Publicaciones académicas

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Esta colección incluye artículos de profesores de la Pontificia Universidad Católica de Chile, publicados en revistas nacionales y extranjeras.

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450 d of Type II SN 2013ej in optical and near-infrared
(OXFORD UNIV PRESS, 2016) Yuan, Fang; Jerkstrand, A.; Valenti, S.; Sollerman, J.; Seitenzahl, I. R.; Pastorello, A.; Schulze, S.; Chen, T. W.; Childress, M. J.; Fraser, M.; Fremling, C.; Kotak, R.; Ruiter, A. J.; Schmidt, B. P.; Smartt, S. J.; Taddia, F.; Terreran, G.; Tucker, B. E.; Barbarino, C.; Benetti, S.; Elias Rosa, N.; Gal Yam, A.; Howell, D. A.; Inserra, C.; Kankare, E.; Lee, M. Y.; Li, K. L.; Maguire, K.; Margheim, S.; Mehner, A.; Ochner, P.; Sullivan, M.; Tomasella, L.; Young, D. R.
We present optical and near-infrared photometric and spectroscopic observations of SN 2013ej, in galaxy M74, from 1 to 450 d after the explosion. SN 2013ej is a hydrogen-rich supernova, classified as a Type IIL due to its relatively fast decline following the initial peak. It has a relatively high peak luminosity (absolute magnitude M-V =-17.6) but a small 56Ni production of similar to 0.023 M-circle dot. Its photospheric evolution is similar to other Type II SNe, with shallow absorption in the H a profile typical for a Type IIL. During transition to the radioactive decay tail at similar to 100 d, we find the SN to grow bluer in B - V colour, in contrast to some other Type II supernovae. At late times, the bolometric light curve declined faster than expected from Co-56 decay and we observed unusually broad and asymmetric nebular emission lines. Based on comparison of nebular emission lines most sensitive to the progenitor core mass, we find our observations are best matched to synthesized spectral models with a M-ZAMS = 12-15 M-circle dot progenitor. The derived mass range is similar to but not higher than the mass estimated for Type IIP progenitors. This is against the idea that Type IIL are from more massive stars. Observations are consistent with the SN having a progenitor with a relatively low-mass envelope.
8-hydroxyquinolinato lithium nano-interlayer in tandem OPV devices
(SPRINGER, 2022) Neculqueo, Gloria; Angel, Felipe A.
8-hydroxyquinolinato lithium (Liq) nano-interlayer was evaluated as part of the interconnection layer (ICL) system Liq|Al|MoO3 to produce tandem organic photovoltaic (OPV) devices. First, the thickness dependence of Liq on the performance of single-stack OPV devices was studied, along with its stability by exposing the devices to different degradation conditions. The results confirmed the benefits of incorporating Liq, providing even further stability, particularly to devices exposed to air. Then, symmetrical tandem OPV devices were prepared by optimizing the thickness of the Al interlayer to obtain an efficient ICL. Although limited power conversion efficiencies were obtained due to the symmetry of the device architecture, electrical, optical, and lifetime measurements confirmed Liq|Al|MoO3 as a suitable ICL to achieve tandem OPV devices.
A Compound Real Option Approach for Determining the Optimal Investment Path for RPV-Storage Systems
(The Energy Journal, 2022) Hassi, Benjamín A.; Reyes Torres, Tomas Hernan; Sauma Santis, Enzo Enrique
The use of residential Photovoltaic-Storage systems may produce large benefits to owners and has expanded rapidly in recent years. Nonetheless, large uncertainties regarding the profitability of these systems make it necessary to incorporate flexibilities in their economic evaluations. This paper offers a new method to evaluate the compound flexibility of both the option of delaying investments and the option of further expanding the capacity of solar photovoltaic modules and batteries during the investment horizon. Flexibility is modeled as a compound real option, whose value is computed using a novel method that we call Compound Least Squares Monte Carlo (CLSM). The model is applied to the investment decisions associated to a residential Photovoltaic-Storage system. Results suggest that investors should use the proposed CLSM method in the economic valuation of multi-stage projects, since considering only a single flexibility could promote sub-optimal decisions. Moreover, in our case study, we show that it is optimal to break the investment down into two steps or more in 36% of future scenarios, on average.
A DESGW Search for the Electromagnetic Counterpart to the LIGO/Virgo Gravitational-wave Binary Neutron Star Merger Candidate S190510g
(2020) Garcia, A.; Morgan, R.; Herner, K.; Palmese, A.; Soares Santos, M.; Annis, J.; Brout, D.; Vivas, A. K.; Drlica Wagner, A.; Quirola Vásquez, Jonathan Alexander; Santana Silva, L.; Tucker, D. L.; Allam, S.; Wiesner, M.; Garcia Bellido, J.; Gill, M. S. S.; Sako, M.; Kessler, R.; Davis, T. M.; Scolnic, D.; Casares, J.; Chen, H.; Conselice, C.; Cooke, J.; Doctor, Z.; Foley, R. J.; Horvath, J.; Howell, D. A.; Kilpatrick, C. D.; Lidman, C.; Olivares, E. F.; Paz Chinchon, F.; Pineda G., J.; Rest, A.; Sherman, N.; Abbott, T. M. C.; Aguena, M.; Avila, S.; Bertin, E.; Bhargava, S.; Brooks, D.; Burke, D. L.; Rosell, A. C.; Kind, M. C.; Carretero, J.; Costanzi, M.; da Costa, L. N.; Desai, S.; Diehl, H. T.; Dietrich, J. P.
A DFT/TDDFT Study of Porphyrazines and Phthalocyanine Oxo-Titanium Derivatives as Potential Dyes in Solar Cells
(2011) Zarate, Ximena; Schott Verdugo, Eduardo Enrique; Arratia Pérez, Ramiro
A fault protection scheme for series active power filters
(IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 1999) Moran, LA; Pastorini, I; Dixon, J; Wallace, R
A protection scheme for series active power filters is presented and analyzed in this paper. The proposed scheme protects series active power filters when short-circuit faults occur in the power distribution system. The principal protection element is a varistor, which is connected in parallel to the secondary of each current transformer. The current transformers used to connect in series the active power filter present a low-magnetic saturation characteristic increasing current ratio error when high currents circulate through the primary winding, thus generating lower secondary currents. In this way, the power dissipated by the varistors is significantly reduced. After a few cycles of short-circuit currents flowing through the varistor, the gating signals applied to the active power filter switches are removed and the pulsewidth-modulation (PWM) voltage-source inverter (VSI) is short circuited through a couple of antiparallel thyristors.
A new mathematic algorithm to analyze power distribution systems with active compensation and nonlinear loads
(IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2008) Mahomar, Jose; Moran, Luis; Guzman, Johan; Dixon, Juan
This paper presents a new procedure to analyze power distribution systems that energize nonlinear loads. The algorithm uses the singular values of the transfer matrix that relates the output variables and the system perturbation. The algorithm is especially developed to analyze the compensation performance of shunt and series active power filters. The algorithm is proved by simulation in a multibus industrial power distribution system and programmed in Matlab.
A NEW POPULATION OF ULTRA-LONG DURATION GAMMA-RAY BURSTS
(IOP PUBLISHING LTD, 2014) Levan, A. J.; Tanvir, N. R.; Starling, R. L. C.; Wiersema, K.; Page, K. L.; Perley, D. A.; Schulze, S.; Wynn, G. A.; Chornock, R.; Hjorth, J.; Cenko, S. B.; Fruchter, A. S.; O'Brien, P. T.; Brown, G. C.; Tunnicliffe, R. L.; Malesani, D.; Jakobsson, P.; Watson, D.; Berger, E.; Bersier, D.; Cobb, B. E.; Covino, S.; Cucchiara, A.; de Ugarte Postigo, A.; Fox, D. B.; Gal Yam, A.; Goldoni, P.; Gorosabel, J.; Kaper, L.; Kruehler, T.; Karjalainen, R.; Osborne, J. P.; Pian, E.; Sanchez Ramirez, R.; Schmidt, B.; Skillen, I.; Tagliaferri, G.; Thoene, C.; Vaduvescu, O.; Wijers, R. A. M. J.; Zauderer, B. A.
We present comprehensive multiwavelength observations of three gamma-ray bursts (GRBs) with durations of several thousand seconds. We demonstrate that these events are extragalactic transients; in particular, we resolve the long-standing conundrum of the distance of GRB 101225A (the "Christmas-day burst"), finding it to have a redshift z = 0.847 and showing that two apparently similar events (GRB 111209A and GRB 121027A) lie at z = 0.677 and z = 1.773, respectively. The systems show extremely unusual X-ray and optical light curves, very different from classical GRBs, with long-lasting, highly variable X-ray emission and optical light curves that exhibit little correlation with the behavior seen in the X-ray. Their host galaxies are faint, compact, and highly star-forming dwarf galaxies, typical of "blue compact galaxies." We propose that these bursts are the prototypes of a hitherto largely unrecognized population of ultra-long GRBs, which while observationally difficult to detect may be astrophysically relatively common. The long durations may naturally be explained by the engine-driven explosions of stars of much larger radii than normally considered for GRB progenitors, which are thought to have compact Wolf-Rayet progenitor stars. However, we cannot unambiguously identify supernova signatures within their light curves or spectra. We also consider the alternative possibility that they arise from the tidal disruption of stars by massive black holes and conclude that the associated timescales are only consistent with the disruption of compact stars (e. g., white dwarfs) by black holes of relatively low mass (<10(5) M-circle dot).
A NOVEL LOAD CURRENT CONTROL METHOD FOR A LEADING POWER-FACTOR VOLTAGE-SOURCE PWM RECTIFIER
(IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 1994) VEAS, DR; DIXON, JW; OOI, BT
A novel PWM voltage source rectifier, controlled by the load de current instead of the de voltage, has been developed. Its main characteristics are: a) there is neither input current sensors nor de voltage sensor; b) it works with an unchangeable and predefined PWM pattern; c) it presents a very strong stability; d) its stability does not depend on the size of the de capacitor; e) it can work at leading power factor for all load conditions, and f) it can also work with zero regulation for all load conditions. Digital simulations, analyses, and experiments confirm all these characteristics of the control method.
A simple control scheme for hybrid active power filter
(INST ENGINEERING TECHNOLOGY-IET, 2002) Rivas, D; Moran, L; Dixon, J; Espinoza, J
A simple control scheme for hybrid active power filters connected in parallel is presented and analysed. The hybrid active power filter combines the compensation characteristics of resonant passive and active power filters. The series active power filter is implemented with a three-phase pluse-width modular (PWM) voltage-source inverter. The proposed scheme is able to compensate displacement power factor and current harmonics simultaneously. The combination of passive and active power filters allows a better performance compensation of high-power nonlinear loads. The proposed control scheme is discussed in tenus of principles of operations under steady-state and transient conditions. The design and implementation of the power and control circuits are reported. Finally, key predicted results are verified experimentally on a 5 kVA prototype model.
A simple frequency-independent method for calculating the reactive and harmonic current in a nonlinear load
(IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 1996) Tepper, JS; Dixon, JW; Venegas, G; Moran, L
A basic criterion that determines the behavior of an active power filter is the method of calculating the reference current, There are many ways of generating this reference, but the methods are generally complex and hard to tune, This paper describes a simple and effective method for calculating the reference current, necessary to feed a shunt active power filter to compensate the power factor and harmonic currents generated by a nonlinear load. Simulations and experimental results are presented, showing that the proposed circuit may operate at frequencies ranging from 40 to 65 Hz without adjustment.
A Trisheteroleptic Cyclometalated Ru-II Sensitizer that Enables High Power Output in a Dye-Sensitized Solar Cell
(2011) Bomben, Paolo G.; Gordon, Terry J.; Schott Verdugo, Eduardo Enrique; Berlinguette, Curtis P.
A young stellar environment for the superluminous supernova PTF12dam
(OXFORD UNIV PRESS, 2015) Thoene, C. C.; Postigo, A. de Ugarte; Garcia Benito, R.; Leloudas, G.; Schulze, S.; Amorin, R.
The progenitors of superluminous supernovae (SLSNe) are still a mystery. Hydrogen-poor SLSN hosts are young, highly star-forming dwarf galaxies and the majority belongs to the class of 'extreme emission line galaxies'. Here we present a resolved long-slit study of the host of the hydrogen-poor SLSN PTF12dam probing the kiloparsec environment of the SN site to determine the age of the progenitor. The SN occurred in a star-forming region in the head of a 'tadpole' galaxy with largely uniform properties. The galaxy experienced a recent starburst superimposed on an underlying old stellar population (SP). We determine a very young SP at the SN site of similar to 3 Myr and a metallicity of 12+log(O/H)=8.0 but do not observe any Wolf-Rayet features. The progenitor of PTF12dam was likely a massive star of >60 M-circle dot and one of the first stars exploding as an SN in the most recent starburst episode.
Alert Classification for the ALeRCE Broker System: The Anomaly Detector
(IOP Publishing Ltd, 2023) Pérez-Carrasco, Manuel; Cabrera-Vives, Guillermo; Hernández-García, Lorena; Forster, F.; Sanchez-Saez, Paula; Muñoz Arancibia, Alejandra M.; Arredondo, Javier; Astorga, Nicolas; Bauer, Franz Erik; Bayo, Amelia; Catelan, Marcio; Dastidar, Raya; Estevez, P. A.; Lira, Paulina; Pignata, Giuliano
Astronomical broker systems, such as Automatic Learning for the Rapid Classification of Events (ALeRCE), are currently analyzing hundreds of thousands of alerts per night, opening up an opportunity to automatically detect anomalous unknown sources. In this work, we present the ALeRCE anomaly detector, composed of three outlier detection algorithms that aim to find transient, periodic, and stochastic anomalous sources within the Zwicky Transient Facility data stream. Our experimental framework consists of cross-validating six anomaly detection algorithms for each of these three classes using the ALeRCE light-curve features. Following the ALeRCE taxonomy, we consider four transient subclasses, five stochastic subclasses, and six periodic subclasses. We evaluate each algorithm by considering each subclass as the anomaly class. For transient and periodic sources the best performance is obtained by a modified version of the deep support vector data description neural network, while for stochastic sources the best results are obtained by calculating the reconstruction error of an autoencoder neural network. Including a visual inspection step for the 10 most promising candidates for each of the 15 ALeRCE subclasses, we detect 31 bogus candidates (i.e., those with photometry or processing issues) and seven potential astrophysical outliers that require follow-up observations for further analysis.
Alkali-driven selectivity of products on carbon-supported Ni-based catalysts during the HDO of guaiacol
(2024) Matos, Juan; Samudio-González, Diana; Blanco, Elodie; Poon, Po S.; Escalona Burgos, Néstor Guillermo
The catalytic hydrodeoxygenation (HDO) of guaiacol as a representative bio-oil molecule was studied using a series of carbon-supported Ni-based catalysts. The promoter effect of alkali metals (Ca and Mg) on the catalytic activity and selectivity was verified. Catalysts were prepared by wetness incipient method and N2 gas adsorp tion/desorption isotherms, X-ray diffraction, reduction/desorption temperature-programed, and CO chemi sorption analysis were performed to characterize the catalysts. In terms of the initial reaction-rate catalysts with 1 wt% alkali-promotors showed an increase in the activity up to ca. 1.4 and 1.2 times higher on Ni-Ca(1 %)/AC and Ni-Mg(1 %)/AC, respectively, compared to Ni/AC catalyst. The increase to 5 wt% in alkali promotors slightly reduced the initial activity of Ni. However, the turn-over frequencies estimated showed higher values when alkali content is increased from 1 wt% to 5 wt%. These apparent contradictorial results suggest the formation of new actives sites along reaction, probably constituted by a mixture of oxides NiO-CaO and NiO-MgO. The selectivity of products showed remarkable changes due to the presence of alkali-promotors and a mechanism or reaction is proposed based on the kinetics of formation and evolution of products. Mg-promoted led to the formation of cyclohexane. On the contrary, Ca-promoted catalysts led the mechanism to representative benzene yields. This is remarkable result regarding the efficiency of a HDO biorefinery. In general, it can be concluded that Ni-based catalysts promoted with alkali metals are an economical alternative for the catalytic conversion of representa tive target molecules from a bio-oil feed.
An AI-Extended Prediction of Erosion-Corrosion Degradation of API 5L X65 Steel
(MDPI, 2023) Espinoza-Jara, Ariel Orlando; Wilk, Igor; Aguirre, Javiera; Walczak, Magdalena
The application of Artificial Neuronal Networks (ANN) offers better statistical accuracy in erosion-corrosion (E-C) predictions compared to the conventional linear regression based on Multifactorial Analysis (MFA). However, the limitations of ANN to require large training datasets and a high number of inputs pose a practical challenge in the field of E-C due to the scarcity of data. To address this challenge, a novel ANN method is proposed, structured to a small training dataset and trained with the aid of synthetic data to produce an E-C neural network (E-C NN), applied for the first time in the study of E-C wear synergy. In the process, transfer learning is applied by pre-training and fine-tuning the model. The initial dataset is created from experimental data produced in a slurry pot setup, exposing API 5L X65 steel to a turbulent copper tailing slurry. To the previously known E-C scenario for selected values of flow velocity, particle concentration, temperature, pH, and the content of the dissolved Cu2+, new experimental data of stand-alone erosion and stand-alone corrosion is added. The prediction of wear loss by E-C NN considers individual parameters and their interactions. The main result is that E-C ANN provides better prediction than MFA as evaluated by a mean squared error (MSE) values of 2.5 and 3.7, respectively. The results are discussed in the context of the cross-effect between the proposed prediction model and the resulting estimation of relative contribution to E-C synergy, which is better predicted by the E-C NN. The E-C NN model is concluded to be a viable alternative to MFA, delivering similar prediction with better sensitivity to E-C synergy at shorter computation times when using the same experimental dataset.
An Information Theory Approach on Deciding Spectroscopic Follow-ups
(2020) Astudillo, J.; Protopapas, P.; Pichara Baksai, Karim Elías; Huijse, P.
Analysis of generation investments under price controls in cross-border trade of electricity
(2023) Muñoz Abogabir, Juan Carlos; Sauma, E.; Muñoz, F.D.; Moreno, R.
Price controls are commonly employed in Latin America and other regions to prevent price increases in exporting regions during cross-border trade of electricity. This paper introduces a methodology to evaluate the economic impact of price controls on generation investments, dispatch decisions, and carbon emissions in the context of cross-border electricity trade. We propose a non-linear adjusting function to represent a price-control rule, which can be incorporated into equilibrium models for generation firms and price-sensitive consumers. By employing fixed-point iterations between the adjusting function and an optimization problem that determines equilibrium investments and dispatch decisions for generation firms in a competitive environment, we obtain an equilibrium solution. We apply the proposed methodology to analyze the current price controls governing cross-border electricity trade between Chile and Argentina, with a focus on the exporting country. Our findings reveal that existing price controls can impede incentives for renewable energy investments, particularly in wind and solar, while stimulating investments in fossil fuel-based generation capacity. Moreover, these controls lead to increased emissions compared to a scenario without price controls. Additionally, we observe that the inefficiency resulting from price controls is proportionate to the volume of exports relative to local demand and the price elasticity of demand in the importing region
Analysis of high-efficiency solar cells in mobile robot applications
(ASME, 2007) Calderon, Francisco; Luders, Allan; Wettergreen, David; Teza, James; Guesalaga, Andres
This technical brief analyzes the performance of triple-junction solar cells on a mobile robot. Although originally designed for satellite use, it is demonstrated that triple-junction cells are effective in terrestrial applications. This makes them particularly suitable for systems with limited size and mass but high-power requirements such as a mobile robot. A testing station was specially constructed to characterize triple-junction and conventional silicon cell performance in different environments and to compare their effectiveness. Additional field tests were carried out with an autonomous robot in order to check the ability to deliver sufficient power to varying loads. Results show that they surpass conventional technologies with efficiencies higher than 22%, so they can be considered as an alternative technology for power sources on board of terrestrial mobile robots.
Analyzing regional and local changes in irradiance during the 2019 total solar eclipse in Chile, using field observations and analytical modeling
(MDPI, 2021) Castillejo Cuberos, Armando; Cardemil Iglesias, José Miguel; Escobar Moragas, Rodrigo
Solar eclipses are astronomic phenomena in which the Earth’s moon transits between the planet and the Sun, projecting a shadow onto the planet’s surface. As solar power installed capacity increases, detailed studies of this region-wide phenomenon’s effect in irradiance is of interest; how-ever, the literature mainly reports its effects on localized scales. A measurement campaign spanning over 1400 km was pursued for the 2 July 2019 total solar eclipse in Chile, to register the event and establish a modeling framework to assess solar eclipse effects in irradiance over wide regional scales. This work describes the event and presents an estimation framework to decompose atmospheric and eclipse effects on irradiance. An analytical model was applied to study irradiance attenuation throughout the Chilean mainland territory, using satellite-derived and astronomical data as inputs compared to ground measurements in eight stations. Results showed good agreement between model and observations, with Mean Bias Errors of −0.008 to 0.98 W/m2 for Global Horizontal Irradiance and −0.004 to −4.664 W/m2 for Direct Normal Irradiance, with Normalized Root Mean Squared Errors of 0.7–5.8% and 1.4–12.2%, respectively. Energy losses due to obscuration corre-sponded between 20–40% for Global Horizontal Irradiance and 25–50% for Direct Normal Irradi-ance over Chilean territory.

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