Doctorado en Ingeniería (tesis)

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https://hdl.handle.net/10784/81

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Compendium on "assessment of intended deformations and kinematic identification of parallel mechanisms under quasi-static condictions"
(Universidad EAFIT, 2010) Durango Idárraga, Sebastián; Ruíz Salguero, Óscar Eduardo
Geometry and topology extraction and visualization from scalar and vector fields
(Universidad EAFIT, 2013) Congote Calle, John Edgar; Ruíz Salguero, Óscar Eduardo; Posada, Jorge León
Effects of topography on 3D seismic ground motion simulation with an application to the Valley of Aburrá in Antioquia, Colombia
(Universidad EAFIT, 2013) Restrepo Sánchez, Doriam Leidin; Jaramillo Fernández, Juan Diego
This dissertation presents a numerical scheme based upon the finite element framework for the numerical modeling of earthquake-induced ground motion in the presence of realistic topographic variations of the Earth’s crust -- We show that by adopting a non-conforming meshing scheme for the numerical representation of the surficial topography we can obtain very accurate representations of earthquake induced ground motion in mountainous regions -- From the computational point of view, our methodology proves to be accurate, efficient, and more importantly, it allows us to preserve the salient features of multi-resolution cubic finite elements -- We implemented the non-conforming scheme for the treatment of realistic topographies into Hercules, the octree-based finite-element earthquake simulator developed by the Quake Group at Carnegie Mellon University -- We tested the benefits of the strategy by benchmarking its results against reference examples, and by means of convergence analyses -- Our qualitative and quantitative comparisons showed an excellent agreement between results -- Moreover, this agreement was obtained using the same mesh refinement as in traditional flat-free simulations -- Our approach was tested under realistic conditions by conducting a comprehensive set of deterministic 3D ground motion numerical simulations in an earthquake-prone region exhibiting moderate-to-strong surficial irregularities known as the Aburr´a Valley in Antioquia-Colombia -- We proposed a 50 50 25 km3 volume to perform our simulations, and four Mw = 5 rupture scenarios along a segment of the Romeral fault; a significant source of seismic activity of Colombia -- We created and used the Initial Velocity Model of the Aburr´a Valley region (IVM-AbV) which takes geology as a proxy for shear-wave velocity -- Each earthquake model was simulated using three different models: (i) realistic 3D structure with realistic topography; (ii) realistic 3D structure without topography; and (iii) homogeneous half space with realistic topography. Our results show how topographic irregularities greatly modify the ground response -- In particular, they highlight the importance of the combined interaction between source-effects, focusing, soft-soil conditions, and 3D topography -- We provide quantitative evidence of this interaction and show that topographic amplification factors at some locations can be as high as 500 percent, while some other areas experience reductions -- These are smaller than the amplifications, on the order of up to 100 percent
Computational Study of Cell Mobility and Transport Phenomena Through Textile Vascular Grafts Using a Multi-Scale Approach
(Universidad EAFIT, 2015) Valencia Cardona, Raúl Adolfo; García Ruíz, Manuel Julio; Bustamante Osorno, John
Textile vascular grafts are biomedical devices that serve as partial replacement of damaged arterial vessels, prevent aneurysms rupture and restore normal blood flow -- It is believed that the success of a textile vascular graft, in the healing process after implantation, is due to the porous micro-structure of the wall -- Among the key properties that take part in the tissue repair process are the type of fabric and degree of porosity and permeability, defining the ability of a well-controlled environment for the neovascularization, nutrient supply, and cellular transport -- Although the transport of fluids through textiles is of great technical interest in biomedical applications, little is known about predicting the micro-flow pattern and the transport and deposition of individual platelets, related with the graft occlusion -- Often, this information is difficult to obtain experimentally both in vivo and in vitro, representing a great deal of research efforts -- The aim of this work is to investigate how the type of fabric, permeability and porosity affect both the local fluid dynamics at several scales and the fluid-particle interaction among platelets in textile grafts with an anastomosis of end-to-end configuration -- Two types of samples were analyzed: woven and electrospun, this last one has been manufactured -- This study involves both experimental and computational tests -- The experimental tests were performed to characterize the permeability and porosity under static conditions -- The computational tests are based on a multiscale approach where the fluid flow was solved with the Finite Element Method and the discrete particles were solved with the Molecular Dynamic Method -- The fluid-particle interaction was accomplished in one-, two-, and four-ways, where the blood was considered as a suspension of platelets in plasma -- The textile wall was considered as a porous media with two scales of length: straight tubular structure with porous walls for the macro-domain and representative unit cells of fabric for the micro-domain. Additionally, it presents the implementation of a numerical case that includes one of the main applications of textile vascular grafts to repair Abdominal Aortic Aneurysms (AAA) -- The results have shown that the type of fabric in textile vascular grafts and the degree of porosity and permeability affect the local fluid dynamics and the level of penetration of platelet particles through the graft wall at several length scales, thus indicating their importance as design parameters -- It was found that the permeability is strongly depends on the micro-structure of the fabric, changing the local fluid dynamics and the time of residence of platelets inside the wall -- Moreover, the porous walls cause deviations from Poiseuille flow due to leakage flow through the wall from a macroscopic viewpoint -- Lastly, it was possible to observe that the textile wall with different porosities, acting like a barrier between the blood and an aneurysmal zone, affects the flow pattern, the number of platelets adhered to the artificial surface and the time of residence of platelets into the aneurysmal zone -- In conclusion, predicting the flow pattern and the mobility of blood cells through the textile wall before the graft is manufactured, the development of new textile grafts can be improved
Computational Geometry in Medical Applications
(Universidad EAFIT, 2016) Cortés Acosta, Camilo Andrés; Ruíz Salguero, Óscar Eduardo; Flórez Esnal, Julián
Handling Heterogeneity in Collaborative Networked Surgical Simulators
(Universidad EAFIT, 2016) Díaz León, Christian Andrés; Trefftz Gómez, Helmuth
Stand-alone and networked surgical virtual reality based simulators have been proposed as means to train surgical skills with or without a supervisor nearby the student or trainee -- However, surgical skills teaching in medicine schools and hospitals is changing, requiring the development of new tools to focus on: (i) importance of mentors role, (ii) teamwork skills and (iii) remote training support -- For these reasons, a surgical simulator should not only allow the training involving a student and an instructor that are located remotely, but also the collaborative training of users adopting different medical roles during the training sesión -- Collaborative Networked Virtual Surgical Simulators (CNVSS) allow collaborative training of surgical procedures where remotely located users with different surgical roles can take part in the training session -- To provide successful training involving good collaborative performance, CNVSS should handle heterogeneity factors such as users’ machine capabilities and network conditions, among others -- Several systems for collaborative training of surgical procedures have been developed as research projects -- To the best of our knowledge none has focused on handling heterogeneity in CNVSS -- Handling heterogeneity in this type of collaborative sessions is important because not all remotely located users have homogeneous internet connections, nor the same interaction devices and displays, nor the same computational resources, among other factors -- Additionally, if heterogeneity is not handled properly, it will have an adverse impact on the performance of each user during the collaborative sesión -- In this document, the development of a context-aware architecture for collaborative networked virtual surgical simulators, in order to handle the heterogeneity involved in the collaboration session, is proposed -- To achieve this, the following main contributions are accomplished in this thesis: (i) Which and how infrastructure heterogeneity factors affect the collaboration of two users performing a virtual surgical procedure were determined and analyzed through a set of experiments involving users collaborating, (ii) a context-aware software architecture for a CNVSS was proposed and implemented -- The architecture handles heterogeneity factors affecting collaboration, applying various adaptation mechanisms and finally, (iii) A mechanism for handling heterogeneity factors involved in a CNVSS is described, implemented and validated in a set of testing scenarios
Implementation of the Moving Particle Semi-implicit method to predict the drag resistance coefficient on 2D
(Universidad EAFIT, 2016) Pérez Gutiérrez, Carlos Andrés; García Ruíz, Manuel Julio
A dam break problem and the flow around a 2D submerged body on different scenarios were solved with the original Moving Particle Semi-implicit (MPS) method proposed by Koshizuka and Oka in 1996 -- The results of this study showed that although the original method reproduces the free surface of the fluid on the dam break computation, it can not accurately compute the pressure distribution over the submerged bodies -- It was found that the free surface was inaccurate when negative pressures were present in the particle domain -- Also, when modelling the interaction of a solid immersed in a fluid, the simulation exhibited stability issues and solid penetration -- Several modifications of the original MPS were studied, implemented and tested -- This thesis proposes a modified Moving Particle Semi-implicit (MPS)method for modelling immerse bodies in an free surface flow -- The MPS method is based on the prediction-correction calculation of the velocity field based on the Helmhotz-Hodge decomposition -- Initially the predicted velocity is calculated based on the viscous and external forces terms and then corrected by the gradient of the pressure which is obtained by the solution of the Poisson Pressure’s equation – This thesis shows how small variations in the source term of the Poisson Pressure’s equation can destabilise or stabilise simulations -- One of the main result of this research is an improved stability by means of a reformulation of the Poisson Pressure equation and the aid of relaxation factors -- Also, the pressure gradient was computed for non free surface particles only -- The results show that, although pressure fluctuations were still present, good results were obtained when compared the drag coefficient to the reported values in the literature
Aide à la décision en conception préliminaire par l'estimation des impacts environnementaux
(Universidad EAFIT, 2016) Agudelo Gutiérrez, Lina María; Mejía Gutiérrez, Ricardo; Nadeau, Jean Pierre; Pailhes, Jérôme
Environmental improvement of operating supply chains: a multi-objective approach for the cement industry
(Universidad EAFIT, 2017) Cadavid Giraldo, Nora; Vélez Gallego, Mario César
Nowadays companies worldwide face a growing pressure to reduce the environmental impact of their manufacturing activities -- However, the strategies used to achieve this goal are not clearly defined because of their conflicting relations with financial outcomes -- In parallel, globalization trends imply that as companies grow, usually through mergers and acquisitions, their supply chains become more complex -- The environmental improvement of these supply chains imply not only technical retrofit decisions aiming at adopting cleaner production technologies but also decisions regarding the structure of the supply chain itself -- Making these decisions becomes a difficult task because of the large number of variables involved, and the diversity of the interactions among them -- To tackle this problem, this research aims at providing a multi-objective solution approach for making technological retrofit decisions within an operating supply chain, so that both environmental and financial goals are best met -- The proposed solution approach is applied to the case of an operating cement supply chain in Colombia -- Several computational experiments were conducted, obtained results demonstrates that the proposed model is an e effective tool for multi-objective improvement decisions making, towards a more sustainable production process
The mechanical behavior of dentin: importance of microstructure, chemical composition and aging
(Universidad EAFIT, 2017) Montoya Mesa, Carolina; Ossa Henao, Alexander
Dental fracture is one of the three most common forms of failure of restored teeth and the most common cause of tooth loss or extraction in elderly patients -- Previous investigations conducted on aging of hard tissues have identified that there is a considerable reduction in the mechanical properties (i.e. fracture toughness, fatigue and flexural resistance) of dentin with aging and that may predispose tooth fracture -- These declines in properties have been attributed to microstructural and chemical composition changes over time -- However, these aging processes have not been really quantified and related with the changes in mechanical properties -- Accordingly, the aim of this work is to evaluate the aging process of coronal dentin in terms of the evolution of microstructure, changes in chemical composition and mechanical properties from selected age groups (young and old donors) -- The changes in these properties were evaluated in three different regions (outer, middle and inner) in order to identify spatial variations within the crown -- A brief description of the main literature on composition, microstructure and mechanical behavior of dentin is presented in chapter 2 -- An extensive experimental study was carried out in chapter 3 to identify the changes in microstructure of dentin with aging by means of optical and electron microscopy; while changes in chemical composition were analyzed using Raman Spectroscopy to calculate the mineral-to-collagen ratio -- Changes in mechanical properties were measured using Vickers micro-hardness -- Chapter 4 describes the importance of tubule density to the fracture toughness of dentin for young and old donor’s groups -- An approach previously proposed to study the mechanical behavior of porous materials was used to model the fracture toughness of coronal dentin in terms of the tubule characteristics -- Results were then compared with published results from previous studies -- The time-dependent deformation response of dentin was analyzed via spherical indentation experiments at different indentation loads in Chapter 5 -- From the experimental observations was proposed a simple model to describe the time dependent deformation behavior of dentin -- This model was based on previously proposed theories for indentation of time dependent materials, showing that the effective strain rate of dentin depends on its chemical composition (i.e. mineral-to-collagen ratio) and microstructure (i.e. lumen area fraction) -- The descriptions of the model were compared with the experimental results showing good agreement -- The same model was validated with experimental results of aged dentin, finding a low change in the deformation response of dentin with aging, as presented in chapter 6 -- Finally, preliminary results made on the mechanical properties of dentin have shown that the microstructure of aged human dentin can vary depending on the ethnic background of the donor and that this quality is critically important to the mechanical properties of the tissue -- In chapter 7 preliminary results on the comparison between the microstructure, chemical composition and mechanical properties of Colombian, Chinese and American donors is presented -- Finally, conclusions for the study are presented in chapter 8
Energy management strategy for a solar race car including meteorologic and probabilistic variable
(2018) Betancur Valencia, Esteban; Osorio Gómez, Gilberto
This thesis describes the energy management strategy for racing solar cars, the racing strategy is treated as an optimal control problem with random variables and uncertain predictions. A computational model is developed for estimating the vehicle performance under speciﬁc circumstances. Two evolutionary heuristic optimization methods are implemented and tested for this case, their eﬀectiveness, convergence and eﬃciency is measured and compared to exhaustive search approaches. The dependency on solar radiation is validated using the computational model with diﬀerent test cases. In order to reduce the uncertainties on the solar radiation estimation, satellite images are used as inputs to image processing and machine learning techniques, their eﬃcacy is compared. Finally, a validation case is executed and diﬀerent scenarios are evaluated with the inclusion of the proposed methods, the experimental performance of a vehicle obtained using the strategy in the World Solar Challenge 2015 is exposed and compared to the predicted results from the simulation.
Bacillus sp. strains and their inducible in vitro antagonism : a biochemical and molecular study
(Universidad EAFIT, 2018) Sierra Zapata, Laura; Villegas Escobar, Valeska; Romero Tabarez, Magally
Discovering novel antibiotic substances from natural sources and revitalizing the pipeline for screenings of naturally sourced substances that could render new bioactive compounds, is a priority nowadays in the face of a world crisis of antimicrobial resistance. This research was focused on disclosing an observed antagonism system composed of Bacillus sp. strains producing inducible antimicrobial activity against the plant pathogen Ralstonia solanacearum, a widespread bacterium that causes bacterial wilt disease to a great variety of plant species, including many agriculturally important ones as are bananas. The inducible phenomenon was discovered during the screening of 1493 aerobic endospore forming bacteria against plant pathogens. It was observed that in the presence of the chemical compound Triphenyl Tetrazolium Chloride (TTC), which belongs to the group of synthetic compounds known as tetrazolium salts used to monitor cell respiration, Bacillus sp. strains produced inhibition zones against the bacterial plant pathogen and other pathogenic bacterial species, while in the absence of the compound they did not have any bioactivity. During biochemical characterization, it was evidenced that although the phenomenon was observable across several species of the order Bacillales, strains belonging to B. cereus, B. pumilus and B. subtilis were outstanding in their inducible antagonism potential, among other species tested. Besides, relevant traits revealed that other tetrazolium salts did not induce antagonistic activity and that the addition of antioxidant compounds did not reduce the inducible antagonistic activity. Also, R. solanacearum sensitivity to antibiotics was not increased by the addition of TTC and the inducible activity was independent of the presence of the pathogenic strain. In order to determine genes and pathways that were activated under TTC conditions, transcriptomic and metabolomics analysis were performed. Transcriptomic results revealed that specific pathways of the nitrogen metabolism, such as pyrimidines, purines and histidine biosynthetic routes, were 2 to 5 fold up-regulated in B. subtilis NCIB-3610 cells growing under TTC presence. On the other hand, metabolomic analysis showed that 28 specific compounds were either unique or 3 to 5 fold more abundant in active extracts obtained from inducible conditions, compared to non-induced controls. Data mining on public chemical databases, using intrinsic properties of the selected compounds, suggests that they mostly belong to chemical families of carbamates, imidazoles, pyrrolidines, pyrimidines, dipeptides and oligopeptides, all of which are part of the nitrogen metabolism. Results suggest that Bacillus cells reduction of TTC into triphenyl formazan (TPF) and its further accumulation inside the cells, induces the production of nitrogen-derived compounds, either by activation of nitrogen metabolism biosynthetic pathways or by a biotransformation of TPF into derivatives. Once produced, the compounds are secreted into the medium and act as antimicrobials against other bacteria.
Fabricación y caracterización mecánica de nanomateriales
(Universidad EAFIT, 2018) Múnera, Juan Camilo; Ossa Henao, Edgar Alexander
Riemannian wavefield extrapolation
(Universidad EAFIT, 2018) Quiceno Echavarría, Héctor Román; Villegas Gutiérrez, Jairo Alberto; Gutiérrez Isaza, Diego Alberto
Exploring the role of system operation modes in failure analysis in the context of first generation cyber-physical systems
(Universidad EAFIT, 2018) Ruíz Arenas, Santiago; Horváth, Imre; Mejía Gutiérrez, Ricardo; Rusák, Zoltan
Processing and characterization of PEI/PBT and PEI/PBT/PTFE high-performance polymer blends
(2018) Vásquez Rendón, Mauricio; Álvarez Láinez, Mónica Lucía
Polymer blending emerged as an attractive strategy to obtain new materials with tailored properties from already existing ones. It has focused mainly on the development of blends from commercial polymers. Fewer works have studied in depth the fabrication of blends from high-performance polymers, since fundamental studies in polymer-polymer interactions are not usually performed with these challenging materials. This work aim to study blends obtained from three high-performance polymers with good flammability characteristics: poly(ether imide) (PEI), poly(butylene terephthalate) (PBT) filled with a flame retardant compound, and poly(tetrafluoroethylene) (PTFE); and presents for the first time, the relationship between processing conditions, viscoelastic properties, interfacial tension, and composition with the morphology and final performance for this kind of systems. Two sets of blends, binary PEI/PBT and ternary (PEI/PBT)/PTFE blend, are prepared by melt processing in an internal mixer. A complete miscibility study is performed from thermal analysis using MDSC and DMA, accompanied by a theoretical approach of the interfacial tension by using the harmonic mean equation. In relation to ternary blends, phase’s interaction is predicted from the Harkin’s spreading coefficient model. Morphological study is contrasted to miscibility results and the distribution of blends constituents is evaluated by SEM and TEM analyses. As blends resulted being partially miscible, the use of selective extraction technique allows us to better evidence the PEI and PBT distribution in binary blends. To evaluate the mechanical performance, tensile tests are performed to Type V samples obtained by injection molding. The thermal stability is studied by TGA and DTG techniques, and flammability tests from a horizon tal burning tests according to the UL-94 standard. The first set of blends is obtained between PEI and PBT, which have notable differences in their processing characteristics. Previous works were found on PEI/PBT blends that mix simultaneously PEI and PBT phases by different solution and melt processing methods. In this work a novel two-step melt processing method to fabricate binary PEI/PBT blends in an internal mixer is proposed. The main processing parameters are defined after the thermal and rheological characterization of pure materials, to obtain binary PEI/PBT blends within the entire compo sition range using the same processing conditions. The second set of blends is obtained with the aim of modify the mechanical properties of PEI/PBT blends by adding PTFE concentrations of 5 wt%, 10 wt%, and 15 wt%. The same two-step melt processing method proposed for binary PEI/PBT blends is used for (PEI/PBT)/PTFE blends fabrication. It is found that PTFE must be added during step 1 in order to enhance phases’ integration during mixing. Ternary blends are obtained for PEI concentrations higher than 50 wt% for the same reason. A complete miscibility study provided information about the phases’ heterogeneity in both, binary and ternary blends. The binary PEI/PBT blends resulted being partially miscible depending on PEI composition, and two groups of blends are identified: PBT-rich blends and PEI-rich blends. Miscibility evaluation by MDSC and DMA reveals that PBT-rich blends are immiscible, since it is no noticed any shift in the glass transition temperatures (Tg) of the pure components. PEI-rich blends on the other hand, exhibit a significant displacements of Tg to higher temperatures suggesting miscibility between PEI and PBT. The study of miscibility in ternary blends, reveals that PTFE does not interfere with the miscibility behavior of PEI and PBT, since there are noticed the same thermal transitions as those for binary blends. Interfacial tension values reveal that all phases are highly immiscible for all possible polymer pairs, due to the no table differences between their polar components. Prediction of phase’s distribution in ternary blends by the spreading coefficient model, reveals there is favored the encapsulation of PTFE phase by PEI when PBT is the matrix. Morphological evaluation of binary PEI/PBT blends is in good agreement to blends microrheology theory proposed by Taylor and Grace. PBT-rich blends exhibit coarse droplets distribution of highly viscous PEI phase, with sub-inclusions of small droplets of low viscous PBT phase. By using the Soxhlet selective extraction technique together with SEM and TEM, it is presented new evidence on the morphological evolution of PBT-rich blends, and we noticed that PBT-rich and PEI-rich blends are separated by an intermediate cocontinuous morphology at even PEI and PBT compositions. PEI-rich blends on the other hand, exhibited tiny droplets of PBT (as small as 120 nm) bonded to PEI matrix through a fibrillar interface, and a new morphology denominated spore-like morphology is presented. In order to validate the addition of PTFE to the PEI phase during step 1 in ternary blends fabrication, we evaluate the morphology formed between PEI/PTFE blends. It is noticed that under these conditions it is favored the distribution of PTFE phase in two major fashions: well-embedded PTFE nano-sized droplets, and debonded PTFE spheres of 1.5 μm of average diameter. SEM and TEM analysis of ternary blends confirm the miscibility study results, and encapsulation of PTFE droplets by PEI phase in ternary blends when PBT is the matrix, is predicted by the spreading coefficient model. Mechanical, thermal, and flame resistance performance is strongly influenced by miscibility and the morphologies obtained in both, binary and ternary blends. The experimental results are discussed in terms of theoretical additivity approaches. In binary bends, the tensile modulus reveal a positive deviation from additivity, and even a synergic contribution is obtained for blends containing 50 wt% and 80 wt% of PEI. The yield strength on the other hand, is strongly affected by phase’s immiscibility and the interfacial adherence between constituents, and a combinatorial deviation from additivity is obtained: negative for PBT rich-blends and positive for PEI-rich blends. In addition, the elongation at break for all blends is compromised by the morphology of PBT-rich blends, and by the densification of PEI-rich blends. The blend with 50 wt% of PEI exhibits the best elongational at break result due to its co-continuous morpholo gy. PTFE phase does not affect PEI/PBT stiffness since any significant variation in tensile modulus values is observed. On the other hand, a progressive decrease in tensile strength with in creasing PTFE concentration caused by the low yielding strength characteristic of PTFE is noticed. The results of elongation at break show that PTFE addition decreases even more the ductility of binary PEI/PBT blends. However, surprising results are found when only 5 wt% of PTFE phase is added to the blends containing 80 wt% of PEI. It is noticed a considerable improve ment of blends ductility due to the highly crystalline PTFE phase inhibits the densification of PEI/PBT blends. On the contrary, PTFE improves substantially PEI/PBT blends thermal stability and flammability, since it enhances blends charring formation.
TAG: modelo teórico de valoración del nivel de ubicuidad de las funciones misionales de una Institución de Educación Superior (IES)
(Universidad EAFIT, 2018) Aguas Núñez, Roberto Luís; Lalinde Pulido, Juan Guillermo
Improving the seismic image in reverse time migration by analysis of wavefields via continuous wavelet transform
(Universidad EAFIT, 2018) Paniagua Castrillón, Juan Guillermo; Quintero Montoya, Olga Lucía
During the last 50 years there has been a lot of effort to obtain subsurface structures on the oil and gas exploration. Some of them even if they are based on the mathematical formulation of the phenomenon, were not easily implemented due to the lack of computational power. Nevertheless, the problem is not only the algorithmic complexity but also, the uncertainty reduction of the scalar field that is obtained after the mathematical modeling and inversion procedures. Specifically, this thesis deals with the well known Reverse time migration (RTM) procedure, which is basically the two-way wave equation migration that is able to generate models with both great structural and velocity complexities, problems arise when the construction of subsurface models take into account seismic signals recorded on the surface. The data is mapped into the subsurface using the acoustic wave equation and the models obtained contain uncertainties that affect their subsequent interpretation. In order to reduce these uncertainties, we seek to improve the algorithm used in RTM before and after the generation of the final model looking for uncertainty reduction and improved scalar fields. We propose a set of strategies of extracting information from the seismic signals in order to obtain characteristics that allow a better and more refined representation of the subsurface structure model. Integral transforms are developed for this purpose. Inspired on the concept of information retrieval from data, we developed a signal procedure algorithm to determine in time-scale domain, the main features of the traveler wave in order to relate temporarily the inherent physics phenomena, locate complex structures by pointing the velocity field singularities due to the main changes on the frequency content revealed within the scalogram obtained by Gaussian wavelet family. Later on, a wavefield separation for the scalar field calculation is proposed based on the same principle and we called it Time Scale Wavefield Separation (TSWS). The space defined by Source wave propagation is decomposed on the subspaces and the analysis in time-domain time-scale of the subset of the wavefield is performed by selecting special features extracted by Wavelet Transform Modulus Maxima (WTMM) and a numerical algorithm is introduced for massive data [1]. Consequently, a Depth Scale Wavefield Separation (DSWS) is developed to the Receiver Wavefield separation by extracting the depth-domain scale-domain features of the relevant information of the reverse traveler wave [2]. Finally and taking into account the need for the proper structure definition for drilling purposes, we introduced the Laguerre Gauss Transform as final part of the Zero lag cross correlation imaging condition (ZL-CC-IC-LG) and provide a useful transformation of the final real scalar field into a complex scalar field with properties of spatial features enhancement.
On object recognition for industrial augmented reality
(Universidad EAFIT, 2018) Arbeláez, Juan Carlos; Osorio Gómez, Gilberto; Viganó, Roberto
Some reasons are market pressure, an increase of functionality, and adaptability to an already complex environment, among others. Therefore, workers face fast-changing and challenging tasks along with all the product lifecycle that reach the human cognitive limits. Although nowadays some operations are automated, many of them still need to be carried out by humans because of their complexity. In addition to management strategies and design for X, Industrial Augmented Reality (IAR) has proven to potentially benefit activities such as maintenance, assembly, manufacturing, and repair, among others. It is also supposed to upgrade the manufacturing processes by improving it, simplifying decision-making activities, reducing time and user movements, diminishing errors, and decreasing mental and physical effort. Nevertheless, IAR has not succeeded in breaking out of the laboratories and establishing itself as a strong solution in the industry, mainly because technical and interaction components are far from ideal. Its advance is limited by its enabling technologies. One of its biggest challenges are the methods for understanding the surroundings considering the different domain variables that affect IAR implementations. Thus, inspired by some systematical methodologies proposing that, for any problemsolving activity, it is required to define the characteristics that constrain the problem and the needs to be satisfied, a general frame of IAR was proposed through the identification of Domain Variables (DV), that are relevant characteristics of the industrial process in the previous Augmented Reality (AR) applications. These DV regard the user, parts, environment, and task that have an impact on the technical implementation and user performance and perception (Chapter 2). Subsequently, a detailed analysis of the influence of the DV on technical implementations related to the processes intended to understand the surroundings was performed. The results of this analysis suggest that the DV influence the technical process in two ways. The first one is that they define the boundaries in the characteristics of the technology, and the second one is that they cause some issues in the process of understanding the surroundings (Chapter 3). Further, an automatic method for creating synthetic datasets using solely the 3D model of the parts was proposed. It is hypothesized that the proposed variables are the main source of visual variations of an object in this context. Thus, the proposed method is derived from physically recreated light-matter interactions of this relevant variables. This method is aimed to create fully labeled datasets for training and testing surrounding understanding algorithms (Chapter 4). Finally, the proposed method is evaluated in a study case of object classification of two cases: a particular industrial case, and a general classification problem (using classes of ImageNet). Results suggest that fine-tuning models with the proposed method reach comparable performance (no statistical difference) than models trained with photos. These results validate the proposed method as a viable alternative for training surrounding understanding algorithms applied to industrial cases (Chapter 5).
Wave propagation in 2d elastic periodic materials : theoretical and computational analysis
(Universidad EAFIT, 2019) Valencia Gómez, Camilo Andrés; Gómez Castaño, Juan David

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