Comparative analysis of numerical computational techniques for determination of the wind turbine aerodynamic performances

The purpose of this paper is to explore and define an adequate numerical setting for the computation of aerodynamic performances of wind turbines of various shapes and sizes, which offers the possibility of choosing a suitable approach of minimal complexity for the future research. Here, mechanical power, thrust, power coefficient, thrust coefficient, pressure coefficient, pressure distribution along the blade, relative velocity contoure, at different wind speeds and streamlines were considered by two different methods: the blade element momentum and CFD, within which three different turbulence models were analyzed. The estimation of the mentioned aerodynamic performances was carried out on two different wind turbine blades. The obtained solutions were compared with the experimental and nominal (up-scaled) values, available in the literature. Although the flow was considered as steady, a satisfactory correlation between numerical and experimental results was achieved. The comparison between results also showed, the significance of selection, regarding the complexity and geometry of the analyzed wind turbine blade, the most appropriate numerical approach for computation of aerodynamic performances

Optimal airfoil design and wing analysis for solar-powered high altitude platform station

The ability of flying continuously over prolonged periods of time has become target of numerous research studies performed in recent years in both the fields of civil aviation and unmanned drones. High altitude platform stations are aircrafts that can operate for an extended period of time at altitudes 17 km above sea level and higher. The aim of this paper is to design and optimize a wing for such platforms and computationally investigate its aerodynamic performance. For that purpose, two-objective genetic algorithm, class shape transformation and panel method were combined and used to define different airfoils with the highest lift-to-drag ratio and maximal lift coefficient. Once the most suitable airfoil was chosen, polyhedral half-wing was modeled and its aerodynamic performances were estimated using the CFD approach. Flow simulations of transitional flow at various angles-of-attack were realized in ANSYS FLUENT and various quantitative and qualitative results are presented, such as aerodynamic coefficient curves and flow visualizations. In the end, daily mission of the aircraft is simulated and its energy requirement is estimated. In order to be able to cruise above Serbia in July, an aircraft weighing 150 kg must accumulate 17 kWh of solar energy per day

Buckling and post-buckling behavior of shell type structures under thermo mechanical loads

The thermo mechanical buckling and post-buckling behavior of layered composite shell type structure are considered with the finite element method under the combination of temperature load and applied mechanical loads. To account for through-thickness shear deformation effects, the thermal elastic, and higher-order shear deformation theory is used in this study. The refined higher order theories, that takes into account the effect of transverse normal deformation, is used to develop discrete finite element models for the thermal buckling analysis of composite laminates. Attention in this study is focused on analyzing the temperature effects on buckling and post-buckling behavior of thin shell structural components. Special attention in this paper is focused on studying of values of the hole in curved panel on thermal buckling behavior and consequently to expend and upgrade previously conducted investigation. Using finite element method, a broader observation of the critical temperature of loss of stability depending on the size of the hole was conducted. The presented numerical results based on higher-order shear deformation theory can be used as versatile and accurate method for buckling and post-buckling analyzes of thin-walled laminated plates under thermo mechanical loads

Buckling and post-buckling behavior of shell type structures under thermo mechanical loads

The thermo mechanical buckling and post-buckling behavior of layered composite shell type structure are considered with the finite element method under the combination of temperature load and applied mechanical loads. To account for through-thickness shear deformation effects, the thermal elastic, and higher-order shear deformation theory is used in this study. The refined higher order theories, that takes into account the effect of transverse normal deformation, is used to develop discrete finite element models for the thermal buckling analysis of composite laminates. Attention in this study is focused on analyzing the temperature effects on buckling and post-buckling behavior of thin shell structural components. Special attention in this paper is focused on studying of values of the hole in curved panel on thermal buckling behavior and consequently to expend and upgrade previously conducted investigation. Using finite element method, a broader observation of the critical temperature of loss of stability depending on the size of the hole was conducted. The presented numerical results based on higher-order shear deformation theory can be used as versatile and accurate method for buckling and post-buckling analyzes of thin-walled laminated plates under thermo mechanical loads

Experimental investigation of spillover effect in system of active vibration control

Piezoelektrični aktuatori se uveliko primenjuju za aktivno upravljanje vibracijama na raznim strukturama sa ciljem povećanja performansi sistema. Razvijeni sistem aktivnog upravljanja vibracijama se sastoji od aktivnije strukture, kontrolera i visokonaponskih pojačivača. U ovom radu, kompozitna greda predstavlja osnovnu strukturu za senzorsku (merne trake) i aktuatorsku (dvoslojni PZT piezoelektrični aktuator) platformu. U cilju unapređenja dinamičkih karakteristika aktivnog sistema vršena je promena koeficijenata PID regulatora. Efikasnost sistema aktivnog upravljanja vibracijama za posmatrani mod oscilovanja se može povećati promenom koeficijenata PID regulatora, ali u isto vreme moguće je narušiti stabilnost sistema. Nestabilnost sistema je najčešće uslovljena pojavom 'spillover' efekta. U ovom radu predstavljen je značaj 'spillover' efekta u zatvorenim petljama piezoelektričnih aktivnih struktura, kao i značaj promene koeficijenata PID regulatora na stabilnost sistema. Eksperimentalni rezultati sistema aktivnog prigušenja vibracija su predstavljeni u radu i daju jednu od mogućnosti za povećanje stabilnosti upravljanih struktura.Piezoelectric actuators are widely used in structural systems for active vibration control with the aim to enhance the performance of systems. The developed system of active vibration control consists of active structure, controller and high voltage amplifier. In this paper, the composite beam is host structure for sensor platform (strain gages) and actuator platform (dual layer PZT piezoelectric actuator). In order to improve the dynamic characteristics of active system, the coefficients of PID controller are changed. The effectiveness of active vibration control system at mode of interest can be improved with change of PID coefficients, but the stability of system can be reduced. The instability of the active structure is often perturbed by spillover effect. In this paper the importance of considering spillover effects in closed loop of piezoelectric active structures is demonstrated and shown the importance of change the PID coefficients in stability of active vibration control system. Experimental results which correspond to the developed active vibration control system are presented and affirmed stability on proposed active structure

Experimental investigation of spillover effect in system of active vibration control

Piezoelektrični aktuatori se uveliko primenjuju za aktivno upravljanje vibracijama na raznim strukturama sa ciljem povećanja performansi sistema. Razvijeni sistem aktivnog upravljanja vibracijama se sastoji od aktivnije strukture, kontrolera i visokonaponskih pojačivača. U ovom radu, kompozitna greda predstavlja osnovnu strukturu za senzorsku (merne trake) i aktuatorsku (dvoslojni PZT piezoelektrični aktuator) platformu. U cilju unapređenja dinamičkih karakteristika aktivnog sistema vršena je promena koeficijenata PID regulatora. Efikasnost sistema aktivnog upravljanja vibracijama za posmatrani mod oscilovanja se može povećati promenom koeficijenata PID regulatora, ali u isto vreme moguće je narušiti stabilnost sistema. Nestabilnost sistema je najčešće uslovljena pojavom 'spillover' efekta. U ovom radu predstavljen je značaj 'spillover' efekta u zatvorenim petljama piezoelektričnih aktivnih struktura, kao i značaj promene koeficijenata PID regulatora na stabilnost sistema. Eksperimentalni rezultati sistema aktivnog prigušenja vibracija su predstavljeni u radu i daju jednu od mogućnosti za povećanje stabilnosti upravljanih struktura.Piezoelectric actuators are widely used in structural systems for active vibration control with the aim to enhance the performance of systems. The developed system of active vibration control consists of active structure, controller and high voltage amplifier. In this paper, the composite beam is host structure for sensor platform (strain gages) and actuator platform (dual layer PZT piezoelectric actuator). In order to improve the dynamic characteristics of active system, the coefficients of PID controller are changed. The effectiveness of active vibration control system at mode of interest can be improved with change of PID coefficients, but the stability of system can be reduced. The instability of the active structure is often perturbed by spillover effect. In this paper the importance of considering spillover effects in closed loop of piezoelectric active structures is demonstrated and shown the importance of change the PID coefficients in stability of active vibration control system. Experimental results which correspond to the developed active vibration control system are presented and affirmed stability on proposed active structure

Dimethyl sulfoxide improves sensitivity and specificity of RT-PCR and qRT-PCR amplification of low-expressed transgenes

The expression of transgenes in a host plant may be low for a number of reasons. Both low expression and poor specificity of amplification were encountered during analysis of the expression of the Arabidopsis cytokinin oxidase/dehydrogenase (AtCKX1) gene in transgenic Centaurium erythraea. The optimization of the PCR protocol involved a gradient of annealing temperatures, as well as the application of seven PCR enhancers: formamide, dimethyl sulfoxide (DMSO), glycerol, ethylene glycol, trehalose, BSA and Tween-20. The best results for AtCKX1 amplification were obtained at 55.1ºC, with the addition of 5% DMSO. Glycerol and trehalose also improved the sensitivity of amplification, while formamide, ethylene glycol and BSA enhanced only the amplification of control purified targets, but not the transcripts. Tween-20 inhibited PCR. DMSO enhanced AtCKX1 PCR amplification and improved the specificity of qPCR amplification, as well as the assay reproducibility. This work emphasizes the usefulness of additives, which are rarely used for PCR optimization in real-time experiments.Projekat ministarstva br. ON173015 i br. ON17302

Lajm neuroborelioza

Lyme borreliosis (LB) is a multisystemic zoonotic disease which in humans can involve the skin, joints, heart and/or nervous system. In this study a total of 11 patients with clinical manifestations have been assessed at the Institute for Occupational Health. Evaluation of the patients was done in order to determine their working capability and further professional orientation. Patients were of different gender, age, education and profession. They fulfilled at least two of the three criteria: tick infestation data (epidemiological criteria), central and/or peripheral neurological symptoms (clinical criteria) and a positive serological finding. Diagnosis was done upon classical clinical criteria: electromyeloneurography (EMNG) analysis, neurological impairments, electroencephalography (EEG), computer tomography (CT) and/or magnetic resonance imaging (MRI). IgM and IgG antibodies against B. burgdorferi were determined by commercial ELISA kits. IgM antibodies were recorded in the serum of 4 (44.4%) and IgG in 6 (66.7%) patients. Electro-myeloneurography findings of the upper and lower limbs were positive in 5 (83.3%), electroencephalography in 4 (66.6%) of the 6 observed patients and CT was positive in 4 (36.4%) of the 5 observed patients. The study has established that in patients with neuroborreliosis (NB) the capability to carry out intellectual tasks, as well as responsible duties is impaired due to poor memory. Patients suffering from peripheral neuropathies are not fit to withstand longterm walks, weight lifting and carrying or any other form of physical stress.Lajm borelioza je multisistemsko oboljenje, iz grupe zoonoza koje kod ljudi može zahvatiti kožu, zglobove, srce i/ili nervni sistem. Istraživanjem je obuhvaćeno 11 bolesnika sa kliničkim manifestacijama neuroborelioze koji su ispitivani u Institutu za medicinu rada Srbije u cilju ocene radne sposobnosti i dalje profesionalne orijentacije. Ispitani su bolesnici različite starosti, pola, nivoa obrazovanja i različitih zanimanja koji su ispunili minimalno dva od tri kriterijuma i to: podatak o ubodu krpelja (epidemiološki kriterijum), ispoljavanje centralnih i/ili, perifernih neuroloških simptoma (klinički kriterijum) i pozitivan serološki nalaz. Dijagnoza neuroborelioze je postavljena na osnovu klasičnih kliničkih kriterijuma: neurološ kih ispada, analize elektro-mioneurografije (EMNG), elektroencefalografije (EEG), kompjuterske tomografije (CT) i/ili magnetne rezonance (MRI). Ispitivanje prisustva antitela IgM i IgG klase u krvnom serumu prema B. burgdorferi vršeno je komercijalnim ELISA testom. Antitela IgM klase registrovana su u serumu četiri (44,4%), dok su IgG antitela registrovana kod 6 (66,7%) ispitanih pacijenata. Nalaz elektro-mioneurografije gornjih i donjih ekstremiteta je bio pozitivan kod pet (83,3%), nalaz elektroencefalografije kod četiri (66,6%) od šest ispitanih pacijenata, dok je nalaz CT bio pozitivan kod 4 (36,4%) od pet ispitanih pacijenata. Sprovedenim ispitivanjem je utvrđeno da je kod bolesnika sa razvijenom neuroboreliozom smanjena sposobnost za bilo koju vrstu intelektualnog rada, kao i za poslove koji su povezani sa moralnom i materijalnom odgovornošću zbog problema sa pamćenjem. Kod bolesnika sa perifernim neuropatijama postoji nesposobnost za poslove koji uključuju dugotrajno stajanje i hodanje, dizanje i nošenje tereta, kao i bilo koju vrstu fizičkog rada

Dimethyl sulfoxide improves sensitivity and specificity of RT-PCR and qRT-PCR amplification of low-expressed transgenes

The expression of transgenes in a host plant may be low for a number of reasons. Both low expression and poor specificity of amplification were encountered during analysis of the expression of the Arabidopsis cytokinin oxidase/dehydrogenase (AtCKX1) gene in transgenic Centaurium erythraea. The optimization of the PCR protocol involved a gradient of annealing temperatures, as well as the application of seven PCR enhancers: formamide, dimethyl sulfoxide (DMSO), glycerol, ethylene glycol, trehalose, BSA and Tween-20. The best results for AtCKX1 amplification were obtained at 55.1ºC, with the addition of 5% DMSO. Glycerol and trehalose also improved the sensitivity of amplification, while formamide, ethylene glycol and BSA enhanced only the amplification of control purified targets, but not the transcripts. Tween-20 inhibited PCR. DMSO enhanced AtCKX1 PCR amplification and improved the specificity of qPCR amplification, as well as the assay reproducibility. This work emphasizes the usefulness of additives, which are rarely used for PCR optimization in real-time experiments.Projekat ministarstva br. ON173015 i br. ON17302