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Flow properties of coolants for metal cutting
Blašková, Daniela ; Poláček, Petr (oponent) ; Bálková, Radka (vedoucí práce)
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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Rakytník řešetlákový – zdroj přírodních látek
Blašková, Daniela ; Vítová, Eva (oponent) ; Veselá, Mária (vedoucí práce)
Hlavným cieľom bakalárskej práce bolo skúmanie rakytníka rešetliakového, často označovaného ako „rastlina budúcnosti.“ Botanická charakteristika daného kra, overenie biologicky aktívnych látok a účinkov extraktov o rôznych koncentráciách na vybrané druhy mikroorganizmov. V teoretickej časti je vypracovaná literárna rešerš, ktorá pojednáva o charakterizácií skúmanej rastliny. Praktická časť sa zaoberá aplikáciou vybraných metód pre skúmanie akými sú: spektrofotometrické stanovenie biologicky aktívnych látok a mikrobiologické overenie antimikrobiálnej aktivity na mikroorganizmy akými sú Bacillus subtilis, Serratia marcenscens a Micrococcus luteus. Z výsledkov práce vyplýva, že dané extrakty nevykazujú príliš veľkú mikrobiálnu aktivitu. Na druhej strane obsahujú v niektorých prípadoch veľké množstvo stanovovaných aktívnych látok.
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Flow properties of coolants for metal cutting
Blašková, Daniela ; Poláček, Petr (oponent) ; Bálková, Radka (vedoucí práce)
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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Rakytník řešetlákový – zdroj přírodních látek
Blašková, Daniela ; Vítová, Eva (oponent) ; Veselá, Mária (vedoucí práce)
Hlavným cieľom bakalárskej práce bolo skúmanie rakytníka rešetliakového, často označovaného ako „rastlina budúcnosti.“ Botanická charakteristika daného kra, overenie biologicky aktívnych látok a účinkov extraktov o rôznych koncentráciách na vybrané druhy mikroorganizmov. V teoretickej časti je vypracovaná literárna rešerš, ktorá pojednáva o charakterizácií skúmanej rastliny. Praktická časť sa zaoberá aplikáciou vybraných metód pre skúmanie akými sú: spektrofotometrické stanovenie biologicky aktívnych látok a mikrobiologické overenie antimikrobiálnej aktivity na mikroorganizmy akými sú Bacillus subtilis, Serratia marcenscens a Micrococcus luteus. Z výsledkov práce vyplýva, že dané extrakty nevykazujú príliš veľkú mikrobiálnu aktivitu. Na druhej strane obsahujú v niektorých prípadoch veľké množstvo stanovovaných aktívnych látok.
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