No description available.

Phenol and its compounds are highly toxic even in low concentration, and have become the subject of intense research during the last two decades. Effluents from industries such as oil refining, paper milling, olive oil extraction, wood processing, coal gasification and textiles and resin manufacturing and agro-industrial wastes discharge phenols at levels much higher than the toxic levels set for this compound. Advanced Oxidation Processes (AOPs) such as UV, UV-TiO2, UV-H2O2, O3 and UV-O3 have become popular in recent years as efficient treatment methods for recalcitrant compounds like phenol. The effect of microwave (MW) and combined MW-UV treatment on degradation of phenol was studied in aqueous solution in the presence and absence of TiO2 under controlled temperature conditions. It was found that the efficiency of MW and MW-UV processes for the degradation of phenol was less than 10% after 120 minutes of treatment. However, the efficiencies of MW-TiO2 (hydrothermal) and MW-TiO2 (sol-gel) were slightly more than those of the above processes at 12 to 15% after 120 minutes, which might be due to adsorption of the phenol on the surface of TiO2 particles. It also was observed that MW-UV-TiO2 was superior to any other process studied for the degradation of phenol. At natural pH, the degradation efficiency of MW-UV-TiO2 (HT) on 1500 ppm of phenol in water was 23%, and for MW-UV-TiO2 (SG) it was 20%. Hence, it can be concluded that the catalyst (TiO2) prepared by the hydrothermal (HT) method had better catalytic activity than TiO2 prepared by the sol-gel (SG) method, which might be due to its structural and optical characteristics. Of the two developed reactors which are MW and a combined MW-UV reactor, MW-UV combined with TiO2 could be used for most successful degradation of phenol.

No description available.

No description available.

Microwave heating is a relatively mature field and is theoretically well understood. However, recently there has been debate as to whether microwaves can interact with chemical and biological systems by means other than heating alone. There is some theoretical justification for such interactions but experimental evidence is often unreliable due to poor or non-existent measurement of heating and/or poor control experiments. Therefore improved techniques for probing these systems are required. One of the reasons why microwave-assisted chemistry is poorly understood is that there is little available dielectric property data even for common solvents. A simple method for the measurement of the dielectric spectra of liquids was verified and used to probe a room temperature ionic liquid and a chemical mixture used in a stage of a microwave-heated industrial process. The temperature and frequency dependence of the dielectric properties explained the observed rapid microwave heating of the ionic liquid and the relative failure of the process as a result of changing the irradiation conditions in order to scale it up. Temperature measurement during microwave-assisted chemistry, whilst crucial to the elucidation of non-thermal effects, is problematic. A method of component specific or spatiallyresolved thermometry during microwave heating of solid-phase organic synthesis (SPOS) suspensions has been developed. Measurements of the temperature-dependent lifetime of a fluorophore covalently attached to SPOS resin beads yield temperature values accurate to within around 0.5°C. Selective microwave heating of the resin was not observed, even for a system artificially designed to have significant dielectric inhomogeneity. Techniques for the in situ and in vitro probing of model biological systems offer significant improvements over previous methods used to determine the possibility of microwaves effecting living things by non-thermal means. Thermally induced changes in the structures of a lipid and a globular protein were followed by small angel neutron scattering and circular dichroism respectively during microwave exposure. No evidence for non-thermal effects was obtained.

Two novel microreactor cells for the investigation of catalysts by in-situ infrared spectroscopy under microwave and conventional heating are presented. A transmission infrared microreactor cell is demonstrated which holds a pressed catalyst disc in a controlled atmosphere and allows study of reactions from ambient temperatures to over 473 K. A cell that allows diffuse reflectance spectroscopy under reaction conditions up to 373 K under microwave heating and 423 K under conventional heating is also described. The optical characteristics of these cells are determined by the choice of CaF2 as the window material, allowing transmission from 77000-1110 cm−1. An oscillating microwave power heating regime was used to study the oxidation of carbon monoxide in air over the supported platinum catalysts EUROPT-1 and EUROPT-3, and their support oxides in these cells. The reaction was followed by time-resolved infrared spectroscopy and mass spectrometry. Both displayed a number of features that oscillated with the same frequency as the microwave perturbation. Production of CO2 appeared to vary with temperature in the same manner whether the catalysts were heated conventionally or with microwave radiation. Although no specific microwave effect for this reaction was observed, accurate thermometry within the cells was limited through the constraints imposed by microwave heating. Preliminary infrared emission and liquid phase experiments using the transmission cell are also reported.

No description available.

Novel characteristics of spin-based phenomena are intensively researched in the hope of discovering effects that could be used to develop new types of high-performance spintronic devices. Recent dynamics studies have revealed new principles for spintronic devices to sense microwaves. The capabilities for detecting both microwave electric field and magnetic field could make the spintronic microwave sensor as ubiquitous as semiconductor devices in microwave applications in the future. In this thesis, the feasibility of spintronic sensors in microwave applications has been researched and developed. Thanks to the high conversion efficiency of microwave rectification in the magnetic tunnel junction (MTJ) based spintronic sensor, it can directly measure the coherent spatially scattered microwave field distribution and detect a hidden object by analyzing the reflected microwave amplitude pattern. To enable the “real-time” vector measurement of the microwave field, a sensor based rapid phase detection technique is also developed. Combining the rapid phase detection technique and the microwave holography principle, a two-dimensional microwave holographic imaging system using a spintronic sensor was built. The high sensitivity of the microwave phase measurement allows the coherent imaging of the target to be reconstructed in noisy environments. By adapting the broadband measurement, not only the shape but also the distance of the target can be determined, which implies that three-dimensional imaging is achievable using a spintronic device. Combining the broadband microwave measurement and a wavefront reconstruction algorithm with a spintronic microwave sensor in circular trajectory, the reconstructed images of targets are obtained. The reconstructed images clearly indicate the targets' positions even when the targets were immersed in a liquid to simulate an inhomogeneous tissue environment. Our spintronic techniques provide a promising approach for microwave imaging, with the potential to be used in various areas, such as biomedical applications, security services, and material characterization. / October 2016

Microwave holography is a well established method of using the Fourier relationship between an antenna’s current distribution and its complex beam-pattern to produce surface maps of large parabolic antennas. As the final part of a surface upgrade, a holographic map of the HartRAO 26 m telescope was produced. This showed that the surface has an RMS error of 0.45 mm. The measurement used a small reference dish to correlate against and retrieve amplitude and phase values. Due to system phase instabilities, this dish had to be attached to the measured antenna in order to enable sharing a high frequency local oscillator (LO). The movement was modelled and corrected for. However, a slight distortion remained. It is recommended that, either the LO distribution system is stabilised by using multiple PLLs or amplifiers and low loss cables are used to enable moving the reference antenna to a stationary position.

by Tam Wai Yip. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1994. / Includes bibliographical references (leaves 139-145). / Acknowledgments --- p.iii / Abstract --- p.iv / List of Symbols --- p.xi / List of Figures --- p.xvii / Chapter 1. --- Introduction / Chapter 1.1 --- Brief Review --- p.1 / Chapter 1.2 --- Statement of Problem --- p.5 / Chapter 1.3 --- Organization --- p.6 / Chapter 2. --- Spherical Circular and Annular Microstrip Antenna / Chapter 2.1 --- Introduction --- p.9 / Chapter 2.2 --- Vector Legendre Series Formulation --- p.10 / Chapter 2.3 --- Galerkin's Procedure --- p.17 / Chapter 2.4 --- Input Impedance --- p.20 / Chapter 2.5 --- Far Zone Radiation Pattern --- p.20 / Chapter 2.6 --- Radiation Resistance using Electric Surface Current Model --- p.22 / Chapter 2.7 --- Numerical Examples --- p.24 / Chapter 2.7.1 --- Input Impedance --- p.25 / Chapter 2.7.2 --- Resonance Radiation Resistance --- p.29 / Chapter 2.7.3 --- Far Zone Radiation Pattern --- p.35 / Chapter 2.8 --- Summary --- p.41 / Chapter 3. --- Cylindrical Rectangular Microstrip Antenna with Coplanar Elements / Chapter 3.1 --- Introduction --- p.42 / Chapter 3.2 --- Integral Equation Formulation --- p.44 / Chapter 3.3 --- Input Impedance with Coplanar Parasitic Elements --- p.50 / Chapter 3.4 --- Far Zone Radiation Pattern --- p.51 / Chapter 3.5 --- Mutual Coupling between Antennas --- p.52 / Chapter 3.6 --- Numerical Examples --- p.56 / Chapter 3.6.1 --- Input Impedance with Coplanar Parasitic Elements --- p.56 / Chapter 3.6.2 --- Mutual Coupling between Antennas --- p.76 / Chapter 3.7 --- Summary --- p.85 / Chapter 4. --- Aperture Coupled Rectangular Cylindrical Microstrip Antenna / Chapter 4.1 --- Introduction --- p.86 / Chapter 4.2 --- Integral Equation Formulation using Reciprocity Method --- p.89 / Chapter 4.3 --- Input Impedance of a Stripline Feed Aperture Coupled Microstrip Antenna --- p.99 / Chapter 4.4 --- Input Impedance of a Microstrip Line Feed Aperture Coupled Microstrip Antenna --- p.100 / Chapter 4.5 --- Numerical Examples --- p.101 / Chapter 4.5.1 --- Stripline Feed Antennas --- p.101 / Chapter 4.5.2 --- Microstrip Line Feed Antennas --- p.110 / Chapter 4.6 --- Summary --- p.115 / Chapter 5. --- Green's Functions for a Electric Current on a Dielectric Coated Sphere / Chapter 5.1 --- Expansion of Fields using Spherical Harmonics --- p.116 / Chapter 5.2 --- Green's Functions in Spectral Domain --- p.119 / Chapter 6. --- Green's Functions for a Current on a Dielectric Coated Cylinder / Chapter 6.1 --- Expansion of Fields with Auxiliary Potentials --- p.121 / Chapter 6.2 --- Green's Functions in Spectral Domain --- p.125 / Chapter 7. --- Green's Functions for a Current inside a Triple Layered Cylinder / Chapter 7.1 --- Expansion of Fields with Auxiliary Potentials --- p.129 / Chapter 7.2 --- Green's Functions in Spectral Domain --- p.132 / Chapter 8. --- Conclusions and Recommendations / Chapter 8.1 --- Conclusions --- p.137 / Chapter 8.2 --- Recommendations for Future Research --- p.138 / References --- p.139 / Appendices / Chapter A. --- Vector Legendre Series --- p.146 / Chapter B. --- Surface Current for Spherical Microstrip Antenna --- p.149 / Chapter C. --- Modified Reciprocity Theorem --- p.152 / Chapter D. --- Spherical Bessel Functions and Legendre Functions --- p.154 / Chapter E. --- Approximated Green's functions Gθθ and Gφφ for large n --- p.157 / Chapter F. --- Current Distributions for Cylindrical Rectangular Microstrip Antenna --- p.163 / Chapter G. --- "Evaluation of Zijmn, V1imand V2im" --- p.165 / Chapter H. --- Deformation of Integration of Path --- p.169 / Chapter I. --- Hankel Functions --- p.170 / Chapter J. --- Current Distributions for Aperture Coupled Antenna --- p.172 / Chapter K. --- "Evaluation of ΔV，Ye1, Ye2, Yai , Vi and Zij" --- p.176 / Chapter L. --- Program Listing for stripline Feed Aperture Coupled Microstrip Antenna --- p.178