumption than other methods in linear wave prediction. Finally, we implemented and improved a spectrum-based ocean wave simulation method which is originally proposed by Tessendorf. It can present the movement of ocean waves realistically and in real time. To sum up, above four methods provide an effective test platform and technical support for the development of our marine mesh network. / Master of Science / With the development of wireless communication technology, WiFi has been an indispensable resource for daily work and pleasure. However, in the marine environments, WiFi is not exist. Thus, passengers and workers on the sea are eager for it. We propose to develop a marine wireless mesh network which is formed by low cost buoyed wireless base stations to provide WiFi for users on the sea. Marine environments are dramatically different from terrestrial environments. The ocean waves have characteristics of rhythmic oscillations and the link between two buoys is often blocked. Therefore, the signals are also intermittent. We decided to develop a new wave-state-aware networking protocol to eliminate the harmful effect of this kind of rhythmic oscillations. Ocean wave simulation and prediction are key technologies in developing networking protocol, in which ocean wave simulation technology can simulate the marine environments and provide a test platform for developing networking protocol. Ocean wave prediction technology can improve the network throughput. Thus, they are indispensable technologies in developing marine mesh network. In this thesis, we mainly research three problems that related to ocean waves, they are ocean wave measurement, ocean wave prediction and ocean wave simulation. Ocean wave measurement can tell us the current wave height of a buoy, ocean wave prediction can tell us the future height of a buoy, after we know these information, we can decide whether allow the buoy to send signal. It can not only save energy, but also improve the success rate of communication. Ocean wave simulation can provide us a dynamic environment to test whether our networking protocol works well. To sum up, these methods provide an effective test platform and technical support for the development of our marine mesh network.

L’approximation de phénomènes physiques, tels qu’une simulation de liquides en informatique graphique, requiert l’utilisation de méthodes complexes nécessitant des temps de calcul et une quantité de mémoire importants. Malgré les avancées récentes dans ce domaine, l’écart en réalisme entre un liquide simulé et la réalité demeure encore aujourd’hui considérable. Cet écart nous séparant du réalisme souhaité nécessite des modèles numériques de simulation dont la complexité ne cesse de croître. L’objectif ultime est de permettre à l’utilisateur de manipuler ces modèles de simulation de liquides sans la nécessité d’avoir une connaissance accrue de la physique requise pour atteindre un niveau de réalisme acceptable et ce, en temps réel. Plusieurs approches ont été revisitées dans les dernières années afin de simplifier ces modèles ou dans le but de les rendre plus facilement paramétrables. Cette thèse par articles encadre bien les trois projets constituant nos contributions dans le but d’améliorer et de faciliter la génération de simulations de liquides en informatique graphique. Tout d’abord, nous introduisons une approche hybride permettant de traiter séparément le volume de liquide non-apparent (i.e., en profondeur) et une couche de particules en surface par la méthode de calcul Smoothed Particle Hydrodynamics (SPH). Nous revisitons l’approche par bandes de particules, mais cette fois nouvellement appliquée à la méthode SPH qui offre un niveau de réalisme supérieur. Comme deuxième projet, nous proposons une approche permettant d’améliorer le niveau de détail des éclaboussures de liquides. En suréchantillonnant une simulation de liquides existante, notre approche est capable de générer des détails réalistes d’éclaboussures grâce à la dynamique de balistique. En complément, nous proposons une méthode de simulation par vagues permettant de reproduire les interactions entre les éclaboussures générées et les portions quasi-statiques de la simulation existante. Finalement, le troisième projet introduit une approche permettant de rehausser la résolution apparente d’un liquide par l’apprentissage automatique. Nous proposons une architecture d’apprentissage inspirée des flux optiques dont l’objectif est de générer une correspondance entre le déplacement des particules de simulations de liquides à différentes résolutions (i.e., basses et hautes résolutions). Notre modèle d’apprentissage permet d’encoder des caractéristiques de hautes résolutions à l’aide de déformations pré-calculées entre deux liquides à différentes résolutions et d’opérations de convolution basées sur le voisinage des particules. / The approximation of natural phenomena such as liquid simulations in computer graphics requires complex methods that are computationally expensive. Despite recent advances in this field, the gap in realism between a simulated liquid and reality remains considerable. This disparity that separates us from the desired realism requires numerical models whose complexity continues to grow. The ultimate goal is to provide users the capacity and tools to manipulate these liquid simulation models to obtain acceptable realism. In the last decade, several approaches have been revisited to simplify and to allow more flexible models. In this dissertation by articles, we present three projects whose contributions support the improvement and flexibility of generating liquid simulations for computer graphics. First, we introduce a hybrid approach allowing us to separately process the volume of non-apparent liquid (i.e., in-depth) and a band of surface particles using the Smoothed Particle Hydrodynamics (SPH) method. We revisit the particle band approach, but this time newly applied to the SPH method, which offers a higher level of realism. Then, as a second project, we propose an approach to improve the level of detail of splashing liquids. By upsampling an existing liquid simulation, our approach is capable of generating realistic splash details through ballistic dynamics. In addition, we propose a wave simulation method to reproduce the interactions between the generated splashes and the quasi-static portions of the existing liquid simulation. Finally, the third project introduces an approach to enhance the apparent resolution of liquids through machine learning. We propose a learning architecture inspired by optical flows by which we generate a correspondence between the displacement of the particles of liquid simulations at different resolutions (i.e., low and high resolutions). Our training model allows high-resolution features to be encoded using pre-computed deformations between two liquids at different resolutions and convolution operations based on the neighborhood of the particles.