Determination of braking force on the aerodynamic brake by numerical simulations

Ovaj rad predstavlja rezultate istraživanja uticaja aerodinamičkih kočnica, postavljenih na krov brzog voza, na strujno polje i ukupnu silu kočenja. Voz se sastoji od dve lokomotive, na svakom kraju, i četiri putnička vagona., ukupne dužine 121m. Aerodinamičke kočnice stvaraju silu kočenja povećavanjem aerodinamičkog otpora pomoću izvučenih panela na krovu voza. Simulacije strujanja su urađene softverom Fluent 12.1, za voz bez, sa jednom, dve i tri aerodinamičke kočnice, pri brzinama od 30, 50 i 70m/s. Sila otpora po jedinici površine panela je određena kao funkcija brzine voza i položaja aerodinamičke kočnice. Doprinosi ukupnoj sili kočenja svake od kočnica, određeni simulacijama su: za prvu 24%, za drugu 15% i za treću 14.8% i pokazali su , zajedno sa raspodelama pritisaka po panelima, dobro slaganje sa proračunima aerodinamičkog otpora za ravnu ploču upravno postavljenu prema strujanju.This work presents the research results of the aerodynamic brake influence, mounted on the high-speed train's roof, on the flow field and overall braking force. The train consists of two locomotives at each end and four passenger cars between, with 121m of overall length. Aerodynamic brakes are designed to generate braking force by means of increasing the aerodynamic drag by opened panels over the train. Flow simulations were made by Fluent 12.1 software, for the train without and with one, two and three aerodynamic brakes, and velocities of 30, 50 and 70m/s. Drag force per unit panel area was determined as a function of train's velocity and the brake position. Contributions to train's gross braking force of each brake, obtained by simulations were: for first 24%, for second 15% and third 14.8%, and showed, also with panels' pressure distribution, good correlation with the aerodynamic drag calculations for flat plate orthogonally disposed to flow stream

Determination of braking force on the aerodynamic brake by numerical simulations

Ovaj rad predstavlja rezultate istraživanja uticaja aerodinamičkih kočnica, postavljenih na krov brzog voza, na strujno polje i ukupnu silu kočenja. Voz se sastoji od dve lokomotive, na svakom kraju, i četiri putnička vagona., ukupne dužine 121m. Aerodinamičke kočnice stvaraju silu kočenja povećavanjem aerodinamičkog otpora pomoću izvučenih panela na krovu voza. Simulacije strujanja su urađene softverom Fluent 12.1, za voz bez, sa jednom, dve i tri aerodinamičke kočnice, pri brzinama od 30, 50 i 70m/s. Sila otpora po jedinici površine panela je određena kao funkcija brzine voza i položaja aerodinamičke kočnice. Doprinosi ukupnoj sili kočenja svake od kočnica, određeni simulacijama su: za prvu 24%, za drugu 15% i za treću 14.8% i pokazali su , zajedno sa raspodelama pritisaka po panelima, dobro slaganje sa proračunima aerodinamičkog otpora za ravnu ploču upravno postavljenu prema strujanju.This work presents the research results of the aerodynamic brake influence, mounted on the high-speed train's roof, on the flow field and overall braking force. The train consists of two locomotives at each end and four passenger cars between, with 121m of overall length. Aerodynamic brakes are designed to generate braking force by means of increasing the aerodynamic drag by opened panels over the train. Flow simulations were made by Fluent 12.1 software, for the train without and with one, two and three aerodynamic brakes, and velocities of 30, 50 and 70m/s. Drag force per unit panel area was determined as a function of train's velocity and the brake position. Contributions to train's gross braking force of each brake, obtained by simulations were: for first 24%, for second 15% and third 14.8%, and showed, also with panels' pressure distribution, good correlation with the aerodynamic drag calculations for flat plate orthogonally disposed to flow stream

The influence of barriers on entrepreneurial intentions: Student entrepreneurship in Western Balkan countries

The paper is based on the findings of the research of students of business administration in the countries of the Western Balkans and aims to identify the impact of entrepreneurial barriers on their intentions to start entrepreneurial ventures. Barriers are classified into four categories. The first category is knowledge and skill barriers. The second group of barriers includes financial barriers. Subjective circumstances represent the third, and administrative procedures and fiscal burdens are the fourth groups of barriers. The research was conducted with 910 respondents, which consists of 71 questions. For the analysis, 6 questions related to the demographic profile and general information were used, while for the second part, 14 were used, which belong to the categories of barriers. The SPSS program was used for the empirical analysis of the results. The results showed that financial barriers, administrative procedures, and fiscal burdens harm entrepreneurial intentions. Within the group of barriers of knowledge and skills, the lack of business plan development skills and the lack of financial skills harm entrepreneurial aspirations, while the other barriers are not statistically significant. It was confirmed that statistically significant barriers to entrepreneurial intentions belong to subjective circumstances: lack of support from the environment and fear of failure

Determination of air and hydrofoil pressure coefficient by laser doppler anemometry

Some results of experiments performed in water cavitation tunnel are presented. Pressure coefficient (Cp) was experimentally determined by Laser Doppler Anemometry (LDA) measurements. Two models were tested: model of airplane G4 (Super Galeb) and hydrofoil of high speed axial pump. These models are not prepared for conventional pressure measurements, so that LDA is applied for Cp determination. Numerical results were obtained using a code for average Navier-Stokes equations solutions. Comparisons between computational and experimental results prove the effectiveness of the LDA. The advantages and disadvantages of LDA application are discussed. Flow visualization was made by air bubbles

Geographic tongue: Does Candida play a role in its pathogenesis

Background/Aim: Geographic tongue (GT), a benign self-limiting condition (inflammation) is commonly seen in practice. Although quite easy for clinical diagnosis, in clinical practice it is commonly misdiagnosed and treated as Candida infection. The main aim of this study was to compare the prevalence of Candida spp. on tongue in patients with GT and subjects with clinically healthy oral mucosa. Additional aims were to evaluate subjective symptoms, uncontrolled usage of prescribed or non-prescribed antifungal topical medications and the presence of the cancerophobia or other health concerns in patients with GT. Material and Methods: A total of 70 subjects were divided into two groups: Group B - patients with diagnosed Geographic tongue and group A - aged and gender matched controls with clinically health oral mucosa. Anamnestic charts designed for this study included information about symptoms (measured by Visual Analogue Scale), previous knowledge or fear about presence of GT and received therapy for this condition. Detection of Candida spp. from tongue was done using sterile cotton swab and Sabouraud dextrose agar. Results: At the time of this study, 18 (52.94%) of subjects with GT were aware of having this condition and even 12 of them (66.7%) used topical antifungal drugs prescribed by physician. Also, 66.7% of them experienced fear about the presence of GT at some moment. Detection of Candida spp. was similarly distributed in both groups (22.2% in group A and 17.6% in group B). Conclusions: Geographic tongue has frequently been treated by topical antifungal drugs. In this study, GT was not associated with presence of Candida spp

Synthesis and preliminary screening for the biological activity of some steroidal Δ4-unsaturated semicarbazone derivatives

Eleven new steroidal mono- and bis(semicarbazones)2a–e, 4d and 3a–e have been prepared starting from various 3-oxo-α,β-unsaturated steroids. Mono-semicarbazones 2a–e were further subjected to ethyl chloroacetate in boiling absolute ethanol but, instead of expected intramolecular cyclocondensation reaction products, the new carbazate esters 5a-e were obtained. The structures of all synthesized compounds and identification of each E/Z isomer were deduced by elemental analysis, HRMS, NMR, and IR spectroscopy. Preliminary screening for the cytotoxic activity in vitro of the new compounds has been conducted against three cancer cell lines, K562, Jurkat and HeLa cells. HeLa cells were the most sensitive while K562 cells were the least sensitive to the cytotoxic action of the novel steroid derivatives. Compounds 2e, 3c and 5e were found to have the best but still moderate cytotoxic effects. All tested compounds showed very weak antimicrobial activities. These results demonstrate that the replacement of thioxo group with carbonyl group in steroidal hydrazone derivatives resulted in decrease in their biological activity.Supplementary material: [http://cherry.chem.bg.ac.rs/handle/123456789/3083]This is peer-reviewed version of the following article: Živković, M. B.; Novaković, I. T.; Matić, I. Z.; Sladić, D. M.; Krstić, N. M. Synthesis and Preliminary Screening for the Biological Activity of Some Steroidal Δ4-Unsaturated Semicarbazone Derivatives. Steroids 2019, 148, 36–46. [https://doi.org/10.1016/j.steroids.2019.04.010

Supplementary data for article: Živković, M. B.; Novaković, I. T.; Matić, I. Z.; Sladić, D. M.; Krstić, N. M. Synthesis and Preliminary Screening for the Biological Activity of Some Steroidal Δ4-Unsaturated Semicarbazone Derivatives. Steroids 2019, 148, 36–46. https://doi.org/10.1016/j.steroids.2019.04.010

Supplementary material for: [https://www.sciencedirect.com/science/article/pii/S0039128X19300893?via%3Dihub#gp005]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/3082]Related to accepted version: [http://cherry.chem.bg.ac.rs/handle/123456789/3084

Supplementary data for article: Krstić, N. M.; Pavlović, V. D.; Novaković, I. T.; Matić, I. Z.; Sladić, D. Synthesis, Characterization and Biological Evaluation of Some Novel P-Heterocyclic Androst-4-Ene Derivatives. Molecular Diversity 2013, 17 (3), 547–561. https://doi.org/10.1007/s11030-013-9455-9

Supplementary material for: [https://doi.org/10.1007/s11030-013-9455-9]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/1376

Supplementary material for the article: Živković, M. B.; Matić, I. Z.; Rodić, M. V.; Novaković, I. T.; Sladić, D. M.; Krstić, N. M. Synthesis, Characterization and in Vitro Cytotoxic Activities of New Steroidal Thiosemicarbazones and Thiadiazolines. RSC Advances 2016, 6 (41), 34312–34333. https://doi.org/10.1039/c6ra01516f

Supplementary material for: [https://doi.org/10.1039/c6ra01516f]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/1913