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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
251

Grid-based Cyclic Multi-robot Allocation for Object Carrying

Jee Hwan Park (9187781) 30 July 2020 (has links)
In this thesis, we are addressing new method of object transportation using multi-robot system. The new method of object transportation is called A grid-based cyclic robot allocation (GCRA) method which consists multiple spherical robots. The object is placed on top of group of spherical robots before the transportation. The rotation of the multiple spherical robots cause the displacement of the object and reach the goal location based on the direction and speed of the rotation of the robots. The GCRA method for spherical robots is proposed along with specific stability criterion, which designs the formation of the multi-robot system. The formation is created based on the customized grid which is to be modified based on the properties of the object. The shape and the center of gravity of the shape define the horizontal gap, $g_x$ and vertical gap, $g_y$. All the possible locations of spherical robots is the cross points of grid which implies that $g_x$ and $g_y$ defines the distance between the robots and based on the boundary of the robots placed underneath the object, the condition of the stability is defined. It also identifies minimum number of robots required based on the arbitrary shape of an object for stable omni-directional translation of the object on a 2 dimensional space. The desired positions and formation of the robots is identified based goal position of the object. Under centralized system, position control is applied to drive the robots to the desired positions. The position control simultaneously makes the object mobile and maintain the stability of the object. Mathematical proof of the proposed method is shown verifying the stability of the transportation process with the assumptions of no slip between the robots and the object. 2 Dimensional Simulation results of robot allocation using GCRA for several arbitrary shapes certify the proposed method.
252

Investigation of acoustic source characterisation and installation effects for small axial fans

Berglund, Per-Olof January 2003 (has links)
Fans are often used in equipment such as home appliances andelectronic equipment where the margin of profit is small butcustomers demands on a low noise level are high. Therefore,methods for predicting the noise emitted by an applicationincluding one or several fans are desirable in order toimprove, accelerate and reduce the cost of low-noise design.The Noise Shaping Technology (NST) has been developed withinthe EC-project NABUCCO in order to fulfil the aboverequirements on a prediction method. According to NST, thenoise source (not necessary a fan) is described by one orseveral noise descriptors, CSSs, and the correspondingtransmission paths through the structure described by one orseveral transfer functions, ACFs. In this thesis, theapplicability of NST is evaluated on a cabinet for electronicequipment where small axial cooling fans constitute the primarysources of the airborne sound. As an axial fan is a complex source of sound,simplifications are necessary when modelling its acousticproperties. Therefore, the sound radiation of an axial fan infree space was examined by expanding the generated soundpressure field into spherical harmonics. The conclusion on asource model for the cabinet example, where the fans are moreor less In-duct mounted, is a modified single axial dipole. Themodel is expected to be valid in the entire frequency range ofinterest except in the mid-frequency range where the modaldensity is low. In order to improve the source model in thisfrequency range, a future model based on a rotating dipole isproposed. The sound power of a small axial fan is measured in an ISO10302 test-rig. In order to take account of flow conditions,acoustically transparent ducts have been developed. These shallbe attached to the test-rig when measuring the sound power ofthe fan. A simple but practical method of how to correct thesound power for the baffling effect of the test-rig has alsobeen developed. Finally, the sound power can be converted intodipole force, which is the airborne CSS corresponding to thesingle axial dipole model. The corresponding airborne transfer function (ACF), i.e.,from dipole force at the source point to sound pressure at thereceiver point, is measured reciprocally by taking use ofLyamshevs reciprocity relation. From multiplication of the CSS and the ACF, the soundpressure can be predicted. The prediction shows quite goodagreement with the measured values. <b>Keywords:</b>axial fan, airborne sound, sourcecharacterisation, transmission path analysis, In-duct,spherical harmonics, rotating dipole, installation effects, ISO10302, flow conditions, baffling effect, acousticallytransparent ducts, Lyamshevs reciprocity relation, reciprocity,CSS, ACF, GSM, NST. / NR 20140805
253

The influence of inertia on the rotational dynamics of spheroidal particles suspended in shear flow

Rosén, Tomas January 2014 (has links)
Dispersed particle flows occur in many industrial, biological and geophysical applications. The knowledge of how these flow behave can for example lead to improved material processes, better predictions of vascular diseases or more accurate climate models. These particle flows have certain properties that depend on single particle motion in fluid flows and especially how they are distributed both in terms of spatial position and, if they are non-spherical, in terms of orientation. Much is already known about the motion of perfectly spherical particles. For non-spherical particles, apart from their translation, it is important to know the the rotational motion due to local velocity gradients. Such studies have usually been restricted by the assumption that particles are extremely small compared to fluid length scales. In this limit, both inertia of the particle and inertia of the fluid can be neglected for the particle motion. This thesis gives a complete picture of how a spheroidal particle (a particle described by a rotation of an ellipse around one of its principal axes) behave in a linear shear flow when including both fluid and particle inertia, using numerical simulations. It is observed that this very simple problem possess very interesting dynamical behavior with different stable rotational states appearing as a competition between the two types of inertia. The effect of particle inertia leads to a rotation where the mass of the particle is concentrated as far away from the rotational axis as possible, i.e.\ a rotation around the minor axis. Typically, the effect of fluid inertia is instead that it tries to force the particle in a rotation where the streamlines of the flow remain as straight as possible. The first effect of fluid inertia is thus the opposite of particle inertia and instead leads to a particle rotation around the major axis. Depending on rotational state, the particles also affect the apparent viscosity of the particle dispersion. The different transitions and bifurcations between rotational states are characterized in terms of non-linear dynamics, which reveal that the particle motion probably can be described by some reduced model. The results in this theses provides fundamental knowledge and is necessary to understand flows containing non-spherical particles. / Flöden med dispergerade partiklar påträffas i många industriella, biologiska och geofysiska tillämpningar. Kunskap om hur dessa flöden beter sig kan bl.a. leda till förbättrade materialprocesser, bättre förutsägelser om hjärt- och kärlsjukdomar eller mer noggranna väderprognoser. Dessa flödens egenskaper beror på hur enskilda partiklar rör sig i en fluid och speciellt hur de är fördelade både i termer av position och, om de är icke-sfäriska, i termer av orientering. Mycket är redan känt om rörelsen av perfekt sfäriska partiklar. För icke-sfäriska partiklar är det inte bara translationen som är av intresse utan det är även viktigt att veta hur partiklarna roterar till följd av lokala hastighetsgradienter. Sådana studier har tidigare varit begränsade av antagandet att partiklarna är extremt små jämfört med fluidens typiska längdskalor. I denna gräns kan både partikelns och fluidens tröghet antas försumbar. Den här avhandlingen ger en komplett bild av hur en sfäroidisk partikel (en partikel som beskrivs av en rotation av en ellips runt en av dess huvudaxlar) beter sig i ett linjärt skjuvflöde när tröghetseffekter inkluderas. Resultaten har erhållits genom numeriska simuleringar. Det visar sig att detta enkla problem är väldigt rikt på olika dynamiska beteenden med flera stabila rotationstillstånd som uppstår tilll följd av både partikel- och fluidtröghet. Inverkan av partikeltröghet leder till en rotation där massan av partikeln är koncentrerad så långt ifrån rotationsaxeln som möjligt, d.v.s. en rotation runt lillaxeln. Den typiska inverkan av fluidtröghet är istället att fluiden försöker påtvinga partikeln en rotation där strömlinjer förblir så raka som möjligt. Primärt leder detta till att partikeln istället roterar runt storaxeln. Beroende på rotationstillstånd, så har partikeln även olika inverkan på den märkbara viskositeten av partikeldispersionen. De olika övergångarna och bifurkationerna mellan rotationstillstånd är karaktäriserade i termer av icke-linjär dynamik, vilket visar på att partikelrörelserna förmodligen kan beskrivas med en reducerad modell. Resultaten i denna avhandling är därför fundamental kunskap och ett nödvändigt steg mot att förstå beteendet av flöden med dispergerade, icke-sfäriska partiklar. / <p>QC 20140328</p>
254

Measurement of Bitumen Relaxation Modulus with Instrumented Indentation

Phan, Trinh Ngoc January 2012 (has links)
Instrumented indentation testing was used to determine viscoelastic properties of bitumen, i.e. shear relaxation modulus. Review of previous studied reveals that indentation testing technique has been drawing increasing attempts in investigations of binder material mechanical properties. Various properties of bitumen, e.g. elastic, viscoelastic, have been successfully determined by indentation testing at different scales and test conditions. The response of bitumen to indentation was studied extensively under a wide range of test parameters such as temperature, loading rate, indenter geometry, etc. This experimental tool was also applied to asphalt cements grading and microstructure study. However, there have been limited numbers of studies at macro levels with the use of spherical indenters to characterize bitumen properties. This motivated the present study. Spherical indentations have been performed with balls of different curvature radii at -5 oC. Load – displacement curves have been measured and used to determine the relaxation moduli of the studied bitumen. Repeatability of the measurements has been evaluated. Obtained results were compared with the observations from DSR relaxation test. The influence of the measurement scale and load level on the results of instrumented indentation testing has been investigated. It has been found that instrumented indentation was able to characterize accurately the viscoelastic behavior of bitumen which can be described by Prony series and agrees well with the results from DSR tests. Nevertheless, the elastic solution failed to produce a proper description of bitumen response during loading phase.
255

Directed-mobility and enhanced-adhesion nano-platelets for local drug delivery : towards a new treatment of bladder diseases / NANO-PLAQUETTES A MOBILITE DIRIGEE ET ADHESION AMPLIFIEE POUR L'ADMINISTRATION LOCALE : VERS UN NOUVEAU TRAITEMENT DES MALADIES VESICALES

Diaz salmeron, Raúl 19 November 2019 (has links)
Titre : Nano-plaquettes à mobilité dirigée et adhésion amplifiée pour l’administration locale: vers un nouveau traitement des maladies vésicalesAbstract : L’administration locale des médicaments, définie comme une voie d’administration où la substance active est directement administrée sur ou proche de la cible ou tissus souhaités, permet d’apporter des grandes quantités des médicaments avec moins d’effets secondaires, et permet une simplification du système nanoparticulaire du fait de la non-extravasation des médicaments. Dans ce contexte, le projet de recherche de cette thèse s’est focalisé sur la voie intra-vésicale comme voie d’administration locale car il existe un besoin clinique de la part des patients, n’étant pas encore résolu. Malgré les hypothétiques avantages fournis par l’administration locale des médicaments, la voie intra-vésicale présente certaines limitations qui diminuent l’efficacité des traitements et l’observance des patients. La plupart des médicaments pour le traitement des maladies vésicales, notamment pour le cancer de la vessie et les cystites interstitielles, sont sous forme de solutions ou suspensions administrées de manière intra-vésicale via un cathéter qui passe à travers l’urètre. Dès leur arrivée à la vessie, les substances actives sont fortement diluées par les urines et éliminées rapidement lors de la miction. Cela conduit à une diminution des concentrations des substances actives au plus proche de l’épithélium, nécessitant plusieurs instillations intra-vésicales, réalisées par des praticiens hospitaliers, pour atteindre des concentrations thérapeutiques. Il y a donc un réel besoin de développer des nouvelles formulations permettant de contrecarrer les phénomènes décrits au préalable.L’objectif de cette thèse de doctorat est de créer un nouveau système nanoparticulaire de morphologie non-sphérique qui serait susceptible d’avoir un mouvement diffèrent et dirigé ainsi qu’une adhésion amplifiée. En conséquence, nous attendons de ces systèmes qu’ils apportent des concentrations en substances actives plus importantes que les systèmes nanoparticulaires sphériques et formulations galéniques traditionnelles.Aux cours de nos travaux expérimentaux, nous avons réussi à développer un système nanoparticulaire de morphologie hexagonale et aplatie. Ces nanoparticules, appellées nano-plaquettes, sont conçues à partir de l’auto-assemblage des molécules d’α-CD et des chaines alkyles greffées sur les squelettes de polysaccharides tels que l’acide hyaluronique, la chondroïtine sulfate ou l’héparine. Ces systèmes présentent l’originalité de ne pas avoir de substance active encapsulé parce que les molécules de polymère elles mêmes agissent à la fois en tant que substance active et de véhicule. Ces nano-plaquettes ont montré un mouvement en milieu isotrope et statique très diffèrent des nano-sphères utilisées comme contrôle. En effet, la majorité d’entre elles diffuse de manière plus importante et dirigée, avec des trajectoires rectilignes. Grâce à leur mouvement et aux propriétés inhérentes liées à leur forme, ces systèmes se sont montrés particulièrement intéressants vis-à-vis des interactions avec des cellules. Ils adhèrent mieux et plus longtemps à la muqueuse vésicale, elles sont mieux internalisées par des cellules et sont éliminées plus lentement une fois adhérées à la surface de l’urothélium.Un modelé in vivo de Syndrome de la Vessie Douloureuse / Cystite Interstitielle développé chez le rat nous a permis de montrer l’efficacité thérapeutique des nano-plaquettes, notamment celle constituées d’acide hyaluronique. En effet, elles présentent une meilleure bioaccumulation dans la vessie et une meilleure activité anti-inflammatoire et de régénération de la muqueuse urothéliale.Ces systèmes nanoparticulaires, conçues lors de nos travaux de thèse, constituent une approche innovante, rationnelle et efficace pouvant ouvrir de nouvelles voies de recherche pour le traitement des maladies vésicales. / Title: Directed-mobility and enhanced-adhesion nano-platelets for local drug delivery: towards a new treatment of bladder diseases.Abstract: Local drug delivery, defined as the administration route where the drug is delivered directly or very close to its target or tissue, allows to bring large amounts of drugs with reduced side effects, in comparison with systemic administration. In this context, our research project has been focused on the intravesical drug delivery as local administration route, because there is a real need to develop new pharmaceutical formulations to thwart several limitations. Despite the advantages provided by the local drug delivery, intravesical drug delivery exhibited some issues which are decreasing the therapeutic efficacy and the patient compliance to the treatment. Most of therapies for the treatment of bladder diseases are simple drug solutions or suspensions administered intravesically by using a catheter through the urethra in order to reach easily the bladder and, consequently, the urothelium. Since the drug is administered into the bladder, drug dilution is occurring because the continuous production of urine. Furthermore, active substances are being eliminated during washout when bladder urine voiding is happening. These two processes lead to the decrease of local drug concentration close to the urothelium. Patients need repeated catheterization, performed by health care practitioners, to reach therapeutic dose of the drug. Therefor, there is a need of new drug formulations to avoid these main limitations.The main goal of this PhD thesis was to create and design a new nanoparticulate system with non-spherical shape susceptible to move in a different manner compared to spherical nanoparticles. These systems may exhibit an amplified mucoadhesion allowing to bring more important amounts of drug than classical and nanoparticle administration.During this thesis, we developed a new nanoparticulate system presenting non-spherical, hexagonal and flattened shape. The driven force for the design of these nanoparticles was the self-assembling of α-cyclodextrin molecules with alkyl chains grafted on the polymer skeleton. Polymers used belong to a polysaccharide family called glycosaminoglycans including hyaluronic acid, chondroitin sulfate or heparin. This original and innovative nanoparticulate system does not encapsulate an active drug. Our polysaccharide will act, at the same time, as the active drug and the carrier. These nanoparticles, called now nano-platelets have shown different movement behavior than the spherical ones. Indeed, they diffuse more rapidly in a straight-line way. Thanks to their oriented and directed motion and to their intrinsic properties, due to the shape, these systems have shown a better mucoadhesion on the bladder tissue, a better uptake in different cell lines and they were far less rapidly eliminated from the urothelium mucosa.An in vivo model of Bladder Painful Syndrome / Interstitial Cystitis in rats demonstrated the therapeutic efficacy of nano-platelets, especially for hyaluronic acid nanoparticles. Indeed, they demonstrated a better bioaccumulation into the bladder and a better therapeutic efficacy as anti-inflammatory and urothelium regenerating agents.These nanoparticulate systems, designed during this work, represent a new innovative, rational and effectiveness approach allowing to open new research pathways for the treatment of bladder diseases.
256

Computational Efficiency of a Hybrid Mass Concentration and Spherical Harmonic Modeling

Piepgrass, Nathan 01 May 2011 (has links)
Through Spherical Harmonics, one can describe complex gravitational fields. However as the order and degree of the spherical harmonics increases, the computation speed rises exponentially. In addition, for onboard applications of spherical harmonics, the processors are radiation hardened in order to mitigate negative effects of the space environment on electronics. But, those processors have outdated processing speeds, resulting in a slower onboard spherical harmonic program. This thesis examines a partial solution to the slow computation speed of spherical harmonics programs. The partial solution was to supplant the gravity models in the flight software. The spherical harmonics gravity model can be replaced by a hybrid model, a mass concentrations model and a secondary (lesser degree or order) spherical harmonics model. That hybrid model can lead to greater processing speeds while maintaining the same level of accuracy. To compute the mass values for the mass concentration model, a potential estimation scheme was selected. In that scheme, mass values were computed by minimizing the integral of the difference between the correct and the estimated potential. The best hybrid model for the 8 degree and 8 order, 15 degree and 15 order, and 30 degree and 30 order lunar potential fields is developed following three different approaches: potential zeros method, gravitational anomalies method, and iterative method. Afterwards, the accuracy and computation time of the models are measured and compared to the primary spherical harmonic lunar model. In the aftermath, while the best hybrid model for all three cases was able to run faster than the primary spherical harmonic model, it was unable to be sufficiently accurate to replace the primary spherical harmonic model. The mass estimation scheme is severely hindered by the condition number and convergence issues resulting in inaccurate estimates for the mass values for a given distribution. It is recommended to alleviate the condition number error by eliminating the inverse in the mass estimation scheme. Other recommendations include fixing the convergence error, investing in software and hardware development, and focusing on other hybrid research objectives.
257

Détection et suivi de personnes par vision omnidirectionnelle : approche 2D et 3D / Detection and tracking of persons by omnidirectional vision : 2D and 3D approaches

Boui, Marouane 14 May 2018 (has links)
Dans cette thèse, nous traiterons du problème de la détection et du suivi 3D de personnes dans des séquences d'images omnidirectionnelles, dans le but de réaliser des applications permettant l'estimation de pose 3D. Ceci nécessite, la mise en place d'un suivi stable et précis de la personne dans un environnement réel. Dans le cadre de cette étude, on utilisera une caméra catadioptrique composée d'un miroir sphérique et d'une caméra perspective. Ce type de capteur est couramment utilisé dans la vision par ordinateur et la robotique. Son principal avantage est son large champ de vision qui lui permet d'acquérir une vue à 360 degrés de la scène avec un seul capteur et en une seule image. Cependant, ce capteur va engendrer des distorsions importantes dans les images, ne permettant pas une application directe des méthodes classiquement utilisées en vision perspective. Cette thèse traite de deux approches de suivi développées durant cette thèse, qui permettent de tenir compte de ces distorsions. Elles illustrent le cheminement suivi par nos travaux, nous permettant de passer de la détection de personne à l'estimation 3D de sa pose. La première étape de nos travaux a consisté à mettre en place un algorithme de détection de personnes dans les images omnidirectionnelles. Nous avons proposé d'étendre l'approche conventionnelle pour la détection humaine en image perspective, basée sur l'Histogramme Orientés du Gradient (HOG), pour l'adapter à des images sphériques. Notre approche utilise les variétés riemanniennes afin d'adapter le calcul du gradient dans le cas des images omnidirectionnelles. Elle utilise aussi le gradient sphérique pour le cas les images sphériques afin de générer notre descripteur d'image omnidirectionnelle. Par la suite, nous nous sommes concentrés sur la mise en place d'un système de suivi 3D de personnes avec des caméras omnidirectionnelles. Nous avons fait le choix de faire du suivi 3D basé sur un modèle de la personne avec 30 degrés de liberté car nous nous sommes imposés comme contrainte l'utilisation d'une seule caméra catadioptrique. / In this thesis we will handle the problem of 3D people detection and tracking in omnidirectional images sequences, in order to realize applications allowing3D pose estimation, we investigate the problem of 3D people detection and tracking in omnidirectional images sequences. This requires a stable and accurate monitoring of the person in a real environment. In order to achieve this, we will use a catadioptric camera composed of a spherical mirror and a perspective camera. This type of sensor is commonly used in computer vision and robotics. Its main advantage is its wide field of vision, which allows it to acquire a 360-degree view of the scene with a single sensor and in a single image. However, this kind of sensor generally generates significant distortions in the images, not allowing a direct application of the methods conventionally used in perspective vision. Our thesis contains a description of two monitoring approaches that take into account these distortions. These methods show the progress of our work during these three years, allowing us to move from person detection to the 3Destimation of its pose. The first step of this work consisted in setting up a person detection algorithm in the omnidirectional images. We proposed to extend the conventional approach for human detection in perspective image, based on the Gradient-Oriented Histogram (HOG), in order to adjust it to spherical images. Our approach uses the Riemannian varieties to adapt the gradient calculation for omnidirectional images as well as the spherical gradient for spherical images to generate our omnidirectional image descriptor.
258

Experimental and kinetic study of burning characteristics of natural gas blends

Khan, Farha 07 1900 (has links)
Following stringent mandates from environmental regulatory authorities worldwide, various steps are being implemented to ensure clean combustion with minimum emissions, including fuel dilution, mild combustion and additives. Due to the need to understand combustion characteristics in primary applications (engines and turbines) with minimum emissions, the laminar burning velocity of natural gas has been measured with CO2 dilution and a wide range of blends with higher hydrocarbons. And because it has improved anti-knock quality to reduce greenhouse gas emissions (GHGE), the demand for oxygenated gasoline is now worldwide, making a compelling case for determining combustion behavior of oxygenated gasoline doped with hydrogen, ozone and carbon monoxide. The first section of this dissertation discusses dilution of methane with CO2 at elevated pressures, providing insight into comparative laminar burning characteristics in a wide range of equivalence ratios, particularly significant at elevated initial pressure. Utilizing CHEMKIN, a detailed kinetic study has been performed that explains the varying dependence on dilution ratio controlled by initial pressure. The second phase of this work reports the laminar burning velocity measurement of commercial gasoline. A TPRFE surrogate was used here to investigate burning characteristics and to provide detailed kinetic analysis of gasoline doped with additives (hydrogen, carbon monoxide and ozone). A study was also made of the behavior of gasoline with these additives in practical applications like engine and turbines. For this purpose, laminar burning velocity was measured at elevated pressures and temperatures, by varying the concentrations of synthetic EGR, and followed by measuring turbulent burning velocity at two turbulent intensities.
259

Infinite-variate extensions of Krawtchouk polynomials and zonal spherical functions over a local field / 無限変数クラウチュク多項式と局所体上の帯球関数

Kawamura, Koei 26 March 2018 (has links)
京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第20881号 / 理博第4333号 / 新制||理||1622(附属図書館) / 京都大学大学院理学研究科数学・数理解析専攻 / (主査)准教授 梅田 亨, 教授 上 正明, 教授 雪江 明彦 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM
260

Adaptive, Wave Guiding Acoustic Arrays using Circularly Symmetric Reconfigurable Structures

Srinivas, Vivek 08 October 2020 (has links)
No description available.

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