Contribution to structural parameters computation: volume models and methods

Bio-CAD and in-silico experimentation are getting a growing interest in biomedical applications where scientific data coming from real samples are used to compute structural parameters that allow to evaluate physical properties. Non-invasive imaging acquisition technologies such as CT, mCT or MRI, plus the constant growth of computer capabilities, allow the acquisition, processing and visualization of scientific data with increasing degree of complexity. Structural parameters computation is based on the existence of two phases (or spaces) in the sample: the solid, which may correspond to the bone or material, and the empty or porous phase and, therefore, they are represented as binary volumes. The most common representation model for these datasets is the voxel model, which is the natural extension to 3D of 2D bitmaps. In this thesis, the Extreme Vertices Model (EVM) and a new proposed model, the Compact Union of Disjoint Boxes (CUDB), are used to represent binary volumes in a much more compact way. EVM stores only a sorted subset of vertices of the object¿s boundary whereas CUDB keeps a compact list of boxes. In this thesis, methods to compute the next structural parameters are proposed: pore-size distribution, connectivity, orientation, sphericity and roundness. The pore-size distribution helps to interpret the characteristics of porous samples by allowing users to observe most common pore diameter ranges as peaks in a graph. Connectivity is a topological property related to the genus of the solid space, measures the level of interconnectivity among elements, and is an indicator of the biomechanical characteristics of bone or other materials. The orientation of a shape can be defined by rotation angles around a set of orthogonal axes. Sphericity is a measure of how spherical is a particle, whereas roundness is the measure of the sharpness of a particle's edges and corners. The study of these parameters requires dealing with real samples scanned at high resolution, which usually generate huge datasets that require a lot of memory and large processing time to analyze them. For this reason, a new method to simplify binary volumes in a progressive and lossless way is presented. This method generates a level-of-detail sequence of objects, where each object is a bounding volume of the previous objects. Besides being used as support in the structural parameter computation, this method can be practical for task such as progressive transmission, collision detection and volume of interest computation. As part of multidisciplinary research, two practical applications have been developed to compute structural parameters of real samples. A software for automatic detection of characteristic viscosity points of basalt rocks and glasses samples, and another to compute sphericity and roundness of complex forms in a silica dataset.El Bio-Diseño Asistido por Computadora (Bio-CAD), y la experimentacion in-silico est an teniendo un creciente interes en aplicaciones biomedicas, en donde se utilizan datos cientificos provenientes de muestras reales para calcular par ametros estructurales que permiten evaluar propiedades físicas. Las tecnologías de adquisicion de imagen no invasivas como la TC, TC o IRM, y el crecimiento constante de las prestaciones de las computadoras, permiten la adquisicion, procesamiento y visualizacion de datos científicos con creciente grado de complejidad. El calculo de parametros estructurales esta basado en la existencia de dos fases (o espacios) en la muestra: la solida, que puede corresponder al hueso o material, y la fase porosa o vacía, por tanto, tales muestras son representadas como volumenes binarios. El modelo de representacion mas comun para estos conjuntos de datos es el modelo de voxeles, el cual es una extension natural a 3D de los mapas de bits 2D. En esta tesis se utilizan el modelo Extreme Verrtices Model (EVM) y un nuevo modelo propuesto, the Compact Union of Disjoint Boxes (CUDB), para representar los volumenes binarios en una forma mucho mas compacta. El modelo EVM almacena solo un subconjunto ordenado de vertices de la frontera del objeto mientras que el modelo CUDB mantiene una lista compacta de cajas. En esta tesis se proponen metodos para calcular los siguientes parametros estructurales: distribucion del tamaño de los poros, conectividad, orientacion, esfericidad y redondez. La distribucion del tamaño de los poros ayuda a interpretar las características de las muestras porosas permitiendo a los usuarios observar los rangos de diametro mas comunes de los poros mediante picos en un grafica. La conectividad es una propiedad topologica relacionada con el genero del espacio solido, mide el nivel de interconectividad entre los elementos, y es un indicador de las características biomecanicas del hueso o de otros materiales. La orientacion de un objeto puede ser definida por medio de angulos de rotacion alrededor de un conjunto de ejes ortogonales. La esfericidad es una medida de que tan esferica es una partícula, mientras que la redondez es la medida de la nitidez de sus aristas y esquinas. En el estudio de estos parametros se trabaja con muestras reales escaneadas a alta resolucion que suelen generar conjuntos de datos enormes, los cuales requieren una gran cantidad de memoria y mucho tiempo de procesamiento para ser analizados. Por esta razon, se presenta un nuevo metodo para simpli car vol umenes binarios de una manera progresiva y sin perdidas. Este metodo genera una secuencia de niveles de detalle de los objetos, en donde cada objeto es un volumen englobante de los objetos previos. Ademas de ser utilizado como apoyo en el calculo de parametros estructurales, este metodo puede ser de utilizado en otras tareas como transmision progresiva, deteccion de colisiones y calculo de volumen de interes. Como parte de una investigacion multidisciplinaria, se han desarrollado dos aplicaciones practicas para calcular parametros estructurales de muestras reales. Un software para la deteccion automatica de puntos de viscosidad característicos en muestras de rocas de basalto y vidrios, y una aplicacion para calcular la esfericidad y redondez de formas complejas en un conjunto de datos de sílice

A new mixed model based on the enhanced-Refined Zigzag Theory for the analysis of thick multilayered composite plates

The Refined Zigzag Theory (RZT) has been widely used in the numerical analysis of multilayered and sandwich plates in the last decay. It has been demonstrated its high accuracy in predicting global quantities, such as maximum displacement, frequencies and buckling loads, and local quantities such as through-the-thickness distribution of displacements and in-plane stresses [1,2]. Moreover, the C0 continuity conditions make this theory appealing to finite element formulations [3]. The standard RZT, due to the derivation of the zigzag functions, cannot be used to investigate the structural behaviour of angle-ply laminated plates. This drawback has been recently solved by introducing a new set of generalized zigzag functions that allow the coupling effect between the local contribution of the zigzag displacements [4]. The newly developed theory has been named enhanced Refined Zigzag Theory (en- RZT) and has been demonstrated to be very accurate in the prediction of displacements, frequencies, buckling loads and stresses. The predictive capabilities of standard RZT for transverse shear stress distributions can be improved using the Reissner’s Mixed Variational Theorem (RMVT). In the mixed RZT, named RZT(m) [5], the assumed transverse shear stresses are derived from the integration of local three-dimensional equilibrium equations. Following the variational statement described by Auricchio and Sacco [6], the purpose of this work is to implement a mixed variational formulation for the en-RZT, in order to improve the accuracy of the predicted transverse stress distributions. The assumed kinematic field is cubic for the in-plane displacements and parabolic for the transverse one. Using an appropriate procedure enforcing the transverse shear stresses null on both the top and bottom surface, a new set of enhanced piecewise cubic zigzag functions are obtained. The transverse normal stress is assumed as a smeared cubic function along the laminate thickness. The assumed transverse shear stresses profile is derived from the integration of local three-dimensional equilibrium equations. The variational functional is the sum of three contributions: (1) one related to the membrane-bending deformation with a full displacement formulation, (2) the Hellinger-Reissner functional for the transverse normal and shear terms and (3) a penalty functional adopted to enforce the compatibility between the strains coming from the displacement field and new “strain” independent variables. The entire formulation is developed and the governing equations are derived for cases with existing analytical solutions. Finally, to assess the proposed model’s predictive capabilities, results are compared with an exact three-dimensional solution, when available, or high-fidelity finite elements 3D models. References: [1] Tessler A, Di Sciuva M, Gherlone M. Refined Zigzag Theory for Laminated Composite and Sandwich Plates. NASA/TP- 2009-215561 2009:1–53. [2] Iurlaro L, Gherlone M, Di Sciuva M, Tessler A. Assessment of the Refined Zigzag Theory for bending, vibration, and buckling of sandwich plates: a comparative study of different theories. Composite Structures 2013;106:777–92. https://doi.org/10.1016/j.compstruct.2013.07.019. [3] Di Sciuva M, Gherlone M, Iurlaro L, Tessler A. A class of higher-order C0 composite and sandwich beam elements based on the Refined Zigzag Theory. Composite Structures 2015;132:784–803. https://doi.org/10.1016/j.compstruct.2015.06.071. [4] Sorrenti M, Di Sciuva M. An enhancement of the warping shear functions of Refined Zigzag Theory. Journal of Applied Mechanics 2021;88:7. https://doi.org/10.1115/1.4050908. [5] Iurlaro L, Gherlone M, Di Sciuva M, Tessler A. A Multi-scale Refined Zigzag Theory for Multilayered Composite and Sandwich Plates with Improved Transverse Shear Stresses, Ibiza, Spain: 2013. [6] Auricchio F, Sacco E. Refined First-Order Shear Deformation Theory Models for Composite Laminates. J Appl Mech 2003;70:381–90. https://doi.org/10.1115/1.1572901

European Union Timber Regulation Impact on International Timber Markets

The trade of illegal timber, often from illegal logging, has severe environmental, social and economic consequences. The EU’s response to this problem came with the Forest Law Enforcement, Governance and Trade (FLEGT) Action Plan, with its specific goal to end illegal logging, thereby improving sustainability of forest resources. In March 2013, an additional step was taken by implementing the EU Timber Regulation (EUTR). The EUTR requires proof of timber’s origin and legality to ensure that no illegal timber is imported into the EU. To this end the EU intends to block imports of any wood or wood product which comes from unknown sources. Certification of sustainable forest management will help EU importers minimize risk, which is an essential part of their required due diligence system. Monitoring organizations are established to assist trade associations and businesses to construct comprehensive due diligence systems. National competent authorities are designated to follow the trade of the new FLEGT-licensed timber and timber products. In the first year of the EUTR there are positive impacts, of which the most important is awareness of the disastrous situation with illegal logging, driven by exports of illegal timber. Another positive development is tropical timber exporters documenting the legality of their wood exports. Yet another positive feature is establishment of due diligence systems by EU importers. However, there are considerable problems for ensuring legal trade; for example the lack of comprehensive documentation of origin and legality. Analysis of recent trends establishes changes in the European timber trade in terms of sourcing, substitution, diversion to less-demanding countries. Short-term forecasts of market trends and changes will enable further policy assessment to achieve the objectives of improved legality in international timber markets.JRC.H.3-Forest Resources and Climat

Visualization of two-phase flow dynamics : techniques for droplet interactions, interfaces, and material transport

Computational visualization allows scientists and engineers to better understand simulation data and gain insights into the studied natural processes. Particularly in the field of computational fluid dynamics, interactive visual presentation is essential in the investigation of physical phenomena related to gases and liquids. To ensure effective analysis, flow visualization techniques must adapt to the advancements in the field of fluid dynamics that benefits substantially from the growing computational power of both commodity desktops and supercomputers on the one hand, and steadily expanding knowledge about fluid physics on the other. A prominent example of these advances can be found in the research of two-phase flow with liquid droplets and jets, where high performance computation and sophisticated algorithms for phase tracking enable well resolved and physically accurate simulations of liquid dynamics. Yet, the field of two-phase flow has remained largely unexplored in visualization research so far, leaving the scientists and engineers with a number of challenges when analyzing the data. These include the difficulty in tracking and investigating topological events in large droplet groups, high complexity of droplet dynamics due to the involved interfaces, and a limited choice of high quality interactive methods for the analysis of related transport phenomena. It is therefore the aim of this thesis to address these challenges by providing a multi-scale approach for the visual investigation of two-phase flow, with the focus on the analysis of droplet interaction, fluid interfaces, and material transport. To address the problem of analyzing highly complex two-phase flow simulations with droplet groups and jets, a linked-view approach with three-dimensional and abstract space-time graph representation of droplet dynamics is proposed. The interactive brushing and linking allows for general exploration of topological events as well as detailed inspection of dynamics in terms of oscillations and rotations of droplets. Another approach further examines the separation of liquid phases by segmenting liquid volumes according to their topological changes in future time. For visualization, boundary surfaces of these volume segments are extracted that reveal intricate details of droplet topology dynamics. Additionally, within this framework, visualization of advected particles corresponding to arbitrarily selected segment provides useful insights into the spatio-temporal evolution of the segment. The analysis of interfaces is necessary to understand the interplay of interface dynamics and the dynamics of droplet interactions. A commonly used technique for interface tracking in the volume of fluid-based simulations is the piecewise linear approximation which, although accurate, can affect the quality of the simulation results. To study the influence of the interface reconstruction on the phase tracking procedure, a visualization method is presented that extracts the interfaces by means of the first-order Taylor approximation, and provides several derived quantities that help assess the simulation results in relation to the interface reconstruction quality. The liquid interface is further investigated from the physical standpoint with an approach based on quantities derived from velocity and surface tension gradients. The developed method supports examination of surface tension forces and their impact on the interface instability, as well as detailed analysis of interface deformation characteristics. A line of research important for engineering applications is the analysis of electric fields on droplet interfaces. It is, however, complicated by higher-order elements used in the simulations to preserve field discontinuities. A visualization method has been developed that correctly visualizes these discontinuities at material boundaries. Additionally, the employed space-time representation of the droplet-insulator contact line reveals characteristics of electric field dynamics. The dynamics of droplets are often examined assuming single-phase flow, for instance when the internal material transport is of interest. From the visualization perspective, this allows for adaption of traditional vector field visualization techniques to the investigation of the studied phenomena. As one such concept, dye based visualization is proposed that extends the transport analysis to advection-diffusion problems, therefore revealing true transport behavior. The employed high quality advection preserves fine details of the dye, while the implementation on graphics processing units ensures interactive visualization. Several streamline-based concepts are applied in space-time representation of 2D unsteady flow. By interpreting time as the third spatial dimension, many 3D streamline-based visualization techniques can be applied to investigate 2D unsteady flow. The introduced vortex core ribbons support the examination of vortical flow behavior by revealing rotation near the core lines. For the study of topological structures, a method has been developed that extracts separatrices implicitly as boundaries of regions with different flow behavior, and therefore avoids potentially complicated explicit extraction of various topological structures. All proposed techniques constitute a novel multi-scale approach for visual analysis of two-phase flow. The analysis of droplet interactions is addressed with visualization of the phenomena leading to breakups and with detailed visual inspection of these breakups. On the interface level, techniques for the interface analysis give insights into the simulation quality, mechanisms behind topology changes, as well as the behavior of electrically charged droplets. Further down the scale, the dye-based visualization, streamline-based concepts for space-time analysis, and the implicit extraction of flow topology allow for the investigation of droplet internal transport as well as general single-phase flow scenarios. The applicability of the proposed methods extends, in a varying degree, beyond the use in two-phase flow. Their usability is demonstrated on data from simulations based on Navier-Stokes equations that exemplify practical problems in the research of fluid dynamics.Die numerische Visualisierung ermöglicht Wissenschaftlern und Ingenieuren, Simulationsergebnisse besser zu verstehen und Einblicke in Naturprozesse zu gewinnen. Insbesondere ist die visuelle Darstellung von Ergebnissen numerischer Strömungsmechanik für die Untersuchung physikalischer Phänomene bei Gasen und Flüssigkeiten äußerst wichtig. Die numerische Strömungsmechanik profitiert einerseits von wachsender Rechenleistung handelsüblicher Desktops und Supercomputer, andererseits von den neuen Entwicklungen in der Strömungsforschung. Um eine effektive Analyse von Strömungen zu gewährleisten, müssen sich die Visualisierungstechniken kontinuierlich den Fortschritten in der Strömungsmechanik anpassen. Ein bemerkenswertes Beispiel hierfür ist die Forschung in der Zweiphasenströmung, in der Hochleistungsrechner und effiziente Algorithmen zur Phasenverfolgung hochaufgelöste und physikalisch genaue Simulationen der Flüssigkeitsdynamik ermöglichen. Dennoch ist die Zweiphasenströmung seitens der Visualisierung weitgehend unerforscht geblieben. Insbesondere sehen sich Wissenschaftler und Ingenieure mit verschiedenen Problemen konfrontiert, die mit angepassten Visualisierungstechniken vermieden werden können. Zu den Problemen zählen beispielweise die Verfolgung und Untersuchung der topologischen Ereignisse in Tropfengruppen, hohe Komplexität der Tropfendynamik und die begrenzte Auswahl an interaktiven Methoden zur Untersuchung der Transportphänomene. Demzufolge ist das Ziel dieser Dissertation, die Entwicklung eines Ansatzes zur visuellen Analyse von Zweiphasenströmung auf mehreren Skalen mit dem Fokus auf Interaktionen zwischen den Tropfen, Dynamik der Oberfläche und Materialtransport. Um die Analyse hochkomplexer Simulationsdaten der Zweiphasenströmung zu behandeln, wird eine auf Linked-View-Verfahren basierte Visualisierungstechnik präsentiert, in der die Tropfen sowohl in einer 3D Darstellung als auch in einer abstrakten Graph-Repräsentation visualisiert werden. Der interaktive Brushing-and-Linking-Ansatz ermöglicht eine globale Exploration der topologischen Ereignisse sowie eine detaillierte Inspektion der Dynamik im Hinblick auf die Oszillation und Rotation der Tropfen. Eine andere Technik zeigt die Aufteilung des Tropfenvolumens im zeitlichen Verlauf. Somit ermöglicht diese Methode eine ausführliche Untersuchung der Topologiedynamik mit Hilfe einer statischen Visualisierung. Dafür werden Grenzflächen erzeugt, die das ursprüngliche Volumen des Tropfens hinsichtlich der sich entwickelnden Zerfallskomponenten aufzeigen. Zusätzlich werden die zur Verfolgung der Tropfen benutzten Partikel visualisiert, um Einblicke in die Dynamik der Separation zu gewähren. Die Analyse der Oberfläche ist notwendig, um die Wechselwirkung zwischen der Oberflächendynamik und der Dynamik der Tropfeninteraktion besser zu verstehen. Eine häufig angewendete Technik zur Verfolgung der Phasengrenzen im Volume-of-Fluid-Verfahren ist die zellenweise planare Approximation. Obwohl diese einen guten Kompromiss zwischen Genauigkeit und Performanz bietet, kann die Approximation die Qualität der Simulationsergebnisse erheblich beeinflussen. Es wird deshalb eine Visualisierungsmethode präsentiert, die die Oberfläche mit Hilfe der Taylor-Approximation erster Ordnung extrahiert und unter anderem darauf basierte Größen bereitstellt, die die Relation zwischen der Simulationsapproximation und Qualität der Ergebnisse zeigt. Die Tropfenoberfläche wird weiterhin mit einer Visualisierungsmethode analysiert, die von den Geschwindigkeits- und Oberflächenspannungsgradienten abgeleitete Größen verwendet. Die entwickelte Methode unterstützt die Untersuchung der Deformation der Oberfläche sowie die Untersuchung der Oberflächenspannung und deren Auswirkung auf die Oberflächenstabilität. Eine wichtige Forschungsrichtung in der Zweiphasenströmung ist die Analyse elektrischer Felder auf der Tropfenoberfläche. Die in der Simulation angewendeten Elemente höherer Ordnung ermöglichen physikalische Diskontinuitäten, die für die visuelle Analyse eine gesonderte Behandlung benötigen. Im Zuge dessen wird eine Methode präsentiert, welche die Diskontinuitäten visuell korrekt darstellt und zusätzlich eine Raum-Zeit-Darstellung anwendet, um Einblicke in die Phänomene an der Kontaktlinie zwischen den Tropfen und dem untersuchten Isolator zu gewähren. Die Tropfendynamik wird oft mit der Annahme einer Einphasenströmung analysiert, beispielsweise für die Untersuchung der internen Strömung des Tropfens. Dies ermöglicht eine Anpassung und Verwendung traditioneller Visualisierungsmethoden für Vektorfelder. Eine solche Technik ist die ,,Dye-Advection'', die in dieser Dissertation nicht nur zur Analyse der Advektion, sondern auch zur Untersuchung der Diffusion verwendet wird. Die eingesetzte hochqualitative Rekonstruktion des virtuellen Pigments bewahrt feine Details, während die Implementierung auf der Grafikkarte eine interaktive Visualisierung ermöglicht. Überdies werden einige auf Stromlinien basierende Konzepte in Raum-Zeit-Darstellung angewendet, in der die Zeit als die dritte Raumachse interpretiert wird. Demzufolge können diese Methoden zur Analyse der zeitabhängigen zweidimensionalen Strömung verwendet werden. Die eingeführten ,,Vortex Core Ribbons" unterstützen die Analyse der rotierenden Strömung um die Wirbelkernlinien. Für die Analyse der topologischen Strukturen wurde eine Methode entwickelt, die die Separatrizen implizit als Ränder einer Segmentierung des Vektorfeldes extrahiert. Damit wird eine möglicherweise komplexe direkte Extraktion der Separatrizen vermieden. Die präsentierten Visualisierungsmethoden bilden ein neuartiges Multiskalen-Verfahren zur visuellen Analyse von Zweiphasenströmungen. Die Tropfeninteraktionen werden mit Hilfe einer Visualisierung dargestellt, die sich auf die Ursache des Tropfenzerfalls und deren Ablauf konzentriert. Für die Untersuchung der Oberfläche zeigen die vorgeschlagenen Techniken die Qualität der Ergebnisse hinsichtlich der Oberflächenrekonstruktion, die Mechanismen hinter den topologischen Ereignissen, als auch die Dynamik der elektrisch geladenen Tropfen auf. Andererseits werden unter Annahme der Einphasenströmung neue Techniken basierend auf Dye-Advection, Stromlinien-basierte Konzepte, sowie Verfahren zur Extraktion der Topologie untersucht, um einen besseren Einblick in den Materialtransport zu gewinnen. Die Anwendung dieser Methoden wird in dieser Dissertation auf Daten demonstriert, die durch Simulation, basierend auf Navier-Stokes-Gleichungen, erzeugt wurden

Friction Force Microscopy of Deep Drawing Made Surfaces

Aim of this paper is to contribute to micro-tribology understanding and friction in micro-scale interpretation in case of metal beverage production, particularly the deep drawing process of cans. In order to bridging the gap between engineering and trial-and-error principles, an experimental AFM-based micro-tribological approach is adopted. For that purpose, the can’s surfaces are imaged with atomic force microscopy (AFM) and the frictional force signal is measured with frictional force microscopy (FFM). In both techniques, the sample surface is scanned with a stylus attached to a cantilever. Vertical motion of the cantilever is recorded in AFM and horizontal motion is recorded in FFM. The presented work evaluates friction over a micro-scale on various samples gathered from cylindrical, bottom and round parts of cans, made of same the material but with different deep drawing process parameters. The main idea is to link the experimental observation with the manufacturing process. Results presented here can advance the knowledge in order to comprehend the tribological phenomena at the contact scales, too small for conventional tribology

Towards a Conceptual Design of an Intelligent Material Transport Based on Machine Learning and Axiomatic Design Theory

Reliable and efficient material transport is one of the basic requirements that affect productivity in sheet metal industry. This paper presents a methodology for conceptual design of intelligent material transport using mobile robot, based on axiomatic design theory, graph theory and artificial intelligence. Developed control algorithm was implemented and tested on the mobile robot system Khepera II within the laboratory model of manufacturing environment. Matlab© software package was used for manufacturing process simulation, implementation of search algorithms and neural network training. Experimental results clearly show that intelligent mobile robot can learn and predict optimal material transport flows thanks to the use of artificial neural networks. Achieved positioning error of mobile robot indicates that conceptual design approach can be used for material transport and handling tasks in intelligent manufacturing systems

Towards a Conceptual Design of an Intelligent Material Transport Based on Machine Learning and Axiomatic Design Theory

Reliable and efficient material transport is one of the basic requirements that affect productivity in sheet metal industry. This paper presents a methodology for conceptual design of intelligent material transport using mobile robot, based on axiomatic design theory, graph theory and artificial intelligence. Developed control algorithm was implemented and tested on the mobile robot system Khepera II within the laboratory model of manufacturing environment. Matlab© software package was used for manufacturing process simulation, implementation of search algorithms and neural network training. Experimental results clearly show that intelligent mobile robot can learn and predict optimal material transport flows thanks to the use of artificial neural networks. Achieved positioning error of mobile robot indicates that conceptual design approach can be used for material transport and handling tasks in intelligent manufacturing systems