This study investigates the dynamics of circular saws at supercritical speeds. A classical governing equation of a circular saw subjected to transverse and membrane forces is derived in both body-fixed and space-fixed coordinate systems. The transverse loads are generalized as spring, damping and out of plane cutting forces, and the membrane loads include rotational, thermal and in-plane cutting forces. Galerkin's Method is used to study the natural and forced response of a saw blade, and the effects of spring and damping on the stability at supercritical speed are discussed. An idling experiment is conducted to comprehend the fundamental behavior of circular saws at supercritical speed. The natural frequency, the steady state response, the flexibility and the runout variation of the circular saws are measured. The nonlinear vibration of the thin blade is observed. The effects of a spring-damper system and heating on the stability of a circular saw are investigated. A cutting test is conducted to find out the dominant parameters of supercritical speed cutting. At first, the prehminary experiments of the standard blade are conducted. Then, tip side cutting marks are discussed, and finally, the phenomenon of unstable cuttings are presented. The general solution of a rotating string subject to an elastic constraint is developed. Based on this, the discrepancy between theoretical and experimental stability results is analysed for a guided rotating disk. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

No description available.

Design of small uninhabited aerial vehicles is hampered by the relatively sparse database available for aerodynamic properties of basic shapes at low Reynolds number (Re). As a step towards remedying this situation, an experimental investigation of the influence of aspect ratio on the drag of circular cylinders at low Re has been conducted. The experiment itself faced the difficulty of measuring the small forces associated with low Re. A novel solution to this problem has been developed and applied in the Patterson Hall low speed wind tunnel at Mississippi State University. Using this method the drag characteristics of cylinders with aspect ratios varying from 16 down to 1 over a Reynolds number range from 10^5 down to 10^4 have been measured. This presentation will discuss the existing database, the present experimental method and the results that have been obtained.

No description available.

The idiom goes, "what is one man's trash is another man's treasure." In our 21st century economy, one man's trash is less commonly another's treasure as often as it is pollution. It is well documented that the majority of human waste ends up in on the side of roads, or in forests and oceans if not in landfills or incinerated. The disposability of items in our consumer culture is now commonplace. We are exacerbating our problems by throwing away single-use and barely-used items again and again without a feasible, realistic, and responsible solution for the end their life cycle. While our habitual buying and scrapping is continually increasing, the industrial buildings that process our waste are pushed to the outskirts of urban centers where they are most needed due to aesthetics, noises, and odors. These suburban and rural locations put an enormous economic and resource strain on cities. Architecture has the opportunity and responsibility to play an important role in remedying these issues related to waste facilities and processes. Architecture as an art form has largely abandoned these and similar industrial typologies as building design problems. They are mostly undertaken by engineers who design them for economic and process efficiencies. But there are unique challenges to be overcome with creative solutions, what architects do best. As a part of this process, architects can better design facilities so that they can be located within city limits and fight the "not in my backyard" stigmas associated with waste management. Ultimately architects can strive to improve civic life for citizens while also improving the means and methods of city-maintenance issues related to waste. At this intersection of waste and architecture, this thesis explores how a facility that settles into the dense urban fabric of Washington D.C. can play a role in the city's waste steam in order to benefit the local community and economy. / Master of Architecture / The idiom goes, “what is one man’s trash is another man’s treasure.” In our 21st century economy, one man’s trash is less commonly another’s treasure as often as it is pollution. It is well documented that the majority of human waste ends up in on the side of roads, or in forests and oceans if not in landfills or incinerated. The disposability of items in our consumer culture is now commonplace. We are exacerbating our problems by throwing away single-use and barely-used items again and again without a feasible, realistic, and responsible solution for the end their life cycle. While our habitual buying and scrapping is continually increasing, the industrial buildings that process our waste are pushed to the outskirts of urban centers where they are most needed due to aesthetics, noises, and odors. These suburban and rural locations put an enormous economic and resource strain on cities. Architecture has the opportunity and responsibility to play an important role in remedying these issues related to waste facilities and processes. Architects rarely design waste-management buildings and other industrial-use buildings. Usually it is engineers who undertake these buildings. They tend to design them in ways that put cost and process efficiency above everything else. One of the main skill-set architects have is problem-solving through design. Waste-management buildings face a lot of challenges beyond cost and process efficiency so it would make sense for architects to be a part of this process. Architects can better design these facilities so that they can be located within city limits and fight the “not in my backyard” stigmas associated with waste management. Ultimately architects would strive to improve civic life for citizens while also improving the means and methods of city-maintenance issues related to waste. At this intersection of waste and architecture, this thesis explores how a facility that settles into the dense urban enivironment of Washington D.C. can play a role in the city’s waste steam in order to benefit the local community and economy.

Os calcógenos de európio (EuX, onde X representa O, S, Se ou Te) possuem propriedades magneto-ópticas únicas e interessantes, devido ao enorme magnetismo gerado dos elétrons na camada f do átomo pertencente a família dos terras raras, tornando estes materiais atraentes para aplicações na spintrônica (eletrônica baseada nos transporte de spins e não de carga). Neste trabalho investigamos em baixa temperatura o espectro de absorção utilizando luz circularmente polarizada na região próxima do limiar da banda para o telureto de európio EuTe e o seleneto de európio EuSe em alto campo magnético no ordenamento ferromagnético dos spins de Eu^{2+} da rede cristalina. As amostras crescidas por epitaxia por feixe molecular apresentaram um dicroísmo circular magnético intenso no espectro de absorção para a configuração de Faraday. O par de linhas estreitas observadas estão separadas de aproximadamente 200 meV para o EuTe e 300 meV para o EuSe. Em seguida, formulamos um modelo teórico para a interpretação deste espectro de absorção no arcabouço do modelo de transições eletrônicas entre o estado fundamental 4f^{7}({8}^S_{7/2}) e o estado excitado formado dos estados do caroço remanescente 4f^{6}({7}^F_{J=0...6}) mais o estado em que o elétron se encontra na banda de condução 5d(t_{2g}), resultando em uma excelente concordancia qualitativa e quantitativa com o experimento. / Europium chalcogenides (EuX, where X stands for O, S, Se or Te) have very interesting and unique magneto-optical properties, due to the huge magnetism that arises from the electrons in the f?shell of the rare earth element and which makes them attractive for spintronics applications ( spin transport electronics or spin basedelectronics) In this work we investigate the band-edge optical absorption in high magnetic fields in the Faraday geometry for EuTe and EuSe in the ferromagnetic order attained at low temperatures. In thin layers grown by molecular beam epitaxy, an intense magnetic circular dichroism were observed. The doublet of absorption lines showed a separation by about 200meV in EuTe and 300meV in EuSe. Next, we developed a theoretical model for the interpretation of the absorption spectrum, based in the framework of the model of an electronic transition from a localized ground state 4f^{7}({8}^S_{7/2)) to an excited state formed by the core states 4f^{6}({7}^F_{J=0...6}) and the electron extended state in the 5d(t_{2g}) conduction band, yielding an excellent qualitative and quantitavie agreement with experiment.

Neste trabalho, utilizando técnicas magneto-ópticas, estudamos tempos de relaxação spin-rede (T1) do estado fundamental de centros \'F\' e, cristais de halogenetos alcalinos (KCl-KBr). Descrevemos um sistema semi-automático para medidas ópticas de T1, capaz de medir tempos de relação curtos (~1mS), baseado na medida do Dicroísmo Circular magnético (DCM) que apresentam aqueles sais quando portadores de centros paramagnéticos. Obtivemos a dependência de T1 com o campo magnético H (até 65 Kgauss), bem como os espectros de DCM para diferentes concentrações nas matrizes mistas. Uma teoria desenvolvida por Panepucci e Mollenauer (1) para matrizes puras, foi adaptadas para explicar a relaxação spin-rede nos cristais mistos. Os resultados obtidos para o processo direto (T~2.0 K), confrontados com auqela teoria, mostram que o mecanismo de relaxação dominante até 25 KGauss continua sendo a modulação por fônons da interação hiperfins entre o elétron \'F\' e os núcleos vizinhos. / Using magneto-optic techniques we have studied the ground state spin- lattice relaxation times (T1) of \'F\' centers in mixed Alkali Halide cristals (KCl-KBr). We describe a computer assisted system to optically measure short relaxation times (~1mS). The technique is based on the measurement of the Magnetic Circular Dicroism (MCD) presented by F centers. We obtained the T1 magnetic field dependency at 2 K up to 65 kGauss), as well as the MCD spectra for different relative concentration at the mixed matrices. The theory developed by Panepucci and Mollenauer for F centers spin-lattice relaxation in pure matrices was modified to explain the behavior of T1 in mixed cristais. The Direct Process results (T~2.0 K) compared against that theory shows that the main relaxation mecanism, Up to 25 kGauss, continues to be phonon modulation of the hyperfine interaction between \'F\' electrons and surrounding nuclei.

Os calcógenos de európio (EuX, onde X representa O, S, Se ou Te) possuem propriedades magneto-ópticas únicas e interessantes, devido ao enorme magnetismo gerado dos elétrons na camada f do átomo pertencente a família dos terras raras, tornando estes materiais atraentes para aplicações na spintrônica (eletrônica baseada nos transporte de spins e não de carga). Neste trabalho investigamos em baixa temperatura o espectro de absorção utilizando luz circularmente polarizada na região próxima do limiar da banda para o telureto de európio EuTe e o seleneto de európio EuSe em alto campo magnético no ordenamento ferromagnético dos spins de Eu^{2+} da rede cristalina. As amostras crescidas por epitaxia por feixe molecular apresentaram um dicroísmo circular magnético intenso no espectro de absorção para a configuração de Faraday. O par de linhas estreitas observadas estão separadas de aproximadamente 200 meV para o EuTe e 300 meV para o EuSe. Em seguida, formulamos um modelo teórico para a interpretação deste espectro de absorção no arcabouço do modelo de transições eletrônicas entre o estado fundamental 4f^{7}({8}^S_{7/2}) e o estado excitado formado dos estados do caroço remanescente 4f^{6}({7}^F_{J=0...6}) mais o estado em que o elétron se encontra na banda de condução 5d(t_{2g}), resultando em uma excelente concordancia qualitativa e quantitativa com o experimento. / Europium chalcogenides (EuX, where X stands for O, S, Se or Te) have very interesting and unique magneto-optical properties, due to the huge magnetism that arises from the electrons in the f?shell of the rare earth element and which makes them attractive for spintronics applications ( spin transport electronics or spin basedelectronics) In this work we investigate the band-edge optical absorption in high magnetic fields in the Faraday geometry for EuTe and EuSe in the ferromagnetic order attained at low temperatures. In thin layers grown by molecular beam epitaxy, an intense magnetic circular dichroism were observed. The doublet of absorption lines showed a separation by about 200meV in EuTe and 300meV in EuSe. Next, we developed a theoretical model for the interpretation of the absorption spectrum, based in the framework of the model of an electronic transition from a localized ground state 4f^{7}({8}^S_{7/2)) to an excited state formed by the core states 4f^{6}({7}^F_{J=0...6}) and the electron extended state in the 5d(t_{2g}) conduction band, yielding an excellent qualitative and quantitavie agreement with experiment.

Neste trabalho, utilizando técnicas magneto-ópticas, estudamos tempos de relaxação spin-rede (T1) do estado fundamental de centros \'F\' e, cristais de halogenetos alcalinos (KCl-KBr). Descrevemos um sistema semi-automático para medidas ópticas de T1, capaz de medir tempos de relação curtos (~1mS), baseado na medida do Dicroísmo Circular magnético (DCM) que apresentam aqueles sais quando portadores de centros paramagnéticos. Obtivemos a dependência de T1 com o campo magnético H (até 65 Kgauss), bem como os espectros de DCM para diferentes concentrações nas matrizes mistas. Uma teoria desenvolvida por Panepucci e Mollenauer (1) para matrizes puras, foi adaptadas para explicar a relaxação spin-rede nos cristais mistos. Os resultados obtidos para o processo direto (T~2.0 K), confrontados com auqela teoria, mostram que o mecanismo de relaxação dominante até 25 KGauss continua sendo a modulação por fônons da interação hiperfins entre o elétron \'F\' e os núcleos vizinhos. / Using magneto-optic techniques we have studied the ground state spin- lattice relaxation times (T1) of \'F\' centers in mixed Alkali Halide cristals (KCl-KBr). We describe a computer assisted system to optically measure short relaxation times (~1mS). The technique is based on the measurement of the Magnetic Circular Dicroism (MCD) presented by F centers. We obtained the T1 magnetic field dependency at 2 K up to 65 kGauss), as well as the MCD spectra for different relative concentration at the mixed matrices. The theory developed by Panepucci and Mollenauer for F centers spin-lattice relaxation in pure matrices was modified to explain the behavior of T1 in mixed cristais. The Direct Process results (T~2.0 K) compared against that theory shows that the main relaxation mecanism, Up to 25 kGauss, continues to be phonon modulation of the hyperfine interaction between \'F\' electrons and surrounding nuclei.

This paper explores how policy makers want a transition towards circular economy to look like and what solutions they visualize, with a focus on the why(?) arguments. By analyzing the discourse in states official roadmaps towards circular economy, this study forms an understanding for what motivates a transition. The findings show that the possibilities for economic gains and the creation of new markets are the main purpose to change. In addition to that, whenever the survivability of humanity and the environment was arguments for a change, it in almost all cases came back to the economical outsets with such transition, how much money can be gained/saved.