Dissertations / Theses on the topic 'Microwave processing'
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Folorunso, Olaosebikan. "Microwave processing of vermiculite." Thesis, University of Nottingham, 2015. http://eprints.nottingham.ac.uk/28802/.
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Vermiculite is a clay mineral that is generally used for a wide range of applications such as in agricultural, horticultural and construction industries. This is due to its various properties which include high porosity, lightweight, thermo-insulating, non-toxic and good absorption capacity when exfoliated. The objective of this research was to critically evaluate the fundamental interaction of electromagnetic waves with vermiculite from different source locations and to understand the mechanism of exfoliation in an applied microwave field. When vermiculite minerals are placed under the influence of high electric fields, they expand due to the rapid heating of their interlayer water, which subsequently builds up pressure that pushes apart the silicate structure. The degree of exfoliation is directly related to the intensity of the applied electric field. The principal areas covered in this thesis include: a detailed review of the fundamentals of microwave processing and issues surrounding scale up; a critical literature review of vermiculite mineralogy, and previous methods of vermiculite processing and their limitations; understanding the interaction of microwave energy with vermiculite by carrying out mineralogical and dielectric characterisation; microwave exfoliation tests of vermiculite minerals from different source locations and a comparative energy and life cycle analysis of microwave and conventional exfoliation of vermiculite. A detailed review of the literature revealed that conventional exfoliation of vermiculite by gas or oil fuelled furnaces has significant limitations such as emissions of greenhouse gases, high-energy requirements (greater than 1 GJ/t), health and safety issues and poor process control. All work reported so far on microwave exfoliation of vermiculite has been limited to laboratory scale using domestic microwave ovens (2.45 GHz, power below 1200 W) and the route to scale up the process to industrial capacity has not given due consideration. Mineralogical characterisation of vermiculite from different geographical locations (Australia, Brazil, China and South Africa) revealed that only the sample from Brazil is a pure form of vermiculite while the other samples are predominantly hydrobiotite. All the samples have varying degrees of hydration with the Brazilian sample having the highest total water content. The presence of water in any form in a material influences its dielectric response and ultimately the microwave absorbing properties. The dielectric characterisation carried out on the different vermiculite samples shows that the vermiculite mineral structure is effectively transparent to microwave energy, but it is possible to selectively heat microwave absorber, which is the interlayer water in the vermiculite structure. The continuous microwave exfoliation tests carried out at both pilot scale at 53-126 kg/h and the scaled up system at 300-860 kg/h demonstrated that microwave energy can be used for the industrial exfoliation of vermiculite at high throughputs and is able to produce products below the specified product bulk densities standard required by The Vermiculite Association (TVA). The degree of vermiculite exfoliation depends on factors such as power density, feedstock throughput, energy input, interlayer water content, particle size of the feedstock, and vermiculite mineralogy. The highest degree of exfoliation was recorded for the Brazilian sample, which also had the highest water content. Life cycle analysis (LCA) frameworks by the International Organisation for Standardisation (The ISO 14040: principles and framework and ISO 14044: Requirements and guidelines) and British standards institution (PAS2050) were used to carry out comparative life cycle analysis of vermiculite exfoliation using microwave heating and conventional (industrial and Torbed) heating systems. The results showed that the microwave system potentially can give an energy saving of about 80 % and 75 % over industrial and Torbed Exfoliators respectively, and a carbon footprint saving potential of about 66 % and 65 %. It can be concluded that the reduced dust emission and noise from the microwave system would improve the working conditions, health and safety. Furthermore, the methodology discussed in this project can be used to understand the fundamental of microwave interaction with perlite and expanded clay, which are minerals with similar physical and chemical compositions as vermiculite.
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Han, Yichen. "All-optical Microwave Signal Processing." Thèse, Université d'Ottawa / University of Ottawa, 2011. http://hdl.handle.net/10393/20234.
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Microwave signal processing in the optical domain is investigated in this thesis. Two signal processors including an all-optical fractional Hilbert transformer and an all-optical microwave differentiator are investigated and experimentally demonstrated.
Specifically, the photonic-assisted fractional Hilbert transformer with tunable fractional order is implemented based on a temporal pulse shaping system incorporating a phase modulator. By applying a step function to the phase modulator to introduce a phase jump, a real-time fractional Hilbert transformer with a tunable fractional order is achieved.
The microwave bandpass differentiator is implemented based on a finite impulse response (FIR) photonic microwave delay-line filter with nonuniformly-spaced taps. A microwave bandpass differentiator based on a six-tap nonuniformly-spaced photonic microwave delay-line filter with all- positive coefficients is designed, simulated, and experimentally demonstrated. The reconfigurability of the microwave bandpass differentiator is experimentally investigated. The employment of the differentiator to perform differentiation of a bandpass microwave signal is also experimentally demonstrated.
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Favreau, Denis. "Microwave processing of maple sap." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=24002.
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Maple sap was successfully transformed into maple syrup and maple syrup products by evaporation of water by microwave heating. Pulsed power supply with duty cycles of 100%, 75% and 60% were used for the microwave application. The dielectric properties of maple syrup at different moisture contents during the process were determined at 25$ sp circ$C. The products obtained were of excellent quality and were comparable to the highest grade prescribed by the industry. Pulsed power supply was found to have better efficiency of heating, but it increased the total time required for the process. The total time was also found to be dependent on the initial mass of the load. The behavior of the dielectric properties of the maple syrup was found to be fairly linear with moisture content and were found to be in close agreement with an empirical model found in literature. Microwave heating seems to have an enormous potential for production of high quality maple syrup.
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Kobusheshe, Joseph. "Microwave enhanced processing of ores." Thesis, University of Nottingham, 2010. http://eprints.nottingham.ac.uk/11393/.
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Recent research developments have suggested that microwave assisted comminution could provide a step change in ore processing. This is based on the fact that microwave-absorbent phases within a multi-mineral ore can be selectively heated by microwave energy hence inducing internal stresses that create fracture. A detailed review of existing literature revealed that little or no information is available which relates and examines the influence of hydrated minerals on microwave assisted fracture despite the fact that most important ores are associated with phyllosilicates, the vast majority of which are hydrated. A study was carried out on two Kimberlite diamond ores containing various types of hydrated minerals but devoid of any semiconducting minerals which are known to be good microwave heaters. The results confirmed that dehydration of minerals containing interlayer adsorbed water induces significant micro and macro fractures after microwave treatment. The significance of microwave induced fracture on beneficiation was investigated by conducting liberation and flotation tests on two porphyry copper ores. It was demonstrated that microwave pre-treatment improves beneficiation at sizes suitable for flotation and that higher improvements in degree of liberation are attained in coarser particle sizes between 212 and 425 µm. Flotation tests demonstrated a potential for real economic benefits in terms of value proposition. An increase of 8-10% in copper sulphides recovery from coarse sized particles (-400+200 µm) and an overall increase in grade/recovery of between 1-2% was obtained. The results also showed that microwave pre-treatment enhances selective mineral recovery as the grade-recovery of iron sulphides decreased in all but one microwave treated samples. The major drawback to further developments towards industrial scale application was found to be the lack of an effective continuous processing microwave applicator. Any future applicator designs must be able to ensure localised hot spots and confinement of all the microwave energy.
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Dastmalchi, Mansour. "Photonic processing of microwave signals." Thesis, Université Laval, 2012. http://www.theses.ulaval.ca/2012/29555/29555.pdf.
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Yi, Chenbo. "Microwave processing of hydrocarbon contaminated soil." Thesis, University of Nottingham, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.601688.
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Across the UK there are many hundreds of sites that have been contaminated by previous industrial use. The wastes and residues left in the soil present a hazard to the general environment and, therefore, can prohibit the redevelopment of the land. Conventional technologies all have significant disadvantages. High temperature based technologies such as thermal desorption are highly energy intensive. Soil vapour extraction requires the soil to be sufficiently permeable to permit the transfer of vapour. Microwave heating methods have the advantage of volumetric and rapid heating as well in situ steam generation from water within the soil. However, previous research on the microwave processing of soils has mainly focused on bench scale tests on artificial soils using a microwave susceptor to overcome issues with heating efficiency, rather than utilising soils from real industrial sites. There is also a significant lack of fundamental understanding in terms of the microwave heating mechanisms of soils, a lack of energy balances and consideration of scale up towards industrial implementation. The microwave heating mechanisms of soils were elucidated and the removal mechanisms of hydrocarbon contaminants have been discussed. According to the differences in the hydrocarbon contaminants, five soils were classified into two groups: light hydrocarbon contaminated soils and heavy hydrocarbon contaminated soils. All five soils could be heated with microwaves without using susceptor, and were stable at 100°C as the energy dissipated was used to overcome the latent heat of vaporisation of water. The major heating mechanism was polarisation due to the inherent water within the soils, and the major remediation mechanisms were found to be steam stripping or distillation. Above 100°C bound or interlayer I I water may be present in some soils, which contributed to low but non-zero values of dielectric loss factor. The maximum bulk temperatures obtained with light hydrocarbon contaminated soils were in excess of 100°C, and is attributed to the equilibrium between microwave energy absorbed and heat loss. In this case the remediation mechanism could be governed by thermal desorption. Heavy hydrocarbon contaminated soils behave very differently during microwave processing, with much higher temperatures obtained than with light hydrocarbon contaminated soils. The major heating mechanism in this case was conduction due to the carbonisation of heavy hydrocarbons within the soil, and remediation resulted from desorption, decomposition and carbonisation. The potential for continuous microwave treatment was ascertained through a series of pilot scale studies at 150-300 kg/h. More than 75% hydrocarbon removal from light hydrocarbon contaminated soils was achieved using a conveyor system, but this technique was not suitable for heavy hydrocarbon contaminated soils due to the high temperatures that were attained. Preliminary studies were carried out using a batch scale microwave rotary kiln system for processing at higher temperatures. ii
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Hong, Yu. "Microwave-enhanced thermal processing of algae." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/46682/.
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Algae are promising substitutes to the widely-used fossil fuels. The thermochemical conversion of algae has been investigated extensively in the past two decades. In this study, systematic investigation of microwave-enhanced pyrolysis of algae together with catalytic reforming was conducted aiming at developing a new approach for the production of more syngas-enriched gas product from algae and other marine biomass. Firstly, the characterisation of algae was conducted to show the nature of the raw materials followed by the kinetic study of the decomposition of a suite of micro- and macro-algae, i.e., spirulina, chlorella and porphyra. The kinetic study was carried out using model algae, i.e. the use of ovalbumin as protein, oil droplets as lipid and cellulose as polysaccharides or carbohydrate to simulate a real alga. The thermogravimetric characteristics of algal samples were studied based on the analysis of TG and DTG curves. Kissinger-Akahira-Sunose method was used to derive the activation energy and pre-exponential factor. Moreover, the optimal reaction mechanism was determined by using Coats-Redfern method of the decomposition of different samples. The morphology and composition of char after TG analysis were characterised by using SEM/EDS. By comparing the characteristics of chars prepared in N2 and CO2 atmosphere, it was found that CO2 atmosphere favored the pyrolysis of algal protein with lower required activation energy (about 235 kJ mol-1) and shortened the pyrolysis time by 5.9-20.2%. But it was also found that the algal lipid increased the difficulty for the pyrolysis of algae with relatively higher activation energy around 200 kJ mol-1 (>180 kJ mol-1 under N2). However, the activation energy of cellulose decomposition remained almost the same around 310 kJ mol-1 in N2 and CO2. Therefore, CO2 atmosphere is more suitable for the pyrolysis of algae with high protein content and low lipid content. It was also found that protein in algae decomposes first, which is followed by the decomposition of carbohydrates and then lipids. Secondly, in order to obtain a high yield of syngas-enriched gas product from algae, microwave-enhanced pyrolysis of algae (spirulina, chlorella, dunaliella, laminaria and porphyra) and primary model algal compounds, i.e. cellulose and ovalbumin, at 400, 550 and 700°C in N2 atmosphere was conducted. The distribution and composition of gaseous, liquid and solid products were also studied in detail. Amongst the five algae, porphyra is the most promising raw material for high syngas-enriched gas production with more than 85 wt.%, while protein-rich spirulina and chlorella favored bio-oil production which yielded in about 10 wt.%. Meanwhile, with 94 wt.% carbohydrate, dunaliella converted most of its carbohydrates into C1-C3 gases. With a high portion of incombustible components (14.7-23.3 vol.% of CO2), laminaria has relatively lower gaseous production which was less than 80 wt.%. It also found that the optimal pyrolysis temperature was in the range of 400 to 550 °C for most of the samples except for spirulina which was at 700 °C. For the production of bio-oil, microalgae, with high protein content, were favored to be the raw materials (oil yield of 5.2-15.4 wt.%), compared to macroalgae (oil yield of 1.8-5.2 wt.%). Moreover, microalgae- spirulina and chlorella-favoured the formation of more phenols and nitrogenated compounds (10.8-17.8% and 20.9- 28.7% respectively) primarily from protein content, while less PAHs of 11.4-29.9% which mainly derived from algal carbohydrates. Finally, microwave-enhanced reforming of algae under CO2 atmosphere was conducted at 400, 550 and 700°C, together with the comparison of the results including the distribution and composition of gas, bio-oil and char in N2 and CO2 atmospheres. Compared with the product distribution derived under N2, the bio-oil yield from most algae in CO2 increased by 50- 170%, whilst the production of gas slightly decreased by 1-7%. Under CO2 atmosphere, the syngas in spirulina and chlorella gas product dramatically decreased by 60.8-69.7% and 7.1-17.6% respectively, while that from dunaliella increased by 23.4-30.4%. The percentage of syngas for the other samples remained similar. For the bio-oil derived from all the five algae samples, there were nearly no PAHs contained. In addition, the ash of algae was used as catalyst and introduced into the pyrolysis of five algae respectively under N2 atmosphere at 550°C. Compared with the non-catalytic pyrolysis, the weight percent of char from most algae increased by 20-90% using laminaria and porphyra ash, due to the decomposition of compounds in bio-oil. The syngas percentage from microalgae significantly increased by 6-45%, while that from macroalgae slightly decreased by 2-15% with the addition of spirulina, chlorella and porphyra ash. The content of PAHs in the bio-oil of spirulina, chlorella, laminaria and porphyra considerably reduced by 29-94%, while the amount of aromatics from spirulina and chlorella increased to around 1.3-7.1 times. In summary, the microwave-enhanced pyrolysis of algae favored the production of more CO/H2 rich gas at lower pyrolysis temperature under N2 atmosphere, while under CO2 atmosphere the yield of bio-oil increased. With the addition of algal ash as catalysts, the CO+H2 percentage in gas production from microalgae increased significantly. Therefore, it can be concluded that the microwave-enhanced pyrolysis of algae is an effective and efficient process for the conversion of algal biomass into value-added fuels.
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Pereira, Igor S. M. "Microwave processing of oil contaminated drill cuttings." Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/28515/.
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Easily accessible oil reserves are currently decreasing, leading to an increase in more complex offshore deep-sea drilling programs, which require increasingly greater depths to be drilled. Such wells are commonly drilled using oil based muds, which leads to the production of drilled rock fragments, drill cuttings, which are contaminated with the base oil present in the mud. It is a legal requirement to reduce oil content to below 1 wt% in order to dispose of these drill cuttings in the North Sea and microwave processing is suggested as a feasible method of achieving the desired oil removal. However, there are currently gaps in our understanding of the mechanisms behind, and variables affecting, the microwave treatment of oil contaminated drill cuttings. The work described in this thesis seeks to address some of these gaps in knowledge. There were three main objectives for this thesis: (1) quantification, for the first time in the literature, of the main mechanisms driving oil and water removal during microwave processing of oil contaminated drill cuttings, (2) determination of key variables affecting performance during pilot scale continuous processing of oil contaminated drill cuttings and, for the first time, (3) treatment of drill cuttings with microwaves continuously at 896 MHz. Bench scale experiments carried out in a single mode applicator were used to quantify the mechanisms involved in oil and water removal from drill cuttings. It was found that both vaporisation and entrainment mechanisms play a role in oil and water removal. Vaporisation was the main mechanism of water and oil removal, and typically accounted for >80-90% of the water and oil removed. For oil removal, vaporisation of the oil phase accounted for 70-100% of the overall removal. The absolute amount of water entrained and vaporised was found to increase with increasing energy input and power density. However, as a percentage of the overall amount removed, entrainment was found to increase with increasing energy input. This was mainly due to higher heating rates at higher energy inputs, leading to pressurised, high velocity steam, which increased liquid carry-over (entrainment). Both the drill cuttings sample composition and applicator type were found to have an effect on the extent of entrainment/vaporisation. Samples consisting of a higher overall liquid content, tended to have a greater amount of surface liquid content. This led to a greater potential of carry over when steam generated internally left the sample. Increasing the power again led an increase in entrainment in this case. Different applicators were found to impact the electric field strength and power density within the water phase of the sample. Oil removal in multimode applicators progressed mainly through vaporisation (steam distillation) until the water content was sufficiently low to generate steam at a velocity high enough to entrain liquid droplets. When treatment was changed to single mode operation, entrainment occurred at an earlier stage, probably due to higher electric field strengths and power densities. It was also noted that the vaporisation mechanism of oil was more efficient at higher field strengths and powers, which could again be attributed to superheating and higher velocity steam, which enabled better mixing and heat transfer. Experiments were also run to determine the main variables affecting the performance of continuous processing of cuttings. Overall continuous processing showed a substantial improvement in the energy required, 150 kWh/t vs. >250 kWh/t, to reduce the oil content of a drill cuttings sample to 1 wt%. It was found that the initial water and oil content of the sample, as well as the sample particle size distribution, had the greatest effect on the efficiency of continuous processing. The effect of initial water and oil content on residual oil content was investigated methodically for the first time for continuous microwave processing of oil contaminated drill cuttings. An increase in initial oil content was found to have a significant impact on the energy input required to treat the sample to 1 wt% oil content. As the oil content increased, the energy input required increased exponentially, mainly as a result of the change in the physical structure of the sample. An increase in the water content led to an increase in energy input without any additional benefit to oil removal. However, as the water content was increased it was noticed that the theoretical energy input required to heat the entire sample approached the actual value measured for the energy input. This occurs as a result of the increasingly greater bulk dielectric properties of the sample as a result of higher levels of water content, which in turn leads to a higher efficiency in the conversion of microwave energy to heat in the sample. The effect of particle size on oil content distribution and removal was investigated. Oil content was found to be substantially higher in particles of size <1.0 mm, with removal also being significantly higher in this particle size range. However, as the majority of the samples tested, >80%, consisted of particles >1.0 mm, this improved removal is diluted by the performance of the coarser particles. The improved removal in finer particles is likely to be due to larger surface area, reduced path length within the particles and potentially higher electric field strength. Finally, samples processed continuously using a continuous microwave setup at 896 MHz showed improvements over both continuous microwave treatment at 2.45 GHz and bench scale setups. Increasing the f10wrate of the system at 896 MHz was also found to improve oil removal efficiency, which can be explained by the higher power requirements that would be required to maintain the energy inputs observed at the lower flowrate. Increasing the power leads to improved heating rates and thus increased removal rates through entrainment and vaporisation.
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Pau, Chew Fuee. "Microwave generated plasma jet for material processing." Thesis, University of Liverpool, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.399341.
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Tailony, Ra'uf. "Ion exchange glass strengthening using microwave processing." University of Toledo / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1449764292.
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Folz, Diane C. "Variable Frequency Microwave Curing of Polyurethane." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/34567.
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Historically, coatings were processed from natural oils, fats, and resins; the first well-known and widely used being lacquer [Meir-Westhues, 2007]. In the 20th century, synthetic resins were developed to achieve coatings with improved properties. Of these coating compositions, polyurethanes (PURs) were one of the most prevalent. Polyurethanes became possible in 1937 when Otto Bayer developed the diisocyanate polyaddition process [Randall et al, 2002]. Since that time, literally thousands of PUR compositions have been used commercially. The primary application of interest in this study is that of coatings for wood substrates.
It is well-known among materials researchers that there can be a number of differences between microwave and conventional materials treatment techniques [Clark et al, 1996], including enhanced reaction rates, lowered processing temperatures for some products, and selective interactions in composite systems.
The primary goals of this research were to determine (1) whether microwave energy affected the cure rate in a water-based, aliphatic PUR, and (2) if there was an effect of microwave frequency on the cure rate.
The primary tool for determining extent of cure in the PUR samples was Fourier transform infrared spectroscopy (FTIR). Using this characterization method, the changes in intensities of four bonds specific to the PUR composition were followed. It was determined that, in the particular PUR composition studied, microwave energy had an effect on the cure rate when compared with conventional heating, and that there was a frequency effect on the cure rate. Additionally, a deeper understanding of the use of FTIR spectroscopy techniques for studying cure kinetics was developed.Master of Science
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Farrant, Luke. "Gallium nitride processing for high power microwave devices." Thesis, Cardiff University, 2005. http://orca.cf.ac.uk/56118/.
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This thesis contains literature reviews relating to inductively coupled plasmas and their use in etching gallium nitride with chlorine based plasmas. The properties of gallium nitride, how these properties make gallium nitride a suitable material for high power microwave transistors and how such transistors will help improve the systems in which they might be used are also reviewed. In this thesis, a novel, non-destructive method of measurement of the conductivity of a semiconductor through measurement of the increase in the bandwidth of the resonant peak of a microwave dielectric resonator when it is brought near a semiconductor wafer is presented. Using this method the conductivity of a thin gallium nitride film is obtained and found to be within the expected range it was found to be very difficult to measure the conductivity of this gallium nitride wafer using a four-point probe, as the film was too thin. Also presented in this thesis are studies of the etch characteristics of gallium nitride and photoresist in mixed boron trichloride and chlorine plasmas generated in two Oxford Instruments inductively coupled plasma etchers (ICP 180 and 380). The ICP 380 was used to etch the mesa isolation of gallium nitride based heteroj unction field effect transistors that were fabricated at Cardiff University. A method of making the angle of the mesa sidewall acute by melting of the photoresist is presented. An acute mesa-sidewall angle facilitated the easy traverse of the mesa edge by the gate metal. Characterisations of ohmic and Schottky contacts that were fabricated as part of the effort to produce a working gallium nitride based heteroj unction field effect transistor are presented and reasons given for the failure of some of the ohmic contacts. The dc characteristics of the best transistor fabricated during the project are presented.
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Yusoff, Rozita. "Microwave assisted RTM processing of carbon/epoxy composites." Thesis, University of Manchester, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.488232.
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El-Sawi, Yehia Ali Reda Ali. "Parallel processing application to nonlinear microwave network design." Thesis, University of Kent, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.257300.
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Abdul-Razzak, M. M. "Picture processing and display methods for microwave thermography." Thesis, University of Leeds, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.354033.
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Vorster, Werner. "The effect of microwave radiation on mineral processing." Thesis, University of Birmingham, 2001. http://etheses.bham.ac.uk//id/eprint/309/.
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Between 50% and 70% of the total energy used in the extraction process may be attributed to comminution. Microwave pre-treatment has been suggested as a means to decrease the energy requirements. A variety of mineral ores have been investigated and the effects of microwave radiation quantified in terms of the mineralogy, changes in the Bond Work Index, flotability and magnetic separation. It has been shown that microwave pre-treatment is most effective for coarse grained ores with consistent mineralogy consisting of good microwave absorbers in a transparent gangue (up to a 90% decrease in Bond work index for Palabora copper ore) whereas fine grained ores consisting predominantly of good absorbers are not affected as well (a reduction of only 25% in work index for Mambula ore). Although the mineralogy of minerals are affected by exposure to microwave radiation, flotability and magnetic separation characteristics have been shown not to be adversely affected, unless the microstructure is completely destroyed after prolonged microwave exposure. Computer simulations have shown that significant changes to comminution circuits are possible as a result of microwave induced work index reductions (three mills reduced to one). Purpose-built microwave units may hold the solution for more efficient mineral extraction in the near future.
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Palací, López Jesús. "Optical processing in the microwave and terahertz regions." Doctoral thesis, Universitat Politècnica de València, 2013. http://hdl.handle.net/10251/18435.
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El objetivo de la tesis es es procesado de señales en las bandas de microondas y terahercios mediante dispositivos ópticos operando en la banda de comunicaciones. El procesado mediante tecnología convencional presenta una serie de limitaciones que la tecnología óptica permite solventar. Por un lado, los dispositivos electrónicos de microondas tienen pérdidas considerables y está limitados en ancho de banda. En este caso la tecnlogía de fibra óptica propociona ventajas en términos de bajas pérdidas y ancho de banda prácticamente ilimitado. Por otro lado, el procesado de señales de terahercios se ha llevado a cabo tradicionalmente mediante elementos en espacio libre con los problemas de tamaño y establilidad que ello implica. Gracias al reciente desarrollo de generadores y detectores de terahercios alimentados por luz a 1.55 um el procesado puede llevarse a cabo utilizando tecnología óptica, lo que proporciona sistemas de procesado más compactos y estables.
La tesis se centra en el desarrollo de arquitecturas basadas en fibra que solventen las limitaciones actuales del procesado de señales cuyas frecuencias se sitúan entre las bandas de radio sy THz. en el área de procesado fotónico de señles de microondas se estudian diversas arquitecturas. Se propone la aplicación del efecto de mezclado de cuatro ondas en cascada como una manera de incrementar el número de coeficientes de filtros de respuesta finita basados en dispersión. También se propone implementaciones de filtros pasobanda no periódicos útiles en aplicaciones de radiofrecuencia basados en la impresión de filtros ópticos en el dominio eléctrico. En un caso se utiliza una red de Bragg en fibra con un desfase sintonizable en su estructura periódica mientras que en el otro se usa un micro anillo resonante fabricado en silicio.
En cuanto al procesado de señales de terahercios de proponen técnicas parea aumentar localmente la densidad espectral de potencia. Una se basa en la distribución no lineal de pulsos ultracortos por fibra óptica mientras que la otra modula el espectro de la fuente óptica en el dominio temporal mediantes despersión y una estructura interferométrica de amplificadores ópticos de semiconductor. Se espera que el aumento de la potencia de terahercios generada, tanto mediante fuentes más eficientes como mediante procesado óptico, permita utlilizar estos sistemas para llevar a cabo espectroscopía no lineal y deteccíon a distancia. Finalmente, también se estudia la generación de retardos ópticos con el objetivo de sustituir las lentas líneas de retardo basadas en espejos y etapas de traslación motorizadas que se utilizan habitualmente. Las soluciones propuestas se basan en saturación de un ampliifcador óptico de semiconductor así como en la modulación banda lateral única con portadora suprimida del espectro de los pulsos. La primera solución proporciona retardos pequeños aunque es escalable y no ensancha los pulsos de femtosegundos, mientras que la segunda consigue retardos considreables a cambio de ensanchar los pulsos debido a la dispersión de tercer orden de la fibra.Palací López, J. (2013). Optical processing in the microwave and terahertz regions [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/18435
Palancia
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Tsubaki, Shuntaro. "Refinery of Food Processing Biomass by Microwave Heating." Kyoto University, 2010. http://hdl.handle.net/2433/120468.
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Kyoto University (京都大学)0048
新制・課程博士
博士(農学)
甲第15425号
農博第1810号
新制||農||979(附属図書館)
学位論文||H22||N4524(農学部図書室)
27903
京都大学大学院農学研究科地域環境科学専攻
(主査)教授 東 順一, 教授 二井 一禎, 教授 縄田 栄治
学位規則第4条第1項該当
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Mallinson, Phillip Martin. "Perovskite Microwave Dielectric Ceramics: Structure, Properties and Processing." Thesis, University of Liverpool, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.490899.
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Perovskite Microwave Dielectric Ceralnics: Structure, Properties and Processing PhD thesis, Phillip M. Mallinson, University of Liverpool This thesis describes the synthesis and characterisation of several new hexagonal perovskite materials and the investigation into the processing of a commercial microwave dielectric. Chapter 1 is in two parts, the first gives an introduction to the perovskite and hexagonal perovskite structural types, and reviews the structure and properties of reported hexagonal perovskites with the AnBn-\03n general formula. The second part reviews the literature on the microwave dielectric material Ba3ZnTa209 (BZT). In Chapter 2 the details of the synthetic and analytical techniques employed are described. Chapter 3 describes the synthesis and characterisation of a number of new hexagonal perovskite materials. The eight layer compounds BagCoNb60 24 and BagCoTa6024 were found to crystallise with different structures in the space groups P 3ml and P63c11l respectively. A detailed structural description and comparison of the structures of the materials is given along with the dielectric and magnetic properties. The structure and dielectric properties of the six layer material Ba6Ca1l3Nb\4/30\g are also presented. Chapter 4 describes the synthesis and characterisation of two isostructural ten layer hexagonal perovskites with the formulas BalOMgo.25Ta7.903o and BaIOCoO.25Ta7.903o. Refinement of combined synchrotron X-ray and neutron powder diffraction data is used to determine the structures of the materials. The dielectric properties of the materials are reported and the links between dielectric loss and ordering and microstructure discussed. In Chapter 5 the results of an in-situ X-ray powder diffraction study of the ordering and domain growth ofBZT at temperatures between 1200 and 1500 °C is presented. The degree of ordering is quantified using two different methods and a rate of ordering calculated at each of the temperatures studied, from the rates of ordering the activation energy for cation transport is calculated. The ordered domain size is also quantified from the diffraction data and the dynamics compared to domain growth in other systems. Supplied by The British Library - 'The world's knowledge'
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Yan, Jie-Feng. "Microwave-induced co-processing of coal and biomass." Thesis, University of Nottingham, 2015. http://eprints.nottingham.ac.uk/30404/.
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Pyrolysis is an attractive alternative for the conversion of solid fuels to valuable chemicals and bio-fuels. In order to obtain more H2 and syngas from pyrolysis of coal and biomass, microwave has been adopted to enhance the co-pyrolysis of coal and biomass, which has been investigated systematically in this study. Firstly, conventional pyrolysis of coal and biomass was carried out using a vertical tube furnace. Characterizations of pyrolytic gas, liquid and solid products were conducted to study the different properties of products from the pyrolysis of coal and biomass. More gas products were produced at higher temperatures and biomass samples produced more H2 and syngas than coals. Bio-oils produced from conventional pyrolysis of biomass samples have relatively simpler compositions compared with those produced from conventional pyrolysis of coals. Char samples produced from conventional pyrolysis of coal and biomass samples show different morphologies due to the different nature of original coal and biomass. Secondly, microwave-induced pyrolysis of coal and biomass was carried out and compared with the results of conventional pyrolysis. Microwave-induced pyrolysis was found to produce pyrolytic gas products with higher contents of H2 and syngas than conventional pyrolysis. The bio-oils produced from microwave-induced pyrolysis were not as complicated as those from conventional pyrolysis. The reason for this is believed to be that both microwave irradiation and the longer residence time favour more complete decomposition of large hydrocarbon molecules in coal and biomass, which subsequently results in less complicated composition compared with bio-oil produced via conventional pyrolysis. Char samples from microwave-induced pyrolysis undergo more complete pyrolysis than char samples from conventional pyrolysis, and results in less volatiles remaining. Because of the thermal annealing process by microwave at the later stage of pyrolysis, char samples produced by microwave-induced pyrolysis have higher peak temperatures and burnout temperatures than those produced by conventional pyrolysis. In char samples prepared via microwave-induced pyrolysis of coal and biomass, special structures are found, such as nano-scale fibers in char samples from gumwood and pine, spheres in char samples from coals as well as coal and biomass blends. Based on the analysis of energy balance, it is evident that microwave-induced pyrolysis is a cost-effective and energy saving method for solid fuel conversion.
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Tanikella, Ravindra V. "Variable frequency microwave processing of materials for microelectronic applications." Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/10271.
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Chaudhry, Mohammed Sabih. "Microwave I.F signal processing strategies for coherent optical communications." Thesis, Bangor University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357247.
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Siguemoto, Érica Sayuri. "Continuous-flow microwave thermal processing of cloudy apple juice." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/3/3137/tde-25092018-075112/.
Full textAbstract:
Continuous-flow microwave heating is an alternative processing technology that can bring advantages to the pasteurization of food products, particularly, fruit-based beverages. This work aimed to study the continuous-flow microwave thermal processing of cloudy apple juice. Dielectric and electric properties of cloudy apple juices, obtained from different varieties and from an industrial plant, were determined from 500 to 3000 MHz and temperatures between 10 °C and 90 °C. At these frequencies, apple variety showed little influence and the permittivity decreased almost linearly with temperature. Inactivation kinetics of pathogen microorganisms (Escherichia coli O157:H7 and Listeria monocytogenes) and enzymes (polyphenol oxidase, peroxidase and pectin methylesterase) were studied and modeled to evaluate non-thermal effects of microwave radiation. For both processing technologies, it was possible to achieve a 5-log10 reduction of E. coli and L. monocytogenes, as recommended by the FDA. Microwave processing in comparison to conventional heating enhanced the microorganism inactivation in 18 out of 28 experiments. Predicted enzyme inactivation curves for pasteurization at 70 °C and 80 °C of the cloudy apple juice showed that pectin methylesterase has the highest thermal resistance and that there was no significant evidence of non-thermal microwave effects. A pilot scale unit used for pasteurizing fruit juices was evaluated and the process was modeled and simulated to determine the average time-temperature history. Mean residence times and dispersion parameters were obtained from internal volume measurements and residence time distribution experiments. Thermal processing experiments using water provided heat transfer coefficients as functions of Reynolds number and also microwave power absorption. Mathematical modeling was used to determine the temperature distribution along the product path and results were validated. Results showed that focused microwave heating provided the necessary temperature increase in a very short time, with a lethality contribution of only 0.7% as compared to 59-68% when using the conventional heat exchanger, which configures over-processing and can decrease product quality. Fresh cloudy apple juice was subjected to continuous flow microwave assisted pasteurization in a pilot scale unit at three processing temperatures (70 °C, 80 °C and 90 °C), two flow rate levels and two heating systems (conventional and focused microwave). Good results were obtained for polyphenol oxidase and peroxidase inactivation, but not for pectin methylesterase, which showed to be the most resistant enzyme. A comparative evaluation on quality changes was performed in cloudy apple juice samples pasteurized in the continuous-flow unit. Profile of volatiles of the microwave pasteurized apple juice was more similar to the nonpasteurized juice, in comparison with the conventionally pasteurized juice. However, total organic acids and total soluble sugar contents were not significantly different between both processing technologies. There was an increase of phenolic contents during processing of cloudy apple juice, possibly due to the extraction of phenolic compounds present in suspension of material. Furthermore, it was observed the same trend of antioxidant capacity by DPPH and ORAC methods. In conclusion, this PhD work presents the potential of the microwave-assisted pasteurization in cloudy apple juice regarding enzymatic, microbiological and quality aspects.Aquecimento de micro-ondas de fluxo contínuo é uma tecnologia de processamento alternativa que pode proporcionar vantagens para a pasteurização de produtos alimentícios, particularmente, bebidas à base de frutas. Este trabalho teve como objetivo estudar o processamento térmico de micro-ondas de fluxo contínuo em suco de maçã não clarificado. As propriedades dielétricas e elétricas dos sucos de maçã não clarificados, obtidos de diferentes variedades de maçãs e de uma planta industrial, foram determinadas entre 500 e 3000 MHz e temperaturas entre 10 °C e 90 ° C. Nessas frequências, a variedade da maçã apresentou pouca influência e a permissividade elétrica diminuiu quase linearmente com a temperatura. Cinéticas de inativação de microrganismos patogênicos (Escherichia coli O157: H7 e Listeria monocytogenes) e enzimas (polifenol oxidase, peroxidase e pectina metilesterase) foram estudadas e modeladas a fim de avaliar os efeitos não térmicos da radiação de micro-ondas. Para ambas tecnologias de processamento foi possível obter uma redução de 5-log10 de E. coli e L. monocytogenes, como recomendado pelo FDA. O processamento de micro-ondas em comparação com o aquecimento convencional aumentou a inativação dos micro-organismos em 18 dos 28 experimentos. As curvas de inativação enzimática preditas para pasteurização a 70 ° C e 80 ° C do suco de maçã mostraram que a pectina metilesterase possui a maior resistência térmica e que não houve evidência de efeitos não térmicos. Uma unidade de escala piloto usada para pasteurizar sucos de frutas foi avaliada e o processo foi modelado e simulado para determinar o histórico de tempo-temperatura. Os tempos médios de residência e os parâmetros de dispersão foram obtidos a partir de experimentos de distribuição do tempo de residência e volumes. Experimentos do processamento térmico utilizando água, como produto alimentício, forneceram coeficientes de transferência de calor em função do número de Reynolds e absorção de energia de micro-ondas. A modelagem matemática foi utilizada para determinar a distribuição de temperatura do percurso do produto, e posteriormente, foram validados. Os resultados mostraram que o aquecimento por microondas focalizadas proporcionou o aumento necessário da temperatura em um tempo curto, com uma contribuição de letalidade de apenas 0,7% em comparação a 59-68%, quando usado somente o trocador de calor convencional, o que configura sobre processamento, podendo diminuir a qualidade do produto. O suco de maçã fresco não clarificado foi submetido à pasteurização por micro-ondas em fluxo contínuo em uma unidade de escala piloto em três temperaturas de processamento (70 ° C, 80 ° C e 90 ° C), dois níveis de vazão e dois sistemas de aquecimento (convencional e micro-ondas). Resultados positivos foram obtidos para polifenol oxidase e peroxidase, mas não para a pectina metilesterase demonstrando ser a enzima mais resistente. Uma avaliação comparativa das mudanças de qualidade foi realizada em amostras de suco de maçã pasteurizado na unidade de fluxo contínuo. O perfil de voláteis do suco de maçã pasteurizado por microondas foi mais semelhante ao suco não pasteurizado em comparação ao suco pasteurizado convencionalmente. Entretanto, ácidos orgânicos totais e açúcares solúveis totais não foram significativamente diferentes no processamento por estas duas tecnologias. Houve um aumento de compostos fenólicos durante o processamento do suco de maçã não clarificado, possivelmente devido a extração de compostos fenólicos presentes no material em suspensão. Além disso, foi observado a mesma tendência na atividade antioxidante determinada pelos métodos de DPPH e ORAC. Em conclusão, este trabalho de doutorado apresenta o potencial da pasteurização por micro-ondas em suco de maçã não clarificado quanto aos aspectos enzimáticos, microbiológicos e de qualidade.
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Iti, Ozunimi Lilian. "Ionic liquids for microwave-assisted processing of biomass waste." Thesis, Imperial College London, 2010. http://hdl.handle.net/10044/1/7075.
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The use of biomass as fuels, feedstock and materials has gained recognition in recent years. Developing sustainable solvents for biomass processing and recovery remains a challenge of the chemical industry. Room temperature ionic liquids have been designed for application in biomass waste recovery. Their polarities have been determined and it was found that protic alkylammonium ionic liquids have high α and β values. A comparison of the Kamlet Taft properties with that of alkylimidazolium ionic liquids shows that polarities can be expanded by changing the functionalities on the anion and cation. The stabilities of ammonium ionic liquids as shown by thermogravimetric analysis are lower than their imidazolium counterparts. All ionic liquids have been found to heat up appreciably under microwave irradiation. Their effectiveness as solvents for carbohydrates and biomass has been examined. It was found that the solubility of carbohydrates by ionic liquids is dependent on the polarity of the ionic liquids and other factors such as temperature and the presence of water. High α HBD ability and high β HBA ability were found to promote solubility of glucose and sucrose in ionic liquids, while high β and low α were found to promote cellulose solubility. A novel extraction protocol for the delignification of lignocellulosic biomass wastes under microwave irradiation has been designed that can reduce the amount of waste effluents produced from the process.
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Lanigan, Brigid. "Microwave processing of lignocellulosic biomass for production of fuels." Thesis, University of York, 2010. http://etheses.whiterose.ac.uk/1237/.
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Current environmental issues and resource demands are driving the global development of renewable energy. The work described in this thesis applies green and energy efficient microwave technology to transform lignocellulosic biomass into solid and liquid fuels suitable for application in coal burning power plants or upgrading into transportation fuels. Current thermochemical biofuel production (e.g. pyrolysis and gasification) suffer many drawbacks such as high energy consumption and poor flexibility. Herein, it is shown that by applying novel low temperature microwave processing, fuels can be produced at temperatures up to 190 oC lower than required in equivalent conventional thermal treatments. Studies on the microwave activation of the major components of biomass give insight into the mode of action. 180 oC was identified as the key temperature in the degradation of cellulose. Softening of the amorphous region of cellulose at this temperature enables microwave induced rearrangement increasing the efficiency of microwave interaction resulting in acid catalysed decomposition. It was shown possible to produce high calorific value chars at 150 oC lower than previously expected. A reduction of 100 oC was observed in the degradation temperature of hemicellulose. The technology is versatile, effective on a variety of biomass species, and has a favourable energy balance. In studies on whole biomass, the processing conditions and energy usage were found to be favourable when compared with conventional methods. Chars were produced at low temperatures with increased calorific values and material properties in parallel with high quality bio-oils. Pilot scale trials were also carried out proving the technology to be scalable and open to industrial application. This thesis shows for the first time the possibility to produce biofuels via microwave processing, while operating at temperatures below 300 oC. The impact of these findings is being further investigated at the dedicated microwave facility at the University of York.
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Zhang, Jiejun. "Photonic Dispersive Delay Line for Broadband Microwave Signal Processing." Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/35866.
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The development of communications technologies has led to an ever-increasing requirement for a wider bandwidth of microwave signal processing systems. To overcome the inherent electronic speed limitations, photonic techniques have been developed for the processing of ultra-broadband microwave signals. A dispersive delay line (DDL) is able to introduce different time delays to different spectral components, which are used to implement signal processing functions, such as time reversal, time delay, dispersion compensation, Fourier transformation and pulse compression. An electrical DDL is usually implemented based on a surface acoustic wave (SAW) device or a synthesized C-sections microwave transmission line, with a bandwidth limited to a few GHz. However, an optical DDL can have a much wider bandwidth up to several THz. Hence, an optical DDL can be used for the processing of an ultra-broadband microwave signal. In this thesis, we will focus on using a DDL based on a linearly chirped fiber Bragg grating (LCFBG) for the processing of broadband microwave signals. Several signal processing functions are investigated in this thesis. 1) A broadband and precise microwave time reversal system using an LCFBG-based DDL is investigated. By working in conjunction with a polarization beam splitter, a wideband microwave waveform modulated on an optical pulse can be temporally reversed after the optical pulse is reflected by the LCFBG for three times thanks to the opposite dispersion coefficient of the LCFBG when the optical pulse is reflected from the opposite ends. A theoretical bandwidth as large as 273 GHz can be achieved for the time reversal. 2) Based on the microwave time reversal using an LCFBG-based DDL, a microwave photonic matched filter is implemented for simultaneously generating and compressing an arbitrary microwave waveform. A temporal convolution system for the calculation of real time convolution of two wideband microwave signals is demonstrated for the first time. 3) The dispersion of an LCFBG is determined by its physical length. To have a large dispersion coefficient while maintaining a short physical length, we can use an optical recirculating loop incorporating an LCFBG. By allowing a microwave waveform to travel in the recirculating loop multiple times, the microwave waveform will be dispersed by the LCFBG multiple times, and the equivalent dispersion will be multiple times as large as that of a single LCFBG. Based on this concept, a time-stretch microwave sampling system with a record stretching factor of 32 is developed. Thanks to the ultra-large dispersion, the system can be used for single-shot sampling of a signal with a bandwidth up to a THz. The study in using the recirculating loop for the stretching of a microwave waveform with a large stretching factor is also performed. 4) Based on the dispersive loop with an extremely large dispersion, a photonic microwave arbitrary waveform generation system is demonstrated with an increased the time-bandwidth product (TBWP). The dispersive loop is also used to achieve tunable time delays by controlling the number of round trips for the implementation of a photonic true time delay beamforming system.
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Ehteshami, Nasrin. "Silicon Photonic Devices for Microwave Signal Generation and Processing." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34111.
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Silicon photonics as a one of the most promising photonic integration technologies has attracted many attentions in recent years. The major feature of this technology is its compatibility with complementary metal-oxide semiconductor (CMOS) processes which makes it possible to integrate optical and electronic devices in a same chip and reduce the cost significantly. Another reason of using silicon photonics is the high index contrast between the silicon core and silicon dioxide cladding which ensures the high density integration of photonic devices on a single chip. Monolithic integration with electronic and optical circuits makes silicon photonics technology suitable for numerous applications. One example is microwave photonics (MWP). MWP is an area that studies the interaction between microwave and optical signal for the generation, processing, control and distribution of microwave signals by means of photonics. Silicon photonics offers a reduction in footprint, losses, packaging cost and power dissipation in MWP systems.
This research in this thesis is focused on the design and fabrication of the silicon photonic devices for MWP signal processing and generation. Four MWP systems based on silicon photonic devices are proposed and experimentally demonstrated.
1) A single pass-band frequency-tunable MWP filter based on phase-modulation to intensity-modulation conversion in an optically pumped silicon-on-insulator (SOI) microring resonator (MRR) is designed and experimentally demonstrated. In the proposed filter, a phase-modulated optical signal is filtered by the SOI MRR, to have one first-order sideband suppressed by the MRR notch. The phase-modulated optical signal is converted to an intensity-modulated single-sideband (SSB) signal and detected at a photodetector (PD). The entire operation is equivalent to a single pass-band filter. The frequency tunability is achieved by tuning the resonance wavelength of the MRR, which is realized by optically pumping the MRR. A single pass-band MWP filter with a tunable center frequency from 16 to 23 GHz is experimentally demonstrated.
2) A broadband optically tunable MWP phase shifter with a tunable phase shift using three cascaded SOI MRRs that are optically pumped is designed and experimentally demonstrated. A microwave signal to be phase shifted is applied to an optical single-sideband (OSSB) modulator to generate an optical carrier and an optical sideband. The phase shift is introduced to the optical carrier by placing the optical carrier within the bandwidth of one resonance of the three cascaded MRRs. The experimental results show that by optically pumping the cascaded MRRs, a broadband MWP phase shifter with a bandwidth of 7 GHz with a tunable phase shift covering the entire 360o phase shift range is achieved.
3) A multi tap MWP filter with positive and negative coefficients using a silicon ring resonator modulator (RRM) is proposed and experimentally demonstrated. The RRM is designed and fabricated to operate based on the carrier depletion effect. The positive and negative coefficients are obtained by using opposite slopes of the modulation transmission response of the RRM. Two filter responses with two and three taps are experimentally demonstrated, showing the proof-of-principle for frequencies up to 18 GHz.
4) An approach to generate microwave signal based on enhanced four wave mixing (FWM) in an active silicon waveguide (SiWG) is studied. This SiWG is designed and fabricated, and the use of the active SiWG for MWP frequency multiplication to generate a frequency-sextupled millimeter-wave signal is experimentally demonstrated. Thanks to a reverse-biased p-n junction across the SiWG, the conversion efficiency of the FWM is improved, which leads to the improvement of the microwave frequency multiplication efficiency.
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Mahmoud, Morsi Mohamed. "Crystallization of Lithium Disilicate Glass Using Variable Frequency Microwave Processing." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/27478.
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The lithium disilicate (LS2) glass system provides the basis for a large number of useful glass-ceramic products. Microwave processing of materials such as glass-ceramics offers unique benefits over conventional processing techniques. Variable frequency microwave (VFM) processing is an advanced processing technique developed to overcome the hot spot and the arcing problems in microwave processing. In general, two main questions are addressed in this dissertation:
1- How does microwave energy couple with a ceramic material to create heat? and,
2- Is there a â microwave effectâ and if so what are the possible explanations for the existence of that effect?
The results of the present study show that VFM processing was successfully used to crystallize LS2 glass at a frequency other than 2.45 GHz and without the aid of other forms of energy (hybrid heating). Crystallization of LS2 glass using VFM heating occurred in a significantly shorter time and at a lower temperature as compared to conventional heating.
Furthermore, the crystallization mechanism of LS2 glass in VFM heating was not exactly the same as in conventional heating. Although LS2 crystal phase (Orthorhombic Ccc2) was developed in the VFM crystallized samples as well as in the conventionally crystallized samples as x-ray diffraction (XRD) confirmed, the structural units of SiO4 tetrahedra (Q species) in the VFM crystallized samples were slightly different than the ones in conventionally crystallized samples as the Raman spectroscopy revealed.
Moreover, the observed reduction in the crystallization time and apparent temperature in addition to the different crystallization mechanism observed in the VFM process both provided experimental evidence to support the presence of the microwave effect in the LS2 crystallization process.
Also, the molecular orbital model was successfully used to predict the microwave absorption in LS2 glass and glass-ceramic. This model was consistent with experiments and indicated that microwave-material interactions were highly dependent on the structure of the material.
Finally, a correlation between the Fourier transform infrared reflectance spectroscopy (FTIRRS) peak intensities and the volume fraction of crystals in partially crystallized LS2 glass samples was established.Ph. D.
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Soraghan, John J. "Synthetic Aperture Radar signal processing on the Distributed Array Processor." Thesis, University of Southampton, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.254743.
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Kim, Jang-Yong. "Processing and On-Wafer Test of Ferroelectric Film Microwave Varactors." Doctoral thesis, Stockholm : Information and Communication Technology (ICT), Kungl. Tekniska högskolan (KTH), 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4226.
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Blais, Sébastien R. "Superstructured Fiber Bragg Gratings and Applications in Microwave Signal Processing." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/30358.
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Since their discovery in 1978 by Hill et al. and the development of the transverse holographic technique for their fabrication by Meltz et al. in 1989, fiber Bragg gratings (FBG) have become an important device for applications in optical communications, optical signal processing and fiber-optical sensors.
A superstructured fiber Bragg grating (SFBG), also called a sampled fiber Bragg grating, is a special FBG that consists of a several small FBGs placed in close proximity to one another. SFBGs have attracted much attention in recent years with the discovery of techniques allowing the creation of equivalent chirp or equivalent phase shifts. The biggest advantage of an SFBG with equivalent chirp or equivalent phase shifts is the possibility to design and fabricate gratings with greatly varying phase and amplitude responses by adjusting the spatial profile of the superstructure. The realization of SFBGs with equivalent chirp or equivalent phase shifts requires only sub-millimeter precision. This is a relief from the sub-micron precision required by traditional approaches.
In this thesis, the mathematical modeling of FBGs and SFBGs is reviewed. The use of SFBGs for various applications in photonic microwave signal processing is considered.
Four main topics are presented in this thesis. The first topic is the use of SFBG as a photonic true-time delay (TTD) beamformer for phased array antennas (PAAs).
The second topic addresses non-linearities in the group delay response of an SFBG with equivalent chirp in its sampling period. An SFBG with an equivalent chirp using only a linear chirp coefficient may yield a group delay response that deviates from the linear response required by a TTD beamformer. In the thesis, a technique to improve the linearity of the group delay response is proposed and an adaptive algorithm to find the optimal linear and non-linear chirp coefficients to produce the best linear group delay response is described. Since no closed-form solution exists to represent the amplitude and phase responses of an SFBG, we rely on a Fourier transform analogy under a weak grating approximation as a starting point in the design of an SFBG. Simulations are then used to refine the response of the SFBG. The algorithm proposed provides an optimal set of chirp coefficients that minimizes the error in the group delay response. Four gratings are fabricated using the optimized chirp coefficients and their application in a TTD PAA system is discussed.
The third topic discusses the use of an SFBG with equivalent phase shifts in its sampling period as a means to realize optical single sideband (SSB) modulation. SSB modulation eliminates the power penalty caused by chromatic dispersion experienced by an optical signal traveling through a long length of optical fiber. By introducing two π phase shifts through equivalent sampling to the SFBG, two ultra-narrow transmission bands are created in the grating stop band of the +/- 1st spectral orders. In the proposed system, a double-sideband plus carrier (DSB+C) modulated optical signal is sent to the input of an optical SSB filter based on the equivalent phase-shift SFBG in order to select the optical carrier and a single sideband, effectively blocking one sideband from propagating.
Finally, the fourth topic focuses on the implementation of a photonic microwave bandpass filter based on an SFBG with equivalent chirp. Photonic microwave filters are used to process microwave signals in the optical domain. By using a technique called phase-modulation to intensity-modulation (PM-IM) conversion, a two-tap delay line filter is created with one negative tap. A single SFBG with a chirp in its sampling period is used as a means to achieve the PM-IM conversion for the two taps. Two phase modulated optical carriers are used to generate the two taps, each entering a different port of the SFBG and thus experiencing an opposite dispersion value. The two optical signals are then recombined before being sent to a photodetector (PD) where the filtered microwave signal is recovered.
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Kotecha, Rutvij. "Atmospheric Pressure Microwave Plasma for Materials Processing and Environmental Applications." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1342544640.
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Sengupta, Arindam. "Multidimensional Signal Processing Using Mixed-Microwave-Digital Circuits and Systems." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1407977367.
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Venkatachalam, Vinothini. "Microwave assisted processing of Nanocrystalline Barium Titanate based capacitor devices." Thesis, Loughborough University, 2011. https://dspace.lboro.ac.uk/2134/8448.
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Interest towards fabrication of nanostructured electro ceramic devices has witnessed exponential growth in recent years, owing to the requirements of miniaturization, multifunctionality and improved reliability. The major hurdle in realising the full potential of nano ceramics is preventing the unwanted grain growth whilst achieving high densification during conventional high temperature processing. In this project, a detailed study was performed on the fabrication of nanostructured barium titanate based X7R multilayer ceramic capacitors (MLCCs) using microwave assisted heating. The main processing stages involved in MLCC manufacture were; (i) nano BT powder synthesis, (ii) making nano BT ink formulations suitable for screen printing, (iii) sintering of components using conventional, microwave, hybrid heating methods and (iv) performance evaluation of the end products.
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St-Denis, Eric. "Performance optimization of a multi-slotted waveguide for microwave processing applications." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0002/MQ44288.pdf.
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Helal, Yaser H. "Submillimeter Spectroscopic Study of Semiconductor Processing Plasmas." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1483396745873412.
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Matkan, Ali Akbar. "Passive microwave monitoring of snow cover and rainfall over Iran, using DMSP F-11 special sensor microwave/imager data." Thesis, University of Bristol, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.300561.
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Ren, Guixing. "Processing of Panax ginseng and Panax quinquefolium by microwave and hot-air techniques /." Hong Kong : University of Hong Kong, 1999. http://sunzi.lib.hku.hk/hkuto/record.jsp?B20735261.
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Dahhan, A. K. "Real-time microwave holography using glow discharge detectors." Thesis, Cardiff University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356739.
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任貴興 and Guixing Ren. "Processing of Panax ginseng and Panax quinquefolium by microwave and hot-air techniques." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1999. http://hub.hku.hk/bib/B31239213.
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Sevimli, Melike Kadriye. "Optimization Of Processing Conditions During Halogen Lamp-microwave Baking Of Cakes." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/2/12605326/index.pdf.
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The main objective of this study was to optimize processing conditions
during halogen lamp-microwave combination baking of cake by using Response
Surface Methodology. It was also aimed to compare quality of products baked in
microwave-halogen lamp combination oven, halogen lamp oven, microwave oven
and conventional oven.
In the first part of the study, as independent variables, baking time for
conventional ovenmicrowave power and baking time for microwave oven
halogen lamp power and baking time for halogen lamp oven and microwave power, halogen lamp power and baking time for halogen lamp-microwave combination oven were used. Weight loss, specific volume, firmness and color of the cakes were measured during the study. Cakes baked in conventional oven at 175°
C for 24 minutes were determined as the control cakes. Weight loss of cakes increased with increasing independent variables for all oven types. Specific volume and firmness of cakes increased with increasing microwave power, but decreased with upper halogen lamp power. Color formation was achieved in the combination baking but not as much as in the conventional baking. Response Surface Methodology was used to optimize the baking conditions in the second part of the study. Upper and lower halogen lamp powers, microwave power and baking time were used as independent variables. Optimum processing conditions were found as 60% for upper halogen lamp power, 70% for lower halogen lamp power, 30% for microwave power and 5 minutes for baking time. Cakes baked at optimum baking conditions had comparable quality with conventionally baked ones, except color. In short, by the usage of halogen lamp-microwave combination oven it was possible to obtain high quality cakes by reducing of conventional baking time about 79%.
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Nagai, Mikio, Masaru Hori, and Toshio Goto. "Properties of atmospheric pressure plasmas with microwave excitations for plasma processing." American Institute of Physics, 2005. http://hdl.handle.net/2237/7072.
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Hedrick, Jeffrey C. "High performance polymeric networks and thermoplastic blends : microwave versus thermal processing /." Diss., This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-07122007-103925/.
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Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1991.Vita. Abstract. No film copy made for this title. Includes bibliographical references (leaves 243-254). Also available via the Internet.
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D'Auria, Mario. "Low cost fabrication processing for microwave and millimetre-wave passive components." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/44184.
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Microwave and millimetre-wave technology has enabled many commercial applications to play a key role in the development of wireless communication. When dissipative attenuation is a critical factor, metal-pipe waveguides are essential in the development of microwave and millimetre-wave systems. However, their cost and weight may represent a limitation for their application. In the first part of this work two 3D printing technologies and electroless plating were employed to fabricate metal pipe rectangular waveguides in X and W-band. The performance for the fabricated waveguides was comparable to the one of commercially available equivalents, showing good impedance matching and low attenuation losses. Using these technologies, a high-performance inductive iris filter in W-band and a dielectric flap phase shifter in X-band were fabricated. Eventually the design and fabrication of a phased antenna array is reported. For microwave and millimetre-wave applications, system-on-substrate technology can be considered a very valuable alternative, where bulky coax and waveguide interconnects are replaced by low-loss transmission lines embedded into a multilayer substrate, which can include a wide range of components and subsystems. In the second part of this work the integration of RF MEMS with LTCC fabrication process is investigated. Three approaches to the manufacture of suspended structures were considered, based on laser micromachining, laser bending of aluminium foil and hybrid thick/thin film technology. Although the fabrication process posed many challenges, resulting in very poor yield, two of the solution investigated showed potential for the fabrication of low-cost RF MEMS fully integrated in LTCC technology. With the experience gained with laser machining, the rapid prototyping of high aspect ratio beams for silicon MEMS was also investigated. In the third part of this work, a statistical study based on the Taguchi design of experiment and analysis of variance was undertaken. The results show a performance comparable with standard cleanroom processing, but at a fraction of the processing costs and greater design flexibility, due to the lack of need for masks.
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Tilford, Timothy James. "Numerical analysis of microwave processing problems using a multidomain solver approach." Thesis, University of Greenwich, 2013. http://gala.gre.ac.uk/11941/.
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This work outlines the process undertaken in the formulation and validation of a numerical model for analysis of practical microwave processing problems. The proposed model adopts a novel multi-domain Eulerian-Lagrangian approach to the problem, defining two discrete numerical domains coupled through a set of data transfer algorithms. One of the numerical domains is defined for analysis of electromagnetic field distribution while the other is used for analysis of the thermophysical aspects of the problem. The thermophysical domain is restricted to the load being processed and is discretised in an Eulerian manner using an unstructured mesh for solution using a finite volume approach. The electromagnetic domain is discretised using a tensor-product rectilinear structured mesh for solution of Maxwell’s equations using a Yee finite difference time domain approach. The thermophysical load is represented within the electromagnetic domain through a mapped Lagrangian complex permittivity distribution rather than being defined explicitly. The two domains are coupled through mapping routines capable of defining the complex permittivity distribution within the electromagnetic domain and transferring the calculated power density distribution into the thermophysical domain. This interdomain coupling allows the meshes in the two domains to be non coincident, enabling the discretisation of the two domains to be completely independent of each other. This approach to analysis of coupled microwave processing problems is novel and provides a number of significant benefits over conventional single-domain methods. The primary benefit of the approach is that the electromagnetic and thermophysical parts of the analysis can be handled by different solvers using differing meshes. This is a very significant advance as the optimal approach to solving one of the parts be be extremely inefficient or indeed unfeasible for the other. The approach allows electromagnetic fields irradiating complex geometries placed inside a rectilinear microwave ovens to be analyses using a tensor product solver. The solution of the electromagnetic field distribution is typically the most computationally expensive part of a coupled solution of microwave heating. The ability to use a Yee finite difference solver rather than a conformal FDTD or finite element approach provides a very significant reduction in computational expense, enabling more complex analyses to be performed. Solution of thermophysical aspects of the problem are most effectively tackled using an unstructured spatial discretisation in cases with complex geometries. The adoption of an unstructured finite volume approach for the thermophysical part of the analysis provides an analysis capability far beyond that of the finite difference approach typically used in analyses with a finite difference electromagnetic solver. Further benefits stem from the inherent capability to alter the discretisation of the electromagnetic domain independently of the thermophysical domain, enabling cases with advection and/or rotation of the load within the oven to be considered with relative ease. Analysis of this type of problem is highly complex when using a single domain approach as the mesh needs to be redefined at regular interval during the solution. The capability to refine the discretisation of the electromagnetic domain also improves efficiency in cases where dielectric properties vary significantly during the process as mesh resolution can be varied as the process progresses. The primary drawback with the adoption of the multidomain approach is that the load is represented in the electromagnetic domain as a mapped Langrian complex permittivity distribution rather than being explicitly defined as part of the domain discretisation. There are therefore issues relating to the smearing of material boundaries which may influence wave scattering across the boundary adversely affecting accuracy of the electric field solution. In order to study the efficiency and accuracy of the approach a series of tests were conducted to assess the performance of each individual component of the analysis framework to ensure that these had been implemented effectively and to determine the magnitude of any apparent errors. The model was subsequently applied to a simple test case to ensure that the components were coupled in an effective manner. This test and validation process showed that individual components to be accurate and fit for purpose with errors due to data transfer between the two computational domains shown to be small. The results obtained from the validation case agreed relatively closely with experimental data demonstrating the implementation and efficacy of the model. The model was subsequently validated against two practical microwave processing problems - thawing of food within a domestic microwave oven and polymer curing using a dual-section microwave system. In the food thawing study, the solution obtained by the numerical model was validated against data obtained during an experimental study. The study was intended to meet the requirements of an industrial partner in research work that eliminated a range of simplifications adopted in alternate studies. The analysis therefore focussed on thawing of a challenging ’real-world’ material, placed in a complex shaped container. The load was placed on the rotating turntable of a domestic microwave oven. Results obtained from the numerical simulations agree moderately well with experimentally derived data. Primary disparities between experimental data and numerical solutions would appear to stem from inaccuracies in modelling the solid-liquid phase change in a complex multi-component material coupled with the very significant variation in dielectric loss over the melting temperature range. The microelectronics study focussed on curing of polymer materials in a microelectronics package using a dual-section microwave oven system. The requirement for this study was to predict the optimal process parameters for operation of the system. Numerical assessment of the development of key variables such as temperatures, degree of cure and stresses during the process was critical to this problem. Experimental measurements of these parameters during microwave processing were not feasible. Numerical comparisons of the microwave system with a conventional convection oven process have additionally been carried out. Key results from the study include optimal temperature profiles, final degree of cure distribution and residual stress magnitudes. Numerical data from the analyses are being integrated into an experimental study as part of ongoing work. An overall assessment of the numerical approach would indicate that it is a viable method of efficiently obtaining solutions to practical microwave processing problems. Further research is required to assess the influence of the smeared dielectric boundary in the finite difference solver on reflection, refraction and focussing effects on the accuracy of the numerical solution.
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Sekak, Fatima. "Microwave radar techniques and dedicated signal processing for Vital Signs measurement." Thesis, Université de Lille (2018-2021), 2021. https://pepite-depot.univ-lille.fr/LIBRE/EDENGSYS/2021/2021LILUN033.pdf.
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Dans le contexte de la sécurisation des systèmes de transport, la surveillance à courte distance de l’activité des personnes, en particulier du conducteur dans un véhicule, constitue un enjeu majeur dans l’amélioration du système d’aide à la conduite. L’application visée dans ce travail concerne principalement le domaine du ferroviaire.Les fréquences respiratoire et cardiaque du conducteur sont des indicateurs clés pour l’évaluation de l’état physiologique. Les méthodes de mesure conventionnelles de ces signes vitaux reposent sur des capteurs opérant en contact direct avec la peau. Par conséquent, le caractère intrusif de ces solutions ne s’avère pas adapté au domaine du transport, en particulier du fait de la gêne induite. Dans le cadre de ces travaux, une solution radar hyperfréquence opérant à faible puissance est proposée pour la mesure en continue des signaux d’activités respiratoire et cardiaque. En particulier, les signaux physiologiques (battements du cœur, mouvement mécanique de la cage thoracique) sont des indicateurs de l’activité humaine qui peuvent être détectés à distance (jusqu’à une dizaine de mètres) au moyen d’ondes électromagnétiques hyperfréquences rayonnées.Bien que la littérature montre un engouement grandissant pour le développement de techniques radars dédiés à la surveillance des personnes, il n’existe pas, à ce jour, de dispositif commercial robuste, sensible et précis. Une analyse fine des paramètres électriques et géométriques de la technique radar est proposée dans ce travail afin d’identifier les sources d’incertitudes, de définir les paramètres optimaux, de valider expérimentalement la solution proposée. Un traitement de signal original, basé sur l’approche cyclostationnaire, est mis en œuvre afin d’extraire les paramètres d’intérêt dans des environnements de mesure de référence ou perturbés. Les solutions matérielles proposées associées à un traitement de signal optimal permettent d’entrevoir des architectures de radar adaptées aux contingences hors laboratoireIn the context of securing transportation systems, short-range monitoring of people's activity, in particular the driver's activity in a vehicle, is a major issue in the improvement of the driver assistance system. The application targeted in this work concerns mainly the railway domain.Respiratory and heart rates of the driver are key indicators for the evaluation of the physiological state. Conventional methods of measuring these vital signs rely on sensors operating in direct contact with the skin. Therefore, the intrusive character of these solutions is not suited for the transportation domain, especially because of the induced discomfort. In this work, a microwave radar solution operating at low power is proposed for the continuous measurement of respiratory and cardiac activity signals. In particular, physiological signals (heartbeat, mechanical movement of the rib cage) are indicators of human activity that can be detected at a distance (up to ten meters) using radiated microwave electromagnetic waves.Although the literature shows a growing interest in the development of radar techniques dedicated to the surveillance of people, there is no robust, sensitive and accurate commercial device available to date. A detailed analysis of the electrical and geometrical parameters of the radar technique is proposed in this work in order to identify the sources of uncertainties, to define the optimal parameters, to validate experimentally the proposed solution. An original signal processing, based on the cyclostationary approach, is implemented in order to extract the parameters of interest in reference or disturbed measurement environments. The proposed hardware solutions associated with an optimal signal processing allow to foresee radar architectures adapted to non-laboratory contingencies
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Ghauri, Farzan Naseer. "Hybrid Photonic Signal Processing." Doctoral diss., University of Central Florida, 2007. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3233.
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This thesis proposes research of novel hybrid photonic signal processing systems in the areas of optical communications, test and measurement, RF signal processing and extreme environment optical sensors. It will be shown that use of innovative hybrid techniques allows design of photonic signal processing systems with superior performance parameters and enhanced capabilities. These applications can be divided into domains of analog-digital hybrid signal processing applications and free-space--fiber-coupled hybrid optical sensors. The analog-digital hybrid signal processing applications include a high-performance analog-digital hybrid MEMS variable optical attenuator that can simultaneously provide high dynamic range as well as high resolution attenuation controls; an analog-digital hybrid MEMS beam profiler that allows high-power watt-level laser beam profiling and also provides both submicron-level high resolution and wide area profiling coverage; and all optical transversal RF filters that operate on the principle of broadband optical spectral control using MEMS and/or Acousto-Optic tunable Filters (AOTF) devices which can provide continuous, digital or hybrid signal time delay and weight selection. The hybrid optical sensors presented in the thesis are extreme environment pressure sensors and dual temperature-pressure sensors. The sensors employ hybrid free-space and fiber-coupled techniques for remotely monitoring a system under simultaneous extremely high temperatures and pressures.Ph.D.
Optics and Photonics
Optics and Photonics
Optics PhD
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Strawser, Richard E. "MEMS Electrostatic Switching Technology for Microwave Systems." University of Cincinnati / OhioLINK, 2000. http://rave.ohiolink.edu/etdc/view?acc_num=ucin974746046.
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Seyhun, Nadide. "Modeling Of Tempering Of Frozen Potato Puree By Microwave, Infrared Assisted Microwave And Ohmic Heating Methods." Phd thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609666/index.pdf.
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The main purpose of this thesis is to develop a model that can predict the temperature profile inside a frozen food sample during microwave tempering and infrared assisted microwave tempering processes. Another goal of the study is to compare the tempering time of frozen foods by using microwave, infrared assisted microwave, and ohmic heating methods. Frozen potato puree was used as the food sample for all studies.
Three different microwave power levels (30%, 40%, and 50%) were used for microwave tempering studies. Three different microwave power levels (30%, 40%, and 50%) and three different infrared power levels (10%, 20%, and 30%) were
combined for infrared assisted microwave tempering. As a control, tempering was done by keeping the sample at 4°C. The increase in microwave power level and infrared power level reduced tempering time in infrared assisted microwave tempering. For the ohmic tempering studies, three different frequencies (10 kHz, 20 kHz, and 30 kHz) and three different salt contents (0.50%, 0.75%, and 1.00%) were used. The increase in frequency of ohmic heating and salt content also decreased tempering times. Microwave tempering and infrared assisted microwave tempering of frozen foods were simulated by using finite difference method. For this purpose, the change in heat capacity and the dielectric properties of frozen potato puree with respect to time were measured. The temperature distribution inside the sample was modeled, and the predicted results were compared with experimental results. The predicted temperatures showed good agreement with the experimental data (r2 >
0.985). It was possible to decrease tempering times by about 75%, 90%, and 95% using ohmic, microwave, and infrared assisted microwave tempering methods, respectively as compared to control.
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Alkhafaji, Nasr Nomas Hussein. "UHF and Microwave Phase-Modulated Scattering Array." PDXScholar, 2019. https://pdxscholar.library.pdx.edu/open_access_etds/4998.
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This dissertation investigates the use an array of active nonlinear elements, with particular emphasis on controlling distortion products generated by nonlinear elements in space rather than using conventional ways such as transmission lines, waveguides, and power dividers and combiners. The nonlinear elements are made of assemblies of antennas and electronic switches, called modulated scatterers (MSs). These so-called MSs elements are utilized in a wide variety of applications such as radio frequency identification (RFID) systems, microwave imaging, Internet-of-Things sensors, etc. However, no research work has been reported in the literature regarding exploiting and controlling several distortion products generated by MSs at the same time according to the best of authors' knowledge. To facilitate controlling distortion products which means suppressing or enhancing distortion products in space, we present a nonlinear array with elements that are MSs instead of conventional antennas. MSs are switched ON-OFF at different times by modulation signals having the same frequency. The time delay of the switching process between array elements represents a relative phase shift difference in the frequency domain. Thus, the presented structure is called the phase-modulated scattering array (PMSA). The PMSA has a similar layout of phased arrays, but it does not have a feeding network and is fed by an external source called the illuminating source. Because our system does not need a feeding network and phase shifters, it is potentially easier to implement with low cost. Two different signals which are the illuminating (incident) and modulation signals interact inside switches to generate a huge number of distortion products due to the nonlinearity of switches and the periodic nature of the presented system. Distortion products then leave the presented PMSA to space again (i.e., scattering distortion products). The PMSA is able to treat distortion products and achieve beamforming functions.
The operation mechanism of the PMSA is explained by developing two different mathematical models. Communication signal processing perspectives are the basis of the first mathematical model developed to show the spatial characteristics of distortion products generated by our presented PMSA. Its root is originated from a mathematical model of the widely-used polyphase multipath technique in RF communication circuits. However, the adopted technique is suitable only for communication circuits with a single output and parameters prescribed in advance. Thus, the model is further developed to circumvent all the problems mentioned above and to be able to detect the spatial characteristics of distortion products at any point in space. Static impacts of the measurement environment, real radiation patterns of actual antennas utilized in prototypes, and phase and gain errors among paths have been taken into account as well. In the model, every single scatterer is represented by a single separate path. Furthermore, the modified model is extended to include single, two, and multi tones modulation signals. Simulation results have been obtained before and after the modification for a different number of paths and modulation signals with different tones. Results show that the modified model can quantify spatial characteristics of distortion products at any point in space where specific distortion products are enhanced, and others are canceled. Because distortion products are independent in their nature (i.e., each single distortion product has different frequency and phase), they have independent radiation patterns (scattered beams). Therefore, the second mathematical model based on phased antenna array perspectives is developed. The relationship between the two models states that a distortion product which is enhanced at a certain point in space has a maximum scattered beam at that point. Also, the second mathematical model being similar to mathematical models of phased arrays considers effects of all distortion products resulting from single, two, and multi tones modulation signals, and it states that each single distortion component has its particular scattered beam.
Next, sub-models for some properties and applications of the presented PMSA such as a diffraction grating-like behavior, nonreciprocity, beamforming, a tool for distortion product analysis of phased arrays and multi-input multi-output (MIMO systems), a reconfigurable-spatial harmonic generator, and a direction finding technique are derived depending on the two main mathematical models. All parts are simulated and results validate all proposed functionalities.
Single antennas, antenna arrays, electronic switches (modulators), and a 4-to-8 phase transformer kit using only resistors have been designed, simulated, fabricated, assembled, and tested.
Eventually, different structures of the presented PMSAs working at 432MHz and 2.3GHz are tested inside the anechoic chamber. Both frequencies are downconverted to the band 2-22kHz. Modulation signals used in the experimental setups are single and two tones. Data are measured using the commercial software SigView running on a laptop and a spectrum analyzer. Both spatial characteristics and scattered beams of distortion products are measured. Comparisons have been made between measured received responses of scattered signals and theoretical results. They are in good agreement although limitations and challenges are encountered with each round of measurement. Measured results confirm practically that as a number of scatterers increases, more distortion products are controlled at the same time. The distortion product rejection ratio DPRR is more than 15dB for all measured distortion products supposed to be canceled. Directions of scattered beams are found at expected locations with errors less than 3%. Furthermore, directions of illuminating signals or distances separating between PMSA elements are varied to change directions of scattered beams when prescribed values of parameters governing the overall performance are being broken. In other words, the beamforming functionality has been validated practically. Different elements of 8*1-PMSA are turned-off at measurements in order to find fault tolerances of the presented system. Measured results show that when two elements are failed simultaneously, responses can be accepted to some extent.