No description available.

No description available.

This study is aimed to compare the fluidized bed and microwave drying with microwave assisted fluidized bed drying. For this purpose, macaroni beads (2.4&plusmn / 0.08 mm diameter) were dried from about 20% to 12% moisture content in a fluidized bed of 7.6 cm diameter, in a domestic microwave oven with a power of 609 W and in the fluidized bed placed in the microwave oven conditions. In the experiments with the fluidized bed three air temperatures / 50, 60 and 70&deg / C at an air velocity of 2.3 m/s and in those with the microwave oven two power levels / 50% and 100% were used. The drying curves indicated that the drying rate increased with the air temperature and microwave power in each drying method. Microwave assisted fluidized bed drying reduced the drying time by about 50% and 11% on the average compared with the fluidized bed and microwave drying, respectively. Therefore, it was concluded that the drying time was reduced more by the effect of microwave energy than the fluidization. The effective diffusivities in the fluidized bed and microwave assisted fluidized bed drying were found to be in the order of 4.125x10-11 and 8.772x10-11 m2/s on the average, respectively. The effective diffusivities for the fluidized bed drying were fitted to an Arrhenius type of equation and the magnitude of the activation energy was found to be in the order of 12595 kJ/kg mol.

Thesis (Ph. D.)--University of Hong Kong, 2000. / Includes bibliographical references.

The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Title from PDF of title page (University of Missouri--Columbia, viewed on October 5, 2009). Thesis advisor: Dr. Alan G. Whittington. Includes bibliographical references.

Thesis (Ph.D)--Mechanical Engineering, Georgia Institute of Technology, 2010. / Committee Co-Chair: Haynes, Comas; Committee Co-Chair: Wepfer, William; Committee Member: Fedorov, Andrei; Committee Member: Liu, Meilin; Committee Member: Paredis, Chris; Committee Member: Teja, Amyn. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Additive Manufacturing (AM), over the years, has seen a tremendous amount of research for improving the manufacturability of materials into final products. The main advantages of additive manufacturing are the minimizing of waste material as it is an additive process. As well as the ability to create custom low-volume products without the need for creation of expensive tooling or programming before manufacturing begins. Because of these advantages, however, AM is susceptible to unique challenges in the quality side of manufacturing. These challenges include minimizing and detecting defects during the build. The focus of this research looks at the capability of using Pulse Thermography (PT), a nondestructive testing method, with longer than typical pulse length on additively manufactured parts for surface and sub-surface defect detection as well as thermal property determination based on a known void depth. The first and second part of this research will look at a range of pulse lengths greater than 100ms to determine if the previously defined assumption is necessary for accurate defect detection. The significance of increasing the pulse length is to have the ability to increase the overall energy input into the part without having to increase the power. Allowing for the capability of defect detection for both shallow and deeper defects with the same overall setup. One-dimensional simulations r using Forward Time Center Space (FTCS) approximation, show that the assumption of an instantaneous pulse is relative, and defects can be accurately calculated within a range of pulse lengths. Based on the simulations, experimentation was conducted to determine the capability of calculating sub-surface defect depths with a longer pulse on a FDM printed ABS part with 100% in fill. The defect depths will range from 0.3mm to 1.8mm and the widths of the defects used for depth calculation will be 8x8mm. Results of the experiments show that even with FDM printed parts defect depths were accurately calculated up to a depth of 1.2mm. The third aspect of this research looks at the infrared reflections emitting off the surface during the longer pulse. With a longer pulse length, there is more time for the infrared camera to collect thermograms of the surface during the pulse. It was noticed during sub-surface defect detection that the infrared reflections paint a picture of the surface characteristics of the part. Characteristics that include surface imperfections not intended in the original build parameters such as under extrusions and cracks. Defects as small as 150μm with a thermal pixel resolution 75μm are detected. The third and final aspect of this research looks at the ability to use PT with a longer pulse to determine thermal properties of a binder jetted additively manufactured part as well as packing factors that may be otherwise be unknown. When a product is binder jetted a chemical binder is added to the powder layer by layer until a product is formed.

abstract: Proton and fluorine diffusivity and ionic conductivity of 2-fluoropyridinium triflate (2-FPTf) and proton and fluorine diffusivity, ionic conductivity, and viscosity of trifluoromethanesulfonic acid (TFMSA) monohydrate have been measured over a wide range of temperatures. Diffusivities were measured using the pulsed-gradient spin-echo (PGSE) technique on a 300 MHz NMR spectrometer. Conductivities were measured using electrochemical impedance spectroscopy (EIS) on standard equipment and viscosities were determined using a Cannon-Ubbelohde viscometer. For 2-FPTF, the diffusivity of mobile protons increased from 1.84+/-0.06 x 10(-11) m2/s at 55 degC to 1.64+/-0.05 x 10(-10) m2/s at 115 degC while the diffusivity of 2-fluoropyridine fluorines increased from 2.22+/-0.07 x 10(-11) m2/s at 70 degC to 9.40+/-0.28 x 10(-11) m2/s at 115 degC. For TFMSA monohydrate, the diffusivity of protons increased from 7.67+/-0.23 x 10(-11) m2/s at 40 degC to 3.92+/-0.12 x 10(-10) m2/s at 110 degC while the diffusivity of fluorines increased from 4.63+/-0.14 x 10(-11) m2/s at 40 degC to 2.79+/-0.08 x 10(-10) m2/s at 110 degC, protons diffusing approximately 1.5 times faster than fluorines over the entire temperature range. NMR spectra indicate that proton diffusion occurs via direct hopping from TFMSA molecule to molecule. The conductivity of 2-FPTf varied from 0.85+/-0.03 mS/cm to 35.9+/-1.08 mS/cm between 25 and 110 degC. The conductivity of TFMSA monohydrate varied from 6.60+/-0.2 mS/cm to 84.6+/-2.5 mS/cm between 23 and 139 degC and its viscosity varied from 27.5+/-1.4 mPa.s to 4.38+/-0.22 mPa.s between 49 and 121.5 degC, in good agreement with literature values. Temperature dependences of the measured properties showed Arrhenius behavior with activation energies for proton diffusion, fluorine diffusion and ionic conduction for 2-FPTf above the melting point of 16.9+/-0.8 kJ/mol, 48.0+/-2.4 kJ/mol and 27.8+/-1.4 kJ/mol respectively. Activation energies for proton diffusion, fluorine diffusion, ionic conduction and viscosity for TFMSA monohydrate were 23.4+/-1.2 kJ/mol, 26.0+/-1.3 kJ/mol, 22.1+/-1.1 kJ/mol, and 26.9+/-1.3 kJ/mol respectively. The degree of dissociation of the charged species, calculated using the Nernst-Einstein relation, varied from 13 to 24% for 2-FPTf and from 25 to 29% for TFMSA monohydrate over the temperature range. / Dissertation/Thesis / Doctoral Dissertation Physics 2015

O objetivo deste trabalho foi desenvolver um software, de fácil operação e eficiente, para determinar a difusividade térmica de biomateriais. A necessidade de se conhecer a difusividade térmica de materiais como, por exemplo, esmalte e dentina, é essencial para o estabelecimento de protocolos de utilização clínica laser, para evitar danos colaterais ao paciente. O software desenvolvido, denominado CZ ThermaDiff, baseia-se no processamento de imagens térmicas adquiridas por uma câmera termográfica no infravermelho (ThermaCam SC3000, FLIR System, EUA). Foi desenvolvido em ambiente LabView, o que permitiu criar um painel de controle de fácil operação, contendo apenas duas funções básicas (Start e Stop). O software arquiva os dados em formato de tabela contendo todas as medidas de difusividade térmica, suas médias para intervalos de 10 °C e suas respectivas temperaturas, para uma amostra. Foi observado, tanto para o esmalte quanto para a dentina, que os valores de difusividade não são constantes e aumentavam em função da temperatura. Os valores encontrados foram aplicados a um modelo de transferência de calor, simulando um dente molar humano com as seguintes estruturas: esmalte, dentina e polpa. O modelo baseia-se no método de resistores térmicos, sendo que para a polpa foi utilizado o modelo de difusão de calor, considerando a circulação sanguínea. Os valores de temperatura obtidos neste modelo teórico, utilizando difusividades dependentes da temperatura foram maiores que as obtidas com um valor constante de difusividade, medido à temperatura ambiente. Este fato realça a importância da mensuração da difusividade em função da temperatura e da interface desenvolvida neste trabalho. / The aim of this work was to develop a software, easy to operate and efficient, to determine the thermal diffusivity of biomaterials as enamel and dentin. It is necessary to know the thermal diffusivity of these materials to establish laser irradiation protocols, to avoid collateral damage to the patient. The software developed named called CZ ThermaDiff, processes thermographic images from a thermographic camera (ThermaCam SC300, FLIR System, USA). The software was programmed in LabView environment, allowing easy operation from a control window with only two buttons (start and stop). Thermal diffusivity values, the mean values for intervals of 10 °C and its respective temperature, for one sample are saved in table form. For both biomaterials, thermal diffusivity increased as function of the temperature increase. The experimental thermal diffusivity data were used in a heat transfer model, for a human molar tooth with three layers: enamel, dentin and pulp. The model was based on the thermal resistors method, for the three layers and for the pulp, it was applied the heat diffusion model, taking into account the blood circulation. Using temperature dependent diffusivities, temperatures where values were higher than the temperatures of the theoretical model using a constant diffusivity value, obtained at ambient temperature. This fact emphasized the importance of both: the temperature dependent diffusivity measurement and the software developed in this work.

Orientador: Miriam Dupas Hubinger / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-05T14:58:57Z (GMT). No. of bitstreams: 1 VivancoPezantes_David_D.pdf: 5009400 bytes, checksum: 9209dcce381309e83df6dfa19aa69001 (MD5) Previous issue date: 2006 / Doutorado / Doutor em Engenharia de Alimentos