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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
91

Influência do eletromagnetismo na biodigestão anaeróbia /

Matos, Júlio César de Souza. January 2017 (has links)
Orientador: Macrus César Avezum Alves Castro / Banca: Michel Brienzo / Banca: Reinaldo Pizani Junior / Resumo: O processo de biodigestão anaeróbia pode ser utilizado no tratamento de resíduos orgânicos, com destaque para recuperação energética do biogás. Estudos recentes apontam aumento na eficiência da atividade microbiológica em processos de biodegradação anaeróbia de compostos orgânicos sob campo magnético. Desse modo, tecnologias que resultem em melhorias desse processo podem contribuir para o avanço do tratamento de resíduos orgânicos e da produção de biogás, via digestão anaeróbia. Nesse sentido, o presente trabalho verificou a influência da aplicação de campo eletromagnético constante sobre o processo de decomposição anaeróbia da glicose. A pesquisa consistiu na operação de reatores (1 L) anaeróbios em batelada, mantidos a 37 ± 2 ºC, sem agitação, sob a influência de diferentes intensidades de campo eletromagnético de 5, 7,5 e 10 mT. Foi usado, como inóculo lodo granular proveniente de estação de tratamento anaeróbio, nos reatores, em meio nutricional sintético não seletivo. A avaliação do desempenho do processo de degradação foi obtida pela estimativa de produção de biogás e metano, bem como da análise da redução da demanda química de oxigênio e da remoção de sólidos. Os resultados demonstraram diferença positiva na produção de gás metano, aumento de 21,5 % com 7,5 mT e aumento de 15 % da remoção de DQO, nas intensidades de 7,5 mT. Esses resultados sinalizam para possível viabilidade de uso de campo magnético constante na bioestimulação de consórcios microbianos anaeróbios / Abstract: Anaerobic digestion processes with biogas production are largely used for organic waste treatment, with emphasis for energy recovery. Some recent studies have demonstrated magnetism influence on microbiological activity, these indicates possible influence on the efficiency of anaerobic digestion. By these means, technologies that act in anaerobic digestion enhancement can contribute for the improvement of organic compounds treatment. The present study aims to verify the influence of constant electromagnetic field on the glucose anaerobic digestion. The research comprises comparison of biogas production in 1 L batch reactors, kept static under 37 ± 2 ºC. In each experiment, reactors were operated with and without the influence of constant electromagnetic field of 5, 7,5 and 10 mT. The inoculum was granular sludge from anaerobic treatment plant in non-selective media culture. Biogas production, COD and solid removal were measured during the experiments. Results show positive difference on methane production of 21,5 % and on COD removal of 15 % in the tests with electromagnetic field of 7,5 mT. These results sign for the viability of the application of constant magnetic field as a bioetimulation agent / Mestre
92

Correlative comparison of prediagnosed malaria, diabetes mellitus and tuberculosis patients with quantum xxroid consciousness interface reactivity readings

Saunders, Brenda-Anne 31 July 2008 (has links)
The field of energetic medicine began generations ago when medical doctors and scientists found an electrical correlate for what Rheinold Voll described, in the Nineteen Fifties, as medication testing on meridian points. These points showed electrical variability through resistance when a patient was exposed to various homoeopathically prepared substances. William Nelson, the developer of the Quantum Xrroid Consciousness Interface (QXCI) Device, calls this phenomenon electrophysiological reactivity. The developers of the QXCI device claim that the QXCI is able to connect deeply with the energies and tissues of the patient’s body, mind and spirit and test his or her reactions or “reactivity” to over eight thousand items. The QXCI then offers a wealth of software programs that make suggestions from many different modalities on balancing and reintegrating the body, mind and spirit of the patient. The QXCI device and software claims to analyse and balance stresses of many types including: toxicity, trauma, deficiency, perverse energy, pathogens, allergy, heredity and mental factors (Nelson, 2003). The results of research published by Nelson (1994b) and Nagy (1994b) showed that there was a correlation of over eighty percent between QXCI reactivity readings and conventional diagnostic tests and analysis for various infections and blood chemicals. As a result of this research the QXCI is recommended by the developers as a useful pre-diagnostic screen. The study aimed to determine whether there was any correlation between prediagnosed malaria, tuberculosis and diabetes mellitus subjects and QXCI reactivity readings. Reactivity readings were taken of twenty healthy individuals and twenty prediagnosed malaria, tuberculosis and diabetes mellitus subjects. Reactivity readings were analysed for increased reactivity to Plasmodium, Mycobacterium and glucose. Results showed no significant statistical relationship between the conventional diagnostic tests for malaria, tuberculosis and diabetes mellitus and the QXCI vi reactivity readings. The Predictive Value Theory tests of Sensitivity, Specificity and Efficiency as well as the Chi-Square Test were used to obtain statistical results. The results are not conclusive and further investigation into the use of the QXCI as a pre-diagnostic tool is required. / Dr. M.R.A. Moiloa Dr. J.L. Du Plessis
93

Development of niobium nitride hot electron bolometric mixer for terahertz frequencies: The phonon-cooled version

Gerecht, Eyal 01 January 1998 (has links)
NbN HEB mixers represent a promising approach for achieving receiver noise temperatures of a few times the quantum noise limit at frequencies above 1 THz. NbN HEB devices have been shown to have sufficient bandwidth for applications in astronomy, remote sensing, and plasma diagnostics in the FIR range. The NbN HEB is a phonon cooled bolometer in which the energy is transfered from the hot electrons to the substrate via inelastic collisions with phonons. The development of an NbN HEB mixer contained two steps: (1) implementing mixing in a comparatively large "direct-coupled" prototype device which required LO power of a few milliwatts, and (2) optimization of the first step by the development of an "antenna-coupled" (quasi-optically coupled) device with an LO power level of less than one $\mu W$. The LO power was coupled to the antenna via an extended hemispherical lens (1.3 mm in diameter). The design, fabrication, and measurement stages were performed by a collaborative effort between a Russian team from the Department of Physics at Moscow State Pedagogical University in Moscow, the Submillimeter Technology Laboratory at UMass/Lowell and the Department of Electrical and Computer Engineering at UMass/Amherst. Mixing at 2.5 THz was demonstrated for the first time using the direct-coupled device achieving an intrinsic conversion loss of 23 dB. Sufficient level of LO power coupling at four different frequencies was demonstrated with the antenna-coupled device. The antenna/lens configuration has performed as well as expected insuring coupling to LO power of less than one $\mu$W. A 3 dB conversion gain was demonstrated with the antenna-coupled device using a laser LO at 1.56 THz with an IF frequency of 500 KHz. A second laser was utilized as the rf source. Noise temperature for the NbN HEB mixer receiver of 5800 K has been demonstrated over the 1.25-1.75 GHz IF band. The mixer temperature was 2500 K and the total conversion loss was 27 dB. Further optimization of the receiver configuration and device fabrication as well as additional development in mixer modeling will gradually lead to lower noise temperatures.
94

The design and synthesis of mono- and bis-nitrenes as models for organic magnetic materials

Walton, Richard 01 January 1998 (has links)
Seven nondisjoint dinitrenes were produced in order to determine the length of chain conjugation that would still allow effective inter-nitrene exchange communication. The dinitrenes were generated in frozen matrices of 2-methyltetrahydrofuran by photolysis of appropriate diazides by a 1000-Watt xenon arc lamp and studied by electron spin resonance (ESR) spectroscopy. Conjugation lengths varied from 17 to 29 atoms between spin sites. In each case, it was determined by variable temperature analysis that the high-spin quintet state was the ground state. Six other dinitrenes were also produced which surprisingly exhibited quintet state spectra at 77 K, despite having possible quinoid biradical resonance structures. Possible reasons for the latter observation include conformational torsion effects, combined with a preference to retain benzenoid sextet resonance structures. In addition to the molecules produced in this lab, numerous samples of mono-, di-, and tri-azidopyridines were jointly studied with Dr. Sergei Chapyshev of the Russian Institute of Chemical Physics. These systems were studied by ESR spectroscopy. The effect of the pyridine heteroatom upon the ESR spectroscopy of these systems was found to be considerable, relative to simpler aryl nitrenes. Several of the triazide of systems were deemed to be ground state septet systems.
95

Processing and Characterization of Superconducting Solenoids Made of Bi-2212/Ag-Alloy Multifilament Round Wire for High Field Magnet Applications

Unknown Date (has links)
As the only high temperature superconductor with round wire (RW) geometry, Bi2Sr2CaCu2O8+x (Bi-2212) superconducting wire has the advantages of being multi-filamentary, macroscopically isotropic and twistable. With overpressure (OP) processing techniques recently developed by our group at the National High Magnetic Field Laboratory (NHMFL), the engineering current density (Je) of Bi-2212 RW can be dramatically increased. For example, Je of more than 600 A/mm2 (4.2 K and 20 T) is achieved after 100 bar OP processing. With these intrinsically beneficial properties and recent processing progress, Bi-2212 RW has become very attractive for high field magnet applications, especially for nuclear magnetic resonance (NMR) magnets and accelerator magnets etc. This thesis summarizes my graduate study on Bi-2212 solenoids for high field and high homogeneity NMR magnet applications, which mainly includes performance study of Bi-2212 RW insulations, 1 bar and OP processing study of Bi-2212 solenoids, and development of superconducting joints between Bi-2212 RW conductors. Electrical insulation is one of the key components of Bi-2212 coils to provide sufficient electrical standoff within coil winding pack. A TiO2/polymer insulation offered by nGimat LLC was systematically investigated by differential thermal analysis (DTA), thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM), dielectric property measurements, and transport critical current (Ic) property measurements. About 29% of the insulation by weight is polymer. When the Bi-2212 wire is fully heat treated, this decomposes with slow heating to 400 °C in flowing O2. After the full reaction, we found that the TiO2 did not degrade the critical current properties, adhered well to the conductor, and provided a breakdown voltage of more than 100 V. A Bi-2212 RW wound solenoid coil was built using this insulation being offered by nGimat LLC. The coil resistance was constant through coil winding, polymer burn-off and full coil reaction. The coil was successfully tested at the NHMFL generating 33.8 T combined magnetic field in a 31.2 T background field. Multiple quenches occurred safely, which also illustrates that the insulation provided sufficient dielectric standoff. For Bi-2212 RW with a typical as-drawn diameter of 1.0-1.5 mm, this 15 µm thick insulation allows a very high coil packing factor of ~0.74, whereas earlier alumino-silicate braid insulation only allows packing factors of 0.38-0.48. In addition to the commercial TiO2/polymer insulation, we have also investigated sol-gel based ceramic coatings through collaboration with Harran University and another TiO2 based insulation coating at the NHMFL. Since Bi-2212 superconducting coils employ the Wind-and-React (W&R) technology, there are some potential issues in processing Bi-2212 coils, in particular for coils with a large thermal mass and dense oxide insulation coating. For this study, several Bi-2212 test solenoids with an outer diameter (OD) of about 90 mm were built and heat treated in 1 bar flowing oxygen with deadweights applied so as to simulate large coil packs. After the heat treatment (HT), coils were epoxy impregnated and cut. Winding pack was checked using SEM in terms of conductor geometry and insulation. Some samples were extracted to measure transport critical current Ic and critical temperature Tc. The results are very promising: test coils presented low creep behavior after standard partial melt HT under mechanical load, and no Ic degradation was found due to the application of mechanical load, and no inadequate oxygenation issue was seen for thick coils with ceramic coating on the wire. However, coils were partially electrically shorted after 1 bar HT under mechanical load, and we believe that increasing insulation coating thickness is necessary. In addition, several small solenoids were manufactured to study OP processing of Bi-2212 coils. The preliminary results indicate that there are some gaps between turns due to densification of wires (~4% wire diameter reduction) during 50-100 bar OP processing, and the diameter shrinking of conductors will potentially lead to coil sagging. So far, we have developed some methods to solve the issue of coil sagging, such as using flexible coil flange to allow smooth sagging of winding pack during OP processing. We have also investigated electrical joints between Bi-2212 RW conductors, which include resistive joints and superconducting joints. For resistive Bi-2212 joints, we evaluated conventional diffusion bonding method and soldering method. In general, the joints (with 42 mm joint length) resistances are below 200 nΩ at 4.2 K and magnetic fields up to 13.5 T, and the effect of magnetoresistance is clearly present. In addition to resistive joints, we successfully developed a superconducting joint between Bi-2212 RW conductors for persistent current mode (PCM) operations. The joint fabrication procedure is effective and practical, enabling Bi-2212 superconducting joints to be achieved during the standard Bi-2212 HT processing. First, the melting temperatures of Bi-2212 precursor mixtures with different amounts of Ag additions were investigated by DTA. Then, test joints were fabricated and heat treated in 1 bar flowing oxygen using the standard Bi-2212 HT schedule. The voltage-current (V-I) properties were measured using the conventional four-point method at 4.2 K in magnetic fields up to 14 T. A maximum supercurrent of ~850 A was achieved at 4.2 K and self-field. With the increase of external field, the supercurrent gradually decreased as expected, but a supercurrent of ~450 A was still presented at 4.2 K and 14 T. Compared with open-ended short samples with identical 1 bar Bi-2212 reaction, we found that the Ic properties of joints did not degrade. Meanwhile, microstructures of joints were examined by SEM, which clearly presented the formation of a Bi-2212 superconducting interface between two independent Bi-2212 RW conductors. Furthermore, a Bi-2212 RW closed-loop solenoid with a superconducting joint was fabricated and fully heat treated in 1 bar flowing oxygen. Using the field decay method, the joint resistance was estimated to be below 5×10-12 Ω at 4.2 K and self-field. / A Dissertation submitted to the Department of Mechanical Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Spring Semester 2016. / March 29, 2016. / Bi-2212, Insulation, Superconducting joint, Superconducting magnet / Includes bibliographical references. / David Larbalestier, Professor Co-Directing Dissertation; Ulf Trociewitz, Professor Co-Directing Dissertation; Irinel Chiorescu, University Representative; Eric Hellstrom, Committee Member; Wei Guo, Committee Member.
96

Numerical simulation of stimulated electromagnetic emissions in the ionosphere

Cheng, K. T. 05 September 2009 (has links)
One-dimensional electrostatic plasma simulation using the particle-in-cell technique is used to study the spectral features of stimulated electromagnetic emission (SEE). SEE is a potential diagnostic tool to study the ionosphere and its spectrum provides a different view of the heated region from the incoherent scatter radar. At this time, a unified and complete theory which explains the SEE phenomena in detail does not exist. The SEE simulations we discuss are proposed to provide interpretation of many of the past puzzles of the experimental data, as well as to facilitate the design of future SEE experiments and the theoretical development of SEE. In the numerical simulation, only the upper hybrid layer where the geomagnetic field is essentially perpendicular to the density gradient is modelled. Three of the SEE features, namely the downshifted maximum (DM), upshifted maximum (UM) and broad upshifted maximum (BUM), are suggested to be generated at the upper hybrid layer. We observed these three features which have many similarities in the simulation. It is evident that the DM and UM are generated by the same parametric instability involving lower hybrid waves while the BUM is produced by other different mechanisms. Boundary effects are found important on the generation of all three features in the simulation. Moreover, detailed investigation of the simulation results raises a number of questions concerning detailed generation mechanisms of SEE which have not been considered and answered in the past. Besides the DM, UM and BUM features, the quenching of DM is also observed in the simulation when the pump frequency is very close to electron cyclotron harmonics. It is concluded that both the cyclotron damping and mode conversion of the upper hybrid wave into electron Bernstein modes are possible causes. Finally, some suggestions for the future SEE simulation are included. / Master of Science
97

Geophysical Electromagnetics at Very-High and Ultra-High Frequencies

Baranyi, Elizabeth January 1985 (has links)
Note:
98

Antibody/Cell Binding and Magnetic Transport in a Microfluidic Device

Adams, Shauna 29 August 2013 (has links)
No description available.
99

Potential drop detection of creep damage in the vicinity of welds

Prajapati, Seeran 21 September 2012 (has links)
No description available.
100

Specular Reflectivity and Hot-Electron Generation in High-Contrast Relativistic Laser-Plasma Interactions

Kemp, Gregory Elijah 17 December 2013 (has links)
No description available.

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