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Self-Feeder Driver for Voltage Balance in Series-Connected IGBT Associations
Guerrero-Guerrero, A.F.,Ustariz-Farfan, A.J.,Tacca, H.E.,Cano-Plata, E.A. The Korean Institute of Power Electronics 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.1
The emergence of high voltage conversion applications has resulted in a trend of using semiconductor device series associations. Series associations allow for operation at blocking voltages, which are higher than the nominal voltage for each of the semiconductor devices. The main challenge with these topologies is finding a way to guarantee the voltage balance between devices in both blocking and switching transients. Most of the methods that have been proposed to mitigate static and dynamic voltage unbalances result in increased losses within the device. This paper introduces a new series stack topology, where the voltage unbalances are reduced. This in turn, mitigates the switching losses. The proposed topology consists of a circuit that ensures the soft switching of each device, and one auxiliary circuit that allows for switching energy recovery. The principle for the topology operation is presented and experimental tests are performed for two modules. The topology performs excellently for switching transients on each of the devices. The voltage static unbalances were limited to 10%, while the activation/deactivation delay introduced by the lower module IGBT driver takes place in the dynamic unbalances. Thus, the switching losses are reduced by 40%, when compared to hard switching configurations.
Latina Romnick A.,Lantican Darlon V.,Guerrero Michelle S.,Rubico Edsel C.,Laquinta Janice F.,Caoili Barbara L. 한국응용곤충학회 2022 Journal of Asia-Pacific Entomology Vol.25 No.1
The Philippine coconut production has been greatly affected by the recent devastating infestation of Aspidiotus spp. However, identification of the outbreak species, Aspidotus rigidus, has been a challenge using morphological approaches. Molecular identification via PCR sequencing of insect barcoding genes has been implemented, but the overall process is time-consuming and costly. Thus, we developed and optimized a species-specific PCR-based molecular marker for rapid, efficient and cost-effective molecular identification of A. rigidus. The molecular marker was designed based on the sequences of the partial 28S ribosomal RNA gene from species of Aspidiotus that feed on coconut in the Philippines, A. rigidus, A. destructor and A. excisus. Multiple alignment of nucleotide se quences revealed a conserved 16-bp insertion-deletion (InDel) site common to all A. rigidus specimens identified from which the A. rigidus-specific oligonucleotide (RIG1) primer targeting an approximately 570 bp fragment size was designed. Results showed that the species-specific DNA marker technology consistently delineated laboratory-reared and field-collected A. rigidus samples from A. destructor and A. excisus. The protocol offers a rapid and reliable method for the early detection of A. rigidus infestation in high-risk areas planted with coconut in the country.
Power Absorption Measurements during NMR Experiments
N. Felix-Gonzalez,A. L. Urbano-Bojorge,C. Sanchez-L de Pablo,V. Ferro-Llanos,F. del Pozo-Guerrero,J. J. Serrano-Olmedo 한국자기학회 2014 Journal of Magnetics Vol.19 No.2
The heating produced by the absorption of radiofrequency (RF) has been considered a secondary undesirable effect during MRI procedures. In this work, we have measured the power absorbed by distilled water, glycerol and egg-albumin during NMR and non-NMR experiments. The samples are dielectric and examples of different biological materials. The samples were irradiated using the same RF pulse sequence, whilst the magnetic field strength was the variable to be changed in the experiments. The measurements show a smooth increase of the thermal power as the magnetic field grows due to the magnetoresistive effect in the copper antenna, a coil around the probe, which is directly heating the sample. However, in the cases when the magnetic field was the adequate for the NMR to take place, some anomalies in the expected thermal powers were observed: the thermal power was higher in the cases of water and glycerol, and lower in the case of albumin. An ANOVA test demonstrated that the observed differences between the measured power and the expected power are significant.
Self-Feeder Driver for Voltage Balance in Series-Connected IGBT Associations
A. F. Guerrero-Guerrero,A. J. Ustariz-Farfan,H. E. Tacca,E. A. Cano-Plata 전력전자학회 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.1
The emergence of high voltage conversion applications has resulted in a trend of using semiconductor device seriesassociations. Series associations allow for operation at blocking voltages, which are higher than the nominal voltage for each ofthe semiconductor devices. The main challenge with these topologies is finding a way to guarantee the voltage balance betweendevices in both blocking and switching transients. Most of the methods that have been proposed to mitigate static and dynamicvoltage unbalances result in increased losses within the device. This paper introduces a new series stack topology, where thevoltage unbalances are reduced. This in turn, mitigates the switching losses. The proposed topology consists of a circuit thatensures the soft switching of each device, and one auxiliary circuit that allows for switching energy recovery. The principle forthe topology operation is presented and experimental tests are performed for two modules. The topology performs excellently forswitching transients on each of the devices. The voltage static unbalances were limited to 10%, while the activation/deactivationdelay introduced by the lower module IGBT driver takes place in the dynamic unbalances. Thus, the switching losses are reducedby 40%, when compared to hard switching configurations.
A Transparent Detector for n_TOF Neutron Beam Monitoring
S. Andriamonje,M. Calviani,Y. Kadi,R. Losito,V. Vlachoudis,E. Berthoumieux,F. Gunsing,A. Giganon,Y. Giomataris,C. Guerrero,R. Sarmento,P. Schillebeeckx,P. Siegler 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
In order to obtain high precision cross-section measurements using the time-of-flight technique, it is important to know with good accuracy the neutron uence at the measuring station. The detector dedicated to these measurements should be placed upstream of the detectors used for capture and fission cross-section measurements. The main requirement is to reduce the material of the detector as much as possible, in order to minimize the perturbation of the neutron beam and, especially, the background produced by the device itself. According to these considerations, a new neutron detector equipped with a small-mass device based on MicroMegas "Micro-bulk" technology has been developed as a monitoring detector for the CERN n TOF neutron beam. A description of the different characteristics of this innovative concept of transparent detector for neutron beam monitoring is presented. The result obtained in the commissioning of the new spallation targetof the n TOF facility at CERN is shown, compared with simulations performed with the FLUKA code.
Guartazaca-Guerrero Sebastián,Rodríguez-Morales Jahir,Rizo-Téllez Salma A.,Solleiro-Villavicencio Helena,Hernández-Valencia Aldo F.,Carrillo-Ruiz José Damián,Escobedo Galileo,Méndez-García Lucía A. 한국뇌신경과학회 2021 Experimental Neurobiology Vol.30 No.3
The coronavirus family has tropism for the Central Nervous System (CNS), however, there is no solid evidence demonstrating that the neurological effects of COVID-19 result from direct viral infection or systemic inflammation. The goals of this study were to examine the cytokine profile and the presence of SARS-CoV-2 messenger ribonucleic acid (mRNA) in cerebrospinal fluids (CSF) from two patients with cerebrovascular disease and COVID-19. Although the SARS-CoV-2 mRNA was not detected in CSF of both patients, we found abnormally high levels of numerous proinflammatory cytokines and chemokines, especially IL-8 and MCP-1. Since these chemokines mediate activation and recruitment of neutrophils, monocytes, and macrophages, it is feasible that cerebrovascular disease related-neuroinflammation found in both patients results from an exacerbated inflammatory response instead of SARS-CoV-2 direct invasion to CNS. These results suggest that neuroinflammation plays a key role in cerebrovascular disease and COVID-19.
Blood-brain Barrier Damage is Pivotal for SARS-CoV-2 Infection to the Central Nervous System
Rodríguez-Morales Jahir,Guartazaca-Guerrero Sebastián,Rizo-Téllez Salma A.,Viurcos-Sanabria Rebeca,Barrón Eira Valeria,Hernández-Valencia Aldo F.,Nava Porfirio,Escobedo Galileo,Carrillo-Ruiz José Dami 한국뇌신경과학회 2022 Experimental Neurobiology Vol.31 No.4
Transsynaptic transport is the most accepted proposal to explain the SARS-CoV-2 infection of the CNS. Nevertheless, emerging evidence shows that neurons do not express the SARS-CoV-2 receptor ACE2, which highlights the importance of the blood-brain barrier (BBB) in preventing virus entry to the brain. In this study, we examine the presence of SARS-CoV-2 messenger ribonucleic acid (mRNA) and the cytokine profile in cerebrospinal fluids (CSF) from two patients with a brain tumor and COVID-19. To determine the BBB damage, we evaluate the Q- albumin index, which is an indirect parameter to assess the permeability of this structure. The Q-albumin index of the patient with an intraventricular brain tumor suggests that the BBB is undamaged, preventing the passage of SARS-CoV-2 and pro-inflammatory molecules. The development of brain tumors that disrupt the BBB (measured by the Q-albumin index), in this case, a petroclival meningioma (Case 1), allows the free passage of the SARS-CoV-2 virus and probably lets the free transit of pro-inflammatory molecules to the CNS, which leads to a possible activation of the microglia (astrogliosis) and an exacerbated immune response represented by IL-13, IFN-γ, and IL-2 trying to inhibit both the infection and the carcinogenic process.
Past, Present and Future of the n_TOF Facility at CERN
E. Chiaveri,S. Andriamonje,M. Calviani,V. Vlachoudis,M. Brugger,P. Cennini,F. Cerutti,M. Chin,A. Ferrari,Y. Kadi,E. Lebbos,R. Losito,C. Guerrero,V. Becares,D. Cano-Ott,M. Fernandez-Ordonez,E. Gonzalez 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
The n_TOF spallation neutron facility is operating at CERN since 2001. Neutrons are produced with a very wide energy range, from thermal up to 1 GeV and with a very high instantaneous flux (10^5n/cm^2/pulse at 200 m from target) thanks to the high intensity (7 × 10^(12) protons/pulse) and low repetition rate of the Proton Synchrotron (PS) which is delivering protons to a lead spallation target. The experimental area is located at 200 m from the target, resulting in a very good energy resolution and beam quality thanks to the adoption of an optimal collimation system. At the end of 2008 the n_TOF facility has resumed operation after a halt of 3 years due to technical issues. This contribution will outline the main physics results obtained by the facility since its inception in 1999, and show the importance of the measured nuclear data in the field of Nuclear Astrophysics and Nuclear Technology. Then it will present the future perspectives of the facility, aiming mainly in the direction of measuring highly radioactive samples, for which the facility has unique capabilities, with a lower background.