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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.
241

Innovative screening conditions for the crystallization of macromolecules : application to solve protein structures by X-ray diffraction / Nouvelles conditions de criblage pour la cristallisation de macromolécules : applications à l'étude structurale des protéines par diffraction aux rayons X

Gorrec, Fabrice 10 March 2015 (has links)
La cristallographie aux rayons X permet la détermination des structures tridimensionnelles de macromolécules biologiques ainsi que de leurs complexes à haute résolution. Cependant, la cristallisation des protéines est un phénomène totalement aléatoire et peu de cristaux sont généralement produits, de plus leur qualité et résistance sont souvent insuffisantes. Ces travaux visent à présenter les différentes étapes pour résoudre des structures de protéines ainsi que deux développements innovants pour formuler des solutions de criblage pour la cristallisation (appelés Pi et MORPHEUS). / X-ray crystallography enables the structure determination of biological macromolecules, their complexes and assemblies to high-resolution. Nevertheless, protein crystallisation is a stochastic process and the yield of crystals is typically very poor. In addition, crystal properties are often deceiving. Herein, we introduce the basic principles of protein structure determination process and we will discuss two innovative developments of screen formulation (called Pi and MORPHEUS).
242

Engineered Nanocomposite Materials for Microwave/Millimeter-Wave Applications of Fused Deposition Modeling

Castro, Juan De Dios 13 March 2017 (has links)
A variety of high-permittivity (high-k) and low-loss ceramic-thermoplastic composite materials as fused deposition modeling (FDM) feedstock, based on cyclo-olefin polymer (COP) embedded with sintered ceramic fillers, have been developed and investigated for direct digital manufacturing (DDM) of microwave components. The composites presented in this dissertation use a high-temperature sintering process up to 1500°C to further enhance the dielectric properties of the ceramic fillers. The electromagnetic (EM) properties of these newly developed FDM composites were characterized up to the Ku-band by using the cavity perturbation technique. Several models for prediction of the effective relative dielectric permittivity of composites based on the filler loading volume fraction have been evaluated, among which Hanai-Bruggeman and Maxwell models have shown the best accuracy with less than 2% and 5% discrepancies, respectively. The 30 vol. % COP-TiO2 FDM-ready composites with fillers sintered at 1200°C have exhibited a relative permittivity (εr) of 4.78 and a dielectric loss tangent (tan δd) lower than 0.0012 at 17 GHz. Meanwhile, the 30 vol. % COP-MgCaTiO2 composites with fillers sintered at 1200°C have exhibited a εr of 4.82 and a tan δd lower than 0.0018. The DDM approach combines FDM of the engineered EM composites and micro-dispensing for deposition of conductive traces to fabricate by 3D-printing edge-fed patch antennas operating at 17.2 GHz and 16.5 GHz. These antennas were demonstrated by employing a 25 vol. % COP-MgCaTiO2 composite FDM filament with the fillers sintered at 1100°C and a pure COP filament, which were both prepared and extruded following the process described in this dissertation. The low dielectric loss of the 25 vol. % COP-MgCaTiO2 composite material (tan δd lower than 0.0018) has been leveraged to achieve a peak realized gain of 6 dBi. Also, the high-permittivity (εr of 4.74), which corresponds to an index of refraction of 2.17, results in a patch area miniaturization of 50% when compared with an antenna designed and DPAM-printed over a Rogers RT/duroid® 5870 laminate core through micro-dispensing of CB028 silver paste. This reference antenna exhibited a measured peak realized gain of 6.27 dBi that is comparable. Also, two low-loss FDM-ready composite materials for DDM technologies are presented and characterized at V-band mm-wave frequencies. Pure COP thermoplastic exhibits a relative permittivity εr of 2.1 and a dielectric loss tangent tan δd below 0.0011 at 69 GHz, whereas 30 vol. % COP-MgCaTiO2 composites with fillers sintered at 1200°C exhibit a εr of 4.88 and a tan δd below 0.0070 at 66 GHz. To the best of my knowledge, these EM properties (combination of high-k and low-loss) are superior to other 3D-printable microwave materials reported by the scientific microwave community and are on par with materials developed for high-performance microwave laminates by RF/microwave industry as shown in Chapter 5 and Chapter 7 and summarized in Table 5.4 and Table 7.1. Meanwhile, the linear coefficient of thermal expansion (CTE) from -25°C to 100°C of the reinforced 30 vol. % COP-MgCaTiO2 composite with fillers sintered at 1200°C is 64.42 ppm/°C, which is about 20 ppm/°C lower when compared with pure ABS and 10 ppm/°C lower as compared to high-temperature polyetherimide (PEI) ULTEM™ 9085 resin from Stratasys, Ltd. The CTE at 20°C of the same composite material is 84.8 ppm/°C which is about 20 ppm/°C lower when compared with pure ABS that is widely used by the research community for 3D printed RF/microwave devices by FDM. The electromagnetic (EM) composites with tailored EM properties studied by this work have a great potential for enabling the next generation of high-performance 3D-printed RF/microwave devices and antennas operating at the Ku-band, K-band, and mm-wave frequencies.
243

A structural analysis of George Enescu’s Piano sonata in D major, op. 24, no. 3

Kvarnstrom, Jonas Erik 05 1900 (has links)
George Enescu (1881-1955) is known primarily today in conjunction with the world of violin playing. Celebrated as a violin virtuoso throughout the capitals of Europe and North America in the first half of this century, and later admired as a teacher of luminary talents such as Yehudi Menuhin, Arthur Grumiaux, and Ida Haendel, Enescu exerted a considerable influence on the developments of the international music scene. This was nowhere more apparent than in Paris and Bucharest, cities in which Enescu spent most of his life active as performer, conductor, and composer. As his career progressed, Enescu dedicated an increasing amount of time and energy to composition, producing an impressive list of works, many of which were of monumental proportions. Contemporary with Bartok and Kodály, Enescu found himself caught in the current of nationalism that asserted itself in Europe during the first decades of the twentieth century. Seeking a personal, expressive idiom in which he could fuse the musical elements of both Western tradition and his native Rumanian folk heritage, Enescu experimented with diverse compositional trends and styles. Expanding the reaches of tonality with heightened chromaticism, in which microtonal as well as modal inflections were both to play significant roles, Enescu’s idiom evolved into a highly plastic language, comprising a great variety of stylistic characteristics. In order to assimilate the heterogeneous elements into one unified expression, Enescu relied on traditional compositional techniques such as sonata form, cyclic thematic structure, and motivic development. The focus of this paper is to examine to what extent these compositional techniques are incorporated into his work and to direct attention to those elements, i.e., both structural and non-structural, that were most distinctive of Enescu’s musical style. Owing to its concentration of key stylistic elements and its stature as perhaps the most accomplished piano composition in Enescu’s output, the Sonata for Piano in D Major, Op. 24, No. 3 (1934) will serve as model for this analytical study. Chapter One provides by way of an introduction a brief overview of the formative years in Enescu’s life and defines the position of the Sonata within the complete ceuvre. Chapters Two, Three, and Four constitute the main body of the paper and contain analyses of each of the Sonata’s three movements. In these chapters discussion revolves around the more significant structural features of the work such as the overall cyclic design, simultaneously examining the methods Enescu employs to integrate folk inflection throughout the Sonata. Chapter Five comprises the summary. The most significant features of the Sonata are recapitulated and parallels to numerous other works are drawn, in an attempt to present the Sonata as a culmination of Enescu’s compositional style. / Arts, Faculty of / Music, School of / Graduate
244

Differential Evolution Based Interceptor Guidance Law

Raghunathan, T 07 1900 (has links) (PDF)
Kinematics based guidance laws like the proportional navigation (PN) and many other linear optimal guidance laws perform well in near-collision course conditions. These have been studied thoroughly in the literature from all aspects, ranging from optimality to capturability, for planar or two dimensional interceptor-target engagements, and to a lesser extent, for three dimensional engagements. But guidance in widely off-collision course conditions like high initial heading errors has been relatively less studied. This is probably due to the inherently high nonlinearity of the problem, which makes it a far more difficult problem to solve. However, with increasing speed and agility of interceptors and targets, solutions of such problems have acquired an increased urgency, as has been reflected in the recent literature. This thesis proposes a guidance law based on differential evolution (DE), a member of the evolutionary algorithms (EA) family. While EAs have been applied extensively to static optimization problems, they have been considered unsuitable for solving dynamic optimization or optimal control problems, due to their computationally intensive nature, and their consequent inability to produce solutions online in real-time, except for systems with very slow dynamics. This thesis proposes an online-implementable optimal control for interceptor guidance, a problem with inherently fast dynamics. The proposed law is applicable to all initial geometries including those that involve high to very high heading errors. While interception by itself is a challenging task in the presence of high heading errors, an additional requirement of optimality is also imposed. The first part of the thesis considers only the 2-D kinematic model with high heading errors. In the second part, a 3-D realistic dynamic model, which includes a time-varying interceptor speed, thrust, drag and mass, besides gravity in the vertical plane of motion, and upper bound on the lateral acceleration, is considered, in addition to high heading errors. It is shown that the same structure of the law that is proposed for the 2-D kinematic model can also be used for the 3-D realistic model, if the rest of the complexities of moving from 2-D space to 3-D space, and from kinematics to dynamics is duly addressed. The guidance law proposed does not require time-to-go, the estimation of which can be a difficult problem in high heading error scenarios in which the closing velocity can be negative. Easy to compute and simple to implement in practice, the proposed law does not need any of the techniques or methods from classical optimal control theory, which are complicated and suffer from several limitations. The empirical pure PN (PPN) law is augmented with a term that is a polynomial function of the heading error. The values of the coefficients of the polynomial are found by using the DE. The computational effort required for this low dimensional polynomial optimization problem is shown to be low enough to enable online implementation in real-time. The performance of the proposed law in nominal and off-nominal conditions is validated through several simulations for the 2-D kinematic model, and the 3-D realistic dynamic model. The results are compared with the PPN, augmented PPN and the all-aspect proportional navigation (AAPN) laws in the literature, as per several criteria like optimality, peak latax required and robustness to off-nominal conditions. A successful online implementation of the proposed law for application in practice is also demonstrated. An obvious limitation of optimization by soft computation methods like differential evolution is that no rigorous proof of either convergence or optimality exists for such methods. A fallback option in the form of a conventional guidance law is included in the scheme in case of failure of convergence, and an indirect proof of optimality is provided in the third and final part of the thesis. The same guidance problem is solved by direct multiple shooting method, and it is shown that the numerical results of the two methods compare favourably. The solution by the shooting method is optimal, but computationally far more intensive and takes a computation time of an order of magnitude that is at least one or two times that of the simulation time of the plant. It also needs a good initial guess solution that lies within the region of convergence, which can be a difficult task by itself. Moreover, the shooting method solution is only open loop, and hence applicable for the given model and initial conditions only. Whereas, the simplicity of the method proposed in the thesis makes the solution or guidance law computable in a fraction of the flight time of the engagement, thereby making it online implementable. Equally important, is the fact that it is closed loop, and hence robust to off-nominal conditions like variations in the plant model and parameters assumed in its design.
245

Segmentations of the intraretinal surfaces, optic disc and retinal blood vessels in 3D-OCT scans

Lee, Kyung Moo 01 May 2009 (has links)
Optical coherence tomography (OCT) is a safe and non-invasive imaging technique providing high axial resolution. A spectral-domain OCT scanner capable of acquiring volumetric data of the retina is becoming an increasingly important modality in ophthalmology for the diagnosis and management of a variety of retinal diseases such as glaucoma, diabetic retinopathy and age related macular degeneration (AMD) which are major causes of a loss of vision. To analyze and track these ocular diseases, developments of the automated methods for detecting intraretinal layers, optic discs and retinal blood vessels from spectral-domain OCT scans are highly required recently. The major contributions of this thesis include: 1) developing a fast method that can automatically segment ten intraretinal layers in the spectral-domain macular OCT scan for the layer thickness analysis, 2) developing a method that can automatically segment the optic disc cup and neuroretinal rim in the spectral-domain OCT scan centered at the optic nerve head (ONH) to measure the cup-to-disc ratio, an important structural indicator for the progression of glaucoma, and 3) developing a method that can automatically segment the 3-D retinal blood vessels in the spectral-domain ONH-centered OCT scan to extract 3-D features of the vessels for the diagnosis of retinal vascular diseases.
246

Quantitative analysis of 3D tissue deformation reveals key cellular mechanism associated with initial heart looping / 初期心ループ形成時における3次元組織動態の定量解析と細胞機構の解明

Kawahira, Naofumi 27 July 2020 (has links)
京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第22687号 / 医博第4631号 / 新制||医||1045(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 山下 潤, 教授 木村 剛, 教授 浅野 雅秀 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM
247

QUANTIFICATION OF THERMAL BRIDGING EFFECTS IN COLD-FORMED STEEL WALL ASSEMBLIES

Kapoor, Divyansh 08 April 2020 (has links)
Thermal bridging can be defined as the phenomenon where a structural element spanning the building envelope acts like a thermal pathway which collects and moves energy (heat) from the interior to the exterior of the structure. CFS construction, due to the high thermal conductivity of steel with respect to its surrounding structural components and repetitive nature of framing, is highly prone to thermal bridging. Thermal bridging significantly alters the thermal performance of wall assemblies. Hence, the objective of this research project was to quantify the magnitude of energy loss through cold-formed steel (CFS) stud wall assemblies at a component level to lay the groundwork for future works that promote sustainable, energy-efficient, and improved building design recommendations. Therefore, a parametric evaluation was performed using ISO 10211:2007, Annex A, conforming heat transfer software Blocon Heat3 version 8 to generate the data required for analysis. 80 unique wall assemblies and the impact of selected parameters on the overall thermal transmittance of the wall assembly were studied as part of the parametric evaluation. The key variables of the study are steel thickness, stud depth, stud spacing, cavity insulation R-value, external insulation thickness (R-value), and fastener diameter and length. Based on the results of the analysis, effects of increasing stud and track thickness, depth, and stud spacing have been discussed in the form of trends in overall heat flow and linear thermal transmittance coefficient values. Additionaly, effects of increasing external insulation have been discussed by addressing changes in heat flow.
248

Návrh a optimalizace ojnice motoru závodního automobilu / Con Rod design and optimization of racing engine

Ulman, Jaroslav January 2010 (has links)
This master thesis describes the design and optimization of connecting rod motor racing car. At the beginning of the whole work is a 3D-model of rods, from which then the whole work is based. Then it analyzes the current model of stress and on the basis of the results are made structural changes to the solution of rods. Newly adapted connecting rod is again analyzed using FEM and newly obtained results are compared with results of the original model of connecting rods. The conclusion deals with sensitivity analysis of selected parameters of rods and their potential effect on the resulting changes in strength connecting rod .Then is an assessment of all results.
249

Investigation of 3-d Heat Transfer Effects in Fenestration Products

Kumar, Sneh 01 January 2010 (has links) (PDF)
Buildings in USA consume close to 40% of overall energy used and fenestration products (e.g. windows, doors, glazed-wall etc.) are the largest components of energy loss from buildings. Accurate evaluation of thermal performances of fenestration systems is critical in predicting the overall building energy use, and improving the product performance. Typically, two-dimensional (2-D) heat transfer analysis is used to evaluate their thermal performance as the 3-D analysis is highly complex process requiring significantly more time, effort, and cost compared to 2-D analysis. Another method of evaluation e.g. physical test in a hotbox is not possible for each product as they are too expensive. Heat transfer in fenestration products is a 3-D process and their effects on overall heat transfer need to be investigated. This thesis investigated 3-D heat transfer effects in fenestration systems in comparison to the 2-D results. No significant work has been done previously in terms of 3-D modeling of windows, which included all the three forms of heat transfer e.g. conduction, convection and radiation. Detailed 2-D and 3-D results were obtained for broad range of fenestration products in the market with a range of frame materials, spacers, insulated glass units (IGU), and sizes. All 2-D results were obtained with Therm5/Window5 (e.g. currently standard method of evaluating thermal performance) and GAMBIT/FLUENT while all 3-D results were obtained with GAMBIT/FLUENT. All the three modes of heat transfer mechanism were incorporated in the heat transfer modeling. The study showed that the overall 3-D heat transfer effects are relatively small (less than 3%) for present day framing and glazing systems. Though at individual component level (e.g. sill, head, Jamb) 3-D effects were quite significant (~10%) but they are cancelled by their opposite sign of variation when overall fenestration system effect is calculated. These 3-D heat transfer effects are higher for low conducting or more energy efficient glazing and framing systems and for smaller size products. The spacer systems did not have much impact on the 3-D effects on heat transfer. As the market transforms towards more insulating and higher performance fenestration products, 3-D effects on heat transfer would be an important factor to consider which it may require correlations to be applied to 2-D models, or may necessitate the development of dedicated 3-D fenestration heat transfer computer programs.
250

N3asics: Designing Nanofabrics with Fine-Grained Cmos Integration

Panchapakeshan, Pavan 01 January 2012 (has links) (PDF)
Nanoscale-computing fabrics based on novel materials such as semiconductor nanowires, carbon nanotubes, graphene, etc. have been proposed in recent years. These fabrics employ unconventional manufacturing techniques like Nano-imprint lithography or Super-lattice Nanowire Pattern Transfer to produce ultra-dense nano-structures. However, one key challenge that has received limited attention is the interfacing of unconventional/self-assembly based approaches with conventional CMOS manufacturing to build integrated systems. We propose a novel nanofabric approach that mixes unconventional nanomanufacturing with CMOS manufacturing flow and design rules to build a reliable nanowire-CMOS 3-D integrated fabric called N3ASICs with no new manufacturing constraints. In N3ASICs active devices are formed on a dense semiconductor nanowire array and standard area distributed pins/vias, metal interconnects route signals in 3D. The proposed N3ASICs fabric is fully described and thoroughly evaluated at all design levels. Novel nanowire based devices are envisioned and characterized based on 3D physics modeling. Overall N3ASICs fabric design, associated circuits, interconnection approach, and a layer-by-layer assembly sequence for the fabric are introduced. System level metrics such as power, performance, and density for a nanoprocessor design built using N3ASICs were evaluated and compared against a functionally equivalent CMOS design. We show that the N3ASICs version of the processor is 3X denser and 5X more power efficient for a comparable performance than the 16-nm scaled CMOS version without any new/unknown-manufacturing requirement. Systematic yield implications due to mask overlay misalignment have been evaluated. A partitioning approach to build complex circuits has been studied.

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