This present study seeks to contribute detailed visualization data on a pool boiling experiments using HFE-7000. Particle Image Velocimetry (PIV) was used to measure the time resolved whole field liquid velocity. Bubble dynamic parameters such as nucleation site density, bubble departure diameter, contact angles and frequency were obtained in shadowgraphy measurements. Infrared thermometry with an IR camera was used for observation of temperature fluctuations of nucleation sites. The experiments were taken for the heat flux from 0.042 kW/m^2 to 0.266 kW/m^2, six experimental conditions in total. To provide a supplementary description of heat transfer mechanism, a novel bubble characterization technique, reflection interference contrast microscopy (RICM), was used to obtain detailed information on bubble dynamic parameters on the microscopic scale. Bubble diameter was obtained from RICM pictures. Comparison between the experiments results and previous empirical correlation were made. Agreements and discrepancies were discussed.

Mon travail de thèse se place dans le cadre du projet ANR TUCCIRM de développement d’un système de thérapie par ultrasons focalisés de haute intensité (HIFU) dédié au cerveau implantable dans un IRM clinique 1,5 T. Les développements IRM ont été l’objet de mon travail. Dans un premier temps, l’IRM a été utilisée pour suivre l’évolution en température des tissus en cours de traitement. Pour cela, nous avons tout d’abord réalisé une étude d’optimisation et de comparaison de séquences de thermométrie basées sur le principe du décalage chimique (PRFS). Puis, nous avons optimisé le rapport signal sur bruit pour améliorer la qualité des images ainsi que la précision en température. Ces développements ont été appliqués au cours de tests HIFU suivi par IRM de têtes de cadavres humains.Dans un deuxième temps, l’IRM a été utilisée pour caractériser la viscoélasticité des tissus cérébraux par la technique d’élastograhie par résonance magnétique. Ces propriétés changeant avec la température, cette méthode permettrait de suivre l’état des tissus pendant le traitement HIFU pour en déterminer l’effet thermique. Dans ce contexte, nous avons développé un nouveau concept de générateur d’onde, testé ensuite sur six rats in vivo. / My Ph.D. work is a part of the ANR TUCCIRM project, which consist in developing a treatment system dedicated to the brain using High Intensity Focalized Ultrasound (HIFU) usable with clinical 1.5T MRI. My work was mainly focus to MRI development.During the first part of my work, we used the MRI to observe the evolution of the temperature of tissue inside the brain during the ultrasound treatment. Firstly, based on the chemical shift principle, we perform an optimization study and thermometric sequence comparison. Then an optimization of the signal-to-noise ratio has been realized to improve the image quality and then the temperature measurement precision. This development has been used during HIFU test on human head corpse following the evolution of the temperature with MRI. In a second part, MRI was used to characterize the viscoelasticity of brain tissue using elastography by magnetic resonances. These properties are evolving with the temperature, so this method should allow following tissue state during HIFU treatment to determine temperature effect on brain tissue. For that purposes we develop a new concept of wave generator, witch has been tested on 6 rats in vivo.

Sensores ópticos possibilitam a determinação da temperatura de maneira rápida e à distância, em ambientes onde os sensores de contato padrão se mostram ineficientes, como centrais elétricas (fortes campos eletromagnéticos), circuitos eletrônicos e células biológicas (escala micrométrica). Estes dispositivos são baseados em variações de uma propriedade óptica de um dado material devido à variação de temperatura. A técnica da razão da intensidade de fluorescência (FIR) faz uso da variação das intensidades relativas das emissões de dois níveis termicamente acoplados de um centro emissor, muitas vezes um íon terra-rara trivalente. O neodímio (Nd3+) é comumente empregado por apresentar emissões na janela biológica óptica do infravermelho próximo. Neste trabalho, vidros fluorofosfatos dopados com Nd3+ são utilizados como materiais para determinação da temperatura através da FIR. As emissões são coletadas por uma fibra óptica conectada a um espectrômetro portátil, cujos espectros medidos são analisados por um software. Este sistema permite a determinação em tempo real das razões das intensidades de fluorescência e, consequentemente, da temperatura. Sensibilidades de até 1,96%/K são obtidas para a razão entre as emissões do Nd3+ em 800 e 870 nm. Já o uso da razão entre as intensidades das emissões em 750 e 870 nm resulta em sensibilidades que chegam a 2,46%/K. A adição de itérbio (Yb3+) aos vidros faz com que a sensibilidade chegue a 2,77%/K quando emissões de ambos os íons são comparadas. O papel dos fônons na transferência de energia entre os íons é analisado. Os valores de razão de fluorescência obtidos a partir da análise pela teoria de Judd-Ofelt são aproximadamente 25% inferiores aos obtidos experimentalmente, não permitindo, neste sistema, o cálculo a priori da curva de calibração do sensor. / Optical sensors enable fast and long-distance temperature measurements in environments where standard contact sensors are ineffective, such as power stations (strong electromagnetic fields), electronic circuits and biological cells (sub-micron scale). These devices are based on temperature induced changes in optical properties of a given material. The fluorescence intensity ratio technique (FIR) makes use of the relative emission intensities variation of two thermally coupled levels of an emission center, usually a trivalent rare-earth ion. Neodymium (Nd3+) is commonly employed as its emissions lie in the near-infrared biological optical window. Here, Nd3+-doped fluorophosphate glasses are employed as a temperature sensing material through the use of FIR. The emissions are collected by an optical fiber connected to a portable spectrometer, whose measured spectra are analyzed by a software. This system enables real-time determination of the fluorescence intensity ratios and, therefore, the temperature. Sensibilities as high as 1.96%/K are obtained through the ratio between 800 and 870 nm Nd3+ emissions. The use of the emission ratio between 750 and 870 nm results in 2,46%/K sensibilities. The addition of ytterbium (Yb3+) dopant to the glasses makes the sensibilities increase to 2,77%/K when the emissions from both ions are compared. The phonons role in the energy tranfer between the ions is analyzed. The fluorescence ratio values obtained via Judd-Ofelt analysis are approximately 25% lower than the experimentally obtained, thus preventing, in this system, a priori calculation of the sensors calibration curve.

This thesis focuses on implementing radio frequency (rf) reflectometry techniques for dispersive detection of charge and spin dynamics in nanoscale devices. I have investigated three aspects of rf reflectometry using state-of-the-art silicon (Si) complementary metal-oxide-semiconductor (CMOS) nanowire field effect transistors (NWFETs). First, a high-sensitivity capacitive gate-based charge sensor is developed by optimising the external matching circuit to detect capacitive changes in the high frequency resonator. A new circuit topology is used where superconducting niobium nitride (NbN) inductor is connected in parallel with a single-gate Si NWFET resulting in resonators with loaded Q-factors in the 400-800 range. For a resonator operating at 330 MHz, I have achieved a charge sensitivity of 7.7 $\mu e/\sqrt{\text{Hz}}$ and, when operating at 616 MHz, I get 1.3 $\mu e/\sqrt{\text{Hz}}$. This gate-based sensor can be used for fast, accurate and scalable techniques for quantum state readout in Si CMOS based quantum computing. Second, this new circuit topology for the resonator is used with a dual-gate Si NWFET. This dual-gate device geometry provides access to a double quantum dot (DQD) system in few electron regime. The spin-state of the two-electron DQD system is detected dispersively using Pauli spin blockade between joint singlet S(2,0) and triplet T$_-$(1,1) states in a finite magnetic field $B$. The singlet-triplet relaxation time $T_1$ at $B=4.5$~T is measured to be $\sim$1 ms using standard homodyne detection technique. Third, I expand the range of applications of gate-based sensing to accurate temperature measurements. I have experimentally demonstrated a primary thermometer by embedding a single-gate Si NWFET with the rf capacitive gate-based sensor. The thermometer, termed as gate-based electron thermometer (GET), relies on cyclic electron tunneling between discrete energy levels of a quantum dot and a single electron reservoir in the NWFET. I have found that the full-width-half-maximum (FWHM) of the resonator phase response depends linearly with temperature via well known physical law by using the ratio $k_\text{B}/e$ between the Boltzmann constant and the electron charge. The GET is also found to be magnetic field independent like other primary thermometers such as Coulomb blockade and shot noise thermometers.

Over the life of nuclear fuel, inhomogeneous structures develop, negatively impacting thermal properties. New fuels are under development, but require more accurate knowledge of how the properties change to model performance and determine safe operational conditions. Measurement systems capable of small–scale, pointwise thermal property measurements and low cost are necessary to measure these properties and integrate into hot cells where electronics are likely to fail during fuel investigation. This project develops a cheaper, smaller, and easily replaceable Fluorescent Scanning Thermal Microscope (FSTM) using the blue laser and focusing circuitry from an Xbox HD-DVD player. The FSTM also incorporates novel fluorescent thermometry methods to determine thermal diffusivity. The FSTM requires minimal sample preparation, does not require access to both sides of the sample, and components can be easily swapped out if damaged, as is likely in irradiated hot cells. Using the optical head from the Xbox for sensing temperature changes, an infrared laser diode provides periodic heating to the sample, and the blue laser induces fluorescence in Rhodamine B deposited on the sample's surface. Thermal properties are fit to modulated temperature models from the literature based on the phase delay response at different modulated heating frequencies. With the FSTM method, the thermal diffusivity of a 10 cent euro coin was found to be 21±5 mm2/s. This value is compared to Laser Flash Analysis and a Thermal Conductivity Microscope (which used thermoreflectance a method), which found the thermal diffusivity to be 30.4±0.1 mm2/s and 19±3 mm2/s, respectively. The hardware and instrumentation performed as expected, but the property measurements show that the device is not yet optimized to provide accurate measurements with current heat transfer models. Future work is discussed to investigate the accuracy and necessary modeling adjustments, as well as refinements to the instrumentation.

Winter road maintenance activities are crucial for maintaining the accessibility and traffic safety of the road network at northerly latitudes during winter. Common winter road maintenance activities include snow ploughing and the use of anti-icing agents (e.g. road salt, NaCl). Since the local weather is decisive in creating an increased risk of slippery conditions, understanding the link between local weather and conditions at the road surface is critically important. Sensors are commonly installed along roads to measure road weather conditions and support road maintenance personnel in taking appropriate actions. In order to improve winter road maintenance, more precise information about road surface conditions is essential. In this thesis, different methods for estimation of road weather are developed, discussed and tested. The methods use the principles of infrared thermometry, image analysis and spectroscopy to describe ice formation, snow accumulation and road surface wetness in specific patches or along road sections. In practical applications, the methods could be used for better planning of snow clearing operations, forecasting of ice formation and spreading of road salt. Implementing the proposed methods could lead to lower maintenance costs, increased traffic safety and reduced environmental impact. / <p>QC 20121116</p>

<p>The purpose of this thesis is to report technological developments in contrast mechanisms for MRI. The search for new forms of contrast is on-going, with the hope that new contrast mechanisms and new contrast agents will provide unique insights into various molecular processes and disease states. In this thesis, we will describe new contrast mechanisms developed by manipulating the inherent physics of the system, as well as the development of exogenous contrast agents. More specifically, we will describe the application of iMQCs (intermolecular multiple quantum coherences) to thermometry and structural imaging, and the unique information provided from these studies. We will also describe methods for migrating iMQC-based pulse sequences from a Bruker research console onto a clinical GE console, thus enabling the application of iMQCs to humans. We will describe the development of hyperpolarized contrast agents which have the potential to provide an unprecedented level of molecular contrast to MRI and the development of techniques to enhance the lifetime of these hyperpolarized contrast agents. Finally, we will discuss a new type of T2 -weighted imaging which significantly improves the refocusing of CPMG-type sequences.</p> / Dissertation

This study has focused on development, optimisation and implementation of the 2-line Planar Laser Induced Fluorescence (2-line PLIF) technique for combustion measurements on a single cylinder optical Gasoline Direct Injection (GDI) engine with both Spark Ignition (SI) and Controlled Auto Ignition (CAI) combustion operations. The CAI combustion was achieved by employing Negative Valve Overlap (NVO). Two excitation wavelengths at 308 nm (directly from a XeCl laser) and 277 nm (via Raman shifting a KrF laser output at 248 nm) were exploited for the measurements. A calibration curve of fluorescence signal intensity ratio of the two laser beams as a function of temperature was obtained by conducting a series of static tests on a specially designed Constant Volume Chamber (CVC). The developed technique was validated by measurements of in-cylinder charge temperature during the compression stroke for both motoring and firing cycles and comparing the PLIF values with the temperature values calculated from in-cylinder pressure data assuming a polytropic compression. Following the validation measurements, the technique was applied to study of fuel spray characteristics and simultaneous measurements of in-cylinder charge temperature and mole fraction of Exhaust Gas Residuals (EGR). Further optimisation of the thermometry technique by enhancing the fluorescence Signal to Noise Ratio (SNR) and improving both the temporal and spatial resolutions as well as measurements precision provided the opportunity to apply the technique to other combustion measurements. The thesis presents the first application of the 2-line PLIF diagnostic in study of direct injection charge cooling effects and study of flame thermal stratification in IC engines.

abstract: A method of determining nanoparticle temperature through fluorescence intensity levels is described. Intracellular processes are often tracked through the use of fluorescence tagging, and ideal temperatures for many of these processes are unknown. Through the use of fluorescence-based thermometry, cellular processes such as intracellular enzyme movement can be studied and their respective temperatures established simultaneously. Polystyrene and silica nanoparticles are synthesized with a variety of temperature-sensitive dyes such as BODIPY, rose Bengal, Rhodamine dyes 6G, 700, and 800, and Nile Blue A and Nile Red. Photographs are taken with a QImaging QM1 Questar EXi Retiga camera while particles are heated from 25 to 70 C and excited at 532 nm with a Coherent DPSS-532 laser. Photographs are converted to intensity images in MATLAB and analyzed for fluorescence intensity, and plots are generated in MATLAB to describe each dye's intensity vs temperature. Regression curves are created to describe change in fluorescence intensity over temperature. Dyes are compared as nanoparticle core material is varied. Large particles are also created to match the camera's optical resolution capabilities, and it is established that intensity values increase proportionally with nanoparticle size. Nile Red yielded the closest-fit model, with R2 values greater than 0.99 for a second-order polynomial fit. By contrast, Rhodamine 6G only yielded an R2 value of 0.88 for a third-order polynomial fit, making it the least reliable dye for temperature measurements using the polynomial model. Of particular interest in this work is Nile Blue A, whose fluorescence-temperature curve yielded a much different shape from the other dyes. It is recommended that future work describe a broader range of dyes and nanoparticle sizes, and use multiple excitation wavelengths to better quantify each dye's quantum efficiency. Further research into the effects of nanoparticle size on fluorescence intensity levels should be considered as the particles used here greatly exceed 2 ìm. In addition, Nile Blue A should be further investigated as to why its fluorescence-temperature curve did not take on a characteristic shape for a temperature-sensitive dye in these experiments. / Dissertation/Thesis / M.S. Mechanical Engineering 2011

Orientador: Alexandre Dal Pai / Banca: Roberto Lyra Villas Bôas / Banca: Francisco Sérgio dos Santos / Resumo: O presente trabalho apresenta o desenvolvimento e implantação de um sistema de aquisição de dados de temperatura, em um silo de armazenamento de grãos, carregado com milho. Os dados foram coletados no silo por um sistema Arduíno ao qual são acoplados os sensores de temperatura. Após a leitura os dados são transmitidos via rádio e exibidos em tempo real em uma tela de computador criada especificamente para que o usuário do sistema consiga identificar os pontos de medição rapidamente. Essa informação é importante para subsidiar o operador do sistema na tomada de decisão sobre intervir ou não no processo de aeração dos grãos para manter a qualidade do produto armazenado. Os dados coletados são armazenados e podem compor uma série histórica do comportamento da temperatura dos grãos durante o armazenamento, bem como serem utilizados em pesquisas acadêmicas. A parte experimental deste trabalho, corroborou para a validação do mesmo. O sistema contou com 12 sensores distribuídos dentro do silo, e as leituras foram realizadas com intervalo de 15 minutos no período entre 16 de julho e 18 de outubro de 2018. Nesse período foram coletados 104640 medidas de temperatura, que permitiram realizar diversas análises. Foi verificado que o sistema pode ser usado para avaliar como foi o comportamento térmico dos grãos e quais foram as reações do milhos depois de atuações para diminuição da temperatura. A partir da variação de temperatura entre o volume do silo sem grãos e com a presença dos mesmo... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This paper presents the development and implementation of a temperature data acquisition system in a grain storage silo loaded with corn. Data were collected in the silo by an Arduino system to which the temperature sensors are coupled. After reading the data is transmitted by radio and displayed in real time on a computer screen specifically designed so that the system user can identify the measuring points quickly. This information is important to support the system operator in deciding whether or not to intervene in the grain aeration process to maintain the quality of the stored product. The collected data are stored and can compose a historical series of grain temperature behavior during storage, as well as being used in academic research. The experimental part of this work corroborated its validation. The system had 12 sensors distributed inside the silo, and the readings were taken with a 15-minute interval between July 16 and October 18, 2018. During this period 104640 temperature measurements were collected, which allowed to perform various analyzes. It was verified that the system can be used to evaluate how was the thermal behavior of the grains and what were the reactions of the corn after actions to decrease the temperature. From the temperature variation between the volume of the silo without grains and with their presence it is possible to estimate the volume occupied by the grain in it. / Mestre