Listar Física por título
Mostrando ítems 77-96 de 112
-
Phototransport Properties of a-SiC:H Alloys
(1995)We report a study of the mobility-lifetime products of the two charge carriers in a-SiC:H alloys. The measurements were carried out as a function of the carbon concentration and the temperature. An analysis, relying on the ... -
Pressure dependence of ferroelectric quantum critical fluctuation
(2019-12-13)Phase transitions to a long-range-ordered state driven by a softened phonon mode are ubiquitous across condensed matter physics, but the evolution of such a mode as the system is tuned to or from the transition has never ... -
Probing the origin of 4FGL J0822.8–4207: cosmic ray illumination from the SNR Puppis A and the Herbig-Haro object HH219
(2021)4FGL J0822.8–4207 is a point source found in the 4FGL-DR2 catalogue by the gamma-ray observatory Fermi-LAT and has no known association. We carry out X-ray observations of 4FGL J0822.8–4207 to help understand its nature. ... -
Propuesta de estrategias metodológicas para el contenido curricular “Oscilaciones y ondas mecánicas” que propicie el aprendizaje significativo en el estudiantado que asiste al curso Laboratorio de Física General II de la Universidad de Costa Rica, Sede de Occidente durante el II semestre del 2020
(2020)El presente trabajo tiene por objetivo general el proponer estrategias metodológicas para el contenido curricular “Oscilaciones y ondas mecánicas” que propicien un aprendizaje significativo en el estudiantado que asiste ... -
Pruebas técnicas de aceptación de la PET/CT del modelo Biograph Vision 450 de Siemens
(2023-11-09)Esta tesis académica, para optar por el título de maestría académica en física médica, versa sobre las pruebas técnicas de aceptación del sistema tomográfico PET/CT BV 450, el cual pertenece al proyecto ciclotrón-PET/CT ... -
QA Programme of the TLD laboratory of the University of Costa Rica: IEC 61066 testing
(2008)The Thermoluminescence Personal Dosimetry Laboratory of the University of Costa Rica provides dose measurements for around 90% of occupational radiation workers in the country. The assessment of doses to workers routinely ... -
Quantum ferroelectric instabilities in superconducting SrTiO3
(2018)We examine the effects of strain and cation substitution on the superconducting phase of polar semiconductors near a ferroelectric quantum phase transition with a model that combines a strong coupling theory of ... -
Quantum Theory of Triboelectricity
(2020-10-30)We propose a microphysical theory of the triboelectric effect by which mechanical rubbing separates charges across the interface between two materials. Surface electrons are treated as an open system coupled to two baths, ... -
Random Electric Field Instabilities of Relaxor Ferroelectrics
(2017-06-13)Relaxor ferroelectrics are complex oxide materials which are rather unique to study the effects of compositional disorder on phase transitions. Here, we study the effects of quenched cubic random electric fields on the ... -
Relation between Luminescence and Electronic Surface Characteristics in p-type Porous Silicon
(1997)Measurements of photoluminescence, electronic surface states and effective surface area, at various stages of the anodization process, are presented. The results show a behavior different from that observed on n-type porous Si. -
Renormalización mejorada y multipolos armónicos
(2023)En este trabajo se proporciona una prueba de la estructura multipolar de los propagadores cinemáticos no regularizados de intensidades de campo de espín superior. Siguiendo el patrón identificado por primera vez en el ... -
Revealing a new region of gamma-ray emission in the vicinity of HESS J1825–137
(2019-02-17)HESS J1825–137 is a bright very high-energy gamma-ray source that has been firmly established as a pulsar wind nebula (PWN), and one of the most extended gamma-ray objects within this category. The progenitor supernova ... -
Search for gamma-ray emission from star-forming galaxies with Fermi LAT
(2016-08)Recent studies have found a positive correlation between the star-formation rate of galaxies and their gamma-ray luminosity. Galaxies with a high star-formation rate are expected to produce a large amount of high-energy ... -
Sesión "Medicina nuclear"
(2017-01)En la sesión dedicada a la Medicina Nuclear (MN) se identificaron los cinco aspectos que se consideran más problemáticos en la protección radiológica en MN. Estos hacen referencia a: 1. Garantizar que la dosis administrada ... -
Short term topological changes of coronal holes associated with prominence eruptions and subsequent CMEs
(2013-03-15)We study the short-term topological changes of equatorial and polar coronal hole (CH) boundaries, such as a variation of their area and disintegration, associated to reconnection with nearby (within 15° distance) quiescent ... -
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 ... -
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 ... -
Study of oxide bands in p-type porous silicon layers
(2019)The interest in developing fast and reliable chemical and biochemical sensors in an inexpensive way is something that has attracted a lot of efforts in the last decades. One of the potential material candidates is ...