Artículos (Física Aplicada III)

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Compositional and microstructural study of joining methods in archaeological gold objects
(John Wiley and Sons Ltd, 2017-03) Scrivano, Simona; Gómez-Tubio, Blanca María; Ortega-Feliú, Inés; Ager Vázquez, Francisco José; Paúl Escolano, Antonio; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Universidad de Sevilla. Departamento de Física Aplicada III; Universidad de Sevilla. Departamento de Física Aplicada I; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Ministerio de Economía y Competitividad (MINECO). España
This work arises in response to the need to understand the production techniques of pre-roman gold jewels, starting from the systematic characterization of the different methods of metal joining used in antiquity to produce these objects. To meet this requirement, different procedures used in antiquity were reproduced by means of experimental archaeology. These models correspond to three metal-joining methods reported by ancient recipes: solid-state diffusion with copper salt, brazing and autogenous welding. These techniques were studied by different analytical methods in order to characterize them at both compositional and microstructural level (SEM-EDS, metallography, μ-XRF and μ-PIXE). The results obtained show that the solid-state diffusion bonding with copper salt presents a crystal hexagonal structure without phase changes in the joining point, where only a variation in the grain size is observed. At the compositional level, this soldering method is characterized by a local increase in copper concentration and a small decrease in gold content. In contrast, brazing shows a dendritic-porous structure due to the superposition of the soldering alloy and the crystal structure of the original foils. Besides, the compositional analysis revealed an increment of silver and copper concentrations and a simultaneous reduction of gold concentration. Finally, in the autogenous welding, no changes at the microstructural and compositional levels were observed. The results obtained have also demonstrated the usefulness of a portable μ-XRF system for the in-situ characterization of ancient jewels.
Combining XRF and GRT for the analysis of ancient silver coins
(Elsevier, 2016-05) Ager Vázquez, Francisco José; Gómez-Tubio, Blanca María; Paúl Escolano, Antonio; Gómez-Morón, A.; Scrivano, Simona; Ortega-Feliú, Inés; Respaldiza Galisteo, Miguel Ángel; 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; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Ministerio de Economía y Competitividad (MINECO). España
Archaeological silver-copper alloys are usually affected by silver enrichment of the near surface layers, either intentional or fortuitous. In previous studies we have shown that surface composition of archaeological bronzes and leaded copper coins obtained by XRF can be corrected by means of gamma-ray transmission (GRT) to obtain the bulk composition. In the present work, we have studied the applicability of this method to silver-copper alloys and established the most suitable conditions for the GRT correction calculation. The analysis of the microstructure of the core and the corrosion layers of a set of silver roman coins shows that copper could be leached from the surface during corrosion and cleaning treatments, resulting in an apparent silver surface enrichment. After the correction calculations by GRT method, the concentrations of the major elements, Ag and Cu, were found to be in good agreement with the bulk composition obtained by direct analysis of the cut cross-sections of the coins. The GRT method shows to be a useful tool to study metal artefacts having a surface composition modified by corrosion or cleaning treatments.
Wigner representation for entanglement swapping using parametric down conversion: the role of vacuum fluctuations in teleportation
(Taylor & Francis, 2015-03-12) Casado Rodríguez, Alberto; Guerra, Santiago; Plácido, José; Universidad de Sevilla. Departamento de Física Aplicada III
We apply the Wigner formalism of quantum optics in the Heisenberg picture to study the role of the zeropoint field fluctuations in entanglement swapping produced via parametric down conversion. It is shown that the generation of mode entanglement between two initially non-interacting photons is related to the quadruple correlation properties of the electromagnetic field, through the stochastic properties of the vacuum. The relationship between the process of transferring entanglement and the different zeropoint inputs at the non-linear crystal and the Bell-state analyser is emphasized.
Spectrum of the parametric down converted radiation calculated in the Wigner function formalism
(Springer, 2001-01) Casado Rodríguez, Alberto; Marshall, Trevor W.; Risco, Ramón; Santos, Emilio; Universidad de Sevilla. Departamento de Física Aplicada III
We continue the study of parametric down conversion within the framework of the Wigner representation, by using a Maxwellian approach developed in a recent paper [A. Casado et al., Eur. Phys. J. D 11, 465 (2000)]. This gives a mechanism, inside the crystal, for the production of the down-converted radiation. We obtain the electric field to second order in the coupling constant by using the Green's function method, and compare our treatment with the standard Hamiltonian approach. The spectrum of the down-converted radiation is calculated as a function of the parameters of the nonlinear crystal (in particular the length) and the radius of the pumping beam.
Wigner representation for experiments on quantum cryptography using two-photon polarization entanglement produced in parametric down-conversion
(IOP Publishing, 2008-02-28) Casado Rodríguez, Alberto; Guerra, Santiago; Plácido, José; Universidad de Sevilla. Departamento de Física Aplicada III
In this paper, the theory of parametric down-conversion in the Wigner representation is applied to Ekert's quantum cryptography protocol. We analyse the relation between two-photon entanglement and (non-secure) quantum key distribution within the Wigner framework in the Heisenberg picture. Experiments using two-qubit polarization entanglement generated in nonlinear crystals are analysed in this formalism, along with the effects of eavesdropping attacks in the case of projective measurements.
Rome teleportation experiment analysed in the Wigner representation: the role of the zeropoint fluctuations in complete one-photon polarization-momentum Bell-state analysis
(Taylor & Francis, 2018-10-07) Casado Rodríguez, Alberto; Guerra, Santiago; Plácido, José; Universidad de Sevilla. Departamento de Física Aplicada III
The Wigner representation of parametric down conversion in the Heisenberg picture is applied to the study of the Rome teleportation experiment. We investigate the physical meaning of the zeropoint inputs at the different areas of the experimental set-up. In particular, we establish a quantitative relationship between the zeropoint sets of modes that are needed for the preparation of the quantum state to be teleported, the idle channels inside the one-photon polarization-momentum Bell-state analyser, and the possibility of performing teleportation of a polarization state with certainty.
Wigner representation for polarization-momentum hyperentanglement generated in parametric down-conversion, and its application to complete Bell-state measurement
(Springer, 2014-11-06) Casado Rodríguez, Alberto; Guerra, Santiago; Plácido, José; Universidad de Sevilla. Departamento de Física Aplicada III
We apply the Wigner function formalism to the study of two-photon polarization-momentum hyperentanglement generated in parametric down-conversion. It is shown that the consideration of a higher number of degrees of freedom is directly related to the extraction of additional uncorrelated sets of zeropoint modes at the source. We present a general expression for the description of the quantum correlations corresponding to the sixteen Bell base states, in terms of four beams whose amplitudes are correlated through the stochastic properties of the zeropoint field. A detailed analysis of the two experiments on complete Bell-state measurement included in [Walborn et al., Phys. Rev. A 68, 042313 (2003)] is made, emphasizing the role of the zeropoint field. Finally, we investigate the relationship between the zeropoint inputs at the source and the analysers, and the limits on optimal Bell-state measurement.
Palladium analysis in gold items from Punic jewellery (Cádiz, Spain)
(Elsevier, 2020-02) Ortega Feliu, Inés; Gómez Tubio, Ana María; Scrivano, Simona; Ager Vázquez, Francisco José; Bandera Romero, María Luisa de la; Respaldiza Galisteo, Miguel Ángel; Universidad de Sevilla. Departamento de Física Aplicada III; Universidad de Sevilla. Departamento de Física Aplicada I; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Ministerio de Ciencia e Innovación (MICIN). España; Universidad de Sevilla; Universidad de Sevilla. RNM138: Física Nuclear Aplicada
Some years ago a group of jewels from the Museum of Cádiz (South Spain) was analysed by micro-PIXE (Particle Induced X-ray Emission) at Centro Nacional de Aceleradores (Sevilla). During this work two similar spiral earrings happened to have significant amounts of palladium in their composition, up to 0.7 wt%, and some hypotheses about the provenance of this palladium-bearing gold were exposed. Many similar gold earrings from the same location and time are kept in the museum, some of them permanently exhibited in the showcases. Now, by means of a portable X-ray spectrometer device, especially designed for the analysis of gold jewels, a second campaign has been accomplished to study the rest of the jewels kept at the museum. This time the equipment was moved to the museum instead of taking the gold items to the laboratory, facilitating the analysis of the samples in the showcases and reducing the costs. A total of 94 jewels have been studied and 24 of them contained palladium up to 1.1 wt%. Copper content was below 2.5 wt% in most of the cases. X Ray Fluorescence technique was employed for this study. A filter of 20 μm of Zn was used in the detector to enhance the detection of palladium, and other potential platinum group elements, by absorbing the Au-Lα emission line. The effects of this method in the quantification was also compared in this work, finding higher uncertainties with the use of the filter, but demonstrating the convenience of its use to discriminate the Pd-Kα line from the sum peaks of the very intense gold lines.
Fluoride exposure duringintrauterine and lactation periods promotes changes in the offspring rats' alveolar bone
(Elsevier, 2022-11) Ferreira, Maria Karolina Martins; Souza-Monteiro, Deiweson; Bittencourt, Leonardo Oliveira; Matos-Sousa, José Mário; Chemelo, Victória Santos; Santos, Vinicius Ruan Neves; Nunes, Paula Beatriz Oliveira; Balbinot, Gabriela de Souza; Prado, Alejandro Ferraz; Collares, Fabricio Mezzomo; Ager Vázquez, Francisco José; Ortega Feliu, Inés; Respaldiza Galisteo, Miguel Ángel; Pessanha, Sofia; Lima, Rafael Rodrigues; Universidad de Sevilla. Departamento de Física Aplicada I; Universidad de Sevilla. Departamento de Física Aplicada III; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Universidad de Sevilla. RNM138: Física Nuclear Aplicada
The importance of fluoride (F) for oral health is well established in the literature. However, evidence suggests that excessive exposure to this mineral is associated with adverse effects at different life stages and may affect many biological systems, especially mineralized tissues. The purpose of this study was to investigate the effects of F exposure during pregnancy and breastfeeding on the alveolar bone of the offspring since the alveolar bone is one of the supporting components of the dental elements. For this, the progeny rats were divided into three groups: control, 10 mg F/L, and 50 mg F/L for 42 (gestational and lactation periods). Analysis of the quantification of F levels in the alveolar bone by particle-induced gamma emission; Raman spectroscopy to investigate the physicochemical aspects and mineral components; computed microtomography to evaluate the alveolar bone microstructure and analyses were performed to evaluate osteocyte density and collagen quantification using polarized light microscopy. The results showed an increase in F levels in the alveolar bone, promoted changes in the chemical components in the bone of the 50 mg F/L animals (p < 0.001), and had repercussions on the microstructure of the alveolar bone, evidenced in the 10 mg F/L and 50 mg F/L groups (p < 0.001). Furthermore, F was able to modulate the content of organic bone matrix, mainly collagen; thus, this damage possibly reduced the amount of bone tissue and consequently increased the root exposure area of the exposed groups in comparison to a control group (p < 0.001). Our findings reveal that Fcan modulate the physicochemical and microstructural dimensions and reduction of alveolar bone height, increasing the exposed root region of the offspring during the prenatal and postnatal period. These findings suggest that F can modulate alveolar bone mechanical strength and force dissipation functionality.
Relaxation time as a control parameter for exploring dynamical phase diagrams
(2023-11) Corps, Ángel L.; Pérez Fernández, Pedro; Relaño, Armando; Universidad de Sevilla. Departamento de Física Aplicada III; Ministerio de Ciencia e Innovación (MICIN). España; Agencia Estatal de Investigación. España; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER); Consejería de Conocimiento, Investigación y Universidad, Junta de Andalucía; Universidad de Sevilla. FQM160: Física Nuclear Básica
We explore a full dynamical phase diagram by means of a double quench protocol that depends on a relaxation time as the only control parameter. The protocol comprises two fixed quenches and an intermediate relaxation time that determines the phase in which the quantum state is placed after the final quench. We apply it to an anharmonic Lipkin-Meshkov-Glick model. We show that its two excited-state quantum phase transitions split the spectrum into three different phases: two symmetry-breaking ones, characterized by different constants of motion, and a disordered phase. As a consequence, our protocol allows us to explore all the dynamical phase transitions arising from two kinds of quenches: the typical one, leading the system from a symmetry-breaking to a disordered phase, and another one in which the system transitions between two different symmetry-breaking phases. We characterize all of them in terms of the constants of motion appearing in all three phases of the model.
The use of high-intensity focused ultrasound for the rewarming of cryopreserved biological material
(IEEE, 2021) Olmo Fernández, Alberto; Barroso, Pablo; Barroso, Fátima; Risco, Ramón; Universidad de Sevilla. Departamento de Tecnología Electrónica; Universidad de Sevilla. Departamento de Física Aplicada III
High-intensity focused ultrasound (HIFU) has been used in differentmedical applications in the last years. In this work, we present for the first time the use of HIFU in the field of cryopreservation, the preservation of biological material at low temperatures. An HIFU system has been designed with the objective of achieving a fast and uniform rewarming in organs, key to overcome the critical problem of devitrification. The finite-element simulations have been carried out using COMSOL Multiphysics software. An array of 26 ultrasonic transducers was simulated, achieving an HIFU focal area in the order of magnitude of a model organ (ovary). A parametric study of the warming rate and temperature gradients, as a function of the frequency and power of ultrasonicwaves,was performed.An optimal value for these parameters was found. The results validate the appropriateness of the technique,which is of utmost importance for the future creation of cryopreserved organ banks.
Overview of the EUROfusion Tokamak Exploitation programme in support of ITER and DEMO
(Institute of Physics Publishing, 2024-11-01) Jet Contributors; Ayllón Guerola, Juan Manuel; Cruz Zabala, Diego José; Domínguez Palacios Durán, Jesús José; Doyle, Scott James; Galdón Quiroga, Joaquín; García Muñoz, Manuel; Hidalgo Salaverri, Javier; Mancini, Alessio; McKay, Kiera Anne; Oyola Domínguez, Pablo; Rivero Rodríguez, Juan Francisco; Romero Madrid, Carlos Francisco; Rueda Rueda, José; Toscano Jiménez, Manuel; Van Vuuren, Anton Jansen; Velarde Gallardo, Lina; Viezzer, Eleonora; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Universidad de Sevilla. Departamento de Física Aplicada III; Universidad de Sevilla. Departamento de Ingeniería Energética; Universidad de Sevilla. Departamento de Ingeniería Mecánica y de Fabricación; EUROfusion Consortium
Within the 9th European Framework programme, since 2021 EUROfusion is operating five tokamaks under the auspices of a single Task Force called ‘Tokamak Exploitation’. The goal is to benefit from the complementary capabilities of each machine in a coordinated way and help in developing a scientific output scalable to future largre machines. The programme of this Task Force ensures that ASDEX Upgrade, MAST-U, TCV, WEST and JET (since 2022) work together to achieve the objectives of Missions 1 and 2 of the EUROfusion Roadmap: i) demonstrate plasma scenarios that increase the success margin of ITER and satisfy the requirements of DEMO and, ii) demonstrate an integrated approach that can handle the large power leaving ITER and DEMO plasmas. The Tokamak Exploitation task force has therefore organized experiments on these two missions with the goal to strengthen the physics and operational basis for the ITER baseline scenario and for exploiting the recent plasma exhaust enhancements in all four devices (PEX: Plasma EXhaust) for exploring the solution for handling heat and particle exhaust in ITER and develop the conceptual solutions for DEMO. The ITER Baseline scenario has been developed in a similar way in ASDEX Upgrade, TCV and JET. Key risks for ITER such as disruptions and run-aways have been also investigated in TCV, ASDEX Upgrade and JET. Experiments have explored successfully different divertor configurations (standard, super-X, snowflakes) in MAST-U and TCV and studied tungsten melting in WEST and ASDEX Upgrade. The input from the smaller devices to JET has also been proven successful to set-up novel control schemes on disruption avoidance and detachment.
An arbitrary waveform neurostimulator for preclinical studies: design and verification
(Springer, 2024-12-12) Guzmán-Miranda, Hipólito; Barriga-Rivera, Alejandro; Universidad de Sevilla. Departamento de Física Aplicada III; Universidad de Sevilla. Departamento de Ingeniería Electrónica; Ministerio de Ciencia, Innovación y Universidades (MICINN). España; Agencia Estatal de Investigación. España; European Union (UE)
Neural electrostimulation has enabled different therapies to treat a number of health problems. For example, the cochlear implant allows for recovering the hearing function and deep brain electrostimulation has been proved to reduce tremor in Parkinson’s disease. Other approaches such as retinal prostheses are progressing rapidly, as researchers continue to investigate new strategies to activate targeted neurons more precisely. The use of arbitrary current waveform electrosimulation is a promising technique that allows exploiting the differences that exist among different neural types to enable preferential activation. This work presents a two-channel arbitrary waveform neurostimulator designed for visual prosthetics research. A field programmable gate array (FPGA) was employed to control and generate voltage waveforms via digital-to-analog converters. Voltage waveforms were then electrically isolated and converted to current waveforms using a modified Howland amplifier. Shorting of the electrodes was provided using multiplexers. The FPGA gateware was verified to a high level of confidence using a transaction-level modeled testbench, achieving a line coverage of 91.4%. The complete system was tested in saline using silver electrodes with diameters from 200 to 1000 µm. The bandwidth obtained was 30 kHz with voltage compliance ± 15 V. The neurostimulator can be easily scaled up using the provided in/out trigger ports and adapted to other applications with minor modifications.
Structural brain preservation: a potential bridge to future medical technologies
(Frontiers Media, 2024-10) McKenzie, Andrew T.; Zeleznikow-Johnston, Ariel; Sparks, Jordan S.; Nnadi, Oge; Smart, John; Wiley, Keith; Risco, Ramón; Universidad de Sevilla. Departamento de Física Aplicada III; Universidad de Sevilla. BIO289: Cryobiotech: Criopreservación de Tejidos y Órganos
When faced with the prospect of death, some people would prefer a form of long-term preservation that may allow them to be restored to healthy life in the future, if technology ever develops to the point that this is feasible and humane. Some believe that we may have the capacity to perform this type of experimental preservation today—although it has never been proven—using contemporary methods to preserve the structure of the brain. The idea is that the morphomolecular organization of the brain encodes the information required for psychological properties such as personality and long-term memories. If these structures in the brain can be maintained intact over time, this could theoretically provide a bridge to access restorative technologies in the future. To consider this hypothesis, we first describe possible metrics that can be used to assess structural brain preservation quality. We next explore several possible methods to preserve structural information in the brain, including the traditional cryonics method of cryopreservation, as well as aldehyde-stabilized cryopreservation and fluid preservation. We focus in-depth on fluid preservation, which relies on aldehyde fixation to induce chemical gel formation in a wide set of biomolecules and appears to be a cost-effective method. We describe two theoretical recovery technologies, alongside several of the ethical and legal complexities of brain preservation, all of which will require a prudent approach. We believe contemporary structural brain preservation methods have a non-negligible chance of allowing successful restoration in the future and that this deserves serious research efforts by the scientific community.
Controlling Equilibrium Vitrification Using Electrical Impedance Spectroscopy
(IEEE, 2024) Alcalá Guerrero, Enrique; Olmo Fernández, Alberto; Pérez García, Pablo; Fernández Scagliusi, Santiago Joaquín; Encabo, Laura; Risco, Ramón; Universidad de Sevilla. Departamento de Tecnología Electrónica; Universidad de Sevilla. Departamento de Farmacia y Tecnología Farmacéutica; Universidad de Sevilla. Departamento de Física Aplicada III; Universidad de Sevilla. TIC178: Diseño y Test de Circuitos Integrados de Señal Mixta; Universidad de Sevilla. CTS480: Investigación y Desarrollo Tecnológico en Nanomedicina; Universidad de Sevilla. BIO289: Cryobiotech: Criopreservación de Tejidos y Órganos
Currently, there is an important need for efficient, affordable, and real-time cryoprotectant monitoring methods in biobanking and organ preservation applications. The precise sensing and control of temperature and cryoprotectant concentration is of utmost importance for the successful implementation of cryopreservation protocols and the design of automated devices for this purpose, especially in liquidus tracking (LT). Electrical impedance spectroscopy (EIS) is proposed and studied here as a noninvasive and affordable method for the real-time monitoring of cryoprotectant concentration. In this work, EIS has been used to provide a complete characterization of the most frequently used cryoprotectants (dimethyl sulfoxide and ethylene glycol), at different concentrations in phosphate buffer saline (from 0% to 90% v/v) and different temperatures (from -40 °C, -17 °C, and -10 °C to 20 °C). Our results show that EIS can successfully control cryoprotectant perfusion by measuring impedance magnitude. An increase in impedance magnitude and a leftward phase shift in the frequency response are observed when cryoprotectant concentration is increased. A decrease on the conductivity of the bulk solution is obtained when temperatures are lowered. These results provide a direct relationship between the cryoprotectant concentration and electrical impedance, thus closing the control loop in perfusion control. Measuring impedance magnitude at near-zero phase angle, corrected against temperature, can verify the proper addition of cryoprotectants in the state-of-the-art cryoprotection techniques.
MHD stability analysis against pressure and current-driven modes in the SMall Aspect Ratio Tokamak
(IOP Publishing, 2024-10-08) Domínguez Palacios Durán, Jesús José; García Muñoz, Manuel; Toscano Jiménez, Manuel; Liu, Y. Q.; Mancini, Alessio; Cruz Zabala, Diego José; Berkery, J. W.; Labbate, J. A.; Viezzer, Eleonora; Oyola Domínguez, Pablo; Futatani, S.; Universidad de Sevilla. Departamento de Física Aplicada III; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Ministerio de Ciencia e Innovación (MICIN). España; European Union (UE); Junta de Andalucía
Linear magnetohydrodynamic (MHD) simulations for the SMall Aspect Ratio Tokamak (SMART) have been carried out for the first time, for both positive (PT) and negative triangularity (NT) shaped plasmas using the MARS-F code. The MHD stability of projected SMART plasmas against internal kinks, infernal modes and edge peeling-ballooning modes have been analyzed for a wide range of realistic equilibria. A stabilization of internal kinks and infernal modes is observed when increasing the safety factor profile and reducing plasma beta. PT shaped plasmas are more stable against both internal kinks and infernal modes than their counterpart NT shaped plasmas. Toroidal flows have little impact on the MHD stability of the internal kinks, but they have a strong stabilizing effect on infernal modes, which can be further mitigated in NT shaped plasmas. The MHD stability of peeling-ballooning modes is reduced in NT shaped plasmas, as observed in conventional tokamaks.
Characterization of Castellani nineteenth-century gold jewellery by in situ micro-XRF spectroscopy
(Nature Research, 2022) Manca, Rosarosa; Scrivano, Simona; Manfriani,Chiara; Ager Vázquez, Francisco José; Ortega-Feliú, Inés; Ferreti, Marco; Respaldiza Galisteo, Miguel Ángel; Benvenuti, Marco; Universidad de Sevilla. Departamento de Física Aplicada I; Universidad de Sevilla. Departamento de Física Aplicada III; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear
The material characterization of nineteenth-century artifacts is of great interest, due both to the breakthrough technological advances and to the unprecedented spread of forgeries of antiquities which took place in that period. However, this type of artifacts has been largely overlooked in the past. In this paper we present the compositional analysis of gold jewels by the Castellani, one of the most important families of goldsmiths in nineteenth-century Europe. The use of a portable micro-XRF spectrometer, specifically developed for jewellery analysis at the Centro Nacional de Aceleradores (Seville), allowed us to analyse, in a completely non-invasive way, the alloys, joining techniques and surface treatments of the jewels of the Castellani collection at the National Etruscan Museum of Villa Giulia in Rome. The addition to the spectrometer of a second X-rays detector with a zinc filter allowed us to check the possible presence of low amounts of cadmium, a metal added to gold soldering only from the nineteenth century and often used in authenticity studies. Moreover, the relative intensities of the Au X-ray lines were studied in order to check non-invasively the presence of surface enrichments in gold.
Winding Optimization for Reducing Parasitic Capacitances of Common-Mode Chokes
(IEEE, 2024-05) Ruiz Morales, Pablo; Ojeda Rodríguez, Álvaro; Bernal Méndez, Joaquín; Martín Prats, María de los Ángeles; Universidad de Sevilla. Departamento de Física Aplicada III; Universidad de Sevilla. Departamento de Ingeniería Electrónica; Ministerio de Ciencia, Innovación y Universidades. España; Agencia Estatal de Investigación. España; European Union (UE); Universidad de Sevilla. TIC112: Microondas
Parasitic capacitances typically undermine the filtering performance of common mode chokes at high frequencies. This work demonstrates that these parasitic capacitances can be reduced by using a wise winding strategy that depends on the physical properties of the core material. Due to its practical interest, we specifically focus on single-layer common mode chokes wounded on NiZn or MnZn ferrite cores. Based on a physical model that enables the identification of parameters influencing the electrical coupling between the turns of the coils of the choke, the hypothesis proposed is that the optimal winding configuration depends on the core material, differing for NiZn and MnZn cores. To verify this hypothesis and to assess improvements actually achieved by optimum winding strategies, an accurate high-frequency model of the common mode choke along with an efficient characterization technique are used to numerically estimate the parasitics of common-mode chokes with different core materials and winding configurations. In addition, the filtering performance of these common mode chokes have been measured and compared.
Analyzing and Characterizing Common Mode Chokes for Three Phase Systems
(IEEE, 2024-05) Ojeda Rodríguez, Álvaro; Domínguez-Palacios, Carlos; Bernal Méndez, Joaquín; Martín Prats, María de los Ángeles; Universidad de Sevilla. Departamento de Física Aplicada III; Universidad de Sevilla. Departamento de Ingeniería Electrónica; Ministerio de Ciencia, Innovación y Universidades. España; Agencia Estatal de Investigación. España; European Union (UE); Universidad de Sevilla. TIC112: Microondas
Common mode chokes (CMCs) are widely employed to reduce common mode emissions of three phase systems. This work presents an advanced technique for analyzing and characterizing CMCs with three or four windings. The central idea of the method is a modal analysis of the choke, where the modes are based on the modes of the noise signal transmitted by the three-phase line. These modes are defined following the criterion of its suitability from the perspective of electromagnetic interference control. This modal analysis is used to propose a circuit model of the choke that accounts for the impact of high-frequency parasitic effects and, at the same time, allows for a straightforward parameter identification. This parameter identification is achieved by using a characterization technique that makes use of measurements of the response of the CMC in simple connections, whose suitability is justified thanks to the ability of the modal analysis to provide analytical and easy-to-interpret expressions of these connections. This makes also possible to predict and quantify mode conversions caused by the device in the three-phases line. The accuracy of the obtained circuit model within a wide frequency range has been demonstrated by comparing measurements with calculated responses for several three- and four-wires CMCs.
Digital-analog quantum computation with arbitrary two-body Hamiltonians
(American Physical Society, 2024-03-14) García de Andoin, Mikel; Sáiz Castillo, Álvaro; Pérez Fernández, Pedro; Lamata Manuel, Lucas; Oregi, Izaskun; Sanz, Mikel; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Universidad de Sevilla. Departamento de Física Aplicada III; Ministerio de Ciencia e Innovación (MICIN). España; Agencia Estatal de Investigación. España; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER); Junta de Andalucía; Ministerio de Economía y Competitividad (MINECO). España
Digital-analog quantum computing is a computational paradigm which employs an analog Hamiltonian resource together with single-qubit gates to reach universality. Here, we design a new scheme which employs an arbitrary two-body source Hamiltonian, extending the experimental applicability of this computational paradigm to most quantum platforms. We show that the simulation of an arbitrary two-body target Hamiltonian of n qubits requires O(n2) analog blocks with guaranteed positive times, providing a polynomial advantage compared to the previous scheme. Additionally, we propose a classical strategy which combines a Bayesian optimization with a gradient descent method, improving the performance by ∼55% for small systems measured in the Frobenius norm.

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