G Jovicic - Academia.edu (original) (raw)

Papers by G Jovicic

Scientific reports, Jan 26, 2018

Despite its two-dimensional nature, X-ray angiography (XRA) has served as the gold standard imagi... more Despite its two-dimensional nature, X-ray angiography (XRA) has served as the gold standard imaging technique in the interventional cardiology for over five decades. Accordingly, demands for tools that could increase efficiency of the XRA procedure for the quantitative analysis of coronary arteries (CA) are constantly increasing. The aim of this study was to propose a novel procedure for three-dimensional modeling of CA from uncalibrated XRA projections. A comprehensive mathematical model of the image formation was developed and used with a robust genetic algorithm optimizer to determine the calibration parameters across XRA views. The frames correspondences between XRA acquisitions were found using a partial-matching approach. Using the same matching method, an efficient procedure for vessel centerline reconstruction was developed. Finally, the problem of meshing complex CA trees was simplified to independent reconstruction and meshing of connected branches using the proposed nonun...

Journal of Serbian Society for Computational Mechanics, 2016

The aim of the present study was to estimate biomechanical weakening of human knee joint assuming... more The aim of the present study was to estimate biomechanical weakening of human knee joint assuming the conditions that occur when a person is standing on one leg. A patient-specific three-dimensional model of the human knee joint was developed from medical scans, while loads and material characteristics were adopted from the literature. The considered model included the following materials: bones, menisci, articular cartilage and relevant ligaments (posterior cruciate ligament, lateral collateral ligament and medial collateral ligament). The finite element analysis was used for numerical calculation of the stress distribution and failure index of posterior cruciate ligament. The obtained failure index showed that there was no possibility for posterior cruciate ligament failure under the considered conditions. It was concluded that application of the finite element analysis can provide a better insight into the biomechanical condition of the injured knee joint.

An extended finite element method (X-FEM) for two-dimensional crack modelling is described in thi... more An extended finite element method (X-FEM) for two-dimensional crack modelling is described in this paper. For the crack calculation, a discontinuous function and the asymptotic crack-tip displacement fields are added to the finite element approximation using the concept Partition of Unity (PU). This enables the domain to be modelled by finite elements with no explicit meshing of the crack faces. Computational geometry issues associated with the representation of the crack and the enrichment of the finite element approximation are discussed. The presented Stress Intensity Factors (SIFs) for crack is in a good agreement with benchmark solutions. For calculation of the SIFs, we used the J-Equivalent Domain Integral (J-EDI) method. Key words: eXtended Finite Element Method (X-FEM); Partition of Unity Method (PUM); local enrichment; elastostatics; Stress Intensity Factors (SIFs); J-Equivalen Domain Integral method (J-EDI method).

International journal of oral and maxillofacial surgery, Jan 2, 2014

It has been suggested that unerupted lower third molars (M3) increase the fragility of the mandib... more It has been suggested that unerupted lower third molars (M3) increase the fragility of the mandibular angle and simultaneously decrease the risk of condylar fracture. However, it is unknown whether this applies regardless of the direction and point of impact of the traumatic force. The aim of this study was to investigate the impact of an unerupted M3 on the fragility of the angle and condyle in terms of a force acting from different directions and affecting different regions of the mandible. Computed tomography scans of a human mandible and finite element methodology were used to obtain two three-dimensional models: a model with, and the other without an unerupted M3. A force of 2000N was applied to three different regions of the models: the symphysis, ipsilateral body, and contralateral body, respectively. When the force was applied to the mandibular body, the results revealed increased angle fragility in cases with unerupted M3. When the force was applied to the symphysis, the co...

Computer Methods and Programs in Biomedicine, 2014

Colorectal carcinoma is acknowledged as the second leading cause of total cancer-related death in... more Colorectal carcinoma is acknowledged as the second leading cause of total cancer-related death in the European Region. The majority of deaths related to colorectal carcinoma are connected with liver metastatic disease. Approximately, in 25% of all patients, liver metastatic disease is diagnosed at the same time as the primary diagnosis, while up to a quarter of others would develop liver metastases in the course of the illness. In this study, we developed reaction-diffusion model and analyzed the effect of drug therapy on liver metastatic disease for a specific patient. Tumor volumes in specific time points were obtained using CT scan images. The nonlinear function for cell proliferation rate as well as data about clinically applied drug therapy was included in the model. Fitting procedure was used for parameter estimation. Good agreement of numerical and experimental results shows the feasibility and efficacy of the proposed system.

Elimination of a large part of dental tissues during root canal treatment affects the mechanical ... more Elimination of a large part of dental tissues during root canal treatment affects the mechanical behavior of devitalized teeth. The present study addresses how much dentin removal affects changes in mechanical behaviors of the intact tooth and tooth with root canal treatment. In order to estimate the tooth weakening, we performed aн experimental assessment of critical force and numerical Finite Element Method (FEM) analysis with the intention to analyze stresses distributions. The results showed that root canal treatment had significant influence on stress distributions. By analysis of retrieved results, it is concluded that this study is an efficient framework which could be applied in a number of different cases, so that practitioners could analyze and prepare the treatment with more certainty.

Annals of Anatomy - Anatomischer Anzeiger, 2015

Understanding of the occlusal load distribution through the mid-facial skeleton in natural dentit... more Understanding of the occlusal load distribution through the mid-facial skeleton in natural dentition is essential because alterations in magnitude and/or direction of occlusal forces may cause remarkable changes in cortical and trabecular bone structure. Previous analyses by strain gauge technique, photoelastic and, more recently, finite element (FE) methods provided no direct evidence for occlusal load distribution through the cortical and trabecular bone compartments individually. Therefore, we developed an improved three-dimensional FE model of the human skull in order to clarify the distribution of occlusal forces through the cortical and trabecular bone during habitual masticatory activities. Particular focus was placed on the load transfer through the anterior and posterior maxilla. The results were presented in von Mises stress (VMS) and the maximum principal stress, and compared to the reported FE and strain gauge data. Our qualitative stress analysis indicates that occlusal forces distribute through the mid-facial skeleton along five vertical and two horizontal buttresses. We demonstrated that cortical bone has a priority in the transfer of occlusal load in the anterior maxilla, whereas both cortical and trabecular bone in the posterior maxilla are equally involved in performing this task. Observed site dependence of the occlusal load distribution may help clinicians in creating strategies for implantology and orthodontic treatments. Additionally, the magnitude of VMS in our model was significantly lower in comparison to previous FE models composed only of cortical bone. This finding suggests that both cortical and trabecular bone should be modeled whenever stress will be quantitatively analyzed.

Archives of Civil and Mechanical Engineering, 2010

For numerical simulation of crack modelling in fracture mechanics the eXtended finite element met... more For numerical simulation of crack modelling in fracture mechanics the eXtended finite element method (Xfem) has been recently accepted as a new powerful and efficiency methodology. In the paper we present the details of implementation of the Xfem algorithm in our in-house finite elements based software. Also, in this study, we investigated the impact of the node enrichment variations on results of the developed numerical procedure. In this study, objective was to examine the properties of standard Xfem algorithm without using of Near Tip enriching functions in order to create possibilities for future application Xfem in the zone of plasticity. In order to evaluate the computational accuracy, numerical results for the Stress Intensity Factors are compared with both theoretical and conventional finite element data. Obtained numerical results have shown a good agreement with the benchmark solutions. For calculation of the Stress Intensity Factors (SIF), we used the J-Equivalent Domain Integral (J-EDI) Method. Computational geometry issues, associated with the representation of the crack and the enrichment of the finite element approximation, are discussed in detail.

Archives of Civil and Mechanical Engineering, 2013

The paper presents an estimation of the residual life of the power plant high-pressure pipe, whic... more The paper presents an estimation of the residual life of the power plant high-pressure pipe, which has been in exploitation for years. A crack was noticed in the pipe, thus it was necessary to estimate the pipe material residual life until its eventual failure. The combined methodology for residual life estimation, which consists of experimental and numerical investigations, was developed. The samples were taken directly from the real high pressure pipe and material properties were determined experimentally, both at room and elevated (operational) temperature. The experimental results also served for the verification of the developed numerical methodologies. The FEM and the X-FEM methods were used for the residual life numerical estimation of the high pressure pipe. The stress and strain fields, used for the estimate, were obtained by application of the Paris' law. The final verification of numerical results was realized by comparing the critical crack length to the experimentally obtained value.

International Endodontic Journal, 2014

Scientific reports, Jan 26, 2018

Despite its two-dimensional nature, X-ray angiography (XRA) has served as the gold standard imagi... more Despite its two-dimensional nature, X-ray angiography (XRA) has served as the gold standard imaging technique in the interventional cardiology for over five decades. Accordingly, demands for tools that could increase efficiency of the XRA procedure for the quantitative analysis of coronary arteries (CA) are constantly increasing. The aim of this study was to propose a novel procedure for three-dimensional modeling of CA from uncalibrated XRA projections. A comprehensive mathematical model of the image formation was developed and used with a robust genetic algorithm optimizer to determine the calibration parameters across XRA views. The frames correspondences between XRA acquisitions were found using a partial-matching approach. Using the same matching method, an efficient procedure for vessel centerline reconstruction was developed. Finally, the problem of meshing complex CA trees was simplified to independent reconstruction and meshing of connected branches using the proposed nonun...

Journal of Serbian Society for Computational Mechanics, 2016

The aim of the present study was to estimate biomechanical weakening of human knee joint assuming... more The aim of the present study was to estimate biomechanical weakening of human knee joint assuming the conditions that occur when a person is standing on one leg. A patient-specific three-dimensional model of the human knee joint was developed from medical scans, while loads and material characteristics were adopted from the literature. The considered model included the following materials: bones, menisci, articular cartilage and relevant ligaments (posterior cruciate ligament, lateral collateral ligament and medial collateral ligament). The finite element analysis was used for numerical calculation of the stress distribution and failure index of posterior cruciate ligament. The obtained failure index showed that there was no possibility for posterior cruciate ligament failure under the considered conditions. It was concluded that application of the finite element analysis can provide a better insight into the biomechanical condition of the injured knee joint.

An extended finite element method (X-FEM) for two-dimensional crack modelling is described in thi... more An extended finite element method (X-FEM) for two-dimensional crack modelling is described in this paper. For the crack calculation, a discontinuous function and the asymptotic crack-tip displacement fields are added to the finite element approximation using the concept Partition of Unity (PU). This enables the domain to be modelled by finite elements with no explicit meshing of the crack faces. Computational geometry issues associated with the representation of the crack and the enrichment of the finite element approximation are discussed. The presented Stress Intensity Factors (SIFs) for crack is in a good agreement with benchmark solutions. For calculation of the SIFs, we used the J-Equivalent Domain Integral (J-EDI) method. Key words: eXtended Finite Element Method (X-FEM); Partition of Unity Method (PUM); local enrichment; elastostatics; Stress Intensity Factors (SIFs); J-Equivalen Domain Integral method (J-EDI method).

International journal of oral and maxillofacial surgery, Jan 2, 2014

It has been suggested that unerupted lower third molars (M3) increase the fragility of the mandib... more It has been suggested that unerupted lower third molars (M3) increase the fragility of the mandibular angle and simultaneously decrease the risk of condylar fracture. However, it is unknown whether this applies regardless of the direction and point of impact of the traumatic force. The aim of this study was to investigate the impact of an unerupted M3 on the fragility of the angle and condyle in terms of a force acting from different directions and affecting different regions of the mandible. Computed tomography scans of a human mandible and finite element methodology were used to obtain two three-dimensional models: a model with, and the other without an unerupted M3. A force of 2000N was applied to three different regions of the models: the symphysis, ipsilateral body, and contralateral body, respectively. When the force was applied to the mandibular body, the results revealed increased angle fragility in cases with unerupted M3. When the force was applied to the symphysis, the co...

Computer Methods and Programs in Biomedicine, 2014

Colorectal carcinoma is acknowledged as the second leading cause of total cancer-related death in... more Colorectal carcinoma is acknowledged as the second leading cause of total cancer-related death in the European Region. The majority of deaths related to colorectal carcinoma are connected with liver metastatic disease. Approximately, in 25% of all patients, liver metastatic disease is diagnosed at the same time as the primary diagnosis, while up to a quarter of others would develop liver metastases in the course of the illness. In this study, we developed reaction-diffusion model and analyzed the effect of drug therapy on liver metastatic disease for a specific patient. Tumor volumes in specific time points were obtained using CT scan images. The nonlinear function for cell proliferation rate as well as data about clinically applied drug therapy was included in the model. Fitting procedure was used for parameter estimation. Good agreement of numerical and experimental results shows the feasibility and efficacy of the proposed system.

Elimination of a large part of dental tissues during root canal treatment affects the mechanical ... more Elimination of a large part of dental tissues during root canal treatment affects the mechanical behavior of devitalized teeth. The present study addresses how much dentin removal affects changes in mechanical behaviors of the intact tooth and tooth with root canal treatment. In order to estimate the tooth weakening, we performed aн experimental assessment of critical force and numerical Finite Element Method (FEM) analysis with the intention to analyze stresses distributions. The results showed that root canal treatment had significant influence on stress distributions. By analysis of retrieved results, it is concluded that this study is an efficient framework which could be applied in a number of different cases, so that practitioners could analyze and prepare the treatment with more certainty.

Annals of Anatomy - Anatomischer Anzeiger, 2015

Understanding of the occlusal load distribution through the mid-facial skeleton in natural dentit... more Understanding of the occlusal load distribution through the mid-facial skeleton in natural dentition is essential because alterations in magnitude and/or direction of occlusal forces may cause remarkable changes in cortical and trabecular bone structure. Previous analyses by strain gauge technique, photoelastic and, more recently, finite element (FE) methods provided no direct evidence for occlusal load distribution through the cortical and trabecular bone compartments individually. Therefore, we developed an improved three-dimensional FE model of the human skull in order to clarify the distribution of occlusal forces through the cortical and trabecular bone during habitual masticatory activities. Particular focus was placed on the load transfer through the anterior and posterior maxilla. The results were presented in von Mises stress (VMS) and the maximum principal stress, and compared to the reported FE and strain gauge data. Our qualitative stress analysis indicates that occlusal forces distribute through the mid-facial skeleton along five vertical and two horizontal buttresses. We demonstrated that cortical bone has a priority in the transfer of occlusal load in the anterior maxilla, whereas both cortical and trabecular bone in the posterior maxilla are equally involved in performing this task. Observed site dependence of the occlusal load distribution may help clinicians in creating strategies for implantology and orthodontic treatments. Additionally, the magnitude of VMS in our model was significantly lower in comparison to previous FE models composed only of cortical bone. This finding suggests that both cortical and trabecular bone should be modeled whenever stress will be quantitatively analyzed.

Archives of Civil and Mechanical Engineering, 2010

For numerical simulation of crack modelling in fracture mechanics the eXtended finite element met... more For numerical simulation of crack modelling in fracture mechanics the eXtended finite element method (Xfem) has been recently accepted as a new powerful and efficiency methodology. In the paper we present the details of implementation of the Xfem algorithm in our in-house finite elements based software. Also, in this study, we investigated the impact of the node enrichment variations on results of the developed numerical procedure. In this study, objective was to examine the properties of standard Xfem algorithm without using of Near Tip enriching functions in order to create possibilities for future application Xfem in the zone of plasticity. In order to evaluate the computational accuracy, numerical results for the Stress Intensity Factors are compared with both theoretical and conventional finite element data. Obtained numerical results have shown a good agreement with the benchmark solutions. For calculation of the Stress Intensity Factors (SIF), we used the J-Equivalent Domain Integral (J-EDI) Method. Computational geometry issues, associated with the representation of the crack and the enrichment of the finite element approximation, are discussed in detail.

Archives of Civil and Mechanical Engineering, 2013

The paper presents an estimation of the residual life of the power plant high-pressure pipe, whic... more The paper presents an estimation of the residual life of the power plant high-pressure pipe, which has been in exploitation for years. A crack was noticed in the pipe, thus it was necessary to estimate the pipe material residual life until its eventual failure. The combined methodology for residual life estimation, which consists of experimental and numerical investigations, was developed. The samples were taken directly from the real high pressure pipe and material properties were determined experimentally, both at room and elevated (operational) temperature. The experimental results also served for the verification of the developed numerical methodologies. The FEM and the X-FEM methods were used for the residual life numerical estimation of the high pressure pipe. The stress and strain fields, used for the estimate, were obtained by application of the Paris' law. The final verification of numerical results was realized by comparing the critical crack length to the experimentally obtained value.

International Endodontic Journal, 2014