Física
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The mechanical career of Councillor Orffyreus, confidence man
(2013-05)In the early 18th century, J. E. E. Bessler, known as Orffyreus, constructed several wheels that he claimed could keep turning forever, powered only by gravity. He never revealed the details of his invention, but he ... -
Irreversibility in an ideal fluid
(2014-10)When a real fluid is expelled quickly from a tube, it forms a jet separated from the surrounding fluid by a thin, turbulent layer. On the other hand, when the same fluid is sucked into the tube, it comes in from all ... -
Chandler wobble: Stochastic and deterministic dynamics
(2016-09-18)We propose a model of the Earth’s torqueless precession, the “Chandler wobble,” as a self-oscillation driven by positive feedback between the wobble and the centrifugal deformation of the portion of the Earth’s mass contained ... -
A thermodynamic cycle for the solar cell
(2017-01-06)A solar cell is a heat engine, but textbook treatments are not wholly satisfactory from a thermodynamic standpoint, since they present solar cells as directly converting the energy of light into electricity, and the current ... -
Large isotropic negative thermal expansion above a structural quantum phase transition
(2015-10-01)Perovskite structured materials contain myriad tunable ordered phases of electronic and magnetic origin with proven technological importance and strong promise for a variety of energy solutions. An always-contributing ... -
Structure factor of a relaxor ferroelectric
(2015-04-14)We study a minimal model for a relaxor ferroelectric including dipolar interactions, and short-range harmonic and anharmonic forces for the critical modes as in the theory of pure ferroelectrics together with quenched ... -
Why is the electrocaloric effect so small in ferroelectrics?
(2016-05-19)Ferroelectrics are attractive candidate materials for environmentally friendly solid state refrigeration free of greenhouse gases. Their thermal response upon variations of external electric fields is largest in the vicinity ... -
Electronic structure of silicon-based nanostructures
(2007-08-30)We have developed a unifying tight-binding Hamiltonian that can account for the electronic properties of recently proposed Si-based nanostructures, namely, Si graphene-like sheets and Si nanotubes. We considered the sp3s∗ ... -
Los albores de la física y el desarrollo de la meteorología en Costa Rica
(2002)El siguiente artículo describe algunos aspectos del desarrollo de la física en Costa Rica, con énfasis en el siglo XIX. El trabajo está basado en una investigación bibliográfica de fuentes históricas, donde se compilaron ... -
Algunas ideas para lograr un mayor desarrollo científico y tecnológico en Costa Rica
(2000)El propósito de este capítulo, el cual está basado en el trabajo de Fernández y Páez (2000), es describir las actividades en Ciencias Espaciales que se están llevando a cabo en Costa Rica, estas actividades están centradas ... -
Tsunamis and tsunami prepardness in Costa Rica, Central America
(2005-12)Pacific and Atlantic sides of Costa Rica there are coastal segments characterised by a flat relief, which increases the vulnerability of the coastal communities. In addition to tsunamis originating in the Middle American ... -
Tsunamis and Tsunami Hazards in Central America
(2000-02)A tsunami catalogue for Central America is compiled containing 49 tsunamis for the period 1539–1996, thirty seven of them are in the Pacific and twelve in the Caribbean. At the Caribbean side, 5 events are related with ... -
The 2:3:6 quasi-periodic oscillation structure in GRS 1915+105 and cubic subharmonics in the context of relativistic discoseismology
(Monthly Notices of the Royal Astronomical Society 440:3011-3015, 2014-06-01)We propose a simple toy model to explain the 2:3:6 quasi-periodic oscillation (QPO) structure in GRS 1915+105 and, more generally, the 2:3 QPO structure in XTE J1550−564, GRO J1655−40 and H1743−322. The model exploits the ... -
Estimation of Silicon Nanocrystalline Sizes from Photoluminescence Measurements of RF Co-Sputtered Si/SiO2 Films
(Materials Research Society Symposium Proceedings 737 (2003), 2003)A stochastic distribution of nanocrystalline sizes model is applied to fit photoluminescence (PL) spectra of luminescent Si nanocrystals in a Si/SiO2 matrix synthesized by RF co-sputtering on the top of quartz substrates. ... -
Design and Characterization of a High Vacuum Metals Deposition System based on Electron Beam Evaporation
(2010-08-03)We describe a high vacuum metals deposition system based ona variation of a pendant-drop type electron beam evaporator.This system uses a Molybdenum crucible as an evaporantinstead of a rod or wire usually used in ultrathin ... -
Stochastic approach to the smart quantum confinement model in porous silicon
(Surface Science 515 (2002) L509-L513, 2002)A model that encompasses two approaches to explain the photoluminescence in p-type porous silicon is proposed. The model considers a stochastic distribution of nanocrystallite sizes within the porous matrix and explain the ...
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