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EN
The article contains comments on the perception of 'homo economicus' concept. They cover the full rationality model and its evolution towards the concept in which a human being is constrained by bounded rationality as well as by the environment influences, who acts routinely and frequently in an opportunistic manner. The article stresses the importance of the exact definition of an individual who constitutes the basic component of an economic system. A special attention is accorded to the comparison of the models of an economic man that are present in economic theories of the main stream and the new institutional economics. The authoresses voice the opinion that despite the recent rendering the model more realistic as well as the convergence of approaches toward an economic agent in economics and sociology, the substitution of the concept of 'homo economicus' by an alternative model seems in the near future very unlikely.
PL
Celem przeprowadzonych badań była ocena wpływu stopnia rozdrobnienia trawy cytrynowej na kinetykę suszenia w złożu fontannowym z wykorzystaniem mikrofal. Suszenie prowadzono przy zastosowaniu prędkości powietrza suszącego 5 m∙s⁻¹, temperatury 50°C oraz mocy mikrofal 250 W, wykorzystując łodygi pocięte na plastry o grubości 1 cm oraz cząstki uzyskane po podzieleniu plastrów o grubości 1 cm na cztery części. Dla poprawy hydrodynamiki złoża zastosowano również szklane kule o średnicy 3 mm. Kinetykę suszenia oznaczono na podstawie ubytku masy złoża, a następnie opisano odpowiednim modelem matematycznym. Stwierdzono, że podzielenie plastrów na drobniejsze cząstki spowodowało zwiększenie tempa odwadniania materiału i skrócenie czasu trwania procesu o 20%. Zarówno w przypadku plastrów, jak i cząstek obserwowano chwilowe zakłócenia fontannowania złoża, których przyczyną było zbijanie się sztywnych cząstek trawy cytrynowej w porowatą, nieruchomą warstwę, a zastosowanie kul inertu pozwoliło wyeliminować ten efekt.
EN
The aim of this study was to determine the effect of lemongrass fragmentation on kinetics of fluidized bed drying combined with microwave heating. Lemongrass leaves were cuted on 1 cm bright slices (fragmentation 1) or 1 cm bright slices divided into quartets (fragmentation 2) and dried by microwave assisted fluidized bed drying method. The drying was performed at inlet air velocity 5 m∙s⁻¹ and temperature 50°C, and at 250 W of microwaves input power. For improving the fluidization process, glass balls about diameter of 3 mm were tested as inert. Kinetics of drying was analyzed on the base of moisture ratio changings and described with appropriate mathematical model. Eight common used mathematical models were selected and tested in order to describe the experimental data. It was found that usage of fragmentation 2 caused improving of drying rate just after 40 min of drying, and shortening of drying process up 150 min to 130 min. During lemongrass drying in form of slices (fragmentation 1) and slice’s quarters as well (fragmentation 2), temporary fluidization inhibition was observed. The reason of this effect was clumping of rigid and curled lemongrass pieces in stationary layer. The application of glass balls as inert let to eliminate this negative result and restore fluidization. Solvation of this technical problem entailed the increase of drying rate during microwave assisted fluidized bed of lemongrass and induced also further shortening of drying time. On the basis of the comparison of the coefficient of determination (R²), root mean square error (RMSE), and standard error (SE), the usefulness of selected mathematical formulas to describe the dehydration process was assessed. It was found that the drying kinetics of lemongrass was best described by the Midilli–Kucuk model, regardless of the material’s fragmentation and inert. For this formula, a high coefficient R² (0.997–0.999) was reported, while at the same time the low values of the SE (0.010– 0.018) and the RSME coefficient (0.010–0.017) were calculated. In conclusion: the fragmentation of lemongrass to smaller pieces (fragmentation 2) gives improvement of microwave assisted fluidized-bed drying rate and process time only when synchronize together with of inert usage.
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