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Flow properties of coolants for metal cutting
Blašková, Daniela ; Poláček, Petr (referee) ; Bálková, Radka (advisor)
The flow properties of two types of operating and clean coolants (A and B) were measured, both used in metalworking. Four samples of both operating liquids were sampled from the process monthly (from the beginning to the end of its use). All liquids were measured at 25 °C with an oil emulsion content of 4%. In addition, flow curves of pure cooling emulsions with concentration of coolant 2, 4, 6 and 8% were measured at 30, 35, 40, 45 and 50 °C. Rheological measurement was performed at geometry of concentric cylinders. Microbial activity and content of additives (Thermogravimetry) was determined in operating liquid A. Both operating liquids exhibited non-Newtonian behavior. Viscosity increased with the shear rate (10–100 s-1) and impurity level. Although the amount of impurity was approximately the same in both liquids, viscosity varied. For pure liquids, the viscosity increased with increasing concentration and decreased with increasing temperature, except for liquid A with concentration of coolants 6 and 8%, which, depending on the temperature, exhibited both shear thinning, shear thickening and Newtonian behavior. The results shown that impurity level of operating liquids has only minor effect on viscosity and flow properties, but it had an effect on cooling effect. Impurities diluted operating liquids, partial decomposition of the oil component may occur, but in particular, microbial activity causes skin problems of staff. Recommended is to introduce a specific control test for the presence of bacteria.
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Sea buckthorn – the source of natural compounds
Blašková, Daniela ; Vítová, Eva (referee) ; Veselá, Mária (advisor)
The main aim of the bachelor thesis was a research of common sea buckthorn, often denoted as "a plant of future". Botanic characteristics of the given bush, verification of biologically active substances and various concentration extract effects on selected kinds of microorganisms. In the theoretical part, the literature search is done, which discusses the characterization of the researched plant. The practical part deals with the application of selected methods of research, as follows: spectrophotometric determination of biologically active substances and microbiological verification of microbial activity on microorganisms, such as Bacillus subtilis, Serratia marcenscens and Micrococcus luteus. Considering the thesis results, it ensues that the given extracts do not show too great bacterial activity. Ex adverso, the extracts contain too big amount of determined active substances, in some cases.
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Flow properties of coolants for metal cutting
Blašková, Daniela ; Poláček, Petr (referee) ; Bálková, Radka (advisor)
The flow properties of two types of operating and clean coolants (A and B) were measured, both used in metalworking. Four samples of both operating liquids were sampled from the process monthly (from the beginning to the end of its use). All liquids were measured at 25 °C with an oil emulsion content of 4%. In addition, flow curves of pure cooling emulsions with concentration of coolant 2, 4, 6 and 8% were measured at 30, 35, 40, 45 and 50 °C. Rheological measurement was performed at geometry of concentric cylinders. Microbial activity and content of additives (Thermogravimetry) was determined in operating liquid A. Both operating liquids exhibited non-Newtonian behavior. Viscosity increased with the shear rate (10–100 s-1) and impurity level. Although the amount of impurity was approximately the same in both liquids, viscosity varied. For pure liquids, the viscosity increased with increasing concentration and decreased with increasing temperature, except for liquid A with concentration of coolants 6 and 8%, which, depending on the temperature, exhibited both shear thinning, shear thickening and Newtonian behavior. The results shown that impurity level of operating liquids has only minor effect on viscosity and flow properties, but it had an effect on cooling effect. Impurities diluted operating liquids, partial decomposition of the oil component may occur, but in particular, microbial activity causes skin problems of staff. Recommended is to introduce a specific control test for the presence of bacteria.
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|
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Sea buckthorn – the source of natural compounds
Blašková, Daniela ; Vítová, Eva (referee) ; Veselá, Mária (advisor)
The main aim of the bachelor thesis was a research of common sea buckthorn, often denoted as "a plant of future". Botanic characteristics of the given bush, verification of biologically active substances and various concentration extract effects on selected kinds of microorganisms. In the theoretical part, the literature search is done, which discusses the characterization of the researched plant. The practical part deals with the application of selected methods of research, as follows: spectrophotometric determination of biologically active substances and microbiological verification of microbial activity on microorganisms, such as Bacillus subtilis, Serratia marcenscens and Micrococcus luteus. Considering the thesis results, it ensues that the given extracts do not show too great bacterial activity. Ex adverso, the extracts contain too big amount of determined active substances, in some cases.
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