6 research outputs found
Numerical studies on zinc oxide synthesis via physical vapor transport
This project examined the transport phenomena in the synthesis of ZnO by physical vapor transport. In the numerical simulations Zn and O2 were treated as diluted species transported in nitrogen. The modes of transport were investigated and the velocity, temperature and concentration profiles in the reactor under reaction conditions elucidated. Also a parametric examination was conducted to determine the effect of physical variables on the flow. It was found that in open reaction conditions at high pressures convective transport dominates, while lower pressures lead to diffusive dominance and significant mass transport resistance. The linear temperature profile assumption was validated; further it was found that thermal expansion is insignificant, hence free convection can be neglected
Magnetoresistance in multilayer fullerene spin valves : a first-principles study
Carbon-based molecular semiconductors are explored for application in
spintronics because their small spin-orbit coupling promises long spin life
times. We calculate the electronic transport from first principles through spin
valves comprising bi- and tri-layers of the fullerene molecules C60 and C70,
sandwiched between two Fe electrodes. The spin polarization of the current, and
the magnetoresistance depend sensitively on the interactions at the interfaces
between the molecules and the metal surfaces. They are much less affected by
the thickness of the molecular layers. A high current polarization (CP > 90%)
and magnetoresistance (MR > 100%) at small bias can be attained using C70
layers. In contrast, the current polarization and the magnetoresistance at
small bias are vanishingly small for C60 layers. Exploiting a generalized
Julli`ere model we can trace the differences in spin-dependent transport
between C60 and C70 layers to differences between the molecule-metal interface
states. These states also allow one to interpret the current polarization and
the magnetoresistance as a function of the applied bias voltage
HARVESTING HELIUM-3 FROM THE MOON
The world is approaching an energy crisis, and it is critical to focus on an alternate long term energy source. Given the current urge to explore space and expand humanity's outreach, harvesting the energetically rich Helium-3 from the Moon's surface is an ideal, yet challenging, objective which is amply motivated by current energy economic realities. He-3 can be used in a nuclear fusion reactor to generate enormous energy outputs with negligible waste. In this project, we study the scientific breakthroughs required in space and fusion technologies to successfully harvest He-3 from the Moon. Additionally, a multitude of interests expressed on a global scale in lunar He-3 are examined and assessed based on a legal space framework, and socio-economic political scenarios are developed that would result from the aforementioned space venture
A theoretical study of atomic wires and atomic junctions created on a Molybdenum disulfide surface
Recursos H铆dricos: Conceptos b谩sicos y estudios de caso en Iberoam茅rica
El agua como fuente de vida y en el desempe帽o de sus funciones: sociales, ambientales, econ贸micas y culturales, condiciona el desarrollo de una regi贸n, naci贸n o continente, pues, la concentraci贸n urbana, el incremento de la superficie de riego para la producci贸n de alimentos y la creciente contaminaci贸n someten a los recursos h铆dricos a una fuerte presi贸n que no es posible soportar, originando situaciones de crisis. As铆, mientras encuentran localidades la satisfacci贸n de las necesidades en agua de sus habitantes representa un esfuerzo cotidiano, en otras, el desperdicio es una pr谩ctica generalizada pero inadmisible. Sin duda alguna en el mediano y largo plazo la tendencia actual en el uso de agua es simplemente insostenible. No es posible sufragar permanentemente el costo econ贸mico, social ay ambiental de abastecer a las grandes urbes con escurrimientos superficiales importados desde enormes distancias, de agotar los acu铆feros de alterar la calidad de las agua rebasando l铆mites de renovaci贸n econ贸micamente factibles. Tampoco es posible enfrentar el problema del agua como si la disponibilidad del recurso fuera ilimitada y gratuita..