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Author Affolter, C.; Kedzierska, J.; Vielma, T.; Weisse, B.; Aiyangar, A.
Title Estimating lumbar passive stiffness behaviour from subject-specific finite element models and in vivo 6DOF kinematics Type Journal Article
Year 2020 Publication Journal Of Biomechanics Abbreviated Journal J. Biomech.
Volume 102 Issue Pages 11 pp
Keywords Lumbar spinal loading; Subject-specific kinematics; Passive stiffness; Neutral position; Rigid-body musculoskeletal modelling
Abstract Passive rotational stiffness of the osseo-ligamentous spine is an important input parameter for estimating in-vivo spinal loading using musculoskeletal models. These data are typically acquired from cadaveric testing. Increasingly, they are also estimated from subject-specific imaging-based finite element (FE) models, which are typically built from CT/MR data obtained in supine position and employ pure rotation kinematics. We explored the sensitivity of FE-based lumbar passive rotational stiffness to two aspects of functional in-vivo kinematics: (a) passive strain changes from supine to upright standing position, and (b) in-vivo coupled translation-rotation kinematics. We developed subject-specific FE models of four subjects' L4L5 segments from supine CT images. Sagittally symmetric flexion was simulated in two ways: (i) pure flexion up to 12 degrees under a 500 N follower load directly from the supine pose. (ii) First, a displacement-based approach was implemented to attain the upright pose, as measured using Dynamic Stereo X-ray (DSX) imaging. We then simulated in-vivo flexion using DSX imaging-derived kinematics. Datasets from weight-bearing motion with three different external weights [(4.5 kg), (9.1 kg), (13.6 kg)] were used. Accounting for supine-upright motion generated compressive pre-loads approximate to 468 N (+/- 188 N) and a “pre-torque” approximate to 2.5 Nm (+/- 2.2 Nm), corresponding to 25% of the reaction moment at 10 degrees flexion (case (i)). Rotational stiffness estimates from DSX-based coupled translation-rotation kinematics were substantially higher compared to pure flexion. Reaction Moments were almost 90% and 60% higher at 5 degrees and 10 degrees of L4L5 flexion, respectively. Within-subject differences in rotational stiffness based on external weight were small, although between-subject variations were large. (C) 2020 Elsevier Ltd. All rights reserved.
Address [Affolter, Christian; Weisse, Bernhard; Aiyangar, Ameet] EMPA Swiss Fed Labs Mat Sci & Technol, Mech Syst Engn, Dubendorf, Switzerland, Email: ameet.aiyangar@empa.ch
Corporate Author Thesis
Publisher Elsevier Sci Ltd Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0021-9290 ISBN Medium
Area Expedition Conference
Notes WOS:000528310700033 Approved no
Call Number UAI @ eduardo.moreno @ Serial 1142
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Author Akian, M.; Gaubert, S.; Hochart, A.
Title A Game Theory Approach To The Existence And Uniqueness Of Nonlinear Perron-Frobenius Eigenvectors Type Journal Article
Year 2020 Publication Discrete And Continuous Dynamical Systems Abbreviated Journal Discret. Contin. Dyn. Syst.
Volume 40 Issue 1 Pages 207-231
Keywords Nonlinear eigenproblem; nonexpansive map; Hilbert's projective metric; hypergraph; zero-sum stochastic game
Abstract We establish a generalized Perron-Frobenius theorem, based on a combinatorial criterion which entails the existence of an eigenvector for any nonlinear order-preserving and positively homogeneous map f acting on the open orthant R->0(n). This criterion involves dominions, i.e., sets of states that can be made invariant by one player in a two-person game that only depends on the behavior of f “at infinity”. In this way, we characterize the situation in which for all alpha, beta > 0, the “slice space” S-alpha(beta) :={x is an element of R->0(n) vertical bar alpha x <= f(x) <= beta x} is bounded in Hilbert's projective metric, or, equivalently, for all uniform perturbations g of f, all the orbits of g are bounded in Hilbert's projective metric. This solves a problem raised by Gaubert and Gunawardena (Trans. AMS, 2004). We also show that the uniqueness of an eigenvector is characterized by a dominion condition, involving a different game depending now on the local behavior of f near an eigenvector. We show that the dominion conditions can be verified by directed hypergraph methods. We finally illustrate these results by considering specific classes of nonlinear maps, including Shapley operators, generalized means and nonnegative tensors.
Address [Akian, Marianne; Gaubert, Stephane] Ecole Polytech, INRIA, CNRS, Inst Polytech Paris, F-91128 Palaiseau, France, Email: marianne.akian@inria.fr;
Corporate Author Thesis
Publisher Amer Inst Mathematical Sciences-Aims Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 1078-0947 ISBN Medium
Area Expedition Conference
Notes WOS:000496748500009 Approved no
Call Number UAI @ eduardo.moreno @ Serial 1075
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Author Alcaino, P.; Santa-Maria, H.; Magna-Verdugo, C.; Lopez, L.
Title Experimental fast-assessment of post-fire residual strength of reinforced concrete frame buildings based on non-destructive tests Type Journal Article
Year 2020 Publication Construction And Building Materials Abbreviated Journal Constr. Build. Mater.
Volume 234 Issue Pages 10 pp
Keywords Post-fire residual strength; Non-destructive tests; Reinforced concrete building; Structural assessment
Abstract Assessment of the residual strength of reinforced concrete buildings subjected to fire is a problem that requires fast and sufficiently reliable resolution, necessary for the action of firefighters, forensic fire investigation, and structural assessment of post-fire condition of the building to take place. In all cases safety and integrity of firefighters and researchers can be at risk, and it is necessary to have rapidly and sufficiently reliable information in order to choose whether to enter freely, to enter with caution, or simply do not enter to the burned structure. This required prompt assessment gives no time or background to develop mathematical models of the structure and damage propagation. This work presents an experimental methodology for a fast assessment of post-fire residual strength of reinforced concrete frame buildings based on the high correlation between the loss of strength and non-destructive test results of frame concrete elements subjected to fire action. (C) 2019 Elsevier Ltd. All rights reserved.
Address [Alcaino, Pablo; Santa-Maria, Hernan] Pontificia Univ Catolica Chile, Dept Struct & Geotech Engn, Santiago 7820436, Chile, Email: palcaino@uc.cl;
Corporate Author Thesis
Publisher Elsevier Sci Ltd Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0950-0618 ISBN Medium
Area Expedition Conference
Notes WOS:000514748700001 Approved no
Call Number UAI @ eduardo.moreno @ Serial 1115
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Author Alejo, L.; Atkinson, J.; Lackner, S.
Title Looking deeper – exploring hidden patterns in reactor data of N-removal systems through clustering analysis Type Journal Article
Year 2020 Publication Water Science and Technology Abbreviated Journal Water Sci. Technol.
Volume to appear Issue Pages
Keywords
Abstract In this work, clustering analysis of two partial nitritation-anammox (PN-A) moving bed biofilm reactors (MBBR) containing different types of carrier material was explored for the identification of patterns and operational conditions that may benefit process performance. The systems ran for two years under fluctuations of temperature and organic matter. Ex situ batch activity tests were performed every other week during the operation of these reactors. These datasets and the parameters, which were monitored online and in the laboratory, were combined and analyzed applying clustering analysis to identify non-obvious information regarding the performance of the systems. The initial results were consistent with the literature and from an operational perspective, which allowed the parameters to be explored further. The new information revealed that the oxidation reduction potential (ORP) and the anaerobic ammonium oxidizing bacteria (AnAOB) activity correlated well. ORP also dropped when the reactors were exposed to real wastewater (presence of organic matter). Moreover, operating conditions during nitrite accumulation were identified through clustering, and also revealed inhibition of anammox bacteria already at low nitrite concentrations.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0273-1223 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number UAI @ eduardo.moreno @ Serial 1123
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Author Arbelaez, H.; Bravo, V.; Hernandez, R.; Sierra, W.; Venegas, O.
Title A new approach for the univalence of certain integral of harmonic mappings Type Journal Article
Year 2020 Publication Indagationes Mathematicae-New Series Abbreviated Journal Indag. Math.-New Ser.
Volume 31 Issue 4 Pages 525-535
Keywords Univalent mappings; Integral transformation; Geometric function theory
Abstract The principal goal of this paper is to extend the classical problem of finding the values of alpha is an element of C for which either (f) over cap (alpha) (z) = integral(z)(0) (f (zeta)/zeta)(alpha) d zeta or f(alpha) (z) = integral(z)(0)(f' (zeta))(alpha)d zeta are univalent, whenever f belongs to some subclasses of univalent mappings in D, to the case of harmonic mappings, by considering the shear construction introduced by Clunie and Sheil-Small in [4]. (C) 2020 Royal Dutch Mathematical Society (KWG). Published by Elsevier B.V. All rights reserved.
Address [Arbelaez, Hugo] Univ Nacl Colombia, Fac Ciencias, Sede Medellin, Medellin, Colombia, Email: hjarbela@unal.edu.co;
Corporate Author Thesis
Publisher Elsevier Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0019-3577 ISBN Medium
Area Expedition Conference
Notes WOS:000552682000001 Approved no
Call Number UAI @ eduardo.moreno @ Serial 1211
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Author Arevalo-Ramirez, T.; Villacres, J.; Fuentes, A.; Reszka, P.; Cheein, F.A.A.
Title Moisture content estimation of Pinus radiata and Eucalyptus globulus from reconstructed leaf reflectance in the SWIR region Type Journal Article
Year 2020 Publication Biosystems Engineering Abbreviated Journal Biosyst. Eng.
Volume 193 Issue Pages 187-205
Keywords SWIR reconstruction; Machine learning; Spectral indices; Fuel moisture content; Equivalent water thickness
Abstract Valparaiso, a central-southern region in Chile, has one of the highest rates of wildfire occurrence in the country. The constant threat of fires is mainly due to its highly flammable forest plantation, composed of 97.5% Pinus radiata and Eucalyptus globulus. Fuel moisture content is one of the most relevant parameters for studying fire spreading and risk, and can be estimated from the reflectance of leaves in the short wave infra-red (SWIR) range, not easily available in most vision-based sensors. Therefore, this work addresses the problem of estimating the water content of leaves from the two previously mentioned species, without any knowledge of their spectrum in the SWIR band. To this end, and for validation purposes, the reflectance of 90 leaves per species, at five dehydration stages, were taken between 350 nm and 2500 nm (full spectrum). Then, two machine-learning regressors were trained with 70% of the data set to determine the unknown reflectance, in the range 1000 nm-2500 nm. Results were validated with the remaining 30% of the data, achieving a root mean square error less than 9% in the spectrum estimation, and an error of 10% in spectral indices related to water content estimation. (C) 2020 IAgrE. Published by Elsevier Ltd. All rights reserved.
Address [Arevalo-Ramirez, Tito; Villacres, Juan; Auat Cheein, Fernando A.] Univ Tecn Fedrico Santa Maria, Dept Ingn Elect, Valparaiso, Chile, Email: fernando.auat@usm.cl
Corporate Author Thesis
Publisher Academic Press Inc Elsevier Science Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 1537-5110 ISBN Medium
Area Expedition Conference
Notes WOS:000526114500016 Approved no
Call Number UAI @ eduardo.moreno @ Serial 1150
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Author Argiz, L.; Reyes, C.; Belmonte, M.; Franchi, O.; Campo, R.; Fra-Vazquez, A.; del Rio, A.V.; Mosquera-Corral, A.; Campos, J.L.
Title Assessment of a fast method to predict the biochemical methane potential based on biodegradable COD obtained by fractionation respirometric tests Type Journal Article
Year 2020 Publication Journal Of Environmental Management Abbreviated Journal J. Environ. Manage.
Volume 269 Issue Pages 9 pp
Keywords Anaerobic digestion; Biodegradability; BMP; COD fractionation; Respirometric test
Abstract The biochemical methane potential test (BMP) is the most common analytical technique to predict the performance of anaerobic digesters. However, this assay is time-consuming (from 20 to over than 100 days) and consequently impractical when it is necessary to obtain a quick result. Several methods are available for faster BMP prediction but, unfortunately, there is still a lack of a clear alternative. Current aerobic tests underestimate the BMP of substrates since they only detect the easily biodegradable COD. In this context, the potential of COD fractionation respirometric assays, which allow the determination of the particulate slowly biodegradable fraction, was evaluated here as an alternative to early predict the BMP of substrates. Seven different origin waste streams were tested and the anaerobically biodegraded organic matter (CODmet) was compared with the different COD fractions. When considering adapted microorganisms, the appropriate operational conditions and the required biodegradation time, the differences between the CODmet, determined through BMP tests, and the biodegradable COD (CODb) obtained by respirometry, were not significant (CODmet (57.8026 +/- 21.2875) and CODb (55.6491 +/- 21.3417), t (5) = 0.189, p = 0.853). Therefore, results suggest that the BMP of a substrate might be early predicted from its CODb in only few hours. This methodology was validated by the performance of an inter-laboratory studyconsidering four additional substrates.
Address [Argiz, L.; Fra-Vazquez, A.; Val del Rio, A.; Mosquera-Corral, A.] Univ Santiago de Compostela, CRETUS Inst, Santiago De Compostela 15782, Galicia, Spain, Email: luciaargiz.montes@usc.es
Corporate Author Thesis
Publisher Academic Press Ltd- Elsevier Science Ltd Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0301-4797 ISBN Medium
Area Expedition Conference
Notes WOS:000541757200008 Approved no
Call Number UAI @ eduardo.moreno @ Serial 1185
Permanent link to this record
 

 
Author Asenjo, F.A.; Mahajan, S.M.
Title Resonant interaction between dispersive gravitational waves and scalar massive particles Type Journal Article
Year 2020 Publication Physical Review D Abbreviated Journal Phys. Rev. D
Volume 101 Issue 6 Pages 4 pp
Keywords
Abstract The Klein-Gordon equation is solved in the curved background spacetime created by a dispersive gravitational wave. Unlike solutions of perturbed Einstein equations in vacuum, dispersive gravitational waves do not travel exactly at the speed of light. As a consequence, the gravitational wave can resonantly exchange energy with scalar massive particles. Some details of the resonant interaction are displayed in a calculation demonstrating how relativistic particles (modeled by the Klein-Gordon equation), feeding on such gravitational waves, may be driven to extreme energies.
Address [Asenjo, Felipe A.] Univ Adolfo Ibanez, Fac Ingn & Ciencias, Santiago 7941169, Chile, Email: felipe.asenjo@uai.cl;
Corporate Author Thesis
Publisher Amer Physical Soc Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 2470-0010 ISBN Medium
Area Expedition Conference
Notes WOS:000518819200001 Approved no
Call Number UAI @ eduardo.moreno @ Serial 1160
Permanent link to this record
 

 
Author Astudillo-Defru, N.; Cloutier, R.; Wang, S.X.; Teske, J.; Brahm, R.; Hellier, C.; Ricker, G.; Vanderspek, R.; Latham, D.; Seager, S.; Winn, J.N.; Jenkins, J.M.; Collins, K.A.; Stassun, K.G.; Ziegler, C.; Almenara, J.M.; Anderson, D.R.; Artigau, E.; Bonfils, X.; Bouchy, F.; Briceno, C.; Butler, R.P.; Charbonneau, D.; Conti, D.M.; Crane, J.; Crossfield, I.J.M.; Davies, M.; Delfosse, X.; Diaz, R.F.; Doyon, R.; Dragomir, D.; Eastman, J.D.; Espinoza, N.; Essack, Z.; Feng, F.; Figueira, P.; Forveille, T.; Gan, T.; Glidden, A.; Guerrero, N.; Hart, R.; Henning, T.; Horch, E.P.; Isopi, G.; Jenkins, J.S.; Jordan, A.; Kielkopf, J.F.; Law, N.; Lovis, C.; Mallia, F.; Mann, A.W.; de Medeiros, J.R.; Melo, C.; Mennickent, R.E.; Mignon, L.; Murgas, F.; Nusdeo, D.A.; Pepe, F.; Relles, H.M.; Rose, M.; Santos, N.C.; Segransan, D.; Shectman, S.; Shporer, A.; Smith, J.C.; Torres, P.; Udry, S.; Villasenor, J.; Winters, J.G.; Zhou, G.
Title A hot terrestrial planet orbiting the bright M dwarf L 168-9 unveiled by TESS Type Journal Article
Year 2020 Publication Astronomy & Astrophysics Abbreviated Journal Astron. Astrophys.
Volume 636 Issue Pages 13 pp
Keywords stars: individual L 168-9; planetary systems; stars: late-type; techniques:photometric; techniques: radial velocities
Abstract We report the detection of a transiting super-Earth-sized planet (R = 1.39 +/- 0.09 R-circle plus) in a 1.4-day orbit around L 168-9 (TOI-134), a bright M1V dwarf (V = 11, K = 7.1) located at 25.15 +/- 0.02 pc. The host star was observed in the first sector of the Transiting Exoplanet Survey Satellite (TESS) mission. For confirmation and planet mass measurement purposes, this was followed up with ground-based photometry, seeing-limited and high-resolution imaging, and precise radial velocity (PRV) observations using the HARPS and Magellan/PFS spectrographs. By combining the TESS data and PRV observations, we find the mass of L 168-9 b to be 4.60 +/- 0.56 M-circle plus and thus the bulk density to be 1.74(-0.33)(+0.44) times higher than that of the Earth. The orbital eccentricity is smaller than 0.21 (95% confidence). This planet is a level one candidate for the TESS mission's scientific objective of measuring the masses of 50 small planets, and it is one of the most observationally accessible terrestrial planets for future atmospheric characterization.
Address [Astudillo-Defru, N.] Univ Catolica Santisima Concepcion, Dept Matemat & Fis Aplicadas, Alonso de Rivera 2850, Concepcion, Chile, Email: nastudillo@ucsc.cl
Corporate Author Thesis
Publisher Edp Sciences S A Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0004-6361 ISBN Medium
Area Expedition Conference
Notes WOS:000528572600001 Approved no
Call Number UAI @ eduardo.moreno @ Serial 1144
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Author Aylwin, R.; Jerez-Hanckes, C.; Pinto, J.
Title On the Properties of Quasi-periodic Boundary Integral Operators for the Helmholtz Equation Type Journal Article
Year 2020 Publication Integral Equations And Operator Theory Abbreviated Journal Integr. Equ. Oper. Theory
Volume 92 Issue 2 Pages 41 pp
Keywords Wave scattering; Gratings; Quasi-periodic functions; Boundary integral equations
Abstract We study the mapping properties of boundary integral operators arising when solving two-dimensional, time-harmonic waves scattered by periodic domains. For domains assumed to be at least Lipschitz regular, we propose a novel explicit representation of Sobolev spaces for quasi-periodic functions that allows for an analysis analogous to that of Helmholtz scattering by bounded objects. Except for Rayleigh-Wood frequencies, continuity and coercivity results are derived to prove wellposedness of the associated first kind boundary integral equations.
Address [Aylwin, Ruben; Pinto, Jose] Pontificia Univ Catolica Chile, Dept Elect Engn, Santiago, Chile, Email: rdaylwin@uc.cl;
Corporate Author Thesis
Publisher Springer Basel Ag Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0378-620x ISBN Medium
Area Expedition Conference
Notes WOS:000522040900001 Approved no
Call Number UAI @ eduardo.moreno @ Serial 1127
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Author Aylwin, R.; Jerez-Hanckes, C.; Schwab, C.; Zech, J.
Title Domain Uncertainty Quantification in Computational Electromagnetics Type Journal Article
Year 2020 Publication Siam-Asa Journal On Uncertainty Quantification Abbreviated Journal SIAM-ASA J. Uncertain. Quantif.
Volume 8 Issue 1 Pages 301-341
Keywords computational electromagnetics; uncertainty quantification; finite elements; shape holomorphy; sparse grid quadrature; Bayesian inverse problems
Abstract We study the numerical approximation of time-harmonic, electromagnetic fields inside a lossy cavity of uncertain geometry. Key assumptions are a possibly high-dimensional parametrization of the uncertain geometry along with a suitable transformation to a fixed, nominal domain. This uncertainty parametrization results in families of countably parametric, Maxwell-like cavity problems that are posed in a single domain, with inhomogeneous coefficients that possess finite, possibly low spatial regularity, but exhibit holomorphic parametric dependence in the differential operator. Our computational scheme is composed of a sparse grid interpolation in the high-dimensional parameter domain and an Hcurl -conforming edge element discretization of the parametric problem in the nominal domain. As a stepping-stone in the analysis, we derive a novel Strang-type lemma for Maxwell-like problems in the nominal domain, which is of independent interest. Moreover, we accommodate arbitrary small Sobolev regularity of the electric field and also cover uncertain isotropic constitutive or material laws. The shape holomorphy and edge-element consistency error analysis for the nominal problem are shown to imply convergence rates for multilevel Monte Carlo and for quasi-Monte Carlo integration, as well as sparse grid approximations, in uncertainty quantification for computational electromagnetics. They also imply expression rate estimates for deep ReLU networks of shape-to-solution maps in this setting. Finally, our computational experiments confirm the presented theoretical results.
Address [Aylwin, Ruben] Pontificia Univ Catolica Chile, Sch Engn, Santiago 7820436, Chile, Email: rdaylwin@uc.cl;
Corporate Author Thesis
Publisher Siam Publications Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 2166-2525 ISBN Medium
Area Expedition Conference
Notes WOS:000551383300011 Approved no
Call Number UAI @ eduardo.moreno @ Serial 1207
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Author Aylwin, R.; Silva-Oelker, G.; Jerez-Hanckes, C.; Fay, P.
Title Optimization methods for achieving high diffraction efficiency with perfect electric conducting gratings Type Journal Article
Year 2020 Publication Journal Of The Optical Society Of America A-Optics Image Science And Vision Abbreviated Journal J. Opt. Soc. Am. A-Opt. Image Sci. Vis.
Volume 37 Issue 8 Pages 1316-1326
Keywords
Abstract This work presents the implementation, numerical examples, and experimental convergence study of first- and second-order optimization methods applied to one-dimensional periodic gratings. Through boundary integral equations and shape derivatives, the profile of a grating is optimized such that it maximizes the diffraction efficiency for given diffraction modes for transverse electric polarization. We provide a thorough comparison of three different optimization methods: a first-order method (gradient descent); a second-order approach based on a Newton iteration, where the usual Newton step is replaced by taking the absolute value of the eigenvalues given by the spectral decomposition of the Hessian matrix to deal with non-convexity; and the Broyden-Fletcher-Goldfarb-Shanno (BFGS) algorithm, a quasi-Newton method. Numerical examples are provided to validate our claims. Moreover, two grating profiles are designed for high efficiency in the Littrow configuration and then compared to a high efficiency commercial grating. Conclusions and recommendations, derived from the numerical experiments, are provided as well as future research avenues. (C) 2020 Optical Society of America
Address [Aylwin, Ruben] Pontificia Univ Catolica Chile, Dept Elect Engn, Santiago, Chile, Email: rdaylwin@uc.cl
Corporate Author Thesis
Publisher Optical Soc Amer Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 1084-7529 ISBN Medium
Area Expedition Conference
Notes WOS:000555713900009 Approved no
Call Number UAI @ eduardo.moreno @ Serial 1216
Permanent link to this record
 

 
Author Azeem, M.; Guérin, A.; Dumais, T.; Caminos, L.; Goldstein, R.E.; Pesci, A.I.; de Dios Rivera, J.; Torres, M.J.; Wiener, J.; Campos, J.L.; Dumais, J.
Title Optimal Design of Multilayer Fog Collectors Type Journal Article
Year 2020 Publication ACS Appl. Mater. Interfaces Abbreviated Journal ACS Applied Materials & Interfaces
Volume 12 Issue 6 Pages 7736-7743
Keywords
Abstract The growing concerns over desertification have spurred research into technologies aimed at acquiring water from nontraditional sources such as dew, fog, and water vapor. Some of the most promising developments have focused on improving designs to collect water from fog. However, the absence of a shared framework to predict, measure, and compare the water collection efficiencies of new prototypes is becoming a major obstacle to progress in the field. We address this problem by providing a general theory to design efficient fog collectors as well as a concrete experimental protocol to furnish our theory with all the necessary parameters to quantify the effective water collection efficiency. We show in particular that multilayer collectors are required for high fog collection efficiency and that all efficient designs are found within a narrow range of mesh porosity. We support our conclusions with measurements on simple multilayer harp collectors.
Address
Corporate Author Thesis
Publisher American Chemical Society Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 1944-8244 ISBN Medium
Area Expedition Conference
Notes doi: 10.1021/acsami.9b19727 Approved no
Call Number UAI @ eduardo.moreno @ Serial 1108
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Author Barrera, J.; Lagos, G.
Title Limit distributions of the upper order statistics for the Levy-frailty Marshall-Olkin distribution Type Journal Article
Year 2020 Publication Extremes Abbreviated Journal Extremes
Volume to appear Issue Pages 26 pp
Keywords Marshall-Olkin distribution; Dependent random variables; Upper order statistics; Extreme-value theory; Reliability
Abstract The Marshall-Olkin (MO) distribution is considered a key model in reliability theory and in risk analysis, where it is used to model the lifetimes of dependent components or entities of a system and dependency is induced by “shocks” that hit one or more components at a time. Of particular interest is the Levy-frailty subfamily of the Marshall-Olkin (LFMO) distribution, since it has few parameters and because the nontrivial dependency structure is driven by an underlying Levy subordinator process. The main contribution of this work is that we derive the precise asymptotic behavior of the upper order statistics of the LFMO distribution. More specifically, we consider a sequence ofnunivariate random variables jointly distributed as a multivariate LFMO distribution and analyze the order statistics of the sequence asngrows. Our main result states that if the underlying Levy subordinator is in the normal domain of attraction of a stable distribution with index of stability alpha then, after certain logarithmic centering and scaling, the upper order statistics converge in distribution to a stable distribution if alpha> 1 or a simple transformation of it if alpha <= 1. Our result can also give easily computable confidence intervals for the last failure times, provided that a proper convergence analysis is carried out first.
Address [Barrera, Javiera; Lagos, Guido] Univ Adolfo Ibanez, Fac Engn & Sci, Av Diagonal Las Torres 2640, Santiago, Chile, Email: javiera.barrera@uai.cl;
Corporate Author Thesis
Publisher Springer Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 1386-1999 ISBN Medium
Area Expedition Conference
Notes WOS:000557129100001 Approved no
Call Number UAI @ eduardo.moreno @ Serial 1218
Permanent link to this record
 

 
Author Barrera, J.; Carrasco, R.A.; Mondschein, S.; Canessa, G.; Rojas-Zalazar, D.
Title Operating room scheduling under waiting time constraints: the Chilean GES plan Type Journal Article
Year 2020 Publication Annals Of Operations Research Abbreviated Journal Ann. Oper. Res.
Volume 286 Issue 1-2 Pages 501-527
Keywords Scheduling; Operating theater; Operating room scheduling
Abstract In 2000, Chile introduced profound health reforms to achieve a more equitable and fairer system (GES plan). The reforms established a maximum waiting time between diagnosis and treatment for a set of diseases, described as an opportunity guarantee within the reform. If the maximum waiting time is exceeded, the patient is referred to another (private) facility and receives a voucher to cover the additional expenses. This voucher is paid by the health provider that had to do the procedure, which generally is a public hospital. In general, this reform has improved the service for patients with GES pathologies at the expense of patients with non-GES pathologies. These new conditions create a complicated planning scenario for hospitals, in which the hospital's OR Manager must balance the fulfillment of these opportunity guarantees and the timely service of patients not covered by the guarantee. With the collaboration of the Instituto de Neurocirugia, in Santiago, Chile, we developed a mathematical model based on stochastic dynamic programming to schedule surgeries in order to minimize the cost of referrals to the private sector. Given the large size of the state space, we developed an heuristic to compute good solutions in reasonable time and analyzed its performance. Our experimental results, with both simulated and real data, show that our algorithm performs close to optimum and improves upon the current practice. When we compared the results of our heuristic against those obtained by the hospital's OR manager in a simulation setting with real data, we reduced the overtime from occurring 21% of the time to zero, and the non-GES average waiting list's length from 71 to 58 patients, without worsening the average throughput.
Address [Barrera, Javiera; Carrasco, Rodrigo A.; Mondschein, Susana; Canessa, Gianpiero] Univ Adolfo Ibanez, Fac Engn & Sci, Santiago, Chile, Email: javiera.barrera@uai.cl;
Corporate Author Thesis
Publisher Springer Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0254-5330 ISBN Medium
Area Expedition Conference
Notes WOS:000511564300021 Approved no
Call Number UAI @ eduardo.moreno @ Serial 1104
Permanent link to this record
 

 
Author Barrera, J.; Carrasco, R.A.; Moreno, E.
Title Real-time fleet management decision support system with security constraints Type Journal Article
Year 2020 Publication TOP Abbreviated Journal TOP
Volume to appear Issue Pages 21 pp
Keywords Fleet management; Real-time control; Data analytics; GPS tracking; Decision support system; Conflict detection and resolution
Abstract Intelligent transportation, and in particular, fleet management, has been a forefront concern for a plethora of industries. This statement is especially true for the production of commodities, where transportation represents a central element for operational continuity. Additionally, in many industries, and in particular those with hazardous environments, fleet control must satisfy a wide range of security restrictions to ensure that risks are kept at bay and accidents are minimum. Furthermore, in these environments, any decision support tool must cope with noisy and incomplete data and give recommendations every few minutes. In this work, a fast and efficient decision support tool is presented to help fleet managers oversee and control ore trucks, in a mining setting. The main objective of this system is to help managers avoid interactions between ore trucks and personnel buses, one of the most critical security constraints in our case study, keeping a minimum security distance between the two at all times. Furthermore, additional algorithms are developed and implemented, so that this approach can work with real-life noisy GPS data. Through the use of historical data, the performance of this decision support system is studied, validating that it works under the real-life conditions presented by the company. The experimental results show that the proposed approach improved truck and road utilization significantly while allowing the fleet manager to control the security distance required by their procedures.
Address [Barrera, Javiera; Carrasco, Rodrigo A.; Moreno, Eduardo] Univ Adolfo Ibanez, Fac Engn & Sci, Santiago, Chile, Email: javiera.barrera@uai.cl;
Corporate Author Thesis
Publisher Springer Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 1134-5764 ISBN Medium
Area Expedition Conference
Notes WOS:000534967700001 Approved no
Call Number UAI @ eduardo.moreno @ Serial 1200
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Author Barrera, J.; Moreno, E.; Varas, S.
Title A decomposition algorithm for computing income taxes with pass-through entities and its application to the Chilean case Type Journal Article
Year 2020 Publication Annals Of Operations Research Abbreviated Journal Ann. Oper. Res.
Volume 286 Issue 1-2 Pages 545-557
Keywords Income taxes; Markov processes; Networks; Algorithms
Abstract Income tax systems with “pass-through” entities transfer a firm's income to shareholders, which are taxed individually. In 2014, a Chilean tax reform introduced this type of entity and changed to an accrual basis that distributes incomes (but not losses) to shareholders. A crucial step for the Chilean taxation authority is to compute the final income of each individual given the complex network of corporations and companies, usually including cycles between them. In this paper, we show the mathematical conceptualization and the solution to the problem, proving that there is only one way to distribute income to taxpayers. Using the theory of absorbing Markov chains, we define a mathematical model for computing the taxable income of each taxpayer, and we propose a decomposition algorithm for this problem. This approach allows us to compute the solution accurately and to efficiently use computational resources. Finally, we present some characteristics of Chilean taxpayers' network and the computational results of the algorithm using this network.
Address [Barrera, Javiera; Moreno, Eduardo] Univ Adolfo Ibanez, Fac Engn & Sci, Santiago, Chile, Email: javiera.barrera@uai.cl;
Corporate Author Thesis
Publisher Springer Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0254-5330 ISBN Medium
Area Expedition Conference
Notes WOS:000511564300023 Approved no
Call Number UAI @ eduardo.moreno @ Serial 1102
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Author Baselli, G.; Contreras, F.; Lillo, M.; Marin, M.; Carrasco, R.A.
Title Optimal decisions for salvage logging after wildfires Type Journal Article
Year 2020 Publication Omega-International Journal Of Management Science Abbreviated Journal Omega-Int. J. Manage. Sci.
Volume 96 Issue Pages 9 pp
Keywords Salvage logging; Forest harvesting; Wildfires; Workforce allocation
Abstract Strategic, tactical, and operational harvesting plans for the forestry and logging industry have been widely studied for more than 60 years. Many different settings and specific constraints due to legal, environmental, and operational requirements have been modeled, improving the performance of the harvesting process significantly. During the summer of 2017, Chile suffered from the most massive wildfires in its history, affecting almost half a million hectares, of which nearly half were forests owned by medium and small forestry companies. Some of the stands were burned by intense crown fires, which always spread fast, that burned the foliage and outer layer of the bark but left standing dead trees that could be salvage harvested before insect and decay processes rendered them unusable for commercial purposes. Unlike the typical operational programming models studied in the past, in this setting, companies can make insurance claims on part or all of the burnt forest, whereas the rest of the forest needs to be harvested before it loses its value. This problem is known as the salvage logging problem. The issue also has an important social component when considering medium and small forestry and logging companies: most of their personnel come from local communities, which have already been affected by the fires. Harvesting part of the remaining forest can allow them to keep their jobs longer and, hopefully, leave the company in a better financial situation if the harvesting areas are correctly selected. In this work, we present a novel mixed-integer optimization-based approach to support salvage logging decisions, which helps in the configuration of an operational-level harvesting and workforce assignment plan. Our model takes into account the payment from an insurance claim as well as future income from harvesting the remaining trees. The model also computes an optimal assignment of personnel to the different activities required. The objective is to improve the cash position of the company by the end of the harvest and ensure that the company is paying all its liabilities and maintaining personnel. We show how our model performs compared to the current decisions made by medium and small-sized forestry companies, and we study the specific case of a small forestry company located in Cauquenes, Chile, which used our model to decide its course of action. (C) 2019 Elsevier Ltd. All rights reserved.
Address [Baselli, Gianluca; Contreras, Felipe; Lillo, Matias; Marin, Magdalena; Carrasco, Rodrigo A.] Univ Adolfo Ibanez, Fac Engn & Sci, Santiago, Chile, Email: gbaselli@alumnos.uai.cl;
Corporate Author Thesis
Publisher Pergamon-Elsevier Science Ltd Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0305-0483 ISBN Medium
Area Expedition Conference
Notes WOS:000541944700003 Approved no
Call Number UAI @ eduardo.moreno @ Serial 1186
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Author Becker, F.; Montealecre, P.; Rapaport, I.; Todinca, I.
Title The Impact Of Locality In The Broadcast Congested Clique Model Type Journal Article
Year 2020 Publication Siam Journal On Discrete Mathematics Abbreviated Journal SIAM Discret. Math.
Volume 34 Issue 1 Pages 682-700
Keywords broadcast congested clique; induced cycles; graph degeneracy
Abstract The broadcast congested clique model (BCLIQUE) is a message-passing model of distributed computation where n nodes communicate with each other in synchronous rounds. First, in this paper we prove that there is a one-round, deterministic algorithm that reconstructs the input graph G if the graph is d-degenerate, and rejects otherwise, using bandwidth b = O(d . log n). Then, we introduce a new parameter to the model. We study the situation where the nodes, initially, instead of knowing their immediate neighbors, know their neighborhood up to a fixed radius r. In this new framework, denoted BCLIQuE[r], we study the problem of detecting, in G, an induced cycle of length at most k (CYCLE <= k) and the problem of detecting an induced cycle of length at least k +1 (CYCLE>k). We give upper and lower bounds. We show that if each node is allowed to see up to distance r = left perpendicular k/2 right perpendicular + 1, then a polylogarithmic bandwidth is sufficient for solving CYCLE>k with only two rounds. Nevertheless, if nodes were allowed to see up to distance r = left perpendicular k/3 right perpendicular, then any one-round algorithm that solves CYCLE>k needs the bandwidth b to be at least Omega(n/ log n). We also show the existence of a one-round, deterministic BCLIQUE algorithm that solves CYCLE <= k with bandwitdh b = O(n(1/left perpendicular k/2 right perpendicular). log n). On the negative side, we prove that, if epsilon <= 1/3 and 0 < r <= k/4, then any epsilon-error, R-round, b-bandwidth algorithm in the BCLIQUE[r] model that solves problem CYCLE(<= k )satisfies R . b = Omega(n(1/left perpendicular k/2 right perpendicular)).
Address [Becker, F.; Todinca, I] Univ Orleans, INSA Ctr Val Loire, LIFO EA 4022, Orleans, France, Email: florent.becker@univ-orleans.fr;
Corporate Author Thesis
Publisher Siam Publications Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0895-4801 ISBN Medium
Area Expedition Conference
Notes WOS:000546886700033 Approved no
Call Number UAI @ eduardo.moreno @ Serial 1182
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Author Bottcher, L.; Montealegre, P.; Goles, E.; Gersbach, H.
Title Competing activists-Political polarization Type Journal Article
Year 2020 Publication Physica A-Statistical Mechanics And Its Applications Abbreviated Journal Physica A
Volume 545 Issue Pages 13 pp
Keywords Political polarization; Opinion formation; Activists; Markov chains; Game theory
Abstract Recent empirical findings suggest that societies have become more polarized in various countries. That is, the median voter of today represents a smaller fraction of society compared to two decades ago and yet, the mechanisms underlying this phenomenon are not fully understood. Since interactions between influential actors ("activists'') and voters play a major role in opinion formation, e.g. through social media, we develop a macroscopic opinion model in which competing activists spread their political ideas in specific groups of society. These ideas spread further to other groups in declining strength. While unilateral spreading shifts the opinion distribution, competition of activists leads to additional phenomena: Small heterogeneities among competing activists cause them to target different groups in society, which amplifies polarization. For moderate heterogeneities, we obtain target cycles and further amplification of polarization. In such cycles, the stronger activist differentiates himself from the weaker one, while the latter aims to imitate the stronger activist. (C) 2019 Elsevier B.V. All rights reserved.
Address [Boettcher, Lucas] Swiss Fed Inst Technol, Inst Theoret Phys, CH-8093 Zurich, Switzerland, Email: lucasb@ethz.ch
Corporate Author Thesis
Publisher Elsevier Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0378-4371 ISBN Medium
Area Expedition Conference
Notes WOS:000526845600034 Approved no
Call Number UAI @ eduardo.moreno @ Serial 1147
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