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Given a set of jobs and two batch processing machines (BPMs) arranged in a flow shop environment, the objective is to batch the jobs and sequence the batches such that the makespan is minimized.

Knock is an abnormal combustion phenomena capable of causing serious damage to spark ignition engines, and is a constraint to reach the maximum potential of the engine, since strategies to increase power output and improve efficiency such as turbocharging, increased compression ratio and the advancement of spark timing, also increase the possibility of knock occurrence. Therefore, it is crucial to take into account the limits imposed by knock in the design and operating conditions of the engine when using an engine computational model. In this article a zero-dimensional two-zone engine model, coupled with a chemical kinetic model for knock detection through end-gas auto-ignition is developed and validated, for a natural gas engine. Given the importance of an accurate knock prediction, five heat transfer coefficient correlations are compared to find the most suitable to predict the knock occurrence, through calculation of a knock criterion. Correlations from Sitkei and Annand were the most suitable to predict this knock criterion for the experimental data used, and the Sitkei correlation was later tested in a parametric study to predict the effect of spark timing, compression ratio, equivalence ratio and inlet temperature in knock occurrence and intensity. Results were in accordance with real engine behaviour when knock occurs. © 2017, Springer-Verlag France SAS, part of Springer Nature.

This paper describes the experiences in the design, construction and validation of a serious game to be used as a support to teach Operations Management (or Operations Programming) in a Production Engineering program. The aim of this publication is to describe the perceptions of the students during the various development stages of the process. A semi-experimental study was conducted in order to determine the pedagogical effectiveness of the use of the game, but in this paper the authors focus on the perceptions of the students, which may become an important input for other faculty interested on using serious games as support for teaching other engineering courses. © 2018 IEEE.

Global collaborative design is a common practice nowadays due to the international nature and business scope of many corporations. Therefore, it is critical to educate future engineers with the knowledge and skills to succeed in the now common multina

This research aims to show how redesigning a product, specifically modular redesign, may lead to changes in factory internal plant distribution, increasing the production levels of a company. This increase was achieved by implementing a methodology that will be discussed in this article and that includes the whole redesigning process of products, from disassembly to plant layout. For this research, tools used include functional analysis, design structure matrix, Theory of Technical Systems, design for assembly, diagram of operations and some management concepts of the platform of a modular product. To illustrate the implementation of the proposed methodology, a blender was chosen as a study case, in which, after applying the methodology, an increase in modularity, in the efficiency of design and in the efficiency of assembly, as well as a reduction in assembly times were obtained. Finally, with the new proposed plant layout, a significant increase in the production of blenders was successfully obtained.

Societal risks associated with debris flow hazards are significant and likely to escalate due to global population growth trends and the compounding effects of climate change. Quantitative risk assessment methods (QRA) provide a means of anticipating the likely impacts and consequences of settlement in areas susceptible to landslide activity and are increasingly being used to inform land use decisions that seek to increase disaster resilience through mitigation and/or adaptation. Current QRA methods for debris flow hazards are based primarily on empirical vulnerability functions that relate hazard intensity (depth, velocity, etc.) to expected levels of loss for a given asset of concern, i.e. most of current methods are dedicated to loss-intensity relations. Though grounded in observed cause-effect relationships, empirical vulnerability functions are not designed to predict the capacity of a building to withstand the physical impacts of a debris flow event, or the related uncertainties associated with modelling building performance as a function of variable debris flow parameters. This paper describes a methodology for developing functions that relate hazard intensity to probability of structural damage, i.e., fragility functions, rather than vulnerability functions, based on the combined hydrodynamic forces of a debris flow event (hazard level) and the inherent structural resistance of building typologies that are common in rural mountainous settings (building performance). Hazard level includes a hydrodynamic force variable (FDF), which accounts for the combined effects of debris flow depth and velocity, i.e. momentum flux (hv2), material density (?) and related flow characteristics including drag (Cd) and impact coefficient (Kd). Building performance is measured in terms of yield strength (Ay), ultimate lateral capacity (AU) and weight to breadth ratios (W/B) defined for a portfolio building types that are common in mountain settlements. Collectively, these model

Bone transport distraction osteogenesis (BTDO) is a surgical procedure that has been used over the last 30 years for the correction of segmental defects produced mainly by trauma and oncological resections. Application of BTDO has several clinical advantages over traditional surgical techniques. Over the past few years, several BTDO devices have been introduced to reconstruct mandibular bone defects. Based on the location and outline of the defect, each device requires a uniquely shaped reconstruction plate. To date, no biomechanical evaluations of mandibular BTDO devices have been reported in the literature. The present study evaluated the mechanical behavior of three different shaped prototypes of a novel mandibular bone transport reconstruction plate and its transport unit for the reconstruction of segmental bone defects of the mandible by using numerical models complemented with mechanical laboratory tests to characterize strength, fatigue, and stability. The strength test evaluated device failures under extreme loads and was complemented with optimization procedures to improve the biomechanical behavior of the devices. The responses of the prototypes were characterized to improve their design and identify weak and strong regions in order to avoid posterior device failure in clinical applications. Combinations of the numerical and mechanical laboratory results were used to compare and validate the models. In addition, the results remark the importance of reducing the number of animals used in experimental tests by increasing computational and in vitro trials. © VC 2014 by ASME.

Introduction: The incidence of vertical root fracture in endodontically treated teeth increases with patient age. This study evaluated the microstructure, chemical composition, and mechanical properties of radicular dentin as a function of aging. Methods: Single-rooted teeth were obtained from adult donors ranging from age 15 to older than 80 years. Beams were extracted from the middle third of the root and subjected to 4-point flexure to failure to evaluate strength of dentin in terms of donor age. Based on the strength distribution, the fatigue strength of root tissue from young (<= 30 years) and old (>= 55 years) donor teeth was evaluated via cyclic flexure loading. The microstructure and chemical composition of radicular dentin from the 2 groups were evaluated as a function of distance from the root apex using microscopy and Raman spectroscopy, respectively. Results: The strength decreased with age by approximately 25 MPa per decade, which resulted in a significant difference (P <= .0001) between the young (199 +/- 36 MPa) and old (122 +/- 11 MPa) groups. There was also a significant difference (P <= .0001) in fatigue strength between the young and old age groups. Both the mineral-to-collagen ratio and degree of cross-linking increased with age, with the largest changes identified in the apical and middle thirds, respectively. Conclusions: There is a reduction in the damage tolerance of radicular dentin with increasing age. This degradation appears to result from changes in the microstructure, corresponding chemical composition, and increase in collagen cross-linking with age, and is most severe near the root apex.

Bitumen is a black material composed of a mixture of various natural hydrocarbons. Bitumen has been commonly used in road paving and roofing applications thanks to its hydrophobic and adhesives properties. The production of Polymer Modified Bitumens (PMB) has allowed the development of materials with better performance in comparison to pure bitumen. This work presents the effect of addition of polymer to a Colombian bitumen from its morphological, rheological and thermal properties, in order to identify different modification levels. The polymers used as modifiers were polyethylene wax (CPE), styrene butadiene styrene (SBS) and crumb rubber (CR). They were added to bitumen in proportions between 3 to 15% w/w. Both neat bitumen and PMB were characterized by penetration and softening point. Thermal and rheological characteristics were analyzed by differential scanning calorimetry (DSC) and rotational rheometry, respectively. Changes in the morphology were measured by atomic force microscopy (AFM). The experimental results showed that the CPE mixtures had the most pronounced effect on the conventional properties, achieving a 75% reduction in penetration and a 250% increase in the softening point compared to neat bitumen. The results obtained by DSC allowed identifying three glass transition temperatures (Tg) in neat bitumen. Mixtures with SBS altered Tg, showing changes on the thermal characteristics of neat bitumen. Mixtures with CPE and SBS showed the highest values of G*. The results obtained by AFM help identifying three different phases in neat bitumen and its variation with the addition of different polymer modifiers, showing considerable structural changes that led to changes in the material properties at the macroscopic level.

El reto de diseñar y construir maquinaria que se ajuste a los procesos productivos dentro de las organizaciones es un desafío que deben asumir de manera continua las áreas de ingeniería

n Colombia there are several funds to finance R&D projects, both public and private. Among the public entities are Colciencias, SENA, Innpulsa, Ruta N and the General System of Royalties -SGR-. Generally the execution of such projects with public resource

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).

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

Total intravenous anesthesia is a widely used technique that relies on the use of intravenous anesthetics, propofol being the most frequently used and studied. At present, there are pharmaceutical and pharmacokinetic tools that are used to generate mathematical models to ensure the safe and moderately effective use of this technique. However, the depth of anesthesia is determined purely on the clinical findings and this requires neurological monitoring such as the bi-spectral index (BIS) in order to correlate the data derived from the pharmacokinetic models used for the administration of the anesthetic with the determination of its desired clinical effect. We designed an operating system for automated control of the propofol infusion that provides feedback on the basis of the data generated by the BIS monitor. The system is programmed to increase or decrease the propofol infusion within a specific BIS range and, consequently, in accordance with the needs of the individual patient. We describe anesthetic management using this technique in a female patient taken to surgery for prosthetic mammary implantation under general anesthesia at the University Hospital. An intraoperative record was generated including the depth of anesthesia and its action on propofol concentration at the effective site using the automated administration and control system. We concluded that the use of closed-loop total intravenous anesthesia under neurologic monitoring is the next step in the evolution of this technique. It is less reliant on the pharmacokinetic models available at present, and is better suited to adapt to the specific needs of individual patients and to the type of surgical intervention. © 2012 Sociedad Colombiana de Anestesiología y Reanimación. Published by Elsevier España, S.L. All rights reserved.

Currently many companies base their marketing strategy around a family of products. Thus, they regularly add new variations to products in order to meet changing market needs, or to attract new customers. Although the basic functionality remains unchanged across products, new features, aesthetic appearance and technologies are incorporated in each new product. This if it is not checked, can generate the "complexity of the product," which leads to a loss of productivity or quality. Thus, the effective management of product variations in design and manufacturing is challenging. The key is minimizing the non-value added variations through models within a range of options without limiting customers. This article discusses the factors that contribute to the "complexity of the product" and this is done through the product line commonality index (PCI) [1], which measures the level of common parts in a product family. A case study of bicycle frame displays its implementation and functionality. The index shows the possibility that the products in a family share parts effectively (modularity) and reduces the total number of parts (multifunctionality). © (2014) Trans Tech Publications, Switzerland.

This paper presents a review and results achieved in some of the most important initiatives about business association in the sector of assembly of motorcycles, which have generated since 2010 in Colombia between several companies with motorcycle assembly plants of this kind of vehicles that are located in the country, with an important group of local suppliers. While, as in some of these projects of innovation and technological development carried out, academia and technological Development Centers have participated as administrators or executors of these, contributing to strengthen university-business-state relationship.

Fish scales are laminated composites that consist of plies of unidirectional collagen fibrils with twisted-plywood stacking arrangement. Owing to their composition, the toughness of scales is dependent on the intermolecular bonding within and between the collagen fibrils. Adjusting the extent of this bonding with an appropriate stimulus has implications for the design of next-generation bioinspired flexible armours. In this investigation, scales were exposed to environments of water or a polar solvent (i.e. ethanol) to influence the extent of intermolecular bonding, and their mechanical behaviour was evaluated in uniaxial tension and transverse puncture. Results showed that the resistance to failure of the scales increased with loading rate in both tension and puncture and that the polar solvent treatment increased both the strength and toughness through interpeptide bonding; the largest increase occurred in the puncture resistance of scales from the tail region (a factor of nearly 7). The increase in strength and damage tolerance with stronger intermolecular bonding is uncommon for structural materials and is a unique characteristic of the low mineral content. Scales from regions of the body with higher mineral content underwent less strengthening, which is most likely the result of interference posed by the mineral crystals to intermolecular bonding. Overall, the results showed that flexible bioinspired composite materials for puncture resistance should enrol constituents and complementary processing that capitalize on interfibril bonds. © 2019 The Author(s) Published by the Royal Society. All rights reserved.

Nowadays, there are plenty of studies that seek to determine which are the skills that should be met by an engineer. Communication and teamwork are some of the most recurrent ones associated with a knowledge of the engineering sciences. However, their application is not straight forward, due to the lack of educational approaches that contributes to develop experience-based knowledge. Learning Factories (LF) have shown to be effective for developing theoretical and practical knowledge in a real production environment. This article describes the transformation process of a training-addressed manufacturing workshop, in order to structure a Learning Factory for the production engineering program at EAFIT University. The proposed transformations were based on the definition of three pillars (didactic, integrative and engineering) for the development of an LF. We argue that a proper transformation process may contribute to ease the path towards new manufacturing trends such as industry 4.0 into an academic context that strengths the engineering training process. © 2017 The Authors

Environmental Stress Screening (ESS) chambers are commonly used to test Printed Circuit Boards (PCBs) to detect early failures before they are used in the field. This research is motivated by our interactions with an electronics manufacturer

The hardware in the loop (HIL) platforms constitute an accelerated engineering design medium that subsequently reduces the risk of failure in the implementation process. This fact is enhanced when the designer is faced with extremely complex tasks and when design errors can lead to destructive and costly testing. The design of complex algorithms such as non-linear controllers applied to electronic control units of combustion engines, is a task of higher complexity level, and tests with incorrectly adjusted drivers can result in engine breakdown. This document reports the performance and effectiveness of a two-HIL scheme as an interactive design platform used for the design of electronic control units ECU, for internal combustion engines. The implementation and adjustment of two NMPC strategies aimed at optimizing the operation of the engine from three fronts: energetic, economic and environmental, involving independent and simultaneous objectives, give an account of the usefulness of the interactive design scheme. © 2017, Springer-Verlag France.

In future industry, defined as Industry 4.0, production planning and control strategies will be executed by human beings backed by computational tools for decision making; One of these tools is shop floor simulation, and a natural scenario to learn about how to use it for productive processes design and control are the Learning Factories. In this paper, shop floor simulation is identified as a tool for planning and controlling production, also a state of the art about its implementation is exposed in academic and industrial environments. In addition, the trends in the construction of the Learning Factories are shown, and some aspects about how they can be used for shop floor simulation. This work also proposes the realization of a digital model in EAFIT University Learning Factory as a first step towards digital learning factory. © 2019 IEEE.

The search for impact-tolerant, light-weight flexible materials has challenged materials scientists and engineers for decades. In this quest, many researchers have focused on studying natural armor as a guide to propose bioinspired materials with enhanced properties. The energy dissipation and flexibility mechanisms activated at different hierarchical structural levels of natural systems are used here as a guide to improve the energy and flexibility of synthetic materials. In particular, fish scales and osteoderms are selected as proper biological models to develop a novel family of cost-effective bioinspired protecto-flexible (Pf) materials. Furthermore, a bullet-proof protecto-flexible prototype is manufactured and tested. The ballistic tests suggest that under real stringent conditions, the system is capable of absorbing high levels of energy while remaining flexible enough to allow movement to the user. Remarkably, the material system developed allows its implementation into realistic high volumes of production with low added costs. Consequently, the proposed strategy for developing bioinspired Pf materials will enable the development of the next generation of high-performance impact-resistant materials. © 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

The problem of improving the environmental performance of a supply chain without entailing excessive cost is becoming a frequent problem as companies face an increasing pressure from governments and customers for reducing the environmental impact of their activities. As the environmental improvement of an operating supply chain implies not only technology upgrading decisions, but also decisions regarding the structure of the supply chain itself, deciding on what strategy to follow is a complex task. The aim of this work is to provide a bi-objective solution approach for finding such strategy so that both the environmental and financial goals are best met.

In Colombia there are several funds to finance R&D projects, both public and private. Among the public entities are Colciencias, SENA, Innpulsa, Ruta N and the General System of Royalties -SGR-. Generally the execution of such projects with public resources is complex because in their various stages of development and implementation must be arranged multiple stakeholders, such as national and local government, academia, the private sector and the communities in the regions where projects or programs are executed, and also instances of evaluation and monitoring. It is under this complex framework that is presented the experience of Eafit University in designing a model of Project Management Office (PMO) and the results of its implementation in the execution of projects of science and technology financed with public resources. As a result, it was evidenced the necessity to structure a management model to coordinate programs that require a higher level of monitoring and supervision, which allows to implement some useful measures to manage these, as they were the definition of communication channels efficiently articulated between stakeholders and implementation of dashboards for monitoring. This model was adjusted based on the knowledge areas and process groups of the guide proposed by PMI.

This Letter describes a low-cost, scalable nanomanufacturing process that enables the continuous forming of thin metallic layers with nanoscale accuracy using roll-to-roll, laser-induced superplasticity (R2RLIS).

Perm. Deformation of Asphaltic Mixtures in the Metropol. Area of Valle de Aburra - Antioquia, Which Are Built under IVIAS' Specifications and Valle de Aburra, Were Studied by Employing A Constitutive Model Proposed Previously. This Model Had Proved to Be Effective in Predicting Deformations of Asphaltic Mixtures in the U. Kingdom under Different Kinds of Loads; under Uniaxial and Triaxial Conditions and Temperatures at Intervals between 0C and 40C. for the Specific Case of Valle de Aburra, Temperatures Ranged between 20C and 50C and the Model Was Implemented in Order to Predict Susceptibility to Perm. Deformation. by Means of An Exp. Stud. on Mixtures, It Was Found That Their Behav. under Steady State Condition Followed the Model Modified by Cross2, Thus Mixtures Showed A Visco-Lin. and Non-Lin. Behav. at Low and High Stress Levels, Respectively. It Was Observed That under Loading and Unloading Conditions, There Is A Temp. Dependence on the Mat. Behav., Which Was Properly Predicted by Arrhenius3 under the Studied Temperatures Interval. When Modeling Mixtures Behav., It Was Found That That Their Strain Susceptibility Varied Widely Depending on the Constituent Mat., Especially on the Aggregate, in Spite of the Fact That the Mixtures Are Similar.

Incremental sheet forming by the method of single point incremental forming Dieless-SPIF, is a widely studied process, experimented and developed in countries with high manufacturing technologies, with friendly costs when the productive configuration in a productivity system is based in small production batches. United states, United kingdom and France lead this type of studies and cases, developing various proof with experimental geometries, different from the national environment such as Colombia, Bolivia, Chile, Ecuador and Peru where this process where discretely studied. Previously mentioned, it pretends develop an experimental case of a particular geometry, identifying the maximum formability angle of material permissible for the forming of a piece in one pass, the analysis of forming limit curve (FLC), with the objective to emphasizes in this innovative method based in CAD-CAM technologies, compare with other analogous process of deformation sheet metal like embossing, take correct decisions about the viability and applicability of this process (Dieless) in a particular industrial piece, which responses to the necessities of productive configurations mentioned and be highly taken like a manufacturing alternative to the other conventional process of forming sheet metal like embossing, for systems with slow batches production. © Published under licence by IOP Publishing Ltd.

UNLABELLED: Spatial variations in the microstructure of dentine contribute to its mechanical behaviour. OBJECTIVE: The objective of this investigation was to compare the microstructure and fatigue behaviour of dentine from donors of two different countries. METHODS: Caries-free third molars were obtained from dental practices in Colombia, South America and the US to assemble two age-matched samples. The microstructure of the coronal dentine was evaluated at three characteristic depths (i.e. deep, middle and superficial dentine) using scanning electron microscopy and image processing techniques. The mechanical behaviour of dentine in these three regions was evaluated by the fatigue crack growth resistance. Cyclic crack growth was achieved in-plane with the dentine tubules and the fatigue crack growth behaviour was characterized in terms of the stress intensity threshold and the Paris Law parameters. RESULTS: There was no difference in the tubule density between the dentine of patients from the two countries. However, there were significant differences (p

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

This work describes an easy to use constitutive model able to predict the mechanical behavior of polymer matrix particulate composites at temperatures above the glass transition temperature Tg. This model was based on both phenomenological and micromechanical theories. With the model proposed it is possible to obtain the properties of the material (macro) using the characteristics of its components (micro). This model exhibits a reasonable agreement with experiments under various volume fractions of particles.

Biodiesel from Jatropha curcas seeds is one promissory option in the biofuels field. This is a crop that develops in tropical countries which can grow on marginal soils with low irrigation and helps to control the erosion. This bush grows quickly and produces seeds with approximately 35% oil content and it does not compete with food crops. However, for the production of biodiesel from Jatropha to be sustainable and profitable it is required research and technological development at all stages of the production chain. This articleshows the results of a research process that aims the determination of some significant physical and mechanical characteristics of Jatropha curcas seeds. This data are important, because they provide necessary information in the design of equipment and processes for Jatropha curcas oil production; especially, for mechanical oil extraction. As a result of the research process different properties were determined, for example: compression (2.8 mm) and energy (332 N.mm) required for fracture, average dimensions of seeds (length: 10.8 mm/width: 17.8 mm/thickness: 8.6 mm), fractions of shell (38%) and albumen (62%) in the seed, moisture content of seed (5.2%), oil content (29%), calorific value of shell (0.3 MJ/kg) and albumen (0.8 MJ/kg). All these variables are important parameters in the design of equipment, but also are useful to evaluate alternative uses for by-products of the oil extraction process, for example as energy source. Besides, the available information in Colombia about Jatropha is not much.

This case of study it is showed how the implementation of two different methods reach the effective interaction of engineering processes that have statistically meaningful differences between the key performance indicators for the reaching, the cost and the time. Both from the identification of projects, products, machines and in general of the technologies involved in the manufacturing of products made of wood. The first one is based on the framework from the Project Management Institute (PMI), meanwhile the second one is based on a mixture of Business Processes Management (BPM) and the Product Lifecycle Management (PLM) for projects management. The case of study describes the key focuses, assumptions and tasks required by them, like the experimental design and the statistically comparison gotten between them. At the end, the effects of both focuses related with the key performance indicators for the reaching, cost and time are discussed. © 2018 Latin American and Caribbean Consortium of Engineering Institutions. All rights reserved.

The purpose of this study was to evaluate the structure and material properties of native mandibular bone and those of early regenerate bone, produced by bone transport distraction osteogenesis. Ten adult foxhounds were divided into two groups of five animals each. In all animals, a 3- to 4-cm defect was created on one side of the mandible. A bone transport reconstruction plate, consisting of a reconstruction plate with an attached intraoral transport unit, was utilized to stabilize the mandible and regenerate bone at a rate of 1 mm/day. After the distraction period was finished, the animals were killed at 6 and 12 weeks of consolidation. Micro-computed tomography was used to assess the morphometric and structural indices of regenerate bone and matching bone from the unoperated contralateral side. Significant new bone was formed within the defect in the 6- and 12-week groups. Significant differences (P = 0.05) between mandibular regenerated and native bone were found in regard to bone volume fraction, mineral density, bone surface ratio, trabecular thickness, trabecular separation, and connectivity density, which increased from 12 to 18 weeks of consolidation. We showed that regenerated bone is still mineralizing and that native bone appears denser because of a thick outer layer of cortical bone that is not yet formed in the regenerate. However, the regenerate showed a significantly higher number of thicker trabeculae. © 2011 Springer Science+Business Media, LLC.

Royalties are income from rights given to the state for the extraction of non-renewable natural resources. In order to guarantee the equal distribution of these funds, Colombia created the General System of Royalties, which allocates 10% of these investments toward science, technology, and innovation programs considered a priority by each region. Carrying out royalty programs is complex due to the fact that each development phase requires that multiple actors be in agreement, including regional and city administrative offices, the academic sector, the private sector, the communities where the programs will be conducted, and the project evaluation and supervision entities, namely the National Planning Department and Colciencias as technical secretariat. Within this complex framework, we present the experience of EAFIT University in the design of a Project Management Office (PMO) model and the partial results of the implementation of two programs funded with royalties, which evidenced the need to structure a management model to coordinate programs requiring a higher level of follow-up and supervision, thus ensuring a responsible management of public resources under the private sector scheme where efficient and articulated communication channels were established amongst those interested and in accordance with their requirements. This model was adjusted based on the areas of knowledge and process groups proposed by the PMI.

This paper presents the development of an exposure model for the residential building stock in Antioquia (the second most populated Department of Colombia), the development of fragility functions for unreinforced masonry buildings, and estimation of building damage for two possible seismic events. Both the exposure and fragility models are publically available and can be used to calculate damage and losses due to single events, or probabilistic seismic hazard. The exposure model includes information regarding the total built-up area, number of buildings and inhabitants, building class, and replacement cost. The methodology used for the creation of the exposure model was based on available cadastral information, survey data, and expert judgment. Fragility functions were derived using nonlinear time history analyses on single-degree-of-freedom oscillators, for unreinforced masonry structures which represent more than 60% of the building stock in the region. Both seismic scenarios indicate that an event corresponding to a return period of 500 years located within the region of interest would cause slight or moderate damage to nearly 95 thousand structures, and about 32 thousand would have severe damage or collapse. This study was developed as part of the South America Risk Assessment project, supported by the Global Earthquake Model and SwissRe Foundation. © 2016, Springer Science+Business Media Dordrecht.

Modern nanofabrication processes on metals, polymers, and ceramics often require deforming these materials at strain rates ranging ~101 – 107 s–1. Therefore, there is a need to develop an appropriate methodology capable of measuring and predicting the effects of these deformation rates on the final mechanical response of the nanomaterial being processed. Here we report an experimental study of the indentation response of three materials with different nature and mechanical properties, but with known time-dependent mechanical responses. These materials allow validation of the findings under a wide variety of conditions. One metal (Pb), and two polymers (PMMA and PS), were indented at the sub-20 nm scale using commercial atomic force microscopy (AFM) probes. Based on our experimental findings, we also propose an analytical model for creeping solids in which their nanoscale mechanical behavior is completely described by two components: an elastic component (characterized by the Hertz contact model) and a time-dependent component (characterized by a power-law model). The proposed experimental protocol is easy to implement, and the analytical model can be extended to a large variety of materials. The ability to characterize the time-dependence of the mechanical response of different materials at the nanoscale will enable a better estimation of the effect of manufacturing processes on the properties and performance of nanomaterials. © 2020 Elsevier Ltd

Freeze casting offers a tremendous opportunity to obtain bio-inspired synthetic materials that mimic microstructural characteristics of natural materials like bone and nacre. These natural materials display high strength and toughness; properties usually desired in synthetic engineering materials. The freeze casting process involves four basic steps. The ceramic slurry preparation consists of fine ceramic particles that are suspended in a fluid. In the current work, water based kaolin suspensions were prepared varying the volume fraction of ceramic particles. After the ceramic slurry is properly prepared, the slurry is frozen. The solidification process is often performed using directional freezing, which creates laminar pores, providing the microstructural characteristics of the final part. When a crystal is formed the frozen front moves the particles around it, allowing particles to agglomerate around the crystal, creating different types of pores. In the present study, freezing rates were varied. Subsequently, the samples have to be lyophilized in order to sublimate the frozen liquid phase. Sublimation is the transformation of a solid phase directly to the gas phase. As a result the lyophilized sample has a porous structure with a replica of the water crystals formed during freezing. As a final step, sintering of ceramics is performed. Results of the microstructural characteristics of the samples revealed that varying the volume fraction of ceramic particles and freezing rates have a direct influence on the pore characteristics, changing from circular to laminar pores.

[No abstract available]

Dentro del proceso de la enseñanza en el área de la Ingeniería, uno de los retos es la integración de los conceptos teóricos con los sistemas productivos industriales en tiempo real, donde se perciba el comportamiento de un producto...

Friction stir welding (FSW) is an alternative method of joining materials with low melting point, patented in 1991 by the American Welding Institute (UK). This method uses the heat generated by mechanical friction between two moving parts...

Flexural behaviour of reinforced concrete (RC) frames is a well-studied topic that has been evaluated both analytical and experimentally. Contrarily, shear failure of RC frames have been studied in a lesser amount

Exposing students to international experiences is becoming a common practice to prepare students with global capabilities. One pedagogical activity used to promote global competencies is the participation of students in multinational design projects. This is a problem-based learning approach in an international setting, where students get immersed in the solution of anengineering design task while they work in teams and collaborate with international partners. The main goal of these projects is to foster international collaboration and to offer an opportunity to the students to develop professional skills through international teamwork effort in the solution of a design problem. However, a real challenge of this practice has been to create an effective interaction among the students participating in this type of projects and to maintain the flow of information, and student engagement in the project and in their learning. The main objective of this work is to investigate the sociotechnical interaction of engineering students working in a multinational collaborative project and the role of information technology tools and the nature of the interaction in this experience. For this purpose an assessment tool was developed and used to determine the interaction among the students (frequency, quantity and quality), the value of social interaction in the flow of the interaction, and the impact of the interaction in the development of the project. The main findings of this instrument are presented in this work. © 2015 TEMPUS Publications.

Cellular materials are formed by solid cells in a gaseous core. They exhibit good strength to mass ratio and they are used as insulators and as a core in sandwich composite manufacture. This work describes an extensive study on the structure and physical-mechanical properties of rigid polyurethane (PU) foams. The effect of composition and processing conditions on the mechanical properties were studied. Morphology, specific strength and density were evaluated to determine the optimal levels of processing for a required application. Foam morphology was characterized using stereoscopy and optical microscopy. A basic mechanical property as compression strength was measured in the plateau zone.