The interaction of fluid and thin-walled structure of open contour

Интеракција флуида и танкозидне структуре коју флуид опструјава или протиче кроз њу је комплексан проблем који се среће у многим инжењерским дисциплинама. Домени две различите области динамике континуума, структуралне механике и динамике флуида, имају заједничку површ раздвајања. Предмет овог рада је интеракција термички оптерећеног канала аеросмеше и струје ваздуха који протиче кроз танкозидну структуру канала затворене контуре, састављену од хомогених, изотропних, челичних плоча. Услед спречених термичких дилатација у средњој површи танкозидног елемента, структура се деформише изазивајући промену облика струјног домена. У новом струјном домену се успоставља струјање другачије од струјања кроз недеформисани канал. Циљ рада је да се оцени утицај деформисане термички оптерећене структуре на струјно поље кроз канал и обратно. Проблем је решен коришћењем нумеричких метода просторне дискретизације континуума. За прорачун напонско-деформационог стања зида канала коришћена је метода коначних елемената. Претпостављена су униформна температурска поља на унутрашњем и спољашњем зиду канала. Дискретизација структуралног домена је извршена коначним елементима љуске формираних на основу Reissner- Mindlin-ове теорије плоча и љуски. Материјал плоче је моделиран серијом билинеарних карактеристика у зависности од температуре, са von Misses-овим условом течења и одговарајућим моделом ојачања материјала. За статичке нелинеарне структуралне прорачуне великих померања и деформација применом Њутн-Рапсонова методе са инкременталним уносом оптерећења коришћени су алгоритми софтверског пакета ANSYS. Дискретизациона метода коначних запремина је коришћена за решавање Рејнолдс усредњених Навије-Стоксових једначина нестишљивог нестационарног струјања ваздуха кроз деформисани канал применом софтверског пакета ANSYS CFX. У циљу оцене дисторзије Апстракт VII мреже коначних запремина у деформисаном струјном простору, деформација мреже је дефинисана фактором крутости који зависи од удаљености од најближег зида. Једначине динамике флуида и структуралне механике су спрегнуте условом да су положај и брзина тачке која лежи на површи раздвајања ова два домена, исте у сваком од домена. У ту сврху је коришћена процедура итеративног узастопног спрезања ова два прорачуна. За пренос оптерећења између различитих домена коришћени су алгоритам претраге по блоковима и метода преноса утицаја интерполацијом са одржањем профила. Резултати прорачуна указују да модел преноса и карактеристике мрежа утичу на конвергенцију и добијени резултат...Fluid - structure interaction is very complex problem that could be faund in many branches of engineering. Structure mechanics and fluid dynamics are interconnecting on the surface of separatin of two different physical domains. The object of this work is interaction of thermally loaded air-coal mixture channel and air flow through the thin walled channel structure of closed conture, made of homogenous, isotropic, steel plates. Thermal load induce deformation of the channel wall into wave - type shapes depending on thermal load and fluid inlet velocity inducing the changes of fluid flow accordingly. The air flow through the new, deformed domain is different than flow through undeformed one. The goal of this work is to evaluate influence of thermally deformed channel on fluid flow and vice versa. The problem is solved using methods of numerical spatial discretization. The finite element method is used for stress-strain calculation. Thermal load is supposed as uniformly distributed temperature fields on inner and outer surface of the channel’s walls. Structure is discretized by shell finite elements based on Reissner-Mindlin formulation. Material model descripte a series of bilinear temperature dependent characteristics, von Misses yield conditions and appropriate flow and hardening rules. The incrementally loaded structural model with geometric and material nonlinearities is solved by Newton-Ralphson method using ANSYS software. The unsteady Navier- Stokes equations are numerically solved using an element-based finite volume method and second order backward Euler discretization scheme. The algorithm of ANSYS CFX software is used for the fluid flow solution. In order to evaluate deformation of flow domain mesh due to deflection of the plates, additional variable, namely mesh stiffnes, is solved. The mesh stiffnes parameterer is related to the distance from the nearest wall, as well as the level of the mesh deformation. The computational structural mechanics and computational fluid dynamics are coupled by the condition that displacement and velocity of the point laying in the interface surface are the same for both domains. The Abstract IX implicit two-way iterative code coupling, partitioned solution approach, were used while solving these numerical tests. The bucket search algorithm and profile preserving interpoaltion method were used for load transfer between disimilar meshes. A set of fluid - structure interaction (FSI) numerical tests have been defined by varying the values of fluid inlet velocity, temperature of inner and outer surface of the channel wall and numerical grid density.The results of this set of numerical calculations indicate that model of load transfer used and meshes charachteristics infuence convergence of the calculation and obtained results..

Ispitivanje antioksidativnih mehanizama kempferola sa hidroksi radikalom i superoksid radikal anjonom

Kaempferol, one of the most bioactive plant flavonoids was theoretically (at M05-2X/6-311G(d,p) level of theory) investigated for its ability scavange potentially highly damaging hydroxyl and superoxide anion radicals. Theoretical calculations point to HAT and SPLET mechanisms as operative for kaempferol in all solvents under investigations.Teoretski (na M05-2X/6-311G(d,p) nivou teorije) je ispitivana sposobnost kempferola, važnog bioaktivnog biljnog jedinjenja flavonoida, da reaguje sa potencijalno veoma štetnim hidroksi radikalom i superoksid radikal anjonom. Proračuni su pokazali da su HAT i SPLET mogući mehanizmi u svim rastvaračima

DFT ispitivanje antioksidativne aktivnosti alizarina Red S

Density functional theory calculations were performed to evaluate the antioxidant activity of alizarin red S molecule. The conformational behavior of molecule were analysed at the M06-2X/6-311++G(d,p) method. The most stable conformer of alizarin red S has two IHBs. The expected antioxidant activity of alizarin red S was justified from ionization potential (IPs) and homolytic O-H bond dissociation enthalpy (BDEs) values. Heterolytic O-H bond cleavages (proton dissociation enthalpies, PDEs) were also computed. Calculated IP, BDE, and PA values suggested that one-step H atom transfer (HAT), rather than SPLET or SET-PT, would be the most favored mechanism for explaining the antioxidant activity of alizarin red S in gas phase. In aqueous solution all of three mechanisms were competitive.Upotrebom DFT metode vršena su izračunavanja u cilju određivanja antioksidativne aktivnosti alizarina red S. Konformaciona priroda molekula analizirana ispitana je primenom M06-2X/6-311++G(d,p) metoda. Najstabilniji konformer alizarina red S ima dve unutrašnje vodonične veze. Očekivana antioksidativna aktivnost alizarina red S određena je izračunavanjem vrednosti jonizacionih potencijala (IP) i i vrednosti entalpija homolitičkog raskidanja O-H veza (BDE). Vrednosti entalpije heterolitičkog raskidanja O-H veza (entalpije disocijacije protona, PDE), su takođe izračunate. Izračunate IP, BDE i PA vrednosti ukazuju na to da je jednostepeni transfer H-atoma (HAT), pre nego SPLET ili SET-PT mehanizam, favorizovan u pogledu antioksidativne aktivnosti alizarina red S u gasnoj fazi. U vodenom rastvoru, sva tri mehanizma su konkurentna

Agriotypus armatus Curtis, 1832, a parasitoid of Silo pallipes Fabricius, 1781: the first record for the Balkan Peninsula

Among the diverse order of Hymenoptera, aquatic species are of special interest. During macrozoobenthos sampling in the rivers of Serbia in 2003 and during the period 2011-2012, pupae of Silo pallipes Fabricius, 1781 were recorded which were parasitized by an ichneumonid wasp Agriotypus armatus Curtis, 1832, this being the first record of it for the Balkan Peninsula. A total of 217 A. armatus specimens were collected at 29 localities situated along 16 watercourses of Serbia. All four parasitoid stages (egg, larva, pupa and resting adult) were recorded. The identity of the parasitoid was confirmed using standard molecular methods. This study also focuses on the ecology of the parasitoid and its host. The widespread distribution of A. armatus in Europe suggests the presence of this species in other Balkan countries, but this has not yet been confirmed due to a lack of surveys and/or the constantly increasing pollution of freshwaters

Transfer Learning with ResNet3D-101 for Global Prediction of High Aerosol Concentrations

In order to better predict the high aerosol concentrations associated with air pollution and climate change, a machine learning model was developed using transfer learning and the segmentation process of global satellite images. The main concept of transfer learning lies on convolutional neural networks and works by initializing the already trained model weights to better adapt the weights when the network is trained on a different dataset. The transfer learning technique was tested with the ResNet3D-101 model pre-trained from a 2D ImageNet dataset. This model has performed well for contrail detection to assess climate impact. Aerosol distributions can be monitored via satellite remote sensing. Satellites can monitor some aerosol optical properties like aerosol optical thickness. Aerosol optical thickness snapshots were the input dataset for the model and were obtained from NASA’s Terra-Modis satellite; the output images were segmented by comparing the pixel values with a threshold value of 0.8 for aerosol optical thickness. Hyperparameter optimization finds a tuple of hyperparameters that yields an optimal model that minimizes a predefined loss function on given independent data. The model structure was adjusted in order to improve the performance of the model by applying methods and hyperparameter optimization techniques such as grid search, batch size, threshold, and input length. According to the criteria defined by the authors, the distance domain criterion and time domain criterion, the developed model is capable of generating adequate data and finding patterns in the time domain. As observed from the comparison of relative coefficients for the criteria metrics proposed by the authors, ddc and dtc, the deep learning model based on ConvLSTM layers developed in our previous studies has better performance than the model developed in this study with transfer learning

The isolation, analytical characterization by HPLC-UV and NMR spectroscopy, cytotoxic and antioxidant activities of baeomycesic acid from Thamnolia vermicularis var. subuliformis

The aim of this work was the analytical characterization of the β-orcinol depside, baeomycesic acid in lichens extracts. The extract of Thamnolia vermicularis var. subuliformis was analyzed by the two different methods, namely HPLC-UV and 1H NMR analysis. The results showed that baeomycesic acid was the most abundant depside in the lichens. These results could be of use for rapid identification of this metabolite in other lichen species. Besides baeomycesic acid, three depsides and one monocyclic phenolic compound were isolated from the lichen extract on the chromatographic column. The structure of baeomycesic acid was confirmed by HPLC-UV and spectroscopic methods. In addition, antioxidant and cytotoxic activities of baeomycesic acid were determined. The result of the testing showed that baeomycesic acid exhibited a moderate radical scavenging activity (IC50 = 602.10 ± 0.54 μg/mL) and good cytotoxic activity. This is the first report of detailed analytical characterization, isolation, as well as antioxidant and cytotoxic activities of baeomycesic acid from Thamnolia vermicularis. These results may be helpful in future industrial production of herbal medicines that include this important natural product

Application of software Efftran in radiological analysis of coal, slag and ash samples from thermal power plants

Ugalj, šljaka i pepeo iz termoelektrana sadrţe prirodne radionuklide čije se specifične aktivnosti mogu odrediti pomoću poluprovodničke gama spektrometrijske analize. Ove specifične aktivnosti su uglavnom niske, pa se stoga uzorci mere na malim rastojanjima od detektora, gde su izraţeni efekti koincidentnog sumiranja. U radu su prikazani korekcioni faktori za sumacione efekte za radionuklide iz uranovog (234mPa, 234Th, 226Ra, 214Bi i 214Pb) i torijumovog niza (228Ac, 224Ra, 212Pb, 212Bi i 208Tl) dobijeni primenom softvera EFFTRAN, kao i korigovane vrednosti specifičnih aktivnosti.Coal, slag and ash from thermal power plants contain natural radionuclides whose specific activity could be determined by semiconductor gamma spectrometry. These specific activities are generally low, and therefore the samples should be measured at small distances from the detector, where coincidence summing effect are very pronounced. The corrections factors, obtained by using software EFFTRAN, for coincidence summing effects in the case of radionuclides from uranium ( 234mPa, 234Th, 226Ra, 214Bi and 214Pb) and thorium (228Ac, 224Ra, 212Pb, 212Bi and 208Tl) serie are presented in this paper, as well as corrected values for specific activities.XXVIII Симпозијум Друштва за заштиту од зрачења Србије и Црне Горе, 30. септембар - 02. октобар 2015

The influence of powder characteristics on two-step sintering behavior of hydroxyapatite

Fabrication of full dense ceramic materials on the basis of hydroxyapatite (HAp) and biphasic calcium phosphate (BCP) with controllable microstructural and compositional characteristics attracts considerable efforts. Various synthesis and sintering methods were applied in order to achieve desirable material properties. In this study different nanopowders were produced and processed via two-step sintering (TSS) approach. Characterization of synthesized nanopowders were done by XRD, BET, FE-SEM, TEM and thermal analysis methods, while microstructural and chemical characterizations of sintered samples were performed through FE-SEM and XRD analysis. A possibility for obtaining full dense ceramics with suppressed grain growth is discussed on the basis of inherent nanopowders characteristics. Certain attention would be paid on thermal behavior of Ca-deficient HAp systems

Pljevlja lignite carbon emission charateristics

The anthropogenic emission of GHG especially CO has to be limited and reduced due to their impact on global warming and climate change. Combustion of fossil fuels in the energy sector has a dominant share in total GHG emissions. In order to reduce GHG emission, European Union established a scheme for GHG allowance trading within the community, and the implementation of the European Union emission trading scheme, which is a key to GHG reduction in a cost-effective way. An important part of emission trading scheme is prescribed methodology for monitoring, reporting, and verification of the emission of GHG including characterization of the local fuels combusted by the energy sector. This paper presents lignite characteristics from open-pit mine Borovica-Pljevlja, which has highest coal production in Montenegro (>1.2 Mt per year), including evaluation of its carbon emission factor based on the laboratory analysis of 72 coal samples. Testing of the samples included proximate and ultimate analysis, as well as, net calorific value determination. In accordance with the obtained results, linear correlations between net calorific value and combustible matter content, carbon content and combustible matter content, hydrogen content and combustible matter content, carbon content and net calorific value, were established. Finally, the non-linear analytical correlation between carbon emission factor and net calorific value for Pljevlja lignite was proposed, as a base for the precise calculation of CO emission evaluation