Browsing by Author "Gonzalez, Alvaro"

Now showing 1 - 12 of 12
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    Assessment of the sustainability of asphalt pavement maintenance using the microwave heating self-healing technique
    (ELSEVIER SCI LTD, 2022) Nalbandian, Kevork Micael; Carpio, Manuel; Gonzalez, Alvaro
    Pavements are the major load-carrying Civil Engineering structures in roads, runways, parking lots, and driveways; hence, they are fundamental for regional or national development. However, the pavement life cycle has significant environmental, economic, and social impacts. The asphalt pavement microwave heating self-healing technique (MWHSHT) is a relatively new alternative to traditional pavement maintenance techniques. Research has mainly focused on its technical feasibility with little attention to its effect on economic, environmental, and social sustainability. This work assesses the sustainability of asphalt pavement maintenance using the MWHSHT through an environmental and socio-economic impact analysis for various scenarios. Results show that pavement maintenance alternatives that include MWHSHT show reductions in energy consumption, feedstock energy, materials consumption, and economic indicators compared to full traditional maintenance during the asphalt pavement life cycle, thus increasing pavement sustainability. In addition, the inclusion of the MWHSHT has potential social benefits for stakeholders. Overall, including the MWHSHT for maintaining asphalt pavements has the potential to improve the economic, environmental, and social aspects of sustainability in comparison to using only traditional asphalt pavement maintenance.
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    Damage Prediction in the Wire Drawing Process
    (2024) Gonzalez, Alvaro; Cruchaga, Marcela; Celentano, Diego; Ponthot, Jean-Philippe
    In this study, the prediction of damage in the wire drawing process of 2011 aluminum alloy was investigated through both experimental and numerical methods. A comprehensive experimental setup was designed involving 20 cases of wire drawing with varying die angles (10 degrees, 15 degrees, 21 degrees, 27 degrees, and 34 degrees) and reductions (21%, 29%, 31%, and 38%). Each case was tested three times, and the drawing forces, as well as occurrences of wire breakage, were recorded. The mechanical behavior of the material was firstly characterized using uniaxial tensile tests, whose results were used to determine the material parameters of both the hardening Voce law and those of uncoupled and coupled damage models. Then, the numerical simulations of the wire drawing process were performed using a finite element model, accounting for axisymmetric conditions and mesh convergence analysis to ensure accuracy. The previously characterized damage models were applied to evaluate their fracture prediction capabilities. A novel presentation method using three-dimensional graphs was employed to indicate the level of damage for each angle and reduction, providing greater sensitivity and insight into the damage values. Good agreement between the experimental and numerical data was demonstrated for the bilinear coupled damage model, validating its effectiveness. This study contributes to a better understanding of damage prediction in the wire drawing process, with implications for improving industrial practices and material performance evaluations.
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    Effect of two different chest compression techniques on ventilation during neonatal resuscitation
    (2021) Jahnsen, Johanne; Gonzalez, Alvaro; Fabres, Jorge; Bahamondes, Alejandra; Estay, Alberto
    Objective To assess tidal volume (Vt) and minute ventilation (MV) during cardiopulmonary resuscitation (CPR) with two different chest compressions techniques: two-finger (TFT) or two-thumb technique (TTT) in a neonatal model. Methods Vt and MV were continuously measured during consecutive periods of resuscitation in an intubated manikin. Thirty participants performed the two compression techniques in a random order for 2-min periods while performing positive pressure ventilation using a T-piece resuscitator (TPR) or a self-inflating bag (SIB). Results Vt during CPR with TFT was significantly higher than TTT with either TPR: 44.9 +/- 4.3 vs 39.2 +/- 5.4 ml (p < 0.001) or SIB: 39.2 +/- 5.7 vs 35.6 +/- 6.5 ml (p < 0.023). Similarly MV was significantly higher in TFT than TTT with either mode: 1346 +/- 130 vs 1175 +/- 162 ml/min, respectively, with TPR (p < 0.001) and 1177 +/- 170 vs 1069 +/- 196 ml/min with SIB (p < 0.03). Conclusions Chest compressions during CPR using the TFT achieved higher Vt and MV than TTT in this model of neonatal resuscitation.
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    Energy consumption comparison for different asphalt pavements rehabilitation techniques used in Chile
    (ELSEVIER SCIENCE BV, 2007) Thenoux, Guillermo; Gonzalez, Alvaro; Dowling, Rafael
    In developing countries without the availability of reliable pavement management systems, recycling techniques may offer the best alternative for pavement structural rehabilitation. However, for many government officials and contractors there is a clear understanding of the technical advantages of recycling but not a clear perspective of cost saving. Since cost is a relative value among different regions of any country the following work makes an energy analysis of the construction process of the three different rehabilitation techniques available in Chile. Three different structural pavement rehabilitation alternatives were studied and compared using an energy consumption methodology:
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    Improvement of survival in infants with congenital diaphragmatic hernia in recent years: effect of ECMO availability and associated factors
    (2010) Kattan, Javier; Godoy, Loreto; Zavala, Alejandro; Faunes, Miriam; Becker, Pedro; Estay, Alberto; Fabres, Jorge; Toso, Paulina; Urzua, Soledad; Becker, Jorge; Cerda, Jaime; Gonzalez, Alvaro
    Survival of patients with congenital diaphragmatic hernia (CDH) depends both on non-modifiable congenital conditions and on modifiable pre and postnatal management. ECMO improves survival up to 80% in neonates with CDH in the best ECMO centers worldwide. The first Neonatal ECMO Program in Chile was started in our University in 2003. Our objective is to determine the impact of a Neonatal ECMO Program in a level III NICU on newborns with CDH.
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    Interpretation of laboratory and full-scale testing of New Zealand foamed bitumen pavements using finite-element modelling
    (TAYLOR & FRANCIS LTD, 2012) Gonzalez, Alvaro; Cubrinovski, Misko; Alabaster, David; Thenoux, Guillermo
    A large research project on foamed bitumen (FB) stabilisation was conducted in New Zealand. The project consisted of an extensive laboratory and full-scale testing of FB pavements. The objective of this paper is to interpret the performance of FB pavements by using finite-element (FE) modelling. The mechanical properties of the materials were calculated using testing data and used as material inputs in the FE modelling. The MohrCoulomb and DruckerPrager material models were adopted to calculate plastic deformation, which is related to pavement rutting. Results of the modelling indicate that increasing the FB content increases the tensile strength and modulus of the pavements, reducing the plastic deformations in the subgrade and the stabilised layer. In addition, adding FB reduces sensitivity to rutting when pavement is overloaded or the asphalt surface layer is cracked.
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    Mode of delivery and antenatal steroids and their association with survival and severe intraventricular hemorrhage in very low birth weight infants
    (2016) Hubner, M. E.; Ramirez, R.; Burgos, J.; Dominguez, A.; Tapia, J. L.; Colantonio, Guillermo; Zapata, Jorge; Perez, Gaston; Ana Pedraza, Susana Garcia; Kurlat, Isabel; Di Siervi, Oscar; Escarate, Adriana; Mariani, Gonzalo; Maria Ceriani, Jose; Fernandez, Silvia; Fustinana, Carlos; Brener, Pablo; Edwards, Eleonora; Tavosnaska, Jorge; Roldan, Liliana; Sexer, Hector; Saa, Gladys; Sabatelli, Debora; Laura Gendra, Maria; Fernanda Buraschi, Maria; Molina, Paula; Daniel, Agost; Morganti, Federico; Fontana, Adriana; Chandias, Daniela; Rinaldi, Monica; Grandi, Carlos; Rojas, Elio; Solana, Claudio; Nieto, Ricardo; Meritano, Javier; Larguia, Miguel; Kasten, Laura; Cuneo, Lucrecia; Decaro, Marcelo; Cracco, Lionel; Bassi, Gustavo; Jacobi, Noemi; Brum, Andrea; Vain, Nestor; Aguilar, Adriana; Guerrero, Miriam; Szyld, Edgardo; Escandar, Alcira; Abdala, Daniel; Guida, Martin; Ferrin, Lucila; Roge, Horacio; Musante, Gabriel; Capelli, Maria C.; Pablo Berazategui, Juan; de Elizalde, Magdalena; Ignacio Fraga, Juan; Keller, Rodolfo; Ahumada, Luis; Ferreyra, Mirta; Ferreira, Vanda; Borges, Roberta; Do Vale, Marynea; Cavalcante, Silvia; Gusmao, Joama; Franco, Patricia; Jose Silva, Maria; Fabres, Jorge; Estay, Alberto; Gonzalez, Alvaro; Kattan, Javier; Quezada, Mariela; Urzua, Soledad; Campos, Lilia; Cifuentes, Lilian; Leon, Jorge; Aguilar, Roxana; Treuer, Sergio; Giaconi, Jimena; Bancalari, Aldo; Standen, Jane; Escobar, Marisol; Veas, Viviana; Sandino, Daniela; Gonzalez, Agustina; Avila, Claudia; Guzman, Carla; Toro, Claudia; Mena, Patricia; Milet, Beatriz; Pittaluga, Enrica; Pena, Veronica; Mendizabal, Rafael; Pizarro, Dagoberto; D'Apremont, Ivonne; Tapia, Jose L.; Marshall, Guillermo; Villarroel, Luis; Quezada, Mariela; Dominguez, Angelica; Lacarruba, Jose; Cespedes, Elizabeth; Mir, Ramon; Mendieta, Elvira; Genes, Larissa; Caballero, Carlos; Webb, Veronica; Rivera, Fabiola; Llontop, Margarita; Bellomo, Sicilia; Zegarra, Jaime; Chumbes, Oscar; Castaneda, Anne; Cabrera, Walter; Llanos, Raul; Mucha, Jorge; Garcia, Gustavo; Ceruti, Beatriz; Borbonet, Daniel; Gugliucci, Sandra; Lain, Ana; Martinez, Mariza; Bazan, Gabriela; Piffaretti, Susana; Cuna, Isabel; Bermudez, Patricia
    OBJECTIVE: To determine whether CS delivery and receipt of antenatal steroids (ANS) in vertex-presenting singletons with a gestational age (GA) between 24 and 30 weeks is associated with improved survival and improved severe intraventricular hemorrhage (sIVH)-free survival.
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    Patient volume, medical and nursing staffing and its relationship with risk-adjusted outcomes of VLBW infants in 15 Neocosur neonatal network NICUs
    (SOC ARGENTINA PEDIATRIA, 2010) Grandi, Carlos; Gonzalez, Alvaro; Meritano, Javier; Grp Colaborativo Neocosur
    Introduction. Few studies have attempted to evaluate the relationship between medical and nursing staffing and neonatal outcomes providing inconclusive evidence. The purpose was to assess whether morbidity and mortality of VLBW infants are associated with levels of patient volume, provision and training of medical and nursing, and if exist differences between public and private centers.
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    Prevalence and risk factors associated with the need for surgical intervention due to necrotizing enterocolitis in very low birth weight infants
    (2024) Bruno, Maria Ailen; Galletti, Maria Fernanda; Dik, Pablo H. Brener; Mariani, Gonzalo L.; Gonzalez, Alvaro; Nieto, Ricardo
    Introduction: Necrotizing enterocolitis (NEC) is one of the most common gastrointestinal emergencies affecting very low birth weight (VLBW) infants with an incidence of 6-15 %. Early recognition is crucial. Mortality is high and variable (30-50 %). Those requiring surgical intervention have a higher mortality rate than those who receive medical treatment.Objectives: 1) To assess the prevalence of surgical NEC and associated risk factors 2) To compare outcomes based on the type of treatment required 3) To estimate the mortality associated with NEC and surgical NEC.Methods: A multicentre retrospective cohort study was designed (level II), including VLBW infants born between 2011 and 2020 in Centers of the Neocosur Network. A multivariate logistic regression analysis was performed to evaluate risk factors associated with the need for surgery.Results: NEC was diagnosed in 1679 (10.4 %) of 16,131 births in this period. The prevalence of surgery was 25 % (95 % CI 23-27 %). In multivariable analysis, variables associated with an increased risk of surgery requirement were birth weight <750 g (aOR 1.73-95%CI 1.2-2.5) and receiving antenatal antibiotics (aOR 1.54-95%CI 1.09-2.74). Those requiring surgery had significantly higher morbidity and mortality than the ones receiving medical treatment.Conclusion: In VLBW infants with NEC, lower birth weight and antenatal antibiotics administration were inde-pendently associated with the need for surgical intervention.
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    Stiffness Evolution of Granular Materials Stabilized with Foamed Bitumen and Cement
    (2013) Halles, Felipe; Thenoux, Guillermo; Gonzalez, Alvaro
    From the literature, it is possible to find two trends regarding the stiffness evolution of foamed bitumen stabilized recycled mixtures. The first trend indicates that once the foamed bitumen mix reaches a constant value because of the curing process, the stiffness decreases with time because of load cycles. The second trend indicates that stiffness remains constant after the curing process. In this research, the stiffness evolution of foamed bitumen mixes stabilized with different bitumen and cement contents was studied. The stiffness was measured by using the indirect tensile fatigue test. Results indicated that once the foamed bitumen mix reached a constant value because of the curing process, stiffness decreased or remained constant depending on the stress level applied to the foamed bitumen layer. If the stress level is lower than a specific value, the stiffness of the mix will remain constant at a value extremely close to the initial stiffness. If the stress level is greater than a specific value, the stiffness of the mix will decrease gradually. In addition, the reduction rate of the stiffness will be greater with higher stress level. The analysis of results from mixes with different bitumen and cement contents allows identification of the effect of both stabilizing agents in the long-term stiffness evolution.
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    Temperature effect of asphalt production on the thermo-chemical properties of Kraft lignin
    (2024) Marquez, J. Waldo; Fuentes, Valentina; Rueda, Eduardo J.; Tundidor-Camba, Alain; Escalona, Nestor; Norambuena-Contreras, Jose; Gonzalez, Alvaro
    Global warming has triggered a series of strategies and efforts to reduce greenhouse gas emissions and increase the reuse and recycling into asphalt pavements. One of these, is the reduction of production temperatures of asphalt mixtures, and the other is using sustainable antioxidants, such as Kraft lignin, with high phenolic content. Kraft lignin is usually mixed at high temperatures without considering the effect of temperature on its antioxidant properties. This research aimed to study the impact of the production temperatures of asphalt mixtures on the thermo-chemical properties of Kraft lignin and its antioxidant capacity. To evaluate these properties, thermogravimetry, infrared spectroscopy, and DPPH tests were done. To validate the results, bitumen-lignin blends were prepared considering representative temperatures for Hot-Mix-Asphalt (HMA), 160 degrees C, and for Warm-Mix-Asphalt (WMA), 135 degrees C. Bitumen-lignin blends were prepared considering 0% and 20% Kraft lignin by total weight bitumen. The blended samples, unaged and aged. were evaluated considering mechanical, rheological, and chemical properties. The main conclusion of the study demonstrated that although Kraft lignin can be used in HMA, using it in mixtures with lower temperatures conserve its properties. WMA production temperatures preserve Kraft lignin's chemical properties, increasing the durability and resilience of bitumen throughout its service life.
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    The Triaxiality Effect on Damage Evolution in Al-2024 Tensile Samples
    (2024) Gonzalez, Alvaro; Celentano, Diego; Cruchaga, Marcela; Ponthot, Jean-Philippe
    The effect of triaxiality on the evolution of damage in Al-2024 aluminum cylindrical specimens is studied in this work. Uncoupled and coupled damage models, all of them explicitly dependent on triaxiality, are assessed and compared. These models are characterized by tensile tests on cylindrical specimens without notches, to obtain the material parameters for each model. The capability of each model to predict fracture when different positive triaxial conditions evolve is then evaluated through tensile tests on notched cylindrical specimens. In particular, the damage index, evaluated at the fracture strain level, is compared with the experimental results validating the models. Moreover, the triaxiality evolution in the different specimens is studied in order to assess its effect on damage, demonstrating that the fracture strain decreases at greater triaxiality values. Observations through scanning electron microscopy confirm this pattern; i.e., an increase in triaxiality reveals a shift in the fracture mechanism from a more ductile condition in the original specimens to a more brittle one as the notch radius decreases. In addition, bilinear damage evolution is proposed to describe the physical behavior of the material when the Lemaitre coupled model is considered. In such a case, special attention must be devoted to the material characterization since coupling between hardening material parameters and damage affects the results.