Numerical study of the hydrodynamics and mass transfer in the external loop airlift reactor

The objective of this study was to investigate the hydrodynamics and the gas-liquid mass transfer coefficient of an external-loop airlift reactor (ELAR). The ELAR was operated in three cases: different inlet velocities of fluids, different alcohols solutions (water, 0.5% methanol, 0.5% ethanol, 0.5% propanol and 0.5% butanol) and different concentration of methanol in solutions (0%, 0.5%, 1%, 2% and 5%). The influence of superficial gas velocity and various diluted alcohol solutions on hydrodynamics and the gas-liquid mass transfer coefficient of the ELAR was studied. Experimentally, the gas hold-up, liquid velocities and volumetric mass transfer coefficient values in the riser and the downcomer were obtained from the literature source. A computational fluid dynamics (CFD) model was developed, based on two-phase flow, investigating different liquids regarding surface tension, assuming the ideal gas flow, applying the finite volume method and Eulerian-Eulerian model. The volumetric mass transfer coefficient was determined using the CFD and artificial neural network model. The effects of liquid parameters and gas velocity on the characteristics of the gas-liquid mass transfer were simulated. These models were compared with the appropriate experimental results. The CFD model successfully simulates the influence of different alcohols regarding the number of C-atoms on hydrodynamics and mass transfer

Numerical simulation of boiling crises mechanism in evaporation pipes

Predmet ovog rada je numerička simulacija i analiza trodimenzionalnog dvofaznog strujanja i istraživanje mehanizama krize ključanja u isparivačkim cevima. Kriza ključanja je nepovoljna pojava. Nagli porast temperature zida cevi izaziva termomehanička naprezanja, koja mogu dovesti do pojave prskotina i pucanja cevi pod pritiskom.Razvijen je matematički model dvofaznog strujanja u isparivačkoj cevi,koji se sastoji od jednačina održanja mase, količine kretanja i energije za obe faze. Sastoji se od sistema parcijalnih diferencijalnih jednačinakoje su rečavane za definisane granične uslove.Bilo je neophodno uvesti i modeliranje i numeričku simulaciju na mikro nivou, jer je bilo potrebno ispitati i proces pojave i rasta mehura, kao i ponašanje dvofazne mešavine na zagrejačkoj površini na makroskopskom nivou.Rezultati numeričkih simulacija su upoređeni sa raspoloživim eksperimentalnim rezultatima.The subject of this thesis is numerical simulation and analyses of three dimensional two-phase flow and mechanism of boiling crises in evaporation pipes. Boiling crises is characterized by a dried out heat surface and can bring physical destruction of the heater. A developed mathematical model of two phase flow in evaporation pipe consists of prescribed mass, momentum and energy conservation equations for liquid and vapor two-phase flow. It consists of set of partial differential equations which were solved for specific boundary conditions. Modeling of the micro scale level was necessary to take into account processes of the bubble rise and behavior of the two-phase mixture at the heating surface. Results of the numerical simulation are compared with similar available results of the experiments from the literature

Numerical simulation of boiling crises mechanism in evaporation pipes

Predmet ovog rada je numerička simulacija i analiza trodimenzionalnog dvofaznog strujanja i istraživanje mehanizama krize ključanja u isparivačkim cevima. Kriza ključanja je nepovoljna pojava. Nagli porast temperature zida cevi izaziva termomehanička naprezanja, koja mogu dovesti do pojave prskotina i pucanja cevi pod pritiskom. Razvijen je matematički model dvofaznog strujanja u isparivačkoj cevi,koji se sastoji od jednačina održanja mase, količine kretanja i energije za obe faze. Sastoji se od sistema parcijalnih diferencijalnih jednačinakoje su rečavane za definisane granične uslove.Bilo je neophodno uvesti i modeliranje i numeričku simulaciju na mikro nivou, jer je bilo potrebno ispitati i proces pojave i rasta mehura, kao i ponašanje dvofazne mešavine na zagrejačkoj površini na makroskopskom nivou. Rezultati numeričkih simulacija su upoređeni sa raspoloživim eksperimentalnim rezultatima.The subject of this thesis is numerical simulation and analyses of three dimensional two-phase flow and mechanism of boiling crises in evaporation pipes. Boiling crises is characterized by a dried out heat surface and can bring physical destruction of the heater. A developed mathematical model of two phase flow in evaporation pipe consists of prescribed mass, momentum and energy conservation equations for liquid and vapor two-phase flow. It consists of set of partial differential equations which were solved for specific boundary conditions. Modeling of the micro scale level was necessary to take into account processes of the bubble rise and behavior of the two-phase mixture at the heating surface. Results of the numerical simulation are compared with similar available results of the experiments from the literature

Biological and chemical diversity of Angelica archangelica L. — case study of essential oil and its biological activity

Garden angelica (Angelica archangelica L.), native to the northern temperate region, is widespread in Europe and Asia. Since the middle ages, it has been used for healing and as a vegetable in traditional dishes. In the modern era, it has been proven that A. archangelica has a complex chemical composition. The main derivatives that contribute to the plant’s biological activities are essential oil and coumarins. In this review, the focus is on the cross-analysis of the taxonomy of A. archangelica, and its distribution in different regions, with the presentation of the richness of its biochemical composition, which overall contributes to the widespread use of the roots of this plant in folk medicine. It belongs to the plants that were introduced to the wider area of Central, Eastern, and Southern Europe; as a medicinal plant, it represents a significant part of the medical flora of many areas. Cluster analysis of pooled data indicates a clear differentiation of chemotypes

In Vitro effects of Plantago major extract, aucubin and baicalein on Candida albicans biofilm formation, metabolic activity and cell surface hydrophobicity

Purpose To determine the in vitro effectiveness of Plantago major extract, along with two of its active components, aucubin and baicalein, on the inhibition of Candida albicans growth, biofilm formation, metabolic activity, and cell surface hydrophobicity. Materials and Methods Twofold dilutions of P. major, aucubin, and baicalein were used to determine the minimum inhibitory concentration (MIC), minimum fungicidal concentration (MFC), and the minimum biofilm inhibitory concentration (MBIC) of each solution. Separately, twofold dilutions of P. major, aucubin, and baicalein were used to determine the metabolic activity of established C. albicans biofilm using a 2,3-bis (2- methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-carboxanilide reduction assay. Twofold dilutions of P. major, aucubin, and baicalein were used to determine the cell surface hydrophobicity of treated C. albicans biofilm by a two-phase assay using hexadecane. The hydrophobicity percentage of the cell surface was then calculated. A mixed-model ANOVA test was used for intergroup comparisons. Results The MICs of P. major extract (diluted 1:2 to 1:8), aucubin (61 to 244 μg/ml), and baicalein (0.0063 to 100 μg/ml) on the total growth of C. albicans were noticeable at their highest concentrations, and the inhibition was dose dependent. The MFC was evaluated after 48 hours of incubation, and aucubin (244 μg/ml) exhibited a strong fungicidal activity at its highest concentration against C. albicans growth. The MBIC indicated no growth or reduced growth of C. albicans biofilm at the highest concentrations of aucubin (61 to 244 μg/ml) and baicalein (25 to 100 μg/ml). Similarly, the effects of these reagents on C. albicans biofilm metabolic activity and hydrophobicity demonstrated high effectiveness at their highest concentrations. Conclusion P. major extract, aucubin, and baicalein caused a dose-dependent reduction on the total growth, biofilm formation, metabolic activity, and cell surface hydrophobicity of C. albicans. This demonstrates their effectiveness as antifungals and suggests their promising potential use as solutions for C. albicans biofilm-related infections

Effects of temperature and immersion time on rehydration of osmotically dehydrated pork meat

The aim of this work was to study the changes in osmotically dehydrated (OD) pork meat during rehydration. Meat samples (lxlxlcm cubes) were osmotically treated in two solutions: (1) solution with 350g of NaCI and 1200g of sucrose diluted in I I of distilled water and (2) sugar beet molasses (80 °Brix) solution at 23±2°C for 1, 2, 3 and 4 hours. In both cases, the solution to sample mass ratio was 10:1 to avoid significant dilution of the medium by water removal. After being osmotically dehydrated, meat samples were rehydrated by immersing meat cubes in water bath at constant temperature (20, 40 and 60 °C). The samples were removed after different immersion periods (15, 30, 45 and 60 min) and examined for mass and volume gain and rehydration percentage was calculated. After relatively short time (15 min), significant weight and volume gains were observed for both treatments. Process temperature was the most significant variable affecting final dry matter content and rehydration kinetics. At the end of rehydration process, conducted at 20 °C and 40 °C, a significant recovery in mass was observed, although the values were lower than for fresh meat. Ruptured and shrunken meat tissue produced as the result of OD had reduced its ability to absorb water. Rehydration percentage at 20 °C for molasses solution was 24.11%, and for sucrose-salt solution was 26.19%. However, rehydration at 40° C brings higher mass gain in case of molasses as a solution (11.33%) compared with sucrose-salt solution (7.88%). Results obtained at 60 °C were negative which means that rehydration didn't take place. The best conditions for meat rehydration were obtained using a temperature of 20 °C and time of 60 min. Volume of samples increased almost linearly with weight increment

Promoting Equity in Health Information: Partners for Health Information and Health Information Partners (HIPS)

In 2004, a community health outreach partnership, funded by the U.S. National Library of Medicine (NLM), was launched. HIPS, Health Information Partners, promoted health literacy and health advocacy for residents of Washington, D.C., who frequented the area community health centers. This poster explores the goals, strategies, and results of the HIPS program

Application of Artificial Neural Networks in performance prediction of cement mortars with various mineral additives

Prediction of physico-mechanical and thermo-mechanical properties of cement mortars with different mineral additives based on materials’ starting compositions by means of machine learning models is an essential feature in contemporary civil engineering. In this study, the prediction of performances of seventeen mortar mixtures based on Portland cement (CEM I 42.5R) with mineral additives and subsequent comparison with properties of mortars in which various cement types were used as binders was conducted using artificial neural network (ANN) modeling. Analytical model comprised discrimination based on similarities and differences between composite mortars and mortars based on 6 different cement types (without additives). The employed cements were: ordinary Portland cement, moderate heat hydration cement, high early strength cement, low heath hydration cement, high sulphate resistant cement, calcium aluminate cement, and high alumina cement. The mineral additives used were: fly ash, bottom ash, zeolite, bentonite, perlite, vermiculite, pyrophyllite, micro silica, silica fume, spinel, chamotte, calcinated clay, kaoline clay, alumina, limestone, talc, and copper slag. This investigation designates the impacts of various process parameters, such as the concentration of SiO2 , Al 2 O3 , Fe 2 O3 , CaO, MgO, K2 O, Na 2 O, TiO2 , SO3 , and LoI, and their effects on the quality of mortars with additives. The characteristics of mortars were evaluated regarding the dependent parameters such as: pozzolanic activity, heath of hydration, setting time, compressive strength, split tensile strength, compressive and split tensile strength under various temperatures up to 1000 °C, refractoriness, and sulphate resistence. Cluster Analysis and Principal Component Analysis were used for estimating the effect of ascertained process parameters on the quality of cements and additives. Artificial neural network model was employed to foresee the quality of cement mortars with additives of discovered outputs and its results show the high suitability level of anticipation: 0.999 during the training period, which can be regarded appropriately enough to correctly predict the observed outputs in a wide range of processing parameters. The developed ANN model displayed high predictive accuracy and it can be used in civil engineering for prediction of properties of novel mineral additives if their chemical composition is known.IX Serbian Ceramic Society Conference - Advanced Ceramics and Application : new frontiers in multifunctional material science and processing : program and the book of abstracts; September 20-21, 2021; Belgrad

Numerical Prediction of Nucleate Pool Boiling Heat Transfer Coefficient under High Heat Fluxes

This paper presents computational fluid dynamics approach to prediction of the heat transfer coefficient for nucleate pool boiling under high heat fluxes. The 3-D numerical simulations of the atmospheric saturated pool boiling are performed. Mathematical modelling of pool boiling requires a treatment of vapor-liquid two-phase mixture on the macro level, as well as on the micro level, such as bubble growth and departure from the heating surface. Two-phase flow is modelled by the two-fluid model, which consists of the mass, momentum, and energy conservation equations for each phase. Interface transfer processes are calculated by the closure laws. Micro level phenomena on the heating surface are modelled with the bubble nucleation site density, the bubble resistance time on the heating wall and with the certain level of randomness in the location of bubble nucleation sites. The developed model was used to determine the heat transfer coefficient and results of numerical simulations are compared with available experimental results and several empirical correlations. A considerable scattering of the predictions of the pool boiling heat transfer coefficient by experimental correlations is observed, while the numerically predicted values are within the range of results calculated by well-known Kutateladze, Mostinski, Kruzhilin, and Rohsenow correlations. The presented numerical modelling approach is original regarding both the application of the two-fluid two-phase model for the determination of heat transfer coefficient in pool boiling and the defined boundary conditions at the heated wall surface

RELATIONSHIP BETWEEN ROTAVIRUS AND FIMBRIATED ESCHERICHIA COLI IN ENTERIC INFECTIONS OF NEONATAL ALPACAS

El objetivo del presente trabajo fue determinar la presencia y la asociación entre rotavirus y la Escherichia coli fimbriada como agentes patógenos causantes de las infecciones entéricas en condiciones naturales en alpacas neonatas. La detección de rotavirus y de antígenos fimbriales se realizó mediante aglutinación con anticuerpos monoclonales embebidos en látex y la biotipificación se realizó mediante el sistema API 20E. En el 9.3% de las muestras de heces se detectó rotavirus. Se encontró 10 biotipos de E. coli, donde se detectó un 26% de antígeno F41 en alpacas neonatas con infección entérica en contraste con el 48% en los aislamientos de E. coli de alpacas clínicamente sanas. Rotavirus se encuentra en asociación con el 18.8% de los aislamientos de E. coli identificados como biotipos A y C. El 57.8% de aislamientos de E. coli de alpacas neonatas con infección entérica que contienen antígeno fimbrial F41 se encuentran en conjunto con la presencia de rotavirus. Por lo tanto, la asociación entre rotavirus, el biotipo de E. coli y el antígeno fimbrial F41 podría ser la causa de diarrea en el 18.8% del 30-40% de la población de alpacas afectadas.The objective of the present research was to determine the presence and the association between rotavirus, biotype E. coli and fimbriated E. coli in the enteric infections of neonatal alpacas under natural conditions. The detection of rotavirus was carried out by agglutination with monoclonal antibodies, the biotyping of E. coli by API 20E system and the detection of fimbrial antigens by agglutination using monoclonal antibodies. In 15 out of 160 (9.4%) of fecal samples from neonatal alpacas with enteric infection was detected rotavirus. Ten biotypes of E. coli was found and 26% of the E. coli isolates from alpaca neonates with enteric infection had the F41 antigen in contrast with 48% from clinically healthy neonatal alpacas. Rotavirus was found in association with 18.8% of the E. coli isolates identified as biotypes A and C. The 57.8 % of E. coli isolates from neonatal alpacas with enteric infections which contained the fimbrial antigen F41 were found in association with rotavirus. In the present research has been found that under natural conditions, rotavirus is present in conjunction with a different biotype of E. coli and fimbrial antigens F41 in 18.8%; therefore, the association between rotavirus, E. coli biotype and fimbrial antigen F41 may be the cause of diarrhea in 18.8% of 30-40% of neonatal alpacas affected