1,066 research outputs found
Continuum Modeling and Simulation in Bone Tissue Engineering
Bone tissue engineering is currently a mature methodology from a research perspective.
Moreover, modeling and simulation of involved processes and phenomena in BTE have been proved
in a number of papers to be an excellent assessment tool in the stages of design and proof of concept
through in-vivo or in-vitro experimentation. In this paper, a review of the most relevant contributions
in modeling and simulation, in silico, in BTE applications is conducted. The most popular in silico
simulations in BTE are classified into: (i) Mechanics modeling and sca old design, (ii) transport and
flow modeling, and (iii) modeling of physical phenomena. The paper is restricted to the review of the
numerical implementation and simulation of continuum theories applied to di erent processes in
BTE, such that molecular dynamics or discrete approaches are out of the scope of the paper. Two main
conclusions are drawn at the end of the paper: First, the great potential and advantages that in silico
simulation o ers in BTE, and second, the need for interdisciplinary collaboration to further validate
numerical models developed in BTE.Ministerio de EconomĂa y Competitividad del Gobierno España DPI2017-82501-
Special Issue on “Biomaterials for Bone Tissue Engineering”
The present Special Issue covers recent advances in the field of tissue engineering applied to bone
tissue. Bone tissue engineering is a wide research topic, so di erent works from di erent transversal
areas of research are shown. This Special Issue is a good example of a multidisciplinary collaboration in
this research field. Authors from di erent disciplines, such as medical scientists, biomedical engineers,
biologists, biomaterial researchers, clinicians, and mechanical engineers, are included from di erent
laboratories and universities across the world. I specially thank the work and time of the reviewers,
listed in Table A1 (in Appendix A), for their time and e orts in reviewing the papers compiled in this
Special Issue.Ministerio de EconomĂa y Competitividad PGC2018-097257-B-C31ConsejerĂa de EconomĂa, Conocimiento, Empresas y Universidad Junta de AndalucĂa US-126169
Cell-Biomaterial Mechanical Interaction in the Framework of Tissue Engineering: Insights, Computational Modeling and Perspectives
Tissue engineering is an emerging field of research which combines the use of
cell-seeded biomaterials both in vitro and/or in vivo with the aim of promoting new tissue
formation or regeneration. In this context, how cells colonize and interact with the
biomaterial is critical in order to get a functional tissue engineering product. Cell-biomaterial
interaction is referred to here as the phenomenon involved in adherent cells attachment to
the biomaterial surface, and their related cell functions such as growth, differentiation,
migration or apoptosis. This process is inherently complex in nature involving many
physico-chemical events which take place at different scales ranging from molecular to
cell body (organelle) levels. Moreover, it has been demonstrated that the mechanical
environment at the cell-biomaterial location may play an important role in the subsequent
cell function, which remains to be elucidated. In this paper, the state-of-the-art research in
the physics and mechanics of cell-biomaterial interaction is reviewed with an emphasis on
focal adhesions. The paper is focused on the different models developed at different scales
available to simulate certain features of cell-biomaterial interaction. A proper understanding
of cell-biomaterial interaction, as well as the development of predictive models in this sense,
may add some light in tissue engineering and regenerative medicine fields.Ministerio de Ciencia y TecnologĂa DPI2010-20399-C04-0
Solución numérica para fractura en sólidos piezoeléctricos tridimensionales
XXIV Encuentro del Grupo Español de Fractura, celebrado en Burgos en 2007En este trabajo se presenta una formulación mixta del Método de los Elementos de Contorno (MEC) para el análisis de
problemas 3D de Mecánica de la Fractura en materiales piezoeléctricos transversalmente isótropos. La formulación
mixta hace uso de la Ecuación Integral de Contorno tanto en Desplazamientos (formulación clásica del método) como
en Tracciones (formulaciĂłn hipersingular). Partiendo de la soluciĂłn fundamental de Dunn y Wienecke, se han obtenido
sus derivadas para la obtención de los términos en tracciones y los núcleos de la formulación hipersingular del MEC.
Los nĂşcleos hipersingulares han sido regularizados analĂticamente para dar lugar finalmente a integrales que son a lo
sumo débilmente singulares.
Una vez que la formulaciĂłn ha sido validada por comparaciĂłn con soluciones analĂticas y resultados obtenidos por
otros autores, se presentan y se analizan una serie de problemas de interĂ©s, con geometrĂas diversas, para los cuales no
existen resultados previos.In this paper, a mixed Boundary Element formulation for the analysis of 3D crack problems in transversely isotropic
piezoelectric solids is presented. When applying this mixed BE formulation, the Displacement Boundary Integral
Equation (classical formulation of BEM) and the Traction Boundary Integral Equation (hypersingular formulation of
BEM ) are used. The displacement expressions of the fundamental solution obtained by Dunn and Wienecke, have
been differentiated in order to obtain the traction terms and kernels for the hypersingular formulation. An analytical
regularization process have been applied to strongly singular and hypersingular kernels, so they are transformed into
weakly singular integrals.
Once the formulation have been validated by comparison with analytical and previous results, some interesting
problems, for which no previous results are known by the authors, are analyzed.Ministerio de EduaciĂłn y Ciencia DPI- 08147-C02-0
Hypersingular BEM for Piezoelectric Solids: Formulation and Applications for FractureMechanics
A general mixed boundary element
formulation for three-dimensional piezoelectric
fracture mechanics problems is presented in this
paper. The numerical procedure is based on the
extended displacement and traction integral equations
for external and crack boundaries, respectively.
Integrals with strongly singular and hypersingular
kernels appearing in the formulation are
analytically transformed into weakly singular and
regular integrals. Quadratic boundary elements
and quarter-point boundary elements are implemented
in a direct way in a computer code. Electric
and stress intensity factors are directly computed
fromnodal values at quarter-point elements.
Crack problems in 3D piezoelectric bounded and
unbounded solids are solved. The obtained results
are shown to be accurate by comparison with
other results existing in the literature. The approach
presented for the first time in this paper
should be useful for future research and development
since it can be used in a simple way for
general 3D piezoelectric fracture mechanics problems.Ministerio de EduaciĂłn y Ciencia DPI2004-08147-C02-0
A Compact Evolutionary Interval-Valued Fuzzy Rule-Based Classification System for the Modeling and Prediction of Real-World Financial Applications with Imbalanced Data
The current financial crisis has
stressed the need of obtaining more accurate
prediction models in order to decrease the risk when
investing money on economic opportunities. In
addition, the transparency of the process followed to
make the decisions in financial applications is
becoming an important issue. Furthermore, there is a
need to handle the real-world imbalanced financial
data sets without using sampling techniques which
might introduce noise in the used data. In this paper,
we present a compact evolutionary interval-valued
fuzzy rule-based classification system, which is
based on IVTURSFARC-HD (Interval-Valued fuzzy rulebased classification system with TUning and Rule
Selection) [22]), for the modeling and prediction of
real-world financial applications. This proposed
system allows obtaining good predictions accuracies
using a small set of short fuzzy rules implying a high
degree of interpretability of the generated linguistic
model. Furthermore, the proposed system deals with
the financial imbalanced datasets with no need for
any preprocessing or sampling method and thus
avoiding the accidental introduction of noise in the
data used in the learning process. The system is also
provided with a mechanism to handle examples that
are not covered by any fuzzy rule in the generated
rule base. To test the quality of our proposal, we will
present an experimental study including eleven realworld financial datasets. We will show that the
proposed system outperforms the original C4.5
decision tree, type-1 and interval-valued fuzzy
counterparts which use the SMOTE sampling
technique to preprocess data and the original FURIA,
which is a fuzzy approximative classifier.
Furthermore, the proposed method enhances the
results achieved by the cost sensitive C4.5 and it
gives competitive results when compared with
FURIA using SMOTE, while our proposal avoids
pre-processing techniques and it provides
interpretable models that allow obtaining more
accurate results.Spanish Government
TIN2011-28488
TIN2013-40765-
Computational Multiscale Solvers for Continuum Approaches
Computational multiscale analyses are currently ubiquitous in science and technology. Different problems of interest-e.g., mechanical, fluid, thermal, or electromagnetic-involving a domain with two or more clearly distinguished spatial or temporal scales, are candidates to be solved by using this technique. Moreover, the predictable capability and potential of multiscale analysis may result in an interesting tool for the development of new concept materials, with desired macroscopic or apparent properties through the design of their microstructure, which is now even more possible with the combination of nanotechnology and additive manufacturing. Indeed, the information in terms of field variables at a finer scale is available by solving its associated localization problem. In this work, a review on the algorithmic treatment of multiscale analyses of several problems with a technological interest is presented. The paper collects both classical and modern techniques of multiscale simulation such as those based on the proper generalized decomposition (PGD) approach. Moreover, an overview of available software for the implementation of such numerical schemes is also carried out. The availability and usefulness of this technique in the design of complex microstructural systems are highlighted along the text. In this review, the fine, and hence the coarse scale, are associated with continuum variables so atomistic approaches and coarse-graining transfer techniques are out of the scope of this paper.Abengoa Researc
Improving the performance of fuzzy rule-based classification systems with interval-valued fuzzy sets and genetic amplitude tuning
Among the computational intelligence techniques employed to solve classification problems,
Fuzzy Rule-Based Classification Systems (FRBCSs) are a popular tool because of their
interpretable models based on linguistic variables, which are easier to understand for the
experts or end-users.
The aim of this paper is to enhance the performance of FRBCSs by extending the Knowledge
Base with the application of the concept of Interval-Valued Fuzzy Sets (IVFSs). We
consider a post-processing genetic tuning step that adjusts the amplitude of the upper
bound of the IVFS to contextualize the fuzzy partitions and to obtain a most accurate solution
to the problem.
We analyze the goodness of this approach using two basic and well-known fuzzy rule
learning algorithms, the Chi et al.’s method and the fuzzy hybrid genetics-based machine
learning algorithm. We show the improvement achieved by this model through an extensive
empirical study with a large collection of data-sets.This work has been supported by the Spanish Ministry of Science and
Technology under projects TIN2008-06681-C06-01 and TIN2007-65981
IVTURS: A linguistic fuzzy rule-based classification system based on a new interval-valued fuzzy reasoning method with tuning and rule selection
Interval-valued fuzzy sets have been shown to be a useful tool for dealing with the ignorance related to the definition of the linguistic labels. Specifically, they have been successfully applied to solve classification problems, performing simple modifications on the fuzzy reasoning method to work with this representation and making the classification based on a single number. In this paper we present IVTURS, a new linguistic fuzzy rule-based classification method based on a new completely interval-valued fuzzy reasoning method. This inference process uses interval-valued restricted equivalence functions to increase the relevance of the rules in which the equivalence of the interval membership degrees of the patterns and the ideal membership degrees is greater, which is a desirable behaviour. Furthermore, their parametrized construction allows the computation of the optimal function for each variable to be performed, which could involve a potential improvement in the system’s behaviour. Additionally, we combine this tuning of the equivalence with rule selection in order to decrease the complexity of the system. In this paper we name our method IVTURS-FARC, since we use the FARC-HD method to accomplish the fuzzy rule learning process. The experimental study is developed in three steps in order to ascertain the quality of our new proposal. First, we determine both the essential role that interval-valued fuzzy sets play in the method and the need for the rule selection process. Next, we show the improvements achieved by IVTURS-FARC with respect to the tuning of the degree of ignorance when it is applied in both an isolated way and when combined with the tuning of the equivalence. Finally, the significance of IVTURS-FARC is further depicted by means of a comparison by which it is proved to outperform the results of FARC-HD and FURIA, which are two high performing fuzzy classification algorithms.This work was supported in part by the Spanish Ministry of Science and Technology under projects TIN2011-28488 and TIN2010-15055 and the Andalusian Research Plan P10-TIC-6858 and P11-TIC-7765
IIVFDT: Ignorance Functions based Interval-Valued Fuzzy Decision Tree with Genetic Tuning
The choice of membership functions plays an essential role in the success of fuzzy systems. This is a complex problem due to the possible lack of knowledge when assigning punctual values as membership degrees. To face this handicap, we propose a methodology called Ignorance functions based Interval-Valued Fuzzy Decision Tree with genetic tuning, IIVFDT for short, which allows to improve the performance of fuzzy decision trees by taking into account the ignorance degree. This ignorance degree is the result of a weak ignorance function applied to the punctual value set as membership degree.
Our IIVFDT proposal is composed of four steps: (1) the base fuzzy decision tree is generated using the fuzzy ID3 algorithm; (2) the linguistic labels are modeled with Interval-Valued Fuzzy Sets. To do so, a new parametrized construction method of Interval-Valued Fuzzy Sets is defined, whose length represents such ignorance degree; (3) the fuzzy reasoning method is extended to work with this representation of the linguistic terms; (4) an evolutionary tuning step is applied for computing the optimal ignorance degree for each Interval-Valued Fuzzy Set.
The experimental study shows that the IIVFDT method allows the results provided by the initial fuzzy ID3 with and without Interval-Valued Fuzzy Sets to be outperformed. The suitability of the proposed methodology is shown with respect to both several state-of-the-art fuzzy decision trees and C4.5. Furthermore, we analyze the quality of our approach versus two methods that learn the fuzzy decision tree using genetic algorithms. Finally, we show that a superior performance can be achieved by means of the positive synergy obtained when applying the well known genetic tuning of the lateral position after the application of the IIVFDT method.Spanish Government
TIN2011-28488
TIN2010-1505
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