A novel framework for fluid/structure interaction in rapid subjectspecific simulations of blood flow in coronary artery bifurcations

Background/Aim. Practical difficulties, particularly long model development time, have limited the types and applicability of computational fluid dynamics simulations in numerical modeling of blood flow in serial manner. In these simulations, the most revealing flow parameters are the endothelial shear stress distribution and oscillatory shear index. The aim of this study was analyze their role in the diagnosis of the occurrence and prognosis of plaque development in coronary artery bifurcations. Methods. We developed a novel modeling technique for rapid cardiovascular hemodynamic simulations taking into account interactions between fluid domain (blood) and solid domain (artery wall). Two numerical models that represent the observed subdomains of an arbitrary patient-specific coronary artery bifurcation were created using multi-slice computed tomography (MSCT) coronagraphy and ultrasound measurements of blood velocity. Coronary flow using an in-house finite element solver PAK-FS was solved. Results. Overall behavior of coronary artery bifurcation during one cardiac cycle is described by: velocity, pressure, endothelial shear stress, oscillatory shear index, stress in arterial wall and nodal displacements. The places where (a) endothelial shear stress is less than 1.5, and (b) oscillatory shear index is very small (close or equal to 0) are prone to plaque genesis. Conclusion. Finite element simulation of fluid-structure interaction was used to investigate patient-specific flow dynamics and wall mechanics at coronary artery bifurcations. Simulation model revealed that lateral walls of the main branch and lateral walls distal to the carina are exposed to low endothelial shear stress which is a predilection site for development of atherosclerosis. This conclusion is confirmed by the low values of oscillatory shear index in those places

Modeling of thermoelectric module operation in inhomogeneous transient temperature field using finite element method

This paper is the result of research and operation modeling of the new systems for cooling of cutting tools based on thermoelectric module. A copper inlay with thermoelectric module on the back side was added to a standard turning tool for metal processing. For modeling and simulating the operation of thermoelectric module, finite element method was used as a method for successful solving the problems of inhomogeneous transient temperature field on the cutting tip of lathe knives. Developed mathematical model is implemented in the software package PAK-T through which numerical results are obtained. Experimental research was done in different conditions of thermoelectric module operation. Cooling of the hot module side was done by a heat exchanger based on fluid using automatic temperature regulator. After the calculation is done, numerical results are in good agreement with experimental. It can be concluded that developed mathe-matical model can be used successfully for modeling of cooling of cutting tools

Non-linear transient heat conduction analysis of insulation wall of tank for transportation of liquid aluminum

This paper deals with transient non-linear heat conduction through the insulation wall of the tank for transportation of liquid aluminum. Tanks designed for this purpose must satisfy certain requirements regarding temperature of loading and unloading, duringtransport. Basic theoretical equations are presented, which describe the problem of heat conduction finite element analysis, starting from the differential equation of energy balance, taking into account the initial and boundary conditions of the problem. General 3-D problem for heat conduction is considered, from which solutions for two- and one-dimensional heat conduction can be obtained, as special cases. Forming of the finite element matrices using Galerkin method is briefly described. The procedure for solving equations of energy balance is discussed, by methods of resolving iterative processes of non-linear transient heat conduction. Solution of this problem illustrates possibilities of PAK-T software package, such as materials properties, given as tabular data, or analytical functions. Software alsooffers the possibility to solve non-linear and transient problems with incremental methods. Obtained results for different thicknesses of the tank wall insulation materials enable its comparison in regards to given conditions

The Prevalence of Spine Deformities and Flat Feet Among 10-12 Year Old Children Who Train Basketball – Cross-Sectional Study

The aim of this study is to estimate the prevalence of spine and feet deformities among children who are regularly involved in basketball trainings, as well as finding differences in the prevalence of those deformities between children of different gender and age. The study included a total of 64 children, of which 43 were boys and 21 were girls, ages 10-12. All subjects have been regularly participating in basketball trainings for at least one year. Postural disorder is defined as an irregularity in posture of the spine and feet, and it is assessed by visual methods from the front, side and rear side of the body. The prevalence of spinal deformities in our group was 53.13%. The boys had a significantly higher prevalence than girls, 65.1% compared to 28.57% (p=0.006). There was no significant difference in prevalence of spine deformities between children of different ages. The prevalence of feet deformities was 64.06%. There was a statistically significant difference between the sexes, where boys had a significantly greater prevalence of the feet deformities than girls, 83.7% compared to 23.81% (p=0.001). Flat feet were the most common in 10 year old children (85.71%). In conclusion, it can be said that despite regular participation in basketball training, subjects in this study have high prevalence of deformities; especially boys who stand out with the high prevalence of flat feet

Analiza čvrstoće teretnog vagona za prevoz naftnih derivata kliznom vijčanom vezom

his paper presents the strength analysis of the wagon for the transport of petroleum products with a sliding bolted connection according to TSI standard and norm EN 12663: 2010 standard. In order to optimize the number of elements of the FEA model and its complexity, the authors had a task to analyse the influence of bolted connections, which would completely correspond to the real connections. The primary objective of the analysis was to show a good agreement of the stress values obtained by FEM analysis with stress values obtained by strain gauges placed on a wagon prototype. According to comparative analysis of obtained and measured stress values, it has been concluded that the bolted connections modelled in the manner shown in this paper really transfer loads to other parts of the wagon construction and can be used to analyse complex structures exposed to different types of loadsPublishe

LIBS Analysis of Geomaterials: Comparative Study of Basalt Plasma Induced by TEA CO 2

We present a study of the plasma generated by transversely excited atmospheric (TEA) CO2 laser irradiation of a basalt sample. The plasma was induced in air at atmospheric pressure. The same sample was also analyzed using a commercial LIBS system based on Nd:YAG laser and time-gated detection. The main plasma parameters, temperature, and electron number density were determined and analytical capabilities of the two systems compared. Despite differences in laser wavelength, pulse duration, applied fluence, and signal detection scheme, the two systems are comparable in terms of element detectability and limits of detection. In both cases, all elements usually present in geological samples were identified. The estimated limits of detection for most elements were below 100 ppm, while for Cu, Cr, and Sr they were around or below 10 ppm. The obtained results led to the conclusion that simple, cost-effective TEA CO2 LIBS system can find applications for geological explorations

The Prevalence of Spine Deformities and Flat Feet Among 10-12 Year Old Children Who Train Basketball – Cross-Sectional Study

The aim of this study is to estimate the prevalence of spine and feet deformities among children who are regularly involved in basketball trainings, as well as finding differences in the prevalence of those deformities between children of different gender and age. The study included a total of 64 children, of which 43 were boys and 21 were girls, ages 10-12. All subjects have been regularly participating in basketball trainings for at least one year. Postural disorder is defined as an irregularity in posture of the spine and feet, and it is assessed by visual methods from the front, side and rear side of the body. The prevalence of spinal deformities in our group was 53.13%. The boys had a significantly higher prevalence than girls, 65.1% compared to 28.57% (p=0.006). There was no significant difference in prevalence of spine deformities between children of different ages. The prevalence of feet deformities was 64.06%. There was a statistically significant difference between the sexes, where boys had a significantly greater prevalence of the feet deformities than girls, 83.7% compared to 23.81% (p=0.001). Flat feet were the most common in 10 year old children (85.71%). In conclusion, it can be said that despite regular participation in basketball training, subjects in this study have high prevalence of deformities; especially boys who stand out with the high prevalence of flat feet