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Adhesion characteristics between keratin fibers and unsaturated polyester
(IMPRENTA UNIV ANTIOQUIA, 2008-12-01) Paniagua, Marco; Ossa, Alexander; Ruiz, Gladys; Paniagua, Marco; Ossa, Alexander; Ruiz, Gladys; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de Ingeniería
This work presents the methods and results employed to find the adhesion characteristics between keratin fibers and unsaturated polyester as matrix material. The fibers were conditioned prior to testing using four different methods in order to establish the effect of these treatments on the adhesion to the matrix by means of i) monofilament pull-out testing, as direct method; and ii) Lamina tensile tests as indirect method to analyze the adhesion in the fracture zone with the help of electron microscopy (SEM).
Análisis de falla de la mordaza plana de una prensa hidráulica
(IMPRENTA UNIV ANTIOQUIA, 2008-01-01) Ossa, E.A.; Paniagua, M.A.; Ossa, E.A.; Paniagua, M.A.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de Ingeniería
This paper describes the analysis and investigation of the causes of the failure of an hydraulic press jaw face grip. Analysis of the fractured surfaces indicated the creation of cracks due to stress concentrators as a result of defective design. On the other hand, metallographic examination revealed the presence of aligned clusters of primary carbides that along with the stress concentrators induced the premature failure of the grip.
Architecture and microstructure of cortical bone in reconstructed canine mandibles after bone transport distraction osteogenesis
(SPRINGER, 2011-11-01) Zapata, Uriel; Halvachs, Emily K.; Dechow, Paul C.; Elsalanty, Mohammed E.; Opperman, Lynne A.; Zapata, Uriel; Halvachs, Emily K.; Dechow, Paul C.; Elsalanty, Mohammed E.; Opperman, Lynne A.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de Ingeniería
Reconstruction of the canine mandible using bone transport distraction osteogenesis has been shown to be a suitable method for correcting segmental bone defects produced by cancer, gunshots, and trauma. Although the mechanical quality of the new regenerate cortical bone seems to be related to the mineralization process, several questions regarding the microstructural patterns of the new bony tissue remain unanswered. The purpose of this study was to quantify any microstructural differences that may exist between the regenerate and control cortical bone. Five adult American foxhound dogs underwent unilateral bone transport distraction of the mandible to repair bone defects of 30-35 mm. Animals were killed 12 weeks after the beginning of the consolidation period. Fourteen cylindrical cortical samples were extracted from the superior, medial, and inferior aspects of the lingual and buccal plates of the reconstructed aspect of the mandible, and 21 specimens were collected similarly from the contralateral aspect of the mandible. Specimens were evaluated using histomorphometric and micro-computed tomographic techniques to compare their microstructure. Except for differences in haversian canal area, histomorphometric analyses suggested no statistical differences in microstructure between regenerate and control cortical bone. Morphological evaluation suggested a consistent level of anisotropy, possibly related to the distraction vector. After 12 weeks' consolidation, bone created during bone transport distraction osteogenesis was comparable to native bone in microstructure, architecture, and mechanical properties. It is proposed that, after enough time, the properties of the regenerate bone will be identical to that of native bone. © Springer Science+Business Media, LLC 2010.
Automatic detection of building typology using deep learning methods on street level images
(PERGAMON-ELSEVIER SCIENCE LTD, 2020-03-20) Duque, J.; Gonzalez, D.; Rueda Plata, Diego; Acevedo, A.; Ramos, R.; Betancourt, A.; García, S.; Duque, J.; Gonzalez, D.; Rueda Plata, Diego; Acevedo, A.; Ramos, R.; Betancourt, A.; García, S.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de Ingeniería
An exposure model is a key component for assessing potential human and economic losses from natural disasters. An exposure model consists of a spatially disaggregated description of the infrastructure and population of a region under study. Depending on the size of the settlement area, developing such models can be a costly and time-consuming task. In this paper we use a manually annotated dataset consisting of approximately 10,000 photos acquired at street level in the urban area of Medellín to explore the potential for using a convolutional neural network (CNN) to automatically detect building materials and types of lateral-load resisting systems, which are attributes that define a building's structural typology (which is a key issue in exposure models for seismic risk assessment). The results of the developed model achieved a precision of 93% and a recall of 95% when identifying nonductile buildings, which are the buildings most likely to be damaged in an earthquake. Identifying fine-grained material typology is more difficult, because many visual clues are physically hidden, but our model matches expert level performances, achieving a recall of 85% and accuracy scores ranging from 60% to 82% on the three most common building typologies, which account for 91% of the total building population in Medellín. Overall, this study shows that a CNN can make a substantial contribution to developing cost-effective exposure models. © 2020 Elsevier Ltd
Bioinspired hierarchical impact tolerant materials
(IOP PUBLISHING LTD, 2020-07-01) Estrada, Susana; Munera, Juan Camilo; Hernandez, Javier; Arroyave, Mauricio; Arola, Dwayne; Ossa, Alex; Estrada, Susana; Munera, Juan Camilo; Hernandez, Javier; Arroyave, Mauricio; Arola, Dwayne; Ossa, Alex; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de Ingeniería
The quest for new light-weight materials with superior mechanical properties is a goal of materials scientists and engineers worldwide. A promising route in this pursuit is drawing inspiration from nature to design and develop materials with enhanced properties. By emulating the graded mineral content and hierarchical structure of fish scales of the Arapaima gigas from the nano to macro scales, we were able to develop bioinspired laminated composites with improved impact resistance. Activated by the addition of nano-particles of Al2O3 and nano-layers of TiN to a thermoplastic fiber substrate, new energy dissipation mechanisms operating at the nanoscale enhanced the energy absorption and stiffness of the bioinspired material. Remarkably, the newly developed materials are easily transferred to the industry with minimum associated manufacturing costs.
Biomechanics of the canine mandible during bone transport distraction osteogenesis
(ASME, 2014-11-01) Zapata, Uriel; Dechow, Paul C.; Watanabe, Ikuya; Elsalanty, Mohammed E.; Opperman, Lynne A.; Zapata, Uriel; Dechow, Paul C.; Watanabe, Ikuya; Elsalanty, Mohammed E.; Opperman, Lynne A.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de Ingeniería
This study compared biomechanical patterns between finite element models (FEMs) and a fresh dog mandible tested under molar and incisal physiological loads in order to clarify the effect of the bone transport distraction osteogenesis (BTDO) surgical process. Three FEMs of dog mandibles were built in order to evaluate the effects of BTDO. The first model evaluated the mandibular response under two physiological loads resembling bite processes. In the second model, a 5.0 cm bone defect was bridged with a bone transport reconstruction plate (BTRP). In the third model, new regenerated bony tissue was incorporated within the defect to mimic the surgical process without the presence of the device. Complementarily, a mandible of a male American foxhound dog was mechanically tested in the laboratory both in the presence and absence of a BTRP, and mechanical responses were measured by attaching rosettes to the bone surface of the mandible to validate the FEM predictions. The relationship between real and predicted values indicates that the stress patterns calculated using FEM are a valid predictor of the biomechanics of the BTDO procedures. The present study provides an interesting correlation between the stiffness of the device and the biomechanical response of the mandible affected for bone transport. Copyright © 2014 by ASME.
Bone regeneration and docking site healing after bone transport distraction osteogenesis in the canine mandible
(W.B. Saunders Ltd, 2012-01-01) Nagashima, L.K.; Rondon-Newby, M.; Zakhary, I.E.; Nagy, W.W.; Zapata, U.; Dechow, P.C.; Opperman, L.A.; Elsalanty, M.E.; Nagashima, L.K.; Rondon-Newby, M.; Zakhary, I.E.; Nagy, W.W.; Zapata, U.; Dechow, P.C.; Opperman, L.A.; Elsalanty, M.E.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de Ingeniería
Purpose: Bone transport distraction osteogenesis provides a promising alternative to traditional grafting techniques. However, existing bone transport distraction osteogenesis devices have many limitations. The purpose of this research was to test a new device, the mandibular bone transport reconstruction plate, in an animal model with comparable mandible size to humans and to histologically and mechanically examine the regenerate bone. Materials and Methods: Eleven adult foxhounds were divided into an unreconstructed control group of 5 animals and an experimental group of 6 animals. In each animal, a 34-mm segmental defect was created in the mandible. The defect was reconstructed with a bone transport reconstruction plate. Histologic and biomechanical characteristics of the regenerate and unrepaired defect were analyzed and compared with bone on the contralateral side of the mandible after 4 weeks of consolidation. Results: The reconstructed defect was bridged with new bone, with little bone in the control defect. Regenerate density and microhardness were 22.3% and 42.6%, respectively, lower than the contralateral normal bone. Likewise, the anisotropy of the experimental group was statistically lower than in the contralateral bone. Half the experimental animals showed nonunion at the docking site. Conclusion: The device was very stable and easy to install and activate. After 1 month of consolidation, the defect was bridged with new bone, with evidence of active bone formation. Regenerate bone was less mature than the control bone. Studies are underway to identify when the regenerate properties compare with normal bone and to identify methods to augment bone union at the docking site. © 2012 American Association of Oral and Maxillofacial Surgeons.
Características de adhesión entre fibras de queratina y poliéster insaturado
(IMPRENTA UNIV ANTIOQUIA, 2008-01-01) Paniagua, M.; Ossa, A.; Ruiz, G.; Paniagua, M.; Ossa, A.; Ruiz, G.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de Ingeniería
This work presents the methods and results employed to find the adhesion characteristics between keratin fibers and unsaturated polyester as matrix material. The fibers were conditioned prior to testing using four different methods in order to establish the effect of these treatments on the adhesion to the matrix by means of i) monofilament pull-out testing, as direct method; and ii) Lamina tensile tests as indirect method to analyze the adhesion in the fracture zone with the help of electron microscopy (SEM).
Características estructurales de escuelas colombianas de pórticos de hormigón reforzado con mampostería no reforzada
(Fondo Editorial Universidad EAFIT, 2017-05-08) Acevedo A.B.; Zora-Mejía, Faver N; Acevedo A.B.; Zora-Mejía, Faver N; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de Ingeniería
Assessment of the seismic vulnerability of the building stock of a region is a key issue for its seismic risk evaluation.
Chemical, structural and mechanical characterization of bovine enamel
(PERGAMON-ELSEVIER SCIENCE LTD, 2020-01-01) Arango-Santander S.; Montoya C.; Pelaez-Vargas A.; Ossa E.A.; Arango-Santander S.; Montoya C.; Pelaez-Vargas A.; Ossa E.A.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de Ingeniería
Objective: The purpose of this investigation was to establish microstructure, microhardness, fracture toughness, chemical composition, and crack repair of bovine enamel and to compare these features with their human counterparts. Design: Bovine enamel fragments were prepared and optical microscopy and atomic force microscopy were used to establish microstructure; Raman spectroscopy was used to estimate composition and microindentation using Vickers testing was performed to evaluate hardness. Results: A strong dependence between indentation load and microhardness values was observed, as was the case in human enamel. Similar microstructure and chemical composition between bovine and human enamel, 7.89% lower microhardness and 40% higher fracture toughness values for bovine enamel were found. Conclusion: From a structural and mechanical standpoint, bovine enamel is a suitable alternative to human enamel for in vitro testing of dental products. © 2019 Elsevier Ltd
Composición química y microestructura de la dentina de pacientes colombianos
(2014-05-01) C. Montoya; Alexander Ossa, E.; C. Montoya; Alexander Ossa, E.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de Ingeniería
La dentina es un tejido duro que ocupa la mayor porción del diente humano. En estudios preliminares realizados en la dentina de pacientes de Estados Unidos y Colombia se han encontrado ciertasdiferencias en cuanto al tamaño y distribucion
Compressive Deformation Behaviour of Asphalt Mixtures
(Association of Asphalt Paving Technologist, 2006-08-01) Ossa, Edgar Alexander; Ossa, Edgar Alexander; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de Ingeniería
Contribution of Root Canal Treatment to the Fracture Resistance of Dentin
(Elsevier Inc., 2019-01-01) Yan W.; Montoya C.; Øilo M.; Ossa A.; Paranjpe A.; Zhang H.; Arola D.D.; Yan W.; Montoya C.; Øilo M.; Ossa A.; Paranjpe A.; Zhang H.; Arola D.D.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de Ingeniería
Introduction: Although the strength and toughness of dentin decrease with age, no study has explored if restorative treatments are a contributing factor. Methods: Multiple extracted teeth were obtained from randomly selected donors and categorized according to donor age and prior root canal treatment. The microstructure and chemical composition of radicular dentin were evaluated using scanning electron microscopy and Raman spectroscopy, respectively, and the strength was evaluated in 4-point flexure to failure. Data were compared using the Student t test. Results: Dentin from the root canal–restored teeth exhibited significantly lower strength (P <.05) than tissue from age- and donor-matched unrestored tooth pairs. Although there was no significant difference in the mineral-to-collagen ratio between the 2 groups, dentin obtained from the root canal–treated teeth exhibited more extensive collagen cross-linking and lower tubule occlusion ratios than the unrestored tooth pairs. Conclusions: There is a decrease in the strength of radicular dentin with aging, but prior root canal treatment increases the extent of degradation. © 2018 American Association of Endodontists
Contributions of intermolecular bonding and lubrication to the mechanical behavior of a natural armor
(ELSEVIER SCI LTD, 2020-01-01) Jiang, H.; Ghods, S.; Weller, E.; Waddell, S.; Ossa, E.A.; Yang, F.; Arola, D.; Jiang, H.; Ghods, S.; Weller, E.; Waddell, S.; Ossa, E.A.; Yang, F.; Arola, D.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de Ingeniería
Among many dermal armors, fish scales have become a source of inspiration in the pursuit of “next-generation” structural materials. Although fish scales function in a hydrated environment, the role of water and intermolecular hydrogen bonding to their unique structural behavior has not been elucidated. Water molecules reside within and adjacent to the interpeptide locations of the collagen fibrils of the elasmodine and provide lubrication to the protein molecules during deformation. We evaluated the contributions of this lubrication and the intermolecular bonding to the mechanical behavior of elasmodine scales from the Black Carp (Mylopharyngodon piceus). Scales were exposed to polar solvents, followed by axial loading to failure and the deformation mechanisms were characterized via optical mechanics. Displacement of intermolecular water molecules by liquid polar solvents caused significant (p = 0.05) increases in stiffness, strength and toughness of the scales. Removal of this lubrication decreased the capacity for non-linear deformation and toughness, which results from the increased resistance to fibril rotations and sliding caused by molecular friction. The intermolecular lubrication is a key component of the “protecto-flexibility” of scales and these natural armors as a system; it can serve as an important component of biomimetic-driven designs for flexible armor systems. Statement of Significance: The natural armor of fish has become a topic of substantial scientific interest. Hydration is important to these materials as water molecules reside within the interpeptide locations of the collagen fibrils of the elasmodine and provide lubrication to the protein molecules during deformation. We explored the opportunity for tuning the mechanical behavior of scales as a model for next-generation engineering materials by adjusting the extent of hydrogen bonding with polar solvents and the corresponding interpeptide molecular lubrication. Removal of this lubrication decreased the capacity for non-linear deformation and toughness due to an increase in resistance to fibril rotations and sliding as imparted by molecular friction. We show that intermolecular lubrication is a key component of the “protecto-flexibility” of natural armors and it is an essential element of biomimetic approaches to develop flexible armor systems. © 2020 Acta Materialia Inc.
Contributions of the layer topology and mineral content to the elastic modulus and strength of fish scales
(ELSEVIER SCIENCE BV, 2018-12-01) Ossa, Edgar Alexander; Ossa, Edgar Alexander; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de Ingeniería
Control of Porosity in Freeze Casting
(J O M Institute, 2020-01-01) Gil-Duran S.; Arola D.; Ossa E.A.; Gil-Duran S.; Arola D.; Ossa E.A.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de Ingeniería
Many biologic structural materials have porous microstructures with a distribution and orientation of pores that are challenging to achieve using traditional methods of processing. In this investigation, numerical and experimental methods of evaluation were used to understand effects from the primary processing parameters on the temperature gradients during solidification in freeze casting of ceramics. The location and orientation of the temperature gradients were found to be highly dependent on the geometrical and thermal properties of the mold material used in processing. Furthermore, it was found that careful control of these processing variables can be used to design bioinspired porous materials with graded orientations and distributions of pores. © 2020, The Minerals, Metals & Materials Society.
Criterios sismológicos para seleccionar acelerogramas reales de la Red Nacional de Acelerógrafos de Colombia para su uso en análisis dinámicos
(Escuela de Ingeniería de Antioquia, 2012-07-01) Acevedo A.B.; Acevedo A.B.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de Ingeniería
Utilizar acelerogramas reales para la realización de análisis dinámicos es deseable ya que contienen información real sobre la naturaleza del movimiento fuerte e indican las características variadas que diferentes sismos en lugares diversos pueden produci
Deformation behaviour of aged coronal dentin
(Blackwell Munksgaard, 2018-06-01) Montoya; C.; Arola; D.; Ossa; E.A.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de Ingeniería
Objective: This study aimed to identify the changes in the time-dependent deformation response of coronal dentin with ageing and its relationship with changes in chemical composition. Background: The structural behaviour of dentin with ageing is affected by changes in the density and diameter of its dentinal tubules (ie porosity), as well as changes in chemical composition throughout the tooth. However, little is known about the time-dependent deformation behaviour of aged dentin and the importance of its hierarchical structure and variations in chemical composition. Materials and methods: The spherical indentation response of aged coronal dentin was analysed in the outer, middle and inner regions, and its time-dependent deformation response was modelled in terms of its microstructure and chemical composition using a model recently proposed for young dentin. Results: The viscous deformation behaviour of aged dentin followed a power-law response with a decrease in the stress exponent when compared to young dentin. These results can be explained by cross-linking of the collagen present in the tissue. Conclusion: A decrease in the deformation ability of aged dentin was found. This behaviour could be a result of a dissolution process and reprecipitation of the minerals present in intertubular dentin into the dentinal tubules. © 2018 John Wiley & Sons A/S and The Gerodontology Association. Published by John Wiley & Sons Ltd
Designed for resistance to puncture: The dynamic response of fish scales
(ELSEVIER SCIENCE BV, 2019-01-01) Ghods S.; Murcia S.; Ossa E.A.; Arola D.; Ghods S.; Murcia S.; Ossa E.A.; Arola D.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de Ingeniería
Natural dermal armors are serving as a source of inspiration in the pursuit of “next-generation” structural materials. Although the dynamic strain response of these materials is arguably the most relevant to their performance as armors, limited work has been performed in this area. Here, uniaxial tension and transverse puncture tests were performed on specimens obtained from the scales of Asian carp over strain rates spanning seven decades, from 10-4 to 103 s-1. The importance of anatomical variations was explored by comparing the performance of scales from the head, middle and tail regions. In both loading orientations, the scales exhibited a significant increase in the resistance to failure with loading rate. The rate sensitivity was substantially higher for transverse loading than for in-plane tension, with average strain rate sensitivity exponents for measures of the toughness of 0.35 and 0.08, respectively. Spatial variations in the properties were largest in the puncture responses, and scales from the head region exhibited the greatest resistance to puncture overall. The results suggest that the layered microstructure of fish scales is most effective at resisting puncture, rather than in-plane tension, and its effectiveness increases with rate of loading. X-ray microCT showed that delamination of plies in the internal elasmodine and stretching of the fibrils were key mechanisms of energy dissipation in response to puncture loading. Understanding contributions from the microstructure to this behavior could guide the development of flexible engineered laminates for penetration resistance and other related applications. © 2018 Elsevier Ltd
Development of a fragility model for the residential building stock in South America
(EARTHQUAKE ENGINEERING RESEARCH INST, 2017-05-01) Villar-Vega, Mabe; Silva, Vitor; Crowley, Helen; Yepes, Catalina; Tarque, Nicola; Acevedo, Ana Beatriz; Hube, Matias A.; Gustavo, Coronel D.; Maria, Hernan Santa; Villar-Vega, Mabe; Silva, Vitor; Crowley, Helen; Yepes, Catalina; Tarque, Nicola; Acevedo, Ana Beatriz; Hube, Matias A.; Gustavo, Coronel D.; Maria, Hernan Santa; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de Ingeniería
South America-in particular, the Andean countries-are exposed to high levels of seismic hazard, which, when combined with the elevated concentration of population and properties, has led to an alarming potential for human and economic losses. Although several fragility models have been developed in recent decades for South America, and occasionally used in probabilistic risk analysis, these models have been developed using distinct methodologies and assumptions, which renders any direct comparison of the results across countries questionable, and thus application at a regional level unreliable. This publication aims at obtaining a uniform fragility model for the most representative building classes in the Andean region, for large-scale risk analysis. To this end, sets of single-degree-of-freedom oscillators were created and subjected to a series of ground motion records using nonlinear time history analyses, and the resulting damage distributions were used to derive sets of fragility functions. © 2017, Earthquake Engineering Research Institute.

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