Advantages and Perspective of Fortified Agarised Media Application

With mechanical fortifying, the solid (agarised) media layers become more suitable and efficient in realising their application purposes. Essentially, the fortified agarised media layers become more suitable for applications mainly because they enable the use of both layer sides to start microbial cultures, or to realise the contacts with other reaction systems. The fortifying can be performed by applying the appropriately designed nets made from inert material, based on the direct use of commercially available wire nets, or on the weaving of metallic or other appropriate filaments, or on the application of other procedures of working out net tissues and perforated sheets as well as devices based on them. Advantages and perspective of the application of fortified agarised media layers are discussed on the basis of author’s own partly already published and discussed experimental data, with taking into account the expected further applications. Authors recommend the further studies and applications, especially because of supposed more efficient realisation of series of research goals (e.g. of microorganism screening and bioactive substance recognition) and expected discovery of relationships generally applicable for microbial populations and populations of other organisms

The impact of the transition radius lower flange-web on local stress of monorail crane girder

Širokopojasne profile sa paralelnom konturom pojaseva, koji se danas dominantno koriste za izradu jednošinskih nosača dizalica, karakteriše relativno veliki radijus tranzicije konture pojasa u konturu rebra. Upravo zbog toga, uticaj pomenutog radijusa na naponsko stanje izazvano lokalnim savijanjem usled dejstva točkova dizaličnih kolica znatno je izraženiji kod širokopojasnih (IPB) profila, u odnosu na klasične I profile i srednje široke (IPE) profile. U radu su prezentirani rezultati numeričko-analitičkog i eksperimentalnog istraživanja lokalnih napona u zoni tranzicije donji pojas/rebro kod širokopojasnih profila. Utvrđeno je da se najveće vrednosti razmatranih napona javljaju na početku tranzicije konture, a ne u tački fiktivnog preseka konture rebra i donje konture donjeg pojasa, kako se navodi u relevantnoj literaturi i aktuelnoj tehničkoj regulativi (standard EN 15011:2014). Osim toga, rezultati istraživanja dokazuju da apsolutne vrednosti lokalnih napona na donjoj i gornjoj konturi nisu jednake.Wide flange I-beams with parallel flange contours, which are now predominantly used in production of monorail crane girders, are characterized by a relatively large radial transition between flange contour and rib contour. Therefore, the influence of the radius on the stress state, due to the local bending caused by the action of crane trolley wheels, is more pronounced in wide-flange I-beams (IPB) than in conventional (I) and mid-wide (IPE) I-beams. This paper presents the results of numerical-analytical and experimental research of local stresses in the lower flange-rib transition zone at wide flange I-beams. It was found that the highest values of the considered stresses occur at the start of the transition contour, and not in the fictive point of intersection of the rib contour and the upper contour of the lower flange, as stated in relevant literature and current technical regulations (standard SRPS EN 15011: 2014). In addition, research results show that the absolute values of local stresses on the lower and upper contours of the lower flange are not equal

Applicability ofMathematicalModels in Defining the Behaviour Kinetics Distinction Among Microbial Strains

Mathematical models were applied to define the behaviour kinetics distinction among microbial strains. In the first series of experiments the growth kinetics of microbial colonies of several S. rimosus mutant strains cultivated on agar plates were compared. Then, the interest was focused on the chosen two strains, in order to express mathematically their differences with respect to their colony growth and antibiotic biosynthesis kinetics. Finally, the behaviour of selected three S. rimosus derivative strains at different culture conditions was subjected to the study, with an aim to define strain distinction parameters. Mathematical models based on the three-dimensional growth concept and describing the microorganism growth, substrate uptake and antibiotic biosynthesis kinetics were developed. The computer simulation was applied to verify the applicability of mathematical models. The excellent agreement of computer simulation with experimental data confirmed the hypothesis that the kinetics parameters can be successfully applied to define the behaviour distinction among different S. rimosus strains. In the case of selected three strains, S. rimosus R6–500, S. rimosus MV9R-1 and MV9R-2, it was established that they can be distinguished by their growth kinetics parameters, their substrate uptake kinetics parameters and their antibiotic biosynthesis kineticsparameters. The strain S. rimosus R6–500 showed to be superior with respect to all kinetics parameters, the strain S. rimosus MV9R-2 showed to be slightly inferior to it, whereas the strain S. rimosus MV9R-1 showed to be inferior with respect to the both mentioned strains, especially because it showed the pronounced active biomass reduction rate at all investigated culture conditions. Based on these and the corresponding previous results one can conclude that appropriate mathematical models can be recommended for defining parameters of microbial behaviour distinction among different microbial strains of S. rimosus species

Environmental Hazard Assessment of Jarosite Waste Using Batch Leaching Tests

Jarosite waste samples from Trepça Zinc Industry in Kosovo were subjected to two batch leaching tests as an attempt to characterize the leaching behavior and mobility of minor and major elements of jarosite waste. To achieve this, deionized water and synthetic acidic rain leaching tests were employed. A two-step acidic treatment in microwave digestion system were used to dissolve jarosite waste samples, followed by determination of Al, Ag, As, Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, P, Pb, S, Si, Sr, and Zn by inductively coupled plasma optical emission spectrometry (ICP-OES). The validation of the procedure was performed by the analysis of two geochemical reference materials, S JR-3 and S Jsy-1. Two toxicity leaching tests revealed a high metal releasing of Cd, Cu, Ni, Mn, Pb, Zn, and As, and the metal release risk for these elements is still very high due the low pH and acid rain. The statistical analysis showed useful data information on the relationship between elements in jarosite samples in two different extraction conditions (deionized water and synthetic acid rain). This work is licensed under a Creative Commons Attribution 4.0 International License

Experimental examination of fatigue life of welded joint with stress concentration

This paper presents results of experimental examinations of stress concentration influence to fatigue life of butt welded joints with K-groove, produced from the most frequently used structural steel S355J2+N. One group of experiments comprised examinations carried out on the K-groove specimens with stress concentrators of edged notch type. Specimens with short cracks (limited length of initial crack), defined on the basis of the experience from fracture mechanics by the three points bending examinations, have been examined according to standard for the determination of S-N curve, and aimed to determine fatigue strengths for different lengths of initial crack and Relationship between fatigue strength and crack length. Other group of experiments comprised examinations of specimens with edge notch, prepared in accordance with ASTM E 399 for three points bending, in order to establish regularity between crack growth and range of exerted stress intensity factor aimed to determine resistance of welded joint to initial crack growth, namely fatigue threshold (ΔKth)