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Author Araya-Letelier, G.; Antico, F.C.; Burbano-Garcia, C.; Concha-Riedeld, J.; Norambuena-Contreras, J.; Concha, J.; Saavedra Flores, E.I. doi  openurl
  Title Experimental evaluation of adobe mixtures reinforced with jute fibers Type
  Year 2021 Publication Construction and Building Materials Abbreviated Journal Constr. Build. Mater.  
  Volume 276 Issue 2021 Pages 122127  
  Keywords Jute fibers; Fiber-reinforced composites; Thermal conductivity; Mechanical characterization; Damage and durability assessment  
  Abstract Due to their sustainability as well as physical and mechanical performance, different natural fibers, both vegetal and animal fibers, have been successfully used in adobe mixtures (AMs) to enhance properties such as cracking control, flexural toughness and water erosion resistance, among others. However, the use of jute fibers (JFs), one of the most largely produced vegetal fiber worldwide, has not been extensively studied on AMs. Consequently, this study evaluates the effects of the incorporation of varying dosages (0.5 and 2.0 wt%) and lengths (7, 15, and 30 mm) of JFs on the physical/thermal/mechanical/fracture and durability performance of AMs, a specific type of earth-based construction material widely used globally. Experimental results showed that the incorporation of 2.0 wt% dosages of JFs increased the capillary water absorption of AMs, which might affect AM durability. The latter result could be explained by the additional porosity generated by the spaces left between the JFs and the matrix of adobe, as well as the inherent water absorption of the JFs. The incorporation of JFs significantly improved the behavior of AMs in terms of thermal conductivity, drying shrinkage cracking control, flexural toughness and water erosion performance, without affecting their compressive and flexural strength. For example, flexural toughness indices were increased by 297% and crack density ratio as well as water erosion depth values were reduced by 93% and 62%, respectively, when 2.0 wt%-15 mm length JFs were incorporated into AM. Since the latter combination of JF dosage and length provided the overall best results among AMs, it is recommended by this study as JF-reinforcement scheme for AMs for construction applications such as adobe masonry and earth plasters.  
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  Series Volume Series Issue Edition  
  ISSN 0950-0618 ISBN Medium  
  Area Expedition Conference  
  Notes Approved  
  Call Number UAI @ alexi.delcanto @ Serial 1315  
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Author Chambolle, A.; Contreras, J.P. doi  openurl
  Title Accelerated Bregman Primal-Dual Methods Applied to Optimal Transport and Wasserstein Barycenter Problems Type
  Year 2023 Publication SIAM Journal on Mathematics of Data Science Abbreviated Journal SIMODS  
  Volume 4 Issue 4 Pages 1369-1395  
  Keywords primal-dual method; optimal transport; Wasserstein barycenter; saddle-point  
  Abstract This paper discusses the efficiency of Hybrid Primal-Dual (HPD) type algorithms to approximately solve discrete Optimal Transport (OT) and Wasserstein Barycenter (WB) problems, with and without entropic regularization. Our first contribution is an analysis showing that these methods yield state-of-the-art convergence rates, both theoretically and practically. Next, we extend the HPD algorithm with the linesearch proposed by Malitsky and Pock in 2018 to the setting where the dual space has a Bregman divergence, and the dual function is relatively strongly convex to the Bregman's kernel. This extension yields a new method for OT and WB problems based on smoothing of the objective that also achieves state-of-the-art convergence rates. Finally, we introduce a new Bregman divergence based on a scaled entropy function that makes the algorithm numerically stable and reduces the smoothing, leading to sparse solutions of OT and WB problems. We complement our findings with numerical experiments and comparisons.  
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  Series Volume Series Issue Edition  
  ISSN 2577-0187 ISBN Medium  
  Area Expedition Conference  
  Notes WOS:000978251900007 Approved  
  Call Number UAI @ alexi.delcanto @ Serial 1809  
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Author Contreras, J.; Lopez, D.; Gomez, G.; Vidal, G. doi  openurl
  Title Seasonal Enhancement of Nitrogen Removal on Domestic Wastewater Treatment Performance by Partially Saturated and Saturated Hybrid Constructed Wetland Type
  Year 2022 Publication Water Abbreviated Journal Water  
  Volume 14 Issue 7 Pages 1089  
  Keywords hybrid constructed wetland; saturation level; organic matter; ammonia  
  Abstract The aim of this study is to evaluate seasonal enhancement of nitrogen removal on domestic wastewater treatment performance by partially saturated and saturated HBCWs. To achieve this, two HBCWs consisting of a vertical subsurface flow constructed wetland, followed by a horizontal subsurface flow constructed wetland (VSSF-HSSF) were evaluated. Two saturation levels were used: (a) partially saturated HB1:VSSF1 (0.6 m)-HSSF1 (0.15 m), (b) saturated HB2: VSSF2 (0.8 m)-HSSF2 (0.25 m). Each unit was planted with Schoenoplectus californicus and was operated for 297 days. The removal efficiencies in HB1 and HB2 were above 70%, 86%, 77% and 55% for chemical oxygen demand (COD), total suspended solids (TSS), nitrogen as ammonium (NH4+-N), and total nitrogen (TN), respectively. For VSSF, a higher level of saturation (from 0.6 to 0.8 m) meant a decrease of 17% in the TN removal efficiencies, and for HSSF, an increase from 0.15 to 0.25 m of saturation meant a decrease of 11 and 10% in the NH4+-N and TN removal efficiencies, respectively. Thus, the increase of saturation level in HBCWs reduces the transformation and/or removal of components of the wastewaters to be treated, particularly nitrogen. Through this research, the possibility of optimizing the transformation of nitrogen with partially saturated hybrids can be examined.  
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  ISSN 2073-4441 ISBN Medium  
  Area Expedition Conference  
  Notes WOS:000781935000001 Approved  
  Call Number UAI @ alexi.delcanto @ Serial 1574  
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Author Contreras, J.P.; Cominetti, R. doi  openurl
  Title Optimal error bounds for non-expansive fixed-point iterations in normed spaces Type
  Year 2022 Publication Mathematical Programming Abbreviated Journal Math. Program.  
  Volume Early Access Issue Pages  
  Keywords Non-expansive maps; Fixed-point iterations; Error bounds; Convergence rates  
  Abstract This paper investigates optimal error bounds and convergence rates for general Mann iterations for computing fixed-points of non-expansive maps. We look for iterations that achieve the smallest fixed-point residual after n steps, by minimizing a worst-case bound parallel to x(n) – Tx(n)parallel to <= R-n derived from a nested family of optimal transport problems. We prove that this bound is tight so that minimizing R-n yields optimal iterations. Inspired from numerical results we identify iterations that attain the rate R-n = O(1/n), which we also show to be the best possible. In particular, we prove that the classical Halpern iteration achieves this optimal rate for several alternative stepsizes, and we determine analytically the optimal stepsizes that attain the smallest worst-case residuals at every step n, with a tight bound R-n approximate to 4/n+4. We also determine the optimal Halpern stepsizes for affine non-expansive maps, for which we get exactly R-n = 1/n+1. Finally, we show that the best rate for the classical Krasnosel'skii-Mann iteration is Si (11 Omega(1/root n), and present numerical evidence suggesting that even extended variants cannot reach a faster rate.  
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  Area Expedition Conference  
  Notes WOS:000805887100002 Approved  
  Call Number UAI @ alexi.delcanto @ Serial 1577  
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Author Contreras, J.P.; Bosch, P.; Varas, M.; Basso, F. doi  openurl
  Title A New Genetic Algorithm Encoding for Coalition Structure Generation Problems Type
  Year 2020 Publication Mathematical Problems In Engineering Abbreviated Journal Math. Probl. Eng.  
  Volume 2020 Issue Pages 13 pp  
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  Abstract Genetic algorithms have proved to be a useful improvement heuristic for tackling several combinatorial problems, including the coalition structure generation problem. In this case, the focus lies on selecting the best partition from a discrete set. A relevant issue when designing a Genetic algorithm for coalition structure generation problems is to choose a proper genetic encoding that enables an efficient computational implementation. In this paper, we present a novel hybrid encoding, and we compare its performance against several genetic encoding proposed in the literature. We show that even in difficult instances of the coalition structure generation problem, the proposed approach is a competitive alternative to obtaining good quality solutions in reasonable computing times. Furthermore, we also show that the encoding relevance increases as the number of players increases.  
  Address [Contreras, Juan Pablo] Univ Adolfo Ibanez, Fac Ingn & Ciencias, Santiago, Chile, Email: ju.contreras@alumnos.uai.cl;  
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  Publisher Hindawi Ltd Place of Publication Editor  
  Language English Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 1024-123x ISBN Medium  
  Area Expedition Conference  
  Notes WOS:000530379800011 Approved  
  Call Number UAI @ eduardo.moreno @ Serial 1141  
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Author Norambuena-Contreras, J.; Arteaga-Perez, L.E.; Guadarrama-Lezama, A.Y.; Briones, R.; Vivanco, J.F.; Gonzalez-Torre, I. doi  openurl
  Title Microencapsulated Bio-Based Rejuvenators for the Self-Healing of Bituminous Materials Type
  Year 2020 Publication Materials Abbreviated Journal Materials  
  Volume 13 Issue 6 Pages 16 pp  
  Keywords asphalt; encapsulated rejuvenators; agricultural waste; bio-oil; self-healing efficiency  
  Abstract Asphalt self-healing by encapsulated rejuvenating agents is considered a revolutionary technology for the autonomic crack-healing of aged asphalt pavements. This paper aims to explore the use of Bio-Oil (BO) obtained from liquefied agricultural biomass waste as a bio-based encapsulated rejuvenating agent for self-healing of bituminous materials. Novel BO capsules were synthesized using two simple dripping methods through dropping funnel and syringe pump devices, where the BO agent was microencapsulated by external ionic gelation in a biopolymer matrix of sodium alginate. Size, surface aspect, and elemental composition of the BO capsules were characterized by optical and scanning electron microscopy and energy-dispersive X-ray spectroscopy. Thermal stability and chemical properties of BO capsules and their components were assessed through thermogravimetric analysis (TGA-DTG) and Fourier-Transform Infrared spectroscopy (FTIR-ATR). The mechanical behavior of the capsules was evaluated by compressive and low-load micro-indentation tests. The self-healing efficiency over time of BO as a rejuvenating agent in cracked bitumen samples was quantified by fluorescence microscopy. Main results showed that the BO capsules presented an adequate morphology for the asphalt self-healing application, with good thermal stability and physical-chemical properties. It was also proven that the BO can diffuse in the bitumen reducing the viscosity and consequently self-healing the open microcracks.  
  Address [Norambuena-Contreras, Jose; Gonzalez-Torre, Irene] Univ Bio Bio, Dept Civil & Environm Engn, LabMAT, Ave Collao 1202, Concepcion, Chile, Email: jnorambuena@ubiobio.cl;  
  Corporate Author Thesis  
  Publisher Mdpi Place of Publication Editor  
  Language English Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 1996-1944 ISBN Medium  
  Area Expedition Conference  
  Notes WOS:000529208000185 Approved  
  Call Number UAI @ eduardo.moreno @ Serial 1140  
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Author Norambuena-Contreras, J.; Gonzalez-Torre, I.; Vivanco, J.F.; Gacitua, W. pdf  doi
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  Title Nanomechanical properties of polymeric fibres used in geosynthetics Type
  Year 2016 Publication Polymer Testing Abbreviated Journal Polym. Test  
  Volume 54 Issue Pages 67-77  
  Keywords Polymeric fibres; Geosynthetics; Nanomechanical properties; Nanoindentation; Damage evaluation  
  Abstract Geosynthetics are composite materials manufactured using different types of polymeric fibres, usually employed as anti-reflective cracking systems in asphalt pavements. Materials that compose geosynthetics can be damaged due to mechanical and thermal effects produced during the installation process under hot mix asphalts. In this paper, different polymeric fibres extracted from geosynthetics have been evaluated using nanoindentation tests. The main objective was to evaluate the effect of installation process (dynamic compaction and thermal damage) on the mechanical behaviour of individual polymeric fibres at nano-scale. To do this, elastic modulus (E) and hardness (H) of three different polymeric fibres commonly used in geosynthetics (polypropylene, polyester and polyvinyl-alcohol), in two testing directions and under two different states have been studied. Main conclusions of this work are that mechanical properties of geosynthetics individual fibres can change after installation, producing changes in the behaviour of geosynthetics at macro-scale with consequences in the pavement functionality, and that these changes are different depending on the material that composed the fibres. (C) 2016 Elsevier Ltd. All rights reserved.  
  Address [Norambuena-Contreras, J.; Gonzalez-Torre, I.] Univ Bio Bio, LabMat UBB, Dept Civil & Environm Engn, Concepcion, Chile, Email: irene.gonzaleztorre@gmail.com  
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  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 0142-9418 ISBN Medium  
  Area Expedition Conference  
  Notes WOS:000382798300009 Approved  
  Call Number UAI @ eduardo.moreno @ Serial 651  
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Author Rivera, J.; Hernandez, N.; Consalvi, JL.; Reszka, P.; Contreras, J.; Fuentes, A. doi  openurl
  Title Ignition of wildland fuels by idealized firebrands Type
  Year 2021 Publication Fire Safety Journal Abbreviated Journal Fire Saf. J.  
  Volume 120 Issue Pages 103036  
  Keywords PILOTED IGNITION; PINE NEEDLES; CONE CALORIMETER; MOISTURE; TIME; BEDS  
  Abstract Experiments were carried out in the Idealized-Firebrand Ignition Test (I-FIT), a bench scale apparatus specifically designed to test the ignition of forest fuel layers from a representative firebrand. A cylindrical heater was used to model the firebrand, which allowed to control the incident radiative heat flux on the specimen, from the critical heat flux up to 25 kW/m2, for five different porosities of the fuel layer. Experimental ignition delay times were interpreted based on a theoretical model of the radiative heating of the fuel layer. Radiative heat transfer within the fuel layer was modeled by using the P1 approximation. In the limit of small ignition delay times an analytical expression was derived to correlate the inverse of the ignition time to the incident heat flux. This analytical expression is used to obtain the ignition temperature and effective properties for the forest fuel layers, namely the product of the fuel volume fraction by solid fuel density and solid heat capacity. Analytical solutions were found to be consistent with experimental data and a correlation relating the inverse of the non-dimensional time-toignition to the non-dimensional heat flux is provided.  
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  ISSN 0379-7112 ISBN Medium  
  Area Expedition Conference  
  Notes WOS:000639876600016 Approved  
  Call Number UAI @ alexi.delcanto @ Serial 1388  
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Author Varas, M.; Basso, F.; Bosch, P.; Contreras, J.P.; Pezoa, R. doi  openurl
  Title A horizontal collaborative approach for planning the wine grape harvesting Type
  Year 2022 Publication Operational Research Abbreviated Journal Oper. Res.  
  Volume 22 Issue 5 Pages 4965-4998  
  Keywords Wine industry; Harvesting planning; Horizontal collaboration; Cooperative game theory  
  Abstract Horizontal collaboration is a strategy that has increasingly been used for improving supply chain operations. In this paper, we analyze the benefits of using a collaborative approach when optimally planning the wine grape harvesting process. Particularly, we assess how labor and machinery collaborative planning impacts harvesting costs. We model cooperation among wineries as a coalitional game with transferable costs for which the characteristic function vector is computed by solving a new formulation for planning the wine grape harvesting. In order to obtain stable coalitions, we devise an optimization problem that incorporates both rationality and efficiency conditions and uses the Gini index as a fairness criterion. Focusing on an illustrative case, we develop several computational experiments that show the positive effect of collaboration in the harvesting process. Moreover, our computational results reveal that the results depend strongly on the fairness criteria used. The Gini index, for example, favors the formation of smaller coalitions compared to other fairness criteria such as entropy.  
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  Series Volume Series Issue Edition  
  ISSN 1109-2858 ISBN Medium  
  Area Expedition Conference  
  Notes WOS:000850030500001 Approved  
  Call Number UAI @ alexi.delcanto @ Serial 1648  
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