Milica Nikolic

Finite element coiled cochlea model

Cochlea is important part of the hearing system, and thanks to special structure converts external sound waves into neural impulses which go to the brain. Shape of the cochlea is like snail, so geometry of the cochlea model is complex. The simplified cochlea coiled model was developed using finite element method inside SIFEM FP7 project. Software application is created on the way that user can prescribe set of the parameters for spiral cochlea, as well as material properties and boundary conditions to the model. Several mathematical models were tested. The acoustic wave equation for describing fluid in the cochlea chambers – scala vestibuli and scala timpani, and Newtonian dynamics for describing vibrations of the basilar membrane are used. The mechanical behavior of the coiled cochlea was analyzed and the third chamber, scala media, was not modeled because it does not have a significant impact on the mechanical vibrations of the basilar membrane. The obtained results are in good agreement with experiment...

3D Modeling of Plaque Progression in the Human Coronary Artery

The inflammation and lipid accumulation in the arterial wall represents a progressive disease known as atherosclerosis. In this study, a numerical model of atherosclerosis progression was developed. The wall shear stress (WSS) and blood analysis data have a big influence on the development of this disease. The real geometry of patients, and the blood analysis data (cholesterol, HDL, LDL, and triglycerides), used in this paper, was obtained within the H2020 SMARTool project. Fluid domain (blood) was modeled using Navier-Stokes equations in conjunction with continuity equation, while the solid domain (arterial wall) was modeled using Darcy’s law. For the purpose of modeling low-density lipoprotein (LDL) and oxygen transport, convection-diffusion equations were used. Kedem-Katchalsky equations were used for coupling fluid and solid dynamics.

Modeling of Self-healing Materials with Nanocontainers Using Discrete and Continuum Methods

Corrosion degradation of materials is an important issue that leads to depreciation of investment goods. In production of materials a huge challenge is to design ‘smart’ synthetic systems that can actively re-establish the continuity and integrity of a damaged area. Nanocontainers represent new technology for smart nanocoating interfaces. This chapter describes the solutions based on an innovative integrated modeling approach, including nano- and macro-scale in the automotive, aerospace and biomedical industry. Two different modeling approaches, discrete and continuum, are used to investigate coating substrates that contain nanoscale defects with healing agents. Dissipative Particle Dynamics (DPD) method uses three forces: repulsive, dissipative and random forces, as well as additional forces which bound healing agents to a metal substrate. Finite Element Method (FEM) is continuum modeling method with different diffusivity and fluxes. The chapter includes the real case examples from industry with different concentrations of inhibitors inside the primer layer. These findings could be used for guidelines for formulating nanocomposite coatings and healing effects of the surfaces through the self-assembly of the particles into the defects.

Computational modeling of plaque development in the coronary arteries

Computational study for plaque formation and development for the patient specific coronary arteries was performed. Transport of macrophages and oxidized LDL distribution for the initial plaque grow model inside the intimal area was implemented. Mass transport of LDL through the wall and the simplified inflammatory process was firstly solved. The Navier-Stokes equations govern the blood motion in the lumen, the Darcy law is used for model blood filtration, Kedem-Katchalsky equations for the solute and flux exchanges between the lumen and the intima. The system of three additional reaction-diffusion equations that models the inflammatory process and lesion growth model in the intima was used. Some examples of computer simulation for plaque formation and progression for the specific patient for left and right coronary arteries are presented. Determination of plaque location and plaque volume with computer simulation for a specific patient shows a potential benefit for prediction of disease progression.

Using of finite element method for modeling of active cochlea

Human hearing system in general, and particularly the cochlea, is very interesting for investigation. The most important reason for it is hearing loss - a health problem that affects a large part of the worlds human population. The highest percentage of people with hearing problems are older people, but the problem also occurs in newborns. Experimental research in this area provides some information about the level of hearing loss. Therefore, it is very useful to have a numerical model of the hearing system that can significantly contribute to the understanding of the origin of the mentioned health problem. Two numerical models are developed to investigate hearing problems: passive 3D cochlea model and 2D cochlea cross-section model. Those models are weakly coupled in order to make an active cochlea model [1].

Electro-mechanical cochlea model

Cochlea is a part of the inner ear and it has complex anatomy and function. The proper functioning of the cochlea includes the generation of a traveling wave along the basilar membrane, which leads to depolarization of hair cells in the Organ of Corti and subsequent auditory nerve excitation (mechanoelectrical transduction). To represent the behavior of the organ of Corti, electro-mechanical cochlea model needs to be developed. This paper presents a simplified electro-mechanical state space model of the cochlea.

Finite element cochlea box model – Mechanical and electrical analysis of the cochlea

The primary role of the cochlea is to transform external sound stimuli into mechanical vibrations and then to neural impulses which are sent to the brain. A simplified cochlea box model was developed using the finite element method. Firstly, a mechanical model of the cochlea was analyzed. The box model consists of the basilar membrane and two fluid chambers – the scala vestibuli and scala tympani. The third chamber, the scala media, was neglected in the mechanical analysis. The best agreement with currently available analytical and experimental results was obtained when behavior of the fluid in the chambers was described using the wave acoustic equation and behavior of the basilar membrane was modeled with Newtonian dynamics. The obtained results show good frequency mapping. The second approach was to use an active model of the cochlea in which the Organ of Corti was included. The operation of the Organ of Corti involves the generation of current, caused by mechanical vibration. This current in turn cause...