Thesis (M.S.)--University of Missouri--Columbia, 2004. / "December 2004." Typescript. Includes bibliographical references (leaves 67-70). Also issued on the Internet.

Thesis (M.S.)--University of Wisconsin--Madison, 1968. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.S.)--Oregon State University, 2008. / Printout. Page 145 left intentionally blank. Includes bibliographical references (leaves 123-125). Also available on the World Wide Web.

This thesis is concerned with the development of new and improved labeling procedures for introducing deuterium and tritium into organic compounds with the intention that some of the methods can be applied to more complex compounds such as biomaterials. The thesis consists of 6 chapters. In the first of these the necessary background information relating to biomaterials and the currently used methods of preparing deuteriated/tritiated compounds is presented, whilst in the second chapter various aspects of the use of our Tri-Sorber unit, unique to universities, are presented. The instrument allows H2, D2 and T2 to be stored on uranium beds and does away with the many problems associated with the use of a glass gas line; this is especially true for T2. In Chapter 3 the advantages of using microwaves in the area of aromatic dehalogenations are explored. The use of solid formates (DCOO-K+) in preference to D2 gas, combined with microwave irradiation, greatly increases the rates of these reactions although there are still instances where reactions do not proceed satisfactorily. In Chapter 4 it is shown for the first time how the pattern of microwave-enhanced Raney nickel isotope exchange reactions can be influenced, depending on the deuteriated solvent employed. General labeling through to specific labeling is reported. In Chapter 5 the benefits of using microwave and solid donors in hydrogenation reactions are explored; some examples of microwave-enhanced hydrogenations in the absence of solvent, as well as in the presence of solvent, are reported. Finally, in the last, brief chapter some of the new developments reported in the earlier chapters are applied to the attempted deuteriation of a biocompatible polymer and a model compound.

Thesis (MTech (Electrical Engineering))--Peninsula Technikon, Cape Town, 2002. / Tne purpose of this research or study was to perform an investigation in the use of optical fibers as sensor elements in order to develop a millimetre wave instrument capable of measuring microwave power within microwave cavities. Included in the scope of the project was an investigation of microwaves and microwave power measurements techniques. The emphasis of the research work was to develop expertise in photonics, by modeling and developing a measuring technique using optical techniques. This was deemed to be highly beneficial in laboratory experimentation and for possible use by microwave technicians. The implementation was amongst others, done by means of computer simulation and associated hardware, together with fiber-optic accessories. In order to conduct this research a literature and technology survey of current non-optical microwave power measurement technique was done. With this a review different power measurements systems and their relationship towards microwave power measurements was conducted. Within the scope of the project, a study of fiber optics sensors and its components was also conducted, which enabled models for a Mach-Zehnder microwave sensor to be developed. This resulted in the development of inexpensive electronic signal conditioning and detection techniques to enable measurements that employed a Mach-Zehnder Interferometer for this sensor technique. Finally, as microwaves are difficult to measure with pure electronic equipment, different approaches were made to investigate the temperature changes and other parameters on optical fiber to avoid damage to it. The specifications of hardware and circuitry suitable to measure these effects were determined.

The purpose of this dissertation is to investigate the effects of non-linear propagation on a proposed digital microwave radio link which employs MSK modulation, in order to specify a suitable form of adaptive equalization. MSK is a coherent modulation technique, having improved spectral roll-off over FSK because it avoids the abrupt phase changes at the bit transitions. However computer simulations and field results indicate that MSK digital radio links do suffer from intersymbol interference and crosstalk. Software and hardware simulations of multipath propagation are based on Rummlers simplified three path model and statistics. The results obtained from the computer simulations of the MSK link and multipath propagation confirm that there is no simple relationship between the multipath parameters and the BER degradation which could be used in the design of an equalizer. The choice of adaptive equalizer is made based on criteria such as construction cost, circuit complexity, and performance improvement. It is known from ray model analysis that at a transmitting frequency of 23 GHz deep fading will only occur on links longer than 5.24 kms. However even on hops of length 5 km' s the fade time is-in the order of 1612 seconds/month (calculated using Rummlers model). A ldB increase in theoretical Eb/No will also be required to overcome potential modem imperfections. It is necessary to have a time domain equalizer which can compensate for both amplitude and phase distortions simultaneously by acting directly on the ISI. The equalizer structure chosen is a 2-by-2, fractionally spaced, decision feedback, complex adaptive equalizer with zero forcing control algorithm.

A thesis submitted to the Faculty of Science, University of Witwatersrand, in the ful lment of the requirements for the degree of Doctor of Philosophy Johannesburg, South Africa, 2017. / According to the standard model of cosmology, the Universe has evolved from a thermal bath of elementary particles and photons towards one comprising of collapsed structures such as stars, galaxies and clusters of galaxies. The Cosmic Microwave Background (CMB) spectrum and its angular anisotropy across the sky contain information on the physical processes, matter distribution and evolution of the Universe across cosmic time. Primordial spectral distortions of the CMB and its anisotropy can be studied through the inverse comptonization process occuring in cosmic structures, known as the Sunyaev-Zel'dovich e ect (SZE). This present study demonstrates how the SZE can be used to obtain information on the 21 cm background produced between the Dark Ages (DA) and the Epoch of Reionization (EoR), on Non-Planckian (NP) modi cations of the CMB due to plasma frequency at the recombination epoch, and on the anisotropy of the CMB at cluster locations, through the study of the polarization of the SZE. To these aims, a full relativistic approach is employed, that allows us to calculate the spectra of the SZE and its polarization component with high precision, and allows to calculate it for any kind of electron population (thermal or nonthermal plasma), and for an input spectrum that can deviate from the standard black-body spectrum. The SZE-21cm, which is the comptonized spectrum of the modi ed CMB due to physical processes occuring during the DA and the EoR, is calculated for four models of the 21-cm background. A full spectral analysis of the signal is performed and the importance of relativistic e ects are highlighted. The results demonstrate that relativistic e ects are nonzero over the entire frequency spectrum and hence cannot be ignored, particularly for hot clusters. It is found that the amplitude of the SZE-21cm signal is of the order of Jy and is within the reach of the SKA instrument. Clusters with high temperature and optical depth are optimal targets to search for the SZE-21cm signal. The SKA can measure the signal in the frequency interval 75-90 MHz for clusters with temperature higher than 5 keV. Discerning the SZE-21cm from the standard SZE can be achieved using the SKA depending on the 21-cm background model for temperatures > 10 keV. Using CMB spectral data at both low and high frequencies, upper limits (206, 346 and 418 MHz at 1, 2, 3 con dence level) are placed on NP e ects associated with a non-zero plasma frequency at the recombination epoch. The SZENP is derived for a CMB spectrum modi ed due to plasma e ects using these upperlimits and a unique spectral feature is obtained. A peak occures at the plasma frequency in the SZENP independent of cluster parameters and the possibility of measuring the plasma frequency with the SKA and eVLA is shown. Plasma e ects are also investigated on the spectrum of the cosmological 21-cm background and it is found that such an e ect is important to consider when recovering the history of the Universe during these epochs. Polarization is a natural outcome of inverse Compton (IC) scattering and the anisotropy of the CMB plays a big role in the production of polarization in Comptonization process. The SZE polarization associated with the anisotropy of the CMB is derived in the full relativistic regime for any general electron distribution. The spectral shapes of the Stokes parameters induced by the IC scattering of the multipoles of the CMB for thermal and non-thermal electrons are derived, focusing mainly on the quadrupole and octupole which provide the largest possible detectable signals in cosmic structures. Our results demonstrate the implication of relativistic e ects, which become important for high temperature or non-thermal cluster environments. When relativistic e ects are accounted for, all the multipoles of the CMB are involved in the production of polarization. The octupole induced polarization spectrum reveals the existence of a cross-over frequency which is dependent on cluster parameters such as temperature, minimum momentum and spectral index. The possibilities to disentangle the quadrupole spectrum from the octupole one are discussed, which would allow the measurments of these multipoles at cluster locations. The generality of our approach allows us to calculate the SZE polarization spectra of the Bullet cluster using multifrequency SZE data in intensity and compare the results with the sensitivities of the SKA, ALMA, Millimetron and CORE++ instruments. Although the e ects that we studied here are small, however, they are still within the detection limits of the SKA, due to its very high sensitivity. Therefore, the SKA will play a big role in the study of cosmological radio backgrounds by providing high precision SZE data. / LG2018

No description available.

The microwave-resonant-cavity technique was employes as a probe to determine the presence of molecular ions of helium in a d.c.-discharge, helium-plasma filament placed coaxially in a TM010 mode cavity. The cavity-resonance profile was displayed on an oscilloscope, and the nature of the perturbation of this resonance was used to determine the nature of the ions present in the plasma stream.

No description available.