Ponencias (Física Aplicada III)

URI permanente para esta colecciónhttps://hdl.handle.net/11441/10861

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Mostrando 1 - 12 de 12

An inexpensive arbitrary waveform neurostimulator for the selective activation of neurons in retinal prosthesis
(Universidad Politécnica de Cartagena, 2023-12-18) Jiménez Fernández, P.; Guzmán-Miranda, Hipólito; Barriga-Rivera, Alejandro; Universidad de Sevilla. Departamento de Física Aplicada III; Universidad de Sevilla. Departamento de Ingeniería Electrónica; European Union (UE); Agencia Estatal de Investigación. España; Foundation for Fighting Blindness (FUNDALUCE)
This contribution presents a two-channel inexpensive arbitrary waveform neurostimulator based on a Raspberry Pi microcomputer platform and a Howland voltage-to-current converter. The system has been designed to enable the delivery of common stimulation strategies used in visual prosthesis research.
A beyond mean-field study of the Tavis- Cummings model
(American Institute of Physics, 2019-09) Tejera-Centeno, C.; Pérez Fernández, Pedro; Arias Carrasco, José Miguel; Universidad de Sevilla. Departamento de Física Aplicada III
A beyond mean-field study of the Tavis-Cummings (TC) model is developed. This is the simplest model for describing the interaction of a radiation field with a system composed by an array of two-level atoms. The first correction to the mean-field ground state energy and the energy gap between the ground and the first excited states are computed. For the ground-state energy our result improves the mean-field calculation, as expected. For the gap, that cannot be calculated at mean-field level, a drop down to zero is obtained at the critical point where the system undergoes a second-order quantum phase transition.
Virtual holographic recognition and its applications in medicine and other fields
(Society of Photo-Optical Instrumentation Engineers (SPIE), 2000-10) Gómez-González, Emilio; Universidad de Sevilla. Departamento de Física Aplicada III; Jeong, Tung H.; Sobotka, Werner K.
Novel digital applications developed from analog holographic recognition techniques are presented. Virtual Holographic Recognition (VHR) substitutes physical processes in matched filtering by digital equations and calculates light distribution on the observation plane. If a certain image is defined as a reference, bright light spots corresponding to coincidences between the searched element and the image under study can be numerically calculated with a high degree of accuracy. Since peak values and radial symmetry of values define the degree of coincidence with the reference, this method can be used to find elements similar-up to any degree- to a given reference in a complex image. Current applications include detection and location of malignant masses and nodules in mammograms, computed-tomography (CT) chest scans and conventional digitized radiographs. If the image taken by a digital video camera is continuously processed and the position of the peak corresponding to a reference is tracked on a screen, it allows for guiding of persons in complex environments. Application to guiding of disabled in sport courts is also described.
Fundamentos y primeras aplicaciones en España de la cirugía no invasiva mediante ultrasonidos concentrados guiados por resonancia magnética (MRgFUS)
(Sociedad Española de Ingeniería Biomédica, 2009) Gómez-González, Emilio; Universidad de Sevilla. Departamento de Física Aplicada III
En este trabajo se presentan los fundamentos y los primeros resultados de aplicación en España de la nueva tecnología de cirugía no invasiva mediante ultrasonidos concentrados guiados por resonancia magnética (Magnetic-Resonance guided Focused Ultrasound Surgery, MRgFUS). En la actualidad, esta tecnología está aprobada para el tratamiento de tumores ginecológicos (fibromas uterinos) y el tratamiento paliativo del dolor en las metástasis óseas. Se presentan los primeros resultados sobre un total de 15 fibromas tratados.
Decoherence as a Signature of an Excited State Quantum Phase Transition in Two Level Boson Systems
(American Institute of Physics, 2009) García Ramos, José Enrique; Arias Carrasco, José Miguel; Dukelsky, Jorge; Pérez Fernández, Pedro; Relaño, Armando; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Universidad de Sevilla. Departamento de Física Aplicada III
We analyze the decoherence induced on a single qubit by the interaction with a two-level boson system with critical internal dynamics. We explore how the decoherence process is affected by the presence of quantum phase transitions in the environment. We conclude that the dynamics of the qubit changes dramatically when the environment passes through a continuous excited state quantum phase transition. If the system-environment coupling energy equals the energy at which the environment has a critical behavior, the decoherence induced on the qubit is maximal and the fidelity tends to zero with finite size scaling obeying a power-law.
Connection between decoherence and excited state quantum phase transitions
(American Institute of Physics, 2009) Pérez Fernández, Pedro; Relaño, Armando; Arias Carrasco, José Miguel; Dukelsky, Jorge; García Ramos, José Enrique; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Universidad de Sevilla. Departamento de Física Aplicada III
In this work we explore the relationship between an excited state quantum phase transition (ESQPT) and the phenomenon of quantum decoherence. For this purpose, we study how the decoherence is affected by the presence of a continuous ESQPT in the environment. This one is modeled as a two level boson system described by a Lipkin Hamiltonian. We will show that the decoherence of the system is maximal when the environment undergoes a continuous ESQPT.
Decoherence and quantum quench: Their relationship with excited state quantum phase transitions
(American Institute of Physics, 2012) García Ramos, José Enrique; Arias Carrasco, José Miguel; Cejnar, Pavel; Dukelsky, Jorge; Pérez Fernández, Pedro; Relaño, Armando; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Universidad de Sevilla. Departamento de Física Aplicada III
We study the similarities and differences between the phenomena of Quantum Decoherence and Quantum Quench in presence of an Excited State Quantum Phase Transition (ESQPT). We analyze, on one hand, the decoherence induced on a single qubit by the interaction with a two-level boson system with critical internal dynamics and, on the other, we treat the quantum relaxation process that follows an abrupt quench in the control parameter of the system Hamiltonian. We explore how the Quantum Decoherence and the quantum relaxation process are affected by the presence of an ESQPT. We conclude that the dynamics of the qubit or the quantum relaxation process change dramatically when the system passes through a continuous ESQPT.
Excited state quantum phase transitions and chaos in the Dicke model
(American Institute of Physics, 2012) Pérez Fernández, Pedro; Relaño, Armando; Cejnar, Pavel; Arias Carrasco, José Miguel; Dukelsky, Jorge; García Ramos, José Enrique; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Universidad de Sevilla. Departamento de Física Aplicada III
In this contribution, the critical behavior of excited state quantum phase transitions (ESQPT's) and its relation to order and chaos in the Dicke model are studied. This model is nonintegrable. For comparison, the same problem is studied for the Jaynes-Cummings model which is, somehow, the integrable version of the Dicke model. The existence of an ESQPT is confirmed in both cases. However, in the Dicke model the signatures of criticality in excited states are blurred by the onset of quantum chaos. It is concluded that the order-to-chaos transition just below the critical energy gives us a chance to study the impact of chaotic dynamics on the signatures of ESQPTs.
A beyond mean field study of Bose gases in a double-well potential with a Feshbach resonance
(American Institute of Physics, 2012) Pérez Fernández, Pedro; Relaño, Armando; Dukelsky, Jorge; Arias Carrasco, José Miguel; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Universidad de Sevilla. Departamento de Física Aplicada III
The Bose-Hubbard model coupled to a Feshbach resonance is studied. Quantum phase transitions are analyzed within a beyond mean field framework in order to get finite size corrections to the simple mean field approach. Analytical results for the ground state energy and the first few energy gaps are presented.
Wavelet-Fourier analysis of electric signal disturbances
(ICREPQ, 2007) Montaño Asquerino, Juan-Carlos; Borrás-Talavera, María Dolores; Bravo-Rodríguez, Juan Carlos; Castilla Ibáñez, Manuel; López Ojeda, Antonio; Gutiérrez Benítez, Jaime; Universidad de Sevilla. Departamento de Ingeniería Eléctrica; Universidad de Sevilla. Departamento de Tecnología Electrónica; Universidad de Sevilla. Departamento de Física Aplicada III
The Fourier transform usually has been used in the past for analysis of stationary and periodic signals. Its interest is the knowledge of spectral components existing in a waveform; it doesn't matter the moment where they happen. However, when the time localization of the spectral components is needed, the Wavelet Transform (WT) can be used to obtain the optimal time frequency representation of the signal. In this paper, the joint wavelet-Fourier transform has been proposed for detecting, analyzing and compacting electrical disturbances. Finally, results of experiments have been included.
Nuevo sistema portátil de micro-fluorescencia de rayos X basado en óptica de policapilares para aplicaciones en Patrimonio Cultural
(Universidad Internacional de Andalucía, 2011-01) Laclavetine, Kilian; Ager Vázquez, Francisco José; Gómez-Tubio, Blanca María; Križnar, Anabelle; Moreno-Suárez, Ana Isabel; Ortega-Feliú, Inés; Respaldiza Galisteo, Miguel Ángel; Scrivano, Simona; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Universidad de Sevilla. Departamento de Física Aplicada I; Universidad de Sevilla. Departamento de Física Aplicada III; García León, Manuel; Ministerio de Ciencia e Innovación (MICIN). España; Junta de Andalucía; Universidad de Sevilla. RNM138: Física Nuclear Aplicada
Aplicaciones de técnicas nucleares de análisis no destructivo al Patrimonio Cultural
(CSIC - Instituto de Recursos Naturales y Agrobiología de Sevilla (IRNAS), 2011) Respaldiza Galisteo, Miguel Ángel; Ager Vázquez, Francisco José; Gómez-Tubio, Blanca María; Križnar, Anabelle; Laclavetine, Kilian; Moreno-Suárez, Ana Isabel; Ortega-Feliú, Inés; Scrivano, Simona; Universidad de Sevilla. Departamento de Física Aplicada III; Universidad de Sevilla. Departamento de Física Aplicada I

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