Praktičan primer povećanja energetske efikasnosti malih pumpnih stanica reprojektovanjem

The suction station "Gnjilan", belonging to the "Water-supply" Pirot municipal enterprise, has been used as an example of small pump stations energy efficiency increasing by replacement of existing old pumps with new ones. It has been shown that it was possible to identify the pipeline characteristic and an optimum system operating point, even in the absence of appropriate flow measuring devices. This has been done using an indirect method of flow estimation by measurement of driving induction motor elecrtical parameters. In accordance with the obtained results, the new pump has been chosen. Huge savings in the electrical energy consumption referred to actual situation will be achieved through the application of the new pump.Na primeru Crpne stanice "Gnjilan" u okviru JP "Vodovod" Pirot, prikazan je način za povećanje energetske efikasnosti malih pumpnih stanica zamenom postojećih pumpnih agregata novim. Pokazano je da je, čak i u situaciji kada ne postoje odgovarajući uređaji za merenje protoka, moguće identifikovati karakteristiku cevovoda i optimalnu radnu tačku sistema primenom indirektne metode merenja električnih veličina pogonskog motora. U skladu sa identifikovanim parametrima, izvršen je izbor novog pumpnog agregata čijom primenom se mogu ostvariti znatne uštede u odnosu na postojeće stanje sistema

Three-dimensional biomechanical model of benign paroxysmal positional vertigo in the semi-circular canal

Benigna paroksizmalna pozicijska vrtoglavica (BPPV) je najčešći poremećaj vestibularnog sustava koji uzrokuju bazofilne čestice u polukružnom kanalu. Trodimenzijski biomehanički model SCC je opisan s potpunom 3D interakcijom fluid-struktura, čestica, zidova, deformacije kupule i endolimfnog strujanja fluida. Prikazan je model SCC s parametarskim definiranim dimenzijama i trodimenzijskim 3D rekonstrukcijama određenog pacijenta. Korištene su pune Navier-Stokes jednadžbe s jednadžbama kontinuiteta opisuje tok fluida dok je Arbitrary-Lagrangian Eulerian (ALE) formulacija korištena za gibanje mreže. Korištena je interakcija fluid-struktura za spajanje tekućine s deformacijom kupule. Primijenjen je algoritam za praćenje čestica. Korištene su različite veličine i broj čestica sa svojom punom interakcijom između sebe, zida i deformacije kupule. Raspodjela brzina, smičnog naprezanja i sila od strane endolimfe je prikazana kao parametar za jedan SCC kao i za tri SCC od određenog pacijenta. Svi modeli se koriste u korelaciji s istim eksperimentalnim protokolima s pokretima glave i gibanjem očiju - nystagmus. Puna interakcija fluid-struktura, čestica otoconia, zidova, deformacije kupula i endolimfnog fluida u tri dimenzije dat će više detalja za razumijevanje patologije specifičnog pacijenta u standardnoj kliničkoj dijagnostici i proceduri terapije za BPPV.Benign Paroxysmal Positional Vertigo (BPPV) is one of the most common vestibular disorders occuring due to the presence of basophilic particles in the semicircular canals (SCC). Three-dimensional biomechanical model of the SCC is described with full 3D fluid-structure interaction of particles, wall, cupula deformation and endolymph fluid flow. The model of the SCC with parametric defined dimension and fully 3D three SCC from patient specific 3D reconstruction is presented. Navier-Stokes equations with continuity equations described fluid flow while Arbitrary-Lagrangian Eulerian (ALE) formulation is used for mesh motion. Fluid-structure interaction for fluid coupling with cupula deformation is used. Particle tracking algorithm has been used for particle motion. Different size and number of particles with their full interaction between themselves, wall and cupula deformation are used. Velocity distribution, shear stress and force from endolymph side are presented for parametric one SCC and patient specific three SCC. All the models are used for correlation with the same experimental protocols with head moving and nystagmus eye tracking. Full fluid-structure interaction of otoconia particles, wall, cupula deflection and endolymph flow in three-dimension give more details and understanding of the pathology of the specific patient in standard clinical diagnostic and therapy procedure for BPPV

Redox interactions of epinephrine with iron at physiological pH

Epinephrine ((R)-4-(1-hydroxy-2-(methylamino)ethyl)-benzene-1,2-diol (Epi) is catecholamine that is released by the sympathetic nervous system and adrenal medulla. It is a physiologically important molecule that acts as a hormone, neurotransmitter, and medication with a broad range of effects 1-3 . Coordinate and redox interaction of Epi with iron affects the interactions with other molecules and its biological effects 4 . In this study, we reported details of redox interactions of Epi with Fe 2+ at pH 7.4, which correspond to the pH value of human plasma Epi and Fe 2+ form a complex that acts as a strong reducing agent. Cyclic voltammetry showed that the positions of E pa and E pc potentials were at approximately -480 and -1100 mV. This implies that Epi and Fe 2+ build a complex with unique redox properties. E1/2 was significantly lower compared to E0' for O 2 /O 2•- (-350 mV). It is important to point out this because superoxide radical anion is produced via spontaneous Fe 2+ reaction with O 2. In other words, Epi-Fe 2+ complex should be capable of reducing transition metals in (patho)physiologicaly relevant complexes that are not susceptible to reduction by O 2. Our results confirmed that Epi-Fe 2+ is capable of reducing the S-S group of glutathione disulfide. On the other hand, Epi acted in a catalyst-like fashion to promote Fe 2+ oxidation by molecular oxygen, and to a facilitated formation of the Epi–Fe 3+ complexes, at physiological pH. In addition, we examined the effects of epinepfrine and Epi/Fe3+ system on glioma cells. Epinephrine alone evokes changes in the membrane currents of glioma cells, but such effects were not observed for the complex with Fe 3+ . This implies that Epi-Fe 3+ might modulate neural activity of Epi in CNS

Development of the software tool for generation and visualization of the finite element head model with bone conduction sounds

© 2015 AIP Publishing LLC. Vibration of the skull causes a hearing sensation. We call it Bone Conduction (BC) sound. There are several investigations about transmission properties of bone conducted sound. The aim of this study was to develop a software tool for easy generation of the finite element (FE) model of the human head with different materials based on human head anatomy and to calculate sound conduction through the head. Developed software tool generates a model in a few steps. The first step is to do segmentation of CT medical images (DICOM) and to generate a surface mesh files (STL). Each STL file presents a different layer of human head with different material properties (brain, CSF, different layers of the skull bone, skin, etc.). The next steps are to make tetrahedral mesh from obtained STL files, to define FE model boundary conditions and to solve FE equations. This tool uses PAK solver, which is the open source software implemented in SIFEM FP7 project, for calculations of the head vibration. Purpose of this tool is to show impact of the bone conduction sound of the head on the hearing system and to estimate matching of obtained results with experimental measurements

Finite element coiled cochlea model

© 2015 AIP Publishing LLC. 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 experimental measurements. Future work is needed for more realistic geometry model. Coiled model of the cochlea was created and results are compared with initial simplified coiled model of the cochlea

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

An investigation into hybrid aluminium/composite cardan shaft

It is a well-known fact that natural resources are becoming increasingly scarce. Consequently, whenever possible in the machine element manufacture, metallic materials should be replaced with new artificial materials. This paper studies the possibility of replacing two cardan shafts of a truck TURBO ZETA 85.14B with one shaft made of aluminium and a composite material, while the basic requirements concerning the given load transfer and fundamental natural frequencies remain satisfied

Mechanical and electro-mechanical box cochlea model

The cochlea is the most important part of the hearing system, due to the fact that it receives sound in the form of vibrations and converts these vibrations into nerve impulses in the organ of Corti that sends information about sounds to the brain. Functioning of the cochlea components and behavior is still not investigated completely because of its complex structure. Human live cochlea is placed in almost inaccessible place. Because of that it is hard to collect experimental measurement. Cochlea works as an electro-mechanical system and it is important to investigate both electrical and mechanical behavior of the cochlea in order to improve treatment of hearing disorders. This study presents a mechanical model of the uncoiled cochlea using full 3D 8-noded finite elements, as well the electro-mechanical 1D state-space model of the cochlea. The results obtained from these two cochlea models show good matching with Greenwood function and properly simulate the behavior of the cochlea

Computational analysis of lung deformation after murine pneumonectomy

In many mammalian species, the removal of one lung (pneumonectomy) is associated with the compensatory growth of the remaining lung. To investigate the hypothesis that parenchymal deformation may trigger lung regeneration, we used microCT scanning to create 3D finite element geometric models of the murine lung pre- and post-pneumonectomy (24 h). The structural correspondence between models was established using anatomic landmarks and an iterative computational algorithm. When compared with the pre-pneumonectomy lung, the post-pneumonectomy models demonstrated significant translation and rotation of the cardiac lobe into the post-pneumonectomy pleural space. 2D maps of lung deformation demonstrated significant heterogeneity; the areas of greatest deformation were present in the subpleural regions of the lobe. Consistent with the previously identified growth patterns, subpleural regions of enhanced deformation are compatible with a mechanical signal - likely involving parenchymal stretch - triggering lung growth. © 2012 © 2012 Taylor & Francis

Three-Dimensional Computer Model of Benign Paroxysmal Positional Vertigo in the Semi-Circular Canal

Benign Paroxysmal Positional Vertigo (BPPV) is the most common vestibular disorder. In this paper we tried to investigate a model of the semi-circular canal (SCC) with parametrically defined dimension and full 3D three SCC from patient-specific 3D reconstruction. Full Navier-Stokes equations and continuity equations are used for fluid domain with Arbitrary-Lagrangian Eulerian (ALE) formulation for mesh motion. Fluid-structure interaction for fluid coupling with cupula deformation is used. Particle tracking algorithm has been used for particle motion. Velocity distribution, shear stress and force from endolymph side are presented for one parametric SCC and three patient-specific SCC. All models are used for correlation with the same experimental protocols with head moving and nystagmus eye tracking